Science.gov

Sample records for h2 partial pressures

  1. Releasing H2 molecules with a partial pressure difference without the use of temperature

    NASA Astrophysics Data System (ADS)

    Lee, Hoonkyung; Huang, Bing; Duan, Wenhui; Ihm, Jisoon

    2010-08-01

    Using the pseudopotential density-functional method as well as equilibrium thermodynamic functions, we explore the process of releasing H2 molecules adsorbed on a transition-metal atom caused by the hydrogen-ammonia partial pressure difference. The H2 molecules bind to a transition-metal atom at H2 pressure- NH3 pressure-temperature 50atm-10-9atm-25°C , and they are released at 3atm-10-6atm-25°C . This process involves the same mechanism responsible for carbon monoxide poisoning of hemoglobin with the O2-CO partial pressure difference. We show that our findings can be applicable to an approach to induce hydrogen desorption on nanostructured hydrogen-storage materials without the need for increasing temperature.

  2. Geometry of α-Cr2O3(0001) as a Function of H2O Partial Pressure

    PubMed Central

    2015-01-01

    Surface X-ray diffraction has been employed to elucidate the surface structure of α-Cr2O3(0001) as a function of water partial pressure at room temperature. In ultra high vacuum, following exposure to ∼2000 Langmuir of H2O, the surface is found to be terminated by a partially occupied double layer of chromium atoms. No evidence of adsorbed OH/H2O is found, which is likely due to either adsorption at minority sites, or X-ray induced desorption. At a water partial pressure of ∼30 mbar, a single OH/H2O species is found to be bound atop each surface Cr atom. This adsorption geometry does not agree with that predicted by ab initio calculations, which may be a result of some differences between the experimental conditions and those modeled. PMID:26877825

  3. Captopril partially decreases the effect of H(2)S on rat blood pressure and inhibits H(2)S-induced nitric oxide release from S-nitrosoglutathione.

    PubMed

    Drobná, M; Misak, A; Holland, T; Kristek, F; Grman, M; Tomasova, L; Berenyiova, A; Cacanyiova, S; Ondrias, K

    2015-01-01

    We studied the effects of the H(2)S donor Na(2)S on the mean arterial blood pressure (MAP) and heart and breathing rates of anesthetized Wistar rats in the presence and absence of captopril. Bolus administration of Na(2)S (1-4 micromol/kg) into the right jugular vein transiently decreased heart and increased breathing rates; at 8-30 micromol/kg, Na(2)S had a biphasic effect, transiently decreasing and increasing MAP, while transiently decreasing heart rate and increasing and decreasing breathing rate. These results may indicate independent mechanisms by which H(2)S influences MAP and heart and breathing rates. The effect of Na(2)S in decreasing MAP was less pronounced in the presence of captopril (2 micromol/l), which may indicate that the renin-angiotensin system is partially involved in the Na(2)S effect. Captopril decreased H(2)S-induced NO release from S-nitrosoglutathione, which may be related to some biological activities of H(2)S. These results contribute to the understanding of the effects of H(2)S on the cardiovascular system.

  4. Partial pressures of H 2O above the diphasic Li 2O(s)-LiOH(s, l) system

    NASA Astrophysics Data System (ADS)

    Tetenbaum, M.; Johnson, C. E.

    1984-09-01

    The temperature dependence of the partial pressure of H 2O(g) above the Li 2O(s)-LiOH(s, l) system was determined for temperatures between 300 and 617°C. The partial pressures were measured by means of a flowing gas technique combined with continuous monitoring of the concentration of water vapor in a helium carrier gas. For the reaction LiOH(s) = Li 2O(s) + H 2O(g) , second law heat and entropy of reaction values of ΔH o = 30.7 ± 0.6 kcal/mol and ΔS o = 29.5 ± 1.0 cal/mol.K were obtained. Above the melting point of LiOH (744 K), these values were ΔH o =19.9 ± 0.6 kcal/mol and ΔS o =14.8 ± 0.8 cal/mol.K . Current measurements yield ΔH mo = 5.4 ± 0.4 kcal/mol for the heat of melting of LiOH, which is in good agreement with the JANAF recommended value of 4.99 kcal/mol. The results of these measurements can be used to partially describe the behavior of a Li 2O solid breeding blanket in anticipated fusion reactor environments.

  5. Maximizing the Hydrogen Photoproduction Yields in Chlamydomonas Reinhardtii Cultures: The Effect of the H2 Partial Pressure

    SciTech Connect

    Kosourov, S. N.; Batyrova, K. A.; Petushkova, E. P.; Tsygankov, A. A.; Ghirardi, M. L.; Seibert, M.

    2012-05-01

    Photoproduction of H{sub 2} gas has been examined in sulfur/phosphorus-deprived Chalmydomonas reinhardtii cultures, placed in photobioreactors (PhBRs) with different gas phase to liquid phase ratios (V{sub g.p.}/V{sub l.p.}). The results demonstrate that an increase in the ratio stimulates H{sub 2} photoproduction activity in both algal suspension cultures and in algae entrapped in thin alginate films. In suspension cultures, a 4x increase (from {approx}0.5 to {approx}2) in V{sub g.p.}/V{sub l.p} results in a 2x increase (from 10.8 to 23.1 mmol l{sup -1} or 264-565 ml l{sup -1}) in the total yield of H{sub 2} gas. Remarkably, 565 ml of H{sub 2} gas per liter of the suspension culture is the highest yield ever reported for a wild-type strain in a time period of less than 190 h. In immobilized algae, where diffusion of H{sub 2} from the medium to the PhBR gas phase is not affected by mixing, the maximum rate and yield of H{sub 2} photoproduction occur in PhBRs with V{sub g.p.}/V{sub l.p} above 7 or in a PhBR with smaller headspace, if the H{sub 2} is effectively removed from the medium by continuous flushing of the headspace with argon. These experiments in combination with studies of the direct inhibitory effect of high H{sub 2} concentrations in the PhBR headspace on H{sub 2} photoproduction activity in algal cultures clearly show that H{sub 2} photoproduction in algae depends significantly on the partial pressure of H{sub 2} (not O{sub 2} as previously thought) in the PhBR gas phase.

  6. Anaerobic granule-based biofilms formation reduces propionate accumulation under high H2 partial pressure using conductive carbon felt particles.

    PubMed

    Xu, Heng; Wang, Cuiping; Yan, Kun; Wu, Jing; Zuo, Jiane; Wang, Kaijun

    2016-09-01

    Syngas based co-digestion is not only more economically attractive than separate syngas methanation but also able to upgrade biogas and increase overall CH4 amount simultaneously. However, high H2 concentration in the syngas could inhibit syntrophic degradation of propionate, resulting in propionate accumulation and even failure of the co-digestion system. In an attempt to reduce propionate accumulation via enhancing both H2 interspecies transfer (HIT) and direct interspecies electron transfer (DIET) pathways, layered granule-based biofilms induced by conductive carbon felt particles (CCFP) was employed. The results showed that propionate accumulation was effectively reduced with influent COD load up to 7gL(-1)d(-1). Two types of granule-based biofilms, namely biofilm adhered to CCFP (B-CCFP) and granules formed by self-immobilization (B-SI) were formed in the reactor. Clostridium, Syntrophobacter, Methanospirillum were possibly involved in HIT and Clostridium, Geobacter, Anaerolineaceae, Methanosaeta in DIET, both of which might be responsible for the high-rate propionate degradation.

  7. 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 Central

    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

  8. High pressure-temperature Raman spectroscopy of H2-H2O clathrate.

    NASA Astrophysics Data System (ADS)

    Somayazulu, Maddury; Levedahl, Alexander; Goncharov, Alexander; Mao, Ho-Kwang; Hemley, Russell

    2007-03-01

    The melting curve of the C2 clathrate H2-H2O has been determined by in-situ Raman spectroscopy measurements in an externally heated diamond anvil cell. We have determined the melting curve to a maximum pressure of 27 GPa. These are the first measurements on the melting line in this clathrate. Depending on the stoichiometry of the starting mixture of H2 and H2O, we are able to study either a mixture of C2 and H2O or C2 and H2. In either case, we were able to pinpoint the melting of the clathrate from the measurements of the molecular stretching mode (vibron) in the clathrate. In the case of C2 + Ice VII, we observe the vibron in the clathrate at a frequency higher than in pure H2 at the same pressure. We have cross-calibrated the melting temperatures using the Stokes-anti Stokes ratio of the diamond first order and Raman active TO phonon of cubic Boron Nitride. We find that the clathrate melts well above the H2 melting at all pressures studied indicating that the stabilization of this clathrate at high pressures is indeed due to interactions between the host and guest molecules.

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

    PubMed Central

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

    2014-01-01

    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. PMID:25382349

  10. 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.

  11. Oxygen partial pressure sensor

    DOEpatents

    Dees, D.W.

    1994-09-06

    A method for detecting oxygen partial pressure and an oxygen partial pressure sensor are provided. The method for measuring oxygen partial pressure includes contacting oxygen to a solid oxide electrolyte and measuring the subsequent change in electrical conductivity of the solid oxide electrolyte. A solid oxide electrolyte is utilized that contacts both a porous electrode and a nonporous electrode. The electrical conductivity of the solid oxide electrolyte is affected when oxygen from an exhaust stream permeates through the porous electrode to establish an equilibrium of oxygen anions in the electrolyte, thereby displacing electrons throughout the electrolyte to form an electron gradient. By adapting the two electrodes to sense a voltage potential between them, the change in electrolyte conductivity due to oxygen presence can be measured. 1 fig.

  12. Oxygen partial pressure sensor

    DOEpatents

    Dees, Dennis W.

    1994-01-01

    A method for detecting oxygen partial pressure and an oxygen partial pressure sensor are provided. The method for measuring oxygen partial pressure includes contacting oxygen to a solid oxide electrolyte and measuring the subsequent change in electrical conductivity of the solid oxide electrolyte. A solid oxide electrolyte is utilized that contacts both a porous electrode and a nonporous electrode. The electrical conductivity of the solid oxide electrolyte is affected when oxygen from an exhaust stream permeates through the porous electrode to establish an equilibrium of oxygen anions in the electrolyte, thereby displacing electrons throughout the electrolyte to form an electron gradient. By adapting the two electrodes to sense a voltage potential between them, the change in electrolyte conductivity due to oxygen presence can be measured.

  13. Association reactions at low pressure. III. The C2H2+/C2H2 system.

    PubMed

    Anicich, V G; Sen, A D; Huntress, W T; McEwan, M J

    1990-11-15

    The association reactions, C4H2(+) + C2H2 and C4H3(+) + C2H2 have been examined at pressures between 8 x 10(-8) and 1 x 10(-4) Torr at 298 K in an ion cyclotron resonance mass spectrometer. Association occurred via two different mechanisms. At pressures below approximately 2 x 10(-6) Torr, the association was bimolecular having rate coefficients k2 = 2.7 x 10(-10) cm3 s-1 and 2.0 x 10(-10) cm3 s-1 for C4H2+ and C4H3+, respectively. At pressures above approximately 2 x 10(-6) Torr, termolecular association was observed with rate coefficients, k3 = 5.7 x 10(-23) cm6 s-1 and 1.3 x 10(-23) cm6 s-1 for C4H2+ and C4H3+, respectively, when M = C2H2. The termolecular rate constants with N2, Ar, Ne, and He as the third body, M, are also reported. We propose that the low pressure bimolecular association process was the result of radiative stabilization of the complex and the termolecular association process was the result of collisional stabilization. Elementary rate coefficients were obtained and the lifetime of the collision complex was > or = 57 microseconds for (C6H4+)* and > or = 18 microseconds for (C6H5+)*. At pressures below 1 x 10(-6) Torr, approximately 11% of the (C6H4+)* were stabilized by photon emission and the remaining approximately 89% reverted back to reactants, while approximately 24% of the (C6H5+)* were stabilized by photon emission and the remaining approximately 76% reverted back to reactants. The ionic products of the C2H2(+) + C2H2 reaction, C4H2+ and C4H3+, were found to be formed with enough internal energy that they did not react by the radiative association channel until relaxed by several nonreactive collisions with the bath gas.

  14. Silicate-H2O Systems at High Pressure Conditions

    NASA Astrophysics Data System (ADS)

    Tailby, N.; Mavrogenes, J. A.; Hermann, J.; O'Neill, H. S.

    2008-12-01

    Since the discovery of the second critical endpoint (CP2) in the albite-water system, numerous attempts have been made to determine the pressure and temperature of this CP2 and the mutual solubilities within more complex systems. The P-T position of the CP2 has been estimated for many systems: SiO2 (<10 kb/900 °C, Newton and Manning, 2008); NaAlSi3O8 (15 kb/800 °C, Burnham and Davis, 1974; Shen and Keppler, 1997); Pelite (50 kb/1,000 °C, Schmidt et al., 2004), basalt (50 kb/ 1000 °C, Kessel et al., 2004), Peridotite (38 kb/1000 °C, Mibe et al., 2007). A number of experimental techniques have been used to determine phase relations and H2O solubility in experiments. These include in-situ experimental techniques (e.g., HYDAC; Shen and Keppler, 1997), fluid trap techniques (e.g., diamond traps; Stalder et al., 2000), and single crystal weight-loss techniques (e.g., SiO2-H2O techniques employed by Newton and Manning, 2008). None of these techniques is without difficulties, as H2O rich experiments need to overcome huge retrograde fluid solubilities upon quench in order to determine mutual solubilities at experimental conditions. We have developed a new technique to determine "rock"-H2O relationships at high-P conditions, with particular focus on the shape and locus of solvi in pressure temperature space. In this series of experiments, an oxygen fugacity buffer (Re-ReO2) and a sliding H-fugacity sensor (NiO-Ni-Pd mixture) are combined to monitor H2O activity over the entire range of pressure and temperature. Unlike other techniques, the use of sensor capsules does not require textural interpretation of experiments. H2O activity is related to oxygen and hydrogen fugacity by the reaction: H2O = H2 + ½O2 NiO-Ni-Pd mixtures were placed within a ZrO2 jacket and sealed within a welded 2.3 mm Pt capsule. This 2.3 mm Pt sensor capsule was then encased within a larger, thick walled 6 mm diameter Ag capsule. Pelite-H2O mixtures and oxygen buffers were held within this larger

  15. Pressure-induced superconductivity in H2-containing hydride PbH4(H2)2

    PubMed Central

    Cheng, Ya; Zhang, Chao; Wang, Tingting; Zhong, Guohua; Yang, Chunlei; Chen, Xiao-Jia; Lin, Hai-Qing

    2015-01-01

    High pressure structure, stability, metallization, and superconductivity of PbH4(H2)2, a H2-containing compound combining one of the heaviest elements with the lightest element, are investigated by the first-principles calculations. The metallic character is found over the whole studied pressure range, although PbH4(H2)2 is metastable and easily decompose at low pressure. The decomposition pressure point of 133 GPa is predicted above which PbH4(H2)2 is stable both thermodynamically and dynamically with the C2/m symmetry. Interestedly, all hydrogen atoms pairwise couple into H2 quasi-molecules and remain this style up to 400 GPa in the C2/m structure. At high-pressure, PbH4(H2)2 tends to form the Pb-H2 alloy. The superconductivity of Tc firstly rising and then falling is observed in the C2/m PbH4(H2)2. The maximum of Tc is about 107 K at 230 GPa. The softening of intermediate-frequency phonon induced by more inserted H2 molecules is the main origin of the high Tc. The results obtained represent a significant step toward the understanding of the high pressure behavior of metallic hydrogen and hydrogen-rich materials, which is helpful for obtaining the higher Tc. PMID:26559369

  16. Pressure-induced superconductivity in H2-containing hydride PbH4(H2)2

    NASA Astrophysics Data System (ADS)

    Cheng, Ya; Zhang, Chao; Wang, Tingting; Zhong, Guohua; Yang, Chunlei; Chen, Xiao-Jia; Lin, Hai-Qing

    2015-11-01

    High pressure structure, stability, metallization, and superconductivity of PbH4(H2)2, a H2-containing compound combining one of the heaviest elements with the lightest element, are investigated by the first-principles calculations. The metallic character is found over the whole studied pressure range, although PbH4(H2)2 is metastable and easily decompose at low pressure. The decomposition pressure point of 133 GPa is predicted above which PbH4(H2)2 is stable both thermodynamically and dynamically with the C2/m symmetry. Interestedly, all hydrogen atoms pairwise couple into H2 quasi-molecules and remain this style up to 400 GPa in the C2/m structure. At high-pressure, PbH4(H2)2 tends to form the Pb-H2 alloy. The superconductivity of Tc firstly rising and then falling is observed in the C2/m PbH4(H2)2. The maximum of Tc is about 107 K at 230 GPa. The softening of intermediate-frequency phonon induced by more inserted H2 molecules is the main origin of the high Tc. The results obtained represent a significant step toward the understanding of the high pressure behavior of metallic hydrogen and hydrogen-rich materials, which is helpful for obtaining the higher Tc.

  17. Melting Temperature and Partial Melt Chemistry of H2O-Saturated Mantle Peridotite to 11 Gigapascals

    PubMed

    Kawamoto; Holloway

    1997-04-11

    The H2O-saturated solidus of a model mantle composition (Kilborne Hole peridotite nodule, KLB-1) was determined to be just above 1000°C from 5 to 11 gigapascals. Given reasonable H2O abundances in Earth's mantle, an H2O-rich fluid could exist only in a region defined by the wet solidus and thermal stability limits of hydrous minerals, at depths between 90 and 330 kilometers. The experimental partial melts monotonously became more mafic with increasing pressure from andesitic composition at 1 gigapascal to more mafic than the starting peridotite at 10 gigapascals. Because the chemistry of the experimental partial melts is similar to that of kimberlites, it is suggested that kimberlites may be derived by low-temperature melting of an H2O-rich mantle at depths of 150 to 300 kilometers.

  18. Vapour pressures of H2SO4/HNO3/HCI/HBr/H2O solutions to low stratospheric temperatures

    SciTech Connect

    Luo, B.; Carslaw, K.S.; Peter, T.; Clegg, S.L. |

    1995-02-01

    Vapor pressures of H2O, HNO3, HCl and HBr over supercooled aqueous mixtures with sulfuric acid have been calculated using an activity coefficient model, for 185 K less than T less than 235 K, 0 less than wt% (H2SO4) + wt% (HNO3) less than 70, and assuming HCl and HBr to be minor constituents. Predicted vapor pressures agree well with most laboratory data, and give confidence in the validity of the model. The results are parameterized as simple formulae, which reproduce the model results to within 40% and cover the entire stratospherically relevant range of composition and temperature.

  19. The effect of H2O on partial melting of garnet peridotite at 3.5 GPa

    NASA Astrophysics Data System (ADS)

    Tenner, Travis J.; Hirschmann, Marc M.; Humayun, Munir

    2012-03-01

    We present experimental determinations of the influence of H2O on partial melting of garnet peridotite (+1.5, 2.5, and 5 wt. % added H2O) at 3.5 GPa and 1200-1450°C. Experiments produced complex polyphase regions of quenched melt and equilibrium partial melt compositions were reconstructed by combined EMP and LA-ICP-MS analyses. Mass balance-derived melt fractions (F) range from 0.18 to 0.33 and dissolved water contents range from 4.5 to 23.5 wt. %. One exceptional experiment quenched glass, allowing independent verification of H2O concentration by FTIR. The influence of H2O on melt production is quantified by the temperature difference required to achieve a given F under dry and wet conditions, ΔT, which is controlled by the H2O concentration in partial melts. Melts with 1.5, 5, 10, and 15 wt. % H2O yield ΔT values of 50, 150, 250, and 320°C, respectively, consistent with a cryoscopic parameterization that assumes 3 oxygens per mole of silicate melt. Based on this parameterization, we calculate that beneath oceanic ridges, peridotite H2O storage capacity increases from 0 to 240 ppm from 66 to 110 km depth. For H2O to be solely responsible for melting in the oceanic low velocity zone (LVZ) at least 5.7 wt. % H2O must be dissolved in the melt at 110 km, and considerably more (e.g., 15 wt.% at 220 km) is required for melting throughout the entire observed interval. The addition of H2O results in 3.5 GPa partial melts of garnet peridotite (normalized anhydrous) that are SiO2 and Al2O3 poor (43-50 and 9-11.5 wt. %, respectively), and MgO and CaO rich (18-27 and 7-12 wt. %, respectively) when compared to anhydrous analogues. These effects become highly pronounced deep in the upper mantle, and are opposite to the effect of H2O on melt compositions in the spinel stability field, potentially owing in part to OH-association with network modifying cations in high pressure, depolymerized melts and in part to low-temperature stabilization of garnet, which enhances CaO/Al2O

  20. Thermal Pressure in Diffuse H2 Gas Measured by Herschel [C II] Emission and FUSE UV H2 Absorption

    NASA Astrophysics Data System (ADS)

    Velusamy, T.; Langer, W. D.; Goldsmith, P. F.; Pineda, J. L.

    2017-04-01

    UV absorption studies with the Far Ultraviolet Spectroscopic Explorer (FUSE) satellite have made important observations of H2 molecular gas in Galactic interstellar translucent and diffuse clouds. Observations of the 158 μm [C ii] fine-structure line with Herschel trace the same H2 molecular gas in emission. We present [C ii] observations along 27 lines of sight (LOSs) toward target stars of which 25 have FUSE H2 UV absorption. Two stars have only HST STIS C ii λ2325 absorption data. We detect [C ii] 158 μm emission features in all but one target LOS. For three target LOSs that are close to the Galactic plane, | {\\text{}}b| < 1°, we also present position–velocity maps of [C ii] emission observed by Herschel Heterodyne Instrument in the Far Infrared (HIFI) in on-the-fly spectral-line mapping. We use the velocity-resolved [C ii] spectra observed by the HIFI instrument toward the target LOSs observed by FUSE to identify [C ii] velocity components associated with the H2 clouds. We analyze the observed velocity integrated [C ii] spectral-line intensities in terms of the densities and thermal pressures in the H2 gas using the H2 column densities and temperatures measured by the UV absorption data. We present the H2 gas densities and thermal pressures for 26 target LOSs and from the [C ii] intensities derive a mean thermal pressure in the range of ∼6100–7700 K cm‑3 in diffuse H2 clouds. We discuss the thermal pressures and densities toward 14 targets, comparing them to results obtained using the UV absorption data for two other tracers C i and CO. Our results demonstrate the richness of the far-IR [C ii] spectral data which is a valuable complement to the UV H2 absorption data for studying diffuse H2 molecular clouds. While the UV absorption is restricted to the directions of the target star, far-IR [C ii] line emission offers an opportunity to employ velocity-resolved spectral-line mapping capability to study in detail the clouds’ spatial and velocity

  1. 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.

  2. Partial covering of the emission regions of Q 0528-250 by intervening H2 clouds

    NASA Astrophysics Data System (ADS)

    Klimenko, V. V.; Balashev, S. A.; Ivanchik, A. V.; Ledoux, C.; Noterdaeme, P.; Petitjean, P.; Srianand, R.; Varshalovich, D. A.

    2015-03-01

    We present an analysis of the molecular hydrogen absorption system at zabs = 2.811 in the spectrum of the blazar Q 0528-250. We demonstrate that the molecular cloud does not cover the background source completely. The partial coverage reveals itself as a residual flux at the bottom of the saturated H2 absorption lines. This amounts to about (2.22 ± 0.54) per cent of the continuum and does not depend on the wavelength. This value is small and it explains why this effect has not been detected in previous studies of this quasar spectrum. However, it is robustly detected and is significantly higher than the zero-flux level at the bottom of the saturated lines of the Lyα forest, (-0.21 ± 0.22) per cent. The presence of the residual flux could be caused by unresolved quasar multicomponents, by light scattered by dust and/or by jet-cloud interaction. The H2 absorption system is very well described by a two-component model without the inclusion of additional components when we take partial coverage into account. The derived total column densities in the H2 absorption components A and B are log N(H2)(cm-2) = 18.10 ± 0.02 and 17.82 ± 0.02, respectively. HD molecules are present only in component B. Given the column density, log N(HD) = 13.33 ± 0.02, we find N(HD)/2N(H2) = (1.48 ± 0.10) × 10- 5, significantly lower than previous estimations. We argue that it is crucial to take into account the partial coverage effects in any analysis of H2 bearing absorption systems, in particular when studying the physical state of the high-redshift interstellar medium.

  3. Equations of state for H2, H2O, and H2-H2O fluid mixtures at temperatures above 0.01° C and at high pressures

    NASA Astrophysics Data System (ADS)

    Rimbach, Helmut; Chatterjee, Niranjan D.

    1987-11-01

    Modified Redlich-Kwong (MRK) equations of state have been derived for the pure fluid species H2 and H2O by expressing the parameter a as a function of T and P, and b as as a function of P only. These equations are valid above 0° and 0.01° C, respectively. For H2O, the prediction of volumes is successful not only in the supercritical, but also in the subcritical range. As a result of this, the saturation curve of H2O can be calculated with a maximum deviation of ±1.4 bar in the range 100 350° C. Between 350° C and the critical point (374.15° C), the uncertainty increases somewhat; this is due to a fundamental inadequacy of the Redlich-Kwong equation itself. These equations of state permit extrapolations to pressures of 100 kbar for H2 and at least 200 kbar for H2O and are, therefore, eminently suited for geochemical applications. Formulation of the MRK of the binary H2-H2O mixtures was achieved by assuming the quadratic mixing rule for the parameters a mix and b+mix. To derive the cross coefficients, aH2-H2Oand b H 2-H 2O, adjustable corrective factors ɛ and τ had to be introduced. The T- and P-dependences of ɛ and τ are based on P-V-T-X H 2 data (Seward and Franck 1981) to 440° C and 2500 bar. The resulting equation of state very satisfactorily reproduces the volumes observed experimentally at various sets of T, P, and X H 2. At a total pressure of 2 kbar, positive deviation from ideal mixing behaviour is still perceptible at as high a temperature as 1000° C. At some temperature around 380° C, phase separation sets in, an aqueous solution with dissolved H2 coexisting in equilibrium with an H2-rich fluid with dissolved H2O. The computed P-T-X H 2 surface of this two-phase region agrees well with that observed in Seward and Franck's (1981) experiments. An independent proof of the validity of this equation of state is the accuracy with which H {m/ex}can be predicted. Calorimetric measurements of H {m/ex}(Smith et al. 1983, Wormald and Colling 1985

  4. Removal of H2S from gas stream using combined plasma photolysis technique at atmospheric pressure.

    PubMed

    Huang, Li; Xia, Lanyan; Ge, Xiaoxue; Jing, Hengye; Dong, Wenbo; Hou, Huiqi

    2012-06-01

    In this paper, H(2)S in gas stream was successfully decomposed at atmospheric pressure by dielectric barrier discharge plasma and VUV-UV radiation from a combined plasma photolysis reactor (CDBD). In comparison with DBD, CDBD enhanced H(2)S removal efficiency significantly at the same applied voltage, inlet H(2)S concentration and gas residence time. H(2)S removal efficiency was determined as a function of Kr pressure, applied voltage, inlet H(2)S concentration, and gas residence time. H(2)S removal efficiency could reach as high as 93% at inlet H(2)S concentration of 27.1 mg m(-3), residence time of 0.4 s, and applied voltage of 7.5 kV. The main products were discerned as H(2)O and SO(4)(2-) based on FTIR and IC analysis.

  5. Advanced High Pressure O2/H2 Technology

    NASA Technical Reports Server (NTRS)

    Morea, S. F. (Editor); Wu, S. T. (Editor)

    1985-01-01

    Activities in the development of advanced high pressure oxygen-hydrogen stage combustion rocket engines are reported. Particular emphasis is given to the Space Shuttle main engine. The areas of engine technology discussed include fracture and fatigue in engine components, manufacturing and producibility engineering, materials, bearing technology, structure dynamics, fluid dynamics, and instrumentation technology.

  6. FT-Raman and high-pressure FT-infrared spectroscopic investigation of monocalcium phosphate monohydrate, Ca(H 2PO 4) 2·H 2O

    NASA Astrophysics Data System (ADS)

    Xu, Jingwei; Gilson, Denis F. R.; Butler, Ian S.

    1998-10-01

    The FT-infrared spectra of monocalcium monohydrate, Ca(H 2PO 4) 2·H 2O, have been measured as a function of pressure up to 50 kbar. A phase transition occurs at 18 kbar. The Lippincott-Schroeder model for the hydrogen bond has been used to explain the pressure dependence of the vibrational frequencies.

  7. The Role of Pressure in GMC Formation II: The H2-Pressure Relation

    NASA Astrophysics Data System (ADS)

    Blitz, Leo; Rosolowsky, Erik

    2006-10-01

    We show that the ratio of molecular to atomic gas in galaxies is determined by hydrostatic pressure and that the relation between the two is nearly linear. The pressure relation is shown to be good over 3 orders of magnitude for 14 galaxies, including dwarfs, H I-rich, and H2-rich galaxies, as well as the Milky Way. The sample spans a factor of 5 in mean metallicity. The rms scatter of individual points of the relation is only about a factor of 2 for all the galaxies, although some show much more scatter than others. Using these results, we propose a modified star formation prescription based on pressure determining the degree to which the ISM is molecular. The formulation is different in high- and low-pressure regimes, defined by whether the gas is primarily atomic or primarily molecular. This formulation can be implemented in simulations and provides a more appropriate treatment of the outer regions of spiral galaxies and molecule-poor systems, such as dwarf irregulars and damped Lyα systems.

  8. A pressure based charge control system for the DSPSE NiH2 CPV battery

    NASA Technical Reports Server (NTRS)

    Garner, Chris; Barnes, W.; Hickman, G.

    1994-01-01

    The following topics are discussed: the Electrical Power Subsystem; the Eclipse Energy Requirements; the NiH2 CPV battery; and the battery pressure transducer. The discussion is presented in viewgraph format.

  9. Rheologies of H2O ices Ih, II, and III at high pressures - A progress report

    NASA Astrophysics Data System (ADS)

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

    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.

  10. Stable solid and aqueous H2CO3 from CO2 and H2O at high pressure and high temperature

    NASA Astrophysics Data System (ADS)

    Wang, Hongbo; Zeuschner, Janek; Eremets, Mikhail; Troyan, Ivan; Willams, Jonathan

    2016-01-01

    Carbonic acid (H2CO3) forms in small amounts when CO2 dissolves in H2O, yet decomposes rapidly under ambient conditions of temperature and pressure. Despite its fleeting existence, H2CO3 plays an important role in the global carbon cycle and in biological carbonate-containing systems. The short lifetime in water and presumed low concentration under all terrestrial conditions has stifled study of this fundamental species. Here, we have examined CO2/H2O mixtures under conditions of high pressure and high temperature to explore the potential for reaction to H2CO3 inside celestial bodies. We present a novel method to prepare solid H2CO3 by heating CO2/H2O mixtures at high pressure with a CO2 laser. Furthermore, we found that, contrary to present understanding, neutral H2CO3 is a significant component in aqueous CO2 solutions above 2.4 GPa and 110 °C as identified by IR-absorption and Raman spectroscopy. This is highly significant for speciation of deep C-O-H fluids with potential consequences for fluid-carbonate-bearing rock interactions. As conditions inside subduction zones on Earth appear to be most favorable for production of aqueous H2CO3, a role in subduction related phenomena is inferred.

  11. Stable solid and aqueous H2CO3 from CO2 and H2O at high pressure and high temperature

    PubMed Central

    Wang, Hongbo; Zeuschner, Janek; Eremets, Mikhail; Troyan, Ivan; Willams, Jonathan

    2016-01-01

    Carbonic acid (H2CO3) forms in small amounts when CO2 dissolves in H2O, yet decomposes rapidly under ambient conditions of temperature and pressure. Despite its fleeting existence, H2CO3 plays an important role in the global carbon cycle and in biological carbonate-containing systems. The short lifetime in water and presumed low concentration under all terrestrial conditions has stifled study of this fundamental species. Here, we have examined CO2/H2O mixtures under conditions of high pressure and high temperature to explore the potential for reaction to H2CO3 inside celestial bodies. We present a novel method to prepare solid H2CO3 by heating CO2/H2O mixtures at high pressure with a CO2 laser. Furthermore, we found that, contrary to present understanding, neutral H2CO3 is a significant component in aqueous CO2 solutions above 2.4 GPa and 110 °C as identified by IR-absorption and Raman spectroscopy. This is highly significant for speciation of deep C–O–H fluids with potential consequences for fluid-carbonate-bearing rock interactions. As conditions inside subduction zones on Earth appear to be most favorable for production of aqueous H2CO3, a role in subduction related phenomena is inferred. PMID:26813580

  12. Stable solid and aqueous H2CO3 from CO2 and H2O at high pressure and high temperature.

    PubMed

    Wang, Hongbo; Zeuschner, Janek; Eremets, Mikhail; Troyan, Ivan; Willams, Jonathan

    2016-01-27

    Carbonic acid (H2CO3) forms in small amounts when CO2 dissolves in H2O, yet decomposes rapidly under ambient conditions of temperature and pressure. Despite its fleeting existence, H2CO3 plays an important role in the global carbon cycle and in biological carbonate-containing systems. The short lifetime in water and presumed low concentration under all terrestrial conditions has stifled study of this fundamental species. Here, we have examined CO2/H2O mixtures under conditions of high pressure and high temperature to explore the potential for reaction to H2CO3 inside celestial bodies. We present a novel method to prepare solid H2CO3 by heating CO2/H2O mixtures at high pressure with a CO2 laser. Furthermore, we found that, contrary to present understanding, neutral H2CO3 is a significant component in aqueous CO2 solutions above 2.4 GPa and 110 °C as identified by IR-absorption and Raman spectroscopy. This is highly significant for speciation of deep C-O-H fluids with potential consequences for fluid-carbonate-bearing rock interactions. As conditions inside subduction zones on Earth appear to be most favorable for production of aqueous H2CO3, a role in subduction related phenomena is inferred.

  13. Thyroid Ca2+/NADPH-dependent H2O2 generation is partially inhibited by propylthiouracil and methimazole.

    PubMed

    Ferreira, Andrea C Freitas; de Carvalho Cardoso, Luciene; Rosenthal, Doris; de Carvalho, Denise Pires

    2003-06-01

    H2O2 generation is a limiting step in thyroid hormone biosynthesis. Biochemical studies have confirmed that H2O2 is generated by a thyroid Ca2+/NADPH-dependent oxidase. Decreased H2O2 availability may be another mechanism of inhibition of thyroperoxidase activity produced by thioureylene compounds, as propylthiouracil (PTU) and methimazole (MMI) are antioxidant agents. Therefore, we analyzed whether PTU or MMI could scavenge H2O2 or inhibit thyroid NADPH oxidase activity in vitro. Our results show that PTU and thiourea did not significantly scavenge H2O2. However, MMI significantly scavenged H2O2 at high concentrations. Only MMI was able to decrease the amount of H2O2 generated by the glucose-glucose oxidase system. On the other hand, both PTU and MMI were able to partially inhibit thyroid NADPH oxidase activity in vitro. As PTU did not scavenge H2O2 under the conditions used here, we presume that this drug may directly inhibit thyroid NADPH oxidase. Also, at the concentration necessary to inhibit NADPH oxidase activity, MMI did not scavenge H2O2, also suggesting a direct effect of MMI on thyroid NADPH oxidase. In conclusion, this study shows that MMI, but not PTU, is able to scavenge H2O2 in the micromolar range and that both PTU and MMI can impair thyroid H2O2 generation in addition to their potent thyroperoxidase inhibitory effects.

  14. Metallization and superconductivity of BeH2 under high pressure

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

    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 (α 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 α 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.

  15. Significant Enhancement of H2 Formation in Disk Galaxies under Strong Ram Pressure

    NASA Astrophysics Data System (ADS)

    Henderson, Benjamin; Bekki, Kenji

    2016-05-01

    We show for the first time that H2 formation on dust grains can be enhanced in disk galaxies under strong ram pressure (RP). We numerically investigate how the time evolution of H i and H2 components in disk galaxies orbiting a group/cluster of galaxies can be influenced by the hydrodynamical interaction between the gaseous components of the galaxies and the hot intracluster medium. We find that compression of H i caused by RP increases H2 formation in disk galaxies before RP rapidly strips H i, cutting off the fuel supply and causing a drop in H2 density. We also find that the level of this H2 formation enhancement in a disk galaxy under RP depends on the mass of its host cluster dark matter halo, the initial positions and velocities of the disk galaxy, and the disk inclination angle with respect to the orbital plane. We demonstrate that dust growth is a key factor in the evolution of the H i and H2 mass in disk galaxies under strong RP. We discuss how the correlation between H2 fractions and surface gas densities of disk galaxies evolves with time in the galaxies under RP. We also discuss whether galaxy-wide star formation rates (SFRs) in cluster disk galaxies can be enhanced by RP if the SFRs depend on H2 densities.

  16. High pressure Raman spectroscopy of H2O-CH3OH mixtures.

    PubMed

    Hsieh, Wen-Pin; Chien, Yu-Hsiang

    2015-02-23

    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 dω/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. These findings indicate the significant influence of volatiles on the crystallization of sub-surface ocean and thermal evolution within large icy planets and satellites.

  17. PVTx properties of H 2 O-H 2 S fluid mixtures at elevated temperature and pressure based on new experimental data

    NASA Astrophysics Data System (ADS)

    Zezin, Denis Yu.; Migdisov, Artashes A.; Williams-Jones, Anthony E.

    2011-10-01

    The volumetric properties of H 2O-H 2S fluid mixtures have been determined experimentally at temperatures of 150 to 400 °C and pressures up to 240 bar. Using these data and existing equations of state, we have developed a thermodynamic model for H 2O-H 2S fluid mixtures. This model is based on an asymmetric description of phases, which includes an activity model and a P-T-dependent Henry's law constant for the liquid, and equations of state with mixing rules for the vapour. The fugacity of the vapour was calculated using the cubic equations of state of Peng and Robinson (1976) and Patel and Teja (1982) with density-dependent and composition-dependent mixing rules. Sets of binary interaction parameters for these equations were fitted to the experimental data obtained in this study supplemented by high-temperature PVTx data for H 2O-H 2S fluid mixtures reported in the literature. The Peng-Robinson equation used in conjunction with density-dependent mixing rules was found to be the most accurate of the available equations in representing the properties of the vapour phase. The errors in the pressure of the homogeneous vapour mixtures estimated using the above equations of state (relative deviation from the experimentally determined pressure) were comparatively low, ˜5% to 8%. However, the errors were significantly higher for the estimated pressure of vapour saturated with liquid, i.e., along the vapour-liquid phase boundary (11-15%), due to the polar nature of H 2O and H 2S and the resulting highly non-ideal behaviour of the fluid mixtures. The results of this study make it possible to reliably estimate the volumetric properties of aqueous fluids containing H 2S at temperatures and pressures up to 400 °C and 240 bar, i.e., for conditions commonly encountered in natural hydrothermal systems.

  18. The Search for Shock-excited H2 in Virgo Spirals Experiencing Ram Pressure Stripping

    NASA Astrophysics Data System (ADS)

    Wong, O. Ivy; Kenney, Jeffrey D. P.; Murphy, Eric J.; Helou, George

    2014-03-01

    We investigate the presence of shock-excited H2 in four Virgo cluster galaxies that show clear evidence of ongoing ram pressure stripping. Mid-infrared spectral mapping of the rotational H2 emission lines were performed using the Infrared Spectrograph on board the Spitzer Space Telescope. We target four regions along the leading side of galaxies where the intracluster medium appears to be pushing back the individual galaxy's interstellar medium. 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 ratios of [Fe II]/[Ne II] found in our sample.

  19. Experimental constraints on H2O activity in high-pressure metamorphic brines

    NASA Astrophysics Data System (ADS)

    Tropper, P.; Manning, C. E.

    2004-12-01

    Subduction of crustal materials is accompanied by metamorphic reactions liberating fluids. Fluid inclusions in eclogite minerals range from dilute solutions to chloride-rich brines; however, the effect of salinity variations on the stability of hydrous phases in subduction zones is poorly understood. To address this problem, we carried out reversed piston-cylinder experiments on the equilibrium (1) paragonite = jadeite + kyanite + H2O at 700° C, 1.5-2.5 GPa, in the presence of H2O-NaCl fluids. The experiments were conducted using fluids with nominal starting compositions: X(H2O)=1.0, 0.90, 0.75 and 0.62. At X(H2O) = 1.0, the equilibrium lies between 2.25 and 2.30 GPa. Lowering X(H2O) decreases the pressure of paragonite breakdown to 2.10 - 2.20 GPa at X(H2O) = 0.90 and 1.85-1.90 GPa at X(H2O) = 0.75. The experiments at X(H2O) = 0.62 yielded albite + corundum at ≤1.60 GPa, and jadeite + kyanite at ≥1.70 GPa. The shift in the equilibrium pressure constrains a-X relations in the sytem H2O-NaCl and indicates that a(H2O) varies as nearly the square of its mole fraction. The results are consistent with the extrapolated non-ideal activity model of Aranovich and Newton (1996, CMP, 125, 200). Our results permit use of appropriate paragonite-bearing or -absent assemblages to quantify a(H2O) in high-P metamorphic environments, such as the Austroalpine units in the Western Alps. For example, jadeite and kyanite in a metapelite from Val Savenca in the Sesia Lanzo Zone formed during the Eo-Alpine high-P metamorphic event at 1.7-2.0 GPa, 550-650° C. The absence of paragonite requires a fluid with low a(H2O) of 0.3-0.6, which could be due to the presence of saline brines. Petrologic investigations of Sesia Lanzo eclogites from Val Ianca show that paragonite occurs as inclusions in garnet cores but gives way to omphacite + kyanite toward rims, suggesting a decrease in a(H2O) from ˜1.0 to <0.81 (Tropper and Essene, 2002, SMPM, 82, 487-514). During the subsequent hydration in

  20. 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.

  1. Appearance of high-pressure H2O ice on ice-covered terrestrial planets

    NASA Astrophysics Data System (ADS)

    Ueta, S.; Sasaki, T.

    2014-03-01

    A lot of terrestrial exoplanets and free-floating planets have been discovered. Whether terrestrial planets with liquid water exist is an important question to consider, especially in terms of their habitability. Even in a globally ice-covered state, liquid water could exist beneath the surface ice shell because sufficient geothermal heat flow from the planetary interior is likely to melt the interior ice, so that an internal ocean under the surface ice shell could appear (e.g., Hoffman & Schrag 2002). In this study, we argue the conditions that must be satisfied for ice-covered terrestrial planets to have an internal ocean on the timescale of planetary evolution (Ueta & Sasaki 2013). Geothermal heat flow calculated by a parameterized convection model (e.g., McGovern & Schubert 1989) is considered as the heat source at the origin of the internal ocean. By applying and improving the model of Tajika (2008), we also examine how the amount of radiogenic heat and H2O mass affect these conditions. Moreover, we investigate the structures of surface H2O layers of ice-covered planets by considering the effects of ice under high pressure (high-pressure ice). At 1 AU from the central star, as shown in Fig. 1, a 1M.+ planet with 0.6-25 times H2O mass of the Earth could have an internal ocean. When the planet has an H2O mass over 25 times that of the Earth, high-pressure ice layers may appear between the internal ocean and the rock-part of the planet. The results indicate that planetary size and surface H2O mass strongly ristrict the conditions under which an extrasolar terrestrial planet could have an internal ocean without high-pressure ice existing under the internal ocean. The habitability of a planet might be influenced by the existence of such high-pressure ice layers.

  2. In situ electrical conductivity measurements of H2O under static pressure up to 28 GPa

    NASA Astrophysics Data System (ADS)

    Liu, Bao; Gao, Yang; Han, Yonghao; Ma, Yanzhang; Gao, Chunxiao

    2016-08-01

    The in situ electrical conductivity measurements on water in both solid state and liquid state were performed under pressure up to 28 GPa and temperature from 77 K to 300 K using a microcircuit fabricated on a diamond anvil cell (DAC). Water chemically ionization mainly contributes to electrical conduction in liquid state, which is in accord with the results obtained under dynamic pressure. Energy band theory of liquid water was used to understand effect of static pressure on electrical conduction of water. The electric conductivity of H2O decreased discontinuously by four orders of magnitude at 0.7-0.96 GPa, indicating water frozen at this P-T condition. Correspondingly, the conduction of H2O in solid state is determined by arrangement and bending of H-bond in ice VI and ice VII. Based on Jaccard theory, we have concluded that the charge carriers of ice are already existing ions and Bjerrum defects.

  3. Particle-in-Cell Simulations of Atmospheric Pressure He/2%H2O Discharges

    NASA Astrophysics Data System (ADS)

    Kawamura, E.; Lieberman, M. A.; Lichtenberg, A. J.; Graves, D. B.; Gopalakrishnan, R.

    2015-09-01

    Atmospheric pressure micro-discharges in contact with liquid surfaces are of increasing interest, especially in the bio-medical field. We conduct 1D3v particle-in-cell (PIC) simulations of a voltage-driven 1 mm width atmospheric pressure He/2% H2O plasma discharge in series with an 0.5 mm width liquid H2O layer and a 1mm width quartz dielectric layer. A previously developed two-temperature hybrid global model of atmospheric pressure He/H2O discharges was used to determine the most important species and collisional reactions to use in the PIC simulations. We found that H13O6+, H5O3-, and electrons were the most prominent charged species, while most of the metastable helium He* was quenched via Penning ionization. The ion-induced secondary emission coefficient γi was assumed to be 0.15 at all surfaces. A series of simulations were conducted at 27.12 MHz with Jrf ~ 800-2200 A/m2. The H2O rotational and vibrational excitation losses were so high that electrons reached the walls at thermal temperatures. We also simulated a much lower frequency case of 50 kHz with Vrf = 10 kV. In this case, the discharge ran in a pure time-varying γ-mode. This work was supported by the Department of Energy Office of Fusion Energy Science Contract DE-SC0001939.

  4. Main species and chemical pathways in cold atmospheric-pressure Ar + H2O plasmas

    NASA Astrophysics Data System (ADS)

    Liu, Dingxin; Sun, Bowen; Iza, Felipe; Xu, Dehui; Wang, Xiaohua; Rong, Mingzhe; Kong, Michael G.

    2017-04-01

    Cold atmospheric-pressure plasmas in Ar + H2O gas mixtures are a promising alternative to He + H2O plasmas as both can produce reactive oxygen species of relevance for many applications and argon is cheaper than helium. Although He + H2O plasmas have been the subject of multiple experimental and computational studies, Ar + H2O plasmas have received less attention. In this work we investigate the composition and chemical pathways in Ar + H2O plasmas by means of a global model that incorporates 57 species and 1228 chemical reactions. Water vapor concentrations from 1 ppm to saturation (32 000 ppm) are considered in the study and abrupt transitions in power dissipation channels, species densities and chemical pathways are found when the water concentration increases from 100 to 1000 ppm. In this region the plasma transitions from an electropositive discharge in which most power is coupled to electrons into an electronegative one in which most power is coupled to ions. While increasing electronegativity is also observed in He + H2O plasmas, in Ar + H2O plasmas the transition is more abrupt because Penning processes do not contribute to gas ionization and the changes in the electron energy distribution function and mean electron energy caused by the increasing water concentration result in electron-neutral excitation and ionization rates changing by many orders of magnitude in a relatively small range of water concentrations. Insights into the main chemical species and pathways governing the production and loss of electrons, O, OH, OH(A) and H2O2 are provided as part of the study.

  5. Characterization of partially reduced graphene oxide as room temperature sensor for H2

    NASA Astrophysics Data System (ADS)

    Zhang, Le-Sheng; Wang, Wei D.; Liang, Xian-Qing; Chu, Wang-Sheng; Song, Wei-Guo; Wang, Wei; Wu, Zi-Yu

    2011-06-01

    Reduced graphene oxide (RGO) was synthesized under H2/Ar treatment from 100 °C to 900 °C. RGO-300 shows excellent sensitivity to H2 and a dual sensing mode was observed. The balance between the chemical adsorption capacity and electronic conductivity, and the dominance of either electrons or holes are the key factors.Reduced graphene oxide (RGO) was synthesized under H2/Ar treatment from 100 °C to 900 °C. RGO-300 shows excellent sensitivity to H2 and a dual sensing mode was observed. The balance between the chemical adsorption capacity and electronic conductivity, and the dominance of either electrons or holes are the key factors. Electronic supplementary information (ESI) available: Experimental details, Photo image, XPS, SEM, TEM, SAED, 13C MAS NMR, Sensor response. See DOI: 10.1039/c1nr10187k

  6. Gasification Mechanism of Carbon with Supercritical Water at Very High Pressures: Effects on H2 Production.

    PubMed

    Martin-Sanchez, Nicolas; Salvador, Francisco; Sanchez-Montero, M Jesus; Izquierdo, Carmen

    2014-08-07

    The scarce data concerning the gasification of carbonaceous solids with supercritical water (SCW) suggest the great potential of this method to produce a valuable green fuel such as H2. However, the extraordinary properties of SCW have not been properly applied to H2 production because the mechanism that governs gasification under these conditions remains unclear. Here, we present a study in which this reaction is explored within the largest pressure range ever assayed in this field, from 1 to 1000 bar. The amplitude of the experimental conditions investigated highlights the various pathways that govern gasification with steam and SCW. Under supercritical conditions, the clusters formed around the superficial groups of the solid reduce the energetic requirements for gasification and generate CO2 as a primary product of the reaction. Consequently, gasification with SCW is significantly faster than that using steam, and the produced gases are richer and more appropriate to obtain pure H2.

  7. Infrared Absorption in Partially Disordered K2CuCl4·2H2O-TYPE Compounds

    NASA Astrophysics Data System (ADS)

    Grado-Caffaro, M. A.; Grado-Caffaro, M.

    An approximate relationship for the coefficient of optical absorption valid, in principle, for the infrared range, corresponding to K2CuCl4·2H2O-type compounds is derived from a model for electronic density of states. These compounds are assumed to be partially disordered from the point of view of the general theory of solids.

  8. High pressure experimental study of eclogite with varying H2O contents

    NASA Astrophysics Data System (ADS)

    Rosenthal, A.; Frost, D. J.; Petitgirard, S.; Yaxley, G. M.; Berry, A.; Woodland, A. B.; Pinter, Z.; Vasilyev, P.; Ionov, D. A.; Jacob, D. E.; Pearson, G. D.; Kovacs, I.; Padron-Navarta, A.

    2014-12-01

    Given the strong influence of volatiles on mantle melting processes, it is critical to understand the behaviour of volatiles (such as H2O) in subducted oceanic crustal material (eclogite) during subduction and subsequent recycling and mantle melting processes, and their impacts on volcanism. As natural samples from subduction zones from the deep Earth's interior are largely inaccessible, the only way to determine the H2O content of eclogite is to simulate high pressure (P) and temperature (T) conditions equivalent to conditions of the Earth's interior using high-P experimental facilities. A particular interest is to determine the H2O content of eclogitic nominally anhydrous minerals (NAMs; such as garnet, clinopyroxene) at the conditions where hydrous phases (such as phengite) are breaking down to release H2O that would then leave the slab. As a starting material, we use average oceanic basalt (GA1, representative of recycled oceanic crust [1]) with varying bulk %H2O (≤7 wt.%). We conducted experiments using GA1 at different P's (6-10 GPa), T's (850-1500°C) and bulk %H2O (up to 7 wt.%) using multi anvil apparatuses. The run products at each P, T, and bulk H2O contents show well-equilibrated eclogitic phase assemblages of garnet ± clinopyroxene ± coesite/stishovite ± rutile ± phengite ± melt ± vapour. Runs (>0.5 wt.% H2O) at 6 GPa and up to ~950°C, and at 8-9 GPa and up to ~1050°C are subsolidus, while towards higher T small melt fractions appear. Similar to previous studies [e.g. 2-6], the stability of phengite varies as a function of P, T, buffering mineral paragenesis and bulk H2O concentration. Phengite breaks down >9 GPa. Eclogitic NAMs and phengite also break down at subsolidus conditions in the presence of excess of hydrous fluids. For instance, K2O in phengite and clinopyroxene decrease with increasing bulk H2O content at subsolidus conditions at given P, T, suggesting a leaching role of K2O by a vapour-rich fluid. [1] Yaxley, G. M. & Green, D. H

  9. In situ observations of a high-pressure phase of H2O ice

    USGS Publications Warehouse

    Chou, I.-Ming; Blank, J.G.; Goncharov, A.F.; Mao, Ho-kwang; Hemley, R.J.

    1998-01-01

    A previously unknown solid phase of H2O has been identified by its peculiar growth patterns, distinct pressure-temperature melting relations, and vibrational Raman spectra. Morphologies of ice crystals and their pressure-temperature melting relations were directly observed in a hydrothermal diamond-anvil cell for H2O bulk densities between 1203 and 1257 kilograms per cubic meter at temperatures between -10??and 50??C. Under these conditions, four different ice forms were observed to melt: two stable phases, ice V and ice VI, and two metastable phases, ice IV and the new ice phase. The Raman spectra and crystal morphology are consistent with a disordered anisotropic structure with some similarities to ice VI.

  10. Thin film oxygen partial pressure sensor

    NASA Technical Reports Server (NTRS)

    Wortman, J. J.; Harrison, J. W.; Honbarrier, H. L.; Yen, J.

    1972-01-01

    The development is described of a laboratory model oxygen partial pressure sensor using a sputtered zinc oxide thin film. The film is operated at about 400 C through the use of a miniature silicon bar. Because of the unique resistance versus temperature relation of the silicon bar, control of the operational temperature is achieved by controlling the resistance. A circuit for accomplishing this is described. The response of sputtered zinc oxide films of various thicknesses to oxygen, nitrogen, argon, carbon dioxide, and water vapor caused a change in the film resistance. Over a large range, film conductance varied approximately as the square root of the oxygen partial pressure. The presence of water vapor in the gas stream caused a shift in the film conductance at a given oxygen partial pressure. A theoretical model is presented to explain the characteristic features of the zinc oxide response to oxygen.

  11. 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

  12. DEVICE FOR CONTROL OF OXYGEN PARTIAL PRESSURE

    DOEpatents

    Bradner, H.; Gordon, H.S.

    1957-12-24

    A device is described that can sense changes in oxygen partial pressure and cause a corresponding mechanical displacement sufficient to actuate meters, valves and similar devices. A piston and cylinder arrangement contains a charge of crystalline metal chelate pellets which have the peculiar property of responding to variations in the oxygen content of the ambient atmosphere by undergoing a change in dimension. A lever system amplifies the relative displacement of the piston in the cylinder, and actuates the controlled valving device. This partial pressure oxygen sensing device is useful in controlled chemical reactions or in respiratory devices such as the oxygen demand meters for high altitude aircraft.

  13. Quantification of the CO2 budget and H2O-CO2 systematics in subduction-zone magmas through the experimental hydration of melt inclusions in olivine at high H2O pressure

    NASA Astrophysics Data System (ADS)

    Mironov, Nikita; Portnyagin, Maxim; Botcharnikov, Roman; Gurenko, Andrey; Hoernle, Kaj; Holtz, François

    2015-09-01

    Reliable evaluation of CO2 contents in parental arc magmas, which can be preserved in melt inclusions in phenocrysts, is required to verify the proposed efficiency of CO2 recycling at convergent margins. Quantification of bulk CO2 concentration in melt inclusions requires their complete homogenization. Using samples from lavas from the Bulochka vent of Klyuchevskoy Volcano (Kamchatka), we applied a novel experimental approach to homogenize and re-equilibrate naturally dehydrated (<1 wt.% H2O) melt inclusions from high-Fo (85-91 mol.%) olivine. The experiments were performed at temperatures of 1150-1400 °C, pressures of up to 500 MPa, under dry to H2O-saturated conditions and with oxygen fugacity ranging from CCO to QFM+3.3. No homogenization was achieved at dry conditions. Complete dissolution of fluid bubbles (homogenization) in the melt inclusions was achieved at H2O pressures of 500 MPa and temperature of 1150 °C, when water content in the melt inclusions reached 4-5 wt.% H2O. The CO2 content in the homogenized inclusions is 3800 ± 140 ppm and CO2/Nb = 3000 ± 420, which are the highest values reported so far for the typical middle-K primitive arc melts and fall within the range of values inferred from the magmatic flux and volcanic gas data for primary arc magma compositions. About 83% of the CO2 in Klyuchevskoy magmas is likely to be derived from the subducting slab and can be attributed to flux melting with a fluid having a CO2/H2O ratio of ∼0.06. The H2O and CO2 contents in the melt inclusions after hydrous experiments were found to correlate positively with each other and negatively with the volume of fluid bubble, reflecting increasing internal pressure in melt inclusions with increasing melt hydration. Therefore, similar trends observed in some natural sets of melt inclusions can be attributed to a partial dehydration of melts after entrapment, operating simultaneously with or following post-entrapment crystallization. Our study implies that the

  14. High pressure synthesis and in situ Raman spectroscopy of H2 and HD clathrate hydrates.

    PubMed

    Zaghloul, Mohamed A S; Celli, Milva; Salem, N M; Elsheikh, S M; Ulivi, Lorenzo

    2012-10-28

    By means of a newly constructed high pressure and low temperature optical apparatus we have measured the Raman spectra of H(2) and HD simple clathrate hydrates, synthesized in situ by the application of more than 2500 bar gas pressure on solid water. High resolution spectra of the molecular vibration have been measured at low temperature (about 20 K). In the case of HD this band is simpler than in the case of H(2), where the presence of the ortho- and para-species complicated the interpretation of the spectrum. We have determined frequency positions of the bands arising from multiple occupancy of the large cages of the sII clathrate, some of which are almost superimposed. The intensity of the bands gives information on the average and distribution of cage occupation, and of the ortho-para (o-p) ratio of H(2) molecules. Hydrogen o-p conversion rate is measured, for molecules in the small cages and in the large cages, and it is observed that these are different. A model considering both intrinsic and extrinsic conversion processes is applied to the measured data. The intrinsic conversion rate so derived is compared favorably to that measured for pure hydrogen in different situations.

  15. Layered structure and re-entrant disproportionation observed in crystalline BeH2 under pressure

    NASA Astrophysics Data System (ADS)

    Pépin, Charles M.; Loubeyre, Paul

    2016-06-01

    The phase diagram of the Be-H system is measured up to 100 GPa. BeH2 is the only stoichiometry observed. Three crystalline phases are identified using synchrotron x-ray diffraction. The I b a m structure, already known at ambient pressure, is stable up to 27 GPa. The P 41212 structure, isotypical to the crystoballite-low SiO2 structure, is stable above 600 K over the same pressure range. The well-known P 3 ¯m 1 layered structure of transition metal dichalcogenides is stable above 80 GPa, making BeH2 a quasi-two-dimensional hydride. Surprisingly, between 27 and 72 GPa, a miscibility gap opens up in the Be-H system and an equilibrium between pure Be and pure H is observed. That is at odds with the current prevailing view of an increase in solubility of H in metals under pressure and contradicts calculations of stable compounds in the Be-H system.

  16. Monte Carlo simulations of high-pressure phase equilibria of CO2-H2O mixtures.

    PubMed

    Liu, Yang; Panagiotopoulos, Athanassios Z; Debenedetti, Pablo G

    2011-05-26

    Histogram-reweighting grand canonical Monte Carlo simulations were used to obtain the phase behavior of CO(2)-H(2)O mixtures over a broad temperature and pressure range (50 °C ≤ T ≤ 350 °C, 0 ≤ P ≤ 1000 bar). We performed a comprehensive test of several existing water (SPC, TIP4P, TIP4P2005, and exponential-6) and carbon dioxide (EPM2, TraPPE, and exponential-6) models using conventional Lorentz-Berthelot combining rules for the unlike-pair parameters. None of the models we studied reproduce adequately experimental data over the entire temperature and pressure range, but critical assessments were made on the range of T and P where particular model pairs perform better. Away from the critical region (T ≤ 250 °C), the exponential-6 model combination yields the best predictions for the CO(2)-rich phase, whereas the TraPPE/TIP4P2005 model combination provides the most accurate coexistence composition and pressure for the H(2)O-rich phase. Near the critical region (250 °C < T ≤ 350 °C), the critical points are not accurately estimated by any of the models studied, but the exponential-6 models are able to qualitatively capture the critical loci and the shape of the phase envelopes. Local improvements can be achieved at specific temperatures by introducing modification factors to the Lorentz-Berthelot combining rules, but the modified combining rule is still not able to achieve global improvements over the entire temperature and pressure range. Our work points to the challenge and importance of improving current atomistic models so as to accurately predict the phase behavior of this important binary mixture.

  17. Ionization instability induced striations in atmospheric pressure He/H2O RF and DC discharges

    NASA Astrophysics Data System (ADS)

    Kawamura, E.; Lieberman, M. A.; Lichtenberg, A. J.

    2017-04-01

    One-dimensional particle-in-cell (PIC) simulations of a 1 mm gap atmospheric pressure He/2%{{\\text{H}}2}\\text{O} rf capacitive discharge showed standing striations in the bulk (Kawamura et al 2016 Plasma Sources Sci. Technol. 25 054009). We found that these striations were consistent with an ionization instability induced by non-local electron kinetics. We developed a theoretical instability criterion in good agreement with the numerical results which showed that discharges with larger bulk recombination rates tend to be more unstable. We also determined a critical wavelength such that shorter wavelengths are suppressed by diffusion while longer wavelengths may be restricted by the gap width. In this paper, we extend the gap size of the atmospheric pressure He/2%{{\\text{H}}2}\\text{O} discharges in the PIC simulations to 2 and 4 mm and drive them by either dc or rf current sources. We compare the results to the 1 mm gap rf simulations and theoretical model in Kawamura et al (2016 Plasma Sources Sci. Technol. 25 054009). We find that wider gap discharges tend to be more unstable as they can accommodate a wider range of wavelengths. Furthermore, the mixture of the various excited modes in the wider gaps can lead to distinctly non-sinusoidal spatial oscillations.

  18. Partial pressure analysis in space testing

    NASA Technical Reports Server (NTRS)

    Tilford, Charles R.

    1994-01-01

    For vacuum-system or test-article analysis it is often desirable to know the species and partial pressures of the vacuum gases. Residual gas or Partial Pressure Analyzers (PPA's) are commonly used for this purpose. These are mass spectrometer-type instruments, most commonly employing quadrupole filters. These instruments can be extremely useful, but they should be used with caution. Depending on the instrument design, calibration procedures, and conditions of use, measurements made with these instruments can be accurate to within a few percent, or in error by two or more orders of magnitude. Significant sources of error can include relative gas sensitivities that differ from handbook values by an order of magnitude, changes in sensitivity with pressure by as much as two orders of magnitude, changes in sensitivity with time after exposure to chemically active gases, and the dependence of the sensitivity for one gas on the pressures of other gases. However, for most instruments, these errors can be greatly reduced with proper operating procedures and conditions of use. In this paper, data are presented illustrating performance characteristics for different instruments and gases, operating parameters are recommended to minimize some errors, and calibrations procedures are described that can detect and/or correct other errors.

  19. Partial coverage of the broad-line region of Q1232+082 by an intervening H2-bearing cloud

    NASA Astrophysics Data System (ADS)

    Balashev, S. A.; Petitjean, P.; Ivanchik, A. V.; Ledoux, C.; Srianand, R.; Noterdaeme, P.; Varshalovich, D. A.

    2011-11-01

    We present a detailed analysis of the partial coverage of the Q1232+082 (zem= 2.57) broad-line region (BLR) by an intervening H2-bearing cloud at zabs= 2.3377. Using curve of growth analysis and line profile fitting, we demonstrate that the H2-bearing component of the cloud covers the quasi-stellar object (QSO) intrinsic continuum source completely but only part of the BLR. We find that only 48 ± 6 per cent of the C IV BLR emission is covered by the C I absorbing gas. We observe residual light (˜6 per cent) as well in the bottom of the O I λ1302 absorption from the cloud, redshifted on top of the QSO Lyman α emission line. Therefore, the extent of the neutral phase of the absorbing cloud is not large enough to cover all of the background source. The most likely explanation for this partial coverage is the small size of the intervening cloud, which is comparable to the BLR size. We estimate the number densities in the cloud: ?˜ 110 cm-3 for the H2-bearing core and nH˜ 30 cm-3 for the neutral envelope. Given the column densities, N(H2) = 3.71 ± 0.97 × 1019 cm-2 and N(H I) = 7.94 ± 1.6 × 1020 cm-2, we derive the linear size of the H2-bearing core and the neutral envelope along the line of sight to be ?˜ 0.15+0.05-0.05 pc and ?˜ 8.2+6.5-4.1 pc, respectively. We estimate the size of the C IV BLR by two ways: (i) extrapolating size-luminosity relations derived from reverberation observations and (ii) assuming that the H2-bearing core and the BLR are spherical in shape and the results are ˜0.26 and ˜0.18 pc, respectively. The large size we derive for the extent of the neutral phase of the absorbing cloud together with a covering factor of ˜0.94 of the Lyman α emission means that the Lyman α BLR is probably fully covered but that the Lyman α emission extends well beyond the limits of the BLR. Based on observations carried out at European Southern Observatory with the Ultraviolet and Visual Echelle Spectrograph (UVES) mounted on the Very Large Telescope

  20. Functionalization of graphene by atmospheric pressure plasma jet in air or H2O2 environments

    NASA Astrophysics Data System (ADS)

    Huang, Weixin; Ptasinska, Sylwia

    2016-03-01

    The functionalization of graphene, which deforms its band structure, can result in a metal-semiconductor transition. In this work, we report a facile strategy to oxidize single-layer graphene using an atmospheric pressure plasma jet (APPJ) that generates a variety of reactive plasma species at close to ambient temperature. We systematically characterized the oxygen content and chemical structure of the graphene films after plasma treatment under different oxidative conditions (ambient air atmosphere or hydrogen peroxide solution) by X-ray Photoelectron Spectroscopy (XPS). Plasma-treated graphene films containing more than 40% oxygen were obtained in both oxidative environments. Interestingly, prolonged irradiation led to the reduction of graphene oxides. N-doping of graphene also occurred during the APPJ treatment in H2O2 solution; the nitrogen content of the doped graphene was dependent on the duration of irradiation and reached up to 8.1% within 40 min. Moreover, the H2O2 solution served as a buffer layer that prevented damage to the graphene during plasma irradiation. Four-point probe measurement revealed an increase in sheet resistance of the plasma-treated graphene, indicating the transition of the material property from semi-metallic to semiconducting.

  1. Thermodynamic states of nanoclusters at low pressure and low temperature: the case of 13 H(2).

    PubMed

    Soullard, Jacques; Santamaria, Ruben; Boyer, Denis

    2011-09-08

    A confinement model of finite-size systems that embodies an equation of state is presented. The temperature and pressure of the system are obtained from the positions and velocities of the enclosed particles after a number of molecular dynamics simulations. The pressure has static and dynamic (thermal) contributions, extending the Mie-Grüneisen equation of state to include weakly interacting anharmonic oscillators. The model is applied to a system of 13 H(2) molecules under low-pressure and low-temperature conditions in the classical regime. The confining cage in this case is a spherical hydrogen cavity. The Born-Oppenheimer molecular dynamics in conjunction with density functional theory are used for the time evolution of the particle system. The hydrogen molecules form a noncrystalline cluster structure with icosahedral symmetry that remains so in the whole temperature range investigated. The fluctuations of the interatomic distances increase with the temperature, while the orientational order of the enclosed system of molecules fades out, suggesting a gradual order-disorder transition.

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

    NASA Astrophysics Data System (ADS)

    Monfared, Shabnam K.; Hüwel, 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 μs 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 Hα and Hβ emission lines. However, in particular for delays up to about 7 μs 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 μs 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.

  3. Partial Melting of Garnet Lherzolite with H2o and CO2 at 3 GPa: Implications for Intraplate Magmatism.

    NASA Astrophysics Data System (ADS)

    Baasner, A.; Medard, E.; Laporte, D.

    2014-12-01

    The origin and source rock of alkali-rich and SiO2-undersatured magmas in the Earth`s upper mantle have been under debate for a long time. The garnet signature in rare earth element patterns of such magmas suggest a garnet-bearing source rock, which could be garnet lherzolite or garnet pyroxenite. Partial melting experiments were performed at 3 GPa and 1345-1445 °C in a piston-cylinder apparatus using mixtures of natural lherzolite with 0.4-0.7 wt% H2O and 0.4-0.7 wt% CO2 as starting materials. Different designs of AuPd capsules were used for melt extraction. Mineral and melt phases were analysed with electron microprobe and laser ablation inductively coupled plasma mass spectrometry. The degree of partial melting in the experiments ranges from ~20% to ~4% and decreases with decreasing temperature and decreasing volatile content in the starting material. All samples contain olivine and orthopyroxene. Garnet is present in experiments performed below 1420 °C. The amount of clinopyroxene decreases with increasing degree of partial melting and volatile concentration in the starting material. Depending on the capsule design the melts quenched to glasses or to a mixture of quench crystals and residual glass. The composition of the partial melts ranges from basalts through picrobasalts to foidites. The alkali concentration increases and the SiO2 concentration decreases with decreasing degree of partial melting and increasing volatile concentration in the starting material. The partial melts are similar in many aspects to alkali intraplate magmas (basanites to melilitites), although they are richer in MgO. Compositions closer to natural basanites could be obtained either at lower degree of melting (and lower volatile contents) or through olivine fractionation. Our results strongly suggests that. SiO2-undersaturated intraplate magmas can be generated by mantle melting of garnet-lherzolite in the presence of H2O and CO2 in the Earth`s upper mantle at 3 GPa (~100 km depth).

  4. Method of detecting oxygen partial pressure and oxygen partial pressure sensor

    SciTech Connect

    Dees, D.W.

    1991-12-31

    This invention is comprised of a method for detecting oxygen partial pressure and an oxygen partial pressure sensor are provided. The method for measuring oxygen partial pressure includes contacting oxygen to a solid oxide electrolyte and measuring the subsequent change in electrical conductivity of the solid oxide electrolyte. A solid oxide electrolyte is utilized that contacts both a porous electrode and a nonporous electrode. The electrical conductivity of the solid oxide electrolyte is affected when oxygen from an exhaust stream permeates through the porous electrode to establish an equilibrium of oxygen anions in the electrolyte, thereby displacing electrons throughout the electrolyte to form an electron gradient. By adapting the two electrodes to sense a voltage potential between them, the change in electrolyte conductivity due to oxygen presence can be measured.

  5. Measurement and Simulation of Spontaneous Raman Scattering Spectra in High-Pressure, Fuel-Rich H2-Air Flames

    NASA Technical Reports Server (NTRS)

    Kojima, Jun; Nguyen, Quang-Viet

    2003-01-01

    Rotational vibrational spontaneous Raman spectra (SRS) of H2, N2, and H2O have been measured in H2-air flames at pressures up to 30 atm as a first stem towards establishing a comprehensive Raman spectral database for temperatures and species in high-pressure combustion. A newly developed high-pressure burner facility provides steady, reproducible flames with a high degree of flow precision. 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 future reference standards. The fully resolved Stokes and anti-Stokes shifted SRS spectra were collected in the visible wavelength range (400-700 nm) using pulse-stretched 532 nm excitation and a non-intensified CCD spectrograph with a high-speed shutter. Reasonable temperatures were determined via the intensity distribution of rotational H2 lines at stoichiometry and fuel-rich conditions. Theoretical Raman spectra of H2 were computed using a semi-classical harmonic-oscillator model with recent pressure broadening data and were compared with experimental results. The data and simulation indicated that high-J rotational lines of H2 might interfere with the N2 vibrational Q-branch lines, and this could lead to errors in N2-Raman thermometry based on the line-fitting method. From a comparison of N2 Q-branch spectra in lean H2 low-pressure (1.2 atm) and high-pressure (30 atm) flames, we found no significant line-narrowing or -broadening effects at the current spectrometer resolution of 0.04 nm.

  6. Partial pressure measurements with an active spectrometer

    SciTech Connect

    Brooks, N.H.; Jensen, T.H.; Colchin, R.J.; Maingi, R.; Wade, M.R.; Finkenthal, D.F.; Naumenko, N.; Tugarinov, S.

    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.

  7. Preferential dissolution of SiO2 from enstatite to H2 fluid under high pressure and temperature

    NASA Astrophysics Data System (ADS)

    Shinozaki, Ayako; Kagi, Hiroyuki; Hirai, Hisako; Ohfuji, Hiroaki; Okada, Taku; Nakano, Satoshi; Yagi, Takehiko

    2016-04-01

    Stability and phase relations of coexisting enstatite and H2 fluid were investigated in the pressure and temperature regions of 3.1-13.9 GPa and 1500-2000 K using laser-heated diamond-anvil cells. XRD measurements showed decomposition of enstatite upon heating to form forsterite, periclase, and coesite/stishovite. In the recovered samples, SiO2 grains were found at the margin of the heating hot spot, suggesting that the SiO2 component dissolved in the H2 fluid during heating, then precipitated when its solubility decreased with decreasing temperature. Raman and infrared spectra of the coexisting fluid phase revealed that SiH4 and H2O molecules formed through the reaction between dissolved SiO2 and H2. In contrast, forsterite and periclase crystals were found within the hot spot, which were assumed to have replaced the initial orthoenstatite crystals without dissolution. Preferential dissolution of SiO2 components of enstatite in H2 fluid, as well as that observed in the forsterite H2 system and the quartz H2 system, implies that H2-rich fluid enhances Mg/Si fractionation between the fluid and solid phases of mantle minerals.

  8. 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.

  9. 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.

  10. High pressure partially ionic phase of water ice.

    PubMed

    Wang, Yanchao; Liu, Hanyu; Lv, Jian; Zhu, Li; Wang, Hui; Ma, Yanming

    2011-11-29

    Water ice dissociates into a superionic solid at high temperature (>2,000 K) and pressure, where oxygen forms the lattice, but hydrogen diffuses completely. At low temperature, however, the dissociation into an ionic ice of hydronium (H(3)O)(+) hydroxide (OH)(-) is not expected because of the extremely high energy cost (~1.5 eV) of proton transfer between H(2)O molecules. Here we show the pressure-induced formation of a partially ionic phase (monoclinic P2(1) structure) consisting of coupled alternate layers of (OH)(δ-) and (H(3)O)(δ+) (δ=0.62) in water ice predicted by particle-swarm optimization structural search at zero temperature and pressures of >14 Mbar. The occurrence of this ionic phase follows the break-up of the typical O-H covalently bonded tetrahedrons in the hydrogen symmetric atomic phases and is originated from the volume reduction favourable for a denser structure packing.

  11. 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.

  12. Rotational excitation in collisions between two rigid rotors - Alternate angular momentum coupling and pressure broadening of HCl by H2

    NASA Technical Reports Server (NTRS)

    Green, S.

    1977-01-01

    In order to compute relaxation 'cross sections' for molecule-molecule collisions, it is convenient to employ a coupled angular-momentum representation which differs from that generally used. An explicit expression for collision-induced spectral pressure broadening in this representation is given, and this is used to examine the difference between para- and ortho-H2 for broadening of HCl.

  13. NO Removal in High Pressure Plasmas of N_2/H_2O/NO Mixtures

    NASA Astrophysics Data System (ADS)

    Fresnet, F.; Baravian, G.; Magne, L.; Pasquiers, S.; Postel, C.; Puech, V.; Rousseau, A.

    2001-10-01

    Influence of H_2O on NO removal has been studied using a homogeneous photo-triggered discharge with a time resolved LIF measurement of the NO density, in N_2/H_2O/NO mixtures at 460 mbar. The H_2O maximum concentration was 2.5 was between 70 and 160 J/l. Measurement of NO density has been performed up to 180 µs after the current pulse excitation of short duration, 50 ns. Kinetic analysis has been made using a self-consistent 0D-discharge model. NO is in great part dissociated, in N_2/NO, through collisions with the excited singlet states of N_2. We have previously shown that addition of ethene induces de-excitation of these states, leading to a decrease of the NO removal ( F. Fresnet, G. Baravian, L. Magne, S. Pasquiers, C. Postel, V. Puech, A. Rousseau, Appl. Phys. Lett., 77 (2000) 4118.). Similar processes take place when C_2H4 is replaced by H_2O. The value of the rate constant for collision of singlet states with water, 3.10-10 cm^3 s-1, is obtained from our study.

  14. Theoretical calculations of pressure broadening coefficients for H2O perturbed by hydrogen or helium gas

    NASA Technical Reports Server (NTRS)

    Gamache, Robert R.; Pollack, James B.

    1995-01-01

    Halfwidths were calculated for H2O with H2 as a broadening gas and were estimated for He as the broadening species. The calculations used the model of Robert and Bonamy with parabolic trajectories and all relevant terms in the interaction potential. The calculations investigated the dependence of the halfwidth on the order of the atom-atom expansion, the rotational states, and the temperature in the range 200 to 400K. Finally, calculations were performed for many transitions of interest in the 5 micrometer window region of the spectrum. The resulting data will be supplied to Dr. R. Freedman for extracting accurate water mixing ratios from the analysis of the thermal channels for the Net Flux experiment on the Galileo probe.

  15. Thermal Conductivity Measurements of H2O-Methanol Mixtures at High Pressure Using Time Domain Thermoreflectance

    NASA Astrophysics Data System (ADS)

    Hsieh, W. P.

    2014-12-01

    It has been proposed that the presence of methanol, a possible anti-freeze compound, in the primordial oceans in icy moons may affect the internal thermal evolution and the crystallization of primordial oceans. We have measured the thermal conductivity of H2O alloyed with methanol at high pressure and room temperature using time-domain thermoreflectance (TDTR) combined with diamond anvil cell techniques. The TDTR utilizes ultrafast optical pulses to pump and probe the dynamics of thermal diffusion, enabling precise measurements of thermal conductivity under extreme conditions. We found that the addition of methanol into the H2O suppresses the effective thermal conductivity of H2O-methanol compound. We will discuss geophysical implications of these measurements to the thermal evolution within the icy moons.

  16. Effect of Nickel Levels on Hydrogen Partial Pressure and Methane Production in Methanogens

    PubMed Central

    2016-01-01

    Hydrogen (H2) consumption and methane (CH4) production in pure cultures of three different methanogens were investigated during cultivation with 0, 0.2 and 4.21 μM added nickel (Ni). The results showed that the level of dissolved Ni in the anaerobic growth medium did not notably affect CH4 production in the cytochrome-free methanogenic species Methanobacterium bryantii and Methanoculleus bourgensis MAB1, but affected CH4 formation rate in the cytochrome-containing Methanosarcina barkeri grown on H2 and CO2. Methanosarcina barkeri also had the highest amounts of Ni in its cells, indicating that more Ni is needed by cytochrome-containing than by cytochrome-free methanogenic species. The concentration of Ni affected threshold values of H2 partial pressure (pH2) for all three methanogen species studied, with M. bourgensis MAB1 reaching pH2 values as low as 0.1 Pa when Ni was available in amounts used in normal anaerobic growth medium. To our knowledge, this is the lowest pH2 threshold recorded to date in pure methanogen culture, which suggests that M.bourgensis MAB1 have a competitive advantage over other species through its ability to grow at low H2 concentrations. Our study has implications for research on the H2-driven deep subsurface biosphere and biogas reactor performance. PMID:27992585

  17. Effect of Nickel Levels on Hydrogen Partial Pressure and Methane Production in Methanogens.

    PubMed

    Neubeck, Anna; Sjöberg, Susanne; Price, Alex; Callac, Nolwenn; Schnürer, Anna

    2016-01-01

    Hydrogen (H2) consumption and methane (CH4) production in pure cultures of three different methanogens were investigated during cultivation with 0, 0.2 and 4.21 μM added nickel (Ni). The results showed that the level of dissolved Ni in the anaerobic growth medium did not notably affect CH4 production in the cytochrome-free methanogenic species Methanobacterium bryantii and Methanoculleus bourgensis MAB1, but affected CH4 formation rate in the cytochrome-containing Methanosarcina barkeri grown on H2 and CO2. Methanosarcina barkeri also had the highest amounts of Ni in its cells, indicating that more Ni is needed by cytochrome-containing than by cytochrome-free methanogenic species. The concentration of Ni affected threshold values of H2 partial pressure (pH2) for all three methanogen species studied, with M. bourgensis MAB1 reaching pH2 values as low as 0.1 Pa when Ni was available in amounts used in normal anaerobic growth medium. To our knowledge, this is the lowest pH2 threshold recorded to date in pure methanogen culture, which suggests that M.bourgensis MAB1 have a competitive advantage over other species through its ability to grow at low H2 concentrations. Our study has implications for research on the H2-driven deep subsurface biosphere and biogas reactor performance.

  18. New insights on the effect of hydrogen to tungsten hexafluoride partial pressure ratio on plasma deposited tungsten thin films

    NASA Astrophysics Data System (ADS)

    Kim, Yong Tae; Hong, Jong Sung; Min, Suk-Ki

    1991-12-01

    Resistivities of tungsten thin films deposited by plasma enhanced chemical vapor deposition are very sensitive to the H2/WF6 partial pressure ratio, while the resistivities of tungsten films deposited by low pressure chemical vapor deposition are insensitive to the H2/WF6 ratio. The reason is investigated with x-ray diffraction, transmission electron microscopy, Auger electron spectroscopy and optical emission spectroscopy. As a result, when the H2/WF6 partial pressure ratio is higher than 15, plasma deposited tungsten has a low resistive (11 μΩ cm) bcc structure without F impurities. However, if the H2/WF6 ratios are decreased, porous and β-phase W films are formed due to the incomplete reduction of F concentrations.

  19. 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

    2015-06-22

    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.

  20. 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 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

  1. Low LET radiolysis escape yields for reducing radicals and H2 in pressurized high temperature water

    NASA Astrophysics Data System (ADS)

    Sterniczuk, Marcin; Yakabuskie, Pamela A.; Wren, J. Clara; Jacob, Jasmine A.; Bartels, David M.

    2016-04-01

    Low Linear Energy Transfer (LET) radiolysis escape yields (G values) are reported for the sum (G(radH)+G(e-)aq) and for G(H2) in subcritical water up to 350 °C. The scavenger system 1-10 mM acetate/0.001 M hydroxide/0.00048 M N2O was used with simultaneous mass spectroscopic detection of H2 and N2 product. Temperature-dependent measurements were carried out with 2.5 MeV electrons from a van de Graaff accelerator, while room temperature calibration measurements were done with a 60Co gamma source. The concentrations and dose range were carefully chosen so that initial spur chemistry is not perturbed and the N2 product yield corresponds to those reducing radicals that escape recombination in pure water. In comparison with a recent review recommendation of Elliot and Bartels (AECL report 153-127160-450-001, 2009), the measured reducing radical yield is seven percent smaller at room temperature but in fairly good agreement above 150 °C. The H2 escape yield is in good agreement throughout the temperature range with several previous studies that used much larger radical scavenging rates. Previous analysis of earlier high temperature measurements of Gesc(radOH) is shown to be flawed, although the actual G values may be nearly correct. The methodology used in the present report greatly reduces the range of possible error and puts the high temperature escape yields for low-LET radiation on a much firmer quantitative foundation than was previously available.

  2. 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-µM concentrations of LPS) and (b) a bulk regime (above µM 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.

  3. Pressure dependence of the contact angle in a CO2-H2O-coal system.

    PubMed

    Siemons, Nikolai; Bruining, Hans; Castelijns, Hein; Wolf, Karl-Heinz

    2006-05-15

    Carbon dioxide injection into coal layers serves the dual purpose to enhance coal bed methane production (ECBM) and to store CO2. The efficiency of this process is expected to be much higher if water is the non-wetting phase in the coal-water-gas system. Therefore, contact angles in the coal-water-CO2 system have been measured using the captive bubble technique in the pressure range between atmospheric pressure and 141 bar at a temperature of 45 degrees C. At atmospheric pressure the contact angle of a shrinking CO2 droplet increases with time, but stays below 90 degrees . At higher pressures (>2.6 bar) the contact angle increases beyond 90 degrees . The pressure dependence of the contact can be represented by theta=(111 degrees +/-10.5 degrees )+(0.17+/-0.14)P [bar]. The exceptional behavior at atmospheric pressure is possibly related to the stability of water patches on the coal surface. It is concluded that water is the non-wetting phase in this coal-water-CO2 system.

  4. Effect of the gas temperature and pressure on the nucleation time of particles in low pressure Ar-C2H2 rf plasmas

    NASA Astrophysics Data System (ADS)

    Lin, Jiashu; Henault, Marie; Orazbayev, Sagi; Boufendi, Laïa; Takahashi, Kazuo; Al Farabi Kazakh National University Collaboration; Kyoto Institute Of Technology Team; Gremi Team

    2016-09-01

    Particle formation in low pressure plasmas is a 3-step process. The first one corresponds to the nucleation and growth of nano-crystallites by ion-molecular reactions, the agglomeration phase to form large particles, and the growth by radical deposition on the particle surface. The nucleation phase was demonstrated to be sensitive to gas temperature and pressure. In this work, time of nucleation phase of particles formation in low pressure cold rf C2H2/Ar plasmas studied by varying gas temperature from 265 K to 375 K, gas pressure from 0.4 mbar to 0.8 mbar and rf power from 6 W to 20 W. The ratio of C2H2/Ar is fixed to 2/98 in terms of pressure. Several previous works reported that particle formation takes a few sec at room temperature in C2 H2 plasmas and the time is much shorter than 0.1 s in SiH4 plasmas. Time evolution of self-bias voltage was mainly used to determine nucleation time. The self-bias voltage was modified by phase transition between the steps from nucleation to coagulation. The experimental results showed that the nucleation time increased with gas temperature, decreased with gas pressure and discharge power. At constant gas pressure of 0.4 mbar and discharge power of 6 W, for example, the nucleation time increased from 5 sec to 30 sec with increas

  5. Study of nanosecond discharges in different H2 air mixtures at atmospheric pressure for plasma-assisted applications

    NASA Astrophysics Data System (ADS)

    Bourdon, Anne; Kobayashi, Sumire; Bonaventura, Zdenek; Tholin, Fabien; Popov, Nikolay

    2016-09-01

    This paper presents 2D simulations of nanosecond pulsed discharges between two point electrodes in different H2/air mixtures and in air at atmospheric pressure. A fluid model is coupled with detailed kinetic schemes for air and different H2/air mixtures to simulate the discharge dynamics. First, as the positive and negative ionization waves propagate in the interelectrode gap, it has been observed that in H2/air mixtures with equivalence ratios between 0.3 and 2, major positive ions produced by the nanosecond discharge are N2+,O2+and HN2+.The discharge dynamics is shown to vary only slightly for equivalence ratios of the H2/air mixture between 0.3 and 2. Then, as the discharge transits to a nanosecond spark discharge, we have studied the different chemical reactions that lead to fast gas heating and to the production of radicals, as O,H and OH. Both thermal and chemical effects of the nanosecond spark discharge are of interest for plasma assisted combustion applications. This work has been supported by the project DRACO (Grant No. ANR-13-IS09-0004) and the french russian LIA Kappa.

  6. H2O storage capacity of olivine at 5-8 GPa and consequences for dehydration partial melting of the upper mantle

    NASA Astrophysics Data System (ADS)

    Ardia, P.; Hirschmann, M. M.; Withers, A. C.; Tenner, T. J.

    2012-09-01

    The H2O storage capacities of peridotitic minerals place crucial constraints on the onset of hydrous partial melting in the mantle. The storage capacities of minerals in equilibrium with a peridotite mineral assemblage (“peridotite-saturated” minerals) are lower than when the minerals coexist only with fluid because hydrous partial melt is stabilized at a lower activity of H2O. Here, we determine peridotite-saturated olivine H2O storage capacities from 5 to 8 GPa and 1400-1500 °C in layered experiments designed to grow large (∼100-150 μm) olivine crystals in equilibrium with the full hydrous peridotite assemblage (melt+ol+opx+gar+cpx). The peridotite-saturated H2O storage capacity of olivine at 1450 °C rises from 57±26 ppm (by wt.) at 5 GPa to 254±60 ppm at 8 GPa. Combining these with results of a parallel study at 10-13 GPa (Tenner et al., 2011, CMP) yields a linear relation applicable from 5 to 13 GPa for peridotite-saturated H2O storage capacity of olivine at 1450 °C, CH2Oolivine(ppm)=57.6(±16)×P(GPa)-169(±18). Storage capacity diminishes with increasing temperature, but is unaffected by variable total H2O concentration between 0.47 and 1.0 wt%. Both of these are as predicted for the condition in which the water activity in the melt is governed principally by the cryoscopic requirement of melt stability for a given temperature below the dry solidus. Measured olivine storage capacities are in agreement or slightly greater than those predicted by a model that combines data from experimental freezing point depression and olivine/melt partition coefficients of H2O (Hirschmann et al., 2009). Considering the temperature along the mantle geotherm, as well as available constraints on garnet/olivine and pyroxene/olivine partitioning of H2O (DH2Ogar/ol,DH2Opx/ol), we estimate the peridotite H2O storage capacity in the low velocity zone. The CH2O required to initiate melting between 150 and 250 km depth is between 270 and 855 ppm. We conclude that hydrous

  7. Standing striations due to ionization instability in atmospheric pressure He/H2O radio frequency capacitive discharges

    NASA Astrophysics Data System (ADS)

    Kawamura, E.; Lieberman, M. A.; Lichtenberg, A. J.

    2016-10-01

    One-dimensional particle-in-cell (PIC) simulations of a narrow gap atmospheric pressure He/2%{{\\text{H}}2}\\text{O} radio frequency capacitive discharge showed standing striations in the bulk plasma region while previously conducted PIC simulations of a narrow gap atmospheric pressure He/0.1%{{\\text{N}}2} discharges [1] showed no such instabilities. We successively modified the base He/{{\\text{H}}2}\\text{O} chemistry to make it more similar to the He/{{\\text{N}}2} chemistry in order to determine the cause of the striations. Setting the e-{{\\text{H}}2}\\text{O} scattering, attachment, vibrational and rotational excitation rates to zero did not suppress the striations. However, a systematic reduction of the e-ion recombination cross section resulted in a transition to a stable state with no striations. The results are interpreted in terms of a model in which the balance between bulk direct ionization and bulk recombination loss determines the bulk plasma equilibrium. Perturbing the equilibrium, we find that the striations are consistent with an ionization instability induced by non-local electron kinetics that form a spatially-varying high energy tail of the electron energy distribution, causing the ionization rate coefficient to decrease with increasing electron temperature T e and root-mean-square electric field E in the instability regime.

  8. CARS Diagnostics of High Pressure Combustion - 2. Measurements of NO, H2O and High Pressure Flames

    DTIC Science & Technology

    1985-12-01

    R85-956328-F CARS DIAGNOSTICS OF r HIGH PRESSURE COMBUSTION -I MEASUREMENTS OF NO, H 0 AND HIGH PRESSURE FLAMES Final Report J.H. Stufflebeam DTIC I7...High Pressure Flames Final Report ~ 5%~ J. H. Stufflebeam J. A. Shirley December 1985 𔃿** U. S. Army Research Office Contract: DAAG29-83-C-OOO1...ClaIiation, CARS Diagnostics of High Pressure Combustion II 12. PERSONAL AUTHOR(S) Stufflebeam , 7. H., ShirleyJA 113a. TYPE OF REPORT 13b. TIME COVERED

  9. Experimental Study of Dehydration and Partial Melting of Biotite-Amphibole Gneiss Under Influence of the H2O-CO2-(K, Na)cl Fluids at 5.5 Kbar and 750 and 800 C

    NASA Astrophysics Data System (ADS)

    Safonov, O.; Kosova, S.

    2012-12-01

    Chloride-rich brines coexisting with CO2-rich fluids are an important agent of high-grade metamorphism and metasomatism in the lower to middle crust. Thermodynamic and transport properties of the chloride-rich fluids are well constrained both theoretically and experimentally. Nevertheless, their effects on complex natural assemblages are poorly understood and demand systematic experimental study. We report results of the experiments on interaction of the biotite-amphibole gneiss from the Sand River formation (Limpopo Complex, South Africa) with the H2O-CO2, H2O-CO2-KCl, H2O-CO2-NaCl, and H2O-CO2-(K, Na)Cl fluids at 5.5 kbar, 750 and 800 C, the chloride/(H2O+CO2) ratio varying from 0 to 0.1, and molar CO2/(CO2+H2O) = 0.5. Experiments were carried out using internally-heated gas pressure vessel. Major purposes of the experiments were to trace changes in phase assemblages in dependence on temperature, salt concentration in a fluid, KCl/NaCl ratio and to show a possibility for partial melting. Heating of the gneiss both at 750 and 800 C without any fluid produced no visible changes in its phase assemblage. Interaction of the gneiss with the H2O-CO2 fluid at 750 C did not significantly influence on its phase assemblage, as well. Addition of KCl in the H2O-CO2 fluid at 750 C resulted in the formation of reaction textures consisting of clinopyroxene and K-feldspar around biotite and amphibole at the contacts with plagioclase. No evidence for partial melting was detected in the samples interacted with the H2O-CO2 and H2O-CO2-KCl fluids at 750 C. Addition of NaCl provokes melting with formation of trachytic and trachyandesitic melts along with the new assemblages Cpx+Kfs+Pl+Ti-Mt and Cpx+Amp+Pl+Ti-Mt. Characteristic of feature of amphiboles, forming in the NaCl-rich fluids is their elevated Na2O content. Products of the runs at 750 C do not contain orthopyroxene. This phase appears at 800 C as a result of biotite breakdown in presence of the H2O-CO2 fluid. It is accompanied

  10. High pressure chemistry in the H2-SiH4 system

    SciTech Connect

    Wang, S.

    2010-02-24

    Understanding the behavior of hydrogen-rich systems at extreme conditions has significance to both condensed matter physics, where it may provide insight into the metallization and superconductivity of element one, and also to applied research areas, where it can provide guidance for designing improved hydrogen storage materials for transportation applications. Here we report the high-pressure study of the SiH{sub 4}-H{sub 2} binary system up to 6.5 GPa at 300 K in a diamond anvil cell. Raman measurements indicate significant intermolecular interactions between H{sub 2} and SiH{sub 4}. We found that the H{sub 2} vibron frequency is softened by the presence of SiH{sub 4} by as much as 40 cm{sup -1} for the fluid with 50 mol% H{sub 2} compared with pure H{sub 2} fluid at the same pressures. In contrast, the Si-H stretching modes of SiH{sub 4} shift to higher frequency in the mixed fluid compared with pure SiH{sub 4}. Pressure-induced solidification of the H{sub 2}-SiH{sub 4} fluid shows a binary eutectic point at 72({+-}2) mol% H{sub 2} and 6.1({+-}0.1) GPa, above which the fluid crystallizes into a mixture of two nearly end-member solids. Neither solid has a pure end-member composition, with the silane-rich solid containing 0.5-1.5 mol% H{sub 2} and the hydrogen-rich solid containing 0.5-1 mol% SiH{sub 4}. These two crystalline phases can be regarded as doped hydrogen-dominant compounds. We were able to superpressurize the sample by 0.2-0.4 GPa above the eutectic before complete crystallization, indicating extended metastability.

  11. The vapor pressures of supercooled NHO3/H2O solutions. [in polar stratospheric clouds

    NASA Technical Reports Server (NTRS)

    Hanson, David R.

    1990-01-01

    A procedure utilizing the Gibbs-Duhem relation is used to extrapolate vapor pressures of supercooled HNO3 mixtures to 190 K. Values of A and B from the equation logP = A - B/T are presented for solutions between 0.20 and 0.25 mole fraction HNO3. In the stratosphere, if sufficient HNO3 vapor is present because it has not come into equilibrium with the nitric acid trihydrate, supercooled nitric acid solutions could condense at temperatures up to 1.5 + or - 0.8 K above the ice point.

  12. Development of pressurized coal partial combustor

    SciTech Connect

    Yoshida, K.; Ino, T.; Yamamoto, T.; Kimura, N.

    1995-12-31

    The integrated gasification combined cycle (IGCC), an environment-friendly power generation system of high thermal efficiency, is being developed via various approaches around the world. The oxygen-blown entrained flow gasification process is a relatively simple method of producing medium calorie coal gas suitable for application to gas turbines. Various systems for this process have been developed to a demonstration level in Europe and America. Japan has actively been developing the air-blown process. However, taking stable molten slag discharge into consideration, coal must be supplied at two stages to raise the combustor temperature in ash molten part. Only two reports have been presented regarding two-stage coal supply. One is the report on an experiment with the Hycol gasifier, in which air feed ratio is varied, with coal feed fixed. The other is report on a simulation study with various gasifier coal feed ratios, conducted at Central Research Institute of Electric Power Industry. It seems that the appropriate feed ratio has not yet been established. Through this activity, a unique furnace construction has been established, and these influences of stoichiometric air ratio, of oxygen enrichment, of char recycling and of coal types on performance have been clarified. The purpose of the present study is to apply this developed CPC techniques to a Pressurized CPC (PCPC), thereby improving the IGCC technology. For the present study, we conducted systematic experiments on the air-blown process with a two stage dry feed system, using a 7 t/d-coal bench scale PCPC test facility, operated at the pressure of 0.4 MPa, and clarified the influence of coal feed ratio on coal gasification performance. This report describes the above-mentioned bench scale test procedures and results, and also some informations about a plan of a 25 t/d-coal pilot test system.

  13. 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.

  14. Pressure drop and heat transfer of Al2O3-H2O nanofluids through silicon microchannels

    NASA Astrophysics Data System (ADS)

    Wu, Xinyu; Wu, Huiying; Cheng, Ping

    2009-10-01

    Experimental investigations were performed on the single-phase flow and heat transfer characteristics through the silicon-based trapezoidal microchannels with a hydraulic diameter of 194.5 µm using Al2O3-H2O nanofluids with particle volume fractions of 0, 0.15% and 0.26% as the working fluids. The effects of the Reynolds number, Prandtl number and nanoparticle concentration on the pressure drop and convective heat transfer were investigated. Experimental results show that the pressure drop and flow friction of the nanofluids increased slightly when compared with that of the pure water, while the Nusselt number increased considerably. At the same pumping power, using nanofluids instead of pure water caused a reduction in the thermal resistance. It was also found that the Nusselt number increased with the increase in the particle concentration, Reynolds number and Prandtl number. Based on the experimental data, the dimensionless correlations for the flow friction and heat transfer of Al2O3-H2O nanofluids through silicon microchannels were proposed for the first time. The agglomeration and deposition of nanoparticles in the silicon microchannels were also examined in this paper. It was found that the Al2O3 nanoparticles deposited on the inner wall of microchannels more easily with increasing wall temperature, and once boiling commenced, there is a severe deposition and adhesion of nanoparticles to the inner wall, which makes the boiling heat transfer of nanofluids in silicon microchannels questionable.

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

    NASA Technical Reports Server (NTRS)

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

    1980-01-01

    The pressure dependence of absolute rate constants for the reaction of OH + C2H2 yields products has been examined at five temperatures ranging from 228 to 413 K. The experimental techniques which was used is flash photolysis-resonance fluoresence. OH was produced by water photolysis and hydroxyl resonance fluorescent photons were measured by multiscaling techniques. The results indicate that the low pressure bimolecular rate constant is 4 x 10 the the minus 13th power cu cm molecule (-1) s(-1) over the temperature range studied. A substantial increase in the bimolecular rate constant with an increase in pressure was observed at all temperatures except 228 K. This indicates the importance of initial adduct formation and subsequent stablization. The high pressure results are well represented by the Arrhenius expression (k sub bi) sub infinity = (6.83 + or - 1.19) x 10 to the minus 12th power exp(-646 + or - 47/T)cu cm molecule (-1) s(-1). The results are compared to previous investigated and are theoretically discussed. The implications of these results on modeling of terrestrial and planetary atmospheres and also in combustion chemistry are discussed.

  16. Removal of H2S and SO2 by CaCO3-Based Sorbents at High Pressure

    SciTech Connect

    Stratis V. Sotirchos

    1998-02-01

    The theoretical and experimental investigation of the mechanism of SO2 and H2S removal by CaCO3 -based sorbents (limestones and dolomites) in pressurized uidized-bed coal combustors (PFBC) and high pressure gasi ers, respectively, is the main objective of this study. It is planned to carry out reactivity evolution experiments under simulated high pressure conditions or in high pressure thermogravimetric and, if needed, uidized- bed reactor (high pressure) arrangements. The pore structure of fresh, heat-treated, and half-calcined solids (dolomites) will be analyzed using a variety of methods. Our work will focus on limestones and dolomites whose reaction with SO2 or H2S under atmospheric conditions has been studied by us or other research groups in past studies. Several theoret- ical tools will be employed to analyze the obtained experimental data including a variable di usivity shrinking-core model and models for di usion, reaction, and structure evolution in chemically reacting porous solids. During the six months of this reporting period, work was primarily done on the study of the behavior of the sul dation of limestones under sequential calcination conditions in the presence of small amounts of oxygen and the development of a stochastic simulation code for determining the extent of pore volume trapping (formation of inaccessible pore space) in gas-solid reactions accompanied by pore volume reduction such as the sulfation and sul dation of calcined limestones and dolomites. The incentive for carrying out sul dation experiments in the presence of oxygen was provided by the observation that some sul dation experiments that were conducted as oxygen was accidentally leaking into the feed mixture of the reactor showed completely di erent behavior from that obtained in the absence of oxygen. Experiments were carried out in the thermogravimetric analysis system that we developed for studying gas-solid reactions at atmospheric or subambient pressures. The two CaCO3

  17. 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.

  18. Hydrous albite magmas at lower crustal pressure: new results on liquidus H2O content, solubility, and H2O activity in the system NaAlSi3O8-H2O-NaCl at 1.0 GPa

    NASA Astrophysics Data System (ADS)

    Makhluf, A. R.; Newton, R. C.; Manning, C. E.

    2016-09-01

    The system albite-H2O serves as an important model for the generation of granitic magmas, yet relatively few experimental investigations have focused on phase relations at high pressure. This study reports new experimental results, at 1.0 GPa and 690-1050 °C, on the temperature and liquid composition at vapor-saturated melting, the H2O content of undersaturated silicate liquids in equilibrium with albite, the solubility of albite in H2O-NaCl fluids immediately below the solidus, and the activity of H2O in hydrous NaAlSi3O8 liquids along the liquidus. Albite melts and dissolves congruently at all temperatures and salinities. In the NaCl-absent system, the temperature of vapor-saturated melting of low albite, confirmed by X-ray diffraction, is 695 ± 5 °C and the liquid composition is 18.14 ± 1.35 wt% H2O. The temperature dependence of the fluid-undersaturated liquidus curve in the system NaAlSi3O8-H2O varies with H2O wt% (w_{{{{H}}2 {{O}}}}) according to T = - 2.0331 × 10^{ - 3} w_{{{{H}}2 {{O}}}}3 + 1.6497w_{{{{H}}2 {{O}}}}2 {-} 58.963w_{{{{H}}2 {{O}}}} + 1235.5°C} indicating positive curvature in temperature-composition coordinates and a dry melting temperature of 1235 °C. At 690 °C, immediately below the solidus, albite solubility decreases drastically with NaCl content of the fluid phase, from 8.8 ± 0.6 wt% in the NaCl-free fluid to ˂2 % at NaCl concentration of only 10 mol%. Experiments determining the activity of H2O (a_{{{{H}}2 {{O}}}}) in liquids at vapor-saturated melting exploited low Cl solubility in liquids and low albite solubility in the presence of H2O-NaCl fluids. The maximum Cl content of quenched glasses, only 0.95 wt%, and very low albite solubility together make possible H2O activity measurement in melts equilibrated with NaCl-H2O solutions. When combined with activity data for H2O-NaCl fluids, experimentally determined a_{{{{H}}2 {{O}}}} along the liquidus is described by T = - {469.16a_{{H2 O}}L}^{{1/2}} {-} 93.382a_{{H2 O}}L + 1235.5

  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. Hydrogen sensor based on Au and YSZ/HgO/Hg electrode for in situ measurement of dissolved H2 in high-temperature and -pressure fluids.

    PubMed

    Zhang, R H; Hu, S M; Zhang, X T; Wang, Y

    2008-11-15

    Gold as a hydrogen-sensing electrode for in situ measurement of dissolved H2 in aqueous solutions under extreme conditions is reported. The dissolved H2 sensor, constructed with a Au-based sensing element and coupled with a YSZ/HgO/Hg electrode, is well suited for determining dissolved H2 concentrations of aqueous fluids at elevated temperatures and pressures. The Au electrode is made of Au wire mounted in a quartz bar, which can be pressurized and heated in the high-pressure and -temperature conditions. The Au-YSZ sensor has been tested for its potential response to the concentrations of dissolved H2 in fluids by using a flow-through reactor at high temperatures up to 400 degrees C and pressures to 38 MPa. Good sensitivity and linear response between the hydrogen concentrations in the fluids and the H2 sensor potentials are reported for hydrogen gas in the concentration range of 0.1-0.001 M H2 in aqueous fluids at temperatures up to 340 degrees C and 30 MPa. Nernstian response of the cell potential to dissolved H2 in fluids was determined at 340 degrees C and 30 MPa, described as follows: DeltaE = 0.9444 + 0. 0603 log m H2 The experimental results indicate that the Au-YSZ/HgO/Hg cell can be used to measure the solubility of H2 in aqueous fluid at temperatures and pressures near to the critical state of water. Thus, this type of Au hydrogen sensor could be easily used for in situ measurement of H2 in hydrothermal fluids in a high-pressure vessel, or at midocean ridge, due to its structure of compression resistance.

  1. Hybrid global model of water cluster ions in atmospheric pressure Ar/ H2O RF capacitive discharges

    NASA Astrophysics Data System (ADS)

    Tavant, A.; Lieberman, M. A.

    2016-11-01

    Water is a trace gas of strong interest for plasma-based medical applications. We use a hybrid global model to simulate a chemically complex Ar/{{\\text{H}}2}\\text{O} atmospheric pressure, radio frequency capacitive discharge, including 47 species with positive ion clusters up to {{\\text{H}}21}\\text{O}10+ . For a discharge gap of 1.5 mm driven at 27.12 MHz, we determine the discharge properties over a range of rf currents (150-500 A m-2) and initial {{\\text{H}}2}\\text{O} concentrations (0.25-2%). An isothermal plug-flow model is used with a gas residence time of 0.2 s for most calculations, with the gas temperature calculated self-consistently from the input power. The cluster density distributions are determined, and we find that the higher mass cluster densities decrease rapidly with increasing gas temperature. A simplified cluster dynamics analytic model is developed and solved to determine the cluster density distributions, which is in good agreement with the hybrid simulation results.

  2. Deducing solid liquid interfacial energy from superheating or supercooling: application to H2O at high pressures

    NASA Astrophysics Data System (ADS)

    Luo, Sheng-Nian; Strachan, Alejandro; Swift, Damian C.

    2005-04-01

    We present a general method to determine the solid-liquid interfacial energy (γsl) from the maximum supercooling (or superheating), and apply it to the water-ice system. For solid-liquid phase transitions, the nucleation-theory-based systematics of maximum superheating and supercooling relate a dimensionless nucleation barrier to the superheating (supercooling) and heating (cooling) rates. Given superheating (or supercooling) values from either experiments or simulations, γsl can then be deduced from the dimensionless nucleation barrier, equilibrium melting temperature and enthalpy of fusion. We demonstrate the accuracy of this approach using molecular dynamics (MD) simulations of the Lennard-Jones system: our predictions of γsl at various pressures are in excellent agreement with independent, direct MD simulations. With this approach, we predict γsl for the water-ice (Ih and III) system using experimental supercooling values in the pressure range of 0-0.3 GPa. The predicted value (28 ± 0.8 mJ m-2) agrees with measurements on H2O-Ih at ambient pressure.

  3. Partial-Redox-Promoted Mn Cycling of Mn(II)-Doped Heterogeneous Catalyst for Efficient H2O2-Mediated Oxidation.

    PubMed

    Li, Hai-Tao; Gao, Qiang; Han, Bo; Ren, Zheng-Hui; Xia, Kai-Sheng; Zhou, Cheng-Gang

    2017-01-11

    The development of a heterogeneous catalyst with high catalytic activity and durability for H2O2-mediated oxidation is one of the most important industrial and environmental issues. In this study, a Mn(II)-doped TiO2 heterogeneous catalyst was developed for H2O2-mediated oxidation. The TiO2 substrate-dependent partial-redox behavior of Mn was identified on the basis of our density functional theory simulations. This unique redox cycle was induced by a moderate electron transfer from Ti to Mn, which compensated for the electron loss of Mn and finally resulted in a high-efficiency cycling of Mn between its oxidized and reduced forms. In light of the theoretical results, a Mn(II)-doped TiO2 composite with well-defined morphology and large surface area (153.3 m(2) g(-1)) was elaborately fabricated through incorporating Mn(II) ions into a TiO2 nanoflower, and further tested as the catalyst for oxidative degradation of organic pollutants in the presence of H2O2. Benefiting from the remarkable textural features and excellent Mn cycling property, this composite exhibited superior catalytic performance for organic pollutant degradation. Moreover, it could retain 98.40% of its initial activity even in the fifth cycle. Our study provides an effective strategy for designing heterogeneous catalytic systems for H2O2-mediated oxidations.

  4. Hydrogen production by coupled catalytic partial oxidation and steam methane reforming at elevated pressure and temperature

    NASA Astrophysics Data System (ADS)

    Chen, Luwei; Hong, Qi; Lin, Jianyi; Dautzenberg, F. M.

    Hydrogen production by coupled catalytic partial oxidation (CPO) and steam methane reforming of methane (OSMR) at industrial conditions (high temperatures and pressures) have been studied over supported 1 wt.% NiB catalysts. Mixture of air/CH 4/H 2O was applied as the feed. The effects of O 2:CH 4 ratio, H 2O:CH 4 ratio and the gas hourly space velocity (GHSV) on oxy-steam reforming (OSRM) were also studied. Results indicate that CH 4 conversion increases significantly with increasing O 2:CH 4 or H 2O:CH 4 ratio. However, the hydrogen mole fraction goes through a maximum, depending on reaction conditions, e.g., pressure, temperature and the feed gases ratios. Carbon deposition on the catalysts has been greatly decreased after steam addition. The supported 1 wt.% NiB catalysts exhibit high stability with 85% methane conversion at 15 bar and 800 °C during 70 h time-on-stream reaction (CH 4:O 2:H 2O:N 2 = 1:0.5:1:1.887). The thermal efficiency was increased from 35.8% by CPO (without steam) to 55.6%. The presented data would be useful references for further design of enlarged scale hydrogen production system.

  5. Nonadiabatic interaction effects on population transfer in H2 by stimulated Raman transition with partially overlapping laser pulses

    NASA Astrophysics Data System (ADS)

    Ghosh, Swaralipi; Sen, Sanjay; Bhattacharyya, S. S.; Saha, Samir

    1999-06-01

    We have theoretically investigated the population transfer in a four-level H2 system by stimulated Raman transition from the ground X 1Σ+g(νg=0,Jg=0) level to higher rovibrational levels (νf,Jf) of the X 1Σ+g state via the excited intermediate B 1Σ+u(νi=14,Ji=1) and C 1Π+u(νi=3,Ji=1) levels coupled with each other by nonadiabatic interaction, using time-dependent overlapping pump and Stokes laser fields. The density-matrix treatment, which permits the convenient inclusion of the spontaneous emissions from the intermediate levels, has been employed to describe the dynamics of the two-photon Raman resonance process. The present study performs the calculations of final populations (after both the pulses are over) of the ground and terminal levels for Q-branch (Jf=0) fundamental (νf=1) and first overtone (νf=2) transitions and the S-branch (Jf=2) fundamental (νf=1) transition as a function of time delay between the two pulses for the cases of on-resonance as well as off-resonance excitations in a wide range (2×105-2×107 W/cm2) of peak intensities I0P (I0S) of the pump (Stokes) fields. Both fields are assumed to have the same temporal shape, duration, peak intensities, and linear parallel polarizations. The accurate values of spontaneous radiative relaxation rates of the intermediate levels to the initial and final levels, taking into account their J and M dependence, are explicitly included in our calculations. The pulse width (full width at half maximum) τp is taken as 170 ns so that total spontaneous decay can occur during the pulse duration. The transfer efficiency is found to be very sensitive to the peak intensities of the laser pulses in each case of transition considered. Special attention is paid to the effects of the nonadiabatic (NA) interaction between B(14,1) and C(3,1) levels on population transfer efficiency. Calculations are also done in some particular cases using the adiabatic Born-Oppenheimer (ABO) approximation. The results with ABO

  6. Mineralogical changes of a well cement in various H2S-CO2(-brine) fluids at high pressure and temperature.

    PubMed

    Jacquemet, Nicolas; Pironon, Jacques; Saint-Marc, Jérémie

    2008-01-01

    The reactivity of a crushed well cement in contact with (1) a brine with dissolved H2S-CO2; (2) a dry H2S-CO2 supercritical phase; (3) a two-phase fluid associating a brine with dissolved H2S-CO2 and a H2S-CO2 supercritical phase was investigated in batch experiments at 500 bar and 120, 200 degrees C. All of the experiments showed that following 15-60 days cement carbonation occurred. The H2S reactivity with cement is limited since it only transformed the ferrites (minor phases) by sulfidation. It appeared that the primary parameter controlling the degree of carbonation (i.e., the rate of calcium carbonates precipitation and CSH (Calcium Silicate Hydrates) decalcification) is the physical state of the fluid phase contacting the minerals. The carbonation degree is complete when the minerals contact at least the dry H2S-CO2 supercritical phase and partial when they contactthe brine with dissolved H2S-CO2. Aragonite (calcium carbonate polymorph) precipitated specifically within the dry H2S-CO2 supercritical phase. CSH cristallinity is improved by partial carbonation while CSH are amorphized by complete carbonation. However, the features evidenced in this study cannot be directly related to effective features of cement as a monolith. Further studies involving cement as a monolith are necessary to ascertain textural, petrophysical, and mechanical evolution of cement.

  7. Using Dalton's Law of Partial Pressures to Determine the Vapor Pressure of a Volatile Liquid

    ERIC Educational Resources Information Center

    Hilgeman, Fred R.; Bertrand, Gary; Wilson, Brent

    2007-01-01

    This experiment, designed for a general chemistry laboratory, illustrates the use of Dalton's law of partial pressures to determine the vapor pressure of a volatile liquid. A predetermined volume of air is injected into a calibrated tube filled with a liquid whose vapor pressure is to be measured. The volume of the liquid displaced is greater than…

  8. Influence of Ar/O2/H2O Feed Gas and N2/O2/H2O Environment on the Interaction of Time Modulated MHz Atmospheric Pressure Plasma Jet (APPJ) with Model Polymers

    NASA Astrophysics Data System (ADS)

    Oehrlein, Gottlieb; Luan, Pingshan; Knoll, Andrew; Kondeti, Santosh; Bruggeman, Peter

    2016-09-01

    An Ar/O2/H2O fed time modulated MHz atmospheric pressure plasma jet (APPJ) in a sealed chamber was used to study plasma interaction with model polymers (polystyrene, poly-methyl methacrylate, etc.). The amount of H2O in the feed gas and/or present in the N2, O2, or N2/O2 environment was controlled. Short lived species such as O atoms and OH radicals play a crucial role in polymer etching and surface modifications (obtained from X-ray photoelectron spectroscopy of treated polymers without additional atmospheric exposure). Polymer etching depth for Ar/air fed APPJ mirrors the decay of gas phase O atoms with distance from the APPJ nozzle in air and is consistent with the estimated O atom flux at the polymer surface. Furthermore, whereas separate O2 or H2O admixture to Ar enhances polymer etching, simultaneous addition of O2 and H2O to Ar quenches polymer etching. This can be explained by the mutual quenching of O with OH, H and HO2 in the gas phase. Results where O2 and/or H2O in the environment were varied are consistent with these mechanisms. All results will be compared with measured and simulated species densities reported in the literature. We gratefully acknowledge funding from US Department of Energy (DE-SC0001939) and National Science Foundation (PHY-1415353).

  9. Diameter control of gold nanoparticles synthesized in gas phase using atmospheric-pressure H2/Ar plasma jet and gold wire as the nanoparticle source: Control by varying the H2/Ar mixture ratio

    NASA Astrophysics Data System (ADS)

    Shimizu, Yoshiki

    2017-01-01

    This report describes diameter control of gold nanoparticles (AuNPs) during synthesis using an atmospheric-pressure H2/Ar plasma jet drive with pulse-modulated ultrahigh frequency, employing Au wire as the NP source material. During this process, where most of the AuNPs are regarded as formed through condensation from Au vapor derived by the Au wire etching, the mean diameter varied in the approximate range of 2-12 nm with H2 volume ratios up to 3.9%. In plasma diagnostics, results showed that the H2 volume ratio influences the plasma discharge behaviour, which affects the heat flux density flowed into the Au wire, and the atomic hydrogen concentration in the plasma. Both seemed to influence the etching rate of the Au wire per unit area, which is directly related to the concentration of Au vapor in the plasma. The concentration is one factor affecting the particle size evolution because of the collisions among vapor species in reaction field. Therefore, the AuNP size variation with the H2 volume ratio was discussed from the perspective of the etching rate of the Au wire at each H2 volume ratio.

  10. Synthesis and investigation of [Cp(PMe(3))Rh(H)(H(2))](+) and its partially deuterated and tritiated isotopomers: evidence for a hydride/dihydrogen structure.

    PubMed

    Taw, Felicia L; Mellows, Heather; White, Peter S; Hollander, Frederick J; Bergman, Robert G; Brookhart, Maurice; Heinekey, D Michael

    2002-05-08

    Hydrogenolysis of [Cp(PMe(3))Rh(Me)(CH(2)Cl(2))](+)BAr'(4)(-) (4, Ar' = 3,5-C(6)H(3)(CF(3))(2)) in dichloromethane afforded the nonclassical polyhydride complex [Cp*PMe(3))Rh(H)(H(2))](+)BAr'(4)(-) (1), which exhibits a single hydride resonance at all accessible temperatures in the (1)H NMR spectrum. Exposure of solutions of 1 to D(2) or T(2) gas resulted in partial isotopic substitution in the hydride sites. Formulation of 1 as a hydride/dihydrogen complex was based upon T(1) (T(1)(min) = 23 ms at 150 K, 500 MHz), J(H-D) (ca. 10 Hz), and J(H-T) (ca. 70 Hz) measurements. The barrier (Delta G(++)) to exchange of hydride with dihydrogen sites was determined to be less than ca. 5 kcal/mol. Protonation of Cp(PMe(3))Rh(H)(2) (2) using H(OEt(2))(2)BAr'(4) resulted in binuclear species [(Cp(PMe(3))Rh(H))(2)(mu-H)](+)BAr'(4)(-) (3), which is formed in a reaction involving 1 as an intermediate. Complex 3 contains two terminal hydrides and one bridging hydride ligand which exchange with a barrier of 9.1 kcal/mol as observed by (1)H NMR spectroscopy. Additionally, the structures of 3 and 4, determined by X-ray diffraction, are reported.

  11. Catalytic oxidative degradation of 17α-ethinylestradiol by FeIII-TAML/H2O2: estrogenicities of the products of partial, and extensive oxidation.

    PubMed

    Chen, Jian Lin; Ravindran, Shanthinie; Swift, Simon; Wright, L James; Singhal, Naresh

    2012-12-01

    The oxidative degradation of the oral contraceptive 17α-ethinylestradiol (EE(2)) in water by a new advanced catalytic oxidation process was investigated. The oxidant employed was hydrogen peroxide in aqueous solution and the catalyst was the iron tetra-amido macrocyclic ligand (Fe(III)-TAML) complex that has been designated Na[Fe(H(2)O)(B*)] (Fe(III)-B*). EE(2) (10 μM) was oxidised rapidly by the Fe(III)-B*/H(2)O(2) (5 nM/4 mM) catalytic oxidation system at 25 °C, and for reactions at pH 8.40-11.00, no unchanged EE2 was detected in the reaction mixtures after 60 min. No oxidation of EE(2) was detected in blank reactions using either H(2)O(2) or Fe(III)-B* alone. The maximum rate of EE(2) loss occurred at pH 10.21. At this pH the half-life of EE(2) was 2.1 min and the oxidised products showed around 30% estrogenicity removal, as determined by the yeast estrogen screen (YES) bioassay. At pH 11.00, partial oxidation of EE(2) by Fe(III)-B*/H(2)O(2) (5 nM/4 mM) was studied (half-life of EE(2) was 14.5 min) and in this case the initial intermediates formed were a mixture of the epimers 17α-ethynyl-1,4-estradiene-10α,17β-diol-3-one (1a) and 17α-ethynyl-1,4-estradiene-10β,17β-diol-3-one (1b) (identified by LC-ToF-MS and (1)H NMR spectroscopy). Significantly, this product mixture displayed a slightly higher estrogenicity than EE(2) itself, as determined by the YES bioassay. Upon the addition of further aliquots of Fe(III)-B* (to give a Fe(III)-B* concentration of 500 nM) and H(2)O(2) (to bring the concentration up to 4 mM assuming the final concentration had dropped to zero) to this reaction mixture the amounts of 1a and 1b slowly decreased to zero over a 60 min period as they were oxidised to unidentified products that showed no estrogenicity. Thus, partial oxidation of EE(2) gave products that have slightly increased estrogenicity, whereas more extensive oxidation by the advanced catalytic oxidation system completely removed all estrogenicity. These results

  12. 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

  13. 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.

  14. FORTRAN programs for generating fluid inclusion isochores and fugacity coefficients for the system H 2O-CO 2-NaCl at high pressures and temperatures

    NASA Astrophysics Data System (ADS)

    Bowers, Teresa Suter; Helgeson, Harold C.

    Program DENFIND permits calculation of pressures and temperatures corresponding to isochores for H 2O-CO 2-NaCl fluids which can be used to generate pressure corrections of fluid inclusion homogenization temperatures. Program FUGCO facilitates calculation of fugacity coefficients in the system H 2O-CO 2-NaCl as a function of pressure, temperature and fluid composition. Both programs employ a modified Redlich-Kwong equation of state for the ternary system (Bowers and Helgeson, 1983a), which is applicable to fluids containing up to 35 wt. % NaCl (relative to H 2O + NaCl) at pressures above 500 bars and temperature from 350 to 600°C.

  15. 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, Gisèle; Sleiman, Chantal; Canosa, André; 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.

  16. Calcite precipitation from CO 2-H 2O-Ca(OH) 2 slurry under high pressure of CO 2

    NASA Astrophysics Data System (ADS)

    Montes-Hernandez, G.; Renard, F.; Geoffroy, N.; Charlet, L.; Pironon, J.

    2007-10-01

    The formation of solid calcium carbonate (CaCO 3) from aqueous solutions or slurries containing calcium and carbon dioxide (CO 2) is a complex process of considerable importance in the ecological, geochemical and biological areas. Moreover, the demand for powdered CaCO 3 has recently increased considerably in various fields of industry. The aim of this study was therefore to synthesize fine particles of calcite with controlled morphology by hydrothermal carbonation of calcium hydroxide at high CO 2 pressure (initial P=55 bar) and at moderate and high temperatures (30 and 90 °C). The morphology of precipitated particles was identified by transmission electron microscopy (TEM/EDS) and scanning electron microscopy (SEM/EDS). In addition, an X-ray diffraction analysis was performed to investigate the carbonation efficiency and purity of the solid product. Carbonation of dispersed calcium hydroxide (Ca(OH) 2(s)+CO 2(aq)→CaCO 3(s)+H 2O) in the presence of supercritical ( PT=90 bar, T=90 °C) or gaseous ( PT=55 bar, T=30 °C) CO 2 led to the precipitation of sub-micrometric isolated particles (<1 μm) and micrometric agglomerates (<5 μm) of calcite. For this study, the carbonation efficiency (Ca(OH) 2-CaCO 3 conversion) was not significantly affected by pressure-temperature (PT) conditions after 24 h of reaction. In contrast, the initial rate of calcium carbonate precipitation increased from 4.3 mol/h in the "90 bar-90 °C" system to 15.9 mol/h in the "55 bar-30 °C" system. The use of high CO 2 pressure may therefore be desirable for increasing the production rate of CaCO 3, carbonation efficiency and purity, to approximately 48 kg/m 3 h, 95% and 96.3%, respectively, in this study. The dissipated heat for this exothermic reaction was estimated by calorimetry to be -32 kJ/mol in the "90 bar-90 °C" system and -42 kJ/mol in the "55 bar-30 °C" system.

  17. High-Pressure Equation of State for Partially Ionic Solids

    NASA Technical Reports Server (NTRS)

    Schlosser, Herbert; Ferrante, John

    1993-01-01

    Recently, we showed that the cohesive energy of partially ionic solids may be characterized by a two-term energy relationship consisting of a Coulomb term arising from the valence-charge transfer delta Z between the atoms, and a scaled universal energy function E(sup *)(a(sup *)), which accounts for the partially covalent character of the bond and for the repulsion between the atomic cores for small R; a(sup *) is a scaled length. Normalized cohesive-energy curves of alkali halide crystals and of Ti and Ag halide crystals were obtained, and the cohesive-energy-curve parameters were used to generate theoretical equation-of-state (EOS) curves for the Li, Na, K, Cs, and Ag halides. Good agreement was obtained with the experimental isothermal compression curves over a wide pressure range (0-90 kbar). In this paper we verify that the cohesive-energy relationship is valid for divalent partially ionic solids; physically reasonable charge-transfer values (1.80 less than delta Z less than 2.0) are obtained for MgO, CaO, and CaS. Next, EOS curves for LiF, NaF, Nal, CsCl, Csl, MgO, CaO, and CaS are generated in terms of the cohesive-energy parameters. These EOS's yield excellent fits to experimental isothermal-compression data and to shock-wave data to very high pressures (P(sub max)= 250-1350 kbar).

  18. 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

  19. Collision efficiency of water in the unimolecular reaction CH4 (+H2O) ⇆ CH3 + H (+H2O): one-dimensional and two-dimensional solutions of the low-pressure-limit master equation.

    PubMed

    Jasper, Ahren W; Miller, James A; Klippenstein, Stephen J

    2013-11-27

    The low-pressure-limit unimolecular decomposition of methane, CH4 (+M) ⇆ CH3 + H (+M), is characterized via low-order moments of the total energy, E, and angular momentum, J, transferred due to collisions. The low-order moments are calculated using ensembles of classical trajectories, with new direct dynamics results for M = H2O and new results for M = O2 compared with previous results for several typical atomic (M = He, Ne, Ar, Kr) and diatomic (M = H2 and N2) bath gases and one polyatomic bath gas, M = CH4. The calculated moments are used to parametrize three different models of the energy transfer function, from which low-pressure-limit rate coefficients for dissociation, k0, are calculated. Both one-dimensional and two-dimensional collisional energy transfer models are considered. The collision efficiency for M = H2O relative to the other bath gases (defined as the ratio of low-pressure limit rate coefficients) is found to depend on temperature, with, e.g., k0(H2O)/k0(Ar) = 7 at 2000 K but only 3 at 300 K. We also consider the rotational collision efficiency of the various baths. Water is the only bath gas found to fully equilibrate rotations, and only at temperatures below 1000 K. At elevated temperatures, the kinetic effect of "weak-collider-in-J" collisions is found to be small. At room temperature, however, the use of an explicitly two-dimensional master equation model that includes weak-collider-in-J effects predicts smaller rate coefficients by 50% relative to the use of a statistical model for rotations. The accuracies of several methods for predicting relative collision efficiencies that do not require solving the master equation and that are based on the calculated low-order moments are tested. Troe's weak collider efficiency, βc, includes the effect of saturation of collision outcomes above threshold and accurately predicts the relative collision efficiencies of the nine baths. Finally, a brief discussion is presented of mechanistic details of the

  20. Determination of the partial pressure of thallium in high-pressure lamp arcs: A comparative study

    SciTech Connect

    Karabourniotis, D.; Couris, S.; Damelincourt, J.J.; Aubes, M.

    1986-08-01

    The partial pressure of thallium in high-pressure Hg-TlI discharges with different mercury, thallium, and electron pressures has been measured by using the optically thin line Tl 655 nm and the self-reversed line Tl 535 nm. The partial pressure of the arc axis has been measured from the line Tl 655nm. The effective partial pressure has been measured from the self-reversed line Tl 535 nm on the basis of the multiparameter method, and it has been calculated from the known axis pressure of thallium and the calculation of its radial variation by taking into account the chemical reactions. The experimental results confirm the dispersion character of the blue wing of the line Tl 535 nm. The systematic difference obtained between the measured and calculated effective pressure, particularly at the moment of minimum electron density, may be interpreted by deviations from the local thermodynamic equilibrium (LTE) caused by overpopulation of the upper level of the line Tl 535 nm.

  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. DEVELOPMENT OF PRESSURIZED CIRCULATING FLUIDIZED BED PARTIAL GASIFICATION MODULE (PGM)

    SciTech Connect

    Unknown

    2003-01-30

    Foster Wheeler Power Group, Inc. is working under US Department of Energy contract No. DE-FC26-00NT40972 to develop a partial gasification module (PGM) that represents a critical element of several potential coal-fired Vision 21 plants. When utilized for electrical power generation, these plants will operate with efficiencies greater than 60% and produce near zero emissions of traditional stack gas pollutants. The new process partially gasifies coal at elevated pressure producing a coal-derived syngas and a char residue. The syngas can be used to fuel the most advanced power producing equipment such as solid oxide fuel cells or gas turbines, or processed to produce clean liquid fuels or chemicals for industrial users. The char residue is not wasted; it can also be used to generate electricity by fueling boilers that drive the most advanced ultra-supercritical pressure steam turbines. The amount of syngas and char produced by the PGM can be tailored to fit the production objectives of the overall plant, i.e., power generation, clean liquid fuel production, chemicals production, etc. Hence, PGM is a robust building bock that offers all the advantages of coal gasification but in a more user-friendly form; it is also fuel flexible in that it can use alternative fuels such as biomass, sewerage sludge, etc. This report describes the work performed during the October 1--December 31, 2002 time period.

  3. Development of Pressurized Circulating Fluidized Bed Partial Gasification Module (PGM)

    SciTech Connect

    A. Robertson

    2003-12-31

    Foster Wheeler Power Group, Inc. is working under US Department of Energy contract No. DE-FC26-00NT40972 to develop a partial gasification module (PGM) that represents a critical element of several potential coal-fired Vision 21 plants. When utilized for electrical power generation, these plants will operate with efficiencies greater than 60% and produce near zero emissions of traditional stack gas pollutants. The new process partially gasifies coal at elevated pressure producing a coal-derived syngas and a char residue. The syngas can be used to fuel the most advanced power producing equipment such as solid oxide fuel cells or gas turbines, or processed to produce clean liquid fuels or chemicals for industrial users. The char residue is not wasted; it can also be used to generate electricity by fueling boilers that drive the most advanced ultra-supercritical pressure steam turbines. The amount of syngas and char produced by the PGM can be tailored to fit the production objectives of the overall plant, i.e., power generation, clean liquid fuel production, chemicals production, etc. Hence, PGM is a robust building bock that offers all the advantages of coal gasification but in a more user-friendly form; it is also fuel flexible in that it can use alternative fuels such as biomass, sewerage sludge, etc. This report describes the work performed during the October 1 - December 31, 2003 time period.

  4. Development of Pressurized Circulating Fluidized Bed Partial Gasification Module (PGM)

    SciTech Connect

    A. Robertson

    2002-09-30

    Foster Wheeler Power Group, Inc. is working under US Department of Energy contract No. DE-FC26-00NT40972 to develop a partial gasification module (PGM) that represents a critical element of several potential coal-fired Vision 21 plants. When utilized for electrical power generation, these plants will operate with efficiencies greater than 60% and produce near zero emissions of traditional stack gas pollutants. The new process partially gasifies coal at elevated pressure producing a coal-derived syngas and a char residue. The syngas can be used to fuel the most advanced power producing equipment such as solid oxide fuel cells or gas turbines, or processed to produce clean liquid fuels or chemicals for industrial users. The char residue is not wasted; it can also be used to generate electricity by fueling boilers that drive the most advanced ultra-supercritical pressure steam turbines. The amount of syngas and char produced by the PGM can be tailored to fit the production objectives of the overall plant, i.e., power generation, clean liquid fuel production, chemicals production, etc. Hence, PGM is a robust building bock that offers all the advantages of coal gasification but in a more user-friendly form; it is also fuel flexible in that it can use alternative fuels such as biomass, sewerage sludge, etc. This report describes the work performed during the July 1-September 30, 2002 time period.

  5. DEVELOPMENT OF PRESSURIZED CIRCULATING FLUDIZED BED PARTIAL GASIFICATION MODULE (PGM)

    SciTech Connect

    Archie Robertson

    2002-07-10

    Foster Wheeler Power Group, Inc. is working under US Department of Energy contract No. DE-FC26-00NT40972 to develop a partial gasification module (PGM) that represents a critical element of several potential coal-fired Vision 21 plants. When utilized for electrical power generation, these plants will operate with efficiencies greater than 60% and produce near zero emissions of traditional stack gas pollutants. The new process partially gasifies coal at elevated pressure producing a coal-derived syngas and a char residue. The syngas can be used to fuel the most advanced power producing equipment such as solid oxide fuel cells or gas turbines, or processed to produce clean liquid fuels or chemicals for industrial users. The char residue is not wasted; it can also be used to generate electricity by fueling boilers that drive the most advanced ultra-supercritical pressure steam turbines. The amount of syngas and char produced by the PGM can be tailored to fit the production objectives of the overall plant, i.e., power generation, clean liquid fuel production, chemicals production, etc. Hence, PGM is a robust building bock that offers all the advantages of coal gasification but in a more user-friendly form; it is also fuel flexible in that it can use alternative fuels such as biomass, sewerage sludge, etc. This report describes the work performed during the April 1--June 30, 2002 time period.

  6. DEVELOPMENT OF PRESSURIZED CIRCULATING FLUIDIZED BED PARTIAL GASIFICATION MODULE (PGM)

    SciTech Connect

    Archie Robertson

    2003-07-23

    Foster Wheeler Power Group, Inc. is working under US Department of Energy contract No. DE-FC26-00NT40972 to develop a partial gasification module (PGM) that represents a critical element of several potential coal-fired Vision 21 plants. When utilized for electrical power generation, these plants will operate with efficiencies greater than 60% and produce near zero emissions of traditional stack gas pollutants. The new process partially gasifies coal at elevated pressure producing a coal-derived syngas and a char residue. The syngas can be used to fuel the most advanced power producing equipment such as solid oxide fuel cells or gas turbines, or processed to produce clean liquid fuels or chemicals for industrial users. The char residue is not wasted; it can also be used to generate electricity by fueling boilers that drive the most advanced ultra-supercritical pressure steam turbines. The amount of syngas and char produced by the PGM can be tailored to fit the production objectives of the overall plant, i.e., power generation, clean liquid fuel production, chemicals production, etc. Hence, PGM is a robust building bock that offers all the advantages of coal gasification but in a more user-friendly form; it is also fuel flexible in that it can use alternative fuels such as biomass, sewerage sludge, etc. This report describes the work performed during the April 1--June 30, 2003 time period.

  7. DEVELOPMENT OF PRESSURIZED CIRCULATING FLUIDIZED BED PARTIAL GASIFICATION MODULE (PGM)

    SciTech Connect

    Archie Robertson

    2003-10-29

    Foster Wheeler Power Group, Inc. is working under US Department of Energy contract No. DE-FC26-00NT40972 to develop a partial gasification module (PGM) that represents a critical element of several potential coal-fired Vision 21 plants. When utilized for electrical power generation, these plants will operate with efficiencies greater than 60% and produce near zero emissions of traditional stack gas pollutants. The new process partially gasifies coal at elevated pressure producing a coal-derived syngas and a char residue. The syngas can be used to fuel the most advanced power producing equipment such as solid oxide fuel cells or gas turbines, or processed to produce clean liquid fuels or chemicals for industrial users. The char residue is not wasted; it can also be used to generate electricity by fueling boilers that drive the most advanced ultra-supercritical pressure steam turbines. The amount of syngas and char produced by the PGM can be tailored to fit the production objectives of the overall plant, i.e., power generation, clean liquid fuel production, chemicals production, etc. Hence, PGM is a robust building bock that offers all the advantages of coal gasification but in a more user-friendly form; it is also fuel flexible in that it can use alternative fuels such as biomass, sewerage sludge, etc. This report describes the work performed during the July 1--September 30, 2003 time period.

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

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Indwelling blood carbon dioxide partial pressure....1150 Indwelling blood carbon dioxide partial pressure (PCO2) analyzer. (a) Identification. An indwelling blood carbon dioxide partial pressure PCO2 analyzer is a device that consists of a...

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

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Indwelling blood carbon dioxide partial pressure....1150 Indwelling blood carbon dioxide partial pressure (PCO2) analyzer. (a) Identification. An indwelling blood carbon dioxide partial pressure PCO2 analyzer is a device that consists of a...

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

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Indwelling blood carbon dioxide partial pressure....1150 Indwelling blood carbon dioxide partial pressure (PCO2) analyzer. (a) Identification. An indwelling blood carbon dioxide partial pressure PCO2 analyzer is a device that consists of a...

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

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Indwelling blood carbon dioxide partial pressure....1150 Indwelling blood carbon dioxide partial pressure (PCO2) analyzer. (a) Identification. An indwelling blood carbon dioxide partial pressure PCO2 analyzer is a device that consists of a...

  12. 21 CFR 868.1150 - Indwelling blood carbon dioxide partial pressure (PCO2) analyzer.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Indwelling blood carbon dioxide partial pressure....1150 Indwelling blood carbon dioxide partial pressure (PCO2) analyzer. (a) Identification. An indwelling blood carbon dioxide partial pressure PCO2 analyzer is a device that consists of a...

  13. 21 CFR 868.1200 - Indwelling blood oxygen partial pressure (PO2) analyzer.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Indwelling blood oxygen partial pressure (PO2... Indwelling blood oxygen partial pressure (PO2) analyzer. (a) Identification. An indwelling blood oxygen... electrode) and that is used to measure, in vivo, the partial pressure of oxygen in blood to aid...

  14. 21 CFR 868.1200 - Indwelling blood oxygen partial pressure (PO2) analyzer.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Indwelling blood oxygen partial pressure (PO2... Indwelling blood oxygen partial pressure (PO2) analyzer. (a) Identification. An indwelling blood oxygen... electrode) and that is used to measure, in vivo, the partial pressure of oxygen in blood to aid...

  15. 21 CFR 868.1200 - Indwelling blood oxygen partial pressure (PO2) analyzer.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Indwelling blood oxygen partial pressure (PO2... Indwelling blood oxygen partial pressure (PO2) analyzer. (a) Identification. An indwelling blood oxygen... electrode) and that is used to measure, in vivo, the partial pressure of oxygen in blood to aid...

  16. 21 CFR 868.1200 - Indwelling blood oxygen partial pressure (PO2) analyzer.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Indwelling blood oxygen partial pressure (PO2... Indwelling blood oxygen partial pressure (PO2) analyzer. (a) Identification. An indwelling blood oxygen... electrode) and that is used to measure, in vivo, the partial pressure of oxygen in blood to aid...

  17. 21 CFR 868.1200 - Indwelling blood oxygen partial pressure (PO2) analyzer.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Indwelling blood oxygen partial pressure (PO2... Indwelling blood oxygen partial pressure (PO2) analyzer. (a) Identification. An indwelling blood oxygen... electrode) and that is used to measure, in vivo, the partial pressure of oxygen in blood to aid...

  18. Akbu-LAAO exhibits potent anti-tumor activity to HepG2 cells partially through produced H2O2 via TGF-β signal pathway

    PubMed Central

    Guo, Chunmei; Liu, Shuqing; Dong, Panpan; Zhao, Dongting; Wang, Chengyi; Tao, Zhiwei; Sun, Ming-Zhong

    2015-01-01

    Previously, we characterized the biological properties of Akbu-LAAO, a novel L-amino acid oxidase from Agkistrodon blomhoffii ussurensis snake venom (SV). Current work investigated its in vitro anti-tumor activity and underlying mechanism on HepG2 cells. Akbu-LAAO inhibited HepG2 growth time and dose-dependently with an IC50 of ~38.82 μg/mL. It could induce the apoptosis of HepG2 cells. Akbu-LAAO exhibited cytotoxicity by inhibiting growth and inducing apoptosis of HepG2 as it showed no effect on its cell cycle. The inhibition of Akbu-LAAO to HepG2 growth partially relied on enzymatic-released H2O2 as catalase only partially antagonized this effect. cDNA microarray results indicated TGF-β signaling pathway was linked to the cytotoxicity of Akbu-LAAO on HepG2. TGF-β pathway related molecules CYR61, p53, GDF15, TOB1, BTG2, BMP2, BMP6, SMAD9, JUN, JUNB, LOX, CCND1, CDK6, GADD45A, CDKN1A were deregulated in HepG2 following Akbu-LAAO stimulation. The presence of catalase only slightly restored the mRNA changes induced by Akbu-LAAO for differentially expressed genes. Meanwhile, LDN-193189, a TGF-β pathway inhibitor reduced Akbu-LAAO cytotoxicity on HepG2. Collectively, we reported, for the first time, SV-LAAO showed anti-tumor cell activity via TGF-β pathway. It provides new insight of SV-LAAO exhibiting anti-tumor effect via a novel signaling pathway. PMID:26655928

  19. Wavelength-modulation spectroscopy near 1.4 µm 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.

  20. Morphology, structure, and properties of Cu-poor and Cu-rich Cu(In,Ga)Se2 films partially selenized using H2Se gas

    NASA Astrophysics Data System (ADS)

    Han, Anjun; Huang, Yongliang; Liu, Xiaohui; Xian, Wang; Meng, Fanying; Liu, Zhengxin

    2016-11-01

    Cu-poor and Cu-rich metallic precursors were prepared by cosputtering from In and Cu-Ga alloy targets and then partially selenized using H2Se gas. The properties of Cu(In,Ga)Se2 (CIGS) films are comparatively studied and the phase transition process is analyzed. The cosputtered metallic precursor has a rough morphology mostly covered by large In-rich nodules. After selenization, a large number of crumblike InSe grains were formed from the nodules on the surface of the Cu-rich film, whereas the Cu-poor film shows a dense surface. The selenized films comprise CIGS, Cu9(In,Ga)4 intermetallic, and the InSe phases. The proportion of the Cu9(In,Ga)4 phase in the Cu-rich film is more than that in the Cu-poor film. After annealing, the residual Cu9(In,Ga)4 of the Cu-poor film is eliminated. A negligible effect of Cu/(In+Ga) on the grain size can be observed. The CIGS solar cell with an efficiency of 15.1% was prepared by this method.

  1. DEVELOPMENT OF PRESSURIZED CIRCULATING FLUIDIZED BED PARTIAL GASIFICATION MODULE (PGM)

    SciTech Connect

    Unknown

    2002-03-29

    Foster Wheeler Development Corporation is working under DOE contract No. DE-FC26-00NT40972 to develop a partial gasification module (PGM) that represents a critical element of several potential coal-fired Vision 21 plants. When utilized for electrical power generation, these plants will operate with efficiencies greater than 60% while producing near zero emissions of traditional stack gas pollutants. The new process partially gasifies coal at elevated pressure producing a coal-derived syngas and a char residue. The syngas can be used to fuel the most advanced power producing equipment such as solid oxide fuel cells or gas turbines or processed to produce clean liquid fuels or chemicals for industrial users. The char residue is not wasted; it can also be used to generate electricity by fueling boilers that drive the most advanced ultra-supercritical pressure steam turbines. The unique aspect of the process is that it utilizes a pressurized circulating fluidized bed partial gasifier and does not attempt to consume the coal in a single step. To convert all the coal to syngas in a single step requires extremely high temperatures ({approx}2500 to 2800 F) that melt and vaporize the coal and essentially drive all coal ash contaminants into the syngas. Since these contaminants can be corrosive to power generating equipment, the syngas must be cooled to near room temperature to enable a series of chemical processes to clean the syngas. Foster Wheeler's process operates at much lower temperatures that control/minimize the release of contaminants; this eliminates/minimizes the need for the expensive, complicated syngas heat exchangers and chemical cleanup systems typical of high temperature gasification. By performing the gasification in a circulating bed, a significant amount of syngas can still be produced despite the reduced temperature and the circulating bed allows easy scale up to large size plants. Rather than air, it can also operate with oxygen to facilitate

  2. H2-,He-and CO2-line broadening coefficients and pressure shifts for the HITRAN database

    NASA Astrophysics Data System (ADS)

    Wilzewski, Jonas; Gordon, Iouli E.; Rothman, Laurence S.

    2014-06-01

    To increase the potential of the HITRAN database in astronomy, experimental and theoretical line broadening coefficients and line shifts of molecules of planetary interest broadened by H2,He,and CO2 have been assembled from available peer-reviewed sources. Since H2 and He are major constituents in the atmospheres of gas giants, and CO2 predominates in atmospheres of some rocky planets with volcanic activity, these spectroscopic data are important for studying planetary atmospheres. The collected data were used to create semi-empirical models for complete data sets from the microwave to the UV part of the spectrum of the studied molecules. The presented work will help identify the need for further investigations of broadening and shifting of spectral lines.

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

    NASA Astrophysics Data System (ADS)

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

    1996-10-01

    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 4.2, 7, 10 and 15 kbar. Fluid compositions in equilibrium with brucite and periclase were reversed to closures of less than 2 mol% by measuring weight changes after drying of punctured Pt capsules. Brucite-periclase equilibrium in the binary system was redetermined using coarsely crystalline synthetic brucite and periclase to inhibit back-reaction in quenching. These data lead to a linear expression for the standard Gibbs free energy of the brucite dehydration reaction in the experimental temperature range: ΔG° (±120J)=73418 134.95 T(K). Using this function as a baseline, the experimental dehydration points in the system MgO-H2O-NaCl lead to a simple systematic relationship of high-temperature H2O activity in NaCl solution. At low pressure and low fluid densities near 2 kbar the H2O activity is closely approximated by its mole fraction. At pressures of 10 kbar and greater, with fluid densities approaching those of condensed H2O, the H2O activity becomes nearly equal to the square of its mole fraction. Isobaric halite saturation points terminating the univariant brucite-periclase curves were determined at each experimental pressure. The five temperature-composition points in the system NaCl-H2O are in close agreement with the halite saturation curves (liquidus curves) given by existing data from differential thermal analysis to 6 kbar. Solubility of MgO in the vapor phase near halite saturation is much less than one mole percent and could not have influenced our determinations. Activity concentration relations in the experimental P-T range may be retrieved for the binary

  4. DEVELOPMENT OF PRESSURIZED CIRCULATING FLUIDIZED BED PARTIAL GASIFICATION MODULE (PGM)

    SciTech Connect

    Archie Robertson

    2004-07-01

    Foster Wheeler Power Group, Inc. is working under US Department of Energy Contract No. DE-FC26-00NT40972 to develop a partial gasification module (PGM) that represents a critical element of several potential coal-fired Vision 21 plants. When utilized for electrical power generation, these plants will operate with efficiencies greater than 60% and produce near zero emissions of traditional stack gas pollutants. The new process partially gasifies coal at elevated pressure producing a coal-derived syngas and a char residue. The syngas can be used to fuel the most advanced power producing equipment such as solid oxide fuel cells or gas turbines, or processed to produce clean liquid fuels or chemicals for industrial users. The char residue is not wasted; it can also be used to generate electricity by fueling boilers that drive the most advanced ultra-supercritical pressure steam turbines. The amount of syngas and char produced by the PGM can be tailored to fit the production objectives of the overall plant, i.e., power generation, clean liquid fuel production, chemicals production, etc. Hence, PGM is a robust building bock that offers all the advantages of coal gasification but in a more user-friendly form; it is also fuel flexible in that it can use alternative fuels such as biomass, sewerage sludge, etc. Under this contract a series of pilot plant tests are being conducted to ascertain PGM performance with a variety of fuels. The performance and economics of a PGM based plant designed for the co-production of hydrogen and electricity will also be determined. This report describes the work performed during the April-June 30, 2004 time period.

  5. 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

  6. [Measurements of surface ocean carbon dioxide partial pressure during WOCE

    SciTech Connect

    Not Available

    1992-01-01

    This paper discusses the research progress of the second year of research under Measurement of Surface Ocean Carbon Dioxide Partial Pressure During WOCE'' and proposes to continue measurements of underway pCO[sub 2]. During most of the first year of this grant, our efforts to measure pCO[sub 2] on WOCE WHP legs were frustrated by ship problems. The R/V Knorr, which was originally scheduled to carry out the first work on WHP lines P19 and P16 in the southeastem Pacific during the 1990-91 austral summer, was delayed in the shipyard during her mid-life refit for more than a year. In the interim, the smaller R/V Thomas Washington, was pressed into service to carry out lower-latitude portions of WHP lines P16 and P17 during mid-1991 (TUNES Expedition). We installed and operated our underway chromatographic system on this expedition, even though space and manpower on this smaller vessel were limited and no one from our group would be aboard any of the 3 WHP expedition legs. The results for carbon dioxide and nitrous oxide are shown. A map of the cruise track is shown for each leg, marked with cumulative distance. Following each track is a figure showing the carbon dioxide and nitrous oxide results as a function of distance along this track. The results are plotted as dry-gas mole fractions (in ppm and ppb, respectively) in air and in gas equilibrated with surface seawater at a total pressure equal to the barometric pressure. The air data are plotted as a 10-point running mean, and appear as a roughly horizontal line. The seawater data are plotted as individual points, using a 5-point Gaussian smoother. Equal values Of xCO[sub 2] in air and surface seawater indicate air-sea equilibrium.

  7. DEVELOPMENT OF PRESSURIZED CIRCULATING FLUIDIZED BED PARTIAL GASIFICATION MODULE (PGM)

    SciTech Connect

    Unknown

    2001-07-10

    Foster Wheeler Development Corporation is working under DOE contract No. DE-FC26-00NT40972 to develop a partial gasification module (PGM) that represents a critical element of several potential coal-fired Vision 21 plants. When utilized for electrical power generation, these plants will operate with efficiencies greater than 60% while producing near zero emissions of traditional stack gas pollutants. The new process partially gasifies coal at elevated pressure producing a coal-derived syngas and a char residue. The syngas can be used to fuel the most advanced power producing equipment such as solid oxide fuel cells or gas turbines or processed to produce clean liquid fuels or chemicals for industrial users. The char residue is not wasted; it can also be used to generate electricity by fueling boilers that drive the most advanced ultra-supercritical pressure steam turbines. The unique aspect of the process is that it utilizes a pressurized circulating fluidized bed partial gasifier and does not attempt to consume the coal in a single step. To convert all the coal to syngas in a single step requires extremely high temperatures ({approx}2500 to 2800F) that melt and vaporize the coal and essentially drive all coal ash contaminants into the syngas. Since these contaminants can be corrosive to power generating equipment, the syngas must be cooled to near room temperature to enable a series of chemical processes to clean the syngas. Foster Wheeler's process operates at much lower temperatures that control/minimize the release of contaminants; this eliminates/minimizes the need for the expensive, complicated syngas heat exchangers and chemical cleanup systems typical of high temperature gasification. By performing the gasification in a circulating bed, a significant amount of syngas can still be produced despite the reduced temperature and the circulating bed allows easy scale up to large size plants. Rather than air, it can also operate with oxygen to facilitate

  8. REMOVAL OF H2S AND SO2 BY CaCO3-BASED SORBENTS AT HIGH PRESSURES

    SciTech Connect

    Prof. Stratis V. Sotirchos

    2000-09-01

    The mechanism of the removal of SO{sub 2} and H{sub 2}S by CaCO{sub 3}-based sorbents in pressurized fluidized-bed coal combustors (PFBC) and high pressure gasifiers was investigated in this project. Reactivity evolution experiments were carried out in thermogravimetric apparatuses both under simulated high pressure conditions and at high pressures. Experiments at high pressure were conducted in a high pressure thermogravimetric arrangement that was set up and developed under this project. Two calcitic solids of high calcium carbonate content (over 97%) were employed in the experiments: a fine-grained distributed by Greer Limestone Co. (Greer Limestone) and a solid supplied in the form of large calcitic crystals (Iceland Spar). The decision to work with these solids was mainly based on the fact that they have been employed in several past studies of sulfation, sulfidation, and calcination in our laboratory, and therefore, a large volume of data on their performance under different conditions was available for comparison purposes. In addition to the experimental studies, work was also done on the development of rigorous mathematical models for the description of the occurrence of simultaneous processes (e.g., calcination and sulfation and carbonation and sulfation) in the interior of porous solids and for the simulation of the evolution of the pore structure of porous solids that undergo chemical transformation in their interior.

  9. Pressure-Induced Amorphization of Small Pore Zeolites—the Role of Cation-H2O Topology and Anti-glass Formation

    PubMed Central

    Chan Hwang, Gil; Joo Shin, Tae; Blom, Douglas A.; Vogt, Thomas; Lee, Yongjae

    2015-01-01

    Systematic studies of pressure-induced amorphization of natrolites (PIA) containing monovalent extra-framework cations (EFC) Li+, Na+, K+, Rb+, Cs+ allow us to assess the role of two different EFC-H2O configurations within the pores of a zeolite: one arrangement has H2O molecules (NATI) and the other the EFC (NATII) in closer proximity to the aluminosilicate framework. We show that NATI materials have a lower onset pressure of PIA than the NATII materials containing Rb and Cs as EFC. The onset pressure of amorphization (PA) of NATII materials increases linearly with the size of the EFC, whereas their initial bulk moduli (P1 phase) decrease linearly. Only Cs- and Rb-NAT reveal a phase separation into a dense form (P2 phase) under pressure. High-Angle Annular Dark Field Scanning Transmission Electron Microscopy (HAADF-STEM) imaging shows that after recovery from pressures near 25 and 20 GPa long-range ordered Rb-Rb and Cs-Cs correlations continue to be present over length scales up to 100 nm while short-range ordering of the aluminosilicate framework is significantly reduced—this opens a new way to form anti-glass structures. PMID:26455345

  10. The role of hydrogen partial pressure on the annealing of copper substrates for graphene CVD synthesis

    NASA Astrophysics Data System (ADS)

    Ramos, Welyson T. S.; Cunha, Thiago H. R.; Barcelos, Ingrid D.; Miquita, Douglas R.; Ferrari, Gustavo A.; de Oliveira, Sergio; Seara, Luciana M.; Silva Neto, Eliel G.; Ferlauto, Andre S.; Lacerda, Rodrigo G.

    2016-04-01

    The influence of hydrogen utilized during the thermal treatment of copper substrates on the subsequent graphene growth is investigated. It is known that various parameters such as nature of the carbon precursor, temperature and pressure strongly affect the quality of the graphene grown by chemical vapor deposition. Another important parameter is the hydrogen partial pressure adjusted during the growth stage and in the pre-growth annealing of the substrate. In attempts to elucidate the role of hydrogen assisted thermal annealing on the copper substrate morphology and on the subsequent graphene growth, we subjected Cu foils to thermal annealing under H2 atmosphere at different pressures. The copper surface was characterized by scanning electronic microscopy (SEM) and atomic force microscopy whereas graphene films and grains were characterized by Raman spectroscopy and SEM. Our findings suggest that hydrogen not only affect the Cu surface but also diffuses into the substrate, being stored in the bulk material during the thermal treatment of the substrate. The release of hydrogen species in the subsequent stages of growth can result in damage to the graphene layer or induce the nucleation of additional layers depending on the growth and pre-growth conditions. Therefore, the use of hydrogen during the annealing of ‘low purity Cu foils’ should be carefully planned in order to obtain high quality graphene via LPCVD.

  11. Low pressure UV/H2O2 treatment for the degradation of the pesticides metaldehyde, clopyralid and mecoprop - Kinetics and reaction product formation.

    PubMed

    Semitsoglou-Tsiapou, Sofia; Templeton, Michael R; Graham, Nigel J D; Hernández Leal, Lucía; Martijn, Bram J; Royce, Alan; Kruithof, Joop C

    2016-03-15

    The degradation kinetics of three pesticides - metaldehyde, clopyralid and mecoprop - by ultraviolet photolysis and hydroxyl radical oxidation by low pressure ultraviolet hydrogen peroxide (LP-UV/H2O2) advanced oxidation was determined. Mecoprop was susceptible to both LP-UV photolysis and hydroxyl radical oxidation, and exhibited the fastest degradation kinetics, achieving 99.6% (2.4-log) degradation with a UV fluence of 800 mJ/cm(2) and 5 mg/L hydrogen peroxide. Metaldehyde was poorly degraded by LP-UV photolysis while 97.7% (1.6-log) degradation was achieved with LP-UV/H2O2 treatment at the maximum tested UV fluence of 1000 mJ/cm(2) and 15 mg/L hydrogen peroxide. Clopyralid was hardly susceptible to LP-UV photolysis and exhibited the lowest degradation by LP-UV/H2O2 among the three pesticides. The second-order reaction rate constants for the reactions between the pesticides and OH-radicals were calculated applying a kinetic model for LP-UV/H2O2 treatment to be 3.6 × 10(8), 2.0 × 10(8) and 1.1 × 10(9) M(-1) s(-1) for metaldehyde, clopyralid and mecoprop, respectively. The main LP-UV photolysis reaction product from mecoprop was 2-(4-hydroxy-2-methylphenoxy) propanoic acid, while photo-oxidation by LP-UV/H2O2 treatment formed several oxidation products. The photo-oxidation of clopyralid involved either hydroxylation or dechlorination of the ring, while metaldehyde underwent hydroxylation and produced acetic acid as a major end product. Based on the findings, degradation pathways for the three pesticides by LP-UV/H2O2 treatment were proposed.

  12. Measurements of Surface Ocean Carbon Dioxide Partial Pressure During WOCE

    SciTech Connect

    Weiss, R.F.

    1998-10-15

    All of the technical goals of the World Ocean Circulation Experiment (WOCE) field program which were supported under the Department of Energy research grant ''Measurements of Surface Ocean Carbon Dioxide Partial Pressure During WOCE'' (DE-FG03-90ER60981) have been met. This has included the measurement of the partial pressures of carbon dioxide (C0{sub 2}) and nitrous oxide (N{sub 2}O) in both the surface ocean and the atmosphere on 24 separate shipboard expedition legs of the WOCE Hydrographic Programme. These measurements were made in the Pacific, Indian and Atlantic Oceans over a six-and-a-half year period, and over a distance of nearly 200,000 kilometers of ship track. The total number of measurements, including ocean measurements, air measurements and standard gas measurements, is about 136,000 for each gas, or about 34,000 measurements of each gas in the ocean and in the air. This global survey effort is directed at obtaining a better understanding of the role of the oceans in the global atmospheric budgets of two important natural and anthropogenic modulators of climate through the ''greenhouse effect'', CO{sub 2} and N{sub 2}O, and an important natural and anthropogenic modulator of the Earth's protective ozone layer through catalytic processes in the stratosphere, N{sub 2}O. For both of these compounds, the oceans play a major role in their global budgets. In the case of CO{sub 2}, roughly half of the anthropogenic production through the combustion of fossil fuels has been absorbed by the world's oceans. In the case of N{sub 2}O, roughly a third of the natural flux to the atmosphere originates in the oceans. As the interpretation of the variability in the oceanic distributions of these compounds improves, measurements such as those supported by this research project are playing an increasingly important role in improving our understanding of natural and anthropogenic influences on climate and ozone. (B204)

  13. Suppression of X-ray-induced dissociation of H2O molecules in dense ice under pressure

    PubMed Central

    Fukui, Hiroshi; Hiraoka, Nozomu; Hirao, Naohisa; Aoki, Katsutoshi; Akahama, Yuichi

    2016-01-01

    We investigated molecular dissociation induced by 10-keV X-ray irradiation in dense ice at pressures up to 40 GPa at 300 K. The dissociation yield estimated from the oxygen K-edge X-ray Raman spectra, showed that the molecular dissociation was enhanced up to 14 GPa and gradually suppressed on further compression to 40 GPa. The molecular dissociation was detected for a rather narrow pressure span of 2–40 GPa by the X-ray spectroscopy. The pressure variation of the dissociation yield was similar to that observed in the electric conductivity of ice VII and likely interpreted in terms of proton mobility. PMID:27221010

  14. Kinetic modelling of NH3 production in N2–H2 non-equilibrium atmospheric-pressure plasma catalysis

    NASA Astrophysics Data System (ADS)

    Hong, Jungmi; Pancheshnyi, Sergey; Tam, Eugene; Lowke, John J.; Prawer, Steven; Murphy, Anthony B.

    2017-04-01

    Detailed plasma kinetics modelling is presented of a low electron energy N2–H2 atmospheric-pressure discharge for ammonia synthesis. The model considers both electron and vibrational kinetics, including excited N2(X, ν) and H2(X, ν) species, and surface reactions such as those occurring by the Eley–Rideal and Langmuir–Hinshelwood mechanisms and dissociative adsorption of molecules. The predictions of the model are compared to the measured NH3 concentration produced in a packed-bed dielectric barrier discharge reactor as a function of process parameters such as input gas composition and applied voltage. Unlike typical low-pressure plasma processes, under the plasma conditions considered here (reduced electric field E/N in the range 30–50 Td, electron density of the order 108 cm‑3), the influence of ions is not significant. Instead, the reactions between radicals and vibrationally-excited molecules are more important. The active species in surface reactions, such as surface-adsorbed atomic nitrogen N(s) or hydrogen H(s), are found to be predominantly generated through the dissociative adsorption of molecules, in contrast to previously proposed mechanisms for plasma catalysis under low-pressure, high-E/N conditions. It is found that NH radicals play an important role at the early stages of the NH3-generation process, NH in turn is produced from N and H2(ν). Electron kinetics is shown to play a critical role in the molecular dissociation and vibrational excitation reactions that produce these precursors. It is further found that surface-adsorbed atomic hydrogen H(s) takes a leading role in the formation of NH3, which is another significant difference from the mechanisms in conventional thermo-chemical processes and low-pressure plasmas. The applied voltage, the gas temperature, the N2:H2 ratio in the input gas mixture and the reactivity of the surface material are all found to influence the ammonia production. The calculated results reproduce the observed

  15. Kinetic of the OH-radical in high pressure plasmas of N_2/H_2O/hydrocarbons mixtures

    NASA Astrophysics Data System (ADS)

    Baravian, G.; Fresnet, F.; Magne, L.; Pasquiers, S.; Postel, C.; Puech, V.; Rousseau, A.

    2001-10-01

    Kinetic of the OH-radical has been studied in homogeneous plasmas achieved in a photo-triggered discharge device, in N_2/H_2O with C_2H4 or C_3H_6, at 460 mbar with 1.2 concentration and a deposited energy in the plasma equal to 92 J/l. Hydrocarbon concentration ranged from 50 ppm up to 1000 ppm. Using the same technique as for NO kinetic studies ( F. Fresnet, G. Baravian, L. Magne, S. Pasquiers, C. Postel, V. Puech, A. Rousseau, Appl. Phys. Lett., 77 (2000) 4118.), a time resolved LIF diagnostic has been performed to measure the OH-radical density up to 180 µs after the short current pulse excitation, 50 ns. At fixed deposited energy, the LIF signal rapidly decreases when hydrocarbon concentration increases. Measurements have been compared to predictions of a self-consistent 0D-model which takes into account a detailed kinetic scheme, including oxidation reactions of hydrocarbons by the radical which are important processes in flue gas non-thermal plasma treatment. Results are discussed.

  16. Diagnostic system for measuring temperature, pressure, CO2 concentration and H2O concentration in a fluid stream

    DOEpatents

    Partridge, Jr., William P.; Jatana, Gurneesh Singh; Yoo, Ji-Hyung; Parks, II, James E.

    2017-01-10

    A diagnostic system for measuring temperature, pressure, CO.sub.2 concentration and H.sub.2O concentration in a fluid stream is described. The system may include one or more probes that sample the fluid stream spatially, temporally and over ranges of pressure and temperature. Laser light sources are directed down pitch optical cables, through a lens and to a mirror, where the light sources are reflected back, through the lens to catch optical cables. The light travels through the catch optical cables to detectors, which provide electrical signals to a processer. The processer utilizes the signals to calculate CO.sub.2 concentration based on the temperatures derived from H.sub.2O vapor concentration. A probe for sampling CO.sub.2 and H.sub.2O vapor concentrations is also disclosed. Various mechanical features interact together to ensure the pitch and catch optical cables are properly aligned with the lens during assembly and use.

  17. Tungsten metallization onto InP prepared by rapid thermal low-pressure chemical vapor deposition of WF6 and H2

    NASA Astrophysics Data System (ADS)

    Katz, A.; Feingold, A.; El-Roy, A.; Pearton, S. J.; Lane, E.; Nakahara, S.; Geva, M.

    1992-09-01

    Tungsten (W) films were deposited onto InP in a cold wall, rapid thermal low-pressure chemical vapor deposition (RT-LPCVD) reactor, using a tungsten hexafluoride (WF6) gas reduced by hydrogen (H2). W films of thickness 50-450 nm were deposited in the temperature range of 350-550 °C, pressure range of 0.5-4.5 Torr, and deposition rates up to 4 nm/s with an apparent activation energy of about 1.12 eV. The film stress varied depending on the deposition pressure, from low compressive (deposition at 0.5 Torr) to moderate tensile (deposition at about 4.5 Torr). Post-deposition sintering of the W films at temperatures up to 600 °C led to reduction of the resistivity with a minimum value of about 55 μΩ cm as a result of heating at 500 °C.

  18. 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.

  19. New Raman measurements for H2O ice VII in the range of 300 cm-1 to 4000 cm-1 at pressures up to 120 GPa

    NASA Astrophysics Data System (ADS)

    Zha, Chang-Sheng; Tse, John S.; Bassett, William A.

    2016-09-01

    Raman spectroscopic measurements for H2O ice VII have been conducted to 120 GPa at 300 K in the spectroscopic range of 300-4000 cm-1. Both moissanite and diamond anvils were used for the experiments. This overcomes the problems of overlapping spectra between the diamond anvil and sample, which had prevented the observation of the stretching modes at pressures higher than ˜23 GPa in all previous measurements. The new results reveal many bands which have not been reported before. The pressure dependences of the Raman modes show anomalous changes at 13-15, ˜27, ˜44, ˜60, and 90 GPa, implying possible structural changes at these pressures. The new results demonstrate that the predicted symmetric hydrogen bond phase X transition does not occur below 120 GPa.

  20. Effect of water vapor on plasma morphology, OH and H2O2 production in He and Ar atmospheric pressure dielectric barrier discharges

    NASA Astrophysics Data System (ADS)

    Du, Yanjun; Nayak, Gaurav; Oinuma, Gaku; Peng, Zhimin; Bruggeman, Peter J.

    2017-04-01

    Although atmospheric pressure dielectric barrier discharges (DBDs) have a long history, the effects of water vapor on the discharge morphology and kinetics have not been studied intensively. We report a simultaneous investigation of discharge morphology, OH and H2O2 production in Ar and He DBDs operated at different water vapor concentrations and powers. The combined study allows us to assess the impact of the discharge morphology and power on the concentration dependence of the OH and H2O2 production. The morphology of the discharge is investigated by ICCD images and current–voltage waveforms. These diagnostics are complemented by broadband absorption and a colorimetric method to measure the gas temperature and the OH and H2O2 concentrations. The number of filaments in Ar DBD increases with increasing water concentration and power. The surface discharge part of the micro-discharge also reduces with increasing water concentration most likely due to a change in surface conductivity of the dielectric with changing water concentration. The OH density in the case of Ar is approximately double the OH density in He for similar power and water admixture. In contrast to the root square dependence of the OH density on the water concentration in He similar to diffuse RF discharges, the OH density in Ar increases for small water concentrations followed by a saturation and reduces for higher water concentrations. This dependence of OH density on water concentration is found to correlate with changes in discharge morphology. An analytical balance of the production and destruction mechanism of H2O2 is shown to be able to reproduce the ratio of the measured OH and H2O2 density for realistic values of electron densities.

  1. Anatoxin-a degradation by Advanced Oxidation Processes: vacuum-UV at 172 nm, photolysis using medium pressure UV and UV/H(2)O(2).

    PubMed

    Afzal, Atefeh; Oppenländer, Thomas; Bolton, James R; El-Din, Mohamed Gamal

    2010-01-01

    Two Advanced Oxidation Processes, namely vacuum-ultraviolet (VUV) photolysis at 172nm and ultraviolet/hydrogen peroxide (UV/H(2)O(2)) were investigated for the degradation of anatoxin-a in aqueous solutions. Solutions of anatoxin-a-fumarate were treated with VUV light at 172nm with a UV dose of 200 mJ/cm(2), where fumaric acid served as a reference compound for a competition kinetics analysis. The second-order rate constant for the reaction between anatoxin-a and the hydroxyl radical was found to be (5.2+/-0.3)x10(9)M(-1) s(-1) and was independent of pH, temperature, and initial concentration of anatoxin-a. The direct photolysis of anatoxin-a using a medium pressure (MP) UV lamp was also investigated, in which case a UV dose of 1285 mJ/cm(2) was required to degrade anatoxin-a by 88% and 50% at concentrations of 0.6mg/L and 1.8mg/L of toxin, respectively. Treatment of anatoxin-a with a low pressure (LP) UV lamp in the presence of 30mg/L of H(2)O(2) was examined, where it was found that more than 70% of toxin could be degraded at a UV dose of 200 mJ/cm(2). The degradation arises from the oxidation of the toxin by hydroxyl radicals. The addition of H(2)O(2) clearly enhanced the degradation of anatoxin-a, up to a concentration of 40mg/L, after which addition of more H(2)O(2) had little effect on the degradation kinetics of anatoxin-a. The effect of background constituents in the water on the degradation of anatoxin-a was also investigated using natural and synthetically produced model waters.

  2. ``H2 sponge'': pressure as a means for reversible high-capacity hydrogen storage in nanoporous Ca-intercalated covalent organic frameworks

    NASA Astrophysics Data System (ADS)

    Gao, Fei; Sun, Jia Tao; Meng, Sheng

    2015-03-01

    We explore the potential and advantages of Ca-intercalated covalent organic framework-1 (CaCOF-1) as a 3-dimensional (3D) layered material for reversible hydrogen storage. Density functional theory calculations show that by varying the interlayer distance of CaCOF-1, a series of metastable structures can be achieved with the interlayer distance falling in the range of 4.3-4.8 Å. When four hydrogen molecules are adsorbed on each Ca, a high hydrogen uptake of 4.54 wt% can be produced, with the binding energy falling in the ideal range of 0.2-0.6 eV per H2. While H2 absorption is a spontaneous process under H2 rich conditions, tuning the interlayer distance by reasonable external pressure could compress CaCOF-1 to release all of the hydrogen molecules and restore the material to its original state for recyclable use. This provides a new method for gradual, controllable extraction of hydrogen molecules in covalent organic frameworks, satisfying the practical demand for reversible hydrogen storage at ambient temperatures.We explore the potential and advantages of Ca-intercalated covalent organic framework-1 (CaCOF-1) as a 3-dimensional (3D) layered material for reversible hydrogen storage. Density functional theory calculations show that by varying the interlayer distance of CaCOF-1, a series of metastable structures can be achieved with the interlayer distance falling in the range of 4.3-4.8 Å. When four hydrogen molecules are adsorbed on each Ca, a high hydrogen uptake of 4.54 wt% can be produced, with the binding energy falling in the ideal range of 0.2-0.6 eV per H2. While H2 absorption is a spontaneous process under H2 rich conditions, tuning the interlayer distance by reasonable external pressure could compress CaCOF-1 to release all of the hydrogen molecules and restore the material to its original state for recyclable use. This provides a new method for gradual, controllable extraction of hydrogen molecules in covalent organic frameworks, satisfying the

  3. Oxygen modulates growth of human cells at physiologic partial pressures

    PubMed Central

    1984-01-01

    We have examined the growth of human diploid fibroblasts (WI-38 and IMR90) as a function of initial seeding density and oxygen tension. Cells at young and mid-passage levels were subcultivated in Dulbecco's modified Eagle's medium with 10% fetal bovine serum at 0.005, 0.01, 0.03, 0.1, 0.3, 1, and 2 X 10(4) cells/cm2. Flasks were equilibrated before and after seeding with 1 of 10 gas mixtures containing the desired oxygen tension (9-591 mm Hg) and placed in incubators that measure and maintain a preset oxygen tension. The partial pressure of oxygen (PO2) in media of all flasks was determined at harvest. Cells were shielded from light of wavelength less than 500 nm. Cell growth varied inversely with oxygen tension and seeding density. At 50 cells/cm2, growth was maximal at PO2 9 and 16 mm Hg. Growth was progressively inhibited as the oxygen tension was increased. The population doubling increase at 14 d was 8.6 for PO2 9 and 16 mm Hg, 5.8 for PO2 42 mm Hg, 3.8 for PO2 78 mm Hg, 3.8 for PO2 104 mm Hg, and 3 for PO2 138 mm Hg. As the seeding density was increased, the differences in growth at PO2 less than 140 mm Hg were progressively minimized, such that at seeding densities of 10(4) cells/cm2 there was little difference in the rate of exponential growth or the final saturation density of cells cultivated between PO2 9 and 96 mm Hg. At all seeding densities tested, growth was progressively inhibited when the PO2 was increased greater than 140 mm Hg. The seeding density dependence of oxygen's influence on cellular growth is not explained by oxygen consumption of higher density cultures. Oxygen acts directly on the cells and not by destroying some essential medium component. We have found that oxygen regulates the growth of human cells under pressures of oxygen physiologic to humans, and that oxygen toxicity contributes to the seeding density dependence of cellular growth commonly seen in cell culture. PMID:6736869

  4. A New Parameterization of H2SO4/H2O Aerosol Composition: Atmospheric Implications

    NASA Technical Reports Server (NTRS)

    Tabazadeh, Azadeh; Toon, Owen B.; Clegg, Simon L.; Hamill, Patrick

    1997-01-01

    Recent results from a thermodynamic model of aqueous sulfuric acid are used to derive a new parameterization for the variation of sulfuric acid aerosol composition with temperature and relative humidity. This formulation is valid for relative humidities above 1 % in the temperature range of 185 to 260 K. An expression for calculating the vapor pressure of supercooled liquid water, consistent with the sulfuric acid model, is also presented. We show that the Steele and Hamill [1981] formulation underestimates the water partial pressure over aqueous H2SOI solutions by up to 12% at low temperatures. This difference results in a corresponding underestimate of the H2SO4 concentration in the aerosol by about 6 % of the weight percent at approximately 190 K. In addition, the relation commonly used for estimating the vapor pressure of H2O over supercooled liquid water differs by up to 10 % from our derived expression. The combined error can result in a 20 % underestimation of water activity over a H2SO4 solution droplet in the stratosphere, which has implications for the parameterization of heterogeneous reaction rates in stratospheric sulfuric acid aerosols. The influence of aerosol composition on the rate of homogeneous ice nucleation from a H2SO4 solution droplet is also discussed. This parameterization can also be used for homogeneous gas phase nucleation calculations of H2SO4 solution droplets under various environmental conditions such as in aircraft exhaust or in volcanic plumes.

  5. 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.

  6. The sticking probability for H 2 in presence of CO on some transition metals at a hydrogen pressure of 1 bar

    NASA Astrophysics Data System (ADS)

    Johansson, M.; Lytken, O.; Chorkendorff, I.

    2008-05-01

    The sticking probability for H2 on Ni, Co, Cu, Rh, Ru, Pd, Ir and Pt metal films supported on graphite has been investigated in a gas mixture consisting of 10 ppm carbon monoxide in hydrogen at a total pressure of 1 bar in the temperature range 40-200 °C. Carbon monoxide inhibits the sticking probability significantly for all the metals, even at 200 °C. In the presence of 10 ppm CO, the sticking probability increases in the order Ir, Pt, Ni, Co, Pd, Rh, Ru, whereas for Cu, it is below the detection limit of the measurement, even in pure H2. The sticking probability for H2 in presence of CO relative to its value in pure hydrogen is largest for Pd and smallest for Pt and Ir. The high sensitivity to CO seen for Ir and Pt is explained by the fact that the difference in desorption energy for H and CO is largest for those metals.

  7. Self-diffusion of protons in H2O ice VII at high pressures: Anomaly around 10 GPa

    NASA Astrophysics Data System (ADS)

    Noguchi, Naoki; Okuchi, Takuo

    2016-06-01

    The self-diffusion of ice VII in the pressure range of 5.5-17 GPa and temperature range of 400-425 K was studied using micro Raman spectroscopy and a diamond anvil cell. The diffusion was monitored by observing the distribution of isotope tracers: D2O and H218O. The diffusion coefficient of hydrogen reached a maximum value around 10 GPa. It was two orders of magnitude greater at 10 GPa than at 6 GPa. Hydrogen diffusion was much faster than oxygen diffusion, which indicates that protonic diffusion is the dominant mechanism for the diffusion of hydrogen in ice VII. This mechanism is in remarkable contrast to the self-diffusion in ice Ih that is dominated by an interstitial mechanism for the whole water molecule. An anomaly around 10 GPa in ice VII indicates that the rate-determining process for the proton diffusion changes from the diffusion of ionic defects to the diffusion of rotational defects, which was suggested by proton conductivity measurements and molecular dynamics simulations.

  8. Key insights into the reacting kinetics of atmospheric pressure plasmas using He +N2 /O2 /CO2 /H2 O/Air mixtures

    NASA Astrophysics Data System (ADS)

    Murakami, Tomoyuki

    2015-09-01

    A zero dimensional kinetic chemistry computational modeling to identify the important collisional mechanisms and the dominant species in atmospheric pressure plasmas has been developed. This modeling provides an enhanced capability to tailor wide variety of reactive intermediates/species in atmospheric pressure plasmas using He +N2 /O2 /CO2 /H2 O/Air mixtures. The influence of the gas constituent, the gas temperature and the excitation frequency (kHz-, RF-, Pulsed-working) on the complex reacting chemical kinetics is clarified. This work also focuses on the benchmarking between the predictive outputs of this computer-based simulations and the diverse experimental diagnostics with particular emphasis on reactive oxygen/nitrogen intermediates/species. This work was partly supported by KAKENHI Grant Number 24561054.

  9. 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

  10. Oxygen Partial Pressure and Oxygen Concentration Flammability: Can They Be Correlated?

    NASA Technical Reports Server (NTRS)

    Harper, Susana A.; Juarez, Alfredo; Perez, Horacio, III; Hirsch, David B.; Beeson, Harold D.

    2016-01-01

    NASA possesses a large quantity of flammability data performed in ISS airlock (30% Oxygen 526mmHg) and ISS cabin (24.1% Oxygen 760 mmHg) conditions. As new programs develop, other oxygen and pressure conditions emerge. In an effort to apply existing data, the question arises: Do equivalent oxygen partial pressures perform similarly with respect to flammability? This paper evaluates how material flammability performance is impacted from both the Maximum Oxygen Concentration (MOC) and Maximum Total Pressures (MTP) perspectives. From these studies, oxygen partial pressures can be compared for both the MOC and MTP methods to determine the role of partial pressure in material flammability. This evaluation also assesses the influence of other variables on flammability performance. The findings presented in this paper suggest flammability is more dependent on oxygen concentration than equivalent partial pressure.

  11. Comparative ecology of H2 cycling in sedimentary and phototrophic ecosystems

    NASA Technical Reports Server (NTRS)

    Hoehler, Tori M.; Albert, Daniel B.; Alperin, Marc J.; Bebout, Brad M.; Martens, Christopher S.; Des Marais, David J.

    2002-01-01

    The simple biochemistry of H2 is critical to a large number of microbial processes, affecting the interaction of organisms with each other and with the environment. The sensitivity of each of these processes to H2 can be described collectively, through the quantitative language of thermodynamics. A necessary prerequisite is to understand the factors that, in turn, control H2 partial pressures. These factors are assessed for two distinctly different ecosystems. In anoxic sediments from Cape Lookout Bight (North Carolina, USA), H2 partial pressures are strictly maintained at low, steady-state levels by H2-consuming organisms, in a fashion that can be quantitatively predicted by simple thermodynamic calculations. In phototrophic microbial mats from Baja California (Mexico), H2 partial pressures are controlled by the activity of light-sensitive H2-producing organisms, and consequently fluctuate over orders of magnitude on a daily basis. The differences in H2 cycling can subsequently impact any of the H2-sensitive microbial processes in these systems. In one example, methanogenesis in Cape Lookout Bight sediments is completely suppressed through the efficient consumption of H2 by sulfate-reducing bacteria; in contrast, elevated levels of H2 prevail in the producer-controlled phototrophic system, and methanogenesis occurs readily in the presence of 40 mM sulfate.

  12. H2, He, and CO2 line-broadening coefficients, pressure shifts and temperature-dependence exponents for the HITRAN database. Part 1: SO2, NH3, HF, HCl, OCS and C2H2

    NASA Astrophysics Data System (ADS)

    Wilzewski, Jonas S.; Gordon, Iouli E.; Kochanov, Roman V.; Hill, Christian; Rothman, Laurence S.

    2016-01-01

    To increase the potential for use of the HITRAN database in astronomy, experimental and theoretical line-broadening coefficients, line shifts and temperature-dependence exponents of molecules of planetary interest broadened by H2, He, and CO2 have been assembled from available peer-reviewed sources. The collected data were used to create semi-empirical models so that every HITRAN line of the studied molecules has corresponding parameters. Since H2 and He are major constituents in the atmospheres of gas giants, and CO2 predominates in atmospheres of some rocky planets with volcanic activity, these spectroscopic data are important for remote sensing studies of planetary atmospheres. In this paper we make the first step in assembling complete sets of these parameters, thereby creating datasets for SO2, NH3, HF, HCl, OCS and C2H2.

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

    SciTech Connect

    Veirs, Douglas K.

    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.

  14. New developments in the theory of pressure-broadening and pressure-shifting of spectral lines of H2O: the complex Robert-Bonamy formalism.

    NASA Astrophysics Data System (ADS)

    Gamache, R. R.; Lynch, R.; Neshyba, S. P.

    1998-05-01

    Calculations of the halfwidth and line shift of water vapor perturbed by N2, O2, CO2 and H2 based on a complex implementation of the formalism of Robert and Bonamy are made. The potentials employ the leading terms of the electrostatic potential, a Lennard-Jones (6-12) atom-atom potential, and the induction and dispersion components of the isotropic potential. The dynamics of the collisions are correct to second order in time. The results are compared with measurements and very good agreement is observed for both halfwidths and line shifts. A new feature in this approach is that the real and imaginary components of the S matrix affect both the halfwidth and the line shift. It is shown here that the imaginary parts of the S matrix strongly affect the calculated halfwidths for some of the systems considered.

  15. Rapid thermal low-pressure chemical vapour deposition of tungsten films onto InP using WF6 and H2

    NASA Astrophysics Data System (ADS)

    Katz, A.; Feingold, A.; El-Roy, A.; Pearton, S. J.; Lane, E.; Nakahara, S.; Geva, M.

    1992-11-01

    Tungsten (W) films were deposited onto InP in a cold wall, rapid thermal low-pressure chemical vapour deposition (RT-LPCVD) reactor, from a tungsten hexafluoride (WF6) gas reduced by hydrogen (H2). W films of thickness 50-450 nm were deposited in the temperature range 350-550 degrees C, pressure range 0.5-4.5 Torr at deposition rates up to 4 nm s-1 with an apparent activation energy of about 1.12 eV. The film stress varied depending upon the deposition pressure, from low compressive for deposition at 0.5 Torr to moderate tensile for deposition at about 4.5 Torr. The films were aged at temperatures as high as 300 degrees C for about 800 h and exhibited an excellent mechanical stability. Post-deposition sintering of the W films at temperatures up to 600 degrees C led to reduction of the resistivity with a minimum value of about 55 mu Omega cm as a result of heating at 500 degrees C. Conditions for both selective and blanket deposition were defined, and a dry etching process for further geometrical definitions of the films was developed, providing etch rates of 40-50 nm min-1. This report reflects the first attempt to deposit W films onto III-V semiconductor at a very high rate by means of RT-LPCVD.

  16. 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.

  17. 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.

  18. Experimental data on the effect of pressure on the volatiles partitioning (Cl, F, H2O) in fluid-magmatic systems

    NASA Astrophysics Data System (ADS)

    Chevychelov, Vitaly

    2014-05-01

    Fluids, separating from the silicate melt with decreasing pressure during magma ascent, will contain all smaller amounts of chlorine and presumably of fluorine due to repartitioning of these halogens into the melt. Effect of pressure on the partitioning of F is expressed more weakly compared with Cl. Experimental studies on the solubility (1N NaCl +0.1N HCl) chloride acidoulous fluid in model melts of granodioritic, granitic and leucogranitic compositions were carried out at T =900-1000oC and P =500 and 100 MPa (Chevychelov, Chevychelova, 1997). The mass ratio of fluid / melt was (2-3): 1. The chlorine content after the experiments was defined only in granitoid melts (glasses). It is shown that, when the pressure is reduced from 500 to 100 MPa, the chlorine content in the silicate melt increases 3-2.5 times (from 0.3 wt.% to 0.9-0.8 wt.% in granodioritic melt, from 0.2% to 0.6-0.5% in granitic melt and from 0.2% to 0.5-0.4% in the leucogranitic melt). At these conditions the content of H2O in granitoid melts decreases approximately 2.5 times from 9-11 wt.% to 4 wt.% (Johannes, Holtz, 1996). Another series of experiments on the solubility of (HCl + HF) fluids of various concentration (from 1N to 16N) in phonolitic melt was held at T =1000°C and P =400, 200 and 50 MPa (Chevychelov, Mukhanova, 2008). The mass ratio of fluid / melt was 0.15:1. The chlorine and fluorine contents in the melt (glass) after the experiments were determined by microprobe analysis. With decreasing pressure the water content in the silicate melts decreased from 8-9 wt.% at 400 MPa to about 6 wt.% at 200 MPa and up to 2-3 wt.% at 50 MPa (Behrens et al., 2009). The Cl, F and H2O contents in the fluid coexisting with phonolitic melt were calculated using the mass balance method. It is shown that with decreasing pressure the chlorine content in phonolitic melt increases (from 0.1 wt.% to 0.35 wt.% at 1N HCl), and the chlorine content in the fluid decreases (from 8-9 wt.% to 1.5 wt.%). With

  19. Partial Pressures of Te2 and Thermodynamic Properties of Ga-Te System

    NASA Technical Reports Server (NTRS)

    Su, Ching-Hua; Curreri, Peter A. (Technical Monitor)

    2001-01-01

    The partial pressures of Te2 in equilibrium with Ga(1-x)Te(x) samples were measured by optical absorption technique from 450 to 1100 C for compositions, x, between 0.333 and 0.612. To establish the relationship between the partial pressure of Te, and the measured optical absorbance, the calibration runs of a pure Te sample were also conducted to determine the Beer's Law constants. The partial pressures of Te2 in equilibrium with the GaTe(s) and Ga2Te3(s)compounds, or the so-called three-phase curves, were established. These partial pressure data imply the existence of the Ga3Te4(s) compound. From the partial pressures of Te2 over the Ga-Te melts, partial molar enthalpy and entropy of mixing for Te were derived and they agree reasonable well with the published data. The activities of Te in the Ga-Te melts were also derived from the measured partial pressures of Te2. These data agree well with most of the previous results. The possible reason for the high activity of Te measured for x less than 0.60 is discussed.

  20. Frequency shifts of vibrational and rotational states of dilute H2, D2, and HD impurities in solid Ar under pressure

    NASA Astrophysics Data System (ADS)

    Silvi, B.; Chandrasekharan, V.; Chergui, M.; Etters, R. D.

    1986-02-01

    The frequency shifts of the vibrational and rotational transitions of H2, D2, and HD molecules trapped in solid Ar are calculated at zero temperature and at pressures 0<=P<=373 kbar. It is found that the pure vibrational and rotational-vibrational transition frequencies are strongly red-shifted in the solid at P=0, compared to gas-phase values, and the agreement with Raman scattering measurements is generally good. The calculated pure rotational transitions also show a small red shift at P=0 in the solid and are in generally good agreement with the measurements of Jodl and Bier, but less so with those of Prochaska and Andrews, who, except for D2(Ar), measure small blue shifts. The calculated local-mode frequencies of the impurity molecules in the solid at P=0 are also in good agreement with experiment, especially when thermal corrections are considered. With increasing pressure all transition frequencies and the local-mode frequencies are strongly blue-shifted with respect to P=0 solid values.

  1. A Priori Analysis of Subgrid Mass Flux Vectors from Massively Parallel Direct Numerical Simulations of High Pressure H2/O2 Reacting Shear Layers

    NASA Astrophysics Data System (ADS)

    Foster, Justin; Miller, Richard

    2011-11-01

    Direct Numerical Simulations (DNS) are conducted for temporally developing reacting H2/O2 shear layers at an ambient pressure of 100atm. The compressible form of the governing equations are coupled with the Peng Robinson real gas equation of state and are solved using eighth order central finite differences and fourth order Runge Kutta time integration with resolutions up to ~3/4 billion grid points. The formulation includes a detailed pressure dependent kinetics mechanism having 8 species and 19 steps, detailed property models, and generalized forms of the multicomponent heat and mass diffusion vectors derived from nonequilibrium thermodynamics and fluctuation theory. The DNS is performed over a range of Reynolds numbers up to 4500 based on the free stream velocity difference and initial vorticity thickness. The results are then analyzed in an a priori manner to illustrate the role of the subgrid mass flux vector within the filtered form of the governing equations relevant to Large Eddy Simulations. The subgrid mass flux vector is found to be a significant term; particularly within localized regions of the flame. Research supported by NSF Grant CBET-0965624 and Clemson University's Palmetto Cluster.

  2. Pressure-induced magnetic crossover driven by hydrogen bonding in CuF2(H2O)2(3-chloropyridine)

    DOE PAGES

    O'Neal, Kenneth R.; Brinzari, Tatiana V.; Wright, Joshua B.; ...

    2014-08-13

    Here, 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 combinedmore » 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.« less

  3. Crystal structure, equation of state, and elasticity of phase H (MgSiO4H2) at Earth’s lower mantle pressures

    PubMed Central

    Tsuchiya, Jun; Mookherjee, Mainak

    2015-01-01

    Dense hydrous magnesium silicate (DHMS) phases play a crucial role in transporting water in to the Earth’s interior. A newly discovered DHMS, phase H (MgSiO4H2), is stable at Earth’s lower mantle, i.e., at pressures greater than 30 GPa. Here we report the crystal structure and elasticity of phase H and its evolution upon compression. Using first principles simulations, we have explored the relative energetics of the candidate crystal structures with ordered and disordered configurations of magnesium and silicon atoms in the octahedral sites. At conditions relevant to Earth’s lower mantle, it is likely that phase H is able to incorporate a significant amount of aluminum, which may enhance the thermodynamic stability of phase H. The sound wave velocities of phase H are ~2–4% smaller than those of isostructural δ-AlOOH. The shear wave impedance contrast due to the transformation of phase D to a mixture of phase H and stishovite at pressures relevant to the upper part of the lower mantle could partly explain the geophysical observations. The calculated elastic wave velocities and anisotropies indicate that phase H can be a source of significant seismic anisotropy in the lower mantle. PMID:26493639

  4. Comparative Ecology of H2 Cycling in Organotrophic and Phototrophic Ecosystems

    NASA Technical Reports Server (NTRS)

    Hoehler, Tori M.; Alperin, Marc J.; Albert, Daniel B.; Bebout, Brad M.; Martens, Christopher S.; DesMarais, David J.; DeVincenzi, Don (Technical Monitor)

    2001-01-01

    The simple biochemistry of H2 is critical to a large number of microbial processes, affecting the interaction of organisms with each other and with the environment. The sensitivity of these many processes to H2 can be described quantitatively, at a basic thermodynamic level. This shared dependence on H2 may provide a means for interpreting the ecology and system-level biogeochemistry of widely variant microbial ecosystems on a common (and quantitative) level. Understanding the factors that control H2 itself is a critical prerequisite. Here, we examine two ecosystems that vary widely with respect to H2 cycling. In anoxic, 'organotrophic' sediments from Cape Lookout Bight (North Carolina, USA), H2 partial pressures are strictly maintained at low, steady-state levels by H2-consuming organisms, in a fashion that can be quantitatively predicted by simple thermodynamic calculations. In phototrophic microbial mats from Baja, Mexico, H2 partial pressures are instead controlled by the activity of light-sensitive H2-producing organisms. In consequence, H2 partial pressures within the system fluctuate by orders of magnitude on hour-long time scales. The differences in H2 cycling subsequently impact H2-sensitive microbial processes, such as methanogenesis. For example, the presence of sulfate in the organotrophic system always yielded low levels of H2 that were inhibitory to methanogenesis; however, the elevated levels of H2 in the phototrophic system favored methane production at significant levels, even in the presence of high sulfate concentrations. The myriad of other H2-sensitive microbial processes are expected to exhibit similar behavior.

  5. Bulk YBa2Cu3O(x) superconductors through pressurized partial melt growth processing

    NASA Technical Reports Server (NTRS)

    Hu, S.; Hojaji, H.; Barkatt, A.; Boroomand, M.; Hung, M.; Buechele, A. C.; Thorpe, A. N.; Davis, D. D.; Alterescu, S.

    1992-01-01

    A novel pressurized partial melt growth process has been developed for producing large pieces of bulk Y-Ba-Cu-O superconductors. During long-time partial melt growth stage, an additional driving force for solidification is obtained by using pressurized oxygen gas. The microstructure and superconducting properties of the resulting samples were investigated. It was found that this new technique can eliminate porosity and inhomogeneity, promote large-scale grain-texturing, and improve interdomain coupling as well.

  6. 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.

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

    SciTech Connect

    Kim, Jong-Ryul; Choi, Gyung-Min; Kim, Duck-Jool

    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)

  8. Melting relations of hydrous pyrolite in CaO-MgO-Al2O3-SiO2-H2O System at the transition zone pressures

    NASA Astrophysics Data System (ADS)

    Litasov, Konstantin; Ohtani, Eiji; Taniguchi, Hiromitsu

    Phase relations and melt compositions in CaO-MgO-Al2O3-SiO2-pyrolite under hydrous (+2% of H2O) and anhydrous conditions have been determined at 13-20 GPa and 1600-2220°C. Liquidus and solidus temperatures for the hydrous system are about 50-100°C and 180-240°C lower than those for the dry system, respectively. Majorite is a liquidus phase of the hydrous pyrolite from 13 to 20 GPa. Olivine is a liquidus phase at 13 GPa and both periclase and majorite are the liquidus phases at 20 GPa in the dry pyrolite. We observed expansion of the stability field of anhydrous phase B in hydrous experiments. Compositions of partial melts at 13-20 GPa are generally similar in dry and hydrous systems, but hydrous melts contain more SiO2 at 13-17 GPa. The melts formed by low degree of melting have Al2O3-depleted and CaO-rich compositions. Trends of hydrous melt compositions are generally consistent with those of aluminum-depleted komatiite magmas.

  9. H2 blockers

    MedlinePlus

    ... ulcer disease - H2 blockers; PUD - H2 blockers; Gastroesophageal reflux - H2 blockers ... blockers are used to: Relieve symptoms of acid reflux, or gastroesophageal reflux disease (GERD). This is a ...

  10. Ionic conductivity measurements of H2O ice at high pressure and temperature and superionic ice in the mantle of ice giants

    NASA Astrophysics Data System (ADS)

    Sugimura, E.; Komabayashi, T.; Ohta, K.; Hirose, K.; Sata, N.; Ohishi, Y.; Shimizu, K.; Dubrovinsky, L. S.

    2011-12-01

    The experimental evidence for the superionic conduction in H2O ice at high pressure (P) and temperature (T) has been long-searched since its theoretical prediction. Melting experiments reported a steep rise of the melting curve at P-T range of 35-43 GP and 1000-1600 K, which could be due to a first-order phase transition in the solid phases, namely the presence of the triple point of water, ice VII, and a high-T phase which was assumed superionic. Nonetheless, there has still been no report on direct experimental evidence for superionic conduction (ca. 0.1 S/cm) in ice at high pressure. Here we examined ionic conductivity and isothermal molar volume of ice at high-P-T based on impedance spectroscopy (IS) and x-ray diffraction measurements in an externally-resistive heated diamond anvil cell. In situ IS measurements up to 62 GPa and 920 K demonstrated that ice exhibits superionic conduction (> 0.1 S/cm) above 580-720 K at 20-60 GPa. This suggests that superionic conduction occurs at sufficiently lower P-T than the triple point. Isothermal P-V data collected at P = 33-101 GPa and T = 873 K revealed that an anomalous volume reduction occurs at P = 50-53 GPa. This compression manner corresponds to the previously reported highly compressible regime at P = 40-60 GPa, T = 300 K, which were attributed to hydrogen bond symmetrization. There is no volume discontinuity in the isothermal compression, which contradicts the proposed first order P-T boundary between ice VII and superionic ice. Furthermore, all the conductivity data is expressed by a single Arrhenius equation so that the superionic conduction occurs regardless of the ongoing hydrogen bond symmetrization upon compression. We suggests that the previously reported steep rise of the melting temperature of ice above 35-43 GPa is independent of superionic transition, and is a consequence of the hydrogen bond symmetrization. Combining above results with the existing planetary isentropes, superionic conduction in H2O ice

  11. Absolute OH and O radical densities in effluent of a He/H2O micro-scaled atmospheric pressure plasma jet

    NASA Astrophysics Data System (ADS)

    Benedikt, J.; Schröder, D.; Schneider, S.; Willems, G.; Pajdarová, A.; Vlček, J.; Schulz-von der Gathen, V.

    2016-08-01

    The effluent of a micro-scaled atmospheric pressure plasma jet (μ-APPJ) operated in helium with admixtures of water vapor (≲ {{10}4} ppm) has been analyzed by means of cavity ring-down laser absorption spectroscopy and molecular beam mass spectrometry to measure hydroxyl (OH) radical densities, and by two-photon absorption laser-induced fluorescence spectroscopy to measure atomic oxygen (O) densities. Additionally, the performance of the bubbler as a source of water vapor in the helium feed gas has been carefully characterized and calibrated. The largest OH and O densities in the effluent of 2× {{10}14}~\\text{c}{{\\text{m}}-3} and 3.2× {{10}13}~\\text{c}{{\\text{m}}-3} , respectively, have been measured at around 6000 ppm. The highest selectivity is reached around 1500 ppm, where the OH density is at  ∼63% of its maximum value and is 14 times larger than the O density. The measured density profiles and distance variations are compared to the results of a 2D axially symmetric fluid model of species transport and reaction kinetics in the plasma effluent. It is shown that the main loss of OH radicals in the effluent is their mutual reaction. In the case of O, reactions with other species than OH also have to be considered to explain the density decay in the effluent. The results presented here provide additional information for understanding the plasma-chemical processes in non-equilibrium atmospheric pressure plasmas. They also open the way to applying μ-APPJ with He/H2O as a selective source of OH radicals.

  12. The stability and Raman spectra of ikaite, CaCO3·6H2O, at high pressure and temperature

    USGS Publications Warehouse

    Shahar, Anat; Bassett, William A.; Mao, Ho-kwang; Chou, I-Ming; Mao, Wendy

    2005-01-01

    Raman analyses of single crystals of ikaite, CaCO3·6H2O, synthesized in a diamond-anvil cell at ambient temperature yield spectra from 0.14 to 4.08 GPa; the most intense peaks are at 228 and 1081 cm−1 corresponding to Eg(external) and A1g (internal) modes of vibrations in CO2− 3 ions, respectively. These are in good agreement with Raman spectra previously published for ikaite in powder form at ambient temperature and pressure. Visual observations of a sample consisting initially of a mixture of calcite + water in a hydrothermal diamond-anvil cell yielded a P-T phase diagram up to 2 GPa and 120 °C; the boundary for the reaction ikaite ↔ aragonite + water has a positive slope and is curved convexly toward the aragonite + water field similar to typical melt curves. This curvature can be explained in terms of the Clapeyron equation for a boundary between a solid phase and a more compressible liquid phase or largely liquid phase assemblage.

  13. High-pressure reactions in polyethylene films, a new development in matrix isolation. The photochemical reaction of Fe (CO) 5 with N 2 and the thermal reaction of Fe (CO) 4 (N 2) with H 2

    NASA Astrophysics Data System (ADS)

    Cooper, Andrew I.; Poliakoff, Martyn

    1993-09-01

    A new miniature high-pressure cell has been developed for the spectroscopic study of reactions between organometallic compounds impregnated into polymer films and gases such as N 2 or H 2 at any temperature between ambient and 20 K. The use of the cell is illustrated by the photochemical reactions of Fe(CO) 5 in polyethylene film (PE) with N 2 and H 2 at 190 K to form Fe (CO) 4(N 2) and Fe (CO) 4H 2 respectively. IR spectra suggest that the N 2 group may occupy an equatorial rather than an axial position. Once formed, Fe (CO) 4(N 2) is shown to react thermally with H 2 at ≈ 210 K to yield the dihydride compound, Fe (CO) 4H 2.

  14. Zinc improves the filterability of sickle erythrocytes at intermediate oxygen partial pressures.

    PubMed

    Taylor, J A; Acharya, J; Pearson, T C; Thompson, R P

    1991-09-01

    1. The deformability of erythrocytes from patients with sickle-cell anaemia was measured with a St George's blood filtrometer at a range of oxygen partial pressures and at four levels of zinc loading. 2. When incubated in buffered saline containing zinc and the chelator ethyl maltol, erythrocytes rapidly accumulated zinc and thus their oxygen affinity was increased. 3. Neither the oxygen partial pressure nor zinc loading affected the filtration of normal erythrocytes. 4. Deoxygenation of sickle erythrocytes greatly impaired filtration, although the initial filtration rate declined sharply at different oxygen partial pressures (between 70 and 35 mmHg) in different patients. 5. Low levels of zinc (0.03 +/- 0.003 mol of zinc/mol of haemoglobin tetramer) were without effect on sickle cells, but at zinc/haemoglobin ratios of 0.6:1 and above, the sharp fall in filtration rate occurred at oxygen partial pressures 8-25 mmHg below the oxygen partial pressure that impaired filtration of untreated cells. 6. Hence, the deformability of sickle erythrocytes in vitro can be improved by increasing the intracellular content of zinc to 20-fold above normal. Further studies are now required to examine the stability of zinc in erythrocytes, the effects of high intracellular zinc concentrations on erythrocyte viability, and the toxicity of zinc released from zinc-laden cells.

  15. Oxygen partial pressure effects on the magnetron sputtered WO3 films

    NASA Astrophysics Data System (ADS)

    Merhan Muğlu, G.; Gür, E.

    2016-04-01

    Electrochromism is changing color of a substance in response to the applied an external electric field and the phenomenon is reversible. WO3 is very attractive material due to its electrochromic properties as well as it is also attractive for many different applications such as gas sensors, phosphorous screen, textile, glass industry. In this study, it is aimed to provide optimization of the optical and structural characteristics of WO3 by changing the growth parameters mainly the oxygen partial pressure. The partial pressure of oxygen was changed with increments of 0.7 mTorr. For the analysis, X-ray Diffraction (XRD), absorption, Raman spectroscopy measurements were used. When O2 gas increased, peaks belong to the WO3 was observed in XRD patterns at the 2 theta angles of 23.0, 11.0, 23.5 and 28.5 angles corresponding to the (002), (020) and (220) planes, respectively. This shows that there is a significant effect of increasing O2 partial pressure in the formation of WO3 films. The bandgap energy of the WO3 thin films are found to be around 3.0 eV. Raman measurements showed vibrational modes of W-O-W stretching and bending modes which shows small shifts depending on the partial pressures of the O2. Obtained results indicated that better crystal structure is obtained with higher O2 gas partial pressure.

  16. 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.

  17. Thermo- and piezochromic properties of [Fe(hyptrz)]A2·H2O spin crossover 1D coordination polymer: Towards spin crossover based temperature and pressure sensors

    NASA Astrophysics Data System (ADS)

    Jureschi, Catalin-Maricel; Rusu, Ionela; Codjovi, Epiphane; Linares, Jorge; Garcia, Yann; Rotaru, Aurelian

    2014-09-01

    We have used reflectance measurements to investigate the effect of a hydrostatic pressure on the molecular 1D spin crossover coordination polymer [Fe(hyptrz)]A2·H2O (hyptrz=4-(3‧-hydroxypropyl)-1,2,4-triazole and A=4-chloro-benzenesulfonate) Rev. Sci. Instrum. 80 (2009) 123901. Both thermal and pressure hysteresis have been recorded at different pressures and temperatures, respectively, in order to obtain valuable information about the optimal conditions of their use as wireless temperature and pressure sensors. The experimental analysis has been completed with a theoretical study and potential applications in terms of temperature and pressure wireless detection are discussed.

  18. Partial pressures of oxygen, phosphorus and fluorine in some lunar lavas

    NASA Technical Reports Server (NTRS)

    Nash, W. P.; Hausel, W. D.

    1973-01-01

    Lunar sample 14310 is a feldspar-rich basalt which shows no evidence of shock deformation or recrystallization. Pyroxenes include Mg-rich orthopyroxene, pigeonite and augite; pyroxferroite occurs in the interstitial residuum. Plagioclase feldspars are zoned from An(96) to An(67), and variations in feldspar compositions do not necessarily indicate loss of Na during eruption of the lava. Opaque phases include ilmenite, ulvospinel, metallic iron, troilite, and schreibersite. Both whitlockite and apatite are present, and the interstitial residua contain baddeleyite, tranquillityite and barium-rich sanidine. Theoretical calculations provide estimates of partial pressures of oxygen, phosphorus, and fluorine in lunar magmas. In general, partial pressures of oxygen are restricted by the limiting assemblages of iron-wuestite and ilmenite-iron-rutile; phosphorus partial pressures are higher in lunar magmas than in terrestrial lavas. The occurrence of whitlockite indicates significantly lower fugacities of fluorine in lunar magmas than in terrestrial magmas.

  19. Hydrogen partial pressures in a thermophilic acetate-oxidizing methanogenic coculture. [THF, Methanobacterium thermoautotrophicum

    SciTech Connect

    Lee, M.J.; Zinder, S.H. )

    1988-06-01

    Hydrogen partial pressures were measured in a thermophilic coculture comprised of a eubacterial rod which oxidized acetate to H{sub 2} and CO{sub 2} and a hydrogenotrophic methanogen, Methanobacterium sp. strain THF. H{sub 2} partial pressures in the coculture were measured to be between 20 and 50 Pa (0.12 to 0.30 {mu}M) during acetate utilization, approximately one order of magnitude higher than originally predicted by Zinder and Koch. However, when {Delta}G{sub f} (free energy of formation) values were corrected for 60{degree}C, the predicted value was near 15 Pa, in closer agreement with the experimentally determined values. The coculture also oxidized ethanol to acetate with H{sub 2} partial pressure values as high as 200 Pa. Acetate was not used until after the ethanol was consumed and the H{sub 2} partial pressure decreased to 40 to 50 Pa. After acetate utilization, H{sub 2} partial pressures fell to approximately 10 Pa and remained there, indicating a threshold for H{sub 2} utilization by the methanogen. Axenic cultures of the acetate-oxidizing organism were combined with pure cultures of either Methanobacterium sp. strain THF or Methanobacterium thermoautotrophicum {Delta}H to form reconstituted acetate-oxidizing cocultures. The H{sub 2} partial pressures measured in both of these reconstituted cocultures were similar to those measured in the original acetate-oxidizing rod coculture. Since M. thermoautotrophicum {Delta}H did not use formate as a substrate, formate is not necessarily involved in interspecies electron transfer in this coculture.

  20. Effects of Oxygen Partial Pressure on the Surface Tension of Liquid Nickel

    NASA Technical Reports Server (NTRS)

    SanSoucie, Michael P.; Rogers, Jan R.; Gowda, Vijaya Kumar Malahalli Shankare; Rodriguez, Justin; Matson, Douglas M.

    2015-01-01

    The NASA Marshall Space Flight Center's electrostatic levitation (ESL) laboratory has been recently upgraded with an oxygen partial pressure controller. This system allows the oxygen partial pressure within the vacuum chamber to be measured and controlled, theoretically in the range from 10-36 to 100 bar. The oxygen control system installed in the ESL laboratory's main chamber consists of an oxygen sensor, oxygen pump, and a control unit. The sensor is a potentiometric device that determines the difference in oxygen activity in two gas compartments (inside the chamber and the air outside of the chamber) separated by an electrolyte, which is yttria-stabilized zirconia. The pump utilizes coulometric titration to either add or remove oxygen. The system is controlled by a desktop control unit, which can also be accessed via a computer. The controller performs temperature control for the sensor and pump, PID-based current loop, and a control algorithm. Oxygen partial pressure has been shown to play a significant role in the surface tension of liquid metals. Oxide films or dissolved oxygen may lead to significant changes in surface tension. The effects of oxygen partial pressure on the surface tension of undercooled liquid nickel will be analyzed, and the results will be presented. The surface tension will be measured at several different oxygen partial pressures while the sample is undercooled. Surface tension will be measured using the oscillating drop method. While undercooled, each sample will be oscillated several times consecutively to investigate how the surface tension behaves with time while at a particular oxygen partial pressure.

  1. FT-Raman and high-pressure infrared spectroscopic studies of dicalcium phosphate dihydrate (CaHPO 4·2H 2O) and anhydrous dicalcium phosphate (CaHPO 4)

    NASA Astrophysics Data System (ADS)

    Xu, Jingwei; Butler, Ian S.; Gilson, Denis F. R.

    1999-12-01

    The FT-Raman spectra and the pressure dependence of the infrared spectra of the hydrated and anhydrous forms of dicalcium phosphate, CaHPO 4 · 2H 2O and CaHPO 4, have been studied. The hydrated salt exhibits a phase transition at 21 kbar (1.0 kbar=0.1 Gpa) but no high pressure transition was observed for anhydrous dicalcium phosphate. The O-H stretching frequencies of the water molecules in CaHPO 4·2H 2O all showed negative pressure dependences and correlate with the O ⋯O distances. The PO-H stretch increased with increasing pressure, indicating a strong hydrogen bond. The frequencies associated with the phosphate ion showed a normal pressure dependence.

  2. Effects of hydrogen partial pressure on autotrophic growth and product formation of Acetobacterium woodii.

    PubMed

    Kantzow, Christina; Weuster-Botz, Dirk

    2016-08-01

    Low aqueous solubility of the gases for autotrophic fermentations (e.g., hydrogen gas) results in low productivities in bioreactors. A frequently suggested approach to overcome mass transfer limitation is to increase the solubility of the limiting gas in the reaction medium by increasing the partial pressure in the gas phase. An increased inlet hydrogen partial pressure of up to 2.1 bar (total pressure of 3.5 bar) was applied for the autotrophic conversion of hydrogen and carbon dioxide with Acetobacterium woodii in a batch-operated stirred-tank bioreactor with continuous gas supply. Compared to the autotrophic batch process with an inlet hydrogen partial pressure of 0.4 bar (total pressure of 1.0 bar) the final acetate concentration after 3.1 days was reduced to 50 % (29.2 g L(-1) compared to 59.3 g L(-1)), but the final formate concentration was increased by a factor of 18 (7.3 g L(-1) compared to 0.4 g L(-1)). Applying recombinant A. woodii strains overexpressing either genes for enzymes in the methyl branch of the Wood-Ljungdahl pathway or the genes phosphotransacetylase and acetate kinase at an inlet hydrogen partial pressure of 1.4 bar reduced the final formate concentration by up to 40 % and increased the final dry cell mass and acetate concentrations compared to the wild type strain. Solely the overexpression of the two genes for ATP regeneration at the end of the Wood-Ljungdahl pathway resulted in an initial switch off of formate production at increased hydrogen partial pressure until the maximum of the hydrogen uptake rate was reached.

  3. Optimizing the physical ergonomics indices for the use of partial pressure suits.

    PubMed

    Ding, Li; Li, Xianxue; Hedge, Alan; Hu, Huimin; Feathers, David; Qin, Zhifeng; Xiao, Huajun; Xue, Lihao; Zhou, Qianxiang

    2015-03-01

    This study developed an ergonomic evaluation system for the design of high-altitude partial pressure suits (PPSs). A total of twenty-one Chinese males participated in the experiment which tested three types of ergonomics indices (manipulative mission, operational reach and operational strength) were studied using a three-dimensional video-based motion capture system, a target-pointing board, a hand dynamometer, and a step-tread apparatus. In total, 36 ergonomics indices were evaluated and optimized using regression and fitting analysis. Some indices that were found to be linearly related and redundant were removed from the study. An optimal ergonomics index system was established that can be used to conveniently and quickly evaluate the performance of different pressurized/non-pressurized suit designs. The resulting ergonomics index system will provide a theoretical basis and practical guidance for mission planners, suit designers and engineers to design equipment for human use, and to aid in assessing partial pressure suits.

  4. 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

  5. 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.

  6. High-pressure experiments on the stability of methane hydrates in the H2O-NH3-CH4 system with applications to Titan's cryovolcanism.

    NASA Astrophysics Data System (ADS)

    Choukroun, M.; Le Menn, E.; Grasset, O.

    2007-08-01

    The current methane abundance in Titan's thick atmosphere cannot be explained without the existence of replenishment processes. Indeed, the intense photochemistry taking place in the atmosphere would destroy the 2-5% CH4 amounts measured by the GCMS onboard the Huygens probe [1] within 10-100 Myr [e.g. 2]. Among the several hypotheses that could explain this replenishment, release of methane during cryovolcanic events seems highly likely. The VIMS [3] and Radar instruments [4] onboard the Cassini spacecraft have brought substantial evidence for cryovolcanic features on Titan's surface. A numerical model has shown the possibility to release CH4 by dissociating methane clathrate hydrates at depth, due to interaction of a clathrate layer with warm ice intrusions [5]. However, the effect of volatile compounds, dissolved (e.g. N2) or in solution (e.g. NH3), would most certainly play a major role in cryovolcanic processes. High-pressure low-temperature experimental investigations on the effect of ammonia on methane hydrates' dissociation are conducted within an optical sapphire-anvil cell. Preliminary results have been previously presented, which lead to contradictory interpretations so far [6,7]. As further experiments are being performed, the reliability of the experimental measurements and the reasons for observing discrepancies in the results can be adressed with more and more confidence. This poster will discuss the experimental issues encountered in the H2O-NH3-CH4 system, up-todate experimental results, as well as their implications for Titan's cryovolcanism. References: [1] Niemann HB et al., Nature 438, 779-784 (2005). [2] Yung YL et al., Astrophys. J. Suppl., 55, 465-506 (1984). [3] Sotin C et al., Nature 435, 786-789 (2005). [4] Lopes RMC et al., Icarus 186, 395-412 (2007). [5] Tobie G et al., Nature 440 (2), 61-64 (2006). [6] Choukroun M et al., 37th Lunar and Planet. Sci. Conf. Abstract #1640 (2006). [7] Choukroun M et al., 38th Lunar and Planet. Sci. Conf

  7. 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.

  8. Measurement and Control of Oxygen Partial Pressure in an Electrostatic Levitator

    NASA Technical Reports Server (NTRS)

    SanSoucie, Michael P.; Rogers, Jan R.

    2014-01-01

    Recently the NASA Marshall Space Flight Center electrostatic levitation (ESL) laboratory has been upgraded to include an oxygen control system. This system allows the oxygen partial pressure within the vacuum chamber to be measured and controlled, at elevated temperatures, theoretically in the range from 10(exp -36) to 10(exp 0) bar. The role of active surface agents in liquid metals is fairly well known; however, published surface tension data typically has large scatter, which has been hypothesized to be caused by the presence of oxygen. The surface tension of metals is affected by even a small amount of adsorption of oxygen. It has even been shown that oxygen partial pressures may need to be as low as 10(exp -24) bar to avoid oxidation. While electrostatic levitation is done under high vacuum, oxide films or dissolved oxygen may have significant effects on materials properties, such as surface tension and viscosity. Therefore, the ability to measure and control the oxygen partial pressure within the chamber is highly desirable. The oxygen control system installed at MSFC contains a potentiometric sensor, which measures the oxygen partial pressure, and an oxygen ion pump. In the pump, a pulse-width modulated electric current is applied to yttrium-stabilized zirconia, resulting in oxygen transfer into or out of the system. Also part of the system is a control unit, which consists of temperature controllers for the sensor and pump, PID-based current loop for the ion pump, and a control algorithm. This system can be used to study the effects of oxygen on the thermophysical properties of metals, ceramics, glasses, and alloys. It can also be used to provide more accurate measurements by processing the samples at very low oxygen partial pressures. The oxygen control system will be explained in more detail and an overview of its use and limitations in an electrostatic levitator will be described. Some preliminary measurements have been made, and the results to date will

  9. Oxidation of C/SiC Composites at Reduced Oxygen Partial Pressures

    NASA Technical Reports Server (NTRS)

    Opila, E. J.; Serra, J. L.

    2007-01-01

    T-300 carbon fibers and T-300 carbon fiber reinforced silicon carbide composites (C/SiC) were oxidized in flowing reduced oxygen partial pressure environments at a total pressure of one atmosphere (0.5 atm O2, 0.05 atm O2 and 0.005 atm O2, balance argon). Experiments were conducted at four temperatures (816deg, 1149deg, 1343deg, and 1538 C). The oxidation kinetics were monitored using thermogravimetric analysis. T-300 fibers were oxidized to completion for times between 0.6 and 90 h. Results indicated that fiber oxidation kinetics were gas phase diffusion controlled. Oxidation rates had an oxygen partial pressure dependence with a power law exponent close to one. In addition, oxidation rates were only weakly dependent on temperature. The C/SiC coupon oxidation kinetics showed some variability, attributed to differences in the number and width of cracks in the SiC seal coat. In general, weight losses were observed indicating oxidation of the carbon fibers dominated the oxidation behavior. Low temperatures and high oxygen pressures resulted in the most rapid consumption of the carbon fibers. At higher temperatures, the lower oxidation rates were primarily attributed to crack closure due to SiC thermal expansion, rather than oxidation of SiC since these reduced rates were observed even at the lowest oxygen partial pressures where SiC oxidation is minimal.

  10. Experimental study of the pressure fluctuations in a pump turbine at large partial flow conditions

    NASA Astrophysics Data System (ADS)

    Ran, Hongjuan; Luo, Xianwu; Zhu, Lei; Zhang, Yao; Wang, Xin; Xu, Hongyuan

    2012-11-01

    Frequent shifts of output and operating mode require a pump turbine with excellent stability. Current researches show that large partial flow conditions in pump mode experience positive-slope phenomena with a large head drop. The pressure fluctuation at the positive slope is crucial to the pump turbine unit safety. The operating instabilities at large partial flow conditions for a pump turbine are analyzed. The hydraulic performance of a model pump turbine is tested with the pressure fluctuations measured at unstable operating points near a positive slope in the performance curve. The hydraulic performance tests show that there are two separated positive-slope regions for the pump turbine, with the flow discharge for the first positive slope from 0.85 to 0.91 times that at the maximum efficiency point. The amplitudes of the pressure fluctuations at these unstable large partial flow conditions near the first positive slope are much larger than those at stable operating condtions. A dominant frequency is measured at 0.2 times the impeller rotational frequency in the flow passage near the impeller exit, which is believed to be induced by the rotating stall in the flow passage of the wicket gates. The test results also show hysteresis with pressure fluctuations when the pump turbine is operated near the first positive slope. The hysteresis creates different pressure fluctuations for those operation points even though their flow rates and heads are similar respectively. The pressure fluctuation characteristics at large partial flow conditions obtained by the present study will be helpful for the safe operation of pumped storage units.

  11. [Device to assess in-socket pressure distribution for partial foot amputation].

    PubMed

    Alvarez-Camacho, Michelín; Urrusti, José Luis; Acero, María Del Carmen; Galván Duque-Gastélum, Carlos; Rodríguez-Reyes, Gerardo; Mendoza-Cruz, Felipe

    2014-07-01

    A device for dynamic acquisition and distribution analysis of in-socket pressure for patients with partial foot amputation is presented in this work. By using the developed system, we measured and generated pressure distribution graphs, obtained maximal pressure, and calculated pressure-time integral (PTI) of three subjects with partial foot amputation and of a group of Healthy subjects (Hs) (n = 10). Average maximal pressure in the healthy group was 19.4 ± 4.11 PSI, while for the three amputated patients, this was 27.8 ± 1.38, 17.6 ± 1.15, 29.10 ± 3.9 PSI, respectively. Maximal pressure-time integral for healthy subjects was 11.56 ± 2.83 PSI*s, and for study subjects was 19.54 ± 1.9, 12.35 ± 1.48, and 13.17 ± 1.31 PSI*s, respectively. The results of the control group agree with those previously reported in the literature. The pressure distribution pattern showed clear differences between study subjects and those of the control group; these graphs allowed us to identify the pressure in regions-of-interest that could be critical, such as surgical scars. The system presented in this work will aid to assess the effectiveness with which prosthetic systems distribute load, given that the formation of ulcers is highly linked to the pressure exercised at the point of contact; in addition, these results will help to investigate the comfort perception of the prosthesis, a factor directly influenced by the stump's pressure distribution.

  12. 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

  13. 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.

  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. The Influence of Different Partial Pressure on the Fabrication of InGaO Ultraviolet Photodetectors

    PubMed Central

    Chang, Sheng-Po; Chang, Li-Yang; Li, Jyun-Yi

    2016-01-01

    A metal–semiconductor–metal ultraviolet photodetector has been fabricated with a radiofrequency (RF)-sputtered InGaO thin film. Results for the devices fabricated under different oxygen partial pressure are here in discussed. Under low oxygen partial pressure, the devices work in the photoconductive mode because of the large number of subgap states. Therefore, the devices exhibit internal gain. These defects in the films result in slow switching times and lower photo/dark current ratios. A higher flow ratio of oxygen during the sputtering process can effectively restrain the oxygen vacancies in the film. The responsivity of the photodetector fabricated under an oxygen flow ratio of 20% can reach 0.31 A/W. The rise time and decay time can reach 21 s and 27 s, respectively. PMID:27983694

  16. 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 893°C to 880°C and further down to 834°C 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.

  17. Oxidation of C/SiC Composites at Reduced Oxygen Partial Pressures

    NASA Technical Reports Server (NTRS)

    Opila, Elizabeth J.; Serra, Jessica

    2009-01-01

    Carbon-fiber reinforced SiC (C/SiC) composites are proposed for leading edge applications of hypersonic vehicles due to the superior strength of carbon fibers at high temperatures (greater than 1500 C). However, the vulnerability of the carbon fibers in C/SiC to oxidation over a wide range of temperatures remains a problem. Previous oxidation studies of C/SiC have mainly been conducted in air or oxygen, so that the oxidation behavior of C/SiC at reduced oxygen partial pressures of the hypersonic flight regime are less well understood. In this study, both carbon fibers and C/SiC composites were oxidized over a wide range of temperatures and oxygen partial pressures to facilitate the understanding and modeling of C/SiC oxidation kinetics for hypersonic flight conditions.

  18. Photocuring Kinetics for Polyfurfurylmethacrylate Doped with Fullerene: The Influence of Oxygen Partial Pressure on Sensitivity

    NASA Astrophysics Data System (ADS)

    Arai, Hisayoshi; Tajima, Yusuke; Takeuchi, Kazuo

    2001-11-01

    A new photosensitive resin, photo-oxidation induced polycondensation (POP) resin, was successfully prepared from poly(furfuryl methacrylate) (PFMA) and fullerene C60. The influence of oxygen supplied from ambient air into the POP resin on the photocuring was studied. The characteristic curves for the PFMA containing C60 film showed that the curing sensitivity was enhanced with increased partial pressure of oxygen. The relationship between sensitivity and oxygen partial pressure for low light intensity was explained reasonably well with a simple kinetic model. On the other hand, the sensitivity decreased for high light intensity. The numerical simulation indicated that the small oxygen solubility and small diffusivity were the cause of insufficient oxygen when the oxygen in PFMA was consumed promptly by high-intensity irradiation.

  19. High-Pressure Synthesis of Manganese Oxyhydride with Partial Anion Order.

    PubMed

    Tassel, Cedric; Goto, Yoshinori; Watabe, Daichi; Tang, Ya; Lu, Honcheng; Kuno, Yoshinori; Takeiri, Fumitaka; Yamamoto, Takafumi; Brown, Craig M; Hester, James; Kobayashi, Yoji; Kageyama, Hiroshi

    2016-08-08

    The high-pressure synthesis of a manganese oxyhydride LaSrMnO3.3 H0.7 is reported. Neutron and X-ray Rietveld analyses showed that this compound adopts the K2 NiF4 structure with hydride ions positioned exclusively at the equatorial site. This result makes a striking contrast to topochemical reductions of LaSrMnO4 that result in only oxygen-deficient phases down to LaSrMnO3.5 . This suggests that high H2 pressure plays a key role in stabilizing the oxyhydride phase, offering an opportunity to synthesize other transition-metal oxyhydrides. Magnetic susceptibility revealed a spin-glass transition at 24 K that is due to competing ferromagnetic (Mn(2+) -Mn(3+) ) and antiferromagnetic (Mn(2+) -Mn(2) , Mn(3+) -Mn(3+) ) interactions.

  20. Repeated Six-Hour Dives 1.35 ATM Oxygen Partial Pressure

    DTIC Science & Technology

    2005-10-01

    hemoglobin and carboxyhemoglobin , visual refraction was tested, and pulmonary function was measured . Additionally, the divers completed the postdive...and single six-hour dives in water or in the dry chamber where divers breathed oxygen at a partial pressure of 1.6 atm.4 In all studies we measured ...bands for each variable, as the lower limits of normal. We did not measure visual refraction daily during the pairs of daily dives or five daily dives

  1. Oxygen supply in aquatic ectotherms: partial pressure and solubility together explain biodiversity and size patterns.

    PubMed

    Verberk, Wilco C E P; Bilton, David T; Calosi, Piero; Spicer, John I

    2011-08-01

    Aquatic ectotherms face the continuous challenge of capturing sufficient oxygen from their environment as the diffusion rate of oxygen in water is 3 x 10(5) times lower than in air. Despite the recognized importance of oxygen in shaping aquatic communities, consensus on what drives environmental oxygen availability is lacking. Physiologists emphasize oxygen partial pressure, while ecologists emphasize oxygen solubility, traditionally expressing oxygen in terms of concentrations. To resolve the question of whether partial pressure or solubility limits oxygen supply in nature, we return to first principles and derive an index of oxygen supply from Fick's classic first law of diffusion. This oxygen supply index (OSI) incorporates both partial pressure and solubility. Our OSI successfully explains published patterns in body size and species across environmental clines linked to differences in oxygen partial pressure (altitude, organic pollution) or oxygen solubility (temperature and salinity). Moreover, the OSI was more accurately and consistently related to these ecological patterns than other measures of oxygen (oxygen saturation, dissolved oxygen concentration, biochemical oxygen demand concentrations) and similarly outperformed temperature and altitude, which covaried with these environmental clines. Intriguingly, by incorporating gas diffusion rates, it becomes clear that actually more oxygen is available to an organism in warmer habitats where lower oxygen concentrations would suggest the reverse. Under our model, the observed reductions in aerobic performance in warmer habitats do not arise from lower oxygen concentrations, but instead through organismal oxygen demand exceeding supply. This reappraisal of how organismal thermal physiology and oxygen demands together shape aerobic performance in aquatic ectotherms and the new insight of how these components change with temperature have broad implications for predicting the responses of aquatic communities to

  2. 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.

  3. EOS7Cm: An improved TOUGH2 module for simulating non-isothermal multiphase and multicomponent flow in CO2-H2S-CH4-brine systems with high pressure, temperature and salinity

    NASA Astrophysics Data System (ADS)

    Lei, Hongwu; Li, Jun; Li, Xiaochun; Jiang, Zhenjiao

    2016-09-01

    Understanding the non-isothermal multiphase and multicomponent flow in a CO2-H2S-CH4-brine system is of critical importance in projects such as CO2 storage in deep saline aquifers, natural gas extraction using CO2 as the displacement fluid, and heat extraction from hot dry rocks using CO2 as the working fluid. Numerical simulation is a necessary tool to evaluate the chemical evolution in these systems. However, an accurate thermodynamic model for CO2-H2S-CH4-brine systems appropriate for high pressure, temperature, and salinity is still lacking. This study establishes the mutual solubility model for CO2-H2S-CH4-brine systems based on the fugacity-activity method for phase equilibrium. The model can predict mutual solubilities for pressure up to 1000 bar for CO2 and CH4, and 200 bar for H2S, for temperature up to 200 °C, and for salinity up to 6 mol/kg water. We incorporated the new model into TOUGH2/EOS7C, forming a new improved module we call EOS7Cm. Compared to the original EOS7C, EOS7Cm considers the effects of H2S and covers a larger range of temperature and salinity. EOS7Cm is employed in five examples, including CO2 injection with and without impurities (CH4 and/or H2S) into deep aquifers, CH4 extraction from aquifers by CO2 injection, and heat extraction from hot dry rock. The results are compared to those from TOUGH2/ECO2N, EOS7C and CMG, agreement among which serves to verify EOS7Cm.

  4. Morphology and gas sensing characteristics of density-controlled CuO nanostructures obtained by varying the oxygen partial pressure during growth

    NASA Astrophysics Data System (ADS)

    Lee, Dongjin; Jin, Changhyun; Noh, Youngwook; Park, Seokhyun; Choi, Sun-Woo

    2016-07-01

    By exerting different O2 partial pressures (0, 20, 40, and 60 sccm) onto copper substrates, we discovered that the growth parameter, namely, the O2 flow rate, affects the degree of nucleation, diameter, length, and crystalline quality of CuO nanowires (NWs). Scanning electron microscopy (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM) were used to analyze the evolution of the morphological and the microstructural changes in the CuO nanostructures. The formation of a Cu2O interlayer between the Cu and the CuO layers could be adjusted by controlling more precisely the O2 flow rate. In addition, the reducing (H2S) and the oxidizing (O2, NO2, and SO2) gas sensing performances of these O2-assisted CuO NWs were compared with those of CuO NWs grown in static air. The response to the reducing H2S of the sensors based on CuO NWs grown using O2 at 40 sccm showed a higher electrical change and faster response and recovery times than the sensors based on CuO NWs grown using lower O2 flow rates, including the ones grown in static air and/or used for sensing oxidizing gases (O2, NO2, and SO2) did. On the basis of their growth and their gas-sensing applications, the possible mechanisms characteristic of the density-controlled CuO NWs grown using various O2 partial pressures are discussed.

  5. Thermodynamic description of equilibria in mixed fluids (H 2O-non-polar gas) over a wide range of temperature (25-700°C) and pressure (1-5000 bars)

    NASA Astrophysics Data System (ADS)

    Akinfiev, Nikolai; Zotov, Alexander

    1999-07-01

    A new method for computing complicated equilibria in hydrothermal mixed fluids, H 2O-non-polar gas, is proposed. The computation algorithm is based on the electrostatic approach for the interaction between aqueous species and H 2O. The approach uses the SUPCRT92 database and the HKF format and may be considered as an application of the revised HKF model for mixed H 2O-non-polar gas fluids. Thermodynamic properties of dissolved gases at high temperatures and pressures are calculated using the Redlich-Kwong approach. Dielectric permittivity of the mixed solvent is estimated by the modified Kirkwood equation. The proposed approach is validated using available experimental data on the dissociation constants of H 2O and NaCl and the solubility of both covalent and ion crystals (SiO 2, AgCl, Ag 2SO 4, Ca(OH) 2, CaCO 3) in H 2O-non-polar component (dioxane, Ar, CO 2) mixtures. Predicted and experimental data are in close agreement over a wide range of P- T- xgas conditions (up to 500°C, 4 kbar and 0.25-0.3 mole fraction of non-polar gas). It is also shown how the computation method can be applied to estimate the Born parameters of aqueous species. The proposed approach enables not only examination of isolated reactions, but the study of equilibria of whole systems. Thus, it allows modelling of mixed natural fluids.

  6. Brazeability of aluminum in vacuum-nitrogen partial-pressure atmosphere brazing

    SciTech Connect

    Hattori, T.; Sakai, S.; Sakamoto, A.; Fujiwara, C. )

    1994-10-01

    In vacuum brazing, Al-10% Si-1.5% Mg filler metal is used. The filler metal is melted and magnesium in the filler metal evaporates actively. The magnesium gas is the effective getter of contaminants such as H[sub 2]O and O[sub 2], which form an oxide film on the surface of aluminum alloys, lowering brazeability. Volatile elements also evaporate and material properties change in high-vacuum brazing. The vapor pressure of zinc in the Al-Zn alloy is high because zinc is a volatile element, but Al-Zn alloy does not melt at the brazing temperature, which is approximately 873 K and zinc does not evaporate actively compared with magnesium. However, evaporation of volatile elements and change in material properties can be minimized in vacuum-nitrogen partial-pressure atmosphere brazing, and Al-Zn alloy may be used as a sacrificial alloy in products made with aluminum alloys. In this study, brazeability in vacuum-nitrogen partial-pressure atmosphere was investigated using T-joints with horizontal Al-Mn or Al-Zn alloy sheet and vertical A4004 clad A3003 alloy brazing sheet. Specimens were brazed over a wide range of brazing pressures and N[sub 2] carrier gas flow rates. The brazing temperature and brazing time were 873 K (600 C) and 5 minutes, respectively. Gas contaminants in brazing atmospheres were measured using a quadruple mass spectrometer.

  7. Phase diagram of the binary H2O-NaCl and salty ice VII at pressure and temperature conditions of exoplanets and large icy moons

    NASA Astrophysics Data System (ADS)

    Journaux, B.; Daniel, I.

    2011-10-01

    We present here the first experimental data for the phase diagram of the H2O-NaCl system at high. Our results show a significant influence of NaCl on the phase diagram. A lot of NaCl is directly disolved into the dense ice phase. This would increase the depth of the solid phase transition inside large icy moons or super-earth exoplanets. These results may have major implication for astrophysical, geophysical and geodynamical modelisations of this water-rich planetary bodies.

  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. An investigation on the effect of high partial pressure of hydrogen on the nanocrystalline structure of silicon carbide thin films prepared by radio-frequency magnetron sputtering.

    PubMed

    Daouahi, Mohsen; Omri, Mourad; Kerm, Abdul Ghani Yousseph; Al-Agel, Faisal Abdulaziz; Rekik, Najeh

    2015-02-05

    The aim of the study reported in this paper is to investigate the role of the high partial pressure of hydrogen introduced during the growth of nanocrystalline silicon carbide thin films (nc-SiC:H). For this purpose, we report the preparation as well as spectroscopic studies of four series of nc-SiC:H obtained by radio-frequency magnetron sputtering at high partial pressure of hydrogen by varying the percentage of H2 in the gas mixture from 70% to 100% at common substrate temperature (TS=500°C). The effects of the dilution on the structural changes and the chemical bonding of the different series have been studied using Fourier transform infrared and Raman spectroscopy. For this range of hydrogen dilution, two groups of films were obtained. The first group is characterized by the dominance of the crystalline phase and the second by a dominance of the amorphous phase. This result confirms the multiphase structure of the grown nc-SiC:H thin films by the coexistence of the SiC network, carbon-like and silicon-like clusters. Furthermore, infrared results show that the SiC bond is the dominant absorption peak and the carbon atom is preferentially bonded to silicon. The maximum value obtained of the crystalline fraction is about 77%, which is relatively important compared to other results obtained by other techniques. In addition, the concentration of CHn bonds was found to be lower than that of SiHn for all series. Raman measurements revealed that the crystallization occurs in all series even at 100% H2 dilution suggesting that high partial pressure of hydrogen favors the formation of silicon nanocrystallites (nc-Si). The absence of both the longitudinal acoustic band and the transverse optical band indicate that the crystalline phase is dominant.

  10. 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 1±0.5 kbars from the Blanco fracture zone to the north along the Cleft segment of the ridge. Calculated pressures remain approximately constant at 0.87±0.53 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

  11. Design of a split Hopkinson pressure bar with partial lateral confinement

    NASA Astrophysics Data System (ADS)

    Barr, Andrew D.; Clarke, Sam D.; Rigby, Sam E.; Tyas, Andrew; Warren, James A.

    2016-12-01

    This paper presents the design of a modified split Hopkinson pressure bar (SHPB) where partial lateral confinement of the specimen is provided by the inertia of a fluid annulus contained in a long steel reservoir. In contrast to unconfined testing, or a constant cell pressure applied before axial loading, lateral restraint is permitted to develop throughout the axial loading: this enables the high-strain-rate shear behaviour of soils to be characterised under conditions which are more representative of buried explosive events. A pressure transducer located in the wall of the reservoir allows lateral stresses to be quantified, and a dispersion-correction technique is used to provide accurate measurements of axial stress and strain. Preliminary numerical modelling is utilised to inform the experimental design, and the capability of the apparatus is demonstrated with specimen results for a dry quartz sand.

  12. Effect of H2O, and combined effects of H2O + F, H2O + CO2, and H2O + F + CO2 on the viscosity of a natural basalt from Fuego volcano, Guatemala

    NASA Astrophysics Data System (ADS)

    Robert, G.; Whittington, A. G.; Knipping, J.; Scherbarth, S.; Stechern, A.; Behrens, H.

    2012-12-01

    We measured the viscosity of 5 series of remelted natural basalt from Fuego volcano, Guatemala. These series include single and multiple volatile species: H2O, F, H2O-F, H2O-CO2, and H2O-CO2-F. The hydrous glasses were synthesized at 3 kbar and 1250°C in Internally Heated Pressure Vessels. The multiple volatile series were synthesized at 5 kbar and 1250°C. CO2 was added as Ag2C2O4, F as AlF3, and H2O as distilled water. The anhydrous, F-bearing series was synthesized at 1 atm by simply remelting the Fuego basalt and adding F as CaF2.The natural, dry, remelted Fuego basalt has an NBO/T of 0.64. The following comparisons are based on parallel-plate viscosity measurements in the range ~108 to 1012 Pa s. The temperature at which the viscosity is 1012 Pa s (T12) is taken to be the viscosimetric glass transition temperature (Tg). The addition of 2 wt.% H2O results in a decrease of T12 of ~150°C for basalt. Fluorine on its own has a measurable, but much smaller effect, than the equivalent amount of water. Indeed, ~2 wt.% F results in a T12 depression of only ~30°C. When H2O and F are both present, their effects are approximately additive. For example, the viscosity of a basalt with 1.44 wt.% H2O is very similar to the viscosity of a basalt with ~1 wt.% H2O and ~1.25 wt.% F, and the viscosities of a basalt with 2.29 wt.% H2O and a basalt with ~1.65 wt.% H2O and ~1.3 wt.% F are also very similar. The effect of CO2 is somewhat ambiguous. The viscosity of a basalt with ~1.7 wt.% H2O, ~1.3 wt.% F and ~0.2 wt.% CO2 is essentially the same as the viscosity of a basalt with 2.29 wt.% H2O, so CO2 seems to have a negligible or even viscosity-increasing effect when F and H2O are also present. However, a basalt with ~0.84 wt.% H2O and ~0.09 wt.% CO2 has about the same viscosity as a basalt with 1.34 wt.% H2O, which could suggest a strong (viscosity-decreasing) effect of very small amounts of CO2. These results suggest that the effects on viscosity of F in basaltic systems are

  13. CARS diagnostics of the burning of H2 — O2 and CH4 — O2 mixtures at high temperatures and pressures

    NASA Astrophysics Data System (ADS)

    Vereshchagin, K. A.; Smirnov, Valery V.; Stel'makh, O. M.; Fabelinskii, V. I.

    2012-01-01

    Coherent anti-Stokes Raman scattering (CARS) spectroscopy is used to determine the parameters of gaseous combustion products of hydrogen and hydrocarbon fuels with oxygen at high temperatures and pressures. The methodical aspects of CARS thermometry, which are related to the optimal choice of molecules (diagnostic references) and specific features of their spectra, dependent on temperature and pressure, are analysed. Burning is modelled under the conditions similar to those of real spacecraft propulsion systems using a specially designed laboratory combustion chamber, operating in the pulse-periodic regime at high temperatures (to 3500 K) and pressures (to 20 MPa) of combustion products.

  14. Suppression of diamagnetism by neutrals pressure in partially ionized, high-beta plasma

    NASA Astrophysics Data System (ADS)

    Shinohara, Shunjiro; Kuwahara, Daisuke; Yano, Kazuki; Fruchtman, Amnon

    2016-12-01

    Suppression of diamagnetism in a partially ionized plasma with high beta was experimentally investigated by the use of Langmuir and Hall sensor probes, focusing on a neutrals pressure effect. The plasma beta, which is the ratio of plasma to vacuum magnetic pressures, varied from ˜1% to >100% while the magnetic field varied from ˜120 G to ˜1 G. Here, a uniform magnetized argon plasma was operated mostly in an inductive mode, using a helicon plasma source of the Large Helicon Plasma Device [S. Shinohara et al., Phys. Plasmas 16, 057104 (2009)] with a diameter of 738 mm and an axial length of 4860 mm. Electron density varied from 5 × 1015 m-3 to <3 × 1018 m-3, while an argon fill pressure was varied from ˜0.02 Pa to 0.75 Pa as well as the magnetic field mentioned above, with the fixed radio frequency (rf) and power of 7 MHz and ˜3.5 kW, respectively. The observed magnetic field reduction rate, a decrease of the magnetic field divided by the vacuum one, was up to 18%. However, in a certain parameter regime, where the product of ion and electron Hall terms is a key parameter, the measured diamagnetic effect was smaller than that expected by the plasma beta. This suppressed diamagnetism is explained by the neutrals pressure replacing magnetic pressure in balancing plasma pressure. Diamagnetism is weakened if neutrals pressure is comparable to the plasma pressure and if the coupling of plasma and neutrals pressures by ion-neutral collisions is strong enough.

  15. Study of low-defect and strain-relaxed GeSn growth via reduced pressure CVD in H2 and N2 carrier gas

    NASA Astrophysics Data System (ADS)

    Margetis, J.; Mosleh, A.; Al-Kabi, S.; Ghetmiri, S. A.; Du, W.; Dou, W.; Benamara, M.; Li, B.; Mortazavi, M.; Naseem, H. A.; Yu, S.-Q.; Tolle, J.

    2017-04-01

    High quality, thick (up to 1.1 μm), strain relaxed GeSn alloys were grown on Ge-buffered Si (1 0 0) in an ASM Epsilon® chemical vapor deposition system using SnCl4 and low-cost commercial GeH4 precursors. The significance of surface chemistry in regards to growth rate and Sn-incorporation is discussed by comparing growth kinetics data in H2 and N2 carrier gas. The role of carrier gas is also explored in the suppression of Sn surface segregation and evolution of layer composition and strain profiles via secondary ion mass spectrometry and X-ray diffraction. Transmission electron microscopy revealed the spontaneous compositional splitting and formation of a thin intermediate layer in which dislocations are pinned. This intermediate layer enables the growth of a thick, strain relaxed, and defect-free epitaxial layer on its top. Last, we present photoluminescence results which indicate that both N2 and H2 growth methods produce optoelectronic device quality material.

  16. 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).

  17. Biomethanation of Syngas Using Anaerobic Sludge: Shift in the Catabolic Routes with the CO Partial Pressure Increase.

    PubMed

    Sancho Navarro, Silvia; Cimpoia, Ruxandra; Bruant, Guillaume; Guiot, Serge R

    2016-01-01

    Syngas generated by thermal gasification of biomass or coal can be steam reformed and purified into methane, which could be used locally for energy needs, or re-injected in the natural gas grid. As an alternative to chemical catalysis, the main components of the syngas (CO, CO2, and H2) can be used as substrates by a wide range of microorganisms, to be converted into gas biofuels, including methane. This study evaluates the carboxydotrophic (CO-consuming) methanogenic potential present in an anaerobic sludge from an upflow anaerobic sludge bed (UASB) reactor treating waste water, and elucidates the CO conversion routes to methane at 35 ± 3°C. Kinetic activity tests under CO at partial pressures (pCO) varying from 0.1 to 1.5 atm (0.09-1.31 mmol/L in the liquid phase) showed a significant carboxydotrophic activity potential for growing conditions on CO alone. A maximum methanogenic activity of 1 mmol CH4 per g of volatile suspended solid and per day was achieved at 0.2 atm of CO (0.17 mmol/L), and then the rate decreased with the amount of CO supplied. The intermediary metabolites such as acetate, H2, and propionate started to accumulate at higher CO concentrations. Inhibition experiments with 2-bromoethanesulfonic acid (BES), fluoroacetate, and vancomycin showed that in a mixed culture CO was converted mainly to acetate by acetogenic bacteria, which was further transformed to methane by acetoclastic methanogens, while direct methanogenic CO conversion was negligible. Methanogenesis was totally blocked at high pCO in the bottles (≥1 atm). However it was possible to achieve higher methanogenic potential under a 100% CO atmosphere after acclimation of the sludge to CO. This adaptation to high CO concentrations led to a shift in the archaeal population, then dominated by hydrogen-utilizing methanogens, which were able to take over acetoclastic methanogens, while syntrophic acetate oxidizing (SAO) bacteria oxidized acetate into CO2 and H2. The disaggregation of the

  18. Biomethanation of Syngas Using Anaerobic Sludge: Shift in the Catabolic Routes with the CO Partial Pressure Increase

    PubMed Central

    Sancho Navarro, Silvia; Cimpoia, Ruxandra; Bruant, Guillaume; Guiot, Serge R.

    2016-01-01

    Syngas generated by thermal gasification of biomass or coal can be steam reformed and purified into methane, which could be used locally for energy needs, or re-injected in the natural gas grid. As an alternative to chemical catalysis, the main components of the syngas (CO, CO2, and H2) can be used as substrates by a wide range of microorganisms, to be converted into gas biofuels, including methane. This study evaluates the carboxydotrophic (CO-consuming) methanogenic potential present in an anaerobic sludge from an upflow anaerobic sludge bed (UASB) reactor treating waste water, and elucidates the CO conversion routes to methane at 35 ± 3°C. Kinetic activity tests under CO at partial pressures (pCO) varying from 0.1 to 1.5 atm (0.09–1.31 mmol/L in the liquid phase) showed a significant carboxydotrophic activity potential for growing conditions on CO alone. A maximum methanogenic activity of 1 mmol CH4 per g of volatile suspended solid and per day was achieved at 0.2 atm of CO (0.17 mmol/L), and then the rate decreased with the amount of CO supplied. The intermediary metabolites such as acetate, H2, and propionate started to accumulate at higher CO concentrations. Inhibition experiments with 2-bromoethanesulfonic acid (BES), fluoroacetate, and vancomycin showed that in a mixed culture CO was converted mainly to acetate by acetogenic bacteria, which was further transformed to methane by acetoclastic methanogens, while direct methanogenic CO conversion was negligible. Methanogenesis was totally blocked at high pCO in the bottles (≥1 atm). However it was possible to achieve higher methanogenic potential under a 100% CO atmosphere after acclimation of the sludge to CO. This adaptation to high CO concentrations led to a shift in the archaeal population, then dominated by hydrogen-utilizing methanogens, which were able to take over acetoclastic methanogens, while syntrophic acetate oxidizing (SAO) bacteria oxidized acetate into CO2 and H2. The disaggregation of the

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

    SciTech Connect

    Kent, Paul R

    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.

  20. Preliminary Measurements Of N2O Partial Pressures In Rivers of Amazon Basin, Brazil

    NASA Astrophysics Data System (ADS)

    Oliveira, C. B.; Rasera, M. F.; Krusche, A. V.; Victoria, R. L.; Richey, J. E.; Cunha, H. B.; Gomes, B. M.

    2006-12-01

    The concentrations of nitrous oxide (N2O), an important component of the greenhouse effect and with a long residence time in the atmosphere, have significantly increased in this century. The reasons for this atmospheric increase in N2O are still partially unexplained. This uncertainty is worse in relation to aquatic environments. Here we report on preliminary measurements of N2O partial pressures in rivers of the Amazon basin. The study areas are in the state of Rondonia (rivers Ji Parana, Urupa, Comemoracao and Pimenta Bueno) and Amazonas (rivers Solimoes and Negro). The rivers were sampled from October 2005 to April 2006, using with immersion pumps, lowered in the middle of the channel to 60% of total depth. Water was pumped directly into a 1 l plastic bottle, which was overflown three times before closing. Using syringes, 60 ml of N2 were injected into the bottle, simultaenously to the withdrawn of 60 ml of sample. N2O was extracted into these 60 ml of N2 by shaking vigorously for 2 minutes. With the same syringes, the gas was taken from the bottles and injected into sealed evacuated 25 ml vials. Atmospheric samples were taken from one meter above the water column and stored the same way. N2O partial pressures were determined on a Shimadzu GC-14 Green House Gas Analyzer. All rivers showed little variations in N2O partial pressures. Average values in the rivers of Rondonia were around 0.41 ± 0.07 μ atm (n=46), whereas the Solimoes and Negro rivers, in the state of Amazonas, showed values around 0.43 ± 0.08 μ atm (n=131). Atmospheric averages were approximately 0.34 ± 0.04 μ atm (n=58) and 0.32 ± 0.03 μ atm (n=134) in the states of Rondonia and Amazonas, respectively. This means that, although these waters are supersatured in CO2, making evasive fluxes of this gas an important component of the C cycle in this basin, the same does not occur in the N cycle. Small differences in partial pressures of N2O between water and air will result in small fluxes of

  1. Experimental and model comparisons of low- and medium-pressure Hg lamps for the direct and H2O2 assisted UV photodegradation of N-nitrosodimethylamine in simulated drinking water.

    PubMed

    Sharpless, Charles M; Linden, Karl G

    2003-05-01

    Both low- and medium-pressure Hg lamps (LP and MP, respectively) were used as ultraviolet light (UV) sources to destroy N-nitrosodimethylamine in a synthetic "natural" water. The lamp performances were directly compared via the UV fluence-based rate constants, which demonstrates that LP and MP have virtually identical photonic efficiencies (fluence-based rate constants of 2.29E-3 and 2.35E-3 cm2/mJ, respectively). This indicates that the quantum yield for NDMA photolysis is independent of wavelength in the UVC region: a value of 0.30 mol/einstein is found at pH 8.1. Addition of 100 mg/L of H2O2 leads to a 30% increase in the LP fluence-based rate constant but does not alter the MP rate constant, likely due to the tradeoff between light screening by H2O2 and additional radical based degradation. However, in terms of the time-based rate constant, this level of H2O2 slightly enhances the LP performance but hinders the MP performance, suggesting that H2O2 is of little or no economic benefit for NDMA removal by UV. All these effects are explained by modeling the photochemistry according to standard equations. The model predicts that H2O2 may enhance NDMA removal for short optical path lengths but that light-screening by H2O2 may decrease the removal rates for optical path lengths typical of those found in UV reactors.

  2. Proximate nutritional composition of CELSS crops grown at different CO2 partial pressures

    NASA Technical Reports Server (NTRS)

    Wheeler, R. M.; Mackowiak, C. L.; Sager, J. C.; Knott, W. M.; Berry, W. L.

    1994-01-01

    Two Controlled Ecological Life Support System (CELSS) candidate crops, soybean (Glycine max) and potato (Solanum tuberosum), were grown hydroponically in controlled environments maintained at carbon dioxide (CO2) partial pressures ranging from 0.05 to 1.00 kPa (500 to 10,000 ppm at 101 kPa atmospheric pressure). Plants were harvested at maturity (90 days for soybean and 105 days for potato) and all tissues analyzed for proximate nutritional composition (i.e. protein, fat, carbohydrate, crude fiber, and ash content). Soybean seed ash and crude fiber were higher and carbohydrate was lower than values reported for field-grown seed. Potato tubers showed little difference from field-grown tubers. Crude fiber of soybean stems and leaves increased with increased CO2, as did soybean leaf protein (total nitrogen). Potato leaf and stem (combined) protein levels also increased with increased CO2, while leaf and stem carbohydrates decreased. Values for leaf and stem protein and ash were higher than values generally reported for field-grown plants for both species. Results suggest that CO2 partial pressure should have little influence on proximate composition of potato tubers or soybean seed, but that high ash and protein levels might be expected from leaves and stems of crops grown in controlled environments of a CELSS.

  3. Dehydration and partial melting of tremolitic amphibole coexisting with zoisite, quartz, anorthite, diopside, and water in the system H2O-CaO-MgO-Al2O3-SiO2

    NASA Astrophysics Data System (ADS)

    Quirion, Diane M.; Jenkins, David M.

    The greenschist to amphibolite transition as modeled by the reaction zoisite+tremolite + quartz= anorthite+diopside+water has been experimentally investigated in the chemical system H2O-CaO- MgO-Al2O3-SiO2 over the range of 0.4-0.8 GPa. This reaction is observed to lie within the stability fields of anorthite + water and of zoisite + quartz, in accord with phase equilibrium principles, and its position is in excellent agreement with the boundary calculated from current internally-consistent data bases. The small dP/dT slope of 0.00216 GPa/K (21.6 bars/K) observed for this reaction supports the pressure-dependency of this transition in this chemical system. Experimental reversals of the Al content in tremolitic amphibole coexisting with zoisite, diopside, quartz, and water were obtained at 600, 650, and 700°C and indicated Al total cations (atoms per formula unit, apfu) of only up to 0.5+/-0.08 at the highest temperature. Thermodynamic analysis of these and previous compositional reversal data for tremolitic amphibole indicated that, of the activity/composition relationships considered, a two-site-coupled cation substitution model yielded the best fit to the data and a S0 (1 bar, 298 K) of 575.4+/-1.6 J/K.mol for magnesio-hornblende. The calculated isopleths of constant Al content in the amphibole are relatively temperature sensitive with Al content increasing with increasing temperature and pressure. Finally, several experiments in the range of 1.0-1.3 GPa were conducted to define the onset of melting, and thus the upper-thermal limit, for this mineral assemblage, which must involve an invariant point located at approximately 1.05 GPa and 770°C.

  4. Growth of soybean and potato at high CO2 partial pressures

    NASA Astrophysics Data System (ADS)

    Wheeler, R. M.; Mackowiak, C. L.; Sager, J. C.; Knott, W. M.

    1994-11-01

    Soybean and potato plants were grown in controlled environments at carbon dioxide (CO2) partial pressures ranging from 0.05 to 1.00 kPa. The highest yields of edible biomass occurred at 0.10 kPa for both species, with higher CO2 levels being supraoptimal, but not injurious to the plants. Stomatal conductance rates of upper canopy leaves were lowest at 0.10 kPa CO2, while conductance rates at 0.50 and 1.00 kPa were significantly greater than 0.10 kPa. Total water use by the plants was greatest at the highest CO2 pressures (i.e. 0.50 and 1.00 kPa); consequently, water use efficiencies (biomass produced / water used) were low at the highest CO2 pressures. Based on previous CO2 studies in the literature, the increased conductance and water use at the highest CO2 pressures were surprising and pose interesting challenges for managing plants in a CELSS, where CO2 pressures may exceed optimal levels.

  5. Solubilities of corundum, wollastonite and quartz in H 2O-NaCl solutions at 800 °C and 10 kbar: Interaction of simple minerals with brines at high pressure and temperature

    NASA Astrophysics Data System (ADS)

    Newton, Robert C.; Manning, Craig E.

    2006-11-01

    Solubilities of corundum (Al 2O 3) and wollastonite (CaSiO 3) were measured in H 2O-NaCl solutions at 800 °C and 10 kbar and NaCl concentrations up to halite saturation by weight-loss methods. Additional data on quartz solubility at a single NaCl concentration were obtained as a supplement to previous work. Single crystals of synthetic corundum, natural wollastonite or natural quartz were equilibrated with H 2O and NaCl at pressure ( P) and temperature ( T) in a piston-cylinder apparatus with NaCl pressure medium and graphite heater sleeves. The three minerals show fundamentally different dissolution behavior. Corundum solubility undergoes large enhancement with NaCl concentration, rising rapidly from Al 2O 3 molality (mO) of 0.0013(1) (1 σ error) in pure H 2O and then leveling off to a maximum of ˜0.015 at halite saturation ( XNaCl ≈ 0.58, where X is mole fraction). Solubility enhancement relative to that in pure H 2O, XO/XAlO°, passes through a maximum at XNaCl ≈ 0.15 and then declines towards halite saturation. Quenched fluids have neutral pH at 25 °C. Wollastonite has low solubility in pure H 2O at this P and T(m=0.0167(6)). It undergoes great enhancement, with a maximum solubility relative to that in H 2O at XNaCl ≈ 0.33, and solubility >0.5 molal at halite saturation. Solute silica is 2.5 times higher than at quartz saturation in the system H 2O-NaCl-SiO 2, and quenched fluids are very basic (pH 11). Quartz shows monotonically decreasing solubility from m=1.248 in pure H 2O to 0.202 at halite saturation. Quenched fluids are pH neutral. A simple ideal-mixing model for quartz-saturated solutions that requires as input only the solubility and speciation of silica in pure H 2O reproduces the data and indicates that hydrogen bonding of molecular H 2O to dissolved silica species is thermodynamically negligible. The maxima in XO/XAlO° for corundum and wollastonite indicate that the solute products include hydrates and Na + and/or Cl - species produced by

  6. Disproportionation and thermochemical sulfate reduction reactions in S-H2O-CH4 and S-D2O-CH4 systems from 200 to 340 °C at elevated pressures

    NASA Astrophysics Data System (ADS)

    Yuan, Shunda; Chou, I.-Ming; Burruss, Robert C.

    2013-10-01

    Elemental sulfur, as a transient intermediate compound, by-product, or catalyst, plays significant roles in thermochemical sulfate reduction (TSR) reactions. However, the mechanisms of the reactions in S-H2O-hydrocarbons systems are not clear. To improve our understanding of reaction mechanisms, we conducted a series of experiments between 200 and 340 °C for S-H2O-CH4, S-D2O-CH4, and S-CH4-1m ZnBr2 systems in fused silica capillary capsules (FSCCs). After a heating period ranging from 24 to 2160 h (hrs), the quenched samples were analyzed by Raman spectroscopy. Combined with the in situ Raman spectra collected at high temperatures and pressures in the S-H2O and S-H2O-CH4 systems, our results showed that (1) the disproportionation of sulfur in the S-H2O-CH4 system occurred at temperatures above 200 °C and produced H2S, SO42-, and possibly trace amount of HSO4-; (2) sulfate (and bisulfate), in the presence of sulfur, can be reduced by methane between 250 and 340 °C to produce CO2 and H2S, and these TSR temperatures are much closer to those of the natural system (<200 °C) than those of any previous experiments; (3) the disproportionation and TSR reactions in the S-H2O-CH4 system may take place simultaneously, with TSR being favored at higher temperatures; and (4) in the system S-D2O-CH4, both TSR and the competitive disproportionation reactions occurred simultaneously at temperatures above 300 °C, but these reactions were very slow at lower temperatures. Our observation of methane reaction at 250 °C in a laboratory time scale suggests that, in a geologic time scale, methane may be destroyed by TSR reactions at temperatures >200 °C that can be reached by deep drilling for hydrocarbon resources.

  7. The high-pressure phase diagram of synthetic epsomite (MgSO4·7H2O and MgSO4·7D2O) 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 MgSO4·7H2O (synthetic epsomite) and MgSO4·7D2O 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 MgSO4·7H2O 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.

  8. 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.

  9. 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 59.4°C-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.

  10. Experimental multi-phase H2O-CO2 brine interactions at elevated temperature and pressure: Implications for CO2 sequestration in deep-saline aquifers

    USGS Publications Warehouse

    Rosenbauer, R.; Koksalan, T.

    2004-01-01

    The burning of fossil fuel and other anthropogenic activities have caused a continuous and dramatic 30% increase of atmospheric CO2 over the past 150 yr. CO2 sequestration is increasingly being viewed as a tool for managing these anthropogenic CO2 emissions to the atmosphere. CO2-saturated brine-rock experiments were carried out to evaluate the effects of multiphase H2O-CO2 fluids on mineral equilibria and the potential for CO2 sequestration in mineral phases within deep-saline aquifers. Experimental results were generally consistent with theoretical thermodynamic calculations. The solubility of CO2 was enhanced in brines in the presence of both limestone and sandstone relative to brines alone. Reactions between CO2 saturated brines and arkosic sandstones were characterized by desiccation of the brine and changes in the chemical composition of the brine suggesting fixation of CO2 in mineral phases. These reactions were occurring on a measurable but kinetically slow time scale at 120??C.

  11. Phase relations in the system NaCl-KCl-H2O: V. Thermodynamic-PTX analysis of solid-liquid equilibria at high temperatures and pressures

    USGS Publications Warehouse

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

    1992-01-01

    The Gibbs energies of mixing for NaCl-KCl binary solids and liquids and solid-saturated NaCl-KCl-H2O ternary liquids were modeled using asymmetric Margules treatments. The coefficients of the expressions were calibrated using an extensive array of binary solvus and solidus data, and both binary and ternary liquidus data. Over the PTX range considered, the system exhibits complete liquid miscibility among all three components and extensive solid solution along the anhydrous binary. Solid-liquid and solid-solid phase equilibria were calculated by using the resulting equations and invoking the equality of chemical potentials of NaCl and KCl between appropriate phases at equilibrium. The equations reproduce the ternary liquidus and predict activity coefficients for NaCl and KCl components in the aqueous liquid under solid-saturation conditions between 673 and 1200 K from vapor saturation up to 5 kbar. In the NaCl-KCl anhydrous binary system, the equations describe phase equilibria and predict activity coefficients of the salt components for all stable compositions of solid and liquid phases between room temperature and 1200 K and from 1 bar to 5 kbar. ?? 1992.

  12. Effect of H2S and COS in the fuel gas on the performance of ambient pressure phosphoric acid fuel cells

    NASA Astrophysics Data System (ADS)

    Ross, P. N., Jr.

    1985-04-01

    The objective of this project was to determine in laboratory cells the tolerance of phosphoric acid fuel cells (PAFC) to hydrogen sulfide and carbonyl sulphide impurities in the anode feed gas. The study was conducted in three phases: the first was testing in a small (1 sq cm) free electrolyte cell to examine the effect of electrode structure on cell tolerance and to determine the order of magnitude of sulfur causing failure in cells at zero utilization; the second was testing in standard 2' x 2' PAFC laboratory hardware at ambient pressure to examine the effect of hydrogen utilization on tolerance and the possible effect of fuel impurities on cathode performance; the final phase was testing with a 2' x 2' cell in a pressure vessel to determine the effect of pressurized operation on cell tolerance. The poisoning effect of hydrogen sulfide was characteristically different from the effects of carbon monoxide, in that it was not manifested by a marginal (e.g., 0 to 50 mV) increase in anode potential but either had no effect or caused catastrophic polarization. Critical levels were derived for hydrogen sulfide as related to cell operating conditions.

  13. Pressure-composition relations for coexisting gases and liquids and the critical points in the system NaCl-H2O at 450, 475, and 500°C

    USGS Publications Warehouse

    Rosenbauer, Robert J.; Bischoff, James L.

    1987-01-01

    Pressure-temperature-composition (P, T, x) relations for the co-existing vapor and liquid phases in the system NaCl-H2O were determined experimentally at 450, 475, and 500°C. Data for each isotherm includeP-x relations near the critical point and extend to the three-phase assemblage vapor-liquid-halite on the vapor side. On the liquid side the P-x data range from the critical point to the room-temperature halite saturation point (~25 wt.% NaCl). Critical pressures were calculated from measured pressures and compositions and classical theory. The results generally support the few data points of Urusova (1974, 1975) and Ölander and Liander (1950) but differ markedly from the extensive data of Sourirajan andKennedy (1962).

  14. Thermodynamics of formate-oxidizing metabolism and implications for H2 production.

    PubMed

    Lim, Jae Kyu; Bae, Seung Seob; Kim, Tae Wan; Lee, Jung-Hyun; Lee, Hyun Sook; Kang, Sung Gyun

    2012-10-01

    Formate-dependent proton reduction to H(2) (HCOO(-) + H(2)O → HCO(3)(-) + H(2)) has been reported for hyperthermophilic Thermococcus strains. In this study, a hyperthermophilic archaeon, Thermococcus onnurineus strain NA1, yielded H(2) accumulation to a partial pressure of 1 × 10(5) to 7 × 10(5) Pa until the values of Gibbs free energy change (ΔG) reached near thermodynamic equilibrium (-1 to -3 kJ mol(-1)). The bioenergetic requirement for the metabolism to conserve energy was demonstrated by ΔG values as small as -5 kJ mol(-1), which are less than the biological minimum energy quantum, -20 kJ mol(-1), as calculated by Schink (B. Schink, Microbiol. Mol. Biol. Rev. 61:262-280, 1997). Considering formate as a possible H(2) storage material, the H(2) production potential of the strain was assessed. The volumetric H(2) production rate increased linearly with increasing cell density, leading to 2,820 mmol liter(-1) h(-1) at an optical density at 600 nm (OD(600)) of 18.6, and resulted in the high specific H(2) production rates of 404 ± 6 mmol g(-1) h(-1). The H(2) productivity indicates the great potential of T. onnurineus strain NA1 for practical application in comparison with H(2)-producing microbes. Our result demonstrates that T. onnurineus strain NA1 has a highly efficient metabolic system to thrive on formate in hydrothermal systems.

  15. New strontium polysulfides, SrS3, and Sr2(OH)2S4.10H2O, obtained by the high-pressure treatment of a Sr-S mixture.

    PubMed

    Fukuoka, Hiroshi; Suga, Rimiko; Komaguchi, Kenji; Yamanaka, Shoji; Shiotani, Masaru

    2004-09-06

    A new polymorph of SrS(3) was obtained by a reaction of SrS and S with an atomic ratio of Sr:S = 1:5 under a pressure of 5 GPa at 1200 degrees C. It crystallized in a tetragonal unit cell with a = 6.708(1) A, c = 3.942(1) A, and V = 177.36(6) A(3). It was isotypic with BaS(3), and contained S3(2-) polysulfide ions. The product obtained from the high-pressure synthesis contained an amorphous component. It was highly deliquescent and formed a yellowish solution. A new layered polysulfide, Sr(2)(OH)(2)S(4).10H(2)O, crystallized in the solution. The sulfide belonged to a triclinic space group of P (No. 2) with lattice constants of a = 5.9107(5) A, b = 7.8682(6) A, c = 9.4134(6) A, alpha = 75.639(6) degrees, beta = 73.824(3) degrees, gamma = 71.639(3) degrees, V = 392.83(5) A(3), and Z = 1. Each Sr ion was coordinated with one OH ligand and eight H(2)O ligands. Six H(2)O ligands out of the eight were bridging ligands to form two-dimensional [Sr(2)(OH)(2)(H(2)O)(10)(2+)]( infinity ) cationic layers, between which S4(2-) tetrapolysulfide ions were situated. The S4(2-) anion had a coplanar configuration with a dihedral angle of 180.0 degrees. The stability of S4(2-) anions having different conformations was discussed from a viewpoint of ab initio MO calculations on changing the dihedral angles of S4(2-).

  16. 13C-NMR studies of the paramagnetic and charge-ordered states of the organic superconductor β''-(BEDT-TTF)3Cl2·2H2O under pressure

    NASA Astrophysics Data System (ADS)

    Nagata, Sanato; Ogura, Takashi; Kawamoto, Atsushi; Taniguchi, Hiromi

    2011-07-01

    β''-(BEDT-TTF)3Cl2·2H2O [BEDT-TTF: b̲is-(e̲thylened̲it̲hio)t̲etrat̲hiaf̲ulvalene] is superconductive under pressures, whereas the salt exhibits metal-insulator (MI) transition under ambient pressure. The insulator phase in the salt was examined using the charge density wave (CDW) phase that was obtained from band calculation. The charge-ordered (CO) state was recently proposed as the insulator phase of the salt, and the mechanism of superconductivity intermediated by charge fluctuation was suggested. We accessed 13C-NMR on β''-(BEDT-TTF)3Cl2·2H2O at ambient pressure and under pressure up to 1.6 GPa. At ambient pressure, the NMR spectrum changed at approximately 100 K. Three isolated peaks appeared at low temperatures, suggesting that the CO state exists below 100 K, and spin-gap behavior was observed. By analyzing the chemical shift, the charges on the three sites were estimated as ˜+0.4e, ˜+0.6e, and ˜+1.0e. The ratio of peak intensity and unsymmetrical peak position suggest the CO state with some symmetry breaking. When pressure is applied, the splitting of the NMR peaks in the CO state is reduced. The salt finally exhibits superconductivity at 1.6 GPa, spin-gap behavior observed at (T1T)-1 below 1.3 GPa suddenly disappears, whereas the NMR spectrum predicts that charge disproportionation coexists with superconductivity. The suppression of the spin-singlet formation observed in (T1T)-1 at 1.6 GPa suggests the metallic state with the charge disproportionation and the CO instability with some symmetry breaking.

  17. In Situ Analysis of the Tribochemical Films Formed by SiC Sliding Against Mo in Partial Pressures of SO2, O2, and H2S Gases

    DTIC Science & Technology

    1996-02-01

    MoO3 or one of the substoichiometric MoOx ~2 ,x, 3! compounds—formed, although MoO2 is the first to crystal- lize from the chemisorbed state with...increasing thermal activity.31,32 We therefore designate the oxide to be MoOx . In SO2 , mixtures of MoS2 and MoOx would be expected. On the SiC wear scar...from Auger data. ~2<xɛ y , z51 or 2.! Gas Solid Mo SiC Tribofilm Transfer Tribofilm Transfer SO2 MoOx /MoS2 None SiOy/SiSz , C MoOx /MoS2 O2 MoOx None

  18. Post-treatment of refinery wastewater effluent using a combination of AOPs (H2O2 photolysis and catalytic wet peroxide oxidation) for possible water reuse. Comparison of low and medium pressure lamp performance.

    PubMed

    Rueda-Márquez, J J; Levchuk, I; Salcedo, I; Acevedo-Merino, A; Manzano, M A

    2016-03-15

    The main aim of this work was to study the feasibility of multi-barrier treatment (MBT) consisting of filtration, hydrogen peroxide photolysis (H2O2/UVC) and catalytic wet peroxide oxidation (CWPO) for post-treatment of petroleum refinery effluent. Also the possibility of water reuse or safe discharge was considered. The performance of MBT using medium (MP) and low (LP) pressure lamps was compared as well as operation and maintenance (O&M) cost. Decomposition of organic compounds was followed by means of gas chromatography-mass spectrometry (GC-MS), total organic carbon (TOC) and chemical oxygen demand (COD) analysis. After filtration step (25 μm) turbidity and concentration of suspended solids decreased by 92% and 80%, respectively. During H2O2/UVC process with LP lamp at optimal conditions (H2O2:TOC ratio 8 and UVC dose received by water 5.28 WUVC s cm(-2)) removal of phenolic compounds, TOC and COD was 100%, 52.3% and 84.3%, respectively. Complete elimination of phenolic compounds, 47.6% of TOC and 91% of COD was achieved during H2O2/UVC process with MP lamp at optimal conditions (H2O2:TOC ratio 5, UVC dose received by water 6.57 WUVC s cm(-2)). In order to compare performance of H2O2/UVC treatment with different experimental set up, the UVC dose required for removal of mg L(-1) of COD was suggested as a parameter and successfully applied. The hydrophilicity of H2O2/UVC effluent significantly increased which in turn enhanced the oxidation of organic compounds during CWPO step. After H2O2/UVC treatment with LP and MP lamps residual H2O2 concentration was 160 mg L(-1) and 96.5 mg L(-1), respectively. Remaining H2O2 was fully consumed during subsequent CWPO step (6 and 3.5 min of contact time for LP and MP, respectively). Total TOC and COD removal after MBT was 94.7% and 92.2% (using LP lamp) and 89.6% and 95%, (using MP lamp), respectively. The O&M cost for MBT with LP lamp was estimated to be 0.44 € m(-3) while with MP lamp it was nearly five

  19. Low tritium partial pressure permeation system for mass transport measurement in lead lithium eutectic

    DOE PAGES

    Pawelko, R. J.; Shimada, M.; Katayama, K.; ...

    2015-11-28

    This paper describes a new experimental system designed to investigate tritium mass transfer properties in materials important to fusion technology. Experimental activities were carried out at the Safety and Tritium Applied Research (STAR) facility located at the Idaho National Laboratory (INL). The tritium permeation measurement system was developed as part of the Japan/US TITAN collaboration to investigate tritium mass transfer properties in liquid lead lithium eutectic (LLE) alloy. The experimental system is configured to measure tritium mass transfer properties at low tritium partial pressures. Initial tritium permeation scoping tests were conducted on a 1 mm thick α-Fe plate to determinemore » operating parameters and to validate the experimental technique. A second series of permeation tests was then conducted with the α-Fe plate covered with an approximately 8.5 mm layer of liquid lead lithium eutectic alloy (α-Fe/LLE). We present preliminary tritium permeation data for α-Fe and α-Fe/LLE at temperatures between 400 and 600°C and at tritium partial pressures between 1.7E-3 and 2.5 Pa in helium. Preliminary results for the α-Fe plate and α-Fe/LLE indicate that the data spans a transition region between the diffusion-limited regime and the surface-limited regime. In conclusion, additional data is required to determine the existence and range of a surface-limited regime.« less

  20. DEVELOPMENT OF PRESSURIZED CIRCULATIONG FLUIDIZED BED PARTIAL GASIFICATION MODULE(PGM)

    SciTech Connect

    Archie Robertson

    2003-04-17

    Foster Wheeler Power Group, Inc. is working under US Department of Energy contract No. DE-FC26-00NT40972 to develop a partial gasification module (PGM) that represents a critical element of several potential coal-fired Vision 21 plants. When utilized for electrical power generation, these plants will operate with efficiencies greater than 60% and produce near zero emissions of traditional stack gas pollutants. The new process partially gasifies coal at elevated pressure producing a coal-derived syngas and a char residue. The syngas can be used to fuel the most advanced power producing equipment such as solid oxide fuel cells or gas turbines, or processed to produce clean liquid fuels or chemicals for industrial users. The char residue is not wasted; it can also be used to generate electricity by fueling boilers that drive the most advanced ultra-supercritical pressure steam turbines. The amount of syngas and char produced by the PGM can be tailored to fit the production objectives of the overall plant, i.e., power generation, clean liquid fuel production, chemicals production, etc. Hence, PGM is a robust building block that offers all the advantages of coal gasification but in a more user-friendly form; it is also fuel flexible in that it can use alternative fuels such as biomass, sewerage sludge, etc. This report describes the work performed during the January 1--March 31, 2003 time period.

  1. Low tritium partial pressure permeation system for mass transport measurement in lead lithium eutectic

    SciTech Connect

    Pawelko, R. J.; Shimada, M.; Katayama, K.; Fukada, S.; Humrickhouse, P. W.; Terai, T.

    2015-11-28

    This paper describes a new experimental system designed to investigate tritium mass transfer properties in materials important to fusion technology. Experimental activities were carried out at the Safety and Tritium Applied Research (STAR) facility located at the Idaho National Laboratory (INL). The tritium permeation measurement system was developed as part of the Japan/US TITAN collaboration to investigate tritium mass transfer properties in liquid lead lithium eutectic (LLE) alloy. The experimental system is configured to measure tritium mass transfer properties at low tritium partial pressures. Initial tritium permeation scoping tests were conducted on a 1 mm thick α-Fe plate to determine operating parameters and to validate the experimental technique. A second series of permeation tests was then conducted with the α-Fe plate covered with an approximately 8.5 mm layer of liquid lead lithium eutectic alloy (α-Fe/LLE). We present preliminary tritium permeation data for α-Fe and α-Fe/LLE at temperatures between 400 and 600°C and at tritium partial pressures between 1.7E-3 and 2.5 Pa in helium. Preliminary results for the α-Fe plate and α-Fe/LLE indicate that the data spans a transition region between the diffusion-limited regime and the surface-limited regime. In conclusion, additional data is required to determine the existence and range of a surface-limited regime.

  2. 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.

  3. Electron ionization of H2O

    NASA Astrophysics Data System (ADS)

    King, Simon J.; Price, Stephen D.

    2008-11-01

    Relative partial ionization cross-sections and precursor-specific relative partial ionization cross-sections for fragment ions formed by electron ionization of H2O have been measured using time-of-flight mass spectrometry coupled with a 2D ion coincidence technique. We report data for the formation of H+, H2+, O2+, O+ and OH+ relative to the formation of H2O+, as a function of ionizing electron energy from 30 to 200 eV. This data includes, for the first time, measurements on the formation all positive ion pairs and ion triples by dissociative multiple electron ionization of H2O. Through determinations of the kinetic energy release involved in ion pair formation we provide further evidence that indirect processes contribute significantly to the yield of H+ + OH+ ion pairs below the vertical double ionization threshold.

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

    PubMed

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

    2014-12-10

    The nature of protons in ice VII up to 368°C and 16GPa was investigated with synchrotron near-infrared spectroscopy. The absorption band of the first OH stretching overtone mode divided into doublet peaks above 5GPa 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.

  5. The Effect of Melt Pressure on the Rheology of Compacting, Partially Molten Peridotite

    NASA Astrophysics Data System (ADS)

    Demartin, B.; Hirth, G.; Evans, B.

    2004-12-01

    The rheology of partially molten rock controls rock strength beneath spreading centers, deformation of the mantle wedge under subduction zones, and migration of melt to hot spots and volcanic arcs. Our understanding of these regions has been predominately shaped by chemical analyses of rocks and by remotely collected geophysical data. To interpret these data, however, requires knowledge of the relationships among deformation, melt topology, and melt migration. Most previous experimental studies of these relationships in partially molten rocks were conducted using undrained experiments, i.e., where melt cannot leave the matrix during deformation. For this configuration, melt pressure is inferred to roughly equal the minimum principle stress, but is actually unknown. By contrast, we have performed drained tests in which both melt pressure and compaction rates were measured independently. First, samples were synthesized by hot-isostatic pressing (HIP) fine-grained olivine power (10-38 μ m) with a prescribed amount of mid-ocean ridge basalt (MORB) powder (< 15 μ m) in a gas-medium apparatus at 1200° C and 300 MPa for 10 hours. Melt fractions (MORB contents) ranged from 0-30 %. Subsequently, samples were reinserted into the apparatus and deformed in the standard triaxial configuration. Melt flow out of the sample was accommodated by a glassy carbon bead reservoir (grain size 80-200 μ m) located above the sample. A small alumina cylinder centered within the reservoir transferred the load from the pistons to the sample. Melt pressure was controlled by regulating the pressure of argon gas in contact with the melt in the reservoir. Sample compaction was measured by recording the position of a piston with the pore pressure generator. Variations of melt fraction on the strength of drained samples at Pm = 30 or 50 MPa, where Pm is the melt pressure, affect strength in the same way as previously observed under undrained conditions. Within the uncertainty of our measurements

  6. 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

  7. Plasma-enhanced CVD of functional coatings in Ar/maleic anhydride/C2H2 homogeneous dielectric barrier discharges at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Zajíčková, Lenka; Jelínek, Petr; Obrusník, Adam; Vodák, Jiří; Nečas, David

    2017-03-01

    In this contribution, we focus on the general problems of plasma-enhanced chemical vapor deposition in atmospheric pressure dielectric barrier discharges, i.e. deposition uniformity, film roughness and the formation of dust particles, and demonstrate them on the example of carboxyl coatings prepared by co-polymerization of acetylene and maleic anhydride. Since the transport of monomers at atmospheric pressure is advection-driven, special attention is paid to the gas dynamics simulations, gas flow patterns, velocity and residence time. By using numerical simulations, we design an optimized gas supply geometry capable of synthesizing uniform layers. The selection of the gas mixture containing acetylene was motivated by two of its characteristics: (i) suppression of filaments in dielectric barrier discharges, and (ii) improved film cross-linking, keeping the amount of functional groups high. However, acetylene discharges are prone to the formation of nanoparticles that can be incorporated into the deposited films, leading to their high roughness. Therefore, we also discuss the role of the gas composition, the spatial position of the substrate with respect to gas flow and the deposition time on the topography of the deposited films.

  8. 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.

    2013-06-30

    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.

  9. Behaviour at high pressure of Rb7NaGa8Si12O40·3H2O (a zeolite with EDI topology): a combined experimental-computational study

    NASA Astrophysics Data System (ADS)

    Gatta, G. D.; Tabacchi, G.; Fois, E.; Lee, Y.

    2016-03-01

    The high-pressure behaviour and the P-induced structural evolution of a synthetic zeolite Rb7NaGa8Si12O40·3H2O (with edingtonite-type structure) were investigated both by in situ synchrotron powder diffraction (with a diamond anvil cell and the methanol:ethanol:water = 16:3:1 mixture as pressure-transmitting fluid) up to 3.27 GPa and by ab initio first-principles computational modelling. No evidence of phase transition or penetration of P-fluid molecules was observed within the P-range investigated. The isothermal equation of state was determined; V 0 and K T0 refined with a second-order Birch-Murnaghan equation of state are V 0 = 1311.3(2) Å3 and K T0 = 29.8(7) GPa. The main deformation mechanism (at the atomic scale) in response to the applied pressure is represented by the cooperative rotation of the secondary building units (SBU) about their chain axis (i.e. [001]). The direct consequence of SBU anti-rotation on the zeolitic channels parallel to [001] is the increase in pore ellipticity with pressure, in response to the extension of the major axis and to the contraction of the minor axis of the elliptical channel parallel to [001]. The effect of the applied pressure on the bonding configuration of the extra-framework content is only secondary. A comparison between the P-induced main deformation mechanisms observed in Rb7NaGa8Si12O40·3H2O and those previously found in natural fibrous zeolites is made.

  10. 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.

  11. New type of phase transformation in gas hydrate forming system at high pressures. Some experimental and computational investigations of clathrate hydrates formed in the SF6-H2O system.

    PubMed

    Aladko, E Ya; Ancharov, A I; Goryainov, S V; Kurnosov, A V; Larionov, E G; Likhacheva, A Yu; Manakov, A Yu; Potemkin, V A; Sheromov, M A; Teplykh, A E; Voronin, V I; Zhurko, F V

    2006-10-26

    In this work, we present a new, previously unknown type of structure transformation in the high-pressure gas hydrates, which is related to the existence of two different isostructural phases of the sulfur hexafluoride clathrate hydrates. Each of these phases has its own stability field on the phase diagram. The difference between these hydrates consists of partial filling of small D cages by SF(6) molecules in the high-pressure phase; at 900 MPa, about half of small cages are occupied. Our calculations indicate that the increase of population of small cavities is improbable, therefore, at any pressure value, a part of the cavities remains vacant and the packing density is relatively low. This fact allowed us to suppose the existence of the upper pressure limit of hydrate formation in this system; the experimental results obtained confirm this assumption.

  12. Revealing sub-μm and μm-scale textures in H2O ice at megabar pressures by time-domain Brillouin scattering

    PubMed Central

    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

  13. Effect of pressure on magnetic properties of mixed ferro-ferrimagnet (Ni0.38Mn0.62)3[Cr(CN)6]2.zH2O

    NASA Astrophysics Data System (ADS)

    Zentková, M.; Mihalik, M.; Arnold, Z.; Kamarád, J.

    2010-01-01

    We present the results of magnetization measurements performed on the ferro-ferrimagnetic (Ni0.38Mn0.62)3[Cr(CN)6]2.zH2O molecule-based magnet under pressures up to 0.8 GPa. Both antiferromagnetic JAF and ferromagnetic interaction JF are present in this magnet and temperature dependence of magnetization μ(T) exhibits the compensation temperature Tcomp at which the sign of the magnetization is reversed. Our results indicate that JAF dominates. The Curie temperature TC of the magnet increases with applied pressure, dTC/dp = 10.6 KGPa-1, due to strengthened JAF. The increase of the JAF is attributed to the enhanced value of the single electron overlapping integral S and the energy gap Δ of the mixed molecular orbitals t2g (Mn2+) and t2g (CrIII) induced by pressure. Magnetization processes are also affected by pressure: magnetization saturates at higher magnetic field and saturated magnetization is reduced. The compensation temperature Tcomp decreases under pressure.

  14. 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.

  15. Extending helium partial pressure measurement technology to JET DTE2 and ITER

    NASA Astrophysics Data System (ADS)

    Klepper, C. C.; Biewer, T. M.; Kruezi, U.; Vartanian, S.; Douai, D.; Hillis, D. L.; Marcus, C.

    2016-11-01

    The detection limit for helium (He) partial pressure monitoring via the Penning discharge optical emission diagnostic, mainly used for tokamak divertor effluent gas analysis, is shown here to be possible for He concentrations down to 0.1% in predominantly deuterium effluents. This result from a dedicated laboratory study means that the technique can now be extended to intrinsically (non-injected) He produced as fusion reaction ash in deuterium-tritium experiments. The paper also examines threshold ionization mass spectroscopy as a potential backup to the optical technique, but finds that further development is needed to attain with plasma pulse-relevant response times. Both these studies are presented in the context of continuing development of plasma pulse-resolving, residual gas analysis for the upcoming JET deuterium-tritium campaign (DTE2) and for ITER.

  16. Diurnal changes in the partial pressure of carbon dioxide in coral reef waters

    SciTech Connect

    Kayanne, Hajime; Suzuki, Atsushi; Saito, Hiroshi

    1995-07-14

    Coral reefs are considered to be a source of atmospheric carbon dioxide because of their high calcium carbonate production and low net primary production. This was tested by direct measurement of diurnal changes in the partial pressure of carbon dioxide (P{sub CO2}) in reef waters during two 3-day periods, one in March 1993 and one in March 1994, on Shiraho reef of the Ryukyu Islands, Japan. Although the P{sub CO2} values in reef waters exhibited large diurnal changes ranging from 160 to 520 microatmospheres, they indicate that the reef flat area is a net sink for atmospheric carbon dioxide. This suggests that the net organic production rate of the reef community exceeded its calcium carbonate production rate during the observation periods. 16 refs., 2 figs., 1 tab.

  17. Extending Helium Partial Pressure Measurement Technology to JET DTE2 and ITER

    SciTech Connect

    Klepper, C Christopher; Biewer, Theodore M; Douai, D.; Hillis, Donald Lee; Marcus, Chris; Kruezi, Uron

    2016-01-01

    The detection limit for helium (He) partial pressure monitoring via the Penning discharge optical emission diagnostic, mainly used for tokamak divertor effluent gas analysis, is shown here to be possible for He concentrations down to 0.1% in predominantly deuterium effluents. This result from a dedicated laboratory study means that the technique can now be extended to intrinsically (non-injected) He produced as fusion reaction ash in deuterium-tritium experiments. The paper also examines threshold ionization mass spectroscopy as a potential backup to the optical technique, but finds that further development is needed to attain with plasma pulse-relevant response times. Both these studies are presented in the context of continuing development of plasma pulse-resolving, residual gas analysis for the upcoming JET deuterium-tritium campaign (DTE-2) and for ITER.

  18. Partial Pressures of In-Se from Optical Absorbance of the Vapor

    NASA Technical Reports Server (NTRS)

    Brebrick, R. F.; Su, Ching-Hua; Curreri, Peter A. (Technical Monitor)

    2001-01-01

    The optical absorbance of the vapor phase over various In-Se compositions between 33.3 and 61 atomic percent and 673 and 1418K has been measured and used to obtain the partial pressures of Se2(g) and In2Se(g). The results are in agreement with silica Bourdon gage measurements for compositions between 50 and 61 atomic percent but significantly higher than those from Knudsen cell and simultaneous Torsion-Knudsen cell measurements. The sequiselenide is found to sublime incongruently. Congruent vaporization occurs for the liquid above 1000 K between 50.08 and 56 at. percent Se. The Gibbs energy of formation of the liquid from its pure liquid elements between 1000 and 1300K is essentially independent of temperature and falls between -36 and -38 kJ per gram atomic weight for 50 and 56 percent Se at 1200 and 1300K.

  19. 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.

  20. MELCOR-H2

    SciTech Connect

    2009-11-10

    Before this LDRD research, no single tool could simulate a very high temperature reactor (VHTR) that is coupled to a secondary system and the sulfur iodine (SI) thermochemistry. Furthermore, the SI chemistry could only be modeled in steady state, typically via flow sheets. Additionally, the MELCOR nuclear reactor analysis code was suitable only for the modeling of light water reactors, not gas-cooled reactors. We extended MELCOR in order to address the above deficiencies. In particular, we developed three VHTR input models, added generalized, modular secondary system components, developed reactor point kinetics, included transient thermochemistry for the most important cycles [SI and the Westinghouse hybrid sulfur], and developed an interactive graphical user interface for full plant visualization. The new tool is called MELCOR-H2, and it allows users to maximize hydrogen and electrical production, as well as enhance overall plant safety. We conducted validation and verification studies on the key models, and showed that the MELCOR-H2 results typically compared to within less than 5% from experimental data, code-to-code comparisons, and/or analytical solutions.

  1. A theoretical study of water equilibria: The cluster distribution versus temperature and pressure for (H2O)n, n=1-60, and ice

    NASA Astrophysics Data System (ADS)

    Lenz, Annika; Ojamäe, Lars

    2009-10-01

    The size distribution of water clusters at equilibrium is studied using quantum-chemical calculations in combination with statistical thermodynamics. The necessary energetic data is obtained by quantum-chemical B3LYP computations and through extrapolations from the B3LYP results for the larger clusters. Clusters with up to 60 molecules are included in the equilibrium computations. Populations of different cluster sizes are calculated using both an ideal gas model with noninteracting clusters and a model where a correction for the interaction energy is included analogous to the van der Waals law. In standard vapor the majority of the water molecules are monomers. For the ideal gas model at 1 atm large clusters [56-mer (0-120 K) and 28-mer (100-260 K)] dominate at low temperatures and separate to smaller clusters [21-22-mer (170-280 K) and 4-6-mer (270-320 K) and to monomers (300-350 K)] when the temperature is increased. At lower pressure the transition from clusters to monomers lies at lower temperatures and fewer cluster sizes are formed. The computed size distribution exhibits enhanced peaks for the clusters consisting of 21 and 28 water molecules; these sizes are for protonated water clusters often referred to as magic numbers. If cluster-cluster interactions are included in the model the transition from clusters to monomers is sharper (i.e., occurs over a smaller temperature interval) than when the ideal-gas model is used. Clusters with 20-22 molecules dominate in the liquid region. When a large icelike cluster is included it will dominate for temperatures up to 325 K for the noninteracting clusters model. Thermodynamic properties (Cp, ΔH) were calculated with in general good agreement with experimental values for the solid and gas phase. A formula for the number of H-bond topologies in a given cluster structure is derived. For the 20-mer it is shown that the number of topologies contributes to making the population of dodecahedron-shaped cluster larger than

  2. Instrument for stable high temperature Seebeck coefficient and resistivity measurements under controlled oxygen partial pressure

    DOE PAGES

    Ihlefeld, Jon F.; Brown-Shaklee, Harlan James; Sharma, Peter Anand

    2015-04-28

    The transport properties of ceramic materials strongly depend on oxygen activity, which is tuned by changing the partial oxygen pressure (pO2) prior to and during measurement. Within, we describe an instrument for highly stable measurements of Seebeck coefficient and electrical resistivity at temperatures up to 1300 K with controlled oxygen partial pressure. An all platinum construction is used to avoid potential materials instabilities that can cause measurement drift. Two independent heaters are employed to establish a small temperature gradient for Seebeck measurements, while keeping the average temperature constant and avoiding errors associated with pO2-induced drifts in thermocouple readings. Oxygen equilibriummore » is monitored using both an O2 sensor and the transient behavior of the resistance as a proxy. A pO2 range of 10-25–100 atm can be established with appropriate gas mixtures. Seebeck measurements were calibrated against a high purity platinum wire, Pt/Pt–Rh thermocouple wire, and a Bi2Te3 Seebeck coefficient Standard Reference Material. To demonstrate the utility of this instrument for oxide materials we present measurements as a function of pO2 on a 1 % Nb-doped SrTiO3 single crystal, and show systematic changes in properties consistent with oxygen vacancy defect chemistry. Thus, an approximately 11% increase in power factor over a pO2 range of 10-19–10-8 atm at 973 K for the donor-doped single crystals is observed.« less

  3. Instrument for stable high temperature Seebeck coefficient and resistivity measurements under controlled oxygen partial pressure

    SciTech Connect

    Ihlefeld, Jon F.; Brown-Shaklee, Harlan James; Sharma, Peter Anand

    2015-04-28

    The transport properties of ceramic materials strongly depend on oxygen activity, which is tuned by changing the partial oxygen pressure (pO2) prior to and during measurement. Within, we describe an instrument for highly stable measurements of Seebeck coefficient and electrical resistivity at temperatures up to 1300 K with controlled oxygen partial pressure. An all platinum construction is used to avoid potential materials instabilities that can cause measurement drift. Two independent heaters are employed to establish a small temperature gradient for Seebeck measurements, while keeping the average temperature constant and avoiding errors associated with pO2-induced drifts in thermocouple readings. Oxygen equilibrium is monitored using both an O2 sensor and the transient behavior of the resistance as a proxy. A pO2 range of 10-25–100 atm can be established with appropriate gas mixtures. Seebeck measurements were calibrated against a high purity platinum wire, Pt/Pt–Rh thermocouple wire, and a Bi2Te3 Seebeck coefficient Standard Reference Material. To demonstrate the utility of this instrument for oxide materials we present measurements as a function of pO2 on a 1 % Nb-doped SrTiO3 single crystal, and show systematic changes in properties consistent with oxygen vacancy defect chemistry. Thus, an approximately 11% increase in power factor over a pO2 range of 10-19–10-8 atm at 973 K for the donor-doped single crystals is observed.

  4. Influence of hydrogen input partial pressure on the polarity of InN on GaAs (1 1 1)A grown by metalorganic vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Murakami, Hisashi; Eriguchi, Ken-ichi; Torii, Jun-ichi; Cho, Hyun-Chol; Kumagai, Yoshinao; Koukitu, Akinori

    2008-04-01

    Influences of hydrogen input partial pressure in the carrier gas ( F=PHo/(PHo+PNo)) on the crystalline quality and polarities of InN on GaAs (1 1 1)A surfaces were investigated by metalorganic vapor phase epitaxy (MOVPE). It was found that the polarity of the InN was affected by the hydrogen gas in the system regardless of the polarity of GaAs starting substrate. The polarity of InN layer grown with the hydrogen partial pressure of Fo=0.004 was a mixture of In-polarity and N-polarity, while that grown with Fo=0 was In-polarity. Degradation of the crystalline quality of InN grown with Fo=0.004 occurred due to the polarity inversion during the growth. The reason why the polarity of InN was influenced by the hydrogen carrier gas could be explained by the preferential growth of N-polarity InN in the H 2 contained ambient and/or the limiting reaction of InN decomposition.

  5. 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.

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

    SciTech Connect

    Brosha, Eric L; Rockward, Tommy; Uribe, Francisco A; Garzon, Fernando H

    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.

  7. Oxidation of SiC/BN/SiC Composites in Reduced Oxygen Partial Pressures

    NASA Technical Reports Server (NTRS)

    Opila, Elizabeth J.; Boyd, Meredith

    2010-01-01

    SiC fiber-reinforced SiC composites with a BN interphase are proposed for use as leading edge structures of hypersonic vehicles. The durability of these materials under hypersonic flight conditions is therefore of interest. Thermogravimetric analysis was used to characterize the oxidation kinetics of both the constituent fibers and composite coupons at four temperatures: 816, 1149, 1343, and 1538 C (1500, 2100, 2450, and 2800 F) and in oxygen partial pressures between 5% and 0.1% (balance argon) at 1 atm total pressure. One edge of the coupons was ground off so the effects of oxygen ingress into the composite could be monitored by post-test SEM and EDS. Additional characterization of the oxidation products was conducted by XPS and TOF-SIMS. Under most conditions, the BN oxidized rapidly, leading to the formation of borosilicate glass. Rapid initial oxidation followed by volatilization of boria lead to protective oxide formation and further oxidation was slow. At 1538C in 5% oxygen, both the fibers and coupons exhibited borosilicate glass formation and bubbling. At 1538C in 0.1% oxygen, active oxidation of both the fibers and the composites was observed leading to rapid SiC degradation. BN oxidation at 1538C in 0.1% oxygen was not significant.

  8. Quantitative absorption spectroscopy of residual water vapor in high-purity gases: pressure broadening of the 1.39253-microm H2O transition by N2, HCl, HBr, Cl2, and O2.

    PubMed

    Vorsa, Vasil; Dheandhanoo, Seksan; Ketkar, Suhas N; Hodges, Joseph T

    2005-02-01

    We determined the respective pressure-broadening coefficients of HCl, HBr, Cl2, and O2 (expressed relative to that of the reference gas N2) for the (v1,v2,v3)J(Ka,Kc) = (0,0,0)3(0,3) --> (1,0,1)2(0,2) rovibrational transition of H2 16O that occurs at 1.39253 microm. The experiment used a continuous-wave cavity ring-down spectroscopy analyzer to measure the peak absorption losses as a function of added moisture concentration. The measured pressure-broadening coefficients for HCl, HBr, Cl2, and O2 are, respectively, 2.76, 2.48, 1.39, and 0.49 times that of the N2 pressure-broadening coefficient, and detection limits for water vapor range from 0.22 nmol mol(-1) for O2 matrix gas to 2.3 nmol mol(-1) for HBr matrix gas. The degradation of the detection limit (relative to the N2 matrix gas) is ascribed to a pressure-broadening-induced reduction in peak absorption cross section and to elevated background loss from the matrix gas.

  9. Dinuclear complexes formed with the triazacyclononane derivative ENOTA4-: high-pressure 17O NMR evidence of an associative water exchange on [MnII2(ENOTA)(H2O)2].

    PubMed

    Balogh, Edina; He, Zhenjie; Hsieh, Wenyuan; Liu, Shuang; Tóth, Eva

    2007-01-08

    Mn2+ has five unpaired d-electrons, a long electronic relaxation time, and labile water exchange, all of which make it an attractive candidate for contrast agent application in medical magnetic resonance imaging. In the quest for stable and nonlabile Mn2+ complexes, we explored a novel dimeric triazacyclononane-based ligand bearing carboxylate functional groups, H4ENOTA. The protonation constants of the ligand and the stability constants of the complexes formed with some endogenously important metals (Ca2+, Cu2+, Zn2+), as well as with Mn2+ and Ce3+, have been assessed by NMR methods, potentiometry, and UV-vis spectrophotometry. Overall, the thermodynamic stability of the complexes is lower as compared to that of the corresponding NOTA analogues (H3NOTA, 1,4,7-triaazacyclononane-1,4,7-triacetic acid). The crystal structure of Mn2(ENOTA)(H2O) x 5H2O contains two six-coordinated Mn2+, in addition to the three amine nitrogens and the two oxygens from the pendent monodentate carboxylate groups, and one water (Mn2) or one bridging carboxylate oxygen (Mn1) completes the coordination sphere of the metal ion. In an aqueous solution, this bridging carboxylate is replaced by a water molecule, as evidenced by the 17O chemical shifts and proton relaxivity data that point to monohydration for both metal ions in the dinuclear complex. A variable-temperature and -pressure 17O NMR study has been performed on [Mn2(ENOTA)(H2O)2] to assess the rate and, for the first time on a Mn2+ chelate, also the mechanism of the water exchange. The inner sphere water is slightly more labile in [Mn2(ENOTA)(H2O)2] (k298ex = 5.5 x 107 s-1) than in the aqua ion (2.1 x 107 s-1, Merbach, A. E.; et al. Inorg. Chem. 1980, 19, 3696). The water exchange proceeds via an almost limiting associative mechanism, as evidenced by the large negative activation volume (deltaV = -10.7 cm3 mol-1). The proton relaxivities measured on [Mn2(ENOTA)(H2O)2] show a low-field dispersion at approximately 0.1 MHz arising from

  10. Feasibility of measuring dissolved carbon dioxide based on head space partial pressures

    USGS Publications Warehouse

    Watten, B.J.; Boyd, C.E.; Schwartz, M.F.; Summerfelt, S.T.; Brazil, B.L.

    2004-01-01

    We describe an instrument prototype that measures dissolved carbon dioxide (DC) without need for standard wetted probe membranes or titration. DC is calculated using Henry's Law, water temperature, and the steady-state partial pressure of carbon dioxide that develops within the instrument's vertical gas-liquid contacting chamber. Gas-phase partial pressures were determined with either an infrared detector (ID) or by measuring voltage developed by a pH electrode immersed in an isolated sodium carbonate solution (SC) sparged with recirculated head space gas. Calculated DC concentrations were compared with those obtained by titration over a range of DC (2, 4, 8, 12, 16, 20, 24, and 28mg/l), total alkalinity (35, 120, and 250mg/l as CaCO3), total dissolved gas pressure (-178 to 120 mmHg), and dissolved oxygen concentrations (7, 14, and 18 mg/l). Statistically significant (P < 0.001) correlations were established between head space (ID) and titrimetrically determined DC concentrations (R2 = 0.987-0.999, N = 96). Millivolt and titrimetric values from the SC solution tests were also correlated (P < 0.001, R 2 = 0.997, N = 16). The absolute and relative error associated with the use of the ID and SC solution averaged 0.9mg/l DC and 7.0% and 0.6 mg/l DC and 9.6%, respectively. The precision of DC estimates established in a second test series was good; coefficients of variation (100(SD/mean)) for the head space (ID) and titration analyses were 0.99% and 1.7%. Precision of the SC solution method was 1.3%. In a third test series, a single ID was coupled with four replicate head space units so as to permit sequential monitoring (15 min intervals) of a common water source. Here, appropriate gas samples were secured using a series of solenoid valves (1.6 mm bore) activated by a time-based controller. This system configuration reduced the capital cost per sample site from US$ 2695 to 876. Absolute error averaged 2.9, 3.1, 3.7, and 2.7 mg/ l for replicates 1-4 (N = 36) during a 21

  11. Spectroscopic study of low pressure, low temperature H2-CH4-CO2 microwave plasmas used for large area deposition of nanocrystalline diamond films. Part I: on temperature determination and energetic aspects

    NASA Astrophysics Data System (ADS)

    Nave, A. S. C.; Baudrillart, B.; Hamann, S.; Bénédic, F.; Lombardi, G.; Gicquel, A.; van Helden, J. H.; Röpcke, J.

    2016-12-01

    In a distributed antenna array (DAA) reactor, microwave H2 plasmas with admixtures of 2.5% CH4 and 1% CO2 used for the deposition of nanocrystalline diamond films have been studied by infrared absorption and optical emission spectroscopy (OES) techniques. The experiments were carried out in order to analyze the dependence of plasma chemical phenomena on power and pressure at relatively low pressures, up to 0.55 mbar, and power values, up to 3 kW. The evolution of the concentration of the methyl radical, CH3, and of five stable molecules, CH4, CO2, CO, C2H2 and C2H6, was monitored in the plasma processes by in situ infrared laser absorption spectroscopy using lead salt diode lasers (TDL) and external-cavity quantum cascade lasers (EC-QCL) as radiation sources. OES was applied simultaneously to obtain complementary information about the degree of dissociation of the H2 precursor gas and of its gas temperature. The experimental results are presented in two separate parts. In Part I, the present paper, the measurement of the gas (T gas), rotational (T rot) and vibrational (T vib) temperatures of the various species in the complex plasma was the main focus of interest. To achieve reliable values for the gas temperature inside and outside the plasma bulk as well as for the rotational and vibrational temperatures in the plasma hot zones, which are of great importance for calculation of species concentrations, five different methods based on the emission and absorption spectroscopy data of H2, CH4, CH3 and CO have been used. In these, line profile analysis has been combined with Boltzmann plot methods. Based on the wide tuning range of the EC-QCL, a variety of CO lines in the ground and three excited states was measured enabling extensive temperature analysis providing new insight into the energetic aspects of this multi-component plasma. Depending on the different plasma zones the gas temperature was found to range between about 360 and 1000 K inside the DAA reactor

  12. [Measurements of surface ocean carbon dioxide partial pressure during WOCE]. Summary of research progress

    SciTech Connect

    Not Available

    1992-12-31

    This paper discusses the research progress of the second year of research under ``Measurement of Surface Ocean Carbon Dioxide Partial Pressure During WOCE`` and proposes to continue measurements of underway pCO{sub 2}. During most of the first year of this grant, our efforts to measure pCO{sub 2} on WOCE WHP legs were frustrated by ship problems. The R/V Knorr, which was originally scheduled to carry out the first work on WHP lines P19 and P16 in the southeastem Pacific during the 1990-91 austral summer, was delayed in the shipyard during her mid-life refit for more than a year. In the interim, the smaller R/V Thomas Washington, was pressed into service to carry out lower-latitude portions of WHP lines P16 and P17 during mid-1991 (TUNES Expedition). We installed and operated our underway chromatographic system on this expedition, even though space and manpower on this smaller vessel were limited and no one from our group would be aboard any of the 3 WHP expedition legs. The results for carbon dioxide and nitrous oxide are shown. A map of the cruise track is shown for each leg, marked with cumulative distance. Following each track is a figure showing the carbon dioxide and nitrous oxide results as a function of distance along this track. The results are plotted as dry-gas mole fractions (in ppm and ppb, respectively) in air and in gas equilibrated with surface seawater at a total pressure equal to the barometric pressure. The air data are plotted as a 10-point running mean, and appear as a roughly horizontal line. The seawater data are plotted as individual points, using a 5-point Gaussian smoother. Equal values Of xCO{sub 2} in air and surface seawater indicate air-sea equilibrium.

  13. Phase transition and optoelectronic properties of MgH2

    NASA Astrophysics Data System (ADS)

    Nayak, Vikas; Verma, U. P.

    2016-05-01

    In this article, structural and electronic properties of MgH2 have been studied. The aim behind this study was to find out the ground state crystal structure of MgH2. For the purpose, density functional theory (DFT)-based full-potential linearized augmented plane wave (FP-LAPW) calculations have been performed in three different space groups: P42/mnm (α-MgH2), Pa3 (β-MgH2) and Pbcn (γ-MgH2). It has been found that the ground state structure of MgH2 is α-MgH2. The present study shows that α-MgH2 transforms into γ-MgH2 at a pressure of 0.41 GPa. After further increase in pressure, γ-MgH2 transforms into β-MgH2 at a pressure of 3.67 GPa. The obtained results are in good agreement with previously reported experimental data. In all the studied phases, the behavior of MgH2 is insulating and its optical conductivity is around 6.0 eV. The α-MgH2 and γ-MgH2 are anisotropic materials while β-MgH2 is isotropic in nature.

  14. Pressure dependence of the electro-optic response function in partially exposed polymer dispersed ferroelectric liquid crystals

    NASA Technical Reports Server (NTRS)

    Parmar, D. S.; Holmes, H. K.

    1993-01-01

    Ferroelectric liquid crystals in a new configuration, termed partially exposed polymer dispersed ferroelectric liquid crystal (PEPDFLC), respond to external pressures and demonstrate pressure-induced electro-optic switching response. When the PEPDFLC thin film is sandwiched between two transparent conducting electrodes, one a glass plate and the other a flexible sheet such as polyvenylidene fluoride, the switching characteristics of the thin film are a function of the pressure applied to the flexible transparent electrode and the bias voltage across the electrodes. Response time measurements reveal a linear dependence of the change in electric field with external pressure.

  15. The H2A.Z/H2B dimer is unstable compared to the dimer containing the major H2A isoform

    PubMed Central

    Placek, Brandon J.; Harrison, L. Nicole; Villers, Brooke M.; Gloss, Lisa M.

    2005-01-01

    The nucleosome, the basic fundamental repeating unit of chromatin, contains two H2A/H2B dimers and an H3/H4 tetramer. Modulation of the structure and dynamics of the nucleosome is an important regulation mechanism of DNA-based chemistries in the eukaryotic cell, such as transcription and replication. One means of altering the properties of the nucleosome is by incorporation of histone variants. To provide insights into how histone variants may impact the thermodynamics of the nucleosome, the stability of the heterodimer between the H2A.Z variant and H2B was determined by urea-induced denaturation, monitored by far-UV circular dichroism, intrinsic Tyr fluorescence intensity, and anisotropy. In the absence of stabilizing agents, the H2A.Z/H2B dimer is only partially folded. The stabilizing cosolute, trimethylamine-N-oxide (TMAO) was used to promote folding of the unstable heterodimer. The equilibrium stability of the H2A.Z/H2B dimer is compared to that of the H2A/H2B dimer. The equilibrium folding of both histone dimers is highly reversible and best described by a two-state model, with no detectable equilibrium intermediates populated. The free energies of unfolding, in the absence of denaturant, of H2A.Z/H2B and H2A/H2B are 7.3 kcal mol−1 and 15.5 kcal mol−1, respectively, in 1 M TMAO. The H2A.Z/H2B dimer is the least stable histone fold characterized to date, while H2A/H2B appears to be the most stable. It is speculated that this difference in stability may contribute to the different biophysical properties of nucleosomes containing the major H2A and the H2A.Z variant. PMID:15632282

  16. The H2A.Z/H2B dimer is unstable compared to the dimer containing the major H2A isoform.

    PubMed

    Placek, Brandon J; Harrison, L Nicole; Villers, Brooke M; Gloss, Lisa M

    2005-02-01

    The nucleosome, the basic fundamental repeating unit of chromatin, contains two H2A/H2B dimers and an H3/H4 tetramer. Modulation of the structure and dynamics of the nucleosome is an important regulation mechanism of DNA-based chemistries in the eukaryotic cell, such as transcription and replication. One means of altering the properties of the nucleosome is by incorporation of histone variants. To provide insights into how histone variants may impact the thermodynamics of the nucleosome, the stability of the heterodimer between the H2A.Z variant and H2B was determined by urea-induced denaturation, monitored by far-UV circular dichroism, intrinsic Tyr fluorescence intensity, and anisotropy. In the absence of stabilizing agents, the H2A.Z/H2B dimer is only partially folded. The stabilizing cosolute, trimethylamine-N-oxide (TMAO) was used to promote folding of the unstable heterodimer. The equilibrium stability of the H2A.Z/H2B dimer is compared to that of the H2A/H2B dimer. The equilibrium folding of both histone dimers is highly reversible and best described by a two-state model, with no detectable equilibrium intermediates populated. The free energies of unfolding, in the absence of denaturant, of H2A.Z/H2B and H2A/H2B are 7.3 kcal mol(-1) and 15.5 kcal mol(-1), respectively, in 1 M TMAO. The H2A.Z/H2B dimer is the least stable histone fold characterized to date, while H2A/H2B appears to be the most stable. It is speculated that this difference in stability may contribute to the different biophysical properties of nucleosomes containing the major H2A and the H2A.Z variant.

  17. Spectroscopic study of low pressure, low temperature H2-CH4-CO2 microwave plasmas used for large area deposition of nanocrystalline diamond films. Part II: on plasma chemical processes

    NASA Astrophysics Data System (ADS)

    Nave, A. S. C.; Baudrillart, B.; Hamann, S.; Bénédic, F.; Lombardi, G.; Gicquel, A.; van Helden, J. H.; Röpcke, J.

    2016-12-01

    In a distributed antenna array (DAA) reactor, microwave H2 plasmas with admixtures of 2.5% CH4 and 1% CO2 used for the deposition of nanocrystalline diamond films have been studied by infrared laser absorption and optical emission spectroscopy (OES) techniques. The experiments were carried out in order to analyze the dependence of plasma chemical phenomena on power and pressure at relatively low pressures, up to 0.55 mbar, and power values, up to 3 kW. The evolution of the concentration of the methyl radical, CH3, of five stable molecules, CH4, CO2, CO, C2H2 and C2H6, and of vibrationally excited CO in the first and second hot band was monitored in the plasma processes by in situ infrared laser absorption spectroscopy using tunable lead salt diode lasers (TDL) and an external-cavity quantum cascade laser (EC-QCL) as radiation sources. OES was applied simultaneously to obtain complementary information about the degree of dissociation of the H2 precursor and of its gas temperature. The experimental results are presented in two separate parts. In Part I, the first paper in a two-part series, the measurement of the gas (T gas), rotational (T rot) and vibrational (T vib) temperatures of the various species in the complex plasma was the main focus of interest. Depending on the different plasma zones the gas temperature was found to range between about 360 and 1000 K inside the DAA reactor (Nave et al 2016 Plasma Sources Sci. Technol. 25 065002). In Part II, the present paper, taking into account the temperatures determined in the first paper, the concentrations of the various species, which were found to be in a range between 1011 and 1015 cm-3, are the focus of interest. The influence of the discharge parameters power and pressure on the molecular concentrations has been studied. To achieve further insight into general plasma chemical aspects the dissociation of the carbon precursor gases including their fragmentation and conversion to the reaction products has been

  18. Applying Chemical Potential and Partial Pressure Concepts to Understand the Spontaneous Mixing of Helium and Air in a Helium-Inflated Balloon

    ERIC Educational Resources Information Center

    Jee-Yon Lee; Hee-Soo Yoo; Jong Sook Park; Kwang-Jin Hwang; Jin Seog Kim

    2005-01-01

    The spontaneous mixing of helium and air in a helium-inflated balloon is described in an experiment in which the partial pressure of the gases in the balloon are determined from the mole factions and the total pressure measured in the balloon. The results described provide a model for teaching concepts of partial pressure, chemical potential, and…

  19. Atmospheric constraints for the CO2 partial pressure on terrestrial planets near the outer edge of the habitable zone

    NASA Astrophysics Data System (ADS)

    von Paris, P.; Grenfell, J. L.; Hedelt, P.; Rauer, H.; Selsis, F.; Stracke, B.

    2013-01-01

    Context. In recent years, several potentially habitable, probably terrestrial exoplanets and exoplanet candidates have been discovered. The amount of CO2 in their atmosphere is of great importance for surface conditions and habitability. In the absence of detailed information on the geochemistry of the planet, this amount could be considered as a free parameter. Aims: Up to now, CO2 partial pressures for terrestrial planets have been obtained assuming an available volatile reservoir and outgassing scenarios. This study aims at calculating the allowed maximum CO2 pressure at the surface of terrestrial exoplanets orbiting near the outer boundary of the habitable zone by coupling the radiative effects of the CO2 and its condensation at the surface. These constraints might limit the permitted amount of atmospheric CO2, independent of the planetary reservoir. Methods: A 1D radiative-convective cloud-free atmospheric model was used to calculate surface conditions for hypothetical terrestrial exoplanets. CO2 partial pressures are fixed according to surface temperature and vapor pressure curve. Considered scenarios cover a wide range of parameters, such as gravity, central star type and orbital distance, atmospheric N2 content and surface albedo. Results: Results show that for planets in the habitable zone around K-, G-, and F-type stars the allowed CO2 pressure is limited by the vapor pressure curve and not by the planetary reservoir. The maximum CO2 pressure lies below the CO2 vapor pressure at the critical point of pcrit = 73.8 bar. For M-type stars, due to the stellar spectrum being shifted to the near-IR, CO2 pressures above pcrit are possible for almost all scenarios considered across the habitable zone. This implies that determining CO2 partial pressures for terrestrial planets by using only geological models is probably too simplified and might over-estimate atmospheric CO2 towards the outer edge of the habitable zone.

  20. 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.

  1. 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.

  2. 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.

  3. [Diffusion flux of partial pressure of dissolved carbon dioxide in Wan'an reservoir in spring].

    PubMed

    Mei, Hang-Yuan; Wang, Fu-Shun; Yao, Chen-Chen; Wang, Bao-Li

    2011-01-01

    In order to understand the emission of greenhouse gases (CO2) from the river-type reservoir, this study investigated the partial pressure of CO2 [p(CO2)], in the surface water, inflow waters, outflow waters of the Wan'an reservoir in China in the May 2009. p(CO2) in the inflow water, outflow water were calculated from titration method, and the surface water p(CO2) was measured underway using a continuous measurement system (equilibrator-NDIR system). Results showed that the inflow water from the Zhangshui, Meijiang, Taojiang have higher p(CO2) than atmosphere level, with the values of 211.5, 91.7, 259.7 Pa respectively. p(CO2) in the surface water of the incoming section of Wan'an reservoir was between 180-210 Pa, and in the middle section and central section near the dam, p(CO2) in the surface water were about 140-180 Pa and 70-110 Pa. In the outflow waters, p(CO2) reached to 176.2 Pa, higher than that in central section. As a result, it can be concluded that the surface water, inflow waters, outflow waters in the Wan'an reservoir are all the source to CO2. However there is clear evidence showing that the reservoir indeed has a role in mitigating the CO2 emission in this case.

  4. Measurement of the oxygen partial pressure and thermodynamic modeling of the U-Nd-O system

    NASA Astrophysics Data System (ADS)

    Lee, Seung Min; Knight, Travis W.; McMurray, Jacob W.; Besmann, Theodore M.

    2016-05-01

    Fission products greatly impact the properties of fuel necessitating a thorough understanding of the thermochemical properties of oxide fuels with fission products. However, thermochemical data for the U-Nd-O system is insufficient even though neodymium is a major fission product. As neodymium will likely be present as a solute in UO2, this research focuses on the study of (U1-yNdy)O2±x. Experimental measurements and analyses of the oxygen partial pressure (pO2)-temperature-oxygen to metal ratio (O/M ratio) relationships were performed using a thermogravimetric analyzer (TGA) and an oxygen analyzer. Thermodynamic computational modeling was performed using the CALPHAD (CALculation of PHAse Diagrams) method with the FactSage software. The Gibbs energy of the (U1-yNdy)O2±x solid solution was described by the compound energy formalism (CEF), which is based on earlier thermodynamic modeling data of the binary U-O system from Guéneau et al.. The thermodynamic and phase diagram data of the U-Nd-O system produced in this work show good agreement with the experimental data.

  5. Effects of varying oxygen partial pressure on molten silicon-ceramic substrate interactions

    NASA Technical Reports Server (NTRS)

    Ownby, D. P.; Barsoum, M. W.

    1980-01-01

    The silicon sessile drop contact angle was measured on hot pressed silicon nitride, silicon nitride coated on hot pressed silicon nitride, silicon carbon coated on graphite, and on Sialon to determine the degree to which silicon wets these substances. The post-sessile drop experiment samples were sectioned and photomicrographs were taken of the silicon-substrate interface to observe the degree of surface dissolution and degradation. Of these materials, silicon did not form a true sessile drop on the SiC on graphite due to infiltration of the silicon through the SiC coating, nor on the Sialon due to the formation of a more-or-less rigid coating on the liquid silicon. The most wetting was obtained on the coated Si3N4 with a value of 42 deg. The oxygen concentrations in a silicon ribbon furnace and in a sessile drop furnace were measured using the protable thoria-yttria solid solution electrolyte oxygen sensor. Oxygen partial pressures of 10 to the minus 7 power atm and 10 to the minus 8 power atm were obtained at the two facilities. These measurements are believed to represent nonequilibrium conditions.

  6. 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.

  7. Effect of oxygen partial pressure and chemical oxygen demand loading on the biofilm properties in membrane-aerated bioreactors.

    PubMed

    Zhu, I X; Alien, D G; Liss, S N

    2009-03-01

    Membrane-aerated biofilms with oxygen and nutrients diffusing from the opposite sides possess distinct properties, including the ability to couple aerobic and anaerobic processes. The objective of this study was to examine the effects of oxygen partial pressure and chemical oxygen demand (COD) loading on biofilm properties. Two laboratory-scale membrane-aerated bioreactors were operated for a total of 283 days, with one reactor operated at 42, 60, and 89 kPa (0.41, 0.59, and 0.88 atm) oxygen, and the other reactor at 25 kPa (0.25 atm) oxygen (air control). The biofilm detached at the oxygen partial pressures of 60 and 89 kPa (0.59 and 0.88 atm) at a COD loading of 11.3 kg COD/1000 m2/d, but was sustained at the oxygen partial pressures of 25 and 42 kPa (0.25 and 0.41 atm), with a porous structure at the membrane interface at the COD loading of 11.3 kg COD/1000 m2/d. Biofilm formation was improved at a higher COD loading. It is proposed that the loss of extracellular polymeric substances at the biofilm bottom is the cause for the biofilm detachment subjected to a higher oxygen partial pressure.

  8. Computer Algorithms Used in Computing the Mk 15/16 Constant 0.7 ATA Oxygen Partial Pressure Decompression Tables.

    DTIC Science & Technology

    1983-01-01

    COMPUTER ALGORITHM USED IN COMPUTING THE FINAL W 15/16 CONSTANT 0.7 ATA OXYGEN PARTIAL . PERFORING ORG. REPORT MUNDER PRESSURE DECOMPRESSION TABLES 7...earlier Model Parameter Input Files bad only one subfile which could then be read and printed before an end of file is encounted and the program stops

  9. Effect of oxygen partial pressure on microstructural and optical properties of titanium oxide thin films prepared by pulsed laser deposition

    SciTech Connect

    Balakrishnan, G.; Bandi, Vengala Rao; Rajeswari, S.M.; Balamurugan, N.; Babu, R. Venkatesh; Song, J.I.

    2013-11-15

    Graphical abstract: - Highlights: • Microstructural and optical properties are studied systematically. • The optical properties are studied by UV–visible and photoluminescence. • The PL spectra shows two peaks correspond to bandgap of anatase and rutile. • The maximum refractive index of 2.73 is obtained for rutile phase of titania. - Abstract: Nanocrystalline titanium oxide (TiO{sub 2}) thin films were deposited on silicon (1 0 0) and quartz substrates at various oxygen partial pressures (1 × 10{sup −5} to 3.5 × 10{sup −1} mbar) with a substrate temperature of 973 K by pulsed laser deposition. The microstructural and optical properties were characterized using Grazing incidence X-ray diffraction, atomic force microscopy, UV–visible spectroscopy and photoluminescence. The X-ray diffraction studies indicated the formation of mixed phases (anatase and rutile) at higher oxygen partial pressures (3.5 × 10{sup −2} to 3.5 × 10{sup −1} mbar) and strong rutile phase at lower oxygen partial pressures (1 × 10{sup −5} to 3.5 × 10{sup −3} mbar). The atomic force microscopy studies showed the dense and uniform distribution of nanocrystallites. The root mean square surface roughness of the films increased with increasing oxygen partial pressures. The UV–visible studies showed that the bandgap of the films increased from 3.20 eV to 3.60 eV with the increase of oxygen partial pressures. The refractive index was found to decrease from 2.73 to 2.06 (at 550 nm) as the oxygen partial pressure increased from 1.5 × 10{sup −4} mbar to 3.5 × 10{sup −1} mbar. The photoluminescence peaks were fitted to Gaussian function and the bandgap was found to be in the range ∼3.28–3.40 eV for anatase and 2.98–3.13 eV for rutile phases with increasing oxygen partial pressure from 1 × 10{sup −5} to 3.5 × 10{sup −1} mbar.

  10. Utilizing a one-dimensional multispecies model to simulate the nutrient reduction and biomass structure in two types of H2-based membrane-aeration biofilm reactors (H2-MBfR): model development and parametric analysis.

    PubMed

    Wang, Zuowei; Xia, Siqing; Xu, Xiaoyin; Wang, Chenhui

    2016-02-01

    In this study, a one-dimensional multispecies model (ODMSM) was utilized to simulate NO3(-)-N and ClO4(-) reduction performances in two kinds of H2-based membrane-aeration biofilm reactors (H2-MBfR) within different operating conditions (e.g., NO3(-)-N/ClO4(-) loading rates, H2 partial pressure, etc.). Before the simulation process, we conducted the sensitivity analysis of some key parameters which would fluctuate in different environmental conditions, then we used the experimental data to calibrate the more sensitive parameters μ1 and μ2 (maximum specific growth rates of denitrification bacteria and perchlorate reduction bacteria) in two H2-MBfRs, and the diversity of the two key parameters' values in two types of reactors may be resulted from the different carbon source fed in the reactors. From the simulation results of six different operating conditions (four in H2-MBfR 1 and two in H2-MBfR 2), the applicability of the model was approved, and the variation of the removal tendency in different operating conditions could be well simulated. Besides, the rationality of operating parameters (H2 partial pressure, etc.) could be judged especially in condition of high nutrients' loading rates. To a certain degree, the model could provide theoretical guidance to determine the operating parameters on some specific conditions in practical application.

  11. Single-component and binary CO2 and H2O adsorption of amine-functionalized cellulose.

    PubMed

    Gebald, Christoph; Wurzbacher, Jan A; Borgschulte, Andreas; Zimmermann, Tanja; Steinfeld, Aldo

    2014-02-18

    A fundamental analysis of single-component and binary CO2 and H2O adsorption of amine-functionalized nanofibrillated cellulose is carried out in the temperature range of 283-353 K and at CO2 partial pressures in the range of 0.02-105 kPa, where the ultralow partial pressure range is relevant for the direct capture of CO2 from atmospheric air. Single-component CO2 and H2O adsorption experimental data are fitted to the Toth and Guggenheim-Anderson-de Boer models, respectively. Corresponding heats of adsorption, derived from explicit solutions of the van't Hoff equation, are -50 kJ/mol CO2 and -48.8 kJ/mol H2O. Binary CO2/H2O adsorption measurements for humid air reveal that the presence of H2O at 2.55 kPa enhances CO2 adsorption, while the presence of CO2 at 0.045 kPa does not influence H2O adsorption. The energy demand of the temperature-vacuum-swing adsorption/desorption cycle for delivering pure CO2 from air increases significantly with H2O adsorption and indicates the need to reduce the hygroscopicity of the adsorbent.

  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. 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

  14. Microwave-assisted wet digestion with H2O2 at high temperature and pressure using single reaction chamber for elemental determination in milk powder by ICP-OES and ICP-MS.

    PubMed

    Muller, Edson I; Souza, Juliana P; Muller, Cristiano C; Muller, Aline L H; Mello, Paola A; Bizzi, Cezar A

    2016-08-15

    In this work a green digestion method which only used H2O2 as an oxidant and high temperature and pressure in the single reaction chamber system (SRC-UltraWave™) was applied for subsequent elemental determination by inductively coupled plasma-based techniques. Milk powder was chosen to demonstrate the feasibility and advantages of the proposed method. Samples masses up to 500mg were efficiently digested, and the determination of Ca, Fe, K, Mg and Na was performed by inductively coupled plasma optical emission spectrometry (ICP-OES), while trace elements (B, Ba, Cd, Cu, Mn, Mo, Pb, Sr and Zn) were determined by inductively coupled plasma mass spectrometry (ICP-MS). Residual carbon (RC) lower than 918mgL(-1) of C was obtained for digests which contributed to minimizing interferences in determination by ICP-OES and ICP-MS. Accuracy was evaluated using certified reference materials NIST 1549 (non-fat milk powder certified reference material) and NIST 8435 (whole milk powder reference material). The results obtained by the proposed method were in agreement with the certified reference values (t-test, 95% confidence level). In addition, no significant difference was observed between results obtained by the proposed method and conventional wet digestion using concentrated HNO3. As digestion was performed without using any kind of acid, the characteristics of final digests were in agreement with green chemistry principles when compared to digests obtained using conventional wet digestion method with concentrated HNO3. Additionally, H2O2 digests were more suitable for subsequent analysis by ICP-based techniques due to of water being the main product of organic matrix oxidation. The proposed method was suitable for quality control of major components and trace elements present in milk powder in consonance with green sample preparation.

  15. Probing of Elastic Properties and Texture of Transparent Solids with sub-μm and μm-Resolution at Mbar Pressures Using Picosecond Laser Ultrasonic Interferometry: H2O Ice

    NASA Astrophysics Data System (ADS)

    Zerr, A.; Nikitin, S. M.; Chigarev, N.; Raetz, S.; Kuriakose, M.; Tournat, V.; Bulou, A.; Gasteau, D.; Castagnede, B.; Gusev, V. E.; Lomonosov, A.

    2015-12-01

    Elastic properties of silicates, oxides and other transparent materials, especially their single crystal elastic moduli, texture and its evolution upon compression at Mbar pressures is a subject of continuous interest in geo- and planetary sciences. Picosecond laser ultrasonic technique was earlier proposed to measure elastic moduli of materials compressed in a diamond anvil cell (DAC) [1]. Recently the applications of picosecond laser ultrasonic interferometry have been extended to evaluation of spatially inhomogeneous samples |2]. In this communication we report characterization by this technique of a transparent polycrystalline sample (H2O ice) compressed in a DAC to ~1 Mbar. The method is suitable for measurements in multi-Mbar region due to a high in-depth resolution approaching 300 nm and limited by the used signal processing. In an inhomogeneous medium the transient reflectivity signal obtained by this technique contains at each time instance the information on the parameters of the medium in the spatial position of laser-generated picosecond acoustic pulse corresponding to this moment of time. The lateral resolution is defined by focusing of the laser radiation which can approach ≤1 μm if advanced focusing methods are applied. Here we present results of examination of characteristic features of micro-crystallinity of H2O ice at P up to 840 kbar by two-dimensional imaging based on this technique which provides, in addition, for each spatial position the value of elastic modulus of the sample material along the DAC axis [2]. A significant elastic anisotropy of H2O ice was recognised, its degree evaluated, and compared with the earlier experimental and theoretical data. Feasibility of extension to a three-dimensional imaging of texture (including information on orientation of crystallites or their groups) as well as its evolution upon further compression in a DAC is discussed. The method can be applied to any transparent compounds (silicates, oxides) or

  16. Experimental investigation on thermochemical sulfate reduction by H2S initiation

    USGS Publications Warehouse

    Zhang, T.; Amrani, A.; Ellis, G.S.; Ma, Q.; Tang, Y.

    2008-01-01

    Hydrogen sulfide (H2S) is known to catalyze thermochemical sulfate reduction (TSR) by hydrocarbons (HC), but the reaction mechanism remains unclear. To understand the mechanism of this catalytic reaction, a series of isothermal gold-tube hydrous pyrolysis experiments were conducted at 330 ??C for 24 h under a constant confining pressure of 24.1 MPa. The reactants used were saturated HC (sulfur-free) and CaSO4 in the presence of variable H2S partial pressures at three different pH conditions. The experimental results showed that the in-situ pH of the aqueous solution (herein, in-situ pH refers to the calculated pH of aqueous solution under the experimental conditions) can significantly affect the rate of the TSR reaction. A substantial increase in the TSR reaction rate was recorded with a decrease in the in-situ pH value of the aqueous solution involved. A positive correlation between the rate of TSR and the initial partial pressure of H2S occurred under acidic conditions (at pH ???3-3.5). However, sulfate reduction at pH ???5.0 was undetectable even at high initial H2S concentrations. To investigate whether the reaction of H2S(aq) and HSO4- occurs at pH ???3, an additional series of isothermal hydrous pyrolysis experiments was conducted with CaSO4 and variable H2S partial pressures in the absence of HC at the same experimental temperature and pressure conditions. CaSO4 reduction was not measurable in the absence of paraffin even with high H2S pressure and acidic conditions. These experimental observations indicate that the formation of organosulfur intermediates from H2S reacting with hydrocarbons may play a significant role in sulfate reduction under our experimental conditions rather than the formation of elemental sulfur from H2S reacting with sulfate as has been suggested previously (Toland W. G. (1960) Oxidation of organic compounds with aqueous sulphate. J. Am. Chem. Soc. 82, 1911-1916). Quantification of labile organosulfur compounds (LSC), such as thiols

  17. 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.

  18. 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 µm) 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 6.5±1.4 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

  19. 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 µm) 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 6.5±1.4 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

  20. Impact of Xe partial pressure on the production of excimer vacuum ultraviolet emission for plasma display panels

    SciTech Connect

    Zhu Di; Zhang Xiong; Kajiyama, Hiroshi

    2012-08-01

    In this work, the effect of the Xe partial pressure on the excimer vacuum ultraviolet (VUV) emission intensity of the plasma display panels is investigated, both by measuring the spectral emission directly and by two-dimensional simulations. Experimentally, we find that at the high Xe partial pressure levels, there is an supra-linear increase of excimer VUV radiation and that determines the strong increase of luminance at the high pressures and high voltage. Due to the increase of the luminance and the almost unchanged discharge current, the luminous efficacy strongly increases with the Xe partial pressure. In addition, we also investigated the dynamics of the VUV generation, by measuring the decay time of the excimer VUV light as a function of the gas pressure. It is found that the decay time decreases with the increase of gas pressure. The spatial characteristics of the excimer VUV emission are also discussed. Different from the Ne and near-infrared emission, the excimer VUV emission is generated near the surface of the electrodes and increases uniformly on both sides of the anode and cathode (i.e., the bulk plasma region). Most importantly, it is found that the VUV production occurs during the afterglow period, while it is almost zero at the moment of the discharge itself. From the simulations, it can be seen that the Xe{sub 2}*({sup 3}{Sigma}{sub u}{sup +}) excimer species, which are generated from Xe*(1s{sub 5}), play a dominant role in the excimer VUV emission output at the high Xe partial pressure. The two-dimensional simulations also show that the strong increase of Xe excimer excitation states in the case of high pressure is mainly the result of the high conversion efficiency of the Xe excimer states, especially in the afterglow period. Due to the high conversion efficiency of Xe excitation species to Xe excimer species by the high collision rate in the case of high pressure, there is a strong increase of excimer VUV production, especially from the cathode.

  1. Recombination studies in a He-Ar-H2 plasma

    NASA Astrophysics Data System (ADS)

    Glosík, J.; Plasil, R.; Pysanenko, A.; Novotný, O.; Hlavenka, P.; Macko, P.; Bánó, G.

    2005-01-01

    The recombination of H+3 ions with electrons has been studied in afterglow plasma in three different experiments. In two experiments, using the Variable Temperature Stationary Afterglow (VT-AISA) and the Variable Temperature Flowing Afterglow (VT-FALP) techniques, a decay of the electron number density was measured by an electrostatic Langmuir probe to determine the recombination rate coefficient. In the third experiment a near infrared Cavity Ring-Down Absorption Spectrometer (CRDS) was used to monitor the decay of the H+3 (v = 0) ion density during the afterglow. Measurements were carried out in helium buffer gas with small admixtures of argon and hydrogen at total pressures ranging from 150 up to 1200 Pa and at buffer gas temperatures ranging from 100 up to 330 K. In the experiments the partial number density of hydrogen was varied from 5 × 1010 up to 1 × 1016 cm-3 and for this broad range of hydrogen number densities effective recombination rate coefficients were obtained, which varied over three orders of magnitude from 2 × 10-9 cm3s-1 at [H2] = 5 × 1010 cm-3 up to 3 × 10-6 cm3s-1 at [H2] = 1 × 1016 cm-3. Using our experimental results we discuss possible mechanisms of recombination in hydrogen plasma in a very broad range of several parameters: buffer gas pressure, temperature, electron number density, hydrogen number density and internal excitation of recombining ions.

  2. 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 μatm), river waters in the remaining watershed were supersaturated with CO2. The average pCO2 for the watershed was estimated at 2810 ± 1985 μatm, 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 μatm to >30 000 μatm 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.

  3. Soil carbon dioxide partial pressure and dissolved inorganic carbonate chemistry under elevated carbon dioxide and ozone.

    PubMed

    Karberg, N J; Pregitzer, K S; King, J S; Friend, A L; Wood, J R

    2005-01-01

    Global emissions of atmospheric CO(2) and tropospheric O(3) are rising and expected to impact large areas of the Earth's forests. While CO(2) stimulates net primary production, O(3) reduces photosynthesis, altering plant C allocation and reducing ecosystem C storage. The effects of multiple air pollutants can alter belowground C allocation, leading to changes in the partial pressure of CO(2) (pCO(2)) in the soil , chemistry of dissolved inorganic carbonate (DIC) and the rate of mineral weathering. As this system represents a linkage between the long- and short-term C cycles and sequestration of atmospheric CO(2), changes in atmospheric chemistry that affect net primary production may alter the fate of C in these ecosystems. To date, little is known about the combined effects of elevated CO(2) and O(3) on the inorganic C cycle in forest systems. Free air CO(2) and O(3) enrichment (FACE) technology was used at the Aspen FACE project in Rhinelander, Wisconsin to understand how elevated atmospheric CO(2) and O(3) interact to alter pCO(2) and DIC concentrations in the soil. Ambient and elevated CO(2) levels were 360+/-16 and 542+/-81 microl l(-1), respectively; ambient and elevated O(3) levels were 33+/-14 and 49+/-24 nl l(-1), respectively. Measured concentrations of soil CO(2) and calculated concentrations of DIC increased over the growing season by 14 and 22%, respectively, under elevated atmospheric CO(2) and were unaffected by elevated tropospheric O(3). The increased concentration of DIC altered inorganic carbonate chemistry by increasing system total alkalinity by 210%, likely due to enhanced chemical weathering. The study also demonstrated the close coupling between the seasonal delta(13)C of soil pCO(2) and DIC, as a mixing model showed that new atmospheric CO(2) accounted for approximately 90% of the C leaving the system as DIC. This study illustrates the potential of using stable isotopic techniques and FACE technology to examine long- and short

  4. H2 Detection via Polarography

    NASA Technical Reports Server (NTRS)

    Dominquez, Jesus; Barile, Ron

    2006-01-01

    Polarography is the measurement of the current that flows in solution as a function of an applied voltage. The actual form of the observed polarographic current depends upon the manner in which the voltage is applied and on the characteristics of the working electrode. The new gas polarographic H2 sensor shows a current level increment with concentration of the gaseous H2 similar to those relating to metal ions in liquid electrolytes in well-known polarography. This phenomenon is caused by the fact that the diffusion of the gaseous H2 through a gas diffusion hole built in the sensor is a rate-determining step in the gaseous-hydrogen sensing mechanism. The diffusion hole artificially limits the diffusion of the gaseous H2 toward the electrode located at the sensor cavity. This gas polarographic H2 sensor is actually an electrochemical-pumping cell since the gaseous H2 is in fact pumped via the electrochemical driving force generated between the electrodes. Gaseous H2 enters the diffusion hole and reaches the first electrode (anode) located in the sensor cavity to be transformed into an H ions or protons; H ions pass through the electrolyte and reach the second electrode (cathode) to be reformed to gaseous H2. Gas polarographic O2 sensors are commercially available; a gas polarographic O2 sensor was used to prove the feasibility of building a new gas polarographic H2 sensor.

  5. Antiproton stopping in H2 and H2O

    NASA Astrophysics Data System (ADS)

    Bailey, J. J.; Kadyrov, A. S.; Abdurakhmanov, I. B.; Fursa, D. V.; Bray, I.

    2015-11-01

    Stopping powers of antiprotons in H2 and H2O targets are calculated using a semiclassical time-dependent convergent close-coupling method. In our approach the H2 target is treated using a two-center molecular multiconfiguration approximation, which fully accounts for the electron-electron correlation. Double-ionization and dissociative ionization channels are taken into account using an independent-event model. The vibrational excitation and nuclear scattering contributions are also included. The H2O target is treated using a neonization method proposed by C. C. Montanari and J. E. Miraglia [J. Phys. B 47, 015201 (2014), 10.1088/0953-4075/47/1/015201], whereby the ten-electron water molecule is described as a dressed Ne-like atom in a pseudospherical potential. Despite being the most comprehensive approach to date, the results obtained for H2 only qualitatively agree with the available experimental measurements.

  6. Tumor-dependent kinetics of partial pressure of oxygen fluctuations during air and oxygen breathing.

    PubMed

    Cárdenas-Navia, L Isabel; Yu, Daohai; Braun, Rod D; Brizel, David M; Secomb, Timothy W; Dewhirst, Mark W

    2004-09-01

    The primary purpose of this study was to examine the kinetics of partial pressure of oxygen (pO2) fluctuations in fibrosarcoma (FSA) and 9L tumors under air and O2 breathing conditions. The overall hypothesis was that key factors relating to oxygen tension fluctuations would vary between the two tumor types and as a function of the oxygen content of the breathing gas. To assist in the interpretation of the temporal data, spatial pO2 distributions were measured in 10 FSA and 8 9L tumors transplanted into the subcutis of the hind leg of Nembutal-anesthetized (50 mg/kg) Fischer 344 rats. Recessed-tip oxygen microelectrodes were inserted into the tumor, and linear pO2 measurements were recorded in 50-microm steps along a 3-mm path, and blood pressure was simultaneously measured via femoral arterial access. Additionally, pO2 was measured at a single location for 90 to 120 minutes in FSA (n=11) or 9L tumors (n=12). Rats were switched from air to 100% O2 breathing after 45 minutes. Temporal pO2 records were evaluated for their potential radiobiological significance by assessing the number of times they crossed a 10-mm-Hg threshold. In addition, the data were subjected to Fourier analysis for air and O2 breathing. FSA and 9L tumors had spatial median pO2 measurements of 4 and 1 mm Hg, respectively. 9L had more low pO2 measurements < or =2.5 mm Hg than did FSA, whereas between 2.5 and 10 mm Hg this pattern was reversed. Pimonidazole staining patterns in FSA and 9L tumors supported these results. Temporal pO2 instability was observed in all experiments during air and O2 breathing. Threshold analyses indicated that the 10 mm Hg threshold was crossed 2 to 5 times per hour, independent of tumor type. However, the magnitude of 9L pO2 fluctuations was approximately eight times greater than FSA fluctuations, as assessed with Fourier transform analysis (Wilcoxon, P < 0.005). O2 breathing significantly increased median pO2 in FSA from 3 to 8 mm Hg (P < 0.005) and caused a

  7. Oxygen partial pressure dependence of electrical conductivity in {gamma}'-Bi{sub 2}MoO{sub 6}

    SciTech Connect

    Vera, C.M.C. Aragon, R.

    2008-05-15

    The electrical conductivity of {gamma}'-Bi{sub 2}MoO{sub 6} was surveyed between 450 and 750 deg. C as a function of oxygen partial pressure, in the range 0.01-1 atm. A -1/6 power law dependence, consistent with a Frenkel defect model of doubly ionized oxygen vacancies and interstitials, is evidence for an n-type semiconductive component, with an optical band gap of 2.9 eV. The absence of this dependence is used to map the onset of dominant ionic conduction. - Graphical abstract: Temporal dependence of electrical conductivity at 500 deg. C for {gamma}'-Bi{sub 2}MoO{sub 6} at controlled partial pressures of oxygen.

  8. Measurement of Local Partial Pressure of Oxygen in the Brain Tissue under Normoxia and Epilepsy with Phosphorescence Lifetime Microscopy

    PubMed Central

    Zhang, Cong; Bélanger, Samuel; Pouliot, Philippe; Lesage, Frédéric

    2015-01-01

    In this work a method for measuring brain oxygen partial pressure with confocal phosphorescence lifetime microscopy system is reported. When used in conjunction with a dendritic phosphorescent probe, Oxyphor G4, this system enabled minimally invasive measurements of oxygen partial pressure (pO2) in cerebral tissue with high spatial and temporal resolution during 4-AP induced epileptic seizures. Investigating epileptic events, we characterized the spatio-temporal distribution of the "initial dip" in pO2 near the probe injection site and along nearby arterioles. Our results reveal a correlation between the percent change in the pO2 signal during the "initial dip" and the duration of seizure-like activity, which can help localize the epileptic focus and predict the length of seizure. PMID:26305777

  9. 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.

  10. 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.

  11. Solubility of water in lunar basalt at low pH2O

    NASA Astrophysics Data System (ADS)

    Newcombe, M. E.; Brett, A.; Beckett, J. R.; Baker, M. B.; Newman, S.; Guan, Y.; Eiler, J. M.; Stolper, E. M.

    2017-03-01

    We report the solubility of water in Apollo 15 basaltic "Yellow Glass" and an iron-free basaltic analog composition at 1 atm and 1350 °C. We equilibrated melts in a 1-atm furnace with flowing H2/CO2 gas mixtures that spanned ∼8 orders of magnitude in fO2 (from three orders of magnitude more reducing than the iron-wüstite buffer, IW-3.0, to IW+4.8) and ∼4 orders of magnitude in pH2/pH2O (from 0.003 to 24). Based on Fourier transform infrared spectroscopy (FTIR), our quenched experimental glasses contain 69-425 ppm total water (by weight). Our results demonstrate that under the conditions of our experiments: (1) hydroxyl is the only H-bearing species detected by FTIR; (2) the solubility of water is proportional to the square root of pH2O in the furnace atmosphere and is independent of fO2 and pH2/pH2O; (3) the solubility of water is very similar in both melt compositions; (4) the concentration of H2 in our iron-free experiments is <∼4 ppm, even at oxygen fugacities as low as IW-2.3 and pH2/pH2O as high as 11; (5) Secondary ion mass spectrometry (SIMS) analyses of water in iron-rich glasses equilibrated under variable fO2 conditions may be strongly influenced by matrix effects, even when the concentration of water in the glasses is low; and (6) Our results can be used to constrain the entrapment pressure of lunar melt inclusions and the partial pressures of water and molecular hydrogen in the carrier gas of the lunar pyroclastic glass beads. We find that the most water-rich melt inclusion of Hauri et al. (2011) would be in equilibrium with a vapor with pH2O ∼ 3 bar and pH2 ∼ 8 bar. We constrain the partial pressures of water and molecular hydrogen in the carrier gas of the lunar pyroclastic glass beads to be 0.0005 bar and 0.0011 bar respectively. We calculate that batch degassing of lunar magmas containing initial volatile contents of 1200 ppm H2O (dissolved primarily as hydroxyl) and 4-64 ppm C would produce enough vapor to reach the critical vapor

  12. 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.

  13. Investigation of Copper Losses to Synthetic Slag at Different Oxygen Partial Pressures in the Presence of Colemanite

    NASA Astrophysics Data System (ADS)

    Rusen, Aydın; Derin, Bora; Geveci, Ahmet; Topkaya, Yavuz Ali

    2016-09-01

    Copper losses to slag are crucial for copper matte smelting and converting stages. One factor affecting the copper losses to slag during these processes is partial pressure of oxygen. In this study, theoretical and experimental investigations of oxygen partial pressure effect on copper losses to fayalite type slag in the presence of colemanite were investigated. Theoretical considerations include liquidus temperatures and phase diagrams of the fayalite type slag calculated by the FactSage software program. In the experiments, a synthetic matte-slag (SM-SS) was produced by melting certain amounts of reagent grade Fe2O3-SiO2 and metallic Fe as starting materials. Experiments were carried out with SM-SS pair by the addition of calcined colemanite (from 0% to 6%) under various partial pressures of oxygen (10-7, 10-9, 10-11 atm) at 1250°C for 2 h. From the experimental results, it was found that the amount of copper in slag decreased slowly when colemanite was increased under all oxidizing atmospheres. The lowest copper content in synthetic slag was obtained as 0.38% after 6% colemanite addition.

  14. Real-Time Monitoring of Singlet Oxygen and Oxygen Partial Pressure During the Deep Photodynamic Therapy In Vitro.

    PubMed

    Li, Weitao; Huang, Dong; Zhang, Yan; Liu, Yangyang; Gu, Yueqing; Qian, Zhiyu

    2016-09-01

    Photodynamic therapy (PDT) is an effective noninvasive method for the tumor treatment. The major challenge in current PDT research is how to quantitatively evaluate therapy effects. To our best knowledge, this is the first time to combine multi-parameter detection methods in PDT. More specifically, we have developed a set of system, including the high-sensitivity measurement of singlet oxygen, oxygen partial pressure and fluorescence image. In this paper, the detection ability of the system was validated by the different concentrations of carbon quantum dots. Moreover, the correlation between singlet oxygen and oxygen partial pressure with laser irradiation was observed. Then, the system could detect the signal up to 0.5 cm tissue depth with 660 nm irradiation and 1 cm tissue depth with 980 nm irradiation by using up-conversion nanoparticles during PDT in vitro. Furthermore, we obtained the relationship among concentration of singlet oxygen, oxygen partial pressure and tumor cell viability under certain conditions. The results indicate that the multi-parameter detection system is a promising asset to evaluate the deep tumor therapy during PDT. Moreover, the system might be potentially used for the further study in biology and molecular imaging.

  15. 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.

  16. Stability and partial oligomerization of naphthalene under high pressure at room temperature

    NASA Astrophysics Data System (ADS)

    Shinozaki, Ayako; Mimura, Koichi; Nishida, Tamihito; Inoue, Toru; Nakano, Satoshi; Kagi, Hiroyuki

    2016-10-01

    The stability and pressure-induced chemical reactions of naphthalene were investigated at room temperature at pressures up to 23 GPa. In-situ X-ray diffraction (XRD) measurements indicated that naphthalene retained its crystal structure up to ∼20 GPa, whereas a solid amorphous phase was observed in the recovered samples. Based on microanalysis of the recovered samples using Gas Chromatograph Mass Spectrometer (GC/MS), naphthalene dimer and trimer isomers were observed at pressures exceeding 15 GPa. The dimers were classified as products of simple dimerization, naphthylation, and condensation, similar to the case of the pressure-induced dimerization of benzene, indicating a similar dimerization mechanism for naphthalene.

  17. Hydrogen constituents of the mesosphere inferred from positive ions - H2O, CH4, H2CO, H2O2, and HCN

    NASA Technical Reports Server (NTRS)

    Kopp, E.

    1990-01-01

    The concentrations in the mesosphere of H2O, CH4, H2CO, H2O2, and HCN were inferred from data on positive ion compositions, obtained from one mid-latitude and four high-latitude rocket flights. The inferred concentrations were found to agree only partially with the ground-based microwave measurements and/or model prediction by Garcia and Solomon (1985). The CH4 concentration was found to vary between 70 and 4 ppb in daytime and 900 and 100 ppbv at night, respectively. Unexpectedly high H2CO concentrations were obtained, with H2CO/H2O ratios between 0.0006 and 0.1, and a mean HCN volume mixing ratio of 6 x 10 to the -10th was inferred.

  18. Experimental Determination of the H2O-undersaturated Peridotite Solidus

    NASA Astrophysics Data System (ADS)

    Sarafian, E. K.; Gaetani, G. A.; Hauri, E.; Sarafian, A.

    2015-12-01

    Knowledge of the H2O-undersaturated lherzolite solidus places important constraints on the process of melt generation beneath oceanic spreading centers. While it is generally accepted that the small concentration of H2O (~50-200 ug/g) dissolved in the oceanic upper mantle has a strong influence on the peridotite solidus, but this effect has not been directly determined through experiments. This is because (1) precisely controlling low concentrations of H2O in high-pressure melting experiments is thought to be difficult, (2) small amounts of melt are difficult to identify, and (3) the size of mineral grains that grow in near-solidus experiments is too small to be analyzed for H2O by either Fourier transform infrared (FTIR) spectroscopy or secondary ion mass spectrometry (SIMS). We have developed an experimental approach for determining the peridotite solidus as a function of H2O content that overcomes these difficulties. Our approach utilizes large (~300 um diameter) spheres of San Carlos olivine to monitor the concentration and behavior of H2O in our experiments.. The spheres are mixed in 5:95 proportions with a synthetic peridotite that has the composition of the depleted MORB mantle of Workman and Hart (2005). Partial melting experiments are conducted in is a piston cylinder device using pre-conditioned Au80Pd20 capsules. During an experiment, the H2O content of the San Carlos olivine spheres diffusively equilibrates with the peridotite matrix. After each experiment, the concentration of H2O dissolved in the olivine spheres is determined by secondary ion mass spectrometry. By analyzing the H2O content of the San Carlos olivine spheres and performing a simple mass balance, we can then calculate the amount of H2O in the capsule. The spheres also provides a means to determine the solidus temperature due to the strong partitioning of H2O into silicate melt compared to olivine, pyroxene, and spinel. When a small amount of melt is present the H2O partitions into the

  19. Measurement of surface tension in an atmosphere with controlled oxygen partial pressure under microgravity using a parabolic flight

    NASA Astrophysics Data System (ADS)

    Hibiya, Taketoshi; Watanabe, Masahito; Ozawa, Shumpei; Adachi, Masayoshi; Takenaga, Noriaki; Aoyagai, Tomowo; Mizuno, Akitoshi; Higuchi, Kensuke

    Use of a levitation technique is an elegant way to determine thermophysical properties of high temperature melts, because this containerless technique can avoid contamination from a container and assures measurement in a wide temperature range including superheated and undercooled conditions. In particular, electromagnetic levitation is suitable for electrically conductive materials, such as molten metals, alloys and semiconductors. For surface tension measurement, the Rayleigh equation can be applicable only under microgravity condition [1]. However, when this technique is applied on earth, the l = 2 mode frequency is split into five frequencies, because a droplet is deformed from a spherical shape into an egg shape due to gravitational force and the Lorentz force. Surface tension must be calculated taking account of correction term [2]. Therefore, measurement under microgravity is required to minimize uncertainty. Furthermore, surface tension is sensitive to oxygen partial pressure of an ambient atmosphere. However, there has been less report on surface tension measurement under microgravity in an atmosphere with controlled oxygen partial pressure. We are going to measure surface tension of high temperature metallic melts under microgravity using a parabolic flight of a jet aircraft, the Gulf Stream II, operated by Diamond Air Service in Japan. In September of 2007, through parabolic flight experiments we confirmed that droplets of Cu and Ag were successfully levitated using a newly designed coil under the 1G and 10-2G conditions. Droplets were also assured to be levitated in the pull-up period (1.5G); we can melt samples before entering microgravity condition, so that we can use 20 second microgravity only for measurement. On earth, surface tension of molten silicon was successfully measured using electromagnetic levitation in an ambient atmosphere with various oxygen partial pressures; surface tension of molten silicon showed a marked dependence of oxygen

  20. The Relationship Between Oxygen Reserve Index and Arterial Partial Pressure of Oxygen During Surgery

    PubMed Central

    Dorotta, Ihab L.; Wells, Briana; Juma, David; Applegate, Patricia M.

    2016-01-01

    BACKGROUND: The use of intraoperative pulse oximetry (Spo2) enhances hypoxia detection and is associated with fewer perioperative hypoxic events. However, Spo2 may be reported as 98% when arterial partial pressure of oxygen (Pao2) is as low as 70 mm Hg. Therefore, Spo2 may not provide advance warning of falling arterial oxygenation until Pao2 approaches this level. Multiwave pulse co-oximetry can provide a calculated oxygen reserve index (ORI) that may add to information from pulse oximetry when Spo2 is >98%. This study evaluates the ORI to Pao2 relationship during surgery. METHODS: We studied patients undergoing scheduled surgery in which arterial catheterization and intraoperative arterial blood gas analysis were planned. Data from multiple pulse co-oximetry sensors on each patient were continuously collected and stored on a research computer. Regression analysis was used to compare ORI with Pao2 obtained from each arterial blood gas measurement and changes in ORI with changes in Pao2 from sequential measurements. Linear mixed-effects regression models for repeated measures were then used to account for within-subject correlation across the repeatedly measured Pao2 and ORI and for the unequal time intervals of Pao2 determination over elapsed surgical time. Regression plots were inspected for ORI values corresponding to Pao2 of 100 and 150 mm Hg. ORI and Pao2 were compared using mixed-effects models with a subject-specific random intercept. RESULTS: ORI values and Pao2 measurements were obtained from intraoperative data collected from 106 patients. Regression analysis showed that the ORI to Pao2 relationship was stronger for Pao2 to 240 mm Hg (r2 = 0.536) than for Pao2 over 240 mm Hg (r2 = 0.0016). Measured Pao2 was ≥100 mm Hg for all ORI over 0.24. Measured Pao2 was ≥150 mm Hg in 96.6% of samples when ORI was over 0.55. A random intercept variance component linear mixed-effects model for repeated measures indicated that Pao2 was significantly related to ORI

  1. Water in Basaltic Melts: an Experimental and Thermodynamic Study of the Effect of H2O on Liquidus Temperatures.

    NASA Astrophysics Data System (ADS)

    Medard, E.; Grove, T. L.

    2006-12-01

    We present a thermodynamic model for the influence of H2O on liquidus temperatures of olivine-saturated primitive basaltic and andesitic melts. The thermodynamic model has been fitted to a suite of H2O-saturated liquidus experiments carried out on a primitive high-alumina basalt from Medicine Lake Volcano (82-72f) over a pressure range of 10 to 1000 MPa. The model of Silver and Stolper (S+S, 1985, J.Geol. 93:161) has been applied to the experimental data. This model uses the assumption of simple ideal mixing between water species and the anionic matrix in the melt. Water in the melt dissolves as molecular H2O, or dissociates to hydroxyl groups and an oxygen atomic network. For 82-72f, the liquidus olivine shows little compositional variability (Fo87.4 to Fo88.4) over the broad range of pressures and temperatures investigated that is not correlated with H2O content of the melt. This observation supports our assumption that major effect of H2O is on the anionic species in the melt and not on the cation equilibria (e.g. Mg and Si). The model reproduces the experimental data well. We find that there is a large influence of H2O addition on melting point for small amounts of H2O, resulting in a concave-down curvature when liquidus depression is plotted against the amount of H2O added. For addition of 0.8 and 5 wt% H2O to 82-72f, the liquidus is depressed by 35 K and 130 K, respectively. The best fits are obtained by assuming partial water dissociation to OH and H2O species, using the equilibrium constant measured by Stolper (1982). S+S applied their model to simple systems (diopside/H2O, albite/H2O, silica/H2O), and recovered the melting behavior extremely well. They also suggested that melt structure/composition influences the amount of liquidus depression caused by H2O addition. We have investigated the influence of bulk composition by performing complementary experiments on a high-magnesian andesite from Mount Shasta, and on a K, Na, and P rich alkali basalt from

  2. Particulate filtration for sorbent-based H2 storage

    NASA Astrophysics Data System (ADS)

    van Hassel, Bart A.; Karra, Jagadeswara R.

    2016-01-01

    A method was developed for sizing the particulate filter that can be used inside a sorption-based onboard hydrogen storage system for light-duty vehicles. The method is based on a trade-off between the pressure drop across the particulate filter (during the fill of the H2 storage tank or during its discharge while driving) and the effect of this pressure drop on the usable amount of H2 gas from the H2 storage system. The permeability and filtration efficiency of the particulate filters (in the absence and presence of MOF-5 particulates) was quantified in this study, with an emphasis on meeting DOE's H2 purity requirements.

  3. Mass spectrometric approach for characterizing the disordered tail regions of the histone H2A/H2B dimer.

    PubMed

    Saikusa, Kazumi; Nagadoi, Aritaka; Hara, Kana; Fuchigami, Sotaro; Kurumizaka, Hitoshi; Nishimura, Yoshifumi; Akashi, Satoko

    2015-02-17

    The histone H2A/H2B dimer is a component of nucleosome core particles (NCPs). The structure of the dimer at the atomic level has not yet been revealed. A possible reason for this is that the dimer has three intrinsically disordered tail regions: the N- and C-termini of H2A and the N-terminus of H2B. To investigate the role of the tail regions of the H2A/H2B dimer structure, we characterized behaviors of the H2A/H2B mutant dimers, in which these functionally important disordered regions were depleted, using mass spectrometry (MS). After verifying that the acetylation of Lys residues in the tail regions had little effect on the gas-phase conformations of the wild-type dimer, we prepared two histone H2A/H2B dimer mutants: an H2A/H2B dimer depleted of both N-termini (dN-H2A/dN-H2B) and a dimer with the N- and C-termini of H2A and the N-terminus of H2B depleted (dNC-H2A/dN-H2B). We analyzed these mutants using ion mobility-mass spectrometry (IM-MS) and hydrogen/deuterium exchange mass spectrometry (HDX-MS). With IM-MS, reduced structural diversity was observed for each of the tail-truncated H2A/H2B mutants. In addition, global HDX-MS proved that the dimer mutant dNC-H2A/dN-H2B was susceptible to deuteration, suggesting that its structure in solution was somewhat loosened. A partial relaxation of the mutant's structure was demonstrated also by IM-MS. In this study, we characterized the relationship between the tail lengths and the conformations of the H2A/H2B dimer in solution and gas phases, and demonstrated, using mass spectrometry, that disordered tail regions play an important role in stabilizing the conformation of the core region of the dimer in both phases.

  4. Influence of N2 partial pressure on structural and microhardness properties of TiN/ZrN multilayers deposited by Ar/N2 vacuum arc discharge

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

    The influence of N2 partial pressure on structural, mechanical and wetting properties of multilayered TiN/ZrN thin films deposited on silicon substrates by vacuum arc discharge of (N2 + Ar) gas mixtures is investigated. X-ray diffraction (XRD) results show that the average texturing coefficient of (1 1 1) orientation and the grain size of both TiN and ZrN individual layers increase with increasing the N2 partial pressure. The Rutherford back scattering (RBS) measurements and analysis reveal that incorporation of the nitrogen in the film increases with increasing the N2 partial pressure and both TiN and ZrN individual layers have a nitrogen over-stoichiometry for N2 partial pressure ⩾50%. The change in the film micro-hardness is correlated to the changes in crystallographic texture, grain size, stoichiometry and the residual stress in the film as a function of the N2 partial pressure. In particular, stoichiometry of ZrN and TiN individual is found to play the vital role in determining the multilayer hardness. The multilayer film deposited at N2 partial pressure of 25% has the best stoichiometric ratio of both TiN and ZrN layers and the highest micro-hardness of about 32 GPa. In addition, water contact angle (WCA) measurements and analysis show a decrease in the work of adhesion on increasing the N2 partial pressure.

  5. Measurement and modeling of neutral, radical, and ion densities in H2-N2-Ar plasmas

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

    A comprehensive experimental investigation of absolute ion and neutral species densities in an inductively coupled H2-N2-Ar plasma was carried out. Additionally, the radical and ion densities were calculated using a zero-dimensional rate equation model. The H2-N2-Ar plasma was studied at a pressure of 1.5 Pa and an rf power of 200 W. The N2 partial pressure fraction was varied between fN2=0 % and 56% by a simultaneous reduction of the H2 partial pressure fraction. The Ar partial pressure fraction was held constant at about 1%. NH3 was found to be produced almost exclusively on the surfaces of the chamber wall. NH3 contributes up to 12% to the background gas. To calculate the radical densities with the rate equation model, it is necessary to know the corresponding wall loss times twrad of the radicals. twrad was determined by the temporal decay of radical densities in the afterglow with ionization threshold mass spectrometry during pulsed operation and based on these experimental data the absolute densities of the radical species were calculated and compared to measurement results. Ion densities were determined using a plasma monitor (mass and energy resolved mass spectrometer). H3+ is the dominant ion in the range of 0.0 ≤fN2<3.4 % . For 3.4 H2+ , ArH+, and NH2+ . Ion species with densities less than 0.5% of ni,tot are H+, Ar+, N+, and NH+. Our model describes the measured ion densities of the H2-N2-Ar plasma reasonably well. The ion chemistry, i.e., the production and loss processes of the ions and radicals, is discussed in detail. The main features, i.e., the qualitative abundance of the ion species and the ion density dependence on the N2 partial pressure fraction, are well

  6. Changes in glucose fermentation pathways by an enriched bacterial culture in response to regulated dissolved H2 concentrations.

    PubMed

    Zheng, Hang; Zeng, Raymond J; Duke, Mikel C; O'Sullivan, Cathryn A; Clarke, William P

    2015-06-01

    It is well established that metabolic pathways in the fermentation of organic waste are primarily controlled by dissolved H2 concentrations, but there is no reported study that compares observed and predicted shifts in fermentation pathways induced by manipulating the dissolved H2 concentration. A perfusion system is presented that was developed to control dissolved H2 concentrations in the continuous fermentation of glucose by a culture highly enriched towards Thermoanaerobacterium thermosaccharolyticum (86 ± 9% relative abundance) from an originally diverse consortia in the leachate of a laboratory digester fed with municipal solid waste. Media from a 2.5 L CSTR was drawn through sintered steel membrane filters to retain biomass, allowing vigorous sparging in a separate chamber without cellular disruption. Through a combination of sparging and variations in glucose feeding rate from 0.8 to 0.2 g/L/d, a range of steady state fermentations were performed with dissolved H2 concentrations as low as an equivalent equilibrated H2 partial pressure of 3 kPa. Trends in product formation rates were simulated using a H2 regulation partitioning model. The model correctly predicted the direction of products redistribution in response to H2 concentration changes and the acetate and butyrate formation rates when H2 concentrations were less than 6 kPa. However, the model over-estimated acetate, ethanol and butanol productions at the expense of butyrate production at higher H2 concentrations. The H2 yield at the lowest dissolved H2 concentration was 2.67 ± 0.08 mol H2 /mol glucose, over 300% higher than the yield achieved in a CSTR operated without sparging.

  7. Non-contact measurement of partial gas pressure and distribution of elemental composition using energy-resolved neutron imaging

    NASA Astrophysics Data System (ADS)

    Tremsin, A. S.; Losko, A. S.; Vogel, S. C.; Byler, D. D.; McClellan, K. J.; Bourke, M. A. M.; Vallerga, J. V.

    2017-01-01

    Neutron resonance absorption imaging is a non-destructive technique that can characterize the elemental composition of a sample by measuring nuclear resonances in the spectrum of a transmitted beam. Recent developments in pixelated time-of-flight imaging detectors coupled with pulsed neutron sources pose new opportunities for energy-resolved imaging. In this paper we demonstrate non-contact measurements of the partial pressure of xenon and krypton gases encapsulated in a steel pipe while simultaneously passing the neutron beam through high-Z materials. The configuration was chosen as a proof of principle demonstration of the potential to make non-destructive measurement of gas composition in nuclear fuel rods. The pressure measured from neutron transmission spectra (˜739 ± 98 kPa and ˜751 ± 154 kPa for two Xe resonances) is in relatively good agreement with the pressure value of ˜758 ± 21 kPa measured by a pressure gauge. This type of imaging has been performed previously for solids with a spatial resolution of ˜ 100 μm. In the present study it is demonstrated that the high penetration capability of epithermal neutrons enables quantitative mapping of gases encapsulate within high-Z materials such as steel, tungsten, urania and others. This technique may be beneficial for the non-destructive testing of bulk composition of objects (such as spent nuclear fuel assemblies and others) containing various elements opaque to other more conventional imaging techniques. The ability to image the gaseous substances concealed within solid materials also allows non-destructive leak testing of various containers and ultimately measurement of gas partial pressures with sub-mm spatial resolution.

  8. 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

  9. Highly Selective H2 Separation Zeolite Membranes for Coal Gasification Membrane Reactor Applications

    SciTech Connect

    Mei Hong; Richard Noble; John Falconer

    2007-09-24

    _dot}s-1{center_dot}Pa-1, and the H2/CO2 separation selectivity was 47. Above 673 K, the silylated membrane catalyzed reverse water gas shift reaction and still separated H2 with high selectivity; and it was thermally stable. However, silylation decreased H2 permeance more than one order of magnitude. Increasing the membrane feed pressure increased the H2 flux and the H2 mole fraction in the permeate stream for both H2/CO2 and H2/CH4 mixtures. The H2 separation performance of the silylated B-ZSM-5 membranes depended on the initial membrane quality and acidity, as well as the silane precursors. Another approach used in this study is optimizing the synthesis of small-pore SAPO-34 (CHA) membranes and/or modifying SAPO-34 membranes by silylation or ion exchange. For SAPO-34 membranes, strong CO2 adsorption inhibited H2 adsorption and decreased H2 permeances, especially at low temperatures. At 253 K, CO2/H2 separation selectivities of a SAPO-34 membrane were greater than 100 with CO2 permeances of about 3 x 10-8 mol{center_dot}m-2{center_dot}s-1{center_dot}Pa-1. The high reverse-selectivity of the SAPO-34 membranes can minimize H2 recompression because H2 remained in the retentate stream at a higher pressure. The CO2/H2 separation selectivity exhibited a maximum with CO2 feed concentration possibly caused by a maximum in the CO2/H2 sorption selectivity with increased CO2 partial pressure. The SAPO-34 membrane separated H2 from CH4 because CH4 is close to the SAPO-34 pore size so its diffusivity (ABSTRACT TRUNCATED)

  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. Pressure of Partial Crystallization of Katla Magmas: Implications for Magma Chamber Depth and for the Magma Plumbing System

    NASA Astrophysics Data System (ADS)

    Tenison, A.; Kelley, D. F.; Barton, M.

    2012-12-01

    Iceland is home to some of the most active volcanoes in the world, and recent eruptions emphasize the need for additional studies to better understand the volcanism and tectonics in this region. Historical patterns of eruptive activity and an increase in seismic activity suggest that Katla is showing signs of an impending eruption. The last major eruption in 1918 caused massive flooding and deposited enough sediment to extend part of Iceland's southern shoreline by 5 km. It also generated sufficient ash over many weeks to cause a brief drop in global temperature. A future eruption similar to the 1918 event could have serious global consequences, including severe disruptions in air travel, short-term global cooling, and shortened growing seasons. Relatively few studies have focused on establishing the depth of the main magma chamber beneath Katla, although knowledge of magma chamber depth is essential for constraining models for magma evolution and for understanding the eruption dynamics of this volcano. The results of seismic and geodetic studies suggest the presence of a shallow magma body at a depth of 2-4 km, but do not provide firm evidence for the presence of deeper chambers in contrast to results obtained for other volcanoes in Iceland. Studies of volcanic ash layers reveal a history of alternating cycles of basaltic and silicic eruptions. We suggest that the shallow magma chamber is primarily the source of silica-rich magma, and postulate that there must be one or more additional chambers in the middle or deep crust that serve as the storage site of the basaltic magma erupted as lava and ash. We have tested this proposal by calculating the pressures of partial crystallization for basalts erupted at Katla using petrological methods. These pressures can be converted to depths and the results provide insight into the likely configuration of the magma plumbing system. Published analyses of volcanic glasses (lava, ash and hyaloclastite) were used as input data

  12. Temperature measurements of partially-melted tin as a function of shock pressure

    SciTech Connect

    Seifter, Achim; Furlanetto, Michael R; Holtkamp, David B; Obst, Andrew W; Payton, J R; Stone, J B; Tabaka, L J; Grover, M; Macrum, G; Stevens, G D; Swift, D C; Turley, W D; Veeser, L R

    2009-01-01

    Equilibrium equation of state theory predicts that the free surface release temperature of shock loaded tin will show a plateau of 505 K in the pressure range from 19.5 to 33.0 GPa, corresponding to the solid-liquid mixed-phase region. In this paper we report free surface temperature measurements on shock-loaded tin from 15 to 31 GPa using multi-wavelength optical pyrometry. The shock waves were generated by direct contact of detonating high explosive with the sample. The pressure in the sample was determined by free surface velocity measurements using Photon Doppler Velocimetry. The emitted thermal radiance was measured at four wavelength bands in the near IR region from 1.5 to 5.0 {micro}m. The samples in most of the experiments had diamond-turned surface finishes, with a few samples being polished or ball rolled. At pressures higher than 25 GPa the measured free surface temperatures were higher than the predicted 505 K and increased with increasing pressure. This deviation could be explained by hot spots and/or variations in surface emissivity and requires a further investigation.

  13. Effect of oxygen partial pressure on the density of states of amorphous InGaZnO thin-film transistors

    NASA Astrophysics Data System (ADS)

    Li, Jun; Huang, Chuan-Xin; Zhu, Wen-Qing; Zhang, Jian-Hua; Jiang, Xue-Yin; Zhang, Zhi-Lin; Li, Xi-Feng

    2016-10-01

    The thin-film transistors (TFTs) with InGaZnO active layer with different oxygen partial pressures are fabricated by radio frequency sputtering. The influence of the oxygen partial pressure on the density of states (DOS) for InGaZnO-TFT is investigated by using temperature-dependent field-effect measurements. It indicates that the DOS become smaller with increasing oxygen partial pressure. The results are verified by the threshold voltage shift of InGaZnO-TFT with different oxygen partial pressures. The trend of the variation of DOS is consistent with that of the threshold voltage shift for InGaZnO-TFT. Thus, the gate bias instability is attributed to the charge trapping mechanism based on DOS. Therefore, this work offered a brief and accurate method to calculate DOS for demonstrating the bias stability of transistor.

  14. Electrical conductivity of MgH2 at multiple shock compression

    NASA Astrophysics Data System (ADS)

    Shakhray, Denis; Molodets, Alexander; Fortov, Vladimir

    2011-06-01

    The electrical conductivity of MgH2 has been studied under multishock compression. Earlier we had been experimentally studied metallization possibility of alane at high pressures in conditions quasiisentropic compression up to 100 GPa. A study of thermodynamic properties of MgH2 under multishock compression has been carried out also. High pressures and temperatures were obtained with an explosive device, which accelerates the metallic impactor up to 3 km/s. Identification of the hydride in experiments was made on the basis of calculations of phase trajectories loading a material in the area of existence of polymorphic phases including high-pressure phases of magnesium hydride (α and γ MgH2, hP1 and hP2). It is shown that occurrence of magnesium hydride electrical conductivity occurs in the field of existence of high-pressure hP2 phase This work was partially supported by the Presidium of the Russian Academy of Sciences within the Program of Basic Research ``Thermal Physics and Mechanics of Extreme Energy Effects and Physics of Strongly Compressed Matter and Russian Foundation for Basic Research Grant No. 10-02-01078.''

  15. Disproportionation and Thermochemical Sulfate Reduction Reactions in S-H2O-CH4 and S-D2O-CH4 Systems from 200 to 340 °C at Elevated Pressures

    NASA Astrophysics Data System (ADS)

    Chou, I.; Yuan, S.; Burruss, R. C.

    2010-12-01

    Elemental sulfur plays significant roles in thermochemical sulfate reduction (TSR) reactions as a transient intermediate oxidation state compound, by-product, or catalyst. However, the mechanisms of the reactions in S-H2O-hydrocarbon systems are not clear. To improve our understanding of reaction mechanisms, we conducted a series of experiments between 200 and 340 °C for S-H2O-CH4, S-D2O-CH4, and S-CH4-1m ZnBr2 systems in fused silica capillary capsules. After a heating period ranging from one to 90 days, the quenched samples were analyzed by Raman spectroscopy. Our results showed that the disproportionation of sulfur in the S-H2O-CH4 system occurred at temperatures above 200 °C and produced H2S, SO42-, and HSO4-. We also observed that the amounts of SO42- and HSO4- decreased for the samples quenched from 250 and 340 °C, and at the same time the amounts of CO2 and H2S increased. To demonstrate that the observed consumption of SO42- and HSO4- in the S-H2O-CH4 system at 300 °C was due to TSR instead of the back reaction between SO42- (or HSO4-) and H2S to form S during and after quench, we introduced 1m ZnBr2 to remove H2S as a ZnS precipitate, as soon as it formed. In these experiments sulfate species decreased and CO2 and H2S increased consistent with TSR and no back reaction. When compared with previously published experiments, our temperatures between 250 and 340 °C are much closer to natural systems (<200 °C) with documented TSR. Also, to demonstrate the relationship between disproportionation and TSR reactions in the S-H2O-CH4 system, we conducted experiments in the S-D2O-CH4 system at 250 and 300 °C. Only small Raman signals for CO2 and no signals for H2S and D2S were detected in the sample quenched from 250 °C, indicating that both the disproportionation reaction and the TSR reaction were very slow at this temperature. After heating at 300 °C for 40 h, Raman signals of the quenched sample indicated significant amount of D2S was produced through the

  16. On the Installation of Jet Engine Nacelles on a Wing Fourth Partial Report: Pressure-Distribution Measurements on a Sweptback Wing with Jet Engine Nacelle

    NASA Technical Reports Server (NTRS)

    Buschner, R.

    1949-01-01

    The present report, which deals with pressure-distribution measurements made on a sweptback wing with a jet engine nacelle, is similar to a report on pressure-distribution measurements on a rectangular wing with a jet engine nacelle (second partial report). Here, in investigations preliminary to high-speed measurements, as in the second partial report, useful arrangements and fillet designs have been discovered.

  17. Surface tension and its temperature coefficient of molten tin determined with the sessile drop method at different oxygen partial pressures.

    PubMed

    Yuan, Zhang Fu; Mukai, Kusuhiro; Takagi, Katsuhiko; Ohtaka, Masahiko; Huang, Wen Lai; Liu, Qiu Sheng

    2002-10-15

    The surface tension of molten tin has been determined by the sessile drop method at temperatures ranging from 523 to 1033 K and in the oxygen partial pressure (P(O(2))) range from 2.85 x 10(-19) to 8.56 x 10(-6) MPa, and its dependence on temperature and oxygen partial pressure has been analyzed. At P(O(2))=2.85 x 10(-19) and 1.06 x 10(-15) MPa, the surface tension decreases linearly with the increase of temperature and its temperature coefficients are -0.151 and -0.094 mN m(-1) K(-1), respectively. However, at high P(O(2)) (3.17 x 10(-10), 8.56 x 10(-6) MPa), the surface tension increases with the temperature near the melting point (505 K) and decreases above 723 K. The surface tension decrease with increasing P(O(2)) is much larger near the melting point than at temperatures above 823 K. The contact angle between the molten tin and the alumina substrate is 158-173 degrees, and the wettability is poor.

  18. The CO2 stimulus for cerebrovascular reactivity: Fixing inspired concentrations vs. targeting end-tidal partial pressures.

    PubMed

    Fisher, Joseph A

    2016-06-01

    Cerebrovascular reactivity (CVR) studies have elucidated the physiology and pathophysiology of cerebral blood flow regulation. A non-invasive, high spatial resolution approach uses carbon dioxide (CO2) as the vasoactive stimulus and magnetic resonance techniques to estimate the cerebral blood flow response. CVR is assessed as the ratio response change to stimulus change. Precise control of the stimulus is sought to minimize CVR variability between tests, and show functional differences. Computerized methods targeting end-tidal CO2 partial pressures are precise, but expensive. Simpler, improvised methods that fix the inspired CO2 concentrations have been recommended as less expensive, and so more widely accessible. However, these methods have drawbacks that have not been previously presented by those that advocate their use, or those that employ them in their studies. As one of the developers of a computerized method, I provide my perspective on the trade-offs between these two methods. The main concern is that declaring the precision of fixed inspired concentration of CO2 is misleading: it does not, as implied, translate to precise control of the actual vasoactive stimulus - the arterial partial pressure of CO2 The inherent test-to-test, and therefore subject-to-subject variability, precludes clinical application of findings. Moreover, improvised methods imply widespread duplication of development, assembly time and costs, yet lack uniformity and quality control. A tabular comparison between approaches is provided.

  19. Monitoring in microvascular tissue transfer by measurement of oxygen partial pressure: four years experience with 125 microsurgical transplants.

    PubMed

    Jonas, René; Schaal, Thomas; Krimmel, Michael; Gülicher, Dirk; Reinert, Siegmar; Hoffmann, Jürgen

    2013-06-01

    In a prospective study, the characteristics and benefit of an invasive measurement of oxygen partial pressure (pO(2)) with the aid of a polarographic sensor were investigated in 125 microsurgical reconstructions of the head and neck area over a period of 45 months. Measurements were performed over 96 h in eight different types of microsurgically revascularized flaps for extra- and intraoral reconstructions and were evaluated separately for each flap type. Of 125 reconstructions the system indicated malperfusion in 18 cases. Salvage surgery was performed in 17 cases due to venous thrombosis (6 cases), arterial thrombosis (3 cases), a combination of arterial and venous thrombosis (2 cases), rheological problems (3 cases), venous insufficiency by hematoma (2 cases) and kinking of vessels (1 case). In 10 cases salvage surgery was successful, 7 flaps were lost despite salvage surgery. In all these cases, the polarographic probe indicated the necessity of salvage surgery correctly. After 96 h no malperfusion was seen. Postoperatively, a common and characteristic development of the oxygen partial pressure in different types of flaps was seen. Initially, a clear increase of pO(2) could be measured. During 96 h, a slow decrease of pO(2) was observed. In conclusion polarographic measurement of pO(2) can be an excellent apparative supplement for the postoperative clinical control of microsurgically revascularized transplants. In buried flaps, this technique represents the only reliable method for transplant monitoring.

  20. H2S: a novel gasotransmitter that signals by sulfhydration

    PubMed Central

    Paul, Bindu D.; Snyder, Solomon H.

    2015-01-01

    Hydrogen sulfide is a member of the growing family of gasotransmitters. Once regarded as a noxious molecule predominantly present in the atmosphere, H2S is now known to be synthesized endogenously in mammals. H2S participates in a myriad of physiological processes ranging from regulation of blood pressure to neuroprotection. Its chemical nature precludes H2S from being stored in vesicles and acting on receptor proteins in the fashion of other chemical messengers. Thus, novel cellular mechanisms have evolved to mediate its effects. This article focuses on sulfhydration (or persulfidation), which appears to be the principal post-translational modification elicited by H2S. PMID:26439534

  1. A shock tube study of OH + H(2)O(2) --> H(2)O + HO(2) and H(2)O(2) + M --> 2OH + M using laser absorption of H(2)O and OH.

    PubMed

    Hong, Zekai; Cook, Robert D; Davidson, David F; Hanson, Ronald K

    2010-05-13

    The rate constants of the reactions: (1) H2O2+M-->2OH+M, (2) OH+H2O2-->H2O+HO2 were measured in shock-heated H(2)O(2)/Ar mixtures using laser absorption diagnostics for H(2)O and OH. Time-histories of H(2)O were monitored using tunable diode laser absorption at 2550.96 nm, and time-histories of OH were achieved using ring dye laser absorption at 306 nm. Initial H(2)O(2) concentrations were also determined utilizing the H(2)O diagnostic. On the basis of simultaneous time-history measurements of OH and H(2)O, k(2) was found to be 4.6 x 10(13) exp(-2630 K/T) [cm(3) mol(-1) s(-1)] over the temperature range 1020-1460 K at 1.8 atm; additional measurements of k(2) near 1 atm showed no significant pressure dependence. Similarly, k(1) was found to be 9.5 x 10(15) exp(-21 250 K/T) [cm(3) mol(-1) s(-1)] over the same temperature and pressure range.

  2. Electronic and chemical structure of the H2O/GaN(0001) interface under ambient conditions

    DOE PAGES

    Zhang, Xueqiang; Ptasinska, Sylwia

    2016-04-25

    We employed ambient pressure X-ray photoelectron spectroscopy to investigate the electronic and chemical properties of the H2O/GaN(0001) interface under elevated pressures and/or temperatures. A pristine GaN(0001) surface exhibited upward band bending, which was partially flattened when exposed to H2O at room temperature. However, the GaN surface work function was slightly reduced due to the adsorption of molecular H2O and its dissociation products. At elevated temperatures, a negative charge generated on the surface by a vigorous H2O/GaN interfacial chemistry induced an increase in both the surface work function and upward band bending. We tracked the dissociative adsorption of H2O onto themore » GaN(0001) surface by recording the core-level photoemission spectra and obtained the electronic and chemical properties at the H2O/GaN interface under operando conditions. In conclusion, our results suggest a strong correlation between the electronic and chemical properties of the material surface, and we expect that their evolutions lead to significantly different properties at the electrolyte/ electrode interface in a photoelectrochemical solar cell.« less

  3. Electronic and chemical structure of the H2O/GaN(0001) interface under ambient conditions

    NASA Astrophysics Data System (ADS)

    Zhang, Xueqiang; Ptasinska, Sylwia

    2016-04-01

    We employed ambient pressure X-ray photoelectron spectroscopy to investigate the electronic and chemical properties of the H2O/GaN(0001) interface under elevated pressures and/or temperatures. A pristine GaN(0001) surface exhibited upward band bending, which was partially flattened when exposed to H2O at room temperature. However, the GaN surface work function was slightly reduced due to the adsorption of molecular H2O and its dissociation products. At elevated temperatures, a negative charge generated on the surface by a vigorous H2O/GaN interfacial chemistry induced an increase in both the surface work function and upward band bending. We tracked the dissociative adsorption of H2O onto the GaN(0001) surface by recording the core-level photoemission spectra and obtained the electronic and chemical properties at the H2O/GaN interface under operando conditions. Our results suggest a strong correlation between the electronic and chemical properties of the material surface, and we expect that their evolutions lead to significantly different properties at the electrolyte/electrode interface in a photoelectrochemical solar cell.

  4. Electronic and chemical structure of the H2O/GaN(0001) interface under ambient conditions

    PubMed Central

    Zhang, Xueqiang; Ptasinska, Sylwia

    2016-01-01

    We employed ambient pressure X-ray photoelectron spectroscopy to investigate the electronic and chemical properties of the H2O/GaN(0001) interface under elevated pressures and/or temperatures. A pristine GaN(0001) surface exhibited upward band bending, which was partially flattened when exposed to H2O at room temperature. However, the GaN surface work function was slightly reduced due to the adsorption of molecular H2O and its dissociation products. At elevated temperatures, a negative charge generated on the surface by a vigorous H2O/GaN interfacial chemistry induced an increase in both the surface work function and upward band bending. We tracked the dissociative adsorption of H2O onto the GaN(0001) surface by recording the core-level photoemission spectra and obtained the electronic and chemical properties at the H2O/GaN interface under operando conditions. Our results suggest a strong correlation between the electronic and chemical properties of the material surface, and we expect that their evolutions lead to significantly different properties at the electrolyte/electrode interface in a photoelectrochemical solar cell. PMID:27108711

  5. Brain tissue partial pressure of oxygen predicts the outcome of severe traumatic brain injury under mild hypothermia treatment

    PubMed Central

    Sun, Hongtao; Zheng, Maohua; Wang, Yanmin; Diao, Yunfeng; Zhao, Wanyong; Wei, Zhengjun

    2016-01-01

    Objective The aim of this study was to investigate the clinical significance and changes of brain tissue partial pressure of oxygen (PbtO2) in the course of mild hypothermia treatment (MHT) for treating severe traumatic brain injury (sTBI). Methods There were 68 cases with sTBI undergoing MHT. PbtO2, intracranial pressure (ICP), jugular venous oxygen saturation (SjvO2), and cerebral perfusion pressure (CPP) were continuously monitored, and clinical outcomes were evaluated using the Glasgow Outcome Scale score. Results Of 68 patients with sTBI, PbtO2, SjvO2, and CPP were obviously increased, but decreased ICP level was observed throughout the MHT. PbtO2 and ICP were negatively linearly correlated, while there was a positive linear correlation between PbtO2 and SjvO2. Monitoring CPP and SjvO2 was performed under normal circumstances, and a large proportion of patients were detected with low PbtO2. Decreased PbtO2 was also found after MHT. Conclusion Continuous PbtO2 monitoring could be introduced to evaluate the condition of regional cerebral oxygen metabolism, thereby guiding the clinical treatment and predicting the outcome. PMID:27601907

  6. Influence of oxygen partial pressures on protein synthesis in feeding crabs.

    PubMed

    Mente, Eleni; Legeay, Alexia; Houlihan, Dominic F; Massabuau, Jean-Charles

    2003-02-01

    Many water-breathing animals have a strategy that consists of maintaining low blood PO2 values in a large range of water oxygenation level (4-40 kPa). This study examines the postprandial changes in O2 consumption, arterial blood PO2, and tissue protein synthesis in the shore crab Carcinus maenas in normoxic, O2-depleted, and O2-enriched waters to study the effects of this strategy on the O2 consumption and peptide bond formation after feeding. In normoxic water (21 kPa), the arterial PO2 was 1.1 kPa before feeding and 1.2 kPa 24 h later. In water with a PO2 of 3 kPa (arterial PO2 0.6 kPa), postprandial stimulation of protein synthesis and O2 consumption were blocked. The blockade was partial at a water PO2 of 4 kPa (arterial PO2 0.8 kPa). An increase in environmental PO2 (60 kPa, arterial PO2 10 kPa) resulted in an increase in protein synthesis compared with normoxic rates. It is concluded that the arterial PO2 spontaneously set in normoxic Carcinus limits the rates of protein synthesis. The rationale for such a strategy is discussed.

  7. Partial amorphization of a Cu-Zr-Ti alloy by high pressure torsion

    SciTech Connect

    Revesz, Adam; Hobor, Sandor; Labar, Janos L.; Zhilyaev, Alex P.; Kovacs, Zsolt

    2006-11-15

    High pressure torsion was applied to produce disk-shape specimen of Cu{sub 60}Zr{sub 20}Ti{sub 20} composition. Radial dependence of the microstructure was monitored by x-ray diffraction, scanning, and transmission electron microscopies. The disk consists of a top surface layer, homogeneous on a micrometer scale with an average thickness of 10-20 {mu}m, and an inhomogeneous bulk region of 200 {mu}m thickness. Calorimetric studies revealed that the disk contains detectable amount of amorphous phase. Characteristics of this amorphous content were compared to a fully amorphous melt-quenched Cu{sub 60}Zr{sub 20}Ti{sub 20} ribbon.

  8. 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 (Δ) 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 Δ 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 Δ 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, Δ 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

  9. Formation of hydrogenated amorphous carbon films by reactive high power impulse magnetron sputtering containing C2H2 gas

    NASA Astrophysics Data System (ADS)

    Kimura, Takashi; Kamata, Hikaru

    2015-09-01

    Diamond-like carbon (DLC) films have attracted interest for material industries, because they have unique properties. Hydrogenated amorphous carbon films are prepared by reactive high power impulse magnetron sputtering (HiPIMS) containing C2H2 gas and the properties of the films produced in Ar/C2H2 and Ne/C2H2 HiPIMS are compared. Production of hydrocarbon radicals and their ions strongly depends on both electron temperature and electron density in HiPIMS. Therefore, the influence of the difference in buffer gas (Ar and Ne) on the film properties is also valuable to investigate. The film preparation is performed at an average power of 60 W and a repetition frequency of 110 Hz. Total pressure ranges between 0.3 and 2 Pa. The maximum of instantaneous power is about 20-25 kW, and the magnitude of the current is 35 A. A negative pulse voltage is applied to the substrates for about 15 μs after the target voltage changed from about -500 V to 0 V. Hardness of the films prepared by Ar/C2H2 HiPIMS monotonically decreases with increasing the total pressure, whereas that of the films prepared by Ne/C2H2 HiPIMS does not strongly depend on the total pressure. This work is partially supported by JSPS KAKENHI Grant Number 26420230.

  10. 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 μm 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 (σ = (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

  11. The role of H2O in the Saturn ionosphere

    NASA Astrophysics Data System (ADS)

    Shemansky, Donald; Liu, Xianming

    2010-05-01

    Stellar occultations in the Cassini Ultraviolet Imaging Spectrograph Experiment observation program have provided measurements of the vertical profiles of H2 and and minor components of the atmosphere. The minor species identified and measured in the extinction spectra to date are CH4, C2H2, and C2H4. Measurements of abundance profiles are reported here, with limits on H2O content. The focus of this paper is on H2O because of the importance of this species to the understanding of upper atmospheric physical chemistry with significant consequences for ionospheric properties and energy budget. Ionospheric theory published in several papers beginning as early as 1984 have a common critical dependence on a sufficiently large H2O mixing ratio to control the lifetime of the assumed dominant ion, H+. The vertical extinction profiles, which extend down to an impact parameter of 300 km above the 1 bar pressure level, show no evidence of H2O in the spectrum at mid and low latitudes, establishing a mixing ratio [H2O]/[H2] ≤ 4 × 10-8, compatible with earlier global average measurements. The upper limit on H2O abundance at mid latitude establishes a mixing ratio more an order of magnitude too low to influence the ionosphere population in competition with calculated H+ + H2 X(v:J) charge capture reaction rates. The analysis of the extinction spectra produces densities and mixing ratios of the observed species and these results are reported and discussed.

  12. Enhancement of atmospheric H2SO4/H2O nucleation: organic oxidation products versus amines

    NASA Astrophysics Data System (ADS)

    Berndt, T.; Sipilä, M.; Stratmann, F.; Petäjä, T.; Vanhanen, J.; Mikkilä, J.; Patokoski, J.; Taipale, R.; Mauldin, R. Lee, III; Kulmala, M.

    2013-06-01

    Atmospheric H2SO4/H2O nucleation influencing effects have been studied in the flow tube IfT-LFT (Institute for Tropospheric Research - Laminar Flow Tube) at 293 ± 0.5 K and a pressure of 1 bar using synthetic air as the carrier gas. The presence of a~possible background amine concentration in the order of 107-108 molecule cm-3 throughout the experiments has to be taken into account. In a first set of investigations, ozonolysis of olefins (tetramethylethylene, 1-methyl-cyclohexene, α-pinene and limonene) for close to atmospheric concentrations, served as the source of OH radicals and possibly other oxidants initiating H2SO4 formation starting from SO2. The oxidant generation is inevitably associated with the formation of a series of organic oxidation products arising from the parent olefins. These products (first generation mainly) showed no clear effect on the number of nucleated particles within a wide range of experimental conditions for H2SO4 concentrations higher than ~107 molecule cm-3. A comparison of the results of two different particle counters (50% cut-off size: about 1.5 nm or 2.5-3 nm) suggested that the early growth process of the nucleated particles was not significantly influenced by the organic oxidation products. An additional, H2SO4-independent process of particle (nano-CN) formation was observed in the case of α-pinene and limonene ozonolysis for H2SO4 concentrations smaller than ~10 7 molecule cm-3. Furthermore, the findings confirm the existence of an additional oxidant for SO2 beside OH radicals, very likely stabilized Criegee Intermediate (sCI). In the case of the ozonolysis of tetramethylethylene, the H2SO4 measurements in the absence and presence of an OH radical scavenger were well described by modelling using recently obtained kinetic data for the sCI reactivity in this system. A second set of experiments has been performed in the presence of added amines (trimethylamine, dimethylamine, aniline and pyridine) in the concentration range

  13. 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).

  14. Variations in Alveolar Partial Pressure for Carbon Dioxide and Oxygen Have Additive Not Synergistic Acute Effects on Human Pulmonary Vasoconstriction

    PubMed Central

    Croft, Quentin P. P.; Formenti, Federico; Talbot, Nick P.; Lunn, Daniel; Robbins, Peter A.; Dorrington, Keith L.

    2013-01-01

    The human pulmonary vasculature constricts in response to hypercapnia and hypoxia, with important consequences for homeostasis and adaptation. One function of these responses is to direct blood flow away from poorly-ventilated regions of the lung. In humans it is not known whether the stimuli of hypercapnia and hypoxia constrict the pulmonary blood vessels independently of each other or whether they act synergistically, such that the combination of hypercapnia and hypoxia is more effective than the sum of the responses to each stimulus on its own. We independently controlled the alveolar partial pressures of carbon dioxide (Paco2) and oxygen (Pao2) to examine their possible interaction on human pulmonary vasoconstriction. Nine volunteers each experienced sixteen possible combinations of four levels of Paco2 (+6, +1, −4 and −9 mmHg, relative to baseline) with four levels of Pao2 (175, 100, 75 and 50 mmHg). During each of these sixteen protocols Doppler echocardiography was used to evaluate cardiac output and systolic tricuspid pressure gradient, an index of pulmonary vasoconstriction. The degree of constriction varied linearly with both Paco2 and the calculated haemoglobin oxygen desaturation (1-So2). Mixed effects modelling delivered coefficients defining the interdependence of cardiac output, systolic tricuspid pressure gradient, ventilation, Paco2 and So2. No interaction was observed in the effects on pulmonary vasoconstriction of carbon dioxide and oxygen (p>0.64). Direct effects of the alveolar gases on systolic tricuspid pressure gradient greatly exceeded indirect effects arising from concurrent changes in cardiac output. PMID:23935847

  15. Oxidation behavior of V-Cr-Ti alloys in low-partial-pressure oxygen environments

    SciTech Connect

    Natesan, K.; Uz, M.

    1998-09-01

    A test program is in progress at Argonne National Laboratory to evaluate the effect of pO{sub 2} in the exposure environment on oxygen uptake, scaling kinetics, and scale microstructure in V-Cr-Ti alloys. The data indicate that the oxidation process follows parabolic kinetics in all of the environments used in the present study. From the weight change data, parabolic rate constants were evaluated as a function of temperature and exposure environment. The temperature dependence of the parabolic rate constants was described by an Arrhenius relationship. Activation energy for the oxidation process was fairly constant in the oxygen pressure range of 1 {times} 10{sup {minus}6} to 1 {times} 10{sup {minus}1} torr for both the alloys. The activation energy for oxidation in air was significantly lower than in low-pO{sub 2} environments, and for oxidation in pure O{sub 2} at 760 torr was much lower than in low-pO{sub 2} environments. X-ray diffraction analysis of the specimens showed that VO{sub 2} was the dominant phase in low-pO{sub 2} environments, while V{sub 2}O{sub 5} was dominant in air and in pure oxygen at 76f0 torr.

  16. Equilibrium partial pressure of CO2 in Callovian-Oxfordian argillite as a function of relative humidity: Experiments and modelling

    NASA Astrophysics Data System (ADS)

    Lassin, Arnault; Marty, Nicolas C. M.; Gailhanou, Hélène; Henry, Benoît; Trémosa, Joachim; Lerouge, Catherine; Madé, Benoît; Altmann, Scott; Gaucher, Eric C.

    2016-08-01

    Having previously demonstrated that the mineral assemblage of claystone can impose its pCO2 under saturated conditions, we here study the effect of rock desaturation, i.e. the evaporation of pore water, on the partial pressure of CO2 (pCO2) in Callovian-Oxfordian argillite from the Paris Basin (France). In this new study, which combines experiments at room temperature and geochemical modelling, we examine the primary role of capillary forces on chemical equilibria for relative humidity values ranging between 50% and 100%. In particular we are able, without any fitting parameters, to model the experimental decrease of pCO2 as a function of decreasing water content in the argillite. This application to a complex natural system not only confirms the theoretical concepts of geochemistry in capillary contexts, but is promising with respect to other systems, both natural (soil, rock) and industrial (ceramics, granular material).

  17. 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.

  18. 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.

  19. X-ray Photoelectron Spectroscopy Study of Indium Tin Oxide Films Deposited at Various Oxygen Partial Pressures

    NASA Astrophysics Data System (ADS)

    Peng, Shou; Cao, Xin; Pan, Jingong; Wang, Xinwei; Tan, Xuehai; Delahoy, Alan E.; Chin, Ken K.

    2017-02-01

    Here, a systematic experimental study on indium tin oxide (ITO) films is presented to investigate the effects of oxygen partial pressure on the film's electrical properties. The results of Hall measurements show that adding more oxygen in the sputtering gas has negative influences on the electrical conductivity of ITO films. As O2/(O2 + Ar)% in the sputtering gas is increased from 0 to 6.98%, the resistivity of ITO film rises almost exponentially from 7.9 × 10-4 to 4.1 × 10-2 Ω cm, with the carrier density decreasing from 4.8 × 1020 to 5.4 × 1018 cm-3. The origins of these negative effects are discussed with focuses on the concentration of ionized impurities and the scattering of grain barriers. Extensive x-ray photoelectron spectroscopy (XPS) analyses were employed to gain insight into the concentration of ionized impurities, demonstrating a strong correlation between the oxygen vacancy concentration and the carrier density in ITO films as a function of sputtering O2 partial pressure. Other microstructural characterization techniques including x-ray diffraction (XRD), high-magnification scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM) analyses were used to evaluate the average grain size of ITO films. For ITO films that have carrier density above 1019 cm-3, scattering on grain boundaries and other crystallographic defects show negligible effects on the carrier transport. The results point to the oxygen vacancy concentration that dictates the carrier density and, thus, the resistivity of magnetron-sputtered ITO films.

  20. Effect of oxygen partial pressure on superconducting properties of Bi-2212/Ag tapes prepared by doctor-blade method

    SciTech Connect

    Inoue, N.; Okada, M.; Higashiyama, K.

    1997-06-01

    The authors have investigated the relationship between oxygen partial pressure (P{sub O{sub 2}}) during the partial-melting process and superconducting properties for doctor-blade processed Bi-2212/Ag tapes. Tapes were heat-treated at various P{sub O{sub 2}} value of 0.01-1.00 atm. The DTA results for the doctor-blade tapes showed the melting point of the oxide rose with increasing P{sub O{sub 2}}. Correspondingly, the optimum heat-treatment temperature also increased with increasing P{sub O{sub 2}}. The tapes at P{sub O{sub 2}}=1.00 atm had the highest J{sub c} values of over 10{sup 5} A/cm{sup 2} at conditions of 4.2K, 10T, and their a.c. susceptibility showed a sharp transition indicating improved intergrain coupling. Examination of cross sections for tapes melted above 0.20atm PO{sub 2} showed the good crystal alignment. From these results, it was concluded that processing at high PO{sub 2} was an effective method to obtain good superconducting properties for doctor-blade tapes.

  1. Experimental determination of carbonation rate in Portland cement at 25°C and relatively high CO2 partial pressure

    NASA Astrophysics Data System (ADS)

    Hernández-Rodríguez, Ana; Montegrossi, Giordano; Huet, Bruno; Virgili, Giorgio; Orlando, Andrea; Vaselli, Orlando; Marini, Luigi

    2016-04-01

    The aim of this work is to study the alteration of Portland class G Cement at ambient temperature under a relatively high CO2 partial pressure through suitably designed laboratory experiments, in which cement hydration and carbonation are taken into account separately. First, the hydration process was carried out for 28 days to identify and quantify the hydrated solid phases formed. After the completion of hydration, accompanied by partial carbonation under atmospheric conditions, the carbonation process was investigated in a stirred micro-reactor (Parr instrument) with crushed cement samples under 10 bar or more of pure CO2(g) and MilliQ water adopting different reaction times. The reaction time was varied to constrain the reaction kinetics of the carbonation process and to investigate the evolution of secondary solid phases. Chemical and mineralogical analyses (calcimetry, chemical composition, SEM and X-ray Powder Diffraction) were carried out to characterize the secondary minerals formed during cement hydration and carbonation. Water analyses were also performed at the end of each experimental run to measure the concentrations of relevant solutes. The specific surface area of hydrated cement was measured by means of the BET method to obtain the rates of cement carbonation. Experimental outcomes were simulated by means of the PhreeqC software package. The obtained results are of interest to understand the comparatively fast cement alteration in CO2 production wells with damaged casing.

  2. Modeling Ice Giant Interiors Using Constraints on the H2-H2O Critical Curve

    NASA Astrophysics Data System (ADS)

    Bailey, E.; Stevenson, D. J.

    2015-12-01

    We present a range of models of Uranus and Neptune, taking into account recent experimental data (Bali, 2013) implying the location of the critical curve of the H2-H2O system at pressures up to 2.6 GPa. The models presented satisfy the observed total mass of each planet and the radius at the observed 1-bar pressure level. We assume the existence of three regions at different depths: an outer adiabatic envelope composed predominately of H2 and He, with a helium mass fraction 0.26, a water-rich layer including varied amounts of rock and hydrogen, and a chemically homogeneous rock core. Using measured rotation rates of Uranus and Neptune, and a density profile obtained for each model using constituent equations of state and the assumption of hydrostatic equilibrium, we calculate the gravitational harmonics J2 and J4 for comparison with observed values as an additional constraint. The H2-H2O critical curve provides information about the nature of the boundary between the outer, hydrogen-rich envelope and underlying water-rich layer. The extrapolated critical curve for hydrogen-water mixtures crosses the adiabat of the outer atmospheric shell in these models at two depths, implying a shallow outer region of limited miscibility, an intermediate region between ~90 and 98 percent of the total planet radius within which hydrogen and water can mix in all proportions, and another, deeper region of limited miscibility at less than ~90 percent of the total planet radius. The pressure and temperature of the gaseous adiabatic shell at the depth of the shallowest extent of the water-rich layer determines whether a gradual compositional transition or an ocean surface boundary may exist at depth in these planets. To satisfy the observed J2, the outer extent of the water-rich layer in these models must be located between approximately 80 and 85 percent of the total planet radius, within the deep region of limited H2-H2O miscibility, implying an ocean surface is possible within the

  3. Structure and electrical properties of epitaxial SrRuO3 thin films controlled by oxygen partial pressure

    NASA Astrophysics Data System (ADS)

    Sun, Yan; Zhong, Ni; Zhang, Yuan-Yuan; Qi, Rui-Juan; Huang, Rong; Tang, Xiao-Dong; Yang, Ping-Xiong; Xiang, Ping-Hua; Duan, Chun-Gang

    2016-12-01

    SrRuO3 (SRO) thin films have been grown on (001)-oriented SrTiO3 substrate under various oxygen partial pressures (PO2). A typical step-and-terrace surface morphology and coherent epitaxy characteristics are found in the SRO films for high oxygen pressure growth (PO2 ≥ 10 Pa). Under such high PO2, SRO films exhibit metallic behavior over a temperature range of 10 K ≤ T ≤ 300 K. A detailed study on the transport properties of the metallic SRO films reveals that the resistivity (ρ) follows the law ρ(T)-ρ0 ∝ Tx (x = 0.5, 1.5, or 2). Below ferromagnetic transition temperature (Tc), ρ(T) follows T2 dependence below 30 K and T1.5 dependence at T > 30 K, respectively. This result demonstrates that a transition between the Fermi-liquid (FL) and non-Fermi-liquid (NFL) behavior occurs at ˜30 K. Furthermore, ρ(T) follows T0.5 dependence at T > Tc in the paramagnetic metal state. We have found that the FL to NFL transitions as well as the ferromagnetic transition are corresponding to the abnormal peaks in the magnetoresistance curves, suggesting the coupling of electronic and magnetic properties. The transition temperature of FL to NFL for metallic SRO films is almost independent on PO2, while Tc slightly increases with PO2.

  4. Experimental determination of the H2O-undersaturated peridotite solidus

    NASA Astrophysics Data System (ADS)

    Sarafian, E. K.; Gaetani, G. A.; Hauri, E. H.; Sarafian, A. R.

    2014-12-01

    Knowledge of the H2O-undersaturated lherzolite solidus places important constraints on the process of melt generation and mantle potential temperatures beneath oceanic spreading centers. The small concentration of H2O (~50-200 μg/g) dissolved in the oceanic mantle is thought to exert a strong influence on the peridotite solidus, but this effect has not been directly determined. The utility of existing experimental data is limited by a lack of information on the concentration of H2O dissolved in the peridotite and uncertainties involved with identifying small amounts of partial melt. We have developed an experimental approach for determining the peridotite solidus as a function of H2O content that overcomes these difficulties. Our initial results demonstrate that the solidus temperature for spinel lherzolite containing 150 μg/g H2O is higher than existing estimates for the anhydrous solidus. Our approach to determining the H2O-undersaturated lherzolite solidus is as follows. First, a small proportion (~5 %) of San Carlos olivine spheres, ~300 μm in diameter, are added to a peridotite synthesized from high-purity oxides and carbonates. Melting experiments are then conducted in pre-conditioned Au80Pd20 capsules over a range of temperatures at a single pressure using a piston-cylinder device. Water diffuses rapidly in olivine resulting in thorough equilibration between the olivine spheres and the surrounding fine-grained peridotite, and allowing the spheres to be used as hygrometers. After the experiment, the concentration of H2O dissolved in the olivine spheres is determined by secondary ion mass spectrometry. Melting experiments, spaced 20°C apart, were performed from 1250 to 1430°C at 1.5 GPa. The starting material has the composition of the depleted MORB mantle of Workman and Hart (2005) containing 0.13 wt% Na2O and 150 µg/g H2O. The concentration of H2O in the olivine spheres remains constant up to 1350°C, and then decreases systematically with increasing

  5. Oxidation and Condensation of Zinc Fume From Zn-CO2-CO-H2O Streams Relevant to Steelmaking Off-Gas Systems

    NASA Astrophysics Data System (ADS)

    Bronson, Tyler M.; Ma, Naiyang; Zhu, Liang Zhu; Sohn, Hong Yong

    2017-01-01

    The objective of this research was to study the condensation of zinc vapor to metallic zinc and zinc oxide solid under varying environments to investigate the feasibility of in-process separation of zinc from steelmaking off-gas dusts. Water vapor content, temperature, degree of cooling, gas composition, and initial zinc partial pressure were varied to simulate the possible conditions that can occur within steelmaking off-gas systems, limited to Zn-CO2-CO-H2O gas compositions. The temperature of deposition and the effect of rapidly quenching the gas were specifically studied. A homogeneous nucleation model for applicable experiments was applied to the analysis of the experimental data. It was determined that under the experimental conditions, oxidation of zinc vapor by H2O or CO2 does not occur above 1108 K (835 °C) even for highly oxidizing streams (CO2/CO = 40/7). Rate expressions that correlate CO2 and H2O oxidation rates to gas composition, partial pressure of water vapor, temperature, and zinc partial pressure were determined to be as follows: Rate ( mol/m2s ) = 406 exp ( -50.2 kJ/mol/RT ) ( p_{Zn} p_{CO}2 - p_{CO} /K_{eq}, CO2 ) mol/m2 × s Rate ( mol/m2 s ) = 32.9 exp ( -13.7 kJ/mol/RT ) ( p_{Zn} p_{H}2 O - p_{H}2 /K_{eq}, H2 O ) mol/m2 × s It was proven that a rapid cooling rate (500 K/s) significantly increases the ratio of metallic zinc to zinc oxide as opposed to a slow cooling rate (250 K/s). SEM analysis found evidence of heterogeneous growth of ZnO as well as of homogeneous formation of metallic zinc. The homogeneous nucleation model fit well with experiments where only metallic zinc deposited. An expanded model with rates of oxidation by CO2 and H2O as shown was combined with the homogenous nucleation model and then compared with experimental data. The calculated results based on the model gave a reasonable fit to the measured data. For the conditions used in this study, the rate equations for the oxidation of zinc by carbon dioxide and water vapor

  6. Oxidation and Condensation of Zinc Fume From Zn-CO2-CO-H2O Streams Relevant to Steelmaking Off-Gas Systems

    NASA Astrophysics Data System (ADS)

    Bronson, Tyler M.; Ma, Naiyang; Zhu, Liang Zhu; Sohn, Hong Yong

    2017-04-01

    The objective of this research was to study the condensation of zinc vapor to metallic zinc and zinc oxide solid under varying environments to investigate the feasibility of in-process separation of zinc from steelmaking off-gas dusts. Water vapor content, temperature, degree of cooling, gas composition, and initial zinc partial pressure were varied to simulate the possible conditions that can occur within steelmaking off-gas systems, limited to Zn-CO2-CO-H2O gas compositions. The temperature of deposition and the effect of rapidly quenching the gas were specifically studied. A homogeneous nucleation model for applicable experiments was applied to the analysis of the experimental data. It was determined that under the experimental conditions, oxidation of zinc vapor by H2O or CO2 does not occur above 1108 K (835 °C) even for highly oxidizing streams (CO2/CO = 40/7). Rate expressions that correlate CO2 and H2O oxidation rates to gas composition, partial pressure of water vapor, temperature, and zinc partial pressure were determined to be as follows: Rate( mol/m2 s ) = 406 \\exp ( - 50.2 kJ/mol/RT )( p_Zn p_{CO2 - p_CO /K_{eq,CO2 ) mol/m2 × s Rate( mol/m2 s ) = 32.9 \\exp ( - 13.7 kJ/mol/RT )( p_Zn p_{H2 O - p_{H2 /K_{eq,H2 O ) mol/m2 × s It was proven that a rapid cooling rate (500 K/s) significantly increases the ratio of metallic zinc to zinc oxide as opposed to a slow cooling rate (250 K/s). SEM analysis found evidence of heterogeneous growth of ZnO as well as of homogeneous formation of metallic zinc. The homogeneous nucleation model fit well with experiments where only metallic zinc deposited. An expanded model with rates of oxidation by CO2 and H2O as shown was combined with the homogenous nucleation model and then compared with experimental data. The calculated results based on the model gave a reasonable fit to the measured data. For the conditions used in this study, the rate equations for the oxidation of zinc by carbon dioxide and water vapor as well

  7. Control of the threshold voltage by using the oxygen partial pressure in sputter-deposited InGaZnO4 thin-film transistors

    NASA Astrophysics Data System (ADS)

    Ahn, Jeung Sun; Lee, Kwang Bae

    2012-05-01

    We investigate the controllability of the threshold voltage ( V th ) by varying the O2 partial pressure in sputter-deposited of InGaZnO4 thin-film transistors (IGZO TFTs). We showed that the V th values could be linearly controlled from a depletion-type of V th ˜ -6 V to an enhancement-type of V th ˜ 2 V, without any abrupt change in µ sat , I on/off , and S, by only changing the O2 partial pressure in a fixed region of the Ar partial pressure. Such V th controllability is thought to be due to the proper reduction of defect states and, in turn, to the preservation of high-performance TFT behavior.

  8. 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.

  9. Investigation of the coupled effects of temperature and partial pressure on catalytic growth of carbon nanotubes using a modified growth rate model

    NASA Astrophysics Data System (ADS)

    Zainal, M. T.; Mohd Yasin, M. F.; Wahid, M. A.

    2016-10-01

    An accurate modelling of catalytic growth of carbon nanotubes (CNTs) is needed to model the physics of carbon adsorption and diffusion into the catalyst surface along with the catalyst deactivation. The model should be able to provide a physical response towards the change of temperature and partial pressure. Though the effects of temperature and partial pressure on the growth rate has been studied individually, the coupled effects of the two parameters has yet to be emphasized. A modified growth rate model that unified the terms from previously developed models successfully captured the essential physics during the growth and provided physical response towards the change of temperature and partial pressure. The model validation was done against a chemical vapour deposition (CVD) experiment that employed acetylene and cobalt as the carbon source and the catalyst respectively where the modified model managed to predict the CNT terminal length more accurately compared to the standard model with 5% maximum error. A comprehensive parametric study on the effects of temperature and partial pressure on the growth rate and terminal length successfully reveals the minimum partial pressure of 5 Torr for a given operating condition below which the growth rate is significantly low regardless of any increase of temperature. Three regions of growth in the partial pressure-temperature domain are identified based on the magnitude of terminal length. The model can serve as a guideline for the determination and optimisation of the baseline operating conditions in future experiments on catalytic growth of CNT, with emphasis on the CVD and flame synthesis techniques.

  10. 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.

  11. H2S, a novel gasotransmitter, involves in gastric accommodation.

    PubMed

    Xiao, Ailin; Wang, Hongjuan; Lu, Xin; Zhu, Jianchun; Huang, Di; Xu, Tonghui; Guo, Jianqiang; Liu, Chuanyong; Li, Jingxin

    2015-11-04

    H2S is produced mainly by two enzymes:cystathionine-β-synthase (CBS) and cystathionine-γ-lyase (CSE), using L-cysteine (L-Cys) as the substrate. In this study, we investigated the role of H2S in gastric accommodation using CBS(+/-) mice, immunohistochemistry, immunoblot, methylene blue assay, intragastric pressure (IGP) recording and electrical field stimulation (EFS). Mouse gastric fundus expressed H2S-generating enzymes (CBS and CSE) and generated detectable amounts of H2S. The H2S donor, NaHS or L-Cys, caused a relaxation in either gastric fundus or body. The gastric compliance was significantly increased in the presence of L-Cys (1 mM). On the contrary, AOAA, an inhibitor for CBS, largely inhibited gastric compliance. Consistently, CBS(+/-) mice shows a lower gastric compliance. However, PAG, a CSE inhibitor, had no effect on gastric compliances. L-Cys enhances the non-adrenergic, non-cholinergic (NANC) relaxation of fundus strips, but AOAA reduces the magnitude of relaxations to EFS. Notably, the expression level of CBS but not CSE protein was elevated after feeding. Consistently, the production of H2S was also increased after feeding in mice gastric fundus. In addition, AOAA largely reduced food intake and body weight in mice. Furthermore, a metabolic aberration of H2S was found in patients with functional dyspepsia (FD). In conclusion, endogenous H2S, a novel gasotransmitter, involves in gastric accommodation.

  12. Partial hydrophilic modification of biaxially oriented polypropylene film by an atmospheric pressure plasma jet with the allylamine monomer

    NASA Astrophysics Data System (ADS)

    Chen, W. X.; Yu, J. S.; Hu, W.; Chen, G. L.

    2016-11-01

    In this paper, the partial modification of the biaxially oriented polypropylene (BOPP) film for potential biological and packaging applications was achieved via hydrophilic modification using atmospheric pressure plasma jet (APPJ). In the APPJ system, the allylamine (ALA) monomer was polymerized on the BOPP surface by either the Ar/O2 or the He/O2 plasma. The results showed that plasmatic modification created many micro/nano sized holes on the BOPP film, which increased the surface roughness dramatically and the increased roughness enhanced the combining intensity between the BOPP film and the ALA polymer. However, such a plasmatic modification increased the water vapor permeability. The FTIR and XPS characterizations showed that the amine groups were grafted onto the BOPP film, and the contact angle of the BOPP film decreases from 98.5° to 8°. Compared with the BOPP films treated by the Ar or He plasma, the barrier property of the modified BOPP film increased significantly when the ALA polymer was incorporated. The bio-affinity/toxicity of ALA polymer was illustrated by the attachment of the cultured SMMC-7721 hepatoma cells on the modified BOPP film. The significant enhancement in the cell density indicated that modified BOPP film was highly bio-compatible and non-toxic, especially treated with the Ar/O2/ALA plasma.

  13. Comparison of Helzel and OxyLite Systems in the Measurements of Tumor Partial Oxygen Pressure (pO2)

    PubMed Central

    Wen, Bixiu; Urano, Muneyasu; Humm, John L.; Seshan, Venkatraman E.; Li, Gloria C.; Ling, C. Clifton

    2009-01-01

    It has been demonstrated in both experimental and human malignancies that hypoxic tumor cells are linked with aggressive disease phenotype. One of the methods to identify these cells is by direct physical measurement of tumor pO2. This study compared pO2 values measured with two systems, the Helzel Hypoximeter (successor of the polarographic Eppen-dorf electrode) and the Oxford-Optronix OxyLite (fiber-optic probe), in R3327-AT and R3327-AT/tkeGFP tumors. Partial oxygen pressure was measured in individual tumors with either system or in the same tumor with both systems. The similarities and discrepancies in pO2 measurements between the two systems were also investigated when tumor-bearing animals were breathing pure oxygen. Our data showed a considerable heterogeneity in pO2 values in each tumor using both the Helzel and OxyLite systems. Similar results were obtained with both systems for the mean and median pO2 values, and the distributions of pO2 values within the interval 0 < pO2 < 40 mmHg (the range important for defining tumor hypoxia) were found to be statistically equivalent However, the frequencies of high pO2 values (>40 mmHg) and zero values measured by the two systems were statistically significantly different. PMID:18159950

  14. The jumbo squid, Dosidicus gigas (Ommastrephidae), living in oxygen minimum zones I: Oxygen consumption rates and critical oxygen partial pressures

    NASA Astrophysics Data System (ADS)

    Trueblood, Lloyd A.; Seibel, Brad A.

    2013-10-01

    Dosidicus gigas is a large, metabolically active, epipelagic squid known to undertake diel vertical migrations across a large temperature and oxygen gradient in the Eastern Pacific. Hypoxia is known to cause metabolic suppression in D. gigas. However, the precise oxygen level at which metabolic suppression sets in is unknown. Here we describe a novel ship-board swim tunnel respirometer that was used to measure metabolic rates and critical oxygen partial pressures (Pcrit) for adult squids (2-7kg). Metabolic rate measurements were validated by comparison to the activity of the Krebs cycle enzyme, citrate synthase, in mantle muscle tissue (2-17kg). We recorded a mean routine metabolic rate of 5.91μmolg-1h-1 at 10°C and 12.62μmolg-1h-1 at 20°C. A temperature coefficient, Q10, of 2.1 was calculated. D. gigas had Pcrits of 1.6 and 3.8kPa at 10 and 20°C, respectively. Oxygen consumption rate (MO2) varied with body mass (M) according to MO2=11.57M-0.12±0.03 at 10°C. Citrate synthase activity varied with body mass according to Y=9.32M-0.19±0.02.

  15. Quadratic function between arterial partial oxygen pressure and mortality risk in sepsis patients: an interaction with simplified acute physiology score

    PubMed Central

    Zhang, Zhongheng; Ji, Xuqing

    2016-01-01

    Oxygen therapy is widely used in emergency and critical care settings, while there is little evidence on its real therapeutic effect. The study aimed to explore the impact of arterial oxygen partial pressure (PaO2) on clinical outcomes in patients with sepsis. A large clinical database was employed for the study. Subjects meeting the diagnostic criteria of sepsis were eligible for the study. All measurements of PaO2 were extracted. The primary endpoint was death from any causes during hospital stay. Survey data analysis was performed by using individual ICU admission as the primary sampling unit. Quadratic function was assumed for PaO2 and its interaction with other covariates were explored. A total of 199,125 PaO2 samples were identified for 11,002 ICU admissions. Each ICU stay comprised 18 PaO2 samples in average. The fitted multivariable model supported our hypothesis that the effect of PaO2 on mortality risk was in quadratic form. There was significant interaction between PaO2 and SAPS-I (p = 0.007). Furthermore, the main effect of PaO2 on SOFA score was nonlinear. The study shows that the effect of PaO2 on mortality risk is in quadratic function form, and there is significant interaction between PaO2 and severity of illness. PMID:27734905

  16. Laser heating and oxygen partial pressure effects on the dynamic magnetic properties of perpendicular CoFeAlO films

    NASA Astrophysics Data System (ADS)

    Wu, Di; Li, Wei; Tang, Minghong; Zhang, Zongzhi; Lou, Shitao; Jin, Q. Y.

    2016-07-01

    The impact of oxidation and laser heating on the dynamic magnetic properties of perpendicularly magnetized Co50Fe25Al25O films has been studied by time-resolved magneto-optical Kerr effect in a fs-laser pump-probe setup. We find that pump laser fluence Fp can affect the effective magnetic anisotropy field and thus the precession frequency f seriously, leading to an increased dependence of effective magnetic damping factor αeff on the external field at higher fluences. Moreover, the αeff increases with increasing the oxygen partial pressure PO2 while the uniaxial anisotropy energy Ku and Landau factor g decrease, owing to the increased proportion of superparamagnetic CoFe oxides formed by over-oxidation. By optimizing both the Fp and PO2, the intrinsic damping factor is determined to be lower than 0.028 for the perpendicular film showing a uniaxial anisotropy energy as high as 4.3×106 erg/cm3. The results in this study provide a promising approach to manipulate the magnetic parameters for possible applications in spintronic devices.

  17. Effect of oxygen partial pressure and Fe doping on growth and properties of metallic and insulating molybdenum oxide thin films

    NASA Astrophysics Data System (ADS)

    Tiwari, Shailja; Master, Ridhi; Choudhary, R. J.; Phase, D. M.; Ahuja, B. L.

    2012-04-01

    We report the effect of oxygen partial pressure (OPP) and 5% Fe doping on the structural, electrical, and magnetic properties of MoOx thin films on c-Al2O3 substrate prepared by pulsed laser deposition technique. Detailed analyses of the structural properties suggest that the grown phase of molybdenum oxides and its orientation strongly depend on the OPP as well as Fe doping. Undoped and Fe doped α-MoO3 films formed at 350 mTorr OPP value show insulating character, where as MoO2 films formed at lower OPP values reveal metallic behavior. Resistivity minima are observed in Fe doped MoO2 films, which could be due to weak localization effect or Kondo scattering of the conduction electrons from the Fe impurities. Interestingly, all the Fe doped molybdenum oxide films show magnetic hysteresis at room temperature irrespective of their insulating (MoO3 phase) or metallic (MoO2 phase) behavior.

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

    PubMed Central

    Sakadžić, 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 µm, 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

  19. Quadratic function between arterial partial oxygen pressure and mortality risk in sepsis patients: an interaction with simplified acute physiology score.

    PubMed

    Zhang, Zhongheng; Ji, Xuqing

    2016-10-13

    Oxygen therapy is widely used in emergency and critical care settings, while there is little evidence on its real therapeutic effect. The study aimed to explore the impact of arterial oxygen partial pressure (PaO2) on clinical outcomes in patients with sepsis. A large clinical database was employed for the study. Subjects meeting the diagnostic criteria of sepsis were eligible for the study. All measurements of PaO2 were extracted. The primary endpoint was death from any causes during hospital stay. Survey data analysis was performed by using individual ICU admission as the primary sampling unit. Quadratic function was assumed for PaO2 and its interaction with other covariates were explored. A total of 199,125 PaO2 samples were identified for 11,002 ICU admissions. Each ICU stay comprised 18 PaO2 samples in average. The fitted multivariable model supported our hypothesis that the effect of PaO2 on mortality risk was in quadratic form. There was significant interaction between PaO2 and SAPS-I (p = 0.007). Furthermore, the main effect of PaO2 on SOFA score was nonlinear. The study shows that the effect of PaO2 on mortality risk is in quadratic function form, and there is significant interaction between PaO2 and severity of illness.

  20. Scavenging of H2O2 by mouse brain mitochondria

    PubMed Central

    Starkov, Anatoly A.; Andreyev, Alexander Yu; Zhang, Steven F.; Starkova, Natalia N.; Korneeva, Maria; Syromyatnikov, Mikhail; Popov, Vasily N.

    2015-01-01

    Mitochondrial reactive oxygen species (ROS) metabolism is unique in that mitochondria both generate and scavenge ROS. Recent estimates of ROS scavenging capacity of brain mitochondria are surprisingly high, ca. 9-12 nmol H2O2/min/mg, which is ~100 times higher than the rate of ROS generation. This raises a question whether brain mitochondria are a source or a sink of ROS. We studied the interaction between ROS generation and scavenging in mouse brain mitochondria by measuring the rate of removal of H2O2 added at a concentration of 0.4 μM, which is close to the reported physiological H2O2 concentrations in tissues, under conditions of low and high levels of mitochondrial H2O2 generation. With NAD-linked substrates, the rate of H2O2 generation by mitochondria was ~50–70 pmol/min/mg. The H2O2 scavenging dynamics was best approximated by the first order reaction equation. H2O2 scavenging was not affected by the uncoupling of mitochondria, phosphorylation of added ADP, or the genetic ablation of glutathione peroxidase 1, but decreased in the absence of respiratory substrates, in the presence of thioredoxin reductase inhibitor auranofin, or in partially disrupted mitochondria. With succinate, the rate of H2O2 generation was ~2,200–2,900 pmol/min/mg; the scavenging of added H2O2 was masked by a significant accumulation of generated H2O2 in the assay medium. The obtained data were fitted into a simple model that reasonably well described the interaction between H2O2 scavenging and production. It showed that mitochondria are neither a sink nor a source of H2O2, but can function as both at the same time, efficiently stabilizing exogenous H2O2 concentration at a level directly proportional to the ratio of the H2O2 generation rate to the rate constant of the first order scavenging reaction. PMID:25248416

  1. 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.

  2. 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.

  3. Temporal resilience and dynamics of anaerobic methane-oxidizing microbial communities to short-term changes in methane partial pressures

    NASA Astrophysics Data System (ADS)

    Klasek, S.; Tiantian, Y.; Torres, M. E.; Colwell, F. S.; Wang, F.; Liang, L.

    2015-12-01

    Marine sediments produce tens to hundreds of teragrams of methane annually, which is released from the seabed at thousands of cold seeps distributed globally along continental margins. Around 80-90% of this methane is consumed in shallower sediment layers before reaching the hydrosphere, in a microbially-mediated process known as anaerobic oxidation of methane (AOM) However, cold seeps appear to exhibit temporal variation in gas flux intensity, and AOM filter efficiency at cold seeps generally decreases with fluid flow rate. To our knowledge, the degree to which temporal heterogeneity in subsurface methane flux stimulates AOM community growth and adaptation to increased methane concentrations has not been investigated. Static high-pressure bioreactors were used to incubate sulfate-methane transition zone (SMTZ) and methanogenic zone sediments underlying a Mediterranean mud volcano gas flare under in situ temperature and pressure at 8 MPa methane. Sulfide production rates of 0.4 μmol/cm3/day in both sediment regimes after 4 months of incubation suggested the resilience of the marine subsurface methane filter may extend well below the SMTZ (40 cm). Similar incubations of SMTZ samples from below a gas flare off Svalbard at saturating (3.8 MPa) and 0.2 MPa methane are being sampled after 1 week, 4 weeks, and 4 months; sulfide production rates of 8-18 nmol/cm3/day were first observed after 4 weeks of incubation. Sediment samples at all specified time points for both sets of incubations were collected for nucleic acid extraction and cell fixation. Anaerobic methanotrophic archaea (ANME) and sulfate-reducing bacteria (SRB) are expected dominant taxa in enriched and non-enriched communities. 16S rDNA community analysis is expected to reveal additional microbial players involved in the short-term adaptation to higher methane partial pressures in the marine subsurface. Increased AOM community activity (RNA/DNA ratio) and copy numbers of methane cycling transcripts (mcr

  4. Effects of Temperature, Oxygen Partial Pressure, and Materials Selection on Slag Infiltration into Porous Refractories for Entrained-Flow Gasifiers

    NASA Astrophysics Data System (ADS)

    Kaneko, Tetsuya Kenneth

    The penetration rate of molten mineral contents (slag) from spent carbonaceous feedstock into porous ceramic-oxide refractory linings is a critical parameter in determining the lifecycle of integrated gasification combined cycle energy production plants. Refractory linings that withstand longer operation without interruption are desirable because they can mitigate consumable and maintenance costs. Although refractory degradation has been extensively studied for many other high-temperature industrial processes, this work focuses on the mechanisms that are unique to entrained-flow gasification systems. The use of unique feedstock mixtures, temperatures from 1450 °C to 1600 °C, and oxygen partial pressures from 10-7 atm to 10-9 atm pose engineering challenges in designing an optimal refractory material. Experimentation, characterization, and modeling show that gasifier slag infiltration into porous refractory is determined by interactions between the slag and the refractory that either form a physical barrier that impedes fluid flow or induce an increased fluid viscosity that decelerates the velocity of the fluid body. The viscosity of the slag is modified by the thermal profile of the refractory along the penetration direction as well as reactions between the slag and refractory that alter the chemistry, and thereby the thermo-physical properties of the fluid. Infiltration experiments reveal that the temperature gradient inherently present along the refractory lining limits penetration. A refractory in near-isothermal conditions demonstrates deeper slag penetration as compared to one that experiences a steeper thermal profile. The decrease in the local temperatures of the slag as it travels deeper into the refractory increases the viscosity of the fluid, which in turn slows the infiltration velocity of fluid body into the pores of the refractory microstructure. With feedstock mixtures that exhibit high iron-oxide concentrations, a transition-metal-oxide, the oxygen

  5. 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. Kearney Agricultural Center, Parlier, CA )

    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.

  6. Modulation of sulfur partial pressure in sulfurization to significantly improve the photoelectrochemical performance over the Cu2ZnSnS4 photocathode.

    PubMed

    Zhang, Yuanfang; Ouyang, Shuxin; Yu, Qing; Li, Peng; Ye, Jinhua

    2015-09-25

    Cu2ZnSnS4 photocathodes with excellent photoelectrochemical properties were fabricated via a facile method of adjusting the sulfur partial pressure in a semi-closed system, which achieved a maximum photocurrent-density of 1.8 mA cm(-2) under irradiation of a solar simulator which is 9-fold larger than that synthesized in an open system.

  7. H2 distribution during the formation of multiphase molecular clouds

    NASA Astrophysics Data System (ADS)

    Valdivia, Valeska; Hennebelle, Patrick; Gérin, Maryvonne; Lesaffre, Pierre

    2016-03-01

    Context. H2 is the simplest and the most abundant molecule in the interstellar medium (ISM), and its formation precedes the formation of other molecules. Aims: Understanding the dynamical influence of the environment and the interplay between the thermal processes related to the formation and destruction of H2 and the structure of the cloud is mandatory to understand correctly the observations of H2. Methods: We performed high-resolution magnetohydrodynamical colliding-flow simulations with the adaptive mesh refinement code RAMSES in which the physics of H2 has been included. We compared the simulation results with various observations of the H2 molecule, including the column densities of excited rotational levels. Results: As a result of a combination of thermal pressure, ram pressure, and gravity, the clouds produced at the converging point of HI streams are highly inhomogeneous. H2 molecules quickly form in relatively dense clumps and spread into the diffuse interclump gas. This in particular leads to the existence of significant abundances of H2 in the diffuse and warm gas that lies in between clumps. Simulations and observations show similar trends, especially for the HI-to-H2 transition (H2 fraction vs. total hydrogen column density). Moreover, the abundances of excited rotational levels, calculated at equilibrium in the simulations, turn out to be very similar to the observed abundances inferred from FUSE results. This is a direct consequence of the presence of the H2 enriched diffuse and warm gas. Conclusions: Our simulations, which self-consistently form molecular clouds out of the diffuse atomic gas, show that H2 rapidly forms in the dense clumps and, due to the complex structure of molecular clouds, quickly spreads at lower densities. Consequently, a significant fraction of warm H2 exists in the low-density gas. This warm H2 leads to column densities of excited rotational levels close to the observed ones and probably reveals the complex intermix between

  8. Low H2O/Ce in Icelandic basalts as evidence for crustal recycling

    NASA Astrophysics Data System (ADS)

    Neave, David; Shorttle, Oliver; Hartley, Margaret; Maclennan, John

    2016-04-01

    The generation of new crust at mid-ocean ridges is balanced by the subduction of partially hydrothermally altered basaltic material back into the mantle. This subducted material may then be recycled and returned via mantle plumes to the Earth's surface at hot spots. Long-identified isotopic and trace element signatures of oceanic crust recycling in ocean island basalts (OIBs) have been recently supplemented by evidence of major element, i.e. lithological, heterogeneity in the melting region. For example, combined major and trace element systematics from Iceland suggest that the mantle source contains at least 5% recycled basalt. Observations of high water (H2O) contents in subglacially quenched basalts from Iceland have previously been attributed to the incorporation of wet recycled material into the mantle source. However, when combined with trace element analyses, recent volatile analyses from the Laki-Grímsvötn and Bárðarbunga-Veiðivötn systems in the Eastern Volcanic Zone (EVZ) of Iceland suggest that the underlying mantle is comparatively depleted in H2O for its degree of major and trace element enrichment. Correlations between H2O and cerium (Ce) within individual mid-ocean ridge basalt (MORB) suites reveal that these elements partition similarly prior to H2O degassing at low pressures; H2O/Ce remains constant during melting and fractionation, and hence reflects the average H2O/Ce of the melting region. MORBs from the Mid-Atlantic Ridge south of Iceland have a mean H2O/Ce value of 304±48 at a mean La/Yb of 2.1±1.5. In contrast, basalts from the EVZ have a lower mean H2O/Ce of 180±20 at a higher mean La/Yb of 3.1±0.5. Thus, despite coming from an enriched section of the Mid-Atlantic ridge in terms of trace element content, basalts from the EVZ have the lowest H2O/Ce values known from the ridge, and are hence comparatively depleted in H2O. Given that H2O/Ce from un-degassed basalts is considered to represent mantle source values, we suggest that low H

  9. CO(2) partial pressure and calcite saturation in springs - useful data for identifying infiltration areas in mountainous environments.

    PubMed

    Hilberg, Sylke; Brandstätter, Jennifer; Glück, Daniel

    2013-04-01

    Mountainous regions such as the Central European Alps host considerable karstified or fractured groundwater bodies, which meet many of the demands concerning drinking water supply, hydropower or agriculture. Alpine hydrogeologists are required to describe the dynamics in fractured aquifers in order to assess potential impacts of human activities on water budget and quality. Delineation of catchment areas by means of stable isotopes and hydrochemical data is a well established method in alpine hydrogeology. To achieve reliable results, time series of (at least) one year and spatial and temporal close-meshed data are necessary. In reality, test sites in mountainous regions are often inaccessible due to the danger of avalanches in winter. The aim of our work was to assess a method based on the processes within the carbonic acid system to delineate infiltration areas by means of single datasets consisting of the main hydrochemical parameters of each spring. In three geologically different mountainous environments we managed to classify the investigated springs into four groups. (1) High PCO2 combined with slight super-saturation in calcite, indicating relatively low infiltration areas. (2) Low PCO2 near atmospheric conditions in combination with calcite saturation, which is indicative of relatively high infiltration areas and a fractured aquifer which is not covered by topsoil layers. (3) High PCO2 in combination with sub-saturation in calcite, representing a shallow aquifer with a significant influence of the topsoil layer. (4) The fourth group of waters is characterized by low PCO2 and sub-saturation in calcite, which is interpreted as evidence for a shallow aquifer without significant influence of any hard rock aquifer or topsoil layer. This study shows that CO2-partial pressure can be an ideal natural tracer to estimate the elevation of infiltration areas, especially in non-karstified fractured groundwater bodies.

  10. 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).

  11. Microstructure, mechanical and optical properties of TiAlON coatings sputter-deposited with varying oxygen partial pressures

    NASA Astrophysics Data System (ADS)

    Schalk, Nina; Thierry Simonet Fotso, J. F.; Holec, David; Fian, Alexander; Jakopic, Georg; Terziyska, Velislava L.; Daniel, Rostislav; Mitterer, Christian

    2016-01-01

    Due to their excellent mechanical and optical properties as well as chemical stability, the synthesis of transition metal oxynitride thin films has attracted growing interest in the last years. Within this work, the evolution of the structure and properties of TiAlON coatings over a wide compositional range, from the nitride to the oxide side, was investigated. The coatings were grown on Si substrates in a laboratory-scale unbalanced magnetron dc sputtering system from powder metallurgical TiAl targets with an Al/Ti atomic ratio of 60/40, using a constant level of nitrogen with rising oxygen partial pressure. Coating composition and microstructure were investigated by energy- and wavelength-dispersive x-ray spectroscopy, x-ray diffraction, x-ray photoelectron spectroscopy, Raman spectroscopy and transmission electron microscopy. Furthermore, the mechanical and optical properties were evaluated using nanoindentation and spectroscopic ellipsometry, respectively. Oxygen concentrations of up to 49 at.% within the films could be obtained, at the expense of the nitrogen content. The oxygen-free coating exhibited a single-phase fcc-Ti1-x Al x N structure. With increasing oxygen content the structure remained fcc-Ti1-x Al x N based, but additional fractions of amorphous oxides were formed. The structural evolution was corroborated by ab initio calculations. Decreasing coating hardness could be observed with increasing oxygen concentration. The refraction index and extinction coefficient were lower for coatings with higher oxygen content, but the behavior of the optical properties remained Ti1-x Al x N-like over the investigated spectral range.

  12. Effects of sample storage time, temperature and syringe type on blood gas tensions in samples with high oxygen partial pressures.

    PubMed Central

    Pretto, J. J.; Rochford, P. D.

    1994-01-01

    BACKGROUND--Although plastic arterial sampling syringes are now commonly used, the effects of sample storage time and temperature on blood gas tensions are poorly described for samples with a high oxygen partial pressure (PaO2) taken with these high density polypropylene syringes. METHODS--Two ml samples of tonometered whole blood (PaO2 86.7 kPa, PaCO2 4.27 kPa) were placed in glass syringes and in three brands of plastic blood gas syringes. The syringes were placed either at room temperature or in iced water and blood gas analysis was performed at baseline and after 5, 10, 20, 40, 60, 90, and 120 minutes. RESULTS--In the first 10 minutes measured PaO2 in plastic syringes at room temperature fell by an average of 1.21 kPa/min; placing the sample on ice reduced the rate of PaO2 decline to 0.19 kPa/min. The rate of fall of PaO2 in glass at room temperature was 0.49 kPa/min. The changes in PaCO2 were less dramatic and at room temperature averaged increases of 0.47 kPa for plastic syringes and 0.71 kPa for glass syringes over the entire two hour period. These changes in gas tension for plastic syringes would lead to an overestimation of pulmonary shunt measured by the 100% oxygen technique of 0.6% for each minute left at room temperature before analysis. CONCLUSIONS--Glass syringes are superior to plastic syringes in preserving samples with a high PaO2, and prompt and adequate cooling of such samples is essential for accurate blood gas analysis. PMID:8016801

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

    USGS Publications Warehouse

    Striegl, R.G.; Kortelainen, Pirkko; 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.

  14. H2AFV — EDRN Public Portal

    Cancer.gov

    H2AFV is a variant histone H2A which replaces conventional H2A in a subset of nucleosomes. The nucleosome is a histone octamer containing two molecules each of H2A, H2B, H3 and H4 assembled in one H3-H4 heterotetramer and two H2A-H2B heterodimers. Nucleosomes wrap and compact DNA into chromatin, limiting DNA accessibility to the cellular machineries which require DNA as a template (the octamer wraps approximately 147 bp of DNA). Histones thereby play a central role in transcription regulation, DNA repair, DNA replication and chromosomal stability. DNA accessibility is regulated via a complex set of post-translational modifications of histones, also called histone code, and nucleosome remodeling. Additionally, H2AFV may be involved in the formation of constitutive heterochromatin, and may be required for chromosome segregation during cell division.

  15. 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.

  16. Thermodynamics of Silicon-Hydroxide Formation in H2O Containing Atmospheres

    NASA Technical Reports Server (NTRS)

    Copland, Evan; Myers, Dwight; Opila, Elizabeth J.; Jacobson, Nathan S.

    2001-01-01

    The formation of volatile silicon-hydroxide species from SiO2 in water containing atmospheres has been identified as a potentially important mode of degradation of Si-based ceramics. Availability of thermodynamic data for these species is a major problem. This study is part of an ongoing effort to obtain reliable, experimentally determined thermodynamic data for these species. The transpiration method was used to measure the pressure of Si-containing vapor in equilibrium with SiO2 (cristobalite) and Ar + H2O(g) with various mole fractions of water vapor, X(sub H2O), at temperatures ranging from 1000 to 1780 K. Enthalpies and entropies for the reaction, SiO2(s) + 2H2O(g) = Si(OH)4(g), were obtained, at X(sub H2O) = 0.15 and 0.37, from the variation of lnK with 1/T according to the 'second law method'. The following data were obtained: delta(H)deg = 52.9 +/- 3.7 kJ/mole and delta(S)deg = -68.6 +/- 2.5 J/mole K at an average temperature of 1550 K, and delta(H)deg = 52.5+/-2.0 kJ/mole and delta(S)deg= -69.7 +/- 1.5 J/moleK at an average temperature of 1384 K, for X(sub H2O)= 0.15 and 0.37, respectively. These data agree with results from the literature obtained at an average temperature of 1600 K, and strongly suggest Si(OH)4(g) is the dominant vapor species. Contradictory results were obtained with the determination of the dependence of Si-containing vapor pressure on the partial pressure of water vapor at 1187 and 1722 K. These results suggested the Si-containing vapor could be a mixture of Si(OH)4 + SiO(OH)2. Further pressure dependent studies are in progress to resolve these issues.

  17. Two-stage high-rate biogas (H2 and CH4) production from food waste using anaerobic mixed microflora

    NASA Astrophysics Data System (ADS)

    Xu, K.; Lee, D.; Kobayashi, T.; Ebie, Y.; Li, Y.; Inamori, Y.

    2010-12-01

    To achieve the high-rate H2 and CH4 production from food waste using fermentative anaerobic microflora, the effects of carbonate-alkalinity in the recirculated digestion sludge on continuous two-stage fermentation were investigated. Higher H2 production rate of 2.9 L-H2/L/day was achieved at the recycle ratio of 1.0 in an alkalinity range of 9000 to 10000 mg-CaCO3/L. The maximum CH4 production rate was stably maintained at the range of 1.85 to 1.88 L-CH4/L/day without alkalinity change. Carbonate alkalinity in digestion sludge could reduce the H2 partial pressure in the headspace of the fermentation reactors, and improve a biogas production capacity in the two-stage fermentation process. The average volatile solids degradation rate in the overall process increased as the digestion sludge recycle increased from 0.5 to 1.0. These results show that the alkalinity in recycle of the digestion sludge is crucial factor in determining biogas (H2 and CH4) production capacity and reducing the total solids.

  18. Spatial and Temporal Variations in the Partial Pressure and Emission of CO2 and CH4 in and Amazon Floodplain Lake

    NASA Astrophysics Data System (ADS)

    Forsberg, B. R.; Amaral, J. H.; Barbosa, P.; Kasper, D.; MacIntyre, S.; Cortes, A.; Sarmento, H.; Borges, A. V.; Melack, J. M.; Farjalla, V.

    2015-12-01

    The Amazon floodplain contains a variety of wetland environments which contribute CO2 and CH4 to the regional and global atmospheres. The partial pressure and emission of these greenhouse gases (GHGs) varies: 1) between habitats, 2) seasonally, as the characteristics these habitats changes and 3) diurnally, in response to diurnal stratification. In this study, we investigated the combined influence of these factors on the partial pressure and emission of GHGs in Lago Janauacá, a central Amazon floodplain lake (3o23' S; 60o18' O). All measurements were made between August of 2014 and April of 2015 at two different sites and in three distinct habitats: open water, flooded forest, flooded macrophytes. Concentrations of CO2 and CH4 in air were measured continuously with a cavity enhanced absorption spectrometer, Los Gatos Research´s Ultraportable Greenhouse Gas Analyzer (UGGA). Vertical profiles o pCO2 and pCH4 were measured using the UGGA connected to an electric pump and equilibrator. Diffusive surface emissions were estimated with the UGGA connected to a static floating chamber. To investigate the influence of vertical stratification and mixing on GHG partial pressure and emissions, a meteorological station and submersible sensor chain were deployed at each site. Meteorological sensors included wind speed and direction. The submersible chains included thermistors and oxygen sensors. Depth profiles of partial pressure and diffusive emissions for both CO2 and CH4 varied diurnally, seasonally and between habitats. Both pCO2 and pCH4 were consistently higher in bottom than surface waters with the largest differences occurring at high water when thermal stratification was most stable. Methane emissions and partial pressures were highest at low water while pCO2 and CO2 fluxes were highest during high water periods, with 35% of CO2 fluxes at low water being negative. The highest average surface value of pCO2 (5491 μatm), encountered during rising water, was ~3 times

  19. Solution structure of the isolated histone H2A-H2B heterodimer

    PubMed Central

    Moriwaki, Yoshihito; Yamane, Tsutomu; Ohtomo, Hideaki; Ikeguchi, Mitsunori; Kurita, Jun-ichi; Sato, Masahiko; Nagadoi, Aritaka; Shimojo, Hideaki; Nishimura, Yoshifumi

    2016-01-01

    During chromatin-regulated processes, the histone H2A-H2B heterodimer functions dynamically in and out of the nucleosome. Although detailed crystal structures of nucleosomes have been established, that of the isolated full-length H2A-H2B heterodimer has remained elusive. Here, we have determined the solution structure of human H2A-H2B by NMR coupled with CS-Rosetta. H2A and H2B each contain a histone fold, comprising four α-helices and two β-strands (α1–β1–α2–β2–α3–αC), together with the long disordered N- and C-terminal H2A tails and the long N-terminal H2B tail. The N-terminal αN helix, C-terminal β3 strand, and 310 helix of H2A observed in the H2A-H2B nucleosome structure are disordered in isolated H2A-H2B. In addition, the H2A α1 and H2B αC helices are not well fixed in the heterodimer, and the H2A and H2B tails are not completely random coils. Comparison of hydrogen-deuterium exchange, fast hydrogen exchange, and {1H}-15N hetero-nuclear NOE data with the CS-Rosetta structure indicates that there is some conformation in the H2A 310 helical and H2B Lys11 regions, while the repression domain of H2B (residues 27–34) exhibits an extended string-like structure. This first structure of the isolated H2A-H2B heterodimer provides insight into its dynamic functions in chromatin. PMID:27181506

  20. High-Resolution Numerical Simulation and Analysis of Mach Reflection Structures in Detonation Waves in Low-Pressure H 2 –O 2 –Ar Mixtures: A Summary of Results Obtained with the Adaptive Mesh Refinement Framework AMROC

    DOE PAGES

    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 techniquesmore » in 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

  1. 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 μatm), river waters in the remaining watershed were supersaturated with CO2. The average pCO2 for the watershed was estimated at 2810 ± 1985 μatm, 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 μatm to > 30 000 μatm 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.

  2. Precise and high-speed control of partial pressures of multiple gas species in plasma process chamber using pulse-controlled gas injection

    SciTech Connect

    Morishita, Sadaharu; Goto, Tetsuya; Nagase, Masaaki; Ohmi, Tadahiro

    2009-05-15

    Multiprocesses in a single plasma process chamber with high throughput require precise, sequential, high-speed alteration of partial pressures of multiple gas species. A conventional gas-distribution system cannot realize this because the system seriously overshoots gas pressure immediately following valve operation. Furthermore, chamber volume and conductance of gas piping between the system and chamber should both be considered because they delay the stabilizing time of gas pressure. Therefore, the authors proposed a new gas-distribution system without overshoot by controlling gas flow rate based on pressure measurement, as well as a method of pulse-controlled gas injection immediately following valve operation. Time variation of measured partial pressure agrees well with a calculation based on an equivalent-circuit model that represents the chamber and gas piping between the system and chamber. Using pulse-controlled gas injection, the stabilizing time can be reduced drastically to 0.6 s for HBr added to pure Ar plasma, and 0.7 s for O{sub 2} added to Ar/HBr plasma; without the pulse control, the stabilizing times are 3 and 7 s, respectively. In the O{sub 2} addition case, rapid stabilization can be achieved during the period of line/space pattern etching of poly-Si on a thin SiO{sub 2} film. This occurs without anomalous etching of the underlying SiO{sub 2} film or the Si substrate near the sidewall, thus obtaining a wide process margin with high throughput.

  3. A flowing liquid test system for assessing the linearity and time-response of rapid fibre optic oxygen partial pressure sensors.

    PubMed

    Chen, R; Hahn, C E W; Farmery, A D

    2012-08-15

    The development of a methodology for testing the time response, linearity and performance characteristics of ultra fast fibre optic oxygen sensors in the liquid phase is presented. Two standard medical paediatric oxygenators are arranged to provide two independent extracorporeal circuits. Flow from either circuit can be diverted over the sensor under test by means of a system of rapid cross-over solenoid valves exposing the sensor to an abrupt change in oxygen partial pressure, P O2. The system is also capable of testing the oxygen sensor responses to changes in temperature, carbon dioxide partial pressure P CO2 and pH in situ. Results are presented for a miniature fibre optic oxygen sensor constructed in-house with a response time ≈ 50 ms and a commercial fibre optic sensor (Ocean Optics Foxy), when tested in flowing saline and stored blood.

  4. [Generation of Superoxide Radicals by Complex III in Heart Mitochondria and Antioxidant Effect of Dinitrosyl Iron Complexes at Different Partial Pressure of Oxygen].

    PubMed

    Dudylina, A L; Ivanova, M V; Shumaev, K B; Ruuge, E K

    2016-01-01

    The EPR spin-trapping technique and EPR-oximetry were used to study generation of superoxide radicals in heart mitochondria isolated from Wistar rats under conditions of variable oxygen concentration. Lithium phthalocyanine and TEMPONE-15N-D16 were chosen to determine oxygen content in a gas-permeable capillary tube containing mitochondria. TIRON was used as a spin trap. We investigated the influence of different oxygen concentrations in incubation mixture and demonstrated that heart mitochondria can generate superoxide in complex III at different partial pressure of oxygen as well as under the conditions of deep hypoxia (< 5% O2). Dinitrosyl iron complexes with glutathione (the pharmaceutical drug "Oxacom") exerted an antioxidant effect, regardless of the value of the partial pressure of oxygen, but the magnitude and kinetic characteristics of the effect depended on the concentration of the drug.

  5. Simultaneous visualization of oxygen partial pressure, current density, and water droplets in serpentine fuel cell during power generation for understanding reaction distributions

    NASA Astrophysics Data System (ADS)

    Takanohashi, Kazuhiro; Suga, Takeo; Uchida, Makoto; Ueda, Toshihide; Nagumo, Yuzo; Inukai, Junji; Nishide, Hiroyuki; Watanabe, Masahiro

    2017-03-01

    Understanding the reaction distributions inside a polymer electrolyte fuel cell (PEFC) is essential for the higher performance and durability. We have developed a new see-through cell and visualized the distributions of oxygen partial pressure and current density inside a running PEFC at the temperature of 40 and 80 °C and the relative humidity of 53%. The oxygen utilization was changed from 0% to 80% by changing the current density. At higher oxygen utilizations, the current density was higher and therefore the water generation. Generated water droplets in the flow channel were also visualized, allowing for the simultaneous visualization of the distribution of the oxygen partial pressure, current density, and water droplets. By combining the observations of all three parameters, the reactions inside a membrane-electrode assembly were discussed.

  6. Enhanced Shrinkage of Lanthanum Strontium Manganite (La0.90Sr0.10MnO3+δ) Resulting from Thermal and Oxygen Partial Pressure Cycling

    SciTech Connect

    McCarthy, Ben; Pederson, Larry R.; Anderson, Harlan U.; Zhou, Xiao Dong; Singh, Prabhakar; Coffey, Greg W.; Thomsen, Ed C.

    2007-10-01

    Exposure of La0.9Sr0.1MnO3+δ to repeated oxygen partial pressure cycles (air/10 ppm O2) resulted in enhanced densification rates, similar to behavior shown previously due to thermal cycling. Shrinkage rates in the temperature range 700 to 1000oC were orders of magnitude higher than Makipirtti-Meng model estimations based on stepwise isothermal dilatometry results at high temperature. A maximum in enhanced shrinkage due to oxygen partial pressure cycling occurred at 900oC. Shrinkage was greatest when LSM-10 bars that were first equilibrated in air were exposed to gas flows of lower oxygen fugacity than in the reverse direction. The former creates transient cation and oxygen vacancies well above the equilibrium concentration, resulting in enhanced mobility. These vacancies annihilate as Schottky equilibria is re-established, whereas the latter condition does not lead to excess vacancy concentrations.

  7. Inhomogeneous speed effects on H2 vibrational line profiles in ternary mixtures

    NASA Astrophysics Data System (ADS)

    Joubert, P.; Bruet, X.; Bonamy, J.; Robert, D.; Chaussard, F.; Saint-Loup, R.; Berger, H.

    2000-12-01

    A study of speed inhomogeneous broadening of the hydrogen vibrational line profiles in the collisional regime for ternary mixtures is reported. The Q(1) line of H2 in H2-Ar-N2, H2-He-Ar, and H2-He-N2 mixtures is investigated by high resolution stimulated Raman spectroscopy for various concentrations and temperatures. A model, successfully used for binary mixtures, is extended to ternary mixtures. An excellent agreement is obtained between theory and experiment for H2-Ar-N2, by using the collisional parameters previously obtained from binary mixtures study. For H2-He-Ar and H2-He-N2, H2-He collisions play a "hardening" effect in the H2 soft speed memory mechanism for H2-Ar or H2-N2. The present experimental results allow us, via the frame of our model, to determine the "hardness" parameter values for H2-He (inaccessible from binary mixtures data) and to get an accurate description of the spectral line shape. This study should be useful for hydrogen coherent anti-Stokes Raman spectroscopy thermometry in H2/air flames at high pressure through its possible extension to the H2-N2-H2O system.

  8. H2 Metabolism in Photosynthetic Organisms

    PubMed Central

    Ben-Amotz, Ami; Erbes, David L.; Riederer-Henderson, Mary Ann; Peavey, Dwight G.; Gibbs, Martin

    1975-01-01

    Dark H2 metabolism was studied in marine and fresh water red algae, the green alga, Chlamydomonas, and mosses. A time variable and temperature-sensitive anaerobic incubation was required prior to H2 evolution. H2 evolution was sensitive to disalicylidenepropanediamine. An immediate H2 uptake was observed in these algae. Immediate dark H2 uptake but no evolution was observed in the mosses. A cell-free hydrogenase preparation was obtained from anaerobically adapted Chlamydomonas reinhardii by means of sonic oscillation. The hydrogenase was not sedimented at 100,000g. It catalyzed the reduction of methylene blue, p-benzoquinone, NAD, NADP, but not spinach ferredoxin. H2 evolution was noted with dithionite and with reduced methyl viologen as donors but not with reduced spinach ferredoxin. Similarly, hydrogenase activities were not affected by disalicylidenepropanediamine. The pH optima for H2 evolution and for H2 uptake were 7.2 and 7.5 to 9.5, respectively. Extracts prepared from the anaerobically adapted red alga, Chondrus crispus, and the moss, Leptobryum pyriforme, consumed but did not evolve H2. Uptake was slightly stimulated by methylene blue. It is proposed that red algae and mosses appear to metabolize H2 by a different pathway than Chlamydomonas. PMID:16659260

  9. Single photon ionization of van der Waals clusters with a soft x-ray laser: (SO2)n and (SO2)n(H2O)m

    NASA Astrophysics Data System (ADS)

    Dong, F.; Heinbuch, S.; Rocca, J. J.; Bernstein, E. R.

    2006-10-01

    van der Waals cluster (SO2)n is investigated by using single photon ionization of a 26.5eV soft x-ray laser. During the ionization process, neutral clusters suffer a small fragmentation because almost all energy is taken away by the photoelectron and a small part of the photon energy is deposited into the (SO2)n cluster. The distribution of (SO2)n clusters decreases roughly exponentially with increasing cluster size. The photoionization dissociation fraction of I[(SO2)n-1SO+]/I[(SO2)n+] decreases with increasing cluster size due to the formation of cluster. The metastable dissociation rate constants of (SO2)n+ are measured in the range of (0.6-1.5)×104s-1 for cluster sizes 5⩽n⩽16. Mixed SO2-H2O clusters are studied at different experimental conditions. At the condition of high SO2 concentration (20% SO2 partial pressure), (SO2)n + cluster ions dominate the mass spectrum, and the unprotonated mixed cluster ions (SO2)nH2O+ (1⩽n⩽5) are observed. At the condition of low SO2 concentration (5% SO2 partial pressure) (H2O)nH+ cluster ions are the dominant signals, and protonated cluster ions (SO2)(H2O)nH+ are observed. The mixed clusters, containing only one SO2 or H2O molecule, SO2(H2O)nH+ and (SO2)nH2O+ are observed, respectively.

  10. Thermodynamic Properties of LiBr/H2O Solution

    NASA Astrophysics Data System (ADS)

    Murakami, Kazuhiko; Sato, Haruki; Watanabe, Koichi

    Although most of the absorption refrigeration/heat pump systems use LiBr/H2O solution for absorbent/refrigerant pair, there exist only a limited number of reliable sets of data on the bubble-point pressures of LiBr/H2O solution. The objective of the present study is to reveal the concentration and temperature dependence of bubble-point pressures of LiBr/H2O solution over a wide range of parameters so as to provide more precise set of thermodynamic property data for advanced design of the absorption refrigeration/heat pump equipments. A total of 44 bubble-point pressures have been measured along seven concentration isopleths of 20, 30, 40, 45, 50, 58 and 60 wt%LiBr solution which cover the range of temperatures 283-413 K and of pressures up to 300 kPa. The experimental uncertainties of temperature, pressure and concentration measurements were not greater than ±20mK, ±0.1 kPa and ±0.1wt%, respectively.

  11. Dynamics of the formation and loss of boron atoms in a H2/B2H6 microwave plasma

    NASA Astrophysics Data System (ADS)

    Duluard, C. Y.; Aubert, X.; Sadeghi, N.; Gicquel, A.

    2016-09-01

    For further improvements in doped-diamond deposition technology, an understanding of the complex chemistry in H2/CH4/B2H6 plasmas is of general importance. In this context, a H2/B2H6 plasma ignited by microwave power in a near resonant cavity at high pressure (100-200 mbar) is studied to measure the B-atom density in the ground state. The discharge is ignited in the gas mixture (0-135 ppm B2H6 in H2) by a 2.45 GHz microwave generator, leading to the formation of a hemispheric plasma core, surrounded by a faint discharge halo filling the remaining reactor volume. Measurements with both laser induced fluorescence and resonant absoption with a boron hollow cathode lamp indicate that the B-atom density is higher in the halo than in the plasma core. When the absorption line-of-sight is positioned in the halo, the absorption is so strong that the upper detection limit is reached. To understand the mechanisms of creation and loss of boron atoms, time-resolved absorption measurements have been carried out in a pulsed plasma regime (10 Hz, duty cycle 50%). The study focuses on the influence of the total pressure, the partial pressure of B2H6, as well as the source power, on the growth and decay rates of boron atoms when the plasma is turned off.

  12. [Effect of oxygen partial pressure on the band-gap of the TiO2 films prepared by DC reactive sputtering].

    PubMed

    Zhao, Qing-nan; Li, Chun-ling; Liu, Bao-shun; Zhao, Xiu-jian

    2004-05-01

    TiO2 films have been deposited on glass substrates using DC reactive magnetron sputtering at different oxygen partial pressures from 0.10 to 0.65 Pa. The photoluminescence (PL) spectra of the films were recorded. The results of the PL spectra showed that there were three emission peaks at 370, 472 and 514 nm for the films sputtered at 0.35 and 0.65 Pa, and there were two peaks at 370 and 490 nm for the films sputtered at 0.10 and 0.15 Pa. The band-gap for the films was 3.35 eV. For the films sputtered at 0.35 and 0.65 Pa there were two defect energy levels at 2.63 and 2.41 eV, corresponding to 0.72 and 0.94 eV below conduction band for the band-gap, respectively. For the films sputtered at 0.10 and 0.15 Pa, there was an energy band formed between 3.12 and 2.06 eV, corresponding to 0.23 and 1.29 eV below the conduction band. With increasing the oxygen partial pressure, the defect energy band changed to two energy levels, and the energy levels nearly disappeared for the film sputtered at 0.65 Pa of oxygen partial pressure.

  13. Effect of oxygen partial pressure on the structural and optical properties of ion beam sputtered TiO2 thin films

    NASA Astrophysics Data System (ADS)

    Tantray, Firdous A.; Chouhan, Romita; Rajput, Swati; Agrawal, Arpana; Andrews, Joseph T.; Sen, Pranay K.; Gupta, Mukul; Sen, Pratima

    2016-10-01

    We report the effect of oxygen partial pressure on the structural, electronic and nonlinear optical properties of ion beam sputtered TiO2 thin films deposited on glass substrate at 40% of oxygen (S1) and 20% of oxygen (S2) partial pressure. XRD data shows the crystalline nature of S1 film while the film S2 was amorphous in nature. The energy band gap of the thin films calculated from their UV-Vis spectra was found to be 3.63 eV (S1) and 3.56 eV (S2). The decrease in the band gap with decrease in oxygen partial pressure may be attributed to the amorphous nature of the film. The nonlinear refractive indices for both the films were obtained from the closed aperture Z-scan experiment performed using a cw He-Ne laser source operating at 632.8 nm and were found to be 17.6×10-9 m2/W and -5.64×10-9 m2/W for S1and S2 films, respectively. The reversal in the sign of the nonlinear refractive index may also be ascribed to the crystallinity of the grown films.

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

    SciTech Connect

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

    2014-02-14

    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.

  15. Effects of various oxygen partial pressures on Ti-doped ZnO thin film transistors fabricated on flexible plastic substrate

    NASA Astrophysics Data System (ADS)

    Cui, Guodong; Han, Dedong; Yu, Wen; Shi, Pan; Zhang, Yi; Huang, Lingling; Cong, Yingying; Zhou, Xiaoliang; Zhang, Xiaomi; Zhang, Shengdong; Zhang, Xing; Wang, Yi

    2016-04-01

    By applying a novel active layer of titanium zinc oxide (TiZO), we have successfully fabricated fully transparent thin-film transistors (TFTs) with a bottom gate structure fabricated on a flexible plastic substrate at low temperatures. The effects of various oxygen partial pressures during channel deposition were studied to improve the device performance. We found that the oxygen partial pressure during channel deposition has a significant impact on the performance of TiZO TFTs, and that the TFT developed under 10% oxygen partial pressure exhibits superior performance with a low threshold voltage (V th) of 2.37 V, a high saturation mobility (μsat) of 125.4 cm2 V-1 s-1, a steep subthreshold swing (SS) of 195 mV/decade and a high I on/I off ratio of 3.05 × 108. These results suggest that TiZO thin films are promising for high-performance fully transparent flexible TFTs and displays.

  16. 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.

  17. Cigarette sidestream smoke induces phosphorylated histone H2AX.

    PubMed

    Toyooka, Tatsushi; Ibuki, Yuko

    2009-05-31

    Cigarette sidestream smoke (CSS) is a widespread environmental pollutant having highly genotoxic potency. In spite of the overwhelming evidence that CSS induces a wide range of DNA damage such as oxidative base damage and DNA adducts, evidence that CSS can result in DNA double strand breaks (DSBs) is little. In this study, we showed that CSS generated phosphorylated histone H2AX (gamma-H2AX), recently considered as a sensitive marker of the generation of DSBs, in a human pulmonary epithelial cell model, A549. Treatment with CSS drastically induced discrete foci of gamma-H2AX within the nucleus in a dose-dependent manner. CSS increased intracellular oxidation, and N-acetylcysteine (NAC), an antioxidant, significantly attenuated the formation of gamma-H2AX, suggesting that reactive oxygen species produced from CSS partially contributed to the phosphorylation. The generation of gamma-H2AX is considered to be accompanied the induction of DSBs. CSS in fact induced DSBs, which was also inhibited by NAC. DSBs are the worst type of DNA damage, related to genomic instability and carcinogenesis. Our results would increase the evidence of the strong genotoxicity of passive smoking.

  18. Electrochemical corrosion of carbon steels in H2S-containing brines

    NASA Astrophysics Data System (ADS)

    Feng, Ruishu

    The electrochemical corrosion behaviors of high strength low alloy carbon steel, Grade S-135, and ultra-high strength low alloy carbon steel, Grade UD-165, were investigated in alkaline brines at pH of 7.9, 10.7, and 12.4 and four H2S partial pressures (P H2S) from 0 to 69 kPa at 85 °C using in situ electrochemical measurements, ex situ surface analyses, and software modeling. HS-(aq) was calculated to be the dominant sulfide species from pH 7.9 to 12.4. After 60 hours, polarization resistance (Rpol) of S-135 and UD-165 generally increased as pH increased at lower PH2S (0 and 0.83 kPa), whereas Rpol decreased and then increased as pH increased at higher PH2S (8.3 and 69 kPa). At each pH, the lower PH2S increased Rpol or did not significantly change R pol, whereas the higher PH2S decreased Rpol. Two opposite effects from H2S were proposed, an accelerating effect due to H2S(aq) and HS-(aq) facilitating the Faradaic reactions and the localized corrosion, and an inhibiting effect due to the protectiveness of the corrosion products. The inhibiting effect was often observed at relatively low H2S concentrations at pH 7.9 and 12.4. The electrochemical impedance did not change significantly at different stir rates for both S-135 and UD-165, indicating that mass transport in the bulk solution was not the rate determining step. The corrosion products generally changed from iron carbonate and sulfides to iron oxide as pH increased, which agreed with the Pourbaix diagrams. Solution pH in the three solutions were calculated to be 8.1, 9.8, and 10.8 at 200 °C, respectively. Polarization resistance values of UD-165 at 200 °C were consistently one to two orders of magnitude lower than at 85 °C, which corresponded to a drastic increase in corrosion rate at elevated temperature. At 200 °C, Rpol at 9.8 was the smallest after 60 hours among the three solutions. The modeled results were in reasonable agreement with the experimental CR values within a factor of 4. A new method

  19. γH2AX and cancer

    PubMed Central

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

    2011-01-01

    Histone H2AX phosphorylation on a serine four residues from the carboxyl terminus (producing γH2AX) 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 γH2AX 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

  20. Global Ocean Surface Water Partial Pressure of CO2 Database: Measurements Performed During 1968-2007 (Version 2007)

    SciTech Connect

    Kozyr, Alex

    2008-09-30

    More than 4.1 million measurements of surface water partial pressure of CO2 obtained over the global oceans during 1968-2007 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 µatm 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 ship’s 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.

  1. Photolysis of H2O-H2O2 Mixtures: The Destruction of H2O2

    NASA Technical Reports Server (NTRS)

    Loeffler, M. J.; Fama, M.; Baragiola, R. A.; Carlson, R. W.

    2013-01-01

    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 micrometer 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.

  2. Flammability and Explosion Limits of H2 and H2/CO: A Literature Review

    DTIC Science & Technology

    1992-09-10

    I, SMC-TR-93-19 AD-A2 4 896AEROSPACE REPORT NOAD-A264 896 TR-92(2534)- ° Flammability and Explosion Limits of H2 and H2/CO: A Literature Review ...ELEMENT NO. NO. NO. ACCESSION NO 11. TITLE (Include Semrmly Ctassltjcation) Flammability and Explosion Limits of H2 and H2 /CO: A Literature Review 12...The literature related to the flammability and explosion limits of H2/O2 H2/0 2 /diluent. CO/O 2 . CO/H,/O 2 , and CO/H2/air mixtures is reviewed

  3. Electrical properties of InGaN thin films grown by RF sputtering at different temperatures, varying nitrogen and argon partial pressure ratios

    NASA Astrophysics Data System (ADS)

    Jakkala, Pratheesh; Kordesch, Martin E.

    2016-10-01

    Indium gallium nitride (InGaN) thin films of varying indium (In) and gallium (Ga) compositions have been fabricated on aluminosilicate glass and silicon (111) substrates using RF magnetron sputtering method at different growth temperatures, varied from 35 °C to 450 °C. Argon (Ar) and nitrogen (N2) are used as Inert and reactive gases respectively. Keeping the total pressure of gas mixture constant, partial pressures of N2 and Ar gases are varied. Ratio of Ar partial pressure to total pressure in the gas mixture is varied from 0 to 0.75. In this study, we present electrical properties of these InGaN thin films. Resistivity values of 2.6 × 10-5 to 1.68 × 10-2 Ω.cm, mobility values of 0.119 to 45.2 cm2/V.s, conductivity values of 0.595 × 103 to 37.3 × 103 mho/cm and bulk carrier concentration values -1020 to -1022/m3 are recorded that are measured through Hall-effect measurement technique.

  4. Freezing temperatures of H2SO4/HNO3/H2O mixtures: Implications for polar stratospheric clouds

    NASA Technical Reports Server (NTRS)

    Song, Naihui

    1994-01-01

    The freezing temperatures of H2SO4/HNO3/H2O mixtures were systematically documented. Nitric acid was found to affect freezing significantly. Measurements show that nitric acid can cause substantial supercooling over a broad composition range. However, some ternary compositions, like to those in polar stratospheric clouds (PSCs), have high freezing temperatures. The freezing of PSC particles could be controlled by the temperature and vapor pressure of both nitric acid and water in a non-linear way. Formation of polar stratospheric clouds may be forecasted on the basic of conditions of temperature and vapor contents of water and nitric acid.

  5. NMR Evidence of Cage-to-Cage Diffusion of H2 in H2-Clathrates

    NASA Astrophysics Data System (ADS)

    Senadheera, Lasitha; Conradi, Mark

    2008-03-01

    H2 and heavy-ice at P>1 kbar and T ˜250 K form H2-D2O clathrate; four and one H2 may occupy each large (L) and small (S) cage, respectively. In H2-THF-H2O clathrate, H2 occupies singly and only S cages. Previous electronic-structure calculations estimate the barriers for H2 passage though hexagonal and pentagonal faces of cages as ˜6 and ˜25 kcal/mol, respectively. Our H2 NMR linewidth data reflect random crystal fields from frozen cage-wall D2O orientations. We find dramatic reductions in linewidth starting at 120 K (175 K) for H2-D2O (H2-TDF-D2O) indicating time-averaging of the crystal fields. Assuming Arrhenius behavior, our data imply energies for escape from L (S) cages of about ˜4 (˜6) kcal/mol. For L cages, the agreement with the calculated (cages were treated as rigid) barrier is reasonable. For H2 in S cages, in H2-TDF-D2O, the extreme disagreement with theory points to another mechanism of time-averaging, reorientations of the cage-wall D2O molecules, as suggested by previous work in TDH-H2O clathrate. Our limited NMR spectra at high T ˜145 K in H2-D2O show evidence of distinct resonances from diffusionally mobile and immobile H2 molecules, as expected.

  6. Energy Conservation Associated with Ethanol Formation from H2 and CO2 in Clostridium autoethanogenum Involving Electron Bifurcation

    PubMed Central

    Mock, Johanna; Zheng, Yanning; Mueller, Alexander P.; Ly, San; Tran, Loan; Segovia, Simon; Nagaraju, Shilpa; Köpke, Michael; Dürre, Peter

    2015-01-01

    ABSTRACT Most acetogens can reduce CO2 with H2 to acetic acid via the Wood-Ljungdahl pathway, in which the ATP required for formate activation is regenerated in the acetate kinase reaction. However, a few acetogens, such as Clostridium autoethanogenum, Clostridium ljungdahlii, and Clostridium ragsdalei, also form large amounts of ethanol from CO2 and H2. How these anaerobes with a growth pH optimum near 5 conserve energy has remained elusive. We investigated this question by determining the specific activities and cofactor specificities of all relevant oxidoreductases in cell extracts of H2/CO2-grown C. autoethanogenum. The activity studies were backed up by transcriptional and mutational analyses. Most notably, despite the presence of six hydrogenase systems of various types encoded in the genome, the cells appear to contain only one active hydrogenase. The active [FeFe]-hydrogenase is electron bifurcating, with ferredoxin and NADP as the two electron acceptors. Consistently, most of the other active oxidoreductases rely on either reduced ferredoxin and/or NADPH as the electron donor. An exception is ethanol dehydrogenase, which was found to be NAD specific. Methylenetetrahydrofolate reductase activity could only be demonstrated with artificial electron donors. Key to the understanding of this energy metabolism is the presence of membrane-associated reduced ferredoxin:NAD+ oxidoreductase (Rnf), of electron-bifurcating and ferredoxin-dependent transhydrogenase (Nfn), and of acetaldehyde:ferredoxin oxidoreductase, which is present with very high specific activities in H2/CO2-grown cells. Based on these findings and on thermodynamic considerations, we propose metabolic schemes that allow, depending on the H2 partial pressure, the chemiosmotic synthesis of 0.14 to 1.5 mol ATP per mol ethanol synthesized from CO2 and H2. IMPORTANCE Ethanol formation from syngas (H2, CO, and CO2) and from H2 and CO2 that is catalyzed by bacteria is presently a much-discussed process for

  7. 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.; GonzáLez MartíNez 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.

  8. Single photon ionization of van der Waals clusters with a soft x-ray laser: (CO2)n and (CO2)n(H2O)m

    NASA Astrophysics Data System (ADS)

    Heinbuch, S.; Dong, F.; Rocca, J. J.; Bernstein, E. R.

    2006-10-01

    Pure neutral (CO2)n cl