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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-25C , and they are released at 3atm-10-6atm-25C . 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. The electrochemical behaviour of 316L austenitic stainless steel in Cl- containing environment under different H2S partial pressures

    NASA Astrophysics Data System (ADS)

    Ding, Jinhui; Zhang, Lei; Lu, Minxu; Wang, Jing; Wen, Zhibin; Hao, Wenhui

    2014-01-01

    In oil-gas production environments, presence of H2S-Cl- can induce deterioration of the passive film, leading to pitting corrosion of stainless steels. In this paper, by using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and capacitance measurements (Mott-Schottky analysis), the electrochemical behaviour of AISI 316L austenitic stainless steel was investigated in Cl- solutions under different H2S partial pressures (from 0 to 1.0 bar). The results indicated that presence of H2S in Cl- solution can accelerate both the cathodic and anodic current density, leading to a metastable passive state in higher passive potential range, changing the semiconductor behaviour from p-type to n-type, increasing its susceptibility to corrosion. XPS analysis was employed to characterize the surface film after potentiostatic polarization, whose results provide good evidences for the electrochemical measurements.

  4. The effect of H2 partial pressure on the reaction progression and reversibility of lithium-containing multicomponent destabilized hydrogen storage systems.

    PubMed

    Price, Tobias E C; Grant, David M; Weston, David; Hansen, Thomas; Arnbjerg, Lene M; Ravnsbk, Dorthe B; Jensen, Torben R; Walker, Gavin S

    2011-08-31

    It is known that the reaction path for the decomposition of LiBH(4):MgH(2) systems is dependent on whether decomposition is performed under vacuum or under a hydrogen pressure (typically 1-5 bar). However, the sensitivity of this multicomponent hydride system to partial pressures of H(2) has not been investigated previously. A combination of in situ powder neutron and X-ray diffraction (deuterides were used for the neutron experiments) have shed light on the effect of low partial pressures of hydrogen on the decomposition of these materials. Different partial pressures have been achieved through the use of different vacuum systems. It was found that all the samples decomposed to form Li-Mg alloys regardless of the vacuum system used or sample stoichiometry of the multicomponent system. However, upon cooling the reaction products, the alloys showed phase instability in all but the highest efficiency pumps (i.e., lowest base pressures), with the alloys reacting to form LiH and Mg. This work has significant impact on the investigation of Li-containing multicomponent systems and the reproducibility of results if different dynamic vacuum conditions are used, as this affects the apparent amount of hydrogen evolved (as determined by ex situ experiments). These results have also helped to explain differences in the reported reversibility of the systems, with Li-rich samples forming a passivating hydride layer, hindering further hydrogenation. PMID:21755995

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

    NASA Astrophysics Data System (ADS)

    Cui, Tian

    2015-03-01

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

  6. Oxygen partial pressure sensor

    DOEpatents

    Dees, Dennis W. (Downers Grove, IL)

    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.

  7. 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.

  8. 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

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

    PubMed

    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

  10. 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.

  11. 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

  12. 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 + O2 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 Ag capsule and sealed by capsule swaging. Changes in H2O activity (measured by shifts in the Ni content of the alloy) that occur with changes in pelite- water ratios at isothermal and isobaric conditions, can be used to determine the shape and position of the melt-H2O solvus. Pelite-H2O experiments at 25 kbar show solvus behaviour at 900 C (temperatures >200 C) above the wet solidus), indicating that the wet solidus and critical curve do not intersect at these conditions. In contrast, experiments at 35 kbar and 800-900 C, show a gradual change in H2O activity with increasing water:pelite ratios, indicating that the critical curve and wet solidus become closer with increasing pressure. Solvus topology in the pelite-H2O system, as determined by this series of experiments at 25 and 35 kbar, can also be used to estimate the shape and orientation of solubility isopleths (in terms of P-T). While the seminal work of Burnham and Davis (1974) demonstrated the importance of pressure on inducing H2O saturation in silicate melts, experiments presented here indicate that temperature may also play an important role. Burnham C. W. and Davis N. F. 1974, American Journal of Science. 274; 8, 902-940. Kessel, R., et al 2005, Earth and Planetary Science Letters, 237, 873-892. Mibe, K et al. 2007, Geochimica et Cosmochimica Acta. 68, 24, 5189-5195. Newton, R. C., and Manning, C. E., 2008, Earth and Planetary Science Letters. Schmidt, M.W.et al, 2004, Earth and Planetary Science Letters, 228, 65-84. Shen, A., and Keppler, H. 1997 Nature, 385, 710-712. Stadler, R., et al, 2000, American Mineralogist, 85, 68-77. class="ab'>

  13. 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. PMID:9092469

  14. 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 1200-1450C. 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, ?T, which is controlled by the H2O concentration in partial melts. Melts with 1.5, 5, 10, and 15 wt. % H2O yield ?T values of 50, 150, 250, and 320C, 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/Al2O3.

  15. Partial pressure analysis of plasmas

    SciTech Connect

    Dylla, H.F.

    1984-11-01

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

  16. 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.

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

    PubMed Central

    Horn, Simon; Barnard, Stephen; Rothkamm, Kai

    2011-01-01

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

  18. Hydrogen storage properties of nanosized MgH2-0.1TiH2 prepared by ultrahigh-energy-high-pressure milling.

    PubMed

    Lu, Jun; Choi, Young Joon; Fang, Zhigang Zak; Sohn, Hong Yong; Rnnebro, Ewa

    2009-11-01

    Magnesium hydride (MgH(2)) is an attractive candidate for solid-state hydrogen storage applications. To improve the kinetics and thermodynamic properties of MgH(2) during dehydrogenation-rehydrogenation cycles, a nanostructured MgH(2)-0.1TiH(2) material system prepared by ultrahigh-energy-high-pressure mechanical milling was investigated. High-resolution transmission electron microscope (TEM) and scanning TEM analysis showed that the grain size of the milled MgH(2)-0.1TiH(2) powder is approximately 5-10 nm with uniform distributions of TiH(2) among MgH(2) particles. Pressure-composition-temperature (PCT) analysis demonstrated that both the nanosize and the addition of TiH(2) contributed to the significant improvement of the kinetics of dehydrogenation and hydrogenation compared to commercial MgH(2). More importantly, PCT cycle analysis demonstrated that the MgH(2)-0.1TiH(2) material system showed excellent cycle stability. The results also showed that the DeltaH value for the dehydrogenation of nanostructured MgH(2)-0.1TiH(2) is significantly lower than that of commercial MgH(2). However, the DeltaS value of the reaction was also lower, which results in minimum net effects of the nanosize and the addition of TiH(2) on the equilibrium pressure of dehydrogenation reaction of MgH(2). PMID:19810732

  19. 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.

  20. Hydrogen Storage Properties of Nanosized MgH2-0.1TiH2 Prepared by Ultrahigh-energy-high-pressure Milling

    SciTech Connect

    Lu, Jun; Choi, Young Joon; Fang, Zhigang Zak; Sohn, Hong Yong; Ronnebro, Ewa

    2010-07-29

    Magnesium hydride (MgH2) is an attractive candidate for solid state hydrogen storage applications. To improve the kinetics and thermodynamic properties of MgH2 during dehydrogenation-rehydrogenation cycles, a nano-structured MgH2-0.1TiH2 material system prepared by ultrahigh-energy-high-pressure mechanical milling was investigated. High-resolution TEM and scanning TEM analysis showed that the grain size of the milled MgH2-0.1TiH2 powder is approximately 5-10 nm with uniform distributions of TiH2 among MgH2 particles. Pressure-Composition-Temperature (PCT) analysis demonstrated that both the nanosize and the addition of TiH2 contributed to the significant improvement of the kinetics of dehydrogenation and hydrogenation compared to commercial MgH2. More importantly, PCT cycle analysis demonstrated that the MgH2-0.1TiH2 material system showed excellent cycle stability which is attributed to the inhibition of coarsening by TiH2. The results also showed that the ?H value for the dehydrogenation of nanostructured MgH2-0.1TiH2 is significantly lower than that of commercial MgH2. However, the ?S value of the reaction was also lower which results in minimum net effects of the nanosize and the addition of TiH2 on the equilibrium pressure of dehydrogenation reaction of MgH2.

  1. 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

  2. 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

    2016-01-01

    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

  3. 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.

  4. High pressure Raman spectroscopy of H2O-CH3OH mixtures

    PubMed Central

    Hsieh, Wen-Pin; Chien, Yu-Hsiang

    2015-01-01

    Complex intra-molecular interactions and the hydrogen-bonding network in H2O-volatile mixtures play critical roles in many dynamics processes in physical chemistry, biology, and Earth and planetary sciences. We used high pressure Raman spectroscopy to study the pressure evolution of vibrational frequencies and bonding behavior in H2O-CH3OH mixtures. We found that the presence of low CH3OH content in H2O increases the transition pressure where water crystallizes to ice VI, but does not significantly change the pressure where ice VI transforms to ice VII. Furthermore, the stiffening rates of C-H stretching frequencies 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. PMID:25704667

  5. High pressure Raman spectroscopy of H2O-CH3OH mixtures

    NASA Astrophysics Data System (ADS)

    Hsieh, Wen-Pin; Chien, Yu-Hsiang

    2015-02-01

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

  6. High pressure Raman spectroscopy of H2O-CH3OH mixtures

    NASA Astrophysics Data System (ADS)

    Hsieh, Wen-Pin; Chien, Yu-Hsiang

    2015-03-01

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

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

    PubMed

    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 H(2)/Ar treatment from 100 C to 900 C. RGO-300 shows excellent sensitivity to H(2) 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. PMID:21566828

  8. Structural Phase Transition in CaH2 at High Pressures

    SciTech Connect

    Tse,J.; Klug, D.; Desgreniers, S.; Smith, J.; R. Flacau, R.; Liu, Z.; Hu, J.; Chen, N.; Jiang, D.

    2007-01-01

    The structural and vibrational properties of CaH2 have been examined up to 30GPa at room temperature. Under ambient conditions, CaH2 has a Pnma (cotunnite-type) structure. A structural phase transformation was observed around 15GPa and completed at 20GPa . The high pressure structure is identified as hexagonal P63/mmc . First-principles calculations reproduced the first-order nature of the transition. Since P63/mmc is a supergroup of Pnma the structural change can be traced back to gradual displacements of the hydrogen atoms from the 4c positions in the cotunnite structure to the special 2a and 2d positions in the hexagonal structure. The observed phase transition pressure is much lower than that predicted for MgH2 .

  9. The effects of H2-He pressure broadening parameters on the retrieval of brown dwarf atmospheres

    NASA Astrophysics Data System (ADS)

    Garland, Ryan; Irwin, Patrick G. J.; Aigrain, Suzanne; Barstow, Joanna K.

    2015-11-01

    Brown dwarf atmospheres are compositionally very similar to the gas giant planets, made up of approximately 85% H2 and 15% He, as well as other trace gases such as CH4 and H2O, depending on the spectral type. We have investigated the effects of using pressure broadening parameters related to H2-He broadening and compared them to using air-broadening parameters for each of the major trace gases involved in brown dwarf atmospheres. We have identified from limited data sets that H2-He broadening, relative to air broadening, can act to increase or decrease the Lorentzian broadening experienced by a given transition. This change in Lorentzian broadening is dependent on the gas considered and the transition's associated quantum numbers (such as rotational and vibrational quantum numbers). By altering the transitions lineshape, we also alter its opacity. Some gases are affected significantly at all pressure levels (NH3, CO2, CH4), some at deep (~1bar) pressure levels (CO, H2O), and others not at all (TiO, VO). We conclude, however, that these limited data sets do not provide the complex and comprehensive dependence of pressure broadening on the relevant quantum numbers that is available to air broadening, and we cannot say for certain how much this limits our results until more data is available. Our conclusions demonstrate the need for further study of H2 and He broadening parameters for the relevant gases from both experimental and computational means. We present preliminary results of the knock-on effects that these broadening parameters have for the retrieval of atmospheric composition and thermal structure.

  10. 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.

  11. Mineral stability in the presence of H2O fluid at high pressure and high temperature

    NASA Astrophysics Data System (ADS)

    Prakapenka, V.

    2013-12-01

    Detail knowledge of the fundamental processes of phase transition and chemistry of minerals at high pressure and temperature in the presence of volatile fluids is one of the key factors in understanding the complexity of the planet interiors, its heterogeneous structure and dynamics. Pressure effects on the mechanism of phase transition, chemistry, crystal growth, melting phenomena and structure of the multi-component phases constituting the terrestrial and giant planets can be effectively studied with state-of-the-art technologies available at 3rd generation synchrotrons. In this work, we report the application of advanced, flat top laser heating technique combined with high resolution micro x-ray diffraction recently developed at GSECARS (APS, Argonne, USA) for in-situ high pressure/temperature studies of minerals in a diamond anvil cell. We were able to perform on-line melting experiments in the Mbar pressure range for the H2O sample surrounded by various minerals. Phase transition of MgO in the presence of H2O fluid was observed above 30 GPa and temperatures above 2000 K while SiO2 phases where stable within studied pressure-temperature range. The experimental details and results of structural stability of MgO, SiO2 , MgSiO3 and C in the presence of molten H2O at pressures up to 150 GPa and implications of these results for understanding the composition and structure of the planet interiors will be discussed.

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

    NASA Astrophysics Data System (ADS)

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

    2003-04-01

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

  13. 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

    2014-08-01

    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. PMID:26277952

  14. 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 (850-1500C) 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 ~950C, and at 8-9 GPa and up to ~1050C 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. Earth Planet Sci Lett 128, 313-325 (1994). [2] Hermann, J. Green, D. H. Earth Planet Sci Lett 188, 149-168 (2001). [3] Hermann J. & Spandler, C. J. J Petrol 49, 717-740 (2008). [4] Schmidt, M. W. Science 272, 1927-1930 (1996). [5] Schmidt, M. W. & Poli, S. Earth Planet Sci Lett 163, 361-379 (1998). [6] Schmidt, M. W. et al. Earth Planet Sci Lett 228, 65-84 (2004).

  15. 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.

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

    PubMed

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

    2006-07-13

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

  17. Characteristics of a VHF H2 plasma at high pressures for different discharge gaps

    NASA Astrophysics Data System (ADS)

    Lien, Cheng-Yang; Chen, Chia-Fu; Yang, Ching-Lung; Kawai, Yoshinobu; Chiu, Kuo-Feng; Shi, Jen-Bin; Huang, Sy-Ruen; Wang, Jui-Hao; Tsai, Yu-Jer; Lien, Ting-Kuei

    2015-09-01

    A capacitively coupled VHF H2 plasma (60 MHz) was produced at high pressures, and plasma parameters were examined as a function of pressure and power at different discharge gaps (10, 15, and 20 mm). Here, a balanced power feeding method was adopted to avoid anomalous discharges. It was found that the electron density peaked at a certain pressure. As the discharge gap decreased, the peak pressure increased. The electron temperatures at the discharge gaps of 10 and 20 mm were approximately 8 and 3 eV at high pressures, respectively. In addition, we found that the sheath potential corresponding to the ion bombardment energy with the discharge gap of 10 mm was lower than the theoretical value calculated on the basis of the sheath theory, suggesting the existence of negative ions. Estimation of negative ion concentration was attempted on the basis of the sheath theory taking into consideration negative ions.

  18. 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.

  19. Experiments on the kinetics of partial melting of a leucogranite at 200 MPa H2O and 690-800C: compositional variability of melts during the onset of H2O-saturated crustal anatexis

    NASA Astrophysics Data System (ADS)

    Acosta-Vigil, Antonio; London, David; Morgan, George B.

    2006-05-01

    We have experimentally investigated the kinetics of melting of an aplitic leucogranite (quartz+sodic plagioclase of ?Ab90+K-feldspar+traces of biotite) at 690, 740, and 800C, all at 200 MPa H2O. Leucogranite cylinders, 3.5 mm in diameter and 7 mm in length, were run in the presence of excess H2O using cold-seal pressure vessels for 11-2,925 h. At 690 and 740C and any experimental time, and 800C and short run times, silicate glass (melt at run conditions) occurs as interconnected films along most of the mineral boundaries and in fractures, with the predominant volume occurring along quartz/feldspars boundaries and quartz/plagioclase/K-feldspar triple junctions. Glass film thickness is roughly constant throughout a given experimental charge and increases with experimental temperature and run duration. The results indicate that H2O-saturated partial melting of a quartzo-feldspathic protolith will produce an interconnected melt phase even at very low degrees (<5 vol%) of partial melting. Crystal grain boundaries are therefore completely occluded with melt films even at the lowest degrees of partial melting, resulting in a change in the mechanism of mass transport through the rock from advection of aqueous vapor to diffusion through silicate melt. At 690 and 740C the compositions of glasses are homogeneous and (at both temperatures) close to, but not on, the H2O-saturated 200 MPa haplogranite eutectic; glass compositions do not change with run duration. At 800C glasses are heterogeneous and plot away from the minimum, although their molar ratios ASI (=mol Al2O3/CaO+Na2O+K2O) and Al/Na are constant throughout the entire charge at any experimental time. Glass compositions within individual 800C experiments form linear trends in (wt%) normative quartz-albite-orthoclase space. The linear trends are oriented perpendicular to the 200 MPa H2O haplogranite cotectic line, reflecting nearly constant albite/orthoclase ratio versus variable quartz/feldspar ratio, and have endpoints between the 800C isotherms on the quartz and feldspar liquidus surfaces. With increasing experimental duration the trends migrate from the potassic side of the minimum toward the bulk rock composition located on the sodic side, due to more rapid (and complete) dissolution of K-feldspar relative to plagioclase. The results indicate that partial melting at or slightly above the solidus (690-740C) is interface reaction-controlled, and produces disequilibrium melts of near-minimum composition that persist metastably for up to at least 3 months. Relict feldspars show no change in composition or texture, and equilibration between melt and feldspars might take from a few to tens of millions of years. Partial melting at temperatures well above the solidus (800C) produces heterogeneous, disequilibrium liquids whose compositions are determined by the diffusive transport properties of the melt and local equilibrium with neighboring mineral phases. Feldspars recrystallize and change composition rapidly. Partial melting and equilibration between liquids and feldspars might take from a few to tens of years (H2O-saturated conditions) at these temperatures well above the solidus.

  20. 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 process of post-entrapment dehydration can be completely reversed under high pressure experimental conditions. If temperature, redox conditions and pressure of melt inclusion entrapment can be independently estimated, then our novel experimental approach (homogenization at high H2O pressure) can be used to reconstruct the initial CO2 content and also the entire composition of melt inclusions in olivine, including their initial H2O content, from any type of volcanic rock. With this approach volatiles in ancient lavas can also be determined, expanding our knowledge of volatile recycling further back in Earth history.

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2008-11-01

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

  3. A separation principle for the H2-control of continuous-time infinite Markov jump linear systems with partial observations

    NASA Astrophysics Data System (ADS)

    Costa, Oswaldo L. V.; Fragoso, Marcelo D.

    2007-07-01

    In this paper we devise a separation principle for the H2 optimal control problem of continuous-time Markov jump linear systems with partial observations and the Markov process taking values in an infinite countable set . We consider that only an output and the jump parameters are available to the controller. It is desired to design a dynamic Markov jump controller such that the closed loop system is stochastically stable and minimizes the H2-norm of the system. As in the case with no jumps, we show that an optimal controller can be obtained from two sets of infinite coupled algebraic Riccati equations, one associated with the optimal control problem when the state variable is available, and the other one associated with the optimal filtering problem. An important feature of our approach, not previously found in the literature, is to introduce an adjoint operator of the continuous-time Markov jump linear system to derive our results.

  4. Dynamical and rheological properties of fluorinated surfactant films adsorbed at the pressurized CO2-H2O interface.

    PubMed

    Tewes, Frederic; Krafft, Marie Pierre; Boury, Frank

    2011-07-01

    The dynamics of adsorption, interfacial tension, and rheological properties of two phosphocholine-derived partially fluorinated surfactants FnHmPC, designed to compensate for the weak CO(2)-surfactant tail interactions, were determined at the pressurized CO(2)-H(2)O interface. The two surfactants differ only by the length of the hydrocarbon spacer (5 CH(2) in F8H5PC and 11 CH(2) in F8H11PC) located between the terminal perfluoroalkyl chain and the polar head. The length of this spacer was found to have a critical impact on the adsorption kinetics and elasticity of the interfacial surfactant film. F8H5PC is soluble in both water and CO(2) phases and presents several distinct successive interfacial behaviors when bulk water concentration (C(W)) increases and displays a nonclassical isotherm shape. The isotherms of F8H5PC are similar for the three CO(2) pressures investigated and comprise four regimes. In the first regime, at low C(W), the interfacial tension is controlled by the organization that occurs between H(2)O and CO(2). The second regime corresponds to the adsorption of the surfactant as a monolayer until the CO(2) phase is saturated with F8H5PC, resulting in a first inflection point. In this regime, F8H5PC molecules reach maximal compaction and display the highest apparent interfacial elasticity. In the third regime, a second inflection is observed that corresponds to the critical micelle concentration of the surfactant in water. At the highest concentrations (fourth regime), the interfacial films are purely viscous and highly flexible, suggesting the capacity for this surfactant to produce water-in-CO(2) microemulsion. In this regime, surfactant adsorption is very fast and equilibrium is reached in less than 100 s. The behavior of F8H11PC is drastically different: it forms micelles only in the water phase, resulting in a classical Gibbs interface. This surfactant decreases the interfacial tension down to 1 mN/m and forms a strongly elastic interface. As this surfactant forms a very cohesive interface, it should be suitable for formulating stable water-in-CO(2) emulsions. The finding that the length of the hydrocarbon spacer in partially fluorinated surfactants can drastically influence film properties at the CO(2)-H(2)O interface should help control the formation of microemulsions versus emulsions and help elaborate a rationale for the design of surfactants specifically adapted to pressurized CO(2). PMID:21630699

  5. Wall pressure fluctuations in rectangular partial enclosures

    NASA Astrophysics Data System (ADS)

    Pagliaroli, T.; Camussi, R.

    2015-04-01

    Wall pressure fluctuations generated within rectangular partial enclosures (RPEs) have been studied experimentally for a broad range of geometrical parameters. The geometry represents a simplified version of a new generation trapped vortex combustor and consisted of a rectangular cavity connected to a neck of smaller size. Wall pressure fluctuations have been measured through wall mounted microphones providing single and multi-variate pressure statistics both in the physical space and in the Fourier domain. In order to interpret the pressure signals, aerodynamic and acoustic investigations have been carried out as well for several cavity-neck ratios. The analysis of the acoustic response of the cavity has been conducted both numerically and experimentally and a simple theoretical model has been proposed to predict the frequency of the acoustic resonances. The aerodynamic study has been carried out through PIV measurements that provided characterization in terms of the geometrical parameters of both the large-scale vortex generated within the cavity and the recirculation zone formed upstream of the neck. The use of the POD decomposition permitted us to correlate the dynamics of the recirculation with the observed pressure statistics. The aerodynamic and acoustic investigations allowed us to interpret exhaustively the wall pressure cross-statistics and to separate contributions induced by hydrodynamic and purely acoustic pressure fluctuations.

  6. 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.

  7. A new type of functional chemical sensitizer {MgH}2 for improving pressure desensitization resistance of emulsion explosives

    NASA Astrophysics Data System (ADS)

    Cheng, Y. F.; Yan, S. L.; Ma, H. H.; Shen, Z. W.; Liu, R.

    2015-07-01

    In millisecond-delay blasting and deep water blasting projects, traditional emulsion explosives sensitized by the chemical sensitizer NaNO2 often encounter incomplete explosion or misfire problems because of the "pressure desensitization" phenomenon, which seriously affects blasting safety and construction progress. A MgH2 -sensitized emulsion explosive was invented to solve these problems. Experimental results show that MgH2 can effectively reduce the problem of pressure desensitization. In this paper, the factors which influence the pressure desensitization of two types of emulsion explosives are studied, and resistance to this phenomenon of MgH2 -sensitized emulsion explosives is discussed.

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

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

  9. Pressure-induced H2 opacity in the 5-micron region. [of outer planet spectra

    NASA Technical Reports Server (NTRS)

    Goorvitch, D.; Tipping, R. H.

    1982-01-01

    The H2 opacity arising from the pure-rotational hexadecapole-induced transitions occurring during H2-H2 and H2-He collisions, and from the hexadecapole-induced and the quadrupole-induced transitions in H2-He collisions, has been calculated. The hexadecapole-induced and quadrupole-induced contributions from H2-H2 collisions are important H2 opacities in the frequency range from 700-3000/cm for temperatures appropriate to the outer planets. It is concluded that this opacity is needed in addition to the opacity from the extrapolation of the 0-0 and 1-0 H2-H2 collisionally-induced bands to interpret the spectrum at 5 microns for the outer planets.

  10. 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).

  11. 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.

  12. Experimental deformation of polycrystalline H2O ice at high pressure and low temperature - Preliminary results

    NASA Astrophysics Data System (ADS)

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

    1983-11-01

    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 Ih. Brittle failure of Ih 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 Ih 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.

  13. H2O-fluid-saturated melting of subducted continental crust facilitates exhumation of ultrahigh-pressure rocks in continental subduction zones

    NASA Astrophysics Data System (ADS)

    Labrousse, L.; Duretz, T.; Gerya, T.

    2015-10-01

    We present two-dimensional numerical models of plate subduction and collision inspired by the Scandinavian Caledonian orogeny to investigate the possible impact of continental crust partial melting on the exhumation of ultra-high pressure metamorphic rocks. Three possible reactions were tested: low temperature solidus representing H2O-fluid-saturated partial melting, and two end-member reaction curves for dehydration melting. Thermo-mechanical effects of partial melting were implemented as (1) a viscosity decrease as a determined rheologically critical melt percentage was reached (here 0.1), (2) a change in effective heat capacity and adiabatic heating/cooling accounting for a latent heat term in the heat equation. Among the 3 tested reactions, only H2O-fluid-saturated partial melting drastically modifies the collision dynamics from the non-melting reference model holding all other parameters constant. A substantially low general viscosity truncation (here 1017 Pa s) is needed to properly resolve the effect of partial melting on deep collision processes. Low temperature melting indeed induces the development of a low viscosity buoyant plume prior to slab detachment, where migmatites exhume from UHP conditions at rates and with pressure-temperature paths similar to the natural values acknowledged for the Norwegian Caledonides. High temperature melting has no drastic influence on early collision dynamics. While positive buoyancy remains the first order driver for the exhumation of buried continental rocks, exhumation initiates in these cases with eduction subsequent to slab detachment. Melting and formation of a migmatite plume can later occur along decompression path while continental crust undergoes thermal reequilibration at temperatures above 900 C. Some of the partially molten material can also relaminate in the overriding plate rather than exhume within the collision zone. Even if minor in terms of amount of magma produced, H2O-fluid-saturated partial melting at UHP conditions could therefore have a dramatic rheological effect and actually limits continental rocks subduction and facilitates their exhumation.

  14. Velocity effects on the shape of pure H2O isolated lines: complementary tests of the partially correlated speed-dependent Keilson-Storer model.

    PubMed

    Tran, H; Ngo, N H; Hartmann, J-M; Gamache, R R; Mondelain, D; Kassi, S; Campargue, A; Gianfrani, L; Castrillo, A; Fasci, E; Rohart, F

    2013-01-21

    Complementary tests of the partially correlated speed-dependent Keilson-Storer (pCSDKS) model for the shape of isolated transition of pure water vapor [N. H. Ngo et al., J. Chem. Phys. 136, 154310 (2012)] are made using new measurements. The latter have been recorded using a high sensitivity cavity ring down spectrometer, for seven self-broadened H(2)O lines in the 1.6 ?m region at room temperature and for pressures from 0.5 to 15 Torr. Furthermore, the H(2) (18)O spectra of [M. D. De Vizia et al., Phys. Rev. A 83, 052506 (2011)] in the 1.38 ?m region, measured at 273.15 K and for pressures from 0.3 to 3.75 Torr have also been used for comparison with the model. Recall that the pCSDKS model takes into account the collision-induced velocity changes, the speed dependences of the broadening and shifting coefficients as well as the partial correlation between velocity and rotational-state changes. All parameters of the model have been fixed at values previously determined, except for a scaling factor applied to the input speed-dependent line broadening. Comparisons between predictions and experiments have been made by looking at the results obtained when fitting the calculated and measured spectra by Voigt profiles. The good agreement obtained for all considered lines, at different temperature and pressure conditions, confirms the consistency and the robustness of the model. Limiting cases of the model have been then derived, showing the influence of different contributions to the line shape. PMID:23343271

  15. Thin film devices used as oxygen partial pressure sensors

    NASA Technical Reports Server (NTRS)

    Canady, K. S.; Wortman, J. J.

    1970-01-01

    Electrical conductivity of zinc oxide films to be used in an oxygen partial pressure sensor is measured as a function of temperature, oxygen partial pressure, and other atmospheric constituents. Time response following partial pressure changes is studied as a function of temperature and environmental changes.

  16. High pressure stability of hydrazine (H2N-NH2) : Implications for energetic hydronitrogen compounds

    NASA Astrophysics Data System (ADS)

    Chellappa, Raja; Dattelbaum, Dana; Liu, Zhenxian

    2013-06-01

    Hydrazine (H2N-NH2) is a metastable, high energy density molecule that is relevant to planetary physics and plays an important role in industrial synthesis and propellant applications. Theoretical calculations have predicted the existence of ``hydronitrogen'' extended solids that hold great potential as a high energy density material (HEDM). Exploring the high pressure-temperature (P - T) stability of hydrazine will provide crucial insights into hydrogen bonded -N-H networks under these conditions. Further, related simple molecules such as CH4, NH3, CO, and CO2 have been shown to have rich high P - T phase diagrams, often forming extended amorphous solids. Here, we report the first comprehensive study of hydrazine to 50 GPa at ambient temperature, using both in situ vibrational spectroscopy and synchrotron x-ray diffraction to elucidate structural changes driven by compression. Liquid hydrazine solidifies into a monoclinic structure at 0.5 GPa that is isomorphous with the low- T solid phase. Further compression drives structural re-ordering and at least 2 phase transformations to 20 GPa, with complex anisotropic hydrogen bonding interactions. Surprisingly, no evidence for the formation of extended amorphous solids was observed to the highest pressure studied.

  17. Partially reduced iridium oxide clusters dispersed on titania as efficient catalysts for facile synthesis of dimethylformamide from CO2, H2 and dimethylamine.

    PubMed

    Bi, Qing-Yuan; Lin, Jian-Dong; Liu, Yong-Mei; Xie, Song-Hai; He, He-Yong; Cao, Yong

    2014-08-21

    A novel bifunctional catalyst based on partially reduced iridium oxide supported on TiO2 was found to be exceedingly efficient for the organic-solvent-free synthesis of dimethylformamide from CO2, H2 and dimethylamine. PMID:24990297

  18. Dehydrating a granulite: The behavior of H2O and CO2 during high-pressure metamorphism

    NASA Astrophysics Data System (ADS)

    Van Lankvelt, A.; Seaman, S. J.; Williams, M. L.

    2013-12-01

    The Athabasca Granulite Terrane, in northern Saskatchewan, consists of isobaric assemblages of high-pressure, high-temperature metamorphic rocks. Within the terrane, is a suite of 2.6 Ga granitoids that were probably intruded into the deep crust and subsequently metamorphosed at granulite facies (emplacement at >900 C and 1.0 GPa and metamorphism at 750 C and 1.0 GPa; Williams et al., 2000). The original mineral assemblage within these granites includes alkali feldspar + plagioclase + quartz orthopyroxene. Several granulite facies metamorphic reactions, including what is locally termed the 'Mary' reaction (orthopyroxene + Ca-plagioclase = garnet + clinopyroxene ( hornblende in more hydrous areas) + Na-plagioclase + quartz), are commonly preserved. Because the Mary reaction typically involves anhydrous mineral phases, studying the distribution of structural H2O and CO2 in the minerals involved in this reaction should reveal the partitioning behavior of these volatile phases during high-grade metamorphism. We used a Bruker Vertex 70 Fourier transform infrared spectrometer with a focal plane array detector to map volatile concentrations in several samples preserving the Mary reaction. Most of our samples contain pyroxene crystals that were partially hydrated to amphibole, but the other mineral phases involved in the reaction are generally pristine. Preliminary results show that CO2 and H2O behave differently during metamorphism. CO2 concentrations are generally low and homogenous within single mineral grains. However, maps of CO2 concentrations indicate that there is slightly more structural CO2 in product minerals (mostly in garnet, but also, in some samples, in quartz and Na-plagioclase mantles on Ca-rich plagioclase) than in reactant minerals. Water, however, is preferentially concentrated along grain boundaries and is zoned in primary, Ca-rich plagioclase and alkali feldspar, both of which commonly contain H2O-poor cores and H2O-rich rims. This zoning could arise from water migrating into or out of feldspars in response to deformation or could be a relict of igneous zoning. Although structural water is mostly absent from garnet crystals and Na-rich overgrowths on plagioclase, it appears to be concentrated in neoblastic quartz associated with garnet. In general, it appears that CO2 can partition into the products of granulite-facies metamorphic reactions (garnet, Na-rich plagioclase, and quartz), while structural water is either lost from reactant mineral phases or relegated to metamorphic quartz. Williams, M. L., Melis, E. A., Kopf, C. F. & Hammer, S. (2000). Microstructural tectonometamorphic processes and the development of gneissic layering: a mechanism for metamorphic segregation. J. Metamorphic Geol. 18, 41-57.

  19. 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.

  20. 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.

  1. 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

    2015-12-01

    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.

  2. 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.

  3. High temperatures and high pressures Brillouin scattering studies of liquid H2O+CO2 mixtures

    NASA Astrophysics Data System (ADS)

    Qin, Junfeng; Li, Min; Li, Jun; Chen, Rongyan; Duan, Zhenhao; Zhou, Qiang; Li, Fangfei; Cui, Qiliang

    2010-10-01

    The Brillouin scattering spectroscopy studies have been conducted in a diamond anvil cell for a liquid mixtures composed of 95 mol % H2O and 5 mol % CO2 under high temperatures and pressures. The sound velocity, refractive index, density, and adiabatic bulk modulus of the H2O+CO2 mixtures were determined under pressures up to the freezing point at 293, 453, and 575 K. It is found from the experiment that sound velocities of the liquid mixture are substantially lower than those of pure water at 575 K, but not at lower temperatures. We presented an empirical relation of the density in terms of pressure and temperature. Our results show that liquid H2O+CO2 mixtures are more compressible than water obtained from an existing equation of state of at 453 and 575 K.

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

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

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

  5. 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.

  6. 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.

  7. Development of pressurized coal partial combustor

    SciTech Connect

    Suda, Masamitsu; Setoguchi, Kazuhide; Hara, Masahiro

    1998-12-31

    Global environmental issues, such as global warming and acid rain, have been recently the focus of much attention on the international scene. Along with various continuing efforts to reduce sulfur oxide and nitrogen oxide emissions, there has been an urgent need to develop technology to reduce emissions of CO{sub 2}, one of the principal materials responsible for global warming. The integrated gasification combined cycle (IGCC), an environmental friendly power generation system of high thermal efficiency, is being developed via various approaches around the world. Kawasaki Heavy Industries, Ltd. has conducted R and D on a Coal Partial Combustor (hereinafter referred to as CPC) as a gasifier since 1984, jointly with the Center for Coal Utilization, Japan. Since 1994, Chubu Electric Power Co., Inc. and Electric Power Development Co., Ltd have been cooperating. Through this activity, a structure of the CPC has been established, and the influences of operating parameters on performance have been clarified. The purpose of the present study is to apply these developed CPC techniques to a Pressurized CPC (hereinafter referred to as PCPC) as a gasifier for the IGCC system. For the present study, the authors conducted systematic experiments on the air-blown process with a two stage dry feed system, using a 7 t/d-coal element test facility and a 25 t/d-coal pilot scale plant, clarified the influence of coal feed ratio, of oxygen enrichment, and of coal types on coal gasification performance. This paper describes conceptual structure of the PCPC, the test results of a 7 t/d-coal PCPC element test facility, and also some information of a 25 t/d-coal PCPC pilot plant which is now under the start-up operation phase.

  8. Development of pressurized coal partial combustor

    SciTech Connect

    Yoshino, Y.; Suda, Y.; Setoguchi, K.; Hara, M.

    1999-07-01

    As an estimated amount of coal deposits is large and coal is widely distributed in the world, supply of coal is stable. It is considered that coal will be one of the most important fuels for power generation in the future. However, the global warming problem has recently become a subject of the world, and one of the principal substances responsible for global warming is CO{sub 2} which coal exhausts. To develop a technology for reducing emissions of CO{sub 2} is an urgent need. 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. Kawasaki Heavy Industries Ltd. has conducted R and D on a Coal Partial Combustor (hereinafter referred to as CPC) as a gasifier since 1984, jointly with Center for Coal Utilization, Japan. Since 1994, Chubu Electric Power Co., Inc. and Electric Power Development Co., Ltd. have been cooperating. Through this activity, a structure of the CPC has been established, and influences of operating parameters on performance have been clarified. The purpose of the present study is to develop a Pressurized CPC (hereinafter referred to as PCPC) as a gasifier for the IGCC system by applying these techniques. For the present study, the authors had conducted systematic experiments using a 7 t/d bench scale test facility. After that they had constructed a 25 t/d pilot plant in the yard of Wakamatsu coal utilization research center, Electric Power Development Co., Ltd., in Japan in November 1997, and have conducted various tests, such as air-blown two-stage gasification, oxygen-enriched gasification, the expansion of coal varieties. This paper describes conceptual structure of the PCPC and the test results of a 25 t/d pilot plant.

  9. Hydrogen CARS thermometry in a high-pressure H2-air flame. Test of H2 temperature accuracy and influence of line width by comparison with N2 CARS as reference

    NASA Astrophysics Data System (ADS)

    Hussong, J.; Lckerath, R.; Stricker, W.; Bruet, X.; Joubert, P.; Bonamy, J.; Robert, D.

    This work describes a further step towards the determination of the temperature accuracy of H2 Q-branch CARS (Coherent Anti-Stokes Raman Scattering) at high pressure with regard to the influence of the H2 line widths. In laminar steady H2/air flames in the pressure range 1-15 bar and at fuel-rich conditions with stoichiometries between two and four, quasi-simultaneous temperature measurements were performed with H2 and N2 CARS. The temperature values deduced from H2 CARS are in good agreement with the reference temperature from N2 CARS. The influence of different line-width contributions on the accuracy of H2 Q-branch thermometry was investigated in detail.

  10. Raman spectroscopic quantitative study of NaCl-CaCl2-H2O system at high temperatures and pressures.

    PubMed

    Li, Jing; Mao, Shi-De; Zheng, Hai-Fei

    2014-07-01

    Raman spectra features of the ternary system NaCl-CaCl2-H2O under high temperatures and high pressures were systematically studied in the present work by using hydrothermal diamond anvil cell (HDAC) and Raman shifts of quartz to determine pressures, and it has been obtained for the quantitative relationship between Raman shifts of the O-H stretching band of water, mass fractions of solutes and pressures was obtained. The mass fractions of salts, where salinity of NaCl equal to that of CaCl2, are 4.0 mass %, 8.0 mass %, and 12.0 mass %, respectively. Experimental results indicate that the standardized Raman frequency shift differences of the O-H stretching vibration (deltav(O0H)) rise with the increasing temperatures when the mass fractions of salts and pressures of the NaCl-CaCl2-H2O system remain constant. deltav(O-H) increases with the increase in mass fractions of salts in the system when the temperatures and pressures are constant. Linear relationship between deltav(O-H) and pressure with similar slopes can be found for the NaCl-CaCl2-H2O system with different salinities. The quantitative relationship between deltav(O-H), temperature (T), pressure (P), and mass fraction of solute (M) is P = -31.892 deltav(O-H) + 10.131T + 222.816M - 3 183.567, where the valid PTM range of the equation is 200 MPa < or = P < or = 1 700 MPa, 273 K < or = T < or = 539 K and M < or = 12 mass %. The equation can be used as a geobarometer in the studies of fluid inclusions of NaCl-CaCl2-H2O system with equal salinities. The method, as a direct geological detecting technique, has a potential application value. PMID:25269273

  11. A theoretical study of MgH2 ambient and high-pressure phases using NQCC parameters

    NASA Astrophysics Data System (ADS)

    Rafiee, Marjan A.

    2014-12-01

    Quadrupolar parameters of nuclei can be used as a tool to understand the electronic structure of the compounds. Magnesium hydride (MgH2) is a potential hydrogen storage material due to its outstanding hydrogen capacity, however, its high thermodynamic stability is unfavorable for dehydrogenation processes. Understanding the bonding nature of Mg and H is essential for improving its dehydrogenation performance. In this work the charge density distribution in MgH2 is studied. For this purpose, using calculated NQCCs of hydrogen atoms, the electronic structure of ?-MgH2 with several high pressure forms of MgH2 were compared. The results show that in the high pressure phases (?, ?, and ?) some hydrogens have very small NQCC and therefore these hydrogens form weaker bond with Mg. In other words, easier condition for dehydrogenation in pressure-induced forms is expected. The electric field gradient (EFG) at the site of quadrupolar nuclei were calculated to obtain NQCC parameters using Gaussian 03 at B3LYP/6-31G level of theory. The selected level and basis set give the rather acceptable qualitative NQCCs of hydrogen atoms.

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

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

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

  13. Saturation vapor pressure and critical constants of H2O, D2O, T2O, and their isotopic mixtures

    NASA Astrophysics Data System (ADS)

    Matsunaga, N.; Nagashima, A.

    1987-11-01

    Reliable data on the vapor pressure and critical constants of H2O isotopes and their isotopic mixtures are required for the generation of thermophysical properties data over a wide range of temperatures and pressures. In this study, vapor pressure equations for D2O and T2O have been developed based on the latest experimental and theoretical information. Considering the similarity among H2O isotopes, the functional form of the Saul and Wagner equation, fully proven for H2O, has been employed. The present equation for D2O shows a lower trend by up to 0.09% than the widely used Hill and MacMillan equation at temperatures below 150C. For the vapor pressure of the isotopic mixtures, the available experimental data have been examined for the validity of Raoult's law. Then it has been shown that the critical temperature and the critical pressure of the isotopic mixture can also be predicted as simple mole-fraction average values.

  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. On the Stark effect in open shell complexes exhibiting partially quenched electronic angular momentum: Infrared laser Stark spectroscopy of OH-C2H2, OH-C2H4, and OH-H2O

    NASA Astrophysics Data System (ADS)

    Moradi, Christopher P.; Douberly, Gary E.

    2015-08-01

    The Stark effect is considered for polyatomic open shell complexes that exhibit partially quenched electronic angular momentum. Matrix elements of the Stark Hamiltonian represented in a parity conserving Hund's case (a) basis are derived for the most general case, in which the permanent dipole moment has projections on all three inertial axes of the system. Transition intensities are derived, again for the most general case, in which the laser polarization has projections onto axes parallel and perpendicular to the Stark electric field, and the transition dipole moment vector is projected onto all three inertial axes in the molecular frame. Simulations derived from this model are compared to experimental rovibrational Stark spectra of OH-C2H2, OH-C2H4, and OH-H2O complexes formed in helium nanodroplets.

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

    PubMed Central

    2013-01-01

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

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

    PubMed Central

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

    2015-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

    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.

  19. 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 ?m) 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 5726 ppm (by wt.) at 5 GPa to 25460 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 partial melting does not occur at these depths for H2O concentrations (50-200 ppm) typical of the convecting upper mantle sampled by mid-ocean ridge basalts.

  20. 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.

  1. 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.

  2. Progress of serpentinization in olivine-H2O system at 250 C and vapor-saturated pressure

    NASA Astrophysics Data System (ADS)

    Okamoto, A.; Ogasawara, Y.; Tsuchiya, N.

    2011-12-01

    Fluids play a crucial role in global-scale mass transfer, metamorphism, volcanism, and seismic processes in subduction zones. Serpentine minerals, which are produced by interaction between ultramafic rocks and fluids, contain about 13% water and are the greatest carrier of H2O into the deep interior of Earth. Therefore, the volume and distribution of hydrated oceanic mantle are of special interest in evaluating the effects of fluids on subduction zone processes. We conducted hydrothermal experiments in olivine (Ol; Fo91)-H2O and orthopyroxenite (Opx; composed of 95% of orthopyroxene, En66)-H2O systems under conditions of 250 C and vapor-saturated pressure (Psat) to examine the temporal evolution of the solution chemistry and products in runs of up to 1008 h in duration. The maximal degree of hydration (i.e., H2O content in the solid sample) in the Ol-H2O experiments (3.6 wt.%) was much higher than that in the Opx-H2O experiments (0.4 wt.%). In the Ol-H2O experiments, Mg and Si in solution showed an initial increase (stage 1) before decreasing (stage 2) and finally attaining a steady state after 504 h (stage 3). Following a drop in silica activity toward the level of brucite stability filed, the products also changed from serpentine + magnetite (stages 1 and 2) to serpentine + brucite + magnetite (stage 3). Serpentine minerals also changed from lizardite (stages 1 and 2) to lizardite + chrysotile (stage 3). The textures observed in this study were similar to those observed in partly serpentinized dunites. In the Opx-H2O experiments, chlorite formed after orthopyroxene grains, which differs from the formation of talc and serpentine after orthopyroxene (bastite), as observed in natural hydrated harzburgites. The Opx-H2O system maintained 10-103 times higher silica activity than Ol-H2O system, suggesting that brucite does not form after olivine during hydration of peridotites when the Ol-H2O system is linked to the Opx-H2O system. The progress of hydration reactions is affected by mechanical properties of host rocks. The hydration reactions observed in this study produced hierarchical fractures in the reactants, which became filled with reaction products, similar to mesh textures after olivine in natural peridotites. This reaction-induced fracturing produced new reaction surfaces and fluid pathways that enhanced the hydration reactions. The overall reaction producing serpentine+brucite in the Ol-H2O experiments showed the large volume expansion (V/V0 = 1.38 at stage 3), whereas that producing only serpentine proceeded with near constant volume (V/V0 = 1.09 at stage 1). The volume expansion is more difficult to occur in the oceanic lithosphere than in our experiments during serpentinization. Thus, in the case that volume expansion is prevented at reaction sites, one of the following outcomes occurs: (1) the hydration reaction stops until new fractures form, or (2) the reaction proceeds with low volume expansion (absence of brucite) by removing Mg from the system. These two outcomes would produce contrasting distributions or extent of hydration in oceanic lithosphere.

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

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

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

  4. Sound velocities of hexagonal close-packed H2 and He under pressure

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    Bulk, shear, and compressional aggregate sound velocities of hydrogen and helium in the close-packed hexagonal structure are calculated over a wide pressure range using two complementary approaches: semiempirical lattice dynamics based on the many-body intermolecular potentials and density-functional theory in the generalized gradient approximation. The sound velocities are used to calculate the pressure dependence of the Debye temperature. The comparisons between experiment and first-principles and semiempirical calculations provide constraints on the density dependence of intermolecular interactions in the zero-temperature limit.

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

    SciTech Connect

    Chung, M.; et al.

    2013-10-01

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

  6. In Situ High-Pressure X-ray Diffraction Study of H2O Ice VII

    SciTech Connect

    Somayazulu,M.; Shu, J.; Zha, C.; Goncharov, A.; Tschauner, O.; Mao, H.; Hemley, R.

    2008-01-01

    Ice VII was examined over the entire range of its pressure stability by a suite of x-ray diffraction techniques in order to understand a number of unexplained characteristics of its high-pressure behavior. Axial and radial polycrystalline (diamond anvil cell) x-ray diffraction measurements reveal a splitting of diffraction lines accompanied by changes in sample texture and elastic anisotropy. In situ laser heating of polycrystalline samples resulted in the sharpening of diffraction peaks due to release of nonhydrostatic stresses but did not remove the splitting. Radial diffraction measurements indicate changes in strength of the material at this pressure. Taken together, these observations provide evidence for a transition in ice VII near 14 GPa involving changes in the character of the proton order/disorder. The results are consistent with previous reports of changes in phase boundaries and equation of state at this pressure. The transition can be interpreted as ferroelastic with the appearance of spontaneous strain that vanishes at the hydrogen bond symmetrization transition near 60 GPa.

  7. Pressure-induced transformations in LiCl-H2O at 77 K.

    PubMed

    Ruiz, G N; Bove, L E; Corti, H R; Loerting, T

    2014-09-14

    A systematic study of the properties of high-density amorphous ice (HDA) in the presence of increasing amounts of salt is missing, especially because it is challenging to avoid ice crystallization upon cooling the pressurized liquid. In order to be able to study HDA also in the presence of small amounts of salt, we have investigated the transformation behaviour of quenched aqueous LiCl solutions (mole fraction x < 0.25) upon pressurization in a piston-cylinder setup at 77 K. The sample properties were characterized by in situ dilatometry under high pressure conditions and after recovery by ex situ powder X-ray diffraction (XRD) and differential scanning calorimetry (DSC) at ambient pressure. Two regimes can be identified, with a rather sharp switch at about x = 0.12. At x < 0.12 the samples show the phenomenology also known for pure water samples. They are composed mainly of hexagonal ice (Ih) and experience pressure-induced amorphization to HDA at P > 1 GPa. The observed densification is consistent with the idea that a freeze concentrated LiCl solution of x = 0.14 (R = 6) segregates, which transforms to the glassy state upon cooling, and that the densification is only due to the Ih ? HDA transition. Also the XRD patterns and DSC scans are almost unaffected by the presence of the segregated glassy LiCl solution. Upon heating at ambient pressure HDA experiences the polyamorphic transition to low-density amorphous ice (LDA) at ?120 K, even at x ? 0.10. Based on the latent heat evolved in the transition we suggest that almost all water in the sample transforms to an LDA-like state, even the water in the vicinity of the ions. The glassy LiCl solution acts as a spectator that does not shift the transformation temperature significantly and experiences a glass-to-liquid transition at ?140 K prior to the crystallization to cubic ice. By contrast, at x > 0.12 the phenomenology completely changes and is now dominated by the salt. Hexagonal ice no longer forms upon quenching the LiCl solution, but instead LDA forms. A broad pressure-induced transformation at >0.6 GPa can be attributed to the densification of LDA, the glassy LiCl solution and/or glassy hydrates. PMID:25072395

  8. CVD growth of large-area graphene over Cu foil by atmospheric pressure and its application in H2 evolution

    NASA Astrophysics Data System (ADS)

    Ye, Shu; Ullah, Kefayat; Zhu, Lei; Ali, Asghar; Jang, Won Kweon; Oh, Won-Chun

    2015-08-01

    This study reports that the atmospheric pressure chemical vapor deposition (CVD) growth of large area graphene (LAG) over a Cu foil. The obtained large area graphene was further decorated with TiO2 nanoparticles via ultrasonic method. The surface structure, crystal phase, and elemental identification of these obtained LAG/TiO2 composite were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray (EDX) analysis, and Raman spectra. The photocatalytic H2 evolution result illustrates Cu-LAG/TiO2 has been found to be a potential catalyst for conversion of solar energy to clean hydrogen energy under visible light-driven despite that the H2 evolution activity is not high enough in this stage.

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

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

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

  10. Partial molar volumes and viscosities of aqueous hippuric acid solutions containing LiCl and MnCl2 4H2O at 303.15 K

    NASA Astrophysics Data System (ADS)

    Deosarkar, S. D.; Tawde, P. D.; Zinjade, A. B.; Shaikh, A. I.

    2015-09-01

    Density (?) and viscosity (?) of aqueous hippuric acid (HA) solutions containing LiCl and MnCl2 4H2O have been studied at 303.15 K in order to understand volumetric and viscometric behavior of these systems. Apparent molar volume (?v) of salts were calculated from density data and fitted to Massons relation and partial molar volumes (?{v/0}) at infinite dilution were determined. Relative viscosity data has been used to determine viscosity A and B coefficients using Jones-Dole relation. Partial molar volume and viscosity coefficients have been discussed in terms of ion-solvent interactions and overall structural fittings in solution.

  11. Xe(H2)7 - A hydrogen-rich van der Waal compound stable to multimegabar pressures

    NASA Astrophysics Data System (ADS)

    Somayazulu, Maddury; Dera, Przemyslaw; Gramsch, Stephen; Hemley, Russell

    2010-03-01

    We have recently reported the occurrence and stability of a sequence of hydrogen-rich compounds of Xe and H2 [1]. The first solid phase that forms at 4 GPa changes stoichiometry at discrete pressures culminating in a solid whose stoichiometry is determined to be Xe(H2)7. The Raman and IR spectra of this solid display remarkable complexity that can be explained in terms of a tripled hydrogen lattice. We report the details of this spectroscopy that have been measured to a maximum pressure of 255 GPa. Single crystal diffraction data of very high quality was collected at the HPCAT beamline 16-BM-D at the APS. The low pressure data was used to identify not only the structural details but also evaluate the changes in the electron density of xenon indicative of interaction between the xenon dimers and the surrounding hydrogen molecules. Acknowledgements: This work was supported by DOE-BES (DE-FG02-06ER46280), NSF-DMR (DMR-0805056) and DOE-NNSA(CDAC). A.P.S. is supported by DOE-BES under contract DE-AC02-06CH11357. [4pt] [1] Somayazulu et. al Nature Chemistry (in press)

  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. 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.

  14. Vibrational dynamics, intermolecular interactions, and compound formation in GeH4H2 under pressure

    SciTech Connect

    Strobel, Timothy A.; Chen, Xiao-Jia; Somayazulu, Maddury; Hemley, Russell J.

    2010-01-01

    Optical microscopy, spectroscopic and x-ray diffraction studies at high-pressure are used to investigate intermolecular interactions in binary mixtures of germane (GeH{sub 4} )+hydrogen (H{sub 2} ) . The measurements reveal the formation of a new molecular compound, with the approximate stoichiometry GeH{sub 4} (H{sub 2} ){sub 2} , when the constituents are compressed above 7.5 GPa. Raman and infrared spectroscopic measurements show multiple H{sub 2} vibrons substantially softened from bulk solid hydrogen. With increasing pressure, the frequencies of several Raman and infrared H{sub 2} vibrons decrease, indicating anomalous attractive interaction for closed-shell, nonpolar molecules. Synchrotron powder x-ray diffraction measurements show that the compound has a structure based on face-centered cubic (fcc) with GeH{sub 4} molecules occupying fcc sites and H{sub 2} molecules likely distributed between O{sub h} and T{sub d} sites. Above ca. 17 GPa, GeH{sub 4} molecules in the compound become unstable with respect to decomposition products (Ge+H{sub 2} ) , however, the compound can be preserved metastably to ca. 27 GPa for time-scales of the order of several hours.

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

    SciTech Connect

    Pint, Bruce A

    2012-08-01

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

  16. 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.

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

    NASA Astrophysics Data System (ADS)

    Feistel, Rainer; Wagner, Wolfgang

    2007-01-01

    The sublimation of water in the region of extremely low pressures and temperatures meets increasing interest for the exploration of icy cosmic bodies. At temperatures below 130 K, the shape of the sublimation curve of H 2O is not known; neither experimental data nor theoretical treatments exist for this region. Based upon theoretical upper and lower bounds for the heat capacity of water vapor in this range, a narrow region in the pressure-temperature diagram is identified which must necessarily enclose the sublimation curve down to virtually any lower pressures and temperatures. Within this region, an approximate sublimation curve is computed from the 2006 Gibbs potential of ice Ih, using available heat capacity data points of water vapor between 10 and 130 K. The theoretical zero-point limiting law of the sublimation pressure is derived. Valid between 20 and 273.16 K, correlation equations for the sublimation enthalpy and the sublimation pressure are fitted to the computed data. All quantities are expressed in the 1990 temperature scale ITS-90. Under cosmic conditions, our results suggest that the sublimation of ice is unlikely below 50 K and impossible below 23 K.

  18. Microwave measurements of water vapor partial pressure at high temperatures

    SciTech Connect

    Latorre, V.R.

    1991-02-01

    One of the desired parameters in the Yucca Mountain Project is the capillary pressure of the rock comprising the repository. This parameter is related to the partial pressure of water vapor in the air when in equilibrium with the rock mass. Although there are a number of devices that will measure the relative humidity (directly related to the water vapor partial pressure), they generally will fail at temperatures on the order of 150C. Since thee author has observed borehole temperatures considerably in excess of this value in G-Tunnel at the Nevada Test Site (NTS), a different scheme is required to obtain the desired partial pressure data at higher temperatures. This chapter presents a microwave technique that has been developed to measure water vapor partial pressure in boreholes at temperatures up to 250C. The heart of the system is a microwave coaxial resonator whose resonant frequency is inversely proportional to the square root of the real part of the complex dielectric constant of the medium (air) filling the resonator. The real part of the dielectric constant of air is approximately equal to the square of the refractive index which, in turn, is proportional to the partial pressure of the water vapor in the air. Thus, a microwave resonant cavity can be used to measure changes in the relative humidity or partial pressure of water vapor in the air. Since this type of device is constructed of metal, it is able to withstand very high temperatures. The actual limitation is the temperature limit of the dielectric material in the cable connecting the resonator to its driving and monitoring equipment-an automatic network analyzer in our case. In the following sections, the theory of operation, design, construction, calibration and installation of the microwave diagnostics system is presented. The results and conclusions are also presented, along with suggestions for future work.

  19. 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.

  20. 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.

  1. 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.

  2. 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#12;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#11;usivity shrinking-core model and models for di#11;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#12;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#12;dation of calcined limestones and dolomites. The incentive for carrying out sul#12;dation experiments in the presence of oxygen was provided by the observation that some sul#12;dation experiments that were conducted as oxygen was accidentally leaking into the feed mixture of the reactor showed completely di#11;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 solids (Greer limestone and Iceland spar) that we employed in our previous experiments were used in the sulfidation.

  3. H2 CARS thermometry in a fuel-rich, premixed, laminar CH4/air flame in the pressure range between 5 and 40 bar

    NASA Astrophysics Data System (ADS)

    Bergmann, V.; Stricker, W.

    1995-07-01

    To establish H2 CARS thermometry at high pressure, accumulated H2 Q-branch CARS spectra were recorded in the exhaust of a fuel-rich CH4/air flame at pressures between 5 and 40 bar. Temperatures were deduced by fitting theoretical spectra to experimental data points. The Energy-Corrected Sudden (ECS) scaling law was employed to set up an empirical model for the calculation of H2 linewidths in high-pressure hydrocarbon flames with H2 as a minority species. Experimental H2 CARS spectra could be simulated very accurately with this model. The evaluated temperatures agreed well with reference temperatures obtained by spontaneous rotational Raman scattering of N2.

  4. New high-pressure van der Waals compound Kr(H2)4 discovered in the krypton-hydrogen binary system

    NASA Astrophysics Data System (ADS)

    Kleppe, Annette K.; Amboage, Mnica; Jephcoat, Andrew P.

    2014-05-01

    The application of pressure to materials can reveal unexpected chemistry. Under compression, noble gases form stoichiometric van der Waals (vdW) compounds with closed-shell molecules such as hydrogen, leading to a variety of unusual structures. We have synthesised Kr(H2)4 for the first time in a diamond-anvil high-pressure cell at pressures >=5.3 GPa and characterised its structural and vibrational properties to above 50 GPa. The structure of Kr(H2)4, as solved by single-crystal synchrotron X-ray diffraction, is face-centred cubic (fcc) with krypton atoms forming isolated octahedra at fcc sites. Rotationally disordered H2 molecules occupy four different, interstitial sites, consistent with the observation of four Raman active H2 vibrons. The discovery of Kr(H2)4 expands the range of pressure-stabilised, hydrogen-rich vdW solids, and, in comparison with the two known rare-gas-H2 compounds, Xe(H2)8 and Ar(H2)2, reveals an increasing change in hydrogen molecular packing with increasing rare gas atomic number.

  5. A Self-consistent Estimation Method of Melting Condition Based on Major Elements in Volcanic Rocks: Degree of Melting, Pressure, H2O Content and Melting Temperature

    NASA Astrophysics Data System (ADS)

    Ogitsu, I.; Ozawa, K.

    2008-12-01

    Estimation of magma generation conditions, including degree of partial melting, melting pressure, H2O content, and melting temperature, is a key step to better understand the magmatism of various tectonic settings including mid ocean ridges, hot spots, and subduction zones. There are many studies that estimated magma generation conditions on the basis of chemical compositions of volcanic rocks, but the most of them are neither comprehensive nor self-consistent in that a part of melting conditions was estimated or assumed to estimate the rest. Moreover, they are mostly applicable only to a specific tectonic setting and are not universal. Chemical compositions of volcanic rocks are results of integration of various magmatic processes that take place in the upper mantle and the crust. Therefore, estimation of melting condition in the mantle is inevitably coupled with estimation of magma evolution during fractional crystallization in the crust. In other words, conditions for melting and fractional crystallization must be determined all together by dealing with all the relevant magmatic processes. Based on this idea, a rigorous least-squares approach to estimate melting conditions in the upper mantle from major element composition of a single volcanic rock, in which crystallization and melting parameters are simultaneously and consistently determined, is proposed. Melting in the mantle was modeled based on the batch melting experiments of KLB-1 peridotite (Takahashi, 1986; Hirose and Kushiro, 1993), and fractional crystallization in the crust was modeled by MELTS program (Ghiorso and Sack, 1995). Unknown parameters are degree of partial melting, melting pressure, and H2O content for mantle melting, and pressure and final temperature of crystallization for fractional crystallization in the crust. The melting temperature is estimated from the relationships among degree of melting, melting pressure, and H2O content. In optimization of these parameters, not only olivine but also plagioclase, clinopyroxene, and orthopyroxene are considered as fractionated phases. This approach is applicable to more differentiated rocks, which are not suitable for olivine addition methods widely used in estimation of primary magmas. Because the amounts and compositions of fractionated phases and degree of partial meting are determined without using trace element data, we can estimate trace element abundances in the source mantle from those of a volcanic rock basically without any assumptions. This method is very general and applicable to wider compositional range of volcanic rocks irrespective of their tectonic settings. Application of this method to several sets of multiple rock samples from a volcano gave consistent melting conditions, substantiating robustness of this approach. If this method is applied to volcanoes distributed in a volcanic region, it is possible to investigate two- or three-dimensional variation of melting conditions, which are strong constraints to understand melting mechanisms, thermal structure, and material transport in the mantle. This method was applied to a frontal volcano of the Izu arc, Aogashima Volcano, and volcanoes distributed in its back arc region in order to understand the across arc variation of magma generation conditions. The melting conditions of the Izu arc shows increases in melting temperature and melting pressure toward the volcanic front from the back-arc side.

  6. Quartz solubility in H 2O-NaCl and H 2O-CO 2 solutions at deep crust-upper mantle pressures and temperatures: 2-15 kbar and 500-900C

    NASA Astrophysics Data System (ADS)

    Newton, Robert C.; Manning, Craig E.

    2000-09-01

    The solubility of quartz in H 2O-NaCl solutions was measured at 2, 4.35, 10 and 15 kbar and 500-900C, and at NaCl concentrations up to halite saturation, usually greater than 75 wt.%. Quartz solubility was also measured in CO 2-H 2O solutions at 10 kbar and 800C. Solubilities were determined by weight loss of ground and polished quartz crystal fragments which were equilibrated with solutions in Pt envelopes for one to four days and then rapidly quenched. Experiments at 2 kbar were made with externally heated cold-seal apparatus; higher pressure experiments were done in a 3/4 inch-diameter piston-cylinder apparatus with NaCl pressure medium and graphite heater sleeve. Equilibrium solubility was demonstrated in several ways, and the present results reproduce those of Manning (1994) in pure H 2O at selected conditions. At pressures below 4 kbar, NaCl in solution causes an initial "salting-in", or quartz solubility enhancement, which, at 2 kbar and 700C, persists to concentrations as great as 70 wt.% NaCl before quartz solubility again becomes as low as in pure H 2O. The maximum solubility occurs at X(H 2O) 0.9 and is 50% higher than in pure H 2O. At 4.35 kbar and 700C, however, quartz solubility decreases slightly with initial NaCl concentration, and then begins to drop rapidly with increasing salinity beyond 45 wt.% NaCl. At 10 and 15 kbar there is a steep initial decline in silica molality at all temperatures in the range 500-900C, leveling off at higher NaCl concentrations. There is thus a pronounced change in solution behavior with pressure, from initial salting-in below 4 kbar to monotonic salting-out above 5 kbar. This pressure-induced change in silica solubility parallels the sharp decrease in H 2O activity in NaCl solutions in the same pressure range found by Aranovich and Newton (1996). Therefore, the pressure-induced change in silica solubility is inferred to be a consequence of the dissociation of the neutral NaCl o complex to Na + and Cl - as solution densities increase above about 0.7 gm/cm 3. At very high salinities, approaching halite saturation, the isobars of quartz solubility as a function of NaCl mole fraction at 700C converge, indicating that, for hypersaline fluids having the constitution of molten salts, pressure has only a minor effect on quartz solubility. Quartz solubility at 10 kbar shows exponential decline with increasing salinity at all temperatures in the range 500C to 900C. This is the expected behavior of a two-component solvent, in which quartz is sparingly soluble in one component. At 10 kbar, isotherms of log silica molality versus H 2O mole fraction are linear between X(H 2O) = 1.0 and 0.5, but begin to curve to lower values at 900C, where high salinities are attained before halite saturation occurs. This behavior implies that the solute silica species is a hydrate that becomes progressively destabilized at low H 2O concentrations of the solvent. Plots of log silica molality versus log H 2O activity suggest that the solute species is neutral H 4SiO 4 with no additional solvated H 2O molecules, assuming no Na-SiO 2 complexing. The solubility of quartz in CO 2-H 2O fluids at 800C and 10 kbar is much smaller than in NaCl solutions at the same P,T and H 2O activity. Thermodynamic analysis suggests that the solute species in CO 2-H 2O fluids is H 4SiO 4 with 1-3 solvated H 2O molecules, which is similar to the solute behavior inferred by Walther and Orville (1983) in CO 2 and Ar solutions with H 2O at lower pressures. The present results show that SiO 2 will partition very strongly into a concentrated salt solution in deep crust-upper mantle metamorphic and metasomatic processes, in preference to a coexisting immiscible CO 2-rich fluid. The much greater permeability of silicate rocks for salt solutions than for CO 2-rich solutions, together with the much higher solubility of silica-rich phases in the former, could be an important factor in geochemical segregation processes involving rising and cooling fluids of magmatic or metamorphic origin.

  7. EQUILIBRIUM PARTIAL PRESSURE OF SULFUR DIOXIDE IN ALKALINE SCRUBBING PROCESSES

    EPA Science Inventory

    The report gives results of IERL-RTP in-house studies in which equilibrium partial pressure of SO2 was measured as a function of pH, temperature, and concentration of sulfur (IV) on various scrubber liquors. These studies were done for potassium-, sodium-, and citrate-based scrub...

  8. Calibration Of Partial-Pressure-Of-Oxygen Sensors

    NASA Technical Reports Server (NTRS)

    Yount, David W.; Heronimus, Kevin

    1995-01-01

    Report and analysis of, and discussion of improvements in, procedure for calibrating partial-pressure-of-oxygen sensors to satisfy Spacelab calibration requirements released. Sensors exhibit fast drift, which results in short calibration period not suitable for Spacelab. By assessing complete process of determining total drift range available, calibration procedure modified to eliminate errors and still satisfy requirements without compromising integrity of system.

  9. 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

  10. 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…

  11. Gradual crossover in molecular organization of stable liquid H2O at moderately high pressure and temperature

    NASA Astrophysics Data System (ADS)

    Koga, Yoshikata; Westh, Peter; Yoshida, Koh; Inaba, Akira; Nakazawa, Yasuhiro

    2014-09-01

    Using the literature raw data of the speed of sound and the specific volume, the isothermal compressibility, κT, a second derivative thermodynamic quantity of G, was evaluated for liquid H2O in the pressure range up to 350 MPa and the temperature to 50 °C. We then obtained its pressure derivative, dκT/dp, a third derivative numerically without using a fitting function to the κT data. On taking yet another p-derivative at a fixed T graphically without resorting to any fitting function, the resulting d2κT/dp2, a fourth derivative, showed a weak but clear step anomaly, with the onset of the step named point X and its end point Y. In analogy with another third and fourth derivative pair in binary aqueous solutions of glycerol, dαp/dxGly and d2αp/dxGly2, at 0.1 MPa (αp is the thermal expansivity and xGly the mole fraction of solute glycerol) in our recent publication [J. Solution Chem. 43, 663-674 (2014); DOI:10.1007/s10953-013-0122-7], we argue that there is a gradual crossover in the molecular organization of pure H2O from a low to a high p-regions starting at point X and ending at Y at a fixed T. The crossover takes place gradually spanning for about 100 MPa at a fixed temperature. The extrapolated temperature to zero p seems to be about 70 - 80 °C for points X and 90 - 110 °C for Y. Furthermore, the mid-points of X and Y seem to extrapolate to the triple point of liquid, ice Ih and ice III. Recalling that the zero xGly extrapolation of point X and Y for binary aqueous glycerol at 0.1 MPa gives about the same T values respectively, we suggest that at zero pressure the region below about 70 °C the hydrogen bond network is bond-percolated, while above about 90 °C there is no hydrogen bond network. Implication of these findings is discussed.

  12. Biological nitrogen fixation under primordial Martian partial pressures of dinitrogen

    NASA Technical Reports Server (NTRS)

    Klingler, J. M.; Mancinelli, R. L.; White, M. R.

    1989-01-01

    One of the most striking differences between the conditions on early Mars and earth was a low (18 mb) partial pressure of N2 (pN2) on early Mars, as opposed to 780 mb N2 on earth. To investigate the possibility of biological nitrogen fixation under conditions of early Mars, experiments were carried out on the growth of Azotobacter vinelandii and Azomonas agilis in nitrogen-free synthetic medium under various partial pressures of N2 (ranging from 780 to 0 mb). It was found that, although the biomass, cell number, and growth rate of these bacteria decreased with decreasing pN2 values below pN2 of 400 mb, both microorganisms were capable of growing at pN2 as low as 5 mb (but not at of below 1 mb), indicating that biological fixation of nitrogen could have occurred on primordial Mars.

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

    NASA Astrophysics Data System (ADS)

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

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

  14. Calibration-free sensor for pressure and H2O concentration in headspace of sterile vial using tunable diode laser absorption spectroscopy.

    PubMed

    Cai, Tingdong; Gao, Guangzhen; Liu, Ying

    2013-11-10

    Tunable diode laser absorption measurements of pressure and H2O concentration in the headspace of vials using a distributed-feedback (DFB) diode laser near 1.4 μm are reported. A H2O line located near 7161.41 cm(-1) is selected based on its strong absorption strength and isolation from interference of neighboring transitions. Direct absorption spectra of H2O are obtained for the measurement path as well as the reference path by scanning the laser wavelength. The pressure and H2O vapor concentration in the headspace of a vial are inferred from a differential absorption signal, which is the difference between the measured and the referenced absorbance spectra. This sensor is calibration-free and no purge gas is needed. The demonstrated capability would enable measurements of pressure and H2O concentration in the headspace of vials within 2.21% and 2.86%, respectively. A precision of 1.02 Torr and 390 ppm is found for the pressure and H2O concentration, respectively. A set of measurements for commercial freeze-dried products are also performed to illustrate the usefulness of this sensor. PMID:24216725

  15. The partial molar volume of carbon dioxide in peridotite partial melt at high pressure

    NASA Astrophysics Data System (ADS)

    Duncan, Megan S.; Agee, Carl B.

    2011-12-01

    The partial molar volume of CO 2 ( V) in silicate melt was determined for a komatiite composition using high pressure sink/float experiments in a multi-anvil press. The density of the experimental melt at pressure was determined by observing sinking and floating of pure forsterite (Fo100) and forsterite (Fo90) buoyancy markers. Values for V were bracketed at 4.3 GPa (23.71 cm 3/mol) and at 5.5 GPa (22.06 cm 3/mol), normalized to 2123 K. Combining the current data with previous work we now more accurately constrain the compression curve of V over the pressure range of 1.0 10 - 4 to 20 GPa. These data allow the calculation of density at pressure of carbonated silicate melts, such as kimberlite and silica undersaturated alkali basalts, and the determination of their buoyancy and eruptibility.

  16. Extrapolation of IAPWS-IF97 data: The saturation pressure of H2O in the critical region

    NASA Astrophysics Data System (ADS)

    Ustyuzhanin, E. E.; Ochkov, V. F.; Shishakov, V. V.; Rykov, A. V.

    2015-11-01

    Some literature sources and web sites are analyzed in this report. These sources contain an information about thermophysical properties of H2O including the vapor pressure Ps. (Ps,T)-data have a form of the international standard tables named as “IAPWS-IF97 data”. Our analysis shows that traditional databases represent (Ps,T)-data at t > 0.002, here t = (Tc ‑ T)/Tc is a reduced temperature. It is an interesting task to extrapolate IAPWS-IF97 data in to the critical region and to get (Ps,T)-data at t < 0.002. We have considered some equations Ps(t) and estimated that previous models do not follow to the degree laws of the scaling theory (ST). A combined model (CM) is chosen as a form, F(t,D,B), to express a function ln(Ps/Pc) in the critical region including t < 0.002, here D = (α, Pc,Tc,...) are critical characteristics, B are adjustable coefficients. CM has a combined structure with scaling and regular parts. The degree laws of ST are taken into account to elaborate F(t, D, B). Adjustable coefficients (B) are determined by fitting CM to input (Ps,T)-points those belong to IAPWS-IF97 data. Application results are got with a help of CM in the critical region including values of the first and the second derivatives for Ps(T). Some models Ps(T) are compared with CM.

  17. Oxygen-Partial-Pressure Sensor for Aircraft Oxygen Mask

    NASA Technical Reports Server (NTRS)

    Kelly, Mark; Pettit, Donald

    2003-01-01

    A device that generates an alarm when the partial pressure of oxygen decreases to less than a preset level has been developed to help prevent hypoxia in a pilot or other crewmember of a military or other high-performance aircraft. Loss of oxygen partial pressure can be caused by poor fit of the mask or failure of a hose or other component of an oxygen distribution system. The deleterious physical and mental effects of hypoxia cause the loss of a military aircraft and crew every few years. The device is installed in the crewmember s oxygen mask and is powered via communication wiring already present in all such oxygen masks. The device (see figure) includes an electrochemical sensor, the output potential of which is proportional to the partial pressure of oxygen. The output of the sensor is amplified and fed to the input of a comparator circuit. A reference potential that corresponds to the amplified sensor output at the alarm oxygen-partial-pressure level is fed to the second input of the comparator. When the sensed partial pressure of oxygen falls below the minimum acceptable level, the output of the comparator goes from the low state (a few millivolts) to the high state (near the supply potential, which is typically 6.8 V for microphone power). The switching of the comparator output to the high state triggers a tactile alarm in the form of a vibration in the mask, generated by a small 1.3-Vdc pager motor spinning an eccentric mass at a rate between 8,000 and 10,000 rpm. The sensation of the mask vibrating against the crewmember s nose is very effective at alerting the crewmember, who may already be groggy from hypoxia and is immersed in an environment that is saturated with visual cues and sounds. Indeed, the sensation is one of rudeness, but such rudeness could be what is needed to stimulate the crewmember to take corrective action in a life-threatening situation.

  18. Structure and Composition of the 200 K-Superconducting Phase of H2 S at Ultrahigh Pressure: The Perovskite (SH(-) )(H3 S(+) ).

    PubMed

    Gordon, Elijah E; Xu, Ke; Xiang, Hongjun; Bussmann-Holder, Annette; Kremer, Reinhard K; Simon, Arndt; Köhler, Jürgen; Whangbo, Myung-Hwan

    2016-03-01

    At ultrahigh pressure (>110 GPa), H2 S is converted into a metallic phase that becomes superconducting with a record Tc of approximately 200 K. It has been proposed that the superconducting phase is body-centered cubic H3 S (Im3‾ m, a=3.089 Å) resulting from the decomposition reaction 3 H2 S→2 H3 S+S. The analogy between H2 S and H2 O led us to a very different conclusion. The well-known dissociation of water into H3 O(+) and OH(-) increases by orders of magnitude under pressure. H2 S is anticipated to behave similarly under pressure, with the dissociation process 2 H2 S→H3 S(+) +SH(-) leading to the perovskite structure (SH(-) )(H3 S(+) ). This phase consists of corner-sharing SH6 octahedra with SH(-) ions at each A site (the centers of the S8 cubes). DFT calculations show that the perovskite (SH(-) )(H3 S(+) ) is thermodynamically more stable than the Im3‾ m structure of H3 S, and suggest that the A site hydrogen atoms are most likely fluxional even at Tc  . PMID:26855072

  19. 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).

  20. Thermo- and piezochromic properties of [Fe(hyptrz)]A2H2O 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)]A2H2O (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.

  1. Broadening of vibrational-rotational lines of the H2S molecule by pressure of monatomic gases

    NASA Astrophysics Data System (ADS)

    Starikov, V. I.

    2013-07-01

    Optimal sets of parameters for a model intermolecular potential that provide the best reproduction of broadening coefficients ? for the absorption lines in the ?2 band of the H2S molecule are determined for systems H2S-A (A = He, Ne, Ar, Kr, and Xe). For H2S-He, the potential is obtained with the temperature dependence of coefficients ? taken into account for two rotational absorption lines 110 ? 101 and 211 ? 202. With the potentials obtained, the coefficients ? are calculated for the ?1 and ?3 bands and compared with the available experimental data. There are significant discrepancies between the calculated and experimental values of ?.

  2. Measurement and calibration techniques used in computer partial pressure analysis

    SciTech Connect

    Mitchell, D.J.

    1985-05-01

    The uses of residual gas analyzers (RGA's) in computer controlled analytical studies and process monitoring applications are discussed in this paper. The relative merits are compared for the two most commonly used RGA's, which are the magnetic sector and the quadrupole mass analyzer. Methods of installing RGA's in vacuum systems and computer interfacing techniques are described. Measurement and calibration methods are outlined for applications where it is desirable to characterize either partial pressures or gas evolution rates. Interpretation of RGA spectra and limitations imposed by analytical errors are also discussed.

  3. 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.

  4. 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, ?c, 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 energy transfer process, as inferred from the trajectories. PMID:24144294

  5. The influence of hydrogen sulfide-to-hydrogen partial pressure ratio on the sulfidization of Pd and 70 mol% Pd-Cu membranes

    SciTech Connect

    Iyoha, O.; Enick, R.M.; Killmeyer, R.P.; Morreale, B.D.

    2007-11-15

    The influence of H2S-to-H2 partial pressure ratio on the sulfidization of Pd and 70 mol% PdCu membrane alloys was studied using various H2S-containing gas mixtures. The Pd membranes exposed to various H2S mixtures were in very good agreement with the thermodynamic calculations used in this study, resisting sulfidization when exposed to H2S-to-H2 ratios below the equilibrium value predicted for Pd4S formation, and experiencing sulfidization when exposed to ratios above the equilibrium values. The 70 mol% PdCu membranes, however, exhibited deviations from the predicted values, resisting sulfidization at some conditions close to the equilibrium values at which sulfidization was expected, and experiencing sulfidization at some conditions at which resistance was expected. This phenomenon was attributed to deviations of the PdCu alloy from ideality, probably due to Cu segregation at the membrane surface.

  6. The influence of hydrogen sulfide-to-hydrogen partial pressure ratio on the sulfidization of Pd and 70 mol% PdCu membranes

    SciTech Connect

    Iyoha, O.; Enick, R.M.; Killmeyer, R.P.; Morreale, B.

    2007-11-15

    The influence of H2S-to-H2 partial pressure ratio on the sulfidization of Pd and 70 mol% PdCu membrane alloys was studied using various H2Scontaining gas mixtures. The Pd membranes exposed to various H2S mixtures were in very good agreement with the thermodynamic calculations used in this study, resisting sulfidization when exposed to H2S-to-H2 ratios below the equilibrium value predicted for Pd4S formation, and experiencing sulfidization when exposed to ratios above the equilibrium values. The 70 mol% PdCu membranes, however, exhibited deviations from the predicted values, resisting sulfidization at some conditions close to the equilibrium values at which sulfidization was expected, and experiencing sulfidization at some conditions at which resistance was expected. This phenomenon was attributed to deviations of the PdCu alloy from ideality, probably due to Cu segregation at the membrane surface.

  7. Effects of Concentration, Temperature and Hydrostatic Pressure on the Local Lattice Structure of Ni2+ Doped Zn(BF4)2 6H2O Crystal

    NASA Astrophysics Data System (ADS)

    Gao, Ming-Liang; Kuang, Xiao-Yu; Li, Hui-Fang; Wanga, Huai-Qian

    2009-08-01

    A theoretical method for studying the inter-relationship between electronic and molecular structure is presented by means of complete energy matrices. As an application, the effects of temperature, concentration and hydrostatic pressure on the local structures of Ni2+ doped Zn(BF4)2 ?6H2O crystal have been studied. Our results show that the local lattice structures of [Ni(H2O)6]2+ coordination complex have expansion distortions as the temperature rises. Meanwhile, we find that the local structure parameter ? becomes smaller with the increasing concentration of Ni2+ ions doped in Zn(BF4)2 ?6H2O crystal. Furthermore, the pressure dependence of ? and anisotropic g-factors are discussed and the relationship between zero-field splitting parameter D and ?g is determined.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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

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

    PubMed

    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??g/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-? signaling pathway was linked to the cytotoxicity of Akbu-LAAO on HepG2. TGF-? 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-? pathway inhibitor reduced Akbu-LAAO cytotoxicity on HepG2. Collectively, we reported, for the first time, SV-LAAO showed anti-tumor cell activity via TGF-? pathway. It provides new insight of SV-LAAO exhibiting anti-tumor effect via a novel signaling pathway. PMID:26655928

  16. First-principles calculations of the high-pressure melt line of SiO2 and strength of H2O: planetary science implications

    NASA Astrophysics Data System (ADS)

    Samanta, Amit; Hamel, Sebastien; Qi, Tingting

    2015-06-01

    We report the results from high-pressure high-temperature quantum molecular dynamics simulations of two materials of importance to planetary science. First, the high-pressure melt line of SiO2 using constrained free energy calculations under condition relevant to the Outer Planets. Second, we explore the stability of the H2O super-ionic phase by calculating the elastic constants at finite temperature and provides insight into the generation of magnetic fields of Uranus and Neptune.

  17. 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 partial pressure (PO2) analyzer is a device that consists of a catheter-tip PO2 transducer (e.g.,...

  18. 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...

  19. 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...

  20. 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...

  1. 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...

  2. 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...

  3. 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 partial pressure (PO2) analyzer is a device that consists of a catheter-tip PO2 transducer (e.g.,...

  4. 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...

  5. 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...

  6. High-pressure dielectric studies of a novel hydrogen-bonded ferroelectric (NH4)2H2P2O6

    NASA Astrophysics Data System (ADS)

    Zdanowska-Frączek, M.; Frączek, Z. J.; Szklarz, P.; Jakubas, R.

    2012-07-01

    The hydrostatic pressure effect on the dielectric properties of (NH4)2H2P2O6 ferroelectric crystal was studied for pressures from 0.1 MPa to 360 MPa and for temperatures from 100 to 190 K. The pressure-temperature phase diagram obtained is linear with increasing pressure. The paraelectric-ferroelectric phase transition temperature decreases with increasing pressure with the pressure coefficient dTc/dp=-5.16×10-2 K MPa-1. Additionally, the pressure dependences of Curie-Weiss constants for the crystal in paraelectric (C+) and ferroelectric (C-) phases are evaluated and discussed. The possible mechanism of paraelectric-ferroelectric phase transition is also discussed.

  7. 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 sequestration of stack gas carbon dioxide gases for a 100% reduction in greenhouse gas emissions.

  8. MgSO4-H2O system at High pressure and its implication for the internal structure and evolution of Ganymede

    NASA Astrophysics Data System (ADS)

    Nakamura, R. S.; Ohtani, E.; Terasaki, H.

    2008-12-01

    Cryovolcanism and active geological alterations have been discovered in many icy satellites. Not only the surface activities but also the possibility of the subsurface ocean in Galilean satellites have been discussed by Shoemaker et al. (1982) and Kargel (1991). In the previous studies (Prockter 2001, Fortes 2007) existence of subsurface ocean has been suggested based on the observed data such as surface structures of alteration and gravity observations which includes the momentum of inertia. We can adopt the three- layered model for Ganymede (Mueller et al. 1988) composed of Fe or FeS inner core, Silicate outer core, and volatile-rich icy mantle. We calculated the density profile for the three-layered model based on the mixture of C1 chondrite Orgueil meteorite and H2O. We constructed a new model which has a deeper icy mantle with the density larger than pure ice. The infrared data of the Galileo survey (McCord et al. 1999,2001) found a large amount of sulfates such as MgSO4•6 H2O, MgSO4•7 H2O. Thus we estimated that the volatile-rich icy mantle contains not only pure ice but also a heavy MgSO4 component with several weight percents. We investigated the phase relations of MgSO4- H2O system under high pressure in order to discuss the internal structure of Ganymede. The sample which consisted of 0 to 30 weight percent of MgSO4 was put in diamond anvil cell with external heating device. The experiments performed up to 5GPa and 600K. This condition is a bit higher than the bottom of icy mantle (around 350K and 2GPa) (Prentice 2000, Sohl 2001). Under our experimental conditions, we found various high pressure phases in MgSO4- H2O system such as Ice VI and VII, and sulfates hydrates such as MgSO4•1H2O, MgSO4•6H2O, and MgSO4•7H2O depending on pressure and temperature conditions. Viscosity and density of the eutectic liquid at high pressure were measured using the falling sphere method with diamond anvil cell.We will present our experimental results and discuss the evolution of the internal structure of Ganymede based on the experiments.

  9. Infrared spectroscopic and modeling studies of H2/CH4 microwave plasma gas phase from low to high pressure and power

    NASA Astrophysics Data System (ADS)

    Rond, C.; Hamann, S.; Wartel, M.; Lombardi, G.; Gicquel, A.; Rpcke, J.

    2014-09-01

    InfraRed Tunable Diode Laser Absorption Spectroscopy technique has been implemented in a H2/CH4 Micro-Wave (MW frequency f = 2.45 GHz) plasma reactor dedicated to diamond deposition under high pressure and high power conditions. Parametric studies such as a function of MW power, pressure, and admixtures of methane have been carried out on a wide range of experimental conditions: the pressure up to 270 mbar and the MW power up to 4 kW. These conditions allow high purity Chemical Vapor Deposition diamond deposition at high growth rates. Line integrated absorption measurements have been performed in order to monitor hydrocarbon species, i.e., CH3, CH4, C2H2, C2H4, and C2H6. The densities of the stable detected species were found to vary in the range of 1012-1017 molecules cm-3, while the methyl radical CH3 (precursor of diamond growth under these conditions) measured into the plasma bulk was found up to 1014 molecules cm-3. The experimental densities have been compared to those provided by 1D-radial thermochemical model for low power and low pressure conditions (up to 100 mbar/2 kW). These densities have been axially integrated. Experimental measurements under high pressure and power conditions confirm a strong increase of the degree of dissociation of the precursor, CH4, associated to an increase of the C2H2 density, the most abundant reaction product in the plasma.

  10. Repetitively pulsed atmospheric pressure discharge treatment of rough polymer surfaces: II. Treatment of micro-beads in He/NH3/H2O and He/O2/H2O mixtures

    NASA Astrophysics Data System (ADS)

    Bhoj, Ananth N.; Kushner, Mark J.

    2008-08-01

    Plasmas are increasingly being used to functionalize the surface of polymers having complex shapes for biomedical applications such as tissue scaffolds and drug delivering micro-beads. The functionalization often requires affixation of amine (NH2) or O-containing groups. In this paper, results are discussed from a two-dimensional computational investigation of the atmospheric pressure plasma functionalization of non-planar and porous surfaces of polypropylene with NHx and O-containing groups. For the former, the discharge is sustained in He/NH3/H2O mixtures in a dielectric barrier-corona configuration. Significant microscopic non-uniformities arise due to competing pathways for reactive gas phase radicals such as OH and NH2, and on the surface by the availability of OH to initiate amine attachment. The treatment of inside surfaces of porous polymer micro-beads placed on an electrode is particularly sensitive to view angles to the discharge and pore size, and is ultimately controlled by the relative rates of radical transport and surface reactions deep into the pores. The functionalization of micro-beads suspended in He/O2/H2O discharges is rapid with comparable treatment of the outer and interior surfaces, but varies with the location of the micro-bead in the discharge volume.

  11. Nitrogenase Activity Is Affected by Reduced Partial Pressures of N2 and NO3- 1.

    PubMed Central

    Blumenthal, J. M.; Russelle, M. P.; Vance, C. P.

    1997-01-01

    Optimal use of legumes in cropping systems requires a thorough understanding of the interaction between inorganic N nutrition and symbiotic N2 fixation. Our objective was to test the hypothesis that increased NO3- uptake by alfalfa (Medicago sativa L.) would compensate for lower N2 fixation caused by low partial pressure of N2. Root systems of hydroponically grown alfalfa at 2 mg L-1 NO3--N were exposed to (a) 80% N2, (b) 7% N2, (c) 2% N2, or (d) 0% N2. Exposure to reduced partial pressures of N2 reduced total nitrogenase activity (TNA, measured as H2 production in 20% O2 and 80% Ar) by 40% within less than 30 min, followed by a recovery period over the next 30 min to initial activity. Five hours after treatments began, the TNA of plants exposed to 7 and 2% N2 was substantially higher than pretreatment activities, whereas the TNA of plants exposed either to 0 or 80% N2 did not differ from pretreatment values. The decline in TNA due to NO3- exposure over 4 d was not affected by reduced partial pressure of N2. During the 1st h the proportion of electrons used for the reduction of N2 fell from 0.52 to 0.23 for plants exposed to 7% N2, and to 0.09 for plants exposed to 2% N2, and remained unchanged for the rest of the experiment. Although the hypothesis that alfalfa compensated with increased NO3- uptake for lower N2 fixation was not validated by our results, we unexpectedly demonstrated that the decline in TNA upon exposure to NO3- was independent of the N2-fixing efficiency (i.e. the amount of N2 reduced by nitrogenase) of the symbiosis. PMID:12223779

  12. 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.

  13. 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.

  14. 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 sequestration of stack gas carbon dioxide gases for a 100% reduction in greenhouse gas emissions. 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. The PGM consists of a pressurized circulating fluidized bed (PCFB) reactor together with a recycle cyclone and a particulate removing barrier filter. Coal, air, steam, and possibly sand are fed to the bottom of the PCFB reactor and establish a relatively dense bed of coal/char in the bottom section. As these constituents react, a hot syngas is produced which conveys the solids residue vertically up through the reactor and into the recycle cyclone. Solids elutriated from the dense bed and contained in the syngas are collected in the cyclone and drain via a dipleg back to the dense bed at the bottom of the PCFB reactor. This recycle loop of hot solids acts as a thermal flywheel and promotes efficient solid-gas chemical reaction.

  15. [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.

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

    PubMed

    Faheber, Nancy; Lamoureux, Nathalie; Friedrichs, Gernot

    2015-06-28

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

  17. Thermal conductivity of H2O-CH3OH mixtures at high pressures: Implications for the dynamics of icy super-Earths outer shells

    NASA Astrophysics Data System (ADS)

    Hsieh, Wen-Pin; Deschamps, Frdric

    2015-10-01

    Thermal conductivity of H2O-volatile mixtures at extreme pressure-temperature conditions is a key factor to determine the heat flux and profile of the interior temperature in icy bodies. We use time domain thermoreflectance and stimulated Brillouin scattering combined with diamond anvil cells to study the thermal conductivity and sound velocity of water (H2O)-methanol (CH3OH) mixtures to pressures as high as 12 GPa. Compared to pure H2O, the presence of 5-20 wt % CH3OH significantly reduces the thermal conductivity and sound velocity when the mixture becomes ice VI-CH3OH and ice VII-CH3OH phases at high pressures, indicating that the heat transfer is hindered within the icy body. We then apply these results to model the heat transfer through the icy mantles of super-Earths, assuming that these mantles are animated by thermal convection. Our calculations indicate that the decrease of thermal conductivity due to the presence of 10 wt % CH3OH induces a twofold decrease of the power transported by convection.

  18. 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. PMID:26803264

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

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

    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.

  20. 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

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

    PubMed

    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

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

    PubMed

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

    2015-06-01

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

  3. Low Pressure Crystallization Paths of H 2O-Saturated Basaltic-Hawaiitic Melts from Mt Etna: Implications for Open-System Degassing of Basaltic Volcanoes

    NASA Astrophysics Data System (ADS)

    Mtrich, Nicole; Rutherford, Malcolm J.

    1998-04-01

    Melt inclusions indicate that the basaltic-hawaiitic magmas from Mt Etna (Sicily) contained up to 2.3 wt% H 2O dissolved in the melt, prior to eruption. The effect of H 2O degassing during magma ascent has been experimentally constrained between 1135 and 1009C, for P H 2O = P total varying from 800 to 270 bars. The starting material was a primitive hawaiitic lava sample (MgO = 7.1 wt%) representative of the less evolved lava emitted at Mt Etna. Experiments were conducted in TZM pressure vessels, with Ag 70Pd 30 capsules in order to minimize the FeO loss. At temperatures of 1135-1090C, P H 2O = 800 bars, with NiNiO and FMQ buffers, olivine (Fo 83-80) is the liquidus phase in equilibrium with a residual hawaiitic melt (Mg# 0.60-0.57; CaO/Al 2O 3 = 0.82). Salitic pyroxene begins to crystallize at 1075C, plagioclase at 1025C and at 1009C, the magma is 33.5% crystallized with olivine, Ca-rich pyroxene, and plagioclase (16:60:24). At P H 2O = 270 bars, FMQ buffer, olivine (Fo 79.3-80) and salitic pyroxene are the main liquidus phases between 1100 and 1090C. They are in equilibrium with hawaiitic melts (Mg# 0.51; CaO/Al 2O 3 = 0.73). At 1070C, the experimental charges are highly crystallized (?51.5%) with olivine (Fo 70), salite, and plagioclase (An 78.4-76.3) in 14:44:42 relative proportions. Increasing the water content of hawaiitic-basaltic magmas expands the stability field of the olivine (relative to the other phases), lowers the crystallization temperatures of pyroxene and plagioclase, and results in the development of a more An-rich plagioclase. When compared to the natural samples, these results support a model of early and moderate crystallization of olivine from Etnean primitive hawaiitic magmas, containing close to 2.5 wt% H 2O, with NNO oxygen buffering conditions, at low pressure (P H 2O =P total). We propose a model of crystallization driven by decompression and water degassing during the emplacement of magma in the volcanic pile itself and possibly concomitant with the opening of fractures.

  4. In Pursuit of Parental Arc Magmas: The effects of pressure on the composition of H2O-saturated peridotite melts

    NASA Astrophysics Data System (ADS)

    Till, C. B.; Grove, T. L.

    2012-12-01

    In the continued pursuit to understand the mantle origin of parental arc magmas, we investigate the nature and composition of quench products in a subset of the super-solidus H2O-saturated peridotite melting experiments of Till et al. (2012) and Grove et al. (2006). We examine a variety of filtering techniques for electron microprobe analyses of the quench products that utilize published mineral-fluid and mineral-melt partition coefficients. Our results suggest melts in equilibrium with olivine, orthopyroxene, clinopyroxene and spinel between 1-2 GPa are silica-saturated quartz tholeiites at melt fractions of 11-14%. We find both a low-alkali silica-undersaturated tholeiitic melt and a high-silica vapor-phase quench in equilibrium with a garnet peridotite assemblage at melt fractions of 10-20% from 3.2-4 GPa, suggesting that the peridotite-H2O system is below the second critical end point at these conditions. Between 860 and 1100C at 3.2 GPa, the H2O-saturated peridotite melting reaction consumes olivine, clinopyroxene and garnet to produce orthopyroxene and melt, while above 1100C olivine and orthopyroxene are consumed to produce melt. The isobaric melt production rates in these experiments are extremely low (dF/dT= 0.05-0.13%/C for 10-30% melt) and may represent a minimum in peridotite melt production rates, which occur when a melt is H2O-saturated. Our melt compositions are similar to those from the landmark experimental studies of Kushiro (1972) and Mysen (1973) who also analyzed the compositions of low degree mantle melts formed in the presence of excess H2O. Together the experimental observations suggest that low-extent melts of H2O-saturated peridotite are silica-saturated at lower pressures but become increasingly silica-undersaturated at higher pressures. Our experimental results also point to the likelihood of multiple inputs into the base of the mantle wedge when melting commences near 100 km depth beneath arcs. We discuss the composition of the hydrous silicate melt input into the mantle wedge relative to that of a coexisting solute-rich H2O fluid, as documented in this and previous experimental studies.

  5. Experimental Evidence for High-Pressure Phase Separation in the H2O-CO2-CaCl2 System: Implications for Rock Rheology

    NASA Astrophysics Data System (ADS)

    Selverstone, J.; Chernak, L.; Tullis, J.; Cooper, R.

    2007-12-01

    As part of a study to examine the effect of CO2 on deformation mechanisms in quartz, axial compression experiments were carried out at 900C and 1500 MPa on cores of Black Hills quartzite (BHQ) with a layer of dolomite powder ( 0.05 wt% H2O) in the center of each charge (some runs included buffer assemblages at sample ends). All runs released CO2 via the reaction dol + qtz = diop + CO2 during run-up to experimental conditions. BHQ starting material contains three types of naturally occurring fluid inclusions (FIs): pure H2O, H2O + 6-18 wt% CaCl2, and pure CO2. Deformation experiments on as-is BHQ (no dol powder) result in destruction of most optical FIs. In contrast, experiments with wet dol powder produced visible FIs in nearly all samples, though most were too small to analyze by microthermometry. One hydrostatic experiment with dolomite generated FIs up to 15 microns across near the reaction zone. FIs within this sample fall into two types: (1) superdense CO2 (homogenization to liquid below -50C), and (2) H2O-CO2-CaCl2 solutions with variable X(CO2) and bulk density and up to 40 wt% CaCl2 (referenced to aqueous phase only). Both inclusion types occur within the same clusters, and likely result from interaction of CO2 released by dol breakdown with H2O and FI fluids released from the starting material. Isochores from the Type 1 CO2 FIs record pressures of 1200- 1400 MPa at 900C. Estimation of bulk density for Type 2 FIs is hampered by complex microthermometric behavior and incomplete equation of state data for this fluid system, but model isochores overlap with those of Type 1 FIs at 900C. Entrapment of the two types of FIs and variable phase proportions in Type 2 inclusions are consistent with fluid phase separation at experimental conditions. Deformation experiments run at f(O2)H2O) and f(H2O), which in turn will facilitate strain accommodation by dislocation and/or diffusion creep. Shmulovich & Graham (2004 CMP) documented a large two-fluid field in the H2O-CO2-CaCl2 system at 800C and 900 MPa. Our study shows that the region of immiscibility extends to higher pressures and temperatures, and can be anticipated in both lower crustal and upper mantle rocks as well as in subducting slabs. Our data also demonstrate that variations in f(O2) may be generated and preserved over short distances, and that strain accommodation mechanisms can co-vary with fluid composition, f(O2) and f(H2O) in COH-salt systems. We thus anticipate that significant localized differences in rock strength will result from metamorphic reactions that move rocks into and out of the two-fluid field at high pressure.

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

    PubMed

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

    2014-01-21

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

  7. 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.

  8. Phase stability of BSCF in low oxygen partial pressures

    SciTech Connect

    Ovenstone, James; Jung, Jae-Il; White, Jeffery S.; Edwards, Doreen D.; Misture, Scott T.

    2008-03-15

    In situ X-ray diffraction has been used to investigate the phase stability of barium strontium cobalt iron oxide (BSCF) with the formula Ba{sub 0.5}Sr{sub 0.5}Fe{sub 1-x}Co{sub x}O{sub 3-{delta}} (x=0, 0.2, 0.4, 0.6, 0.8, and 1). The thermal decomposition processes in both low partial pressures of oxygen (air -10{sup -5} atm pO{sub 2}) and in reducing conditions have been detailed. BSCF manifests excellent stability down to 10{sup -5} atm pO{sub 2}; however, it decomposes through a complex series of oxides under reducing conditions. Increasing the cobalt content results in a decrease in the temperature range of stability of the material under 4% H{sub 2} in N{sub 2}, with the initial decomposition taking place at 375, 425, 550, 600, 650 and 675 deg. C, for x=1, 0.8, 0.6, 0.4, 0.2 and 0, respectively. Further, the thermal expansion is a strong function of the oxygen activity and Co content. The x=0, 1 end member, BSC, undergoes a phase transition from rhombohedral to cubic symmetry at {approx}800 deg. C under 10{sup -5} atm pO{sub 2}, resulting in an ideal perovskite with a=3.9892(3) A at room temperature. - Graphical abstract: The phase stability of the fuel cell cathode Ba{sub 0.5}Sr{sub 0.5}Fe{sub 1-x}Co{sub x}O{sub 3-{delta}} in low pO{sub 2} and high temperature has been investigated using in situ X-ray diffraction. Both stability and thermal expansion coefficient were found to increase with increasing iron content. Decomposition products under reducing conditions have been identified.

  9. ``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 . 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 . 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. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr07447e

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

    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 500C. Data for each isotherm includeP-xrelations near the critical point and extend to the three-phase assemblage vapor-liquid-halite on the vapor side. On the liquid side theP-xdata 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 ofUrusova(1974, 1975) and lander andLiander(1950) but differ markedly from the extensive data ofSourirajanandKennedy(1962).

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

    PubMed

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

    2010-05-01

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

  12. Subduction Factory 3: An Excel worksheet and macro for calculating the densities, seismic wave speeds, and H2O contents of minerals and rocks at pressure and temperature

    NASA Astrophysics Data System (ADS)

    Hacker, Bradley R.; Abers, Geoffrey A.

    2004-01-01

    An Excel macro to calculate mineral and rock physical properties at elevated pressure and temperature is presented. The workbook includes an expandable database of physical parameters for 52 rock-forming minerals stable at high pressures and temperatures. For these minerals the elastic moduli, densities, seismic velocities, and H2O contents are calculated at any specified P and T conditions, using basic thermodynamic relationships and third-order finite strain theory. The mineral modes of suites of rocks are also specifiable, so that their predicted aggregate properties can be calculated using standard solid mixing theories. A suite of sample rock modes taken from the literature provides a useful starting point. The results of these calculations can be applied to a wide variety of geophysical questions including estimating the alteration of the oceanic crust and mantle; predicting the seismic velocities of lower-crustal xenoliths; estimating the effects of changes in mineralogy, pressure and temperature on buoyancy; and assessing the H2O content and mineralogy of subducted lithosphere from seismic observations.

  13. 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) analyzer. 868.1200 Section 868.1200 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES ANESTHESIOLOGY DEVICES Diagnostic Devices § 868.1200 Indwelling blood oxygen partial pressure...

  14. 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.

  15. 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.

  16. 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.

  17. Partial Fe-Ti alloy phase diagrams at high pressure

    SciTech Connect

    Yamane, Toshimi; Hisayuki, Koji; Nakao, Riyuichiro; Minamino, Yoritoshi; Araki, Hideki; Hirao, Keiichi

    1999-11-01

    Recently, high pressure treatments such as hot isostatic pressing have become more familiar in industrial processes. The high pressure induces changes of both the phase equilibrium and the kinetics of the phase transformation in alloys. The iron-rich phase diagrams under high pressure have been previously reported in the Fe-Mo, Fe-W, Fe-Cr, Fe-V, and Fe-Si systems, which have the {gamma} loop in the iron-rich side at the ordinary pressure. These systems exhibit the astonishing changes in phase equilibrium under high pressure: the {gamma} loop expands under high pressure, and especially the {gamma} loop type phase diagrams of Fe-Mo and Fe-W systems transform to the {gamma} shrink type phase diagram at higher pressures. So, it is very interesting to investigate the effect of high pressure on phase equilibrium in the {gamma} loop phase diagram of the Fe-Ti system, which is practically important for hydrogen storage alloys, titanium clad steels, and so on. Therefore, the authors have established the iron-rich Fe-Ti phase diagrams at the high pressure up to 2.7 GPa.

  18. Influence of oxygen partial pressure on surface tension and its temperature coefficient of molten iron

    NASA Astrophysics Data System (ADS)

    Ozawa, S.; Suzuki, S.; Hibiya, T.; Fukuyama, H.

    2011-01-01

    Influences of oxygen partial pressure, PO2, of ambient atmosphere and temperature on surface tension and its temperature coefficient for molten iron were experimentally investigated by an oscillating droplet method using an electromagnetic levitation furnace. We successfully measured the surface tension of molten iron over a very wide temperature range of 780 K including undercooling condition in a well controlled PO2 atmosphere. When PO2 is fixed at 10-2 Pa at the inlet of the chamber, a "boomerang shape" temperature dependence of surface tension was experimentally observed; surface tension increased and then decreased with increasing temperature. The pure surface tension of molten iron was deduced from the negative temperature coefficient in the boomerang shape temperature dependence. When the surface tension was measured under the H2-containing gas atmosphere, surface tension did not show a linear relationship against temperature. The temperature dependence of the surface tension shows anomalous kink at around 1850 K due to competition between the temperature dependence of PO2 and that of the equilibrium constant of oxygen adsorption.

  19. Equation of state and pressure-induced structural changes in mirabilite (Na2SO410H2O) determined from ab initio density functional theory calculations

    NASA Astrophysics Data System (ADS)

    Brand, Helen E. A.; Fortes, A. Dominic; Wood, Ian G.; Vo?adlo, Lidunka

    2009-09-01

    We have carried out ab initio calculations using density functional theory to determine the bulk elastic properties of mirabilite, Na2SO410H2O, and to obtain information on structural trends caused by the application of high pressure up to ~60 GPa. We have found that there are substantial isosymmetric discontinuous structural re-organisations at ~7.7 and ~20 GPa caused by changes in the manner in which the sodium cations are coordinated by water molecules. The low-pressure and intermediate-pressure phases both have sodium in sixfold coordination but in the high-pressure phase the coordination changes from sixfold to sevenfold. These coordination changes force a re-arrangement of the hydrogen-bond network in the crystal. The trend is towards a reduction in the number of hydrogen bonds donated to the sulphate group (from twelve down to six over the range 0-60 GPa) and an increase in hydrogen bonding amongst the Na-coordinated water molecules and the two interstitial water molecules. Ultimately, we observe proton transfers from the interstitial waters (forming OH- ions) to two of the Na-coordinated waters (forming a pair of H3O+ ions). The equation of state in the athermal limit of the low-pressure phase of mirabilite, parameterised by fitting an integrated form of the third-order Birch-Murnaghan expression to the calculated energy as a function of unit-cell volume, yields the zero-pressure unit-cell volume, V 0 = 1468.6(9) 3, the incompressibility, K 0 = 22.21(9) GPa, and the first pressure derivative K 0' = (?K/?P)0 = 5.6(1).

  20. 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.

  1. 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.

  2. Impact of hydrogen partial pressure on coal liquefaction. Final technical report

    SciTech Connect

    Kang, D.; Hoover, D.S.; Schweighardt, F.K.

    1984-06-01

    This program was conducted to determine the effects of hydrogen partial pressure on the SRC-I direct coal liquefaction process and SRC-I Demonstration Plant design. A native solvent was produced in quantity and slurried with Kentucky number 9 Mulford coal in a series of coal liquefaction runs under varying hydrogen gas rates, temperatures, residence times, and hydrogen partial pressures. The results showed that hydrogen partial pressure significantly affected product distribution; the magnitude of the effect was comparable to changes in temperature and residence time. Also, the impact of hydrogen partial pressure was enhanced by increases in both temperature and residence time. Operating at low hydrogen partial pressure did not show any apparent advantage; it reduced coal conversion, reduced oil yield, and had a detrimental effect on the yield distribution of other products. An increase in hydrogen partial pressure had the following effects: increased coal conversion; increased conversion of asphaltenes and preasphaltenes to lighter products; significantly increased the oil yield; increased light gas yields; decreased sulfur content in the SRC; increased hydrogen content of the recycle solvent; and increased hydrogen consumption. This study strongly suggests that further studies should be conducted to optimize the effects of hydrogen partial pressure on the process, both within and, preferably, beyond the constraints of the current basic SRC-I design, considering the major impact of this variable on the process. 10 references, 37 figures, 10 tables.

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

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

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

  4. 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.

  5. Microwave Spectra and Structures of H_2S-CuCl and H_2O-CuCl.

    NASA Astrophysics Data System (ADS)

    Walker, N. R.; Wheatley, D. E.; Stephens, S. L.; Roberts, F. J.; Mikhailov, V. A.; Legon, A. C.

    2010-06-01

    A Balle-Flygare FT-MW spectrometer coupled to a laser ablation source has been used to measure the pure rotational spectra of H2S-CuCl and H2O-CuCl. Both molecules are generated via laser ablation (532 nm) of a metal rod in the presence of CCl4, argon, a low partial pressure of H2S or H2O and are stabilized by supersonic expansion. Rotational constants and centrifugal distortion constants have been measured for eight isotopologues of H2S-CuCl with substitutions available at the copper, chlorine and hydrogen atoms. Transitions in the spectra of nine isotopologues of H2O-CuCl have been measured with isotopic substitutions achieved for every atom. The spectra of both H2S-CuCl and H2O-CuCl are consistent with a linear arrangement of sulphur or oxygen, metal and chlorine atoms. The structure of H2S-CuCl is pyramidal with CS symmetry. The structure of H2O-CuCl is either C2v planar at equilibrium or CS pyramidal but with a low potential-energy barrier to planarity such that the v=0 and 1 states associated with the motion that inverts the configuration at the O atom are well separated. Nuclear quadrupole coupling constants have been measured for the chlorine and copper atoms in each molecule. Nuclear spin-rotation constants have been determined for the copper atom.

  6. 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.

  7. 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.

  8. 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 =1000C 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 increasing concentration of fluid the pressure effect on the partitioning of Cl decreases. The pressure has a weaker influence on the partitioning of F compared with Cl. At 3-7N HF fluid with decreasing pressure the fluorine content in the fluid coexisting with phonolitic melt decreases. At 1N HF fluid the pressure effect on the partitioning of F is not identified.

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

    EPA Science Inventory

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

  10. Infrared rovibrational spectroscopy of OH-C2H2 in 4He nanodroplets: Parity splitting due to partially quenched electronic angular momentum

    NASA Astrophysics Data System (ADS)

    Douberly, Gary E.; Raston, Paul L.; Liang, Tao; Marshall, Mark D.

    2015-04-01

    The T-shaped OH-C2H2 complex is formed in helium droplets via the sequential pick-up and solvation of the monomer fragments. Rovibrational spectra of the a-type OH stretch and b-type antisymmetric CH stretch vibrations contain resolved parity splitting that reveals the extent to which electronic angular momentum of the OH moiety is quenched upon complex formation. The energy difference between the spin-orbit coupled 2B1 (A″) and 2B2 (A') electronic states is determined spectroscopically to be 216 cm-1 in helium droplets, which is 13 cm-1 larger than in the gas phase [Marshall et al., J. Chem. Phys. 121, 5845 (2004)]. The effect of the helium is rationalized as a difference in the solvation free energies of the two electronic states. This interpretation is motivated by the separation between the Q(3/2) and R(3/2) transitions in the infrared spectrum of the helium-solvated 2Π3/2 OH radical. Despite the expectation of a reduced rotational constant, the observed Q(3/2) to R(3/2) splitting is larger than in the gas phase by ≈0.3 cm-1. This observation can be accounted for quantitatively by assuming the energetic separation between 2Π3/2 and 2Π1/2 manifolds is increased by ≈40 cm-1 upon helium solvation.

  11. 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.

  12. 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)

  13. Crystal structure, equation of state, and elasticity of phase H (MgSiO4H2) at Earths lower mantle pressures

    NASA Astrophysics Data System (ADS)

    Tsuchiya, Jun; Mookherjee, Mainak

    2015-10-01

    Dense hydrous magnesium silicate (DHMS) phases play a crucial role in transporting water in to the Earths interior. A newly discovered DHMS, phase H (MgSiO4H2), is stable at Earths 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 Earths 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 ~24% smaller than those of isostructural ?-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.

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

    PubMed

    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 ?-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

  15. 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

  16. Experimental study of the dehydration reactions gypsum-bassanite and bassanite-anhydrite at high pressure: indication of anomalous behavior of H(2)O at high pressure in the temperature range of 50-300 degrees C.

    PubMed

    Mirwald, Peter W

    2008-02-21

    The system CaSO(4)-H(2)O, characterized by the three dehydration reactions gypsum-anhydrite, gypsum-bassanite, and bassanite-anhydrite, was reexamined by in situ differential pressure analysis in the temperature range of 60-350 degrees C up to 3.5 GPa pressure. The investigation revealed a fine structure in the dehydration boundaries of gypsum-bassanite and bassanite-anhydrite, each characterized by three inflections at 0.9-1.0, 1.9-2.0, and 2.6-28 GPa. In addition, the phase transition of anhydrite high pressure anhydrite (monazite structure) was established for the first time at high P-T conditions intersecting the bassanite-anhydrite dehydration boundary at 2.15 GPa250 degrees C. Furthermore, the triple point gypsum-bassanite-anhydrite was redetermined with 235 MPa80.5 degrees C. The evaluation of the gypsum-bassanite dehydration boundary with respect to the volume and entropy change of the reaction, DeltaV(react) and DeltaS(react), by means of the Clausius-Clapeyron relation yields for the entropy parameter an unusually large increase over the range of the noted inflections. This is interpreted as anomalous entropy behavior of H(2)O related presumably to a dramatic increase in fluctuations of the hydrogen network of the liquid leading possibly into a new structural state. The effect is strongly related to the three noted pressure levels of 0.9-1.0, 1.9-2.0, and 2.6-28 GPa. In a synopsis of data including also a previous high pressure study in the temperature range between 0 and 80 degrees C, a tentative P-T diagram of H(2)O is proposed. PMID:18298152

  17. 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.

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

    PubMed Central

    Tadimalla, Sirisha; Momot, Konstantin I.

    2014-01-01

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

  19. Effect of partial H2O-D2O replacement on the anisotropy of transverse proton spin relaxation in bovine articular cartilage.

    PubMed

    Tadimalla, Sirisha; Momot, Konstantin I

    2014-01-01

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

  20. The stability and Raman spectra of ikaite, CaCO36H2O, 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, CaCO36H2O, 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?1corresponding toEg(external) andA1g(internal) modes of vibrations in CO2?3ions, 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 aP-Tphase 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.

  1. Preliminary modeling of high pressure partial melting - Implications for early lunar differentiation

    NASA Technical Reports Server (NTRS)

    Longhi, J.

    1982-01-01

    A quantitative model is presented for equilibrium crystallization of lunar magmas at high pressure, which, viewed in reverse, is equivalent to equilibrium partial melting. Data are extrapolated from simple systems, mare basalt systems, and from experiments on terrestrial compositions. Liquidus phase equilibria in a portion of the CaO-MgO-Al2O3-SiO2 system serve as a guide for predicting phase equilibria in the natural system. High pressure partial melting sequences are calculated for several proposed whole moon compositions at nominal pressure of 10 and 20 kb. Results show that compositions with chondritic Ca/Al have quite different melting paths from those with subchondritic Ca/Al, and as a result the types of magmas produced are quite different. If the moon possesses a chondritic Ca/Al ratio, models which rely on small degrees of partial melting to produce the early lunar magnetism are suspect.

  2. 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.

  3. Near-solidus rhyolitic melts of MORB+4 wt% H2O from base-of-crust through shallow subducted slab pressures

    NASA Astrophysics Data System (ADS)

    Sisson, T. W.; Kelemen, P. B.; Vazquez, J. A.

    2012-12-01

    Recent numerical models of subduction dynamics indicate that uncommon circumstances (slab edges, slow subduction of young oceanic crust) are required for slabs to heat beyond the H2O-saturated basalt solidus at sub-arc depths (Syracuse et al. 2010 EPSL, among others). In contrast, some geochemical evidence points to widespread incipient slab melting (Cooper et al. 2012 G3). Irrespective of current conditions, hotter mantle in the early Earth may have led to ubiquitous slab melting, and the thickening, foundering, and detaching roots of protocontinents could also have melted to low degrees. Experimental information on melting under such conditions helps to develop and test these hypotheses. Liu et al. (1996 EPSL) performed long duration (commonly 10 days) oxygen buffered (QFM, QFsM) experiments on N-MORB glass+4 wt% H2O from 0.8 to 3 GPa mainly to study slab metamorphism. The H2O-saturated basalt solidus was bracketed between 700 and 750 C. Many runs 800 C and hotter have analyzable melt that are examined in this study. Normalized anhydrous, 800 C melts range from evolved low-K rhyodacite (or leuco-tonalite: 68.9 wt% SiO2) at 1 GPa to low-K high-silica rhyolite (or leuco-trondhjemite: 76.5 wt% SiO2) at 2.7 GPa, coexisting with residual assemblages of garnet-plagioclase amphibolite (0.9-1.2 GPa), amphibole eclogite (1.4-1.8 GPa), eclogite (2.0-2.6 GPa), and quartz eclogite (2.7 GPa) (+apatite, ilmenite, or rutile above 1.4 GPa). Mass-balance based estimates of melt fraction diminish modestly from ~0.3 at 1 GPa to ~0.17 at 2.7 GPa along the 800 C isotherm. The consistently rhyolitic character of 800 C melts at upper mantle pressures indicates that liquids closer to the solidus would also be evolved rhyolites. Limited trace element analyses (SIMS) are as expected, with the most evolved liquids coexisting with rutile-quartz eclogite having high Sr/Y (180-240) and Zr/Nb (90-110). Rare earth element-rich accessory minerals (allanite, monazite) have not been found, consistent with only weak Ba/La fractionation in glasses. Notably, estimated bulk solid/liquid Ds for Ba and Sr are low and similar (?0.02), and are only slightly exceeded by those for K and La (0.03-0.05, 0.06-0.08) for high-silica rhyolite melt coexisting with rutile-quartz eclogite. An implication is that if low-degree hydrous melting of basalt, leaving residual eclogite, were the dominant source of element enrichment during continental growth, the continents would be similarly enriched in Ba, Sr, and K, relative to bulk earth. This is true for K and Ba, but not for Sr (35-60, 40-80, vs. 15-20 primitive mantle), suggesting that (1) Sr was sequestered somewhere (delaminated eclogized continental roots?) after release from slabs, (2) much element transfer from slabs is via fluid, not melt, for which the D for Sr>Ba (Kessel et al., 2005, Nature), (3) the elevated Ba/Sr and K/Sr of the continents reflects early Earth MORB values transferred to the continents by subduction processing, or (4) the bulk Sr concentration of the continents has been underestimated.

  4. 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.

  5. 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.

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

    SciTech Connect

    Yang, S.J.; Xiao, Y.H.

    2008-06-15

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

  7. The ? 1+? 3 and the ? 1+? 2+? 41+? 5-1 Combination Bands of 13C 2H 2. Linestrengths, Broadening Parameters, and Pressure Shifts

    NASA Astrophysics Data System (ADS)

    Kusaba, Mitsuhiro; Henningsen, Jes

    2001-10-01

    The ?1+?3 and the ?1+?2+?41+?5-1 combination bands of 13C2H2 at 6521.9 and 6535.1 cm-1, respectively, are studied with diode laser spectroscopy. Line center wavelengths have been determined with 0.00012-nm standard uncertainty up to J=40 for ?1+?3 and up to J=25 for ?1+?2+?41+?5-1. Linestrengths are modeled with a Herman-Wallis expansion F(m)=1+c1m+c2m2+with c1=-1.3310-3, c2=-0.8510-4, c3=0, c4=1.1310-7 for ?1+?3 and c1=-1.1110-3, c2=-3.8510-4 for ?1+?2+?41+?5-1. Collision broadening parameters are extracted from Voigt fits to the line profiles and can be modeled for both bands by the analytical expression ?=5.221-0.0839|m|+1.46 exp(-0.45|m|) MHz/mbar, indicating independence of vibrational state. Collisional narrowing is studied on selected lines and the model dependence of linestrengths and broadening parameters is determined. Pressure shifts are studied in ?1+?3, and a characteristic difference in the shifts for the P-branch and the R-branch is explained in terms of a simple ad hoc assumption about the level shifts. These bands have a potential for providing wavelength standards for optical fiber communication.

  8. On the sensitivity to partial pressure of oxygen of the mobility in cadmium oxide

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

    The partial pressure of oxygen during the deposition process of cadmium oxide is a crucial quantity whose influence on the electrical and optical properties of this material is really very significant (consider, for example, the experimental technique known as activated reactive evaporation). In fact, this paper is a theoretical formulation to evaluate the sensitivity changes of the aforementioned pressure of the electron drift-mobility and velocity in CdO. Indeed, as we will see later, given that the electron relaxation time depends upon the oxygen partial pressure, then the electron drift-mobility, mean free path and velocity also depend on this pressure. Relevant calculations involving the above physical quantities are carried out.

  9. 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. PMID:25479976

  10. Simulation of in situ uraninite leaching. part I: A partial equilibrium model of the NH4HCO3-(NH4)2CO3-H2O2 leaching system

    NASA Astrophysics Data System (ADS)

    Liddell, Knona C.; Bautista, Renato G.

    1994-04-01

    In situ leaching of uraninite and calcite by H2O2-NH4HCO2-(NH4)2CO3 solutions has been simulated using a partial equilibrium model which incorporates a one-parameter mixing cell model of solution flow. Rate laws for UO2 dissolution and for CaCO2 dissolution/precipitation were taken from the literature, as were equilibrium constants for solution phase reactions. Parameters of the model include the UO2 and CaCO3 ore grades, the concentrations of the H2O2, NH4HCO3, and (NH4)2CO3 components, porosity, exit solution flow rate, ore and mineral densities, and mineral rate constants and surface areas. Mineral conversions, component and species concentrations, and porosity are among the time-dependent quantities calculated using the model. For the conditions simulated, calcite dissolved somewhat faster than uraninite. The results emphasize the importance of the coupling between the mineral reactions and solution flow. Changes in the concentrations of the CO{3/2-} and HCO{3/-} species are particularly complicated and not predictable from the calcite kinetics alone or from a purely equilibrium model; although the simulations did not reveal any conditions under which the solution would become saturated with CaCO3, the pH continued to change throughout the calcite dissolution and is buffered only after calcite has been consumed.

  11. 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.

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

    PubMed Central

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

    2014-01-01

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

  13. Accelerated carbon sequestration in mine tailings using elevated CO2 partial pressure

    NASA Astrophysics Data System (ADS)

    Harrison, A. L.; Power, I. M.; Dipple, G. M.; Mayer, K. U.

    2011-12-01

    Mineralization of atmospheric CO2 within hydrated Mg-carbonate minerals occurs passively in ultramafic mine tailings at low temperature via weathering of Mg-silicate minerals [1]. If this process were accelerated, large mines may have the capacity to sequester millions of tonnes of CO2 annually, providing the potential to offset the greenhouse gas emissions of mining. Recent laboratory evidence indicates the rate-limiting step for sequestration in mine tailings is the uptake of atmospheric CO2 into solution [2]. Supplying elevated partial pressures of CO2 (pCO2) into mine tailings may accelerate carbon sequestration by increasing dissolved inorganic carbon and enhancing mineral dissolution. Passive carbon mineralization has been documented at the Mount Keith Nickel Mine (MKM), Western Australia [3]. MKM produces ~11 Mt of tailings annually, consisting primarily of Mg-silicate serpentine minerals. Brucite [Mg(OH)2] is present at lower abundance (~1-2.5 wt.%) [3], yet is more rapidly carbonated. The effect of elevated pCO2 on the carbonation rate of brucite was investigated experimentally with solutions mimicking process water chemistry and temperature conditions in tailings at MKM. Gas streams ranging in composition from 10 to 100% CO2 (balance N2) were sparged into 3.0 L alkaline slurries containing 5% brucite. Brucite was completely replaced by nesquehonite [MgCO3?3H2O] ± dypingite [Mg5(CO3)4(OH)2?5H2O] within 75, 12, and 7 hours with 10%, 50%, and 100% CO2 gas, respectively. This corresponds to a linear increase in carbon mineralization rate with pCO2. Approximately 30% of supplied CO2 was sequestered within these time periods. PHREEQC geochemical modelling using experimentally determined mineral dissolution rate laws suggests acceleration of the brucite carbonation rate with pCO2 is attributable to HCO3- promoted dissolution. Modelling of experimental conditions indicates that equilibrium between CO2 in the gas and aqueous phases is not attained during the carbonation reaction. This implies CO2 uptake into solution remains the rate-limiting step during brucite carbonation at elevated pCO2, providing further potential for acceleration. An increase in carbonation rate of serpentine with pCO2 is expected due to increased acidity, but the effect of HCO3- requires further investigation. Modelling reveals a non-linear relationship between both acidity and HCO3- promoted dissolution and carbonation rate of serpentine and brucite with pCO2. This implies use of lower pCO2 gas (e.g. 10%) may be sufficient to achieve similar carbonation rates as 100% CO2 gas if CO2 uptake were enhanced. The minimum experimental brucite carbonation rate is in excess of that required to completely carbonate the average mass of brucite produced annually at MKM. Achievement of this rate at the mine scale would sequester 80 - 210 kt CO2/year, offsetting annual mine emissions by ~22 - 56%. [1] Wilson et al. (2009), Econ. Geol. 104: 95-112. [2] Wilson et al. (2010), Environ. Sci. Technol. 44: 9522-9529. [3] Wilson (2009), PhD thesis, UBC, Vancouver, Canada.

  14. H2O nucleation around Au+.

    PubMed

    Reveles, J Ulises; Calaminici, Patrizia; Beltrn, Marcela R; Kster, Andres M; Khanna, Shiv N

    2007-12-19

    First principles electronic structure calculations have been carried out to investigate the ground state geometry, electronic structure, and the binding energy of [Au(H2O)n]+ clusters containing up to 10 H2O molecules. It is shown that the first coordination shell of Au+ contains two H2O molecules forming a H2O-Au+-H2O structure with C2 symmetry. Subsequent H2O molecules bind to the previous H2O molecules forming stable and fairly rigid rings, each composed of 4 H2O molecules, and leading to a dumbbell structure at [Au(H2O)8]+. The 9th and the 10th H2O molecules occupy locations above the Au+ cation mainly bonded to one H2O from each ring, leading to structures where the side rings are partially distorted and forming structures that resemble droplet formation around the Au+ cation. The investigations highlight quantum effects in nucleation at small sizes and provide a microscopic understanding of the observed incremental binding energy deduced from collision induced dissociation that indicates that [Au(H2O)n]+ clusters with 7-10 H2O molecules have comparable binding energy. The charge on the Au+ is shown to migrate to the outside H2O molecules, suggesting an interesting screening phenomenon. PMID:18034477

  15. 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 be provided.

  16. 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.

  17. 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.

  18. 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. Abstract #1606 (2007).

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

    PubMed

    Alvarez-Camacho, Micheln; Urrusti, Jos Luis; Acero, Mara Del Carmen; Galvn Duque-Gastlum, Carlos; Rodrguez-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. PMID:25264793

  20. Experimental and numerical analysis of pressure pulses characteristics in a Francis turbine with partial load

    NASA Astrophysics Data System (ADS)

    Yexiang, X.; Zhengwei, W.; Zongguo, Y.; Jin, Z.

    2010-08-01

    This study experimentally and numerically investigates the pressure pulses characteristics and unsteady flow behavior in a Francis turbine with partial load. Unsteady wall pressure measurements with partial load condition are performs to investigate thoroughly pressure fields in the spiral case, runner head cover and straight draft tube dynamically. The unsteady Reynolds- averaged Navier-Stokes equations with the k-?based SST turbulence model were used to model the unsteady flow within the entire flow passage of the Francis turbine. The dominate frequency of the predicted pressure pulses at runner inlet agree with the experimental results in the head cover. The influence of the blade passing frequency causes the simulated peak-to-peak amplitudes in the runner inlet to be larger than in the head cover. The measured and predicted pressure pulses at different positions along the runner are comparable. The predicted pressure fluctuations in the draft tube agree well with the experimental results. However the peak-to-peak amplitudes in the spiral case are not as well predicted so the calculation domain and the inlet boundary conditions need to be improved. At the most unstable operating condition, the pulse in the flow passage are due to the rotor-stator interference (RSI) between the runner and the guide vanes, the blade channel vortex in the runner blade passage and the vortex rope in the draft tube. The unsteady flow patterns in the turbine, including the blade channel vortex in the runner and the helical vortex rope in the draft tube, are classified numerically.

  1. 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.

  2. 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.

  3. Measured pressure distributions inside nonaxisymmetric nozzles with partially deployed thrust reversers

    NASA Technical Reports Server (NTRS)

    Green, Robert S.; Carson, George T., Jr.

    1987-01-01

    An investigation was conducted in the Langley 16-Foot Transonic Tunnel at static conditions to measure the pressure distributions inside a nonaxisymmetric nozzle with simultaneous partial thrust reversing (50-percent deployment) and thrust vectoring of the primary (forward-thrust) nozzle flow. Geometric forward-thrust-vector angles of 0 and 15 deg. were tested. Test data were obtained at static conditions while nozzle pressure ratio was varied from 2.0 to 4.0. Results indicate that, unlike the 0 deg. vector angle nozzle, a complicated, asymmetric exhaust flow pattern exists in the primary-flow exhaust duct of the 15 deg. vectored nozzle.

  4. Development of an infrared absorption transducer to monitor partial pressure of carbon dioxide for space applications

    NASA Technical Reports Server (NTRS)

    Lutz, Glenn; Margiott, Victoria; Murray, Sean; Schaff, James

    1993-01-01

    An infrared (IR) carbon dioxide (CO2) transducers has been designed, developed, and produced for space applications. The transducer provides measurement of partial pressure of CO2 in life support applications, including the Extravehicular Mobility Unit (EMU), Space Shuttle Orbiter and Spacehab. The electrochemical sensor presently used for these applications has a slow reponse time and has reliability concerns due to the electrolyte. The new microprocessor based unit has a fast response time and can be tailored to other space applications.

  5. 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.

  6. 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 ongoing global climate shifts. PMID:21905423

  7. 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.

  8. 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 1250C in Internally Heated Pressure Vessels. The multiple volatile series were synthesized at 5 kbar and 1250C. 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 ~150C 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 ~30C. 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 small, and that the effects of combined F and H2O are approximately additive. CO2, when present in significant amounts (~1000s of ppm) seems to have a negligible or even a slight viscosity-increasing effect, which may partially counteract the effects of dissolved H2O or H2O + F. However, small amounts of CO2 (a few 100 ppm) may further decrease the viscosity of hydrous basalt. Because the viscosity-reducing effect of added H2O is strongest at low water contents, degassed basaltic lavas containing only small amounts of H2O, CO2 and F may still be substantially more fluid than truly volatile-free liquids.

  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

    2014-10-22

    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=500C). 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. PMID:25459700

  10. Thermodynamic description of equilibria in mixed fluids (H 2O-non-polar gas) over a wide range of temperature (25-700C) 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 500C, 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.

  11. 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.

  12. 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 ? atm (n=46), whereas the Solimoes and Negro rivers, in the state of Amazonas, showed values around 0.43 0.08 ? atm (n=131). Atmospheric averages were approximately 0.34 0.04 ? atm (n=58) and 0.32 0.03 ? 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 this gas to the atmosphere from the middle of the river channels. However, at the river margins and riparian zones, significantly different redox conditions may occur, which should be further investigated to fully understand the role of N2O fluxes in these riverine systems.

  13. Low-temperature reduction of Ge oxide by Si and SiH4 in low-pressure H2 and Ar environment

    NASA Astrophysics Data System (ADS)

    Minami, Kaichiro; Moriya, Atsushi; Yuasa, Kazuhiro; Maeda, Kiyohiko; Yamada, Masayuki; Kunii, Yasuo; Niwano, Michio; Murota, Junichi

    2015-08-01

    Introduction of Ge into ULSIs has become increasingly attractive because of the higher carrier mobility of Ge. Since Ge native oxide is formed easily in cleanroom air, the control of formation and reduction of the Ge oxide is requested for the introduction of Ge layers into Si process. Here, the reactions between gas phase Ge oxide and Si substrate and between the Ge oxide on Ge epitaxial layer and SiH4 are investigated. The native-oxidized Ge amount is obtained by calculating from chemically shifted peak intensity of Ge 3d measured by X-ray photoelectron spectroscopy. By the adsorption of the Ge oxide on Si(1 0 0) surface, pure Ge and Si oxide are formed on the Si surface even at 350 C and the formed Ge amount tends to correspond to the oxidized Si amount, independently of the heat-treatment environment of H2 and Ar under the condition that Si oxide is not reduced by H2. By SiH4 treatment, the amount of the oxidized Ge on the Ge layer decreases drastically even at 350 C and Si oxide is formed on the Ge layer. From these results, it is suggested that the Ge oxide is reduced even at 350 C by Si or SiH4, and the Si oxide and the pure Ge are formed.

  14. 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).

  15. 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 700C 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 770C.

  16. Studies of Zero-field Splitting and its Pressure and Stress Dependence for Ni2+ in La2Mg3(NO3)12 24 H2O Crystal

    NASA Astrophysics Data System (ADS)

    Zheng, Wen-Chen; Wu, Shao-Yi; Dong, Hui-Ning

    2001-12-01

    By using the high-order perturbation formulas, the g factors g||and g?, the zero-field splittings D and the pressure and uniaxial stress dependences of zero-field splitting are studied for Ni2+ ions in both Mg + sites of La2Mg3(NO3)12 24 H2O crystal. It is found that the local trigonal distortion angles iof the two Ni + centers are only slightly different from the corresponding host ones, but the local angular compressibilities under pressure and stress for both Ni centers are quite different not only from the corresponding host ones, but also from each other.

  17. 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.

  18. Proximate nutritional composition of celss crops grown at different CO2 partial pressures

    NASA Astrophysics Data System (ADS)

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

    1994-11-01

    Two 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. With the exception of increased crude fiber of soybean seed with increased CO2, no trends were apparent with regard to CO2 effects on proximate composition of soybean seed and potato 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.

  19. 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.

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

    PubMed

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

    1994-11-01

    Two 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. With the exception of increased crude fiber of soybean seed with increased CO2, no trends were apparent with regard to CO2 effects on proximate composition of soybean seed and potato 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. PMID:11540178

  1. Relating oxygen partial pressure, saturation and content: the haemoglobinoxygen dissociation curve

    PubMed Central

    Rudenski, Aram; Gibson, John; Howard, Luke; ODriscoll, Ronan

    2015-01-01

    Key Points In clinical practice, the level of arterial oxygenation can be measured either directly by blood gas sampling to measure partial pressure (PaO2) and percentage saturation (SaO2) or indirectly by pulse oximetry (SpO2). This review addresses the strengths and weaknesses of each of these tests and gives advice on their clinical use. The haemoglobinoxygen dissociation curve describing the relationship between oxygen partial pressure and saturation can be modelled mathematically and routinely obtained clinical data support the accuracy of a historical equation used to describe this relationship. Educational Aims To understand how oxygen is delivered to the tissues. To understand the relationships between oxygen saturation, partial pressure, content and tissue delivery. The clinical relevance of the haemoglobinoxygen dissociation curve will be reviewed and we will show how a mathematical model of the curve, derived in the 1960s from limited laboratory data, accurately describes the relationship between oxygen saturation and partial pressure in a large number of routinely obtained clinical samples. To understand the role of pulse oximetry in clinical practice. To understand the differences between arterial, capillary and venous blood gas samples and the role of their measurement in clinical practice. The delivery of oxygen by arterial blood to the tissues of the body has a number of critical determinants including blood oxygen concentration (content), saturation (SO2) and partial pressure, haemoglobin concentration and cardiac output, including its distribution. The haemoglobinoxygen dissociation curve, a graphical representation of the relationship between oxygen saturation and oxygen partial pressure helps us to understand some of the principles underpinning this process. Historically this curve was derived from very limited data based on blood samples from small numbers of healthy subjects which were manipulated in vitro and ultimately determined by equations such as those described by Severinghaus in 1979. In a study of 3524 clinical specimens, we found that this equation estimated the SO2 in blood from patients with normal pH and SO2 >70% with remarkable accuracy and, to our knowledge, this is the first large-scale validation of this equation using clinical samples. Oxygen saturation by pulse oximetry (SpO2) is nowadays the standard clinical method for assessing arterial oxygen saturation, providing a convenient, pain-free means of continuously assessing oxygenation, provided the interpreting clinician is aware of important limitations. The use of pulse oximetry reduces the need for arterial blood gas analysis (SaO2) as many patients who are not at risk of hypercapnic respiratory failure or metabolic acidosis and have acceptable SpO2 do not necessarily require blood gas analysis. While arterial sampling remains the gold-standard method of assessing ventilation and oxygenation, in those patients in whom blood gas analysis is indicated, arterialised capillary samples also have a valuable role in patient care. The clinical role of venous blood gases however remains less well defined. PMID:26632351

  2. Effect of Plasma Treatment on Multi-Walled Carbon Nanotubes for the Detection of H2S and SO2

    PubMed Central

    Zhang, Xiaoxing; Yang, Bing; Wang, Xiaojing; Luo, Chenchen

    2012-01-01

    H2S and SO2 are important characteristic gases of partial discharge (PD) generated by latent insulated defects in gas insulated switchgear (GIS). The detection of H2S and SO2 is of great significance in the diagnosis and assessment of the operating status of GIS. In this paper, we perform experiments on the gas sensitivity of unmodified multi-walled carbon nanotubes (MWNTs) and those modified by atmospheric pressure dielectric barrier discharge (DBD) air plasma at different times (30, 60 and 120 s) for H2S and SO2, respectively. The results show that the sensitivity and response time of modified MWNTs to H2S are both improved, whereas the opposite effects are observed for SO2. The modified MWNTs have almost zero sensitivity to SO2. Thus, the MWNTs modified by atmospheric pressure DBD air plasma present good selectivity to H2S, and have great potential in H2S detection. PMID:23012548

  3. Effect of plasma treatment on multi-walled carbon nanotubes for the detection of H2S and SO2.

    PubMed

    Zhang, Xiaoxing; Yang, Bing; Wang, Xiaojing; Luo, Chenchen

    2012-01-01

    H(2)S and SO(2) are important characteristic gases of partial discharge (PD) generated by latent insulated defects in gas insulated switchgear (GIS). The detection of H(2)S and SO(2) is of great significance in the diagnosis and assessment of the operating status of GIS. In this paper, we perform experiments on the gas sensitivity of unmodified multi-walled carbon nanotubes (MWNTs) and those modified by atmospheric pressure dielectric barrier discharge (DBD) air plasma at different times (30, 60 and 120 s) for H(2)S and SO(2), respectively. The results show that the sensitivity and response time of modified MWNTs to H(2)S are both improved, whereas the opposite effects are observed for SO(2). The modified MWNTs have almost zero sensitivity to SO(2). Thus, the MWNTs modified by atmospheric pressure DBD air plasma present good selectivity to H(2)S, and have great potential in H(2)S detection. PMID:23012548

  4. 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 ? 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 molar ratios of reactant H 2O to NaCl of 6:1 and 2:1, respectively. Our results imply that quite simple mechanisms may exist in the dissolution of common rock-forming minerals in saline fluids at high P and T and allow assessment of the interaction of simple, congruently soluble rock-forming minerals with brines associated with deep-crustal metamorphism.

  5. Oxygen partial pressure on the structural and electrical properties of CdZnO thin films

    NASA Astrophysics Data System (ADS)

    Kumar, A. Guru Sampath; Obulapathi, L.; Maddaiah, M.; Sarmash, T. Sofi; Rani, D. Jhansi; Rao, J. V. V. N. Kesava; Rao, T. Subba; Asokan, K.

    2015-06-01

    The Cd doped ZnO have versatile applications in the field of solar cells, Optoelectronic devices. The Cd doped ZnO thin films were prepared by reactive dc magnetron sputtering at different O2 Partial Pressures (1-3sccm) on glass substrate. The structure of the compound was determined by XRD, the mictro structure was studied by FE-SEM, the absorption spectra studies were measured with UV-Vis-NIR spectrometer and electrical properties were studied by four probe method. The optical band gap was variation reported in this study. The minimum resistivity found at PO2=2.0sccm.

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

    NASA Technical Reports Server (NTRS)

    Wenzinger, Carl J; Harris, Thomas A

    1937-01-01

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

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

    NASA Technical Reports Server (NTRS)

    1996-01-01

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

  8. 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.

  9. Oxygen partial pressure dependence of electrical conductivity in ??-Bi2MoO6

    NASA Astrophysics Data System (ADS)

    Vera, C. M. C.; Aragn, R.

    2008-05-01

    The electrical conductivity of ?'-Bi 2MoO 6 was surveyed between 450 and 750 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.

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

    PubMed

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

    2012-08-01

    The authors tested the efficacy of elevated partial pressures of CO(2) 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 CO(2) may be an effective and inexpensive lethal tool to treat substrates, tanks, or materials infested with New Zealand mudsnails. PMID:22573531

  11. [Redifferentiation of dedifferentiated joint cartilage cells in alginate culture. Effect of intermittent hydrostatic pressure and low oxygen partial pressure].

    PubMed

    Domm, C; Fay, J; Schnke, M; Kurz, B

    2000-02-01

    One of the goals in the field of tissue engineering is the development of artificial cartilage for the treatment of cartilage defects. Therefore autologous chondrocytes are seeded on different artificial matrices to test their possible use as implants (resorption, antigenicity, toxicity and their integration in the tissue). One of the main problems in these experiments is that usually the amount of available chondrocytes is too low for treating large-scale defects or for comparing different matrices. An in-vitro-multiplication of the cells is needed which causes the chondrocytes to dedifferentiate and become fibroblast-like. Therefore parameters which induce a redifferentiation are of great interest. The objective of this study was to determine the influence of intermittent hydrostatic pressure and low oxygen partial pressure on the redifferentiation of dedifferentiated bovine articular chondrocytes in monolayer and three-dimensional alginate bead culture. The redifferentiation process was monitored by immunocytochemical detection of newly synthesized collagen type II. The viability of the cells was determined by the trypanblue exclusion test. The chondrocytes were dedifferentiated by a two week culture in plastic flasks with an oxygen level of 20%. After this they were subcultured in monolayer or three-dimensional alginate culture and subjected to three different stimuli for three weeks in order to redifferentiate: 1.) 20% O2 (= 20.26 kPa PO2) + 5% CO2 + 75% N2; 2.) 5% O2 (= 5.07 kPa PO2) + 5% CO2 + 90% N2; 3.) 5% O2 (= 5.07 kPa PO2) + 5% CO2 + 90% N2 + 8 h/d of intermittent hydrostatic pressure (frequency: 3 bar absolute for 30 min and 1 bar absolute for 2 min). In the monolayer there was no detectable collagen type II found by immunocytochemistry under either of the three culture conditions. Therefore a redifferentiation of dedifferentiated chondrocytes was not possible in monolayer cultures with the tested parameters. In the three-dimensional alginate culture there was no immunocytochemical staining of collagen type II found in the beads cultured with 20% oxygen. With 5% oxygen we found a strong collagen type II-production by chondrocytes throughout the whole bead. The intermittent hydrostatic pressure combined with 5% oxygen lead to a decreased collagen type II-production compared to cells subjected to 5% oxygen only. Also chondrocytes closer to the edge of these beads were more often immunopositive and seemed to produce more immunoreactive collagen type II. The viability of the chondrocytes in the alginate culture was close to 90% after three weeks. Our experiments showed that oxygen partial pressure is an important parameter in the cultivation of articular chondrocytes. Reduced partial oxygen pressure promoted or induced the redifferentiation of dedifferentiated chondrocytes in alginate culture. PMID:10743629

  12. An experimental study on the ergonomics indices of partial pressure suits.

    PubMed

    Li, Xianxue; Ding, Li; Hedge, Alan; Hu, Huimin; Qin, Zhifeng; Zhou, Qianxiang

    2013-05-01

    Partial pressure suits (PPSs) are used under high altitude, low-pressure conditions to protect the pilots. However, the suit often limits pilot's mobility and work efficiency. The lack of ergonomic data on the effects of PPSs on mobility and performance creates difficulties for human factor engineers and cockpit layout specialists. This study investigated the effects of PPSs on different ergonomic mobility and performance indices in order to evaluate the suit's impact on pilot's body mobility and work efficiency. Three types of ergonomics indices were studied: the manipulative mission, operational reach and operational strength. Research results indicated that a PPS significantly affects the mobility and operational performance of the wearers. The results may provide mission planners and human factors engineers with better insight into the understanding of pilots' operational function, mobility and strength capabilities when wearing PPS. PMID:23102522

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

    PubMed Central

    2014-01-01

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

  14. 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.

  15. Theoretical studies of the spin-Hamiltonian parameters and the effects of the temperature and pressure on the zero-field splitting for Ni 2+: Zn(BF 4) 26H 2O crystal

    NASA Astrophysics Data System (ADS)

    Feng, Wen-Lin; Zheng, Wen-Chen; Wu, Xiao-Xuan; Liu, Hong-Gang

    2007-01-01

    The spin-Hamiltonian parameters (the g factors g?, g? and the zero-field splitting D) and the effects of the temperature and pressure on D for Ni 2+ ion at the trigonal Zn 2+ site in the low- and room-temperature phase of Zn(BF 4) 26H 2O crystal are calculated. The calculations are based on the microscopic spin Hamiltonian theory in teams of the diagonalization of the complete energy matrix of 3 d8 ions in trigonal symmetry. The crystal-field parameters related to the impurity structure are obtained from the superposition model. Thus, the local trigonal distortion angle ?, the local angular thermal expansion coefficient and local angular compressibility for Ni 2+ impurity centers in Zn(BF 4) 26H 2O crystal are estimated. The reasonableness of these local values is discussed.

  16. 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.

  17. 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.

  18. Ions in carbon dioxide at atmospheric pressure5. Reactions in CO 2-CO-CH 4-H 2O mixtures and coolant chemistry

    NASA Astrophysics Data System (ADS)

    Ikezoe, Yasumasa; Onuki, Kaoru; Shimizu, Saburo; Nakamura, Hirone; Tagawa, Seiichi; Tabata, Yoneho

    Ionic reactions in carbon dioxide mixtures were studied in order to obtain experimental data for chemical reactions in the nuclear reactor coolant. At 298 K, major ionsformed in 1 atm CO 2-CO-CH 4 by irradiation were (CO) +2 nCO 2 ( n=0-4). At 518 K, CH 3CO + nCO 2 ( n=0, 1) and HCO + nCO 2 ( n=0, 1) were the major ions. When trace amounts of water were added, the major ions shifted to H 3O + mH 2O nCO 2( m=0-4, n=0-3) at 298and 518 K. At 518 K, CH 3CO + nCO 2( n=0, 1) were also observed. These ions were stable enough to survive gas phase ion-molecule reactions till they react with the surface of reactor materials or with negative ions in the gas phase. Rate constants for the reaction [(CO) +2CO 2+CH 4?CH 3CO +CO 2, HCO +CO 2] at 298 and 518 K were 1 x 10 -12 and 1.30.610 -10 cm 3s -1, respectively. Product ratios of this reaction depended on temperature.

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

    NASA Astrophysics Data System (ADS)

    Chakraborty, Mahua; Banerjee, Amit; Das, Debajyoti

    2014-07-01

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

  20. 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.

  1. 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 times higher. Toxicity assessment was performed using two marine species (Vibrio fischeri and Paracentrotus lividus sea-urchin) after each treatment step. The highest toxicity was attributed to H2O2/UVC effluent for both tested species. After MBT a drastic decrease of toxicity was achieved. PMID:26773490

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

    NASA Astrophysics Data System (ADS)

    Jing, Zhicheng; Karato, Shun-ichiro

    2012-05-01

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

  3. H2 Reconstitution

    NASA Astrophysics Data System (ADS)

    Skipper, Mike

    2002-02-01

    The high power microwave program at the Air Force Research Laboratory (AFRL) includes high power source development in narrow band and wideband technologies. The H2 source is an existing wideband source that was developed at the AFRL. A recent AFRL requirement for a wideband impulse generator to use in materials tests has provided the need to update the H2 source for the current test requirements. The H2 source is composed of a dual resonant transformer that charges a short length of coaxial transmission line. The transmission line is then discharged into an output coaxial transmission line with a self-break hydrogen switch. The dual resonant transformer is driven by a low inductance primary capacitor bank operating through a self-break gas switch. The upgrade of the coaxial hydrogen output switch is the focus of this report. The hydrogen output switch was developed through extensive electrical and mechanical simulations. The switch insulator is made of Ultem 2300 and is designed to operate with a mechanical factor of safety equal to 4.0 at 1,000 psi. The design criteria, design data and operational data will be presented.

  4. Pressure broadening and shift of the cesium D1 transition by the noble gases and N2 , H2 , HD, D2 , CH4 , C2H6 , CF4 , and H3e

    NASA Astrophysics Data System (ADS)

    Pitz, Greg A.; Wertepny, Douglas E.; Perram, Glen P.

    2009-12-01

    The pressure broadening and shift rates for the cesium D1 (6P21/2?6S21/2) transition with the noble gases and N2 , H2 , HD, D2 , CH4 , C2H6 , CF4 , and H3e were obtained for pressures less than 300 torr at temperatures under 65C by means of laser absorption spectroscopy. The collisional broadening rate, ?L , for He, Ne, Ar, Kr, Xe, N2 , H2 , HD, D2 , CH4 , C2H6 , CF4 , and H3e are 24.13, 10.85, 18.31, 17.82, 19.74, 16.64, 20.81, 20.06, 18.04, 29.00, 26.70, 18.84, and 26.00 MHz/torr, respectively. The corresponding pressure-induced shift rates, ? , are 4.24, -1.60 , -6.47 , -5.46 , -6.43 , -7.76 , 1.11, 0.47, 0.00, -9.28 , -8.54 , -6.06 , and 6.01 MHz/torr. These rates have then been utilized to calculate Lennard-Jones potential coefficients to quantify the interatomic potential surfaces. The broadening cross section has also been shown to correlate with the polarizability of the collision partner.

  5. 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.

  6. Partial Melting in the Iron-Sulfur System at High Pressures

    NASA Astrophysics Data System (ADS)

    Campbell, A. J.; Seagle, C. T.; Heinz, D. L.; Shen, G.; Prakapenka, V. B.

    2005-12-01

    Melting in the Fe-rich portion of the Fe-S system was investigated to pressures of 80 GPa, using in situ synchrotron x-ray diffraction through a laser-heated diamond anvil cell at the GSECARS sector of APS. Intimately mixed Fe-FeS powders were compressed between insulating layers of NaCl in the diamond anvil cell. Double-sided laser heating was used to reduce axial temperature gradients, and temperatures were measured spectroradiometrically on both sides of the cell. Only the central, hottest part of the laser-heated region was probed with the 5x7 micron x-ray beam. At high pressures, Fe3S was formed by reaction between Fe and FeS upon laser heating, with excess Fe remaining. The Fe was used as an internal, high-temperature pressure standard based on existing equation of state data. Diffraction data were collected during laser heating and also from the quenched sample following each heating episode. The use of an image plate area detector greatly improved our ability to verify the presence of both metal and sulfide during heating. The eutectic temperature was bracketed by the absence of one phase above the melting point and the presence of both phases at lower temperature. The reappearance of the absent component (sulfide or metal) upon rapid quenching was taken as confirmation that partial melting had been achieved. Our results using this method are in broad agreement with earlier data that were based on textural criteria.

  7. The system H 2O-NaCl. Part I: Correlation formulae for phase relations in temperature-pressure-composition space from 0 to 1000 C, 0 to 5000 bar, and 0 to 1 XNaCl

    NASA Astrophysics Data System (ADS)

    Driesner, Thomas; Heinrich, Christoph A.

    2007-10-01

    Realistic simulations of fluid flow in geologic systems have severely been hampered by the lack of a consistent formulation for fluid properties for binary salt-water fluids over the temperature-pressure-composition ranges encountered in the Earth's crust. As the first of two companion studies, a set of correlations describing the phase stability relations in the system H 2O-NaCl is developed. Pure water is described by the IAPS-84 equation of state. New correlations comprise the vapor pressure of halite and molten NaCl, the NaCl melting curve, the composition of halite-saturated liquid and vapor, the pressure of vapor + liquid + halite coexistence, the temperature-pressure and temperature-composition relations for the critical curve, and the compositions of liquid and vapor on the vapor + liquid coexistence surface. The correlations yield accurate values for temperatures from 0 to 1000 C, pressures from 0 to 5000 bar, and compositions from 0 to 1 XNaCl (mole fraction of NaCl). To facilitate their use in fluid flow simulations, the correlations are entirely formulated as functions of temperature, pressure and composition.

  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.

    2013-01-01

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

  9. Behaviour at high pressure of Rb7NaGa8Si12O403H2O (a zeolite with EDI topology): a combined experimental-computational study

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    The high-pressure behaviour and the P-induced structural evolution of a synthetic zeolite Rb7NaGa8Si12O403H2O (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) 3 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 Rb7NaGa8Si12O403H2O and those previously found in natural fibrous zeolites is made.

  10. 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.

  11. 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.

  12. Electrical conduction of bis(1,2-diondioximato)metals(II) and their partially oxidized complexes at high pressures

    NASA Astrophysics Data System (ADS)

    Shirotani, Ichimin; Onodera, Akifumi; Hara, Yoji

    1981-11-01

    The resistivity of one-dimensional d8-metal complexes with various kinds of 1,2-diondioxime(dimethylglyoxime, nioxime, and diphenylglyoxime) ligands has been measured at high pressures. The resistivity of M(dmg) 2 and M(niox) 2 decreased with increasing pressure. The resistivity of M(dmg) 2 is much lower than that of M(niox) 2 at high pressure, though M- M distances and optical energy gaps in both salts are almost the same at atmospheric pressure. An anomalous low resistivity has been observed in Pt(dmg) 2 at about 40 kbar. The electrical resistivity of M(niox) 2 and M(dmg) 2, oxidized by oxidizing agents, decreased with increasing pressure. The resistivity of partially oxidized Pt complexes is significantly higher than that of the parent compounds at high pressure. On the contrary, partially oxidized Ni and Pd complexes are more conductive than unoxidized compounds at high pressures. The electrocal resistivity of unoxidized and partially oxidized Pt complexes increased with increasing pressure at higher pressures. The resistivity minimum at high pressure has been observed only in Pt complexes. The infrared spectra of the d8-metal complexes and their partially oxidized complexes have been investigated. The frequency of the C?N stretching vibration in M(dmg) 2 and M(niox) 2 salts increases in the order Ni > Pd > Pt; on the other hand, the frequency of M(niox) 2Xn increases in the order Ni < Pd < Pt. The frequency of the C?N stretching vibration is closely related to the effect of metal-ligand ?? back bonding in d8-metal complexes. Some anomalies in the resistance-pressure curve have been found in Ni(dpg) 2, Ni(dpg) 2I, Ni(dpg) 2I 0.5, and Ni(dpg) 2I 0.14. The anomalies are explained by new pressure-induced phase transitions.

  13. 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.

  14. 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.

  15. 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.

  16. Nitrogen Partial Pressure in the Archean Atmosphere From Analysis of Hydrothermal Quartz

    NASA Astrophysics Data System (ADS)

    Marty, B.; Zimmermann, L.; Burgess, R.; Pujol, M.; Philippot, P.

    2012-12-01

    Atmospheric nitrogen constitutes the main pool of one of the major biogenic elements, it may provide a record of the terrestrial magnetic field, and it might have been instrumental to maintain clement temperatures despite a lower energy provided by the ancient Sun. We have investigated the partial pressure of di-nitrogen in the Archean atmosphere by analyzing the ratio between N2 and argon-36 (a primordial, chemically inert noble gas for which there is no reason to suspect abundance variation in the atmosphere through time) in fluid inclusions (FI) trapped in two hydrothermal quartz from the 3.5 Ga-old Dresser formation, North Pole, Pilbara (NE Australia). These samples have different histories of fluid trapping and deposition, and their ages are constrained within 3.0-3.5 Ga from U-Xe, and Ar-Ar dating. FI nitrogen is a mixture between hydrothermal and air-saturated water (ASW) end-members, that can be identified through geochemical correlations between Cl/36Ar, 40Ar/36Ar and N2/36Ar ratios. The ASW component has a N2/36Ar ratio within 30 % of the modern value, implying a N2 partial pressure during the Archean was within 0.6-1 bar. The nitrogen isotopic composition of the ASW end-member is also found similar to the present-day one within 3 permil. Combined with the recent proposal from ancient raindrop imprints that the total atmospheric pressure was 0.5-1.14 bar, this leaves less than 0.7 bar for the pressure of other atmospheric gases including CO2. Thus nitrogen did not play a significant role in the thermal budget of the ancient Earth, and the terrestrial magnetic field was already strong enough at that time to shield the upper atmosphere from interaction with the solar wind, and therefore to prevent atmospheric escape that would have been recorded otherwise in the nitrogen composition. These results also imply that exchanges of nitrogen between the Earth's mantle and the surface were limited, or proceeded at similar rates in both ways from the Archean to Present.

  17. 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.

  18. 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.

  19. Modeling the exhumation path of partially melted ultrahigh-pressure metapelites, North-East Greenland Caledonides

    NASA Astrophysics Data System (ADS)

    Lang, Helen M.; Gilotti, Jane A.

    2015-06-01

    Pseudosection modeling constrains the pressure-temperature (P-T) exhumation path of partially melted ultrahigh-pressure (UHP) metapelites exposed in the North-East Greenland UHP terrane. A robust peak P and T estimate of 3.6 GPa and 970 C based on mineral assemblages in nearby kyanite eclogites is the starting point for the P-T path. Although the peak assemblage for the metapelite is not preserved, the calculated modeled peak assemblage contained substantial clinopyroxene, garnet, phengite, K-feldspar and coesite with minor kyanite and rutile. Combining the pseudosection and observed textures, the decompression path crosses the coesite-quartz transition before reaching the dry phengite dehydration melting reaction where phengite is abruptly consumed. In the range of 2.5 to 2.2 GPa, clinopyroxene is completely consumed and garnet grows to its maximum volume and grossular content, matching the high grossular rims of relict megacrysts. Plagioclase joins the assemblage and the pseudosection predicts up to 12-13 vol.% melt in the supersolidus assemblage, which contained garnet, liquid, K-feldspar, plagioclase, kyanite, quartz and rutile. At this stage, the steep decompression path flattened out and became nearly isobaric. The melt crystallization assemblage that formed when the path crossed the solidus with decreasing temperature contains phengite, garnet, biotite, 2 feldspars, kyanite, quartz and rutile. Therefore, the path must have intersected the solidus at approximately 1.2 GPa, 825 C. The pseudosection predicts that garnet is consumed on the cooling path, but little evidence of late garnet consumption or other retrograde effects is observed. This may be due to partial melt loss from the rock. Isochemical PT-n and PT-X sections calculated along the P-T path display changes in mineral assemblage and composition that are consistent with preserved assemblages.

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

    DOE PAGESBeta

    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

  1. 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.

  2. 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.

  3. MELCOR-H2

    Energy Science and Technology Software Center (ESTSC)

    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,more » 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.« less

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

    SciTech Connect

    Atul Sharma; Ikuo Saito; Toshimasa Takanohashi

    2009-09-15

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

  5. Two-dimensional simulation of an atmospheric-pressure RF DBD in a H2 : O2 mixture: discharge structures and plasma chemistry

    NASA Astrophysics Data System (ADS)

    Shkurenkov, I. A.; Mankelevich, Yu A.; Rakhimova, T. V.

    2013-02-01

    The results of two-dimensional modelling of a radio-frequency dielectric barrier discharge (RF DBD) in a hydrogen-oxygen stoichiometric mixture under atmospheric pressure are presented. The production of active species and the possibility of ignition of the mixture are studied. It is shown that the production of active species in the discharge is enough to reduce the ignition temperature significantly. A detailed description of the ion production and loss is presented. The processes of electron attachment are very fast, while the detachment processes depend on the type of ion. The electron detachment, charge recombination, and conversion of negative and positive ions are very important here. The current discharge consists of breakdowns that occur in each half-period, and it resembles the standard DBDs of kilohertz frequency. The surface charge is not uniform over the electrode area and the RF DBD consists of micro-discharges, which are not so pronounced as in the DBDs of kilohertz frequency. Two additional types of RF DBDs, the dual-frequency RF DBD and frequency-modulated RF DBD, are simulated for the purpose of controlling the ratio between the input power absorbed by electrons and ions in this discharge.

  6. Revealing sub-?m and ?m-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

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

    NASA Astrophysics Data System (ADS)

    Zentkov, M.; Mihalik, M.; Arnold, Z.; Kamard, 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 ?(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 ? 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.

  8. 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.

  9. 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-day test period (DC range, 36-40 mg/l). The ID meter was then modified so as to provide for DO as well as DC measurements across components of an intensive fish production system. ?? 2003 Elsevier B.V. All rights reserved.

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

    PubMed

    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 (C(p), DeltaH) 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 that of a lower-energy fused prism cluster at high temperatures. PMID:19814548

  11. [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.

  12. Observation of different core water cluster ions Y-(H2O)n (Y = O2, HCN, HOx, NOx, COx) and magic number in atmospheric pressure negative corona discharge mass spectrometry

    NASA Astrophysics Data System (ADS)

    Sekimoto, K.; Takayama, M.

    2010-12-01

    Atmospheric ion water clusters have been of long-standing interest in the field of atmospheric sciences, because of them playing a central role in the formation of tropospheric aerosols which affect the photochemistry, radiation budget of the atmosphere and climate. On the basis of a mechanism of aerosol formation in the troposphere proposed by Yu and Turco, termed “ion-mediated nucleation” (Geophys. Res. Lett. 2000, 27, 883), atmospheric ion water clusters are most likely to be produced via two processes; 1) direct attachment of polar solvent molecules H2O to atmospheric ions due to them having strong binding energy via ion-dipole interactions, and 2) growth of ion-induced hydrates into larger water clusters bound via hydrogen-bonding networks by condensation with H2O molecules. The stability and growth rates of water clusters are strongly dependent on the thermochemical properties of individual atmospheric core ions. A large number of thermochemical information of the positive atmospheric ion H3O+ and its hydrates H3O+(H2O)n have been reported so far, while there has been little information of the water clusters with the negative atmospheric core ions. Therefore, fundamental studies of the thermochemistry of various negative atmospheric ion water clusters will contribute towards furthering an understanding of their unique role in atmospheric sciences and climate change. We have recently established an atmospheric pressure DC corona discharge device containing a specific corona needle electrode that made it possible to reproducibly generate negative core ions Y- originating from ambient air (Int. J. Mass Spectrom. 2007, 261, 38; Eur. Phys. J. D 2008, 50, 297). The change in electric field strength on the needle tip resulted in the formation of negative atmospheric core ions Y- with various different lifetimes in air. The low field strength brought about the dominant formation of core ions with short lifetimes in air such as O2- and HOx-, while the longer-lived core ions HCN-, NOx- and COx- were mainly produced at higher field strength. Furthermore, the use of the discharge system coupled to mass spectrometers led to the stable formation of large water clusters Y-(H2O)n due to adiabatic expansion caused by the pressure difference between the ambient discharge area (760 torr) and vacuum region in the mass spectrometers (≈ 1 torr). Here we show the resulting mass spectra of large water clusters Y-(H2O)n (0 ≤ n ≥ 80) with the dominant negative core ion Y- such as O2-, HO-, HO2-, HCN-, NO2-, NO3-, NO3-(HNO3)2, CO3- and HCO4- which play a central role in tropospheric ion chemistry, as well as the detailed mechanism of formation of those negative ion water clusters by atmospheric pressure DC corona discharge mass spectrometry. Here we also provide new thermochemical information about magic numbers and first hydrated shells for individual negative core ions Y-, which have particular stability in the Y-(H2O)n cluster series, by using the reliable mass spectrometry data obtained and the relationship between the temperature condition in a reaction chamber and the resulting cluster distribution.

  13. 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. PMID:15726959

  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. Effects of oxygen partial pressure on packing density and laser damage threshold of TiO{sub 2} thin films

    SciTech Connect

    Yao Jianke; Fan Zhengxiu; Jin Yunxia; Zhao Yuanan; He Hongbo; Shao Jianda

    2007-09-15

    TiO{sub 2} films are deposited by electron beam evaporation as a function of oxygen partial pressure. The packing density, refractive index, and extinction coefficient all decrease with the increase of pressure, which also induces the change of the film's microstructure, such as the increase of voids and H{sub 2}O concentration in the film. The laser-induced damage threshold (LIDT) of the film increases monotonically with the rise of pressure in this experiment. The porous structure and low nonstoichiometric defects absorption contribute to the film's high LIDT. The films prepared at the lowest and the highest pressure show nonstoichiometric and surface-defects-induced damage features, respectively.

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

    SciTech Connect

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

    1997-09-01

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

  17. Stigmatically focusing partial pressure analyzer with dual chamber ion source. Ph.D. Thesis - Technical Univ. of Munich, 1971

    NASA Technical Reports Server (NTRS)

    Rasskopf, Klaus F.

    1987-01-01

    The partial pressure analyzer developed has a high absolute sensitivity and high resolution. Interaction effects, as they occur in conventional partial pressure analyzers between the heating filament for the emission of electrons and the residual gas, are suppressed by removing the heating filament from the measurement area. The electron beam is generated in an auxiliary vacuum compartment, and passes subsequently through an aperture into the ionization compartment. The probability is small, therefore, that the presence of substances produced at the heating filament by chemical reactions and thermal decompositions will have disturbing effects. The high sensitivity and resolution of the instrument are obtained with the aid of an electron path configuration of unconventional characteristics.

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

    PubMed Central

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

    2011-01-01

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

  19. Partial Defect Verification of the Pressurized Water Reactor Spent Fuel Assemblies

    SciTech Connect

    Ham, Y S; Sitaraman, S

    2010-02-05

    The International Atomic Energy Agency (IAEA) has the responsibility to carry out independent inspections of all nuclear material and facilities subject to safeguards agreements in order to verify compliance with non-proliferation commitments. New technologies have been continuously explored by the IAEA and Member States to improve the verification measures to account for declared inventory of nuclear material and detect clandestine diversion and production of nuclear materials. Even with these efforts, a technical safeguards challenge has remained for decades for the case of developing a method in identifying possible diversion of nuclear fuel pins from the Light Water Reactor (LWR) spent fuel assemblies. We had embarked on this challenging task and successfully developed a novel methodology in detecting partial removal of fuel from pressurized water reactor spent fuel assemblies. The methodology uses multiple tiny neutron and gamma detectors in the form of a cluster and a high precision driving system to obtain underwater radiation measurements inside a Pressurized Water Reactor (PWR) spent fuel assembly without any movement of the fuel. The data obtained in such a manner can provide spatial distribution of neutron and gamma flux within a spent fuel assembly. The combined information of gamma and neutron signature is used to produce base signatures and they are principally dependent on the geometry of the detector locations, and exhibit little sensitivity to initial enrichment, burn-up or cooling time. A small variation in the fuel bundle such as a few missing pins changes the shape of the signature to enable detection. This resulted in a breakthrough method which can be used to detect pin diversion without relying on the nuclear power plant operator's declared operation data. Presented are the results of various Monte Carlo simulation studies and experiments from actual commercial PWR spent fuel assemblies.

  20. The high-pressure stability of chlorite and other hydrates in subduction mlanges: experiments in the system Cr2O3-MgO-Al2O3-SiO2-H2O

    NASA Astrophysics Data System (ADS)

    Fumagalli, Patrizia; Poli, Stefano; Fischer, Johannes; Merlini, Marco; Gemmi, Mauro

    2014-02-01

    The solubility of chromium in chlorite as a function of pressure, temperature, and bulk composition was investigated in the system Cr2O3-MgO-Al2O3-SiO2-H2O, and its effect on phase relations evaluated. Three different compositions with X Cr = Cr/(Cr + Al) = 0.075, 0.25, and 0.5 respectively, were investigated at 1.5-6.5 GPa, 650-900 C. Cr-chlorite only occurs in the bulk composition with X Cr = 0.075; otherwise, spinel and garnet are the major aluminous phases. In the experiments, Cr-chlorite coexists with enstatite up to 3.5 GPa, 800-850 C, and with forsterite, pyrope, and spinel at higher pressure. At P > 5 GPa other hydrates occur: a Cr-bearing phase-HAPY (Mg2.2Al1.5Cr0.1Si1.1O6(OH)2) is stable in assemblage with pyrope, forsterite, and spinel; Mg-sursassite coexists at 6.0 GPa, 650 C with forsterite and spinel and a new Cr-bearing phase, named 11.5 phase (Mg:Al:Si = 6.3:1.2:2.4) after the first diffraction peak observed in high-resolution X-ray diffraction pattern. Cr affects the stability of chlorite by shifting its breakdown reactions toward higher temperature, but Cr solubility at high pressure is reduced compared with the solubility observed in low-pressure occurrences in hydrothermal environments. Chromium partitions generally according to ? > ? > . At 5 GPa, 750 C (bulk with X Cr = 0.075) equilibrium values are = 0.27, = 0.08, = 0.05; at 5.4 GPa, 720 C = 0.33, = 0.06, and = 0.04; and at 3.5 GPa, 850 C = 0.12 and = 0.07. Results on Cr-Al partitioning between spinel and garnet suggest that at low temperature the spinel- to garnet-peridotite transition has a negative slope of 0.5 GPa/100 C. The formation of phase-HAPY, in assemblage with garnet and spinel, at pressures above chlorite breakdown, provides a viable mechanism to promote H2O transport in metasomatized ultramafic mlanges of subduction channels.

  1. 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

  2. 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…

  3. 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.

  4. Non-site-specific allosteric effect of oxygen on human hemoglobin under high oxygen partial pressure

    PubMed Central

    Takayanagi, Masayoshi; Kurisaki, Ikuo; Nagaoka, Masataka

    2014-01-01

    Protein allostery is essential for vital activities. Allosteric regulation of human hemoglobin (HbA) with two quaternary states T and R has been a paradigm of allosteric structural regulation of proteins. It is widely accepted that oxygen molecules (O2) act as a “site-specific” homotropic effector, or the successive O2 binding to the heme brings about the quaternary regulation. However, here we show that the site-specific allosteric effect is not necessarily only a unique mechanism of O2 allostery. Our simulation results revealed that the solution environment of high O2 partial pressure enhances the quaternary change from T to R without binding to the heme, suggesting an additional “non-site-specific” allosteric effect of O2. The latter effect should play a complementary role in the quaternary change by affecting the intersubunit contacts. This analysis must become a milestone in comprehensive understanding of the allosteric regulation of HbA from the molecular point of view. PMID:24710521

  5. Spectroscopic study of partially-ordered semiconductor heterojunction under high pressure and high magnetic field

    SciTech Connect

    Yu, P.Y.; Martinez, G.; Zeman, J.; Uchida, K.

    2000-12-31

    Photoluminescence upconversion (PLU) is a phenomenon in which a sample emits photons with energy higher than that of the excitation photon. This effect has been observed in many materials including rare earth ions doped in insulating hosts and semiconductor heterostructures without using high power lasers as the excitation source. Recently, this effect has been observed also in partially CuPt-ordered GaInP{sub 2} epilayers grown on GaAs substrates. As a spectroscopic technique photoluminescence upconversion is particularly well suited for studying band alignment at heterojunction interface. The value of band-offset has been determined with meV precision using magneto-photoluminescence. Using the fact that the pressure coefficient of electrons in GaAs is higher than those in GaInP{sub 2} they have been able to manipulate the band-offset at the GaInP/GaAs interface. By converting the band-offset from Type I to Type II they were able to demonstrate that the efficiency of the upconversion process is greatly enhanced by a Type II band-offset.

  6. Quantification of Regional Intrapulmonary Oxygen Partial Pressure Evolution during Apnea by 3He MRI

    NASA Astrophysics Data System (ADS)

    Deninger, A. J.; Eberle, B.; Ebert, M.; Gromann, T.; Heil, W.; Kauczor, H.-U.; Lauer, L.; Markstaller, K.; Otten, E.; Schmiedeskamp, J.; Schreiber, W.; Surkau, R.; Thelen, M.; Weiler, N.

    1999-12-01

    We present a new method to determine in vivo the temporal evolution of intrapulmonary oxygen concentrations by functional lung imaging with hyperpolarized 3Helium (3He?). Single-breath, single-bolus visualization of 3He? administered to the airspaces is used to analyze nuclear spin relaxation caused by the local oxygen partial pressure pO2(t). We model the dynamics of hyperpolarization in the lung by rate equations. Based hereupon, a double acquisition technique is presented to separate depolarization by RF pulses and oxygen induced relaxation. It permits the determination of pO2 with a high accuracy of up to 3% with simultaneous flip angle calibration using no additional input parameters. The time course of pO2 during short periods of breathholding is found to be linear in a pig as well as in a human volunteer. We also measured the wall relaxation time in the lung and deduced a lower limit of 4.3 min.

  7. 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.

  8. [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. PMID:21404665

  9. 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.

  10. Influence of oxygen partial pressure on surface tension of molten silver

    NASA Astrophysics Data System (ADS)

    Ozawa, S.; Morohoshi, K.; Hibiya, T.; Fukuyama, H.

    2010-01-01

    Influences of oxygen partial pressure, PO2, of ambient atmosphere and temperature on surface tension of molten silver were experimentally investigated by an oscillating droplet method using an electromagnetic levitation furnace. We successfully measured surface tension of molten silver within a very wide temperature range of over 550 K under a well-controlled PO2 atmosphere. Surface tension of pure melt surface, ?p, was determined without any contamination such as oxygen adsorption and the reaction between the melt and a measurement device at a PO2 of less than 10-12 Pa. When the PO2 was controlled at 102 Pa, the "boomerang shape" temperature dependence of surface tension was experimentally observed; surface tension was increased and then decreased with increasing temperature. From these experimental data, the temperature dependence of equilibrium constant for oxygen adsorption was determined using the Szyszkowski equation. We successfully expressed the surface tension of molten silver as functions of both PO2 and temperature. Furthermore, the changes in enthalpy and entropy for oxygen adsorption on molten silver were also estimated.

  11. Development of pressurized coal partial combustor -- Pilot scale (25t/d-coal) test results

    SciTech Connect

    Suda, Masamitsu; Harada, Eiichi; Setoguchi, Kazuhide; Hara, Masahiro

    1999-07-01

    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. Kawasaki Heavy Industries Ltd. has conducted R and D on a Coal Partial Combustor (hereinafter referred to as CPC) as a gasifier since 1984, jointly with the Center for Coal Utilization, Japan. Since 1994, Chubu Electric Power Co., Inc. and Electric Power Development Co, Ltd have been cooperating. Through this activity, a structure of the CPC has been established, and these influences of operating parameters on performance have been clarified. The purpose of the present study is to apply this developed CPC techniques to a Pressurized CPC (hereinafter referred to as PCPC) as a gasifier for the IGCC system. For the present study, the authors conducted systematic experiments on the air-blown process with a two stage dry feed system, using a 7 t/d-coal bench scale test facility and a 25 t/d-coal pilot scale plant, clarified the influence of coal feed ratio, of oxygen enrichment, and of coal types on coal gasification performance. This paper describes conceptual structure of the PCPC, the test results of a 7 t/d-coal bench scale test facility, and 25 t/d-coal pilot plant.

  12. 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.

  13. 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 ?1 and ?2 (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. PMID:26490919

  14. Oxygen partial pressure influenced structural and optical properties of DC magnetron sputtered ZrO{sub 2} films

    SciTech Connect

    Kondaiah, P.; Madhavi, V.; Uthanna, S.

    2013-02-05

    Thin films of zirconium oxide (ZrO{sub 2}) were deposited on (100) p-silicon and quartz substrates by sputtering of metallic zirconium target under different oxygen partial pressures in the range 8 Multiplication-Sign 10{sup -3}-6 Multiplication-Sign 10{sup -2}Pa. The effect of oxygen partial pressure on the structural and optical properties of the deposited films was systematically investigated. The deposition rate of the films decreased from 3.3 to 1.83 nm/min with the increase of oxygen partial pressure from 8 Multiplication-Sign 10{sup -3}-6 Multiplication-Sign 10{sup -2}Pa respectively. The X-ray diffraction profiles revealed that the films exhibit (111) refection of zirconium oxide in monoclinic phase. The optical band gap of the films increased from 5.62 to 5.80 eV and refractive index increased from 2.01 to 2.08 with the increase of oxygen partial pressure from 8 Multiplication-Sign 10{sup -3}-6 Multiplication-Sign 10{sup -2}Pa respectively.

  15. 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.

  16. The effect of different atmospheric ozone partial pressures on photosynthesis and growth of nine fruit and nut tree species.

    PubMed

    Retzlaff, W A; Williams, L E; DeJong, T M

    1991-01-01

    Nursery stock of peach (Prunus persica L. Batsch, cv. O'Henry), nectarine (P. persica L. Batsch, cv. Fantasia), plum (P. salicina Lindel., cv. Casselman), apricot (P. armeniaca L., cv. Tilton), almond (P. dulcis Mill., cv. Nonpareil), prune (P. domestica L., cv. Improved French), cherry (P. avium L., cv. Bing), oriental pear (Pyrus pyrifolia Rehd., cv. 20th Century), and apple (Malus pumula Mill., cv. Granny Smith) were planted in open-top chambers on April 1, 1988 at the University of California's Kearney Agricultural Center located in the San Joaquin Valley (30 degrees 40' N 119 degrees 40' W). Trees were exposed to three atmospheric ozone partial pressures (charcoal-filtered air (C), ambient air (A), or ambient air + ozone (T)) from August 1 to November 17, 1988. The mean 12-h (0800 to 2000 h) ozone partial pressures measured in open-top chambers during the experimental period were 0.030, 0.051, and 0.117 microPa Pa(-1) in the C, A and T treatments, respectively. Leaf net CO(2) assimilation rate decreased linearly with increasing 12-h mean ozone partial pressure for the almond, plum, apricot, prune, pear, and apple cultivars. Stomatal conductances of apricot, apple, almond, and plum decreased linearly with increasing ozone partial pressure. Cross-sectional area relative growth rates of almond, plum, apricot, and pear decreased linearly with increasing ozone partial pressure. Net CO(2) assimilation rate, stomatal conductance, and trunk growth of cherry, peach and nectarine were unaffected by the ozone treatments. Reduced leaf gas exchange probably contributed to ozone-induced growth reduction of the susceptible species and cultivars. Several of the commercial fruit tree species and cultivars studied were relatively tolerant to the ozone treatments. PMID:14972900

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  18. 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 and sulfides, was performed on the products of the reaction of H2S and HC from a series of gold-tube non-isothermal hydrous pyrolysis experiments conducted at about pH 3 from 300 to 370 ??C and a 0.1-??C/h heating rate. Incorporation of sulfur into HC resulted in an appreciable amount of thiol and sulfide formation. The rate of LSC formation positively correlated with the initial H2S pressure. Thus, we propose that the LSC produced from H2S reaction with HC are most likely the reactive intermediates for H2S initiation of sulfate reduction. We further propose a three-step reaction scheme of sulfate reduction by HC under reservoir conditions, and discuss the geological implications of our experimental findings with regard to the effect of formation water and oil chemistry, in particular LSC content. ?? 2008 Elsevier Ltd. All rights reserved.

  19. H 2O?CH 4?NaCl?CO 2 inclusions from the footwall contact of the Tanco granitic pegmatite: Estimates of internal pressure and composition from microthermometry, laser Raman spectroscopy, and gas chromatography

    NASA Astrophysics Data System (ADS)

    Thomas, A. V.; Pasteris, J. D.; Bray, C. J.; Spooner, E. T. C.

    1990-03-01

    Fluid inclusions in tourmaline and quartz from the footwall contact of the Tanco granitic pegmatite, S.E. Manitoba were studied using microthermometry (MT), laser Raman spectroscopy (LRS) and gas chromatography (GC). CH 4-bearing, aqueous inclusions occur in metasomatic tourmaline of the footwall amphibolite contact. The internal pressures estimated from MT are lower than those obtained from LRS (mean difference = 54 19 bars). The difference is probably due to errors in the measurement of Th CH 4 (V) and to the presence of clathrate at Th CH 4 (V) into which CO 2 had been preferentially partitioned. LRS estimates of pressure (125-184 bars) are believed to be more accurate. Aqueous phase salinities based on LRS estimates of pressure are higher than those derived using the data from MT: 10-20 eq. wt% NaCl. The composition of the inclusions determined by GC bulk analysis is 97.3 mol% H 2O, 2.2 mol% CH 4, 0.4 mol% CO 2, 250 ppm C 2H 6, 130 ppm N 2, 33 ppm C 3H 8, 11 ppm C 2H 4, and 3 ppm C 3H 6, plus trace amounts of C 4 hydrocarbons. The composition is broadly similar to that calculated from MT (92% H 2O and 8% CH 4, with 7 eq. wt% NaCl dissolved in the aqueous phase and 2 mol% CO 2 dissolved in the CH 4 phase), as expected due to the dominance of a single generation of inclusions in the tourmaline. However, two important differences in composition are: (i) the CH 4 to CO 2 ratio of this fluid determined by GC is 5.33, which is significantly lower than that indicated by MT (49.0); and (ii) the H 2O content estimated from MT is 92 mol% compared to 98 mol% from GC. GC analyses may have been contaminated by the presence of secondary inclusions in the tourmaline. However, the rarity of the latter suggests that they cannot be completely responsible for the discrepancy. The differences may be accounted for by the presence of clathrate during measurement of Th CH 4 (critical), which would reduce CO 2 relative to CH 4 in the residual fluid, and by errors in visually estimating vol% H 2O. The compositions of the primary inclusions in tourmaline are unlike any of those found within the pegmatite and indicate that the fluid was externally derived, probably of metamorphic origin. Inclusions in quartz of the border unit of the pegmatite are secondary and are either aqueous (18 to 30 eq. wt% CaCl 2; Th total = 184 14 C) or carbonic. Tm CO 2 for the carbonic inclusions ranges from -57.5 to -65.4C and is positively correlated with Th CO 2. Analyses of X CH 4 based on LRS agree within 5 mol% of those derived from MT and together indicate a range of compositions from 5 to 50 mol% CH 4 in the CO 2 phase. Bulk analysis by GC gives 99.0 mol% H 2O, 0.6 mol% CO 2, 0.4 mol% CH 4, 160 ppm N 2, 7 ppm C 2H 6, 4 ppm C 3H 8, and 2 ppm C 2H 4, with trace amounts of COS (carbonyl sulphide) and C 3H 6. The level of H 2O in the analysis is consistent with the dominance of the aqueous inclusions in these samples, and the CH4: CO2 ratios are consistent with estimates from MT and LRS. The preservation of variable ratios of CH 4:CO 2 in inclusions < 50 ?m apart indicates that neither H 2 diffusion out of the inclusions nor reduction of fluids leaving the pegmatite were responsible for the more oxidized chemistries of the border unit inclusions relative to those in the tourmaline of the metasomatised amphibolite. The compositions of the inclusions in the quartz lie between those of the fluid trapped by the tourmaline (externally derived) and the measured composition of a CO 2-bearing pegmatitic fluid, which indicates that the secondary fluids trapped in the border unit quartz were produced by late mixing.

  20. Microvascular oxygen partial pressure during hyperbaric oxygen in diabetic rat skeletal muscle.

    PubMed

    Yamakoshi, Kohei; Yagishita, Kazuyoshi; Tsuchimochi, Hirotsugu; Inagaki, Tadakatsu; Shirai, Mikiyasu; Poole, David C; Kano, Yutaka

    2015-12-15

    Hyperbaric oxygen (HBO) is a major therapeutic treatment for ischemic ulcerations that perforate skin and underlying muscle in diabetic patients. These lesions do not heal effectively, in part, because of the hypoxic microvascular O2 partial pressures (PmvO2 ) resulting from diabetes-induced cardiovascular dysfunction, which alters the dynamic balance between O2 delivery (Q?o2) and utilization (V?o2) rates. We tested the hypothesis that HBO in diabetic muscle would exacerbate the hyperoxic PmvO2 dynamics due, in part, to a reduction or slowing of the cardiovascular, sympathetic nervous, and respiratory system responses to acute HBO exposure. Adult male Wistar rats were divided randomly into diabetic (DIA: streptozotocin ip) and healthy (control) groups. A small animal hyperbaric chamber was pressurized with oxygen (100% O2) to 3.0 atmospheres absolute (ATA) at 0.2 ATA/min. Phosphorescence quenching techniques were used to measure PmvO2 in tibialis anterior muscle of anesthetized rats during HBO. Lumbar sympathetic nerve activity (LSNA), heart rate (HR), and respiratory rate (RR) were measured electrophysiologically. During the normobaric hyperoxia and HBO, DIA tibialis anterior PmvO2 increased faster (mean response time, CONT 78 8, DIA 55 8 s, P < 0.05) than CONT. Subsequently, PmvO2 remained elevated at similar levels in CONT and DIA muscles until normobaric normoxic recovery where the DIA PmvO2 retained its hyperoxic level longer than CONT. Sympathetic nervous system and cardiac and respiratory responses to HBO were slower in DIA vs. CONT. Specifically the mean response times for RR (CONT: 6 1 s, DIA: 29 4 s, P < 0.05), HR (CONT: 16 1 s, DIA: 45 5 s, P < 0.05), and LSNA (CONT: 140 16 s, DIA: 247 34 s, P < 0.05) were greater following HBO onset in DIA than CONT. HBO treatment increases tibialis anterior muscle PmvO2 more rapidly and for a longer duration in DIA than CONT, but not to a greater level. Whereas respiratory, cardiovascular, and LSNA responses to HBO are profoundly slowed in DIA, only the cardiovascular arm (via HR) may contribute to the muscle vascular incompetence and these faster PmvO2 kinetics. PMID:26468263

  1. 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

  2. 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.

  3. Interpenetrated three-dimensional MnIIMIII ferrimagnets, [Mn(4dmap)4]3[M(CN)6]2.10 H2O (M=Cr, Mn): structures, magnetic properties, and pressure-responsive magnetic modulation.

    PubMed

    Kaneko, Wakako; Mito, Masaki; Kitagawa, Susumu; Ohba, Masaaki

    2008-01-01

    Two novel cyanide-bridged ferrimagnets, [Mn(4dmap)(4)](3)[M(CN)(6)](2)- 10 H(2)O (4dmap=4-dimethylaminopyridine, M=Cr (1) and Mn (2)), have been prepared from the reaction of MnCl(2)4 H(2)O, a monodentate coligand (4dmap), with K(3)[M(CN)(6)]. X-ray crystallographic results show that these are isomorphous, and form a unique twofold interpenetrated three-dimensional framework with a triconnected 6.10(2) net. The framework contains two types of one-dimensional channel: hexagonal channels based on a cyanide-bridged Mn(6)M(6) hexagon, and triangle channels segmented by CN-Mn-NC linkages, which are filled with lattice water molecules. The dimethylamino groups of the 4dmap coligands are located around a pore and form the basic inner space. Variable-temperature X-ray powder diffraction and thermogravimetric analysis results show that the frameworks of both compounds are susceptible to dehydration through the loss of strongly hydrogen-bonded lattice water molecules. Magnetic measurements on both compounds show a ferrimagnetic ordering occurs at low temperature, T(C)=17 K for 1 and 6 K for 2. Application of hydrostatic pressure showed a positive effect on the magnetic ordering. Both values of T(C) increased linearly, to 25 K for 1 and 15 K for 2 at 1.0 GPa. The magnetic properties of both compounds were reversibly modulated by the external stress. PMID:18283701

  4. The H2O content of granite embryos

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  5. The H2O Content of Granite Embryos

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  6. 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.

  7. 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-term ecosystem C sequestration. PMID:15378342

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

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

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. Measurements of Pressure Distributions and Force Coefficients in a Squeeze Film Damper. Part 2: Partially Sealed Configuration

    NASA Technical Reports Server (NTRS)

    Jung, S. Y.; Sanandres, Luis A.; Vance, J. M.

    1991-01-01

    Experimental results from a partially sealed squeeze film damper (SFD) test rig, executing a circular centered orbit are presented and discussed. A serrated piston ring is installed at the damper exit. This device involves a new sealing concept which produces high damping values while allowing for oil flow to cool the damper. In the partially sealed damper, large cavitation regions are observed in the pressure fields at orbit radii epsilon equals 0.5 and epsilon equals 0.8. The cavitated pressure distributions and the corresponding force coefficients are compared with a cavitated bearing solution. The experimental results show the significance of fluid inertia and vapor cavitation in the operation of squeeze film dampers. Squeeze film Reynolds numbers tested reach up to Re equals 50, spanning the range of contemporary applications.

  14. Thermal expansion measurement of (U,Pu)O2-x in oxygen partial pressure-controlled atmosphere

    NASA Astrophysics Data System (ADS)

    Kato, Masato; Ikusawa, Yoshihisa; Sunaoshi, Takeo; Nelson, Andrew T.; McClellan, Kenneth J.

    2016-02-01

    Thermal expansion of U0.7Pu0.3O2-x (x = 0, 0.01, 0.02, 0.03) and U0.52Pu0.48O2.00 was investigated by a unique dilatometry which measured in an oxygen partial pressure-controlled atmosphere. The oxygen partial pressure was controlled to hold a constant oxygen-to-metal ratio in the (U,Pu)O2-x during the measurement. Thermal expansion slightly increased with the decrease in oxygen-to-metal ratio. We proposed a relationship to describe thermal expansion as a function of temperature, O/M and Pu content.

  15. 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

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

    PubMed Central

    Klingerman, Candice M.; Trushin, Neil; Prokopczyk, Bogdan

    2013-01-01

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

  17. Tuning magnetic properties of yttrium iron garnet film with oxygen partial pressure in sputtering and annealing process

    SciTech Connect

    Yang Qinghui; Zhang Huaiwu; Wen Qiye; Liu Yingli; Xiao, John Q.

    2009-04-01

    In this paper, the magnetic properties of these films which deposited and annealed at different atmospheres were investigated. The experimental results show that the magnetic properties of yttrium iron garnet films prepared by rf magnetron sputtering method can be tuned with oxygen partial pressure in sputtering and annealing processes. The optimal condition is depositing in atmosphere of R=0 and annealing at 0.5 Pa O{sub 2}, or depositing in atmosphere of R=2% and annealed in vacuum.

  18. 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.

  19. 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 Tibet. With these alkali-rich compositions, H2O has a slightly smaller effect on liquidus depression, with a liquidus depression around 110 K at 5 wt% H2O. This may suggest that alkalis counteract the effect of H2O, by forming NaOH complexes in the cation matrix of the melt.

  20. "Molecular basket" sorbents for separation of CO(2) and H(2)S from various gas streams.

    PubMed

    Ma, Xiaoliang; Wang, Xiaoxing; Song, Chunshan

    2009-04-29

    A new generation of "molecular basket" sorbents (MBS) has been developed by the optimum combination of the nanoporous material and CO(2)/H(2)S-philic polymer sorbent to increase the accessible sorption sites for CO(2) capture from flue gas (Postdecarbonization), and for CO(2) and H(2)S separation from the reduced gases, such as synthesis gas, reformate (Predecarbonization), natural gas, coal/biomass gasification gas, and biogas. The sorption capacity of 140 mg of CO(2)/g of sorb was achieved at 15 kPa CO(2) partial pressure, which shows superior performance in comparison with other known sorbents. In addition, an exceptional dependence of MBS sorption performance on temperature for CO(2) and H(2)S was found and discussed at a molecular level via the computational chemistry approach. On the basis of the fundamental understanding of MBS sorption characteristics, an innovative sorption process was proposed and demonstrated at the laboratory scale for removing and recovering CO(2) and H(2)S, respectively, from a model gas. The present study provides a new approach for development of the novel CO(2)/H(2)S sorbents and may have a major impact on the advance of science and technology for CO(2)/H(2)S capture and separation from various gases. PMID:19348482

  1. 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.

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

    NASA Astrophysics Data System (ADS)

    Berndt, T.; Sipil, M.; Stratmann, F.; Petj, T.; Vanhanen, J.; Mikkil, J.; Patokoski, J.; Taipale, R.; Mauldin, R. L., III; Kulmala, M.

    2014-01-01

    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, ?-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 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. Also the early growth process of the nucleated particles was not significantly influenced by the organic oxidation products in line with the expected growth by organic products using literature data. An additional, H2SO4-independent process of particle (nano-CN) formation was observed in the case of ?-pinene and limonene ozonolysis for H2SO4 concentrations smaller than ~107 molecule cm-3. Furthermore, the findings confirm the appearance of an additional oxidant for SO2 beside OH radicals, very likely stabilized Criegee Intermediates (sCI). A second set of experiments has been performed in the presence of added amines in the concentrations range of a few 107-1010 molecule cm-3 applying photolytic OH radical generation for H2SO4 production without addition of other organics. All amines showed significant nucleation enhancement with increasing efficiency in the order pyridine < aniline < dimethylamine < trimethylamine. This result supports the idea of H2SO4 cluster stabilization by amines due to strong H2SO4?amine interactions. On the other hand, this study indicates that for organic oxidation products (in presence of the possible amine background as stated) a distinct H2SO4 / H2O nucleation enhancement can be due to increased H2SO4 formation caused by additional organic oxidant production (sCI) rather than by stabilization of H2SO4 clusters due to H2SO4?organics interactions.

  3. 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 reproduced by the model.

  4. CO2 Solubility in Natural Rhyolitic Melts at High Pressures - Implications for Carbon Flux in Subduction Zones by Sediment Partial Melts

    NASA Astrophysics Data System (ADS)

    Duncan, M. S.; Dasgupta, R.

    2011-12-01

    Partial melts of subducting sediments is thought to be a critical agent in carrying trace elements and water to arc basalt source regions. For subduction zones that contain significant amount of carbonates in ocean-floor sediments, sediment melts likely also act as a carrier of CO2. However, the CO2 carrying capacity of natural rhyolitic melts at sub-arc depths remains unconstrained. We conducted experiments on a synthetic composition, similar to average, low-degree experimental partial melt of pelitic sediments. The composition was constructed with reagent grade oxides and carbonates, the source of excess CO2. Experiments were conducted between 1 and 3 GPa at 1200 °C in Au80Pd20 capsules using a piston cylinder apparatus with a half-inch BaCO3 assembly at Rice University. Quench products showed glasses with bubbles, the latter suggesting saturation of the melt with a CO2-rich vapor phase. Oxygen fugacity during the experiments was not strictly controlled but the presence of CO2 bubbles and absence of graphite indicates fO2 above the CCO buffer. Major element concentrations of glasses were measured using EPMA. The CO2 and H2O contents of experimental doubly polished (50-110 μm), bubble-free portions of the glass chips were determined using a Thermo Nicolet Fourier Transform Infrared Spectrometer. Spectra were recorded with a resolution of 4 cm-1, 512 scans, from 650 to 4000 cm-1, under a nitrogen purge to eliminate atmospheric gases. Dissolved volatile concentrations were quantified using the Beer-Lambert law and linear molar absorption coefficients from previous studies [1, 2]. Total dissolved carbon dioxide of experimental glasses was determined from the intensity of the ν3 antisymmetric stretch bands of CO32- at 1430 cm-1 and CO2mol at 2348 cm-1. Dissolved water content of experimental glasses was determined from the intensity of O-H stretching at 3520 cm-1. Estimated total CO2 concentrations at 3 GPa are in the range of 1-2 wt%, for melts with H2O contents between 1.5 and 2.5 wt%. Compared to previous work on CO2 solubility in complex rhyolitic melts at lower pressures [3-5], there is a general trend of increasing CO2 solubility with pressure. Dissolved CO2 is present both as molecular CO2 and as CO32-, consistent with previous, simple system studies at high pressures [e.g. 2, 6]. The CO2mol/CO2Tot values are within the range of previous high pressure studies [e.g. 7] and range from 0.35 to 0.55. Experiments at variable P, T, and melt water content are underway. [1] Fine and Stolper (1985), CMP, 91, 105-121; [2] Stolper et al. (1987), AM, 72, 1071-1085; [3] Blank et al. (1993), EPSL, 119, 27-36; [4] Fogel and Rutherford (1990), AM, 75, 1331-1326; [5] Tamic et al. (2001), CG, 174, 333-347; [6] Mysen and Virgo (1980), AM, 65, 855-899; [7] Mysen (1976), AJS, 276, 969-996.

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

    SciTech Connect

    Mei Hong; Richard Noble; John Falconer

    2007-09-24

    Zeolite membranes are thermally, chemically, and mechanically stable. They also have tunable molecular sieving and catalytic ability. These unique properties make zeolite membrane an excellent candidate for use in catalytic membrane reactor applications related to coal conversion and gasification, which need high temperature and high pressure range separation in chemically challenging environment where existing technologies are inefficient or unable to operate. Small pore, good quality, and thin zeolite membranes are needed for highly selective H2 separation from other light gases (CO2, CH4, CO). However, current zeolite membranes have either too big zeolite pores or a large number of defects and have not been successful for H2 separation from light gases. The objective of this study is to develop zeolite membranes that are more suitable for H2 separation. In an effort to tune the size of zeolite pores and/or to decrease the number of defects, medium-pore zeolite B-ZSM-5 (MFI) membranes were synthesized and silylated. Silylation on B-ZSM-5 crystals reduced MFI-zeolite pore volume, but had little effect on CO2 and CH4 adsorption. Silylation on B-ZSM-5 membranes increased H2 selectivity both in single component and in mixtures with CO2, CH4, or N2. Single gas and binary mixtures of H2/CO2 and H2/CH4 were permeated through silylated B-ZSM-5 membranes at feed pressures up to 1.7 MPa and temperatures up to 773 K. For one B-ZSM-5 membrane after silylation, the H2/CO2 separation selectivity at 473 K increased from 1.4 to 37, whereas the H2/CH4 separation selectivity increased from 1.6 to 33. Hydrogen permeance through a silylated BZSM-5 membrane was activated with activation energy of {approx}10 kJ/mol, but the CO2 and CH4 permeances decreased slightly with temperature in both single gas and in mixtures. Therefore, the H2 permeance and H2/CO2 and H2/CH4 separation selectivities increased with temperature. At 673 K, the H2 permeance was 1.0x10-7 mol{center_dot}m-2{center_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)

  6. Biogeochemistry of dihydrogen (H2).

    PubMed

    Hoehler, Tori M

    2005-01-01

    Hydrogen has had an important and evolving role in Earth's geo- and biogeochemistry, from prebiotic to modern times. On the earliest Earth, abiotic sources of H2 were likely stronger than in the present. Volcanic out-gassing and hydrothermal circulation probably occurred at several times the modern rate, due to presumably higher heat flux. The H2 component of volcanic emissions was likely buffered close to the modern value by an approximately constant mantle oxidation state since 3.9 billion years ago, and may have been higher before that, if the early mantle was more reducing. The predominantly ultramafic character of the early, undifferentiated crust could have led to increased serpentinization and release of H2 by hydrothermal circulation, as in modern ultramafic-hosted vents. At the same time, the reactive atmospheric sink for H2 was likely weaker. Collectively, these factors suggest that steady state levels of H2 in the prebiotic atmosphere were 3-4 orders of magnitude higher than at present, and possibly higher still during transient periods following the delivery of Fe and Ni by large impact events. These elevated levels had direct or indirect impacts on the redox state of the atmosphere, the radiation budget, the production of aerosol hazes, and the genesis of biochemical precursor compounds. The early abiotic cycling of H2 helped to establish the environmental and chemical context for the origins of life on Earth. The potential for H2 to serve as a source of energy and reducing power, and to afford a means of energy storage by the establishment of proton gradients, could have afforded it a highly utilitarian role in the earliest metabolic chemistry. Some origin of life theories suggest the involvement of H2 in the first energy-generating metabolism, and the widespread and deeply-branching nature of H2-utilization in the modern tree of life suggests that it was at least a very early biochemical innovation. The abiotic production of H2 via several mechanisms of water-rock interaction could have supported an early chemosynthetic biosphere. Such processes offer the continued potential for a deep, rock-hosted biosphere on Earth or other bodies in the solar system. The continued evolution of metabolic and community-level versatility among microbes led to an expanded ability to completely exploit the energy available in complex organic matter. Under the anoxic conditions that prevailed on the early Earth, this was accomplished through the linked and sequential action of several metabolic classes of organisms. By transporting electrons between cells, H2 provides a means of linking the activities of these organisms into a highly functional and interactive network. At the same time, H2 concentrations exert a powerful thermodynamic control on many aspects of metabolism and biogeochemical function in these systems. Anaerobic communities based on the consumption of organic matter continue to play an important role in global biogeochemistry even into the present day. As the principal arbiters of chemistry in most aquatic sediments and animal digestive systems, these microbes affect the redox and trace-gas chemistry of our oceans and atmosphere, and constitute the ultimate biological filter on material passing into the rock record. It is in such communities that the significance of H2 in mediating biogeochemical function is most strongly expressed. The advent of phototrophic metabolism added another layer of complexity to microbial communities, and to the role of H2 therein. Anoxygenic and oxygenic phototrophs retained and expanded on the utilization of H2 in metabolic processes. Both groups produce and consume H2 through a variety of mechanisms. In the natural world, phototrophic organisms are often closely juxtaposed with a variety of other metabolic types, through the formation of biofilms and microbial mats. In the few examples studied, phototrophs contribute an often swamping term to the H2 economy of these communities, with important implications for their overall function-including regulation of the redox state of gaseous products, and direct release of large quantities of H2 to the environment. As one of the dominant sources of biological productivity for as much as 2 billion years of Earth's history, these communities have been among the most important agents of long-term global biogeochemical change. On the modern Earth, H2 is present at only trace levels in the atmosphere and oceans. Nonetheless, its function as an arbiter of microbial interactions and chemistry ensures an important role in biogeochemical cycling. The significance of H2 in a global sense may soon increase, as the search for alternative fuels casts attention on the clean-energy potential of hydrogen fuel cells. Already, H2 utilization plays an important role in all three phylogenetic domains of life. Humans may soon add an important new term to this economy. Considerable research is focused on the H2-producing capacities of phototrophic and other microorganisms as potential contributors in this regard. Regardless of source, the large scale utilization of H2 as an energy source could carry important consequences for biogeochemistry. PMID:16370113

  7. 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

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

    PubMed

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

    2015-02-26

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

  9. 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.

  10. 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. The raw data were filtered to remove non basalts and to exclude basalt samples with anomalous chemical compositions. Pressures of partial crystallization were calculated by quantitatively comparing the compositions of the glasses with those of experimental liquids in equilibrium with olivine, plagioclase, and augite at different pressures and temperatures using the approach described by Yang and co-workers (1996). The results for samples that yielded pressures associated with unrealistically large uncertainties were filtered out of the database. Pressures for the remaining samples were converted to depths assuming an average crustal density of 2900 kg/m3. The results indicate that most magmas partially crystallized over a range of pressures corresponding to a range of depths from 20 to 25 km. We conclude that one or more magma chamber occur in this depth range, or at slightly shallower depths if the effects of water on calculated pressures of partial crystallization are taken into account. Most erupted basalts have ascended from this depth directly to the surface, presumably via dikes. The Katla plumbing system is thus similar to that at other major volcanoes (Hekla, Bardarbunga, Grimsvotn) in the eastern volcanic zone inasmuch as the majority of the erupted magmas are supplied from chambers in the middle and lower crust at depths of 10 to 30 km.

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

    SciTech Connect

    Campbell, A.J.; Seagle, C.T.; Heinz, D.L.; Shen, G.; Prakapenka, V.

    2008-09-18

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

  12. 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.

  13. A different approach for predicting H(2)S((g)) emission rates in gravity sewers.

    PubMed

    Lahav, Ori; Sagiv, Amitai; Friedler, Eran

    2006-01-01

    All detrimental phenomena (mal odors, metal corrosion, concrete disintegration, health hazard) associated with hydrogen sulfide in gravity sewers depend on the rate of H(2)S emission from the aqueous phase to the gas phase of the pipe. In this paper a different approach for predicting H(2)S((g)) emission rates from gravity sewers is presented, using concepts adapted from mixing theory. The mean velocity gradient (G=gamma SV/micro; S is the slope, V the mean velocity), representing mixing conditions in gravity flow, was used to quantify the rate of H(2)S((g)) emission in part-full gravity sewers. Based on this approach an emission equation was developed. The equation was verified and calibrated by performing 20 experiments in a 27-m gravity-flow experimental-sewer (D=0.16 m) at various hydraulic conditions. Results indicate a clear dependency of the sulfide stripping-rate on G(1) (R(2)=0.94) with the following overall emission equation: where S(T) is the total sulfide concentration in the aqueous phase, mg/L; w the flow surface width, m; A(cs) the cross-sectional area, m(2); T the temperature, degrees C; K(H) the Henry's constant, molL(-1)atm(-1); and P(pH2S) the partial pressure of H(2)S((g)) in the sewer atmosphere, atm. PMID:16343590

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

    PubMed

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

    2013-10-01

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

  15. Effects of oxygen partial pressure on the characteristics of magnetron-sputtered ZnMgBeO thin films

    NASA Astrophysics Data System (ADS)

    Cuong, Hoang Ba; Lee, Byung-Teak

    2015-11-01

    Effects of oxygen partial pressure within the Ar process plasma on the optical, structural, and electrical properties of magnetron-sputtered ZnMgBeO films were investigated in detail. It was observed that the optical energy bandgap (Eg) values of the ZnMgBeO films substantially decrease with the oxygen addition, from 5.3 to 4.3 eV as the oxygen partial pressure increases from zero to one. The full-width-at-half-maximum (FWHM) values of the (0 0 0 2) XRD peaks drastically decrease with the addition of a small amount of oxygen but then increase with further oxygen addition. All the films had very high sheet resistance, 1.3-1.4 G?/?. It was also observed that the concentration of Zn within the films significantly increased with the oxygen addition, which was proposed to be mainly responsible for the observed decrease in Eg. It was also proposed that the FWHM change due to the oxygen addition may be attributable to three factors, film composition, grain size, and point defect density, as confirmed by results of TEM and XPS investigations.

  16. Laser-induced damage threshold of ZrO{sub 2} thin films prepared at different oxygen partial pressures by electron-beam evaporation

    SciTech Connect

    Zhang Dongping; Shao Jianda; Zhao Yuanan; Fan Shuhai; Hong Ruijing; Fan Zhengxiu

    2005-01-01

    ZrO{sub 2} films were deposited by electron-beam evaporation with the oxygen partial pressure varying from 3x10{sup -3} Pa to 11x10{sup -3} Pa. The phase structure of the samples was characterized by x-ray diffraction (XRD). The thermal absorption of the films was measured by the surface thermal lensing technique. A spectrophotometer was employed to measure the refractive indices of the samples. The laser-induced damage threshold (LIDT) was assessed using a 1064 nm Nd: yttritium-aluminum-garnet pulsed laser at pulse width of 12 ns. The influence of oxygen partial pressure on the microstructure and LIDT of ZrO{sub 2} films was investigated. XRD data revealed that the films changed from polycrystalline to amorphous as the oxygen partial pressure increased. The variation of refractive index at 550 nm wavelength indicated that the packing density of the films decreased gradually with increasing oxygen partial pressure. The absorptance of the samples decreased monotonically from 125.2 to 84.5 ppm with increasing oxygen partial pressure. The damage threshold values increased from 18.5 to 26.7 J/cm{sup 2} for oxygen partial pressures varying from 3x10{sup -3} Pa to 9x10{sup -3} Pa, but decreased to 17.3 J/cm{sup 2} in the case of 11x10{sup -3} Pa.

  17. The abundance of Fe(C0 3) OH in goethite and a possible constraint on minimum atmospheric oxygen partial pressures in the Phanerozoic

    NASA Astrophysics Data System (ADS)

    YAPP, Crayton J.

    1996-11-01

    Concentrations of the Fe(CO 3)OH component in goethites from Phanerozoic oolitic ironstones appear to record information on the partial pressures of soil CO 2 in ancient subaerial weathering environments. Application of a simple steady-state, one-dimensional, Fickian diffusion model to ancient goethite-bearing soils suggests that it may be possible to calculate lower limits for the partial pressure of oxygen in the Earth's atmosphere by using both the inferred soil CO 2 partial pressure and estimates of the partial pressure of atmospheric CO 2. Extant data from colitic goethites indicate that the atmospheric PO 2 value was no lower than about 13% of the present atmospheric level (PAL) in the Late Ordovician. This value affirms existing evidence for abundant molecular oxygen in the Earth's atmosphere in the Early Paleozoic, i.e., before the widespread advent of vascular plants. Extensive colonization of the continents by vascular plants in the Devonian was associated with calculated atmospheric oxygen partial pressures that were no lower than about 39% of PAL at 360 Ma BP. For Early Jurassic to Late Cretaceous samples, the calculated lower limit of atmospheric oxygen ranged from about 20 to 25% of the present value. It remains to be established whether or not there is a systematic relationship between calculated minimum Po 2 values (or soil respiration rates) and the actual partial pressure of atmospheric oxygen.

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

    NASA Astrophysics Data System (ADS)

    Chiesa, S.; Rossi, M. J.

    2013-07-01

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

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

    PubMed Central

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

    1988-01-01

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

  20. H2 Gas Improves Functional Outcome After Cardiac Arrest to an Extent Comparable to Therapeutic Hypothermia in a Rat Model

    PubMed Central

    Hayashida, Kei; Sano, Motoaki; Kamimura, Naomi; Yokota, Takashi; Suzuki, Masaru; Maekawa, Yuichiro; Kawamura, Akio; Abe, Takayuki; Ohta, Shigeo; Fukuda, Keiichi; Hori, Shingo

    2012-01-01

    Background All clinical and biological manifestations related to postcardiac arrest (CA) syndrome are attributed to ischemiareperfusion injury in various organs including brain and heart. Molecular hydrogen (H2) has potential as a novel antioxidant. This study tested the hypothesis that inhalation of H2 gas starting at the beginning of cardiopulmonary resuscitation (CPR) could improve the outcome of CA. Methods and Results Ventricular fibrillation was induced by transcutaneous electrical epicardial stimulation in rats. After 5 minutes of the subsequent CA, rats were randomly assigned to 1 of 4 experimental groups at the beginning of CPR: mechanical ventilation (MV) with 2% N2 and 98% O2 under normothermia (37C), the control group; MV with 2% H2 and 98% O2 under normothermia; MV with 2% N2 and 98% O2 under therapeutic hypothermia (TH), 33C; and MV with 2% H2 and 98% O2 under TH. Mixed gas inhalation and TH continued until 2 hours after the return of spontaneous circulation (ROSC). H2 gas inhalation yielded better improvement in survival and neurological deficit score (NDS) after ROSC to an extent comparable to TH. H2 gas inhalation, but not TH, prevented a rise in left ventricular end-diastolic pressure and increase in serum IL-6 level after ROSC. The salutary impact of H2 gas was at least partially attributed to the radical-scavenging effects of H2 gas, because both 8-OHdG- and 4-HNE-positive cardiomyocytes were markedly suppressed by H2 gas inhalation after ROSC. Conclusions Inhalation of H2 gas is a favorable strategy to mitigate mortality and functional outcome of post-CA syndrome in a rat model, either alone or in combination with TH. PMID:23316300

  1. Partial Gene Deletions of PMP22 Causing Hereditary Neuropathy with Liability to Pressure Palsies.

    PubMed

    Cho, Sun-Mi; Hong, Bo Young; Kim, Yoonjung; Lee, Sang Guk; Yang, Jin-Young; Kim, Juwon; Lee, Kyung-A

    2014-01-01

    Hereditary neuropathy with liability to pressure palsies (HNPP) is an autosomal neuropathy that is commonly caused by a reciprocal 1.5 Mb deletion on chromosome 17p11.2, at the site of the peripheral myelin protein 22 (PMP22) gene. Other patients with similar phenotypes have been shown to harbor point mutations or small deletions, although there is some clinical variation across these patients. In this report, we describe a case of HNPP with copy number changes in exon or promoter regions of PMP22. Multiplex ligation-dependent probe analysis revealed an exon 1b deletion in the patient, who had been diagnosed with HNPP in the first decade of life using molecular analysis. PMID:25506001

  2. Partial Gene Deletions of PMP22 Causing Hereditary Neuropathy with Liability to Pressure Palsies

    PubMed Central

    Cho, Sun-Mi; Kim, Yoonjung; Lee, Sang Guk; Yang, Jin-Young

    2014-01-01

    Hereditary neuropathy with liability to pressure palsies (HNPP) is an autosomal neuropathy that is commonly caused by a reciprocal 1.5 Mb deletion on chromosome 17p11.2, at the site of the peripheral myelin protein 22 (PMP22) gene. Other patients with similar phenotypes have been shown to harbor point mutations or small deletions, although there is some clinical variation across these patients. In this report, we describe a case of HNPP with copy number changes in exon or promoter regions of PMP22. Multiplex ligation-dependent probe analysis revealed an exon 1b deletion in the patient, who had been diagnosed with HNPP in the first decade of life using molecular analysis. PMID:25506001

  3. Highly oriented NdFeCoB nanocrystalline magnets from partially disproportionated compacts by reactive deformation under low pressure

    SciTech Connect

    Zheng, Qing; Li, Jun; Liu, Ying Yu, Yunping; Lian, Lixian

    2014-05-07

    In the present investigation, we take advantage of the ultrafine grain size of NdFeCoB partially hydrogen-disproportionated phases, and prepare anisotropic nanocrystalline magnets with full density and homogenous microstructure and texture by reactive deformation under low pressure. Our results suggest that the pressure could properly promote an occurrence of desorption-recombination reaction due to a shorter-range rearrangement of the atoms, and the newly recombined Nd{sub 2}Fe{sub 14}B grains with fine grain size could undergo deformation immediately after the phase transformation, and then an obvious anisotropy and uniform alignment would be obtained. The maximum magnetic properties, (BH){sub max} = 25.8 MGOe, Br = 11.8 kG, H{sub cj} = 5.5 kOe, were obtained after being treated for 5 min at 820 °C in vacuum. The present study highlights the feasibility to prepare anisotropic nanocrystalline magnets with homogeneous microstructure and a strong (00l) texture of uniform grain size under low pressure.

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

    NASA Astrophysics Data System (ADS)

    Berndt, T.; Sipil, M.; Stratmann, F.; Petj, T.; Vanhanen, J.; Mikkil, 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, ?-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 ?-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 of a few 107-1010 molecule cm-3. Here, photolytic OH radical generation was applied for H2SO4 production with no addition of other organics. All amines showed a significant nucleation enhancement with increasing efficiency in the order pyridine < aniline < dimethylamine < trimethylamine. This result supports the idea of H2SO4 cluster stabilization by amines due to strong H2SO4 \\leftrightarrow amine interactions. On the other hand, this study reveals that for organic oxidation products (in presence of the possible amine background as stated) a distinct H2SO4/H2O nucleation enhancement can be due to increased H2SO4 formation caused by additional organic oxidant production (sCI) rather than by stabilization of H2SO4 clusters due to H2SO4 \\leftrightarrow organics interactions. However, because the molecular composition of nucleating clusters was not measured, the role of any background substances, unavoidably present in any system, to experimental data remains unclear. Also the experimental conditions do not cover fully the range of atmospheric observations, e.g., the concentration of precursor vapours represents rather the upper end of the atmospheric range. More experimental work is needed before definite conclusions about the nucleation mechanisms in the atmosphere can be drawn.

  5. 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

  6. Equilibrium polarization of ultrathin PbTiO{<_3} with surface compensation controlled by oxygen partial pressure.

    SciTech Connect

    Highland, M. J.; Fister, T. T.; Fong, D. D.; Fuoss, P. H.; Thompson, C.; Eastman, J. A.; Streiffer, S. K.; Stephenson, G. B.

    2011-01-01

    We present a synchrotron x-ray study of the equilibrium polarization structure of ultrathin PbTiO{sub 3} films on SrRuO{sub 3} electrodes epitaxially grown on SrTiO{sub 3} (001) substrates, as a function of temperature and the external oxygen partial pressure (pO{sub 2}) controlling their surface charge compensation. We find that the ferroelectric Curie temperature (T{sub c}) varies with pO{sub 2} and has a minimum at the intermediate pO{sub 2}, where the polarization below T{sub c} changes sign. The experiments are in qualitative agreement with a model based on Landau theory that takes into account the interaction of the phase transition with the electrochemical equilibria for charged surface species. The paraelectric phase is stabilized at intermediate pO2 when the concentrations of surface species are insufficient to compensate either polar orientation.

  7. Influence of Ca content and oxygen partial pressure on microstructural evolution of (Co,Ca)O at elevated temperatures.

    PubMed

    Kusinski, J; Cieniek, L; Petot-Ervas, G; Petot, C; Baldinozzi, G

    2006-10-01

    Ca-doped (1, 1.7, 5 and 10 mol% CaO) cobalt oxide single-crystal samples, with an [001] orientation, were annealed at elevated temperatures of 1000-1200 degrees C for different times and at different oxygen partial pressures. The microstructure was examined by means of transmission light and electron microscopy. High-temperature X-ray diffractometry was used, with the aim of determining the temperature of the CoO <--> Co(3)O(4) transition in these materials. Extensive precipitation of Ca-free Co(3)O(4) spinel crystals was observed with increasing Ca content and oxygen activity. It is suggested that the electrical conductivity changes in this material may be related to this precipitation, because it changes the electronic state of cobalt cations. PMID:17100900

  8. Correlation Between Partial Pressure of Arterial Carbon Dioxide and End Tidal Carbon Dioxide in Patients with Severe Alcohol Withdrawal

    PubMed Central

    Yousuf, Tariq; Brinton, Taylor; Kramer, Jason; Khan, Basharath; Ziffra, Jeffrey; Villines, Dana; Shah, Poorvi; Hanif, Tabassum

    2015-01-01

    Background Respiratory depression is a common adverse effect of benzodiazepine administration to patients with severe alcoholic withdrawal. This study was conducted to assess the value of end tidal carbon dioxide (ETCO2) levels compared to partial pressure of arterial carbon dioxide (PaCO2) levels in monitoring respiratory depression secondary to benzodiazepine treatment in patients with severe alcohol withdrawal. Methods We retrospectively analyzed 36 patients admitted to the intensive care unit for severe alcohol withdrawal who had been administered sedative agents. Results We observed a statistically significant correlation between PaCO2 and ETCO2 at time 1 (r=0.74, P<0.01) and time 3 (r=0.52, P=0.02) but not at time 2 (r=0.22, P=0.31). Conclusion Our study confirms a positive correlation between PaCO2 and ETCO2 levels in patients experiencing severe alcohol withdrawal. PMID:26730226

  9. Aldehydes in hydrothermal solution - Standard partial molal thermodynamic properties and relative stabilities at high temperatures and pressures

    NASA Technical Reports Server (NTRS)

    Schulte, Mitchell D.; Shock, Everett L.

    1993-01-01

    Aldehydes are common in a variety of geologic environments and are derived from a number of sources, both natural and anthropogenic. Experimental data for aqueous aldehydes were taken from the literature and used, along with parameters for the revised Helgeson-Kirkham-Flowers (HKF) equations of state, to estimate standard partial molal thermodynamic data for aqueous straight-chain alkyl aldehydes at high temperatures and pressures. Examples of calculations involving aldehydes in geological environments are given, and the stability of aldehydes relative to carboxylic acids is evaluated. These calculations indicate that aldehydes may be intermediates in the formation of carboxylic acids from hydrocarbons in sedimentary basin brines and hydrothermal systems like they are in the atmosphere. The data and parameters summarized here allow evaluation of the role of aldehydes in the formation of prebiotic precursors, such as amino acids and hydroxy acids on the early Earth and in carbonaceous chondrite parent bodies.

  10. 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.

  11. 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.

  12. 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 temperature. This indicates a solidus temperature of ~1360°C, which is ~25-50°C above the existing estimates for anhydrous solidus corrected for our starting composition. The H2O-undersaturated solidus indicated by our experimental results suggests that potential temperatures for the oceanic mantle are higher than current estimates.

  13. Decomposition Process of Benzene in a Low Pressure DC Glow Discharge

    NASA Astrophysics Data System (ADS)

    Hayashi, Shinobu; Satoh, Kohki; Itoh, Hidenori

    The variations in the partial pressures of gaseous molecules produced by the decomposition of C6H6 in a low pressure DC glow discharge in N2/C6H6 and Ar/C6H6 mixtures are measured by the mass spectrometry. Also, rate equations for the partial pressure variations, which consider possible reaction among the gaseous molecules in the low pressure DC glow discharge, with the electrical energy-input, are proposed, and rate constants are determined by fitting the calculated partial pressure variations to the measured partial pressure variations. The rate constants deduced here indicate that C6H6 is mainly decomposed into an intermediate, which is regarded as a fragment of C6H6, the intermediate is decomposed into mainly C2H2, and then C2H2 is converted into H2 and HCN (only in N2/C6H6).

  14. Partial Molar Volume of CO2 in Peridotitic Melt at High Pressure and Applications to Melt Mobility in the Mantle

    NASA Astrophysics Data System (ADS)

    Duncan, M. S.; Agee, C. B.

    2009-12-01

    The partial molar volume of CO2 (VCO2) is a quantity that may be used for elucidating the role of volatiles in silicate melt at high pressure, such as magma mobility during mantle differentiation when CO2 is present. Because CO2 tends to decrease silicate melt density, its presence should cause crystal-liquid density crossovers to occur at higher pressures than for non-carbonated silicate melts with the same major element composition. Experimental data presented here are crucial to understanding the driving force of carbonated magma eruption, such as kimberlite and nephelinite, especially in the pressure range of 0-3 GPa where extreme changes are observed in the compressibility and solubility of CO2 in peridotite partial melt.High pressure, sink/float experiments were conducted on a synthetic peridotite composition with ~5 wt.% CO2 added as CaCO3 (DG-5), and no CO2 added (DG-N). The mixtures were placed in Mo capsules with two synthetic forsterite spheres or two San Carlos spheres near the top and bottom of the capsule. Experiments were run in a Walker style multi-anvil using 8 mm TEL.Using the known compressibility of the spheres, the density (ρ) of each melt was determined at neutral buoyancy pressures and temperatures using the third order Birch-Murnaghan EOS. The forsterite crossover occurred at 4.6 GPa for DG-5 (ρ=3.14 g/cm3), and 4.0 GPa for DG-N (ρ=3.12 g/cm3). The San Carlos crossover occurred at 6.1 GPa for DG-5 (ρ=3.29 g/cm3), and ~5.0 GPa for DG-N (ρ=3.26 g/cm3).The VCO2 was determined using a modified version of the Bottinga and Weill (1970) equation: ρ=Σ XiMi / XiVi, the calculated ρ, the analyzed compositions, and the assumption that CO2 remained in the melt during sink/float. Preliminary values for VCO2 are 25.35 cm3/mol at 4.3 GPa and 22.92 cm3/mol at 5.6 GPa, both corrected to 1850°C. Based on the VCO2 at 1 bar (Liu & Lange, 2003) and at 19.5 GPa (Ghosh et al., 2007), the compressibility curve for CO2 may now be better constrained. The calculated curve shows a rapid decrease in VCO2 at low pressures indicating a high compressibility in the upper mantle.Currently, we are exploring electron microprobe and FTIR transmission and reflectance methods to better quantify the CO2 in our experimental run products which contain quench crystals and small pockets of glass. We believe the assumption that CO2 remains in the melt during sink/float experiment is valid because crossover positions differ between the DG-5 and DG-N samples. However, we are investigating this assumption because CO32-, CO2 and CO are not observed in the run products with FTIR transmission and reflectance, and the microprobe results for C are ambiguous. There are several possibilities that we are testing at this time.

  15. Effect of organic complexing and carbon dioxide partial pressure on metal transport in low-temperature hydrothermal systems

    SciTech Connect

    Hennet, R.J.C.

    1987-01-01

    The study has widespread geological applications in the genesis of metal-sulfide ore deposits or the transport and deposition of base metal in active hydrothermal environments. This study also presents the chemical analysis of natural sedimentary brines with emphasis on their trace metal and trace organic content. The first chapter summarizes the experimental data collected to quantify metal-organic complexation reactions at temperature up to 90/sup 0/C, and discusses equilibrium constants extrapolation to temperature up to 200/sup 0/C. The second chapter describes some experimental observations of the effects of increased CO/sub 2/ partial pressure on the solubility of ZnS in water, and the concentrations of base metals in sedimentary brines and oils. Also discussed is the possibility of a new, potentially important, transport mechanism for base metals in reduced-sulfur bearing solutions; it consists of base metal complexation with pressure-sensitive, thiocarbonate-like molecules. Chapter 3 presents the chemical analyses of three sedimentary brines from the Central Mississippi Salt Dome Basin. Several organic molecules were identified, including acetic and formic acids. Chapter 4 presents the theory and experimental results for the measurement of lead-organic complex stability constants by two independent polarographic techniques up to 90/sup 0/C, Anodic Stripping Voltametry and Differential Pulse Polarography. Chapter 5 describes the application of /sup 207/Pb Nuclear Magnetic Resonance (NMR) spectroscopy for measuring equilibrium constants of lead-organic complexes at high temperatures. Results are presented for equilibrium of the lead-acetate system up to 80/sup 0/C. A proposal is made for further development of NMR for direct study of chemical equilibria at high pressures and temperatures.

  16. 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.

  17. H2S, a novel gasotransmitter, involves in gastric accommodation

    PubMed Central

    Xiao, Ailin; Wang, Hongjuan; Lu, Xin; Zhu, Jianchun; Huang, Di; Xu, Tonghui; Guo, Jianqiang; Liu, Chuanyong; Li, Jingxin

    2015-01-01

    H2S is produced mainly by two enzymes:cystathionine-?-synthase (CBS) and cystathionine-?-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. PMID:26531221

  18. Electrochemical and Sulfide Stress Corrosion Cracking Behaviors of Tubing Steels in a H2S/CO2 Annular Environment

    NASA Astrophysics Data System (ADS)

    Liu, Z. Y.; Wang, X. Z.; Liu, R. K.; Du, C. W.; Li, X. G.

    2014-04-01

    The electrochemical and sulfide stress corrosion cracking (SSCC) behaviors of 13Cr stainless steel and P110 steel were investigated in a simulated acidic annular environment with low-temperature and high-pressure H2S/CO2 using electrochemical methods, U-bend immersion tests, and scanning electron microscopy. In the solution containing high pressure CO2, 13Cr, and P110 steels exhibited general corrosion and severe pitting, respectively. Compared with sweet corrosion, additional H2S in the solution enhanced the corrosion of 13Cr steel but inhibited the corrosion of P110 steel. By contrast, in a solution containing 4 MPa CO2 and different (0-0.3 MPa), the susceptibility of both 13Cr stainless steel and P110 steel toward SSCC was significantly promoted by increases in H2S partial pressure. The 13Cr stainless steel exhibited higher susceptibility toward SSCC than P110 steel under a H2S/CO2 environment but lower susceptibility under a pure CO2 environment.

  19. Scavenging of H2O2 by mouse brain mitochondria.

    PubMed

    Starkov, Anatoly A; Andreyev, Alexander Yu; Zhang, Steven F; Starkova, Natalia N; Korneeva, Maria; Syromyatnikov, Mikhail; Popov, Vasily N

    2014-12-01

    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. 9-12nmol 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 ?M, 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

  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 ?M, 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 ~5070 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 ~2,2002,900 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. Hydrogen Bonding, Hydration of Species, Ion Pairing and Clusterization in H2O-NaCl-CaCl2-CO2-NaHCO3-Na2CO3 Fluids: Molecular Dynamics Simulation of the Effects of Temperature, Pressure and Composition

    NASA Astrophysics Data System (ADS)

    Kalinichev, A. G.; Kirkpatrick, R. J.; Wang, J.

    2004-12-01

    Molecular computer simulation is an especially valuable tool to study the structural and dynamic properties of carbon-bearing aqueous fluids on the fundamental atomic time- and length- scale because these fluids are not readily studied experimentally using conventional X-ray or EXAFS methods. In this case, experimental methods can produce ambiguous results, because the carbon and oxygen atoms of the solute species are not easily distinguishable from the oxygen atoms of solvent water. Systematic molecular dynamics (MD) computer simulation studies of several fluid compositions - H2O-CO2, H2O-CO2-NaCl, H2O-NaHCO3, and H2O-Na2CO3 - were performed to study the effects of temperature, pressure (fluid density) and concentration on the structural, energetic, spectroscopic and dynamic properties of these solutions characterized on the atomic scale via the statistical parameters of individual hydrogen bonds and H-bonding networks, local hydration structures of dissolved species, and ion pair formation. Similar molecular-level characteristics of pure water and H2O-NaCl and H2O-CaCl2 solutions are calculated and used for comparison with the properties of carbon-bearing fluids. H2O-rich and CO2-rich compositions of the ternary H2O-CO2-NaCl system demonstrate strikingly different structural and dynamic behavior at about the same average density. In dense CO2-rich fluids, dissolved H2O molecules exhibit a high degree of hydrogen bonding and form relatively stable H-bonded clusters structurally similar to those observed in supercritical water at a much lower density. In contrast, CO2 molecules dissolved in water-rich fluids occur in clathrate-like cages formed by surrounding H-bonded water molecules. The hydration shells of carbonate and bicarbonate ions both contain approximately 10 water molecules, but the water structure around the carbonate ion is much more pronounced due to the higher anion charge. This also leads to the formation of very stable ion pairs and larger ionic clusters of Na+ and CO32- even under ambient conditions. Due to the ion cluster formation, the diffusion rates of both Na+ and CO32- are 3-6 times lower than in similar NaCl solutions. The effect of dissolved Na2CO3 on the water structure is comparable to that of CaCl2. In contrast, the structure and dynamics of NaHCO3 solutions is very similar to that of H2O-NaCl, where ion pairing is non-existent at lower temperatures, and the diffusion rates of HCO3- are about the same as those of Cl-. The molecular simulations also predict that a high-density fluid (? 1.1 g/cm3) of the composition H2O/CO2/NaCl=60/28/12 mol%, homogeneous at 1000 C, should experience a phase separation upon cooling at approximately 700 C by forming a low-salinity CO2-rich phase (H2O/CO2/NaCl 50/48/2 mol%) and a concentrated brine (H2O/CO2/NaCl 66/20/14 mol%) in good agreement with available experimental data and thermodynamic calculations. The structural and dynamic properties of both fluid phases are rationalized on the molecular level in terms of the electrostatic and H-bonding interactions between the fluid species in order to understand physical mechanisms driving this phase separation process.

  2. 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.

  3. 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.

  4. 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 ?-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.

  5. 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

  6. 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.

  7. Investigations on tailoring the deposition conditions in HIPIMS by varying the pulse durations and the argon partial pressure

    NASA Astrophysics Data System (ADS)

    Balzer, M.; Fenker, M.

    2012-09-01

    In most cases HIPIMS is used to get the highest possible ionisation of the deposition particles, which is realised by pulse durations with short on- and very long off-times. These conditions are combined with a more or less pronounced decrease in deposition rate. In this work the pulse configuration has been varied. A three dimensional matrix of parameters was spanned, made of 3 on- and 3 off-times at 4 argon partial pressures. The average power was kept constant and the data achieved were additionally compared to DC-magnetron sputtering. The experiments were carried out using 50 mm diameter targets made of Ti, powered by a MELEC SPIK1000A pulser unit. The deposition rate was measured by quartz microbalance mounted in front of the target. Peak current density and target voltage were recorded and time averaged optical emission spectroscopy (t.a.OES) measurements provided information about the ionisation conditions in the plasma. The results of the data analysis provide a coherent overview of the impact of the HIPIMS parameters as well as of their complex interrelations.

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

    NASA Astrophysics Data System (ADS)

    Aroutiounian, Svetlana

    2002-10-01

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

  9. 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.

  10. 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 the warm and cold gas in molecular clouds. This suggests that the two-phase structure of molecular clouds is an essential ingredient for fully understanding molecular hydrogen in these objects.

  11. 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 partial pressure of the operating atmosphere regulates the penetration of slag into refractory. The viscosity of the slag, which dictates its penetration rate, is influenced by the oxidation state of the Fe cation. Slag penetrations are shallower in oxidizing conditions than they are in reducing conditions because the iron-oxide from the slag solutions into the corundum-structured refractory and the slag is depleted of iron-oxide, increasing the viscosity of slags. Equally, the chemistries of both the refractory and slag materials dictate the course of penetration. Cr2O3-Al2O3 refractory limits mixed feedstock slag penetration through formation of a chromium spinel layer that functions as a physical obstacle against fluid flow. Al2O 3-SiO2 refractory limits eastern coal feedstock slag penetration as a result of refractory dissolution of SiO2, which increases the viscosity of slags. A physical model, which considers unidirectional fluid flow of slag through each pore of the porous microstructure of the refractory, sufficiently approximates the penetration depth of the slag into the refractory. Agreement between experiments and the physical model demonstrates that the slag is driven into the refractory by capillary pressure. Since the viscosity of the slag continuously changes as the slag travels through the inherent temperature gradient of the refractory lining, the model incorporates dynamic viscosities that are dependent on both temperature and composition to project depths that are unique to the experimental parameters. The significantly different length scales of the radial and penetration directions of the pores allows for the application of a lubrication approximation onto the momentum equation. This process produces an analytical solution that effectively envelopes the variable viscosity into a single term.

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

    PubMed Central

    Roper, Teryl R.; Williams, Larry E.

    1989-01-01

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

  13. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

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

  15. Long-Term Stroke Risk Due to Partial White-Coat or Masked Hypertension Based on Home and Ambulatory Blood Pressure Measurements: The Ohasama Study.

    PubMed

    Satoh, Michihiro; Asayama, Kei; Kikuya, Masahiro; Inoue, Ryusuke; Metoki, Hirohito; Hosaka, Miki; Tsubota-Utsugi, Megumi; Obara, Taku; Ishiguro, Aya; Murakami, Keiko; Matsuda, Ayako; Yasui, Daisaku; Murakami, Takahisa; Mano, Nariyasu; Imai, Yutaka; Ohkubo, Takayoshi

    2016-01-01

    The prognostic significance of white-coat hypertension (WCHT) is controversial, and different findings on self-measured home measurements and 24-h ambulatory monitoring make identifying WCHT difficult. We examined whether individuals with partially or completely defined WCHT, as well as masked hypertension, as determined by different out-of-office blood pressure measurements, have a distinct long-term stroke risk. We followed 1464 participants (31.8% men; mean age, 60.610.8 years) in the general population of Ohasama, Japan, for a median of 17.1 years. A first stroke occurred in 212 subjects. Using sustained normal blood pressure (events/n=61/776) as a reference, adjusted hazard ratios for stroke (95% confidence intervals; events/n) were 1.38 (0.82-2.32; 19/137) for complete WCHT (isolated office hypertension), 2.16 (1.36-3.43; 29/117) for partial WCHT (either home or ambulatory normotension with office hypertension), 2.05 (1.24-3.41; 23/100) for complete masked hypertension (both home and ambulatory hypertension with office normotension), 2.08 (1.37-3.16; 38/180) for partial masked hypertension (either home or ambulatory hypertension with office normotension), and 2.46 (1.61-3.77; 42/154) for sustained hypertension. When partial WCHT and partial masked hypertension groups were further divided into participants only with home hypertension and those only with ambulatory hypertension, all subgroups had a significantly higher stroke risk (adjusted hazard ratio ?1.84, P?0.04). In conclusion, impacts of partial WCHT as well as partial masked hypertension for long-term stroke risk were comparable to those of complete masked hypertension or sustained hypertension. We need both home and 24-h ambulatory blood pressure measurements to evaluate stroke risk accurately. PMID:26527046

  16. Effects of occlusal rest design on pressure distribution beneath the denture base of a distal extension removable partial denture-an in vivo study.

    PubMed

    Suenaga, Hanako; Kubo, Kei; Hosokawa, Ryoichi; Kuriyagawa, Tsunemoto; Sasaki, Keiichi

    2014-01-01

    This study aimed to investigate the pressure distribution beneath the denture bases of removable partial dentures (RPDs) with different occlusal rest designs (ORDs) by in vivo measurement. Four types of detachable occlusal rests (mesial and distal, distal, mesial, and nonrest) were placed on the direct abutment teeth of distal extension RPDs in four patients with free-end edentulous mandibles. Pressure measurements were obtained by using thin and flexible tactile sensors. The results showed significant variances with different ORDs in all four patients (P < .05), leading to the conclusion that the pressure distribution on the residual ridge beneath the RPD base was dependent on the ORD. PMID:25191891

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

    PubMed Central

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

    2013-01-01

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

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

    USGS Publications Warehouse

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

    2001-01-01

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

  19. CO(2) partial pressure and calcite saturation in springs - useful data for identifying infiltration areas in mountainous environments.

    PubMed

    Hilberg, Sylke; Brandsttter, Jennifer; Glck, 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. PMID:23429574

  20. Changes in transcutaneous oxygen partial pressure as an index of response to inhaled methacholine in asthmatic patients.

    PubMed

    Fontana, G A; Cardellicchio, S; Camiciottoli, G; Panuccio, P; Boddi, V

    1993-05-01

    Bronchoconstriction and hypoxemia have been reported to occur during airway challenges, but the correlation between changes in forced expiratory volume in 1 s (FEV1) and transcutaneous oxygen partial pressure (tcPO2) during methacholine provocation tests has not yet been established (to our knowledge). In 15 symptom-free atopic asthmatic patients and 5 normal subjects, variations in tcPO2 and FEV1 were simultaneously measured during inhalation of doubling methacholine concentrations; the drug concentrations causing a 20 percent decrease in control FEV1 and tcPO2 (PC20FEV1 and PC20tcPO2, respectively) were subsequently calculated. In patients, geometric mean PC20FEV1 and PC20TcPO2 were 1.31 (range, 0.16 to 5.19) and 1.26 (range, 0.29 to 5.82) mg/ml, respectively. In addition, in six patients, methacholine-induced fall in tcPO2 was accompanied by similar changes in arterial PO2. Methacholine inhalation caused no change in tcPO2 or FEV1 in normal subjects. The independent effects of deep breath tests and bronchoconstriction on PC20tcPO2 were studied in five patients challenged on two separate occasions, with and without FEV1 assessment; in these patients, PC20tcPO2 were similar on both the study days. The results indicate that, in asthmatic patients, methacholine-induced bronchoconstriction causes parallel decreases in FEV1 and tcPO2. The tcPO2 monitoring may serve as a tool in the assessment of airway hyperreactivity when active patient's cooperation is scarce. PMID:8486013

  1. Residual oxygen time model for oxygen partial pressure near 130 kPa (1.3 atm).

    PubMed

    Shykoff, Barbara E

    2015-01-01

    A two-part residual oxygen time model predicts the probability of detectible pulmonary oxygen toxicity P(P[O2tox]) after dives with oxygen partial pressure (PO2) approximately 130 kPa, and provides a tool to plan dive series with selected risk of P[O2tox]. Data suggest that pulmonary oxygen injury at this PO2 is additive between dives. Recovery begins after a delay and continues during any following dive. A logistic relation expresses P(P[O2tox]) as a function of dive duration (T(dur)) [hours]: P(P[O2tox]) = 100/[1+exp (3.586-0.49 x T(dur))] This expression maps T(dur) to P(P[O2tox]) or, in the linear mid-portion of the curve, P(P[O2tox]) usefully to T(dur). For multiple dives or during recovery, it maps to an equivalent dive duration, T(eq). T(eq) was found after second dives of duration T(dur 2). Residual time from the first dive t(r) = T(eq) - T(dur2). With known t(r), t and T(dur) a recovery model was fitted. t(r) = T(dur) x exp [-k x((t-5)/T(dur)2], where t = t - 5 hours, k = 0.149 for resting, and 0.047 for exercising divers, and t represents time after surfacing. The fits were assessed for 1,352 man-dives. Standard deviations of the residuals were 8.5% and 18.3% probability for resting or exercise dives, respectively. PMID:26742255

  2. 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.

  3. Intracellular Carbonic Anhydrase Activity Sensitizes Cancer Cell pH Signaling to Dynamic Changes in CO2 Partial Pressure*

    PubMed Central

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

    2014-01-01

    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 [Ca2+] oscillations and stronger inhibition of the mTORC1 pathway reported by S6 kinase phosphorylation. In contrast, the pHi of cells with low CAi activity was less responsive to pCO2 fluctuations. Such low pass filtering would buffer cancer cell pHi from non-steady-state extracellular pCO2. Thus, CAi activity determines the coupling between pCO2 (a function of tumor perfusion) and pHi (a potent modulator of cancer cell physiology). PMID:25059669

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

    PubMed Central

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

    1988-01-01

    The end tidal partial pressure of carbon dioxide (Pco2) was measured during treadmill exercise in 30 normal controls and 113 patients referred for assessment of chest pain. Among the 92 patients without significant ST depression hypocapnia occurred more often in those reporting typical than atypical chest pain (17 of 22 patients compared with 29 of 70; p<001). Hypocapnia was uncommon in patients with significant ST depression whether reporting typical or atypical chest pain (one of 10 patients and two of 11, respectively). Hypocapnia at rest (Pco2 <4 kPa) occurred in 16 (14%) patients but in only one control. Hypocapnia occurred during or after exercise in only one control and three of the 21 patients with significant ST depression on exercise (group 1). The remaining 92 patients were divided into those with a history suggestive of hyperventilation (group 2; n=30) and those without (group 3; n=62). Hypocapnia developed significantly more often in both these groups (21 and 25 patients respectively) than in controls or patients with significant ST depression. An abnormal response of the Pco2 to exercise provided objective data to support a clinical suspicion of chest pain induced by hyperventilation in 24 cases, suggested a cause for equivocal ST depression other than coronary stenosis in five patients, and led to the diagnosis of previously unsuspected respiratory disease in 14 patients. Measurement of end tidal Pco2 gives additional valuable diagnostic information during the conventional treadmill exercise test in patients with both typical and atypical chest pain. PMID:3133051

  5. 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.

  6. 42 CFR 52h.2 - Definitions.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 42 Public Health 1 2011-10-01 2011-10-01 false Definitions. 52h.2 Section 52h.2 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND HUMAN SERVICES GRANTS SCIENTIFIC PEER REVIEW OF RESEARCH GRANT APPLICATIONS AND RESEARCH AND DEVELOPMENT CONTRACT PROJECTS § 52h.2 Definitions. As used in this part: (a) Act means the Public Health...

  7. 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.

  8. Multiple emissive triarylborane-A2H2 and triarylborane-Zn-A2H2 porphyrin conjugates.

    PubMed

    P, Chinna Ayya Swamy; Thilagar, Pakkirisamy

    2016-03-21

    Triarylborane-A2H2 (1) and triarylborane-Zn-A2H2 porphyrins (2) have been synthesized by acid catalyzed condensation of 4-dimesitylboryl-benzaldehyde and dipyrromethane under ambient conditions. Compounds 1 and 2 showed multiple emission bands upon excitation at the triarylborane dominated absorption region (350 nm). Detailed experimental and computational studies show that the multiple emission features of 1 and 2 arise as a result of a partial energy transfer from the donor (triarylborane) to the acceptor (porphyrin) moieties. Compounds 1 and 2 showed very high selectivities towards fluoride ions compared to other competing anions. PMID:26859387

  9. Experimental determination of the solubility of natural wollastonite in pure water up to pressures of 5 GPa and at temperatures of 400-800 C

    NASA Astrophysics Data System (ADS)

    Fockenberg, Thomas; Burchard, Michael; Maresch, Walter V.

    2006-04-01

    The solubility of natural, near-end-member wollastonite-I (>99.5% CaSiO 3) has been determined at temperatures from 400 to 800 C and pressures between 0.8 and 5 GPa in piston-cylinder apparatus with the weight-loss method. Chemical analysis of quench products and optical monitoring in a hydrothermal diamond anvil cell demonstrates that no additional phases form during dissolution. Wollastonite-I, therefore, dissolves congruently in the pressure-temperature range investigated. The solubility of CaSiO 3 varies between 0.175 and 13.485 wt% and increases systematically with both temperature and pressure up to 3.0 GPa. Above 3.0 GPa wollastonite-I reacts rapidly to the high-pressure modification wollastonite-II. No obvious trends are evident in the solubility of wollastonite-II, with values between 1.93 and 10.61 wt%. The systematics of wollastonite-I solubility can be described well by a composite polynomial expression that leads to isothermal linear correlation with the density of water. The molality of dissolved wollastonite-I in pure water is then log(mwoll)=2.2288-3418.23T-1+671386.84T-2+log?(5.4578+2359.11T-1). By combining the present experimental data with literature data on the solubility of quartz (Manning, C.E., Boettcher, S.L., 1994. Rapid-quench hydrothermal experiments at mantle pressures and temperatures. Am. Mineral. 79, 1153-1158.) and wollastonite-I + quartz (Xie, Z., Walther, J.V., 1993b. Wollastonite + quartz solubility in supercritical NaCl aqueous solutions. Am. J. Sci. 293, 235-255.) in pure water, an analogous expression can be derived for the solubility of wollastonite in quartz-saturated aqueous solution as follows: log(mwoll)=2.5930-3660.98T-1+671402.32T-2+log?(-1.3609+6775.13T-1).(all temperatures are inC) This expression adequately describes wollastonite-I solubility between 0.2-3 GPa and 300-800 C.

  10. Measurements of seismic attenuation and transient fluid pressure in partially saturated Berea sandstone: evidence of fluid flow on the mesoscopic scale

    NASA Astrophysics Data System (ADS)

    Tisato, Nicola; Quintal, Beatriz

    2013-10-01

    A novel laboratory technique is proposed to investigate wave-induced fluid flow on the mesoscopic scale as a mechanism for seismic attenuation in partially saturated rocks. This technique combines measurements of seismic attenuation in the frequency range from 1 to 100 Hz with measurements of transient fluid pressure as a response of a step stress applied on top of the sample. We used a Berea sandstone sample partially saturated with water. The laboratory results suggest that wave-induced fluid flow on the mesoscopic scale is dominant in partially saturated samples. A 3-D numerical model representing the sample was used to verify the experimental results. Biot's equations of consolidation were solved with the finite-element method. Wave-induced fluid flow on the mesoscopic scale was the only attenuation mechanism accounted for in the numerical solution. The numerically calculated transient fluid pressure reproduced the laboratory data. Moreover, the numerically calculated attenuation, superposed to the frequency-independent matrix anelasticity, reproduced the attenuation measured in the laboratory in the partially saturated sample. This experimental-numerical fit demonstrates that wave-induced fluid flow on the mesoscopic scale and matrix anelasticity are the dominant mechanisms for seismic attenuation in partially saturated Berea sandstone.

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

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

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

  12. Changes in partial pressures of respiratory gases during submerged voluntary breath hold across odontocetes: is body mass important?

    PubMed

    Noren, S R; Williams, T M; Ramirez, K; Boehm, J; Glenn, M; Cornell, L

    2012-02-01

    Odontocetes have an exceptional range in body mass spanning 10(3) kg across species. Because, size influences oxygen utilization and carbon dioxide production rates in mammals, this lineage likely displays an extraordinary variation in oxygen store management compared to other marine mammal groups. To examine this, we measured changes in the partial pressures of respiratory gases ([Formula: see text], [Formula: see text]), pH, and lactate in the blood during voluntary, quiescent, submerged breath holds in Pacific white-sided dolphins (Lagenorhynchus obliquidens), bottlenose dolphins (Tursiops truncatus), and a killer whale (Orcinus orca) representing a mass range of 96-3,850 kg. These measurements provided an empirical determination of the effect of body size on the variability in blood biochemistry during breath hold and experimentally determined aerobic dive limits (ADL) within one taxonomic group (odontocetes). For the species in this study, maximum voluntary breath-hold duration was positively correlated with body mass, ranging from 3.5 min in white-sided dolphins to 13.3 min for the killer whale. Variation in breath-hold duration was associated with differences in the rate of change for [Formula: see text] throughout breath hold; [Formula: see text] decreased twice as fast for the two smaller species (-0.6 mmHg O(2) min(-1)) compared to the largest species (-0.3 mmHg O(2) min(-1)). In contrast, the rate of increase in [Formula: see text] during breath hold was similar across species. These results demonstrate that large body size in odontocetes facilitates increased aerobic breath-hold capacity as mediated by decreased mass-specific metabolic rates (rates of change in [Formula: see text] served as a proxy for oxygen utilization). Indeed the experimentally determined 5 min ADL for bottlenose dolphins was surpassed by the 13.3 min maximum breath hold of the killer whale, which did not end in a rise in lactate. Rather, breath hold ended voluntarily as respiratory gases and pH fell within a narrow range for both large and small species, likely providing cues for ventilation. PMID:21935721

  13. [Partial pressure of CO2 and CO2 degassing fluxes of Huayuankou and Xiaolangdi Station affected by Xiaolangdi Reservoir].

    PubMed

    Zhang, Yong-ling; Yang, Xiao-lin; Zhang, Dong

    2015-01-01

    According to periodic sampling analysis per month in Xiaolangdi station and Huayuankou station from November 2011 to October 2012, combined with continuous sampling analysis of Xiaolangdi Reservoir during runoff and sediment control period in 2012, partial pressure of CO2 (pCO2) in surface water were calculated based on Henry's Law, pCO2 features and air-water CO2 degassing fluxes of Huayuankou station and Xiaolangdi station affected by Xiaolangdi Reservoir were studied. The results were listed as follows, when Xiaolangdi Reservoir operated normally, pCO2 in surface water of Xiaolangdi station and Huayuankou station varied from 82 to 195 Pa and from 99 to 228 Pa, moreover, pCO2 in surface water from July to September were distinctly higher than those in other months; meanwhile, pCO, in surface water from Huayuankou station were higher than that from Xiaolangdi station. During runoff and sediment control period of Xiaolangdi Reservoir, two hydrological stations commonly indicated that pCO2 in surface water during water draining were obviously lower than those during sediment releasing. Whether in the period of normal operation or runoff and sediment control, pCO2 in surface water had positive relations to DIC content in two hydrological stations. Since the EpCO,/AOU value was higher than the theoretical value of 0. 62, the biological aerobic respiration effect had distinct contribution to pCO2. Throughout the whole year, air-water CO2 degassing fluxes from Xiaolangdi station and Huayuankou station were 0.486 p.mol (m2 s) -l and 0.588 pmol (m2 x s)(-1) respectively; When Xiaolangdi Reservoir operated normally, air-water CO, degassing fluxes in Huayuankou station were higher than that in Xiaolangdi station; during runoff and sediment control from Xiaolangdi Reservoir, two hydrological stations had one observation result in common, namely, air-water CO2 degassing fluxes in the period of water draining were obviously lower than that in the period of sediment releasing. PMID:25898645

  14. Hydrogen Storage Properties of New Hydrogen-Rich BH3NH3-Metal Hydride (TiH2, ZrH2, MgH2, and/or CaH2) Composite Systems

    SciTech Connect

    Choi, Young Joon; Xu, Yimin; Shaw, Wendy J.; Ronnebro, Ewa

    2012-04-19

    Ammonia borane (AB = NH3BH3) is one of the most attractive materials for chemical hydrogen storage due to its high hydrogen contents of 19.6 wt.%, however, impurity levels of borazine, ammonia and diborane in conjunction with foaming and exothermic hydrogen release calls for finding ways to mitigate the decomposition reactions. In this paper we present a solution by mixing AB with metal hydrides (TiH2, ZrH2, MgH2 and CaH2) which have endothermic hydrogen release in order to control the heat release and impurity levels from AB upon decomposition. The composite materials were prepared by mechanical ball milling, and their H2 release properties were characterized by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The formation of volatile products from decomposition side reactions, such as borazine (N3B3H6) was determined by mass spectrometry (MS). Sieverts type pressure-composition-temperature (PCT) gas-solid reaction instrument was adopted to observe the kinetics of the H2 release reactions of the combined systems and neat AB. In situ 11B MAS-NMR revealed a destabilized decomposition pathway. We found that by adding specific metal hydrides to AB we can eliminate the impurities and mitigate the heat release.

  15. Oxygen partial pressure dependence of magnetic, optical and magneto-optical properties of epitaxial cobalt-substituted SrTiO? films.

    PubMed

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

    2015-05-18

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

  16. 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

  17. Enhanced Shrinkage of Lanthanum Strontium Manganite (La0.90Sr0.10MnO3+?) 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+? 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.

  18. Selective modulation of cellular voltage-dependent calcium channels by hyperbaric pressurea suggested HPNS partial mechanism

    PubMed Central

    Aviner, Ben; Gradwohl, Gideon; Mor Aviner, Merav; Levy, Shiri; Grossman, Yoram

    2014-01-01

    Professional deep sea divers experience motor and cognitive impairment, known as High Pressure Neurological Syndrome (HPNS), when exposed to pressures of 100 msw (1.1 MPa) and above, considered to be the result of synaptic transmission alteration. Previous studies have indicated modulation of presynaptic Ca2+ currents at high pressure. We directly measured for the first time pressure effects on the currents of voltage dependent Ca2+ channels (VDCCs) expressed in Xenopus oocytes. Pressure selectivity augmented the current in CaV1.2 and depressed it in CaV3.2 channels. Pressure application also affected the channels' kinetics, such as ?Rise, ?Decay. Pressure modulation of VDCCs seems to play an important role in generation of HPNS signs and symptoms. PMID:24904281

  19. Fine-tuning control on CNT diameter distribution, length and density using thermal CVD growth at atmospheric pressure: an in-depth analysis on the role of flow rate and flow duration of acetylene (C2H2) gas

    NASA Astrophysics Data System (ADS)

    Tripathi, Nishant; Mishra, Prabhash; Harsh, Harsh; Islam, S. S.

    2015-01-01

    An optimization control has been demonstrated to obtain carbon nanotubes having specific diameter distribution, length, homogeneity, and yield during its growth by thermal chemical vapor deposition technique under atmospheric pressure. Carbon nanotubes (CNTs) were grown on silicon wafer where a predeposition of iron catalyst of 2 nm thickness was made by sputtering. The growth was conducted under two variable parameters, i.e., flow rate and flow duration. Argon and hydrogen mixture was used for pretreatment of catalyst and as etching gas, and acetylene as a carbon precursor. In-depth analysis shows that increase in flow rate from 10 to 50 sccm resulted in increase in the concentration of amorphous carbon, CNTs diameter range and decrease in length, we found best result at 20 sccm flow rate of acetylene gas. On the other hand, as we varied flow duration from 6 to 14 min, with keeping flow rate of acetylene 20 sccm constant, dense homogeneous growth of horizontal CNTs network plus an increase in length and diameter range were observed. An optimization of flow rate and flow duration is presented here to obtain a selective diameter distribution and length as expected by this growth technique. Atomic force microscopy, field emission scanning electron microscopy and Raman spectroscopy were used to investigate the samples' morphologies in support of the observations made.

  20. High-Resolution Numerical Simulation and Analysis of Mach Reflection Structures in Detonation Waves in Low-Pressure H2O2Ar Mixtures: A Summary of Results Obtained with the Adaptive Mesh Refinement Framework AMROC

    DOE PAGESBeta

    Deiterding, Ralf

    2011-01-01

    Numerical simulation can be key to the understanding of the multidimensional nature of transient detonation waves. However, the accurate approximation of realistic detonations is demanding as a wide range of scales needs to be resolved. This paper describes a successful solution strategy that utilizes logically rectangular dynamically adaptive meshes. The hydrodynamic transport scheme and the treatment of the nonequilibrium reaction terms are sketched. A ghost fluid approach is integrated into the method to allow for embedded geometrically complex boundaries. Large-scale parallel simulations of unstable detonation structures of Chapman-Jouguet detonations in low-pressure hydrogen-oxygen-argon mixtures demonstrate the efficiency of the described techniquesmorein practice. In particular, computations of regular cellular structures in two and three space dimensions and their development under transient conditions, that is, under diffraction and for propagation through bends are presented. Some of the observed patterns are classified by shock polar analysis, and a diagram of the transition boundaries between possible Mach reflection structures is constructed.less

  1. 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 PAGESBeta

    Deiterding, Ralf

    2011-01-01

    Numerical simulation can be key to the understanding of the multidimensional nature of transient detonation waves. However, the accurate approximation of realistic detonations is demanding as a wide range of scales needs to be resolved. This paper describes a successful solution strategy that utilizes logically rectangular dynamically adaptive meshes. The hydrodynamic transport scheme and the treatment of the nonequilibrium reaction terms are sketched. A ghost fluid approach is integrated into the method to allow for embedded geometrically complex boundaries. Large-scale parallel simulations of unstable detonation structures of Chapman-Jouguet detonations in low-pressure hydrogen-oxygen-argon mixtures demonstrate the efficiency of the described 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

  2. 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.

  3. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-02-01

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

  5. Reliability study of the NiH2 strain gage

    NASA Technical Reports Server (NTRS)

    Klein, Glenn C.; Rash, Donald E., Jr.

    1993-01-01

    This paper summarizes a joint study by Gates Aerospace Batteries (GAB) and the Reliability Analysis Center (RAC). This study characterizes the reliability and robustness of the temperature compensated strain gages currently specified for sensing of internal pressure of NiH2 cells. These strain gages are characterized as fully encapsulated, metallic foil grids with known resistance that varies with deformation. The measurable deformation, when typically installed on the hemispherical portion of a NiH2 cell, is proportional to the material stresses as generated by internal cell pressures. The internal pressure sensed in this manner is calibrated to indicate the state-of-charge for the cell. This study analyzes and assesses both robustness and reliability for the basic design of the strain gage, the installation of the strain gage, and the circuitry involved.

  6. 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.

  7. 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.

  8. 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 sustainable production of biofuels. Although the process is already in use, its biochemistry is only incompletely understood. The most pertinent question is how the bacteria conserve energy for growth during ethanol formation from H2 and CO2, considering that acetyl coenzyme A (acetyl-CoA), is an intermediate. Can reduction of the activated acetic acid to ethanol with H2 be coupled with the phosphorylation of ADP? Evidence is presented that this is indeed possible, via both substrate-level phosphorylation and electron transport phosphorylation. In the case of substrate-level phosphorylation, acetyl-CoA reduction to ethanol proceeds via free acetic acid involving acetaldehyde:ferredoxin oxidoreductase (carboxylate reductase). PMID:26148714

  9. 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.

  10. Degassing of volatiles (H 2O, CO 2, S, Cl) during ascent, crystallization, and eruption at mafic monogenetic volcanoes in central Mexico

    NASA Astrophysics Data System (ADS)

    Johnson, Emily R.; Wallace, Paul J.; Cashman, Katharine V.; Delgado Granados, Hugo

    2010-11-01

    Mafic monogenetic volcanoes (cinder cones, maars) have eruption styles that include highly explosive, mildly explosive, and effusive regimes. Here we investigate the degassing and vapor-melt partitioning of volatiles (H 2O, CO 2, S, Cl) in monogenetic volcanoes from the subduction-related Michoacán-Guanajuato Volcanic Field (MGVF) in central Mexico. Olivine-hosted melt inclusions from these volcanoes contain variably degassed melts that were trapped over a wide range of pressures from < 50 MPa to ˜ 300 MPa. Variations in melt compositions and volatile contents provide evidence that crystallization and differentiation were driven by degassing of H 2O. Melt CO 2 and H 2O concentrations are highly variable, and much of the variation does not conform to equilibrium open- or closed-system degassing paths. Instead, we suggest that gas-fluxing - partial re-equilibration of magmas with CO 2-rich gases rising from depth - can explain the variable CO 2 and H 2O concentrations in the melts. Such fluxing may be common in basaltic systems, and it increases the extent of crystallization during magma ascent by removing dissolved H 2O from vapor-saturated (but H 2O-undersaturated) melts. Strong degassing of S and Cl during magma ascent and crystallization begins at pressures of approximately 50 MPa. Using the relationship between degassing and crystallization, we calculate apparent vapor-melt partition coefficients for S and Cl. Our results show that, overall, S partitions more strongly into the vapor phase than Cl, consistent with published experimental data and thermodynamic models, and that vapor-melt partitioning of S increases more strongly with decreasing pressure than Cl. The S and Cl partitioning behavior inferred from the melt inclusion data are consistent with the gas fluxing model suggested by the H 2O and CO 2 data.

  11. H2 fuel prototype hydride bed performance tests

    SciTech Connect

    Dyer, E.F.

    1996-10-01

    H2Fuel is a project to design, build, and demonstrate a hydrogen-electric hybrid city bus for Augusta, GA. The H2Fuel bus uses metal hydride technology for on-board hydrogen fuel storage. This document reports on tests by the Savannah River Technology Center (SRTC) to measure the performance of the H2Fuel prototype hydride bed. Bed diameter measurements were made before and after hydrogen testing. Seven hydrogen absorption-desorption cycles were completed. Significant results include: - maximum hydrogen capacity of approximately 3500 STP liters (0.315 kg) - practical hydrogen capacity of approximately 3000 STP liters (0.270 kg) - absorption tests at four hydrogen supply pressures (75, 100, 140, and 300 psia) - desorption tests at three hydrogen rates (20, 30, and 50 slpm) - no measurable swelling of the hydride bed

  12. Interaction between sulphide and H 2O in silicate melts

    NASA Astrophysics Data System (ADS)

    Stelling, Jan; Behrens, Harald; Wilke, Max; Gttlicher, Jrg; Chalmin-Aljanabi, Emilie

    2011-06-01

    Reaction between dissolved water and sulphide was experimentally investigated in soda-lime-silicate (NCS) and sodium trisilicate (NS3) melts at temperatures from 1000 to 1200 C and pressures of 100 or 200 MPa in internally heated gas pressure vessels. Diffusion couple experiments were conducted at water-undersaturated conditions with one half of the couple being doped with sulphide (added as FeS or Na 2S; 1500-2000 ppm S by weight) and the other with H 2O (3.0 wt.%). Additionally, two experiments were performed using a dry NCS glass cylinder and a free H 2O fluid. Here, the melt was water-saturated at least at the melt/fluid interface. Profiling by electron microprobe (sulphur) and infrared microscopy (H 2O) demonstrate that H 2O diffusion in the melts is faster by 1.5-2.3 orders of magnitude than sulphur diffusion and, hence, H 2O can be considered as a rapidly diffusing oxidant while sulphur is quasi immobile in these experiments. In Raman spectra a band at 2576 cm -1 appears in the sulphide - H 2O transition zone which is attributed to fundamental S-H stretching vibrations. Formation of new IR absorption bands at 5025 cm -1 (on expense of the combination band of molecular H 2O at 5225 cm -1) and at 3400 cm -1 was observed at the front of the in-diffusing water in the sulphide bearing melt. The appearance and intensity of these two IR bands is correlated with systematic changes in S K-edge XANES spectra. A pre-edge excitation at 2466.5 eV grows with increasing H 2O concentration while the sulphide peak at 2474.0 eV decreases in intensity relative to the peak at 2477.0 eV and the feature at 2472.3 eV becomes more pronounced (all energies are relative to the sulphate excitation, calibrated to 2482.5 eV). The observations by Raman, IR and XANES spectroscopy indicate a well coordinated S 2- - H 2O complex which was probably formed in the glasses during cooling at the glass transition. No oxidation of sulphide was observed in any of the diffusion couple experiments. On the contrary, XANES spectra from experiments conducted with a free H 2O fluid show complete transformation of sulphide to sulphate near the melt surface and coexistence of sulphate and sulphide in the center of the melt. This can be explained by a lower H 2O activity in the diffusion couple experiments or by the need of a sink for hydrogen (e.g., a fluid which can dissolve high concentration of hydrogen) to promote oxidation of sulphide by H 2O via the reaction S 2- + 4H 2O = SO 42- + 4H 2. Sulphite could not be detected in any of the XANES spectra implying that this species, if it exists in the melt, it is a subordinate or transient species only.

  13. Phase Transitions and Phase Decomposition of La{1-x}Sr{x}CoO{3-delta} in Low Oxygen Partial Pressures

    SciTech Connect

    Ovenstone,J.; White, J.; Misture, S.

    2008-01-01

    High-temperature X-ray diffraction has been used to investigate the phase stability of lanthanum strontium cobalt oxide (LSC) for a range of materials with the formula La1-xSrxCoO3-{delta} (x = 0.7, 0.4, and 0.2). The stability of LSC increases with La content in low oxygen partial pressures at high temperature. Oxygen vacancy ordering has been observed for all three compositions in either low oxygen pressure or under reducing gas, as evidenced by the formation of the brownmillerite phase. The crystal structure of the vacancy-ordered phase was determined using Rietveld analysis of synchrotron X-ray diffraction data. The decomposition products under low oxygen pressure and in reducing conditions have been identified and characterized, including the phase transition and thermal expansion of the primary decomposition products, LaSrCoO4 and LaSrCoO3.5.

  14. Mass spectrometric determination of partial pressures of ions in the saturated vapor over the NaF-Na3AlF6 system

    NASA Astrophysics Data System (ADS)

    Abramov, S. V.; Chilingarov, N. S.; Borshchevsky, A. Ya; Sidorov, L. N.

    2004-01-01

    Mass spectrometric determination of absolute partial pressures of basic charged species Na2F+ and AlF4- in the saturated vapor over the NaF-Na3AlF6 system (1:1 molar ratio) was carried out in the 974-1090 K temperature range. The ion pressures were 5-8 orders of magnitude lower than the pressures of basic molecular components NaAlF4 and NaF. Particular attention was given to the equality of device sensitivity constants for positive and negative ions. Absolute device calibration was carried out using the measured ion currents Na2F+ and AlF4- and the equilibrium constant of heterolytic dissociation available in the literature.

  15. Availability of O(2) and H(2)O(2) on pre-photosynthetic Earth.

    PubMed

    Haqq-Misra, Jacob; Kasting, James F; Lee, Sukyoung

    2011-05-01

    Old arguments that free O(2) must have been available at Earth's surface prior to the origin of photosynthesis have been revived by a new study that shows that aerobic respiration can occur at dissolved oxygen concentrations much lower than had previously been thought, perhaps as low as 0.05?nM, which corresponds to a partial pressure for O(2) of about 4??10(-8) bar. We used numerical models to study whether such O(2) concentrations might have been provided by atmospheric photochemistry. Results show that disproportionation of H(2)O(2) near the surface might have yielded enough O(2) to satisfy this constraint. Alternatively, poleward transport of O(2) from the equatorial stratosphere into the polar night region, followed by downward transport in the polar vortex, may have brought O(2) directly to the surface. Thus, our calculations indicate that this "early respiration" hypothesis might be physically reasonable. PMID:21545266

  16. 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.

  17. Persulfidation (S-sulfhydration) and H2S.

    PubMed

    Filipovic, Milos R

    2015-01-01

    The past decade has witnessed the discovery of hydrogen sulfide (H2S) as a new signalling molecule. Its ability to act as a neurotransmitter, regulator of blood pressure, immunomodulator or anti-apoptotic agent, together with its great pharmacological potential, is now well established. Notwithstanding the growing body of evidence showing the biological roles of H2S, the gap between the macroscopic descriptions and the actual mechanism(s) behind these processes is getting larger. The reactivity towards reactive oxygen and nitrogen species and/or metal centres cannot explain this plethora of biological effects. Therefore, a mechanism involving modification of protein cysteine residues to form protein persulfides is proposed. It is alternatively called S-sulfhydration. Persulfides are not particularly stable and show increased reactivity when compared to free thiols. Detection of protein persulfides is still facing methodological limitations, and mechanisms by which H2S causes this modification are still largely scarce. Persulfidation of protein such as KATP could contribute to H2S-induced vasodilation, while S-sulfhydration of GAPDH and NF-?B inhibits apoptosis. H2S regulates endoplasmic reticulum stress by causing persulfidation of PTP-1B. Several other proteins have been found to be regulated by this posttranslational modification of cysteine. This review article provides a critical overview of the current state of the literature addressing protein S-sulfhydration, with particular emphasis on the challenges and future research directions in this particular field. PMID:26162828

  18. Catalytic effect of nanoparticle 3d-transition metals on hydrogen storage properties in magnesium hydride MgH2 prepared by mechanical milling.

    PubMed

    Hanada, Nobuko; Ichikawa, Takayuki; Fujii, Hironobu

    2005-04-21

    We examined the catalytic effect of nanoparticle 3d-transition metals on hydrogen desorption (HD) properties of MgH(2) prepared by mechanical ball milling method. All the MgH(2) composites prepared by adding a small amount of nanoparticle Fe(nano), Co(nano), Ni(nano), and Cu(nano) metals and by ball milling for 2 h showed much better HD properties than the pure ball-milled MgH(2) itself. In particular, the 2 mol % Ni(nano)-doped MgH(2) composite prepared by soft milling for a short milling time of 15 min under a slow milling revolution speed of 200 rpm shows the most superior hydrogen storage properties: A large amount of hydrogen ( approximately 6.5 wt %) is desorbed in the temperature range from 150 to 250 degrees C at a heating rate of 5 degrees C/min under He gas flow with no partial pressure of hydrogen. The EDX micrographs corresponding to Mg and Ni elemental profiles indicated that nanoparticle Ni metals as catalyst homogeneously dispersed on the surface of MgH(2). In addition, it was confirmed that the product revealed good reversible hydriding/dehydriding cycles even at 150 degrees C. The hydrogen desorption kinetics of catalyzed and noncatalyzed MgH(2) could be understood by a modified first-order reaction model, in which the surface condition was taken into account. PMID:16851820

  19. Effect of the oxygen partial pressure on the properties of ZnO thin films grown by metalorganic vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Ma, Y.; Du, G. T.; Yang, T. P.; Qiu, D. L.; Zhang, X.; Yang, H. J.; Zhang, Y. T.; Zhao, B. J.; Yang, X. T.; Liu, D. L.

    2003-08-01

    ZnO thin films were grown on c-plane sapphire substrate at 600C by metalorganic vapor phase epitaxy (MOVPE). The effect of one of the main deposition parameters, the oxygen partial pressure, on the properties of the ZnO thin films was investigated by means of X-ray diffraction (XRD), photoluminescence (PL) spectrum, atomic force microscopy (AFM) and Hall measurements. Increasing the oxygen partial pressure up to 65 Pa was found to degrade the crystallinity of the ZnO thin films because of the formation of the oxygen-induced defects, but the UV emission in PL spectra was enhanced and deep level emission was weakened. It might be attributed to the reduction of the oxygen vacancies concentration. So the UV emission might be more dependent on the stoichiometry than the microstructural quality of the ZnO thin films. At the same time, Hall measurements showed that the electrical resistivity of the ZnO thin films increased with the oxygen pressure and the electron mobility decreased. The origin of n-type character in undoped ZnO films was the oxygen vacancies.

  20. Possible H2/+/ ultraviolet spectrum of Jupiter

    NASA Technical Reports Server (NTRS)

    Wu, F.-M.; Beckel, C. L.; Shafi, M.; Hyder, C. L.

    1974-01-01

    An ultraviolet spectral probe for a hydrogen-rich planetary atmosphere, such as that of Jupiter, is suggested, utilizing discrete lines in the H2(+) 2p pi u - /s sigma g electronic transition. For the Jovian atmosphere, the dominant mechanism for exciting H2(+) to its 2p pi u state appears to be photoexcitation, principally through absorption of the solar Lyman-alpha line. The critical role of corrections to the Born-Oppenheimer approximation in the use of an H2(+) probe is discussed.

  1. The influence of oxygen partial pressure on material properties of Eu3+-doped Y2O2S thin film deposited by Pulsed Laser Deposition

    NASA Astrophysics Data System (ADS)

    Ali, A. G.; Dejene, B. F.; Swart, H. C.

    2016-01-01

    Eu3+-doping has been of interest to improve the luminescent characteristics of thin-film phosphors. Y2O2S:Eu3+ films have been grown on Si (100) substrates by using a Pulsed Laser Deposition technique. The thin films grown under different oxygen deposition pressure conditions have been characterized using structural and luminescent measurements. The X-ray diffraction patterns showed mixed phases of cubic and hexagonal crystal structures. As the oxygen partial pressure increased, the crystallinity of the films improved. Further increase of the O2 pressure to 140 mtorr reduced the crystallinity of the film. Similarly, both scanning electron microscopy and Atomic Force Microscopy confirmed that an increase in O2 pressure affected the morphology of the films. The average band gap of the films calculated from diffuse reflectance spectra using the Kubelka-Munk function was about 4.75 eV. The photoluminescence measurements indicated red emission of Y2O2S:Eu3+ thin films with the most intense peak appearing at 619 nm, which is assigned to the 5D0-7F2 transition of Eu3+. This most intense peak was totally quenched at higher O2 pressures. This phosphor may be a promising material for applications in the flat panel displays.

  2. Maps of [HDO]/[H2O] near Mars’ Aphelion

    NASA Astrophysics Data System (ADS)

    Novak, Robert E.; Mumma, M. J.; Villanueva, G. L.

    2013-10-01

    We report maps of HDO and H2O taken at three seasonal points before and near Mars’ aphelion (Ls = 71°). These observations were taken at Ls = 357° (15 January 2006), Ls = 50° (26 March 2008) and Ls = 72° (2/3 April 2010) using CSHELL at the NASA Infrared Telescope Facility. For these three seasonal dates, the entrance slit of the spectrometer was positioned N-S on Mars centered at the sub-Earth point; on 3 April 2010, the slit was positioned E-W. Data were extracted at 0.6 arc-second intervals from the spectral-spatial images. Individual spectral lines were measured near 3.67 μm (HDO) and 3.29 μm (H2O). The column densities were obtained by comparing the observed lines to those of a multi-layered, radiative transfer model. The model includes solar Fraunhofer lines, two-way transmission through Mars’ atmosphere, thermal emission from Mars’ surface and atmosphere, and a one-way transmission through the Earth’s atmosphere. Latitudinal maps of HDO, H2O, and their ratios were then constructed. The [HDO]/[H2O] ratios have been found to be larger than those on Earth and they vary with both latitude and season. For the Ls = 357° and 50° observations, the ratio peaks near the sub-solar latitude ([HDO]/[H2O] ~ 6.9 VSMOW) and decreases towards both the North and South polar-regions. At Ls = 72°, column densities of both HDO and H2O and their ratios increase from the Southern hemisphere to the North polar-region. Observations from 3 April 2013 show diurnal variations of both the column densities and their ratio. Specific points on Mars’ surface were tracked for four hours. It is believed that this variation is caused by the vaporization of ground frost and water ice clouds that are formed during the night and disappear during daytime. Our results for H2O column densities will be compared to TES results. The results for HDO and the [HDO]/[H2O] ratios will be compared to model results.This work was partially funded by grants from NASA's Planetary Astronomy (344-32-51-96) and Astrobiology Programs (344-53-51), and the NSF-RUI Program (AST-805540). We thank the administration and staff of the NASA IRTF for awarding observing times and coordinating our observations.

  3. In-Situ Partial Pressure Measurements and Visual Observation during Crystal Growth of ZnSe by Seeded Physical Vapor Transport

    NASA Technical Reports Server (NTRS)

    Su, Ching-Hua; Feth, Shari; Lehoczky, Sandor L.

    1999-01-01

    An in-situ monitoring furnace was constructed with side windows to perform partial pressure measurements by optical absorption and visual observation of the growing crystal. A fused silica -rowth ampoule with a 4.5 cm long square tube between the source and the seed was prepared for the optical absorption measurements. A ZnSe crystal was grown by the seeded physical vapor transport (PVT) technique in the horizontal configuration. The growth temperature was 1120 C and the furnace translation rate was 3nmVday. Partial pressures of Se2, P(sub Se2), at three locations along the length of the growth ampoule were measured at 90 min intervals during the growth process. The measured P (sub Se2) were in the range of 2.0 to 6.5 x 10(exp -3) atm. The P(sub Se2) results indicated that the partial pressure profile was inconsistent with the results of the one-dimensional diffusion mass transport model and that the source composition shifted toward Se-rich during the run, i.e. the grown crystal was more Zn-rich than the source. The visual observation showed that the seed crystal first etched back, with greater thermal etching occurring along the edges of the seed crystal. Once the growth started, the crystal crew in a predominately contactless mode and facets were evident during growth. The crystal did not grow symmetrically which is believed to be due to the unintentional asymmetry of the radial thermal profile in the furnace.

  4. Piperidine hydrogenolysis on a commercial hydrocracking catalyst. II. The effects of initial piperidine concentration, temperature, catalyst presulfidation, and hydrogen partial pressure on catalyst activity, deactivation, and coke formation

    SciTech Connect

    Hadjiloizou, G.C.; Butt, J.B.; Dranoff, J.S. )

    1992-05-01

    The formation of coke in the piperidine hydrogenolysis reaction over a fresh sulfided hydrocracking catalyst was examined at temperatures ranging from 281 to 321 C, hydrogen partial pressures of 11.2 to 15.9 atm (1.1 to 1.6 MPa), and initial concentrations of piperidine of 3.94 [times] 10[sup [minus]3] to 11.84 [times] 10[sup [minus]3]g mol/liter using elemental analysis, [sup 13]C NMR spectroscopy, and ESCA. The results indicated that most of the coke present on the catalyst after 17 h on stream was deposited in the initial 90 min of the reaction. Coke formation and hence catalyst deactivation were found to increase with both reaction temperature and initial concentration of piperidine. Reducing the catalyst instead of sulfiding it had no effect on the final coke content. Nitrogen was found to be present on the catalyst surface after reaction indicating that nitrogen-containing compound were participating in the formation of coke. The H/C ratio of the coke decreased very slowly with reaction time and was invariant to changes in temperature, initial concentration of piperidine, or catlayst pretreatment method. Comparing the activity of reduced versus sulfided fresh catalysts in the hydrogenolysis of piperidine, it was found that under the present conditions, catalyst presulfidation increased the activity of the metallic catalyst function and decreased the rate of catalyst deactivation. Furthermore, decreasing the partial pressure of hydrogen resulted in an activity decrease of the metallic catalyst function and had a negative effect on the overall catalyst activity maintenance. The intrinsic activity of the acidic catalyst function was not affected by the change in hydrogen partial pressure.

  5. Long-lasting effect of prolonged hypoxemia after birth on the immediate ventilatory response to changes in arterial partial pressure of oxygen in young lambs.

    PubMed

    Sladek, M; Parker, R A; Gr?gaard, J B; Sundell, H W

    1993-12-01

    The effect of prolonged hypoxemia (H) after birth on the evolution of the ventilatory response to changes in arterial partial pressure of O2 was determined in unanesthetized, awake lambs. H was induced for 12 d after birth in seven lambs through exposure to 0.10 fraction of inspired O2 (FiO2). Five control (C) lambs were kept in 0.21 FiO2. The ventilatory response (percent increase from baseline) to acute hypoxia was tested with 0.14 FiO2 and 0.10 FiO2. The tonic activity of the peripheral chemoreceptors was assessed by the transient pure oxygen inhalation test (Dejours' test). The occlusion technique was used to measure the baseline neuromuscular drive of breathing. A markedly decreased early ventilatory response to acute hypoxia persisted in the H lambs for at least 5 wk after termination of H compared with the C group. The second phase of the response was significantly lower only at 12 d (the end of H) and was thereafter comparable to that in the C lambs. The ventilatory response to hyperoxia was significantly lower in the H lambs only at the end of hypoxemia at 12 d and rapidly normalized after return to normoxia. H did not significantly affect resting neuromuscular drive. These results show that postnatal maturation of the ventilatory response to changes in arterial partial pressure of O2 can be delayed by prolonged postnatal hypoxemia. The effect on the response to hyperoxia is transient, whereas the response to acute hypoxia is affected for an extended time. This study illustrates the importance of an adequate postnatal arterial partial pressure of O2 for the development of the ventilatory response to acute hypoxia. PMID:8108201

  6. TES/Aura L2 Water Vapor (H2O) Limb (TL2H2OL)

    Atmospheric Science Data Center

    2015-02-06

    TES/Aura L2 Water Vapor (H2O) Limb (TL2H2OL) News:  TES News ... Level:  L2 Platform:  TES/Aura L2 Water Vapor Spatial Coverage:  27 x 23 km Limb ... Access: OPeNDAP Parameters:  H2O Water Volume Mixing Radio Precision Vertical Resolution Order ...

  7. Interstellar clouds containing optically thin H2

    NASA Technical Reports Server (NTRS)

    Jura, M.

    1975-01-01

    The theory of Black and Delgarno that the relative populations of the excited rotational levels of H2 can be understood in terms of cascading following absorption in the Lyman and Werner bands is employed to infer the gas densities and radiation fields within diffuse interstellar clouds containing H2 that is optically thin in those bands. The procedure is described for computing the populations of the different rotation levels, the relative distribution among the different rotation levels of newly formed H2 is determined on the basis of five simplified models, and the rate of H2 formation is estimated. The results are applied to delta Ori, two components of iota Ori, the second components of rho Leo and zeta Ori, tau Sco, gamma Vel, and zeta Pup. The inferred parameters are summarized for each cloud.

  8. The composition of Saturn's atmosphere at northern temperate latitudes from Voyager IRIS spectra - NH3, PH3, C2H2, C2H6, CH3D, CH4, and the Saturnian D/H isotopic ratio

    NASA Technical Reports Server (NTRS)

    Courtin, R.; Gautier, D.; Marten, A.; Bezard, B.; Hanel, R.

    1984-01-01

    The vertical distributions and mixing ratios of minor constituents in the northern hemisphere of Saturn are investigated. Results are obtained for NH3, PH3, C2H2, C2H6, CH3D, and CH4; the D/H ratio is obtained from the CH4 and CH3D abundances. The NH3 mixing ratio in the upper atmosphere is found to be compatible with the saturated partial pressure. The inferred PH3/H2 ratio of 1.4 + or - 0.8 x 10 to the -6th is higher than the value derived from the solar P/H ratio. The stratospheric C2H2/