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1

Effect of partial pressure ratio H2S\\/CO2 on mechanical properties of 3Cr oil tube steel  

Microsoft Academic Search

3. com A6sfrtlcl-With the exploitation of high sour and deep oil weD in China, the corrosion medium containing CO2, H2S and Cl­ threaten to the safety of oil equipment and tube steel severely. In this article, solution immersion environments containing H2S\\/C02 were simulated in a high temperature and high pressure autoclave respectively. The effect of partial pressure ratio H2S1C02 on

Qian Jinsen; Chen Changfeng; Zheng Shuqi; Weng Yongji

2011-01-01

2

The electrochemical behaviour of 316L austenitic stainless steel in Cl- containing environment under different H2S partial pressures  

NASA Astrophysics Data System (ADS)

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.

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

2014-01-01

3

Laser induced fluorescence of formaldehyde and Raman measurements of major species during partial catalytic oxidation of methane with large H 2O and CO 2 dilution at pressures up to 10 bar  

Microsoft Academic Search

The catalytic partial oxidation (CPO) of CH4\\/O2 mixtures diluted with large amounts of H2O and CO2 (up to 43% and 21%vol., respectively) was investigated experimentally and numerically in the pressure range 4bar?p?10bar. Experiments were carried out in an optically accessible channel-flow catalytic reactor coated with Rh\\/ZrO2, and included planar laser induced fluorescence (LIF) of formaldehyde for the assessment of homogeneous

Adrian Schneider; John Mantzaras; Rolf Bombach; Sabine Schenker; Niclas Tylli; Peter Jansohn

2007-01-01

4

Effect of H2 Pressure on Pulsed H2 + F2 Laser, Experiment and Theory.  

National Technical Information Service (NTIS)

Stimulated emission predictions and measurements for an H2 + F2 laser are compared for H2 pressures from threshold to stoichiometric, a range of several orders of magnitude. Slowly flowing, helium-diluted, 50-Torr mixtures are initiated photolytically. Tw...

G. Emanuel J. S. Whittier R. L. Kerber S. N. Suchard

1973-01-01

5

Melting of albite and dehydration of brucite in H 2 O–NaCl fluids to 9 kbars and 700–900°C: implications for partial melting and water activities during high pressure metamorphism  

Microsoft Academic Search

The melting reaction: albite(solid)+ H2O(fluid) =albite-H2O(melt) has been determined in the presence of H2O–NaCl fluids at 5 and 9.2?kbar, and results compared with those obtained in presence of H2O–CO2 fluids. To a good approximation, albite melts congruently at 9?kbar, indicating that the melting temperature at constant\\u000a pressure is principally determined by water activity. At 5?kbar, the temperature (T)- mole fraction

Kirill I. Shmulovich; Colin M. Graham

1996-01-01

6

Oxygen partial pressure sensor  

DOEpatents

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.

Dees, Dennis W. (Downers Grove, IL)

1994-01-01

7

Oxygen partial pressure sensor  

DOEpatents

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.

Dees, D.W.

1994-09-06

8

High Pressure Study of NH3 - H2 System  

NASA Astrophysics Data System (ADS)

We have conducted exploratory studies in NH_3-H2 system up to 10 GPa at 300K with 5-50 mol % of NH_3. Raman measurements and visual observations revealed the tendency for phase separation of individual components. At low pressures below 1.2 GPa the equilibrium of the NH_3- and H_2- rich fluids was observed. Mutual solubilities of species are low and estimated from the intensities of their stretching vibrations. The frequency of H-H vibron in fluid NH_3- rich phase is significantly lower in comparison to that in pure H_2. In H_2- rich fluid phase and at low pressures, H-H vibrons and rotons are much sharper that those of pure H2 possibly due to the collisonal effects of NH3 molecules. Upon pressure increase the system undergoes a sequence of the phase transions which closely folows that of individual components. Spectra of the solid phases found in the studied pressure range could be identified as those of pure ammonia and hydrogen, i.e. clathrate formation has not been observed. *Supported by NSF DMR-9304028 and NASA NAGW-1722.

Lazor, P.; Hemley, R. J.; Mao, H. K.

1996-03-01

9

H2SO4 vapor pressure of sulfuric acid and ammonium sulfate solutions  

NASA Astrophysics Data System (ADS)

Few measurements of H2SO4 vapor pressure have been made for sulfuric acid in the temperature and concentration ranges of atmospheric interest because of the very low pressures involved (below 10-4 Pa, or 10-6 torr); no such measurements appear to have been made for sulfuric acid solutions neutralized with ammonia. This work presents measurements of H2SO4 vapor pressure for aqueous sulfuric acid solutions between 55 and 77 wt% H2SO4 (corresponding to about 5-25% relative humidity), ammonium sulfate solids at low humidities, and partially neutralized sulfate solutions with [NH4+]: [SO4=] ratios between 0.13 and 1.0. The vapor pressure data collected over sulfuric acid solutions generally agree with the predictions of Ayers, et al. [1980], although positive deviation was observed for the more dilute solutions. The good agreement between this measurement and previous efforts by absolute techniques suggests that the evaporative coefficient for the H2SO4-H2O system is near unity. H2SO4 vapor pressures over solid ammonium sulfate were measured between 27°C and 60°C; the data were fitted to In p = A/T + B, with A = -5928 and B = -3.77. The H2SO4 vapor pressures of mixed H2SO4-H2O-(NH4)2SO4 solutions dropped significantly as the [NH4+]:[SO4=] ratio exceeded 0.5. The results suggest that ammonia could very effectively stabilize molecular clusters of sulfuric acid and water in the atmosphere against evaporation, leading to rates of new particle formation higher than those predicted by binary H2SO4-H2O theory.

Marti, James J.; Jefferson, Anne; Cai, Xiao Ping; Richert, Chad; McMurry, Peter H.; Eisele, Fred

1997-02-01

10

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

Microsoft Academic Search

Vapor pressures of H2O, HNO3, HCl and HBr over supercooled aqueous mixtures with sulfuric acid have been calculated using an activity coefficient model, for 185 K less than T less than 235 K, 0 less than wt% (H2SO4) + wt% (HNO3) less than 70, and assuming HCl and HBr to be minor constituents. Predicted vapor pressures agree well with most

Beiping Luo; Kenneth S. Carslaw; Thomas Peter; Simon L. Clegg

1995-01-01

11

Stability of H2O ice polymorphs at high pressure  

NASA Astrophysics Data System (ADS)

We employ the generalized gradient approximation within the density functional theory as implemented in the ABINIT package [1] to investigate the high-pressure behavior of H2O ice. We find that ice VIII is dynamically stable to at least 100 GPa. From static (0K) calculations we show that ice X is more stable than ice VIII above 80- 100 GPa. Ice X is dynamically stable in the 120-400 GPa pressure range. Below 120 GPa it is characterized by one unstable flat phonon band, which leads to the amorphization of the structure. In its dynamical stability field, ice X shows a softening of the lowest phonon mode in M (=1/2 1/2 0) under compression, which becomes unstable above 400 GPa. The instability corresponds to the bending of the O-H-O angle. The structure that results after the lock-in of the unstable mode agrees well with the Pbcm orthorhombic structure obtained from molecular-dynamics calculations [2]. We propose a high-pressure low-temperature phase-transition sequence as ice VIII - amorphous - ice X - ice Pbcm. [1] Gonze et al., Comp. Mat. Sci. 25, 478 (2002); Z. Kristall. 220, 558 (2005). [2] Benoit et al., Phys. Rev. Lett., 76, 2934, 1996.

Caracas, R.

2007-12-01

12

Maximizing H 2 production by combined partial oxidation of CH 4 and water gas shift reaction  

Microsoft Academic Search

A dense ceramic membrane reactor has been constructed to exclusively transport oxygen for the partial oxidation of methane (CH4) to syngas (a mixture of CO and H2) at temperatures of 850–900°C. H2 production is enhanced in a second catalytic reactor through the water gas shift reaction, in which the CO reacts with steam that is injected into the reactor at

P. S. Maiya; T. J. Anderson; R. L. Mieville; J. T. Dusek; J. J. Picciolo; U. Balachandran

2000-01-01

13

Atmospheric Pressure Atomic Layer Epitaxy of ZnSe Using Zn and H2Se  

NASA Astrophysics Data System (ADS)

Atmospheric pressure ALE (atomic layer epitaxy) has been achieved to grow ZnSe for the first time using Zn and H2Se. It is confirmed that the growth rate is controlled by the self-limiting process itself. The ALE growth of ZnSe is observed in the substrate temperature range of 350-500°C and in the input partial pressure ranges of 5× 10-6--1× 10-4 atm for Zn and 4× 10-5--2× 10-3 atm for H2Se. Lattice parameters perpendicular to the surface plane and the values of FWHM for the diffraction pattern were obtained by the X-ray double-crystal diffraction measurement.

Koukitu, Akinori; Saegusa, Akihiko; Kitho, Masanori; Ikeda, Hitoshi; Seki, Hisashi

1990-12-01

14

The solubility of gold in H 2 O-H 2 S vapour at elevated temperature and pressure  

NASA Astrophysics Data System (ADS)

This experimental study sheds light on the complexation of gold in reduced sulphur-bearing vapour, specifically, in H 2O-H 2S gas mixtures. The solubility of gold was determined in experiments at temperatures of 300, 350 and 365 °C and reached 2.2, 6.6 and 6.3 ?g/kg, respectively. The density of the vapour varied from 0.02 to 0.22 g/cm 3, the mole fraction of H 2S varied from 0.03 to 0.96, and the pressure in the cell reached 263 bar. Statistically significant correlations of the amount of gold dissolved in the fluid with the fugacity of H 2O and H 2S permit the experimental data to be fitted to a solvation/hydration model. According to this model, the solubility of gold in H 2O-H 2S gas mixtures is controlled by the formation of sulphide or bisulphide species solvated by H 2S or H 2O molecules. Formation of gold sulphide species is favoured statistically over gold bisulphide species and thus the gold is interpreted to dissolve according to reactions of the form: Au(s)+(n+1)HS(g)=AuS·(HS)n(g)+H(g) Au(s)+HS(g)+mHO(g)=AuS·(HO)m(g)+H(g) Equilibrium constants for Reaction (A1) and the corresponding solvation numbers ( K A1 and n) were evaluated from the study of Zezin et al. (2007). The equilibrium constants as well as the hydration numbers for Reaction (A2) ( K A2 and m) were adjusted simultaneously by a custom-designed optimization algorithm and were tested statistically. The resulting values of log K A2 and m are -15.3 and 2.3 at 300 and 350 °C and -15.1 and 2.2 at 365 °C, respectively. Using the calculated stoichiometry and stability of Reactions (A1) and (A2), it is now possible to quantitatively evaluate the contribution of reduced sulphur species to the transport of gold in aqueous vapour at temperatures up to 365 °C. This information will find application in modelling gold ore-forming processes in vapour-bearing magmatic hydrothermal systems, notably those of epithermal environments.

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

2011-09-01

15

Brillouin scattering of H2O ice to megabar pressures  

Microsoft Academic Search

The sound velocity in polycrystalline ice was measured as a function of pressure at room temperature to 100 GPa, through the phase field of ice VII and crossing the ice X transition, by Brillouin scattering in order to examine the elasticity, compression mechanism, and structural transitions in this pressure range. In particular, we focused on previously proposed phase transitions below

Muhtar Ahart; Maddury Somayazulu; Stephen A. Gramsch; Reinhard Boehler; Ho-Kwang Mao; Russell J. Hemley

2011-01-01

16

Pressure-induced transformation plasticity of H(2)O ice.  

PubMed

Transformation plasticity is a deformation mechanism which occurs during phase transformation of an externally stressed material. Pressure-induced transformation plasticity of ice could be relevant to the geology of the moons of the outer solar system, and has long been postulated to occur in olivine in the earth's interior. In the present work, ice specimens were subjected to isostatic pressure cycling between 0 and 300 MPa to induce reversible polymorphic transformation between ice I and II at 230 K. When a small uniaxial compressive stress was applied during cycling, the specimens exhibited a compressive strain (as large as 18.5% after a single cycle) proportional to the applied stress, in agreement with observations and theory for transformation plasticity of metals induced by polymorphic thermal cycling. PMID:11177908

Dunand, D C; Schuh, C; Goldsby, D L

2001-01-22

17

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

SciTech Connect

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.

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

2010-07-29

18

H2SO4 vapor pressure of sulfuric acid and ammonium sulfate solutions  

Microsoft Academic Search

Few measurements of H2SO4 vapor pressure have been made for sulfuric acid in the temperature and concentration ranges of atmospheric interest because of the very low pressures involved (below 10-4Pa, or 10-6torr); no such measurements appear to have been made for sulfuric acid solutions neutralized with ammonia. This work presents measurements of H2SO4 vapor pressure for aqueous sulfuric acid solutions

James J. Marti; Anne Jefferson; Xiao Ping Cai; Chad Richert; Peter H. McMurry; Fred Eisele

1997-01-01

19

Fuel processor integrated H 2S catalytic partial oxidation technology for sulfur removal in fuel cell power plants  

Microsoft Academic Search

H2S catalytic partial oxidation technology with an activated carbon catalyst was found to be a promising method for the removal of hydrogen sulfide from fuel cell hydrocarbon feedstocks. Three different fuel cell feedstocks were considered for analysis: sour natural gas, sour effluent from a liquid middle distillate fuel processor and a Texaco O2-blown coal-derived synthesis gas. The H2S catalytic partial

Todd H Gardner; David A Berry; K David Lyons; Stephen K Beer; Adam D Freed

2002-01-01

20

Modelling of OH production in cold atmospheric-pressure He-H2O plasma jets  

NASA Astrophysics Data System (ADS)

Results of the modelling of OH production in the plasma bullet mode of cold atmospheric-pressure He-H2O plasma jets are presented. It is shown that the dominant source of OH molecules is related to the Penning and charge transfer reactions of H2O molecules with excited and charged helium species produced by guided streamers (plasma bullets), in contrast to the case of He-H2O glow discharges where OH production is mainly due to the dissociation of H2O molecules by electron impact.

Naidis, G. V.

2013-06-01

21

Temperature induced immiscibility in the NaCl–H 2O system at high pressure  

Microsoft Academic Search

High-pressure polymorphs of H2O are a major component in many outer planets, extra solar bodies, and icy satellites. This study sought to examine the influence of ionic impurities on the phase stability, thermal expansion, and melting curve of ice VII. Powder diffraction patterns of ice VII formed from pure H2O and 5wt.% NaCl aqueous solutions were taken at room temperature

Mark R. Frank; Henry P. Scott; Steven J. Maglio; Vitali B. Prakapenka; Guoyin Shen

2008-01-01

22

Temperature induced immiscibility in the NaCl H2O system at high pressure  

Microsoft Academic Search

High-pressure polymorphs of H2O are a major component in many outer planets, extra solar bodies, and icy satellites. This study sought to examine the influence of ionic impurities on the phase stability, thermal expansion, and melting curve of ice VII. Powder diffraction patterns of ice VII formed from pure H2O and 5 wt.% NaCl aqueous solutions were taken at room

Mark R. Frank; Henry P. Scott; Steven J. Maglio; Vitali B. Prakapenka; Guoyin Shen

2008-01-01

23

Melting behavior of H2O at high pressures and temperatures  

Microsoft Academic Search

Water plays an important role in the physics and chemistry of planetary interiors. In situ high pressure-temperature Raman spectroscopy and synchrotron x-ray diffraction have been used to examine the phase diagram of H2O. A discontinuous change in the melting curve of H2O is observed at approximately 35 GPa and 1040 K, indicating a triple point on the melting line. The

Jung-Fu Lin; Eugene Gregoryanz; Viktor V. Struzhkin; Maddury Somayazulu; Ho-kwang Mao; Russell J. Hemley

2005-01-01

24

High-pressure phase transitions of solid H2S probed by Fouriertransform infrared spectroscopy  

Microsoft Academic Search

Infrared-absorption spectra of solid H2S have been measured at high pressures up to 50 GPa and room temperature. The symmetric stretching overtone vibration 2nu1 shows a redshift in frequency with increasing pressure, and changes into two components at about 11 GPa for the II-IV phase transition. The pressure dependence of the observed 2nu1, nu2+nu3 (bending plus asymmetric-stretching combination bands), and

H. Shimizu; T. Ushida; S. Sasaki; M. Sakashita; H. Yamawaki; K. Aoki

1997-01-01

25

Metallization and superconductivity of BeH2 under high pressure.  

PubMed

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

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

2014-03-28

26

High pressure chemistry in the H2-SiH4 system  

PubMed Central

Understanding the behavior of hydrogen-rich systems at extreme conditions has significance to both condensed matter physics, where it may provide insight into the metallization and superconductivity of element one, and also to applied research areas, where it can provide guidance for designing improved hydrogen storage materials for transportation applications. Here we report the high-pressure study of the SiH4-H2 binary system up to 6.5 GPa at 300 K in a diamond anvil cell. Raman measurements indicate significant intermolecular interactions between H2 and SiH4. We found that the H2 vibron frequency is softened by the presence of SiH4 by as much as 40 cm?1 for the fluid with 50 mol% H2 compared with pure H2 fluid at the same pressures. In contrast, the Si-H stretching modes of SiH4 shift to higher frequency in the mixed fluid compared with pure SiH4. Pressure-induced solidification of the H2-SiH4 fluid shows a binary eutectic point at 72(±2) mol% H2 and 6.1(±0.1) GPa, above which the fluid crystallizes into a mixture of two nearly end-member solids. Neither solid has a pure end-member composition, with the silane-rich solid containing 0.5–1.5 mol% H2 and the hydrogen-rich solid containing 0.5–1 mol% SiH4. These two crystalline phases can be regarded as doped hydrogen-dominant compounds. We were able to superpressurize the sample by 0.2–0.4 GPa above the eutectic before complete crystallization, indicating extended metastability.

Wang, Shibing; Mao, Ho-kwang; Chen, Xiao-Jia; Mao, Wendy L.

2009-01-01

27

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

NASA Astrophysics Data System (ADS)

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

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

2011-10-01

28

Pressure and Temperature Dependence of Dielectric Properties of Squaric Acid H2C4O4  

Microsoft Academic Search

The pressure (0-10 kbar) and temperature (10-130°C) dependence of the dielectric properties of squaric acid (H2C4O4) were investigated. From the large isotope effect on the transition temperature of Tnd\\/Tn{=}1.38 (the superscript d stands for deuteration) and the large decrease of Tn with pressure of dTn\\/dp{=}-13°C\\/kbar, the phase transition mechanism for H2C4O4 is discussed microscopically using the tunneling model of the

Naohiko Yasuda; Kazunori Sumi; Hiroyasu Shimizu; Sanji Fujimoto; Yoshio Inuishi

1979-01-01

29

Vibrational dynamics, intermolecular interactions, and compound formation in GeH4-H2 under pressure  

NASA Astrophysics Data System (ADS)

Optical microscopy, spectroscopic and x-ray diffraction studies at high-pressure are used to investigate intermolecular interactions in binary mixtures of germane (GeH4)+hydrogen (H2). The measurements reveal the formation of a new molecular compound, with the approximate stoichiometry GeH4(H2)2, when the constituents are compressed above 7.5 GPa. Raman and infrared spectroscopic measurements show multiple H2 vibrons substantially softened from bulk solid hydrogen. With increasing pressure, the frequencies of several Raman and infrared H2 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 GeH4 molecules occupying fcc sites and H2 molecules likely distributed between Oh and Td sites. Above ca. 17 GPa, GeH4 molecules in the compound become unstable with respect to decomposition products (Ge+H2), however, the compound can be preserved metastably to ca. 27 GPa for time-scales of the order of several hours.

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

2010-10-01

30

Vibrational dynamics, intermolecular interactions, and compound formation in GeH4-H2 under pressure.  

PubMed

Optical microscopy, spectroscopic and x-ray diffraction studies at high-pressure are used to investigate intermolecular interactions in binary mixtures of germane (GeH(4)) + hydrogen (H(2)). The measurements reveal the formation of a new molecular compound, with the approximate stoichiometry GeH(4)(H(2))(2), when the constituents are compressed above 7.5 GPa. Raman and infrared spectroscopic measurements show multiple H(2) vibrons substantially softened from bulk solid hydrogen. With increasing pressure, the frequencies of several Raman and infrared H(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(4) molecules occupying fcc sites and H(2) molecules likely distributed between O(h) and T(d) sites. Above ca. 17 GPa, GeH(4) molecules in the compound become unstable with respect to decomposition products (Ge + H(2)), however, the compound can be preserved metastably to ca. 27 GPa for time-scales of the order of several hours. PMID:21033810

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

2010-10-28

31

Calculations of the low temperature pressure broadening of HCO + rotational spectral lines by H2  

Microsoft Academic Search

Calculations on the pressure broadening by H2 of HCO+ rotational spectral lines have been performed in the temperature range 11–300 K. Recent low temperature measurements of the pressure broadening of the J=3–2 line at 11–30 K are reproduced to within 10–20% by the results of a capture theory. The results of Anderson theory in this temperature range, on the other

Qing Liao; Eric Herbst

1996-01-01

32

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

NASA Astrophysics Data System (ADS)

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.

Prakapenka, V.

2013-12-01

33

Histone H2A.Z Regulates Transcription and Is Partially Redundant with Nucleosome Remodeling Complexes  

Microsoft Academic Search

Nucleosomes impose a block to transcription that can be overcome in vivo by remodeling complexes such as SNF\\/SWI and histone modification complexes such as SAGA. Mutations in the major core histones relieve transcriptional repression and bypass the requirement for SNF\\/SWI and SAGA. We have found that the variant histone H2A.Z regulates gene transcription, and deletion of the gene encoding H2A.Z

Maria Soledad Santisteban; Tatyana Kalashnikova; M. Mitchell Smith

2000-01-01

34

A System for Incubations at High Gas Partial Pressure  

PubMed Central

High-pressure is a key feature of deep subsurface environments. High partial pressure of dissolved gasses plays an important role in microbial metabolism, because thermodynamic feasibility of many reactions depends on the concentration of reactants. For gases, this is controlled by their partial pressure, which can exceed 1?MPa at in situ conditions. Therefore, high hydrostatic pressure alone is not sufficient to recreate true deep subsurface in situ conditions, but the partial pressure of dissolved gasses has to be controlled as well. We developed an incubation system that allows for incubations at hydrostatic pressure up to 60?MPa, temperatures up to 120°C, and at high gas partial pressure. The composition and partial pressure of gasses can be manipulated during the experiment. To keep costs low, the system is mainly made from off-the-shelf components with only very few custom-made parts. A flexible and inert PVDF (polyvinylidene fluoride) incubator sleeve, which is almost impermeable for gases, holds the sample and separates it from the pressure fluid. The flexibility of the incubator sleeve allows for sub-sampling of the medium without loss of pressure. Experiments can be run in both static and flow-through mode. The incubation system described here is usable for versatile purposes, not only the incubation of microorganisms and determination of growth rates, but also for chemical degradation or extraction experiments under high gas saturation, e.g., fluid–gas–rock-interactions in relation to carbon dioxide sequestration. As an application of the system we extracted organic compounds from sub-bituminous coal using H2O as well as a H2O–CO2 mixture at elevated temperature (90°C) and pressure (5?MPa). Subsamples were taken at different time points during the incubation and analyzed by ion chromatography. Furthermore we demonstrated the applicability of the system for studies of microbial activity, using samples from the Isis mud volcano. We could detect an increase in sulfate reduction rate upon the addition of methane to the sample.

Sauer, Patrick; Glombitza, Clemens; Kallmeyer, Jens

2012-01-01

35

Superconductivity in GeH4(H2)2 above 220 GPa high-pressure  

NASA Astrophysics Data System (ADS)

Hydrogen-rich materials have fascinating physical and chemical properties such as various structures and superconductivity under high-pressure. They are believed as an alternative approach to realize the hydrogen superconducting. In the previous report ([17] Zhong et al., J. Phys. Chem. C 116 (2012) 5225), we had presented structural phase-transitions and bonding interaction variations induced by pressure, and predicted a stable and superconductive phase above 220 GPa, P21/c. In this study, we focus on the change of superconducting transition temperature induced by pressure above 220 GPa for GeH4(H2)2. The variations of bond lengths, electronic structures, phonon spectra, and electron-phonon interaction with the increases of pressure are investigated. We find that the superconducting transition temperature monotonously decreases with the increase of pressure from 230 to 350 GPa. The origin is mainly the stiff of phonon frequency induced by pressurization.

Zhong, Guohua; Zhang, Chao; Wu, Guangfen; Song, Jianjun; Liu, Zhuang; Yang, Chunlei

2013-02-01

36

Thin film oxygen partial pressure sensor  

NASA Technical Reports Server (NTRS)

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.

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

1972-01-01

37

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

USGS Publications Warehouse

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.

Chou, I. -M.; Blank, J. G.; Goncharov, A. F.; Mao, H. -K.; Hemley, R. J.

1998-01-01

38

New high-pressure phase of MgH2: An ab initio constant-pressure study  

NASA Astrophysics Data System (ADS)

The stability of magnesium hydride (MgH2) at high pressure is studied using a constant-pressure ab initio technique. Two phase transformations are successfully observed through the simulations. The rutile structure undergoes a phase transformation into a CaCl2-type phase. Further increase in pressure results into a first-order phase transition into an orthorhombic state within Pbcm symmetry. This phase can be considered as a distorted CaF2-type crystal and does not correspond to the previously proposed MgH2 phases. The transformation mechanism of the CaCl2-Pbcm phase change at the atomistic level is successfully characterized and it is found that the CaCl2-to-Pbcm phase change proceeds via an ideal CaF2-type intermediate phase. These phase transformations are also analyzed using total energy-volume calculations.

Durandurdu, Murat

2014-02-01

39

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

40

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

PubMed

By means of a newly constructed high pressure and low temperature optical apparatus we have measured the Raman spectra of H(2) and HD simple clathrate hydrates, synthesized in situ by the application of more than 2500 bar gas pressure on solid water. High resolution spectra of the molecular vibration have been measured at low temperature (about 20 K). In the case of HD this band is simpler than in the case of H(2), where the presence of the ortho- and para-species complicated the interpretation of the spectrum. We have determined frequency positions of the bands arising from multiple occupancy of the large cages of the sII clathrate, some of which are almost superimposed. The intensity of the bands gives information on the average and distribution of cage occupation, and of the ortho-para (o-p) ratio of H(2) molecules. Hydrogen o-p conversion rate is measured, for molecules in the small cages and in the large cages, and it is observed that these are different. A model considering both intrinsic and extrinsic conversion processes is applied to the measured data. The intrinsic conversion rate so derived is compared favorably to that measured for pure hydrogen in different situations. PMID:23126723

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

2012-10-28

41

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

NASA Astrophysics Data System (ADS)

By means of a newly constructed high pressure and low temperature optical apparatus we have measured the Raman spectra of H2 and HD simple clathrate hydrates, synthesized in situ by the application of more than 2500 bar gas pressure on solid water. High resolution spectra of the molecular vibration have been measured at low temperature (about 20 K). In the case of HD this band is simpler than in the case of H2, where the presence of the ortho- and para-species complicated the interpretation of the spectrum. We have determined frequency positions of the bands arising from multiple occupancy of the large cages of the sII clathrate, some of which are almost superimposed. The intensity of the bands gives information on the average and distribution of cage occupation, and of the ortho-para (o-p) ratio of H2 molecules. Hydrogen o-p conversion rate is measured, for molecules in the small cages and in the large cages, and it is observed that these are different. A model considering both intrinsic and extrinsic conversion processes is applied to the measured data. The intrinsic conversion rate so derived is compared favorably to that measured for pure hydrogen in different situations.

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

2012-10-01

42

Dynamical (in)stabilities of high-pressure H2O ices VII, VIII and X  

NASA Astrophysics Data System (ADS)

We study high-pressure solid H2O ice: the lattice dynamical properties of ice X and the transition path between molecular ices VII/VIII and the ionic ice X with first-principles calculations using density functional theory in the ABINIT implementation. Our work [PRL 101, 085502] defines the dynamical stability of ice X between about 120 GPa up to about 400 GPa. Based on phonon band dispersion we show that the phase transition sequence at low temperature and high pressures in ice is ice VIII - disordered ice X - ice X - ice Pbcm. The disordered ice X is due to a phonon collapse in the whole Brillouin zone at pressures below 120 GPa, phonon that corresponds to hydrogen atoms bouncing back and forth between every two oxygen neighbors in a double well potential. Post-ice X is orthorhombic Pbcm and appears due to a phonon instability in M at pressures higher than 400 GPa that distorts the bcc cubic sublattice of oxygen atoms into a hcp-like structure. Our calculations validate earlier theoretical predictions for a phase transition to a post-ice X structure in H2O [Benoit et al. PRL 76, 2934]. We also identify and discuss the (meta)stability of several intermediate phases between ice VIII and ice X.

Caracas, Razvan

2009-03-01

43

Partial-pressure measurement of atmospheric-pressure binary gas using two pressure gauges  

Microsoft Academic Search

We investigated a new method to measure the partial pressure of a binary gas system at near-atmospheric pressure conditions. The method utilizes two types of vacuum gauges, a capacitance manometer and a quartz friction pressure gauge. The partial pressure of the binary gas can be estimated by measuring the impedance change with a quartz friction pressure gauge, which depends on

Akira Kurokawa; Kenji Odaka; Shingo Ichimura

2004-01-01

44

CO2\\/CH4, CH4\\/H-2 and CO2\\/CH4\\/H-2 separations at high pressures using Mg2(dobdc)  

Microsoft Academic Search

High-pressure separations of binary and ternary mixtures of CO2, CH4, and H2 are relevant to carbon dioxide capture as well as hydrogen and natural gas purification. Metal–organic frameworks represent a class of porous materials that could be used to accomplish these separations, and Mg2(dobdc) (dobdc4? = 1,4-dioxido-2,5-benzenedicarboxylate), also sometimes referred to as Mg–MOF-74 or CPO-27–Mg, is an especially lightweight metal–organic

Z. R. Herm; R. Krishna; J. R. Long

2012-01-01

45

Confined H2O molecules as local probes of pressure-induced amorphisation in faujasite.  

PubMed

Confined H2O molecules act as local probes for depressurization phenomena during the pressure induced amorphisation of faujasite NaX at which the OH stretching frequency first decreases and then increases almost to its room pressure value upon further compression. Pair distribution function (PDF) analysis provides evidence that amorphisation corresponds to a collapse of the structure around hydrated sodium cations with strong distortion of the secondary building units (double six-membered rings, sodalite cages). Both the use of guest molecules as local probes in far- and mid-infrared spectroscopy, where we correlate intermolecular water H bonding vibrations and internal mode behaviour under confinement, and PDF analysis could be of great use to study the mechanical behaviour of other hydrated materials. PMID:24816994

Catafesta, Jadna; Alabarse, Frederico; Levelut, Claire; Isambert, Aude; Hébert, Philippe; Kohara, Shinji; Maurin, David; Bantignies, Jean-Louis; Cambon, Olivier; Creff, Gaëlle; Roy, Pascale; Brubach, Jean-Blaise; Hammouda, Tahar; Andrault, Denis; Haines, Julien

2014-06-28

46

Compressional, temporal, and compositional behavior of H2-O2 compound formed by high pressure x-ray irradiation  

NASA Astrophysics Data System (ADS)

X-ray irradiation was found to convert H2O at pressures above 2 GPa into a novel molecular H2-O2 compound. We used optical Raman spectroscopy to explore the behavior of x-ray irradiated H2O samples as a function of pressure, time, and composition. The compound was found to be stable over a period of two years, as long as high pressure conditions (>2 GPa) were maintained. The Raman shifts for the H2 and O2 vibrons behaved differently from pure H2 and O2 as pressure was increased on the compound up to 70 GPa, indicating that it remains a distinct, molecular compound. Based on spectra taken from different locations in a single sample, it appears that multiple forms of the H2-O2 compound exist. The structure and composition of the starting material plays an important role in compound formation, as we found that hydrogen-filled ice clathrate C2 (H2)H2O did not undergo the same dissociation as observed in ice VII upon x-ray irradiation until pressure was increased to above 10 GPa.

Kung, Andrew; Goncharov, Alexander F.; Zha, Chang Sheng; Eng, Peter; Mao, Wendy L.

2011-06-01

47

Compressional, temporal, and compositional behavior of H2-O2 compound formed by high pressure x-ray irradiation.  

PubMed

X-ray irradiation was found to convert H(2)O at pressures above 2 GPa into a novel molecular H(2)-O(2) compound. We used optical Raman spectroscopy to explore the behavior of x-ray irradiated H(2)O samples as a function of pressure, time, and composition. The compound was found to be stable over a period of two years, as long as high pressure conditions (>2 GPa) were maintained. The Raman shifts for the H(2) and O(2) vibrons behaved differently from pure H(2) and O(2) as pressure was increased on the compound up to 70 GPa, indicating that it remains a distinct, molecular compound. Based on spectra taken from different locations in a single sample, it appears that multiple forms of the H(2)-O(2) compound exist. The structure and composition of the starting material plays an important role in compound formation, as we found that hydrogen-filled ice clathrate C(2) (H(2))H(2)O did not undergo the same dissociation as observed in ice VII upon x-ray irradiation until pressure was increased to above 10 GPa. PMID:21702562

Kung, Andrew; Goncharov, Alexander F; Zha, Chang sheng; Eng, Peter; Mao, Wendy L

2011-06-21

48

Partial pressure analysis in space testing  

NASA Technical Reports Server (NTRS)

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.

Tilford, Charles R.

1994-01-01

49

CO 2\\/CH 4, CH 4\\/H 2 and CO 2\\/CH 4\\/H 2 separations at high pressures using Mg 2(dobdc)  

Microsoft Academic Search

High-pressure separations of binary and ternary mixtures of CO2, CH4, and H2 are relevant to carbon dioxide capture as well as hydrogen and natural gas purification. Metal–organic frameworks represent a class of porous materials that could be used to accomplish these separations, and Mg2(dobdc) (dobdc4?=1,4-dioxido-2,5-benzenedicarboxylate), also sometimes referred to as Mg–MOF-74 or CPO-27–Mg, is an especially lightweight metal–organic framework with

Zoey R. Herm; Rajamani Krishna; Jeffrey R. Long

50

Thin film devices used as oxygen partial pressure sensors  

NASA Technical Reports Server (NTRS)

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.

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

1970-01-01

51

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

NASA Astrophysics Data System (ADS)

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.

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

2013-12-01

52

Partial pressure measurements with an active spectrometer  

SciTech Connect

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.

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

1998-07-01

53

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

NASA Technical Reports Server (NTRS)

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.

Kojima, Jun; Nguyen, Quang-Viet

2003-01-01

54

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

NASA Astrophysics Data System (ADS)

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.

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

2014-07-01

55

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

NASA Technical Reports Server (NTRS)

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.

Brunning, J.; Stief, L. J.

1985-01-01

56

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

PubMed Central

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

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

2013-01-01

57

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

SciTech Connect

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

Xu, Tianfu; Senger, Rainer; Finstele, Stefan

2007-01-02

58

The effect of H2O and CO2 on the viscosity of sanidine liquid at high pressures  

Microsoft Academic Search

As part of our continuing research on the nature of silicate liquids at high pressures and to provide insight into the flow properties of granitic magmas at depth, we determined the viscosity (?) of liquid KAlSi3O8, and the viscosities of liquids in the systems KAlSi3O8-CO2 and KAlSi3O8-H2O, as a function of pressure and temperature using the falling-sphere method. At 1500°C,

Bradford S. White; Art Montana

1990-01-01

59

CH3OH in High-Pressure Phases of H2O: Implications for Ice-Rich Planets  

Microsoft Academic Search

A significant body of research exists on the structure, lattice parameters, and density of high-pressure ice polymorphs, namely Ice VI and Ice VII, as these ices may make up a considerable part of the interior of large icy satellites and select extra solar planets; though most research thus far has been constrained to the pure H2O system. Salty subsurface oceans

B. Aarestad; M. R. Frank; H. P. Scott; S. Maglio; V. Prakapenka

2007-01-01

60

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

NASA Technical Reports Server (NTRS)

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

Green, S.

1977-01-01

61

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)

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.

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

62

Experiments on the kinetics of partial melting of a leucogranite at 200 MPa H 2 O and 690–800°C: compositional variability of melts during the onset of H 2 O-saturated crustal anatexis  

Microsoft Academic Search

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 800°C, 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 740°C and any experimental time, and 800°C

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

2006-01-01

63

Gamma-radiolysis of hydrogen—Oxygen-mixtures— Part I. Influences of temperature, vessel wall, pressure and added gases (N 2, Ar, H 2) on the reactivity of H 2/O 2-mixtures  

NASA Astrophysics Data System (ADS)

The influence of pressure, temperature, of "matrix gases" N 2, Ar, H 2 and of the pretreatment of the vessel wall on the rate of reaction from 60Co ?-radiolysis of hydrogen—oxygen-mixtures, in the region of slow reaction, was investigated. The G(-H 2)-value† of H 2/O 2-mixtures (H 2:O 2 = 1:9-2:1) ranges from 1 to 14 with only slight dependence on pressure, temperature, H 2/O 2-ratio, and surface/volume ratio ( S/V). The temperature has little influence (35-210°C). Replacing most of the O 2 in the H 2:O 2 (1:9)-mixtures with N 2, Ar or excess H 2 at higher temperature, causes the G(-H 2)-values to increase. The influence of these matrix gases increases with increasing temperature (35-210°C) and decreasing S/V ratio (0.59 and 3.8 cm -1) of the reaction vessel; it depends also on the pretreatment of the wall surface. Varying the total pressure, the G(-H 2)-values show a temperature and gas mixture dependent maximum between about 20 and 200 mb. At higher temperature (210°C) we observed an influence of dose for 50 mb H 2/air-mixtures, whereas at 1 b and 35-90°C no influence of the dose on the rate of reaction of such mixtures was found. The activation by N 2, Ar, H 2 is discussed on the base of the H 2/O 2-reaction being a radical-chain reaction, built up by at least 38 coupled elementary steps (Ref (1) or see part 2). O 2 reacts with H 2, at increased rates of conversions (> 25%), in the expected stoichiometric ratio of 2:1. Oxygen may however also be converted in non-stiochiometric amounts under certain conditions.

Dautzenberg, Dirk

64

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

NASA Technical Reports Server (NTRS)

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.

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

1990-01-01

65

Pressure-induced amorphization of Na2Al2Si3O10 · 2H2O and KAlSi2O6 zeolites  

NASA Astrophysics Data System (ADS)

Pressure-induced amorphization has been observed in two zeolites, natrolite Na2Al2Si3O10 · 2H2O and leucite KAlSi2O6. Using Raman microprobe, amorphized samples were analysed in situ at high pressures at compression in methanol-ethanol medium in diamond anvil cell and also after release of pressure. Before amorphization, one crystal-to-crystal phase transition was observed in each zeolite. It was shown for Na2Al2Si3O10 · 2H2O that the transition from crystalline to amorphous phase is partially reversible for compression to the peak pressure in the range of 7-10 GPa and practically irreversible above 10 GPa. Surprising, the dehydrated crystal KAlSi2O6 exhibited very high quasi-stability, at compression up to 16 GPa for one day. Long time compression (for 15 days) led to almost full amorphization of KAlSi2O6.

Goryainov, Sergei

2005-02-01

66

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

NASA Astrophysics Data System (ADS)

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

Verreycken, T.; Bruggeman, P. J.

2014-02-01

67

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

NASA Technical Reports Server (NTRS)

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.

Gamache, Robert R.; Pollack, James B.

1995-01-01

68

Ab initio calculations of structure and thermodynamic properties of tetragonal-TiH2 under high temperatures and pressures  

NASA Astrophysics Data System (ADS)

The structural and thermodynamic properties of tetragonal-TiH2 under high temperatures and pressures are investigated by Ab initio calculations based on pseudo-potential plane-wave density functional theory method within using the generalized gradient approximation (GGA) and quasi-harmonic Debye model. Some ground state properties such as lattice constants, bulk modulus and elastic constants are good agreement with the available experimental results and other theoretical data. Through the quasiharmonic Debye model, in which the phononic effects are considered, the thermodynamic properties of tetragonal-TiH2 such as thermal expansion coefficient, Debye temperature, heat capacity and Grüneisen parameters dependence of temperature and pressure in the range of 0-1000 K and 0-10 GPa are also presented, respectively.

Liu, X. K.; Tang, B.; Zhang, Y.

2013-10-01

69

BRIEF COMMUNICATIONS: Investigation of a pulsed chemical H2-F2 laser at high pressures of the working mixture  

Microsoft Academic Search

A report is given of the experimental results and qualitative analysis of the operation of a chemical H2-F2 laser at pressures up to 5 atm in the mixture. The mixture was initiated optically with a flux of 1.5×1023 photons·cm-2·sec-1 using pulses of 0.7 musec duration. Reduction of the duration of the initiation pulses at a constant pump energy increased the

Yu A. Kolchin; V. B. Kolovskii; S. Ya Pshezhetskii; N. F. Chebotarev

1978-01-01

70

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

NASA Technical Reports Server (NTRS)

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

Green, Sheldon

1991-01-01

71

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

NASA Astrophysics Data System (ADS)

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 57±26 ppm (by wt.) at 5 GPa to 254±60 ppm at 8 GPa. Combining these with results of a parallel study at 10-13 GPa (Tenner et al., 2011, CMP) yields a linear relation applicable from 5 to 13 GPa for peridotite-saturated H2O storage capacity of olivine at 1450 °C, CH2Oolivine(ppm)=57.6(±16)×P(GPa)-169(±18). Storage capacity diminishes with increasing temperature, but is unaffected by variable total H2O concentration between 0.47 and 1.0 wt%. Both of these are as predicted for the condition in which the water activity in the melt is governed principally by the cryoscopic requirement of melt stability for a given temperature below the dry solidus. Measured olivine storage capacities are in agreement or slightly greater than those predicted by a model that combines data from experimental freezing point depression and olivine/melt partition coefficients of H2O (Hirschmann et al., 2009). Considering the temperature along the mantle geotherm, as well as available constraints on garnet/olivine and pyroxene/olivine partitioning of H2O (DH2Ogar/ol,DH2Opx/ol), we estimate the peridotite H2O storage capacity in the low velocity zone. The C 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.

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

2012-09-01

72

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

NASA Astrophysics Data System (ADS)

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.

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

73

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

NASA Astrophysics Data System (ADS)

Chloride-rich brines coexisting with CO2-rich fluids are an important agent of high-grade metamorphism and metasomatism in the lower to middle crust. Thermodynamic and transport properties of the chloride-rich fluids are well constrained both theoretically and experimentally. Nevertheless, their effects on complex natural assemblages are poorly understood and demand systematic experimental study. We report results of the experiments on interaction of the biotite-amphibole gneiss from the Sand River formation (Limpopo Complex, South Africa) with the H2O-CO2, H2O-CO2-KCl, H2O-CO2-NaCl, and H2O-CO2-(K, Na)Cl fluids at 5.5 kbar, 750 and 800 C, the chloride/(H2O+CO2) ratio varying from 0 to 0.1, and molar CO2/(CO2+H2O) = 0.5. Experiments were carried out using internally-heated gas pressure vessel. Major purposes of the experiments were to trace changes in phase assemblages in dependence on temperature, salt concentration in a fluid, KCl/NaCl ratio and to show a possibility for partial melting. Heating of the gneiss both at 750 and 800 C without any fluid produced no visible changes in its phase assemblage. Interaction of the gneiss with the H2O-CO2 fluid at 750 C did not significantly influence on its phase assemblage, as well. Addition of KCl in the H2O-CO2 fluid at 750 C resulted in the formation of reaction textures consisting of clinopyroxene and K-feldspar around biotite and amphibole at the contacts with plagioclase. No evidence for partial melting was detected in the samples interacted with the H2O-CO2 and H2O-CO2-KCl fluids at 750 C. Addition of NaCl provokes melting with formation of trachytic and trachyandesitic melts along with the new assemblages Cpx+Kfs+Pl+Ti-Mt and Cpx+Amp+Pl+Ti-Mt. Characteristic of feature of amphiboles, forming in the NaCl-rich fluids is their elevated Na2O content. Products of the runs at 750 C do not contain orthopyroxene. This phase appears at 800 C as a result of biotite breakdown in presence of the H2O-CO2 fluid. It is accompanied by dacitic melt and Ti-magnetite. Newly formed assemblages regularly change with an increase of the KCl content in the fluid: Opx+Ti-Mt+melt, Opx+Amp+Ilm+Ti-Mt + melt, Opx+Cpx+Ilm+melt, Cpx+ Ilm+melt. In this sequence, the melt evolves toward potassic rhyolitic composition. Orthopyroxene appears in assemblage with sodic amphibole in equilibrium with NaCl-rich fluids, as well. Present experiments allow conclusion that the interaction of the biotite-amphibole gneiss with the H2O-CO2-(K, Na)Cl fluids can be accompanied by a partial melting at 750-800 C. Melting progress is vitally depends on the NaCl/KCl ratio in a fluid. NaCl intensifies melting because of higher solubility of Cl and CO2 in the sodic melts in comparison to the potassic varieties. Charnockitic and mangeritic assemblages (Opx+Cpx+Kfs+Pl) form in presence of the partial melts at temperature 800 C and are stable in presence of KCl-bearing fluids with relatively low salt concentrations (H2O/(KCl+H2O) < 0.015). Fluids of higher salinity result in formation syenitic and monzonitic assemblages (Cpx+Amp+Kfs+Pl). Applicability of the experimental data is demonstrated by mineral assemblages of local-scale dehydration zones in the high-grade terrains.

Safonov, O.; Kosova, S.

2012-12-01

74

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

NASA Astrophysics Data System (ADS)

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.

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

2011-12-01

75

In situ high-pressure x-ray diffraction study of H2O ice VII  

Microsoft Academic Search

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

Maddury Somayazulu; Jinfu Shu; Chang-Sheng Zha; Alexander F. Goncharov; Oliver Tschauner; Ho-Kwang Mao; Russell J. Hemley

2008-01-01

76

The origin of Kenya rift plateau-type flood phonolites: Results of high-pressure/high-temperature experiments in the systems phonolite-H2O and phonolite-H2O-CO2  

NASA Astrophysics Data System (ADS)

Near-liquidus melting relations have been determined for a mafic, plateau-type, flood phonolite from the Kenya rift at 0.5, 0.7, 0.9, and 1.2 GPa, with H2O added through saturation, and at 0.7 GPa with H2O and CO2 added. Mixed-volatile experiments at 0.7 GPa delineate a near-liquidus multiple saturation of augite, andesine, phlogopite, oxides, and apatite at 1000 C, X(sub CO2) = 0.42, with calcic amphibole melting above 975 C. The multiple saturation and pahse assemblage are interpreted to indicate that plateau phonolites were in equilibrium with the residuum of a parental alkali basaltic composition at 0.7 GPa consisting of augite, andesine, titanomagnetite, and olivine (a product of incongruent melting of phlogopite and, possibly, amphibole). This evidence for lower crustal equilibration refutes suggestions that plateau phonolites are low-pressure differentiates. Their enormous volumes (about 50,000 cubic km), restricted eruptive period (14-11 Ma), uniform major element compositions, and the paucity of associated mafic-intermediate rocks also argue against a deep origin by fractional crystallization. A two-stage process for the origin of the phonolites is consistent with the thermal evolution of the rift. The lower crust was pervasively injected by alkali basaltic magmas during the period of voluminous eruption of early to middle Miocene basalts. Rising isotherms during rift evolution caused subsequent partial melting of this predominantly basaltic lower crust in the late Miocene, generating the plateau phonolites.

Hay, David E.; Wendlandt, Richard F.

1995-01-01

77

Measurements of Surface Ocean Carbon Dioxide Partial Pressure During WOCE  

Microsoft Academic Search

All of the technical goals of the World Ocean Circulation Experiment (WOCE) field program which were supported under the Department of Energy research grant ''Measurements of Surface Ocean Carbon Dioxide Partial Pressure During WOCE'' (DE-FG03-90ER60981) have been met. This has included the measurement of the partial pressures of carbon dioxide (C0â) and nitrous oxide (NâO) in both the surface ocean

1998-01-01

78

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

NASA Astrophysics Data System (ADS)

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.

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

2013-12-01

79

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

NASA Technical Reports Server (NTRS)

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.

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

1989-01-01

80

Photodegradation of emerging micropollutants using the medium-pressure UV/H2O2 Advanced Oxidation Process.  

PubMed

A medium-pressure (MP) ultraviolet (UV) process has been applied to investigate the direct UV photolysis and UV/H2O2 oxidation of selected model micropollutants (naproxen, carbamazepine, diclofenac, gemfibrozil, ibuprofen, caffeine, 2,4-D, 2,4-DCP, and mecoprop). The quantum yields were found to be between 0.0010 and 0.13 at pH = 7. In the MP UV/H2O2 oxidation, the pseudo first-order rate constants for the selected compounds were found to be dependent on their initial concentrations (at mg/L levels) and on the H2O2 concentration. The UV doses required for 50% and 90% removal at various H2O2 levels varied widely among the compounds tested. Second-order rate constants (ranging from 4.1 × 10(9) to 1.4 × 10(10) M(-1) s(-1)) for the reaction between the selected compounds and hydroxyl radicals were determined using a competition-kinetics approach, where para-chlorobenzoic acid (pCBA) was chosen as the reference compound. Further, as an evaluation of electrical energy efficiency, the Figure-of-Merit, Electrical Energy per Order (EEO) was determined for the selected compounds using a batch reactor at 25 and 50 mg/L H2O2 concentrations. The electrical energy (in kWh) required to reduce a pollutant concentration by 90% ranged from 1.3 to 7.1 kWh m(-3). PMID:23517874

Shu, Zengquan; Bolton, James R; Belosevic, Miodrag; El Din, Mohamed Gamal

2013-05-15

81

Pressurized H2 RF cavities in ionizing beams and magnetic fields.  

PubMed

A major technological challenge in building a muon cooling channel is operating rf cavities in multitesla external magnetic fields. We report the first proof-of-principle experiment of a high pressure gas-filled rf cavity for use with intense ionizing beams and strong external magnetic fields. rf power consumption by beam-induced plasma is investigated with hydrogen and deuterium gases with pressures between 20 and 100 atm and peak rf gradients between 5 and 50 MV/m. The low pressure case agrees well with an analytical model based on electron and ion mobilities. Varying concentrations of oxygen gas are 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 are 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. All these results indicate that a high pressure gas-filled cavity is a viable technology for muon ionization cooling. PMID:24237526

Chung, M; Collura, M G; Flanagan, G; Freemire, B; Hanlet, P M; Jana, M R; Johnson, R P; Kaplan, D M; Leonova, M; Moretti, A; Popovic, M; Schwarz, T; Tollestrup, A; Torun, Y; Yonehara, K

2013-11-01

82

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

SciTech Connect

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.

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

2008-01-01

83

Catalytic Oxidation of Methane to Methanol with H 2-O 2 Gas Mixture at Atmospheric Pressure  

Microsoft Academic Search

Oxidation of methane with oxygen in the presence of hydrogen has been performed at atmospheric pressure over a large variety of catalysts. Among the catalysts tested, iron phosphate showed a very unique catalytic property. The presence of hydrogen initiates the selective oxidation of methane to methanol at ?623 K over FePO4 catalyst. Formaldehyde as a secondary product is produced through

Ye Wang; Kiyoshi Otsuka

1995-01-01

84

Ignition and Extinction in Catalytic Partial Oxidation of Methane-Oxygen Mixtures with Large H2O and CO2 Dilution  

Microsoft Academic Search

The ignition and extinction in catalytic partial oxidation (CPO) of CH4\\/O2 mixtures with large exhaust gas dilution (46.3% H2O and 23.1% CO2 vol.) has been investigated experimentally and numerically at 5 bar. Experiments were carried out in a short contact time Rh-coated honeycomb reactor and involved temperature measurements along the reactor and exhaust gas analysis. Numerical predictions were performed with

Adrian Schneider; John Mantzaras; Sara Eriksson

2007-01-01

85

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

SciTech Connect

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

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

2011-06-06

86

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

SciTech Connect

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

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

2011-12-31

87

Characteristics of Fe2O3 Nanoparticles from Doped Low-pressure H2\\/O2\\/Ar Flames  

Microsoft Academic Search

A burner stabilized premixed low-pressure flame has been used to generate iron-oxide (Fe2O3) nanoparticles with sizes in the range 7–20?nm. The H2\\/O2\\/Ar flames were doped with different amounts of iron-pentacarbonyl (Fe(CO)5) with concentrations in the range 524–2096?ppm. The influence of precursor concentration on composition, structure, morphology, and size have been studied utilizing transmission electron microscopy (TEM), X-ray powder diffraction (XRD),

C. Janzen; P. Roth; B. Rellinghaus

1999-01-01

88

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

SciTech Connect

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.

Pint, Bruce A [ORNL

2012-08-01

89

High-pressure elastic properties of the VI and VII phase of ice in dense H2O and D2O  

Microsoft Academic Search

High-pressure Brillouin spectroscopy has been used to determine acoustic velocities in any direction, refractive index, adiabatic elastic constants, and adiabatic bulk modulus of H2O and D2O ices at 300 K and at pressures between 1.05 and 2.1 GPa for tetragonal ice VI and above pressures up to 8 GPa for cubic ice VII. Typical values of elastic constants for H2O

H. Shimizu; T. Nabetani; T. Nishiba; S. Sasaki

1996-01-01

90

Intensity and pressure shift of the H2 /4,0/ S/1/ quadrupole line. [in giant planet atmospheres  

NASA Technical Reports Server (NTRS)

Results are presented for two laboratory measurements of the intensity and central frequency of the (4, 0) S(1) quadrupole line of H2, which were made at pressures of 2.658 and 1.494 atm through a 0.456-km path length. It is found that the absolute line intensity is significantly lower than the value predicted from theoretical matrix elements but is essentially identical to the value derived by Rank et al. (1966). The central-frequency results are shown to verify the pressure shift predicted by McKellar (1974). It is concluded that hydrogen abundances estimated from the equivalent width of the (4,0) S(1) quadrupole line in the spectra of the outer planets will have to be revised upward by nearly a factor of 2.

Bergstralh, J. T.; Margolis, J. S.; Brault, J. W.

1978-01-01

91

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

USGS Publications Warehouse

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.

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

2007-01-01

92

A unified equation for calculating methane vapor pressures in the CH 4-H 2O system with measured Raman shifts  

NASA Astrophysics Data System (ADS)

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 CH 4-H 2O 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 CH 4?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 CH 4-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.

Lu, Wanjun; Chou, I.-Ming; Burruss, R. C.; Song, Yucai

2007-08-01

93

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

NASA Astrophysics Data System (ADS)

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

Wu, Xinyu; Wu, Huiying; Cheng, Ping

2009-10-01

94

Optimal actuator placement and model reduction for a class of parabolic partial differential equations using spatial H2 norm  

Microsoft Academic Search

The present work focuses on the optimal, with respect to certain criteria, placement of control actuators for transport-reaction processes, mathematically modelled by linear parabolic partial differential equations. Using model decomposition to discretize the spatial coordinate, and the notions of spatial and modal controllability, the semi-infinite optimization problem is formulated as a nonlinear optimization problem in appropriate L2 spaces. The formulated

Michael A. Demetriou; Antonios Armaou

2005-01-01

95

Microwave Dielectric Properties of NH4H2PO4, and Partially Deuterated KH2PO4  

Microsoft Academic Search

The temperature dependence of the complex dielectric constants at 9.2 Gc\\/sec are reported for a series of partially deuterated potassium dihydrogen phosphate crystals as well as for a potassium dihydrogen arsenate and an ammonium dihydrogen phosphate crystal. The transition temperature, the high-temperature loss tangent, and the temperature-independent ratio deltac?c' all increase monotonically with increasing deuteration. Proton tunneling in the four

I. P. Kaminow

1965-01-01

96

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

NASA Technical Reports Server (NTRS)

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.

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

1980-01-01

97

Laboratory measurement of H2O2 pressure broadening parameter for JEM/SMILES Observation from International Space Station  

NASA Astrophysics Data System (ADS)

A new generation of sub-millimeter-wave receivers employing sensitive SIS (Superconductor Insulator Superconductor) detector technology will provide new opportunities for precise remote sensing measurements of minor constituents in the earth and planetary atmosphere.Superconducting Sub-Millimeter-Wave Limb-Emission Sounder (SMILES) was designed to be onboard the Japanese Experiment Module (JEM) on the International Space Station (ISS) as a collaboration project of National Institute of Information and Communications Technology (NICT) and Japan Aerospace Exploration Agency (JAXA).SMILES in Transfer Vehicle (HTV) plan to launch in September 11 2009 by Japanese H-IIB rocket. JEM/SMILES will allow to observe the atmospheric species such as O3, H35Cl, H37Cl, ClO, BrO, HOCl, HO2, H2O2, HNO3 and CH3CN, Ozone isotope species, and water vapor with the precisions in a few to several tens percents [1] in the altitude region upper troposphere (about 8km in mid-latitude) and the mesosphere (about 90km in mid-latitude). In this paper, laboratory measurement of the pressure broadening parameter (?) of Hydrogen peroxide (H2O2) at JKa,Kc = 201,19 - 192,17 rotational transition (625.044 GHz) will be presented. This is one of the target transitions of JEM/SMILES observation. ? of H2O2 in sub-millimeter-wave region was measured for the first time. The measurement was carried out using a sub-millimeter-wave absorption spectrometric system in Tokyo Institute of Technology.The radiation source from a backward wave oscillator (BWO) was phase-locked to the harmonics of a synthesized sweeper with two-step phase lock loop. The BWO source frequency was modulated with the modulation frequency of 51 kHz. H2O2 sample was prerpared by distillation of commercial available 30% solution. The pressures of sample and buffer gas (N2 and O2) were controlled by a mass flow meter and monitored by two Baratron monitors in the cell. From the observed profiles of the spectrum, the pressure broadening line widths were determined using a convolution method proposed by Pickett [2], [3]. ? was determined by fitting the measured line widths to a linear function with a least-square method. ? (N2) = 4.03 ± 0.06 [MHz/Torr] (1.4%), ? (O2) = 2.49 ± 0.04 [MHz/Torr] (1.7%). The errors are presumably caused by representational accuracy fluctuation of Baratron pressure monitor. Precision of JEM/SMILES sensitive observation requires the precise value of ? of H2O2 within the error of 3%. We confirmed that the precision of the measurement fulfills the SMILES observation requirement. Refferences [1] JEM/SMILES mission plan. Version 2.1, November 15, 2002. [2] M. M. Yamada, M. Kobayashi, M. Habara, T. Amano, and B. J. Drouin, J. Quant. Spectrosc. Radiat. Transfer 82, 391-399 (2003). [3] H. M. Pickett, Appl. Opt. 19, 2745 (1980).

Sato, T.; Mizoguchi, A.; Kasai, Y.; Kanamori, H.

2009-12-01

98

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

SciTech Connect

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.

Stratis V. Sotirchos

1998-02-01

99

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

PubMed

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. PMID:24832812

Kleppe, Annette K; Amboage, Mónica; Jephcoat, Andrew P

2014-01-01

100

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

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

101

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)

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.

Ogitsu, I.; Ozawa, K.

2008-12-01

102

Pressure and temperature dependence of the dielectric properties of CsH2PO4 and CsD2PO4  

Microsoft Academic Search

The pressure (0-7 kbar) and temperature (-200-+10°C) dependence of the dielectric properties (relative permittivity ?r and spontaneous polarization Ps) of CsH2PO4 and CsD2PO4 were investigated. By the observation of the P-E double hysteresis loops it is confirmed that the pressure-induced phase (at pressures above the critical pressure pc) is antiferroelectric for both compounds. The pressure-temperature phase diagrams of both compounds

Naohiko Yasuda; Sanji Fujimoto; Motohide Okamoto; Hiroyasu Shimizu; Katsumi Yoshino; Yoshio Inuishi

1979-01-01

103

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

Microsoft Academic Search

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

Lin-Gun Liu

1987-01-01

104

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...

105

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

ERIC Educational Resources Information Center

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…

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

2007-01-01

106

Effect of high-pressure H2O treatment on elimination of interfacial GeOX layer between ZrO2 and Ge stack  

NASA Astrophysics Data System (ADS)

This investigation demonstrates the effect of high-pressure H2O treatment on the elimination of the interfacial germanium suboxide (GeOX) layer between ZrO2 and Ge. The formation of GeOX interlayer increases the gate-leakage current and worsen the controllability of the gate during deposition or thermal cycles. X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy reveal that high-pressure H2O treatment eliminates the interfacial GeOX layer. The physical mechanism involves the oxidation of non-oxidized Zr with H2O and the reduction of GeOX by H2. Treatment with H2O reduces the gate-leakage current of a ZrO2/Ge capacitor by a factor of 1000.

Huang, Chen-Shuo; Liu, Po-Tsun

2011-08-01

107

Effect of Hydrostatic Pressure on the Antiferroelectric Phase Transitions in Ammonium Dihydrogen Arsenate NH4H2AsO4 and Deuterated Analogue  

NASA Astrophysics Data System (ADS)

Effect of hydrostatic pressure on the antiferroelectric phase transitions in NH4H2AsO4 and deuterated analogue (deuterium concentration ˜80%) was studied by dielectric constant measurements at high pressures up to about 0.8 GPa. The transition temperature linearly decreases with increasing pressure with the ratios of -19.7 K GPa-1 and -14.5 K GPa-1 for NH4H2AsO4 and the deuterated compound, respectively. The pressure effect is compared with previously reported results of other KH2PO4-type ferro- and antiferroelectric crystals.

Gesi, Kazuo; Ozawa, Kunio

1984-12-01

108

Partial melting of the Appin Quartzite driven by fracture-controlled H2O infiltration in the aureole of the Ballachulish Igneous Complex, Scottish Highlands  

NASA Astrophysics Data System (ADS)

The Ballachulish Igneous Complex consists of an outer quartz diorite and an inner granite, emplaced at about 300MPa, initially at 1000 to 1050°C. The contact aureole (0.5-2km wide) occurs in metapelites and metapsammites plus minor graphitic slates, carbonate rocks and metaquartzites. A textural examination of the arkosic Appin Quartzite, which was previously believed to have melted only within a few metres of the intrusion, demonstrates that partial melting occurred up to 500m away from the vertical eastern contact. Coupling petrographic observations with Qtz-Ab-Or-H2O phase relations, we determined both the amounts of actual melt and the maximum possible amounts of melt in the samples. Melting efficiency was everywhere less than 100% and decreased with distance from the intrusion. Though perhaps not the only possible source of fluid throughout the aureole, simple models demonstrate that H2O evolution from the pluton would have been volumetrically sufficient and persisted long enough to account for the observed partial melting. A time-integrated fluid flux of 7000kg/m2 from the pluton is necessary to account for the observed amounts of partial melt in the Appin Quartzite. From its inefficiency, we infer that infiltration of the Appin Quartzite cannot have occurred along interconnected grain-edge channels. Rather, it was controlled by hydraulic fracturing, with fracture density determining melting efficiency. Bulk-rock permeability is calculated to be 10-20 m2, an order of magnitude lower than that necessary to permit pervasive flow of all the fluid exsolving from the pluton. There is little difference between the calculated time-integrated fluid flux through the Appin Quartzite on the eastern flank and an estimate of the infiltrating flux through the pelitic Leven Schist on the western flank in the time interval during which both rock types were above their solidus temperature, despite differences in their equilibrium quartz-H2O dihedral angles at temperatures immediately below the solidus, and differences in the attitude of the contact. The rates of H2O expulsion from the cooling pluton are consistent with highly efficient fracture-dominated flow, allowing insufficient time for textural equilibration.

Holness, Marian B.; Clemens, John D.

109

Electrodischarge VUV radiator of low pressure on the mixtures He(Ar, Kr, Xe)/H2O  

NASA Astrophysics Data System (ADS)

The results of development and optimization of the working medium of ecological pure radiator working in the range of 130 - 190 nm are presented in this paper. A decaying discharge of a constant current in the quartz or sapphire tube with an interelectrode distance of 50 mm was used for pumping. As working media the mixtures He(Ar, Kr, Xe)/H(subscript 2)O were used. It was shown that by falling the pressure on discharge interval U(subscript ch) equals 800 - 1700 V, in discharge current I(subscript ch) equals 5 - 50 mA and partial pressure of water vapor P(H(subscript 2)O) partial pressure of water vapor was in the range of 50 - 150 Pa, and the optimum composition of Helium in the mixture made 1.0 kPa. The replacement of a Helium to heavier inert gases (Ar, Kr, Xe) resulted the falling the brightness of VUV-radiation OH. The estimation of power and efficiency of VUV-radiation have shown, that they are on the level characteristic for lamps with (lambda) equals 175 ArCl (W

Shuaibov, Alexandr K.; Shimon, Ludwig L.; Dashchenko, Arkadij; Shevera, Igor

2002-03-01

110

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

NASA Astrophysics Data System (ADS)

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

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

111

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  

Microsoft Academic Search

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

Bradley R. Hacker; Geoffrey A. Abers

2004-01-01

112

Effect of total pressure on the absorption line blackbody distribution function and radiative transfer in H2O, CO2, and CO  

NASA Astrophysics Data System (ADS)

The absorption spectrum has been generated for H2O, CO2, and CO at total pressures varying from 0.1 to 50 atm using the HITEMP 2010 spectroscopic database. From these spectra the absorption line blackbody distribution function (ALBDF) has been calculated at variable total pressure in order to understand the importance of accounting for pressure changes on this parameter. The ALBDF is used in the SLW solution method to the radiative transfer equation. ALBDF data for H2O, CO2, and CO are presented, revealing a shift in the ALBDF to lower values as total pressure increases. This shift is weaker at high temperature. The shift due to increase in mole fraction of H2O and CO2 was shown to be modest, and similar at different pressures. The ALBDF was shown to become less smooth as pressure increases. Total emissivity calculations are presented for variable total pressure, and it is seen that pressure changes account for a significant change in total emissivity. Total radiative flux and radiative flux divergence were calculated from line-by-line spectral integrations for one-dimensional layers of constant length and constant mass cases, showing that total pressure changes result in a significant impact on radiative transfer in a layer of gas. Radiative flux exiting a layer of gas can change by more than a factor of four over the pressure range investigated when the pressure change is the only variable considered.

Pearson, John T.; Webb, Brent W.; Solovjov, Vladimir P.; Ma, Jiefu

2014-08-01

113

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

PubMed

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

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

2013-01-10

114

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

Microsoft Academic Search

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

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

2011-01-01

115

Oxygen-Partial-Pressure Sensor for Aircraft Oxygen Mask  

NASA Technical Reports Server (NTRS)

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.

Kelly, Mark; Pettit, Donald

2003-01-01

116

Pressure-induced behavior of the hydrogen-dominant compound SiH4(H2)2 from first-principles calculation  

SciTech Connect

The structural and electronic properties of the high pressure molecular compound SiH4(H2)2 have been calculated using density functional theory. We identify the molecular hydrogen positions within the face-centered cubic unit cell and further find that pressure-induced intermolecular interaction between SiH4 and H2 units plays an important role in stabilizing this new compound. The electronic structure is characterized by a wide band gap of 6.1 eV at 6.8 GPa, which closes with pressure and finally becomes metallic at 200 GPa due to electronic band overlap accompanied by a structure change. These findings have potential implications for understanding metallization and superconductivity in H2.

Chen, Xing-Qiu [Shangyang National Laboratory for Materials Science, China; Wang, Shibing [Stanford University; Mao, Wendy [Stanford University; Fu, Chong Long [ORNL

2010-01-01

117

LETTER TO THE EDITOR: Hydrogen Lyman-? ; and Lyman-? emissions from high-pressure microhollow cathode discharges in Ne-H2 mixtures  

NASA Astrophysics Data System (ADS)

We observed intense emission of the atomic hydrogen Lyman-? (121.6 nm) and Lyman-? (102.5 nm) lines from microhollow cathode discharges in high-pressure Ne (740 Torr) with a small admixture of H2 (up to 3 Torr). The atomic emission lines are spectrally clean with essentially no background of molecular emissions from the H2 Lyman and Werner bands. We attribute these atomic emissions to near-resonant energy transfer processes in the high-pressure discharge. In one case, near-resonant energy transfer between the Ne2* excimer and H2 leads to the formation of H(n = 2) atoms, a process similar to what was observed recently by Wieser et al (1998 J. Phys. B: At. Mol. Opt. Phys. 31 4589) in a high-pressure Ne/H2 mixture excited by energetic ion and electron impact. In the other case, near-resonant energy transfer between excited N* atoms (or vibrationally excited neon excimer molecules) and H2 leads to the formation of H(n = 3) atoms. The ratio of Lyman-? to Lyman-? emission intensity depends on the operating parameters of the discharge (gas pressure, gas mixture, discharge current) which supports the notion that different processes are involved in the formation of the H(n = 2) and H(n = 3) atoms, respectively.

Kurunczi, P.; Shah, H.; Becker, K.

1999-11-01

118

High-Pressure Equation of State for Partially Ionic Solids  

NASA Technical Reports Server (NTRS)

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).

Schlosser, Herbert; Ferrante, John

1993-01-01

119

A model for the viscosity of rhyolite as a function of H 2O-content and pressure: A calibration based on centrifuge piston cylinder experiments  

NASA Astrophysics Data System (ADS)

The Newtonian viscosity of synthetic rhyolitic liquids with 0.15-5.24 wt% dissolved water was determined in the interval between 580 and 1640 °C and pressures of 1 atm and 5-25 kbar. Measurements were performed by combining static and accelerated (up to 1000 g) falling sphere experiments on water-bearing samples, with high temperature concentric cylinder experiments on 0.15 wt% H 2O melts. These methods allowed viscosity determinations between 10 2 and 10 7 Pa s, and cover the complete range of naturally occurring magmatic temperatures, pressures, and H 2O-contents for rhyolites. Our viscosity data, combined with those from previous studies, were modeled by an expression based on the empirical Vogel-Fulcher-Tammann equation, which describes viscosities and derivative properties (glass transition temperature T g, fragility m, and activation volume of viscous flow Va) of silicic liquids as a function of P- T- X(H2O). The fitted expressions do not account for composition-dependent parameters other than X(H2O) and reproduce the entire viscosity database for silicic liquids to within 3.0% average relative error on log ? (i.e. std. error of estimate of 0.26 log units). The results yield the expected strong decrease of viscosity with temperature and water content, but show variable pressure dependencies. Viscosity results to be strongly affected by pressure at low pressures; an effect amplified at low temperatures and water contents. Fragility, as a measure for the deviation from Arrhenian behavior, decreases with H 2O-content but is insensitive to pressure. Activation volumes are always largely negative (e.g., less than -10 cm 3/mol) and increase strongly with H 2O-content. Variations in melt structure that may account for the observed property variations are discussed.

Ardia, Paola; Giordano, Daniele; Schmidt, Max W.

2008-12-01

120

Interface chemistry of H2O on GaAs nanowires probed by near ambient pressure X-ray photoelectron spectroscopy  

NASA Astrophysics Data System (ADS)

Interface chemistry of H2O on GaAs nanowires is investigated by in situ X-ray photoelectron spectroscopy (XPS) at elevated water vapor pressures (from UHV to 5 mbar) and temperatures (from room temperature to 400 °C). Surface-assisted water dissociation leads to oxidation and hydroxylation of surface Ga atoms. In comparison with the simple planar GaAs(1 0 0) crystal, the H2O dissociation process on GaAs nanowires is greatly enhanced at elevated pressures and temperatures.

Zhang, Xueqiang; Lamere, Edward; Liu, Xinyu; Furdyna, Jacek K.; Ptasinska, Sylwia

2014-06-01

121

Photochemical stability of partially fluorinated acrylic protective coatings I. Poly(2,2,2-trifluoroethyl methacrylate) and poly(1H,1H,2H,2H-perfluorodecyl methacrylate- co-2-ethylhexyl methacrylate)s  

Microsoft Academic Search

The photochemical stability and photodegradation pathways of poly(2,2,2-trifluoroethyl methacrylate) (PTFEMA) and copolymers of 1H,1H,2H,2H-perfluorodecyl methacrylate with 2-ethylhexyl methacrylate (XFDMA–EHMA) have been investigated under artificial solar light irradiation. The extent of degradation was assessed by weight loss and gel content determination, size exclusion chromatography and FTIR spectroscopy. PTFEMA exposed up to 2000 h showed only molecular changes due to a low

Oscar Chiantore; Massimo Lazzari; Mauro Aglietto; Valter Castelvetro; Francesco Ciardelli

2000-01-01

122

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

SciTech Connect

The influence of H2S-to-H2 partial pressure ratio on the sulfidization of Pd and 70 mol% Pd–Cu 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% Pd–Cu 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 Pd–Cu alloy from ideality, probably due to Cu segregation at the membrane surface.

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

2007-11-15

123

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

SciTech Connect

The influence of H2S-to-H2 partial pressure ratio on the sulfidization of Pd and 70 mol% Pd–Cu 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% Pd–Cu 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 Pd–Cu alloy from ideality, probably due to Cu segregation at the membrane surface.

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

2007-11-15

124

The Structure and Elastic and Thermodynamic Properties of Cubic-NbH2 under High Pressures from First-Principles Calculations  

NASA Astrophysics Data System (ADS)

NbH2 hydride is an important material in hydrogen storage materials. However, until now there have been no experimental and theoretical data on the elastic and thermodynamic properties. The structure and thermodynamic properties of cubic-NbH2 under high temperatures and pressure are investigated by first-principles study based on the pseudo-potential plane-wave density functional theory method using the generalized gradient approximation and quasi-harmonic Debye model. The results show that the calculated structural parameters of NbH2 are in good agreement with the available experimental results and other theoretical data. The obtained elastic constants satisfy the requirement for mechanical stability, indicating that the NbH2 crystal is stable in the investigated pressure and temperature ranges. Through the quasi-harmonic Debye model, in which the phononic effects are considered, the thermodynamic properties of NbH2, such as the thermal expansion coefficient and the heat capacity dependence of temperature and pressure in the ranges 0-1100 K and 0-70 GPa, are also obtained, respectively.

Liu, Xian-Kun; Tang, Bin

2013-06-01

125

Measurement of Hydrogen Radical Density and Its Impact on Reduction of Copper Oxide in Atmospheric-Pressure Remote Plasma Using H2 and Ar Mixture Gases  

NASA Astrophysics Data System (ADS)

A 60 Hz alternating current excited atmospheric-pressure plasma with an ultrahigh electron density of over 1016 cm-3 employing H2/Ar [\\aku p(H2)/p(H2+Ar) 1--3%] gases was used to reduce copper oxides on copper. The remote plasma reduced CuO and Cu2O at room temperature. The ground-state hydrogen (H) radical density in the atmospheric-pressure plasma was measured by vacuum ultraviolet absorption spectroscopy using a micro hollow cathode lamp. The ratio of reduction of amount of CuO flux to the H radical flux was determined from the measured H radical density and gas temperature.

Inui, Hirotoshi; Takeda, Keigo; Kondo, Hiroki; Ishikawa, Kenji; Sekine, Makoto; Kano, Hiroyuki; Yoshida, Naofumi; Hori, Masaru

2010-12-01

126

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

NASA Astrophysics Data System (ADS)

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

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

1994-09-01

127

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

Code of Federal Regulations, 2010 CFR

...868.1200 Indwelling blood oxygen partial pressure (PO2 ) analyzer...Identification. An indwelling blood oxygen partial pressure (PO2 ...vivo, the partial pressure of oxygen in blood to aid in determining...Document: Indwelling Blood Gas Analyzers; Final Guidance...

2010-04-01

128

Pressure dependence of the static dielectric properties of K(H1-xDx)2PO4 and RbH2PO4  

Microsoft Academic Search

The effects of hydrostatic pressure on the static dielectric constant, ?c, Curie-Weiss constant, C, saturation polarization, Ps, and transition temperature, Ts, of the ferroelectrics K(H1-xDx)2PO4, and RbH2PO4 were investigated. The pressure dependence of Tc is known from earlier work and the present work extends the results to other deuterium concentrations, x; however, the results on C and Ps are largely

G. A. Samara

1978-01-01

129

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

SciTech Connect

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.

A. Robertson

2002-09-30

130

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

SciTech Connect

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.

A. Robertson

2003-12-31

131

Chemistry of Low Degree Hydrous Partial Melt at High Pressures  

NASA Astrophysics Data System (ADS)

Geophysical evidence hints towards the possibility that silicate melt may reside on top of the 410 km seismic discontinuity in some regions of the mantle. Based on the difference in the water storage capacity of upper mantle (dominantly olivine) and transition zone minerals (primarily wadsleyite), it has been suggested that if there is any melting at the top of the transition zone, it is likely to be hydrous melt. This hydrous melt phase might be able to reconcile the differences between geochemists view of stratified mantle (based on trace element differences in MORB and OIB) as opposed to geophysicsts view of whole mantle convection (based on seismic tomography of slabs). Fundamental questions remain unanswered: what is the composition of low degree hydrous partial melts at these conditions? Is this melt gravitationaly stable? Could this melt be detectable geophysically? In this study, we are determining the compositions of low degree hydrous partial melts that would be in equilibrium with the mineral assemblage at the base of the upper mantle. Initial experiments employ an estimated melt composition in the system CaO-MgO-Al2O3-SiO2- H2O which was sandwiched between layers of peridotite (CAMS). By examining the shift in the composition of melt and mineral phases as the melt tries to equilibrate with the solid phases, the melt composition can be iteratively modified until the melt composition remains unchanged. Experiments are performed at 14 GPa and 1723 K i.e, conditions pertinent to the top of the transition zone. The effect of iron on the melting relations is also being explored.

Mookherjee, M.; Frost, D. J.

2008-12-01

132

Solubility of H 2O and CO 2 in shoshonitic melts at 1250 °C and pressures from 50 to 400 MPa: Implications for Campi Flegrei magmatic systems  

NASA Astrophysics Data System (ADS)

The solubility of H 2O-CO 2-bearing fluids in shoshonitic melts relevant to magmas of the Vulcanello peninsula and to mafic melts from magmas erupted at Campi Flegrei (Italy) was experimentally determined at pressures from 50 to 400 MPa and at temperature of 1250 °C. No quench crystals and less than 1 vol.% bubles were observed in the rapid quenched glasses. H 2O and CO 2 contents in the experimental glasses were determined via Karl-Fischer Titration (KFT) and FTIR spectroscopy. For the quantification of volatile concentrations by IR spectroscopy we have calibrated the absorption coefficients of water-related and carbon-related IR bands for the shoshonitic composition. The determined absorption coefficients are 0.80 ± 0.06 L mol - 1 cm - 1 for the band at ~ 4500 cm - 1 (OH groups) and 1.02 ± 0.03 L mol - 1 cm - 1 for the band at ~ 5200 cm - 1 (H 2O molecules). CO 2 is bound in the shoshonitic glass as CO 32- exclusively; its concentration was quantified by the peak height of the low wavenumber band of the doublet near 1430 cm - 1 using the calibrated absorption coefficient of 356 ± 18 L mol - 1 cm - 1 . The H 2O solubility in the shoshonitic melts is in the same range as observed for other natural aluminosilicate melts, i.e. 5.12 ± 0.07 wt.% at 200 MPa and 7.92 ± 0.07 wt.% H 2O at 400 MPa. A non-linear variation of the H 2O and CO 2 solubility in the melts with increasing mole fraction of H 2O (and thus decreasing mole fraction of CO 2) in the fluid was observed at each investigated pressure. At 1250 °C, the concentration of dissolved carbonate (expressed as CO 2 component) in melts coexisting with nearly pure CO 2 fluid increases from 307 to 2932 ppm (± 10% relative) as the pressure increases from 50 to 400 MPa. The comparison of the dataset with available models predicting the H 2O and CO 2 concentrations in silicate melts coexisting with H 2O-CO 2-bearing fluids shows that the effect of melt composition is not calibrated appropriately in the models. The experimental data are used to re-evaluate the typical pressures of glass inclusions entrapment in phenocrysts from Minopoli2 eruption and the results indicate that the main magma chamber may have been located at a depth of ~ 4000 m.

Vetere, Francesco; Botcharnikov, Roman E.; Holtz, Francois; Behrens, Harald; De Rosa, Rosanna

2011-05-01

133

Pressure-induced Jahn-Teller suppression in Rb2 CuCl4 ( H2 O ) 2 : Pseudo-Jahn-Teller effect  

NASA Astrophysics Data System (ADS)

In this work we investigate the variation of the local structure around Cu2+ as well as the crystal structure in Rb2CuCl4(H2O)2 through x-ray absorption spectroscopy (XAS) and x-ray diffraction (XRD) as a function of pressure. We show that the application of pressure induces a local structural change in the Jahn-Teller (JT) CuCl4(H2O)22- complex from an axially elongated complex to a compressed one, yielding disappearance of the JT distortion related to the four in-plane Cl- ligands, which are responsible for the antiferrodistortive structure displayed by the crystal at ambient pressure. According to the Pseudo-Jahn-Teller (PJT) theory (electron-phonon coupling E?e ), the presence of water ligands enhances the JT release at pressures well below the metallization pressure. The results are compared with recent pressure experiments on A2CuCl4 layered perovskites and heteronuclear CuCl4L2 complex series, L:Cl?H2O?NH3 , and explained on the basis of the PJT model.

Aguado, F.; Rodríguez, F.; Valiente, R.; Itié, J. P.; Munsch, P.

2004-12-01

134

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

135

Pressure broadening of deuterium hydride lines in the 5-0 vibrational band between 77 and 295 K. [Application to outer planets H2-He atmospheres  

SciTech Connect

Pressure-broadening coefficients and temperature-dependence indices have been derived from self-broadening measurements for the R(0) and R(1) lines of deuterium hydride's 5-0 vibration-rotation band at 77-295 K. In addition to deriving a temperature-dependent index of 0.31 for these HD lines, a temperature dependence index which is not larger than the HD index is suggested for H2 vibrational-rotational line broadening. The small temperature-dependence index increases outer-planet D/H ratios in inverse proportion to its reduction of the derived H2 abundances. 19 refs.

Smith, W.H.; Keffer, C.E.; Conner, C.P. (Washington Univ., Saint Louis, MO (USA))

1991-06-01

136

Phase diagram of H2O: Thermodynamic functions of the phase transitions of high-pressure ices  

Microsoft Academic Search

The analysis of the internal structure of the ice satellites of the Solar System's giant planets, Jupiter and Saturn, and the estimation of the composition of other water-containing cosmic bodies require thermodynamic information on the phase transformations in the water-ice system. This work presents experimental and theoretical data on the studies of the phase diagram of water (H2O) and the

A. N. Dunaeva; D. V. Antsyshkin; O. L. Kuskov

2010-01-01

137

Phase diagram of H 2 O: Thermodynamic functions of the phase transitions of high-pressure ices  

Microsoft Academic Search

The analysis of the internal structure of the ice satellites of the Solar System’s giant planets, Jupiter and Saturn, and\\u000a the estimation of the composition of other water-containing cosmic bodies require thermodynamic information on the phase transformations\\u000a in the water-ice system. This work presents experimental and theoretical data on the studies of the phase diagram of water\\u000a (H2O) and the

A. N. Dunaeva; D. V. Antsyshkin; O. L. Kuskov

2010-01-01

138

Simultaneous high-pressure and -temperature volume measurements of H2O ice and the phase transition of ice VII  

Microsoft Academic Search

A recent 300 K compression study on H2O ice by Sugimura et al. (2008, Phys. Rev. B) showed that ice changes its compressibility at 40 and 60 GPa, possibly due to phase transitions of ice VII to dynamically-disordered ice VII, and subsequently to dynamically-disordered ice X. The intermediate phase, dynamically-disordered ice VII, is highly compressible due to quantum effects of

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

2009-01-01

139

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

PubMed Central

Summary NAD(P)H:H2 pathways are theoretically predicted to reach equilibrium at very low partial headspace H2 pressure. An evaluation of the directionality of such near?equilibrium pathways in vivo, using a defined experimental system, is therefore important in order to determine its potential for application. Many anaerobic microorganisms have evolved NAD(P)H:H2 pathways; however, they are either not genetically tractable, and/or contain multiple H2 synthesis/consumption pathways linked with other more thermodynamically favourable substrates, such as pyruvate. We therefore constructed a synthetic ferredoxin?dependent NAD(P)H:H2 pathway model system in Escherichia coli BL21(DE3) and experimentally evaluated the thermodynamic limitations of nucleotide pyridine?dependent H2 synthesis under closed batch conditions. NADPH?dependent H2 accumulation was observed with a maximum partial H2 pressure equivalent to a biochemically effective intracellular NADPH/NADP+ ratio of 13:1. The molar yield of the NADPH:H2 pathway was restricted by thermodynamic limitations as it was strongly dependent on the headspace?:?liquid ratio of the culture vessels. When the substrate specificity was extended to NADH, only the reverse pathway directionality, H2 consumption, was observed above a partial H2 pressure of 40?Pa. Substitution of NADH with NADPH or other intermediates, as the main electron acceptor/donor of glucose catabolism and precursor of H2, is more likely to be applicable for H2 production.

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

2008-01-01

140

[Measurements of surface ocean carbon dioxide partial pressure during WOCE  

SciTech Connect

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.

Not Available

1992-01-01

141

Partial melting of carbonated pelite at 3-7 GPa and deep cycling of CO2 and H2O in subduction zones  

NASA Astrophysics Data System (ADS)

The exchange of water and carbon dioxide between the Earth's crustal rocks and the interior is important for understanding geochemical and geophysical evolution of the planet on geologic timescale. Subduction of pelitic sediments is a key mechanism for volatile introduction to the mantle but the high-pressure behavior of H2O+ CO2 bearing sediments is only constrained for alumina-rich, low-Mg# bulk compositions [1, 2]. However, the ocean-floor sediments for many subduction zones that contain both water and CO2 are alumina-poor and have higher Mg#. To constrain the melting behavior of a model alumina poor carbonated pelite, we performed new experiments. Piston cylinder (3 GPa) and multianvil (5 and 7 GPa) experiments were conducted between 800 and 1150 °C, using a model sediment composition containing 1 wt.% H2O and 5 wt.% CO2 (trace vapor-present at subsolidus conditions). The choice of the bulk composition was aimed to model the loss of siliceous hydrous fluid during the shallow part of subduction. We determined the solidus temperatures between 800 and 850 °C at 3 GPa, 900 and 950 °C at 5 GPa, and <1000 °C at 7 GPa. The subsolidus phases include cpx, garnet, coesite, rutile, phengite, and calcitess at 3 GPa, and kyanite comes in at 5 GPa. Hydrous rhyolitic silicate melt was observed at 3 GPa and up to 1150 °C. The near-solidus melt at 5-7 GPa was K-rich and calcio-carbonatitic, in contrast to the previous experimental results in alumina-rich and low Mg# bulk composition [1, 2], which showed the stability of Al-rich trachyitic silicate melt at near-solidus temperatures up to 5 GPa, and replaced by carbonate melt only at ?5.5 GPa. Carbonate-silicate melt immiscibility was observed at 5 GPa, 1100 °C in our study. The phengite-out boundary is located between 850 and 900 °C at 3 GPa, between 1000 and 1100 °C at 5 GPa, and <1000 °C at 7 GPa. The crystalline carbonate-out boundary is between 950 and 1000 °C at 3 and 5 GPa, and <1000 °C at 7 GPa. Comparison of our results, in terms of the P-T locations of the solidus, phengite- and carbonate-out boundaries, to the thermal structures of the slab-surface in cold-intermediate subduction zones indicates that most of the phengite-bound H2O and carbonate-bound CO2 are recycled into the deep upper mantle (~200 km depth). On the other hand, substantial amounts of C-O-H volatiles, in the form of either hydrous silicate melt or K-rich calcio-carbonatitic melt, are likely to be released from relatively hot subducting slabs. The observation of carbonate melt inclusion in cpx and garnet in deeply subducted carbonate-rich sediments [3] might be explained by our experimental results that carbonatite is the stable near-solidus sediment melt at deep sub-arc depths. [1] Thomsen, T.B. and Schmidt, M.W. 2008, EPSL 267, 17-31. [2] Grassi, D. and Schmidt, M.W. 2011, J. Petrol. 52, 765-789. [3] Korsakov, A.V., and Hermann, J. 2006, EPSL, 104-118.

Tsuno, K.; Dasgupta, R.; Danielson, L. R.; Righter, K.

2011-12-01

142

Pressure broadening of deuterium hydride lines in the 5-0 vibrational band between 77 and 295 K. [Application to outer planets H2He atmospheres  

Microsoft Academic Search

Pressure-broadening coefficients and temperature-dependence indices have been derived from self-broadening measurements for the R(0) and R(1) lines of deuterium hydride's 5-0 vibration-rotation band at 77-295 K. In addition to deriving a temperature-dependent index of 0.31 for these HD lines, a temperature dependence index which is not larger than the HD index is suggested for H2 vibrational-rotational line broadening. The small

W. H. Smith; C. E. Keffer; C. P. Conner

1991-01-01

143

Pressure Dependences of Gas Temperature and Electron Density in Microhollow Cathode Discharges in He and He+H2O Gases  

NASA Astrophysics Data System (ADS)

Microplasmas were generated using a cylindrical hollow cathode with a diameter of 0.5 mm and a length of 3 mm in He and He+H2O gases at pressures in the range of 20 to 765 Torr. Spectral line profiles of He I (667.8 nm) and H? (656.3 nm) were measured to determine the plasma parameters. Gas temperature and electron density were evaluated by the analysis of spectral line broadening. These parameters linearly increased with gas pressure in the range of 300 to 765 Torr. The gas temperatures and electron densities at atmospheric pressure were obtained to be 610 K and 5.0× 1014 cm-3 for He and 820 K and 3.5× 1014 cm-3 for He+H2O microplasmas, respectively. A comparison of these values with those obtained in a previous work [M. Miclea et al.: J. Phys. D 38 (2005) 1709] demonstrated that our device could generate high-density plasmas with a large volume and a high degree of nonequilibrium. The influences of an admixture of H2O on the discharge properties and plasma parameters were also discussed.

Yamasaki, Tsutomu; Namba, Shinichi; Takiyama, Ken; Nojima, Hideo

2012-12-01

144

Investigation of the noble gas solubility in H 2O-CO 2 bearing silicate liquids at moderate pressure II: the extended ionic porosity (EIP) model  

NASA Astrophysics Data System (ADS)

A semi-theoretical model is proposed to predict partitioning of noble gases between any silicate liquid and a H 2O-CO 2 gas phase with noble gas as a minor component, in a large range of pressures (at least up to 300 MPa). The model is based on the relationship between the concentration of dissolved noble gas and ionic porosity of the melt, found by Carroll and Stolper [Geochim. Cosmochim. Acta 57 (1993) 5039-5051] for H 2O-CO 2 free melts. It evaluates the effect of dissolved H 2O and CO 2 on the melt ionic porosity and, consequently on Henry's constants of noble gases. The fugacities of the noble gases in the H 2O-CO 2-noble gas mixtures are also considered in our equilibrium calculations of dissolved gas by using a modified Redlich-Kwong equation of state for the H 2O-CO 2-noble gas system. The formulated model (referred to as the extended ionic porosity model) clearly predicts a positive dependence of noble gas solubility on dissolved H 2O in melt, which becomes negligible when water concentration is higher than 3 wt%. Oppositely, noble gas solubility decreases as a consequence of increasing CO 2 in both basaltic and rhyolitic melts. The increase of noble gas solubility as a consequence of H 2O addition to the melt grows exponentially with the increase of the noble gas atomic size. As a result, although xenon solubility is much lower than the helium solubility in anhydrous melts, they become almost comparable at several percent of dissolved H 2O in the melt. On this basis, an exponential augmentation of the number of large free spaces in silicate liquid can be inferred in relation to increasing dissolved H 2O. Comparison between our predicted values and available experimental data [A. Paonita et al., Earth Planet. Sci. Lett. 181 (2000) 595-604] shows good agreement. At present, the EIP model is the unique tool which predicts how the main volatiles in magmatic systems affect the noble gas solubility in silicate melts, therefore it should be taken into account for future studies of noble gas fractionation in degassing natural magmas.

Nuccio, P. M.; Paonita, A.

2000-12-01

145

Line shape cross sections of HD immersed in He and H2 gas. I - Pressure broadening cross sections  

NASA Astrophysics Data System (ADS)

The results of two tests of the electronic potential energy surface of hydrogenlike systems are reported here, including the second virial coefficient of para hydrogen at low temperatures and HD-D2 elastic and inelastic differential scattering cross sections. Formulas are given for Dicke narrowing as well as for the line broadening and calculated shift cross sections. Close coupling calculations are performed for the R(0) and R(1) transitions of HD immersed in He and for the R(0) transition of HD immersed in H2. These cross sections are anticipated to be reliable at temperatures above 50 K.

Schaefer, Joachim; Monchick, Louis

1987-07-01

146

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

Microsoft Academic Search

H2O activities in concentrated NaCl solutions were measured in the ranges 600–900?C and 2–15 kbar and at NaCl concentrations\\u000a up to halite saturation by depression of the brucite (Mg(OH)2) – periclase (MgO) dehydration equilibrium. Experiments were made in internally heated Ar pressure apparatus at 2 and 4.2\\u000a kbar and in 1.91-cm-diameter piston-cylinder apparatus with NaCl pressure medium at 4.2, 7,

L. Y. Aranovich; R. C. Newton

1996-01-01

147

Effects of Sputtering Gas Pressure on Electrochromic Properties of Ni Oxyhydroxide Thin Films Prepared by Reactive Sputtering in H2O Atmosphere  

NASA Astrophysics Data System (ADS)

Ni oxyhydroxide (NiOOH) thin films were prepared by reactive sputtering in an atmosphere of H2O gas, and the effects of sputtering gas pressure on their electrochromic properties in KOH aqueous electrolyte were studied. The largest optical density change was obtained for the thin films deposited under high sputtering gas pressures of approximately 6.7 Pa because of their low film density and chemical composition close to NiOOH. Stable transmittance change during coloring and bleaching cycles was obtained for the film from the first cycle up to 100 cycles.

Abe, Yoshio; Ueta, Hideaki; Obata, Takeshi; Kawamura, Midori; Sasaki, Katsutaka; Itoh, Hidenobu

2010-11-01

148

Measurements of Surface Ocean Carbon Dioxide Partial Pressure During WOCE  

SciTech Connect

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

Weiss, R.F.

1998-10-15

149

The partial (1)H NMR spectra of Al-OH and molecular H(2)O in hydrous aluminosilicate glasses: Component-Resolved analysis of (27)Al-(1)H cross polarization and (1)H spin-echo MAS NMR spectra.  

PubMed

The Component-Resolved methodology was applied to (1)H spin-echo and (27)Al-(1)H cross polarization (CP) MAS NMR data of aluminosilicate glasses. The method was able to resolve two components with different T2 relaxation rates, hydroxyl groups (OH) and molecular water (H(2)O(mol)), from the spin-echo data and to determine partial spectra and the relative abundances of OH and H(2)O(mol). The algorithm resolved two to three components with different (27)Al-(1)H CP dynamics from the (27)Al-(1)H cross polarization data; the obtained partial NMR spectra for Al-OH are in excellent agreement with those obtained previously from the difference spectra between spectra with various contact times and confirm previous quantitative results and models for the Al-OH, Si-OH and H(2)O(mol) speciation (Malfait and Xue, 2010). PMID:20418075

Malfait, Wim J; Xue, Xianyu

2010-01-01

150

Evidence of PVT anomaly boundaries of water at high pressure from compression and NaCl.2H2O dehydration experiments  

NASA Astrophysics Data System (ADS)

Isothermal compression experiments on water have been performed between 0 to 80 °C and up to 1.3 GPa pressure. The compressibilities derived from the water compression experiments reveal a nonsmooth PVT behavior forming two anomaly boundaries. These boundaries originate at the melting line of ice III at about 0.25 GPa/-20 °C, and of ice VI at about 0.8 GPa/13 °C. Both boundaries have a positive sloped course separating three areas of different PVT properties of water. However, this P-T topology is obscured by an unresolved complication in the temperature range of 40-60 °C, which allows different topological interpretations of the data. As a cross-check for the compression experiment the dehydration boundary of sodium chloride-dihydrate (NaCl.2H2O) has been determined up to 1.5 GPa. The dehydration curve of NaCl.2H2O which traverses the two anomaly boundaries shows two inflections at the intersection, at 0.27 GPa/12 °C and at 0.77 GPa/22 °C, respectively. While the isothermal compressibility curves as well as the dP/dT course of the two anomaly boundaries give evidence of two densifications of water, the slope analysis of the inflections of the NaCl.2H2O dehydration curve suggests that the entropy change plays an important role. A recent model of water at high pressure conditions proposes a gradual structural transition from a low density water (LDW) at low pressures to a high density water (HDW) at high pressures. The compression data as well as the inflections of the dehydration boundary indicate, however, two discrete structural changes of water. Data comparison with that model suggests that the anomaly boundary at lower pressure corresponds to a volume fraction [VHDW/(VLDW+VHDW)] of 0.8, while the upper one approaches a volume fraction of 1.

Mirwald, P. W.

2005-09-01

151

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

NASA Astrophysics Data System (ADS)

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 1100°C at 3.2 GPa, the H2O-saturated peridotite melting reaction consumes olivine, clinopyroxene and garnet to produce orthopyroxene and melt, while above 1100°C 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.

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

2012-12-01

152

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)

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 1009°C, 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 1135-1090°C, 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 1075°C, plagioclase at 1025°C and at 1009°C, 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 1090°C. They are in equilibrium with hawaiitic melts (Mg# 0.51; CaO/Al 2O 3 = 0.73). At 1070°C, 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.

Métrich, Nicole; Rutherford, Malcolm J.

1998-04-01

153

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

SciTech Connect

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

Prof. Stratis V. Sotirchos

2000-09-01

154

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

NASA Technical Reports Server (NTRS)

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.

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

1997-01-01

155

A general model for predicting the solubility behavior of H2O-CO2 fluids in silicate melts over a wide range of pressure, temperature and compositions  

NASA Astrophysics Data System (ADS)

In this study, a general thermodynamically-based model is presented for the solubility of H2O-CO2 in silicate melts over a wide range of temperatures (from 933 K to 2003 K), pressures (up to 30 kbar) and melt compositions (from ultramafic to silicic, from metaluminous to peraluminous, and from subalkaline to peralkaline). Using an equation of state for the fluid phase that differs from previous models and deriving activity coefficients of species in silicate melts based on a specific interaction theory, this model can not only reproduce the data used for calibrations, but also predict the solubility well beyond the data range. The accuracies of solubilities predicted from this model are shown to be 7.2% for H2O and 9.7% for CO2, respectively, which are well within the experimental uncertainty. In addition, this model can be applied to the determination of equilibrium saturation pressure at which silicate melts are saturated with a fluid phase, modeling the evolution of ascending magmas through degassing processes, and elucidating the fluid-melt partitioning behavior of CO2 and H2O. An online version of this model is available at the website: http://calc.geochem-model.org/Test/Services/WebForm1.aspx and the program can be downloaded at: www.geochem-model.org/archives/programs.htm.

Duan, Xianzhe

2014-01-01

156

Wavelength-modulation spectroscopy near 2.5 ?m for H2O and temperature in high-pressure and -temperature gases  

NASA Astrophysics Data System (ADS)

The design and validation of a tunable diode laser (TDL) sensor for temperature and H2O in high-pressure and -temperature gases are presented. High-fidelity measurements are enabled through the use of: (1) strong H2O fundamental-band absorption near 2.5 ?m, (2) calibration-free first-harmonic-normalized wavelength-modulation spectroscopy with second-harmonic detection (WMS-2f/1f), (3) an experimentally derived and validated spectroscopic database, and (4) a new approach to selecting the optimal wavelength and modulation depth of each laser. This sensor uses two TDLs near 2,474 and 2,482 nm that were fiber coupled in free space and frequency multiplexed to enable measurements along a single line-of-sight. The lasers were modulated at 35 and 45.5 kHz, respectively, to achieve a sensor bandwidth of 4.5 kHz. This sensor was validated in a shock tube at temperatures and pressures ranging from 1,000 to 2,700 K and 8 to 50 bar. There the sensor resolved transients and recovered the known steady-state temperature and H2O mole fraction with a precision of 3.2 and 2.6 % RMS, respectively.

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

2014-01-01

157

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

PubMed

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

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

2014-01-21

158

Regeneration of zeolite catalysts deactivated in isobutane\\/butene alkylation: an in situ FTIR investigation at elevated H 2 pressure  

Microsoft Academic Search

The influence of temperature and hydrogen pressure on the regeneration of zeolite catalysts coked in the isobutane\\/butene alkylation is studied using in situ FTIR spectroscopy. By regeneration at suitable conditions, the activity of the catalyst for the alkylation reaction can be completely restored.

Rouven Josl; Raoul Klingmann; Yvonne Traa; Roger Gläser; Jens Weitkamp

2004-01-01

159

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

USGS Publications Warehouse

Pressure-temperature-composition (P, T, x) relations for the co-existing vapor and liquid phases in the system NaCl-H2O were determined experimentally at 450, 475, and 500??C. Data for each isotherm include P-x relations near the critical point and extend to the three-phase assemblage vapor-liquid-halite on the vapor side. On the liquid side the P-x data range from the critical point to the room-temperature halite saturation point (~25 wt.% NaCl). Critical pressures were calculated from measured pressures and compositions and classical theory. The results generally support the few data points of Urusova (1974, 1975) and O??lander and Liander (1950) but differ markedly from the extensive data of Sourirajan and Kennedy (1962). ?? 1987.

Rosenbauer, R. J.; Bischoff, J. L.

1987-01-01

160

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

PubMed

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

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

2010-05-01

161

High-temperature phase transitions in CsH2PO4 under ambient and high-pressure conditions: a synchrotron x-ray diffraction study.  

PubMed

To clarify the microscopic origin of the temperature-induced three-order-of-magnitude jump in the proton conductivity of CsH(2)PO(4) (superprotonic behavior), we have investigated its crystal structure modifications within the 25-300 degrees C temperature range under both ambient- and high-pressure conditions using synchrotron x-ray diffraction. Our high-pressure data show no indication of the thermal decomposition/polymerization at the crystal surface recently proposed as the origin of the enhanced proton conductivity [Phys. Rev. B 69, 054104 (2004)]. Instead, we found direct evidence that the superprotonic behavior of the title material is associated with a polymorphic structural transition to a high-temperature cubic phase. Our results are in excellent agreement with previous high-pressure ac impedance measurements. PMID:18035892

Botez, Cristian E; Hermosillo, Juan D; Zhang, Jianzhong; Qian, Jiang; Zhao, Yusheng; Majzlan, Juraj; Chianelli, Russell R; Pantea, Cristian

2007-11-21

162

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

SciTech Connect

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

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

2007-01-01

163

Analytic equation of state and thermodynamic properties for He-H 2 fluid mixtures over a wide range of pressures and temperatures  

NASA Astrophysics Data System (ADS)

The analytical expressions for the equation of state and thermo-physical quantities of Exp-6 fluid are derived based on the Ross variational perturbation theory and with the quantum effect taken into account. The formalism developed is applied to the He-H 2 mixtures. The agreement of numerical results of pressure and internal energy with MC simulations is shown far better than the analytic equation of state developed by [I. Ali, S.M. Osman, N. Sulaiman, R.N. Singh, Phys. Rev. E 69 (2004) 0561045]. The isotherms for pressure, internal energy and packing factor for five concentrations and four temperatures versus volume are calculated and analyzed. The numerical results for excess Gibbs free energy and entropy of mixing are presented. The variation of the excess Gibbs free energy of mixing, and the variation of the excess entropy of mixing versus temperature and pressure are different from and similar to that of Ali et al., respectively.

Xue, Xinying; Sun, Jiuxun

2007-08-01

164

Pressure-Temperature Phase Diagram of Quasi-One-Dimensional Hydrogen Bonded Ferroelectrics CsH2PO4 and CsD2PO4  

NASA Astrophysics Data System (ADS)

The pressure-temperature ( p-T) phase diagram of the hydrogen-bonded ferroelectric CsD2PO4 (DCDP) was studied by measurements of the dielectric constant. Two pressure-induced phases (phase III and phase IV) were observed. The phase III is an antiferroelectric phase stable at 0.65 GPa< p<1.05 GPa. The phase IV is a new phase stable at p>1.05 GPa, which is probably the other antiferroelectric (antiferrodistortive) phase. The temperature and pressure dependences of the dielectric constant were analyzed on the basis of the quasi-one-dimensional model. The results were compared with the results of CsH2PO4 (CDP) reported previously.

Deguchi, Kiyoshi; Azuma, Shinji; Kobayashi, Yuki

2005-09-01

165

Effects of complex formation in flowing fluids on the hydrothermal solubilities of minerals as a function of fluid pressure and temperature in the critical and supercritical regions of the system H 2O  

NASA Astrophysics Data System (ADS)

Consideration of Darcy's law and its analogs for open channel flow, together with the thermodynamics of hydrolysis reactions in hydrothermal systems indicates that either fluid pressure and/or isothermal mineral solubilities or both may decrease or increase in the direction of fluid flow, depending on the volume of reaction and the permeability or aperture, cross-sectional area, and angle of flow as a function of distance along the flow path. Recent progress in theoretical geochemistry has led to improved equations of state which can be used to calculate the standard partial molal thermodynamic properties of both charged and neutral inorganic and organic aqueous species at pressures and temperatures to 1000°C and 5 kb ( TANGER and HELGESON, 1988; SHOCK and HELGESON, 1988, 1990; SHOCK, et al., 1989, 1992; SVERJENSKY et al., 1992). Thermodynamic properties generated from these revised equations of state for the hydrolysis of minerals to form aqueous complexes at high pressures and temperatures indicate that the signs of the standard partial molal volume, enthalpy, and heat capacity of reaction depend primarily on the number of ligands in the complexes, as well as their charge. If polyligand complexes and/or certain neutral aqueous species appear on the right side of the reaction, the isobaric and isothermal partial derivatives of the logarithm of the equilibrium constant ( logK) at PSAT may tend toward infinity and negative infinity, respectively, as fluid pressure and temperature increase in the liquid phase region and approach the critical point of H 2O. This behavior results in positive values of ( ?logK/ ?T) p and negative values of ( ?logK/ ?P) T at supercritical pressures and temperatures. For example, thermodynamic calculations indicate that values of log K for reactions representing hydrothermal sulfide solubilities in the acid pH range where the predominant sulfide species is H 2S (aq) decrease with increasing fluid pressure to an increasing degree with increasing temperature, which is consistent with experimental data reported by HEMLEY et al. (1986, 1992). In contrast, ( ?logK/ ?T) p and ( ?logK/ ?P) T in the supercritical region may be negative and positive, respectively, for reactions representing sulfide solubilities in hydrothermal solutions with higher pHs where HS - predominates over H 2S, but only if the chloride concentration is low. The opposite may be the case in concentrated alkali chloride solutions, regardless of the pH. Similar calculations indicate that log K for the incongruent reaction of K-feldspar or other aluminosilicates with supercritical hydrothermal solutions to form quartz and A1(OH) 4-increases monotonically with increasing fluid pressure at constant temperature. However, the log K values maximize with increasing temperature at all pressures to at least ~3 kb, which is not true of the solubility of quartz. In contrast, values of log K for analogous reactions written in terms of Al 3+ or Al (OH) 2+ minimize with increasing temperature at constant pressure.

Helgeson, Harold C.

1992-08-01

166

Structural characterization of biomass pyrolysis tars\\/oils from eucalyptus wood waste: effect of H 2 pressure and sample configuration  

Microsoft Academic Search

Changes in yields and structural characteristics of tars\\/oils produced in the first stage of a two-stage fixed-bed (‘hot-rod’) reactor were determined as a function of sample configuration and pressure. The work included a critical evaluation of analytical methods for monitoring structural changes in biomass-derived liquids. Total volatile and tar\\/oil yields decreased and significant structural changes were observed with increasing sample

Ramesh V. Pindoria; Jin-Yee Lim; Janet E. Hawkes; Maria-Jesus Lazaro; Alan A. Herod; Rafael Kandiyoti

1997-01-01

167

Calculation of the thermodynamic and transport properties of aqueous species at high pressures and temperatures: Standard partial molal properties of organic species  

NASA Astrophysics Data System (ADS)

The standard partial molal properties of organic aqueous species at high pressures and temperatures can be predicted using an adaptation of a revised equation of state for inorganic aqueous ions and electrolytes (Tanger and Helgeson, 1988), together with correlations among equation of state parameters (SHOCK and Helgeson, 1988). These correlations include a charge-dependent relation between Born coefficients and the standard partial molal entropies of aqueous species at 25°C and 1 bar (SHOCK. et al., 1989). Thermodynamic calculations indicate that in the liquid phase the standard partial molal volumes (V¯°), heat capacities (C¯° p), and entropies (S¯°), as well as the apparent standard partial molal enthalpies of formation (?H°) of aqueous electrolytes with organic anions maximize with increasing temperature at Psat and approach - ? at the critical point of H 2O. In contrast, the corresponding properties of neutral organic aqueous species in the liquid phase minimize with increasing temperature Psat and approach ? at the critical point of H 2O. Predicted equilibrium constants for alkane solubilities and carboxylic acid dissociation reactions at elevated pressures and temperatures are in close agreement with experimental data reported in the literature, which supports the validity and generality of the equations of state as well as the predictive algorithms used in the calculations. As a consequence, high temperature/ pressure standard partial molal properties, as well as equilibrium constants and other reaction properties, can be predicted for reactions involving a wide variety of organic aqueous species for which little or no experimental data are available at temperatures > 25°C. Present capabilities permit such predictions to be made for hydrothermal and magmatic conditions at pressures and temperatures as high as 5 kb and 1000°C Psat represents pressures corresponding to liquid-vapor equilibrium for the system H 2O, except at temperature < 100°C where it refers to the reference pressure of 1 bar.

Shock, Everett L.; Helgeson, Harold C.

1990-04-01

168

The high-pressure stability of Mg-sursassite in a model hydrous peridotite: a possible mechanism for the deep subduction of significant volumes of H 2 O  

Microsoft Academic Search

The stability of the high-pressure phase Mg-sursassite, previously MgMgAl-pumpellyite, in ultramafic compositions has been determined in experiments in the system MgO-Al2O3-SiO2-H2O (MASH). The breakdown of Mg-sursassite + forsterite + enstatite to pyrope + vapour with increasing temperature was bracketed at 6.0 and 7.0 GPa. Below 6.0 GPa, Mg-sursassite + forsterite + vapour reacts to chlorite + enstatite. This reaction provides

Geoffrey D. Bromiley; Alison R. Pawley

2002-01-01

169

Characteristics of high-purity Cu thin films deposited on polyimide by radio-frequency Ar/H2 atmospheric-pressure plasma jet  

NASA Astrophysics Data System (ADS)

With a view to fabricating future flexible electronic devices, an atmospheric-pressure plasma jet driven by 13.56 MHz radio-frequency power is developed for depositing Cu thin films on polyimide, where a Cu wire inserted inside the quartz tube was used as the evaporation source. A polyimide substrate is placed on a water-cooled copper heat sink to prevent it from being thermally damaged. With the aim of preventing oxidation of the deposited Cu film, we investigated the effect of adding H2 to Ar plasma on film characteristics. Theoretical fitting of the OH emission line in OES spectrum revealed that adding H2 gas significantly increased the rotational temperature roughly from 800 to 1500 K. The LMM Auger spectroscopy analysis revealed that higher-purity Cu films were synthesized on polyimide by adding hydrogen gas. A possible explanation for the enhancement in the Cu film deposition rate and improvement of purity of Cu films by H2 gas addition is that atomic hydrogen produced by the plasma plays important roles in heating the gas to promote the evaporation of Cu atoms from the Cu wire and removing oxygen from copper oxide components via reduction reaction.

Zhao, P.; Zheng, W.; Meng, Y. D.; Nagatsu, M.

2013-03-01

170

Measurements of surface ocean carbon dioxide partial pressure during WOCE  

SciTech Connect

Progress during the past year of research under Measurements of Surface Ocean Carbon Dioxide Partial Pressure During WOCE'' has been significant. As was described in our previous progress report, the startup phase of this research was severely frustrated by delays in the US WOCE Hydrographic Program (WHP), which in turn were caused by delays in the mid-life refit of the R/V Knorr. As a result the high latitude southeastern Pacific work (WHP lines P19S and P16S) originally scheduled for the 1990 austral summer has still not been carried out. As a substitute, the smaller R/V Thomas Washington was pressed into service during mid-1991 to carry out lower-latitude portions of the WHP P16 and P17 lines - the TUNES Expedition. Because this ship is much smaller than the R/V Knorr, she could not carry a full complement of WHP programs and seagoing personnel and was restricted by her size and the time of year to lower-latitude work. Our original proposal for carbon dioxide measurements was designed to divide the work between legs in which we participated as part of the WHP dissolved CFC program (under separate NSF funding) and legs in which we entrusted the operation of our system to other CFC or carbon dioxide laboratories with expertise in gas chromatography. Since we were not involved in any CFC work on the substituted Washington expedition, and since all the seagoing programs on the Washington were additionally stressed by a shortage of people and space, this placed our carbon dioxide program at an unwelcome disadvantage. The preliminary results for carbon dioxide and nitrous oxide are shown. We are forced to rely on spotty manual observations and station CTD temperatures to reconstruct our equilibrator temperature solubility corrections for portions of that leg. We did not get our usual reliable data return, but the results were surely worth effort, especially for this vast and rarely-visited region of the world oceans.

Weiss, R.F.

1992-02-25

171

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

Microsoft Academic Search

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

2002-01-01

172

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

Microsoft Academic Search

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

2001-01-01

173

New developments in the theory of pressure-broadening and pressure-shifting of spectral lines of H 2O: The complex Robert-Bonamy formalism  

Microsoft Academic Search

Calculations of the halfwidth and line shift of water vapor perturbed by N2, O2, CO2, and H2 based on a complex implementation of the formalism of Robert and Bonamy are made. The potentials employ the leading terms of the electrostatic potential, a Lennard -Jones (6–12) atom-atom potential, and the induction and dispersion components of the isotropic potential. The dynamics of

Robert R. Gamache; Richard Lynch; Steven P. Neshyba

1998-01-01

174

Experimental and numerical investigation of the catalytic partial oxidation of CH 4 \\/ O 2 mixtures diluted with H 2 O and CO 2 in a short contact time reactor  

Microsoft Academic Search

The catalytic partial oxidation (CPO) of fuel-rich CH4\\/O2 mixtures, heavily diluted with H2O and CO2 (46.3% and 23.1% volumetric feed composition, respectively), was investigated experimentally and numerically at 5bar. Experiments were carried out in an ?8ms residence time prototype gas-turbine honeycomb reactor coated with a Rh\\/ZrO2 catalyst and included temperature measurements along the reactor and exhaust gas analysis. Simulations with

Adrian Schneider; John Mantzaras; Peter Jansohn

2006-01-01

175

Proton exchange membrane for DMFC and H 2\\/air fuel cells: Synthesis and characterization of partially fluorinated disulfonated poly(arylene ether benzonitrile) copolymers  

Microsoft Academic Search

Partially fluorinated disulfonated poly(arylene ether benzonitrile) random or statistical copolymers were synthesized by direct nucleophilic substitution copolymerization reactions. The 2,6-dichlorobenzonitrile and 3,3?-disulfonated 4,4?-difluorodiphenyl sulfone (SDFDPS) and controlled amounts of 4,4?-biphenol and hexafluoroisopropylidene diphenol (hexafluorobisphenol A, 6F) were used to produce partially fluorinated disulfonated copolymers with various degrees of fluorination (0–100mol% 6F). NMR analysis coupled with titration of sulfonated moieties confirmed

M. Sankir; Yu Seung Kim; Bryan S. Pivovar; James E. McGrath

2007-01-01

176

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

SciTech Connect

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.

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

1984-06-01

177

The effect of partial weight bearing in a walking boot on plantar pressure distribution and center of pressure.  

PubMed

Physicians routinely prescribe partial weight bearing in a walking boot following fractures of the lower limbs in order to produce the needed mechanical environment to facilitate healing. Plantar pressure measurements can provide key information regarding the mechanical environment experienced by lower limb bones. The effect of walking boots on plantar pressure distribution has been well reported, however, the combined effects of partial weight bearing and walking boots on plantar pressure distribution and center of pressure is unknown. Thirteen healthy volunteers with no known gait pathologies were fitted with a multi-pressure sensor insole that recorded their plantar pressure distribution during four walking trials: (i) normal walking, (ii) full weight bearing in a walking boot, (iii) 27 kg partial weight bearing in a walking boot and (iv) 9 kg partial weight bearing in a walking boot. Results demonstrated that changing from trial (i) to (iv) resulted in a posterior shift in weight distribution; the percentage of total weight experienced at the heel increased while the percentage of total weight experienced at the forefoot (both medial and lateral) and the hallux decreased. Center of pressure trajectories also shifted more posteriorly. Additionally, while in a walking boot the gait during full and partial weight bearing resulted in more even foot loading. PMID:22633830

North, Kylee; Potter, Michael Q; Kubiak, Erik N; Bamberg, Stacy J Morris; Hitchcock, Robert W

2012-07-01

178

Efficient representation of the absorption line blackbody distribution function for H2O, CO2, and CO at variable temperature, mole fraction, and total pressure  

NASA Astrophysics Data System (ADS)

The absorption line blackbody distribution function (ALBDF) is the primary tool used in the SLW model for calculating the weights of gray gases. The ALBDF for H2O, CO2, and CO is calculated rigorously using the HITEMP 2010 spectroscopic database. The line-by-line data is the basis for an updated and improved hyperbolic tangent correlation of the ALBDF, valid for temperatures ranging from 400 K to 3000 K and total pressures ranging from 0.1 atm to 50 atm. The correlations are first established at atmospheric pressure, and variable total pressure is accounted for as a shift from the atmospheric pressure calculation. Further, the line-by-line ALBDF data have been tabulated to directly represent the ALBDF; the ALBDF has been tabulated for discrete temperatures ranging from 300 K to 3000 K, mole fractions (where appropriate) from 0 to 1, and total pressures ranging from 0.1 atm to 50 atm. The data have been made available on the website http://albdf.byu.edu. Improvements made compared to other representations of the ALBDF include more rigorous generation of the detailed spectral absorption cross-section, correlation and tabulation of the ALBDF for CO, expansion to variable total pressure, and a higher temperature ceiling. The accuracy of the hyperbolic tangent correlation is characterized and regimes of relative lower accuracy identified, and it is demonstrated to be sufficiently accurate for engineering applications. The tabulated ALBDF data, which can be used directly in place of the correlation, are shown to be considerably more accurate than the correlation. There is an initial computational cost to read the tabulated data after which interpolation is used to obtain the ALBDF at specified conditions.

Pearson, John T.; Webb, Brent W.; Solovjov, Vladimir P.; Ma, Jiefu

2014-05-01

179

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

NASA Astrophysics Data System (ADS)

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.

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

2010-06-01

180

Experimental Study and Modeling of the Reaction H + O2 + M yields HO2 + M (M= Ar, N2, H2O) at Elevated Pressures and Temperatures Between 1050-1250K.  

National Technical Information Service (NTIS)

The H + O2 + M yields HO2 + M reaction was investigated at temperatures between 1050-1250 K and pressures from 7 to 152 bar behind reflected shock waves in gas mixtures of H2, 02, NO, and bath gases of Ar, N2, and H2O. Narrow linewidth laser absorption of...

R. W. Bates D. M. Golden R. K. Hanson C. T. Bowman

2001-01-01

181

Method and apparatus for monitoring oxygen partial pressure in air masks  

NASA Technical Reports Server (NTRS)

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.

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

2006-01-01

182

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

NASA Technical Reports Server (NTRS)

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.

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

2001-01-01

183

Generation and loss of reactive oxygen species in low-temperature atmospheric-pressure RF He + O2 + H2O plasmas  

NASA Astrophysics Data System (ADS)

This study focuses on the generation and loss of reactive oxygen species (ROS) in low-temperature atmospheric-pressure RF (13.56 MHz) He + O2 + H2O plasmas, which are of interest for many biomedical applications. These plasmas create cocktails of ROS containing ozone, singlet oxygen, atomic oxygen, hydroxyl radicals, hydrogen peroxide and hydroperoxyl radicals, i.e. ROS of great significance as recognized by the free-radical biology community. By means of one-dimensional fluid simulations (61 species, 878 reactions), the key ROS and their generation and loss mechanisms are identified as a function of the oxygen and water content in the feed gas. Identification of the main chemical pathways can guide the optimization of He + O2 + H2O plasmas for the production of particular ROS. It is found that for a given oxygen concentration, the presence of water in the feed gas decreases the net production of oxygen-derived ROS, while for a given water concentration, the presence of oxygen enhances the net production of water-derived ROS. Although most ROS can be generated in a wide range of oxygen and water admixtures, the chemical pathways leading to their generation change significantly as a function of the feed gas composition. Therefore, care must be taken when selecting reduced chemical sets to study these plasmas.

McKay, K.; Liu, D. X.; Rong, M. Z.; Iza, F.; Kong, M. G.

2012-05-01

184

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

Microsoft Academic Search

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

A. Robertson

2003-01-01

185

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

Microsoft Academic Search

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

Archie Robertson

2004-01-01

186

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

Microsoft Academic Search

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

A. Robertson

2002-01-01

187

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

Microsoft Academic Search

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

2003-01-01

188

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

Microsoft Academic Search

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

Archie Robertson

2002-01-01

189

Absolute calibration of OH density in a nanosecond pulsed plasma filament in atmospheric pressure He-H2O: comparison of independent calibration methods  

NASA Astrophysics Data System (ADS)

The absolute density of OH radicals generated in a nanosecond pulsed filamentary discharge in atmospheric pressure He +0.84% H2O is measured independently by UV absorption and laser induced fluorescence (LIF) calibrated with Rayleigh scattering. For the calibration of LIF with Rayleigh scattering, two LIF models, with six levels and four levels, are studied to investigate the influence of the rotational and vibrational energy transfers. In addition, a chemical model is used to deduce the OH density in the afterglow from the relative LIF intensity as function of time. The different models show good correspondence and by comparing these different methods, the accuracy and the effect of assumptions on the obtained OH density are discussed in detail. This analysis includes an analysis of the sensitivity to parameters used in the LIF models.

Verreycken, T.; van der Horst, R. M.; Sadeghi, N.; Bruggeman, P. J.

2013-11-01

190

Pressure broadening and shift of the cesium D2 transition by the noble gases and N2, H2, HD, D2, CH4, C2H6, CF4, and He3 with comparison to the D1 transition  

Microsoft Academic Search

The pressure broadening and shift rates for the cesium D2 (62P3\\/2 <-- 62S1\\/2) transition with the noble gases and N2, H2, HD, D2, CH4, C2H6, CF4, and He3 were obtained for pressures less than 300 Torr at a temperature of 40°C by means of laser absorption spectroscopy. The collisional broadening rate gammaL for He, Ne, Ar, Kr, Xe, N2, H2,

Greg A. Pitz; Charles D. Fox; Glen P. Perram

2010-01-01

191

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

NASA Astrophysics Data System (ADS)

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

Chevychelov, Vitaly

2014-05-01

192

Oxidation behaviour of zirconium diboride–silicon carbide ceramic composites under low oxygen partial pressure  

Microsoft Academic Search

The oxidation behaviour of ZrB2-based ceramics under low oxygen partial pressure ranged from 0.5 to 1.5kPa was investigated. Low oxygen partial pressure was found to have remarkable effect on phase composition of the surface and the structures of oxide scale. And the thickness and microstructures of oxide scale was characterized by using scanning electron microscopy and X-ray diffraction analysis. The

Chengyi Tian; Dong Gao; Yue Zhang; Chunlai Xu; Yang Song; Xiaobin Shi

2011-01-01

193

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

NASA Technical Reports Server (NTRS)

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.

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

1992-01-01

194

Application of wavelength-scanned wavelength-modulation spectroscopy H2O absorption measurements in an engineering-scale high-pressure coal gasifier  

NASA Astrophysics Data System (ADS)

A real-time, in situ water vapor (H2O) sensor using a tunable diode laser near 1,352 nm was developed to continuously monitor water vapor in the synthesis gas of an engineering-scale high-pressure coal gasifier. Wavelength-scanned wavelength-modulation spectroscopy with second harmonic detection (WMS-2f) was used to determine the absorption magnitude. The 1f-normalized, WMS-2f signal (WMS-2f/1f) was insensitive to non-absorption transmission losses including beam steering and light scattering by the particulate in the synthesis gas. A fitting strategy was used to simultaneously determine the water vapor mole fraction and the collisional-broadening width of the transition from the scanned 1f-normalized WMS-2f waveform at pressures up to 15 atm, which can be used for large absorbance values. This strategy is analogous to the fitting strategy for wavelength-scanned direct absorption measurements. In a test campaign at the US National Carbon Capture Center, the sensor demonstrated a water vapor detection limit of ~800 ppm (25 Hz bandwidth) at conditions with more than 99.99 % non-absorption transmission losses. Successful unattended monitoring was demonstrated over a 435 h period. Strong correlations between the sensor measurements and transient gasifier operation conditions were observed, demonstrating the capability of laser absorption to monitor the gasification process.

Sun, Kai; Sur, Ritobrata; Jeffries, Jay B.; Hanson, Ronald K.; Clark, Tommy; Anthony, Justin; Machovec, Scott; Northington, John

2014-05-01

195

STUDENT AWARD FINALIST: Simulation of the ignition of a H2-air mixture at atmospheric pressure by a nanosecond repetitively pulsed discharge  

NASA Astrophysics Data System (ADS)

Nanosecond repetitively Pulsed Discharges (NRPD) have a great potential for many applications at atmospheric pressure due to their ability to produce efficiently many reactive chemical species at a low energy cost. Recent measurements have shown that in the ``spark'' regime of NRP discharges, an ultra-fast local heating of the gas could be obtained. This effect is of great interest for applications as flow control and plasma assisted combustion (PAC). In this work, we have carried out 2D numerical simulations of the coupling of the NRP discharge in air at atmospheric pressure in a point-point geometry with the background air. In particular, we have simulated shock waves generated by the NRPD in the spark regime and we have compared our results with experiments. Then, we have studied the production of active species by the NRP discharge in the spark regime. Finally, for plasma assisted combustion applications, we have simulated the ignition of a flame kernel in a lean H2-air mixture by a spark NRPD. Based on this work, the relative importance for the combustion ignition of gas heating and production of active species by the spark NRP is discussed.

Tholin, Fabien; Bourdon, Anne

2012-10-01

196

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

NASA Astrophysics Data System (ADS)

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

Foster, Justin; Miller, Richard

2011-11-01

197

Thermodynamic and transport properties of a ternary Ar H2 He mixture out of equilibrium up to 30 000 K at atmospheric pressure  

NASA Astrophysics Data System (ADS)

This paper is devoted to a study of the effect of the non-equilibrium parameter thgr = Te/Th on the plasma composition and thermodynamic and transport properties of ternary mixtures Ar-H2-He, which are commonly used in dc plasma spraying. Calculations are performed in the temperature range 300-30 000 K and at atmospheric pressure. First, to calculate the non-equilibrium composition, two techniques are used: the equilibrium constant (van de Sanden) and pseudo-kinetic methods. Second, the specific heat at constant pressure is obtained by a five-point numerical differentiation of the specific mass enthalpy. Third, the most recent data of potential interactions or elastic differential cross sections are carefully examined in order to choose the most appropriate ones to determine the collision integrals. Finally a convergence study of transport coefficients (thermal conductivity, viscosity and electrical conductivity) is conducted to evaluate the influence of the non-equilibrium parameter thgr on this convergence. It has to be pointed out that the latter has a non-negligible influence on transport coefficients.

Aubreton, J.; Elchinger, M. F.; Fauchais, P.; Rat, V.; André, P.

2004-08-01

198

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

NASA Technical Reports Server (NTRS)

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.

Holy, John A.

1993-01-01

199

Azolla-Anabaena azollae Relationship: V. N(2) Fixation, Acetylene Reduction, and H(2) Production.  

PubMed

In order to characterize the reactions catalyzed by nitrogenase in the Azolla-Anabaena association, (15)N(2) fixation, C(2)H(2) reduction, and ATP-dependent H(2) production were measured in both the Azolla-Anabaena complex and in the alga isolated from the complex.The rate of reduction of substrates and of ATP-dependent H(2) evolution was determined at various partial pressures of C(2)H(2) and N(2). A pC(2)H(2) of 0.1 atm was nearly optimal for C(2)H(4) production and inhibited H(2) production by 95%. The ratio of C(2)H(2) reduced to N(2) fixed was determined as a function of constant pC(2)H(2) (0.1 atm) and variable pN(2). This ratio decreased with increasing pN(2) and the decrease was correlated with less H(2) production. Ratios obtained at N(2) partial pressures of approximately 0.3, 0.6, and 0.8 atm, respectively, were 3.2, 2.0, and 1.7 for the association and 4.4, 3.0, and 2.5 for the isolated symbiont. Rates obtained for C(2)H(2) reduction, N(2) fixation, and H(2) production were used to obtain an expression of the electron balance in vivo. PMID:16659984

Peters, G A; Toia, R E; Lough, S M

1977-06-01

200

In-situ Raman spectroscopic study of aluminate speciation in H2O-KOH solutions at high pressures and temperatures  

NASA Astrophysics Data System (ADS)

The solubility of corundum in H2O is low even at high pressure and temperatures. Therefore, it is commonly assumed that alumina remains essentially immobile during fluid-rock interaction. However, field and experimental evidence suggests that alumina solubility is strongly enhanced in the presence of silica as well as in alkaline solutions. In order to understand what controls the alumina solubility and how it is enhanced as a function of fluid composition, we conducted Raman-spectroscopic study of Al speciation in aqueous fluids at high pressure and temperature. Experiments were carried out in an externally heated hydrothermal diamond-anvil cell equipped with low-fluorescence diamonds and iridium gaskets. Raman spectra were collected with a Horiba Jobin-Yvon Labram HR spectrometer using the 514 nm line of an argon laser for excitation. In a first series of experiments, the speciation of alumina was studied in a 1 M KOH solution in equilibrium with corundum up to 700 oC and ~1 GPa. The Raman spectra show a prominent band at 618 cm-1 interpreted to arise from Al-O stretching vibrations associated with the tetrahedral [Al(OH)4]1- species. At higher pressure and temperature, an additional vibrational mode appears in the spectra at 374 cm-1 (full width at half maximum ~ 20 cm-1). This feature is tentatively attributed to [(OH)3Al-O-Al(OH)3]2- (Moolenaar et al. 1970, Jour. Phys. Chem., 74, 3629-3636). No evidence for KAl(OH)4 was observed, consistent with piston cylinder experiments at 700 oC and 1 GPa (Wohlers & Manning, 2009, Chem. Geol., 262, 310). Upon cooling from high-pressure and high temperature, slow kinetics of corundum regrowth lead to oversaturation in the solutions, as evidenced by sharp peaks at 930 and 1066 cm-1 observed upon cooling. These features are probably due to colloidal aluminum hydroxide. The results provide the first evidence for aluminate polymerization at high pressure and temperature, and offer insights into the causes for enhancement of corundum solubility in alkaline solutions.

Mookherjee, M.; Keppler, H.; Manning, C. E.

2009-12-01

201

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

NASA Astrophysics Data System (ADS)

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

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

2011-08-01

202

Low-Pressure Partial-Discharge Measurements: Monitoring the Insulation Integrity of Aircraft Power Wiring Systems  

Microsoft Academic Search

Partial-discharge (PD) characteristics in three gases (air, argon and helium) at pressures between 101 kPa (760 Torr) and about 0.27 kPa (2 Torr) under 60-Hz ac energization were studied. Measurements for two representative electrode configurations showed that the electrical characteristics of PD (specifically, electric pulse waveforms) at low pressures differ significantly from those at sea-level pressures. Difficulties in obtaining accurate

D. L. Schweickart; D. F. Grosjean; D. G. Kasten; S. A. Sebo; X. Liu

2008-01-01

203

The stability and Raman spectra of ikaite, CaCO3??6H2O, at high pressure and temperature  

USGS Publications Warehouse

Raman analyses of single crystals of ikaite, CaCO3??6H2O, synthesized in a diamond-anvil cell at ambient temperature yield spectra from 0.14 to 4.08 GPa; the most intense peaks are at 228 and 1081 cm-1 corresponding to Eg (external) and A1g (internal) modes of vibrations in CO32- ions, respectively. These are in good agreement with Raman spectra previously published for ikaite in powder form at ambient temperature and pressure. Visual observations of a sample consisting initially of a mixture of calcite + water in a hydrothermal diamond-anvil cell yielded a P-T phase diagram up to 2 GPa and 120 ??C; the boundary for the reaction ikaite ??? aragonite + water has a positive slope and is curved convexly toward the aragonite + water field similar to typical melt curves. This curvature can be explained in terms of the Clapeyron equation for a boundary between a solid phase and a more compressible liquid phase or largely liquid phase assemblage.

Shahar, A.; Bassett, W. A.; Mao, H. -K.; Chou, I. -M.; Mao, W.

2005-01-01

204

Thermodynamic description of equilibria in mixed fluids (H 2 O-nonpolar gas) in a wide range of temperatures (25–700°C) and pressures (1–5000 bar)  

Microsoft Academic Search

A new method is proposed for calculating equilibria in mixed multicomponent systems H2O-nonpolar gas at high temperatures and pressures. The method is based on calculation of electrostatic interactions between\\u000a a solute component and surrounding molecules of a solvent (H2O). The SUPCRT98 database and the Helgeson-Kirkham-Flowers equation of state for components of an aqueous solution were used\\u000a for computer realization of

N. N. Akinfiev; A. V. Zotov

2006-01-01

205

Determination of permeabilities for two gases from recording the partial pressure of one gas.  

PubMed

When a flexible diffusion layer separates two closed gas chambers containing different mixtures of several gases, the different permeabilities of the layer for these gases lead to differences in the total gas pressures of the two chambers resulting in bulging of the layer and consequent changes in the chamber volumes. Application of the gas laws to binary gas mixtures provides two equations relating the partial pressure changes of one gas in any of the two chambers to the partial pressure difference between the two chambers across the layer. This permits the calculation of the two unknown factors, permeability (or Krogh's diffusion coefficient) of the layer for the measured gas and the permeability ratio of the two gases. Thus the permeabilities of both gases can be determined from recording the partial pressure of one of the gases only. We filled the gas chambers with different mixtures of oxygen and a second gas (nitrogen or carbon dioxide) at atmospheric pressure, closed the chambers, and measured the diffusion of the gases across thin (12-500 microns) layers of various materials by recording the oxygen partial pressure in both chambers with polarographic oxygen electrodes. Permeabilities of these layers for oxygen and the other gas were determined for plastic layers (MEM213, Silastic, Teflon), as well as water and methemoglobin solutions either in a fluid layer or soaked in Millipore filters. The data agreed well with those obtained from other studies in most cases. PMID:3763378

Hoofd, L; de Koning, J; Kreuzer, F; Lamboo, A

1986-09-01

206

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

NASA Technical Reports Server (NTRS)

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.

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

1973-01-01

207

Partial pressure analysis of CF/sub 4//O/sub 2/ plasmas  

SciTech Connect

This work will examine a simple down-stream sampling arrangement for effluent analysis in a typical plasma environment. This method offers the advantage of simplicity when compared to the need for extraction optics and energy analyzing stages required for flux-type analysis. In addition, partial pressure analysis provides information on the plasma/surface interactions occurring over the entire surface area of the reactor as opposed to just those occurring at the sampling orifice in flux-type analysis. This fact makes partial-pressure analysis particularly attractive for such tasks as plasma-etch end-point monitoring. In this example, experimental partial-pressure measurements of a CF/sub 4//O/sub 2/ plasma are presented as is the application of the technique to plasma etch end-point detection. 12 refs., 2 figs.

Martz, J.C.; Hess, D.W.; Anderson, W.E.

1989-01-01

208

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

Microsoft Academic Search

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

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

2006-01-01

209

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

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.

Chou, I. -M.; Sterner, S. M.; Pitzer, K. S.

1992-01-01

210

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

NASA Astrophysics Data System (ADS)

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.

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

2012-12-01

211

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

Microsoft Academic Search

The FT-Raman spectra and the pressure dependence of the infrared spectra of the hydrated and anhydrous forms of dicalcium phosphate, CaHPO4·2H2O and CaHPO4, have been studied. The hydrated salt exhibits a phase transition at 21 kbar (1.0 kbar=0.1 Gpa) but no high pressure transition was observed for anhydrous dicalcium phosphate. The O–H stretching frequencies of the water molecules in CaHPO4·2H2O

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

1999-01-01

212

A Direct Confirmation of the Standard Method of Estimating Intercellular Partial Pressure of CO2  

PubMed Central

The partial pressure of CO2 inside leaves of several species was measured directly. Small gas exchange chambers were clamped above and below the same section of an amphistomatous leaf. A flowing gas stream through one chamber allowed normal CO2 and water vapor exchange. The other chamber was in a closed circuit consisting of the chamber, an infrared gas analyzer, and a peristaltic pump. The CO2 in the closed system rapidly reached a steady pressure which it is believed was identical to the CO2 pressure inside the leaf, because there was no flux of CO2 across the epidermis. This measured partial pressure was in close agreement with that estimated from a consideration of the fluxes of CO2 and vapor at the other surface.

Sharkey, Thomas D.; Imai, Katsu; Farquhar, Graham D.; Cowan, Ian R.

1982-01-01

213

A NUMERICAL INVESTIGATION OF METHANE AIR PARTIALLY PREMIXED FLAMES AT ELEVATED PRESSURES  

Microsoft Academic Search

A numerical investigation of high pressure, counterflow methane-air partially premixed flames (PPFs) is presented to characterize the effect of pressure on flame structure. Four different mechanisms, namely GRI-2.11, GRI-3.0, the San Diego, and the C2 mechanisms have been examined. The mechanisms have been validated by comparing the predicted laminar flame speeds with experimental data. While there is excellent agreement between

SIBENDU SOM; SURESH K. AGGARWAL

2007-01-01

214

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

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.

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

2014-01-01

215

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

Microsoft Academic Search

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

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

2005-01-01

216

Partial discharges at sub-atmospheric pressures — insulation evaluation procedures for aerospace applications  

Microsoft Academic Search

Partial discharge (PD) testing in a low pressure environment is a diagnostic method for evaluating the integrity of electrical insulation in aircraft and spacecraft capable of operating at high altitudes. This evaluation is essential in order to ensure the reliable performance and proper functioning of power system components of aerospace equipment under operating conditions. The paper outlines an experimental PD

D. G. Kasten; S. A. Sebo; X. Liu

2007-01-01

217

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

NASA Astrophysics Data System (ADS)

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

Safonov, O.; Kozhukhantseva, S.

2012-04-01

218

Noninvasive monitoring of carbon dioxide: A comparison of the partial pressure of transcutaneous and end-tidal carbon dioxide with the partial pressure of arterial carbon dioxide  

Microsoft Academic Search

This study compares two noninvasive techniques for monitoring the partial pressure of carbon dioxide (Pco2) in 24 anesthetized\\u000a adult patients. End-tidal PCO2 (PETCO2) and transcutaneous Pco2 (PtcCO2) were simultaneously monitored and compared with arterial Pco2 (PaCO2) determined by intermittent analysis of arterial blood samples. PETCO2 and PtcCO2 values were compared with PaCO2 values corrected to patient body temperature (PaC02T) and

Can Q. Phan; Kevin K. Tremper; Steven E. Lee; Steven J. Barker

1987-01-01

219

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

Microsoft Academic Search

Melt inclusions indicate that the basaltic-hawaiitic magmas from Mt Etna (Sicily) contained up to 2.3 wt% H2O dissolved in the melt, prior to eruption. The effect of H2O degassing during magma ascent has been experimentally constrained between 1135 and 1009°C, for PH2O = Ptotal varying from 800 to 270 bars. The starting material was a primitive hawaiitic lava sample (MgO

Nicole Métrich; Malcolm J Rutherford

1998-01-01

220

H2O Adsorption Kinetics on Smectites  

NASA Technical Reports Server (NTRS)

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.

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

2000-01-01

221

Oxidation of C/SiC Composites at Reduced Oxygen Partial Pressures  

NASA Technical Reports Server (NTRS)

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.

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

2007-01-01

222

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

Microsoft Academic Search

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 65°C by means of laser absorption spectroscopy. The collisional broadening rate, gammaL , for He, Ne, Ar,

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

2009-01-01

223

Germination, Respiration, and Adenylate Energy Charge of Seeds at Various Oxygen Partial Pressures  

PubMed Central

The effect of O2 partial pressure on the germination and the respiration of 12 cultivated species was studied. The reciprocal of the time necessary to observe rootlet emergence in 50% of the seeds was used to approach the germination rate. The maximum germination and respiration rates were reached in most seeds at O2 pressures close to that of air. Decreasing the O2 pressure produced a gradual decrease of the germination rate. The seeds could be classed in two groups according to their response to low O2 pressures. Group I includes lettuce, sunflower, radish, turnip, cabbage, flax, and soybean: at O2 pressures close to 2 kilopascals, the germination in this group was stopped and the adenylate energy charge was lower than 0.6. Group II includes rice, wheat, maize, sorghum, and pea. The germination rate of these seeds was also gradually decreased by lowering the O2 partial pressure but germination still occured, very slowly, at 0.1 kilopascal; the adenylate energy charge remained higher than 0.6. These differences in the germination rates and adenylate energy charge values could not be explained by differences in the sensitivity of respiration to O2.

Al-Ani, Ali; Bruzau, Francoise; Raymond, Philippe; Saint-Ges, Veronique; Leblanc, Jean Marc; Pradet, Alain

1985-01-01

224

A two-electrode sensor cell for CO detection in a H 2-rich gas  

Microsoft Academic Search

A two-electrode chemical cell, with a proton-conducting polymer as electrolyte, is used to detect the CO concentration in a H2-rich gas. The anode is exposed to the gas flow, while the cathode is immersed in water to retain the polymer conductivity. The disturbance of the H2-oxidation current is a measure of the partial CO pressure. The proposed model describes well

W. G. Planje; G. J. M. Janssen; M. P. de Heer

2004-01-01

225

Spatial and seasonal features of the climatic distribution of the total content and partial pressure of ozone  

Microsoft Academic Search

Longitudinal irregularities, features of the seasonal and latitudinal variations at different longitudes, and interhemispheric variations in the total content and partial pressure of ozone are considered on the basis of previously developed models for the total content and vertical distribution of ozone. The latitudinal and longitudinal variations of total ozone content and the variations of partial ozone pressure are illustrated.

V. I. Bekoriukov

1991-01-01

226

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

NASA Technical Reports Server (NTRS)

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.

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

1979-01-01

227

{13}C-NMR study of the S = 1/2 antiferromagnetically coupled spin chain compound {[PM{\\cdot}Cu(NO_3)_2{\\cdot}(H_2O)_2]textit{n}} under pressure  

NASA Astrophysics Data System (ADS)

We present an investigation of the S=1/2 antiferromagnetically coupled Heisenberg spin chain [ PM\\cdotCu(NO3)2\\cdot(H2O)2] n (PM = pyrimidine = C4N2H4) with field-induced gap by means of 13C NMR experiments. From the measurements of NMR shift and spin-lattice relaxation rate 1/T1 we extract the magnetic exchange parameter J/kB and the size of the spin gap ? as function of pressure. The observed pressure response is discussed in comparison to related molecular materials. Key words. NMR, hydrostatic pressure, 1-D HAF, field-induced spin gap

Wolter, A. U. B.; Wzietek, P.; Süllow, S.; Litterst, F. J.; Auban-Senzier, P.; Jérome, D.; Feyerherm, R.; Klauss, H.-H.

2004-04-01

228

Oxygen partial pressure dependent electrical conductivity type conversion of phosphorus-doped ZnO thin films  

NASA Astrophysics Data System (ADS)

In this study, the oxygen partial pressure dependent physical properties of phosphorous-doped ZnO thin films were investigated. All thin films, grown on Al2O3(0?0?0?1) substrates using pulsed laser deposition, exhibited (0?0?2) orientation regardless of the oxygen partial pressure. However, as the oxygen partial pressure increased, the degree of crystallinity and the concentration of oxygen vacancies in the films decreased. All the thin-film samples showed n-type characteristics except for a sample grown at 100 mTorr, which exhibited p-type characteristics. The optical band gap energy also changed with the oxygen partial pressure. The feasible microscopic mechanism of conductivity conversion is explained in terms of the lattice constant, crystallinity, and the relative roles of the substituted phosphorous in the Zn-site and/or oxygen vacancies depending on the oxygen partial pressure.

Lee, S.; Jeong, Y. E.; Lee, D.; Bae, J. S.; Lee, W. J.; Park, K. H.; Bu, S. D.; Park, S.

2014-02-01

229

Oxidation of C/SiC Composites at Reduced Oxygen Partial Pressures  

NASA Technical Reports Server (NTRS)

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.

Opila, Elizabeth J.; Serra, Jessica

2009-01-01

230

Measured pressure distributions inside nonaxisymmetric nozzles with partially deployed thrust reversers  

NASA Technical Reports Server (NTRS)

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.

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

1987-01-01

231

Strength and ductility of four dry igneous rocks at low pressures and temperatures to partial melting  

Microsoft Academic Search

Energy extraction from magma requires stable boreholes at relatively shallow depths (< 10 km) in rocks at temperatures of the order of 1000°C. Accordingly, the failure strengths, strains at failure, and associated deformation mechanisms of room-dry andesite, besalt, granodiorite, and obsidian are determined at temperatures to partial melting (> 1050°C), at confining pressures of 0 and 50 MPa, and strain

M. Friedman; J. Handin; N. G. Higgs; J. R. Lantz

1979-01-01

232

Microstructure and fatigue of partial pressure carburized SAE 8620 and EX 24 steels  

Microsoft Academic Search

SAE 8620 and EX 24 steels have been partial pressure carburized at 930 °C (1710 °F) and 1050 °C (1920 °F), and tested in bending\\u000a fatigue in both as-quenched and reheated conditions. Endurance limits at or above 827 MPa (120 Ksi) were measured in carburized\\u000a specimens not subzero cooled. No surface oxidation was noted, but a high carbon content retained

Kevin D. Jones; George Krauss

1979-01-01

233

A partial pressure monitor and controller for stable ozone flow from a silica gel trap  

NASA Astrophysics Data System (ADS)

A new ozone trapping system designed for safe and consistent delivery to a reaction vessel is described. Silica gel is used to trap the ozone because of its known safety advantages over traps that store ozone in liquid form. The new design is free of any liquid baths, such as freon or flammable solvents. A circuit design for monitoring and controlling the ozone partial pressure of 6-25 Torr is also described.

Stevens, R. E.; Hsiao, C.-W.; Le, Linh; Curro, N. J.; Monton, B. J.; Chang, B.-Y.; Kung, C.-Y.; Kittrell, C.; Kinsey, J. L.

1998-06-01

234

Photosynthesis and growth response of almond to increased atmospheric ozone partial pressures  

Microsoft Academic Search

Uniform nursery stock of five almond cultivars [Prunus dulcis (Mill) D.A. Webb syn. P. amygdalus Batsch, cv. Butte, Carmel, Mission, Nonpareil, and Sonora] propagated on peach (P. domstica L. Batsch.) rootstock were exposed to three different atmospheric ozone (O[sub 3]) partial pressures. The trees were planted in open-top fumigation chambers on 19 Apr. 1989 at the University of California Kearny

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

2009-01-01

235

Prediction of arterial partial pressure of oxygen with pulse oxygen saturation measurements  

Microsoft Academic Search

Objectives: We studied 22 neonates with gestational ages from 26 to 40 weeks to determine how accurately pulse oxygen saturation (SpO2) could predict arterial partial pressure of oxygen (PaO2) and how much time and effort would be required to achieve and maintain a desired SpO2 value.Study design: SpO2 was maintained at 90%, 92%, 94%, 96%, and 98% by adjustment of

Julia Brockway; William W. Hay

1998-01-01

236

Noninvasive Oxygen Partial Pressure Measurement of Human Body Fluids In Vivo Using Magnetic Resonance Imaging1  

Microsoft Academic Search

Rationale and Objectives. The oxygen partial pressure (pO2) of human body fluids reflects the oxygenation status of sur- rounding tissues. All existing fluid pO2 measurements are invasive, requiring either microelectrode\\/optode placement or fluid removal. The purpose of this study is to develop a noninvasive magnetic resonance imaging method to measure the pO2 of human body fluids. Materials and Methods. We

Greg Zaharchuk; Reed F. Busse; Guy Rosenthal; Geoffery T. Manley; Orit A. Glenn; William P. Dillon

237

Tumor-dependent Kinetics of Partial Pressure of Oxygen Fluctuations during Air and Oxygen Breathing  

Microsoft Academic Search

The primary purpose of this study was to examine the kinetics of partial pressure of oxygen (pO2) fluctuations in fibrosarcoma (FSA) and 9L tumors under air and O2 breathing conditions. The overall hypothesis was that key factors relating to oxygen tension fluctuations would vary be- tween the two tumor types and as a function of the oxygen content of the

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

2004-01-01

238

Decompression and H 2 O exsolution driven crystallization and fractionation: development of a new model for low-pressure fractional crystallization in calc-alkaline magmatic systems  

Microsoft Academic Search

Magma ascent, decompression-induced H2O exsolution and crystallization is now recognized as an important process in hydrous subduction zone magmas. During the course\\u000a of such a process calculations suggest that the ascent rate of a degassing and crystallizing mafic magma will be greater than\\u000a crystal settling velocities. Thus, any crystals formed as a consequence of volatile exsolution will remain suspended in

James Gerald Brophy

2009-01-01

239

BRIEF COMMUNICATIONS: Quasi-cw emission of violet stimulated radiation by N2+ ions in a high-pressure HeN2-H2 mixture  

Microsoft Academic Search

High-power quasi-cw lasing was observed for the first time in the near ultraviolet (lambda = 391 nm) and visible (lambda = 428 nm) parts of the spectrum. The emission was due to molecular nitrogen ions and it was observed when an He-N2-H2 mixture was excited by an electron beam. An increase in the lasing energy was observed when an electron-beam-controlled

N. G. Basov; A. Yu Aleksandrov; V. A. Danilychev; V. A. Dolgikh; O. M. Kerimov; Yu F. Myznikov; I. G. Rudoi; A. Yu Samarin; A. M. Soroka

1985-01-01

240

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

NASA Astrophysics Data System (ADS)

Plate spreading at the mid-ocean ridges is accompanied by intrusion of dikes and eruption of lava along the ridge axis. It has been suggested that the depth of magma chambers that feed the flows and dikes is related to the rate of spreading. As part of a larger effort to examine this hypothesis, we determined the depths of magma chambers beneath the intermediate spreading Juan de Fuca Ridge (JdF) which extends from the Blanco fracture zone at about 44.5 degrees North to the Triple junction of the JdF, Nootka Fault, and the Socanco fracture zone at 48.7 degrees North. Pressures of partial crystallization were determined by comparing the compositions of natural liquids (glasses) with those of experimental liquids in equilibrium with olivine, plagioclase, and clinopyroxene at different pressures and temperatures using the method described by Kelley and Barton (2008). Chemical analyses mid-ocean ridge basalts glasses sampled from along the JdF were used as liquid compositions. Samples with anomalous chemical compositions and samples that yielded pressures associated with unrealistically large uncertainties were filtered out of the database. The calculated pressures for the remaining 533 samples were used to calculate the depths of partial crystallization and to identify the likely location of magma chambers. Preliminary results indicate that the pressure of partial crystallization decreases from 2 to 1±0.5 kbars from the Blanco fracture zone to the north along the Cleft segment of the ridge. Calculated pressures remain approximately constant at 0.87±0.53 kbars along ridge segments to the north of the Cleft. These low pressures for the remaining segments of the ridge are interpreted to indicate magma chambers at depths of 1.3-4.9 km and agree reasonably well with the depths of seismically imaged tops of axial magma chambers (2-3 km) (Canales et al 2009). The higher pressures obtained for lavas erupted along the Cleft segment of the JdF agree very well with recent seismic imaging of chambers beneath the Cleft segment. Pressures calculated for samples from single lava flows along the cleft segment described by Stakes et al (2006) allow identification of two magma chambers at depths of 5.0±1.1 km and 5.6±0.8 km which is to the depth of 5 to 6 km for the seismically imaged sill (Canales et al 2009). The higher depths inferred for chambers beneath the Cleft segment are consistent with cooling and/or thickening of crust along ridges toward fracture zones. While calculated pressures provide evidence for crystallization in axial magma chambers, results obtained for some samples from virtually every locality also suggest partial crystallization in the crust beneath these chambers, and therefore support the many sill or crystal mush models for accretion of oceanic crust. This conclusion is strengthened by comparing the results with those calculated using Herzberg’s (2004) method. The average difference between pressures calculated with both methods is 0.7 kbars ( 2.5 km) which is within the uncertainty in the calculation. .The Herzberg method returns slightly lower pressures for most samples

Scott, J. L.; Barton, M.

2010-12-01

241

The roles of the saturation vapor pressure and water vapor partial pressure in controlling different stages of the polar mesospheric cloud season  

NASA Astrophysics Data System (ADS)

SOFIE (Solar Occultation For Ice Experiment) daily zonal mean temperature (T), water vapor (H2O), and PMC measurements made from the AIM satellite, have been used to study the roles of temperature and water vapor in controlling the start, end, and PMC variability during the 2007 to 2009 northern summer PMC seasons. A necessary condition for PMCs to exist is that the ratio of PH2O (water vapor partial pressure) to Psat (saturation vapor pressure of the environment) must be greater than one. The start or end date of the season is defined here as the day when the first or last PMC is detected. SOFIE measurements show that these detections generally coincide with days when the daily maximum PH2O/Psat enters or exits the PH2O/Psat>1 domain. At the start or end of the PMC season, Psat, which is controlled only by temperature, rapidly changes by several orders of magnitude from above/below to below/above PH2O, signaling that temperature is in dominant control of entry to or exit from the PMC season. Similar to Psat, the SOFIE measured PMC frequency of occurrence rises/drops rapidly to/from ~100% within a few days, at the start/end of the PMC season. During the main period of the PMC season, on the other hand, Psat is negligibly small compared to PH2O, despite significant changes in temperature. As a result PH2O is in dominant control of the ice mass density variation. At the daily mean SOFIE PMC centroid height, PH2O correlates with the observed ice mass density on a range of intra-seasonal time scales both short and long (i.e., ~daily to monthly). Correlation on a seasonal scale is poor at the start and end of the season, reinforcing the argument that Psat dominates in these stages.

Rong, P.; Russell, J.; Hervig, M. E.; Bailey, S. M.

2010-12-01

242

Pressure overload regulates expression of cytokines, ?H2AX, and growth arrest- and DNA-damage inducible protein 153 via glycogen synthase kinase-3? in ischemic-reperfused hearts.  

PubMed

The growth arrest- and DNA-damage inducible protein 153 (GADD153) regulates both apoptosis and inflammatory response. Importantly, glycogen synthase kinase-3? (GSK-3?) may provide a mechanistic link for cellular expression of GADD153, inflammatory response, and cell death. We previously showed that pressure overload exacerbates myocardial ischemia reperfusion injury associated with significant reduction in phosphorylated (inactive) GSK-3?. This raises the possibility that pressure overload, through a GSK-3?-dependent mechanism, increases GADD153 expression, thereby upregulating inflammatory cytokine production and contributing to worsening of myocardial ischemia reperfusion injury. Accordingly, Langendorff-perfused rat hearts were subjected to global ischemia reperfusion protocol in the absence or presence of the GSK-3? inhibitor, lithium chloride (1 mmol/L), with perfusion pressure set at 80 or 160 cmH(2)O; normoxic hearts served as controls. Compared with normoxia, an ischemia reperfusion insult increased expressions of proinflammatory cytokines, ?H2AX, and GADD153 in association with increased cell death. In the ischemic-reperfused hearts, pressure overload did the following: (1) reduced interleukin-10 but increased interleukin-17 (cardiomyocytes), without affecting interleukin-23; (2) increased expressions of ?H2AX and GADD153; (3) decreased 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolylcarbocyanine iodide (JC-1) aggregates but increased JC-1 monomers (suggestive of reduced mitochondrial membrane potential, ?(m)); and (4) increased annexin V immunostaining as well as apoptotic and necrotic cell death. Treatment with lithium chloride caused a robust increase in interleukin-10, preserved ?(m), and markedly decreased all other parameters with the effect being most prominent for hearts perfused at the high pressure. In conclusion, pressure overload, via a GSK-3?-dependent mechanism, exacerbates cell death in the isolated ischemic-reperfused heart involving regulation of inflammatory response, DNA injury, and GADD153 expression. PMID:23108649

Baban, Babak; Liu, Jun Yao; Mozaffari, Mahmood S

2013-01-01

243

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

PubMed Central

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.

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

2012-01-01

244

Thermodynamics of Formate-Oxidizing Metabolism and Implications for H2 Production  

PubMed Central

Formate-dependent proton reduction to H2 (HCOO? + H2O ? HCO3? + H2) has been reported for hyperthermophilic Thermococcus strains. In this study, a hyperthermophilic archaeon, Thermococcus onnurineus strain NA1, yielded H2 accumulation to a partial pressure of 1 × 105 to 7 × 105 Pa until the values of Gibbs free energy change (?G) reached near thermodynamic equilibrium (?1 to ?3 kJ mol?1). The bioenergetic requirement for the metabolism to conserve energy was demonstrated by ?G values as small as ?5 kJ mol?1, which are less than the biological minimum energy quantum, ?20 kJ mol?1, as calculated by Schink (B. Schink, Microbiol. Mol. Biol. Rev. 61:262-280, 1997). Considering formate as a possible H2 storage material, the H2 production potential of the strain was assessed. The volumetric H2 production rate increased linearly with increasing cell density, leading to 2,820 mmol liter?1 h?1 at an optical density at 600 nm (OD600) of 18.6, and resulted in the high specific H2 production rates of 404 ± 6 mmol g?1 h?1. The H2 productivity indicates the great potential of T. onnurineus strain NA1 for practical application in comparison with H2-producing microbes. Our result demonstrates that T. onnurineus strain NA1 has a highly efficient metabolic system to thrive on formate in hydrothermal systems.

Lim, Jae Kyu; Bae, Seung Seob; Kim, Tae Wan; Lee, Jung-Hyun

2012-01-01

245

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)

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).

Brophy, James Gerald

2009-06-01

246

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

NASA Astrophysics Data System (ADS)

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.

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

1994-11-01

247

Growth of soybean and potato at high CO2 partial pressures  

NASA Astrophysics Data System (ADS)

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

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

1994-11-01

248

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)

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.

Newton, Robert C.; Manning, Craig E.

2006-11-01

249

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

USGS Publications Warehouse

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.

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

2012-01-01

250

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

Microsoft Academic Search

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

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

1993-01-01

251

Modeling of chemical processes in the low pressure capacitive radio frequency discharges in a mixture of Ar/C2H2  

NASA Astrophysics Data System (ADS)

We study the properties of a capacitive 13.56 MHz discharge with a mixture of Ar/C2H2 taking into account the plasmochemistry and growth of heavy hydrocarbons. A hybrid model was developed to combine the kinetic description for electron motion and the fluid approach for negative and positive ion transports and plasmochemical processes. A significant change in plasma parameters related to injection of 5.8% portion of acetylene in argon was observed and analyzed. We found that the electronegativity of the mixture is about 30%. The densities of negatively and positively charged heavy hydrocarbons are sufficiently large to be precursors for the formation of nanoparticles in the discharge volume.

Ariskin, D. A.; Schweigert, I. V.; Alexandrov, A. L.; Bogaerts, A.; Peeters, F. M.

2009-03-01

252

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

PubMed Central

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.

2014-01-01

253

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

PubMed

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

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

2013-09-15

254

Some Aspects of Heterogeneous Equilibria: Equilibria Between Metal Solutions and Oxide Solutions in Atmospheres of Known Partial Pressure of Oxygen.  

National Technical Information Service (NTIS)

Consideration is given to the thermodynamics of equilibria involving metal solutions, oxide solutions, and atmospheres of known 02 partial pressures. The standard free energy of formation of the oxides of the metals involved are regarded, in one case, as ...

W. C. Hahn

1964-01-01

255

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

Microsoft Academic Search

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

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

2009-01-01

256

A phase relation study of Bi-based copper oxide super conductors as a function of partial oxygen pressure  

Microsoft Academic Search

Influence of partial oxygen pressure on the stabilities of Bi4Sr8Cu5Ox (Bi-4805) and Bi2Sr2Ca2Cu3Ox (Bi-2223) have been investigated for the first time, using a newly developed apparatus in which high-temperature X-ray diffraction measurements and microscope observations are simultaneously performed under a quantitative control of atmosphere in the temperature range between 780 and 1100°C under the partial oxygen pressure ranged from 0

Mikito Mamiya; Takuya Suzuki; Humihiko Takei

1999-01-01

257

Influence of the low oxygen partial pressures on thick YBCO coated conductor by sol–gel process  

Microsoft Academic Search

The effects of annealing under varying oxygen partial pressures on the formation of YBa2Cu3O7?x (YBCO) superconducting thick films by sol–gel process were investigated. Superconducting thick films of YBCO were prepared on nickel tapes buffered with yttrium stabilized zirconia layers by continuous sol–gel dip coating method. Annealing of YBCO coated conductor was performed under varying low oxygen partial pressures. SEM, EDS,

Ziya Aslanoglu; Yalcin Akin; Marwan I. El-Kawni; Wolfgang Sigmund; Yusuf S. Hascicek

2003-01-01

258

The high-pressure phase diagram of synthetic epsomite (MgSO4·7H2O and MgSO4·7D2O) from ultrasonic and neutron powder diffraction measurements  

NASA Astrophysics Data System (ADS)

We present an ultrasonic and neutron powder diffraction study of crystalline MgSO4·7H2O (synthetic epsomite) and MgSO4·7D2O under pressure up to ~3 GPa near room temperature and up to ~2 GPa at lower temperatures. Both methods provide complementary data on the phase transitions and elasticity of magnesium sulphate heptahydrate, where protonated and deuterated counterparts exhibit very similar behaviour and properties. Under compression in the declared pressure intervals, we observed three different sequences of phase transitions: between 280 and 295 K, phase transitions occurred at approximately 1.4, 1.6, and 2.5 GPa; between 240 and 280 K, only a single phase transition occurred; below 240 K, there were no phase transformations. Overall, we have identified four new phase fields at high pressure, in addition to that of the room-pressure orthorhombic structure. Of these, we present neutron powder diffraction data obtained in situ in the three phase fields observed near room temperature. We present evidence that these high-pressure phase fields correspond to regions where MgSO4·7H2O decomposes to a lower hydrate by exsolving water. Upon cooling to liquid nitrogen temperatures, the ratio of shear modulus G to bulk modulus B increases and we observe elastic softening of both moduli with pressure, which may be a precursor to pressure-induced amorphization. These observations may have important consequences for modelling the interiors of icy planetary bodies in which hydrated sulphates are important rock-forming minerals, such as the large icy moons of Jupiter, influencing their internal structure, dynamics, and potential for supporting life.

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

2013-03-01

259

H2 Reconstitution.  

National Technical Information Service (NTIS)

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 requir...

M. Skipper

2002-01-01

260

Role of interspecies H 2 transfer to sulfate and ferric iron-reducing bacteria in acetate consumption in anoxic paddy soil  

Microsoft Academic Search

Addition of sulfate resulted in complete inhibition of methanogenesis in anoxic paddy soil. About 20% of the CH4 was produced from H214CO2, the rest from acetate. Inhibition of H2-dependent methanogenesis was explained by successful competition by sulfate reducers for H2, as the H2 partial pressures decreased upon addition of sulfate. However, acetate concentrations did not decrease. Sulfate reduction was stimulated

Christof Achtnich; Alexandra Schuhmann; Thorsten Wind; Ralf Conrad

1995-01-01

261

Thermal decomposition kinetics of Brazilian limestones: effect of CO2 partial pressure.  

PubMed

The influence of the partial pressure of carbon dioxide (CO2) on the thermal decomposition process of a calcite (CI) and a dolomite (DP) is investigated in this paper using a thermogravimetric analyser. The tests were non-isothermal at five different heating rates in dynamic atmosphere of air with 0% and 15% carbon dioxide (CO2). In the atmosphere without CO2, the average activation energies (E(alpha)) were 197.4 kJ mol(-1) and 188.1 kJ mol(-1) for CI and DP, respectively. For the DP with 15% CO2, two decomposition steps were observed, indicating a change of mechanism. The values of E(alpha) for 15% CO2 were 378.7 kJ mol(-1) for the CI, and 299.8 kJ mol(-1) (first decomposition) and 453.4 kJ mol(-1) (second decomposition) for the DP, showing that the determination of E(alpha) for DP should in this case be considered separately in those two distinct regions. The results obtained in this study are relevant to understanding the behaviour changes in the thermal decomposition of limestones with CO2 partial pressure when applied to technologies, such as carbon capture and storage (CCS), in which carbon dioxide is present in high concentrations. PMID:22856287

Avila, Ivonete; Crnkovic, Paula M; Milioli, Fernando E; Luo, Kai H

2012-06-01

262

Hypothesis: the regulation of the partial pressure of oxygen by the serotonergic nervous system in hypoxia.  

PubMed

The regulation of the partial pressure of oxygen by the serotonergic nervous system in hypoxia is a hypothesis, which proposes an inherent operative system in homo sapiens that allows central nervous system and endocrine-mediated vascular system adaption to variables in partial pressure of oxygen, pH and body composition, while maintaining sufficient oxygen saturation for the immune system and ensuring protection of major organs in hypoxic and suboptimal conditions. While acknowledging the importance of the Henderson-Hasselbalch equation in the regulation of acid base balance, the hypothesis seeks to define the specific neuroendocrine/vascular mechanisms at work in regulating acid base balance in hypoxia and infection. The SIA (serotonin-immune-adrenergic) system is proposed as a working model, which allows central nervous system and endocrine-mediated macro- and micro vascular 'fine tuning'. The neurotransmitter serotonin serves as a 'hypoxic sensor' in concert with other operators to orchestrate homeostatic balance in normal and pathological states. The SIA system finely regulates oxygen, fuel and metabolic buffering systems at local sites to ensure optimum conditions for the immune response. The SIA system is fragile and its operation may be affected by infection, stress, diet, environmental toxins and lack of exercise. The hypothesis provides new insight in the area of neuro-gastroenterology, and emphasizes the importance of diet and nutrition as a complement in the treatment of infection, as well as the normalization of intestinal flora following antibiotic therapy. PMID:23312111

Devereux, Diana; Ikomi-Kumm, Julie

2013-03-01

263

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

USGS Publications Warehouse

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.

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

1992-01-01

264

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

USGS Publications Warehouse

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.

Rosenbauer, R.; Koksalan, T.

2004-01-01

265

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)

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.

Chakraborty, Mahua; Banerjee, Amit; Das, Debajyoti

2014-07-01

266

Effect of H 2S partial pressure on the transformation of a model FCC gasoline olefin over unsupported molybdenum sulfide-based catalysts  

Microsoft Academic Search

The selective HDS of FCC gasoline is a sensitive option for reducing sulfur content in commercial gasoline. For such applications, a minimum activity of the catalyst toward olefin hydrogenation is required to preserve the high octane number of the feedstock. The conversion of a model FCC olefin (2,3-dimethyl-2-ene: 23BMB2N) under close HDS conditions was investigated over unsupported molybdenum sulfide-based catalysts

A.-F. Lamic; A. Daudin; S. Brunet; C. Legens; C. Bouchy; E. Devers

2008-01-01

267

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

NASA Astrophysics Data System (ADS)

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

Ross, P. N., Jr.

1985-04-01

268

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)

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 65°C 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.

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

2009-12-01

269

Low-energy BO and BO 2 emission from H 2BO 3 sputtered in a low-pressure high-frequency SNMS plasma  

NASA Astrophysics Data System (ADS)

Background corrected secondary neutral energy spectra derived from Cu powder pellets with H 3BO 3, MgO, Al 2O 3, TiO 2, Y 2O 3 and ZrO 2, show energy distributions being more or less typical for collision cascades in the cases of the metal ions M +, of O + at energies >5 eV above the ion generation potential, and of the molecules Cu 2+, AlO +, TiO +, YO + and ZrO +, whereas the larger parts of the energy distributions of BO +and BO 2+exhibit a similar shape as the Ar +plasma gas ions. From this, and from the background of the low decomposition and melting temperatures of H 3BO 3 and B 2O 3, respectively, we conclude that the detected BO and BO 2 molecules have been emitted with thermal energies in processes implying lower energies than collision cascades. Evidence was found that the same holds for HBO 2 and H 2BO 2. In order to obtain relative correction factors for MO + molecular ion intensities, electron impact ionization cross sections have been calculated for the light MO molecules using the binary-encounter Bethe (BEB) formula, and for the respective metal M atoms by means of the semiempirical Lotz formula. For the heavy MO molecules YO and ZrO, cross sections have been estimated using the Thomson formula. The comparison of corrected relative MO/M and M/Cu intensities yields evidence that thermal (H)BO x emission amounts to the same order of magnitude as B emission from collision cascades, and that this situation is comparable to the high yield of MO molecules emitted in collision cascades from oxides with high M masses. Since the normal energy window of an HF-plasma secondary neutral mass spectrometer does not accept particles with originally thermal energies, it is concluded that these findings are relevant for quantification.

Jenett, Holger; Ai, Xingtao; Hodoroaba, Vasile-Dan; Iga, Ione; Mu Tao, Lee

1999-07-01

270

H2 Reconstitution  

NASA Astrophysics Data System (ADS)

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.

Skipper, Mike

2002-02-01

271

Partial Melting in the Iron-Sulfur System at High Pressures  

NASA Astrophysics Data System (ADS)

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.

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

2005-12-01

272

The effects of pressure, oxygen partial pressure, and temperature on the formation of N 2O, NO, and NO 2 from pulverized coal  

Microsoft Academic Search

The main features of a new, pressurized, entrained-flow reactor are described and results presented of experiments investigating the formation of nitrogen oxides (N2O, NO, and NO2) from pulverized Polish coal, burned in the reactor at temperatures (T) 800–1300°C, pressures (p) 1–20, bar and oxygen partial pressures (pO2) 0.05–2.4 bar. The experimental results are compared with the results of detailed gas-phase

P. Kilpinen; M. Hupa; P. M. Pirkonen

1995-01-01

273

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

PubMed

The nature of protons in ice VII up to 368°C and 16GPa was investigated with synchrotron near-infrared spectroscopy. The absorption band of the first OH stretching overtone mode divided into doublet peaks above 5GPa at room temperature, suggesting that proton tunneling occurs at the overtone level. As the temperature increased, the doublet peaks gradually reduced to a singlet. This result implies that thermally activated protons hop between the two potential minima along the oxygen-oxygen axis. A pressure-temperature diagram for the proton state was constructed from the changing band shape of the overtone mode. PMID:24975636

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

2014-12-10

274

Sensor-supported high resolution profiling of the excess partial pressure of carbon dioxide in low order fluvial systems.  

NASA Astrophysics Data System (ADS)

The excess partial pressure of carbon dioxide in a surface freshwater is a dynamic representation of the interacting biogeochemical processes that consume and produce carbon dioxide. As efflux of the excess gas represents direct linkage of the terrestrial with the atmospheric C cycle, describing this interaction is important as it allows us to identify controls on the process. Here we present an almost complete time series of excess partial pressure of carbon dioxide in a small order river system close to the terrestrial-aquatic interface for the hydrological years 2003-2008. This record would not be possible without the use of continuously logged measurement of stage height to estimate the concentration of the fluvial dissolved inorganic C (DIC) pool and pH, temperature and atmospheric pressure to speciate the DIC pool and calculate atmospheric equilibrium concentrations. Here we will explain how this time series was generated, and from the five year time series, consider some of the detail that high resolution sensor-generated profiles reveals e.g. a consistent drop in excess partial pressure of carbon dioxide prior to the commencement of rising stage height; diurnal variation excess partial pressure of carbon dioxide although temperatures are low; the response of excess partial pressure of carbon dioxide to event flow.

Waldron, Susan; Scott, Marian

2013-04-01

275

Nb films sputtered with a (Ar, H2) mixture and application to superconductor-insulator-superconductor junctions  

Microsoft Academic Search

Effects of hydrogen trapping in Nb base electrodes on the superconductivity of Nb itself and superconductor-insulator-superconductor (SIS) junction characteristics have been investigated. The Nb films were prepared by sputter deposition in an atmosphere of (Ar, H2) mixture. The gap parameter ?Nb and the critical temperature Tc gradually decreased with increasing H2 partial pressure. The SIS junctions exhibited a sudden extinction

Takeshi Kobayashi; Ken Sakuta; Kazuo Fujisawa

1985-01-01

276

Controlled undercooling of liquid iron in contact with ZrO2 and MgO substrates under varying oxygen partial pressures  

NASA Astrophysics Data System (ADS)

The objective of this study is to determine the conditions under which the inclusions present in liquid steel can act as heterogeneous nucleants for solidification. In order to study the factors that define the undercooling of a given metal/oxide couple, the undercooling of a pure iron sessile droplet in contact with Al2O3, ZrO2, and MgO substrates was measured under controlled oxygen partial pressures by observing droplet recalescence. The results showed that the undercooling of iron, in contact with a particular substrate, did not have a unique value, but was significantly affected by the oxygen content on the gas phase. For oxygen partial pressures between 10-21 and 10-19, the undercooling of iron on ZrO2 substrates was stable and around 290 °C. In the same range of oxygen partial pressure, the undercooling of iron on MgO substrates remained below 100 °C due to the low stability of this oxide. At lower oxygen contents, substrate decomposition might be the cause for the observed drop in the undercooling of iron on ZrO2 substrates to below 100 °C. The undercooling also decreased for increasing oxygen content as verified when the gas was changed from gettered Ar/Ar-H2 to CO/CO2 mixtures. The variation in undercooling was related to the wetting of the substrate by the liquid metal, where the deep undercooling observed in the ZrO2 experiments occurred when the highest contact angle between the liquid metal and the substrate was achieved.

Valdez, Martin E.; Shibata, H.; Cramb, Alan W.

2006-12-01

277

Partial melting, fluid supercriticality and element mobility in ultrahigh-pressure metamorphic rocks during continental collision  

NASA Astrophysics Data System (ADS)

Partial melting at continental lithosphere depths plays an important role in generating geochemical variations in igneous rocks. In particular, dehydration melting of ultrahigh-pressure (UHP) metamorphic rocks during continental collision provides a petrological link to intracrustal differentiation with respect to the compositional evolution of continental crust. While island arc magmatism represents one end-member of fluid-induced large-scale melting in the mantle wedge during subduction of the oceanic crust, the partial melting of UHP rocks can be viewed as the other end-member of fluid-induced small-scale anatexis during exhumation of the deeply subducted continental crust. This latter type of melting is also triggered by metamorphic dehydration in response to P-T changes during the continental collision. It results in local occurrences of hydrous melts (even supercritical fluids) as felsic veinlets between boundaries of and multiphase solid inclusions in UHP metamorphic minerals as well as local accumulation of veinlet-like felsic leucosomes in foliated UHP metamorphic rocks and metamorphically grown zircons in orogenic peridotites. Thus, very low-degree melts of UHP rocks provide a window into magmatic processes that operated in continental subduction zones. This article presents a review on available results from experimental petrology concerning the possibility of partial melting under conditions of continental subduction-zone metamorphism, and petrological evidence for the occurrence of dehydration-driven in-situ partial melting in natural UHP rocks during the continental collision. Although the deeply subducted continental crust is characterized by a relative lack of aqueous fluids, the partial melting in UHP rocks commonly takes place during decompression exhumation to result in local in-situ occurrences of felsic melts at small scales. This is caused by the local accumulation of aqueous fluids due to the breakdown of hydrous minerals and the exsolution of structural hydroxyl and molecular water from nominally anhydrous minerals in UHP rocks during the exhumation. The dehydration melting of UHP rocks would not only have bearing on the formation of supercritical fluids during subduction-zone metamorphism, but also contribute to element mobility and ultrapotassic magmatism in continental collision orogens. Therefore, the study of dehydration melting and its effects on element transport in UHP slabs, rocks and minerals is a key to chemical geodynamics of continental subduction zones.

Zheng, Yong-Fei; Xia, Qiong-Xia; Chen, Ren-Xu; Gao, Xiao-Ying

2011-08-01

278

Correlation between end-tidal and arterial carbon dioxide partial pressure in patients undergoing craniotomy  

PubMed Central

Abstract: Background: Both end-tidal carbon dioxide pressure (ETCO2) is used routinely as an indicator of arterial partial pressure of carbon dioxide (PaCO2) and thus adequacy of ventilation. Accurate determination of the PaCO2 level in neuroanesthesia is quite important because of its effect on cerebral blood flow and also hyperventilation is often used to reduce intracranial pressure in neurosurgical patients. This study was aimed to evaluate the relationship between ETCO2 and arterial PaCO2 in neurosurgical patients undergoing craniotomy to assess the predictive value of ETCO2 as an indicator of PaCO2 level. Methods: Forty-five consecutive adult patients with inclusion criteria, scheduled to undergo elective craniotomy surgery were enrolled in this prospective study. Measurements of PaCO2 and ETCO2 were performed at three different intervals: Time 1: 10 min after induction of general anesthesia; time 2: after cranium opening prior to dural incision; and at time 3: start of dural closure. All patients received the same anesthetic agent (propofol, sufentanil, atracurium, oxygen). Data were initially analyzed using Pearson’s Correlation to assess the relationship between PaCO2 and ETCO2 at different stages of the operation. A p-value (P) of less than 0.05 was considered significant. The agreement between the measures of CO2 was assessed using Bland-Altman method, where mean difference and average between PaCO2 and ETCO2 were calculated. The 95% confidence intervals for the lower and upper limits of agreement were presented. Results: A total of 44 patients, aged 18 to 65 years, ASA grades 1 and 2 were participated in the study. Mean difference, standard deviation and correlation coefficient of the parameters were calculated for three time periods. The values for PaCO2, ETCO2, (PaCO2- ETCO2), and correlation coefficient for 10 min after anesthetic induction, prior to dural incision, and start of dural closure were 35.4 ± 3.2, 32.1 ± 3.2, 3.8 ± 2.1, and 0.565, 36.2 ± 3.1, 32.6 ± 3.2,4.8 ± 3.1, and 0.574, and 36.7 ± 2.4, 33 ± 3.2,3.8 ± 2.3, and 0.627, respectively (p less than 0.01 for all analyses). The greatest mean difference occurred just prior to dural incision. The lowest mean difference was observed at 10 min post-anesthetic induction. Conclusions: To the present study was aimed to correlate between End-tidal and arterial carbon dioxide partial pressure in neurosurgical patients undergoing craniotomy. Findings of this study showed that ETCO2 consistently underestimates the value of PaCO2 during craniotomy indicating that ETCO2 value can be used instead of PaCO2. Keywords: End-tidal carbon dioxide pressure, Arterial partial pressure of carbon dioxide, Craniotomy

Hemmati, Naser; Zokaei, Abdol Hamid; Karbasforooshan, Ali

2012-01-01

279

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

SciTech Connect

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.

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

2009-09-15

280

H2O Adsorption Kinetics on Smectites  

NASA Technical Reports Server (NTRS)

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.

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

2000-01-01

281

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

SciTech Connect

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.

Kayanne, Hajime; Suzuki, Atsushi [Geological Survey of Japan, Tsukuba (Japan); Saito, Hiroshi [National Research Laboratory of Metrology, Tsukuba (Japan)

1995-07-14

282

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

PubMed

In this work, we present a new, previously unknown type of structure transformation in the high-pressure gas hydrates, which is related to the existence of two different isostructural phases of the sulfur hexafluoride clathrate hydrates. Each of these phases has its own stability field on the phase diagram. The difference between these hydrates consists of partial filling of small D cages by SF(6) molecules in the high-pressure phase; at 900 MPa, about half of small cages are occupied. Our calculations indicate that the increase of population of small cavities is improbable, therefore, at any pressure value, a part of the cavities remains vacant and the packing density is relatively low. This fact allowed us to suppose the existence of the upper pressure limit of hydrate formation in this system; the experimental results obtained confirm this assumption. PMID:17048967

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

2006-10-26

283

Direct conversion of methane to methanol by a high pressure partial oxidation reaction  

SciTech Connect

The conversion of methane to a liquid storageable fuel is a desirable alternative to compressed natural gas. The simplest liquid is methanol presently formed by the steam reforming of methane to synthesis gas followed by the high pressure catalytic conversion of the synthesis gas to methanol. The process is most economic for large (2000 tonne/day) plants and must be located near large reserves of natural gas or near an appropriate pipeline. The simpler partial oxidation route offers the advantage of directly converting methane to methanol in a single step reaction. The potential for the partial oxidation route together with an economic evaluation has been reported by Edwards and Foster who showed that, provided the selectivity for methanol formation is about 77%, the partial oxidation route has an economic advantage over the conventional synthesis route with no penalty for conversions as low as 4%. Much has been published on the combustion of methane to CO/sub 2/ and H/sub 2/O but very little has been concerned with the intermediate formation of methanol. Gesser et al. recently reviewed the controlled oxidation of CH/sub 4/ to CH/sub 3/OH emphasizing the free radical mechanistic aspects. The heterogeneous catalytic studies was reviewed by Foster and Pitchai and Kleir. Although the literature indicated some potential catalysts no commercial viable reaction system has been developed. Before embarking on a study of the catalytic conversion of CH/sub 4/ to CH/sub 3/OH we attempted to establish a base-line study by examining the homogeneous reaction and here report a summary of the results with methane.

Gesser, H.D.; Hunter, N.R.; Morton, L.A.; Yarlagadda, P.S.; Fung, D.P.C.

1988-01-01

284

Oxygen partial pressure dependence of suppressing oxidation-induced stacking fault generation in argon ambient annealing including oxygen and HCl  

NASA Astrophysics Data System (ADS)

The effect of adding HCl during annealing in argon with reduced oxygen to suppress the generation of oxidation-induced stacking faults (OSFs), which adversely affect the yield and reliability of thermally grown oxide, was investigated for p-type Si wafer. Adding HCl affected OSF generation in two ways depending on the oxygen partial pressures above and below the critical value at 6×10 -3 atm. When the oxygen partial pressure was lower than the critical value, adding HCl did not suppress this generation any more than the degree brought by annealing without HCl, when an OSF density of about 10 3 cm -2 was reduced to 20 cm -2 or less. At an oxygen partial pressure greater than the critical value, adding HCl suppressed the generation of OSFs almost completely. The mechanism responsible for the two ways to suppress OSF generation by adding HCl is discussed, including the oxidation mechanism when oxygen partial pressures are reduced. This difference is attributed to the difference in the transport mechanisms of oxidation-related species at reduced oxygen partial pressures.

Suzuki, Toshiharu

2001-08-01

285

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

NASA Technical Reports Server (NTRS)

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.

Opila, Elizabeth J.; Boyd, Meredith

2010-01-01

286

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

SciTech Connect

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.

Not Available

1992-12-31

287

An Experimental Study of Magnetite Solubility as a Function of Pressure Along the Dewpoint Curve in the NaCl-, KCl-, HCl-H2O-Melt System.  

NASA Astrophysics Data System (ADS)

Magnetite (Mt) is a ubiquitous phase in magmatic-hydrothermal ore deposits and, thus, any model which aims to predict the evolving physical chemistry of porphyry-ore deposit environments must incorporate data on the equilibria that control the precipitation of Mt in such systems. Extant experimental data indicate that Mt solubility is controlled via the equilibrium Fe3O4Mt + 6HClV + H2V = 3FeCl2V + 4H2OV (Chou and Eugster, 1977, AJS, p 1296); however their experiments were performed at T=500-650° C by equilibrating Mt with a HCl-bearing supercritical aqueous fluid (NaCl-, KCl-free). Conversely, data from some natural Fe-bearing fluid inclusions have evinced that initial temperatures of magmatic volatile phases (MVP) in magmatic-hydrothermal environments may exceed 800° C, possibly even approaching 900° C, in the presence of melt (Clark and Arancibia, 1995, Giant Ore Deposits-II Conference, p. 511). Thus, there currently are no data constraining Mt solubility in the high-temperature regime obtained in natural magmatic systems. Additionally, there are no data on Mt solubility as a function of changes in the chemistry of the MVP. In the system NaCl-H2O, the composition and, thus, the density of brine-saturated vapor change significantly as a function of pressure along a given isotherm and the components KCl and HCl act to shift the limbs of the solvii (Bodnar et al., 1985, GCA, p 1861; Anderko and Pitzer, 1993, GCA, p 1657; Shinohara and Fujimoto, 1994, GCA, p 4857). The absence of data constraining Mt solubility as a function of pressure along a given isotherm, the resultant change in composition and density, as well as deviations in the Na:K:H ratio of the MVP hinder the development of forward models of magmatic-hydrothermal systems. In order to provide these critical data constraining Mt solubility in geologically reasonable magmatic systems we have performed a set of experiments as a function of pressure in the vapor-only field near the 800° C isotherm in the NaCl-H2O system. Natural Mt (aFe3O4 ~1), a synthetic haplogranitic minimum melt (100 MPa) and an aqueous phase (molar K:Na:H=1) were reacted in Au capsules in rapid-quench Stellite-25 vessels, using water as the pressure medium, at 800° C, log fO2 controlled by the NNO buffer, pressures of 100 and 120 MPa, and aqueous salinities of 1.8 and 3.0 wt. % NaCl equivalent, respectively. In all experiments the mass ratio of Mt:melt:fluid was 1:1:4. Detailed petrographic examination of run products did not reveal the presence of brine inclusions; however, fluid inclusions do contain opaque phases. Using the newly determined mFeCl2 (0.0345 at 100 MPa and 0.0359 at 120 MPa) and mHCl (0.0769 at 100 MPa and 0.0947 at 120 MPa) in the quenched MVP and the known fugacities of H2O (? =1) and H2 (? =1) at P and T, apparent equilibrium constants were calculated as log K' = (CFeCl2)3 \\times (fH2O)4 \\div (CHCl)6 \\times fH2. The values of log K' are 1.605 at 100 MPa and 13.01 at 120 MPa. K is fixed for a given P and T except for the effect of activity coefficients for HCl and FeCl2. The values of log K obtained in this study will facilitate more detailed characterization of the chemistry of magmatic-hydrothermal MVPs; both fossil MVPs and those that obtain in modern geothermal reservoirs. Determination of P, T, fH2 and mFeCl2 in fluid inclusions will allow for the direct calculation of a model HCl concentration in the MVP.

Simon, A. C.

2001-12-01

288

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

NASA Astrophysics Data System (ADS)

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

Lenz, Annika; Ojamäe, Lars

2009-10-01

289

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

NASA Technical Reports Server (NTRS)

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.

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

1993-01-01

290

Pressure broadening and shift of the cesium D2 transition by the noble gases and N2, H2, HD, D2, CH4, C2H6, CF4, and He3 with comparison to the D1 transition  

NASA Astrophysics Data System (ADS)

The pressure broadening and shift rates for the cesium D2 (62P3/2 ? 62S1/2) transition with the noble gases and N2, H2, HD, D2, CH4, C2H6, CF4, and He3 were obtained for pressures less than 300 Torr at a temperature of 40°C 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 He3 are 20.59, 9.81, 16.47, 15.54, 18.41, 19.18, 27.13, 28.24, 22.84, 25.84, 26.14, 17.81, and 22.35 MHz/Torr, respectively. The uncertainty in the broadening rates is typically less than 0.3%. The corresponding pressure-induced shift rates ? are 0.69, -2.58, -6.18, -6.09, -6.75, -6.20, -4.83, -4.49, -4.54, -8.86, -9.38, -6.47, and 0.60 MHz/Torr with an uncertainty of less than 0.04 MHz/Torr. With the exception of diatomic collision partners, the broadening rates for Cs D2 are 5%-15% less than the rates for Cs D1. For light collision partners with a blue shift, the D1 is shifted more than the D2 line. The broadening cross sections for Cs and Rb are similar. However, the cross sections for K are about 70% larger and for Na, about 30% less.

Pitz, Greg A.; Fox, Charles D.; Perram, Glen P.

2010-10-01

291

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

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.

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

1997-09-01

292

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

NASA Technical Reports Server (NTRS)

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.

Rasskopf, Klaus F.

1987-01-01

293

Phase diagram in the (Bi,Pb)?Sr?Ca?Cu?O system: influence of partial constraint oxygen pressure  

NASA Astrophysics Data System (ADS)

DTA-DTG, X ray diffraction and metallographic measurements at different temperatures and partial oxygen pressure in the isoplethic cut “(Bi,Pb) 2Sr 2CuO x?CaCuO 2”, were carried out to analyze the influence of partial constraint oxygen pressure on phase transformations. An isobaric invariant equilibrium has been found in the P o2 range 0.5-1. Supplementary phase appearing at invariant equilibrium is (Sr,Ca) 3Cu 5O y. That phase fixes oxygen and then the weight loss is stopped.

Mansori, M.; Satre, P.; Roubin, M.; Vacquier, G.; Strobel, P.; Sebaoun, A.

1994-12-01

294

Chemical vapor infiltration of pyrocarbon —II. The influence of increasing methane partial pressure at constant total pressure on infiltration rate and degree of pore filling  

Microsoft Academic Search

Chemical vapor infiltration of pyrocarbon with methane as the carbon source was studied at a total pressure of 20 kPa, a temperature of 1100 °C and methane partial pressures from 2.5 to 20 kPa. A cylindrically-shaped porous alumina ceramic, 20 mm in height and 16 mm in diameter, was used as the substrate. The pore entrance diameters of the porous

W. Benzinger; K. J. Hüttinger

1998-01-01

295

Hydrogen production reaction with a metal oxide catalyst in high pressure high temperature water  

NASA Astrophysics Data System (ADS)

Hydrogen production from biomass was attempted in high pressure high temperature water at 573 K by adopting partial oxidation to increase the yield of H2 via CO production in the presence of ZnO. The results revealed that an addition of H2O2 as an oxidant to the reaction of glucose and sugarcane bagasse brought about the trend of increasing the yields of H2, CO, and CO2. However, the sensitivity of H2 yield on H2O2 amount was different from those of CO and CO2, namely the excess amount of H2O2 tends to decrease the H2 yield with giving a maximum at a certain H2O2 amount. These indicated that the controllability of partial oxidation would be a key factor for maximizing the H2 yield through biomass conversion by partial oxidative gasification in high pressure high temperature water

Watanabe, M.; Takahashi, M.; Inomata, H.

2008-07-01

296

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

PubMed Central

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.

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

2011-01-01

297

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

298

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

NASA Astrophysics Data System (ADS)

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 Å 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 mélanges of subduction channels.

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

2014-02-01

299

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

NASA Astrophysics Data System (ADS)

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

Kim, Tae Jin; Hidrovo, Carlos

2012-11-01

300

Partial Defect Verification of the Pressurized Water Reactor Spent Fuel Assemblies  

SciTech Connect

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.

Ham, Y S; Sitaraman, S

2010-02-05

301

Partial pressure of oxygen in arterial blood in normal pregnant women in Dhaka city.  

PubMed

In the present study the partial pressure of oxygen in arterial blood (PaO2) was estimated in 32 women in Dhaka city. For this purpose a total 32 women subjects with age ranged from 25 years to 35 years without any recent history of respiratory diseases were selected and divided into 8 healthy non-pregnant women as control and 24 normal pregnant women as experimental group. Experimental group was further divided into 8 first trimester, 8 second trimester & 8 third trimester of pregnant women. The PaO2 was estimated by using "Easy Blood Gas Auto Analyzer". The PaO2 was estimated during the 1st, 2nd, 3rd trimesters of pregnant women and non-pregnant women. The mean of measured values of PaO2 were analyzed statistically in relation to 1st, 2nd, 3rd trimesters of pregnant women & non-pregnant women. The PaO2 was significantly higher in 1st trimester, 2nd trimester & 3rd trimester of pregnant women than that of non-pregnant women. There were no statistically significant difference of PaO2 between the 1st trimester and 2nd trimester; between the 1st trimester and 3rd trimester; and between the 2nd trimester and 3rd trimester of pregnant women. It may be concluded that the causes of progressively increased PaO2 throughout the pregnancy were most likely to be due to effect of progesterone causing hyperventilation. PMID:18946450

Sunyal, D K; Amin, M R; Ahmed, A; Begum, M; Rahman, N; Begum, S

2008-07-01

302

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

PubMed

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

Takayanagi, Masayoshi; Kurisaki, Ikuo; Nagaoka, Masataka

2014-01-01

303

Energy metabolism in relation to oxygen partial pressure in human skeletal muscle during exercise.  

PubMed Central

1. The intramuscular oxygen partial pressure (pO2) in human gastrocnemius muscle was monitored during exercise and compared with metabolite concentrations reflecting the energy and the redox state in the tissue. Ten normal subjects and ten patients with peripheral vascular occlusive disease were investigated. 2. In normal subjects the pO2 at the end of exercise was related to the intensity of the exercise, expressed as effect (J/s) per contraction. 3. In both patients and normal subject the pO2 was related to the [ATP]/[ADP] ratio, the [lactate/[pyruvate] ratio and the phosphocreatine concentration in the muscle tissue at rest and during exercise. 4. At each pO2 value, a lower [lactate/[pyruvate] ratio was found in the muscle tissue of the patients compared with that of normal subjects. This was interpreted as a beneficial effect of the higher oxidative-enzyme capacity in the muscle of the patients. 5. The results show the importance of pO2 for the regulation of the energy and the redox state of the tissue. During exercise the changes induced in pO2 and thus the energy state will stimulate the respiratory rate. This might be an important link in triggering the oxidative-enzyme capacity in response to physical training as well as in peripheral vascular occlusive disease.

Bylund-Fellenius, A C; Walker, P M; Elander, A; Holm, S; Holm, J; Schersten, T

1981-01-01

304

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

NASA Technical Reports Server (NTRS)

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.

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

1980-01-01

305

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

SciTech Connect

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.

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

2000-12-31

306

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

PubMed Central

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.

Takayanagi, Masayoshi; Kurisaki, Ikuo; Nagaoka, Masataka

2014-01-01

307

Critical hematocrit and oxygen partial pressure in the beating heart of pigs.  

PubMed

In cardiac surgery the substitution of lost blood volume by plasma substitutes is a common therapeutical approach. None of the currently available blood substitutes has a sufficient oxygen transport capacity. This can limit the functional integrity of the myocardium known as highly oxygen consumptive. The study was aimed to get information about the minimal hematocrit, also known as critical hematocrit (cHct), which guarantees a stable and adequate oxygen partial pressure in the myocardium (pO2). In adult female pigs (n=7) the hematocrit was reduced by isovolemic blood dilution with an intravenous infusion of isotonic 4% gelatine polysuccinate solution, The substituted blood volume ranged between 3000ml and 7780ml (mean: 5254±1672ml). In all animals the pO2 of the myocardium of the beating heart and of the resting skeletal muscle increased until blood dilution resulted in a Hct decrease down to 15%. Further blood dilution resulted in a decrease of the pO2. Only after the Hct was <10% the pO2 was lower than before blood dilution and accompanied by a lethal ischemia of the myocardium. These data indicate a cHct of about 10% in the pig animal model. PMID:20621104

Hiebl, B; Mrowietz, C; Ploetze, K; Matschke, K; Jung, F

2010-12-01

308

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

SciTech Connect

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.

Kondaiah, P.; Madhavi, V.; Uthanna, S. [Department of Physics, Sri Venkateswara University, Tirupati-517502 (India)

2013-02-05

309

Properties of ITO films deposited by r.f.-PERTE on unheated polymer substrates—dependence on oxygen partial pressure  

Microsoft Academic Search

The study of the influence of oxygen partial pressure on the properties of indium tin oxide (ITO) thin films deposited onto polymer substrates at room temperature is presented. Two types of polymer substrates were used: polyethylene terephthalate (PET) and polyethylene naphathalate (PEN). The deposition technique used is the radio frequency plasma enhanced reactive thermal evaporation of a 90% In–10% Sn

C. Nunes de Carvalho; G. Lavareda; E. Fortunato; A. Amaral

2003-01-01

310

Growth of the microalgae Neochloris oleoabundans at high partial oxygen pressures and sub-saturating light intensity.  

PubMed

The effect of partial oxygen pressure on growth of Neochloris oleoabundans was studied at sub-saturating light intensity in a fully-controlled stirred tank photobioreactor. At the three partial oxygen pressures tested (P(O)?= 0.24; 0.63; 0.84 bar), the specific growth rate was 1.38; 1.36 and 1.06 day(-1), respectively. An increase of the P(CO)?from 0.007 to 0.02 bar at P(O?) of 0.84 bar resulted in an increase in the growth rate from 1.06 to 1.36 day(-1). These results confirm that the reduction of algal growth at high oxygen concentrations at sub-saturating light conditions is mainly caused by competitive inhibition of Rubisco. This negative effect on growth can be overcome by restoring the O(2)/CO(2) ratio by an increase in the partial carbon dioxide pressure. In comparison to general practice (P(O(2)) = 0.42 bar), working at partial O(2) pressure of 0.84 bar could reduce the energy requirement for degassing by a factor of 3-4. PMID:22079686

Sousa, Cláudia; de Winter, Lenneke; Janssen, Marcel; Vermuë, Marian H; Wijffels, René H

2012-01-01

311

Growth and Yield Response of Commercial Bearing-age ‘Casselman’ Plum Trees to Various Ozone Partial Pressures  

Microsoft Academic Search

Nursery stock of plum (Prunus salicina Lindel., cv, Casselman) was planted 1 Apr. 1988 in an experimental orchard at the Univ, of California Kearney Agricultural Center near Fresno, CA. Trees in this study were enclosed in open-top fumigation chambers on 1 May 1989, and exposed to three atmospheric ozone partial pressures (char­ coal filtered air, ambient air, and ambient air

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

1997-01-01

312

Hydroelastic vibration of partially liquid-filled circular cylindrical shells under combined internal pressure and axial compression  

Microsoft Academic Search

In the present study, a hybrid finite element method is applied to investigate the dynamic stability of a partially fluid-filled circular cylindrical shell under constant lateral pressure and compressive load. The structural formulation is a combination of Sanders shell theory and the classic finite element method. Nodal displacements are derived from exact solution of Sanders shell theory. Initial stress stiffness

Farhad Sabri; Aouni A. Lakis

2011-01-01

313

Experimental Deformation, Partial Melting, and Compositional Changes in Perthitic K-feldspar at High Pressure and Temperature  

NASA Astrophysics Data System (ADS)

In order to study the relationship between partial melting, cracking and transition to diffusion creep processes, we have performed (i) axial compression experiments on natural perthitic K-feldspar single crystals (compression normal to the {010} plane), (ii) shear experiments (on 10-20 ?m grain size powder obtained from the same perthitic K-feldspar) and (iii) hydrostatic experiments (on powder and single crystals) with a solid medium Griggs-type deformation apparatus at T=900°C, Pc varying from 0.75-1.5 GPa and axial shortening ranging from 3 to 40% at a constant strain rate of 10-6 s-1. Samples were deformed as-is and with added H2O (up to 0.2 wt %). Deformation in the single crystal samples at 900°C is largely accommodated by shear fractures. The mechanical data, however, show an inverse normal stress dependence (flow stress at 1.5 GPa is 330 MPa, at 1.0 GPa it is 450-500MPa, and at 0.75GPa it is 680 MPa) and peak stresses below the Goetze criterion, indicating that along the cracks deformation is not dominantly friction controlled. Melt (less than 7%vol.) is distributed along cracks and shear zones are oriented at 40° to ?1 . EPMA analysis reveals inhomogenous melt compositions, suggesting that the melt pockets along cracks are not interconnected. Hydrostatic experiments performed at the same P, T conditions for the same amount of time as the deformation experiments do not contain any melt, indicating that melt kinetics are - at least in part - controlled by the cracking process (solidus T=725°C). Chemical homogenization is evident in the fine-grained fragments of the fault gouges, which have variable intermediate chemical compositions between the K-feldspar (Ab8 An0 Or92) and the albite lamellae (Ab98 An1 Or1) of the starting material. In powder shear experiments the melt fraction is higher than in single crystals. Melt is distributed along shear bands and around single grains, which are completely homogenized (Ab21 An0 Or79). The strength of the material is as high (100-150 MPa) as the strength of pure labradorite deformed in shear, where no melt was detected. These observations suggest that the deformation of single feldspar crystals at high pressure and temperature is controlled by a simultaneous formation of micro-cracks and melt. The formation of wet melt is accelerated by cracking as demonstrated by the absence of melt in hydrostatic experiments. Melt formation occurs faster at higher confining pressure, and weakens the sample as demonstrated by the inverse dependence of peak-strength with confining pressure. The melt along the cracks accommodates the deformation by viscous processes, but it does not dramatically weaken the samples because the melt pockets are not interconnected at the low melt fraction of 7%. The coalescence of the initial micro-cracks generates conjugate cracks in which the fine grained fragments of the gouge undergoes chemical homogenization. The deformation mechanism in the gouge is likely to be melt-enhanced diffusion creep, which is likely to also assist the chemical homogenization process.

Negrini, M.; Stunitz, H.; Menegon, L.; Nasipuri, P.

2011-12-01

314

Amphibole stability in primitive arc magmas: effects of temperature, H2O content, and oxygen fugacity  

NASA Astrophysics Data System (ADS)

The water-saturated phase relations have been determined for a primitive magnesian andesite (57 wt% SiO2, 9 wt% MgO) from the Mt. Shasta, CA region over the pressure range 200-800 MPa, temperature range of 915-1,070 °C, and oxygen fugacities varying from the nickel-nickel oxide (NNO) buffer to three log units above NNO (NNO+3). The phase diagram of a primitive basaltic andesite (52 wt% SiO2, 10.5 wt% MgO) also from the Mt. Shasta region (Grove et al. in Contrib Miner Petrol 145:515-533; 2003) has been supplemented with additional experimental data at 500 MPa. Hydrous phase relations for these compositions allow a comparison of the dramatic effects of dissolved H2O on the crystallization sequence. Liquidus mineral phase stability and appearance temperatures vary sensitively in response to variation in pressure and H2O content, and this information is used to calibrate magmatic barometers-hygrometers for primitive arc magmas. H2O-saturated experiments on both compositions reveal the strong dependence of amphibole stability on the partial pressure of H2O. A narrow stability field is identified where olivine and amphibole are coexisting phases in the primitive andesite composition above 500 MPa and at least until 800 MPa, between 975-1,025 °C. With increasing H2O pressure ({P}_{{H}_2O}), the temperature difference between the liquidus and amphibole appearance decreases, causing a change in chemical composition of the first amphibole to crystallize. An empirical calibration is proposed for an amphibole first appearance barometer-hygrometer that uses Mg# of the amphibole and f_{{O}_2}: P_{{H}2O}(MPa)=[{Mg#/52.7}-0.014 * Updelta NNO]^{15.12} This barometer gives a minimum {P}_{{H}2O} recorded by the first appearance of amphibole in primitive arc basaltic andesite and andesite. We apply this barometer to amphibole antecrysts erupted in mixed andesite and dacite lavas from the Mt. Shasta, CA stratocone. Both high H2O pressures (500-900 MPa) and high pre-eruptive magmatic H2O contents (10-14 wt% H2O) are indicated for the primitive end members of magma mixing that are preserved in the Shasta lavas. We also use these new experimental data to explore and evaluate the empirical hornblende barometer of Larocque and Canil (2010).

Krawczynski, Michael J.; Grove, Timothy L.; Behrens, Harald

2012-08-01

315

Experimental investigation on thermochemical sulfate reduction by H2S initiation  

USGS Publications Warehouse

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.

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

2008-01-01

316

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

PubMed

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

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

1991-01-01

317

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)

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 -65.4°C 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.

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

1990-03-01

318

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

PubMed Central

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

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

2012-01-01

319

Global Autocorrelation Scales of the Partial Pressure of Oceanic CO2  

NASA Technical Reports Server (NTRS)

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.

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

2004-01-01

320

The effects of total gas pressure and Xe partial pressure on the properties of plasma display panels with two-opposite-electrode cells  

NASA Astrophysics Data System (ADS)

The effects of total pressure and Xe partial pressure on the characteristics of an alternating-current plasma display panel with a two-opposite-electrode discharge cell configuration and a three-electrode surface-discharge cell configuration were investigated in terms of the following electro-optical properties: breakdown voltage, sustain voltage, wall charge transfer curve, infrared emission characteristics, luminance and luminous efficacy. Despite the longer discharge gap length, the results of the experiment and three-dimensional plasma simulation indicated that the opposite-discharge configuration has a significantly lower breakdown voltage than the surface-discharge configuration. Furthermore, the ratio of the increase in the breakdown voltage for the opposite-discharge configuration to the incremental Xe partial pressure was found to be smaller than that of the surface-discharge configuration. Because of its low driving voltage and possible use of high-Xe partial pressure, the opposite-discharge mode exhibited a higher luminous efficacy compared with the surface-discharge mode. These results indicated that the two-opposite-electrode discharge cell configuration has a cost reduction potential in electronics as well as high efficacy for plasma displays.

Ok, Jung-Woo; Lee, Byoung-Seob; Choi, Seyong; Won, Mi-Sook; Kim, Dong-Hyun; Lee, Hae June; Lee, Ho-Jun

2014-04-01

321

The H2O content of granite embryos  

NASA Astrophysics Data System (ADS)

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 6.5±1.4 wt%) in these low-temperature, low-pressure granitic melts. We demonstrate that, when the entire population from the same host is considered, MI reveal the H2O content of melt in the specific volume of rock where the host garnet grew. Mean H2O values for the MI in different host crystals range from 5.4 to 9.1 wt%. This range is in rather good agreement with experimental models for granitic melts at the inferred P-T conditions. Our study documents for the first time the occurrence of H2O heterogeneities in natural granitic melts at the source region. These heterogeneities are interpreted to reflect the birth of granitic melts under conditions of “mosaic” equilibrium, where the distinct fractions of melt experience different buffering assemblages at the micro-scale, with concomitant differences in melt H2O content. These results confirm the need for small-scale geochemical studies on natural samples to improve our quantitative understanding of crustal melting and granite formation. The same approach adopted here can be applied to 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.

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

2014-06-01

322

H2 temperatures in the Crab Nebula  

NASA Astrophysics Data System (ADS)

We used K-band spectra to measure the H2 excitation temperatures in six molecular knots associated with the filaments in the Crab Nebula. The temperatures are quite high - in the range T˜ 2000-3000 K, just below the H2 dissociation temperature. This is the temperature range over which the H2 1-0 S(1) line at ?2.121 ?m has its maximum emissivity per unit mass, so there may be many additional H2 cores with lower temperatures that are too faint to detect. We also measured the electron density in adjacent ionized gas, which on the assumption of gas pressure balance indicates densities in the molecular region nmol˜ 20 000 H baryons cm-3, although this really is just a lower limit since the H2 gas may be confined by other means. The excited region may be just a thin skin on a much more extensive blob of molecular gas that does not have the correct temperature and density to be as easily detectable. At the opposite extreme, the observed knots could consist of a fine mist of molecular gas in which we are detecting essentially all of the H2. Future CO observations could distinguish between these two cases. The Crab filaments serve as the nearby laboratories for understanding the very much larger filamentary structures that have formed in the intracluster medium of cool-core galaxy clusters.

Loh, E. D.; Baldwin, J. A.; Ferland, G. J.; Curtis, Z. K.; Richardson, C. T.; Fabian, A. C.; Salomé, Philippe

2012-03-01

323

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

NASA Astrophysics Data System (ADS)

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

Lu, Yi; Wang, Li

2012-11-01

324

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

NASA Astrophysics Data System (ADS)

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 Xe2*(3?u+) excimer species, which are generated from Xe*(1s5), 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.

Zhu, Di; Zhang, Xiong; Kajiyama, Hiroshi

2012-08-01

325

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

Microsoft Academic Search

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

Rei Fang; R. F. Brebrick

1996-01-01

326

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

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.

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

1997-02-01

327

?H2AX and cancer  

PubMed Central

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

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

2011-01-01

328

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

SciTech Connect

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

Vera, C.M.C. [Laboratorio de Peliculas Delgadas, Facultad de Ingenieria, Universidad de Buenos Aires, Paseo Colon 850, (1063) Buenos Aires (Argentina)], E-mail: cvera@fi.uba.ar; Aragon, R. [Laboratorio de Peliculas Delgadas, Facultad de Ingenieria, Universidad de Buenos Aires, Paseo Colon 850, (1063) Buenos Aires (Argentina); CINSO, CONICET, CITEFA, Lasalle 4397, Villa Martelli, Buenos Aires (Argentina)

2008-05-15

329

Measurements of pressure distributions and force coefficients in a squeeze film damper. Part 2: Partially sealed configuration  

NASA Technical Reports Server (NTRS)

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.

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

1991-01-01

330

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

NASA Technical Reports Server (NTRS)

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.

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

2006-01-01

331

H2 Detection via Polarography  

NASA Technical Reports Server (NTRS)

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.

Dominquez, Jesus; Barile, Ron

2006-01-01

332

Oxidation of zirconium diboride–silicon carbide ceramics under an oxygen partial pressure of 200 Pa: Formation of zircon  

Microsoft Academic Search

The formation and evolution of zircon during oxidation of ZrB2–20vol.% SiC ceramics under a low oxygen partial pressure of 200Pa is studied. The formation mechanism of zircon is proposed according to experimental results and thermodynamic consideration. And the main reason to the formation of zircon can be attributed to the active oxidation of SiC. Two steps can be divided for

Dong Gao; Yue Zhang; Jingying Fu; Chunlai Xu; Yang Song; Xiaobin Shi

2010-01-01

333

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

SciTech Connect

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.

Yang Qinghui; Zhang Huaiwu; Wen Qiye; Liu Yingli [State Key Laboratory of Electronic Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054 (China); Xiao, John Q. [Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716 (United States)

2009-04-01

334

Development of a silicone membrane tube equilibrator for measuring partial pressures of volatile organic compounds in natural water.  

PubMed

Methods for determining volatile organic compounds (VOCs) in water and air are required so that the VOCs' fluxes in water environments can be estimated. We developed a silicone membrane tube equilibrator for collecting gas-phase samples containing VOCs at equilibrium with natural water. The equilibrator consists of six silicone tubes housed in a polyvinyl chloride pipe. Equilibrated air samples collected from the equilibrator were analyzed with an automated preconcentration gas chromatography-mass spectrometry system for hourly measurements of VOC partial pressures. The partial pressures of all the target VOCs reached equilibrium within 1 h in the equilibrator. The system was used to determine VOC partial pressures in Lake Kasumigaura, a shallow eutrophic lake with a high concentration of suspended particulate matter (SPM). Compressed air was used daily to remove SPM deposited on the inner wall of the equilibrator and to maintain the equilibrium conditions for more than a week without the need to shut the system down. CH2Br2, CHCl3, CHBrCl2, CH2BrCl, C2H5I, C2Cl4, CH3I, and CH3Br in the lake were supersaturated with respect to the air, whereas CH3CI was undersaturated. CHCl3 had the highest flux (6.2 nmol m(-2) hr(-1)) during the observation period. PMID:18754497

Ooki, Atsushi; Yokouchi, Yoko

2008-08-01

335

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

DOEpatents

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.

Findl, E.

1984-12-21

336

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

Microsoft Academic Search

A new method for computing complicated equilibria in hydrothermal mixed fluids, H2O-non-polar gas, is proposed. The computation algorithm is based on the electrostatic approach for the interaction between aqueous species and H2O. The approach uses the SUPCRT92 database and the HKF format and may be considered as an application of the revised HKF model for mixed H2O-non-polar gas fluids. Thermodynamic

Nikolai Akinfiev; Alexander Zotov

1999-01-01

337

Study of partial melting at high-pressure using in situ X-ray diffraction  

Microsoft Academic Search

The high-pressure melting behavior of different iron alloys was investigated using the classical synchrotron-based in situ X-ray diffraction techniques. As they offer specific advantages and disadvantages, both energy-dispersive (EDX) and angle-dispersive (ADX) X-ray diffraction methods were performed at the BL04B1 beamline of SPring8 (Japan) and at the ID27-30 beamline of the ESRF (France), respectively. High-pressure vessels and pressure ranges investigated

D. Andrault; G. Morard; N. Bolfan-Casanova; O. Ohtaka; H. Fukui; H. Arima; N. Guignot; K. Funakoshi; P. Lazor; M. Mezouar

2006-01-01

338

( p, ?, T ) measurements of (ammonia + water) in the temperature range 310 K to 400 K at pressures up to 17 MPa. I. Measurements of { x NH 3 + (1 ? x ) H 2 O } at x = (0.8952, 0.8041, 0.6985, 0.5052 , and 0.1016)  

Microsoft Academic Search

Measurements of ( p, ?, T) for{xNH3+ (1 ?x)H2O} at x= (0.8952, 0.8041, 0.6985, 0.5052, and 0.1016) and at specified temperatures and pressures in the compressed liquid phase were carried out with a metal-bellows variable volumometer between T= 310 K and T= 400 K at pressures from the bubble point pressure to p= 17 MPa. The results cover the high-density

T Munakata; K Kasahara; M Uematsu

2002-01-01

339

The influence of H2O-H2 fluids and redox conditions on melting temperatures in the haplogranite system  

NASA Astrophysics Data System (ADS)

Solidus temperatures of quartz-alkali feldspar assemblages in the haplogranite system (Qz-Ab-Or) and subsystems in the presence of H2O-H2 fluids have been determined at 1, 2, 5 and 8 kbar vapour pressure to constrain the effects of redox conditions on phase relations in quartzofeldspathic assemblages. The hydrogen fugacity ( f H2) in the fluid phase has been controlled using the Shaw membrane technique for moderately reducing conditions ( f H2 < 60 bars) at 1 and 2 kbar total pressure. Solid oxygen buffer assemblages in double capsule experiments have been used to obtain more reducing conditions at 1 and 2 kbar and for all investigations at 5 and 8 kbar. The systems Qz-Or-H2O-H2 and Qz-Ab-H2O-H2 have only been investigated at moderately reducing conditions (1 and 5 kbar) and the system Qz-Ab-Or-H2O-H2 has been investigated at redox conditions down to IW (1 to 8 kbar). The results obtained for the water saturated solidi are in good agreement with those of previous studies. At a given pressure, the solidus temperature is found to be constant (within the experimental precision of ± 5°C) in the f H2 range of 0-75 bars. At higher f H2, generated by the oxygen buffers FeO-Fe3O4 (WM) and Fe-FeO (IW), the solidus temperatures increase with increasing H2 content in the vapour phase. The solidus curves obtained at 2 and 5 kbar have similar shapes to those determined for the same quartz - alkali feldspar assemblages with H2O-CO2- or H2O-N2-bearing systems. This suggests that H2 has the behaviour of an inert diluent of the fluid phase and that H2 solubility in aluminosilicate melts is very low. The application of the results to geological relevant conditions [HM (hematite-magnetite) > f O2 > WM] shows that increasing f H2 produces a slight increase of the solidus temperatures (up to 30 °C) of quartz-alkali feldspar assemblages in the presence of H2O-H2 fluids between 1 and 5 kbar total pressure.

Schmidt, B. C.; Holtz, François; Scaillet, Bruno; Pichavant, Michel

1997-02-01

340

The H2O solubility of alkali basaltic melts: an experimental study  

NASA Astrophysics Data System (ADS)

Experiments were conducted to determine the water solubility of alkali basalts from Etna, Stromboli and Vesuvius volcanoes, Italy. The basaltic melts were equilibrated at 1,200°C with pure water, under oxidized conditions, and at pressures ranging from 163 to 3,842 bars. Our results show that at pressures above 1 kbar, alkali basalts dissolve more water than typical mid-ocean ridge basalts (MORB). Combination of our data with those from previous studies allows the following simple empirical model for the water solubility of basalts of varying alkalinity and fO2 to be derived: {{H}}_{ 2} {{O}}( {{{wt}}% } ) = {{ H}}_{ 2} {{O}}_{{MORB}} ( {{{wt}}% } ) + ( {5.84 × 10^{ - 5} *{{P}} - 2.29 × 10^{ - 2} } ) × ( {{{Na}}2 {{O}} + {{K}}2 {{O}}} )( {{{wt}}% } ) + 4.67 × 10^{ - 2} × Updelta {{NNO}} - 2.29 × 10^{ - 1} where H2OMORB is the water solubility at the calculated P, using the model of Dixon et al. (1995). This equation reproduces the existing database on water solubilities in basaltic melts to within 5%. Interpretation of the speciation data in the context of the glass transition theory shows that water speciation in basalt melts is severely modified during quench. At magmatic temperatures, more than 90% of dissolved water forms hydroxyl groups at all water contents, whilst in natural or synthetic glasses, the amount of molecular water is much larger. A regular solution model with an explicit temperature dependence reproduces well-observed water species. Derivation of the partial molar volume of molecular water using standard thermodynamic considerations yields values close to previous findings if room temperature water species are used. When high temperature species proportions are used, a negative partial molar volume is obtained for molecular water. Calculation of the partial molar volume of total water using H2O solubility data on basaltic melts at pressures above 1 kbar yields a value of 19 cm3/mol in reasonable agreement with estimates obtained from density measurements.

Lesne, Priscille; Scaillet, Bruno; Pichavant, Michel; Iacono-Marziano, Giada; Beny, Jean-Michel

2011-07-01

341

Direct conversion of ethane to ethanol by the homogeneous partial oxidation at high pressures  

Microsoft Academic Search

The results of the homogeneous high-pressure (10-100 atm) oxidation of ethane to ethanol are reported. The products identified and analyzed were ethanol, methanol, acetaldehyde, methane, carbon monoxide, carbon dioxide, and water. The highest value of the ratio ethanol\\/methanol in the products was 6, obtained at the highest pressure studied (100 atm). A mechanism is proposed to account for the products.

H. D. Gesser; N. R. Hunter; L. A. Morton; P. S. Yarlagadda

2009-01-01

342

The effect of hydrostatic pressure on magnetic properties of partially crystallized Co-based amorphous alloy  

Microsoft Academic Search

Melt-spun Co66Nb9Cu1Si12B12 metallic glass ribbon (TC?150K) was used to produce nanocrystalline samples by annealing at 590°C and 610°C for 1 h. Their magnetic properties were measured in a superconducting quantum interference device (SQUID) magnetometer as a function of temperature (10–250 K) in fields to 3 kOe at zero and ?7 kbar hydrostatic pressure. The pressure shifts the Curie point of

H. K. Lachowicz; K. Zaveta; Z. Arnold; J. Kamarad; M. Marysko

2001-01-01

343

The 50 Ah NiH2 CPV qualification tests  

Microsoft Academic Search

In 1992, the Naval Research Laboratory (NRL) started a program to qualify a large diameter common pressure vessel (CPV) nickel-hydrogen (NiH2) batteries for use on future Navy\\/NRL spacecraft electrical power subsystems. NRL's involvement with the qualification of CPV NiH2 batteries dates back to 1988 when COMSAT and Johnson Controls, Inc. initiated a joint effort to fly the first ever NiH2

J. C. Garner; Wilbert L. Barnes; Gary L. Hickman

1995-01-01

344

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

Microsoft Academic Search

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

Archie Robertson

2003-01-01

345

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

PubMed Central

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.

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

2012-01-01

346

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

NASA Astrophysics Data System (ADS)

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.

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

2012-12-01

347

Effect of Zn Partial Pressure during Growth on Electrical Properties of ZnSe Crystals Grown from the Melt  

NASA Astrophysics Data System (ADS)

This paper describes the melt growth of ZnSe crystals by a modified Bridgman method under argon pressure. A definite Zn partial pressure over the melt is maintained by controlling the temperature of a Zn zeservoir. Electrical properties of as-grown crystals depend on the temperature of the reservoir. Low-resistivity n-type crystals are obtained when the temperature of the reservoir is kept above 1040°C during growth. The resistivity of the crystals is 0.2 to 5 ?\\cdotcm and the Hall mobility is 380 to 500 cm2/V\\cdots at room temperature (290± 5 K). The temperature of the Zn reservoir during the cooling process after solidification also affects the electrical properties.

Kikuma, Isao; Kikuchi, Atsushi; Furukoshi, Mitsuo

1990-11-01

348

The interaction of H2S with the ZnO(1010) surface.  

PubMed

Using density functional theory with and without Hubbard-U correction we have calculated the geometric structure and the binding energy of H2S molecules adsorbed on the main cleavage plane of ZnO. We find that H2S molecules preferentially dissociate upon adsorption, with a negligible barrier for the first and an activation energy of about 0.5 eV for the second SH bond dissociation. In the low coverage limit of individual molecules single and double dissociation are energetically almost degenerate. At higher coverage double dissociation is favored because of attractive adsorbate-adsorbate interactions. Thermodynamic analysis shows that the double-dissociated state at full saturation with a coverage of 1/2 monolayer is the most stable adsorbate structure for a wide range of temperatures and partial pressures. However, at high H2S chemical potential a full monolayer of single-dissociated H2S becomes thermodynamically more favorable. In addition, at low temperature this structure may exist as a metastable configuration due to the activation barrier for the second SH bond cleavage. Finally we show that it is thermodynamically favorable for adsorbed H2S to react with the first ZnO surface layer to form ZnS and water. PMID:23619935

Goclon, Jakub; Meyer, Bernd

2013-06-01

349

Acoustic pressure wound therapy for management of mixed partial- and full-thickness burns in a rural wound center.  

PubMed

Infection, pain, and cosmetically unacceptable scarring frequently complicate full-thickness burns. Outpatient management can be difficult without specialized care. A retrospective case series study was conducted in a rural wound center lacking specialized burn care to assess the clinical effectiveness of acoustic pressure wound therapy, a noncontact low-frequency, nonthermal ultrasound wound therapy that accelerates healing through positive pressure, stimulating fibroblasts, clearing bacteria and debris, and relieving pain. Data from the records of 14 consecutively treated outpatients (age range 5 months to 78 years old) with mixed partial- and full-thickness burns involving the trunk, extremities, or both, averaging 7% of body surface area (range: 1% to 24%), were reviewed. Patients received acoustic pressure wound therapy with standard burn care. Burn thickness was determined by clinical appearance. Treatment effectiveness was evaluated based on scarring characteristics of healed wounds (ie, cosmetic appearance) and pain resolution. Pain was patient-rated using a 10-point visual analog scale (0 = no pain, 10 = severe). Patients were followed for 6 months post-healing. Pain improved with therapy (range: two to 10 treatments). No patient required hospitalization or developed complications related to infection. Pliable, nonhypertrophic scars developed in 86% of patients and hypertrophic scars developed in 14%. Repigmentation was seen in 79% of patients, with only minor irregularities; hypopigmentation occurred in 21%. Scars available for follow-up (71%) remained unchanged. Acoustic pressure wound therapy with standard burn care was found to heal mixed partial- and full-thickness burns and reduced pain in outpatients, resulting in cosmetically acceptable scarring without infectious complications, surgery, or skin grafts and may prove beneficial for inpatient management of extensive full-thickness burns. Further study is warranted. PMID:18456962

Samies, John; Gehling, Marie

2008-03-01

350

H2 Physisorbed on Graphane  

NASA Astrophysics Data System (ADS)

We study the zero-temperature phase diagrams of H2 adsorbed on the three structures predicted for graphane (chair, boat and washboard graphane), using a diffusion Monte Carlo technique. Graphane is the hydrogenated version of graphene, in which each carbon atom changes its hybridization to sp 3 and forms a covalent bond with a hydrogen atom. Our results show that the ground state of H2 adsorbed on all three types of graphane is a sqrt{3}×sqrt{3} solid, similar to the structures found both for H2 and D2 on graphene. When the H2 density increases, the system undergoes a first order phase transition to a triangular incommensurate solid. This change is direct in the case of washboard graphane, but indirect via different commensurate structures in the other cases. The total hydrogen weight percentage on the three graphane types in their ground states is in the range 10 % to 12 %, depending on if one or both graphane surfaces are covered with H2.

Carbonell-Coronado, C.; de Soto, F.; Cazorla, C.; Boronat, J.; Gordillo, M. C.

2013-06-01

351

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

Microsoft Academic Search

Concentrations of the Fe(CO3)OH component in goethites from Phanerozoic oolitic ironstones appear to record information on the partial pressures of soil CO2 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

Crayton J. YAPP

1996-01-01

352

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

Microsoft Academic Search

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

T. R. Roper; L. E. Williams

1989-01-01

353

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

SciTech Connect

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.

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

2009-01-01

354

Photosynthesis and Growth Response of Almond to Increased Atmospheric Ozone Partial Pressures1  

Microsoft Academic Search

Uniform nursery stock of five almond cultivars (Prunus dulcis (Mill) D.A. Webb syn. P. amygdalus Batsch, ev. Butte, Carmel, Mission, Nonpareil, and Sonora) propagated on peach (P. domestiea L. Batsch.) rootstock were exposed to three different atmospheric ozone (03) par- tial pressures. The trees were planted in open-top fumigation cham- bers on 19 Apr. 1989 at the University of California

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

1992-01-01

355

Direct conversion of methane to methanol by a high pressure partial oxidation reaction  

Microsoft Academic Search

The conversion of methane to a liquid storageable fuel is a desirable alternative to compressed natural gas. The simplest liquid is methanol presently formed by the steam reforming of methane to synthesis gas followed by the high pressure catalytic conversion of the synthesis gas to methanol. The process is most economic for large (2000 tonne\\/day) plants and must be located

H. D. Gesser; N. R. Hunter; L. A. Morton; P. S. Yarlagadda; D. P. C. Fung

1988-01-01

356

( p, ?, T) measurements of (ammonia + water) in the temperature range 310 K to 400 K at pressures up to 17 MPa. II. Measurements of { x NH 3 + (1 ? x ) H 2O } at x = (1.0000, 0.8374, 0.6005, and 0.2973)  

Microsoft Academic Search

Measurements of (p, ?, T) for{xNH3+ (1 ?x)H2O} at x= (1.0000, 0.8374, 0.6005, and 0.2973) and at specified temperatures and pressures in the compressed liquid phase were carried out with a metal-bellows variable volumometer between T= 310 K and T= 400 K at pressures up to 17 MPa. The results cover the high-density region from ?= 345 kg · m?3

J. Kondo; Y. Yasukawa; M. Uematsu

2002-01-01

357

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

SciTech Connect

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

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

2009-06-01

358

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

PubMed

In a prospective study, the characteristics and benefit of an invasive measurement of oxygen partial pressure (pO(2)) with the aid of a polarographic sensor were investigated in 125 microsurgical reconstructions of the head and neck area over a period of 45 months. Measurements were performed over 96 h in eight different types of microsurgically revascularized flaps for extra- and intraoral reconstructions and were evaluated separately for each flap type. Of 125 reconstructions the system indicated malperfusion in 18 cases. Salvage surgery was performed in 17 cases due to venous thrombosis (6 cases), arterial thrombosis (3 cases), a combination of arterial and venous thrombosis (2 cases), rheological problems (3 cases), venous insufficiency by hematoma (2 cases) and kinking of vessels (1 case). In 10 cases salvage surgery was successful, 7 flaps were lost despite salvage surgery. In all these cases, the polarographic probe indicated the necessity of salvage surgery correctly. After 96 h no malperfusion was seen. Postoperatively, a common and characteristic development of the oxygen partial pressure in different types of flaps was seen. Initially, a clear increase of pO(2) could be measured. During 96 h, a slow decrease of pO(2) was observed. In conclusion polarographic measurement of pO(2) can be an excellent apparative supplement for the postoperative clinical control of microsurgically revascularized transplants. In buried flaps, this technique represents the only reliable method for transplant monitoring. PMID:23176981

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

2013-06-01

359

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

NASA Astrophysics Data System (ADS)

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.

Chiesa, S.; Rossi, M. J.

2013-07-01

360

Measurement of inter-particle forces from the osmotic pressure of partially frozen dispersions  

NASA Astrophysics Data System (ADS)

When an oil-continuous dispersion is frozen two microdomains are formed: one, the pure oil solvent which is selectively solidified (I), the other, a concentrated `liquid' dispersion of particles in oil (II). These two domains are intimately mixed within the frozen colloid and exist in a state of equilibrium determined by the system pressure and temperature. The position of equilibrium controls the proportion of the solvent which is solidified, and thereby the concentration of particles within the fluid microdomains (II). Combined with SANS measurements, to determine the inter-particle separation in these microdomains, an analysis based on osmotic pressure provides a measure of the inter-particle repulsion forces presented by the surfactant layers.

Steytler, David C.; Robinson, Brian H.; Eastoe, Julian; MacDonald, Isabel; Ibel, Konrad; Dore, John C.

1996-11-01

361

Conversion of ethane to methanol and ethanol by ozone sensitized partial oxidation at near atmospheric pressure  

Microsoft Academic Search

The reaction of ethane-oxygen mixtures with ozone as a sensitizer in the feed-gas was quantitatively studied at near atmospheric pressure in a dual-flow system. Ozone was generated by silent discharge. The influence of reaction temperature, oxygen concentration in the feed-gas, residence time in the reactor, and ozone concentration in oxygen on the reaction were investigated.Ethanol selectivities (based on carbon) between

H. D. Gesser; G. Zhu; N. R. Hunter

1995-01-01

362

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

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

363

Biogeochemistry of dihydrogen (H2).  

PubMed

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

Hoehler, Tori M

2005-01-01

364

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

PubMed Central

Background All clinical and biological manifestations related to postcardiac arrest (CA) syndrome are attributed to ischemia–reperfusion 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 (37°C), the control group; MV with 2% H2 and 98% O2 under normothermia; MV with 2% N2 and 98% O2 under therapeutic hypothermia (TH), 33°C; 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.

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

365

Production of synthesis gas by partial oxidation and high-pressure shift conversion  

SciTech Connect

A fifteen-year history account of process improvements at the BASF ammonia plant at Ludwigshafen, West Germany is presented. Heavy fuel oil with a sulfur content of 1.75% (by weight) and with an ash content of about 0.015% (by weight) is used as feedstock at the plant. The fuel oil is converted with oxygen and steam to synthesis gas at a pressure of 80 bar. The synthesis gas generation is followed by raw-gas preheater, a two-step water-gas shift conversion, and a subsequent waste heat recovery. Sulfur compounds and CO/sub 4/ are removed from converted gas in a combination of a TEA- and an Alkazid-scrubber. Final purification and nitrogen enrichment is achieved in a liquid-nitrogen scrubber. The NH/sub 3/ synthesis operated at 350-430 bar, at which pressure NH/sub 3/-refrigeration of the recycle loop and purge gas removal are not necessary. (JMT)

Balz, D.F.; Gettert, H.F.; Gruendler, K.H.

1983-01-01

366

Transport behavior and electronic structure of phase pure VO2 thin films grown on c-plane sapphire under different O2 partial pressure  

NASA Astrophysics Data System (ADS)

We grew highly textured phase pure VO2 thin films on c-plane Al2O3 substrates with different oxygen partial pressure. X-ray absorption and photoemission spectroscopy confirm the identical valence state of vanadium ions despite the different oxygen pressure during the deposition. As the O2 flow rate increases, the [010] lattice parameter for monoclinic VO2 was reduced and coincidently distinctive changes in the metal-semiconductor transition (MST) and transport behaviors were observed despite the identical valence state of vanadium in these samples. We discuss the effect of the oxygen partial pressure on the monoclinic structure and electronic structure of VO2, and consequently the MST.

Kittiwatanakul, Salinporn; Laverock, Jude; Newby, Dave; Smith, Kevin E.; Wolf, Stuart A.; Lu, Jiwei

2013-08-01

367

Disappearance of Peak Effect in Critical Current Density of NdBa2Cu3O7-? Single Crystals Grown under Very Low Oxygen Partial Pressures  

NASA Astrophysics Data System (ADS)

NdBa2Cu3O7-?(Nd123) single crystals were grown by horizontal Bridgman-like method under various partial O2 pressures (0.1 0.04%) in Ar atmosphere. High quality Nd123 single crystals with superconducting transition temperature, Tc˜95.0 K were obtained using yttrium stabilized ZrO2 boats. The enhancement of the magnetization with increasing field, i.e., fishtail or peak effect was observed in the magnetization hysteresis at around 77 K in the field parallel to the c-axis of the Nd123 single crystals grown under 0.1 0.06% partial O2 pressures, but not for the crystals grown under 0.05 and 0.04% O2 pressures. This indicates the existence of certain partial O2 pressures under which the amount of Nd/Ba substitution is remarkably reduced in Nd123 single crystals.

Shibata, Susumu; Pradhan, Aswini; Koshizuka, Naoki

1999-10-01

368

QED Effects in H_2  

NASA Astrophysics Data System (ADS)

The electron self-interaction and the vacuum polarization, the two effects predicted by Quantum Electrodynamics (QED), have been accurately calculated for H_2 and its isotopomers. The resulting theoretical predictions will be compared with state of the art measurements of dissociation energies, vibrational and rotational transitions. New developments for the calculation of higher order QED effects will be presented. J. Komasa, K. Piszczatowski, G. Lach, M. Przybytek, B. Jeziorski, and K. Pachucki, JCTC {7}, 3105 (2011)

Pachucki, Krzysztof; Komasa, Jacek

2013-06-01

369

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

SciTech Connect

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.

Highland, M. J.; Fister, T. T.; Fong, D. D.; Fuoss, P. H.; Thompson, C.; Eastman, J. A.; Streiffer, S. K.; Stephenson, G. B. (Chemical Sciences and Engineering Division); ( MSD); ( OTD-PSE); (Northern Illinois Univ.)

2011-01-01

370

Equilibrium Polarization of Ultrathin PbTiO3 with Surface Compensation Controlled by Oxygen Partial Pressure  

NASA Astrophysics Data System (ADS)

We present a synchrotron x-ray study of the equilibrium polarization structure of ultrathin PbTiO3 films on SrRuO3 electrodes epitaxially grown on SrTiO3 (001) substrates, as a function of temperature and the external oxygen partial pressure (pO2) controlling their surface charge compensation. We find that the ferroelectric Curie temperature (TC) varies with pO2 and has a minimum at the intermediate pO2, where the polarization below TC 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.

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

2011-10-01

371

The 50 Ah NiH2 CPV qualification tests  

NASA Astrophysics Data System (ADS)

In 1992, the Naval Research Laboratory (NRL) started a program to qualify a large diameter common pressure vessel (CPV) nickel-hydrogen (NiH2) batteries for use on future Navy/NRL spacecraft electrical power subsystems. NRL's involvement with the qualification of CPV NiH2 batteries dates back to 1988 when COMSAT and Johnson Controls, Inc. initiated a joint effort to fly the first ever NiH2 CPV in space. A later NRL-JCI cooperative research and development agreement led to the launch of a space experiment in 1993 and to the use of a single NiH2 CPV battery on the BMDO Clementine spacecraft in 1994. NRL initiated procurement of two, 50 Ah CPV NiH2 batteries in the Fall of 1992. The two batteries were delivered to NRL in June 1994. NiH2 CPV batteries have almost 2x the specific energy (Wh/kg) of nickel cadium batteries and 2x the energy density (Wh/l) of individual pressure vessel NiH2 CPV's. This presentation discusses the results of electrical and mechanical qualification tests conducted at NRL. The tests included electrical characterization, standard capacity, random vibration, peak load, and thermal vacuum. The last slides of the presentation show initial results from the life cycle tests of the second NiH2 CPV battery at 40% depth of discharge and a temperature of 10 C.

Garner, J. C.; Barnes, Wilbert L.; Hickman, Gary L.

1995-02-01

372

Direct Formation of H2O2 from H2 and O2  

Microsoft Academic Search

The direct combination of hydrogen and oxygen to form hydrogen peroxide in liquid media with preparedcatalysts was carriedout in a slurry reactor at atmospheric pressure androom temperature. An O2\\/H2 ratio of 2:1 with a 50 mL\\/min flow rate was usedin these experiments. Catalyst activity measurements were testedby the iod ometric titration methodusing KMnO 4. The results are discussed basedon the

Meltem YILDIZ; Ayse Nilgun AKIN

373

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

SciTech Connect

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

Inoue, N.; Okada, M.; Higashiyama, K. [Hitachi Research Lab. (Japan)] [and others

1997-06-01

374

Phase relationships of S-type granite with H2O to 35 kbar: Muscovite granite from Harney Peak, South Dakota  

NASA Astrophysics Data System (ADS)

Muscovite granite (13.8% muscovite, 4.8% normative corundum) was reacted, with varying percentages of H2O, in cold-seal vessels at 2 kbar and in piston-cylinder apparatus between 10 and 35 kbar. The diagrams illustrating melting/crystallization relationships are: P- T sections with both excess H2O and with no H2O added (0.66% H2O in rock); T-XH2O sections at 15 kbar and 25 kbar showing H2O-undersaturated conditions; the H2O-undersaturated surface for the crystallization of quartz/coesite (small amounts of aluminosilicate minerals persist to higher temperatures). Glass compositions measured by electron microprobe from samples with 5% H2O at 15 kbar confirm that liquids are syenitic through at least 100°C above the solidus, as predicted from the effect of pressure on the Residua System. Results are explained successfully by phase relationships involving muscovite, quartz, and orthoclase in K2O-Al2O3-SiO2-H2O, with reactions depicted in a Ptotal-PeH2O-T model, with special reference to the divariant surfaces in the region PeH2O < Ptotal. With reduced PeH2O (or aH2O), produced either by small amounts of H2O (and H2O-undersaturation) or by CO2 + H2O mixtures, subsolidus dehydration reaction temperatures decrease, vapor-present solidus temperatures increase, and muscovite stability in presence of liquid increases. In general, muscovite, biotite, and amphibole can be precipitated from magmas containing only a few tenths per cent H2O (although the H2O-undersaturated liquids coexisting with crystals may contain 3% or more dissolved H2O). This particular granite cannot be a primary magma from mantle or subducted oceanic crust. It is a possible product of partial fusion of pelitic rocks between about 20 km and 40 km depth given sufficient H2O, and xenocrystal muscovite or sillimanite from the source rocks. The phase relationships are consistent with the idea of S-type granites, but not sufficient to prove the origin of this rock. Additional tests require phase relationships of other associated granitic rocks, and details of geochemistry, geophysics, and field relationships.

Huang, W. L.; Wyllie, P. J.

1981-11-01

375

Canopy position and needle age affect photosynthetic response in field-grown Pinus radiata after five years of exposure to elevated carbon dioxide partial pressure.  

PubMed

Photosynthesis of tree seedlings is generally enhanced during short-term exposure to elevated atmospheric CO2 partial pressure, but longer-term studies often indicate some degree of photosynthetic adjustment. We present physiological and biochemical evidence to explain observed long-term photosynthetic responses to elevated CO2 partial pressure as influenced by needle age and canopy position. We grew Pinus radiata D. Don. trees in open-top chambers for 5 years in sandy soil at ambient (36 Pa) and elevated (65 Pa) CO2 partial pressures. The trees were well watered and exposed to natural light and ambient temperature. In the fourth year of CO2 exposure (fall 1997), when foliage growth had ceased for the year, photosynthetic down-regulation was observed in 1-year-old needles, but not in current-year needles, suggesting a reduction in carbohydrate sink strength as a result of increasing needle age (Turnbull et al. 1998). In 5-year-old trees (spring 1997), when foliage expansion was occurring, photosynthetic down-regulation was not observed, reflecting significantly large sinks for carbohydrates throughout the tree. Net photosynthesis was stimulated by 79% in trees growing in elevated CO2 partial pressure, but there was no significant effect on photosynthetic capacity or Rubisco activity and concentration. Current-year needles were more responsive to elevated CO2 partial pressure than 1-year-old needles, exhibiting larger relative increases in net photosynthesis to elevated CO2 partial pressure (98 versus 64%). Lower canopy and upper canopy leaves exhibited similar relative responses to growth in elevated CO2 partial pressure. However, needles in the upper canopy exhibited higher net photosynthesis, photosynthetic capacity, and Rubisco activity and concentration than needles in the lower canopy. Given that the ratio of mature to juvenile foliage mass in the canopy will increase as trees mature, we suggest that trees may become less responsive to elevated CO2 partial pressure with increasing age. We conclude that tree response to elevated CO2 partial pressure is based primarily on sink strength and not on the duration of exposure. PMID:11498338

Tissue, D T; Griffin, K L; Turnbull, M H; Whitehead, D

2001-08-01

376

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

NASA Technical Reports Server (NTRS)

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.

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

1989-01-01

377

Evaluation of the Cs Mo I O and Cs U I O diagrams and determination of iodine and oxygen partial pressure in spent nuclear fuel rods  

NASA Astrophysics Data System (ADS)

This work provides three dimensions potential diagrams calculated in view of the evaluation of the iodine partial pressure in spent PWR fuel pellets intended to be stored for 100 years. These diagrams can be interpreted, on the basis of spent fuel examinations. It is shown that the iodine partial pressure could be controlled by the formation of cesium uranate Cs2UO4 from cesium iodide CsI in the fuel. If the formation of cesium molybdate Cs2MoO4 would take place during the storage, the iodine partial pressure is expected to increase. Such an evolution can't be excluded because of the temperature that could reach the spent fuel assemblies during the transport step up to the place of the storage.

Walle, Eric; Perrot, Pierre; Foct, Jacques; Parise, Marion

2005-02-01

378

Unconventional spin freezing in the highly two-dimensional spin-1/2 kagome antiferromagnet Cd2Cu3(OH)6(SO4)24H2O: Evidence of partial order and coexisting spin singlet state on a distorted kagome lattice  

NASA Astrophysics Data System (ADS)

S = 1/2 quantum-spin systems of the kagome lattice have received intense recent attention because they are expected to be promising candidates for novel quantum states such as spin liquid, spin nematic, and other unknown exotic states. Here we report an unusual transition in a highly two-dimensional and slightly distorted S = 1/2 quantum kagome system Cd2Cu3(OH)6(SO4)24H2O, which is a purified compound of the recently identified mineral edwardsite, Cd1.89Zn0.11Cu3(OH)6(SO4)24H2O. The S = 1/2 spins of Cu2+ ions form a highly two-dimensional kagome lattice with an extraordinarily large interlayer spacing >10 Å, thus providing a unique kagome lattice with minimum interlayer perturbation. The magnetization shows a Curie-Weiss temperature of 40.5 K and moment freezing below around TF = 5 K and a magnetic transition feature near 3 K. The muon spin relaxation shows static magnetism below 5 K and saturation below 3 K. However, distinct features have been observed distinguishing it from a spin glass or a conventional order: High-field magnetization until 50 T showed a saturated value of only 1/3 of the full expected moment. Analysis of specific heat suggests that only 1/3 of the spins are related to the magnetic order; on the other hand, the order is destroyed in external field and 1/3 of the spins respond to the field with a Schottky-like behavior while the other 2/3 of the spins remain inactive. These experimental results suggest an unconventional coexistence of the partial order and most probably spin singlets.

Fujihala, Masayoshi; Zheng, Xu-Guang; Morodomi, Hiroki; Kawae, Tatsuya; Matsuo, Akira; Kindo, Koichi; Watanabe, Isao

2014-03-01

379

Effect of oxygen partial pressure on the crystallization of CeO 2 and La 2Zr 2O 7 bi-axially textured thin films  

Microsoft Academic Search

Films of CeO2 and La2Zr2O7 have been formed by metal-organic decomposition and their crystallization studied under different oxygen partial pressures. Single crystalline substrates were use to model the phenomenon: (001)SrTiO3 (STO) for CeO2 and (001)LaAlO3 (LAO) for La2Zr2O7. A chemical interaction has been noticed in the case of CeO2\\/STO above 900°C, which also depends on the oxygen partial pressure, such

A. Guibadj; P. Odier; B. Benbarta; L. Ortega

2011-01-01

380

Role of oxygen partial pressure and seed layer chemistry in flux mediated epitaxy of single phase multiferroic BiFeO3 thin films  

NASA Astrophysics Data System (ADS)

Multiferroic BiFeO3 (BFO) thin films have been fabricated via flux mediated epitaxy with varying oxygen partial pressure and flux composition (Bi2O3:CuO) conditions. Transmission electron microscopy coupled with energy dispersive x-ray spectroscopy as well as piezoresponse force microscopy confirm, that with the correct flux and seed layer conditions, even at very low partial pressures (3 mTorr) no secondary phases are formed. The study reveals the crucial role of the bottom seed layer and flux chemistry in epitaxy of BFO thin films and provides alternate routes to BFO epitaxy in oxygen-deficient environments.

Anbusathaiah, Varatharajan; Cheng, Ching Jung; Lim, Sung Hwan; Murakami, Makoto; Salamanca-Riba, Lourdes G.; Takeuchi, Ichiro; Nagarajan, Valanoor

2008-11-01

381

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

NASA Astrophysics Data System (ADS)

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.

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

2014-04-01

382

Phase diagram and thermodynamic properties of H2.  

PubMed

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

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

2013-01-01

383

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

NASA Technical Reports Server (NTRS)

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 m