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1

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

NASA Astrophysics Data System (ADS)

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

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

2010-08-01

2

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

3

Effect of pressure on counterflow H 2air partially premixed flames  

Microsoft Academic Search

A computational investigation of high-pressure hydrogenair partially premixed flames (PPFs) is reported to characterize the effect of pressure on the flame structure, and the relevance of reaction limits for these flames. The flames are computed using the Mueller mechanism consisting of 19 elementary reactions and 9 species. Although the mechanism has been validated during previous investigations, additional validations are provided

Alejandro Briones; Ishwar K. Puri; Suresh K. Aggarwal

2005-01-01

4

Partial vapor pressure of CO 2 and H 2S over aqueous methyldiethanolamine solutions  

Microsoft Academic Search

A new apparatus is presented to measure low partial vapor pressures of acid gas. New measurements are given for carbon dioxide and hydrogen sulfide into aqueous solutions of methyldiethanolamine (MDEA). Large discrepancies among the measured VLE data and the slopes of their solubility curves are found between the authors due to systematic experimental errors, and particularly in the low acid

B. Lemoine; Yi-Gui Li; R. Cadours; C. Bouallou; D. Richon

2000-01-01

5

Partial Pressures of Gaseous HCl and H2O Over Aqueous Solutions of HCl, AlCl3, and FeCl3.  

National Technical Information Service (NTIS)

Equilibrium partial pressures of gaseous HCl and H2O over aqueous binary and ternary solutions of HCl and AlCl3 were calculated or estimated in the range of 20 to 110 C, and up to saturation with AlCl3.6H2O. The results were extended to solutions containi...

N. A. Gokcen

1980-01-01

6

Effect on methane digestion of decreased H 2 partial pressure by means of phototrophic or sulfate-reducing bacteria grown in an auxiliary reactor  

Microsoft Academic Search

H2 is a central metabolite in the process of methane digestion. In this study, the partial pressure of H2 was decreased by sparging the gas phase of the digester through an auxiliary reactor in which a Rhodomicrobium vaniellii culture or a mixed culture of sulfate-reducing bacteria was allowed to develop at the expense of H2 and CO2 present in the

B. De Corte; K. Verhaegen; P. Bossier; W. Verstraete

1988-01-01

7

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

8

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

9

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

10

Production of H 2 from catalytic partial oxidation of H 2S in a short-contact-time reactor  

Microsoft Academic Search

Partial oxidation of H2S over alumina catalysts in a short-contact-time reactor (SCTR) has been shown to yield hydrogen, sulfur and water as the predominant products. At a set temperature of 400 C and a contact time of 13 ms, the conversion of H2S is 64.6% with a H2 selectivity of 20.8%, while the amount of SO2 in the products was

P. D. Clark; N. I. Dowling; M. Huang

2004-01-01

11

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 27C and 60C; 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

12

Deuterium Concentrations of H2PO4- and NH4+ Radicals in Partially Deuterated NH4H2PO4  

NASA Astrophysics Data System (ADS)

The deuteration rates (D-rates) of H2PO4- radicals (RP) in partially deuterated NH4H2PO4 crystals are measured by ESR of SeO43- doped in the crystals. It is found that the phase transition temperatures (Tc) of the crystals depend linearly on RP; Tc(RP){=}148+94RP [K]. Using this relation and data about total D-rate of highly deuterated ADP obtained by others, D-rates of NH4+ radicals (RN) in the crystals are calculated. It is pointed out that the shift of Tc does not depend on RN but on RP.

Fukami, Takanori; Akahoshi, Shin; Hukuda, Kenzi

1986-10-01

13

Silicate-H2O Systems at High Pressure Conditions  

NASA Astrophysics Data System (ADS)

Since the discovery of the second critical endpoint (CP2) in the albite-water system, numerous attempts have been made to determine the pressure and temperature of this CP2 and the mutual solubilities within more complex systems. The P-T position of the CP2 has been estimated for many systems: SiO2 (<10 kb/900 C, Newton and Manning, 2008); NaAlSi3O8 (15 kb/800 C, Burnham and Davis, 1974; Shen and Keppler, 1997); Pelite (50 kb/1,000 C, Schmidt et al., 2004), basalt (50 kb/ 1000 C, Kessel et al., 2004), Peridotite (38 kb/1000 C, Mibe et al., 2007). A number of experimental techniques have been used to determine phase relations and H2O solubility in experiments. These include in-situ experimental techniques (e.g., HYDAC; Shen and Keppler, 1997), fluid trap techniques (e.g., diamond traps; Stalder et al., 2000), and single crystal weight-loss techniques (e.g., SiO2-H2O techniques employed by Newton and Manning, 2008). None of these techniques is without difficulties, as H2O rich experiments need to overcome huge retrograde fluid solubilities upon quench in order to determine mutual solubilities at experimental conditions. We have developed a new technique to determine "rock"-H2O relationships at high-P conditions, with particular focus on the shape and locus of solvi in pressure temperature space. In this series of experiments, an oxygen fugacity buffer (Re-ReO2) and a sliding H-fugacity sensor (NiO-Ni-Pd mixture) are combined to monitor H2O activity over the entire range of pressure and temperature. Unlike other techniques, the use of sensor capsules does not require textural interpretation of experiments. H2O activity is related to oxygen and hydrogen fugacity by the reaction: H2O = H2 + O2 NiO-Ni-Pd mixtures were placed within a ZrO2 jacket and sealed within a welded 2.3 mm Pt capsule. This 2.3 mm Pt sensor capsule was then encased within a larger, thick walled 6 mm diameter Ag capsule. Pelite-H2O mixtures and oxygen buffers were held within this larger Ag capsule and sealed by capsule swaging. Changes in H2O activity (measured by shifts in the Ni content of the alloy) that occur with changes in pelite- water ratios at isothermal and isobaric conditions, can be used to determine the shape and position of the melt-H2O solvus. Pelite-H2O experiments at 25 kbar show solvus behaviour at 900 C (temperatures >200 C) above the wet solidus), indicating that the wet solidus and critical curve do not intersect at these conditions. In contrast, experiments at 35 kbar and 800-900 C, show a gradual change in H2O activity with increasing water:pelite ratios, indicating that the critical curve and wet solidus become closer with increasing pressure. Solvus topology in the pelite-H2O system, as determined by this series of experiments at 25 and 35 kbar, can also be used to estimate the shape and orientation of solubility isopleths (in terms of P-T). While the seminal work of Burnham and Davis (1974) demonstrated the importance of pressure on inducing H2O saturation in silicate melts, experiments presented here indicate that temperature may also play an important role. Burnham C. W. and Davis N. F. 1974, American Journal of Science. 274; 8, 902-940. Kessel, R., et al 2005, Earth and Planetary Science Letters, 237, 873-892. Mibe, K et al. 2007, Geochimica et Cosmochimica Acta. 68, 24, 5189-5195. Newton, R. C., and Manning, C. E., 2008, Earth and Planetary Science Letters. Schmidt, M.W.et al, 2004, Earth and Planetary Science Letters, 228, 65-84. Shen, A., and Keppler, H. 1997 Nature, 385, 710-712. Stadler, R., et al, 2000, American Mineralogist, 85, 68-77. class="ab'>

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

2008-12-01

14

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

15

An oxygen partial pressure sensor  

Microsoft Academic Search

The oxygen partial pressure of the gas mixture man breathes is an important measurement. A sensor is described which makes\\u000a use of the reaction of oxygen with hydrogen in the presence of catalytic platinum to produce water and electrical energy.\\u000a The voltage output is a direct function of the oxygen partial pressure. Performance data are presented and a package design

H. Warner; Valley Forge

1963-01-01

16

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

NASA Astrophysics Data System (ADS)

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

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

2012-03-01

17

Q?-H2AX, an analysis method for partial-body radiation exposure using ?-H2AX in nonhuman primate lymphocytes  

PubMed Central

We previously used the ?-H2AX assay as a biodosimeter for total-body-irradiation (TBI) exposure (?-rays) in a rhesus macaque (Macaca mulatta) model. Utilizing peripheral blood lymphocytes and plucked hairs, we obtained statistically significant ?-H2AX responses days after total-body exposure to 18.5 Gy (60Co ?-rays at 55 cGy min?1). Here, we introduce a partial-body exposure analysis method, Q?-H2AX, which is based on the number of ?-H2AX foci per damaged cells as evident by having one or more ?-H2AX foci per cell. Results from the rhesus monkey TBI study were used to establish Q?-H2AX dose-response calibration curves to assess acute partial-body exposures. ?-H2AX foci were detected in plucked hairs for several days after in vivo irradiation demonstrating this assays utility for dose assessment in various body regions. The quantitation of ?-H2AX may provide a robust biodosimeter for analyzing partial body exposures to ionizing radiation in humans.

Redon, Christophe E.; Nakamura, Asako J.; Gouliaeva, Ksenia; Rahman, Arifur; Blakely, William F.; Bonner, William M.

2011-01-01

18

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 2 O-H 2 S 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 2 S 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 2 O and H 2 S permit the experimental data to be fitted to a solvation/hydration model. According to this model, the solubility of gold in H 2 O-H 2 S gas mixtures is controlled by the formation of sulphide or bisulphide species solvated by H 2 S or H 2 O 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 ) H S ( g ) = AuS ( H S ) n ( g ) + H ( g ) Au(s) + H S ( g ) + m H O ( g ) = AuS ( H O ) m ( g ) + H ( g ) Equilibrium constants for Reaction (A1) and the corresponding solvation numbers ( K A 1 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 A 2 and m ) were adjusted simultaneously by a custom-designed optimization algorithm and were tested statistically. The resulting values of log K A 2 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

19

Brillouin scattering of H2O ice to megabar pressures.  

PubMed

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 60 GPa. Throughout this pressure range, we find no evidence for anomalous changes in compressibility, and the sound velocities and elastic moduli do not exhibit measurable discontinuous shifts with pressure. Subtle changes in the pressure dependence of the bulk modulus at intermediate pressures can be attributed to high shear stresses at these compressions. The C(11) and C(12) moduli are consistent with previously reported results to 40 GPa and increase monotonically at higher pressures. PMID:21456686

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

2011-03-28

20

Brillouin scattering of H2O ice to megabar pressures  

NASA Astrophysics Data System (ADS)

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 60 GPa. Throughout this pressure range, we find no evidence for anomalous changes in compressibility, and the sound velocities and elastic moduli do not exhibit measurable discontinuous shifts with pressure. Subtle changes in the pressure dependence of the bulk modulus at intermediate pressures can be attributed to high shear stresses at these compressions. The C11 and C12 moduli are consistent with previously reported results to 40 GPa and increase monotonically at higher pressures.

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

2011-03-01

21

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

22

Thermodynamics of high-pressure H2O phases  

NASA Astrophysics Data System (ADS)

New P-V-T EOS of ices III and V have been derived [1], as well as new isothermal EOS of ices VII and VIII. MD simulations have been carried out to calculate the densities of ices III, V and VIII as functions of pressure and temperature; the TIP4P and TIP5P models have been adopted. A scheme [2] for calculating the heat capacity of ices II, III, V, VI, and VII has been applied. Recently developed new Gibbs thermodynamic potential function of ice Ih [3] has been used to calculate the 100 K Hugoniot of ice for pressures up to 0.5 GPa; the results are in good agreement with experimental data of Stewart [4]. The validity of the existing EOS of liquid water in the metastable region at high pressures has also been investigated. The IAPWS-95 Formulation was found to be the only EOS of liquid water valid in the low-temperature metastable region both at low and at very high pressures. [1] V. Tchijov, R. Baltazar Ayala, G. Cruz Leon, O. Nagornov, J. Phys. Chem. Solids 65, 1277 (2004). [2] V. Tchijov, J. Phys. Chem. Solids 65, 851 (2004). [3] R. Feistel, W. Wagner, J. Mar. Res. (2005, in press). [4] S. T. Stewart, PhD Thesis, California Institute of Technology (2002).

Tchijov, Vladimir; Feistel, Rainer

2005-03-01

23

Observation of partial wave resonances in low-energy O2-H2 inelastic collisions.  

PubMed

Partial wave resonances predicted to occur in bimolecular collision processes have proven challenging to observe experimentally. Here, we report crossed-beam experiments and quantum-scattering calculations on inelastic collisions between ground-state O2 and H2 molecules that provide state-to-state cross sections for rotational excitation of O2 (rotational state N = 1, j = 0) to O2 (N = 1, j = 1) in the vicinity of the thermodynamic threshold at 3.96 centimeter(-1). The close agreement between experimental and theoretical results confirms the classically forbidden character of this collision-induced transition, which occurs exclusively in a purely quantum mechanical regime via shape and Feshbach resonances arising from partial waves with total angular momentum (J) = 2 to 4. PMID:24009389

Chefdeville, Simon; Kalugina, Yulia; van de Meerakker, Sebastiaan Y T; Naulin, Christian; Lique, Franois; Costes, Michel

2013-09-01

24

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

25

Atmospheric Pressure-Induced Effects in the VUV Absorption Spectrum of C2H2  

NASA Astrophysics Data System (ADS)

It is well known that high pressure in an absorbing system can cause line broadening, line shifts, and pressure-induced transitions. Real planetary atmospheres consist of a mixture of various molecules. It is well known that the pressure effects vary in nature depending on the characteristics of the collision constituents. It is thus desirable to measure the cross sections of molecules under the planetary atmosphere conditions of interest. For example, in Jupiter's atmosphere typical absorber (e.g., C2H2) abundances vary from 0.2 cm-atms to 5 cm-atms in the presence of H2. The pressure of H2 is in fact about 10(7) times that of C2H2. We have investigated the absorption cross section of C2H2 in the presence of Ar and N2 up to the highest pressure possible using our existing apparatus, namely, a factor of about 1.6 x 10(5) times that of C2H2. We have initially carried out a study of pressure effects in the 150-153.5 nm, 124-126 nm, 119.5-123.0 nm, and 116.5-118.5 nm regions, which covers three different Rydberg transitions of C2H2. In the case of Ar only pressure broadening effects are observed whereas, in the case of N2, pronounced pressure-induced transitions are also observed in addition to the well known spectral broadening. In the future we will investigate the pressure effects on C2H2 in the presence of H2. The preliminary results obtained to date will be presented. This research is based on work supported by the NASA Planetary Atmospheres Program under Grant NAG5-11042.

Chen, F.; Wu, R.; Judge, D.

2002-09-01

26

E-pH diagram of ZnS-H 2O system during high pressure leaching of zinc sulfide  

Microsoft Academic Search

The values of GT, ET or pH from 110 to 160 C were calculated and the relevant potential expressions were obtained. E-pH diagrams of ZnS-H2O system at oxygen partial pressure of 0.8 MPa, ionic activity of 1.0 and different temperatures were drawn through thermodynamical calculation. With the temperature increasing, the stable regions of S and Zn(II) in the E-pH diagrams

Wang-zhong MU; Ting-an ZHANG; Yan LIU; Yan GU; Zhi-he DOU; Guo-zhi L; Li BAO; Wei-guang ZHANG

2010-01-01

27

Synthesis of MnPO 4H 2O by refluxing process at atmospheric pressure  

Microsoft Academic Search

Serrabrancaite (MnPO4H2O) was synthesized by oxidizing Mn(H2PO4)2 with NaClO solution using a refluxing process at atmospheric pressure, and a mixed solution of MnCl2 and H3PO4 could substitute for Mn(H2PO4)2 in the process. The products were characterized by X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy. Hureaulite was formed when single solution of Mn(H2PO4)2 was refluxed for 12h at

Guohong Qiu; Zhiyun Gao; Hui Yin; Xionghan Feng; Wenfeng Tan; Fan Liu

2010-01-01

28

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

29

A theoretical insight into low-temperature atmospheric-pressure He+H2 plasmas  

NASA Astrophysics Data System (ADS)

H2-containing low-temperature plasmas are used in a wide range of industrial applications. In recent decades, efforts have been made to understand and improve the performance of these plasmas, mainly when operated at low and medium pressures. Studies of hydrogen-containing plasmas at atmospheric pressure, however, are scarce despite the potential advantage of operation in a vacuum-free environment. Here the chemistry of low-temperature atmospheric-pressure He + H2 plasmas is studied by means of a global model that incorporates 20 species and 168 reactions. It is found that for a fixed average input power the plasma density decreases sharply when the H2 concentration is higher than 0.2%, whereas the atomic H density peaks at a H2 concentration of 2%. Operation at larger H2 concentrations leads to lower plasma densities and lower H concentrations because at high H2 concentrations significant power is dissipated via vibrational excitation of H2 and there is an increasing presence of negative ions (H-). Key plasma species and chemical processes are identified and reduced sets of reactions that capture the main physicochemical processes of the discharge are proposed for use in computationally demanding models. The actual waveform of the input power is found to affect the average density of electrons, ions and metastables but it has little influence on the density of species requiring low energy for their formation, such as atomic hydrogen and vibrational states of hydrogen.

Liu, Ding-Xin; Iza, Felipe; Wang, Xiao-Hua; Ma, Zhi-Zhen; Rong, Ming-Zhe; Kong, Michael G.

2013-10-01

30

Fundamental Combustion Properties of H2\\/CO Mixtures: Ignition and Flame Propagation at Elevated Pressures  

Microsoft Academic Search

Because of the current interest in the use of syngas in gas turbine applications, this article provides an overview of the fundamental combustion characteristics of H2\\/CO mixtures, with emphasis on ignition and flame propagation at high pressures. Specifically, the effects of pressure on the fundamental combustion properties, including auto-ignition delays, forced ignition limits, and laminar flame speeds, are demonstrated and

Chih-Jen Sung; Chung K. Law

2008-01-01

31

The high-pressure synthesis of lawsonite in the MORB1H2O system  

Microsoft Academic Search

Lawsonite is an important water reservoir in subducting oceanic crust below the am- phibole dehydration depth ;70 km. To determine the maximum pressure stability of law- sonite in the MORB1H2O system, experiments were carried out using a 1000 ton uniaxial multi-anvil apparatus (SPI-1000). Mixtures of synthetic gel12wt% H2O were used for the starting materials with the average MORB composition. Experimental

KAZUAKI OKAMOTO; SHIGENORI MARUYAMA

1999-01-01

32

High pressure chemistry in the H2-SiH4 system.  

PubMed

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. PMID:19706419

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

2009-08-19

33

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 0.51.5 mol% H2 and the hydrogen-rich solid containing 0.51 mol% SiH4. These two crystalline phases can be regarded as doped hydrogen-dominant compounds. We were able to superpressurize the sample by 0.20.4 GPa above the eutectic before complete crystallization, indicating extended metastability.

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

2009-01-01

34

Structural Phase Transition in CaH2 at High Pressures  

SciTech Connect

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

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

2007-01-01

35

Pressure-Induced Molecular Dissociation and Metallization in Hydrogen-Bonded H2S Solid  

Microsoft Academic Search

Infrared spectra at high pressure and room temperature reveal that molecular dissociation and metallization occur in solid H2S near 46 and 96 GPa, respectively. The disappearance of SH stretching bands in the 2300-2500 cm-1 region and simultaneous appearance of a lattice vibrational mode around 1300 cm-1 signal the molecular dissociation. At higher pressures, a low-energy electronic absorption band develops and

M. Sakashita; H. Yamawaki; H. Fujihisa; K. Aoki; S. Sasaki; H. Shimizu

1997-01-01

36

Traces of H2O in Ultrahigh-Pressure Metamorphic Rocks  

Microsoft Academic Search

Ultrahigh-pressure (UHP) metamorphic rocks accommodate a significant amount of H2O at high pressures and temperatures during their deep subduction. Fluid-driven processes are responsible for mineral reactions; they may trigger phase transformations and provide a decisive weakening effect on the rheological behavior of the rocks during deep subduction, or they may lead to brittle failure and earthquakes. Dehydration reactions, producing fluid

L. F. Dobrzhinetskaya

2007-01-01

37

Effect of increased hydrogen partial pressure on the acetone-butanol fermentation by Clostridium acetobutylicum  

Microsoft Academic Search

Elevated H2 partial pressure in the acetone-butanol fermentation increased the butanol and ethanol yields on glucose by an average of 18% and 13%, respectively, while the respective yields of acetone and of the endogenous H2 decreased by an average of 40% and 30%, and almost no effect was observed on the growth of the culture. The butanol to acetone ratio

L. Yerushalmi; B. Volesky; T. Szczesny

1985-01-01

38

A system for incubations at high gas partial pressure.  

PubMed

High-pressure is a key feature of deep subsurface environments. High partial pressure of dissolved gasses plays an important role in microbial metabolism, because thermodynamic feasibility of many reactions depends on the concentration of reactants. For gases, this is controlled by their partial pressure, which can exceed 1?MPa at in situ conditions. Therefore, high hydrostatic pressure alone is not sufficient to recreate true deep subsurface in situ conditions, but the partial pressure of dissolved gasses has to be controlled as well. We developed an incubation system that allows for incubations at hydrostatic pressure up to 60?MPa, temperatures up to 120C, and at high gas partial pressure. The composition and partial pressure of gasses can be manipulated during the experiment. To keep costs low, the system is mainly made from off-the-shelf components with only very few custom-made parts. A flexible and inert PVDF (polyvinylidene fluoride) incubator sleeve, which is almost impermeable for gases, holds the sample and separates it from the pressure fluid. The flexibility of the incubator sleeve allows for sub-sampling of the medium without loss of pressure. Experiments can be run in both static and flow-through mode. The incubation system described here is usable for versatile purposes, not only the incubation of microorganisms and determination of growth rates, but also for chemical degradation or extraction experiments under high gas saturation, e.g., 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 H(2)O as well as a H(2)O-CO(2) mixture at elevated temperature (90C) and pressure (5?MPa). Subsamples were taken at different time points during the incubation and analyzed by ion chromatography. Furthermore we demonstrated the applicability of the system for studies of microbial activity, using samples from the Isis mud volcano. We could detect an increase in sulfate reduction rate upon the addition of methane to the sample. PMID:22347218

Sauer, Patrick; Glombitza, Clemens; Kallmeyer, Jens

2012-02-03

39

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 120C, and at high gas partial pressure. The composition and partial pressure of gasses can be manipulated during the experiment. To keep costs low, the system is mainly made from off-the-shelf components with only very few custom-made parts. A flexible and inert PVDF (polyvinylidene fluoride) incubator sleeve, which is almost impermeable for gases, holds the sample and separates it from the pressure fluid. The flexibility of the incubator sleeve allows for sub-sampling of the medium without loss of pressure. Experiments can be run in both static and flow-through mode. The incubation system described here is usable for versatile purposes, not only the incubation of microorganisms and determination of growth rates, but also for chemical degradation or extraction experiments under high gas saturation, e.g., fluidgasrock-interactions in relation to carbon dioxide sequestration. As an application of the system we extracted organic compounds from sub-bituminous coal using H2O as well as a H2OCO2 mixture at elevated temperature (90C) and pressure (5?MPa). Subsamples were taken at different time points during the incubation and analyzed by ion chromatography. Furthermore we demonstrated the applicability of the system for studies of microbial activity, using samples from the Isis mud volcano. We could detect an increase in sulfate reduction rate upon the addition of methane to the sample.

Sauer, Patrick; Glombitza, Clemens; Kallmeyer, Jens

2012-01-01

40

Search for H2-He alloy formation at low pressures and cosmic snowballs  

SciTech Connect

If a substantial fraction of the dark matter in the universe were in the form of relatively small lumps of solid hydrogen (cosmic snowballs) the He mass fraction (Y) should have changed over the history of the universe contrary to present belief. A laboratory experiment has been performed at 4.2 K to see if an unexpected H2-He alloy might form at low pressures and relieve this basic objection. A limit of less than one part in 1000 by mass for He in the bulk solid H2 deposited from the vapor on a copper cold finger has been established. However, less than about 1 monolayer of He atoms can plate on the solid H2 surface. The basic objection to cosmic snow-balls remains intact. 12 refs.

Leventhal, M.; Mills, A.P. Jr. (AT T Bell Laboratories, Murray Hill, NJ (USA))

1991-02-01

41

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

42

Traces of H2O in Ultrahigh-Pressure Metamorphic Rocks  

NASA Astrophysics Data System (ADS)

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

Dobrzhinetskaya, L. F.

2007-05-01

43

DEVICE FOR CONTROL OF OXYGEN PARTIAL PRESSURE  

DOEpatents

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

Bradner, H.; Gordon, H.S.

1957-12-24

44

Ultrahigh-pressure phases of H2O ice predicted using an adaptive genetic algorithm  

NASA Astrophysics Data System (ADS)

We propose three phases of H2O under ultrahigh pressure. Our structural search was performed using an adaptive genetic algorithm which allows an extensive exploration of crystal structure at density functional theory accuracy. The sequence of pressure-induced transitions beyond ice X at 0 K should be ice X?Pbcm?Pbca?Pmc21?P21?P21/c phases. Across the Pmc21-P21 transition, the coordination number of oxygen increases from 4 to 5 with a significant increase of density. All stable crystalline phases have nonmetallic band structures up to 7 TPa.

Ji, Min; Umemoto, Koichiro; Wang, Cai-Zhuang; Ho, Kai-Ming; Wentzcovitch, Renata M.

2011-12-01

45

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

National Technical Information Service (NTIS)

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-press...

J. Kojima Q. V. Nguyen

2003-01-01

46

The pressure-temperature phase diagram of MgH2 and isotopic substitution  

NASA Astrophysics Data System (ADS)

Computational thermodynamics using density functional theory ab initio codes is a powerful tool for calculating phase diagrams. The method is usually applied at the standard pressure of p = 1 bar and where the Gibbs energy is assumed to be equal to the Helmholtz energy. In this work, we have calculated the Gibbs energy in order to study the release temperature and phase modifications of MgH2 at high pressures up to 10 GPa (100 kbar). The isotopic substitution of hydrogen with deuterium (or tritium) does not bring about any strong effects on the phase diagram. These considerations are of extreme importance for (i) the synthesis of novel substitutional magnesium based materials at high pressure and (ii) the determination of the correct reference states for the calculation of phase diagrams at high pressure. The calculated results are compared with experimental data obtained with an in situ neutron diffraction measurement.

Moser, D.; Baldissin, G.; Bull, D. J.; Riley, D. J.; Morrison, I.; Ross, D. K.; Oates, W. A.; Norus, D.

2011-08-01

47

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

NASA Astrophysics Data System (ADS)

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 are also believed to exist within some of these icy bodies which may have prolonged interaction with the Ice VII phase present, incorporating foreign ions or molecules into the lattice of high-pressure ices. Recent research concerning the effects that charged ions have on Ice VII has shown that the presence of these ions notably affects the structure, increasing the Ice VII molar density at any given pressure relative to pure Ice VII (Frank et al., 2006, PEPI, 155, 152-162). This study focused on the incorporation of CH3OH into Ice VII to determine if the change in density was predominantly a result of charge-induced partial ordering of the hydrogen in Ice VII (as outlined in Frank et al., 2006) or if it was controlled solely by the addition of large foreign molecules into the lattice structure. Solutions of 1.60, 5.00 and 10.0 mol% CH3OH in H2O were loaded into a diamond anvil cell. The experiments were performed at GSECARS 13-BM-D at the Advanced Photon Source at Argonne National Laboratory. The unit cell parameters were measured using monochromatic X-ray radiation, 0.3344 , and a MAR 345 online imaging system. Powder diffraction patterns were collected in ~1 GPa increments up to ~31, ~48, and ~35 GPa, respectively. The volume-pressure relations (at 300 K) were used to determine an equation of state (EOS) for select compositions in the CH3OH - H2O system. Diffraction data indicate that the unit cell volume of Ice VII formed from a 1.60 mol% CH3OH aqueous solution did not deviate significantly from that of Ice VII formed from pure H2O. Conversely, the volumes of Ice VII formed from 5.00 and 10.0 mol% solutions had reduced unit cell volumes relative to pure Ice VII. Zero-pressure volumes and bulk moduli were calculated with a pressure derivative fixed (4.40): 1.6 mol% CH3OH - H2O had values of 40.40.2 3 and 24.40.7 GPa, respectively, whereas 5.0 mol% CH3OH - H2O had values of 39.20.2 3 and 26.20.5 GPa, respectively. We hypothesize that charged ions will have a greater influence at lower concentrations on the properties of Ice VII than neutral species due to electrostatic interactions within the unit cell and crystallographic constraints imposed by the body-centered cubic structure of Ice VII. In conclusion, these results suggest that ice-phases formed in a solute-rich environment (or by reaction with other phases within the interior of an icy body) will most likely have a greater molar density than ice formed from pure H2O.

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

2007-12-01

48

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

Microsoft Academic Search

Rotational and vibrational spontaneous Raman scattering (SRS) spectra of H2, N2 and H2O have been measured in H2-air flames at pressures up to 30.4 bar as a first step towards establishing a comprehensive Raman spectral database for temperatures and species in high-pressure combustion. We have obtained an initial set of measurements that indicate the spectra are of sufficient quality in

Jun Kojima; Quang-Viet Nguyen

2004-01-01

49

Hydrogen CARS thermometry in H 2 -N 2 mixtures at high pressure and medium temperatures: influence of linewidths models  

Microsoft Academic Search

In order to improve the accuracy of H2 CARS thermometry, H2 Q-branch CARS spectra have been recorded for various H2-N2 mixtures in a high-pressure cell at different pressures and temperatures (up to 40 bar and 875 K). Due to the low spectral resolution of broadband CARS experiments, the relevant spectral lineshape factor is the linewidth ratio &(Q(3))\\/&(Q(1)), since Q(1) and

J. Hussong; W. Stricker; X. Bruet; P. Joubert; J. Bonamy; D. Robert; X. Michaut; T. Gabard; H. Berger

2000-01-01

50

High pressure partially ionic phase of water ice.  

PubMed

Water ice dissociates into a superionic solid at high temperature (>2,000?K) and pressure, where oxygen forms the lattice, but hydrogen diffuses completely. At low temperature, however, the dissociation into an ionic ice of hydronium (H(3)O)(+) hydroxide (OH)(-) is not expected because of the extremely high energy cost (~1.5?eV) of proton transfer between H(2)O molecules. Here we show the pressure-induced formation of a partially ionic phase (monoclinic P2(1) structure) consisting of coupled alternate layers of (OH)(?-) and (H(3)O)(?+) (?=0.62) in water ice predicted by particle-swarm optimization structural search at zero temperature and pressures of >14?Mbar. The occurrence of this ionic phase follows the break-up of the typical O-H covalently bonded tetrahedrons in the hydrogen symmetric atomic phases and is originated from the volume reduction favourable for a denser structure packing. PMID:22127059

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

2011-11-29

51

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. Metalorganic 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 MgMOF-74 or CPO-27Mg, is an especially lightweight metalorganic

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

2012-01-01

52

Hydrogen Partial Pressures in a Thermophilic Acetate-Oxidizing Methanogenic Coculture  

PubMed Central

Hydrogen partial pressures were measured in a thermophilic coculture comprised of a eubacterial rod which oxidized acetate to H2 and CO2 and a hydrogenotrophic methanogen, Methanobacterium sp. strain THF. Zinder and Koch (S. H. Zinder and M. Koch, Arch. Microbiol. 138:263-272, 1984) originally predicted, on the basis of calculations of Gibbs free energies of reactions, that the H2 partial pressure near the midpoint of growth of the coculture should be near 4 Pa (ca. 4 10?5 atm; ca. 0.024 ?M dissolved H2) for both organisms to be able to conserve energy for growth. H2 partial pressures in the coculture were measured to be between 20 and 50 Pa (0.12 to 0.30 ?M) during acetate utilization, approximately one order of magnitude higher than originally predicted. However, when ?Gf (free energy of formation) values were corrected for 60C by using the relationship ?Gf = ?Hf ? T?S (?Hf is the enthalpy or heat of formation, ?S is the entropy value, and T is the temperature in kelvins), the predicted value was near 15 Pa, in closer agreement with the experimentally determined values. The coculture also oxidized ethanol to acetate, a more thermodynamically favorable reaction than oxidation of acetate to CO2. During ethanol oxidation, the H2 partial pressure reached values as high as 200 Pa. Acetate was not used until after the ethanol was consumed and the H2 partial pressure decreased to 40 to 50 Pa. After acetate utilization, H2 partial pressures fell to approximately 10 Pa and remained there, indicating a threshold for H2 utilization by the methanogen. Axenic cultures of the acetate-oxidizing organism were combined with pure cultures of either Methanobacterium sp. strain THF or Methanobacterium thermoautotrophicum ?H to form reconstituted acetate-oxidizing cocultures. The H2 partial pressures measured in both of these reconstituted cocultures were similar to those measured in the original acetate-oxidizing rod coculture. Since M. thermoautotrophicum ?H did not use formate as a substrate, formate is not necessarily involved in interspecies electron transfer in this coculture.

Lee, Monica J.; Zinder, Stephen H.

1988-01-01

53

Shock-tube study of high-pressure H 2 O spectroscopy  

NASA Astrophysics Data System (ADS)

Water-vapor absorption features near 7117, 7185, and 7462 cm 1 were probed at pressures to 65 atm (1 atm 760 Torr) and temperatures to 1800 K in shock-heated mixtures of H 2 O in N 2 and Ar with a diode-laser source. Calculated absorbances based on Voigt line shapes and measured line parameters were in good agreement, within 10%, with measured absorbances at 7185.4 and 7117.4 cm 1 . We obtained temperature-dependent N 2 and Ar shift parameters for H 2 O absorption features by shifting the calculated spectra to match the recorded absorption scan. Absorbance simulations based on line parameters from HITRAN and HITEMP were found to be similar over the range of temperatures 600 1800 K and were within 25% of the measurements. The combined use of Toth s Appl. Opt. 36, 4851 (1994) line positions and strengths and HITRAN broadening parameters resulted in calculated absorption coefficients that were within 15% of the measurements at all three probed wavelengths.

Nagali, Venu; Herbon, John T.; Horning, David C.; Davidson, David F.; Hanson, Ronald K.

1999-11-01

54

Structural and Valence Changes of Europium Hydride Induced by Application of High-Pressure H2  

NASA Astrophysics Data System (ADS)

Europium hydride EuHx, when exposed to high-pressure H2, has been found to exhibit the following structural and valence changes: Pnma(x=2,divalent)?P63/mmc(x=2,7.2-8.7GPa)?I4/m(x>2,8.7-9.7GPa)?I4/mmm(x>2,9.7GPa-,trivalent). With a trivalent character and a distorted cubic fcc structure, the I4/mmm structure is the ? phase commonly observed for other rare-earth metal hydrides. Our study clearly demonstrates that EuHx is no longer an irregular member of the rare-earth metal hydrides.

Matsuoka, T.; Fujihisa, H.; Hirao, N.; Ohishi, Y.; Mitsui, T.; Masuda, R.; Seto, M.; Yoda, Y.; Shimizu, K.; Machida, A.; Aoki, K.

2011-07-01

55

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

NASA Astrophysics Data System (ADS)

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

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

1983-11-01

56

Dense nucleation of polycrystalline diamond films using CF4H2 low pressure RF discharges  

NASA Astrophysics Data System (ADS)

Dense nucleation of small-grain polycrystalline diamond films on Si (100) substrates has been accomplished without the use of any surface pretreatment such as abrasive diamond scratching, surface oil treatments, or diamond-like carbon predeposition. The depositions occurred in a low pressure RF plasma assisted CVD system using mixtures of CF4 and H2. Films deposited at 5 Torr and 850 C on as-received silicon wafers show dense nucleation, well-defined facets, and crystallites which ranged in size from 500 to 10,000 A. X-ray photoelectron spectroscopy and electron energy loss show the films to be diamond with no major impurity and no detectable graphitic component. Raman spectroscopy shows a pronounced 1332/cm line accompanied with a broad band centered about 1500/cm. Preliminary data indicates that this process is applicable to substrates other than silicon; it will have important applications in areas where surface pretreatments, such as diamond polishing, are not viable.

Rudder, R. A.; Hudson, G. C.; Malta, D. P.; Posthill, J. B.; Thomas, R. E.; Markunas, R. J.

57

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. Metalorganic 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 MgMOF-74 or CPO-27Mg, is an especially lightweight metalorganic framework with

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

58

Comparison of Low Pressure and Medium Pressure UV Lamps for UV\\/H2O2 Treatment of Natural Waters Containing Micro Pollutants  

Microsoft Academic Search

UV\\/H2O2 advanced oxidation is an effective barrier against organic micro pollutants. Several studies have focused on the degradation of a wide range of pollutants, but regarding the comparison of low-pressure mercury lamps (LP) with medium-pressure mercury lamps (MP) with respect to energy consumption by the UV\\/H2O2 process, little is known so far. Although the absorbance of H2O2 at 254 nm

Guus F. IJpelaar; Danny J. H. Harmsen; Erwin F. Beerendonk; Robin C. van Leerdam; Debbie H. Metz; Antonie H. Knol; Alice Fulmer; Simon Krijnen

2010-01-01

59

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

NASA Astrophysics Data System (ADS)

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

Monfared, Shabnam K.; Hwel, Lutz

2012-10-01

60

Method of detecting oxygen partial pressure and oxygen partial pressure sensor  

DOEpatents

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

Dees, D.W.

1991-12-31

61

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

62

Partial pressure measurements with an active spectrometer  

SciTech Connect

Partial pressure neutral gas measurements have been made using a commercial Penning gauge in conjunction with an {open_quotes}active spectrometer.{close_quotes} In prior work utilizing band pass 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 limitation 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. {copyright} {ital 1999 American Institute of Physics.}

Brooks, N.H.; Jensen, T.H. [General Atomics, San Diego, California 92186-5608 (United States); Colchin, R.J.; Maingi, R.; Wade, M.R. [Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-8072 (United States); Finkenthal, D.F. [Palomar College, San Marcos, California 92069 (United States); Naumenko, N. [Institute for Atomic and Molecular Physics, 220072 Minsk (Belarus); Tugarinov, S. [TRINITI, 142092 Troitsk (Russian Federation)

1999-01-01

63

Hydrogen CARS thermometry in a high-pressure H2air flame. Test of H2 temperature accuracy and influence of line width by comparison with N2 CARS as reference  

Microsoft Academic Search

. 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 115bar and at fuel-rich conditions with stoichiometries between two and four, quasi-simultaneous\\u000a temperature measurements were performed

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

2001-01-01

64

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

NASA Astrophysics Data System (ADS)

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

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

2010-10-01

65

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

NASA Astrophysics Data System (ADS)

Complementary tests of the partially correlated speed-dependent Keilson-Storer (pCSDKS) model for the shape of isolated transition of pure water vapor [N. H. Ngo et al., J. Chem. Phys. 136, 154310 (2012)] are made using new measurements. The latter have been recorded using a high sensitivity cavity ring down spectrometer, for seven self-broadened H2O lines in the 1.6 ?m region at room temperature and for pressures from 0.5 to 15 Torr. Furthermore, the H218O spectra of [M. D. De Vizia et al., Phys. Rev. A 83, 052506 (2011)] in the 1.38 ?m region, measured at 273.15 K and for pressures from 0.3 to 3.75 Torr have also been used for comparison with the model. Recall that the pCSDKS model takes into account the collision-induced velocity changes, the speed dependences of the broadening and shifting coefficients as well as the partial correlation between velocity and rotational-state changes. All parameters of the model have been fixed at values previously determined, except for a scaling factor applied to the input speed-dependent line broadening. Comparisons between predictions and experiments have been made by looking at the results obtained when fitting the calculated and measured spectra by Voigt profiles. The good agreement obtained for all considered lines, at different temperature and pressure conditions, confirms the consistency and the robustness of the model. Limiting cases of the model have been then derived, showing the influence of different contributions to the line shape.

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

2013-01-01

66

Elevated atmospheric partial pressure of CO2 and plant growth  

Microsoft Academic Search

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

Suan-Chin Wong

1990-01-01

67

Alterations in the Molecular Determinants of Bladder Compliance at Hydrostatic Pressures less than 40 cm. H 2O  

Microsoft Academic Search

PurposeBladder outlet obstruction with intravesical pressures exceeding 40 cm. H2O often results in irreversible renal damage. Bladder outlet obstruction also results in alterations in bladder physiology, including wall thickening, reduced compliance and decreased capacity. If unchecked these changes may lead to the subsequent need for bladder augmentation. From a biomechanical standpoint, compliance is primarily related to extracellular matrix deposition, which

BJRN O. BACKHAUS; MARTIN KAEFER; KAREN M. HABERSTROH; KAREN HILE; JIRO NAGATOMI; RICHARD C. RINK; MARK P. CAIN; ANTHONY CASALE; RENA BIZIOS

2002-01-01

68

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

69

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

NASA Astrophysics Data System (ADS)

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

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

1990-03-01

70

Cars Diagnostics of High Pressure Combustion. 2. Measurements of NO, H2O and High Pressure Flames.  

National Technical Information Service (NTIS)

Spectroscopic investigations into the coherent anti-Stokes Raman spectroscopy (CARS) spectra of NO and H2O and were conducted CARS is a remote laser diagnostic technique for temperature and species measurements in hostile combustion environments. As such ...

J. A. Shirley J. H. Stufflebeam

1985-01-01

71

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

NASA Astrophysics Data System (ADS)

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

Kojima, Jun; Nguyen, Quang-Viet

2004-03-01

72

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 Grneisen 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

73

X-ray Diffraction and Raman Spectroscopy Studies of D_2O and H_2O Ices to Ultrahigh Pressures  

Microsoft Academic Search

We report spectroscopic and diffraction data on H_2O and D_2O ices obtained to maximum pressures of the order of 100 GPa. X-ray diffraction data was obtained at the x17c beamline of the NSLS and the ID-13 beamline of the APS. Simultaneously,Raman spectra were collected using a single stage spectrograph equipped with notch filters. To remove the effects of preferred texturing,

Maddury Somayazulu; Alexander Goncharov; Guoyin Shen; Russell Hemley; Ho-Kwang Mao

2000-01-01

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

The Structure of Surface H2O Layers of Ice-covered Planets with High-pressure Ice  

NASA Astrophysics Data System (ADS)

Many extrasolar (bound) terrestrial planets and free-floating (unbound) planets have been discovered. While the existence of bound and unbound terrestrial planets with liquid water is an important question, of particular importance is the question of these planets' habitability. Even for a globally ice-covered planet, geothermal heat from the planetary interior may melt the interior ice, creating an internal ocean covered by an ice shell. In this paper, we discuss the conditions that terrestrial planets must satisfy for such an internal ocean to exist on the timescale of planetary evolution. The question is addressed in terms of planetary mass, distance from a central star, water abundance, and abundance of radiogenic heat sources. In addition, we investigate the structure of the surface H2O layers of ice-covered planets by considering the effects of ice under high pressure (high-pressure ice). As a fiducial case, a 1 M ? planet at 1 AU from its central star and with 0.6-25 times the H2O mass of the Earth could have an internal ocean. We find that high-pressure ice layers may appear between the internal ocean and the rock portion on a planet with an H2O mass over 25 times that of the Earth. The planetary mass and abundance of surface water strongly restrict the conditions under which an extrasolar terrestrial planet may have an internal ocean with no high-pressure ice under the ocean. Such high-pressure ice layers underlying the internal ocean are likely to affect the habitability of the planet.

Ueta, S.; Sasaki, T.

2013-10-01

76

Preliminary Studies on a New Partial-Pressure Suit Concept.  

National Technical Information Service (NTIS)

In preliminary studies, a new partial-pressure suit has been developed as an emergency garment for high-altitude aircraft flight, for continuous wear in extended space flight, and for crewmembers of the proposed supersonic transport. The USAFSAM experimen...

J. C. Davis J. Boyle F. R. Ritzinger

1967-01-01

77

Elevated atmospheric partial pressure of CO 2 and plant growth  

Microsoft Academic Search

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

S. C. Wong

1979-01-01

78

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

2013-03-13

79

Liver tissue partial pressure of oxygen and carbon dioxide during partial hepatectomy  

Microsoft Academic Search

Background. Data on tissue oxygen partial pressure (PtO2) and carbon dioxide partial pressure (PtCO2) in human liver tissue are limited. We set out to measure changes in liver PtO2 and PtCO2 during changes in ventilation and a 10 min period of ischaemia in patients undergoing liver resection using a multiple sensor (Paratrend Diametrics Medical Ltd, High Wycombe, UK). Methods. Liver

A. J. Brooks; J. Eastwood; I. J. Beckingham; K. J. Girling

2004-01-01

80

The vapor pressures of supercooled HNO3\\/H2O solutions  

Microsoft Academic Search

A procedure utilizing the Gibbs-Duhem relation is used to extrapolate vapor pressures of supercooled HNO3 mixtures to 190 K. Values of A and B from the equation logP=A-B\\/T are presented for nitric acid solutions between 0.20 and 0.25 mole fraction HNO3. In the stratosphere, if sufficient HNO3 vapor is present because it has not come into equilibrium with the nitric

David R. Hanson

1990-01-01

81

The vapor pressures of supercooled HNO3\\/H2O solutions  

Microsoft Academic Search

A procedure utilizing the Gibbs-Duhem relation is used to extrapolate vapor pressures of supercooled HNO3 mixtures to 190 K. Values of A and B from the equation logP = A ? B\\/T are presented for nitric acid solutions between 0.20 and 0.25 mole fraction HNO3. In the stratosphere, if sufficient HNO3 vapor is present because it has not come into

David R. Hanson

1990-01-01

82

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

83

Molecular-Gas-Pressure-Induced Line-Shift and Line-Broadening in the ?2-Band of H2S  

NASA Astrophysics Data System (ADS)

The pressure-induced shift and broadening of H2S absorption lines in the ?2-band due to collisions between H2S molecules and quadrupole molecules, such as O2, H2, D2, N2, and CO2, were studied in the spectral region between 1050 and 1325 cm-1. The measurements were carried out using a pulse-driven diode laser spectrometer with two multipass Herriott cells. The data concerning the collisional broadening and shift coefficients, ? and ?, respectively, and their dependencies on the rotational quantum number J'' and the quadrupole moment Q of the molecular perturber are presented for 14 P-branch transitions (3<=J''<=8,0<=KaPrime<=3, 2<=KcPrime<=8), 7 Q-branch transitions (7<=JPrime<=10, 1<=KaPrime<=2, 6<=KcPrime<=9), and 18 R-branch transitions (2<=JPrime<=11, 0<=KaPrime<=4, 0<=KcPrime<=11). The broadening coefficients ? were determined with an accuracy to within 2% and shift coefficients ? were determined with an uncertainty of less than 10-3 cm-1/atm for the majority of lines and broadening gases.

Kissel, A.; Sumpf, B.; Kronfeldt, H.-D.; Tikhomirov, B. A.; Ponomarev, Yu. N.

2002-12-01

84

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

Code of Federal Regulations, 2010 CFR

...false Indwelling blood oxygen partial pressure (PO2) analyzer. 868.1200...1200 Indwelling blood oxygen partial pressure (PO2 ) analyzer. (a... An indwelling blood oxygen partial pressure (PO2 ) analyzer is a...

2010-04-01

85

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

Code of Federal Regulations, 2010 CFR

...false Indwelling blood oxygen partial pressure (PO2) analyzer. 868.1200...1200 Indwelling blood oxygen partial pressure (PO2 ) analyzer. (a... An indwelling blood oxygen partial pressure (PO2 ) analyzer is a...

2009-04-01

86

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

Code of Federal Regulations, 2010 CFR

...Indwelling blood carbon dioxide partial pressure (PCO2) analyzer. 868...Indwelling blood carbon dioxide partial pressure (PCO2 ) analyzer. (a...indwelling blood carbon dioxide partial pressure PCO2 analyzer is a...

2010-04-01

87

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

Code of Federal Regulations, 2010 CFR

...Indwelling blood carbon dioxide partial pressure (PCO2) analyzer. 868...Indwelling blood carbon dioxide partial pressure (PCO2 ) analyzer. (a...indwelling blood carbon dioxide partial pressure PCO2 analyzer is a...

2009-04-01

88

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

Code of Federal Regulations, 2013 CFR

...2013-04-01 false Indwelling blood oxygen partial pressure (PO2) analyzer. 868...868.1200 Indwelling blood oxygen partial pressure (PO2 ) analyzer...Identification. An indwelling blood oxygen partial pressure (PO2 ) analyzer...

2013-04-01

89

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

Code of Federal Regulations, 2013 CFR

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

2013-04-01

90

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

NASA Astrophysics Data System (ADS)

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

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

91

Sublimation pressure and sublimation enthalpy of H2O ice Ih between 0 and 273.16 K  

NASA Astrophysics Data System (ADS)

The sublimation of water in the region of extremely low pressures and temperatures meets increasing interest for the exploration of icy cosmic bodies. At temperatures below 130 K, the shape of the sublimation curve of H2O is not known; neither experimental data nor theoretical treatments exist for this region. Based upon theoretical upper and lower bounds for the heat capacity of water vapor in this range, a narrow region in the pressure temperature diagram is identified which must necessarily enclose the sublimation curve down to virtually any lower pressures and temperatures. Within this region, an approximate sublimation curve is computed from the 2006 Gibbs potential of ice Ih, using available heat capacity data points of water vapor between 10 and 130 K. The theoretical zero-point limiting law of the sublimation pressure is derived. Valid between 20 and 273.16 K, correlation equations for the sublimation enthalpy and the sublimation pressure are fitted to the computed data. All quantities are expressed in the 1990 temperature scale ITS-90. Under cosmic conditions, our results suggest that the sublimation of ice is unlikely below 50 K and impossible below 23 K.

Feistel, Rainer; Wagner, Wolfgang

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 broadening and shift coefficients of H2O due to perturbation by N2, O2, H2 and He in the 1.39 ?m region: experiment and calculations  

NASA Astrophysics Data System (ADS)

Near-infrared diode laser spectrometry was used to determine the pressure broadening and shift effect on H2O due to N2, O2, H2 and He in the 1.39 m region. Halfwidths and shifts of water vapour were measured for six transitions. These lines are from the ?1+?3 and 2?1 bands. A complete set of H2O transitions with various J values was investigated, including the lines selected to monitor in situ stratospheric H2O with the SDLA, a balloon-borne diode laser spectrometer. Experimental results are compared with theoretical calculations based on a semi-empiric technique that incorporates various corrections to the Anderson theory. This approach is performed in the framework of the impact approximation, which makes interpretation of the collision process simpler and allows reliable results to be obtained.

Zeninari, V.; Parvitte, B.; Courtois, D.; Lavrentieva, N. N.; Ponomarev, Yu. N.; Durry, G.

94

Calibration Service for Partial Pressure Analyzers by Two-stage Flow-dividing Method  

NASA Astrophysics Data System (ADS)

The calibration service for partial pressure analyzers (PPA) has been carried out from April in 2007 at NMIJ/AIST using a two-stage flow-dividing system. The pressure range is from 10-6 to 10-4 Pa and the test gases are N2, Ar, He and H2. Results of the calibration for two types of PPA were also shown. The sensitivities of both PPAs were almost constant in the pressure range from 10-6 to 10-4 Pa, while they changed significantly with pressure higher than 10-4 Pa. The calibration uncertainties mainly caused by the instability of PPA indication were about 7% (confidence level 95%). The stability of sensitivities of both PPAs was in about 15% for 7 months.

Yoshida, Hajime; Arai, Kenta; Akimichi, Hitoshi; Hirata, Masahiro

95

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

96

Low-energy regeneration and high productivity in a lanthanide-hexacarboxylate framework for high-pressure CO2-CH4-H2 separation.  

PubMed

A porous lanthanide-organic framework UTSA-62a of a topology has been synthesized from a hexacarboxylate and structurally characterized, exhibiting significant potential for use in CO2-CH4-H2 separation (H2 purification) processes with high productivities and low regeneration costs when operating at high pressure and room temperature. PMID:23783245

He, Yabing; Furukawa, Hiroyasu; Wu, Chuande; O'Keeffe, Michael; Krishna, Rajamani; Chen, Banglin

2013-08-01

97

Effect of polarization on population transfer in H2 by stimulated Raman transition with partially overlapping laser pulses  

NASA Astrophysics Data System (ADS)

Polarization effects on population transfer by stimulated Raman transition using overlapping time dependent pump and Stokes laser pulses from the ground X1Sg+(ng = 0, Jg = 1) level of H2 to the final X1Sg+(nf = 1, Jf = 1) level via the intermediate B1Su+(ni = 14, Ji = 0, 2), C1P+u (ni = 3, Ji = 2) and C1P-u (ni = 3, Ji = 1) levels have been theoretically investigated by applying the density matrix formalism. We have studied in detail the dependence of the population transfer on time delay between two pulses for the cases of on-resonance excitations considering linear parallel and same-sense circular polarizations of the fields. The pump and Stokes fields are taken as having Gaussian pulse shapes with peak intensities I0P(I0S) = 2 ×106 and 1 ×107 W/cm2. Density matrix equations have been solved for each value of the magnetic quantum number Mg (0, +/-1) of the initial ground level taking into account the Mg dependence of the Rabi frequencies. Mg - averaged population transfer to the final level has also been calculated. For resonance excitations to the B(14, 0) or C(3, 1) levels, appreciable population transfer is achieved for intuitive pulse order for some particular values of Mg and Mi (magnetic quantum number of the resonant intermediate level) depending on the nature of polarizations. The calculated values of Mg - averaged population transfer for the two cases of polarizations show that for on-resonance excitation to the B(14, 0) or the C(3, 1) level, linear parallel polarization of the laser fields yield more transfer efficiency whereas for resonance excitation to the B(14, 2) level, larger population transfer results from the same-sense circular polarizations. For resonance excitation to the C(3, 2) level, Mg - averaged population is found to be almost polarization independent. The calculations for the six-level H2 system reveal some interesting features of polarization effects on the population transfer efficiency.

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

2000-06-01

98

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

PubMed

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

Kakiuchi, Hiroaki; Ohmi, Hiromasa; Yasutake, Kiyoshi

2011-04-01

99

Defect Reduction Treatment for Plasma-Tetraethylorthosilicate-SiO2 by High-Pressure H2O Vapor Heat Treatment  

NASA Astrophysics Data System (ADS)

Improvements in the electrical and structural properties of tetraethylorthosilicate (TEOS) SiO2 films fabricated by plasma-enhanced chemical vapor deposition (PECVD) method were investigated using high-pressure H2O vapor heat treatment. The density of interface trap states was reduced from 3.3 1012 (initial) to 5.1 1010 cm-2 eV-1 by 1.3 106 Pa H2O vapor heat treatment at 260C for 9 h. The density of fixed charges was also reduced from 6.1 1011 to 1.3 1011 cm-2. The full width at half-maximum (FWHM) of the optical absorption band corresponding to vibration of Si--O--Si bonding was reduced from 82.9 to 78.1 cm-1. Narrowing in FWHM of the Si 2p core level peak measured by X-ray photoelectron spectroscopy (XPS) was also observed. The reduction in the FWHM probably results from improvement of the Si--O bonding network.

Watakabe, Hajime; Sameshima, Toshiyuki; Strutz, Thomas; Oitome, Teruki; Kohno, Atsushi

2005-12-01

100

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

NASA Astrophysics Data System (ADS)

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

Newton, Robert C.; Manning, Craig E.

2000-09-01

101

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

PubMed

The reactivity of a crushed well cement in contact with (1) a brine with dissolved H2S-CO2; (2) a dry H2S-CO2 supercritical phase; (3) a two-phase fluid associating a brine with dissolved H2S-CO2 and a H2S-CO2 supercritical phase was investigated in batch experiments at 500 bar and 120, 200 degrees C. All of the experiments showed that following 15-60 days cement carbonation occurred. The H2S reactivity with cement is limited since it only transformed the ferrites (minor phases) by sulfidation. It appeared that the primary parameter controlling the degree of carbonation (i.e., the rate of calcium carbonates precipitation and CSH (Calcium Silicate Hydrates) decalcification) is the physical state of the fluid phase contacting the minerals. The carbonation degree is complete when the minerals contact at least the dry H2S-CO2 supercritical phase and partial when they contactthe brine with dissolved H2S-CO2. Aragonite (calcium carbonate polymorph) precipitated specifically within the dry H2S-CO2 supercritical phase. CSH cristallinity is improved by partial carbonation while CSH are amorphized by complete carbonation. However, the features evidenced in this study cannot be directly related to effective features of cement as a monolith. Further studies involving cement as a monolith are necessary to ascertain textural, petrophysical, and mechanical evolution of cement. PMID:18350909

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

2008-01-01

102

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

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

2007-01-01

103

Helium partial pressure measurement in a deuterium environment  

Microsoft Academic Search

To study the removal of helium ash in present day, medium sized tokamaks, experiments with deuterium plasmas and helium puffs are conducted. Because D2 and He have almost the same mass, a spectroscopic method had been developed at TEXTOR where the He partial pressure in the exhaust line was measured by exciting the neutral gas in a Penning gauge and

T. Denner; K. H. Finken; G. Mank

1996-01-01

104

Solution mechanisms of silicate in aqueous fluid and H 2O in coexisting silicate melts determined in-situ at high pressure and high temperature  

NASA Astrophysics Data System (ADS)

The structure of H 2O-saturated silicate melts, coexisting silicate-saturated aqueous solutions, and supercritical silicate liquids in the system Na 2O4SiO 2-H 2O has been characterized with the sample at high temperature and pressure in a hydrothermal diamond anvil cell (HDAC). Structural information was obtained with confocal microRaman and with FTIR microscopy. Fluids and melts were examined along pressure-temperature trajectories defined by the isochores of H 2O at nominal densities, ?fluid, (from EOS of pure H 2O) of 0.90 and 0.78 g/cm 3. With ?fluid = 0.78 g/cm 3, water-saturated melt and silicate-saturated aqueous fluid coexist to the highest temperature (800 C) and pressure (677 MPa), whereas with ?fluid = 0.90 g/cm 3, a homogeneous single-phase liquid phase exists through the temperature and pressure range (25-800 C, 0.1-1033 MPa). Less than 5 vol% quartz precipitates near 650 C in both experimental series, thus driving Na/Si-ratios of melt + fluid phase assemblages to higher values than that of the Na 2O4SiO 2 starting material. Molecular H 2O (H 2O) and structurally bonded OH groups were observed in coexisting melts and fluids as well as in supercritical liquids. Their OH/(H 2O)-ratio is positively correlated with temperature. The OH/(H 2O) in melts is greater than in coexisting fluids. Structural units of Q 3, Q 2, Q 1, and Q 0 type are observed in all phases under all conditions. An expression of the form, 12Q 3 + 13H 2O ?2Q 2 + 6Q 1 + 4Q 0, describes the equilibrium among those structural units. This equilibrium shifts to the right with increasing pressure and temperature with a ?H of the reaction near 425 kJ/mol.

Mysen, Bjorn O.

2009-10-01

105

Elastic properties of phase D (MgSi2O6H2) under pressure: Ab initio investigation  

NASA Astrophysics Data System (ADS)

Recently, the hydrogen bond of phase D (MgSi2O6H2) has been predicted to transform from the asymmetric to the symmetric one at 40 GPa. We have investigated the effects of hydrogen bond symmetrization on the elastic properties of phase D by first-principles calculation. We found some of the elastic constants of phase D with the symmetric hydrogen bond ordering are significantly larger than those with the asymmetric one. Among them, diagonal C33, which corresponds to the uniaxial compression along the hydrogen bond in phase D, anomalously increases across the hydrogen bond symmetrization, while shear C44, C55 and C66 smoothly increase with pressure showing no anomalous behavior. Accordingly, the bulk modulus, VP and V? irregularly increase and the shear modulus and VS do not across the hydrogen bond symmetrization. Since such elastic hardenings have not been reported in other structural model of phase D which does not show hydrogen bond symmetrization under high pressure, these elastic behavior may be a characteristic aspect of the hydrogen bond symmetrization.

Tsuchiya, Jun; Tsuchiya, Taku

2008-11-01

106

Fugacity coefficients of H 2 , CO 2 , CH 4 , H 2 O and of H 2 O- CO 2 CH 4 mixtures: A virial equation treatment for moderate pressures and temperatures applicable to calculations of hydrothermal boiling  

Microsoft Academic Search

Equations derived from a quadratic virial equation in pressure, with virial coefficients expressed as a function of temperature, are fitted to published P - V - T and solubility data to yield values of second and third virial coefficients for pure and mixed gases. These coefficients are not virial coefficients sensu stricto and are used to compute fugacity coefficients of

Nicolas F. Spycher; Mark H. Reed

1988-01-01

107

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

108

High pressure invesigatn of elasic properties under partial melting conditions  

Microsoft Academic Search

Abstract: The presented method and device allow the measurement of the elastic wave velocioies, vp and vs in a gas pressure chamber up to 2 GPa and 1, 000C under the conditions of partial melting. For the investigated rock samples the velocity versus depth function is given.Resume: La mthode et l'appareil prsente permettent le mesurage des vitesses d'onde vp et

H. J. Mueller

1991-01-01

109

Oxygen partial pressure dependence of optical absorption in lithium niobate  

Microsoft Academic Search

Optical absorption of undoped and Fe-doped LiNbO3 crystals grown under various oxygen partial pressures, PO2, has been investigated. The 2.9 eV band found in undoped crystal forms only during the growth process and is proportional to P14O2. This band consists of the superposition of three broad absorption bands A1, A2, and A3, and is assigned to a hole localized on

Tetsuro Suzuki

1996-01-01

110

Three-Dimensional Porous Cd(II) Coordination Polymer with Large One-Dimensional Hexagonal Channels: High Pressure CH(4) and H(2) Adsorption Studies.  

PubMed

A new porous and hydrothermally stable three-dimensional (3D) coordination polymer {[Cd(bpydb)]6H(2)O}(n) (1) has been synthesized under solvothermal condition from a new rigid ligand 4,4'-(4,4'-bipyridine-2,6-diyl) dibenzoic acid (H(2)bpydb) and Cd(NO(3))(2)6H(2)O. Single crystal X-ray analysis shows that 1 has a 5-connected 4(4)6(6) vma net with one-dimensional (1D) hexagonal channels filled with water molecules. Integrity of the framework is maintained upon removal of the water molecules by heating to result in a porous framework. Low pressure N(2) and high pressure H(2) and CH(4) sorption studies along with water adsorption studies were performed on this framework. PMID:21142118

Sharma, Manish K; Senkovska, Irena; Kaskel, Stefan; Bharadwaj, Parimal K

2010-12-13

111

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

NASA Astrophysics Data System (ADS)

The analysis of the internal structure of the ice satellites of the Solar Systems 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 thermodynamic properties of water ices that were generalized, analyzed, and systematized. A brief description of the equations of state for different modifications of high-pressure ices that are most frequently used in thermodynamic calculations is presented. Based on the mathematical treatment of available experimental data for phase equilibria in the water-ice system, the boundaries of the phase transitions between crystal ices I, II, III, V, VI, VII, VIII, and X and liquid water are constructed; in addition, the thermal dependences of the thermodynamic functions (changes in enthalpy, entropy, and volume) of most water-ice phase transitions are obtained.

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

2010-06-01

112

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

2012-12-24

113

Calcite precipitation from CO2 H2O Ca(OH)2 slurry under high pressure of CO2  

NASA Astrophysics Data System (ADS)

The formation of solid calcium carbonate (CaCO3) from aqueous solutions or slurries containing calcium and carbon dioxide (CO2) is a complex process of considerable importance in the ecological, geochemical and biological areas. Moreover, the demand for powdered CaCO3 has recently increased considerably in various fields of industry. The aim of this study was therefore to synthesize fine particles of calcite with controlled morphology by hydrothermal carbonation of calcium hydroxide at high CO2 pressure (initialP=55bar) and at moderate and high temperatures (30 and 90 C). The morphology of precipitated particles was identified by transmission electron microscopy (TEM/EDS) and scanning electron microscopy (SEM/EDS). In addition, an X-ray diffraction analysis was performed to investigate the carbonation efficiency and purity of the solid product. Carbonation of dispersed calcium hydroxide (Ca(OH)2(s)+CO2(aq)?CaCO3(s)+H2O) in the presence of supercritical (PT=90 bar, T=90 C) or gaseous (PT=55 bar, T=30 C) CO2 led to the precipitation of sub-micrometric isolated particles (<1 ?m) and micrometric agglomerates (<5 ?m) of calcite. For this study, the carbonation efficiency (Ca(OH)2 CaCO3 conversion) was not significantly affected by pressure temperature (PT) conditions after 24 h of reaction. In contrast, the initial rate of calcium carbonate precipitation increased from 4.3 mol/h in the 90 bar 90 C system to 15.9 mol/h in the 55 bar 30 C system. The use of high CO2 pressure may therefore be desirable for increasing the production rate of CaCO3, carbonation efficiency and purity, to approximately 48 kg/m3 h, 95% and 96.3%, respectively, in this study. The dissipated heat for this exothermic reaction was estimated by calorimetry to be -32 kJ/mol in the 90 bar 90 C system and -42 kJ/mol in the 55 bar 30 C system.

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

2007-10-01

114

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

115

Defect reduction and surface passivation of SiO2\\/Si by heat treatment with high-pressure H2O vapor  

Microsoft Academic Search

. Heat treatment with high-pressure H2O vapor was applied to improve interface properties of SiO2\\/Si and passivate the silicon surface. Heat treatment at 180420C with high-pressure H2O vapor changed SiOx films, 150nm thick formed at room temperature by thermal evaporation in vacuum, into SiO2 films with a Si-O-Si bonding network similar to that of thermally grown SiO2 films. Heat treatment

T. Sameshima; K. Sakamoto; K. Asada

1999-01-01

116

Thermodynamic modelling of clay dehydration, stability and compositional evolution with temperature, pressure and H 2O activity  

NASA Astrophysics Data System (ADS)

We propose a thermodynamic approach to model the stepwise dehydration with increasing temperature or decreasing H 2O activity of K, Na, Ca and Mg-smectite. The approach relies on the relative stability of the different solid-solutions that describe the hydration of di- or trioctahedral-smectites containing 0, 1, 2 or 3 interlayer water layers. The inclusion of anhydrous mica end-members makes it possible to cover, with the same solid-solution model, the entire range of composition from low-charge smectite to mica, through high-charge smectite and illite. Non-ideal Margules parameters were used to describe the non-ideality of the solid solutions between the hydrated and dehydrated smectite end-members. Standard state properties of all smectite end-members as well as Ca- and Mg-muscovite and -phlogopite were initially estimated by oxide summation. These values were then refined and the other non-ideal interactions were estimated on the basis of different experimental data. The stepwise dehydration of smectite, and its stability and compatibility relations were calculated by Gibbs free energy minimising. Our results account for the progressive evolution of smectite to interlayered illite/smectite and then to mica, as observed in nature and experiments, and our model provides an explanation for the thermodynamic stability of smectite and illite/smectite compared to mica + kaolinite or pyrophyllite assemblages. The results suggest that the enthalpic contribution of interlayer water is a function of the ionic potential of the interlayer cation and the number of interlayer water molecules. This evolution makes possible to estimate the standard-state thermodynamic parameters and hydration-temperature behaviour of smectite of virtually all possible compositions. For the four-interlayer cations considered in the study, our model reproduces the 3 ? 2 ? 1 water-layer transitions that accompany a reduction of water activity or an increase of temperature at ambient pressure. The range of water content and interlayer distance calculated for the 3w, 2w and 1w states are also in fair agreement with the experimental values at ambient pressure.

Vidal, O.; Dubacq, B.

2009-11-01

117

Helium partial pressure measurement in a deuterium environment  

SciTech Connect

To study the removal of helium ash in present day, medium sized tokamaks, experiments with deuterium plasmas and helium puffs are conducted. Because D{sub 2} and He have almost the same mass, a spectroscopic method had been developed at TEXTOR where the He partial pressure in the exhaust line was measured by exciting the neutral gas in a Penning gauge and observing the characteristic emission lines of helium and deuterium. This method was limited to low pressures and concentrations because broad spectral lines from the deuterium molecules superimpose the He lines. By using a spectrometer and an intensified charge coupled device camera instead of optical filters and photomultipliers, it is now possible to record the interesting part of the spectrum with a time resolution of 20 ms. By subtracting the molecular spectrum of deuterium, helium concentrations from 2{percent} on can be detected over about three orders of magnitude in pressure down to 2{times}10{sup {minus}6} mbar. He and D{sub 2} pressures are measured simultaneously. By another method the 58 nm resonance line of helium is observed and the crosstalk of the deuterium gas could be eliminated. Pressure measurements as low as 5{times}10{sup {minus}8} mbar and 1{percent} He concentration are possible. A detection system utilizing a vacuum ultraviolet monochromator in combination with a channeltron has been tested. {copyright} {ital 1996 American Institute of Physics.}

Denner, T.; Finken, K.H.; Mank, G. [Institut fuer Plasmaphysik, Forschungszentrum Juelich, Association Euratom KFA (Germany)

1996-10-01

118

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

SciTech Connect

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

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

1986-08-01

119

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

Microsoft Academic Search

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

Tianfu Xu; Rainer Senger; Stefan Finstele

2007-01-01

120

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

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

2007-11-15

121

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

SciTech Connect

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

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

2007-11-15

122

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

123

Numerical Analysis of Extremely-rich CH4\\/O2\\/H2O Premixed Flames at High Pressure and High Temperature Considering Production of Higher Hydrocarbons  

Microsoft Academic Search

Numerical analysis of CH4\\/O2\\/H2O laminar premixed flame under various conditions of pressure, equivalence ratio and steam concentration was performed using GRI-Mech 3.0 and the mechanism proposed by Davis and Law, which consists of C1 to C6 hydrocarbons in addition to GRI-Mech 3.0. The pressure dependence of laminar burning velocity and flame structure under fuel-rich conditions was focused on. Effects of

Manabu Kumagami; Yasuhiro Ogami; Yuichi Tamaki; Hideaki Kobayashi

2010-01-01

124

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

Microsoft Academic Search

Tungsten (W) films were deposited onto InP in a cold wall, rapid thermal low-pressure chemical vapor deposition (RT-LPCVD) reactor, using a tungsten hexafluoride (WF6) gas reduced by hydrogen (H2). W films of thickness 50450 nm were deposited in the temperature range of 350550 C, pressure range of 0.54.5 Torr, and deposition rates up to 4 nm\\/s with an apparent activation

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

1992-01-01

125

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

Microsoft Academic Search

Tungsten (W) films were deposited onto InP in a cold wall, rapid thermal low-pressure chemical vapour deposition (RT-LPCVD) reactor, from a tungsten hexafluoride (WF6) gas reduced by hydrogen (H2). W films of thickness 50-450 nm were deposited in the temperature range 350-550 degrees C, pressure range 0.5-4.5 Torr at deposition rates up to 4 nm s-1 with an apparent activation

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

1992-01-01

126

Film deposition on the inner surface of tubes using atmospheric-pressure Ar-CH4, Ar-C2H2 and Ar-C2H2-H2 plasmas: interpretation of film properties from plasma-chemical kinetics  

NASA Astrophysics Data System (ADS)

A hard hydrocarbon film is deposited on the inner surface of glass tubes using a filamentary discharge at atmospheric pressure in Ar-C2H2-H2 and Ar-CH4 mixtures. Under similar conditions, a soft film is deposited with a high deposition rate in an Ar-C2H2 mixture. These differences in film hardness and deposition rate are interpreted on the basis of carbon and hydrogen elemental composition in the plasma. The deposition rate is varied along the axis of the tubes in the Ar-C2H2-H2 plasma. This can be controlled by controlling the substrate (tube) temperature. Chemical erosion of the deposited film by hydrogen atoms is the probable reason for this effect. The plasma conditions (gas temperature, electron distribution function and electron density) are characterized by applying optical emission spectroscopy (OES), microphotography and numerical simulation for all three gas mixtures. The density of hydrogen atoms in the inter-electrode region of the tube is determined by applying OES in all gas mixtures. The rates of precursor molecule excitation and follow-up plasma-chemical reactions are calculated on the basis of the determined plasma parameters. Correlations between plasma conditions and film properties are discussed.

Pothiraja, Ramasamy; Engelhardt, Max; Bibinov, Nikita; Awakowicz, Peter

2012-08-01

127

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

128

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

NASA Astrophysics Data System (ADS)

Cryovolcanism and active geological alterations have been discovered in many icy satellites. Not only the surface activities but also the possibility of the subsurface ocean in Galilean satellites have been discussed by Shoemaker et al. (1982) and Kargel (1991). In the previous studies (Prockter 2001, Fortes 2007) existence of subsurface ocean has been suggested based on the observed data such as surface structures of alteration and gravity observations which includes the momentum of inertia. We can adopt the three- layered model for Ganymede (Mueller et al. 1988) composed of Fe or FeS inner core, Silicate outer core, and volatile-rich icy mantle. We calculated the density profile for the three-layered model based on the mixture of C1 chondrite Orgueil meteorite and H2O. We constructed a new model which has a deeper icy mantle with the density larger than pure ice. The infrared data of the Galileo survey (McCord et al. 1999,2001) found a large amount of sulfates such as MgSO46 H2O, MgSO47 H2O. Thus we estimated that the volatile-rich icy mantle contains not only pure ice but also a heavy MgSO4 component with several weight percents. We investigated the phase relations of MgSO4- H2O system under high pressure in order to discuss the internal structure of Ganymede. The sample which consisted of 0 to 30 weight percent of MgSO4 was put in diamond anvil cell with external heating device. The experiments performed up to 5GPa and 600K. This condition is a bit higher than the bottom of icy mantle (around 350K and 2GPa) (Prentice 2000, Sohl 2001). Under our experimental conditions, we found various high pressure phases in MgSO4- H2O system such as Ice VI and VII, and sulfates hydrates such as MgSO41H2O, MgSO46H2O, and MgSO47H2O depending on pressure and temperature conditions. Viscosity and density of the eutectic liquid at high pressure were measured using the falling sphere method with diamond anvil cell.We will present our experimental results and discuss the evolution of the internal structure of Ganymede based on the experiments.

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

2008-12-01

129

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

SciTech Connect

Foster Wheeler Development Corporation is working under DOE contract No. DE-FC26-00NT40972 to develop a partial gasification module (PGM) that represents a critical element of several potential coal-fired Vision 21 plants. When utilized for electrical power generation, these plants will operate with efficiencies greater than 60% while producing near zero emissions of traditional stack gas pollutants. The new process partially gasifies coal at elevated pressure producing a coal-derived syngas and a char residue. The syngas can be used to fuel the most advanced power producing equipment such as solid oxide fuel cells or gas turbines or processed to produce clean liquid fuels or chemicals for industrial users. The char residue is not wasted; it can also be used to generate electricity by fueling boilers that drive the most advanced ultra-supercritical pressure steam turbines. The unique aspect of the process is that it utilizes a pressurized circulating fluidized bed partial gasifier and does not attempt to consume the coal in a single step. To convert all the coal to syngas in a single step requires extremely high temperatures ({approx}2500 to 2800 F) that melt and vaporize the coal and essentially drive all coal ash contaminants into the syngas. Since these contaminants can be corrosive to power generating equipment, the syngas must be cooled to near room temperature to enable a series of chemical processes to clean the syngas. Foster Wheeler's process operates at much lower temperatures that control/minimize the release of contaminants; this eliminates/minimizes the need for the expensive, complicated syngas heat exchangers and chemical cleanup systems typical of high temperature gasification. By performing the gasification in a circulating bed, a significant amount of syngas can still be produced despite the reduced temperature and the circulating bed allows easy scale up to large size plants. Rather than air, it can also operate with oxygen to facilitate sequestration of stack gas carbon dioxide gases for a 100% reduction in greenhouse gas emissions.

Unknown

2002-03-29

130

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

NASA Astrophysics Data System (ADS)

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

Bhoj, Ananth N.; Kushner, Mark J.

2008-08-01

131

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. Under this contract a series of pilot plant tests are being conducted to ascertain PGM performance with a variety of fuels. The performance and economics of a PGM based plant designed for the co-production of hydrogen and electricity will also be determined. This report describes the work performed during the April-June 30, 2004 time period.

Archie Robertson

2004-07-01

132

Zircon solubility and zirconium complexation in H2O+Na2O+SiO2Al2O3 fluids at high pressure and temperature  

NASA Astrophysics Data System (ADS)

Zircon is an important host mineral for many high-field strength elements (HFSE), particularly Zr and Hf. Thus, its solubility in geologic fluids at high pressure and temperature plays an important role in terrestrial cycling of these elements during processes in the Earth's crust and mantle. We performed in-situ high-pressure, high-temperature measurements of zircon solubility in H2O-Na2Si3O7, H2O-Na2Si3O7+Al2O3, H2O-Na2Si2O5, H2O-NaAlSi3O8 fluids, as well as of baddeleyite solubility in H2O-NaOH fluids, by in-situ synchrotron radiation X-ray fluorescence analysis using hydrothermal diamond-anvil cells. Zirconium complexation in fluids in equilibrium with zircon was constrained by in-situ X-ray absorption near-edge structure (XANES) spectroscopy. Zircon solubility is strongly enhanced by addition of Na2Si3O7 to H2O. The degree of enhancement increases with Na2Si3O7 concentration. The Zr content of fluids containing 10 wt% Na2Si3O7 reached up to 862 ppm Zr at 550 C and 400 MPa. At 30 wt% Na2Si3O7, the maximum Zr concentration was 9976 ppm at 600 C and 440 MPa. Zircon solubility in these fluids decreases considerably with pressure and increases slightly with temperature. Addition of Al2O3 decreases the zircon solubility. In H2O-NaAlSi3O8 fluids, the Zr concentrations are in the sub-ppm to ppm range. Zr concentrations in NaOH solutions in equilibrium with baddeleyite reached up to 3902 ppm at 600 C and 930 MPa and increase with pressure and temperature. In-situ XANES spectra collected on Zr in H2O-Na2Si3O7, H2O-Na2Si3O7+Al2O3, H2O-NaOH, and H2O-HCl fluids in equilibrium with zircon provide evidence for strong differences in the Zr complexation between these fluids. Comparison of XANES spectra to those of model compounds and ab-initio simulation of XANES spectra revealed [8]Zr for the HCl solution, [7]Zr for the NaOH solution, and [6]Zr for the Na-Al-silicate-bearing solutions. For the latter solutions, formation of alkali zircono-silicate complexes is indicated by the strong dependence of zircon solubility on Na/Al and the similarity of the XANES spectra to spectra simulated based on the local structure around Zr in the alkali zircono-silicates vlasovite and catapleite. Alkali zircono-silicate complexes are responsible for the enhancement of Zr concentrations in Na-Al-silicate-bearing solutions and very likely play an important role for mobilization of HFSE during fluid-rock interaction. Because high alkali/Al can be expected in aqueous fluids at high pressure and temperature due to incongruent dissolution of feldspar and mica, the increase of zircon solubility along the NaAlSi3O8-Na2Si3O7 join points to potentially considerable Zr or HFSE transport by silicate-bearing aqueous fluids in the lower crust and upper mantle.

Wilke, Max; Schmidt, Christian; Dubrail, Julien; Appel, Karen; Borchert, Manuela; Kvashnina, Kristina; Manning, Craig E.

2012-10-01

133

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

SciTech Connect

Foster Wheeler Development Corporation is working under DOE contract No. DE-FC26-00NT40972 to develop a partial gasification module (PGM) that represents a critical element of several potential coal-fired Vision 21 plants. When utilized for electrical power generation, these plants will operate with efficiencies greater than 60% while producing near zero emissions of traditional stack gas pollutants. The new process partially gasifies coal at elevated pressure producing a coal-derived syngas and a char residue. The syngas can be used to fuel the most advanced power producing equipment such as solid oxide fuel cells or gas turbines or processed to produce clean liquid fuels or chemicals for industrial users. The char residue is not wasted; it can also be used to generate electricity by fueling boilers that drive the most advanced ultra-supercritical pressure steam turbines. The unique aspect of the process is that it utilizes a pressurized circulating fluidized bed partial gasifier and does not attempt to consume the coal in a single step. To convert all the coal to syngas in a single step requires extremely high temperatures ({approx}2500 to 2800F) that melt and vaporize the coal and essentially drive all coal ash contaminants into the syngas. Since these contaminants can be corrosive to power generating equipment, the syngas must be cooled to near room temperature to enable a series of chemical processes to clean the syngas. Foster Wheeler's process operates at much lower temperatures that control/minimize the release of contaminants; this eliminates/minimizes the need for the expensive, complicated syngas heat exchangers and chemical cleanup systems typical of high temperature gasification. By performing the gasification in a circulating bed, a significant amount of syngas can still be produced despite the reduced temperature and the circulating bed allows easy scale up to large size plants. Rather than air, it can also operate with oxygen to facilitate sequestration of stack gas carbon dioxide gases for a 100% reduction in greenhouse gas emissions. The amount of syngas and char produced by the PGM can be tailored to fit the production objectives of the overall plant, i.e., power generation, clean liquid fuel production, chemicals production, etc. Hence, PGM is a robust building block that offers all the advantages of coal gasification but in a more user friendly form; it is also fuel flexible in that it can use alternative fuels such as biomass, sewerage sludge, etc. The PGM consists of a pressurized circulating fluidized bed (PCFB) reactor together with a recycle cyclone and a particulate removing barrier filter. Coal, air, steam, and possibly sand are fed to the bottom of the PCFB reactor and establish a relatively dense bed of coal/char in the bottom section. As these constituents react, a hot syngas is produced which conveys the solids residue vertically up through the reactor and into the recycle cyclone. Solids elutriated from the dense bed and contained in the syngas are collected in the cyclone and drain via a dipleg back to the dense bed at the bottom of the PCFB reactor. This recycle loop of hot solids acts as a thermal flywheel and promotes efficient solid-gas chemical reaction.

Unknown

2001-07-10

134

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

Microsoft Academic Search

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

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

2007-01-01

135

Investigation of the noble gas solubility in H2O-CO2 bearing silicate liquids at moderate pressure II: the extended ionic porosity (EIP) model  

Microsoft Academic Search

A semi-theoretical model is proposed to predict partitioning of noble gases between any silicate liquid and a H2O-CO2 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

P. M. Nuccio; A. Paonita

2000-01-01

136

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

Microsoft Academic Search

A semi-theoretical model is proposed to predict partitioning of noble gases between any silicate liquid and a H2OCO2 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

P. M. Nuccio; A. Paonita

2000-01-01

137

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

138

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

139

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

L. Y. Aranovich; R. C. Newton

1996-01-01

140

Effect of total and partial pressure (oxygen and carbon dioxide) on aerobic microbial processes  

Microsoft Academic Search

In industrial bioreactors, levels and gradients of total and partial pressures are considerably higher than on the laboratory scale. In the relevant range (in general up to 2 or 3 bar, maximum approx. 10 bar), effects of total pressure on aerobic cultures are neglegibly small. CO2 partial pressures of more than approx. 100 mbar may have inhibitory effects on aerobic

U. Onken; E. Liefke

141

A new parameterization of H2SO4/H2O aerosol composition: Atmospheric implications  

NASA Astrophysics Data System (ADS)

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 H2SO4 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

142

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

NASA Astrophysics Data System (ADS)

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

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

2007-12-01

143

Pressure-temperature phase diagram for charge-transfer transition in Cs[Co(3-CNpy)2][W(CN)8]H2O  

NASA Astrophysics Data System (ADS)

Effects of the hydrostatic pressure on the magnetic and structural properties are investigated in a charge-transfer material, Cs[Co(3-CNpy)2][W(CN)8]H2O (CNpy=cyanopyridine) , with two-dimensional Co-W network bridged by CN anions. We have found that the compound shows a pressure-induced charge-transfer (CT) transition at 0.5GPa at room temperature, accompanied by a remarkable color change from transparent red to green. The upper critical temperature (TCT,up) for the CT transition increases at a huge rate of 250K/GPa under pressures, reflecting the concomitant significant volume change (?V/V=0.08) .

Kim, J. E.; Ohishi, Y.; Moritomo, Y.; Kato, K.; Takata, M.; Ohkoshi, S.

2008-01-01

144

Analytic equation of state and thermodynamic properties for He H2 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 H2 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

145

Oxygen modulates growth of human cells at physiologic partial pressures  

PubMed Central

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

1984-01-01

146

Hydrogen-induced cracking in 4340-type steel: Effects of composition, yield strength, and H 2 pressure  

Microsoft Academic Search

Measurements of the threshold stress intensity for hydrogen-induced crack extension,Kth at room temperature were made on bolt-loaded WOL specimens of a commercial 4340 steel and of laboratory heats in which the\\u000a bulk concentrations of manganese, silicon, phosphorus, and sulfur were varied. The hydrogen pressure was varied from 200 to\\u000a 1600 torr (~0.03 to 0.22 MPa), and the yield strengths were

N. Bandyopadhyay; Jun Kameda; C. J. Mcmahon

1983-01-01

147

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

148

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

NASA Astrophysics Data System (ADS)

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

Hacker, Bradley R.; Abers, Geoffrey A.

2004-01-01

149

H2 consumption by anaerobic non-methanogenic mixed cultures.  

PubMed

The impact of H2 consumption, by homoacetogens, on the overall hydrogen yield in mixed culture fermentation is the focus of this study. Batch reactors were used to test the ability of anaerobic digested sludge, heat treated to eliminate methanogens, to produce and consume molecular hydrogen. The measured average hydrogen production rate from 4.2 g glucose/L was 44 +/- 4 mmol H2/L sludge . d, while the H2 consumption rate varied much more, in the range from 4 to 62 mmol H2/L sludge . d. Hydrogen consumption rate depends on acetic acid concentration, headspace H2 partial pressure and mass transfer rates. Different but relatively long lag-phases for hydrogen consumption were observed. It is concluded that homoacetogenesis can have a significant negative effect on bio-H2 production by mixed cultures, limiting the possibilities for sustainable solutions. PMID:21866755

Dinamarca, C; Gan, M; Liu, J; Bakke, R

2011-01-01

150

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

151

Variable mass energy transformation and storage (VMETS) system using NH 3H 2O as working fluid. Part 2: Modeling and simulation under partial storage strategy  

Microsoft Academic Search

This paper is the second part of our study on a new variable mass energy transformation and storage (VMETS) system using NH3H2O as working fluid. In the previous study, the working principle and flow of the new system have been introduced, whilst the dynamic models of the new system have been developed and the simulation under the full storage strategy

S. M. Xu; L. Zhang; J. Liang; R. Du

2007-01-01

152

A simple method of partial inflation of the LMA cuff before insertion in children to allow cuff pressure without adjustment after insertion  

PubMed Central

Background The cuff of the laryngeal mask airway (LMA) is preferred to be partially inflated before insertion in pediatric cases. However, it is not known how much inflation is appropriate. In addition, intra-cuff pressure is not routinely monitored in many institutions despite the fact that a neglected high cuff pressure could cause several complications. This study was conducted to determine whether the cuff inflated with its resting volume before insertion could have a clinically tolerable intra-cuff pressure after insertion. Methods One hundred fifty unpremedicated children aged 0 to 9 yrs were enrolled. The pilot balloon valve was connected to a piston-free syringe to keep the valve open to the atmosphere and allowing the pressure within the cuff of to LMA to equalize to atmospheric pressure. Anesthesia was induced with 6 vol% of sevoflurane in oxygen. After insertion and final positioning of the LMA, the intra-cuff pressure was measured using a cuff pressure manometer. Results The mean intra-cuff pressure was 50 12.9 cmH2O; intra-cuff pressures were 39.1 9.3, 51.6 11.2, and 64.6 12.5 cmH2O for LMAs of sizes 1.5, 2, and 2.5, respectively. Intra-cuff pressure of more than 60 cmH2O was measured in 26 patients, and the median value was 70 cmH2O. There was weak statistical correlation among age, height, and weight with intra-cuff pressure. Conclusions The cuff inflated by the resting volume before insertion may be a simple method for guaranteeing tolerable cuff pressure after insertion.

Moon, Bo-Eun; Kim, Min-Soo

2012-01-01

153

Quartz solubility in H 2O-NaCl and H 2O-CO 2 solutions at deep crust-upper mantle pressures and temperatures: 215 kbar and 500900C  

Microsoft Academic Search

The solubility of quartz in H2O-NaCl solutions was measured at 2, 4.35, 10 and 15 kbar and 500900C, and at NaCl concentrations up to halite saturation, usually greater than 75 wt.%. Quartz solubility was also measured in CO2-H2O solutions at 10 kbar and 800C. Solubilities were determined by weight loss of ground and polished quartz crystal fragments which were equilibrated

Robert C Newton; Craig E Manning

2000-01-01

154

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 (0100mol% 6F). NMR analysis coupled with titration of sulfonated moieties confirmed

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

2007-01-01

155

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

156

Solubility of nonpolar gases in tetrahydropyran at 0 to 30C and 101.33 kPa partial pressure of gas  

Microsoft Academic Search

Solubility measurements of several nonpolar gases (He, Ne, Ar, Kr, Xe, H2, D2, N2, CH4, C2H4, C2H6, CF4, and SF6) in tetrahydropyran at the temperature range 0 to 30C and 101.33 kPa partial pressure of gas are reported. Thermodynamic functions for the solution process (Gibbs energy, enthalpy, and entropies) at 25C are evaluated from the experimental values of the solubility

F. Gibanel; M. C. Lpez; F. M. Royo; V. Rodrguez; J. S. Urieta

1994-01-01

157

Numerical Analysis of Extremely-rich CH4/O2/H2O Premixed Flames at High Pressure and High Temperature Considering Production of Higher Hydrocarbons  

NASA Astrophysics Data System (ADS)

Numerical analysis of CH4/O2/H2O laminar premixed flame under various conditions of pressure, equivalence ratio and steam concentration was performed using GRI-Mech 3.0 and the mechanism proposed by Davis and Law, which consists of C1 to C6 hydrocarbons in addition to GRI-Mech 3.0. The pressure dependence of laminar burning velocity and flame structure under fuel-rich conditions was focused on. Effects of the formation of higher hydrocarbons under fuel-rich conditions were also clarified using the mechanism proposed by Davis and Law. Results showed that for extremely fuel-rich conditions, laminar burning velocity increases as pressure increases for both mechanisms. The increase of laminar burning velocity is caused by the shift of the oxidation pathway of CH3 radical from the C2 Route to the C1 Route. The formation of C3-C6 hydrocarbons has only a small effect on laminar burning velocity. Under fuel-rich conditions, super-adiabatic flame temperature (SAFT) occurs and its pressure dependency was clarified.

Kumagami, Manabu; Ogami, Yasuhiro; Tamaki, Yuichi; Kobayashi, Hideaki

158

Synthesis of ammonium and organic compounds from N2,H2O vapor, and CO2 gas mixtures by synchrotron radiation induced photochemical reactions at atmospheric pressure and at room temperature  

NASA Astrophysics Data System (ADS)

Several compound materials were synthesized from N2,H2O vapor, and CO2 gas mixtures using synchrotron radiation induced photochemical reactions at atmospheric pressure and at room temperature. Ammonium and nitrogen oxides were successfully synthesized from N2,H2O vapor, and O2 gas mixtures. It was also found that organic compounds such as carboxyl acids and amino acids were formed from a N2,H2O vapor, and CO2 gas mixture.

Utsumi, Yuichi; Hattori, Tadashi

2002-03-01

159

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

2012-05-26

160

Effects of Partial Ionization and Pressure on Hydromagnetic Ionizing Waves.  

National Technical Information Service (NTIS)

The transverse hydromagnetic ionizing wave is studied theoretically without the assumption of infinite conductivity behind the wave. Finite gas pressures are included, as well as a variable degree of ionization behind the wave. The electric field in front...

R. S. Kushwaha A. G. Rubin

1966-01-01

161

Cryo-chamber simulation of stratospheric H2SO4/H2O particles: Composition analysis and model comparison  

NASA Astrophysics Data System (ADS)

The combination of a large aerosol chamber and a recently developed Aerosol Composition Mass Spectrometer (ACMS) was used to investigate sulfuric acid aerosols at low temperatures. Concentrations of condensed phase H2SO4 and H2O were determined with an accuracy of better than 4 wt.%. Simultaneous measurements of temperature, partial pressure of water, total sulfate amount and particle size distribution permit to calculate the particle equilibrium composition. The model description of Carslaw et al. [1995a] for H2SO4/H2O solutions was confirmed in the composition range from 35 to 68 wt.% H2SO4 for temperatures between 188 and 236 K, extending the experimental verification to lower temperatures. Although the sub-micron particles were up to 25 K super-cooled with respect to solid sulfuric acid hydrates such as the tetrahydrate (SAT), they remained liquid for days.

Zink, Peter; Knopf, Daniel A.; Schreiner, Jochen; Mauersberger, Konrad; Mhler, Ottmar; Saathoff, Harald; Seifert, Marco; Tiede, Ralph; Schurath, Ulrich

2002-06-01

162

The System NaAlSi 2 O 6 -H 2 O-Argon: Total Pressure and Water Pressure in Metamorphism  

Microsoft Academic Search

Phase equilibrium in metamorphic rocks is affected by temperature, pressure, the proportions of nonvolatile components, and the chemical potentials of the reacting volatile components. Theory interrelating these variables has been tested by studying the reaction analcite --) albite - nepheline - water inhe presence of mixtures of water and argon. New data on the system Ar--tLO permit calculation of the

H. J. Greenwood

1961-01-01

163

Comparative ecology of H 2 cycling in sedimentary and phototrophic ecosystems  

Microsoft Academic Search

The simple biochemistry of H2 is critical to a large number of microbial processes, affecting the interaction of organisms with each other and with the\\u000a environment. The sensitivity of each of these processes to H2 can be described collectively, through the quantitative language of thermodynamics. A necessary prerequisite is to understand\\u000a the factors that, in turn, control H2 partial pressures.

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

2002-01-01

164

The partial pressure effect on the growth of YSZ film and YSZ buffered multilayers on silicon  

Microsoft Academic Search

YSZ thin film was deposited on native Si wafer without prior removal of surface amorphous SiOx layer with pulsed laser deposition (PLD) technique by varying oxygen partial pressure during deposition. Initial oxygen partial pressure was about 10?6mbar followed by 510?4mbar. High quality YSZ thin film can be successfully fabricated without an amorphous interfacial SiOx layer. The YSZ thin film grows

Shue Yin Chow; Shijie Wang

2004-01-01

165

Oxidation behavior of modified SUS316 (PNC316) stainless steel under low oxygen partial pressure  

Microsoft Academic Search

Oxidation behaviors of modified SUS316 (PNC316) and SUS316 stainless steels were investigated under the low oxygen partial pressure of 10?31?10?22 atm at 600800 C. Oxygen uptake by these materials parabolically increased with time, and the kinetic rate constants depended on both oxygen partial pressure and temperature. Thus, semi-empirical equations of the parabolic rate constants were obtained to be 2.70104exp(?109\\/RT)PO20.279 for

I. Sato; M. Takaki; T. Arima; H. Furuya; K. Idemitsu; Y. Inagaki; M. Momoda; T. Namekawa

2002-01-01

166

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

Microsoft Academic Search

We describe an instrument prototype that measures dissolved carbon dioxide (DC) without need for standard wetted probe membranes or titration. DC is calculated using Henrys Law, water temperature, and the steady-state partial pressure of carbon dioxide that develops within the instruments vertical gasliquid contacting chamber. Gas-phase partial pressures were determined with either an infrared detector (ID) or by measuring voltage

Barnaby J. Watten; Claude E. Boyd; Michael F. Schwartz; Steven T. Summerfelt; Brian L. Brazil

2004-01-01

167

Partial Pressures in Equilibrium with Group IV Tellurides. Iii. Germanium Telluride.  

National Technical Information Service (NTIS)

The partial pressures of Te2(g) and GeTe(g) over Ge-Te condensed phases between 1 and 52 at. % Te have been determined between 525 and 940 C by measuring the optical density of the vapor. Partial optical densities due to each species are calculated and co...

R. F. Brebrick

1964-01-01

168

Characteristics of anodic polarization of solid oxide fuel cells under pressurized conditions  

Microsoft Academic Search

AC impedance measurements were carried out under pressurized conditions by using a NiY2O3-stabilized zirconia (YSZ)\\/YSZ half cell in order to investigate anodic polarization at high-pressure conditions. AC impedance spectra were measured at 900 and 1000 C in H2H2O system with a constant H2\\/H2O ratio, or a constant partial pressure of H2 or H2O for different total pressures of 1 to

Ryuji Kikuchi; Tatsuya Yano; Tatsuya Takeguchi; Koichi Eguchi

2004-01-01

169

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

Microsoft Academic Search

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

Bairagi C. Mallick; Nand Kishore

2006-01-01

170

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

171

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

172

Influence of pressure on the formation of products of partial oxidation of methane  

SciTech Connect

The influence of pressure (varying from 30 to 230 atm) on the output of products of partial oxidation of methane under jet conditions at T = 400{degrees}C and [O{sub 2}] = 2.8 vol % is studied experimentally. The growth of pressure above 100 atm is shown to have little effect on the output of the main products.

Arutyunov, V.S.; Vedeneev, V.I.; Klimovetskaya, S.Y.; Leonov, V.E.; Pavlii, L.V. [Semenov Institute of Chemical Physics, Moscow (Russian Federation)

1994-11-01

173

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

174

Equilibrium partial pressures of strong acids over concentrated solutionsIII. The temperature variation of HNO 3 solubility  

NASA Astrophysics Data System (ADS)

The mole fraction Henry's Law constant ( KH x/atm -1) of nitric acid is described by the equation K Hx = x H+ x NO3- f ?/p HNO3, where f ? is the mean rational activity coefficient, prefix ' x' indicates mole fraction (calculated on the basis of complete dissociation in solution), and ' p' denotes partial pressure. From 215< T<400 K, ln( KH x) is given by: 385.972199-3020.3522/ T - 71.001998 ln T + 0.131442311 T - 0.420928363 10 -4T2. The mean activity coefficient of pure aqueous HNO 3 is described from 0 to 100% HNO 3 by an empirical extension to the Pitzer and Simonson thermodynamic model, allowing activities of both HNO 3 and H 2O to be easily calculated. This approach, in addition to its utility at normal and high temperatures, offers a considerable improvement over the methods previously used for estimating the partial pressure of HNO 3 over the low temperature, highly concentrated aerosols found in the stratosphere.

Brimblecombe, Peter; Clegg, Simon L.

175

The Partial Pressures of Formic and Acetic Acids above Some Aqueous Solutions; and Their Partial Molal Free Energies at 1.0 Molal Concentration  

Microsoft Academic Search

The paucity of data pertaining to the vapor pressures of aqueous solutions of the organic acids has hitherto retarded thermodynamic calculations in this field. In the present study the partial pressures of formic acid above three of its solutions and those of acetic acid above two solutions have been measured at 25C. From these results the partial molal free energies

Wm. A. Kaye; George S. Parks

1934-01-01

176

Pressure-broadening coefficients and line strengths of H2O near 1.39 ?m: application to the in situ sensing of the middle atmosphere with balloonborne diode lasers  

NASA Astrophysics Data System (ADS)

Since 1998, we have developed two balloonborne diode laser spectrometers, SDLA and micro-SDLA, to yield in situ concentration data of H2O in the middle atmosphere by absorption spectroscopy in the 1.39-?m spectral range. In this paper, we revisit the molecular parameters, line intensities and pressure-broadening coefficients, for several lines of the ?1+?3 and 2?1 bands, which are useful for the monitoring of atmospheric H2O. The new values are thoroughly compared to existing molecular database and previous determinations. Calculations are performed to yield the pressure-effect coefficients: the theoretical model is described and the ab initio predictions are compared to laboratory measurements achieved with a laser diode spectrometer. The improvement in the H2O monitoring obtained with the new set of molecular data is evaluated directly from vertical H2O concentration profiles.

Durry, G.; Zeninari, V.; Parvitte, B.; Le Barbu, T.; Lefevre, F.; Ovarlez, J.; Gamache, R. R.

2005-09-01

177

Absolute OH density measurements in the effluent of a cold atmospheric-pressure Ar-H2O RF plasma jet in air  

NASA Astrophysics Data System (ADS)

Absolute OH densities are obtained in a radio-frequency-driven Ar-H2O atmospheric-pressure plasma jet by laser-induced fluorescence (LIF), calibrated by Rayleigh scattering and by UV broadband absorption. The measurements are carried out in ambient air and the effect of air entrainment into the Ar jet is measured by analyzing the time-resolved fluorescence signals. The OH densities are obtained for different water vapor concentrations admixed to the Ar and as a function of the axial distance from the nozzle. A sensitivity analysis to deduce the accuracy of the model-calculated OH density from the LIF measurement is reported. It is found that the UV absorption and the LIF results correspond within experimental accuracy close to the nozzle and deviate in the far effluent. The possible reasons are discussed. The OH densities found in the plasma jet are in the range (0.1-2.5) 1021 m-3 depending on the water concentration and plasma conditions.

Verreycken, Tiny; Mensink, Rob; van der Horst, Ruud; Sadeghi, Nader; Bruggeman, Peter J.

2013-10-01

178

Influences of oxygen partial pressure on YBCO grain growth by a zone melting method  

SciTech Connect

This study reports investigation on influences of Y{endash}Ba{endash}Cu{endash}O compounds solidification under different oxygen partial pressures by a zone melting method. In Y{endash}Ba{endash}Cu{endash}O system, {ital P}(O{sub 2}) ranged from 0.02 to 1 atm, following reaction occurred during heating: YBa{sub 2}Cu{sub 3}O{sub 6+{delta}}(Y123){r_arrow}Y{sub 2}BaCuO{sub 5}(Y211)+L. With an increase of oxygen partial pressure or decrease of pulling rate, the morphology of solidified interface changed from mushy to equiaxed, cellular, and planar. The continuous Y123 grains were readily obtained under high oxygen partial pressure. Based on the constitutional supercooling theory and combining the result of the yttrium solubility limit for different oxygen partial pressures, the influences of oxygen partial pressure on Y123 morphological evolution were clarified. {copyright} {ital 1996 Materials Research Society.}

Yao, X.; Sumida, M.; Shiohara, Y. [Superconductivity Research Laboratory, ISTEC, 1-10-13 Shinonome Koto-ku, Tokyo 135 (Japan)

1996-11-01

179

Thermodynamic description of equilibria in mixed fluids (H 2 O-nonpolar gas) in a wide range of temperatures (25700C) and pressures (15000 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

180

Adsorption of CO 2 from dry gases on MCM-41 silica at ambient temperature and high pressure. 2: Adsorption of CO 2\\/N 2, CO 2\\/CH 4 and CO 2\\/H 2 binary mixtures  

Microsoft Academic Search

Adsorption equilibrium capacity of CO2, CH4, N2, H2 and O2 on periodic mesoporous MCM-41 silica was measured gravimetrically at room temperature and pressure up to 25bar. The ideal adsorption solution theory (IAST) was validated and used for the prediction of CO2\\/N2, CO2\\/CH4, CO2\\/H2 binary mixture adsorption equilibria on MCM-41 using single components adsorption data. In all cases, MCM-41 showed preferential

Youssef Belmabkhout; Abdelhamid Sayari

2009-01-01

181

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

PubMed

Reliable mass spectrometry data from large water clusters Y(-)(H(2)O)(n) with various negative core ions Y(-) such as O(2)(-), HO(-), HO(2)(-), NO(2)(-), NO(3)(-), NO(3)(-)(HNO(3))(2), CO(3)(-) and HCO(4)(-) have been obtained using atmospheric pressure negative corona discharge mass spectrometry. All the core Y(-) ions observed were ionic species that play a central role in tropospheric ion chemistry. These mass spectra exhibited discontinuities in ion peak intensity at certain size clusters Y(-)(H(2)O)(m) indicating specific thermochemical stability. Thus, Y(-)(H(2)O)(m) may correspond to the magic number or first hydrated shell in the cluster series Y(-)(H(2)O)(n). The high intensity discontinuity at HO(-)(H(2)O)(3) observed was the first mass spectrometric evidence for the specific stability of HO(-)(H(2)O)(3) as the first hydrated shell which Eigen postulated in 1964. The negative ion water clusters Y(-)(H(2)O)(n) observed in the mass spectra are most likely to be formed via core ion formation in the ambient discharge area (760 torr) and the growth of water clusters by adiabatic expansion in the vacuum region of the mass spectrometers (?1 torr). The detailed mechanism of the formation of the different core water cluster ions Y(-)(H(2)O)(n) is described. PMID:21184434

Sekimoto, Kanako; Takayama, Mitsuo

2011-01-01

182

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

183

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

184

Generation of extremely high vacuum by ordinary procedures with a SUS304 vacuum chamber and total and partial pressure measurements by hot cathode ionization gauges and a quadrupole mass spectrometer  

NASA Astrophysics Data System (ADS)

The present study generated an extremely high vacuum of 10-10 Pa by very common methods such as using SUS304 chamber material, electropolishing surface treatment and turbomolecular pumping technology. We examined the gas phase and electron-stimulated desorption ions of the ion gauges, the effect of ambient temperature, total pressure and H2 partial pressure. One of the results showed that, as is well known, most of the residual gas in the extremely high vacuum chamber was H2 but there was also a little F, which is not so well known.

Hong, S. S.; Chung, K. H.; Shin, Y. H.; Arakawa, I.

2006-01-01

185

Theoretical Calculations of H2O Linewidths and Pressure Shifts: Comparison of Anderson Theory with Quantum Many-Body Theory for N2 and Air Broadened Lines.  

National Technical Information Service (NTIS)

The purpose of this paper is to make specific comparisons of two theoretical methods with available experimental measurements of H2O widths and shifts for the case of N2 (or air) broadening. The earliest calculations of H2O-n2 half widths were carried out...

R. W. Davies B. A. Oli

1977-01-01

186

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

187

The kinetics of dissolution of muscovites at 25C and 1 atm CO 2 partial pressure  

Microsoft Academic Search

Two different dry-ground muscovites were placed separately in deionized water saturated with 1 atm partial pressure of carbon dioxide at room temperature and pressure for about 1000 hr. The carbonic acid formed buffered the bulk solution between 4.6 and 5.1 during the whole time of the experiment. K and Na were rapidly released by a reaction with hydrogen ions in

Feng-Chih Lin; Charles V. Clemency

1981-01-01

188

Modern state of direct high pressure partial oxidation of natural gas to methanol  

SciTech Connect

The survey of existing experimental results on direct partial oxidation of methane to methanol (DMTM) is followed by theoretical analysis of the process. Special attention is paid to the role of the pressure. The cause of failure of many attempts to promote a high pressure DMTM process by means of catalysts is elucidated. The modern industrial significance and future prospects of the process and the most important directions of future investigations are discussed.

Arutyunov, V.S.; Basevich, V.Ya.; Vedeneev, V.I. [Russian Academy of Science, Moscow (Russian Federation). Semenov Inst. of Chemical Physics

1995-12-01

189

Determination of gas pressure in vacuum interrupter based on partial discharge  

Microsoft Academic Search

Partial discharge characteristics in air under a low vacuum region were studied to develop a diagnosis technique to determine the gas pressure in a vacuum interrupter. The pressures were set at from 1.3 Pa to 2.6 kPa in order to simulate the leakage of gas into the vacuum interrupter. The structure of the vacuum interrupter, the measurement and the circuit

Mohamad Kamarol; Shinya Ohtsuka; Masayuki Hikita; Hitoshi Saitou; Masayuki Sakaki

2007-01-01

190

Role of partial melting in the evolution of the Sulu (eastern China) ultrahigh-pressure terrane  

Microsoft Academic Search

Strongly deformed potassium feldspar rich dikes are widely distributed in the northern part of the Sulu ultrahigh-pressure (UHP) metamorphic terrane, eastern China. The fact that the crystallization ages of these dikes overlap with the age of peak UHP metamorphic conditions implies the presence of melt during metamorphism. Sr isotopic ratios of the dikes are compatible with their origin as partial

Simon Wallis; Motohiro Tsuboi; Kazuhiro Suzuki; Mark Fanning; Laili Jiang; Tsuyoshi Tanaka

2005-01-01

191

Measurement of sea surface partial pressure of C02 from a moored buoy  

Microsoft Academic Search

An autonomous analytical system for measuring the difference in partial pressure of CO2 between the sea surface and the atmosphere was constructed and deployed on a buoy moored off the central coast of California. The apparatus was based on the conventional analytical techniques of sea surface gas equilibrium and non-dispersive infrared spectrometry. Hourly data were collected for a 70 day

G. E. Friederich; P. G. Brewer; R. Herlien; F. P. Chavez

1995-01-01

192

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

Microsoft Academic Search

Aqueous monoethanolamine (MEA) and diethanolamine (DEA) solutions are used extensively for the removal of HS and CO from gas streams. Advantages of the use of these particular chemical solvents include high reactivity, low cost, ease of reclamation, low absorption of hydrocarbons, and relatively high capacity at low acid gas partial pressures. The rational design and operation of MEA and DEA

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

1980-01-01

193

Oxygen Partial Pressure: A Key to Alloying and Discovery in Metal Oxide--Metal Eutectic Systems.  

National Technical Information Service (NTIS)

Control of oxygen partial pressure is essential in the directional solidification of oxide--metal eutectic composites by techniques involving gas-solid and gas-liquid interactions. The existence of end components in the eutectic composite is Po sub 2 sens...

J. D. Holder G. W. Clark B. F. Oliver

1978-01-01

194

Measurement of partial vapor pressure of ammonia over acid ammonium sulfate solutions by an integral method  

Microsoft Academic Search

We present a simple, integral, passive method for measuring partial vapor pressure. Integral methods are useful tools when dealing with very low concentrations because collection over extended periods increases the analytical sensitivity. Passive methods have the advantage of not introducing constraints external to the system. The principle of the method used here is to selectively react the substance in the

P. Koutrakis; B. Aurian-Blajeni

1993-01-01

195

Diurnal Changes in the Partial Pressure of Carbon Dioxide in Coral Reef Water  

Microsoft Academic Search

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 (PCO_2) in reef waters during two 3-day periods, one in March 1993 and one in March 1994, on Shiraho reef

Hajime Kayanne; Atsushi Suzuki; Hiroshi Saito

1995-01-01

196

Effect of nitrogen partial pressure on Al-Ti-N films deposited by arc ion plating  

NASA Astrophysics Data System (ADS)

AlTiN films with different nitrogen partial pressures were deposited using arc ion plating (AIP) technique. In this study, we systematically investigated the effect of the nitrogen partial pressure on composition, deposition efficiency, microstructure, macroparticles (MPs), hardness and adhesion strength of the AlTiN films. The results showed that with increasing the nitrogen partial pressure, the deposition rate exhibited a maximum at 1.2 Pa. Results of X-ray photoelectron spectroscopy (XPS) analysis revealed that AlTiN films were comprised of Ti-N and Al-N bonds. XRD results showed that the films exhibited a (1 1 1) preferred growth, and AlTi 3N and TiAl x phases were observed in the film deposited at 1.7 Pa. Analysis of MPs statistics showed MPs decreased with the increase in the nitrogen partial pressure. In addition, the film deposited at 1.2 Pa possessed the maximum hardness of 38 GPa and the better adhesion strength.

Cai, Fei; Zhang, Shihong; Li, Jinlong; Chen, Zhong; Li, Mingxi; Wang, Lei

2011-12-01

197

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 Earths 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

198

Accelerated carbon sequestration in mine tailings using elevated CO2 partial pressure  

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

199

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

200

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

201

Investigation of the H2 Oxidation System in Rhizobium japonicum 122 DES Nodule Bacteroids 1  

PubMed Central

The H2-oxidizing complex in Rhizobium japonicum 122 DES bacteroids failed to catalyze, at a measurable rate, 2H1H exchange from a mixture of 2H2 and 1H2 in presence of 2H2O and 1H2O, providing no evidence for reversibility of the hydrogenase reaction in vivo. In the H2 oxidation reaction, there was no significant discrimination between 2H2 and 1H2, indicating that the initial H2-activation step in the over-all H2 oxidation reaction is not rate-limiting. By use of improved methods, an apparent Km for H2 of 0.05 micromolar was determined. The H2 oxidation reaction in bacteroids was strongly inhibited by cyanide (88% at 0.05 millimolar), theonyltrifluoroacetone, and other metal-complexing agents. Carbonyl cyanide m-chlorophenylhydrazone at 0.005 millimolar and 2,4-dinitrophenol at 0.5 millimolar inhibited H2 oxidation and stimulated O2 uptake. This and other evidence suggest the involvement of cytochromes and nonheme iron proteins in the pathway of electron transport from H2 to O2. Partial pressures of H2 at 0.03 atmosphere and below had a pronounced inhibitory effect on endogenous respiration by bacteroid suspensions. The inhibition of CO2 evolution by low partial pressures of H2 suggests that H2 utilization may result in conservation of oxidizable substrates and benefits the symbiosis under physiological conditions. Succinate, acetate, and formate at concentrations of 50 millimolar inhibited rates of H2 uptake by 8, 29, and 25%, respectively. The inhibition by succinate was noncompetitive and that by acetate and formate was uncompetitive. A concentration of 11.6 millimolar CO2 (initial concentration) in solution inhibited H2 uptake by bacteroid suspensions by 18%. Further research is necessary to establish the significance of the inhibition of H2 uptake by succinate, acetate, formate, and CO2 in the metabolism of the H2-uptake-positive strains of Rhizobium.

Emerich, David W.; Ruiz-Argueso, Tomas; Russell, Sterling A.; Evans, Harold J.

1980-01-01

202

Partial alignment and measurement of residual dipolar couplings of proteins under high hydrostatic pressure.  

PubMed

High-pressure NMR spectroscopy has emerged as a complementary approach for investigating various structural and thermodynamic properties of macromolecules. Noticeably absent from the array of experimental restraints that have been employed to characterize protein structures at high hydrostatic pressure is the residual dipolar coupling, which requires the partial alignment of the macromolecule of interest. Here we examine five alignment media that are commonly used at ambient pressure for this purpose. We find that the spontaneous alignment of Pf1 phage, d(GpG) and a C12E5/n-hexnanol mixture in a magnetic field is preserved under high hydrostatic pressure. However, DMPC/DHPC bicelles and collagen gel are found to be unsuitable. Evidence is presented to demonstrate that pressure-induced structural changes can be identified using the residual dipolar coupling. PMID:23807390

Fu, Yinan; Wand, A Joshua

2013-06-27

203

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

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

204

Growth of Streptococcus faecalis under High Hydrostatic Pressure and High Partial Pressures of Inert Gases  

PubMed Central

Growth of Streptococcus faecalis in a complex medium was inhibited by xenon, nitrous oxide, argon, and nitrogen at gas pressures of 41 atm or less. The order of inhibitory potency was: xenon and nitrous oxide > argon > nitrogen. Helium appeared to be impotent. Oxygen also inhibited streptococcal growth and it acted synergistically with narcotic gases. Growth was slowed somewhat by 41 atm hydrostatic pressure in the absence of narcotic gases, but the gas effects were greater than those due to pressure. In relation to the sensitivity of this bacterium to pressure, we found that the volume of cultures increased during growth in a volumeter or dilatometer, and that this dilatation was due mainly to glycolysis. A volume increase of 20.3 3.6 ml/mole of lactic acid produced was measured, and this value was close to one of 24 ml/mole lactic acid given for muscle glycolysis, and interestingly, close to the theoretic volume increase of activation calculated from the depression of growth rate by pressure.

Fenn, Wallace O.; Marquis, Robert E.

1968-01-01

205

Growth of Streptococcus faecalis under high hydrostatic pressure and high partial pressures of inert gases.  

PubMed

Growth of Streptococcus faecalis in a complex medium was inhibited by xenon, nitrous oxide, argon, and nitrogen at gas pressures of 41 atm or less. The order of inhibitory potency was: xenon and nitrous oxide > argon > nitrogen. Helium appeared to be impotent. Oxygen also inhibited streptococcal growth and it acted synergistically with narcotic gases. Growth was slowed somewhat by 41 atm hydrostatic pressure in the absence of narcotic gases, but the gas effects were greater than those due to pressure. In relation to the sensitivity of this bacterium to pressure, we found that the volume of cultures increased during growth in a volumeter or dilatometer, and that this dilatation was due mainly to glycolysis. A volume increase of 20.3 +/- 3.6 ml/mole of lactic acid produced was measured, and this value was close to one of 24 ml/mole lactic acid given for muscle glycolysis, and interestingly, close to the theoretic volume increase of activation calculated from the depression of growth rate by pressure. PMID:4972126

Fenn, W O; Marquis, R E

1968-11-01

206

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

PubMed Central

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

Pan, Bo; Vessey, J. Kevin

2001-01-01

207

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

NASA Astrophysics Data System (ADS)

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

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

2010-08-01

208

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

209

High-pressure partial melting of gabbro and its role in the Hawaiian magma source  

NASA Astrophysics Data System (ADS)

We have conducted high-pressure experiments on a natural oceanic gabbro composition (Gb108). Our aim was to test recent proposals that Sr-enrichment in rare primitive melt inclusions from Mauna Loa, Hawaii, may have resulted from melting of garnet pyroxenite formed in the magma source regions by reaction of peridotite with siliceous, Sr-enriched partial melts of eclogite of gabbroic composition. Gb108 is a natural, Sr-enriched olivine gabbro, which has a strong positive Sr anomaly superimposed on an overall depleted incompatible trace element pattern, reflecting its origin as a plagioclase-rich cumulate. At high pressures it crystallises as a coesite eclogite assemblage, with the solidus between 1,300 and 1,350C at 3.5 GPa and 1,450 and 1,500C at 4.5 GPa. Clinopyroxenes contain 4 9% Ca-eskolaite component, which varies systematically with pressure and temperature. Garnets are almandine and grossular-rich. Low degree partial melts are highly siliceous in composition, resembling dacites. Coesite is eliminated between 50 and 100C above the solidus. The whole-rock Sr-enrichment is primarily hosted by clinopyroxene. This phase dominates the mode (>75 wt%) at all investigated PT conditions, and is the major contributor to partial melts of this eclogite composition. Hence the partial melts have trace element patterns sub-parallel to those of clinopyroxene with ?10 greater overall abundances and with strong positive Sr anomalies. Recent studies of primitive Hawaiian volcanics have suggested the incorporation into their source regions of eclogite, formerly gabbroic material recycled through the mantle at subduction zones. The models suggest that formerly gabbroic material, present as eclogite in the Hawaiian plume, partially melted earlier than surrounding peridotite (i.e. at higher pressure) because of the lower solidus temperature of eclogite compared with peridotite. This produced highly siliceous melts which reacted with surrounding peridotite producing hybrid pyroxene + garnet lithologies. The Sr-enriched nature of the formerly plagioclase-rich gabbro was present in the siliceous partial melts, as demonstrated by these experiments, and was transferred to the reactive pyroxenite. These in turn partially melted, producing Sr-enriched picritic liquids which mixed with normal picritic partial melts of peridotite before eruption. On rare occasions these mixed, relatively Sr-rich melts were trapped as melt inclusions in primitive olivine phenocrysts.

Goggi, A. Susana; Lopez-Sanchez, Higinio; Caragea, Petrutza; Westgate, Mark; Arritt, Raymond; Clark, Craig A.

2007-10-01

210

Kinetically enhanced copper vapour lasers employing H2-HCl-Ne buffer gas mixtures  

NASA Astrophysics Data System (ADS)

The output powers from 25 mm (volume 0.49 l) and 40 mm (volume 1.9 l) diameter copper vapour lasers (nominally 20 and 55 W devices) are approximately doubled to >50 and >100 W respectively by adding small partial pressures of both H2 and HCl to the neon buffer gas. Our studies show that this gas mixture performs better than a H2-HBr admix, a result we attribute to more efficient reassociation of HCl in the plasma region.

Withford, Michael J.; Brown, Daniel J. W.; Carman, Robert J.; Piper, James A.

1998-08-01

211

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

Microsoft Academic Search

This study was undertaken to develop an experimental apparatus that would allow direct measurements of gas equilibrium solubility in aqueous alkanolamine solutions at low gas partial pressures. Carbon dioxide and hydrogen sulfide solubility in 20, 35 and 50% by weight diethanolamine aqueous solutions was measured. The measurements were made at acid gas partial pressures between 0.003 and 10.9 psia and

Elizondo-Villarreal

1989-01-01

212

Nitriding of Titanium and Its Alloys by N2, NH3 or Mixtures of N2 + H2 in a DC Arc Plasma at Low Pressures.  

National Technical Information Service (NTIS)

The dc glow discharges in different gas mixtures of Ar + N2, Ar + NH3 or Ar + N2 + H2 result in the surface nitriding of Ti metal and its alloy (Ti6Al4V). Various gas mixtures were used in order to establish the main active species governing the nitriding...

R. Avni

1984-01-01

213

72 Effects of hydrogen pressure and H 2\\/Oil ratio on deactivation of atmospheric residue hydrotreating catalysts at early process time  

Microsoft Academic Search

A pilot plant test of hydrodesulfurization (HDS) of an atmospheric residue (AR) was carried out to elucidate the effect of start-up conditions on catalytic performance and catalyst deactivation. When the AR containing a large amount of asphaltenes or related compounds was fed at start of run (SOR) to the HDS catalyst bed operated at low H2\\/HC ratio and low hydrogen

Hidehiro Higashi; Takeshige Takahashi; Takami Kai

2003-01-01

214

The change of steel surface chemistry regarding oxygen partial pressure and dew point  

NASA Astrophysics Data System (ADS)

By investigating the surface state of a Ti-IF, TiNb-IF and a MnCr-DP after several series of intercritical annealing, the impact of the annealing gas composition on the selective oxidation process is discussed. On behalf of the presented results, it can be concluded that not the general oxygen partial pressure in the annealing furnace, which is a result of the equilibrium reaction of water and hydrogen, is the main driving force for the selective oxidation process. It is shown that the amounts of adsorbed gases at the strip surface and the effective oxygen partial pressure resulting from the adsorbed gases, which is mainly dependent on the water content of the annealing furnace, is driving the selective oxidation processes occurring during intercritical annealing. Thus it is concluded, that for industrial applications the dew point must be the key parameter value for process control.

Norden, Martin; Blumenau, Marc; Wuttke, Thiemo; Peters, Klaus-Josef

2013-04-01

215

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

NASA Astrophysics Data System (ADS)

The solidus temperature Tsolidus of Bi2Sr2CaCu2Ox (Bi-2212) is decreased from 893C to 880C and further down to 834C when the oxygen partial pressure of the atmosphere is changed from pO2 = 1 atm to 0.21 atm and further to 0.001 atm. Silver additions to the superconductor exceeding 2 wt% lower Tsolidus by up to 25 K in a pure oxygen atmosphere. The weight loss during melting, which is related to oxygen release, is highest at low oxygen partial pressures and can be reduced by silver additions due to increased oxygen solubility of the Bi-2212 melt in presence of dissolved silver. The experimental results are compared with thermodynamic data of the Bi-Sr-Ca-Cu-O system.

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

1997-02-01

216

Equilibrations of copper matte and fayalite slag under controlled partial pressures of SO 2  

Microsoft Academic Search

Equilibrium distributions of Cu, S and O between silica saturated fayalite slags and copper mattes (25 to 79 pct Cu) have\\u000a been examined experimentally under controlled partial pressures of SO2. The temperature range of the experiments was 1423 to 1573 K and pSO2 was varied between 0.1 and 1 atm. Concentrations of copper in the experimental slags were found to

Francisco J. Tavera; William G. Davenport

1979-01-01

217

Exhaled breath condensate pH standardised for CO2 partial pressure  

Microsoft Academic Search

Exhaled breath condensate (EBC) pH is considered to reflect the acid-base balance of the airways. Current pH measurements do not take into account the effect of CO2. The aim of the present study was to determine the effect of condensate CO2 partial pressure on pH and to provide a more precise mode of EBC pH determination. Condensate pH and CO2

T. Kullmann; I. Barta; Z. Lazar; B. Szili; E. Barat; M. Valyon; M. Kollai; I. Horvath

2007-01-01

218

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

Microsoft Academic Search

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

Ivonete vila; Paula M. Crnkovic; Fernando E. Milioli; Kai H. Luo

2012-01-01

219

Oxygen partial pressure: a key to alloying and discovery in metal oxide--metal eutectic systems  

Microsoft Academic Search

Control of oxygen partial pressure is essential in the directional solidification of oxide--metal eutectic composites by techniques involving gas-solid and gas-liquid interactions. The existence of end components in the eutectic composite is Po sensitive as are melt stoichiometry, solid phase compositions, and vapor losses due to oxidation-volatilization. Simple criteria are postulated which can aid the experimentalist in selecting the proper

J. D. Holder; G. W. Clark; B. F. Oliver

1978-01-01

220

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

Microsoft Academic Search

We present a new method to determine in vivo the temporal evolution of intrapulmonary oxygen concentrations by functional lung imaging with hyperpolarized 3Helium (3He?). Single-breath, single-bolus visualization of 3He? administered to the airspaces is used to analyze nuclear spin relaxation caused by the local oxygen partial pressure pO2(t). We model the dynamics of hyperpolarization in the lung by rate equations.

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

1999-01-01

221

Effect of water density and air pressure on partial oxidation of bitumen in supercritical water  

Microsoft Academic Search

Partial oxidation of bitumen was examined in supercritical water from 653 to 723K at a water\\/oil ratio from 0 to 3 and up to 5.1MPa of initial air pressure. The contents in the reactor were separated into water rich phase and oil rich phase. Most of oxygen was quickly consumed within 30min and the main gases produced were CO, CO2

Takafumi Sato; Phan Hieu Trung; Tomoyuki Tomita; Naotsugu Itoh

222

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

SciTech Connect

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

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

1991-10-01

223

Alveolar partial pressures of carbon dioxide and oxygen measured by a helium washout technique  

Microsoft Academic Search

A non-invasive technique was developed for measuring alveolar carbon dioxide and oxygen tension during tidal breathing. This was achieved by solving the Bohr equations for mean alveolar carbon dioxide and oxygen tensions (PACO2, PAO2) from known values of the dead-space:tidal volume ratio measured by helium washout, and from the mixed expired partial pressure of carbon dioxide and oxygen. The derived

J Jordanoglou; G Tatsis; J Danos; S Gougoulakis; D Orfanidou; M Gaga

1990-01-01

224

Physiological changes in marine picocyanobacterial Synechococcus strains exposed to elevated CO2 partial pressure  

Microsoft Academic Search

Unicellular marine cyanobacteria are abundant in both coastal and oligotrophic environments, where they contribute substantially to primary production. The physiological effect of future increases in atmospheric CO2 concentrations on the marine picocyanobacteria is still poorly known. We studied the physiological changes in marine phycocyanin (PC)-rich and phycoerythrin (PE)-rich Synechococcus strains under different CO2 partial pressures (350, 600 and 800 ppm).

ZHIQIANG LU; NIANZHI JIAO; HUIYONG ZHANG

2006-01-01

225

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

226

Pressure-induced rotational energy transfer in H2CO A~ 1A2 v4 = 1: Dipolar M-dependence with no single-collision elastic contribution  

Microsoft Academic Search

We have performed a series of measurements on H2CO A~ 1A2 v4 = 1 single rotational levels using Transient Gain Spectroscopy (TGS), which was designed to provide detailed information on state-to-state population transfer and on the relaxation and transfer of rotational alignment. Measurements of the time dependence of the population of the directly populated JKa,Kc = 10,1 level, and of

Stephen L. Coy; Scott D. Halle; James L. Kinsey; Robert W. Field

1992-01-01

227

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

NASA Astrophysics Data System (ADS)

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

Akinfiev, Nikolai; Zotov, Alexander

1999-07-01

228

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

SciTech Connect

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

Hattori, T.; Sakai, S.; Sakamoto, A.; Fujiwara, C. (Mitsubishi Heavy Industries, Ltd., Nagoya (Japan))

1994-10-01

229

Novel cooperative interactions and structural ordering in H2S-H2.  

PubMed

Hydrogen sulfide (H(2)S) and hydrogen (H(2)) crystallize into a 'guest-host' structure at 3.5 GPa and, at the initial formation pressure, the rotationally disordered component molecules exhibit weak van der Waals-type interactions. With increasing pressure, hydrogen bonding develops and strengthens between neighboring H(2)S molecules, reflected in a pronounced drop in S-H vibrational stretching frequency and also observed in first-principles calculations. At 17 GPa, an ordering process occurs where H(2)S molecules orient themselves to maximize hydrogen bonding and H(2) molecules simultaneously occupy a chemically distinct lattice site. Intermolecular forces in the H(2)S+H(2) system may be tuned with pressure from the weak hydrogen-bonding limit to the ordered hydrogen-bonding regime, resulting in a novel clathrate structure stabilized by cooperative interactions. PMID:22243091

Strobel, Timothy A; Ganesh, P; Somayazulu, Maddury; Kent, P R C; Hemley, Russell J

2011-12-16

230

Novel Cooperative Interactions and Structural Ordering in H2S-H2  

NASA Astrophysics Data System (ADS)

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

Strobel, Timothy A.; Ganesh, P.; Somayazulu, Maddury; Kent, P. R. C.; Hemley, Russell J.

2011-12-01

231

Pressure broadening and shift coefficients for H2, He and N2 in the 3?2 band of 12CH3D retrieved by a multispectrum fitting technique.  

NASA Astrophysics Data System (ADS)

Improved determinations of CH3D abundances, as well as of the deuterium to hydrogen ratio (D/H) in the atmospheric methane of Saturn, Uranus, Neptune and Titan are reachable with a complete set of spectroscopic parameters for the 3?2 band of 12CH3D which take into account the dominant gases in these atmospheres (i.e. H2, He and N2). Line intensities and self-broadening coefficients derived from a previous analysis made by the authors for 255 lines in the region of the 3?2 band of 12CH3D at 1.55 ?m have been recently reported. In this paper the authors present 12CH3D line broadening coefficients and pressure-induced shifts by H2, He and N2. A set of Fourier transform spectra recorded at Kitt Peak National Observatory with pressures of 100, 250 and 500 Torr for H2 and N2, and 600 Torr for He, has been used for this study. Data reduction was performed using a non-linear least-squares fitting multispectrum program developed for this purpose. The broadening coefficients, averaged over K, range roughly between 0.0685 and 0.0569 cm-1atm-1 for 12CH3D-H2, between 0.0434 and 0.0335 cm-1atm-1 for 12CH3D-He, and between 0.0665 and 0.0533 cm-1atm-1 for 12CH3D-N2, up to a maximum J of 14. The uncertainties are estimated to about 1.5% in the H2 and N2 broadening cases, and 3% in the He case. The pressure shift coefficients averaged over both J and K are found to be -0.0067 cm-1atm-1 for 12CH3D-H2, +0.0021 cm-1atm-1 for 12CH3D-He, and -0.0119 cm-1atm-1 for 12CH3D-N2. The authors estimate an uncertainty in these average shift coefficients of 15% in the H2 and N2, broadening cases, and of 35% in the He case. Dependences in J and K for these parameters have also been investigated with empirical expressions.

Boussin, C.; Lutz, B. L.; Hamdounia, A.; de Bergh, C.

1999-09-01

232

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

NASA Astrophysics Data System (ADS)

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

Journaux, B.; Daniel, I.

2011-10-01

233

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

NASA Astrophysics Data System (ADS)

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

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

2006-12-01

234

The role of pH in the fermentative H2 production from an acidogenic granule-based reactor.  

PubMed

The role of pH in the fermentative H(2) production from an upflow acidogenic granule-based reactor was investigated in this study. Experimental results show that all H(2) partial pressure, H(2) production rate and H(2) yield were pH-dependent, in the range of 2.8 x 10(4)-5.2 x 10(4)Pa, 61-145 ml-H(2)l(-1)h(-1) and 0.68-1.61 mol-H(2)mol-glucose(-1), respectively. The maximum H(2) partial pressure was observed at pH 3.4, while both maximum H(2) production rate and H(2) yield were found at pH 4.2. Acetate, propionate, butyrate, i-butyrate, valerate, caporate and ethanol were present in the effluent of this UASB reactor, and their distribution was also pH-dependent. As pH was decreased from 4.2 to a lower level of 3.4 or increased to a higher level of 6.3, the fermentative type of this H(2)-producing reactor would shift from butyrate-type to caporate- or ethanol-type. Thermodynamic analysis was performed to explore the possible metabolic pathways of caproate and valerate formation. The metabolic pathway of caproate formation was pH-dependent, while that of valerate formation was pH-independent. A neural network model was designed, trained and validated. It was able to successfully describe the daily variations of H(2) partial pressure and H(2) yield of the reactor, and to predict its steady state performance at various pHs. PMID:16466779

Mu, Yang; Yu, Han-Qing; Wang, Yi

2006-02-08

235

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

236

The Study of the Hydrostatic Pressure Effect on the Thermodynamic Properties of the Rochelle Salt NaKC_4H_4O_6\\cdot4H_2O  

NASA Astrophysics Data System (ADS)

The effect of hydrostatic pressure on thermodynamic properties of Rs was theoretically considered within the framework of the Mitsui model adjusted by taking into account piezoelectric interaction with the shear strain eps_4. The approach, according to which theory model parameters are linearly dependent on hydrostatic pressure, was proposed for consideration. The calculations were carried out in molecular field approximation. Theoretical results for thermodynamic characteristics were compared to experimental data. Basing on theoretical study, the explanation for discrepancies in experimental data derived by different researchers for static dielectric permittivity of a free crystal was proposed. The increase of saturation polarization due to application of hydrostatic pressure is predicted.

Levitskii, R. R.; Moina, A. P.; Andrusyk, A. Ya.; Slivka, A. G.; Kedyulich, V. M.

237

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

NASA Astrophysics Data System (ADS)

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

Quirion, Diane M.; Jenkins, David M.

238

Equilibrium water partial pressures and salt solubilities in aqueous NHHSO to low temperatures  

Microsoft Academic Search

Acidic ammonium sulfate aerosols in the troposphere form cloud condensation nuclei, affect visibility, and are also an important component of urban aerosols. Equilibrium water partial pressures (pHO) above 3.69, 5.67, and 8.65 mol kg⁻¹ NHHSO{sub 4(aq)}, and 10.19 mol kg⁻¹ HSO{sub 4(aq)}, have been determined using a capacitance manometer over the temperature ranges 288.1--239.5 K and 298.1--238.5 K, respectively. Measured

Yan Yao; Mario Massucci; Simon L. Clegg; Peter Brimblecombe

1999-01-01

239

Combined effects of photosynthesis and calcification on the partial pressure of carbon dioxide in seawater  

Microsoft Academic Search

The effects of marine photosynthesis and calcification on the partial pressure of carbon dioxide in seawater (P\\u000a CO\\u000a 2) are examined in the light of recent studies and using original model calculations. The ratio of organic carbon to inorganic\\u000a carbon production (R\\u000a OI) determines whether an ecosystem is a net sink or source for atmospheric CO2. TheP\\u000a CO\\u000a 2 maintains

Atsushi Suzuki

1998-01-01

240

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

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

241

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

PubMed

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

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

2000-02-01

242

Oxygen partial pressure influenced structural and optical properties of DC magnetron sputtered ZrO2 films  

NASA Astrophysics Data System (ADS)

Thin films of zirconium oxide (ZrO2) were deposited on (100) p-silicon and quartz substrates by sputtering of metallic zirconium target under different oxygen partial pressures in the range 810-3-610-2Pa. 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 810-3-610-2Pa 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 810-3-610-2Pa respectively.

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

2013-02-01

243

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

244

Changes in respiration and ethylene production of apples in response to internal and external oxygen partial pressures  

Microsoft Academic Search

Variations in respiration rate and ethylene production of Cox's Orange Pippin and Granny Smith apples in response to reduced oxygen partial pressures were characterised by studying O2, CO2 and C2H4 partial pressure differences between the internal and external atmospheres (?pO2, ?pCO2 and ?pC2H4, Pa) of individual fruit maintained in different O2 atmospheres at 20 1C. ?pO2 decreased at low

Benjamin K. Dadzie; Nigel H. Banks; Donald J. Cleland; Errol W. Hewett

1996-01-01

245

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

Microsoft Academic Search

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

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

1992-01-01

246

Oxidizer partial pressure window for YBa2Cu3O7?x thin film formation by metalorganic chemical vapor deposition  

Microsoft Academic Search

We have conducted a systematic study of oxidizer partial pressure effects on both the superconducting transport properties and structural properties of YBa2Cu3O7?x (YBCO) films grown by conventional metalorganic chemical vapor deposition (MOCVD). Superconducting YBCO thin films were grown in partial N2O pressures ranging from 0.4 to 45 Torr and at substrate temperatures of 500 and 700 C. We have observed

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

1992-01-01

247

Agreement between values for arterial and end-tidal partial pressures of carbon dioxide in spontaneously breathing, critically ill dogs  

Microsoft Academic Search

Objective-To determine agreement between arterial partial pressures of carbon dioxide (Paco(2)) and end-tidal partial pressures of carbon dioxide (P-ETCO2) measured with a nasal catheter in spontaneously breathing, critically ill dogs. Design-Validation study. Animals-26 client-owned dogs admitted to an intensive care unit for various conditions. Procedures-Paco(2) was measured with a commercial blood gas analyzer, and P-ETCO2 was measured with a sidestream

Efrat Kelmer; Lindsey C. Scanson; Lydia C Love

2009-01-01

248

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

2013-07-31

249

Pressure-Dependent Melting Curve of Natural Carnallite, KMgCl3.6H2O, in a Closed System, Where Evaporation Is Prevented.  

National Technical Information Service (NTIS)

The evaporite mineral carnallite, KMgCl/sub 3/x6H/sub 2/O, melts incongruently at 167.5 deg. C under atmospheric pressure in a closed space, where evaporation is prevented. The incongruent melting results in a melt consisting of MgCl/sub 2/x6H/sub 2/Ox0.2...

J. Fabricius J. Rose-Hansen

1988-01-01

250

Calculation of the center shift of H 2 O absorption lines due to air pressure in the solution of atmospheric optics problems  

Microsoft Academic Search

The goal of the present work is the experimental study of the center shifts of the absorption lines of atmospheric H20, falling within the generation bands of ruby and neodymium lasers, with air pressure, and also the analysis of possible errors caused by not taking this phenomenon into account in estimates of the energetic losses during propagation, and analysis of

V. V. Zuev; Yu. N. Ponomarev; A. M. Solodov; B. A. Tikhomirov; T. V. Parfenova; O. A. Romanovskii

1986-01-01

251

Elasticity and Strength of CaSiO3 Perovskite and Phase D (MgSi2H2O6) at Lower Mantle Pressures  

NASA Astrophysics Data System (ADS)

Knowledge of the elastic tensor of deep earth materials is essential for understanding the radial and lateral variation of seismic velocities and seismic anisotropy. The yield strength is one of the most important but poorly understood mechanical properties of materials. Ca-perovskite is considered to be the third most abundant phase in the deep mantle, and its existence in natural samples has been inferred from CaSiO3 compositions in diamond inclusions (Joswig et al., 1999). Phase D is a possible reservoir for hydrogen in subducting slabs under lower mantle conditions (Shieh et al. 1998). Both phases contain silicon in 6-fold coordination. Here we report the first measurements of yield strength and elasticity of Ca-perovskite and phase D to lower mantle pressures using radial x-ray diffraction together with lattice strain theory. Ca-perovskite was synthesized in a diamond cell by laser heating, and phase D was synthesized in a multianvil apparatus. Samples were compressed non-hydrostatically in a diamond anvil cell while contained in a 100-? m hole of a Be gasket. Energy-dispersive x-ray diffraction data were collected at NSLS and APS. Our results indicate that the ratio of differential stress to shear modulus is 0.016(5)-0.039(4) for Ca-perovskite at pressure up to 61 GPa and 0.012(5)-0.020(3) for phase D at pressure up to 28 GPa. These values are similar to those found for stishovite, but generally lower than found for 4-coordinated silicates. The yield strength of Ca-perovskite increases from 3 GPa to 10 GPa over the pressure range from 19-61 GPa, whereas the strength of phase D increases from 1.5 to 3.1 GPa over the pressure range from 9-28 GPa. Systematic trends for 6-coordinated silicates allow us to predict the room-temperature strength of Mg-perovskite and the results are in good agreement with recent micro strain experiments (Weidner et al. 2001). The hydrostatic equation of state is inferred from measured lattice strains for both materials. Single-crystal elastic constants for Ca-perovskite are in agreement with theoretical calculations (Karki and Crain 1998) and indicate the elastic anisotropy decreases with pressure.

Shieh, S. R.; Duffy, T. S.; Shen, G.; Ohtani, E.

2002-05-01

252

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

253

The high pressure structures and the phase transitions of K2[Pt(CN)4]Br0.33H2O  

NASA Astrophysics Data System (ADS)

The lattice constants of KCP were determined by single crystla X-ray diffraction experiments up to 3 109Pa. The pressure dependence of the compressibilities is anomalous around 7 108Pa and 2 109Pa. The platinum chains are shortened abruptly at 7 108 Pa, where the compressibility perpendicular to the platinum chain is normal. The other anomaly around 2 109Pa was found in the compression along the direction perpendicular to the platinum chain. The crystal structure analyses showed that the pressure-induced displacement of a water molecule is coupled with the shortening of the Pt chains observed at 7 108Pa. The other anomaly at 2 109Pa is associated with the transformation of the molecular structure of the tetracyanoplatinate complex anions.

Kobayashi, H.; Kobayashi, A.; Asaumi, K.; Minomura, S.

1980-07-01

254

Laser-Induced fluorescence measurements and modeling of nitric oxide in premixed flames of CO+H 2+CH 4 and air at high pressures  

Microsoft Academic Search

Laser-induced fluorescence measurements of NO concentrations in flames of synthesized coal-gas having temperatures of 1535 to 1790 K were obtained at pressures of 1.0 to 11.9 atm. Specifically, quantitative measurements of [NO] as a function of equivalence ratio (0.71.3), fuel-CH4 (014.9%), flow rate and axial distance were obtained in the burnt gas of a series of flat, laminar, premixed low

B. L Chadwick; R. J. S Morrison; A Campisi; D. D Thomsen; N. M Laurendeau

2001-01-01

255

Development of Partial Pressure Gauge for Silane-Hydrogen Gas Mixtures Used for Production of Thin Film Silicon Solar Cell Materials  

NASA Astrophysics Data System (ADS)

A partial pressure gauge was developed with a quartz sensor to measure partial pressures of silane and hydrogen gases in gas mixtures, which are used as the sources of thin film silicon solar cells. The partial pressures were derived from the dependencies on viscosity and molecular weight of these mixtures, which can be measured using the quartz sensor. The partial pressure gauge developed based on this principle measured partial pressures of silane and hydrogen in gas mixtures for 133-1,333 Pa and 0, 20, 40, 60, 80, and 100vol.% silane with resolution of 0.01vol.% for gas mixtures including over 20% silane partial pressures, which are typical preparation conditions for thin film silicon solar cell materials. This pressure gauge can be used in practical application to measure the partial pressures of silane and hydrogen in mixtures.

Suzuki, Atsushi; Kurokawa, Akira; Nagai, Takehiko; Matsui, Takuya; Kondo, Michio

256

Low-energy BO and BO2 emission from H2BO3 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 H3BO3, MgO, Al2O3, TiO2, Y2O3 and ZrO2, show energy distributions being more or less typical for collision cascades in the cases of the metal ions M+, of O+ at energies >5eV 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 BO2+ exhibit a similar shape as the Ar+ plasma gas ions. From this, and from the background of the low decomposition and melting temperatures of H3BO3 and B2O3, respectively, we conclude that the detected BO and BO2 molecules have been emitted with thermal energies in processes implying lower energies than collision cascades. Evidence was found that the same holds for HBO2 and H2BO2. 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)BOx 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; Tao, Lee Mu

1999-07-01

257

Computation of partial vapor pressures of aqueous volatile organic compound solutions. Final report, July 1993December 1995  

Microsoft Academic Search

A program is described for the evaluation of the partial vapor pressures of solution components dependent on the concentration in solution, total pressure, and temperature. The object of the program is to provide reliable values that represent the best estimate based on the large body of experimental data available in the literature. The basis of the estimate is the evaluation

P. E. Field; R. J. Combs; R. B. Knapp

1996-01-01

258

Effect of oxygen partial pressure during sintering on the microstructure of Mg-PSZ with strontia and silica additions  

SciTech Connect

The microstructure, average grain size, and density of Mg-PSZ sintered with SrO and SiO[sub 2] additions are found to depend on the partial pressure of oxygen in the sintering atmosphere. Over the range of 10[sup [minus]12] to 10[sup 0] atm, both the average grain size and density increase with oxygen partial pressure, for a constant SrO/SiO[sub 2] ratio. The partial pressure of oxygen also affects the microstructural distribution of the remnant liquid phase. At high partial pressures the liquid phase is uniformly distributed, whereas at lower oxygen pressures it is preferentially located near the surface. It is proposed that the microstructure produced by sintering is the result of a competition between liquid-phase-enhanced densification and the migration of the liquid phase to the free surface. The migration is attributed to vaporization of MgO from the liquid phase which increases with decreasing partial pressure of oxygen.

Drennan, J.; Hannink, R.H.J. (CSIRO, Clayton (Australia). Div. of Materials Science and Technology); Clarke, D.R. (Univ. of California, Santa Barbara, CA (United States). Materials Dept.); Shaw, T.M. (IBM Research Div., Yorktown Heights, NY (United States))

1994-08-01

259

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

260

High temperature electrical conduction in nanoscale hafnia films under varying oxygen partial pressure  

NASA Astrophysics Data System (ADS)

Point defect equilibration in nanocrystalline hafnium oxide thin films in the monoclinic (m-HfO2) phase was studied by electrochemical measurements performed under varying temperature and oxygen partial pressure (PO2) on films of 35-63 nm thickness on single crystal MgO and Al2O3 substrates. The conductance varied as (PO2)n, where n is the in the range ~+1/11 to ~+1/14, at high PO2. The increasing conductance with PO2 suggests that the electronic conduction in the HfO2 films is p-type and oxygen interstitials or hafnium vacancies, rather than oxygen vacancies, could be dominant charged point defects in nanocrystalline, undoped m-HfO2 films.

Ko, Changhyun; Shandalov, Michael; McIntyre, Paul C.; Ramanathan, Shriram

2010-08-01

261

Partial pressures of PCB-11 in air from several Great Lakes sites.  

PubMed

Relatively high concentrations of 3,3'-dichlorobiphenyl (PCB-11) have been reported in water and air, and it has been suggested that this compound did not come from commercial PCB products. We report here data on atmospheric partial pressures of PCB-11 and of total PCBs at five sites around the Great Lakes and demonstrate that both total PCBs and PCB-11 track human population density. In addition, we show that with the exception of Chicago, the PCB congener pattern at our sampling sites is best represented by Aroclor 1242; in Chicago, the pattern is best represented by a 1:1 mixture of Aroclors 1242 and 1254. With the possible exception of Sturgeon Point New York, the levels of PCB-11 in air have not changed between January 2004 and December 2007. The source of PCB-11 may be related to yellow pigments, to the degradation of more highly chlorinated PCB congeners, or to both. PMID:19764206

Basu, Ilora; Arnold, Karen A; Venier, Marta; Hites, Ronald A

2009-09-01

262

H2FC: Materials  

NSDL National Science Digital Library

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

1999-01-01

263

Differential haemoglobin gene expression in the crustacean Daphnia magna exposed to different oxygen partial pressures.  

PubMed

The quantity and quality of the haemoglobin (Hb) of Daphnia magna is related to oxygen partial pressure in the water. Both the dynamics of hypoxia-induced Hb gene transcription, as well as Hb properties in animals incubated long-term at hyperoxia, normoxia and hypoxia, were investigated. Examination of Hb gene (dhb1-dhb3) transcription showed the expression of dhb2 and especially dhb3 to increase markedly approximately one hour after the onset of hypoxia, whereas dhb1 was expressed more or less constitutively. At an incubation close to anoxia, an onset of dhb3 transcription was found already after two minutes. In long-term incubated animals, concentration and oxygen affinity of Hb were lower at higher oxygen partial pressures. With decreasing oxygen availability, the subunit composition of Hb macromolecules changed. The share of the dhb2-encoded subunit, DHbF, increased already during moderate hypoxia. The increase of dhb3 mRNA (encoding DHbC) may be related to a transient increase of DHbC in the first days of hypoxia and/or to an additional coding of dhb3 for DHbD. The rise of DHbD, and particularly DHbA, only at severe hypoxia coincided with the increase of Hb oxygen affinity. The dhb1-encoded subunits DHbB and DHbE showed either a relatively moderate increase or even a decrease in concentration at hypoxia. In small animals with restricted homeostasis capabilities such as Daphnia, adaptation of the protein equipment seems to be a more effective strategy than allosteric modulator control. PMID:12974382

Zeis, Bettina; Becher, Bertram; Goldmann, Torsten; Clark, Ryan; Vollmer, Ekkehard; Blke, Birgit; Bredebusch, Ilona; Lamkemeyer, Tobias; Pinkhaus, Olaf; Pirow, Ralph; Paul, Rdiger J

2003-08-01

264

Uptake of gas-phase nitric acid to ice at low partial pressures: evidence for unsaturated surface coverage.  

PubMed

The adsorption of gas-phase nitric acid onto water-ice surfaces at temperatures between 200 and 239 K has been studied over short time scales using a coated-wall flow tube coupled to a chemical ionization mass spectrometer. The nitric acid partial pressures used were between 10(-8) hPa and 10(-6) hPa, making this the first systematic study under partial pressure conditions present in the upper troposphere. Whereas previous findings using this technique have shown that the surface coverages are saturated at 2 to 3 x 10(14) molecules cm(-2) (referenced to the geometric surface area of the ice film) when partial pressures are larger than about 10(-7) hPa, the principal finding from this study is that the surface coverages are in the unsaturated regime at lower partial pressures. A conventional Langmuir adsorption isotherm describes the uptake in a quantitative manner while dissociative Langmuir isotherms that have been used in the past to model this process do not. The unsaturated surface coverages are strongly temperature dependent, in agreement with a number of field measurements of the nitric acid (or NOy) component of cirrus cloud particles. These laboratory results match those in the field better than do those measured at significantly higher partial pressures but, nevertheless, they still indicate somewhat greater uptake, particularly at higher temperatures. PMID:16161786

Ullerstam, Maria; Thornberry, Troy; Abbatt, Jonathan P D

2005-01-01

265

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

USGS Publications Warehouse

We describe an instrument prototype that measures dissolved carbon dioxide (DC) without need for standard wetted probe membranes or titration. DC is calculated using Henry's Law, water temperature, and the steady-state partial pressure of carbon dioxide that develops within the instrument's vertical gas-liquid contacting chamber. Gas-phase partial pressures were determined with either an infrared detector (ID) or by measuring voltage developed by a pH electrode immersed in an isolated sodium carbonate solution (SC) sparged with recirculated head space gas. Calculated DC concentrations were compared with those obtained by titration over a range of DC (2, 4, 8, 12, 16, 20, 24, and 28mg/l), total alkalinity (35, 120, and 250mg/l as CaCO3), total dissolved gas pressure (-178 to 120 mmHg), and dissolved oxygen concentrations (7, 14, and 18 mg/l). Statistically significant (P < 0.001) correlations were established between head space (ID) and titrimetrically determined DC concentrations (R2 = 0.987-0.999, N = 96). Millivolt and titrimetric values from the SC solution tests were also correlated (P < 0.001, R 2 = 0.997, N = 16). The absolute and relative error associated with the use of the ID and SC solution averaged 0.9mg/l DC and 7.0% and 0.6 mg/l DC and 9.6%, respectively. The precision of DC estimates established in a second test series was good; coefficients of variation (100(SD/mean)) for the head space (ID) and titration analyses were 0.99% and 1.7%. Precision of the SC solution method was 1.3%. In a third test series, a single ID was coupled with four replicate head space units so as to permit sequential monitoring (15 min intervals) of a common water source. Here, appropriate gas samples were secured using a series of solenoid valves (1.6 mm bore) activated by a time-based controller. This system configuration reduced the capital cost per sample site from US$ 2695 to 876. Absolute error averaged 2.9, 3.1, 3.7, and 2.7 mg/ l for replicates 1-4 (N = 36) during a 21-day test period (DC range, 36-40 mg/l). The ID meter was then modified so as to provide for DO as well as DC measurements across components of an intensive fish production system. ?? 2003 Elsevier B.V. All rights reserved.

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

2004-01-01

266

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; Ojame, Lars

2009-10-01

267

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

268

LIF MEASUREMENTS AND CHEMICAL KINETIC ANALYSIS OF NITRIC OXIDE FORMATION IN HIGH-PRESSURE COUNTERFLOW PARTIALLY PREMIXED AND NONPREMIXED FLAMES  

Microsoft Academic Search

We report quantitative, spatially resolved, linear laser-induced fluorescence (LIF) measurements of nitric oxide concentration ([NO]) in laminar, methane\\/air counterflow partially premixed and nonpremixed flames at six pressures up to 15?atm using excitation near 226.03?nm in the ?(0,0) band of NO. For partially premixed flames, fuel-side equivalence ratios (?B) of 1.45, 1.6, and 2.0 are studied at a global strain rate

SAMEER V. NAIK; NORMAND M. LAURENDEAU

2004-01-01

269

Effect of Oxygen Partial Pressure on the Cyclic Oxidation Behavior of Mo76Si14B10  

NASA Astrophysics Data System (ADS)

Hot-pressed and arc-melted Mo76Si14B10 (at. pct) exhibits ?-Mo solid solution, Mo3Si, and Mo5SiB2 in microstructures with varying morphologies. Cyclic oxidation tests performed at oxygen partial pressures of 0.21 and 1 atm show the mass loss of the hot-pressed alloy to be ?1.5 and ?4 times less, respectively, than that of the arc-melted alloy. The thickness of the protective silicate layer increases with an increase of both Moss grain size and oxygen partial pressure in the environment.

Roy, Barna; Khushboo; Das, Jayanta; Mitra, Rahul; Roy, Sanat Kumar

2013-07-01

270

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

271

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

ERIC Educational Resources Information Center

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

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

2005-01-01

272

Antioxidant and Prooxidant Role of ?-Carotene in Murine Normal and Tumor Thymocytes: Effects of Oxygen Partial Pressure  

Microsoft Academic Search

The effects of the partial pressure of oxygen (pO2) on antioxidant efficiency of ?-carotene in inhibiting radical-initiated lipid peroxidation were studied in murine normal and tumor thymocytes. At 150 mm Hg pO2 (the pressure of oxygen in normal air), ?-carotene acted as an antioxidant, inhibiting radical-induced lipid peroxidation in both normal and tumor thymocytes. At 760 mm Hg pO2, ?-carotene

Paola Palozza; Chiara Luberto; Gabriella Calviello; Paola Ricci; Gianna Maria Bartoli

1997-01-01

273

Acute mountain sickness relates to sea-level partial pressure of oxygen.  

PubMed

The aim of this study was to clarify the relationships between acute mountain sickness (AMS), studied during an expedition in the Andes, and some physiological parameters determined before the expedition, i.e. biometrical characteristics of the subjects [maximal oxygen consumption (VO2max), body fat content, body mass index], functional pulmonary tests (forced vital capacity, forced expiratory volume at the first second), ventilatory or cardiac responses measured at 4,500 m [hypoxic ventilatory responses (HVR) 4,500 and hypoxic cardiac responses (HCR) 4,500, respectively), cold pressor responses. To achieve this objective, 11 subjects were firstly submitted to a hypobaric pokilocapnic hypoxic test (589 hPa, 4,500 m) at rest and during exercise to study minute volume, respiratory frequency, end tidal partial pressure of O2 (PETO2) and CO2, HVR 4,500, HCR 4,500 and to a cold pressor test of the hand (5 min in 5 degrees C cold water) to study heart rate, blood pressure and skin temperature changes. The AMS was assessed daily by questionnaire during a 12-day expedition in the Andes following both Hackett's method and Environmental Symptoms Questionnaire (modified ESQ II). Maximal AMS-Hackett score, maximal AMS-ESQ score and mean AMS-ESQ score were defined. The quantifications of AMS following the two methods were correlated. No significant relationships were observed between mean AMS-ESQ score and the biometrical characteristics of the subjects, the functional pulmonary tests, HVR 4,500, HCR 4,500 or the cold pressor responses. However, it appeared that the mean AMS-ESQ score was correlated with PETO2 measured at rest and during exercise (50% VO2max) both in hypoxia and normoxia. A closer linear relationship was observed during the exercise in normoxia (r = -0.92, P < 0.0001). These results could suggest that AMS was related to a relative alveolar hypoventilation more in relation to breathing pattern than HVR. PMID:7556117

Savourey, G; Moirant, C; Eterradossi, J; Bittel, J

1995-01-01

274

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

275

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

276

Dynamics of entangled H(2p) pair generated in the photodissociation of H2  

NASA Astrophysics Data System (ADS)

We have measured the coincidence time spectra of two Lyman-? photons emitted by a pair of H(2p) atoms in the photodissociation of H2 at the incident photon energy of 33.66 eV and at the hydrogen gas pressures of 0.40 Pa and 0.02 Pa, from which the angular distributions of two Lyman-? photons have been obtained. The experimental angular distributions indicate the generation of the entangled pair of H(2p) atoms as predicted by the theory of our group (Miyagi et al 2007 J. Phys. B 40 617) and the role of a new kind of reaction, i.e. the reaction of the entangled pair of H(2p) atoms with an H2 molecule that efficiently changes the entanglement. It has turned out that more entangled pairs of H(2p) atoms survive at 0.02 Pa than at 0.40 Pa. The decay time constant in the coincidence time spectrum at 0.02 Pa is approximately half the lifetime of a single H(2p) atom, 1.60 ns, while the decay time constant at 0.40 Pa is in agreement with the lifetime of a single H(2p) atom. It follows that the decay faster than the lifetime of a single H(2p) atom originates from the entanglement in the pair of H(2p) atoms.

Odagiri, Takeshi; Tanabe, Takehiko; Kouchi, Noriyuki

2012-11-01

277

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

2013-07-01

278

The concentration, behavior and storage of H 2O in the suboceanic upper mantle: Implications for mantle metasomatism  

NASA Astrophysics Data System (ADS)

Mid-ocean ridge basalt glasses from the Pacific-Nazca Ridge and the northern Juan de Fuca Ridge were analyzed for H 2O by gas chromatography. Incompatible element enriched (IEE) glasses have higher H 2O contents than depleted (IED) glasses. H 2O increases systematically with decreasing Mg/Mg + Fe 2+ within each group. Near-primary IED MORBs have an average of about 800 ppm H 2O, while near-primary IEE MORBs (with chondrite normalized Nb/ Zr or La/ Sm ?2) have about 2100 ppm H 2O. If these basalts formed by 10-20% partial melting then the IED mantle source had 100-180 ppm H 2O, while the IEE source had 250-450 ppm H 2O. The ratio H 2O/(Ce + Nd) is fairly constant at 95 30 for all oceanic basalts from the Pacific. During trace element fractionation in the suboceanic upper mantle, H 2O behaves more compatibly than K, Rb, Nb, and Cl, but less compatibly than Sm, Zr and Ti. H 2O is contained mostly in amphibole in the shallow upper mantle. At pressures greater than the amphibole stability limit, it is likely that a significant proportion of H 2O is contained in a mantle phase which is more refractory than phlogopite at these pressures. The role of H 2O in mantle enrichment processes is examined by assuming that an enriched component was added. The modelled concentrations of K, Na, Ti and incompatible trace elements in this component are high relative to H 2O, indicating that suboceanic mantle enrichment is caused by silicate melts such as basanites and not by aqueous fluids.

Michael, Peter J.

1988-02-01

279

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

NASA Astrophysics Data System (ADS)

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

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

1999-12-01

280

Impedance analysis for oxygen reduction in lithium carbonate melt: Effect of partial pressure of oxygen  

SciTech Connect

Effects of partial pressure of oxygen and temperature on oxygen reduction kinetics on a submerged gold electrode in lithium carbonate melt were investigated using cyclic voltammetry and impedance analysis. Cyclic voltammetry measurements indicated that the oxygen reduction reaction in Li{sub 2}CO{sub 3} melt is reversible up to 200 mV/s. The impedance analysis was carried out using a Complex Nonlinear Least Square (CNLS) paxameter estimation program based on the Randles-Ershler equivalent circlet. This analysis technique was used to estimate the electrode kinetics and the mass transfer related parameters such as the charge transfer resistance (R{sub ct}) and the Warburg coefficient {sigma}. The mass transfer related parameters obtained from cyclic voltammetry and impedance analysis were in good agreement. The reaction orders for oxygen at 800{degrees}C were calculated to be 0.38 for the exchange current density and 0.5 for the product D{sub o}{sup {1/2}}C{sub o}*; these values are consistent with the mechanism proposed in the literature for oxygen reduction in Li{sub 2}CO{sub 3} melt on a submerged gold electrode.

Dave, B.B.; White, R.E.; Srinivasan, S.; Appleby, A.J.

1989-12-31

281

Impedance analysis for oxygen reduction in lithium carbonate melt: Effect of partial pressure of oxygen  

SciTech Connect

Effects of partial pressure of oxygen and temperature on oxygen reduction kinetics on a submerged gold electrode in lithium carbonate melt were investigated using cyclic voltammetry and impedance analysis. Cyclic voltammetry measurements indicated that the oxygen reduction reaction in Li{sub 2}CO{sub 3} melt is reversible up to 200 mV/s. The impedance analysis was carried out using a Complex Nonlinear Least Square (CNLS) paxameter estimation program based on the Randles-Ershler equivalent circlet. This analysis technique was used to estimate the electrode kinetics and the mass transfer related parameters such as the charge transfer resistance (R{sub ct}) and the Warburg coefficient {sigma}. The mass transfer related parameters obtained from cyclic voltammetry and impedance analysis were in good agreement. The reaction orders for oxygen at 800{degrees}C were calculated to be 0.38 for the exchange current density and 0.5 for the product D{sub o}{sup {1/2}}C{sub o}*; these values are consistent with the mechanism proposed in the literature for oxygen reduction in Li{sub 2}CO{sub 3} melt on a submerged gold electrode.

Dave, B.B.; White, R.E.; Srinivasan, S.; Appleby, A.J.

1989-01-01

282

Effect of oxygen partial pressure on the superconductivity of Bi-2212 wires during post-annealing  

NASA Astrophysics Data System (ADS)

Bi2Sr2CaCu2O8+? (Bi-2212) silver sheathed round wire is a promising and practical material for high field superconducting insert magnet in the range of 25-30 T. The effect of oxygen content of Bi-2212 on the critical current density (Jc) of multi-filamentary Bi-2212/Ag wires has been investigated. During the Bi-2212 wire fabrication, partial melting and solidification process was employed. Short samples which were cut from the same wire were annealed at 500 C in various atmospheres for post-annealing. The morphology, lattice parameters and oxygen contents were characterized by SEM, XRD and a thermal gravimetric analyzer (TGA). The critical current (Ic) and the superconducting transition temperature (Tc) were measured by a four-probe method. Lower O2 pressure can break the Bi-O chains, reduce the oxygen contents and change the lattice structure of Bi-2212 from tetragonal into orthorhombic. The Tc values of samples increase from 81.6 K to 91 K and the highest Jc of samples after post-annealing is almost three times higher than that of the initial sample.

Hao, Q. B.; Li, C. S.; Zhang, S. N.; Feng, J. Q.; Du, M. H.

2011-11-01

283

Crystallographic texture control of sputtered HfN thin films using low oxygen partial pressures  

SciTech Connect

The authors studied the development of crystallographic texture in hafnium nitride (HfN) films deposited by off-normal incidence reactive magnetron sputtering at room temperature. Films are prepared with and without added oxygen in N{sub 2}/Ar mixtures. Texture measurements were performed by x-ray pole figure analysis of the (111) and (200) diffraction peaks. The authors found that HfN deposited at 40 deg. without added oxygen has a strong <100> fiber texture with no in-plane alignments showing the dominance of thermodynamic effects in the course of texture evolution. Oxygen is deliberately introduced into the sputtering gas ambient to study its effects on microstructure formation. As the oxygen partial pressure (O{sub 2} pp) is increased in the range of 1.33x10{sup -5} to 1.33x10{sup -4} Pa, HfN out-of-plane orientation changed to <111> with a substantial in-plane alignment in <100> direction as well. In this case, texture analysis of each individual diffraction peak revealed the existence of two populations of grains indicating a competition between (111) and (200) planes. A transition towards hafnium oxynitride phases occurred at high O{sub 2} pp's. The authors propose that oxygen presence during deposition reduces the adatom surface mobility, which enables kinetic effects to govern the texture formation and thus leads to a biaxial alignment in HfN films.

Deniz, D.; Harper, J. M. E. [Department of Physics, University of New Hampshire, Durham, New Hampshire 03824 (United States)

2009-01-15

284

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

285

Solubility of gases in butanols. I. Solubilities of nonpolar gases in 1-butanol from 263.15 to 303.15 K at 101.33 kPa partial pressure of gas  

Microsoft Academic Search

Solubility measurements of 15 nonpolar gases (He, Ne, Ar, Kr, Xe, H2, D2, N2, O2, CH4, C2H4, C2H6, CF4, SF6 and CO2) in 1-butanol were carried out at 263.15, 273.15, 283.15, 293.15, and 303.15 K and partial pressure of gas of 101.33 kPa. Standard changes in thermodynamic functions for the solution process at 298.15 K (Gibbs energy, enthalpy and entropy)

J Pardo; M. C Lpez; J Santaf; F. M Royo; J. S Urieta

1995-01-01

286

Ferredoxin- and Nicotinamide Adenine Dinucleotide-Dependent H2 Production from Ethanol and Formate in Extracts of S Organism Isolated from "Methanobacillus omelianskii"1  

PubMed Central

S organism ferments ethanol to acetate and H2 but grows poorly on ethanol unless the partial pressure of H2 is kept low, as when it is grown in combination with an H2-utilizing methanogenic bacterium. The present study shows that S organism contains an alcohol dehydrogenase and a formate dehydrogenase, both of which require nicotinamide adenine dinucleotide (NAD) for activity. Hydrogen is evolved from NADH generated by these activities via a ferredoxin-dependent oxidation of NADH to NAD and H2. NADH:NADP oxido-reductase activity was also demonstrated. The relationship of these activities to the growth of S organism is discussed.

Reddy, C. Adinarayana; Bryant, M. P.; Wolin, M. J.

1972-01-01

287

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

288

Relationship between end-tidal and arterial carbon dioxide partial pressure using a cuffed oropharyngeal airway and a tracheal tube  

Microsoft Academic Search

CO a carbon dioxide partial pressures during general anaesthesia using either a cuffed oropharyngeal airway (COPA) or a tracheal tube (TT) in spontaneously breathing adult patients. After induction of anaesthesia, a COPA was inserted in 20 patients who were allowed to breathe spontaneously. When steady state was reached, ' and P 2 CO a were recorded. The COPA was removed,

Y. NAKATA; T. GOTO; S. UEZONO; F. SASAKI; S. MORITA

1998-01-01

289

An assessment of excess carbon dioxide partial pressures in natural waters based on pH and alkalinity measurements  

Microsoft Academic Search

Methods of estimating excess partial pressures of carbon dioxide in river waters using pH and Gran alkalinity measurements are considered using data from several UK lowland rivers covering a spectrum of industrial, urban and agricultural catchments. Two simple equations are shown to be eminently suitable except for the most demanding accuracies at pH values greater than 9 when carbonate and

Colin Neal; W. Alan House; Kevin Down

1998-01-01

290

CO2 Partial Pressure and the Enthalpy and Thermodynamic Efficiency of the Oxidation of Nitrite by Nitrobacter.  

National Technical Information Service (NTIS)

The heat of reaction of the oxidation of nitrate by NITROBACTER was determined at different partial pressures of CO2. Its value decreases from the theoretical value of -24.6 keal x 1/mole to -18.5 keal.1/mole, and levels at this value, as pCO2 is increase...

L. A. Kiesow J. B. Shelton J. W. Bless

1972-01-01

291

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

292

Experimental investigation on thermochemical sulfate reduction by H 2S initiation  

NASA Astrophysics Data System (ADS)

Hydrogen sulfide (H 2S) 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 CaSO 4 in the presence of variable H 2S 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 H 2S occurred under acidic conditions (at pH 3-3.5). However, sulfate reduction at pH 5.0 was undetectable even at high initial H 2S concentrations. To investigate whether the reaction of H 2S (aq) and HSO4- occurs at pH 3, an additional series of isothermal hydrous pyrolysis experiments was conducted with CaSO 4 and variable H 2S partial pressures in the absence of HC at the same experimental temperature and pressure conditions. CaSO 4 reduction was not measurable in the absence of paraffin even with high H 2S pressure and acidic conditions. These experimental observations indicate that the formation of organosulfur intermediates from H 2S reacting with hydrocarbons may play a significant role in sulfate reduction under our experimental conditions rather than the formation of elemental sulfur from H 2S 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 H 2S 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 H 2S pressure. Thus, we propose that the LSC produced from H 2S reaction with HC are most likely the reactive intermediates for H 2S 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.

Zhang, Tongwei; Amrani, Alon; Ellis, Geoffrey S.; Ma, Qisheng; Tang, Yongchun

2008-07-01

293

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

294

Equilibrium relationships in the uranium-tungsten-oxygen system in oxygen partial pressures from 0. 01 to 1 atm  

SciTech Connect

Equilibrium relationships in the uranium-tungsten-oxygen system have been established as a function of temperature at different oxygen pressures. Isobaric sections in air and oxygen and oxygen partial pressures of 0.01 and 0.07 were constructed, using the thermobalance. Mixtures of U3O8 and WO3 pick up weight in air, forming UWO6, which exists over a wide range of compositions taking both uranium oxides and WO3 in solid solution. The compound WO3 takes a limited amount of uranium oxide in solid solution and U3O8 also dissolves a limited amount of WO3 The miscibility gap between the solid solutions of UWO/sub 6-x/ and U3O/sub 8-y/ on the one hand and the solid solutions of UWO/sub 6-x/ and WO/sub 3-z/ on the other hand decreases by decreasing oxygen partial pressure and/or by increasing temperature. Each group of compatible solutions finally merges into a single phase deficient in oxygen. The two single phases exist over a wide range of compositions and melt over ranges of temperatures depending on the initial composition. Above a critical oxygen partial pressure (between 0.01 and 0.07 atm), solid solutions of UWO/sub 6-x/ and U3O/sub 8-y/, as well as solid solutions of UWO/sub 6-x/ and WO/sub 3-z/, melt partially with isothermal oxygen loss. Increasing the oxygen partial pressure increases the melting temperatures and produces eutectic liquids richer in oxygen.

Gadalla, A.M.; Mansour, N.A.L.

1985-07-01

295

Rate coefficients for the gas-phase reaction of OH radicals with dimethyl sulfide: temperature and O2 partial pressure dependence.  

PubMed

Rate coefficients for the gas-phase reaction of hydroxyl (OH) radicals with dimethyl sulfide (CH(3)SCH(3), DMS) have been determined using a relative rate technique. The experiments were performed under different conditions of temperature (250-299 K) and O(2) partial pressure (approximately 0 Torr O(2)-380 Torr O(2)), at a total pressure of 760 Torr bath gas (N(2) + O(2)), in a 336 l reaction chamber, using long path in situ Fourier transform (FTIR) absorption spectroscopy to monitor the disappearance rates of DMS and the reference compounds (ethene, propene and 2-methylpropene). OH was produced by the photolysis of H(2)O(2). The following Arrhenius expressions adequately describe the rate coefficients as a function of temperature (units are cm(3) molecule(-1) s(-1)): k = (1.56 +/- 0.20) x 10(-12) exp[(369 +/- 27)/T], for approximately 0 Torr O(2); (1.31 +/- 0.08) x 10(-14) exp[(1910 +/- 69)/T], for 155 Torr O(2); (5.18 +/- 0.71) x 10(-14) exp[(1587 +/- 24)/T], for 380 Torr O(2). The results are compared with previous investigations. PMID:16482313

Albu, Mihaela; Barnes, Ian; Becker, Karl H; Patroescu-Klotz, Iulia; Mocanu, Raluca; Benter, Thorsten

2005-11-23

296

[Derivation of the working equations of a CO2-CO-H2O-H2-N2 gas mixture for the cathode space of an electrolyzer with solid electrolyte taking into account its oxygen extraction].  

PubMed

Equations of thermodynamic equilibrium of the gas mixture CO2-CO--H2O-H2--N2 for the cathode space of the electrolyzer containing a solid electrolyte with extracted oxygen taken into consideration were derived. Equilibrium partial gas pressures, thermal effect of reactions, theoretical voltage of dissociation (the system of equations included 11 unknown parameters) were determined. These parameters are functions of temperature, total pressure of the gas mixture, initial gas composition, and the coefficient characterizing the degree of oxygen transfer from the cathode cell to the anode cell of the electrolyzer. PMID:2879964

Grishaenkov, B G; Vasil'ev, V K; Zorina, N G; Zhukov, A K

297

New method for H(2)S removal in acid solutions.  

PubMed

Several different technologies are available for H(2)S removal from the gas stream of medium capacity. Among them, the most widely used is Locat with more than 120 plants worldwide. In the last decade, many new processes, such as Sulfatreat-DO, Crystasulf, Caltech, and UCSR, were proposed to overcome the drawbacks of the state-of-the-art processes (low sulfur purity, chemical degradation, thiosulfate formation). We have developed a new H(2)S conversion method based on acid ferric nitrate solution, co-catalyzed by a heteropolyacid. H(2)S was converted to pure sulfur (>99.9 %), with no traces of organic compounds. Due to the acid pH of the solution, no chelant or surfactant was needed and iron content in the solution could reach very high levels. Keggin heteropolyacid (H(6)PW(9)V(3)O(40)) catalyzed the reoxidation of reduced ferrous solution with air at mild temperature and at very high reaction rate. The undesired side reaction (NO(x) formation) could be avoided by simply increasing the oxygen partial pressure. PMID:20564280

de Angelis, Alberto; Bellussi, Giuseppe; Pollesel, Paolo; Perego, Carlo

2010-07-19

298

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

NASA Astrophysics Data System (ADS)

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

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

1996-11-01

299

Reliability and accuracy of total and partial pressure measurements in the uhv pressure range under real experimental conditions  

Microsoft Academic Search

Comparative tests of Bayerd-Alpert and inverted magnetron gauges from diverse manufacturers were carried out in the laboratory. Commercial residual gas analysers from four different producers were tested to determine (i) linearity, stability and sensitivity of output signals on the pressure response ; (ii) high-pressure performance ; (iii) hysteresis ; (iv) fragment ion and electron stimulated desorption (ESD) peaks ; (v)

J Miertusova

1998-01-01

300

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

SciTech Connect

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

Zhu Di [Display R and D center, School of Electronic Science and Engineering, Southeast University, Nanjing (China); Graduate School of Advanced Science of Matter, Hiroshima University, Higashi-Hiroshima, Hiroshima (Japan); Zhang Xiong [Display R and D center, School of Electronic Science and Engineering, Southeast University, Nanjing (China); Kajiyama, Hiroshi [Graduate School of Advanced Science of Matter, Hiroshima University, Higashi-Hiroshima, Hiroshima (Japan)

2012-08-01

301

Acid gases partial pressures above a 50 wt% aqueous methyldiethanolamine solution: Experimental work and modeling  

Microsoft Academic Search

Aqueous amine solutions are widely used in the industry for acid gas removal. In order to treat natural gas or refinery process streams, an accurate knowledge of solubility data of carbon dioxide, hydrogen sulfide and other sulfur species in aqueous amine solutions is required. In this paper, new equilibrium measurements on 50wt% aqueous methyldiethanolamine solution with CO2 and H2S have

Moussa Dicko; Christophe Coquelet; Carmen Jarne; Scott Northrop; Dominique Richon

2010-01-01

302

An experimental study of phase equilibria in the systems H2OCO2CaCl2 and H2OCO2NaCl at high pressures and temperatures (500800C, 0.50.9GPa): geological and geophysical applications  

Microsoft Academic Search

Phase equilibria in the ternary systems H 2OCO 2NaCl and H 2OCO 2CaCl 2 have been determined from the study of synthetic fluid inclusions in quartz at 500 and 800C, 0.5 and 0.9GPa. The crystallographic control on rates of quartz overgrowth on synthetic quartz crystals was exploited to prevent trapping of fluid inclusions prior to attainment of run conditions. Two

Kirill I. Shmulovich; Colin M. Graham

2004-01-01

303

Carbon dioxide partial pressure and carbon fluxes of air-water interface in Taihu Lake, China  

NASA Astrophysics Data System (ADS)

To obtain carbon dioxide (CO2) flux between water-air interface of Taihu lake, monthly water samplers at 14 sites and the local meteorological data of the lake were collected and analyzed in 1998. Carbon dioxide partial pressures (pCO2) at air-water interface in the lake were calculated using alkalinity, pH, ionic strength, active coefficient, and water temperature. The carbon fluxes at different sublakes and areas were estimated by concentration gradient between water and air in consideration of Schmidt numbers of 600 and daily mean windspeed at 10 m above water surface. The results indicated that the mean values of pCO2 in Wuli Lake, Meiliang Bay, hydrophyte area, west littoral zone, riverine mouths, and the open lake areas were 1 807.81 071.4 (meanstandard deviation) ?atm (1atm=1.013 25105Pa), 416.3217.0 ?atm, 576.5758.8 ?atm, 304.2243.5 ?atm, 1 933.61 144.7 ?atm, and 448.5202.6 ?atm, respectively. Maximum and minimum pCO2 values were found in the hypertrophic (4 053.7 ?atm) and the eutrophic (3.2 ?atm) areas. The riverine mouth areas have the maximum fluxes (82.062.8 mmol/m2a). But there was no significant difference between eutrophic and mesotrophic areas in pCO2 and the flux of CO2. The hydrophyte area, however, has the minimum (-0.5812.9 mmol/m2a). In respect to CO2 equilibrium, input of the rivers will obviously influence inorganic carbon distribution in the riverine estuary. For example, the annual mean CO2 flux in Zhihugang River estuary was 19 times of that in Meiliang Bay, although the former is only a part of the latter. The sites in the body of the lake show a clear seasonal cycle with pCO2 higher than atmospheric equilibrium in winter, and much lower than atmospheric in summer due to CO2 consumption by photosynthesis. The CO2 amount of the net annual evasion that enters the atmosphere is 28.42104 t/a, of which those from the west littoral zone and the open lake account for 53.8% and 36.7%, respectively.

Fan, Chengxin; Hu, Weiping; Ford, Phillip W.; Chen, Yuwei; Qu, Wenchuan; Zhang, Lu

2005-03-01

304

Understanding H2-H2 interactions in Metal Organic Frameworks (MOFs) with unsaturated metal centers  

NASA Astrophysics Data System (ADS)

Unsaturated Metal Organic Frameworks (MOFs) are particularly interesting due to their high H2 uptakes with relatively large isosteric heats of adsorption (Qst >8 kJ/mol). This work explores H2-H2 interactions between adsorbed H2 at the different sites in MOF-74 (M2(dhtp),dhtp=2,5-dihydroxyterephthalate) and combines IR spectroscopy with vdW-DFT calculations. The adsorption sites in MOF-74 are from highest to lowest binding energies the metal, oxygen, benzene and pore-center sites. The frequency of adsorbed H2 at the metal site suffers an additional -30 cm-1 red shift (for Mg and Zn) and -84 cm-1 (for Co) when the neighboring oxygen site is occupied. The dipole moment of adsorbed H2 is also affected. These interactions extend to the benzene sites for MOF-74-Co. A decrease in dipole moment of H2 adsorbed at the metal site is observed with the partial occupation of the benzene sites. However, the complete occupation of the benzene sites induces an additional -10 cm-1 red shift.

Nijem, Nour; Veyan, Jean F.; Kong, Lingzhu; Zhao, Yonggang; Li, Jing; Langreth, David; Chabal, Yves J.

2011-03-01

305

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

Microsoft Academic Search

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

Simon L. Clegg; Peter. Brimblecombe

1990-01-01

306

A new formula for the effect of temperature on the partial pressure of CO2 in seawater  

Microsoft Academic Search

Copin-Montegut, C., 1988. A new formula for the effect of temperature on the partial pressure of C02 in seawater. Mar. Chem., 25: 29-37. For the ranges of values of total alkalinity and total COx encountered in natural seawater, it is possible, using an empirical equation, to determine a precise estimate (error < 0.04 At% ) ofpCO: at temperature t (0~<

CLAIRE COPIN-MONTEGUT

1988-01-01

307

Thermodynamic properties of peptide solutions: 7. Partial molar isentropic pressure coefficients of some dipeptides in aqueous solution  

Microsoft Academic Search

The partial molar isentropic pressure coefficients at infinite dilution, KS,2o, have been determined for a number of dipeptides in aqueous solution at 25C. For a series of dipeptides of sequence gly-X, where X is an amino acid with a neutral side chain, the KS,2o values are all more negative than that for diglycine. The results are discussed in terms of

Gavin R. Hedwig; Harald Hiland

1991-01-01

308

Is the partial pressure of carbon dioxide in the blood related to the development of retinopathy of prematurity?  

Microsoft Academic Search

AIMSTo determine the role of carbon dioxide in the development of retinopathy of prematurity (ROP).METHODSThis was a retrospective cohort study of 25 consecutive infants admitted to the neonatal unit with continuously recorded physiological data. The daily mean and standard deviation (SD) of transcutaneous carbon dioxide partial pressure (tcPco2) was compared between infants who had stage 1 or 2 ROP and

Balazs Gellen; Neil McIntosh; Janet R McColm; Brian W Fleck

2001-01-01

309

Short-term variations of the partial pressure of CO 2 in surface waters of the Galician upwelling system  

Microsoft Academic Search

The partial pressure of CO2 (pCO2) and dissolved oxygen saturation level (%O2) were monitored continuously during a cruise in August 1998, which sampled surface waters off the Galician coast. Data are presented from two Lagrangian experiments carried out in an upwelling on the continental shelf and in the core of an offshore filament. The data show that daily variations in

Alberto V. Borges; Michel Frankignoulle

2001-01-01

310

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

Microsoft Academic Search

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

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

2011-01-01

311

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

312

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

NASA Astrophysics Data System (ADS)

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

Kopp, E.

1990-04-01

313

Resistance of the protozoan Colpoda maupasi to Martian conditions of atmospheric pressure and low partial pressure of oxygen.  

PubMed

Among the most important factors limiting the active life of animal organisms in Martian conditions are low atmospheric pressure and insignificant amounts of oxygen in the atmosphere (no more than 0.15% of the Earth's atmosphere). The experiments with aerobic protozoon C. maupasi have shown that in conditions of hermetically sealed chambers, for instance in 2.5 liter anaerostats, the protozoon can survive for a long time and reproduce in an atmosphere of air or nitrogen containing 1 or 0.0005% oxygen at a pressure from 15 mm Hg and higher. At the atmospheric pressure 10 mm Hg we observed a considerable decrease in the survival percentage and no reproduction. The exposure to 5 mm Hg resulted in a 100 per cent mortality of the protozoon. In a specially-constructed chamber "Photostat", in which current atmosphere pressure were automatically maintained during an experiment of many days, the reaction of the infusoria was somewhat different: they reproduced and existed not only at the pressure of 10-15 mm Hg, but also at 5 mm Hg, in an atmosphere of both air and nitrogen containing from 1 to 0.0005% O2. This indicates not only low-oxygen consumption of unicellular animals but also the capability of cells to extract some traces of this gas from the atmosphere. Low pressure and some traces of oxygen in the Martian atmosphere are not an impediment for the existence of some of the Earth's animals, such as the protozoon C. maupasi for example. PMID:11949684

Lozina-Lozinsky, L K; Bychenkova, V N

1969-01-01

314

Acetate production from lactose by Clostridium thermolacticum and hydrogen-scavenging microorganisms in continuous culture--effect of hydrogen partial pressure.  

PubMed

The effect of the addition of hydrogen-consuming microorganisms on the metabolism of Clostridium thermolacticum was studied. By growing this bacterium in continuous culture at 58 degrees C, on 29 mmol lactose l(-1) (10 gl(-1)) in the feed, with the H2-consuming microorganisms Methanothermobacter thermoautotrophicus and Moorella thermoautotrophica, the volumetric productivity of acetate was increased up to 3.9 mmol l(-1)h(-1) at a dilution rate of 0.058 h(-1). This was about three times higher than the maximal acetate volumetric productivity quantified when C. thermolacticum was cultivated alone. In the consortium, C. thermolacticum was the only species able to metabolize lactose; it produced not only acetate, but also hydrogen, carbon dioxide and lactate. The other species of the consortium were growing on these by-products. Meth. thermoautotrophicus played an important role as a very efficient hydrogen scavenger and decreased the hydrogen partial pressure drastically: hydrogen was converted to methane. Moor. thermoautotrophica converted lactate as well as hydrogen and carbon dioxide into acetate. As a consequence, lactose was efficiently consumed and the only organic product in the liquid phase was acetate. PMID:15992956

Collet, Christophe; Gaudard, Olivier; Pringer, Paul; Schwitzgubel, Jean-Paul

2005-08-22

315

On the adsorption of NO and NO2 on cold H2O/H2SO4 surfaces  

NASA Astrophysics Data System (ADS)

A static reaction chamber attached to a mass spectrometer was employed to study the adsorption of NO and NO2 onto cold surfaces of pure ice and liquid/solid 70 wt % H2SO4. No significant adsorption could be observed for surface temperatures in the range 193-243 K and NO/NO2 partial pressures of 10-2-10-5 mbar. This sets an upper limit on the uptake coefficients for both NO and NO2 of 5 10-5. The possible formation of nitrosyl sulphuric acid by adsorption of NO and NO2 on cold sulphuric acid particles is therefore unlikely to be of importance in the stratosphere.

Saastad, Ole W.; Ellermann, Thomas; Nielsen, Claus J.

1993-06-01

316

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 1,200C 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

317

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

Microsoft Academic Search

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

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

318

Structure of H 2O-saturated peralkaline aluminosilicate melt and coexisting aluminosilicate-saturated aqueous fluid determined in-situ to 800 C and 800 MPa  

NASA Astrophysics Data System (ADS)

The structure of H 2O-saturated silicate melts and of silicate-saturated aqueous solutions, as well as that of supercritical silicate-rich aqueous liquids, has been characterized in-situ while the sample was at high temperature (to 800 C) and pressure (up to 796 MPa). Structural information was obtained with confocal microRaman and with FTIR spectroscopy. Two Al-bearing glasses compositionally along the join Na 2O4SiO 2-Na 2O4(NaAl)O 2-H 2O (5 and 10 mol% Al 2O 3, denoted NA5 and NA10) were used as starting materials. Fluids and melts were examined along pressure-temperature trajectories of isochores of H 2O at nominal densities (from PVT properties of pure H 2O) of 0.85 g/cm 3 (NA10 experiments) and 0.86 g/cm 3 (NA5 experiments) with the aluminosilicate + H 2O sample contained in an externally-heated, Ir-gasketed hydrothermal diamond anvil cell. Molecular H 2O (H 2O) and OH groups that form bonds with cations exist in all three phases. The OH/H 2O ratio is positively correlated with temperature and pressure (and, therefore, fugacity of H 2O, f H2O) with (OH/H 2O) melt > (OH/H 2O) fluid at all pressures and temperatures. Structural units of Q3, Q2, Q1, and Q0 type occur together in fluids, in melts, and, when outside the two-phase melt + fluid boundary, in single-phase liquids. The abundance of Q0 and Q1 increases and Q2 and Q3 decrease with f H2O. Therefore, the NBO/ T (nonbridging oxygen per tetrahedrally coordination cations), of melt is a positive function of f H2O. The NBO/ T of silicate in coexisting aqueous fluid, although greater than in melt, is less sensitive to f H2O. The melt structural data are used to describe relationships between activity of H 2O and melting phase relations of silicate systems at high pressure and temperature. The data were also combined with available partial molar configurational heat capacity of Q n-species in melts to illustrate how these quantities can be employed to estimate relationships between heat capacity of melts and their H 2O content.

Mysen, Bjorn

2010-07-01

319

Staphylococcal enterotoxin A: Partial unfolding caused by high pressure or denaturing agents enhances superantigenicity.  

PubMed

The effect of transient exposure of Staphylococcus aureus enterotoxin A (SEA) to high pressure and/or denaturing agents was examined by assessing the toxin superantigenicity and immunoreactivity, and by monitoring pressure-induced changes in fluorescence emission spectra. Pressurization of SEA at 600 MPa and 45 degrees C in Tris-HCl buffer (20 mM, pH 7.4) resulted in a marked increase in both T-cell proliferation (superantigenicity) and immunoreactivity. In opposite, pressurization at 20 degrees C did not change significantly SEA superantigenicity and immunoreactivity, indicating some toxin baro-resistance. Exposure of SEA to 8 M urea at atmospheric pressure or at 600 MPa and 20 degrees C, also led to a marked increase of superantigenicity (but not of immunoreactivity). In contrast, exposure of SEA to sodium-dodecylsulfate (30 mM) led to an increase of immunoreactivity with some effect on superantigenicity after pressurization at 45 degrees C only. High pressure up to 600 MPa induced spectral changes which at 20 degrees C were fully reversible upon decompression. At 45 degrees C, however, a sharp break of the centre of spectral mass mainly due to tryptophan residues was observed at 300 MPa, and irreversible spectral changes mainly related to tyrosine residues subsisted after pressure release, indicating a marked protein conformational transition. Urea 8 M further increased SEA structural changes at 600 MPa and 20 degrees C. These results indicate that SEA, under a combination of high pressure and mild temperature, as well as in the presence of urea, partly unfolds to a structure of strongly increased T-cell proliferative ability. PMID:20116459

Ren-Trouillefou, Malika; Benzaria, Amal; Marchal, Stphane; Lange, Reinhard; Caporiccio, Bertrand; Dumay, Eliane

2010-01-29

320

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

SciTech Connect

Zeolite membranes are thermally, chemically, and mechanically stable. They also have tunable molecular sieving and catalytic ability. These unique properties make zeolite membrane an excellent candidate for use in catalytic membrane reactor applications related to coal conversion and gasification, which need high temperature and high pressure range separation in chemically challenging environment where existing technologies are inefficient or unable to operate. Small pore, good quality, and thin zeolite membranes are needed for highly selective H2 separation from other light gases (CO2, CH4, CO). However, current zeolite membranes have either too big zeolite pores or a large number of defects and have not been successful for H2 separation from light gases. The objective of this study is to develop zeolite membranes that are more suitable for H2 separation. In an effort to tune the size of zeolite pores and/or to decrease the number of defects, medium-pore zeolite B-ZSM-5 (MFI) membranes were synthesized and silylated. Silylation on B-ZSM-5 crystals reduced MFI-zeolite pore volume, but had little effect on CO2 and CH4 adsorption. Silylation on B-ZSM-5 membranes increased H2 selectivity both in single component and in mixtures with CO2, CH4, or N2. Single gas and binary mixtures of H2/CO2 and H2/CH4 were permeated through silylated B-ZSM-5 membranes at feed pressures up to 1.7 MPa and temperatures up to 773 K. For one B-ZSM-5 membrane after silylation, the H2/CO2 separation selectivity at 473 K increased from 1.4 to 37, whereas the H2/CH4 separation selectivity increased from 1.6 to 33. Hydrogen permeance through a silylated BZSM-5 membrane was activated with activation energy of {approx}10 kJ/mol, but the CO2 and CH4 permeances decreased slightly with temperature in both single gas and in mixtures. Therefore, the H2 permeance and H2/CO2 and H2/CH4 separation selectivities increased with temperature. At 673 K, the H2 permeance was 1.0x10-7 mol{center_dot}m-2{center_dot}s-1{center_dot}Pa-1, and the H2/CO2 separation selectivity was 47. Above 673 K, the silylated membrane catalyzed reverse water gas shift reaction and still separated H2 with high selectivity; and it was thermally stable. However, silylation decreased H2 permeance more than one order of magnitude. Increasing the membrane feed pressure increased the H2 flux and the H2 mole fraction in the permeate stream for both H2/CO2 and H2/CH4 mixtures. The H2 separation performance of the silylated B-ZSM-5 membranes depended on the initial membrane quality and acidity, as well as the silane precursors. Another approach used in this study is optimizing the synthesis of small-pore SAPO-34 (CHA) membranes and/or modifying SAPO-34 membranes by silylation or ion exchange. For SAPO-34 membranes, strong CO2 adsorption inhibited H2 adsorption and decreased H2 permeances, especially at low temperatures. At 253 K, CO2/H2 separation selectivities of a SAPO-34 membrane were greater than 100 with CO2 permeances of about 3 x 10-8 mol{center_dot}m-2{center_dot}s-1{center_dot}Pa-1. The high reverse-selectivity of the SAPO-34 membranes can minimize H2 recompression because H2 remained in the retentate stream at a higher pressure. The CO2/H2 separation selectivity exhibited a maximum with CO2 feed concentration possibly caused by a maximum in the CO2/H2 sorption selectivity with increased CO2 partial pressure. The SAPO-34 membrane separated H2 from CH4 because CH4 is close to the SAPO-34 pore size so its diffusivity (ABSTRACT TRUNCATED)

Mei Hong; Richard Noble; John Falconer

2007-09-24

321

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

Microsoft Academic Search

The rheology of partially molten rock controls rock strength beneath spreading centers, deformation of the mantle wedge under subduction zones, and migration of melt to hot spots and volcanic arcs. Our understanding of these regions has been predominately shaped by chemical analyses of rocks and by remotely collected geophysical data. To interpret these data, however, requires knowledge of the relationships

B. Demartin; G. Hirth; B. Evans

2004-01-01

322

RNase H2-Initiated Ribonucleotide Excision Repair  

PubMed Central

SUMMARY Ribonucleotides are incorporated into DNA by the replicative DNA polymerases at frequencies of about 2 per kb which makes them by far the most abundant form of potential DNA damage in the cell. Their removal is essential for restoring a stable intact chromosome. Here we present a complete biochemical reconstitution of the ribonucleotide excision repair (RER) pathway with enzymes purified from Saccharomyces cerevisiae. RER is most efficient when the ribonucleotide is incised by RNase H2, and further excised by the flap endonuclease FEN1 with strand displacement synthesis carried out by DNA polymerase ?, the PCNA clamp, its loader RFC, and completed by DNA ligase I. We observed partial redundancy for several of the enzymes in this pathway. Exo1 substitutes for FEN1 and Pol ? for Pol ? with reasonable efficiency. However, RNase H1 fails to substitute for RNase H2 in the incision step of RER.

Sparks, Justin L.; Chon, Hyongi; Cerritelli, Susana M.; Kunkel, Thomas A.; Johansson, Erik; Crouch, Robert J.; Burgers, Peter M.

2012-01-01

323

Deoxidatlon rate of copper droplet levitated in Ar-H2 gas stream  

NASA Astrophysics Data System (ADS)

Levitated copper droplets, 5 mm in diameter with initial oxygen contents of 0.036 to 1.9 wt pct, were deoxidized at about 1970 K in an Ar-H2 gas stream. The Ar-H2 gas mixture having hydrogen partial pressure less than 4 kPa was introduced into a silica reaction tube of 11-mm ID at gas flow rates up to 2 x 10-4 Nm3s-1. The effects of initial oxygen content of the droplets, hydrogen partial pressure, and gas flow rate on the deoxidation process were examined. A mixed control model for the deoxidation rate involving both gas and liquid film mass-transfer resistances was combined with a thermodynamic relationship for the dissolved species in molten copper. The value of 2 10-4 m 73x00D7; s-1 was assigned to the liquid film mass-transfer coefficient of dissolved oxygen throughout all experimental conditions. Under the experimental conditions of low initial oxygen content and high hydrogen partial pressure, the liquid film mass-transfer resistance was significant. When a droplet of high initial oxygen content was deoxidized, transition phenomena from gas to liquid film mass-transfer control were noticed in the later stage of reaction. It was deduced from the present model that the accumulation of dissolved hydrogen was indispensable to these phenomena.

Fukunaka, Y.; Tamura, K.; Taguchi, N.; Asaki, Z.

1991-10-01

324

Effect of oxygen partial pressure on the superconductivity of Bi2212 wires during post-annealing  

Microsoft Academic Search

Bi2Sr2CaCu2O8+delta (Bi-2212) silver sheathed round wire is a promising and practical material for high field superconducting insert magnet in the range of 25-30 T. The effect of oxygen content of Bi-2212 on the critical current density (Jc) of multi-filamentary Bi-2212\\/Ag wires has been investigated. During the Bi-2212 wire fabrication, partial melting and solidification process was employed. Short samples which were

Q. B. Hao; C. S. Li; S. N. Zhang; J. Q. Feng; M. H. Du

2011-01-01

325

Effect of oxygen partial pressure on the superconductivity of Bi2212 wires during post-annealing  

Microsoft Academic Search

Bi2Sr2CaCu2O8+? (Bi-2212) silver sheathed round wire is a promising and practical material for high field superconducting insert magnet in the range of 2530T. The effect of oxygen content of Bi-2212 on the critical current density (Jc) of multi-filamentary Bi-2212\\/Ag wires has been investigated. During the Bi-2212 wire fabrication, partial melting and solidification process was employed. Short samples which were cut

Q. B. Hao; C. S. Li; S. N. Zhang; J. Q. Feng; M. H. Du

2011-01-01

326

Association between administered oxygen, arterial partial oxygen pressure and mortality in mechanically ventilated intensive care unit patients  

Microsoft Academic Search

IntroductionThe aim of this study was to investigate whether in-hospital mortality was associated with the administered fraction of oxygen\\u000a in inspired air (FiO2) and achieved arterial partial pressure of oxygen (PaO2).\\u000a \\u000a \\u000a \\u000a \\u000a MethodsThis was a retrospective, observational study on data from the first 24 h after admission from 36,307 consecutive patients\\u000a admitted to 50 Dutch intensive care units (ICUs) and treated

Evert de Jonge; Linda Peelen; Peter J Keijzers; Hans Joore; Dylan de Lange; Peter HJ van der Voort; Robert J Bosman; Ruud AL de Waal; Ronald Wesselink; Nicolette F de Keizer

2008-01-01

327

Raman scattering study of ?-MgH2 and ?-MgH2  

NASA Astrophysics Data System (ADS)

Two modifications of MgH2 have been studied by Raman spectroscopy: ?-MgH2 with the P42/mnm space group and ?-MgH2 with the Pbcn space group. The latter was prepared from ?-MgH2 by exposing it to a pressure of 5.6 GPa at 470 C for 1.5 h. A comparison of the experimental spectra with ab-initio calculations allowed identification of a few phonon modes. A broad feature in the Raman spectrum of ?-MgH2 in the range 1470-1790 cm-1 was identified as the B2g phonon mode. A Raman spectrum of ?-MgH2 consists of five discernible peaks at 186 cm-1, 313 cm-1, 509 cm-1, 660 cm-1, 706 cm-1 and of three broad features in the regions 890-980 cm-1, 1010-1220 cm-1 and 1240-1430 cm-1. The peaks are identified as the 1Ag (186 cm-1), 3B3g (509 cm-1), 2Ag (660 cm-1) and 3B1g (706 cm-1) phonon modes.

Kuzovnikov, M. A.; Efimchenko, V. S.; Filatov, E. V.; Maksimov, A. A.; Tartakovskii, I. I.; Ramirez-Cuesta, A. J.

2013-01-01

328

Computation of partial vapor pressures of aqueous volatile organic compound solutions. Final report, July 1993-December 1995  

SciTech Connect

A program is described for the evaluation of the partial vapor pressures of solution components dependent on the concentration in solution, total pressure, and temperature. The object of the program is to provide reliable values that represent the best estimate based on the large body of experimental data available in the literature. The basis of the estimate is the evaluation of the Wilson coefficients for calculating the activity coefficients of the components using an iterative least squares algorithm to minimize the excess Gibbs free energy of solution. The computational programs are applied to binary aqueous solutions of volatile organic compounds: methanol, ethanol, iso-propanol, acetone, and methyl ethyl ketone. The results are applied to the evaluation of the vapor concentration dependence of the absorbance of selected peaks in the infrared spectrum of the compounds evaluated.

Field, P.E.; Combs, R.J.; Knapp, R.B.

1996-06-01

329

Partial and Total Vapor Pressures over Molten Bi2Te3.  

National Technical Information Service (NTIS)

The total vapor pressure, P(Sigma), over Bi2Te3 (1) has been determined between 980 and 1169K by using a new manometric technique. The lower end of an evacuated, inverted, fused silica U-tube was immersed in a large reservoir of melt inside a transparent ...

F. T. Smith R. F. Brebrick

1971-01-01

330

Influence of oxygen partial pressure on creep of a chromia refractory  

SciTech Connect

This report covers the effects of low oxygen pressures on the creep of high chromic refractories. The creep results in controlled atmosphere are compared to the creep results in air. Results from a selected refractory are discussed. Creep experiments have been done for other refractories. (JL)

Kasi, B.

1987-08-01

331

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

332

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

333

Long-term trend of the partial pressure of carbon dioxide (pCO2) in surface waters of the western North Pacific, 1984 1993  

Microsoft Academic Search

The ocean is an important sink for anthropogenic CO2 emissions, but there are only a few measurements which confirm the oceanic CO2 uptake. Since 1981, partial pressure of CO2 (pCO2) in the western North Pacific (35N-3N, 128E-155E) and the overlying air have been measured periodically to clarify the seasonal and long-term trends of the oceanic carbonate system. The partial pressure

Hisayuki Yoshikawa Inoue; Hidekazu Matsueda; Masao Ishii; Katsuhiko Fushimi; Michio Hirota; Ichio Asanuma; Yoshio Takasugi

1995-01-01

334

Physical Chemistry of the H2SO4/H2O Binary System at Low Temperatures: Stratospheric Implications.  

National Technical Information Service (NTIS)

Laboratory experiments have been carried out to investigate the physical chemistry of the H2SO4/H2O binary system under conditions characteristic of the stratosphere. Water vapor pressures of sulfuric acid solutions (20-70 wt %) and of liquid-solid and so...

R. Zhang P. J. Wooldridge J. P. D. Abbatt M. J. Molina

1993-01-01

335

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

PubMed

Knowledge of blood (1) H(2) O T(1) is critical for perfusion-based quantification experiments such as arterial spin labeling and cerebral blood volume-weighted MRI using vascular space occupancy. The dependence of blood (1) H(2) O T(1) on hematocrit fraction (Hct) and oxygen saturation fraction (Y) was determined at 7 T using in vitro bovine blood in a circulating system under physiological conditions. Blood (1) H(2) O R(1) values for different conditions could be readily fitted using a two-compartment (erythrocyte and plasma) model, which are described by a monoexponential longitudinal relaxation rate constant dependence. It was found that T(1) = 2171 39 ms for Y = 1 (arterial blood) and 2010 41 ms for Y = 0.6 (venous blood), for a typical Hct of 0.42. The blood (1) H(2) O T(1) values in the normal physiological range (Hct from 0.35 to 0.45, and Y from 0.6 to 1.0) were determined to range from 1900 to 2300 ms. The influence of oxygen partial pressure (pO(2) ) and the effect of plasma osmolality for different anticoagulants were also investigated. It is discussed why blood (1) H(2) O T(1) values measured in vivo for human blood may be about 10-20% larger than found in vitro for bovine blood at the same field strength. Magn Reson Med, 2012. 2012 Wiley Periodicals, Inc. PMID:23169066

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

2012-11-20

336

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

SciTech Connect

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

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

2008-09-18

337

Hydrolysis of N2O5 and ClONO2 on the H2SO4/HNO3/H2O ternary solutions under stratospheric conditions  

NASA Astrophysics Data System (ADS)

The reaction probabilities of N2O5 and ClONO2 with H2O on liquid sulfuric acid surfaces have been reexamined to determine the effect of HNO3 on these two hydrolysis rates, using a fast flow reactor coupled to a chemical ionization mass spectrometer. The measurements were carried out by maintaining constant H2O and HNO3 partial pressures and by varying temperatures between 227 and 195 K in order to mimic compositions representative of stratospheric aerosols. For experiments excluding HNO3, the reaction probability of N2O5 hydrolysis was found to be near 0.1, independent of temperature and H2SO4 content. This is in agreement with results previously measured under similar conditions. In the presence of gaseous HNO3 at stratospheric concentrations, the reaction probability was observed to decrease from about 0.09 at 218 K to about 0.02-0.03 at 195 K for PH2O = 3.8 10-4-1.0 10-3 Torr, showing that incorporation of HNO3 into liquid sulfuric acid greatly retarded the N2O5 hydrolysis. The ClONO2 reaction with H2O on liquid sulfuric acid, on the other hand, did not appear to be affected by the presence of HNO3.

Zhang, Renyi; Leu, Ming-Taun; Keyser, Leon F.

338

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

339

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

340

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

341

Modeling the H2 + H2 Reaction in Restricted Geometries  

NASA Astrophysics Data System (ADS)

Quasiclassical trajectory studies have been carried out on the H_2(v_ab,j_ab=0) + H_2(v_cd,j_cd=0) system in two restricted geometries to study the effects of collider orientation on the relative probabilities of dissociative and inelastic collisions. These restricted geometries are the isosceles tetrahedron and ``T'' conformations. Preliminary results indicate that differences occur with translational energy of less than 0.035 E_h, v_ab <= 11, and v_cd = 0. These differences are attributed to the differences in the potential energy surface cuts corresponding to these two conformations. ``Pass-through'' trajectories, in which one molecule passes through the center of the other molecule without dissociation occurring, were observed in these conformations, consistent with results of previous studies of the isosceles trapezoid conformation.(M. E. Mandy and P. G. Martin, J. Chem. Phys. (in preparation)) Implications for further study are discussed.

Rothwell, T. A.; Mandy, M. E.

1999-05-01

342

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

PubMed Central

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

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

1988-01-01

343

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

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

344

Photosynthetic water oxidation at elevated dioxygen partial pressure monitored by time-resolved X-ray absorption measurements  

PubMed Central

The atmospheric dioxygen (O2) is produced at a tetramanganese complex bound to the proteins of photosystem II (PSII). To investigate product inhibition at elevated oxygen partial pressure (pO2 ranging from 0.2 to 16 bar), we monitored specifically the redox reactions of the Mn complex in its catalytic S-state cycle by rapid-scan and time-resolved X-ray absorption near-edge spectroscopy (XANES) at the Mn K-edge. By using a pressure cell for X-ray measurements after laser-flash excitation of PSII particles, we found a clear pO2 influence on the redox reactions of the Mn complex, with a similar half-effect pressure as determined (23 bar). However, XANES spectra and the time courses of the X-ray fluorescence collected with microsecond resolution suggested that the O2 evolution transition itself (S3?S0+O2) was not affected. Additional (nonstandard) oxidation of the Mn complex at high pO2 explains our experimental findings more readily. Our results suggest that photosynthesis at ambient conditions is not limited by product inhibition of the O2 formation step.

Haumann, Michael; Grundmeier, Alexander; Zaharieva, Ivelina; Dau, Holger

2008-01-01

345

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

346

High-pressure partial melting of eclogite and garnet amphibolite rocks during decompression and heating, the Tromso Nappe, Norway.  

NASA Astrophysics Data System (ADS)

It has recently been argued that melting of high-P, high-T rocks in thickened arcs is an important process in magma genesis (e.g. Petford and Atherton, 1993; Rapp et al., 2003), producing rocks such as adakites. Such melting, however, has rarely been studied in-situ, and has instead relied on inferences from experimental and numerical studies, often based on quite different oceanic crustal lithologies. 452 Ma eclogites and garnet amphibolites in the Tromso Nappe, Norway provide one of the first opportunities to examine such melting in-situ. Evidence for a variety of melt forming reactions is preserved, involving melting of some or all of the eclogitic or retrograded eclogite components to form melt and peritectic garnet or amphibole. Thermobarometry shows that melting of eclogite involving peritectic garnet occurred at the highest pressures (P: 1.8 - 2.3 GPa), but lower than peak eclogite conditions of 3.3 GPa (Krogh-Ravna, pers.comm. 2004). Partial melting involving peritectic amphibole and melting of garnet amphibolite involving peritectic garnet both yield lower pressures (P: 1.1 GPa). These results suggest that melting of eclogite rock in continental arcs may be intimately linked to exhumation of those arcs. Temperatures remained high (T: 800 C), most likely in response to the emplacement of the neighbouring Skattora Migmatite Complex (Selbekk and Skjerlie, 2002). This supports the modelling of Petford & Gallagher (2001) that suggests that melting in lower continental arcs may be in response to intrusion of magmatic bodies nearby, and suggests that melting of the eclogites and garnet amphibolites in the Tromso Nappe was due to both decompression and heating. Four reactions are inferred qualitatively: (1) Omphacite +/- Zoisite +/- Kyanite +/- Phengite +/- Quartz goes to Garnet + Melt; (2) Omphacite + Garnet +/- Zoisite +/- Kyanite +/- Phengite +/- Quartz goes to Amphibole + Melt; (3) Omphacite +/- Zoisite +/- Kyanite +/- Phengite +/- Quartz goes to Amphibole + Melt; (4) Amphibole +/- Omphacite +/- Quartz +/- Biotite goes to Garnet + Melt. Current work is focusing on fully quantifying these reactions and the composition of melts produced. References: Petford, N. and Atherton, M. 1996. Na-rich partial melts from newly underplated basaltic crust: the Cordillera Blanca Batholith, Peru. J. Pet. 37, 1491-1521. Petford, N. and Gallagher, K. 2001. Partial melting of mafic (amphibolitic) lower crust by periodic influx of basaltic magma. EPSL, 193, 483-499. Rapp, R. P., Shimizu, N. and Norman, M. D. 2003. Growth of early continental crust by partial melting of eclogite. Nature, 425, 605-609. Selbekk, R. and Skjerlie, K-P. 2002. Petrogenesis of the Anorthosiste Dyke Swarm of Tromso, North Norway: Experimental evidence for Hydrous Anatexis of an Alkaline Mafic Complex. J. Pet. 43, 943-962.

Stevenson, J. A.

2004-12-01

347

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

NASA Astrophysics Data System (ADS)

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

Mansuripur, Masud; Zakharian, Armis R.

2012-07-01

348

Regional Blood Flow in Respiratory Muscles During Partial Ventilatory Assistance in Rabbits  

Microsoft Academic Search

We tested the hypothesis that even partial ventilatory assistancewouldreducerespiratorymusclebloodflow to levels similar to those found during control mechan- icalventilation(CMV).Threelevelsofpressuresupport ventilation(PSV)and2CMVsettingswerecomparedin 10 rabbits. PSV 0, 6, and 12 cm H2O, under continuous positive airway pressure mode, were applied, and then pressure control ventilation (PCV) values of 6 (36 breaths\\/min) and 12 cm H2O (18 per breaths\\/min) were applied to each CMV

Akinori Uchiyama; Yuji Fujino; Kikumi Hosotsubo; Eriko Miyoshi; Takashi Mashimo; Masaji Nishimura

2006-01-01

349

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

350

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

SciTech Connect

Aldehydes are common in a variety of geologic environments and are derived from a number of sources, both natural and anthropogenic. Experimental data for aqueous aldehydes were taken from the literature and used, along with parameters for the revised Helgeson-Kirkham-Flowers (HKF) equations of state, to estimate standard partial molal thermodynamic data for aqueous straight-chain alkyl aldehydes at high temperatures and pressures. Examples of calculations involving aldehydes in geological environments are given, and the stability of aldehydes relative to carboxylic acids is evaluated. These calculations indicate that aldehydes may be intermediates in the formation of carboxylic acids from hydrocarbons in sedimentary basins brines and hydrothermal systems like they are in the atmosphere. The data and parameters summarized here allow evaluation of the role of aldehydes in the formation of prebiotic precursors, such as amino acids and hydroxy acids on the early Earth and in carbonaceous chondrite parent bodies. 97 refs., 5 figs., 3 tabs.

Schulte, M.D.; Shock, E.L. (Washington Univ., St. Louis, MO (United States))

1993-08-01

351

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

352

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

SciTech Connect

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

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

1990-06-28

353

H2 receptor antagonists overdose  

MedlinePLUS

... signs, including temperature, pulse, breathing rate, and blood pressure. Symptoms will be treated as appropriate. The patient may receive: Activated charcoal Breathing support Fluids by IV Laxative

354

Effect of oxygen partial pressure on the crystallization of CeO2 and La2Zr2O7 bi-axially textured thin films  

NASA Astrophysics Data System (ADS)

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: (0 0 1)SrTiO3 (STO) for CeO2 and (0 0 1)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 an effect was not observed for LZO/LAO. The presence of oxygen, even in traces (10-100 ppm), favors the growth of randomly oriented grains while low oxygen partial pressure provides conditions where the heterogeneous nucleation on the substrate dominates. Once nucleated under low oxygen partial pressure, annealing can be performed under increasing controlled oxygen partial pressure without modification of the texture but with an improved crystallization. Application of this to coated conductors must be restricted in the field where oxidation of the substrate can be avoided.

Guibadj, A.; Odier, P.; Benbarta, B.; Ortega, L.

2011-08-01

355

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

Microsoft Academic Search

The vertical distributions and mixing ratios of minor constituents in the northern hemisphere of Saturn are investigated. Results are obtained for NH3, PH3, C2H2, C2H6, CH3D, and CH4; the D\\/H ratio is obtained from the CH4 and CH3D abundances. The NH3 mixing ratio in the upper atmosphere is found to be compatible with the saturated partial pressure. The inferred PH3\\/H2

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

1984-01-01

356

Liquid-Vapor Equilibrium and Ionization of HCl in the System HCl-H2SO4-H2O at 298 K  

Microsoft Academic Search

The equilibrium pressures and compositions of the vapor over HCl-H2SO4-H2O solutions with a low content of HCl and several fixed concentrations of H2SO4 were measured by the flow method at 298 K. The semiconcentration values of the mixed dissociation constants of HCl were calculated and extrapolated to infinite dilution.

G. M. Poltoratskii; S. B. Andreev; I. I. Osovskaya; V. A. Yakovlev

2002-01-01

357

Study on the formation of the liquid phase during heating process of Bi-2223/Ag superconducting tapes at various oxygen partial pressure by using in situ resistance measurement  

NASA Astrophysics Data System (ADS)

Two kinds of green mono-filament Bi-2223/Ag superconducting tapes (T-phase tape and O-phase tape) were investigated, the initial superconducting phase of which was tetragonal Bi-2212 phase and orthorhombic (Bi,Pb)-2212 phase, respectively. The resistance of these tapes was in situ measured during heating at various oxygen partial pressures. It was found that the resistance increased at a characteristic temperature at every oxygen partial pressure. This resistance behavior was related to the formation of the liquid phase. The formation temperature of the liquid phase increased with increasing oxygen partial pressure. And the formation temperature of the liquid phase of T-phase tape was about 6 C higher than that of O-phase tape. The above results demonstrated that the in situ resistance measurement is a sensitive method for studying the formation of the liquid phase in superconducting materials.

Huang, K.-T.; Qu, T.-M.; Lai, L.-F.; Han, Z.

2011-11-01

358

Partial molar isentropic pressure coefficients of some N-acetyl amino acid and peptide amides at infinite dilution in aqueous solutions at the temperature 298.15 K  

Microsoft Academic Search

The partial molar isentropic pressure coefficients at infinite dilutionk?S,2= ?(?V?\\/?p)S, whereV?2is the partial molar volume at infinite dilution, have been determined for sixN-acetyl amino acid and peptide amides in aqueous solution at the temperature 298.15 K. The results obtained have been rationalized in terms of the likely solute water interactions. The contribution of an alanyl side-chain to the value

Gavin R. Hedwig; Harald Hiland

1995-01-01

359

Measurements of Absolute CH Concentrations by Cavity Ring-Down Spectroscopy and Linear Laser-Induced Fluorescence in Laminar, Counterflow Partially Premixed and Nonpremixed Flames at Atmospheric Pressure  

Microsoft Academic Search

We report quantitative, spatially resolved measurements of methylidyne concentration ([CH]) in laminar, counterflow partially premixed and nonpremixed flames at atmospheric pressure by using both cavity ring-down spectroscopy (CRDS) and linear laser-induced fluorescence (LIF) in the A-X (0, 0) band. Three partially premixed (phi_B = 1.45, 1.6, 2.0) flames plus a single nonpremixed methane-air flame are investigated at a global strain

Sameer V. Naik; Normand M. Laurendeau

2004-01-01

360

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 900C, which also depends on the oxygen partial pressure, such

A. Guibadj; P. Odier; B. Benbarta; L. Ortega

2011-01-01

361

Evaluation of the Fatigue Life of High-Strength Low-Alloy Steel Girth Welds in Aqueous Saline Environments with Varying Carbon Dioxide Partial Pressures  

NASA Astrophysics Data System (ADS)

High-strength low-alloy steel girth weld specimens were subjected to fatigue tests in saline environments saturated with different carbon dioxide partial pressures. As expected, results show that increases in gas concentration initially affect fatigue life adversely, but when higher partial pressures are associated with low stresses, a reduction in the negative impact of environmental conditions is seen. This may be related to a competition between corrosion rates and mechanisms of crack initiation and propagation. Data is presented with the aim of contributing toward the establishment of a database of results in literature which may lead to better understanding of the phenomena involved through association of these with ongoing research.

Lemos, M.; Kwietniewski, C.; Clarke, T.; Joia, C. J. B.; Altenhofen, A.

2012-07-01

362

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

2013-01-18

363

Phase diagram and thermodynamic properties of H2  

NASA Astrophysics Data System (ADS)

A statistical mechanical-based theory is used to develop the equation of state for the molecular fluid of H2. We incorporate in this equation the long-range correlations through the double Yukawa potential, dimerization of the H2 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 H2, including the temperature and pressure dependence of compressibility factor, entropy, specific heat, compressibility, and sound velocity.

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

2013-01-01

364

Absolute Line Intensities for the nu6 Band of H2O2.  

PubMed

The purpose of this work was to obtain reliable absolute intensities for the nu6 band of H2O2. It was undertaken because strong discrepancies exist between the different nu6 band intensities which are presently available in the literature (A. Perrin, A. Valentin, J.-M. Flaud, C. Camy-Peyret, L. Schriver, A. Schriver, and P. Arcas, J. Mol. Spectrosc. 1995. 171, 358), (R. May, J. Quant. Radiat. Transfer 1991. 45, 267), and (R. L. Sams, personal communication). The method which was chosen in the present work was to measure simultaneously the far-infrared absorptions and the nu6 absorptions of H2O2. Consequently, Fourier transform spectra of H2O2 were recorded at Giessen in a spectral range (370-1270 cm-1) which covers both the R branch of the torsion-rotation band and the P branch of the nu6 band which appear at low and high wavenumbers, respectively. From the low wavenumber data, the partial pressure of H2O2 present in the cell during the recording of the spectra was determined by calibrating the observed absorptions in the torsion-rotation band with intensities computed using the permanent H2O2 dipole moment measured by Stark effect (A. Perrin, J.-M. Flaud, C. Camy-Peyret, R. Schermaul, M. Winnewisser, J.-Y. Mandin, V. Dana, M. Badaoui, and J. Koput, J. Mol. Spectrosc. 1996. 176, 287-296) and [E. A. Cohen and H. M. Pickett, J. Mol. Spectrosc. 1981. 87, 582-583). In the high frequency range, this value of the partial pressure of H2O2 was used to measure absolute line intensities in the nu6 band. Finally, the line intensities in the nu6 band were fitted using the theoretical methods described in detail in our previous works. Using these new results on line intensities together with the line position parameters that we obtained previously, a new synthetic spectra of the nu6 band was generated, leading to a total band intensity of 0.185 x 10(-16) cm-1/(molecule.cm-2) at 296 K. It has to be pointed out that the new line intensities agree to within the experimental uncertainties with the individual line intensity measurements performed previously by May and by Sams. Copyright 1999 Academic Press. PMID:10191160

Klee; Winnewisser; Perrin; Flaud

1999-05-01

365

Experimental study on equilibrium solubility (at low partial pressures), density, viscosity and corrosion rate of carbon dioxide in aqueous solutions of ascorbic acid  

Microsoft Academic Search

In this paper, ascorbic acid as a new carbon dioxide (CO2) absorbent was investigated. The equilibrium solubility of CO2 into 0.5, 1 and 1.5moldm?3 (M) aqueous ascorbic acid solutions were measured experimentally with a stirred batch reactor at total atmospheric pressure over the CO2 partial pressure ranging from 0 to 45kPa and temperatures between 298 and 313K. The results of

S. Mazinani; A. Samsami; A. Jahanmiri; A. R. Sardarian

2011-01-01

366

Equilibrium partial pressures, thermodynamic properties of aqueous and solid phases, and Cl production from aqueous HCl and HNO and their mixtures  

Microsoft Academic Search

Equilibrium total pressures have been measured above aqueous HNO and aqueous HCl using a capacitance manometer. Equilibrium partial pressures of the acids have also been determined, by mass spectrometry, from 274.8 to 234.6 K for both HCl solutions, and from 265.0 to 240.1 K for 15.73 mol kg⁻¹ HNO. Results are generally consistent with model predictions, though with small systematic

M. Massucci; S. L. Clegg; P. Brimblecombe

1999-01-01

367

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

Microsoft Academic Search

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

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

1996-01-01

368

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

NASA Astrophysics Data System (ADS)

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

Aroutiounian, Svetlana

2002-10-01

369

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

PubMed Central

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

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

2010-01-01

370

Comparison of Helzel and OxyLite Systems in the Measurements of Tumor Partial Oxygen Pressure (pO2)  

PubMed Central

It has been demonstrated in both experimental and human malignancies that hypoxic tumor cells are linked with aggressive disease phenotype. One of the methods to identify these cells is by direct physical measurement of tumor pO2. This study compared pO2 values measured with two systems, the Helzel Hypoximeter (successor of the polarographic Eppen-dorf electrode) and the Oxford-Optronix OxyLite (fiber-optic probe), in R3327-AT and R3327-AT/tkeGFP tumors. Partial oxygen pressure was measured in individual tumors with either system or in the same tumor with both systems. The similarities and discrepancies in pO2 measurements between the two systems were also investigated when tumor-bearing animals were breathing pure oxygen. Our data showed a considerable heterogeneity in pO2 values in each tumor using both the Helzel and OxyLite systems. Similar results were obtained with both systems for the mean and median pO2 values, and the distributions of pO2 values within the interval 0 < pO2 < 40 mmHg (the range important for defining tumor hypoxia) were found to be statistically equivalent However, the frequencies of high pO2 values (>40 mmHg) and zero values measured by the two systems were statistically significantly different.

Wen, Bixiu; Urano, Muneyasu; Humm, John L.; Seshan, Venkatraman E.; Li, Gloria C.; Ling, C. Clifton

2009-01-01

371

Dynamics of CO 2 partial pressure and CO 2 outgassing in the lower reaches of the Xijiang River, a subtropical monsoon river in China  

Microsoft Academic Search

The partial pressure of carbon dioxide (pCO2) in surface water was surveyed monthly at 6 sampling sites along the entire length of the lower reaches of the Xijiang River, a subtropical monsoon river in China, and at the mouths of its major tributaries, over a whole hydrological year from April 2005 to March 2006, to reveal the seasonal and spatial

Guanrong Yao; Quanzhou Gao; Zhengang Wang; Xiakun Huang; Tong He; Yongling Zhang; Shulin Jiao; Jian Ding

2007-01-01

372

Influence of TaCl 5 partial pressure on texture structure of TaC coating deposited by chemical vapor deposition  

NASA Astrophysics Data System (ADS)

TaC was deposited on graphite substrate with different TaCl 5 partial pressure at 800 C and 1200 C by chemical vapor deposition. Microstructures and texture structures of the prepared coatings were researched with X-ray diffraction and scanning electronic microscopy. When the coating deposition process is controlled by surface reaction kinetics (800 C), TaCl 5 partial pressure had little influence on the microstructure and texture structure of the coating. When the coating formation process is controlled by diffusion kinetics (1200 C), the microstructure, texture structure of the prepared TaC grains vary greatly with TaCl 5 partial pressure. In the diffusion controlled process, the increasing of TaCl 5 partial pressure will result in the changing of gas supersaturation, and then the occurrence of secondary nucleation, which is the main reason for the changing of coating morphology and texture structure. With the help of competitive growth in (1 0 0) and (1 1 1) directions, the formation mechanism of the different texture coatings are discussed in detail. In addition, a diffusion model of deposition species around step-edge-corner was also proposed to explain the growth mechanism of the texture coatings.

Chen, Zhao-Ke; Xiong, Xiang; Long, Ying

2011-02-01

373

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

Microsoft Academic Search

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

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

1995-01-01

374

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

Microsoft Academic Search

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

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

2004-01-01

375

Influence of the N2 partial pressure on the characteristics of CrZrN coatings synthesized Using a segment CrZr target.  

PubMed

In this study, CrZrN films were synthesized by unbalanced magnetron sputtering (UBM) under various N2 partial pressures and their characteristics such as crystalline structure, surface morphology, microstructure and mechanical properties as a function of the N2 partial pressures were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), nanoindentation, wear tests, and corrosion tests. Results revealed that, with increasing the N2 partial pressure from 0.05 to 0.21 Pa, the nitrogen content of the films increased from approximately 40.9 to 53.7 at%, the deposition rate decreased from approximately 100 to 59 nm/min and the surface roughness (Rms value) was increased from approximately 0.57 to 1.79 nm. The Cr37.3-Zr9.0-N53.7 film has the highest hardness, elastic modulus, and plastic deformation resistance of 36 GPa, 380 GPa, and 0.41, respectively. The Cr37.3-Zr9.0-N53.7 film also has the lowest friction coefficient and wear rate of 0.19 and 3.01 (10(-6)m3/Nm) at room temperature. In addition, the potentiodynamic test results showed the corrosion resistance of the CrZrN films became increased significantly and their corrosion current density (i(corr)), corrosion potentials (Ecorr) and corrosion rate decreased with increasing N2 partial pressure. PMID:22400261

Kim, YoungSu; Kim, GwangSeok; Lee, SangYul

2011-10-01

376

Effects of Temperature, Oxygen Partial Pressure, and Materials Selection on Slag Infiltration into Porous Refractories for Entrained-Flow Gasifiers  

NASA Astrophysics Data System (ADS)

The penetration rate of molten mineral contents (slag) from spent carbonaceous feedstock into porous ceramic-oxide refractory linings is a critical parameter in determining the lifecycle of integrated gasification combined cycle energy production plants. Refractory linings that withstand longer operation without interruption are desirable because they can mitigate consumable and maintenance costs. Although refractory degradation has been extensively studied for many other high-temperature industrial processes, this work focuses on the mechanisms that are unique to entrained-flow gasification systems. The use of unique feedstock mixtures, temperatures from 1450 C to 1600 C, and oxygen partial pressures from 10-7 atm to 10-9 atm pose engineering challenges in designing an optimal refractory material. Experimentation, characterization, and modeling show that gasifier slag infiltration into porous refractory is determined by interactions between the slag and the refractory that either form a physical barrier that impedes fluid flow or induce an increased fluid viscosity that decelerates the velocity of the fluid body. The viscosity of the slag is modified by the thermal profile of the refractory along the penetration direction as well as reactions between the slag and refractory that alter the chemistry, and thereby the thermo-physical properties of the fluid. Infiltration experiments reveal that the temperature gradient inherently present along the refractory lining limits penetration. A refractory in near-isothermal conditions demonstrates deeper slag penetration as compared to one that experiences a steeper thermal profile. The decrease in the local temperatures of the slag as it travels deeper into the refractory increases the viscosity of the fluid, which in turn slows the infiltration velocity of fluid body into the pores of the refractory microstructure. With feedstock mixtures that exhibit high iron-oxide concentrations, a transition-metal-oxide, the oxygen partial pressure of the operating atmosphere regulates the penetration of slag into refractory. The viscosity of the slag, which dictates its penetration rate, is influenced by the oxidation state of the Fe cation. Slag penetrations are shallower in oxidizing conditions than they are in reducing conditions because the iron-oxide from the slag solutions into the corundum-structured refractory and the slag is depleted of iron-oxide, increasing the viscosity of slags. Equally, the chemistries of both the refractory and slag materials dictate the course of penetration. Cr2O3-Al2O3 refractory limits mixed feedstock slag penetration through formation of a chromium spinel layer that functions as a physical obstacle against fluid flow. Al2O 3-SiO2 refractory limits eastern coal feedstock slag penetration as a result of refractory dissolution of SiO2, which increases the viscosity of slags. A physical model, which considers unidirectional fluid flow of slag through each pore of the porous microstructure of the refractory, sufficiently approximates the penetration depth of the slag into the refractory. Agreement between experiments and the physical model demonstrates that the slag is driven into the refractory by capillary pressure. Since the viscosity of the slag continuously changes as the slag travels through the inherent temperature gradient of the refractory lining, the model incorporates dynamic viscosities that are dependent on both temperature and composition to project depths that are unique to the experimental parameters. The significantly different length scales of the radial and penetration directions of the pores allows for the application of a lubrication approximation onto the momentum equation. This process produces an analytical solution that effectively envelopes the variable viscosity into a single term.

Kaneko, Tetsuya Kenneth

377

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: CARS study of linewidths of the Q-branch of hydrogen molecules at high temperatures in a pulsed high-pressure H2O2 combustion chamber  

NASA Astrophysics Data System (ADS)

The results of measurements of individual line widths of the Q-branch of a hydrogen molecule and the corresponding coefficients of broadening caused by collisions with water molecules at T = 2700 K in a repetitively pulsed high-pressure (50-200 atm) hydrogen-oxygen combustion chamber are presented. CARS spectra of individual Q1Q7 hydrogen lines, pressure pulses, and the broadband CARS spectra of the entire Q-branch of hydrogen are recorded simultaneously during a single laser pulse. The shape of line profiles was analysed using a FabryPerot interferometer. The temperature in the volume being probed was determined from the 'broadband' CARS spectra. The entire body of the experimental results gives information on the spectral linewidths, temperature and pressure in the combustion chamber during CARS probing.

Vereschagin, Konstantin A.; Vereschagin, Alexey K.; Clauss, W.; Klimenko, D. N.; Oschwald, M.; Smirnov, Valery V.; Stelmakh, O. M.; Fabelinskii, V. I.

2005-03-01

378

Reversible effects of oxygen partial pressure on genes associated with placental angiogenesis and differentiation in primary-term cytotrophoblast cell culture.  

PubMed

Timely regulated changes in oxygen partial pressure are important for placental formation. Disturbances could be responsible for pregnancy-related diseases like preeclampsia and intrauterine growth restriction. We aimed to (i) determine the effect of oxygen partial pressure on cytotrophoblast differentiation; (ii) measure mRNA expression and protein secretion from genes associated with placental angiogenesis; and (iii) determine the reversibility of these effects at different oxygen partial pressures. Term cytotrophoblasts were incubated at 21% and 2.5% O2 for 96?hr, or were switched between the two oxygen concentrations after 48?hr. Real-time PCR and enzyme-linked immunosorbent assays (ELISAs) were used to evaluate cell fusion and differentiation, measuring transcript levels for those genes involved in cell fusion and placental angiogenesis, including VEGF, PlGF, VEGFR1, sVEGFR1, sENG, INHA, and GCM1. Cytotrophoblasts underwent fusion and differentiation in 2.5% O2 . PlGF expression was inhibited while sVEGFR1 expression increased. VEGF and sENG mRNA expressions increased in 2.5% compared to 21% O2 , but no protein was detected in the cell supernatants. Finally, GCM1 mRNA expression increased during trophoblast differentiation at 21% O2 , but was inhibited at 2.5% O2 . These mRNA expression effects were reversed by returning the cells to 21% O2 . Thus, low-oxygen partial pressure does not inhibit term-cytotrophoblast cell fusion and differentiation in vitro. Lowering the oxygen partial pressure from 21% to 2.5% caused normal-term trophoblasts to reversibly modify their expression of genes associated with placental angiogenesis. This suggests that modifications observed in pregnancy diseases such as preeclampsia or growth retardation are probably due to an extrinsic effect on trophoblasts. Mol. Reprod. Dev. 80: 774-784, 2013. 2013 Wiley Periodicals, Inc. PMID:23794249

Debive, F; Depoix, C; Gruson, D; Hubinont, C

2013-07-19

379

Structural Aspects of the Dehydration and Dehydroxylation of gamma-Titanium Phosphate, gamma-Ti(PO(4))(H(2)PO(4)).2H(2)O.  

PubMed

The thermal transformations of gamma-titanium phosphate, gamma-Ti(PO(4))(H(2)PO(4)).2H(2)O, have been studied using thermogravimetric analysis, differential scanning calorimetry, X-ray powder diffraction, and temperature-resolved in-situ powder diffraction. The transformation sequence goes from gamma-Ti(PO(4))(H(2)PO(4)).2H(2)O over a new partially dehydrated form gamma'-Ti(PO(4))(H(2)PO(4)).(2-x)H(2)O (x approximately 1) to the anhydrous form beta-Ti(PO(4))(H(2)PO(4)) and then through a two-step condensation process where layered titanium pyrophosphate, Ti(PO(4))(H(2)P(2)O(7))(0.5), is formed first and finally cubic titanium pyrophosphate TiP(2)O(7). The dehydration of gamma-Ti(PO(4))(H(2)PO(4)).2H(2)O and the dehydroxylation/condensation process from beta-Ti(PO(4))(H(2)PO(4)) to layered titanium pyrophosphate,Ti(PO(4))(H(2)P(2)O(7))(0.5), was followed in-situ. A new partially dehydrated phase, gamma'-Ti(PO(4))(H(2)PO(4)).(2-x)H(2)O (x approximately 1), which forms at approximately 50 degrees C has been detected and characterized. The unit cell is monoclinic with the lattice parameters a = 23.670(1) , b = 6.264(1) , c = 5.036(1) , beta = 102.41(1) degrees, and Z = 4. Layered titanium pyrophosphate, Ti(PO(4))(H(2)P(2)O(7))(0.5), which forms at 375 degrees C has been characterized. The unit cell is monoclinic with lattice parameters a = 16.271(3) , b = 6.319(1) , c = 5.122(1) , beta = 90.59(2) degrees, and Z = 4. PMID:11670567

Krogh Andersen, Anne Marie; Norby, Poul

1998-08-24

380

Kinetics of Al + H2O reaction: theoretical study.  

PubMed

Quantum chemical calculations were carried out to study the reaction of Al atom in the ground electronic state with H(2)O molecule. Examination of the potential energy surface revealed that the Al + H(2)O ? AlO + H(2) reaction must be treated as a complex process involving two steps: Al + H(2)O ? AlOH + H and AlOH + H ? AlO + H(2). Activation barriers for these elementary reaction channels were calculated at B3LYP/6-311+G(3df,2p), CBS-QB3, and G3 levels of theory, and appropriate rate constants were estimated by using a canonical variational theory. Theoretical analysis exhibited that the rate constant for the Al + H(2)O ? products reaction measured by McClean et al. must be associated with the Al + H(2)O ? AlOH + H reaction path only. The process of direct HAlOH formation was found to be negligible at a pressure smaller than 100 atm. PMID:21469719

Sharipov, Alexander; Titova, Nataliya; Starik, Alexander

2011-04-06

381

Partial volumes and compressibilities of extended polypeptide chains in aqueous solution: additivity scheme and implication of protein unfolding at normal and high pressure.  

PubMed

An empirical additivity method for calculation of the partial volumes and adiabatic compressibilities of extended oligo- and polypeptides having arbitrary amino acid compositions has been developed and tested by comparison with available experimental data. Its accuracy is the best among the known empirical approaches. Comparison of experimental data on protein denaturation with the results of calculation allows one to discriminate between the unfolded and molten globule states of globular proteins and to estimate the extent of unfolding. For the first time, experimental nonlinear data for the volume-pressure relationship in proteins and model compounds have been used to interpret the high-pressure denaturation of proteins. It has been shown that the two denatured states, molten globule and unfolded ones, can be attained by a pressure rise: the molten globule state by moderate pressure and the unfolded one by high pressure. The relationship between volumetric properties and hydration is briefly discussed. PMID:9254626

Kharakoz, D P

1997-08-19

382

The heterogeneous reaction of HOCl + HCl ? Cl2 + H2O on ice and nitric acid trihydrate: Reaction probabilities and stratospheric implications  

Microsoft Academic Search

The heterogeneous reaction HOCl + HCl ? Cl2(g) + H2O(s) has been observed to proceed readily on cold water-ice and nitric acid trihydrate (NAT) surfaces. For reactant partial pressures in the 10?710?5 torr range, the reaction probability (?) on water-ice is found to be 0.16 0.10 at 202 K, and 0.24 +0.5\\/?0.15 at 195 K, as measured by the

J. P. D. Abbatt; M. J. Molina

1992-01-01

383

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

USGS Publications Warehouse

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

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

2001-01-01

384

Effects of sample storage time, temperature and syringe type on blood gas tensions in samples with high oxygen partial pressures.  

PubMed Central

BACKGROUND--Although plastic arterial sampling syringes are now commonly used, the effects of sample storage time and temperature on blood gas tensions are poorly described for samples with a high oxygen partial pressure (PaO2) taken with these high density polypropylene syringes. METHODS--Two ml samples of tonometered whole blood (PaO2 86.7 kPa, PaCO2 4.27 kPa) were placed in glass syringes and in three brands of plastic blood gas syringes. The syringes were placed either at room temperature or in iced water and blood gas analysis was performed at baseline and after 5, 10, 20, 40, 60, 90, and 120 minutes. RESULTS--In the first 10 minutes measured PaO2 in plastic syringes at room temperature fell by an average of 1.21 kPa/min; placing the sample on ice reduced the rate of PaO2 decline to 0.19 kPa/min. The rate of fall of PaO2 in glass at room temperature was 0.49 kPa/min. The changes in PaCO2 were less dramatic and at room temperature averaged increases of 0.47 kPa for plastic syringes and 0.71 kPa for glass syringes over the entire two hour period. These changes in gas tension for plastic syringes would lead to an overestimation of pulmonary shunt measured by the 100% oxygen technique of 0.6% for each minute left at room temperature before analysis. CONCLUSIONS--Glass syringes are superior to plastic syringes in preserving samples with a high PaO2, and prompt and adequate cooling of such samples is essential for accurate blood gas analysis.

Pretto, J J; Rochford, P D

1994-01-01

385

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

NASA Astrophysics Data System (ADS)

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

Tisato, Nicola; Quintal, Beatriz

2013-10-01

386

An empirical model for the solubility of H2O in magmas to 3 kilobars  

Microsoft Academic Search

We present 16 new manometric determinations of H2O solubility for a range of natural silicate liquid compositions equilibrated up to 3 kbar of H 2O pressure. As the threshold temperature of dehydration of the quenched glasses during measurements of the H2O con- tent becomes lower as a function both of bulk silicate composition and the dissolved H2O content, we measured

GORDON MOORE; TORSTEN VENNEMANN; I. S. E. CARMICHAEL

1998-01-01

387

Immiscible CO2-H2O fluids in the shallow crust  

Microsoft Academic Search

The significance of a single CO2-H2O fluid phase is well known for metamorphic systems, and CO2-H2O immiscibility is explicit in fluid inclusion literature, especially regarding hydrothermal ores. Complex multiphase CO2-H2O behavior exists over wide temperature and pressure ranges overlapping other important geochemical processes. The character and physical-chemical properties of multiple phases possible for CO2 and H2O, and the potential impact

John P. Kaszuba; Laurie L. Williams; David R. Janecky; W. Kirk Hollis; Ioannis N. Tsimpanogiannis

2006-01-01

388

Nonthermal starch hydrolysis using ultra high pressure: I. Effects of acids and starch concentrations  

Microsoft Academic Search

Corn starches with 2mol\\/l hydrochloric acid (HCl), 2mol\\/l sulfuric acid (H2SO4) and 2mol\\/l oxalic acid (C2H2O4) were pressurized at 600MPa for 30min. Corn starch with C2H2O4 formed a gel after ultra-high-pressure (UHP) treatment. Corn starch with HCl showed partial disintegration but starch with H2SO4 maintained its shape. Corn starch with HCl showed higher (0.420.47) degree of hydrolysis compared to starch

Jae-Hwang Lee; Hyun-Wook Choi; Byung-Yong Kim; Myong-Soo Chung; Dong-Seob Kim; Sung Won Choi; Dong-Un Lee; Seok-Jun Park; Nam-Yoon Hur; Moo-Yeol Baik

2006-01-01

389

Reactive collisions of atomic antihydrogen with H, He^+, He, H2^+, and H2  

NASA Astrophysics Data System (ADS)

The fermion molecular dynamics (FMD) method has been used to determine the rearrangement and destruction cross sections for collisions of antihydrogen (H) with H, He^+, He, H2^+, and H2 at collision energies above 0.1 au. The results for the H and He^+ targets satisfactorily merge with previous calculations done for lower collision energies. There are no previous calculations for the other targets. Despite the absence of a critical distance, the destruction cross section for collisions of H with He is found to be comparable with the destruction cross sections for H collisions with H and He^+, for which there are critical distances. The three atomic cross sections are shown to be given quite reasonably by simple classical orbiting formulas at energies that are very low but still high enough for L>0 partial waves to be dominant. The cross sections for formation of the antiprotonic atoms (Pn or pHe) and their initial quantum numbers are found to be significantly different from the analogous cross sections for p projectiles. The cross sections for the molecular targets are significantly larger.

Cohen, James S.

2006-05-01

390

The Iceland Deep Drilling Project (IDDP): (6) Hydrothermal minerals record CO2 partial pressures in the Reykjanes Geothermal System, Iceland  

NASA Astrophysics Data System (ADS)

The Reykjanes Geothermal system, a target site for drilling by the IDDP, is located on the Reykjanes Peninsula in southwest Iceland, the landward extension of the Mid-Atlantic Ridge spreading center. Seawater penetrates the coastal Reykjanes geothermal system at depth, mixing with magmatic volatiles and reacting with the basaltic host rock to form secondary hydrothermal minerals. Within this system, epidote-prehnite-calcite- quartz-fluid constitutes a quadra-variant assemblage that, under conditions of specified temperature, pressure, and activity of H2O allows prediction of geothermal fluid pCO2 as a function of the composition of the solid solution minerals epidote or prehnite. This assemblage is typically found at temperatures >250C and <~310C, and potentially provides a mineralogical recorder that constrains fluid CO2 concentrations based on compositional zoning in hydrothermal epidote. Analysis of epidote crystals separated from drillhole-cuttings from three geothermal wells (RN-9, RN-10, RN-17) display complex chemical zoning, generally with Fe(III)-rich cores and Al-rich rims. The Fe(III)-mol fraction of epidote ranges 0.17 to 0.48. The Fe(III)-mol fraction of prehnite ranges from 0.11 to 0.59 in the upper portions of drillhole RN-17, where the highest Fe(III) content in epidote is 0.36, which serves as the upper Fe(III) limit for epidotes coexisting with prehnite in this study. Because most observed prehnite crystals in the drillhole-cuttings are too small for electron microprobe analyses (<20?m), we employed a sigmoidal correlation of available compositional data from active geothermal systems to calculate the Fe(III)-Al composition of prehnite using measured compositions of epidote in the Reykjanes system. In drill cuttings that contain epidote, prehnite, quartz and calcite, using measured epidote compositions between the reference temperatures of 275C and 310C, we calculated values of pCO2 for the geothermal fluids range from ~0.6 to ~6.2 bars. When only epidote, prehnite and quartz are observed in the drill cuttings, the calculated range of pCO2 is from ~1.3 to ~6.8 bars, which provides the maximum value of pCO2 at which calcite will not be present. Present day pCO2 values of geothermal fluids from the Reykjanes system were derived from analytical data on liquid and vapor samples collected at the surface using both the WATCH and SOLVEQ. At reference temperatures between 275C and 310C, these fluids have pCO2 concentrations ranging from 1.3 bars to 4.0 bars. The calculated pCO2 values based on epidote compositions are in close agreement with present-day fluid pCO2 in the Reykjanes geothermal system. 72% of the calculated pCO2 values based on epidote compositions where the assemblage of epidote, prehnite, quartz and calcite are observed in drill cuttings are within the range of measured present-day fluids, while 58% of the calculated pCO2 values fall within the range when calcite is not present in the drill cuttings.

Freedman, A. J.; Bird, D. K.; Arnrsson, S.; Fridriksson, T.; Elders, W. A.; Fridleifsson, G. O.

2009-12-01

391

LIF measurements and chemical kinetic analysis of methylidyne formation in high-pressure counter-flow partially premixed and non-premixed flames  

NASA Astrophysics Data System (ADS)

We report quantitative, spatially resolved, linear laser-induced fluorescence (LIF) measurements of methylidyne concentration ([CH]) in laminar, methane air, counter-flow partially premixed and non-premixed flames using excitation near 431.5 nm in the A X (0,0) band. For partially premixed flames, fuel-side equivalence ratios (?B) of 1.45, 1.6 and 2.0 are studied at pressures of 1, 3, 6, 9 and 12 atm. For non-premixed flames, the fuel-side mixture consists of 25% CH4 and 75% N2; measurements are obtained at pressures of 1, 2, 3, 4, 5, 6, 9 and 12 atm. The quantitative CH measurements are compared with predictions from an opposed-flow flame code utilizing two GRI chemical kinetic mechanisms (versions 2.11 and 3.0). LIF measurements of [CH] are corrected for variations in the quenching rate coefficient by using major species concentrations and temperatures generated by the code along with suitable quenching cross sections for CH available from the literature. A pathway analysis provides relative contributions from important elementary reactions to the total amount of CH produced at various pressures. Key reactions controlling peak CH concentrations are also identified by using a sensitivity analysis. For the partially premixed flames, measured CH profiles are reproduced reasonably well by GRI 3.0, although some quantitative disagreement exists at all pressures. Two CH radical peaks are observed for ?B=1.45 and ?B=1.6 at pressures above 3 atm. Peak CH concentrations for the non-premixed flames are significantly underpredicted by GRI 3.0. The latter agrees with previously reported NO concentrations, which are also underpredicted in these same high-pressure counter-flow diffusion flames.

Naik, S. V.; Laurendeau, N. M.

2004-11-01

392

Ion chemistry in H2-Ar low temperature plasmas  

NASA Astrophysics Data System (ADS)

A rate equation model is devised to study the ion composition of inductively coupled H2-Ar plasmas with different H2-Ar mixing ratios. The model is applied to calculate the ion densities ni, the wall loss probability of atomic hydrogen ?H, and the electron temperature Te. The calculated ni's of Ar+, H+, H2+, H3+, and ArH+ are compared with experimental results. Calculations were made for a total gas pressure of 1.0 Pa. The production and loss channels of all ions are presented and discussed in detail. With the production and loss rates, the density dependence of each ion on the plasma parameters is explained. It is shown that the primary ions H2+ and Ar+ which are produced by ionization of the background gas by electron collisions are effectively converted into H3+ and ArH+. The high density of ArH+ and Ar+ is attributed to the low loss to the walls compared to hydrogen ions. It is shown that the H+/H2+ density ratio is strongly correlated to the H/H2 density ratio. The dissociation degree is around 1.7%. From matching the calculated to the measured atomic hydrogen density nH, the wall loss probability of atomic hydrogen on stainless steel ?H was determined to be ?H=0.24. The model results were compared with recently published experimental results. The calculated and experimentally obtained data are in fair agreement.

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

2013-08-01

393

Precise and high-speed control of partial pressures of multiple gas species in plasma process chamber using pulse-controlled gas injection  

SciTech Connect

Multiprocesses in a single plasma process chamber with high throughput require precise, sequential, high-speed alteration of partial pressures of multiple gas species. A conventional gas-distribution system cannot realize this because the system seriously overshoots gas pressure immediately following valve operation. Furthermore, chamber volume and conductance of gas piping between the system and chamber should both be considered because they delay the stabilizing time of gas pressure. Therefore, the authors proposed a new gas-distribution system without overshoot by controlling gas flow rate based on pressure measurement, as well as a method of pulse-controlled gas injection immediately following valve operation. Time variation of measured partial pressure agrees well with a calculation based on an equivalent-circuit model that represents the chamber and gas piping between the system and chamber. Using pulse-controlled gas injection, the stabilizing time can be reduced drastically to 0.6 s for HBr added to pure Ar plasma, and 0.7 s for O{sub 2} added to Ar/HBr plasma; without the pulse control, the stabilizing times are 3 and 7 s, respectively. In the O{sub 2} addition case, rapid stabilization can be achieved during the period of line/space pattern etching of poly-Si on a thin SiO{sub 2} film. This occurs without anomalous etching of the underlying SiO{sub 2} film or the Si substrate near the sidewall, thus obtaining a wide process margin with high throughput.

Morishita, Sadaharu; Goto, Tetsuya; Nagase, Masaaki; Ohmi, Tadahiro [EES Technology Department of Technology, Development Center HQ, Industrial Automation Co., OMRON Corporation, Tokyo 141-0032 (Japan); New Industry Creation Hatchery Center, Tohoku University, Sendai 980-8579 (Japan); Osaka High-Tech Research and Development Center, Fujikin Incorporated, Osaka 559-0031 (Japan); New Industry Creation Hatchery Center, Tohoku University, Sendai 980-8579 (Japan)

2009-05-15

394

Investigation of the Oxidation Kinetics of Fe-Cr and Fe-Cr-C Melts under Controlled Oxygen Partial Pressures  

NASA Astrophysics Data System (ADS)

In the current work, oxidation kinetics of Fe-Cr and Fe-Cr-C melts by gas mixtures containing CO2 was investigated by Thermogravimetric Analysis (TGA). The experiments were conducted keeping the melt in alumina crucibles, allowing the alloy melt to get oxidized by an oxidant gas. The oxidation rate was followed by the weight changes as a function of time. The oxidation experiments were conducted using various mixtures of O2 and CO2 with P_{{{{O}}2 }} = 10-2 to 104 Pa. In order to understand the mechanism of oxidation, the wetting properties between the alumina container and the alloys used in the thermogravimetric analysis (TGA) experiments and the change of the alloy drop shape during the course of the oxidation were investigated by X-ray radiography.The experiments demonstrated that the oxidation rate of Fe-Cr melt increased slightly with temperature under the current experimental conditions, but it is strongly related to the Cr-content of the alloy as well as the oxygen partial pressure in the oxidant gas mixture, both of which caused an increase in the rate. For the Fe-Cr-C system, the oxidation rate has a negative relationship with carbon content, viz. with increasing carbon, the oxidation rate of the alloy melt slightly decreased. The chemical reaction was found to be the rate determining step during the initial stages, whereas as the reaction progressed, the diffusion of oxygen ions through slag phase to the slag-melt interface was found to have a strong impact on the oxidation rate. The overall impact of different factors on the chemical reaction rate for the oxidation process derived from the current experimental results can be expressed by the relationship: k1 = {dm}/{dt} = Uplambda {C}_{{Cr}}^{0. 2 3} {{C}}_{{{CO}}_{ 2} } ^{ 0. 4 1}{{exp}}({{{ - E}}_{{a}} }/{{{R}T}} ). A model for describing the kinetics of oxidation of Fe-Cr and Fe-Cr-C alloys under pure CO2 was developed. Simulation of the oxidation kinetics using this model showed good agreement with the experimental results.

Wang, Haijuan; Teng, Lidong; Seetharaman, Seshadri

2012-12-01

395

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

PubMed

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

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

2011-09-21

396

Partial pressure of CO2 and CO2 emission in a monsoon-driven hydroelectric reservoir (Danjiangkou Reservoir), China  

NASA Astrophysics Data System (ADS)

Hydroelectric reservoirs have been under sampled to establish them as sources or sinks of the atmospheric carbon dioxide (CO2). Such poor coverage is well known for subtropic, particularly monsoon driven reservoirs in China. Our study presented the spatiotemporal changes of the carbonate system and CO2 flux in a hydroelectric reservoir (Dangjiankou Reservoir) locating in a subtropical monsoon climate region. Our 21 filed surveys conducted during 2004-2011 revealed significantly spatial and monthly variations of surface water partial pressure of CO2 (pCO2) in the Reservoir. pCO2, showing higher concentrations in the wet and warm seasons, averaged 595 545 atm (ranging from 53-3751 atm) in the reservoir surface, while substantially higher pCO2 (1132 1220 atm) was observed in the river downstream the dam. A clear pCO2 drawdown in the reservoir as water flows demonstrated a significantly descending order of Dan Reservoir > site close to dam > Han Reservoir. This spatial contrast can also be seen in the distributions of dissolved inorganic carbon and total alkalinity. Pronounced seasonality in pCO2 was controlled by seasonal monsoon rainfall, while photosynthetic CO2 uptake dominated spatial patterns and dry-month variability of pCO2. We further related pCO2 to water chemical properties and indicated that pCO2 had strong positive correlations with Si, TP and DOC, negative correlations with DO saturation, TN and Chl a, while weak correlations with other variables including biogenic elements. CO2 flux from the Reservoir surface showed a bottom average of 9 mmol m-2 d-2 in comparison with other hydroelectric reservoir in China. River downstream the dam had quite high flux of CO2 (119 mmol m-2 d-2), which was intermediate between temperate rivers and compared to global rivers' average. This means that water releasing from reservoir would be an important channel for atmospheric CO2 sources. The annual CO2 emission from the Danjiangkou Reservoir was estimated to be 3.4 109 mol C. Remarkably spatial and temporal heterogeneities in CO2 flux from China's hydroelectric reservoirs are urgently included for advancing global models of reservoirs' carbon emissions.

Li, S. Y.; Zhang, Q. F.

2013-06-01

397

Enhanced Shrinkage of Lanthanum Strontium Manganite (La0.90Sr0.10MnO3+?) Resulting from Thermal and Oxygen Partial Pressure Cycling  

SciTech Connect

Exposure of La0.9Sr0.1MnO3+? to repeated oxygen partial pressure cycles (air/10 ppm O2) resulted in enhanced densification rates, similar to behavior shown previously due to thermal cycling. Shrinkage rates in the temperature range 700 to 1000oC were orders of magnitude higher than Makipirtti-Meng model estimations based on stepwise isothermal dilatometry results at high temperature. A maximum in enhanced shrinkage due to oxygen partial pressure cycling occurred at 900oC. Shrinkage was greatest when LSM-10 bars that were first equilibrated in air were exposed to gas flows of lower oxygen fugacity than in the reverse direction. The former creates transient cation and oxygen vacancies well above the equilibrium concentration, resulting in enhanced mobility. These vacancies annihilate as Schottky equilibria is re-established, whereas the latter condition does not lead to excess vacancy concentrations.

McCarthy, Ben; Pederson, Larry R.; Anderson, Harlan U.; Zhou, Xiao Dong; Singh, Prabhakar; Coffey, Greg W.; Thomsen, Ed C.

2007-10-01

398

H2 Separation From H2\\/N2 and H2\\/CO Mixtures with Co-Polyimide Hollow Fiber Module  

Microsoft Academic Search

A lab-scale membrane module, packed with more than 150 hollow fibers of P84 co-polyimide, was used for the separation of hydrogen mixtures. The ideal membrane performance was analysed with pure gases (H2, N2, CO, CO2, CH4) and H2\\/N2 and H2\\/CO mixtures at 50C and up to 6bar. Significant differences were observed between ideal selectivities and separation factors of mixtures. In

Seung-Hak Choi; Adele Brunetti; Enrico Drioli; Giuseppe Barbieri

2010-01-01

399

High metalinsulator transition temperature in La 1? x Sr x MnO 3 thin films grown in low oxygen partial pressure by molecular beam epitaxy  

Microsoft Academic Search

We grew La1-xSrxMnO3 films by MBE carefully controlling the rates of La, Sr and Mn, using substrate temperature of about 700C and low partial pressure (?210?5Torr) of O2+5% Ozone. RHEED analysis were performed to check in situ the structural properties of the films. Samples on different substrates and with different thickness have been fabricated to investigate the effects of the

Luigi Maritato; Aleksandr Yu. Petrov

2004-01-01