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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

Quantitative estimation of NH3 partial pressure in H2 desorbed from the Li-N-H system by Raman spectroscopy.  

PubMed

The partial pressure of NH3 gas estimated by Raman spectroscopy indicates that approximately 0.1% NH3 inevitably contaminates the H2 desorbed from a hydrogen storage material composed of LiH and LiNH2 at any temperature up to 400 degrees C in a closed system. PMID:15959577

Hino, Satoshi; Ichikawa, Takayuki; Ogita, Norio; Udagawa, Masayuki; Fujii, Hironobu

2005-06-28

4

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

PubMed

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

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

2011-08-31

5

Lyman-band fluorescence intensity vs H2 pressure  

NASA Technical Reports Server (NTRS)

The fluorescence intensity of the H2 Lyman bands excited by the argon 1066 A line is found to be a linear function of the H2 pressure. The fluorescence from naturally occurring HD is linearly dependent on the HD partial pressure. The experiments described show that these fluorescence intensities can be used to measure the H2 and HD densities below 10 trillion molecules per cu cm.

Inn, E. C. Y.; Starr, W. L.

1975-01-01

6

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

7

Shifts of H2O absorption lines in the nu1 + 3nu3 band induced by H2, CO2, and H2O pressure  

NASA Astrophysics Data System (ADS)

Results of measurements and calculations of H2O absorption line widths and shifts in the nu1 + 3nu3 band induced by H2O pressure and also by H2 and CO2 pressure are reported. The measurements have been carried out using a two-channel optoacoustic spectrometer with a frequency-tunable ruby laser. The calculations of the shift and broadening coefficients have been performed using the Anderson-Tsao-Curnutte-Frost method. Possible physical mechanisms which can account for the nonlinear change of the measured H2O line shift with H2 pressure are examined.

Lazarev, V. V.; Ponomarev, Iu. N.; Stroinova, V. N.; Tikhomirov, B. A.

1992-09-01

8

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

E-print Network

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

Manning, Craig

9

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

10

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

PubMed

The H2O-saturated solidus of a model mantle composition (Kilborne Hole peridotite nodule, KLB-1) was determined to be just above 1000C from 5 to 11 gigapascals. Given reasonable H2O abundances in Earth's mantle, an H2O-rich fluid could exist only in a region defined by the wet solidus and thermal stability limits of hydrous minerals, at depths between 90 and 330 kilometers. The experimental partial melts monotonously became more mafic with increasing pressure from andesitic composition at 1 gigapascal to more mafic than the starting peridotite at 10 gigapascals. Because the chemistry of the experimental partial melts is similar to that of kimberlites, it is suggested that kimberlites may be derived by low-temperature melting of an H2O-rich mantle at depths of 150 to 300 kilometers. PMID:9092469

Kawamoto; Holloway

1997-04-11

11

LIF diagnostics of hydroxyl radical in atmospheric pressure He-H2O dielectric barrier discharges  

NASA Astrophysics Data System (ADS)

In this paper we present laser induced fluorescence (LIF) measurements of OH relative density in a He-H2O atmospheric pressure dielectric barrier discharge, with an estimation of the absolute density based on the quantitative analysis of the LIF signal and on the decay of OH density in the post-discharge. The possible interference of H2O2 photo-dissociation is discussed and finally excluded. Densities of the order of 1013 cm-3 have been estimated in mixtures with water vapour content ranging from 2.3 to 23 Torr partial pressure. LIF diagnostic characteristics and sensitivity in the OH case at atmospheric pressure are discussed in comparison with absorption techniques.

Dilecce, G.; Ambrico, P. F.; Simek, M.; De Benedictis, S.

2012-04-01

12

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

NASA Technical Reports Server (NTRS)

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

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

1984-01-01

13

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

PubMed Central

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

Horn, Simon; Barnard, Stephen; Rothkamm, Kai

2011-01-01

14

H2SO4 vapor pressure of sulfuric acid and ammonium sulfate solutions  

Microsoft Academic Search

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

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

1997-01-01

15

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

16

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

17

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. PMID:22347218

Sauer, Patrick; Glombitza, Clemens; Kallmeyer, Jens

2012-01-01

18

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

E-print Network

H2O diffusion models in rhyolitic melt with new high pressure data Huaiwei Ni, Youxue Zhang in silicate melts, especially rhyolitic melt. However, the pressure dependence of H2O diffusion is not constrained satisfactorily. We investigated H2O diffusion in rhyolitic melt at 0.95­1.9 GPa and 407­1629 °C

Zhang, Youxue

19

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

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

20

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

21

Stable structures of He and H2O at high pressure  

NASA Astrophysics Data System (ADS)

The knowledge of the structures that can exist in compounds containing helium is of interest for understanding the conditions where and if this inert element can form structures where closed shell electrons of helium can participate in bonding that is not describable exclusively by van der Waals interactions alone. In this study we examine stable mixtures of He and H2O at high pressures using a first-principles structure searching method. We find a thermodynamically stable structure that can be characterized by interactions comparable in strength to that of conventional hydrogen bonds. An orthorhombic structure with space group Ibam is identified that has progressively lower enthalpy with increasing pressure above 296 GPa than a mixture of He and H2O . This mechanically and dynamically stable structure is found at pressures that are now becoming accessible to high-pressure techniques.

Liu, Hanyu; Yao, Yansun; Klug, Dennis D.

2015-01-01

22

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

NASA Astrophysics Data System (ADS)

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

Prakapenka, V.

2013-12-01

23

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

NASA Astrophysics Data System (ADS)

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

Ueta, S.; Sasaki, T.

2014-03-01

24

Mechanism of H2O Insertion and Chemical Bond Formation in AlPO4-54xH2O at High Pressure.  

PubMed

The insertion of H2O in AlPO4-54xH2O at high pressure was investigated by single-crystal X-ray diffraction and Monte Carlo molecular simulation. H2O molecules are concentrated, in particular, near the pore walls. Upon insertion, the additional water is highly disordered. Insertion of H2O (superhydration) is found to impede pore collapse in the material, thereby strongly modifying its mechanical behavior. However, instead of stabilizing the structure with respect to amorphization, the results provide evidence for the early stages of chemical bond formation between H2O molecules and tetrahedrally coordinated aluminum, which is at the origin of the amorphization/reaction process. PMID:25564928

Alabarse, Frederico G; Rouquette, Jrme; Coasne, Benot; Haidoux, Abel; Paulmann, Carsten; Cambon, Olivier; Haines, Julien

2015-01-21

25

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

NASA Technical Reports Server (NTRS)

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

Isham, M. A.

1992-01-01

26

Partial pressure analysis in space testing  

NASA Technical Reports Server (NTRS)

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

Tilford, Charles R.

1994-01-01

27

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

28

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

29

A High-Pressure Study of the NH3-H2 System  

NASA Astrophysics Data System (ADS)

As it is the simplest and most abundant element in the universe, hydrogen and hydrogen-rich molecules are ubiquitous to current scientific study. Molecular hydrogen (H2) has been studied extensively under pressure as a lone entity and in conjunction with other simple molecules. However, studies on ammonia-hydrogen mixtures have been limited. The NH3+H2 system is applicable to a number of research areas including gaseous and icy planets, the chemistry of hydrogen-bonded clathrate structures, and to further the understanding of intermolecular interactions at high density. In this study we compressed binary mixtures of hydrogen and ammonia in diamond anvil cells to 13 GPa at 300K over a range of compositions, and characterized the behavior using optical microscopy, Raman spectroscopy and synchrotron X-ray diffraction. Below 1.0 GPa we observe limited mutual solubility in the fluid phases, but beyond 1 GPa (and up to 13 GPa) NH3 and H2 tend to remain phase-separated. Two phase transitions in ammonia and one in hydrogen were observed, all of which occurred at pressures comparable to those of the pure substances. A preliminary phase diagram, structural analysis and equation of state are provided.

Chidester, B.; Strobel, T. A.

2010-12-01

30

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

31

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

PubMed

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

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

2014-06-28

32

New high-pressure phase of BaH2 predicted by ab initio studies  

NASA Astrophysics Data System (ADS)

Pressure-induced phase transitions of BaH2 have been studied by ab initio calculations. Our results show that BaH2 transforms from the cotunnite structure to the InNi2-type structure at about 2.3 GPa, which is in agreement with experimental results. The InNi2 phase is predicted to be an insulator and transforms to a metallic phase with an AlB2-type structure at about 34 GPa. Under higher pressure, a post-AlB2 phase with the YbZn2-type structure (space group Imma, 4 f.u./cell) is predicted, which is both dynamically and mechanically stable. Analysis of the enthalpies for both AlB2 and YbZn2 phases further supports the existence of this new phase. The \\mathrm {AlB_{2}} \\to \\mathrm {YbZn_{2}} structural phase transition is identified as a second-order nature, driven by the softening of the transverse acoustic phonon mode at the L point (0.5, 0.0, 0.5).

Chen, Changbo; Tian, Fubo; Wang, Liancheng; Duan, Defang; Cui, Tian; Liu, Bingbing; Zou, Guangtian

2010-06-01

33

Solubility of Anhydrite, CaSO4, in NaClH2O Solutions at High Pressures and  

E-print Network

Solubility of Anhydrite, CaSO4, in NaCl­H2O Solutions at High Pressures and Temperatures; ACCEPTED OCTOBER 22, 2004 ADVANCE ACCESS PUBLICATION DECEMBER 10, 2004 Anhydrite solubility in H2O­cylinder apparatus. Solubilities were determined by weight changes of natural anhydrite in perforated Pt envel- opes

Manning, Craig

34

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

35

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

36

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

37

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

38

Role of initial conductance and gas pressure on the conductance response of single-crystal SnO2 thin films to H2, O2, and CO  

NASA Astrophysics Data System (ADS)

Gas-induced conductance changes were measured on palladium-dosed single-crystal tin oxide (SnO2) thin films having well-characterized surface properties. Films were fabricated using two methods: reactive sputtering and chemical vapor deposition. Film orientation and crystal structure were determined by x-ray diffraction, while surface morphology was characterized using atomic force microscopy. Conductance changes were measured continuously on film surfaces during alternating exposure and evacuation cycles to partial pressures of H2, O2, and CO in a vacuum chamber. The conductance change was found to be proportional to the square root of the initial film conductance and was interpreted in terms of gas-induced changes in the width of a near-surface space-charge layer. The variation of conductance as a function of gas pressure during alternating exposure and evacuation cycles of H2 and O2 is consistent with a model that involves surface reactions between coadsorbates.

Vetrone, J.; Chung, Y.-W.; Cavicchi, R.; Semancik, S.

1993-06-01

39

Pressure and preheat dependence of laminar flame speeds of H 2\\/CO\\/CO 2\\/O 2\\/He mixtures  

Microsoft Academic Search

Laminar flame speeds of lean H2\\/CO\\/CO2 (syngas) fuel mixtures have been measured for a range of H2 levels (2090% of the fuel) at pressures and reactant preheat temperatures relevant to gas turbine combustors (15atm and up to 600K). A conical flame stabilized on a contoured nozzle is used for the flame speed measurement, which is based on the reaction zone

J. Natarajan; Y. Kochar; T. Lieuwen; J. Seitzman

2009-01-01

40

Laminar flame speeds of H 2\\/CO mixtures: Effect of CO 2 dilution, preheat temperature, and pressure  

Microsoft Academic Search

Laminar flame speeds of lean H2\\/CO\\/CO2 (syngas) fuel mixtures have been measured over a range of fuel compositions (595% for H2 and CO and up to 40% for CO2 by volume), reactant preheat temperatures (up to 700 K), and pressures (15 atm). Two measurement approaches were employed: one using flame area images of a conical Bunsen flame and the other

J. Natarajan; T. Lieuwen; J. Seitzman

2007-01-01

41

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

42

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

NASA Astrophysics Data System (ADS)

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

Ding, Ke; Lieberman, M. A.

2015-01-01

43

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

PubMed

This study focuses on the description of the static forces in CO2-H2O and CO2-H2O-IPA cleaning solutions with a separate fluid phase entrapped between nano-scale copper particles and a silicon surface. Calculations demonstrate that increasing the pressure of the cleaning system decreases net adhesion force (NAF) between the particle and silicon. The NAF of a particle for in CO2-H2O-IPA system is less than that in CO2-H2O system, suggesting that the particles enter into bulk layer more easily as the CO2-H2O cleaning system is added IPA. PMID:22408995

Tan, Xin; Chai, Jiajue; Zhang, Xiaogang; Chen, Jiawei

2011-12-01

44

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)], 10.1063/1.4704675 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)], 10.1103/PhysRevA.83.052506 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

45

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

46

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

E-print Network

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

Manning, Craig

47

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

48

Effects of oxygen partial pressure on oxidation of Zircaloy  

NASA Astrophysics Data System (ADS)

The effects of oxygen partial pressure on the oxidation of Zircaloy-4 were examined at 773 K under the oxygen partial pressure between 0.1 and 2 10 -5MPa to study the oxidation behavior of spent fuel during dry storage. The oxidation rate at first obeyed a cubic rate law, and changed to obey a linear rate law at almost the same weight gains even at different oxygen partial pressures. The oxidation rate during posttransition period showed pO20.15 dependence. The dependency of the oxidation rate in the posttransition region agreed with the results of the oxygen diffusion coefficient in zirconium oxide measured by Keneshea and Douglass. Degradation of the protective oxide film of Zircaloy-4 under low oxygen partial pressures was not observed within the oxygen partial pressure range examined. The results of this experiment showed that the oxidation rate in air can be adopted to estimate the cladding oxidation rate during dry fuel storage in air and under low oxygen partial pressures.

Nakamura, J.; Hashimoto, M.; Otomo, T.; Kawasaki, S.

1993-04-01

49

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

Code of Federal Regulations, 2010 CFR

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

2010-04-01

50

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

NASA Astrophysics Data System (ADS)

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

Safonov, O.; Kosova, S.

2012-12-01

51

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

52

Measurement of partial pressures in vacuum technology and vacuum physics  

NASA Technical Reports Server (NTRS)

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

Huber, W. K.

1986-01-01

53

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

ERIC Educational Resources Information Center

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

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

2007-01-01

54

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

SciTech Connect

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

Chung, M.; et al.

2013-10-01

55

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

PubMed

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

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

2014-09-14

56

Electrical conductivity and partial melting of mafic rocks under pressure  

Microsoft Academic Search

We demonstrate the importance of electric conductivity measurements of partially molten mafic rocks by examining of Oman gabbro, Karelia olivinite, Ronda and Spitzbergen peridotites. The electrical conductivities of these rocks were estimated using the impedance spectroscopy at temperatures between 800C and 1450C and at pressures between 0.3 and 2 GPa in experiments performed in a piston cylinder apparatus. At temperatures

J. Maumus; N. Bagdassarov; H. Schmeling

2005-01-01

57

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

USGS Publications Warehouse

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

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

2007-01-01

58

Internal motion and its pressure dependence in FeSiF6+6/H2O/.  

NASA Technical Reports Server (NTRS)

Both wideline and pulsed NMR techniques were used to examine the internal motion in FeSiF6+6(H2O). Corrections of second moments for bulk paramagnetic effects were essential. At room temperature and pressure, the fluorine-fluorine contribution to the 19F second moment is 0.38 (plus or minus 0.06) G2, and indicates rapid orientation of the SiF6(--) group. Analysis of the second moment within the transition region allows calculation of an activation volume which is 2.4 (plus or minus 0.4) % of the molar volume. The application of pressure slows the internal motion such that the rigid lattice values of the 19F second moment are obtained above 50 kbar.

Vaughan, R. W.; Nicolaides, G. L.; Elleman, D. D.

1972-01-01

59

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

NASA Technical Reports Server (NTRS)

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

Hanson, David R.

1990-01-01

60

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

61

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

SciTech Connect

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

Pint, Bruce A [ORNL

2012-08-01

62

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

63

The solubility of corundum in H2O at high pressure and temperature and its implications for Al mobility in the deep  

E-print Network

The solubility of corundum in H2O at high pressure and temperature and its implications for Al: D. Rickard Abstract The solubility of corundum in H2O was measured at 700­1100 °C and 0.5­2.0 GPa.41±0.15 millimolal (1 analytical error). Corundum solubility increases strongly with pressure (P) and temperature (T

Manning, Craig

64

Determining residence time and hydrocarbon partial pressure in pyrolysis furnaces  

SciTech Connect

A method of calculating residence time and hydrocarbon partial pressure which is applicable to both pilot and commercial pyrolysis coils has been developed. This method allows direct comparison of pilot unit and plant sampler data. Experimental data obtained with ARCO's pilot unit and olefins plant sampling device demonstrate good agreement between the two units. This method has also been extended to ARCO's millisecond pyrolysis furnaces, with similar results.

Cozzone, G.E.; Vavra, F.J.

1987-01-01

65

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

66

Oxygen-Partial-Pressure Sensor for Aircraft Oxygen Mask  

NASA Technical Reports Server (NTRS)

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

Kelly, Mark; Pettit, Donald

2003-01-01

67

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

68

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

NASA Astrophysics Data System (ADS)

Using the literature raw data of the speed of sound and the specific volume, the isothermal compressibility, ?T, a second derivative thermodynamic quantity of G, was evaluated for liquid H2O in the pressure range up to 350 MPa and the temperature to 50 C. We then obtained its pressure derivative, d?T/dp, a third derivative numerically without using a fitting function to the ?T data. On taking yet another p-derivative at a fixed T graphically without resorting to any fitting function, the resulting d2?T/dp2, a fourth derivative, showed a weak but clear step anomaly, with the onset of the step named point X and its end point Y. In analogy with another third and fourth derivative pair in binary aqueous solutions of glycerol, d?p/dxGly and d2?p/dxGly2, at 0.1 MPa (?p is the thermal expansivity and xGly the mole fraction of solute glycerol) in our recent publication [J. Solution Chem. 43, 663-674 (2014); DOI:10.1007/s10953-013-0122-7], we argue that there is a gradual crossover in the molecular organization of pure H2O from a low to a high p-regions starting at point X and ending at Y at a fixed T. The crossover takes place gradually spanning for about 100 MPa at a fixed temperature. The extrapolated temperature to zero p seems to be about 70 - 80 C for points X and 90 - 110 C for Y. Furthermore, the mid-points of X and Y seem to extrapolate to the triple point of liquid, ice Ih and ice III. Recalling that the zero xGly extrapolation of point X and Y for binary aqueous glycerol at 0.1 MPa gives about the same T values respectively, we suggest that at zero pressure the region below about 70 C the hydrogen bond network is bond-percolated, while above about 90 C there is no hydrogen bond network. Implication of these findings is discussed.

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

2014-09-01

69

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

NASA Astrophysics Data System (ADS)

H2O activities in concentrated NaCl solutions were measured in the ranges 600 900 C and 2 15 kbar and at NaCl concentrations up to halite saturation by depression of the brucite (Mg(OH)2) periclase (MgO) dehydration equilibrium. Experiments were made in internally heated Ar pressure apparatus at 2 and 4.2 kbar and in 1.91-cm-diameter piston-cylinder apparatus with NaCl pressure medium at 4.2, 7, 10 and 15 kbar. Fluid compositions in equilibrium with brucite and periclase were reversed to closures of less than 2 mol% by measuring weight changes after drying of punctured Pt capsules. Brucite-periclase equilibrium in the binary system was redetermined using coarsely crystalline synthetic brucite and periclase to inhibit back-reaction in quenching. These data lead to a linear expression for the standard Gibbs free energy of the brucite dehydration reaction in the experimental temperature range: ?G (120J)=73418 134.95 T(K). Using this function as a baseline, the experimental dehydration points in the system MgO-H2O-NaCl lead to a simple systematic relationship of high-temperature H2O activity in NaCl solution. At low pressure and low fluid densities near 2 kbar the H2O activity is closely approximated by its mole fraction. At pressures of 10 kbar and greater, with fluid densities approaching those of condensed H2O, the H2O activity becomes nearly equal to the square of its mole fraction. Isobaric halite saturation points terminating the univariant brucite-periclase curves were determined at each experimental pressure. The five temperature-composition points in the system NaCl-H2O are in close agreement with the halite saturation curves (liquidus curves) given by existing data from differential thermal analysis to 6 kbar. Solubility of MgO in the vapor phase near halite saturation is much less than one mole percent and could not have influenced our determinations. Activity concentration relations in the experimental P-T range may be retrieved for the binary system H2O-NaCl from our brucite-periclase data and from halite liquidus data with minor extrapolation. At two kbar, solutions closely approach an ideal gas mixture, whereas at 10 kbar and above the solutions closely approximate an ideal fused salt mixture, where the activities of H2O and NaCl correspond to an ideal activity formulation. This profound pressure-induced change of state may be characterized by the activity ( a) concentration ( X) expression: a H 2O= X H 2O/(1+? X NaCl), and a NaCl=(1+?)(1+?)[ X NaCl/(1+? X NaCl)](1+?). The parameter ? is determined by regression of the brucite-periclase H2O activity data: ?=exp[A B/?H 2O ]-C P/ T, where A=4.226, B=2.9605, C=164.984, and P is in kbar, T is in Kelvins, and ?H 2O is the density of H2O at given P and T in g/cm3. These formulas reproduce both the H2O activity data and the NaCl activity data with a standard deviation of 0.010. The thermodynamic behavior of concentrated NaCl solutions at high temperature and pressure is thus much simpler than portrayed by extended Debye-Hckel theory. The low H2O activity at high pressures in concentrated supercritical NaCl solutions (or hydrosaline melts) indicates that such solutions should be feasible as chemically active fluids capable of coexisting with solid rocks and silicate liquids (and a CO2-rich vapor) in many processes of deep crustal and upper mantle metamorphism and metasomatism.

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

1996-10-01

70

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

Code of Federal Regulations, 2010 CFR

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

2010-04-01

71

Electrical conductivity and partial melting of mafic rocks under pressure  

NASA Astrophysics Data System (ADS)

We demonstrate the importance of electric conductivity measurements of partially molten mafic rocks by examining of Oman gabbro, Karelia olivinite, Ronda and Spitzbergen peridotites. The electrical conductivities of these rocks were estimated using the impedance spectroscopy at temperatures between 800C and 1450C and at pressures between 0.3 and 2 GPa in experiments performed in a piston cylinder apparatus. At temperatures below and above melting, samples were equilibrated during durations on the order of 200 h. Our results show that a jump in electrical conductivity can be correlated with the temperature range slightly above the solidus, due to the delayed formation of an interconnected melt phase. Thin sections of quenched samples were used to estimate volume fractions and chemical compositions of the partial melts. The increase of the electrical conductivity compares well with the connectivity of melt in partially molten samples. Above the solidus, the electrical conductivity increases by 1 to 2 orders of magnitude in comparison with the conductivity of non-melted rock below solidus. When a complete melt connectivity is established, the charge transport follows the network of the formed melt films at grain boundaries. Durations of up to ?200 h are required in order to reach a steady state electrical resistance in a partially molten rock sample. The experimental results were compared with the conductivity data obtained from magnetotelluric (MT) and electromagnetic (EM) measurements in the Northern part of the mid-Atlantic ridge where a series of axial magma chambers (AMC) are presumably located. There is good agreement between the measured electric conductivity of gabbroic samples with a melt fraction of 10 to 13 vol.% and the conductivity estimated at AMC, beneath the central part of Reykjanes ridge, as well as between the conductivity of partially molten peridotites and the source zone beneath the mid-Atlantic ridge at ?60 km.

Maumus, J.; Bagdassarov, N.; Schmeling, H.

2005-10-01

72

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

SciTech Connect

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

A. Robertson

2003-12-31

73

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

SciTech Connect

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

Archie Robertson

2003-10-29

74

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

SciTech Connect

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

Archie Robertson

2002-07-10

75

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

SciTech Connect

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

Unknown

2003-01-30

76

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

SciTech Connect

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

Archie Robertson

2003-07-23

77

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

SciTech Connect

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

A. Robertson

2002-09-30

78

Time-resolved OES of nanosecond pulsed discharges in N$_{2}$ and N$_{2}$/H$_{2}$O mixtures]{Time-resolved optical emission spectroscopy of nanosecond pulsed discharges in atmospheric pressure N$_{2}$ and N$_{2}$/H$_{2}$O mixtures  

E-print Network

In this contribution, nanosecond pulsed discharges in N$_{2}$ and N$_{2}$/0.9% H$_{2}$O at atmospheric pressure (at 300 K) are studied with time-resolved imaging, optical emission spectroscopy and Rayleigh scattering. A 170 ns high voltage pulse is applied across two pin-shaped electrodes at a frequency of 1 kHz. The discharge consists of three phases: an ignition phase, a spark phase and a recombination phase. During the ignition phase the emission is mainly caused by molecular nitrogen (N$_{2}$(C-B)). In the spark and recombination phase mainly atomic nitrogen emission is observed. The emission when H$_{2}$O is added is very similar, except the small contribution of H$_{\\alpha}$ and the intensity of the molecular N$_{2}$(C-B) emission is less.

van der Horst, R M; van Veldhuizen, E M; Bruggeman, P J

2014-01-01

79

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

80

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

81

Biological nitrogen fixation under primordial Martian partial pressures of dinitrogen.  

PubMed

Early Earth and early Mars were similar enough such that past geochemical and climatic conditions on Mars may have also been favorable for the origin of life. However, one of the most striking differences between the two planets was the low partial pressure of dinitrogen (pN2) on early Mars (18 mb). On Earth, nitrogen is a key biological element and in many ecosystems the low availability of fixed nitrogen compounds is the main factor limiting growth. Biological fixation of dinitrogen on Earth is a crucial source of fixed nitrogen. Could the low availability of dinitrogen in the primordial Martian atmosphere have prevented the existence, or evolution of Martian microbiota? Azotobacter vinelandii and Azomonas agilis were grown in nitrogen free synthetic medium under various partial pressures of dinitrogen ranging from 780-0 mb (total atmosphere=1 bar). Below 400 mb the biomass, cell number, and growth rate decreased with decreasing pN2. Both microorganisms were capable of growth at a pN2 as low as 5 mb, but no growth was observed at a pN2 < or = 1 mb. The data appear to indicate that biological nitrogen fixation could have occurred on primordial Mars (pN2=18 mb) making it possible for a biotic system to have played a role in the Martian nitrogen cycle. It is possible that nitrogen may have played a key role in the early evolution of life on Mars, and that later a lack of available nitrogen on that planet (currently, pN2=0.2 mb) may have been involved in its subsequent extinction. PMID:11537369

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

1989-01-01

82

A comparison of the effects of pressure, temperature, and H2O adsorption and desorption on the electrical conductivity of basalts  

Microsoft Academic Search

At 16C and 10-7 torr the conductivity of basalt is of the order of 10-14 (Omega cm)-1. Raising the H2O vapor pressure from zero to saturation increases the conuctivity to 10-6 (Omega cm)-1. A change in conductivity of the same order of magnitude can be accomplished by heating a dry sample at 10-7 torr to 450C-500C. Quasi-hydrostatic pressure of 50

H. H. Schloessin

1976-01-01

83

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

84

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

PubMed

The low-pressure-limit unimolecular decomposition of methane, CH4 (+M) ? CH3 + H (+M), is characterized via low-order moments of the total energy, E, and angular momentum, J, transferred due to collisions. The low-order moments are calculated using ensembles of classical trajectories, with new direct dynamics results for M = H2O and new results for M = O2 compared with previous results for several typical atomic (M = He, Ne, Ar, Kr) and diatomic (M = H2 and N2) bath gases and one polyatomic bath gas, M = CH4. The calculated moments are used to parametrize three different models of the energy transfer function, from which low-pressure-limit rate coefficients for dissociation, k0, are calculated. Both one-dimensional and two-dimensional collisional energy transfer models are considered. The collision efficiency for M = H2O relative to the other bath gases (defined as the ratio of low-pressure limit rate coefficients) is found to depend on temperature, with, e.g., k0(H2O)/k0(Ar) = 7 at 2000 K but only 3 at 300 K. We also consider the rotational collision efficiency of the various baths. Water is the only bath gas found to fully equilibrate rotations, and only at temperatures below 1000 K. At elevated temperatures, the kinetic effect of "weak-collider-in-J" collisions is found to be small. At room temperature, however, the use of an explicitly two-dimensional master equation model that includes weak-collider-in-J effects predicts smaller rate coefficients by 50% relative to the use of a statistical model for rotations. The accuracies of several methods for predicting relative collision efficiencies that do not require solving the master equation and that are based on the calculated low-order moments are tested. Troe's weak collider efficiency, ?c, includes the effect of saturation of collision outcomes above threshold and accurately predicts the relative collision efficiencies of the nine baths. Finally, a brief discussion is presented of mechanistic details of the energy transfer process, as inferred from the trajectories. PMID:24144294

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

2013-11-27

85

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

E-print Network

.0, flame temperatures from 1400 to 1800 K, pressures from 1 to 25 atm, CH4 fuel fractions from 0 to 0.1. The experimental data show negative pressure dependence of burning rate at high-pressure, low-flame-temperature pressure dependence for very low equivalence ratios. The effect of pressure on the kinetics of lean flames

Ju, Yiguang

86

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

87

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

88

Water vapour partial pressure control in neonatal incubator using prevision by multiple models  

Microsoft Academic Search

One of the phenomena that affect the water loss in newborn infants is the humidity. The evaporation is determined by the vapour partial pressure. As well as temperature control, the reduction of the vapour partial pressure oscillations has an important role in the establishment of thermal comfort for newborn infants in incubators. This work presents an algorithm based on multiple

M. F. Amorim; G. H. C. Oliveira; D. S. R. Silva; L. M. Kiapuchinski

2004-01-01

89

Local pressure changes in lipid bilayers due to adsorption of melittin and magainin-h2 antimicrobial peptides: results from computer simulations.  

PubMed

We performed a series of coarse-grained computer simulations in order to study how the placement of melittin and magainin-h2 antimicrobial peptides on the surface of the bilayer changes the local pressure profiles in the bilayer. The simulations were done using the NPT ensemble when the total stress on the bilayer was zero and also using the NP(z)AT ensemble, with a nonzero total stress. In the NPT ensemble, although the total stress was zero, each leaflet of the bilayer experienced a nonzero stress, and the stresses are equal by magnitude, but opposite in their direction. The observed stresses acting on the monolayers may cause the rupture of the monolayers to release the stress. Our simulations were done at different peptide to lipid ratio (P/L). When the P/L ratio was 1/50 there was no large difference in the local pressure profile for bilayers with melittin versus bilayers with magainin-h2. When simulations were performed in the NP(z)AT ensemble at P/L = 3/100 we observed a large difference in the pressure profiles in the bilayers with melittin peptides compared to the bilayer with magainin-h2. The observed in this case difference in stress may explain the difference in actions of melittin and magainin at high P/L. PMID:25299589

Goliaei, Ardeshir; Santo, Kolattukudy P; Berkowitz, Max L

2014-11-01

90

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

NASA Astrophysics Data System (ADS)

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

Mtrich, Nicole; Rutherford, Malcolm J.

1998-04-01

91

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

NASA Astrophysics Data System (ADS)

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

Helgeson, Harold C.

1992-08-01

92

Comparative ecology of H2 cycling in sedimentary and phototrophic ecosystems  

NASA Technical Reports Server (NTRS)

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

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

2002-01-01

93

Determination of the second critical end point in silicate-H 2O systems using high-pressure and high-temperature X-ray radiography  

NASA Astrophysics Data System (ADS)

To determine the second critical end point in silicate-H 2O systems, a new method for the direct observations of immiscible fluids has been developed using a synchrotron X-ray radiography technique. High-pressure and high-temperature experiments were carried out with a Kawai-type, double-stage, multi-anvil high-pressure apparatus (SPEED-1500) installed at BL04B1, SPring-8, Japan. The Sr-plagioclase (SrAl 2Si 2O 8)-H 2O system was used as an illustrative example. A new sample container composed of a metal (Pt) tube with a pair of lids, made of single crystal diamonds, was used under pressures between 3.0 and 4.3 GPa, and temperatures up to 1600C. The sample in the container could be directly observed through the diamond lids with X-ray radiography. At around 980 to 1060C and pressures between 3.0 and 4.0 GPa, light gray spherical bubbles moving upward through the dark gray matrix were observed. The light gray spheres that absorb less X-rays represent an aqueous fluid, whereas the dark gray matrix represents a silicate melt. These two immiscible phases (aqueous fluid and silicate melt) were observed up to 4.0 GPa. At 4.3 GPa, no bubbles were observed. These observations suggest that the second critical end point in the Sr-plagioclase-H 2O system occurs at around 4.2 0.2 GPa and 1020 50C. Our new technique can be applied to the direct observations of various systems with two coexisting fluids under deep mantle conditions.

Mibe, Kenji; Kanzaki, Masami; Kawamoto, Tatsuhiko; Matsukage, Kyoko N.; Fei, Yingwei; Ono, Shigeaki

2004-12-01

94

Stepped pressure profile equilibria in cylindrical plasmas via partial Taylor relaxation  

E-print Network

Stepped pressure profile equilibria in cylindrical plasmas via partial Taylor relaxation HOLE conducting wall. In such plasma states the pressure gradient is zero, and the magnetic field B satisfies, equilibria with stepped pressure profiles can be constructed. Subject to the imposed constraints, these new

Hudson, Stuart

95

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

SciTech Connect

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

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

1984-06-01

96

An optimised scalable synthesis of H2O@C60 and a new synthesis of H2@C60.  

PubMed

New high-yielding synthetic routes to the small-molecule endofullerenes H2O@C60, D2O@C60 and H2@C60 are described. The use of high temperatures and pressures for the endohedral molecule incorporation are avoided. A new partial closure step using PPh3, and final suturing using a novel Diels-Alder/retro-Diels-Alder sequence are amongst the advances reported. PMID:25228024

Krachmalnicoff, Andrea; Levitt, Malcolm H; Whitby, Richard J

2014-11-01

97

Noble Gas Pressure-Induced Broadening and Shift of H 2O and SO 2 Absorption Lines  

NASA Astrophysics Data System (ADS)

Measurements of line broadening and lineshifts induced by collisions with He, Ne, Ar, Kr, and Xe for absorption lines of the ? 1 + 3? 3 band of H 2O and the ? 1 and ? 3 bands of SO 2 were performed by applying laser photoacoustic and diode laser spectroscopy. A modified version of the Anderson-Tsao-Curnutte theory, neglecting Anderson's interrupting, was employed for the description of the collisional half-width and shift behavior of the spectral lines in the case of dipole molecule interactions with noble gas atoms. The comparison of the experimental and calculated data shows that the derived formulae describe precisely the behavior of broadening and shift coefficients and their dependence on the polarizabilities of the perturbing atoms and of the absorbing molecule.

Lazarev, V. V.; Ponomarev, Y. N.; Sumpf, B.; Fleischmann, O.; Waschull, J.; Kronfeldt, H. D.; Stroinova, V. N.

1995-09-01

98

Neutral and ion chemistry in low pressure dc plasmas of H2/N2 mixtures: routes for the efficient production of NH3 and NH4(+).  

PubMed

The chemistry in low pressure (0.8-8 Pa) plasmas of H(2) + 10% N(2) mixtures has been experimentally investigated in a hollow cathode dc reactor using electrical probes for the estimation of electron temperatures and densities, and mass spectrometry to determine the concentration of ions and stable neutral species. The analysis of the measurements by means of a kinetic model has allowed the identification of the main physicochemical mechanisms responsible for the observed distributions of neutrals and ions and for their evolution with discharge pressure. The chemistry of neutral species is dominated by the formation of appreciable amounts of NH(3) at the metallic walls of the reactor through the successive hydrogenation of atomic nitrogen and nitrogen containing radicals. Both Eley-Rideal and Langmuir-Hinshelwood mechanisms are needed in the chain of hydrogenation steps in order to account satisfactorily for the observed ammonia concentrations, which, in the steady state, are found to reach values ~30-70% of those of N(2). The ionic composition of the plasma, which is entirely due to gas-phase processes, is the result of a competition between direct electron impact dissociation, more relevant for high electron temperatures (lower pressures), and ion-molecule chemistry that prevails for the lower electron temperatures (higher pressures). At the lowest pressure, products from the protonation of the precursor molecules (H(3)(+), N(2)H(+) and NH(4)(+)) and others from direct ionization (H(2)(+) and NH(3)(+)) are found in comparable amounts. At the higher pressures, the ionic distribution is largely dominated by ammonium. It is found that collisions of H(3)(+), NH(3)(+) and N(2)H(+) with the minor neutral component NH(3) are to a great extent responsible for the final prevalence of NH(4)(+). PMID:21984202

Carrasco, Esther; Jimnez-Redondo, Miguel; Tanarro, Isabel; Herrero, Vctor J

2011-11-21

99

Method and apparatus for monitoring oxygen partial pressure in air masks  

NASA Technical Reports Server (NTRS)

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

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

2006-01-01

100

Raman and NMR spectroscopic characterization of high-pressure K-cymrite (KAlSi3O8.H2O) and its anhydrous form (kokchetavite)  

NASA Astrophysics Data System (ADS)

To facilitate identification of high-pressure K-cymrite (KAlSi3O8H2O) phase and its anhydrous form (kokchetavite) in natural rocks, we have synthesized both phases and have characterized them by micro-Raman and NMR spectroscopy. K-cymrite was synthesized at 5 GPa and 800 C. Kokchetavite was obtained by dehydrating K-cymrite at ambient pressure and 550 C. The 1H MAS and 1H-29Si CP MAS NMR spectra of K-cymrite are consistent with the reported crystal structure that contains H2O molecules and has a disordered Si-Al distribution. The Raman spectra obtained under ambient conditions for K-cymrite (and kokchetavite) contain major peaks at 114.0 (109.1), 380.2 (390.0) and 832.5 (835.8) cm-1. For K-cymrite, OH stretching vibration is also observed at 3541 cm-1 with a shoulder at 3623 cm-1. The Raman spectrum for kokchetavite is consistent with that previously reported for a natural sample found as inclusions in clinopyroxenes and garnets in a garnet-pyroxene rock. However, the data for K-cymrite are inconsistent with the Raman features of a previously reported relict K-cymrite in K-feldspar from an eclogite. Pressure- and temperature-dependencies of the Raman shifts for the strongest peak of both phases are also reported.

Kanzaki, Masami; Xue, Xianyu; Amalberti, Julien; Zhang, Qian

101

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

102

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

103

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

104

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

EPA Science Inventory

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

105

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

106

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

PubMed Central

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

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

2014-01-01

107

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

108

Comparative Ecology of H2 Cycling in Organotrophic and Phototrophic Ecosystems  

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

109

Synthesis, Separation and Electrical Properties of WO3-x Nanopowders via Partial Pressure High Energy Ball Milling  

NASA Astrophysics Data System (ADS)

Full Text PDF Reduction processes of WO3 nanopowder either with carbon or with hydrogen were observed using X-ray powder diffraction and transmission electron microscope. The phase transformations, separation, grain size and electrical conductivity of WO3-x nanopowder during reductions via partial pressure high energy ball milling have been studied. During the carbon reduction process the monoclinic WO3 structure transforms to nonstoichiometric Magneli phases W40O118, WO2.9 and finally to WO2 and W mixed phases. The Magneli WO3-x phases exhibit specific fringe contrast imaging of well ordered crystallographic shear planes. In comparison, the monoclinic WO3 structure transforms to hydrate WO31/3H2O, hexagonal WO3, non stoichiometric WO2.7 and finally to WO2 and W mixed phases during the hydrogen reduction process. The inclusion of hydrogen atoms between the WO6 octahedral structure shifts the reduction steps to lower milling times. It demonstrates that the formation of hydrate WO3 phases enhances the amenability of the system to reduction. The activation energy for conduction was deduced from the Arrhenius equation and was found to depend on oxygen partial pressure or presence of the hydrogen atoms. The defect band model was used for interpretation of these behaviors. It supposes that the surface oxygen vacancies introduce donor levels in the gap of semiconductor, so free electrons are produced by reduction.

Mohammad, A. Al

2009-08-01

110

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

NASA Technical Reports Server (NTRS)

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

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

1973-01-01

111

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

112

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

NASA Technical Reports Server (NTRS)

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

Holy, John A.

1993-01-01

113

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

Microsoft Academic Search

Deformation mechanisms in room-dry and water-saturated specimens of Charcoal Granodiorite, shortened at 10⁻⁴s⁻¹, at effective pressures (Pe) to 100 MPa and temperatures to partial melting (less than or equal to 1050°C) are documented with a view toward providing criteria to recognize and characterize the deformation for geological and engienering applications. Above 800°C strength decreases dramatically at effective pressures greater than

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

1981-01-01

114

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

Microsoft Academic Search

Two CELSS candidate crops, soybean (Glycine max) and potato (Solanum tuberosum), were grown hydroponically in controlled environments maintained at carbon dioxide (CO2) partial pressures ranging from 0.05 to 1.00 kPa (500 to 10,000 ppm at 101 kPa atmospheric pressure). Plants were harvested at maturity (90 days for soybean and 105 days for potato) and all tissues analyzed for proximate nutritional

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

1994-01-01

115

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

E-print Network

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

Manning, Craig

116

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

NASA Astrophysics Data System (ADS)

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

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

2011-07-01

117

Effect of gas pressure on partial discharge in voids in epoxy  

Microsoft Academic Search

The pressure inside an enclosed void in a solid dielectric is generally determined by calculation based on equating the measured partial discharge (PD) onset voltage and the breakdown voltage from the Paschen curve for a particular gas. Here it is assumed that the gas is known or that physical properties remain approximately constant. In the present experiment, two different large

D. R. James; I. Sauers; A. R. Ellis; M. O. Pace; D. J. Deschenes

2003-01-01

118

Measurement and Control of Oxygen Partial Pressure in an Electrostatic Levitator  

NASA Technical Reports Server (NTRS)

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

SanSoucie, Michael P.; Rogers, Jan R.

2014-01-01

119

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

NASA Astrophysics Data System (ADS)

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 melts of the dominant felsic Sulu gneiss. Partial melting may be the key to solving several unusual features of the Sulu and other UHP terranes, such as the almost complete lack of mineralogical evidence for UHP conditions and the limited growth of zircon during UHP conditions in the dominant felsic gneiss. In addition, because partial melting will cause a drastic reduction in the strength of the UHP gneisses, the most likely exhumation mechanism is diapiric rise of a low-viscosity, partially molten mass containing entrained blocks of eclogite, and not a thin sheet as usually proposed.

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

2005-02-01

120

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

121

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

122

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

USGS Publications Warehouse

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

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

2005-01-01

123

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

124

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

125

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

NASA Technical Reports Server (NTRS)

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

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

1979-01-01

126

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

PubMed Central

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

Tadimalla, Sirisha; Momot, Konstantin I.

2014-01-01

127

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

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

128

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

PubMed

The aim of the study reported in this paper is to investigate the role of the high partial pressure of hydrogen introduced during the growth of nanocrystalline silicon carbide thin films (nc-SiC:H). For this purpose, we report the preparation as well as spectroscopic studies of four series of nc-SiC:H obtained by radio-frequency magnetron sputtering at high partial pressure of hydrogen by varying the percentage of H2 in the gas mixture from 70% to 100% at common substrate temperature (TS=500C). The effects of the dilution on the structural changes and the chemical bonding of the different series have been studied using Fourier transform infrared and Raman spectroscopy. For this range of hydrogen dilution, two groups of films were obtained. The first group is characterized by the dominance of the crystalline phase and the second by a dominance of the amorphous phase. This result confirms the multiphase structure of the grown nc-SiC:H thin films by the coexistence of the SiC network, carbon-like and silicon-like clusters. Furthermore, infrared results show that the SiC bond is the dominant absorption peak and the carbon atom is preferentially bonded to silicon. The maximum value obtained of the crystalline fraction is about 77%, which is relatively important compared to other results obtained by other techniques. In addition, the concentration of CHn bonds was found to be lower than that of SiHn for all series. Raman measurements revealed that the crystallization occurs in all series even at 100% H2 dilution suggesting that high partial pressure of hydrogen favors the formation of silicon nanocrystallites (nc-Si). The absence of both the longitudinal acoustic band and the transverse optical band indicate that the crystalline phase is dominant. PMID:25459700

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

2014-10-22

129

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

NASA Astrophysics Data System (ADS)

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

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

1997-02-01

130

Oxidation of C/SiC Composites at Reduced Oxygen Partial Pressures  

NASA Technical Reports Server (NTRS)

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

Opila, Elizabeth J.; Serra, Jessica

2009-01-01

131

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

Microsoft Academic Search

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

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

2009-01-01

132

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

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

133

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

SciTech Connect

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

Elizondo-Villarreal, E.M.

1989-01-01

134

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

SciTech Connect

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

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

1980-01-01

135

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

136

Influence of Oxygen Partial Pressure on the Fermi Level of ZnO Films Investigated by Kelvin Probe Force Microscopy  

NASA Astrophysics Data System (ADS)

The influence of oxygen partial pressure on the Fermi level of ZnO films prepared by pulsed laser deposition is investigated. The contact potential difference of the ZnO films fabricated under various oxygen partial pressures is studied systematically using Kelvin probe force microscopy. The Fermi level shifted by 0.35 eV as oxygen partial pressure increased. This indicates a significant change in the electronic structure and energy balance in ZnO films. This fact provides a consistent explanation that the changes in carrier concentration, resistivity and mobility of ZnO films are attributed to oxygen vacancy induced shift of the Fermi level.

Su, Ting; Zhang, Hai-Feng

2012-12-01

137

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

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

138

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

PubMed

Two CELSS candidate crops, soybean (Glycine max) and potato (Solanum tuberosum), were grown hydroponically in controlled environments maintained at carbon dioxide (CO2) partial pressures ranging from 0.05 to 1.00 kPa (500 to 10,000 ppm at 101 kPa atmospheric pressure). Plants were harvested at maturity (90 days for soybean and 105 days for potato) and all tissues analyzed for proximate nutritional composition (i.e. protein, fat, carbohydrate, crude fiber, and ash content). Soybean seed ash and crude fiber were higher and carbohydrate was lower than values reported for field-grown seed. Potato tubers showed little difference from field-grown tubers. With the exception of increased crude fiber of soybean seed with increased CO2, no trends were apparent with regard to CO2 effects on proximate composition of soybean seed and potato tubers. Crude fiber of soybean stems and leaves increased with increased CO2, as did soybean leaf protein (total nitrogen). Potato leaf and stem (combined) protein levels also increased with increased CO2, while leaf and stem carbohydrates decreased. Values for leaf and stem protein and ash were higher than values generally reported for field-grown plants for both species. Results suggest that CO2 partial pressure should have little influence on proximate composition of potato tubers or soybean seed, but that high ash and protein levels might be expected from leaves and stems of crops grown in controlled environments of a CELSS. PMID:11540178

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

1994-11-01

139

Catalytic hydrodechlorination at low hydrogen partial pressures: Activity and selectivity response  

Microsoft Academic Search

The gas phase hydrodechlorination (HDC) of chlorobenzene (CB) and 1,3-dichlorobenzene (DCB) (373K?T?423K, Ptotal=1atm) was performed over Pd\\/SiO2 (1.48.3%, w\\/w Pd) where the hydrogen partial pressure (PH2) was varied from 0.046 to 0.925atm. The catalysts have been characterized in terms of BET area, temperature programmed reduction (TPR), hydrogen chemisorption\\/temperature programmed desorption (TPD) and TEM analyses. The HDC response to changes in

Satyakrishna Jujjuri; Mark A. Keane

2010-01-01

140

[Transcutaneous determination of partial oxygen pressure and local blood flow in human orthostatic exposure].  

PubMed

Using a Drger oximeter (the FRG) modified by a Clark polarographic electrode, transdermal measurements of partial pressure of oxygen (PtdO2) and local blood flow (Q) were carried out in 46 test subjects during tilt tests (20 min). As a result of blood redistribution, at minute 1 Q increased significantly in the lower body (p less than 0.01) and decreased in the upper body (p less than 0.01). Regardless of the sensor location, PtdO2 increased in most cases. PMID:7120907

Ozerova, O E; Asiamolova, N M; Kochetov, A K

1982-01-01

141

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

NASA Technical Reports Server (NTRS)

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

1996-01-01

142

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

143

Partial melting of dry peridotites at high pressures: Determination of compositions of melts segregated from peridotite using aggregates of diamond  

Microsoft Academic Search

The compositions of melts formed by partial melting of two relatively fertile spinel lherzolites were determined at pressures between 10 and 30 kbar under dry conditions using a layer of diamond aggregates sandwiched between peridotite layers. Partial melts segregate and migrate into the pore space between diamond grains soon after their formation. Overgrowth of minerals at quenching modifies the composition

Kei Hirose; Ikuo Kushiro

1993-01-01

144

The influence of pressure on the activity coefficients of the solutes and on the solubility of minerals in the system Na-Ca-Cl-SO 4-H 2O to 200C and 1 kbar and to high NaCl concentration  

NASA Astrophysics Data System (ADS)

A model is presented which is used to calculate the effect of pressure on activity coefficients of aqueous solutes in the system Na-Ca-Cl-SO 4-H 2O to 200C. Literature data for the density and compressibility of aqueous binary solutions of Na 2SO 4 and CaCl 2 to 200C are used to calculate the first and second pressure derivatives of Pitzer's ion interaction model parameters, as well as the standard molal compressibility and volume of these two salts. Empirical correlations between the apparent molal volume and compressibility of the aqueous electrolytes are used to guide the choice of the temperature dependent expressions used for the numerical representation of the derivatives of Pitzer's parameters with respect to pressure. For sodium sulfate solutions, such correlations are used to extrapolate compressibilities to 200C. The change in the thermodynamic properties of the-CaSO 04 ion pair with pressure is taken into account by the variation of its dissociation constant. The volumetric properties (partial molal volumes and compressibilities) of multicomponent solutions in the Na-Ca-Cl-SO 4-H 2O system can be predicted from the information generated here and the volumetric equations of ROGERS and PITZER (1982) for NaCl. This model is then combined with the high temperature model of MOLLER (1988) of the same system in order to calculate activity coefficients at high pressures to 200C. The resulting model is validated by comparing calculated and measured solubilities of anhydrite and gypsum in pure water and in NaCl solutions up to 6 M. The agreement between the calculated and measured solubilities of the calcium sulfates is typically better than 10% up to 200C and 1 kbar. The relevance of temperature and pressure corrections to the activity coefficients of aqueous solutes is discussed in regard to the assumed accuracy with which geochemical models are able to calculate mineral solubilities.

Monnin, Christophe

1990-12-01

145

Molecular simulation study of the competitive adsorption of H2O and CO2 in zeolite 13X.  

PubMed

The presence of H2O in postcombustion gas streams is an important technical issue for deploying CO2-selective adsorbents. Because of its permanent dipole, H2O can interact strongly with materials where the selectivity for CO2 is a consequence of its quadrupole interacting with charges in the material. We performed molecular simulations to model the adsorption of pure H2O and CO2 as well as H2O/CO2 mixtures in 13X, a popular zeolite for CO2 capture processes that is commercially available. The simulations show that H2O reduces the capacity of these materials for adsorbing CO2 by an order of magnitude and that at the partial pressures of H2O relevant for postcombustion capture, 13X will be essentially saturated with H2O . PMID:24313865

Joos, Lennart; Swisher, Joseph A; Smit, Berend

2013-12-23

146

DEVELOPMENT OF PRESSURIZED CIRCULATIONG 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 block that offers all the advantages of coal gasification but in a more user-friendly form; it is also fuel flexible in that it can use alternative fuels such as biomass, sewerage sludge, etc. This report describes the work performed during the January 1--March 31, 2003 time period.

Archie Robertson

2003-04-17

147

Pressure-induced elastic and structural changes in hydrous basalt glasses: The effect of H2O on the gravitational stability of basalt melts at the base of the upper mantle  

NASA Astrophysics Data System (ADS)

To understand the effect of hydration on the elastic properties of silicate melts, we conducted in situ high-pressure Brillouin scattering measurements on two hydrous basalt glasses with different water contents in diamond anvil cells. Second-order phase transitions were observed in the hydrous basalt glasses and are due to the topological rearrangement of the silicate network to a high [Si, Al]-O coordination. Up to a pressure of 10 GPa at 300 K, the extra 2.23 wt% H2O lowers the elastic moduli of FX-2 basalt glass (2.69 wt% H2O) by 10%-18%, but does not affect the pressure derivatives of the elastic moduli, compared with FX-1 (0.46 wt% H2O) basalt glass. The phase transition takes place at a higher pressure in FX-2 compared with FX-1, possibly because of the depolymerization of water to silicate glass. Water interacts with network-forming cations and creates Si-OH and Al-OH groups, and prohibits nonbridging oxygen ions from being connected to other nearby framework cations (i.e., [5,6](Si, Al)), resulting in the hysteresis of the second-order phase transition. The density contrasts of our hydrous basalt melts with previous mid-ocean ridge basalt and preliminary reference Earth model data indicate that basalt melts may need very low water content (<0.46 wt% H2O) to maintain gravitational stability at the base of the upper mantle. Our results show that the elastic properties of hydrous silicate melts may have important implications for the dynamic evolution and chemical differentiation of the mantle.

Wu, Lei; Yang, De-Bin; Xie, Hong-Sen; Li, Fang-Fei; Hu, Bo; Yu, Yang; Xu, Wen-Liang; Gao, Chun-Xiao

2014-11-01

148

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

NASA Technical Reports Server (NTRS)

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

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

1995-01-01

149

Direct synthesis of H 2O 2 in methanol at low pressures over Pd\\/C catalyst: Semi-continuous process  

Microsoft Academic Search

The production of H2O2via direct synthesis has been studied in depth over the last decades, due to the possibilities given by the discovery of active catalysts based on nanotechnology and selective active metals. However, the process is also complicated because of the coexistence of three phases, where mass transfer between gas and liquid (solvent) limits the concentration of O2 and

Teresa Moreno; Juan Garca-Serna; Pawel Plucinski; Mara Jess Snchez-Montero; Mara Jos Cocero

2010-01-01

150

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

151

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

SciTech Connect

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

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

2009-09-15

152

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

SciTech Connect

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

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

1981-01-01

153

Speciation and kinetics related to catalytic carbonylation in the presence of cis-[Ir(CO)2I2]P(C6H5)4 under CO and H2 pressures.  

PubMed

The differences in the reactivities of the square-planar complexes cis-[Rh(CO)2I2]- (1) and cis-[Ir(CO)2I2]- (2), involved in the catalytic carbonylation of olefins, are investigated, with P(C6H5)4+ as the counterion, by ambient- and high-pressure NMR and IR spectroscopy. Under an elevated pressure of CO, 1 and 2 form the [M(CO)3I] complexes with the equilibrium constants KIr approximately 1.8 x 10(-3) and KRh approximately 4 x 10(-5). The ratio KIr/KRh close to 50 shows that, under catalytic conditions (a few megapascals), only complex 1 remains in the anionic form, while a major amount of the iridium analogue 2 is converted to a neutral species. The oxidative addition reactions of HI with 1 and 2 give two monohydrides of different geometries, mer,trans-[HRh(CO)2I3]- (3) and fac,cis-[HIr(CO)2I3]- (4), respectively. Both hydrides are unstable at ambient temperature and form, within minutes for Rh and within hours for Ir, the corresponding cis-[M(CO)2I2]- (1 or 2) and [M(CO)2I4]- (5 or 6) species and H2. When an H2 pressure of 5.5 MPa is applied to a nitromethane solution of complex 2, ca. 50% of 2 is transformed to cis-dihydride complexes. The formation of cis,cis,cis-[IrH2(CO)2I2]- (8a) is followed by intermolecular rearrangements to form cis,trans,cis-[IrH2(CO)2I2]- (8b) and cis,cis,trans-[IrH2(CO)2I2]- (8c). A small amount of a dinuclear species, [Ir2H(CO)4I4]x- (9), is also observed. The formation rate constants for 8a and 8b at 262 K are k1(262) = (4.42 +/- 0.18) x 10(-4) M-1 s-1, k-1(262) = (1.49 +/- 0.07) x 10(-4) s-1, k2(262) = (2.81 +/- 0.04) x 10(-5) s-1, and k-2(262) = (5.47 +/- 0.16) x 10(-6) s-1. The two equilibrium constants K1(262) = [8a]/([2][H2]) = 2.97 +/- 0.03 M-1 and K2(262) = [8b]/[8a] = 5.13 +/- 0.10 show that complex 8b is the thermodynamically stable addition product. However, no similar H2 addition products of the rhodium analogue 1 are observed. The pressurization with H2 of a solution containing 2 and 6 give the monohydride 4, the dihydrides 8a and 8b, the dinuclear complex 9, and the two new complexes [Ir(CO)2I3] (10) and [HIr(CO)2I2] (11). The reactions of the iridium complexes with H2 and HI are summarized in a single scheme. PMID:11198871

Churlaud, R; Frey, U; Metz, F; Merbach, A E

2000-09-01

154

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

PubMed Central

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

2013-01-01

155

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

NASA Astrophysics Data System (ADS)

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

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

2011-08-01

156

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

157

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

158

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

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

159

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

160

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

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

161

Soybean seed growth in response to long-term exposures to differing oxygen partial pressures.  

PubMed

Short-term studies have indicated that alterations in the oxygen partial pressure (pO(2)) around developing soybean (Glycine max [L.] Merr.) seeds may alter seed growth characteristics. A 2-year field study was undertaken to determine the effects on seed development of long-term exposures of individual pods to either sub-ambient or supra-ambient pO(2). Pod chambers were used through which fixed pO(2) were continuously flowed throughout seed development. No effects on maturity date were observed from exposures to either sub-ambient or supra-ambient pO(2). On the other hand, seed weight was reduced by 0.10 pO(2) in both years of the study implicating an O(2) limitation on seed growth rate at this fairly high pO(2). In 1 of the 2 years, supra-ambient pO(2) resulted in increased seed weight. PMID:16665271

Sinclair, T R; Ward, J P; Randall, C A

1987-03-01

162

Physical Mechanisms of Failure, Ultralow Partial Pressure Lubrication, and the Reservoir Effect in MEMS  

NASA Astrophysics Data System (ADS)

The aim of this work is to examine the effectiveness of self-assembled monolayer (SAM) coatings as long term lubrication coatings in microsystems, to examine the failure regimes of SAM coated devices, to examine the role of mobility in adsorbed lubricating films, and to examine evolution of the coefficient of friction of devices surrounded by ultralow partial pressures of alcohols up to saturation. Finally the role of self assembled monlayers in vapor phase lubrication is examined. Self-assembled monolayers are ubiquitous in fabrication of free-standing microdevices because of their ability to prevent release related and dormancy related stiction. However their ability to lubricate under sliding and normal contact conditions is not well documented. It can be shown that the energy dissipated per unit area in one sliding cycle due to friction is significant under general loading conditions. Therefore from an energy dissipated standpoint the bond energies of the silane molecules should not be enough to withstand even a short number of cycles. An extension of this is the energy imparted to the surface through a normal loading cycle through a loss of kinetic energy. It can also be shown that this is enough to break the silicon oxygen bonds however this is over a longer time scale than in sliding. Also there is an open question on the role of mobile and non-mobile adsorbed species on friction. Is the mobility of a molecule/layer on a surface an indicator of the effectiveness of the lubrication potential of the layer? Do submonolayer coverages of alcohols "lock-up" to contacting surfaces by disrupting non-corrogated potentials? Is there a distinct lowering of frictional forces at the formation of a monolayer? Controlled adsorption of mobile and non-mobile species on rubbing contacts is necessary to elucidate this physical relationship. To accomplish this one must take into account that friction measurements are highly scale dependant. Therefore to ensure the accuracy of measurements relating to microsystem contact conditions experiments must be conducted on actual microdevices. In the work presented here I have used microelectromechanical system (MEMS) tribometers to measure the friction and adhesive forces of SAM coated surfaces over the coarse of many sliding cycles as well as normal contacting cycles. It is shown that robustly adhered monolayer coatings degrade extremely rapidly and there is a direct correlation between the respective energies dissipated both in sliding and normal contacting cycles and the time it takes for the layers to degrade. Also it is shown that devices fail in two main modes: one where wear of the devices in the form of dislocation of polysilicon grains leads to a low/adhesion high wear regime and another where high adhesive forces are developed and the devices fail with little to no wear. In the studies of ultra low partial pressure lubrication of devices a clear correlation between lubricant mobility to device lubrication is observed even in the presence of a vapor, which should in principle be able to replenish removed lubricant in between sliding cycles. We show that ultralow partial pressures nominally corresponding to submonolayer coverages of ethanol and pentanol show a distinct decrease in coefficient of friction and lubricate MEMS microcontacts however this is only loosely correlated to their effectiveness as lubricants. Pentanol was only shown to lubricate at the point at which it becomes mobile on the surface where as ethanol is mobile at all times and lubricates effectively at very low partial pressures. Trifluoroethanol is not mobile at any portion of its isotherm and does not effectively lubricate the contacts. We also show the ability of the surrounding SAM to act as a lubricant reservoir when vapors of ethanol are removed. The correlation of lubricant mobility to lubrication can be used to predict the effectiveness to new lubricants as well as allow for the tailoring of lubricants to specific applications.

Hook, David Adam

163

Real-time visualization of oxygen partial pressures in straight channels of running polymer electrolyte fuel cell with water plugging  

NASA Astrophysics Data System (ADS)

Visualization inside polymer electrolyte fuel cells (PEFCs) for elucidating the reaction distributions is expected to improve the performance, durability, and stability. An oxygen-sensitive film of a luminescent porphyrin was used to visualize the oxygen partial pressures in five straight gas-flow channels of a running PEFC with liquid-water blockages formed at the end of the channels. The blockage greatly lowered and unstabilized the cell voltage. The oxygen partial pressure decreased nearly to 0 kPa in the blocked channel. With a water blockage in a channel, the oxygen partial pressures in the adjacent channels were lowered due to an extra demand of oxygen consumption. When the number of the blocked channels increased, the oxygen partial pressure in the unblocked channels became much lowered. When the water blockages disappeared, the oxygen partial pressures quickly returned to the values before plugging. The influence of the cross flows of air through the gas diffusion layers in straight channels was much smaller than that in serpentine flow channels.

Nagase, Katsuya; Suga, Takeo; Nagumo, Yuzo; Uchida, Makoto; Inukai, Junji; Nishide, Hiroyuki; Watanabe, Masahiro

2015-01-01

164

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

165

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

SciTech Connect

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

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

2008-01-01

166

H2 in Galaxies  

E-print Network

The bulk of the molecular gas in spiral galaxies is under the form of cold H2, that does not radiate and is only suspected through tracer molecules, such as CO. All tracers are biased, and in particular H2 could be highly underestimated in low metallicity regions. Our knowledge is reviewed of the H2 content of galaxies, according to their types, environment, or star-forming activities. The HI and CO components are generally well-mixed (spiral arms, vertical distribution), although their radial distributions are radically different, certainly due to radial abundance gradients. The hypothesis of H2 as dark matter is discussed, as well as the implications on galaxy dynamics, or the best perspectives for observational tests.

F. Combes

1999-10-15

167

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

168

Formation of Plutonium Hydride PuH2: Description of the Reaction Rate Surface as a Function of Pressure and Temperature  

Microsoft Academic Search

T he hydriding reaction of plutonium metal is used increasingly in the recovery and processing of plutonium. There is thus an increased need for an understanding not only of the thermodynamic parameters governing the reaction, but also of the kinetic behavior to be expected with variations in process parameters such as pressure and temperature . A mathematical description of the

Roberta N. Mulford; Damian C. Swift

2003-01-01

169

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

170

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

USGS Publications Warehouse

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

Rosenbauer, R.; Koksalan, T.

2004-01-01

171

Formation of plutonium hydride PuH2: description of the reaction rate surface as a function of pressure and temperature.  

SciTech Connect

T he hydriding reaction of plutonium metal is used increasingly in the recovery and processing of plutonium. There is thus an increased need for an understanding not only of the thermodynamic parameters governing the reaction, but also of the kinetic behavior to be expected with variations in process parameters such as pressure and temperature . A mathematical description of the behavior of the hydriding process in the entire reaction space in P, T, and rate provides a predictive capability, and enables the reaction rate to be optimized. In addition, given a well-defined description of this rate surface as a function of pressure and temperature, process parameters may be selected to optimize other important parameters such as particle size . These parameters may in some cases be mapped as regions or separate functions onto the surface described here .

Mulford, R. N. (Roberta N.); Swift, D. C. (Damian C.)

2003-01-01

172

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

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

173

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

174

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

NASA Astrophysics Data System (ADS)

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

Zentkov, M.; Mihalik, M.; Arnold, Z.; Kamard, J.

2010-01-01

175

Internally consistent thermodynamic data for high-pressure and ultrahigh-pressure phases in the system CaO-MgO-Al2O3-SiO2-H2O  

NASA Astrophysics Data System (ADS)

In order to enable reliable calculations of phase relations among high-pressure phases the Berman [1] data set was augmented by data for the high-pressure phases stishovite (stv), topaz-OH (toz-OH), phase pi (pi), Mg-staurolite (Mg-st), Mg-sursassite (Mg-sur), and Mg-chloritoid (Mg-cld) using a similar optimization technique as described by Berman et al. [2]. The data of several other phases of the system CaO-MgO- Al2O3-SiO2-H2O obtained in the Berman data base were slightly refined to keep the consistency to the reversal brackets and the originally measured data: andalusite (and), clinochlore (chl), coesite (cs), diaspore (dsp), kaolinite (kln), kyanite (ky), lawsonite (lws), pyrophyllite (prl), sillimanite (sil), zoisite (zo). CP-data were kept constant [1] or estimated [3]. phase; ?fH0298 (kJ mol-1); S0298 (J K-1 mol-1); V0298 (J K-1 mol-1); v1105 (bar-1); v21012 (bar-2); v3105 (K-1); v4108 (K-2) and; -2589.857; 91.47; 5.146; -0.0653; 0.000; 2.291; 0.170 chl; -8903.532; 437.92; 21.000; -0.1328; 3.837; 2.142; 0.962 Mg-cld; -3551.657; 142.20; 6.874; -0.0692; 0.000; 2.544; 0.000 cs; -907.510; 39.63; 2.064; -0.0998; 1.823; 0.620; 0.960 dsp; -999.115; 35.22; 1.776; -0.0719; 0.629; 3.245; 0.684 kln; -4119.400; 204.18; 9.952; -0.1200; 0.000; 3.200; 0.000 ky; -2593.767; 82.71; 4.408; -0.0593; 1.021; 1.730; 0.787 lws; -4866.665; 228.04; 10.155; -0.0825; 0.000; 3.339; 0.000 Mg-sur; -13907.329; 608.39; 26.888; -0.0826; 0.923; 3.187; 0.087 pi; -9586.742; 403.23; 18.559; -0.0678; 0.000; 2.254; 0.000 prl; -5640.501; 239.43; 12.782; -0.1800; 0.000; 2.621; 0.000 sil; -2586.169; 95.40; 4.984; -0.0601; 1.341; 1.138; 0.605 Mg-st; -24998.289; 944.53; 44.260; -0.0579; 0.000; 2.017; 0.000 stv; -870.861; 25.59; 1.401; -0.0318; 0.000; 1.849; 0.000 toz-OH; -2885.939; 117.40; 5.352; -0.0630; 0.000; 1.938; 0.000 zo; -6889.494; 297.20; 13.565; -0.0695; 0.000; 2.752; 0.000 References [1] R.G. Berman, J. Petrol., 1988, 29, 445 [2] R.G. Berman et al., J. Petrol., 1986, 27, 1331 [3] R.G. Berman, T.H. Brown, Con. Min. Pet., 1985, 89, 168

Grevel, K. D.

2008-12-01

176

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

177

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

PubMed

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

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

2014-12-10

178

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

179

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

180

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

181

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

NASA Astrophysics Data System (ADS)

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

Takayanagi, Masayoshi; Kurisaki, Ikuo; Nagaoka, Masataka

2014-04-01

182

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

PubMed

In order to understand the emission of greenhouse gases (CO2) from the river-type reservoir, this study investigated the partial pressure of CO2 [p(CO2)], in the surface water, inflow waters, outflow waters of the Wan'an reservoir in China in the May 2009. p(CO2) in the inflow water, outflow water were calculated from titration method, and the surface water p(CO2) was measured underway using a continuous measurement system (equilibrator-NDIR system). Results showed that the inflow water from the Zhangshui, Meijiang, Taojiang have higher p(CO2) than atmosphere level, with the values of 211.5, 91.7, 259.7 Pa respectively. p(CO2) in the surface water of the incoming section of Wan'an reservoir was between 180-210 Pa, and in the middle section and central section near the dam, p(CO2) in the surface water were about 140-180 Pa and 70-110 Pa. In the outflow waters, p(CO2) reached to 176.2 Pa, higher than that in central section. As a result, it can be concluded that the surface water, inflow waters, outflow waters in the Wan'an reservoir are all the source to CO2. However there is clear evidence showing that the reservoir indeed has a role in mitigating the CO2 emission in this case. PMID:21404665

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

2011-01-01

183

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

SciTech Connect

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

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

1992-02-01

184

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

SciTech Connect

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

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

1992-02-01

185

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

NASA Technical Reports Server (NTRS)

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

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

1980-01-01

186

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

SciTech Connect

Graphical abstract: - Highlights: Microstructural and optical properties are studied systematically. The optical properties are studied by UVvisible and photoluminescence. The PL spectra shows two peaks correspond to bandgap of anatase and rutile. The maximum refractive index of 2.73 is obtained for rutile phase of titania. - Abstract: Nanocrystalline titanium oxide (TiO{sub 2}) thin films were deposited on silicon (1 0 0) and quartz substrates at various oxygen partial pressures (1 10{sup ?5} to 3.5 10{sup ?1} mbar) with a substrate temperature of 973 K by pulsed laser deposition. The microstructural and optical properties were characterized using Grazing incidence X-ray diffraction, atomic force microscopy, UVvisible spectroscopy and photoluminescence. The X-ray diffraction studies indicated the formation of mixed phases (anatase and rutile) at higher oxygen partial pressures (3.5 10{sup ?2} to 3.5 10{sup ?1} mbar) and strong rutile phase at lower oxygen partial pressures (1 10{sup ?5} to 3.5 10{sup ?3} mbar). The atomic force microscopy studies showed the dense and uniform distribution of nanocrystallites. The root mean square surface roughness of the films increased with increasing oxygen partial pressures. The UVvisible studies showed that the bandgap of the films increased from 3.20 eV to 3.60 eV with the increase of oxygen partial pressures. The refractive index was found to decrease from 2.73 to 2.06 (at 550 nm) as the oxygen partial pressure increased from 1.5 10{sup ?4} mbar to 3.5 10{sup ?1} mbar. The photoluminescence peaks were fitted to Gaussian function and the bandgap was found to be in the range ?3.283.40 eV for anatase and 2.983.13 eV for rutile phases with increasing oxygen partial pressure from 1 10{sup ?5} to 3.5 10{sup ?1} mbar.

Balakrishnan, G., E-mail: bala_physics76@yahoo.co.uk [Department of Mechanical Engineering, Changwon National University, Changwon 641773 (Korea, Republic of); Department of Mechanical Engineering, Bharath University, Chennai 600073 (India); Bandi, Vengala Rao [Department of Physics, Changwon National University, Changwon 641773 (Korea, Republic of); Rajeswari, S.M.; Balamurugan, N. [Department of Physics, PERI Institute of Technology, Chennai 600048 (India); Babu, R. Venkatesh [Department of Mechanical Engineering, Bharath University, Chennai 600073 (India); Song, J.I., E-mail: jisong@changwon.ac.kr [Department of Mechanical Engineering, Changwon National University, Changwon 641773 (Korea, Republic of)

2013-11-15

187

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

188

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

NASA Astrophysics Data System (ADS)

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

Sekimoto, K.; Takayama, M.

2010-12-01

189

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

190

H2O subduction beyond arcs  

NASA Astrophysics Data System (ADS)

The amount of H2O subducted to postarc depths dictates such disparate factors as the generation of arc and back-arc magmas, the rheology of the mantle wedge and slab, and the global circulation of H2O. Perple_X was used to calculate phase diagrams and rock physical properties for pressures of 0.5-4.0 GPa and temperatures of 300-900C for a range of bulk compositions appropriate to subduction zones. These data were merged with global subduction zone rock fluxes to generate a model for global H2O flux to postarc depths. For metasomatized igneous rocks, subducted H2O scales with bulk rock K2O in hot slabs. Metasomatized ultramafic rocks behave similarly in cold slabs, but in hot slabs carry no H2O to magma generation depths because they lack K2O. Chert and carbonate are responsible for minimal H2O subduction, whereas clay-rich and terrigenous sediments stabilize several hydrous phases at low temperature, resulting in significant postarc slab H2O flux in cold and hot slabs. Continental crust also subducts much H2O in cold slabs because of the stability of lawsonite and phengite; in hot slabs it is phengite that carries the bulk of this H2O to postarc depth. All told, the postarc flux of H2O in cold slabs is dominated by terrigenous sediment and the igneous lower crust and mantle and is proportional to bulk rock H2O. In contrast, in hot slabs the major contributors of postarc slab H2O are metasomatized volcanic rocks and subducted continental crust, with the amount of postarc slab H2O scaling with K2O. The Andes and Java-Sumatra-Andaman slabs are the principal suppliers of pelagic and terrigenous sediment hosted H2O to postarc depths, respectively. The Chile and Solomon arcs contribute the greatest H2O flux from subducted continental and oceanic forearc, respectively. The Andean arc has the greatest H2O flux provided through subduction of hydrated ocean crust and mantle. No correlation was observed between postarc slab H2O flux and slab seismicity.

Hacker, Bradley R.

2008-03-01

191

Structural studies of diorganotin(IV) sulphonates The crystal structures of [( nC 4H 9) 2Sn{?-OSO 2C 6H 2(CH 3) 3} 2] n and its partially hydrolyzed product [( nC 4H 9) 2Sn{(?-OH)(?-OSO 2C 6H 2(CH 3) 3)}] n  

Microsoft Academic Search

The X-ray crystal structures of [(n-C4H9)2Sn{?-OSO2C6H2(CH3)3}2]n (1) and [(n-C4H9)2Sn{(?-OH)(?-OSO2C6H2(CH3)3)}]n (2) were determined to delineate the coordination behaviour of the sulphonate group with tin(IV) and to evaluate the metal sulphonate bonding interactions. The synthesis of 1 has been achieved by azeotropic dehydration of di-n-butyltin(IV) oxide and mesitylenesulphonic acid. 1 is polymeric containing six-coordinate tin and crystallizes from anhydrous toluene in the

Ramesh Kapoor; Anand Gupta; Pratibha Kapoor; Paloth Venugopalan

2001-01-01

192

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

PubMed

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

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

2014-08-15

193

Global Autocorrelation Scales of the Partial Pressure of Oceanic CO2  

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

194

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

E-print Network

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

Antonovics, Janis

195

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

NASA Astrophysics Data System (ADS)

In this work, the effect of the Xe partial pressure on the excimer vacuum ultraviolet (VUV) emission intensity of the plasma display panels is investigated, both by measuring the spectral emission directly and by two-dimensional simulations. Experimentally, we find that at the high Xe partial pressure levels, there is an supra-linear increase of excimer VUV radiation and that determines the strong increase of luminance at the high pressures and high voltage. Due to the increase of the luminance and the almost unchanged discharge current, the luminous efficacy strongly increases with the Xe partial pressure. In addition, we also investigated the dynamics of the VUV generation, by measuring the decay time of the excimer VUV light as a function of the gas pressure. It is found that the decay time decreases with the increase of gas pressure. The spatial characteristics of the excimer VUV emission are also discussed. Different from the Ne and near-infrared emission, the excimer VUV emission is generated near the surface of the electrodes and increases uniformly on both sides of the anode and cathode (i.e., the bulk plasma region). Most importantly, it is found that the VUV production occurs during the afterglow period, while it is almost zero at the moment of the discharge itself. From the simulations, it can be seen that the Xe2*(3?u+) excimer species, which are generated from Xe*(1s5), play a dominant role in the excimer VUV emission output at the high Xe partial pressure. The two-dimensional simulations also show that the strong increase of Xe excimer excitation states in the case of high pressure is mainly the result of the high conversion efficiency of the Xe excimer states, especially in the afterglow period. Due to the high conversion efficiency of Xe excitation species to Xe excimer species by the high collision rate in the case of high pressure, there is a strong increase of excimer VUV production, especially from the cathode.

Zhu, Di; Zhang, Xiong; Kajiyama, Hiroshi

2012-08-01

196

[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

1986-01-01

197

Experimental investigation on thermochemical sulfate reduction by H2S initiation  

USGS Publications Warehouse

Hydrogen sulfide (H2S) is known to catalyze thermochemical sulfate reduction (TSR) by hydrocarbons (HC), but the reaction mechanism remains unclear. To understand the mechanism of this catalytic reaction, a series of isothermal gold-tube hydrous pyrolysis experiments were conducted at 330 ??C for 24 h under a constant confining pressure of 24.1 MPa. The reactants used were saturated HC (sulfur-free) and CaSO4 in the presence of variable H2S partial pressures at three different pH conditions. The experimental results showed that the in-situ pH of the aqueous solution (herein, in-situ pH refers to the calculated pH of aqueous solution under the experimental conditions) can significantly affect the rate of the TSR reaction. A substantial increase in the TSR reaction rate was recorded with a decrease in the in-situ pH value of the aqueous solution involved. A positive correlation between the rate of TSR and the initial partial pressure of H2S occurred under acidic conditions (at pH ???3-3.5). However, sulfate reduction at pH ???5.0 was undetectable even at high initial H2S concentrations. To investigate whether the reaction of H2S(aq) and HSO4- occurs at pH ???3, an additional series of isothermal hydrous pyrolysis experiments was conducted with CaSO4 and variable H2S partial pressures in the absence of HC at the same experimental temperature and pressure conditions. CaSO4 reduction was not measurable in the absence of paraffin even with high H2S pressure and acidic conditions. These experimental observations indicate that the formation of organosulfur intermediates from H2S reacting with hydrocarbons may play a significant role in sulfate reduction under our experimental conditions rather than the formation of elemental sulfur from H2S reacting with sulfate as has been suggested previously (Toland W. G. (1960) Oxidation of organic compounds with aqueous sulphate. J. Am. Chem. Soc. 82, 1911-1916). Quantification of labile organosulfur compounds (LSC), such as thiols and sulfides, was performed on the products of the reaction of H2S and HC from a series of gold-tube non-isothermal hydrous pyrolysis experiments conducted at about pH 3 from 300 to 370 ??C and a 0.1-??C/h heating rate. Incorporation of sulfur into HC resulted in an appreciable amount of thiol and sulfide formation. The rate of LSC formation positively correlated with the initial H2S pressure. Thus, we propose that the LSC produced from H2S reaction with HC are most likely the reactive intermediates for H2S initiation of sulfate reduction. We further propose a three-step reaction scheme of sulfate reduction by HC under reservoir conditions, and discuss the geological implications of our experimental findings with regard to the effect of formation water and oil chemistry, in particular LSC content. ?? 2008 Elsevier Ltd. All rights reserved.

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

2008-01-01

198

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

NASA Technical Reports Server (NTRS)

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

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

2006-01-01

199

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

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

200

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

201

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

202

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

SciTech Connect

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

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

2009-04-01

203

Acute and Short-Term Effects of Partial Left Ventriculectomy in Dilated Cardiomyopathy Assessment by Pressure-Volume Loops  

Microsoft Academic Search

OBJECTIVES The aim of this study was to evaluate the short-term effects of partial left ventriculectomy (PLV) on left ventricular (LV) pressure-volume (P-V) loops, wall stress, and the synchrony of LV segmental volume motions in patients with dilated cardiomyopathy. BACKGROUND Surgical LV volume reduction is under investigation as an alternative for, or bridge to, heart transplantation for patients with end-stage

Jan J. Schreuder; Paul Steendijk; Frederik H. van der Veen; Ottavio Alfieri; Theo van der Nagel; Roberto Lorusso; Jan-Melle van Dantzig; Kees B. Prenger; Jan Baan; Hein J. J. Wellens; Randas J. V. Batista

204

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

205

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

PubMed

Global emissions of atmospheric CO(2) and tropospheric O(3) are rising and expected to impact large areas of the Earth's forests. While CO(2) stimulates net primary production, O(3) reduces photosynthesis, altering plant C allocation and reducing ecosystem C storage. The effects of multiple air pollutants can alter belowground C allocation, leading to changes in the partial pressure of CO(2) (pCO(2)) in the soil , chemistry of dissolved inorganic carbonate (DIC) and the rate of mineral weathering. As this system represents a linkage between the long- and short-term C cycles and sequestration of atmospheric CO(2), changes in atmospheric chemistry that affect net primary production may alter the fate of C in these ecosystems. To date, little is known about the combined effects of elevated CO(2) and O(3) on the inorganic C cycle in forest systems. Free air CO(2) and O(3) enrichment (FACE) technology was used at the Aspen FACE project in Rhinelander, Wisconsin to understand how elevated atmospheric CO(2) and O(3) interact to alter pCO(2) and DIC concentrations in the soil. Ambient and elevated CO(2) levels were 360+/-16 and 542+/-81 microl l(-1), respectively; ambient and elevated O(3) levels were 33+/-14 and 49+/-24 nl l(-1), respectively. Measured concentrations of soil CO(2) and calculated concentrations of DIC increased over the growing season by 14 and 22%, respectively, under elevated atmospheric CO(2) and were unaffected by elevated tropospheric O(3). The increased concentration of DIC altered inorganic carbonate chemistry by increasing system total alkalinity by 210%, likely due to enhanced chemical weathering. The study also demonstrated the close coupling between the seasonal delta(13)C of soil pCO(2) and DIC, as a mixing model showed that new atmospheric CO(2) accounted for approximately 90% of the C leaving the system as DIC. This study illustrates the potential of using stable isotopic techniques and FACE technology to examine long- and short-term ecosystem C sequestration. PMID:15378342

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

2005-01-01

206

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

207

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

DOEpatents

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

Findl, E.

1984-12-21

208

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

SciTech Connect

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

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

1998-04-30

209

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

210

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

NASA Astrophysics Data System (ADS)

Use of a levitation technique is an elegant way to determine thermophysical properties of high temperature melts, because this containerless technique can avoid contamination from a container and assures measurement in a wide temperature range including superheated and undercooled conditions. In particular, electromagnetic levitation is suitable for electrically conductive materials, such as molten metals, alloys and semiconductors. For surface tension measurement, the Rayleigh equation can be applicable only under microgravity condition [1]. However, when this technique is applied on earth, the l = 2 mode frequency is split into five frequencies, because a droplet is deformed from a spherical shape into an egg shape due to gravitational force and the Lorentz force. Surface tension must be calculated taking account of correction term [2]. Therefore, measurement under microgravity is required to minimize uncertainty. Furthermore, surface tension is sensitive to oxygen partial pressure of an ambient atmosphere. However, there has been less report on surface tension measurement under microgravity in an atmosphere with controlled oxygen partial pressure. We are going to measure surface tension of high temperature metallic melts under microgravity using a parabolic flight of a jet aircraft, the Gulf Stream II, operated by Diamond Air Service in Japan. In September of 2007, through parabolic flight experiments we confirmed that droplets of Cu and Ag were successfully levitated using a newly designed coil under the 1G and 10-2G conditions. Droplets were also assured to be levitated in the pull-up period (1.5G); we can melt samples before entering microgravity condition, so that we can use 20 second microgravity only for measurement. On earth, surface tension of molten silicon was successfully measured using electromagnetic levitation in an ambient atmosphere with various oxygen partial pressures; surface tension of molten silicon showed a marked dependence of oxygen partial pressure. Oxygen partial pressure control system has been designed and installed within an electromagnetic levitation facility for parabolic flight experiments. References [1] Lord Rayleigh: Proc. Royal Soc. London, 29, 71 (1879). [2] D. L. Cummings and D. A. Blackburn: J. Fluid Mech. 224, 395 (1991).

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

211

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

NASA Astrophysics Data System (ADS)

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

Duncan, M. S.; Dasgupta, R.

2011-12-01

212

H2A Delivery H2A Hydrogen Delivery  

E-print Network

, contingency ­ Options to use H2A, Peters and Timmerhaus or other data · O&M Costs ­ Labor, feedstock costs ­ All component capital costs ­ Options to use H2A data, or user-entered data #12;H2A Delivery Component to determine a "generic" hydrogen cost for a particular component · Each storage and delivery component has

213

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

PubMed

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

Ma, Xiaoliang; Wang, Xiaoxing; Song, Chunshan

2009-04-29

214

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

PubMed Central

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

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

2012-01-01

215

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

NASA Astrophysics Data System (ADS)

Iceland is home to some of the most active volcanoes in the world, and recent eruptions emphasize the need for additional studies to better understand the volcanism and tectonics in this region. Historical patterns of eruptive activity and an increase in seismic activity suggest that Katla is showing signs of an impending eruption. The last major eruption in 1918 caused massive flooding and deposited enough sediment to extend part of Iceland's southern shoreline by 5 km. It also generated sufficient ash over many weeks to cause a brief drop in global temperature. A future eruption similar to the 1918 event could have serious global consequences, including severe disruptions in air travel, short-term global cooling, and shortened growing seasons. Relatively few studies have focused on establishing the depth of the main magma chamber beneath Katla, although knowledge of magma chamber depth is essential for constraining models for magma evolution and for understanding the eruption dynamics of this volcano. The results of seismic and geodetic studies suggest the presence of a shallow magma body at a depth of 2-4 km, but do not provide firm evidence for the presence of deeper chambers in contrast to results obtained for other volcanoes in Iceland. Studies of volcanic ash layers reveal a history of alternating cycles of basaltic and silicic eruptions. We suggest that the shallow magma chamber is primarily the source of silica-rich magma, and postulate that there must be one or more additional chambers in the middle or deep crust that serve as the storage site of the basaltic magma erupted as lava and ash. We have tested this proposal by calculating the pressures of partial crystallization for basalts erupted at Katla using petrological methods. These pressures can be converted to depths and the results provide insight into the likely configuration of the magma plumbing system. Published analyses of volcanic glasses (lava, ash and hyaloclastite) were used as input data. The raw data were filtered to remove non basalts and to exclude basalt samples with anomalous chemical compositions. Pressures of partial crystallization were calculated by quantitatively comparing the compositions of the glasses with those of experimental liquids in equilibrium with olivine, plagioclase, and augite at different pressures and temperatures using the approach described by Yang and co-workers (1996). The results for samples that yielded pressures associated with unrealistically large uncertainties were filtered out of the database. Pressures for the remaining samples were converted to depths assuming an average crustal density of 2900 kg/m3. The results indicate that most magmas partially crystallized over a range of pressures corresponding to a range of depths from 20 to 25 km. We conclude that one or more magma chamber occur in this depth range, or at slightly shallower depths if the effects of water on calculated pressures of partial crystallization are taken into account. Most erupted basalts have ascended from this depth directly to the surface, presumably via dikes. The Katla plumbing system is thus similar to that at other major volcanoes (Hekla, Bardarbunga, Grimsvotn) in the eastern volcanic zone inasmuch as the majority of the erupted magmas are supplied from chambers in the middle and lower crust at depths of 10 to 30 km.

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

2012-12-01

216

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

217

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

218

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

SciTech Connect

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

Zhang Dongping; Shao Jianda; Zhao Yuanan; Fan Shuhai; Hong Ruijing; Fan Zhengxiu [R and D Center for Optical Thin Film Coatings, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, P.O. Box 800-211, Shanghai 201800 (China)

2005-01-01

219

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

220

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

221

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

222

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

223

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

224

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

225

Mass Spectrometric Approach for Characterizing the Disordered Tail Regions of the Histone H2A/H2B Dimer.  

PubMed

The histone H2A/H2B dimer is a component of nucleosome core particles (NCPs). The structure of the dimer at the atomic level has not yet been revealed. A possible reason for this is that the dimer has three intrinsically disordered tail regions: the N- and C-termini of H2A and the N-terminus of H2B. To investigate the role of the tail regions of the H2A/H2B dimer structure, we characterized behaviors of the H2A/H2B mutant dimers, in which these functionally important disordered regions were depleted, using mass spectrometry (MS). After verifying that the acetylation of Lys residues in the tail regions had little effect on the gas-phase conformations of the wild-type dimer, we prepared two histone H2A/H2B dimer mutants: an H2A/H2B dimer depleted of both N-termini (dN-H2A/dN-H2B) and a dimer with the N- and C-termini of H2A and the N-terminus of H2B depleted (dNC-H2A/dN-H2B). We analyzed these mutants using ion mobility-mass spectrometry (IM-MS) and hydrogen/deuterium exchange mass spectrometry (HDX-MS). With IM-MS, reduced structural diversity was observed for each of the tail-truncated H2A/H2B mutants. In addition, global HDX-MS proved that the dimer mutant dNC-H2A/dN-H2B was susceptible to deuteration, suggesting that its structure in solution was somewhat loosened. A partial relaxation of the mutant's structure was demonstrated also by IM-MS. In this study, we characterized the relationship between the tail lengths and the conformations of the H2A/H2B dimer in solution and gas phases, and demonstrated, using mass spectrometry, that disordered tail regions play an important role in stabilizing the conformation of the core region of the dimer in both phases. PMID:25594579

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

2015-02-17

226

Determination of the partial molar volume of SiO{sub 2} in silicate liquids at elevated pressures and temperatures: A new experimental approach  

SciTech Connect

This study presents a new approach for determining the partial molar volume and its pressure derivative for a silicate liquid component through an experimental determination of the isothermal pressure dependence of the solubility in the liquid of a crystalline phase having the composition of the component. Because this approach allows the determination of partial molar volumes of liquid components at elevated pressure, it has the potential to detect pressure-induced structural changes associated with particular components in silicate liquid through their influence on partial molar volumes. To illustrate the approach, an experimental determination of the solubility of quartz in a rhyolitic liquid was used to determine the partial molar volume of SiO{sub 2} at pressures up to 35 kbar and a temperature of 1,350 C. The 1 bar partial molar volume for SiO{sub 2} determined in this way, 2.635 {+-} 0.009 J/bar, is slightly smaller than the 2.690 {+-} 0.006 J/bar determined by Lange and Carmichael (1987) (all uncertainties are 1{sigma}). The isothermal pressure dependence of the partial molar volume of SiO{sub 2} at 10 to 35 kbar is approximately one-half of the value determined by Kress and Carmichael (1991) at 1 bar. The high pressure determination can be reconciled with the existing 1 bar volume and compressibility data if the isothermal pressure dependence of the partial molar volume of SiO{sub 2} in silicate liquids decreases rapidly between 1 bar and 10 kbar, then remains approximately constant to at least 35 kbar.

Gaetani, G.A.; Asimow, P.D.; Stolper, E.M. [California Inst. of Tech., Pasadena, CA (United States). Div. of Geological and Planetary Sciences] [California Inst. of Tech., Pasadena, CA (United States). Div. of Geological and Planetary Sciences

1998-07-01

227

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. PMID:16666476

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

1988-01-01

228

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

229

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

NASA Astrophysics Data System (ADS)

Atmospheric H2SO4 / H2O nucleation influencing effects have been studied in the flow tube IfT-LFT (Institute for Tropospheric Research - Laminar Flow Tube) at 293 0.5 K and a pressure of 1 bar using synthetic air as the carrier gas. The presence of a possible background amine concentration in the order of 107-108 molecule cm-3 throughout the experiments has to be taken into account. In a first set of investigations, ozonolysis of olefins (tetramethylethylene, 1-methyl-cyclohexene, ?-pinene and limonene) for close to atmospheric concentrations, served as the source of OH radicals and possibly other oxidants initiating H2SO4 formation starting from SO2. The oxidant generation is inevitably associated with the formation of organic oxidation products arising from the parent olefins. These products (first generation mainly) showed no clear effect on the number of nucleated particles within a wide range of experimental conditions for H2SO4 concentrations higher than ~107 molecule cm-3. Also the early growth process of the nucleated particles was not significantly influenced by the organic oxidation products in line with the expected growth by organic products using literature data. An additional, H2SO4-independent process of particle (nano-CN) formation was observed in the case of ?-pinene and limonene ozonolysis for H2SO4 concentrations smaller than ~107 molecule cm-3. Furthermore, the findings confirm the appearance of an additional oxidant for SO2 beside OH radicals, very likely stabilized Criegee Intermediates (sCI). A second set of experiments has been performed in the presence of added amines in the concentrations range of a few 107-1010 molecule cm-3 applying photolytic OH radical generation for H2SO4 production without addition of other organics. All amines showed significant nucleation enhancement with increasing efficiency in the order pyridine < aniline < dimethylamine < trimethylamine. This result supports the idea of H2SO4 cluster stabilization by amines due to strong H2SO4?amine interactions. On the other hand, this study indicates that for organic oxidation products (in presence of the possible amine background as stated) a distinct H2SO4 / H2O nucleation enhancement can be due to increased H2SO4 formation caused by additional organic oxidant production (sCI) rather than by stabilization of H2SO4 clusters due to H2SO4?organics interactions.

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

2014-01-01

230

?H2AX and cancer  

PubMed Central

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

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

2011-01-01

231

Quantitative evaluation of the counterbalance between photosynthetic stimulation and depression caused by low partial pressure of O 2 and CO 2 in alpine atmospheres  

Microsoft Academic Search

To evaluate the effects of low atmospheric pressure on leaf photosynthesis, we compared the photosynthesis of identical leaves of Fagus crenata at lowland (0m a.s.l.) and at highland (2360m a.s.l.). At the high altitude, the atmospheric pressure and partial pressure of CO2 at intercellular air spaces in the leaf (Ci360) decreased to 77% and 78% of those at the low

Tsuyoshi Sakata; Naoki Kachi; Yota Yokoi

2007-01-01

232

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

SciTech Connect

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

Zheng, Qing; Li, Jun; Liu, Ying, E-mail: liuying5536@163.com; Yu, Yunping; Lian, Lixian [College of Materials Science and Engineering, Sichuan University, Chengdu 610065 (China)

2014-05-07

233

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

234

H2 Detection via Polarography  

NASA Technical Reports Server (NTRS)

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

Dominquez, Jesus; Barile, Ron

2006-01-01

235

The solubility of water in NaAlSi3O8 melts: a re-examination of Ab-H2O phase relationships and critical behaviour at high pressures  

NASA Astrophysics Data System (ADS)

The solubility of water in melts in the NaAlSi3O8-H2O system at high P and T was deduced from the appearance of quenched products and from water concentrations in the quenched glasses measured by ion probe, calibrated by hydrogen manometry. Starting materials were gels with sufficient water added to ensure saturation of the melts under the run conditions. Experiments were carried out for 10 30 h in an internally heated argon pressure vessel (eight at 1400 C and 0.2 0.73 GPa and three at 0.5 GPa and 900 1200 C) and for 1 h in a piston-cylinder apparatus (three at 1200 C, 1 1.3 GPa). No bubbles were observed in the glasses quenched at P<0.5 GPa or from T<1300 C at 0.5 GPa. Bubble concentration in glasses quenched from 1400 C was low at 0.5, moderate at 0.55 GPa and very high at 0.73 GPa and still higher in glasses quenched in the piston cylinder. Water concentration was measured in all glasses, except for the one at 0.55 GPa, for which it was only estimated, and for those at ?0.73 GPa because bubble concentration was too high. Inferred water solubilities in the melt increase strongly with increasing P at 1400 C (from 6.0 wt% at 0.2 GPa to 15 at 0.55 GPa) and also with increasing T at 0.5 GPa (from 9.0 wt% at 900 C to 12.9 at 1400 C). The T variation of water solubility is fundamental for understanding the behaviour of melts on quenching. If the solubility decreases with T at constant P (retrograde solubility), bubbles cannot form by exsolution on isobaric quenching, whereas if the solubility is prograde they may do so if the cooling rate is not too fast. It is inferred from observed bubble concentrations and from our and previous solubility data that water solubility is retrograde at low P and prograde at and above 0.45 GPa; it probably changes with T from retrograde below to prograde above 900 C at 0.5 GPa. Moreover, the solubility is very large at higher pressures (possibly>30 wt% at 1.3 GPa and 1200 C) and critical behaviour is approached at 1.3 GPa and 1200 C. The critical curve rises to slightly higher P at lower T and intersects the three-phase or melting curve at a critical end point near 670 C and 1.5 GPa, above which albite coexists only with a supercritical fluid.

Paillat, Olivier; Elphick, Stephen C.; Brown, William L.

1992-12-01

236

Thermal conductivity and quantum diffusion in solid H 2  

Microsoft Academic Search

The thermal conductivity ? of solid H2 and the NMR absorption signal of isolated o-H2 were measured simultaneously along isotherms 0.07T2 concentration ranged from 3.4% to 0.4%, and the pressure was ?90 atm. During the measurements, clustering of o-H2 particles occurred as seen from the changes both of the NMR signal amplitude and of ? with time t. The difference

X. Li; D. Clarkson; H. Meyer

1990-01-01

237

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

PubMed Central

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

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

2014-01-01

238

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

PubMed

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

Goclon, Jakub; Meyer, Bernd

2013-06-01

239

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

PubMed

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

Lahav, Ori; Sagiv, Amitai; Friedler, Eran

2006-01-01

240

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

PubMed Central

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

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

2012-01-01

241

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

PubMed Central

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

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

2013-01-01

242

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

NASA Technical Reports Server (NTRS)

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

Schulte, Mitchell D.; Shock, Everett L.

1993-01-01

243

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

NASA Technical Reports Server (NTRS)

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

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

1988-01-01

244

On the phase formation of titanium oxide thin films deposited by reactive DC magnetron sputtering: influence of oxygen partial pressure and nitrogen doping  

NASA Astrophysics Data System (ADS)

This work describes about the control on phase formation in titanium oxide thin films deposited by reactive dc magnetron sputtering. Various phases of titanium oxide thin films were deposited by controlling the oxygen partial pressure during the sputtering process. By adding nitrogen gas to sputter gas mixture of oxygen and argon, the oxygen partial pressure was decreased further below the usual critical value, below and above which the sputtering yields metallic and oxide films, respectively. Furthermore, nitrogen addition eliminated the typical hysteretic behaviour between the flow rate and oxygen partial pressure, and significantly influenced the sputter rate. On increasing the oxygen partial pressure, the ratio between anatase and rutile fraction and grain size increases. The fracture cross-sectional scanning electron microscopy together with the complementary information from X-ray diffraction and micro-Raman investigations revealed the evolution and spatial distribution of the anatase and rutile phases. Both the energy delivered to the growing film and oxygen vacancy concentrations are correlated with the formation of various phases upon varying the oxygen partial pressure.

Pandian, Ramanathaswamy; Natarajan, Gomathi; Rajagopalan, S.; Kamruddin, M.; Tyagi, A. K.

2014-09-01

245

H2O-H2O Collision Rate Coefficients  

NASA Astrophysics Data System (ADS)

H2O-H2O collision cross sections are calculated by adapting the method developed by Anderson and Tsao and Cornette for the calculation of collision broadening of molecular spectral lines. Cross sections are computed with a cutoff limit at 20 2 for the rotational levels of water with J<=10 and E<2000 cm-1 in the temperature range 100-800 K. The accuracy of the calculated values is estimated to be 10%-20%.

Buffa, Giovanni; Tarrini, Ottavio; Scappini, Flavio; Cecchi-Pestellini, Cesare

2000-06-01

246

Effect of substrate temperature and oxygen partial pressure on microstructure and optical properties of pulsed laser deposited yttrium oxide thin films  

NASA Astrophysics Data System (ADS)

Yttrium oxide thin films were deposited on Si (1 1 1) and quartz substrates by pulsed laser deposition technique at different substrate temperature and oxygen partial pressure. XRD analysis shows that crystallite size of the yttrium oxide thin films increases as the substrate temperature increases from 300 to 873 K. However the films deposited at constant substrate temperature with variable oxygen partial pressure show opposite effect on the crystallite size. Band gap energies determined from UV-visible spectroscopy indicated higher values than that of the reported bulk value.

Mishra, Maneesha; Kuppusami, P.; Sairam, T. N.; Singh, Akash; Mohandas, E.

2011-06-01

247

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

248

H2 Educate Teacher Guide  

NSDL National Science Digital Library

This guide was developed by the National Energy Education Development (NEED) Project's Teacher Advisory Board for the DOE Hydrogen Program. The guide provides information and hands-on activities to teach students about hydrogen as a fuel for the future. There is also a student guide available for download from DOE. Materials for the H2 Educate kit can be purchased from NEED (http://www.need.org/needpdf/H2EducatePriceList.pdf).

249

Microwave Spectra and Structures of H_2O\\cdotsAgF  

NASA Astrophysics Data System (ADS)

A Balle-Flygare FT-MW spectrometer coupled to a laser ablation source has been used to measure the pure rotational spectra of H2O\\cdotsAgF. Generation is via laser ablation (532 nm) of a silver rod in the presence of SF6, argon, a low partial pressure of H2O and the molecules are stabilized by supersonic expansion. The spectra of eight isotopologues have been measured. Rotational constants, B0 and C0, and the centrifugal distortion constant, ? _J have been determined. Isotopic substitutions are available at the silver, oxygen and hydrogen atoms. The spectra are consistent with a linear arrangement of oxygen, silver and fluorine atoms and the structure is either C2v planar at equilibrium or CS pyramidal but with a low potential-energy barrier to planarity such that the v = 0 and 1 states associated with the motion that inverts the configuration at the O atom are well separated.

Stephens, S. L.; Walker, N. R.; Tew, D. P.; Legon, A. C.

2011-06-01

250

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

251

Role of composition and oxygen partial pressure on microstructural and crystalline phase evolution in aluminosilicate derived aggregates  

NASA Astrophysics Data System (ADS)

Spherical aggregates, approximately 1mm in diameter, derived from either kaolinite or bauxite are used in tonnage quantities to aid the extraction of oil and natural gas. Aggregates intended for this application are referred to as proppants and key characteristics include low density and high strength, which are influenced by processing temperature and variation in raw ore chemistry. Kaolinite and bauxite ores doped with varying concentrations of K2O and Fe2O3 were sintered at different temperatures to elucidate composition-processing-property relationships. The dopants are known to form low temperature ternary eutectics with Al2O3 and SiO2 and are anticipated to facilitate low temperature densification and enhance mullite formation. In addition, proppants doped with Fe2 O3 were studied under varying oxygen partial pressures to further enhance low temperature densification by manipulating the valence state of iron. Microstructure and crystalline phase assemblage were evaluated by scanning electron microscopy and X-ray diffraction, respectively, and correlated with results of density and strength measurements obtained by gas pycnometry and diametral compression, respectively. Results indicate that dopant enhanced densification can simultaneously improve strength and processing economy of proppants by lowering sintering temperatures up to 100C. Controlled atmosphere studies revealed that manipulating the valence of iron produces unique microstructures that may be useful in a number of different applications. These microstructures include aggregates with metallic coatings and aggregates with core-shell microstructures, which exhibit a porous core enclosed by a relatively dense outer shell.

Luscher, Walter G.

252

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

253

The jumbo squid, Dosidicus gigas (Ommastrephidae), living in oxygen minimum zones I: Oxygen consumption rates and critical oxygen partial pressures  

NASA Astrophysics Data System (ADS)

Dosidicus gigas is a large, metabolically active, epipelagic squid known to undertake diel vertical migrations across a large temperature and oxygen gradient in the Eastern Pacific. Hypoxia is known to cause metabolic suppression in D. gigas. However, the precise oxygen level at which metabolic suppression sets in is unknown. Here we describe a novel ship-board swim tunnel respirometer that was used to measure metabolic rates and critical oxygen partial pressures (Pcrit) for adult squids (2-7kg). Metabolic rate measurements were validated by comparison to the activity of the Krebs cycle enzyme, citrate synthase, in mantle muscle tissue (2-17kg). We recorded a mean routine metabolic rate of 5.91?molg-1h-1 at 10C and 12.62?molg-1h-1 at 20C. A temperature coefficient, Q10, of 2.1 was calculated. D. gigas had Pcrits of 1.6 and 3.8kPa at 10 and 20C, respectively. Oxygen consumption rate (MO2) varied with body mass (M) according to MO2=11.57M-0.120.03 at 10C. Citrate synthase activity varied with body mass according to Y=9.32M-0.190.02.

Trueblood, Lloyd A.; Seibel, Brad A.

2013-10-01

254

Microstructural observations on the oxidation of gamma-prime-Ni3Al at low oxygen partial pressure  

SciTech Connect

Electron microscopy is used to investigate microstructural development during the oxidation of the 001-plane-oriented gamma-prime-Ni3Al single crystals at 1223 K under an oxygen partial pressure of 4 x 10 exp -19. After 1-min oxidation, TEM cross sections revealed a continuous 4-nm-thick film of gamma-Al2O3 with equiaxed 20-nm protrusions into the metal. Continued oxidation resulted in thickening of the gamma-Al2O3 scale, no grain growth, and the development of a plane metal/gamma-Al2O3 interface. Depletion of Al from the adjoining metal resulted in a well-defined disordered zone of Ni-Al solid solution between the Al2O3 scale and the gamma-prime-Ni3Al. After 5-h oxidation, large randomly oriented alpha-Al2O3 grains nucleated at the metal/gamma-Al2O3 interface, growing inward and transforming from the gamma-Al2O3 outward. The alpha-Al2O3 contained intragranular and intergranular voids. The gamma-Al2O3 exhibited a high density of planar defects and the interface between the gamma-Al2O3 and alpha-Al2O3 contained many voids. Voids were never observed at the metal/oxide interface. 19 refs.

Schumann, E.; Schnotz, G.; Trumble, K.P.; Ruehle, M. (Max-Planck-Institut fuer Metallforschung, Stuttgart (Germany))

1992-06-01

255

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

NASA Technical Reports Server (NTRS)

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

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

1995-01-01

256

H2A Delivery: H2A Delivery  

E-print Network

calculation than that used in previous H2A model All components sized with a 70% capacity factor or hard hoses 1 Moore, Graham; Chevron. 5/8/2007 3 #12;6% 7% 8% 9% emand Forecourt Capacity & Demand Scenario must maintain high output for many consecutive hours 2 Moore, Graham; Chevron. 5/8/2007 4 #12;Modified

257

The 50 Ah NiH2 CPV qualification tests  

NASA Technical Reports Server (NTRS)

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

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

1995-01-01

258

The 50 Ah NiH2 CPV qualification tests  

NASA Astrophysics Data System (ADS)

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

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

1995-02-01

259

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

NASA Astrophysics Data System (ADS)

Atmospheric H2SO4/H2O nucleation influencing effects have been studied in the flow tube IfT-LFT (Institute for Tropospheric Research - Laminar Flow Tube) at 293 0.5 K and a pressure of 1 bar using synthetic air as the carrier gas. The presence of a~possible background amine concentration in the order of 107-108 molecule cm-3 throughout the experiments has to be taken into account. In a first set of investigations, ozonolysis of olefins (tetramethylethylene, 1-methyl-cyclohexene, ?-pinene and limonene) for close to atmospheric concentrations, served as the source of OH radicals and possibly other oxidants initiating H2SO4 formation starting from SO2. The oxidant generation is inevitably associated with the formation of a series of organic oxidation products arising from the parent olefins. These products (first generation mainly) showed no clear effect on the number of nucleated particles within a wide range of experimental conditions for H2SO4 concentrations higher than ~107 molecule cm-3. A comparison of the results of two different particle counters (50% cut-off size: about 1.5 nm or 2.5-3 nm) suggested that the early growth process of the nucleated particles was not significantly influenced by the organic oxidation products. An additional, H2SO4-independent process of particle (nano-CN) formation was observed in the case of ?-pinene and limonene ozonolysis for H2SO4 concentrations smaller than ~10 7 molecule cm-3. Furthermore, the findings confirm the existence of an additional oxidant for SO2 beside OH radicals, very likely stabilized Criegee Intermediate (sCI). In the case of the ozonolysis of tetramethylethylene, the H2SO4 measurements in the absence and presence of an OH radical scavenger were well described by modelling using recently obtained kinetic data for the sCI reactivity in this system. A second set of experiments has been performed in the presence of added amines (trimethylamine, dimethylamine, aniline and pyridine) in the concentration range of a few 107-1010 molecule cm-3. Here, photolytic OH radical generation was applied for H2SO4 production with no addition of other organics. All amines showed a significant nucleation enhancement with increasing efficiency in the order pyridine < aniline < dimethylamine < trimethylamine. This result supports the idea of H2SO4 cluster stabilization by amines due to strong H2SO4 \\leftrightarrow amine interactions. On the other hand, this study reveals that for organic oxidation products (in presence of the possible amine background as stated) a distinct H2SO4/H2O nucleation enhancement can be due to increased H2SO4 formation caused by additional organic oxidant production (sCI) rather than by stabilization of H2SO4 clusters due to H2SO4 \\leftrightarrow organics interactions. However, because the molecular composition of nucleating clusters was not measured, the role of any background substances, unavoidably present in any system, to experimental data remains unclear. Also the experimental conditions do not cover fully the range of atmospheric observations, e.g., the concentration of precursor vapours represents rather the upper end of the atmospheric range. More experimental work is needed before definite conclusions about the nucleation mechanisms in the atmosphere can be drawn.

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

2013-06-01

260

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

261

The solubility of water in NaAlSi 3 O 8 melts: a re-examination of Ab?H 2 O phase relationships and critical behaviour at high pressures  

Microsoft Academic Search

The solubility of water in melts in the NaAlSi3O8-H2O system at high P and T was deduced from the appearance of quenched products and from water concentrations in the quenched glasses measured by ion probe, calibrated by hydrogen manometry. Starting materials were gels with sufficient water added to ensure saturation of the melts under the run conditions. Experiments were carried

Olivier Paillat; Stephen C. Elphick; William L. Brown

1992-01-01

262

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

PubMed

Mountainous regions such as the Central European Alps host considerable karstified or fractured groundwater bodies, which meet many of the demands concerning drinking water supply, hydropower or agriculture. Alpine hydrogeologists are required to describe the dynamics in fractured aquifers in order to assess potential impacts of human activities on water budget and quality. Delineation of catchment areas by means of stable isotopes and hydrochemical data is a well established method in alpine hydrogeology. To achieve reliable results, time series of (at least) one year and spatial and temporal close-meshed data are necessary. In reality, test sites in mountainous regions are often inaccessible due to the danger of avalanches in winter. The aim of our work was to assess a method based on the processes within the carbonic acid system to delineate infiltration areas by means of single datasets consisting of the main hydrochemical parameters of each spring. In three geologically different mountainous environments we managed to classify the investigated springs into four groups. (1) High PCO2 combined with slight super-saturation in calcite, indicating relatively low infiltration areas. (2) Low PCO2 near atmospheric conditions in combination with calcite saturation, which is indicative of relatively high infiltration areas and a fractured aquifer which is not covered by topsoil layers. (3) High PCO2 in combination with sub-saturation in calcite, representing a shallow aquifer with a significant influence of the topsoil layer. (4) The fourth group of waters is characterized by low PCO2 and sub-saturation in calcite, which is interpreted as evidence for a shallow aquifer without significant influence of any hard rock aquifer or topsoil layer. This study shows that CO2-partial pressure can be an ideal natural tracer to estimate the elevation of infiltration areas, especially in non-karstified fractured groundwater bodies. PMID:23429574

Hilberg, Sylke; Brandsttter, Jennifer; Glck, Daniel

2013-04-01

263

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

264

Mineralization of Basalts in the CO2-H2O-H2S System  

SciTech Connect

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

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

2013-08-01

265

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

NASA Astrophysics Data System (ADS)

This paper presents the simultaneous measurement and calculation of the electron drift velocity in binary and ternary mixtures of N2, O2, CO2 with H2O. The main aim of this study has been the generation of a self-consistent set of validated collision cross sections that explain thoroughly the dependence of the electron drift velocity in the above pure gases and their mixtures. In doing this, changes to the collision cross section set for H2O had to be made, while all other cross section sets remained unchanged. It is worth mentioning that only a few experiments had been performed before dealing with water mixtures. The electron drift velocities in the binary and ternary mixtures under study show the effects of negative differential conductivity, and this has been explained thoroughly in terms of the collision cross sections and electron distribution functions through a multi-term Boltzmann code. It is important to note that two-term codes fail to predict the dependence of the drift velocity at low water concentrations and low E/N values. Calculated values of longitudinal and transverse diffusion coefficients, mean energies and distribution functions are also given over the E/N range 0.1 Td-2 kTd (1 Td = 10-17 V cm2).

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

2010-11-01

266

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

267

Two-stage high-rate biogas (H2 and CH4) production from food waste using anaerobic mixed microflora  

NASA Astrophysics Data System (ADS)

To achieve the high-rate H2 and CH4 production from food waste using fermentative anaerobic microflora, the effects of carbonate-alkalinity in the recirculated digestion sludge on continuous two-stage fermentation were investigated. Higher H2 production rate of 2.9 L-H2/L/day was achieved at the recycle ratio of 1.0 in an alkalinity range of 9000 to 10000 mg-CaCO3/L. The maximum CH4 production rate was stably maintained at the range of 1.85 to 1.88 L-CH4/L/day without alkalinity change. Carbonate alkalinity in digestion sludge could reduce the H2 partial pressure in the headspace of the fermentation reactors, and improve a biogas production capacity in the two-stage fermentation process. The average volatile solids degradation rate in the overall process increased as the digestion sludge recycle increased from 0.5 to 1.0. These results show that the alkalinity in recycle of the digestion sludge is crucial factor in determining biogas (H2 and CH4) production capacity and reducing the total solids.

Xu, K.; Lee, D.; Kobayashi, T.; Ebie, Y.; Li, Y.; Inamori, Y.

2010-12-01

268

Scavenging of H2O 2 by mouse brain mitochondria.  

PubMed

Mitochondrial reactive oxygen species (ROS) metabolism is unique in that mitochondria both generate and scavenge ROS. Recent estimates of ROS scavenging capacity of brain mitochondria are surprisingly high, ca. 9-12nmol H2O2/min/mg, which is ~100 times higher than the rate of ROS generation. This raises a question whether brain mitochondria are a source or a sink of ROS. We studied the interaction between ROS generation and scavenging in mouse brain mitochondria by measuring the rate of removal of H2O2 added at a concentration of 0.4 ?M, which is close to the reported physiological H2O2 concentrations in tissues, under conditions of low and high levels of mitochondrial H2O2 generation. With NAD-linked substrates, the rate of H2O2 generation by mitochondria was ~50-70 pmol/min/mg. The H2O2 scavenging dynamics was best approximated by the first order reaction equation. H2O2 scavenging was not affected by the uncoupling of mitochondria, phosphorylation of added ADP, or the genetic ablation of glutathione peroxidase 1, but decreased in the absence of respiratory substrates, in the presence of thioredoxin reductase inhibitor auranofin, or in partially disrupted mitochondria. With succinate, the rate of H2O2 generation was ~2,200-2,900 pmol/min/mg; the scavenging of added H2O2 was masked by a significant accumulation of generated H2O2 in the assay medium. The obtained data were fitted into a simple model that reasonably well described the interaction between H2O2 scavenging and production. It showed that mitochondria are neither a sink nor a source of H2O2, but can function as both at the same time, efficiently stabilizing exogenous H2O2 concentration at a level directly proportional to the ratio of the H2O2 generation rate to the rate constant of the first order scavenging reaction. PMID:25248416

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

2014-12-01

269

Effects of oxygen partial pressure and substrate temperature on the structure and optical properties of Mg x Zn 1? x O thin films prepared by magnetron sputtering  

Microsoft Academic Search

Deposited with different oxygen partial pressures and substrate temperatures, MgxZn1?xO thin films were prepared using a Mg0.6Zn0.4O ceramic target by magnetron sputtering. The structural and optical properties of the prepared thin films were investigated. The X-ray diffraction spectra reveal that all the films on quartz substrate are grown along (200) orientation with cubic structure. The lattice constant decreases and the

Xinghua Zhang; Zunming Lu; Fanbin Meng; Yongzhong Wang; Ying Li; Xiao Yu; Chengchun Tang

2011-01-01

270

Partial pressure of end-tidal carbon dioxide successful predicts cardiopulmonary resuscitation in the field: a prospective observational study  

PubMed Central

Introduction Prognosis in patients suffering out-of-hospital cardiac arrest is poor. Higher survival rates have been observed only in patients with ventricular fibrillation who were fortunate enough to have basic and advanced life support initiated soon after cardiac arrest. An ability to predict cardiac arrest outcomes would be useful for resuscitation. Changes in expired end-tidal carbon dioxide levels during cardiopulmonary resuscitation (CPR) may be a useful, noninvasive predictor of successful resuscitation and survival from cardiac arrest, and could help in determining when to cease CPR efforts. Methods This is a prospective, observational study of 737 cases of out-of-hospital cardiac arrest. The patients were intubated and measurements of end-tidal carbon dioxide taken. Data according to the Utstein criteria, demographic information, medical data, and partial pressure of end-tidal carbon dioxide (PetCO2) values were collected for each patient in cardiac arrest by the emergency physician. We hypothesized that an end-tidal carbon dioxide level of 1.9 kPa (14.3 mmHg) or more after 20 minutes of standard advanced cardiac life support would predict restoration of spontaneous circulation (ROSC). Results PetCO2 after 20 minutes of advanced life support averaged 0.92 0.29 kPa (6.9 2.2 mmHg) in patients who did not have ROSC and 4.36 1.11 kPa (32.8 9.1 mmHg) in those who did (P < 0.001). End-tidal carbon dioxide values of 1.9 kPa (14.3 mmHg) or less discriminated between the 402 patients with ROSC and 335 patients without. When a 20-minute end-tidal carbon dioxide value of 1.9 kPa (14.3 mmHg) or less was used as a screening test to predict ROSC, the sensitivity, specificity, positive predictive value, and negative predictive value were all 100%. Conclusions End-tidal carbon dioxide levels of more than 1.9 kPa (14.3 mmHg) after 20 minutes may be used to predict ROSC with accuracy. End-tidal carbon dioxide levels should be monitored during CPR and considered a useful prognostic value for determining the outcome of resuscitative efforts and when to cease CPR in the field. PMID:18786260

Kolar, Miran; Krimari?, Miljenko; Klemen2, Petra; Grmec, tefek

2008-01-01

271

A comparison of ice VII formed in the H2O, NaCl-H2O, and CH3OH-H2O systems: Implications for H2O-rich planets  

NASA Astrophysics Data System (ADS)

High-pressure H2O polymorphs, namely ice VI, ice VII, and ice X, are hypothesized to make up a considerable portion of the interiors of large icy satellites and select extra-solar planets. The incorporation of foreign ions or molecules into these high-pressure phases is possible through ocean-ice interaction, rock-ice interaction at depth, or processes that occurred during accretion. Recent research concerning the effects charged ions have on ice VII has shown that these ions notably affect the structure of ice VII (Frank et al., 2006; Klotz et al., 2009). This study was designed to determine the effects of a molecular impurity on ice VII and compare those effects to both pure H2O ice and ice with an ionic impurity. Ice samples were formed in this study via compression in a diamond anvil cell from either H2O, a 1.60 mol% NaCl aqueous solution, a 1.60 mol% CH3OH aqueous solution, or a 5.00 mol% CH3OH aqueous solution and were compressed up to 71 GPa at room temperature. Ice formed from pure H2O had no impurities whereas ices formed in the NaCl-H2O and CH3OH-H2O systems contained the impurities Na+ and Cl- and CH3OH, respectively. Pressure-volume relations were observed in situ by using synchrotron based X-ray diffraction and were used to determine the equations of state for ices formed in the H2O, NaCl-H2O and CH3OH-H2O systems. The data illustrate that ice VII formed from a NaCl-bearing aqueous solution exhibited a depressed volume when compared to that of H2O-only ice VII at any given pressure, whereas ice VII formed from CH3OH-bearing aqueous solutions showed an opposite trend, with an increase in volume relative to that of pure ice VII. The ices within planetary bodies will most likely have both ionic and molecular impurities and the trends outlined in this study can be used to improve density profiles of H2O-rich planetary bodies.

Frank, Mark R.; Aarestad, Elizabeth; Scott, Henry P.; Prakapenka, Vitali B.

2013-02-01

272

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

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

273

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

SciTech Connect

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

Zhu, Di [School of Electronics and Information Engineering, Tianjin Polytechnic University, Tianjin (China); Song, Le, E-mail: songle@tju.edu.cn [State Key Laboratory of Precision Measuring Technology and Instruments, Tianjin University, Tianjin (China); Zhang, Xiong [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)

2014-02-14

274

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

NASA Technical Reports Server (NTRS)

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

Avni, R.

1984-01-01

275

Thermodynamics of Silicon-Hydroxide Formation in H2O Containing Atmospheres  

NASA Technical Reports Server (NTRS)

The formation of volatile silicon-hydroxide species from SiO2 in water containing atmospheres has been identified as a potentially important mode of degradation of Si-based ceramics. Availability of thermodynamic data for these species is a major problem. This study is part of an ongoing effort to obtain reliable, experimentally determined thermodynamic data for these species. The transpiration method was used to measure the pressure of Si-containing vapor in equilibrium with SiO2 (cristobalite) and Ar + H2O(g) with various mole fractions of water vapor, X(sub H2O), at temperatures ranging from 1000 to 1780 K. Enthalpies and entropies for the reaction, SiO2(s) + 2H2O(g) = Si(OH)4(g), were obtained, at X(sub H2O) = 0.15 and 0.37, from the variation of lnK with 1/T according to the 'second law method'. The following data were obtained: delta(H)deg = 52.9 +/- 3.7 kJ/mole and delta(S)deg = -68.6 +/- 2.5 J/mole K at an average temperature of 1550 K, and delta(H)deg = 52.5+/-2.0 kJ/mole and delta(S)deg= -69.7 +/- 1.5 J/moleK at an average temperature of 1384 K, for X(sub H2O)= 0.15 and 0.37, respectively. These data agree with results from the literature obtained at an average temperature of 1600 K, and strongly suggest Si(OH)4(g) is the dominant vapor species. Contradictory results were obtained with the determination of the dependence of Si-containing vapor pressure on the partial pressure of water vapor at 1187 and 1722 K. These results suggested the Si-containing vapor could be a mixture of Si(OH)4 + SiO(OH)2. Further pressure dependent studies are in progress to resolve these issues.

Copland, Evan; Myers, Dwight; Opila, Elizabeth J.; Jacobson, Nathan S.

2001-01-01

276

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

Microsoft Academic Search

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

Tetsu Kogiso; Marc M. Hirschmann; Daniel J Frost

2003-01-01

277

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

Microsoft Academic Search

Consideration of Darcy's law and its analogs for open channel flow, together with the thermodynamics of hydrolysis reactions in hydrothermal systems indicates that either fluid pressure and\\/or isothermal mineral solubilities or both may decrease or increase in the direction of fluid flow, depending on the volume of reaction and the permeability or aperture, cross-sectional area, and angle of flow as

Harold C. Helgeson

1992-01-01

278

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

279

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

280

A high-efficiency electric-discharge H2-F2 chemical laser  

Microsoft Academic Search

The paper presents the results of investigations of an electric-discharge-initiated H2-F2 chemical laser. The F2: O2: SF6: H2 = 5:1:3:2 mixture (pressure = 84 mm Hg) yielded a lasing energy of 5.8 J, the physical efficiency being 240 percent. In an F2: O2: He: H2 = 10:2:30:2.5 mixture (pressure = 340 mm Hg) in which the SF6 gas is absent,

E. B. Gordon; V. V. Gorokhov; V. I. Matiushenko; V. I. Karelin; A. I. Pavlovskii

1986-01-01

281

Excitation of H_2 and HD in shocks and PDRs  

E-print Network

Photodissociation regions (PDRs) and shocks give rise to conspicuous emission from rotationally and vibrationally excited molecular hydrogen. This line emission has now been studied with ISO and from the ground in great detail. A remarkable discovery has been that toward the Orion outflow and other shock-excited regions, the H_2 level populations show a very high excitation component. We suggest that these high-excitation populations may arise from non-thermal pumping processes, such as H_2 formation and high-velocity ion-molecule collision in partially dissociative shocks. In PDRs such as NGC 7023 however, formation pumping is always less important than fluorescent pumping. We furthermore present two HD emission line detections toward Orion Peak 1. This enables the first comparison of the H_2 and the HD excitation, which surprisingly turn out to be identical.

F. Bertoldi; B. T. Draine; D. Rosenthal; R. Timmermann; S. K. Ramsay Howat; T. Geballe; H. Feuchtgruber; S. Drapatz

2000-09-24

282

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

NASA Technical Reports Server (NTRS)

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

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

1999-01-01

283

Studies of H-2Kb mutant mice. II. Definition of new H-2 specificities (H-2.68, 69, 71, 72) using the H-2Kb mutant, B6.C-H-2bm10.  

PubMed

Using the H-2Kb mutant strain, B6.C-H-2bm10, antibodies were produced which define four new H-2 specificities. This is in contrast to other H-2Kb mutant strains in which attempts to produce antibodies against the mutation have failed with the exception of H-2bm3 in which a new specificity, H-2.62, was described by absorption analysis of an H-2.33 antiserum. With the mutant strain as immunization donor in the combination (C57BL/10 x 129)F1 anti B6.C-H-2bm10, two new H-2 specificities, H-2.68 and H-2.69, were produced. H-2.68 is found only on B6.C-H-2bm10, while H-2.69 is present on B6.C-H-2bm10 and on all cells of the H-2k haplotype. By testing the appropriate H-2 recombinant strains, the reaction with the H-2k haplotype could be mapped to the H-2D locus, whereas in B6.C-H-2bm10 it must have occurred in the H-2Kb gene. The reciprocal immunization of congenic strains failed, but with B6.C-H-2bm10 anti-A.BY, the specificities H-2.71 and H-2.72 were produced: H-2.71 was present on cells of the b,d, and k haplotypes, while H-2.72 was found only on the b haplotype. Genetic mapping using H-2 recombinant strains showed the H-2.72 reaction to be associated with the H-2Kb, H-2Dd and H-2Kk genes. The specificities described were shown to be of the H-2 type by their reactivity with H-2 congenic and recombinant strains, their segregation in a backcross and their ability to precipitate a molecule of 45,000 daltons molecular weight on SDS-PAGE. Therefore, the mutation carried by B6.C-H-2bm10, which resulted in a marked alteration of the H-2Kb specificities H-2.33 and H-2.5, is such that specific antibodies were able to be produced against both the gain and loss alterations produced by the mutation. PMID:6160097

Morgan, G M; McKenzie, I F; Melvold, R W

1980-07-01

284

Production of B atoms and BH radicals from B2H6/He/H2 mixtures activated on heated W wires.  

PubMed

B atoms and BH radicals could be identified by laser-induced fluorescence when B2H6/He/H2 mixtures were activated on heated tungsten wires. The densities of these radical species increased not only with the wire temperature but also with the partial pressure of H2. The densities in the presence of 0.026 Pa of B2H6 and 2.6 Pa of H2 were on the order of 10(11) cm(-3) both for B and BH when the wire temperature was 2000 K. Densities in the absence of a H2 flow were much smaller, suggesting that the direct production of these species on wire surfaces is minor. B and BH must be produced in the H atom shifting reactions, BH(x) + H ? BH(x-1) + H2 (x = 1-3), in the gas phase, while H atoms are produced from H2 on wire surfaces. The B atom density increased monotonously with the H atom density, while the BH density showed saturation. These tendencies could be reproduced by simple modeling based on ab initio potential energy calculations and the transition-state theoretical calculations of the rate constants. The absolute densities could also be reproduced within a factor of 2.5. PMID:24960473

Umemoto, Hironobu; Kanemitsu, Taijiro; Tanaka, Akihito

2014-07-17

285

Plant and environment interactions: Growth and yield response of commercial bearing-age {open_quote}Casselman{close_quote} plum trees to various ozone partial pressures  

SciTech Connect

Nursery stock of plum (Prunus salicina Lindel., cv. Casselman) was planted 1 Apr. 1988 in an experimental orchard at the Univ. of California Kearney Agricultural Center near Fresno, CA. Trees in this study were enclosed in open-top fumigation chambers on 1 May 1989, and exposed to three atmospheric ozone partial pressures (charcoal filtered air, ambient air, and ambient air + ozone) during the 1989 through 1992 growing seasons (typically 1 Apr. - 1 Nov.). A nonchamber treatment plot was used to assess chamber effects on tree performance. This study details the results of the exposures during the initial commercial bearing period (1991 through 1993) in this orchard. The mean 12-h (0800-2000 h Pacific Daylight Time [PDT]) ozone partial pressures during the experimental periods in the charcoal filtered, ambient, ambient + ozone, and nonchamber treatments averaged 0.031, 0.048, 0.091, and 0.056 {mu}Pa Pa{sup {minus}1} in 1991 and 1992, respectively. Fruit number per tree decreased as atmospheric ozone partial pressure increased from the charcoal filtered to ambient + ozone treatment, significantly affecting yield. Yield of plum trees averaged 23.6, 19.8, 13.7, and 17.9 kg tree{sup {minus}1} in 1991 and 1992 in the charcoal filtered, ambient, ambient + ozone, and nonchamber treatments, respectively. Only one out of the five original treatment plots was exposed to ozone treatments during the 1993 growing season. Yield of plum trees in this single replicate in 1993 was reduced by increased atmospheric ozone partial pressure. Yield of plum trees in the four remaining unexposed treatment plots in 1993 was 16.7, 17.9, and 16.0 kg tree{sup {minus}1} in the previous charcoal filtered, ambient, and ambient + ozone treatments respectively. The similarity in yield of the post-chamber treatments indicates that a change in air quality in the current growing season can affect yield of Casselman plum trees. 26 refs., 6 figs., 4 tabs.

Retzlaff, W.A.; Williams, L.E. [Univ. of California, Parlier, CA (United States); DeJong, T.M. [Univ. of California, Davis, CA (United States)

1997-05-01

286

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

SciTech Connect

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

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

2012-04-19

287

Development of a Turnkey H2 Fueling  

E-print Network

& Chemicals, Inc., 2003 apci Task 1.1.1. Reformer Reformer PSA Compr. Storage Dispenser NG H2 H2 H2O Goals: 1 Products & Chemicals, Inc., 2003 apci Task 1.1.2. PSA Development Reformer PSA Compr. Storage Dispenser NG

288

Influence of the Cs partial pressure on the optical and electrical properties of ITO films prepared by dc sputter type negative metal ion beam deposition  

NASA Astrophysics Data System (ADS)

The influence of cesium (Cs) partial pressure ( PCs) in the sputtering atmosphere on the opto-electrical and surface morphological property of ITO thin films deposited onto unheated polycarbonate substrate was investigated. The deposition technique used was a dc sputter type negative metal ion beam source which uses Cs as a surface negative ionization agent. During deposition Ar gas flow rate, deposition pressure and bipolar dc power were kept constant at 30 sccm, 9 10 -2 Pa, and 250 W, respectively. As increase PCs both electrical conductivity and optical transmittance of the film were increased. The lowest resistivity of 5.1 10 -4 ? cm and optical transmittance of 89% at 550 nm were measured in the ITO film deposited at PCs of 1.7 10 -3 Pa. Surface morphology of ITO film was also varied with PCs and the lowest surface roughness (Ra: 1.16 nm) was obtained a tCs of 1.7 10 -3 Pa.

Kim, Daeil

2003-12-01

289

Geochemical signatures of metasedimentary rocks of high-pressure granulite facies and their relation with partial melting: Carvalhos Klippe, Southern Braslia Belt, Brazil  

NASA Astrophysics Data System (ADS)

High-grade metasedimentary rocks can preserve geochemical signatures of their sedimentary protolith if significant melt extraction did not occur. Retrograde reaction textures provide the main evidence for trapped melt in the rock fabrics. Carvalhos Klippe rocks in Southern Braslia Orogen, Brazil, present a typical high-pressure granulite assemblage with evidence of mica breakdown partial melting (Ky + Grt + Kfs Bt Rt). The metamorphic peak temperatures obtained by Zr-in-Rt and ternary feldspar geothermometers are between 850 C and 900 C. The GASP baric peak pressure obtained using grossular rich garnet core is 16 kbar. Retrograde reaction textures in which the garnet crystals are partially to totally replaced by Bt + Qtz Fsp intergrowths are very common in the Carvalhos Klippe rocks. These reactions are interpreted as a result of interactions between residual phases and trapped melt during the retrograde path. In the present study the geochemical signatures of three groups of Carvalhos Klippe metasedimentary rocks are analysed. Despite the high metamorphic grade these three groups show well-defined geochemical features and their REE patterns are similar to average compositions of post-Archean sedimentary rocks (PAAS, NASC). The high-pressure granulite facies Grt-Bt-Pl gneisses with immature arenite (wacke, arkose or lithic-arenite) geochemical signatures present in the Carvalhos Klippe are compared to similar rocks in amphibolite facies from the same tectonic framework (Andrelndia Nappe System). The similar geochemical signatures between Grt-Bt-Pl gneisses metamorphosed in high-pressure granulite facies and Grt-Bt-Pl-Qtz schists from the Andrelndia and Liberdade Nappes, with minimal to absent melting conditions, are suggestive of low rates of melt extraction in these high-grade rocks. The rocks with pelitic compositions most likely had higher melt extraction and even under such circumstances nevertheless tend to show REE patterns similar to average compositions of post-Archean sedimentary rocks (PAAS, NASC).

Cioffi, Caue Rodrigues; Campos Neto, Mario da Costa; da Rocha, Brenda Chung; Moraes, Renato; Henrique-Pinto, Renato

2012-12-01

290

Reliability study of the NiH2 strain gage  

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

291

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

292

Partial discharges and breakdown in SF6 in the pressure range 25-150 kPa in non-uniform background fields  

NASA Astrophysics Data System (ADS)

The partial discharge (PD) and electric breakdown mechanisms in SF6 at a plug contact in the pressure range 25-150 kPa were investigated at ambient temperature in a plug-plate arrangement. This parameter range has similar particle number densities as in the previous investigation of the dielectric recovery in a high-voltage circuit breaker (Seeger et al 2012 J. Phys. D: Appl. Phys. 45 395204), where optical access was limited and the relevant parameters of pressure and temperature could only be determined indirectly by computational fluid dynamic simulations. The present investigation did not have these limitations, since the pressure and temperature were well defined. Optical observation by an image intensified high speed camera in combination with a photo multiplier tube allowed an understanding of the various mechanisms for the PDs and breakdown to be gained. The breakdown fields and PD parameters could be well described by a simple leader model in the pressure range 75-150 kPa for negative polarity and above 25 kPa for positive polarity. Discrepancies with the model are observed below 75 kPa for negative polarity and at 25 kPa for positive polarity. This could be explained by a slow, repetitive heating mechanism which has not been reported so far.

Seeger, M.; Clemen, M.

2014-01-01

293

Effect of residual stresses on design assessment of partial penetration laser welds in a pressure valve component  

SciTech Connect

An autogenous CO{sub 2} laser weld joining a cap fitting to a valve body was analyzed using the ANSYS code. This stress analysis evaluated various weld penetration conditions from 0.02 to 0.04 in. The evaluation criteria included fracture, fatigue and general yielding of the weld at three load conditions: maximum operating pressure (500 lb/in.{sup 2}), proof pressure (750 lb/in.{sup 2}) and burst pressure (1,250 lb/in.{sup 2}). It is concluded that, without considering welding-induced residual stresses, weld penetration of 0.02-in. (0.50 mm) is adequate for normal use of the investigated valve component. The factor of safety for 0.02-in. weld penetration is greater than four for the valve fitting. The residual stresses are found to affect the plastic zone size and shape. Weld shrinkage causes compressive radial stress at the weld root. The midsection of the weld penetration is in tension at radial, circumferential and longitudinal directions. The Von Mises equivalent stress in the weld is increased due to residual stresses, which reduces the safety factor by a range of around 40%. However, the factors of safety for all cases are still greater than three at rupture pressure. The root openings of the weld fitting with penetration greater than 0.02 in. are nonpropogating and fracture stable under the proof pressure due to the compressive residual stress surrounding the root opening. For a conservation design to relax the postweld inspection requirement or to prevent failure from an unexpected over-loading situation, a minimum of 0.03-in. (0.76 mm) weld penetration is recommended for the cap fitting.

Tsai, C.L.; Liaw, M.L. [Ohio State Univ., Columbus, OH (United States); Teng, J.I. [Marotta Scientific Controls, Inc. (United States)

1998-10-01

294

Effects of Pleistocene, pre-industrial, current, and future CO[sub 2] partial pressures on C[sub 3] and C[sub 4] plant growth  

SciTech Connect

To study plant growth in atmospheric CO[sub 2] concentrations ranging from Pleistocene through predicted future levels, Amaranthus retroflexus (C[sub 4]) and Abutilon theophrasti (C[sub 3]) were grown in growth chambers at four CO[sub 2] levels (15 Pa, Pleistocene minimum; 27 Pa, pre-industrial; 35 Pa, current; 70 Pa, future). Thirty-five days after emergence, shoot dry weight, root dry weight and leaf area did not differ between any CO[sub 2] levels for the C[sub 4] species. The C[sub 3] species showed increased root and shoot dry weights and leaf areas when grown in CO[sub 2] partial pressures of 15 Pa, 27 Pa and 35 Pa. This evidence indicates that plant growth in C[sub 4] species is unaffected by atmospheric CO[sub 2] levels ranging from the Pleistocene minimum through the future; whereas, C[sub 3] species show growth increases as CO[sub 2] partial pressures rise above the Pleistocene minimum.

Dippery, J.K.; Strain, B.R. (Duke Univ., Durham, NC (United States))

1993-06-01

295

Forming Free Bipolar ReRAM of Ag/a-IGZO/Pt with Improved Resistive Switching Uniformity Through Controlling Oxygen Partial Pressure  

NASA Astrophysics Data System (ADS)

Bipolar resistive switching properties of Ag/a-IGZO/Pt structure resistive random-access memories (ReRAMs) were investigated. The amorphous In-Ga-Zn-O (a-IGZO) films were prepared by a radio frequency magnetron sputtering system at room temperature in mixed gas ambient of argon (Ar) and oxygen (O2). The oxygen partial pressures during sputtering deposition were varied from 0% to 17% to engineer defects in an a-IGZO layer. When the oxygen partial pressure increased to 17%, forming-free bipolar resistive switching properties were observed with nearly 100% device yield. In addition, the forming-free ReRAM device presents an enhanced resistive switching uniformity and an enhanced endurance. The forming-free resistive switching is attributed to the concentration of oxygen-related defects in an a-IGZO thin film via analyses of x-ray photoelectron spectroscopy and current-voltage (I-V) curves, with which it is possible to reduce the forming energy of silver (Ag) conductive filaments.

Pei, Yanli; Mai, Biaoren; Zhang, Xiaoke; Hu, Ruiqin; Li, Ya; Chen, Zimin; Fan, Bingfeng; Liang, Jun; Wang, Gang

2014-12-01

296

Forming Free Bipolar ReRAM of Ag/a-IGZO/Pt with Improved Resistive Switching Uniformity Through Controlling Oxygen Partial Pressure  

NASA Astrophysics Data System (ADS)

Bipolar resistive switching properties of Ag/a-IGZO/Pt structure resistive random-access memories (ReRAMs) were investigated. The amorphous In-Ga-Zn-O (a-IGZO) films were prepared by a radio frequency magnetron sputtering system at room temperature in mixed gas ambient of argon (Ar) and oxygen (O2). The oxygen partial pressures during sputtering deposition were varied from 0% to 17% to engineer defects in an a-IGZO layer. When the oxygen partial pressure increased to 17%, forming-free bipolar resistive switching properties were observed with nearly 100% device yield. In addition, the forming-free ReRAM device presents an enhanced resistive switching uniformity and an enhanced endurance. The forming-free resistive switching is attributed to the concentration of oxygen-related defects in an a-IGZO thin film via analyses of x-ray photoelectron spectroscopy and current-voltage ( I- V) curves, with which it is possible to reduce the forming energy of silver (Ag) conductive filaments.

Pei, Yanli; Mai, Biaoren; Zhang, Xiaoke; Hu, Ruiqin; Li, Ya; Chen, Zimin; Fan, Bingfeng; Liang, Jun; Wang, Gang

2015-02-01

297

Comparison of the effects of pressure on three layered hydrates: a partially successful attempt to predict a high-pressure phase transition.  

PubMed

We report the effect of pressure on the crystal structures of betaine monohydrate (BTM), L-cysteic acid monohydrate (CAM) and S-4-sulfo-L-phenylalanine monohydrate (SPM). All three structures are composed of layers of zwitterionic molecules separated by layers of water molecules. In BTM the water molecules make donor interactions with the same layer of betaine molecules, and the structure remains in a compressed form of its ambient-pressure phase up to 7.8 GPa. CAM contains bi-layers of L-cysteic acid molecules separated by water molecules which form donor interactions to the bi-layers above and below. This phase is stable up to 6.8 GPa. SPM also contains layers of zwitterionic molecules with the waters acting as hydrogen-bond donors to the layers above and below. SPM undergoes a single-crystal to single-crystal phase transition above 1 GPa in which half the water molecules reorient so as to form one donor interaction with another water molecule within the same layer. In addition, half of the S-4-sulfo-L-phenylalanine molecules change their conformation. The high-pressure phase is stable up to 6.9 GPa, although modest rearrangements in hydrogen bonding and molecular conformation occur at 6.4 GPa. The three hydrates had been selected on the basis of their topological similarity (CAM and SPM) or dissimilarity (BTM) with serine hydrate, which undergoes a phase transition at 5 GPa in which the water molecules change orientation. The phase transition in SPM shows some common features with that in serine hydrate. The principal directions of compression in all three structures were found to correlate with directions of hydrogen bonds and distributions of interstitial voids. PMID:19923702

Johnstone, Russell D L; Lennie, Alistair R; Parsons, Simon; Pidcock, Elna; Warren, John E

2009-12-01

298

H2 Metabolism in Photosynthetic Organisms  

PubMed Central

Dark H2 metabolism was studied in marine and fresh water red algae, the green alga, Chlamydomonas, and mosses. A time variable and temperature-sensitive anaerobic incubation was required prior to H2 evolution. H2 evolution was sensitive to disalicylidenepropanediamine. An immediate H2 uptake was observed in these algae. Immediate dark H2 uptake but no evolution was observed in the mosses. A cell-free hydrogenase preparation was obtained from anaerobically adapted Chlamydomonas reinhardii by means of sonic oscillation. The hydrogenase was not sedimented at 100,000g. It catalyzed the reduction of methylene blue, p-benzoquinone, NAD, NADP, but not spinach ferredoxin. H2 evolution was noted with dithionite and with reduced methyl viologen as donors but not with reduced spinach ferredoxin. Similarly, hydrogenase activities were not affected by disalicylidenepropanediamine. The pH optima for H2 evolution and for H2 uptake were 7.2 and 7.5 to 9.5, respectively. Extracts prepared from the anaerobically adapted red alga, Chondrus crispus, and the moss, Leptobryum pyriforme, consumed but did not evolve H2. Uptake was slightly stimulated by methylene blue. It is proposed that red algae and mosses appear to metabolize H2 by a different pathway than Chlamydomonas. PMID:16659260

Ben-Amotz, Ami; Erbes, David L.; Riederer-Henderson, Mary Ann; Peavey, Dwight G.; Gibbs, Martin

1975-01-01

299

Synthesis of mixed-valent {alpha}- and {beta}-NaFe{sub 2}O{sub 3} polymorphs under controlled partial oxygen pressure  

SciTech Connect

Synthesis of mixed valent compounds, especially when multiple polymorphs exist, requires careful control of the preparation conditions. {alpha}- and {beta}-NaFe{sub 2}O{sub 3} polymorphs were synthesized under controlled partial oxygen pressure (pO{sub 2}). pO{sub 2} regions of stability at 850 Degree-Sign C were determined for both phases for the first time. A modified oxygen buffer method was developed for the facile preparation of mixed valent oxides under controlled pO{sub 2}. {beta}-NaFe{sub 2}O{sub 3} is the only known n=2 member of the AM{sub n}O{sub n+1} (A=alkali metal, M=3d metal) rock-salt related homolog series with layered cation ordering. The possibility of new members of the homolog series with other 3d metals is considered. - Graphical abstract: Schematic section of phase composition vs. partial O{sub 2} pressure diagram at 850 Degree-Sign C for Na/Fe=1/2 and structure models of {alpha}- and {beta}-NaFe{sub 2}O{sub 3}. Highlights: Black-Right-Pointing-Pointer {alpha}- and {beta}-NaFe{sub 2}O{sub 3} polymorphs were synthesized under controlled oxygen pressure. Black-Right-Pointing-Pointer {beta}-NaFe{sub 2}O{sub 3} has rock-salt related structure with layered cation ordering. Black-Right-Pointing-Pointer Existence of the rock-salt related homolog series AM{sub n}O{sub n+1} is discussed.

Bruno, Shaun R.; Blakely, Colin K. [Department of Chemistry, Michigan State University, East Lansing, MI 48824 (United States); Poltavets, Viktor V., E-mail: poltavets@chemistry.msu.edu [Department of Chemistry, Michigan State University, East Lansing, MI 48824 (United States)

2012-08-15

300

The effect of the partial pressure of water vapor on the surface tension of the liquid water-air interface.  

PubMed

Precise measurements of the surface tension of water in air vs. humidity at 5, 10, 15, and 20 C are shown. For constant temperature, surface tension decreases linearly for increasing humidity in air. These experimental data are in good agreement with a simple model based on Newton's laws here proposed. It is assumed that evaporating molecules of water are ejected from liquid to gas with a mean normal component of the speed of "ejection" greater than zero. A high humidity in the air reduces the net flow of evaporating water molecules lowering the effective surface tension on the drop. Therefore, just steam in air acts as an effective surfactant for the water-air interface. It can partially substitute chemical surfactants helping to reduce their environmental impact. PMID:22717083

Prez-Daz, Jos L; lvarez-Valenzuela, Marco A; Garca-Prada, Juan C

2012-09-01

301

Fluid resuscitation guided by sublingual partial pressure of carbon dioxide during hemorrhagic shock in a porcine model.  

PubMed

To avoid aggressive fluid resuscitation during hemorrhagic shock, fluid resuscitation is best guided by a specific measurement of tissue perfusion. We investigated whether fluid resuscitation guided by sublingual PCO2 would reduce the amount of resuscitation fluid without compromising the outcomes of hemorrhagic shock. Ten male domestic pigs weighing between 34 and 37 kg were used. Forty-five percent of estimated blood volume was removed during an interval of 1 h. The animals were then randomized to receive fluid resuscitation based on either sublingual PCO2 or blood pressure (BP). In the sublingual PCO2-guided group, resuscitation was initiated when sublingual PCO2 exceeded 70 Torr and stopped when it decreased to 50 Torr. In the BP-guided group, resuscitation was initiated when mean aortic pressure decreased to 60 mmHg and stopped when it increased to 90 mmHg. First, Ringer's lactate solution (RLS) of 30 mL kg was administered; subsequently, the shed blood was transfused if sublingual PCO2 remained greater than 50 Torr in the sublingual PCO2-guided group or mean aortic pressure was less than 90 mmHg in the BP-guided group. All the animals were monitored for 4 h and observed for an additional 68 h. In the sublingual PCO2-guided group, fluid resuscitation was required in only 40% of the animals. In addition, a significantly lower volume of RLS (170 239 mL, P = 0.005 vs. BP-guided group) was administered without the need for blood infusion in this group. However, in the BP-guided group, all the animals required a significantly larger volume of fluid (955 381 mL), including both RLS and blood. There were no differences in postresuscitation tissue microcirculation, myocardial and neurologic function, and 72-h survival between groups. During hemorrhagic shock, fluid resuscitation guided by sublingual PCO2 significantly reduced the amount of resuscitation fluid without compromising the outcomes of hemorrhagic shock. PMID:23364438

Xu, Jiefeng; Ma, Linhao; Sun, Shijie; Lu, Xiaoye; Wu, Xiaobo; Li, Zilong; Tang, Wanchun

2013-04-01

302

Ultraviolet elimination of H2 from chloroethylenes  

NASA Astrophysics Data System (ADS)

The elimination of H2 in the photodissociation of mono- and di-chloroethylenes was studied with a pump-and-probe technique. A 193 nm excimer laser was used to photodissociate the parent molecules, and a tunable dye laser was used to probe the H2 fragment by 2+1 resonance-enhanced multiphoton ionization (REMPI). The nascent rotational state distributions of H2(X 1?+g,v?=0-4) were extracted from the REMPI spectra, and were found to have Boltzmann-type distributions. The maximum and average translational energies for some of the rovibrational levels of H2 were measured using magic angle Doppler spectroscopy. The translational energy of the fragments plus the internal energy of H2 was found to exceed the available energy for a three-center elimination mechanism. It is concluded that a migration mechanism plays a significant role in H2 elimination.

He, Guoxin; Yang, Yuangan; Huang, Yibo; Hashimoto, Satoshi; Gordon, Robert J.

1995-10-01

303

Pressure-distribution measurements on a rectangular wing with a partial-span split flap in curved flight  

NASA Technical Reports Server (NTRS)

Pressure-distribution tests were made on the 32-foot whirling arm of the Daniel Guggenheim Airship Institute of a rectangular wing of NACA 23012 section to determine the rolling and the yawing moment due to angular velocity in yaw. The model was tested at 0 and 5 degree pitch; 0, +/- 5, and +/- 10 degrees yaw; and with no flap and with split flaps 25, 50 and 75 percent of the wing span and deflected 60 degrees. The results are given in the form of span load distributions and as calculated moment coefficients. The experimental values of rolling- and yawing-moment coefficients were in fairly close agreement with theory.

Rokus, Frank G

1939-01-01

304

A shock origin for interstellar H2O masers  

NASA Technical Reports Server (NTRS)

We present a comprehensive model for the powerful H2O masers observed in starforming regions. In this model the masers occur behind dissociative shocks propagating in dense regions. This paper focuses on high-velocity dissociative shocks in which the heat of H2 reformation on dust grains maintains a large column of 300 - 400 K gas, where the chemistry drives a considerable fraction of the oxygen not in CO to form H2O. The H2O column densities, the hydrogen densities, and the warm temperatures produced by these shocks are sufficiently high to enable powerful maser action, where the maser is excited by thermal collisions with H atoms and H2 molecules. A critical ingredient in determining the shock structure is the magnetic pressure, and the fields required by our models are in agreement with recent observations. The observed brightness temperatures are the result of coherent velocity regions which have dimensions in the shock plane that are five to 50 times the postshock thickness.

Hollenbach, David; Elitzur, Moshe; Mckee, Christopher F.

1993-01-01

305

Enhanced Resistance to CO Poisoning of Pd-based H2 Purification Membranes by Internal Oxidation  

SciTech Connect

There have been many investigations of the permeation of Pd membranes by H2. The purpose of this one is to compare H2 permeation rates of pure Pd and internally oxidized Pd-Al alloys in the presence and absence of CO. It was shown recently that the rates of H2 absorption by the Pd matrix in a Pd /Al2O3 composite prepared by internal oxidation of Pd-Al alloys were significantly faster than by a pure Pd sample. Partially internally oxidized Pd-Al alloys also exhibited faster rates of H2 absorption than pure Pd. The most important observation was that the poisoning of H2 permeation by CO(g) was smaller for the internally oxidized alloys than for pure Pd. These results suggested that partially internally oxidized Pd-Al alloys may be useful for H2 purification membranes. Completely internally oxidized Pd-Al alloys would not be as suitable because internal oxidation may cause them to become brittle and to develop microcracks whereas partial internal oxidation maintains the inner, unoxidized portion ductile and crack free. This research describes H2 permeation measurements using Pd and a partially internally oxidized Pd0.955Al0.045 alloy in the presence and absence of CO.

Shanahan, K.L.

2003-06-24

306

Pressure  

NSDL National Science Digital Library

This page contains three Physlets that are able to share data using a connection made by a common superclass, SApplet. The ensemble walls keep track of the change in momentum, i.e., the pressure, during each time step, dt, and provides this data to the DataGraph Physlet and the DataTable Physlet.

Wolfgang Christian

307

Pressure  

NSDL National Science Digital Library

This lab is not inquiry-based because the teacher must explain how to calculate pressure before doing the activity, but the lab gives students a great concept of what PSI means. They usually have no idea if 10 PSI is a lot or a little. They also don't und

Horton, Michael

2009-05-30

308

Chipping Away at ?-H2AX Foci  

PubMed Central

The mammalian histone H2AX protein functions as a dosage-dependent genomic caretaker and tumor suppressor. Phosphorylation of H2AX to form ?-H2AX in chromatin around DNA double strand breaks (DSBs) is an early event following induction of these hazardous lesions. For a decade, mechanisms that regulate H2AX phosphorylation have been investigated mainly through two-dimensional immunofluorescence (IF). We recently used chromatin immunoprecipitation (ChIP) to measure ?-H2AX densities along chromosomal DNA strands broken in G1 phase mouse lymphocytes. Our experiments revealed that 1) ?-H2AX densities in nucleosomes form at high levels near DSBs and at diminishing levels farther and farther away from DNA ends, and 2) ATM regulates H2AX phosphorylation through both MDC1-dependent and MDC1-independent means. Neither of these mechanisms were discovered by previous IF studies due to the inherent limitations of light microscopy. Here, we compare data obtained from parallel ?-H2AX ChIP and three-dimensional IF analyses and discuss the impact of our findings upon molecular mechanisms that regulate H2AX phosphorylation in chromatin around DNA breakage sites. PMID:19770593

Savic, Velibor; Sanborn, Keri B.; Orange, Jordan S.; Bassing, Craig H.

2010-01-01

309

Techniques for Elastic Properties Measurements of Partial Molten Rocks, Hydrous Minerals and Melts in Gas Pressure Vessels and Multi-Anvil Devices  

NASA Astrophysics Data System (ADS)

The interpretation of highly resolved seismic data from Earth's deep interior require measurements of the physical properties of Earth materials under experimental simulated mantle conditions. For deep crustal to uppermost mantle conditions high performance gas pressure vessels enable a virtually unrestricted optimization of the measuring configurations for high p-T-conditions [1]. Exhumed high pressure rocks can be used as representative samples. The paper presents transient measurements of elastic wave velocities for granulite facies rocks under partial melting conditions. Despite the compact natural rock samples as a result of long-term experiments exceeding pressures of 1.5 GPa and temperatures of 1,000C newly-formed garnets, orthopyroxenes and potash feldspars could be found in the samples after the experiments. Discovering the huge water storage capacity of nominally anhydrous minerals (NAMs) under high pressure conditions dramatically changed our image of state and dynamics of Earth's deep interior [2]. The simulation of these in situ conditions require using of diamond anvil cells (DAC) and multi-anvil devices (MAD) as well as mostly synthetical samples. MADs are more limited in pressure, but provide sample volumes 3 to 7 orders of magnitude bigger. They offer small and even adjustable temperature gradients over the whole sample. The bigger samples make anisotropy and structural effects in complex systems accessible for measurements in principle. Using ultrasonic interferometry the measurement of both elastic wave velocities have no limits for opaque and encapsulated samples. Using the 6 to 8 anvils of a MAD as buffers allow the simultaneous recording of acoustic emissions from different directions of space and consequently the localization of the spikes during ongoing phase transitions and dehydration. The recent development of deformation-DIA MADs (D-DIA) make not only deformation measurements under simulated mantle conditions possible, but also the measurement of elastic attenuation even in the seismic frequency range [3]. An indispensable condition for all these MAD techniques is the installation at a synchrotron. Only application of synchrotron radiation allows in situ pressure measurement, in situ X-ray diffraction (XRD), in situ deformation measurement, as well as in situ density and viscosity measurements of melts. We review recent techniques and present developments and results for MADs [4, 5]. (1) Mueller & Massonne, Phys. Chem. Earth (A) 2001, 26, 325-332.(2) Ohtani & Litasov, Rev. Min. Chem. 2006, 62, 397-420.(3) Li et al., Am. Min. 2006, 91, 517-527.(4) Mueller et al., High Press. Res. 2006, 26, 1-9.(5) Mueller et al., In: E. Ohtani (ed), Advances in High-Pressure Mineralogy 2007, 207-226.

Mueller, H. J.; Roetzler, K.; Schilling, F. R.; Wehber, M.; Lathe, C.

2008-12-01

310

Photolysis of H2O-H2O2 mixtures: The destruction of H2O2  

NASA Astrophysics Data System (ADS)

We present laboratory results on the loss of H2O2 in solid H2O + H2O2 mixtures at temperatures between 21 and 145 K initiated by UV photolysis (193 nm). Using infrared spectroscopy and microbalance gravimetry, we measured the decrease of the 3.5 ?m infrared absorption band during UV irradiation and obtained a photodestruction cross section that varies with temperature, being lowest at 70 K. We use our results, along with our previously measured H2O2 production rates via ionizing radiation and ion energy fluxes from the spacecraft to compare H2O2 creation and destruction at icy satellites by ions from their planetary magnetosphere and from solar UV photons. We conclude that, in many cases, H2O2 is not observed on icy satellite surfaces because the H2O2 photodestruction rate is much higher than the production rate via energetic particles, effectively keeping the H2O2 infrared signature at or below the noise level.

Loeffler, M. J.; Fama, M.; Baragiola, R. A.; Carlson, R. W.

2013-09-01

311

[Maintenance therapy of mild form of GERD by H2 receptor antagonists].  

PubMed

Because of high relapse rate after the healing by proton pump inhibitor(PPI) or H2 receptor antagonist(H2RA), GERD usually needs long time maintenance therapy. PPI is superior to H2RA in the first line as well as maintenance therapy. PPI is necessary for severe cases of GERD. However, H2RA is sufficient for milder form of GERD patients. Among the H2RA using in Japan, nizatidine has known to stimulate gastric emptying and elevate LES pressure. Nizatidine may be superior to other H2RAs in the treatment of GERD. Recently, nocturnal acid breakthrough which night time acid is secreted even PPI is administered twice daily has been documented. H2RAs are stronger than PPI to inhibit nocturnal acid breakthrough and may be better than night time acid reflux. PMID:11004816

Kurosawa, S

2000-09-01

312

On the mechanism of H atom production in hot filament activated H2 and CH4/H2 gas mixtures.  

PubMed

This article reports systematic measurements of the power utilization by Ta (and Re) hot filaments (HFs) operating in a poor vacuum, in pure He, N(2), and H(2), and in CH(4)/H(2) gas mixtures of relevance to diamond growth by HF chemical vapor deposition, as functions of filament temperature T(fil) (in the range of 1800-2700 K) and gas pressure p (in the range of 10(-2)-100 Torr). In the cases of H(2) and the CH(4)/H(2) gas mixtures, the power consumption studies are complemented by in situ measurements of the relative H atom densities [H] near the HF--which are seen to maximize at p approximately 10-20 Torr and thereafter to remain constant or, at the highest T(fil), to decline at higher p. These (and many previous) findings are rationalized by a companion theoretical analysis, which reduces the complex array of chemisorption and desorption processes that must contribute to the HF-surface mediated dissociation of H(2) to a two-step mechanism involving H atom formation by dissociative adsorption at bare (S(*)) sites and by desorption at hydrogenated (SH) sites on the HF surface. PMID:19655886

Comerford, Dane W; Smith, James A; Ashfold, Michael N R; Mankelevich, Yuri A

2009-07-28

313

Synthesis of mixed-valent [alpha]- and [beta]-NaFe[subscript 2]O[subscript 3] polymorphs under controlled partial oxygen pressure  

SciTech Connect

Synthesis of mixed valent compounds, especially when multiple polymorphs exist, requires careful control of the preparation conditions. {alpha}- and {beta}-NaFe{sub 2}O{sub 3} polymorphs were synthesized under controlled partial oxygen pressure (pO{sub 2}). pO{sub 2} regions of stability at 850 C were determined for both phases for the first time. A modified oxygen buffer method was developed for the facile preparation of mixed valent oxides under controlled pO{sub 2}. {beta}-NaFe{sub 2}O{sub 3} is the only known n = 2 member of the AM{sub n}O{sub n+1} (A = alkali metal, M = 3d metal) rock-salt related homolog series with layered cation ordering. The possibility of new members of the homolog series with other 3d metals is considered.

Bruno, Shaun R.; Blakely, Colin K.; Poltavets, Viktor V. (MSU)

2012-09-05

314

Effect of high pN2 and high pD2 on NH3 production, H2 evolution, and HD formation by nitrogenases  

SciTech Connect

We have investigated the effect of the partial pressure of N2 and D2 on HD formation, H2 evolution, and NH3 production by nitrogenase from Klebsiella pneumoniae and Clostridium pasteurianum. By using pressures up to 4 atm, we have been able to extend the concentration range of N2 and D2 in our investigations beyond that used in previous studies. The pN2 dependence of HD formation with constant pD2 ideally shows no HD formation under zero pN2, reaches a peak which depends on the pD2, and then decreases to zero at very high pN2. K. pneumoniae and C. pasteurianum nitrogenases differ in their Ki(D2) for nitrogen fixation. C. pasteurianum nitrogenase had the lower activity for formation of HD. With K. pneumoniae nitrogenase, D2 enhanced H2 evolution from 31% of the electron flux partitioned to H2 in the absence of D2 to 51% of the electron flux partitioned to H2 at 400 kPa of D2. With C. pasteurianum nitrogenase, the equivalent values were 33% and 48% of the total electron flux. Our results support previou findings on the mechanism for nitrogenase-catalyzed reductions proposed by W. W. Cleland.

Jensen, B.B.; Burris, R.H.

1985-02-26

315

Thermally pressure-induced partial structural phase transitions in core-shell InSb-SiO2 nanoballs/microballs: characterization, size and interface effect  

NASA Astrophysics Data System (ADS)

Core-shell InSb-SiO2 nanoballs/microballs were synthesized on a Si substrate by carbonthermal reactions at a temperature of 900 C. High-resolution transmission microscopy (HRTEM) images revealed that the surfaces of the InSb nanoballs/microballs were covered by amorphous SiO2 layers. On the basis of our theoretical calculation, the thermal expansion coefficient (TEC) of the InSb crystals is ten times higher than that of the SiO2 shell. Therefore, the SiO2 serves as a constraining shell for the InSb core so that the compressive stress of -94 MPa can accumulate in the InSb core while a tensile stress of 196 MPa forms in the SiO2 shell. The thermal excitation accumulated compressive stress in the InSb core, causing a partial structural phase transition from a cubic zinc-blende structure to a hexagonal wurtzite structure. Many lattice defects, such as stacking faults and Moir fringes, have been observed on the surface of the InSb core. In situ temperature-dependent XRD patterns showed that a reversible InSb hexagonal (002) peak appeared and disappeared as the temperature increased and decreased at a transit point of 200 C, respectively. As the temperature increased, the XRD diffraction peaks of the InSb wurtzite phase shifted significantly to lower angles because of the formation of compressive stress in the InSb nanoballs. The pressure-induced partial structural phase transitions of the nanostructured InSb occurred at -94 MPa of the compressive stress. This is the first report of this value, which is the lowest value in the pressure-induced phase transition of the nanostructure InSb from the cubic zinc-blende structure to the hexagonal wurtzite structure.

Wu, Jyh Ming; Huang, Hsiao Jung; Lin, Ying Hong

2014-09-01

316

Thermally pressure-induced partial structural phase transitions in core-shell InSb-SiO2 nanoballs/microballs: characterization, size and interface effect.  

PubMed

Core-shell InSb-SiO(2) nanoballs/microballs were synthesized on a Si substrate by carbonthermal reactions at a temperature of 900 C. High-resolution transmission microscopy (HRTEM) images revealed that the surfaces of the InSb nanoballs/microballs were covered by amorphous SiO(2) layers. On the basis of our theoretical calculation, the thermal expansion coefficient (TEC) of the InSb crystals is ten times higher than that of the SiO(2) shell. Therefore, the SiO(2) serves as a constraining shell for the InSb core so that the compressive stress of ?-94 MPa can accumulate in the InSb core while a tensile stress of 196 MPa forms in the SiO(2) shell. The thermal excitation accumulated compressive stress in the InSb core, causing a partial structural phase transition from a cubic zinc-blende structure to a hexagonal wurtzite structure. Many lattice defects, such as stacking faults and Moir fringes, have been observed on the surface of the InSb core. In situ temperature-dependent XRD patterns showed that a reversible InSb hexagonal (002) peak appeared and disappeared as the temperature increased and decreased at a transit point of 200 C, respectively. As the temperature increased, the XRD diffraction peaks of the InSb wurtzite phase shifted significantly to lower angles because of the formation of compressive stress in the InSb nanoballs. The pressure-induced partial structural phase transitions of the nanostructured InSb occurred at -94 MPa of the compressive stress. This is the first report of this value, which is the lowest value in the pressure-induced phase transition of the nanostructure InSb from the cubic zinc-blende structure to the hexagonal wurtzite structure. PMID:25208586

Wu, Jyh Ming; Huang, Hsiao Jung; Lin, Ying Hong

2014-10-01

317

Stabilization of H2 by Organic Acids  

E-print Network

Stabilization of H2 SO4 ­H2 O Clusters by Organic Acids A.B. Nadykto1 and F. Yu1 Abstract While understood. In the present study, bonding among formic, acetic and benzoic acids, sulfuric acid, ammonia. The stabilizing effect of formic, acetic, and benzoic acids is found to be close that of ammonia that indicates

Yu, Fangqun

318

A SAFT equation of state for the quaternary H2S-CO2-H2O-NaCl system  

NASA Astrophysics Data System (ADS)

Phase equilibria and thermodynamic properties of the quaternary H2S-CO2-H2O-NaCl system were studied using a statistical associating fluid theory (SAFT)-based equation of state (EOS) at temperatures from 0 to 200 C (373.15-473.15 K), pressures up to 600 bar (60 MPa) and concentrations of NaCl up to 6 mol/kgH2O. The understanding of the physical-chemical properties of this system is critical for predicting the consequences of co-injection of CO2 and H2S into geological formations (geological carbon sequestration) as an option for mitigating the global warming trend. Equation of state parameters were generated from regression of available and reliable experimental data and incorporation of existing parameters for some subsystems. Densities were predicted and compared with available experimental results. Using the EOS developed in this study, we predicted equilibrium compositions in both liquid and vapor phases, fugacity coefficients of components, the equilibrium pressures at a given composition of the H2O-rich phase in electrolyte solutions with NaCl varying from 0 to 4 mol/kgH2O, and the aqueous solution densities. These predicted values are tabulated and available as supplementary data in the electronic version online. These predictions provide information and guidance for future experiments regarding the thermodynamic properties and phase behaviors in the H2S-CO2-H2O-NaCl system.

Ji, Xiaoyan; Zhu, Chen

2012-08-01

319

Subduction factory: 4. Depthdependent flux of H2O from subducting slabs worldwide  

E-print Network

and depend strongly on composition (gabbro versus peridotite) and local pressure and temperature conditions and roughly equally in the gabbro and peridotite sections. The predicted global flux of H2O to the deep mantle

van Keken, Peter

320

Partial Eval Partial Eval  

E-print Network

. . . . -- -- -- . . #12; A Naive Onl ine Partial val at r E (expression) ::= x | l l l lx.E | E@E #12; A Naive Onl ine Partial val at r E (expression) ::= x | l l l lx.E | E@E onpe : exp® ® ® ®env® ® ® ®value option ? ? ? ? exp (symbolic value) #12; A Naive Onl ine Partial val at r E (expression) ::= x | l l l lx.E | E

Sumii, Eijiro

321

Effects of fluid-induced metasomatism on 40Ar/39Ar geochronology in partially recrystallized high-pressure rocks  

NASA Astrophysics Data System (ADS)

Mineral replacement processes during metasomatism play an important role for the re-equilibration of major and trace elements and their isotopic compositions between reacting rocks and percolating fluids. However, the effects of recrystallization processes during metamorphism on the Ar isotopic composition and the implications on 40Ar/39Ar age determinations are not well understood. We use concentrations and isotopic compositions of boron and lithium as highly fluid-mobile elements in amphiboles and phengites from partially overprinted eclogite-facies rocks from the Western Alpine Sesia-Lanzo zone (SLZ) to quantify metamorphic fluid fluxes. TEM investigations are used to constrain recrystallization processes during this metasomatic overprint. These data are combined with in situ analyses of Ar isotopic zoning to systematically evaluate the effects of fluid-rock interaction and recrystallization mechanisms on the Ar isotope system. The samples were taken along a structural profile across a strain- and recrystallization gradient induced by a km-scale blueschist-facies shear zone that separates two tectonometamorphic subunits in the SLZ. In all samples, phengite and sodic amphibole show significant major element compositional differences between pristine cores and overprinted areas. TEM observations demonstrate that solution-reprecipitation was the major recrystallization mechanism. Boron and Li are leached from overprinted parts as a result of fluid percolation. Lithium and B concentrations and B isotopic data show that retrograde fluid influx increases from weakly deformed samples towards highly deformed mylonites. Samples from within the shear zone have the lowest B concentrations and the highest ?11B values, suggesting equilibration with an external fluid with high ?11B. Argon isotopic compositions show scatter in the calculated apparent ages depending on strain intensity and the amount of fluid influx. 40Ar/39Ar laser spot ages in the unmodified cores of all samples yield apparent ages consistently between 843 Ma and 874 Ma. The calculated ages in the overprinted rims of the weakly deformed samples are between 703 and 862 Ma, suggesting an incomplete isotopic resetting during fluid influx. In contrast, the samples that show an intense deformational overprint associated with a strong mylonitisation of larger mica grains yield bimodal apparent ages: Ages around 853 Ma for large mica clasts that are surrounded by the foliation and ages around 654 Ma for the smaller mylonitic mica. The significant decrease in apparent age can clearly be associated with high fluid flux in the shear zone, which is supported by the B isotope data. In summary, fluid-induced resetting of Ar isotopes in phengitic mica is controlled by mylonitic deformation and associated fluid flux during exhumation and juxtaposition of two tectonometamorphic segments in the SLZ. Our study demonstrates that high spatial resolution is critical to fully understand the temporal information in 40Ar/39Ar dates of metasomatized rocks and underlines the importance of metasomatic processes for geochronology.

Halama, R.; Konrad-Schmolke, M.; Sudo, M.; Wirth, R.

2012-12-01

322

Photolysis Of H2O2-H2O Mixtures: The Destruction Of H2O2  

NASA Astrophysics Data System (ADS)

Numerous laboratory studies have shown that small, but easily detectable, amounts of hydrogen peroxide can be formed by irradiating water ice with many different types of energetic particles. Thus it seems likely that hydrogen peroxide would be a common component detected in the outer solar system, as both water ice and radiation are almost everywhere. However, hydrogen peroxide has only been observed in the reflectance spectra of a few objects. One possibility for the lack of hydrogen peroxide is that UV photons > 180 nm, which are not absorbed by H2O, preferentially destroy H2O2 that may have formed from Lyman-alpha or other ionizing radiation. To test this hypothesis, we will present data on the photodestruction rates of H2O2 in H2O mixtures using UV photons (193 nm) and discuss possible implications for outer solar system bodies. This work is being funded by NASA Outer Solar System Program

Loeffler, Mark; Fama, M.; Baragiola, R. A.; Carlson, R. W.

2008-09-01

323

Effects of water-saturation on strength and ductility of three igneous rocks at effective pressures to 50 MPA and temperatures to partial melting  

SciTech Connect

The short-term failure strengths and strains at failure of room-dry and water-saturated, cylindrical specimens (2 by 4 cm) of Charcoal Granodiorite (CG), Mt. Hood Andesite (MHA), and Cuerbio Basalt (CB) at a strain rate of 10/sup -4/s/sup -1/, at effective confining pressures of 0, 50, and 100 MPa and at temperatures to partial melting were investigated. Data from water-saturated specimens of the granodiorite and andesite, compared to room-dry counterparts, indicate (1) the pore pressures are essentially communicated throughout each test specimen so that they are fully effective; (2) at P/sub e/ = 0 and 50 MPa the granodiorite does not water-weaken; (3) at these same effective pressures the more porous and finer-grained andesite begins to exhibit water-weakening at about 600/sup 0/C; (4) at P/sub e/ = 0 and 870 to 900/sup 0/C the andesite's strength averages 20 MPa while the strength of dry specimens at the same P and T exhibit a strength of 100 MPa; (5) at P/sub e/ = 50 MPa compared to 160 MPa dry; (6) the basalt at P/sub e/ = 0, appears to be water-weakened at 800/sup 0/C; (7) water saturated specimens deformed at temperatures less than that of melting exhibit ultimate strengths at less than 2% shortening and then work-soften along faults; (8) again as do the dry counterparts, the wet specimens deform primarily by microscopic fracturing that coalesces into one or more macroscopic faults; and (9) the temperature for incipient melting of the andesite is decreased >150/sup 0/C in the water-saturated tests.

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

1981-01-01

324

H2 enrichment from synthesis gas by Desulfotomaculum carboxydivorans for potential applications in synthesis gas purification and biodesulfurization.  

PubMed

Desulfotomaculum carboxydivorans, recently isolated from a full-scale anaerobic wastewater treatment facility, is a sulfate reducer capable of hydrogenogenic growth on carbon monoxide (CO). In the presence of sulfate, the hydrogen formed is used for sulfate reduction. The organism grows rapidly at 200 kPa CO, pH 7.0, and 55 degrees C, with a generation time of 100 min, producing nearly equimolar amounts of H(2) and CO(2) from CO and H(2)O. The high specific CO conversion rates, exceeding 0.8 mol CO (g protein)(-1) h(-1), makes this bacterium an interesting candidate for a biological alternative of the currently employed chemical catalytic water-gas shift reaction to purify synthesis gas (contains mainly H(2), CO, and CO(2)). Furthermore, as D. carboxydivorans is capable of hydrogenotrophic sulfate reduction at partial CO pressures exceeding 100 kPa, it is also a good candidate for biodesulfurization processes using synthesis gas as electron donor at elevated temperatures, e.g., in biological flue gas desulfurization. Although high maximal specific sulfate reduction rates (32 mmol (g protein)(-1) h(-1)) can be obtained, its sulfide tolerance is rather low and pH dependent, i.e., maximally 9 and 5 mM sulfide at pH 7.2 and pH 6.5, respectively. PMID:17583809

Sipma, Jan; Osuna, M Begoa; Parshina, Sofiya N; Lettinga, Gatze; Stams, Alfons J M; Lens, Piet N L

2007-08-01

325

Progression into the First Meiotic Division Is Sensitive to Histone H2a-H2b Dimer Concentration in Saccharomyces Cerevisiae  

PubMed Central

The yeast Saccharomyces cerevisiae contains two genes for histone H2A and two for histone H2B located in two divergently transcribed gene pairs: HTA1-HTB1 and HTA2-HTB2. Diploid strains lacking HTA1-HTB1 (hta1-htb1?/hta1-htb1?, HTA2-HTB2/HTA2-HTB2) grow vegetatively, but will not sporulate. This sporulation phenotype results from a partial depletion of H2A-H2B dimers. Since the expression patterns of HTA1-HTB1 and HTA2-HTB2 are similar in mitosis and meiosis, the sporulation pathway is therefore more sensitive than the mitotic cycle to depletion of H2A-H2B dimers. After completing premeiotic DNA replication, commitment to meiotic recombination, and chiasma resolution, the hta1-htb1?/hta1-htb1?, HTA2-HTB2/HTA2-HTB2 mutant arrests before the first meiotic division. The arrest is not due to any obvious disruptions in spindle pole bodies or microtubules. The meiotic block is not bypassed in backgrounds homozygous for spo13, rad50?, or rad9? mutations, but is bypassed in the presence of hydroxyurea, a drug known to inhibit DNA chain elongation. We hypothesize that the deposition of H2A-H2B dimers in the mutant is unable to keep pace with the replication fork, thereby leading to a disruption in chromosome structure that interferes with the meiotic divisions. PMID:9055075

Tsui, K.; Simon, L.; Norris, D.

1997-01-01

326

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

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

2014-12-09

327

TES/Aura L2 Water Vapor (H2O) Limb (TL2H2OLS)  

TES/Aura L2 Water Vapor (H2O) Limb (TL2H2OLS) News: TES News ... Level: L2 Platform: TES/Aura L2 Water Vapor Spatial Coverage: 27 x 23 km Limb ... Access: OPeNDAP Parameters: H2O Water Volume Mixing Radio Precision Vertical Resolution Order ...

2015-01-30

328

Aerobic oxidation of starch catalyzed by isopolyoxovanadate Na4Co(H2O)6V10O28.  

PubMed

The partial oxidation of starch was achieved in the presence of oxygen with Na4Co(H2O)6V10O2818H2O (abbreviated as CoV10) as catalyst. The oxidation degree of starch was determined by FT-IR, XRD and SEM measurements, which indicated that the aerobic oxidation of starch was promoted by oxidative catalyst CoV10. The application of CoV10 could give a high oxidation degree (DO) of 1.35 COOH/100GU and 2.07 CO/100GU with 86wt.% yield of solid starch under mild reaction conditions (pH=6; reaction time, 8h; temperature, 50C; catalyst amount, 8mg, when 1.5g starch was used as substrate; atmospheric pressure). Among some vanadium compounds, CoV10 exhibited 4-fold activity higher than orthovanadate due to its coordination effect of cobalt and V10O28. Meanwhile, CoV10 could be recycled for six times with only a slight decrease in activity. Thus, CoV10/O2 is one of the most efficient systems for partial oxidation of starch reported so far. PMID:25498687

Chen, Xiaoli; Yan, Siqi; Wang, Hang; Hu, Zhiyun; Wang, Xiaohong; Huo, Mingxin

2015-03-01

329

Interstellar clouds containing optically thin H2  

NASA Technical Reports Server (NTRS)

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

Jura, M.

1975-01-01

330

Thermal modeling of NiH2 batteries  

NASA Technical Reports Server (NTRS)

The following are discussed: NiH2 battery mission and environment; NiH2 cell heat dissipation; Nodal software; model development general philosophy; NiH2 battery model development; and NiH2 experimental developments.

Ponthus, Agnes-Marie; Alexandre, Alain

1994-01-01

331

Theoretical studies of photoexcitation and ionization in H2O  

NASA Technical Reports Server (NTRS)

Theoretical studies using Franck-Condon and static-exchange approximations are reported for the complete dipole excitation and ionization spectrum in H2O, where (1) large Cartesian Gaussian basis sets are used to represent the required discrete and continuum electronic eigenfunctions at the ground state equilibrium geometry, and (2) previously devised moment-theory techniques are employed in constructing the continuum oscillator-strength densities from the calculated spectra. Comparisons are made of the calculated excitation and ionization profiles with recent experimental photoabsorption studies and corresponding spectral assignments, electron impact-excitation cross sections, and dipole and synchrotron-radiation studies of partial-channel photoionization cross sections. The calculated partial-channel cross sections are found to be atomic-like, and dominated by 2p-kd components. It is suggested that the latter transition couples with the underlying 1b(1)-kb(1) channel, accounting for a prominent feature in recent synchrotron-radiation measurements.

Diercksen, G. H. F.; Kraemer, W. P.; Rescigno, T. N.; Bender, C. F.; Mckoy, B. V.; Langhoff, S. R.; Langhoff, P. W.

1982-01-01

332

Effects of water-saturation on strength and ductility of three igneous rocks at effective pressures to 50 MPa and temperatures to partial melting  

SciTech Connect

Instantaneous-failure strengths and ductilities of water-saturated cylindrical specimens of Charcoal Granodiorite, Mount Hood Andesite, and Cuerbio Basalt are determined at a strain rate of 10{sup -4}s{sup -1} and at effective confining pressures (Pe) of 0 and 50 MPa and at temperatures to partial melting. The data indicate: (1) at Pe = 0 and 50 MPa (Pc and Pp of 50 MPa and of 100 and 50 MPa, respectively) the granodiorite does not water-weaken; (2) at these same Pe the more porous and finer-grained andesite begins to exhibit water-weakening at about 600/sup 0/C; (3) at Pe = 0 and 870-900{sup 0}C the andesite's wet strength averages 20 MPa compared to 100 MPa, dry; (4) at Pe = 50 MPa and 920{sup 0}C its wet strength is 45 MPa compared to 160 MPa dry; (5) at Pe = 0, the basalt appears to be water-weakened above 800{sup 0}C; (6) water-saturated specimens deformed at temperatures less than T{sub m} exhibit ultimate strengths at less than 2 percent shortening and then work-soften along faults; and (7) both dry and wet specimens deform primarily by brittle fracture. Extrapolations indicate: (1) crystalline rocks should be drillable because they remain brittle until partial melting occurs, and penetration rates should increase with temperature because there is a corresponding decrease in brittle fracture strength; (2) boreholes in ''water-filled'' holes will be stable to >10 km at temperatures 10 km; and (4) open boreholes in the andesite are apt to be much less stable, and at similar temperatures would fail at 2 to 5-km depth.

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

1981-01-01

333

The Sulfidation of a Co15 wt.% Ce Alloy in H2-H2S Mixtures at 600-800C  

Microsoft Academic Search

The sulfidation behavior of a Co-Ce alloycontaining approximately 15 wt.% Ce has been studied at600-800C in H2-H2S mixturesproviding a sulfur pressure of 10-8 atm, butalso of 10-7 atm at 800C. At 600 and 700C the alloy corrodes moreslowly than pure cobalt, but more rapidly than purecerium. At 800C under 10-8 atmS2, which is below the stability of thecobalt sulfides, the

P. Castello; G. Y. Fu; Y. Niu; F. Gesmundo; F. Viani

1998-01-01

334

Research paper Solubility of CePO4 monazite and YPO4 xenotime in H2O and H2ONaCl at 800 C and  

E-print Network

Research paper Solubility of CePO4 monazite and YPO4 xenotime in H2O and H2O­NaCl at 800 °C and 1. In order to constrain the solubility of monazite and YPO4 xenotime at high pressure and temperature, we carried out weight-loss experiments on synthetic single crystals of CePO4 (monazite) and YPO4 (xenotime

Manning, Craig

335

Dual bonding between H2O/H2S and AgCl/CuCl: Cu/Ag bond, sister bond to Au bond.  

PubMed

Recently, Legon et al. reported the first generation and characterization of H2O/H2SAgCl complexes by rotational spectroscopy and proposed whether there is a silver bond analogous to the more familiar hydrogen and halogen bonds. In this study, a theoretical investigation was performed to answer this question and to deepen the nature of intermolecular interactions for H2O/H2SM-Cl (M = Cu, Ag, and Au) complexes. NBO analyses reveal that two types of delocalization interactions coexist in these complexes. Apart from the expected ?-donation interaction, the hyperconjugation interaction between H2O/H2S and M-Cl also takes part in the bonding. On the basis of such a dual-bonding mechanism, one class of bond, termed Cu/Ag bond, was defined in this study. In addition, the topological properties at a bond critical point, binding energies, and stretching frequency shifts studied here support that Cu/Ag bond is a sister bond to Au bond put forward previously by Sadlej et al. The Cu/Ag/Au bond is partially covalent and partially electrostatic in nature. Finally, the dual-bonding mechanism of Cu/Ag/Au bond was further discussed. This dual-bonding scheme may be considered a new synergistic bonding model for coordination compounds. PMID:24070212

Zhang, Guiqiu; Zhao, Xingjuan; Chen, Dezhan

2013-10-24

336

Reconstruction of pH and partial pressure of carbon dioxide during the Mesozoic era period using boron and oxygen isotopic compositions of fresh ammonoids & nautiloids  

NASA Astrophysics Data System (ADS)

The increase of partial pressure of carbon dioxide (pCO2) in the atmosphere induces global warming and ocean acidification at the modern condition. The reconstruction of pCO2 during the geological time is required together with proxy calibration by laboratory experiments to predict the future environments. Boron isotopic ratio is an excellent proxy for pH and the relevant partial pressure of carbon dioxide in the seawater (PCO2). This study is the first to quantify pH dependence of delta 11B of the ammonoids and nautiloids mainly in the Cretaceous and in Jurassic (70-162 Ma), which are expected to be much warmer due to higher PCO2. However, no reliable reconstruction data using foraminiferal delta 11B before Cenozoic era has been reported. We used the very fresh aragonite shells of ammonoids and nautiloids by big advantages. Since aragonite changes into secondary calcite by diagenesis, it is easy and effective to identify the degree of alteration at each sample by measuring calcite/aragonite ratio. Also we carefully conducted the assessment of secondary alteration from three perspectives: 1) Determination of calcite/aragonite ratio by X-ray diffraction (XRD), 2) Observation of microstructures of the nacreous layers by scanning electron microscope (SEM), and 3) Measurement of trace element contents and stable isotope ratios. We conducted high precision boron isotope analysis of biogenic carbonates with +/- 0.1 per mil reproducibility by adopting positive thermal ionization mass spectrometry (P-TIMS) methods. Also we analyzed delta 18O to estimate paleo-temperature, at which biogenic aragonite was formed. Combination of delta 11B and delta 18O of biogenic aragonite in 80 Ma and 86 Ma revealed that deeper dwellers showed lower delta 11B values, which corresponded to lower pH. This feature is consistent with those observed in the modern vertical water column. The respective shallow water temperature was 19.7 and 19.1 centigrade. Based on these results, the reconstructed maximum PCO2 levels at late Cretaceous (80 Ma and 86 Ma) were estimated to be 1750 and 1540 ppm, respectively. This coincides with the suggestion by Breecker et al. (2010) that pCO2 for the last 400 millions was usually at below 2000 ppm by reassessing the delta 13C proxy in soils.

Kawahata, Hodaka; Fukushima, Ayaka; Moriya, Kazuyori; Ishikawa, Tsuyoshi; Suzuki, Atsushi; Tanabe, Kazushige

2013-04-01

337

Search for H2- N2 Dimer in Titan's Atmosphere  

NASA Astrophysics Data System (ADS)

Molecular dimers (van der Waals bound associations of two molecules) involving H2 are useful for investigating the dynamics of planetary atmospheres because they can provide the ratio of ortho-H2 and para-H2 even for uncertain temperature. Because of the long transition time to achieve equilibrium between these states compared to the characteristic times of convection and advection, differences in the ratio of these species vs position over a planetary disk can provide information on dynamical phenomena. Since Voyager, dimers have now been detected for all of the outer planets and Titan, except Uranus and Titan, using ground-based near-IR vibrational-band spectra. We report our search for the H2-N2 dimer in Titan's near-IR spectrum ( 2.122 ?m) using the new Gemini Integral Field Spectrograph (NIFS) on 7 and 8 Feb 2006 with adaptive optics to resolve Titan's 0.9" disk with a resolution of about 0."1. This is an improvement upon previous searches, which necessarily averaged Titan's whole disk, because clear regions where the surface is visible can be spatially resolved from clouds and haze. Our search strategy was to sort the spectra for all the disk pixels in order of increasing pressure-induced (PIA) H2- N2 absorption. This facilitates locating the maximum clear absorption path through the atmosphere because local haze or clouds raises the albedo, and PIA absorption is weighted more to lower altitudes than CH4 is by virtue of its pressure-squared dependence. The PIA H2 S(1) band "turns on" between 2.02 ?m (where the surface is least attenuated) and 2.121 ?m (peaking near the quadrupole line, where the surface is essentially obscured). One unanticipated problem is the presence of weak CH4 lines spanning the broad dimer wavelengths, which are enhanced at the longer paths. It is necessary to model these in order to detect and reveal the dimer structure. We describe our progress.

Trafton, Laurence M.; Geballe, T. R.; Kim, S. J.

2006-09-01

338

H2CO in the Horsehead nebula  

NASA Astrophysics Data System (ADS)

Photodissociation region (PDR) models are used to understand the evolution of the far-UV illuminated matter both in our Galaxy and in external galaxies. The spectacular instrumental improvements, which happens in radioastronomy with the advent of Herschel, ALMA and NOEMA, call for matching progresses in PDR modeling. While it is now confirmed that some interstellar species are mostly formed in the gas phase (CO for instance) and others on grains (CH3OH, Garrod et al. 2007), the chemical routes for other species, like H2CO, are still debated because it is likely that solid and gas phase processes are both needed. The availability of well defined observations is essential here to discriminate between chemical assumptions about the important grain surface processes: adsorption, desorption and reactivity. Due to its closeness (~400 pc) and simple geometry, the Horsehead PDR is particularly well suited to investigate the grain surface chemistry. We present observations of 7 transitions of formaldehyde (H2CO) toward two positions: the edge of the nebula exposed to the UV-field (PDR), and a colder region (cold core) shielded from the UV radiation. A non-LTE Montecarlo radiative transfer code is used to determine the H2CO abundance from the observed intensities and line profiles. We find that the H2CO abundance is very similar in the warm PDR and in the cold dense core. The inferred abundances are compared with PDR models, including both gas-phase and grain surface reactions, in order to study the dominant formation routes of H2CO. Pure gas-phase chemistry models fail to reproduce the observed H2CO abundance by a factor ~10 in the PDR, while surface grain chemistry increases the H2CO abundance up to 3 orders of magnitude in the PDR.

Guzman, Viviana

2011-07-01

339

Isolation and Characterization of a Thermophilic Bacterium Which Oxidizes Acetate in Syntrophic Association with a Methanogen and Which Grows Acetogenically on H(2)-CO(2).  

PubMed

We previously described a thermophilic (60 degrees C), syntrophic, two-membered culture which converted acetate to methane via a two-step mechanism in which acetate was oxidized to H(2) and CO(2). While the hydrogenotrophic methanogen Methanobacterium sp. strain THF in the biculture was readily isolated, we were unable to find a substrate that was suitable for isolation of the acetate-oxidizing member of the biculture. In this study, we found that the biculture grew on ethylene glycol, and an acetate-oxidizing, rod-shaped bacterium (AOR) was isolated from the biculture by dilution into medium containing ethylene glycol as the growth substrate. When the axenic culture of the AOR was recombined with a pure culture of Methanobacterium sp. strain THF, the reconstituted biculture grew on acetate and converted it to CH(4). The AOR used ethylene glycol, 1,2-propanediol, formate, pyruvate, glycine-betaine, and H(2)-CO(2) as growth substrates. Acetate was the major fermentation product detected from these substrates, except for 1,2-propanediol, which was converted to 1-propanol and propionate. N,N-Dimethylglycine was also formed from glycine-betaine. Acetate was formed in stoichiometric amounts during growth on H(2)-CO(2), demonstrating that the AOR is an acetogen. This reaction, which was carried out by the pure culture of the AOR in the presence of high partial pressures of H(2), was the reverse of the acetate oxidation reaction carried out by the AOR when hydrogen partial pressures were kept low by coculturing it with Methanobacterium sp. strain THF. The DNA base composition of the AOR was 47 mol% guanine plus cytosine, and no cytochromes were detected. PMID:16347518

Lee, Monica J; Zinder, Stephen H

1988-01-01

340

Metabolic Acclimation to Anoxia Induced by Low (2-4 kPa Partial Pressure) Oxygen Pretreatment (Hypoxia) in Root Tips of Zea mays.  

PubMed

Young intact plants of maize (Zea mays L. cv INRA 508) were exposed to 2 to 4 kilopascals partial pressure oxygen (hypoxic pretreatment) for 18 hours before excision of the 5 millimeter root apex and treatment with strictly anaerobic conditions (anoxia). Hypoxic acclimation gave rise to larger amounts of ATP, to larger ATP/ADP and adenylate energy charge ratios, and to higher rates of ethanol production when excised root tips were subsequently made anaerobic, compared with root tips transferred directly from aerobic to anaerobic media. Improved energy metabolism following hypoxic pretreatment was associated with increased activity of alcohol dehydrogenase (ADH), and induction of ADH-2 isozymes. Roots of Adh1(-) mutant plants lacked constitutive ADH and only slowly produced ethanol when made anaerobic. Those that were hypoxically pretreated acclimated to anoxia with induction of ADH2 and a higher energy metabolism, and a rate of ethanol production comparable to that of nonmutants. All these responses were insensitive to the presence or absence of NO(3) (-). Additionally, the rate of ethanol production was about 50 times greater than the rate of reduction of NO(3) (-) to NO(2) (-). These results indicate that nitrate reductase does not compete effectively with ADH for NADH, or contribute to energy metabolism during anaerobic respiration in this tissue through nitrate reduction. Unacclimated root tips of wild type and Adhl(-) mutants appeared not to survive more than 8 to 9 hours in strict anoxia; when hypoxically pretreated they tolerated periods under anoxia in excess of 22 hours. PMID:16665894

Saglio, P H; Drew, M C; Pradet, A

1988-01-01

341

Piezoelectric and dielectric properties of Sn-doped (Na0.5K0.5)NbO3 ceramics processed under low oxygen partial pressure atmosphere  

NASA Astrophysics Data System (ADS)

Sn-doped (Na0.5K0.5)NbO3 (Sn-NKN) ceramics fired under various oxygen partial pressure (pO2) conditions have been investigated and discussed in terms of bulk piezoelectric and dielectric properties. X-ray diffraction measurements and Rayleigh analysis indicate that the substitution site of the Sn cations depend on the pO2 atmosphere in the firing process. For pO2 higher than 1.0 10-10 atm, Sn cations mainly substitute as Sn4+ at the B-site of perovskite NKN, whereas Sn2+ A-site substitution is favored under a low-pO2 atmosphere. Low-pO2 fired Sn-NKN ceramics exhibit higher relative permittivity, Curie temperature, and piezoelectric coefficient (d33). Sn2+ at A-site acts as a donor and reduces the p-type carrier concentrations that result from an electronic compensation of metal vacancies created through the high volatility of Na and K suboxides. The higher piezoelectricity and resistivity in low-pO2 fired Sn-NKN ceramics make this material suitable for base-metal cofired devices such as Ni-inner-electrode multilayer capacitors and actuators.

Kobayashi, Keisuke; Doshida, Yutaka; Mizuno, Youichi; Randall, Clive A.

2014-01-01

342

Effects of elevated partial pressure of carbon dioxide and season of the year on forage quality and cyanide concentration of Trifolium repens L. from a FACE experiment  

NASA Astrophysics Data System (ADS)

Differently managed (cutting frequency and N fertilization) Trifolium repens monocultures were grown at 60 Pa and 35 Pa of pCO 2 (partial pressure of CO 2) in a Free Air Carbon dioxide Enrichment (FACE) array. The concentrations of cyanide, digestible organic matter, crude protein and net energy for lactation were measured at different harvests throughout the growing season. The average cyanide concentrations differed significantly in the years and the seasons within the year; however, the concentrations were not affected by CO 2. Digestible organic matter, crude protein and net energy for lactation differed significantly with the seasons of the year and cutting frequencies. While digestible organic matter and net energy for lactation were not affected by elevated pCO 2, the concentration of crude protein decreased from 288 g kg -1 at ambient to 251 g kg -1 at elevated pCO 2. Since the crude protein concentration in herbage from Trifolium monocultures was very high even at elevated CO 2, it is suggested that this decrease in crude protein concentration does not negatively affect forage quality. We conclude that, in Trifolium herbage, the seasons of the year and management practices are more decisive for forage quality than changes in pCO 2. We shall discuss how forage quality and cyanide intake by ruminants may, however, be affected by CO 2-induced shifts in the proportion of species in mixed plant communities.

Frehner, Marco; Lscher, Andreas; Hebeisen, Thomas; Zanetti, Silvia; Schubiger, Franz; Scalet, Mario

343

Determination of octane numbers and Reid vapor pressure of commercial petroleum fuels using FT-Raman spectroscopy and partial least-squares regression analysis  

SciTech Connect

A Fourier transform Raman spectrometer was used to collect the Raman spectra of 208 commercial petroleum fuels. The individual motor and research octane numbers (MON and RON, respectively) were determined experimentally using the industry standard ASTM knock engine method. Partial least-squares regression analysis was used to build regression models which correlate the Raman spectra of 175 of the fuels with the experimentally determined values for MON, RON, and pump octane number (the average of MON and RON) of the fuels. Each of the models was validated using leave-one-out validation. The standard errors of validation are 0.415, 0.535, and 0.410 octane units for MON, RON, and pump octane number, respectively. It is evident that the accuracy of the Raman determined values is limited by the accuracy of the training set used in creating the models. The Raman regression models were used to predict the octane numbers for the fuels which were not used to build the models. The results compare favorably with the leave-one-out validation. Also, it is demonstrated that the experimentally determined Reid vapor pressures are highly correlated with the Raman spectra of the fuel samples and can be predicted with a standard error of 0.568 psi. 11 refs., 6 figs., 2 tabs.

Cooper, J.B.; Wise, K.L.; Groves, J. [Old Dominion Univ., Norfolk, VA (United States); Welch, W.T. [Ashland Petroleum Co., VA (United States)

1995-11-15

344

Conductivity of porous Sm2O3-doped CeO2 as a function of temperature and oxygen partial pressure  

NASA Astrophysics Data System (ADS)

Porous samples of Sm2O3-doped CeO2 (samaria-doped ceria, SDC) of composition Sm0.15Ce0.85O2-? were made by conventional ceramic processing and sintering in air at 1400 C. Crystal structure and microstructure of the samples were characterized, respectively, by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Electrical conductivity was measured using a four probe DC method over a temperature range from 200 C to 800 C, and over a wide range of oxygen partial pressures corresponding to testing in oxygen and in nearly dry hydrogen. Conductivity rapidly stabilized at any given temperature consistent with the attainment of thermodynamic equilibrium corresponding to the imposed conditions. At and below 300 C, the conduction was predominantly due to oxygen ion transport. At and above 400 C, however, significant electronic conduction occurred in reducing atmospheres. The ionic transference number of SDC at 400 C in hydrogen is only ?0.4. This result shows that the electrolytic domain of SDC at and above 400 C is rather narrow. These results also suggest that SDC (and possibly other rare earth oxide-doped CeO2) is not a suitable electrolyte without a thin electron blocking layer such as yttria-stabilized zirconia (YSZ).

Wright, James; Virkar, Anil V.

2011-08-01

345

A SAFT Equation of State for the Quaternary H2S-CO2-H2O-NaCl system  

NASA Astrophysics Data System (ADS)

Phase equilibria and thermodynamic properties of the quaternary H2S-CO2-H2O-NaCl system were studied using a statistical associating fluid theory (SAFT)-based equation of state (EOS). The understanding of the physical-chemical properties of this system is critical for predicting the consequences of co-injection of CO2 and H2S into geological formations (geological carbon sequestration) as an option for mitigating the global warming trend. Previous studies of the subsystems within this quaternary have provided many parameters for the EOS. In this study, the subsystems of H2S-CO2 and H2S-H2O-NaCl were investigated in order to obtain the cross parameters for the EOS. For the binary system H2S-CO2, cross association between the site H in H2S and the site O in CO2 was allowed and temperature-independent parameters were used to describe this cross association. Meanwhile, a temperature-dependent binary interaction parameter was used to adjust the cross dispersive energy for this binary system. For the H2S-H2O-NaCl system, one temperature-dependent cross parameter was allowed in order to adjust the cross dispersive energy between H2S and ions of Na+ and Cl-. All cross parameters were fitted to the reliable phase equilibrium experimental data. Densities were predicted and compared with available experimental results. Using the EOS developed in this study, we predicted equilibrium composition in both liquid and vapor phases, the equilibrium pressures at a given composition of the H2O-rich phase in electrolyte solutions with NaCl varying from 0 to 4 mol/kgH2O, and the aqueous solution densities. These predictions provide information and guidance for future experiments regarding the thermodynamic properties and phase behaviors in the H2S-CO2-H2O-NaCl system.

Ji, X.; Zhu, C.

2011-12-01

346

Neutral H2 and H2+ ions in the Saturnian magnetosphere  

Microsoft Academic Search

The Saturnian system is immersed in an extended cloud of neutrals. Although water vapor ejected from Enceladus' south pole is the dominant neutral source, photolysis and radiolysis of ices can release H2O, O2, and H2 from the icy ring particles and the icy satellites, and Titan's atmosphere is a source of H2. Once ionized, these neutrals are the source of

Wei-Ling Tseng; Robert E. Johnson; Michelle F. Thomsen; Timothy A. Cassidy; Meredith K. Elrod

2011-01-01

347

Measurement of alveolar oxygen partial pressure in the rat lung using Carr-Purcell-Meiboom-Gill spin-spin relaxation times of hyperpolarized 3He and 129Xe at 74 mT.  

PubMed

Regional measurement of alveolar oxygen partial pressure can be obtained from the relaxation rates of hyperpolarized noble gases, (3) He and (129) Xe, in the lungs. Recently, it has been demonstrated that measurements of alveolar oxygen partial pressure can be obtained using the spin-spin relaxation rate (R(2) ) of (3) He at low magnetic field strengths (<0.1 T) in vivo. R(2) measurements can be achieved efficiently using the Carr-Purcell-Meiboom-Gill pulse sequence. In this work, alveolar oxygen partial pressure measurements based on Carr-Purcell-Meiboom-Gill R(2) values of hyperpolarized (3) He and (129) Xe in vitro and in vivo in the rat lung at low magnetic field strength (74 mT) are presented. In vitro spin-spin relaxivity constants for (3) He and (129) Xe were determined to be (5.2 0.6) 10(-6) Pa(-1) sec(-1) and (7.3 0.4) 10(-6) Pa(-1) s(-1) compared with spin-lattice relaxivity constants of (4.0 0.4) 10(-6) Pa(-1) s(-1) and (4.3 1.3) 10(-6) Pa(-1) s(-1), respectively. In vivo experimental measurements of alveolar oxygen partial pressure using (3) He in whole rat lung show good agreement (r(2) = 0.973) with predictions based on lung volumes and ventilation parameters. For (129) Xe, multicomponent relaxation was observed with one component exhibiting an increase in R(2) with decreasing alveolar oxygen partial pressure. PMID:20593371

Kraayvanger, Ryan J; Bidinosti, Christopher P; Dominguez-Viqueira, William; Parra-Robles, Juan; Fox, Matthew; Lam, Wilfred W; Santyr, Giles E

2010-11-01

348

A semi-empirical thermodynamic formalism for high-pressure aqueous silicate solutions in the model system K2O-Na2O-CaO-MgO-Al2O3-SiO2-H2O-CO2, a first approach  

NASA Astrophysics Data System (ADS)

The results of experimental solubility determinations in aqueous solutions at high pressures up to 5 GPa are often difficult to gauge with respect to precision and accuracy, because of the potential uncertainties inherent in the available experimental approaches. Existing models of aqueous silicate solutions at low pressures are either unsuitable for extrapolation beyond 0.5 to 1.0 GPa or involve polynomial fits in which the fit parameters lack direct physical meaning. An approach described by Gerya et al. [1,2], based on statistical thermodynamics, allows aqueous silicate solutions to be described as mixtures of fictive oxide "components" together with water molecules in both clustered and "gas-like", i.e. unassociated, states. Burchard et al. [3] presented a first data set for fluids in the system CaO-SiO2-H2O, using the statistical thermodynamic formulation of Gerya et al [1,2] and extending it to include charged fluid species such as Ca2+, Ca(OH)+, Ca(OH)2, OH- and H+. We have now further developed the data set of Burchard et al. [3] by including carbonic fluid species and extending the model system to include MgO and Al2O3. In addition, initial progress has been made in including potassium and sodium model species. Solid phase data were obtained by mathematical conversion of existing thermodynamic mineral data into the semi-empirical form. With this semi-empirical data set calculations for simple, "wet" silicate rocks are now possible. We present applications to suites of jadeitites and jadeite-lawsonite-quartz rocks from the Rio San Juan serpentinite mlanges of the northern Dominican Republic. These rocks have crystallized from high-pressure aqueous fluids in a long-lived intra-oceanic subduction-zone environment at various times and at different P-T conditions (Schertl et al. [4]). The fluid-rock interactions leading to these spectacular rocks are still poorly understood. [1] Gerya et al. (2004) Phys. Chem. Minerals 31, 429-455; [2] Gerya et al. (2005) Eur. J. Mineral. 17, 269-283; [3] Burchard et al. (2011) Eur. J. Mineral. 23, 409-424; Schertl et al. (2012) Eur. J. Mineral. 24, 199-216.

Schertl, H.; Burchard, M.; Hertwig, A.; Maresch, W. V.

2012-12-01

349

Search for H2COH+ and H2(13)CO in dense interstellar molecular clouds  

NASA Technical Reports Server (NTRS)

We have searched for the 2 mm transitions of H2COH+ (2(02) - 1(01)) and H2(13)CO (2(02) - 1(01), 2(12) - 1(11), and 2(11) - 1(10)) toward the dense interstellar molecular clouds Orion A, TMC-1 and L134N using the FCRAO 14m telescope. None of the transitions have been detected except the H2(13)CO transitions toward Orion-KL. We set upper limits for the abundances of the protonated formaldehyde ion (H2COH+), which are close to the abundances expected from ion-molecule chemistry.

Minh, Y. C.; Irvine, W. M.; McGonagle, D.

1993-01-01

350

Effect of oxygen partial pressure on the magnetic properties of La2/3Sr1/3MnO3 films grown on SrTiO3 (1 1 1) substrates by pulsed laser deposition  

NASA Astrophysics Data System (ADS)

The influence of oxygen partial pressure on phase formation and magnetic properties of LSMO (La2/3Sr1/3MnO3) thin films deposited on STO (1 1 1) substrates by pulsed laser deposition was investigated. Phase formation and epitaxial growth were confirmed by X-ray diffraction. Good crystalline mosaic is observed for oxygen partial pressures ranging from 0.3 to 1.0 mbar. For each of the pressures, the lattice parameters were estimated assuming the lattice distortion is volume conserving. The Curie temperatures TC vs lattice strain relation thus obtained is comparable to the available data in literature. Variation in coercive field of the films can be accounted for by the variation in TC.

Prajapat, C. L.; Kalita, Parswajit; Sastry, P. U.; Singh, M. R.; Gupta, S. K.; Ravikumar, G.

2014-09-01

351

H2+ in a weak magnetic field  

NASA Astrophysics Data System (ADS)

The electronic energy of H2+ in magnetic fields of up to B=0.2{{B}0} (or 4.7 {{10}4} T) is investigated. Numerical values of the magnetic susceptibility for both the diamagnetic and paramagnetic contributions are reported for arbitrary orientations of the molecule in the magnetic field. It is shown that both diamagnetic and paramagnetic susceptibilities grow with inclination, while paramagnetic susceptibility is systematically much smaller than the diamagnetic one. Accurate two-dimensional BornOppenheimer surfaces are obtained with special trial functions. Using these surfaces, vibrational and rotational states are computed and analyzed for the isotopologues H2+ and D2+.

Medel Cobaxin, Hctor; Alijah, Alexander; Lpez Vieyra, Juan Carlos; Turbiner, Alexander V.

2015-02-01

352

Pressure (Or No Royal Road)  

ERIC Educational Resources Information Center

Discusses how difficult the various problems of pressure, partial pressure, gas laws, and vapor pressure are for students. Outlines the evolution of the concept of pressure, the gas equation for a perfect gas, partial pressures, saturated vapor pressure, Avogadro's hypothesis, Raoult's law, and the vapor pressure of ideal solutions. (JR)

Bradley, J.

1973-01-01

353

Functions of MgH2 in hydrogen storage reactions of the 6LiBH4-CaH2 reactive hydride composite.  

PubMed

A significant improvement of hydrogen storage properties was achieved by introducing MgH(2) into the 6LiBH(4)-CaH(2) system. It was found that ~8.0 wt% of hydrogen could be reversibly stored in a 6LiBH(4)-CaH(2)-3MgH(2) composite below 400 C and 100 bar of hydrogen pressure with a stepwise reaction, which is superior to the pristine 6LiBH(4)-CaH(2) and LiBH(4) samples. Upon dehydriding, MgH(2) first decomposed to convert to Mg and liberate hydrogen with an on-set temperature of ~290 C. Subsequently, LiBH(4) reacted with CaH(2) to form CaB(6) and LiH in addition to further hydrogen release. Hydrogen desorption from the 6LiBH(4)-CaH(2)-3MgH(2) composite finished at ~430 C in non-isothermal model, a 160 C reduction relative to the 6LiBH(4)-CaH(2) sample. JMA analyses revealed that hydrogen desorption was a diffusion-controlled reaction rather than an interface reaction-controlled process. The newly produced Mg of the first-step dehydrogenation possibly acts as the heterogeneous nucleation center of the resultant products of the second-step dehydrogenation, which diminishes the energy barrier and facilitates nucleation and growth, consequently reducing the operating temperature and improving the kinetics of hydrogen storage. PMID:22842399

Zhou, Yifan; Liu, Yongfeng; Zhang, Yu; Gao, Mingxia; Pan, Hongge

2012-08-28

354

Kinetics of H2-O2 Redox Equilibria and Metastable Formation of H2O2 Under low Temperature Hydrothermal Conditions  

NASA Astrophysics Data System (ADS)

Low-temperature diffuse fluid-flow in submarine hydrothermal systems represents an important mechanism of heat and mass transfer in mid-ocean ridges. Generally, diffuse flow can be described as the subseafloor mixing between oxygenated cold seawater and high-temperature reducing vent fluids. The strongly differentiated nature of these two endmembers, induces sharp thermal and chemical gradients across the mixing boundary, imposing significant constraints on the distribution of redox- and pH-sensitive aqueous species. One particular redox equilibrium, directly linked to subsurface mixing processes, involves dissolved H2 and O2 species. However, for the kinetics of the Knallgas reaction, that controls this fundamental redox couple, experimental data do not exist. To address the need for such kinetic constraints, a series of flow-through and closed system hydrothermal experiments (flexible gold cell) were conducted to evaluate the extent of H2 oxidation in the homogeneous H2-O2-H2O system and at pressure/temperature conditions reflecting near-seafloor hydrothermal environments (55-200, 250-400bars). Results support the inhibiting role of cooling in the kinetics of H2-O2 equilibration, allowing for excess H2 to remain in solution. Most importantly, however, establishment of highly reducing conditions is accompanied by the metastable formation of hydrogen peroxide at concentrations significantly greater than those predicted based on known H2O2 decomposition rates. Moreover, by adjusting the relative abundances of H2 and O2 during the course of the experiments, changes in the rate of H2O2 formation appear to be directly linked with the slow kinetics of H2 oxidation at low- temperature hydrothermal conditions. Identifying metastable equilibria conditions that likely accompany redox and pH gradients not only helps to elucidate subseafloor hydrothermal alteration processes, but may contribute important insights into the nature of energy resources for the subseafloor biosphere.

Foustoukos, D. I.; Houghton, J. L.; Seyfried, W. E.; Cody, G. D.

2008-12-01

355

Warming early Mars with CO2 and H2  

NASA Astrophysics Data System (ADS)

The presence of valleys on ancient terrains of Mars suggests that liquid water flowed on the martian surface 3.8Gyr ago or before. The above-freezing temperatures required to explain valley formation could have been transient, in response to the frequent large meteorite impacts on early Mars, or they could have been caused by long-lived greenhouse warming. Climate models that consider only the greenhouse gases carbon dioxide and water have been unable to recreate warm surface conditions, given the lower solar luminosity at that time. Here we use a one-dimensional climate model to demonstrate that an atmosphere containing 1.3-4bar of CO2 and water, in addition to 5-20% H2, could have raised the mean surface temperature of early Mars above the freezing point of water. Vigorous volcanic outgassing from a highly reduced early martian mantle is expected to provide sufficient atmospheric H2 and CO2--the latter from the photochemical oxidation of outgassed CH4 and CO--to form a CO2 and H2 greenhouse. Such a dense early martian atmosphere is consistent with independent estimates of surface pressure based on cratering data.

Ramirez, Ramses M.; Kopparapu, Ravi; Zugger, Michael E.; Robinson, Tyler D.; Freedman, Richard; Kasting, James F.

2014-01-01

356

Velocity-changing collisions in pure H2 and H2-Ar mixture.  

PubMed

We show how to effectively introduce a proper description of the velocity-changing collisions into the model of isolated molecular transition for the case of self- and Ar-perturbed H2. We demonstrate that the billiard-ball (BB) approximation of the H2-H2 and H2-Ar potentials gives an accurate description of the velocity-changing collisions. The BB model results are compared with ab initio classical molecular dynamics simulations. It is shown that the BB model correctly reproduces not only the principal properties such as frequencies of velocity-changing collisions or collision kernels, but also other characteristics of H2-H2 and H2-Ar gas kinetics like rate of speed-changing collisions. Finally, we present line-shape measurement of the Q(1) line of the first overtone band of self-perturbed H2. We quantify the systematic errors of line-shape analysis caused by the use of oversimplified description of velocity-changing collisions. These conclusions will have significant impact on recent rapidly developing ultra-accurate metrology based on Doppler-limited spectroscopic measurements such as Doppler-width thermometry, atmosphere monitoring, Boltzmann constant determination, or transition position and intensity determination for fundamental studies. PMID:25149780

Wcis?o, P; Tran, H; Kassi, S; Campargue, A; Thibault, F; Ciury?o, R

2014-08-21

357

Velocity-changing collisions in pure H2 and H2-Ar mixture  

NASA Astrophysics Data System (ADS)

We show how to effectively introduce a proper description of the velocity-changing collisions into the model of isolated molecular transition for the case of self- and Ar-perturbed H2. We demonstrate that the billiard-ball (BB) approximation of the H2-H2 and H2-Ar potentials gives an accurate description of the velocity-changing collisions. The BB model results are compared with ab initio classical molecular dynamics simulations. It is shown that the BB model correctly reproduces not only the principal properties such as frequencies of velocity-changing collisions or collision kernels, but also other characteristics of H2-H2 and H2-Ar gas kinetics like rate of speed-changing collisions. Finally, we present line-shape measurement of the Q(1) line of the first overtone band of self-perturbed H2. We quantify the systematic errors of line-shape analysis caused by the use of oversimplified description of velocity-changing collisions. These conclusions will have significant impact on recent rapidly developing ultra-accurate metrology based on Doppler-limited spectroscopic measurements such as Doppler-width thermometry, atmosphere monitoring, Boltzmann constant determination, or transition position and intensity determination for fundamental studies.

Wcis?o, P.; Tran, H.; Kassi, S.; Campargue, A.; Thibault, F.; Ciury?o, R.

2014-08-01

358

Impact of Partial Pressure of Oxygen in Blood Samples on the Performance of Systems for Self-Monitoring of Blood Glucose  

PubMed Central

Abstract Background: The partial pressure of oxygen (pO2) in blood samples can affect glucose measurements with oxygen-sensitive systems. In this study, we assessed the influence of different pO2 levels on blood glucose (BG) measurements with five glucose oxidase (GOD) systems and one glucose dehydrogenase (GDH) system. All selected GOD systems were indicated by the manufacturers to be sensitive to increased oxygen content of the blood sample. Materials and Methods: Venous blood samples of 16 subjects (eight women, eight men; mean age, 52 years; three with type 1 diabetes, four with type 2 diabetes, and nine without diabetes) were collected. Aliquots of each sample were adjusted to the following pO2 values: ?45?mm Hg, approximately 70?mm Hg, and ?150?mm Hg. For each system, five consecutive measurements on each sample were performed using the same test strip lot. Relative differences between the mean BG value at a pO2 level of approximately 70?mm Hg, which was considered to be similar to pO2 values in capillary blood samples, and the mean BG value at pO2 levels ?45?mm Hg and ?150?mm Hg were calculated. Results: The GOD systems showed mean relative differences between 11.8% and 44.5% at pO2 values ?45?mm Hg and between ?14.6% and ?21.2% at pO2 values ?150?mm Hg. For the GDH system, the mean relative differences were ?0.3% and ?0.2% at pO2 values ?45?mm Hg and ?150?mm Hg, respectively. Conclusions: The magnitude of the pO2 impact on BG measurements seems to vary among the tested oxygen-sensitive GOD systems. The pO2 range in which oxygen-sensitive systems operate well should be provided in the product information. PMID:24205977

Baumstark, Annette; Pleus, Stefan; Haug, Cornelia; Tesar, Martina; Freckmann, Guido

2014-01-01

359

The Successive H2O Binding Energies for Fe(H2O)n(+)  

NASA Technical Reports Server (NTRS)

The binding energy, computed using density functional theory (DFT), are in good agreement with experiment. The bonding is electrostatic (charge-dipole) in origin for all systems. The structures are therefore determined mostly by metal-ligand and ligand-ligand repulsion. The computed structure for FeH2O(+) is C(2v) where sp hybridization is important in reducing the Fe-H2O repulsion. Fe(H2O)2(+) has D2d symmetry where sdo hybridization is the primary factor leading to the linear O-Fe-O geometry. The bonding in Fe(H2O)3(+) and Fe(H2O)4(+) are very complex because ligand-ligand and metal-ligand repulsion, both for the in-plane and out-of-plane water lone-pair orbitals, are important.

Ricca, Alessandra; Bauschlicher, Charles W., Jr.; Langhoff, Stephen R. (Technical Monitor)

1994-01-01

360

Leaf conductance in relation to rate of CO/sub 2/ assimilation. I. Influence of nitrogen nutrition, phosphorus nutrition, photon flux density, and ambient partial pressure of CO/sub 2/ during ontogeny. [Zea mays  

SciTech Connect

Plants of Zea mays were grown with different concentrations of nitrate (0.6, 4, 12, and 24 millimolar) and phosphate (0.04, 0.13, 0.53, and 1.33 millimolar) supplied to the roots, photon flux densities (0.04, 0.13, 0.53, and 1.33 millimolar) supplied to the roots, photon flux densities (0.12, 0.5, and 2 millimoles per square meter per second), and ambient partial pressures of CO/sub 2/ (305 and 610 microbars). Differences in mineral nutrition and irradiance led to a large variation in rate of CO/sub 2/ assimilation per unit leaf area (A, 11 to 58 micromoles per square meter per second) when measured under standard conditions. The variation was shown, with the plants that had received different amounts of nitrate, to be related to variations in the nitrogen and chlorophyll contents, and phosphoenolpyruvate and ribulose-1,5-bisphosphate carboxylase activities per unit leaf area. Irrespective of growth treatment, A and leaf conductance to CO/sub 2/ transfer (g), measured under standard conditions were in almost constant proportion, implying that intercellular partial pressure of CO/sub 2/ (p/sub i/), was almost constant at 95 microbars. The same proportionality was maintained as A and g increased in an initially nitrogen-deficient plant that had been supplied with abundant nitrate. It was shown that p/sub i/ measured at a given ambient partial pressure was not affected by the ambient partial pressure at which the plants had been grown, although it was different when measured at different ambient partial pressures. This suggests that the close coupling between A and g in these experiments is not associated with sensitivity of stomata to change in p/sub i/. Similar, though less comprehensive, experiments were done with Gosypium hirsutum, and yielded similar conclusions, except that the proportionality between A and g at normal ambient partial pressure of CO/sub 2/ implied p/sub i/ approx. = 200 microbars. 11 references, 6 figures, 1 table.

Wong, S.C.; Cowan, I.R.; Farquhar, G.D.

1985-01-01

361

D/H fractionation in the H2-H2O system at supercritical water conditions: Compositional and hydrogen bonding effects  

NASA Astrophysics Data System (ADS)

A series of experiments has been conducted in the H2-D2-D2O-H2O-Ti-TiO2 system at temperatures ranging from 300 to 800 C and pressures between ?0.3 and 1.3 GPa in a hydrothermal diamond anvil cell, utilizing Raman spectroscopy as a quantitative tool to explore the relative distribution of hydrogen and deuterium isotopologues of the H2 and H2O in supercritical fluids. In detail, H2O-D2O solutions (1:1) were reacted with Ti metal (3-9 h) in the diamond cell, leading to formation of H2, D2, HD, and HDO species through Ti oxidation and H-D isotope exchange reactions. Experimental results obtained in situ and at ambient conditions on quenched samples indicate significant differences from the theoretical estimates of the equilibrium thermodynamic properties of the H-D exchange reactions. In fact, the estimated enthalpy for the H2(aq)-D2(aq) disproportionation reaction (?Hrxn) is about -3.4 kcal/mol, which differs greatly from the +0.16 kcal/mol predicted for the exchange reaction in the gas phase by statistical mechanics models. The exothermic behavior of the exchange reaction implies enhanced stability of H2 and D2 relative to HD. Accordingly, the significant energy difference of the internal H2(aq)-D2(aq)-HD(aq) equilibrium translates to strong differences of the fractionation effects between the H2O-H2 and D2O-D2 isotope exchange relationships. The D/H fractionation factors between H2O-H2(aq) and D2O-D2(aq) differ by 365 in the 600-800 C temperature range, and are indicative of the greater effect of D2O contribution to the ?D isotopic composition of supercritical fluids. The negative ?Hrxn values for the H2(aq)-D2(aq)-HD(aq) equilibrium and the apparent decrease of the equilibrium constant with increasing temperature might be because of differences of the Henrys law constant between the H- and D-bearing species dissolved in supercritical aqueous solutions. Such effects may be attributed to the stronger hydrogen bonding in the O-H⋯O relative to the O-D⋯O environment. This difference allows enhanced gas solubility in the denser and more polar H2O clusters, and thus, affects the D/H exchange between the H2-D2 volatiles and the coexisting H2O-D2O mixtures. The proposed role of temperature in promoting differences in the density and polarity of hydrogen-bonded OHO and ODO molecules may be explained with isotope-specific molar volume effects similar to those suggested to account for the hydrogen isotope fractionation between H2O and hydroxide mineral phases (e.g. brucite) across large pressure intervals.

Foustoukos, Dionysis I.; Mysen, Bjorn O.

2012-06-01

362

Heterogeneous bubble nucleation and disequilibrium H 2O exsolution in Vesuvius K-phonolite melts  

Microsoft Academic Search

This study focuses on constraining bubble nucleation and H2O exsolution processes in alkalic K-phonolite melts, using white pumice of the 79 AD eruption of Vesuvius as starting material. The first set of experiments consisted of H2O solubility runs at 1153 to 1250K and pressures between 50 and 200MPa, to constrain equilibrium water concentrations along the decompression pathways. The decompression experiments

Jessica F. Larsen

2008-01-01

363

Partitioning of F between H 2 O and CO 2 fluids and topaz rhyolite melt  

Microsoft Academic Search

Fluid\\/melt distribution coefficients for F have been determined in experiments conducted with peraluminous topaz rhyolite melts and fluids consisting of H2O and H2O+CO2 at pressures of 0.5 to 5 kbar, temperatures of 7751000C, and concentrations of F in the melt ranging from 0.5 to 6.9 wt%. The major element, F, and Cl concentrations of the starting material and run product

James D. Webster

1990-01-01

364

Characterization of the histone H2A.Z-1 and H2A.Z-2 isoforms in vertebrates  

E-print Network

of two H2A.Z protein isoforms in chicken that differ by 3Total H2A.Z protein was purified from chicken erythrocytesprotein isoforms (H2A.Z-1/H2A.Z-2) that was first determined by mass spectrometry in total H2A.Z isolated from chicken

2009-01-01

365

Mutational Studies Uncover Non-Native Structure in the Dimeric Kinetic Intermediate of the H2A-H2B Heterodimer  

PubMed Central

The folding pathway of the histone H2A-H2B heterodimer minimally includes an on-pathway, dimeric, burst-phase intermediate, I2. The partially folded H2A and H2B monomers populated at equilibrium were characterized as potential monomeric kinetic intermediates. Folding kinetics were compared for initiation from isolated, folded monomers and the heterodimer unfolded in 4 M urea. The observed rates were virtually identical above 0.4 M urea, exhibiting a log-linear relationship on the final denaturant concentration. Below ~0.4 M urea (concentrations inaccessible from the 4 M urea unfolded state), a roll-over in the rates was observed; this suggests that a component of the I2 ensemble contains non-native structure that rearranges/isomerizes to a more native-like species. The contribution of helix propensity to the stability of the I2 ensemble was assessed with a set of H2A-H2B mutants containing Ala and Gly replacements at nine sites, focusing mainly on the long, central ?2 helix. Equilibrium and kinetic folding/unfolding data were collected to determine the effects of the mutations on the stability of I2 and the transition state between I2 and N2. This limited mutational study indicated that residues in the ?2 helices of H2A and H2B, as well as ?1 of H2B and both the C-terminus of ?3 and the short ?C helix of H2A contribute to the stability of the I2 burst phase species. Interestingly, at least eight of the nine targeted residues stabilize I2 by interactions that are non-native to some extent. Given that destabilizing I2 and these non-native interactions does not accelerate folding, it is concluded that the native and non-native structure present in the I2 ensemble enables efficient folding of H2A-H2B. PMID:20600120

Stump, Matthew R.; Gloss, Lisa M.

2010-01-01

366

Observations of cumulene carbenes, H2CCCC and H2CCC, in TMC-1  

NASA Technical Reports Server (NTRS)

Attention is given to the carbon chain molecule H2CCCC, detected in the dark cloud TMC-1 for the first time in the course of a molecular line survey using the Nobeyama 45-m telescope. From nine transitions observed in the frequency region of 17-45 GHz, the total column density of H2CCCC in TMC-1 is derived to be 7.5(+/-2.0) x 10 exp 12/sq cm, which is about half of the value reported in IRC + 10216. Five transitions of a related carbon chain molecule, H2CCC, were also detected in TMC-1. The column density of H2CCC obtained in TMC-1, 2.8(+/-0.9) x 10 exp 12/sq cm, is a factor of three smaller than that of H2CCCC. The ortho-to-para abundance ratios of H2CCCC and H2CCC were found to be 4.2 +/-1.5 and 5.9 +/-2.0, respectively. The chemical reactions of these carbon-chain molecules in dark clouds are discussed.

Kawaguchi, Kentarou; Kaifu, Norio; Ohishi, Masatoshi; Ishikawa, Shin-Ichi; Hirahara, Yasuhiro; Yamamoto, Satoshi; Saito, Shuji; Takano, Shuro; Murakami, Akinori; Vrtilek, J. M.

1991-01-01

367

Dissociative recombination of LiH2+  

NASA Astrophysics Data System (ADS)

In this paper, we report results regarding how LiH2+ fragments as a result of a low-energy collision with an electron (dissociative recombination), a reaction that contains only elements and particles created during the very first phase of the universe. The collision-energy-dependent reaction rate and cross sections show detailed structures, more so than predicted by theory, suggesting significant rovibrational coupling in the ion and a complex reaction surface. From the structure of the molecule, the reaction predominantly results in the formation of Li + H2. However, 23% of the reaction flux leads to more interesting products, with 17% producing Li + 2H and 6% producing LiH + H. These last two channels break the strongest molecular bond in the system and, in the case of the latter channel, form a significantly weaker ionic bond. Possible reasons behind this interesting behavior are discussed, together with the interaction between the available reaction channels.

Thomas, R. D.; Ehlerding, A.; Geppert, W. D.; Hellberg, F.; Zhaunerchyk, V.; Larsson, M.; Bahati, E.; Bannister, M. E.; Fogle, M. R.; Vane, C. R.

2014-05-01

368

Heart-to-Heart (H2H): Authentication for Implanted Medical Devices  

E-print Network

Heart-to-Heart (H2H): Authentication for Implanted Medical Devices Masoud Rostami Rice University to authenticate external medical device controllers and programmers to Implantable Medi- cal Devices (IMDs). IMDs, which include pacemakers and cardiac defibrillators, are therapeutic medical devices partially or wholly

369

RbH2AsO4  

PubMed Central

RbH2AsO4, rubidium dihydrogenarsenate (RDA), was synthesized by partial neutralization of an aqueous H3AsO4 solution with aqueous Rb2CO3. Its paraelectric room-temperature phase is composed of virtually regular tetrahedral [AsO2(OH)2]? anions and Rb+ cations, both located on -4 positions. The [AsO2(OH)2] units are connected via OH?O hydrogen bonds into a three-dimensional network, whereby the H atoms are equally disordered between the O atoms. The Rb+ cations are located in channels running along the <100> directions and coordinated by eight O atoms located at the vertices of a snub disphenoid. PMID:24454010

Stger, Berthold

2013-01-01

370

Design of H2-O2 space shuttle APU. Volume 1: APU design  

NASA Technical Reports Server (NTRS)

The H2-O2 space shuttle auxiliary power unit (APU) program is a NASA-Lewis effort aimed at hardware demonstration of the technology required for potential use on the space shuttle. It has been shown that a hydrogen-oxygen power unit (APU) system is an attractive alternate to the space shuttle baseline hydrazine APU system for minimum weight. It has the capability for meeting many of the heat sink requirements for the space shuttle vehicle, thereby reducing the amount of expendable evaporants required for cooling in the baseline APU. Volume 1 of this report covers preliminary design and analysis of the current reference system and detail design of the test version of this reference system. Combustor test results are also included. Volume 2 contains the results of the analysis of an initial version of the reference system and the computer printouts of system performance. The APU consists of subsystems for propellant feed and conditioning, turbopower, and control. Propellant feed and conditioning contains all heat exchangers, valves, and the combustor. The turbopower subsystem contains a two-stage partial-admission pressure-modulated, 400-hp, 63,000-rpm turbine, a 0-to 4-g lubrication system, and a gearbox with output pads for two hydraulic pumps and an alternator (alternator not included on test unit). The electronic control functions include regulation of speed and system temperatures; and start-and-stop sequences, overspeed (rpm) and temperature limits, failsafe provisions, and automatic shutdown provisions.

Harris, E.

1974-01-01

371

Sulfidation Kinetics of Natural Chromite Ore Using H2S Gas  

NASA Astrophysics Data System (ADS)

The kinetics and mechanism of natural chromite (FeCr2O4) sulfidation using 5 pct H2S (balance Ar) gas were studied in the temperature range 1173 K to 1473 K (900 C to 1200 C). Reaction products were examined using combined X-ray diffraction, scanning electron microscopy, and energy dispersive X-ray spectroscopy. Results indicated the formation of an outer sulfide-rich layer comprising mixed (Fe,Cr)1-x S and (Cr,Fe)1-x S phases, underlain by a cation-depleted diffusion zone. The kinetics investigation indicated that the reaction rate increased with increasing temperature and that the sulfidation of chromite followed a shrinking unreacted core model. It is proposed that Cr3+ cation diffusion through the reaction product was the rate controlling step with an apparent activation energy of 166 4 kJ mol-1. The calculated activation energy lies between the activation energy for Fe2+ and Cr3+ diffusion through pure chromite spinel and Fe-Cr alloy. Possible reasons for the discrepancy from pure chromite are expected to be the presence of minor Al and Mg in the natural chromite sample, and the partial pressure of oxygen under the reaction conditions used.

Ahmad, Sazzad; Rhamdhani, M. Akbar; Pownceby, Mark I.; Bruckard, Warren J.

2015-01-01

372

Availability of O2 and H2O2 on Pre-Photosynthetic Earth  

PubMed Central

Abstract Old arguments that free O2 must have been available at Earth's surface prior to the origin of photosynthesis have been revived by a new study that shows that aerobic respiration can occur at dissolved oxygen concentrations much lower than had previously been thought, perhaps as low as 0.05?nM, which corresponds to a partial pressure for O2 of about 4??10?8 bar. We used numerical models to study whether such O2 concentrations might have been provided by atmospheric photochemistry. Results show that disproportionation of H2O2 near the surface might have yielded enough O2 to satisfy this constraint. Alternatively, poleward transport of O2 from the equatorial stratosphere into the polar night region, followed by downward transport in the polar vortex, may have brought O2 directly to the surface. Thus, our calculations indicate that this early respiration hypothesis might be physically reasonable. Key Words: Early EarthOxygenRespirationTracer transportGeneral circulation. Astrobiology 11, 293302. PMID:21545266

Kasting, James F.; Lee, Sukyoung

2011-01-01

373

Oxidation of Si during the growth of SiO{sub x} by ion-beam sputter deposition: In situ x-ray photoelectron spectroscopy as a function of oxygen partial pressure and deposition temperature  

SciTech Connect

Oxidation of silicon during the growth of silicon oxide by ion beam sputter deposition was studied by in situ x-ray photoelectron spectroscopy as a function of oxygen partial pressure at various deposition temperatures below 600 deg. C. At low temperatures, the variation of incorporated oxygen content is similar to a dissociative adsorption isotherm of O{sub 2} on Si indicating that the surface-confined reaction of the deposited Si atoms with the adsorbed oxygen atoms is the main process. However, it shows a three-step variation with the oxygen partial pressure at high temperatures. The evolution of SiO species confirmed by the XPS indicates that an adsorption-induced surface reaction and a diffusion-induced internal reaction are the main pathways for the Si oxidation.

Kim, Kyung Joong; Kim, Jeong Won; Yang, Moon-Seung; Shin, Jung Hoon [Nano Surface Group, Korea Research Institute of Standards and Science (KRISS), P.O. Box 102, Yusong, Taejon 305-600 (Korea, Republic of); Department of Physics, Korea Advanced Institute of Science and Technology (KAIST), 373-1 Kusung-dong, Yusong-gu, Taejon (Korea, Republic of)

2006-10-15

374

Leaf conductance in relation to rate of CO assimilation. I. Influence of nitrogen nutrition, phosphorus nutrition, photon flux density, and ambient partial pressure of CO during ontogeny. [Zea mays  

Microsoft Academic Search

Plants of Zea mays were grown with different concentrations of nitrate (0.6, 4, 12, and 24 millimolar) and phosphate (0.04, 0.13, 0.53, and 1.33 millimolar) supplied to the roots, photon flux densities (0.04, 0.13, 0.53, and 1.33 millimolar) supplied to the roots, photon flux densities (0.12, 0.5, and 2 millimoles per square meter per second), and ambient partial pressures of

S.-C. Wong; I. R. Cowan; G. D. Farquhar

1985-01-01

375

Decolorization and mineralization of reactive dyes, by the H2O2/UV process with electrochemically produced H2O2.  

PubMed

Decolorization of Reactive Red 238, Reactive Orange 16, Reactive Black 5 and Reactive Blue 4 was studied in the UV/H2O2 process with H2O2 being produced electrochemically. The experimental results show that decolorization increased considerably when switching on the electrochemical production of H2O2. Complete decolorization (>99%) was achieved for all dyes under the applied experimental conditions, partial mineralization (49-85%) was obtained, which depends on the type of dye. Reactive Red 238 was used to investigate operational parameters and it was found that decolorization was influenced by the applied electrical current of the electrochemical cell and flow rate. Decolorization and mineralization of Reactive Red 238 can be described by pseudo-first order kinetics. It was found that the initial concentration of Reactive Red 238 has a negative influence on the pseudo-first order reaction constant. PMID:24169722

Jeri?, Tina; Bisselink, Roel J M; van Tongeren, Willy; Le Marechal, Alenka M

2013-01-01

376

Study of H2 physical adsorption in single-walled carbon nanotube array  

NASA Astrophysics Data System (ADS)

The potential energies of a single H2 inside and outside an armchair single-walled carbon nanotube (SWCNT) are calculated by the electronic density functional theory (DFT), and influences of the SWCNT tube diameter on the potential energy minimum and equilibrium position are studied. Hydrogen storage capacity of the armchair SWCNTs in the rhombic arrays is estimated by using grand canonical Monte Carlo (GCMC) simulations in a pressure range from 10 to 100 bar and at temperatures of 77 K, 150 K, 220 K, 298 K, and 318 K, respectively; influences of the SWCNT diameter and VDW distance on the hydrogen storage capacity, and the isosteric heats of the H2-armchair SWCNTs arrays at several discrete temperatures and pressures are also investigated. The present main discoveries include (i) variation pattern of the H2 adsorption saturation pressure with the tube diameter and temperature; (ii) existence of extremum of the hydrogen storage capacity as a function of the VDW distance and tube diameter; (iii) diametrically opposite change of H2 storage capacity with the tube diameter in different pressure domains; (iv) layered distribution of the H2 adsorbed inside the tube. A theoretical mode is suggested to explain self-consistently all of these discoveries by combining the potential field information with the arguments of liquid state theories, and further verified by snapshots of representative configuration. The present discoveries, particularly, the theoretical mode explaining them, may serve to provide some guidance in improving the hydrogen storage capacity by doping the CNT and optimization of parameters.

Zhou, Shiqi; Liu, Xuejuan; Yang, Kaiwei; Zou, Hui

2013-08-01

377

Temporal changes in surface partial pressure of carbon dioxide and carbonate saturation state in the eastern equatorial Indian Ocean during the 1962-2012 period  

NASA Astrophysics Data System (ADS)

Information on changes in the oceanic carbon dioxide (CO2) concentration and air-sea CO2 flux as well as on ocean acidification in the Indian Ocean is very limited. In this study, temporal changes of the inorganic carbon system in the eastern equatorial Indian Ocean (EIO, 5 N-5 S, 90-95 E) are examined using partial pressure of carbon dioxide (pCO2) data collected in May 2012, historical pCO2 data since 1962, and total alkalinity (TA) data calculated from salinity. Results show that sea surface pCO2 in the equatorial belt (2 N-2 S, 90-95 E) increased from ∼307 ?atm in April 1963 to ∼373 ?atm in May 1999, ∼381 ?atm in April 2007, and ∼385 ?atm in May 2012. The mean rate of pCO2 increase in this area (∼1.56 ?atm yr-1) was close to that in the atmosphere (∼1.46 ?atm yr-1). Despite the steady pCO2 increase in this region, no significant change in air-sea CO2 fluxes was detected during this period. Ocean acidification as indicated by pH and saturation states for carbonate minerals has indeed taken place in this region. Surface water pH (total hydrogen scale) and saturation state for aragonite (?arag), calculated from pCO2 and TA, decreased significantly at rates of -0.0016 0.0001 and -0.0095 0.0005 yr-1, respectively. The respective contributions of temperature, salinity, TA, and dissolved inorganic carbon (DIC) to the increase in surface pCO2 and the decreases in pH and ?arag are quantified. We find that the increase in DIC dominated these changes, while contributions from temperature, salinity, and TA were insignificant. The increase in DIC was most likely associated with the increasing atmospheric CO2 concentration, and the transport of accumulated anthropogenic CO2 from a CO2 sink region via basin-scale ocean circulations. These two processes may combine to drive oceanic DIC to follow atmospheric CO2 increase.

Xue, L.; Yu, W.; Wang, H.; Jiang, L.-Q.; Feng, L.; Gao, L.; Li, K.; Li, Z.; Wei, Q.; Ning, C.

2014-11-01