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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

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

SciTech Connect

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

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

2012-05-01

3

Effects of the H 2S partial pressure on the performance of bimetallic noble-metal molybdenum catalysts in simultaneous hydrogenation and hydrodesulfurization reactions  

Microsoft Academic Search

The influence of the H2S concentration on the activity and selectivity to hydrodesulfurization (HDS) of bimetallic noble-metal molybdenum (NMMo, NM=Pt, Ru, Pd) supported on ?-Al2O3 catalysts was studied. The effect of H2S on the modification of the HDS pathway and the influence of the Mo loading on the sulfur resistance of catalysts were also analyzed. NMMo\\/?-Al2O3 and conventional CoMo\\/?-Al2O3 catalysts

David Prez-Martnez; Sonia A. Giraldo; Aristbulo Centeno

2006-01-01

4

Oxygen partial pressure sensor  

DOEpatents

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

Dees, D.W.

1994-09-06

5

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

PubMed Central

The high pressure structures, metallization, and superconductivity of recently synthesized H2-containing compounds (H2S)2H2 are elucidated by ab initio calculations. The ordered crystal structure with P1 symmetry is determined, supported by the good agreement between theoretical and experimental X-ray diffraction data, equation of states, and Raman spectra. The Cccm structure is favorable with partial hydrogen bond symmetrization above 37?GPa. Upon further compression, H2 molecules disappear and two intriguing metallic structures with R3m and Im-3m symmetries are reconstructive above 111 and 180?GPa, respectively. The predicted metallization pressure is 111?GPa, which is approximately one-third of the currently suggested metallization pressure of bulk molecular hydrogen. Application of the Allen-Dynes-modified McMillan equation for the Im-3m structure yields high Tc values of 191?K to 204?K at 200?GPa, which is among the highest values reported for H2-rich van der Waals compounds and MH3 type hydride thus far. PMID:25382349

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

2014-01-01

6

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

PubMed

The high pressure structures, metallization, and superconductivity of recently synthesized H2-containing compounds (H2S)2H2 are elucidated by ab initio calculations. The ordered crystal structure with P1 symmetry is determined, supported by the good agreement between theoretical and experimental X-ray diffraction data, equation of states, and Raman spectra. The Cccm structure is favorable with partial hydrogen bond symmetrization above 37?GPa. Upon further compression, H2 molecules disappear and two intriguing metallic structures with R3m and Im-3m symmetries are reconstructive above 111 and 180?GPa, respectively. The predicted metallization pressure is 111?GPa, which is approximately one-third of the currently suggested metallization pressure of bulk molecular hydrogen. Application of the Allen-Dynes-modified McMillan equation for the Im-3m structure yields high Tc values of 191?K to 204?K at 200?GPa, which is among the highest values reported for H2-rich van der Waals compounds and MH3 type hydride thus far. PMID:25382349

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

2014-01-01

7

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

8

High-pressure studies of NaCo(H 2PO 3) 3H 2O phosphite by Raman spectroscopy  

NASA Astrophysics Data System (ADS)

High-pressure investigations of NaCo(H 2PO 3) 3H 2O dihydrogenphosphite, in diamond anvil cell have been performed at room temperature using in situ Raman spectroscopy. The endeavor was to acquire information on pressure-induced structural transformations such as phase transitions and amorphization occurring in the crystal lattice. Group theory yields to 69A g + 69B 1g + 69B 2g + 69B 3g Raman active modes for NaCo(H 2PO 3) 3H 2O, of which only 36 bands are observed at ambient conditions. The pressure-induced phase transition sequence of NaCo(H 2PO 3) 3H 2O dihydrogenphosphite to pressures up to 20 GPa was explored. Raman spectra showed that the investigated compound, NaCo(H 2PO 3) 3H 2O, compressed smoothly up to 4.2 GPa and starts amorphizing at 6.8 GPa. The amorphous phase persists down to 1 atm upon release of pressure. The amorphization was due to a chemical decomposition and also might be due to pressure-induced distortions of the lattice upon compression associated with the Na + and Co 2+ cation displacements and strongly coupled with rigid rotations of the (PO 3) units. No P-H vibrations were seen after pressure release which means that P-H bonds were broken. The frequencies seen in the Raman spectra for the amorphous phase are characteristic of (PO 4) 3- or PO74- tetrahedral short-range structure.

Manoun, Bouchaib; El Bali, Brahim; Saxena, Surendra K.; Lachkar, Mohammed

2008-03-01

9

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

NASA Astrophysics Data System (ADS)

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

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

2012-03-01

10

Partial pressure analysis of plasmas  

SciTech Connect

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

Dylla, H.F.

1984-11-01

11

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

12

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

PubMed

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

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

2009-11-01

13

Partial pressure gradients due to temperature gradients in a mixture of reactive gases  

Microsoft Academic Search

Partial pressure gradients due to temperature gradients in a mixture of reactive gases, limit the possible use of sensors. Problems arise when a partial pressure sensor is subjected to a temperature, different from that of the sample. A model is proposed that allows the calculation of the partial pressure distributions in a temperature gradient. Experiments conducted using O2, H2, and

O. Porat; I. Riess

1992-01-01

14

Advanced High Pressure O2/H2 Technology  

NASA Technical Reports Server (NTRS)

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

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

1985-01-01

15

Solubility of H2O in rhyolitic melts at low pressures and a new empirical model for mixed H2OCO2 solubility in rhyolitic melts  

E-print Network

Solubility of H2O in rhyolitic melts at low pressures and a new empirical model for mixed H2O­CO2 solubility in rhyolitic melts Yang Liua,T, Youxue Zhanga , Harald Behrensb a Department of Geological Experiments of H2O solubility in synthetic haplogranitic and natural rhyolitic melts were conducted at 700

Zhang, Youxue

16

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

NASA Astrophysics Data System (ADS)

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

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

1998-10-01

17

Kinetic studies on the first dihydrogen aquacomplex, [Ru(H 2)(H 2O) 5] 2+: Formation under H 2 pressure and catalytic H\\/D isotope exchange in water  

Microsoft Academic Search

The ruthenium(II) hexaaqua complex [Ru(H2O)6]2+ reacts with dihydrogen under pressure to give the ?2-dihydrogen ruthenium(II) pentaaqua complex [Ru(H2)(H2O)5]2+.The complex was characterized by 1H, 2H and 17O NMR: ?H=?7.65ppm, JHD=31.2Hz, ?O=?80.4 ppm (trans to H2) and ?O=?177.4ppm (cis to H2).The HH distance in coordinated dihydrogen was estimated to 0.889 from JHD, which is close to the value obtained from DFT calculations

Pascal V. Grundler; Oleg V. Yazyev; Nicolas Aebischer; Lothar Helm; Gbor Laurenczy; Andr E. Merbach

2006-01-01

18

Structure and Transport Properties of Hydrogen Filled Ices (H2O:1/6H2 and H2O:H2) at Pressures to 4 GPa by Solid State Diamond-Anvil-Cell NMR  

NASA Astrophysics Data System (ADS)

Hydrogen filled ices are composed of H2O-ice lattice and hydrogen molecules intercalated to interstitial cavities of the lattice. They can accommodate large amount of hydrogen while keeping the host structure of ices (Vos et al., 1993). At room temperature, their stability field begins at 0.7 GPa and expands to at least 30 GPa. Their properties are important to understand evolution of icy satellites as well as of icy giant planets. However, as for guest hydrogen molecules, not only their local site structures, but also their transport properties, have not yet been reported. We therefore conducted in-situ solid-state NMR of these ices using our state-of-the-art, diamond-anvil-cell high-resolution NMR technique (Okuchi et al, 2005, JCP 122, 244509). Experiments were made at ISSP with 300 MHz custom-made spectrometer. We have developed a novel method to load H2O-H2 fluid mixture into sample chambers with almost desired ratio, which is essential to measure the target phase with the maximum S/N. Two known hydrogen filled ice phases and their mixtures have been synthesized at room temperature by finely tuning the applied pressure: The C1 with ice II host structure and H2O:H2 = 6:1, and the C2 with ice Ic host structure and H2O:H2 = 1:1. The H2O proton resonance in both C1 and C2 phases gave broad single-pulse spectrum due to strong dipolar coupling, as fully expected. On the other hand, three molecular hydrogen species in different phases, including fluid H2, gave rather sharp peaks with well-defined different chemical shifts. These peaks in single-pulse or Hahn-echo measurements indicate fast molecular exchange among the cavity sites, much faster than Larmor frequency. The guest dynamics is therefore quite contrastive to the host lattice. Some interesting mechanical and thermodynamic properties could be predicted from this unique dynamics of hydrogen filled ices.

Okuchi, T.; Takigawa, M.; Shu, J.; Mao, H.; Hemley, R. J.; Yagi, T.

2005-12-01

19

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

20

Temperature induced immiscibility in the NaClH 2O system at high pressure  

Microsoft Academic Search

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

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

2008-01-01

21

Temperature induced immiscibility in the NaCl H2O system at high pressure  

Microsoft Academic Search

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

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

2008-01-01

22

Metallization and superconductivity of BeH2 under high pressure  

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

23

Hydrous partial melting of lherzolite at 1 GPa: The effect of H 2O on the genesis of basaltic magmas  

Microsoft Academic Search

Partial melting of a natural lherzolite (KLB-1) under H2O-undersaturated conditions was experimentally investigated at 1 GPa over the temperature range from 1100 to 1350C. The effect of H2O added to the dry lherzolite ranged from 0.1 to 0.9 wt% of the melt composition and the extent of melting was quantitatively estimated by comparison with the results of anhydrous melting experiments

Kei Hirose; Tatsuhiko Kawamoto

1995-01-01

24

The search for shock-excited H2 in Virgo spirals experiencing ram pressure stripping  

E-print Network

We investigate the presence of shock-excited H2 in four Virgo cluster galaxies that show clear evidence of ongoing ram pressure stripping. Mid-infrared (MIR) spectral mapping of the rotational H2 emission lines were performed using the Infrared Spectrograph (IRS) on board the Spitzer space telescope. We target four regions along the leading side of galaxies where the intracluster medium (ICM) appears to be pushing back the individual galaxy's interstellar medium (ISM). 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 fractions of FeII/NeII found in...

Wong, O Ivy; Murphy, Eric J; Helou, George

2014-01-01

25

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

26

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

NASA Astrophysics Data System (ADS)

Serrabrancaite (MnPO 4H 2O) was synthesized by oxidizing Mn(H 2PO 4) 2 with NaClO solution using a refluxing process at atmospheric pressure, and a mixed solution of MnCl 2 and H 3PO 4 could substitute for Mn(H 2PO 4) 2 in the process. The products were characterized by X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy. Hureaulite was formed when single solution of Mn(H 2PO 4) 2 was refluxed for 12 h at 60 C. Rodlike hureaulite was fabricated by refluxing reaction of 30 mmol Mn(H 2PO 4) 2 and 60 mmol NaClO solution with adding hydrochloric acid within 40 mmol. Granular hureaulite was formed by refluxing of 30 mmol MnCl 2 and 60 mmol NaClO solution with adding phosphoric acid within 30 mmol. For the two above-mentioned reaction systems, MnPO 4H 2O was prepared by adding hydrochloric acid no less than 80 mmol and phosphoric acid no less than 60 mmol respectively. MnPO 4H 2O yield increased with elevating reflux temperature, and increased firstly and then decreased with increasing additional amount of acid. The highest recovery yield of MnPO 4H 2O reached 84.1% when Mn(H 2PO 4) 2 was performed as bivalent manganese source, and approached 74.0% when MnCl 2 and H 3PO 4 were used instead.

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

2010-05-01

27

In situ Raman spectroscopy of low-temperature/high-pressure transformations of H2O  

E-print Network

and transforms to a highly viscous liquid LDL when heated to its proposed glass transition temperature e.g., 130In situ Raman spectroscopy of low-temperature/high-pressure transformations of H2O Yukihiro and temperature have been measured starting from high-density amorphous ice HDA . Changes above Tx

Stewart, Sarah T.

28

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

29

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

30

EFFECTS ON CHP PLANT EFFICIENCY OF H2 PRODUCTION THROUGH PARTIAL OXYDATION OF NATURAL GAS OVER TWO GROUP VIII METAL  

E-print Network

exhaust gas recirculation (RGR) has been identified a potentially advantageous approach: RGR5 uses are presented for11 the electric efficiency and exhaust gas (CO and HC) composition of the overall system (SIEFFECTS ON CHP PLANT EFFICIENCY OF H2 PRODUCTION THROUGH PARTIAL OXYDATION OF NATURAL GAS OVER TWO

Paris-Sud XI, Université de

31

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

32

A system for incubations at high gas partial pressure.  

PubMed

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

Sauer, Patrick; Glombitza, Clemens; Kallmeyer, Jens

2012-01-01

33

Thin film oxygen partial pressure sensor  

NASA Technical Reports Server (NTRS)

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

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

1972-01-01

34

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

USGS Publications Warehouse

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

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

1998-01-01

35

Evidence for H 2 at high pressure in the silicon nanocavities after dipping in HF solution  

NASA Astrophysics Data System (ADS)

The immersion in HF solutions of silicon containing nanocavities (produced by the annealing at high temperature, 950 C, of silicon implanted with helium at high fluence, 2 10 16 cm -2) results in the injection of hydrogen in an infrared-mute state (most likely H 2) into the nanocavities. The pressure achieved in the cavities is sufficiently high to stabilize the hydrogen coverage of the inner surfaces at temperatures exceeding by 200 C the one of complete desorption from the outer surface.

Romano, E.; Cerofolini, G. F.; Narducci, D.; Corni, F.; Frabboni, S.; Ottaviani, G.; Tonini, R.

2009-07-01

36

Effect of H 2 ambient annealing on silicon nanowires prepared by atmospheric pressure chemical vapor deposition  

Microsoft Academic Search

We report the effect of H2 ambient annealing on the microstructure and vibrational properties of silicon nanowires (SiNWs) grown by atmospheric pressure chemical vapor depositions. The SiNWs were characterized by Fourier Transform Infrared Spectroscopy (FTIR), Field-Emission Scanning Electron Microscopy (FESEM) and High-Resolution Transmission Electron Microscopy (HRTEM). The HRTEM study revealed that the thickness of oxide sheath surrounded by core silicon

Bhabani S. Swain; Sung S. Lee; Sang H. Lee; Bibhu P. Swain; Nong M. Hwang

2010-01-01

37

Structural and dynamical properties of H2S under high pressure: ab initio molecular dynamics studies  

Microsoft Academic Search

The structural and dynamical properties of H2S in the region 0 GPapressure reaches 3.8 GPa,

Liancheng Wang; Zhi He; Yanming Ma; Tian Cui; Bingbing Liu; Guangtian Zou

2007-01-01

38

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

NASA Astrophysics Data System (ADS)

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

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

2006-05-01

39

Low-Temperature Crystallization of Amorphous Silicon by Atmospheric-Pressure Plasma Treatment in H2/He or H2/Ar Mixture  

NASA Astrophysics Data System (ADS)

To crystallize amorphous silicon (a-Si) films at temperatures less than 600 C, we propose an atmospheric pressure plasma (APP) treatment method using a H2/He or H2/Ar mixture. An atmospheric-pressure stable-glow plasma was generated using a 150 MHz very high frequency power supply. After APP treatment, the Si films were characterized by reflection high-energy electron diffraction analysis, Fourier-transform infrared spectroscopy and scanning electron microscopy. In addition, optical emission spectroscopy (OES) was employed to study the plasma. In the case of treatment with the H2/He plasma, the crystallization of the a-Si films started with in negligible incubation time at a substrate temperature as low as 200 C, and the resulting Si crystallites showed anisotropic morphology. It was found that a-Si layers still existed under the crystallized layers. This result suggests that crystallization of a-Si by APP was predominated by chemical interactions between atomic hydrogen in the plasma and the treated surface. However, in the case of treatment with the H2/Ar plasma, Si crystallites of the treated film did not show anisotropic morphology, and film peeling was partly observed in the treated area. Additionally, from the OES, emission lines from atomic hydrogen were hardly observed in the H2/Ar plasma. This implies that physical interactions between Ar atoms and the film surface play a significant role in the crystallization of a-Si.

Ohmi, Hiromasa; Kakiuchi, Hiroaki; Nishijima, Kenichi; Watanabe, Heiji; Yasutake, Kiyoshi

2006-10-01

40

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

NASA Astrophysics Data System (ADS)

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

Durandurdu, Murat

2014-02-01

41

The new high-pressure borate hydrate Cu 3B 6O 12 H 2O  

NASA Astrophysics Data System (ADS)

The new compound Cu 3B 6O 12 H 2O, synthesized under high-pressure/high-temperature conditions of 7.5 GPa and 700 C in a Walker-type multianvil apparatus, possesses a structure similar to CuB 2O 4 (3 CuB 2O 4 = Cu 3B 6O 12). Via the high-pressure technique, it was possible to incorporate water molecules into the structure, leading to a symmetry reduction compared to the water free compound ( I42 d ? Fdd2). Cu 3B 6O 12 H 2O crystallizes in the orthorhombic space group Fdd2 ( Z = 8) with the lattice parameters a = 1620.4(3), b = 1657.6(3), c = 564.2(2) pm, V = 1.5154(5) nm 3, R1 = 0.0375, wR2 = 0.0640 (all data). The crystal structure of Cu 3B 6O 12 H 2O is built up from corner-sharing BO 4 tetrahedra forming a three-dimensional network with channels along the c-axis. Inside these channels, the water molecules and a part of the copper ions are arranged.

Neumair, Stephanie C.; Kaindl, Reinhard; Hoffmann, Rolf-Dieter; Huppertz, Hubert

2012-02-01

42

Pressure-induced phase transition of BaH 2 : Post Ni 2In phase  

NASA Astrophysics Data System (ADS)

Up to now a Ni 2In structure is a final step in the structural sequence of ionic AX 2 compounds under high pressure. Powder X-ray diffraction experiments on BaH 2 were performed at room temperature and high pressures up to 69 GPa. Successive phase transformations were observed to occur in two stages. The first was from the cotunnite to the Ni 2In structure at 2.5 GPa. The second transition commenced at pressures around 50 GPa and was completed at 65 GPa. At the transition the arrangement of a cation sublattice changes from an hcp to a simple hexagonal lattice. This is the first observation of the post Ni 2In phase.

Kinoshita, K.; Nishimura, M.; Akahama, Y.; Kawamura, H.

2007-01-01

43

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

44

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

NASA Astrophysics Data System (ADS)

We present a detailed analysis of the partial coverage of the Q1232+082 (zem= 2.57) broad-line region (BLR) by an intervening H2-bearing cloud at zabs= 2.3377. Using curve of growth analysis and line profile fitting, we demonstrate that the H2-bearing component of the cloud covers the quasi-stellar object (QSO) intrinsic continuum source completely but only part of the BLR. We find that only 48 6 per cent of the C IV BLR emission is covered by the C I absorbing gas. We observe residual light (6 per cent) as well in the bottom of the O I ?1302 absorption from the cloud, redshifted on top of the QSO Lyman ? emission line. Therefore, the extent of the neutral phase of the absorbing cloud is not large enough to cover all of the background source. The most likely explanation for this partial coverage is the small size of the intervening cloud, which is comparable to the BLR size. We estimate the number densities in the cloud: ? 110 cm-3 for the H2-bearing core and nH 30 cm-3 for the neutral envelope. Given the column densities, N(H2) = 3.71 0.97 1019 cm-2 and N(H I) = 7.94 1.6 1020 cm-2, we derive the linear size of the H2-bearing core and the neutral envelope along the line of sight to be ? 0.15+0.05-0.05 pc and ? 8.2+6.5-4.1 pc, respectively. We estimate the size of the C IV BLR by two ways: (i) extrapolating size-luminosity relations derived from reverberation observations and (ii) assuming that the H2-bearing core and the BLR are spherical in shape and the results are 0.26 and 0.18 pc, respectively. The large size we derive for the extent of the neutral phase of the absorbing cloud together with a covering factor of 0.94 of the Lyman ? emission means that the Lyman ? BLR is probably fully covered but that the Lyman ? emission extends well beyond the limits of the BLR. Based on observations carried out at European Southern Observatory with the Ultraviolet and Visual Echelle Spectrograph (UVES) mounted on the Very Large Telescope (VLT), unit Kueyen, on Cerro Paranal in Chile, under programmes ID 65.P-0038 (P.I. Srianand), 68.A-0106, 69.A-0061, 70.A-0017 (P.I. Petitjean) and 71.B-0136 (P.I. Srianand).

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

2011-11-01

45

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

46

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

NASA Technical Reports Server (NTRS)

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

Goorvitch, D.; Tipping, R. H.

1982-01-01

47

Method of detecting oxygen partial pressure and oxygen partial pressure sensor  

SciTech Connect

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

Dees, D.W.

1991-12-31

48

Thin film devices used as oxygen partial pressure sensors  

NASA Technical Reports Server (NTRS)

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

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

1970-01-01

49

First principles study of pressure induced structural phase transition in hydrogen storage materialMgH2  

NASA Astrophysics Data System (ADS)

First principles calculation were performed using Vienna ab-initio simulation package within the frame work of density functional theory (DFT) to understand the electronic properties of magnesium hydride. At normal pressure, the most stable structure of MgH 2 is rutile type with a wide band gap of 3.52 eV, which agrees well with the available data. A pressure induced semi-conductor to metallic transition at a pressure of 92.54 GPa is predicted. Our results indicate a sequence of pressure induced structural phase transition in MgH 2. The obtained sequence of phase transition was ????????? at a pressure of 0.37 GPa, 3.89 GPa,7.23 GPa and 11.26 GPa, respectively. Thus our results indicate that MgH 2 is one of the best hydrogen storage material and the maximum storage capacity achieved was 7.7%.

Kanagaprabha, S.; Asvinimeenaatci, A. T.; Rajeswarapalanichamy, R.; Iyakutti, K.

2012-01-01

50

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

51

High-pressure investigations under CO/H2 of rhodium complexes containing hemispherical diphosphites.  

PubMed

The two rhodium complexes [Rh(acac)(L(R))] (L(R)=(S,S)-5,11,17,23-tetra-tert-butyl-25,27-di(OR)-26,28-bis(1,1'-binaphthyl-2,2'-dioxyphosphanyloxy)calix[4]arene; 6: R=benzyl, 7: R=fluorenyl), each based on a hemispherical chelator forming a pocket about the metal centre upon chelation, are active in the hydroformylation of 1-octene and styrene. As expected for this family of diphosphanes, both complexes resulted in remarkably high selectivity towards the linear aldehyde in the hydroformylation of 1-octene (l/b?15 for both complexes). Linear aldehyde selectivity was also observed when using styrene, but surprisingly only 6 displayed a marked preference for the linear product (l/b=12.4 (6) vs. 1.9 (7)). A detailed study of the structure of the complexes under CO or CO/H(2) in toluene was performed by high-pressure NMR (HP NMR) and FT-IR (HP-IR) spectroscopies. The spectroscopic data revealed that treatment of 6 with CO gave [Rh(acac)(CO)(?(1)-L(benzyl))] (8), in which the diphosphite behaves as a unidentate ligand. Subsequent addition of H(2) to the solution resulted in a well-defined chelate complex with the formula [RhH(CO)(2)(L(benzyl))] (9). Unlike 6, treatment of complex 7 with CO only led to ligand dissociation and concomitant formation of [Rh(acac)(CO)(2)], but upon addition of H(2) a chelate complex analogous to 9 was formed quantitatively. In both [RhH(CO)(2)(L(R))] complexes the diphosphite adopts the bis-equatorial coordination mode, a structural feature known to favour the formation of linear aldehydes. As revealed by variable-temperature NMR spectroscopy, these complexes show the typical fluxionality of trigonal bipyramidal [RhH(CO)(2)(diphosphane)] complexes. The lower linear selectivity of 7 versus 6 in the hydroformylation of styrene was assigned to steric effects, due to the pocket in which the catalysis takes place being less adapted to accommodate CO or larger olefins and, therefore, possibly leading to facile ligand decoordination. This interpretation was corroborated by an X-ray structure determination carried out for 7. PMID:20957623

Smeril, David; Matt, Dominique; Toupet, Loc; Oberhauser, Werner; Bianchini, Claudio

2010-12-10

52

Quantitative Analysis of Spectral Interference of Spontaneous Raman Scattering in High-Pressure Fuel-Rich H2-Air Combustion  

NASA Technical Reports Server (NTRS)

We present a theoretical study of the spectral interferences in the spontaneous Raman scattering spectra of major combustion products in 30-atm fuel-rich hydrogen-air flames. An effective methodology is introduced to choose an appropriate line-shape model for simulating Raman spectra in high-pressure combustion environments. The Voigt profile with the additive approximation assumption was found to provide a reasonable model of the spectral line shape for the present analysis. The rotational/vibrational Raman spectra of H2, N2, and H2O were calculated using an anharmonic-oscillator model using the latest collisional broadening coefficients. The calculated spectra were validated with data obtained in a 10-atm fuel-rich H2-air flame and showed excellent agreement. Our quantitative spectral analysis for equivalence ratios ranging from 1.5 to 5.0 revealed substantial amounts of spectral cross-talk between the rotational H2 lines and the N2 O-/Q-branch; and between the vibrational H2O(0,3) line and the vibrational H2O spectrum. We also address the temperature dependence of the spectral cross-talk and extend our analysis to include a cross-talk compensation technique that removes the nterference arising from the H2 Raman spectra onto the N2, or H2O spectra.

Kojima, Jun; Nguyen, Quang-Viet

2004-01-01

53

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

NASA Astrophysics Data System (ADS)

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

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

54

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

PubMed

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

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

2014-07-01

55

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

56

Determination of the Relative Partial Molar Enthalpy of Decyldimethylphospine Oxide in H 2O and D 2O at 25C  

Microsoft Academic Search

The relative partial molar enthalpy of decyldimethylphosphine oxide has been determined in H2O and D2O from infinite dilution to about 8 mm at 25C. The shapes of the resulting curves resemble those previously reported forionicbut notnonionicsurfactants and are inconsistent with existing models of micelle formation. The enthalpy of micelle formation (corresponding to the maximum value of the relative partial molar

Gordon C. Kresheck

1997-01-01

57

Apparent and partial molal volumes in mixed salt solutions. I. The ternary systems LiCl-LiNO3-H2O, NaCl-NaNO3-H2O and KCl-KNO3-H2O  

Microsoft Academic Search

The densities of aqueous mixtures of LiCl-LiNO3, NaCl-NaNO3, and KCl-KNO3 were determined at 25 C at constant chloride-nitrate molality ratios. The mean apparent molal volumes were calculated and found to obey the limiting law modified by additional terms in ionic strength. The partial molal volumes for the electrolytes in each mixture were calculated and the conditions under which Young and

J. Padova; I. Lewkowicz

1976-01-01

58

Boron doped amorphous carbon thin films grown by r.f. PECVD under different partial pressure  

Microsoft Academic Search

Boron doped hydrogenated amorphous carbon (a-C) thin films have been deposited by r.f.-plasma CVD with a frequency of 13.56 MHz at room temperature using pure methane as a precursor of carbon source mixed with hydrogen (H2) as a carrier gas. The films were prepared by varying the r.f. power, different flow rates of CH4, and partial pressure of mixed gas

J. Podder; M. Rusop; T. Soga; T. Jimbo

2005-01-01

59

Determination of the Relative Partial Molar Enthalpy of Decyldimethylphospine Oxide in H2O and D2O at 25C  

PubMed

The relative partial molar enthalpy of decyldimethylphosphine oxide has been determined in H2O and D2O from infinite dilution to about 8 mm at 25C. The shapes of the resulting curves resemble those previously reported for ionic but not nonionic surfactants and are inconsistent with existing models of micelle formation. The enthalpy of micelle formation (corresponding to the maximum value of the relative partial molar enthalpy of the surfactant) was 12,900 200 cal/mol in H2O and 10,600 200 cal/mol in D2O. The cmc was lower in D2O than in H2O as expected (3.64 versus 4.2 mm). PMID:9073432

Kresheck

1997-03-15

60

The rate of carburization of iron in CO-H 2 atmospheres: Part I. Effect of temperature and CO and H 2 -pressures  

Microsoft Academic Search

The rates of carburization of iron strips in CO-He and CO-H2 atmospheres at 1188 and 1273 K have been investigated. The rates in CO-He and the initial rates in CO-H2 mixtures are controlled by a slow chemical reaction on the surface of iron. The rate controlling reaction in CO-He atmospheres\\u000a is interpreted to be the formation of the activated complex

R. J. Fruehan

1973-01-01

61

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

NASA Technical Reports Server (NTRS)

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

Green, Sheldon

1991-01-01

62

Measurements of Surface Ocean Carbon Dioxide Partial Pressure During WOCE  

Microsoft Academic Search

All of the technical goals of the World Ocean Circulation Experiment (WOCE) field program which were supported under the Department of Energy research grant ''Measurements of Surface Ocean Carbon Dioxide Partial Pressure During WOCE'' (DE-FG03-90ER60981) have been met. This has included the measurement of the partial pressures of carbon dioxide (C0) and nitrous oxide (NO) in both the surface ocean

1998-01-01

63

Pressure derivatives of elastic constants of monoclinic M(NO 3 ) 3 9H 2 O (M=Al, Fe, Cr) and third-order elastic constants of Al(NO 3 ) 3 9H 2 O  

Microsoft Academic Search

The elastic constants and their pressure and temperature derivatives of monoclinic M(NO3)39H2O (M=Al, Fe, Cr) have been determined from ultrasonic resonance frequencies of thick plates and from their temperature- and\\u000a pressure-induced shifts. In addition, the complete third-order elasticity tensor of Al(NO3)39H2O has been evaluated from a combination of measurements of shifts of ultrasonic resonance frequencies produced by hydrostatic\\u000a pressure and

E. Behnke; S. Hausshl

1989-01-01

64

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

65

A scanned-wavelength-modulation absorption-spectroscopy sensor for temperature and H2O in low-pressure flames  

NASA Astrophysics Data System (ADS)

The design and demonstration of a tunable diode laser sensor for in situ temperature and water (H2O) measurements in laboratory flames is presented. A newly-designed probe consisting of two single-crystal sapphire rods is used to guide 2.9??m laser light across the core of a flame while avoiding absorption by water outside of the flame. The sensor probes two H2O transitions near 2.9??m using a scanned-wavelength-modulation absorption-spectroscopy spectral-fitting technique, which enables measurements without calibration or knowledge of the mixture collisional-broadening coefficient. To demonstrate the sensor, temperature and water mole fraction measurements were acquired in stoichiometric, burner-stabilized flames of methane/oxygen/argon at pressures of 25?Torr and 60?Torr. Typical total uncertainties in the temperature and water mole fraction measurements were 50?K and 0.016, respectively. This sensor is simple, robust and accurate and enables improved chemical kinetics studies of low-pressure flames. Improvements to reduce temperature and H2O precision to 20?K and 0.008, respectively, are discussed.

Smith, Colin H.; Goldenstein, Christopher S.; Hanson, Ronald K.

2014-11-01

66

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

Microsoft Academic Search

H2O activities in supercritical fluids in the system KCl-H2O-(MgO) were measured at pressures of 1, 2, 4, 7, 10 and 15? kbar by numerous reversals of vapor compositions in equilibrium\\u000a with brucite and periclase. Measurements spanned the range 550900?C. A change of state of solute KCl occurs as pressures\\u000a increase above 2?kbar, by which H2O activity becomes very low and,

L. Y. Aranovich; R. C. Newton

1997-01-01

67

Olivine-Pyroxene-H2O system as a practical analogue for estimating the elastic properties of fluid-bearing mantle rocks at high pressures and temperatures  

Microsoft Academic Search

By using Grneisen theory and third-order finite strain theory, elastic-wave velocities in olivine-pyroxene assemblages are accurately determined as a function of pressure and temperature. Equilibrium distributions of H2O fluid in mantle rocks have been determined at high pressure and temperature, and are used to estimate Vp and Vs in the olivine-pyroxene-H2O system. Importantly, velocities calculated for the peridotite-H2O system successively

Hiroki Sato; Kazuhiko Ito

2002-01-01

68

Pressurized H2 rf Cavities in Ionizing Beams and Magnetic Fields  

NASA Astrophysics Data System (ADS)

A major technological challenge in building a muon cooling channel is operating rf cavities in multitesla external magnetic fields. We report the first proof-of-principle experiment of a high pressure gas-filled rf cavity for use with intense ionizing beams and strong external magnetic fields. rf power consumption by beam-induced plasma is investigated with hydrogen and deuterium gases with pressures between 20 and 100 atm and peak rf gradients between 5 and 50MV/m. The low pressure case agrees well with an analytical model based on electron and ion mobilities. Varying concentrations of oxygen gas are investigated to remove free electrons from the cavity and reduce the rf power consumption. Measurements of the electron attachment time to oxygen and rate of ion-ion recombination are also made. Additionally, we demonstrate the operation of the gas-filled rf cavity in a solenoidal field of up to 3 T, finding no major magnetic field dependence. All these results indicate that a high pressure gas-filled cavity is a viable technology for muon ionization cooling.

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

2013-11-01

69

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

70

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

71

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

72

Report on ISS Oxygen Production, Resupply, and Partial Pressure Management  

NASA Technical Reports Server (NTRS)

The majority of oxygen used on International Space Station (ISS) is for metabolic support and denitrogenation procedures prior to Extra-Vehicular Activities. Oxygen is supplied by various visiting vehicles such as the Progress and Shuttle in addition to oxygen production capability on both the United States On-Orbit Segment (USOS) and Russian Segment (RS). To maintain a habitable atmosphere the oxygen partial pressure is controlled between upper and lower bounds. The full range of the allowable oxygen partial pressure along with the increased ISS cabin volume is utilized as a buffer allowing days to pass between oxygen production or direct addition of oxygen to the atmosphere from reserves. This paper summarizes amount of oxygen supplied and produced from all of the sources and describes past experience of managing oxygen partial pressure along with the range of management options available to the ISS.

Schaezler, Ryan; Ghariani, Ahmed; Leonard, Daniel; Lehman, Daniel

2011-01-01

73

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

NASA Technical Reports Server (NTRS)

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

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

1980-01-01

74

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

75

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

76

Calibration Of Partial-Pressure-Of-Oxygen Sensors  

NASA Technical Reports Server (NTRS)

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

Yount, David W.; Heronimus, Kevin

1995-01-01

77

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

78

Surface loss probability of atomic hydrogen for different electrode cover materials investigated in H2-Ar low-pressure plasmas  

NASA Astrophysics Data System (ADS)

In an inductively coupled H2-Ar plasma at a total pressure of 1.5 Pa, the influence of the electrode cover material on selected line intensities of H, H2, and Ar are determined by optical emission spectroscopy and actinometry for the electrode cover materials stainless steel, copper, tungsten, Macor, and aluminum. Hydrogen dissociation degrees for the considered conditions are determined experimentally from the measured emission intensity ratios. The surface loss probability ?H of atomic hydrogen is correlated with the measured line intensities, and ?H values are determined for the considered materials. Without the knowledge of the atomic hydrogen temperature, ?H cannot be determined exactly. However, ratios of ?H values for different surface materials are in first order approximation independent of the atomic hydrogen temperature. Our results show that ?H of copper is equal to the value of stainless steel, ?H of Macor and tungsten is about 2 times smaller and ?H of aluminum about 5 times smaller compared with stainless steel. The latter ratio is in reasonable agreement with literature. The influence of the atomic hydrogen temperature TH on the absolute value is thoroughly discussed. For our assumption of TH = 600 K, we determine a ?H for stainless steel of 0.39 0.13.

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

2014-07-01

79

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

Microsoft Academic Search

In this work we investigate the variation of the local structure around Cu2+ as well as the crystal structure in Rb2CuCl4(H2O)2 through x-ray absorption spectroscopy (XAS) and x-ray diffraction (XRD) as a function of pressure. We show that the application of pressure induces a local structural change in the Jahn-Teller (JT) CuCl4(H2O)22- complex from an axially elongated complex to a

F. Aguado; F. Rodrguez; R. Valiente; J. P. Iti; P. Munsch

2004-01-01

80

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

81

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

82

Biological nitrogen fixation under primordial Martian partial pressures of dinitrogen  

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

83

Low carbon dioxide partial pressure in a productive subtropical lake  

Microsoft Academic Search

The purposes of this study were to assess if Lake Apopka (FL, USA) was autotrophic or heterotrophic based on the partial pressure\\u000a of dissolved carbon dioxide (pCO2) in the surface water and to evaluate factors that influence the long-term changes in pCO2. Monthly average pH, alkalinity and other limnological variables collected between 1987 and 2006 were used to estimate dissolved

Binhe GuClaire; Claire L. Schelske; Michael F. Coveney

84

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

85

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

Microsoft Academic Search

An Excel macro to calculate mineral and rock physical properties at elevated pressure and temperature is presented. The workbook includes an expandable database of physical parameters for 52 rock-forming minerals stable at high pressures and temperatures. For these minerals the elastic moduli, densities, seismic velocities, and H2O contents are calculated at any specified P and T conditions, using basic thermodynamic

Bradley R. Hacker; Geoffrey A. Abers

2004-01-01

86

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

87

Olivine-Pyroxene-H2O system as a practical analogue for estimating the elastic properties of fluid-bearing mantle rocks at high pressures and temperatures  

NASA Astrophysics Data System (ADS)

By using Grneisen theory and third-order finite strain theory, elastic-wave velocities in olivine-pyroxene assemblages are accurately determined as a function of pressure and temperature. Equilibrium distributions of H2O fluid in mantle rocks have been determined at high pressure and temperature, and are used to estimate Vp and Vs in the olivine-pyroxene-H2O system. Importantly, velocities calculated for the peridotite-H2O system successively reproduce the absolute Vp and Vs values measured in the laboratory for dehydrated serpentinite. Known equilibrium distributions of H2O-CO2 fluid in peridotite-liquid systems allow one to estimate elastic properties of fluid-bearing mantle rocks from mineral and liquid elasticity data.

Sato, Hiroki; Ito, Kazuhiko

2002-05-01

88

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

89

High-Pressure Equation of State for Partially Ionic Solids  

NASA Technical Reports Server (NTRS)

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

Schlosser, Herbert; Ferrante, John

1993-01-01

90

Partial discharge detection and analysis in low pressure environments  

NASA Astrophysics Data System (ADS)

Typical aerospace vehicles (aircraft and spacecraft) experience a wide range of operating pressures during ascending and returning to earth. Compared to the sea-level atmospheric pressure (760 Torr), the pressure at about 60 km altitude is 2 Torr. The performance of the electric power system components of the aerospace vehicles must remain reliable even under such sub-atmospheric operating conditions. It is well known that the dielectric strength of gaseous insulators, while the electrode arrangement remains unchanged, is pressure dependent. Therefore, characterization of the performance and behavior of the electrical insulation in flight vehicles in low-pressure environments is extremely important. Partial discharge testing is one of the practical methods for evaluating the integrity of electrical insulation in aerospace vehicles. This dissertation describes partial discharge (PD) measurements performed mainly with 60 Hz ac energization in air, argon and helium, for pressures between 2 and 760 Torr. Two main electrode arrangements were used. One was a needle-plane electrode arrangement with a Teflon insulating barrier. The other one was a twisted pair of insulated conductors taken from a standard aircraft wiring harness. The measurement results are presented in terms of typical PD current pulse waveforms and waveform analysis for both main electrode arrangements. The evaluation criteria are the waveform polarity, magnitude, shape, rise time, and phase angle (temporal location) relative to the source voltage. Two-variable histograms and statistical averages of the PD parameters are presented. The PD physical mechanisms are analyzed. For PD pattern recognition, both statistical methods (such as discharge parameter dot pattern representation, discharge parameter phase distribution, statistical operator calculations, and PD fingerprint development) and wavelet transform applications are investigated. The main conclusions of the dissertation include: (1) The PD current pulse waveforms are dependent on the pressure. (2) The rise time of the waveform is another effective PD current pulse characteristic indicator. (3) PD fingerprint patterns that are already available for atmospheric pressure (760 Torr) conditions are inadequate for the evaluation of PD pulses at low pressures. (4) Various wavelet transform techniques can be used effectively for PD pulse signal denoising purposes, and for PD pulse waveform transient feature recognition.

Liu, Xin

91

Thermo- and piezochromic properties of [Fe(hyptrz)]A2H2O spin crossover 1D coordination polymer: Towards spin crossover based temperature and pressure sensors  

NASA Astrophysics Data System (ADS)

We have used reflectance measurements to investigate the effect of a hydrostatic pressure on the molecular 1D spin crossover coordination polymer [Fe(hyptrz)]A2H2O (hyptrz=4-(3?-hydroxypropyl)-1,2,4-triazole and A=4-chloro-benzenesulfonate) Rev. Sci. Instrum. 80 (2009) 123901. Both thermal and pressure hysteresis have been recorded at different pressures and temperatures, respectively, in order to obtain valuable information about the optimal conditions of their use as wireless temperature and pressure sensors. The experimental analysis has been completed with a theoretical study and potential applications in terms of temperature and pressure wireless detection are discussed.

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

2014-09-01

92

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

93

Cheyne-Stokes respiration in congestive heart failure: continuous positive airway pressure of 5-8 cm H2O for 1 year in five cases.  

PubMed

Five adult patients with congestive heart failure (CHF) due to dilated cardiomyopathy complicated by Cheyne-Stokes respiration/central sleep apnea (CSR/CSA) were treated with continuous positive airway pressure (CPAP) with an initial pressure of 5 cm H2O. Four patients were followed up for 12 months with CPAP of 5 cm H2O. The rest, a 93-year-old patient, was followed up for 30 months, and the CPAP was reset at 8 cm H2O due to worsened cardiac function after 6 months and it was reset at 6 cm H2O due to dryness of the nose after 23 months. For all the patients with nightly CPAP use for 6.0+/-1.4 h per day for a year, frequency of CSR/CSA was significantly reduced after 3 and 12 months with CPAP (p<0.05). Moreover, their symptoms, cardiac function and sleep quality were significantly improved after 3 months (p<0.05), and were maintained above the pre-CPAP levels after 12 months, except for the oldest patient whose cardiac function tended to deteriorate. The results suggest that CSR/CSA in CHF can be treated with CPAP set at a lower pressure than the conventional method, and that CPAP at 5-8 cm H2O is often effective in eliminating CSR/CSA, improving sleep quality, and presumably maintaining cardiac function. PMID:15824532

Yasuma, Fumihiko

2005-01-01

94

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

NASA Astrophysics Data System (ADS)

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

Aguado, F.; Rodrguez, F.; Valiente, R.; Iti, J. P.; Munsch, P.

2004-12-01

95

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

96

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

PubMed Central

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

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

1997-01-01

97

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

98

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

99

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

100

Influence of water vapor pressure on the induction period during Li2SO4H2O single crystals dehydration  

E-print Network

dehydration Loïc Favergeon* , Michèle Pijolat, ?cole Nationale Supérieure des Mines de Saint-?tienne, Centre Abstract The dehydration of Li2SO4·H2O single crystals at 80°C has been studied by means of both isothermal crystallography [7-8] on the nuclei shape has been put in evidence in the case of the dehydration of copper

Paris-Sud XI, Université de

101

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

PubMed Central

Summary NAD(P)H:H2 pathways are theoretically predicted to reach equilibrium at very low partial headspace H2 pressure. An evaluation of the directionality of such near?equilibrium pathways in vivo, using a defined experimental system, is therefore important in order to determine its potential for application. Many anaerobic microorganisms have evolved NAD(P)H:H2 pathways; however, they are either not genetically tractable, and/or contain multiple H2 synthesis/consumption pathways linked with other more thermodynamically favourable substrates, such as pyruvate. We therefore constructed a synthetic ferredoxin?dependent NAD(P)H:H2 pathway model system in Escherichia coli BL21(DE3) and experimentally evaluated the thermodynamic limitations of nucleotide pyridine?dependent H2 synthesis under closed batch conditions. NADPH?dependent H2 accumulation was observed with a maximum partial H2 pressure equivalent to a biochemically effective intracellular NADPH/NADP+ ratio of 13:1. The molar yield of the NADPH:H2 pathway was restricted by thermodynamic limitations as it was strongly dependent on the headspace?:?liquid ratio of the culture vessels. When the substrate specificity was extended to NADH, only the reverse pathway directionality, H2 consumption, was observed above a partial H2 pressure of 40?Pa. Substitution of NADH with NADPH or other intermediates, as the main electron acceptor/donor of glucose catabolism and precursor of H2, is more likely to be applicable for H2 production. PMID:21261858

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

2008-01-01

102

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

Microsoft Academic Search

This study experimentally and numerically investigates the pressure pulses characteristics and unsteady flow behavior in a Francis turbine with partial load. Unsteady wall pressure measurements with partial load condition are performs to investigate thoroughly pressure fields in the spiral case, runner head cover and straight draft tube dynamically. The unsteady Reynolds- averaged Navier-Stokes equations with the k-omegabased SST turbulence model

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

2010-01-01

103

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 NPzAT 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 NPzAT 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

104

High pressure-temperature Raman measurements of H2O melting to 22 GPa and 900 K  

E-print Network

conditions where the state of water changes from hydrogen-bonded to dissociation dominated. The melt- ing in this respect and have been used to characterize dissociation processes in water under pressure.12­13 Ab initio-stretching bands of liquid water at high pressure are very similar to those obtained in shock-wave Raman

Lin, Jung-Fu "Afu"

105

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

SciTech Connect

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

Prof. Stratis V. Sotirchos

2000-09-01

106

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

NASA Astrophysics Data System (ADS)

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

Duan, Xianzhe

2014-01-01

107

Catalytic activity of synthesized nanosized molybdenum disulfide for the hydrodesulfurization of dibenzothiophene: Effect of H 2S partial pressure  

Microsoft Academic Search

Nanosized MoS2 catalysts with basal planes of ?4nm were synthesized by thermally annealing ammonium tetrathiomolybdate. The structure and morphology of the obtained phases were determined by XRD, SEM and TEM. These nanosized MoS2 clusters have a truncated hexagonal shape. The MoS2 layers in these batches were found to be curved to some extent. Catalytic performance was evaluated by the hydrodesulfurization

Hamdy Farag; Abdel-Nasser A. El-Hendawy; Kinya Sakanishi; Masahiro Kishida; Isao Mochida

2009-01-01

108

Factors affecting the accuracy of volume-oscillometric blood pressure measurement during partial pressurization of the wrist.  

PubMed

We compared the volume-oscillometric responses of the airbag pressure sensor and the contact force sensor across and along the radial artery on the wrist during partial pressurization by an airbag. Because of the anatomic structure and non-uniform pressurization pressure distribution, elongated and shifted oscillometric pressure waveform envelope variations are observed. For the contact force sensors directly above the radial artery, S-shaped pressurization curves can be seen possibly due to temporal softening of the radial artery stiffness at near zero transmural pressure. These differences in the shape of oscillometric envelope as well as pressurization curve may be the leading factors for inaccuracies of volume-oscillometric blood pressure measurement by partial pressurization method using an airbag. PMID:19963727

Kim, Jong Pal; Kim, Youn Ho; Bae, Sangkon; Kim, Seok Chan; Shin, Kunsoo

2009-01-01

109

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

USGS Publications Warehouse

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

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

1987-01-01

110

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

2014-10-01

111

Narrowing Effects in the H(2)(18)O Near-IR Spectrum: Experimental Test of the Partially-Correlated Quadratic-Speed-Dependent Hard-Collision Profile  

NASA Astrophysics Data System (ADS)

We present the outcomes of a specific study on the quadratic approximation in the partially-Correlated Speed-Dependent Hard-Collision profile (pC-SDHC), which is currently the recommended profile to replace the Voigt convolution for the shape of isolated high-resolution rotational-vibrational transitions, when perturbed by neutral gas-phase molecules. It includes the main effects occurring in the line formation, in particular the Dicke narrowing and the speed-dependent effects, as well as the possible correlation between them. We tested the quadratic (q-) and hypergeometric (hg-) versions for the speed dependence of the pC-SDHC on high quality H218O absorption spectra, in coincidence with three vibration-rotation transitions of the ?1 + ?3 band, at 1.39m, looking for possible differences in the retrieved parameters. The absorption spectra were observed in the Doppler regime, with unprecedented spectral fidelity, by using a dual-laser absorption spectrometer, recently developed for the aim of a spectroscopic determination of the Boltzmann constant. The investigated transitions were: 22,1 ? 22,0 , 44,1 ? 44,0 and 30,3 ? 20,2. The pC-SDHC profile is found to be quite robust, regardless of the choice of the particular speed dependence, provided that the velocity-changing collision frequency is considered as a free parameter. In particular, the pressure broadening and shifting parameters, retrieved by using the quadratic and hypergeometric versions, were found to be fully consistent. Similarly, the integrated absorbance was found to be completely unaffected by the choice of the speed-dependence, in the whole pressure range that we have explored. It should be said, however, that the velocity-changing collision frequency resulted to be physically meaningful only for the hg-version, but not for the q-version. Therefore, in the quadratic approximation, the collision frequency must be considered just as an indispensable parameter to be included in the fitting procedure for the aims of a successful fit.

De Vizia, Maria Domenica; Castrillo, Antonio; Amodio, Pasquale; Fasci, Eugenio; Moretti, Luigi; Gianfrani, Livio

2014-06-01

112

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

Microsoft Academic Search

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

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

1983-01-01

113

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

114

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

115

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

PubMed Central

Background The cuff of the laryngeal mask airway (LMA) is preferred to be partially inflated before insertion in pediatric cases. However, it is not known how much inflation is appropriate. In addition, intra-cuff pressure is not routinely monitored in many institutions despite the fact that a neglected high cuff pressure could cause several complications. This study was conducted to determine whether the cuff inflated with its resting volume before insertion could have a clinically tolerable intra-cuff pressure after insertion. Methods One hundred fifty unpremedicated children aged 0 to 9 yrs were enrolled. The pilot balloon valve was connected to a piston-free syringe to keep the valve open to the atmosphere and allowing the pressure within the cuff of to LMA to equalize to atmospheric pressure. Anesthesia was induced with 6 vol% of sevoflurane in oxygen. After insertion and final positioning of the LMA, the intra-cuff pressure was measured using a cuff pressure manometer. Results The mean intra-cuff pressure was 50 12.9 cmH2O; intra-cuff pressures were 39.1 9.3, 51.6 11.2, and 64.6 12.5 cmH2O for LMAs of sizes 1.5, 2, and 2.5, respectively. Intra-cuff pressure of more than 60 cmH2O was measured in 26 patients, and the median value was 70 cmH2O. There was weak statistical correlation among age, height, and weight with intra-cuff pressure. Conclusions The cuff inflated by the resting volume before insertion may be a simple method for guaranteeing tolerable cuff pressure after insertion. PMID:22778887

Moon, Bo-Eun; Kim, Min-Soo

2012-01-01

116

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

117

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

118

Influence of oxygen partial pressure on the quasi-ternary system Cr-Mn-Ti oxide  

SciTech Connect

The quasi-ternary system Cr-Mn-Ti oxide was investigated at 1,000 C under oxygen partial pressures ranging from 0.21 bar to 10[sup [minus]21] bar (1 bar = 10[sup 5] Pa). X-ray diffraction analysis was used to identify phases and determine lattice parameters. The positions of phase boundaries as a function of oxygen partial pressure were measured using the emf method. The spinel MnCr[sub 2]O[sub 4] may be regarded as the most interesting compound in this system. Part of the chromium can be replaced by trivalent titanium at low oxygen partial pressures and by trivalent manganese at high pressures, and the formation of a limited solid solution with the spinel Mn[sub 2]TiO[sub 4] is possible in all cases. As a result, a coherent single-phase spinel region exists over the entire oxygen partial pressure range at 1,000 C.

Garcia-Rosales, C.; Schulze, H.A.; Naoumidis, A.; Nickel, H. (Inst. for Reactor Materials, Juelich (Germany). Research Centre Juelich)

1993-11-01

119

Continental exhumation triggered by partial melting at ultrahigh pressure  

E-print Network

as the WGR rocks reached their hydrated solidus, at the peak pressure recorded by the eclogites. The limited and Harley, 2010). Comparison of P-T paths for UHP units with undersaturated solidus for continental crust

Paris-Sud XI, Université de

120

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

121

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

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

122

Influence of partial pressure on base-growth of single carbon nanotube  

NASA Astrophysics Data System (ADS)

Influence of hydrocarbon partial pressure on single carbon nanotube (CNT) growth in chemical vapor deposition is investigated by a new theoretical model based on kinetic theory of gases and, phonon vibrations of carbon nanotube on catalyst. Results show that CNTs with larger diameter grow lesser owing to higher damping factors and CNT inertia. In addition, an optimum temperature for the growth is obtained for a CNT with a specific diameter and catalyst. Also it is shown that the optimum temperature is changed by using different catalysts. Finally effect of the partial pressure on the growth is also discussed. It is demonstrated that increasing partial pressure leads to the longest CNTs and also, influence of partial pressure on CNTs with smaller diameters is stronger. All results of the presented mechanism are in good agreement with reported experimental results.

Saeidi, M.

2014-10-01

123

Pressure of a partially ionized hydrogen gas: numerical results from exact low temperature expansions  

E-print Network

Pressure of a partially ionized hydrogen gas: numerical results from exact low temperature expansions A. Alastuey , V. Ballenegger Abstract We consider a partially ionized hydrogen gas at low interest for hydrogen described as a gas of quantum protons and electrons interacting via the Coulomb

Paris-Sud XI, Université de

124

Dynamics of partially oriented L-phenylalanine-d(8) in the CsPFO/H(2)O lyotropic system via (2)H NMR relaxation studies.  

PubMed

Dynamics of the l-phenylalanine-d(8) has been here investigated by analyzing the (2)H NMR spin-lattice relaxation times of this selectively deuterium enriched amino acid diluted in the cesium pentadecafluorooctanoate/water (CsPFO/H(2)O) lyotropic system both in the nematic (N(+)(D)) and in the lamellar (L(D)) phases. Information on the internal and overall molecular motions as well as on collective motions has been achieved by a global fitting procedure. The dynamic processes affecting this probe molecule reflect its particular conformational and interaction properties with respect to the lyotropic environment. The best reproduction of the experimental data is obtained by assuming free internal reorientations of the benzylic moiety, which results in diffusion constants of the same order of magnitude of the overall molecular spinning motion. Moreover, the contribution of collective motions (order director fluctuations and layer undulations) is estimated to be greater than that commonly observed by other techniques in lyotropic systems. PMID:19761270

Domenici, Valentina; Marchetti, Alessandro; Cifelli, Mario; Veracini, Carlo Alberto

2009-12-01

125

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

126

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

127

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

Microsoft Academic Search

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

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

2008-01-01

128

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

NASA Astrophysics Data System (ADS)

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

Kusaba, Mitsuhiro; Henningsen, Jes

2001-10-01

129

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

130

Responses of cotton foliage to short-term fluctuations in CO{sub 2} partial pressures  

SciTech Connect

Global atmospheric carbon dioxide partial pressures are increasing, with a projected doubling during the 21st century. Determination of the effects of elevated levels of CO{sub 2} partial pressures on vegetation in both agricultural fields and natural ecosystems is the topic of a major research effort which is now underway. One goal of this effort is to predict plant growth under elevated levels of CO{sub 2} as well as natural conditions of temperature, rainfall, humidity, etc. Due to the cost of CO{sub 2} and difficulty in controlling CO{sub 2} partial pressures in free-air carbon dioxide experiments, little research has been conducted under natural conditions. 10 refs., 6 figs., 1 tab.

Evans, L.S. [Manhattan College, Bronx, NY (United States); Hendrey, G.R. [Brookhaven National Lab., Upton, NY (United States)

1992-12-31

131

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

Microsoft Academic Search

The concentrations of nitrous oxide (N2O), an important component of the greenhouse effect and with a long residence time in the atmosphere, have significantly increased in this century. The reasons for this atmospheric increase in N2O are still partially unexplained. This uncertainty is worse in relation to aquatic environments. Here we report on preliminary measurements of N2O partial pressures in

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

2006-01-01

132

Equilibrium partial pressures and crystal growth of Cd 1? x Zn x Te  

Microsoft Academic Search

The partial pressures, pCd and pZn, over Cd1?xZnxTe (CZT) and Cd1?xZnx melts were estimated based on known thermodynamic data and the partial pressures, pCd and pZn, over Cd0.86Zn0.14 alloy melt at a temperature of about 980C could be equilibrium with those over Cd0.8Zn0.2Te melt at a melting temperature of 1162C. The Cd0.8Zn0.2Te crystal growth from the melt under controlled constituent

Wenbin Sang; Yongbiao Qian; Weiming Shi; Linjun Wang; Ju Yang; Donghua Liu

2000-01-01

133

Steam catalysis in CaO carbonation under low steam partial pressure  

SciTech Connect

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

Yang, S.J.; Xiao, Y.H. [Chinese Academy of Science, Beijing (China)

2008-06-15

134

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

135

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

136

Melting relations of the hydrous primitive mantle in the CMASH 2O system at high pressures and temperatures, and implications for generation of komatiites  

Microsoft Academic Search

The hydrous phase relations of primitive mantle compositions in the CaOMgOAl2O3SiO2H2O system with 1, 2, and 5wt.% H2O have been investigated at 4, 6.5, and 8GPa. The stability field of orthopyroxene in the residue expands with increasing H2O content at 48GPa. Dissolution temperature of garnet decreases more rapidly than that of the other phases at 4 and 6.5GPa. The dissolution

Yuki Asahara; Eiji Ohtani

2001-01-01

137

Oxidation of C/SiC Composites at Reduced Oxygen Partial Pressures  

NASA Technical Reports Server (NTRS)

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

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

2007-01-01

138

H2O Adsorption Kinetics on Smectites  

NASA Technical Reports Server (NTRS)

The adsorptive equilibration of H2O with montomorillonite has been measured. At low temperatures and pressures equilibration can require many hours, effectively preventing smectites at the martian surface from responding to diurnal pressure and temperature variations.

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

2000-01-01

139

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

140

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

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

141

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

142

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

Microsoft Academic Search

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

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

143

Carbon dioxide partial pressures in North Pacific surface waters Time variations  

Microsoft Academic Search

Observations were made of time variations of the carbon dioxide partial pressures (Pco2) of the atmosphere and surface sea waters in the Pacific subarctic region. Data were obtained on a cruise of the USC & GSSSURVEYOR in October, 1968 and on the TRANSPAC expedition of the CNAVENDEAVOUR in MarchApril, 1969. A rise in surface water Pco2 of 1810?6 atm occurred

Louis I. Gordon; Stephen W. Hager; Timothy R. Parsons

1971-01-01

144

Low-temperature normal-pressure CVD of carbon nanotubes from CO + H2 gas mixture: Thermodynamic analysis and experimental observation  

NASA Astrophysics Data System (ADS)

It has been shown that the deposition of carbon nanotubes from CO could take place at very low temperatures by adding hydrogen to the gas mixture. Adding hydrogen significantly changes the nature of the chemical vapor deposition process. It has been demonstrated that at a certain ratio CO : H2 this gas mixture on the one hand could be used for the deposition of carbon structures at low temperatures and on the other hand for the etching of carbon structures at high temperatures. Thus, the same gas mixture can be both a source of carbon and its etchant depending on temperature. We have also demonstrated that carbon nanotubes of good quality without impurities of amorphous carbon, soot or graphite can be formed from the gas mixture of CO + H2 at low temperatures.

Mironov, A. E.; Gromov, D. G.; Gavrilov, S. A.; Galperin, V. A.

2013-01-01

145

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

146

Novel cooperative interactions and structural ordering in H2S-H2  

SciTech Connect

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

Kent, Paul R [ORNL

2011-01-01

147

Influence of gel aging and Na 2SiO 3\\/H 2O molar ratio on monolithicity and physical properties of waterglass-based aerogels dried at atmospheric pressure  

Microsoft Academic Search

The experimental results on the effects of gel aging and molar ratio of Na2SiO3\\/H2O on monolithicity and physical properties of waterglass-based silica aerogels are presented. The aerogels were prepared by atmospheric pressure drying using a silylation process. The gel-aging period was varied from 1 to 96h. The percentage of volume shrinkage and hence the density and optical transmission of the

A. Venkateswara Rao; A. Parvathy Rao; M. M. Kulkarni

2004-01-01

148

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

149

Influence of oxygen partial pressure on the physical properties of Ag doped NiO thin films  

NASA Astrophysics Data System (ADS)

Ag doped p-type NiO thin films were successfully deposited by DC reactive magnetron sputtering technique at different oxygen partial pressures in the range 1 10-4 - 9 10-4 mbar. The structural and morphological properties of the films were characterized by X-ray diffraction (XRD) and atomic force microscopy (AFM). All the deposited films were of polycrystalline nature and exhibited cubic structure with preferential growth. The morphological studies revealed that the surface roughness was increased with increasing oxygen partial pressure up to 5 10-4 mbar and decreased at higher oxygen partial pressures.

Reddy, Y. Ashok Kumar; Reddy, A. Sivasankar; Reddy, P. Sreedhara

2013-06-01

150

Thermodynamics of Formate-Oxidizing Metabolism and Implications for H2 Production  

PubMed Central

Formate-dependent proton reduction to H2 (HCOO? + H2O ? HCO3? + H2) has been reported for hyperthermophilic Thermococcus strains. In this study, a hyperthermophilic archaeon, Thermococcus onnurineus strain NA1, yielded H2 accumulation to a partial pressure of 1 105 to 7 105 Pa until the values of Gibbs free energy change (?G) reached near thermodynamic equilibrium (?1 to ?3 kJ mol?1). The bioenergetic requirement for the metabolism to conserve energy was demonstrated by ?G values as small as ?5 kJ mol?1, which are less than the biological minimum energy quantum, ?20 kJ mol?1, as calculated by Schink (B. Schink, Microbiol. Mol. Biol. Rev. 61:262-280, 1997). Considering formate as a possible H2 storage material, the H2 production potential of the strain was assessed. The volumetric H2 production rate increased linearly with increasing cell density, leading to 2,820 mmol liter?1 h?1 at an optical density at 600 nm (OD600) of 18.6, and resulted in the high specific H2 production rates of 404 6 mmol g?1 h?1. The H2 productivity indicates the great potential of T. onnurineus strain NA1 for practical application in comparison with H2-producing microbes. Our result demonstrates that T. onnurineus strain NA1 has a highly efficient metabolic system to thrive on formate in hydrothermal systems. PMID:22885755

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

2012-01-01

151

Mutational Analysis of the Stability of the H2A and H2B Histone Monomers  

PubMed Central

The eukaryotic histone heterodimer H2A-H2B folds through an obligatory dimeric intermediate that forms in a nearly diffusion-limited association reaction in the stopped-flow dead time. It is unclear whether there is partial folding of the isolated monomers before association. To address the possible contributions of structure in the monomers to the rapid association, we characterized H2A and H2B monomers in the absence of their heterodimeric partner. By far-UV circular dichroism, the H2A and H2B monomers are 15% and 31% helical, respectivelysignificantly less than observed in X-ray crystal structures. Acrylamide quenching of the intrinsic Tyr fluorescence was indicative of tertiary structure. The H2A and H2B monomers exhibit free energies of unfolding of 2.5 and 2.9 kcal mol?1, respectively; at 10 ?M, the sum of the stability of the monomers is ~60% of the stability of the native dimer. The helical content, stability and m values indicate that H2B has a more stable, compact structure than H2A. The monomer m values are larger than expected for the extended histone fold motif, suggesting that the monomers adopt an overly-collapsed structure. Stopped-flow refoldinginitiated from urea-denatured monomers or the partially folded monomers populated at low denaturant concentrationsyielded essentially identical rates, indicating that monomer folding is productive in the rapid association and folding of the heterodimer. A series of Ala and Gly mutations were introduced into H2A and H2B to probe the importance of helix propensity on the structure and stability of the monomers. The mutational studies show that the central ?-helix of the histone fold, which makes extensive inter-monomer contacts, is structured in H2B but only partially folded in H2A. PMID:18976667

Stump, Matthew R.; Gloss, Lisa M.

2008-01-01

152

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

Microsoft Academic Search

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

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

1999-01-01

153

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

Microsoft Academic Search

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

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

1993-01-01

154

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

PubMed

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

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

2013-05-01

155

LETTER TO THE EDITOR: Cd1-xZnx Te crystal growth controlled by Cd\\/Zn partial pressures  

Microsoft Academic Search

We have estimated the partial pressures, PCd and PZn, over Cd1-xZnx Te (CZT) and Cd1-xZnx melts based on known thermodynamic data. The partial pressures, PCd and PZn, over the Cd0.81Zn0.19 alloy melt at a temperature of about 1003 C could be in equilibrium with those over the Cd0.9Zn0.1 Te melt at a melting temperature of 1120 C. In this work,

Wanwan Li; Wenbin Sang; Jihua Min; Fang Yu; Bin Zhang; Kunsu Wang

2002-01-01

156

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

157

H2 blockers  

MedlinePLUS

H2 blockers are most often taken by mouth. You can get them in the form of tablets, liquids, or capsules. These medicines are most often taken with the first meal of the day. In some cases, you may also take them before your evening meal. ...

158

Thermodynamic properties of aqueous species and the solubilities of minerals at high pressures and temperatures: the system Al 2O 3?H 2O?KOH  

Microsoft Academic Search

Experimental solubilities of gibbsite and corundum in aqueous KOH solutions at elevated temperatures and pressures reported by Fricke and Jucaitis (1930), Wesolowski (1992), and Pascal and Anderson (1989) were used together with the Hckel (1925) and Setchnow (1892) equations for activity coefficients of aqueous species and the thermodynamic properties of the aluminate ion AlO2? to retrieve dissociation constants for the

Vitalii A. Pokrovskii; Harold C. Helgeson

1997-01-01

159

Master equation calculations to parameterize the pressure and temperature dependence of OH + C2H4 and OH + C2H2: consideration of pre-reaction complexes  

Microsoft Academic Search

Many reactions in the atmosphere include 3-body stabilization of hot adduct. The complex pressure and temperature dependence of these reactions depend on the potential energy surface for the reaction and the efficiency of energy transfer during collisions. These reactions must be parameterized for the full extent of tropospheric conditions for use in models. Ethene and acetylene are both used as

P. A. Cleary; M. A. Blitz; K. J. Hughes; M. J. Pilling; L. Wang

2005-01-01

160

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

161

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

162

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

163

Autothermal Cyclic Reforming Based H2 Generating & Dispensing System  

E-print Network

Separated H2 Fuel Regeneration Step 3 (2 min)Vent Air Regeneration Step 2 (3 min) Air Steam + Natural Gas capital cost & inherent CO2 separation #12;Praxair/ BP 5 High Pressure vs. Low Pressure Reforming High Pressure Reforming Comp- ressor 100 psig 100 psig Reformer H2 PSA SyngasNatural Gas Low Pressure Reforming

164

Sapwood development in Pinus radiata trees grown for three years at ambient and elevated carbon dioxide partial pressures.  

PubMed

Clonal trees of Pinus radiata D. Don were grown in open-top chambers at a field site in New Zealand for 3 years at ambient (37 Pa) or elevated (65 Pa) carbon dioxide (CO2) partial pressure. Nitrogen (N) was supplied to half of the trees in each CO2 treatment, at 15 g N m-2 in the first year and 60 g N m-2 in the subsequent 2 years (high-N treatment). Trees in the low-N treatment were not supplied with N but received the same amount of other nutrients as trees in the high-N treatment. In the first year, stem basal area increased more in trees growing at elevated CO2 partial pressure and high-N supply than in control trees, suggesting a positive interaction between these resources. However, the relative rate of growth became the same across trees in all treatments after 450 days, resulting in trees growing at elevated CO2 partial pressure and high-N supply having larger basal areas than trees in the other treatments. Sapwood N content per unit dry mass was consistently about 0.09% in all treatments, indicating that N status was not suppressed by elevated CO2 partial pressure. Thus, during the first year of growth, an elevated CO2 partial pressure enhanced carbon (C) and N storage in woody stems, but there was no further stimulus to C and N deposition after the first year. The chemical composition of sapwood was unaffected by elevated CO2 partial pressure, indicating that no additional C was sequestered through lignification. However, independent of the treatments, early wood was 13% richer in lignin than late wood. Elevated CO2 partial pressure decreased the proportion of sapwood occupied by the lumina of tracheids by up to 12%, indicating increased sapwood density in response to CO2 enrichment. This effect was probably a result of thicker tracheid walls rather than narrower lumina. PMID:12511300

Atwell, B J; Henery, M L; Whitehead, D

2003-01-01

165

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

166

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

SciTech Connect

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

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

1995-07-14

167

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

168

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

169

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

170

H2O Adsorption Kinetics on Smectites  

NASA Technical Reports Server (NTRS)

The adsorptive equilibration of H2O a with montomorillonite, a smectite clay has been measured. At low temperatures and pressures, equilibration can require many hours, effectively preventing smectites at the martian surface from responding rapidly to diurnal pressure and temperature variations.

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

2000-01-01

171

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

172

Structural and electrical properties of pure and Cu doped NiO films deposited at various oxygen partial pressures  

NASA Astrophysics Data System (ADS)

Pure and Cu doped NiO thin films were successfully deposited by dc reactive magnetron sputtering technique at various oxygen partial pressures in the range 9 10-5 to 6 10-4 mbar. It was observed that oxygen partial pressure influence the structural and electrical properties. All the deposited films were polycrystalline and exhibited cubic structure with preferential growth along (220) plane for NiO films and (111) and (220) planes for Cu doped NiO films. All the deposited films exhibited p-type conductivity. The electrical resistivity decreased from 62.24 to 9.94 ? cm and the mobility and carrier concentration were increased with oxygen partial pressure.

Reddy, Y. Ashok Kumar; Reddy, A. Mallikarjuna; Reddy, A. Sivasankar; Reddy, P. Sreedhara

2013-02-01

173

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

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

174

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

175

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

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

176

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

PubMed Central

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

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

2011-01-01

177

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

NASA Astrophysics Data System (ADS)

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

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

2008-07-01

178

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

179

Distinct differences in partial oxygen pressure at micrometer ranges in the rat hippocampal region.  

PubMed

A mapping at micrometer ranges of the partial oxygen pressure in the rat hippocampus was performed. The oxygen tension in the rat hippocampal region was measured using a glass oxygen microsensor in 30-microm steps along straight lines at a set of stereotactic coordinates. In the hippocampus the pattern of the oxygen tensions reflected the autometallographic zinc sulphide (AMG(ZnS)) pattern, i.e. the pattern of zinc enriched (ZEN) terminals. The highest levels of oxygen tension were recorded in the areas that are most heavily stained with the autometallographic zinc sulphide (AMG(ZnS)) method, like hilus fasciae dentatae. The zinc ions located in synaptic vesicles of the ZEN terminals can also be demonstrated by AMG silver amplification in brains from animals in vivo treated with sodium selenite. This method depends on the presence of a substantial reduction capacity of the tissues as selenite ions (SeO(2)(3)-) must to be reduced to selenide ions (Se2-) before the catalytic zinc selenide crystals can be formed. At some point, either during the transport from the infusion site to the actual target tissue or in the target tissue itself, selenium is reduced from Se(+ IV) to Se(- II). The importance of the reduction capacity of the target tissue in this process is demonstrated by the fact that areas found to have the highest concentration of zinc ions, e.g. hilus fasciae dentatae and the mossy fibres of CA3, are almost unstained after 1 h of i.p. Na2SeO3 exposure. An explanation of this phenomenon could be that the reduction process Se(+ IV) <==> Se(- II) leading to the formation of Se2- is moved to the left by the presence of oxygen, thus inhibiting the precipitation of ZnSe crystals. It is suggested that the subtle oxygen pressure pattern found in the rat hippocampus might also reflect essential biological zinc-related mechanisms vital to brain function. PMID:9128163

Andreasen, A; Danscher, G; Juhl, S; Stoltenberg, M; Revsbech, N P; Jensen, H; Jensen, K B

1997-03-01

180

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

SciTech Connect

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

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

2013-02-05

181

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

Microsoft Academic Search

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

Colin Neal; W. Alan House; Kevin Down

1998-01-01

182

Partial Melting in the Iron-Sulfur System at High1 Pressure: A Synchrotron X-ray Diffraction Study2  

E-print Network

1 Partial Melting in the Iron-Sulfur System at High1 Pressure: A Synchrotron X-ray Diffraction meteorites, sulfur is a primary40 constituent. Sulfur easily compounds with iron, producing a metallic melt is mostly iron-nickel alloy, with a small proportion of "light37 element" component, whose precise

Campbell, Andrew

183

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

184

Flow-independent dynamics in aneurysm (FIDA): pressure measurements following partial and complete flow impairment in experimental aneurysm model  

PubMed Central

Background: There have been growing concerns regarding delayed aneurysm rupture subsequent to the flow-diverting stent deployment. Therefore, more investigations are needed regarding hemodynamic changes secondary to flow-diverting stent deployment. Objective: To study intra-aneurysmal and perianeurysmal pressures after partial and complete flow impairment into the aneurysm. Methods A silicone model of an 8-mm-sized aneurysm (neck diameter: 5 mm, vessel size: 4 mm) was used. The aneurysm wall was encapsulated and sealed within a 5 ml syringe filled with saline and a pressure sensor guide wire (ComboWire, Volcano Corp.) to detect pressure changes in the perivascular compartment (outer aneurysm wall). A second pressure sensor guide wire was advanced inside the aneurysm sac. Both pressure sensors were continuously measuring pressure inside and outside the aneurysm under pulsatile flow under the following conditions: 1) baseline (reference); 2) a 16 mm by 3.75 mm flow-diverting stent (ev3/Covidien Vascular, Mansfield, MA) deployed in front of the aneurysm; 3) two flow-diverting stents (16 mm by 3.5 mm) were deployed; and 4) a covered stent (4 mm by 16 mm VeriFlex coronary artery stent covered with rubber sheet) was deployed. Results: Mean (SD) baseline pressures inside and outside the aneurysm were 53.9 (2.4) mmHg (range 12040 mmHg) and 15.4 (0.7) mmHg (range 408mmHg), respectively. There was no change in pressure inside and outside the aneurysm after deploying the first and second flow-diverting stents (partial flow impairment) and it remained at 53.9 (2.7) mmHg and 14.9 (1) mmHg for the pressure inside and outside the aneurysm, respectively. The pressure recording from outside the aneurysm dropped from 15.4 (0.7) mmHg to 0.3 (0.7) mmHg after deploying the covered stent (complete flow impairment). There was no change in pressure inside the aneurysm after deploying the covered stent. Mean (SD) pressure within the aneurysm was 55.1 (1.7) mmHg and it remained 54.7 (1.7) mmHg after covered stent deployment. Conclusion: Our findings suggest a major discordance between the pressures within the aneurysm and partial or complete flow impairment (flow independent). The outer wall pressure is reduced after covered stent placement. These finding may assist clinicians in better understanding of aneurysm hemodynamics and rupture after flow-diverting stent deployment. PMID:25298859

Watanabe, Masaki; Chaudhry, Saqib A; Qureshi, Adnan I

2014-01-01

185

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

186

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

NASA Astrophysics Data System (ADS)

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

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

1990-03-01

187

The H2O content of granite embryos  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

188

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

Microsoft Academic Search

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

Rei Fang; R. F. Brebrick

1996-01-01

189

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

190

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

191

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

192

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

Microsoft Academic Search

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,

E. Schumann; G. Schnotz; K. P. Trumble; M. Ruehle

1992-01-01

193

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

194

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

195

?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, Stephanie; Pommier, Yves

2011-01-01

196

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

197

Evaluation of a three-dimensional ultrasound localisation system incorporating probe pressure correction for use in partial breast irradiation.  

PubMed

This work evaluates a three-dimensional (3D) freehand ultrasound-based localisation system with new probe pressure correction for use in partial breast irradiation. Accuracy and precision of absolute position measurement was measured as a function of imaging depth (ID), object depth, scanning direction and time using a water phantom containing crossed wires. To quantify the improvement in accuracy due to pressure correction, 3D scans of a breast phantom containing ball bearings were obtained with and without pressure. Ball bearing displacements were then measured with and without pressure correction. Using a single scan direction (for all imaging depths), the mean error was <1.3 mm, with the exception of the wires at 68.5 mm imaged with an ID of 85 mm, which gave a mean error of -2.3 mm. Precision was greater than 1 mm for any single scan direction. For multiple scan directions, precision was within 1.7 mm. Probe pressure corrections of between 0 mm and 2.2 mm have been observed for pressure displacements of 1.1 mm to 4.2 mm. Overall, anteroposterior position measurement accuracy increased from 2.2 mm to 1.6 mm and to 1.4 mm for the two opposing scanning directions. Precision is comparable to that reported for other commercially available ultrasound localisation systems, provided that 3D image acquisition is performed in the same scan direction. The existing temporal calibration is imperfect and a "per installation" calibration would further improve the accuracy and precision. Probe pressure correction was shown to improve the accuracy and will be useful for the localisation of the excision cavity in partial breast radiotherapy. PMID:19433484

Harris, E J; Symonds-Taylor, R; Treece, G M; Gee, A H; Prager, R W; Brabants, P; Evans, P M

2009-10-01

198

"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

199

Optimization of Intermolecular Potential Parameters for the CO2/H2O Mixture.  

PubMed

Monte Carlo simulations in the Gibbs ensemble were used to obtain optimized intermolecular potential parameters to describe the phase behavior of the mixture CO2/H2O, over a range of temperatures and pressures relevant for carbon capture and sequestration processes. Commonly used fixed-point-charge force fields that include Lennard-Jones 12-6 (LJ) or exponential-6 (Exp-6) terms were used to describe CO2 and H2O intermolecular interactions. For force fields based on the LJ functional form, changes of the unlike interactions produced higher variations in the H2O-rich phase than in the CO2-rich phase. A major finding of the present study is that for these potentials, no combination of unlike interaction parameters is able to adequately represent properties of both phases. Changes to the partial charges of H2O were found to produce significant variations in both phases and are able to fit experimental data in both phases, at the cost of inaccuracies for the pure H2O properties. By contrast, for the Exp-6 case, optimization of a single parameter, the oxygen-oxygen unlike-pair interaction, was found sufficient to give accurate predictions of the solubilities in both phases while preserving accuracy in the pure component properties. These models are thus recommended for future molecular simulation studies of CO2/H2O mixtures. PMID:25198539

Orozco, Gustavo A; Economou, Ioannis G; Panagiotopoulos, Athanassios Z

2014-10-01

200

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

Microsoft Academic Search

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

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

2006-01-01

201

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

202

Transient pressure analysis for partially-penetrating wells in naturally-fractured reservoirs  

E-print Network

ON PRESSURE CALCULATION, Tp=1. 33 3. 3 EFFECT OF STEHFEST NUMBER ON PRESSURE CALCULATION, Tp=IO' . 33 3. 4 EFFECT OF THE NUMBER OF TERMS IN SERIES FOR Tp=l. . . 34 3. 5 EFFECT OF THE NUMBER OF TERMS IN SERIES FOR Tp=10 . . . . . . 34 3. 6 PRESSURE... in the Kucuk et al. solution 30 3. 4 Infinite series in the Turhan et al. solution. . 31 3. 5 Effect of the Stehfest number on the inversion result. . . 35 3. 6 L'ffect of the number of summation terms on the inversion result. . . 35 3. 7 Pressure...

Bui, Thang Dinh

2012-06-07

203

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

204

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

205

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

206

H2A Delivery Miscellaneous Costs and H2 Losses  

E-print Network

· Labor costs basis (from gas station data): ­ 135,000 gall/month ­ Approximately 1,500 kg/day H2 station BLS ­ Petroleum (approximately 3 days Plant Operators Gas H2 day, and 365 days per Plant Operators per/day ($15.05) Terminal day, and 365 days per Plant Operators Geologic 1 person, 24 hours/day,

207

RNase H2-Initiated Ribonucleotide Excision Repair  

PubMed Central

SUMMARY Ribonucleotides are incorporated into DNA by the replicative DNA polymerases at frequencies of about 2 per kb which makes them by far the most abundant form of potential DNA damage in the cell. Their removal is essential for restoring a stable intact chromosome. Here we present a complete biochemical reconstitution of the ribonucleotide excision repair (RER) pathway with enzymes purified from Saccharomyces cerevisiae. RER is most efficient when the ribonucleotide is incised by RNase H2, and further excised by the flap endonuclease FEN1 with strand displacement synthesis carried out by DNA polymerase ?, the PCNA clamp, its loader RFC, and completed by DNA ligase I. We observed partial redundancy for several of the enzymes in this pathway. Exo1 substitutes for FEN1 and Pol ? for Pol ? with reasonable efficiency. However, RNase H1 fails to substitute for RNase H2 in the incision step of RER. PMID:22864116

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

2012-01-01

208

Dehydration behavior of the superprotonic conductor CsH2PO4 at moderate temperatures: 230 to 260 uC{  

E-print Network

in ionic conductivity on heating and confirmed by weight change measurements under isothermal conditions conductivity. This dehydration can be suppressed by maintaining sufficient water partial pressure in the fuel have reported that CsH2PO4 dehydrates under dry or vacuum conditions10,11 to ultimately yield caesium

209

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

210

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

211

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).

2010-12-01

212

Measured Gas Concentrations and Flow Properties in SiH4-H2 Mixtures  

NASA Astrophysics Data System (ADS)

Each gas concentration in silane-hydrogen (SiH4-H2) gas mixtures was measured using a diaphragm gauge and a quartz friction pressure gauge (D- and Q-gauges). At constant pressures of 0.13-1.3 kPa, the Q-gauge pressure readings depended on the densities of SiH4 and H2. Therefore, the dependence of the Q-gauge pressure readings on the partial pressures of SiH4 could be used to measure the concentrations of these gases in the gas mixtures. The relative SiH4 density in the flow of gas mixtures was higher than the SiH4 flow rate ratio, indicating that the flow of the mixtures was intermediate between molecular and viscous. The viscosities of the gas mixtures estimated from the pressure-normalized Q-gauge pressures were compared with the calculations by Wilke's equation, with the finding that the viscosity of the gas mixture can be derived using the present measurement.

Suzuki, Atsushi; Nonaka, Hidehiko

2008-05-01

213

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

214

Effect of hydrogen sulfide partial pressure, pH, and chloride content on the SSC resistance of martensitic stainless steels and martensitic precipitation hardening stainless steels  

SciTech Connect

Centrifugal compressor applications require the use of martensitic stainless and martensitic precipitation hardening stainless steels at high hydrogen sulfide partial pressures. These materials do not perform well when tested with standard TM0177 test solutions. This paper describes the effect of hydrogen sulfide partial pressure, pH, and chloride content on their SSC resistance and explains their successful field operational experience. Environmental limits are determined for several materials and heat treat conditions.

Vitale, D.D. [Dresser-Rand Turbo Products, Olean, NY (United States)

1999-11-01

215

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

PubMed

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

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

2013-10-01

216

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

217

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

PubMed

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

Jonas, Ren; Schaal, Thomas; Krimmel, Michael; Glicher, Dirk; Reinert, Siegmar; Hoffmann, Jrgen

2013-06-01

218

H2A Delivery H2A Hydrogen Delivery  

E-print Network

-Truck ­ Tube Trailer -Truck - LH2 -Pipeline -Liquefier -Compressor (one-stage and multi Input User Input Required Calculated Cells #12;H2A Delivery Component Model Hierarchy Component Design Inputs Component Design/Scenario Calculations Financial Analysis Direct/Indirect Capital Costs Component

219

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

220

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

PubMed Central

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

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

2012-01-01

221

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

222

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

SciTech Connect

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

Revesz, Adam; Hobor, Sandor; Labar, Janos L.; Zhilyaev, Alex P.; Kovacs, Zsolt [Department of Materials Physics, P.O. Box 32, Eoetvoes University, Budapest H-1518 (Hungary); Department of Materials Physics, P.O. Box 32, Eoetvoes University, Budapest H-1518, Hungary and Research Institute for Techical Physics and Materials Science, Hungarian Academy of Sciences, P.O. Box 49, H-1525 Budapest (Hungary); Institute for Metals Superplasticity Problems, RAS, 39 Khalturin Street, Ufa 450001 (Russian Federation); Department of Materials Physics, P.O. Box 32, Eoetvoes University, Budapest H-1518 (Hungary)

2006-11-15

223

The Probability of Collision for Slow H+, (H1H1)+, (H1H2)+, (H2H2)+, (H2)+ and He+ Ions in Argon  

Microsoft Academic Search

The probability of collision Pc for slow H+, (H1H1)+, (H1H2)+, (H2H2)+, (H2)+ and He+ ions in argon has been measured. The energy range studied was 225 to 4200 volts for the H+ and (H1H1)+ ions, 225 to 1300 volts for the (H1H2)+, (H2H2)+ and He+ ions and 300 to 1225 volts for the deuteron hydrogen molecular ion (H1H1)+ beam. The

Edward B. Jordan

1935-01-01

224

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

225

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

226

Reduction of RuO2 Film to Metallic Ru Film Using Atomic Layer Deposition under Different Oxygen Partial Pressure  

NASA Astrophysics Data System (ADS)

Thin ruthenium oxide film deposition on 100 nm SiO2 substrate by thermal atomic layer deposition (ALD) prior to ruthenium deposition. RuO2 was totally reduced to metallic Ru film when Ru deposition process with low oxygen partial pressure. Using this technique, we can improve overall deposition speed by reducing incubation time which is major problem of deposition Ru film. In addition, we compare properties of Ru film deposited by thermal ALD directly deposited on SiO2 substrate and Ru film obtained from reduction of RuO2 film. The Ru film from RuO2 has smoother surface RMS roughness than Ru film directly deposited on SiO2 substrate.

Park, Taeyong; Lee, Jaesang; Park, Jingyu; Jeon, Heeyoung; Jeon, Hyeongtag

2013-05-01

227

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

228

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

NASA Astrophysics Data System (ADS)

We present a synchrotron x-ray study of the equilibrium polarization structure of ultrathin PbTiO3 films on SrRuO3 electrodes epitaxially grown on SrTiO3 (001) substrates, as a function of temperature and the external oxygen partial pressure (pO2) controlling their surface charge compensation. We find that the ferroelectric Curie temperature (TC) varies with pO2 and has a minimum at the intermediate pO2, where the polarization below TC changes sign. The experiments are in qualitative agreement with a model based on Landau theory that takes into account the interaction of the phase transition with the electrochemical equilibria for charged surface species. The paraelectric phase is stabilized at intermediate pO2 when the concentrations of surface species are insufficient to compensate either polar orientation.

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

2011-10-01

229

Modeling of axial vibrational control technique for CdTe VGF crystal growth under controlled cadmium partial pressure  

NASA Astrophysics Data System (ADS)

A VGF growth setup assisted by axial vibrations of baffle submerged into CdTe melt with controlled Cd partial pressure was designed. An influence of baffle shape on flow velocity map, temperature distribution in CdTe melt and interface shape of growing crystal was analyzed by numerical simulation and physical modeling. To produce the desirable shape of crystal melt interface we slant under different angles vertical generatrix in a cylindrical disk and made chasing on faceplates of a disk. It was ascertained that a disk with conical generatrix formed more intensive convective flows from a faceplate with larger diameter. It was shown that at CdTe VGF crystal growth rate about 10 mm/h application of AVC technique made it possible to produce convex interface for 2 in. crystal diameter.

Avetissov, I.; Kostikov, V.; Meshkov, V.; Sukhanova, E.; Grishechkin, M.; Belov, S.; Sadovskiy, A.

2014-01-01

230

Canopy position and needle age affect photosynthetic response in field-grown Pinus radiata after five years of exposure to elevated carbon dioxide partial pressure.  

PubMed

Photosynthesis of tree seedlings is generally enhanced during short-term exposure to elevated atmospheric CO2 partial pressure, but longer-term studies often indicate some degree of photosynthetic adjustment. We present physiological and biochemical evidence to explain observed long-term photosynthetic responses to elevated CO2 partial pressure as influenced by needle age and canopy position. We grew Pinus radiata D. Don. trees in open-top chambers for 5 years in sandy soil at ambient (36 Pa) and elevated (65 Pa) CO2 partial pressures. The trees were well watered and exposed to natural light and ambient temperature. In the fourth year of CO2 exposure (fall 1997), when foliage growth had ceased for the year, photosynthetic down-regulation was observed in 1-year-old needles, but not in current-year needles, suggesting a reduction in carbohydrate sink strength as a result of increasing needle age (Turnbull et al. 1998). In 5-year-old trees (spring 1997), when foliage expansion was occurring, photosynthetic down-regulation was not observed, reflecting significantly large sinks for carbohydrates throughout the tree. Net photosynthesis was stimulated by 79% in trees growing in elevated CO2 partial pressure, but there was no significant effect on photosynthetic capacity or Rubisco activity and concentration. Current-year needles were more responsive to elevated CO2 partial pressure than 1-year-old needles, exhibiting larger relative increases in net photosynthesis to elevated CO2 partial pressure (98 versus 64%). Lower canopy and upper canopy leaves exhibited similar relative responses to growth in elevated CO2 partial pressure. However, needles in the upper canopy exhibited higher net photosynthesis, photosynthetic capacity, and Rubisco activity and concentration than needles in the lower canopy. Given that the ratio of mature to juvenile foliage mass in the canopy will increase as trees mature, we suggest that trees may become less responsive to elevated CO2 partial pressure with increasing age. We conclude that tree response to elevated CO2 partial pressure is based primarily on sink strength and not on the duration of exposure. PMID:11498338

Tissue, D T; Griffin, K L; Turnbull, M H; Whitehead, D

2001-08-01

231

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

232

1 setting H 2 setting  

E-print Network

Outb: outside bright Outd: outside dark N: night 2 Inb ind outb outd n Canon + Sony + Iphone 1 h 2 0-50300-360 3 51-299 Iphone: 0 50 100 150 200 250 300 350 0 50 100 150 200 250 300 350 inb Nokia: 0 50 100 150 200 250 300 350 0 50 100 150 200 250 300 350 inb canonh nokiah inb inb nokia=iphone

Wu, Dapeng Oliver

233

Control of the threshold voltage by using the oxygen partial pressure in sputter-deposited InGaZnO4 thin-film transistors  

NASA Astrophysics Data System (ADS)

We investigate the controllability of the threshold voltage ( V th ) by varying the O2 partial pressure in sputter-deposited of InGaZnO4 thin-film transistors (IGZO TFTs). We showed that the V th values could be linearly controlled from a depletion-type of V th -6 V to an enhancement-type of V th 2 V, without any abrupt change in sat , I on/off , and S, by only changing the O2 partial pressure in a fixed region of the Ar partial pressure. Such V th controllability is thought to be due to the proper reduction of defect states and, in turn, to the preservation of high-performance TFT behavior.

Ahn, Jeung Sun; Lee, Kwang Bae

2012-05-01

234

Excess Chemical Potentials, Excess Partial Molar Enthalpies, Entropies, Volumes, and Isobaric Thermal Expansivities of Aqueous Glycerol at 25C  

Microsoft Academic Search

The vapor pressures p the excess partial molar enthalpies of glycerol HGlyE the densities d and the thermal expansivities ap of aqueous glycerol were measured at 25C. From the vapor pressure data, the excess chemical potential of H2O WE was calculated, assuming that the partial pressure of glycerol pGly is negligibly small. The excess chemical potential of glycerol GlyE

Eric C. H. To; James V. Davies; Michael Tucker; Peter Westh; Christa Trandum; Kennth S. H. Suh; Yoshikata Koga

1999-01-01

235

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

236

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

237

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

238

Simutaneous 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 CO2, implying that the adsorbate inventories previously derived may be accurate, not more than 3-4 kPa (30-40 mbar). No substantial increase in atmospheric pressure is predicted at higher obliquities because high-latitude ground ice buffers the partial pressure of H2O in the pores, preventing high monolayer coverages of H2O from displacing CO2. The peak atmospheric pressure at high obliquity does increase as the total inventory of exchangeable CO2 increases.

Zent, Aaron P.; Quinn, Richard C.

1995-01-01

239

High temperature a.c. electrical properties of olivine single crystal with varying oxygen partial pressure: implications for the point defect chemistry  

Microsoft Academic Search

The electrical conductivity and dielectric constant of a natural olivine single crystal were measured as a function of frequency over 0.1-1000 Hz. The measurements were made at temperatures of 1000-1400C under a controlled oxygen partial pressure that was varied within the range of the olivine stability field. The observed dielectric constant of olivine increased with increasing oxygen pressure, and the

Hiroki Sato

1986-01-01

240

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

241

Reversible hydrogen storage property and structural analysis for face-centered cubic hydride Mg0.82Zr0.18H2 prepared by gigapascal hydrogen pressure method.  

PubMed

The face-centered cubic (fcc) type magnesium-zirconium hydride (Mg0.82Zr0.18Hx) was synthesized by means of the ultrahigh pressure (UHP) technique, which could generate 8 GPa of hydrogen pressure. The differential scanning calorimeter (DSC) measurements indicated that the fcc phase exhibited reversible hydrogen releasing and restoring properties under 0.5 MPa of hydrogen pressure. On the pressure-composition isotherms, the released and restored hydrogen capacities were estimated to be 3 approximately 3.5 wt %. The Rietveld analysis for synchrotron X-ray diffraction (XRD) data showed that the fcc phase had around 70 wt % mass fraction and was preserved without decomposition during hydrogen releasing and restoring cycles. PMID:18052358

Takasaki, Tomoaki; Kyoi, Daisuke; Kitamura, Naoyuki; Tanase, Shigeo; Sakai, Tetsuo

2007-12-27

242

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

Microsoft Academic Search

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

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

1995-01-01

243

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

SciTech Connect

Mature, field-grown Vitis vinifera L. grapevines grown in open-top chambers were exposed to either charcoal-filtered air or ambient ozone partial pressures throughout the growing season. Individual leaves also were exposed to ozone partial pressures of 0.2, 0.4, or 0.6 micropascals per pascal for 5 hours. No visual ozone damage was found on leaves exposed to any of the treatments. Chronic exposure to ambient O{sub 3} partial pressures reduced net CO{sub 2} assimilation rate (A) between 5 and 13% at various times throughout the season when compared to the filtered treatment. Exposure of leaves to 0.2 micropascals per pascal O{sub 3} for 5 hours had no significant effect on A; however, A was reduced 84% for leaves exposed to 0.6 micropascals per pascal O{sub 3} when compared to the controls after 5 hours. Intercellular CO{sub 2} partial pressure (c{sub i}) was lower for leaves exposed to 0.2 micropascals per pascal O{sub 3} when compared to the controls, while c{sub i} of the leaves treated with 0.6 micropascals per pascal of O{sub 3} increased during the fumigation. The long-term effects of ambient O{sub 3} and short-term exposure to acute levels of O{sub 3} reduced grape leaf photosynthesis due to a reduction in both stomatal and mesophyll conductances.

Roper, T.R.; Williams, L.E. (Univ. of California, Davis (USA) Kearney Agricultural Center, Parlier, CA (USA))

1989-12-01

244

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

Microsoft Academic Search

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

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

2004-01-01

245

Effect of oxygen partial pressure on the Fermi level of ZnO1-x films fabricated by pulsed laser deposition  

E-print Network

investigated the influence of oxygen deficiency on the Fermi level EF of ZnO thin film prepared by pulsed laser that the very large change in the resistivity of ZnO thin films resulting from the oxygen deficiency couldEffect of oxygen partial pressure on the Fermi level of ZnO1-x films fabricated by pulsed laser

Oh, Se-Jung

246

A Theoretical Analysis of the Formation of Nonstoichiometric Point Defects in SiC Single Crystals Grown under Equilibrium Conditions at Different Partial Pressures of Silicon Vapor  

Microsoft Academic Search

Formation of Schottky and Frenkel vacancy-type point defects in silicon carbide single crystals is analyzed. Relevant equations for numerical analysis are derived and a method for their solution is proposed. The partial pressure of silicon vapor over the growing crystal is shown to play a role in the formation of defects in SiC single crystals.

A. P. Garshin; E. N. Mokhov; V. E. Shvaiko-Shvaikovskii

2003-01-01

247

Chaperone Nap1 shields histone surfaces used in a nucleosome and can put H2A-H2B in an unconventional tetrameric form  

PubMed Central

Summary The histone H2A-H2B heterodimer is an integral component of the nucleosome. The cellular localization and deposition of H2A-H2B into chromatin is regulated by numerous factors including histone chaperones such as Nucleosome Assembly Protein 1 (Nap1). We use hydrogen-deuterium exchange coupled to mass spectrometry to characterize H2A-H2B and Nap1. Unexpectedly, we find that at low ionic strength the ?-helices in H2A-H2B are frequently sampling partially disordered conformations, and that binding to Nap1 reduces this conformational sampling. We identify the interaction surface between H2A-H2B and Nap1, and confirm its relevance both in vitro and in vivo. We show that two copies of H2A-H2B bound to a Nap1 homodimer form a tetramer with contacts between H2B chains similar to those in the four-helix bundle structural motif. The organization of the complex reveals that Nap1 competes with histone-DNA and inter-histone interactions observed in the nucleosome, thereby regulating the availability of histones for chromatin assembly. PMID:23973327

DArcy, Sheena; Martin, Kyle W.; Panchenko, Tanya; Chen, Xu; Bergeron, Serge; Stargell, Laurie A.; Black, Ben E.; Luger, Karolin

2013-01-01

248

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

249

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

PubMed

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

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

2014-01-01

250

Hydrothermal phase equilibria in Ln 2O 3-H 2O-CO 2 systems . I. The lighter lanthanides  

NASA Astrophysics Data System (ADS)

Phase diagrams for Nd 2O 3-H 2O-CO 2 and Gd 2O 3-H 2O-CO 2 systems at 1500 atm are given along with the results of selected runs in La, Sm and Eu systems. The stable phases in systems of La and Nd, are Ln(OH)CO 3-B, Ln 2O 2CO 3-II and LnOOH, in addition to the Ln(OH) 3 phase at extremely low partial pressures of CO 2 in the system. The systems become more and more complex with decreasing ionic radi and the number of stable carbonate phases increases. Ln 2(CO 3) 3 3H 2O orthorhombic (tengerate-like phase) is stable from Sm to Gd in addition to the other phases. The Gd(OH)CO 3-A (ancylite-like phase) is hydrothermally stable at XCO 2 ? 0.5 while its hexagonal polymorph, Gd(OH)CO 3-B is stable at low partial pressures of CO 2 in the system.

Tareen, J. A. K.; Kutty, T. R. N.

1980-10-01

251

15N2 Fixation by Bacteria Associated with Maize Roots at a Low Partial O2 Pressure  

PubMed Central

Nitrogen fixation by bacteria associated with roots of intact maize plants was measured by exposing the roots to 15N2 at a partial O2 pressure (pO2) of 2 or 10 kPa. The plants were grown in a mixture of Weswood soil and sand and then transferred to plastic cylinders containing an N-free plant nutrient solution. The solution was sparged continuously with a mixture of air and N2 at a pO2 of 2 or 10 kPa. Acetylene reduction was measured after the roots were exposed to the low pO2 overnight. The air-N2 atmosphere in the cylinders was then replaced with an O2-He atmosphere at the same pO2, and the roots were exposed to 20 kPa of 15N2 for 20 to 22 h. Incorporation of 15N into the roots was 200 times greater at 2 kPa of O2 than at 10 kPa of O2. Adding l-malate (1 g of C liter?1) to the nutrient solution increased root-associated nitrogenase activity, producing a strong 15N label which could be traced into the shoots. Fixed 15N was detected in the shoots within 5 days after the plants were returned to unfertilized soil. In a similar experiment with undisturbed plants grown in fritted clay, movement of fixed 15N into the shoots was evident within 4 days after the roots were exposed to 15N2 at 2 kPa of O2. Inoculation with Azospirillum lipoferum yielded no significant differences in shoot dry weight, total nitrogen content, percent nitrogen, or 15N enrichment of plant tissues. Inoculated plants did exhibit greater root dry weight than uninoculated plants, however. PMID:16347968

Alexander, David B.; Zuberer, David A.

1989-01-01

252

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

PubMed

Carbonic anhydrase (CA) enzymes catalyze the chemical equilibration among CO2, HCO3 (-) and H(+). Intracellular CA (CAi) isoforms are present in certain types of cancer, and growing evidence suggests that low levels correlate with disease severity. However, their physiological role remains unclear. Cancer cell CAi activity, measured as cytoplasmic CO2 hydration rate (kf), ranged from high in colorectal HCT116 (?2 s(-1)), bladder RT112 and colorectal HT29, moderate in fibrosarcoma HT1080 to negligible (i.e. spontaneous kf = 0.18 s(-1)) in cervical HeLa and breast MDA-MB-468 cells. CAi activity in cells correlated with CAII immunoreactivity and enzymatic activity in membrane-free lysates, suggesting that soluble CAII is an important intracellular isoform. CAi catalysis was not obligatory for supporting acid extrusion by H(+) efflux or HCO3 (-) influx, nor for maintaining intracellular pH (pHi) uniformity. However, in the absence of CAi activity, acid loading from a highly alkaline pHi was rate-limited by HCO3 (-) supply from spontaneous CO2 hydration. In solid tumors, time-dependence of blood flow can result in fluctuations of CO2 partial pressure (pCO2) that disturb cytoplasmic CO2-HCO3 (-)-H(+) equilibrium. In cancer cells with high CAi activity, extracellular pCO2 fluctuations evoked faster and larger pHi oscillations. Functionally, these resulted in larger pH-dependent intracellular [Ca(2+)] oscillations and stronger inhibition of the mTORC1 pathway reported by S6 kinase phosphorylation. In contrast, the pHi of cells with low CAi activity was less responsive to pCO2 fluctuations. Such low pass filtering would "buffer" cancer cell pHi from non-steady-state extracellular pCO2. Thus, CAi activity determines the coupling between pCO2 (a function of tumor perfusion) and pHi (a potent modulator of cancer cell physiology). PMID:25059669

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

2014-09-12

253

The inhibiting action of intrinsic impurities in natural calcium carbonate minerals to their dissolution kinetics in aqueous H 2OCO 2 solutions  

Microsoft Academic Search

We have measured the surface controlled dissolution rates of natural calcium carbonate minerals (limestone and marble) in H2OCO2 solutions by using free drift batch experiments under closed system conditions with respect to CO2, at 10C with an initial partial pressure of carbon dioxide of 5 10?2 atm. All experiments revealed reaction rates F, which can be described by the

Laurent Eisenlohr; Krassimira Meteva; Franci Gabrovek; Wolfgang Dreybrodt

1999-01-01

254

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

255

Phase relations of peridotites under H 2O-saturated conditions and ability of subducting plates for transportation of H 2O  

Microsoft Academic Search

Phase relations of peridotites under H2O-saturated conditions up to 28 GPa and 2600 C have been clarified based on the high-pressure experimental results in the MgO(FeO)SiO2H2O, MgOSiO2Al2O3H2O, CaOMgOAl2O3SiO2H2O and natural systems. Based on the phase assemblages deduced and the chemical compositions of the phases, the maximum H2O contents for two bulk rock compositions (lherzolite and harzburgite) have been calculated using

Hikaru Iwamori

2004-01-01

256

Permeance of H2 through porous graphene from molecular dynamics  

NASA Astrophysics Data System (ADS)

A recent experiment (Koenig et al., 2012 [15]) demonstrated the capability of porous graphene as one-atom-thin membrane to separate gases by molecular sieving. A quantitative connection between the measured leak rate and the simulated gas permeance has yet to be established. Using H2 as a model gas, here we determine its permeance through porous graphene from molecular dynamics (MD) simulations. Trajectories are used to directly obtain H2 flux, pressure drop across the graphene membrane, and subsequently, H2 permeance. The permeance is determined to be on the order of 105 GPU (gas permeance unit) for pressure driving forces ranging from 2 to 163 atm. By relating to the experimental leak rate, we then use the permeation data to estimate the pore density in the experimentally created porous graphene.

Liu, Hongjun; Dai, Sheng; Jiang, De-en

2013-12-01

257

20 CFR 655.132 - H-2A labor contractor (H-2ALC) filing requirements.  

...Benefits 3 2014-04-01 2014-04-01 false H-2A labor contractor (H-2ALC) filing requirements. 655.132 Section...Temporary Agricultural Employment in the United States (H-2A Workers) Application for Temporary...

2014-04-01

258

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

NASA Astrophysics Data System (ADS)

Hydroelectric reservoirs have been under sampled to establish them as sources or sinks of the atmospheric carbon dioxide (CO2). Such poor coverage is well known for subtropic, particularly monsoon driven reservoirs in China. Our study presented the spatiotemporal changes of the carbonate system and CO2 flux in a hydroelectric reservoir (Dangjiankou Reservoir) locating in a subtropical monsoon climate region. Our 21 filed surveys conducted during 2004-2011 revealed significantly spatial and monthly variations of surface water partial pressure of CO2 (pCO2) in the Reservoir. pCO2, showing higher concentrations in the wet and warm seasons, averaged 595 545 atm (ranging from 53-3751 atm) in the reservoir surface, while substantially higher pCO2 (1132 1220 atm) was observed in the river downstream the dam. A clear pCO2 drawdown in the reservoir as water flows demonstrated a significantly descending order of Dan Reservoir > site close to dam > Han Reservoir. This spatial contrast can also be seen in the distributions of dissolved inorganic carbon and total alkalinity. Pronounced seasonality in pCO2 was controlled by seasonal monsoon rainfall, while photosynthetic CO2 uptake dominated spatial patterns and dry-month variability of pCO2. We further related pCO2 to water chemical properties and indicated that pCO2 had strong positive correlations with Si, TP and DOC, negative correlations with DO saturation, TN and Chl a, while weak correlations with other variables including biogenic elements. CO2 flux from the Reservoir surface showed a bottom average of 9 mmol m-2 d-2 in comparison with other hydroelectric reservoir in China. River downstream the dam had quite high flux of CO2 (119 mmol m-2 d-2), which was intermediate between temperate rivers and compared to global rivers' average. This means that water releasing from reservoir would be an important channel for atmospheric CO2 sources. The annual CO2 emission from the Danjiangkou Reservoir was estimated to be 3.4 109 mol C. Remarkably spatial and temporal heterogeneities in CO2 flux from China's hydroelectric reservoirs are urgently included for advancing global models of reservoirs' carbon emissions.

Li, S. Y.; Zhang, Q. F.

2013-06-01

259

Equilibrium water partial pressures and salt solubilities in aqueous NH{sub 4}HSO{sub 4} to low temperatures  

SciTech Connect

Acidic ammonium sulfate aerosols in the troposphere form cloud condensation nuclei, affect visibility, and are also an important component of urban aerosols. Equilibrium water partial pressures (pH{sub 2}O) above 3.69{sub 5}, 5.67{sub 2}, and 8.65{sub 1} mol kg{sup {minus}1} NH{sub 4}HSO{sub 4(aq)}, and 10.19 mol kg{sup {minus}1} H{sub 2}SO{sub 4(aq)}, have been determined using a capacitance manometer over the temperature ranges 288.1{sub 1}--239.5{sub 6} K and 298.1{sub 2}--238.5{sub 2} K, respectively. Measured pH{sub 2}O above the aqueous H{sub 2}SO{sub 4} solution agree with values calculated using the model of Clegg et al. to within +5.3% to {minus}2.8% at all temperatures. Results for the NH{sub 4}HSO{sub 4(aq)} solutions are also consistent with calculated pH{sub 2}O, with deviations of +0.45% to +6.27% (measured -- calculated) for all data. The formation of solids was observed in the NH{sub 4}HSO{sub 4(aq)} solutions at the following temperatures: 258.0{sub 6} {+-} 0.1 K [3.69{sub 5} mol kg{sup {minus}1}], 246.4{sub 7} {+-} 0.1 K [5.67{sub 2} mol kg{sup {minus}1}], and 261.0{sub 1} {+-} 0.1 K [8.65{sub 1} mol kg{sup {minus}1}]. The data are consistent with predictions of ice precipitation in the 3.69{sub 5} mol kg{sup {minus}1} test solution, letovicite ((NH{sub 4}){sub 3}H(SO{sub 4}){sub 2(cr)}) in the 8.65{sub 1} mol kg{sup {minus}1} solution, and both ice and letovicite in the 5.67{sub 2} mol kg{sup {minus}1} solution. The liquid-phase compositions of the solutions containing precipitates are calculated for different temperatures. The results of the experiments are compared with solubility data from other studies and with model predictions of solid/liquid equilibrium for NH{sub 4}HSO{sub 4}-H{sub 2}SO{sub 4}-H{sub 2}O mixtures to low temperature over a wide range of composition.

Yao, Y. [Chinese Academy of Sciences, Xi`an (China). Inst. of Salt Lakes] [Chinese Academy of Sciences, Xi`an (China). Inst. of Salt Lakes; Massucci, M.; Clegg, S.L.; Brimblecombe, P. [Univ. of East Anglia, Norwich (United Kingdom). School of Environmental Sciences] [Univ. of East Anglia, Norwich (United Kingdom). School of Environmental Sciences

1999-05-13

260

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

NASA Astrophysics Data System (ADS)

To evaluate the effects of low atmospheric pressure on leaf photosynthesis, we compared the photosynthesis of identical leaves of Fagus crenata at lowland (0 m a.s.l.) and at highland (2360 m a.s.l.). At the high altitude, the atmospheric pressure and partial pressure of CO 2 at intercellular air spaces in the leaf ( Ci360) decreased to 77% and 78% of those at the low altitude, respectively. On the other hand, the efficiency of photosynthetic CO 2-utilization was apparently higher at the high altitude because of a mitigation of the O 2-inhibition of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) under low ambient partial pressure of O 2. This stimulation of photosynthesis partly compensated a photosynthetic depression due to the low Ci360, and the net assimilation rate ( An360) at the high altitude retained 94% of the value at the low altitude. A theoretical model indicated that the stimulation of photosynthesis at high altitudes depend on internal conductance ( gi) and/or on Rubisco content. The model demonstrated that low atmospheric pressure at high altitudes caused severe restrictions of photosynthesis when leaves had a small gi and/or a large amount of Rubisco, whichever are repeatedly reported in alpine plants.

Sakata, Tsuyoshi; Kachi, Naoki; Yokoi, Yota

261

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 and is projected to increase from 36 to 70 Pa CO2 before the end of the 21st century. High pCO2 often increases the growth and repro- duction of C3 annuals, whereas low pCO2 decreases growth and may reduce or prevent

Antonovics, Janis

262

Effects of climate and atmospheric CO 2 partial pressure on the global distribution of C 4 grasses: present, past, and future  

Microsoft Academic Search

C4 photosynthetic physiologies exhibit fundamentally different responses to temperature and atmospheric CO2 partial pressures (pCO2) compared to the evolutionarily more primitive C3 type. All else being equal, C4 plants tend to be favored over C3 plants in warm humid climates and, conversely, C3 plants tend to be favored over C4 plants in cool climates. Empirical observations supported by a photosynthesis

G. James Collatz; Joseph A. Berry; James S. Clark

1998-01-01

263

Stimulation of ethylene production and gas-space (aerenchyma) formation in adventitious roots of Zea mays L. by small partial pressures of oxygen  

Microsoft Academic Search

Adventitious roots of two to four-weekold intact plants of Zea mays L. (cv. LG11) were shorter but less dense after extending into stagnant, non-aerated nutrient solution than into solution continuously aerated with air. Dissolved oxygen in the non-aerated solutions decreased from 21 kPa to 39 kPa within 24 h. When oxygen partial pressures similar to those found in non-aerated solutions

M. B. Jackson; T. M. Fenning; M. C. Drew; L. R. Saker

1985-01-01

264

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

265

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

PubMed

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

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

2014-01-01

266

Composition-Temperature-Partial Pressures Data for Cd(sub 0.8)Zn(sub 0.2)Te by Optical Absorption Measurements  

NASA Technical Reports Server (NTRS)

Known weights of Cd, Zn and Te were reacted in silica optical cells of known volume and the partial pressure of Te2 and Zn between 485 and 1160 C were determined by measuring the optical density of the vapor in the ultra-violet to visible range. The composition of the condensed phase or phases was calculated from the original weights and the amount of material in the vapor phase. The corresponding composition - temperature - partial pressures, x(sub Te)-T-P(sub Te2), data, including five Te-rich solidus points, were established. The solubility range for the Te-rich Cd(sub 0.8)Zn(sub 0.2)Te(s) is similar to that of CdTe(s) with x(sub Te) = 0.50005 at 809 C and an estimated maximum solubility of x(sub Te) = 0.50012 at about 1000 C. The partial pressure of Cd and Te(sub 2) measured over the Cd(sub 0.8)Zn(sub 0.2)Te melt at 1140 C were about 1.55 and 0.02 atm, respectively, and the corresponding P(Sub Zn) was estimated to be 0.05 atm. It was recommended that a Cd reservoir maintaining at 800 to 820 C should be used during directional solidification of Cd(sub o.8)Zn(sub 0.2)Te to prevent the preferential loss of Cd to the vapor phase.

Su, Ching-Hua

2005-01-01

267

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

268

Revealing sub-{\\mu}m inhomogeneities and {\\mu}m-scale texture in H2O ice at Megabar pressures via sound velocity measurements by time-domain Brillouin scattering  

E-print Network

Time-domain Brillouin scattering technique, also known as picosecond ultrasonic interferometry, which provides opportunity to monitor propagation of nanometers to sub-micrometers length coherent acoustic pulses in the samples of sub-micrometers to tens of micrometers dimensions, was applied to depth-profiling of polycrystalline aggregate of ice compressed in a diamond anvil cell to Megabar pressures. The technique allowed examination of characteristic dimensions of elastic inhomogeneities and texturing of polycrystalline ice in the direction normal to the diamond anvil surfaces with sub-micrometer spatial resolution via time-resolved measurements of variations in the propagation velocity of the acoustic pulse traveling in the compressed sample. The achieved two-dimensional imaging of the polycrystalline ice aggregate in-depth and in one of the lateral directions indicates the feasibility of three-dimensional imaging and quantitative characterization of acoustical, optical and acousto-optical properties of tra...

Nikitin, Sergey M; Tournat, Vincent; Bulou, Alain; Gasteau, Damien; Castagnede, Bernard; Zerr, Andreas; Gusev, Vitalyi E

2014-01-01

269

Thermodynamic and Raman spectroscopic studies on H 2 + tetrahydrofuran + water and H 2 + tetra- n-butyl ammonium bromide + water mixtures containing gas hydrates  

Microsoft Academic Search

Phase equilibrium curves of H2+ tetrahydrofuran and H2+ tetra-n-butyl ammonium bromide mixed gas hydrates were measured in a pressure range from 0.1 to 13.6MPa. Each three-phase equilibrium curve converges at the maximum temperature point of pure tetrahydrofuran and tetra-n-butyl ammonium bromide hydrates, respectively. The difference of maximum temperatures is about 8K, that is, the equilibrium curve of H2+ tetra-n-butyl ammonium

Shunsuke Hashimoto; Shu Murayama; Takeshi Sugahara; Hiroshi Sato; Kazunari Ohgaki

2006-01-01

270

Collisional excitation of vinylidene (H2CC)  

NASA Astrophysics Data System (ADS)

Though H2CO, H2CS, H2CCC, H2CCCC, H2CCO have been identified in cool interstellar molecular clouds, identification of H2CC is still awaited. To analyze its spectrum, collisional rate coefficients are required. We have calculated collisional rate coefficients for rotational transitions between 23 levels of ortho and para H2CC for kinetic temperatures 10, 20, 30, 40, and 50 K. The scattering problem is analyzed using the computer code MOLSCAT where the colliding partner is He atom. The interaction between H2CC and He has been calculated with GAUSSIAN 2003. For the interaction potential obtained with GAUSSIAN 2003, MOLSCAT is used to derive the parameters q(L,M,M?|E) as a function of energy E of the colliding partner. After averaging the parameters q(L,M,M?|E) over a Maxwellian distribution, the parameters Q(L,M,M?|T) as a function of the kinetic temperature T in the cloud are obtained. Finally, the collisional rate coefficients have been calculated. We have also calculated radiative transition probabilities for the transitions between the rotational levels. Finally, for ortho-H2CC, we have solved a set of statistical equilibrium equations coupled with the equations of radiative transfer and found that the H2CC may be identified through anomalous absorption of its transition 111-110 at 4.89 GHz.

Sharma, M. K.; Sharma, Monika; Verma, U. P.; Chandra, Suresh

2014-11-01

271

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

272

The influence of H 2O on mantle wedge melting  

Microsoft Academic Search

The solidus and near-solidus melting behavior of a primitive undepleted peridotite composition has been determined over a pressure range of 1.23.2GPa at H2O saturated conditions. Vapor-saturated melting (melting in the presence of an H2O-rich supercritical fluid) begins at 940C at 1.2GPa and the solidus temperature decreases continuously to 860C at 2GPa and 800C at 3.2GPa. This solidus is similar to

Timothy L. Grove; Nilanjan Chatterjee; Stephen W. Parman; Etienne Mdard

2006-01-01

273

High-resolution numerical simulation and analysis of Mach reflection structures in detonation waves in low-pressure H2 - O2 - Ar mixtures: a summary of results obtained with the adaptive mesh refinement framework AMROC  

SciTech Connect

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

Deiterding, Ralf [ORNL

2011-01-01

274

Multi Frequency Phase Fluorimetry (MFPF) for Oxygen Partial Pressure Measurement: Ex Vivo Validation by Polarographic Clark-Type Electrode  

PubMed Central

Background Measurement of partial pressure of oxygen (PO2) at high temporal resolution remains a technological challenge. This study introduces a novel PO2 sensing technology based on Multi-Frequency Phase Fluorimetry (MFPF). The aim was to validate MFPF against polarographic Clark-type electrode (CTE) PO2 measurements. Methodology/Principal Findings MFPF technology was first investigated in N?=?8 anaesthetised pigs at FIO2 of 0.21, 0.4, 0.6, 0.8 and 1.0. At each FIO2 level, blood samples were withdrawn and PO2 was measured in vitro with MFPF using two FOXY-AL300 probes immediately followed by CTE measurement. Secondly, MFPF-PO2 readings were compared to CTE in an artificial circulatory setup (human packed red blood cells, haematocrit of 30%). The impacts of temperature (20, 30, 40C) and blood flow (0.8, 1.6, 2.4, 3.2, 4.0 L min?1) on MFPF-PO2 measurements were assessed. MFPF response time in the gas- and blood-phase was determined. Porcine MFPF-PO2 ranged from 63 to 749 mmHg; the corresponding CTE samples from 43 to 712 mmHg. Linear regression: CTE?=?15.59+1.18*MFPF (R2?=?0.93; P<0.0001). Bland Altman analysis: meandiff 69.2 mmHg, rangediff -50.1/215.6 mmHg, 1.96-SD limits -56.3/194.8 mmHg. In artificial circulatory setup, MFPF-PO2 ranged from 20 to 567 mmHg and CTE samples from 11 to 575 mmHg. Linear regression: CTE?=??8.73+1.05*MFPF (R2?=?0.99; P<0.0001). Bland-Altman analysis: meandiff 6.6 mmHg, rangediff -9.7/20.5 mmHg, 1.96-SD limits -12.7/25.8 mmHg. Differences between MFPF and CTE-PO2 due to variations of temperature were less than 6 mmHg (range 0140 mmHg) and less than 35 mmHg (range 140750 mmHg); differences due to variations in blood flow were less than 15 mmHg (all P-values>0.05). MFPF response-time (monoexponential) was 1.480.26 s for the gas-phase and 1.510.20 s for the blood-phase. Conclusions/Significance MFPF-derived PO2 readings were reproducible and showed excellent correlation and good agreement with Clark-type electrode-based PO2 measurements. There was no relevant impact of temperature and blood flow upon MFPF-PO2 measurements. The response time of the MFPF FOXY-AL300 probe was adequate for real-time sensing in the blood phase. PMID:23565259

Boehme, Stefan; Duenges, Bastian; Klein, Klaus U.; Hartwich, Volker; Mayr, Beate; Consiglio, Jolanda; Baumgardner, James E.; Markstaller, Klaus; Basciani, Reto; Vogt, Andreas

2013-01-01

275

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 Available online 19 January 2011 Editor: D.B. Dingwell Keywords: Monazite Xenotime Solubility Piston. In order to constrain the solubility of monazite and YPO4 xenotime at high pressure and temperature, we

Manning, Craig

276

Writing and reading H2B monoubiquitylation.  

PubMed

Monoubiquitylation of histone H2B (H2Bub1), catalyzed by the heterodimeric ubiquitin ligase complex RNF20/40, regulates multiple molecular and biological processes. The addition of a large ubiquitin moiety to the small H2B is believed to change the biochemical features of the chromatin. H2B monoubiquitylation alters nucleosome stability, nucleosome reassembly and higher order compaction of the chromatin. While these effects explain some of the direct roles of H2Bub1, there is growing evidence that H2Bub1 can also regulate multiple DNA-templated processes indirectly, by recruitment of specific factors ("readers") to the chromatin. H2Bub1 readers mediate much of the effect of H2Bub1 on histone crosstalk, transcriptional outcome and probably other chromatin-related activities. Here we summarize the current knowledge about H2Bub1-specific readers and their role in various biological processes. This article is part of a Special Issue entitled: Molecular mechanisms of histone modification function. PMID:24412854

Fuchs, Gilad; Oren, Moshe

2014-08-01

277

Application of a quantum cascade laser for time-resolved, in situ probing of CH4/H2 and C2H2/H2 gas mixtures during microwave plasma enhanced chemical vapor deposition of diamond.  

PubMed

First illustrations of the utility of pulsed quantum cascade lasers for in situ probing of the chemistry prevailing in microwave plasma activated hydrocarbon/Ar/H2 gas mixtures used for diamond thin film growth are reported. CH4 and C2H2 molecules, and their interconversion, have been monitored by line-of-sight single pass absorption methods, as a function of process conditions (e.g., choice of input hydrocarbon (CH4 or C2H2), hydrocarbon mole fraction, total gas pressure, and applied microwave power). The observed trends can be rationalized, qualitatively, within the framework of the previously reported modeling of the gas-phase chemistry prevailing in hot filament activated hydrocarbon/H2 gas mixtures (Ashfold et al. Phys. Chem. Chem. Phys. 2001, 3, 3471). Column densities of vibrationally excited C2H2(v5=1) molecules at low input carbon fractions are shown to be far higher than expected on the basis of local thermodynamic equilibrium. The presence of vibrationally excited C2H2 molecules (C2H2(double dagger)) can be attributed to the exothermicity of the C2H3 + H <==> C2H2 + H2 elementary reaction within the overall multistep CH4 --> C2H2 conversion. Diagnostic methods that sample just C2H2(v=0) molecules thus run the risk of underestimating total C2H2 column densities in hydrocarbon/H2 mixtures operated under conditions where the production rate of C2H2(double dagger) molecules exceeds their vibrational relaxation (and thermal equilibration) rates. PMID:16494395

Cheesman, A; Smith, J A; Ashfold, M N R; Langford, N; Wright, S; Duxbury, G

2006-03-01

278

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

279

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

PubMed

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

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

2011-05-01

280

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

PubMed

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

Hanada, Nobuko; Ichikawa, Takayuki; Fujii, Hironobu

2005-04-21

281

The mechanism of Klebsiella pneumoniae nitrogenase action. The determination of rate constants required for the simulation of the kinetics of N2 reduction and H2 evolution.  

PubMed Central

Kinetic data for Klebsiella pneumoniae nitrogenase were used to determine the values of nine of the 17 rate constants that define the scheme for nitrogenase action described by Lowe & Thorneley [(1984) Biochem. J. 224, 877-886]. Stopped-flow spectrophotometric monitoring of the MgATP-induced oxidation of the Fe protein (Kp2) by the MoFe protein (Kp1) was used to determine the rates of association (k+1) and dissociation (k-1) of reduced Kp2(MgATP)2 with Kp1. The dependences of the apparent KNm2 on Fe protein/MoFe protein ratio and H2 partial pressure were used to determine the mutual displacement rates of N2 and H2 (k+10, k-10, k+11 and k-11). These data also allowed the rate constants for H2 evolution from progressively more reduced forms of Kp1 to be determined (k+7, k+8 and k+9). A mechanism for N2-dependent catalysis of 1H2H formation from 2H2 that requires H2 to be a competitive inhibitor of N2 reduction is also presented. PMID:6395863

Lowe, D J; Thorneley, R N

1984-01-01

282

H2 for HIFOO Denis Arzelier1  

E-print Network

, and the package is aimed at designing a stabilizing linear controller of fixed-order for a linear plant multiple plant stabilization and multiple conflicting objectives and the second major release of HIFOO, we feel that it is now timely to extend HIFOO to H2 norm specifications. Indeed, H2 optimal design

Henrion, Didier

283

Characterization of four different effects elicited by H 2O 2 in rat aorta  

Microsoft Academic Search

Four main vascular effects of hydrogen peroxide (H2O2) were studied in intact and rubbed aortic rings from WKY rats. In rings partially precontracted with phenylephrine: 130 ?M H2O2 induced an increase of tone, 100 ?M H2O2 produced a transient contraction followed by a fast-developing endothelium-independent relaxation, and 0.3 mM H2O2 induced a fast-developing relaxation followed by a slow-developing endothelium-independent relaxation.

Jos Gil-Longo; Cristina Gonzlez-Vzquez

2005-01-01

284

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

285

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

286

Anomalous absorption in H_{2}CO molecule  

NASA Astrophysics Data System (ADS)

Formaldehyde (H_2CO) is the first organic molecule identified in a number of galactic and extragalactic radio sources through its transition 1_{10}-1_{11} at 4.830 GHz in absorption in 1969. Later on, this transition was found in anomalous absorption. In some cosmic objects, this transition however was found in emission and even as a maser radiation. Since the transition 1_{10}-1_{11} of ortho-H_2CO is considered as a unique probe of high density gas at low temperature, the study of H_2CO has always been of great importance for astrophysicists as well as for spectroscopists. In the present investigation, we have solved a set of statistical equilibrium equations coupled with the equations of radiative transfer for H_2CO. Since the kinetic temperature in the medium where H_2CO is identified is few tens of Kelvin, we have considered 22 rotational levels of ortho-H_2CO in the ground vibrational and ground electronic states. The input data required in the present investigation are the radiative transition probabilities and the collisional rates. Using the latest data for radiative transition probabilities and the collisional rates, we have found anomalous absorption of 1_{10}-1_{11}, 2_{11}-2_{12} and 3_{12} - 3_{13} transitions of ortho-H_2CO.

Sharma, Monika; Kumar Sharma, Mohit

287

Hunt for cold H2 molecules  

E-print Network

The bulk of the molecular component in galaxies is made of cold H2, which is not observed directly, but which abundance is derived from indirect tracers such as CO emission. The CO to H2 conversion ratio remains uncertain, and may vary by large factors in special environments with different excitation or metallicity. Recent cold gas discoveries (through gamma-rays or cold dust emission) are reviewed and the most promising tracers in the future are discussed, such as the primordial molecules HD and LiH, or the pure rotational lines of excited H2*.

F. Combes

2006-01-30

288

Isotope effect in the formation of H2 from H2CO studied at the atmospheric simulation chamber SAPHIR  

NASA Astrophysics Data System (ADS)

Formaldehyde of known, near-natural isotopic composition was photolyzed in the SAPHIR atmosphere simulation chamber under ambient conditions. The isotopic composition of the product H2 was used to determine the isotope effects in formaldehyde photolysis. The experiments are sensitive to the molecular photolysis channel, and the radical channel has only an indirect effect and cannot be effectively constrained. The molecular channel kinetic isotope effect KIEmol, the ratio of photolysis frequencies j(HCHO?CO+H2)/j(HCDO?CO+HD) at surface pressure, is determined to be KIEmol=1.63-0.046+0.038. This is similar to the kinetic isotope effect for the total removal of HCHO from a recent relative rate experiment (KIEtot=1.580.03), which indicates that the KIEs in the molecular and radical photolysis channels at surface pressure (?100 kPa) may not be as different as described previously in the literature.

Rckmann, T.; Walter, S.; Bohn, B.; Wegener, R.; Spahn, H.; Brauers, T.; Tillmann, R.; Schlosser, E.; Koppmann, R.; Rohrer, F.

2010-06-01

289

KINE--A one-dimensional dynamics program for pressurized water reactors with partial boiling in the core  

SciTech Connect

A short description of the reactor dynamics program KINE is given. The KINE code is a onedimensional code solving the time-dependent neutron diffusion equations in a two-group representation, taking into account six groups of delayed neutron precursors, one heating channel composed of fuel, canning, and a coolant region in which boiling may occur. Special attention is given to radial averaging of coolant density and fuel temperature in a core in which partial boiling can exist. The method of solution is a modified backward extrapolation procedure. Stationary starting conditions are achieved by adjustment of control rod position or liquid poison concentration.

Fiebig, R.; Kruger, A.

1982-06-01

290

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 ...

2014-08-04

291

Experimental Constraints on Ar and Ne Solubility in H2O-CO2 Bearing Basaltic Melts  

NASA Astrophysics Data System (ADS)

Although noble gases are only trace components of magmatic volatile phases, generally dominated by H2O and CO2, they represent a powerful tool to study the degassing behavior of ascending magmas. Current models of noble gas degassing from magmas use theoretical values of noble gas solubilities, because experimental measurements in hydrous melts are very rare. Here we report an experimental study of Ar and Ne solubilities in anhydrous and H2O-CO2 bearing basaltic melts. The starting material was represented by an Etnean lava erupted in 2002. High pressure experiments were performed at superliquidus temperature (1200C) and pressures of 1-3 kbar in internally heated pressure vessels. Investigated volatile phases were represented either by Ar or Ne (open capsule experiments) or by Ar, Ne, H2O and/or CO2 (sealed capsule experiments). In sealed capsule experiments the charged amounts of volatiles were computed to have a H2O-CO2 dominated vapor, with noble gases as minor species (partial pressure of a few bars), similarly to natural magmatic systems. Rapidly quenched glasses have been analyzed by electron microprobe (major elements), FTIR spectroscopy (H2O and CO2), bulk extraction and quadrupole mass spectrometry (noble gases). Ne and Ar molar fractions in the vapor were calculated by mass balance considering loaded and dissolved aliquots of volatiles. In some cases, the capsule was directly opened in an ultra-high-vacuum line and the pressure of each volatile was measured by a vacuometer, cryogenically separating the species. Experimental Ar solubility is comparable to the theoretical one predicted by the IP model, while Ne solubility results much higher. The effect of water on Ar and Ne solubility is in agreement with the predictions by the EIP model: increasing concentrations of dissolved water decrease the Henry's constant values for both Ar and Ne. Nonetheless, the model overestimates the intensity of the water effect on Ar solubility. The theoretical model has been therefore refitted to the experimental data. The obtained results can be directly employed for a reliable modeling of noble gas degassing from Etnean melts. The adopted experimental setting avoids any extrapolation and/or assumption deriving from the use of experimental data achieved in conditions unlike those of natural magmatic systems.

Rizzo, A.; Iacono Marziano, G.; Paonita, A.; Scaillet, B.; Gaillard, F.; Nuccio, P. M.

2007-12-01

292

SUBSCRIBE TO MAGAZINE H2CARSBIZ  

E-print Network

Minister Endangers ITER Negotiations to Solve Domestic Brain Drain Crisis By PEB Jan 12, 2004, 21:55 France Endangers ITER Negotiations to Solve Domestic Brain Drain Crisis Page 1 of 1http://www.h2cars

293

H2 production from simulated coal syngas containing H2S in multi-tubular Pd and 80 wt% Pd-20 wt% Cu membrane reactors  

SciTech Connect

99.7% conversion of CO in a simulated syngas feed containing 53% CO, 35% H2 and 12% CO2 was achieved via the watergas shift (WGS) reaction in a counter-current Pd multi-tube membrane reactor (MR) at 1173 K and 2 s residence time. This conversion is significantly greater than the 32% equilibrium conversion associated with a conventional (non-membrane) reactor primarily due to the high rate of H2 extraction from the reaction zone through the Pd membranes at elevated temperatures. Furthermore, nearly complete H2 recovery was attained in the permeate, resulting in the simultaneous production of a high-pressure CO2 (>99%) retentate stream after condensation of the steam. When Pd80 wt%Cu tubes were used in the reactor, a significantly lower CO conversion of 68% was attained at comparable residence times, probably due to the lower H2 permeance of the alloy. When H2S was added to the syngas feed and the H2S-to-H2 ratio was maintained below the threshold required for thermodynamically stable sulfides to form, the Pd and Pd80 wt%Cu MRs retained their mechanical integrity and H2 selectivity, but a precipitous drop in CO conversion was observed due to deactivation of the catalytic surface. The Pd and Pd80 wt%Cu MRs were observed to fail within minutes after increasing the H2S-to-H2 ratio to levels above that expected for thermodynamically stable sulfides to form, as evidenced by rupturing of the membrane tubes. SEMEDS analyses of the membranes suggested that at high H2S-to-H2 ratios, the H2S compromised the mechanical integrity of the MRs by preferentially attacking the grain boundary region.

Iyoha, O.; Enick, R.M.; Killmeyer, R.P.; Howard, B.H.; Ciocco, M.V.; Morreale, B.

2007-12-01

294

H2O and HCl trace gas kinetics on crystalline HCl hydrates and amorphous HCl / H2O in the range 170 to 205 K: the HCl / H2O phase diagram revisited  

NASA Astrophysics Data System (ADS)

In this laboratory study, H2O ice films of 1 to 2 ?m thickness have been used as surrogates for ice particles at atmospherically relevant conditions in a stirred flow reactor (SFR) to measure the kinetics of evaporation and condensation of HCl and H2O on crystalline and amorphous HCl hydrates. A multidiagnostic approach has been employed using Fourier transform infrared spectroscopy (FTIR) absorption in transmission to monitor the condensed phase and residual gas mass spectrometry (MS) for the gas phase. An average stoichiometric ratio of H2O : HCl = 5.8 0.7 has been measured for HCl . 6H2O, and a mass balance ratio between HCl adsorbed onto ice and the quantity of HCl measured using FTIR absorption (Nin - Nesc - Nads) / NFTIR = 1.18 0.12 has been obtained. The rate of evaporation Rev(HCl) for crystalline HCl hexahydrate (HCl . 6H2O) films and amorphous HCl / H2O mixtures has been found to be lower by a factor of 10 to 250 compared to Rev(H2O) in the overlapping temperature range 175 to 190 K. Variations of the accommodation coefficient ?(HCl) on pure HCl . 6H2O up to a factor of 10 at nominally identical conditions have been observed. The kinetics (?, Rev) are thermochemically consistent with the corresponding equilibrium vapour pressure. In addition, we propose an extension of the HCl / H2O phase diagram of crystalline HCl . 6H2O based on the analysis of deconvoluted FTIR spectra of samples outside its known existence area. A brief evaluation of the atmospheric importance of both condensed phases - amorphous HCl / H2O and crystalline HCl . 6H2O - is performed in favour of the amorphous phase.

Iannarelli, R.; Rossi, M. J.

2014-05-01

295

The molecular hydrogen explorer H2EX  

Microsoft Academic Search

The Molecular Hydrogen Explorer, H2EX, was proposed in response to the ESA 2015 - 2025 Cosmic Vision Call as a medium class space mission with NASA and CSA participations.\\u000a The mission, conceived to understand the formation of galaxies, stars and planets from molecular hydrogen, is designed to\\u000a observe the first rotational lines of the H2 molecule (28.2, 17.0, 12.3 and

F. Boulanger; J. P. Maillard; P. Appleton; E. Falgarone; G. Lagache; B. Schulz; B. P. Wakker; A. Bressan; J. Cernicharo; V. Charmandaris; L. Drissen; G. Helou; T. Henning; T. L. Lim; E. A. Valentjin; A. Abergel; J. Le Bourlot; M. Bouzit; S. Cabrit; F. Combes; J. M. Deharveng; P. Desmet; H. Dole; C. Dumesnil; A. Dutrey; J. J. Fourmond; E. Gavila; R. Grang; C. Gry; P. Guillard; S. Guilloteau; E. Habart; B. Huet; C. Joblin; M. Langer; Y. Longval; S. C. Madden; C. Martin; M. A. Miville-Deschnes; G. Pineau des Forts; E. Pointecouteau; H. Roussel; L. Tresse; L. Verstraete; F. Viallefond; F. Bertoldi; J. Jorgensen; J. Bouwman; A. Carmona; O. Krause; A. Baruffolo; C. Bonoli; F. Bortoletto; L. Danese; G. L. Granato; C. Pernechele; R. Rampazzo; L. Silva; G. de Zotti; J. Pardo; M. Spaans; W. Wild; M. J. Ferlet; S. K. Ramsay Howat; M. D. Smith; B. Swinyard; G. S. Wright; G. Joncas; P. G. Martin; C. J. Davis; B. T. Draine; P. F. Goldsmith; A. K. Mainzer; P. Ogle; S. A. Rinehart; G. J. Stacey; A. G. G. M. Tielens

2009-01-01

296

The Rotational Spectrum of H 2Te  

Microsoft Academic Search

In the present work, we study the spectrum of the H2Te molecule in the submillimeter-wave and far infrared region. An important aim of this investigation is the further experimental characterization of the anomalous four-fold cluster effect exhibited by the rotational energy levels in the vibrational ground state of H2Te. The spectrum in the region 90472 GHz was measured with a

Igor N. Kozin; Per Jensen; Oliver Polanz; Stefan Klee; Laurent Poteau; Jean Demaison

1996-01-01

297

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

298

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

299

Ab Initio Study of H2 Desorption from Magnesium Hydride MgH2 Cluster  

NASA Astrophysics Data System (ADS)

In the present study, we investigate H2 desorption from a magnesium hydride MgH2 cluster by performing total energy calculations based on the density functional theory (DFT). We calculate the potential energy surface (PES) for the H2 desorption from a (MgH2)5 cluster. According to the total atomic charges of the Mg and H atoms at the initial (MgH2)5 cluster, the Mg-H bond is ionic-like. Because of this, the activation barrier for the H2 desorption is considerably high (3.30 eV). Moreover, the structural relaxation for the system, allowing for only the two Mg atoms closest to the two desorbing H atoms, does not largely affect the potential energy of the system. The results indicate that the ionic-like Mg-H interaction is related to the thermodynamical stability of MgH2.

Tsuda, Muneyuki; Dio, Wilson Agerico; Nakanishi, Hiroshi; Kasai, Hideaki

2004-10-01

300

Evaluation of Protected Metal Hydride Slurries in a H2 Mini-  

E-print Network

storage replaces need for battery Synergies with transportation developments #12;SL_PT_DOE_D0021_H2&FC waste heat can be used for hot water or space heating in buildings (i.e. "cogen") Distributed FCPS if dehydrogenation heat can be supplied by waste heat (e.g. fuel cell) Requires less space than low pressure cH2

301

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

302

The Molecular Hydrogen Explorer H2EX  

E-print Network

The Molecular Hydrogen Explorer, H2EX, was proposed in response to the ESA 2015 - 2025 Cosmic Vision Call as a medium class space mission with NASA and CSA participations. The mission, conceived to understand the formation of galaxies, stars and planets from molecular hydrogen, is designed to observe the first rotational lines of the H2 molecule (28.2, 17.0, 12.3 and 9.7 micron) over a wide field, and at high spectral resolution. H2EX can provide an inventory of warm (> 100 K) molecular gas in a broad variety of objects, including nearby young star clusters, galactic molecular clouds, active galactic nuclei, local and distant galaxies. The rich array of molecular, atomic and ionic lines, as well as solid state features available in the 8 to 29 micron spectral range brings additional science dimensions to H2EX. We present the optical and mechanical design of the H2EX payload based on an innovative Imaging Fourier Transform Spectrometer (IFTS) fed by a 1.2m telescope. The 20'x20' field of view is imaged on two 1024x1024 Si:As detectors. The maximum resolution of 0.032 cm^-1 (FWHM) means a velocity resolution of 10 km s^-1 for the 0-0 S(3) line at 9.7 micron. This instrument offers the large field of view necessary to survey extended emission in the Galaxy and local Universe galaxies as well as to perform unbiased extragalactic and circumstellar disks surveys. The high spectral resolution makes H2EX uniquely suited to study the dynamics of H2 in all these environments. The mission plan is made of seven wide-field spectro-imaging legacy programs, from the cosmic web to galactic young star clusters, within a nominal two years mission. The payload has been designed to re-use the Planck platform and passive cooling design.

F. Boulanger; J. P. Maillard; P. Appleton; E. Falgarone; G. Lagache; B. Schulz; B. P. Wakker; A. Bressan; J. Cernicharo; L. Drissen; G. Helou; T. Henning; T. L. Lim; E. A. Valentijn; the H2EX collaboration

2008-05-20

303

The molecular hydrogen explorer H2EX  

NASA Astrophysics Data System (ADS)

The Molecular Hydrogen Explorer, H2 EX, was proposed in response to the ESA 2015 - 2025 Cosmic Vision Call as a medium class space mission with NASA and CSA participations. The mission, conceived to understand the formation of galaxies, stars and planets from molecular hydrogen, is designed to observe the first rotational lines of the H2 molecule (28.2, 17.0, 12.3 and 9.7 ?m) over a wide field, and at high spectral resolution. H2 EX can provide an inventory of warm (? 100 K) molecular gas in a broad variety of objects, including nearby young star clusters, galactic molecular clouds, active galactic nuclei, local and distant galaxies. The rich array of molecular, atomic and ionic lines, as well as solid state features available in the 8 to 29 ?m spectral range brings additional science dimensions to H2 EX. We present the optical and mechanical design of the H2 EX payload based on an innovative Imaging Fourier Transform Spectrometer fed by a 1.2 m telescope. The 2020 field of view is imaged on two 10241024 Si:As detectors. The maximum resolution of 0.032 cm - 1 (full width at half maximum) means a velocity resolution of 10 km s - 1 for the 0 - 0 S(3) line at 9.7 ?m. This instrument offers the large field of view necessary to survey extended emission in the Galaxy and local Universe galaxies as well as to perform unbiased extragalactic and circumstellar disks surveys. The high spectral resolution makes H2 EX uniquely suited to study the dynamics of H2 in all these environments. The mission plan is made of seven wide-field spectro-imaging legacy programs, from the cosmic web to galactic young star clusters, within a nominal two years mission. The payload has been designed to re-use the Planck platform and passive cooling design.

Boulanger, F.; Maillard, J. P.; Appleton, P.; Falgarone, E.; Lagache, G.; Schulz, B.; Wakker, B. P.; Bressan, A.; Cernicharo, J.; Charmandaris, V.; Drissen, L.; Helou, G.; Henning, T.; Lim, T. L.; Valentjin, E. A.; Abergel, A.; Bourlot, J. Le; Bouzit, M.; Cabrit, S.; Combes, F.; Deharveng, J. M.; Desmet, P.; Dole, H.; Dumesnil, C.; Dutrey, A.; Fourmond, J. J.; Gavila, E.; Grang, R.; Gry, C.; Guillard, P.; Guilloteau, S.; Habart, E.; Huet, B.; Joblin, C.; Langer, M.; Longval, Y.; Madden, S. C.; Martin, C.; Miville-Deschnes, M. A.; Pineau Des Forts, G.; Pointecouteau, E.; Roussel, H.; Tresse, L.; Verstraete, L.; Viallefond, F.; Bertoldi, F.; Jorgensen, J.; Bouwman, J.; Carmona, A.; Krause, O.; Baruffolo, A.; Bonoli, C.; Bortoletto, F.; Danese, L.; Granato, G. L.; Pernechele, C.; Rampazzo, R.; Silva, L.; Zotti, G. De; Pardo, J.; Spaans, M.; van der Tak, F. F. S.; Wild, W.; Ferlet, M. J.; Ramsay Howat, S. K.; Smith, M. D.; Swinyard, B.; Wright, G. S.; Joncas, G.; Martin, P. G.; Davis, C. J.; Draine, B. T.; Goldsmith, P. F.; Mainzer, A. K.; Ogle, P.; Rinehart, S. A.; Stacey, G. J.; Tielens, A. G. G. M.

2009-03-01

304

The Molecular Hydrogen Explorer H2EX  

E-print Network

The Molecular Hydrogen Explorer, H2EX, was proposed in response to the ESA 2015 - 2025 Cosmic Vision Call as a medium class space mission with NASA and CSA participations. The mission, conceived to understand the formation of galaxies, stars and planets from molecular hydrogen, is designed to observe the first rotational lines of the H2 molecule (28.2, 17.0, 12.3 and 9.7 micron) over a wide field, and at high spectral resolution. H2EX can provide an inventory of warm (> 100 K) molecular gas in a broad variety of objects, including nearby young star clusters, galactic molecular clouds, active galactic nuclei, local and distant galaxies. The rich array of molecular, atomic and ionic lines, as well as solid state features available in the 8 to 29 micron spectral range brings additional science dimensions to H2EX. We present the optical and mechanical design of the H2EX payload based on an innovative Imaging Fourier Transform Spectrometer (IFTS) fed by a 1.2m telescope. The 20'x20' field of view is imaged on two ...

Boulanger, F; Appleton, P; Falgarone, E; Lagache, G; Schulz, B; Wakker, B P; Bressan, A; Cernicharo, J; Drissen, L; Helou, G; Henning, T; Lim, T L; Valentijn, E A

2008-01-01

305

Discontinuous phase formation and selective attack of SiC materials exposed to low oxygen partial pressure environments  

SciTech Connect

Three SiC materials were exposed to gas mixtures containing N{sub 2}, H{sub 2}, and CO at 1000-1300C, 1-740 torr for a few to 1000 h. Kinetic and thermodynamic studies indicate that CO is the predominant oxidizing species. A variety of corrosion processes were observed, including surface and internal pit formation, needle growth, grain boundary attack, and attack of impurities and surrounding material. In the case of a siliconized SiC, impurities such as Ca, Al, and Fe diffused rapidly through the Si matrix forming complex calcium aluminosilicates on the surface, leaving behind internal voids. Evaluation of the mechanical properties, including fractography, revealed a variety of degradative phenomena. Efforts to identify causes of pit formation suggested that the overall process was complex. Pits formed during attack of grain boundaries and regions containing transition metal impurities. Studies of single crystals showed preferential attack near impurities and crystalline defects, indicating that damaged crystals or certain crystal orientations in the polycrystalline materials are susceptible to attack. In addition, under some conditions where pit formation was observed, the strength of certain materials increased apparently due to flaw healing. It is suggested that flaws can heal in the absence of mechanical stress due to their high surface energy. However, second phases observed within partially healed surface cracks suggest impurities also contribute to the flaw healing processes.

Butt, D.P. [Los Alamos National Lab., NM (United States); Tressler, R.E.; Spear, K.E. [Pennsylvania State Univ., University Park, PA (United States). Dept. of Materials Science and Engineering

1993-09-01

306

The Structure of Neuroglobin at High Xe and Kr Pressure Reveals Partial Conservation of Globin Internal Cavities  

PubMed Central

Neuroglobin (Ngb) is a hexacoordinate globin expressed in the brain of vertebrates. Ferrous Ngb binds dioxygen with high affinity and the O2 adduct is able to scavenge NO. Convincing invitro and invivo data indicate that Ngb is involved in neuroprotection during hypoxia and ischemia. The 3D structure of Ngb reveals the presence of a wide internal cavity connecting its heme active site with the bulk. To explore the role of this tunnel in the control of ligand binding, we determined the structure of metNgb and NgbCO equilibrated with Xe or Kr. We show four docking sites for Xe (only two for Kr); two of the four Xe sites are within the large cavity. They are only partially conserved in globins, since the two proximal Xe sites identified in myoglobin (Xe1 and Xe2) are absent in Ngb, as well as in cytoglobin. The Xe docking sites in Ngb map a pathway within the protein matrix, leading to the heme, which becomes more accessible in the ligand-bound species. This may be of significance in connection with the redox chemistry that may be the primary function of this hexacoordinate globin. PMID:19751675

Moschetti, Tommaso; Mueller, Uwe; Schulze, Jorg; Brunori, Maurizio; Vallone, Beatrice

2009-01-01

307

Vibrationally Excited H2 In Triton's Thermosphere  

NASA Astrophysics Data System (ADS)

We explore the possible impact that H2 vibrational excitation (expressed by an effec- tive vibrational temperature, Tv) might have on the ionospheric structure of Triton. Although our approach assumes that individual vibrational levels are in collisional equilibrium, it provides a useful way to represent the H2(v) distribution in Triton's thermosphere that allows us to assess the opening of nominally endothermic ion- neutral reaction channels. Some recent models of Triton have identified C+ as the main thermospheric ion, ignoring reaction with H2 as a loss mechanism since it is en- dothermic. However, the reaction of C+ with H2(v) becomes exothermic for the levels with v > 1. These vibrational levels may be populated by electron impact excitation and solar-induced resonance fluorescence of Lyman and Werner bands of H2. By including H2 vibrational excitation in our modified version of 1-D chemical dif- fusive model, together with a model of atmospheric temperatures and composition inferred from the Voyager-2 UVS solar occultation, we show that an ionosphere of mostly C+ or N+ ions is significantly modified for Tv exceeding 500 K. For a model with Tv of 2000 K and an extra ionization source of magnetospheric origin (equivalent to that estimated by Majeed et al. GRL, vol. 17, 1721, 1990)) an excellent agreement is obtained between the measured and calculated electron density profiles. N+ is the main ion at and above the ionospheric peak. For the same model, the calculated den- sities of atomic nitrogen at two altitudes (200 and 400 km) are also in good agreement with measured densities. Further details of the model and related results will be dis- cussed.

Majeed, T.; McConnell, J. C.; Gladstone, G. R.; Link, R.

308

Photodegradation of the antibiotic sulphamethoxazole in water with UV\\/H2O2 advanced oxidation process  

Microsoft Academic Search

Photodegradation of the antibiotic sulphamethoxazole (SMX) in water using a medium?pressure UV lamp combined with H2O2 (UV\\/H2O2) was used to generate the advanced oxidation process (AOP). The photodegradation process was steadily improved with addition of H2O2 at relatively low to moderate concentrations (5 to 50 mg L). However, the addition of H2O2 to the photolysis process at higher concentrations (50

Y. Lester; D. Avisar; H. Mamane

2010-01-01

309

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

310

Bio-reduction of tetrachloroethen using a H2-based membrane biofilm reactor and community fingerprinting.  

PubMed

Chlorinated ethenes in drinking water could be reductively dechlorinated to non-toxic ethene by using a hydrogen based membrane biofilm reactor (H2-MBfR) under denitrifying conditions as it provides an appropriate environment for dechlorinating bacteria in biofilm communities. This study evaluates the reductive dechlorination of perchloroethene (PCE) to non-toxic ethene (ETH) and comparative community analysis of the biofilm grown on the gas permeable membrane fibers. For these purposes, three H2-MBfRs receiving three different chlorinated ethenes (PCE, TCE and DCE) were operated under different hydraulic retention times (HRTs) and H2 pressures. Among these reactors, the H2-MBfR fed with PCE (H2-MBfR 1) accomplished a complete dechlorination, whereas cis-DCE accumulated in the TCE receiving H2-MBfR 2 and no dechlorination was detected in the DCE receiving H2-MBfR 3. The results showed that 95% of PCE dechlorinated to ETH together with over 99.8% dechlorination efficiency. Nitrate was the preferred electron acceptor as the most of electrons generated from H2 oxidation used for denitrification and dechlorination started under nitrate deficient conditions at increased H2 pressures. PCR-DGGE analysis showed that Dehalococcoides were present in autotrophic biofilm community dechlorinating PCE to ethene, and RDase genes analysis revealed that pceA, tceA, bvcA and vcrA, responsible for complete dechlorination step, were available in Dehalococcoides strains. PMID:24731873

Karata?, Serdar; Hasar, Halil; Ta?kan, Ergin; zkaya, Bestamin; ?ahinkaya, Erkan

2014-07-01

311

Ni(II) affects ubiquitination of core histones H2B and H2A  

SciTech Connect

The molecular mechanisms of nickel-induced malignant cell transformation include effects altering the structure and covalent modifications of core histones. Previously, we found that exposure of cells to Ni(II) resulted in truncation of histones H2A and H2B and thus elimination of some modification sites. Here, we investigated the effect of Ni(II) on one such modification, ubiquitination, of histones H2B and H2A in nuclei of cultured 1HAEo- and HPL1D human lung cells. After 1-5 days of exposure, Ni(II) up to 0.25 mM stimulated mono-ubiquitination of both histones, while at higher concentrations a suppression was found. Di-ubiquitination of H2A was not affected except for a drop after 5 days at 0.5 mM Ni(II). The decrease in mono-ubiquitination coincided with the appearance of truncated H2B that lacks the K120 ubiquitination site. However, prevention of truncation did not avert the decrease of H2B ubiquitination, indicating mechanistic independence of these effects. The changes in H2B ubiquitination did not fully coincide with concurrent changes in the nuclear levels of the ubiquitin-conjugating enzymes Rad6 and UbcH6. Overall, our results suggest that dysregulation of H2B ubiquitination is a part of Ni(II) adverse effects on gene expression and DNA repair which may assist in cell transformation.

Karaczyn, Aldona A. [Laboratory of Comparative Carcinogenesis, National Cancer Institute at Frederick, Bldg. 538, Room 205E, Frederick, MD 21702-1201 (United States); Golebiowski, Filip [Laboratory of Comparative Carcinogenesis, National Cancer Institute at Frederick, Bldg. 538, Room 205E, Frederick, MD 21702-1201 (United States); Kasprzak, Kazimierz S. [Laboratory of Comparative Carcinogenesis, National Cancer Institute at Frederick, Bldg. 538, Room 205E, Frederick, MD 21702-1201 (United States)]. E-mail: kasprkaz@mail.ncifcrf.gov

2006-10-15

312

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

313

Phase equilibria and volumetric properties of the systems KCl-H 2 O and NaCl-KCl-H 2 O above 573 K: Equation of state representation  

Microsoft Academic Search

A comprehensive equation of state has been developed for the system KC1-H 2 O at high temperatures and pressures. The equation is based on a theoretical model developed earlier for the system NaCl-H 2 O. Experimental vapor-liquid equilibrium, solid-liquid equilibrium, and density data have been critically evaluated and used to fit the adjustable parameters of the model. The equation of

Andrzej Anderko; Kenneth S. Pitzer

1993-01-01

314

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

315

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

PubMed

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. PMID:25208586

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

2014-09-01

316

Effect of O{sub 2} gas partial pressure on mechanical properties of Al{sub 2}O{sub 3} films deposited by inductively coupled plasma-assisted radio frequency magnetron sputtering  

SciTech Connect

The effect of O{sub 2} partial pressure on the mechanical properties of Al{sub 2}O{sub 3} films is studied. Using films prepared by inductively coupled plasma-assisted radio frequency magnetron sputtering, the deposition rate of Al{sub 2}O{sub 3} decreases rapidly when oxygen is added to the argon sputtering gas. The internal stresses in the films are compressive, with magnitude decreasing steeply from 1.6 GPa for films sputtered in pure argon gas to 0.5 GPa for films sputtered in argon gas at an O{sub 2} partial pressure of 0.89 Multiplication-Sign 10{sup -2} Pa. Stress increases gradually with increasing O{sub 2} partial pressure. Using a nanoindentation tester with a Berkovich indenter, film hardness was measured to be about 14 GPa for films sputtered in pure argon gas. Hardness decreases rapidly on the addition of O{sub 2} gas, but increases when the O{sub 2} partial pressure is increased. Adhesion, measured using a Vickers microhardness tester, increases with increasing O{sub 2} partial pressure. Electron probe microanalyzer measurements reveal that the argon content of films decreases with increasing O{sub 2} partial pressure, whereas the O to Al composition ratio increases from 1.15 for films sputtered in pure argon gas to 1.5 for films sputtered in argon gas at O{sub 2} partial pressures over 2.4 Multiplication-Sign 10{sup -2} Pa. X-ray diffraction measurements reveal that films sputtered in pure argon gas have an amorphous crystal structure, whereas {gamma}-Al{sub 2}O{sub 3} is produced for films sputtered in argon gas with added O{sub 2} gas. Atomic force microscopy observations reveal that the surface topography of sputtered Al{sub 2}O{sub 3} films changes from spherical to needlelike as O{sub 2} partial pressure is increased. Fracture cross sections of the films observed by scanning electron microscopy reveal that the film morphology exhibits no discernible features at all O{sub 2} partial pressures.

Fujiyama, Hirokazu; Sumomogi, Tsunetaka; Nakamura, Masayoshi [Faculty of Engineering, Fukuoka Institute of Technology, 3-30-1 Wajirohigashi, Higashi-ku, Fukuoka 811-0295 (Japan); Faculty of Engineering, Hiroshima Kokusai Gakuin University, 6-20-1 Nakano, Aki-ku, Hiroshima 739-0321 (Japan)

2012-09-15

317

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

318

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

319

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

320

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

321

The Origin and Evolution of Kimberlite Melts: Stabilizing Phlogopite in the CMAS-CO2- H2O-K2O System  

NASA Astrophysics Data System (ADS)

This project aims to investigate the melting phase relations of model lherzolite in the system CMAS- CO2-H2O-K2O to better understand the role of potassium (K) in the evolution and origin of kimberlitic melts. High-pressure multi-anvil and piston cylinder experiments are used to study this system at upper mantle pressures (3-9 GPa). This study aims at constraining the temperature and composition of primary melts at the volatile-rich mantle solidus at which kimberlite melts form. Kimberlites are potassium-rich, ultrabasic magmas (<35% SiO2), have a low viscosity (0.1-1 Pa s), and contain a very high volatile content (CO2 and H2O). A number of models have been suggested for the generation of carbonatite and kimberlite magmas, with the presence of volatiles being particularly important (eg. CO2). Together, H2O and CO2, show a much greater influence on the solidus of mantle lherzolite than when either are present alone. Melts of carbonatitic and kimberlitic composition can be produced under comparable P-T conditions by partial melting of carbonated lherzolite. Petrogenetic links between carbonatites and kimberlites are therefore implied in the CO2-bearing mantle source region (Gudfinnsson, 2005). The isobaric univariant equilibrium for melting of model lherzolite in CMAS-CO2-H2O-K2O is tracked at upper mantle conditions. This is done by constructing a series of bulk compositions that will saturate all phases and yield enough of each phase for EPMA analysis. The compositions of all phases along a portion of the isobaric univariant melting curves will be traced at a series of pressures. In this way, we can rigorously calculate the melting behaviour of lherzolite compositions as a function of pressure, temperature and bulk composition.

Buisman, I.; Sparks, S.; Walter, M.

2008-12-01

322

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

323

Tyrosine nitration in prostaglandin H(2) synthase  

Microsoft Academic Search

In this study, we investigated the effects of various nitrogen oxide (NO(x)) species on the extent of prostaglandin H(2) synthase-1 (PGHS-1) nitration in purified protein and in vascular smooth muscle cells. We also examined PGHS-1 activity under these conditions and found the degree of nitration to correlate inversely with enzyme activity. In addition, since NO(x) species are thought to invoke

Ruba S. Deeb; Matthew J. Resnick; Dev Mittar; Timothy McCaffrey; David P. Hajjar; Rita K. Upmacis

2002-01-01

324

Terahertz Rotational Spectrum of H 2S  

Microsoft Academic Search

The rotational transition frequencies of H2S in the terahertz region were measured precisely up to 1.08 THz by a BWO-based scanning spectrometer at Cologne, Germany, and up to 2.56 THz by a laser sideband spectrometer at Lille, France. The data obtained were analyzed together with the available mmW, sub-mmW, and FIR data using the Watson-type Hamiltonian with the power series

S. P. Belov; K. M. T. Yamada; G. Winnewisser; L. Poteau; R. Bocquet; J. Demaison; O. Polyansky; M. Y. Tretyakov

1995-01-01

325

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

326

Ribonuclease H2 in health and disease.  

PubMed

Innate immune sensing of nucleic acids provides resistance against viral infection and is important in the aetiology of autoimmune diseases. AGS (Aicardi-Goutires syndrome) is a monogenic autoinflammatory disorder mimicking in utero viral infection of the brain. Phenotypically and immunologically, it also exhibits similarities to SLE (systemic lupus erythaematosus). Three of the six genes identified to date encode components of the ribonuclease H2 complex. As all six encode enzymes involved in nucleic acid metabolism, it is thought that pathogenesis involves the accumulation of nucleic acids to stimulate an inappropriate innate immune response. Given that AGS is a monogenic disorder with a defined molecular basis, we use it as a model for common autoimmune disease to investigate cellular processes and molecular pathways responsible for nucleic-acid-mediated autoimmunity. These investigations have also provided fundamental insights into the biological roles of the RNase H2 endonuclease enzyme. In the present article, we describe how human RNase H2 and its role in AGS were first identified, and give an overview of subsequent structural, biochemical, cellular and developmental studies of this enzyme. These investigations have culminated in establishing this enzyme as a key genome-surveillance enzyme required for mammalian genome stability. PMID:25109948

Reijns, Martin A M; Jackson, Andrew P

2014-08-01

327

The Rotational Spectrum of H2Te  

PubMed

In the present work, we study the spectrum of the H2Te molecule in the submillimeter-wave and far infrared region. An important aim of this investigation is the further experimental characterization of the anomalous "four-fold cluster effect" exhibited by the rotational energy levels in the vibrational ground state of H2Te. The spectrum in the region 90-472 GHz was measured with a source-modulated millimeter-wave spectrometer and that between 600 and 1600 GHz with a far-infrared sideband spectrometer. The far infrared spectrum from 30 to 360 cm-1 was measured with a Bruker IFS 120 HR interferometer attached to a 3 m long cell. We have assigned 224 submillimeter-wave lines and 1695 FIR lines. These observed data were supplemented by a large number of ground state combination differences derived from rotation-vibration bands of H2Te, and the resulting large data set was analyzed by means of a modified Watson Hamiltonian. Accurate sets of rotational and centrifugal distortion constants for all eight tellurium isotopomers were obtained. PMID:8979998

Kozin; Jensen; Polanz; Klee; Poteau; Demaison

1996-12-01

328

H2O diffusion in Mount Changbai peralkaline rhyolitic melt  

NASA Astrophysics Data System (ADS)

For quantitative modeling of bubble growth and volcanic eruption dynamics, it is necessary to know H2O diffusivity in the melt. Mount Changbai Volcano at the border of China and North Korea has produced explosive peralkaline rhyolitic eruptions, including a 30-km3 eruption with an age of 1 ky (Horn and Schmincke, 2000). H2O diffusivity is expected to be greater in a peralkaline rhyolitic melt than a calc-alkaline rhyolitic melt. We have experimentally investigated H2O diffusion in Mount Changbai peralkaline rhyolite. Because phenocryst-free glass is not available from Mount Changbai eruption products, the starting materials (nominally dry and hydrous) are synthesized. The diffusion couple technique, with one half dry and the other half wet, is adopted. Three high- temperature experiments have been carried out at 500 MPa and one at 1500 MPa in a piston-cylinder apparatus. After the experiment, the sample is prepared into a doubly-polished section of about 0.2 mm thickness, which is analyzed by a Perkin-Elmer FTIR microscope. The data are fit following the procedures of Zhang and Behrens (2000) and Ni and Zhang (2008). Preliminary data show that H2O diffusivity in peralkaline rhyolitic melt is greater than that in calc-alkaline rhyolitic melt (Zhang and Behrens, 2000), as expected. The exact difference depends on temperature and pressure, and the ratio of diffusivity in the peralkaline rhyolitic melt to that in the calc-alkaline rhyolitic melt ranges from 1 to 3. More experiments will be conducted on this melt to provide the basic data for specific modeling of bubble growth and volcanic eruption dynamics in past and future Mount Changbai eruptions and other peralkaline rhyolitic eruptions. References: Horn S and Schmincke H U (2000) Bull. Volcanol., 61, 537. Ni H and Zhang Y (2008) Chem. Geol., doi: 10.1016/j.chemgeo.2008.01.011. Zhang Y and Behrens H (2000) Chem. Geol., 169, 243.

Zhang, Y.; Xu, Z.; Wang, H.; Behrens, H.

2008-05-01

329

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

330

Removing textile mill effluent recalcitrant COD and toxicity using the H2O2/UV system.  

PubMed

The potential of the H2O2/UV process for improving quality of an industrial textile effluent before biological treatment was evaluated in the laboratory using a multivariate experimental design to determine the effects of pH, H2O2 dose and reaction time on colour, COD and toxicity removal efficiencies. Increasing reaction time (from 10 to 120 min) and H2O2 dose (from 0 to 5 mmol L(-1)) significantly improved removal efficiencies, while increasing pH (from 4 to 10) had a negative effect on colour and toxicity removals. Laboratory H2O2/UV treatment of the mill effluent under optimum conditions (pH 7, 5 mmol L(-1) H2O2, 120 min) resulted in decreases in colour (70%), COD (21%) and toxicity (67%), without lowering BOD. H2O2 was consumed within the first 30-60 min, while the effluent average oxidation state stabilized after 60 min. Decreasing reaction time to 60 min resulted in similar colour (63%) and COD (20%) removals but lower toxicity removal (44%). Spectrophotometric monitoring of the optimized reaction indicated partial destruction of residual aromatic azo dyes. H2O2 and residual peroxide and average oxidation state of the effluent Effluent biodegradability (BOD/COD) increased by 28% after the H2O2/UV treatment. Improvements observed in effluent quality are expected to enhance combined AOP-biological treatment efficiency of the mill effluent. PMID:19809153

Mounteer, A H; Leite, T A; Lopes, A C; Medeiros, R C

2009-01-01

331

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

332

26 CFR 31.3406(h)-2 - Special rules.  

...2014-04-01 false Special rules. 31.3406(h)-2 Section 31.3406(h)-2 Internal Revenue INTERNAL REVENUE SERVICE... Collection of Income Tax at Source 31.3406(h)-2 Special rules. (a) Joint accounts...

2014-04-01

333

26 CFR 31.3406(h)-2 - Special rules.  

Code of Federal Regulations, 2011 CFR

...2011-04-01 false Special rules. 31.3406(h)-2 Section 31.3406(h)-2 Internal Revenue INTERNAL REVENUE SERVICE... Collection of Income Tax at Source 31.3406(h)-2 Special rules. (a) Joint accounts...

2011-04-01

334

26 CFR 31.3406(h)-2 - Special rules.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 false Special rules. 31.3406(h)-2 Section 31.3406(h)-2 Internal Revenue INTERNAL REVENUE SERVICE... Collection of Income Tax at Source 31.3406(h)-2 Special rules. (a) Joint accounts...

2013-04-01

335

26 CFR 31.3406(h)-2 - Special rules.  

Code of Federal Regulations, 2012 CFR

...2012-04-01 false Special rules. 31.3406(h)-2 Section 31.3406(h)-2 Internal Revenue INTERNAL REVENUE SERVICE... Collection of Income Tax at Source 31.3406(h)-2 Special rules. (a) Joint accounts...

2012-04-01

336

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

337

P0703-Hoegh The H2/H2O/Ni/Zirconia Point Electrode  

E-print Network

(O2H2 )SZ( O)g(2H -+-+ (1) )currentCathodic(2 )SZ( O)g(2H)Ni(e2)g(O2H -+-+ (2) Reaction (1) and (2 of hydrogen and the reduction of water, as given by equation (1) and (2) respectively. )currentAnodic()Ni(e2)g the three phase boundary where the fuel gas, Ni and electrolyte meet. The electrochemical reaction

338

Contrail formation: Homogeneous nucleation of H2SO4\\/H2O droplets  

Microsoft Academic Search

Homogeneous nucleation of sub-nanometer H2SO4\\/H2O germs, their growth and freezing probability in the cooling wake of a subsonic jet aircraft at tropopause altitude are investigated. Heteromolecular condensation, water uptake, and coagulation cause a small subset of the germs to grow into nm-sized solution droplets which overcome the Kelvin barrier. These droplets efficiently take up water vapor from the gas phase,

B. Kaercher; Th. Peter; R. Ottmann

1995-01-01

339

Refinements in an Mg/MgH2/H2O-Based Hydrogen Generator  

NASA Technical Reports Server (NTRS)

Some refinements have been conceived for a proposed apparatus that would generate hydrogen (for use in a fuel cell) by means of chemical reactions among magnesium, magnesium hydride, and steam. The refinements lie in tailoring spatial and temporal distributions of steam and liquid water so as to obtain greater overall energy-storage or energy-generation efficiency than would otherwise be possible. A description of the prior art is prerequisite to a meaningful description of the present refinements. The hydrogen-generating apparatus in question is one of two versions of what was called the "advanced hydrogen generator" in "Fuel-Cell Power Systems Incorporating Mg-Based H2 Generators" (NPO-43554), NASA Tech Briefs, Vol. 33, No. 1 (January 2009), page 52. To recapitulate: The apparatus would include a reactor vessel that would be initially charged with magnesium hydride. The apparatus would exploit two reactions: The endothermic decomposition reaction MgH2-->Mg + H2, which occurs at a temperature greater than or equal to 300 C, and The exothermic oxidation reaction MgH2 + H2O MgO + 2H2, which occurs at a temperature greater than or equal to 330 C.

Kindler, Andrew; Huang, Yuhong

2010-01-01

340

Spontaneous H2 loss through the interaction of squaric acid derivatives and BeH2.  

PubMed

The most stable complexes between squaric acid and its sulfur- and selenium-containing analogues (C4X4H2 ; X = O, S, Se) with BeY2 (Y = H, F) were studied by means of the Gaussian?04 (G4) composite ab initio theory. Squaric acid derivatives are predicted to be very strong acids in the gas phase; their acidity increases with the size of the chalcogen, with C4Se4H2 being the strongest acid of the series and stronger than sulfuric acid. The relative stability of the C4X4H2?BeY2 (X = O, S, Se; Y = H, F) complexes changes with the nature of the chalcogen atom; but more importantly, the formation of the C4X4H2?BeF2 complexes results in a substantial acidity enhancement of the squaric moiety owing to the dramatic electron-density redistribution undergone by the system when the beryllium bond is formed. The most significant consequence of this acidity enhancement is that when BeF2 is replaced by BeH2, a spontaneous exergonic loss of H2 is observed regardless of the nature of the chalcogen atom. This is another clear piece of evidence of the important role that closed-shell interactions play in the modulation of physicochemical properties of the Lewis acid and/or the Lewis base. PMID:24665080

Montero-Campillo, M Merced; Yez, Manuel; Lamsabhi, Al Mokhtar; M, Otilia

2014-04-25

341

Hydrothermal crystallization of Na2Ti6O13, Na2Ti3O7, and Na16Ti10O28 in the NaOH-TiO2-H2O system at a temperature of 500C and a pressure of 0.1 GPa: The structural mechanism of self-assembly of titanates from suprapolyhedral clusters  

NASA Astrophysics Data System (ADS)

An increase in the NaOH concentration in the NaOH-TiO2 (rutile)-H2O system at a temperature of 500C and a pressure of 0.1 GPa leads to the crystallization R-TiO2 + Na2Ti6O13 ? Na2Ti3O7 ? Na16Ti10O28. Crystals of the Na2Ti6O13 titanate (space group C2/m) have the three-dimensional framework structure Ti6O13. The structure of the Na2Ti3O7 titanate (space group P2 1/ m) contains the two-dimensional layers Ti3O7. The structure of the Na16Ti10O28 titanate (space group P-1) is composed of the isolated ten-polyhedron cluster precursors Ti10O28. In all the structures, the titanium atoms have an octahedral coordination ( MTiO6). The matrix self-assembly of the Na2Ti6O13 and Na2Ti3O7 (Na4Ti6O14) crystal structures from Na4 M 12 invariant precursors is modeled. These precursors are clusters consisting of twelve M polyhedra linked through the edges. It is demonstrated that the structurally rigid precursors Na4 M 12 control all processes of the subsequent evolution of the crystal-forming titanate clusters. The specific features of the self-assembly of the Na2Ti3O7 structure that result from the additional incorporation of twice the number of sodium atoms into the composition of the high-level clusters are considered.

Hyushin, G. D.

2006-07-01

342

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; it holds CO2 as adsorbate, and can exchange that CO2 with the atmosphere-cap system over timescales of 10(exp 5) to 10(exp 6) years. The climatic response to insolation changes caused by obliquity and eccentricity variations depends in part on the total reservoir of adsorbed CO2. Previous estimates of the adsorbate inventory have been made by measuring the adsorptive behavior of one or more Mars-analyog materials, and deriving an empirical equation that described that adsorption as a function of the partial pressure of CO2 and the temperature of the regolith. The current CO2 inventory is that which satisfies adsorptive equilibrium, observed atmospheric pressure, and no permanent CO2 caps. There is laboratory evidence that H2O poisons the CO2 adsorptive capacity of most materials. No consideration of CO2 - H2O co-adsorption was given in previous estimates of the Martian CO2 inventory, although H2O is present in the vapor phase, and so as adsorbate, throughout the regolith.

Zent, Aaron P.; Quinn, Richard

1994-01-01

343

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

344

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

PubMed Central

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 NO3?. Additionally, the rate of ethanol production was about 50 times greater than the rate of reduction of NO3? to NO2?. 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. Images Fig. 5 PMID:16665894

Saglio, Pierre H.; Drew, Malcolm C.; Pradet, Alain

1988-01-01

345

Direct linkage between dimethyl sulfide production and microzooplankton grazing, resulting from prey composition change under high partial pressure of carbon dioxide conditions.  

PubMed

Oceanic dimethyl sulfide (DMS) is the enzymatic cleavage product of the algal metabolite dimethylsulfoniopropionate (DMSP) and is the most abundant form of sulfur released into the atmosphere. To investigate the effects of two emerging environmental threats (ocean acidification and warming) on marine DMS production, we performed a large-scale perturbation experiment in a coastal environment. At both ambient temperature and ? 2 C warmer, an increase in partial pressure of carbon dioxide (pCO2) in seawater (160-830 ppmv pCO2) favored the growth of large diatoms, which outcompeted other phytoplankton species in a natural phytoplankton assemblage and reduced the growth rate of smaller, DMSP-rich phototrophic dinoflagellates. This decreased the grazing rate of heterotrophic dinoflagellates (ubiquitous micrograzers), resulting in reduced DMS production via grazing activity. Both the magnitude and sign of the effect of pCO2 on possible future oceanic DMS production were strongly linked to pCO2-induced alterations to the phytoplankton community and the cellular DMSP content of the dominant species and its association with micrograzers. PMID:24724561

Park, Ki-Tae; Lee, Kitack; Shin, Kyoungsoon; Yang, Eun Jin; Hyun, Bonggil; Kim, Ja-Myung; Noh, Jae Hoon; Kim, Miok; Kong, Bokyung; Choi, Dong Han; Choi, Su-Jin; Jang, Pung-Guk; Jeong, Hae Jin

2014-05-01

346

Slow B^5++ H2 Collisions  

NASA Astrophysics Data System (ADS)

The charge-exchange processes involving ions and atomic targets have received considerable theoretical and experimental considerable attentions over the last decades owing to its immense applications in both astrophysical and magnetically confined thermonuclear fusion plasmas. However, for molecular targets there are not many accurate calculations although the charge-exchange processes provide valuable inputs on the radiation research, multi-charged ion source developments, and lasers radiating in the visible ultraviolet (VUV) and X-ray regions. The electron capture cross sections in such an environment are appreciably larger. The recently observed X-ray emission data from the comets suggest that the charge exchange between solar wind and cometary gases is the most likely mechanism for X-ray production. We report our MO calculation for the process B^5++ H2 ? B^4+(nl) + H^+2 at low energies. We use a semi-classical, impact parameter, close coupling approach based on the molecular-state expansion augmented with the plane-wave electron translation factor, freezing the molecular details of the target [1], the effective binding of the active electron inside the transient molecule is simulated employing the pseudo-potential techniques [2]. Details will be presented at the conference. [1] B. C. Saha and A. Kumar, Theo. Chem 487, 11 (1999). [2] A. Kumar and B. C. Saha, Phys. Rev. A.59, 1273 (1999).

Saha, Bidhan

2005-05-01

347

Photodegradation and toxicity changes of antibiotics in UV and UV\\/H 2O 2 process  

Microsoft Academic Search

The photodegradation of three antibiotics, oxytetracycline (OTC), doxycycline (DTC), and ciprofloxacin (CIP) in UV and UV\\/H2O2 process was investigated with a low-pressure UV lamp system. Experiments were performed in buffered ultrapure water (UW), local surface water (SW), and treated water from local municipal drinking water treatment plant (DW) and wastewater treatment plant (WW). The efficiency of UV\\/H2O2 process was affected

Fang Yuan; Chun Hu; Xuexiang Hu; Dongbin Wei; Yong Chen; Jiuhui Qu

2011-01-01

348

On the dynamics of NaCl-H2O fluid convection in the Earth's crust  

Microsoft Academic Search

Numerical simulations of transient porous media thermohaline convection including phase separation into a high-density, high-salinity brine phase and a low-density, low-salinity vapor phase at pressures and temperatures well above the critical point of pure H2O are presented. Using a novel finite elementfinite volume (FEFV) solution technique and a new equation of state for the binary NaCl-H2O system, convection of a

S. Geiger; T. Driesner; C. A. Heinrich; S. K. Matthi

2005-01-01

349

New magnetic frameworks of [(CuF2(H2O)2)x(pyz)].  

PubMed

Pressure-driven orbital reordering in the quantum magnet [CuF2(H2O)2(pyz)], (pyz = pyrazine), dramatically affects its magnetic exchange interactions. The crystal chemistry of this system is enriched with a new phase above 3 GPa, surprisingly concomitant with other polymorphs. Moreover, we discovered an unprecedented compound with a different stoichiometry, [(CuF2(H2O)2)2(pyz)], featuring magnetic bi-layers. PMID:25308125

Lanza, A; Fiolka, C; Fisch, M; Casati, N; Skoulatos, M; Regg, C; Krmer, K W; Macchi, Piero

2014-12-01

350

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

351

Characterization of four different effects elicited by H2O2 in rat aorta.  

PubMed

Four main vascular effects of hydrogen peroxide (H2O2) were studied in intact and rubbed aortic rings from WKY rats. In rings partially precontracted with phenylephrine: 1-30 microM H2O2 induced an increase of tone, 100 microM H2O2 produced a transient contraction followed by a fast-developing endothelium-independent relaxation, and 0.3 mM H2O2 induced a fast-developing relaxation followed by a slow-developing endothelium-independent relaxation. Superoxide dismutase (SOD) or dimethyl sulfoxide (DMSO)/manitol did not significantly modify the H2O2 effects, while catalase suppressed them. Indomethacin abolished the increase of tone elicited by H2O2 and revealed a small endothelium-dependent relaxation, which was suppressed by N(G)-nitro-L-arginine (L-NA), high K+ or tetraethylammonium (TEA). TEA strongly inhibited the fast-developing relaxation while indomethacin, glybenclamide, 1H-[1,2,4]Oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), cafeic acid or eicosatriynoic acid (ETI) did not affect the relaxation. In rings precontracted with 70 mM KCl, 1-100 microM H2O2 induced a small increase of tone and 0.3 mM a slow-developing relaxation. Catalase or Fe2+-EDTA/vitamin C suppressed the slow-developing relaxation while deferoxamine did not modify it. In rings partially precontracted with arachidonic acid, 1-30 microM H2O2 induced higher contractile effects than in rings partially precontracted with phenylephrine. H2O2 at 0.3 mM for one hour induced a persistent impairment on the reactivity of the rings and the release of lactate dehydrogenase. In summary, H2O2 produces: (1) contractions mediated by direct activation of cyclooxygenase; 2) endothelium-dependent relaxations related to activation of endothelial K+ channels and NO synthesis; 3) reversible endothelium-independent relaxations mediated by activation of smooth muscle K+ channels; and 4) irreversible endothelium-independent relaxations related to cellular damage, caused by H2O2 but not by hydroxyl radicals. PMID:15994130

Gil-Longo, Jos; Gonzlez-Vzquez, Cristina

2005-08-01

352

Interaction of sulfur-bearing silicate melts with H2O and H2 bearing fluids (Invited)  

NASA Astrophysics Data System (ADS)

Reactions between fluids and melts, which are not in redox-equilibrium, may potentially change the oxidation state of species in both phases. Diffusion of hydrogen and water in the melt is expected to be a controlling parameter for the adjustment of the redox state of multivalent elements in the melt, at least over short distances. In the present paper we have investigated experimentally the interaction of sulfur-bearing silicate melts with either oxidizing or reducing fluid components. Two scenarios were studied: (i) Diffusion of water into an initial dry melt containing sulfide and (ii) diffusion of hydrogen into a water-poor melt containing sulfate. The experiments were performed in an internally heated gas pressure vessel at 100 or 200 MPa confining pressure and temperatures between 1000 and 1200C using as model systems soda-lime-silicate and sodiumtrisilicate melts containing ca. 1000 ppm sulfur. Type (i) experiments were carried out either at water-undersaturated conditions (max. 3 wt% H2O) using the diffusion couple technique or at water-saturated conditions by adding 10 wt% of H2O to the glass melt. Run time was always short (4 - 20 min), resulting in H2O diffusion profiles up 3 mm and S diffusion profiles up to 400 m in length. In the diffusion couple experiments new IR absorption bands at 3400 and 5020 cm-1 were observed while the characteristic combination band of molecular H2O at 5225 cm-1 strongly decreases in intensity. X-ray Absorption Near Edge Structure (XANES) spectroscopy demonstrate the appearance of a new S K pre-edge excitation at 2466.5 eV and a relative decrease in the intensity of the sulfide peak at 2474.0 eV, but no signal of sulfate at 2482.5 eV was detected. The intensity of the XANES pre-edge peak correlates directly with the intensities of the IR bands at 3400 and 5020 cm-1. On the basis of the spectroscopic results we infer the formation of a stable complex of S2- with probably 2 H2O molecules in the glasses. The lack of oxidation of sulfide can be explained by local redox buffering of the melt with hydrogen due to the low hydrogen solubility in the melt or by a relatively low oxygen fugacity. Oxidation of sulfide to sulfate was observed only in experiments with a free H2O fluid which may act as a sink for hydrogen. In all type (ii) experiments reaction rims were formed in the sulfate bearing part of the sample where sulfide was generated by in-diffusion of hydrogen from the pressure vessel. For instance after 8 h at 1100C, 100 MPa the reduced layer had a thickness of ca. 200 m. Neither in the reduction nor in the oxidation experiments a sulfite peak was observed in XANES spectra. Hence, we conclude that sulfite is not a stable (major) sulfur species in the melt or it is not quenchable, consistent with findings of Wilke et al. (2008). Ref.: M. Wilke, P.J. Jugo, J. Susini, R. Botcharnikov, S.C. Kohn, M. Janousch (2008). The origin of S4+ detected in silicate glasses by XANES. Am. Mineral. 93, 235-240.

Behrens, H.; Stelling, J.; Wilke, M.; Backnaes, L.; Deubener, J.

2009-12-01

353

Dynamics of ?H2AX formation and elimination in mammalian cells after X-irradiation.  

PubMed

Phosphorylation of the replacement histone H2AX occurs in megabase chromatin domains around DNA double-strand breaks (DSBs), and this modification called ?H2AX can be used as an effective marker for DSB repair and DNA damage response. In this study, we examined a bystander effect (BE) in locally irradiated embryonic human fibroblasts. Using fluorescence microscopy, we found that BE could be observed 1 h after X-ray irradiation (IR) and was completely eliminated 24 h after IR. Using immunohistochemistry and immunoblotting, we also studied kinetics of ?H2AX formation and elimination in Syrian hamster and mouse tissues after whole body IR of animals. Analysis of hamster tissues at different times after IR at the dose 5 Gy showed that ?H2AX-associated fluorescence in heart was decreased slowly with about a half level remaining 24 h after IR; at the same time, in brain, the level of ?H2AX was about 3 times increased over the control level, and in liver, ?H2AX level decreased to control values. We also report that in mouse heart the level of ?H2AX measured by immunoblotting is lower than in brain, kidney and liver at different times after IR at the dose 3 Gy. Our observations indicate that there are significant variations in dynamics of ?H2AX formation and elimination between non-proliferating mammalian tissues. These variations in ?H2AX dynamics in indicated organs partially correlated with the expression level of the major kinase genes involved in H2AX phosphorylation (ATM and DNA-PK). PMID:22766016

Firsanov, Denis; Vasilishina, Anastasia; Kropotov, Andrey; Mikhailov, Vyacheslav

2012-11-01

354

Disruption of histamine H2 receptor slows heart failure progression through reducing myocardial apoptosis and fibrosis.  

PubMed

Histamine H2 receptor (H2R) blockade has been reported to be beneficial for patients with chronic heart failure (CHF), but the mechanisms involved are not entirely clear. In the present study, we assessed the influences of H2R disruption on left ventricular (LV) dysfunction and the mechanisms involved in mitochondrial dysfunction and calcineurin-mediated myocardial fibrosis. H2R-knockout mice and their wild-type littermates were subjected to transverse aortic constriction (TAC) or sham surgery. The influences of H2R activation or inactivation on mitochondrial function, apoptosis and fibrosis were evaluated in cultured neonatal rat cardiomyocytes and fibroblasts as well as in murine hearts. After 4 weeks, H2R-knockout mice had higher echocardiographic LV fractional shortening, a larger contractility index, a significantly lower LV end-diastolic pressure, and more importantly, markedly lower pulmonary congestion compared with the wild-type mice. Similar results were obtained in wild-type TAC mice treated with H2R blocker famotidine. Histological examinations showed a lower degree of cardiac fibrosis and apoptosis in H2R-knockout mice. H2R activation increased mitochondrial permeability and induced cell apoptosis in cultured cardiomyocytes, and also enhanced the protein expression of calcineurin, nuclear factor of activated T-cell and fibronectin in fibroblasts rather than in cardiomyocytes. These findings indicate that a lack of H2R generates resistance towards heart failure and the process is associated with the inhibition of cardiac fibrosis and apoptosis, adding to the rationale for using H2R blockers to treat patients with CHF. PMID:24655024

Zeng, Zhi; Shen, Liang; Li, Xixian; Luo, Tao; Wei, Xuan; Zhang, Jingwen; Cao, Shiping; Huang, Xiaobo; Fukushima, Yasushi; Bin, Jianping; Kitakaze, Masafumi; Xu, Dingli; Liao, Yulin

2014-10-01

355

Solutions to Problem Set 11 19.5.3 H2 = {h2 D[0, ] : function h2 with bounded total variation};22  

E-print Network

operator, i.e the range of h 2(h) over the unit ball in H2 lies within a compact set. This is because the second term of (1) is bounded ranging over the unit ball. For any g2 H2, there exists h2 = g2(·)/g(·) H, ] h(u) = 0, a.s u [0, ] Therefore, 22 0 is one-to-one since h is arbitary satisfying 22 0 = 0.The

Kosorok, Michael R.

356

ArH2+ and NeH2+ as Global Minima in the Ar+/Ne+ + H2 Reactions: Energetic, Spectroscopic, and Structural Data  

E-print Network

In light of the recent discovery of ArH+ in the Crab nebula, it is shown through high-level quantum chemical comptuations that the global minima on the Ar+/Ne+ + H2 potential energy surfaces are ArH2+ and NeH2+. Hence, ArH2+ may be a necessary intermediate in the Ar+ + H2 -> ArH+ + H formation reaction proposed in the same work where ArH+ is first reported in the Crab nebula. ArH2+ is also probably an intermediate in the alternative Ar + H+2 -> ArH+ + H reaction. Additionally, it is shown that Ne+ + H2 -> NeH+2 will subsequently most likely yield Ne + H+2 and not NeH+ + H offering a possible rationale as to the absence of NeH+ in spectra obtained from the interstellar medium (ISM). Following from this, spectroscopic data (both rotational and vibrational) are provided for NeH2+ and ArH2+ through the use of highly-accurate quantum chemical quartic and cubic force fields. All possible isotopologues are also included for 20Ne, 22Ne, 36Ar, 38Ar, 40Ar, 1H, and D. The dipole moments for these systems are quite large...

Theis, Riley A; Fortenberry, Ryan C

2014-01-01

357

FLYING-WATER Renewables-H2-H2O TERRAFORMING: PERMANENT Drought(s)-Elimination FOREVER!!!  

NASA Astrophysics Data System (ADS)

"H2O H2O everywhere; ne'er a drop to drink"[Coleridge(1798)]; now: "H2 H2 everywhere; STILL ne'er a drop to drink": ONLY H2 (or methane CH4) can be FLYING-WATER(F-W) chemical-rain-in-pipelines Hindenberg-effect (H2-UP;H2O-DOWN): O/H2O=[16]/[18] 90%; O already in air uphill; NO H2O pumping need! In global-warming driven H2O-starved glacial-melting world, rescue is possible ONLY by Siegel [3rd Intl. Conf. Alt.-Energy (1980)-vol.5/p.459!!!] Renewables-H2-H2O purposely flexible versatile agile customizable scaleable retrofitable integrated operating-system. Rosenfeld[Science 315,1396(3/9/2007)]-Biello [Sci.Am.(3/9/2007)] crucial geomorph-ology which ONLY maximal-buoyancy H2 can exploit, to again make "Mountains into Fountains", "upthrust rocks trapping the clouds to precipitate their rain/snow/H2O": "terraforming"(and ocean-rebasificaton!!!) Siegel proprietary magnetic-hydrogen-valve (MHV) permits H2 flow in already in-ground dense BCC/ferritic-steels pipelines-network (NO new infrastructure) counters Tromp[Science 300,1740(2003)] dire warning of global-pandemics (cancers/ blindness/famine) Hydrogen-economy CATASTROPHIC H2 ozone-layer destruction sobering cavat to dangerous H2-automotion-economy panacea hype!!!

Ertl, G.; Alefeld, G.; Youdelis, W.; Radd, H.; Oertle, G.; Siegel, Edward

2011-03-01

358

A New Equation of State for H2O Ice Ih  

NASA Astrophysics Data System (ADS)

Various thermodynamic equilibrium properties of naturally abundant, hexagonal ice (ice Ih) of water (H2O) have been used to develop a Gibbs energy function g(T,p) of temperature and pressure, covering the ranges 0-273.16 K and 0 Pa-210 MPa, expressed in the temperature scale ITS-90. It serves as a fundamental equation from which additional properties are obtained as partial derivatives by thermodynamic rules. Extending previously developed Gibbs functions, it covers the entire existence region of ice Ih in the T-p diagram. Close to zero temperature, it obeys the theoretical cubic limiting law of Debye for heat capacity and Pauling's residual entropy. It is based on a significantly enlarged experimental data set compared to its predecessors. Due to the inherent thermodynamic cross relations, the formulas for particular quantities like density, thermal expansion, or compressibility are thus fully consistent with each other, are more reliable now, and extended in their ranges of validity. In conjunction with the IAPWS-95 formulation for the fluid phases of water, the new chemical potential of ice allows an alternative computation of the melting and sublimation curves, being improved especially near the triple point, and valid down to 130 K sublimation temperature. It provides an absolute entropy reference value for liquid water at the triple point.

Feistel, Rainer; Wagner, Wolfgang

2006-06-01

359

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

360

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

361

Cysteine Activated Hydrogen Sulfide (H2S) Donors  

PubMed Central

H2S, the newly discovered gasotransmitter, plays important roles in biological systems. However, the research on H2S has been hindered by lacking controllable H2S donors which could mimic the slow and continuous H2S generation process in vivo. Herein we report a series of cysteine-activated H2S donors. Structural modifications on these molecules can regulate the rates of H2S generation. These compounds can be useful tools in H2S research. PMID:21142018

Zhao, Yu; Wang, Hua

2010-01-01

362

Effect of Varying CO2 Partial Pressure on Photosynthesis and on Carbon Isotope Composition of Carbon-4 of Malate from the Crassulacean Acid Metabolism Plant Kalancho daigremontiana Hamet et Perr. 1  

PubMed Central

Intact leaves of Kalancho daigremontiana were exposed to CO2 partial pressures of 100, 300, and 1000 microbars. Malic acid was extracted, purified, and degraded in order to obtain isotopic composition of carbon-1 and carbon-4. From these data, it is possible to calculate the carbon isotope composition of newly fixed carbon in malate. In all three treatments, the isotopic composition of newly introduced carbon is the same as that of the CO2 source and is independent of CO2 partial pressures over the range tested. Comparison with numerical models described previously (O'Leary 1981 Phytochemistry 20: 553-567) indicates that we would expect carbon 4 of malate to be 4 more negative than source CO2 if diffusion is totally limiting or 7 more positive than source CO2 if carboxylation is totally limiting. Our results demonstrate that stomatal aperture adjusts to changing CO2 partial pressures and maintains the ratio of diffusion resistance to carboxylation resistance approximately constant. In this study, carboxylation and diffusion resistances balance so that essentially no fractionation occurs during malate synthesis. Gas exchange studies of the same leaves from which malate was extracted show that the extent of malate synthesis over the whole night is nearly independent of CO2 partial pressure, although there are small variations in CO2 uptake rate. Both the gas exchange and the isotope studies indicate that the ratio of external to internal CO2 partial pressure is the same in all three treatments. Inasmuch as a constant ratio will result in constant isotope fractionation, this observation may explain why plants in general have fairly invariable 13C contents, despite growing under a variety of environmental conditions. PMID:16662874

Holtum, Joseph A. M.; O'Leary, Marion H.; Osmond, C. Barry

1983-01-01

363

CO/H2 in Translucent Clouds  

NASA Technical Reports Server (NTRS)

A thorough examination of techniques to improve the resolution of the FUSE spectrograph was undertaken. These involved co-adding time tagged data very carefully so as to remove any blurs caused by drift. In addition, data was binned by detector pulse height bin (to eliminate any positional vs. gain variations, e.g. "walk"). These techniques only resulted in an extremely modest increase in the spectral resolution, insufficient to allow the CO/H2 studies to be performed. The only remaining potential source of blur was defocus - implying the instrument was never properly focused on orbit. Private discussions with B.G. Anderson of the FUSE team resulted in my learning that this was in fact the case - the slidgrating distance was never optimized on orbit - resulting in a degradation of the peak performance of the instrument. Unfortunately, this was never publicized, even to myself, a member of the instrument tem and the spectrograph designer.

Green, James

2005-01-01

364

Kinetic Energy Distribution of H(2p) Atoms from Dissociative Excitation of H2  

NASA Technical Reports Server (NTRS)

The kinetic energy distribution of H(2p) atoms resulting from electron impact dissociation of H2 has been measured for the first time with uv spectroscopy. A high resolution uv spectrometer was used for the measurement of the H Lyman-alpha emission line profiles at 20 and 100 eV electron impact energies. Analysis of the deconvolved 100 eV line profile reveals the existence of a narrow line peak and a broad pedestal base. Slow H(2p) atoms with peak energy near 80 meV produce the peak profile, which is nearly independent of impact energy. The wings of H Lyman-alpha arise from dissociative excitation of a series of doubly excited Q(sub 1) and Q(sub 2) states, which define the core orbitals. The fast atom energy distribution peaks at 4 eV.

Ajello, Joseph M.; Ahmed, Syed M.; Kanik, Isik; Multari, Rosalie

1995-01-01

365

Application of Symmetry-Broken H2-H2 Potential Energy Surface to Low Energy o-/p-H2+HD Collisions of Astrophysical Interest  

NASA Astrophysics Data System (ADS)

A possibility of correct description of non-symmetrical HD+H2 collision at low temperatures (T?300 K) is considered by applying symmetrical H2-H2 potential energy surface (PES) [Diep, P. & Johnson, K. 2000, J. Chem. Phys. 113, 3480 (DJ PES)]. With the use of a special mathematical transformation technique, which was applied to this surface, and a quantum dynamical method we obtained a quite satisfactory agreement with previous results when another H2-H2 PES was used [Boothroyd, A.I. et al. 2002, J. Chem. Phys. 116, 666 (BMKP PES)].

Sultanov, R. A.; Guster, D.; Adhukari, S. K.

2011-05-01

366

Vanadium oxide-porous phosphate heterostructure catalysts for the selective oxidation of H 2S to sulphur  

NASA Astrophysics Data System (ADS)

Vanadium oxide-containing mesoporous materials, based on a surfactant expanded zirconium phosphate with silica galleries into the interlayer space, named porous phosphate heterostructure (PPH), were prepared by using TEOS and vanadium oxytripropoxide in n-propanol as sources of Si and V, respectively; with different Si/V molar ratios of 1, 2, 5 and 25; and calcining at 550 C for 6 h. Using this method, vanadium can be partially incorporated to the structure of the gallery, but the surface area strongly decreases and the appearance of V 2O 5 crystallites increases when increasing the vanadium content. The catalysts were characterized by XRD, XPS, TEM, and Raman, and tested in the selective catalytic oxidation of H 2S using a fixed bed reactor, at atmospheric pressure, at 180-260 C. The catalysts with high contents of vanadium are very active at 200 C, showing H 2S conversions of 85-99%, with a high selectivity to elemental sulphur and with a low formation of SO 2. Accordingly V 2O 5 crystallites can be proposed as active and selective although the catalytic behavior is related to the number of accessible V-sites in the surface of the catalyst.

Len, Marta; Jimnez-Jimnez, Jos; Jimnez-Lpez, Antonio; Rodrguez-Castelln, Enrique; Soriano, Dolores; Lpez Nieto, Jos M.

2010-06-01

367

Fugacity of H2O from 0?? to 350??C at the liquid-vapor equilibrium and at 1 atmosphere  

USGS Publications Warehouse

The fugacity and fugacity coefficient of H2O at the liquid-vapor equilibrium, the fugacity and the Gibbs free energy of formation of H2O at 1 atm (1.01325 bars) total pressure have been calculated from published data on the physical and thermodynamic properties of H2O and are presented at ten-degree intervals from 0?? to 350??C. ?? 1970.

Hass, J.L., Jr.

1970-01-01

368

The influence of H 2 OH 2 fluids and redox conditions on melting temperatures in the haplogranite system  

Microsoft Academic Search

Solidus temperatures of quartzalkali feldspar assemblages in the haplogranite system (Qz-Ab-Or) and subsystems in the presence\\u000a of H2O-H2 fluids have been determined at 1, 2, 5 and 8 kbar vapour pressure to constrain the effects of redox conditions on phase relations\\u000a in quartzofeldspathic assemblages. The hydrogen fugacity (f\\u000a H2) in the fluid phase has been controlled using the Shaw membrane

Burkhard C. Schmidt; Franois Holtz; Bruno Scaillet; Michel Pichavant

1997-01-01

369

H2O maser pumping: The effect of quasi-resonance energy transfer in collisions between H2 and H2O molecules  

NASA Astrophysics Data System (ADS)

The effect of quasi-resonance energy transfer in collisions between H2 and H2O molecules in H2O maser sources is investigated. New data on the state-to-state rate coefficients for collisional transitions for H2O and H2 molecules are used in the calculations. The results of ortho-H2O level population inversion calculations for the 22.2-, 380-, 439-, and 621-GHz transitions are presented. The ortho-H2O level population inversion is shown to depend significantly on the population distribution of the para-H2 J = 0 and 2 rotational levels. The possibility of quasi-resonance energy transfer in collisions between H2 molecules at highly excited rotational-vibrational levels and H2O molecules is considered. The quasi-resonance energy transfer effect can play a significant role in pumping H2O masers in the central regions of active galactic nuclei and in star-forming regions.

Nesterenok, A. V.; Varshalovich, D. A.

2014-07-01

370

Magnetic properties of La-Sr-Mn-O/Si thin film as a function of RF magnetron power and O 2 partial pressure  

NASA Astrophysics Data System (ADS)

Polycrystalline perovskite compound sputtering target La 0.67Sr 0.33MnO 3 has been prepared by a conventional ceramic method. La-Sr-Mn-O/Si thin films have been produced under various applied RF sputtering power and oxygen partial pressure at 700C. Deposited thin films were annealed for 1 h at 800C in O 2 atmosphere. Structures, magnetic properties and compositions of the La-Sr-Mn-O films have been studied with X-ray diffraction, Rutherford back-scattering spectroscopy (RBS), atomic force microscopy, scanning electron microscopy and vibrating sample magnetometer. Crystalline La-Sr-Mn-O thin films was perovskite monoclinic. In the case of RF-power 2.46 W/cm 2 and PO 2=20%, La 0.85Sr 0.15MnO 3 films have lattice parameters a0=5.489 , b0=5.517 , c0=7.769 and ?=89.07. The thickness of La 0.85Sr 0.15MnO 3 film was found to be 90050 by ?-step and RBS measurement. The coercive force and the saturation magnetization of the La 0.85Sr 0.15MnO 3 film at room temperature was HC?=5 Oe and MS?=235 emu/cm 2 with applied field 5 kOe. The temperature dependence of the resistance under zero and 15 kOe applied fields shows that a semiconductor-metal transition, TSC-M, occurs at 240 K. The relative magnetoresistance, MR, is about 9.6%.

Park, Seung-Iel; Kim, Yeon Hee; Lee, Bo Wha; Cho, Young Suk; Kim, Chul Sung

2000-06-01

371

A method for measuring brain partial pressure of oxygen in unanesthetized unrestrained subjects: the effect of acute and chronic hypoxia on brain tissue PO2  

PubMed Central

The level of tissue oxygenation provides information related to the balance between oxygen delivery, oxygen utilization, tissue reactivity and morphology during physiological conditions. Tissue partial pressure of oxygen (PtO2) is influenced by the use of anesthesia or restraint. These factors may impact the absolute level of PtO2. In this study we present a novel fibre optic method to measure brain PtO2. This method can be used in unanesthetized, unrestrained animals, provides absolute values for PO2, has a stable calibration, does not consume oxygen and is MRI compatible. Brain PtO2 was studied during acute hypoxia, as well as before and after 28 days of high altitude acclimatization. A sensor was chronically implanted in the frontal cortex of 8 Wistar rats. It is comprised of a fiber optic probe with a tip containing material that fluoresces with an oxygen dependent lifetime. Brain PtO2 declines by 80% and 76% pre- and post-acclimatization respectively, when the fraction of inspired oxygen declines from 0.21 to 0.08. In addition, a linear relationship between brain PtO2 and inspired O2 levels was demonstrated r2=0.98 and r2=0.99 (pre- and post-acclimatization). Hypoxia acclimatization resulted in an increase in the overall brain PtO2 by approximately 35%. This paper demonstrates the use of a novel chronically implanted fibre optic based sensor for measuring absolute PtO2. It shows a very strong linear relationship in awake animals between inspired O2 and tissue O2, and shows that there is a proportional increase in PtO2 over a range of inspired values after exposure to chronic hypoxia. PMID:20817029

Ortiz-Prado, E.; Natah, Siraj; Srinivasan, Sathyanarayanan; Dunn, Jeff F.

2011-01-01

372

Metabolism of cholesterol and phospholipids in cultured human vascular smooth muscle cells: differences between artery and vein-derived cells and the effect of oxygen partial pressure.  

PubMed

Human smooth muscle (SM) cells derived from vena saphena magna, aorta abdominalis and arteria mamaria were grown in culture under 40 or 145 mmHg oxygen partial pressure (pO2) and their lipid metabolism studied. Esterification of the cellular [3H]cholesterol was higher by 2.5-fold in artery derived than in vein-derived cells and was slightly higher in cultures exposed to 145 mmHg than to 40 mmHg pO2. Cholesterol efflux in the presence of high density lipoprotein (HDL) in the incubation medium was higher in artery-derived than vein-derived cells. Apolipoprotein (apo) AI also supported cholesterol efflux to a higher extent in artery than in vein-derived cells. Cholesterol efflux in the presence of apo AI was accompanied by a decrease of 50% in cellular [3H]cholesteryl ester in both cell types. SM cultures exposed to [3H]choline incorporated about 90% of the radioactivity to phosphatidylcholine (PC) and 10% to sphingomyelin (SPM). During 5 days exposure to [3H]choline, 10 to 15% and 20 to 30% of the newly synthesized PC and SPM, respectively, were released by vein-derived cells into the incubation medium. The relative amount of SPM of the total radioactive phospholipids released by vein-derived cultures was significantly higher in cultures growing under 40 mmHg than 145 mmHg pO2 reaching a value of up to 33% of the radioactive phospholipids in the incubation medium. HDL was shown to serve as an acceptor for phospholipids released by both vein and artery-derived SM cells, while free apo AI supported phospholipid efflux in artery but not in vein-derived SM cells.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1935994

Savion, N; Greemland, M; Kotev-Emeth, S; Thilo-Krner, D G

1991-08-01

373

Characteristics of storage related capacity loss in Ni/H2 cells  

NASA Technical Reports Server (NTRS)

The changes in the capacity, voltage and pressure profile of flight configuration Ni/H2 cells when they are stored for extended periods is examined. The Ni/H2 cells exhibit capacity fade phenomenon regardless of their design when they are stored at room temperature. Capacity loss also occurs if old cells (5 years old) are stored in a very low rate trickle charge (C/200 rate) condition. A periodic recharge technique leads to pressure rise in the cells. Conventional trickle charge (C/100 rate) helps in minimizing or eliminating the second plateau which is one of the characteristics of the capacity fade phenomenon.

Vaidyanathan, Hari

1993-01-01

374

The soil H2 uptake in a future hydrogen economy  

NASA Astrophysics Data System (ADS)

Hydrogen as a source of energy has been proposed as the next generation of fuel that would decrease dependence on fossil fuels. Using H2 as an alternative energy source could lead to an increase in atmospheric H2 concentration above the current level of 0.55 ppm. Recent studies have proposed that the potential increase in atmospheric H2 concentration may lead to changes in atmospheric chemistry, notably that the atmospheric lifetime of methane (CH4, a potent greenhouse gas) will increase. In terms of hydrogen sinks, soil microbes currently account for about 80% of the H2 removed from our current atmosphere. A key question is whether the sink strength of soil will change with an increase in atmospheric H2 concentrations. Soil microbes would be expected to respond by increasing their number or capacity for H2 consumption. This study tests the hypothesis that H2 uptake by soils will adapt to long term exposure to elevated H2 and provide an increased feedback regulation over atmospheric H2 levels. In a laboratory study with constant soil temperature and moisture, soil was exposed to 0.5 ppm (current atmospheric), 1.4 ppm (two and half-fold enrichment) and 2.5 ppm (five-fold enrichment) H2 for 243 days. After 67 days, H2 uptake rates increase linearly in response to different H2 concentrations with a 4 and 7 fold increase in the 1.4 ppm and 2.5 ppm H2 treatment, respectively, relative to current atmospheric H2. However, at a longer term H2 exposure, a convex relationship of H2 uptake rates to H2 concentrations was found. After 8 months H2 exposure, soil showed a 7 and 10 fold increase in the 1.4 ppm and 2.5 ppm H2 treatment respectively, relative to current atmospheric H2. The active site of soil H2 uptake was found to be in the very surface soil layer, and was only active as long as soils were kept moist. This suggests that soil has a high capacity of H2 deposition, but some factor may ultimately limit H2 uptake rates in soils, and that soil may not have an infinite capacity to absorb extra H2 in the atmosphere arising from the use of H2 as an energy source.

Cen, Y.; Chan, W.; Scott, N. A.; Layzell, D. B.

2009-05-01

375

Phase relations of peridotites under H 2O-saturated conditions and ability of subducting plates for transportation of H 2O  

NASA Astrophysics Data System (ADS)

Phase relations of peridotites under H 2O-saturated conditions up to 28 GPa and 2600 C have been clarified based on the high-pressure experimental results in the MgO(-FeO)-SiO 2-H 2O, MgO-SiO 2-Al 2O 3-H 2O, CaO-MgO-Al 2O 3-SiO 2-H 2O and natural systems. Based on the phase assemblages deduced and the chemical compositions of the phases, the maximum H 2O contents for two bulk rock compositions (lherzolite and harzburgite) have been calculated using mass balance. Then the potential ability of subducting plates for transportation of H 2O is discussed by simple models combining the phase relations and the thermal structures of subduction zones as a function of the age of subducting plate a (15-130 Ma), the subduction velocity u0 (2.25-18 cm/year) and angle ? (30 and 60), and the mantle potential temperature Tp (1300 and 1350 C). The results confirm the importance of "choke point" (a cusp around 6.2 GPa and 550 C at which the stability field of major hydrous phases is minimized in terms of temperature), although the choke point is exceeded by the Mg-sursassite-bearing assemblage that has the maximum H 2O content of 0.4-0.7 wt.% around 5-7 GPa and 550-700 C. If the geotherm of the coldest part across the subducting plate passes below the choke point, maximum 4.6 wt.% H 2O can subduct, whereas H 2O less than 0.4-0.7 wt.% can subduct above the choke point. The critical conditions are clarified as follows: if ?=30 and Tp=1300 C, a15 Ma with u0=9 cm/year, or a30 Ma with u0=2.25 cm/year is the critical condition. If ?=60 and Tp=1300 C, or ?=30 and Tp=1350 C, the critical conditions slightly shift to an older age or a greater velocity (e.g., a30 Ma with u0=3.5 cm/year). The slab thermal parameter ( au0sin ?) is useful to predict roughly the critical condition. However, within the younger plate, the spatial extent of a cold region with major hydrous phases is thinner, hence less H 2O is subducted, even with the same slab thermal parameter. This indicates that the age of the plate and the subduction velocity act differently on the H 2O-transportation ability of subducting plates.

Iwamori, Hikaru

2004-10-01

376

H2 production from reactions between water and small molybdenum suboxide cluster anions  

NASA Astrophysics Data System (ADS)

Reactions between molybdenum suboxide cluster anions, MoxOy- (x=1-4y<=3x), and water (H2O and D2O) have been studied using mass spectrometric analysis of products formed in a high-pressure, fast-flow reactor. Product distributions vary with the number of metal atoms in the cluster. Within the MoOy- oxide series, product masses correspond to the addition of one water molecule, as well as a H/D exchange with MoO4H-. Within the Mo2Oy- oxide series, product evolution and distribution suggest sequential oxidation via Mo2Oy-+H2O/D2O-->Mo2Oy+1-+H2/D2 reactions for y<5, while for Mo2O5-, Mo2O6H2/D2- is produced. Mo2O6- does not appear to be reactive toward water. For the Mo3Oy- oxide series, sequential oxidation similarly is suggested for y<5, while Mo3O5- reactions result in Mo3O6H2/D2- formation. Mo3O6- appears uniquely unreactive. Mo3O7- and Mo3O8- react to form Mo3O8H2/D2- and Mo3O9H2/D2-, respectively. Lower mass resolution in the Mo4Oy- mass range prevents unambiguous mass analysis, but intensity changes in the mass spectra do suggest that sequential oxidation with H2/D2 evolution occurs for y<6, while Mo4Oy+1H2/D2- addition products are formed in Mo4O6- and Mo4O7- reactions with water. The relative rate constants for sequential oxidation and H2O/D2O addition for the x=2 series were determined. There is no evidence of a kinetic isotope effect when comparing reaction rates of H2O with D2O, suggesting that the H2 and D2 losses from the lower-oxide/hydroxide intermediates are very fast relative to initial reaction complex formation with H2O or D2O. The rate constants determined here are two times higher than those determined in identical reactions between W2Oy-+H2O/D2O.

Rothgeb, David W.; Mann, Jennifer E.; Jarrold, Caroline Chick

2010-08-01

377

H2 arcjet performance mapping program  

NASA Technical Reports Server (NTRS)

Work performed during the period of Mar. 1991 to Jan. 1992 is reviewed. High power H2 arcjets are being considered for electric powered orbit transfer vehicles (EOTV). Mission analyses indicate that the overall arcjet thrust efficiency is very important since increasing the efficiency increases the thrust, and thereby reduces the total trip time for the same power. For example, increasing the thrust efficiency at the same specific impulse from 30 to 40 percent will reduce the trip time by 25 percent. For a 200 day mission, this equates to 50 days, which results in lower ground costs and less time during which the payload is dormant. Arcjet performance levels of 1200 seconds specific impulse (lsp) at 35 to 40 percent efficiency with lifetimes over 1000 hours are needed to support EOTV missions. Because of the potential very high efficiency levels, the objective of this program was to evaluate the ability of a scaled Giannini-style thruster to achieve the performance levels while operating at a reduced nominal power of 10 kW. To meet this objective, a review of past literature was conducted; scaling relationships were developed and applied to establish critical dimensions; a development thruster was designed with the aid of the plasma analysis model KARNAC and finite element thermal modeling; test hardware was fabricated; and a series of performance tests were conducted in RRC's Cell 11 vacuum chamber with its null-balance thrust stand.

1992-01-01

378

H2O2 space shuttle APU  

NASA Technical Reports Server (NTRS)

A cryogenic H2-O2 auxiliary power unit (APU) was developed and successfully demonstrated. It has potential application as a minimum weight alternate to the space shuttle baseline APU because of its (1) low specific propellant consumption and (2) heat sink capabilities that reduce the amount of expendable evaporants. A reference system was designed with the necessary heat exchangers, combustor, turbine-gearbox, valves, and electronic controls to provide 400 shp to two aircraft hydraulic pumps. Development testing was carried out first on the combustor and control valves. This was followed by development of the control subsystem including the controller, the hydrogen and oxygen control valves, the combustor, and a turbine simulator. The complete APU system was hot tested for 10 hr with ambient and cryogenic propellants. Demonstrated at 95 percent of design power was 2.25 lb/hp-hr. At 10 percent design power, specific propellant consumption was 4 lb/hp-hr with space simulated exhaust and 5.2 lb/hp-hr with ambient exhaust. A 10 percent specific propellant consumption improvement is possible with some seal modifications. It was demonstrated that APU power levels could be changed by several hundred horsepower in less than 100 msec without exceeding allowable turbine inlet temperatures or turbine speed.

1975-01-01

379

H2O-H2SO4 system in Venus' clouds and OCS, CO, and H2SO4 profiles in Venus' troposphere  

NASA Technical Reports Server (NTRS)

A coupled problem of diffusion and condensation is solved for the H2SO4-H2O system in Venus' cloud layer. The position of the lower cloud boundary, profiles of the H2O and H2SO vapor mixing ratios, and of the H2O/H2SO4 ratio of sulfuric acid aerosol and its flux are calculated as functions of the column photochemical production rate of sulfuric acid. Variations of the lower cloud boundary are considered. Our basic model, which is constrained to yield f(sub H2O)(30km) = 30 ppm, predicts the position of the lower cloud boundary at 48.4 km coinciding with the mean Pioneer Venus value, the peak H2SO4 mixing ratio of 5.4 ppm, and the H2SO4 production rate phi(sub H2SO4) = 2.2 x 10(exp 12) cm(exp -2)s(exp -1).

Krasnopolsky, V. A.; Pollack, J. B.

1994-01-01

380

Hydrogen effects on materials for CNG/H2 blends.  

SciTech Connect

No concerns for Hydrogen-Enriched Compressed Natural gas (HCNG) in steel storage tanks if material strength is < 950 MPa. Recommend evaluating H{sub 2}-assisted fatigue cracking in higher strength steels at H{sub 2} partial pressure in blend. Limited fatigue testing on higher strength steel cylinders in H{sub 2} shows promising results. Impurities in Compressed Natural Gas (CNG) (e.g., CO) may provide extrinsic mechanism for mitigating H{sub 2}-assisted fatigue cracking in steel tanks.

Farese, David (Air Products, USA); Keller, Jay O.; Somerday, Brian P.

2010-09-01

381

Direct detection of C4H2 photochemical products - Possible routes to complex hydrocarbons in planetary atmospheres  

NASA Technical Reports Server (NTRS)

The photochemistry of diacetylene (C4H2), the largest hydrocarbon to be unambiguously identified in planetary atmospheres, is of considerable importance to understanding the mechanisms by which complex molecules are formed in the solar system. In this work, the primary products of C4H2's ultraviolet photochemistry were determined in a two-laser pump-probe scheme in which the products of C4H2 photoexcitation are detected by vacuum ultraviolet photoionization in a time-of-flight mass spectrometer. Three larger hydrocarbon primary products were observed with good yield in the C4H2 + C4H2 reaction: C6H2, C8H2, and C8H3. Neither C6H2 or C8H3 is anticipated by current photochemical models of the atmospheres of Titan, Uranus, Neptune, Pluto, and Triton. The free hydrogen atoms that are released during the formation of the C8H3 and C8H2 products also may partially offset the role of C4H2 in catalyzing the recombination of free hydrogen atoms in the planetary atmospheres.

Bandy, Ralph E.; Lakshminarayan, Chitra; Frost, Rex K.; Zwier, Timothy S.

1992-01-01

382

H2AX: functional roles and potential applications  

PubMed Central

Upon DNA double-strand break (DSB) induction in mammals, the histone H2A variant, H2AX, becomes rapidly phosphorylated at serine 139. This modified form, termed ?-H2AX, is easily identified with antibodies and serves as a sensitive indicator of DNA DSB formation. This review focuses on the potential clinical applications of ?-H2AX detection in cancer and in response to other cellular stresses. In addition, the role of H2AX in homeostasis and disease will be discussed. Recent work indicates that ?-H2AX detection may become a powerful tool for monitoring genotoxic events associated with cancer development and tumor progression. PMID:19707781

Redon, Christophe E.; Nakamura, Asa