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

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

Uniform nursery stock of five almond cultivars [Prunus dulcis (Mill) D.A. Webb syn. P. amygdalus Batsch, cv. Butte, Carmel, Mission, Nonpareil, and Sonora] propagated on peach (P. domstica L. Batsch.) rootstock were exposed to three different atmospheric ozone (O[sub 3]) partial pressures. The trees were planted in open-top fumigation chambers on 19 Apr. 1989 at the University of California Kearny Agricultural Center located in the San Joaquin Valley of California. Exposures of the trees to three atmospheric O[sub 3] partial pressures lasted from 1 June to 2 Nov. 1989. The mean 12-h [0800-2000 h Pacific Daylight Time (PDT)] O[sub 3]more » partial pressures measured in the open-top chambers during the experimental period were 0.038, 0.060, and 0.112 [mu]Pa Pa[sup [minus]1] O[sub 3] in the charcoal filtered, ambient, and ambient + O[sub 3] treatments, respectively. Leaf net CO[sub 2] assimilation, trunk cross-sectional area growth, and root, trunk, foliage, and total dry weight of Nonpareil were reduced by increased atmospheric O[sub 3] partial pressures. Mission was unaffected by O[sub 3] and Butte, Carmel, and Sonora were intermediate in their responses. Foliage of Nonpareil also abscised prematurely in the ambient and ambient + O[sub 3] treatments. The results indicate that there are almond cultivars that are sensitive to O[sub 3] exposure.« less

Oxidation of C/SiC Composites at Reduced Oxygen Partial Pressures

NASA Technical Reports Server (NTRS)

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

2007-01-01

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

Oxygen partial pressure effects on the RF sputtered p-type NiO hydrogen gas sensors

NASA Astrophysics Data System (ADS)

Turgut, Erdal; Çoban, Ömer; Sarıtaş, Sevda; Tüzemen, Sebahattin; Yıldırım, Muhammet; Gür, Emre

2018-03-01

NiO thin films were grown by Radio Frequency (RF) Magnetron Sputtering method under different oxygen partial pressures, which are 0.6 mTorr, 1.3 mTorr and 2.0 mTorr. The effects of oxygen partial pressures on the thin films were analyzed through Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS) and Hall measurements. The change in the surface morphology of the thin films has been observed with the SEM and AFM measurements. While nano-pyramids have been obtained on the thin film grown at the lowest oxygen partial pressure, the spherical granules lower than 60 nm in size has been observed for the samples grown at higher oxygen partial pressures. The shift in the dominant XRD peak is realized to the lower two theta angle with increasing the oxygen partial pressures. XPS measurements showed that the Ni2p peak involves satellite peaks and two oxidation states of Ni, Ni2+ and Ni3+, have been existed together with the corresponding splitting in O1s spectrum. P-type conductivity of the grown NiO thin films are confirmed by the Hall measurements with concentrations on the order of 1013 holes/cm-3. Gas sensor measurements revealed minimum of 10% response to the 10 ppm H2 level. Enhanced responsivity of the gas sensor devices of NiO thin films is shown as the oxygen partial pressure increases.

Oxygen partial pressure sensor

DOEpatents

Dees, D.W.

1994-09-06

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

Oxygen partial pressure sensor

DOEpatents

Dees, Dennis W.

1994-01-01

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

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

2013-02-05

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

Effect of O 2 gas partial pressure on structures and dielectric characteristics of rf sputtered ZrO 2 thin films

NASA Astrophysics Data System (ADS)

Ma, C. Y.; Lapostolle, F.; Briois, P.; Zhang, Q. Y.

2007-08-01

Amorphous and polycrystalline zirconium oxide thin films have been deposited by reactive rf magnetron sputtering in a mixed argon/oxygen or pure oxygen atmosphere with no intentional heating of the substrate. The films were characterized by high-resolution transmission electron microscopy (HR-TEM), atomic force microscopy (AFM), spectroscopic ellipsometry (SE), and capacitance versus voltage ( C- V) measurements to investigate the variation of structure, surface morphology, thickness of SiO 2-like interfacial layer as well as dielectric characteristics with different oxygen partial pressures. The films deposited at low oxygen partial pressures (less than 15%) are amorphous and dense with a smooth surface. In contrast, the films prepared at an oxygen partial pressure higher than 73% are crystallized with the microstructure changing from the mixture of monoclinic and tetragonal phases to a single monoclinic structure. The film structural transition is believed to be consequences of decrease in the oxygen vacancy concentration in the film and of increase of the energetically neutral particles in the plasma due to an increased oxygen partial pressure. SE measurements showed that significant interfacial SiO 2 growth has taken place above approximately 51%. The best C- V results in terms of relative dielectric constant values are obtained for thin films prepared at an oxygen partial pressure of 15%.

Report on ISS O2 Production, Gas Supply and Partial Pressure Management

NASA Technical Reports Server (NTRS)

Schaezler, Ryan N.; Cook, Anthony J.

2015-01-01

Oxygen is used on International Space Station (ISS) for metabolic support and denitrogenation procedures prior to Extra-Vehicular Activities. Nitrogen is used to maintain total pressure and account for losses associated with leakage and operational losses. Oxygen and nitrogen have been supplied by various visiting vehicles such as the Progress and Shuttle in addition to the on-orbit oxygen production capability. Starting in 2014, new high pressure oxygen/nitrogen tanks are available to launch on commercial cargo vehicles and will replace the high pressure gas source that Shuttle used to provide. To maintain a habitable atmosphere the oxygen and nitrogen partial pressures are controlled between upper and lower bounds. The full range of the allowable partial pressures along with the increased ISS cabin volume are utilized as a buffer allowing days to pass between oxygen production or direct addition of oxygen and nitrogen to the atmosphere from reserves. This paper summarizes the amount of gas supplied and produced from all of the sources and describes past experience of managing partial pressures along with the range of management options available to the ISS.

Effects of oxygen partial pressure on Li-air battery performance

NASA Astrophysics Data System (ADS)

Kwon, Hyuk Jae; Lee, Heung Chan; Ko, Jeongsik; Jung, In Sun; Lee, Hyun Chul; Lee, Hyunpyo; Kim, Mokwon; Lee, Dong Joon; Kim, Hyunjin; Kim, Tae Young; Im, Dongmin

2017-10-01

For application in electric vehicles (EVs), the Li-air battery system needs an air intake system to supply dry oxygen at controlled concentration and feeding rate as the cathode active material. To facilitate the design of such air intake systems, we have investigated the effects of oxygen partial pressure (≤1 atm) on the performance of the Li-air cell, which has not been systematically examined. The amounts of consumed O2 and evolved CO2 from the Li-air cell are measured with a custom in situ differential electrochemical gas chromatography-mass spectrometry (DEGC-MS). The amounts of consumed O2 suggest that the oxygen partial pressure does not affect the reaction mechanism during discharge, and the two-electron reaction occurs under all test conditions. On the other hand, the charging behavior varies by the oxygen partial pressure. The highest O2 evolution ratio is attained under 70% O2, along with the lowest CO2 evolution. The cell cycle life also peaks at 70% O2 condition. Overall, an oxygen partial pressure of about 0.5-0.7 atm maximizes the Li-air cell capacity and stability at 1 atm condition. The findings here indicate that the appropriate oxygen partial pressure can be a key factor when developing practical Li-air battery systems.

Influence of N2 partial pressure on structural and microhardness properties of TiN/ZrN multilayers deposited by Ar/N2 vacuum arc discharge

NASA Astrophysics Data System (ADS)

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

2016-08-01

The influence of N2 partial pressure on structural, mechanical and wetting properties of multilayered TiN/ZrN thin films deposited on silicon substrates by vacuum arc discharge of (N2 + Ar) gas mixtures is investigated. X-ray diffraction (XRD) results show that the average texturing coefficient of (1 1 1) orientation and the grain size of both TiN and ZrN individual layers increase with increasing the N2 partial pressure. The Rutherford back scattering (RBS) measurements and analysis reveal that incorporation of the nitrogen in the film increases with increasing the N2 partial pressure and both TiN and ZrN individual layers have a nitrogen over-stoichiometry for N2 partial pressure ⩾50%. The change in the film micro-hardness is correlated to the changes in crystallographic texture, grain size, stoichiometry and the residual stress in the film as a function of the N2 partial pressure. In particular, stoichiometry of ZrN and TiN individual is found to play the vital role in determining the multilayer hardness. The multilayer film deposited at N2 partial pressure of 25% has the best stoichiometric ratio of both TiN and ZrN layers and the highest micro-hardness of about 32 GPa. In addition, water contact angle (WCA) measurements and analysis show a decrease in the work of adhesion on increasing the N2 partial pressure.

Growth responses of Neurospora crassa to increased partial pressures of the noble gases and nitrogen.

PubMed

Buchheit, R G; Schreiner, H R; Doebbler, G F

1966-02-01

Buchheit, R. G. (Union Carbide Corp., Tonawanda, N.Y.), H. R. Schreiner, and G. F. Doebbler. Growth responses of Neurospora crassa to increased partial pressures of the noble gases and nitrogen. J. Bacteriol. 91:622-627. 1966.-Growth rate of the fungus Neurospora crassa depends in part on the nature of metabolically "inert gas" present in its environment. At high partial pressures, the noble gas elements (helium, neon, argon, krypton, and xenon) inhibit growth in the order: Xe > Kr> Ar > Ne > He. Nitrogen (N(2)) closely resembles He in inhibitory effectiveness. Partial pressures required for 50% inhibition of growth were: Xe (0.8 atm), Kr (1.6 atm), Ar (3.8 atm), Ne (35 atm), and He ( approximately 300 atm). With respect to inhibition of growth, the noble gases and N(2) differ qualitatively and quantitatively from the order of effectiveness found with other biological effects, i.e., narcosis, inhibition of insect development, depression of O(2)-dependent radiation sensitivity, and effects on tissue-slice glycolysis and respiration. Partial pressures giving 50% inhibition of N. crassa growth parallel various physical properties (i.e., solubilities, solubility ratios, etc.) of the noble gases. Linear correlation of 50% inhibition pressures to the polarizability and of the logarithm of pressure to the first and second ionization potentials suggests the involvement of weak intermolecular interactions or charge-transfer in the biological activity of the noble gases.

Comparative ecology of H2 cycling in sedimentary and phototrophic ecosystems

NASA Technical Reports Server (NTRS)

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

2002-01-01

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

Calculational and Experimental Investigations of the Pressure Effects on Radical - Radical Cross Combinations Reactions: C2H5 + C2H3

NASA Technical Reports Server (NTRS)

Fahr, Askar; Halpern, Joshua B.; Tardy, Dwight C.

2007-01-01

Pressure-dependent product yields have been experimentally determined for the cross-radical reaction C2H5 + C2H3. These results have been extended by calculations. It is shown that the chemically activated combination adduct, 1-C4H8*, is either stabilized by bimolecular collisions or subject to a variety of unimolecular reactions including cyclizations and decompositions. Therefore the "apparent" combination/disproportionation ratio exhibits a complex pressure dependence. The experimental studies were performed at 298 K and at selected pressures between about 4 Torr (0.5 kPa) and 760 Torr (101 kPa). Ethyl and vinyl radicals were simultaneously produced by 193 nm excimer laser photolysis of C2H5COC2H3 or photolysis of C2H3Br and C2H5COC2H5. Gas chromatograph/mass spectrometry/flame ionization detection (GC/MS/FID) were used to identify and quantify the final reaction products. The major combination reactions at pressures between 500 (66.5 kPa) and 760 Torr are (1c) C2H5 + C2H3 yields 1-butene, (2c) C2H5 + C2H5 yields n-butane, and (3c) C2H3 + C2H3 yields 1,3-butadiene. The major products of the disproportionation reactions are ethane, ethylene, and acetylene. At moderate and lower pressures, secondary products, including propene, propane, isobutene, 2-butene (cis and trans), 1-pentene, 1,4-pentadiene, and 1,5-hexadiene are also observed. Two isomers of C4H6, cyclobutene and/or 1,2-butadiene, were also among the likely products. The pressure-dependent yield of the cross-combination product, 1-butene, was compared to the yield of n-butane, the combination product of reaction (2c), which was found to be independent of pressure over the range of this study. The [ 1-C4H8]/[C4H10] ratio was reduced from approx.1.2 at 760 Torr (101 kPa) to approx.0.5 at 100 Torr (13.3 kPa) and approx.0.1 at pressures lower than about 5 Torr (approx.0.7 kPa). Electronic structure and RRKM calculations were used to simulate both unimolecular and bimolecular processes. The relative importance

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

NASA Technical Reports Server (NTRS)

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

1994-01-01

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

Growth Responses of Neurospora crassa to Increased Partial Pressures of the Noble Gases and Nitrogen

PubMed Central

Buchheit, R. G.; Schreiner, H. R.; Doebbler, G. F.

1966-01-01

Buchheit, R. G. (Union Carbide Corp., Tonawanda, N.Y.), H. R. Schreiner, and G. F. Doebbler. Growth responses of Neurospora crassa to increased partial pressures of the noble gases and nitrogen. J. Bacteriol. 91:622–627. 1966.—Growth rate of the fungus Neurospora crassa depends in part on the nature of metabolically “inert gas” present in its environment. At high partial pressures, the noble gas elements (helium, neon, argon, krypton, and xenon) inhibit growth in the order: Xe > Kr> Ar ≫ Ne ≫ He. Nitrogen (N2) closely resembles He in inhibitory effectiveness. Partial pressures required for 50% inhibition of growth were: Xe (0.8 atm), Kr (1.6 atm), Ar (3.8 atm), Ne (35 atm), and He (∼ 300 atm). With respect to inhibition of growth, the noble gases and N2 differ qualitatively and quantitatively from the order of effectiveness found with other biological effects, i.e., narcosis, inhibition of insect development, depression of O2-dependent radiation sensitivity, and effects on tissue-slice glycolysis and respiration. Partial pressures giving 50% inhibition of N. crassa growth parallel various physical properties (i.e., solubilities, solubility ratios, etc.) of the noble gases. Linear correlation of 50% inhibition pressures to the polarizability and of the logarithm of pressure to the first and second ionization potentials suggests the involvement of weak intermolecular interactions or charge-transfer in the biological activity of the noble gases. PMID:5883104

Stable solid and aqueous H2CO3 from CO2 and H2O at high pressure and high temperature

NASA Astrophysics Data System (ADS)

Wang, Hongbo; Zeuschner, Janek; Eremets, Mikhail; Troyan, Ivan; Willams, Jonathan

2016-01-01

Carbonic acid (H2CO3) forms in small amounts when CO2 dissolves in H2O, yet decomposes rapidly under ambient conditions of temperature and pressure. Despite its fleeting existence, H2CO3 plays an important role in the global carbon cycle and in biological carbonate-containing systems. The short lifetime in water and presumed low concentration under all terrestrial conditions has stifled study of this fundamental species. Here, we have examined CO2/H2O mixtures under conditions of high pressure and high temperature to explore the potential for reaction to H2CO3 inside celestial bodies. We present a novel method to prepare solid H2CO3 by heating CO2/H2O mixtures at high pressure with a CO2 laser. Furthermore, we found that, contrary to present understanding, neutral H2CO3 is a significant component in aqueous CO2 solutions above 2.4 GPa and 110 °C as identified by IR-absorption and Raman spectroscopy. This is highly significant for speciation of deep C-O-H fluids with potential consequences for fluid-carbonate-bearing rock interactions. As conditions inside subduction zones on Earth appear to be most favorable for production of aqueous H2CO3, a role in subduction related phenomena is inferred.

Stable solid and aqueous H2CO3 from CO2 and H2O at high pressure and high temperature

PubMed Central

Wang, Hongbo; Zeuschner, Janek; Eremets, Mikhail; Troyan, Ivan; Willams, Jonathan

2016-01-01

Carbonic acid (H2CO3) forms in small amounts when CO2 dissolves in H2O, yet decomposes rapidly under ambient conditions of temperature and pressure. Despite its fleeting existence, H2CO3 plays an important role in the global carbon cycle and in biological carbonate-containing systems. The short lifetime in water and presumed low concentration under all terrestrial conditions has stifled study of this fundamental species. Here, we have examined CO2/H2O mixtures under conditions of high pressure and high temperature to explore the potential for reaction to H2CO3 inside celestial bodies. We present a novel method to prepare solid H2CO3 by heating CO2/H2O mixtures at high pressure with a CO2 laser. Furthermore, we found that, contrary to present understanding, neutral H2CO3 is a significant component in aqueous CO2 solutions above 2.4 GPa and 110 °C as identified by IR-absorption and Raman spectroscopy. This is highly significant for speciation of deep C–O–H fluids with potential consequences for fluid-carbonate-bearing rock interactions. As conditions inside subduction zones on Earth appear to be most favorable for production of aqueous H2CO3, a role in subduction related phenomena is inferred. PMID:26813580

Stable solid and aqueous H2CO3 from CO2 and H2O at high pressure and high temperature.

PubMed

Wang, Hongbo; Zeuschner, Janek; Eremets, Mikhail; Troyan, Ivan; Willams, Jonathan

2016-01-27

Carbonic acid (H2CO3) forms in small amounts when CO2 dissolves in H2O, yet decomposes rapidly under ambient conditions of temperature and pressure. Despite its fleeting existence, H2CO3 plays an important role in the global carbon cycle and in biological carbonate-containing systems. The short lifetime in water and presumed low concentration under all terrestrial conditions has stifled study of this fundamental species. Here, we have examined CO2/H2O mixtures under conditions of high pressure and high temperature to explore the potential for reaction to H2CO3 inside celestial bodies. We present a novel method to prepare solid H2CO3 by heating CO2/H2O mixtures at high pressure with a CO2 laser. Furthermore, we found that, contrary to present understanding, neutral H2CO3 is a significant component in aqueous CO2 solutions above 2.4 GPa and 110 °C as identified by IR-absorption and Raman spectroscopy. This is highly significant for speciation of deep C-O-H fluids with potential consequences for fluid-carbonate-bearing rock interactions. As conditions inside subduction zones on Earth appear to be most favorable for production of aqueous H2CO3, a role in subduction related phenomena is inferred.

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

PubMed

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

2009-11-04

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).

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

USGS Publications Warehouse

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

2012-01-01

The authors tested the efficacy of elevated partial pressures of CO2 to kill invasive New Zealand mudsnails. The New Zealand mudsnails were exposed to 100 kPa at three water temperatures, and the survival was modeled versus dose as cumulative °C-h. We estimated an LD50 of 59.4°C-h for adult and juvenile New Zealand mudsnails. The results suggest that CO2 may be an effective and inexpensive lethal tool to treat substrates, tanks, or materials infested with New Zealand mudsnails.

Comparative Ecology of H2 Cycling in Organotrophic and Phototrophic Ecosystems

NASA Technical Reports Server (NTRS)

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

2001-01-01

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

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

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Indwelling blood carbon dioxide partial pressure (PCO2) analyzer. 868.1150 Section 868.1150 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF... “Class II Special Controls Guidance Document: Indwelling Blood Gas Analyzers; Final Guidance for Industry...

Density functional theory study of 3R- and 2H-CuAlO2 under pressure

NASA Astrophysics Data System (ADS)

Liu, Qi-Jun; Liu, Zheng-Tang; Feng, Li-Ping; Tian, Hao; Liu, Wen-Ting; Yan, Feng

2010-10-01

We present a first-principles density-functional theory based study of the impact of pressure on the structural and elastic properties of bulk 3R- and 2H-CuAlO2. The ground state properties of 3R- and 2H-CuAlO2 are obtained, which are in good agreement with previous experimental and theoretical data. The analysis of enthalpy variation with pressure indicates the phase transition pressure between 3R and 2H is 15.4 GPa. The independent elastic constants of 3R- and 2H-CuAlO2 are calculated. As the applied pressure increases, the calculations show the presences of mechanical instability at 26.2 and 27.8 GPa for 3R- and 2H-CuAlO2, which are possibly related with the phase transitions.

Effect of CO2 partial pressure and different CO2 phases on carbon steel corrosion

NASA Astrophysics Data System (ADS)

Mahlobo, MGR; Premlall, K.; Olubambi, PA

2017-12-01

Carbon capture and storage (CCS) is the recent promising technology aimed at reducing greenhouse gas emission. Like many other developed technologies, CCS is faced with great challenges such as pipeline transportation failure due to corrosion. There are many factors contributing to steel corrosion during the pipeline transportation of carbon dioxide (CO2). This study focuses on CO2 partial pressure and different phases of CO2 as some of the factors contributing to steel corrosion. Carbon steel was used as a testing specimen. High pressure reactor was used in this study to compress CO2 from low to high pressures ultimately changing the CO2 from gaseous phase to gas/liquid phase (subcritical) and to dense phase (supercritical). Weight loss method was employed to determine the corrosion rate while scanning electron microscopy (SEM) and X-Ray diffraction (XRD) were used to study the carbon steel morphology and phase analysis. Using low magnification digital camera, the type of corrosion that took place on the carbon steel surface was identified.

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

NASA Astrophysics Data System (ADS)

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

2013-03-01

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

Thin film devices used as oxygen partial pressure sensors

NASA Technical Reports Server (NTRS)

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

1970-01-01

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

Chemistry through cocrystals: pressure-induced polymerization of C 2H 2·C 6H 6 to an extended crystalline hydrocarbon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ward, Matthew D.; Huang, Haw-Tyng; Zhu, Li

The 1:1 acetylene–benzene cocrystal, C 2H 2·C 6H 6, was synthesized under pressure in a diamond anvil cell (DAC) and its evolution under pressure was studied with single-crystal X-ray diffraction and Raman spectroscopy.

Chemistry through cocrystals: pressure-induced polymerization of C 2H 2·C 6H 6 to an extended crystalline hydrocarbon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ward, Matthew D.; Huang, Haw-Tyng; Zhu, Li

The 1 : 1 acetylene–benzene cocrystal, C 2H 2·C 6H 6, was synthesized under pressure in a diamond anvil cell (DAC) and its evolution under pressure was studied with single-crystal X-ray diffraction and Raman spectroscopy.

High pressure Raman spectroscopy of H2O-CH3OH mixtures.

PubMed

Hsieh, Wen-Pin; Chien, Yu-Hsiang

2015-02-23

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

Thin film oxygen partial pressure sensor

NASA Technical Reports Server (NTRS)

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

1972-01-01

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

Thermal Pressure in Diffuse H2 Gas Measured by Herschel [C II] Emission and FUSE UV H2 Absorption

NASA Astrophysics Data System (ADS)

Velusamy, T.; Langer, W. D.; Goldsmith, P. F.; Pineda, J. L.

2017-04-01

UV absorption studies with the Far Ultraviolet Spectroscopic Explorer (FUSE) satellite have made important observations of H2 molecular gas in Galactic interstellar translucent and diffuse clouds. Observations of the 158 μm [C II] fine-structure line with Herschel trace the same H2 molecular gas in emission. We present [C II] observations along 27 lines of sight (LOSs) toward target stars of which 25 have FUSE H2 UV absorption. Two stars have only HST STIS C II λ2325 absorption data. We detect [C II] 158 μm emission features in all but one target LOS. For three target LOSs that are close to the Galactic plane, | {\\text{}}b| < 1°, we also present position-velocity maps of [C II] emission observed by Herschel Heterodyne Instrument in the Far Infrared (HIFI) in on-the-fly spectral-line mapping. We use the velocity-resolved [C II] spectra observed by the HIFI instrument toward the target LOSs observed by FUSE to identify [C II] velocity components associated with the H2 clouds. We analyze the observed velocity integrated [C II] spectral-line intensities in terms of the densities and thermal pressures in the H2 gas using the H2 column densities and temperatures measured by the UV absorption data. We present the H2 gas densities and thermal pressures for 26 target LOSs and from the [C II] intensities derive a mean thermal pressure in the range of ˜6100-7700 K cm-3 in diffuse H2 clouds. We discuss the thermal pressures and densities toward 14 targets, comparing them to results obtained using the UV absorption data for two other tracers C I and CO. Our results demonstrate the richness of the far-IR [C II] spectral data which is a valuable complement to the UV H2 absorption data for studying diffuse H2 molecular clouds. While the UV absorption is restricted to the directions of the target star, far-IR [C II] line emission offers an opportunity to employ velocity-resolved spectral-line mapping capability to study in detail the clouds’ spatial and velocity structures.

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

NASA Technical Reports Server (NTRS)

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

1984-01-01

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

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

NASA Technical Reports Server (NTRS)

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

1992-01-01

A novel pressurized partial melt growth process has been developed for producing large pieces of bulk Y-Ba-Cu-O superconductors. During long-time partial melt growth stage, an additional driving force for solidification is obtained by using pressurized oxygen gas. The microstructure and superconducting properties of the resulting samples were investigated. It was found that this new technique can eliminate porosity and inhomogeneity, promote large-scale grain-texturing, and improve interdomain coupling as well.

Single-component and binary CO2 and H2O adsorption of amine-functionalized cellulose.

PubMed

Gebald, Christoph; Wurzbacher, Jan A; Borgschulte, Andreas; Zimmermann, Tanja; Steinfeld, Aldo

2014-02-18

A fundamental analysis of single-component and binary CO2 and H2O adsorption of amine-functionalized nanofibrillated cellulose is carried out in the temperature range of 283-353 K and at CO2 partial pressures in the range of 0.02-105 kPa, where the ultralow partial pressure range is relevant for the direct capture of CO2 from atmospheric air. Single-component CO2 and H2O adsorption experimental data are fitted to the Toth and Guggenheim-Anderson-de Boer models, respectively. Corresponding heats of adsorption, derived from explicit solutions of the van't Hoff equation, are -50 kJ/mol CO2 and -48.8 kJ/mol H2O. Binary CO2/H2O adsorption measurements for humid air reveal that the presence of H2O at 2.55 kPa enhances CO2 adsorption, while the presence of CO2 at 0.045 kPa does not influence H2O adsorption. The energy demand of the temperature-vacuum-swing adsorption/desorption cycle for delivering pure CO2 from air increases significantly with H2O adsorption and indicates the need to reduce the hygroscopicity of the adsorbent.

Gamma-H2AX-based dose estimation for whole and partial body radiation exposure.

PubMed

Horn, Simon; Barnard, Stephen; Rothkamm, Kai

2011-01-01

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

Precise predictions of H2O line shapes over a wide pressure range using simulations corrected by a single measurement

NASA Astrophysics Data System (ADS)

Ngo, N. H.; Nguyen, H. T.; Tran, H.

2018-03-01

In this work, we show that precise predictions of the shapes of H2O rovibrational lines broadened by N2, over a wide pressure range, can be made using simulations corrected by a single measurement. For that, we use the partially-correlated speed-dependent Keilson-Storer (pcsdKS) model whose parameters are deduced from molecular dynamics simulations and semi-classical calculations. This model takes into account the collision-induced velocity-changes effects, the speed dependences of the collisional line width and shift as well as the correlation between velocity and internal-state changes. For each considered transition, the model is corrected by using a parameter deduced from its broadening coefficient measured for a single pressure. The corrected-pcsdKS model is then used to simulate spectra for a wide pressure range. Direct comparisons of the corrected-pcsdKS calculated and measured spectra of 5 rovibrational lines of H2O for various pressures, from 0.1 to 1.2 atm, show very good agreements. Their maximum differences are in most cases well below 1%, much smaller than residuals obtained when fitting the measurements with the Voigt line shape. This shows that the present procedure can be used to predict H2O line shapes for various pressure conditions and thus the simulated spectra can be used to deduce the refined line-shape parameters to complete spectroscopic databases, in the absence of relevant experimental values.

Photosynthetic induction and its diffusional, carboxylation and electron transport processes as affected by CO2 partial pressure, temperature, air humidity and blue irradiance.

PubMed

Kaiser, Elias; Kromdijk, Johannes; Harbinson, Jeremy; Heuvelink, Ep; Marcelis, Leo F M

2017-01-01

Plants depend on photosynthesis for growth. In nature, factors such as temperature, humidity, CO 2 partial pressure, and spectrum and intensity of irradiance often fluctuate. Whereas irradiance intensity is most influential and has been studied in detail, understanding of interactions with other factors is lacking. We tested how photosynthetic induction after dark-light transitions was affected by CO 2 partial pressure (20, 40, 80 Pa), leaf temperatures (15·5, 22·8, 30·5 °C), leaf-to-air vapour pressure deficits (VPD leaf-air ; 0·5, 0·8, 1·6, 2·3 kPa) and blue irradiance (0-20 %) in tomato leaves (Solanum lycopersicum). Rates of photosynthetic induction strongly increased with CO 2 partial pressure, due to increased apparent Rubisco activation rates and reduced diffusional limitations. High leaf temperature produced slightly higher induction rates, and increased intrinsic water use efficiency and diffusional limitation. High VPD leaf-air slowed down induction rates and apparent Rubisco activation and (at 2·3 kPa) induced damped stomatal oscillations. Blue irradiance had no effect. Slower apparent Rubisco activation in elevated VPD leaf-air may be explained by low leaf internal CO 2 partial pressure at the beginning of induction. The environmental factors CO 2 partial pressure, temperature and VPD leaf-air had significant impacts on rates of photosynthetic induction, as well as on underlying diffusional, carboxylation and electron transport processes. Furthermore, maximizing Rubisco activation rates would increase photosynthesis by at most 6-8 % in ambient CO 2 partial pressure (across temperatures and humidities), while maximizing rates of stomatal opening would increase photosynthesis by at most 1-3 %. © The Author 2016. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

A Thermodynamic Approach for Modeling H2O-CO2 Solubility in Alkali-rich Mafic Magmas at Mid-crustal Pressures

NASA Astrophysics Data System (ADS)

Allison, C. M.; Roggensack, K.; Clarke, A. B.

2017-12-01

Volatile solubility in magmas is dependent on several factors, including composition and pressure. Mafic (basaltic) magmas with high concentrations of alkali elements (Na and K) are capable of dissolving larger quantities of H2O and CO2 than low-alkali basalt. The exsolution of abundant gases dissolved in alkali-rich mafic magmas can contribute to large explosive eruptions. Existing volatile solubility models for alkali-rich mafic magmas are well calibrated below 200 MPa, but at greater pressures the experimental data is sparse. To allow for accurate interpretation of mafic magmatic systems at higher pressures, we conducted a set of mixed H2O-CO2 volatile solubility experiments between 400 and 600 MPa at 1200 °C in six mafic compositions with variable alkali contents. Compositions include magmas from volcanoes in Italy, Antarctica, and Arizona. Results from our experiments indicate that existing volatile solubility models for alkali-rich mafic magmas, if extrapolated beyond their calibrated range, over-predict CO2 solubility at mid-crustal pressures. Physically, these results suggest that volatile exsolution can occur at deeper levels than what can be resolved from the lower-pressure experimental data. Existing thermodynamic models used to calculate volatile solubility at different pressures require two experimentally derived parameters. These parameters represent the partial molar volume of the condensed volatile species in the melt and its equilibrium constant, both calculated at a standard temperature and pressure. We derived these parameters for each studied composition and the corresponding thermodynamic model shows good agreement with the CO2 solubility data of the experiments. A general alkali basalt solubility model was also constructed by establishing a relationship between magma composition and the thermodynamic parameters. We utilize cation fractions from our six compositions along with four compositions from the experimental literature in a linear

Hydrogen effects on materials for CNG/H2 blends.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Farese, David; Keller, Jay O.; Somerday, Brian P.

2010-09-01

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.

Experimental investigation on thermochemical sulfate reduction by H2S initiation

USGS Publications Warehouse

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

2008-01-01

Hydrogen sulfide (H2S) is known to catalyze thermochemical sulfate reduction (TSR) by hydrocarbons (HC), but the reaction mechanism remains unclear. To understand the mechanism of this catalytic reaction, a series of isothermal gold-tube hydrous pyrolysis experiments were conducted at 330 ??C for 24 h under a constant confining pressure of 24.1 MPa. The reactants used were saturated HC (sulfur-free) and CaSO4 in the presence of variable H2S partial pressures at three different pH conditions. The experimental results showed that the in-situ pH of the aqueous solution (herein, in-situ pH refers to the calculated pH of aqueous solution under the experimental conditions) can significantly affect the rate of the TSR reaction. A substantial increase in the TSR reaction rate was recorded with a decrease in the in-situ pH value of the aqueous solution involved. A positive correlation between the rate of TSR and the initial partial pressure of H2S occurred under acidic conditions (at pH ???3-3.5). However, sulfate reduction at pH ???5.0 was undetectable even at high initial H2S concentrations. To investigate whether the reaction of H2S(aq) and HSO4- occurs at pH ???3, an additional series of isothermal hydrous pyrolysis experiments was conducted with CaSO4 and variable H2S partial pressures in the absence of HC at the same experimental temperature and pressure conditions. CaSO4 reduction was not measurable in the absence of paraffin even with high H2S pressure and acidic conditions. These experimental observations indicate that the formation of organosulfur intermediates from H2S reacting with hydrocarbons may play a significant role in sulfate reduction under our experimental conditions rather than the formation of elemental sulfur from H2S reacting with sulfate as has been suggested previously (Toland W. G. (1960) Oxidation of organic compounds with aqueous sulphate. J. Am. Chem. Soc. 82, 1911-1916). Quantification of labile organosulfur compounds (LSC), such as thiols

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

NASA Technical Reports Server (NTRS)

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

1997-01-01

Recent results from a thermodynamic model of aqueous sulfuric acid are used to derive a new parameterization for the variation of sulfuric acid aerosol composition with temperature and relative humidity. This formulation is valid for relative humidities above 1 % in the temperature range of 185 to 260 K. An expression for calculating the vapor pressure of supercooled liquid water, consistent with the sulfuric acid model, is also presented. We show that the Steele and Hamill [1981] formulation underestimates the water partial pressure over aqueous H2SOI solutions by up to 12% at low temperatures. This difference results in a corresponding underestimate of the H2SO4 concentration in the aerosol by about 6 % of the weight percent at approximately 190 K. In addition, the relation commonly used for estimating the vapor pressure of H2O over supercooled liquid water differs by up to 10 % from our derived expression. The combined error can result in a 20 % underestimation of water activity over a H2SO4 solution droplet in the stratosphere, which has implications for the parameterization of heterogeneous reaction rates in stratospheric sulfuric acid aerosols. The influence of aerosol composition on the rate of homogeneous ice nucleation from a H2SO4 solution droplet is also discussed. This parameterization can also be used for homogeneous gas phase nucleation calculations of H2SO4 solution droplets under various environmental conditions such as in aircraft exhaust or in volcanic plumes.

[Bio-electrochemical effect on hydrogenotrophic sulfate reduction stimulated by electrical field in the presence of H2 under atmospheric pressure].

PubMed

Xu, Hui-Wei; Zhang, Xu; Yang, Shan-Shan; Li, Guang-He

2009-07-15

Microbial sulfate reduction rate is limited with H2 as electron donor. In order to improve hydrogenotrophic sulfate reduction under normal atmospheric H2 pressure, a bio-electrochemical system with direct current was designed and performed in this study. Results indicates that sulfate reduction rate (SRR) increases with the augment of current intensity under lower current intensity (I < or = 1.50 mA). When optimum current intensity of 1.50 mA is applied, the SRR is 1.7 to 2.1 times higher than that of the control reactor. The synergistic effect of electrochemistry and microbiology on sulfate reduction varies at different current intensity. Under the condition of I < or = 1.50 mA, the most probable mechanism of SRR increase is that electric or magnetic field stimulates the proliferation of sulfate-reducing bacteria (SRB) and the activity of the enzymes. When I is higher than 1.50 mA, the activity of SRB is inhibited, resulting in lower reduction rate compared with that at lower current. If controlling the cathode potential lower than -0.69 V and H2 partial pressure 1.01 x 10(5) Pa, electro-catalytic sulfate reduction process takes place with H2 as reductant in this bio-electrochemical system. However, the overall reduction rate is still lower than that when I = 1.50 mA is applied, and additionally the energy consumption is much higher. Therefore, electric field of low intensity can enhance hydrogenotrophic sulfate reduction in the presence of H2 under atmospheric pressure.

Spatial and Temporal Variations in the Partial Pressure and Emission of CO2 and CH4 in and Amazon Floodplain Lake

NASA Astrophysics Data System (ADS)

Forsberg, B. R.; Amaral, J. H.; Barbosa, P.; Kasper, D.; MacIntyre, S.; Cortes, A.; Sarmento, H.; Borges, A. V.; Melack, J. M.; Farjalla, V.

2015-12-01

The Amazon floodplain contains a variety of wetland environments which contribute CO2 and CH4 to the regional and global atmospheres. The partial pressure and emission of these greenhouse gases (GHGs) varies: 1) between habitats, 2) seasonally, as the characteristics these habitats changes and 3) diurnally, in response to diurnal stratification. In this study, we investigated the combined influence of these factors on the partial pressure and emission of GHGs in Lago Janauacá, a central Amazon floodplain lake (3o23' S; 60o18' O). All measurements were made between August of 2014 and April of 2015 at two different sites and in three distinct habitats: open water, flooded forest, flooded macrophytes. Concentrations of CO2 and CH4 in air were measured continuously with a cavity enhanced absorption spectrometer, Los Gatos Research´s Ultraportable Greenhouse Gas Analyzer (UGGA). Vertical profiles o pCO2 and pCH4 were measured using the UGGA connected to an electric pump and equilibrator. Diffusive surface emissions were estimated with the UGGA connected to a static floating chamber. To investigate the influence of vertical stratification and mixing on GHG partial pressure and emissions, a meteorological station and submersible sensor chain were deployed at each site. Meteorological sensors included wind speed and direction. The submersible chains included thermistors and oxygen sensors. Depth profiles of partial pressure and diffusive emissions for both CO2 and CH4 varied diurnally, seasonally and between habitats. Both pCO2 and pCH4 were consistently higher in bottom than surface waters with the largest differences occurring at high water when thermal stratification was most stable. Methane emissions and partial pressures were highest at low water while pCO2 and CO2 fluxes were highest during high water periods, with 35% of CO2 fluxes at low water being negative. The highest average surface value of pCO2 (5491 μatm), encountered during rising water, was ~3 times

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

NASA Astrophysics Data System (ADS)

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

2011-12-01

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

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

PubMed

Hoseini, Mohammad; Nabizadeh, Ramin; Nazmara, Shahrokh; Safari, Gholam Hossein

2013-12-20

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

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

PubMed Central

2013-01-01

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

X-ray-induced dissociation of H.sub.2O and formation of an O.sub.2-H.sub.2 alloy at high pressure

DOEpatents

Mao, Ho-kwang [Washington, DC; Mao, Wendy L [Washington, DC

2011-11-29

A novel molecular alloy of O.sub.2 and H.sub.2 and a method of producing such a molecular alloy are provided. When subjected to high pressure and extensive x-radiation, H.sub.2O molecules cleaved, forming O--O and H--H bonds. In the method of the present invention, the O and H framework in ice VII was converted into a molecular alloy of O.sub.2 and H.sub.2. X-ray diffraction, x-ray Raman scattering, and optical Raman spectroscopy demonstrate that this crystalline solid differs from previously known phases.

Phase development in the Bi 2Sr 2CaCu 2O y system . Effects of oxygen pressure

NASA Astrophysics Data System (ADS)

List, F. A.; Hsu, H.; Cavin, O. B.; Porter, W. D.; Hubbard, C. R.; Kroeger, D. M.

1992-11-01

Studies have been undertaken using thermal analysis, in conjunction with high-temperature and room temperature X-ray diffraction, fraction, to elucidate phase relationships during thermal processing of thick films of initially phase pure Bi 2Sr 2CaCu 2O y (2212) on silver substrates in various oxygen-containing atmospheres (0.001 to 100% O 2). Exothermic events on cooling at 10°C/min from a partially liquid state vary with oxygen partial pressure and can be grouped into three sets (I-III). Set I is prominent for 0.001% and 0.1% O 2 in the range of 740-775°C and is believed to be associated with the crystallization of a Cu-free ∼ Bi 5Sr 3Ca 1 oxide phase. Set II results from the crystallization of 2212; it is observed for p(O 2)≥1.0% in the temperature range 800-870°C. Set III appears for 21% and 100% O 2 in the temperature range 880-910°C, and its origin is not clear from the results of this study. Subsequent room temperature X-ray diffraction from these samples suggests that in general high oxygen partial pressures (100% O 2) tend to favor the formation of Bi 2Sr 2CuO 6 (2201), whereas low oxygen partial pressures (0.001-0.1% O 2) lead to the formation of a Cu-free, Bi-Sr-Ca oxide phase. The 2212 phase forms at this cooling rate predominantly for intermediate oxygen partial pressures (7.6-21% O 2). High-temperature X-ray diffraction during cooling (2°C/h) from the partially liquid state shows a pronounced dependence of the order of evolution of crystalline 2212 and 2201 phases on p(O 2). For an oxygen partial pressure of 1.0% the formation of 2212 precedes that of 2201, whereas for 0.01% O 2 2201 crystallizes at a higher temperature than 2212. The implications of these results pertaining to thermal processing of thick 2212 films are discussed.

Biodosimetry Based on γ-H2AX Quantification and Cytogenetics after Partial- and Total-Body Irradiation during Fractionated Radiotherapy.

PubMed

Zahnreich, Sebastian; Ebersberger, Anne; Kaina, Bernd; Schmidberger, Heinz

2015-04-01

The aim of this current study was to quantitatively describe radiation-induced DNA damage and its distribution in leukocytes of cancer patients after fractionated partial- or total-body radiotherapy. Specifically, the impact of exposed anatomic region and administered dose was investigated in breast and prostate cancer patients receiving partial-body radiotherapy. DNA double-strand breaks (DSBs) were quantified by γ-H2AX immunostaining. The frequency of unstable chromosomal aberrations in stimulated lymphocytes was also determined and compared with the frequency of DNA DSBs in the same samples. The frequency of radiation-induced DNA damage was converted into dose, using ex vivo generated calibration curves, and was then compared with the administered physical dose. This study showed that 0.5 h after partial-body radiotherapy the quantity of radiation-induced γ-H2AX foci increased linearly with the administered equivalent whole-body dose for both tumor entities. Foci frequencies dropped 1 day thereafter but proportionality to the equivalent whole-body dose was maintained. Conversely, the frequency of radiation-induced cytogenetic damage increased from 0.5 h to 1 day after the first partial-body exposure with a linear dependence on the administered equivalent whole-body dose, for prostate cancer patients only. Only γ-H2AX foci assessment immediately after partial-body radiotherapy was a reliable measure of the expected equivalent whole-body dose. Local tumor doses could be approximated with both assays after one day. After total-body radiotherapy satisfactory dose estimates were achieved with both assays up to 8 h after exposure. In conclusion, the quantification of radiation-induced γ-H2AX foci, but not cytogenetic damage in peripheral leukocytes was a sensitive and rapid biodosimeter after acute heterogeneous irradiation of partial body volumes that was able to primarily assess the absorbed equivalent whole-body dose.

Superconducting H5S2 phase in sulfur-hydrogen system under high-pressure

NASA Astrophysics Data System (ADS)

Ishikawa, Takahiro; Nakanishi, Akitaka; Shimizu, Katsuya; Katayama-Yoshida, Hiroshi; Oda, Tatsuki; Suzuki, Naoshi

2016-03-01

Recently, hydrogen sulfide was experimentally found to show the high superconducting critical temperature (Tc) under high-pressure. The superconducting Tc shows 30-70 K in pressure range of 100-170 GPa (low-Tc phase) and increases to 203 K, which sets a record for the highest Tc in all materials, for the samples annealed by heating it to room temperature at pressures above 150 GPa (high-Tc phase). Here we present a solid H5S2 phase predicted as the low-Tc phase by the application of the genetic algorithm technique for crystal structure searching and first-principles calculations to sulfur-hydrogen system under high-pressure. The H5S2 phase is thermodynamically stabilized at 110 GPa, in which asymmetric hydrogen bonds are formed between H2S and H3S molecules. Calculated Tc values show 50-70 K in pressure range of 100-150 GPa within the harmonic approximation, which can reproduce the experimentally observed low-Tc phase. These findings give a new aspect of the excellent superconductivity in compressed sulfur-hydrogen system.

Superconducting H5S2 phase in sulfur-hydrogen system under high-pressure

PubMed Central

Ishikawa, Takahiro; Nakanishi, Akitaka; Shimizu, Katsuya; Katayama-Yoshida, Hiroshi; Oda, Tatsuki; Suzuki, Naoshi

2016-01-01

Recently, hydrogen sulfide was experimentally found to show the high superconducting critical temperature (Tc) under high-pressure. The superconducting Tc shows 30–70 K in pressure range of 100–170 GPa (low-Tc phase) and increases to 203 K, which sets a record for the highest Tc in all materials, for the samples annealed by heating it to room temperature at pressures above 150 GPa (high-Tc phase). Here we present a solid H5S2 phase predicted as the low-Tc phase by the application of the genetic algorithm technique for crystal structure searching and first-principles calculations to sulfur-hydrogen system under high-pressure. The H5S2 phase is thermodynamically stabilized at 110 GPa, in which asymmetric hydrogen bonds are formed between H2S and H3S molecules. Calculated Tc values show 50–70 K in pressure range of 100–150 GPa within the harmonic approximation, which can reproduce the experimentally observed low-Tc phase. These findings give a new aspect of the excellent superconductivity in compressed sulfur-hydrogen system. PMID:26983593

Effects of Chamber Pressure and Partial Pressure of Water Vapor on Secondary Drying in Lyophilization.

PubMed

Searles, James A; Aravapalli, Sridhar; Hodge, Cody

2017-10-01

Secondary drying is the final step of lyophilization before stoppering, during which water is desorbed from the product to yield the final moisture content. We studied how chamber pressure and partial pressure of water vapor during this step affected the time course of water content of aqueous solutions of polyvinylpyrrolidone (PVP) in glass vials. The total chamber pressure had no effect when the partial pressure of water vapor was very low. However, when the vapor phase contained a substantial fraction of water vapor, the PVP moisture content was much higher. We carried out dynamic vapor sorption experiments (DVS) to demonstrate that the higher PVP moisture content was a straightforward result of the higher water vapor content in the lyophilizer. The results highlight that the partial pressure of water vapor is extremely important during secondary drying in lyophilization, and that lower chamber pressure set points for secondary drying may sometimes be justified as a strategy for ensuring low partial pressure of water vapor, especially for lyophilizers that do not inject dry gas to control pressure. These findings have direct application for process transfers/scale ups from freeze-dryers that do not inject dry gas for pressure control to those that do, and vice versa.

Fabrication of lead-free piezoelectric Li2CO3-added (Ba,Ca)(Ti,Sn)O3 ceramics under controlled low oxygen partial pressure and their properties

NASA Astrophysics Data System (ADS)

Noritake, Kouta; Sakamoto, Wataru; Yuitoo, Isamu; Takeuchi, Teruaki; Hayashi, Koichiro; Yogo, Toshinobu

2018-02-01

Reduction-resistant lead-free (Ba,Ca)(Ti,Sn)O3 piezoceramics with high piezoelectric constants were fabricated by optimizing the amount of Li2CO3 added. Oxygen partial pressure was controlled during the sintering of (Ba,Ca)(Ti,Sn)O3 ceramics in a reducing atmosphere using H2-CO2 gas. Enhanced grain growth and a high-polarization state after poling treatment were achieved by adding Li2CO3. Optimizing the amount of Li2CO3 added to (Ba0.95Ca0.05)(Ti0.95Sn0.05)O3 ceramics sintered under a low oxygen partial pressure resulted in improved piezoelectric properties while maintaining the high sintered density. The prepared Li2CO3-added ceramic samples had homogeneous microstructures with a uniform dispersion of each major constituent element. However, the residual Li content in the 3 mol % Li2CO3-added (Ba0.95Ca0.05)(Ti0.95Sn0.05)O3 ceramics after sintering was less than 0.3 mol %. Sintered bodies of this ceramic prepared in a CO2 (1.5%)-H2 (0.3%)/Ar reducing atmosphere (PO2 = 10-8 atm at 1350 °C), exhibited sufficient electrical resistivity and a piezoelectric constant (d 33) exceeding 500 pC/N. The piezoelectric properties of this nonreducible ceramic were comparable or superior to those of the same ceramic sintered in air.

Biological nitrogen fixation under primordial Martian partial pressures of dinitrogen

NASA Technical Reports Server (NTRS)

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

1989-01-01

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

Effect of Nickel Levels on Hydrogen Partial Pressure and Methane Production in Methanogens

PubMed Central

2016-01-01

Hydrogen (H2) consumption and methane (CH4) production in pure cultures of three different methanogens were investigated during cultivation with 0, 0.2 and 4.21 μM added nickel (Ni). The results showed that the level of dissolved Ni in the anaerobic growth medium did not notably affect CH4 production in the cytochrome-free methanogenic species Methanobacterium bryantii and Methanoculleus bourgensis MAB1, but affected CH4 formation rate in the cytochrome-containing Methanosarcina barkeri grown on H2 and CO2. Methanosarcina barkeri also had the highest amounts of Ni in its cells, indicating that more Ni is needed by cytochrome-containing than by cytochrome-free methanogenic species. The concentration of Ni affected threshold values of H2 partial pressure (pH2) for all three methanogen species studied, with M. bourgensis MAB1 reaching pH2 values as low as 0.1 Pa when Ni was available in amounts used in normal anaerobic growth medium. To our knowledge, this is the lowest pH2 threshold recorded to date in pure methanogen culture, which suggests that M.bourgensis MAB1 have a competitive advantage over other species through its ability to grow at low H2 concentrations. Our study has implications for research on the H2-driven deep subsurface biosphere and biogas reactor performance. PMID:27992585

Effect of Nickel Levels on Hydrogen Partial Pressure and Methane Production in Methanogens.

PubMed

Neubeck, Anna; Sjöberg, Susanne; Price, Alex; Callac, Nolwenn; Schnürer, Anna

2016-01-01

Hydrogen (H2) consumption and methane (CH4) production in pure cultures of three different methanogens were investigated during cultivation with 0, 0.2 and 4.21 μM added nickel (Ni). The results showed that the level of dissolved Ni in the anaerobic growth medium did not notably affect CH4 production in the cytochrome-free methanogenic species Methanobacterium bryantii and Methanoculleus bourgensis MAB1, but affected CH4 formation rate in the cytochrome-containing Methanosarcina barkeri grown on H2 and CO2. Methanosarcina barkeri also had the highest amounts of Ni in its cells, indicating that more Ni is needed by cytochrome-containing than by cytochrome-free methanogenic species. The concentration of Ni affected threshold values of H2 partial pressure (pH2) for all three methanogen species studied, with M. bourgensis MAB1 reaching pH2 values as low as 0.1 Pa when Ni was available in amounts used in normal anaerobic growth medium. To our knowledge, this is the lowest pH2 threshold recorded to date in pure methanogen culture, which suggests that M.bourgensis MAB1 have a competitive advantage over other species through its ability to grow at low H2 concentrations. Our study has implications for research on the H2-driven deep subsurface biosphere and biogas reactor performance.

Electrical conductivity of MgH2 at multiple shock compression

NASA Astrophysics Data System (ADS)

Shakhray, Denis; Molodets, Alexander; Fortov, Vladimir

2011-06-01

The electrical conductivity of MgH2 has been studied under multishock compression. Earlier we had been experimentally studied metallization possibility of alane at high pressures in conditions quasiisentropic compression up to 100 GPa. A study of thermodynamic properties of MgH2 under multishock compression has been carried out also. High pressures and temperatures were obtained with an explosive device, which accelerates the metallic impactor up to 3 km/s. Identification of the hydride in experiments was made on the basis of calculations of phase trajectories loading a material in the area of existence of polymorphic phases including high-pressure phases of magnesium hydride (α and γ MgH2, hP1 and hP2). It is shown that occurrence of magnesium hydride electrical conductivity occurs in the field of existence of high-pressure hP2 phase This work was partially supported by the Presidium of the Russian Academy of Sciences within the Program of Basic Research ``Thermal Physics and Mechanics of Extreme Energy Effects and Physics of Strongly Compressed Matter and Russian Foundation for Basic Research Grant No. 10-02-01078.''

Dynamics of the formation and loss of boron atoms in a H2/B2H6 microwave plasma

NASA Astrophysics Data System (ADS)

Duluard, C. Y.; Aubert, X.; Sadeghi, N.; Gicquel, A.

2016-09-01

For further improvements in doped-diamond deposition technology, an understanding of the complex chemistry in H2/CH4/B2H6 plasmas is of general importance. In this context, a H2/B2H6 plasma ignited by microwave power in a near resonant cavity at high pressure (100-200 mbar) is studied to measure the B-atom density in the ground state. The discharge is ignited in the gas mixture (0-135 ppm B2H6 in H2) by a 2.45 GHz microwave generator, leading to the formation of a hemispheric plasma core, surrounded by a faint discharge halo filling the remaining reactor volume. Measurements with both laser induced fluorescence and resonant absoption with a boron hollow cathode lamp indicate that the B-atom density is higher in the halo than in the plasma core. When the absorption line-of-sight is positioned in the halo, the absorption is so strong that the upper detection limit is reached. To understand the mechanisms of creation and loss of boron atoms, time-resolved absorption measurements have been carried out in a pulsed plasma regime (10 Hz, duty cycle 50%). The study focuses on the influence of the total pressure, the partial pressure of B2H6, as well as the source power, on the growth and decay rates of boron atoms when the plasma is turned off.

Oxygen Partial Pressure and Oxygen Concentration Flammability: Can They Be Correlated?

NASA Technical Reports Server (NTRS)

Harper, Susana A.; Juarez, Alfredo; Perez, Horacio, III; Hirsch, David B.; Beeson, Harold D.

2016-01-01

NASA possesses a large quantity of flammability data performed in ISS airlock (30% Oxygen 526mmHg) and ISS cabin (24.1% Oxygen 760 mmHg) conditions. As new programs develop, other oxygen and pressure conditions emerge. In an effort to apply existing data, the question arises: Do equivalent oxygen partial pressures perform similarly with respect to flammability? This paper evaluates how material flammability performance is impacted from both the Maximum Oxygen Concentration (MOC) and Maximum Total Pressures (MTP) perspectives. From these studies, oxygen partial pressures can be compared for both the MOC and MTP methods to determine the role of partial pressure in material flammability. This evaluation also assesses the influence of other variables on flammability performance. The findings presented in this paper suggest flammability is more dependent on oxygen concentration than equivalent partial pressure.

Influence of Oxygen Partial Pressure during Processing on the Thermoelectric Properties of Aerosol-Deposited CuFeO2

PubMed Central

Stöcker, Thomas; Exner, Jörg; Schubert, Michael; Streibl, Maximilian; Moos, Ralf

2016-01-01

In the field of thermoelectric energy conversion, oxide materials show promising potential due to their good stability in oxidizing environments. Hence, the influence of oxygen partial pressure during synthesis on the thermoelectric properties of Cu-Delafossites at high temperatures was investigated in this study. For these purposes, CuFeO2 powders were synthetized using a conventional mixed-oxide technique. X-ray diffraction (XRD) studies were conducted to determine the crystal structures of the delafossites associated with the oxygen content during the synthesis. Out of these powders, films with a thickness of about 25 µm were prepared by the relatively new aerosol-deposition (AD) coating technique. It is based on a room temperature impact consolidation process (RTIC) to deposit dense solid films of ceramic materials on various substrates without using a high-temperature step during the coating process. On these dense CuFeO2 films deposited on alumina substrates with electrode structures, the Seebeck coefficient and the electrical conductivity were measured as a function of temperature and oxygen partial pressure. We compared the thermoelectric properties of both standard processed and aerosol deposited CuFeO2 up to 900 °C and investigated the influence of oxygen partial pressure on the electrical conductivity, on the Seebeck coefficient and on the high temperature stability of CuFeO2. These studies may not only help to improve the thermoelectric material in the high-temperature case, but may also serve as an initial basis to establish a defect chemical model. PMID:28773351

Simultaneous high efficiency capture of CO.sub.2 and H.sub.2S from pressurized gas

DOEpatents

Gal, Eli; Krishnan, Gopala N.; Jayaweera, Indira S.

2016-10-11

Low-cost and energy-efficient CO.sub.2 and H.sub.2S capture is provided obtaining greater than 99.9% capture efficiency from pressurized gas. The acid species are captured in an ammonia solution, which is then regenerated by stripping the absorbed species. The solution can capture as much as 330 grams of CO.sub.2 and H.sub.2S per 1000 gram of water and when regenerated it produces pure pressurized acid gas containing more than 99.7% CO.sub.2 and H2S. The absorption of the acid species is accomplished in two absorbers in-series, each having multiple stages. More than 95% of the acid species are captured in the first absorber and the balance is captured in the second absorber to below 10 ppm concentration in the outlet gas. The two absorbers operate at temperatures ranging from 20-70 degrees Celsius. The two absorbers and the main stripper of the alkaline solution operate at similar pressures ranging from 5-200 bara.

The ExoMol pressure broadening diet: H2 and He line-broadening parameters

NASA Astrophysics Data System (ADS)

Barton, Emma J.; Hill, C.; Czurylo, M.; Li, H. Y.; Hyslop, A.; Yurchenko, Sergei N.; Tennyson, Jonathan

2017-12-01

In a variety of astronomical objects including gas giant (exo-)planets, brown dwarfs and cool stars, molecular hydrogen and helium are the major line broadeners. However, there is currently no systematic source for these parameters, particularly at the elevated temperatures encountered in many of these objects. The ExoMol project provides comprehensive molecular line lists for exoplanet and other hot atmospheres. The ExoMol database has recently been extended to provide additional data including temperature-dependent, pressure-broadening parameters. Here we assemble H2 and He pressure-broadening datasets for the molecules H2O, NH3, SO2, CH4, PH3, HCN and H2CO using available experimental and theoretical studies.

DEVICE FOR CONTROL OF OXYGEN PARTIAL PRESSURE

DOEpatents

Bradner, H.; Gordon, H.S.

1957-12-24

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

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

NASA Astrophysics Data System (ADS)

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

2014-10-01

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

Partial pressure analysis in space testing

NASA Technical Reports Server (NTRS)

Tilford, Charles R.

1994-01-01

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

Oxidation and Condensation of Zinc Fume From Zn-CO 2-CO-H 2O Streams Relevant to Steelmaking Off-Gas Systems

DOE PAGES

Bronson, Tyler Mark; Ma, Naiyang; Zhu, Liang Zhu; ...

2017-01-23

Here the objective of this research was to study the condensation of zinc vapor to metallic zinc and zinc oxide solid under varying environments to investigate the feasibility of in-process separation of zinc from steelmaking off-gas dusts. Water vapor content, temperature, degree of cooling, gas composition, and initial zinc partial pressure were varied to simulate the possible conditions that can occur within steelmaking off-gas systems, limited to Zn-CO 2-CO-H 2O gas compositions. The temperature of deposition and the effect of rapidly quenching the gas were specifically studied. A homogeneous nucleation model for applicable experiments was applied to the analysis of the experimental data. It was determined that under the experimental conditions, oxidation of zinc vapor by H 2O or CO 2 does not occur above 1108 K (835 °C) even for highly oxidizing streams (CO 2/CO = 40/7). Rate expressions that correlate CO 2 and H 2O oxidation rates to gas composition, partial pressure of water vapor, temperature, and zinc partial pressure were determined to be as follows: Ratemore » $$ \\left(\\frac{mol}{m^2s}\\right) $$ = 406 exp $$ \\left(\\frac{-50.2 kJ/mol}{RT}\\right) $$ (pZnpCO 2 $-$ PCO/K eqCO 2) $$\\frac{mol}{m^2 x s}$$ Rate $$ \\left(\\frac{mol}{m^2s}\\right) $$ = 32.9 exp $$ \\left(\\frac{-13.7 kJ/mol}{RT}\\right) $$ (pZnPH 2O $-$ PH 2/K eqH 2O) $$\\frac{mol}{m^2 x s}$$. It was proven that a rapid cooling rate (500 K/s) significantly increases the ratio of metallic zinc to zinc oxide as opposed to a slow cooling rate (250 K/s). SEM analysis found evidence of heterogeneous growth of ZnO as well as of homogeneous formation of metallic zinc. The homogeneous nucleation model fit well with experiments where only metallic zinc deposited. An expanded model with rates of oxidation by CO 2 and H 2O as shown was combined with the homogenous nucleation model and then compared with experimental data. The calculated results based on the model gave a reasonable fit to the

Oxidation and Condensation of Zinc Fume From Zn-CO 2-CO-H 2O Streams Relevant to Steelmaking Off-Gas Systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bronson, Tyler Mark; Ma, Naiyang; Zhu, Liang Zhu

Here the objective of this research was to study the condensation of zinc vapor to metallic zinc and zinc oxide solid under varying environments to investigate the feasibility of in-process separation of zinc from steelmaking off-gas dusts. Water vapor content, temperature, degree of cooling, gas composition, and initial zinc partial pressure were varied to simulate the possible conditions that can occur within steelmaking off-gas systems, limited to Zn-CO 2-CO-H 2O gas compositions. The temperature of deposition and the effect of rapidly quenching the gas were specifically studied. A homogeneous nucleation model for applicable experiments was applied to the analysis of the experimental data. It was determined that under the experimental conditions, oxidation of zinc vapor by H 2O or CO 2 does not occur above 1108 K (835 °C) even for highly oxidizing streams (CO 2/CO = 40/7). Rate expressions that correlate CO 2 and H 2O oxidation rates to gas composition, partial pressure of water vapor, temperature, and zinc partial pressure were determined to be as follows: Ratemore » $$ \\left(\\frac{mol}{m^2s}\\right) $$ = 406 exp $$ \\left(\\frac{-50.2 kJ/mol}{RT}\\right) $$ (pZnpCO 2 $-$ PCO/K eqCO 2) $$\\frac{mol}{m^2 x s}$$ Rate $$ \\left(\\frac{mol}{m^2s}\\right) $$ = 32.9 exp $$ \\left(\\frac{-13.7 kJ/mol}{RT}\\right) $$ (pZnPH 2O $-$ PH 2/K eqH 2O) $$\\frac{mol}{m^2 x s}$$. It was proven that a rapid cooling rate (500 K/s) significantly increases the ratio of metallic zinc to zinc oxide as opposed to a slow cooling rate (250 K/s). SEM analysis found evidence of heterogeneous growth of ZnO as well as of homogeneous formation of metallic zinc. The homogeneous nucleation model fit well with experiments where only metallic zinc deposited. An expanded model with rates of oxidation by CO 2 and H 2O as shown was combined with the homogenous nucleation model and then compared with experimental data. The calculated results based on the model gave a reasonable fit to the

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

NASA Astrophysics Data System (ADS)

Duncan, M. S.; Dasgupta, R.

2011-12-01

Partial melts of subducting sediments is thought to be a critical agent in carrying trace elements and water to arc basalt source regions. For subduction zones that contain significant amount of carbonates in ocean-floor sediments, sediment melts likely also act as a carrier of CO2. However, the CO2 carrying capacity of natural rhyolitic melts at sub-arc depths remains unconstrained. We conducted experiments on a synthetic composition, similar to average, low-degree experimental partial melt of pelitic sediments. The composition was constructed with reagent grade oxides and carbonates, the source of excess CO2. Experiments were conducted between 1 and 3 GPa at 1200 °C in Au80Pd20 capsules using a piston cylinder apparatus with a half-inch BaCO3 assembly at Rice University. Quench products showed glasses with bubbles, the latter suggesting saturation of the melt with a CO2-rich vapor phase. Oxygen fugacity during the experiments was not strictly controlled but the presence of CO2 bubbles and absence of graphite indicates fO2 above the CCO buffer. Major element concentrations of glasses were measured using EPMA. The CO2 and H2O contents of experimental doubly polished (50-110 μm), bubble-free portions of the glass chips were determined using a Thermo Nicolet Fourier Transform Infrared Spectrometer. Spectra were recorded with a resolution of 4 cm-1, 512 scans, from 650 to 4000 cm-1, under a nitrogen purge to eliminate atmospheric gases. Dissolved volatile concentrations were quantified using the Beer-Lambert law and linear molar absorption coefficients from previous studies [1, 2]. Total dissolved carbon dioxide of experimental glasses was determined from the intensity of the ν3 antisymmetric stretch bands of CO32- at 1430 cm-1 and CO2mol at 2348 cm-1. Dissolved water content of experimental glasses was determined from the intensity of O-H stretching at 3520 cm-1. Estimated total CO2 concentrations at 3 GPa are in the range of 1-2 wt%, for melts with H2O contents

Investigation of H2S separation from H2S/CH4 mixtures using functionalized and non-functionalized vertically aligned carbon nanotube membranes

NASA Astrophysics Data System (ADS)

Gilani, Neda; Towfighi, Jafar; Rashidi, Alimorad; Mohammadi, Toraj; Omidkhah, Mohammad Reza; Sadeghian, Ahmad

2013-04-01

Separation of H2S from binary mixtures of H2S/CH4 using vertically aligned carbon nanotube membranes fabricated in anodic aluminum oxide (AAO) template was studied experimentally. Carbon nanotubes (CNTs) were grown in five AAO templates with different pore diameters using chemical vapor deposition, and CNT/AAO membranes with tubular carbon nanotube structure and open caps were selected for separation of H2S. For this, two tubular CNT/AAO membranes were fabricated with the CNT inner diameters of 23 and 8 nm. It was found that permeability and selectivity of the membrane with inner diameter of 23 nm for CNT were independent of upstream feed pressure and H2S feed concentration unlike that of CNT having an inner diameter of 8 nm. Selectivity of these membranes for separation of H2S was obtained in the ranges of 1.36-1.58 and 2.11-2.86, for CNTs with internal diameters of 23 and 8 nm, respectively. In order to enhance the separation of H2S from H2S/CH4 mixtures, dodecylamine was used to functionalize the CNT/AAO membrane with higher selectivity. The results showed that for amido-functionalized membrane, both upstream feed pressure and H2S partial pressure in the feed significantly increased H2S permeability, and selectivity for H2S being in the range of 3.0-5.57 respectively.

Comparing CT perfusion with oxygen partial pressure in a rabbit VX2 soft-tissue tumor model.

PubMed

Sun, Chang-Jin; Li, Chao; Lv, Hai-Bo; Zhao, Cong; Yu, Jin-Ming; Wang, Guang-Hui; Luo, Yun-Xiu; Li, Yan; Xiao, Mingyong; Yin, Jun; Lang, Jin-Yi

2014-01-01

The aim of this study was to evaluate the oxygen partial pressure of the rabbit model of the VX2 tumor using a 64-slice perfusion CT and to compare the results with that obtained using the oxygen microelectrode method. Perfusion CT was performed for 45 successfully constructed rabbit models of a VX2 brain tumor. The perfusion values of the brain tumor region of interest, the blood volume (BV), the time to peak (TTP) and the peak enhancement intensity (PEI) were measured. The results were compared with the partial pressure of oxygen (PO2) of that region of interest obtained using the oxygen microelectrode method. The perfusion values of the brain tumor region of interest in 45 successfully constructed rabbit models of a VX2 brain tumor ranged from 1.3-127.0 (average, 21.1 ± 26.7 ml/min/ml); BV ranged from 1.2-53.5 ml/100g (average, 22.2 ± 13.7 ml/100g); PEI ranged from 8.7-124.6 HU (average, 43.5 ± 28.7 HU); and TTP ranged from 8.2-62.3 s (average, 38.8 ± 14.8 s). The PO2 in the corresponding region ranged from 0.14-47 mmHg (average, 16 ± 14.8 mmHg). The perfusion CT positively correlated with the tumor PO2, which can be used for evaluating the tumor hypoxia in clinical practice.

Effect of oxygen partial pressure on oxidation of Mo-metal

NASA Astrophysics Data System (ADS)

Sharma, Rabindar Kumar; Kumar, Prabhat; Singh, Megha; Gopal, Pawar; Reddy, G. B.

2018-05-01

This report explains the effect of oxygen partial pressure (PO2 ) on oxidation of Mo-metal in oxygen plasma. XRD results indulge that oxide layers formed on Mo-surfaces at different oxygen partial pressures have two different oxide phases (i.e. orthorhombic MoO3 and monoclinic Mo8O23). Intense XRD peaks at high pressure (i.e. 2.0×10-1 Torr) points out the formation of thick oxide layer on Mo-surface due to presence of large oxygen species in chamber and less oxide volatilization. Whereas, at low PO2 (6.5×10-2 and 7.5×10-2 Torr.) the reduced peak strength is owing to high oxide volatilization rate. SEM micrographs and thickness measurements also support XRD results and confirm that the optimum -2value of PO2 to deposited thicker and uniform oxide film on glass substrate is 7.5×10-2 Torr through plasma assistedoxidation process. Further to study the compositional properties, EDX of the sample M2 (the best sample) is carried out, which confirms that the stoichiometric ratio is less than 3 (i.e. 2.88). Less stoichiometric ratio again confirms the presence of sub oxides in oxide layers on Mo metal as evidenced by XRD results. All the observed results are well in consonance with each other.

Plateau Waves of Intracranial Pressure and Partial Pressure of Cerebral Oxygen.

PubMed

Lang, Erhard W; Kasprowicz, Magdalena; Smielewski, Peter; Pickard, John; Czosnyka, Marek

2016-01-01

This study investigates 55 intracranial pressure (ICP) plateau waves recorded in 20 patients after severe traumatic brain injury (TBI) with a focus on a moving correlation coefficient between mean arterial pressure (ABP) and ICP, called PRx, which serves as a marker of cerebrovascular reactivity, and a moving correlation coefficient between ABP and cerebral partial pressure of oxygen (pbtO2), called ORx, which serves as a marker for cerebral oxygen reactivity. ICP and ICPamplitude increased significantly during the plateau waves, whereas CPP and pbtO2 decreased significantly. ABP, ABP amplitude, and heart rate remained unchanged. In 73 % of plateau waves PRx increased during the wave. ORx showed an increase during and a decrease after the plateau waves, which was not statistically significant. Our data show profound cerebral vasoparalysis on top of the wave and, to a lesser extent, impairment of cerebral oxygen reactivity. The different behavior of the indices may be due to the different latencies of the cerebral blood flow and oxygen level control mechanisms. While cerebrovascular reactivity is a rapidly reacting mechanism, cerebral oxygen reactivity is slower.

Milk pH as a function of CO2 concentration, temperature, and pressure in a heat exchanger.

PubMed

Ma, Y; Barbano, D M

2003-12-01

Raw skim milk, with or without added CO2, was heated, held, and cooled in a small pilot-scale tubular heat exchanger (372 ml/min). The experiment was replicated twice, and, for each replication, milk was first carbonated at 0 to 1 degree C to contain 0 (control), 600, 1200, 1800, and 2400 ppm added CO2 using a continuous carbonation unit. After storage at 0 to 1 degree C, portions of milk at each CO2 concentration were heated to 40, 56, 72, and 80 degrees C, held at the desired temperature for 30 s (except 80 degrees C, holding 20 s) and cooled to 0 to 1 degree C. At each temperature, five pressures were applied: 69, 138, 207, 276, and 345 kPa. Pressure was controlled with a needle valve at the heat exchanger exit. Both the pressure gauge and pH probe were inline at the end of the holding section. Milk pH during heating depended on CO2 concentration, temperature, and pressure. During heating of milk without added CO2, pH decreased linearly as a function of increasing temperature but was independent of pressure. In general, the pH of milk with added CO2 decreased with increasing CO2 concentration and pressure. For milk with added CO2, at a fixed CO2 concentration, the effect of pressure on pH decrease was greater at a higher temperature. At a fixed temperature, the effect of pressure on pH decrease was greater for milk with a higher CO2 concentration. Thermal death of bacteria during pasteurization of milk without added CO2 is probably due not only to temperature but also to the decrease in pH that occurs during the process. Increasing milk CO2 concentration and pressure decreases the milk pH even further during heating and may further enhance the microbial killing power of pasteurization.

Oxygen-Partial-Pressure Sensor for Aircraft Oxygen Mask

NASA Technical Reports Server (NTRS)

Kelly, Mark; Pettit, Donald

2003-01-01

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

Temperature and pressure dependent thermodynamic behavior of 2H-CuInO2

NASA Astrophysics Data System (ADS)

Bhamu, K. C.

2018-05-01

Density functional theory and quasi-harmonic Debye model has been used to study the thermodynamic properties of 2H-CuInO2. At the optimized structural parameters, pressure (0 to 80 GPa) dependent variation in the various thermodynamic properties, i.e. unit cell volume (V), bulk modulus (B), specific heat (Cv), Debye temperature (θD), Grüneisen parameter (γ) and thermal expansion coefficient (α) are calculated for various temperature values. The results predict that the pressure has significant effect on unit cell volume and bulk modulus while the temperature shows negligible effect on both parameters. With increasing temperature thermal expansion coefficient increase while with increasing pressure it decreases. The specific heat remains close to zero for ambient pressure and temperature values and it increases with increasing temperature. It is observed that the pressure has high impact on Debye temperature and Grüneisen parameter instead of temperature. Debye temperature and Grüneisen parameter both remains almost constant for the temperature range (0-300K) while Grüneisen parameter decrease with increasing pressure at constant temperature and Debye temperature increases rapidly with increasing pressure. An increase in Debye temperature with respect to pressure shows that the thermal vibration frequency changes rapidly.

Melatonin partially protects 661W cells from H2O2-induced death by inhibiting Fas/FasL-caspase-3.

PubMed

Sánchez-Bretaño, Aída; Baba, Kenkichi; Janjua, Uzair; Piano, Ilaria; Gargini, Claudia; Tosini, Gianluca

2017-01-01

Previous studies have shown that melatonin (MEL) signaling is involved in the modulation of photoreceptor viability during aging. Recent work by our laboratory suggested that MEL may protect cones by modulating the Fas/FasL-caspase-3 pathway. In this study, we first investigated the presence of MEL receptors (MT 1 and MT 2 ) in 661W cells, then whether MEL can prevent H 2 O 2 -induced cell death, and last, through which pathway MEL confers protection. The mRNA and proteins of the MEL receptors were detected with quantitative PCR (q-PCR) and immunocytochemistry, respectively. To test the protective effect of MEL, 661W cells were treated with H 2 O 2 for 2 h in the presence or absence of MEL, a MEL agonist, and an antagonist. To study the pathways involved in H 2 O 2 -mediated cell death, a Fas/FasL antagonist was used before the exposure to H 2 O 2 . Finally, Fas/FasL and caspase-3 mRNA was analyzed with q-PCR and immunocytochemistry in cells treated with H 2 O 2 and/or MEL. Cell viability was analyzed by using Trypan Blue. Both MEL receptors (MT 1 and MT 2 ) were detected at the mRNA and protein levels in 661W cells. MEL partially prevented H 2 O 2 -mediated cell death (20-25%). This effect was replicated with IIK7 (a melatonin receptor agonist) when used at a concentration of 1 µM. Preincubation with luzindole (a melatonin receptor antagonist) blocked MEL protection. Kp7-6, an antagonist of Fas/FasL, blocked cell death caused by H 2 O 2 similarly to what was observed for MEL. Fas, FasL, and caspase-3 expression was increased in cells treated with H 2 O 2 , and this effect was prevented by MEL. Finally, MEL treatment partially prevented the activation of caspase-3 caused by H 2 O 2 . The results demonstrate that MEL receptors are present and functional in 661W cells. MEL can prevent photoreceptor cell death induced by H 2 O 2 via the inhibition of the proapoptotic pathway Fas/FasL-caspase-3.

On the Stark effect in open shell complexes exhibiting partially quenched electronic angular momentum: Infrared laser Stark spectroscopy of OH–C 2H 2, OH–C 2H 4, and OH–H 2O

DOE PAGES

Moradi, Christopher P.; Douberly, Gary E.

2015-06-22

The Stark effect is considered for polyatomic open shell complexes that exhibit partially quenched electronic angular momentum. Matrix elements of the Stark Hamiltonian represented in a parity conserving Hund's case (a) basis are derived for the most general case, in which the permanent dipole moment has projections on all three inertial axes of the system. Transition intensities are derived, again for the most general case, in which the laser polarization has projections onto axes parallel and perpendicular to the Stark electric field, and the transition dipole moment vector is projected onto all three inertial axes in the molecular frame. Asmore » a result, simulations derived from this model are compared to experimental rovibrational Stark spectra of OH-C 2H 2, OH-C 2H 4, and OH-H 2O complexes formed in helium nanodroplets.« less

Gas-liquid equilibrium in a CO{sub 2}-MDEA-H{sub 2}O system and the effect of piperazine on it

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, G.W.; Zhang, C.F.; Qin, S.J.

1998-04-01

Aqueous N-methyldiethanolamine (MDEA) solutions are widely used for removal of the acid gas (H{sub 2}S and CO{sub 2}) from natural gas synthesis and refinery gas streams. Solubility data of CO{sub 2} and vapor pressure of water in 3.04--4.28 kmol/m{sup 3} aqueous N-methyldiethanolamine (MDEA) solutions were obtained at temperatures ranging from 40 to 100 C and CO{sub 2} partial pressures ranging from 0.876 to 1,013 kPa. A thermodynamic model was proposed and used for predicting CO{sub 2} solubility and water vapor pressure. An enthalpy change of absorption of CO{sub 2} in 4.28 kmol/m{sup 3} MDEA solution was estimated. The effect ofmore » piperazine (PZ) concentration on CO{sub 2} loading in MDEA solutions was determined at piperazine concentration ranging from 0 to 0.515 kmol/m{sup 3}. The results show that piperazine is beneficial to the CO{sub 2} loading. The equilibrium partial pressure of piperazine in the PZ-MDEA-H{sub 2}O system was measured in an Ellis Cell. Results show that the PZ-MDEA-H{sub 2}O system is a typical negative deviation system, with the strength of deviation decreasing with MDEA solutions.« less

Partitioning of H2O on high pressure phase transformation of olivine

NASA Astrophysics Data System (ADS)

Inoue, T.; Wada, T.; Sasaki, R.; Irifune, T.; Yurimoto, H.

2003-12-01

Water is the most abundant volatile component on the Earth's surface, and it has been supplied to the Earth's interiors by subducted slab. Water influences the physical properties and melting temperature of minerals. Olivine is the most abundant mineral in the mantle, and it is clarified that the high-pressure polymorphs of olivine, wadsleyite and ringwoodite, can contain 3wt% of H2O in their crystal structures (e.g. Inoue et al., 1995, 1998). However, the partitioning of H2O among these minerals has not been clarified yet except for olivine-wadsleyite transformation (Chen et al., 2003). We have determined the partitioning of H2O between wadsleyite and ringwoodite and between ringwoodite and perovskite, and clarified the distribution of H2O among upper mantle, mantle transition zone and lower mantle. High-pressure experiments were conducted by MA-8 type (Kawai-type) high-pressure apparatus in Ehime University, and the chemical compositions were determined by EPMA. The water contents of minerals were measured by SIMS in Tokyo Institute of Technology. We succeeded to synthesize large (approximately 50 μ m) coexisting crystals of wadsleyite and ringwoodite, and of ringwoodite and perovskite, and we could clarify the partitioning of H2O between those coexisting minerals. The partition coefficients between wadsleyite and ringwoodite and between ringwoodite and perovskite were about 2 and about 10 or more, respectively. We (Chen et al., 2003) have already determined that the partition coefficients between wadsleyite and olivine is about 5, so the partitioning among upper mantle, 410-520km and 520-660km of mantle transition zone, and lower mantle are 4:20:10:1. Thus the mantle transition zone should be a strong water reservoir in the Earth's interiors.

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

PubMed

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

2013-06-01

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. Copyright © 2012 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.

A simple kinetic model of a Ne-H2 Penning-plasma laser

NASA Astrophysics Data System (ADS)

Petrov, G. M.; Stefanova, M. S.; Pramatarov, P. M.

1995-09-01

A simple kinetic model of the Ne-H2 Penning-Plasma Laser (PPL) (NeI 585.3 nm) is proposed. The negative glow of a hollow cathode discharge at intermediate pressures is considered as the active medium. The balance equations for the upper and lower laser levels, electrons, ions and electron energy are solved. The dependences of the laser gain on the discharge conditions (Ne and H2 partial pressures, discharge current) are calculated and measured. The calculated values are in a good agreement with the experimental data.

[Effect of oxygen tubing connection site on percutaneous oxygen partial pressure and percutaneous carbon dioxide partial pressure in patients with chronic obstructive pulmonary disease during noninvasive positive pressure ventilation].

PubMed

Mi, S; Zhang, L M

2017-04-12

Objective: We evaluated the effects of administering oxygen through nasal catheters inside the mask or through the mask on percutaneous oxygen partial pressure (PcO(2))and percutaneous carbon dioxide partial pressure (PcCO(2)) during noninvasive positive pressure ventilation (NPPV) to find a better way of administering oxygen, which could increase PcO(2) by increasing the inspired oxygen concentration. Methods: Ten healthy volunteers and 9 patients with chronic obstructive pulmonary disease complicated by type Ⅱ respiratory failure were included in this study. Oxygen was administered through a nasal catheter inside the mask or through the mask (oxygen flow was 3 and 5 L/min) during NPPV. PcO(2) and PcCO(2) were measured to evaluate the effects of administering oxygen through a nasal catheter inside the mask or through the mask, indirectly reflecting the effects of administering oxygen through nasal catheter inside the mask or through the mask on inspired oxygen concentration. Results: Compared to administering oxygen through the mask during NPPV, elevated PcO(2) was measured in administering oxygen through the nasal catheter inside the mask, and the differences were statistically significant ( P <0.05). At the same time, there was no significant change in PcCO(2) ( P >0.05). Conclusion: Administering oxygen through a nasal catheter inside the mask during NPPV increased PcO(2) by increasing the inspired oxygen concentration but did not increase PcCO(2). This method of administering oxygen could conserve oxygen and be suitable for family NPPV. Our results also provided theoretical basis for the development of new masks.

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

NASA Technical Reports Server (NTRS)

Isham, M. A.

1992-01-01

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

Pressures of Partial Crystallization of Magmas Along Transforms: Implications for Crustal Accretion

NASA Astrophysics Data System (ADS)

Scott, J. L.; Zerda, C.; Brown, D.; Ciaramitaro, S. C.; Barton, M.

2016-12-01

Plate spreading at mid-ocean ridges is responsible for the creation of most of the crust on earth. The ridge system is very complex and many questions remain unresolved. Among these is the nature of magma plumbing systems beneath transform faults. Pervious workers have suggested that increased conductive cooling along transforms promotes higher pressures of partial crystallization, and that this explains the higher partial pressures of crystallization inferred for magmas erupted along slow spreading ridges compared to magmas erupted along faster spreading ridges. To test this hypothesis, we undertook a detailed analysis of pressures of partial crystallization for magmas erupted at 3 transforms along the fast to intermediate spreading East Pacific Rise(Blanco, Clipperton, and Siqueiros) and 3 transforms along the slow spreading Mid Atlantic Ridge(Famous Transform B, Kane, and 15°20'N). Pressures of partial crystallization were calculated from the compositions of glasses (quenched liquids) lying along the P (and T) dependent olivine, plagioclase, and augite cotectic using the method described by Kelley and Barton (2008). Published analyses of mid-ocean ridge basalt glasses sampled from these transforms and surrounding ridge segments were used as input data. Samples with anomalous chemical compositions and samples that yielded pressures associated with unrealistically large uncertainties were filtered out of the database. The pressures of partial crystallization for the remaining 916 samples ranged from 0 to 520 MPa with the great majority ( 95%) of sample returning pressures of less than 300 MPa. Pressures of < 300 MPa are within error of the pressure range associated with partial crystallization within oceanic crust with a thickness of 7 km. Higher (sub-crustal) pressures (>300 MPa) are associated with a small number of samples from the Pacific segments. Except for the Blanco, pressures of partial crystallization do not increase as transforms are approached. These

Partial discharge detection and analysis in low pressure environments

NASA Astrophysics Data System (ADS)

Liu, Xin

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

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

PubMed

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

2003-01-01

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.

Effects of hydrogen partial pressure on autotrophic growth and product formation of Acetobacterium woodii.

PubMed

Kantzow, Christina; Weuster-Botz, Dirk

2016-08-01

Low aqueous solubility of the gases for autotrophic fermentations (e.g., hydrogen gas) results in low productivities in bioreactors. A frequently suggested approach to overcome mass transfer limitation is to increase the solubility of the limiting gas in the reaction medium by increasing the partial pressure in the gas phase. An increased inlet hydrogen partial pressure of up to 2.1 bar (total pressure of 3.5 bar) was applied for the autotrophic conversion of hydrogen and carbon dioxide with Acetobacterium woodii in a batch-operated stirred-tank bioreactor with continuous gas supply. Compared to the autotrophic batch process with an inlet hydrogen partial pressure of 0.4 bar (total pressure of 1.0 bar) the final acetate concentration after 3.1 days was reduced to 50 % (29.2 g L(-1) compared to 59.3 g L(-1)), but the final formate concentration was increased by a factor of 18 (7.3 g L(-1) compared to 0.4 g L(-1)). Applying recombinant A. woodii strains overexpressing either genes for enzymes in the methyl branch of the Wood-Ljungdahl pathway or the genes phosphotransacetylase and acetate kinase at an inlet hydrogen partial pressure of 1.4 bar reduced the final formate concentration by up to 40 % and increased the final dry cell mass and acetate concentrations compared to the wild type strain. Solely the overexpression of the two genes for ATP regeneration at the end of the Wood-Ljungdahl pathway resulted in an initial switch off of formate production at increased hydrogen partial pressure until the maximum of the hydrogen uptake rate was reached.

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

PubMed

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

2011-12-01

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

The CO2 stimulus for cerebrovascular reactivity: Fixing inspired concentrations vs. targeting end-tidal partial pressures.

PubMed

Fisher, Joseph A

2016-06-01

Cerebrovascular reactivity (CVR) studies have elucidated the physiology and pathophysiology of cerebral blood flow regulation. A non-invasive, high spatial resolution approach uses carbon dioxide (CO2) as the vasoactive stimulus and magnetic resonance techniques to estimate the cerebral blood flow response. CVR is assessed as the ratio response change to stimulus change. Precise control of the stimulus is sought to minimize CVR variability between tests, and show functional differences. Computerized methods targeting end-tidal CO2 partial pressures are precise, but expensive. Simpler, improvised methods that fix the inspired CO2 concentrations have been recommended as less expensive, and so more widely accessible. However, these methods have drawbacks that have not been previously presented by those that advocate their use, or those that employ them in their studies. As one of the developers of a computerized method, I provide my perspective on the trade-offs between these two methods. The main concern is that declaring the precision of fixed inspired concentration of CO2 is misleading: it does not, as implied, translate to precise control of the actual vasoactive stimulus - the arterial partial pressure of CO2 The inherent test-to-test, and therefore subject-to-subject variability, precludes clinical application of findings. Moreover, improvised methods imply widespread duplication of development, assembly time and costs, yet lack uniformity and quality control. A tabular comparison between approaches is provided. © The Author(s) 2016.

Extending helium partial pressure measurement technology to JET DTE2 and ITER.

PubMed

Klepper, C C; Biewer, T M; Kruezi, U; Vartanian, S; Douai, D; Hillis, D L; Marcus, C

2016-11-01

The detection limit for helium (He) partial pressure monitoring via the Penning discharge optical emission diagnostic, mainly used for tokamak divertor effluent gas analysis, is shown here to be possible for He concentrations down to 0.1% in predominantly deuterium effluents. This result from a dedicated laboratory study means that the technique can now be extended to intrinsically (non-injected) He produced as fusion reaction ash in deuterium-tritium experiments. The paper also examines threshold ionization mass spectroscopy as a potential backup to the optical technique, but finds that further development is needed to attain with plasma pulse-relevant response times. Both these studies are presented in the context of continuing development of plasma pulse-resolving, residual gas analysis for the upcoming JET deuterium-tritium campaign (DTE2) and for ITER.

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

NASA Technical Reports Server (NTRS)

Kojima, Jun; Nguyen, Quang-Viet

2003-01-01

Rotational vibrational spontaneous Raman spectra (SRS) of H2, N2, and H2O have been measured in H2-air flames at pressures up to 30 atm as a first stem towards establishing a comprehensive Raman spectral database for temperatures and species in high-pressure combustion. A newly developed high-pressure burner facility provides steady, reproducible flames with a high degree of flow precision. We have obtained an initial set of measurements that indicate the spectra are of sufficient quality in terms of spectral resolution, wavelength coverage, and signal-to-noise ratio for use in future reference standards. The fully resolved Stokes and anti-Stokes shifted SRS spectra were collected in the visible wavelength range (400-700 nm) using pulse-stretched 532 nm excitation and a non-intensified CCD spectrograph with a high-speed shutter. Reasonable temperatures were determined via the intensity distribution of rotational H2 lines at stoichiometry and fuel-rich conditions. Theoretical Raman spectra of H2 were computed using a semi-classical harmonic-oscillator model with recent pressure broadening data and were compared with experimental results. The data and simulation indicated that high-J rotational lines of H2 might interfere with the N2 vibrational Q-branch lines, and this could lead to errors in N2-Raman thermometry based on the line-fitting method. From a comparison of N2 Q-branch spectra in lean H2 low-pressure (1.2 atm) and high-pressure (30 atm) flames, we found no significant line-narrowing or -broadening effects at the current spectrometer resolution of 0.04 nm.

Ab initio molecular dynamics study of fluid H2O-CO2 mixture in broad pressure-temperature range

NASA Astrophysics Data System (ADS)

Fu, Jie; Zhao, Jijun; Plyasunov, Andrey V.; Belonoshko, Anatoly B.

2017-11-01

Properties of H2O and CO2 fluid and their mixtures under extreme pressures and temperatures are poorly known yet critically important in a number of applications. Several hundreds of first-principles molecular dynamics (FPMD) runs have been performed to obtain the pressure-volume-temperature (P-V-T) data on supercritical H2O, CO2, and H2O-CO2 mixtures. The pressure-temperature (P-T) range are from 0.5 GPa to 104 GPa (48.5 GPa for CO2) and from 600 K to 4000 K. Based on these data, we evaluate several existing equations of state (EOS) for the fluid H2O, CO2, and H2O-CO2 mixture. The results show that the EOS for H2O from Belonoshko et al. [Geochim. Cosmochim. Acta 55, 381-387; Geochim. Cosmochim. Acta 55, 3191-3208; Geochim. Cosmochim. Acta 56, 3611-3626; Comput. Geosci. 18, 1267-1269] not only can be used in the studied P-T range but also is accurate enough to be used for prediction of P-V-T data. In addition, IAPWS-95 EOS for H2O shows excellent extrapolation behavior beyond 1.0 GPa and 1273 K. However, for the case of CO2, none of the existing EOS produces data in agreement with the FPMD results. We created new EOS for CO2. The precision of the new EOS is tested by comparison to the calculated P-V-T data, fugacity coefficient of the CO2 fluid derived from high P-T experimental data as well as to the (very scarce) experimental volumetric data in the high P-T range. On the basis of our FPMD data we created a new EOS for H2O-CO2 mixture. The new EOS for the mixture is in reasonable agreement with experimental data.

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

NASA Astrophysics Data System (ADS)

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

2011-09-01

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

Method and apparatus for monitoring oxygen partial pressure in air masks

NASA Technical Reports Server (NTRS)

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

2006-01-01

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

H2O Paradox and its Implications on H2O in Moon

NASA Astrophysics Data System (ADS)

Zhang, Youxue

2017-04-01

The concentration of H2O in the mantle of a planetary body plays a significant role in the viscosity and partial melting and hence the convection and evolution of the planetary body. Even though the composition of the primitive terrestrial mantle (PTM) is thought to be well known [1-2], the concentration of H2O in PTM remains paradoxial because different methods of estimation give different results [3]: Using H2O/Ce ratio in MORB and OIB and Ce concentration in PTM, the H2O concentration in PTM would be (300÷×1.5) ppm; using mass balance by adding surface water to the mantle [3-4], H2O concentration in PTM would be (900÷×1.3) ppm [2-3]. The inconsistency based on these two seemingly reliable methods is referred to as the H2O paradox [3]. For Moon, H2O contents in the primitive lunar mantle (PLM) estimated from H2O in plagioclase in lunar anorthosite and that from H2O/Ce ratio in melt inclusions are roughly consistent at ˜110 ppm [5-6] even though there is still debate about the volatile depletion trend [7]. One possible solution to the H2O paradox in PTM is to assume that early Earth experienced whole mantle degassing, which lowered the H2O/Ce ratio in the whole mantle but without depleting Ce in the mantle. The second possible solution is that some deep Earth reservoirs with high H2O/Ce ratios have not been sampled by MORB and OIB. Candidates include the transition zone [8] and the D" layer. The third possible solution is that ocean water only partially originated from mantle degassing, but partially from extraterrestrial sources such as comets [9-10]. At present, there is not enough information to determine which scenario is the answer to the H2O paradox. On the other hand, each scenario would have its own implications to H2O in PLM. If the first scenario applies to Moon, because degassed H2O or H2 would have escaped from the lunar surface, the very early lunar mantle could have much higher H2O [11] than that obtained using the H2O/Ce ratio method. The

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

PubMed

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

2012-01-01

The effect of partial oxygen pressure on growth of Neochloris oleoabundans was studied at sub-saturating light intensity in a fully-controlled stirred tank photobioreactor. At the three partial oxygen pressures tested (P(O)₂= 0.24; 0.63; 0.84 bar), the specific growth rate was 1.38; 1.36 and 1.06 day(-1), respectively. An increase of the P(CO)₂from 0.007 to 0.02 bar at P(O₂) of 0.84 bar resulted in an increase in the growth rate from 1.06 to 1.36 day(-1). These results confirm that the reduction of algal growth at high oxygen concentrations at sub-saturating light conditions is mainly caused by competitive inhibition of Rubisco. This negative effect on growth can be overcome by restoring the O(2)/CO(2) ratio by an increase in the partial carbon dioxide pressure. In comparison to general practice (P(O(2)) = 0.42 bar), working at partial O(2) pressure of 0.84 bar could reduce the energy requirement for degassing by a factor of 3-4. Copyright © 2011 Elsevier Ltd. All rights reserved.

The search for shock-excited H{sub 2} in Virgo spirals experiencing ram pressure stripping

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

We investigate the presence of shock-excited H{sub 2} in four Virgo cluster galaxies that show clear evidence of ongoing ram pressure stripping. Mid-infrared spectral mapping of the rotational H{sub 2} 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 2.6more » excess of warm H{sub 2}/PAH in our sample relative to the observed fractions in other nearby galaxies. We attribute the H{sub 2}/PAH excess to contributions of shock-excited H{sub 2} 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.« less

Simulation of gas bubbles in hypobaric decompressions: roles of O2, CO2, and H2O.

PubMed

Van Liew, H D; Burkard, M E

1995-01-01

To gain insight into the special features of bubbles that may form in aviators and astronauts, we simulated the growth and decay of bubbles in two hypobaric decompressions and a hyperbaric one, all with the same tissue ratio (TR), where TR is defined as tissue PN2 before decompression divided by barometric pressure after. We used an equation system which is solved by numerical methods and accounts for simultaneous diffusion of any number of gases as well as other major determinants of bubble growth and absorption. We also considered two extremes of the number of bubbles which form per unit of tissue. A) Because physiological mechanisms keep the partial pressures of the "metabolic" gases (O2, CO2, and H2O) nearly constant over a range of hypobaric pressures, their fractions in bubbles are inversely proportional to pressure and their large volumes at low pressure add to bubble size. B) In addition, the large fractions facilitate the entry of N2 into bubbles, and when bubble density is low, enhance an autocatalytic feedback on bubble growth due to increasing surface area. C) The TR is not closely related to bubble size; that is when two different decompressions have the same TR, metabolic gases cause bubbles to grow larger at lower hypobaric pressures. We conclude that the constancy of partial pressures of metabolic gases, unimportant in hyperbaric decompressions, affects bubble size in hypobaric decompressions in inverse relation to the exposure pressure.

The use of high pressure CO2 -facilitated pH swings to enhance in situ product recovery of butyric acid in a two-phase partitioning bioreactor.

PubMed

Peterson, Eric C; Daugulis, Andrew J

2014-11-01

Through the use of high partial pressures of CO2 (pCO2 ) to facilitate temporary pH reductions in two-phase partitioning bioreactors (TPPBs), improved pH dependent partitioning of butyric acid was observed which achieved in situ product recovery (ISPR), alleviating end-product inhibition (EPI) during the production of butyric acid by Clostridium tyrobutyricum (ATCC 25755). Through high pressure pCO2 studies, media buffering effects were shown to be substantially overcome at 60 bar pCO2 , resulting in effective extraction of the organic acid by the absorptive polymer Pebax® 2533, yielding a distribution coefficient (D) of 2.4 ± 0.1 after 1 h of contact at this pressure. Importantly, it was also found that C. tyrobutyricum cultures were able to withstand 60 bar pCO2 for 1 h with no decrease in growth ability when returned to atmospheric pressure in batch reactors after several extraction cycles. A fed-batch reactor with cyclic high pCO2 polymer extraction recovered 92 g of butyric acid to produce a total of 213 g compared to 121 g generated in a control reactor. This recovery reduced EPI in the TPPB, resulting in both higher productivity (0.65 vs. 0.33 g L(-1)  h(-1) ) and yield (0.54 vs. 0.40). Fortuitously, it was also found that repeated high pCO2 -facilitated polymer extractions of butyric acid during batch growth of C. tyrobutyricum lessened the need for pH control, and reduced base requirements by approximately 50%. Thus, high pCO2 -mediated absorptive polymer extraction presents a novel method for improving process performance in butyric acid fermentation, and this technique could be applied to the bioproduction of other organic acids as well. © 2014 Wiley Periodicals, Inc.

Non-invasive multiwavelength photoplethysmography under low partial pressure of oxygen.

PubMed

Fang, Yung Chieh; Tai, Cheng-Chi

2016-08-01

A reduction in partial pressure of oxygen in the environment may be caused by a gain in altitude, which reduces the atmospheric pressure; it may also be caused by the carbon dioxide generated from breathing in an enclosed space. Does inhaling oxygen of lower partial pressure affect the oxygen-carrying function of haemoglobin in vivo? This study uses non-invasive multiwavelength photoplethysmography to measure the effects that inhaling this type of oxygen can have on the plethysmography of the appendages of the body (fingertips). The results indicate that under low partial pressure of oxygen, be it the result of a gain in carbon dioxide concentration or altitude, the change in visible light absorption is the biggest for short wavelengths (approximately 620 or 640 nm) near deoxyhaemoglobin, which has higher absorption coefficient. Moreover, increasing carbon dioxide concentration from 5000 to 10,000 ppm doubly reduces the absorption rate of these short wavelengths.

Reproducing early Martian atmospheric carbon dioxide partial pressure by modeling the formation of Mg-Fe-Ca carbonate identified in the Comanche rock outcrops on Mars

NASA Astrophysics Data System (ADS)

Berk, Wolfgang; Fu, Yunjiao; Ilger, Jan-Michael

2012-10-01

The well defined composition of the Comanche rock's carbonate (Magnesite0.62Siderite0.25Calcite0.11Rhodochrosite0.02) and its host rock's composition, dominated by Mg-rich olivine, enable us to reproduce the atmospheric CO2partial pressure that may have triggered the formation of these carbonates. Hydrogeochemical one-dimensional transport modeling reveals that similar aqueous rock alteration conditions (including CO2partial pressure) may have led to the formation of Mg-Fe-Ca carbonate identified in the Comanche rock outcrops (Gusev Crater) and also in the ultramafic rocks exposed in the Nili Fossae region. Hydrogeochemical conditions enabling the formation of Mg-rich solid solution carbonate result from equilibrium species distributions involving (1) ultramafic rocks (ca. 32 wt% olivine; Fo0.72Fa0.28), (2) pure water, and (3) CO2partial pressures of ca. 0.5 to 2.0 bar at water-to-rock ratios of ca. 500 molH2O mol-1rock and ca. 5°C (278 K). Our modeled carbonate composition (Magnesite0.64Siderite0.28Calcite0.08) matches the measured composition of carbonates preserved in the Comanche rocks. Considerably different carbonate compositions are achieved at (1) higher temperature (85°C), (2) water-to-rock ratios considerably higher and lower than 500 mol mol-1 and (3) CO2partial pressures differing from 1.0 bar in the model set up. The Comanche rocks, hosting the carbonate, may have been subjected to long-lasting (>104 to 105 years) aqueous alteration processes triggered by atmospheric CO2partial pressures of ca. 1.0 bar at low temperature. Their outcrop may represent a fragment of the upper layers of an altered olivine-rich rock column, which is characterized by newly formed Mg-Fe-Ca solid solution carbonate, and phyllosilicate-rich alteration assemblages within deeper (unexposed) units.

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

PubMed

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

2008-01-01

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

Relating oxygen partial pressure, saturation and content: the haemoglobin-oxygen dissociation curve.

PubMed

Collins, Julie-Ann; Rudenski, Aram; Gibson, John; Howard, Luke; O'Driscoll, Ronan

2015-09-01

The delivery of oxygen by arterial blood to the tissues of the body has a number of critical determinants including blood oxygen concentration (content), saturation (S O2 ) and partial pressure, haemoglobin concentration and cardiac output, including its distribution. The haemoglobin-oxygen dissociation curve, a graphical representation of the relationship between oxygen satur-ation and oxygen partial pressure helps us to understand some of the principles underpinning this process. Historically this curve was derived from very limited data based on blood samples from small numbers of healthy subjects which were manipulated in vitro and ultimately determined by equations such as those described by Severinghaus in 1979. In a study of 3524 clinical specimens, we found that this equation estimated the S O2 in blood from patients with normal pH and S O2 >70% with remarkable accuracy and, to our knowledge, this is the first large-scale validation of this equation using clinical samples. Oxygen saturation by pulse oximetry (S pO2 ) is nowadays the standard clinical method for assessing arterial oxygen saturation, providing a convenient, pain-free means of continuously assessing oxygenation, provided the interpreting clinician is aware of important limitations. The use of pulse oximetry reduces the need for arterial blood gas analysis (S aO2 ) as many patients who are not at risk of hypercapnic respiratory failure or metabolic acidosis and have acceptable S pO2 do not necessarily require blood gas analysis. While arterial sampling remains the gold-standard method of assessing ventilation and oxygenation, in those patients in whom blood gas analysis is indicated, arterialised capillary samples also have a valuable role in patient care. The clinical role of venous blood gases however remains less well defined.

A flowing liquid test system for assessing the linearity and time-response of rapid fibre optic oxygen partial pressure sensors.

PubMed

Chen, R; Hahn, C E W; Farmery, A D

2012-08-15

The development of a methodology for testing the time response, linearity and performance characteristics of ultra fast fibre optic oxygen sensors in the liquid phase is presented. Two standard medical paediatric oxygenators are arranged to provide two independent extracorporeal circuits. Flow from either circuit can be diverted over the sensor under test by means of a system of rapid cross-over solenoid valves exposing the sensor to an abrupt change in oxygen partial pressure, P O2. The system is also capable of testing the oxygen sensor responses to changes in temperature, carbon dioxide partial pressure P CO2 and pH in situ. Results are presented for a miniature fibre optic oxygen sensor constructed in-house with a response time ≈ 50 ms and a commercial fibre optic sensor (Ocean Optics Foxy), when tested in flowing saline and stored blood. Copyright © 2012 Elsevier B.V. All rights reserved.

H2(15)O or 13NH3 PET and electromagnetic tomography (LORETA) during partial status epilepticus.

PubMed

Zumsteg, D; Wennberg, R A; Treyer, V; Buck, A; Wieser, H G

2005-11-22

The authors evaluated the feasibility and source localization utility of H2(15)O or 13NH3 PET and low-resolution electromagnetic tomography (LORETA) in three patients with partial status epilepticus (SE). Results were correlated with findings from intraoperative electrocorticographic recordings and surgical outcomes. PET studies of cerebral blood flow and noninvasive source modeling with LORETA using statistical nonparametric mapping provided useful information for localizing the ictal activity in patients with partial SE.

Regimes of an atmospheric pressure nanosecond repetitively pulsed discharge for methane partial oxidation

NASA Astrophysics Data System (ADS)

Maqueo, P. D. G.; Maier, M.; Evans, M. D. G.; Coulombe, S.; Bergthorson, J. M.

2018-04-01

The operation of a nanosecond repetitively pulsed discharge for partial oxidation of CH4 is characterized at atmospheric pressure and room temperature. Two regimes are observed: diffuse and filamentary. The first is a low power regime, characterized by low rotational temperatures around 400 K. The second is much more energetic with rotational temperatures close to 600 K. Both have vibrational temperatures of at least 10 times their rotational temperatures. The average electron number density was determined to be 8.9×1015 and 4.0×1017 cm-3, respectively, showing an increase in the ionization fraction in the more powerful filamentary regime. Results of CH4 conversion to H2, CO, CO2 and C2H6 are presented for the filamentary regime, while the diffuse regime shows no measurable conversion ability. As expected, oxidative mixtures show higher conversion ability than pure CH4. A maximum conversion efficiency of 26.3% and a maximum energy efficiency of 19.7% were reached for the oxidative mixtures.

Temperature dependence of partial conductivities of the BaZr0.7Ce0.2Y0.1O3-δ proton conductor

NASA Astrophysics Data System (ADS)

Heras-Juaristi, Gemma; Pérez-Coll, Domingo; Mather, Glenn C.

2017-10-01

Partial conductivities are presented for BaZr0.7Ce0.2Y0.1O3-δ, an important proton conductor for protonic-ceramic fuel cells and membrane reactors. Atmospheric dependencies of impedance performed in humidified and dry O2, air, N2 and H2(10%)/N2(90%) in the temperature range 300-900 °C, supported by the modified emf method, confirm significant electron-hole and protonic contributions to transport. For very reducing and wet atmospheres, the conductivity is predominantly ionic, with a higher participation of protons with decreasing temperature and increasing water-vapour partial pressure (pH2O). From moderately reducing conditions of wet N2 to wet O2, however, the conductivity is considerably influenced by electron holes as revealed by a significant dependence of total conductivity on oxygen partial pressure (pO2). With higher pH2O, proton transport increases, with a concomitant decrease of holes and oxygen vacancies. However, the effect of pH2O is also influenced by temperature, with a greater protonic contribution at both lower temperature and pO2. Values of proton transport number tH ≈ 0.63 and electronic transport number th ≈ 0.37 are obtained at 600 °C for pH2O = 0.022 atm and pO2 = 0.2 atm, whereas tH ≈ 0.95 and th ≈ 0.05 for pO2 = 10-5 atm. A hydration enthalpy of -109 kJ mol-1 is obtained in the range 600-900 °C.

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

NASA Technical Reports Server (NTRS)

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

2011-01-01

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

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

USGS Publications Warehouse

Chou, I.-Ming; Blank, J.G.; Goncharov, A.F.; Mao, Ho-kwang; Hemley, R.J.

1998-01-01

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

Effects of Oxygen Partial Pressure on the Surface Tension of Liquid Nickel

NASA Technical Reports Server (NTRS)

SanSoucie, Michael P.; Rogers, Jan R.; Gowda, Vijaya Kumar Malahalli Shankare; Rodriguez, Justin; Matson, Douglas M.

2015-01-01

The NASA Marshall Space Flight Center's electrostatic levitation (ESL) laboratory has been recently upgraded with an oxygen partial pressure controller. This system allows the oxygen partial pressure within the vacuum chamber to be measured and controlled, theoretically in the range from 10-36 to 100 bar. The oxygen control system installed in the ESL laboratory's main chamber consists of an oxygen sensor, oxygen pump, and a control unit. The sensor is a potentiometric device that determines the difference in oxygen activity in two gas compartments (inside the chamber and the air outside of the chamber) separated by an electrolyte, which is yttria-stabilized zirconia. The pump utilizes coulometric titration to either add or remove oxygen. The system is controlled by a desktop control unit, which can also be accessed via a computer. The controller performs temperature control for the sensor and pump, PID-based current loop, and a control algorithm. Oxygen partial pressure has been shown to play a significant role in the surface tension of liquid metals. Oxide films or dissolved oxygen may lead to significant changes in surface tension. The effects of oxygen partial pressure on the surface tension of undercooled liquid nickel will be analyzed, and the results will be presented. The surface tension will be measured at several different oxygen partial pressures while the sample is undercooled. Surface tension will be measured using the oscillating drop method. While undercooled, each sample will be oscillated several times consecutively to investigate how the surface tension behaves with time while at a particular oxygen partial pressure.

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

PubMed

Alvarez-Camacho, Michelín; Urrusti, José Luis; Acero, María Del Carmen; Galván Duque-Gastélum, Carlos; Rodríguez-Reyes, Gerardo; Mendoza-Cruz, Felipe

2014-07-01

A device for dynamic acquisition and distribution analysis of in-socket pressure for patients with partial foot amputation is presented in this work. By using the developed system, we measured and generated pressure distribution graphs, obtained maximal pressure, and calculated pressure-time integral (PTI) of three subjects with partial foot amputation and of a group of Healthy subjects (Hs) (n = 10). Average maximal pressure in the healthy group was 19.4 ± 4.11 PSI, while for the three amputated patients, this was 27.8 ± 1.38, 17.6 ± 1.15, 29.10 ± 3.9 PSI, respectively. Maximal pressure-time integral for healthy subjects was 11.56 ± 2.83 PSI*s, and for study subjects was 19.54 ± 1.9, 12.35 ± 1.48, and 13.17 ± 1.31 PSI*s, respectively. The results of the control group agree with those previously reported in the literature. The pressure distribution pattern showed clear differences between study subjects and those of the control group; these graphs allowed us to identify the pressure in regions-of-interest that could be critical, such as surgical scars. The system presented in this work will aid to assess the effectiveness with which prosthetic systems distribute load, given that the formation of ulcers is highly linked to the pressure exercised at the point of contact; in addition, these results will help to investigate the comfort perception of the prosthesis, a factor directly influenced by the stump's pressure distribution.

Effect of oxygen partial pressure and VO2 content on hexagonal WO3 thin films synthesized by pulsed laser deposition technique

NASA Astrophysics Data System (ADS)

Kaushal, Ajay; Kaur, Davinder

2011-06-01

We report on the effect of oxygen partial pressure and vacuum annealing on structural and optical properties of pulsed laser-deposited nanocrystalline WO3 thin films. XRD results show the hexagonal phase of deposited WO3 thin films. The crystallite size was observed to increase with increase in oxygen partial pressure. Vacuum annealing changed the transparent as-deposited WO3 thin film to deep shade of blue color which increases the optical absorption of the film. The origin of this blue color could be due to the presence of oxygen vacancies associated with tungsten ions in lower oxidation states. In addition, the effects of VO2 content on structural, electrochemical, and optical properties of (WO3)1- x (VO2) x nanocomposite thin films have also been systematically investigated. Cyclic voltammogram exhibits a modification with the appearance of an extra cathodic peak for VO2-WO3 thin film electrode with higher VO2 content ( x ≥ 0.2). Increase of VO2 content in (WO3)1- x (VO2) x films leads to red shift in optical band gap.

Utilizing a one-dimensional multispecies model to simulate the nutrient reduction and biomass structure in two types of H2-based membrane-aeration biofilm reactors (H2-MBfR): model development and parametric analysis.

PubMed

Wang, Zuowei; Xia, Siqing; Xu, Xiaoyin; Wang, Chenhui

2016-02-01

In this study, a one-dimensional multispecies model (ODMSM) was utilized to simulate NO3(-)-N and ClO4(-) reduction performances in two kinds of H2-based membrane-aeration biofilm reactors (H2-MBfR) within different operating conditions (e.g., NO3(-)-N/ClO4(-) loading rates, H2 partial pressure, etc.). Before the simulation process, we conducted the sensitivity analysis of some key parameters which would fluctuate in different environmental conditions, then we used the experimental data to calibrate the more sensitive parameters μ1 and μ2 (maximum specific growth rates of denitrification bacteria and perchlorate reduction bacteria) in two H2-MBfRs, and the diversity of the two key parameters' values in two types of reactors may be resulted from the different carbon source fed in the reactors. From the simulation results of six different operating conditions (four in H2-MBfR 1 and two in H2-MBfR 2), the applicability of the model was approved, and the variation of the removal tendency in different operating conditions could be well simulated. Besides, the rationality of operating parameters (H2 partial pressure, etc.) could be judged especially in condition of high nutrients' loading rates. To a certain degree, the model could provide theoretical guidance to determine the operating parameters on some specific conditions in practical application.

[Effects of gap junction blocking on the oxygen partial pressure in acupoints of the bladder meridian].

PubMed

Wang, Qi; Yu, Wei-Chang; Jiang, Hong-Zhi; Chen, Sheng-Li; Zhang, Ming-Min; Kong, E-Sheng; Huang, Guang-Ying

2010-12-01

To explore the relation between gap junction and meridian phenomenon. The oxygen partial pressure in acupoints [see text for formula] and in their corresponding non-acupoints of the Bladder Meridian was observed with the needle-type tissue oxygen tension sensor in the gap junction blocking goats by 1-Heptanol injection and the Connexin 43 (Cx43) gene knockout mice. (1) The oxygen partial pressure in acupoints of Bladder Meridian on goats was higher than that in non-acupoints after 1-Heptanol injection with significant differences between them (both P < 0.01). (2) The oxygen partial pressure in acupoints of Bladder Meridian on goats increased significantly after injecting 1-Heptanol as compare with that either injecting normal saline or injecting nothing with significant differences between them (all P < 0.01). (3) The oxygen partial pressure in acupoints of the Bladder Meridian was significantly higher than that in the non-acupoint controls in Cx43 wild type (WT) mice (all P < 0.01). In Cx43 heterozygote (HT) mice, the oxygen partial pressure between acupoints and non-acupoint controls showed no significant differences (all P > 0.05). (4) In acupoints, the oxygen partial pressure in Cx43 WT mice was significantly higher than that in Cx43 HT mice (all P < 0.05), while in the corresponding non-acupoints, this difference had no statistically significant (all P > 0.05). Gap junction maybe the essential factor in signal transduction of acupuncture.

Modulation of paraquat toxicity by beta-carotene at low oxygen partial pressure in chicken embryo fibroblasts.

PubMed

Lawlor, S M; O'Brien, N M

1997-01-01

The efficiency with which beta-carotene protects against oxidative stress in chicken embryo fibroblasts (CEF) at low O2 partial pressures was assessed. Primary cultures of CEF were grown at low O2 partial pressures and oxidatively stressed by exposure to paraquat (PQ). Activities of the antioxidant enzymes superoxide dismutase (EC 1.15.1.1; SOD), catalase (EC 1.11.1.6; CAT) and glutathione peroxidase (EC 1.11.1.9; GSH-Px) were measured as indices of oxidative stress. CEF incubated with 0.25-1.0 mM-PQ for 18 h exhibited increased SOD and CAT activities compared with non-PQ-treated control cells (P < 0.001). No cytotoxicity as indicated by lactate dehydrogenase (EC 1.1.1.27; LDH) release was observed at PQ concentrations below 2.0 mM. Incorporation of added beta-carotene into 0.25 mM-PQ-treated cells prevented the PQ-induced increases in SOD and CAT, and activities were similar to those seen in non-PQ-treated control cells. GSH-Px activity decreased relative to its control value on exposure to 0.25 mM-PQ and beta-carotene prevented this decrease in a dose-dependent manner. The proportion of LDH released from the CEF treated with beta-carotene remained below the control value of 2.5% at all times.

Mechanisms of scale formation and carbon dioxide partial pressure influence. Part II. Application in the study of mineral waters of reference.

PubMed

Gal, Jean-Yves; Fovet, Yannick; Gache, Nathalie

2002-02-01

In the first part, we have designed a new model of evolution for the calco-carbonic system which includes the hydrated forms of CaCO3: CaCO3 amorphous, CaCO3 x 6H2O (ikaite) and CaCO3 x H2O (monohydrate) (J. Eur. Hydr. 30 (1999) 47). According to this model, it is the precipitation of one or other of these hydrated forms which could be responsible for the breakdown of the metastable state. After this first step, the precipitates evolve to dehydrated solid forms. Through the elaboration of computer programs in which the CaCO3(0) (aq) ion pair formation was considered, this model was compared to experimental data obtained by the critical pH method applied to synthetic solutions. In the present article, the same method was applied for four French mineral waters, at 25 degrees C under study. Three samples formed a precipitation during the sodium hydroxide addition. For these three cases, this precipitation began for the CaCO3 H2O saturation. The added volume of sodium hydroxide was more than what was required for neutralizing free CO2 initially in solution. These results indicate that during a spontaneous scaling phenomenon, the pH rises at the same time by loss of the initial free CO2 and of the one produced by the hydrogen carbonate ions decomposition. Then we calculated, at various temperatures for the three studied scaling waters: CO2 partial pressures and loss of total carbon corresponding to the solubility products of CaCO3 hydrated forms. The results show that the partial pressure monitoring of the carbon dioxide is important in managing the behavior of scaling waters.

Solubility of water in lunar basalt at low pH2O

NASA Astrophysics Data System (ADS)

Newcombe, M. E.; Brett, A.; Beckett, J. R.; Baker, M. B.; Newman, S.; Guan, Y.; Eiler, J. M.; Stolper, E. M.

2017-03-01

We report the solubility of water in Apollo 15 basaltic "Yellow Glass" and an iron-free basaltic analog composition at 1 atm and 1350 °C. We equilibrated melts in a 1-atm furnace with flowing H2/CO2 gas mixtures that spanned ∼8 orders of magnitude in fO2 (from three orders of magnitude more reducing than the iron-wüstite buffer, IW-3.0, to IW+4.8) and ∼4 orders of magnitude in pH2/pH2O (from 0.003 to 24). Based on Fourier transform infrared spectroscopy (FTIR), our quenched experimental glasses contain 69-425 ppm total water (by weight). Our results demonstrate that under the conditions of our experiments: (1) hydroxyl is the only H-bearing species detected by FTIR; (2) the solubility of water is proportional to the square root of pH2O in the furnace atmosphere and is independent of fO2 and pH2/pH2O; (3) the solubility of water is very similar in both melt compositions; (4) the concentration of H2 in our iron-free experiments is <∼4 ppm, even at oxygen fugacities as low as IW-2.3 and pH2/pH2O as high as 11; (5) Secondary ion mass spectrometry (SIMS) analyses of water in iron-rich glasses equilibrated under variable fO2 conditions may be strongly influenced by matrix effects, even when the concentration of water in the glasses is low; and (6) Our results can be used to constrain the entrapment pressure of lunar melt inclusions and the partial pressures of water and molecular hydrogen in the carrier gas of the lunar pyroclastic glass beads. We find that the most water-rich melt inclusion of Hauri et al. (2011) would be in equilibrium with a vapor with pH2O ∼ 3 bar and pH2 ∼ 8 bar. We constrain the partial pressures of water and molecular hydrogen in the carrier gas of the lunar pyroclastic glass beads to be 0.0005 bar and 0.0011 bar respectively. We calculate that batch degassing of lunar magmas containing initial volatile contents of 1200 ppm H2O (dissolved primarily as hydroxyl) and 4-64 ppm C would produce enough vapor to reach the critical vapor

Effect of pressure on the tetragonal distortion in TiH2: a first-principles study

NASA Astrophysics Data System (ADS)

de Coss, R.; Quijano, R.; Singh, D. J.

2009-03-01

The transition metal dihydride TiH2 present the fluorite structure (CaF2) at high temperature but undergoes a tetragonal distortion with c/a<1 at low temperature. Early electronic band structure calculations have shown that TiH2 in the cubic phase display a nearly flat double degenerated band at the Fermi level. Thus the low temperature tetragonal distortion has been associated to a Jahn-Teller effect. Nevertheless, recently we have show that the instability of fcc-TiH2 is likely to be related with a van Hove singularity. In the present work, we have performed ab-initio calculations of the electronic structure and the tetragonal distortion for TiH2 under pressure (0-30 GPa). We found that the fcc-fct energy barrier and the tetragonal distortion increases with pressure. The evolution of the tetragonal distortion is analyzed in terms of the electronic band structure. This research was supported by Consejo Nacional de Ciencia y Tecnolog'ia (Conacyt) under Grant No. 49985.

Diagnostic system for measuring temperature, pressure, CO2 concentration and H2O concentration in a fluid stream

DOE Office of Scientific and Technical Information (OSTI.GOV)

Partridge, Jr., William P.; Jatana, Gurneesh Singh; Yoo, Ji-Hyung

A diagnostic system for measuring temperature, pressure, CO.sub.2 concentration and H.sub.2O concentration in a fluid stream is described. The system may include one or more probes that sample the fluid stream spatially, temporally and over ranges of pressure and temperature. Laser light sources are directed down pitch optical cables, through a lens and to a mirror, where the light sources are reflected back, through the lens to catch optical cables. The light travels through the catch optical cables to detectors, which provide electrical signals to a processer. The processer utilizes the signals to calculate CO.sub.2 concentration based on the temperaturesmore » derived from H.sub.2O vapor concentration. A probe for sampling CO.sub.2 and H.sub.2O vapor concentrations is also disclosed. Various mechanical features interact together to ensure the pitch and catch optical cables are properly aligned with the lens during assembly and use.« less

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

ERIC Educational Resources Information Center

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

2007-01-01

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

Effect of pressure on the magnetic properties of TM3[Cr(CN)6]2·12H2O

NASA Astrophysics Data System (ADS)

Zentková, M.; Arnold, Z.; Kamarád, J.; Kavecanský, V.; Lukácová, M.; Mat'aš, S.; Mihalik, M.; Mitróová, Z.; Zentko, A.

2007-07-01

We present the results of magnetization and AC susceptibility measurements performed on ferrimagnetic Mn32+[CrIII(CN)6]2·12H2O and ferromagnetic Ni32+[CrIII(CN)6]2·12H2O systems under pressures up to 0.9 GPa in a commercial SQUID magnetometer. The magnetization process is affected by pressure: magnetization saturates at higher magnetic field, saturated magnetization μs of Ni3[Cr(CN)6]2 is reduced and almost unaffected for Mn3[Cr(CN)6]2 at low temperatures. The Curie temperature TC of Mn3[Cr(CN)6]2 increases with the applied pressure, ΔTC/Δp = 25.5 K GPa-1, due to a strengthened super-exchange antiferromagnetic interaction JAF, but it is not affected significantly in the case of Ni3[Cr(CN)6]2 with a dominant ferromagnetic JF super-exchange interaction. The increase in the JAF interaction is attributed to the enhanced value of the single electron overlapping integral S and the energy gap Δ of the mixed molecular orbitals t2g (Mn2+) and t2g (CrIII) induced by pressure.

The pH and pCO2 dependence of sulfate reduction in shallow-sea hydrothermal CO2 - venting sediments (Milos Island, Greece).

PubMed

Bayraktarov, Elisa; Price, Roy E; Ferdelman, Timothy G; Finster, Kai

2013-01-01

Microbial sulfate reduction (SR) is a dominant process of organic matter mineralization in sulfate-rich anoxic environments at neutral pH. Recent studies have demonstrated SR in low pH environments, but investigations on the microbial activity at variable pH and CO2 partial pressure are still lacking. In this study, the effect of pH and pCO2 on microbial activity was investigated by incubation experiments with radioactive (35)S targeting SR in sediments from the shallow-sea hydrothermal vent system of Milos, Greece, where pH is naturally decreased by CO2 release. Sediments differed in their physicochemical characteristics with distance from the main site of fluid discharge. Adjacent to the vent site (T ~40-75°C, pH ~5), maximal sulfate reduction rates (SRR) were observed between pH 5 and 6. SR in hydrothermally influenced sediments decreased at neutral pH. Sediments unaffected by hydrothermal venting (T ~26°C, pH ~8) expressed the highest SRR between pH 6 and 7. Further experiments investigating the effect of pCO2 on SR revealed a steep decrease in activity when the partial pressure increased from 2 to 3 bar. Findings suggest that sulfate reducing microbial communities associated with hydrothermal vent system are adapted to low pH and high CO2, while communities at control sites required a higher pH for optimal activity.

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

PubMed

Umemoto, Hironobu; Kanemitsu, Taijiro; Tanaka, Akihito

2014-07-17

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

Optical and electronic properties of 2 H -Mo S2 under pressure: Revealing the spin-polarized nature of bulk electronic bands

NASA Astrophysics Data System (ADS)

Brotons-Gisbert, Mauro; Segura, Alfredo; Robles, Roberto; Canadell, Enric; Ordejón, Pablo; Sánchez-Royo, Juan F.

2018-05-01

Monolayers of transition-metal dichalcogenide semiconductors present spin-valley locked electronic bands, a property with applications in valleytronics and spintronics that is usually believed to be absent in their centrosymmetric (as the bilayer or bulk) counterparts. Here we show that bulk 2 H -Mo S2 hides a spin-polarized nature of states determining its direct band gap, with the spin sequence of valence and conduction bands expected for its single layer. This relevant finding is attained by investigating the behavior of the binding energy of A and B excitons under high pressure, by means of absorption measurements and density-functional-theory calculations. These results raise an unusual situation in which bright and dark exciton degeneracy is naturally broken in a centrosymmetric material. Additionally, the phonon-assisted scattering process of excitons has been studied by analyzing the pressure dependence of the linewidth of discrete excitons observed at the absorption coefficient edge of 2 H -Mo S2 . Also, the pressure dependence of the indirect optical transitions of bulk 2 H -Mo S2 has been analyzed by absorption measurements and density-functional-theory calculations. These results reflect a progressive closure of the indirect band gap as pressure increases, indicating that metallization of bulk Mo S2 may occur at pressures higher than 26 GPa.

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

NASA Astrophysics Data System (ADS)

Mathias, Simon A.; Gluyas, Jon G.; GonzáLez MartíNez de Miguel, Gerardo J.; Hosseini, Seyyed A.

2011-12-01

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

Na2S, a fast-releasing H2S donor, given as suppository lowers blood pressure in rats.

PubMed

Tomasova, Lenka; Drapala, Adrian; Jurkowska, Halina; Wróbel, Maria; Ufnal, Marcin

2017-10-01

Hydrogen sulfide (H 2 S) is involved in blood pressure control. The available slow-releasing H 2 S-donors are poorly soluble in water and their ability to release H 2 S in biologically relevant amounts under physiological conditions is questionable. Therefore, new slow-releasing donors or new experimental approaches to fast-releasing H 2 S donors are needed. Hemodynamics and ECG were recorded in male, anesthetized Wistar Kyoto rats (WKY) and in Spontaneously hypertensive rats (SHR) at baseline and after: 1) intravenous (iv) infusion of vehicle or Na 2 S; 2) administration of vehicle suppositories or Na 2 S suppositories. Intravenously administered vehicle and vehicle suppositories did not affect mean arterial blood pressure (MABP) and heart rate (HR). Na 2 S administered iv caused a significant, but transient (2-5min) decrease in MABP. Na 2 S suppositories produced a dose-dependent hypotensive response that lasted ∼45min in WKY and ∼75-80min in SHR. It was accompanied by a decrease in HR in WKY, and an increase in HR in SHR. Na 2 S suppositories did not produce a significant change in corrected QT, an indicator of cardiotoxicity. Na 2 S suppositories increased blood level of thiosulfates, products of H 2 S oxidation. Na 2 S administered in suppositories exerts a prolonged hypotensive effect in rats, with no apparent cardiotoxic effect. SHR and WKY differ in hemodynamic response to the H 2 S donor. Suppository formulation of fast-releasing H 2 S donors may be useful in research, if a reference slow-releasing H 2 S donor is not available. Copyright © 2017 Institute of Pharmacology, Polish Academy of Sciences. Published by Elsevier Urban & Partner Sp. z o.o. All rights reserved.

Thermodynamics of Silicon-Hydroxide Formation in H2O Containing Atmospheres

NASA Technical Reports Server (NTRS)

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

2001-01-01

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

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

NASA Technical Reports Server (NTRS)

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

1973-01-01

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

Significant Enhancement of H2 Formation in Disk Galaxies under Strong Ram Pressure

NASA Astrophysics Data System (ADS)

Henderson, Benjamin; Bekki, Kenji

2016-05-01

We show for the first time that H2 formation on dust grains can be enhanced in disk galaxies under strong ram pressure (RP). We numerically investigate how the time evolution of H I and H2 components in disk galaxies orbiting a group/cluster of galaxies can be influenced by the hydrodynamical interaction between the gaseous components of the galaxies and the hot intracluster medium. We find that compression of H I caused by RP increases H2 formation in disk galaxies before RP rapidly strips H I, cutting off the fuel supply and causing a drop in H2 density. We also find that the level of this H2 formation enhancement in a disk galaxy under RP depends on the mass of its host cluster dark matter halo, the initial positions and velocities of the disk galaxy, and the disk inclination angle with respect to the orbital plane. We demonstrate that dust growth is a key factor in the evolution of the H I and H2 mass in disk galaxies under strong RP. We discuss how the correlation between H2 fractions and surface gas densities of disk galaxies evolves with time in the galaxies under RP. We also discuss whether galaxy-wide star formation rates (SFRs) in cluster disk galaxies can be enhanced by RP if the SFRs depend on H2 densities.

Turbulence in Supercritical O2/H2 and C7H16/N2 Mixing Layers

NASA Technical Reports Server (NTRS)

Bellan, Josette; Harstad, Kenneth; Okong'o, Nora

2003-01-01

This report presents a study of numerical simulations of mixing layers developing between opposing flows of paired fluids under supercritical conditions, the purpose of the study being to elucidate chemical-species-specific aspects of turbulence. The simulations were performed for two different fluid pairs O2/H2 and C7H16/N2 at similar reduced initial pressures (reduced pressure is defined as pressure divided by critical pressure). Thermodynamically, O2/H2 behaves more nearly like an ideal mixture and has greater solubility, relative to C7H16/N2, which departs strongly from ideality. Because of a specified smaller initial density stratification, the C7H16/N2 layers exhibited greater levels of growth, global molecular mixing, and turbulence. However, smaller density gradients at the transitional state for the O2/H2 system were interpreted as indicating that locally, this system exhibits enhanced mixing as a consequence of its greater solubility and closer approach to ideality. These thermodynamic features were shown to affect entropy dissipation, which was found to be larger for O2/H2 and concentrated in high-density-gradient-magnitude regions that are distortions of the initial density-stratification boundary. In C7H16/N2, the regions of largest dissipation were found to lie in high-density-gradient-magnitude regions that result from mixing of the two fluids.

The pH and pCO2 dependence of sulfate reduction in shallow-sea hydrothermal CO2 – venting sediments (Milos Island, Greece)

PubMed Central

Bayraktarov, Elisa; Price, Roy E.; Ferdelman, Timothy G.; Finster, Kai

2013-01-01

Microbial sulfate reduction (SR) is a dominant process of organic matter mineralization in sulfate-rich anoxic environments at neutral pH. Recent studies have demonstrated SR in low pH environments, but investigations on the microbial activity at variable pH and CO2 partial pressure are still lacking. In this study, the effect of pH and pCO2 on microbial activity was investigated by incubation experiments with radioactive 35S targeting SR in sediments from the shallow-sea hydrothermal vent system of Milos, Greece, where pH is naturally decreased by CO2 release. Sediments differed in their physicochemical characteristics with distance from the main site of fluid discharge. Adjacent to the vent site (T ~40–75°C, pH ~5), maximal sulfate reduction rates (SRR) were observed between pH 5 and 6. SR in hydrothermally influenced sediments decreased at neutral pH. Sediments unaffected by hydrothermal venting (T ~26°C, pH ~8) expressed the highest SRR between pH 6 and 7. Further experiments investigating the effect of pCO2 on SR revealed a steep decrease in activity when the partial pressure increased from 2 to 3 bar. Findings suggest that sulfate reducing microbial communities associated with hydrothermal vent system are adapted to low pH and high CO2, while communities at control sites required a higher pH for optimal activity. PMID:23658555

Fluid responsiveness predicted by transcutaneous partial pressure of oxygen in patients with circulatory failure: a prospective study.

PubMed

Xu, Jingyuan; Peng, Xiao; Pan, Chun; Cai, Shixia; Zhang, Xiwen; Xue, Ming; Yang, Yi; Qiu, Haibo

2017-12-01

Significant effort has been devoted to defining parameters for predicting fluid responsiveness. Our goal was to study the feasibility of predicting fluid responsiveness by transcutaneous partial pressure of oxygen (PtcO 2 ) in the critically ill patients. This was a single-center prospective study conducted in the intensive care unit of a tertiary care teaching hospital. Shock patients who presented with at least one clinical sign of inadequate tissue perfusion, defined as systolic blood pressure <90 mmHg or a decrease >40 mmHg in previously hypertensive patients or the need for vasopressive drugs; urine output <0.5 ml/kg/h for 2 h; tachycardia; lactate >4 mmol/l, for less than 24 h in the absence of a contraindication for fluids were eligible to participate in the study. PtcO 2 was continuously recorded before and during a passive leg raising (PLR) test, and then before and after a 250 ml rapid saline infusion in 10 min. Fluid responsiveness is defined as a change in the stroke volume ≥10% after 250 ml of volume infusion. Thirty-four patients were included, and 14 responded to volume expansion. In the responders, the mean arterial pressure, central venous pressure, cardiac output, stroke volume and PtcO 2 increased significantly, while the heart rate decreased significantly by both PLR and volume expansion. Changes in the stroke volume induced either by PLR or volume expansion were significantly greater in responders than in non-responders. The correlation between the changes in PtcO 2 and stroke volume induced by volume expansion was significant. Volume expansion induced an increase in the PtcO 2 of 14% and PLR induced an increase in PtcO 2 of 13% predicted fluid responsiveness. This study suggested the changes in PtcO 2 induced by volume expansion and a PLR test predicted fluid responsiveness in critically ill patients. Trial registration NCT02083757.

Measurements and Modeling of SiCl(4) Combustion in a Low-Pressure H2/O2 Flame

DTIC Science & Technology

2006-11-10

temperature and OH concentration profiles as a function of distance from a McKenna-style burner in premixed, one-dimensional, low-pressure H2/0 2/Ar SiCl4 ...profiles for hydrogen/oxygen flames with and without SiCl4 ....... . .. . .. . . . . . 15 111,o Tables 1. Silicon Tetrachloride Proposed Combustion...studied with and without SiCI4 precursor at concentrations of 0.5% of the H 2 + 02 flow. For the experiments doped with SiCl4 , the oxygen flow exiting the

Comparison of exogenous surfactant therapy, mechanical ventilation with high end-expiratory pressure and partial liquid ventilation in a model of acute lung injury.

PubMed

Hartog, A; Vazquez de Anda, G F; Gommers, D; Kaisers, U; Verbrugge, S J; Schnabel, R; Lachmann, B

1999-01-01

We have compared three treatment strategies, that aim to prevent repetitive alveolar collapse, for their effect on gas exchange, lung mechanics, lung injury, protein transfer into the alveoli and surfactant system, in a model of acute lung injury. In adult rats, the lungs were ventilated mechanically with 100% oxygen and a PEEP of 6 cm H2O, and acute lung injury was induced by repeated lung lavage to obtain a PaO2 value < 13 kPa. Animals were then allocated randomly (n = 12 in each group) to receive exogenous surfactant therapy, ventilation with high PEEP (18 cm H2O), partial liquid ventilation or ventilation with low PEEP (8 cm H2O) (ventilated controls). Blood-gas values were measured hourly. At the end of the 4-h study, in six animals per group, pressure-volume curves were constructed and bronchoalveolar lavage (BAL) was performed, whereas in the remaining animals lung injury was assessed. In the ventilated control group, arterial oxygenation did not improve and protein concentration of BAL and conversion of active to non-active surfactant components increased significantly. In the three treatment groups, PaO2 increased rapidly to > 50 kPa and remained stable over the next 4 h. The protein concentration of BAL fluid increased significantly only in the partial liquid ventilation group. Conversion of active to non-active surfactant components increased significantly in the partial liquid ventilation group and in the group ventilated with high PEEP. In the surfactant group and partial liquid ventilation groups, less lung injury was found compared with the ventilated control group and the group ventilated with high PEEP. We conclude that although all three strategies improved PaO2 to > 50 kPa, the impact on protein transfer into the alveoli, surfactant system and lung injury differed markedly.

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

NASA Technical Reports Server (NTRS)

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

1991-01-01

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

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

PubMed

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

2013-12-23

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

Annealing temperature and O2 partial pressure dependence of T(sub c) in HgBa2CuO(4+delta)

NASA Technical Reports Server (NTRS)

Xiong, Q.; Cao, Y.; Chen, F.; Xue, Y. Y.; Chu, C. W.

1994-01-01

Samples of HgBa2CuO(4+delta) (Hg-1201) were annealed under various conditions. After carefully controlling annealing time, annealing temperature (T(sub a)) and O2 partial pressure (P(sub 0)), we were able to find the reversible annealing conditions for Hg-1201. Under 1 atm O2 at 260 C less than or equal to T(sub a) less than or equal to 400 C, the obtained T(sub c) is nearly the same (approximately 97 K). However, it decreases quickly with T(sub a) greater than 300 C in high vacuum (P(sub 0) approximately 10(exp -8) atm), and reaches zero at T(sub a) = 400 C. On the other hand, T(sub c) decreases with the decrease of T(sub a) in high-pressure O2 (approximately 500 atm) and reaches approximately 20 K at about 240 C. In the entire annealing region, the oxygen surplus varies significantly from 0.03 to 0.4, and a wide range of T(sub c) variation (0 goes to 97 K goes to 20 K) was obtained with anion doping alone.

Calibration Of Partial-Pressure-Of-Oxygen Sensors

NASA Technical Reports Server (NTRS)

Yount, David W.; Heronimus, Kevin

1995-01-01

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

Neutron and X-ray investigations of the Jahn–Teller switch in partially deuterated ammonium copper Tutton salt, (NH 4 ) 2 [Cu(H 2 O) 6 ](SO 4 ) 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jørgensen, Mads R. V.; Piccoli, Paula M. B.; Hathwar, Venkatesha R.

2017-01-31

The structural phase transition accompanied by a Jahn–Teller switch has been studied over a range of H/D ratios in (NH 4) 2[Cu(H 2O) 6](SO 4) 2(ACTS). In particular, single-crystal neutron diffraction investigations of crystals with deuteration in the range 50 to 82% are shown to be consistent with previous electron paramagnetic resonance (EPR) experiments exhibiting a phase boundary at 50% deuteration under ambient pressure. Polycrystalline samples show that the two phases can co-exist. In addition, single-crystal neutron and polycrystalline X-ray diffraction pressure experiments show a shift to lower pressure at 60% deuterationversusprevious measurements at 100% deuteration.

Investigation of hydrate formation in the system H2-CH4-H2O at a pressure up to 250 MPa.

PubMed

Skiba, Sergei S; Larionov, Eduard G; Manakov, Andrey Y; Kolesov, Boris A; Kosyakov, Viktor I

2007-09-27

Phase equilibria in the system H2-CH4-H2O are investigated by means of differential thermal analysis within hydrogen concentration range 0-70 mol % and at a pressure up to 250 MPa. All the experiments were carried out under the conditions of gas excess. With an increase in hydrogen concentration in the initial gas mixture, decomposition temperature of the formed hydrates decreased. X-ray diffraction patterns and Raman spectra of the quenched hydrate samples obtained at a pressure of 20 MPA from a gas mixture containing 40 mol % hydrogen were recorded. It turned out that the hydrate has cubic structure I under these conditions. The Raman spectra showed that hydrogen molecules are not detected in the hydrate within the sensitivity of the method, that is, almost pure methane hydrate is formed. The general view of the phase diagram of the investigated system is proposed. A thermodynamic model was proposed to explain a decrease in hydrate decomposition temperature in the system with an increase in the concentration of hydrogen in the initial mixture.

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

NASA Astrophysics Data System (ADS)

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

2014-07-01

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

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

USGS Publications Warehouse

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

2004-01-01

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

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

PubMed

Tsuchiya, Jun; Mookherjee, Mainak

2015-10-23

Dense hydrous magnesium silicate (DHMS) phases play a crucial role in transporting water in to the Earth's interior. A newly discovered DHMS, phase H (MgSiO4H2), is stable at Earth's lower mantle, i.e., at pressures greater than 30 GPa. Here we report the crystal structure and elasticity of phase H and its evolution upon compression. Using first principles simulations, we have explored the relative energetics of the candidate crystal structures with ordered and disordered configurations of magnesium and silicon atoms in the octahedral sites. At conditions relevant to Earth's lower mantle, it is likely that phase H is able to incorporate a significant amount of aluminum, which may enhance the thermodynamic stability of phase H. The sound wave velocities of phase H are ~2-4% smaller than those of isostructural δ-AlOOH. The shear wave impedance contrast due to the transformation of phase D to a mixture of phase H and stishovite at pressures relevant to the upper part of the lower mantle could partly explain the geophysical observations. The calculated elastic wave velocities and anisotropies indicate that phase H can be a source of significant seismic anisotropy in the lower mantle.

U 3Si 2 behavior in H 2O environments: Part II, pressurized water with controlled redox chemistry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nelson, Andrew Thomas; Migdisov, Artaches; Wood, Elizabeth Sooby

Recent interest in U 3Si 2 as an advanced light water reactor fuel has driven assessment of numerous properties, but characterization of its response to H 2O environments is sparse in available literature. The behavior of U 3Si 2 in H 2O containing atmospheres is investigated and presented in a two-part series of articles. This work examines the behavior of U 3Si 2 following exposure to pressurized H 2O at temperatures from 300 to 350 °C. Testing was performed using two autoclave configurations and multiple redox conditions. Use of solid state buffers to attain a controlled water chemistry is alsomore » presented as a means to test actinide-bearing systems. Buffers were used to vary the hydrogen concentration between 1 and 30 parts per million H 2. Testing included UN, U 3Si 5, and UO 2. Both UN and U 3Si 5 were found to rapidly pulverize in less than 5 h at 300 °C. Uranium dioxide was included as a control for the autoclave system, and was found to be minimally impacted by exposure to pressurized water at the conditions tested for extended time periods. Testing of U 3Si 2 at 300 °C found reasonable stability through 30 days in 1–5 ppm H 2. However, pulverization was observed following 35 days. The redox condition of testing strongly affected pulverization. Characterization of the resulting microstructures suggests that the mechanism responsible for pulverization under more strongly reducing conditions differs from that previously identified. Hydride formation is hypothesized to drive this transition. In conclusion, testing performed at 350 °C resulted in rapid pulverization of U 3Si 2 in under 50 h.« less

U 3Si 2 behavior in H 2O environments: Part II, pressurized water with controlled redox chemistry

DOE PAGES

Nelson, Andrew Thomas; Migdisov, Artaches; Wood, Elizabeth Sooby; ...

2017-12-16

Recent interest in U 3Si 2 as an advanced light water reactor fuel has driven assessment of numerous properties, but characterization of its response to H 2O environments is sparse in available literature. The behavior of U 3Si 2 in H 2O containing atmospheres is investigated and presented in a two-part series of articles. This work examines the behavior of U 3Si 2 following exposure to pressurized H 2O at temperatures from 300 to 350 °C. Testing was performed using two autoclave configurations and multiple redox conditions. Use of solid state buffers to attain a controlled water chemistry is alsomore » presented as a means to test actinide-bearing systems. Buffers were used to vary the hydrogen concentration between 1 and 30 parts per million H 2. Testing included UN, U 3Si 5, and UO 2. Both UN and U 3Si 5 were found to rapidly pulverize in less than 5 h at 300 °C. Uranium dioxide was included as a control for the autoclave system, and was found to be minimally impacted by exposure to pressurized water at the conditions tested for extended time periods. Testing of U 3Si 2 at 300 °C found reasonable stability through 30 days in 1–5 ppm H 2. However, pulverization was observed following 35 days. The redox condition of testing strongly affected pulverization. Characterization of the resulting microstructures suggests that the mechanism responsible for pulverization under more strongly reducing conditions differs from that previously identified. Hydride formation is hypothesized to drive this transition. In conclusion, testing performed at 350 °C resulted in rapid pulverization of U 3Si 2 in under 50 h.« less

U3Si2 behavior in H2O environments: Part II, pressurized water with controlled redox chemistry

NASA Astrophysics Data System (ADS)

Nelson, A. T.; Migdisov, A.; Wood, E. Sooby; Grote, C. J.

2018-03-01

Recent interest in U3Si2 as an advanced light water reactor fuel has driven assessment of numerous properties, but characterization of its response to H2O environments is sparse in available literature. The behavior of U3Si2 in H2O containing atmospheres is investigated and presented in a two-part series of articles. This work examines the behavior of U3Si2 following exposure to pressurized H2O at temperatures from 300 to 350 °C. Testing was performed using two autoclave configurations and multiple redox conditions. Use of solid state buffers to attain a controlled water chemistry is also presented as a means to test actinide-bearing systems. Buffers were used to vary the hydrogen concentration between 1 and 30 parts per million H2. Testing included UN, U3Si5, and UO2. Both UN and U3Si5 were found to rapidly pulverize in less than 50 h at 300 °C. Uranium dioxide was included as a control for the autoclave system, and was found to be minimally impacted by exposure to pressurized water at the conditions tested for extended time periods. Testing of U3Si2 at 300 °C found reasonable stability through 30 days in 1-5 ppm H2. However, pulverization was observed following 35 days. The redox condition of testing strongly affected pulverization. Characterization of the resulting microstructures suggests that the mechanism responsible for pulverization under more strongly reducing conditions differs from that previously identified. Hydride formation is hypothesized to drive this transition. Testing performed at 350 °C resulted in rapid pulverization of U3Si2 in under 50 h.

Influence of oxygen partial pressure on the microstructural and magnetic properties of Er-doped ZnO thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Wei-Bin; Li, Fei; Chen, Hong-Ming

2015-06-15

Er-doped ZnO thin films have been prepared by using inductively coupled plasma enhanced physical vapor deposition at different O{sub 2}:Ar gas flow ratio (R = 0:30, 1:30, 1:15, 1:10 and 1:6). The influence of oxygen partial pressure on the structural, optical and magnetic properties was studied. It is found that an appropriate oxygen partial pressure (R=1:10) can produce the best crystalline quality with a maximum grain size. The internal strain, estimated by fitting the X-ray diffraction peaks, varied with oxygen partial pressure during growth. PL measurements show that plenty of defects, especially zinc vacancy, exist in Er-doped ZnO films. Allmore » the samples show room-temperature ferromagnetism. Importantly, the saturation magnetization exhibits similar dependency on oxygen partial pressure with the internal strain, which indicates that internal strain has an important effect on the magnetic properties of Er-doped ZnO thin films.« less

Peak Sound Pressure Levels and Associated Auditory Risk from an H[subscript 2]-Air "Egg-Splosion"

ERIC Educational Resources Information Center

Dolhun, John J.

2016-01-01

The noise level from exploding chemical demonstrations and the effect they could have on audiences, especially young children, needs attention. Auditory risk from H[subscript 2]- O2 balloon explosions have been studied, but no studies have been done on H[subscript 2]-air "eggsplosions." The peak sound pressure level (SPL) was measured…

Measured pressure distributions inside nonaxisymmetric nozzles with partially deployed thrust reversers

NASA Technical Reports Server (NTRS)

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

1987-01-01

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

Five meters of H(2)O: the pressure at the urinary bladder neck during human ejaculation.

PubMed

Böhlen, D; Hugonnet, C L; Mills, R D; Weise, E S; Schmid, H P

2000-09-01

There are no data in the literature on pressure changes in the prostatic urethra during ejaculation. In healthy men, it has always been postulated that there must be a pressure gradient in order to prevent retrograde ejaculation, but scientific proof for that is pending. In five healthy male volunteers, the pressure profile in the prostatic urethra was registered during ejaculation, using a 10 French balloon catheter with 16 pressure channels. The channels were arranged in pairs at 5-mm intervals, beginning just below the balloon at the bladder neck and extending down to the external urethral sphincter. In the proximal part of the prostatic urethra, a pressure of up to 500 cm of H(2)O was measured in all subjects. Contrary to that, pressures did not exceed 400 cm of H(2)O distally to the verumontanum. A novel method to register the pressure profile in the lower urinary tract during ejaculation (ejaculomanometry) is presented. This study adds to the knowledge of the normal physiology of reproductive function and may be useful in the evaluation of male sexual and reproductive disorders. Copyright 2000 Wiley-Liss, Inc.

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

NASA Astrophysics Data System (ADS)

Lu, Yi; Wang, Li

2012-11-01

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

Measurement and Control of Oxygen Partial Pressure in an Electrostatic Levitator

NASA Technical Reports Server (NTRS)

SanSoucie, Michael P.; Rogers, Jan R.

2014-01-01

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

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

PubMed Central

Stump, Matthew R.; Gloss, Lisa M.

2008-01-01

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, respectively—significantly 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 μM, 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 refolding—initiated from urea-denatured monomers or the partially folded monomers populated at low denaturant concentrations—yielded 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 α-helix of the histone fold, which makes extensive inter-monomer contacts, is structured in H2B but only partially folded in H2A. PMID:18976667

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

PubMed

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

2013-09-01

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

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

NASA Technical Reports Server (NTRS)

Zent, Aaron P.; Quinn, Richard C.

1995-01-01

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

Broadening of spectral lines of CO2, N2O , H2CO, HCN, and H2S by pressure of gases dominant in planetary atmospheres (H2, He and CO2)

NASA Astrophysics Data System (ADS)

Samuels, Shanelle; Gordon, Iouli; Tan, Yan

2018-01-01

HITRAN1,2 is a compilation of spectroscopic parameters that a variety of computer codes use to predict and simulate the transmission and emission of light in planetary atmospheres. The goal of this project is to add to the potential of the HITRAN database towards the exploration of the planetary atmospheres by including parameters describing broadening of spectral lines by H2, CO2, and He. These spectroscopic data are very important for the study of the hydrogen and helium-rich atmospheres of gas giants as well as rocky planets with volcanic activities, including Venus and Mars, since their atmospheres are dominated by CO2. First step in this direction was accomplished by Wilzewski et al.3 where this was done for SO2, NH3, HF, HCl, OCS and C2H2. The molecules investigated in this work were CO2, N2O, H2CO, HCN and H2S. Line-broadening coefficients, line shifts and temperature-dependence exponents for transitions of these molecules perturbed by H2, CO2 and He have been assembled from available peer-reviewed experimental and theoretical sources. The data was evaluated and the database was populated with these data and their extrapolations/interpolations using semi-empirical models that were developed to this end.Acknowledgements: Financial support from NASA PDART grant NNX16AG51G and the Smithsonian Astrophysical Observatory Latino Initiative Program from the Latino Initiatives Pool, administered by the Smithsonian Latino Center is gratefully acknowledged.References: 1. HITRAN online http://hitran.org/2. Gordon, I.E., Rothman, L.S., Hill, C., Kochanov, R.V., Tan, Y., et al., 2017. The HITRAN2016 Molecular Spectroscopic Database. J. Quant. Spectrosc. Radiat. Transf. doi:10.1016/j.jqsrt.2017.06.0383. Wilzewski, J.S., Gordon, I.E., Kochanov, R. V., Hill, C., Rothman, L.S., 2016. H2, He, and CO2 line-broadening coefficients, pressure shifts and temperature-dependence exponents for the HITRAN database. Part 1: SO2, NH3, HF, HCl, OCS and C2H2. J. Quant. Spectrosc. Radiat

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

NASA Technical Reports Server (NTRS)

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

1995-01-01

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

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

NASA Astrophysics Data System (ADS)

Monfared, Shabnam K.; Hüwel, Lutz

2012-10-01

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

Diagnostic system for measuring temperature, pressure, CO.sub.2 concentration and H.sub.2O concentration in a fluid stream

DOE Office of Scientific and Technical Information (OSTI.GOV)

Partridge, Jr., William P.; Jatana, Gurneesh Singh; Yoo, Ji Hyung

A diagnostic system for measuring temperature, pressure, CO.sub.2 concentration and H.sub.2O concentration in a fluid stream is described. The system may include one or more probes that sample the fluid stream spatially, temporally and over ranges of pressure and temperature. Laser light sources are directed down pitch optical cables, through a lens and to a mirror, where the light sources are reflected back, through the lens to catch optical cables. The light travels through the catch optical cables to detectors, which provide electrical signals to a processer. The processer utilizes the signals to calculate CO.sub.2 concentration based on the temperaturesmore » derived from H.sub.2O vapor concentration. A probe for sampling CO.sub.2 and H.sub.2O vapor concentrations is also disclosed. Various mechanical features interact together to ensure the pitch and catch optical cables are properly aligned with the lens during assembly and use.« less

Nb-H system at high pressures and temperatures

NASA Astrophysics Data System (ADS)

Liu, Guangtao; Besedin, Stanislav; Irodova, Alla; Liu, Hanyu; Gao, Guoying; Eremets, Mikhail; Wang, Xin; Ma, Yanming

2017-03-01

We studied the Nb-H system over extended pressure and temperature ranges to establish the highest level of hydrogen abundance we could achieve from the resulting alloy. We probed the Nb-H system with laser heating and x-ray diffraction complemented by numerical density functional theory-based simulations. New quenched double hexagonal close-packed (hcp) Nb H2.5 appears under 46 GPa, and above 56 GPa cubic Nb H3 is formed as theoretically predicted. Nb atoms are arranged in close-packed lattices which are martensitically transformed in the sequence: face-centered cubic (fcc) → hcp → double hcp (dhcp) → distorted body-centered cubic (bcc) as pressure increases. The appearance of fcc Nb H2.5 -3 and dhcp Nb H2.5 cannot be understood in terms of enthalpic stability, but can be rationalized when finite temperatures are taken into account. The structural and compressional behavior of Nb Hx >2 is similar to that of NbH. Nevertheless, a direct H-H interaction emerges with hydrogen concentration increases, which manifests itself via a reduction in the lattice expansion induced by hydrogen dissolution.

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

NASA Technical Reports Server (NTRS)

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

1984-01-01

The vertical distributions and mixing ratios of minor constituents in the northern hemisphere of Saturn are investigated. Results are obtained for NH3, PH3, C2H2, C2H6, CH3D, and CH4; the D/H ratio is obtained from the CH4 and CH3D abundances. The NH3 mixing ratio in the upper atmosphere is found to be compatible with the saturated partial pressure. The inferred PH3/H2 ratio of 1.4 + or - 0.8 x 10 to the -6th is higher than the value derived from the solar P/H ratio. The stratospheric C2H2/H2 and C2H6/H2 ratios are, respectively, 2.1 + or - 1.4 x 10 to the -7th and 3.0 + or - 1.1 x 10 to the -6th; the latter decreases sharply below the 20-50 mbar level. The results for CH3D/H2 and CH4/H2 imply an enrichment of Saturn's upper atmosphere in carbon by a factor of at least three over the solar abundance. The interpretation of two NH3 lines in the five-micron window suggests a NH3/H2 ratio at the two bar level below the solar value.

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

PubMed

Cai, Tingdong; Gao, Guangzhen; Liu, Ying

2013-11-10

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

[Correlation between the inspired fraction of oxygen, maternal partial oxygen pressure, and fetal partial oxygen pressure during cesarean section of normal pregnancies].

PubMed

Castro, Carlos Henrique Viana de; Cruvinel, Marcos Guilherme Cunha; Carneiro, Fabiano Soares; Silva, Yerkes Pereira; Cabral, Antônio Carlos Vieira; Bessa, Roberto Cardoso

2009-01-01

Despite changes in pulmonary function, maternal oxygenation is maintained during obstetric regional blocks. But in those situations, the administration of supplementary oxygen to parturients is a common practice. Good fetal oxygenation is the main justification; however, this has not been proven. The objective of this randomized, prospective study was to test the hypothesis of whether maternal hyperoxia is correlated with an increase in fetal gasometric parameters in elective cesarean sections. Arterial blood gases of 20 parturients undergoing spinal block with different inspired fractions of oxygen were evaluated and correlated with fetal arterial blood gases. An increase in maternal inspired fraction of oxygen did not show any correlation with an increase of fetal partial oxygen pressure. Induction of maternal hyperoxia by the administration of supplementary oxygen did not increase fetal partial oxygen pressure. Fetal gasometric parameters did not change even when maternal parameters changed, induced by hyperoxia, during cesarean section under spinal block.

Effect of substrate temperature and oxygen partial pressure on RF sputtered NiO thin films

NASA Astrophysics Data System (ADS)

Cheemadan, Saheer; Santhosh Kumar, M. C.

2018-04-01

Nickel oxide (NiO) thin films were deposited by RF sputtering process and the physical properties were investigated for varying substrate temperatures and oxygen partial pressure. The variation of the crystallographic orientation and microstructure of the NiO thin films with an increase in substrate temperature were studied. It was observed that NiO thin films deposited at 350 °C shows relatively good crystalline characteristics with a preferential orientation along (111) plane. With the optimum substrate temperature of 350 °C, the NiO thin films were deposited under various oxygen partial pressures at the same experimental conditions. The structural, optical and electrical properties of NiO thin films under varying oxygen partial pressure of 10%–50% were investigated. From XRD it is clear that the films prepared in the pure argon atmosphere were amorphous while the films in oxygen partial pressure exhibited polycrystalline NiO phase. SEM and AFM investigations unveil that the higher substrate temperature improves the microstructure of the thin films. It is revealed that the NiO thin films deposited at oxygen partial pressure of 40% and a substrate temperature of 350 °C, showed higher electrical conductivity with p-type characteristics.

Hydrogen-bond symmetrization breakdown and dehydrogenation mechanism in FeO2H at high pressure

NASA Astrophysics Data System (ADS)

Hu, Q.; Zhu, S.; Mao, H. K.; Mao, W. L.; Sheng, H.

2017-12-01

The cycling of hydrogen plays an important role in the geochemical evolution of our planet. In Earth's interiors, hydrogen cycling is mainly carried out by hydrous minerals. Under high-pressure conditions, asymmetric hydroxyl bonds in hydrous minerals tend to form a symmetric O-H-O configuration that improves their thermal stability. Therefore it is possible to transport water into the deeper part of the Earth's lower mantle. Here, we employ first-principles free-energy landscape sampling methods based on a recently developed stochastic surface walking algorithm to reveal the transition mechanism of a water-bearing mineral, FeO2H, at deep mantle conditions. By resolving the lowest-energy transition pathway from ɛ-FeO2H to the high-pressure Py-phase, we demonstrate that half of the O-H bonds in the mineral rupture during the structural transition, leading toward the breakdown of symmetrized hydrogen bonds and eventual dehydrogenation. Our study sheds new light on the stability of symmetric hydrogen bonds in hydrous minerals during structural transitions and suggests a dehydrogenation mechanism from water in the deep mantle.

Ternary recombination of H3+, H2D+, HD2+, and D3+ with electrons in He/Ar/H2/D2 gas mixtures

NASA Astrophysics Data System (ADS)

Kalosi, Abel; Dohnal, Petr; Plasil, Radek; Johnsen, Rainer; Glosik, Juraj

2016-09-01

The temperature dependence of the ternary recombination rate coefficients of H2D+ and HD2+ ions has been studied in the temperature range of 80-150 K at pressures from 500 to 1700 Pa in a stationary afterglow apparatus equipped with a cavity ring-down spectrometer. Neutral gas mixtures consisting of He/Ar/H2/D2 (with typical number densities 1017 /1014 /1014 /1014 cm-3) were employed to produce the desired ionic species and their fractional abundances were monitored as a function of helium pressure and the [D2]/[H2] ratio of the neutral gas. In addition, the translational and the rotational temperature and the ortho to para ratio were monitored for both H2D+ and HD2+ ions. A fairly strong pressure dependence of the effective recombination rate coefficient was observed for both ion species, leading to ternary recombination rate coefficients close to those previously found for (helium assisted) ternary recombination of H3+ and D3+. Work supported by: Czech Science Foundation projects GACR 14-14649P, GACR 15-15077S, GACR P209/12/0233, and by Charles University in Prague Project Nr. GAUK 692214.

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

NASA Astrophysics Data System (ADS)

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

1996-10-01

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: ΔG° (±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

Measurement of partial pressures in vacuum technology and vacuum physics

NASA Technical Reports Server (NTRS)

Huber, W. K.

1986-01-01

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

SIGNIFICANT ENHANCEMENT OF H{sub 2} FORMATION IN DISK GALAXIES UNDER STRONG RAM PRESSURE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Henderson, Benjamin; Bekki, Kenji

We show for the first time that H{sub 2} formation on dust grains can be enhanced in disk galaxies under strong ram pressure (RP). We numerically investigate how the time evolution of H i and H{sub 2} components in disk galaxies orbiting a group/cluster of galaxies can be influenced by the hydrodynamical interaction between the gaseous components of the galaxies and the hot intracluster medium. We find that compression of H i caused by RP increases H{sub 2} formation in disk galaxies before RP rapidly strips H i, cutting off the fuel supply and causing a drop in H{sub 2}more » density. We also find that the level of this H{sub 2} formation enhancement in a disk galaxy under RP depends on the mass of its host cluster dark matter halo, the initial positions and velocities of the disk galaxy, and the disk inclination angle with respect to the orbital plane. We demonstrate that dust growth is a key factor in the evolution of the H i and H{sub 2} mass in disk galaxies under strong RP. We discuss how the correlation between H{sub 2} fractions and surface gas densities of disk galaxies evolves with time in the galaxies under RP. We also discuss whether galaxy-wide star formation rates (SFRs) in cluster disk galaxies can be enhanced by RP if the SFRs depend on H{sub 2} densities.« less

Rotational quenching of H2CO by molecular hydrogen: cross-sections, rates and pressure broadening

NASA Astrophysics Data System (ADS)

Wiesenfeld, L.; Faure, A.

2013-07-01

We compute the rotational quenching rates of the first 81 rotational levels of ortho- and para-H2CO in collision with ortho- and para-H2, for a temperature range of 10-300 K. We make use of the quantum close-coupling and coupled-state scattering methods combined with the high accuracy potential energy surface of Troscompt et al. Rates are significantly different from the scaled rates of H2CO in collision with He; consequently, critical densities are notably lower. We compare a full close-coupling computation of pressure broadening cross-sections with experimental data and show that our results are compatible with the low-temperature measurements of Mengel & De Lucia, for a spin temperature of H2 around 50 K.

The Stability of Hydrous Silicates in Earth's Lower Mantle: Experimental constraints from the System MgO-Al2O3-SiO2-H2O

NASA Astrophysics Data System (ADS)

Walter, M. J.; Thomson, A. R.; Wang, W.; Lord, O. T.; Kleppe, A. K.; Ross, J.; Kohn, S. C.

2014-12-01

Laser-heated diamond anvil cell experiments were performed at pressures from ~ 30 to 125 GPa on bulk compositions in the system MgO-Al2O3-SiO2-H2O (MASH) to constrain the stability of hydrous phases in Earth's lower mantle. Phase identification in run products by synchrotron powder diffraction reveals a consistent set of stability relations for the high-pressure, dense hydrous silicate phases D and H. Experiments show that aluminous phase D is stable to ~ 55 GPa. Aluminous phase H becomes stable at ~ 40 GPa and remains stable to higher pressures throughout the lower mantle depth range in both model peridotitic and basaltic lithologies. Preliminary FEG-probe analyses indicate that Phase H is alumina-rich at ~ 50 GPa, with only 5 to 10 wt% each of MgO and SiO2. Variations in ambient unit cell volumes show that Mg-perovskite becomes more aluminous with pressure throughout the pressure range studied, and that Phase H may become more Mg- and Si-rich with pressure. We also find that at pressures above ~ 90 GPa stishovite is replaced in Si-rich compositions by seifertite, at which point there is a corresponding increase in the Al-content of phase H. The melting curves of MASH compositions have been determined using thermal perturbations in power versus temperature curves, and are observed to be shallow with dT/dP slopes of ~ 4K/GPa. Our results show that hydrated peridotitic or basaltic compositions in the lower mantle should be partially molten at all depths along an adiabatic mantle geotherm. Aluminous Phase H will be stable in colder, hydrated subducting slabs, potentially to the core-mantle boundary. Thus, aluminous phase H is the primary vessel for transport of hydrogen to the deepest mantle, but hydrous silicate melt will be the host of hydrogen at ambient mantle temperatures.

Longitudinal sound velocities, elastic anisotropy, and phase transition of high-pressure cubic H2O ice to 82 GPa

NASA Astrophysics Data System (ADS)

Kuriakose, Maju; Raetz, Samuel; Hu, Qing Miao; Nikitin, Sergey M.; Chigarev, Nikolay; Tournat, Vincent; Bulou, Alain; Lomonosov, Alexey; Djemia, Philippe; Gusev, Vitalyi E.; Zerr, Andreas

2017-10-01

Water ice is a molecular solid whose behavior under compression reveals the interplay of covalent bonding in molecules and forces acting between them. This interplay determines high-pressure phase transitions, the elastic and plastic behavior of H2O ice, which are the properties needed for modeling the convection and internal structure of the giant planets and moons of the solar system as well as H2O -rich exoplanets. We investigated experimentally and theoretically elastic properties and phase transitions of cubic H2O ice at room temperature and high pressures between 10 and 82 GPa. The time-domain Brillouin scattering (TDBS) technique was used to measure longitudinal sound velocities (VL) in polycrystalline ice samples compressed in a diamond anvil cell. The high spatial resolution of the TDBS technique revealed variations of VL caused by elastic anisotropy, allowing us to reliably determine the fastest and the slowest sound velocity in a single crystal of cubic H2O ice and thus to evaluate existing equations of state. Pressure dependencies of the single-crystal elastic moduli Ci j(P ) of cubic H2O ice to 82 GPa have been obtained which indicate its hardness and brittleness. These results were compared with ab initio calculations. It is suggested that the transition from molecular ice VII to ionic ice X occurs at much higher pressures than proposed earlier, probably above 80 GPa.

Measuring N2 Pressure Using Cyanobacteria

NASA Astrophysics Data System (ADS)

Silverman, S. N.; Kopf, S.; Gordon, R.; Bebout, B.; Som, S.

2017-11-01

We have shown that cyanobacteria can record information about N2 partial pressure both morphologically and isotopically, and thus may serve as useful geobarometers to help us better understand Earth's ancient atmosphere.

NMR spectroscopic properties (1H at 500 MHz) of deuterated* ribonucleotide-dimers ApU*, GpC*, partially deuterated 2'-deoxyribonucleotide-dimers d(TpA*), d(ApT*), d(GpC*) and their comparison with natural counterparts (1H-NMR window).

PubMed

Földesi, A; Nilson, F P; Glemarec, C; Gioeli, C; Chattopadhyaya, J

1993-02-01

Pure 1'#,2',3',4'#,5',5''-2H6-ribonucleoside derivatives 10-14, 1'#,2',2'',3',4'#,5',5''-2H7-2'-deoxynucleoside blocks 15-18 and their natural-abundance counterparts were used to assemble partially deuterated ribonucleotide-dimers (* indicates deuteration at 1'#,2',3',4'#,5',5''(2H6)): ApU* 21, GpC* 22 and partially deuterated 2'-deoxyribonucleotide-dimers d(TpA*) 23, d(ApT*) 25, d(GpC*) 26 (* indicates deuteration at 1'#,2',2'',3',4'#,5',5''(2H7)) according to the procedure described by Földesi et al. (Tetrahedron, in press). These five partially deuterated oligonucleotides were subsequently compared with their corresponding natural-abundance counterparts by 500 MHz 1H-NMR spectroscopy to evaluate the actual NMR simplifications achieved in the non-deuterated part (1H-NMR window) as a result of specific deuterium incorporation. Detailed one-dimensional 1H-NMR (500 MHz), two-dimensional correlation spectra (DQF-COSY and TOCSY) and deuterium isotope effect on the chemical shifts of oligonucleotides have been presented.

Pressure-induced effects and phase relations in Mg2NiH4

NASA Astrophysics Data System (ADS)

Gavra, Z.; Kimmel, G.; Gefen, Y.; Mintz, Moshe H.

1985-05-01

The low-temperature (<210 °C) crystallographic structure, electrical conductivity, and thermal stability of Mg2NiH4 powders compacted under isostatic pressures of up to 10 kbar were studied. A comparison is made with the corresponding properties of the noncompressed material. It has been concluded that under stress-free hydriding conditions performed below 210 °C, a two-phase hydride mixture is formed. Each of the hydride particles consists of an inner core composed of an hydrogen-deficient monoclinic phase coated by a layer of a stoichiometric orthorhombic phase. The monoclinic phase has a metalliclike electrical conductivity while the orthorhombic phase is insulating. High compaction pressures cause the transformation of the orthorhombic structure into the monoclinic one, thereby resulting in a pressure-induced insulator-to-conductor transition. Reduced decomposition temperatures are obtained for the compressed hydrides. This reduction is attributed to kinetic factors rather than to a reduced thermodynamic stability.

Global Autocorrelation Scales of the Partial Pressure of Oceanic CO2

NASA Technical Reports Server (NTRS)

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

2004-01-01

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

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

NASA Astrophysics Data System (ADS)

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

2011-01-01

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

Surface reconstruction of GaAs(001) nitrided under the controlled As partial pressure [rapid communication

NASA Astrophysics Data System (ADS)

Imayoshi, Takahiro; Oigawa, Haruhiro; Shigekawa, Hidemi; Tokumoto, Hiroshi

2003-08-01

Under the controlled As partial pressure, the nitridation process of GaAs(0 0 1)-(2 × 4) surface was studied using a scanning tunneling microscope (STM) combined with an electron cyclotron resonance plasma-assisted molecular beam epitaxy system. With either prolonging the nitridation time or decreasing the As partial pressure, the previously reported (3 × 3) structure with two dimers per surface cell ((3 × 3)-2D) was found to progressively convert into a new (3 × 3) structure characterized by one dimer per surface cell ((3 × 3)-1D). Reversely the exposure to arsenic transformed the structure from (3 × 3)-1D to (3 × 3)-2D, suggesting that the topmost layer is composed of As 2-dimers. Based on these STM images together with the X-ray photoelectron spectroscopy data, we propose the new As 2-dimer coverage models to explain both (3 × 3)-1D and -2D structures involving the exchange reaction of arsenic with nitrogen in the subsurface region of GaAs.

Effects of various oxygen partial pressures on Ti-doped ZnO thin film transistors fabricated on flexible plastic substrate

NASA Astrophysics Data System (ADS)

Cui, Guodong; Han, Dedong; Yu, Wen; Shi, Pan; Zhang, Yi; Huang, Lingling; Cong, Yingying; Zhou, Xiaoliang; Zhang, Xiaomi; Zhang, Shengdong; Zhang, Xing; Wang, Yi

2016-04-01

By applying a novel active layer of titanium zinc oxide (TiZO), we have successfully fabricated fully transparent thin-film transistors (TFTs) with a bottom gate structure fabricated on a flexible plastic substrate at low temperatures. The effects of various oxygen partial pressures during channel deposition were studied to improve the device performance. We found that the oxygen partial pressure during channel deposition has a significant impact on the performance of TiZO TFTs, and that the TFT developed under 10% oxygen partial pressure exhibits superior performance with a low threshold voltage (V th) of 2.37 V, a high saturation mobility (μsat) of 125.4 cm2 V-1 s-1, a steep subthreshold swing (SS) of 195 mV/decade and a high I on/I off ratio of 3.05 × 108. These results suggest that TiZO thin films are promising for high-performance fully transparent flexible TFTs and displays.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng, Qing; Li, Jun; Liu, Ying, E-mail: liuying5536@163.com

2014-05-07

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

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

NASA Technical Reports Server (NTRS)

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

2000-01-01

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

CO2 solubility and speciation in rhyolitic sediment partial melts at 1.5-3.0 GPa - Implications for carbon flux in subduction zones

NASA Astrophysics Data System (ADS)

Duncan, Megan S.; Dasgupta, Rajdeep

2014-01-01

Partial melts of subducting sediments are thought to be critical agents in carrying trace elements and water to arc basalt source regions. Sediment partial melts may also act as a carrier of CO2. However, the CO2 carrying capacity of natural rhyolitic melts that derive from partial fusion of downgoing sediment at sub-arc depths remains unconstrained. We conducted CO2-solubility experiments on a rhyolitic composition similar to average, low-degree experimental partial melt of pelitic sediments between 1.5 and 3.0 GPa at 1300 °C and containing variable water content. Concentrations of water and carbon dioxide were measured using FTIR. Molecular CO2(CO2mol.) and carbonate anions (CO32-) both appear as equilibrium species in our experimental melts. Estimated total CO2 concentrations (CO2mol.+CO32-) increased with increasing pressure and water content. At 3.0 GPa, the bulk CO2 solubility are in the range of ∼1-2.5 wt.%, for melts with H2O contents between 0.5 and 3.5 wt.%. For melts with low H2O content (∼0.5 wt.%), CO2mol. is the dominant carbon species, while in more H2O-rich melts CO32- becomes dominant. The experimentally determined, speciation-specific CO2 solubilities yielded thermodynamic parameters that control dissolution of CO2 vapor both as CO2mol. and as CO32- in silicate melt for each of our compositions with different water content; CO2vapor ↔CO2melt :lnK0=-15 to -18, ΔV0 = 29 to 14 cm3 mol-1 and CO2vapor +Omelt →CO32-melt :lnK0=-20 to -14, ΔV0 = 9 to 27 cm3 mol-1, with ΔV0 of reaction being larger for formation of CO2mol. in water-poor melts and for formation of CO32- in water-rich melts. Our bulk CO2 solubility data, [CO2] (in wt.%) can be fitted as a function of pressure, P (in GPa) and melt water content, [H2O] (in wt.%) with the following function: [CO2](wt.%)=(-0.01108[H2O]+0.03969)P2+(0.10328[H2O]+0.41165)P. This parameterization suggests that over the range of sub-arc depths of 72-173 km, water-rich sediment partial melt may carry as

Optimizing the physical ergonomics indices for the use of partial pressure suits.

PubMed

Ding, Li; Li, Xianxue; Hedge, Alan; Hu, Huimin; Feathers, David; Qin, Zhifeng; Xiao, Huajun; Xue, Lihao; Zhou, Qianxiang

2015-03-01

This study developed an ergonomic evaluation system for the design of high-altitude partial pressure suits (PPSs). A total of twenty-one Chinese males participated in the experiment which tested three types of ergonomics indices (manipulative mission, operational reach and operational strength) were studied using a three-dimensional video-based motion capture system, a target-pointing board, a hand dynamometer, and a step-tread apparatus. In total, 36 ergonomics indices were evaluated and optimized using regression and fitting analysis. Some indices that were found to be linearly related and redundant were removed from the study. An optimal ergonomics index system was established that can be used to conveniently and quickly evaluate the performance of different pressurized/non-pressurized suit designs. The resulting ergonomics index system will provide a theoretical basis and practical guidance for mission planners, suit designers and engineers to design equipment for human use, and to aid in assessing partial pressure suits. Copyright © 2014 Elsevier Ltd and The Ergonomics Society. All rights reserved.

Coadsorption of H2O and CO2 on the Martian surface

NASA Technical Reports Server (NTRS)

Zent, A. P.

1987-01-01

The adsorption of both CO2 and H2O was measured, under conditions of temperature and partial pressure similar to Mars, for a variety of absorbents. Both adsorb at coverages that exceed a monolayer at their respective Martian abundances. Clearly, their simultaneous presence in the Martian atmosphere will result in coadsorption of both at concentrations that may differ greatly from those measured during separate measurements. To the best of our knowledge, no data exists on the coadsorption of both gases. Co-adsorption experiments were begun and pertinent results will be reported. In the meantime the predicted behavior of such a system was mathematically explored as a compliment to the data, and to aid in its eventual interpretation.

Effect of O2 partial pressure on post annealed Ba2YCu3O(7-delta) thin films

NASA Astrophysics Data System (ADS)

Phillps, J. M.; Siegal, M. P.; Hou, S. Y.; Tiefel, T. H.; Marshall, J. H.

1992-04-01

Epitaxial films of Ba2YCu3O(7-delta) (BYCO) as thin as 250 A and with J(sub c)'s approaching those of the best in situ grown films can be formed by co-evaporating BaF2, Y, and Cu followed by a two-stage anneal. High quality films of these thicknesses become possible if low oxygen partial pressure (p(O2) = 4.3 Torr) is used during the high temperature portion of the anneal (T(sub a)). The BYCO melt line is the upper limit for T(sub a). The use of low p(O2) shifts the window for stable BYCO film growth to lower temperature, which allows the formation of smooth films with greater microstructural disorder than is found in films grown in p(O2) = 740 Torr at higher T(sub a). The best films annealed in p(O2) = 4.3 Torr have J(sub c) values a factor of four higher than do comparable films annealed in p(O2) = 740 Torr. The relationship between the T(sub a) required to grow films with the strongest pinning force and p(O2) is log (p(O2)) proportional to T(sub a) exp(1 exp a) independent of growth method (in situ or ex situ) over a range of five orders of magnitude of p(O2).

Optimization of intermolecular potential parameters for the CO2/H2O mixture.

PubMed

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

2014-10-02

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.

Pressure-dependent semiconductor to semimetal and Lifshitz transitions in 2H-MoTe2: Raman and first-principles studies

NASA Astrophysics Data System (ADS)

Bera, Achintya; Singh, Anjali; Muthu, D. V. S.; Waghmare, U. V.; Sood, A. K.

2017-03-01

High pressure Raman spectroscopy of bulk 2H-MoTe2 up to  ∼29 GPa is shown to reveal two phase transitions (at  ∼6 and 16.5 GPa), which are analyzed using first-principles density functional theoretical calculations. The transition at 6 GPa is marked by changes in the pressure coefficients of A 1g and E2g1 Raman mode frequencies as well as in their relative intensity. Our calculations show that this is an isostructural semiconductor to a semimetal transition. The transition at  ∼16.5 GPa is identified with the changes in linewidths of the Raman modes as well as in the pressure coefficients of their frequencies. Our theoretical analysis clearly shows that the structure remains the same up to 30 GPa. However, the topology of the Fermi-surface evolves as a function of pressure, and abrupt appearance of electron and hole pockets at P∼ 20 GPa marks a Lifshitz transition.

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

NASA Astrophysics Data System (ADS)

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

2003-04-01

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

Randomized trial of low versus high carbon dioxide insufflation pressures in posterior retroperitoneoscopic adrenalectomy.

PubMed

Fraser, Sheila; Norlén, Olov; Bender, Kyle; Davidson, Joanne; Bajenov, Sonya; Fahey, David; Li, Shawn; Sidhu, Stan; Sywak, Mark

2018-05-01

Posterior retroperitoneoscopic adrenalectomy has gained widespread acceptance for the removal of benign adrenal tumors. Higher insufflation pressures using carbon dioxide (CO 2 ) are required, although the ideal starting pressure is unclear. This prospective, randomized, single-blinded, study aims to compare physiologic differences with 2 different CO 2 insufflation pressures during posterior retroperitoneoscopic adrenalectomy. Participants were randomly assigned to a starting insufflation pressure of 20 mm Hg (low pressure) or 25 mm Hg (high pressure). The primary outcome measure was partial pressure of arterial CO 2 at 60 minutes. Secondary outcomes included end-tidal CO 2 , arterial pH, blood pressure, and peak airway pressure. Breaches of protocol to change insufflation pressure were permitted if required and were recorded. A prospective randomized trial including 31 patients (low pressure: n = 16; high pressure: n = 15) was undertaken. At 60 minutes, the high pressure group had greater mean partial pressure of arterial CO 2 (64 vs 50 mm Hg, P = .003) and end-tidal CO 2 (54 vs 45 mm Hg, P = .008) and a lesser pH (7.21 vs 7.29, P = .0005). There were no significant differences in base excess, peak airway pressure, operative time, or duration of hospital stay. Clinically indicated protocol breaches were more common in the low pressure than the high pressure group (8 vs 3, P = .03). In posterior retroperitoneoscopic adrenalectomy, greater insufflation pressures are associated with greater partial pressure of arterial CO 2 and end-tidal CO 2 and lesser pH at 60 minutes, be significant. Commencing with lesser CO 2 insufflation pressures decreases intraoperative acidosis. Copyright © 2017 Elsevier Inc. All rights reserved.

The effect of pH on N2O production under aerobic conditions in a partial nitritation system.

PubMed

Law, Yingyu; Lant, Paul; Yuan, Zhiguo

2011-11-15

Ammonia-oxidising bacteria (AOB) are a major contributor to nitrous oxide (N(2)O) emissions during nitrogen transformation. N(2)O production was observed under both anoxic and aerobic conditions in a lab-scale partial nitritation system operated as a sequencing batch reactor (SBR). The system achieved 55 ± 5% conversion of the 1g NH(4)(+)-N/L contained in a synthetic anaerobic digester liquor to nitrite. The N(2)O emission factor was 1.0 ± 0.1% of the ammonium converted. pH was shown to have a major impact on the N(2)O production rate of the AOB enriched culture. In the investigated pH range of 6.0-8.5, the specific N(2)O production was the lowest between pH 6.0 and 7.0 at a rate of 0.15 ± 0.01 mg N(2)O-N/h/g VSS, but increased with pH to a maximum of 0.53 ± 0.04 mg N(2)O-N/h/g VSS at pH 8.0. The same trend was also observed for the specific ammonium oxidation rate (AOR) with the maximum AOR reached at pH 8.0. A linear relationship between the N(2)O production rate and AOR was observed suggesting that increased ammonium oxidation activity may have promoted N(2)O production. The N(2)O production rate was constant across free ammonia (FA) and free nitrous acid (FNA) concentrations of 5-78 mg NH(3)-N/L and 0.15-4.6 mg HNO(2)-N/L, respectively, indicating that the observed pH effect was not due to changes in FA or FNA concentrations. Copyright © 2011 Elsevier Ltd. All rights reserved.

VAPOR PRESSURES, LIQUID MOLAR VOLUMES, VAPOR NON- IDEALITIES, AND CRITICAL PROPERTIES OF SOME FLUORINATED ETHERS: CF3OCF2OCF3, CF3OCF2 CF2H, c-CF2CF2CF2O, CF3OCF2H, AND CF3OCH3; AND OF CCl3F AND CF2ClH

EPA Science Inventory

Vapor pressures, compressibilities, expansivities, and molar volumes of the liquid phase have been measured between room temperature and the critical temperature for a series of fluorinated ethers: CF3OCF2OCF3, CF3OCF2CF2H, c-CF2CF2CF2O, CF3OCF2H, and CF3OCH3. Vapor-phase non-ide...

Thermal evolution of a partially differentiated H chondrite parent body

NASA Astrophysics Data System (ADS)

Abrahams, J. N. H.; Bryson, J. F. J.; Weiss, B. P.; Nimmo, F.

2016-12-01

It has traditionally been assumed that planetesimals either melted entirely or remained completely undifferentiated as they accreted. The unmelted textures and cooling histories of chondrites have been used to argue that these meteorites originated from bodies that never differentiated. However, paleomagnetic measurements indicate that some chondrites (e.g., the H chondrite Portales Valley and several CV chondrites) were magnetized by a core dynamo magnetic field, implying that their parent bodies were partially differentiated. It has been unclear, however, whether planetesimal histories consistent with dynamo production can also be consistent with the diversity of chondrite cooling rates and ages. To address this, we modeled the thermal evolution of the H chondrite parent body, considering a variety of accretion histories and parent body radii. We considered partial differentiation using two-stage accretion involving the initial formation and differentiation of a small body, followed by the later addition of low thermal conductivity chondritic material that remains mostly unmelted. We were able to reproduce the measured thermal evolution of multiple H chondrites for a range of parent body parameters, including initial radii from 70-150 km, chondritic layer thicknesses from 50 km to over 100 km, and second stage accretion times of 2.5-3 Myr after solar system formation. Our predicted rates of core cooling and crystallization are consistent with dynamo generation by compositional convection beginning 60-200 Myr after solar system formation and lasting for at least tens of millions of years. This is consistent with magnetic studies of Portales Valley [Bryson et al., this meeting]. In summary, we find that thermal models of partial differentiation are consistent the radiometric ages, magnetization, and cooling rates of a diversity H chondrites.

Negative pressure wound therapy for partial-thickness burns.

PubMed

Dumville, Jo C; Munson, Christopher

2012-12-12

A burn wound is a complex and evolving injury, with both local and systemic consequences. Burn treatments include a variety of dressings, as well as newer strategies, such as negative pressure wound therapy (NPWT), which, by means of a suction force that drains excess fluids from the burn, tries to promote the wound healing process and minimise progression of the burn wound. To assess the effectiveness of NPWT for people with partial-thickness burns. For this third update we searched the Cochrane Wounds Group Specialised Register (searched 18 May 2012); The Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2012, Issue 5); Ovid MEDLINE (2010 to May Week 2 2012); Ovid MEDLINE (In-Process & Other Non-Indexed Citations 17 May 2012); Ovid EMBASE (2010 to 2012 Week 19); and EBSCO CINAHL (2010 to 16 May 2012). All randomised controlled trials (RCTs) and controlled clinical trials (CCTs) that evaluated the safety and effectiveness of NPWT for partial-thickness burns. Two review authors used standardised forms, and extracted the data independently. We assessed each trial for risk of bias, and resolved differences by discussion. One RCT, that was an interim report, satisfied the inclusion criteria. We undertook a narrative synthesis of results, as the absence of data and poor reporting precluded us from carrying out any formal statistical analysis. The trial was at high risk of bias. There was not enough evidence available to permit any conclusions to be drawn regarding the use of NPWT for treatment of partial-thickness burn wounds.

Application of a High-Throughput Analyzer in Evaluating Solid Adsorbents for Post-Combustion Carbon Capture via Multicomponent Adsorption of CO2, N-2, and H2O

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mason, JA; McDonald, TM; Bae, TH

Despite the large number of metal-organic frameworks that have been studied in the context of post-combustion carbon capture, adsorption equilibria of gas mixtures including CO2, N-2, and H2O, which are the three biggest components of the flue gas emanating from a coal- or natural gas-fired power plant, have never been reported. Here, we disclose the design and validation of a high-throughput multicomponent adsorption instrument that can measure equilibrium adsorption isotherms for mixtures of gases at conditions that are representative of an actual flue gas from a power plant. This instrument is used to study 15 different metal-organic frameworks, zeolites, mesoporousmore » silicas, and activated carbons representative of the broad range of solid adsorbents that have received attention for CO2 capture. While the multicomponent results presented in this work provide many interesting fundamental insights, only adsorbents functionalized with alkylamines are shown to have any significant CO2 capacity in the presence of N-2 and H2O at equilibrium partial pressures similar to those expected in a carbon capture process. Most significantly, the amine-appended metal organic framework mmen-Mg-2(dobpdc) (mmen = N,N'-dimethylethylenediamine, dobpdc (4-) = 4,4'-dioxido-3,3'-biphenyldicarboxylate) exhibits a record CO2 capacity of 4.2 +/- 0.2 mmol/g (16 wt %) at 0.1 bar and 40 degrees C in the presence of a high partial pressure of H2O.« less

Application of a high-throughput analyzer in evaluating solid adsorbents for post-combustion carbon capture via multicomponent adsorption of CO2, N2, and H2O.

PubMed

Mason, Jarad A; McDonald, Thomas M; Bae, Tae-Hyun; Bachman, Jonathan E; Sumida, Kenji; Dutton, Justin J; Kaye, Steven S; Long, Jeffrey R

2015-04-15

Despite the large number of metal-organic frameworks that have been studied in the context of post-combustion carbon capture, adsorption equilibria of gas mixtures including CO2, N2, and H2O, which are the three biggest components of the flue gas emanating from a coal- or natural gas-fired power plant, have never been reported. Here, we disclose the design and validation of a high-throughput multicomponent adsorption instrument that can measure equilibrium adsorption isotherms for mixtures of gases at conditions that are representative of an actual flue gas from a power plant. This instrument is used to study 15 different metal-organic frameworks, zeolites, mesoporous silicas, and activated carbons representative of the broad range of solid adsorbents that have received attention for CO2 capture. While the multicomponent results presented in this work provide many interesting fundamental insights, only adsorbents functionalized with alkylamines are shown to have any significant CO2 capacity in the presence of N2 and H2O at equilibrium partial pressures similar to those expected in a carbon capture process. Most significantly, the amine-appended metal organic framework mmen-Mg2(dobpdc) (mmen = N,N'-dimethylethylenediamine, dobpdc (4-) = 4,4'-dioxido-3,3'-biphenyldicarboxylate) exhibits a record CO2 capacity of 4.2 ± 0.2 mmol/g (16 wt %) at 0.1 bar and 40 °C in the presence of a high partial pressure of H2O.

Exploration of H2O-CO2 Solubility in Alkali Basalt at low-H2O

NASA Astrophysics Data System (ADS)

Roggensack, K.; Allison, C. M.; Clarke, A. B.

2017-12-01

A number of recent experimental studies have found conflicting evidence for and against the influence of H2O on CO2 solubility in basalt and alkali-rich mafic magma (e.g. Behrens et al., 2009; Shishkina et al., 2010;2014; Iacono-Marziano et al., 2012). Some of the uncertainty is due to the error with spectroscopic determination (FTIR) of carbon and the challenge of controlling H2O abundance in experiments. It's been widely observed that even experimental capsules without added H2O may produce hydrous glasses containing several wt.% H2O. We conducted fluid-saturated, mixed-fluid (H2O-CO2) experiments to determine the solubility in alkali basalt with particular emphasis on conditions at low-H2O. To limit possible H2O contamination, materials were dried prior to loading and experimental capsules were sealed under vacuum. Experiments were run using a piston-cylinder, in Pt (pre-soaked in Fe) or AuPd capsules and operating at pressures from 400 to 600 MPa. Post-run the capsules were punctured under vacuum and fluids were condensed, separated, and measured by mercury manometry. A comparison between two experiments run at the same temperature and pressure conditions but with different fluid compositions illustrates the correlation between carbonate and H2O solubility. Uncertainties associated with using concentrations calculated from FTIR data can be reduced by directly comparing analyses on wafers of similar thickness. We observe that the experiment with greater H2O absorbance also has a higher carbonate absorbance than the experiment with lower H2O absorbance. Since the experiments were run at the same pressure, the experiment with more water-rich fluid, and higher dissolved H2O, has lower CO2 fugacity, but surprisingly has higher dissolved CO2 content. Overall, the results show two distinct trends. Experiments conducted at low-H2O (0.5 to 0.8 wt.%) show lower dissolved CO2 than those conducted at moderate-H2O (2 to 3 wt.%) at similar CO2 fugacity. These data show that

Loss Process for the C2H5 Radical in the Atmospheres of Jupiter and Saturn: First Direct, Absolute Measurement of the Rate Constant for the Reaction H + C2H5 at Low Pressure and Temperature

NASA Astrophysics Data System (ADS)

Stief, L. J.; Pimentel, A. S.; Payne, W. A.; Nesbitt, F. L.; Cody, R. J.

2003-05-01

Photochemical models of the atmospheres of Jupiter and Saturn predict the reaction H + C2H5 to be the most important loss process for C2H5 in these atmospheres. In addition, the reaction channel H + C2H5 -> 2 CH3 is a significant source of the methyl radical. There are only two relatively modern studies of the H + C2H5 reaction, both of which depend on extensive modeling involving eight elementary reactions. The motivation for the present study is the lack of direct, absolute measurements of the rate constant for the H + C2H5 reaction at low pressures and temperatures appropriate for outer planet models. In the present experiments the reactants H and C2H5 are rapidly and simultaneously generated by reaction of F with appropriate mixtures of H2 and C2H6. Using the technique of discharge-flow with collision-free sampling to a mass spectrometer, we monitor the decay of C2H5 in excess H. In contrast to previous studies of this reaction, the primary H + C2H5 reaction is isolated and the radical decays only by reaction with H and by loss at the wall. Secondary reactions such as the self-reaction of C2H5 are negligible. At P = 1 Torr He we measure k (298K) = 1.13 x 10-10 cm3 molecule-1 s-1 and k (202K) = 1.18 x 10-10 cm3 molecule-1 s-1. Experiments at T = 155 K are in progress. The reaction is temperature independent as expected based on studies of other atom-radical reactions. Our result at T = 298 K lies between those of the two relatively modern but complex studies of this reaction. The present total rate constant data and planned product yield studies at low pressures and temperatures will then be available for use in future photochemical models of the atmospheres of the outer planets. The Planetary Atmospheres Program of NASA Headquarters is supporting this research.

Oxidation of C/SiC Composites at Reduced Oxygen Partial Pressures

NASA Technical Reports Server (NTRS)

Opila, Elizabeth J.; Serra, Jessica

2009-01-01

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

Electronic and chemical structure of the H 2O/GaN(0001) interface under ambient conditions

DOE PAGES

Zhang, Xueqiang; Ptasinska, Sylwia

2016-04-25

We employed ambient pressure X-ray photoelectron spectroscopy to investigate the electronic and chemical properties of the H 2O/GaN(0001) interface under elevated pressures and/or temperatures. A pristine GaN(0001) surface exhibited upward band bending, which was partially flattened when exposed to H 2O at room temperature. However, the GaN surface work function was slightly reduced due to the adsorption of molecular H 2O and its dissociation products. At elevated temperatures, a negative charge generated on the surface by a vigorous H 2O/GaN interfacial chemistry induced an increase in both the surface work function and upward band bending. We tracked the dissociative adsorptionmore » of H 2O onto the GaN(0001) surface by recording the core-level photoemission spectra and obtained the electronic and chemical properties at the H 2O/GaN interface under operando conditions. In conclusion, our results suggest a strong correlation between the electronic and chemical properties of the material surface, and we expect that their evolutions lead to significantly different properties at the electrolyte/ electrode interface in a photoelectrochemical solar cell.« less

Single photon ionization of van der Waals clusters with a soft x-ray laser: (CO2)n and (CO2)n(H2O)m.

PubMed

Heinbuch, S; Dong, F; Rocca, J J; Bernstein, E R

2006-10-21

Pure neutral (CO2)n clusters and mixed (CO2)n(H2O)m clusters are investigated employing time of flight mass spectroscopy and single photon ionization at 26.5 eV. The distribution of pure (CO2)n clusters decreases roughly exponentially with increasing cluster size. During the ionization process, neutral clusters suffer little fragmentation because almost all excess cluster energy above the vertical ionization energy is taken away by the photoelectron and only a small part of the photon energy is deposited into the (CO2)n cluster. Metastable dissociation rate constants of (CO2)n+ are measured in the range of (0.2-1.5) x 10(4) s(-1) for cluster sizes of 5< or =n< or =16. Mixed CO2-H2O clusters are studied under different generation conditions (5% and 20% CO2 partial pressures and high and low expansion pressures). At high CO2 concentration, predominant signals in the mass spectrum are the (CO2)n+ cluster ions. The unprotonated cluster ion series (CO2)nH2O+ and (CO2)n(H2O)2+ are also observed under these conditions. At low CO2 concentration, protonated cluster ions (H2O)nH+ are the dominant signals, and the protonated CO2(H2O)nH+ and unprotonated (H2O)n+ and (CO2)(H2O)n+ cluster ion series are also observed. The mechanisms and dynamics of the formation of these neutral and ionic clusters are discussed.

Effect of high-pressure H{sub 2}O treatment on elimination of interfacial GeO{sub X} layer between ZrO{sub 2} and Ge stack

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Chen-Shuo; Liu, Po-Tsun

2011-08-22

This investigation demonstrates the effect of high-pressure H{sub 2}O treatment on the elimination of the interfacial germanium suboxide (GeO{sub X}) layer between ZrO{sub 2} and Ge. The formation of GeO{sub X} interlayer increases the gate-leakage current and worsen the controllability of the gate during deposition or thermal cycles. X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy reveal that high-pressure H{sub 2}O treatment eliminates the interfacial GeO{sub X} layer. The physical mechanism involves the oxidation of non-oxidized Zr with H{sub 2}O and the reduction of GeO{sub X} by H{sub 2}. Treatment with H{sub 2}O reduces the gate-leakage current of a ZrO{submore » 2}/Ge capacitor by a factor of 1000.« less

[Ejaculatory profile: a pressure of 5 meters H2O at the level of the bladder neck during ejaculation].

PubMed

Hugonnet, Christophe L; Böhlen, Dominik; Schmid, Hans-Peter

2002-12-01

The existence of a pressure gradient in order to prevent retrograde ejaculation in men with no ejaculatory disorders has always been postulated, but without any scientific evidence. The profile of the prostatic urethra was recorded during ejaculation in 5 men with no ejaculatory disorders using a 10 F balloon catheter with 16 pressure channels, situated in pairs every 5 mm, starting just below the balloon in the bladder neck and extending as far as the external urethral sphincter. The pressure in the proximal part of the proximal urethra was 500 cm H2O in the five men, but this pressure did not exceed 400 cm H2O distally as far as the colliculus seminalis. The authors present a new method for recording the urethral pressure profile during ejaculation (ejaculatory profile). This study provides a better understanding of the mechanisms of normal ejaculation and could be useful for the evaluation of disorders of ejaculation.

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

PubMed

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

2011-05-01

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

Impact of carbon monoxide partial pressures on methanogenesis and medium chain fatty acids production during ethanol fermentation.

PubMed

Esquivel-Elizondo, Sofia; Miceli, Joseph; Torres, Cesar I; Krajmalnik-Brown, Rosa

2018-02-01

Medium-chain fatty acids (MCFA) are important biofuel precursors. Carbon monoxide (CO) is a sustainable electron and carbon donor for fatty acid elongation, since it is metabolized to MCFA precursors, it is toxic to most methanogens, and it is a waste product generated in the gasification of waste biomass. The main objective of this work was to determine if the inhibition of methanogenesis through the continuous addition of CO would lead to increased acetate or MCFA production during fermentation of ethanol. The effects of CO partial pressures (P CO ; 0.08-0.3 atm) on methanogenesis, fatty acids production, and the associated microbial communities were studied in batch cultures fed with CO and ethanol. Methanogenesis was partially inhibited at P CO  ≥ 0.11 atm. This inhibition led to increased acetate production during the first phase of fermentation (0-19 days). However, a second addition of ethanol (day 19) triggered MCFA production only at P CO  ≥ 0.11 atm, which probably occurred through the elongation of acetate with CO-derived ethanol and H 2 :CO 2 . Accordingly, during the second phase of fermentation (days 20-36), the distribution of electrons to acetate decreased at higher P CO , while electrons channeled to MCFA increased. Most probably, Acetobacterium, Clostridium, Pleomorphomonas, Oscillospira, and Blautia metabolized CO to H 2 :CO 2 , ethanol and/or fatty acids, while Peptostreptococcaceae, Lachnospiraceae, and other Clostridiales utilized these metabolites, along with the provided ethanol, for MCFA production. These results are important for biotechnological systems where fatty acids production are preferred over methanogenesis, such as in chain elongation systems and microbial fuel cells. © 2017 Wiley Periodicals, Inc.

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

NASA Astrophysics Data System (ADS)

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

2015-09-01

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

Changes in Cerebral Partial Oxygen Pressure and Cerebrovascular Reactivity During Intracranial Pressure Plateau Waves.

PubMed

Lang, Erhard W; Kasprowicz, Magdalena; Smielewski, Peter; Pickard, John; Czosnyka, Marek

2015-08-01

Plateau waves in intracranial pressure (ICP) are frequently recorded in neuro intensive care and are not yet fully understood. To further investigate this phenomenon, we analyzed partial pressure of cerebral oxygen (pbtO2) and a moving correlation coefficient between ICP and mean arterial blood pressure (ABP), called PRx, along with the cerebral oxygen reactivity index (ORx), which is a moving correlation coefficient between cerebral perfusion pressure (CPP) and pbtO2 in an observational study. We analyzed 55 plateau waves in 20 patients after severe traumatic brain injury. We calculated ABP, ABP pulse amplitude (ampABP), ICP, CPP, pbtO2, heart rate (HR), ICP pulse amplitude (ampICP), PRx, and ORx, before, during, and after each plateau wave. The analysis of variance with Bonferroni post hoc test was used to compare the differences in the variables before, during, and after the plateau wave. We considered all plateau waves, even in the same patient, independent because they are separated by long intervals. We found increases for ICP and ampICP according to our operational definitions for plateau waves. PRx increased significantly (p = 0.00026), CPP (p < 0.00001) and pbtO2 (p = 0.00007) decreased significantly during the plateau waves. ABP, ampABP, and HR remained unchanged. PRx during the plateau was higher than before the onset of wave in 40 cases (73 %) with no differences in baseline parameters for those with negative and positive ΔPRx (difference during and after). ORx showed an increase during and a decrease after the plateau waves, however, not statistically significant. PbtO2 overshoot after the wave occurred in 35 times (64 %), the mean difference was 4.9 ± 4.6 Hg (mean ± SD), and we found no difference in baseline parameters between those who overshoot and those who did not overshoot. Arterial blood pressure remains stable in ICP plateau waves, while cerebral autoregulatory indices show distinct changes, which indicate cerebrovascular

Gd Ba Cu O bulk superconductors fabricated by a seeded infiltration growth technique under reduced oxygen partial pressure

NASA Astrophysics Data System (ADS)

Iida, K.; Babu, N. H.; Shi, Y. H.; Cardwell, D. A.; Murakami, M.

2006-06-01

Single-grain Gd-Ba-Cu-O (GdBCO) bulk superconductors have been grown by a seeded infiltration and growth (SIG) technique under a 1% O2+N2 atmosphere using a generic MgO-doped Nd-Ba-Cu-O (MgO-NdBCO) seed placed on the sample surface at room temperature (the so-called the cold-seeding method). Partial melting of the MgO-NdBCO seeds fabricated in air under notionally identical thermal processing conditions, however, limited the reliability of this bulk GdBCO single-grain process. The observed seed decomposition is attributed to the dependence of the peritectic temperature Tp of MgO-doped Nd1+xBa2-xCu3Oy solid solution (MgO-doped Nd-123ss, where ss indicates solid solution) compounds on both oxygen partial pressure during the melt process and the level of solid solution (x). The peritectic decomposition temperature of MgO-doped Nd-123ss, with x ranging from 0 to 0.5 under p(O2) = 1.00 atm, was observed to remain constant at 1120 °C. Tp was observed to decrease linearly as a function of solid solution level, on the other hand, under oxygen partial pressures of both p(O2) = 0.21 and 0.01 atm. Based on these results, MgO-doped NdBCO seed crystals should be grown under reduced oxygen partial pressure in order to obtain a stable MgO-doped NdBCO seed crystal suitable for cold-seeding processes of large-grain (RE)BCO bulk superconductors (where RE is a rare earth element).

Tibiofemoral contact pressures in radial tears of the meniscus treated with all-inside repair, inside-out repair and partial meniscectomy.

PubMed

Zhang, Alan L; Miller, Stephanie L; Coughlin, Dezba G; Lotz, Jeffrey C; Feeley, Brian T

2015-10-01

To test contact pressures in the knee after treatment of a radial meniscus tear with an all-inside meniscal repair technique and compare the results with inside-out repair and partial meniscectomy. Six non-paired cadaveric knees were analyzed with intra-compartment pressures measured at loads of 250 N, 500 N and 1000 N at 0°, eight degrees, 15°, and 30° of knee flexion. Compartmental contact pressures were measured for the intact medial meniscus, radial tear in the posterior horn, all-inside repair using the NovoStitch suture passer device (Ceterix Orthopaedics Inc., Menlo Park, CA), inside-out repair method, and partial meniscectomy. One-way ANOVA was used for statistical analysis. The greatest differences in peak pressures between treatments were observed under 1000 N load at 30° flexion (0.8± (SD) 0.1 MPa (intact meniscus), 0.8± (SD) 0.1 MPa (all-inside), 0.9± (SD) 0.1 MPa (inside-out) and 1.6± (SD) 0.2 MPa (partial meniscectomy)). Treatment with partial meniscectomy resulted in the highest peak pressures compared to all other states (p<0.0001 at each angle). Repair of the radial tear using the all-inside technique as well as the inside-out technique resulted in significantly decreased compartment pressures compared to partial meniscectomies (p<0.0001 at each angle). There were no significant differences between peak pressures in the intact state and after repair with the all-inside or inside-out techniques. An all-inside repair technique using the NovoStitch suture passer can decrease contact pressures for a radial meniscus tear similarly to the inside-out repair technique when compared to partial meniscectomy. This novel arthroscopic suture passer warrants further analysis in the clinical setting as it may be a reliable method for repair of radial meniscal tears through an arthroscopic all-inside technique. Copyright © 2015 Elsevier B.V. All rights reserved.

Compositional dependent partial molar volume and compressibility of CO2 in rhyolite, phonolite and basalt glasses

NASA Astrophysics Data System (ADS)

Lerch, P.; Seifert, R.; Malfait, W. J.; Sanchez-Valle, C.

2012-12-01

Carbon dioxide is the second most abundant volatile in magmatic systems and plays an important role in many magmatic processes, e.g. partial melting, volatile saturation, outgassing. Despite this relevance, the volumetric properties of carbon-bearing silicates at relevant pressure and temperature conditions remain largely unknown because of considerable experimental difficulties associated with in situ measurements. Density and elasticity measurements on quenched glasses can provide an alternative source of information. For dissolved water, such measurements indicate that the partial molar volume is independent of compositions at ambient pressure [1], but the partial molar compressibility is not [2, 3]. Thus the partial molar volume of water may depend on melt composition at elevated pressure. For dissolved CO2, no such data is available. In order to constrain the effect of magma composition on the partial molar volume and compressibility of dissolved carbon, we determined the density and elasticity for three series of carbon-bearing basalt, phonolite and rhyolite glasses, quenched from 3.5 GPa and relaxed at ambient pressure. The CO2 content varies between 0 to 3.90 wt% depending on the glass composition. Glass densities were determined using the sink/float method in a diiodomethane (CH2I2) - acetone mixture. Brillouin measurements were conducted on relaxed and unrelaxed silicate glasses in platelet geometry to determine the compressional (VP) and shear (VS) wave velocities and elastic moduli. The partial molar volume of CO2 in rhyolite, phonolite and basalt glasses is 25.4 ± 0.9, 22.1 ± 0.6 and 26.6 ±1.8 cm3/mol, respectively. Thus, unlike for dissolved water, the partial molar volume of CO2 displays a resolvable compositional effect. Although the composition and CO2/carbonate speciation of the phonolite glasses is intermediate between that of the rhyolite and basalt glasses, the molar volume is not. Similar to dissolved water, the partial molar bulk modulus

Average rainwater pH, concepts of atmospheric acidity, and buffering in open systems

NASA Astrophysics Data System (ADS)

Liljestrand, Howard M.

The system of water equilibrated with a constant partial pressure of CO 2, as a reference point for pH acidity-alkalinity relationships, has nonvolatile acidity and alkalinity components as conservative quantities, but not [H +]. Simple algorithms are presented for the determination of the average pH for combinations of samples both above and below pH 5.6. Averaging the nonconservative quantity [H +] yields erroneously low mean pH values. To extend the open CO 2 system to include other volatile atmospheric acids and bases distributed among the gas, liquid and particulate matter phases, a theoretical framework for atmospheric acidity is presented. Within certain oxidation-reduction limitations, the total atmospheric acidity (but not free acidity) is a conservative quantity. The concept of atmospheric acidity is applied to air-water systems approximating aerosols, fogwater, cloudwater and rainwater. The buffer intensity in hydrometeors is described as a function of net strong acidity, partial pressures of acid and base gases and the water to air ratio. For high liquid to air volume ratios, the equilibrium partial pressures of trace acid and base gases are set by the pH or net acidity controlled by the nonvolatile acid and base concentrations. For low water to air volume ratios as well as stationary state systems such as precipitation scavenging with continuous emissions, the partial pressures of trace gases (NH 3, HCl, HNO 3, SO 2 and CH 3COOH) appear to be of greater or equal importance as carbonate species as buffers in the aqueous phase.

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

NASA Technical Reports Server (NTRS)

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

1972-01-01

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

Lithium amide (LiNH2) under pressure.

PubMed

Prasad, Dasari L V K; Ashcroft, N W; Hoffmann, Roald

2012-10-11

Static high pressure lithium amide (LiNH(2)) crystal structures are predicted using evolutionary structure search methodologies and intuitive approaches. In the process, we explore the relationship of the structure and properties of solid LiNH(2) to its molecular monomer and dimer, as well as its valence-isoelectronic crystalline phases of methane, water, and ammonia all under pressure. A NaNH(2) (Fddd) structure type is found to be competitive for the ground state of LiNH(2) above 6 GPa with the P = 1 atm I4[overline] phase. Three novel phases emerge at 11 (P4[overline]2(1)m), 13 (P4(2)/ncm), and 46 GPa (P2(1)2(1)2(1)), still containing molecular amide anions, which begin to form N-H···N hydrogen bonds. The P2(1)2(1)2(1) phase remains stable over a wide pressure range. This phase and another Pmc2(1) structure found at 280 GPa have infinite ···(H)N···H···N(H)···H polymeric zigzag chains comprising symmetric N···H···N hydrogen bonds with one NH bond kept out of the chain, an interesting general feature found in many of our high pressure (>280 GPa) LiNH(2) structures, with analogies in high pressure H(2)O-ices. All the predicted low enthalpy LiNH(2) phases are calculated to be enthalpically stable with respect to their elements but resist metallization with increasing pressure up to several TPa. The possibility of Li sublattice melting in the intermediate pressure range structures is raised.

H2MBH2 and M(μ-H)2BH2 Molecules Isolated in Solid Argon: Interelement M-B and M-H-B Bonds (M = Ge, Sn).

PubMed

Zhao, Jie; Beckers, Helmut; Huang, Tengfei; Wang, Xuefeng; Riedel, Sebastian

2018-02-19

Laser-ablated boron atoms react with GeH 4 molecules to form novel germylidene borane H 2 GeBH 2 , which undergoes a photochemical rearrangement to the germanium tetrahydroborate Ge(μ-H) 2 BH 2 upon irradiation with light of λ = 405 nm. For comparison, the boron atom reactions with SnH 4 only gave the tin tetrahydroborate Sn(μ-H) 2 BH 2 . Infrared matrix-isolation spectroscopy with deuterium substitution and the state-of-the-art quantum-chemical calculations are used to identify these species in solid argon. A planar structure of H 2 GeBH 2 with an electron-deficient B-Ge bond with a partial multiple bond character (bond order = 1.5) is predicted by quantum-chemical calculations. In the case of M(μ-H) 2 BH 2 (M = Ge, Sn) two 3c-2e B-H-M hydrogen bridged bonds are formed by donation of electrons from the B-H σ-bonds into empty p-orbitals of M.

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

NASA Astrophysics Data System (ADS)

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

2014-01-01

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

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

PubMed

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

2015-02-26

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

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

PubMed

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

2013-11-27

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

Measurement of Local Partial Pressure of Oxygen in the Brain Tissue under Normoxia and Epilepsy with Phosphorescence Lifetime Microscopy

PubMed Central

Zhang, Cong; Bélanger, Samuel; Pouliot, Philippe; Lesage, Frédéric

2015-01-01

In this work a method for measuring brain oxygen partial pressure with confocal phosphorescence lifetime microscopy system is reported. When used in conjunction with a dendritic phosphorescent probe, Oxyphor G4, this system enabled minimally invasive measurements of oxygen partial pressure (pO2) in cerebral tissue with high spatial and temporal resolution during 4-AP induced epileptic seizures. Investigating epileptic events, we characterized the spatio-temporal distribution of the "initial dip" in pO2 near the probe injection site and along nearby arterioles. Our results reveal a correlation between the percent change in the pO2 signal during the "initial dip" and the duration of seizure-like activity, which can help localize the epileptic focus and predict the length of seizure. PMID:26305777

Measurement of Local Partial Pressure of Oxygen in the Brain Tissue under Normoxia and Epilepsy with Phosphorescence Lifetime Microscopy.

PubMed

Zhang, Cong; Bélanger, Samuel; Pouliot, Philippe; Lesage, Frédéric

2015-01-01

In this work a method for measuring brain oxygen partial pressure with confocal phosphorescence lifetime microscopy system is reported. When used in conjunction with a dendritic phosphorescent probe, Oxyphor G4, this system enabled minimally invasive measurements of oxygen partial pressure (pO2) in cerebral tissue with high spatial and temporal resolution during 4-AP induced epileptic seizures. Investigating epileptic events, we characterized the spatio-temporal distribution of the "initial dip" in pO2 near the probe injection site and along nearby arterioles. Our results reveal a correlation between the percent change in the pO2 signal during the "initial dip" and the duration of seizure-like activity, which can help localize the epileptic focus and predict the length of seizure.

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

PubMed Central

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

2015-01-01

Systematic studies of pressure-induced amorphization of natrolites (PIA) containing monovalent extra-framework cations (EFC) Li+, Na+, K+, Rb+, Cs+ allow us to assess the role of two different EFC-H2O configurations within the pores of a zeolite: one arrangement has H2O molecules (NATI) and the other the EFC (NATII) in closer proximity to the aluminosilicate framework. We show that NATI materials have a lower onset pressure of PIA than the NATII materials containing Rb and Cs as EFC. The onset pressure of amorphization (PA) of NATII materials increases linearly with the size of the EFC, whereas their initial bulk moduli (P1 phase) decrease linearly. Only Cs- and Rb-NAT reveal a phase separation into a dense form (P2 phase) under pressure. High-Angle Annular Dark Field Scanning Transmission Electron Microscopy (HAADF-STEM) imaging shows that after recovery from pressures near 25 and 20 GPa long-range ordered Rb-Rb and Cs-Cs correlations continue to be present over length scales up to 100 nm while short-range ordering of the aluminosilicate framework is significantly reduced—this opens a new way to form anti-glass structures. PMID:26455345

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

PubMed

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

2015-10-12

Systematic studies of pressure-induced amorphization of natrolites (PIA) containing monovalent extra-framework cations (EFC) Li(+), Na(+), K(+), Rb(+), Cs(+) allow us to assess the role of two different EFC-H2O configurations within the pores of a zeolite: one arrangement has H2O molecules (NATI) and the other the EFC (NATII) in closer proximity to the aluminosilicate framework. We show that NATI materials have a lower onset pressure of PIA than the NATII materials containing Rb and Cs as EFC. The onset pressure of amorphization (PA) of NATII materials increases linearly with the size of the EFC, whereas their initial bulk moduli (P1 phase) decrease linearly. Only Cs- and Rb-NAT reveal a phase separation into a dense form (P2 phase) under pressure. High-Angle Annular Dark Field Scanning Transmission Electron Microscopy (HAADF-STEM) imaging shows that after recovery from pressures near 25 and 20 GPa long-range ordered Rb-Rb and Cs-Cs correlations continue to be present over length scales up to 100 nm while short-range ordering of the aluminosilicate framework is significantly reduced-this opens a new way to form anti-glass structures.

Anisotropic H c 2 , thermodynamic and transport measurements, and pressure dependence of T c in K 2 Cr 3 As 3 single crystals

DOE PAGES

Kong, Tai; Bud'ko, Sergey L.; Canfield, Paul C.

2015-01-30

We present a detailed study of single crystalline K 2Cr 3As 3 and analyze its thermodynamic and transport properties, anisotropic H c2(T), and initial pressure dependence of T c. In zero field, the temperature-dependent resistivity is metallic. Deviation from a linear temperature dependence is evident below 100 K and a T 3 dependence is roughly followed from just above T c (~10K) to ~40K. Anisotropic H c2(T) data were measured up to 140 kOe with field applied along and perpendicular to the rodlike crystals. For the applied field perpendicular to the rod, H c2(T) is linear with a slope ~–70more » kOe/K. For field applied along the rod, the slope is about –120 kOe/K below 70 kOe. Above 70 kOe, the magnitude of the slope decreases to ~–70 kOe/K. The electronic specific heat coefficient γ, just above T c, is 73 mJ/mol K 2; the Debye temperature Θ D is 220 K. As a result, the specific heat jump at the superconducting transition ΔC~2.2γT c. Finally, for hydrostatic pressures up to ~7 kbar, T c decreases under pressure linearly at a rate of –0.034K/kbar.« less

Effects of elevated artificial pneumoperitoneum pressure on invasive blood pressure and levels of blood gases.

PubMed

Hypolito, Octavio; Azevedo, João Luiz; Gama, Fernanda; Azevedo, Otavio; Miyahira, Susana Abe; Pires, Oscar César; Caldeira, Fabiana Alvarenga; Silva, Thamiris

2014-01-01

to evaluate the clinical, hemodynamic, gas analysis and metabolic repercussions of high transient pressures of pneumoperitoneum for a short period of time to ensure greater security for introduction of the first trocar. sixty-seven patients undergoing laparoscopic procedures were studied and randomly distributed in P12 group: n=30 (intraperitoneal pressure [IPP] 12mmHg) and P20 group: n=37 (IPP of 20mmHg). Mean arterial pressure (MAP) was evaluated by catheterization of the radial artery; and through gas analysis, pH, partial pressure of oxygen (PaO2), partial pressure of CO2 (PaCO2), bicarbonate (HCO3) and alkalinity (BE) were evaluated. These parameters were measured in both groups at time zero before pneumoperitoneum (TP0); at time 1 (TP1) when IPP reaches 12mmHg in both groups; at time 2 (TP2) after five min with IPP=12mmHg in P12 and after 5min with IPP=20mmHg at P20; and at time 3 (TP3) after 10min with IPP=12mmHg in P12 and with return of IPP from 20 to 12mmHg, starting 10min after TP1 in P20. Different values from those considered normal for all parameters assessed, or the appearance of atypical organic phenomena, were considered as clinical changes. there were statistically significant differences in P20 group in MAP, pH, HCO3 and BE, but within normal limits. No clinical and pathological changes were observed. high and transient intra-abdominal pressure causes changes in MAP, pH, HCO3 and BE, but without any clinical impact on the patient. Copyright © 2014 Sociedade Brasileira de Anestesiologia. Published by Elsevier Editora Ltda. All rights reserved.

Influence of Ar/O2/H2O Feed Gas and N2/O2/H2O Environment on the Interaction of Time Modulated MHz Atmospheric Pressure Plasma Jet (APPJ) with Model Polymers

NASA Astrophysics Data System (ADS)

Oehrlein, Gottlieb; Luan, Pingshan; Knoll, Andrew; Kondeti, Santosh; Bruggeman, Peter

2016-09-01

An Ar/O2/H2O fed time modulated MHz atmospheric pressure plasma jet (APPJ) in a sealed chamber was used to study plasma interaction with model polymers (polystyrene, poly-methyl methacrylate, etc.). The amount of H2O in the feed gas and/or present in the N2, O2, or N2/O2 environment was controlled. Short lived species such as O atoms and OH radicals play a crucial role in polymer etching and surface modifications (obtained from X-ray photoelectron spectroscopy of treated polymers without additional atmospheric exposure). Polymer etching depth for Ar/air fed APPJ mirrors the decay of gas phase O atoms with distance from the APPJ nozzle in air and is consistent with the estimated O atom flux at the polymer surface. Furthermore, whereas separate O2 or H2O admixture to Ar enhances polymer etching, simultaneous addition of O2 and H2O to Ar quenches polymer etching. This can be explained by the mutual quenching of O with OH, H and HO2 in the gas phase. Results where O2 and/or H2O in the environment were varied are consistent with these mechanisms. All results will be compared with measured and simulated species densities reported in the literature. We gratefully acknowledge funding from US Department of Energy (DE-SC0001939) and National Science Foundation (PHY-1415353).

H 2 Adsorbed Site-to-Site Electronic Delocalization within IRMOF-1: Understanding Non-Negligible Interactions at High Pressure

DOE PAGES

Wu, Jian; Kucukkal, Mustafa U.; Clark, Aurora E.

2016-07-15

Isoreticular metal organic frameworks (IRMOFs) have shown high uptake capabilities for storage of H 2 (11.5 wt % at 77 K and 170 bar). A significant literature has employed fragment models and a single adsorbed H 2 to identify adsorption sites within IRMOFs, as well as the necessary adsorbate–adsorbent interactions needed to reach sufficient adsorption enthalpy for practical usage, however at high pressures it remains to be seen if H 2···H 2 intermolecular interactions may influence the energetics. This study focuses upon IRMOF-1 (also known as MOF-5), and examines the individual H 2 stabilization energies at different sites using Möller–Plessetmore » perturbation theory and density functional theory alongside chemical models that consist of isolated fragment models and a cubic super cell cluster consisting of both the face- and edge-cube’s of IRMOF-1. Optimization of twenty stable configurations of singly adsorbed H 2 in the super-cell cluster is observed to be essential to obtain energy ordering of the five primary sites consistent with experiment and prior benchmark calculations (α >> β > γ > δ ≈ ε). To examine site-to-site interactions that may occur in the high-pressure regime, 64 co-adsorbed H2 within a super-cell cluster have been studied (a theoretical maximum of all adsorption sites, 14 wt %). There, delocalization and/or charge transfer of electrons is observed from the σ orbitals of the H 2 bound at the γ positions into the σ* orbitals of H 2 bound at the α sites leads to stabilization of the interaction of H 2 at the γ, by 1.4 kJ/mol, respectively (using M06-2X/LANL2DZ). Furthermore, this effect has been confirmed to be charge transfer, and not a manifestation of enhanced dispersion at high loading, through natural bond order (NBO) analysis and by comparisons of the square of off-diagonal NBO Fock matrix elements for both density functionals that account for dispersion interactions and Hartree–Fock calculations that ignore

Classifying Acute Respiratory Distress Syndrome Severity: Correcting the Arterial Oxygen Partial Pressure to Fractional Inspired Oxygen at Altitude.

PubMed

Pérez-Padilla, Rogelio; Hernández-Cárdenas, Carmen Margarita; Lugo-Goytia, Gustavo

2016-01-01

In the well-known Berlin definition of acute respiratory distress syndrome (ARDS), there is a recommended adjustment for arterial oxygen partial pressure to fractional inspired oxygen (PaO2/FIO2) at altitude, but without a reference as to how it was derived.

Negative pressure wound therapy for partial-thickness burns.

PubMed

Dumville, Jo C; Munson, Christopher; Christie, Janice

2014-12-15

A burn wound is a complex and evolving injury, with both local and systemic consequences. Burn treatments include a variety of dressings, as well as newer strategies, such as negative pressure wound therapy (NPWT), which, by means of a suction force that drains excess fluids from the burn, tries to promote the wound healing process and minimise progression of the burn wound. To assess the effectiveness of NPWT for people with partial-thickness burns. We searched the Cochrane Wounds Group Specialised Register (searched 04 September 2014); The Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2014, Issue 8). All randomised controlled trials (RCTs) and controlled clinical trials (CCTs) that evaluated the safety and effectiveness of NPWT for partial-thickness burns. Two review authors used standardised forms, and extracted the data independently. We assessed each trial for risk of bias, and resolved differences by discussion. One RCT, that was an interim report, satisfied the inclusion criteria. We undertook a narrative synthesis of results, as the absence of data and poor reporting precluded us from carrying out any formal statistical analysis. The trial was at high risk of bias. There was not enough evidence available to permit any conclusions to be drawn regarding the use of NPWT for treatment of partial-thickness burn wounds.

Chemical Reactions Between Fe and H2O up to Megabar Pressures and Implications for Water Storage in the Earth's Mantle and Core

NASA Astrophysics Data System (ADS)

Yuan, Liang; Ohtani, Eiji; Ikuta, Daijo; Kamada, Seiji; Tsuchiya, Jun; Naohisa, Hirao; Ohishi, Yasuo; Suzuki, Akio

2018-02-01

We investigated the phase relations of the Fe-H2O system at high pressures based on in situ X-ray diffraction experiments and first-principles calculations and demonstrate that FeHx and FeO are present at pressures less than 78 GPa. A recently reported pyrite-structured FeO2 was identified in the Fe-H2O system at pressures greater than 78 GPa after laser heating. The phase observed in this study has a unit cell volume 8%-11% larger than that of FeO2, produced in the Fe-O binary system reported previously, suggesting that hydrogen might be retained in a FeO2Hx crystal structure. Our observations indicate that H2O is likely introduced into the deep Earth through reaction between iron and water during the accretion and separation of the metallic core. Additionally, reaction between Fe and H2O would occur at the core-mantle boundary, given water released from hydrous subducting slabs that intersect with the metallic core. Accumulation of volatile-bearing iron compounds may provide new insights into the enigmatic seismic structures observed at the base of the lower mantle.

Influence of H 2O and H 2S on the composition, activity, and stability of sulfided Mo, CoMo, and NiMo supported on MgAl 2O 4 for hydrodeoxygenation of ethylene glycol

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dabros, Trine Marie Hartmann; Gaur, Abhijeet; Pintos, Delfina Garcia

Here in this work, density functional theory (DFT), catalytic activity tests, and in-situ X-ray absorption spectroscopy (XAS) was performed to gain detailed insights into the activity and stability of MoS 2, Ni-MoS 2, and Co-MoS 2 catalysts used for hydrodeoxygenation (HDO) of ethylene glycol upon variation of the partial pressures of H 2O and H 2S. The results show high water tolerance of the catalysts and highlight the importance of promotion and H 2S level during HDO. DFT calculations unraveled that the active edge of MoS 2 could be stabilized against SO exchanges by increasing the partial pressure of Hmore » 2S or by promotion with either Ni or Co. The Mo, NiMo, and CoMo catalysts of the present study were all active and fairly selective for ethylene glycol HDO at 400 °C, 27 bar H 2, and 550–2200 ppm H 2S, and conversions of ≈50–100%. The unpromoted Mo/MgAl 2O 4 catalyst had a lower stability and activity per gram catalyst than the promoted analogues. The NiMo and CoMo catalysts produced ethane, ethylene, and C1 cracking products with a C 2/C 1 ratio of 1.5–2.0 at 550 ppm H 2S. This ratio of HDO to cracking could be increased to ≈2 at 2200 ppm H 2S which also stabilized the activity. Removing H 2S from the feed caused severe catalyst deactivation. Both DFT and catalytic activity tests indicated that increasing the H 2S concentration increased the concentration of SH groups on the catalyst, which correspondingly activated and stabilized the catalytic HDO performance. In-situ XAS further supported that the catalysts were tolerant towards water when exposed to increasing water concentration with H2O/H2S ratios up to 300 at 400–450 °C. Raman spectroscopy and XAS showed that MoS2 was present in the prepared catalysts as small and highly dispersed particles, probably owing to a strong interaction with the support. Linear combination fitting (LCF) analysis of the X-ray absorption near edge structure (XANES) spectra obtained during in-situ sulfidation

Influence of H 2O and H 2S on the composition, activity, and stability of sulfided Mo, CoMo, and NiMo supported on MgAl 2O 4 for hydrodeoxygenation of ethylene glycol

DOE PAGES

Dabros, Trine Marie Hartmann; Gaur, Abhijeet; Pintos, Delfina Garcia; ...

2017-12-10

Here in this work, density functional theory (DFT), catalytic activity tests, and in-situ X-ray absorption spectroscopy (XAS) was performed to gain detailed insights into the activity and stability of MoS 2, Ni-MoS 2, and Co-MoS 2 catalysts used for hydrodeoxygenation (HDO) of ethylene glycol upon variation of the partial pressures of H 2O and H 2S. The results show high water tolerance of the catalysts and highlight the importance of promotion and H 2S level during HDO. DFT calculations unraveled that the active edge of MoS 2 could be stabilized against SO exchanges by increasing the partial pressure of Hmore » 2S or by promotion with either Ni or Co. The Mo, NiMo, and CoMo catalysts of the present study were all active and fairly selective for ethylene glycol HDO at 400 °C, 27 bar H 2, and 550–2200 ppm H 2S, and conversions of ≈50–100%. The unpromoted Mo/MgAl 2O 4 catalyst had a lower stability and activity per gram catalyst than the promoted analogues. The NiMo and CoMo catalysts produced ethane, ethylene, and C1 cracking products with a C 2/C 1 ratio of 1.5–2.0 at 550 ppm H 2S. This ratio of HDO to cracking could be increased to ≈2 at 2200 ppm H 2S which also stabilized the activity. Removing H 2S from the feed caused severe catalyst deactivation. Both DFT and catalytic activity tests indicated that increasing the H 2S concentration increased the concentration of SH groups on the catalyst, which correspondingly activated and stabilized the catalytic HDO performance. In-situ XAS further supported that the catalysts were tolerant towards water when exposed to increasing water concentration with H2O/H2S ratios up to 300 at 400–450 °C. Raman spectroscopy and XAS showed that MoS2 was present in the prepared catalysts as small and highly dispersed particles, probably owing to a strong interaction with the support. Linear combination fitting (LCF) analysis of the X-ray absorption near edge structure (XANES) spectra obtained during in-situ sulfidation

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

NASA Astrophysics Data System (ADS)

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

2014-05-01

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.

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

NASA Technical Reports Server (NTRS)

Zent, Aaron P.; Quinn, Richard

1994-01-01

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.

AC calorimetry of H2O at pressures up to 9 GPa in diamond anvil cells

NASA Astrophysics Data System (ADS)

Geballe, Zachary M.; Struzhkin, Viktor V.

2017-06-01

If successfully developed, calorimetry at tens of GPa of pressure could help characterize phase transitions in materials such as high-pressure minerals, metals, and molecular solids. Here, we extend alternating-current calorimetry to 9 GPa and 300 K in a diamond anvil cell and use it to study phase transitions in H2O. In particular, water is loaded into the sample chambers of diamond-cells, along with thin metal heaters (1 μm-thick platinum or 20 nm-thick gold on a glass substrate) that drive high-frequency temperature oscillations (20 Hz to 600 kHz; 1 to 10 K). The heaters also act as thermometers via the third-harmonic technique, yielding calorimetric data on (1) heat conduction to the diamonds and (2) heat transport into substrate and sample. Using this method during temperature cycles from 300 to 200 K, we document melting, freezing, and proton ordering and disordering transitions of H2O at 0 to 9 GPa, and characterize changes in thermal conductivity and heat capacity across these transitions. The technique and analysis pave the way for calorimetry experiments on any non-metal at pressures up to ˜100 GPa, provided a thin layer (several μm-thick) of thermal insulation supports a metallic thin-film (tens of nm thick) Joule-heater attached to low contact resistance leads inside the sample chamber of a diamond-cell.

Calculation of the rate constant for state-selected recombination of H+O2(v) as a function of temperature and pressure

NASA Astrophysics Data System (ADS)

Teitelbaum, Heshel; Caridade, Pedro J. S. B.; Varandas, António J. C.

2004-06-01

Classical trajectory calculations using the MERCURY/VENUS code have been carried out on the H+O2 reactive system using the DMBE-IV potential energy surface. The vibrational quantum number and the temperature were selected over the ranges v=0 to 15, and T=300 to 10 000 K, respectively. All other variables were averaged. Rate constants were determined for the energy transfer process, H+O2(v)-->H+O2(v''), for the bimolecular exchange process, H+O2(v)-->OH(v')+O, and for the dissociative process, H+O2(v)-->H+O+O. The dissociative process appears to be a mere extension of the process of transferring large amounts of energy. State-to-state rate constants are given for the exchange reaction, and they are in reasonable agreement with previous results, while the energy transfer and dissociative rate constants have never been reported previously. The lifetime distributions of the HO2 complex, calculated as a function of v and temperature, were used as a basis for determining the relative contributions of various vibrational states of O2 to the thermal rate coefficients for recombination at various pressures. This novel approach, based on the complex's ability to survive until it collides in a secondary process with an inert gas, is used here for the first time. Complete falloff curves for the recombination of H+O2 are also calculated over a wide range of temperatures and pressures. The combination of the two separate studies results in pressure- and temperature-dependent rate constants for H+O2(v)(+Ar)⇄HO2(+Ar). It is found that, unlike the exchange reaction, vibrational and rotational-translational energy are liabilities in promoting recombination.

Oxygen partial pressure modulates 67-kDa laminin receptor expression, leading to altered activity of the green tea polyphenol, EGCG.

PubMed

Tsukamoto, Shuntaro; Yamashita, Shuya; Kim, Yoon Hee; Kumazoe, Motofumi; Huang, Yuhui; Yamada, Koji; Tachibana, Hirofumi

2012-09-21

(-)-Epigallocatechin-3-O-gallate (EGCG) exhibits anti-tumor activity mediated via the 67-kDa laminin receptor (67LR). In this study, we found that 67LR protein levels are reduced by exposure to low O(2) levels (5%), without affecting the expression of HIF-1α. We also found that EGCG-induced anti-cancer activity is abrogated under low O(2) levels (5%) in various cancer cells. Notably, treatment with the proteasome inhibitor, prevented down-regulation of 67LR and restored sensitivity to EGCG under 5% O(2). In summary, 67LR expression is highly sensitive to O(2) partial pressure, and the activity of EGCG can be regulated in cancer cells by O(2) partial pressure. Copyright © 2012 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

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

PubMed Central

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

2014-01-01

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 120–40 mmHg) and 15.4 (±0.7) mmHg (range 40–8mmHg), 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

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

NASA Astrophysics Data System (ADS)

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

2004-11-01

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

[The influence of oxygen partial pressure change and vascularization of rabbit wound through negative pressure wound therapy].

PubMed

Yang, Fan; Hu, Duan; Bai, Xiang-jun; Zhang, Kun; Li, Ren-jie; Xue, Chen-chen

2012-07-01

To investigate the effect of vacuum sealing drainage (VSD) on variation of oxygen partial pressure (PtO2) and vascularization. The 12 cases of rabbit's wound models were undergoing the VSD (vacuum group, n = 6) or conventional therapy (conventional group, n = 6). Variation of PtO2 was measured by oxygen partial pressure admeasuring apparatus, expression of hypoxia inducible factor 1α (HIF-1α) mRNA was measured by real-time fluorescent quantitative PCR, content of vascular endothelial growth factor (VEGF) was measured by ELISA after tissue homogenate in 7 days. Vascular endothelial cell (VEC) and new blood capillary (NBC) of hematoxylin-eosin slice of tissue were counted by using light microscope. Average value of PtO2 of vacuum group was significant lower than conventional group (t = -99.780 to -5.305, P < 0.01). Expression of HIF-1α (30 minutes, 1, 6, 12 hours were 3.11 ± 0.07, 3.68 ± 0.26, 4.16 ± 0.13 and 3.91 ± 0.26 respectively) and content of VEGF (30 minutes, 1, 6, 12 hours were 103.3 ± 2.4, 134.2 ± 9.0, 167.8 ± 3.8 and 232.1 ± 9.5 respectively) of vacuum group were increased after 30 minutes and significant lower than conventional group (t = 13.038 - 80.208, P < 0.01), and both of them were reduced after 24 hours (P < 0.05). Counting numbers of VEC (2.47 ± 0.45 to 4.70 ± 0.38) and NBC (1.33 ± 0.49 to 4.33 ± 0.68) of vacuum group were increased at the same time-point and significant higher than conventional group (t = -0.670 to 16.500, P < 0.05). PtO2 of wound surface could be reduced significantly by VSD. Expression of HIF-1α and content of VEGF were increased by VSD for enhancing differentiated state of VEC and construction of NBC, which were better for vascularization and wound healing.

29Si nuclear magnetic resonance study of URu 2Si 2 under pressure

DOE PAGES

Shirer, K. R.; Dioguardi, A. P.; Bush, B. T.; ...

2015-12-01

Here, we report 29Si nuclear magnetic resonance measurements of single crystals and aligned powders of URu 2Si 2 under pressure in the hidden order and paramagnetic phases. We find evidence for a reduction of the Knight shift with applied pressure, consistent with previous measurements of the static magnetic susceptibility. Previous measurements of the spin lattice relaxation time revealed a partial suppression of the density of states below 30 K. Here, we find that the temperature at which this suppression occurs is enhanced with applied pressure.

The Effect of Oxygen Partial Pressure on Microstructure and Properties of Fe40Al Alloy Sintered under Vacuum

PubMed Central

Siemiaszko, Dariusz; Kowalska, Beata; Jóźwik, Paweł; Kwiatkowska, Monika

2015-01-01

This paper presents the results of studies on the influence of oxygen partial pressure (vacuum level in the chamber) on the properties of FeAl intermetallics. One of the problems in the application of classical methods of prepared Fe-Al intermetallic is the occurrence of oxides. Applying a vacuum during sintering should reduce this effect. In order to analyze the effect of oxygen partial pressure on sample properties, five samples were processed (by a pressure-assisted induction sintering—PAIS method) under the following pressures: 3, 8, 30, 80, and 300 mbar (corresponding to oxygen partial pressures of 0.63, 1.68, 6.3, 16.8, and 63 mbar, respectively). The chemical and phase composition, hardness, density, and microstructure observations indicate that applying a vacuum significantly impacts intermetallic samples. The compact sintered at pressure 3 mbar is characterized by the most homogeneous microstructure, the highest density, high hardness, and nearly homogeneous chemical composition. PMID:28788015

Subsurface Pressure-Temperature Conditions and H2(aq) Generation at the Piccard Hydro-Thermal Field, Mid-Cayman Rise

NASA Astrophysics Data System (ADS)

Scheuermann, P. P.; Seyfried, W. E.

2018-05-01

The subsurface pressure-temperature conditions at the Piccard hydrothermal field are constrained using the Si-Cl geothermobarometer. Ol-Mgt and Opx-Mgt are proposed as assemblages that buffer H2(aq) at Piccard.

Effect of methane partial pressure on the performance of a membrane biofilm reactor coupling methane-dependent denitrification and anammox.

PubMed

Cai, Chen; Hu, Shihu; Chen, Xueming; Ni, Bing-Jie; Pu, Jiaoyang; Yuan, Zhiguo

2018-10-15

Complete nitrogen removal has recently been demonstrated by integrating anaerobic ammonium oxidation (anammox) and denitrifying anaerobic methane oxidation (DAMO) processes. In this work, the effect of methane partial pressure on the performance of a membrane biofilm reactor (MBfR) consisting of DAMO and anammox microorganisms was evaluated. The activities of DAMO archaea and DAMO bacteria in the biofilm increased significantly with increased methane partial pressure, from 367 ± 9 and 58 ± 22 mg-N L -1 d -1 to 580 ± 12 and 222 ± 22 mg-N L -1 d -1 , respectively, while the activity of anammox bacteria only increased slightly, when the methane partial pressure was elevated from 0.24 to 1.39 atm in the short-term batch tests. The results were supported by a long-term (seven weeks) continuous test, when the methane partial pressure was dropped from 1.39 to 0.78 atm. The methane utilization efficiency was always above 96% during both short-term and long-term tests. Taken together, nitrogen removal rate (especially the nitrate reduction rate by DAMO archaea) and methane utilization efficiency could be maintained at high levels in a broad range of methane partial pressure (0.24-1.39 atm in this study). In addition, a previously established DAMO/anammox biofilm model was used to analyze the experimental data. The observed impacts of methane partial pressure on biofilm activity were well explained by the modeling results. These results suggest that methane partial pressure can potentially be used as a manipulated variable to control reaction rates, ultimately to maintain high nitrogen removal efficiency, according to nitrogen loading rate. Copyright © 2018 Elsevier B.V. All rights reserved.

Relationships between 24-h blood pressure variability and 24-h central arterial pressure, pulse wave velocity and augmentation index in hypertensive patients.

PubMed

Omboni, Stefano; Posokhov, Igor N; Rogoza, Anatoly N

2017-04-01

Twenty-four-h blood pressure variability (BPV) predicts cardiovascular complications in hypertension, but its association with pulse wave indices (central arterial pressure, pulse wave velocity (PWV) and augmentation index (AIx)) is poorly understood. In the present study, we assessed the degree of the effect of 24-h BPV on 24-h pulse wave indices. Brachial blood pressure was measured non-invasively over the 24 h with an electronic, oscillometric, automated device (BPLab) in 661 uncomplicated treated or untreated hypertensive patients. Digitalized oscillometric waveforms were analyzed with a validated algorithm to obtain pulse wave indices. Twenty-four-h BPV was calculated as the unweighted (SDu) or weighted s.d. (SDw) of the mean blood pressure or as the average real variability (ARV). Twenty-four-h systolic BPV showed a direct and significant relationship with the central arterial systolic pressure (r=0.28 SDu, r=0.40 SDw, r=0.34 ARV), PWV (r=0.10 SDu, r=0.21 SDw, r=0.19 ARV) and AIx (r=0.17 SDu, r=0.27 SDw, r=0.23 ARV). After adjustment for age, sex, body mass index, antihypertensive treatment and 24-h systolic blood pressure, the relationship lost some power but was still significant for all measures, except for the AIx. Pulse wave indices were higher in patients with high BPV than in those with low BPV: after adjustment, these differences were abolished for the AIx. The diastolic BPV showed a weak association with the pulse wave indices. In conclusion, in hypertensive patients, 24-h systolic BPV is moderately and independently associated with 24-h central arterial pressure and stiffness.

Mechanism of VHF H2 plasma production at high pressures

NASA Astrophysics Data System (ADS)

Chen, Kuan-Chen; Chiu, Kuo-Feng; Chen, Chia-Fu; Lien, Cheng-Yang; Tsai, Yu-Jer; Lien, Ting-Kuei; Ogiwara, Kohei; Uchino, Kiichiro; Kawai, Yoshinobu

2016-06-01

A VHF H2 plasma was produced by a narrow-gap discharge at high pressures, and the plasma parameters were examined with the Langmuir probe. A bi-Maxwellian electron distribution was observed near the discharge electrode at a discharge gap of 10 mm, while a Maxwellian distribution was seen near the center. When the discharge gap was 15 mm, electrons had a Maxwellian distribution independent of the position. It was found that there must be a threshold in the discharge gap for stochastic heating to occur. The plasma potential near the discharge electrode was higher than that near the center of the interelectrode gap, suggesting the existence of negative ions. The simulation using the plasma hybrid code was carried out. The spatial profiles of the density and temperature of electrons were similar to the experimental results. The plasma potential had a hill-like profile that was quite different from the measured one. The negative ion density was negligible.

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

NASA Technical Reports Server (NTRS)

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

1989-01-01

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

Effect of CH4 on the CO2 breakthrough pressure and permeability of partially saturated low-permeability sandstone in the Ordos Basin, China

NASA Astrophysics Data System (ADS)

Zhao, Yan; Yu, Qingchun

2018-01-01

The behavior of CO2 that coexists with CH4 and the effect of CH4 on the CO2 stream need to be deeply analyzed and studied, especially in the presence of water. Our previous studies investigated the breakthrough pressure and permeability of pure CO2 in five partially saturated low-permeability sandstone core samples from the Ordos Basin, and we concluded that rocks with a small pore size and low permeability show considerable sealing capacity even under unsaturated conditions. In this paper, we selected three of these samples for CO2-CH4 gas-mixture breakthrough experiments under various degrees of water saturation. The breakthrough experiments were performed by increasing the gas pressure step by step until breakthrough occurred. Then, the effluent gas mixture was collected for chromatographic partitioning analysis. The results indicate that CH4 significantly affects the breakthrough pressure and permeability of CO2. The presence of CH4 in the gas mixture increases the interfacial tension and, thus, the breakthrough pressure. Therefore, the injected gas mixture that contains the highest (lowest) mole fraction of CH4 results in the largest (smallest) breakthrough pressure. The permeability of the gas mixture is greater than that for pure CO2 because of CH4, and the effective permeability decreases with increased breakthrough pressure. Chromatographic partitioning of the effluent mixture gases indicates that CH4 breaks through ahead of CO2 as a result of its weaker solubility in water. Correlations are established between (1) the breakthrough pressure and water saturation, (2) the effective permeability and water saturation, (3) the breakthrough pressure and effective permeability, and (4) the mole fraction of CO2/CH4 in the effluent mixture gases and water saturation. These results deepen our understanding of the multi-phase flow behavior in the porous media under unsaturated conditions, which have implications for formulating emergency response plans for gas

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

1997-05-01

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

The effect of oxygen partial pressure on protein synthesis and collagen hydroxylation by mature periodontal tissues maintained in organ cultures

PubMed Central

Yen, Edwin H. K.; Sodek, Jaro; Melcher, Antony H.

1979-01-01

Mature periodontal tissues from adult-mouse first mandibular molars were cultured in a continuous-flow organ-culture system which allowed the regulation of both ascorbic acid concentration and pO2 (oxygen partial pressure). Protein synthesis was measured by analysing the incorporation of [3H]proline into collagenous and non-collagenous proteins during the last 24h of a 2-day culture. At low pO2 [16.0kPa (approx. 120mmHg)] approx. 60% of protein-incorporated [3H]proline was found in collagenous proteins. However, it was evident that this collagen was considerably underhydroxylated. At high pO2 [56.0kPa (approx. 420mmHg)], both the amount of collagen deposited in the tissues and the degree of hydroxylation were increased considerably. In contrast, no significant effect on non-collagenous protein was observed. Tissues cultured at low pO2 for the first 48h were unable to respond to a subsequent increase in pO2 during the last 24h. Analysis of pepsin-solubilized collagen α-chains labelled with [14C]glycine demonstrated the synthesis of both type-I and type-III collagens by explants cultured for 48h at high pO2. Type-III collagen comprised 20–30% of the radioactivity in α-chains in both the periodontal ligament and the tissues of the alveolar process. The pattern of protein synthesis in the alveolar tissues at high pO2 was similar to that observed in these tissues in vivo. However, in the cultured periodontal ligament the proportions of non-collagenous proteins and type-III collagens were increased in comparison with the tissue in vivo. PMID:454369

First principles investigation of high pressure behavior of FeOOH-AlOOH-phase H (MgSiO4H2) system.

NASA Astrophysics Data System (ADS)

Tsuchiya, J.; Thompson, E. C.; Tsuchiya, T.; Nishi, M.; Kuwayama, Y.

2017-12-01

It has been believed that water is carried into the deep Earth's interior by hydrous minerals such as the dense hydrous magnesium silicates (DHMSs) in the descending cold plate. A numbers of researches have been conducted so far about the high pressure behaviors of DHMSs. In recent years, we found new DHMS, phase H, at lower mantle pressure condition and the solid solution between phase H and d-AlOOH has been proposed as the most important carrier of water in the deepest part of Earth's mantle (Tsuchiya 2013 GRL, Nishi et al. 2014 Nature Geo., Ohira et al. 2014 EPSL). However, those hydrous minerals are actually not denser than surrounding (dry) mantle minerals (Tsuchiya and Mookherjee 2015 Scientific Reports) and the gravitational stability in deeper part of the Earth is questionable. Therefore, the effects of denser element such as Fe on the stability of DHMS are intimately connected to the ability of transportation of water into Earth's deep interiors. In order to assess the effect of Fe on the phase relation of phase H and d-AlOOH, we first investigated the high pressure behavior of the end-member composition of this system, the e-FeOOH. We have found the new high pressure transformation of FeOOH in the lower mantle conditions both theoretically and experimentally(Nishi et al. 2017 Nature). Here we show high pressure structures and the physical properties of FeOOH-AlOOH-phase H system using first principles calculation and discuss the possible geophysical implications of these phases.

Novel high pressure hexagonal OsB2 by mechanochemistry

NASA Astrophysics Data System (ADS)

Xie, Zhilin; Graule, Moritz; Orlovskaya, Nina; Andrew Payzant, E.; Cullen, David A.; Blair, Richard G.

2014-07-01

Hexagonal OsB2, a theoretically predicted high-pressure phase, has been synthesized for the first time by a mechanochemical method, i.e., high energy ball milling. X-ray diffraction indicated that formation of hexagonal OsB2 begins after 2.5 h of milling, and the reaction reaches equilibrium after 18 h of milling. Rietveld refinement of the powder data indicated that hexagonal OsB2 crystallizes in the P63/mmc space group (No. 194) with lattice parameters of a=2.916 Å and c=7.376 Å. Transmission electron microscopy confirmed the appearance of the hexagonal OsB2 phase after high energy ball milling. in situ X-ray diffraction experiments showed that the phase is stable from -225 °C to 1050 °C. The hexagonal OsB2 powder was annealed at 1050 °C for 6 days in vacuo to improve crystallinity and remove strain induced during the mechanochemical synthesis. The structure partially converted to the orthorhombic phase (20 wt%) after fast current assisted sintering of hexagonal OsB2 at 1500 °C for 5 min. Mechanochemical approaches to the synthesis of hard boride materials allow new phases to be produced that cannot be prepared using conventional methods.

Effects of different pressure levels of CO2 pneumoperitoneum on liver regeneration after liver resection in a rat model.

PubMed

Komori, Yoko; Iwashita, Yukio; Ohta, Masayuki; Kawano, Yuichiro; Inomata, Masafumi; Kitano, Seigo

2014-08-01

A recent study demonstrated that high pressure of carbon dioxide (CO2) pneumoperitoneum before liver resection impairs postoperative liver regeneration. This study was aimed to investigate effects of varying insufflation pressures of CO2 pneumoperitoneum on liver regeneration using a rat model. 180 male Wistar rats were randomly divided into three groups: control group (without preoperative pneumoperitoneum), low-pressure group (with preoperative pneumoperitoneum at 5 mmHg), and high-pressure group (with preoperative pneumoperitoneum at 10 mmHg). After pneumoperitoneum, all rats were subjected to 70% partial hepatic resection and then euthanized at 0 min, 12 h, and on postoperative days (PODs) 1, 2, 4, and 7. Following outcome parameters were used: liver regeneration (liver regeneration rate, mitotic count, Ki-67 labeling index), hepatocellular damage (serum aminotransferases), oxidative stress [serum malondialdehyde (MDA)], interleukin-6 (IL-6), and hepatocyte growth factor (HGF) expression in the liver tissue. No significant differences were observed for all parameters between control and low-pressure groups. The liver regeneration rate and mitotic count were significantly decreased in the high-pressure group than in control and low-pressure groups on PODs 2 and 4. Postoperative hepatocellular damage was significantly greater in the high-pressure group on PODs 1, 2, 4, and 7 compared with control and/or low-pressure groups. Serum MDA levels were significantly higher in the high-pressure group on PODs 1 and 2, and serum IL-6 levels were significantly higher in the high-pressure group at 12 h and on POD 1, compared with control and/or low-pressure groups. The HGF tissue expression was significantly lower in the high-pressure group at 12 h and on PODs 1 and 4, compared with that in control and/or low-pressure groups. High-pressure pneumoperitoneum before 70% liver resection impairs postoperative liver regeneration, but low-pressure pneumoperitoneum has no adverse

Determining pH at elevated pressure and temperature using in situ ¹³C NMR.

PubMed

Surface, J Andrew; Wang, Fei; Zhu, Yanzhe; Hayes, Sophia E; Giammar, Daniel E; Conradi, Mark S

2015-02-03

We have developed an approach for determining pH at elevated pressures and temperatures by using (13)C NMR measurements of inorganic carbon species together with a geochemical equilibrium model. The approach can determine in situ pH with precision better than 0.1 pH units at pressures, temperatures, and ionic strengths typical of geologic carbon sequestration systems. A custom-built high pressure NMR probe was used to collect (13)C NMR spectra of (13)C-labeled CO2 reactions with NaOH solutions and Mg(OH)2 suspensions at pressures up to 107 bar and temperatures of 80 °C. The quantitative nature of NMR spectroscopy allows the concentration ratio [CO2]/[HCO3(-)] to be experimentally determined. This ratio is then used with equilibrium constants calculated for the specific pressure and temperature conditions and appropriate activity coefficients for the solutes to calculate the in situ pH. The experimentally determined [CO2]/[HCO3(-)] ratios agree well with the predicted values for experiments performed with three different concentrations of NaOH and equilibration with multiple pressures of CO2. The approach was then applied to experiments with Mg(OH)2 slurries in which the change in pH could track the dissolution of CO2 into solution, rapid initial Mg(OH)2 dissolution, and onset of magnesium carbonate precipitation.

The primary solar-type atmosphere surrounding the accreting Earth: H2O-induced high surface temperature.

NASA Astrophysics Data System (ADS)

Sasaki, S.

In the solar nebula, a growing planet attracts ambient gas to form a solar-type atmosphere. The structure of this H2-He atmosphere is calculated assuming the Earth was formed in the nebula. The blanketing effect of the atmosphere renders the planetary surface molten when the planetary mass exceeds 0.2 ME (ME being the present Earth's mass). Reduction of the surface melt by atmospheric H2 should add a large amount of H2O to the atmosphere: under the quartz-iron-fayalite oxygen buffer, partial pressure ratio P(H2O)/P(H2) becomes higher than 0.1. Enhancing opacity and gas mean molecular weight, the excess H2O raises the temperature and renders the atmosphere in convective equilibrium, while the dissociation of H2 suppresses the adiabatic temperature gradient. The surface temperature of the proto-Earth can be as high as 4700K when its mass is 1 ME. Such a high temperature may accelerate the evaporation of surface materials. A deep totally-molten magma ocean should exist in the accretion Earth.

High-pressure polymorphism of Pb F 2 to 75 GPa

DOE PAGES

Stan, Camelia V.; Dutta, Rajkrishna; White, Claire E.; ...

2016-07-06

Lead fluoride, PbF 2, was investigated experimentally in the laser-heated diamond anvil cell by x-ray diffraction to pressures of 75 GPa at room temperature and to 64.5 GPa and 2430 K, as well as through first-principles density functional theory calculations up to 70 GPa. During room temperature compression, no discontinuous changes in the x-ray diffraction pattern or volume were observed, but the lattice parameters displayed highly anomalous trends between 10-22 GPa with enhanced compressibility along the a direction and reduced or even negative compressibility along b and c. Theoretical calculations of valence electron densities at 22 GPa showed that α-PbFmore » 2 underwent a pressure-induced isosymmetric phase transition to a postcotunnite Co 2Si structure and also revealed the detailed atomic rearrangements associated with the development of an extra Pb-F bond in the high-pressure phase. Our x-ray results and theoretical calculations are consistent with an isosymmetric phase transition smoothly occurring over 10-22 GPa rather than abruptly as previously suggested. The characteristic values for the cell constants a/c and (a+c)/b, which are used to distinguish among cotunnite-, Co 2Si-, and Ni 2In-type phases, require modification based on our results. An equation of state fit yields a bulk modulus, K 0, of 72(3) GPa for the cotunnite-type, and an ambient-pressure volume, V 0, of 182(2)Å 3, and K 0=81(4)GPa for the Co 2Si-type phase when fixing the pressure derivative of the bulk modulus, K 0'=4. Upon heating above 1200 K at pressures at or above 25.9 GPa, PbF 2 partially transformed to the hexagonal Ni 2In-type phase but wholly or partially reverted back to Co 2Si-type phase upon temperature quench. From 43-65 GPa, nearly complete transformation to the Ni 2In-type PbF 2 was observed at high temperature, but the material partially transformed back to the orthorhombic phase upon temperature quench. Our results show that high-pressure behavior of PbF 2 is

High-pressure polymorphism of Pb F2 to 75 GPa

NASA Astrophysics Data System (ADS)

Stan, Camelia V.; Dutta, Rajkrishna; White, Claire E.; Prakapenka, Vitali; Duffy, Thomas S.

2016-07-01