Note: This page contains sample records for the topic calculated oxygen fugacity from Science.gov.
While these samples are representative of the content of Science.gov,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of Science.gov
to obtain the most current and comprehensive results.
Last update: August 15, 2014.
1

Calculation of Oxygen Fugacity in High Pressure Metal-Silicate Experiments and Comparison to Standard Approaches  

NASA Technical Reports Server (NTRS)

Calculation of oxygen fugacity in high pressure and temperature experiments in metal-silicate systems is usually approximated by the ratio of Fe in the metal and FeO in the silicate melt: (Delta)IW=2*log(X(sub Fe)/X(sub FeO)), where IW is the iron-wustite reference oxygen buffer. Although this is a quick and easy calculation to make, it has been applied to a huge variety of metallic (Fe- Ni-S-C-O-Si systems) and silicate liquids (SiO2, Al2O3, TiO2, FeO, MgO, CaO, Na2O, K2O systems). This approach has surely led to values that have little meaning, yet are applied with great confidence, for example, to a terrestrial mantle at "IW-2". Although fO2 can be circumvented in some cases by consideration of Fe-M distribution coefficient, these do not eliminate the effects of alloy or silicate liquid compositional variation, or the specific chemical effects of S in the silicate liquid, for example. In order to address the issue of what the actual value of fO2 is in any given experiment, we have calculated fO2 from the equilibria 2Fe (metal) + SiO2 (liq) + O2 = Fe2SiO4 (liq).

Righter, K.; Ghiorso, M.

2009-01-01

2

Oxygen fugacities of basaltic and andesitic magmas  

Microsoft Academic Search

Experimentally determined oxygen fugacities in equilibrium with the original ferrous to ferric iron ratios of nine basalts and andesites range from 10 -8·5 to 10 -6·4 atm at 1200°C. There is a strong tendency for the f O 2 to increase with increasing acidity of the rocks studied. Theoretical calculations of equilibrium f O 2 's, using equilibrium constants determined

R. F. Fudali

1965-01-01

3

Oxygen fugacity constraints on the southern African lithosphere  

NASA Astrophysics Data System (ADS)

Oxygen fugacities are calculated for olivine—spinel ±orthopyroxene assemblages recovered from diamonds and the concentrate of the Dokolwayo kimberlite, Swaziland. In addition thermobarometric oxygen fugacities are obtained for chrome spinel-garnet peridotites and diamonds from several other southern African kimberlites. The southern African lithosphere appears to be laterally homogeneous with respect to oxygen fugacity. Vertically the oxygen fugacity of the lithospheric upper mantle decreases with an increase in pressure. Locally, oxygen fugacities calculated for Dokolwayo mineral assemblages are indicative of an upper mantle characterised by diverse redox conditions within the range FMQ-IW. Reduced oxygen fugacities, calculated for the majority of the Dokolwayo samples, suggest that CH4 may be the dominant carbon volatile species in the lower lithosphere. These reduced conditions also suggest that the Dokolwayo kimberlite is unlikely to be a product of redox melting, but may be the product of a thermal anomaly. Calculated equilibrium temperatures for olivine-spinel pairs from Dokolwayo diamonds and concentrate indicate that the upper mantle in the vicinity of Dokolwayo was characterised by cool subsolidus conditions.

Daniels, Leon R. M.; Gurney, John J.

1991-07-01

4

Oxygen fugacities directly measured in magmatic gases  

USGS Publications Warehouse

An electrochemical device was used to measure the fugacity of oxygen (fO2) in holes drilled through the crust of Makaopuhi lava lake, Kilauea Volcano, Hawaii. Results obtained within 6 months of the lake formation show that log fO2 normally varies linearly with the reciprocal of the absolute temperature, and that chemical changes occurring in the cooling tholeiitic basalt are reflected in the fO2 values measured in the holes.

Sato, M.; Wright, T. L.

1966-01-01

5

Intrinsic oxygen fugacity measurements of some Allende Type B inclusions  

NASA Technical Reports Server (NTRS)

The intrinsic oxygen fugacities (IOFs) of two type B Ca-rich and Al-rich inclusions (CAI) from the Allende meteorite were measured using the solid-electrolyte double-cell IOF technique of Ulmer et al. (1976). The measurements were compared to calculated and experimentally extrapolated fO2 of type B phases. It was found that the IOFs of the type B are 6-8 orders of magnitude more oxidized (H2/H2O = 1-10) than the canonical solar nebular gas (H2/H2O = 100-2000). It is suggested that some local fO2 enhancing mechanism, such as dust or gas concentrations, or the release of oxygen-rich vapors during CAI volatilization in the type B inclusions was in operation at temperatures higher than 700 C.

Kozul, Jean M.; Hewins, Roger H.; Ulmer, Gene C.

1988-01-01

6

The color of meteoritic hibonite - an indicator of oxygen fugacity  

NASA Astrophysics Data System (ADS)

Hibonites similar in composition to those found in Ca-Al-rich inclusions change color from blue, to green, to orange, to nearly colorless as oxygen fugacity is increased at high temperature from below the iron-wustite buffer up to air. The development of the blue color is correlated with the growth of an absorption band at 715 nm in the optical spectra of the hibonites as the oxygen fugacity is reduced. The growth of this band is attributed to the increasing concentration of Ti(3+) in these hibonites with decreasing oxygen fugacity. The blue hibonites in meteorites reflect equilibration under reducing conditions based on the intensity of 715 nm band, it is estimated that the hibonite in the Blue Angel inclusion indicates an oxygen fugacity four to five orders of magnitude more oxidizing than that expected in the early solar nebula. This may be due to formation in an anomalously oxidizing region of the nebula or to oxidation during cooling or later alteration. The orange hibonites in Allende reflect oxygen fugacities approximately ten or more orders of magnitude more oxidizing than the expected primitive nebula; this color probably indicates alteration of initially more reduced (blue?) hibonites. The colorless hibonite in the HAL inclusion reflects highly oxidizing conditions and/or its low Ti content.

Ihinger, P. D.; Stolper, E.

1986-05-01

7

Iron-Titanium Oxides and Oxygen Fugacities in Volcanic Rocks  

Microsoft Academic Search

It is shown that in silicate liquids the ferric-ferrous equilibrium is controlled by temperature, oxygen fugacity, and the composition of the liquid, particularly its alkali content. Thus, if the iron-titanium oxide minerals that precipitate from a silicate liquid reflect the ferricferrous equilibrium, the oxygen geobarometer of Buddington and Lindsley will have to be calibrated, especially for such volcanics as phonolites

I. S. E. Carmichael; J. Nicholls

1967-01-01

8

Iron Isotope Fractionation and the Oxygen Fugacity of the Mantle  

NASA Astrophysics Data System (ADS)

The oxygen fugacity of the mantle exerts a fundamental influence on mantle melting, volatile speciation, and the development of the atmosphere. However, its evolution through time is poorly understood. Changes in mantle oxidation state should be reflected in the Fe3+/Fe2+ of mantle minerals, and hence in stable iron isotope fractionation. Here it is shown that there are substantial (1.7 per mil) systematic variations in the iron isotope compositions (?57/54Fe) of mantle spinels. Spinel ?57/54Fe values correlate with relative oxygen fugacity, Fe3+/?Fe, and chromium number, and provide a proxy of changes in mantle oxidation state, melting, and volatile recycling.

Williams, Helen M.; McCammon, Catherine A.; Peslier, Anne H.; Halliday, Alex N.; Teutsch, Nadya; Levasseur, Sylvain; Burg, Jean-Pierre

2004-06-01

9

The oxidation state of europium as an indicator of oxygen fugacity. [lunar and terrestrial rocks, achondritic meteorites  

NASA Technical Reports Server (NTRS)

Empirical oxygen barometers based on Eu(2+)/Eu(3+) ratios in plagioclase feldspar and magmatic liquid were developed using Philpott's (1970) approach and the experimental data of Drake (1972). Oxygen fugacities calculated on the basis of Eu(2+)/Eu(3+) ratios for terrestrial basalts cluster tightly around 10 to the negative seventh power. Oxygen fugacities for Apollo 11 and 12 lunar ferrobasalts cluster tightly around 10 to the negative 12.7 power. Calculated oxygen fugacities for achondritic meteorites are lower than for lunar samples by several orders of magnitude.

Drake, M. J.

1975-01-01

10

Iron isotope fractionation and the oxygen fugacity of the mantle.  

PubMed

The oxygen fugacity of the mantle exerts a fundamental influence on mantle melting, volatile speciation, and the development of the atmosphere. However, its evolution through time is poorly understood. Changes in mantle oxidation state should be reflected in the Fe3+/Fe2+ of mantle minerals, and hence in stable iron isotope fractionation. Here it is shown that there are substantial (1.7 per mil) systematic variations in the iron isotope compositions (delta57/54Fe) of mantle spinels. Spinel delta57/54Fe values correlate with relative oxygen fugacity, Fe3+/sigmaFe, and chromium number, and provide a proxy of changes in mantle oxidation state, melting, and volatile recycling. PMID:15192225

Williams, Helen M; McCammon, Catherine A; Peslier, Anne H; Halliday, Alex N; Teutsch, Nadya; Levasseur, Sylvain; Burg, Jean-Pierre

2004-06-11

11

Oxygen fugacity control in piston-cylinder experiments  

NASA Astrophysics Data System (ADS)

The main goal of this study was to develop and test a capsule assembly for use in piston-cylinder experiments where oxygen fugacity could be controlled in the vicinity of the QFM buffer without H2O loss or carbon contamination of the sample material. The assembly consists of an outer Pt-capsule containing a solid buffer (Ni-NiO or Co-CoO) plus H2O and an inner AuPd-capsule, containing the sample, H2O and a Pt-wire. No H2O loss is observed from the sample, even after 48 h, but a slight increase in H2O content is found in longer runs due to oxygen and hydrogen diffusion into the AuPd-capsule. Oxygen fugacity of runs in equilibrium with the Ni-NiO (NNO) and Co-CoO (CoCO) buffers was measured by analyzing Fe dissolved in the Pt-wire and in the AuPd-capsule. The second method gives values that are in good agreement with established buffer values, whereas results from the first method are one half to one log units higher than the established values.

Jakobsson, Sigurdur

2012-09-01

12

Variations in Oxygen Fugacity among Forearc Peridotites from the Tonga Trench  

NASA Astrophysics Data System (ADS)

The Tonga subduction zone is an extension-dominated, non-accreting convergent plate margin in the South Pacific, characterized by rapid slab rollback [1]. It is unusual among subduction zones in that forearc peridotites, thought to be pieces of lithospheric mantle originating from the overriding plate, have been dredged from the trench. These spinel peridotites appear in dredges along almost 1000 km of the trench's length, from near the Samoa hotspot in the north to the Louisville seamounts in the south, and have been dredged from 4-9 km depth. The samples are very depleted, consisting entirely of dunites and harzburgites, with no observed lherzolites. Low modal abundances of orthopyroxene and high spinel Cr# (Cr/(Cr+Al)) also indicate large degrees of melt extraction. While some samples have been variably altered by hydrothermal processes, a large fraction of them are remarkably unaltered, making them ideal targets for geochemical investigation. Oxygen fugacity is an important geochemical control on phase stability, the composition of volatiles, and the position of the mantle solidus, thus rendering it critical to the understanding of mantle processes. Previous studies have suggested that subduction zone processes result in arc magmas with increased oxygen fugacity (fO2) relative to ridge magmas [2], but few direct observations of mantle wedge fO2 are available. In order to investigate the oxygen fugacity of the Tonga peridotites, mineral major element compositions were determined via electron microprobe. Fe3+/?Fe ratios were calculated for the spinel phase, calibrated with spinel standards of known Fe3+/?Fe ratio provided by B.J. Wood to the Smithsonian following the procedure of Lopez et al [3]. Oxygen fugacity was calculated according to the olivine-orthopyroxene-spinel oxybarometer method of Wood et al. [4]. Results from five dredges along approximately 600 km of trench showed oxygen fugacity values of 1 log unit above the QFM buffer, compared to the global ridge peridotite average of QFM -1. A sixth dredge from the middle of the sample area showed significantly more reduced values of QFM -2. Interactions with oxidized fluids in the mantle wedge have been proposed as a mechanism for oxidizing forearc peridotites relative to ridge peridotites. The additional observation of small length-scale variations in fO2 suggests that the interaction of fluids with the mantle is not a pervasive process, leading to the observed heterogeneity in oxygen fugacity values. [1] Wright et al., Marine Geophys Res (2000); [2] Kelley et al., Science (2009); [3] Lopez et al., EOS Transactions, T51D-2632 (2012); [4] Wood et al., Science (1990).

Birner, S.; Warren, J. M.; Cottrell, E.; Lopez, O. G.; Davis, F. A.; Falloon, T.

2013-12-01

13

The Relationship Between Clinopyroxene Fe3+ Content and Oxygen Fugacity  

NASA Technical Reports Server (NTRS)

The intrinsic oxygen fugacity (fO2) imposed on a magma has the ability to influence the crystallization sequence of the melt, as well as the composition of the resulting minerals. fO2 is an easily controlled parameter in the lab, either through gas-mixing equilibria or with a solid-state buffer assemblage. In nature, the fO2 of a closed system is imposed on the system internally through multivalent equilibria involving the phenocryst-melt assemblage. This results in a characteristic oxidation state. The physical parameter used to quantify oxidation state is oxygen fugacity. Iron is the only major rock forming element in basaltic melts to exist in multiple valence states and, therefore, it is commonly used to assess fO2. Traditional methods to quantify fO2 utilize the ferric content of glasses or coexisting Fe-Ti oxides. However, many rocks, such as the Martian meteorites, do not contain the necessary phases or have oxides which have suffered reequilibration, thereby rendering them unmeasureable by current techniques. For these rocks, new methods, utilizing other phases are needed. Mafic minerals have Fe(3+)/SigmaFe ratios that are a function of two factors: 1) crystal chemistry and 2) their intrinsic fO2 during crystallization. Olivine and orthopyroxene, for example, have steric constraints on the extent to which Fe(3+) can be incorporated in their structures, and may not record changes in magmatic fO2 in a way that can easily be measured. The chemistry of clinopyroxene, however, allows for extensive incorporation of Fe(3+) in its crystal structure, making it a potentially useful oxybarometer. To date, there have been few, if any, systematic experimental studies of the variation of the Fe(3+)/SigmaFe ratio as a function of fO2 in clinopyroxene. This study seeks to address this lack of data.

McCanta, M. C.; Rutherford, M. J.; Dyar, M. J.; Delaney, J. S.

2004-01-01

14

Oxygen buffering of Kilauea volcanic gases and the oxygen fugacity of Kilauea basalt  

USGS Publications Warehouse

Volcanic gases collected during episode 1 of the Puu Oo eruption along the east rift zone of Kilauea Volcano, Hawaii, have uniform C-O-H-S-Cl-F compositions that are sharply depleted in CO2. The CO2-poor gases are typical of Type II volcanic gases (gerlach and Graeber, 1985) and were emitted from evolved magma stored for a prolonged period of time in the east rift zone after releasing CO2-rich gases during an earlier period of temporary residence in the summit magma chamber. The samples are remarkably free of contamination by atmospheric gases and meteoric water. Thermodynamic evaluation of the analytical data shows that the episode 1 gases have equilibrium compositions appropriate for temperatures between 935 and 1032??C. Open- and closed-system equilibrium models of species distributions for the episode 1 gases show unequivocally that coexisting lavas buffered the gas oxygen fugacities during cooling. These models indicate that the fO2 buffering process occurs by transfer of oxygen from the major species in the gas phase (H2O, CO2, SO2) to the lava during cooling and that the transfer of oxygen also controls the fugacities of several minor and trace species (H2, CO, H2S, S2, Cl2, F2), in addition to O2 during cooling. Gas/lava exchanges of other components are apparently insignificant and exert little influence, compared to oxygen exchange, during cooling. Oxygen transfer during cooling is variable, presumably reflecting short-term fluctuations in gas flow rates. Higher flow rates restrict the time available for gas/lava oxygen transfer and result in gases with higher equilibrium temperatures. Lower flow rates favor fO2-constrained equilibration by oxygen transfer down to lower temperatures. Thus, the chemical equilibrium preserved in these gases is a heterogeneous equilibrium constrained by oxygen fugacity, and the equilibrium temperatures implied by the compositions of the gases reflect the temperatures at which gas/lava oxygen exchange ceased. This conclusion challenges the common assumption that volcanic gases are released from lava in a state of chemical equilibrium and then continue equilibrating homogeneously with falling temperature until reaction rates are unable to keep pace with cooling. No evidence is found, moreover, that certain gas species are kinetically more responsive and able to equilibrate down to lower temperatures than those of the last gas/lava oxygen exchange. Homogeneous reaction rates in the gas phase are apparently slow compared to the time it took for the gases to move from the last site of gas/lava equilibration to the site of collection. An earlier set of data for higher temperature CO2-rich Type I volcanic gases, which come from sustained summit lava lake eruptions supplied by magma that experienced substantially shorter periods of crustal storage, shows fO2 buffering by oxygen transfer up to 1185??C. Oxygen fugacity measurements in drill holes into ponded lava flows suggest that buffering by oxygen transfer may control the fO2 of residual gases down to several hundred degrees below the solidus in the early stages of cooling. Although the details of the fO2 buffering mechanisms for oxygen transfer are unknown, the fact that fO2 buffering is effective from molten to subsolidus conditions suggests that the reaction mechanisms must change with cooling as the reactants change from predominantly melt, to melt plus crystals, to glass plus crystals. Mass balance calculations suggest that redox reactions between the gas and ferrous/ferric iron in the lava are plausible mechanisms for the oxygen transfer and that the fO2 of the gases is buffered by sliding ferrous/ferric equilibria in the erupting lavas. Contrary to expectations based on models predicting the oxidation of basalt by H2 and CO escape during crustal storage, CO2-rich Type I gases and CO2-poor Type II gases have identical oxygen fugacities despite greatly different crustal storage and degassing histories. Volcanic gas data give a tightly co

Gerlach, T. M.

1993-01-01

15

Oxygen fugacity of basaltic magmas and the role of gas-forming elements  

NASA Technical Reports Server (NTRS)

It is suggested that major variations in the relative oxygen fugacity of a basaltic magma are caused primarily by gas-forming elements, especially carbon and hydrogen. According to this theory, carbon, present in the source region of a basaltic magma, reduces the host magma during ascent, as isothermally carbon becomes more reducing with decreasing pressure. For an anhydrous magma such as lunar basalts, this reduction continues through the extrusive phase and the relative oxygen fugacity decreases rapidly until buffered by the precipitation of a metallic phase. For hydrous magmas such as terrestrial basalts, reduction by carbon is eventually superceded by oxidation due to loss of H2 generated by the reaction of C with H2O and by thermal dissociation of H2O. The relative oxygen fugacity of a hydrous magma initially decreases as a magma ascends from the source region and then increases until magnetite crystallization curbs the rising trend of the relative oxygen fugacity.

Sato, M.

1978-01-01

16

The effect of oxygen fugacity on the solubility of carbon-oxygen fluids in basaltic melt  

NASA Technical Reports Server (NTRS)

The solubility of CO2-CO fluids in a midocean ridge basalt have been measured at 1200 C, 500-1500 bar, and oxygen fugacities between NNO and NNO-4. In agreement with results of previous studies, the results reported here imply that, at least at low pressures, CO2 dissolves in basaltic melt only in the form of carbonate groups. The dissolution reaction is heterogeneous, with CO2 molecules in the fluid reacting directly with reactive oxygens in the melt to produce CO3(2-). CO, on the other hand, is insoluble, dissolving neither as carbon, molecular CO, nor CO3(2-). It is shown that, for a given pressure and temperature, the concentration of dissolved carbon-bearing species in basaltic melt in equilibrium with a carbon-oxygen fluid is proportional to the mole fraction of CO2 in the fluid, which is a function of fO2. At low pressures CO2 solubility is a linear function of CO2 fugacity at constant temperatures.

Pawley, Alison R.; Holloway, John R.; Mcmillan, Paul F.

1992-01-01

17

CO2-CO fluid inclusions in a composite peridotite xenolith: implications for upper mantle oxygen fugacity  

NASA Astrophysics Data System (ADS)

Fluid inclusions occur in a composite xenolith from the Lunar Crater Volcanic Field, Nevada, U.S.A. The xenolith is an amphibole-bearing wehrlite that is cut by an andesine-amphibole vein. The compositions of individual fluid inclusions in both portions of the xenolith have been determined using microthermometry and micro Laser-Raman spectroscopy. Fluids in the host wehrlite are nearly pure CO2 (>99 mol%) whereas those in the vein contain from 8.5 to 12.0 mol % CO in CO2. Chemical modelling shows that the composition of the vein fluids at T room is representative of the composition at the high P, T conditions of trapping. Graphite has not been observed by optical microscopy in any of the fluid inclusions. Graphite is probably absent (although stable at T<800° C) most probably because of the kinetically unfavorable CO decomposition reaction and rapid quenching. By combining the measured fluid compositions with fluid P-V-T data and the chemical equilibrium CO2?CO +1/2 O2, we have calculated the oxygen fugacity of the fluid inclusions at 1200° C: log f_{O_2 }?8.6 (vein) and -6 (host). If the f_{O_2 } of the fluid in the vein represents that in equilibrium with the magma that crystallized to produce the vein, then the f_{O_2 } of the basalt magma is near QFM at 1200° C and 10.3 kbar. This is similar to values reported for extrusive basaltic lavas. If the much lower intrinsic oxygen fugacity-values for divines and spinels from alkali basalt nodules are representative of upper mantle conditions, then oxidation of basaltic magmas must occur in the upper mantle prior to ascent to the surface. Implications for the origin of CO2-rich fluids and carbon isotope geochemistry are also discussed.

Bergman, Steven C.; Dubessy, Jean

1984-01-01

18

Influence of oxygen fugacity on the electrical conductivity of hydrous olivine: Implications for the mechanism of conduction  

NASA Astrophysics Data System (ADS)

Various mechanisms of hydrogen-assisted electrical conductivity predict different dependence of conductivity on oxygen fugacity. If a majority of hydrogen-related defects (i.e., two protons at M-site) carries the electrical current, then the conductivity will be independent of oxygen fugacity, whereas if a minority defect such as free proton carries the electrical conductivity, then the electrical conductivity will decrease with oxygen fugacity. We have determined the dependence of hydrogen-assisted electrical conductivity on oxygen fugacity in hydrous olivine. We found that the hydrogen-assisted electrical conductivity in olivine decreases with oxygen fugacity. This result supports a model where hydrogen-related defect with minor concentration (e.g., free proton or one hydrogen at M-site) carries most of the electric charge.

Dai, Lidong; Karato, Shun-ichiro

2014-07-01

19

Mössbauer Spectroscopy and Oxygen Fugacity of Amphibole-bearing R-Chondrite LAP04840  

NASA Astrophysics Data System (ADS)

Mössbauer spectra of olivine, amphibole, mica, and whole rock from amphibole-bearing R-chondrite LAP 04840 are presented. All three minerals and the whole rock are rich in ferric iron, suggesting an oxygen fugacity of QFM+0.75 (+/-~0.75) log units.

Dyar, M. D.; McCanta, M. C.; Treiman, A. H.; Sklute, E. C.; Marchand, G. J.

2007-03-01

20

Oxygen fugacity control in piston-cylinder experiments: a re-evaluation  

NASA Astrophysics Data System (ADS)

Jakobsson (Contrib Miner Petrol 164(3):397-407, 2012) investigated a double capsule assembly for use in piston-cylinder experiments that would allow hydrous, high-temperature, and high-pressure experiments to be conducted under controlled oxygen fugacity conditions. Using a platinum outer capsule containing a metal oxide oxygen buffer (Ni-NiO or Co-CoO) and H2O, with an inner gold-palladium capsule containing hydrous melt, this study was able to compare the oxygen fugacity imposed by the outer capsule oxygen buffer with an oxygen fugacity estimated by the AuPdFe ternary system calibrated by Barr and Grove (Contrib Miner Petrol 160(5):631-643, 2010). H2O loss or gain, as well as iron loss to the capsule walls and carbon contamination, is often observed in piston-cylinder experiments and often go unexplained. Only a few have attempted to actually quantify various aspects of these changes (Brooker et al. in Am Miner 83(9-10):985-994, 1998; Truckenbrodt and Johannes in Am Miner 84:1333-1335, 1999). It was one of the goals of Jakobsson (Contrib Miner Petrol 164(3):397-407, 2012) to address these issues by using and testing the AuPdFe solution model of Barr and Grove (Contrib Miner Petrol 160(5):631-643, 2010), as well as to constrain the oxygen fugacity of the inner capsule. The oxygen fugacities of the analyzed melts were assumed to be equal to those of the solid Ni-NiO and Co-CoO buffers, which is incorrect since the melts are all undersaturated in H2O and the oxygen fugacities should therefore be lower than that of the buffer by 2 log.

Jakobsson, Sigurdur; Blundy, Jon; Moore, Gordon

2014-06-01

21

The speciation of carbon in the Earth's mantle as a function of oxygen fugacity  

NASA Astrophysics Data System (ADS)

The residence time of carbon in the mantle depends crucially on the conditions under which it is stable within melts or fluids, compared with conditions under which it forms solid phases. At a given pressure and temperature the stability of carbonate- bearing minerals and melts (carbonatites and kimberlites) relative to graphite/diamond depends on oxygen fugacity. In this study, the oxygen fugacity buffered by equilibria involving both elemental carbon (graphite or diamond) and carbonate (minerals or melts) were determined in a simplified Fe-Ca-Mg-Si-O-C model peridotite composition at pressures between 2.5 and 25 GPa and temperatures at and above the carbonated peridotite solidus (1100-1600°C). Oxygen fugacities were measured using iridium-iron alloy as a sliding redox sensor. Above the carbonate peridotite solidus the silicate component of the melt increases with increasing temperature. The results show that this dilution of the carbonate melt with increasing temperature drives the equilibrium oxygen fugacity down compared to the extrapolation of carbon/carbonate equilibrium from previous studies. In addition we have performed experiments in the Fe-Ca-Mg-Al-Si-O-C system to determine the Fe3+ content of garnet at an oxygen fugacity buffered by the carbon-carbonate equilibria in a peridotite assemblage. The ferric iron contents of the garnet in the run products were determined by 57Moessbauer spectroscopy. The results from these experiments allow the redox conditions of carbon and carbonate stability to be compared directly to the expected Fe3+/Fetot ratios of mantle rocks. Further experiments were performed at pressures compatible with the Earth's mid lower mantle (approximately 50 GPa) and 1600-1700 °C using sintered diamond anvils. Such runs allowed us to estimate the likely redox conditions occurring in the lower mantle at which elemental carbon (diamond) might be equilibrated with carbonate, ferropericlase and a metal phase. Our results imply that: (1) in up-welling mantle beneath mid-ocean ridges, the relative oxygen fugacity of peridotitic rocks will increase on decompression. Diamond and then graphite are the dominant C-bearing phases at depth, but become oxidized by ferric Fe in garnet as a result of decompression. Only once graphite is oxidized, which will occur at relatively shallow depths, can small degree carbonate-rich melts form; (2) measurements of Fe3+/?Fe ratios of garnets in equilibrium with graphite and carbonate are inconsistent with extrapolations of previously published oxythermobarometers; (3) the effect of pressure on the carbonate/carbon buffer indicates that the diamond stability field may not persist deep into the lower mantle, with carbonates being the stable host for carbon, probably in equilibrium with Fe-Ni carbide.

Stagno, Vincenzo; Frost, Daniel J.; McCammon, Catherine

2010-05-01

22

Oxygen diffusion in olivine: Effect of oxygen fugacity and implications for creep  

SciTech Connect

Oxygen self-diffusion experiments on single crystals of San Carlosolivine (/similar to/Fo/sub 92/) at 1200/degree/less than or equal to/ital T/less than or equal to1400 /degree/C, oxygen fugacities(/ital f//sub O2/) along the Ni-NiO and Fe-FeO buffers, and silica activityat the olivine-orthopyroxene buffer yielded results that follow therelationship /ital D/=2.6/times/10/sup /minus/10//ital f/ /sub O2//sup 0.21+-0.03/ exp (/minus/266+-11)(kJ mol/sup /minus/1///ital RT/), where/ital D/ is the diffusion coefficient in m/sup 2/ s/sup /minus/1/ and /ital f//sub O2/ is givenin pascals. The activation energy compares reasonably well with results forpure forsterite. The positive dependence of /ital f//sub O/sub 2// implies that theoxygen defect responsible for diffusion is an interstitial rather than a morestericaly reasonable oxygen vacancy. Diffusion of oxygen in other close-packedoxides has also shown a positive dependence on /ital f//sub O2/. The rate ofcreep of single-crystal olivine at fixed orthopyroxene activity also showsa positive /ital f//sub O2/ dependence. If oxygen interstitials should be shown tobe unimportant in oxygen diffusion in oxides, then coupled mechanisms such ascountervacancy diffusion must be appealed to in order to explain the positive/ital f//sub O2/ dependence. Such processes are rate-limited by the diffusion ofmetal vacancies which also display a positive /ital f//sub O2/ dependence inolivine. Compared with data for silicon diffusion in forsterite, our dataindicate that oxygen is not the slowest diffusing species in olivine.

Ryerson, F. J.; Durham, W. B.; Cherniak, D. J.; Lanford, W. A.

1989-04-10

23

The Aurora volcanic field, California-Nevada: oxygen fugacity constraints on the development of andesitic magma  

NASA Astrophysics Data System (ADS)

The Aurora volcanic field, located along the northeastern margin of Mono Lake in the Western Great Basin, has erupted a diverse suite of high-K and shoshonitic lava types, with 48 to 76 wt% SiO2, over the last 3.6 million years. There is no correlation between the age and composition of the lavas. Three-quarters of the volcanic field consists of evolved (<4 wt% MgO) basaltic andesite and andesite lava cones and flows, the majority of which contain sparse, euhedral phenocrysts that are normally zoned; there is no evidence of mixed, hybrid magmas. The average eruption rate over this time period was ˜200 m3/km2/year, which is typical of continental arcs and an order of magnitude lower than that for the slow-spreading mid-Atlantic ridge. All of the Aurora lavas display a trace-element signature common to subduction-related magmas, as exemplified by Ba/Nb ratios between 52 and 151. Pre-eruptive water contents ranged from 1.5 wt% in plagioclase-rich two-pyroxene andesites to ˜6 wt% in a single hornblende lamprophyre and several biotite-hornblende andesites. Calculated oxygen fugacities fall within 0.4 and +2.4 log units of the Ni-NiO buffer. The Aurora potassic suite follows a classic, calc-alkaline trend in a plot of FeOT/MgO vs SiO2 and displays linear decreasing trends in FeOT and TiO2 with SiO2 content, suggesting a prominent role for Fe-Ti oxides during differentiation. However, development of the calc-alkaline trend through fractional crystallization of titanomagnetite would have caused the residual liquid to become so depleted in ferric iron that its oxygen fugacity would have fallen several log units below that of the Ni-NiO buffer. Nor can fractionation of hornblende be invoked, since it has the same effect as titanomagnetite in depleting the residual liquid in ferric iron, together with a thermal stability limit that is lower than the eruption temperatures of several andesites (˜1040 1080°C; derived from two-pyroxene thermometry). Unless some progressive oxidation process occurs, fractionation of titanomagnetite or hornblende cannot explain a calc-alkaline trend in which all erupted lavas have oxygen fugacites ? the Ni-NiO buffer. In contrast to fractional crystallization, closed-system equilibrium crystallization will produce residual liquids with an oxygen fugacity that is similar to that of the initial melt. However, the eruption of nearly aphryic lavas argues against tapping from a magma chamber during equilibrium crystallization, a process that requires crystals to remain in contact with the liquid. A preferred model involves the accumulation of basaltic magmas at the mantle-crust interface, which solidify and are later remelted during repeated intrusion of basalt. As an end-member case, closed-system equilibrium crystallization of a basalt, followed by equilibrium partial melting of the gabbro will produce a calc-alkaline evolved liquid (namely, high SiO2 and low FeOT/MgO) with a relative f O 2 (corrected for the effect of changing temperature) that is similar to that of the initial basalt. Differentiation of the Aurora magmas by repeated partial melting of previous underplates in the lower crust rather than by crystal fractionation in large, stable magma chambers is consistent with the low eruption rate at the Aurora volcanic field.

Lange, R. A.; Carmichael, Ian S. E.

1996-10-01

24

Iron isotope fractionation in mantle minerals and the effects of partial melting and oxygen fugacity  

NASA Astrophysics Data System (ADS)

The oxygen fugacity of the mantle exerts a fundamental influence on mantle melting, volatile speciation and the development of the Earth's atmosphere. As changes in mantle oxidation state are generally reflected in the ferric iron contents of mantle minerals, the iron isotope signatures of mantle rocks should provide information about spatial and secular changes in mantle oxidation state. However, the exact nature of the processes governing iron isotope fractionation in igneous rocks remains poorly understood, limiting the use of iron isotopes as a proxy. We have investigated the relationships between Fe isotope fractionation, oxygen fugacity, melting and metasomatism with a combined MC-ICPMS Fe isotope and Mössbauer spectroscopy study of spinels and silicate minerals from mantle xenoliths and massif samples originating from different tectonic settings. There exist large variations in the iron isotope compositions of olivines, pyroxenes and spinels. Clear correlations exist between the ? 57/54Fe values of coexisting minerals, implying equilibrium isotope fractionation. Spinel ? 57/54Fe values correlate negatively with relative oxygen fugacity, spinel Fe3+/? Fe and Cr number; clinopyroxene ? 57/54Fe values correlate negatively with clinopyroxene MgO content and Cr number. There do not appear to be strong relationships between the ? 57/54Fe values of the minerals and chemical or isotopic indices of metasomatism. Taken together these observations imply that variations in the iron isotopic compositions of mantle rocks and minerals are largely a function of melting coupled with changes in mantle oxidation state.

Williams, H. M.; McCammon, C.; Peslier, A. H.; Halliday, A. N.; Levasseur, S.; Teutsch, N.; Burg, J.

2004-12-01

25

Hydration of mantle olivine under variable water and oxygen fugacity conditions  

NASA Astrophysics Data System (ADS)

The incorporation of H into olivine is influenced by a significant number of thermodynamic variables (pressure, temperature, oxygen fugacity, etc.). Given the strong influence that H has on the solidus temperature and rheological behavior of mantle peridotite, it is necessary to determine its solubility in olivine over the range of conditions found in the upper mantle. This study presents results from hydration experiments carried out to determine the effects of pressure, temperature, and the fugacities of H2O and O2 on H solubility in San Carlos olivine at upper mantle conditions. Experiments were carried out at 1-2 GPa and 1,200 °C using a piston-cylinder device. The fugacity of O2 was controlled at the Fe0-FeO, FeO-Fe3O4, or Ni0-NiO buffer. Variable duration experiments indicate that equilibration is achieved within 6 h. Hydrogen contents of the experimental products were measured by secondary ion mass spectrometry, and relative changes to the point defect populations were investigated using Fourier transform infrared spectroscopy. Results from our experiments demonstrate that H solubility in San Carlos olivine is sensitive to pressure, the activity of SiO2, and the fugacities of H2O and O2. Of these variables, the fugacity of H2O has the strongest influence. The solubility of H in olivine increases with increasing SiO2 activity, indicating incorporation into vacancies on octahedral lattice sites. The forsterite content of the olivine has no discernible effect on H solubility between 88.17 and 91.41, and there is no correlation between the concentrations of Ti and H. Further, in all but one of our experimentally hydrated olivines, the concentration of Ti is too low for H to be incorporated dominantly as a Ti-clinohumite-like defect. Our experimentally hydrated olivines are characterized by strong infrared absorption peaks at wavenumbers of 3,330, 3,356, 3,525, and 3,572 cm-1. The heights of peaks at 3,330 and 3,356 cm-1 correlate positively with O2 fugacity, while those at 3,525 and 3,572 cm-1 correlate with H2O fugacity.

Gaetani, Glenn A.; O'Leary, Julie A.; Koga, Kenneth T.; Hauri, Erik H.; Rose-Koga, Estelle F.; Monteleone, Brian D.

2014-02-01

26

The stability of magnesite in the transition zone and the lower mantle as function of oxygen fugacity  

Microsoft Academic Search

Oxygen fugacity required for magnesite being stable at high pressure conditionsFerric iron content of mantle minerals coexisting with diamond and magnesiteRedox reactions involving ferric iron bearing minerals and diamond\\/magnesite

V. Stagno; Y. Tange; N. Miyajima; C. A. McCammon; T. Irifune; D. J. Frost

2011-01-01

27

Tracing Oxygen Fugacity in Asteroids and Meteorites Through Olivine Composition  

NASA Technical Reports Server (NTRS)

Olivine absorptions are known to dominate telescopic spectra of several asteroids. Among the meteorite collection, three groups (excluding Martian meteorites), the pallasites, brachinites, and R group chondrites are plausible analogs to olivine-rich asteroids in that they are dominated by olivine. These meteorite groups have distinct petrologic origins. The primitive achondrite brachinites (which include both depleted and undeleted subgroups) are products of relatively minor differentiation and evolved in oxidizing environments. R chondrites are also thought to have formed in high oxygen states, but are closely related to ordinary chondrites (yet with their own distinct compositions and oxygen isotopic signatures). In contrast, pallasites, widely thought to be mantle components from much more evolved bodies, formed in more reducing environments. Petrologic indicators that are identifiable in spectral data must be used in order to infer the petrologic history of asteroids from surveys of their actual population. As discussed below, olivine composition (e.g. Fa#) can provide key constraints in exploring the origin and significance of olivine dominated asteroids.

Sunshine, J. M.; Bus, S. J.; Burbine, T. H.; McCoy, T. J.

2005-01-01

28

Oxygen buffering of Kilauea volcanic gases and the oxygen fugacity of Kilauea basalt  

SciTech Connect

Volcanic gases collected during episode 1 of the Puu Oo eruption along the east rift zone of Kilauea Volcano, Hawaii, have uniform C-O-H-S-Cl-F compositions that are sharply depleted in CO[sub 2]. The CO[sub 2]-poor gases are typical of Type II volcanic gases (GERLACH and GRAEBER, 1985) and were emitted from evolved magma stored for a prolonged period of time in the east rift zone after releasing CO[sub 2]-rich gases during an earlier period of temporary residence in the summit magma chamber. The samples are remarkably free of contamination by atmospheric gases and meteoric water. Thermodynamic evaluation of the analytical data shows that the episode 1 gases have equilibrium compositions appropriate for temperatures between 935 and 1032[degrees]C. Open- and closed-system equilibrium models of species distributions for the episode 1 gases show unequivocally that coexisting lavas buffered the gas oxygen fugacities during cooling. These models indicate that the F[sub o[sub 2

Gerlach, T.M. (Geological Survey, Vancouver, WA (United States))

1993-02-01

29

Electrochemical manipulation of apparent oxygen fugacity in a piston cylinder apparatus  

NASA Astrophysics Data System (ADS)

Phase stability of mineral assemblages and their physical properties, especially transport properties, are influenced by oxygen fugacity. Redox effects in earth and planetary systems at high pressure include setting of ferric/ferrous iron ratios [controlling the electrical conductivity of crustal and mantle materials] and possible chemical reactions at the Earth's core-mantle boundary. Experimental controls of oxygen fugacity in high-pressure devices have been limited to discrete electrochemical potentials set by buffers such as C-CO, Ni-NiO, and QFM. By contrast, an electric field applied across a silicate sample inside a piston cylinder apparatus establishes a smoothly-varying electrochemical gradient that can be quantified and tied to the oxygen fugacity scale through synchrotron microXANES of polyvalent V and Fe within the silicate. Fugacity gradient samples were synthesized in a modified Boyd-England piston-cylinder configuration. Platinum electrodes were placed at both ends of a 2-mm cylinder of basaltic composition silicate glass containing ~5% Fe and ~2% V. The sample assembly was surrounded by MgO ceramic, sheathed within a Mo faraday sleeve to insulate the sample from the AC field of the heater, and placed within a 0.5 inch diameter pressure vessel. The assembly was sintered at 800°C for 72 hours to eliminate porosity in the MgO capsule, and then heated to 1400°C for 23 hrs at 10 kbar. At high temperature, a 1V potential difference was applied across the electrodes via an external power supply. The sample was then quenched, potted in epoxy, and polished to a thickness of ~30 ?m, and analyzed via optical and scanning electron microscopy. Vanadium, with oxidation states of 0 and +II to +V, was used as a chemical marker to evaluate the absolute value of the fO2 conditions across the silicate sample. Synchrotron-based microXANES techniques at GSECARS at the Advanced Photon Source in Argonne, IL were used to measure the pre-edge peak height at the vanadium absorption edge, as a function of distance between the anodic and cathodic electrodes of the recovered piston cylinder experiments. The intensity of the pre-edge peaks varied greatly across the sample, from ~5% near the cathode end to ~70% of the absorption edge level adjacent to the anode. The systematic increase in the pre-edge peak was calibrated to the vanadium valence state and oxygen fugacity by comparison with vanadium microXANES spectra obtained for synthetic komatiite charges (known fO2; Canil 1997) and basaltic glasses (known fO2 and oxidation state; Schreiber 1987). The average vanadium oxidation state varies monotonically from +2.5 at the cathode (reducing) electrode to +4.5 at the anode (oxidizing) electrode, corresponding to an oxygen fugacity varying from -11 to -5 (log units) from cathode to anode. The sample appears reddish at the anode (oxidizing) end and grayer at the cathode (reducing) end, due in part to reducing the iron ferric/ferrous ratio from anode to cathode, in harmony with the V results. In summary, the application of an electric field creates an oxygen fugacity continuum in high-pressure apparati.

Kavner, A.; Newville, M.; Sutton, S.; Walker, D.; Wheeler, K.

2002-12-01

30

Using vanadium in spinel as a sensor of oxygen fugacity in meteorites: Applications to Mars, Vesta, and other asteroids.  

SciTech Connect

Some meteorites do not contain mineral assemblages required to apply traditional oxy-barometers. Here we introduce a technique using vanadium X-ray absorption features in spinels to characterize the oxygen fugacity of meteoritic dunites, pyroxenites, and chondrites. Igneous and metamorphic rocks commonly contain a mineral assemblage that allows oxygen fugacity to be calculated or constrained such as FeTi oxides, olivine-opx-spinel, or some other oxybarometer. Some rocks, however, contain a limited mineral assemblage and do not provide constraints on fO{sub 2} using mineral equilibria. Good examples of the latter are orthopyroxenites or dunites, such as diogenites, ALH 84001, chassignites, or brachinites. In fact it is no surprise that the fO{sub 2} of many of these samples is not well known, other than being 'reduced' and below the metal saturation value. In order to bridge this gap in our understanding, we have initiated a study of V in chromites in natural meteorite samples. Because the V pre-edge peak intensity and energy in chromites varies with fO{sub 2}, and this has been calibrated over a large fO{sub 2} range, we can apply this relation to rocks for which we otherwise have no fO{sub 2} constraints.

Righter, K.; Sutton, S.; Danielson, L.; Pando, K.; Le, L.; Newville, M. (Jacobs Engineering); (NASA JSC); (Hamilton Sundstrand); (UC)

2009-03-23

31

A system using solid ceramic oxygen electrolyte cells to measure oxygen fugacities in gas-mixing systems  

NASA Technical Reports Server (NTRS)

Details are given for the construction and operation of a 101.3 kN/sq m (1 atmosphere) redox control system. A solid ceramic oxygen electrolyte cell is used to monitor the oxygen fugacity in the furnace. The system consists of a vertical quench, gas mixing furnace with heads designed for mounting the electrolyte cell and with facilities for inserting and removing the samples. The system also contains the high input impedance electronics necessary for measurements, a simplified version of a gas mixing apparatus, and devices for experiments under controlled rates of change relative to temperature and redox state. The calibration and maintenance of the system are discussed.

Williams, R. J.; Mullins, O.

1976-01-01

32

Sulfur Speciation and Oxygen Fugacity in Primitive Magmas From the Trans-Mexican Volcanic Belt  

NASA Astrophysics Data System (ADS)

Sulfur dissolves in silicate melts in both reduced (S-2) and oxidized (S+6) forms, and the ratio of species depends on the oxygen fugacity of the melt. The more oxidized the magma, the more sulfur is disolved as sulfate and the higher the overall S solubility (e.g., Luhr, 1990). We have measured the speciation of S in olivine- hosted melt inclusions from 11 mafic cinder cones and 1 maar in the Trans-Mexican Volcanic Belt using the S K? wavelength shift method (Carroll and Rutherford, 1988). Four of the cinder cones are from the Colima Graben and are high-Mg silica-undersaturated potassic rocks. The other cinder cones are from the Michoacan- Guanajuato Volcanic Field (MGVF) and include calc-alkaline high-Mg basalts and basaltic andesites. The maar, also in the MGVF, erupted alkali basalt. A basaltic andesite from the Colima Graben was also analyzed due to its transitional chemical composition between the potassic magmas and the MGVF calc-alkaline magmas. For the calc-alkaline melt inclusions, S+6 accounts for 65-90% of total dissolved S. Similarly, the potassic and basaltic andesite melt inclusions have 60-90% and 78-94% of total S as S+6 respectively. In contrast the alkali basalt melt inclusions have lower values, with 50-60% of total S dissolved as S+6. Some cinder cones exhibit nearly the entire range of melt S speciation whereas others have restricted ranges, but there does not appear to be a correlation between melt degassing (based on H2O contents of the melt inclusions) and either oxygen fugacity or S speciation. Based on the average value of melt inclusions from each cone and the relationship of S speciation to oxygen fugacity (Wallace and Carmichael, 1994), the calc-alkaline cinder cones, including the basaltic andesite, have oxygen fugacity values of NNO+0.9 to +1.3. The potassic cinder cones have similar values of NNO+0.9 to +1.3. The alkali basalt averages NNO+0.5. The values have 1 standard deviation uncertainties of ±0.2 log units for the calc-alkaline basalts, ±0.4 for the potassic cones, ±0.5 for the basaltic andesite and ±0.08 for the alkali basalt, which emphasizes the distinction of the alkali basalt with respect to the other magma types. The potassic and calc-alkaline magmas appear to have similar oxygen fugacities that are distinctly higher than the alkali basalt. This distinction cannot be explained by compositional differences but appears to be related to the mantle source of the magmas and the presence or absence of a subduction derived H2O-rich component.

Vigouroux, N.; Wallace, P. J.; Johnson, E. R.

2007-12-01

33

SNC Oxygen Fugacity Recorded in Pyroxenes and its Implications for the Oxidation State of the Martian Interior: An Experimental and Analytical Study  

NASA Technical Reports Server (NTRS)

Knowledge of the oxidation state of a magma is critical as it is one of the parameters which controls the nature and composition of the resulting crystals. In terrestrial magmatic systems, oxygen fugacity (fo2) is known to vary by over nine orders of magnitude. With variations of this magnitude, understanding the compositional differences, phase changes, and crystallization sequence variations, caused by the magma fo2, is essential in deciphering the origin of all igneous rocks. Magmatic oxidation state is of great importance in that it reflects the degree of oxidation of the source region and can provide insight into magmatic processes, such as metasomatism, degassing, and assimilation, which may have changed them. Carmichael [1991] argues that most magmas are unlikely to have their redox states altered from those of their source region. This assumption allows for estimation of the oxidation state of planetary interiors. Conversely, it is known that the fo2 of the magma can be affected by other processes, which occur outside of the source region and therefore, the oxidation state may record those too. Processes which could overprint source region fugacities include melt dehydrogenation or other volatile loss, water or melt infiltration, or assimilation of oxidized or reduced wallrock. Understanding which of these processes is responsible for the redox state of a magma can provide crucial information regarding igneous processes and other forces active in the region. The composition of the SNC basalts and their widely varying proposed oxidation states raise some interesting questions. Do the SNC meteorites have an oxidized or reduced signature? What was the oxygen fugacity of the SNC source region at the time of melt generation? Is the fugacity calculated for the various SNC samples the fugacity of the magma source region or was it overprinted by later events? Are there different oxidation states in the Martian interior or a single one? This proposal seeks to address all of these questions.

McCanta, M. C.; Rutherford, M. J.

2003-01-01

34

Measured oxygen fugacities of the Angra dos Reis achondrite as a function of temperature  

USGS Publications Warehouse

Measurements of the oxygen fugacity (f{hook}O2) as a function of temperature (T) were made on an interior bulk sample of the cumulate achondrite, Angra dos Reis. Data clustered between the f{hook}O2-T relationship of the iron-wu??stite assemblage and 1.2 log atm units above iron-wu??stite. Interpretation of the data indicates that, throughout most of the cooling history of the meteorite, f{hook}O2 values were defined by equilibria involving iron-bearing species at values close to the f{hook}O2 of the assemblage iron-wu??stite. Measured f{hook}O2 data are compatible with crystallization and cooling at pressures greater than 50 bars. ?? 1977.

Brett, R.; Stephen, Huebner, J.; Sato, M.

1977-01-01

35

Measured oxygen fugacities of the Angra dos Reis achondrite as a function of temperature  

NASA Technical Reports Server (NTRS)

Measurements of the oxygen fugacity, f(O2), as a function of temperature, T, were made on an interior bulk sample of the cumulate achondrite, Angra dos Reis. Data clustered between the f(O2)-T relationship of the iron-wustite assemblage and 1.2 log atm units above iron-wustite. Interpretation of the data indicates that, throughout most of the cooling history of the meteorite, f(O2) values were defined by equilibria involving iron-bearing species at values close to the f(O2) of the assemblage iron-wustite. Measured f(O2) data are compatible with crystallization and cooling at pressures greater than 50 bars.

Brett, R.; Huebner, J. S.; Sato, M.

1977-01-01

36

Oxygen fugacity calibration for (Fe)Au75Pd25 alloys in rock-melting experiments  

NASA Astrophysics Data System (ADS)

Iron loss from silicate melt to gold-palladium capsules is strongly dependent on oxygen fugacity and, once calibrated, may be used as a tool to determine the fO2 of rock-melting experiments, provided that Fe partitioning between the melt and capsule is independent of melt composition. We performed nine rock-melting experiments in a gas-mixing furnace at 1 atm on three compositions of mafic rock: a MORB (9.5 wt% FeOT) and two subduction-related Mexican basaltic andesites (7.5 wt% and 7.0 wt% FeOT). The samples were melted for 48 hours in Au75Pd25 capsules at 1300°C and three different oxygen fugacities spanning -1 to +2 log units relative to the nickel-nickel oxide buffer. Electron microprobe analyses for Fe in both the melt and capsule material yield Fe-partition coefficients that vary linearly with log fO2 and are essentially constant and independent of melt composition at any given fO2. This relationship permits making post-run estimates of the prevailing fO2 in rock-melting experiments at 1300°C from the partitioning of Fe between the melt and capsule for bulk compositions within our calibrated limits. Work is now underway to extend this calibration to lower temperatures. Our plan is to use this calibration to estimate the fO2 in H2O-undersaturated piston-cylinder experiments in which fO2 cannot be buffered by conventional double capsule methods.

Weber, R. M.; Weaver, S.; Johnston, A.; Wallace, P. J.

2009-12-01

37

Ultra-oxidized redox conditions in subduction mélanges? Decoupling between oxygen fugacity and oxygen availability in a metasomatic environment  

NASA Astrophysics Data System (ADS)

The manganese ore of Praborna (Italian Western Alps) is embedded within a metasedimentary sequence belonging to a subduction mélange equilibrated at high-pressure conditions (~2 GPa) during the Alpine orogenesis and record environmental conditions typical for a subducting slab setting. The pervasive veining of the ore and the growth of "pegmatoid" HP minerals suggest an open system with large fluid/rock ratio and a strong interaction with slab-derived fluids. This natural case provides an excellent natural laboratory for the study of the oxygen mobility in subducting oceanic slab mélanges at high-P, fluid-present conditions. The Mn-rich rocks in contact with the underlying sulphide- and magnetite-bearing metabasites, in textural and chemical equilibrium with the veins, contain braunite (Mn2+Mn3+6SiO12) + quartz + pyroxmangite (Mn2+SiO3), and minor hematite, omphacite, the epidote piemontite and spessartine-rich garnet. Similarly to Fe-bearing systems, Mn oxides and silicates can be regarded as natural redox-sensors, capable to monitor a process of fluid infiltration that could fix externally the intensive variable fO2 (or ?O2). Sulphides are absent in these Mn-rich rocks, sulphates (barite, celestine) occurring instead together with As- and Sb oxides and silicates. On the basis of the observed assemblages, new thermodynamic calculations show that these mélange rocks are characterized by unrealistic ultra-oxidized states (?FMQ up to +12) if the chemical potential of oxygen (or the oxygen fugacity) is accounted for. However, if the molar quantity of oxygen in excess with reference to with reference to a system where all iron and manganese are considered to be ferrous, the ore appears only moderately oxidized, and comparable to typical subduction-slab mafic eclogites. Therefore, oxygen can be hardly considered a perfectly mobile component, even in the most favourable conditions. In the Earth's interior redox reactions take place mainly among solid oxides and silicates, as oxygen is a negligible species in the fluid phase, if any. Therefore, the description of the redox state of petrological systems requires the introduction of the conjugate oxygen molar quantity, becoming the oxygen chemical potential a dependent variable. As a consequence, µO2, and therefore fO2, should not be regarded as long-range properties, indicative of the redox state of the entire rock column of a subduction zone, from the dehydrating oceanic crust to the overlying mantle wedge. On a more general basis, the comparison of fO2s retrieved from different bulk compositions and different phase assemblages may lead to apparent redox heterogeneities. On the contrary, the distribution of oxygen is expected to be much more continuous moving from a maximum in the subducted mafic eclogites, formed from the altered oceanic basalts and gabbros, down (upward) to a minimum in the peridotites of the mantle hanging-wall.

Tumiati, Simone; Poli, Stefano; Godard, Gaston; Martin, Silvana; Malaspina, Nadia

2014-05-01

38

Upper mantle oxygen fugacity in ridge and subduction zone settings recorded by spinel peridotite  

NASA Astrophysics Data System (ADS)

Oxygen fugacity (fO2) influences upper mantle phase stability, volatile speciation, and the mantle solidus. We calculate the fO2 recorded by spinel peridotites using microprobe analysis of spinels calibrated with standards provided by [1] and [2]. We do not observe the correlation, reported by [1], between the Cr# and ?Fe3+/?FeMössbauer-microprobe of the standards. Rather, we observe a strong correlation (R2=0.85-0.97) between Fe3+/?FeMössbauer and Fe3+/?Femicroprobe, which we use to determine Fe3+/?Fe in spinel unknowns. Peridotites were analyzed from three localities: the Southwest Indian Ridge, the Tonga Forearc, and Cerro Mercedes, Costa Rica. Southwest Indian Ridge samples range from typical depleted abyssal peridotites to peridotites influenced by nearby Bouvet Hotspot. Tonga Forearc samples are from the trench and represent forearc lithospheric mantle. The Cerro Mercedes xenoliths are from a distance of 70km behind the active arc, thus representing back-arc mantle. The ridge peridotites have moderate degrees of hydrothermal alteration, whereas the Tonga peridotites vary from completely fresh to moderately altered. The xenoliths have no hydrothermal alteration, but have undergone minor reaction with the host basalt. The upper mantle fO2 recorded by spinels in these samples, calculated at 10kb and 1150°C, varies with proximity to subducted lithosphere. SWIR peridotite records QFM - 0.8 ± 0.3 (n = 7; ± 1?) while peridotite influenced by the Bouvet plume records QFM - 0.3 ± 0.1 (n = 2). Peridotites from Tonga and Costa Rica record QFM + 1.5 ± 0.8 (n=4, excluding one outlier at -0.2) and QFM + 1.1 ± 0.5 (n = 2) respectively. The fO2 we calculate for SWIR agrees very well with [3] for the same locality. Peridotite influenced by the Bouvet hotspot exhibits a similar or slightly elevated oxidation state relative to adjacent sections of SWIR with no Bouvet influence. In contrast, previous work by [3] on peridotite associated with Bouvet hotspot from the Islas Orcadas Fracture Zone found highly reducing fO2s. The Islas Orcadas peridotites are highly altered, however, with almost complete replacement of the primary mineralogy by hydrothermal minerals. Peridotites from Tonga and Costa Rica are more oxidized than abyssal peridotites and record some of the highest reported mantle fO2s . These results suggest that mantle associated with arc volcanism is oxidized relative to the MORB mantle, consistent with the oxidation state of derived basalts. The oxidation state of relatively unaltered peridotites influenced by Bouvet suggests that this hotspot is not reduced relative to ambient SWIR mantle. [1]Wood & Virgo, GCA (1989) [2] Wood et al., Science (1990) [3] Brynzdia and Wood, Am.J.Sci. (1990)

Lopez, O. G.; Cottrell, E.; Warren, J. M.

2012-12-01

39

The influence of oxygen fugacity on melt evolution: 1 atmosphere experiments on Aleutian basaltic andesites  

NASA Astrophysics Data System (ADS)

Magmatic differentiation trends can be approximated geochemically by liquid lines of descent, which can be modeled using high pressure and temperature experiments. Prior experimental studies indicate that oxygen fugacity (fO2) influences the compositional evolution of the melt phase during equilibrium crystallization, with more oxidized systems producing melts along a calc-alkaline differentiation trend, while more reduced systems produced tholeiitic melts. This study focuses on the influence of oxygen fugacity on equilibrium crystallization in natural basaltic andesites from Westdahl and Okmok volcanoes, Aleutians, Alaska. We conducted a series of experiments at 1 atmosphere with fO2 approximating the Ni-NiO (NNO) and Quartz-Fayalite-Magnetite (QFM) buffers, using H2-CO2 gas mixtures, at temperatures between 1053 and 1262 °C. We employed Fe-plated Pt wire loops as sample containers to minimize experiment Fe-loss. Melting experiments run above 1150 °C were texturally glassy with generally sparse, well-formed phenocrysts. Experiments that were aimed at crystallization at much lower temperatures (1100 °C or lower), required a controlled cooling-rate approach, and the experiments were first equilibrated for 24 hours at 1180 °C, and then temperature was ramped down at a rate of 0.8 °C per hour, resulting in well-crystallized run products. Basaltic andesite (52.4 wt. % SiO2) from the 1997 Okmok eruption run at fO2 ~NNO crystallized plagioclase, clinopyroxene, and Fe-Ti oxides at relatively high temperatures between 1200 and 1250 °C, with olivine forming at temperatures below 1200 °C. At NNO, the 1992 Westdahl basaltic andesite (54.2 wt. % SiO2) starting material produced plagioclase and Fe-Ti oxides between 1200 and 1250 °C, with clinopyroxene forming below about 1180 °C. Olivine did not form in the Westdahl starting composition in the NNO experiments. In both starting compositions run at fO2 ~ QFM, the experiments remained more melt-rich to lower temperatures. At QFM, the Okmok composition produced plagioclase on the liquidus at temperatures above 1200 °C, but Fe-bearing phases did not form until olivine appeared at 1150 °C, followed by clinopyroxene at ~1125 °C. At QFM, the Westdahl basaltic andesite produced only glass and plagioclase to temperatures as low as 1113 °C, with olivine, clinopyroxene, and Fe-Ti oxides crystallizing between 1053 and 1113 °C. Our preliminary results agree with those of prior experimental studies, which predict that higher oxygen fugacities enhance the early crystallization of Fe-Ti oxides, pyroxenes, and olivine, thus influencing the liquid line of descent towards early Fe-depletion and a higher degree of melt compositional evolution. Our experiments demonstrate that at NNO, both Westdahl and Okmok starting materials produced early crystallization of all Fe-bearing phases, while at QFM, the system remained more melt-rich, with plagioclase dominating at higher temperatures, and mafic phases crystallizing only at temperatures below about 1150 to 1100 °C.

Larsen, J. F.; Rader, E. L.

2010-12-01

40

Vanadium and niobium behavior in rutile as a function of oxygen fugacity: evidence from natural samples  

NASA Astrophysics Data System (ADS)

Vanadium occurs in multiple valence states in nature, whereas Nb is exclusively pentavalent. Both are compatible in rutile, but the relationship of V-Nb partitioning and dependence on oxygen fugacity (expressed as fO2) has not yet been systematically investigated. We acquired trace-element concentrations on rutile grains ( n = 86) in nine eclogitic samples from the Dabie-Sulu orogenic belt by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and combined them with published results in order to assess the direct and indirect effects of oxygen fugacity on the partitioning of V and Nb into rutile. A well-defined negative correlation between Nb (7-1,200 ppm) and V concentrations (50-3,200 ppm) was found, documenting a competitive relationship in the rutile crystal that does not appear to be controlled by bulk rock or mineral compositions. Based on the published relationship of RtDV and V valence with ?QFM, we suggest that the priority order of V incorporation into rutile is V4+ > V3+ > V5+. The inferred Nb-V competitive relationship in rutile from the Dabie-Sulu orogenic belt could be explained by decreasing fO2 due to dehydration reactions involving loss of oxidizing fluids during continental subduction: The increased proportion of V3+ (expressed as V3+/?V) and attendant decrease in RtDV is suggested to lead to an increase in rutile lattice sites available for Nb5+. A similar effect may be observed under more oxidizing conditions. When V5+/?V increases, RtDV shows a dramatic decline and Nb concentration increases considerably. This is possibly documented by rutile in highly metasomatized and oxidized MARID-type (MARID: mica-amphibole-rutile-ilmenite-diopside) mantle xenoliths from the Kaapvaal craton, which also show a negative V-Nb covariation. In addition, their Nb/Ta covaries with V concentrations: For V concentrations <1,250 ppm, Nb/Ta ranges between 35 and 45, whereas for V > 1,250 ppm, Nb/Ta is considerably lower (5-15). This relationship is mainly controlled by a change in Nb concentrations, suggesting that the indirect dependence of RtDNb on fO2, which is not mirrored in RtDTa, can exert considerable influence on rutile Nb-Ta fractionation.

Liu, Lei; Xiao, Yilin; Aulbach, Sonja; Li, Dongyong; Hou, Zhenhui

2014-06-01

41

Fugacity Examples  

ERIC Educational Resources Information Center

Equations related to the computation of fugacity of nonideal gases is presented, with special emphasize on a nontraditional equation of State's fugacity and the van der Waals fugacity. It is seen that both the equations include long-range attractive forces and short-range repulsive forces and thus have similar behaviour.

David, Carl W.

2004-01-01

42

Oxygen Fugacity at High Pressure: Equations of State of Metal-Oxide Pairs  

NASA Technical Reports Server (NTRS)

Oxygen fugacity (fO2) varies by orders of magnitude in nature, and can induce profound changes in the chemical state of a substance, and also in the chemical equilibrium of multicomponent systems. One prominent area in high pressure geochemistry, in which fO2 is widely recognized as a principal controlling factor, is that of metal-silicate partitioning of siderophile trace elements (e.g., [1]). Numerous experiments have shown that high pressures and temperatures can significantly affect metal/silicate partitioning of siderophile and moderately siderophile elements. Parameterization of these experimental results over P, T, X, and fO2 can allow the observed siderophile element composition of the mantle to be associated with particular thermodynamic conditions [2]. However, this is best done only if quantitative control exists over each thermodynamic variable relevant to the experiments. The fO2 values for many of these partitioning experiments were determined relative to a particular metal-oxide buffer (e.g., Fe-FeO (IW), Ni-NiO (NNO), Co-CoO, Re-ReO2 (RRO)), but the parameterization of all experimental results is weakened by the fact that the pressure-induced relative changes between these buffer systems are imprecisely known.

Campbell A. J.; Danielson, L.; Righter, K.; Wang, Y.; Davidson, G.; Wang, Y.

2006-01-01

43

Temperature and oxygen fugacity constraints on CK and R chondrites and implications for water and oxidation in the early solar system  

NASA Astrophysics Data System (ADS)

Recent chondritic meteorite finds in Antarctica have included CB, CH, CK and R chondrites, the latter two of which are among the most oxidized materials found in meteorite collections. In this study we present petrographic and mineralogic data for a suite of CK and R chondrites, and compare to previous CK and R chondrites, as well as some CV. In particular we focus on the opaque minerals - magnetite, chromite, sulfides, and metal - as well as unusual silicates - hornblende, biotite, and plagioclase. Several mineral thermometers and oxy-barometers are utilized to calculate temperatures and oxygen fugacities for these unusual meteorites compared to other more common chondrite groups. R and CK chondrites show lower equilibrium temperatures than ordinary chondrites, even though they are at similar petrologic grades (e.g., thermal type 6). Oxygen fugacity calculated for CV and R chondrites ranges from values near the iron-wustite (IW) oxygen buffer to near the fayalite-magnetite-quartz (FMQ) buffer. In comparison, the fO 2 recorded by ilmenite-magnetite pairs from CK chondrites are much higher, from FMQ + 2 to FMQ + 4.5. The latter values are the highest recorded for materials in meteorites, and place some constraints on the formation conditions of these magnetite-bearing chondrites. Differences between mineralogic and O isotopic compositions of CK and R chondrites suggest two different oxidation mechanisms, which may be due to high and low water:rock ratios during metamorphism, or to different fluid compositions, or both.

Righter, K.; Neff, K. E.

44

Temperature and Oxygen Fugacity Constraints on CK and R Chondrites and Implications for Water and Oxidation in the Early Solar System  

NASA Technical Reports Server (NTRS)

Recent chondritic meteorite finds in Antarctica have included CB, CH, CK and R chondrites, the latter two of which are among the most oxidized materials found in meteorite collections. In this study we present petrographic and mineralogic data for a suite of CK and R chondrites, and compare to previous studies of CK and R, as well as some CV chondrites. In particular we focus on the opaque minerals magnetite, chromite, sulfides, and metal as well as unusual silicates hornblende, biotite, and plagioclase. Several mineral thermometers and oxy-barometers are utilized to calculate temperatures and oxygen fugacities for these unusual meteorites compared to other more common chondrite groups. R and CK chondrites show lower equilibrium temperatures than ordinary chondrites, even though they are at similar petrologic grades (e.g., thermal type 6). Oxygen fugacity calculated for CV and R chondrites ranges from values near the iron-wustite (IW) oxygen buffer to near the fayalite-magnetite-quartz (FMQ) buffer. In comparison, the fO2 recorded by ilmenite-magnetite pairs from CK chondrites are much higher, from FMQ+3.1 to FMQ+5.2. The latter values are the highest recorded for materials in meteorites, and place some constraints on the formation conditions of these magnetite-bearing chondrites. Differences between mineralogic and O isotopic compositions of CK and R chondrites suggest two different oxidation mechanisms, which may be due to high and low water: rock ratios during metamorphism, or to different fluid compositions, or both.

Righter, K.; Neff, K. E.

2007-01-01

45

Using Vanadium in Spinel as a Sensor of Oxygen Fugacity in Meteorites: Applications to Mars, Vesta, and Other Asteroids  

NASA Technical Reports Server (NTRS)

Igneous and metamorphic rocks commonly contain a mineral assemblage that allows oxygen fugacity to be calculated or constrained such as FeTi oxides, olivine-opx-spinel, or some other oxybarometer [1]. Some rocks, however, contain a limited mineral assemblage and do not provide constraints on fO2 using mineral equilibria. Good examples of the latter are orthopyroxenites or dunites, such as diogenites, ALH 84001, chassignites, or brachinites. In fact it is no surprise that the fO2 of many of these samples is not well known, other than being "reduced" and below the metal saturation value. In order to bridge this gap in our understanding, we have initiated a study of V in chromites in natural meteorite samples. Because the V pre-edge peak intensity and energy in chromites varies with fO2 (Fig. 1) [2], and this has been calibrated over a large fO 2 range, we can apply this relation to rocks for which we otherwise have no fO2 constraints.

Righter, K.; Sutton, S.; Danielson, L.; Le, L.; Newville, M.; Pando, K.

2009-01-01

46

The Fidelity of Olivine-Hosted Melt Inclusions as Recorders of Pre-Eruptive Water Content and Oxygen Fugacity  

NASA Astrophysics Data System (ADS)

Olivine-hosted melt inclusions represent an important source of information on both the pre-eruptive H2O contents and oxygen fugacities of basaltic magmas [1]. The principal uncertainty involved with deriving pre-eruptive H2O concentrations from melt inclusions is the potential for diffusive loss or gain of H+ (protons) through the host olivine. Further, it has been proposed that the proton flux associated with H2O loss/gain affects the oxidation state of the inclusion [2,3]. Results from hydration and dehydration experiments carried out on natural inclusion-bearing olivines analyzed by SIMS and XANES confirm that H2O re-equilibratrion occurs rapidly via proton diffusion through the host olivine, and demonstrate that re-equilibration of oxygen fugacity within the inclusion occurs on comparable timescales via diffusion of point defects. Therefore, an olivine-hosted melt inclusion provides a reliable record of both the H2O content and oxygen fugacity of the external melt with which it most recently equilibrated. However, efficient re-equilibration of both H2O and oxygen fugacity limits the utility of olivine-hosted melt inclusions as indicators of mantle processes. Hydration experiments were performed on olivines from Puu Wahi, a scoria cone on the NE rift zone of Mauna Loa volcano. Melt inclusions initially containing 0.36±0.05 wt% H2O were held at 1 GPa and 1250° C in water enriched in 18O (18O/?O = 0.977) and D (2H/?H = 0.998) to map the transport of protons and oxygen during equilibration of melt inclusions with an external fluid. Dehydration experiments were carried out for 1 to 18 hrs at 1 bar and 1250 ° C on inclusion-bearing olivines in scoria erupted from Cerro Negro volcano, Nicaragua, in 1999. The initial concentration of H2O in these melt inclusions was uniformly high (3.6±0.6 wt%). All run products were analyzed for major elements by electron microprobe and for H2O by SIMS on the Cameca 1280 ion microprobe at WHOI. The oxidation state of Fe was determined by XANES at beamline 13-IDC of the Advanced Photon Source at Argonne National Laboratory. The D/H ratios of the melt inclusions from our hydration experiments range from 18.4-25.6, as compared to ~1.448 x 10-4 for mantle-derived basalt, indicating significant addition of deuterium. The 18O/17O ratios of melt inclusions are within uncertainty of natural ratios for mantle-derived materials. The H2O content of individual melt inclusions increased by as much as 3.9 wt %, while the oxidation state of Fe in the hydrated melt inclusions is not significantly different from the starting materials. The concentration of H2O in melt inclusions from the dehydration experiments ranges from 2.8 to 0.05 wt%, and dehydration is nearly complete after 18 hours. The ?D value of the melt inclusions increases significantly as dehydration progresses and is consistent with a calculated diffusive fractionation of hydrogen isotopes. Neither diffusive fractionation of H2O nor equilibrium fractionation via vapor loss is consistent with the isotopic enrichment observed in dehydrated melt inclusions. The oxidation state of Fe ranges from Fe3+/?Fe = 0.58±0.04 (NiNiO+4) for the starting materials to Fe3+/?Fe = 0.21±0.03 (NiNiO+0.6) for melt inclusions that were heated for 18 hours, and re-equilibrates on the same timescale as H2O. References: [1] K.A. Kelley, E. Cottrell, Science 325, 605 (2009); [2] A. V. Sobolev, L. V. Danyushevsky, J Petrol 35, 1183 (1994); [3] L. V. Danyushevsky, A. W. McNeill, A. V. Sobolev, Chem Geol 183, 5 (2002).

Gaetani, Glenn; O'Leary, Julie; Shimizu, Nobumichi

2010-05-01

47

Hydration of mantle olivine under variable water and oxygen fugacity conditions: a combined SIMS and FTIR study  

NASA Astrophysics Data System (ADS)

Trace concentrations of H+ dissolved in peridotite strongly affect both its rheology and solidus. Olivine comprises ~70% of a peridotite mode and is capable of incorporating substantial H+ at upper mantle conditions. Recently, Grant et al. (2007) conducted olivine hydration experiments to determine the influence of oxygen fugacity on H+ incorporation. FTIR analyses of their run products show that absorption bands at 3325 and 3355 cm-1 (Group II bands of Bai and Kohlstedt (1993)) are sensitive to oxygen fugacity and, therefore, likely correspond to Fe3+-bearing point defects. New olivine hydration experiments were conducted to quantify H+ concentration changes associated with these defects. SIMS was used to quantify the H+ concentration and FTIR analyses were used to monitor changes in point defect populations. Our results agree with those of Grant et al. (2007) that Group II absorption bands are sensitive to fO2, but SIMS analyses indicate that changing oxygen fugacity from Fe-Fe1-XO to Ni-NiO at constant P, T and olivine composition only increases the concentration of H+ by ~50%. Olivine hydration experiments were conducted at 1.0, 1.5, or 2.0 GPa and 1200 °C using a piston cylinder device. Oxygen fugacity was controlled at the Fe-Fe1-XO, Fe1-XO-Fe3O4, or Ni-NiO buffer. Mixed H2O-CO2 experiments were used to resolve the influence of P from that of H2O fugacity. Starting materials, fabricated from large single crystals of San Carlos olivine (Fo88-91), were pressure-sealed in either a Fe0 or Ni0 capsule. The H+ concentration of run products were measured using a Cameca 6F ion microprobe and the protocols of Koga et al. (2003). Total infrared absorption spectra were determined by a combined polarized absorption spectra taken at three orthogonal orientation, roughly parallel to crystallographic orientation. Spectra were taken on single crystal olivines shaped as parallelapipeds with several 100s of micron thicknesses. Results from our experiments confirm that H2O fugacity is the dominant influence on the solubility of H+ in mantle olivine. Increasing the fugacity of oxygen produces a modest increase in H+ solubility despite a significant increase in Group II absorption bands. Increasing pressure or Al3+ produce modest decreases. The negative dependence on Al3+ concentration is thought to reflect changing SiO2 activity. The solubility of H+ is insensitive to the Fe/Mg ratio of the olivine over the compositional range explored in our experiments. References. Grant et al. (2007) Earth Planet Sci Lett 261:217-229; Bai and Kohlstedt (1993) Phys Chem Minerals 19:460-471; Koga et al. (2003) Geochem, Geophys, Geosys doi: 10.1029/2002GC000378.

Gaetani, G. A.; O'Leary, J. A.; Koga, K. T.; Hauri, E. H.; Rose-Koga, E. F.

2012-12-01

48

The stability of magnesite in the transition zone and the lower mantle as function of oxygen fugacity  

NASA Astrophysics Data System (ADS)

The oxygen fugacity at which magnesite (MgCO3) is reduced to diamond in a typical mantle assemblage has been determined between 16 and 45 GPa and 1500-1700°C in experiments employing a multianvil device. This oxygen fugacity for carbonate stability, measured using a sliding redox sensor that employs IrFe alloy, was found to be greater than 2 log units above the iron-wüstite oxygen buffer (?IW+2). Reversal experiments employing FeNi alloy confirmed complete oxidation of Ni in the presence of magnesite and diamond even at 45 GPa. As the oxygen fugacity of the transition zone and lower mantle is most likely at or below the IW buffer, mantle carbon, if distributed relatively homogeneously, is unlikely to be hosted in carbonates throughout most of the mantle but is more likely present as diamond, methane, Fe-rich carbide or as a carbon-component dissolved in Fe-Ni metal. The existence of carbonate at these depths would imply the presence of unusually oxidized regions of the deeper mantle. Such regions could form in the deeper mantle from an influx of subduction related carbonate melt, which would reduce by causing oxidation of the surrounding silicates. Due to changes in the degree of oxidation of the surrounding mantle such melts could potentially travel further in the transition zone mantle than in the lower mantle. The results do not exclude the possibility that carbonate could coexist with Fe-Ni metal or carbide at the very base of the lower mantle.

Stagno, V.; Tange, Y.; Miyajima, N.; McCammon, C. A.; Irifune, T.; Frost, D. J.

2011-10-01

49

Post-entrapment modification of volatiles and oxygen fugacity in olivine-hosted melt inclusions  

NASA Astrophysics Data System (ADS)

The solubilities of volatiles (H2O, CO2, S, F, and Cl) in basaltic melts are dependent on variables such as temperature, pressure, melt composition, and redox state. Accordingly, volatile concentrations can change dramatically during the various stages of a magma's existence: from generation, to ascent through the mantle and crust, to final eruption at the Earth's surface. Olivine-hosted melt inclusions have the potential to preserve volatile concentrations at the time of entrapment due to the protection afforded by the host olivine against decompression and changes to the oxidation state of the external magma. Recent studies, however, have demonstrated that rapid diffusive re-equilibration of H2O and oxygen fugacity (f) can occur within olivine-hosted melt inclusions. Here we present volatile, hydrogen isotope, and major element data from dehydration experiments and a quantitative model that assesses proposed mechanisms for diffusive re-equilibration of H2O and f in olivine-hosted melt inclusions. Our comprehensive set of data for the behavior of common magmatic volatiles (H2O, CO2, F, Cl, and S) demonstrates that post-entrapment modification of CO2, and to a lesser extent S, can also occur. We show that the CO2 and S concentrations within an included melt decrease with progressive diffusive H2O loss, and propose that this occurs due to dehydration-induced changes to the internal pressure of the inclusion. Therefore, deriving accurate estimates for pre-eruptive CO2 and S concentrations from olivine-hosted melt inclusions requires accounting for the amount of CO2 and S hosted in vapor bubbles. We find, however, that Cl and F concentrations in olivine-hosted melt inclusions are not affected by diffusive re-equilibration through the host olivine nor by dehydration-induced pressure changes within the melt inclusion. Our results indicate that measured H2O, CO2 and S concentrations and Fe3+/?Fe ratios of included melts are not necessarily representative of the melt at the time of entrapment and thus are not reliable proxies for upper mantle conditions.

Bucholz, Claire E.; Gaetani, Glenn A.; Behn, Mark D.; Shimizu, Nobumichi

2013-07-01

50

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

NASA Astrophysics Data System (ADS)

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

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

2012-08-01

51

Importance of oxygen fugacity for temperatures and melting regimes beneath ridges, arcs, and hot spots  

NASA Astrophysics Data System (ADS)

Oxygen fugacity (fO2) plays a central role in controlling phase equilibria and the behavior of multi-valent elements (e.g., Fe, C). Primitive basalts are petrologic indicators of the conditions of mantle melting, and Fe is particularly important because its behavior and abundance in basalt are highly sensitive to P and T of mantle melting. Yet, Fe is also uniquely sensitive to the fO2 of the mantle source, which controls the relative abundances of the two major species of Fe in the upper mantle (Fe2+, Fe3+). Because Fe2+ is the more sensitive geothermometer, constraining Fe speciation in basalts is key to accurately interpreting Fe as a sensor of magmatic and mantle conditions. Here, we present new constraints on the Fe3+/?Fe ratios (i.e., Fe3+/[Fe2++Fe3+]) of basalts from ridges, arcs, and hot spots, determined using ?-XANES analysis of glasses and melt inclusions, and assess how fO2 influences the use of basalt Fe content to interpret P-T conditions of magmas and melting. Using ol-liquid or ol-opx-liquid thermometry (Putirka, 2007; Lee et al., 2010), modeled basalt temperatures decrease by ~0.4-0.6°C, and equilibration temperatures of basalt with the mantle decrease by ~4.4°C, for every 1% increase in Fe3+/?Fe ratio of the melt. Global mid-ocean ridge basalts (MORB) have a narrow range of Fe3+/?Fe (0.13-0.17; Cottrell & Kelley, 2011), significantly higher than prior bulk analyses have shown (0.07-0.12; Christie et al., 1986; Bezos & Humler, 2005). This upward revision has a small impact on modeled magmatic temperatures (max. ?T of -4 to -6°C), but it significantly impacts the modeled temperature of the MORB mantle source (max. ?T of -44°C), shallowing the base of the melting triangle by ~15 km. This decrease in potential temperature may be overshadowed, however, by the impact of fO2 on the depth of the graphite-CO2 transition. Reduced C has low solubility in silicate melts, but oxidized C will act as a flux (Dasgupta and Hirschmann, 2006). The upward revision of the MORB source fO2 may therefore expand the melt triangle by expanding the field of carbonatitic silicate melts (Dasgupta & Hirschmann, 2010). At arcs, both high dissolved H2O contents and high Fe3+/?Fe ratios (0.18 to 0.30, globally) in basalts impact thermobarometric models used to constrain mantle source conditions. An arc basalt with 6 wt.% H2O and Fe3+/?Fe=0.30 is ~80°C cooler than the same basalt with 2 wt.% H2O and Fe3+/?Fe=0.20, although only ~5°C of this difference is attributed to Fe speciation. At conditions of the arc mantle source, higher H2O contents and Fe3+/?Fe ratios of basalts indicate ambient mantle temperatures ranging from MORB-like to ~100°C cooler than the MORB source. Despite lower temperatures, however, melting beneath arcs may occur at higher pressures due to the inverted geothermal gradient and H2O input flux in the lower half of the mantle wedge beneath arc volcanoes. For ocean island basalts (OIB), Fe3+/?Fe ratios vary from MORB-like to relatively oxidized (0.14-0.25). Although OIBs may have both elevated Fe3+/?Fe ratios and higher dissolved H2O relative to MORB, higher total Fe concentrations than average MORB offset the effects of H2O and Fe3+ on modeled mantle temperatures. Mantle temperature beneath Samoa is modeled at ~150°C in excess of the average MORB source.

Kelley, K. A.; Cottrell, E.

2011-12-01

52

The effect of water activity and oxygen fugacity on the phase relations and oxidation state of Fe in parental ferrobasaltic magma of Skaergaard  

NASA Astrophysics Data System (ADS)

Phase relations and differentiation in the ferrobasaltic (FeO*=13wt%) system "SC1", an assumed parental liquid of the Skaergaard layered intrusion, have been investigated experimentally at dry conditions (1 atm) [1, 2]. However, the Skaergaard magma is believed to contain water. The present study investigates the role of water and fO2 on the phase relations and differentiation of the "SC1" ferrobasaltic system. The crystallization experiments have been performed in an internally heated pressure vessel equipped with a rapid quench facility and Shaw-membrane to determine the prevailing oxygen fugacity within the sample capsule [3]. To prevent the Fe-loss into the capsule material and ensure the desired conditions inside the capsule, the AuPd capsules were presaturated with iron and starting glasses were preequilibrated at the expected fO2 of the run. Water activity was varied by changing the H2O/CO2 ratio in the fluid phase. The first results of the experiments at P=200 MPa, T=1200-1000°C, various oxygen fugacities (logfO2=FMQ+4 to FMQ-1) and water activities (0 to 1) show that water influences not only the liquidus temperatures and temperature interval of mineral crystallization but also the sequence of crystallizing minerals; when compared with the dry system. Since water solubility strongly depends on pressure in the pressure range of 200-300 MPa, corresponding to the storage conditions of Skaergaard magma, the aH2O of hydrous magma may change significantly as a result of convection. Thus, convection has the potential to produce significant differences in stability and proportions of the prevailing minerals. This, in turn, may contribute to the formation of complex layering of the Skaergaard intrusion. The Moessbauer analysis of the quenched glasses shows that the Fe3+ / Sum Fe ratio of the silicate melt is a positive function of the water activity and has a linear dependence on water mole fraction in the system at 1200°C. The decrease of Fe3+ / Sum Fe ratio of the water-bearing melt with decreasing oxygen fugacity is more pronounced than that calculated for dry melts after [4]. [1] Toplis MJ &Carroll MR, J. Petrol., 36, 1137-1170, 1995. [2] Lattard D &Partsch GM, Eur. J. Mineral., 13, 467-478, 2001. [3] Berndt J et al., Am. Mineral., 87, 1717-1726, 2002. [4] Kress VC &Carmichael ISE, Contr.Min.Petrol., 108, 82-92, 1991.

Botcharnikov, R.; Koepke, J.; Holtz, F.; McCammon, C.

2003-04-01

53

Single grain estimations of oxygen fugacity in subcratonic mantle lithosphere using compositions of Ilmenite, Chromite , Garnet and Pyroxenes.  

NASA Astrophysics Data System (ADS)

Calculated oxygen fugacity conditions for ilmenites and chromites were obtained using the monomineral version of the Taylor (1998) oxygen barometers with the calculation of Fe#Ol according to (Ashchepkov et al., 2010). The monomineral version of the Gar- Ol- Opx method (Gudmundsson & Wood, 1995) was obtained using the regression between FO2 and Fe3 in garnet and additional correlation to P and T. F5=Fe#Gar/FeGar; Fo2= 2030.2*Ff5**3-1061.4*F5**2+190.89*F5-12.644 Fo2 = (Fo2-0.01*P (kbar)+(ToC-500)/(3500 -05.)*0.9 The obtained values wee regression and the new Cpx method constructed by the cross correlations of the Fe3+ in Cpx with the oxygen fugacity values obtained for garnets were used for the additional characterization of the mantle SCLM section. The statistical between regression obtained from the work (Gudmundsson, Wood , 1995) and corrections for the temperature and pressure justified by the comparisons obtained with the Ol- Sp and Ilm- Ol oxybarometers (Taylor et al., 1998) allow to estimate the FO2 (? log QMF) by following simple equations: For clinopyroxene the cross calibration allow to receive the following regression. Fo2=-186.71*Fe3**2+48.617*Fe3 - 2.3262; Fo2 = Fo2+(T0-500)/3500-0.01*P Fo2 = (Fo2-0.01*P (kbar)+(ToC-500)/3500 -05.)*0.7 For clinopyroxene the cross calibration allow to receive the following regression. Fo2=-186.71*Fe3**2+48.617*Fe3 - 2.3262; Fo2 = Fo2+(T0-500)/3500-0.01*P Fo2=(Fo2-0.5)*0.8 For the orthopyroxene the correlating with the CPx parameter was calculated as following The Fe3'Opx was corrected as Fe3Opx-0.03;Fo2=23.882*Fe3'Opx*(Fe1*15)**2-1.8805 Fo2= Fo2+((T0-400)/1000)*(Fe1*20)-0.0175*P; Fo2=(Fo2*(Fe1*15)**2-0.9*P/70)*0.9 Fo2=(Fo2-0.5)*0.9 Despite on the rather low resolution of the Fe3+ EPMA estimates statistically the determined parameters are rather useful and mark major levels in the SCLM beneath Siberian and other cratons. The rise of FO2 is marked in the three major intervals - in the lithosphere base near the base of lithosphere marking cumulates and shearing peridotites. Near the boundary of the upper and lower mantle at 40 kbar marking so called pyroxenite layer and within basaltic trap - cresponding to the level of water bearing malt interaction , Despite there several layer corresponding to the mantle layering and levels of polybaric hydraulic shearing coused by the protokimberlite melt intrusion. The garnets commonly give some additional trends of joined rising of Fo2 and decreasing of the pressures. There amount in the lower part of the mantle columns is reaching 5-6 units. They are very often correlating with the values determined for the Cpx but later are generally more oxidized. The diamond bearing associations including eclogites are commonly less oxidized belonging to the diamond stability field found by (McCammon et al ., 2001) . Sometimes these values are as low as -5.5 log u. ? log QMF. Interesting feature the upper part of the SCLM is sometimes less oxidized then pyroxenite lens and even lower part of SCLM. The trends of the ilmenites commonly are just marking the line of diamong stability in DSCLM od became higher and (even SCLM) in the upper part . The Ti- bearing spinel are commonly marking slightly lower values then ilmenites while Ti-less chromites are commonly less oxidized marking major units in mantle layering. RBRF grant 11-05-00060.

Ashchepkov, I.

2012-04-01

54

Intrinsic oxygen fugacity measurements on seven chondrites, a pallasite, and a tektite and the redox state of meteorite parent bodies  

USGS Publications Warehouse

Intrinsic oxygen-fugacity (fO2) measurements were made on five ordinary chondrites, a carbonaceous chondrite, an enstatite chondrite, a pallasite, and a tektite. Results are of the form of linear log fO2 - 1 T plots. Except for the enstatite chondrite, measured results agree well with calculated estimates by others. The tektite produced fO2 values well below the range measured for terrestrial and lunar rocks. The lowpressure atmospheric regime that is reported to follow large terrestrial explosions, coupled with a very high temperature, could produce glass with fO2 in the range measured. The meteorite Salta (pallasite) has low fO2 and lies close to Hvittis (E6). Unlike the other samples, results for Salta do not parallel the iron-wu??stite buffer, but are close to the fayalite-quartz-iron buffer in slope. Minor reduction by graphite appears to have taken place during metamorphism of ordinary chondrites. fO2 values of unequilibrated chondrites show large scatter during early heating suggesting that the constituent phases were exposed to a range of fO2 conditions. The samples equilibrated with respect to fO2 in relatively short time on heating. Equilibration with respect to fO2 in ordinary chondrites takes place between grades 3 and 4 of metamorphism. Application of P - T - fO2 relations in the system C-CO-CO2 indicates that the ordinary chondrites were metamorphosed at pressures of 3-20 bars, as it appears that they lay on the graphite surface. A steep positive thermal gradient in a meteorite parent body lying at the graphite surface will produce thin reduced exterior, an oxidized near-surface layer, and an interior that is increasingly reduced with depth; a shallow thermal gradient will produce the reverse. A body heated by accretion on the outside will have a reduced exterior and oxidized interior. Meteorites from the same parent body clearly are not required to have similar redox states. ?? 1984.

Brett, R.; Sato, M.

1984-01-01

55

Theoretical phase relations involving cordierite and garnet revisited: the influence of oxygen fugacity on the stability of sapphirine and spinel in the system Mg-Fe-Al-Si-O  

Microsoft Academic Search

The theoreticalP-T grid for stability relations of the phases cordierite (Cd), sapphirine (Sa), hypersthene (Hy), garnet (Ga), spinel (Sp), sillimanite (Si), and quartz (Qz) of Hensen (1971), has proved useful in the interpretation of metamorphic mineral assemblages formed at low oxygen fugacity. Both experimental data and evidence from natural rocks indicate that at high oxygen fugacity compatability relations change as

B. J. Hensen

1986-01-01

56

The effect of oxygen fugacity on the partitioning of nickel and cobalt between olivine, silicate melt, and metal  

NASA Technical Reports Server (NTRS)

The effect of oxygen fugacity, f(O2), on the partitioning behavior of Ni and Co between olivine, silicate melt, and metal was investigated in the CaO-MgO-Al2O3-SiO2-FeO-Na2O system, an analogue of a chondrule composition from an ordinary chondrite. The conditions were 1350 C and 1 atm, with values of f(O2) varying between 10 exp -5.5 and 10 exp -12.6 atm (i.e., the f(O2) range relevant for crystal/liquid processes in terrestrial planets and meteorite parent bodies). Results of chemical analysis showed that the values of the Ni and Co partitioning coefficients begin to decrease at values of f(O2) that are about 3.9 log units below the nickel-nickel oxide and cobalt-cobalt oxide buffers, respectively, near the metal saturation for the chondrule analogue composition.

Ehlers, Karin; Grove, Timothy L.; Sisson, Thomas W.; Recca, Steven I.; Zervas, Deborah A.

1992-01-01

57

Determining the Oxygen Fugacity of Lunar Pyroclastic Glasses Using Vanadium Valence - An Update  

NASA Technical Reports Server (NTRS)

We have been developing an oxygen barometer based on the valence state of V (V(2+), V(3+), V(4+), and V(5+)) in solar system basaltic glasses. The V valence is determined by synchrotron micro x-ray absorption near edge structure (XANES), which uses x-ray absorption associated with core-electronic transitions (absorption edges) to reveal a pre-edge peak whose intensity is directly proportional to the valence state of an element. XANES has advantages over other techniques that determine elemental valence because measurements can be made non-destructively in air and in situ on conventional thin sections at a micrometer spatial resolution with elemental sensitivities of approx. 100 ppm. Recent results show that fO2 values derived from the V valence technique are consistent with fO2 estimates determined by other techniques for materials that crystallized above the IW buffer. The fO2's determined by V valence (IW-3.8 to IW-2) for the lunar pyroclastic glasses, however, are on the order of 1 to 2.8 log units below previous estimates. Furthermore, the calculated fO2's decrease with increasing TiO2 contents from the A17 VLT to the A17 Orange glasses. In order to investigate these results further, we have synthesized lunar green and orange glasses and examined them by XANES.

Karner, J. M.; Sutton, S. R.; Papike, J. J.; Shearer, C. K.; Jones, J. H.; Newville, M.

2004-01-01

58

Fe Mg diffusion in olivine I: experimental determination between 700 and 1,200°C as a function of composition, crystal orientation and oxygen fugacity  

NASA Astrophysics Data System (ADS)

We have determined Fe Mg diffusion coefficients in olivines from different sources (Nanga Parbat, Pakistan and San Carlos, Arizona, USA) at atmospheric pressure as a function of composition, oxygen fugacity (10-5 10-12 Pa) and temperature (700 1200°C) using thin films produced by pulsed laser deposition and RBS to analyze the concentration profiles. We have characterized the nano-scale structure and composition of the thin films annealed at various conditions and shown that the nature of the film (e.g. crystallinity, wetting behavior) depends strongly on the annealing conditions. If these variations are not taken into account in the form of boundary conditions for modeling the diffusion profiles, artifacts would result in the diffusion data. The diffusion coefficients obtained from 75 experiments reveal that (i) between fO2 of 10-5 and 10-10 Pa, diffusion along all three principal crystallographic directions in olivine, [100], [010] and [001], are described by a constant activation energy of ˜200 kJ/mol, precluding any temperature dependence of diffusion anisotropy and change of mechanism of diffusion at temperatures between 950 and 1200°C, (ii) diffusion coefficients increase with oxygen fugacity at fO2 > 10-10 Pa, with an fO2 exponent that lies between 1/4 and 1/7, and (iii) at fO2 below 10-10 Pa, and consequently at temperatures below ˜900°C, diffusion becomes weakly dependent/independent of fO2, indicating a change of diffusion mechanism. Activation energy of diffusion at these conditions is slightly higher, ˜220 kJ/mol. The data, including the change of mechanism, are analyzed in terms of point defect chemistry in Part II of this work to derive an equation that allows calculation of diffusivities in olivine over its entire field of stability. Availability of directly measured data at temperatures down to 700°C imply that for the first time diffusion coefficients can be interpolated, rather than extrapolated, for modeling most natural systems.

Dohmen, Ralf; Becker, Hans-Werner; Chakraborty, Sumit

2007-08-01

59

An experimental study of H solubility in feldspars: Effect of composition, oxygen fugacity, temperature and pressure and implications for crustal processes  

NASA Astrophysics Data System (ADS)

A series of experiments, with run durations of ˜100-240 h, have been carried out on H solubility in natural labradorite, albite and anorthoclase at 2-10 kbar and 700-850 °C, in equilibrium with different oxygen buffer materials: Fe-FeO, Ni-NiO, Re-ReO2 and Fe2O3-Fe3O4. Attainment of equilibrium water contents were examined by conducting experiments with different run-durations and by performing profile analysis along crystal core-to-rim paths. The annealed products generally show typical OH-related infrared absorption bands in the range 3700-2600 cm-1: the spectra of the labradorite and anorthoclase are dominated by broad bands at ˜3300-3100 cm-1, while the spectra of the albite consist of broad bands at ˜3100-3000 cm-1 and sharp bands at ˜3600-3400 cm-1. The measured H solubility, ranging from ˜80 to 285 ppm H2O, differs greatly between the feldspars with different chemical compositions, depends strongly on oxygen fugacity, and increases with increasing temperature and pressure. The H solubility is significantly higher, e.g., by a factor of ˜3 or even more, at very reducing conditions than at oxidizing conditions. The high H solubility of feldspar at reduced conditions indicates that, at least locally, the Earth's ancient deep continental crust was probably more hydrous than the modern one. Crustal dehydration can be caused by a change of oxygen fugacity and a corresponding change of water solubility in the constituent feldspar under isothermal conditions, without the requirement of high temperature and/or additional heat sources.

Yang, Xiaozhi

2012-11-01

60

Oxygen Fugacity of Mare Basalts and the Lunar Mantle Application of a New Microscale Oxybarometer Based on the Valence State of Vanadium  

NASA Technical Reports Server (NTRS)

The ability to estimate oxygen fugacities for mare basalts and to extend these observations to the lunar mantle is limited using bulk analysis techniques based on buffering assemblages or the valence state of iron. These limitations are due to reequilibration of mineral assemblages at subsolidus conditions, deviations of mineral compositions from thermodynamic ideality, size requirements, and the limits of the iron valence at very low fO2. Still, these approaches have been helpful and indicate that mare basalts crystallized at fO2 between the iron-w stite buffer (IW) and the ilmenite breakdown reaction (ilmenite = rutile + iron). It has also been inferred from these estimates that the lunar mantle is also highly reduced lying at conditions below IW. Generally, these data cannot be used to determine if the mare basalts become increasingly reduced during transport from their mantle source and eruption at the lunar surface and if there are differences in fO2 among mare basalts or mantle sources. One promising approach to determining the fO2 of mare basalts is using the mean valence of vanadium (2+, 3+, 4+, 5+) determined on spots of a few micrometers in diameter using synchrotron x-ray absorption fine structure (XAFS) spectroscopy. The average valence state of V in basaltic glasses is a function of fO2, temperature, V coordination, and melt composition. Here, we report the initial results of this approach applied to lunar pyroclastic glasses.

Shearer, C. K.; Karner, J.; Papike, J. J.; Sutton, S. R.

2004-01-01

61

Synchrotron Micro-XANES Measurements of Vanadium Oxidation State in Glasses as a Function of Oxygen Fugacity: Experimental Calibration of Data Relevant to Partition Coefficient Determination  

NASA Technical Reports Server (NTRS)

Oxidation state microanalyses for V in glass have been made by calibrating XANES spectral features with optical spectroscopic measurements. The oxidation state change with fugacity of O2 will strongly influence partitioning results.

Delaney, J. S.; Sutton, S. R.; Newville, M.; Jones, J. H.; Hanson, B.; Dyar, M. D.; Schreiber, H.

2000-01-01

62

Comparative Planetary Mineralogy: V/(Cr+Al) Systematics in Chromites as an Indicator of Relative Oxygen Fugacity  

NASA Technical Reports Server (NTRS)

As our contribution to the new "Oxygen in the Solar System" initiative of the Lunar and Planetary Institute and the NASA Cosmochemistry Program, we have been developing oxygen barometers based largely on behavior of V which can occur in four valence states V2+, V3+, V4+, and V5+, and record at least 8 orders of magnitude of fO2. Our first efforts in measuring these valence proportions were by XANES techniques in basaltic glasses from Earth, Moon, and Mars. We now address the behavior of V valence states in chromite in basalts from Earth, Moon, and Mars. We have been looking for a "V in chromite oxybarometer" that works with data collected by the electron microprobe and thus is readily accessible to a large segment of the planetary materials community. This paper describes very early results that will be refined over the next two years.

Papike, J. J.; Kamer, J. M.; Shearer, C. K.

2004-01-01

63

Effect of oxygen fugacity on the H 2O storage capacity of forsterite in the carbon-saturated systems  

NASA Astrophysics Data System (ADS)

High pressure experiments have been performed in the systems Mg 2SiO 4-C-O-H and Mg 2SiO 4-K 2CO 3-C at 6.3 GPa and 1200 to 1600 °C using a split-sphere multi-anvil apparatus. In the Mg 2SiO 4-C-O-H system the composition of fluid was modeled by adding different amounts of water and stearic acid. The fO 2 was controlled by the Mo-MoO 2 or Fe-FeO oxygen buffers. Several experiments in the Mg 2SiO 4-C-O-H system and all experiments in the Mg 2SiO 4-K 2CO 3-C system have been conducted without buffering the fO 2. Forsterite in the system Mg 2SiO 4-K 2CO 3-C does not reveal OH absorption bands in the IR spectra, while forsterite coexisting with carbon-bearing fluid and silicate melt at log fO 2 from FMQ-2 to FMQ-5 (from 2 to 5 log units below fayalite-magnetite-quartz oxygen buffer) contains 800-1850 wt. ppm H 2O. The maximum concentrations were detected at 1400 °C and FMQ-3.5. We observed an increase in the solidus temperature in the system Mg 2SiO 4-C-O-H from 1200 to above 1600 °C with log fO 2 decreasing from FMQ-2 to FMQ-5. The increase of the solidus temperature and the broadening of the stability field of the H 2O-H 2-CH 4 subsolidus fluid phase at 1400-1600 °C explain the high H 2O storage capacity of forsterite relative to that crystallized from carbon-free, oxidized, hydrous, silicic melt. At temperatures above 1400 °C liquidus forsterite precipitated along with diamond from oxidized (FMQ-1) carbonate-silicate melt and from silicate melt dissolving the moderately reduced C-O-H fluid (from FMQ-2 to FMQ-3.5). Formation of diamond was not detected under ultra-reduced conditions (FMQ-5) at 1200-1600 °C. Olivine co-precipitating with diamond from dry carbonate-silicate or hydrous-silicic fluid/melt can provide information on the H 2O contents and speciation of the diamond-forming media in the mantle. The conditions for minimum post-crystallization alteration of olivine and its hydrogen content are discussed.

Sokol, Alexander G.; Palyanov, Yury N.; Kupriyanov, Igor N.; Litasov, Konstantin D.; Polovinka, Mariya P.

2010-08-01

64

Systematic iron isotope variations in mantle rocks and minerals: The effects of partial melting and oxygen fugacity [rapid communication  

NASA Astrophysics Data System (ADS)

Iron isotopic compositions potentially provide a powerful new tracer of planetary formation and differentiation processes and of secular and spatial changes in mantle oxidation state. However, the processes governing iron isotope fractionation in igneous rocks remain poorly understood. Here we show that there are significant variations in the iron isotope compositions ( ?57/54Fe) of mantle rocks (0.9‰) and minerals (olivines 0.6‰, clinopyroxenes 0.9‰ and orthopyroxenes 0.8‰), with spinels showing the greatest total variation of 1.7‰. Positive linear functional relationships with slopes that are, within error, equal to unity are found between the ?57/54Fe values of coexisting orthopyroxene, clinopyroxene and olivine, strongly suggesting that the ?57/54Fe values of these minerals reflect intra-sample mineral-mineral isotopic equilibrium. Positive correlations between the ?57/54Fe values of silicate minerals and spinels also exist, although they are more scattered, which could be caused by late disturbance of mineral-spinel isotopic equilibrium. Bulk-rock, clinopyroxene and spinel ?57/54Fe values correlate with chemical indices of both melt extraction and oxidation. Iron isotope fractionation during spinel-facies partial melting is investigated using simple models, which demonstrate that the maximum expected fractionation between melt and residue will be ˜0.5‰, with the residue becoming isotopically light relative to the melt and to the initial source region. Hence melt extraction, in combination with significant changes in mantle oxidation state, may be an explanation for Fe isotopic variations in mantle peridotites. Metasomatism of the sub-arc mantle by iron-rich silicate melts originating from the subducting slab may also explain the light bulk-sample ?57/54Fe values of some arc peridotites (- 0.2‰ to - 0.6‰), but mass-balance calculations require these metasomatic agents to have extreme ?57/54Fe values (e.g. - 3.0‰). The large differences in the ?57/54Fe values of garnet and spinel facies rocks are likely to be caused by the contrasting behaviour of Fe 3+ during melting in the spinel and garnet facies. However, there is little difference in the ?57/54Fe values of MORB and OIB, despite the fact that OIB are considered, on the basis of incompatible element abundances, to arise dominantly by melting in the garnet stability field. Given that iron is a relatively compatible element, the similarities in the ?57/54Fe values of MORB and OIB provide strong evidence that MORB and OIB are both dominated by melting in the spinel facies.

Williams, H. M.; Peslier, A. H.; McCammon, C.; Halliday, A. N.; Levasseur, S.; Teutsch, N.; Burg, J.-P.

2005-06-01

65

Thermal state, oxygen fugacity and C?O?H fluid speciation in cratonic lithospheric mantle: New data on peridotite xenoliths from the Udachnaya kimberlite, Siberia  

NASA Astrophysics Data System (ADS)

Oxygen fugacity (fO2) and temperature variations in a complete lithospheric mantle section (70-220 km) of the central Siberian craton are estimated based on 42 peridotite xenoliths in the Udachnaya kimberlite. Pressure and temperature (P-T) estimates for the 70-140 km depth range closely follow the 40 mW/m2 model conductive geotherm but show a bimodal distribution at greater depths. A subset of coarse garnet peridotites at 145-180 km plots near the "cold" 35 mW/m2 geotherm whereas the majority of coarse and sheared rocks at ?145 km scatter between the 40 and 45 mW/m2 geotherms. This P-T profile may reflect a perturbation of an initially "cold" lithospheric mantle through a combination of (1) magmatic under-plating close to the crust-mantle boundary and (2) intrusion of melts/fluids in the lower lithosphere accompanied by shearing. fO2 values estimated from Fe3+/?Fe in spinel and/or garnet obtained by Mössbauer spectroscopy decrease from +1 to -4 ?log fO2 (FMQ) from the top to the bottom of the lithospheric mantle (˜0.25 log units per 10 km) due to pressure effects on Fe2+-Fe3+ equilibria in garnet. Garnet peridotites from Udachnaya appear to be more oxidized than those from the Kaapvaal craton but show fO2 distribution with depth similar to those in the Slave craton. Published fO2 estimates for Udachnaya xenoliths based on C-O-H fluid speciation in inclusions in minerals from gas chromatography are similar to our results at ?120 km, but are 1-2 orders of magnitude higher for the deeper mantle, possibly due to uncertainties of fO2 estimates based on experimental calibrations at ?3.5 GPa. Sheared peridotites containing garnets with u-shaped, sinusoidal and humped REE patterns are usually more oxidized than Yb, Lu-rich, melt-equilibrated garnets, which show a continuous decrease from heavy to light REE. This further indicates that mantle redox state may be related to sources and modes of metasomatism.

Goncharov, A. G.; Ionov, D. A.; Doucet, L. S.; Pokhilenko, L. N.

2012-12-01

66

The stability of sapphirine + quartz in magnetite-bearing high oxygen fugacity granulites: a case study of the Madurai Block (Southern India) and the Inner Mongolia Suture Zone (North China)  

NASA Astrophysics Data System (ADS)

Sapphirine has been the focus of many petrological investigations for the last two decades as the mineral often occurs in Mg-Al rich and pelitic rocks formed at high temperature to ultrahigh temperature (UHT). Particularly, sapphirine coexisting with quartz is considered as one of the most diagnostic mineral assemblages of UHT metamorphism. It is also known that sapphirine often occurs in magnetite-bearing high oxygen fugacity rocks, and, in such cases, the mineral can incorporate considerable quantity of ferric iron as well as Fe2+. It is therefore important to evaluate the effect of Fe3+ content on the stability of sapphirine-bearing assemblages for estimating peak conditions as well as constructing P-T paths. In this study, we evaluated the stability of sapphirine + quartz in magnetite-bearing high-oxygen fugacity rocks in UHT granulites from India (Madurai Block in the southern granulite terrane) and China (Inner Mongolia Suture Zone) using mineral equilibrium modeling technique, and constructed P-T paths of the areas. The calculations have been done in NCKFMASHTO system using THERMOCALC 3.33 with an updated version of the internally consistent data set. The Madurai Block is the largest granulite block in the Southern Granulite Terrane, India, which was formed by collisional orogeny related to the assembly of the Gondwana Supercontinent. The block contains granulites with various UHT mineral assemblages including sapphirine + quartz, orthopyroxene + sillimanite + quartz, and Al-rich orthopyroxene. Quartzo-feldspathic garnet-sillimanite granulites from Rajapalaiyam area in the southern part of the block, for example, contain sapphirine + quartz inclusion in garnet as a stable mineral assemblage at the peak of metamorphism. The calculated T-X pseudosections suggest that the stability temperature of sapphirine + quartz is lowered from 1000°C at reduced condition (XFe2O3 = 0.02) to 910°C at oxidized condition (XFe2O3 = 1.0). The Inner Mongolia Suture Zone within the North China Block rarely contains sapphirine-bearing UHT granulites. Tuguiwula area within the suture zone contains coarse-grained sapphirine granulites. Although both sapphirine and quartz occur quartzo-feldspathic layers of the rocks, the two minerals are separated by thin film of sillimanite. This indicates sapphirine was in equilibrium with quartz at prograde or peak metamorphic conditions and separated during retrograde metamorphism. The T-X pseudosection of the rocks indicate that the stability field of sapphirine + quartz lowered in more oxidized condition (T > 1050°C at XFe2O3 = 0.1 to T > 920°C at XFe2O3 = 0.9). The results of this study demonstrated that the occurrence of sapphirine + quartz in UHT rocks is strongly controlled by the oxidation state of the rocks. Lowering of the stability field of sapphirine + quartz by increasing XFe2O3 ratio was also confirmed for UHT granulites from the Madurai Block and the Inner Mongolia Suture Zone.

Shimizu, H.; Tsunogae, T.; Santosh, M.

2012-04-01

67

The oxidation state of subcontinental mantle: oxygen thermobarometry of mantle xenoliths from central Asia  

Microsoft Academic Search

The oxygen fugacities of 48 mantle xenoliths from 5 localities in southern Siberia (USSR) and Mongolia have been determined. Ferric iron contents of spinels were measured by 57Fe Mössbauer spectroscopy and oxygen fugacities calculated from spinel-olivineorthopyroxene equilibrium. The samples studied represent the major types of upper mantle lithologies including spinel and garnet peridotites and pyroxenites, fertile and depleted peridotites and

D. A. Ionov; B. J. Wood

1992-01-01

68

Computer program for calculation of oxygen uptake  

NASA Technical Reports Server (NTRS)

A description and operational precedures are presented for a computer program, written in Super Basic, that calculates oxygen uptake, carbon dioxide production, and related ventilation parameters. Program features include: (1) the option of entering slope and intercept values of calibration curves for the O2 and CO2 and analyzers; (2) calculation of expired water vapor pressure; and (3) the option of entering inspured O2 and CO2 concentrations. The program is easily adaptable for programmable laboratory calculators.

Castle, B. L.; Castle, G.; Greenleaf, J. E.

1979-01-01

69

MHD performance calculations with oxygen enrichment  

NASA Technical Reports Server (NTRS)

The impact of oxygen enrichment of the combustion air on the generator and overall plant performance was studied for the ECAS-scale MHD/steam plants. A channel optimization technique is described and the results of generator performance calculations using this technique are presented. Performance maps were generated to assess the impact of various generator parameters. Directly and separately preheated plant performance with varying O2 enrichment was calculated. The optimal level of enrichment was a function of plant type and preheat temperature. The sensitivity of overall plant performance to critical channel assumptions and oxygen plant performance characteristics was also examined.

Pian, C. C. P.; Staiger, P. J.; Seikel, G. R.

1979-01-01

70

A New Spinel-Olivine Oxybarometer: Near-Liquidus Partitioning of V between Olivine-Melt, Spinel-Melt, and Spinel-Olivine in Martian Basalt Composition Y980459 as a Function of Oxygen Fugacity  

NASA Technical Reports Server (NTRS)

Our research on valence state partitioning began in 2005 with a review of Cr, Fe, Ti, and V partitioning among crystallographic sites in olivine, pyroxene, and spinel [1]. That paper was followed by several on QUE94201 melt composition and specifically on Cr, V, and Eu partitioning between pyroxene and melt [2-5]. This paper represents the continuation of our examination of the partitioning of multivalent V between olivine, spinel, and melt in martian olivine-phyric basalts of Y980459 composition [6, 7]. Here we introduce a new, potentially powerful oxybarometer, V partitioning between spinel and olivine, which can be used when no melt is preserved in the meteorite. The bulk composition of QUE94201 was ideal for our study of martian pyroxene-phyric basalts and specifically the partitioning between pyroxene-melt for Cr, V, and Eu. Likewise, bulk composition Y980459 is ideal for the study of martian olivine-phyric basalts and specifically for olivine-melt, spinel-melt, and spinel-olivine partitioning of V as a function of oxygen fugacity.

Papike, J. J.; Le, L.; Burger, P. V.; Shearer, C. K.; Bell, A. S.; Jones, J.

2013-01-01

71

Transport of Pb and Zn by carboxylate complexes in basinal ore fluids and related petroleum-field brines at 100?C: the influence of pH and oxygen fugacity  

PubMed Central

It is well established through field observations, experiments, and chemical models that oxidation (redox) state and pH exert a strong influence on the speciation of dissolved components and the solubility of minerals in hydrothermal fluids. log –pH diagrams were used to depict the influence of oxygen fugacity and pH on monocarboxylate- and dicarboxylate-transport of Pb and Zn in low-temperature (100°C) hydrothermal ore fluids that are related to diagenetic processes in deep sedimentary basins, and allow a first-order comparison of Pb and Zn transport among proposed model fluids for Mississippi Valley-type (MVT) and red-bed related base metal (RBRBM) deposits in terms of their approximate pH and conditions. To construct these diagrams, total Pb and Zn concentrations and Pb and Zn speciation were calculated as a function of log and pH for a composite ore-brine with concentrations of major elements, total sulfur, and total carbonate that approximate the composition of MVT and RBRBM model ore fluids and modern basinal brines. In addition to acetate and malonate complexation, complexes involving the ligands Cl-, HS-, H2S, and OH- were included in the model of calculated total metal concentration and metal speciation. Also, in the model, Zn and Pb are competing with the common-rock forming metals Ca, Mg, Na, Fe, and Al for the same ligands. Calculated total Pb concentration and calculated total Zn concentration are constrained by galena and sphalerite solubility, respectively. Isopleths, in log –pH space, of the concentration of Pb and concentration of Zn in carboxylate (acetate + malonate) complexes illustrate that the oxidized model fluids of T. H. Giordano (in Organic Acids in Geological Processes, ed. E. D. Pittman and M. D. Lewan, Springer-Verlag, New York, 1994, pp. 319–354) and G. M. Anderson (Econ. Geol., 1975, 70, 937–942) are capable of transporting sufficient amounts of Pb (up to 10 ppm) and Zn (up to 100 ppm) in the form of carboxylate complexes to form economic deposits of these metals. On the other hand, the reduced ore fluid models of D. A. Sverjensky (Econ. Geol., 1984, 79, 23–37) and T. H. Giordano and H. L. Barnes (Econ. Geol., 1981, 76, 2200–2211) can at best transport amounts of Pb and Zn, as carboxylate complexes, that are many orders of magnitude below the 1 to 10 ppm minimum required to form economic deposits. Lead and zinc speciation (mol% of total Pb or Zn) in the model ore fluid was calculated at specific log –pH conditions along the 100, 0.01, and 0.001 ppm total Pb and total Zn isopleths. Along the 100 ppm isopleth conditions are oxidized (?SO4 >> ?H2S) with Pb and Zn predominantly in the form of chloride complexes under acid to mildly alkaline conditions (pH from 3 to approximately 7.5), while hydroxide complexes dominate Pb and Zn speciation under more alkaline conditions. Sulfide complexes are insignificant under these oxidized conditions. For more reduced conditions along the 0.01 and 0.001 ppm isopleths chloride complexes dominate Pb and Zn speciation in the SO42- field and near the SO42--reduced sulfur boundary from pH = 4 to approximately 7.5, while hydroxide complexes dominate Pb and Zn speciation under alkaline conditions above pH = 7.5 in the SO42- field. In the most reduced fluids (?H2S >> ?SO4) along the 0.01 and 0.001 isopleths, sulfide complexes account for almost 100% of the Pb and Zn in the model fluid. Acetate (monocarboxylate) complexation is significant only under conditions of chloride and hydroxide complex dominance and its effect is maximized in the pH range 5 to 7, where it complexes 2 to 2.6% of the total Pb and 1 to 1.25% of the total Zn. Malonate (dicarboxylate) complexes are insignificant along all isopleths. The speciation results from this study show that deep formation waters characterized by temperatures near 100°C, high oxidation states and ?H2S < 0.03 mg L-1 ( < 10-6), high chlorinities (~ 100000 mg L-1), and high but reasonable concentrations of carboxyla

Giordano, Thomas H

2002-01-01

72

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

USGS Publications Warehouse

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

Hass, Jr. , J. L.

1970-01-01

73

Polarizability calculations on water, hydrogen, oxygen, and carbon dioxide  

NASA Technical Reports Server (NTRS)

A semiclassical model of damped oscillators is used as a basis for the calculation of the dispersion of the refractive index, polarizability, and dielectric permeability in water, hydrogen, and oxygen in liquid and gaseous states, and in gaseous carbon dioxide. The absorption coefficient and the imaginary part of the refractive index are also calculated at corresponding wavelengths. A good agreement is obtained between the observed and calculated values of refractive indices, and between those of absorption coefficients in the region of absorption bands. The calculated values of oscillator strengths and damping factors are also discussed. The value of the polarizability of liquid water was about 2.8 times that of previous calculations.

Nir, S.; Adams, S.; Rein, R.

1973-01-01

74

Oxygen adsorption on Cu(100): First-principles pseudopotential calculations  

Microsoft Academic Search

We have studied the adsorption characteristics of atomic and molecular oxygen, incident on the Cu(100) surface. Our pseudopotential first-principles calculations yield trajectories for the O2 molecule without dissociation barriers at the entrance channel. We discuss the energetics of the O2 adsorption and dissociation in terms of the elbow plots which are two-dimensional cuts of the full six-dimensional potential-energy surface. The

M. Alatalo; S. Jaatinen; P. Salo; K. Laasonen

2004-01-01

75

Control of the Water Fugacity Under High Pressures and Temperatures: Applications to the Water Solubility in Olivine  

NASA Astrophysics Data System (ADS)

Previous experimental studies have shown significant influence of water on the physical and chemical properties of mantle materials, such as diffusivity, viscosity, and electrical conductivity. Those experiments were, however, conducted either at water-saturated conditions with the excess fluid phases or at water under-saturated conditions without controlling the amount of water. In these cases, the influence of water fugacity can not be easily quantified, which leads to large uncertainties in the interpretation of experimental observations. Here we propose a novel approach to control water fugacity in the upper mantle conditions by the use of water fugacity buffers. We use a modified double capsule method, which is schematically shown in the figure. An inner Ni, Mo, or Re capsule separating the sample charge from a water fugacity buffer acts as a semi-permeable membrane for hydrogen, and an outer Pt capsule minimizes the water input and loss from the surrounding environment. The advantage of the semi-permeable metal membrane is to prevent the sample from changing its bulk composition except for hydrogen, while it maintains water fugacity in the sample same as the water fugacity buffer. This method was applied to investigate the water solubility in olivine at various water fugacities. The high-pressure annealing experiments were conducted at 5-10 GPa and 1273-1373 K by a Kawai-type multianvil apparatus. We utilized the following divariant assemblages in MSH (MgO-SiO2-H2O) system as water fugacity buffers: clinohumite-forsterite-periclase, chondrodite-clinohumite-periclase, phase A-chodrodite-periclase, and brucite-periclase. The run products show that reduction of the oxide phase and transformation of orthopyroxene into olivine, suggesting that hydrogen diffused into the sample charge through the metal membrane. The presence of all the relevant phases demonstrates that water and oxygen fugacities were buffered during the experiments. This technique will allow us to (i) determine the relation between water concentration and fugacity at fixed pressures and temperatures, (ii) identify the solubility mechanism through the determination of water fugacity exponent, and (iii) quantify the influence of water fugacity on various properties at water-undersaturated conditions.

Otsuka, K.; Karato, S.

2009-12-01

76

The hard hexagon partition function for complex fugacity  

NASA Astrophysics Data System (ADS)

We study the analyticity of the partition function of the hard hexagon model in the complex fugacity plane by computing zeros and transfer matrix eigenvalues for large finite size systems. We find that the partition function per site computed by Baxter in the thermodynamic limit for positive real values of the fugacity is not sufficient to describe the analyticity in the full complex fugacity plane. We also obtain a new algebraic equation for the low density partition function per site.

Assis, M.; Jacobsen, J. L.; Jensen, I.; Maillard, J.-M.; McCoy, B. M.

2013-11-01

77

Comparison of measured and calculated thermospheric molecular oxygen densities  

NASA Technical Reports Server (NTRS)

The open source neutral mass spectrometers on the AE-C, -D, and -E satellites were equipped with a 'fly-through' mode of operation which has provided direct measurements of molecular oxygen densities over a large portion of the globe. A complementary set of O2 densities is derived by using AE ion measurements and a scheme based on the daytime ion chemistry of O2(+) in the thermosphere. A comparison of the two data sets reveals general agreement over northern latitudes during periods of relatively low Ap and F10.7. The simplifying assumptions made in the photochemical scheme require that caution be used in calculating O2, especially at high latitudes and altitudes below 200 km

Potter, W. E.; Kayser, D. C.; Brinton, H. C.; Brace, L. H.; Oppenheimer, M.

1977-01-01

78

Comparing different methods of calculating volume-weighted hypolimnetic oxygen (VWHO) in lakes  

Microsoft Academic Search

In the limnological literature there is no standard method for calculating hypolimnetic volumes using temperature profile data. Consequently, calculations of hypolimnetic dissolved oxygen concentrations differ based on the method chosen. This study examined the differences in calculations of volume-weighted hypolimnetic oxygen (VWHO) concentrations based on different methodologies and profile sampling resolution. Comparisons of VWHO values indicated that differences among methods

Roberto Quinlan; Andrew M. Paterson; John P. Smol; Marianne S. V. Douglas; Bev J. Clark

2005-01-01

79

Partitioning of Eu between augite and a highly spiked martian basalt composition as a function of oxygen fugacity (IW-1 to QFM): Determination of Eu[superscript 2+]/Eu[superscript 3+] ratios by XANES  

SciTech Connect

We have determined D{sub Eu} between augite and melt in samples that crystallized from a highly spiked martian basalt composition at four f{sub O{sub 2}} conditions. D{sub Eu} augite/melt shows a steady increase with f{sub O{sub 2}} from 0.086 at IW-1 to 0.274 at IW+3.5. This increase is because Eu{sup 3+} is more compatible than Eu{sup 2+} in the pyroxene structure; thus increasing f{sub O{sub 2}} leads to greater Eu{sup 3+}/Eu{sup 2+} in the melt and more Eu (total) can partition into the crystallizing pyroxene. This interpretation is supported by direct determinations of Eu valence state by XANES, which show a steady increase of Eu{sup 3+}/Eu{sup 2+} with increasing f{sub O{sub 2}} in both pyroxene (0.38 to 14.6) and glass (0.20 to 12.6) in the samples. Also, pyroxene Eu{sup 3+}/Eu{sup 2+} is higher than that of adjacent glass in all the samples, which verifies that Eu{sup 3+} is more compatible than Eu{sup 2+} in the pyroxene structure. Combining partitioning data with XANES data allows for the calculation of specific valence state D-values for augite/melt where D{sub Eu{sup 3+}} = 0.28 and D{sub Eu{sup 2+}} = 0.07.

Karner, J.M.; Papike, J.J.; Sutton, S.R.; Burger, P.V.; Shearer, C.K.; Le, L.; Newville, M.; Choi, Y. (UNM); (ESC); (UC)

2010-03-16

80

The Evolution and Future of Environmental Fugacity Models  

Microsoft Academic Search

\\u000a In this chapter we first review the concept of fugacity as a thermodynamic equilibrium criterion applied to chemical fate\\u000a in environmental systems. We then discuss the evolution of fugacity-based models applied to the multimedia environmental distribution\\u000a of chemicals and more specifically to bioaccumulation and food web models. It is shown that the combination of multimedia\\u000a and bioaccumulation models can provide

Donald Mackay; Jon A. Arnot; Eva Webster; Lüsa Reid

81

Third Bose fugacity coefficient in one dimension, as a function of asymptotic quantities  

SciTech Connect

In one of the very few exact quantum mechanical calculations of fugacity coefficients, [L.R. Dodd, A.M. Gibbs. J. Math. Phys. 15 (1974) 41] obtained b{sub 2} and b{sub 3} for a one dimensional Bose gas, subject to repulsive delta-function interactions, by direct integration of the wave functions. For b{sub 2}, we have shown [A. Amaya-Tapia, S.Y. Larsen, M. Lassaut. Mol. Phys. 103 (2005) 1301-1306. < (arXiv:physics/0405150)>] that Dodd and Gibbs' result can be obtained from a phase shift formalism, if one also includes the contribution of oscillating terms, usually contributing only in one dimension. Now, we develop an exact expression for b{sub 3}-b{sub 3}{sup 0} (where b{sub 3}{sup 0} is the free particle fugacity coefficient) in terms of sums and differences of three-body eigenphase shifts. Further, we show that if we obtain these eigenphase shifts in a Distorted-Born approximation, then, to first order, we reproduce the leading low temperature behaviour, obtained from an expansion of the twofold integral of Dodd and Gibbs. The contributions of the oscillating terms cancel. The formalism that we propose is not limited to one dimension, but seeks to provide a general method to obtain virial coefficients, fugacity coefficients, in terms of asymptotic quantities. The exact one dimensional results allow us to confirm the validity of our approach in this domain.

Amaya-Tapia, A., E-mail: jano@fis.unam.mx [Instituto de Ciencias Fisicas, Universidad Nacional Autonoma de Mexico AP 48-3, Cuernavaca, Mor. 62251 (Mexico); Larsen, S.Y. [Department of Physics, Temple University, Philadelphia, PA 19122 (United States); Lassaut, M. [Institut de Physique Nucleaire, IN2P3-CNRS, Universite Paris-Sud 11, F-91406 Orsay Cedex (France)

2011-02-15

82

Electronic structure calculation for the oxygen vacancy in cubic tungsten oxide crystals  

Microsoft Academic Search

Due to its technological importance, tungsten oxide, a perovskite-type material, has been subject to numerous ab initio electronic structure calculations [1]. In this work we calculate the electronic structure of a cubic tungsten oxide with oxygen vacancies, using a total energy pseudopotential method. We first calculate the band structure of an ideal cubic tungsten oxide, with a lattice constant of

Smagul Karazhanov; Yong Zhang; Wang Lin-Wang; Angelo Mascarenhas; Satyen Deb

2002-01-01

83

First principles calculations of the vibrational properties of icosahedral solid boron oxygen B 12O 2  

Microsoft Academic Search

In this paper, the geometrical structure and vibrational properties of icosahedral solid boron oxygen B12O2 have been calculated using first principles calculations. The symmetry of crystal vibration modes at the center of Brillouin zone is analyzed based on our numeric results and structure symmetry. The calculated results are compared with available experimental investigations.

Bin Wang; Zhaochuan Fan; Qi Zhou; Xiaoxuan Xu; Min Feng; Xuewei Cao; Yufang Wang

2011-01-01

84

Oxygen Diffusion in the Brain. Part 1: Spatial Conception and Calculation of Oxygen Diffusion.  

National Technical Information Service (NTIS)

A new model of oxygen diffusion in the brain is developed, based on anatomical investigations and theoretical considerations. In this cone model it is assumed that the diffusion path is determined by the difference between the pO sub 2 at a given point in...

K. Diemer

1972-01-01

85

Thermodynamic Calculations of Hydrogen-Oxygen Detonation Parameters for Various Initial Pressures  

NASA Technical Reports Server (NTRS)

Composition, temperature, pressure and density behind a stable detonation wave and its propagation rate have been calculated for seven hydrogen-oxygen mixture at 1, 5, 25 and 100 atm initial pressure, and at an initial temperature of 40C. For stoichiometric mixtures that calculations also include an initial temperature of 200C. According to these calculations the detonation velocities of hydrogen-oxygen mixtures increase with increasing initial pressure, but decrease slightly when the initial temperature is raised from 40 to 200 C. The calculated detonation velocities agree satisfactorily with values determined experimentally. These values will be published in the near future.

Bollinger, Loren E.; Edse, Rudolph

1961-01-01

86

A Graphical Representation for the Fugacity of a Pure Substance  

ERIC Educational Resources Information Center

The thermodynamic equations used to define and compute the fugacity of a pure substance are depicted as processes on a semi-logarithmic plot of pressure vs. molar Gibbs energy (PG diagram) with isotherms for the substance behaving as an ideal gas superimposed. The PG diagram clearly demonstrates the physical basis for the definitions and the…

Book, Neil L.; Sitton, Oliver C.

2010-01-01

87

Structure of densified vitreous silica: Silicon and oxygen XANES spectra and multiple scattering calculations  

Microsoft Academic Search

The decrease of the mean Si-O-Si angle in vitreous silica upon densification from 2.20 to 2.36 gcm-3 has been followed by oxygen and silicon K-edge XANES spectroscopy. Multiple scattering calculations using clusters of two shells around the oxygen and silicon atoms, respectively, are in good agreement with experimental absorption spectra and confirm mean Si-O-Si angles between 130 and 144° for

I. Davoli; S. Stizza; M. Benfatto; M. Fanfoni; A. Gargano; A. Bianconi; F. Seifert

1992-01-01

88

Experimental calibration of oxygen isotope fractionation between quartz and zircon  

NASA Astrophysics Data System (ADS)

We report the results of an experimental calibration of oxygen isotope fractionation between quartz and zircon. Data were collected from 700 to 1000 °C, 10-20 kbar, and in some experiments the oxygen fugacity was buffered at the fayalite-magnetite-quartz equilibrium. Oxygen isotope fractionation shows no clear dependence on oxygen fugacity or pressure. Unexpectedly, some high-temperature data (900-1000 °C) show evidence for disequilibrium oxygen isotope partitioning. This is based in part on ion microprobe data from these samples that indicate some high-temperature quartz grains may be isotopically zoned. Excluding data that probably represent non-equilibrium conditions, our preferred calibration for oxygen isotope fractionation between quartz and zircon can be described by: 1000ln?=(2.33±0.24)×106/T2(in K) This relationship can be used to calculate fractionation factors between zircon and other minerals. In addition, results have been used to calculate WR/melt-zircon fractionations during magma differentiation. Modeling demonstrates that silicic magmas show relatively small changes in ? 18O values during differentiation, though late-stage mafic residuals capable of zircon saturation contain elevated ? 18O values. However, residuals also have larger predicted melt-zircon fractionations meaning zircons will not record enriched ? 18O values generally attributed to a granitic protolith. These results agree with data from natural samples if the zircon fractionation factor presented here or from natural studies is applied.

Trail, Dustin; Bindeman, Ilya N.; Watson, E. Bruce; Schmitt, Axel K.

2009-12-01

89

Similarity criteria in calculations of the energy characteristics of a cw oxygen - iodine laser  

NASA Astrophysics Data System (ADS)

The calculated and experimental data on the energy efficiency of a cw oxygen - iodine laser (OIL) are analysed based on two similarity criteria, namely, on the ratio of the residence time of the gas mixture in the resonator to the characteristic time of extraction of the energy stored in singlet oxygen td and on the gain-to-loss ratio ?. It is shown that the simplified two-level laser model satisfactorily predicts the output characteristics of OILs with a stable resonator at ?d <= 7. Efficient energy extraction from the OIL active medium is achieved in the case of ?d = 5 - 7, ? = 4 - 8.

Mezhenin, A. V.; Azyazov, V. N.

2012-12-01

90

Investigation of oxygen adsorption on Pt nanoparticles with large-scale DFT calculations  

NASA Astrophysics Data System (ADS)

The oxygen reduction reaction (ORR) is of central importance to the operation of fuel cells. An understanding of the chemistry of the adsorption of oxygen on the metallic surface of the cathode electrode, which is one of the stages involved in this reaction, can be acquired through ab initio calculations based on Density Functional Theory (DFT). The use of metallic nanoparticles can improve the performance of fuel cells, so it is important to understand how their material, shape, surface and size affect their chemical properties. However, traditional DFT approaches for metallic systems have constrained the investigations to a small number of atoms. Our recent developments within the ONETEP program for large-scale DFT calculations enable us to study much larger metallic systems consisting of hundreds or even thousands of atoms. In this work we use such calculations to perform a study of oxygen adsorption on platinum nanoparticles of a range of sizes, and examine properties such as the optimized structures, electronic effects and adsorption energies.

Ruiz-Serrano, Alvaro; Cherry, Peter; Skylaris, Chris-Kriton

2013-03-01

91

Phase diagram calculations of the U?Pu?N system with carbon and oxygen impurities  

NASA Astrophysics Data System (ADS)

The most common method for the preparation of mixed nitride fuels is the carbothermic reduction of a UO 2 + PuO 2 + C mixture in a nitrogen atmosphere. A mixed nitride fuel thus formed has carbon and oxygen impurities which are kept well below 5000 ppm. For a given overall composition of the nitride fuel and the temperature, the present work calculates the stable phases in equilibrium and the amounts of those phases. These calculations are based on the principle of mass balance and minimization of the Gibbs free energy for the system. The Gibbs free energy of formation of the binary compounds UN, PuN, UO, PUO, UC, PUC, UO 2, PuO 2 and UN 1.5 are used for the calculations. In general, the binary compounds are assumed to form ideal solid solutions, but in certain cases, available or estimated interaction parameters were used to see the effect of deviation from the ideal solution assumption on the phase diagram. Partial phase diagrams of (U, Pu)?C?N were drawn for different oxygen impurity concentrations at various temperatures. Comparison with the experimental data available in the literature is carried out. Based on these calculations it is suggested that a separate oxide phase has to be left deliberately in the mixed nitride fuel matrix during preparation to ensure fuel clad chemical compatibility.

Sood, D. D.; Agarwal, R.; Venugopal, V.

1997-08-01

92

Electronic structure and excitations in oxygen deficient CeO2-? from DFT calculations  

NASA Astrophysics Data System (ADS)

The electronic structures of supercells of CeO2-? have been calculated within the density functional theory (DFT). The equilibrium properties such as lattice constants, bulk moduli, and magnetic moments are well reproduced by the generalized gradient approximation (GGA). Electronic excitations are simulated by robust total-energy calculations for constrained states with atomic core holes or valence holes. Pristine ceria CeO2 is found to be a nonmagnetic insulator with magnetism setting in as soon as oxygens are removed from the structure. In the ground state of defective ceria, the Ce-f majority band resides near the Fermi level but appears at about 2 eV below the Fermi level in photoemission spectroscopy experiments due to final-state effects. We also tested our computational method by calculating threshold energies in Ce-M5 and O-K x-ray absorption spectroscopy and comparing theoretical predictions with the corresponding measurements. Our result that f electrons reside near the Fermi level in the ground state of oxygen-deficient ceria is crucial for understanding the catalytic properties of CeO2 and related materials.

Jarlborg, T.; Barbiellini, B.; Lane, C.; Wang, Yung Jui; Markiewicz, R. S.; Liu, Zhi; Hussain, Zahid; Bansil, A.

2014-04-01

93

Density functional theory calculations for the oxygen dissociation on nitrogen and transition metal doped graphenes  

NASA Astrophysics Data System (ADS)

Oxygen adsorption and dissociation on a pristine graphene, nitrogen doped graphene (N-graphene), and transition metal doped graphene (M-graphene) are studied with density functional theory calculations coupled with nudged elastic band (NEB) method. Four 3d transition metals (Fe, Co, Ni, and Cu) are selected as the doping atoms. The O binding energies on the Co-graphene and Ni-graphene have intermediate strength. The O2 dissociation barriers for these two types of doped graphenes are also lower than that on the pristine graphene and N-graphene. The Co and Ni doped graphenes are predicted to be promising ORR catalysts.

Zheng, Yongping; Xiao, Wei; Cho, Maenghyo; Cho, Kyeongjae

2013-10-01

94

Oxygen K-edge XANES of germanates investigated using first-principles calculations  

SciTech Connect

O K-edge x-ray absorption near-edge structure (XANES) spectra of {alpha}-quartz-type and rutile-type GeO{sub 2} polymorphs and of K{sub 2}Ge{sub 8}O{sub 17} have been analyzed using first-principles plane-wave pseudopotential calculations. XANES spectra have been calculated using supercell including core-hole effects and good agreement with experiment has been obtained. In the the case of GeO{sub 2} polymorphs, local density of empty states has been performed and peaks in the experimental spectra can be assigned to transitions involving hybridization of the O p orbitals with the Ge s, Ge p, Ge sp, and Ge d orbitals. Furthermore, peak positions in the theoretical spectra appear to be correlated with changes in the Ge-O-Ge angle as well as indirectly with the Ge coordination geometry. Analysis of O K-edge XANES spectra for individual O sites in K{sub 2}Ge{sub 8}O{sub 17} shows that oxygens shared between two fivefold Ge atoms or one fourfold and one fivefold Ge atom exhibit subtle shifts to lower energy of the peaks, which have been previously observed in alkali germanate glasses at and above the germanate anomaly.

Cabaret, Delphine; Mauri, Francesco; Henderson, Grant S. [Institut de Mineralogie et de Physique des Milieux Condenses, UMR CNRS 7590, Universite Pierre et Marie Curie, Paris 6, 140 rue de Lourmel, F-75015 Paris (France); Department of Geology, University of Toronto, 22 Russell Street, Toronto, Ontario M5S 3B1 (Canada)

2007-05-01

95

Experimental determination of coexisting iron titanium oxides in the systems FeTiAlO, FeTiAlMgO, FeTiAlMnO, and FeTiAlMgMnO at 800 and 900°C, 1 4 kbar, and relatively high oxygen fugacity  

Microsoft Academic Search

A synthetic, low-melting rhyolite composition containing TiO2 and iron oxide, with further separate additions of MgO, MnO, and MgO + MnO, was used in hydrothermal experiments to crystallize Ilm-Hem and Usp-Mt solid solutions at 800 and 900°C under redox conditions slightly below nickel nickel oxide (NNO) to ≈ 3 log_{10} f_{{{text{O}}2}} units above the NNO oxygen buffer. These experiments provide

Bernard W. Evans; Bruno Scaillet; Scott M. Kuehner

2006-01-01

96

“Dead Zone” dynamics in Lake Erie: the importance of weather and sampling intensity for calculated hypolimnetic oxygen depletion rates  

Microsoft Academic Search

Calculated hypolimnetic oxygen depletion (HOD) rates depend not only on environmental factors but also logistical ones. In\\u000a particular, lack of understanding of the effects of weather in addition to how sampling effort determines calculated HOD rates\\u000a complicates ecological understanding and environmental management of lake ecosystems. To better determine the roles of weather\\u000a and sampling effort, we combined (1) weekly measurements

Joseph D. Conroy; Leon Boegman; Hongyan Zhang; William J. Edwards; David A. Culver

2011-01-01

97

Experimental determination of coexisting iron–titanium oxides in the systems FeTiAlO, FeTiAlMgO, FeTiAlMnO, and FeTiAlMgMnO at 800 and 900°C, 1–4 kbar, and relatively high oxygen fugacity  

Microsoft Academic Search

A synthetic, low-melting rhyolite composition containing TiO2 and iron oxide, with further separate additions of MgO, MnO, and MgO + MnO, was used in hydrothermal experiments to crystallize Ilm-Hem and Usp-Mt solid solutions at 800 and 900C under redox conditions slightly below nickel–nickel oxide (NNO) to\\u000a$$\\\\approx 3\\\\,\\\\log_{10} f_{{{\\\\text{O}}_{2}}}$$ units above the NNO oxygen buffer. These experiments provide calibration of the FeTi-oxide

Bernard W. Evans; Bruno Scaillet; Scott M. Kuehner

2006-01-01

98

Oxygen potential of diamond formation in the lower mantle  

NASA Astrophysics Data System (ADS)

Thermodynamic calculations have shown that when a metallic phase arising due to ferroan ion disproportionation is contained in lower-mantle rocks, carbon occurs as iron carbide and the oxygen fugacity corresponds to the equilibrium of ferropericlase with Fe-Ni alloy. The typical values of oxygen fugacity in zones of diamond formation in the lower mantle lie between the iron-wüstite buffer and six logarithmic units above this level. The processes that proceed in the lower mantle give rise to variation of f_{O_2 } within several orders of magnitude above the elevated f_{O_2 } values, which are necessary for the formation of diamond, as compared with a common level typical of the lower mantle. The mechanisms responsible for redox differentiation in the lower mantle comprise the subduction of oxidized crustal material, mechanical separation of metallic phase and silicate-oxide mineral assemblage enriched in ferric ions, as well as transfer of fused silicate material presumably enriched in Fe3+ through the mantle.

Ryabchikov, I. D.; Kaminsky, F. V.

2013-02-01

99

Lunar and Planetary Science XXXV: Oxygen in the Solar System  

NASA Technical Reports Server (NTRS)

The session "Oxygen in the Solar System" contained the following reports: Oxygen Isotopes in Lunar Metal Grains: A Natural Genesis Experiment; Determining Possible Building Blocks of the Earth and Mars; and Oxygen Fugacity of the Martian Mantle from Pigeonite/Melt Partitioning of Samarium.

2004-01-01

100

Calculated values of atomic oxygen fluences and solar exposure on selected surfaces of LDEF  

NASA Technical Reports Server (NTRS)

Atomic oxygen (AO) fluences and solar exposure have been modeled for selected hardware from the Long Duration Exposure Facility (LDEF). The atomic oxygen exposure was modeled using the microenvironment modeling code SHADOWV2. The solar exposure was modeled using the microenvironment modeling code SOLSHAD version 1.0.

Gillis, J. R.; Pippin, H. G.; Bourassa, R. J.; Gruenbaum, P. E.

1995-01-01

101

Quantum mechanical calculations suggest that lytic polysaccharide monooxygenases use a copper-oxyl, oxygen-rebound mechanism  

PubMed Central

Lytic polysaccharide monooxygenases (LPMOs) exhibit a mononuclear copper-containing active site and use dioxygen and a reducing agent to oxidatively cleave glycosidic linkages in polysaccharides. LPMOs represent a unique paradigm in carbohydrate turnover and exhibit synergy with hydrolytic enzymes in biomass depolymerization. To date, several features of copper binding to LPMOs have been elucidated, but the identity of the reactive oxygen species and the key steps in the oxidative mechanism have not been elucidated. Here, density functional theory calculations are used with an enzyme active site model to identify the reactive oxygen species and compare two hypothesized reaction pathways in LPMOs for hydrogen abstraction and polysaccharide hydroxylation; namely, a mechanism that employs a ?1-superoxo intermediate, which abstracts a substrate hydrogen and a hydroperoxo species is responsible for substrate hydroxylation, and a mechanism wherein a copper-oxyl radical abstracts a hydrogen and subsequently hydroxylates the substrate via an oxygen-rebound mechanism. The results predict that oxygen binds end-on (?1) to copper, and that a copper-oxyl–mediated, oxygen-rebound mechanism is energetically preferred. The N-terminal histidine methylation is also examined, which is thought to modify the structure and reactivity of the enzyme. Density functional theory calculations suggest that this posttranslational modification has only a minor effect on the LPMO active site structure or reactivity for the examined steps. Overall, this study suggests the steps in the LPMO mechanism for oxidative cleavage of glycosidic bonds.

Kim, Seonah; Stahlberg, Jerry; Sandgren, Mats; Paton, Robert S.; Beckham, Gregg T.

2014-01-01

102

RELATIVISTIC CALCULATION OF TRANSITION PROBABILITIES FOR 557.7 nm AND 297.2 nm EMISSION LINES IN OXYGEN  

SciTech Connect

The 557.7 nm green line and the 297.2 nm ultraviolet line in oxygen have been studied extensively due to their importance in astrophysics and atmospheric science. Despite the enormous effort devoted to these two prominent transition lines over 30 years, and in fact going back to 1934, the ratio of their transition probabilities remains a subject of major discrepancies amongst various theoretical calculations for many decades. Moreover, theoretical results are inconsistent with available laboratory results, as well as recent spacecraft measurements of Earth's airglow. This work presents new relativistic theoretical calculations of the transition probabilities of these two photoemission lines from neutral oxygen using the multi-configuration Dirac-Hartree-Fock method. Our calculations were performed in both length and velocity gauges in order to check for accuracy and consistency, with agreement to 8%. Whilst remaining a challenging computation, these results directly bear upon interpretations of plasma processes and ionization regimes in the universe.

Chantler, C. T.; Nguyen, T. V. B.; Lowe, J. A. [School of Physics, University of Melbourne (Australia); Grant, I. P., E-mail: chantler@unimelb.edu.au [Mathematical Institute, Oxford University, Oxford (United Kingdom)

2013-05-20

103

First-principles calculation on oxygen ion migration in alkaline-earth doped La2GeO5  

NASA Astrophysics Data System (ADS)

By using first-principles calculations based on the density functional theory, we investigated the doping effects of alkaline-earth metals (Ba, Sr and Ca) in monoclinic lanthanum germanate La2GeO5 on its oxygen ion conduction. Although the lattice parameters of the doped systems changed due to the ionic radii mismatch, the crystal structures remained monoclinic. The contribution of each atomic orbital to electronic densities of states was evaluated from the partial densities of states and partial charge densities. It was confirmed that the materials behaved as ionic crystals comprising of cations of La and dopants and anions of oxygen and covalently formed GeO4. The doping effect on the activation barrier for oxygen hopping to the most stable oxygen vacancy site was investigated by the climbing-image nudged elastic band method. By tracing the charge density change during the hopping, it was confirmed that the oxygen motion is governed by covalent interactions. The obtained activation barriers showed excellent quantitative agreements with an experiment for the Ca- and Sr-doped systems in low temperatures as well as the qualitative trend, including the Ba-doped system.

Phan Thuy Linh, Tran; Sakaue, Mamoru; Meñez Aspera, Susan; Alaydrus, Musa; Dewi Kencana Wungu, Triati; Hoang Linh, Nguyen; Kasai, Hideaki; Mohri, Takahiro; Ishihara, Tatsumi

2014-06-01

104

“SIGMELTS”: A web portal for electrical conductivity calculations in geosciences  

NASA Astrophysics Data System (ADS)

Electrical conductivity measurements in the laboratory are critical for interpreting geoelectric and magnetotelluric profiles of the Earth's crust and mantle. In order to facilitate access to the current database on electrical conductivity of geomaterials, we have developed a freely available web application (SIGMELTS) dedicated to the calculation of electrical properties. Based on a compilation of previous studies, SIGMELTS computes the electrical conductivity of silicate melts, carbonatites, minerals, fluids, and mantle materials as a function of different parameters, such as composition, temperature, pressure, water content, and oxygen fugacity. Calculations on two-phase mixtures are also implemented using existing mixing models for different geometries. An illustration of the use of SIGMELTS is provided, in which calculations are applied to the subduction zone-related volcanic zone in the Central Andes. Along with petrological considerations, field and laboratory electrical data allow discrimination between the different hypotheses regarding the formation and rise from depth of melts and fluids and quantification of their storage conditions.

Pommier, A.; Le-Trong, E.

2011-09-01

105

Singlet oxygen generation in PUVA therapy studied using electronic structure calculations  

NASA Astrophysics Data System (ADS)

The ability of furocoumarins to participate in the PUVA (Psoralen + UV-A) therapy against skin disorders and some types of cancer, is analyzed on quantum chemical grounds. The efficiency of the process relies on its capability to populate its lowest triplet excited state, and then either form adducts with thymine which interfere DNA replication or transfer its energy, generating singlet molecular oxygen damaging the cell membrane in photoactivated tissues. By determining the spin-orbit couplings, shown to be the key property, in the intersystem crossing yielding the triplet state of the furocoumarin, the electronic couplings in the triplet-triplet energy transfer process producing the singlet oxygen, and the reaction rates and lifetimes, the efficiency in the phototherapeutic action of the furocoumarin family is predicted as: khellin < 5-methoxypsoralen (5-MOP) < 8-methoxypsoralen (8-MOP) < psoralen < 4,5',8-trimethylpsoralen (TMP) < 3-carbethoxypsoralen (3-CPS), the latter being the most efficient photosensitizer and singlet oxygen generator.

Serrano-Pérez, Juan José; Olaso-González, Gloria; Merchán, Manuela; Serrano-Andrés, Luis

2009-06-01

106

Effect of oxygen and zinc vacancies in ferromagnetic C-doped ZnO: Density-functional calculations  

NASA Astrophysics Data System (ADS)

The electronic and magnetic properties of pristine and defective ZnO solids, with some O atoms substituted by C, are investigated based on density functional theory. We reveal using the GGA+U and hybrid functional calculations that two neighboring substitutional C impurities prefer to form nonmagnetic C2 dimer. Moreover, our calculations show that both oxygen and zinc vacancies suppress the ferromagnetism in C-doped ZnO and zinc vacancy can even result in antiferromagnetic coupling among C impurities, elucidating the recent experiments.

Fang, D. Q.; Zhang, R. Q.; Zhang, Y.; Zhang, S. L.

2014-03-01

107

An oxygen barometer for rutile-ilmenite assemblages: oxidation state of metasomatic agents in the mantle  

NASA Astrophysics Data System (ADS)

Oxygen fugacity has been calculated for rutile-ilmenite assemblages from the reaction 2Fe 2O 3 (in ilmenite) + 4TiO 2 (rutile) = 4FeTiO 3 (in ilmenite) + O 2. The equation log fO 2=22.59-25925/ T-3.09log T+0.0016535 P+48.836 P/ T-4log aIlmFeTiO 3+2log aIlmFe 2O 3+4log aRutTiO 2, where T is in kelvin and P is in kbar, was derived from available thermodynamic data. The hypothetical end-member rutile-ilmenite reaction is located between the magnetite-hematite and Ni-NiO (NNO) buffers. The rutile-ilmenite oxygen barometer has been applied to ilmenite-bearing assemblages in mantle xenoliths from kimberlites, including the metasomatic MARID (mica-amphibole-rutile-ilmenite-diopside) suite and a MORID (mica-orthopyroxene-rutile-ilmenite-diopside) vein, along with rutile-ilmenite assemblages in eclogites and in Granny Smith diopside megacrysts. The oxygen fugacities of MARID and MORID lie around the NNO buffer and are comparable to those in metasomatized spinel lherzolites. Most MARID and MORID assemblages yield a more oxidizing fO 2 than the EMOD (enstatite-magnesite-olivine-diamond) buffer, such that MARID and MORID fluid or melt would tend to destroy diamond or graphite by oxidation.

Zhao, Donggao; Essene, Eric J.; Zhang, Youxue

1999-03-01

108

Oxygen vacancy in cubic WO 3 studied by first-principles pseudopotential calculation  

Microsoft Academic Search

In this work, the oxygen vacancy in WO3 has been studied by an ab initio pseudopotential method within the local density approximation (LDA). It is shown that with the charge state change of the vacancy, a strong lattice relaxation, swing from one to the other side of the un-relaxed position, is found for the nearest W ions, accompanied by large

S. Zh. Karazhanov; Yong Zhang; A. Mascarenhas; S. Deb; L.-W. Wang

2003-01-01

109

A Compensated-Redlich-Kwong (CORK) equation for volumes and fugacities of CO2 and H2O in the range 1 bar to 50 kbar and 100 1600°C  

NASA Astrophysics Data System (ADS)

We present a simple virial-type extension to the modified Redlich-Kwong (MRK) equation for calculation of the volumes and fugacities of H2O and CO2 over the pressure range 0.001 50 kbar and 100 to 1400°C (H2O) and 100 to 1600°C (CO2). This extension has been designed to: (a) compensate for the tendency of the MRK equation to overestimate volumes at high pressures, and (b) accommodate the volume behaviour of coexisting gas and liquid phases along the saturation curve. The equation developed for CO2 may be used to derive volumes and fugacities of CO, H2, CH4, N2, O2 and other gases which conform to the corresponding states principle. For H2O the measured volumes of Burnham et al. are significantly higher in the range 4 10 kbar than those presented by other workers. For CO2 the volume behaviour at high pressures derived from published MRK equations are very different (larger volumes, steeper ( ?P/ ?T)V, and hence larger fugacities) from the virial-type equations of Saxena and Fei. Our CORK equation for CO2 yields fugacities which are in closer agreement with the available high pressure experimental decarbonation reactions.

Holland, Tim; Powell, Roger

1991-12-01

110

A fugacity based continuous and dynamic fate and transport model for river networks and its application to Altamaha River  

Microsoft Academic Search

In this paper, a continuous and dynamic fugacity-based contaminant fate and transport model is developed. The dynamic interactions among all phases in the physical domain are addressed through the use of the fugacity approach instead of the use of concentration as the unknown variable. The full form of Saint Venant equations is used in order to solve for the hydrodynamic

Sinem Gokgoz Kilic; Mustafa M. Aral

2009-01-01

111

Utilizing Polymer-Coated Vials to Illustrate the Fugacity and Bioavailability of Chlorinated Pesticide Residues in Contaminated Soils  

ERIC Educational Resources Information Center

Fugacity and bioavailability can be used to facilitate students' understanding of potential environmental risks associated with toxic chemicals and, therefore, should be incorporated in environmental chemistry and science laboratories. Although the concept of concentration is easy to grasp, fugacity and bioavailability can be challenging…

Andrade, Natasha A.; McConnell, Laura L.; Torrents, Alba; Hapeman, Cathleen J.

2013-01-01

112

Comparative oxygen barometry in granulites, Bamble sector, SE Norway  

SciTech Connect

Oxygen fugacities have been estimated for the high-grade portion of the Bamble granulite facies terrane, SE Norway, using both titaniferous magnetite-ilmenite and orthopyroxene-titaniferous magnetite-quartz oxygen barometers. The two oxygen barometers show good agreement, for samples indicating high titaniferous magnetite-ilmenite temperatures whereas agreement is poor for low-temperature samples. Oxygen fugacities estimated from titaniferous magnetite-ilmenite are considerably lower than those estimated from orthopyroxene-titaniferous magnetite-quartz. This discrepancy increases with a decrease in temperature, which appears to reflect preferential resetting of the hematite content in the ilmenite grains, without much alteration of the more numerous titaniferous magnetite or orthopyroxene grains. The mean temperature for non-reset samples, 795 {plus minus} 60C (1{sigma}), agrees well with temperatures obtained from garnet-orthopyroxene K{sub D} exchange thermometry in the same region, 785 {plus minus} 60C (1{sigma}). The non-reset oxygen fugacities also agree well with an independent study of the Bamble granulites by Cameron. The QUIlP equilibrium (Quartz-Ulvospinel-Ilmenite-Pyroxene) is used to project self-consistent equilibrium temperatures and oxygen fugacities for samples reset due to hematite loss from the ilmenite grains. These projected temperatures and oxygen fugacities agree reasonably well with non-reset samples. The mean projected temperature is 830 {plus minus} 40C (1{sigma}). This agreement strongly supports the conclusion that low titaniferous magnetite-ilmenite temperatures (down to 485C) and accompanying low-oxygen fugacities are the result of hematite loss from the ilmenite grains at some time after granulite-facies metamorphism.

Harlov, D.E. (Purdue Univ., West Lafayette, IN (United States))

1992-07-01

113

Application of a fugacity model for assessing chemical fate in ecodistricts of southern Ontario  

Microsoft Academic Search

A fugacity model that was developed to assess the chemical fate of organic chemicals in regions of Canada has been incorporated into the RAISON (Regional Analysis by Intelligent Systems ON a microcomputer) expert system and has been modified and applied to ecodistricts of southern Ontario, Canada. The model is used to estimate a selected chemical's distribution between four bulk compartments

W. G. Booty; I. W. S. Wong

1996-01-01

114

Fugacity based modeling for pollutant fate and transport during floods. Preliminary results  

Microsoft Academic Search

Fugacity based modeling for pollutant fate and transport during floods. Preliminary results Miranda Deda, Mattia Fiorini, Marco Massabò, Roberto Rudari One of the concerns that arises during floods is whether the wide-spreading of chemical contamination is associated with the flooding. Many potential sources of toxics releases during floods exists in cities or rural area; hydrocarbons fuel storage system, distribution facilities,

M. Deda; M. Fiorini; M. Massabo; R. Rudari

2010-01-01

115

Use of Physicochemical Parameters to Assess the Environmental Fate of Organic Pollutants: The Fugacity Model  

ERIC Educational Resources Information Center

The environmental fate and behavior of different organic pollutants based on the qualitative analysis of thermodynamic and kinetic data is presented. The Fugacity model allows the use of different partition constants in an easy way, to determine the distribution of chemical between different phases in equilibrium of an environmental system.

Domenech, Xavier; Ayllon, Jose Antonio; Peral, Jose

2006-01-01

116

Computation of decompression schedules for single inert gas-oxygen dives using a hand-held programmable calculator.  

PubMed

An algorithm for on-site computation with a hand-held programmable calculator (TI-59, Texas Instruments) of single inert-gas decompression schedules is described. This program is based on Workman's 'M-value' method. It can compute decompression schedules with changes in the oxygen content of the breathing mixture and extension of stay at any decompression stop. The features of the program that enable calculation of atypical dive profiles, along with the portability of small calculators, would make such an algorithm suitable for on-site applications. However, since dive profiles generated by the program have not yet been tested, divers are warned not to generate schedules until their safety has been established by field tests. PMID:6257447

Ranade, A; Peterson, R E

1980-08-01

117

Workshop on Oxygen in the Terrestrial Planets  

NASA Technical Reports Server (NTRS)

This volume contains abstracts that have been accepted for presentation at the Workshop on Oxygen in the Terrestrial Planets, July 20-23,2004, Santa Fe, New Mexico. The contents include: 1) Experimental Constraints on Oxygen and Other Light Element Partitioning During Planetary Core Formation; 2) In Situ Determination of Fe(3+)/SigmaFe of Spinels by Electron Microprobe: An Evaluation of the Flank Method; 3) The Effect of Oxygen Fugacity on Large-Strain Deformation and Recrystallization of Olivine; 4) Plagioclase-Liquid Trace Element Oxygen Barometry and Oxygen Behaviour in Closed and Open System Magmatic Processes; 5) Core Formation in the Earth: Constraints from Ni and Co; 6) Oxygen Isotopic Compositions of the Terrestrial Planets; 7) The Effect of Oxygen Fugacity on Electrical Conduction of Olivine and Implications for Earth s Mantle; 8) Redox Chemical Diffusion in Silicate Melts: The Impact of the Semiconductor Condition; 9) Ultra-High Temperature Effects in Earth s Magma Ocean: Pt and W Partitioning; 10) Terrestrial Oxygen and Hydrogen Isotope Variations: Primordial Values, Systematics, Subsolidus Effects, Planetary Comparisons, and the Role of Water; 11) Redox State of the Moon s Interior; 12) How did the Terrestrial Planets Acquire Their Water?; 13) Molecular Oxygen Mixing Ratio and Its Seasonal Variability in the Martian Atmosphere; 14) Exchange Between the Atmosphere and the Regolith of Mars: Discussion of Oxygen and Sulfur Isotope Evidence; 15) Oxygen and Hydrogen Isotope Systematics of Atmospheric Water Vapor and Meteoric Waters: Evidence from North Texas; 16) Implications of Isotopic and Redox Heterogeneities in Silicate Reservoirs on Mars; 17) Oxygen Isotopic Variation of the Terrestrial Planets; 18) Redox Exchanges in Hydrous Magma; 19) Hydrothermal Systems on Terrestrial Planets: Lessons from Earth; 20) Oxygen in Martian Meteorites: A Review of Results from Mineral Equilibria Oxybarometers; 21) Non-Linear Fractionation of Oxygen Isotopes Implanted in Lunar Metal Grains: Solar, Lunar or Terrestrial Origin? 22) Isotopic Zoning in the Inner Solar System; 23) Redox Conditions on Small Bodies; 24) Determining the Oxygen Fugacity of Lunar Pyroclastic Glasses Using Vanadium Valence - An Update; 25) Mantle Redox Evolution and the Rise of Atmospheric O2; 26) Variation of Kd for Fe-Mg Exchange Between Olivine and Melt for Compositions Ranging from Alkaline Basalt to Rhyolite; 27) Determining the Partial Pressure of Oxygen (PO,) in Solutions on Mars; 28) The Influence of Oxygen Environment on Kinetic Properties of Silicate Rocks and Minerals; 29) Redox Evolution of Magmatic Systems; 30) The Constancy of Upper Mantlefo, Through Time Inferred from V/Sc Ratios in Basalts: Implications for the Rise in Atmospheric 0 2; 31) Nitrogen Solubility in Basaltic Melt. Effects of Oxygen Fugacity, Melt Composition and Gas Speciation; 32) Oxygen Isotope Anomalies in the Atmospheres of Earth and Mars; 33) The Effect of Oxygen Fugacity on Interdiffusion of Iron and Magnesium in Magnesiowiistite 34) The Calibration of the Pyroxene Eu-Oxybarometer for the Martian Meteorites; 35) The Europium Oxybarometer: Power and Pitfalls; 36) Oxygen Fugacity of the Martian Mantle from PigeoniteMelt Partitioning of Samarium, Europium and Gadolinium; 37) Oxidation-Reduction Processes on the Moon: Experimental Verification of Graphite Oxidation in the Apollo 17 Orange Glasses; 38) Oxygen and Core Formation in the Earth; 39) Geologic Record of the Atmospheric Sulfur Chemistry Before the Oxygenation of the Early Earth s Atmosphere; 40) Comparative Planetary Mineralogy: V/(CrCAl) Systematics in Chromite as an Indicator of Relative Oxygen Fugacity; 41) How Well do Sulfur Isotopes Constrain Oxygen Abundance in the Ancient Atmospheres? 42) Experimental Constraints on the Oxygen Isotope (O-18/ O-16) Fractionation in the Ice vapor and Adsorbant vapor Systems of CO2 at Conditions Relevant to the Surface of Mars; 43) Micro-XANES Measurements on Experimental Spinels andhe Oxidation State of Vanadium in Spinel-Melt Pairs; 44) Testing the Magma Ocean Hypothesis Using

2004-01-01

118

Density functional theory based first-principle calculation of Nb-doped anatase TiO2 and its interactions with oxygen vacancies and interstitial oxygen.  

PubMed

The structure and electronic properties of Nb-doped anatase (TNO) were studied from first principles using the density functional theory based band structure method. Four independent types of unit cells were studied; i.e., pure anatase, anatase with Nb dopant at Ti sites (Nb(Ti)), and cells with either interstitial oxygen (O(i)) or oxygen vacancies (V(O)). In addition, a unit cell with a Nb(Ti) and O(i), and a cell with Nb(Ti) and V(O) were investigated to clarify the role of nonstoichiometry in TNO. From the calculated results, the importance of the adjacent Nb(Ti)-V(O) and Nb(Ti)-O(i) structures was pointed out, and the experimental observation of the relationship between nonstoichiometry and electronic conductivity was rationalized. The shape of the impurity states found in these structures was used to comprehend the experimental observation of carrier concentration and the charge state of Nb dopant. The changes in lattice constants supported the existence of these structures as well. On the contrary, the cell with a simple Nb(Ti) did not show significant changes in structure and electronic properties, other than the emission of an electron in the conduction band. A stabilization of the impurity state was observed in the adjacent Nb(Ti)-V(O) structure compared to the V(O). The possibility of an essential role of this state in electric conduction was discussed. The formation of the adjacent Nb(Ti)-O(i) structure by O(2) gas annealing was discussed using statistical mechanics. The Gibbs free energies were calculated for O(i) atoms in TNO and compared to that of O(2) molecules in the gas phase. The analysis was qualitatively consistent with experimental behavior under the assumption of the Nb(Ti)-V(O) structures. PMID:19624216

Kamisaka, Hideyuki; Hitosugi, Taro; Suenaga, Takahiro; Hasegawa, Tetsuya; Yamashita, Koichi

2009-07-21

119

Oxygen Fugacity of the Martian Mantle From Pyroxene/Melt Partitioning of REE  

NASA Technical Reports Server (NTRS)

This study is part of an ongoing effort to calibrate the pyroxene/melt REE oxybarometer for conditions relevant to the martian meteorites. Redox variations have been reported among the shergottites. Wadhwa used the Eu and Gd augite/melt partitioning experiments of McKay, designed for the LEW86010 angrite, to infer a range of fo2 for the shergottites. Others inferred fo2 using equilibria between Fe-Ti oxides. There is fairly good agreement between the Fe-Ti oxide determinations and the estimates from Eu anomalies in terms of which meteorites are more or less oxidized. The Eu anomaly technique and the Fe-Ti oxide technique both essentially show the same trend, with Shergotty and Zagami being the most oxidized and QUE94201 and DaG 476 being the most reduced. Thus, the variation in fo2 appears to be both real and substantive. However, although the redox trends indicated by the two techniques are similar, there is as much as two log unit offset between the results of three researchers. One explanation for this offset is that the Eu calibration used for the shergottites was actually designed for the LEW86010 angrite, a silica-undersaturated basalt whose pyroxene (diopside) compositions are rather extreme. To correct this, experiments have been conducted on the redox relationship of Eu partitioning relative to Sm and Gd for pyroxene/melt compositions more relevant to Martian meteorites. We report here preliminary results for experiments on pigeonite/melt partitioning as a function of fO2.

Musselwhite, D. S.; Jones, J. H.

2003-01-01

120

Oxygen Fugacity of the Martian Mantle from Pigeonite/Melt Partitioning of Samarium, Europium and Gadolinium  

NASA Technical Reports Server (NTRS)

This study is part of an ongoing effort to calibrate the pyroxene/melt Eu oxybarometer for conditions relevant to the martian meteorites. There is fairly good agreement between a determinations using equilibria between Fe-Ti oxides and the estimates from Eu anomalies in shergottite augites in tenns of which meteorites are more or less oxidized. The Eu calibration was for angrite composition pyroxenes which are rather extreme. However, application of a calibration for martian composition augites 113 does not significantly reduce the discrepancy between the two methods. One possible reason for this discrepancy is that augites are non-liquidus. The use of pigeonite rather than augite as the oxy-barometer phase is considered. We have conducted experiments on martian composition pigeonite/melt REE partitioning as a function of fO2.

Musselwhite, S.; Jones, J. H.; Shearer, C.

2004-01-01

121

Oxygen Fugacity of the Martian Mantle from Pigeonite/Melt Partitioning of Samarium, Europium and Gadolinium  

NASA Technical Reports Server (NTRS)

This study is part of an ongoing effort to calibrate the pyroxene/melt REE oxybarometer for conditions relevant to the martian meteorites. These efforts have been motivated by reports of redox variations among the shergottites . We have conducted experiments on martian composition pigeonite/melt rare earth element partitioning as a function of fO2.

Musselwhite, D. S.; Jnes, J. H.; Shearer, C.

2004-01-01

122

Metal–silicate partitioning and constraints on core composition and oxygen fugacity during Earth accretion  

Microsoft Academic Search

We present the results of new partitioning experiments between metal and silicate melts for a series of elements normally regarded as refractory lithophile and moderately siderophile and volatile. These include Si, Ti, Ni, Cr, Mn, Ga, Nb, Ta, Cu and Zn. Our new data obtained at 3.6 and 7.7GPa and between 2123 and 2473K are combined with literature data to

Alexandre Corgne; Shantanu Keshav; Bernard J. Wood; William F. McDonough; Yingwei Fei

2008-01-01

123

Electrical conductivity in oxygen-deficient phases of tantalum pentoxide from first-principles calculations  

NASA Astrophysics Data System (ADS)

We apply first-principles density-functional theory (DFT) calculations, ab-initio molecular dynamics, and the Kubo-Greenwood formula to predict electrical conductivity in Ta2Ox (0 ? x ? 5) as a function of composition, phase, and temperature, where additional focus is given to various oxidation states of the O monovacancy (VOn; n = 0,1+,2+). In the crystalline phase, our DFT calculations suggest that VO0 prefers equatorial O sites, while VO1+ and VO2+ are energetically preferred in the O cap sites of TaO7 polyhedra. Our calculations of DC conductivity at 300 K agree well with experimental measurements taken on Ta2Ox thin films (0.18 ? x ? 4.72) and bulk Ta2O5 powder-sintered pellets, although simulation accuracy can be improved for the most insulating, stoichiometric compositions. Our conductivity calculations and further interrogation of the O-deficient Ta2O5 electronic structure provide further theoretical basis to substantiate VO0 as a donor dopant in Ta2O5. Furthermore, this dopant-like behavior is specific to the neutral case and not observed in either the 1+ or 2+ oxidation states, which suggests that reduction and oxidation reactions may effectively act as donor activation and deactivation mechanisms, respectively, for VOn in Ta2O5.

Bondi, Robert J.; Desjarlais, Michael P.; Thompson, Aidan P.; Brennecka, Geoff L.; Marinella, Matthew J.

2013-11-01

124

Impact of tensile strain on the oxygen vacancy migration in SrTiO3: Density functional theory calculations  

NASA Astrophysics Data System (ADS)

Strontium titanate is a promising dielectric material for device applications including capacitors and gate dielectrics. However, oxygen vacancies, which are inevitable donor defects mobile under bias at room temperature, lead to undesirable leakage current in SrTiO3 thin films. Epitaxially grown SrTiO3 on lattice mismatched substrates leads to strained SrTiO3, inducing structural phase transitions from a cubosymmetric non-ferroelectric geometry to tetragonal and orthorhombic structures, depending upon the sign of the strain. In this study, density functional calculations have been performed to determine the impact of isotropic biaxial tensile strain in a (001) plane upon the phase of SrTiO3 and the activation energy for the migration of oxygen vacancies in such strained SrTiO3. The phase transition of the host material yields anisotropy in oxygen vacancy diffusion for diffusion within and between planes parallel to the strain. We found a general reduction in the barrier for diffusion within and normal to the plane of tensile strain. The inter-plane diffusion barrier reduces up to 25% at high values of strain. The variation in the barrier corresponding to in-plane diffusion is smaller in comparison to inter-plane diffusion. Finally, we reflect upon how the interplay between lattice strain with native defects plays a crucial role in the conduction mechanism of thin film, strained SrTiO3.

AL-Hamadany, Raied; Goss, J. P.; Briddon, P. R.; Mojarad, Shahin A.; O'Neill, A. G.; Rayson, M. J.

2013-06-01

125

Differing effects of water fugacity deformation of quartzites and milky quartz single crystals  

NASA Astrophysics Data System (ADS)

Previous studies of quartzite deformation by dislocation creep have documented a strong dependence of mechanical properties on pressure, which has been interpreted as a relationship between strain rate and water fugacity (Kronenberg and Tullis, 1984; Kohlstedt et al., 1995; Chernak et al. 2009). However, natural milky quartz single crystals deformed by basal slip can be water-weakened over a wide range of pressure (and water fugacities), with strengths that appear to depend on total water content at a fixed water fugacity. The difference of behavior between these two is perplexing since infrared spectra collected from quartzites and milky quartz single crystals indicate that they have the same forms of intragranular water and microstructures indicate the same slip system is activated. The only difference between these materials is that quartzites include populations of grains of all orientations, separated by grain boundaries. In order to resolve this discrepancy we have performed deformation experiments on a natural quartzite (Black Hills quartzite) and natural milky quartz single crystals oriented for easy slip on the basal slip system at identical conditions (800°C, strain rate = 10-6/s) with no added water. During each experiment cores of each material, which have a fixed water content, were subjected to pressure stepping; an initial deformation step was performed at 1.5 GPa, then the sample was unloaded and one or more deformation steps were performed at lower pressures (as low as 0.6 GPa) prior to returning to 1.5 GPa for a final deformation step. The strength of quartzite increases dramatically at lower pressure and lower water fugacity, but strength decreases again returning to high pressure during the final deformation step. The strength of milky quartz single crystals increases as well, but by far less than observed for quartzites. The water fugacity exponents (m) of the quartzite and single crystals are 1.9 and 0.8, respectively, (assuming power law creep with n=4). The exponent for Black Hills quartzite is consistent with previous studies for quartzites, while the exponent (m nearly 1.0) for single crystals is more readily understood in terms of point defects and their influence on deformation. Microstructures in the quartzites include wavy grain boundaries and undulatory extinction, indicating deformation by climb-accommodated dislocation creep and the onset of bulge recrystallization. Microstructures observed in the single crystals include deformation bands perpendicular to elongate zones of undulatory extinction, with no recrystallization, indicating deformation by climb-accommodated dislocation creep. These results indicate that much of the effect of increasing water fugacity on quartzite rheology is due to enhanced recovery near grain boundaries facilitated by grain boundary migration.

Holyoke, C. W.; Kronenberg, A. K.

2010-12-01

126

Many-body GW calculation of the oxygen vacancy in ZnO  

SciTech Connect

Density-functional theory (DFT) calculations of defect levels in semiconductors based on approximate functionals are subject to considerable uncertainties, in particular due to inaccurate band-gap energies. Testing previous correction methods by many-body GW calculations for the O vacancy in ZnO, we find that: (i) The GW quasiparticle shifts of the V{sub O} defect states increase the spitting between occupied and unoccupied states due to self-interaction correction, and do not reflect the conduction- versus valence-band character. (ii) The GW quasiparticle energies of charged defect states require important corrections for supercell finite-size effects. (iii) The GW results are robust with respect to the choice of the underlying DFT or hybrid-DFT functional, and the (2+/0) donor transition lies below midgap, close to our previous prediction employing rigid band-edge shifts.

Lany, Stephan; Zunger, Alex

2010-01-01

127

Effect of oxygen on single-wall silicon carbide nanotubes studied by first-principles calculations  

Microsoft Academic Search

According to the predictions of first-principles calculations, single-wall silicon carbide nanotubes exhibit several unusual properties: they are semiconducting independently of their chirality, superior material for hydrogen storage, and have strong nonlinear optical coefficients. Nevertheless, only a single experiment indicates, in our knowledge, that a tubular form of silicon carbide (SiC) exists. It is known that the surface of bulk silicon

Á. Szabó; A. Gali

2009-01-01

128

Gamow shell-model calculations of drip-line oxygen isotopes  

SciTech Connect

We employ the Gamow shell model (GSM) to describe low-lying states of the oxygen isotopes {sup 24}O and {sup 25}O. The many-body Schroedinger equation is solved starting from a two-body Hamiltonian defined by a renormalized low-momentum nucleon-nucleon (NN) interaction and a spherical Berggren basis. The Berggren basis treats bound, resonant, and continuum states on an equal footing and is therefore an appropriate representation of loosely bound and unbound nuclear states near threshold. We show that the inclusion of continuum effects has a significant effect on the low-lying 1{sup +} and 2{sup +} excited states in {sup 24}O. On the other hand, we find that a correct description of binding energy systematics of the ground states is driven by the proper treatment and inclusion of many-body correlation effects. This is supported by the fact that we get {sup 25}O unstable with respect to {sup 24}O in both oscillator and Berggren representations starting from a {sup 22}O core. Furthermore, we show that the structure of these loosely bound or unbound isotopes is strongly influenced by the {sup 1}S{sub 0} component of the NN interaction. This has important consequences for our understanding of nuclear stability.

Tsukiyama, K. [Department of Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo (Japan); Hjorth-Jensen, M. [Department of Physics and Center of Mathematics for Applications, University of Oslo, N-0316 Oslo (Norway); Hagen, G. [Physics Division, Oak Ridge National Laboratory, P. O. Box 2008, Oak Ridge, Tennessee 37831 (United States)

2009-11-15

129

Gamow Shell-Model Calculations of Drip-Line Oxygen Isotopes  

SciTech Connect

We employ the Gamow shell model (GSM) to describe low-lying states of the oxygen isotopes ^{24}O and ^{25}O. The many-body Schroedinger equation is solved starting from a two-body Hamiltonian defined by a renormalized low-momentum nucleon-nucleon (NN) interaction and a spherical Berggren basis. The Berggren basis treats bound, resonant, and continuum states on an equal footing and is therefore an appropriate representation of loosely bound and unbound nuclear states near threshold. We show that such a basis is necessary in order to obtain a detailed and correct description of the low-lying 1^{+} and 2^{+} excited states in ^{24}O. On the other hand, we find that a correct description of binding energy systematics of the ground states is driven by proper treatment and inclusion of many-body correlation effects. This is supported by the fact that we get ^{25}O unstable with respect to ^{24}O in both oscillator and Berggren representations starting from a ^{22}O core. Furthermore, we show that the structure of these loosely bound or unbound isotopes is strongly influenced by the ^{1}S_{0} component of the NN interaction. This has important consequences for our understanding of nuclear stability.

Tsukiyama, K. [University of Tokyo, Tokyo, Japan; Hjorth-Jensen, M. [University of Oslo, Norway; Hagen, Gaute [ORNL

2009-01-01

130

Calculator.  

ERIC Educational Resources Information Center

Five activities are presented in this student workbook on using the electronic calculator. Following the directions for using the machine, problems are given on multiplying and dividing, finding percentages, calculating the area of assorted polygons, changing fractions to decimals, and finding squares and square roots. (JH)

Parma City School District, OH.

131

Hydrogen component fugacity in binary mixtures with carbon monoxide: Temperature dependence  

NASA Astrophysics Data System (ADS)

The fugacity coefficients of hydrogen in binary mixtures with carbon monoxide were measured using a physical equilibrium technique. This technique involves the use of an experimental chamber which is divided into two regions by a semipermeable membrane through which hydrogen, but not carbon monoxide, can penetrate. Measurement of the gas pressures inside and outside of the membrane allows a direct measurement of the hydrogen component fugacity at a given temperature and binary mixture mole fraction. In this paper, results are reported at 130, 160, and 190°C. In each case, the total pressure of the mixture was maintained at a nominal value of 3.39 MPa. The general qualitative features of the data are discussed, and comparisons are made with predictions obtained from the Redlich-Kwong, Peng-Robinson-Soave, and extended corresponding-state models.

Bruno, T. J.; Schroeder, J. A.

1988-07-01

132

Hydrogen component fugacity coefficients in binary mixtures with ethane: Pressure dependence  

NASA Astrophysics Data System (ADS)

The fugacity coefficients of hydrogen in binary mixtures with ethane were measured. Data were taken using an experimental chamber which is divided into two regions by a semipermeable membrane through which hydrogen, but not ethane, can penetrate. The measurement of the gas pressures inside and outside the membrane gives the hydrogen component fugacity at a given temperature, binary mixture mole fraction, and mixture pressure. In this paper, results are reported at mixture pressures of 5.25, 6.97, 10.21, and 13.47 MPa. In each case, the temperature of the mixture was maintained at an average value of 130°C (403.15 K). The general qualitative features of the data are discussed, and comparisons are made with predictions obtained from the Redlich-Kwong and Peng-Robinson equations of state.

Bruno, T. J.; Schroeder, J. A.; Outcalt, S. L.

1990-09-01

133

Hydrogen-component fugacity coefficients in binary mixtures with isobutane: temperature dependence  

NASA Astrophysics Data System (ADS)

The fugacity coefficients of hydrogen in binary mixtures with isobutane were measured using a physical equilibrium technique. This technique involves the use of an experimental chamber which is divided into two regions by a semipermeable membrane through which hydrogen, but not isobutane, can penetrate. Measurement of the gas pressures inside and outside the membrane allow a direct measurement of the hydrogen component fugacity at a given temperature, binary mixture mole fraction, and mixture pressure. In this paper, results are reported at 120, 140, 160, and 180°C. In each case, the total pressure of the mixture was maintained at an average value of 3.40 MPa. The general qualitative features of the data are discussed, and comparisions are made with predictions obtained from the Redlich-Kwong and the Peng-Robinson equations of state.

Bruno, T. J.; Outcalt, S. L.

1990-01-01

134

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

NASA Technical Reports Server (NTRS)

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

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

1973-01-01

135

An oxygen barometer for rutile–ilmenite assemblages: oxidation state of metasomatic agents in the mantle  

Microsoft Academic Search

Oxygen fugacity has been calculated for rutile–ilmenite assemblages from the reaction 2Fe2O3 (in ilmenite) + 4TiO2 (rutile) = 4FeTiO3 (in ilmenite) + O2. The equation logfO2=22.59?25925\\/T?3.09logT+0.0016535P+48.836P\\/T?4logaIlmFeTiO3+2logaIlmFe2O3+4logaRutTiO2, where T is in kelvin and P is in kbar, was derived from available thermodynamic data. The hypothetical end-member rutile–ilmenite reaction is located between the magnetite–hematite and Ni–NiO (NNO) buffers. The rutile–ilmenite oxygen barometer

Donggao Zhao; Eric J Essene; Youxue Zhang

1999-01-01

136

Electrochemical measurements and thermodynamic calculations of redox equilibria in pallasite meteorites - Implications for the eucrite parent body  

NASA Astrophysics Data System (ADS)

The intrinsic oxygen fugacity (IOF) of olivine separates from the Salta, Springwater, and Eagle Station pallasites was measured between 850 and 1150 C using oxygen-specific solid zirconia electrolytes at 100,000 Pa. Thermodynamic calculations of redox equilibria involving equalibrium pallasite assemblages are in good agreement with the experimental results and provide a lower limit to pallasite redox stability; others involving disequilibrium assemblages, suggest that pallasites experienced localized, late-stage oxidation and reduction effects. Consideration of the redox buffer metal-olivine-orthopyroxene utilizing calculated Eucrite Parent Body (EPB) mantle phase compositions indicates that small redox gradients may have existed in the EPB. Such gradients may have produced strong compositional variation within the EPB. In addition, there is apparently significant redox heterogeneity in the source area of Eagle Station Trio pallasites and Bocaiuva iron meteorites.

Righter, K.; Arculus, R. J.; Delano, J. W.; Paslick, C.

1990-06-01

137

Electrochemical measurements and thermodynamic calculations of redox equilibria in pallasite meteorites - Implications for the eucrite parent body  

NASA Technical Reports Server (NTRS)

The intrinsic oxygen fugacity (IOF) of olivine separates from the Salta, Springwater, and Eagle Station pallasites was measured between 850 and 1150 C using oxygen-specific solid zirconia electrolytes at 100,000 Pa. Thermodynamic calculations of redox equilibria involving equalibrium pallasite assemblages are in good agreement with the experimental results and provide a lower limit to pallasite redox stability; others involving disequilibrium assemblages, suggest that pallasites experienced localized, late-stage oxidation and reduction effects. Consideration of the redox buffer metal-olivine-orthopyroxene utilizing calculated Eucrite Parent Body (EPB) mantle phase compositions indicates that small redox gradients may have existed in the EPB. Such gradients may have produced strong compositional variation within the EPB. In addition, there is apparently significant redox heterogeneity in the source area of Eagle Station Trio pallasites and Bocaiuva iron meteorites.

Righter, Kevin; Arculus, Richard J.; Paslick, Cassi; Delano, John W.

1990-01-01

138

Fugacity based modeling for pollutant fate and transport during floods. Preliminary results  

NASA Astrophysics Data System (ADS)

Fugacity based modeling for pollutant fate and transport during floods. Preliminary results Miranda Deda, Mattia Fiorini, Marco Massabò, Roberto Rudari One of the concerns that arises during floods is whether the wide-spreading of chemical contamination is associated with the flooding. Many potential sources of toxics releases during floods exists in cities or rural area; hydrocarbons fuel storage system, distribution facilities, commercial chemical storage, sewerage system are only few examples. When inundated homes and vehicles can also be source of toxics contaminants such as gasoline/diesel, detergents and sewage. Hazardous substances released into the environment are transported and dispersed in complex environmental systems that include air, plant, soil, water and sediment. Effective environmental models demand holistic modelling of the transport and transformation of the materials in the multimedia arena. Among these models, fugacity-based models are distribution based models incorporating all environmental compartments and are based on steady-state fluxes of pollutants across compartment interfaces (Mackay "Multimedia Environmental Models" 2001). They satisfy the primary objective of environmental chemistry which is to forecast the concentrations of pollutants in the environments with respect to space and time variables. Multimedia fugacity based-models has been used to assess contaminant distribution at very different spatial and temporal scales. The applications range from contaminant leaching to groundwater, runoff to surface water, partitioning in lakes and streams, distribution at regional and even global scale. We developped a two-dimensional fugacity based model for fate and transport of chemicals during floods. The model has three modules: the first module estimates toxins emission rates during floods; the second modules is the hydrodynamic model that simulates the water flood and the third module simulate the dynamic distribution of chemicals in the domain during and after the flood. The chemical emissions rate are estimated based on land use and population for three different classes of contaminants; the classes are representative of contaminants released from agricultural sources, sewage disposal and industrial/commercial emissions. The module for source estimation provides the spatial distribution of the potential emissions rates in the area. Emission rates are forcing input for the third simulation module whenever the pertinent area is inundated. The second module simulates the flood dynamics by using a parabolic approximation of the two dimensional shallow water equation. The model is properly developed in order to utilize simplified initial and boundary conditions, such as flooding points and flooding voulmes or satellite derived DTMs and land use . Thanks to its computational efficiency it is possible to run several simulations in order to adjust initial and boundary conditions, which are partly unknown, to satellite delineation of the flooded areas which are used as constrain for the 2D dynamic simulation. In this way the result is a dynamically consistent flooded map enriched with important information about hydraulic forcing parameters (i.e. hydraulic depths, flow velocities at every temporal step). The third module simulates the two-dimensional spatial distribution of pollutants concentration in all the environmental media. The mass balance equation for the chemicals is here derived in term of chemical fugacity instead the classical molar concentration. The advatage of the fugacity instead of concentration is that, since fugacity is continuous among phase interfaces and concentration is not, it renders the analysis of contaminat transfer between the phases easier. The two dimensional - depth averaged- mass balance equation is solved numerically by a finite volume tecnique over a rectangular regular grid. The model has been applied to the inundation of SHKODRA region in Albania during the January- February 2010. This inundation was produced by two rivers: DRINI and BUNA. The flooded

Deda, M.; Fiorini, M.; Massabo, M.; Rudari, R.

2010-09-01

139

Predicting PCB concentrations in cow milk: validation of a fugacity model in high-mountain pasture conditions.  

PubMed

A fugacity model reported in the literature was applied to a high-altitude pasture in the Italian Alps. The model takes into account three compartments (digestive tract, blood and fat tissues) in unsteady-state conditions using food as the contamination source. Disregarding biotransformation inside cow tissues, the predicted concentrations of 14 polychlorinated biphenyls (PCBs) in milk were in good agreement with the observed data, especially for congeners known for their resistance to biotransformation (e.g., CB-138 and 153). In contrast, the predicted concentrations were clearly overestimated for congeners with high biotransformation susceptibilities. Therefore data measured in milk and faeces were used to calculate the first-order-biotransformation rate constants in dairy cows. The PCB absorption efficiency observed for pasture conditions was lower than that observed in the cowshed. The final version of the model included biotransformation and observed PCB absorption and was able to predict PCB concentrations in cow milk with mean differences between the predicted and measured data below ±20% for most congeners. PMID:24802270

Tremolada, Paolo; Guazzoni, Niccolò; Parolini, Marco; Rossaro, Bruno; Bignazzi, Marta Maria; Binelli, Andrea

2014-07-15

140

Simulation of the Fate and Seasonal Variations of ?-Hexachlorocyclohexane in Lake Chaohu Using a Dynamic Fugacity Model  

PubMed Central

Fate and seasonal variations of ?-hexachlorocyclohexane (?-HCH) were simulated using a dynamic fugacity model in Lake Chaohu, China. Sensitivity analyses were performed to identify influential parameters and Monte Carlo simulation was conducted to assess model uncertainty. The calculated and measured values of the model were in good agreement except for suspended solids, which might be due to disregarding the plankton in water. The major source of ?-HCH was an input from atmospheric advection, while the major environmental outputs were atmospheric advection and sediment degradation. The net annual input and output of ?-HCH were approximately 0.294?t and 0.412?t, respectively. Sediment was an important sink for ?-HCH. Seasonal patterns in various media were successfully modeled and factors leading to this seasonality were discussed. Sensitivity analysis found that parameters of source and degradation were more important than the other parameters. The sediment was influenced more by various parameters than air and water were. Temperature variation had a greater impact on the dynamics of the model output than other dynamic parameters. Uncertainty analysis showed that the model uncertainty was relatively low but significantly increased in the second half of the simulation period due to the increase in the gas-water diffusion flux variability.

Kong, Xiang-zhen; He, Wei; Qin, Ning; He, Qi-Shuang; Yang, Bin; Ouyang, Huiling; Wang, Qingmei; Yang, Chen; Jiang, Yujiao; Xu, Fuliu

2012-01-01

141

Olivine-Pyroxene-PtFe alloy as an oxygen geobarometer  

SciTech Connect

An equilibrium assemblage of olivine, Ca-free pyroxene, and PtFe alloy can be used to calculate oxygen fugacity at a known temperature and pressure. This oxygen geobarometer has been tested T = 1,300-1,450C, P = 1 bar and 10 kbar. The calculated log fO{sub 2} may be compared with that determined by the CO{sub 2}-H{sub 2} mixture used to control the furnace atmosphere in the 1 bar experiments and, in the case of the 10 kbar experiments, the log fO{sub 2} determined from the graphite-fluid equilibrium. The average deviation of the calculated log fO{sub 2} determined from the graphite-fluid equilibrium. The average deviation of the calculated log fO{sub 2} and that determined by other means is 0.2; the maximum absolute difference is 0.4. The distribution coefficient (K{sub d}) for Fe and Mg between coexisting olivine and pyroxene was found to range from 1.14 at x{sub Fe{sub 2}SiO{sub 4}}{sup ol} = 0.164 to 1.54 at x{sub Fe{sub 2}SiO{sub 4}}{sup ol} = 0.655, and varies systematically with the Fe/(Fe + Mg) of the phases.

Jamieson, H.E.; Roeder, P.L.; Grant, A.H. (Queen's Univ., Kingston, Ontario (Canada))

1992-01-01

142

Using fugacity to predict volatile emissions from layered materials with a clay/polymer diffusion barrier  

NASA Astrophysics Data System (ADS)

Structural insulated panels (SIPs) have significant environmental and energy advantages. However, the tight structure that results may cause degraded indoor air quality and the potential release of volatile organic compounds (VOCs) from these layered materials must be considered. A physically based model for predicting VOC emissions from multi-layer materials is described. Fugacity is used to eliminate the concentration discontinuities at the interface between layers. This avoids an obstacle associated with numerically simulating mass transfer in composite materials. The numerical model is verified for a double-layer system by comparing predicted concentrations to those obtained with a previously published analytical model. In addition, hexanal emissions from multi-layer SIPs are simulated to demonstrate the usefulness of the fugacity approach. Finally, the multi-layer model is used to investigate the impact that clay/polyurethane nanocomposite diffusion barriers can have on VOC emissions. Indoor gas-phase concentrations can be greatly reduced with a barrier layer on the surface, thereby minimizing the environmental impact of SIPs.

Yuan, Huali; Little, John C.; Marand, Eva; Liu, Zhe

143

Screening nitrogen-rich bases and oxygen-rich acids by theoretical calculations for forming highly stable salts.  

PubMed

Nitrogen-rich heterocyclic bases and oxygen-rich acids react to produce energetic salts with potential application in the field of composite explosives and propellants. In this study, 12 salts formed by the reaction of the bases 4-amino-1,2,4-trizole (A), 1-amino-1,2,4-trizole (B), and 5-aminotetrazole (C), upon reaction with the acids HNO3 (I), HN(NO2 )2 (II), HClO4 (III), and HC(NO2 )3 (IV), are studied using DFT calculations at the B97-D/6-311++G** level of theory. For the reactions with the same base, those of HClO4 are the most exothermic and spontaneous, and the most negative ?r Gm in the formation reaction also corresponds to the highest decomposition temperature of the resulting salt. The ability of anions and cations to form hydrogen bonds decreases in the order NO3 (-) >N(NO2 )2 (-) >ClO4 (-) >C(NO2 )3 (-) , and C(+) >B(+) >A(+) . In particular, those different cation abilities are mainly due to their different conformations and charge distributions. For the salts with the same anion, the larger total hydrogen-bond energy (EH,tot ) leads to a higher melting point. The order of cations and anions on charge transfer (q), second-order perturbation energy (E2 ), and binding energy (Eb ) are the same to that of EH,tot , so larger q leads to larger E2 , Eb , and EH,tot . All salts have similar frontier orbitals distributions, and their HOMO and LUMO are derived from the anion and the cation, respectively. The molecular orbital shapes are kept as the ions form a salt. To produce energetic salts, 5-aminotetrazole and HClO4 are the preferred base and acid, respectively. PMID:24782247

Zhang, Xueli; Gong, Xuedong

2014-08-01

144

Electronic structure of {delta}-Ta{sub 2}O{sub 5} with oxygen vacancy: ab initio calculations and comparison with experiment  

SciTech Connect

Electronic structure of oxygen vacancies in Ta{sub 2}O{sub 5} have been studied theoretically by first-principles calculations and experimentally by x-ray photoelectron spectroscopy. Calculations of {delta}-Ta{sub 2}O{sub 5} were performed using density functional theory within gradient-corrected approximation with the +U approach. Results indicate that the oxygen vacancy causes a defect level in the energy gap at 1.2 eV above the top of the valence band. To produce oxygen vacancies, amorphous films of Ta{sub 2}O{sub 5} were bombarded with Ar{sup +} ions. XPS results indicate that the Ar-ion bombardment leads to the generation of the oxygen vacancies in Ta{sub 2}O{sub 5} that characterize the peak at 2 eV above the valence band. The calculated spectrum of crystalline {delta}-Ta{sub 2}O{sub 5} demonstrates qualitative correspondence with the XPS spectrum of the amorphous Ta{sub 2}O{sub 5} film after Ar-ion bombardment.

Ivanov, Maxim V.; Perevalov, Timofey V.; Aliev, Vladimir S.; Gritsenko, Vladimir A. [A. V. Rzhanov Institute of Semiconductor Physics SB RAS, Novosibirsk, 630090 (Russian Federation); Kaichev, Vasily V. [Boreskov Institute of Catalysis SB RAS, Novosibirsk, 630090 (Russian Federation)

2011-07-15

145

Evaluating the fate of organic compounds in the Cameroon environment using a level III multimedia fugacity model  

Microsoft Academic Search

A level III fugacity model was developed to evaluate the fate of chemicals in the Cameroon environment. The model required as input physical-chemical properties, mode and amount of chemical released and environmental characteristics. These were used to predict the distribution of the chemical in the environment, quantify intermedia transfer processes and the major loss mechanisms from the environmental compartments. Five

Lydia Lifongo; Erick Nfon

2009-01-01

146

Oxygen-aromatic contacts in intra-strand base pairs: Analysis of high-resolution DNA crystal structures and quantum chemical calculations.  

PubMed

Three-dimensional structures of biomolecules are stabilized by a large number of non-covalent interactions and some of them such as van der Waals, electrostatic and hydrogen bond interactions are well characterized. Delocalized ?-electron clouds of aromatic residues are known to be involved in cation-?, CH-?, OH-? and ?-? interactions. In proteins, many examples have been found in which the backbone carbonyl oxygen of one residue makes close contact with the aromatic center of aromatic residues. Quantum chemical calculations suggest that such contacts may provide stability to the protein secondary structures. In this study, we have systematically analyzed the experimentally determined high-resolution DNA crystal structures and identified 91 examples in which the aromatic center of one base is in close contact (<3.5?) with the oxygen atom of preceding (Group-I) or succeeding base (Group-II). Examples from Group-I are overwhelmingly observed and cytosine or thymine is the preferred base contributing oxygen atom in Group-I base pairs. A similar analysis of high-resolution RNA structures surprisingly did not yield many examples of oxygen-aromatic contact of similar type between bases. Ab initio quantum chemical calculations on compounds based on DNA crystal structures and model compounds show that interactions between the bases in base pairs with oxygen-aromatic contacts are energetically favorable. Decomposition of interaction energies indicates that dispersion forces are the major cause for energetically stable interaction in these base pairs. We speculate that oxygen-aromatic contacts in intra-strand base pairs in a DNA structure may have biological significance. PMID:24816369

Jain, Alok; Krishna Deepak, R N V; Sankararamakrishnan, Ramasubbu

2014-07-01

147

Ab initio Calculation of Thermodynamic Data for Oxygenated Hydrocarbon Fuels and Radial Breakdown Species: R(OMe)n  

SciTech Connect

There has long been interest in the use of oxygenated hydrocarbon additives to conventional fuels. These oxygenates have been shown to reduce soot emissions in diesel engines and CO emissions in spark-ignition engines; and often allow diesel operation with decreased NO{sub x}. The current widely used additive, MTBE is targeted for elimination as a gasoline additive due to its damaging effects on the environment. This creates a need for alternative oxygenated additives; and more importantly, amplifies the importance to fully understand the thermochemical and kinetic properties on these oxyhydrocarbons fuels and for their intermediate and radical breakdown products. We use CBS-Q and density-functional methods with isodesmic reactions (with group balance when possible) to compute thermodynamic quantities for these species. We have studied hydrocarbons with multiple substituted methoxy groups. In several cases, multioxygenated species are evaluated that may have potential use as new oxygenated fuel additives. Thermodynamic quantities (H{sub 298}{sup 0}, S{sub 298}{sup 0}, C{sub p}(T)) as well as group additivity contributions for the new oxygenated groups are reported. We also report trends in bond-energies with increasing methoxy substitution.

Kubota, A; Pitz, W J; Westbrook, C K; Bozzelli, J; Glaude, P-A

2001-03-23

148

Calculation of hydrogen and oxygen uptake in fuel rod cladding during severe accidents using the integral diffusion method -- Final Design Report  

SciTech Connect

Final designs are described for models of hydrogen and oxygen uptake in fuel rod cladding during severe accidents. Calculation of the uptake involves the modeling of seven processes: (1) diffusion of oxygen from the bulk gas into the boundary layer at the external cladding surface, (2) diffusion from the boundary layer into the oxide layer, (3) diffusion from the inner surface of the oxide layer into the metallic part of the cladding, (4) uptake of hydrogen in the event that the cladding oxide layer is dissolved in a steam-starved region, (5) embrittlement of cladding due to hydrogen uptake, (6) cracking of cladding during quenching due to its embrittlement and (7) release of hydrogen from the cladding after cracking of the cladding. An integral diffusion method is described for calculating the diffusion processes in the cladding. Experimental results are presented that show a rapid uptake of hydrogen in the event of dissolution of the oxide layer and a rapid release of hydrogen in the event of cracking of the oxide layer. These experimental results are used as a basis for calculating the rate of hydrogen uptake and the rate of hydrogen release. A description is given of the implementation of the models for hydrogen and oxygen uptake and cladding embrittlement into the programming framework of the SCDAP/RELAP5/MOD3.3 code.

Siefken, L.J.

1999-05-01

149

Calculation of Hydrogen and Oxygen Uptake in Fuel Rod Cladding During Severe Accidents Using the Integral Diffusion Method - Final Design Report  

SciTech Connect

Final designs are described for models of hydrogen and oxygen uptake in fuel rod cladding during severe accidents. Calculation of the uptake involves the modeling of seven processes: (1) diffusion of oxygen from the bulk gas into the boundary layer at the external cladding surface, (2) diffusion from the boundary layer into the oxide layer, (3) diffusion from the inner surface of the oxide layer into the metallic part of the cladding, (4) uptake of hydrogen in the event that the cladding oxide layer is dissolved in a steam-starved region, (5) embrittlement of cladding due to hydrogen uptake, (6) cracking of cladding during quenching due to its embrittlement and (7) release of hydrogen from the cladding after cracking of the cladding. An integral diffusion method is described for calculating the diffusion processes in the cladding. Experimental results are presented that show a rapid uptake of hydrogen in the event of dissolution of the oxide layer and a rapid release of hydrogen in the event of cracking of the oxide layer. These experimental results are used as a basis for calculating the rate of hydrogen uptake and the rate of hydrogen release. A description is given of the implementation of the models for hydrogen and oxygen uptake and cladding embrittlement into the programming framework of the SCDAP/RELAP5/MOD3.3 code.

Siefken, Larry James

1999-06-01

150

The Effects of Oxygen Fugacity on the Crystallization Sequence and Cr Partitioning of an Analog Y-98 Liquid  

NASA Technical Reports Server (NTRS)

Interpreting the relationship between "enriched" olivine-phyric shergottites (e.g. NWA 1068/1110) and the "enriched" pyroxene-plagioclase shergottites (e.g. Shergotty, Los Angeles) is problematic. Symes et al. [1] and Shearer et al. [2]) proposed that the basaltic magma that crystallized to produce olivine-phyric shergottite NWA 1068/1110 could produce pyroxene-plagioclase shergottites with additional fractional crystallization. However, additional observations indicate that the relationship among the enriched shergottites may be more complex [1-3]. For example, Herd [3] concluded that some portion of the olivine megacrysts in this meteorite was xenocrystic in origin, seemingly derived from more reduced basaltic liquids. This conclusion may imply that a variety of complex processes such as magma mixing, entrainment, and assimilation may play important roles in the petrologic history of these meteorites. It is therefore possible that these processes have obscured the petrogenetic linkages between the enriched olivine-phyric shergottites and the pyroxene-plagioclase shergottites. As a first order step in attempting to unravel these petrologic complexities, this study focuses upon exploring the effect of fO2 on the crystallization history for an analog primitive shergottite liquid composition (Y98). Results from this work will provide a basis for reconstructing the record of fO2 in shergottites, its effect on both mineral chemistries and valence state partitioning, and a means for examining the role of crystallization on the petrologic linkages between olivine-phyric and pyroxene-plagioclase shergottites. A companion abstract [4] explores the behavior of V over this range of fO2.

Bell, A. S.; Burger, P. V.; Le, Loan; Papike, J. J.; Jones, J.; Shearer, C. K.

2013-01-01

151

The effect of oxygen fugacity on the partitioning of Re between crystals and silicate melt during mantle melting  

Microsoft Academic Search

Interpretation of Re–Os isotopic systematics applied to mantle and mantle-derived rocks is currently hindered by the poorly understood behaviour of Re and Os during partial melting. Of particular interest is the incompatibility of Re and how it partitions between melt and the different mantle phases. Here, we study the partitioning behaviour of Re between the common upper mantle minerals (garnet,

Guilherme Mallmann; Hugh St. C. O’Neill

2007-01-01

152

Effect of Cooling Rate and Oxygen Fugacity on the Crystallization of the Queen Alexandra Range 94201 Martian Melt Composition  

NASA Technical Reports Server (NTRS)

Although many basaltic shergottites have been recently found in north African deserts, QUE94201 basaltic shergottite (QUE) is still important because of its particular mineralogical and petrological features. This meteorite is thought to represent its parent melt composition [1 -3] and to crystallize under most reduced condition in this group [1,4]. We performed experimental study by using the synthetic glass that has the same composition as the bulk of QUE. After homogenization for 48 hours at 1300 C, isothermal and cooling experiments were done under various conditions (e.g. temperature, cooling rates, and redox states). Our goals are (1) to verify that QUE really represents its parent melt composition, (2) to estimate a cooling rate of this meteorite, (3) to clarify the crystallization sequences of present minerals, and (4) to verity that this meteorite really crystallized under reduced condition.

Koizumi, E.; Mikouchi, T.; McKay, G.; Schwandt, C.; Monkawa, A.; Miyamoto, M.

2002-01-01

153

Valence State Partitioning of Cr and V Between Pyroxene - Melt: Estimates of Oxygen Fugacity for Martian Basalt QUE 94201  

NASA Technical Reports Server (NTRS)

Several studies, using different oxybarometers, have suggested that the variation of fO2 in martian basalts spans about 3 log units from approx. IW-1 to IW+2. The relatively oxidized basalts (e.g., pyroxene-phyric Shergotty) are enriched in incompatible elements, while the relatively reduced basalts (e.g., olivine-phyric Y980459) are depleted in incompatible elements. A popular interpretation of the above observations is that the martian mantle contains two reservoirs; 1) oxidized and enriched, and 2) reduced and depleted. The basalts are thus thought to represent mixing between these two reservoirs. Recently, Shearer et al. determined the fO2 of primitive olivine-phyric basalt Y980459 to be IW+0.9 using the partitioning of V between olivine and melt. In applying this technique to other basalts, Shearer et al. concluded that the martian mantle shergottite source was depleted and varied only slightly in fO2 (IW to IW+1). Thus the more oxidized, enriched basalts had assimilated a crustal component on their path to the martian surface. In this study we attempt to address the above debate on martian mantle fO2 using the partitioning of Cr and V into pyroxene in pyroxene-phyric basalt QUE 94201.

Karner, J. M.; Papike, J. J.; Shearer, C. K.; McKay, G.; Le, L.; Burger, P.

2007-01-01

154

Workshop on Oxygen in Asteroids and Meteorites  

NASA Technical Reports Server (NTRS)

Contents include the following: Constraints on the detection of solar nebula's oxidation state through asteroid observation. Oxidation/Reduction Processes in Primitive Achondrites. Low-Temperature Chemical Processing on Asteroids. On the Formation Location of Asteroids and Meteorites. The Spectral Properties of Angritic Basalts. Correlation Between Chemical and Oxygen Isotopic Compositions in Chondrites. Effect of In-Situ Aqueous Alteration on Thermal Model Heat Budgets. Oxidation-Reduction in Meteorites: The Case of High-Ni Irons. Ureilite Atmospherics: Coming up for Air on a Parent Body. High Temperature Effects Including Oxygen Fugacity, in Pre-Planetary and Planetary Meteorites and Asteroids. Oxygen Isotopic Variation of Asteroidal Materials. High-Temperature Chemical Processing on Asteroids: An Oxygen Isotope Perspective. Oxygen Isotopes and Origin of Opaque Assemblages from the Ningqiang Carbonaceous Chondrite. Water Distribution in the Asteroid Belt. Comparative Planetary Mineralogy: V Systematics in Planetary Pyroxenes and fo 2 Estimates for Basalts from Vesta.

2005-01-01

155

Experimental measurements of the fugacity of C0 2 and graphite/diamond stability from 35 to 77 kbar at 925 to 1650°C  

NASA Astrophysics Data System (ADS)

The f O2 of the equilibrium between graphite and C-O fluid has been determined at 35-77 kbar and 925-1650°C using metal-metal oxide reactions as redox sensors and by employing an assemblage of Co-Pd alloy and CoO as a sliding redox sensor. In the latter case, the equilibrium composition of the Co-Pd alloy was approached from two starting compositions of initially higher and lower Co contents. The measurements translate into measurements of the fugacity of CO 2 with uncertainties in the range 0.13-0.20 log units. Our determinations of f CO2 show reasonable, but not perfect agreement, with the equations of state of Saxena and Fei (1987) and Sterner and Pitzer (1994). Modified forms of the Redlich-Kwong equation of state ( Holloway, 1977; Flowers, 1979; Kerrick and Jacobs, 1981) predict values of f CO2 that, in some parts of P, T space, are over 1 log unit higher than those determined experimentally. An equation of state for CO 2 has been parameterised using our new measurements and existing low pressure data ( Kennedy and Holser, 1966; Shmonov and Shmulovich, 1974). The equation of state is suitable for the calculation of CO 2 properties in the range 1 bar to 77 kbar and 925-1650°C.

Frost, Daniel J.; Wood, Bernard J.

1997-04-01

156

A model-free method for mass spectrometer response correction. [for oxygen consumption and cardiac output calculation  

NASA Technical Reports Server (NTRS)

A new method for correction of mass spectrometer output signals is described. Response-time distortion is reduced independently of any model of mass spectrometer behavior. The delay of the system is found first from the cross-correlation function of a step change and its response. A two-sided time-domain digital correction filter (deconvolution filter) is generated next from the same step response data using a regression procedure. Other data are corrected using the filter and delay. The mean squared error between a step response and a step is reduced considerably more after the use of a deconvolution filter than after the application of a second-order model correction. O2 consumption and CO2 production values calculated from data corrupted by a simulated dynamic process return to near the uncorrupted values after correction. Although a clean step response or the ensemble average of several responses contaminated with noise is needed for the generation of the filter, random noise of magnitude not above 0.5 percent added to the response to be corrected does not impair the correction severely.

Shykoff, Barbara E.; Swanson, Harvey T.

1987-01-01

157

JSC systems using solid ceramic oxygen electrolyte cells to measure oxygen fugacites in gas-mixing systems  

NASA Technical Reports Server (NTRS)

Details are given for the construction and operation of a 101.3 KN/sq meter (1 atmosphere) redox control system. A solid ceramic oxygen electrolyte cell is used to monitor the oxygen fugacity in the furnace. The system consists of a vertical quench gas mixing furnace with heads designed for mounting the electrolyte cell and with facilities for inserting and removing the samples, a simplified version of a gas mixing apparatus, and devices for experiments under controlled rates of change of temperature. A thermogravimetric analysis system employing these techniques of redox control and measurement is also described. The calibration and maintenance of the system are discussed.

Williams, R. J.; Mullins, O.

1981-01-01

158

Lunar and Planetary Science XXXV: Special Session: Oxygen in the Solar System, II  

NASA Technical Reports Server (NTRS)

The Special Session: Oxygen in the Solar System, II, included the following reports:Evolution of Oxygen Isotopes in the Solar Nebula; Disequilibrium Melting of Refractory Inclusions: A Mechanism for High-Temperature Oxygen; Isotope Exchange in the Solar Nebula; Oxygen Isotopic Compositions of the Al-rich Chondrules in the CR Carbonaceous Chondrites: Evidence for a Genetic Link to Ca-Al-rich Inclusions and for Oxygen Isotope Exchange During Chondrule Melting; Nebular Formation of Fayalitic Olivine: Ineffectiveness of Dust Enrichment; Water in Terrestrial Planets: Always an Oxidant?; Oxygen Barometry of Basaltic Glasses Based on Vanadium Valence Determination Using Synchrotron MicroXANES; A New Oxygen Barometer for Solar System Basaltic Glasses Based on Vanadium Valence; The Relationship Between Clinopyroxene Fe3+ Content and Oxygen Fugacity ; and Olivine-Silicate Melt Partitioning of Iridium.

2004-01-01

159

Applying the Ce-in-zircon oxygen geobarometer to diverse silicic magmatic systems  

NASA Astrophysics Data System (ADS)

Zircon provides information on age, temperature, and composition of the magma from which it grew. In systems such as Mount St. Helens, where zircon is not coeval with the rest of the crystal cargo, it provides the only accessible record of the extended history of the magmatic system, including cycles of intrusion, crystallization and rejuvenation beneath an active volcano (Claiborne et al., 2010). The rare earth elements, which are present in measureable quantities in zircon, provide information about the composition of the magma from which zircon grew. Unique among the generally trivalent rare earth elements, cerium can exist as either trivalent or tetravalent, depending on the oxidation state of the magma. The tetravalent ion is highly compatible in zircon, in the site that usually hosts tetravalent zirconium, and so the amount of Cerium in zircon relative (relative to what would be expected of trivalent Ce) depends the oxidation state of the magma from which it grew. Trail et al. (2011) proposed a calibration based on experimental data that uses the Ce anomaly in zircon as a direct proxy for magma oxidation (fugacity), describing the relationship between Ce in zircon and magma oxygen fugacity as ln(Ce/Ce*)D = (0.1156±0.0050)xln(fO2)+(13860±708)/T-(6.125±0.484). For systems like Mount St. Helens, where the major minerals record only events in the hundreds to thousands of years leading to eruption, (including the Fe-Ti oxides traditionally relied upon for records of oxidation state of the magmas), this presents a novel approach for understanding more extended histories of oxidation of magmas in the tens and hundreds of thousands of years of magmatism at a volcanic center. This calibration also promises to help us better constrain conditions of crystallization in intrusive portions of volcanic systems, as well as plutonic bodes. We apply this new oxygen geobarometer to natural volcanic and plutonic zircons from a variety of tectonic settings, and compare to existing indicators of oxidation state for each system, as available. Zircons included this study are from Mount St. Helens (?NNO +1.5 log units; Smith, 1984), the Peach Spring Tuff and Spirit Mountain Batholith (sphene-bearing, silicic, Miocene-aged rocks from the Colorado River Extensional Corridor), Alid Volcano in Eritrea, and rhyolites and granites from Iceland. Median log fO2 for these systems, calculated from the Cerium anomaly in zircons following Trail et al. (2011) using temperatures from Ti-in-zircon thermometry (Ferry and Watson, 2007) are as follows: Alid -12 bars (?NNO +3 log units) at 750 degrees C; Iceland -11 bars (?NNO +3 log units) at 800 degrees C; Mount St. Helens -8.6 bars (?NNO +6 log units) at 750 degrees C; Peach Spring Tuff -3.4 (?NNO +10 log units) at 830 degrees C. While ubiquitous sphene in the Spirit Mountain granites suggest relatively high fO2, calculations based on the cerium anomaly in zircon suggest median log fO2 of >0 at 770 degrees C, which is certainly erroneous. While median values for our natural zircons are, for the most part, above expected fugacities for each system when compared with other indicators, and extreme values for each system are almost certainly erroneous, many are within expected values for terrestrial magmas and they vary relative to one another as might be expected given the magma types and tectonic settings.

Claiborne, L. L.; Miller, C. F.

2012-12-01

160

Calculation of arrangement of oxygen ions and vacancies in double perovskite GdBaCo2O(5+?) by first-principles DFT with Monte Carlo simulations.  

PubMed

The configurations of oxygen ions and vacancies at various oxygen stoichiometries and temperatures in double perovskite oxides (GdBaCo2O(5+?), 0 ? ? ? 1) have been determined by density functional theory (DFT) combined with Monte Carlo (MC) simulations. The MC simulations confirmed the existence of a superstructure at ? = 0.5, showing alternating linear ordering of oxygen ions and vacancies along the b-axis in the GdO layer. This structure is identical to that reported experimentally. Increasing the temperature up to 1200 K induces a phase transition manifested in the breaking of the oxygen/vacancy arrangement at around ? = 0.5. In the high-temperature phase, vacancies are distributed in the GdO and CoO2 layers, whereas there are no vacancies in the BaO layer. In addition, the characteristic linear arrangement is partly preserved even in the disordered high-temperature phase. Consequently, oxygen ions can migrate between the GdO and CoO2 layers, as reported in previous classical molecular dynamics simulation studies. PMID:23677012

Shiiba, Hiromasa; Nakayama, Masanobu; Kasuga, Toshihiro; Grimes, Robin W; Kilner, John A

2013-07-01

161

Experimental measurements of the graphite C-O equilibrium and CO2 fugacities at high temperature and pressure  

NASA Astrophysics Data System (ADS)

The f o 2 of the equilibrium between graphite and C-O fluid has been determined from 15-30 kbar and 1100-1400°C using a sliding redox sensor consisting of (Ni, Mn) O+Ni metal. The equilibrium composition of oxide coexisting with metal was approached from both directions in each experiment with convergence to within 1 mol% NiO. Since, in the P-T range of the experiments, C-O fluids are >90% CO2 our measurements of f o 2 translate into determinations of CO2 fugacity with an uncertainty of ±0.1 log units. These new determinations of the P-T-f o 2 plane of GCO equilibrium are in excellent agreement with the mainly unreversed measurements of Ulmer and Luth (1991) using pure metal-metal oxide sensors and with the equation of state of Saxena and Fei (1987). Modified forms of the Redlich-Kwong (MRK) equation of state (Holloway 1977; Flowers 1979; Kerrick and Jacobs 1981) predict higher values of f o 2 for the GCO equilibrium than determined experimentally. This implies that CO2 is more compressible than the MRK predicts.

Frost, Daniel J.; Wood, Bernard J.

1995-09-01

162

Electrical conductivity of San Carlos olivine along [100] under oxygen- and pyroxene-buffered conditions and implications for defect equilibria  

Microsoft Academic Search

The electrical conductivity along [100] of single crystal San Carlos olivine was measured as a function of temperature between 1100[degrees] and 1200[degrees]C and oxygen fugacity between 10[sup [minus]6] and 10[sup +0.5] Pa (at 1200[degrees]C), and either with (pyroxene-buffered) or without (self-buffered) an added natural pyroxene buffer from a San Carlos Iherzolite. Under these temperature and fO[sub 2] conditions, electrical conduction

B. J. Wanamaker; A. G. Duba

1993-01-01

163

Calculation of the relative metastabilities of proteins using the CHNOSZ software package  

PubMed Central

Background Proteins of various compositions are required by organisms inhabiting different environments. The energetic demands for protein formation are a function of the compositions of proteins as well as geochemical variables including temperature, pressure, oxygen fugacity and pH. The purpose of this study was to explore the dependence of metastable equilibrium states of protein systems on changes in the geochemical variables. Results A software package called CHNOSZ implementing the revised Helgeson-Kirkham-Flowers (HKF) equations of state and group additivity for ionized unfolded aqueous proteins was developed. The program can be used to calculate standard molal Gibbs energies and other thermodynamic properties of reactions and to make chemical speciation and predominance diagrams that represent the metastable equilibrium distributions of proteins. The approach takes account of the chemical affinities of reactions in open systems characterized by the chemical potentials of basis species. The thermodynamic database included with the package permits application of the software to mineral and other inorganic systems as well as systems of proteins or other biomolecules. Conclusion Metastable equilibrium activity diagrams were generated for model cell-surface proteins from archaea and bacteria adapted to growth in environments that differ in temperature and chemical conditions. The predicted metastable equilibrium distributions of the proteins can be compared with the optimal growth temperatures of the organisms and with geochemical variables. The results suggest that a thermodynamic assessment of protein metastability may be useful for integrating bio- and geochemical observations.

Dick, Jeffrey M

2008-01-01

164

EQ3NR, a computer program for geochemical aqueous speciation-solubility calculations: Theoretical manual, user`s guide, and related documentation (Version 7.0); Part 3  

SciTech Connect

EQ3NR is an aqueous solution speciation-solubility modeling code. It is part of the EQ3/6 software package for geochemical modeling. It computes the thermodynamic state of an aqueous solution by determining the distribution of chemical species, including simple ions, ion pairs, and complexes, using standard state thermodynamic data and various equations which describe the thermodynamic activity coefficients of these species. The input to the code describes the aqueous solution in terms of analytical data, including total (analytical) concentrations of dissolved components and such other parameters as the pH, pHCl, Eh, pe, and oxygen fugacity. The input may also include a desired electrical balancing adjustment and various constraints which impose equilibrium with special pure minerals, solid solution end-member components (of specified mole fractions), and gases (of specified fugacities). The code evaluates the degree of disequilibrium in terms of the saturation index (SI = 1og Q/K) and the thermodynamic affinity (A = {minus}2.303 RT log Q/K) for various reactions, such as mineral dissolution or oxidation-reduction in the aqueous solution itself. Individual values of Eh, pe, oxygen fugacity, and Ah (redox affinity) are computed for aqueous redox couples. Equilibrium fugacities are computed for gas species. The code is highly flexible in dealing with various parameters as either model inputs or outputs. The user can specify modification or substitution of equilibrium constants at run time by using options on the input file.

Wolery, T.J.

1992-09-14

165

Exploring haem-based alternatives for oxygen reduction catalysis in fuel cells—a status report of our first principles calculations  

NASA Astrophysics Data System (ADS)

For hydrogen fuel cells to become commercially viable, an alternative catalyst to platinum surfaces that is both efficient and affordable must be discovered. We consider haem and haem derivatives as potentials substitutes. In this paper, we discuss the oxygen reduction reaction on both the platinum surface and on haem. We then introduce our suggestions based on density-functional studies on how to improve haem's oxygen-reduction capabilities, which can be summarized as follows: inducing the singlet state, inducing side-on interaction, mimicking cytochrome c oxidase by adding a copper-imidazole complex, using platinum deposited on tin porphyrin instead of haem, and using oxomolybdenum porphyrin instead of haem. We shall focus on the last three methods because of their experimental practicability.

Dy, E. S.; Roman, T. A.; Kubota, Y.; Miyamoto, K.; Kasai, H.

2007-11-01

166

Investigations of the structure of alkali- and alkaline earth disilicates by oxygen-17 nuclear magnetic resonance and by ab initio calculations  

Microsoft Academic Search

O-17 Dynamic Angle Spinning NMR has revealed that there are four oxygen sites (two bridging and two nonbridging) in crystalline potassium disilicate. The 2D DAS NMR spectra for this crystalline compound and for the compounds CaSiOsb3, CaMgSisb2Osb6 and MgSiOsb3 has been obtained and fitted to extract the relevant NMR parameters. The distribution of alkali in a mixed sodium\\/potassium disilicate glass

Karl Edward Vermillion

1998-01-01

167

Precipitates/Salts Model Sensitivity Calculation  

SciTech Connect

The objective and scope of this calculation is to assist Performance Assessment Operations and the Engineered Barrier System (EBS) Department in modeling the geochemical effects of evaporation on potential seepage waters within a potential repository drift. This work is developed and documented using procedure AP-3.12Q, ''Calculations'', in support of ''Technical Work Plan For Engineered Barrier System Department Modeling and Testing FY 02 Work Activities'' (BSC 2001a). The specific objective of this calculation is to examine the sensitivity and uncertainties of the Precipitates/Salts model. The Precipitates/Salts model is documented in an Analysis/Model Report (AMR), ''In-Drift Precipitates/Salts Analysis'' (BSC 2001b). The calculation in the current document examines the effects of starting water composition, mineral suppressions, and the fugacity of carbon dioxide (CO{sub 2}) on the chemical evolution of water in the drift.

P. Mariner

2001-12-20

168

Oxygen concentrators.  

PubMed

Oxygen concentrators offer an alternative source of oxygen to conventional methods of supply. The disadvantage of their high initial purchase price is offset by low running costs. In hospitals they may find a place in providing "oxygen" for some gas pipeline systems. They are the method of choice for supplying oxygen for long-term domiciliary oxygen therapy. PMID:4092132

Howell, R S

1985-10-01

169

Measuring tissue oxygenation  

NASA Technical Reports Server (NTRS)

Methods and systems for calculating tissue oxygenation, e.g., oxygen saturation, in a target tissue are disclosed. In some embodiments, the methods include: (a) directing incident radiation to a target tissue and determining reflectance spectra of the target tissue by measuring intensities of reflected radiation from the target tissue at a plurality of radiation wavelengths; (b) correcting the measured intensities of the reflectance spectra to reduce contributions thereto from skin and fat layers through which the incident radiation propagates; (c) determining oxygen saturation in the target tissue based on the corrected reflectance spectra; and (d) outputting the determined value of oxygen saturation.

Soyemi, Olusola O. (Inventor); Soller, Babs R. (Inventor); Yang, Ye (Inventor)

2009-01-01

170

THE INDOOR FUGACITY MODEL  

EPA Science Inventory

Dermal and non-dietary pathways are potentially significant exposure pathways to pesticides used in the home. The exposure pathways include dermal contact through the hands and skin, ingestion from hand to mouth activities, ingestion through contact with toys and other items, ...

171

Phase relations of a simulated lunar basalt as a function of oxygen fugacity, and their bearing on the petrogenesis of the Apollo 11 basalts  

USGS Publications Warehouse

A glass of Apollo 11 basalt composition crystallizing at 1 atm at low f{hook}02 showed the following crystallization sequence; ferropseudobrookite at 1210??C, olivine at 1200??C, ilmenite and plagioclase at 1140??C, clinopyroxene at 1113??C. Ferropseudobrookite and olivine have a reaction relation to the melt. This sequence agrees with that assumed on textural grounds for some Apollo 11 basalts. It also indicates that the Apollo 11 basalts cannot have been modified by low-pressure fractionation. ?? 1970.

Tuthill, R. L.; Sato, M.

1970-01-01

172

Mineralogy, Petrology and Oxygen Fugacity of the LaPaz Icefield Lunar Basaltic Meteorites and the Origin of Evolved Lunar Basalts  

NASA Technical Reports Server (NTRS)

LAP 02205 is a 1.2 kg lunar mare basalt meteorite found in the Lap Paz ice field of Antarctica in 2002 [1]. Four similar meteorites were also found within the same region [1] and all five have a combined mass of 1.9 kg (LAP 02224, LAP 02226, LAP 02436 and LAP 03632, hereafter called the LAP meteorites). The LAP meteorites all contain a similar texture, mineral assemblage, and composition. A lunar origin for these samples comes from O isotopic data for LAP 02205 [1], Fe/Mn ratios of pyroxenes [1-5], and the presence of distinct lunar mineralogy such as Fe metal and baddeleyite. The LAP meteorites may represent an area of the Moon, which has never been sampled by Apollo missions, or by other lunar meteorites. The data from this study will be used to compare the LAP meteorites to Apollo mare basalts and lunar basaltic meteorites, and will ultimately help to constrain their origin.

Collins, S. J.; Righter, K.; Brandon, A. D.

2005-01-01

173

Temperature and oxygen fugacity constraints on CK and R chondrites and implications for water and oxidation in the early solar system  

Microsoft Academic Search

Recent chondritic meteorite finds in Antarctica have included CB, CH, CK and R chondrites, the latter two of which are among the most oxidized materials found in meteorite collections. In this study we present petrographic and mineralogic data for a suite of CK and R chondrites, and compare to previous CK and R chondrites, as well as some CV. In

K. Righter; K. E. Neff

2007-01-01

174

The compressibility of silicate liquids containing Fe 2 O 3 and the effect of composition, temperature, oxygen fugacity and pressure on their redox states  

Microsoft Academic Search

Ultrasonic longitudinal acoustic velocities in oxidized silicate liquids indicate that the pressure derivative of the partial-molar\\u000a volume of Fe2O3 is the same in iron-rich alkali-, alkaline earth- and natural silicate melt compositions at 1 bar. The dV\\/dP for multicomponent silicate liquids can be expressed as a linear combination of partial-molar constants plus a positive excess\\u000a term for Na2O?Al2O3 mixing. Partial-molar

Victor C. Kress; Ian S. E. Carmichael

1991-01-01

175

GASP: A computer code for calculating the thermodynamic and transport properties for ten fluids: Parahydrogen, helium, neon, methane, nitrogen, carbon monoxide, oxygen, fluorine, argon, and carbon dioxide. [enthalpy, entropy, thermal conductivity, and specific heat  

NASA Technical Reports Server (NTRS)

A FORTRAN IV subprogram called GASP is discussed which calculates the thermodynamic and transport properties for 10 pure fluids: parahydrogen, helium, neon, methane, nitrogen, carbon monoxide, oxygen, fluorine, argon, and carbon dioxide. The pressure range is generally from 0.1 to 400 atmospheres (to 100 atm for helium and to 1000 atm for hydrogen). The temperature ranges are from the triple point to 300 K for neon; to 500 K for carbon monoxide, oxygen, and fluorine; to 600 K for methane and nitrogen; to 1000 K for argon and carbon dioxide; to 2000 K for hydrogen; and from 6 to 500 K for helium. GASP accepts any two of pressure, temperature and density as input conditions along with pressure, and either entropy or enthalpy. The properties available in any combination as output include temperature, density, pressure, entropy, enthalpy, specific heats, sonic velocity, viscosity, thermal conductivity, and surface tension. The subprogram design is modular so that the user can choose only those subroutines necessary to the calculations.

Hendricks, R. C.; Baron, A. K.; Peller, I. C.

1975-01-01

176

Summary of Simplified Two Time Step Method for Calculating Combustion Rates and Nitrogen Oxide Emissions for Hydrogen/Air and Hydrogen/Oxygen  

NASA Technical Reports Server (NTRS)

A simplified single rate expression for hydrogen combustion and nitrogen oxide production was developed. Detailed kinetics are predicted for the chemical kinetic times using the complete chemical mechanism over the entire operating space. These times are then correlated to the reactor conditions using an exponential fit. Simple first order reaction expressions are then used to find the conversion in the reactor. The method uses a two time step kinetic scheme. The first time averaged step is used at the initial times with smaller water concentrations. This gives the average chemical kinetic time as a function of initial overall fuel air ratio, temperature, and pressure. The second instantaneous step is used at higher water concentrations (greater than l x 10(exp -20)) moles per cc) in the mixture which gives the chemical kinetic time as a function of the instantaneous fuel and water mole concentrations, pressure and temperature (T(sub 4)). The simple correlations are then compared to the turbulent mixing times to determine the limiting properties of the reaction. The NASA Glenn GLSENS kinetics code calculates the reaction rates and rate constants for each species in a kinetic scheme for finite kinetic rates. These reaction rates are used to calculate the necessary chemical kinetic times. This time is regressed over the complete initial conditions using the Excel regression routine. Chemical kinetic time equations for H2 and NOx are obtained for H2/Air fuel and for H2/O2. A similar correlation is also developed using data from NASA's Chemical Equilibrium Applications (CEA) code to determine the equilibrium temperature (T(sub 4)) as a function of overall fuel/air ratio, pressure and initial temperature (T(sub 3)). High values of the regression coefficient R squared are obtained.

Marek, C. John; Molnar, Melissa

2005-01-01

177

Simplified Two-Time Step Method for Calculating Combustion Rates and Nitrogen Oxide Emissions for Hydrogen/Air and Hydorgen/Oxygen  

NASA Technical Reports Server (NTRS)

A simplified single rate expression for hydrogen combustion and nitrogen oxide production was developed. Detailed kinetics are predicted for the chemical kinetic times using the complete chemical mechanism over the entire operating space. These times are then correlated to the reactor conditions using an exponential fit. Simple first order reaction expressions are then used to find the conversion in the reactor. The method uses a two-time step kinetic scheme. The first time averaged step is used at the initial times with smaller water concentrations. This gives the average chemical kinetic time as a function of initial overall fuel air ratio, temperature, and pressure. The second instantaneous step is used at higher water concentrations (> 1 x 10(exp -20) moles/cc) in the mixture which gives the chemical kinetic time as a function of the instantaneous fuel and water mole concentrations, pressure and temperature (T4). The simple correlations are then compared to the turbulent mixing times to determine the limiting properties of the reaction. The NASA Glenn GLSENS kinetics code calculates the reaction rates and rate constants for each species in a kinetic scheme for finite kinetic rates. These reaction rates are used to calculate the necessary chemical kinetic times. This time is regressed over the complete initial conditions using the Excel regression routine. Chemical kinetic time equations for H2 and NOx are obtained for H2/air fuel and for the H2/O2. A similar correlation is also developed using data from NASA s Chemical Equilibrium Applications (CEA) code to determine the equilibrium temperature (T4) as a function of overall fuel/air ratio, pressure and initial temperature (T3). High values of the regression coefficient R2 are obtained.

Molnar, Melissa; Marek, C. John

2005-01-01

178

Angular dependence of core hole screening in LiCoO2 : A DFT+U calculation of the oxygen and cobalt K -edge x-ray absorption spectra  

NASA Astrophysics Data System (ADS)

Angular-dependent core hole screening effects have been found in the cobalt K -edge x-ray absorption spectrum of LiCoO2 , using high-resolution data and parameter-free general gradient approximation plus U calculations. The Co1s core hole on the absorber causes strong local attraction. The core hole screening on the cobalt nearest-neighbors induces a 2 eV shift in the density of states with respect to the on-site 1s-3d transitions, as detected in the CoK pre-edge spectrum. Our density functional theory plus U calculations reveal that the off-site screening is different in the out-of-plane direction, where a 3 eV shift is visible in both calculations and experiment. The detailed analysis of the inclusion of the core hole potential and the Hubbard parameter U shows that the core hole is essential for the off-site screening while U improves the description of the angular-dependent screening effects. In the case of oxygen K edge, both the core hole potential and the Hubbard parameter improve the relative positions of the spectral features.

Juhin, Amélie; de Groot, Frank; Vankó, György; Calandra, Matteo; Brouder, Christian

2010-03-01

179

Escape of Oxygen from Mars: Monte Carlo Calculations Using Energy Dependent Cross Sections and including both O(3P) and O(1D) as energetic O atoms  

NASA Astrophysics Data System (ADS)

We report here escape fluxes of O from Mars, computed using a one-dimensional Monte Carlo code that has been described previously. We follow the energetic O atoms from their altitude of origin from collision to collision in spherical geometry until the O atoms reach the top altitude of the atmosphere, with an energy that is equal to or greater than the escape energy or their energy decreases below an energy that is less than the escape energy by an amount that will be determined in this research. The source of energetic O atoms is assumed to be dissociative recombination of O2+, which produces energetic O(3P) and O(1D). We use energy-dependent elastic cross sections for the interactions of O(3P) and O(1D) with 12 background species. We include in the calculations the excitation of O(3P) to the O(1D) state by collisions with energetic O atoms, and quenching of O(1D) by background O atoms; the latter two processes are inelastic, and take energy out of the system, or add it to the system, respectively.

Fox, J. L.; Hac, A. B.

2013-12-01

180

Atmospheric Oxygen  

NSDL National Science Digital Library

In this feature, adapted from Interactive NOVA: Earth, students explore the relationship between oxygen concentration and the well-being of various organisms by simulating a change in oxygen levels and observing what happens.

Foundation, Wgbh E.

2003-09-26

181

Hyperbaric Oxygenation.  

National Technical Information Service (NTIS)

The characteristics and possibilities of hyperbaric oxygenation were studied. The effect of hyperoxygenation of the organism under various conditions was examined, and periods of same exclusion of circulation when breathing oxygen under increased pressure...

I. P. Berezin

1974-01-01

182

Thermodynamic properties of oxygen  

NASA Astrophysics Data System (ADS)

This volume incorporates current information about the density and isochoric specific heat of oxygen into a reliable set of tables. Temperatures and pressures covered range from the triple point to 1500 K and 0.1 to 1900 MPa. The information describes oxygen in both the liquid and gaseous phases. A unified equation of state is presented and discussed, and the method used to calculate the tables is described.

Sychev, Viacheslav Vladimirovich; Vasserman, A. A.; Kozlov, A. D.; Spiridonov, G. A.; Tsymarnyi, V. A.

183

Quantitative reconstruction of East Asian summer monsoon precipitation during the Holocene based on oxygen isotope mass-balance calculation in the East China Sea  

NASA Astrophysics Data System (ADS)

The ?18O of seawater (?18Ow), an indirect indicator of sea surface salinity, in the northern East China Sea (ECS) was reconstructed for the last 7 kyr using paired Mg/Ca ratio and ?18O of planktic foraminiferal tests. According to modern observation, interannual variations in sea surface salinity during summer in the northern part of the ECS are mainly controlled by the discharge from the Changjiang (Yangtze River), which reflects summer rainfall in the drainage area of the Changjiang. Thus, changes in the summer sea surface salinity in the northern ECS are interpreted as reflecting variations in the East Asian summer monsoon (EASM) precipitation in South China. This interpretation is confirmed by the strong relationship between salinity in the northern ECS and the discharge from the Changjiang during wet season (May-October) based on the observational salinity data from 1951 to 2000. On the other hand, it is difficult to estimate absolute salinity value in the past with high accuracy, because there are large uncertainties in salinity-?18Ow regression slope, end-member salinity, and ?18Ow values. For this reason, in order to reconstruct the discharge in the past, we conducted ?18Ow mass-balance calculation to estimate freshwater contribution to the surface water of the northern ECS during the Holocene. We assumed a simple mixing between two end-members: the seawater and the freshwater from the Changjiang. Temporal variations in the relative contribution of the freshwater from the Changjiang indicates that there was no long-term decreasing trend in the Changjiang freshwater discharge since the middle Holocene, but centennial to millennial scale variations were predominant. This suggests that changes in summer insolation in the Northern Hemisphere did not mainly control the changes in summer precipitation in the South China. Our results also indicate that variability of the Changjiang freshwater during the Holocene on sub-millennial timescale was much lower than interannual time scale, but similar to decadal time scale.

Kubota, Y.; Tada, R.; Kimoto, K.

2014-04-01

184

A New Oxygen Barometer for Solar System Basaltic Glasses Based on Vanadium Valence  

NASA Technical Reports Server (NTRS)

The determination of oxidation conditions for basaltic magmas derived by the melting of planetary mantles is critical to our understanding of the nature and evolution of planetary interiors. Yet, these determinations are compromised in terrestrial and especially extraterrestrial basalts by our analytical and computational methods for estimating oxygen fugacity (fO2). For example, mineralogical barometers (1, 2) can be reduced in effectiveness by subsolidus re-equilibration of mineral assemblages, inversion of mineralogical data to melt characteristics, and deviations of the natural mineral compositions from ideal thermodynamic parameters.

Karner, J. M.; Sutton, S. R.; Papike, S. R.; Delaney, J. S.; Shearer, C. K.; Newville, M.; Eng, P.; Rivers, M.; Dyar, M. D.

2004-01-01

185

Oxygen therapies.  

PubMed

Oxygen therapies are unproven alternatives promoted as a cure for cancer, acquired immune deficiency syndrome (AIDS), and other degenerative diseases. These "therapies" are offered at clinics in Mexico, the United States, and Europe. Proponents claim that many diseases, including cancer, are caused by oxygen deficiency and that oxygenation can restore health by destroying cancer cells, eliminating pathogens, stimulating metabolism, and by producing "oxidative detoxification." There is no scientific evidence to support any of these claims. Oxygen therapies include: (1) hydrogen peroxide therapy involving intravenous infusion, ingestion, colonic administration, or soaking in hydrogen peroxide solution; (2) ozone colonies and ozone autohemotherapy, in which blood is withdrawn and treated with ozone before reinfusion, and (3) "oxygenated" water, pills, and solutions. The use of oxygen therapies has resulted in serious adverse events and several deaths. Oxygen therapies should not be confused with those commonly used in respiratory care. PMID:20043470

Cassileth, Barrie

2009-11-30

186

Oxygen toxicity.  

PubMed

Oxygen is one of the most widely available and used therapeutic agents in the world. However, it is all too easy forget that oxygen is a prescribable drug with specific biochemical and physiologic actions, a distinct range of effective doses and well-defined adverse effects at high doses. The human body is affected in different ways depending on the type of exposure. Short exposures to high partial pressures at greater than atmospheric pressure lead to central nervous system toxicity, most commonly seen in divers or in hyperbaric oxygen therapy. Pulmonary and ocular toxicity results from longer exposure to elevated oxygen levels at normal atmospheric pressure. PMID:24767867

Thomson, Louise; Paton, James

2014-06-01

187

Transport properties of oxygen  

NASA Technical Reports Server (NTRS)

Tables of viscosity, thermal conductivity, and thermal diffusivity of oxygen as a function of temperature and pressure from the triple point to 320 K and at pressures to 100 MPa are presented. Auxiliary tables in engineering units are also given. Viscosity and thermal conductivity are calculated from published correlations. Density and specific heat at constant pressure, required to calculate thermal diffusivity, are obtained from an equation of state. The Prandtl number can be obtained quite easily from the values tabulated.

Roder, H. M.

1983-01-01

188

Oxygen stoichiometry, phase stability, and thermodynamic behavior of the lead-doped and lead-free Bi-2212 systems.  

SciTech Connect

Electromotive-force (EMF) measurements of oxygen fugacities as a function of stoichiometry have been made on lead-doped and lead-free Bi{sub 2-z}Pb{sub z}Sr{sub 2}Ca{sub 1}Cu{sub 2}O{sub x} superconducting ceramics in the temperature range {approx} 700-815 C by means of an oxygen-titration technique that employs an yttria-stabilized zirconia electrolyte. Equations for the variation of oxygen partial pressure with composition and temperature have been derived from our EMF measurements. Thermodynamic assessments of the partial molar quantities {Delta}{bar H} (O{sub 2}) and {Delta}{bar S}(O{sub 2}) for lead-doped Bi-2212 and lead-free Bi-2212 indicate that the solid-state decomposition of these bismuth cuprates at low oxygen partial pressure can be represented by the diphasic CuO---Cu{sub 2}O system.

Tetenbaum, M.; Hash, M.; Tani, B. S.; Maroni, V. A.; Chemical Engineering

1996-01-01

189

Oxygen stoichiometry, phase stability, and thermodynamic behavior of the lead-doped and lead-free Bi-2212 systems  

NASA Astrophysics Data System (ADS)

Electromotive-force (EMF) measurements of oxygen fugacities as a function of stoichiometry have been made on lead-doped and lead-free Bi 2- zPb zSr 2Ca 1Cu 2O x superconducting ceramics in the temperature range ? 700-815°C by means of an oxygen-titration techique that employs an yttria-stabilized zirconia electrolyte. Equations for the variation of oxygen partial pressure with composition and temperature have been derived from our EMF measurements. Thermodynamic assessments of the partial molar quantities ? overlineH(O 2) and ? overlineS(O 2) for lead-doped Bi-2212 and lead-free Bi-2212 indicate that the solid-state decomposition of these bismuth cuprates at low oxygen partial pressure can be represented by the diphasic CuO?Cu 2O system.

Tetenbaum, M.; Hash, M.; Tani, B. S.; Maroni, V. A.

1996-02-01

190

Electrical conductivity of San Carlos olivine along [100] under oxygen- and pyroxene-buffered conditions and implications for defect equilibria  

SciTech Connect

The electrical conductivity along [100] of single crystal San Carlos olivine was measured as a function of temperature between 1100[degrees] and 1200[degrees]C and oxygen fugacity between 10[sup [minus]6] and 10[sup +0.5] Pa (at 1200[degrees]C), and either with (pyroxene-buffered) or without (self-buffered) an added natural pyroxene buffer from a San Carlos Iherzolite. Under these temperature and fO[sub 2] conditions, electrical conduction in the self-buffered sample is attributed to polarons (Fe[sup [sm bullet

Wanamaker, B.J.; Duba, A.G. (Lawrence Livermore National Lab., CA (United States))

1993-01-10

191

Oxygen production and consumption in sediments determined at high spatial resolution by computer simulation of oxygen microelectrode data  

Microsoft Academic Search

Microprofiles of oxygen and oxygenic photosynthesis were measured in a photosynthetically active sediment by an oxygen microelectrode. The di&.tsion coefficient of oxygen in the uppermost 1 mm of the sediment was determined in poisoned sediment by microelectrode measurement of changes in the oxygen profile during nonsteady state conditions. The experimentally obtained data were inserted into computer models to calculate the

NIELS PETER REVSBECH; BENT MADSEN; BO BARKER JØRGENSEN

1986-01-01

192

Oxygen transfer in foods using oxygen luminescence sensors: Influence of oxygen partial pressure and food nature and composition  

Microsoft Academic Search

A rapid and easy to handle (on-line monitoring) method to achieve oxygen sorption kinetics was developed and tested on a large range of food products. Measurements were performed using luminescence sensors placed into of a thin layer of food material exposed to increasing oxygen contents in the atmosphere. From oxygen sorption kinetics diffusivity values could be calculated using a mathematical

C. Pénicaud; S. Guilbert; S. Peyron; N. Gontard; V. Guillard

2010-01-01

193

Generalized approximate spin projection calculations of effective exchange integrals of the CaMn4O5 cluster in the S1 and S3 states of the oxygen evolving complex of photosystem II.  

PubMed

Full geometry optimizations followed by the vibrational analysis were performed for eight spin configurations of the CaMn4O4X(H2O)3Y (X = O, OH; Y = H2O, OH) cluster in the S1 and S3 states of the oxygen evolution complex (OEC) of photosystem II (PSII). The energy gaps among these configurations obtained by vertical, adiabatic and adiabatic plus zero-point-energy (ZPE) correction procedures have been used for computation of the effective exchange integrals (J) in the spin Hamiltonian model. The J values are calculated by the (1) analytical method and the (2) generalized approximate spin projection (AP) method that eliminates the spin contamination errors of UB3LYP solutions. Using J values derived from these methods, exact diagonalization of the spin Hamiltonian matrix was carried out, yielding excitation energies and spin densities of the ground and lower-excited states of the cluster. The obtained results for the right (R)- and left (L)-opened structures in the S1 and S3 states are found to be consistent with available optical and magnetic experimental results. Implications of the computational results are discussed in relation to (a) the necessity of the exact diagonalization for computations of reliable energy levels, (b) magneto-structural correlations in the CaMn4O5 cluster of the OEC of PSII, (c) structural symmetry breaking in the S1 and S3 states, and (d) the right- and left-handed scenarios for the O-O bond formation for water oxidation. PMID:24632787

Isobe, H; Shoji, M; Yamanaka, S; Mino, H; Umena, Y; Kawakami, K; Kamiya, N; Shen, J-R; Yamaguchi, K

2014-06-28

194

Oxygen-Concentrating Cell  

NASA Technical Reports Server (NTRS)

High-purity oxygen produced from breathing air or from propellantgrade oxygen in oxygen-concentrating cell. Operating economics of concentrator attractive: Energy consumption about 4 Wh per liter of oxygen, slightly lower than conventional electrochemical oxygen extractors.

Buehler, K.

1986-01-01

195

Oxidation of Graphene Nanoribbon by Molecular Oxygen  

Microsoft Academic Search

Density-functional theory based on first principles is used to investigate oxidation of a semiconducting graphene nanoribbon with armchair edges (9-AGNR) by oxygen. The calculated results demonstrate that the oxygen is favorably physisorbed on the inner of 9-AGNR, while the oxygen is chemisorbed at the edge of 9-AGNR. Compared to the oxygen chemisorbed (cyclo- addition) 9-AGNR, two epoxy groups formed from

Shan Sheng Yu; Wei Tao Zheng; Qing Jiang

2008-01-01

196

Enhanced Shrinkage of Lanthanum Strontium Manganite (La0.90Sr0.10MnO3+?) Resulting from Thermal and Oxygen Partial Pressure Cycling  

SciTech Connect

Exposure of La0.9Sr0.1MnO3+? to repeated oxygen partial pressure cycles (air/10 ppm O2) resulted in enhanced densification rates, similar to behavior shown previously due to thermal cycling. Shrinkage rates in the temperature range 700 to 1000oC were orders of magnitude higher than Makipirtti-Meng model estimations based on stepwise isothermal dilatometry results at high temperature. A maximum in enhanced shrinkage due to oxygen partial pressure cycling occurred at 900oC. Shrinkage was greatest when LSM-10 bars that were first equilibrated in air were exposed to gas flows of lower oxygen fugacity than in the reverse direction. The former creates transient cation and oxygen vacancies well above the equilibrium concentration, resulting in enhanced mobility. These vacancies annihilate as Schottky equilibria is re-established, whereas the latter condition does not lead to excess vacancy concentrations.

McCarthy, Ben; Pederson, Larry R.; Anderson, Harlan U.; Zhou, Xiao Dong; Singh, Prabhakar; Coffey, Greg W.; Thomsen, Ed C.

2007-10-01

197

Oxygen concentration inside a functioning photosynthetic cell.  

PubMed

The excess oxygen concentration in the photosynthetic membranes of functioning oxygenic photosynthetic cells was estimated using classical diffusion theory combined with experimental data on oxygen production rates of cyanobacterial cells. The excess oxygen concentration within the plesiomorphic cyanobacterium Gloeobactor violaceus is only 0.025 ?M, or four orders of magnitude lower than the oxygen concentration in air-saturated water. Such a low concentration suggests that the first oxygenic photosynthetic bacteria in solitary form could have evolved ?2.8 billion years ago without special mechanisms to protect them against reactive oxygen species. These mechanisms instead could have been developed during the following ?500 million years while the oxygen level in the Earth's atmosphere was slowly rising. Excess oxygen concentrations within individual cells of the apomorphic cyanobacteria Synechocystis and Synechococcus are 0.064 and 0.25 ?M, respectively. These numbers suggest that intramembrane and intracellular proteins in isolated oxygenic photosynthetic cells are not subjected to excessively high oxygen levels. The situation is different for closely packed colonies of photosynthetic cells. Calculations show that the excess concentration within colonies that are ?40 ?m or larger in diameter can be comparable to the oxygen concentration in air-saturated water, suggesting that species forming colonies require protection against reactive oxygen species even in the absence of oxygen in the surrounding atmosphere. PMID:24806920

Kihara, Shigeharu; Hartzler, Daniel A; Savikhin, Sergei

2014-05-01

198

Wildlife monitoring, modeling, and fugacity  

SciTech Connect

Observations of wildlife populations and their state of health have played a key role in identifying situations in which chemical contaminants have reached unacceptable concentrations in the environment. The reproductive failure of several species - including the peregrine falcon (Falco peregrinus), the double crested cormorant (Phalocrocorax auritus), the brown pelican (Pelicanus occidentalis), and the osprey (Pandion haliaetus) - has been attributed to organochlorine contamination. As the mine canary can warn of the presence of a poisonous gas in a coal mine, wildlife populations can act as sentinels for excessive chemical contamination. This blunt and often tragic exploitation of wildlife as a sentinel is, to be sure, an extreme example of the more subtle and far-reaching issue of the extent to which wildlife tissues can be used to indicate general levels of environmental contamination and provide guidance to the scientific and regulatory communities about the state of the environment.

Clark, T.; Clark, K.; Paterson, S.; Mackay, D.; Norstrom, R.J. (Univ. of Toronto, Ontario (Canada))

1988-02-01

199

Monitoring oxygenation.  

PubMed

Cyanosis was used for a century after dentists began pulling teeth under 100% N(2)O in 1844 because brief (2 min) severe hypoxia is harmless. Deaths came with curare and potent anesthetic respiratory arrest. Leland Clark's invention of a polarographic blood oxygen tension electrode (1954) was introduced for transcutaneous PO2 monitoring to adjust PEEP and CPAP PO2 to prevent premature infant blindness from excess O2 (1972). Oximetry for warning military aviators was tried after WW II but not used for routine monitoring until Takuo Aoyagi (1973) discovered an equation to measure SaO2 by the ratio of ratios of red and IR light transmitted through tissue as it changed with arterial pulses. Pulse oximetry (1982) depended on simultaneous technology improvements of light emitting red and IR diodes, tiny cheap solid state sensors and micro-chip computers. Continuous monitoring of airway anesthetic concentration and oxygen also became very common after 1980. Death from anesthesia fell 10 fold between 1985 and 2000 as pulse oximetry became universally used, but no proof of a causative relationship to pulse oximetry exists. It is now assumed that all anesthesiologist became much more aware of the dangers of prolonged hypoxia, perhaps by using the pulse oximeters. PMID:21717228

Severinghaus, John W

2011-06-01

200

Oxygen species  

NASA Technical Reports Server (NTRS)

The spatial distribution of ozone, as predicted by numerical models, is compared with observations. A set of reference ozone profiles was developed against which to compare current numerical calculations. Most of the analyses will focus on ozone between 30 and 70 km altitude.

Brasseur, G.; Miller, A. J.; Bhartia, P. K.; Fleig, A.; Froidevaux, L.; Heath, D.; Hilsenrath, E.; Logan, J. A.; Mccormick, P.; Megie, G.

1985-01-01

201

Oxygen chemisorption cryogenic refrigerator  

Microsoft Academic Search

The present invention relates to a chemisorption compressor cryogenic refrigerator which employs oxygen to provide cooling at 60 to 100 K. The invention includes dual vessels containing an oxygen absorbent material, alternately heated and cooled to provide a continuous flow of high pressure oxygen, multiple heat exchangers for precooling the oxygen, a Joule-Thomson expansion valve system for expanding the oxygen

Jack A. Jones

1987-01-01

202

Modeling [15O] oxygen tracer data for estimating oxygen consumption  

PubMed Central

The most direct measure of oxidative tissue metabolism is the conversion rate of oxygen to water via mitochondrial respiration. To calculate oxygen consumption from the analysis of tissue residue curves or outflow dilution curves after injection of labeled oxygen one needs realistic mathematical models that account for convection, diffusion, and transformation in the tissue. A linear, three-region, axially distributed model accounts for intravascular convection, penetration of capillary and parenchymal cell barriers (with the use of appropriate binding spaces to account for oxygen binding to hemoglobin and myoglobin), the metabolism to [15O]water in parenchymal cells, and [15O]water transport into the venous effluent. Model solutions fit residue and outflow dilution data obtained in an isolated, red blood cell-perfused rabbit heart preparation and give estimates of the rate of oxygen consumption similar to those obtained experimentally from the flow times the arteriovenous differences in oxygen contents. The proposed application is for the assessment of regional oxidative metabolism in vivo from tissue 15O-residue curves obtained by positron emission tomography.

Deussen, Andreas; Bassingthwaighte, James B.

2010-01-01

203

Determination of oxygen self-diffusion in akermanite, anorthite, diopside, and spinel: Implications for oxygen isotopic anomalies and the thermal histories of Ca-Al-rich inclusions  

SciTech Connect

Oxygen self-diffusion coefficients have been measured for three natural diopsidic clinopyroxenes, a natural anorthite, a synthetic magnesium aluminate spinel, and a synthetic akermanite for oxygen fugacities ranging from the NNO to IW buffers. The oxygen diffusion data are used to evaluate the effects of three different types of thermal histories upon the oxygen isotopic compositions of minerals found in Type B Ca-Al-rich inclusions (CAIBs) in carbonaceous chondrites: (1) gas-solid exchange during isothermal heating, (2) gas-solid exchange as a function of cooling rate subsequent to instantaneous heating, and (3) isotopic exchange with a gaseous reservoir during partial melting and recrystallization. With the assumptions that the mineral compositions within a CAIB were uniformly enriched in [sup 16]O prior to any thermal processing, that effective diffusion dimensions may be estimated from observed grain sizes, and that diffusion in diopside is similar to that in fassaitic clinopyroxene, none of the above scenarios can reproduce the relative oxygen isotopic anomalies observed in CAIBs without improbably long or unrealistically intense thermal histories relative to current theoretical models of nebular evolution. The failure of these simple models, coupled with recent observations of disturbed magnesium isotopic abundances and correlated petrographic features in anorthite and melilite indicative of alteration and recrystallization, suggests that the oxygen isotopic compositions of these phases may have also been modified by alteration and recrystallization possibly interspersed with multiple melting events. Because the modal abundance of spinel remains relatively constant for plausible melting scenarios, and its relatively sluggish diffusion kinetics prevent substantial equilibration, Mg-Al spinel is the most reliable indicator of the oxygen isotopic composition of precursor material which formed Type B CAIs.

Ryerson, F.J. (Lawrence Livermore National Lab., CA (United States)); McKeegan, K.D. (Univ. of California, Los Angeles, CA (United States))

1994-09-01

204

Hyperbaric oxygen therapy  

MedlinePLUS

Hyperbaric oxygen therapy uses a special chamber, sometimes called a pressure chamber, to increase the amount of oxygen in ... the atmosphere. This helps your blood carry more oxygen to organs ... therapy can help wounds, especially infected wounds, heal more ...

205

Living with Oxygen Therapy  

MedlinePLUS

... page from the NHLBI on Twitter. Living With Oxygen Therapy Oxygen therapy helps many people function better and be ... chronic obstructive pulmonary disease) Although you may need oxygen therapy continuously or for long periods, it doesn' ...

206

Oxygen Injection System.  

National Technical Information Service (NTIS)

The oxygen injection system is for afterburners and ramjets which employs a particular type of flameholder structure for assisting in the distribution of oxygen. The design of the concentric flameholders is such that only a single oxygen line is required ...

R. E. Meyer W. E. Helfrich

1965-01-01

207

Oxygen stoichiometry, phase stability, and thermodynamic behavior of the lead-doped Bi-2223 and Ag/Bi-2223 systems.  

SciTech Connect

Electromotive-force (EMF) measurements of oxygen fugacities as a function of stoichiometry have been made in the lead-doped Bi-2223 superconducting system in the temperature range 700-815 C by means of an oxygen titration technique that employs an yttria-stabilized zirconia electrolyte. The results of our studies indicate that processing or annealing lead-doped Bi-2223 at temperatures ranging from 750 to 815 C and at oxygen partial pressures ranging from {approx} 0.02 to 0.2 atm should preserve Bi-2223 as essentially single-phase material. Thermodynamic assessments of the partial molar quantities {Delta}{bar S}(O{sub 2}) and {Delta}{bar H}(O{sub 2})indicate that the plateau regions in the plot of oxygen partial pressure versus oxygen stoichiometry (x) can be represented by the diphasic CuO---Cu2O system. In accord with the EMF measurements, it was found that lead-doped Bi-2223 in a silver sheath is stable at 815 C for oxygen partial pressures between 0.02 and 0.13 atm.

Tetenbaum, M.; Hash, M. C.; Tani, B. S.; Luo, J. S.; Maroni, V. A.; Chemical Engineering

1995-07-15

208

MEMS Calculator  

National Institute of Standards and Technology Data Gateway

SRD 166 MEMS Calculator (Web, free access)   This MEMS Calculator determines the following thin film properties from data taken with an optical interferometer or comparable instrument: a) residual strain from fixed-fixed beams, b) strain gradient from cantilevers, c) step heights or thicknesses from step-height test structures, and d) in-plane lengths or deflections. Then, residual stress and stress gradient calculations can be made after an optical vibrometer or comparable instrument is used to obtain Young's modulus from resonating cantilevers or fixed-fixed beams. In addition, wafer bond strength is determined from micro-chevron test structures using a material test machine.

209

Angular dependence of core hole screening in LiCoO2 : A DFT+U calculation of the oxygen and cobalt K -edge x-ray absorption spectra  

Microsoft Academic Search

Angular-dependent core hole screening effects have been found in the cobalt K -edge x-ray absorption spectrum of LiCoO2 , using high-resolution data and parameter-free general gradient approximation plus U calculations. The Co1s core hole on the absorber causes strong local attraction. The core hole screening on the cobalt nearest-neighbors induces a 2 eV shift in the density of states with

Amélie Juhin; Frank de Groot; György Vankó; Matteo Calandra; Christian Brouder

2010-01-01

210

Oxygen delivery from red cells.  

PubMed Central

This paper deals with the theoretical analysis of the unloading of oxygen from a red cell. A scale analysis of the governing transport equations shows that the solutions have a boundary layer structure near the red-cell membrane. The boundary layer is a region of chemical nonequilibrium, and it owes its existence to the fact that the kinetic time scales are shorter than the diffusion time scales in the red cell. The presence of the boundary layer allows an analytical solution to be obtained by the method of matched asymptotic expansions. A very useful result from the analysis is a simple, lumped-parameter description of the oxygen delivery from a red cell. The accuracy of the lumped-parameter description has been verified by comparing its predictions with results obtained by numerical integration of the full equations for a one-dimensional slab. As an application, we calculate minimum oxygen unloading times for red cells.

Clark, A; Federspiel, W J; Clark, P A; Cokelet, G R

1985-01-01

211

OXYGEN TRANSPORT CERAMIC MEMBRANES  

SciTech Connect

This is the third quarterly report on oxygen Transport Ceramic Membranes. In the following, the report describes the progress made by our university partners in Tasks 1 through 6, experimental apparatus that was designed and built for various tasks of this project, thermodynamic calculations, where applicable and work planned for the future. (Task 1) Design, fabricate and evaluate ceramic to metal seals based on graded ceramic powder/metal braze joints. (Task 2) Evaluate the effect of defect configuration on ceramic membrane conductivity and long term chemical and structural stability. (Task 3) Determine materials mechanical properties under conditions of high temperatures and reactive atmospheres. (Task 4) Evaluate phase stability and thermal expansion of candidate perovskite membranes and develop techniques to support these materials on porous metal structures. (Task 5) Assess the microstructure of membrane materials to evaluate the effects of vacancy-impurity association, defect clusters, and vacancy-dopant association on the membrane performance and stability. (Task 6) Measure kinetics of oxygen uptake and transport in ceramic membrane materials under commercially relevant conditions using isotope labeling techniques.

Dr. Sukumar Bandopadhyay; Dr. Nagendra Nagabhushana

2000-10-01

212

Oxygen supply and limiting oxygen pressures in an insect larva.  

PubMed

Larvae of the moth, Carpocapsa saltitans, demonstrate a diurnal activity pattern of rhythmic twitching which, under conditions of controlled light and temperature, is characterized by a predictable frequency and regularity. The twitching activity is shown to be sensitive to the partial pressure of environmental oxygen, and it ceases altogether at a particular PO2 called 'critical'. Use is made of the 'critical' PO2 in normobaric and hypobaric conditions to deduce the roles of diffusion and convection in the larval oxygen transport mechanisms; and also as a value for the total decrement of PO2 from ambient air to mitochondria, in order to evaluate predicted values based on calculations of resistance to oxygen flow. For this latter study 'porosity' of the larva and the seed pod in which it is normally housed was inferred from measured rates of water vapor loss, and oxygen uptake rates of the larvae were measured by the manometric technique of Warburg. Applying these data to a model system the conclusion was reached that almost the total resistance to oxygen flow is at the spiracle. PMID:4039837

Tenney, S M

1985-04-01

213

Oxygen-iodine laser research at RFNC-VNIIEF  

Microsoft Academic Search

The paper presents the most important efforts in the Chemical Oxygen-Iodine Laser (COIL) research carried on at Russian Federal Nuclear Center VNIIEF and some of their results. In particular, they include experimental data on the laser generation output of subsonic COIL on the water vapor concentration in singlet oxygen, calculated generation values of a supersonic COIL having high singlet oxygen

Anatoliy A. Adamenkov; Yuri N. Deryugin; Boris A. Vyskubenko; S. P. Ilyin; V. V. Kalinovsky; Yuriy V. Kolobyanin; V. V. Konovalov; Ivan M. Krukovsky; Evgeniy A. Kudryashov; V. D. Nikolaev

1998-01-01

214

The thermodynamic similarity of nitrogen, oxygen, and air  

Microsoft Academic Search

The thermodynamic similarity of nitrogen, oxygen, and air is established. The data for nitrogen are used to calculate the thermodynamic properties of oxygen at pressures of (1 1500)·105 N\\/m2 and temperatures of 170 1000 deg K. Tables of specific volume, enthalpy, entropy, and heat capacity of oxygen are given.

P. M. Kessel'Man; S. F. Gorykin

1965-01-01

215

The thermodynamic similarity of nitrogen, oxygen, and air  

Microsoft Academic Search

The thermodynamic similarity of nitrogen, oxygen, and air is established. The data for nitrogen are used to calculate the thermodynamic properties of oxygen at pressures of (1–1500)·105 N\\/m2 and temperatures of 170–1000 deg K. Tables of specific volume, enthalpy, entropy, and heat capacity of oxygen are given.

P. M. Kessel'man; S. F. Gorykin

1965-01-01

216

Oxygen Toxicity Risk Assessment.  

National Technical Information Service (NTIS)

Oxygen toxicity is a consequence of breathing oxygen partial pressures greater than in atmospheric air. While oxygen itself is not toxic, the evidence indicates that toxic derivatives of oxygen are a by-product of cellular respiration. The production of t...

R. D. Vann

1988-01-01

217

EXPERIMENTAL STUDY OF CONCENTRATION DEPENDENCE OF Ta2O5 SOLUBILITY IN THE ALKALINE SOLUTIONS AT T=550 o C, P=1000 BAR AND LOW OXYGEN FUGACITY (Co-CoO BUFFER)  

Microsoft Academic Search

To estimate quantitatively a possible role of postmagmatic processes in genesis of rare-metal de- posits of tantalum and niobium we performed systematic experimental investigations on mineral solu- bility of Ta and Nb under hydrothermal conditions, because the available experimental data are not enough to solve this problem. Earlier we investigated Ta oxide solubility in fluoride and chloride solu- tions what

IEM RAS

218

Vibrational modes of oxygen complexes in CdSe  

NASA Astrophysics Data System (ADS)

We have studied the doping of oxygen in CdSe using first principle calculations. In particular we have considered the possible formation of oxygen molecules and their complexes. We found that in CdSe oxygen molecules can form in interstitial locations in addition to substitutional sites associated with Cd vacancies. The localized phonon mode frequencies of these oxygen molecules and complexes have been calculated. Our results provide a plausible explanation for the unusual high frequency infrared absorption peaks observed experimentally in CdSe doped with oxygen.

Cheng, Wei; Liu, Lei; Yu, Peter Y.

2013-12-01

219

Oxygen-iodine laser research at RFNC-VNIIEF  

NASA Astrophysics Data System (ADS)

The paper presents the most important efforts in the Chemical Oxygen-Iodine Laser (COIL) research carried on at Russian Federal Nuclear Center VNIIEF and some of their results. In particular, they include experimental data on the laser generation output of subsonic COIL on the water vapor concentration in singlet oxygen, calculated generation values of a supersonic COIL having high singlet oxygen pressure at the nozzle inlet, and experiments with the twisted-aerosol- flow singlet oxygen generator (TASOG) for up to 100 Torr pressures. Requirements are discussed for the supersonic high- pressure COIL components, such as singlet oxygen generator and the system for singlet oxygen mixing with iodine.

Adamenkov, Anatoliy A.; Deryugin, Yuri N.; Vyskubenko, Boris A.; Ilyin, S. P.; Kalinovsky, V. V.; Kolobyanin, Yuriy V.; Konovalov, V. V.; Krukovsky, Ivan M.; Kudryashov, Evgeniy A.; Nikolaev, V. D.

1998-12-01

220

Survey calculations  

Microsoft Academic Search

One of my passions in life is to try and understand how we have developed the wonderful calculating ability we currently possess. Anyone with this hobby will undoubtedly start by looking back to see how the first PCs were developed, then progress back to older \\

Michael R. Williams

2004-01-01

221

Calculation Nation  

NSDL National Science Digital Library

This web site, which is part of the NCTM Illuminations project, allows students to challenge themselves or opponents from anywhere in the world by playing games that are organized around content from the upper elementary and middle grades math curriculum. The games allow students to learn about fractions, factors, multiples, symmetry, as well as practice important skills like basic multiplication and calculating area.

2011-01-01

222

Mercury Calculator  

NSDL National Science Digital Library

This interactive calculator produced by Teachers' Domain helps you determine the mercury levels in various types of fish, and enables you to make more informed choices about which fish are safe to eat and which should be avoided or eaten infrequently.

Foundation, Wgbh E.

2010-12-23

223

Inflation Calculator  

NSDL National Science Digital Library

This simple inflation calculator uses the Consumer Price Index to adjust any given amount of money, from 1800 to 1998. Creator S. Morgan Friedman uses data from the Historical Statistics of the United States for statistics predating 1975 and the annual Statistics Abstracts of the United States for data from 1975 to 1998. Links to other online inflation information are also included.

Friedman, S. M.

224

Oxygen chemisorption cryogenic refrigerator  

NASA Astrophysics Data System (ADS)

The present invention relates to a chemisorption compressor cryogenic refrigerator which employs oxygen to provide cooling at 60 to 100 K. The invention includes dual vessels containing an oxygen absorbent material, alternately heated and cooled to provide a continuous flow of high pressure oxygen, multiple heat exchangers for precooling the oxygen, a Joule-Thomson expansion valve system for expanding the oxygen to partially liquefy it and a liquid oxygen pressure vessel. The primary novelty is that, while it was believed that once oxygen combined with an element or compound the reaction could not reverse to release gaseous oxygen, in this case oxygen will indeed react in a reversible fashion with certain materials and will do so at temperatures and pressures which make it practical for incorporation into a cryogenic refrigeration system.

Jones, Jack A.

1987-10-01

225

Solid state oxygen sensor  

DOEpatents

Solid state oxygen sensors are provided with a yttria-doped zirconia as an electrolyte and use the electrochemical oxygen pumping of the zirconia electrolyte. A linear relationship between oxygen concentration and the voltage arising at a current plateau occurs when oxygen accessing the electrolyte is limited by a diffusion barrier. A diffusion barrier is formed herein with a mixed electronic and oxygen ion-conducting membrane of lanthanum-containing perovskite or zirconia-containing fluorite. A heater may be used to maintain an adequate oxygen diffusion coefficient in the mixed conducting layer. 4 figs.

Garzon, F.H.; Chung, B.W.; Raistrick, I.D.; Brosha, E.L.

1996-08-06

226

Living Without Oxygen: Oxygen Tolerance in Bacteria  

NSDL National Science Digital Library

This activity focuses on chemical processes, such as nitrogen fixation and denitrification, which are carried out by bacteria. Often the efficacy of these processes is determined by the amount of oxygen present in the environment in which the bacteria live. Much of the time, these processes are carried out by facultatively anaerobic bacteria in the suboxic region of lakes, oceans, sediments, and leaf litter. Students will discover whether facultatively anaerobic photoautotrophs share the same tolerance for oxygen, how differences in oxygen tolerance can be tested, and of what significance the tolerance for oxygen is in the nitrogen cycle. They will practice aseptic technique, monitor the growth of bacterial cultures, display their results graphically, and propose environmental problems associated with the oxygen tolerance of nitrogen fixers and denitifiers.

Harris, Sharon

227

Broken Calculator  

NSDL National Science Digital Library

This interactive applet helps students develop fluency and flexibility with numbers. At each of 6 difficulty levels the user is presented with 8 target numbers and a partial set of keys on a basic calculator (does not follow order of operations). The goal is to use the given keys to make as many of the target numbers as possible within the 3-minute time limit. Some levels include memory keys.

Barrow, Mandy

2008-01-01

228

Fe/Mn and Oxygen Constraints on the Composition of the Basaltic Achondrite Parent Body  

NASA Astrophysics Data System (ADS)

Introduction: The Fe/Mn ratios of basaltic achondrites (~30-40) do not match any chondrites [1]. The oxygen isotope ratios of these meteorites fall to the ^16O rich side of the terrestrial oxygen mass fractionation line and do not match any known chondrites [2]. Fe/Mn ratios of the achondrite precursors were low and reflect reflect oxygen fugacity driven variations in the Fe^2+/Fe^O ratio of the nebular precursor [3] instead of the volatility controlled depletion of Mn seen in C-chondrites [3,4]. Oxygen constraints favor a C-chondrite precursor to the basaltic achondrites, but the Fe-Mn-Mg constraints suggest an H-chondrite like precursor is more likely. Both constraints cannot be reconciled simultaneously with any known precursor nebular material and require either an unidentified (untestable) preplanetary precursor or a mixture of precursors that satisfies both constraints in combination. To test this later model, the oxygen isotopic ratios of basaltic achondrites are assumed to lie on the same mass fractionation line as their parent body bulk composition, and mixtures of different nebular materials were created using the oxygen isotope ratios of known potential precursors [5]. The mixing lines between a variety of Ochondrite and C-chondrite precursors intersect the basaltic achondrite mass fractionation line at the potential starting compositions from which basaltic achondrites fractionated. Several different mixtures of O- and C-chondrites produce potential compositions on the basaltic achondrite mass fractionation line. Mixing H and CM Chondrite Precursors: A mixture of average H chondrite and CM chondrites (represented by bulk Murchison) [6,7] illustrates this model. Mixing ~35 wt% Murchison and 65% average H chondrite gives an oxygen isotope ratio for the achondrite planetoid with delta^17O < 1 per mil heavier than the average basaltic achondrite. Although there is no data for solid-gas reactions on the parent body, this value may be a reasonable starting composition. With this H/CM ratio, the major and minor element bulk composition of the achondrite precursor can be calculated. This bulk composition strongly resembles the eucrite parent body generated by [8] with three exceptions: (i) The mixture contains ~19% FeO instead of the 14.4% [8]; (ii) The Fe/Mn ratio is 53 instead of 43; (iii) alkali elements Na and K are one order of magnitude too abundant. If the C content (~0.7 wt%) reacted with the FeO, it would reduce both the FeO content and Fe/Mn ratio (silicate) to values similar to Dreibus et al. Only the alkalis remain unexplained. Alkalis in the achondrite precursors cannot be depleted by simple volatility effects as Mn is undepleted and K isotopic systematics are presently incompatible with volatile depletion of K in basaltic achondrites [9]. The alkali elements remain unexplained by this model. Summary: Using oxygen isotopic ratios to constrain their ratio, at least one mix of H-chondrite (65 wt%) and carbonaceous- chondrite (35 wt%) precursors can provide a plausible basaltic achondrite parent body composition. This bulk composition contains sufficient C to reduce 19 wt% FeO in the mixture to 15%, a level compatible with reasonable estimates of the eucrite parent body. and also satisfies the Fe-Mn constraint on the parent body. This model predicts that the basaltic achondrite parent body contains about 16 wt% Fe metal and 6 wt% FeS that possibly formed a core. Trace element constraints can be applied to test this aspect of the model. References: [1] Delaney J. S. (1991) Meteoritics, 26. [2] Clayton et al. (1983) EPSL, 62. [3] Delaney J. S., this volume. [4] Kallemeyn and Wasson (1981) GCA, 45. [5] Clayton and Mayeda, (1992) Ann Rev. Earth Planet Sci. [6] Jarosewich (1990) Meteoritics, 25. [7] Wasson and Kallemeyn (1988) Trans. R. Soc. London, A325. [8] Dreibus et al (1977) Proc. LPSC, 8th. [9] Humayan and Clayton (1993) LPS XXIV. Acknowledgments: NASA Grant: NAG9-304.

Delaney, J. S.

1993-07-01

229

Miniature oxygen resuscitator  

NASA Technical Reports Server (NTRS)

Miniature, portable resuscitation system is used during evacuation of patients to medical facilities. A carrying case contains a modified resuscitator head, cylinder of oxygen, two-stage oxygen regulator, low pressure tube, and a mask for mouth and nose.

Johnson, G.; Teegen, J. T.; Waddell, H.

1969-01-01

230

Simulated Oxygen Breathing Apparatus.  

National Technical Information Service (NTIS)

A filter replaces the oxygen canister of an oxygen breathing apparatus and the air flow path is modified to provide a realistic simulation for training Personnel. in the use of closed circuit breathing units. (Author)

E. Swiatosz W. V. Dykes

1979-01-01

231

Home Oxygen Therapy  

MedlinePLUS

... important advantage of liquid oxygen is you can transfer some of the liquid oxygen into a smaller, ... from gas stoves, candles, lighted fireplaces, or other heat sources. Don't use any flammable products like ...

232

Oxygen Chemisorption Cryogenic Refrigerator.  

National Technical Information Service (NTIS)

The present invention relates to a chemisorption compressor cryogenic refrigerator which employs oxygen to provide cooling at 60 K to 100 K. The invention includes dual vessels containing an oxygen absorbent material, alternately heated and cooled to prov...

J. A. Jones

1986-01-01

233

Chemical Calculations  

NSDL National Science Digital Library

This site contains many chemistry applets created by Jonathan Goodman and his group at Cambridge University. An example of an applet available is the Molecular Weight Calculation; whereby entering in a molecular formula, users are able to discover the HRMS weight, the molecular weight, the element percents, and the Molecular Ion Isotope Pattern. Interactive graphs are also available to assist chemistry students with concepts such as boiling points, pressure, and Consecutive First Step Reversible Reactions. Educators and students will also find many three dimensional depictions of the molecules including fused rings, aromatic rings, and Fullerenes.

Goodman, Jonathan

234

Automatic Electronic Oxygen Supply  

PubMed Central

An automatic electronic oxygen system has been devised to supply an intensive care unit with a “fail-safe” supply of continuous oxygen. All parts of the system are fitted with alarms, as the oxygen powers gas-driven ventilators. Since the system is cheap it can be installed in hospitals where finance is limited.

Ford, Patricia; Hoodless, D. J.

1971-01-01

235

Atomic Oxygen Profile Measurements  

Microsoft Academic Search

A series of atomic oxygen profiles are presented that show evidence that silver film sensors provide reliable measurements of atomic oxygen density in the 90- to 120-km altitude range, Measurements were made at Wallops Island, Virginia, and Point Barrow, Alaska. The much lower atomic oxygen density observed for the high-latitude winter and spring shots is discussed in terms of the

Watson R. Henderson

1974-01-01

236

Determination of Oxygen Demand  

NASA Astrophysics Data System (ADS)

Oxygen demand is a commonly used parameter to evaluate the potential effect of organic pollutants on either a wastewater treatment process or a receiving water body. Because microorganisms utilize these organic materials, the concentration of dissolved oxygen is greatly depleted from the water. The oxygen depletion in the environment can have a detrimental effect on fish and plant life.

Hang, Yong D.

237

Oxygen sensitive microwells.  

PubMed

Oxygen tension is critical in a number of cell pathways but is often overlooked in cell culture. One reason for this is the difficulty in modulating and assessing oxygen tensions without disturbing the culture conditions. Toward this end, a simple method to generate oxygen-sensitive microwells was developed through embossing polystyrene (PS) and platinum(ii) octaethylporphyrin ketone (PtOEPK) thin films. In addition to monitoring the oxygen tension, microwells were employed in order to isolate uniform clusters of cells in microwells. The depth and width of the microwells can be adapted to different experimental parameters easily by altering the thin film processing or embossing stamp geometries. The thin oxygen sensitive microwell substrate is also compatible with high magnification modalities such as confocal imaging. The incorporation of the oxygen sensor into the microwells produces measurements of the oxygen tension near the cell surface. The oxygen sensitive microwells were calibrated and used to monitor oxygen tensions of Madin-Darby Canine Kidney Cells (MDCKs) cultured at high and low densities as a proof of concept. Wells 500 µm in diameter seeded with an average of 330 cells exhibited an oxygen level of 12.6% whereas wells seeded with an average of 20 cells per well exhibited an oxygen level of 19.5%, a 35.7% difference. This platform represents a new tool for culturing cells in microwells in a format amenable to high magnification imaging while monitoring the oxygen state of the culture media. PMID:20938500

Sinkala, Elly; Eddington, David T

2010-12-01

238

Operational Considerations for Oxygen Flammability Risks: Concentrated Oxygen Diffusion and Permeation Behaviors  

NASA Technical Reports Server (NTRS)

Increased human spaceflight operations utilize oxygen concentrations that are frequently varied with use of concentrations up to 100 percent oxygen. Even after exiting a higher percentage oxygen environment, high oxygen concentrations can still be maintained due to material saturation and oxygen entrapment between barrier materials. This paper examines the material flammability concerns that arise from changing oxygen environments during spaceflight operations. We examine the time required for common spacecraft and spacesuit materials exposed to oxygen to return to reduced ignitability and flammability once removed from the increased concentration. Various common spacecraft materials were considered: spacecraft cabin environment foams, Extra Vehicular Mobility Unit materials and foams, Advanced Crew Escape Suit materials, and other materials of interest such as Cotton, Nomex^ HT90-40, and Tiburon Surgical Drape. This paper presents calculated diffusion coefficients derived from experimentally obtained oxygen transmission rates for the tested materials and the analytically derived times necessary for reduced flammability to be achieved based on NASA flammability criteria. Oxygen material saturation and entrapment scenarios are examined. Experimental verification data on oxygen diffusion in saturation scenarios are also presented and discussed. We examine how to use obtained data to address flammability concerns during operational planning to reduce the likelihood of fires while improving efficiency for procedures.

Harper, Susana; Smith, Sarah; Juarez, Alfredo; Hirsch, David

2010-01-01

239

Core-mantle partitioning of oxygen on Earth and Mars (Invited)  

NASA Astrophysics Data System (ADS)

Oxygen is potentially one of the important light elements in the Earth’s core, based on geophysical observations and high-pressure experimental studies of the solubility and partitioning of oxygen into liquid Fe metal. However, its concentrations in the Earth’s core, as well as in the cores of Mercury, Venus and Mars, are still poorly constrained. In addition to Fe, Ni and S are important components in the cores of terrestrial planets. For example, based on cosmochemical constraints, the Earth’s core is considered to have a low S content (e.g. <2 wt%), whereas the Martian core is likely to have a much higher S concentration of up to 14 wt%. It is therefore important to understand how O partitions between silicates/oxides and liquid Fe alloy in Ni- and S-bearing systems. We have experimentally investigated the partitioning of oxygen between ferropericlase, and liquid Fe-Ni, Fe-S, and Fe-Ni-S metal at conditions up to 24.5 GPa and 2746 K using the Kawai-type multi-anvil apparatus. Our experimental results show that adding 10-20 mol% Ni to the metallic Fe at a fixed oxygen fugacity reduces the concentration of oxygen in the liquid metal, for example, from ~3 mol % to ~2 mol %. In contrast, adding up to 30 mol % S to liquid Fe increases the oxygen concentration by as much as 10 mol %. Experiments to determine the combined effects of Ni and S show a decrease in the effect of Ni on oxygen partitioning as the concentration of S in the metal increases. Our experimental data, together with previous studies of melting phase relations of Fe-Ni and Fe-S metals, are fitted using a thermodynamic model (asymmetric, regular solution model). By extrapolating to CMB conditions, oxygen concentrations in the core can be constrained, assuming equilibrium with the bulk of the mantle. Given that the maximum oxygen content of the core, based on the density deficit, is 6-9 wt%, this extrapolation shows that the core must be undersaturated in oxygen with respect to the bulk of the mantle. Two end-member consequences of this conclusion are (1) that the very base of the mantle is strongly depleted in FeO and (2) the uppermost part of the outer core consists of a thin buoyant FeO-rich liquid layer, as suggested by some seismological studies. Assuming core-mantle equilibrium, the Martian core could contain up to 2-4 wt% oxygen and, due to cooling since core formation, a solid FeO-rich layer may have formed at the base of the Martian mantle.

Tsuno, K.; Frost, D. J.; Rubie, D. C.

2010-12-01

240

Oxygen pressure measurement using singlet oxygen emission  

SciTech Connect

Pressure sensitive paint (PSP) provides a visualization of two-dimensional pressure distributions on airfoil and model automobile surfaces. One type of PSP utilizes platinum tetra(pentafluorophenyl)porphine (PtTFPP) dissolved in a fluoro-polymer film. Since the intense 650 nm triplet emission of PtTFPP is quenched by ground state oxygen, it is possible to measure two-dimensional oxygen concentration from the 650 nm emission intensity using a Stern-Volmer-type relationship. This article reports an alternative luminescence method to measure oxygen concentration based on the porphyrin-sensitized 1270 nm singlet oxygen emission, which can be imaged with an InGaAs near infrared camera. This direct measurement of oxygen emission complements and further validates the oxygen measurement based on PtTFPP phosphorescence quenching. Initial success at obtaining a negative correlation between the 650 nm PtTFPP emission and the 1270 nm O{sub 2} emission in solution led us to additional two-dimensional film studies using surfaces coated with PtTFPP, MgTFPP, and H{sub 2}TFPP in polymers in a pressure and temperature controlled chamber.

Khalil, Gamal E.; Chang, Alvin; Gouterman, Martin; Callis, James B.; Dalton, Larry R.; Turro, Nicholas J.; Jockusch, Steffen [Department of Chemistry, University of Washington, Seattle, Washington 98195 (United States); Department of Chemistry, Columbia University, New York, New York 10027 (United States)

2005-05-15

241

Oxygen partial pressure sensor  

DOEpatents

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

Dees, Dennis W. (Downers Grove, IL)

1994-01-01

242

Oxygen partial pressure sensor  

DOEpatents

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

Dees, D.W.

1994-09-06

243

An ab initio study of oxygen on strained graphene.  

PubMed

Graphene under strain exhibits new fascinating properties. In this work, I show that lattice strain introduced by uniform expansion of unit cells can strongly modify the chemical properties of graphene. By employing density functional theory calculations I found that strain enhances the bonding between atomic oxygen and graphene. Strain also increases the diffusion energy barrier of atomic oxygen on graphene; however, it reduces the activation energy for oxygen migrating through the graphene sheet. Strong stability enhancement of atomic oxygen on graphene induced by strain would also change molecular oxygen dissociation reactions from endothermic to exothermic. PMID:23945352

Nguyen, Manh-Thuong

2013-10-01

244

Reactive Oxygen Species and Cellular Oxygen Sensing  

PubMed Central

Many organisms activate adaptive transcriptional programs to help them cope with decreased oxygen levels, or hypoxia, in their environment. These responses are triggered by various oxygen sensing systems in bacteria, yeast and metazoans. In metazoans, the hypoxia inducible factors (HIFs) mediate the adaptive transcriptional response to hypoxia by upregulating genes involved in maintaining bioenergetic homeostasis. The HIFs in turn are regulated by HIF-specific prolyl hydroxlase activity, which is sensitive to cellular oxygen levels and other factors such as tricarboxylic acid cycle metabolites and reactive oxygen species (ROS). Establishing a role for ROS in cellular oxygen sensing has been challenging since ROS are intrinsically unstable and difficult to measure. However, recent advances in fluorescence energy transfer resonance (FRET)-based methods for measuring ROS are alleviating some of the previous difficulties associated with dyes and luminescent chemicals. In addition, new genetic models have demonstrated that functional mitochondrial electron transport and associated ROS production during hypoxia are required for HIF stabilization in mammalian cells. Current efforts are directed at how ROS mediate prolyl hydroxylase activity and hypoxic HIF stabilization. Progress in understanding this process has been enhanced by the development of the FRET-based ROS probe, an vivo prolyl hydroxylase reporter and various genetic models harboring mutations in components of the mitochondrial electron transport chain.

Cash, Timothy P; Pan, Yi; Simon, M. Celeste

2008-01-01

245

Simultaneous Monitoring of Vascular Oxygenation and Tissue Oxygen Tension of Breast Tumors under Hyperbaric Oxygen Exposure.  

National Technical Information Service (NTIS)

The goals of the study in the second stage is to investigate vascular oxygenation and tissue oxygen tension of breast tumor under four different hyperbaric oxygen exposures, using near-infrared spectroscopy and FOXY oxygen sensor simultaneously. Hyperbari...

M. Xia

2006-01-01

246

Oxygen ion conducting materials  

DOEpatents

An oxygen ion conducting ceramic oxide that has applications in industry including fuel cells, oxygen pumps, oxygen sensors, and separation membranes. The material is based on the idea that substituting a dopant into the host perovskite lattice of (La,Sr)MnO.sub.3 that prefers a coordination number lower than 6 will induce oxygen ion vacancies to form in the lattice. Because the oxygen ion conductivity of (La,Sr)MnO.sub.3 is low over a very large temperature range, the material exhibits a high overpotential when used. The inclusion of oxygen vacancies into the lattice by doping the material has been found to maintain the desirable properties of (La,Sr)MnO.sub.3, while significantly decreasing the experimentally observed overpotential.

Vaughey, John (Elmhurst, IL); Krumpelt, Michael (Naperville, IL); Wang, Xiaoping (Downers Grove, IL); Carter, J. David (Bolingbrook, IL)

2003-01-01

247

Ambient Oxygen Promotes Tumorigenesis  

PubMed Central

Oxygen serves as an essential factor for oxidative stress, and it has been shown to be a mutagen in bacteria. While it is well established that ambient oxygen can also cause genomic instability in cultured mammalian cells, its effect on de novo tumorigenesis at the organismal level is unclear. Herein, by decreasing ambient oxygen exposure, we report a ?50% increase in the median tumor-free survival time of p53?/? mice. In the thymus, reducing oxygen exposure decreased the levels of oxidative DNA damage and RAG recombinase, both of which are known to promote lymphomagenesis in p53?/? mice. Oxygen is further shown to be associated with genomic instability in two additional cancer models involving the APC tumor suppressor gene and chemical carcinogenesis. Together, these observations represent the first report directly testing the effect of ambient oxygen on de novo tumorigenesis and provide important physiologic evidence demonstrating its critical role in increasing genomic instability in vivo.

Starost, Matthew F.; Lago, Cory U.; Lim, Philip K.; Sack, Michael N.; Kang, Ju-Gyeong; Wang, Ping-yuan; Hwang, Paul M.

2011-01-01

248

Carbon substituting for oxygen in silicates: A novel mechanism for carbon incorporation in the deep Earth  

NASA Astrophysics Data System (ADS)

Traditionally, carbon in the deep Earth has been thought of in terms of either carbonate at high oxygen fugacities or graphite or diamond under more reducing conditions. However, material science studies of amorphous Si-O-C polymer derived ceramics have demonstrated that carbon can be accommodated as an anion substituting for oxygen in mixed silica tetrahedra. Furthermore these structures are energetically favorable relative to a mixture of crystalline silica, silicon carbide, and graphite by ten or more kJ/g.atom. Thermodynamic stability suggests that these nano-structured composites are a potentially important storage mechanism for carbon under moderately reducing conditions. Here we expand the scope of the previous work by examining the compositional effect of geologically relevant cations (calcium and magnesium) on the thermodynamic stability, nanostructure, and ability to accommodate carbon of these composites. Silicon oxy-carbides doped with magnesium, magnesium and calcium or undoped resisted crystallization at 1100 C under inert atmosphere. 29Si NMR of the samples shows a similar distribution of silicon between end-member and mixed sites (Table 1). Results are presented from studies utilizing NMR, high temperature solution calorimetry, and microprobe. Table 1. Percentages of Si species in each material as determined by 29Si NMR.

Armentrout, M. M.; Tavakoli, A.; Ionescu, E.; Mera, G.; Riedel, R.; Navrotsky, A.

2013-12-01

249

Comparative quantification of oxygen release by wetland plants: electrode technique and oxygen consumption model.  

PubMed

Understanding oxygen release by plants is important to the design of constructed wetlands for wastewater treatment. Lab-scale systems planted with Phragmites australis were studied to evaluate the amount of oxygen release by plants using electrode techniques and oxygen consumption model. Oxygen release rate (0.14 g O2/m(2)/day) measured using electrode techniques was much lower than that (3.94-25.20 gO2/m(2)/day) calculated using the oxygen consumption model. The results revealed that oxygen release by plants was significantly influenced by the oxygen demand for the degradation of pollutants, and the oxygen release rate increased with the rising of the concentration of degradable materials in the solution. The summary of the methods in qualifying oxygen release by wetland plants demonstrated that variations existed among different measuring methods and even in the same measuring approach. The results would be helpful for understanding the contribution of plants in constructed wetlands toward actual wastewater treatment. PMID:23872897

Wu, Haiming; Liu, Jufeng; Zhang, Jian; Li, Cong; Fan, Jinlin; Xu, Xiaoli

2014-01-01

250

Rockets using Liquid Oxygen  

NASA Technical Reports Server (NTRS)

It is my task to discuss rocket propulsion using liquid oxygen and my treatment must be highly condensed for the ideas and experiments pertaining to this classic type of rocket are so numerous that one could occupy a whole morning with a detailed presentation. First, with regard to oxygen itself as compared with competing oxygen carriers, it is known that the liquid state of oxygen, in spite of the low boiling point, is more advantageous than the gaseous form of oxygen in pressure tanks, therefore only liquid oxygen need be compared with the oxygen carriers. The advantages of liquid oxygen are absolute purity and unlimited availability at relatively small cost in energy. The disadvantages are those arising from the impossibility of absolute isolation from heat; consequently, allowance must always be made for a certain degree of vaporization and only vented vessels can be used for storage and transportation. This necessity alone eliminates many fields of application, for example, at the front lines. In addition, liquid oxygen has a lower specific weight than other oxygen carriers, therefore many accessories become relatively larger and heavier in the case of an oxygen rocket, for example, the supply tanks and the pumps. The advantages thus become effective only in those cases where definitely scheduled operation and a large ground organization are possible and when the flight requires a great concentration of energy relative to weight. With the aim of brevity, a diagram of an oxygen rocket will be presented and the problem of various component parts that receive particularly thorough investigation in this classic case but which are also often applicable to other rocket types will be referred to.

Busemann, Adolf

1947-01-01

251

Solid state oxygen sensor  

DOEpatents

A potentiometric oxygen sensor is formed having a logarithmic response to a differential oxygen concentration while operating as a Nernstian-type sensor. Very thin films of mixed conducting oxide materials form electrode services while permitting diffusional oxygen access to the interface between the zirconia electrolyte and the electrode. Diffusion of oxygen through the mixed oxide is not rate-limiting. Metal electrodes are not used so that morphological changes in the electrode structure do not occur during extended operation at elevated temperatures. 6 figs.

Garzon, F.H.; Brosha, E.L.

1997-12-09

252

Elastomer Compatible With Oxygen  

NASA Technical Reports Server (NTRS)

Artificial rubber resists ignition on impact and seals at low temperatures. Filled fluoroelastomer called "Katiflex" developed for use in seals of vessels holding cold liquid and gaseous oxygen. New material more compatible with liquid oxygen than polytetrafluoroethylene. Provides dynamic seal at -196 degrees C with only 4 times seal stress required at room temperature. In contrast, conventional rubber seals burn or explode on impact in high-pressure oxygen, and turn hard or even brittle at liquid-oxygen temperatures, do not seal reliably, also see (MFS-28124).

Martin, Jon W.

1987-01-01

253

Radiative accelerations on carbon, nitrogen and oxygen  

Microsoft Academic Search

Radiative accelerations acting on the elements carbon, nitrogen and oxygen are calculated over a large range of plasma parameters which covers the conditions of A-F star envelopes. The theoretical atomic data available from the OPACITY project (OP) have been extensively used to perform a detailed computation of radiative accelerations including the contribution of lines and photoionization for all ions of

J.-F. Gonzalez; M.-C. Artru; G. Michaud

1995-01-01

254

Aircrew oxygen system  

NASA Technical Reports Server (NTRS)

Closed-loop rebreather system which includes pilot provides oxygen for use in aircraft by safe, reliable method of low weight and size and reduces expense of ground equipment. Water electrolysis generated oxygen is fed into rebreather loop which allows nitrogen elimination and water and carbon dioxide removal.

Babinsky, A. D.; Kiraly, R. J.; Wynveen, R. A.

1972-01-01

255

Production of Oxygen  

NSDL National Science Digital Library

In this chemistry activity, learners use yeast and hydrogen peroxide to generate a gas (oxygen) and test some of its properties. This resource includes brief questions for learners to answer after the experiment. Use this activity to introduce learners to oxygen as well as combustion. Note: this activity involves an open flame.

House, The S.

2014-01-28

256

Small Oxygen Concentrator.  

National Technical Information Service (NTIS)

Onboard oxygen generating systems (OBOGS) require large quantities of air. When toxic contaminants are present, this air volume can become a problem. A small oxygen concentrator (SOC) was developed to operate at 10% the air volume and 4% the molecular sie...

C. F. Theis K. G. Ikels R. G. Dornes

1985-01-01

257

Oxygen Poisoning in Drosophila.  

National Technical Information Service (NTIS)

Fruit flies live longer at the partial pressure of oxygen found in air than at either larger or smaller partial pressures. Flies exposed to 1 atm of oxygen for 8 hr every day do not recover completely in the remaining 16 hr. In general, intermittent expos...

W. O. Fenn M. Henning M. Philpott

1967-01-01

258

Durability of oxygen sensors  

NASA Astrophysics Data System (ADS)

This report describes the results of dynamometer and vehicle durability testing from a variety of sources, as well as common causes of failure for oxygen sensors. The data indicates that oxygen sensors show low failure rates, even at mileages of 80,000 miles and beyond.

Snapp, L.

1985-03-01

259

Pumping oxygen into gasoline  

Microsoft Academic Search

To reduce atmospheric concentration of certain pollutants notably carbon monoxide (CO), incompletely combusted hydrocarbons and nitrogen oxides (NOx), EPA as early as January 1988 began testing oxygenated fuels in such cities as Denver and Albuquerque, N.M. The CAA Amendments require using oxygenated gasoline in cities where CO levels exceed National Ambient Air Quality standards. The law, which became effective Nov.

Wray

1993-01-01

260

Oxygen Therapy for Children  

MedlinePLUS

... around the mask so the lowest level of oxygen flow used with a face mask is 5 liters. If you use a very high flow with nasal cannula, it can be more irritating to the nose. If more than that is needed, you should switch to a ... to help keep the oxygen moist can help prevent nose irritation from dry ...

261

Atomic oxygen textured polymers  

NASA Technical Reports Server (NTRS)

Atomic oxygen can be used to microscopically alter the surface morphology of polymeric materials in space or in ground laboratory facilities. For polymeric materials whose sole oxidation products are volatile species, directed atomic oxygen reactions produce surfaces of microscopic cones. However, isotropic atomic oxygen exposure results in polymer surfaces covered with lower aspect ratio sharp-edged craters. Isotropic atomic oxygen plasma exposure of polymers typically causes a significant decrease in water contact angle as well as altered coefficient of static friction. Such surface alterations may be of benefit for industrial and biomedical applications. The results of atomic oxygen plasma exposure of thirty-three (33) different polymers are presented, including typical morphology changes, effects on water contact angle, and coefficient of static friction.

Banks, Bruce A.; Rutledge, Sharon K.; Hunt, Jason D.; Drobotij, Erin; Cales, Michael R.; Cantrell, Gidget

1995-01-01

262

Mössbauer spectroscopic determination of Fe3+/Fe2+ in synthetic basaltic glass: a test of empirical fO2 equations under superliquidus and subliquidus conditions  

NASA Astrophysics Data System (ADS)

One of the most widely used methods to estimate magmatic oxygen fugacity involves the use of empirical equations relating fO2 to the iron redox state in quenched silicate liquids; however none of the equations have been calibrated experimentally under subliquidus conditions at temperatures and oxygen fugacities that are relevant to natural magmas. To address this problem, we tested two empirical relationships [Eq. (1) in Kress and Carmichael 1991; Eq. (6) in Nikolaev et al. 1996] on synthetic glasses synthesized from a ferrobasaltic and a transitional alkali-basaltic composition at sub- to superliquidus temperatures (1,132-1,222°C) and controlled oxygen fugacities (?FMQ=-2 to +1.4). Fe3+/?Fe was determined using conventional and milliprobe Mössbauer spectroscopy, and verified using wet chemical analysis on selected samples. For the ferrobasaltic bulk composition ``SC1-P'', both empirical models reproduce the Fe3+/?Fe ratio of the quenched liquids generally within 0.03 for sub- as well as superliquidus temperatures, although agreement is worse at higher oxygen fugacities (?FMQ>+1) at subliquidus temperatures. For the transitional alkali-basaltic composition ``7159V-P'', both models reproduce the Fe3+/?Fe ratio of the quenched liquids generally within 0.04, although agreement is worse for both models at high oxygen fugacities (?FMQ>+1). Such behaviour may be related to a change in melt structure, where a progressive change in Fe3+ coordination is inferred to occur as a function of Fe3+/?Fe based on Mössbauer center shifts. Recasting the data in terms of oxygen fugacity shows that calculated oxygen fugacities deviate from those actually maintained during the equilibration of the sample material by generally no more than 0.5 log-bar unit, with maximum deviations that only rarely exceed one log-bar unit.

Partzsch, Georg M.; Lattard, Dominique; McCammon, Catherine

263

Polarized thermal microwave emission from oxygen in the mesosphere  

Microsoft Academic Search

The thermally emitted microwave spectrum of the terrestrial atmosphere, viewed from above, is calculated for frequencies in the vicinity of a Zeeman-split oxygen line. Previously omitted phase terms are included; their effect on brightness temperature can be as large as 1.5 K for linearly polarized measurements. For the purpose of using oxygen lines as a probe of the atmospheric temperature

P. W. Rosenkranz; D. H. Staelin

1988-01-01

264

The measurement of hemoglobin oxygen saturation using multiwavelength photoacoustic microscopy  

Microsoft Academic Search

Hemoglobin oxygen saturation (SO2) is one of the most critical functional parameters to the metabolism. In this paper, we mainly introduced some initial results of measuring blood oxygen using multi-wavelength photoacoustic microscopy (PAM). In phantom study, we demonstrate the photoacoustic signal amplitude increases linearly with the concentration of red or blue ink. Then the calculated concentration of red ink in

Zilin Deng; Xiaoquan Yang; Lejun Yu; Hui Gong

2009-01-01

265

Structural and Symmetric Properties of Oxygen at 350 GPa  

Microsoft Academic Search

We have performed density functional electronic structure calculations for oxygen at 350 GPa, using the quantum espresso package with ultrasoft pseudopotentials and PBE exchange and correlation functional. The random search method was used to determine the enthalpies and lattice parameters of monatomic oxygen at 350 GPa. Other chalcogen elements (Po, Te, Se, S) all take a rhombohedral beta-Po structure when

C. V. Farnsworth; J. A. Montoya

2008-01-01

266

Free-Bound Radiation from Nitrogen, Oxygen, and Air.  

National Technical Information Service (NTIS)

Photoabsorption cross sections for nitrogen and oxygen atoms were computed using the method of Burgess and Seaton (Burgess, A. and Seaton, M. F., 'A General Formula for the Calculation of Photo-ionization Cross Sections,' Monthly Notices Royal Astronautic...

J. L. Kulander M. P. Sherman

1965-01-01

267

Interaction of oxygen vacancies in yttrium germanates.  

PubMed

Forming a good Ge/dielectric interface is important to improve the electron mobility of a Ge metal oxide semiconductor field-effect transistor. A thin yttrium germanate capping layer can improve the properties of the Ge/GeO(2) system. We employ electronic structure calculations to investigate the effect of oxygen vacancies in yttrium-doped GeO(2) and the yttrium germanates Y(2)Ge(2)O(7) and Y(2)GeO(5). The calculated densities of states indicate that dangling bonds from oxygen vacancies introduce in-gap states, but the system remains insulating. However, yttrium-doped GeO(2) becomes metallic under oxygen deficiency. Y-doped GeO(2), Y(2)Ge(2)O(7) and Y(2)GeO(5) are calculated to be oxygen substoichiometric under low Fermi energy conditions. The use of yttrium germanates is proposed as a way to effectively passivate the Ge/dielectric interface. PMID:23032364

Wang, H; Chroneos, A; Dimoulas, A; Schwingenschlögl, U

2012-11-14

268

Oxygen and Biological Evolution.  

ERIC Educational Resources Information Center

Discussed is the evolution of aerobic organisms from anaerobic organisms and the accompanying biochemistry that developed to motivate and enable this evolution. Uses of oxygen by aerobic organisms are described. (CW)

Baugh, Mark A.

1990-01-01

269

[An oxygen delivery device with a jet nebulizer function (Inspiron Nebulizer or Aquapak Nebulizer) can not provide high concentrations of oxygen to adult patients with respiratory failure].  

PubMed

Oxygen delivery devices with a jet nebulizer function are widely used in Japan. The device, utilizing the Bernoulli principle, can provide oxygen concentrations of 24-100%. The present study demonstrated that maximal inspired oxygen concentration provided by this oxygen delivery device is theoretically 60%, as total gas flow is insufficient to meet all inspiratory requirements to provide oxygen concentrations of greater than 60%. This theoretical calculation was verified using a face model to which oxygen was delivered using an Inspiron Nebulizer or Aquapak Nebulizer. PMID:16218417

Miyamoto, Kenji

2005-09-01

270

Collect Oxygen Over Water  

NSDL National Science Digital Library

In this activity, learners use a pneumatic trough (see related activity) to generate and collect pure oxygen. Learners will test to see if they've generated oxygen by observing the combustion of elemental sulfur, which yields a brilliant blue flame of sulfur oxidation. The manganese dioxide catalyst used in this process is easily recovered from a spent zinc-carbon battery (see related activity).

Ragan, Sean M.

2011-01-01

271

Oxygen Movement in Seagrasses  

Microsoft Academic Search

Seagrasses are, like all vascular plants, obligate aerobes, which require a continuous supply of oxygen to sustain aerobic\\u000a metabolism of both above- and below-ground tissues. Compared to their leaves, seagrass roots and rhizomes may experience oxygen\\u000a deprivation for shorter periods, but these below-ground tissues exhibit physiological adaptations which allow them to rely\\u000a temporarily on anaerobic fermentative metabolism (Pregnall et al.,

Jens Borum; Kaj Sand-Jensen; Thomas Binzer; Ole Pedersen; Tina Maria Greve

272

Oxygen toxicity in Astasia  

PubMed Central

1. Exposure of Astasia longa to oxygen+carbon dioxide (95:5) at atmospheric pressure leads to an inhibition of growth rate and of respiration. Growth resumes at the normal rate as soon as the oxygenation is discontinued, but respiration recovers more slowly. 2. Mitochondria prepared from cells exposed to oxygen+carbon dioxide (95:5) during growth have considerably decreased activities of succinate–cytochrome c oxidoreductase, NADH–cytochrome c oxidoreductase, succinate dehydrogenase and succinate oxidase activities as compared with mitochondria obtained from cells exposed to air+carbon dioxide (95:5). Cytochrome oxidase activity is not appreciably inhibited by exposure of the cells to 95% oxygen. 3. The mitochondrial fraction of Astasia contains rhodoquinone. The rhodoquinone concentration increases in cells exposed to 95% oxygen. The content of ergosterol-containing compounds also increases in the mitochondria of cells exposed to 95% oxygen. There is little change in the ubiquinone content of the mitochondrial fraction. The ubiquinone of Astasia appears to be ubiquinone-45.

Begin-Heick, Nicole; Blum, J. J.

1967-01-01

273

Excitation of the [sup 3][ital P][sub [ital J]=0,1,2] fine-structure levels of atomic oxygen in collisions with oxygen atoms  

SciTech Connect

A fully quantal calculation of the excitation cross sections for the fine-structure levels of ground-state atomic oxygen, in collisions with oxygen atoms at low energies, is presented. The results are compared with the cross sections obtained in a previous calculation.

Zygelman, B. (Department of Physics, University of Nevada at Las Vegas, Las Vegas, Nevada 89154 (United States)); Dalgarno, A. (Harvard Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138 (United States)); Sharma, R.D. (Optical Environment Division, Phillips Laboratory, 29 Randolph Road, Hanscom Air Force Base, Massachusetts 01731-3010 (United States))

1994-11-01

274

Oxygen solubility in silicon-containing Fe-Co melts  

NASA Astrophysics Data System (ADS)

Thermodynamic analysis of the oxygen solutions in silicon-containing Fe-Co melts is performed. The equilibrium constant of silicon deoxidation of iron-cobalt melts, the activity coefficients for infinite dilution, and the interaction parameters for melts differing in composition are determined. The dependences of the oxygen solubility in the melts under study are calculated for different cobalt and silicon contents. The deoxidizing capacity of silicon increases substantially as the cobalt content in a melt increases. The curves of oxygen solubility in Fe-Co melts have a minimum; the minimum oxygen solubility shifts to a low silicon content as the cobalt content in the melts increases. The silicon contents for the minima in the curves of oxygen solubility and the minimum oxygen concentrations corresponding to the silicon contents are determined.

Aleksandrov, A. A.; Dashevskii, V. Ya.

2013-11-01

275

Effects of atomic oxygen on graphite ablation  

NASA Technical Reports Server (NTRS)

It is shown that a previously derived semiempirical equation for describing observed ablation rates of isotropic graphites cannot be applied to low-density flows containing dissociated oxygen. Experimentally determined reaction probabilities of isotropic graphites to molecular and atomic oxygen are used to calculate heat-transfer rates and stagnation-point ablation rates for typical conditions. Integrated mass losses are computed for a group of flight trajectories which start from geosynchronous orbit and enter earth's atmosphere in a skipping motion following near-elliptic decaying orbits. A comparison of the results with those obtained by the equation under question shows excellent agreement for steep trajectories, but large discrepancies for shallow trajectories. The differences are attributed to surface oxidation by atomic oxygen.

Park, C.

1976-01-01

276

Lunar oxygen production by pyrolysis of regolith  

NASA Technical Reports Server (NTRS)

Oxygen represents one of the most desirable products of lunar mining and manufacturing. Among the many processes which have been proposed for oxygen production, pyrolysis stands out as one which is uncomplicated and easy to bootstrap. Pyrolysis or vapor-phase reduction involves heating regolith to temperatures sufficient to allow partial decomposition and vaporization. Some metal oxides give up oxygen upon heating, either in the gas phase to form reduced gaseous species or in the condensed phase to form a metallic phase. Based on preliminary experiments and equilibrium calculations, the temperatures needed for pyrolysis are expected to be in the range of 2000 to 2200 K, giving total gas pressures of 0.001 to 0.1 torr. Bulk regolith can be used as a feedstock without beneficiation with concentrated solar radiation supplying most of energy needed. Further, selective condensation of metal-containing species from the gas phase may yield metallic iron and silicon as byproducts.

Senior, Constance L.

1991-01-01

277

Activation of molecular oxygen in trifluoroacetic acid  

NASA Astrophysics Data System (ADS)

The interaction of molecular oxygen with aqueous trifluoroacetic acid (TFA) led to an increase in pH. This effect was explained by a decrease in the concentration of the protonated CF3CO2H{2/+} and H3O+ species after oxygen was fed in the reactor. Quantum-chemical calculations show that a radical pair can be formed in an activation-free exothermal reaction involving the radical residue of the acid, the CF3CO2H{2/+}...3O2...CF3CO{2/-} peroxide radical, and the acid molecule in the CF3C{2/·}...HOO· collision complex. It was assumed that the activation of molecular oxygen in aqueous TFA solutions, providing the activity of the system in oxidations of various organic and inorganic substrates, is related to the formation of peroxide radicals in them.

Vishnetskaya, M. V.; Vasin, A. V.; Solkan, V. N.; Zhidomirov, G. M.; Mel'Nikov, M. Ya.

2010-11-01

278

Using Excel to Calculate Mineral Chemical Analyses  

NSDL National Science Digital Library

In this assignment, students are provided instructions to make an Excel spreadsheet to calculate mineral chemical analyses from weight percent to atoms per given number of oxygen atoms. This skill will be useful for the major rock-forming mineral groups.

279

Calculating Thermophysical Properties Of 12 Fluids  

NASA Technical Reports Server (NTRS)

MIPROPS is set of computer programs giving thermophysical and transport properties of selected fluids. Calculates properties of fluids in both liquid and vapor states over wide range of temperatures and pressures. Fluids included: helium, hydrogen, nitrogen, oxygen, argon, nitrogen trifluoride, methane, ethylene, ethane, propane, isobutane, and normal butane. All programs except helium program incorporate same equation of state. Written in FORTRAN 77.

Cleghorn, T. F.; Mccarty, R. D.

1991-01-01

280

HENRY'S LAW CALCULATOR  

EPA Science Inventory

On-Site was developed to provide modelers and model reviewers with prepackaged tools ("calculators") for performing site assessment calculations. The philosophy behind OnSite is that the convenience of the prepackaged calculators helps provide consistency for simple calculations,...

281

Optical oxygen concentration monitor  

DOEpatents

A system for measuring and monitoring the concentration of oxygen uses as a light source an argon discharge lamp, which inherently emits light with a spectral line that is close to one of oxygen`s A-band absorption lines. In a preferred embodiment, the argon line is split into sets of components of shorter and longer wavelengths by a magnetic field of approximately 2,000 Gauss that is parallel to the light propagation from the lamp. The longer wavelength components are centered on an absorption line of oxygen and thus readily absorbed, and the shorter wavelength components are moved away from that line and minimally absorbed. A polarization modulator alternately selects the set of the longer wavelength, or upshifted, components or the set of the shorter wavelength, or downshifted, components and passes the selected set to an environment of interest. After transmission over a path through that environment, the transmitted optical flux of the argon line varies as a result of the differential absorption. The system then determines the concentration of oxygen in the environment based on the changes in the transmitted optical flux between the two sets of components. In alternative embodiments modulation is achieved by selectively reversing the polarity of the magnetic field or by selectively supplying the magnetic field to either the emitting plasma of the lamp or the environment of interest. 4 figs.

Kebabian, P.

1997-07-22

282

Oxygen consumption through metabolism and photodynamic reactions in cells cultured on microbeads  

Microsoft Academic Search

Oxygen consumption by cultured cells, through metabolism and photosensitization reactions, has been calculated theoretically. From this result, we have derived the partial oxygen pressure PO2 in the perfusion medium flowing across sensitized cultured cells during photodynamic experiments. The PO2 variations in the perfusate during light irradiation are related to the rate of oxygen consumption through photoreactions, and to the number

T. Schunck; P. Poulet

2000-01-01

283

Regulation of tissue oxygen levels in the mammalian lens  

PubMed Central

Opacification of the lens nucleus is a major cause of blindness and is thought to result from oxidation of key cellular components. Thus, long-term preservation of lens clarity may depend on the maintenance of hypoxia in the lens nucleus. We mapped the distribution of dissolved oxygen within isolated bovine lenses and also measured the rate of oxygen consumption (Q?O2) by lenses, or parts thereof. To assess the contribution of mitochondrial metabolism to the lens oxygen budget, we tested the effect of mitochondrial inhibitors on Q?O2 and partial pressure of oxygen (PO2). The distribution of mitochondria was mapped in living lenses by 2-photon microscopy. We found that a steep gradient of PO2 was maintained within the tissue, leading to PO2 < 2 mmHg in the core. Mitochondrial respiration accounted for approximately 90% of the oxygen consumed by the lens; however, PO2 gradients extended beyond the boundaries of the mitochondria-containing cell layer, indicating the presence of non-mitochondrial oxygen consumers. Time constants for oxygen consumption in various regions of the lens and an effective oxygen diffusion coefficient were calculated from a diffusion–consumption model. Typical values were 3 × 10?5 cm2 s?1 for the effective diffusion coefficient and a 5 min time constant for oxygen consumption. Surprisingly, the calculated time constants did not differ between differentiating fibres (DF) that contained mitochondria and mature fibres (MF) that did not. Based on these parameters, DF cells were responsible for approximately 88% of lens oxygen consumption. A modest reduction in tissue temperature resulted in a marked decrease in Q?O2 and the subsequent flooding of the lens core with oxygen. This phenomenon may be of clinical relevance because cold, oxygen-rich solutions are often infused into the eye during intraocular surgery. Such procedures are associated with a strikingly high incidence of postsurgical nuclear cataract.

McNulty, Richard; Wang, Huan; Mathias, Richard T; Ortwerth, Beryl J; Truscott, Roger J W; Bassnett, Steven

2004-01-01

284

Mitochondrial regulation of oxygen sensing  

Microsoft Academic Search

Maintenance of oxygen homoeostasis is required for the survival of higher organisms. The transcription factor hypoxia inducible factor (HIF) has a crucial role in oxygen homoeostasis by integrating the decrease in oxygen levels to increase hypoxic gene expression. How cells sense decrease in oxygen levels to elicit an increase in HIF dependent gene expression is not fully understood. In this

Eric L. Bell; Brooke M. Emerling; Navdeep S. Chandel

2005-01-01

285

Electric properties, spectroscopy, and singlet delta oxygen yield of electron-beam sustained discharge in oxygen gas mixtures  

NASA Astrophysics Data System (ADS)

Electric properties and spectroscopy of an e-beam sustained discharge (EBSD) in oxygen and oxygen gas mixtures at gas pressures up to 100 Torr was experimentally studied in large excitation volume (~18 liter). The discharge in pure oxygen and its mixtures with noble gases was shown to be very unstable and characterized by low input energy. When adding small amount of carbon monoxide or hydrogen, the electric stability of the discharge increases, specific input energy per molecular component being higher more than order of magnitude and coming up to 6.5 kJ/(l atm). Theoretical calculations demonstrated that for the experimental conditions the singlet delta oxygen yield may reach ~20% exceeding its threshold value needed for oxygen-iodine laser operation at room temperature. The results of experiments on spectroscopy of the singlet delta and singlet sigma oxygen states in the EBSD are presented.

Frolov, Michail P.; Hager, Gordon D.; Ionin, Andrei A.; Klimachev, Yurii M.; Kochetov, Igor V.; Kotkov, Andrei A.; McIver, Jack; Napartovich, Anatolii P.; Podmar'kov, Yurii P.; Seleznev, Leonid V.; Sinitsyn, Dmitrii V.; Vagin, Nikolai P.; Yuryshev, Nikolai N.

2004-05-01

286

Lunar Oxygen as Monopropellant  

NASA Astrophysics Data System (ADS)

This paper explores the feasibility of beamed energy propulsion to provide transportation to and from the lunar surface to low lunar orbit using lunar oxygen as propellant. Oxygen, as an Electro-Thermal Propulsion (ETP) monopropellant, has specific impulse comparing favorably with chemical bipropellants, though not as high as cryogenic LO2+LH2. Lunar hydrogen is not available in non-polar regions and costly to transport from earth for use as fuel for lunar operations. However, oxygen is a major component of lunar soil and available given ISRU (In Situ Resource Utilization) infrastructure. Low-gravity and vacuum environment plus low velocity increments are distinct advantages favoring lunar-based beamed energy propulsion. In lunar vacuum and low gravity environment, energy storage devices such as SMES (Superconductor Magnet Energy Storage) and FES (Flywheel Energy Storage) should exhibit improved efficiency. Microwave source design also favors vacuum operation.

Johansen, Donald G.

2008-04-01

287

The Rise of Oxygen  

NSDL National Science Digital Library

This story follow geologists as they hunt for, pickaxe, and test rock samples from the 2.5 billion year old Huronian Supergroup, a sedimentary formation in Ontario, Canada. The scientists are in search of an exact record of how much oxygen gas Earth's developing atmosphere contained at key moments in geologic time. These crustal relics, which have interacted directly with ancient atmospheres, have the power to tell scientists when and how the Earth built up its incredible life-support system to foster more and more complex organisms. The story includes links to the essays "Earth Without Oxygen," "An Ode to O," "Footprints of the Air," and "Life Makes a Mark."

288

Life with Oxygen  

NSDL National Science Digital Library

Access to the article is free, however registration and sign-in are required. Hypoxia-inducible factor 1 (HIF-1) is a transcription factor that functions as a master regulator of oxygen homeostasis and has essential roles in metazoan development, physiology, and disease pathogenesis. Remarkable progress has been made in delineating the molecular mechanisms whereby changes in cellular oxygenation are transduced to the nucleus as changes in gene transcription through the activity of HIF-1. Pharmacologic agents that activate or inhibit the hypoxia signal transduction pathway may be useful therapies for ischemic and neoplastic disorders, respectively, which are the major causes of mortality in industrialized societies.

Gregg L. Semenza (The Johns Hopkins University School of Medicine;Vascular Program, Institute for Cell Engineering; Departments of Pediatrics, Medicine, Oncology, Radiation Oncology; and McKusick-Nathans Institute of Genetic Medicine)

2007-10-05

289

Novel nanostructured oxygen sensor  

NASA Astrophysics Data System (ADS)

New government regulations and industry requirements for medical oxygen sensors require the development of alternate materials and process optimization of primary sensor components. Current oxygen sensors are not compliant with the Restriction of Hazardous Substances (RoHS) Directive. This work focused on two areas. First, was finding suitable readily available materials for the sensor anodes. Second was optimizing the processing of the sensor cathode membrane for reduced delamination. Oxygen sensors were made using tin (Sn) and bismuth (Bi) electrodes, potassium hydroxide (KOH) and acetic acid (CH3COOH) electrolytes with platinum (Pt) and gold (Au) reference electrodes. Bi electrodes were fabricated by casting and pressing processes. Electrochemical characterization of the Sn and Bi electrodes was performed by Cyclic Voltammetry (CV), Electrochemical Impedance Spectroscopy (EIS) and sensing characterization per BSEN ISO 21647:2009 at various oxygen percentages, 0%, 20.9% and 100% oxygen levels with an automated test apparatus. The Sn anode with both electrolyte solutions showed good oxygen sensing properties and performance in a sensor. This system shows promise for replacement of Pb electrodes as required by the RoHS Directive. The Bi anode with Au cathode in both KOH and CH3COOH electrolytes showed acceptable performance and oxygen sensing properties. The Bi anodes fabricated by separate manufacturing methods demonstrated effectiveness for use in medical oxygen sensors. Gold thin films were prepared by magnetron sputtering on Flouroethylene Polymer (FEP) films. The FEP substrate temperature ranged from -77°C to 50°C. X-Ray Diffraction (XRD) and 4-point resistivity characterized the effects of substrate temperature to Au thin film particle size. XRD peak broadening and resistivity measurements showed a strong correlation of particle size to FEP substrate temperature. Particle size at 50°C was 594A and the -77°C particle size was 2.4 x 103A. Substrate temperature exhibited a strong correlation to adhesion of the Au thin film to the FEP. Adhesion of the Au thin film with a FEP temperature of 50°C was rated a 3B per the ASTM D3359-02 peel test standard. At FEP substrate temperature of -77°C it was rated at 1B. The morphology of the deposited Au thin films was observed using optical microscopy and Scanning Electron Microscopy (SEM).

Boardman, Alan James

290

Hyperbaric oxygen therapy.  

PubMed

Hyperbaric oxygen therapy (HBOT) is emerging in veterinary medicine as an effective treatment or adjunct therapy for a variety of disorders in which improving oxygen delivery to tissues is a priority. The primary mechanisms of action of HBOT are (1) immediate hyperoxygenation of plasma and tissues and (2) decreased gas bubble (air embolus) size. With each hyperbaric 'dive,' secondary physiologic effects are set into motion. This article provides an introduction to HBOT, as well as its benefits, potential indications, contraindications, complications, and future directions in small animal veterinary medicine. PMID:22487778

Braswell, Cheryl; Crowe, D Tim

2012-03-01

291

Absolute photoionization cross sections of atomic oxygen  

NASA Technical Reports Server (NTRS)

The absolute values of photoionization cross sections of atomic oxygen were measured from the ionization threshold to 120 A. An auto-ionizing resonance belonging to the 2S2P4(4P)3P(3Do, 3So) transition was observed at 479.43 A and another line at 389.97 A. The experimental data is in excellent agreement with rigorous close-coupling calculations that include electron correlations in both the initial and final states.

Samson, J. A. R.; Pareek, P. N.

1985-01-01

292

Absolute photoionization cross sections of atomic oxygen  

NASA Technical Reports Server (NTRS)

The absolute values of photoionization cross sections of atomic oxygen were measured from the ionization threshold to 120 A. An auto-ionizing resonance belonging to the 2S2P4(4P)3P(3Do, 3So) transition was observed at 479.43 A and another line at 389.97 A. The experimental data is in excellent agreement with rigorous close-coupling calculations that include electron correlations in both the initial and final states.

Samson, J. A. R.; Pareek, P. N.

1982-01-01

293

Interactions of Oxygen and Hydrogen on Pd(111) surface  

SciTech Connect

The coadsorption and interactions of oxygen and hydrogen on Pd(1 1 1) was studied by scanning tunneling microscopy and density functional theory calculations. In the absence of hydrogen oxygen forms a (2 x 2) ordered structure. Coadsorption of hydrogen leads to a structural transformation from (2 x 2) to a ({radical}3 x {radical}3)R30 degree structure. In addition to this transformation, hydrogen enhances the mobility of oxygen. To explain these observations, the interaction of oxygen and hydrogen on Pd(1 1 1) was studied within the density functional theory. In agreement with the experiment the calculations find a total energy minimum for the oxygen (2 x 2) structure. The interaction between H and O atoms was found to be repulsive and short ranged, leading to a compression of the O islands from (2 x 2) to ({radical}3 x {radical}3)R30 degree ordered structure at high H coverage. The computed energy barriers for the oxygen diffusion were found to be reduced due to the coadsorption of hydrogen, in agreement with the experimentally observed enhancement of oxygen mobility. The calculations also support the finding that at low temperatures the water formation reaction does not occur on Pd(1 1 1).

Demchenko, D.O.; Sacha, G.M.; Salmeron, M.; Wang, L.-W.

2008-06-25

294

Spacecraft oxygen recovery system  

NASA Technical Reports Server (NTRS)

Recovery system is comprised of three integrated subsystems: electrochemical carbon dioxide concentrator which removes carbon dioxide from atmosphere, Sabatier reactor in which carbon dioxide is reduced with hydrogen to form methane and water, and static-feed water electrolysis cell to recover oxygen from water.

Quattrone, P. D.

1974-01-01

295

OXYGEN TRANSPORT CERAMIC MEMBRANES  

SciTech Connect

In the present quarter, the possibility of using a more complex interfacial engineering approach to the development of reliable and stable oxygen transport perovskite ceramic membranes/metal seals is discussed. Experiments are presented and ceramic/metal interactions are characterized. Crack growth and fracture toughness of the membrane in the reducing conditions are also discussed. Future work regarding this approach is proposed are evaluated for strength and fracture in oxygen gradient conditions. Oxygen gradients are created in tubular membranes by insulating the inner surface from the reducing environment by platinum foils. Fracture in these test conditions is observed to have a gradient in trans and inter-granular fracture as opposed to pure trans-granular fracture observed in homogeneous conditions. Fracture gradients are reasoned to be due to oxygen gradient set up in the membrane, variation in stoichiometry across the thickness and due to varying decomposition of the parent perovskite. The studies are useful in predicting fracture criterion in actual reactor conditions and in understanding the initial evolution of fracture processes.

Dr. Sukumar Bandopadhyay; Dr. Nagendra Nagabhushana

2003-01-01

296

Oxygen for Limelight  

Microsoft Academic Search

THE employment of oxygen for limelight and other purposes has increased enormously since the commercial introduction of the Brin method, by which the gas is separated from atmospheric air by a now well-known chemical process. The gas so obtained is practically pure, analysis showing that as now supplied by the Brin companies it contains on an average 95 per cent.

T. C. Hepworth

1892-01-01

297

Atomic Oxygen Task  

NASA Technical Reports Server (NTRS)

This report details work performed by the Center for Applied Optics (CAO) at the University of Alabama in Huntsville (UAH) on the contract entitled 'Atomic Oxygen Task' for NASA's Marshall Space Flight Center (contract NAS8-38609, Delivery Order 109, modification number 1). Atomic oxygen effects on exposed materials remain a critical concern in designing spacecraft to withstand exposure in the Low Earth Orbit (LEO) environment. The basic objective of atomic oxygen research in NASA's Materials & Processes (M&P) Laboratory is to provide the solutions to material problems facing present and future space missions. The objective of this work was to provide the necessary research for the design of specialized experimental test configurations and development of techniques for evaluating in-situ space environmental effects, including the effects of atomic oxygen and electromagnetic radiation on candidate materials. Specific tasks were performed to address materials issues concerning accelerated environmental testing as well as specifically addressing materials issues of particular concern for LDEF analysis and Space Station materials selection.

Hadaway, James B.

1997-01-01

298

Optical oxygen concentration monitor  

DOEpatents

A system for measuring and monitoring the concentration of oxygen uses as a light source an argon discharge lamp, which inherently emits light with a spectral line that is close to one of oxygen's A-band absorption lines. In a preferred embodiment, the argon line is split into sets of components of shorter and longer wavelengths by a magnetic field of approximately 2000 Gauss that is parallel to the light propagation from the lamp. The longer wavelength components are centered on an absorption line of oxygen and thus readily absorbed, and the shorter wavelength components are moved away from that line and minimally absorbed. A polarization modulator alternately selects the set of the longer wavelength, or upshifted, components or the set of the shorter wavelength, or downshifted, components and passes the selected set to an environment of interest. After transmission over a path through that environment, the transmitted optical flux of the argon line varies as a result of the differential absorption. The system then determines the concentration of oxygen in the environment based on the changes in the transmitted optical flux between the two sets of components. In alternative embodiments modulation is achieved by selectively reversing the polarity of the magnetic field or by selectively supplying the magnetic field to either the emitting plasma of the lamp or the environment of interest.

Kebabian, Paul (Acton, MA)

1997-01-01

299

The Oxygen Flask Method  

ERIC Educational Resources Information Center

Discusses application of Schoniger's method of quantitative organic elemental analysis in teaching of qualitative analysis of the halogens, nitrogen, sulphur, and phosphorus. Indicates that the oxygen flask method is safe and suitable for both high school and college courses because of simple apparatus requirements. (CC)

Boulton, L. H.

1973-01-01

300

OXYGEN DIFFUSION IN FORSTERITE  

Microsoft Academic Search

Oxygen self-diffusion coefficients for forsteritc single crystals were determined in different orientations by the single-spectrum proton activation technique. In the temperature range 1275ø-1625C chdiffusion coefficients in b direction can be represented by D b = 3.5 x 10 '3 exp ((-89 _ 3 kcal\\/mol)\\/RT) cm2\\/s. Int roduct ion

K. P. R. Reddy; S. M. Oh; L. D. Major; A. R. Cooper

1980-01-01

301

The Oxygen Cycle.  

ERIC Educational Resources Information Center

Produced for primary grades, this booklet provides study of the oxygen-carbon dioxide cycle in nature. Line drawings, a minimum amount of narrative, and a glossary of terms make up its content. The booklet is designed to be used as reading material, a coloring book, or for dramatic arts with students acting out parts of the cycle. This work was…

Swant, Gary D.

302

Oxygen reduction reactions on pure and nitrogen-doped graphene: a first-principles modeling  

Microsoft Academic Search

Based on first principles density functional theory calculations we explored energetics of oxygen reduction reaction over pristine and nitrogen-doped graphene with different amounts of nitrogen doping. The process of oxygen reduction requires one more step then same reaction catalyzed by metals. Results of calculations evidence that for the case of light doped graphene (about 4% of nitrogen) energy barrier for

Danil W. Boukhvalov; Young-Woo Son

2011-01-01

303

Vintage Calculators Web Museum  

NSDL National Science Digital Library

This "web museum" devoted to vintage calculators shows "the evolution from mechanical calculator to hand held electronic calculator." Some items featured include: Mechanical and early electronic desk calculators, "strange hand-held calculators," and articles, photographs, and databases from the archives of the International Association of Calculator Collectors. A history of the technology and information on British and sterling currency calculators are also posted here. The website also offers a Calculator time-line (chronicling calculator developments), background on the technology used by mechanical and early electronic calculators, and information on The Calculator Business. An index allows visitors to search the calculators featured on this site. The Puzzle Corner section asks visitors to contact them with any information that may answer unresolved questions regarding vintage calculators.

Tout, Nigel

304

Organic carbon flux and remineralization in surface sediments from the northern North Atlantic derived from pore-water oxygen microprofiles  

Microsoft Academic Search

Organic carbon fluxes through the sediment\\/water interface in the high-latitude North Atlantic were calculated from oxygen microprofiles. A wire-operated in situ oxygen bottom profiler was deployed, and oxygen profiles were also measured onboard (ex situ). Diffusive oxygen fluxes, obtained by fitting exponential functions to the oxygen profiles, were translated into organic carbon fluxes and organic carbon degradation rates. The mean

Eberhard J. Sauter; Michael Schlüter; Erwin Suess

2001-01-01

305

Oxygen Diffusion in Titanite  

NASA Astrophysics Data System (ADS)

Oxygen diffusion in natural and synthetic single-crystal titanite was characterized under both dry and water-present conditions. For the dry experiments, pre-polished titanite samples were packed in 18O-enriched quartz powder inside Ag-Pd capsules, along with an FMQ buffer assemblage maintained physically separate by Ag-Pd strips. The sealed Ag-Pd capsules were themselves sealed inside evacuated silica glass tubes and run at 700-1050° C and atmospheric pressure for durations ranging from 1 hour to several weeks. The hydrothermal experiments were conducted by encapsulating polished titanite crystals with 18O enriched water and running them at 700-900° C and 10-160MPa in standard cold-seal pressure vessels for durations of 1 day to several weeks. Diffusive uptake profiles of 18O were measured in all cases by nuclear reaction analysis (NRA) using the 18O (p,? ) 15N reaction. For the experiments on natural crystals, under both dry and hydrothermal conditions, two mechanisms could be recognized responsible for oxygen diffusion. The diffusion profiles showed two segments: a steep one close to the initial surface attributed to self-diffusion in the titanite lattice; and a "tail" reaching deeper into the sample attributable to diffusion in a "fast path" such as sub-grain boundaries or dislocations. For the dry experiments, the following Arrhenius relation was obtained: D{dry lattice} = 2.6×10-8exp (-275 kJmol-1/RT) m2/s Under wet conditions at PH2O = 100MPa, Oxygen diffusion conforms to the following Arrehenius relation: D{wet lattice} = 9.7× 10-13exp (-174 kJmol-1/RT) m2/s Oxygen diffusivity shows only a slight dependence on water pressure at the following conditions we explored: temperatures 800° C, PH2O = 10-160MPa, and 880° C, PH2O =10-100MPa. For diffusive anisotropy, we explored it only at hydrothermal conditions, and no diffusive anisotropy was observed. Like many other silicates, titanite shows lower activation energy for oxygen diffusion in the presence of H2O than under dry conditions. The difference between the "dry" and "wet" diffusivities increases as temperature decreases below those of this study. For example, at 500° C, dry diffusion is almost 2.5 orders of magnitude slower than wet diffusion. Accordingly, the retentivity of oxygen isotope signatures will be quite different between dry and wet systems at geologically interesting conditions. For most cases, wet diffusion results may be the appropriate choice for modeling natural systems.

Zhang, X. Y.; Cherniak, D. J.; Watson, E. B.

2004-05-01

306

High pressure oxygen furnace  

DOEpatents

A high temperature high pressure oxygen furnace having a hybrid partially externally heated construction is disclosed. A metallic bar fabricated from an alloy having a composition of at least 45% nickel, 15% chrome, and 10% tungsten is utilized (the preferred alloy including 55% nickel, 22% chrome, 14% tungsten, 2% molybdenum, 3% iron (maximum) and 5% cobalt (maximum). The disclosed alloy is fabricated into 11/4 inch bar stock and has a length of about 17 inches. This bar stock is gun drilled for over 16 inches of its length with 0.400 inch aperture to define a closed high temperature, high pressure oxygen chamber. The opposite and closed end of the bar is provided with a small support aperture into which both a support and a thermocouple can be inserted. The closed end of the gun drilled bar is inserted into an oven, preferably heated by standard nickel chrome electrical elements and having a heavily insulated exterior.

Morris, Donald E. (Kensington, CA)

1992-01-01

307

High pressure oxygen furnace  

DOEpatents

A high temperature high pressure oxygen furnace having a hybrid partially externally heated construction is disclosed. A metallic bar fabricated from an alloy having a composition of at least 45% nickel, 15% chrome, and 10% tungsten is utilized, the preferred alloy including 55% nickel, 22% chrome, 14% tungsten, 2% molybdenum, 3% iron (maximum) and 5% cobalt (maximum). The disclosed alloy is fabricated into 11/4 inch bar stock and has a length of about 17 inches. This bar stock is gun drilled for over 16 inches of its length with 0.400 inch aperture to define a closed high temperature, high pressure oxygen chamber. The opposite and closed end of the bar is provided with a small support aperture into which both a support and a thermocouple can be inserted. The closed end of the gun drilled bar is inserted into an oven, preferably heated by standard nickel chrome electrical elements and having a heavily insulated exterior. 5 figs.

Morris, D.E.

1992-07-14

308

Integrated oxygen recovery system  

NASA Technical Reports Server (NTRS)

Life Systems has conceptualized an innovative Integrated Oxygen Recovery System (IORS) applicable to advanced mission air revitalization. The IORS provides the capability to electrochemically generate metabolic oxygen (O2) and recover O2 from the space habitat atmosphere via a carbon dioxide (CO2) reduction process within a single assembly. To achieve this capability, the IORS utilizes a Solid Metal Cathode (SMC) water electrolysis unit that simultaneously serves as the Sabatier CO2 reduction reactor. The IORS enables two major life support systems currently baselined in closed loop air revitalization systems to be combined into one smaller, less complex system. This concept reduces fluidic and electrical interface requirements and eliminates a hydrogen (H2) interface. Life Systems is performing an evaluation of the IORS process directed at demonstrating performance and quantifying key physical characteristics including power, weight, and volume. Technical progress achieved during the first two months of the program is summarized.

Lee, M. Gene; Davenport, Ronald J.

1993-01-01

309

Integrated oxygen recovery system  

NASA Technical Reports Server (NTRS)

Life Systems has conceptualized an innovative Integrated Oxygen Recovery System (IORS) applicable to advanced mission air revitalization. The IORS provides the capability to electrochemically generate metabolic oxygen (O2) and recover O2 from the space habitat atmosphere via a carbon dioxide (CO2) reduction process within a single assembly. To achieve this capability, the IORS utilizes a Solid Metal Cathode (SMC) water electrolysis unit that simultaneously serves as the Sabatier CO2 reduction reactor. The IORS enables two major life support systems currently baselined in closed loop air revitalization systems to be combined into one smaller, less complex system. This concept reduces fluidic and electrical interface requirements and eliminates a hydrogen (H2) interface. Life Systems is performing an evaluation of the IORS process directed at demonstrating performance and quantifying key physical characteristics including power, weight, and volume. The results of the checkout, shakedown, and initial parametric tests are summarized.

Lee, M. Gene; Davenport, Ronald J.

1993-01-01

310

Assessing hafnium on hafnia as an oxygen getter  

NASA Astrophysics Data System (ADS)

Hafnium dioxide or hafnia is a wide band gap dielectric used in a range of electronic applications from field effect transistors to resistive memory. In many of these applications, it is important to maintain control over oxygen stoichiometry, which can be realized in practice by using a metal layer, specifically hafnium, to getter oxygen from the adjacent dielectric. In this paper, we employ density functional theory to study the thermodynamic stability of an interface between (100)-oriented monoclinic hafnia and hafnium metal. The nudged elastic band method is used to calculate the energy barrier for migration of oxygen from the oxide to the metal. Our investigation shows that the presence of hafnium lowers the formation energy of oxygen vacancies in hafnia, but more importantly the oxidation of hafnium through the migration of oxygen from hafnia is favored energetically.

O'Hara, Andrew; Bersuker, Gennadi; Demkov, Alexander A.

2014-05-01

311

Surface acoustic wave oxygen sensor  

NASA Technical Reports Server (NTRS)

A surface acoustic wave (SAW) device that responds to oxygen pressure was developed by coating a 158 MHz quartz surface acoustic wave (SAW) device with an oxygen binding agent. Two types of coatings were used. One type was prepared by dissolving an oxygen binding agent in a toluene solution of a copolymer containing the axial ligand. A second type was prepared with an oxygen binding porphyrin solution containing excess axial ligand without a polymer matrix. In the polymer based coatings, the copolymer served to provide the axial ligand to the oxygen binding agent and as a coating matrix on the surface of the SAW device. The oxygen sensing SAW device has been shown to bind oxygen following a Langmuir isotherm and may be used to measure the equilibrium constant of the oxygen binding compound in the coating matrix.

Collman, James P.; Oglesby, Donald M.; Upchurch, Billy T.; Leighty, Bradley D.; Zhang, Xumu; Herrmann, Paul C.

1994-01-01

312

SINGLET OXYGEN IN NATURAL WATERS  

EPA Science Inventory

Singlet oxygen is a reactive, electronically excited form of molecular oxygen that rapidly oxidizes a wide variety of organic substances, such as the polycyclic aromatics in petroleum hydrocarbon and the amino acids, histidine, tryptophan, and methionine. Studies of water samples...

313

electrocatalysts for oxygen reduction  

Microsoft Academic Search

Experience gained during efforts towards optimization of noble-metal-free electrocatalysts for oxygen reduction is simultaneously used to understand the chemical and morphological necessities for inducing efficient multi-electron transfer catalysis. The analysis of many preparative experimental steps between the moderately performing metal porphyrines and the highly efficient transition metal- and sulfur- containing pyrolised catalyst material contributes to the following model of the

Helmut Tributsch; Ulrike I. Koslowski; Iris Dorbandt

314

Fuel cell oxygen electrode  

DOEpatents

An oxygen electrode for a fuel cell utilizing an acid electrolyte has a substrate of an alkali metal tungsten bronze of the formula: A.sub.x WO.sub.3 where A is an alkali metal and x is at least 0.2, which is covered with a thin layer of platinum tungsten bronze of the formula: Pt.sub.y WO.sub.3 where y is at least 0.8.

Shanks, Howard R. (Ames, IA); Bevolo, Albert J. (Ames, IA); Danielson, Gordon C. (Ames, IA); Weber, Michael F. (Wichita, KS)

1980-11-04

315

Distillation Calculations with a Programmable Calculator.  

ERIC Educational Resources Information Center

Describes a three-step approach for teaching multicomponent distillation to undergraduates, emphasizing patterns of distribution as an aid to understanding the separation processes. Indicates that the second step can be carried out by programmable calculators. (A more complete set of programs for additional calculations is available from the…

Walker, Charles A.; Halpern, Bret L.

1983-01-01

316

On the magnetism of liquid nitrogen-liquid oxygen mixture  

NASA Astrophysics Data System (ADS)

The measurements of EPR line width in liquid nitrogen-liquid oxygen mixtures are presented. The observed anomalous dependence of line width on oxygen concentration can be understood if the existence of O 2-O 2-O 2 and N 2-O 2-O 2 molecular clusters is assumed. The provided quantum chemical calculations give the spatial structure as well as the bond energy for these clusters.

Tagirov, M. S.; Aminova, R. M.; Frossati, G.; Efimov, V. N.; Mamin, G. V.; Naletov, V. V.; Tayurskii, D. A.; Yudin, A. N.

2003-05-01

317

Low-lying Continuum States in Oxygen Isotopes  

SciTech Connect

Low-lying continuum states of exotic oxygen isotopes are studied, by introducing the Continuum-Coupled Shell Model (CCSM) and an interaction for continuum coupling constructed in a close relation to realistic shell-model interaction. Neutron emission spectra from exotic oxygen isotopes are calculated. The results agree with experiment remarkably well, as an evidence that the continuum effects are stronger than {approx}1 MeV.

Tsukiyama, K. [Department of Physics, University of Tokyo, Hongo, Tokyo, 113-0033 (Japan); Otsuka, T. [Department of Physics, University of Tokyo, Hongo, Tokyo, 113-0033 (Japan); Center for Nuclear Study University of Tokyo, Hongo, Tokyo, 113-0033, Japan and RIKEN Nishina Center, Hirosawa, Wako-shi, Saitama 351-0198 (Japan); Fujimoto, R. [Energy and Environmental Systems Laboratory, Hitachi, Ltd., Hitachi-shi, Ibaraki (Japan)

2009-08-26

318

Quantification of global myocardial oxygenation in humans: initial experience  

Microsoft Academic Search

PURPOSE: To assess the feasibility of our newly developed cardiovascular magnetic resonance (CMR) methods to quantify global and\\/or regional myocardial oxygen consumption rate (MVO2) at rest and during pharmacologically-induced vasodilation in normal volunteers. METHODS: A breath-hold T2 quantification method is developed to calculate oxygen extraction fraction (OEF) and MVO2 rate at rest and\\/or during hyperemia, using a two-compartment model. A

Kyle S McCommis; Robert O'Connor; Donna Lesniak; Matt Lyons; Pamela K Woodard; Robert J Gropler; Jie Zheng

2010-01-01

319

Atmospheric Oxygen Photoabsorption  

NASA Technical Reports Server (NTRS)

The work conducted on this grant was devoted to various aspects of the photophysics and photochemistry of the oxygen molecule. Predissociation linewidths were measured for several vibrational levels in the O2(B3 Sigma(sub u)(sup -)) state, providing good agreement with other groups working on this important problem. Extensive measurements were made on the loss kinetics of vibrationally excited oxygen, where levels between v = 5 and v = 22 were investigated. Cavity ring-down spectroscopy was used to measure oscillator strengths in the oxygen Herzberg bands. The great sensitivity of this technique made it possible to extend the known absorption bands to the dissociation limit as well as providing many new absorption lines that seem to be associated with new O2 transitions. The literature concerning the Herzberg band strengths was evaluated in light of our new measurements, and we made recommendations for the appropriate Herzberg continuum cross sections to be used in stratospheric chemistry. The transition probabilities for all three Herzberg band systems were re-evaluated, and we are recommending a new set of values.

Slanger, Tom G.

1996-01-01

320

Oxygen requirements of yeasts.  

PubMed Central

Type species of 75 yeast genera were examined for their ability to grow anaerobically in complex and mineral media. To define anaerobic conditions, we added a redox indicator, resazurin, to the media to determine low redox potentials. All strains tested were capable of fermenting glucose to ethanol in oxygen-limited shake-flask cultures, even those of species generally regarded as nonfermentative. However, only 23% of the yeast species tested grew under anaerobic conditions. A comparative study with a number of selected strains revealed that Saccharomyces cerevisiae stands out as a yeast capable of rapid growth at low redox potentials. Other yeasts, such as Torulaspora delbrueckii and Candida tropicalis, grew poorly mu max, 0.03 and 0.05 h-1, respectively) under anaerobic conditions in mineral medium supplemented with Tween 80 and ergosterol. The latter organisms grew rapidly under oxygen limitation and then displayed a high rate of alcoholic fermentation. It can be concluded that these yeasts have hitherto-unidentified oxygen requirements for growth. Images

Visser, W; Scheffers, W A; Batenburg-van der Vegte, W H; van Dijken, J P

1990-01-01

321

Onboard oxygen generation systems.  

PubMed

During the 1970s, the development of onboard oxygen generation systems (OBOGS) progressed through ground and flight test phases to the point where a second-generation concept is now production qualified and additional alternatives are being evaluated. This paper reviews the development of OBOGS and assesses the current state of the art of these systems. High-purity fluomine systems, developed for flight demonstration and qualified for production application, are discussed. Development of enriched air molecular sieve systems for laboratory and flight applications is described, along with a recent study of a permeable membrane-based aircraft oxygen enrichment concept. Capabilities and characteristics of the various OBOGS concepts are compared, showing the greater compliance of high-purity fluomine systems with the current oxygen military standards while noting the advantages of the reduced interface complexity of enriched air systems. Recommendations for future OBOGS development are presented, emphasizing the need to coordinate the development of specifications and hardware so the optimum compromises between physiological requirements and engineering feasibilities can result in OBOGS that best satisfy the metabolic needs of aircrew members. PMID:7305791

Manatt, S A

1981-11-01

322

Oxygen Sag and Stream Purification.  

ERIC Educational Resources Information Center

Presents a literature review of water quality related to oxygen sag and stream purification, covering publications of 1976-77. This review includes: (1) self-purification models; (2) oxygen demand; and (3) reaeration and oxygen transfer. A list of 60 references is also presented. (HM)

Neal, Larry; Herwig, Roy

1978-01-01

323

Analytic Reviews : Hyperbaric Oxygen Therapy  

Microsoft Academic Search

The physiological effects of hyperbaric oxygen extend beyond the elevation of oxygen concentration in body tissues, and clinical data is available to support its use in more than gas bubble diseases. Hyperbaric medicine is discussed within the context of its recognized mecha nisms of action. The experimental data and clinical ex perience for hyperbaric oxygen therapy are reviewed for the

Stephen R. Thom

1989-01-01

324

Oxygen Transport Membranes  

SciTech Connect

The focus of this research was to develop new membrane materials by synthesizing different compounds and determining their defect structures, crystallographic structures and electrical properties. In addition to measuring electrical conductivity, oxygen vacancy concentration was also evaluated using thermogravimetry, Neutron diffraction and Moessbauer Spectroscopy. The reducing conditions (CO{sub 2}/CO/H{sub 2} gas mixtures with steam) as encountered in a reactor environment can be expected to have significant influence on the mechanical properties of the oxides membranes. Various La based materials with and without Ti were selected as candidate membrane materials for OTM. The maximum electrical conductivity of LSF in air as a function of temperature was achieved at < 600 C and depends on the concentration of Sr (acceptor dopant). Oxygen occupancy in LSF was estimated using Neutron diffractometry and Moessbauer Spectroscopy by measuring magnetic moment changes depending on the Fe{sup 3+} and Fe{sup 4+} ratio. After extensive studies of candidate materials, lanthanum ferrites (LSF and LSFT) were selected as the favored materials for the oxygen transport membrane (OTM). LSF is a very good material for an OTM because of its high electronic and oxygen ionic conductivity if long term stability and mechanical strength are improved. LSFT not only exhibits p-type behavior in the high oxygen activity regime, but also has n-type conduction in reducing atmospheres. Higher concentrations of oxygen vacancies in the low oxygen activity regime may improve the performance of LSFT as an OTM. The hole concentration is related to the difference in the acceptor and donor concentration by the relation p = [Sr'{sub La}]-[Ti{sm_bullet}{sub Fe}]. The chemical formulation predicts that the hole concentration is, p = 0.8-0.45 or 0.35. Experimental measurements indicated that p is about {approx} 0.35. The activation energy of conduction is 0.2 eV which implies that LSCF conducts via the small polaron conduction mechanism. Scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS) were used to develop strategies to detect and characterize vacancy creation, dopant segregations and defect association in the oxygen conducting membrane material. The pO{sub 2} and temperature dependence of the conductivity, non-stoichiometry and thermal-expansion behavior of compositions with increasing complexity of substitution on the perovskite A and B sites were studied. Studies with the perovskite structure show anomalous behavior at low oxygen partial pressures (<10{sup -5} atm). The anomalies are due to non-equilibrium effects and can be avoided by using very strict criteria for the attainment of equilibrium. The slowness of the oxygen equilibration kinetics arises from two different mechanisms. In the first, a two phase region occurs between an oxygen vacancy ordered phase such as brownmillerite SrFeO{sub 2.5} and perovskite SrFeO{sub 3-x}. The slow kinetics is associated with crossing the two phase region. The width of the miscibility gap decreases with increasing temperature and consequently the effect is less pronounced at higher temperature. The preferred kinetic pathway to reduction of perovskite ferrites when the vacancy concentration corresponds to the formation of significant concentrations of Fe{sup 2+} is via the formation of a Ruddlesden-Popper (RP) phases as clearly observed in the case of La{sub 0.5}Sr{sub 0.5}FeO{sub 3-x} where LaSrFeO{sub 4} is found together with Fe. In more complex compositions, such as LSFTO, iron or iron rich phases are observed locally with no evidence for the presence of discrete RP phase. Fracture strength of tubular perovskite membranes was determined in air and in reducing atmospheric conditions. The strength of the membrane decreased with temperature and severity of reducing conditions although the strength distribution (Weibull parameter, m) was relatively unaltered. Surface and volume dominated the fracture origins and the overall fracture was purely transgranular. The dual phas

S. Bandopadhyay

2008-08-30

325

MISSE PEACE Polymers Atomic Oxygen Erosion Results  

NASA Technical Reports Server (NTRS)

Forty-one different polymer samples, collectively called the Polymer Erosion and Contamination Experiment (PEACE) Polymers, have been exposed to the low Earth orbit (LEO) environment on the exterior of the International Space Station (ISS) for nearly 4 years as part of Materials International Space Station Experiment 2 (MISSE 2). The objective of the PEACE Polymers experiment was to determine the atomic oxygen erosion yield of a wide variety of polymeric materials after long term exposure to the space environment. The polymers range from those commonly used for spacecraft applications, such as Teflon (DuPont) FEP, to more recently developed polymers, such as high temperature polyimide PMR (polymerization of monomer reactants). Additional polymers were included to explore erosion yield dependence upon chemical composition. The MISSE PEACE Polymers experiment was flown in MISSE Passive Experiment Carrier 2 (PEC 2), tray 1, on the exterior of the ISS Quest Airlock and was exposed to atomic oxygen along with solar and charged particle radiation. MISSE 2 was successfully retrieved during a space walk on July 30, 2005, during Discovery s STS-114 Return to Flight mission. Details on the specific polymers flown, flight sample fabrication, pre-flight and post-flight characterization techniques, and atomic oxygen fluence calculations are discussed along with a summary of the atomic oxygen erosion yield results. The MISSE 2 PEACE Polymers experiment is unique because it has the widest variety of polymers flown in LEO for a long duration and provides extremely valuable erosion yield data for spacecraft design purposes.

deGroh, Kim, K.; Banks, Bruce A.; McCarthy, Catherine E.; Rucker, Rochelle N.; Roberts, Lily M.; Berger, Lauren A.

2006-01-01

326

Investigation of oxygen point defects in cubic ZrO2 by density functional theory  

SciTech Connect

The energetics of formation and migration of the oxygen vacancy and interstitial in cubic ZrO2 are investigated by density functional theory calculations. In an O-rich environment, the negatively charged oxygen interstitial is the most dominant defect whereas, the positively charged oxygen vacancy is the most dominant defect under O-poor conditions. Oxygen interstitial migration occurs by the interstitialcy and the direct interstitial mechanisms, with calculated migration energy barriers of 2.94 eV and 2.15 eV, respectively. For the oxygen vacancy, diffusion is preferred along the <100> direction, and the calculated energy barriers are 0.26 eV for , 0.27 eV for and 0.54 eV for . These results indicate that oxygen diffusivity is higher through the vacancy-migration mechanism.

Liu, Bin [ORNL] [ORNL; Xiao, Haiyan [University of Tennessee, Knoxville (UTK)] [University of Tennessee, Knoxville (UTK); Zhang, Yanwen [ORNL] [ORNL; Aidhy, Dilpuneet S [ORNL] [ORNL; Weber, William J [ORNL] [ORNL

2014-01-01

327

Model calculations of nuclear data for biologically-important elements  

SciTech Connect

We describe calculations of neutron-induced reactions on carbon and oxygen for incident energies up to 70 MeV, the relevant clinical energy in radiation neutron therapy. Our calculations using the FKK-GNASH, GNASH, and ALICE codes are compared with experimental measurements, and their usefulness for modeling reactions on biologically-important elements is assessed.

Chadwick, M.B.; Blann, M.; Reffo, G. [Lawrence Livermore National Lab., CA (United States); Young, P.G. [Los Alamos National Lab., NM (United States)

1994-05-01

328

Exploring the diffusion of molecular oxygen in the red fluorescent protein mCherry using explicit oxygen molecular dynamics simulations.  

PubMed

The development of fluorescent proteins (FPs) has revolutionized cell biology research. The monomeric variants of red fluorescent proteins (RFPs), known as mFruits, have been especially valuable for tagging and tracking cellular processes in vivo. Determining oxygen diffusion pathways in FPs can be important for improving photostability and for understanding maturation of the chromophore. We use molecular dynamics (MD) calculations to investigate the diffusion of molecular oxygen in one of the most useful monomeric RFPs, mCherry. We describe a pathway that allows oxygen molecules to enter from the solvent and travel through the protein barrel to the chromophore. We calculate the free-energy of an oxygen molecule at points along the path. The pathway contains several oxygen hosting pockets, which are identified by the amino acid residues that form the pocket. We also investigate an RFP variant known to be significantly less photostable than mCherry and find much easier oxygen access in this variant. The results provide a better understanding of the mechanism of molecular oxygen access into the fully folded mCherry protein barrel and provide insight into the photobleaching process in these proteins. PMID:23363049

Regmi, Chola K; Bhandari, Yuba R; Gerstman, Bernard S; Chapagain, Prem P

2013-02-28

329

Oxidation-reduction relations in basic magma: a case for homogeneous equilibria  

Microsoft Academic Search

Published analyses of Fe2O3 and FeO in basaltic glassy lavas allow their equilibrium oxygen fugacities to be calculated. These values are plotted relative to NNO (nickel-nickel oxide oxygen buffer) at the same temperature (1200°C), so that the relative fO2, DeltaNNO, becomes essentially independent of temperature. For 61 submarine tholeiitic lavas from the Pacific, DeltaNNO lies between FMQ (fayalite-magnetite-quartz oxygen buffer)

Ian S. E. Carmichael; Mark S. Ghiorso

1986-01-01

330

Dynamic Oxygen-Enhanced MRI of Cerebrospinal Fluid  

PubMed Central

Oxygen causes an increase in the longitudinal relaxation rate of tissues through its T1-shortening effect owing to its paramagnetic properties. Due to such effects, MRI has been used to study oxygen-related signal intensity changes in various body parts including cerebrospinal fluid (CSF) space. Oxygen enhancement of CSF has been mainly studied using MRI sequences with relatively longer time resolution such as FLAIR, and T1 value calculation. In this study, fifteen healthy volunteers were scanned using fast advanced spin echo MRI sequence with and without inversion recovery pulse in order to dynamically track oxygen enhancement of CSF. We also focused on the differences of oxygen enhancement at sulcal and ventricular CSF. Our results revealed that CSF signal after administration of oxygen shows rapid signal increase in both sulcal CSF and ventricular CSF on both sequences, with statistically significant predominant increase in sulcal CSF compared with ventricular CSF. CSF is traditionally thought to mainly form from the choroid plexus in the ventricles and is absorbed at the arachnoid villi, however, it is also believed that cerebral arterioles contribute to the production and absorption of CSF, and controversy remains in terms of the precise mechanism. Our results demonstrated rapid oxygen enhancement in sulcal CSF, which may suggest inhaled oxygen may diffuse into sulcal CSF space rapidly probably due to the abundance of pial arterioles on the brain sulci.

Mehemed, Taha M.; Fushimi, Yasutaka; Okada, Tomohisa; Yamamoto, Akira; Kanagaki, Mitsunori; Kido, Aki; Fujimoto, Koji; Sakashita, Naotaka; Togashi, Kaori

2014-01-01

331

Dynamic oxygen-enhanced MRI of cerebrospinal fluid.  

PubMed

Oxygen causes an increase in the longitudinal relaxation rate of tissues through its T1-shortening effect owing to its paramagnetic properties. Due to such effects, MRI has been used to study oxygen-related signal intensity changes in various body parts including cerebrospinal fluid (CSF) space. Oxygen enhancement of CSF has been mainly studied using MRI sequences with relatively longer time resolution such as FLAIR, and T1 value calculation. In this study, fifteen healthy volunteers were scanned using fast advanced spin echo MRI sequence with and without inversion recovery pulse in order to dynamically track oxygen enhancement of CSF. We also focused on the differences of oxygen enhancement at sulcal and ventricular CSF. Our results revealed that CSF signal after administration of oxygen shows rapid signal increase in both sulcal CSF and ventricular CSF on both sequences, with statistically significant predominant increase in sulcal CSF compared with ventricular CSF. CSF is traditionally thought to mainly form from the choroid plexus in the ventricles and is absorbed at the arachnoid villi, however, it is also believed that cerebral arterioles contribute to the production and absorption of CSF, and controversy remains in terms of the precise mechanism. Our results demonstrated rapid oxygen enhancement in sulcal CSF, which may suggest inhaled oxygen may diffuse into sulcal CSF space rapidly probably due to the abundance of pial arterioles on the brain sulci. PMID:24956198

Mehemed, Taha M; Fushimi, Yasutaka; Okada, Tomohisa; Yamamoto, Akira; Kanagaki, Mitsunori; Kido, Aki; Fujimoto, Koji; Sakashita, Naotaka; Togashi, Kaori

2014-01-01

332

Oxygen diffusion of anodic surface oxide film on titanium studied by Auger electron spectroscopy. [Oxygen diffusivity  

SciTech Connect

TiO/sub 2/ films of about 1000 A were grown onto titanium foils anodically under galvanostatic conditions at 20 mA/cm/sup 2/ in saturated aqueous solutions of ammonium tetraborate. The samples were then aged at 450, 500, and 550/sup 0/C, and oxygen diffusion was observed by Auger electron spectroscopy (AES) profilings. The oxygen diffusivities were calculated by Fick's Second Law, using the Boltzmann-Matano solution, to be 9.4 x 10/sup -17/, 2.6 x 10/sup -16/, and 1.2 x 10/sup -15/ cm/sup 2//sec at 450, 500, and 550/sup 0/C, respectively. The diffusivities obtained by this method were also compared with those obtained using an exact solution to Fick's Second Law. The activation energy was calculated to be 30 kcal/mole.

Wang, P.S.; Wittberg, T.N.; Keil, R.G.

1982-01-01

333

Direct oxygen imaging in titania nanocrystals  

NASA Astrophysics Data System (ADS)

Recently, rutile nanotwins were synthesized using high temperature organic solvent methods, yielding two kinds of common high-quality rutile twinned nanocrystals, (101) and (301) twins, accompanied by minor rutile nanorods (Lu et al 2012 CrystEngComm 14 3120-4). In this report, the atomic structures of the rutile and anatase nanocrystals are directly resolved with no need for calculation or image simulation using atomic resolution STEM techniques. The locations of the oxygen rows in the rutile twins’ boundaries are directly determined from both HAADF images and ABF images. To the best of our knowledge, this is the first time oxygen columns have been distinguished in rutile twin boundaries using HAADF and BF imaging.

Lu, Weigang; Bruner, Britain; Casillas, Gilberto; Mejía-Rosales, Sergio; Farmer, Patrick J.; José-Yacamán, Miguel

2012-08-01

334

Oxygen Gradients in the Microcirculation  

PubMed Central

Early in the last century August Krogh embarked on a series of seminal studies to understand the connection between tissue metabolism and mechanisms by which the cardiovascular system supplied oxygen to meet those needs. Krogh recognized that oxygen was supplied from blood to the tissues by passive diffusion and that the most likely site for oxygen exchange was the capillary network. Studies of tissue oxygen consumption and diffusion coefficient, coupled with anatomical studies of capillarity in various tissues, led him to formulate a model of oxygen diffusion from a single capillary. Fifty years after the publication of this work, new methods were developed which allowed the direct measurement of oxygen in and around microvessels. These direct measurements have confirmed the predictions by Krogh and have led to extensions of his ideas resulting in our current understanding of oxygenation within the microcirculation. Developments during the last 40 years are reviewed, including studies of oxygen gradients in arterioles, capillaries, venules, microvessel wall and surrounding tissue. These measurements were made possible by the development and use of new methods to investigate oxygen in the microcirculation, so mention is made of oxygen microelectrodes, microspectrophotometry of haemoglobin and phosphorescence quenching microscopy. Our understanding of oxygen transport from the perspective of the microcirculation has gone from a consideration of oxygen gradients in capillaries and tissue to the realization that oxygen has the ability to diffuse from any microvessel to another location under the conditions that there exists a large enough PO2 gradient and that the permeability for oxygen along the intervening pathway is sufficient.

Pittman, Roland N.

2010-01-01

335

Oxygen impurity radiation from Tokamak-like plasmas  

NASA Technical Reports Server (NTRS)

We have constructed a nonhydrodynamic coronal model for calculating radiation from impurity atoms in a heated plasma. Some recent developments in the calculation of dielectronic recombination rate coefficients and collisional excitation rate coefficients are included. The model is applied to oxygen impurity radiation during the first few milliseconds of a TFR Tokamak plasma discharge, and good agreement with experimental results is obtained. Estimates of total line and continuum radiation from the oxygen impurity are given. It is shown that impurity radiation represents a considerable energy loss.

Rogerson, J. E.; Davis, J.; Jacobs, V. L.

1977-01-01

336

Oxygen variance and meridional oxygen supply in the Tropical North East Atlantic oxygen minimum zone  

NASA Astrophysics Data System (ADS)

The distribution of the mean oceanic oxygen concentration results from a balance between ventilation and consumption. In the eastern tropical Pacific and Atlantic, this balance creates extended oxygen minimum zones (OMZ) at intermediate depth. Here, we analyze hydrographic and velocity data from shipboard and moored observations, which were taken along the 23°W meridian cutting through the Tropical North East Atlantic (TNEA) OMZ, to study the distribution and generation of oxygen variability. By applying the extended Osborn-Cox model, the respective role of mesoscale stirring and diapycnal mixing in producing enhanced oxygen variability, found at the southern and upper boundary of the OMZ, is quantified. From the well-ventilated equatorial region toward the OMZ core a northward eddy-driven oxygen flux is observed whose divergence corresponds to an oxygen supply of about 2.4 ?mol kg-1 year-1 at the OMZ core depth. Above the OMZ core, mesoscale eddies act to redistribute low- and high-oxygen waters associated with westward and eastward currents, respectively. Here, absolute values of the local oxygen supply >10 ?mol kg-1 year-1 are found, likely balanced by mean zonal advection. Combining our results with recent studies, a refined oxygen budget for the TNEA OMZ is derived. Eddy-driven meridional oxygen supply contributes more than 50 % of the supply required to balance the estimated oxygen consumption. The oxygen tendency in the OMZ, as given by the multidecadal oxygen decline, is maximum slightly above the OMZ core and represents a substantial imbalance of the oxygen budget reaching about 20 % of the magnitude of the eddy-driven oxygen supply.

Hahn, J.; Brandt, P.; Greatbatch, R. J.; Krahmann, G.; Körtzinger, A.

2014-02-01

337

The Calculator Reference  

NSDL National Science Digital Library

If you remember the days when calculators were as big as today's laptops, then you'll definitely feel nostalgic when you visit the Calculator Reference. Operated by an avid collector of vintage calculators, the site covers Texas Instruments and Hewlett-Packard brands, as well as the pioneering Curta. Several other models are included in the Desktop Calculators section. Even some interesting trivia is given on the site, like why calculator key pads are numbered in a different order than telephone key pads. There are many links to other sites and articles related to classic calculator technology.

Furr, Rick.

1997-01-01

338

Brain Energetics in Oxygen-Induced Convulsions.  

National Technical Information Service (NTIS)

Mice were exposed to 6 ATA of 100% oxygen. The effect of high oxygen pressure (OHP), disulphiram and both disulphiram and oxygen as a function of the length of oxygen exposure on cerebral cortical adenosine triphosphate (ATP), phosphocreatine, lactate, py...

R. J. Nolan M. D. Faiman

1973-01-01

339

Cerebral oxygenation and hyperthermia.  

PubMed

Hyperthermia is associated with marked reductions in cerebral blood flow (CBF). Increased distribution of cardiac output to the periphery, increases in alveolar ventilation and resultant hypocapnia each contribute to the fall in CBF during passive hyperthermia; however, their relative contribution remains a point of contention, and probably depends on the experimental condition (e.g., posture and degree of hyperthermia). The hyperthermia-induced hyperventilatory response reduces arterial CO2 pressure (PaCO2) causing cerebral vasoconstriction and subsequent reductions in flow. During supine passive hyperthermia, the majority of recent data indicate that reductions in PaCO2 may be the primary, if not sole, culprit for reduced CBF. On the other hand, during more dynamic conditions (e.g., hemorrhage or orthostatic challenges), an inability to appropriately decrease peripheral vascular conductance presents a condition whereby adequate cerebral perfusion pressure may be compromised secondary to reductions in systemic blood pressure. Although studies have reported maintenance of pre-frontal cortex oxygenation (assessed by near-infrared spectroscopy) during exercise and severe heat stress, the influence of cutaneous blood flow is known to contaminate this measure. This review discusses the governing mechanisms associated with changes in CBF and oxygenation during moderate to severe (i.e., 1.0°C to 2.0°C increase in body core temperature) levels of hyperthermia. Future research directions are provided. PMID:24624095

Bain, Anthony R; Morrison, Shawnda A; Ainslie, Philip N

2014-01-01

340

OXYGEN ABUNDANCES IN CEPHEIDS  

SciTech Connect

Oxygen abundances in later-type stars, and intermediate-mass stars in particular, are usually determined from the [O I] line at 630.0 nm, and to a lesser extent, from the O I triplet at 615.7 nm. The near-IR triplets at 777.4 nm and 844.6 nm are strong in these stars and generally do not suffer from severe blending with other species. However, these latter two triplets suffer from strong non-local thermodynamic equilibrium (NLTE) effects and thus see limited use in abundance analyses. In this paper, we derive oxygen abundances in a large sample of Cepheids using the near-IR triplets from an NLTE analysis, and compare those abundances to values derived from a local thermodynamic equilibrium (LTE) analysis of the [O I] 630.0 nm line and the O I 615.7 nm triplet as well as LTE abundances for the 777.4 nm triplet. All of these lines suffer from line strength problems making them sensitive to either measurement complications (weak lines) or to line saturation difficulties (strong lines). Upon this realization, the LTE results for the [O I] lines and the O I 615.7 nm triplet are in adequate agreement with the abundance from the NLTE analysis of the near-IR triplets.

Luck, R. E.; Andrievsky, S. M. [Department of Astronomy, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106-7215 (United States); Korotin, S. N.; Kovtyukh, V. V., E-mail: luck@fafnir.astr.cwru.edu, E-mail: serkor@skyline.od.ua, E-mail: val@deneb1.odessa.ua, E-mail: scan@deneb1.odessa.ua [Department of Astronomy and Astronomical Observatory, Odessa National University, Isaac Newton Institute of Chile, Odessa Branch, Shevchenko Park, 65014 Odessa (Ukraine)

2013-07-01

341

Sterilization by oxygen plasma  

NASA Astrophysics Data System (ADS)

The use of polymeric medical devices has stimulated the development of new sterilization methods. The traditional techniques rely on ethylene oxide, but there are many questions concerning the carcinogenic properties of the ethylene oxide residues adsorbed on the materials after processing. Another common technique is the gamma irradiation process, but it is costly, its safe operation requires an isolated site and it also affects the bulk properties of the polymers. The use of a gas plasma is an elegant alternative sterilization technique. The plasma promotes an efficient inactivation of the micro-organisms, minimises the damage to the materials and presents very little danger for personnel and the environment. Pure oxygen reactive ion etching type of plasmas were applied to inactivate a biologic indicator, the Bacillus stearothermophilus, to confirm the efficiency of this process. The sterilization processes took a short time, in a few minutes the mortality was complete. In situ analysis of the micro-organisms' inactivating time was possible using emission spectrophotometry. The increase in the intensity of the 777.5 nm oxygen line shows the end of the oxidation of the biologic materials. The results were also observed and corroborated by scanning electron microscopy.

Moreira, Adir José; Mansano, Ronaldo Domingues; Andreoli Pinto, Terezinha de Jesus; Ruas, Ronaldo; Zambon, Luis da Silva; da Silva, Mônica Valero; Verdonck, Patrick Bernard

2004-07-01

342

Extracorporeal Membrane Oxygenation Circuitry  

PubMed Central

The extracorporeal membrane oxygenation (ECMO) circuit is made of a number of components that have been customized to provide adequate tissue oxygen delivery in patients with severe cardiac and/or respiratory failure for a prolonged period of time (days to weeks). A standard ECMO circuit consists of a mechanical blood pump, gas exchange device, and a heat exchanger all connected together with circuit tubing. ECMO circuits can vary from simple to complex and may include a variety of blood flow and pressure monitors, continuous oxyhemoglobin saturation monitors, circuit access sites and a bridge connecting the venous access and arterial infusion limbs of the circuit. Significant technical advancements have been made in the equipment available for short and long term ECMO applications. Contemporary ECMO circuits have greater biocompatibility and allow for more prolonged cardiopulmonary support time, while minimizing the procedure-related complications of bleeding, thrombosis and other physiologic derangements that were so common with the early application of ECMO. Modern era ECMO circuitry and components are simpler, safer, more compact and can be used across a wide variety of patient sizes from neonates to adults.

Horton, Stephen B.; McMullan, D. Michael; Bartlett, Robert H

2013-01-01

343

Extracorporeal membrane oxygenation  

PubMed Central

Extracorporeal membrane oxygenation (ECMO) is an advanced form of life support technology whereby venous blood is oxygenated outside of the body and returned to the patient. ECMO was initially used as last-resort rescue therapy for patients with severe respiratory failure. Over the last four decades, it has developed into a safe, standard therapy for newborns with progressive cardiorespiratory failure, as a resuscitation therapy after cardiac arrest, and in combination with other treatments such as hypothermia and various blood filtration therapies. ECMO has also become routine for children and adults with all forms of cardiogenic shock and is also routine in early graft failure after transplantation. The one area of ongoing debate is the role of ECMO in adults with hypoxemic respiratory failure. As ECMO equipment becomes safer, earlier use improves patient outcomes. Several modifications of the two basic venovenous and venoarterial ECMO systems are now occurring, as are many minor variations in cannulation strategies and systems of care for patients receiving ECMO. The indications and situations in which ECMO have been tried continue to change, and ECMO for sub-acute and chronic illnesses is now commonplace, as is the use of ECMO in patients with clinical problems previously regarded as contraindications, such as sepsis, malignancy, and immunosuppression.

Butt, Warwick

2013-01-01

344

Hyperthermal atomic oxygen generator  

NASA Technical Reports Server (NTRS)

Characterization of the transport properties of oxygen through silver was continued. Specifically, experiments measuring the transport through Ag(111), Ag(110), Ag(100) single crystals and through Ag0.05 Zr alloy were completed. In addition, experiments using glow discharge excitation of oxygen to assist in the transport were completed. It was found that the permeability through the different orientations of single crystal Ag was the same, but significant differences existed in the diffusivity. The experimental ratio of diffusivities, however, was in reasonable agreement with theoretical estimates. Since the solubilities of orientations must be the same, this suggests some problems with the assumption K = DS. The glow discharge experiments show that there is a substantial increase in transport (factor of six) when the upstream pressure is dissociated to some fraction of atoms (which have a much higher sticking coefficient). These results indicate that there is a significant surface limitation because of dissociative adsorption of the molecules. Experiments with the Ag0.05 Zr alloy and its high-grain boundary and defect density show a permeability of greater than a factor of two over ordinary polycrystalline Ag, but it is unclear as to whether this is because of enhanced transport through these defects or whether the Zr and defects on the surface increased the sticking coefficient and therefore the transport.

Khandelwal, Govind S.; Wu, Dongchuan

1990-01-01

345

Measurement of oxygen saturation in small retinal vessels with adaptive optics confocal scanning laser ophthalmoscope.  

PubMed

We have used an adaptive optics confocal scanning laser ophthalmoscope to assess oxygen saturation in small retinal vessels. Images of the vessels with a diameter smaller than 50 ?m are recorded at oxygen sensitive and isosbestic wavelengths (680 and 796 nm, respectively). The vessel optical densities (ODs) are determined by a computer algorithm. Then, OD ratios (ODRs), which are inversely proportional to oxygen saturation, are calculated. The results show that arterial ODRs are significantly smaller than venous ODRs, indicating that oxygen saturation in the artery is higher than that in the vein. To the best of our knowledge, this is the first noninvasive measurement of oxygen saturation in small retinal vessels. PMID:22112100

Li, Hao; Lu, Jing; Shi, Guohua; Zhang, Yudong

2011-11-01

346

Measurement of oxygen saturation in small retinal vessels with adaptive optics confocal scanning laser ophthalmoscope  

NASA Astrophysics Data System (ADS)

We have used an adaptive optics confocal scanning laser ophthalmoscope to assess oxygen saturation in small retinal vessels. Images of the vessels with a diameter smaller than 50 ?m are recorded at oxygen sensitive and isosbestic wavelengths (680 and 796 nm, respectively). The vessel optical densities (ODs) are determined by a computer algorithm. Then, OD ratios (ODRs), which are inversely proportional to oxygen saturation, are calculated. The results show that arterial ODRs are significantly smaller than venous ODRs, indicating that oxygen saturation in the artery is higher than that in the vein. To the best of our knowledge, this is the first noninvasive measurement of oxygen saturation in small retinal vessels.

Li, Hao; Lu, Jing; Shi, Guohua; Zhang, Yudong

2011-11-01

347

Deciphering mechanisms of enhanced-retarded oxygen diffusion in doped Si  

NASA Astrophysics Data System (ADS)

We study enhanced/retarded diffusion of oxygen in doped silicon by means of first principle calculations. We evidence that the migration energy of oxygen dimers cannot be significantly affected by strain, doping type, or concentration. We attribute the enhanced oxygen diffusion in p-doped silicon to reduced monomer migration energy and the retarded oxygen diffusion in Sb-doped to monomer trapping close to a dopant site. These two mechanisms can appear simultaneously for a given dopant leading to contradictory experimental results. More generally, our findings cast a new light on phenomena involving oxygen diffusion: precipitation, thermal donors formation, and light induced degradation.

Timerkaeva, Dilyara; Caliste, Damien; Pochet, Pascal

2013-12-01

348

Increase in whole-body peripheral vascular resistance during three hours of air or oxygen prebreathing  

NASA Technical Reports Server (NTRS)

Male and female subjects prebreathed air or 100% oxygen through a mask for 3.0 hours while comfortably reclined. Blood pressures, heart rate, and cardiac output were collected before and after the prebreathe. Peripheral vascular resistance (PVR) was calculated from these parameters and increased by 29% during oxygen prebreathing and 15% during air prebreathing. The oxygen contributed substantially to the increase in PVR. Diastolic blood pressure increased by 18% during the oxygen prebreathe while stystolic blood pressure showed no change under either procedure. The increase in PVR during air prebreathing was attributed to procedural stress common to air and oxygen prebreathing.

Waligora, J. M.; Horrigan, D. J., Jr.; Conkin, J.; Dierlam, J. J.; Stanford, J., Jr.; Riddle, J. R.

1984-01-01

349

Calculators In Class  

ERIC Educational Resources Information Center

Calculators are fast becoming accepted as needed household appliances. Certainly, children in school now will, as adults, look on calculators as being as necessary to everyday life as telephones. (Author)

Denman, Theresa

1974-01-01

350

Test Your Calculator IQ.  

ERIC Educational Resources Information Center

This short quiz for teachers is intended to help them to brush up on their calculator operating skills and to prepare for the types of questions their students will ask about calculator idiosyncracies. (SJL)

Williams, David E.

1981-01-01

351

Personal Finance Calculations.  

ERIC Educational Resources Information Center

Contains explanations and examples of mathematical calculations for a secondary level course on personal finance. How to calculate total monetary cost of an item, monthly payments, different types of interest, annual percentage rates, and unit pricing is explained. (RM)

Argo, Mark

1982-01-01

352

Prediction of Benthic Impact for Salmon Net-Pens Based on the Balance of Benthic Oxygen Supply and Demand  

Microsoft Academic Search

The ratio between oxygen supply and oxygen demand was examined as a predictor of benthic response to organic enrichment caused by salmon net-pen aquaculture. Oxygen supply to the benthos was calculated based on Fickian diffusion and near-bottom flow velocities. A strong linear correlation was found between measured carbon sedimentation rates and rates of benthic metabolism. This relationship allowed an estimation

R. H. Findlay; Les Watling

1997-01-01

353

Comparing Carbon Calculators  

NSDL National Science Digital Library

Carbon calculators, no matter how well intended as tools to help measure energy footprints, tend to be black boxes and can produce wildly different results, depending on the calculations used to weigh various energy factors. By comparing different calculators, learners can analyze which ones are the most accurate and relevant, and which are the most transparent.

Mccaffrey, Mark

354

Ecological Footprint Calculators  

NSDL National Science Digital Library

This website contains interactive calculators for determining various environmental impacts. The site includes more than 15 different calculators to determine greenhouse gas emissions, ecological footprints, electricity pollution, air travel pollution, commuting costs, appliance costs, pollution prevention and more. These calculators can be used for computer-based classroom activities or to enable students to see which types of activities have the greatest environmental impact.

Ecobusinesslinks

355

Obesity Decreases Perioperative Tissue Oxygenation  

PubMed Central

Background: Obesity is an important risk factor for surgical site infections. The incidence of surgical wound infections is directly related to tissue perfusion and oxygenation. Fat tissue mass expands without a concomitant increase in blood flow per cell, which might result in a relative hypoperfusion with decreased tissue oxygenation. Consequently, we tested the hypotheses that perioperative tissue oxygen tension is reduced in obese surgical patients. Furthermore, we compared the effect of supplemental oxygen administration on tissue oxygenation in obese and non-obese patients. Methods: Forty-six patients undergoing major abdominal surgery were assigned to one of two groups according to their body mass index (BMI): BMI < 30 kg/m2 (non-obese) and BMI ? 30 kg/m2 (obese). Intraoperative oxygen administration was adjusted to arterial oxygen tensions of ?150 mmHg and ?300 mmHg in random order. Anesthesia technique and perioperative fluid management were standardized. Subcutaneous tissue oxygen tension was measured with a polarographic electrode positioned within a subcutaneous tonometer in the lateral upper arm during surgery, in the recovery room, and on the first postoperative day. Postoperative tissue oxygen was also measured adjacent to the wound. Data were compared with unpaired two tailed t-tests and Wilcoxon rank-sum tests; P < 0.05 was considered statistically significant. Results: Intraoperative subcutaneous tissue oxygen tension was significantly less in the obese patients at baseline (36 vs. 57 mmHg, P = 0.002) and with supplemental oxygen administration (47 vs. 76 mmHg, P = 0.014). Immediate postoperative tissue oxygen tension was also significantly less in subcutaneous tissue of the upper arm (43 vs. 54 mmHg, P = 0.011) as well as near the incision (42 vs. 62 mmHg, P = 0.012) in obese patients. In contrast, tissue oxygen tension was comparable in each group on the first postoperative morning. Conclusion: Wound and tissue hypoxia were common in obese patients in the perioperative period and most pronounced during surgery. Even with supplemental oxygen tissue, oxygen tension in obese patients was reduced to levels that are associated with a substantial increase in infection risk. Summary Statement: Wound and tissue hypoxia were both common in obese patients in the perioperative period and most pronounced during surgery. Supplemental oxygen only slightly increased tissue oxygenation in obese patients.

Kabon, Barbara; Nagele, Angelika; Reddy, Dayakar; Eagon, Chris; Fleshman, James W.; Sessler, Daniel I.; Kurz, Andrea

2005-01-01

356

Evidence for greater oxygen decline rates in the coastal ocean than in the open ocean  

NASA Astrophysics Data System (ADS)

In the global ocean, the number of reported hypoxic sites (oxygen <30% saturation) is on the rise both near the coast and in the open ocean. But unfortunately, most of the papers on hypoxia only present oxygen data from one or two years, so that we often lack a long-term perspective on whether oxygen levels at these locations are decreasing, steady or increasing. Consequently, we cannot rule out the possibility that many of the newly reported hypoxic areas were hypoxic in the past, and that the increasing number of hypoxic areas partly reflects increased research and monitoring efforts. Here we address this shortcoming by computing oxygen concentration trends in the global ocean from published time series and from time series that we calculated using a global oxygen database. Our calculations reveal that median oxygen decline rates are more severe in a 30 km band near the coast than in the open ocean (>100 km from the coast). Percentages of oxygen time series with negative oxygen trends are also greater in the coastal ocean than in the open ocean. Finally, a significant difference between median published oxygen trends and median trends calculated from raw oxygen data suggests the existence of a publication bias in favor of negative trends in the open ocean.

Gilbert, D.; Rabalais, N. N.; Díaz, R. J.; Zhang, J.

2010-07-01

357

Microdistribution of oxygen in silicon  

NASA Technical Reports Server (NTRS)

The microdistribution of oxygen in Czochralskii-grown, p-type silicon crystals was determined by using the SEM in the EBIC mode in conjunction with spreading resistance measurements. When the conductivity remained p-type, bands of contrast were observed in the EBIC image which corresponded to maxima in resistivity. When at the oxygen concentration maxima the oxygen donor concentration exceeded the p-type dopant concentration, an inversion of the conductivity occurred. It resulted in the formation of p-n junctions in a striated configuration and the local inversion of the EBIC image contrast. By heat-treating silicon at 1000 C prior to the activation of oxygen donors, some silicon-oxygen micro-precipitates were observed in the EBIC image within the striated oxygen concentration maxima.

Murgai, A.; Chi, J. Y.; Gatos, H. C.

1980-01-01

358

Structural modification of twin boundaries in YBa2Cu3O6+? oxides: Effects of oxygen concentration and temperature  

NASA Astrophysics Data System (ADS)

The modification of the twin boundaries in YBa2Cu3O6+? due to the oxygen ordering below the temperature of the tetragonal-orthorhombic phase transformation has been studied using mean field theory and spatial gradient terms for the oxygen concentration variation. The distribution of the oxygen atoms across the twin boundaries was calculated at various temperatures and oxygen concentration. Based on these calculations, we deduced the interfacial energy, the equilibrium thickness, and the associated oxygen ordering of the twin boundaries. Their effects on twinning and tweed morphology are also discussed.

Meng, Qingping; Zhu, Yimei

2007-05-01

359

Two photon excitation of atomic oxygen  

NASA Technical Reports Server (NTRS)

A standard perturbation expansion in the atom-radiation field interaction is used to calculate the two photon excitation cross section for 1s(2) 2s(2) 2p(4) p3 to 1s(2) 2s(2) 2p(3) (s4) 3p p3 transition in atomic oxygen. The summation over bound and continuum intermediate states is handled by solving the equivalent inhomogeneous differential equation. Exact summation results differ by a factor of 2 from a rough estimate obtained by limiting the intermediate state summation to one bound state. Higher order electron correlation effects are also examined.

Pindzola, M. S.

1977-01-01

360

Pickup ions near Mars associated with escaping oxygen atoms  

NASA Astrophysics Data System (ADS)

Ions produced by ionization of Martian neutral atoms or molecules and picked up by the solar wind flow are expected to be an important ingredient of the Martian plasma environment. Significant fluxes of energetic (55-72 keV) oxygen ions were recorded in the wake of Mars and near the bow shock by the solar low-energy detector (SLED) charged particle detector onboard the Phobos 2 spacecraft. Also, copious fluxes of oxygen ions in the ranges 0.5-25 and 0.01-6 keV/q were detected in the Martian wake by the Automatic Space Plasma Experiment with Rotating Analyzer (ASPERA) instrument on Phobos 2. This paper provides a quantitative analysis of the SLED energetic ion data using a test particle model in which one million ion trajectories were numerically calculated. These trajectories were used to determine the ion flux as a function of energy in the vicinity of Mars for conditions appropriate for Circular Orbit 42 of Phobos 2. The electric and magnetic fields required by the test particle model were taken from a three-dimensional magnetohydrodynamic (MHD) model of the solar wind interaction with Mars. The ions were started at rest with a probability proportional to the density expected for exospheric hot oxygen. The test particle model supports the identification of the ions observed in channel 1 of the SLED instrument as pick-up oxygen ions that are created by the ionization of oxygen atoms in the distant part of the exosphere. The flux of 55-72 keV oxygen ions near the orbit of the Phobos 2 should be proportional to the oxygen density at radial distances from Mars of about 10 Rm (Martian radii) and hence proportional to the direct oxygen escape rate from Mars that is an important part of the overall oxygen loss rate at Mars. The modeled energetic oxygen fluxes also exhibit a spin modulation as did the SLED fluxes during Circular Orbit 42.

Cravens, T. E.; Hoppe, A.; Ledvina, S. A.; McKenna-Lawlor, S.

2002-08-01

361

Bifunctional oxygen electrodes  

NASA Astrophysics Data System (ADS)

The objective of the research on bifunctional oxygen electrodes for alkaline electrolytes was to improve significantly both the cathodic and anodic polarization as well as the cycle life of such electrodes. The research has focused on finding high-efficiency, long-life electrocatalysts for O2 reduction and generation and achieving an understanding of the mechanisms of the catalysis. Catalyst systems which have been examined in alkaline electrolytes have included the following:various types of carbons and graphites; chemically-modified carbons and graphites using adsorptive attachment (e.g., various quinones, macrocycles and chemical linkages); silver and various intermetallics; various oxide systems including perovskites, spinels, pyrochlores and other mixed transition metal oxides; transition metal macrocycles including porphyrins, phthalocyanines, naphthalocyanines and tetraazaannulenes; and thermally-treated macrocycles. Mechanistic studies have particularly focused on the reduction of O2 on various carbon/graphite surfaces and the role of the O2(-) radical ion.

Tryk, D.; Aldred, W.; Chen, Z.; Fierro, C.; Hashiguchi, J.; Hossain, M.; Zhang, Z.; Zhao, F.

1985-01-01

362

Oxygen-reducing catalyst layer  

DOEpatents

An oxygen-reducing catalyst layer, and a method of making the oxygen-reducing catalyst layer, where the oxygen-reducing catalyst layer includes a catalytic material film disposed on a substrate with the use of physical vapor deposition and thermal treatment. The catalytic material film includes a transition metal that is substantially free of platinum. At least one of the physical vapor deposition and the thermal treatment is performed in a processing environment comprising a nitrogen-containing gas.

O'Brien, Dennis P. (Maplewood, MN) [Maplewood, MN; Schmoeckel, Alison K. (Stillwater, MN) [Stillwater, MN; Vernstrom, George D. (Cottage Grove, MN) [Cottage Grove, MN; Atanasoski, Radoslav (Edina, MN) [Edina, MN; Wood, Thomas E. (Stillwater, MN) [Stillwater, MN; Yang, Ruizhi (Halifax, CA) [Halifax, CA; Easton, E. Bradley (Halifax, CA) [Halifax, CA; Dahn, Jeffrey R. (Hubley, CA) [Hubley, CA; O'Neill, David G. (Lake Elmo, MN) [Lake Elmo, MN

2011-03-22

363

Oxygen reduction on stainless steel  

Microsoft Academic Search

Oxygen reduction was studied on AISI 304 stainless steel in 0.51 m NaCl solution at pH values ranging from 4 to 10. A rotating disc electrode was employed. It was found that oxygen reduction is under mixed activation-diffusion control. The reaction order with respect to oxygen was found to be one. The values of the Tafel slope depend on the

R. Babi?; M. Metikoš-Hukovi?

1993-01-01

364

OXYGEN TRANSPORT CERAMIC MEMBRANES  

SciTech Connect

Conversion of natural gas to liquid fuels and chemicals is a major goal for the Nation as it enters the 21st Century. Technically robust and economically viable processes are needed to capture the value of the vast reserves of natural gas on Alaska's North Slope, and wean the Nation from dependence on foreign petroleum sources. Technologies that are emerging to fulfill this need are all based syngas as an intermediate. Syngas (a mixture of hydrogen and carbon monoxide) is a fundamental building block from which chemicals and fuels can be derived. Lower cost syngas translates directly into more cost-competitive fuels and chemicals. The currently practiced commercial technology for making syngas is either steam methane reforming (SMR) or a two-step process involving cryogenic oxygen separation followed by natural gas partial oxidation (POX). These high-energy, capital-intensive processes do not always produce syngas at a cost that makes its derivatives competitive with current petroleum-based fuels and chemicals. This project has the following 6 main tasks: Task 1--Design, fabricate and evaluate ceramic to metal seals based on graded ceramic powder/metal braze joints. Task 2--Evaluate the effect of defect configuration on ceramic membrane conductivity and long term chemical and structural stability. Task 3--Determine materials mechanical properties under conditions of high temperatures and reactive atmospheres. Task 4--Evaluate phase stability and thermal expansion of candidate perovskite membranes and develop techniques to support these materials on porous metal structures. Task 5--Assess the microstructure of membrane materials to evaluate the effects of vacancy-impurity association, defect clusters, and vacancy-dopant association on the membrane performance and stability. Task 6--Measure kinetics of oxygen uptake and transport in ceramic membrane materials under commercially relevant conditions using isotope labeling techniques.

Dr. Sukumar Bandopadhyay; Dr. Nagendra Nagabhushana

2001-12-01

365

Economical oxygen-delivery system.  

PubMed

The conservation of aircraft oxygen supplies is becoming of considerable interest to the Air Force. Onboard oxygen-generating systems are being developed which could support an aircrew if oxygen produced by these systems were used conservatively. These experiments studied the conservation potential of a rebreather bag placed in a vented container near the regulator in an oxygen-delivery system. The bag's volume was close to that of the subject's physiologic dead space. When the subject exhaled, oxygen in the mouth, trachea, and mask dead space went to the rebreather bag, to be rebreathed with the next breath. The CO2-contaminated oxygen from the alveoli was vented to the cabin. The dead-space oxygen could be separated from contaminated oxygen because dead-space air is exhaled first with each breath. When the rebreather-bag volume matched the subject's physiologic dead space so that no CO2 accumulated, a 30% oxygen savings was realized. When the bag was large enough to realize a 50% savings, CO2 accumulation was only 2%. PMID:1275837

Olson, R M

1976-04-01

366

When did oxygenic photosynthesis evolve?  

PubMed

The atmosphere has apparently been oxygenated since the 'Great Oxidation Event' ca 2.4 Ga ago, but when the photosynthetic oxygen production began is debatable. However, geological and geochemical evidence from older sedimentary rocks indicates that oxygenic photosynthesis evolved well before this oxygenation event. Fluid-inclusion oils in ca 2.45 Ga sandstones contain hydrocarbon biomarkers evidently sourced from similarly ancient kerogen, preserved without subsequent contamination, and derived from organisms producing and requiring molecular oxygen. Mo and Re abundances and sulphur isotope systematics of slightly older (2.5 Ga) kerogenous shales record a transient pulse of atmospheric oxygen. As early as ca 2.7 Ga, stromatolites and biomarkers from evaporative lake sediments deficient in exogenous reducing power strongly imply that oxygen-producing cyanobacteria had already evolved. Even at ca 3.2 Ga, thick and widespread kerogenous shales are consistent with aerobic photoautrophic marine plankton, and U-Pb data from ca 3.8 Ga metasediments suggest that this metabolism could have arisen by the start of the geological record. Hence, the hypothesis that oxygenic photosynthesis evolved well before the atmosphere became permanently oxygenated seems well supported. PMID:18468984

Buick, Roger

2008-08-27

367

Mass spectrometers and atomic oxygen  

NASA Technical Reports Server (NTRS)

The likely role of atmospheric atomic oxygen in the recession of spacecraft surfaces and in the shuttle glow has revived interest in the accurate measurement of atomic oxygen densities in the upper atmosphere. The Air Force Geophysics Laboratory is supplying a quadrupole mass spectrometer for a materials interactions flight experiment being planned by the Johnson Space Center. The mass spectrometer will measure the flux of oxygen on test materials and will also identify the products of surface reactions. The instrument will be calibrated at a new facility for producing high energy beams of atomic oxygen at the Los Alamos National Laboratory. The plans for these calibration experiments are summarized.

Hunton, D. E.; Trzcinski, E.; Cross, J. B.; Spangler, L. H.; Hoffbauer, M. H.; Archuleta, F. H.; Visentine, J. T.

1987-01-01

368

LDEF atomic oxygen fluence update  

NASA Technical Reports Server (NTRS)

The definition of LDEF atomic oxygen exposure involves theoretical prediction of fluxes, modeling of shielding and scattering effects, and comparison of predicted with observed atomic oxygen effects on LDEF experiments. Work is proceeding as follows: atomic oxygen fluxes and fluences have been recalculated using a more detailed orbit prediction program; a micro-environments program is being developed to account for the effects of experiment geometry on atomic oxygen flux; and chemical and physical measurements are being made on copper grounding straps to verify correspondence between predicted exposures and observed surface property variations. These three areas of work are reported briefly.

Bourassa, Roger J.; Gillis, J. R.

1992-01-01

369

Oxygen reduction in tetrafluoroethane-1,2-disulfonic acid  

SciTech Connect

The kinetics of oxygen reduction on platinum in tetrafluoroethane-1,2-disulfonic acid (TFEDSA) and trifluoromethane sulfonic acid (TFMSA) have been studied with the rotating disk electrode technique at pH 1. The resulting Tafel plots coincide within the error of the experiment, indicating similar kinetics in the two electrolytes. The reaction order with respect to oxygen concentration was studied by varying the partial pressure of oxygen above the electrolyte. The rotation-independent currents at 0.90V vs. DHE were used to calculate a reaction order equal to one. A first-order analysis of the rotation-dependent currents was then used to extract kinetic currents at lower potentials. These kinetic currents also exhibited first-order dependence on oxygen concentration. 12 references, 7 figures.

Striebel, K.A.; Andricacos, P.C.; Cairns, E.J.; Ross, P.N.; McLarnon, F.R.

1985-10-01

370

How oxygen damages microbes: Oxygen tolerance and obligate anaerobiosis  

Microsoft Academic Search

The orbital structure of molecular oxygen constrains it to accept electrons one at a time, and its unfavourable univalent reduction potential ensures that it can do so only with low-potential redox partners. In E. coli, this restriction prevents oxygen from oxidizing structural molecules. Instead, it primarily oxidizes reduced flavins, a reaction that is harmful only in that it generates superoxide

James A. Imlay

2002-01-01

371

DIAGENETIC OXYGEN EQUIVALENTS MODEL OF SEDIMENT OXYGEN DEMAND  

EPA Science Inventory

The consumption of oxygen in the overlying water by sediments is an important component in the oxygen balance of most natural waters. Conventional practice is to specify the magnitude of this sink using direct uptake measurements. Unfortunately, if the management alternative bein...

372

Oxygen Gasifier for Prolonged Maintenance of Liquid Oxygen under Pressure.  

National Technical Information Service (NTIS)

The object of the invention is an oxygen gasifier for prolonged maintenance of the liquid oxygen under pressure, consisting of a thick-walled vessel with heat insulation, a system of gasification, and regulation of the pressure, to prevent over-heating th...

G. I. Voronin M. V. Zolotukhin

1966-01-01

373

Thermodynamic, transport, and flow properties of gaseous products resulting from combustion of methane-air-oxygen  

NASA Technical Reports Server (NTRS)

Results of calculations to determine thermodynamic, transport, and flow properties of combustion product gases are presented. The product gases are those resulting from combustion of methane-air-oxygen and methane-oxygen mixtures. The oxygen content of products resulting from the combustion of methane-air-oxygen mixtures was similiar to that of air; however, the oxygen contained in products of methane-oxygen combustion ranged from 20 percent by volume to zero for stoichiometric combustion. Calculations were made for products of reactant mixtures with fuel percentages, by mass, of 7.5 to 20. Results are presented for specific mixtures for a range of pressures varying from 0.0001 to 1,000 atm and for temperatures ranging from 200 to 3,800 K.

Klich, G. F.

1976-01-01

374

The chemical effects of auroral oxygen precipitation at Jupiter  

NASA Technical Reports Server (NTRS)

A numerical model of the auroral ionosphere and thermosphere of Jupiter, which includes odd oxygen species, is presented. Density profiles of neutral species O, OH, and H2O and the ion species H2(+), H3(+), H(+), H2O(+), H3O(+), O(+), and OH(+) are calculated. The total neutral odd oxygen density is found to be about 10 exp 5/cu cm near the auroral ionosphere peak. The major ionospheric ion, H(+) reacts rapidly with both O and H2O and the presence of these species in the model calculations significantly reduces the H(+) density and thus the electron density. The chemical lifetime against reaction of H(+) with odd oxygen is about 1000 s near the peak, whereas the radiative recombination lifetime is roughly 10,000 s.

Cravens, T. E.; Eisenhower, G. M.

1992-01-01

375

The ancient oxygen exosphere of Mars - Implications for atmosphere evolution  

NASA Technical Reports Server (NTRS)

The paper considers absorption of oxygen (atoms and ions) by the surface as a mechanism for the early Martian atmosphere escape, due to the effect of high EUV flux of the ancient sun. Hot oxygen exosphere densities in ancient atmosphere and ionosphere are calculated for different EUV fluxes and the escape fluxes associated with these exposures. Using these densities, the ion production rate above the ionopause is calculated for different epochs including photoionization, charge exchange, and solar wind electron impact. It is found that, when the inferred high solar EUV fluxes of the past are taken into account, oxygen equivalent to that in several tens of meters of water, planet-wide, should have escaped Martian atmosphere to space over the last 3 Gyr.

Zhang, M. H. G.; Luhmann, J. G.; Bougher, S. W.; Nagy, A. F.

1993-01-01

376

Angular distribution of photoelectrons from atomic oxygen, nitrogen, and carbon  

NASA Technical Reports Server (NTRS)

The angular distribution of photoelectrons from atomic oxygen is investigated using Hartree-Fock (HF) wave functions. The correct formulation is used to compare HS and HF results. Agreement between these results is good and the HS calculations have been extended to atomic nitrogen and carbon as well.

Manson, S. T.; Kennedy, D. J.; Starace, A. F.; Dill, D.

1974-01-01

377

Red blood cell transfusion does not increase oxygen consumption in critically ill septic patients  

Microsoft Academic Search

BACKGROUND: Red blood cell (RBC) transfusion is commonly used to increase oxygen transport in patients with sepsis. However it does not consistently increase oxygen uptake at either the whole-body level, as calculated by the Fick method, or within individual organs, as assessed by gastric intra-mucosal pH. AIM: This study evaluates the hemodynamic and oxygen utilization effects of hemoglobin infusion on

Constantino J Fernandes Jr; Nelson Akamine; Fernando VC De Marco; José AM De Souza; Sofia Lagudis; Elias Knobel

2001-01-01

378

Control of oxygen concentration in liquid lead and lead–bismuth  

Microsoft Academic Search

Conditions for control of the oxygen concentration in liquid lead alloys are described using the gas phase as a control medium. Calculation of the Gibbs energy of oxygen in liquid Pb45Bi55 is conducted using the data for the binary Pb–O and Bi–O systems. The data obtained are employed to estimate the solubility of oxygen in the Pb45Bi55 melt between 200

G. Muller; A. Heinzel; G. Schumacher; A. Weisenburger

2003-01-01

379

Ceramic oxides with high oxygen exchange: The system Sr–Co–O  

Microsoft Academic Search

Oxide compositions in the system Sr–Co–O were prepared by solid-state reaction. The oxide–oxygen reactions were investigated by thermo-gravimetric measurements. Equilibration was controlled by an amperometric lambda sensor. Thermodynamic data for the oxide–oxygen reaction were calculated. For the reaction CoO\\/Co3O4 with complete change of crystal structure between ferrite-and NaCl-types, the amount of oxygen exchanged (?=1), and the absolute values of changes

E. Girdauskaite; H. Ullmann; V. Vashook; M. Bülow; U. Guth

2006-01-01

380

An Oxygen-Sparing Mask.  

National Technical Information Service (NTIS)

A mask has been developed which leads to very substantial oxygen saving without compromising the purity of the oxygen breathed, and without adding clumsy equipment to the subject's gear. The mask is designed so that during exhalation the CO2-contaminated ...

R. M. Olson R. D. Holden E. W. Koegel

1974-01-01

381

Work, heat, and oxygen cost  

NASA Technical Reports Server (NTRS)

Human energy is discussed in terms of the whole man. The physical work a man does, the heat he produces, and the quantity of oxygen he takes from the air to combine with food, the fuel source of his energy, are described. The daily energy exchange, work and heat dissipation, oxygen costs of specific activities, anaerobic work, and working in space suits are summarized.

Webb, P.

1973-01-01

382

The Biology of Oxygen Radicals  

Microsoft Academic Search

The reactive superoxide radical, O2{}-, formerly of concern only to radiation chemists and radiobiologists, is now understood to be a normal product of the biological reduction of molecular oxygen. An unusual family of enzymes, the superoxide dismutases, protect against the deleterious actions of this radical by catalyzing its dismutation to hydrogen peroxide plus oxygen.

Irwin Fridovich

1978-01-01

383

Oxygen Therapy for Spontaneous Pneumothorax  

Microsoft Academic Search

The rate of absorption of gas from a pneumothorax was studied in 12 patients breathing air and in 10 patients breathing air and a high concentration of oxygen alternately. The mean rate of absorption while breathing air was the same in both groups of patients. In the second group the rate consistently increased during periods of oxygen therapy and decreased

T. C. Northfield

1971-01-01

384

Novel Membranes and Processes for Oxygen Enrichment  

SciTech Connect

The overall goal of this project is to develop a membrane process that produces air containing 25-35% oxygen, at a cost of $25-40/ton of equivalent pure oxygen (EPO2). Oxygen-enriched air at such a low cost will allow existing air-fueled furnaces to be converted economically to oxygen-enriched furnaces, which in turn will improve the economic and energy efficiency of combustion processes significantly, and reduce the cost of CO{sub 2} capture and sequestration from flue gases throughout the U.S. manufacturing industries. During the 12-month Concept Definition project: We identified a series of perfluoropolymers (PFPs) with promising oxygen/nitrogen separation properties, which were successfully made into thin film composite membranes. The membranes showed oxygen permeance as high as 1,200 gpu and oxygen/nitrogen selectivity of 3.0, and the permeance and selectivity were stable over the time period tested (60 days). We successfully scaled up the production of high-flux PFP-based membranes, using MTR's commercial coaters. Two bench-scale spiral-wound modules with countercurrent designs were made and parametric tests were performed to understand the effect of feed flow rate and pressure, permeate pressure and sweep flow rate on the membrane module separation properties. At various operating conditions that modeled potential industrial operating conditions, the module separation properties were similar to the pure-gas separation properties in the membrane stamps. We also identified and synthesized new polymers [including polymers of intrinsic microporosity (PIMs) and polyimides] with higher oxygen/nitrogen selectivity (3.5-5.0) than the PFPs, and made these polymers into thin film composite membranes. However, these membranes were susceptible to severe aging; pure-gas permeance decreased nearly six-fold within two weeks, making them impractical for industrial applications of oxygen enrichment. We tested the effect of oxygen-enriched air on NO{sub x} emissions using a Bloom baffle burner at GTI. The results are positive and confirm that oxygen-enriched combustion can be carried out without producing higher levels of NOx than normal air firing, if lancing of combustion air is used and the excess air levels are controlled. A simple economic study shows that the membrane processes can produce O{sub 2} at less than $40/ton EPO{sub 2} and an energy cost of 1.1-1.5 MMBtu/ton EPO{sub 2}, which are very favorable compared with conventional technologies such as cryogenics and vacuum pressure swing adsorption processes. The benefits of integrated membrane processes/combustion process trains have been evaluated, and show good savings in process costs and energy consumption, as well as reduced CO{sub 2} emissions. For example, if air containing 30% oxygen is used in natural gas furnaces, the net natural gas savings are an estimated 18% at a burner temperature of 2,500 F, and 32% at a burner temperature of 3,000 F. With a 20% market penetration of membrane-based oxygen-enriched combustion in all combustion processes by 2020, the energy savings would be 414-736 TBtu/y in the U.S. The comparable net cost savings are estimated at $1.2-2.1 billion per year by 2020, calculated as the value of fuel savings subtracted from the cost of oxygen production. The fuel savings of 18%-32% by the membrane/oxygen-enriched combustion corresponds to an 18%-32% reduction in CO{sub 2} emissions, or 23-40 MM ton/y less CO{sub 2} from natural gas-fired furnaces by 2020. In summary, results from this project (Concept Definition phase) are highly promising and clearly demonstrate that membrane processes can produce oxygen-enriched air in a low cost manner that will lower operating costs and energy consumption in industrial combustion processes. Future work will focus on proof-of-concept bench-scale demonstration in the laboratory.

Lin, Haiqing

2011-11-15

385

Multiphase flow calculation software  

DOEpatents

Multiphase flow calculation software and computer-readable media carrying computer executable instructions for calculating liquid and gas phase mass flow rates of high void fraction multiphase flows. The multiphase flow calculation software employs various given, or experimentally determined, parameters in conjunction with a plurality of pressure differentials of a multiphase flow, preferably supplied by a differential pressure flowmeter or the like, to determine liquid and gas phase mass flow rates of the high void fraction multiphase flows. Embodiments of the multiphase flow calculation software are suitable for use in a variety of applications, including real-time management and control of an object system.

Fincke, James R. (Idaho Falls, ID)

2003-04-15

386

Oxygen configurations and their effect on charge transfer in YBa{sub 2}Cu{sub 3}O{sub z}  

SciTech Connect

The relationship between oxygen structure, charge transfer (hole count), and oxygen content in the YBa{sub 2}Cu{sub 3}O{sub z} superconductor is studied by combining Monte-Carlo simulation with existing electronic structure calculations. The present model proposed an expansion of the hole count in terms of oxygen configuration variables for states of an arbitrary degree of order. Calculations of hole count as a function of oxygen content suggest that oxygen ordering is, at least in part, responsible for the observed plateau structure of T{sub c} vs. oxygen content z.

McCormack, R.; Fontaine, D. de [Lawrence Berkeley Lab., CA (United States); Ceder, G. [Massachusetts Inst. of Tech., Cambridge, MA (United States)

1992-04-01

387

Oxygen configurations and their effect on charge transfer in YBa[sub 2]Cu[sub 3]O[sub z  

SciTech Connect

The relationship between oxygen structure, charge transfer (hole count), and oxygen content in the YBa[sub 2]Cu[sub 3]O[sub z] superconductor is studied by combining Monte-Carlo simulation with existing electronic structure calculations. The present model proposed an expansion of the hole count in terms of oxygen configuration variables for states of an arbitrary degree of order. Calculations of hole count as a function of oxygen content suggest that oxygen ordering is, at least in part, responsible for the observed plateau structure of T[sub c] vs. oxygen content z.

McCormack, R.; Fontaine, D. de (Lawrence Berkeley Lab., CA (United States)); Ceder, G. (Massachusetts Inst. of Tech., Cambridge, MA (United States))

1992-04-01

388

Oxygen detection using evanescent fields  

DOEpatents

An apparatus and method for the detection of oxygen using optical fiber based evanescent light absorption. Methylene blue was immobilized using a sol-gel process on a portion of the exterior surface of an optical fiber for which the cladding has been removed, thereby forming an optical oxygen sensor. When light is directed through the optical fiber, transmitted light intensity varies as a result of changes in the absorption of evanescent light by the methylene blue in response to the oxygen concentration to which the sensor is exposed. The sensor was found to have a linear response to oxygen concentration on a semi-logarithmic scale within the oxygen concentration range between 0.6% and 20.9%, a response time and a recovery time of about 3 s, ant to exhibit good reversibility and repeatability. An increase in temperature from 21.degree. C. to 35.degree. C. does not affect the net absorption of the sensor.

Duan, Yixiang (Los Alamos, NM) [Los Alamos, NM; Cao, Weenqing (Los Alamos, NM) [Los Alamos, NM

2007-08-28

389

Oxygen on an Fe monolayer on W(110): From chemisorption to oxidation?  

PubMed Central

The adsorption of oxygen on a pseudomorphic iron monolayer deposited on a W(110) surface was studied experimentally and theoretically. Standard surface characterization methods, such as Auger electron spectroscopy and low energy electron diffraction, and specific nuclear methods, such as conversion electron Mössbauer spectroscopy (CEMS) and nuclear resonant scattering of synchrotron radiation, combined with theoretical calculations based on the density functional theory allowed us to determine the structure of the oxygen adsorbate and the electronic properties of iron atoms with different oxygen coordinations. The oxygen-(3 × 2) structure on the iron monolayer was recognized and was interpreted to be a state with oxygen chemisorbed on the non-reconstructed surface with modest electron transfer from iron to oxygen. A transition from chemisorbed oxygen to the onset of Fe-oxidation is revealed by distinct changes in the CEMS spectra.

Freindl, K.; Partyka-Jankowska, E.; Karas, W.; Zajac, M.; Madej, E.; Spiridis, N.; Slezak, M.; Slezak, T.; Wisnios, D.; Korecki, J.

2013-01-01

390

OXYGEN TRANSPORT CERAMIC MEMBRANES  

SciTech Connect

Conversion of natural gas to liquid fuels and chemicals is a major goal for the Nation as it enters the 21st Century. Technically robust and economically viable processes are needed to capture the value of the vast reserves of natural gas on Alaska's North Slope, and wean the Nation from dependence on foreign petroleum sources. Technologies that are emerging to fulfill this need are all based syngas as an intermediate. Syngas (a mixture of hydrogen and carbon monoxide) is a fundamental building block from which chemicals and fuels can be derived. Lower cost syngas translates directly into more cost-competitive fuels and chemicals. The currently practiced commercial technology for making syngas is either steam methane reforming (SMR) or a two-step process involving cryogenic oxygen separation followed by natural gas partial oxidation (POX). These high-energy, capital-intensive processes do not always produce syngas at a cost that makes its derivatives competitive with current petroleum-based fuels and chemicals.

Dr. Sukumar Bandopadhyay; Dr. Nagendra Nagabhushana

2002-01-01

391

Oxygen variability and meridional oxygen supply in the tropical North East Atlantic oxygen minimum zone  

NASA Astrophysics Data System (ADS)

The oxygen minimum zone (OMZ) of the tropical North East Atlantic (TNEA) is located between the oxygen-rich equatorial region and the Cape Verde Frontal Zone at about 20°N in a depth range of 300 - 700 m. Its horizontal extent is predominantly defined by the North Equatorial Current and by the equatorial zonal current system ventilating the region to the north and south of the OMZ, respectively. The interior of the OMZ is characterized by a sluggish flow regime, where mesoscale eddies play a major role in the ventilation. In this study we focus on the oxygen variability in the TNEA as well as the eddy driven lateral ventilation of the TNEA OMZ across its southern boundary. During recent years an intense measurement program was executed along 23°W cutting meridionally through the TNEA OMZ. Hydrographic and velocity data has been acquired from ship sections and moorings, together covering the latitude range between 6°S and 14°N with particularly high meridional resolution of shipboard and high temporal resolution of moored observations. Based on shipboard data we derived a meridional section of oxygen variance, which reveals numerous local maxima of oxygen variability. Exemplary, strong oxygen variability is observed at the upper (300m, 5° - 12°N) and the southern boundary (400m - 700m, 5°N - 8°N) of the OMZ, whereas the interior of the OMZ is characterized by weak variability. An application of the extended Osborn-Cox model shows that the strong oxygen variability at the southern boundary is mainly generated by mesoscale eddies. The strong variability at the upper boundary is generated by mesoscale eddies as well as microscale turbulence. We apply two methods to estimate the meridional oxygen flux: 1) a flux gradient parameterization and 2) a correlation of oxygen and velocity mooring time series. From the analysis of the 5°N mooring data we find a northward oxygen flux directed towards the OMZ at its core depth, that is mainly due to variability of mesoscale eddy motions (10 - 50 days). The magnitude of the oxygen flux is well represented by the flux gradient parameterization, which moreover reveals an overall northward oxygen flux from the southern boundary to the centre of the OMZ. We further estimate the oxygen supply (divergence of oxygen flux) by mesoscale eddies and discuss its contribution to the oxygen budget of the TNEA OMZ.

Hahn, Johannes; Brandt, Peter; Greatbatch, Richard J.; Krahmann, Gerd; Körtzinger, Arne

2013-04-01

392

Monitor hemoglobin concentration and oxygen saturation in living mouse tail using photoacoustic CT scanner  

NASA Astrophysics Data System (ADS)

Purpose: The purpose of this study is to use PCT spectroscopy scanner to monitor the hemoglobin concentration and oxygen saturation change of living mouse by imaging the artery and veins in a mouse tail. Materials and Methods: One mouse tail was scanned using the PCT small animal scanner at the isosbestic wavelength (796nm) to obtain its hemoglobin concentration. Immediately after the scan, the mouse was euthanized and its blood was extracted from the heart. The true hemoglobin concentration was measured using a co-oximeter. Reconstruction correction algorithm to compensate the acoustic signal loss due to the existence of bone structure in the mouse tail was developed. After the correction, the hemoglobin concentration was calculated from the PCT images and compared with co-oximeter result. Next, one mouse were immobilized in the PCT scanner. Gas with different concentrations of oxygen was given to mouse to change the oxygen saturation. PCT tail vessel spectroscopy scans were performed 15 minutes after the introduction of gas. The oxygen saturation values were then calculated to monitor the oxygen saturation change of mouse. Results: The systematic error for hemoglobin concentration measurement was less than 5% based on preliminary analysis. Same correction technique was used for oxygen saturation calculation. After correction, the oxygen saturation level change matches the oxygen volume ratio change of the introduced gas. Conclusion: This living mouse tail experiment has shown that NIR PCT-spectroscopy can be used to monitor the oxygen saturation status in living small animals.

Liu, Bo; Kruger, Robert; Reinecke, Daniel; Stantz, Keith M.

2010-02-01

393

Sources of oxygen flux in groundwater during induced bank filtration at a site in Berlin, Germany  

NASA Astrophysics Data System (ADS)

The microbial degradation of pharmaceuticals found in surface water used for artificial recharge is strongly dependent on redox conditions of the subsurface. Furthermore the durability of production wells may decrease considerably with the presence of oxygen and ferrous iron due to the precipitation of trivalent iron oxides and subsequent clogging. Field measurements are presented for oxygen at a bank filtration site in Berlin, Germany, along with simplified calculations of different oxygen pathways into the groundwater. For a two-dimensional vertical cross-section, oxygen input has been calculated for six scenarios related to different water management strategies. Calculations were carried out in order to assess the amount of oxygen input due to (1) the infiltration of oxic lake water, (2) air entrapment as a result of water table oscillations, (3) diffusive oxygen flux from soil air and (4) infiltrating rainwater. The results show that air entrapment and infiltrating lake water during winter constitute by far the most important mechanism of oxygen input. Oxygen input by percolating rainwater and by diffusive delivery of oxygen in the gas phase is negligible. The results exemplify the importance of well management as a determining factor for water oscillations and redox conditions during artificial recharge.

Kohfahl, Claus; Massmann, Gudrun; Pekdeger, Asaf

2009-05-01

394

Oxygen incorporation in acceptor-doped perovskites  

NASA Astrophysics Data System (ADS)

Oxygen is experimentally known to be incorporated in acceptor-doped perovskites at high temperatures, leading to a hole conductivity proportional to pO21/4 and increasing with temperature [(1)/(2)O2+VO••?OOX+2h•]. Either this high-temperature incorporation is thermodynamically favored by temperature, suggesting an endothermic process (?H0 > 0), or it is exothermic. In the latter case, since it is obviously associated with a ?S0 < 0, the process should be favorable only at low temperatures, except if kinetically blocked. To examine this phenomenon, the reaction of O2 incorporation into the acceptor-doped perovskites BaSnO3 and BaZrO3, doped by trivalent dopants (Ga, Sc, In, Y), according to BaSn/Zr1-xMxO3-x/2+x/4O2?BaSn/Zr1-xMxO3, is studied by density-functional calculations for a high dopant concentration (x=0.25). In this process, the charged vacancies VO•• resulting from the charge compensation produced by doping, are filled with oxygen atoms, yielding a metallic compound with holes. It is found to be exothermic in all cases, showing that these acceptor-doped perovskites are able to incorporate oxygen at low temperatures, whereas the reaction is unfavorable above a given temperature, whose value is discussed. At any rate, it is suggested that the process is kinetically blocked at low temperatures due to very slow thermally activated vacancy diffusion. A thermochemical approach is presented that tentatively explains why the hole conductivity increases with temperature at high temperatures, although the hole concentration decreases, yielding a model compatible with experimental observations and theoretical calculations.

Bévillon, Emile; Dezanneau, Guilhem; Geneste, Grégory

2011-05-01

395

Mixed oxygen ion/electron-conducting ceramics for oxygen separation  

SciTech Connect

Solid mixed-conducting electrolytes in the series La{sub l-x}A{sub x}Co{sub l-y}Fe{sub y}O{sub 3-{delta}} (A = Sr,Ca,Ba) are potentially useful as passive membranes to separate high purity oxygen from air and as cathodes in fuel cells. All of the compositions studied exhibited very high electrical conductivities. At lower temperatures, conductivities increased with increasing temperature, characterized by activation energies of 0.05 to 0.16 eV that are consistent with a small polaron (localized electronic carrier) conduction mechanism. At higher temperatures, electronic conductivities tended to decrease with increasing temperature, which is attributed to decreased electronic carrier populations associated with lattice oxygen loss. Oxygen ion conductivities were higher than that of yttria stabilized zirconia and increased with the cobalt content and also increased with the extent of divalent A-site substitution. Thermogravimetric studies were conducted to establish the extent of oxygen vacancy formation as a function of temperature, oxygen partial pressure, and composition. These vacancy populations strongly depend on the extent of A-site substitution. Passive oxygen permeation rates were established for each of the compositions as a function of temperature and oxygen partial pressure gradient. For 2.5 mm thick membranes in an oxygen vs nitrogen partial pressure gradient, oxygen fluxes at 900 C ranged from approximately 0.3 sccm/cm{sup 2} for compositions high in iron and with low amounts of strontium A-site substitution to approximately 0.8 sccm/cm{sup 2} for compositions high in cobalt and strontium. A-site substitution with calcium instead of strontium resulted in substantially lower fluxes.

Stevenson, J.W.; Armstrong, B.L.; Armstrong, T.R.; Bates, J.L.; Pederson, L.R.; Weber, W.J.

1995-05-01

396

STRAIN-DEPENDENT OXYGEN DIFFUSIVITY IN BOVINE ANNULUS FIBROSUS  

PubMed Central

Background The intervertebral disc (IVD) is the largest avascular structure in human body. Transport of small molecules in IVD is mainly through diffusion from the endplates and the peripheral blood vessels surrounding IVD. Studies have investigated the structure, chemical components and water content in IVD, but to our knowledge no study has investigated the effect of mechanical loading on oxygen transport in IVD. The objective of this study was to determine the stain-dependent behavior of oxygen diffusivity in IVD tissue. Method of Approach A one-dimensional steady-state diffusion experiment was designed and performed to determine the oxygen diffusivity in bovine annulus fibrosus (AF). The oxygen diffusivity was calculated using equation derived from Fick’s law. A total of 20 AF specimens (d=6 mm, h~0.5 mm) from bovine coccygeal IVD were used to determine oxygen diffusivity at three levels of compressive strain. Results The average oxygen diffusivity (mean ± SD) of bovine AF in the axial direction was 1.43 ± 0.242×10?5 cm2/s (n=20) at 4.68 ± 1.67% compressive strain level, 1.05 ± 0.282×10?5 cm2/s (n=20) at 14.2 ± 1.50% strain level, and 7.71 ± 1.63×10?6 cm2/s (n=20) at 23.7±1.34% strain level. There was a significant decrease in oxygen diffusivity with increasing level of compressive strain (ANOVA, p<0.05). Conclusions Oxygen diffusivity of bovine AF in the axial direction has been determined. The mechanical loading has a significant effect on oxygen transport in IVD tissues. This study is important in understanding nutritional transport in IVD tissues and related disc degeneration.

Yuan, T-Y; Jackson, AR; Huang, C-Y; Gu, W Y

2009-01-01

397

Mathematical determination of total oxygen in solid wastes. Open-file report  

Microsoft Academic Search

The oxygen analysis of solid wastes is one of the important ultimate analysis necessary to determine: the efficiency of operation of an incinerator, the design of furnaces for incineration, and a complete materials balance of incoming and outgoing material. The oxygen content of solid wastes samples must be known if their calorific values are to be calculated from ultimate analyses.

1971-01-01

398

A 12-kW continuous-wave chemical oxygen-iodine laser  

SciTech Connect

A 12-kW continuous-wave chemical oxygen-iodine laser, provided with an original jet-type singlet oxygen generator, is developed and tested. The experimental and numerical techniques applied for the diagnostics and mathematical simulation of processes in the laser active medium are introduced. Some of the calculation and experimental results are presented. (lasers)

Boreysho, A S; Mal'kov, V M; Savin, Aleksandr V; Vasil'ev, D N; Evdokimov, I M; Trilis, A V; Strakhov, S Yu [Institute of Laser Instruments and Technologies, D F Ustinov 'VOENMEKh' Baltic State Technical University, St Petersburg (Russian Federation)

2003-04-30

399

VENTILATION AND OXYGEN EXTRACTION IN THE BAT PTEROPUS GOULDII DURING REST AND STEADY FLIGHT  

Microsoft Academic Search

SUMMARY Tidal volume (VT) breathing frequency (\\/) and oxygen consumption (j£)8) were simultaneously measured in the bat Pteropus gouldii during quiet rest at 24 °C, and oxygen extraction (E) values were calculated from these data. VT and \\/ were also measured at 24 °C from P. gouldii undertaking steady wind-tunnel flight at different speeds and angles, and this information together

STEVEN P. THOMAS

1981-01-01

400

A New Method of measuring Oxygen consumed in the Metabolism of Small Animals  

Microsoft Academic Search

THE principle of replacing, by means of electrolysis, the oxygen consumed in measurements of metabolism offers the threefold possibility of having a high degree of sensitivity, of controlling the phenomenon for an unlimited time and avoiding calculation entirely. An electrolytic cell (30 per cent sodium hydroxide), capable of producing oxygen, is connected by means of a tube to the thermostatic

V. Capraro

1953-01-01

401

Measuring the viscosity of whole bovine lens using a fiber optic oxygen sensing system  

PubMed Central

Purpose To obtain a better understanding of oxygen and nutrient transport within the lens, the viscosity of whole lenses was investigated using a fiber optic oxygen sensor (optode). The diffusion coefficient of oxygen was calculated using the Stokes-Einstein equation at the slip boundary condition. Methods The optode was used to measure the oxygen decay signal in samples consisting of different glycerol/water solutions with known viscosities. The oxygen decay signal was fitted to a double exponential decay rate equation, and the lifetimes (tau) were calculated. It was determined that the tau-viscosity relationship is linear, which served as the standard curve. The same procedure was applied to fresh bovine lenses, and the unknown viscosity of the bovine lens was calculated from the tau-viscosity relationship. Results The average viscosity in a whole bovine lens was determined to be 5.74±0.88 cP by our method. Using the Stokes-Einstein equation at the slip boundary condition, the diffusion coefficient for oxygen was calculated to be 8.2 × 10?6 cm2/s. Conclusions These data indicate a higher resistance to flow for oxygen and nutrients in the lens than what is currently assumed in the literature. Overall, this study allows a better understanding of oxygen transport within the lens.

Thao, Mai T.; Perez, Daniel; Dillon, James

2014-01-01

402

Global climatic interpretation of the deuterium-oxygen 18 relationship for precipitation  

Microsoft Academic Search

A theoretical model is derived to account for the deuterium-oxygen 18 relationship measured in meteorice waters. A steady state regime is assumed for the evaporation of water at the ocean surface and the subsequent formation of precipitation. The calculations show that the deuterium and oxygen 18 content in precipitation can be taken as linearly related. From the slope and the

Liliane Merlivat; Jean Jouzel

1979-01-01

403

Effect of oxygen limitation on solid-bed bioleaching of heavy metals from contaminated sediments.  

PubMed

The effects of oxygen limitation on solid-bed bioleaching of heavy metals (Me) were studied in a laboratory percolator system using contaminated sediment supplemented with 2% elemental sulfur (So). Oxygen limitation was realized by controlling the gas flow and oxygen concentration in the aeration gas. The oxygen supply varied between 150 and 0.5 mol So (-1) over 28 d of leaching. Moderate oxygen limitation led to temporarily suppression of acidification, rate of sulfate generation and Me solubilization. Lowering the oxygen supply to 0.5 mol O2 mol So (-1) resulted in retarding acidification over a period of three weeks and in poor Me solubilization. Oxidation of So occurred even under strong oxygen limitation at a low rate. High surplus of oxygen was necessary for almost complete oxidation of the added So. The maximum Me solubilization was reached at an oxygen supply of 7.5 mol O2 mol So (-1). Thus, the oxygen input during solid-bed bioleaching can be reduced considerably by controlling the gas flow without loss of metal removal efficiency. Oxygen consumption rates, ranging from 0.4 x 10(-8) to 0.8 x 10(-8) Kg O2 Kg dm (-1) S(-1), are primarily attributed to high reactivity of the sulfur flower and high tolerance of indigenous autotrophic bacteria to low oxygen concentrations. The So related oxygen consumption was calculated assuming a molar yield coefficient Y O2/S of 1.21. The oxygen conversion degree, defined as part of oxygen feed consumed by So oxidation, increased from 0.7% to 68% when the oxygen supply was reduced from 150 to 0.5 mol O2 mol So (-1). PMID:16581107

Seidel, Heinz; Görsch, Kati; Schümichen, Antje

2006-09-01

404

Heat Loss Calculation Exercise  

NSDL National Science Digital Library

This class exercise from Kirk Garrison is intended for construction students learning about home insulation and heating. The class will learn to calculate heat loss in a home by using an online home heat loss calculator. This exercise document includes student worksheets. This document may be downloaded in PDF file format.

Garrison, Kirk

2012-03-27

405

Calculations of Coherent Scattering  

Microsoft Academic Search

We present calculations for time dependent electrons scattering from a model molecule and a model atom. We concentrate on the physical effects that arise from the time dependent nature of the electron-target interaction. In both calculations, we investigate the dependence of electronic transitions on the parameters of the incident electron. Simple coherence properties of the incident electron can qualitatively change

Francis Robicheaux; Mitch Ferrero; Michael Witthoeft; Mitch Pindzola

2001-01-01

406

Coping with Calculators  

ERIC Educational Resources Information Center

This is the second of a two-part article on the controversy over hand-held calculators in the classroom. The first portion considered the pros and cons of the issue (AA 526 915) Here the author points out the possible effective uses for the calculator and suggests guidelines for those who wish to incorporate it into their classroom approaches.…

Yates, Daniel S.

1977-01-01

407

Calculators and Polynomial Evaluation.  

ERIC Educational Resources Information Center

The intent of this paper is to suggest and illustrate how electronic hand-held calculators, especially non-programmable ones with limited data-storage capacity, can be used to advantage by students in one particular aspect of work with polynomial functions. The basic mathematical background upon which calculator application is built is summarized.…

Weaver, J. F.

408

Calculating Molecular Weight  

NSDL National Science Digital Library

This video and online calculator show how to calculate the molecular weight of a substance from the atomic weights given on the periodic table. Use the molecular weight to convert between the macroscopic scale (grams of a substance) and the microscopic scale (number of molecules of that substance).

2013-06-17

409

Robust optode-based method for measuring in situ oxygen profiles in gravelly streambeds.  

PubMed

One of the key environmental conditions controlling biogeochemical reactions in aquatic sediments like streambeds is the distribution of dissolved oxygen. We present a novel approach for the in situ measurement of vertical oxygen profiles using a planar luminescence-based optical sensor. The instrument consists of a transparent acrylic tube with the oxygen-sensitive layer mounted on the outside. The luminescence is excited and detected by a moveable piston inside the acrylic tube. Since no moving parts are in contact with the streambed, the disturbance of the subsurface flow field is minimized. The precision of the distributed oxygen sensor (DOS) was assessed by a comparison with spot optodes. Although the precision of the DOS, expressed as standard deviation of calculated oxygen air saturation, is lower (0.2-6.2%) compared to spot optodes (<0.1-0.6%), variations of the oxygen content along the profile can be resolved. The uncertainty of the calculated oxygen is assessed with a Monte Carlo uncertainty assessment. The obtained vertical oxygen profiles of 40 cm in length reveal variations of the oxygen content reaching from 90% to 0% air saturation and are characterized by patches of low oxygen rather than a continuous decrease with depth. PMID:23889085

Vieweg, Michael; Trauth, Nico; Fleckenstein, Jan H; Schmidt, Christian

2013-09-01

410

Thermodynamics of oxygen solutions in liquid Ni, Co, Fe, and Mn metals  

NASA Astrophysics Data System (ADS)

Pure gaseous oxygen at a pressure is taken as the standard state of oxygen dissolved in a liquid metal. In the case of such a standard state of oxygen, its activity is equal to the equilibrium oxygen partial pressure in the vapor, which is risen to a power of 1/2. This allowed us, using two thermodynamic functions, i.e., the standard Gibbs energy for the oxidation reaction of liquid metal with oxygen to form a lower oxide and the experimentally determined oxygen solubility in a liquid metal, to obtain equations for the energies of mixing of each metal with oxygen and to calculate them, to find linear temperature dependences of the energies of mixing, and to describe oxygen solutions in liquid metals by pseudoregular-solution model equations. Linear dependences of the solubility functions on the standard Gibbs energies for oxidation reactions of liquid metals are found. The aim of the study is to suggest the energies of mixing of four metals (Ni, Co, Fe, and Mn) with oxygen and their temperature dependences for the calculations of the activity coefficients and the activity of oxygen in the solutions of these liquid metals by the pseudoregular-solution model equations.

Shil'nikov, E. V.; Paderin, S. N.

2013-12-01

411

Simultaneous Monitoring of Vascular Oxygenation and Tissue Oxygen Tension of Breast Tumors Under Hyperbaric Oxygen Exposure.  

National Technical Information Service (NTIS)

The goals of the study in the first stage are 1) to develop a mathematic model by which we can derive tumor blood flow and metabolic rate of oxygen from hemoglobin concentration during interventions, 2) to investigate vascular oxygenation and tissue oxyge...

M. Xia

2005-01-01

412

Arto New String Calculator  

NSDL National Science Digital Library

Designed by a senior lecturer at the Department of Computer Science at the University of Helsinki in Finland, this website is a stand-alone Pascal program for string calculations. The idea came to him while visiting a French lute maker friend and the site has been continually updated since the original program was conceived. The calculator is useful only for calculating the tensions and diameters of strings made of homogenous material, thus wound strings, catlines and other such strings are excluded. The calculator is designed with lute instruments in mind but can be used for any stringed instrument: harpsichord, harp, guitar and pianos. The site provides easy to follow instructions and a glossary of the terms. Java 1.4 or 1.5 must be enabled to use this calculator.

Wikla, Arto

2006-10-04

413

Oxygen Transport Ceramic Membranes  

SciTech Connect

In the present quarter, experiments are presented on ceramic/metal interactions of Zirconia/ Ni-B-Si system and with a thin Ti coating deposited on zirconia surface. Existing facilities were modified for evaluation of environmental assisted slow crack growth and creep in flexural mode. Processing of perovskites of LSC, LSF and LSCF composition were continued for evaluation of mechanical properties as a function of environment. These studies in parallel to those on the LSFCO composition is expect to yield important information on questions such as the role of cation segregation and the stability of the perovskite structure on crack initiation vs. crack growth. Studies have been continued on the La{sub 1-x}Sr{sub x}FeO{sub 3-d} composition using neutron diffraction and TGA studies. A transition from p-type to n-type of conductor was observed at relative low pO{sub 2}, at which the majority carriers changed from the holes to electrons because of the valence state decreases in Fe due to the further loss of oxygen. Investigation on the thermodynamic properties of the membrane materials are continued to develop a complete model for the membrane transport. Data obtained at 850 C show that the stoichiometry in La{sub 0.2}Sr{sub 0.8}Fe{sub 0.8}Cr{sub 0.2}O{sub 3-x} vary from {approx}2.85 to 2.6 over the pressure range studied. From the stoichiometry a lower limit of 2.6 corresponding to the reduction of all Fe{sup 4+} to Fe{sup 3+} and no reduction of Cr{sup 3+} is expected.

S. Bandopadhyay; N. Nagabhushana

2003-08-07

414

Measurement of Intracellular Oxygen Concentration During Photodynamic Therapy in vitro.  

PubMed

A technique is introduced that monitors the depletion of intracellular ground state oxygen concentration ([(3) O2 ]) during photodynamic therapy of Mat-LyLu cell monolayers and cell suspensions. The photosensitizer Pd(II) meso-tetra(4-carboxyphenyl)porphine (PdT790) is used to manipulate and indicate intracellular [(3) O2 ] in both of the in vitro models. The Stern-Volmer relationship for PdT790 phosphorescence was characterized in suspensions by flowing nitrogen over the suspension while short pulses of 405 nm light were used to excite the sensitizer. The bleaching of sensitizer and the oxygen consumption rate were also measured during continuous exposure of the cell suspension to the 405 nm laser. Photodynamic therapy (PDT) was conducted in both cell suspensions and in cell monolayers under different treatment conditions while the phosphorescence signal was acquired. The intracellular [(3) O2 ] during PDT was calculated by using the measured Stern-Volmer relationship and correcting for sensitizer photobleaching. In addition, the amount of oxygen that was consumed during the treatments was calculated. It was found that even at large oxygen consumption rates, cells remain well oxygenated during PDT of cell suspensions. For monolayer treatments, it was found that intracellular [(3) O2 ] is rapidly depleted over the course of PDT. PMID:24521344

Weston, Mark A; Patterson, Michael S

2014-07-01

415

Oxygen Compatibility Screening Tests in Oxygen-Rich Combustion Environment  

NASA Technical Reports Server (NTRS)

The identification and characterization of oxygen-rich compatible materials enables full-flow, staged combustion designs. Although these oxygen-rich designs offer significant cost, performance, and reliability benefits over existing systems, they have never been used operationally by the United States. If these systems are to be realized, it is critical to understand the long-term oxidative stability in high-temperature, high-pressure, oxygen-rich combustion environments. A unique facility has been constructed at the NASA Lewis Research Center to conduct tests of small-scale rocket engine materials and subcomponents in an oxygen-rich combustion environment that closely approximates a full-scale rocket engine. Thus, a broad range of advanced materials and concepts can be screened in a timely manner and at a relatively low cost.

Eckel, Anerew J.

1997-01-01

416

Oxygen kinetics in preretinal perfluorotributylamine.  

PubMed

Previous studies have relied on various electrodes or probes to monitor preretinal oxygen tension in an effort to gain insight into retinal oxygenation. In order to corroborate and extend the results of such studies, we developed a relatively non-invasive method of determining preretinal oxygen tension using 19F nuclear magnetic resonance (NMR) spectroscopy. Small liquid perfluorocarbon (LPFC) droplets were injected into the preretinal vitreous space of the rabbit eye. The T1 value obtained from the fluorine nuclide could then be used to determine preretinal oxygen tension (PO2) with a high degree of sensitivity, since the fluorine spin-lattice relaxation rate (T1)-1 in LPFCs is directly proportional to PO2 under conditions of no flow and known temperature. In the present study, we investigated the oxygen uptake and clearance rates from small preretinal droplets of the LPFC perfluorotributylamine (FTBA) in response to step changes in arterial PO2. At all FTBA volumes examined (2, 10 and 100 microliters), the oxygen uptake and clearance curves were well approximated by a simple exponential equation with mean time constants 9.8/15.3, 21.4/19.4 and 77.7/45.3 min (uptake/clearance), respectively. Following return to normoxemic (baseline) conditions, FTBA droplets provided a preretinal PO2 of 39.4 +/- 9.2 mmHg (mean +/- S.D., n = 12). The 19F NMR method provides a measure of steady-state preretinal PO2 that independently verifies and complements information obtained using oxygen-sensitive microelectrodes or probes. However, the long time constants for oxygen uptake and clearance, particularly in FTBA volumes on the order of 10 microliters and greater, may represent a practical limitation of this method for determining rapid oxygen flux in the preretinal vitreous space.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1397120

Wilson, C A; Berkowitz, B A; Hatchell, D L

1992-07-01

417

Band structure of cubic ZrO2 containing oxygen vacancies and calcium ions  

Microsoft Academic Search

The theoretical analysis of the electronic structure of ZrO2 containing oxygen vacancies and calcium ions is carried out. The electronic band-structure calculations for zirconium dioxide in the cubic fluorite structure containing oxygen vacancies and calcium ions are made according to the LMTO method. The values of the total and partial densities of states are calculated. The results are used for

G. A. Ol'khovic; I. I. Naumov; O. I. Velikokhatnyi

1995-01-01

418

Electronic structure of oxygen-terminated zigzag graphene nanoribbons: A hybrid density functional theory study  

Microsoft Academic Search

The size-dependent electronic structure of oxygen-terminated zigzag graphene nanoribbons is investigated using standard density functional theory (DFT) with an exchange-correlation functional of the generalized gradient approximation form as well as hybrid DFT calculations with two different exchange-correlation functionals. Hybrid DFT calculations, which typically provide more accurate band gaps than standard DFT, are found to predict semiconducting behavior in oxygen-terminated zigzag

Ashwin Ramasubramaniam

2010-01-01

419