These are representative sample records from Science.gov related to your search topic.
For comprehensive and current results, perform a real-time search at Science.gov.
1

Electrolyte cells measure oxygen fugacities  

NASA Technical Reports Server (NTRS)

System that uses calcia-stabilized zirconia-ceramic electrolyte in oxygen concentration cell can directly measure oxygen fugacity in vertical-quench furnace, redox-control system. System can independently vary temperature and oxygen fugacity during experiments, and can record these parameters as function of time.

Williams, R. J.; Mullins, O.

1977-01-01

2

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

3

System Controls and Measures Oxygen Fugacity  

NASA Technical Reports Server (NTRS)

System developed at Johnson Space Center controls and measures oxygen fugacity in high-temperature chemical research. A ceramic-electrolyte cell is the sensing element. All hardware needed to control gas flow and temperature and to measure cell electromotive force is included. An analytic balance allows in situ thermogravimetric sample analysis.

Williams, R. J.

1982-01-01

4

Oxygen fugacity and piston cylinder capsule assemblies  

NASA Astrophysics Data System (ADS)

A double capsule assembly designed to control oxygen fugacity in piston cylinder experiments has been tested at 1200 °C and 10 kbar. 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. To prevent direct contact with the buffer phases the AuPd-capsule is embedded in finely ground Al2O3 along with some coarser, fractured Al2O3 facilitating fluid inclusion formation. No water loss is observed in the sample even after 48 hrs but a slight increase in water content is observed in longer duration runs due to oxygen and hydrogen diffusion into the AuPd-capsule. Carbon from the furnace also diffuses through the outer Pt-capsule but reacts with H2O in the outer capsule to form CO2 and never reaches the inner capsule. Oxygen fugacity of runs in equilibrium with the Ni-NiO and Co-CoO buffers was measured by analyzing the Fe content of the Pt-wire in the sample1 and by analyzing Fe dissolved in the AuPd capsule2. The second method gives values that are in good agreement with established buffer whereas results from the first method are one half to one log units higher than the established values. References 1. E. Medard, C. A. McCammon, J. A. Barr, T. L. Grove, Am. Mineral. 93, 1838 (2008). 2. J. Barr, T. Grove, Contrib. Mineral. Petrol. 160, 631 (2010)

Jakobsson, S.

2011-12-01

5

The color of meteoritic hibonite - An indicator of oxygen fugacity  

NASA Technical Reports Server (NTRS)

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.

1986-01-01

6

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

7

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

8

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

9

Control and monitoring of oxygen fugacity in piston cylinder experiments  

NASA Astrophysics Data System (ADS)

We present a newly developed capsule design that resolves some common problems associated with the monitoring and control of oxygen fugacity ( fO2) in high-pressure piston cylinder experiments. The new fO2 control assembly consists of an AuPd outer capsule enclosing two inner capsules: one of AuPd capsule containing the experimental charge (including some water), and the other of Pt containing a solid oxygen buffer plus water. The inner capsules are separated by crushable alumina. The outer capsule is surrounded by a Pyrex sleeve to simultaneously minimise hydrogen loss from the cell and carbon infiltration from the graphite furnace. Controlled fO2 experiments using this cell design were carried out at 1.0 GPa and 1,000 °C. We used NiPd, CoPd and (Ni, Mg)O fO2 sensors, whose pressure sensitivity is well calibrated, to monitor the redox states achieved in experiments buffered by Re-ReO2, Ni-NiO and Co-CoO, respectively. Results for the fO2 sensors are in good agreement with the intended fO2 established by the buffer, demonstrating excellent control for durations of 24-48 h, with uncertainties less than ± 0.3 log bar units of fO2.

Matjuschkin, Vladimir; Brooker, Richard A.; Tattitch, Brian; Blundy, Jon D.; Stamper, Charlotte C.

2015-01-01

10

Oxygen fugacity of gases and rocks from Momotombo Volcano, Nicaragua: Application to volcanological monitoring  

NASA Astrophysics Data System (ADS)

The oxygen fugacity (fO2) and the fO2 versus T°C relationship of high-temperature (600°-860°C) gas emissions from Momotombo volcano, Nicaragua, was determined from both field electrochemical measurements (electrolytic cell assembly) and thermodynamic computations on gas samples collected between 1978 and 1985. It was then compared with the intrinsic fO2 of fresh and altered lavas from the last eruption (1905), as measured between 500° and 1100°C in laboratory. The electrochemical results show that the oxygen fugacity of Momotombo fumaroles, at equivalent temperature, is much higher than that of the fresh 1905 lava (˜FMQ buffer) and closer to that of their altered wall rocks (˜FMQ buffer). The equilibrium O2 fugacities calculated from the chemistry of gas samples confirm this pattern. However, they suggest that the gas mixtures preserve the (variable) memory of a higher thermal equilibrium achieved at depth, under temperature and fO2 conditions of up to 1050°C and 10-9.0 atm, respectively, which correspond to the cross over between the fO2-T gas and lava trends. These data thus support the idea that Momotombo volcanic gases, released in a period of increasing activity, escape from a shallow magma body before suffering a variable oxidation during their ascent through both unbuffered cooling and reactions with environmental fluids and rocks. This late oxidation is weaker at central fumaroles than at peripherical ones. While between 1978 and 1985 the temperature of the hottest fumarole increased from 750° to 865°-900°C, the equilibrium fO2 of the gas decreased by nearly one order of magnitude (at comparable equilibrium temperature). Such an evolution presumably reflects an increasing connection between the surface exhalations and the magma degassing at depth along with time. This work underlines the possibility of monitoring the processes of magma ascent and gas-magma separation within a volcano before an eruption by continuously recording the changes of both oxygen fugacity and temperature in hot fumaroles.

Benhamou, G.; Allard, P.; Sabroux, J. C.; Vitter, G.; Dajlevic, D.; Creusot, A.

1988-12-01

11

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

12

SPINELS AND OXYGEN FUGACITY IN OLIVINE-PHYRIC AND LHERZOLITIC SHERGOTTITES. C.A. Goodrich, 2  

E-print Network

SPINELS AND OXYGEN FUGACITY IN OLIVINE-PHYRIC AND LHERZOLITIC SHERGOTTITES. 1 C.A. Goodrich, 2 C (possibly paired with NWA 1068 [9,10]), and to lherzolitic shergottite ALHA77005. Spinels in Olivine-Phyric Shergottites: Spinels in SaU 005 and EET-A are described by [11,12]. Spinels in Dhofar 019 (see also [8

Taylor, Lawrence A.

13

Solubility of Hydrogen in Olivine as a Function of Pressure and Oxygen Fugacity  

NASA Astrophysics Data System (ADS)

The incorporation of hydrogen into olivine is influenced by many of thermodynamic variables (pressure, temperature, oxygen fugacity, etc.) [1, 2, 3]. Given the strong influence that water has on the melting and mechanical behavior of mantle peridotite, it is necessary to determine the solubility of hydrogen in olivine over the range of chemical environments found in the upper mantle. We present results from new high temperature water-saturated hydration experiments to determine the effect of pressure and oxygen fugacity on hydrogen solubility in San Carlos olivine at upper mantle conditions. Our results indicate that at 1 to 2 GPa varying the fugacity of oxygen between the Fe-FeO and Ni-NiO buffers produces significantly smaller change in the concentration of hydrogen in the olivine than has been found at in previous experiments carried out at 300 MPa. Experiments were carried out in a piston-cylinder device at 1 to 2 GPa and 1200 °C using natural San Carlos olivine as a starting material. The fugacity of oxygen was controlled at Fe-FeO, FeO-Fe3O4 and Ni-NiO using solid buffers. Water content in experimental products was measured by secondary ionization mass spectrometry. Variable duration experiments indicate that hydrogen is homogeneously distributed in the olivine at 12 hrs. Our experimental results indicate that pressure strongly effects water content, in agreement with previous studies. For example, as pressure increases from 1 to 2 GPa, the water content of olivine increases from 32 ± 3 to 78 ± 7 ppm at the Ni-NiO buffer, and from 29 ± 3 to 69 ± 3 ppm at the FeO- Fe3O4 buffer. At each pressure the water content is only weakly affected by changing oxygen fugacity conditions, a result that disagrees with a recent report of a 5 times increase in water content between Fe-FeO and Ni-NiO at 2 GPa [3]. Differences between studies may result from variable degrees of defect equilibration or from differences in measurement techniques. However, when compared with the relationship between olivine water content and fslash O2 determined by [2], data from both this study and [3] suggest that the effect of oxygen fugacity on total water content is significantly weaker at upper mantle pressures than at 300 MPa. [1] Kohlstedt, Keppler, and Rubie (1996) Contrib Mineral Petrol 123:345-357. [2] Bai and Kohlstedt (1993) Phys Chem Minerals 19:460-471. [3] Grant et al. (2007) EPSL, doi:10.1016/j.epsl.2007.06.024

O'Leary, J. A.; Hauri, E. H.; Gaetani, G. A.

2007-12-01

14

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

15

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

16

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

17

The dependence of the partitioning of iron and europium between plagioclase and hydrous tonalitic melt on oxygen fugacity  

Microsoft Academic Search

The dependence of iron and europium partitioning between plagioclase and melt on oxygen fugacity was studied in the system\\u000a SiO2(Qz)—NaAlSi3O8(Ab)—CaAl2Si2O8(An)—H2O. Experiments were performed at 500?MPa and 850?°C\\/750?°C under water saturated conditions. The oxygen fugacity was varied\\u000a in the log f\\u000a O2-range from ?7.27 to ?15.78. To work at the most reducing conditions the classical double-capsule technique was modified.\\u000a The sample

Max Wilke; Harald Behrens

1999-01-01

18

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

19

Ferric iron in SNC meteorites as determined by Mossbauer spectroscopy: Implications for martian landers and martian oxygen fugacity  

NASA Astrophysics Data System (ADS)

Mossbauer spectra of martian meteorites are currently of great interest due to the Mossbauer spectrometers on the Athena mission MER rovers as well as the European Space Agency Mars Express mission, with its Beagle 2 payload. Also, considerable current effort is being made to understand the oxygen fugacity of martian magmas because of the effect of fO2 on mineral chemistry and crystallization processes. For these 2 reasons, the present study was conceived to acquire room temperature Mossbauer spectra of mineral separates and whole rock samples of 10 SNC meteorites. The results suggest that mineral identification using remote application of this technique will be most useful when the phases present have distinctive parameters arising from Fe in very different coordination polyhedra; for example, pyroxene coexisting with olivine can be discriminated easily, but opx versus cpx cannot. The MER goal of using Mossbauer spectroscopy to quantify the relative amounts of individual mineral species present will be difficult to satisfy if silicates are present because the lack of constraints on wt% FeO contents of individual silicate phases present will make modal calculations impossible. The remote Mossbauer spectroscopy will be most advantageous if the rocks analyzed are predominantly oxides with known stoichiometries, though these phases are not present in the SNCs. As for the detection of martian oxygen fugacity, no evidence exists in the SNC samples studied of a relationship between Fe3+ content and fO2 as calculated by independent methods. Possibly, all of the Fe3+ observed in olivine is the result of dehydrogenation rather than oxidation, and this process may also be the source of all the Fe3+ observed in pyroxene. The observed Fe3+ in pyroxene also likely records an equilibrium between pyroxene and melt at such low fO2 that little or no Fe3+ would be expected.

Dyar, M. D.

2003-12-01

20

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

21

Oxidation state of vanadium in glass and olivine from terrestrial and Martian basalts: Implications for oxygen fugacity estimates  

SciTech Connect

Several studies have demonstrated the usefulness of synchrotron micro x-ray absorption near-edge structure ({mu}-XANES or SmX) spectroscopy in determining the oxidation state of elements in planetary materials. Delaney et al. used SmX to investigate the oxidation states of Fe, Cr, and V in extraterrestrial samples, and they later determined the oxidation state of V in experimental glasses as a function of oxygen fugacity. More recently, Sutton et al. studied the oxidation state of V in meteoritic fassaite and also in synthetic pyroxene. This report discusses our first results using SmX spectroscopy to determine the oxidation state of V in olivine and glass from a terrestrial ocean floor (OF) basalt and a martian basaltic shergottite meteorite, Dar Al Gani 476. The goal of this and future studies is to use V (and Cr, Fe) valence states to determine the oxygen fugacity of basalts from different planetary bodies.

Karner, J.M.; Sutton, S.R.; Papike, J.J.; Shearer, C.K.; Newville, M. (Univ New Mexico); (UC)

2005-04-22

22

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

23

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

24

The relative effects of pressure, temperature and oxygen fugacity on the solubility of sulfide in mafic magmas  

Microsoft Academic Search

The sulfur contents at sulfide saturation (SCSS) of a basaltic and a picritic melt have been measured experimentally as a function of pressure and temperature from 5 to 90 kb and 1400–1800°C, using piston-cylinder and multi-anvil solid media pressure devices. Three distinct regimes of oxygen fugacity were investigated, imposed by the use of Fe100, Fe40Ir60, and Fe20Ir80 capsules. The compositions

JOHN A. MAVROGENES; Hugh St. C O’Neill

1999-01-01

25

Solubility of CO 2 in a Ca-rich leucitite: effects of pressure, temperature, and oxygen fugacity  

Microsoft Academic Search

The solubility of carbon dioxide in a Ca-rich leucitite has been investigated as a function of pressure (0.1–2.0 GPa), temperature (1200–1600°C), and oxygen fugacity. The experiments were done in a rapid-quench internally-heated pressure vessel (0.1 GPa) and a piston cylinder (0.5–2.0 GPa). The leucitite glass, previously equilibrated at NNO, and silver oxalate were loaded in Fe-doped Pt capsules (oxidized conditions)

Yves Thibault; John R. Holloway

1994-01-01

26

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

27

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

28

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

29

The Oxidation State of Fe in MORB Glasses and the Oxygen Fugacity of the Upper Mantle  

SciTech Connect

Micro-analytical determination of Fe{sup 3+}/{Sigma}Fe ratios in mid-ocean ridge basalt (MORB) glasses using micro X-ray absorption near edge structure ({mu}-XANES) spectroscopy reveals a substantially more oxidized upper mantle than determined by previous studies. Here, we show that global MORBs yield average Fe{sup 3+}/{Sigma}Fe ratios of 0.16 {+-} 0.01 (n = 103), which trace back to primary MORB melts equilibrated at the conditions of the quartz-fayalite-magnetite (QFM) buffer. Our results necessitate an upward revision of the Fe{sup 3+}/{Sigma}Fe ratios of MORBs, mantle oxygen fugacity, and the ferric iron content of the mantle relative to previous wet chemical determinations. We show that only 0.01 (absolute, or < 10%) of the difference between Fe{sup 3+}/{Sigma}Fe ratios determined by micro-colorimety and XANES can be attributed to the Moessbauer-based XANES calibration. The difference must instead derive from a bias between micro-colorimetry performed on experimental vs. natural basalts. Co-variations of Fe{sup 3+}/{Sigma}Fe ratios in global MORB with indices of low-pressure fractional crystallization are consistent with Fe{sup 3+} behaving incompatibly in shallow MORB magma chambers. MORB Fe{sup 3+}/{Sigma}Fe ratios do not, however, vary with indices of the extent of mantle melting (e.g., Na{sub 2}O(8)) or water concentration. We offer two hypotheses to explain these observations: The bulk partition coefficient of Fe{sup 3+} may be higher during peridotite melting than previously thought, and may vary with temperature, or redox exchange between sulfide and sulfate species could buffer mantle melting at {approx} QFM. Both explanations, in combination with the measured MORB Fe{sup 3+}/{Sigma}Fe ratios, point to a fertile MORB source with greater than 0.3 wt.% Fe{sub 2}O{sub 3}.

E Cottrell; K Kelley

2011-12-31

30

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

31

An experimental study of the partitioning of trace elements between rutile and silicate melt as a function of oxygen fugacity.  

PubMed

Subduction zone or arc magmas are known to display a characteristic depletion of High Field Strength Elements (HFSE) relative to other similarly incompatible elements, which can be attributed to the presence of the accessory mineral rutile (TiO2) in the residual slab. Here we show that the partitioning behavior of vanadium between rutile and silicate melt varies from incompatible (?0.1) to compatible (?18) as a function of oxygen fugacity. We also confirm that the HFSE are compatible in rutile, with D(Ta)> D(Nb)> (D(Hf)>/? D(Zr), but that the level of compatibility is strongly dependent on melt composition, with partition coefficients increasing about one order of magnitude with increasing melt polymerization (or decreasing basicity). Our partitioning results also indicate that residual rutile may fractionate U from Th due to the contrasting (over 2 orders of magnitude) partitioning between these two elements. We confirm that, in addition to the HFSE, Cr, Cu, Zn and W are compatible in rutile at all oxygen fugacity conditions. PMID:25590703

Mallmann, Guilherme; Fonseca, Raúl O C; Silva, Adolfo B

2014-12-01

32

An experimental study of the partitioning of trace elements between rutile and silicate melt as a function of oxygen fugacity.  

PubMed

Subduction zone or arc magmas are known to display a characteristic depletion of High Field Strength Elements (HFSE) relative to other similarly incompatible elements, which can be attributed to the presence of the accessory mineral rutile (TiO2) in the residual slab. Here we show that the partitioning behavior of vanadium between rutile and silicate melt varies from incompatible (?0.1) to compatible (?18) as a function of oxygen fugacity. We also confirm that the HFSE are compatible in rutile, with D(Ta)> D(Nb)> (D(Hf)>/? D(Zr), but that the level of compatibility is strongly dependent on melt composition, with partition coefficients increasing about one order of magnitude with increasing melt polymerization (or decreasing basicity). Our partitioning results also indicate that residual rutile may fractionate U from Th due to the contrasting (over 2 orders of magnitude) partitioning between these two elements. We confirm that, in addition to the HFSE, Cr, Cu, Zn and W are compatible in rutile at all oxygen fugacity conditions. PMID:25337667

Mallmann, Guilherme; Fonseca, Raúl O C; Silva, Adolfo B

2014-10-21

33

Partition coefficients for iron between plagioclase and basalt as a function of oxygen fugacity - Implications for Archean and lunar anorthosites  

NASA Technical Reports Server (NTRS)

As a prelude to determinations of the content of total iron as FeO(T) in melts in equilibrium with calcic anorthosites, the partition coefficients (Ds) for FeO(T) between calcic plagioclase and basaltic melt were determined, as a function of oxygen fugacity (f(O2)), for a basaltic composition that occurs as matrices for plagioclase megacrysts. Results showed that, at the liquidus conditions, the value of D for FeO(T) between calcic plagioclase and tholeiitic basalt changed little (from 0.030 to 0.044) between the very low f(O2) of the iron-wustite buffer and that of the quartz-fayalite-magnetite (QFM) buffer. At fugacities above QFM, the value for D increased rapidly to 0.14 at the magnetite-hematite buffer and to 0.33 in air. The increase in D results from the fact that, at f(O2) below QFM, nearly all of the Fe is in the Fe(2+) state; above QFM, the Fe(3+)/Fe(2+) ratio in the melt increases rapidly, causing more Fe to enter the plagioclase which accepts Fe(3+) more readily than Fe(2+).

Phinney, W. C.

1992-01-01

34

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

35

Diffusive Re-equilibration of Volatiles and Oxygen Fugacity in Olivine-Hosted Melt Inclusions: Experiments and Numerical Models  

NASA Astrophysics Data System (ADS)

Determining the pre-eruptive volatile contents of magmas is of critical importance to understanding their generation and evolution. Mineral-hosted melt inclusions can provide information on the pre-eruptive H2O content of the magma as the host mineral shields the interior melt inclusion from decompression that the exterior magma undergoes as it ascends through the crust [1]. Consequently, melt inclusions have been widely used to provide pre-eruptive water contents (eg. [2]). Yet, there is strong evidence of rapid changes to H2O via proton diffusion through the olivine host crystal [3] that are not limited by redox reactions within the melt inclusion [4]. To quantify the extent to which H2O and other volatiles are faithfully recorded in olivine-hosted melt inclusions, we have combined experiments with numerical models to investigate the processes controlling diffusive re-equilibration of water and oxygen fugacity in an olivine-hosted melt inclusion. Dehydration experiments were performed on olivines from the 1999 Cerro Negro Volcano (Nicaragua) eruption. Melt inclusions with initially high water contents (~3.6 ± 0.6 wt. % H2O) were held at 1 atm and 1100°C at the Ni-NiO buffer for 4 to 72 hours. All run products were analyzed by SIMS on the Cameca 1280 ion microprobe at WHOI for H2O, CO2, SO2, F, and Cl. Using COMSOL Multiphysics finite-element modeling software we modeled the diffusive re-equilibration of water, oxygen fugacity, and other volatiles. To interpret our experimental results we used the geometry of the olivines and melt inclusions from the experiments in the numerical models. Our work confirms that the mechanism for loss or gain of H2O from an olivine-hosted melt inclusion is lattice diffusion of protons. Results from XANES analyses on previous dehydration experiments at 1250 °C indicate that H loss occurs through a process decoupled from fO2 re-equilibration. Re-equilibration of fO2 occurs independently via diffusion of point defects on timescales comparable to proton diffusion. Our numerical model is the first to incorporate this point-defect mediated re-equilibration mechanism. Furthermore, the ability to model not only water contents, but also the oxygen fugacity and multiple volatile species is a powerful tool to assess the degree, temperature, and duration of diffusive re-equilibration that a melt inclusion has undergone and the integrity of its composition in yielding estimates of pre-eruptive volatile contents.

Bucholz, C. E.; Gaetani, G. A.; Behn, M. D.

2011-12-01

36

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

37

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

38

An Experimental Study of Eu/Gd Partitioning Between a Shergottite Melt and Pigeonite: Implications for the Oxygen Fugacity of the Martian Interior  

NASA Technical Reports Server (NTRS)

We experimentally investigated the partitioning behavior of Eu/Gd between a synthetic shergottite melt and pigeonite as a function of oxygen fugacity. This has implications for the oxidation state of the source region of the martian meteorites. Additional information is contained in the original extended abstract.

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

2002-01-01

39

Platinum solubility in a haplobasaltic melt at 1250°C and 0.2 GPa: The effect of water content and oxygen fugacity  

NASA Astrophysics Data System (ADS)

Haplobasaltic melts with a 101 kPa dry eutectic composition (An 42Di 58) and varying water contents were equilibrated with their platinum capsule at 1523 K and 200 MPa in an internally heated pressure vessel (IHPV) equipped with a rapid quench device. Experimental products were inclusion-free glasses representative of the Pt-saturated silicate melts at the experimental conditions. Platinum concentrations were determined using an isotope dilution multicollector inductively coupled plasma mass spectrometer and water contents and distribution by Karl Fischer titration and Fourier transform infrared spectroscopy, respectively. The water content of the melt has no intrinsic effect on platinum solubility, for concentrations between 0.9 wt.% and 4.4 wt.% H 2O (saturation). Platinum solubility increases with increasing water content, but this effect is an indirect effect because increasing water content at fixed f H 2 (imposed by the IHPV) increases the oxygen fugacity of the experiment. The positive oxygen fugacity dependence of Pt solubility in a hydrous silicate melt at 200 MPa is identical to that in anhydrous melts of the same composition determined in previous studies at 101 kPa. This study extends the range of platinum solubilities to oxygen fugacities lower than was previously possible. Combining the data of this and previous studies, Pt solubility is related to oxygen fugacity (in bar) at 1523 K by the equation: [=1389×f+7531×(

Blaine, Fred A.; Linnen, Robert L.; Holtz, Francois; Brügmann, Gerhard E.

2005-03-01

40

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

41

An experimental study of trace element partitioning between zircon and melt as a function of oxygen fugacity  

NASA Astrophysics Data System (ADS)

The partitioning of P, Sc, Ti, Sr, Y, Nb, the rare earth elements (REE), Hf, Ta, Th and U between zircon and a synthetic andesitic melt was determined as a function of oxygen fugacity (fO2) over a range of fourteen log units, from QFM-8 to QFM+6 (where QFM is the quartz-fayalite-magnetite oxygen buffer) at ˜1300 °C and 1 atm, using SIMS and LA-ICP-MS. The partition coefficients of Ce and Eu were found to vary systematically with fO2, relative to those of the other REE, producing Ce and Eu anomalies similar to those that are characteristic of natural igneous zircon. These anomalies coexist at terrestrial fO2s and were used to quantify Eu3+/(Eu2+ + Eu3+) and Ce4+/(Ce3+ + Ce4+) in the melt. The partition coefficients of the redox invariant trivalent cations are in excellent agreement with lattice strain theory. The values of DREE are related to those determined for natural samples by the expected dependence on temperature. The incorporation of REE3+ in zircon was independent of the presence of P. DU/DTh was found to vary systematically with fO2 indicating the presence of U4+, U5+ and U6+ in the melt at terrestrial conditions. DTi was independent of fO2 despite an expectation of significant Ti3+ in the most reduced experiments.

Burnham, Antony D.; Berry, Andrew J.

2012-10-01

42

Effect of pressure, temperature, and oxygen fugacity on the metal-silicate partitioning of Te, Se, and S: Implications for earth differentiation  

Microsoft Academic Search

We have measured liquid Fe metal–liquid silicate partitioning (Di) of tellurium, selenium, and sulfur over a range of pressure, temperature, and oxygen fugacity (1–19GPa, 2023–2693K, fO2 ?0.4 to ?5.5 log units relative to the iron-wüstite buffer) to better assess the role of metallic melts in fractionating these elements during mantle melting and early Earth evolution. We find that metal-silicate partitioning

Lesley Rose-Weston; James M. Brenan; Yingwei Fei; Richard A. Secco; Daniel J. Frost

2009-01-01

43

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

Microsoft Academic Search

We have determined Fe–Mg diffusion coefficients in olivines from different sources (Nanga Parbat, Pakistan and San Carlos,\\u000a 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\\u000a profiles. We have characterized the nano-scale structure and composition of the thin films

Ralf Dohmen; Hans-Werner Becker; Sumit Chakraborty

2007-01-01

44

Oxygen Fugacity Constraints During Core Formation - Metal-Silicate Partitioning of Nominally Lithophile Elements  

NASA Astrophysics Data System (ADS)

Based on the relative depletion in Si of the Earth's mantle compared to chondritic material it has frequently been proposed that some Si was extracted into the Earth's core during accretion. However, in order to generate a core containing ~ 7 wt% Si relatively reducing conditions would have been required during core formation. Important constraints can be placed on the lowest redox state attained during core formation, however, by studying the partitioning of nominally lithophile elements. Ta for example is not depleted in the Earth's mantle, although simple thermodynamic calculations suggest that Ta should have metal-silicate partition coefficients similar to Si. Other elements that could be used as such indicators are In, Ga and Zn which are only depleted in the Earth's mantle compared to CI due to volatility. Liquid metal-liquid silicate partitioning experiments on Ta, Ga, In and Zn have been performed between 6 and 20 GPa at 2100oC. In each experiment the staring material was doped with 4 wt% of these elements added to 56 wt% synthetic primitive mantle composition and 40 wt% Fe-alloy. The metallic component was mixed from varying proportions of Fe powder and Fe84Si16 or Fe71Si29 and doped with 2 wt% Ni and 1 wt% Co. Various redox conditions were achieved by adjusting the amount of Si metal. Graphite and MgO single crystal capsules were employed. Recovered liquid metal and quenched silicate melt phases were analyzed with EMP and SIMS was employed for some silicate melt measurements. In contrast to previous studies, our results show that between 6 and 20 GPa metal-silicate partition coefficients for Ta are 1 to 2 orders of magnitude higher than those of Si. There seems to be no pressure dependency of the partition coefficient for the 4 elements studied. These results imply that if metal silicate equilibration occurred at pressures below 25 GPa Si is unlikely to be the light element in the core as this would have caused a strong depletion of Ta from the mantle.

Mann, U.; Frost, D. J.; Rubie, D. C.; Agee, C. B.; Shearer, C. K.

2005-12-01

45

Experimental study of trace element partitioning between enstatite and melt in enstatite chondrites at low oxygen fugacities and 5 GPa  

NASA Astrophysics Data System (ADS)

In order to investigate the influence of very reducing conditions, we report enstatite-melt trace element partition coefficients (D) obtained on enstatite chondrite material at 5 GPa and under oxygen fugacities (fO2) ranging between 0.8 and 8.2 log units below the iron-wustite (IW) buffer. Experiments were conducted in a multianvil apparatus between 1580 and 1850 °C, using doped (Sc, V, REE, HFSE, U, Th) starting materials. We used a two-site lattice strain model and a Monte-Carlo-type approach to model experimentally determined partition coefficient data. The model can fit our partitioning data, i.e. trace elements repartition in enstatite, which provides evidence for the attainment of equilibrium in our experiments. The precision on the lattice strain model parameters obtained from modelling does not enable determination of the influence of intensive parameters on crystal chemical partitioning, within our range of conditions (fO2, P, T, composition). We document the effect of variable oxygen fugacity on the partitioning of multivalent elements. Cr and V, which are trivalent in the pyroxene at around IW - 1 are reduced to 2+ state with increasingly reducing conditions, thus affecting their partition coefficients. In our range of redox conditions Ti is always present as a mixture between 4+ and 3+ states. However the Ti3+-Ti4+ ratio increases strongly with increasingly reducing conditions. Moreover in highly reducing conditions, Nb and Ta, that usually are pentavalent in magmatic systems, appear to be reduced to lower valence species, which may be Nb2+ and Ta3+. We propose a new proxy for fO2 based on D(Cr)/D(V). Our new data extend the redox range covered by previous studies and allows this proxy to be used in the whole range of redox conditions of the solar system objects. We selected trace-element literature data of six chondrules on the criterion of their equilibrium. Applying the proxy to opx-matrix systems, we estimated that three type I chondrules have equilibrated at IW - 7 ± 1, one type I chondrule at IW - 4 ± 1, and two type II chondrules at IW + 3 ± 1. This first accurate estimation of enstatite-melt fO2 for type I chondrules is very close to CAI values. Find the best-fit for trivalent elements. We set the r0M1 (3+) range to 0.55-0.75 Å, based on visual observations of the datapoints. For the other variables we have set boundary values beyond which the solutions would be unacceptable. For example, r0M2 (3+) has to be larger than r0M1 (3+). Finally we restricted the D0 range as follow: 0.2 r0(3+) > r0(4+) (see van Westrenen et al., 2000, for explanation), together with visual observation of our experimental data. D0 ranges: 1 < D0M1(2+) < 100; D0M2 (3+) < D0M2(2+) < 100 ; 0.01 < D0M1(4+) < 0.1 ; 0.0001 < D0M2(4+) < 0.01. These ranges are based on visual observation of our experimental data.

Cartier, Camille; Hammouda, Tahar; Doucelance, Régis; Boyet, Maud; Devidal, Jean-Luc; Moine, Bertrand

2014-04-01

46

The effect of chemical composition and oxygen fugacity on the electrical conductivity of dry and hydrous garnet at high temperatures and pressures  

NASA Astrophysics Data System (ADS)

The in situ electrical conductivity of hydrous garnet samples (Py20Alm76Grs4-Py73Alm14Grs13) was determined at pressures of 1.0-4.0 GPa and temperatures of 873-1273 K in the YJ-3000t apparatus using a Solartron-1260 impedance/gain-phase analyzer for various chemical compositions and oxygen fugacities. The oxygen fugacity was controlled by five solid-state oxygen buffers (Fe2O3 + Fe3O4, Ni + NiO, Fe + Fe3O4, Fe + FeO, and Mo + MoO2). Experimental results indicate that within a frequency range from 10-2 to 106 Hz, electrical conductivity is strongly dependent on signal frequency. Electrical conductivity shows an Arrhenius increase with temperature. At 2.0 GPa, the electrical conductivity of anhydrous garnet single crystals with various chemical compositions (Py20Alm76Grs4, Py30Alm67Grs3, Py56Alm43Grs1, and Py73Alm14Grs13) decreases with increasing pyrope component (Py). With increasing oxygen fugacity, the electrical conductivity of dry Py73Alm14Grs13 garnet single crystal shows an increase, whereas that of a hydrous sample with 465 ppm water shows a decrease, both following a power law (exponents of 0.061 and -0.071, respectively). With increasing pressure, the electrical conductivity of this hydrous garnet increases, along with the pre-exponential factors, and the activation energy and activation volume of hydrous samples are 0.7731 ± 0.0041 eV and -1.4 ± 0.15 cm3/mol, respectively. The results show that small hopping polarons left( {{text{Fe}}_{text{Mg}}^{ \\cdot } } right) and protons ( {text{H}}^{ \\cdot } ) are the dominant conduction mechanisms for dry and wet garnet single crystals, respectively. Based on these results and the effective medium theory, we established the electrical conductivity of an eclogite model with different mineral contents at high temperatures and high pressures, thereby providing constraints on the inversion of field magnetotelluric sounding results in future studies.

Dai, Lidong; Li, Heping; Hu, Haiying; Shan, Shuangming; Jiang, Jianjun; Hui, Keshi

2012-04-01

47

Decoupling of H2O, Oxygen Fugacity and Incompatible Elements in Olivine-Hosted Melt Inclusions By Diffusive Re-Equilibration (Invited)  

NASA Astrophysics Data System (ADS)

Mineral-hosted melt inclusions provide information on the pre-eruptive H2O contents of degassed magmas. The strength of the host mineral protects included silicate melts from the decompression experienced by the entraining magma. This allows melt inclusions to retain their pre-eruptive volatiles and, thereby, provides a source of information on the amount of H2O in magmatic systems. Recent studies have used this to investigate (1) relationships between H2O and oxygen fugacity [1] and (2) the influence of H2O on extent of peridotite partial melting beneath back arc spreading centers [2,3]. We combined experiments and numerical models to investigate the potential for decoupling of these variables through diffusive re-equilibration during episodes of degassing or magma mixing. Our results demonstrate that re-equilibration of H2O and oxygen fugacity occur on short timescales and are independent of one another. Therefore, relationships between H2O and oxygen fugacity are likely to be robust, reflecting pre-eruptive condition. For incompatible elements, such as TiO2, slow diffusivity and low concentration in olivine results in inefficient diffusive re-equilibration. Therefore, relationships between H2O and incompatible elements, such as TiO2, can be significantly perturbed by loss or gain of protons through the host olivine. Hydration experiments were performed on olivines from 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. Initial concentrations of H2O in these melt inclusions are uniformly high (3.6±0.6 wt%). All run products were analyzed 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. Results from our experiments confirm that the mechanism for loss or gain of H2O from olivine-hosted melt inclusions is lattice diffusion of protons, and that the concentration of H2O in melt inclusions changes rapidly. Re-equilibration of oxygen fugacity occurs via diffusion of point defects on timescales comparable to proton diffusion. Further, our results demonstrate that these processes are independent of one another, so that correlations between H2O concentration and the oxidation state of Fe in the melt do not result from diffusive re-equilibration. However, melt inclusions that initially had significantly different H2O and TiO2 contents can end up with a range of TiO2 at nearly constant H2O following loss or gain of protons. In this case, use of TiO2 as an indicator of extent of peridotite partial melting results in erroneous conclusions about the influence of H2O on peridotite partial melting. References: [1] Kelley, K. A. & Cottrell, E., Science 325, 605-607 (2009); [2] Kelley, K. A. et al., J Geophys Res 111 (2006); [3] Kelley, K. A. et al., J Petrol 51, 1711-1738 (2010).

Gaetani, G. A.; O'Leary, J. A.; Shimizu, N.; Bucholz, C. E.

2010-12-01

48

Role of hydrogen and oxygen fugacity on incorporation of nitrogen and carbon in reduced magmas of the early Earth  

NASA Astrophysics Data System (ADS)

Role of hydrogen and oxygen fugacity on incorporation of nitrogen and carbon in reduced magmas of the early Earth A. A. Kadik (1) and Yu. A. Litvin (2)., (1) V.I.Vernadsky Institute of Geochemistry and Analytical Chemistry, RAS, Kosygin St. 19, Moscow 119991, Russia, (2) Institute of Experimental Mineralogy, RAS, Chernogolovka, Mos?ow distr. 142432, Russia kadik@geokhi.ru / 7-495-137-7200 In a series of experiments in the system Fe-bearing melt + molten Fe metallic phase + N+ H conducted at 4 GPa and 1550°C and logfO2 from 2 to 4 below logfO2 (IW), we have characterised the nature and quantified the abundance's of N- and H-compound dissolved in an model silicate melt (NaAlSi3O8 80% wt +FeO 20% wt). Experiments were carried out in an anvil-with-hole apparatus. The technique of fO2 buffering employed relies upon the diffusion of H2 through Pt to achieve equal chemical potentials of H2 in the inner Pt capsule and outer solid fO2 buffer assembly in the presence of H2O. The fO2 imposed on the charge is controlled by the equilibrium between H2 buffered externally, and the Fe-bearing melt. To create a low fO2 in the experiments, 2, 3, 5 and 7 wt % of finely dispersed Si3N4 was added to the glass powder (NaAlSi3O8 80% + FeO 20% wt). The initial Si3N4 was unstable under experimental conditions and was completely consumed according to the reactions: Si3N4(initial) + 3O2 ? 3SiO2(melt) + 4N(melt) with the subsequent participation of nitrogen in reactions with hydrogen and components of silicate melts. The infrared and Raman spectroscopy of glasses indicates a remarkable feature of N-H interaction with a reduced silicate: an appreciable change in the mechanism of their dissolution with a decrease in fO2. The most part of nitrogen reacts with hydrogen with formation of N-H complexes. The most likely nitrogen-bearing species is represented by NH3 and NH4+ group. Except for N-H complexes hydrogen is expressed under the oxidized form OH and H2O. Some hydrogen is present in a melt in the molecular form. The amount of H and N dissolved in the glasses was measured by ion microprobe and microprobe analysis. Hydrogen content increases with decreasing fO2 from 0.3 wt % at ?logfO2(IW) = -2.2 to 0.4 wt % at ?logfO2(IW) = -3.9. Nitrogen content increases with decreasing fO2 from 0.5 wt% at ?logfO2(IW)= -2.2 to 1.9 wt % at ?logfO2(IW)= -3.9. It is suggested, that significant amounts of nitrogen, comparable to those estimated for the present-day mantle, could have been incorporated in the early Earth by dissolution in a magma ocean, under fO2 conditions relevant to those prevailing during metal segregation. The experimental results in the system model silicate melt (NaAlSi3O8 80% wt +FeO 20% wt) + molten Fe metallic phase + C+ H conducted at 4 GPa and 1550°C and logfO2 from 2 to 4 logfO2 (IW) allow to assume that the formation of compounds with C-H-type bonds (e.g., H2, CH4 and other molecules with such a bond) should be expected in primary melts of the reduced mantle, together with oxidized H species (as the OH-group). The relationship between them substantially depends on fO2. We assume that the magmatic transport and chemical evolution of nitrogen, carbon and hydrogen during the reduced episode of early mantle evolution could be very much influenced by low fO2 values in presence of the metallic Fe phase. The primary melting is a way of providing the formation of the reduced forms of nitrogen, carbon and hydrogen (H2, CH4, NH3 together with H2O, OH) in magmas of the early Earth. Support: Prog. No 15 RAS, RFBR grant No 08-05-00377, ESD RAS project No 8.

Kadik, A. A.; Litvin, Yu. A.

2009-04-01

49

The W-W02 Oxygen Fugacity Buffer at High Pressures and Temperatures: Implications for f02 Buffering and Metal-silicate Partitioning  

NASA Technical Reports Server (NTRS)

Oxygen fugacity (fO2) controls multivalent phase equilibria and partitioning of redox-sensitive elements, and it is important to understand this thermodynamic parameter in experimental and natural systems. The coexistence of a metal and its oxide at equilibrium constitutes an oxygen buffer which can be used to control or calculate fO2 in high pressure experiments. Application of 1-bar buffers to high pressure conditions can lead to inaccuracies in fO2 calculations because of unconstrained pressure dependencies. Extending fO2 buffers to pressures and temperatures corresponding to the Earth's deep interior requires precise determinations of the difference in volume (Delta) V) between the buffer phases. Synchrotron x-ray diffraction data were obtained using diamond anvil cells (DAC) and a multi anvil press (MAP) to measure unit cell volumes of W and WO2 at pressures and temperatures up to 70 GPa and 2300 K. These data were fitted to Birch-Murnaghan 3rd-order thermal equations of state using a thermal pressure approach; parameters for W are KT = 306 GPa, KT' = 4.06, and aKT = 0.00417 GPa K-1. Two structural phase transitions were observed for WO2 at 4 and 32 GPa with structures in P21/c, Pnma and C2/c space groups. Equations of state were fitted for these phases over their respective pressure ranges yielding the parameters KT = 190, 213, 300 GPa, KT' = 4.24, 5.17, 4 (fixed), and aKT = 0.00506, 0.00419, 0.00467 GPa K-1 for the P21/c, Pnma and C2/c phases, respectively. The W-WO2 buffer (WWO) was extended to high pressure by inverting the W and WO2 equations of state to obtain phase volumes at discrete pressures (1-bar to 100 GPa, 1 GPa increments) along isotherms (300 to 3000K, 100 K increments). The slope of the absolute fO2 of the WWO buffer is positive with increasing temperature up to approximately 70 GPa and is negative above this pressure. The slope is positive along isotherms from 1000 to 3000K with increasing pressure up to at least 100 GPa. The WWO buffer is at a higher fO2 than the IW buffer at pressures lower than 40 GPa, and the magnitude of this difference decreases at higher pressures. This qualitatively indicates an increasingly lithophile character for W at higher pressures. The WWO buffer was quantitatively applied to W metal-silicate partitioning by using the WWO-IW buffer difference in combination with literature data on W metal-silicate partitioning to model the exchange coefficient (KD) for the Fe-W exchange reaction. This approach captures the pressure dependence of W metal-silicate partitioning using the WWO-IW buffer difference and models the activities of the components in the silicate and metallic phases using an expression of the Gibbs excess energy of mixing. Calculation of KD along a peridotite liquidus predicts a decrease in W siderophility at higher pressures that supports the qualitative behavior predicted by the WWO-IW buffer difference, and agrees with findings of others. Comparing the competing effects of temperature and pressure on W metal-silicate partitioning, our results indicate that pressure exerts a greater effect.

Shofner, G. A.; Campbell, A. J.; Danielson, L.; Righter, K.

2013-01-01

50

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

51

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  

Microsoft Academic Search

: 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

Thomas H. Giordano

2002-01-01

52

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

53

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

54

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

55

P-T-Fluid evolution and graphite deposition during retrograde metamorphism in Ribeira Fold Belt, SE Brazil: Oxygen fugacity, fluid inclusions and C-O-H isotopic evidence  

NASA Astrophysics Data System (ADS)

Combined fluid inclusion (FI) microthermometry, Raman spectroscopy, X-ray diffraction, C-O-H isotopes and oxygen fugacities of granulites from central Ribeira Fold Belt, SE Brazil, provided the following results: i) Magnetite-Hematite ƒO2 estimates range from 10-11.5 bar (QFM +1) to 10-18.3 bar (QFM -1) for the temperature range of 896 °C-656 °C, implying ƒO2 decrease from metamorphic peak temperatures to retrograde conditions; ii) 5 main types of fluid inclusions were observed: a) CO2 and CO2-N2 (0-11 mol%) high to medium density (1.01-0.59 g/cm3) FI; b) CO2 and CO2-N2 (0-36 mol%) low density (0.19-0.29 g/cm3) FI; c) CO2 (94-95 mol%)-N2 (3 mol%)-CH4 (2-3 mol%)-H2O (water ?v (25 °C) = 0.1) FI; d) low-salinity H2O-CO2 FI; and e) late low-salinity H2O FI; iii) Raman analyses evidence two graphite types in khondalites: an early highly ordered graphite (T?450 °C) overgrown by a disordered kind (T?330 °C); iv) ?18O quartz results of 10.3-10.7‰ imply high-temperature CO2 ?18O values of 14.4-14.8‰, suggesting the involvement of a metamorphic fluid, whereas lower temperature biotite ?18O and ?D results of 7.5-8.5‰ and -54 to -67‰, respectively imply H2O ?18O values of 10-11‰ and ?DH2O of -23 to -36‰, suggesting ?18O depletion and increasing fluid/rock ratio from metamorphic peak to retrograde conditions. Isotopic results are compatible with low-temperature H2O influx and ƒO2 decrease that promoted graphite deposition in retrograde granulites, simultaneous with low density CO2, CO2-N2 and CO2-N2-CH4-H2O fluid inclusions at T = 450-330 °C. Graphite ?13C results of -10.9 to -11.4‰ imply CO2 ?13C values of -0.8 to -1.3‰, suggesting decarbonation of Cambrian marine carbonates with small admixture of lighter biogenic or mantle derived fluids. Based on these results, it is suggested that metamorphic fluids from the central segment of Ribeira Fold Belt evolved to CO2-N2 fluids during granulitic metamorphism at high ƒO2, followed by rapid pressure drop at T?400-450 °C during late exhumation that caused ƒO2 reduction induced by temperature decrease and water influx, turning carbonic fluids into CO2-H2O (depleting biotite ?18O and ?D values), and progressively into H2O. When ƒO2 decreased substantially by mixture of carbonic and aqueous fluids, graphite deposited forming khondalites.

Bento dos Santos, Telmo M.; Munhá, José M. U.; Tassinari, Colombo C. G.; Noronha, Fernando M.; Guedes, Alexandra; Fonseca, Paulo E.; Neto, Coriolano Dias; Dória, Armanda

2011-02-01

56

Oxygen Toxicity Calculations by Erik C. Baker, P.E.  

E-print Network

1 Oxygen Toxicity Calculations by Erik C. Baker, P.E. Management of exposure to oxygen toxicity myself using the good ole' FORTRAN programming language, I found that incorporating oxygen toxicity for others. Background Two oxygen toxicity parameters are typically "tracked" in technical diving

Read, Charles

57

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

58

A liquid oxygen calculator for fasted channel catfish  

Technology Transfer Automated Retrieval System (TEKTRAN)

An interactive liquid oxygen (LOX) calculator for fasted channel catfish confined in grading nets or in live haul tanks has been developed, using Microsoft Visual Studio 2005©. The calculator is based on results of scientific experiments on channel catfish metabolism, and estimates oxygen consumptio...

59

Titaniferous magnetite–ilmenite thermometry and titaniferous magnetite–ilmenite–orthopyroxene–quartz oxygen barometry in granulite facies gneisses, Bamble Sector, SE Norway: implications for the role of high-grade CO 2 -rich fluids during granulite genesis  

Microsoft Academic Search

Oxygen fugacities have been estimated for a wide distribution of samples from the granulite facies terrane (region C) of\\u000a the Bamble Sector, SE Norway using both the titaniferous magnetite–ilmenite and orthopyroxene–titaniferous magnetite–quartz\\u000a oxygen barometers. These oxygen fugacities are estimated using temperatures calculated from the titaniferous magnetite–ilmenite\\u000a thermometer of Ghiorso and Sack (1991) and are both internally consistent with each other

Daniel E. Harlov

2000-01-01

60

Assessment of the air-soil partitioning of polycyclic aromatic hydrocarbons in a paddy field using a modified fugacity sampler.  

PubMed

Rice, one of the most widely cultivated crops, has received great attention in contaminant uptake from soil and air, especially for the special approaches used for its cultivation. The dry-wet alternation method can influence the air-soil partitioning of semivolatile organic compounds (SVOCs) in the paddy ecosystem. Here, we modified a fugacity sampler to investigate the air-surface in situ partitioning of ubiquitous polycyclic aromatic hydrocarbons (PAHs) at different growth stages in a suburban paddy field in South China. The canopy of rice can form a closed space, which acts like a chamber that can force the air under the canopy to equilibrate with the field surface. When we compared the fugacities calculated using a fugacity model of the partition coefficients to the measured fugacities, we observed similar trends in the variation, but significantly different values between different growing stages, especially during the flooding stages. However, the measured and calculated fugacity fractions were comparable when uncertainties in our calculations were considered, with the exception of the high molecular weight (HMW) PAHs. The measured fugacity fractions suggested that the HMW PAHs were also closed to equilibrium between the paddy field and atmosphere. The modified fugacity sampler provided a novel way of accurately determining the in situ air-soil partitioning of SVOCs in a wet paddy field. PMID:25453511

Wang, Yan; Luo, Chunling; Wang, Shaorui; Liu, Junwen; Pan, Suhong; Li, Jun; Ming, Lili; Zhang, Gan; Li, Xiangdong

2015-01-01

61

A liquid oxygen calculator for fasted channel catfish  

Technology Transfer Automated Retrieval System (TEKTRAN)

A review of scientific literature concerning channel catfish Ictalurus punctatus respiration resulted in development of a Microsoft Excel© spreadsheet for estimating the volume of oxygen consumed by a given fasted channel catfish biomass. Entry of ten variables into the spreadsheet provides estimate...

62

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  

NASA Astrophysics Data System (ADS)

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 calibration of the FeTi-oxide thermometer + oxygen barometer at conditions of temperature and oxygen fugacity poorly covered by previous equilibrium experiments. Isotherms for our data in Roozeboom diagrams of projected %usp vs. %ilm show a change in slope at ? 60% ilm, consistent with the second-order transition from FeTi-ordered Ilm to FeTi-disordered Ilm-Hem. This feature of the system accounts for some, but not all, of the differences from earlier thermodynamic calibrations of the thermobarometer. In rhyolite containing 1.0 wt.% MgO, 0.8 wt.% MnO, or MgO + MnO, Usp-Mt crystallized with up to 14% of aluminate components, and Ilm-Hem crystallized with up to 13% geikielite component and 17% pyrophanite component. Relative to the FeTiAlO system, these components displace the ferrite components in Usp-Mt, and the hematite component in Ilm-Hem. As a result, projected contents of ulvöspinel and ilmenite are increased. These changes are attributed to increased non-ideality along joins from end-member hematite and magnetite to their respective Mg- and Mn-bearing titanate and aluminate end-members. The compositional shifts are most pronounced in Ilm-Hem in the range Ilm50 80, a solvus region where the chemical potentials of the hematite and ilmenite components are nearly independent of composition. The solvus gap widens with addition of Mg and even further with Mn. The Bacon Hirschmann correlation of Mg/Mn in Usp-Mt and coexisting Ilm-Hem is displaced toward increasing Mg/Mn in ilmenite with passage from ordered ilmenite to disordered hematite. Orthopyroxene and biotite crystallized in experiments with added MgO and MgO + MnO; their X Fe varies with log_{10} f_{{{text{O}}2}} and T consistent with equilibria among ferrosilite, annite, and ferrite components, and the chemical potentials of SiO2 and orthoclase in the liquid. Experimental equilibration rates increased in the order: Opx < Bt < Ilm-Hem < Usp-Mag.

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

2006-08-01

63

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

64

Calculation of thermodynamic parameters of U–Pu–N system with carbon and oxygen impurities  

Microsoft Academic Search

Mixed nitride fuels are being considered for advanced FBR, but very little is known about the thermodynamic properties of these fuels. For an overall composition of the nitride fuel with small amounts of oxygen and carbon impurities, thermodynamic properties, e.g. carbon activity and partial pressures of nitrogen, carbon-monoxide, plutonium and uranium, were calculated in present work. These calculations were based

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

1999-01-01

65

Computer program for calculating pressure-broadened Raman spectra for molecular nitrogen and oxygen  

NASA Technical Reports Server (NTRS)

A computer program is given for calculating the rotational Raman spectrum for molecular nitrogen and oxygen. Provision is made for pressure broadening. Several sample calculations at various pressures are shown. The relative heights of some of the lines are affected by pressure broadening.

Fralick, G. C.

1976-01-01

66

Toward calculating heliospheric filtration of interstellar oxygen on its way to IBEX  

NASA Astrophysics Data System (ADS)

Direct, primary interstellar oxygen (O) has been detected by IBEX. We use output from a realistic numerical hydrogen+proton global heliosphere model run (3D MHD/kinetic), together with novel neutral oxygen trajectory calculations, to investigate: From where in the ISM come those neutral O that make it to 1 AU? To 1 AU in the ecliptic? Into the IBEX detectors? What filtration due to charge exchange losses with plasma protons and due to photoionization suffer those neutral O sightlines that make it into the IBEX detector? This information is important to infer the ISM neutral oxygen density from fluxes measured by IBEX.

Mueller, H.; Moebius, E.; Bzowski, M.; Pogorelov, N. V.; Heerikhuisen, J.

2009-12-01

67

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

NASA Astrophysics Data System (ADS)

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 b2 and b3 for a one dimensional Bose gas, subject to repulsive delta-function interactions, by direct integration of the wave functions. For b2, 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 b3-b30 (where b30 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.; Larsen, S. Y.; Lassaut, M.

2011-02-01

68

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

69

Uncertainties in the thermodynamics of basalt-oxygen and basalt-water reactions  

SciTech Connect

A knowledge of basalt-oxygen equilibria and basalt-water equilibria are required to predict the performance of a high-level waste package in a basalt repository. In this report we have evaluated uncertainties in these equilibria using thermodynamic data from two sources, the JANAF Thermochemical Tables (1971) and from Kubaschewski (1974). Our analysis indicates that the uncertainties in the basic thermodynamic data lead to 30 orders of magnitude in uncertainty in the oxygen fugacity for the magnetite-hematite reaction (10/sup -57/ to 10/sup -86/ atm) and about 15 orders of magnitude uncertainty in the hydrogen equilibrium pressure (10/sup -12/ to 10/sup +3/ atm). A vast volume of literature exists on reactions involving magnetite and hematite in water at temperatures pertinent to basalt repositories (50/sup 0/ to 350/sup 0/C). These data show that Fe/sub 3/O/sub 4/ and Fe/sub 2/O/sub 3/ can coexist in water with oxygen fugacities from about 10/sup -4/ to 1 rather than the calculated oxygen fugacities of approx. 10/sup -60/ to 10/sup -30/ assumed in the past. 5 references.

Schweitzer, D.G.; Davis, M.S.

1983-08-01

70

First Principles Calculations of Oxygen Adsorption on the UN(001) Surface  

SciTech Connect

Fabrication, handling and disposal of nuclear fuel materials require comprehensive knowledge of their surface morphology and reactivity. Due to unavoidable contact with air components (even at low partial pressures), UN samples contain considerable amount of oxygen impurities affecting fuel properties. In this study we focus on reactivity of the energetically most stable (001) substrate of uranium nitride towards the atomic oxygen as one of initial stages for further UN oxidation. The basic properties of O atoms adsorbed on the UN(001) surface are simulated here combining the two first principles calculation methods based on the plane wave basis set and that of the localized orbitals.

Zhukovskii, Yuri F.; Bocharov, Dmitry; Kotomin, Eugene Alexej; Evarestov, Robert; Bandura, A. V.

2009-01-01

71

First principles calculations of oxygen adsorption on the UN(0 0 1) surface  

NASA Astrophysics Data System (ADS)

Fabrication, handling and disposal of nuclear fuel materials require comprehensive knowledge of their surface morphology and reactivity. Due to unavoidable contact with air components (even at low partial pressures), UN samples contain considerable amount of oxygen impurities affecting fuel properties. In this study we focus on reactivity of the energetically most stable (0 0 1) substrate of uranium nitride towards the atomic oxygen as one of initial stages for further UN oxidation. The basic properties of O atoms adsorbed on the UN(0 0 1) surface are simulated here combining the two first principles calculation methods based on the plane wave basis set and that of the localized orbitals.

Zhukovskii, Yu. F.; Bocharov, D.; Kotomin, E. A.; Evarestov, R. A.; Bandura, A. V.

2009-01-01

72

ccsd-00000318(version1):29Apr2003 Calculation of muon transfer from muonic hydrogen to atomic oxygen  

E-print Network

oxygen Arnaud Dupays, Bruno Lepetit, J. Alberto Beswick, Carlo Rizzo Laboratoire Collisions, Agrgats and an oxygen atom are calculated in a constrained geometry one dimensional model for collision energies between energy dependence of muon transfer from the muonic hydrogen to an oxygen molecule, has been proposed [3

Boyer, Edmond

73

Inverse calculation of biochemical oxygen demand models based on time domain for the tidal Foshan River.  

PubMed

To simulate the variation of biochemical oxygen demand (BOD) in the tidal Foshan River, inverse calculations based on time domain are applied to the longitudinal dispersion coefficient (E(x)) and BOD decay rate (K(x)) in the BOD model for the tidal Foshan River. The derivatives of the inverse calculation have been respectively established on the basis of different flow directions in the tidal river. The results of this paper indicate that the calculated values of BOD based on the inverse calculation developed for the tidal Foshan River match the measured ones well. According to the calibration and verification of the inversely calculated BOD models, K(x) is more sensitive to the models than E(x) and different data sets of E(x) and K(x) hardly affect the precision of the models. PMID:25026574

Er, Li; Xiangying, Zeng

2014-01-01

74

Method to obtain the high contrast images of blood vessel for oxygen saturation calculation  

NASA Astrophysics Data System (ADS)

The skin illuminated of two lights at different wavelength can be applied to detect the oxygen saturation of human blood. Due to the absorption coefficient of oxy- (HbO2) and deoxy- (Hb) hemoglobin are different at the wavelength 660 nm and 890 nm, the transmitted and reflected light within the skin can be used to compute the oxygen saturation image of skin. However, the intensities of skin images illuminated by a 20 mW NIR-LED are too low to determine the position of blood vessel when acquired by the color CCD camera. In order to improve the disadvantages, a mono camera was used and the irradiated distance and angle between LED light and test hand were adjusted to acquire the higher resolution and contrast blood vessel images for the oxygen saturation calculation. In the experiment, we developed the suitable angle to irradiate NIR light is at 75 degrees because the reflected and scattered effect could be generated significantly from both vertical and horizontal direction. In addition, the best contrast vessel images can be obtained when the shutter time is set at 44.030 ms and the irradiated distance was at the range 140-160 mm due to the intensity ratio between tissue and vessel region is the highest and the intensities of image would not be saturated or become too low when these two parameters were adjusted slightly. In future, the proposed parameters and results can be applied to the oxygen saturation measurement in the clinical diagnosis.

Tsai, Hsin-Yi; Chen, Yi-Ju; Chang, Han-Chao; Huang, Kuo-Cheng

2013-06-01

75

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

76

Nitrogen-broadened lineshapes in the oxygen A-band: Experimental results and theoretical calculations  

NASA Astrophysics Data System (ADS)

We report measurements for N 2-broadening, pressure-shift and line mixing coefficients for 55 oxygen transitions in the A-band retrieved using a multispectrum fitting technique. Nineteen laboratory absorption spectra were recorded at 0.02 cm -1 resolution using a multi-pass absorption cell with path length of 1636.9 cm and the IFS 120 Fourier transform spectrometer located at Justus-Liebig-University in Giessen, Germany. The total sample pressures ranged from 8.8 to 3004.5 Torr with oxygen volume mixing ratios in nitrogen ranging between 0.057 and 0.62. An Exponential Power Gap (EPG) scaling law was used to calculate the N 2-broadening and N 2-line mixing coefficients. The line broadening and shift coefficients for the A-band of oxygen self-perturbed and perturbed by N 2 are modeled using semiclassical calculations based on the Robert-Bonamy formalism and two intermolecular potentials. These potentials involve electrostatic contributions including the hexadecapole moment of the molecules and (a) a simple dispersion contribution with one adjustable parameter to fit the broadening coefficients or (b) the atom-atom Lennard-Jones model without such adjustable parameters. The first potential leads to very weak broadening coefficients for high J transitions whereas the second potential gives much more improved results at medium and large J values, in reasonable agreement with the experimental data. For the line shifts which mainly arise in our calculation from the electronic state dependence of the isotropic potential, their general trends with increasing J values can be well predicted, especially from the first potential. From the theoretical results, we have derived air-broadening and air-induced shift coefficients with an agreement comparable to that obtained for O 2-O 2 and O 2-N 2.

Predoi-Cross, Adriana; Holladay, Christopher; Heung, Henry; Bouanich, Jean-Pierre; Mellau, Georg Ch.; Keller, Reimund; Hurtmans, Daniel R.

2008-09-01

77

Density functional theory calculations on oxygen adsorption on the Cu2O surfaces  

NASA Astrophysics Data System (ADS)

In order to understand various surface properties such as corrosion and potential catalytic activity of Cu2O surfaces in the presence of environmental gases, we report here spin-polarized density functional theory calculations of the adsorptions of atomic and molecular oxygen on three surface Cu2O facets. Atomic oxygen adsorbs at the hollow site formed with copper atoms of Cu2O(111), while its adsorption on the Cu2O(110) and Cu2O(100) induces surface reconstruction. Molecular oxygen adsorbs on one coordinated unsaturated surface copper atom and two coordinated saturated copper atoms of Cu2O(111), on the top of two surface copper atoms of Cu2O(110), and on four surface copper atoms on Cu2O(100). It was found that atomic O and molecular O2 adsorption on the Cu2O(100) surface is stronger than on the Cu2O(111) surface. Atomic O and molecular O2 adsorption on the surface of Cu2O(111) induces magnetism. This is different from other systems previously known to exhibit point defect ferromagnetism. On all three surfaces, dissociative adsorption was found to be energetically favorable.

Yu, Xiaohu; Zhang, Xuemei; Tian, Xinxin; Wang, Shengguang; Feng, Gang

2015-01-01

78

Calculation of thermodynamic parameters of U-Pu-N system with carbon and oxygen impurities  

NASA Astrophysics Data System (ADS)

Mixed nitride fuels are being considered for advanced FBR, but very little is known about the thermodynamic properties of these fuels. For an overall composition of the nitride fuel with small amounts of oxygen and carbon impurities, thermodynamic properties, e.g. carbon activity and partial pressures of nitrogen, carbon-monoxide, plutonium and uranium, were calculated in present work. These calculations were based on standard Gibbs free energies of the binary compounds, present in this multi-component system (U,Pu)-C-N-O. For an over all composition of the fuel, stable phase-field was determined by minimization of the Gibbs free energy of the system. The fabrication experiences of various workers, reported in literature, have shown that depending on the impurity content, nitride fuel can exist in two phase fields, mono-nitride phase in equilibrium with sesquinitride phase or mono-nitride phase in equilibrium with dioxide phase. Therefore, in present calculations special attention was given to the thermodynamic behavior of these two phase-fields. A comparison of calculated thermodynamic properties indicated that nitride fuel with dioxide as second phase will be superior to the one with sesquinitride.

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

79

A fugacity-based indoor residential pesticide fate model  

SciTech Connect

Dermal and non-dietary pathways are potentially significant exposure pathways to pesticides used in residences. Exposure pathways include dermal contact with residues on surfaces, ingestion from hand- and object-to-mouth activities, and absorption of pesticides into food. A limited amount of data has been collected on pesticide concentrations in various residential compartments following an application. But models are needed to interpret this data and make predictions about other pesticides based on chemical properties. In this paper, we propose a mass-balance compartment model based on fugacity principles. We include air (both gas phase and aerosols), carpet, smooth flooring, and walls as model compartments. Pesticide concentrations on furniture and toys, and in food, are being added to the model as data becomes available. We determine the compartmental fugacity capacity and mass transfer-rate coefficient for wallboard as an example. We also present the framework and equations needed for a dynamic mass-balance model.

Bennett, Deborah H.; Furtaw, Edward J.; McKone, Thomas E.

2002-06-01

80

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

Microsoft Academic Search

Oxygen self-diffusion coefficients have been measured for three natural diopsidic clinopyroxenes, a natural anorthite, a synthetic magnesium aluminate spinel, and a synthetic åkermanite for oxygen fugacities ranging from the NNO to IW buffers. The experiments employed a gas-solid isotopic exchange technique utilizing 99% 18 O-enriched CO-CO 2 gas mixtures to control both the oxygen fugacity and the isotopic composition of

F. J. Ryerson; D. Kevin McKeegan

1994-01-01

81

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  

Microsoft Academic Search

Oxygen self-diffusion coefficients have been measured for three natural clinopyroxenes (diopside end member), a natural anorthite, a synthetic magnesium aluminate spinel, and a synthetic akermanite over oxygen fugacities ranging from the NNO to IW buffers. The experiments employed a gas-solid isotopic exchange technique utilizing 99% ^18O-enriched COCO2 gas mixtures to control both the oxygen fugacity and the isotopic composition of

F. J. Ryerson; K. D. McKeegan

1993-01-01

82

Ab Initio calculations of even oxygen isotopes with chiral two-plus-three-nucleon interactions.  

PubMed

We formulate the in-medium similarity renormalization group (IM-SRG) for open-shell nuclei using a multireference formalism based on a generalized Wick theorem introduced in quantum chemistry. The resulting multireference IM-SRG (MR-IM-SRG) is used to perform the first ab initio study of all even oxygen isotopes with chiral nucleon-nucleon and three-nucleon interactions, from the proton to the neutron drip lines. We obtain an excellent reproduction of experimental ground-state energies with quantified uncertainties, which is validated by results from the importance-truncated no-core shell model and the coupled cluster method. The agreement between conceptually different many-body approaches and experiment highlights the predictive power of current chiral two- and three-nucleon interactions, and establishes the MR-IM-SRG as a promising new tool for ab initio calculations of medium-mass nuclei far from shell closures. PMID:25165916

Hergert, H; Binder, S; Calci, A; Langhammer, J; Roth, R

2013-06-14

83

Estimating the uncertainty in thermochemical calculations for oxygen-hydrogen combustors  

NASA Astrophysics Data System (ADS)

The thermochemistry program CEA2 was combined with the statistical thermodynamics program PAC99 in a Monte Carlo simulation to determine the uncertainty in several CEA2 output variables due to uncertainty in thermodynamic reference values for the reactant and combustion species. In all, six typical performance parameters were examined, along with the required intermediate calculations (five gas properties and eight stoichiometric coefficients), for three hydrogen-oxygen combustors: a main combustor, an oxidizer preburner and a fuel preburner. The three combustors were analyzed in two different modes: design mode, where, for the first time, the uncertainty in thermodynamic reference values---taken from the literature---was considered (inputs to CEA2 were specified and so had no uncertainty); and data reduction mode, where inputs to CEA2 did have uncertainty. The inputs to CEA2 were contrived experimental measurements that were intended to represent the typical combustor testing facility. In design mode, uncertainties in the performance parameters were on the order of 0.1% for the main combustor, on the order of 0.05% for the oxidizer preburner and on the order of 0.01% for the fuel preburner. Thermodynamic reference values for H2O were the dominant sources of uncertainty, as was the assigned enthalpy for liquid oxygen. In data reduction mode, uncertainties in performance parameters increased significantly as a result of the uncertainties in experimental measurements compared to uncertainties in thermodynamic reference values. Main combustor and fuel preburner theoretical performance values had uncertainties of about 0.5%, while the oxidizer preburner had nearly 2%. Associated experimentally-determined performance values for all three combustors were 3% to 4%. The dominant sources of uncertainty in this mode were the propellant flowrates. These results only apply to hydrogen-oxygen combustors and should not be generalized to every propellant combination. Species for a hydrogen-oxygen system are relatively simple, thereby resulting in low thermodynamic reference value uncertainties. Hydrocarbon combustors, solid rocket motors and hybrid rocket motors have combustion gases containing complex molecules that will likely have thermodynamic reference values with large uncertainties. Thus, every chemical system should be analyzed in a similar manner as that shown in this work.

Sims, Joseph David

84

The Effect of Sulfur Fugacity on Pt, Pd and Au in Magmatic-Hydrothermal Systems  

NASA Astrophysics Data System (ADS)

We have constrained experimentally the effect of sulfur fugacity (fS2) and sulfide saturation on the fractionation and partitioning behavior of Pt, Pd and Au in a felsic silicate melt + sulfide crystal/melt + oxide + supercritical aqueous fluid phase + Pt + Pd + Au system. Experiments were performed at 800°C, 150 MPa, with oxygen fugacity (fO2) fixed at approximately the nickel + nickel oxide buffer (NNO). Sulfur fugacity in the experiments was varied five orders of magnitude from approximately logfS2 = 0 to logfS2 = -5 by using two different sulfide phase assemblages. Sulfide assemblage one consisted initially of chalcopyrite plus pyrrhotite and assemblage two consisted of chalcopyrite plus bornite. At run conditions, in both assemblages, pyrrhotite transformed compositionally to monosulfide solid solution (mss), chalcopyrite to intermediate solid solution (Iss), and in assemblage two chalcopyrite and bornite formed a sulfide melt. Run- product silicate glass (i.e., quenched silicate melt) and crystalline materials were analyzed by using both electron probe microanalysis (EPMA) for major elements and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) for major and trace elements. The measured concentrations of Pt, Pd, and Au in quenched silicate melt in runs with logfS2 values ranging from approximately 0 to -5, do not exhibit any apparent dependence on the dissolved sulfur content of the melt. The measured Pt, Pd and Au concentrations in mss vary as a function of fS2. The measured Pt, Pd and Au concentrations in Iss do not appear to be dependent on fS2. The system variables fS2 and fO2, working in concert with each other, control the stable magmatic sulfide phase assemblage. Additionally, the system fS2 strongly influences the solubility of Pt, Pd, and Au as lattice bound components in some common crystalline magmatic sulfide phases. Both the stable magmatic sulfide phase assemblage and the solubility of Pt, Pd, and Au as constituents in stable crystalline sulfide phases vary as a function of fS2. Our data suggest that the dynamic, temporal evolution of fS2, inherently linked with fO2, plays a determinate role in the Pt, Pd, and Au budget in sulfide-oxide saturated, ore-genitive magmatic systems.

Bell, A.; Simon, A.

2009-05-01

85

First-Principles Calculations of Oxygen Vacancy Formation and Metallic Behavior at a ?-MnO2 Grain Boundary.  

PubMed

Nanostructured MnO2 is renowned for its excellent energy storage capability and high catalytic activity. While the electronic and structural properties of MnO2 surfaces have received significant attention, the properties of the grain boundaries (GBs) and their contribution to the electrochemical performance of the material remains unknown. Through density functional theory (DFT) calculations, the structure and electronic properties of the ?-MnO2 ? 5(210)/[001] GB are studied. Our calculations show this low energy GB has a significantly reduced band gap compared to the pristine material and that the formation of oxygen vacancies produces spin-polarized states that further reduce the band gap. Calculated formation energies of oxygen vacancy defects and Mn reduction at the GB core are all lower than the equivalent bulk value and in some cases lower than values recently calculated for ?-MnO2 surfaces. Oxygen vacancy formation is also shown to produce a metallic behavior at the GB with defect charge distributed over a number of oxygen and manganese sites. The low energies of oxygen defect formation and the potential creation of conductive GB pathways are likely to be important to the electrochemical performance of ?-MnO2. PMID:25559707

Dawson, James A; Chen, Hungru; Tanaka, Isao

2015-01-28

86

OH in Rutile: an Oxygen and Water Barometer  

NASA Astrophysics Data System (ADS)

Dehydration of the subducting lithosphere induces oxidation and partial melting in the mantle wedge above subduction zones, and storage of water in the form of hydroxyl in high-pressure mineral phases may be an important mechanism for transfer of water to the mantle. It is therefore important to quantify water content of fluids and oxygen fugacity in subduction zones, but these variables can be difficult to measure or infer in many rocks. This study investigates the possibility of determining oxygen fugacity or water activity based on OH concentration measurements in rutile. The solubility of OH in pure rutile has been determined using rutile grains from aqueous fluid solubility experiments (Tropper and Manning 2005, Am Min, 90, 502). In pure rutile, H+ is stoichiometrically incorporated into the structure via reduction of Ti4+ to Ti3+, resulting in a change in color from pale yellow to deep blue. Synthetic rutile crystals were equilibrated in pure H2O or a H2O-NaCl solution at 1-2 GPa and 600-1100°C. The runs were unbuffered with respect to oxygen fugacity but were close to the NNO buffer (Newton and Manning 2005, J Petr, 46, 701). Rutile OH concentrations were determined using FTIR spectroscopy and the calibration of Maldener (2001, Min Pet, 71, 21). At a constant pressure of 1 GPa, OH concentrations of rutile in equilibrium with pure H2O increase exponentially from 600 to 1100°C. The data are fit with the equation [OH] = 17.7exp(4.00×10-3T) (R=0.998), where [OH] is in ppm H2O wt. and T is in °C. Increasing pressure from 1 to 2 GPa at 1100°C results in an increase in OH solubility from 1540 to 2220 ppm H2O. OH solubility in rutile decreases from 2220 to 1290 ppm H2O by lowering the water activity of the fluid from 1 to 0.49 at P = 2 GPa and T = 1100°C. Using the solubility data and the exchange reaction, Ti3+O(OH) + O2 = Ti4+O2 + <calculate ?H = -29.2 kJ/mol, ?S = -6.54 J/mol, and ?V = 0.80 cm3/mol for this reaction. Preliminary models indicate that OH in rutile is an effective barometer for water activity and may be a particularly sensitive indicator of oxygen fugacity for systems in which pressure and temperature of formation are constrained.

Johnson, E. A.; Manning, C. E.; Antignano, A.; Tropper, P.

2005-12-01

87

Photon path length distributions for cloudy skies  oxygen A-Band measurements and model calculations  

NASA Astrophysics Data System (ADS)

This paper addresses the statistics underlying cloudy sky radiative transfer (RT) by inspection of the distribution of the path lengths of solar photons. Recent studies indicate that this approach is promising, since it might reveal characteristics about the diffusion process underlying atmospheric radiative transfer (Pfeilsticker, 1999). Moreover, it uses an observable that is directly related to the atmospheric absorption and, therefore, of climatic relevance. However, these studies are based largely on the accuracy of the measurement of the photon path length distribution (PPD). This paper presents a refined analysis method based on high resolution spectroscopy of the oxygen A-band. The method is validated by Monte Carlo simulation atmospheric spectra. Additionally, a new method to measure the effective optical thickness of cloud layers, based on fitting the measured differential transmissions with a 1-dimensional (discrete ordinate) RT model, is presented. These methods are applied to measurements conducted during the cloud radar inter-comparison campaign CLARE’98, which supplied detailed cloud structure information, required for the further analysis. For some exemplary cases, measured path length distributions and optical thicknesses are presented and backed by detailed RT model calculations. For all cases, reasonable PPDs can be retrieved and the effects of the vertical cloud structure are found. The inferred cloud optical thicknesses are in agreement with liquid water path measurements.

Funk, O.; Pfeilsticker, K.

2003-03-01

88

The first-principles calculation of the effects oxygen defect on the electronic structure of SnO2  

Microsoft Academic Search

In order to investigate the effects oxygen defect on the electronic structure of SnO2, the structural change, band structure, density of states, and electron density difference of (11macr0) surface of SnO2 in the rutile lattice phase were performed by the first-principles calculation of plane wave ultra-soft pseudo-potential technology based on the density function theory. The calculated conclusions were revealed that

Yan Jun-Feng; Zhang Zhi-Yong; Zhang Fu-Chun; Yun Jiang-Ni; Zhao Wu; Deng Zhou-Hu

2008-01-01

89

Estimation of pre-eruptive magmatic water fugacity in the Phlegrean Fields, Naples, Italy  

E-print Network

Camerino, Camerino 62032, Italy Abstract We estimated the water fugacity (f H2O) in the trachytic magma experiments were carried out on a representative sample of trachytic Breccia Museo eruption, Naples, Italy experiments, geohygrometer, trachytic magmas, water fugacity. Introduction The magmatic system of Phlegrean

Paris-Sud XI, Université de

90

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

91

The Influence of Oxygen Environment on Kinetic Properties of Minerals  

NASA Astrophysics Data System (ADS)

In this presentation, we review experimental determinations of the influence of oxygen environment on the physical properties of olivine. Kinetic properties of solids such as electrical conductivity and viscosity that are often functions of ionic diffusivity depend on the oxygen fugacity. Ionic diffusivity in solids can be expressed as the product of point defect concentration and point defect diffusivity. While thermogravimetry experiments reveal a pronounced dependence of point defect concentration on oxygen fugacity, electrical conductivity and thermogravimetry point defect relaxation experiments yield the point defect mobility. Results from these two types of experiments on olivine demonstrate that the power law dependence of ionic diffusivity on oxygen fugacity arises from the oxygen fugacity dependence of the point defect concentration alone. We also discuss experimental determination of the influence of oxygen environment on dislocation structures (i.e., deformation mechanisms) of olivine. Results from creep tests on single crystals of olivine indicate that for crystals compressed along a direction 45 {o} to the [100] and [001] crystallographic directions, the deformation mechanism changed from glide or cross slip of screw dislocations to the motion of near-edge dislocations as the oxygen fugacity was increased from 10-11 to 10-3 atm.

Kohlstedt, D. L.; Hier-Majumder, S.

2004-12-01

92

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. PMID:24344312

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

2014-01-01

93

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

94

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  

Microsoft Academic Search

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

F. J. Ryerson; K. D. McKeegan

1994-01-01

95

Hydrothermal hydration of Martian crust: illustration via geochemical model calculations.  

PubMed

If hydrothermal Systems existed on Mars, hydration of crustal rocks may have had the potential to affect the water budget of the planet. We have conducted geochemical model calculations to investigate the relative roles of host rock composition, temperature, water-to-rock ratio, and initial fluid oxygen fugacity on the mineralogy of hydrothermal alteration assemblages, as well as the effectiveness of alteration to store water in the crust as hydrous minerals. In order to place calculations for Mars in perspective, models of hydrothermal alteration of three genetically related Icelandic volcanics (a basalt, andesite, and rhyolite) are presented, together with results for compositions based on SNC meteorite samples (Shergotty and Chassigny). Temperatures from 150 degrees C to 250 degrees C, water-to-rock ratios from 0.1 to 1000, and two initial fluid oxygen fugacities are considered in the models. Model results for water-to-rock ratios less than 10 are emphasized because they are likely to be more applicable to Mars. In accord with studies of low-grade alteration of terrestrial rocks, we find that the major controls on hydrous mineral production are host rock composition and temperature. Over the range of conditions considered, the alteration of Shergotty shows the greatest potential for storing water as hydrous minerals, and the alteration of Icelandic rhyolite has the lowest potential. PMID:11541456

Griffith, L L; Shock, E L

1997-04-25

96

Hydrothermal hydration of Martian crust: illustration via geochemical model calculations  

NASA Technical Reports Server (NTRS)

If hydrothermal Systems existed on Mars, hydration of crustal rocks may have had the potential to affect the water budget of the planet. We have conducted geochemical model calculations to investigate the relative roles of host rock composition, temperature, water-to-rock ratio, and initial fluid oxygen fugacity on the mineralogy of hydrothermal alteration assemblages, as well as the effectiveness of alteration to store water in the crust as hydrous minerals. In order to place calculations for Mars in perspective, models of hydrothermal alteration of three genetically related Icelandic volcanics (a basalt, andesite, and rhyolite) are presented, together with results for compositions based on SNC meteorite samples (Shergotty and Chassigny). Temperatures from 150 degrees C to 250 degrees C, water-to-rock ratios from 0.1 to 1000, and two initial fluid oxygen fugacities are considered in the models. Model results for water-to-rock ratios less than 10 are emphasized because they are likely to be more applicable to Mars. In accord with studies of low-grade alteration of terrestrial rocks, we find that the major controls on hydrous mineral production are host rock composition and temperature. Over the range of conditions considered, the alteration of Shergotty shows the greatest potential for storing water as hydrous minerals, and the alteration of Icelandic rhyolite has the lowest potential.

Griffith, L. L.; Shock, E. L.

1997-01-01

97

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

PubMed

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. PMID:24888249

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

2014-06-25

98

Virial Approximation of the TEOS-10 Equation for the Fugacity of Water in Humid Air  

NASA Astrophysics Data System (ADS)

Fugacity is considered the proper real-gas substitute for the partial pressure commonly used to describe ideal-gas mixtures. However, in several fields such as geophysics, meteorology, or air conditioning, partial pressure is still preferred over fugacity when non-equilibrium conditions of humid air are quantified. One reason may be that for ambient air, the deviations from ideal-gas behavior are small, another that explicit correlation equations for the fugacity of water vapor in humid air are scarce in the literature. This situation has improved with the publication of the new oceanographic standard TEOS-10, the International Thermodynamic Equation of Seawater 2010, which provides highly accurate values for the chemical potential and the fugacity of water vapor in humid air over wide ranges of pressure and temperature. This paper describes the way fugacity is obtained from the fundamental equations of TEOS-10, and it derives computationally more convenient virial approximations for the fugacity, consistent with TEOS-10. Analytically extracted from the TEOS-10 equation of state of humid air, equations for the 2nd and 3rd virial coefficients are reported and compared with correlations available from the literature. The virial fugacity equation is valid in the temperature range between and +200 at pressures up to 5 MPa, and between and +1000 at low pressures such as those encountered in the terrestrial atmosphere at higher altitudes.

Feistel, Rainer; Lovell-Smith, Jeremy W.; Hellmuth, Olaf

2015-01-01

99

Interpolation constants for calculation of transmittance and rate of dissociation of molecular oxygen in the mesosphere and lower thermosphere  

NASA Technical Reports Server (NTRS)

Values of band oscillator strengths and rotational line widths for the Schumann-Runge band system have been used to derive interpolation constants from which the transmittance and rate of dissociation of molecular oxygen can be calculated. These constants, valid for temperatures between 150 and 300 K and for column densities between 1 x 10 to the 17th power/cm sq and 7 x 10 to the 24th power/cm sq, cover the wavelength range 1750 and 2050A.

Hudson, R. D.; Mahle, S. H.

1972-01-01

100

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

101

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

102

Lipid Extraction and the Fugacity of Stable Isotope Values  

NASA Astrophysics Data System (ADS)

Stable isotope analysis of blood, feathers, and other tissues are often used to infer migration patterns, diet composition and trophic status of seabirds. Tissues contain variable amounts of lipids that are depleted in the heavy carbon isotope (13C) and may introduce a bias in these values. There is evidence that lipid extraction may affect other stable isotope ratios, such as ?15N. Consequently, correction factors need to be applied to appropriately interpret ?13C and ?15N values for individual species and tissue type. In this study, we collected seven species of seabirds from the Near Islands, the western most group of islands in the Aleutian Island archipelago. We sampled kidney, liver, heart and muscle samples from each bird and after freeze drying, individual tissue samples were divided into two subsamples. We left one subsample unaltered and extracted lipids from the other subsample using a 2:1 chloroform-methanol solution. We found that the change in ?13C values after lipid extraction (??13C) varied widely among categories (eg., species, tissue type) from 0 - 4 ‰, while ??15N values ranged from 0 to 2‰. Notably, within category variation was nonsignificant and the ?? values were linear against the covariant C:N ratio of the isotopic data, which allows us to use arithmetic corrections for categorical values. Our data strongly indicate that the effects of lipid extraction on stable isotopic values, while linear within category, vary widely by species, tissue, geographic area, year of collection, and isotope. Fugacity is usually employed as a thermodynamic quantity related to the chemical potential or activity that characterizes the escaping tendency from a phase (eg. Mackay & Paterson 1982). Here we use fugacity in the earlier, broader sense of fleeting, transitory, or instable states (eg., S. Johnson 1751), and its measure may be approximated by the higher order variance of ??13C and ??15N among data categories. Clearly, understanding the nature of variation and the physiological processes responsible for stable isotope values from biological tissues are critical for their interpretation. Change in carbon and nitrogen stable isotopes (??C13, ??15N) after lipid extraction for Tufted Puffins (Fratercula cirrhata) collected July 2010 at Attu Island, Aleutians.

Padula, V.; Causey, D.; Wolf, N.; Welker, J. M.

2013-12-01

103

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

104

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

105

Use of a vial equilibration technique to measure the change in fugacity capacity of avian food and feces samples for 1,2,3,4-tetrachlorobenzene.  

PubMed

A vial equilibration technique was used to estimate the fugacity capacities of food and feces samples for 1,2,3,4-tetrachlorobenzene (TCB). The method was calibrated using different volumes of n-octanol and by comparing the measured and predicted fugacity capacity (Zoct) of n-octanol for TCB. The vial equilibration technique showed linearity with increasing amounts of n-octanol added to the vial. However, the measured Zoct was on average 8.5 times lower than the literature estimate and interpreted to be influenced by co-solvent effects. The ratio of fugacity capacities of food/feces was 2.9 and was consistent with the ratio estimated using Zt calculation methods (4.3) which considers partitioning capacity of both lipids and non-lipid organic matter. These results provide experimental support to the use of lipid equivalent approaches as opposed to lipid normalization when estimating the partition capacity of biological samples containing low lipid contents. PMID:24934706

Drouillard, Ken G; Norstrom, R J

2014-11-01

106

Apparent oxygen utilization rates calculated from tritium and helium-3 profiles at the Bermuda Atlantic Time-series Study site  

NASA Astrophysics Data System (ADS)

We present three years of Apparent Oxygen Utilization Rates (AOUR) estimated from oxygen and tracer data collected over the ocean thermocline at monthly resolution between 2003 and 2006 at the Bermuda Atlantic Time-series Study (BATS) site. We estimate water ages by calculating a transit time distribution from tritium and helium-3 data. The vertically integrated AOUR over the upper 500 m, which is a regional estimate of export, during the three years is 3.1 ± 0.5 mol O2 m-2 yr-1. This is comparable to previous AOUR-based estimates of export production at the BATS site but is several times larger than export estimates derived from sediment traps or 234Th fluxes. We compare AOUR determined in this study to AOUR measured in the 1980s and show AOUR is significantly greater today than decades earlier because of changes in AOU, rather than changes in ventilation rates. The changes in AOU are likely a methodological artefact associated with problems with early oxygen measurements.

Stanley, R. H. R.; Doney, S. C.; Jenkins, W. J.; Lott, D. E., III

2012-06-01

107

Apparent oxygen utilization rates calculated from tritium and helium-3 profiles at the Bermuda Atlantic Time-series Study site  

NASA Astrophysics Data System (ADS)

We present three years of Apparent Oxygen Utilization Rates (AOUR) estimated from oxygen and tracer data collected over the ocean thermocline at monthly resolution between 2003 and 2006 at the Bermuda Atlantic Time-series Study (BATS) site. We estimate water ages by calculating a transit time distribution from tritium and helium-3 data. The vertically integrated AOUR over the upper 500 m, which is a regional estimate of export, during the three years is 3.1 ± 0.5 mol O2 m-2 yr-1. This is comparable to previous AOUR-based estimates of export production at the BATS site but is several times larger than export estimates derived from sediment traps or 234Th fluxes. We compare AOUR determined in this study to AOUR measured in the 1980s and show AOUR is significantly greater today than decades earlier because of changes in AOU, rather than changes in ventilation rates. The changes in AOU may be a methodological artefact associated with problems with early oxygen measurements.

Stanley, R. H. R.; Doney, S. C.; Jenkins, W. J.; Lott, D. E., III

2011-10-01

108

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

109

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

SciTech Connect

We apply first-principles density-functional theory (DFT) calculations, ab-initio molecular dynamics, and the Kubo-Greenwood formula to predict electrical conductivity in Ta{sub 2}O{sub x} (0???x???5) as a function of composition, phase, and temperature, where additional focus is given to various oxidation states of the O monovacancy (V{sub O}{sup n}; n?=?0,1+,2+). In the crystalline phase, our DFT calculations suggest that V{sub O}{sup 0} prefers equatorial O sites, while V{sub O}{sup 1+} and V{sub O}{sup 2+} are energetically preferred in the O cap sites of TaO{sub 7} polyhedra. Our calculations of DC conductivity at 300?K agree well with experimental measurements taken on Ta{sub 2}O{sub x} thin films (0.18???x???4.72) and bulk Ta{sub 2}O{sub 5} 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 Ta{sub 2}O{sub 5} electronic structure provide further theoretical basis to substantiate V{sub O}{sup 0} as a donor dopant in Ta{sub 2}O{sub 5}. 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 V{sub O}{sup n} in Ta{sub 2}O{sub 5}.

Bondi, Robert J., E-mail: rjbondi@sandia.gov; Desjarlais, Michael P.; Thompson, Aidan P.; Brennecka, Geoff L.; Marinella, Matthew J. [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)

2013-11-28

110

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

111

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

112

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

113

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

114

Experimental constraints on Pt, Pd and Au partitioning and fractionation in silicate melt-sulfide-oxide-aqueous fluid systems at 800 °C, 150 MPa and variable sulfur fugacity  

NASA Astrophysics Data System (ADS)

We have performed experiments to constrain the effect of sulfur fugacity ( fS 2) and sulfide saturation on the fractionation and partitioning behavior of Pt, Pd and Au in a silicate melt-sulfide crystal/melt-oxide-supercritical aqueous fluid phase-Pt-Pd-Au system. Experiments were performed at 800 °C, 150 MPa, with oxygen fugacity ( fO 2) fixed at approximately the nickel-nickel oxide buffer (NNO). Sulfur fugacity in the experiments was varied five orders of magnitude from approximately log fS 2 = 0 to log fS 2 = -5 by using two different sulfide phase assemblages. Assemblage one consisted initially of chalcopyrite plus pyrrhotite and assemblage two was loaded with chalcopyrite plus bornite. At run conditions pyrrhotite transformed compositionally to monosulfide solid solution (mss), chalcopyrite to intermediate solid solution (iss), and in assemblage two chalcopyrite and bornite formed a sulfide melt. Run-product silicate glass (i.e., quenched silicate melt) and crystalline materials were analyzed by using both electron probe microanalysis and laser ablation inductively coupled plasma mass spectrometry. The measured concentrations of Pt, Pd and Au in quenched silicate melt in runs with log fS 2 values ranging from approximately 0.0 to -5.0 do not exhibit any apparent dependence on fS 2. The measured Pt, Pd and Au concentrations in mss do vary as a function of fS 2. The measured Pt, Pd and Au concentrations in iss do not appear dependent on fS 2. The data suggest that fS 2, working in concert with fO 2, via the determinant role that these variables play in controlling the magmatic sulfide phase assemblage and the solubility of Pt, Pd and Au as lattice bound components in magmatic sulfide phases, is a controlling factor on the budgets of Pt, Pd and Au during the evolution of magmatic systems.

Bell, Aaron S.; Simon, Adam; Guillong, Marcel

2009-10-01

115

A fugacity based multimedia environmental fate model of organic contaminants in Massachusetts Bay  

SciTech Connect

A new sewage outfall is being constructed in Massachusetts Bay as part of the pollution abatement program in Boston Harbor. Previous models of potential environmental impact from the new sewage outfall in Massachusetts Bay have either relied upon hydrodynamic transport models that assume conservative behavior of the contaminants or on non-quantitative conceptual models of non-conservative behavior. The authors have found that a more quantitative mass balance model is necessary to better predict contaminant exposure resulting from effluent discharge through the new outfall. Hence, the authors have developed a time-variant, multimedia environmental model of organic contaminants in the air, water, and sediment phases of Massachusetts Bay. This model is based on the fugacity approach developed by Donald Mackay and is a level 4 unsteady-state model that includes flows through the system. Advection, reaction, and intermedia transport processes are incorporated into the model as first order rate processes and parameters for the model include environmental parameters, physical-chemical properties, contaminant loading estimates from major sources, and transport parameters. The model was applied to several organic contaminants found in Massachusetts Bay water and sediment: naphthalene, benzo(a)pyrene, fluoranthene, dieldrin, 4,4{prime}-DDT, and the polychlorinated biphenyl C16(153). Model output includes a steady-state bay-wide average of water and sediment concentrations, relative distribution of mass after one month at steady state, time to reach steady-state, and residence times. The calculated steady-state concentrations were compared to recent observed values. In addition, sensitivity analysis of the model was performed to indicate which model parameters are most sensitive to perturbation.

Keys, D.; Shea, D. [North Carolina State Univ., Raleigh, NC (United States)

1995-12-31

116

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

117

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

118

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

119

Calculating intermolecular potentials with SIMPER: the water–nitrogen and water–oxygen interactions, dispersion energy coefficients, and preliminary results for larger molecules  

Microsoft Academic Search

Recent theoretical studies of the van der Waals complexes formed between water and the two main components of air, nitrogen and oxygen, are reviewed. Combined with previous work on the water–argon complex, the results allow non-ideal thermodynamic properties of water–air mixtures to be calculated. The intermolecular potential energy surfaces for these complexes have been calculated using a combination of supermolecule

Richard J. Wheatley; Timothy C. Lillestolen

2007-01-01

120

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

121

An experimental study of oxygen transport in dry rocks and related kinetic phenomena  

NASA Astrophysics Data System (ADS)

Several series of experiments were carried out at 1 GPa and 900°-1100° in which grain boundary chemical diffusion of oxygen in dry quartzite and dunite was characterized by use of "indicator mineral" techniques. Most experiments involved mixing a small amount of Fe2O3 with coarse quartz or olivine powder, placing the mixture in an iron container, pressurizing in a piston-cylinder apparatus, and heating rapidly to the desired run temperature. In response to the large gradient in oxygen fugacity resulting from the juxtaposition of iron metal (i.e., the container) with Fe2O3 disseminated through the sample, oxygen transport along quartz or olivine grain boundaries took place, causing reduction of ferric iron in regions of the sample nearest the container (producing wüstite in the dunite experiments and fayalite in those on quartz). The flux of oxygen, and hence the diffusivity, could be calculated from the width of the observed reduction zone. Variations on the method just described included use of CuO rather than Fe2O3 as the "indicator mineral," use of graphite rather than iron as the container, and placement of the Fe2O3 as a single pellet at the center of the dunite or quartzite sample rather than as a dispersed minor phase. For the dispersed-Fe2O3 experiments on dunite at 1000° and 1100°C, the width of the reduced (wüstite-bearing) zone was found to be generally proportional to the square root of run duration, in accordance with a diffusion-controlled transport/reduction process. At 900°, however, this relation does not hold, and the data suggest vapor phase transport of oxygen prior to closure of sample porosity. All experiments on quartzite (900°-1100°) were plagued by the same problem, but in this case, sufficiently long experiment durations eventually resulted in no further measurable oxygen transport, demonstrating that well-annealed quartzite is impermeable to oxygen at the run conditions. The net outcome of the experiments is a bulk grain boundary diffusivity for oxygen in dunite given approximately by D = 106exp (-355,500/RT) (D in cm2/s; R in J/deg mol). Values for quartzite are too low to measure by the techniques attempted. The information can be used to argue that heterogeneities in oxygen fugacity on the scale of centimeters to meters can be maintained indefinitely in fluid-absent, high-grade rocks of the continental crust, but similar features in a fluid-absent mantle would be quickly erased.

Watson, E. Bruce

1986-12-01

122

Calculation of hydrogen and oxygen uptake in fuel rod cladding during severe accidents using the integral diffusion method -- Preliminary design report  

SciTech Connect

Preliminary 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. The uptake of hydrogen is limited to the equilibrium solubility calculated by applying Sievert's law. The uptake of hydrogen is an exothermic reaction that accelerates the heatup of a fuel rod. An embrittlement criteria is described that accounts for hydrogen and oxygen concentration and the extent of oxidation. A design is described for implementing the models for hydrogen and oxygen uptake and cladding embrittlement into the programming framework of the SCDAP/RELAP5 code. A test matrix is described for assessing the impact of the proposed models on the calculated behavior of fuel rods in severe accident conditions. This report is a revision and reissue of the report entitled; ``Preliminary Design Report for Modeling of Hydrogen Uptake in Fuel Rod Cladding During Severe Accidents.''

Siefken, L.J.

1999-02-01

123

Scaling of Gene Expression with Transcription-Factor Fugacity  

NASA Astrophysics Data System (ADS)

The proteins associated with gene regulation are often shared between multiple pathways simultaneously. By way of contrast, models in regulatory biology often assume these pathways act independently. We demonstrate a framework for calculating the change in gene expression for the interacting case by decoupling repressor occupancy across the cell from the gene of interest by way of a chemical potential. The details of the interacting regulatory architecture are encompassed in an effective concentration, and thus, a single scaling function describes a collection of gene expression data from diverse regulatory situations and collapses it onto a single master curve.

Weinert, Franz M.; Brewster, Robert C.; Rydenfelt, Mattias; Phillips, Rob; Kegel, Willem K.

2014-12-01

124

Scaling of gene expression with transcription-factor fugacity.  

PubMed

The proteins associated with gene regulation are often shared between multiple pathways simultaneously. By way of contrast, models in regulatory biology often assume these pathways act independently. We demonstrate a framework for calculating the change in gene expression for the interacting case by decoupling repressor occupancy across the cell from the gene of interest by way of a chemical potential. The details of the interacting regulatory architecture are encompassed in an effective concentration, and thus, a single scaling function describes a collection of gene expression data from diverse regulatory situations and collapses it onto a single master curve. PMID:25554908

Weinert, Franz M; Brewster, Robert C; Rydenfelt, Mattias; Phillips, Rob; Kegel, Willem K

2014-12-19

125

Oxygen adsorbates on the Si(111)4×1-In metallic atomic wire: Scanning tunneling microscopy and density-functional theory calculations  

NASA Astrophysics Data System (ADS)

The Si(111)4×1-In surface is composed of metallic atomic wires, which undergo a transition into a charge density wave phase at a transition temperature (Tc) of 125 K. This Tc was reported recently to substantially increase upon the oxygen adsorption, for which the underlying mechanism is not understood. We investigate the structures of oxygen adsorbates on the Si(111)4×1-In surface by scanning tunneling microscopy (STM) and density-functional theory calculations. We identify three distinct atomic-scale structures induced by the oxygen adsorption with high-resolution STM topography. The calculations find two energetically favorable adsorption sites on and between In zigzag chains, respectively. In conjunction with an additional adsorption configuration, where O is buried underneath the In chain, three stable structures are thus identified that reproduce very well the characteristic bias-dependent STM images. Experimentally, a switching between two specific adsorption structures is observed and is consistent with the structure models proposed. The structural distortions and the charge transfer of In atomic wires around the adsorbates are also characterized. This work provides a solid basis for the microscopic understanding of the intriguing oxygen impurity effect on the phase transition.

Oh, Deok Mahn; Wippermann, S.; Schmidt, W. G.; Yeom, Han Woong

2014-10-01

126

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

127

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

128

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

129

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

130

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. PMID:23365527

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

131

Carbon-free and two-dimensional cathode structure based on silicene for lithium-oxygen batteries: A first-principles calculation  

NASA Astrophysics Data System (ADS)

The lithium-oxygen (Li-O2) battery is one of the most promising technologies for energy storage due to its extremely high-energy density. However, the design still faces many challenges for practical use including the decomposition of cathodes, which are typically composed of carbon-based materials. In this study, a carbon-free and two-dimensional cathode structure based on silicene is first proposed for Li-O2 batteries using density functional theory calculations. In contrast to graphene, oxygen reduction reactions (ORR) and oxygen evolution reactions (OER) can occur on the pristine form of silicene without any defect sites. In addition, it was found that reactions on silicene strongly correlate with strong adsorptions of the ORR intermediates, which are caused not only by ionic bonding between the oxygen atoms in the ORR intermediates and silicene but also by the structural stabilization of silicene. Theoretical observations demonstrate the great potential of silicene as a carbon-free cathode structure for Li-O2 batteries and provide further insights for designing a new cathode material architecture based on two-dimensional structured materials.

Hwang, Yubin; Yun, Kyung-Han; Chung, Yong-Chae

2015-02-01

132

Quaternary ammonium room-temperature ionic liquid including an oxygen atom in side chain/lithium salt binary electrolytes: ab initio molecular orbital calculations of interactions between ions.  

PubMed

Interactions of the lithium bis(trifluoromethylsulfonyl)amide (LiTFSA) complex with N, N-diethyl-N-methyl-N-(2-methoxyethyl) ammonium (DEME), 1-ethyl-3-methylimidazolium (EMIM) cations, neutral diethylether (DEE), and the DEMETFSA complex were studied by ab initio molecular orbital calculations. An interaction energy potential calculated for the DEME cation with the LiTFSA complex has a minimum when the Li atom has contact with the oxygen atom of DEME cation, while potentials for the EMIM cation with the LiTFSA complex are always repulsive. The MP2/6-311G**//HF/6-311G** level interaction energy calculated for the DEME cation with the LiTFSA complex was -18.4 kcal/mol. The interaction energy for the neutral DEE with the LiTFSA complex was larger (-21.1 kcal/mol). The interaction energy for the DEMETFSA complex with LiTFSA complex is greater (-23.2 kcal/mol). The electrostatic and induction interactions are the major source of the attraction in the two systems. The substantial attraction between the DEME cation and the LiTFSA complex suggests that the interaction between the Li cation and the oxygen atom of DEME cation plays important roles in determining the mobility of the Li cation in DEME-based room temperature ionic liquids. PMID:18636771

Tsuzuki, Seiji; Hayamizu, Kikuko; Seki, Shiro; Ohno, Yasutaka; Kobayashi, Yo; Miyashiro, Hajime

2008-08-14

133

Optical noninvasive calculation of hemoglobin components concentrations and fractional oxygen saturation using a ring-scattering pulse oximeter  

NASA Astrophysics Data System (ADS)

The deficiencies of the currently used pulse oximeter are discussed in diverse literature. A hazardous pitfalls of this method is that the pulse oximeter will not detect carboxyhemoglobin (COHb) and methemoglobin (metHb) concentrations. This leads to incorrect measurement of oxygen saturation by carbon monoxide poisoning and methemoglobinemia. Also the total hemoglobin concentration will not be considered and can only be measured in-vitro up to now. A second pitfall of the standard pulse oximetry is that it will not be able to show a result by low perfusion of tissues. This case is available inter alia when the patient is under shock or has a low blood pressure. The new non-invasive system we designed measures the actual (fractional) oxygen saturation and hemoglobin concentration. It will enable us also to measure COHb and metHb. The measurement can be applied at better perfused body central parts. Four or more light emitting diodes (LEDs) or laser diodes (LDs) and five photodiodes (PDs) are used. The reflected light signal detected by photodiodes is processed using a modified Lambert-Beer law (I=I0×e-?.d ). According to this law, when a non scattering probe is irradiated with light having the incident intensity I0, the intensity of transmitted light I decays exponentially with the absorption coefficient a of that probe and its thickness d. Modifications of this law have been performed following the theoretical developed models in literature, Monte Carlo simulation and experimental measurement.

Abdallah, Omar; Stork, Wilhelm; Muller-Glaser, Klaus

2004-06-01

134

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

135

Control of the water fugacity at high pressures and temperatures: Applications to the incorporation mechanisms of water in olivine  

E-print Network

be applicable to investigate the role of water in various important properties including water solubility). To understand the microscopic mechanisms of water-sensitive properties, it is important to place these resultsControl of the water fugacity at high pressures and temperatures: Applications to the incorporation

136

Error propagation in fugacity level-III models in the case of uncertain physicochemical compound properties  

SciTech Connect

For a level-III fugacity model to predict the steady-state environmental distribution of chemicals on a regional scale, the effect of erroneous physicochemical input data on the model output was studied using Monte Carlo simulations. Uncertainty analyses were performed for the octanol/water partition coefficient and Henry`s law constant with assumed standard errors of 0.5 and 0.1 log units according to corresponding Gauss distributions, using phenol, pentachlorophenol, ethanol, acetone, and anthracene as model compounds. The results showed considerable variations of factors up to 2.5 for the predicted relative distributions among the major compartments. The output variations were greater for compounds with more than one sink. The results demonstrate the need for addressing error propagation in multimedia models in a systematic way.

Kuehne, R.; Breitkopf, C.; Schueuermann, G. [UFZ Centre for Environmental Research. Leipzig (Germany). Dept. of Chemical Ecotoxicology

1997-10-01

137

The precision of a fugacity-based model for estimating dermal uptake of chemicals from soil  

SciTech Connect

Uncertainty about the predicted uptake of hydrocarbons from dusts and soils on human skin is addressed using a fugacity model. Methods available for sensitivity and uncertainty analysis are reviewed and assessed. A fugacity-based compartment model for dermal uptake from soil is presented. A major assumption of the uptake model is that soil on human skin behaves as a layer of soil particles mixed with air and water such that a tortuousity model applies. The possibility that soil instead attaches to skin as individual particles introduces uncertainty to the estimates of uptake derived from this model. In order to assess the magnitude of this uncertainty, the model is derived with and without the soil-layer assumption. Using 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and hexachlorobenzene (HCB) as test chemicals, a differential sensitivity analysis is applied to the layer and no-layer models in order to estimate the relative sensitivity of model output (uptake fraction) to all of the input parameters. A Monte Carlo simulation is used to carry out an uncertainty analysis in order to quantify the precision of the dermal-uptake prediction when applied to TCDD and HCB using both the soil-layer and no-soil layer assumptions. The predicted uptake fraction of HCB has an arithmetic-mean value of 0.15 and arithmetic standard deviation of 0.18; the predicted uptake fraction of TCDD has an arithmetic-mean value of 0.30 and arithmetic standard deviation of 0.28. 19 refs., 3 figs., 3 tabs.

McKone, T.E.

1990-10-01

138

[The calculation of the oxygen saturation as function of pO2, pH, temperature and base deviation (author's transl)].  

PubMed

The paper describes a mathematical relationship between the partial pressure of oxygen and the oxygen saturation of the blood which approximates the standard oxygen dissociation curve. This approximation is based on a consideration of the electro-chemical equilibria of the reduced and the oxygenated blood. PMID:7966

Marsoner, H J; Harnoncourt, K

1976-07-01

139

Thermodynamics of Si(OH)4 in the vapor phase of water: Henry’s and vapor-liquid distribution constants, fugacity and cross virial coefficients  

NASA Astrophysics Data System (ADS)

The fugacity coefficients of Si(OH)4 are evaluated from solubilities of solid phases of SiO2 in the vapor phase of water. The virial equation of state, truncated at the third virial coefficient, is employed to describe the fugacity coefficients of Si(OH)4. The temperature dependencies of the second, B12, and the third, C112, cross virial coefficients for H2O-Si(OH)4 interactions are approximated by empirical relations. It is found that silica-water interactions in the vapor phase are significantly more non-ideal compared to water-water interactions. Knowledge of B12 and C112 allows calculation of solubilities of quartz (Q) and amorphous silica (AS) in steam up to the density of 200 kg m-3 in satisfactory agreement with available data, and should provide reasonable solubility values at temperatures where no experimental results exist. The calculated values of the solubility of Q and AS in saturated vapor up to the critical temperature of water, Tc, are tabulated. The partial molar properties of dilute solutes close to the critical point of water are governed by the Krichevskii parameter, the value of which for Si(OH)4 is evaluated from available data (mainly vapor-liquid distribution constants for silica) to be equal to -187 ± 10 MPa. The knowledge of the thermodynamic properties of Si(OH)4 in the ideal gas state and in the state of the standard solution in liquid water allows calculating Henry’s constant, kH, for Si(OH)4 up to 623.15 K at water saturation pressure P1?. The theoretically-based equation, containing the Krichevskii parameter, allows extrapolating kH values all the way toward the critical temperature of water. This, in turn, makes possible calculation of the solubility of quartz and amorphous silica in liquid water at P1? at all temperatures up to Tc. The presented results should be useful for modeling solid-liquid-vapor, solid-vapor and liquid-vapor equilibria in the H2O-SiO2 system at steam densities up to 200 kg m-3.

Plyasunov, Andrey V.

2012-01-01

140

Factors affecting the accuracy of near-infrared spectroscopy concentration calculations for focal changes in oxygenation parameters  

NASA Technical Reports Server (NTRS)

Near-infrared spectroscopy (NIRS) can be used to noninvasively measure changes in the concentrations of oxy- and deoxyhemoglobin in tissue. We have previously shown that while global changes can be reliably measured, focal changes can produce erroneous estimates of concentration changes (NeuroImage 13 (2001), 76). Here, we describe four separate sources for systematic error in the calculation of focal hemoglobin changes from NIRS data and use experimental methods and Monte Carlo simulations to examine the importance and mitigation methods of each. The sources of error are: (1). the absolute magnitudes and relative differences in pathlength factors as a function of wavelength, (2). the location and spatial extent of the absorption change with respect to the optical probe, (3). possible differences in the spatial distribution of hemoglobin species, and (4). the potential for simultaneous monitoring of multiple regions of activation. We found wavelength selection and optode placement to be important variables in minimizing such errors, and our findings indicate that appropriate experimental procedures could reduce each of these errors to a small fraction (<10%) of the observed concentration changes.

Strangman, Gary; Franceschini, Maria Angela; Boas, David A.; Sutton, J. P. (Principal Investigator)

2003-01-01

141

The Role of Hydrogen and Oxygen Fugacity on the Incorporation of Nitrogen in Reduced Magmas of the Early Earth's Mantle  

NASA Astrophysics Data System (ADS)

According to experiments at 4 GPa, 1550°C, significant amounts of nitrogen (NH3, NH4) could have been incorporated in the early Earth by dissolution in a magma ocean, under fO2 conditions relevant to those prevailing during metal segregation.

Kadik, A. A.; Litvin, Yu. A.

2008-03-01

142

Upper mantle oxidation state: Ferric iron contents of Iherzolite spinels by 57 Fe Mössbauer spectroscopy and resultant oxygen fugacities  

Microsoft Academic Search

The ferric iron contents of spinels from 30 spinel Iherzolite xenoliths have been measured by 57 Fe Mössbauer spectroscopy. The samples are widely dispersed in geographic and tectonic setting, coming from Southwest United States (San Carlos, Kilbourne Hole), Japan (Ichinomegata), Massif Central, France (Mont Briançon) and Central Asia (Tariat Depression, Vitim Plateau). The total range of Fe 3 O 4

Bernard J. Wood; David Virgo

1989-01-01

143

Nature Macmillan Publishers Ltd 1997 of composition, temperature, oxygen fugacity and pressure on their redox states. Contrib. Mineral.  

E-print Network

of interest can be defined with respect to the observer's head if the position of the eyes in the orbit for the selected part of the body, such as the eye, head or arms1­4 . To achieve this transformation, visual parietal lobe, the ventral intraparietal area (VIP), the activity of visual neurons is modulated by eye

Dominey, Peter F.

144

Chromium Oxidation State in Planetary Basalts: Oxygen Fugacity Indicator and Critical Variable for Cr-Spinel Stability  

NASA Technical Reports Server (NTRS)

Cr is a ubiquitous and relatively abundant minor element in basaltic, planetary magmas. At the reduced oxidation states (

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

2014-01-01

145

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

146

Explosive volcanism and the graphite-oxygen fugacity buffer on the parent asteroid(s) of the ureilite meteorites  

NASA Technical Reports Server (NTRS)

A new model of the production of the uniformly low plagioclase and Al contents of ureilites is proposed. It is argued that those contents are consequences of widespread explosive volcanism during the evolution of the parent asteroid(s). It is noted that the great abundance of graphite on the ureilite asteroid(s) made them ideal sites for explosive volcanism driven by oxidation of graphite in partial melts ascending within the asteroid(s).

Warren, Paul H.; Kallemeyn, Gregory W.

1992-01-01

147

Fe-Mg partitioning between ringwoodite and magnesiowüstite and the effect of pressure, temperature and oxygen fugacity  

Microsoft Academic Search

The partitioning of Mg and Fe between magnesiowüstite and ringwoodite solid solutions has been measured between 15 and 23GPa and 1200-1600oC using both Fe and Re capsule materials to vary the oxidation conditions. The partitioning results show a clear dependence on the capsule material used due to the variation in Fe3+ concentrations as a consequence of the different oxidation environments.

D. J. Frost; F. Langenhorst; P. A. van Aken

2001-01-01

148

Fe–Mg partitioning between ringwoodite and magnesiowüstite and the effect of pressure, temperature and oxygen fugacity  

Microsoft Academic Search

The partitioning of Mg and Fe between magnesiowüstite and ringwoodite solid solutions has been measured between 15 and 23?GPa\\u000a and 1200–1600??C using both Fe and Re capsule materials to vary the oxidation conditions. The partitioning results show a clear dependence\\u000a on the capsule material used due to the variation in Fe3+ concentrations as a consequence of the different oxidation environments.

D. J. Frost; F. Langenhorst; P. A. van Aken

2001-01-01

149

Calculating specific denitrification rates in pre-denitrification by assessing the influence of dissolved oxygen, sludge loading and mixed-liquor recycle.  

PubMed

This article presents the results of an experimental study on the correlation among the specific denitrification rate (SDNR), the dissolved oxygen concentration (DO), the F:M ratio (F:M) and the mixed-liquor (ML) recycle in the pre-denitrification reactors fed by domestic sewage. The experimental curves reveal a 28.8-32.0% reduction in the SDNR at 20 degrees C (SDNR(20 degrees C)) with DO equal to 0.1 mgO2 L(-1) and F:M in the range 0.2-0.4 kgBOD5 kgMLVSS(-1) d(-1). The SDNR reduction increases to 50.0-55.9% with DO = 0.3 mgO2 L(-1). A mathematical correlation of these results and an equation for calculating SDNR(20 degrees C) as function of the F:M as well as the average DO and BOD5 in the total flow rate fed in the denitrification stage are proposed. The conducted experience gives useful suggestions for practical usage, in particular regarding the denitrification reactor design, and represents a good starting point for future applications with the aim to optimize the biological process in domestic sewage treatment plants. PMID:25145214

Raboni, Massimo; Torretta, Vincenzo; Viotti, Paolo; Urbini, Giordano

2014-01-01

150

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

151

Oxygen Defects in Phosphorene  

NASA Astrophysics Data System (ADS)

Surface reactions with oxygen are a fundamental cause of the degradation of phosphorene. Using first-principles calculations, we show that for each oxygen atom adsorbed onto phosphorene there is an energy release of about 2 eV. Although the most stable oxygen adsorbed forms are electrically inactive and lead only to minor distortions of the lattice, there are low energy metastable forms which introduce deep donor and/or acceptor levels in the gap. We also propose a mechanism for phosphorene oxidation involving reactive dangling oxygen atoms and we suggest that dangling oxygen atoms increase the hydrophilicity of phosphorene.

Ziletti, A.; Carvalho, A.; Campbell, D. K.; Coker, D. F.; Castro Neto, A. H.

2015-01-01

152

The Gibbs free energy of mixing of natural silicate liquids; an expanded regular solution approximation for the calculation of magmatic intensive variables  

Microsoft Academic Search

The compositions of liquids coexisting with experimentally grown crystals of olivine, plagioclase, clinopyroxene, orthopyroxene, leucite, spinel, rhombohedral oxide, melilite and potassium feldspar are used to define, through mass action expressions of liquid\\/solid equilibrium, compositional derivatives of the Gibbs free energy of mixing of naturally occuring silicate liquids as a function of temperature, pressure and the fugacity of oxygen. The available

Mark S. Ghiorso; Ian S. E. Carmichael; Mark L. Rivers; Richard O. Sack

1983-01-01

153

Non-Maxwellian velocity distribution functions associated with steep temperature gradients in the solar transition region. Paper 2: The effect of non-Maxwellian electron distribution functions on ionization equilibrium calculations for carbon, nitrogen and oxygen  

NASA Technical Reports Server (NTRS)

Non-Maxwellian electron velocity distribution functions, previously computed for Dupree's model of the solar transition region are used to calculate ionization rates for ions of carbon, nitrogen, and oxygen. Ionization equilibrium populations for these ions are then computed and compared with similar calculations assuming Maxwellian distribution functions for the electrons. The results show that the ion populations change (compared to the values computed with a Maxwellian) in some cases by several orders of magnitude depending on the ion and its temperature of formation.

Roussel-Dupre, R.

1979-01-01

154

A periclase-dolomite-calcite carbonatite from the Oka complex, Quebec, and its calculated volatile composition  

NASA Astrophysics Data System (ADS)

The eutectic mineral assemblage calcite-dolomite-periclase-apatite-forsterite-magnesioferrite-pyrrhotite-alabandite in a carbonatite dike within the Oka complex, Quebec, buffers the fugacities (and partial pressures) of all gas species in C-O-H-S-F, assuming vapor saturation. At the inferred eutectic (640° C, 1 kbar), the most important gas species and their partial pressures (bars) were: H2O, 882; CO2, 110; H2, 4.6; H2S, 2.7; CO, 0.5; and CH4, 0.1. Oxygen fugacity was near the QFM buffer, log f(O2)=-18.6, and sulfur fugacity was near the QFM-pyrrhotite buffer, log f(S2)=-5.9. Fluorine fugacity was low, logf(F2)=-43.9, consistent with the absence of fluoride minerals other than apatite. Presence of a water-rich gas phase is consistent with experiments on synthetic carbonatite systems (e.g. Fanelli et al. 1981), although compositions of the gas phase in published experiments cannot be determined exactly.

Treiman, Allan H.; Essene, Eric J.

1984-02-01

155

Evaluating potential non-point source loading of PAHs from contaminated soils: A fugacity-based modeling approach.  

PubMed

Soils contaminated by Polycyclic Aromatic Hydrocarbons (PAHs) are subject to significant non-point source (NPS) pollution during rainfall events. Recent studies revealed that the classic enrichment ratio (ER) approach may not be applicable to PAHs. This study developed a model to estimate the ER of PAHs which innovatively applies the fugacity concept. The ER model has been validated with experimental data, which suggested that the transport of PAHs not only depends on their physicochemical properties, but on the sediment composition and how the composition evolves during the event. The modeling uncertainty was systematically examined, and found to be highly compound-dependent. Based on the ER model, a strategy was proposed to practically evaluate the potential NPS loading of PAHs in watersheds with heterogeneous soils. The study results have important implications to modeling and managing the NPS pollution of PAHs (or other chemicals alike) at a watershed scale. PMID:25282126

Luo, Xiaolin; Zheng, Yi; Lin, Zhongrong; Wu, Bin; Han, Feng; Tian, Yong; Zhang, Wei; Wang, Xuejun

2015-01-01

156

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

157

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

158

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

159

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

160

SIGMELTS: A Web-portal for Electrical Conductivity Calculations in Geosciences  

NASA Astrophysics Data System (ADS)

We present a freely available and easy-to-use web application called SIGMELTS allowing the calculation of the electrical conductivity of geomaterials at relevant conditions for the Earth’s crust and mantle. By compiling previous results of electrical measurements in laboratory, this software enables to discriminate between the effect of different parameters on the bulk conductivity of silicate melts, carbonatites, fluids, minerals and mantle materials, such as the temperature (T), the pressure (P), the composition, the water content, the oxygen fugacity (fO2) and the crystal content. Different existing geometrical models are proposed to calculate the bulk conductivity of a two-phase mixture. Based on the electrical conductivity value of a mantle anomaly, an application has also been developed to determine the corresponding melt fraction at defined conditions (T, P, composition). This web application aims at improving the accessibility to laboratory data in order to precise the interpretation of MT profiles. Although there are examples of where the laboratory data have been used to interpret field data, there are also many instances where there are disconnects between those interpreting field MT data and the laboratory results. SIGMELTS also underlines that new electrical measurements in laboratory are needed to enlarge the present electrical database, particularly at high pressure conditions. An illustration of the use of SIGMELTS will be presented, in which calculations are applied to 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 to quantify their storage conditions.

Le Trong, E.; Pommier, A.

2010-12-01

161

Hot oxygen corona at Europa  

NASA Astrophysics Data System (ADS)

A model of the hot oxygen exosphere at Europa was constructed. The source term for the hot atoms was assumed to be dissociative recombination of O2+ and Liouville's theorem was used to calculate their altitude distribution. It was found that near the surface the hot oxygen density is in excess of 200 cm-3, dropping to a value on the order of 50 cm-3 at 1500 km. These calculations indicate that the hot atomic oxygen densities are considerably less than the thermal molecular oxygen ones, but slightly larger than the measured sodium values. The escape flux of the hot oxygen atoms was calculated to be on the order of 1.4×108 atoms cm-2 sec-1. This corresponds to a global escape rate of 4.4×1025 atoms sec-1, which is more than an order of magnitude less than the estimated atmospheric sputtering rate.

Nagy, Andrew F.; Kim, Jhoon; Cravens, Thomas E.; Kliore, Arvydas J.

162

Appreciating Oxygen  

ERIC Educational Resources Information Center

Photosynthetic flora and microfauna utilize light from the sun to convert carbon dioxide and water into carbohydrates and oxygen. While these carbohydrates and their derivative hydrocarbons are generally considered to be fuels, it is the thermodynamically energetic oxygen molecule that traps, stores, and provides almost all of the energy that…

Weiss, Hilton M.

2008-01-01

163

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

164

Oxygen and nitrogen raman spectra  

NASA Technical Reports Server (NTRS)

Engineering design computer program that calculates rotational Raman spectrum of either nitrogen or oxygen can be used to increase performance of gas-turbine engines by predicting extent of pressure broadening associated with temperature measurements at elevated pressure.

Fralick, G. C.

1979-01-01

165

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

166

Prediction of siderophile element metal-silicate partition coefficients to 20 GPa and 2800°C: the effects of pressure, temperature, oxygen fugacity, and silicate and metallic melt compositions  

Microsoft Academic Search

We report new metal-silicate partition coefficients for Ni, Co and P at 7.0 GPa (1650–1750°C), and Ni, Co, Mo, W and P at 0.8, 1.0 and 1.5 GPa (1300–1400°C). Guided by thermodynamics, all available metal-silicate partition coefficients, D(i), where i is Ni, Co, P, Mo and W, are regressed against 1T, PT, lnf(O2), ln(1 ? Xs) (XS is mole fraction

K. Righter; M. J. Drake; G. Yaxley

1997-01-01

167

Risk assessment of butyltins based on a fugacity-based food web bioaccumulation model in the Jincheng Bay mariculture area: II. Risk assessment.  

PubMed

A fugacity-based food web bioaccumulation model was constructed, and the biotic concentrations of butyltins in the food web of the Jincheng Bay mariculture area were estimated accordingly, using the water and sediment concentrations described in the accompanying paper (Part I). This paper presents an ecological risk assessment (ERA) and a human health risk assessment (HHRA) of the butyltins, based on the estimated tissue residues in the marine life in this area. The results showed that the ecological risk probability was greater than 0.05. At this level, management control is critical since sensitive marine species would be profoundly endangered by butyltin contamination. Few if any detrimental effects, however, would be generated for humans from exposure to butyltins through seafood consumption. The fugacity-based model can refine the ERA and HHRA of pollutants in marine areas, provide a basis for protecting marine ecology and the security of fishery products, and thus help determine the feasibility of a proposed aquaculture project. PMID:24947127

Hu, Yanbing; Song, Xiukai; Gong, Xianghong; Xu, Yingjiang; Liu, Huihui; Deng, Xuxiu; Ru, Shaoguo

2014-08-01

168

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

169

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

170

Formation and migration of oxygen vacancies in La(1-x)Sr(x)Co(1-y)Fe(y)O(3-?) perovskites: insight from ab initio calculations and comparison with Ba(1-x)Sr(x)Co(1-y)Fe(y)O(3-?).  

PubMed

The formation and migration of oxygen vacancies in the series of (La,Sr)(Co,Fe)O(3-?) perovskites, which can be used as mixed conducting SOFC cathode materials and oxygen permeation membranes, are explored in detail by means of first principles density functional calculations. Structure distortions, charge redistributions and transition state energies during the oxygen ion migration are obtained and analyzed. Both the overall chemical composition and vacancy formation energy are found to have only a small impact on the migration barrier; it is rather the local cation configuration which affects the barrier. The electron charge transfer from the migrating O ion towards the transition metal ion in the transition state is much smaller in (La,Sr)(Co,Fe)O(3-?) compared to (Ba,Sr)(Co,Fe)O(3-?) perovskites where such a charge transfer makes a significant contribution to the low migration barriers observed (in particular for high Ba and Co content). PMID:23202751

Mastrikov, Yuri A; Merkle, Rotraut; Kotomin, Eugene A; Kuklja, Maija M; Maier, Joachim

2013-01-21

171

Traveling with Portable Oxygen  

MedlinePLUS

... cient to meet their needs. Will I Need Oxygen on My Trip? If you use oxygen on ... airplane cabin at cruising altitude. Types of Portable Oxygen Several types of portable oxygen equipment are available ...

172

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

173

Measurement of oxygen flux as a function of oxygen activity for selected ceramic materials  

NASA Astrophysics Data System (ADS)

For materials that possess an ionic conductivity that is dependent upon the oxygen activity, such as those used for gas separation membranes, it is difficult to relate the oxygen flux generated by a material under an oxygen chemical potential gradient to the actual ionic conductivity values. It is possible to determine average values for the ionic conductivity or to indirectly measure it at a single oxygen activity using some electrical and thermodynamic measurements. In real gas separation systems, however, it would be beneficial to use actual oxygen flux measurements when determining the oxygen activity dependence of the ionic conductivity. This measurement would be a more direct approach than others and would be performed under the actual conditions that a material would be exposed to in a real system. When making these measurements of the oxygen flux, however, it is important to consider the influence of adding oxygen into the reducing gas stream. This additional oxygen, which may arise from a leak in the seal or delivery systems or due to the oxygen flux itself, can shift the oxygen activity of the reducing gas and limit the oxygen flux. A method for calculating the ionic conductivity as a function of oxygen activity has been developed. This method requires that the oxygen flux be measured as the oxygen activity is systematically changed on one side of the oxygen chemical potential gradient. Corrections can be made to the oxygen flux for leaks into the system and also for the shift in the oxygen chemical potential due to the addition of oxygen into the reducing gas. This method was used to determine the ionic conductivity of (Lasb{0.80}Srsb{0.20})(Cosb{0.20}Fesb{0.80})Osb3 membranes and to correlate it to the defect chemistry of the material.

Stephens, Walter Timothy

174

High pressure experimental calibration of the olivine-orthopyroxene-spinel oxygen geobarometer: implications for the oxidation state of the upper mantle  

Microsoft Academic Search

Synthetic spinel harzburgite and lherzolite assemblages were equilibrated between 1040 and 1300 C and 0.3 to 2.7 GPa, under\\u000a controlled oxygen fugacity (f\\u000a O\\u000a 2). f\\u000a O\\u000a 2 was buffered with conventional and open double-capsule techniques, using the Fe?FeO, WC-WO2-C, Ni?NiO, and Fe3O4?Fe2O3 buffers, and graphite, olivine, and PdAg alloys as sample containers. Experiments were carried out in a piston-cylinder

C. Ballhaus; R. F. Berry; D. H. Green

1991-01-01

175

Dissolved Oxygen and Biochemical Oxygen Demand  

NSDL National Science Digital Library

This EPA website provides general information about dissolved oxygen, including what it is, sampling and equipment considerations, and sampling and analysis protocols. The site also features a chart of dissolved oxygen solubility as a function of temperature.

Agency, U. S.

176

On the physical and biogeochemical processes driving the high frequency variability of CO2 fugacity at 6°S, 10°W: Potential role of the internal waves  

NASA Astrophysics Data System (ADS)

availability of nutrients in the mixed layer is the main limitation to organic carbon biological production in the tropical regions. In this paper, we investigate the potential role of internal waves at promoting the development of biological activity on a PIRATA mooring at 6°S, 10°W. This mooring is located above the Mid-Atlantic Ridge where we observe strong internal waves. Using a one-dimensional physical and biogeochemical coupled model, we simulate dissolved inorganic carbon (DIC). Providing the influence of vertical advection and turbulent diapycnal diffusivity are (it is vertical advection + turbulent dipycnal mixing) accounted for, we find that this model provides a good fit with observed in situ CO2 fugacity (fCO2). Main effect of internal waves is to rapidly increase the DIC, thus the fCO2 and the nutrients in the mixed layer. The latter induce progressive development of biological activity leading to gradual DIC decrease. Our study highlights the importance of correctly taking into account the effect of internal waves in tropical regions.

Parard, Gaëlle; Boutin, J.; Cuypers, Y.; Bouruet-Aubertot, P.; Caniaux, G.

2014-12-01

177

Electron-impact excitation of neutral oxygen  

E-print Network

Aims: To calculate transition rates from ground and excited states in neutral oxygen atoms due to electron collisions for non-LTE modelling of oxygen in late-type stellar atmospheres, thus enabling reliable interpretation of oxygen lines in stellar spectra. Methods: A 38-state R-matrix calculation in LS-coupling has been performed. Basis orbitals from the literature (Thomas et al.) are adopted, and a large set of configurations are included to obtain good representations of the target wavefunctions. Rate coefficients are calculated by averaging over a Maxwellian velocity distribution. Results: Estimates for the cross sections and rate coefficients are presented for transitions between the seven lowest LS states of neutral oxygen. The cross sections for excitation from the ground state compare well with existing experimental and recent theoretical results.

P. S. Barklem

2006-09-25

178

The accuracy of oxygen flux measurements using microelectrodes  

Microsoft Academic Search

An electrochemical analog of a biofilm was constructed to test the accuracy of oxygen flux measurements using microelectrodes. We used a cathodically polarized graphite felt attached to the bottom of a flat plate open channel reactor as the reactive surface consuming oxygen. The oxygen flux to the felt was calculated from the polarization current. Microelectrodes were used to measure the

Kjetil Rasmussen; Zbigniew Lewandowski

1998-01-01

179

Dissolved Oxygen Protocol  

NSDL National Science Digital Library

The purpose of this resource is to measure the amount of oxygen dissolved in water. Students use a dissolved oxygen kit or meter to measure the dissolved oxygen in the water at their hydrology site. The exact procedure depends on the instructions in the dissolved oxygen kit or meter used. The meter requires calibration before use.

The GLOBE Program, UCAR (University Corporation for Atmospheric Research)

2003-08-01

180

Artificial oxygen transport protein  

SciTech Connect

This invention provides heme-containing peptides capable of binding molecular oxygen at room temperature. These compounds may be useful in the absorption of molecular oxygen from molecular oxygen-containing atmospheres. Also included in the invention are methods for treating an oxygen transport deficiency in a mammal.

Dutton, P. Leslie

2014-09-30

181

A new oxygen barometer for solar system basaltic glasses based on vanadium valence  

SciTech Connect

An oxybarometer based on vanadium valence and applicable to basaltic glasses covers eight orders of magnitude in oxygen fugacity. 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 (fO{sub 2}). 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. Likewise, techniques to estimate fO{sub 2} based on the valence state of Fe (i.e. Fe{sup 3+}/Fe{sup 2+}) are ineffective for materials that crystallized at or below the IW buffer, and only contain Fe{sup 2+} and Fe{sup 0} (3). For these reasons, we have developed an oxybarometer based on the valence state of vanadium in basaltic glasses. This oxybarometer has enormous potential because (1) V valence is measured in basaltic glasses that have been quenched at near liquidus temperatures, thereby recording magmatic fO{sub 2} conditions, and (2) V is a multivalent element, existing as V{sup 2+}, V{sup 3+}, V{sup 4+}, and V{sup 5+}, thus allowing for applicability over a range of redox conditions from the most reduced materials in the solar system, (e.g. calcium aluminum rich inclusions in chondritic meteorites [4]) to the most oxidized terrestrial magmas (this work).

Karner, J.M.; Sutton, S.R.; Papike, J.J.; Delaney, J.S.; Shearer, C.K.; Newville, M.; Eng, P.; Rivers, M.; Dyar, M.D. (Rutgers Univ.); (UofC); (Mount Holyoke); (Univ. of New Mexico)

2004-05-10

182

Transport coefficients of argon, nitrogen, oxygen, argon-nitrogen, and argon-oxygen plasmas  

Microsoft Academic Search

Calculated values of the viscosity, thermal conductivity, and electrical conductivity of argon, nitrogen, and oxygen plasmas, and mixtures of argon anti nitrogen and of argon anti oxygen, are presented. In addition, combined ordinary, pressure, and thermal diffusion coefficients are given for the gas mixtures. These three combined diffusion coefficients fully describe di fusion of the two gases, irrespective of their

A. B. Murphy; C. J. Arundelli

1994-01-01

183

Bonding, Conductance and Magnetization of Oxygenated Au Nanowires  

NASA Astrophysics Data System (ADS)

Spin-density-functional calculations of tip-suspended gold chains, with molecular oxygen, or dissociated oxygen atoms, incorporated in them, reveal structural transitions for varying lengths. The nanowires exhibit enhanced strength for both oxygen incorporation modes, and upon stretching tip atoms join the wire. With incorporated molecular oxygen the wire conductance is about 1(2e^2/h), transforming to an insulating state beyond a critical length. The nanowire conductance with embedded oxygen atoms is low, 0.2 (2e^2/h), and it develops magnetic moments localized on the oxygens and the neighboring Au atoms. Physical Review Letters (in press)

Zhang, Chun; Barnett, Robert; Landman, Uzi

2008-03-01

184

Bonding, conductance, and magnetization of oxygenated Au nanowires.  

PubMed

Spin-density-functional calculations of tip-suspended gold chains, with molecular oxygen, or dissociated oxygen atoms, incorporated in them, reveal structural transitions for varying lengths. The nanowires exhibit enhanced strength for both oxygen incorporation modes, and upon stretching tip atoms join the wire. With incorporated molecular oxygen the wire conductance is about 1(2e2/h), transforming to an insulating state beyond a critical length. The nanowire conductance with embedded oxygen atoms is low, 0.2 (2e2/h), and it develops magnetic moments localized on the oxygens and the neighboring Au atoms. PMID:18352314

Zhang, Chun; Barnett, Robert N; Landman, Uzi

2008-02-01

185

Uncertainty analysis using a fugacity-based multimedia mass-balance model: application of the updated EQC model to decamethylcyclopentasiloxane (D5).  

PubMed

The EQuilibrium Criterion (EQC) model developed and published in 1996 was recently revised to include improved treatment of input partitioning and reactivity data, temperature dependence and an easier sensitivity and uncertainty analysis. This New EQC model was used to evaluate the multimedia, fugacity-based fate of decamethylcyclopentasiloxane (D5; CAS No. 541-02-6) in the environment over a temperature range of 1-25°C. In addition, Monte Carlo uncertainty analysis was used to quantitatively determine the influence of temperature and input partitioning and reactivity data on the behavior of D5 under various emission scenarios. Results indicated that emission mode was the most influential factor determining the fate and distribution of D5 in the model environment. When emitted to air and soil, D5 partitioned to and remained in the air compartment where rates of removal from degradation and advection processes were relatively rapid. In contrast, D5 emitted to water resulted in a substantial mass fraction of D5 being accumulated in the sediment compartment, where rates of removal from degradation and advection processes were slow. The mass distributions and fate of D5 in the model environment were strongly influenced by multiple input parameters, including temperature, the mode of emission (especially emission rate to water), KOC and half-life in air. As temperature decreased from 25°C to 1°C, KOC and half-life in air became increasingly more influential such that the mass distribution of D5 increased in air and decreased in sediment, resulting in decreased overall persistence. PMID:23219081

Kim, Jaeshin; Powell, David E; Hughes, Lauren; Mackay, Don

2013-10-01

186

Carbon distribution and fluxes during the SERIES iron fertilization experiment with special reference to the fugacity of carbon dioxide (fCO 2)  

NASA Astrophysics Data System (ADS)

Surface seawater fugacity of carbon dioxide (fCO 2) was measured during the Subarctic Ecosystem Response to Iron Enrichment Study (SERIES), July 9-August 5, 2002. Three ships sampled the iron-fertilized waters near Ocean Station P (50°N, 145°W): the Canadian CCGS J.P. Tully (July 9-23, 2002), the chartered Mexican M/V El Puma (July 9-28, 2002), and the Japanese fisheries research ship M/V Kaiyo Maru (July 24-August 5, 2002). Data used here are from the CCGS J.P. Tully and the M/V Kaiyo Maru. From the onset of the experiment to the peak of the iron-induced diatom bloom on day 19, sea-surface fCO 2 decreased from 350 to 265 ?atm and average DIC concentration in the upper 30 m decreased from 2030 to 1990 ?mol kg -1. Changes in fCO 2 in and near the iron patch as observed from the CCGS J.P. Tully and later from the M/V Kaiyo Maru were used to estimate CO 2 drawdown and air-sea fluxes, and in generating a carbon budget during the growth phase (days 3-19) of the experiment. Without considering patch dilution, sources of dissolved inorganic carbon to the patch (1.6±0.25 mol m -2) were nearly double the sum (0.87±0.34 mol m -2) of the sinks: accumulations of dissolved organic and particulate carbon, and the flux of particulate carbon to sediment traps below the patch. However, the budget is balanced after considerations of the effects of patch expansion on property concentrations within the patch. A comparison with other iron fertilization experiments from 1995 to present was made to assess the CO 2 drawdown values.

Wong, Chi Shing; Timothy, David A.; Law, Cliff S.; Nojiri, Yukihiro; Xie, Liusen; Wong, Shau-King Emmy; Page, John S.

2006-10-01

187

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

188

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.

Garzon, Fernando H. (Sante Fe, NM); Chung, Brandon W. (Los Alamos, NM); Raistrick, Ian D. (Los Alamos, NM); Brosha, Eric L. (Los Alamos, NM)

1996-01-01

189

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.

Sharon Harris

190

Gravity Calculator  

NSDL National Science Digital Library

The gravity calculator calculates the gravitational force between two masses. Also included is a visualization of the typical measurement of gravitational force (weight) in different environments (stationary and free fall).

Brendan Cannell, Ronnie Johnson, The Shodor Education Foundation, Inc.

191

Bayesian Calculator  

NSDL National Science Digital Library

This page, created by Michael H. Birnbaum of Fullerton University, uses Bayes' Theorem to calculate the probability of a hypothesis given a datum. An example about cancer is given to help users understand Bayes' Theorem and the calculator. This page is a great representation of conditional probability. Detailed instructions are provided on proper use of the calculator.

Birnbaum, Michael H.

192

Modelling Hydrogen Reduction and Hydrodeoxygenation of Oxygenates  

SciTech Connect

Based on Density Functional Theory (DFT) simulations, we have studied the reduction of nickel oxide and biomass derived oxygenates (catechol, guaiacol, etc.) in hydrogen. Both the kinetic barrier and thermodynamic favorability are calculated with respect to the modeled reaction pathways. In early-stage reduction of the NiO(100) surface by hydrogen, the pull-off of the surface oxygen atom and simultaneous activation of the nearby Ni atoms coordinately dissociate the hydrogen molecules so that a water molecule can be formed, leaving an oxygen vacancy on the surface. In hydrogen reaction with oxygenates catalyzed by transition metals, hydrogenation of the aromatic carbon ring normally dominates. However, selective deoxygenation is of particular interest for practical application such as biofuel conversion. Our modeling shows that doping of the transition metal catalysts can change the orientation of oxygenates adsorbed on metal surfaces. The correlation between the selectivity of reaction and the orientation of adsorption are discussed.

Zhao, Y.; Xu, Q.; Cheah, S.

2013-01-01

193

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.

Garzon, Fernando H. (Santa Fe, NM); Brosha, Eric L. (Los Alamos, NM)

1997-01-01

194

Thermographic observation of hydrocarbon oxygen explosions  

SciTech Connect

Balloons containing methane-oxygen mixtures were detonated to simulate ordinance fireballs. To establish fireball characteristics, analyses were required of reacting temperatures, thermal profiles, and mixing patterns of the methane-oxygen products with the atmosphere. Infrared videothermography measured and recorded the detonation and gas cloud mixing. Image digitization and in-band energy calculations were done to compare reaction parameters for different balloon tests.

Abney, L.D.; Kelly, M.D.; Mohler, J.H.

1985-01-01

195

Mobile extracorporeal membrane oxygenation.  

PubMed

Transport of critically ill neonates in need of extracorporeal membrane oxygenation can be risky. Their extreme cardiorespiratory instability may delay or even preclude conventional transport to an extracorporeal membrane oxygenation center. We report the use of a UH-1 helicopter specially adapted for mobile extracorporeal membrane oxygenation support to transport a critically ill neonate. PMID:8494441

Faulkner, S C; Taylor, B J; Chipman, C W; Baker, L L; Fasules, J W; Van DeVanter, S H; Harrell, J E

1993-05-01

196

Medical Oxygen Safety  

MedlinePLUS

... to the air a patient uses to breath. Fire needs oxygen to burn. If a fire should start in an oxygen-enriched area, the ... Homes where medical oxygen is used need specific fire safety rules to keep people safe from fire ...

197

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. PMID:5278618

Ford, Patricia; Hoodless, D. J.

1971-01-01

198

Atomic oxygen exposure of LDEF experiment trays  

NASA Technical Reports Server (NTRS)

Atomic oxygen exposures were determined analytically for rows, longerons, and end bays of the Long Duration Exposure Facility (LDEF). The calculations are based on an analytical model that accounts for the effects of thermal molecular velocity, atmospheric temperature, number density, spacecraft velocity, incidence angle, and atmospheric rotation on atomic oxygen flux. Results incorporate variations in solar activity, geomagnetic index, and orbital parameters occurring over the 6-year flight of the spacecraft. To facilitate use of the data, both detailed tabulations and summary charts for atomic oxygen fluences are presented.

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

1992-01-01

199

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

200

42 CFR 414.226 - Oxygen and oxygen equipment.  

...Health 3 2014-10-01 2014-10-01 false Oxygen and oxygen equipment. 414.226 Section 414.226 Public...Orthotic Devices, and Surgical Dressings § 414.226 Oxygen and oxygen equipment. (a) Payment rules...

2014-10-01

201

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

202

BTU Calculator  

NSDL National Science Digital Library

A calculator that estimates the heating needs of a room, a combination of rooms, or an entire home. Enter the length and width of the area to be heated and select the climate and insulation factors from the pop-up boxes. A Java version of this calculator is also available.

203

An ab initio study of oxygen on strained graphene  

NASA Astrophysics Data System (ADS)

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.

Nguyen, Manh-Thuong

2013-10-01

204

Oxygen transmissibility of disposable hydrogel contact lenses.  

PubMed

We measured the central and mid-peripheral thicknesses of three "disposable" hydrogel contact lens designs of varying powers. These measurements allowed calculation of the areal average lens thicknesses (over a central 6 mm chord), which in turn allowed calculation of predicted oxygen transmissibility (Dk/L) for the lenses studied (using previously reported values for measured oxygen permeability [Dk] of these materials). Dk/L values for the disposable hydrogel lenses tested were found to range from 9 to 17 x 10(-9) cm mL O2/sec mL mmHg. PMID:2007288

Weissman, B A; Schwartz, S D; Lee, D A

1991-01-01

205

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

206

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

207

Integrated turbomachine oxygen plant  

SciTech Connect

An integrated turbomachine oxygen plant includes a turbomachine and an air separation unit. One or more compressor pathways flow compressed air from a compressor through one or more of a combustor and a turbine expander to cool the combustor and/or the turbine expander. An air separation unit is operably connected to the one or more compressor pathways and is configured to separate the compressed air into oxygen and oxygen-depleted air. A method of air separation in an integrated turbomachine oxygen plant includes compressing a flow of air in a compressor of a turbomachine. The compressed flow of air is flowed through one or more of a combustor and a turbine expander of the turbomachine to cool the combustor and/or the turbine expander. The compressed flow of air is directed to an air separation unit and is separated into oxygen and oxygen-depleted air.

Anand, Ashok Kumar; DePuy, Richard Anthony; Muthaiah, Veerappan

2014-06-17

208

Martindale Calculators  

NSDL National Science Digital Library

Martindale Calculators is a Web-based tool collection that contains over 19,000 online calculators created by over "3,450" very "creative" individuals, businesses and âÂÂtax supported entities world wide.â The collection is organized by the following topics: mathematics; statistics; science A-Z; chemistry; physics, astrophysics and astronomy; engineering A-Z; and electrical engineering, computer engineering, & computer science. Each section includes a wealth of websites to explore, all related to mathematical calculations, mostly course materials and articles. Another section lists online calculators relevant for various industries, such as aviation, cosmetics, insurance, and library science. The list is organized alphabetically and creatively stretches the meaning of âÂÂcalculatorâ to include such things as name translators and databases on animal breeds.

209

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

210

Generating Hyperthermal Atomic Oxygen  

NASA Technical Reports Server (NTRS)

Atomic oxygen diffused through silver desorbed by low-energy electron impact. Oxygen atoms diffuse through silver foil and emerge on high-vacuum side, aided by electron-stimulated desorption. Atomic-oxygen flux levels range up to 10 to the 12th power cm to the negative 2 power S to the negative 1 power, and kinetic energies range from 1 to 10 eV. O positive and O negative ions swept aside by charged cylindrical grids.

Outlaw, Ronald A.

1988-01-01

211

Atomic Oxygen Effects  

NASA Technical Reports Server (NTRS)

Atomic oxygen, which is the most predominant species in low Earth orbit, is highly reactive and can break chemical bonds on the surface of a wide variety of materials leading to volatilization or surface oxidation which can result in failure of spacecraft materials and components. This presentation will give an overview of how atomic oxygen reacts with spacecraft materials, results of space exposure testing of a variety of materials, and examples of failures caused by atomic oxygen.

Miller, Sharon K. R.

2014-01-01

212

Optical Oxygen Sensor  

Microsoft Academic Search

Photoexcited triplet state of porphyrins and phthalocyanines is efficiently quenched by molecular oxygen and the quenching\\u000a reaction is based on the first-order kinetics on the oxygen concentration. Therefore, phosphorescence measurement and lifetime\\u000a measurement of the photoexcited triplet state are applied for optical oxygen sensing techniques. In the case of phosphorescence\\u000a measurement platinum or palladium porphyrins, which emit only phosphorescence under

N. Asakura; I. Okura

213

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

214

Life Before Oxygen  

NSDL National Science Digital Library

About three billion years ago, single-celled underwater bacteria similar to modern cyanobacteria consumed carbon dioxide as they photosynthesized, releasing oxygen in the process. In this way, an atmosphere full of volcanic carbon dioxide gradually changed into an oxygen-rich atmosphere in which animal life could survive, except for some primitive organisms, who retreated to oxygen-poor environments. This video segment shows researchers as they search for these organisms, which are now considered tiny time capsules from the time before there was oxygen on Earth. The segment is one minute thirty-nine seconds in length. A background essay and list of discussion questions are also provided.

215

Interstitial oxygen in germanium and silicon  

SciTech Connect

The microscopic structure of interstitial oxygen in germanium and its associated dynamics are studied both experimentally and theoretically. The infrared absorption spectrum is calculated with a dynamical matrix model based on first-principles total-energy calculations describing the potential energy for the nuclear motions. Spectral features and isotope shifts are calculated and compared with available experimental results. From new spectroscopic data on natural and on quasimonoisotopic germanium samples, new isotope shifts have been obtained and compared with the theoretical predictions. The low-energy spectrum is analyzed in terms of a hindered rotor model. A fair understanding of the center is achieved, which is then compared with interstitial oxygen in silicon. The oxygen atom is nontrivially quantum delocalized both in silicon and in germanium, but the physics is shown to be very different: while the Si-O-Si quasimolecule is essentially linear, the Ge-O-Ge structure is puckered. The delocalization in a highly anharmonic potential well of oxygen in silicon is addressed using path-integral Monte Carlo simulations, for comparison with the oxygen rotation in germanium. The understanding achieved with this new information allows us to explain the striking differences between both systems, in both the infrared and the far-infrared spectral regions, and the prediction of the existence of hidden vibrational modes, never directly observed experimentally, but soundly supported by the isotope-shift analysis. {copyright} {ital 1997} {ital The American Physical Society}

Artacho, E.; Yndurain, F. [Instituto Nicolas Cabrera and Departamento de Fisica de la Materia Condensada, C-III Universidad Autonoma de Madrid, 28049 Madrid (Spain)] [Instituto Nicolas Cabrera and Departamento de Fisica de la Materia Condensada, C-III Universidad Autonoma de Madrid, 28049 Madrid (Spain); Pajot, B. [Groupe de Physique des Solides (Unite Associee au CNRS), Tour 23, Universite Denis Diderot, 2 Place Jussieu, 75251 Paris Cedex 05 (France)] [Groupe de Physique des Solides (Unite Associee au CNRS), Tour 23, Universite Denis Diderot, 2 Place Jussieu, 75251 Paris Cedex 05 (France); Ramirez, R.; Herrero, C.P. [Instituto de Ciencia de Materiales, Consejo Superior de Investigaciones Cientificas, Cantoblanco, 28049 Madrid (Spain)] [Instituto de Ciencia de Materiales, Consejo Superior de Investigaciones Cientificas, Cantoblanco, 28049 Madrid (Spain); Khirunenko, L.I. [Institute of Physics, National Academy of Sciences of Ukraine, Prospect Nauki 46, 252650 Kiev 22 (Ukraine)] [Institute of Physics, National Academy of Sciences of Ukraine, Prospect Nauki 46, 252650 Kiev 22 (Ukraine); Itoh, K.M. [Department of Applied Physics and Physico-Informatics, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223 (Japan)] [Department of Applied Physics and Physico-Informatics, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223 (Japan); Haller, E.E. [Lawrence Berkeley National Laboratory and University of California, Berkeley, California 94720 (United States)] [Lawrence Berkeley National Laboratory and University of California, Berkeley, California 94720 (United States)

1997-08-01

216

Silicon in Mars' Core: A Prediction Based on Mars Model Using Nitrogen and Oxygen Isotopes in SNC Meteorites  

NASA Technical Reports Server (NTRS)

Chemical and (oxygen) isotopic compositions of SNC meteorites have been used by a number of workers to infer the nature of precursor materials for the accretion of Mars. The idea that chondritic materials played a key role in the formation of Mars has been the central assumption in these works. Wanke and Dreibus have proposed a mixture of two types of chondritic materials, differing in oxygen fugacity but having CI type bulk chemical composition for the nonvolatile elements, for Mars' precursor. But a number of studies based on high pressure and temperature melting experiments do not favor a CI type bulk planet composition for Mars, as it predicts a bulk planet Fe/Si ratio much higher than that reported from the recent Pathfinder data. Oxygen forms the bulk of Mars (approximately 40% by wt.) and might provide clues to the type of materials that formed Mars. But models based on the oxygen isotopic compositions of SNC meteorites predict three different mixtures of precursor materials for Mars: 90% H + 10% CM, 85% H + 11% CV + 4% CI and 45% EH + 55% H. As each of these models has been shown to be consistent with the bulk geophysical properties (such as mean density, and moment of inertia factor) of Mars, the nature of the material that accreted to form Mars remains ambiguous.

Mohapatra, R. K.; Murty, S. V. S.

2002-01-01

217

New sources for the hot oxygen geocorona  

NASA Technical Reports Server (NTRS)

This paper investigates new sources of thermospheric non thermal (hot) oxygen due to exothermic reactions involving numerous minor (ion and neutral) and metastable species. Numerical calculations are performed for low altitude, daytime, winter conditions, with moderately high solar activity and low magnetic activity. Under these conditions we find that the quenching of metastable species are a significant source of hot oxygen, with kinetic energy production rates a factor of ten higher than those due to previously considered O2(+) and NO(+) dissociative recombination reactions. Some of the most significant new sources of hot oxygen are reactions involving quenching of O(+)((sup 2)D), O((sup 1)D), N((sup 2)D), O(+)((sup 2)P) and vibrationally excited N2 by atomic oxygen.

Richards, P. G.; Hickey, M. P.; Torr, D. G.

1994-01-01

218

Collision-induced intensity of the b{sup 1}{Sigma}{sub g}{sup +}-a{sup 1}{triangle}g transition in molecular oxygen: Model calculations for the collision complex O{sub 2} + H{sub 2}  

SciTech Connect

Ab initio configuration interaction (CI) calculations have been performed for the O{sub 2} + H{sub 2} complex in a trapezoidlike collision arrangement with C{sub 2v} symmetry. The potential energy surfaces of the four lowest states of this van der Waals complex (arising from the X{sup 3}{Sigma}{sub g}{sup +} states of the oxygen moiety), as well as the collision-induced b{sup 1}{Sigma}{sub g}{sup +}-a{sup 1}{triangle}g electric dipole transition moment (M{sub b-a}), have been analyzed for different CI expansions, using as a reference determinant the restricted open-shell Hartree-Fock (ROHF) function for the ground state of the complex H{sub 2}(X{sup 1}{Sigma}{sub g}{sup +}) + O{sub 2}(X{sup 3}{Sigma}{sub g}{sup -}). The geometry optimized at the ROHF/6-311G level was refined by a partial optimization at the CI level scanning intermolecular distance. The equilibrium distances for the X, a, and b states have been found to be a slightly different in the region 3.02-2.98 A. The larger binding energy of the b{sup 1}{Sigma}{sub g}{sup +} state (2.96 kJ/mol) in comparison with the a{sup 1}{triangle}g (2.1 kJ/mol) and ground X{sup 3}{Sigma}{sub g}{sup -} states (1.35 kJ/mol) presumably could be explained as resulting from charge-transfer interactions. A good convergence of the calculated transition moment M{sub b-a} for the larger CI expansions (approximately 50,000 configuration-state functions) has been obtained. The calculated collision-induced intensity of the b{sup 1}{Sigma}{sub g}{sup +} - a{sup 1}{triangle}g and a{sup 1}{triangle}g - X{sup 3}{Sigma}{sub g}{sup -} transitions in molecular oxygen are in reasonable agreement with recent experimental data for several foreign gases.

Minaev, B.F.; Kobzev, G.I. [Uppsala Univ., Cherkassy (Ukraine); Lunell, S. [Uppsala Univ., Uppsala (Sweden)

1994-12-31

219

Oxygen isotope fractionation in double carbonates.  

PubMed

Oxygen isotope fractionations in double carbonates of different crystal structures were calculated by the increment method. Synthesis experiments were performed at 60?°C and 100?°C to determine oxygen and carbon isotope fractionations involving PbMg[CO3]2. The calculations suggest that the double carbonates of calcite structure are systematically enriched in (18)O relative to those of aragonite and mixture structures. Internally consistent oxygen isotope fractionation factors are obtained for these minerals with respect to quartz, calcite and water at a temperature range of 0-1200?°C. The calculated fractionation factors for double carbonate-water systems are generally consistent with the data available from laboratory experiments. The experimentally determined fractionation factors for PbMg[CO3]2, BaMg[CO3]2 and CaMg[CO3]2 against H2O not only fall between fractionation factors involving pure carbonate end-members but are also close to the calculated fractionation factors. In contrast, experimentally determined carbon isotope fractionation factors between PbMg[CO3]2 and CO2 are much closer to theoretical predictions for the cerussite-CO2 system than for the magnesite-CO2 system, similar to the fractionation behavior for BaMg[CO3]2. Therefore, the combined theoretical and experimental results provide insights into the effects of crystal structure and exchange kinetics on oxygen isotope partitioning in double carbonates. PMID:25393769

Zheng, Yong-Fei; Böttcher, Michael E

2014-11-13

220

Activation of molecular oxygen in trifluoroacetic acid  

NASA Astrophysics Data System (ADS)

The possibility of the formation of the H2O{2/+·} cation-radical was determined according to the data from nonempirical calculations for liquid trifluoroacetic acid, which forms a hydroperoxide radical after deprotonation. A catalytic cycle was obtained in which CF3COOH serves as a catalyst in the oxidation of a substrate by dissolved molecular oxygen.

Vishnetskaya, M. V.; Ivanova, M. S.; Solkan, V. N.; Zhidomirov, G. M.; Mel'nikov, M. Ya.

2012-05-01

221

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.

2014-01-28

222

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

223

Oxygen sensitive paper  

NASA Technical Reports Server (NTRS)

Paper is impregnated with mixture of methylene blue and ethylenediaminetetraacetic acid. Methylene blue is photo-reduced to leuco-form. Paper is kept isolated from oxygen until ready for use. Paper can be reused by photo-reduction after oxygen exposure.

Whidby, J. F.

1973-01-01

224

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

225

Molecular Structure of Oxygen  

NSDL National Science Digital Library

Diatomic oxygen (O2) is a highly reactive, paramagnetic molecule (containing two unpaired electrons) that occurs as a colorless gas at ambient temperatures but is a sapphire-blue liquid at very low temperatures (below –183 ºC). It is the second most abundant gas present in Earth's atmosphere. But it wasn't that way 4.5 billion years ago when the Earth's atmosphere was forming and N2 and CO2 were the dominant atmospheric gases. During that time, our planet was essentially devoid of oxygen, except for a small amount formed from the photodissociation of water and carbon dioxide by ultraviolet light from the sun. The oxygen that we breath today started to enter the atmosphere as a byproduct of photosynthesis carried out by early cyanobacteria 2.5 billion years ago. These bacteria thrived in the primordial oceans and were able to make organic nutrients using the light of the sun and the CO2 and water around them. During those early days, all the oxygen produced by bacteria was used up to oxidize iron that was dissolved in the oceans. It took about a hundred million years of oxygen production before all the iron precipitated, whereupon the oceans became saturated with oxygen and outgassed oxygen into the atmosphere. Today, oxygen continues to be produced photosynthetically by phytoplankton and green plants that have since evolved on Earth. Marine and terrestrial animals alike use the oxidizing power of dioxygen to pull electrons from organic molecules in electron transport systems that make up their metabolisms (aerobic respiration). Related to this is the best known reaction of diatomic oxygen: the reaction of O2 with the protein hemoglobin that that is responsible for oxygen transport in our blood.

2006-05-01

226

Singlet oxygen potentiates thrombolysis.  

PubMed

Activated polymorphonuclear neutrophils (PMN) participate in physiologic thrombolysis. PMN produce large amounts of urokinase (u-PA) and oxidants of the hypochlorite/chloramine-type that generate nonradical excited singlet oxygen ((1)O(2)). The u-PA/(1)O(2)-mediated thrombolysis was imitated in vitro. One hundred microliters microclots of normal human plasma were oxidized with 25 microL 0 to 5.0 micromoles of chloramine-T in physiol. NaCl in the absence or presence of 100 microL 6% bovine serum albumin or 100 microL normal plasma. Twenty-five microliters 0 to 167 IU/mL (related to 150 microL added supernatant) u-PA or 0 to 2.08 microg/mL t-PA were added. The absorbance at 405 nm was determined after 0 to 27 hours (37 degrees C). The specific clot turbidity was calculated, subtracting the 100% lysis absorbance from the respective measured absorbance. The chloramine-effective dose 50% (ED(50)) after 27 hours was determined in the presence of 2.6 IU/mL u-PA. The plasminogen activator-ED(25) was determined after 2 hours (37 degrees C), and the ET(25); i.e., the time needed to lyse a microclot by 25%, was determined for each respective clot-oxidation. The ED(25) of u-PA depends on the oxidation of the microclots: 1.25 micromoles chloramine/100 microL clot enhances thrombolysis approximately 20-fold; here, 25% of clot lysis is achieved within 50 minutes (using approximately 20 IU/mL u-PA), whereas approximately 5 hours are needed to lyse an unoxidized microclot by 25%. The present global assay technique imitates the u-PA/(1)O(2) aspects of physiologic thrombolysis by PMN. PMID:17636188

Stief, Thomas W

2007-07-01

227

Biphasic Oxygen Kinetics of Cellular Respiration and Linear Oxygen Dependence of Antimycin A Inhibited Oxygen Consumption  

Microsoft Academic Search

Oxygen kinetics in fibroblasts was biphasic. This was quantitatively explained by a major mitochondrial hyperbolic component in the low-oxygen range and a linear increase of rotenone-and antimycin A-inhibited oxygen consumption in the high-oxygen range. This suggests an increased production of reactive oxygen species and oxidative stress at elevated, air-level oxygen concentrations. The high oxygen affinity of mitochondrial respiration provides the

Eveline Hütter; Kathrin Renner; Pidder Jansen-Dürr; Erich Gnaiger

2002-01-01

228

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

229

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.

WGBH Educational Foundation

2010-12-23

230

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

231

Firewood calculator  

SciTech Connect

Rotating cardboard discs are used to read off total tree or topwood firewood volume (tons or cords) that can be expected from trees of d.b.h. 6 to 24 inches and tree height 10 to 90 feet. One side of the calculator is used for broadleaved species with deliquescent crowns and the other side for braodleaves with excurrent crowns.

Clark, A.; Curtis, A.B.; Darwin, W.N.

1981-01-01

232

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

233

An improved program to calculate intrapulmonary shunting.  

PubMed

A computer program was developed to calculate intrapulmonary venous admixture on a Texas Instruments TI 59 programmable calculator. The program incorporates the following characteristics: 1) a correction for saturated water vapor pressure which varies with body temperature; 2) a mathematical model of the standard oxyhemoglobin dissociation curve; and 3) correction factors for shifts of the dissociation curve due to variations in pH and carbon dioxide tension. It also corrects oxygen tensions obtained at electrode temperature to those at patient temperature, and calculates variations of the Bunsen solubility coefficient of oxygen in blood with body temperature. PMID:446063

Siegel, D; Ramanathan, S; Chalon, J; Turndorf, H

1979-06-01

234

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.

Mandy Barrow

2008-01-01

235

Electrochemical oxygen concentrator as an oxygen compressor  

NASA Technical Reports Server (NTRS)

A solid polymer electrolyte (SPE) oxygen compressor is described which generates pressures of 3000 psi. The SPE is a cation exchange membrane with chemical compatibility, and has the capability of withstanding 5000 psi. Other features of the compressor described include: gasketless sealing, porus plate cell supports, and conductive cooling. Results are presented of a computer program which defines the power of the system as a function of density, temperature, pressure, membrane thickness, and water content.

1975-01-01

236

Magnetism in lithium-oxygen discharge product.  

PubMed

Nonaqueous lithium-oxygen batteries have a much superior theoretical gravimetric energy density compared to conventional lithium-ion batteries, and thus could render long-range electric vehicles a reality. A molecular-level understanding of the reversible formation of lithium peroxide in these batteries, the properties of major/minor discharge products, and the stability of the nonaqueous electrolytes is required to achieve successful lithium-oxygen batteries. We demonstrate that the major discharge product formed in the lithium-oxygen cell, lithium peroxide, exhibits a magnetic moment. These results are based on dc-magnetization measurements and a lithium-oxygen cell containing an ether-based electrolyte. The results are unexpected because bulk lithium peroxide has a significant band gap. Density functional calculations predict that superoxide-type surface oxygen groups with unpaired electrons exist on stoichiometric lithium peroxide crystalline surfaces and on nanoparticle surfaces; these computational results are consistent with the magnetic measurement of the discharged lithium peroxide product as well as EPR measurements on commercial lithium peroxide. The presence of superoxide-type surface oxygen groups with spin can play a role in the reversible formation and decomposition of lithium peroxide as well as the reversible formation and decomposition of electrolyte molecules. PMID:23670967

Lu, Jun; Jung, Hun-Ji; Lau, Kah Chun; Zhang, Zhengcheng; Schlueter, John A; Du, Peng; Assary, Rajeev S; Greeley, Jeffrey; Ferguson, Glen A; Wang, Hsien-Hau; Hassoun, Jusef; Iddir, Hakim; Zhou, Jigang; Zuin, Lucia; Hu, Yongfeng; Sun, Yang-Kook; Scrosati, Bruno; Curtiss, Larry A; Amine, Kahlil

2013-07-01

237

Magnetism in Lithium–Oxygen Discharge Product  

SciTech Connect

Nonaqueous lithium–oxygen batteries have a much superior theoretical gravimetric energy density compared to conventional lithium-ion batteries, and thus could render long-range electric vehicles a reality. A molecular-level understanding of the reversible formation of lithium peroxide in these batteries, the properties of major/minor discharge products, and the stability of the nonaqueous electrolytes is required to achieve successful lithium–oxygen batteries. We demonstrate that the major discharge product formed in the lithium–oxygen cell, lithium peroxide, exhibits a magnetic moment. These results are based on dc-magnetization measurements and a lithium– oxygen cell containing an ether-based electrolyte. The results are unexpected because bulk lithium peroxide has a significant band gap. Density functional calculations predict that superoxide- type surface oxygen groups with unpaired electrons exist on stoichiometric lithium peroxide crystalline surfaces and on nanoparticle surfaces; these computational results are consistent with the magnetic measurement of the discharged lithium peroxide product as well as EPR measurements on commercial lithium peroxide. The presence of superoxide-type surface oxygen groups with spin can play a role in the reversible formation and decomposition of lithium peroxide as well as the reversible formation and decomposition of electrolyte molecules.

Lu, Jun; Jung, Hun-Ji; Lau, Kah Chun; Zhang, Zhengcheng; Schlueter, John A.; Du, Peng; Assary, Rajeev S.; Greeley, Jeffrey P.; Ferguson, Glen A.; Wang, Hsien-Hau; Hassoun, Jusef; Iddir, Hakim; Zhou, Jigang; Zuin, Lucia; Hu, Yongfeng; Sun, Yang-Kook; Scrosati, Bruno; Curtiss, Larry A.; Amine, Khalil

2013-05-13

238

A theoretical analysis of intracellular oxygen diffusion.  

PubMed

Oxygen diffusion rates within cells may be heterogeneous, with more rapid diffusion occurring along intracellular pathways of high oxygen solubility, such as mitochondria. Recent experimental data indicate that tissue oxygen permeability rises sharply in a temperature range associated with phase transitions in lipid membranes suggesting that membranes may function as oxygen "pathway". The experimental data have been analyzed using theoretical models of diffusion in two-phase media. By assuming muscles to be composed entirely of aqueous cytosol and lipids, cytosolic permeability was determined as a function of temperature by matching the experimental values of tissue permeability with those of model predictions using in vitro values of lipid permeability. Cytosolic permeability ranged from 50% of water permeability (low temperature) to 90% of water permeability (high temperature) and its temperature dependence was distinctly different from that of water. An upper bound for cytosolic permeability was calculated using a physiologic value for protein volume fraction, and lipid permeability was obtained using this cytosolic permeability. A model with a parallel arrangement of lipid and cytosol yielded a value of lipid permeability that was 71% higher than the in vitro value. Intracellular permeabilities calculated from tissue permeability values were found to be inconsistent with experimentally reported values for rat cardiac myocytes. Comparison of three different muscles exhibited the same trend of higher permeability with higher lipid content. It is concluded that both lipid and cytosol permeabilities and, hence, tissue permeabilities are different among different muscles and one should exercise caution when data from one muscle is used to calculate or extrapolate values in other muscles. It is conceivable that muscles with very high mitochondrial content, such as diaphragm and cardiac muscles may exhibit an oxygen permeability which is significantly higher than commonly accepted values. These results warrant additional measurements of tissue oxygen permeability at 37 degrees C, especially for oxidative muscles with high lipid content. PMID:8551742

Dutta, A; Popel, A S

1995-10-21

239

OXYGEN TRANSPORT CERAMIC MEMBRANES  

SciTech Connect

In the present quarter, oxygen transport perovskite ceramic membranes 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

2002-07-01

240

High Selectivity Oxygen Delignification  

SciTech Connect

Project Objective: The objectives of this project are as follows: (1) Examine the physical and chemical characteristics of a partner mill pre- and post-oxygen delignified pulp and compare them to lab generated oxygen delignified pulps; (2) Apply the chemical selectivity enhancement system to the partner pre-oxygen delignified pulps under mill conditions (with and without any predetermined amounts of carryover) to determine how efficiently viscosity is preserved, how well selectivity is enhanced, if strength is improved, measure any yield differences and/or bleachability differences; and (3) Initiate a mill scale oxygen delignification run using the selectivity enhancement agent, collect the mill data, analyze it, and propose any future plans for implementation.

Lucian A. Lucia

2005-11-15

241

Oxygen transfer in liquids.  

PubMed

In the laboratory-type airlift tower reactor oxygen transfer from air in tap water and/or polyacrylamide solutions (Neuperm WF) was studied. In order to characterize the system, volumetric coefficient of oxygen transfer was determined by the gassing-out method. Two arrangements of the airlift tower reactor were compared, namely the reactor with and without motionless mixer. In addition, mean relative gas holdup and gas power output were determined for both arrangements. PMID:18553699

Stejskal, J; Pot?cek, F

1985-04-01

242

Photoperiod Calculator  

NSDL National Science Digital Library

Jarmo Lammi has developed this simple, easy-to-use tool that provides information useful for teaching and research purposes. Users select a day, month, location (city or latitude and longitude) and time-of-day, and then submit their entry. The Calculator then generates the following information: latitude and longitude for the city/location, declination of the sun, height of sun at noon that day, daylength, and time of sunrise and sunset. This is a useful tool for ecological research and teaching.

Lammi, Jarmo J.

243

Direct observation of the oxygenated species during oxygen reduction on a platinum fuel cell cathode  

NASA Astrophysics Data System (ADS)

The performance of polymer electrolyte membrane fuel cells is limited by the reduction at the cathode of various oxygenated intermediates in the four-electron pathway of the oxygen reduction reaction. Here we use ambient pressure X-ray photoelectron spectroscopy, and directly probe the correlation between the adsorbed species on the surface and the electrochemical potential. We demonstrate that, during the oxygen reduction reaction, hydroxyl intermediates on the cathode surface occur in several configurations with significantly different structures and reactivities. In particular, we find that near the open-circuit potential, non-hydrated hydroxyl is the dominant surface species. On the basis of density functional theory calculations, we show that the removal of hydration enhances the reactivity of oxygen species. Tuning the hydration of hydroxyl near the triple phase boundary will be crucial for designing more active fuel cell cathodes.

Casalongue, Hernan Sanchez; Kaya, Sarp; Viswanathan, Venkatasubramanian; Miller, Daniel J.; Friebel, Daniel; Hansen, Heine A.; Nørskov, Jens K.; Nilsson, Anders; Ogasawara, Hirohito

2013-12-01

244

Oxygen chemistry of shocked interstellar clouds. III - Sulfur and oxygen species in dense clouds  

NASA Technical Reports Server (NTRS)

The chemical evolution of oxygen and sulfur species in shocked dense clouds is studied. Reaction rate constants for several important neutral reactions are examined, and revised values are suggested. The one-fluid magnetohydrodynamic shock structure and postshock chemical evolution are calculated for shocks of velocity v(s) = 10 km/s through clouds of initial number density n(0) = 100,000/cu cm and of molecule/atom ratios H2/H = 10, 1000, and 100,000 with most sulfur contained initially in molecules SO2 and SO. Abundances of SO2, SO, CS, and OCS remain near their preshock values, except in clouds containing substantial amounts of atomic hydrogen, where significant destruction of sulfur-oxygen species occurs. Abundances of shock-enhanced molecules HS and H2O are sensitive to the molecule/atom ratio. Nonthermal oxygen-hydrogen chemistry has a minor effect on oxygen-sulfur molecules in the case H2/H = 10.

Leen, T. M.; Graff, M. M.

1988-01-01

245

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

246

Electron-beam sustained discharge in oxygen gas mixtures: singlet delta oxygen production for oxygen-iodine laser  

NASA Astrophysics Data System (ADS)

Electric properties and spectroscopy of an e-beam sustained discharge (EBSD) in oxygen and oxygen gas mixtures at gas pressure up to 100 Torr were experimentally studied. The pulsed 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 (SIE) per molecular component being more than order of magnitude higher and coming up to 6.5 kJ/(l atm) for gas mixture O2:Ar:CO = 1:1:0.1. The results of experiments on spectroscopy of the singlet delta oxygen O2(a1?g)(SDO) and O2(b1?g+) states in the EBSD are presented. The calibration of the optical scheme for measuring the SDO absolute concentration and yield using the detection of luminescence of the SDO going from a chemical SDO generator was done. The preliminary measurement of the SDO yield demonstrated that it was ~3% for the SIE of ~1 kJ/(l atm), which is close to the results of theoretical calculations for such a SIE. Theoretical calculations demonstrated that for the SIE of 6.5 kJ/(l atm) the SDO yield may reach ~20% exceeding its threshold value needed for oxygen-iodine laser operation at room temperature, although a part of the energy loaded into the EBSD goes into the vibrational energy of the molecular admixture, (which was experimentally demonstrated by launching a CO laser operating on an oxygen-rich mixture O2:Ar:CO = 1:1:0.1 and measuring its small-signal gain).

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

2004-09-01

247

Oxygen electrode in molten carbonate fuel cells  

NASA Astrophysics Data System (ADS)

Effects of partial pressure of oxygen and temperature on oxygen reduction kinetics on a submerged gold electrode in lithium carbonate melt were investigated using cyclic voltammetry and impedance analysis. Cyclic voltammetry measurements show that the peroxide reduction reaction in Li2CO3 melt is reversible up to 200 mV/s. The impedance analysis was carried out using a Complex Nonlinear Least Square (CNLS) parameter estimation program based upon the Randles-Ershler equivalent circuit. This analysis estimated electrode kinetics and mass transfer related parameters such as charge transfer resistance and Warburg coefficient. The mass transfer related parameters obtained from cyclic voltammetry and impedance analysis show good agreement. The oxygen reaction orders for mass transfer parameter and exchange current density at 800 C were calculated to be 0.5 and 0.377 respectively; these values are consistent with the peroxide mechanism.

Dave, B. B.; Adanuvor, P. K.; Enayetullah, M. A.; White, R. E.; Srinivasan, S.; Appleby, A. J.

248

Photochemical Escape of Oxygen from Early Mars  

E-print Network

Photochemical escape is an important process for oxygen escape from present Mars. In this work, a 1-D Monte-Carlo Model is developed to calculate escape rates of energetic oxygen atoms produced from O2+ dissociative recombination reactions (DR) under 1, 3, 10, and 20 times present solar XUV fluxes. We found that although the overall DR rates increase with solar XUV flux almost linearly, oxygen escape rate increases from 1 to 10 times present solar XUV conditions but decreases when increasing solar XUV flux further. Analysis shows that atomic species in the upper thermosphere of early Mars increases more rapidly than O2+ when increasing XUV fluxes. While the latter is the source of energetic O atoms, the former increases the collision probability and thus decreases the escape probability of energetic O. Our results suggest that photochemical escape be a less important escape mechanism than previously thought for the loss of water and/or CO2 from early Mars.

Zhao, Jinjin

2015-01-01

249

Experimental and theoretical investigation of oxygen diffusion in stabilised zirconia  

NASA Astrophysics Data System (ADS)

Oxygen diffusion in stabilised zirconias is investigated by the simultaneous application of computer modelling and experimental techniques to yttria-stabilised zirconia. Using the Mott-Littleton method, migration pathways for oxygen ions have been calculated in perfect cubic zirconia. The oxygen migration occurs through a straight pathway, but not starting from the ideal lattice positions. The calculated activation energy of migration is about 0.2 eV. Oxygen transport is investigated experimentally in YSZ containing 8-24 mol% Y2O3 as a function of stabiliser content by combining the stable isotope (O-18(2)) method with ionic conductivity measurements. It was found that for a given temperature, diffusion and conductivity are highest for YSZ containing 8-10 mol% yttria, but with differing activation energies which can be compared to the calculated values.

Kilo, M.; Fundenberger, C.; Argirusis, C.; Taylor, M. A.; Borchardt, G.; Weller, M.; Jackson, R. A.

250

Program developed for CO{sub 2} system calculations  

SciTech Connect

The program CO2SYS performs calculations relating parameters of the carbon dioxide (CO{sub 2}) system in seawater and freshwater. The program uses two of the four measurable parameters of the CO{sub 2} system [total alkalinity (TA), total inorganic CO{sub 2} (TCO{sub 2}), pH, and either fugacity (fCO{sub 2}) or partial pressure of CO{sub 2} (pCO{sub 2})] to calculate the other two parameters at a set of input conditions (temperature and pressure) and a set of output conditions chosen by the user. It replaces and extends the programs CO2SYSTM.EXE, FCO2TCO2.EXE, PHTCO2.EXE, and CO2BTCH.EXE, which were released in May 1995. It may be run in single-input mode or batch-input mode and has a variety of options for the various constants and parameters used. An on-screen information section is available that includes documentation on various topics relevant to the program. This program may be run on any 80 x 86 computer equipped with the DOS operating system by simply typing CO2SYS at the prompt after loading the executable file CO2SYS.EXE.

Lewis, E.; Wallace, D. [Brookhaven National Lab., Upton, NY (United States). Dept. of Applied Science; Allison, L.J. [Oak Ridge National Lab., TN (United States). Carbon Dioxide Information Analysis Center

1998-02-01

251

Dissolved oxygen and fish behavior  

Microsoft Academic Search

Synopsis This essay reviews the behavioral responses of fish to reduced levels of dissolved oxygen from the perspective of optimization theory as used in contemporary behavioral ecology. A consideration of oxygen as a resource suggests that net oxygen gain per unit of energy expenditure will be the most useful currency for ecological models of breathing. In the process of oxygen

Donald L. Kramer

1987-01-01

252

Venous oxygen saturation.  

PubMed

Early detection and rapid treatment of tissue hypoxia are important goals. Venous oxygen saturation is an indirect index of global oxygen supply-to-demand ratio. Central venous oxygen saturation (ScvO2) measurement has become a surrogate for mixed venous oxygen saturation (SvO2). ScvO2 is measured by a catheter placed in the superior vena cava. After results from a single-center study suggested that maintaining ScvO2 values >70% might improve survival rates in septic patients, international practice guidelines included this target in a bundle strategy to treat early sepsis. However, a recent multicenter study with >1500 patients found that the use of central hemodynamic and ScvO2 monitoring did not improve long-term survival when compared to the clinical assessment of the adequacy of circulation. It seems that if sepsis is recognized early, a rapid initiation of antibiotics and adequate fluid resuscitation are more important than measuring venous oxygen saturation. PMID:25480771

Hartog, Christiane; Bloos, Frank

2014-12-01

253

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

254

Monolithic solid electrolyte oxygen pump  

DOEpatents

A multi-layer oxygen pump having a one-piece, monolithic ceramic structure affords high oxygen production per unit weight and volume and is thus particularly adapted for use as a portable oxygen supply. The oxygen pump is comprised of a large number of small cells on the order of 1-2 millimeters in diameter which form the walls of the pump and which are comprised of thin, i.e., 25-50 micrometers, ceramic layers of cell components. The cell components include an air electrode, an oxygen electrode, an electrolyte and interconnection materials. The cell walls form the passages for input air and for exhausting the oxygen which is transferred from a relatively dilute gaseous mixture to a higher concentration by applying a DC voltage across the electrodes so as to ionize the oxygen at the air electrode, whereupon the ionized oxygen travels through the electrolyte and is converted to oxygen gas at the oxygen electrode.

Fee, Darrell C. (2529 Lee St., Woodridge, IL 60517); Poeppel, Roger B. (67 Stephanie La., Glen Ellyn, IL 60137); Easler, Timothy E. (564 N. Pinecrest, Bolingbrook, IL 60439); Dees, Dennis W. (6224 Middaugh Ave., Downers Grove, IL 60517)

1989-01-01

255

Battling for Oxygen  

NSDL National Science Digital Library

Working in groups, learners model the continuous destruction and creation of ozone (O3) molecules, which occur in the ozone layer. Some learners act as ultraviolet (UV) light and break apart gumdrop and toothpick models of ozone molecules into oxygen molecules and atoms. Meanwhile, other learners assemble ozone molecules from the oxygen molecules and atoms. In a second round, learners model the situation when pollutants such as chlorofluorocarbons (CFCs) are present. In subsequent rounds, the amount of CFCs changes according to historical data, and learners can see what happens to the proportion of ozone and oxygen in the ozone layer over time. Resource contains vocabulary definitions and suggestions for assessment, extensions, and scaling for different levels of learners.

Amy Kolenbrander

2004-01-01

256

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

257

The history of extracorporeal oxygenators.  

PubMed

Extracorporeal oxygenators are artificial devices that substitute for anatomical lungs by delivering oxygen to, and extracting carbon dioxide from, blood. They were first conceptualised by the English scientist Robert Hooke (1635-1703) and developed into practical extracorporeal oxygenators by French and German experimental physiologists in the 19th century. Indeed, most of the extracorporeal oxygenators used until the late 1970s were derived from von Schroder's 1882 bubble oxygenator and Frey and Gruber's 1885 film oxygenator. As there is no intervening barrier between blood and oxygen, these are called 'direct contact' oxygenators; they contributed significantly to the development and practice of cardiac surgery till the 1980s. Membrane extracorporeal oxygenators introduce a gas-permeable interface between blood and oxygen. This greatly decreased the blood trauma of direct-contact extracorporeal oxygenators, and enabled extracorporeal oxygenators to be used in longer-term applications such as the intensive therapy of respiratory distress syndrome; this was demonstrably beneficial for neonates but less so for older patients. Much work since the 1960s focused on overcoming the gas exchange handicap of the membrane barrier, leading to the development of high-performance microporous hollow-fibre oxygenators that eventually replaced direct-contact oxygenators in cardiac theatres. PMID:16978315

Lim, M W

2006-10-01

258

FUEL OXYGENATES HEALTH ISSUES  

EPA Science Inventory

Oxygenates (e.g., methyl tertiary butyl ether [MTBE], ethanol) are required in certain areas of the United States by the 1990 Clean Air Act Amendments. MTBE and ethanol have also been used to increase octane ratings in U.S. gasoline since the 1970s. In 1996 alone, 10 billion Kg...

259

High Selectivity Oxygen Delignification  

Microsoft Academic Search

The overall objective of this program was to develop improved extended oxygen delignification (EOD) technologies for current U.S. pulp mill operations. This was accomplished by: (1) Identifying pulping conditions that optimize O and OO performance; (2) Identifying structural features of lignin that enhance reactivity towards EOD of high kappa pulps; (3) Identifying factors minimizing carbohydrate degradation and improve pulp strength

Arthur J. Ragauskas; Lucian A. Lucia; Hasan Jameel

2005-01-01

260

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.

261

Using oxygen at home  

MedlinePLUS

... K-Y jelly) to add moisture to them. Aloe vera is OK to use. Do not use petroleum jelly (Vaseline) or any oil-based products. Place some gauze under the oxygen tubing behind your ear. This will help keep the skin from getting sore. Do not stop or change ...

262

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

263

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

264

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

265

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

266

Oxygen transport by oxygen potential gradient in dense ceramic oxide membranes  

SciTech Connect

Numerous studies have been conducted in recent years on the partial oxidation of methane to synthesis gas (syngas: CO + H{sub 2}) with air as the oxidant. In partial oxidation, a mixed-oxide ceramic membrane selectively transports oxygen from the air; this transport is driven by the oxygen potential gradient. Of the several ceramic materials the authors have tested, a mixed oxide based on the Sr-Fe-Co-O system has been found to be very attractive. Extensive oxygen permeability data have been obtained for this material in methane conversion experiments carried out in a reactor. The data have been analyzed by a transport equation based on the phenomenological theory of diffusion under oxygen potential gradients. Thermodynamic calculations were used to estimate the driving force for the transport of oxygen ions. The results show that the transport equation deduced from the literature describes the permeability data reasonably well and can be used to determine the diffusion coefficients and the associated activation energy of oxygen ions in the ceramic membrane material.

Maiya, P.S.; Balachandran, U.; Dusek, J.T.; Mieville, R.L. [Argonne National Lab., IL (United States). Energy Technology Div.; Kleefisch, M.S.; Udovich, C.A. [Amoco Exploration/Production, Naperville, IL (United States)

1996-05-01

267

Oxygen Transport Ceramic Membranes  

SciTech Connect

The present quarterly report describes some of the investigations on the structural properties of dense OTM bars provided by Praxair and studies on newer composition of Ti doped LSF. In this report, in situ neutron diffraction was used to characterize the chemical and structural properties of La{sub 0.2}Sr{sub 0.8}Fe{sub 0.55}Ti{sub 0.45}O{sub 3-{delta}} (here after as L2SF55T) specimen, which was subject to measurements of neutron diffraction from room temperature to 900 C in N{sub 2}. Space group of R3c was found to result in a better refinement and is used in this study. The difference for crystal structure, lattice parameters and local crystal chemistry for LSFT nearly unchanged when gas environment switched from air to N{sub 2}. Stable crack growth studies on Dense OTM bars provided by Praxair were done at room temperature in air. A bridge-compression fixture was fabricated to achieve stable pre-cracks from Vickers indents. Post fracture evaluation indicated stable crack growth from the indent and a regime of fast fracture. Post-fracture X-ray data of the OTM fractured at 1000 C in environment were refined by FullProf code and results indicate a distortion of the parent cubic perovskite to orthorhombic structure with reduced symmetry. TGA-DTA studies on the post-fracture samples also indicated residual effect arising from the thermal and stress history of the samples. The thermal and chemical expansion of La{sub 0.2}Sr{sub 0.8}Fe{sub 0.55}Ti{sub 0.45}O{sub 3-{delta}} were studied at 800 {le} T {le} 1000 C and at {approx} 1 x 10{sup -15} {le} pO{sub 2} {le} 0.21 atm. The thermal expansion coefficient of the sample was calculated from the dilatometric analysis in the temperature range between room temperature and 1200 C in air. A series of isotope transients under air separation mode (small gradient) were completed on the membrane of LSCrF-2828 at 900 C. Low pO{sub 2} atmospheres based on with CO-CO{sub 2} mixtures have also been admitted to the delivery side of the LSCrF-2828 membrane to produce the gradients which exist under syngas generation conditions. The CO-CO{sub 2} mixtures have normal isotopic {sup 18}O abundances. The evolution of {sup 18}O on the delivery side in these experiments after an {sup 18}O pulse on the air side reveals a wealth of information about the oxygen transport processes.

S. Bandopadhyay; N. Nagabhushana; X.-D Zhou; Q. Cai; J. Yang; W.B. Yelon; W.J. James; H.U. Anderson; Alan Jacobson; C.A. Mims

2004-05-01

268

The Effects of Photosynthesis and Cellular Respiration on Dissolved Oxygen Concentration  

Microsoft Academic Search

Photosynthesis and cellular respiration are two processes that transform energy and affect concentrations of carbon dioxide and oxygen in air and water. In this lesson, middle school students use graphing calculators and calculator-based laboratory units to measure dissolved oxygen in water and graph their results to gain an under-standing of the relationship between photosynthesis and cellular respiration.

Darren Proppe; Sherry Harrel

2007-01-01

269

Analytical theory of oxygen transport in the human placenta.  

PubMed

We propose an analytical approach to solving the diffusion-convection equations governing oxygen transport in the human placenta. We show that only two geometrical characteristics of a placental cross-section, villi density and the effective villi radius, are needed to predict fetal oxygen uptake. We also identify two combinations of physiological parameters that determine oxygen uptake in a given placenta: (i) the maximal oxygen inflow of a placentone if there were no tissue blocking the flow and (ii) the ratio of transit time of maternal blood through the intervillous space to oxygen extraction time. We derive analytical formulas for fast and simple calculation of oxygen uptake and provide two diagrams of efficiency of oxygen transport in an arbitrary placental cross-section. We finally show that artificial perfusion experiments with no-hemoglobin blood tend to give a two-orders-of-magnitude underestimation of the in vivo oxygen uptake and that the optimal geometry for such setup alters significantly. The theory allows one to adjust the results of artificial placenta perfusion experiments to account for oxygen-hemoglobin dissociation. Combined with image analysis techniques, the presented model can give an easy-to-use tool for prediction of the human placenta efficiency. PMID:25580015

Serov, A S; Salafia, C M; Filoche, M; Grebenkov, D S

2015-03-01

270

Oxidation-Reduction Calculations in the Biochemistry Course  

ERIC Educational Resources Information Center

Redox calculations have the potential to reinforce important concepts in bioenergetics. The intermediacy of the NAD[superscript +]/NADH couple in the oxidation of food by oxygen, for example, can be brought out by such calculations. In practice, students have great difficulty and, even when adept at the calculations, frequently do not understand…

Feinman, Richard D.

2004-01-01

271

Singlet delta oxygen generation for Chemical Oxygen-Iodine Lasers  

Microsoft Academic Search

The development of Chemical Oxygen-Iodine Lasers is based on the generation of singlet delta oxygen. To improve the overall efficiency of these lasers, it is necessary to increase the generator production and yield of singlet delta oxygen at low and high pressure, respectively, for subsonic and supersonic lasers. Furthermore, the water vapor content must be as low as possible. A

E. Georges; A. Mouthon; R. Barraud

1991-01-01

272

How Do Calculators Calculate? Helmut Knaust  

E-print Network

How Do Calculators Calculate? Helmut Knaust Department of Mathematical Sciences University of Texas at El Paso Helmut Knaust How Do Calculators Calculate? April 25, 1997 1 / 18 #12;History We give an introduction to the CORDIC method used my most handheld calculators (such as the ones by Texas Instruments

Knaust, Helmut

273

Assessing hafnium on hafnia as an oxygen getter  

SciTech Connect

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; Demkov, Alexander A., E-mail: demkov@physics.utexas.edu [Department of Physics, The University of Texas at Austin, Austin, Texas 78712 (United States); Bersuker, Gennadi [SEMATECH, Albany, New York 12203 (United States)

2014-05-14

274

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...

275

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

276

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

NASA Astrophysics Data System (ADS)

Dosidicus gigas is a large, metabolically active, epipelagic squid known to undertake diel vertical migrations across a large temperature and oxygen gradient in the Eastern Pacific. Hypoxia is known to cause metabolic suppression in D. gigas. However, the precise oxygen level at which metabolic suppression sets in is unknown. Here we describe a novel ship-board swim tunnel respirometer that was used to measure metabolic rates and critical oxygen partial pressures (Pcrit) for adult squids (2-7kg). Metabolic rate measurements were validated by comparison to the activity of the Krebs cycle enzyme, citrate synthase, in mantle muscle tissue (2-17kg). We recorded a mean routine metabolic rate of 5.91?molg-1h-1 at 10°C and 12.62?molg-1h-1 at 20°C. A temperature coefficient, Q10, of 2.1 was calculated. D. gigas had Pcrits of 1.6 and 3.8kPa at 10 and 20°C, respectively. Oxygen consumption rate (MO2) varied with body mass (M) according to MO2=11.57M-0.12±0.03 at 10°C. Citrate synthase activity varied with body mass according to Y=9.32M-0.19±0.02.

Trueblood, Lloyd A.; Seibel, Brad A.

2013-10-01

277

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

278

Oxygenic photosynthesis without galactolipids  

PubMed Central

The thylakoid membranes of oxygenic photosynthetic organisms are dominated by the galactolipids monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG). In cyanobacteria, MGDG is synthesized via monoglucosyldiacylglycerol (GlcDG). However, the putative epimerase involved in the conversion of GlcDG to MGDG has not been identified. Here we report the identification of the gene for the glucolipid epimerase (mgdE) by comparative genomic analysis. Knockout mutants of mgdE in Synechocystis sp. PCC 6803 lacked both MGDG and DGDG and accumulated GlcDG. The mutants did possess thylakoid membranes and showed normal maximal photosynthetic activity, albeit with reduced utilization of light energy. These results cast doubt on the long-standing belief that oxygenic photosynthesis is absolutely dependent on galactolipids. PMID:25197079

Awai, Koichiro; Ohta, Hiroyuki; Sato, Naoki

2014-01-01

279

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

280

Oxygen Transport Ceramic Membranes  

SciTech Connect

The present quarterly report describes some of the investigations on the structural properties of dense OTM bars provided by Praxair and studies on newer composition of Ti doped LSF. The in situ electrical conductivity and Seebeck coefficient measurements were made on LSFT at 1000 and 1200 C over the oxygen activity range from air to 10{sup -15} atm. The electrical conductivity measurements exhibited a p to n type transition at an oxygen activity of 1 x 10{sup -10} at 1000 C and 1 x 10{sup -6} at 1200 C. Thermogravimetric studies were also carried out over the same oxygen activities and temperatures. Based on the results of these measurements, the chemical and mechanical stability range of LSFT were determined and defect structure was established. The studies on the fracture toughness of the LSFT and dual phase membranes exposed to air and N{sub 2} at 1000 C was done and the XRD and SEM analysis of the specimens were carried out to understand the structural and microstructural changes. The membranes that are exposed to high temperatures at an inert and a reactive atmosphere undergo many structural and chemical changes which affect the mechanical properties. A complete transformation of fracture behavior was observed in the N{sub 2} treated LSFT samples. Further results to investigate the origin of the slow kinetics on reduction of ferrites have been obtained. The slow kinetics appear to be related to a non-equilibrium reduction pathway that initially results in the formation of iron particles. At long times, equilibrium can be reestablished with recovery of the perovskite phase. Recent results on transient kinetic data are presented. The 2-D modeling of oxygen movement has been undertaken in order to fit isotope data. The model is used to study ''frozen'' profiles in patterned or composite membranes.

S. Bandopadhyay; T. Nithyanantham; X.-D Zhou; Y-W. Sin; H.U. Anderson; Alan Jacobson; C.A. Mims

2005-02-01

281

Electrocatalyst for oxygen reduction  

NASA Technical Reports Server (NTRS)

The performance and costs of an electrochemical catalyst as compared to a pure platinum catalyst is evaluated. The catalysts are used to reduce oxygen in low temperature alkaline fuel cells. The electrochemical catalyst is composed of silver and platinum and is dispersed in a resinous inert binder to provide a cell electrode. The results indicate the electrochemical catalyst is superior structurally to the platinum one for high current density operation, and is at least as active as the platinum catalyst in other operations.

Swette, L. L. (inventor)

1971-01-01

282

Singlet Oxygen Potentiates Thrombolysis  

Microsoft Academic Search

Activated polymorphonuclear neutrophils (PMN) participate in physiologic thrombolysis. PMN produce large amounts of urokinase (u-PA) and oxidants of the hypochlorite\\/chloramine-type that generate nonradical excited singlet oxygen (1O2). The u-PA\\/1O2—mediated thrombolysis was imitated in vitro. One hundred microliters microclots of normal human plasma were oxidized with 25 ?L 0 to 5.0 ?moles of chloramine-T in physiol. NaCl in the absence or

Thomas W. Stief

2007-01-01

283

Microsoft EXCEL spreadsheet-based program for calculating equilibrium gas speciation in the C-O-H-S-Cl-F system  

NASA Astrophysics Data System (ADS)

A high-temperature gas is a relatively simple mixture of gas species in homogeneous equilibrium. Volcanic gases are composed of the elements C, O, H, S, Cl and F along with trace amounts of other components. We present an Microsoft EXCEL spread sheet and add-in for calculation of homogeneous equilibrium in this system. This EXCEL extension allows users to calculate equilibrium species fugacities at 1 bar for any volcanic or laboratory gas mixture in the C-O-H-S-Cl-F system. Homogeneous equilibrium is calculated using the RAND algorithm based on the assumption of ideal mixing of 66 molecular gas species. This is implemented as a hierarchy of class objects written in C++. This computation engine is compiled into a dynamically linked EXCEL add-in which can be accessed by any EXCEL spread sheet. An easy to use spread sheet is provided which implements this add-in.

Kress, Victor C.; Ghiorso, Mark S.; Lastuka, Coby

2004-04-01

284

Oxygen abundances in the most oxygen-rich spiral galaxies  

E-print Network

Oxygen abundances in the spiral galaxies expected to be richest in oxygen are estimated. The new abundance determinations are based on the recently discovered ff-relation between auroral and nebular oxygen line fluxes in HII regions. We find that the maximum gas-phase oxygen abundance in the central regions of spiral galaxies is 12+log(O/H)~8.75. This value is significantly lower than the previously accepted value. The central oxygen abundance in the Milky Way is similar to that in other large spirals.

L. S. Pilyugin; T. X. Thuan; J. M. Vilchez

2006-01-06

285

Oxygen requirements of yeasts.  

PubMed

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. PMID:2082825

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

1990-12-01

286

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

287

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

288

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 PMID:2082825

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

1990-01-01

289

Effect of surface strain on oxygen adsorption on Zr (0001) surface  

SciTech Connect

The effect of surface strain on oxygen adsorption on Zr (0 0 0 1) surface is investigated by density functional theory (DFT) calculations. It is demonstrated that both surface strain and interactions between oxygen adsorbates influence the adsorption process. Oxygen binding to zirconium becomes stronger as the strain changes from compressive to tensile. When oxygen coverage is low and the oxygen interactions are negligible, surface face-centered cubic sites are the most stable for O binding. At high coverage and under compression, octahedral sites between second and third Zr layers become most favorable because the interactions between adsorbates are weakened by positive charge screening. Calculations with both single-layer adsorption model and multiple-layer adsorption model demonstrate that compressive strain at the Zr/oxide interface will provide a thermodynamic driving force for oxygen to incorporate from the surface into the bulk of Zr, while binding oxygen to the Zr surface will be easier when tensile strain is applied.

Xing Wang [Univ. of Wisconsin-Madison, Madison, WI (United States). Dept. of Engineering Physics; Marat Khafizov [Idaho National Laboratory (INL), Idaho Falls, ID (United States); Izabela Szlufarska [Univ. of Wisconsin-Madison, Madison, WI (United States). Dept. of Engineering Physics; Univ. of Wisconsin-Madison, Madison, WI (United States). Dept. of Materials Science and Engineering

2014-02-01

290

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

291

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

292

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

293

Exploring the Diffusion of Molecular Oxygen in the Red Fluorescent Protein mCherry Using Explicit Oxygen Molecular Dynamics Simulations  

PubMed Central

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.

2013-01-01

294

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

SciTech Connect

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

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

1989-01-01

295

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

SciTech Connect

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

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

1989-12-31

296

Oxygen Transport Ceramic Membranes  

SciTech Connect

Ti doping on La{sub 1-x}Sr{sub x}FeO{sub 3-{delta}} (LSF) tends to increase the oxygen equilibration kinetics of LSF in lower oxygen activity environment because of the high valence state of Ti. However, the addition of Ti decreases the total conductivity because the acceptor ([Sr{prime}{sub La}]) is compensated by the donor ([Ti{sub Fe}{sup {sm_bullet}}]) which decreases the carrier concentration. The properties of La{sub 0.2}Sr{sub 0.8}Fe{sub 1-x}Ti{sub x}O{sub 3-{delta}} (LSFT, x = 0.45) have been experimentally and theoretically investigated to elucidate (1) the dependence of oxygen occupancy and electrochemical properties on temperature and oxygen activity by thermogravimetric analysis (TGA) and (2) the electrical conductivity and carrier concentration by Seebeck coefficient and electrical measurements. In the present study, dual phase (La{sub 0.2}Sr{sub 0.8}Fe{sub 0.6}Ti{sub 0.4}O{sub 3-{delta}}/Ce{sub 0.9}Gd{sub 0.1}O{sub 2-{delta}}) membranes have been evaluated for structural properties such as hardness, fracture toughness and flexural strength. The effect of high temperature and slightly reducing atmosphere on the structural properties of the membranes was studied. The flexural strength of the membrane decreases upon exposure to slightly reducing conditions at 1000 C. The as-received and post-fractured membranes were characterized using XRD, SEM and TG-DTA to understand the fracture mechanisms. Changes in structural properties of the composite were sought to be correlated with the physiochemical features of the two-phases. We have reviewed the electrical conductivity data and stoichiometry data for La{sub 0.2}Sr{sub 0.8}Cr{sub 0.2}Fe{sub 0.8}O{sub 3-{delta}} some of which was reported previously. Electrical conductivity data for La{sub 0.2}Sr{sub 0.8}Cr{sub 0.2}Fe{sub 0.8}O{sub 3-{delta}} (LSCrF) were obtained in the temperature range, 752 {approx} 1055 C and in the pO{sub 2} range, 10{sup -18} {approx} 0.5 atm. The slope of the plot of log {sigma} vs. log pO{sub 2} is {approx} 1/5 in the p-type region, pO{sub 2} = 10{sup -5} {approx} 10{sup -1} atm. The pO{sub 2} at which the p-n transition is observed increases with increasing temperature. The activation energy for ionic conduction was estimated to be 0.86 eV from an Arrhenius plot of the minimum conductivity vs. reciprocal temperature. At temperatures below 940 C, a plateau in the conductivity isotherm suggests the presence of a two-phase region. Most likely, phase separation occurs to form a mixture of a perovskite phase and an oxygen vacancy ordered phase related to brownmillerite. Additional data for the oxygen non stoichiometry are presented.

S. Bandopadhyay; T. Nithyanantham

2006-12-31

297

46 CFR 197.452 - Oxygen cleaning.  

...2014-10-01 2014-10-01 false Oxygen cleaning. 197.452 Section 197...of Diving Equipment § 197.452 Oxygen cleaning. The diving supervisor shall ensure that equipment used with oxygen or oxygen mixtures greater than...

2014-10-01

298

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

299

HYDROGEN-OXYGEN ROCKETS  

NSDL National Science Digital Library

During this activity students build a plastic pipette rocket. The first concept will to learn how igniting varying mixtures of hydrogen and oxygen will affect how far the rocket will fly. Second students will observe and manipulate variables to better understand the fundamental chemistry concepts: principles of combustion reactions, kinetics, stoichiometry, gas mixtures, rocketry, and different types of chemical reactions. Finally, students will assess their own understanding of these chemistry concepts by investigating how NASA scientists launch real rockets into space. One follow-up activity would be to investigate and collect data on a launching a heavier object at the school football field.

Reierson, David

300

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

301

Strain effects on oxygen migration in perovskites.  

PubMed

Fast oxygen transport materials are necessary for a range of technologies, including efficient and cost-effective solid oxide fuel cells, gas separation membranes, oxygen sensors, chemical looping devices, and memristors. Strain is often proposed as a method to enhance the performance of oxygen transport materials, but the magnitude of its effect and its underlying mechanisms are not well-understood, particularly in the widely-used perovskite-structured oxygen conductors. This work reports on an ab initio prediction of strain effects on migration energetics for nine perovskite systems of the form LaBO3, where B = [Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Ga]. Biaxial strain, as might be easily produced in epitaxial systems, is predicted to lead to approximately linear changes in migration energy. We find that tensile biaxial strain reduces the oxygen vacancy migration barrier across the systems studied by an average of 66 meV per percent strain for a single selected hop, with a low of 36 and a high of 89 meV decrease in migration barrier per percent strain across all systems. The estimated range for the change in migration barrier within each system is ±25 meV per percent strain when considering all hops. These results suggest that strain can significantly impact transport in these materials, e.g., a 2% tensile strain can increase the diffusion coefficient by about three orders of magnitude at 300 K (one order of magnitude at 500 °C or 773 K) for one of the most strain-responsive materials calculated here (LaCrO3). We show that a simple elasticity model, which assumes only dilative or compressive strain in a cubic environment and a fixed migration volume, can qualitatively but not quantitatively model the strain dependence of the migration energy, suggesting that factors not captured by continuum elasticity play a significant role in the strain response. PMID:25503536

Mayeshiba, Tam; Morgan, Dane

2015-01-28

302

Copper Proteins and Oxygen  

PubMed Central

A comprehensive survey of the interaction of the copper proteins and oxygen is presented including a correlation of structure, function, and other properties of the known copper oxidases and of hemocyanin. The origin of their blue color and the structure of copper complexes and copper proteins are related to the oxidation state of copper ion and relevant electronic transitions probably arising from the formation of charge transfer complexes. The oxygen reactions of hemocyanin, ceruloplasmin, and cytochrome oxidase show half-saturation values far below the other Cu enzymes. The formation of hydrogen peroxide as a reaction product is associated with the presence of one Cu atom per oxidase molecule or catalytic system. Water is the corresponding product of the other Cu oxidases with four or more Cu atoms per molecule, except for monoamine oxidase. Mechanisms for the oxidase action of the two and four electron transfer Cu oxidases and tyrosinase are proposed. These reactions account for the number, the oxidation-reduction potential, and the oxidation state of Cu in the resting enzyme, the cyclical change from Cu(II) to Cu(I), the diatomic nature of O2, the sequence of the oxidation and reduction reactions, and other salient features. The catalytic reactions involved in the oxidation of ascorbic acid by plant ascorbate oxidase, ceruloplasmin, and Cu(II) are compared. Finally the substrate specificity, inhibitory control, and the detailed mechanism of the oxidase activity of ceruloplasmin are summarized. PMID:4285728

Frieden, Earl; Osaki, Shigemasa; Kobayashi, Hiroshi

1965-01-01

303

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. PMID:23735989

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

2013-01-01

304

Composite oxygen transport membrane  

DOEpatents

A method of producing a composite oxygen ion membrane and a composite oxygen ion membrane in which a porous fuel oxidation layer and a dense separation layer and optionally, a porous surface exchange layer are formed on a porous support from mixtures of (Ln.sub.1-xA.sub.x).sub.wCr.sub.1-yB.sub.yO.sub.3-.delta. and a doped zirconia. In the porous fuel oxidation layer and the optional porous surface exchange layer, A is Calcium and in the dense separation layer A is not Calcium and, preferably is Strontium. Preferred materials are (La.sub.0.8Ca.sub.0.2).sub.0.95Cr.sub.0.5Mn.sub.0.5O.sub.3-.delta. for the porous fuel oxidation and optional porous surface exchange layers and (La.sub.0.8Sr.sub.0.2).sub.0.95Cr.sub.0.5Fe.sub.0.5O.sub.3-.delta. for the dense separation layer. The use of such materials allows the membrane to sintered in air and without the use of pore formers to reduce membrane manufacturing costs. The use of materials, as described herein, for forming the porous layers have application for forming any type of porous structure, such as a catalyst support.

Christie, Gervase Maxwell; Lane, Jonathan A.

2014-08-05

305

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

306

Cerebral oxygenation and hyperthermia  

PubMed Central

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

307

Oxygen isotope fractionation in dissolved oxygen in the deep sea  

Microsoft Academic Search

18O variations in dissolved oxygen have been measured at five stations from the eastern equatorial Pacific, at the GEOSECS-I and -II intercalibration stations in the North Pacific and North Atlantic, and along an Antarctic-South Pacific section from MONSOON expedition. Relative to atmospheric oxygen, dissolved oxygen in the ocean is enriched in 18O up to a maximum of 140\\/00, the extreme

P. Kroopnick; H. Craig

1976-01-01

308

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. PMID:14739800

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

2005-01-01

309

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

2011-03-22

310

Hyperthermal-Atomic-Oxygen Generator  

NASA Technical Reports Server (NTRS)

Small hyperthermal-atomic-oxygen generator (HAOG) compatible with ultrahigh vacuum (UHV) developed. Provides pure flux of ground-state oxygen atoms with mean kinetic energy of approximately 5 eV, accurately simulating conditions in low orbit around Earth, and mounted on any existing UHV processing or analysis system. HAOG clean and compatible with other UHV processing or diagnostic systems and relatively inexpensive and simple to operate. Valuable in studies involving atomic oxygen because added easily to existing systems.

Outlaw, R. A.

1993-01-01

311

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

312

Oxygen abundance in the Sloan Digital Sky Survey  

E-print Network

We present two samples of $\\hii$ galaxies from the Sloan Digital Sky Survey (SDSS) spectroscopic observations data release 3. The electron temperatures($T_e$) of 225 galaxies are calculated with the photoionized $\\hii$ model and $T_e$ of 3997 galaxies are calculated with an empirical method. The oxygen abundances from the $T_e$ methods of the two samples are determined reliably. The oxygen abundances from a strong line metallicity indicator, such as $R_{23}$, $P$, $N2$, and $O3N2$, are also calculated. We compared oxygen abundances of $\\hii$ galaxies obtained with the $T_e$ method, $R_{23}$ method, $P$ method, $N2$ method, and $O3N2$method. The oxygen abundances derived with the $T_e$ method are systematically lower by $\\sim$0.2 dex than those derived with the $R_{23}$ method, consistent with previous studies based on $\\hii$ region samples. No clear offset for oxygen abundance was found between $T_e$ metallicity and $P$, $N2$ and $O3N2$ metallicity. When we studied the relation between N/O and O/H, we found that in the metallicity regime of $\\zoh > 7.95$, the large scatter of the relation can be explained by the contribution of small mass stars to the production of nitrogen. In the high metallicity regime, $\\zoh > 8.2$, nitrogen is primarily a secondary element produced by stars of all masses.

F. Shi; X. Kong; F. Z. Cheng

2006-03-10

313

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

314

Oxygenates from synthesis gas  

SciTech Connect

The direct synthesis of oxygenates starting from synthesis gas is feasible by homogeneous and heterogeneous catalysis. Homogeneous Rh and Ru based catalysts yielding methyl formate and alcohols will be presented. Interestingly, modified heterogeneous catalysts based on {open_quotes}Isobutyl Oel{close_quotes} catalysis, practized in Germany (BRD) up to 1952 and in the former DDR until recently, yield isobutanol in addition to methanol. These {open_quotes}Isobutyl Oel{close_quotes} catalysts are obtained by adding a base such as Li < Na < K < Cs to a Zn-Cr{sub 2}O{sub 3} methanol catalyst. Isobutanol is obtained in up to 15% yield. Our best catalyst a Zr-Zn-Mn-Li-Pd catalyst produced isobotanol up to 60% at a rate of 740g isobutanol per liter catalyst and hour.

Falter, W.; Keim, W. [Institute fur Technische Chemie, Aschen (Germany)

1994-12-31

315

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

316

Distribution of thermal oxygen ions in the near earth magnetosphere  

NASA Astrophysics Data System (ADS)

Based on eleven years of Cluster particle observations, we investigate the distribution of thermal oxygen ions in the near earth magnetosphere with full spatial coverage between 4 to 20 Re. Averaged oxygen ion fluxes are calculated for three energy ranges (E1: 25-136eV; E2: 136eV-3keV; E3 3-35keV) based on measurements from CIS instrument. In a preliminary analysis, we found that oxygen ions of E1 energy are observed mostly in the Polar Regions flowing toward the nightside with average speed of ~20 km/s at 5 Re. They are accelerated to E2 energy range before they arrive at plasmasheet. Clear dawn-dusk asymmetry is observed in the plasmasheet for oxygen ions of the E1 and E2 energy that they are distributed beyond 10 Re on the duskside and beyond 15 Re on the dawnside, suggesting the transportation from ionosphere to plasmasheet is asymmetric for dawn and dusk sides. These oxygen ions are further accelerated in the plasmasheet to E3 energy range and are transported toward the Earth, while they drift westward. These oxygen ions finally reach the dayside, and then either return to the ionosphere or escape from the dayside magnetopause to magnetosheeth. This study provides background knowledge on complete distribution of thermal oxygen ions in the near earth magnetosphere for the modelling and simulation studies on ionosphere-magnetosphere coupling.

Liu, W.; Cao, J.

2013-12-01

317

Clinical oxygen enhancement ratio of tumors in carbon ion radiotherapy: the influence of local oxygenation changes.  

PubMed

The effect of carbon ion radiotherapy on hypoxic tumors has recently been questioned because of low linear energy transfer (LET) values in the spread-out Bragg peak (SOBP). The aim of this study was to investigate the role of hypoxia and local oxygenation changes (LOCs) in fractionated carbon ion radiotherapy. Three-dimensional tumors with hypoxic subvolumes were simulated assuming interfraction LOCs. Different fractionations were applied using a clinically relevant treatment plan with a known LET distribution. The surviving fraction was calculated, taking oxygen tension, dose and LET into account, using the repairable-conditionally repairable (RCR) damage model with parameters for human salivary gland tumor cells. The clinical oxygen enhancement ratio (OER) was defined as the ratio of doses required for a tumor control probability of 50% for hypoxic and well-oxygenated tumors. The resulting OER was well above unity for all fractionations. For the hypoxic tumor, the tumor control probability was considerably higher if LOCs were assumed, rather than static oxygenation. The beneficial effect of LOCs increased with the number of fractions. However, for very low fraction doses, the improvement related to LOCs did not compensate for the increase in total dose required for tumor control. In conclusion, our results suggest that hypoxia can influence the outcome of carbon ion radiotherapy because of the non-negligible oxygen effect at the low LETs in the SOBP. However, if LOCs occur, a relatively high level of tumor control probability is achievable with a large range of fractionation schedules for tumors with hypoxic subvolumes, but both hyperfractionation and hypofractionation should be pursued with caution. PMID:24728013

Antonovic, Laura; Lindblom, Emely; Dasu, Alexandru; Bassler, Niels; Furusawa, Yoshiya; Toma-Dasu, Iuliana

2014-09-01

318

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...

319

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

320

Localized states due to oxygen in II-VI semiconductors  

NASA Astrophysics Data System (ADS)

We study the electronic structure of dilute oxygen impurities in II-VIs (ZnTe, ZnSe, ZnS, CdTe, CdSe, CdS) using fully-relaxed large supercell density functional calculations. We analyze the ensuing localized electronic states, finding that oxygen induces ``cluster states'' (CS) near the conduction band edge, similar to nitrogen localized states in the III-Vs. In contrast to nitrogen in the III-Vs however, the CS in II-VI's exhibit a greater degree of delocalization owing to a greater hybridization with the host band structure. The fundamental character, origin, and energetic alignment of the CS is analyzed using the spectral projection method and hydrostatic pressure calculations. We discuss the ramifications of the CS on the band gap bowing, effective masses, absorption and emission spectra of dilute oxygen alloys.

Kent, Paul; Persson, Clas; Zunger, Alex

2005-03-01

321

Oxygen nonstoichiometry, defect structure and oxygen diffusion in the double perovskite GdBaCo2O6-?.  

PubMed

Oxygen nonstoichiometry of GdBaCo2O6-? was studied by means of the thermogravimetric technique in the temperature range 600-1000 °C. The defect structure model based on the simple cubic perovskite GdCoO3-? was shown to be valid for GdBaCo2O6-? up to temperatures as low as 600 °C. Two independent methods, namely dc-polarization with the YSZ microelectrode and (18)O-isotope exchange with gas phase analysis, were used to determine the oxygen self-diffusion coefficient in the double perovskite GdBaCo2O6-?. All measurements were carried out using ceramic samples identically prepared from the same single phase powder of GdBaCo2O6-?. The experimental data on oxygen nonstoichiometry of GdBaCo2O6-? allowed a precise calculation of the oxygen interphase exchange rate and the oxygen tracer diffusion coefficient on the basis of the isotope exchange measurements. The values of the oxygen self-diffusion coefficient measured by the dc-polarization technique were found to be in very good agreement with the ones of the oxygen tracer diffusion coefficient. PMID:25231733

Tsvetkov, D S; Ananjev, M V; Eremin, V A; Zuev, A Yu; Kurumchin, E Kh

2014-11-14

322

Simulation of the Combustion of Thin Iron Rods in Oxygen in the Adiabatic Approximation  

NASA Astrophysics Data System (ADS)

A mathematical model of the combustion of a thin iron rod in the atmosphere of oxygen with no forced air flow around it has been constructed. This model includes an adjustment parameter that relates the rate of combustion of the rod with its diameter and the content of oxygen. The problem on the combustion of a thin iron rod in oxygen was solved analytically in the adiabatic approximation. The results of calculations were compared with the corresponding experimental data.

Shabunya, S. I.; Martynenko, V. V.; Ignatenko, V. I.; Rostaing, J.-Ch.

2014-11-01

323

Solar-wind interactions with the moon - Role of oxygen ions  

NASA Technical Reports Server (NTRS)

The role of oxygen ions in the solar-wind interactions with the lunar surface due to tenuous atmosphere and magnetic field is examined. The interaction results in an absorption of the solar-wind corpuscles producing no upstream bowshock but a cavity downstream, and the oxygen ionic species undergo a set of reactions with the lunar minerals and the solar-wind derived trapped gases. The oxygen concentrations in the lunar surface material and the solar-wind species flux are discussed, noting that for the contributions of oxygen from the lunar surface grains to the atmosphere, the diffusion coefficients of oxygen atom and molecules should be known. The coefficients are calculated by using the apparent lifetimes of oxygen in the lunar material, and the atmospheric concentration of oxygen atoms and molecules near the lunar surface were compared with the Apollo 17 lunar orbital data.

Mukherjee, N. R.

1979-01-01

324

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. PMID:24748690

Freindl, K.; Partyka-Jankowska, E.; Kara?, W.; Zaj?c, M.; Madej, E.; Spiridis, N.; ?l?zak, M.; ?l?zak, T.; Wi?nios, D.; Korecki, J.

2013-01-01

325

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

PubMed

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. PMID:24748690

Freindl, K; Partyka-Jankowska, E; Kara?, W; Zaj?c, M; Madej, E; Spiridis, N; Sl?zak, M; Sl?zak, T; Wi?nios, D; Korecki, J

2013-11-01

326

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

NASA Astrophysics Data System (ADS)

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.; Kara?, W.; Zaj?c, M.; Madej, E.; Spiridis, N.; ?l?zak, M.; ?l?zak, T.; Wi?nios, D.; Korecki, J.

2013-11-01

327

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

328

Mars oxygen production system design  

NASA Technical Reports Server (NTRS)

The design and construction phase is summarized of the Mars oxygen demonstration project. The basic hardware required to produce oxygen from simulated Mars atmosphere was assembled and tested. Some design problems still remain with the sample collection and storage system. In addition, design and development of computer compatible data acquisition and control instrumentation is ongoing.

Cotton, Charles E.; Pillow, Linda K.; Perkinson, Robert C.; Brownlie, R. P.; Chwalowski, P.; Carmona, M. F.; Coopersmith, J. P.; Goff, J. C.; Harvey, L. L.; Kovacs, L. A.

1989-01-01

329

ANALYTICAL METHODS FOR FUEL OXYGENATES  

EPA Science Inventory

MTBE (and potentially any other oxygenate) may be present at any petroleum UST site, whether the release is new or old, virtually anywhere in the United States. Consequently, it is prudent to analyze samples for the entire suite of oxygenates as identified in this protocol (i.e....

330

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

331

Phase fluorometric dissolved oxygen sensor  

Microsoft Academic Search

The design and performance of a ruggedised dissolved oxygen (DO) probe, which is based on phase fluorometric detection of the quenched fluorescence of an oxygen-sensitive ruthenium complex, is reported. The complex is entrapped in a porous hydrophobic sol–gel matrix that has been optimised for this application. The LED excitation and photodiode detection are employed in a dipstick probe configuration, with

C. McDonagh; C. Kolle; A. K. McEvoy; D. L. Dowling; A. A. Cafolla; S. J. Cullen; B. D. MacCraith

2001-01-01

332

How to Measure Dissolved Oxygen  

NSDL National Science Digital Library

This web page, hosted by the Washington State Department of Ecology, offers a general overview of dissolved oxygen and how it is measured. It includes protocols for measuring dissolved oxygen in turbulent waters as well as using the Winkler titration method. The site also features links to measuring other water quality parameters such as pH, nutrients, and turbidity.

Washington State University Department of Ecology

333

Effect of bladderbox alarms during venoarterial extracorporeal membrane oxygenation on cerebral oxygenation and hemodynamics in lambs.  

PubMed

To determine the effects of bladderbox alarms during venoarterial extracorporeal membrane oxygenation (va-ECMO) on cerebral oxygenation and hemodynamics, six lambs were prospectively treated with va-ECMO and bladderbox alarms were simulated. Changes in concentrations of oxyhemoglobin (deltacO2Hb), deoxyhemoglobin (deltacHHb), and total Hb (deltactHb) were measured using near infrared spectrophotometry. Fluctuations in Hb oxygenation index (deltaHbD) and cerebral blood volume (deltaCBV) were calculated. Heart rate (HR), mean arterial pressure (MAP), blood flow in the left carotid artery (Qcar), and central venous pressure (CVP) were registered. Bladderbox alarms were simulated by increasing the ECMO flow or partially clamping the venous cannula and resolved by decreasing the ECMO flow, unclamping the cannula, or intravascular volume administration. CBV, HbD, MAP, and Qcar decreased significantly during bladderbox alarms, whereas HR and CVP increased. After the bladderbox alarms, CBV and HbD increased significantly to values above baseline. For HbD, this increase was higher during intravascular volume administration.MAP, Qcar, and CVP recovered to preexperiment values but increased further with volume administration. HR was increased at the end of our measurements. We conclude that Bladderbox alarms during va-ECMO treatment result in significant fluctuations in cerebral oxygenation and hemodynamics, a possible risk factor for intracranial lesions. PMID:19707177

de Mol, Amerik C; Gerrits, Luella C; van Heijst, Arno F J; Menssen, Jan; van der Staak, Frans H J M; Liem, Kian D

2009-12-01

334

K-shell Photoabsorption of Oxygen Ions  

E-print Network

Extensive calculations of the atomic data required for the spectral modelling of the K-shell photoabsorption of oxygen ions have been carried out in a multi-code approach. The present level energies and wavelengths for the highly ionized species (electron occupancies 2 4, lack of measurements, wide experimental scatter, and discrepancies among theoretical values are handicaps in reliable accuracy assessments. The radiative and Auger rates are expected to be accurate to 10% and 20%, respectively, except for transitions involving strongly mixed levels. Radiative and Auger dampings have been taken into account in the calculation of photoabsorption cross sections in the K-threshold region, leading to overlapping lorentzian shaped resonances of constant widths that cause edge smearing. The behavior of the improved opacities in this region has been studied with the XSTAR modelling code using simple constant density slab models, and is displayed for a range of ionization parameters.

J. Garcia; C. Mendoza; M. A. Bautista; T. W. Gorczyca; T. R. Kallman; P. Palmeri

2004-11-13

335

Method for Trace Oxygen Detection  

NASA Technical Reports Server (NTRS)

Trace levels of molecular oxygen are measured by introducing a gas containing the molecular oxygen into a target zone, and impacting the molecular oxygen in the target zone with electrons at the O(-) resonant energy level for dissociative electron attachment to produce O(-) ions. Preferably, the electrons have an energy of about 4 to about 10 eV. The amount of O(-) ions produced is measured, and is correlated with the molecular oxygen content in the target zone. The technique is effective for measuring levels of oxygen below 50 ppb. and even less than 1 ppb. The amount of O(-) can be measured in a quadrupole mass analyzer. Best results are obtained when the electrons have an energy of about 6 to about 8 eV. and preferably about 6.8 eV. The method can be used for other species by selecting the appropriate electron energy level.

Man, Kim Fung (Inventor); Boumsellek, Said (Inventor); Chutjian, Ara (Inventor)

1997-01-01

336

Research on rechargeable oxygen electrodes  

NASA Technical Reports Server (NTRS)

Studies were carried out on a number of factors which may influence the behavior of the platinum electrocatalyst of oxygen electrodes for use in rechargeable metal-oxygen batteries or hydrogen-oxygen fuel cells. The effects of pretreatments for various potentials and added ionic species, which could be present in such systems, were studied with reguard to: (1) the state of surface oxidation, (2) platinum dissolution, (3) the kinetics of oxygen evolution and reduction (including the role of hydrogen peroxide), and (4) changes in porous electrode structure. These studies were carried out on smooth platinum, platinized platinum, and Teflon-bonded platinum black electrodes in carefully purified electrolyte solutions. The main factors which appear to affect rechargeable oxygen electrode performance and life are: (1) the buildup of a refractory anodic layer on extended cycling, and (2) the dissolution of platinum.

Giner, J.; Malachesky, P. A.; Holleck, G.

1971-01-01

337

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); Cao, Weenqing (Los Alamos, NM)

2007-08-28

338

The role of oxygen and water on molybdenum nanoclusters for electro catalytic ammonia production.  

PubMed

The presence of water often gives rise to oxygen adsorption on catalyst surfaces through decomposition of water and the adsorbed oxygen or hydroxide species often occupy important surfaces sites, resulting in a decrease or a total hindrance of other chemical reactions taking place at that site. In this study, we present theoretical investigations of the influence of oxygen adsorption and reduction on pure and nitrogen covered molybdenum nanocluster electro catalysts for electrochemical reduction of N2 to NH3 with the purpose of understanding oxygen and water poisoning of the catalyst. Density functional theory calculations are used in combination with the computational hydrogen electrode approach to calculate the free energy profile for electrochemical protonation of O and N2 species on cuboctahedral Mo13 nanoclusters. The calculations show that the molybdenum nanocluster will preferentially bind oxygen over nitrogen and hydrogen at neutral bias, but under electrochemical reaction conditions needed for nitrogen reduction, oxygen adsorption is severely weakened and the adsorption energy is comparable to hydrogen and nitrogen adsorption. The potentials required to reduce oxygen off the surface are -0.72 V or lower for all oxygen coverages studied, and it is thus possible to (re)activate (partially) oxidized nanoclusters for electrochemical ammonia production, e.g., using a dry proton conductor or an aqueous electrolyte. At lower oxygen coverages, nitrogen molecules can adsorb to the surface and electrochemical ammonia production via the associative mechanism is possible at potentials as low as -0.45 V to -0.7 V. PMID:24605277

Howalt, Jakob G; Vegge, Tejs

2014-01-01

339

The role of oxygen and water on molybdenum nanoclusters for electro catalytic ammonia production  

PubMed Central

Summary The presence of water often gives rise to oxygen adsorption on catalyst surfaces through decomposition of water and the adsorbed oxygen or hydroxide species often occupy important surfaces sites, resulting in a decrease or a total hindrance of other chemical reactions taking place at that site. In this study, we present theoretical investigations of the influence of oxygen adsorption and reduction on pure and nitrogen covered molybdenum nanocluster electro catalysts for electrochemical reduction of N2 to NH3 with the purpose of understanding oxygen and water poisoning of the catalyst. Density functional theory calculations are used in combination with the computational hydrogen electrode approach to calculate the free energy profile for electrochemical protonation of O and N2 species on cuboctahedral Mo13 nanoclusters. The calculations show that the molybdenum nanocluster will preferentially bind oxygen over nitrogen and hydrogen at neutral bias, but under electrochemical reaction conditions needed for nitrogen reduction, oxygen adsorption is severely weakened and the adsorption energy is comparable to hydrogen and nitrogen adsorption. The potentials required to reduce oxygen off the surface are ?0.72 V or lower for all oxygen coverages studied, and it is thus possible to (re)activate (partially) oxidized nanoclusters for electrochemical ammonia production, e.g., using a dry proton conductor or an aqueous electrolyte. At lower oxygen coverages, nitrogen molecules can adsorb to the surface and electrochemical ammonia production via the associative mechanism is possible at potentials as low as ?0.45 V to ?0.7 V. PMID:24605277

Howalt, Jakob G

2014-01-01

340

Phanerozoic Atmospheric Oxygen  

NASA Astrophysics Data System (ADS)

Theoretical calculations, based on both the chemical and isotopic composition of sedimentary rocks, indicate that atmospheric O2 has varied appreciably over Phanerozoic time, with a notable excursion during the Permo-Carboniferous reaching levels as high as 35% O2. This agrees with measurements of the carbon isotopic composition of fossil plants together with experiments and calculations on the effect of O2 on photosynthetic carbon isotope fractionation. The principal cause of the excursion was the rise of large vascular land plants and the consequent increased global burial of organic matter. Higher levels of O2 are consistent with the presence of Permo-Carboniferous giant insects, and preliminary experiments indicate that insect body size can increase with elevated O2. Higher O2 also may have caused more extensive, possibly catastrophic, wildfires. To check this, realistic burning experiments are needed to examine the effects of elevated O2 on fire behavior.

Berner, Robert A.

341

Short communication Nonlinear analysis of gait kinematics to track changes in oxygen consumption  

E-print Network

Short communication Nonlinear analysis of gait kinematics to track changes in oxygen consumption the effectiveness of dynamical systems and fractal analysis in this study. Further, we selected, oxygen consumption. For the fractal analysis, utilizing stride interval data, we calculated fractal dimension. For the dynamical

Chelidze, David

342

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

343

Electrocatalysts for oxygen electrodes  

NASA Astrophysics Data System (ADS)

The overall objective of this research was an in-depth understanding of the factors controlling O2 reduction and generation on various electrocatalysts and the use of this understanding to identify much higher activity, stable catalysts. The following is a brief summary of the research for the period 1 April 1989 to 31 March 1990. (1) Transition metal monomeric and sheet-polymeric macrocycle catalysts -- The iron tetrasulfonated phthalocyanine (FeTsPc) complex adsorbed on an electrode surface has high activity for the 4-electron reduction of O2 to water or OH(exp -) in alkaline solutions. (2) Polymer-modified electrodes -- Poly(4-vinyl pyridine) (PVP)-modified electrodes with adsorbed CoTsPc exhibited much higher catalytic activity for O2 reduction than the electrode with only adsorbed CoTsPc in acid solutions. (3) Transition metal oxide catalysts and bifunctional electrodes -- Anion-exchange membranes were found to greatly improve the performance of the pyrochlore-based bifunctional oxygen electrodes when operating in the O2 generation mode. (4) Catalyst supports -- The use of mildly fluorinated carbon blacks as catalyst supports for platinum was explored in cooperation with the Electrosynthesis Company (ESC).

Yeager, E.

1990-10-01

344

The history of subcutaneous oxygen therapy  

Microsoft Academic Search

Soon after the discovery of oxygen, experiments began on the use of oxygen for therapeutic purposes, including subcutaneous administration of oxygen, on humans and animals. The history of subcutaneous oxygen therapy (SQOT) is examined in the context of the growing understanding of the use and methods of oxygen administration. Little was written about this therapy until the 19th century, despite

Timothy B. Curry; Douglas R. Bacon; Richard H. Rho

2006-01-01

345

Low Oxygen Environments in Chesapeake Bay  

E-print Network

Low Oxygen Environments in Chesapeake Bay Jeremy Testa Chesapeake Biological Laboratory University of Maryland Center for Environmental Science Why we care about low oxygen? What causes low oxygen? Where and When does Chesapeake Bay lose oxygen? #12;#12;Hypoxia and Chesapeake Animals Low dissolved oxygen

Boynton, Walter R.

346

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

347

Insensitivity of cerebral oxygen transport to oxygen affinity of hemoglobin-based oxygen carriers  

PubMed Central

The cerebrovascular effects of exchange transfusion of various cell-free hemoglobins that possess different oxygen affinities are reviewed. Reducing hematocrit by transfusion of a non-oxygen-carrying solution dilates pial arterioles on the brain surface and increases cerebral blood flow to maintain a constant bulk oxygen transport to the brain. In contrast, transfusion of hemoglobins with P50 of 4–34 Torr causes constriction of pial arterioles that offsets the decrease in blood viscosity to maintain cerebral blood flow and oxygen transport. The autoregulatory constriction is dependent on synthesis of 20-HETE from arachidonic acid. This oxygen-dependent reaction is apparently enhanced by facilitated oxygen diffusion from the red cell to the endothelium arising from increased plasma oxygen solubility in the presence of low or high-affinity hemoglobin. Exchange transfusion of recombinant hemoglobin polymers with P50 of 3 and 18 Torr reduces infarct volume from experimental stroke. Cell-free hemoglobins do not require a P50 as high as red blood cell hemoglobin to facilitate oxygen delivery. PMID:18230370

Koehler, Raymond C.; Fronticelli, Clara; Bucci, Enrico

2008-01-01

348

Calcul scientifique et serveurs de calculCalcul scientifique et serveurs de calcul Serveurs de calcul : contexte,Serveurs de calcul : contexte,  

E-print Network

Calcul scientifique et serveurs de calculCalcul scientifique et serveurs de calcul Serveurs de calcul : contexte,Serveurs de calcul : contexte, enjeux et administrationenjeux et administration Violaine Louvet, 13 septembre 2007 #12;Calcul scientifique et serveurs de calculCalcul scientifique et

van Tiggelen, Bart

349

Association between oxygen vacancies and trivalent dopants in crystalline and amorphous ZnO  

E-print Network

Density functional theory calculations are used to investigate the structure and binding energies of clusters formed between oxygen vacancies and trivalent dopant atoms (indium, gallium and aluminium) substituted into zinc oxide. Our results show...

Muñoz Ramo, D.; Chroneos, A.; Rushton, M. J. D.; Bristowe, P .D.

2014-03-31

350

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

351

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

352

Electric and magnetic susceptibilities of gaseous oxygen: Present data and modern theory compared  

NASA Astrophysics Data System (ADS)

We used a cross capacitor to measure the relative dielectric permittivity ?r of O2 at 273, 293, and 323K and at pressures up to 6.5MPa . Simultaneously we measured oxygen’s complex refractive index n using a quasispherical cavity resonator at frequencies between 2.4 and 7.3GHz . The combined results from these measurements determine oxygen’s frequency-dependent, relative magnetic permeability ?r(f,p,T) with an uncertainty of less than 1% of (?r-1) at pressures above 2MPa . Regression of these data to a model for oxygen’s impact—broadened microwave spectrum allowed us to determine two quantities that are, in principle, amenable to calculation: the molar magnetic susceptibility in the limits of zero pressure and zero frequency ?M00meas??M(0,0,293.15K) and the second magnetic virial coefficient b? . With oxygen’s electronic g factor constrained to 2.0039±0.0003 (the value known from laser magnetic resonance, EPR, and molecular beam experiments) we obtained ?M00meas=(42.92±0.06)×10-9m3mol-1 and b?=-1.8±0.5cm3mol-1 . The result for ?M00meas is consistent with a recent ab initio calculation ?M00meas/?M00calc=0.9998±0.0014 . Our measurements of oxygen’s magnetic susceptibility are the first made relative to the susceptibility of helium calculated ab initio. All previous measurements were made relative to the diamagnetic susceptibility of water. These previous measurements, published in 1943 or earlier, span the wider range 0.975oxygen: (1.7456±0.0003)×10-40Fm2 , which deviates by +0.7 and -0.1% from two recent ab initio calculations.

May, Eric F.; Moldover, Michael R.; Schmidt, James W.

2008-09-01

353

Oxygenates vs. synthesis gas  

SciTech Connect

Methanol synthesis from H{sub 2}/CO has been carried out at 7.6 MPa over zirconia-supported copper catalysts. Catalysts with nominal compositions of 10/90 mol% and 30/70 mol% Cu/ZrO{sub 2} were used in this study. Additionally, a 3 mol% cesium-doped 10/90 catalyst was prepared to study the effect of doping with heavy alkali, and this promoter greatly increased the methanol productivity. The effects of CO{sub 2} addition, water injection, reaction temperature, and H{sub 2}/C0 ratio have been investigated. Both CO{sub 2} addition to the synthesis gas and cesium doping of the catalyst promoted methanol synthesis, while inhibiting the synthesis of dimethyl ether. Injection of water, however, was found to slightly suppress methanol and dimethyl ether formation while being converted to CO{sub 2} via the water gas shift reaction over these catalysts. There was no clear correlation between copper surface area and catalyst activity. Surface analysis of the tested samples revealed that copper tended to migrate and enrich the catalyst surface. The concept of employing a double-bed reactor with a pronounced temperature gradient to enhance higher alcohol synthesis was explored, and it was found that utilization of a Cs-promoted Cu/ZnO/Cr{sub 2}O{sub 3} catalyst as a first lower temperature bed and a Cs-promoted ZnO/Cr{sub 2}O{sub 3} catalyst as a second high-temperature bed significantly promoted the productivity of 2-methyl-1-propanol (isobutanol) from H{sub 2}/CO synthesis gas mixtures. While the conversion of CO to C{sub 2+} oxygenates over the double-bed configuration was comparable to that observed over the single Cu-based catalyst, major changes in the product distribution occurred by the coupling to the zinc chromite catalyst; that is, the productivity of the C{sub 1}-C{sub 3} alcohols decreased dramatically, and 2-methyl branched alcohols were selectively formed. The desirable methanol/2-methyl oxygenate molar ratios close to 1 were obtained in the present double-bed system that provides the feedstock for the synthesis of high octane and high cetane ethers, where the isobutanol productivity was as high as 139 g/kg cat/hr. Higher alcohol synthesis has been investigated over a Cs/Cu/ZnO/Cr{sub 2}O{sub 3} catalyst at temperatures higher (up to 703K) than those previously utilized, and no sintering of the catalyst was observed during the short-term testing. However, the higher reaction temperatures led to lower CO conversion levels and lower yield of alcohols, especially of methanol, because of equilibrium limitations. With the double catalyst bed configuration, the effect of pressure in the range of 7.6--12.4 MPa on catalyst activity and selectivity was studied. The upper bed was composed of the copper-based catalyst at 598K, and the lower bed consisted of a copper-free Cs-ZnO/Cr{sub 2}O{sub 3} catalyst at a high temperature of 678K. High pressure was found to increase CO conversion to oxygenated products, although the increase in isobutanol productivity did not keep pace with that of methanol. It was also shown that the Cs/Cu/ZnO/Cr{sub 2}O{sub 3} catalyst could be utilized to advantage as the second-bed catalyst at 613--643K instead of the previously used copper-free Cs-ZnO/ Cr{sub 2}O{sub 3} catalyst at higher temperature, With double Cs/Cu/ZnO/Cr{sub 2}O{sub 3} catalysts, high space time yields of up to 202 g/kg cat/hr, with high selectivity to isobutanol, were achieved.

Kamil Klier; Richard G. Herman; Alessandra Beretta; Maria A. Burcham; Qun Sun; Yeping Cai; Biswanath Roy

1999-04-01

354

Hemoglobin–Oxygen Equilibrium Curves Measured during Enzymatic Oxygen Consumption  

Microsoft Academic Search

A rapid, new method to measure hemoglobin–oxygen equilibrium curves is described using the protocatechuic acid\\/protocatechuic acid 3,4-dioxygenase system [C. Bull and D. P. Ballou (1981)J. Biol. Chem.256, 12673–12680] to deoxygenate hemoglobin solutions enzymatically. The reaction is followed by simultaneous measurements of hemoglobin spectra using a diode array spectrophotometer and oxygen tensions using a polarographic O2microelectrode. Multicomponent analysis allows the determination

Kim D. Vandegriff; Ronald J. Rohlfs; Michael D. Magde; Robert M. Winslow

1998-01-01

355

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

356

Feasibility Analysis of Liquefying Oxygen Generated from Water Electrolysis Units on Lunar Surface  

NASA Technical Reports Server (NTRS)

Concepts for liquefying oxygen (O2) generated from water electrolysis subsystems on the Lunar surface were explored. Concepts for O2 liquefaction units capable of generating 1.38 lb/hr (0.63 kg/hr) liquid oxygen (LOX) were developed. Heat and mass balance calculations for the liquefaction concepts were conducted. Stream properties, duties of radiators, heat exchangers and compressors for the selected concepts were calculated and compared.

Jeng, Frank F.

2009-01-01

357

Electronic Structure of Oxygen Dangling Bond in Glassy SiO2: The Role of Hyperconjugation  

Microsoft Academic Search

The electronic structure and the nature of optical transitions in oxygen dangling bond in silica glass, the nonbridging oxygen hole center (NBOHC), were calculated. The calculation reproduced well the peak positions and oscillator strengths of the well-known optical absorption bands at 2.0 and 4.8eV, and of the recently discovered absorption band at 6.8eV. The 2.0eV band was attributed to transition

Takenobu Suzuki; Linards Skuja; Koichi Kajihara; Masahiro Hirano; Toshio Kamiya; Hideo Hosono

2003-01-01

358

Vertical distribution of triple oxygen isotopic composition of dissolved oxygen in the northwestern Pacific  

NASA Astrophysics Data System (ADS)

Oxygen-17 excess of dissolved oxygen calculated from ?18O and ?17O is not affected by oxygen consumption process but controlled only by processes of primary production and air-water gas transfer. Evaluating gross primary productivity using the 17O-excess in ocean surface water are one of the most advanced geochemical researches for last 10 years. Oxygen-17 excess below ocean mixed/photic layer has not been much investigated because it might be out of focus for estimating present primary productivity, except for the purpose to correct diapycnal mixing effect on surface water. In principle, water mass which has not been affected both by photosynthesis and gas transfer after its separation from ocean surface could preserve 17O-excess value where the water mass was at the surface. The purpose of this study is to determine the vertical distribution of 17O-excess from the surface to the bottom of northwestern Pacific to know whether 17O-excess could really preserve its "original" value after the long and dark travel. Near stations K2 and KNOT, water mass which has a density of 26.8 ?? is observed at depth between 100 and 300 m. This water mass is mainly originated from bottom water in the Okhotsk Sea and spreading widely to entire northwestern Pacific, which is called North Pacific Intermediate Water (NPIW). NPIW is found at depth of 700 m at station S1. Samplings were conducted by two R/V Mirai cruises (MR10-06, Oct-Nov 2010; MR11-02, Feb-Mar 2011). Dissolved oxygen gas was purified by the method of Sarma et al. (2003) and its isotopic composition was determined by dual-inlet isotope ratio mass spectrometer (Thermo Scientific Delta Plus). Gross primary productivities at mixed layer estimated by 17O-excess were well consistent with those by conventional light and dark bottle incubations for stations K2 and S1.

Abe, Osamu; Honda, Makio; Saino, Toshiro

2013-04-01

359

A clinical evaluation of the Terumo Capiox SX18R hollow fiber oxygenator.  

PubMed

The Terumo Capiox SX18R is a commercially available, low prime, reverse phase, hollow fiber membrane oxygenator. The oxygenator consists of a 1.8 m2 microporous polypropylene hollow fiber bundle, a 2200 cm2 tubular stainless steel heat exchanger, and an open hard shell venous reservoir with integral cardiotomy filter. The Terumo Capiox SX18R oxygenator was evaluated to determine its clinical oxygenating performance. Blood samples were drawn from 25 patients yielding 114 data points. The following parameters were recorded: blood flow, cardiac index, gas flow, gas to blood flow ratio, and oxygen fraction. Samples were assayed for hematocrit, hemoglobin, arterial and venous blood gas values, and venous oxygen saturation. The data and assay results were used to calculate arterial, venous, and membrane gas oxygen content, oxygen transfer, shunt fraction, and oxygen diffusion capacity. The Terumo Capiox SX18R oxygenator performed adequately with sufficient oxygen transfer reserve and carbon dioxide clearance under a variety of clinical conditions for the tested population. PMID:10155360

Dekkers, P A; Lawson, D S; Smigla, G R; Shearer, I R

1995-09-01

360

Spatiotemporal oxygen sensing using dual emissive boron dye-polylactide nanofibers.  

PubMed

Oxygenation in tissue scaffolds continues to be a limiting factor in regenerative medicine despite efforts to induce neovascularization or to use oxygen-generating materials. Unfortunately, many established methods to measure oxygen concentration, such as using electrodes, require mechanical disturbance of the tissue structure. To address the need for scaffold-based oxygen concentration monitoring, a single-component, self-referenced oxygen sensor was made into nanofibers. Electrospinning process parameters were tuned to produce a biomaterial scaffold with specific morphological features. The ratio of an oxygen sensitive phosphorescence signal to an oxygen insensitive fluorescence signal was calculated at each image pixel to determine an oxygenation value. A single component boron dye-polymer conjugate was chosen for additional investigation due to improved resistance to degradation in aqueous media compared to a boron dye polymer blend. Standardization curves show that in fully supplemented media, the fibers are responsive to dissolved oxygen concentrations less than 15 ppm. Spatial (millimeters) and temporal (minutes) ratiometric gradients were observed in vitro radiating outward from the center of a dense adherent cell grouping on scaffolds. Sensor activation in ischemia and cell transplant models in vivo show oxygenation decreases on the scale of minutes. The nanofiber construct offers a robust approach to biomaterial scaffold oxygen sensing. PMID:25426706

Bowers, Daniel T; Tanes, Michael L; Das, Anusuya; Lin, Yong; Keane, Nicole A; Neal, Rebekah A; Ogle, Molly E; Brayman, Kenneth L; Fraser, Cassandra L; Botchwey, Edward A

2014-12-23

361

PRIMARY RESEARCH PAPER Water column oxygen demand and sediment oxygen flux  

E-print Network

PRIMARY RESEARCH PAPER Water column oxygen demand and sediment oxygen flux: patterns of oxygen dissolved oxygen (DO) levels often occur during summer in tidal creeks along the southeastern coast of the USA. We analyzed rates of oxygen loss as water-column biochemical oxygen demand (BOD5) and sediment

Mallin, Michael

362

Local order in liquid oxygen: computer simulations with point charge model  

NASA Astrophysics Data System (ADS)

Molecular dynamics (MD) simulations are performed to study liquid oxygen in the temperature range from 84 to 120 K. The oxygen molecule is modeled as the Lennard-Jones diatomic carrying three point charges. This potential model is shown to reproduce the second virial coefficient in the temperatures range from 80 to 400 K and the heats of vaporization. The calculated structure factor for liquid oxygen is found to be in good agreement with neutron scattering data at 84 K. The orientational correlations in liquid oxygen are examined.

Zasetsky, Alexander Yu.; Svishchev, Igor M.

2001-02-01

363

Polycyclic Aromatic Triptycenes: Oxygen Substitution Cyclization Strategies  

E-print Network

The cyclization and planarization of polycyclic aromatic hydrocarbons with concomitant oxygen substitution was achieved through acid catalyzed transetherification and oxygen-radical reactions. The triptycene scaffold ...

VanVeller, Brett

364

Productivity and heat generation of fermentation under oxygen limitation  

Microsoft Academic Search

The elemental balance equation of microbial growth on carbon substrate of generalized composition is given. Yield of dried\\u000a bio-mass per oxygenY\\u000a o is calculated. Yield per oxygenY\\u000a o is found to be determined by two factors—carbon yieldy and the reducing power of substrate ?\\u000a s\\u000a . The mode of dependence ofY\\u000a o on these two quantities is studied. The energetic

I. G. Minkevich; V. K. Eroshin

1973-01-01

365

Effective Potential Energies and Transport Properties for Nitrogen and Oxygen  

NASA Technical Reports Server (NTRS)

The results of recent theoretical studies for N--N2, O--O2, N2--N2 interactions are applied to the transport properties of nitrogen and oxygen gases. The theoretical results are used to select suitable oxygen interaction energies from previous work for determining the diffusion and viscosity coefficients at high temperatures. A universal formulation is applied to determine the collision integrals for O2--O2 interactions at high temperatures and to calculate certain ratios for determining higher-order collision integrals.

Stallcop, James R.; Partridge, Harry; Levin, Eugene; Kwak, Dochan (Technical Monitor)

2001-01-01

366

Oxygen sensing and metabolic homeostasis.  

PubMed

Oxygen-sensing mechanisms have evolved to maintain cell and tissue homeostasis since the ability to sense and respond to changes in oxygen is essential for survival. The primary site of oxygen sensing occurs at the level of the carotid body which in response to hypoxia signals increased ventilation without the need for new protein synthesis. Chronic hypoxia activates cellular sensing mechanisms which lead to protein synthesis designed to alter cellular metabolism so cells can adapt to the low oxygen environment without suffering toxicity. The master regulator of the cellular response is hypoxia-inducible factor (HIF). Activation of this system under condition of hypobaric hypoxia leads to weight loss accompanied by increased basal metabolic rate and suppression of appetite. These effects are dose dependent, gender and genetic specific, and results in adverse effects if the exposure is extreme. Hypoxic adipose tissue may represent a unified cellular mechanism for variety of metabolic disorders, and insulin resistance in patients with metabolic syndrome. PMID:25132648

Palmer, Biff F; Clegg, Deborah J

2014-11-01

367

The Measurement of Dissolved Oxygen  

ERIC Educational Resources Information Center

Describes an experiment in environmental chemistry which serves to determine the dissolved oxygen concentration in both fresh and saline water. Applications of the method at the undergraduate and secondary school levels are recommended. (CC)

Thistlethwayte, D.; And Others

1974-01-01

368

Voice over IP Calculator  

NSDL National Science Digital Library

The Voice over IP Calculator Web site actually consists of four free online tools that can be used to estimate bandwidth requirements and voice paths for a planned VoIP system. The four tools are: Lines and IP Bandwidth Calculator, Erlangs and Bandwidth Calculator, Minutes and Lines Calculator, and Erlangs and Lines Calculator. Each utility is very easy to use, but is mainly intended for experienced IT workers.

369

Dilute Oxygen Combustion Phase IV Final Report  

SciTech Connect

Novel furnace designs based on Dilute Oxygen Combustion (DOC) technology were developed under subcontract by Techint Technologies, Coraopolis, PA, to fully exploit the energy and environmental capabilities of DOC technology and to provide a competitive offering for new furnace construction opportunities. Capital cost, fuel, oxygen and utility costs, NOx emissions, oxide scaling performance, and maintenance requirements were compared for five DOC-based designs and three conventional air5-fired designs using a 10-year net present value calculation. A furnace direct completely with DOC burners offers low capital cost, low fuel rate, and minimal NOx emissions. However, these benefits do not offset the cost of oxygen and a full DOC-fired furnace is projected to cost $1.30 per ton more to operate than a conventional air-fired furnace. The incremental cost of the improved NOx performance is roughly $6/lb NOx, compared with an estimated $3/lb. NOx for equ8pping a conventional furnace with selective catalytic reduction (SCCR) technology. A furnace fired with DOC burners in the heating zone and ambient temperature (cold) air-fired burners in the soak zone offers low capital cost with less oxygen consumption. However, the improvement in fuel rate is not as great as the full DOC-fired design, and the DOC-cold soak design is also projected to cost $1.30 per ton more to operate than a conventional air-fired furnace. The NOx improvement with the DOC-cold soak design is also not as great as the full DOC fired design, and the incremental cost of the improved NOx performance is nearly $9/lb NOx. These results indicate that a DOC-based furnace design will not be generally competitive with conventional technology for new furnace construction under current market conditions. Fuel prices of $7/MMBtu or oxygen prices of $23/ton are needed to make the DOC furnace economics favorable. Niche applications may exist, particularly where access to capital is limited or floor space limitations are critical. DOC technology will continue to have a highly competitive role in retrofit applications requiring increases in furnace productivity.

Riley, M.F.

2003-04-30

370

Oxygen chemisorption on copper (110)  

NASA Astrophysics Data System (ADS)

High resolution electron energy loss spectroscopy (EELS) and angle-resolved ultra-violet photoelectron spectroscopy (UPS) have been used: (1) to study a surface phonon of Cu(110) as a function of oxygen coverage, (2) to identify oxygen adsorption site(s) in the p(2×1)O, c(6×2)O, and disordered oxygen overlayer (formed by O 2 exposure at 100 K), and (3) to determine whether molecular adsorption or dissociation of O 2 followed by atomic adsorption occurs after oxygen exposure at 100 K. With EELS, a continuous shift in energy of the surface phonon as a function of oxygen exposure at 300 K is observed. Our EELS data for the p(2×1)O overlayer support previous reports of a single long-bridge adsorption site, while indicating two sites are populated in the c(6×2)O overlayer: a long-bridge site and a four-coordinated site. The long-bridge site is populated at all coverages while the four-coordinated sites is occupied only after high exposures (?2×10 4 L) at room temperature, or after exposures >2 L at low temperature (100 K). For both conditions the oxygen coverages are greater than 0.5 monolayer. Also, EELS and complementary UPS data clearly show that oxygen adsorbs dissociatively on Cu(110) after O 2 exposure at 100 K. At this temperature, LEED results indicate that the oxygen atoms are adsorbed without long-range order; however, local adsorption sites, which are similar to those in the c(6×2)O surface, are observed.

Mundenar, J. M.; Baddorf, A. P.; Plummer, E. W.; Sneddon, L. G.; Didio, R. A.; Zehner, D. M.

1987-09-01

371

Oxygen and Early Animal Evolution  

NASA Astrophysics Data System (ADS)

It is often hypothesized that the rise of animals was triggered by an increase in O2 levels in the atmosphere and oceans. However, this hypothesis is remarkably difficult to test, because the timing of animal divergences is poorly resolved, the physiology of early animals is often unknown, estimates of past pO2 levels come with large error bars, and causal relationships between oxygenation and animal evolution are difficult to establish. Nonetheless, existing phylogenetic, paleontological, and geochemical data indicate that the evolution of macroscopic animals and motile macrometazoans with energetically expensive lifestyles may be temporally coupled with ocean oxygenation events in the Ediacaran Period. Thus, it is plausible that ocean oxygenation may have been a limiting factor in the early evolution of macroscopic, complex, and metabolically aggressive animals (particularly bilaterian animals). However, ocean oxygenation and animal evolution were likely engaged in two-way interactions: Ediacaran oxygenation may have initially lifted a physiological barrier for the evolution of animal size, motility, and active lifestyles, but subsequent animal diversification in the Paleozoic may have also changed oceanic redox structures. Viewed in a broader context, the early evolutionary history of animals was contingent upon a series of events, including genetic preparation (developmental genetics), environmental facilitation (oceanic oxygenation), and ecological escalation (Cambrian explosion), but the rise of animals to ecological importance also had important geobiological impacts on oceanic redox structures, sedimentary fabrics, and global geochemical cycles.

Xiao, S.

2012-12-01

372

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

E-print Network

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 each step is lower than for the same process on Pt surface. In contrast to the catalysis on metal surface the maximal coverage of doped graphene is lower and depends on the corrugation of graphene. Changes of the energy barriers caused by oxygen load and corrugation are also discussed.

Boukhvalov, Danil W

2011-01-01

373

Structure Evolution of Graphene Oxide during Thermally Driven Phase Transformation: Is the Oxygen Content Really Preserved?  

E-print Network

A mild annealing procedure was recently proposed for the scalable enhancement of graphene oxide (GO) properties with the oxygen content preserved, which was demonstrated to be attributed to the thermally driven phase separation. In this work, the structure evolution of GO with mild annealing is closely investigated. It reveals that in addition to phase separation, the transformation of oxygen functionalities also occurs, which leads to the slight reduction of GO membranes and further the enhancement of GO properties. These results are further supported by the density functional theory based calculations. The results also show that the amount of chemically bonded oxygen atoms on graphene decreases gradually and we propose that the strongly physisorbed oxygen species constrained in the holes and vacancies on GO lattice might be responsible for the preserved oxygen content during the mild annealing procedure. The present experimental results and calculations indicate that both the diffusion and transformation of...

Sun, Pengzhan; Liu, He; Wang, Kunlin; Wu, Dehai; Xu, Zhiping; Zhu, Hongwei

2014-01-01

374

Oxygen discharge and post-discharge kinetics experiments and modeling for the electric oxygen-iodine laser system.  

PubMed

Laser oscillation at 1315 nm on the I(2P1/2)-->I(2P3/2) transition of atomic iodine has been obtained by a near resonant energy transfer from O2(a1Delta) produced using a low-pressure oxygen/helium/nitric oxide discharge. In the electric discharge oxygen-iodine laser (ElectricOIL) the discharge production of atomic oxygen, ozone, and other excited species adds levels of complexity to the singlet oxygen generator (SOG) kinetics which are not encountered in a classic purely chemical O2(a1Delta) generation system. The advanced model BLAZE-IV has been introduced to study the energy-transfer laser system dynamics and kinetics. Levels of singlet oxygen, oxygen atoms, and ozone are measured experimentally and compared with calculations. The new BLAZE-IV model is in reasonable agreement with O3, O atom, and gas temperature measurements but is under-predicting the increase in O2(a1Delta) concentration resulting from the presence of NO in the discharge and under-predicting the O2(b1Sigma) concentrations. A key conclusion is that the removal of oxygen atoms by NOX species leads to a significant increase in O2(a1Delta) concentrations downstream of the discharge in part via a recycling process; however, there are still some important processes related to the NOX discharge kinetics that are missing from the present modeling. Further, the removal of oxygen atoms dramatically inhibits the production of ozone in the downstream kinetics. PMID:17461557

Palla, A D; Zimmerman, J W; Woodard, B S; Carroll, D L; Verdeyen, J T; Lim, T C; Solomon, W C

2007-07-26

375

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.

376

Origin of deep subgap states in amorphous indium gallium zinc oxide: Chemically disordered coordination of oxygen  

NASA Astrophysics Data System (ADS)

The origin of the deep subgap states in amorphous indium gallium zinc oxide (a-IGZO), whether intrinsic to the amorphous structure or not, has serious implications for the development of p-type transparent amorphous oxide semiconductors. We report that the deep subgap feature in a-IGZO originates from local variations in the oxygen coordination and not from oxygen vacancies. This is shown by the positive correlation between oxygen composition and subgap intensity as observed with X-ray photoelectron spectroscopy. We also demonstrate that the subgap feature is not intrinsic to the amorphous phase because the deep subgap feature can be removed by low-temperature annealing in a reducing environment. Atomistic calculations of a-IGZO reveal that the subgap state originates from certain oxygen environments associated with the disorder. Specifically, the subgap states originate from oxygen environments with a lower coordination number and/or a larger metal-oxygen separation.

Sallis, S.; Butler, K. T.; Quackenbush, N. F.; Williams, D. S.; Junda, M.; Fischer, D. A.; Woicik, J. C.; Podraza, N. J.; White, B. E.; Walsh, A.; Piper, L. F. J.

2014-06-01

377

In situ global method for measurement of oxygen demand and mass transfer  

SciTech Connect

Two aerobic microorganisms, Saccharomycopsis lipolytica and Brevibacterium lactofermentum, have been used in a study of mass transfer and oxygen uptake from a global perspective using a closed gas system. Oxygen concentrations in the gas and liquid were followed using oxygen electrodes, and the results allowed for easy calculation of in situ oxygen transport. The cell yields on oxygen for S. lipolytica and B. lactofermentum were 1.01 and 1.53 g/g respectively. The mass transfer coefficient was estimated as 10 h{sup {minus}1} at 500 rpm for both fermentations. The advantages with this method are noticeable since the use of model systems may be avoided, and the in situ measurements of oxygen demand assure reliable data for scale-up.

Klasson, K.T. [Oak Ridge National Lab., TN (United States). Chemical Technology Div.; Lundbaeck, K.M.O.; Clausen, E.C.; Gaddy, J.L. [Univ. of Arkansas, Fayetteville, AR (United States). Dept. of Chemical Engineering

1997-05-01

378

Predicting oxygen vacancy non-stoichiometric concentration in perovskites from first principles  

NASA Astrophysics Data System (ADS)

Formation of oxygen vacancies by introducing various mixed-valent cation dopants is a common practice to improve the cathode performance in solid oxide fuel cells. A computational procedure is developed in this work to predict the equilibrium oxygen vacancy non-stoichiometric concentrations at experimentally relevant temperatures and oxygen partial pressures for both bulk and surface oxide phases. The calculations are based on the first-principles density functional theory and a constrained free-energy functional. Quantitative agreements are found by direct comparisons to the thermogravimetry and solid electrolyte coulometry measurements for the strontium-doped lanthanum cobalt iron oxides at different compositions. Our results indicate that the oxygen vacancies are energetically stabilized at surfaces for all temperatures and all oxygen partial pressures, while such surface stabilization effects become stronger at higher temperatures and lower oxygen partial pressures.

Luo, Heng; Shin, Yongwoo; Yu, Yang; Cetin, Deniz; Ludwig, Karl; Pal, Uday; Basu, Soumendra N.; Gopalan, Srikanth; Lin, Xi

2014-12-01

379

DFT studies of oxygen dissociation on the 116-atom platinum truncated octahedron particle.  

PubMed

Density functional theory calculations are performed to investigate oxygen dissociation on 116-atom truncated octahedron platinum particles. This work builds on results presented previously [Jennings et al., Nanoscale, 2014, 6, 1153], where it was shown that shell flexibility played an important role in facilitating fast oxygen dissociation. In this study, through investigation of the larger particle size, it is shown that oxygen dissociation on the (111) facet of pure platinum species is still aided by shell flexibility at larger sizes. Only the hollow sites close to the edges of the (111) facet mediate oxygen dissociation; oxygen is bound too weakly at other hollow sites for dissociation to occur. Further studies are performed on the (100) facet, which is larger for the Pt116 particle than for either the Pt38 or Pt79 ones. Much higher dissociation barriers are found on the (100) facet compared to the (111) facet, where the bridge sites are favourable for oxygen dissociation. PMID:25070716

Jennings, Paul C; Aleksandrov, Hristiyan A; Neyman, Konstantin M; Johnston, Roy L

2014-11-19

380

Origin of deep subgap states in amorphous indium gallium zinc oxide: Chemically disordered coordination of oxygen  

SciTech Connect

The origin of the deep subgap states in amorphous indium gallium zinc oxide (a-IGZO), whether intrinsic to the amorphous structure or not, has serious implications for the development of p-type transparent amorphous oxide semiconductors. We report that the deep subgap feature in a-IGZO originates from local variations in the oxygen coordination and not from oxygen vacancies. This is shown by the positive correlation between oxygen composition and subgap intensity as observed with X-ray photoelectron spectroscopy. We also demonstrate that the subgap feature is not intrinsic to the amorphous phase because the deep subgap feature can be removed by low-temperature annealing in a reducing environment. Atomistic calculations of a-IGZO reveal that the subgap state originates from certain oxygen environments associated with the disorder. Specifically, the subgap states originate from oxygen environments with a lower coordination number and/or a larger metal-oxygen separation.

Sallis, S.; Williams, D. S. [Materials Science and Engineering, Binghamton University, Binghamton, New York 13902 (United States); Butler, K. T.; Walsh, A. [Center for Sustainable Technologies and Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY (United Kingdom); Quackenbush, N. F. [Department of Physics, Applied Physics, and Astronomy, Binghamton University, Binghamton, New York 13902 (United States); Junda, M.; Podraza, N. J. [Department of Physics and Astronomy, University of Toledo, Toledo, Ohio 43606 (United States); Fischer, D. A.; Woicik, J. C. [Materials Science and Engineering Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States); White, B. E.; Piper, L. F. J., E-mail: lpiper@binghamton.edu [Department of Physics, Applied Physics, and Astronomy, Binghamton University, Binghamton, New York 13902 (United States); Materials Science and Engineering, Binghamton University, Binghamton, New York 13902 (United States)

2014-06-09

381

Existence of basal oxygen vacancies on the rutile TiO2(110 ) surface  

NASA Astrophysics Data System (ADS)

On a rutile TiO2(110 ) surface, vacancies at the bridging oxygen sites are thought to be major surface point defects and strongly influence the surface phenomena. Using systematic density functional theory (DFT) calculations, however, we show that vacancies at the basal oxygen sites have comparable formation energies to the bridging oxygen vacancies. The correction of self-interaction error for localized Ti 3 d states in DFT plays an important role for correctly describing the relative stability of the oxygen vacancies as well as the electronic structures. This new type of stable surface oxygen vacancy can be formed with a similar amount of the bridging oxygen vacancy in a relatively dilute condition, which may affect atom deposition and chemical reactions on the surface.

Matsunaga, Katsuyuki; Tanaka, Yusuke; Toyoura, Kazuaki; Nakamura, Atsutomo; Ikuhara, Yuichi; Shibata, Naoya

2014-11-01

382

Development of oxygen meters for the use in lead-bismuth  

NASA Astrophysics Data System (ADS)

Liquid lead and the eutectic lead-bismuth alloy (PbBi) are considered both as a spallation target and coolant of an accelerator driven system (ADS) for the transmutation of long-lived actinides from nuclear waste into shorter living isotopes. It is known that both, pure lead and PbBi, exhibit a high corrosivity against austenitic and ferritic steels, because of the high solubility of nickel and iron in PbBi. One way of reducing the strong corrosion is the in situ formation of stable oxide scales on the steel surfaces. Thermodynamic calculations and experimental results have confirmed, that the control of oxygen in lead or PbBi within a defined activity range can lead to acceptable corrosion rates. To control the level of oxygen dissolved in lead or PbBi, a sensor for measuring the oxygen activity is required. Within the sodium fast breeder reactor development, an adequate technique was established for estimating oxygen in liquid sodium. This knowledge can be used for other metal/oxygen systems like oxygen in PbBi. For measuring the oxygen activity and calculating its concentration, the relevant thermodynamic and solubility data have to be considered. Two reference electrode systems: Pt/air and In/In 2O 3 (both based on yttria-stabilized zirconia as solid electrolyte) are investigated to evaluate their electromotive force (EMF)-temperature dependency in saturated and unsaturated oxygen solutions. Results with both types of oxygen meters in PbBi at different oxygen levels were compared with theoretical calculations. The experimental data indicate that the design, construction and integration of an oxygen control unit in a large scale PbBi-loop seems to be very feasible.

Konys, J.; Muscher, H.; Voß, Z.; Wedemeyer, O.

2001-07-01

383

Oxygen isotope corrections for online ?34S analysis  

USGS Publications Warehouse

Elemental analyzers have been successfully coupled to stable-isotope-ratio mass spectrometers for online measurements of the ?34S isotopic composition of plants, animals and soils. We found that the online technology for automated ?34S isotopic determinations did not yield reproducible oxygen isotopic compositions in the SO2 produced, and as a result calculated ?34S values were often 1–3‰ too high versus their correct values, particularly for plant and animal samples with high C/S ratio. Here we provide empirical and analytical methods for correcting the S isotope values for oxygen isotope variations, and further detail a new SO2-SiO2 buffering method that minimizes detrimental oxygen isotope variations in SO2.

Fry, B.; Silva, S.R.; Kendall, C.; Anderson, R.K.

2002-01-01

384

Alternative Method for the Thermospheric Atomic Oxygen Density Determination  

NASA Technical Reports Server (NTRS)

Atomic oxygen density in the upper thermosphere (approximately 300 km) can be calculated using ground based incoherent scatter radar and Fabry-Perot interferometer measurements. Burnside et al. was the first to try this method, but Buonsanto et al. provided an extensive treatment of the method in 1997. This paper further examines the method using 46 nights of data collected over six years and the latest information on the oxygen collision frequency. The method is compared with the MSIS (Mass Spectrometer Incoherent Scatter)-86 atomic oxygen prediction values, which are based upon in situ rocket born and satellite measurements from the 70s to the mid-80s. In general, the method supports the MSIS-86 model, but indicates several areas of discrepancy. Furthermore, no direct correlation is found between the geomagnetic conditions and the difference between the method and MSIS-86 predictions.

Bennett, A. C.; Omidvar, K.; Atlas, Robert (Technical Monitor)

2001-01-01

385

Metallurgy. Origin of dramatic oxygen solute strengthening effect in titanium.  

PubMed

Structural alloys are often strengthened through the addition of solute atoms. However, given that solute atoms interact weakly with the elastic fields of screw dislocations, it has long been accepted that solution hardening is only marginally effective in materials with mobile screw dislocations. By using transmission electron microscopy and nanomechanical characterization, we report that the intense hardening effect of dilute oxygen solutes in pure ?-Ti is due to the interaction between oxygen and the core of screw dislocations that mainly glide on prismatic planes. First-principles calculations reveal that distortion of the interstitial sites at the screw dislocation core creates a very strong but short-range repulsion for oxygen that is consistent with experimental observations. These results establish a highly effective mechanism for strengthening by interstitial solutes. PMID:25657243

Yu, Qian; Qi, Liang; Tsuru, Tomohito; Traylor, Rachel; Rugg, David; Morris, J W; Asta, Mark; Chrzan, D C; Minor, Andrew M

2015-02-01

386

EVALUATING AN INNOVATIVE OXYGEN SENSOR FOR REMOTE SUBSURFACE OXYGEN MEASUREMENTS  

SciTech Connect

Oxygen is a primary indicator of whether anaerobic reductive dechlorination and similar redox based processes contribute to natural attenuation remedies at chlorinated solvent contaminated sites. Thus, oxygen is a viable indicator parameter for documenting that a system is being sustained in an anaerobic condition. A team of researchers investigated the adaptation of an optical sensor that was developed for oceanographic applications. The optical sensor, because of its design and operating principle, has potential for extended deployment and sensitivity at the low oxygen levels relevant to natural attenuation. The results of the research indicate this tool will be useful for in situ long-term monitoring applications, but that the traditional characterization tools continue to be appropriate for characterization activities.

Millings, M; Brian Riha, B; Warren Hyde, W; Karen Vangelas, K; Brian02 Looney, B

2006-10-12

387

Superposition of Waves Calculator  

NSDL National Science Digital Library

The Superposition of Waves Calculators show the result of adding two or more waves of the form y = A * cos ( k * x + phi ) or y = A * cos ( k * x + phi - omega * t ). The calculation of wave packets is also included.

Joiner, David; The Shodor Education Foundation, Inc.

388

Calculate Your Radiation Dose  

MedlinePLUS

... Ionizing & Non-Ionizing Radiation Understanding Radiation: Calculate Your Radiation Dose Health Effects Main Page Exposure Pathways Calculate ... of the US do you live in? Internal radiation (in your body): From food and water, (e. ...

389

On Approximate Calculations.  

ERIC Educational Resources Information Center

The ability to undertake approximate calculations and to get a rough feel for data is an important skill which should not be overlooked. Presents some ideas for teaching and assessing approximate calculation. Contains 13 references. (Author/ASK)

Jolliffe, Flavia

1999-01-01

390

Calculate Your Radiation Dose  

NSDL National Science Digital Library

This calculator by the Environmental Protection Agency allows you to estimate your annual radiation dose. The calculator is easy to use and the bottom of the page includes links to more information about radiation dosage.

2011-05-12

391

OXYGEN ADSORPTION ON NITROGEN CONTAINING CARBON SURFACES  

E-print Network

OXYGEN ADSORPTION ON NITROGEN CONTAINING CARBON SURFACES Alejandro Montoya, Jorge O. Gil, Fanor-rich site of the carbon basal plane of graphite and then, it dissociates into oxygen atoms.1,2 Oxygen atoms at the edge of the carbon surface can form covalent bonds with oxygen. These sites can chemisorb

Truong, Thanh N.

392

Sources of Weld Metal Oxygen Contamination During  

E-print Network

) Sources of Weld Metal Oxygen Contamination During Submerged Arc Welding The oxygen level of submerged arc weld metal is controlled by Si02 decomposition in most acidic fluxes whereas the oxygen level of weld metal oxygen contamination and pro- vide guidelines for design and selec- tion of welding

Eagar, Thomas W.

393

Oxygen-Partial-Pressure Sensor for Aircraft Oxygen Mask  

NASA Technical Reports Server (NTRS)

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

Kelly, Mark; Pettit, Donald

2003-01-01

394

Geochemical Calculations Using Spreadsheets.  

ERIC Educational Resources Information Center

Spreadsheets are well suited to many geochemical calculations, especially those that are highly repetitive. Some of the kinds of problems that can be conveniently solved with spreadsheets include elemental abundance calculations, equilibrium abundances in nuclear decay chains, and isochron calculations. (Author/PR)

Dutch, Steven Ian

1991-01-01

395

Calculating a Mineral's Density  

NSDL National Science Digital Library

Students will use the Density=Mass/Volume formula to calculate the density of an unknown mineral. By using water displacement and a triple beam balance students will collect measurements of volume and mass for an unknown mineral. With this data, they will calculate the mineral's density then identify the mineral based on calculated density.

Andrea Distelhurst

2011-10-05

396

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.

Mark McCaffrey

397

The calculation phase equilibria  

E-print Network

Chapter 15 The calculation phase equilibria Geothermometry of metamorphic I: and geobarometry to examine how to calculate metamorphic phase equilibria in systems that approach real rocks. All and it is the equation that forms the basis of all calculations of mineral equilibria as a function of these variables

Holliday, Vance T.

398

Long-term oxygen therapy.  

PubMed

This article provides an overview of the status of long-term oxygen therapy (LTOT). In the United States, payment cutbacks are occurring as a result of congressionally mandated competitive bidding and capped rental programs. These Medicare programs are discussed. These legislative and regulatory changes may result in reduced patient access to appropriate oxygen-delivery systems that meet medical needs, including optimal ambulation. Prescribing LTOT is addressed in this article, as is the need for adequate patient education. The importance of appropriate monitoring and reassessment is presented. The use of an LTOT collaborative care model is discussed. Although the new intermittent flow oxygen-delivery systems have potential benefits, there is consensus that each patient should be tested on the specific device because of variability in delivery and patient response. Feasible locations for patient education and monitoring are identified. PMID:21285057

Christopher, Kent L; Porte, Phillip

2011-02-01

399

The interaction of oxygen with small gold clusters  

NASA Astrophysics Data System (ADS)

Presented in this work are the results of a quantum chemical study of oxygen adsorption on small Aun and Aun- (n=2,3) clusters. Density functional theory (DFT), second order perturbation theory (MP2), and singles and doubles coupled cluster theory with perturbative triples [CCSD(T)] methods have been used to determine the geometry and the binding energy of oxygen to Aun. The multireference character of the wave functions has been studied using the complete active space self-consistent field method. There is considerable disagreement between the oxygen binding energies provided by CCSD(T) calculations and those obtained with DFT. The disagreement is often qualitative, with DFT predicting strong bonds where CCSD(T) predicts no bonds or structures that are bonded but have energies that exceed those of the separated components. The CCSD(T) results are consistent with experimental measurements, while DFT calculations show, at best, a qualitative agreement. Finally, the lack of a regular pattern in the size and the sign of the errors [as compared to CCSD(T)] is a disappointing feature of the DFT results for the present system: it is not possible to give a simple rule for correcting the DFT predictions (e.g., a useful rule would be that DFT predicts stronger binding of O2 by about 0.3 eV). It is likely that the errors in DFT appear not because of gold, but because oxygen binding to a metal cluster is a particularly difficult problem.

Varganov, Sergey A.; Olson, Ryan M.; Gordon, Mark S.; Metiu, Horia

2003-08-01

400

Energetic oxygen and sulfur in the Jovian magnetosphere  

NASA Astrophysics Data System (ADS)

Measurements made in the Jovian magnetosphere by the cosmic ray subsystem on Voyager 1 and 2 are reported. Energy spectra of oxygen ions in the energy range 1-20 MeV/nuc between 5 and 20 Jovian radii are presented, and phase space densities are calculated. A steep positive radial gradient in the phase space density of the energetic oxygen ions is observed, indicating an inward diffusive flow. The upper limit on the rate at which oxygen ions with greater than 400 MeV/nuc-G diffuse across 10 Jovian radii is calculated to be 5 x 10 to the 21st ions per second, indicating that about 10 to the -7th of the ions from Io are accelerated to over 400 MeV/nuc-G and diffuse to 10 Jovian radii. Observations also suggest that oxygen and sulfur ions in the Io plasma torus diffuse radially outward, are nonadiabatically accelerated in a region outside 17 Jovian radii, and diffuse inward and outward from the accelerated region.

Gehrels, N.; Stone, E. C.; Trainor, J. H.

1981-10-01

401

Study of the reaction of atomic oxygen with aerosols  

NASA Technical Reports Server (NTRS)

The rate of disappearance of atomic oxygen was measured at several pressures in a fast flow pyrex reactor system with its walls treated with (NH4)2SO4 (s), H2SO4 (l), and NH4CL (s). Atomic oxygen, P-3 was generated by dissociation of pure, low pressure oxygen in a microwave discharge. Concentrations of atomic oxygen were measured at several stations in the reactor system using chemiluminescent titration with NO2. Recombination efficiencies calculated from experimentally determined wall recombination rate constants are in good agreement with reported values for clean Pyrex and an H2SO4 coated wall. The recombination efficiency for (NH4)2SO4, results in a slightly lower value than for H2S04. A rapid exothermic reaction between atomic oxygen and the NH4Cl wall coating prevented recombination efficiency determination for this coating. The results show that the technique is highly useful for wall recombination measurements and as a means of extrapolating to the case of free stream aerosol-gas interactions.

Akers, F. I.; Wightman, J. P.

1975-01-01

402

Oxygen electrode reaction in molten carbonate fuel cells  

SciTech Connect

Molten carbonate fuel cell system is a leading candidate for the utility power generation because of its high efficiency for fuel to AC power conversion, capability for an internal reforming, and a very low environmental impact. However, the performance of the molten carbonate fuel cell is limited by the oxygen reduction reaction and the cell life time is limited by the stability of the cathode material. An elucidation of oxygen reduction reaction in molten alkali carbonate is essential because overpotential losses in the molten carbonate fuel cell are considerably greater at the oxygen cathode than at the fuel anode. Oxygen reduction on a fully-immersed gold electrode in a lithium carbonate melt was investigated by electrochemical impedance spectroscopy and cyclic voltammetry to determine electrode kinetic and mass transfer parameters. The dependences of electrode kinetic and mass transfer parameters on gas composition and temperature were examined to determine the reaction orders and the activation energies. The results showed that oxygen reduction in a pure lithium carbonate melt occurs via the peroxide mechanism. A mass transfer parameter, D{sub O}{sup 1/2}C{sub O}, estimated by the cyclic voltammetry concurred with that calculated by the EIS technique. The temperature dependence of the exchange current density and the product D{sub O}{sup 1/2}C{sub O} were examined and the apparent activation energies were determined to be about 122 and 175 kJ/ mol, respectively.

Appleby, A.J.; White, R.E.

1992-07-07

403

Influence of disease state on oxygen transport in newborn piglets.  

PubMed

Optimally, oxygen delivery (DO2) should be sufficient to provide for adequate oxygen consumption (VO2) while avoiding O2 toxicity. Physiologically a critical level of DO2 has been described, below which decreases in oxygen supply begin to impair VO2, leading to venous hypercarbia and tissue acidosis. We predicted that this critical level would be influenced by factors such as underlying disease state and oxygen needs. Newborn piglets were exposed either to hypoxia (n = 6) or to group-B beta-hemolytic streptococcal sepsis (n = 6). Hemodynamic parameters were measured; DO2 and VO2 were calculated and compared within and between the groups. 'Critical DO2' was defined as the point at which decreases in DO2 began to produce concomitant decreases in VO2. This was observed at 9 ml/kg/min in hypoxic vs. 21 ml/kg/min in septic piglets. The 'critical Vsat' was defined as the venous O2 saturation beyond which tissue acidosis, as defined by base excess, developed. 'Critical VsatS' were 17% for hypoxic vs. 21% for septic animals. In summary, septic newborn piglets had higher critical DO2 and critical Vsat than hypoxic piglets, implying that they became oxygen supply dependent and developed tissue acidosis at higher levels of DO2 and Vsat, respectively. PMID:7993946

Hammerman, C

1994-01-01

404

Inner Retinal Oxygen Delivery and Metabolism in Streptozotocin Diabetic Rats  

PubMed Central

Purpose. The purpose of the study is to report global measurements of inner retinal oxygen delivery (DO2_IR) and oxygen metabolism (MO2_IR) in streptozotocin (STZ) diabetic rats. Methods. Phosphorescence lifetime and blood flow imaging were performed in rats 4 (STZ/4wk; n = 10) and 6 (STZ/6wk; n = 10) weeks following injection of STZ to measure retinal arterial (O2A) and venous (O2V) oxygen contents and total retinal blood flow (F). DO2_IR and MO2_IR were calculated from measurements of F and O2A and of F and the arteriovenous oxygen content difference, respectively. Data in STZ rats were compared to those in healthy control rats (n = 10). Results. Measurements of O2A and O2V were not significantly different among STZ/4wk, STZ/6wk, and control rats (P ? 0.28). Likewise, F was similar among all groups of rats (P = 0.81). DO2_IR measurements were 941 ± 231, 956 ± 232, and 973 ± 243 nL O2/min in control, STZ/4wk, and STZ/6wk rats, respectively (P = 0.95). MO2_IR measurements were 516 ± 175, 444 ± 103, and 496 ± 84 nL O2/min in control, STZ/4wk, and STZ/6wk rats, respectively (P = 0.37). Conclusions. Global inner retinal oxygen delivery and metabolism were not significantly impaired in STZ rats in early diabetes. PMID:24550355

Wanek, Justin; Teng, Pang-yu; Blair, Norman P.; Shahidi, Mahnaz

2014-01-01

405

Oxygen isotopic exchange: A useful tool for characterizing oxygen conducting oxides  

E-print Network

Oxygen isotopic exchange: A useful tool for characterizing oxygen conducting oxides Bassat J we obtain in both cases data concerning the oxygen diffusion in the bulk and the oxygen exchange with regards to the oxygen reduction reaction. Detailed experimental and analytical processes are given

Paris-Sud XI, Université de

406

High temperature sorbents for oxygen  

NASA Technical Reports Server (NTRS)

A sorbent capable of removing trace amounts of oxygen (ppt) from a gas stream at a high temperature above 200 C comprising a porous alumina silicate support, such as zeolite, containing from 1 to 10 percent by weight of ion exchanged transition metal, such as copper or cobalt ions, and 0.05 to 1.0 percent by weight of an activator selected from a platinum group metal such as platinum is described. The activation temperature, oxygen sorption, and reducibility are all improved by the presence of the platinum activator.

Sharma, Pramod K. (inventor)

1994-01-01

407

High Temperature Sorbents for Oxygen  

NASA Technical Reports Server (NTRS)

A sorbent capable of removing trace amounts of oxygen (ppt) from a gas stream at a high temperature above 200 C is introduced. The sorbent comprises a porous alumina silicate support such as zeolite containing from 1 to 10 percent by weight of ion exchanged transition metal such as copper or cobalt ions and 0.05 to 1.0 percent by weight of an activator selected from a platinum group metal such as platinum. The activation temperature, oxygen sorption and reducibility are all improved by the presence of the platinum activator.

Sharma, Pramod K. (Inventor)

1996-01-01

408

Microcirculatory oxygen transport and utilization.  

PubMed

The cardiovascular system (macrocirculation) circulates blood throughout the body, but the microcirculation is responsible for modifying tissue perfusion and adapting it to metabolic demand. Hemodynamic assessment and monitoring of the critically ill patient is typically focused on global measures of oxygen transport and utilization, which do not evaluate the status of the microcirculation. Despite achievement and maintenance of global hemodynamic and oxygenation goals, patients may develop microcirculatory dysfunction with associated organ failure. A thorough understanding of the microcirculatory system under physiologic conditions will assist the clinician in early recognition of microcirculatory dysfunction in impending and actual disease states. PMID:25169685

Hamlin, Shannan K; Parmley, C Lee; Hanneman, Sandra K

2014-09-01

409

Integrated Oxygen-Recovery System  

NASA Technical Reports Server (NTRS)

System for revitalizing breathing air in enclosed environment converts carbon dioxide and water to oxygen and methane. Chemical conversions take place in reactor module containing solid-metal-cathode water electrolyzer integrated with Sabatier reactor. According to design estimates, fully developed version of system sized to maintain breathable air for four persons, occupies 67 percent less volume, weighs 60 percent less, and consumes 3.4 percent less power than system of same capacity in which electrolyzer and Sabatier reactor are distinct components. Although oxygen primary desired end product in system originally contemplated, product methane also of value in industrial version of system.

Schubert, F. H.; Davenport, R. J.; Lee, M. G.

1996-01-01

410

A lithium oxygen secondary battery  

NASA Technical Reports Server (NTRS)

Some recent work on a lithium-oxygen secondary battery is reported in which stabilized zirconia oxygen vacancy conducting solid electrolytes were used for the effective separation of respective half-cell reactions. The electroactive material consisted of alloys possessing the general composition Li(x)FeSi2 immersed in a ternary molten salt comprising LiF, LiCl, and Li2O. The manufacture of the cell is described, and discharge-current voltage curves for partially charged cells are shown and discussed. A galvanostatic IR free-changing curve and an IR-free charge-discharge curve are also shown.

Semkow, Krystyna W.; Sammells, Anthony F.

1987-01-01

411

Pilot Plant Makes Oxygen Difluoride  

NASA Technical Reports Server (NTRS)

Pilot plant makes oxygen difluoride highly-energetic, space-storable oxidizer not made commercially. Designed to handle reactants, product, and byproduct, most of which highly reactive, corrosive, and toxic. Oxygen difluoride evolves continuously from reactor containing potassium hydroxide in water at 10 degree C. Collection tanks alternated; one filled while other drained to storage cylinder. Excess OF2 and F2 dissipated in combustion of charcoal in burn barrel. Toxic byproduct, potassium fluoride, reacted with calcium hydroxide to form nontoxic calcium fluoride and to regenerate potassium hydroxide. Equipment processes toxic, difficult-to-make substance efficiently and safely.

Humphrey, Marshall F.; Lawton, Emil A.

1989-01-01

412

Materials International Space Station Experiment-6 (MISSE-6) Atomic Oxygen Fluence Monitor Experiment  

NASA Technical Reports Server (NTRS)

An atomic oxygen fluence monitor was flown as part of the Materials International Space Station Experiment-6 (MISSE-6). The monitor was designed to measure the accumulation of atomic oxygen fluence with time as it impinged upon the ram surface of the MISSE 6B Passive Experiment Container (PEC). This was an active experiment for which data was to be stored on a battery-powered data logger for post-flight retrieval and analysis. The atomic oxygen fluence measurement was accomplished by allowing atomic oxygen to erode two opposing wedges of pyrolytic graphite that partially covered a photodiode. As the wedges of pyrolytic graphite erode, the area of the photodiode that is illuminated by the Sun increases. The short circuit current, which is proportional to the area of illumination, was to be measured and recorded as a function of time. The short circuit current from a different photodiode, which was oriented in the same direction and had an unobstructed view of the Sun, was also to be recorded as a reference current. The ratio of the two separate recorded currents should bear a linear relationship with the accumulated atomic oxygen fluence and be independent of the intensity of solar illumination. Ground hyperthermal atomic oxygen exposure facilities were used to evaluate the linearity of the ratio of short circuit current to the atomic oxygen fluence. In flight, the current measurement circuitry failed to operate properly, thus the overall atomic oxygen mission fluence could only be estimated based on the physical erosion of the pyrolytic graphite wedges. The atomic oxygen fluence was calculated based on the knowledge of the space atomic oxygen erosion yield of pyrolytic graphite measured from samples on the MISSE 2. The atomic oxygen fluence monitor, the expected result and comparison of mission atomic oxygen fluence based on the erosion of the pyrolytic graphite and Kapton H atomic oxygen fluence witness samples are presented in this paper.

Banks, Bruce A.; Miller, Sharon K.; Waters, Deborah L.

2010-01-01

413

A mechanism for production of singlet oxygen by acidification of hypochlorite  

NASA Astrophysics Data System (ADS)

A mechanism for the production of singlet oxygen by acidification of hypochlorite in aqueous solution is proposed based on electron structure calculations. The mechanism involves two transition states and a peroxyhypochlorous acid intermediate. The calculations include six explicit water molecules to give some allowance for solvation of the produced electrolyte. The theoretical level is the density functional theory and the isodensity polarized continuum method.

Jacobsen, Jan; Knak Jensen, Svend J.

2007-11-01

414

Transport coefficients of air, argon-air, nitrogen-air, and oxygen-air plasmas  

Microsoft Academic Search

Calculated values of the viscosity, thermal conductivity and electrical conductivity of air and mixtures of air and argon, air and nitrogen, and air and oxygen at high temperatures are presented. In addition, combined ordinary, pressure, and thermal diffusion coefficients are given for the gas mixtures. The calculations, which assione local thermodynamic equilibrium, are performed for atmospheric pressure plasmas in the

A. B. Murphy

1995-01-01

415

Evaluation of worn SSME low pressure liquid oxygen turbopump bearing  

NASA Technical Reports Server (NTRS)

The larger of two ball bearings used to support the rotor of the low pressure liquid oxygen turbopump in each of the shuttle main engines was analyzed to identify the cause of severe internal wear. The actual operating loads were calculated along with their direction and length of time at each load based on the size and location of the race contact paths. It is suggested that the engine component design be modified to reduce bearing stress and enhance lubrication.

Dufrane, K. F.; Kannel, J. W.

1978-01-01

416

First results on oxygen self-diffusion in ?-Pu2O3 investigated by molecular dynamics  

NASA Astrophysics Data System (ADS)

The oxygen self-diffusion of ?-Pu2O3 has been investigated by molecular dynamics method. The empirical potential of ?-Pu2O3 has been fitted. Based on this new potential, the calculation results, such as cell parameters, bulk modulus and dielectric constants, are well consistent with experimental data and previous reports. In this study, we systematically calculated the oxygen self-diffusion coefficients of ?-Pu2O3 in the temperature range of 750-2100 K and the activation energy of ?-Pu2O3 was obtained from these calculations.

Yu, Huilong; Meng, Daqiao; Huang, He; Li, Gan

2014-09-01

417

Oxygen Transport Ceramic Membranes  

SciTech Connect

The present quarterly report describes some of the investigations on the structural properties of dense OTM bars provided by Praxair and studies on newer composition of Ti doped Ti-substituted perovskites, La{sub 0.7}Sr{sub 0.3}Mn{sub 1-x}Ti{sub x}O{sub 3}, with 0 {le} x {le} 0.20, were investigated by neutron diffraction, magnetization, electric resistivity, and magnetoresistance (MR) measurements. All samples show a rhombohedral structure (space group R3C) from 10 K to room temperature. At room temperature, the cell parameters a, c and the unit cell volume increase with increasing Ti content. However, at 10 K, the cell parameter a has a maximum value for x = 0.10, and decreases for x > 0.10, while the unit cell volume remains nearly constant for x > 0.10. The average (Mn,Ti)-O bond length increases up to x = 0.15, and the (Mn,Ti)-O-(Mn,Ti) bond angle decreases with increasing Ti content to its minimum value at x = 0.15 at room temperature. Below the Curie temperature TC, the resistance exhibits metallic behavior for the x {le} 0.05 samples. A metal (semiconductor) to insulator transition is observed for the x {ge} 0.10 samples. A peak in resistivity appears below TC for all samples, and shifts to a lower temperature as x increases. The substitution of Mn by Ti decreases the 2p-3d hybridization between O and Mn ions, reduces the bandwidth W, and increases the electron-phonon coupling. Therefore, the TC shifts to a lower temperature and the resistivity increases with increasing Ti content. A field-induced shift of the resistivity maximum occurs at x {le} 0.10 compounds. The maximum MR effect is about 70% for La{sub 0.7}Sr{sub 0.3}Mn{sub 0.8}Ti{sub 0.2}O{sub 3}. The separation of TC and the resistivity maximum temperature T{sub {rho},max} enhances the MR effect in these compounds due to the weak coupling between the magnetic ordering and the resistivity as compared with La{sub 0.7}Sr{sub 0.3}MnO{sub 3}. The bulk densities of the membranes were determined using the Archimedes method. The bulk density was 5.029 and 5.57 g/cc for LSFT and dual phase membranes, respectively. The microstructure of the dual phase membrane was analyzed using SEM. It is evident from the micrograph that the microstructure is composed of dual phases. The dense circular regions are enclosed by the less dense, continuous phase which accommodates most of the pores. The pores are normally aggregated and found clustered along the dense regions where as the dense regions do not have pores. Upon closer observation of the micrograph it is revealed that the dense region has a clear circular cleavage or crack as their boundary. The circular cleavage clearly encompasses a dense region and which consists of no pore or any flaw that is visible. The size distribution of the dense, discontinuous regions is varying from 5 to 20 {micro}m with a D{sub 50} of 15 {micro}m. The grain size distribution was estimated from the micrographs using image analysis and a unimodal distribution of grains was observed with an average grain size of 1.99 {micro}m. The chemical compositions of the membranes were analyzed using EDS analysis and no other impurities were observed. The XRD analysis was carried out for the membranes and the phase purity was confirmed. The fracture toughness of LSFT membranes at room temperature has to be calculated using the Vickers indentation method. An electrochemical cell has been designed and built for measurements of the ionic conductivity by the use of blocking electrodes. Preliminary measurements on La{sub 0.2}Sr{sub 0.8}Fe{sub 0.55}Ti{sub 0.45}O{sub 3-{delta}} are reported. Modifications to the apparatus to improve the data quality have been completed. Electron microscopy studies of the origin of the slow kinetics on reduction of ferrites have been initiated. A series of isotope transients under air separation mode (small gradient) were completed on the membrane of LSCrF-2828 at 900 C. Low pO{sub 2} atmospheres based on with CO-CO{sub 2} mixtures have also been admitted to the delivery side of the LSCrF-2828 membrane to produce the gradient

S. Bandopadhyay; T. Nithyanantham; X.-D Zhou; Y-W. Sin; H.U. Anderson; Alan Jacobson; C.A. Mims

2005-05-01

418

Oxygen -- abundances and model atmospheres  

Microsoft Academic Search

The uncertainties in current determinations of oxygen abundances of Pop II stars, resulting from systematic errors in models used to represent the stellar atmospheres, are analysed and discussed. Recommendations are given for abundance criteria to be selected and for model atmosperes to be used and developed further.

Bengt Gustafsson

2000-01-01

419

DISSOLVED OXYGEN DIURNAL FLUX STUDY  

EPA Science Inventory

Stream monitoring study of a 24 Western Corn Belt Plains streams designed to assess any correlation of nutrient loads and the level of dissolved oxygen in wadeable streams and any subsequent affect on aquatic life. Study currently being conducted under a cooperative agreement be...

420

Anomalous oxygen isotope enrichment in CO2 produced from O+CO: Estimates based on experimental results and model predictions  

Microsoft Academic Search

The oxygen isotope fractionation associated with O+CO-->CO2 reaction was investigated experimentally where the oxygen atom was derived from ozone or oxygen photolysis. The isotopic composition of the product CO2 was analyzed by mass spectrometry. A kinetic model was used to calculate the expected CO2 composition based on available reaction rates and their modifications for isotopic variants of the participating molecules.

Antra Pandey; S. K. Bhattacharya

2006-01-01

421

Failure Rate Calculations Using a Programmable Calculator  

Microsoft Academic Search

This paper describes a TI 59 program which calculates the acceleration factor between any two temperatures, equivalent unit-hours at one temperature based on actual test hours at a second temperature, the x2 approximation at any of seven s-confidence levels, and the s-confidence limit failure rate estimate in both %\\/1000 hours and FITs. The program allows numerous entries of separate sample

Donald L. Denton

1982-01-01

422

Matrix calculations on hand-held calculators  

Microsoft Academic Search

Recently there have appeared three hand-held calculators of such large capacity that they might well be called computers. They are the Texas Instruments TI-59, the Hewlit-Packard HP-41C and the Radie Shack TRS-80PC. These computers are characterized by a comparatively large memory which can be variably partitioned into an instruction bank and a data bank. In all three computers the memory

G. W. Stewart

1981-01-01

423

Retinal Oxygenation and Oxygen Metabolism in Abyssinian Cats with a Hereditary Retinal Degeneration  

E-print Network

Retinal Oxygenation and Oxygen Metabolism in Abyssinian Cats with a Hereditary Retinal Degeneration circulation in hereditary photoreceptor degenerations. METHODS. Seven adult Abyssinian cats affected- phic) one as well. In the present study, we further examined the hypothesis that oxygen from

Linsenmeier, Robert

424

Climate Change Calculator  

NSDL National Science Digital Library

This calculator allows users to calculate their ecological footprint in terms of trees required to sequester the carbon from carbon dioxide emissions produced by household use and transportation. Exact emissions figures or national averages can entered into the calculator, and the amount of carbon dioxide generated by burning of fossil fuels is calclulated, as well as the number of trees it will take to remove that amount of carbon dioxide.

425

Imaging oxygen distribution in marine sediments. The importance of bioturbation and sediment heterogeneity.  

PubMed

The influence of sediment oxygen heterogeneity, due to bioturbation, on diffusive oxygen flux was investigated. Laboratory experiments were carried out with 3 macrobenthic species presenting different bioturbation behaviour patterns: the polychaetes Nereis diversicolor and Nereis virens, both constructing ventilated galleries in the sediment column, and the gastropod Cyclope neritea, a burrowing species which does not build any structure. Oxygen two-dimensional distribution in sediments was quantified by means of the optical planar optode technique. Diffusive oxygen fluxes (mean and integrated) and a variability index were calculated on the captured oxygen images. All species increased sediment oxygen heterogeneity compared to the controls without animals. This was particularly noticeable with the polychaetes because of the construction of more or less complex burrows. Integrated diffusive oxygen flux increased with oxygen heterogeneity due to the production of interface available for solute exchanges between overlying water and sediments. This work shows that sediment heterogeneity is an important feature of the control of oxygen exchanges at the sediment-water interface. PMID:18247133

Pischedda, L; Poggiale, J C; Cuny, P; Gilbert, F

2008-06-01

426

Kinetic Monte Carlo Simulation of Oxygen and Cation Diffusion in Yttria-Stabilized Zirconia  

NASA Technical Reports Server (NTRS)

Yttria-stabilized zirconia (YSZ) is of interest to the aerospace community, notably for its application as a thermal barrier coating for turbine engine components. In such an application, diffusion of both oxygen ions and cations is of concern. Oxygen diffusion can lead to deterioration of a coated part, and often necessitates an environmental barrier coating. Cation diffusion in YSZ is much slower than oxygen diffusion. However, such diffusion is a mechanism by which creep takes place, potentially affecting the mechanical integrity and phase stability of the coating. In other applications, the high oxygen diffusivity of YSZ is useful, and makes the material of interest for use as a solid-state electrolyte in fuel cells. The kinetic Monte Carlo (kMC) method offers a number of advantages compared with the more widely known molecular dynamics simulation method. In particular, kMC is much more efficient for the study of processes, such as diffusion, that involve infrequent events. We describe the results of kinetic Monte Carlo computer simulations of oxygen and cation diffusion in YSZ. Using diffusive energy barriers from ab initio calculations and from the literature, we present results on the temperature dependence of oxygen and cation diffusivity, and on the dependence of the diffusivities on yttria concentration and oxygen sublattice vacancy concentration. We also present results of the effect on diffusivity of oxygen vacancies in the vicinity of the barrier cations that determine the oxygen diffusion energy barriers.

Good, Brian

2011-01-01

427

[Whole-body oxygen consumption at different temperatures during cardiopulmonary bypass].  

PubMed

For evaluation of the adequacy of tissue perfusion during cardiopulmonary bypass (CPB), whole-body oxygen consumption rates at different body weights and temperatures are basic and important data. But few studies have analyzed the oxygen consumption estimated from real-time data during CPB in clinical situations. We analyzed retrospectively the oxygen consumption at different body weights (BW) during normothermia (VO2 37) and the oxygen consumption ratio at different body temperatures (BT; %VO2X; X = BT) from the CPB charts of 189 cases. From these charts, 877 data points for oxygen consumption during total CPB were calculated by Fick's law. By statistical analysis of these data, we derived the following formulae: VO2 37 (ml/kg/min) = 7.6481 x BW0.0679, R2 = 1.0 (BW < 8 kg) VO2 37 (ml/kg/min) = 32.394 x BW-0.625, R2 = 0.92 (BW > or = 8 kg) %VO2X (%) = 4 x 10(-5) x BT4.0777, R2 = 0.42. These formulae indicate that (1) the whole-body oxygen consumption during total CPB can be measured by subtracting the oxygen consumption associated with circulatory and respiratory processes from the oxygen consumption derived from the basal metabolism; and (2) although the change in oxygen consumption induced by hypothermia is variable depending on body weight, the rate of change shows no difference regardless of the patient's weight. PMID:10998863

Higuchi, H; Yoshii, S; Osawa, H; Suzuki, S; Samuel, A; Hosaka, S; Shindou, S; Tada, Y

2000-09-01

428

On the oxygen thresholds for the reactions of liquid sodium with urania and urania-plutonia solid solutions  

NASA Astrophysics Data System (ADS)

Some calculations of the oxygen potential thresholds for the reactions of liquid sodium with urania and urania—plutonia solid solutions are presented and compared with experimental data. The reactions relevant to the understanding of the behaviour of breached sodium-cooled fast reactor breeder and fuel pins are those which form a sodium uranate, Na 3UO 4 (tri-sodium uranium(V) tetroxide) and a sodium urano-plutonate ( Na3U1- xPuxO4). The oxygen potential thresholds are thus those for the three-phase fields; sodium, urania and sodium uranate, and sodium, urania—plutonia and sodium urano—plutonate. It has been shown that there is reasonable agreement between the calculated and measured values of oxygen potential in the ternary system. For the quaternary system with plutonium concentrations equivalent to Pu: (U + Pu) ratios of 0.25 there is also reasonable agreement between experimental and calculated values of the oxygen potential of the appropriate phase field. The measured threshold oxygen potentials are very similar for the ternary and quaternary systems as predicted. The difficulty of estimating the threshold oxygen concentration in liquid sodium from oxygen potential thresholds is illustrated by the use of different data for oxygen solubilities in sodium. The use of the vanadium wire equilibration technique to measure the threshold oxygen potentials in these systems is possible in principle; however, existing experimental results suggest that its application is not straightforward in complex systems.

Adamson, M. G.; Mignanelli, M. A.; Potter, P. E.; Rand, M. H.

1981-03-01

429

Cerebral oxygenation and cerebral oxygen extraction in the preterm infant: the impact of respiratory distress syndrome.  

PubMed

Haemodynamic factors play an important role in the etiology of cerebral lesions in preterm infants. Respiratory distress syndrome (RDS), a common problem in preterms, is strongly related with low and fluctuating arterial blood pressure. This study investigated the relation between mean arterial blood pressure (MABP), fractional cerebral oxygen saturation (ScO2) and fractional (cerebral) tissue oxygen extraction (FTOE), a measure of oxygen utilisation of the brain, during the first 72 h of life. Thirty-eight infants (gestational age < 32 week) were included, 18 with and 20 without RDS. Arterial oxygen saturation (SaO2), MABP and near infrared spectroscopy-determined ScO2 were continuously measured. FTOE was calculated as a ratio: (SaO2-ScO2)/SaO2. Gestational age and birth weight did not differ between groups, but assisted ventilation and use of inotropic drugs were more common in RDS infants (P<0.01). MABP was lower in RDS patients (P<0.05 from 12 up to 36 h after birth), but increased in both groups over time. ScO2 and FTOE were not different between groups over time, but in RDS infants ScO2 and FTOE had substantial larger variance (P<0.05 at all time points except at 36-48 h for ScO2 and P<0.05 at 12-18, 18-24, 36-48 and 48-60 h for FTOE). During the first 72 h of life, RDS infants showed more periods of positive correlation between MABP and ScO2 (P<0.05 at 18-24, 24-36 36-48 48-60 h) and negative correlation between MABP and FTOE (P<0.05 at 18-24, 36-48 h). Although we found that the patterns of cerebral oxygenation and extraction in RDS infants were not different as compared to infants without RDS, we suggest that the frequent periods with possible lack of cerebral autoregulation in RDS infants may make these infants more vulnerable to cerebral damage. PMID:16506004

Lemmers, Petra M A; Toet, Mona; van Schelven, Leonard J;