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1

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

NASA Technical Reports Server (NTRS)

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

Righter, K.; Ghiorso, M.

2009-01-01

2

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

3

Intrinsic oxygen fugacities of diogenites and mesosiderite clasts  

NASA Technical Reports Server (NTRS)

Oxygen fugacities of diogenite and mesosiderite clast material were measured with the double ZrO2 cell technique between 800 and 1150 C. The samples were taken from large clasts in the diogenites Johnstown (En73) and Tatahouine (En75), and the mesosiderites Estherville (En81), West Point (Fo88) and Emery (En68). Fugacity values for all except Emery plot near the wuestite-iron buffer curve and are interpreted as indicating similar source regions and environments of crystallization for the two suites. Emery orthopyroxene records a lower fugacity, close to the fayalite-quartz-iron buffer curve, probably as a result of equilibration with the mesosiderite matrix assemblage. The similarity of redox conditions experienced by mesosiderite orthopyroxenite and diogenites is not sufficient to require a single parent body and, if the common achondrites were derived from Vesta, mesosiderites probably came from a different body.

Hewins, R. H.; Ulmer, G. C.

1984-01-01

4

Oxygen isotope diffusion and zoning in diopside: The importance of water fugacity during cooling  

SciTech Connect

The oxygen isotope ratio of diopside correlates with crystal size in many high grade marbles, permitting the intracrystalline self-diffusion rate of oxygen in diopside to be empirically evaluated. Small (75--300 {micro}m) and large (1.2--1.5 mm) diopside grains were analyzed in bulk for their oxygen isotope ratios by laser extraction. Cooling histories were calculated using the Fast Grain Boundary diffusion model, assuming equilibrium at peak metamorphic temperatures (700--800 C), slow cooling of 1.5--4 C/Ma, and experimentally determined diffusion coefficients for oxygen in minerals. Measurements and calculations to predict differences in {delta}{sup 18}O between large and small diopside grains lead to the following conclusions. (1) Natural diopsides in this study exhibit variations in oxygen isotope ratios between grains of different size, which are related to the peak temperature, cooling rate, and water fugacity during cooling. Diffusion distances are properly modeled by the size of an entire grain; there is no evidence for subdomains. (2) In slowly cooled high grade metamorphic terrains, water fugacity can be highly variable from rock to rock during cooling. For many rocks, water fugacity is the most important constraint on the degree of oxygen isotope retrograde exchange.

Edwards, K.J.; Valley, J.W. [Univ. of Wisconsin, Madison, WI (United States). Dept. of Geology and Geophysics] [Univ. of Wisconsin, Madison, WI (United States). Dept. of Geology and Geophysics

1998-07-01

5

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

6

The Relationship Between Clinopyroxene Fe3+ Content and Oxygen Fugacity  

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

7

High Pressure Effects on the Iron-Iron Oxide and Nickel-Nickel Oxide Oxygen Fugacity Buffers  

E-print Network

High Pressure Effects on the Iron-Iron Oxide and Nickel- Nickel Oxide Oxygen Fugacity Buffers fugacity (fO2) buffer. These buffers are precisely known at 1 bar, but under high pressures corresponding to the conditions of the deep Earth, oxygen fugacity buffers are poorly calibrated. Reference (1 bar) fO2 buffers

Campbell, Andrew

8

Oxygen isotope diffusion and zoning in diopside: the importance of water fugacity during cooling  

NASA Astrophysics Data System (ADS)

The oxygen isotope ratio of diopside correlates with crystal size in many high grade marbles, permitting the intracrystalline self-diffusion rate of oxygen in diopside to be empirically evaluated. Small (75-300 ?m) and large (1.2-1.5 mm) diopside grains were analyzed in bulk for their oxygen isotope ratios by laser extraction. In many samples, ? 18O correlates to size; smaller grains have lower ? 18O. Published ion microprobe analyses of diopside in one sample which displays this correlation are in good agreement with predictions based on diffusion modeling and analyses of whole crystals. Other samples analyzed by laser extraction have little or no measurable correlation of ? 18O to size. Investigation using cold cathode luminescence, reflected differential interference contrast microscopy, electron microprobe analysis, and scanning electron microscopy shows that diopside in some of the samples that do not show ? 18O correlation with size were partially dissolved at grain boundaries during cooling, indicating processes in addition to diffusion have affected ? 18O. Cooling histories were calculated using the Fast Grain Boundary diffusion model (Eiler et al., 1992, 1993), assuming equilibrium at peak metamorphic temperatures (700-800°C), slow cooling of 1.5-4°C/Ma, and experimentally determined diffusion coefficients for oxygen in minerals. Predicted ? 18O for diopsides of different sizes are significantly different using diffusion coefficients determined under anhydrous (Pco 2 = 1-100 bars) vs. hydrothermal (P H 2O = 1 kbar) conditions. Samples that show a ? 18O correlation to size are best predicted using the diffusion data measured under hydrothermal conditions. Measurements and calculations to predict differences in ? 18O between large and small diopside grains lead to the following conclusions. (1) Natural diopsides in this study exhibit variations in oxygen isotope ratios between grains of different size, which are related to the peak temperature, cooling rate, and water fugacity during cooling. Diffusion distances are properly modeled by the size of an entire grain; there is no evidence for subdomains. (2) In slowly cooled high grade metamorphic terrains, water fugacity can be highly variable from rock to rock during cooling. For many rocks, water fugacity is the most important constraint on the degree of oxygen isotope retrograde exchange.

Edwards, Katrina J.; Valley, John W.

1998-07-01

9

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

10

Czochralski growth of single-crystal fayalite under controlled oxygen fugacity conditionsl  

Microsoft Academic Search

Single-crystal boules of fayalite (FerSiOo) were grown in the temperature range 1165 to 1200'C at I bar total pressure from high-purity oxide melts of 1.95:l to 2.10:l Fe:Si atom ratio. A modified Czochralski technique was used, with platinum crucibles inductively heated under oxygen fugacities, \\/(Or), between l0-e and l0-'2 bar. The boules are up to l0 mm in diameter by

Cennrr B. FrNcH; G. WayNn Cram; Orro C. Kopp

11

Technical Update: Johnson Space Center system using a solid electrolytic cell in a remote location to measure oxygen fugacities in CO/CO2 controlled-atmosphere furnaces  

NASA Technical Reports Server (NTRS)

Details are given for the design and application of a (one atmosphere) redox-control system. This system differs from that given in NASA Technical Memorandum 58234 in that it uses a single solid-electrolytic cell in a remote location to measure the oxygen fugacities of multiple CO/CO2 controlled-atmosphere furnaces. This remote measurement extends the range of sample-furnace conditions that can be measured using a solid-electrolytic cell, and cuts costs by extending the life of the sensors and by minimizing the number of sensors in use. The system consists of a reference furnace and an exhaust-gas manifold. The reference furnace is designed according to the redox control system of NASA Technical Memorandum 58234, and any number of CO/CO2 controlled-atmosphere furnaces can be attached to the exhaust-gas manifold. Using the manifold, the exhaust gas from individual CO/CO2 controlled atmosphere furnaces can be diverted through the reference furnace, where a solid-electrolyte cell is used to read the ambient oxygen fugacity. The oxygen fugacity measured in the reference furnace can then be used to calculate the oxygen fugacity in the individual CO/CO2 controlled-atmosphere furnace. A BASIC computer program was developed to expedite this calculation.

Jurewicz, A. J. G.; Williams, R. J.; Le, L.; Wagstaff, J.; Lofgren, G.; Lanier, A.; Carter, W.; Roshko, A.

1993-01-01

12

Electrochemical manipulation of apparent oxygen fugacity in a piston cylinder apparatus  

NASA Astrophysics Data System (ADS)

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

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

2002-12-01

13

Techniques for the Control of Water Fugacity and Oxygen Fugacity for Experimentation in Solid-Media High-Pressure Apparatus  

Microsoft Academic Search

Techniques for the encapsulation of H sO with sample in welded noble-metal containers have been used routinely in solid-media, high-pressure apparatus (e.g., the piston cylinder apparatus) since the early 1960's [e.g., Newton and Kennedy, 1963]. Recently, it has bedome desirable to regulate the fugacity of HsO 0H2o) at some value less than that which occurs in a vapor consisting of

A. L. Boettcher; B. O. Mysen; J. C. Allen

1973-01-01

14

Microstructural evolution in high oxygen fugacity processed bismuth strontium calcium copper oxide  

NASA Astrophysics Data System (ADS)

A decomposition/reformation process that uses a high oxygen fugacity (2 MPa) heat treatment followed by low oxygen fugacity (<1 MPa) annealing was applied to silver-sheathed Bisb2Srsb2CaCusb2Osb{8±delta} (Bi-2212) tapes. The rate at which the Bi-2212 phase reforms was studied using X-ray diffractometry and image analyses. The kinetic data was fitted to an Avrami-type equation and was found to be consistent with that predicted for diffusion-controlled growth of plate-like grains. The effect of varying the oxygen fugacity during reformation annealing was also studied and the rate of Bi-2212 phase formation slowed considerably with increasing oxygen fugacity. The rate of oxygen exsolution from the core is a key parameter for the overall transformation kinetics. Two of the decomposition products produced by high-fOsb2 processing of the Bi-2212 compound are a copper-free alkaline-earth bismuthate (a Bisb9Srsb{11}Casb5Osb{x}-type) and CuO. Blended mixtures of these two compounds were used to form two-powder reaction couples used to study Bi-2212 phase formation. Samples were annealed in flowing oxygen at temperatures below the Bi-2212 solidus. The formation of apparent Bi-2212/Bi-2201 intergrowths along with some alkaline-earth cuprate phases were detected. The 14:24-type alkaline-earth cuprate phase was formed in fine CuO powder couples but not in couples containing large CuO particles. The reaction leading to Bi-2212 phase formation was confirmed to be solid-state at temperatures below 875sp°C. The development of c-axis grain alignment in high-fOsb2 decomposed Bi-2212 tapes that were reformed with low-fOsb2 annealing was studied. Such processing can produce enhanced 00l grain alignment and the evolution of this texture was examined in tapes at intermediate points in the reformation process. Some of the mechanisms associated with texture development in melt-processed tapes were found to be inadequate for describing the alignment in high-fOsb2 processed Bi-2212 grains. Microstructural texture was found to develop uniformly throughout the thickness of the oxide core and a number of factors that could contribute to this behavior were identified. Critical current density (Jsbc) measurements were made on a number of tapes and intermediate mechanical deformation (pressing) operations were found to be a possible approach for enhancing Jsbc in tapes processed with high-fOsb2 heat treatments.

Gannon, John J., Jr.

15

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

16

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

NASA Astrophysics Data System (ADS)

The ferric iron contents of spinels from 30 spinel Iherzolite xenoliths have been measured by 57Fe 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 3O 4 contents of the spinels is from 1.7 to 5.2 mol% with an uncertainty of 0.2 to 0.3 mol%. These data were used to calculate the oxygen fugacities recorded by the spinel Iherzolites using the oxygen thermobarometer 6 Fe 2SiO 4 + O 2 = 3 Fe 2Si 2O 6 + 2 Fe 3O 4. olivine orthopyroxene spinel The Fe(III) contents of the spinels translate to oxygen fugacities which, at 15 kb, range between 1.7 log units below and 1.2 log units above FMQ using either the Mattioli and Wood (1988) or O'neill and Wall (1987) version of Fe 3O 4 activity. There are distinct regional differences ƒO 2, the specimens from SW U.S.A. and Central Asia exhibiting values from slightly above FMQ to 1.5 log units below FMQ. At an estimated pressure of 15 kb, these values overlap with the ƒO 2- T field of MORB glasses, indicating, in agreement with trace element abundances, that many of these samples are related to the MORB source region. Samples from Ichinomegata and Mont Briançon are all above the MORB range, however, suggesting progressive oxidation related to subduction processes. All of our samples give oxygen fugacities more than 2 log units above IW, implying that C?H?O fluids in the upper mantle are dominated by CO 2 and H 2O and that CH 4 is a minor (< 10%) component. A detailed comparison of Fe(III) contents determined by Mössbauer spectroscopy and those obtained from microprobe analysis indicates that the latter are sufficiently precise (± 0.002 fXFe3O 4) but, in general, too inaccurate for oxygen thermobarometry. Use of Mössbauer-analyzed spinels as microprobe standards enables accuracy to approach precision, however, and appropriate standards are available on request.

Wood, Bernard J.; Virgo, David

1989-06-01

17

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

NASA Technical Reports Server (NTRS)

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

Williams, R. J.; Mullins, O.

1976-01-01

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

Sulfur degassing at Erta Ale (Ethiopia) and Masaya (Nicaragua) volcanoes: Implications for degassing processes and oxygen fugacities of basaltic systems  

NASA Astrophysics Data System (ADS)

We investigate the relationship between sulfur and oxygen fugacity at Erta Ale and Masaya volcanoes. Oxygen fugacity was assessed utilizing Fe3+/?Fe and major element compositions measured in olivine-hosted melt inclusions and matrix glasses. Erta Ale melts have Fe3+/?Fe of 0.15-0.16, reflecting fO2 of ?QFM 0.0 ± 0.3, which is indistinguishable from fO2 calculated from CO2/CO ratios in high-temperature gases. Masaya is more oxidized at ?QFM +1.7 ± 0.4, typical of arc settings. Sulfur isotope compositions of gases and scoria at Erta Ale (?34Sgas - 0.5‰; ?34Sscoria + 0.9‰) and Masaya (?34Sgas + 4.8‰; ?34Sscoria + 7.4‰) reflect distinct sulfur sources, as well as isotopic fractionation during degassing (equilibrium and kinetic fractionation effects). Sulfur speciation in melts plays an important role in isotope fractionation during degassing and S6+/?S is <0.07 in Erta Ale melt inclusions compared to >0.67 in Masaya melt inclusions. No change is observed in Fe3+/?Fe or S6+/?S with extent of S degassing at Erta Ale, indicating negligible effect on fO2, and further suggesting that H2S is the dominant gas species exsolved from the S2--rich melt (i.e., no redistribution of electrons). High SO2/H2S observed in Erta Ale gas emissions is due to gas re-equilibration at low pressure and fixed fO2. Sulfur budget considerations indicate that the majority of S injected into the systems is emitted as gas, which is therefore representative of the magmatic S isotope composition. The composition of the Masaya gas plume (+4.8‰) cannot be explained by fractionation effects but rather reflects recycling of high ?34S oxidized sulfur through the subduction zone.

Moor, J. M.; Fischer, T. P.; Sharp, Z. D.; King, P. L.; Wilke, M.; Botcharnikov, R. E.; Cottrell, E.; Zelenski, M.; Marty, B.; Klimm, K.; Rivard, C.; Ayalew, D.; Ramirez, C.; Kelley, K. A.

2013-10-01

20

Vanadium Stable Isotope Variations in the Mariana Island Arc: Oxygen Fugacity Versus Magmatic Differentiation  

NASA Astrophysics Data System (ADS)

A widely held view in igneous geochemistry is that the sub-arc mantle has elevated oxygen fugacity (fO2) compared to the upper mantle source of Mid-Ocean Ridge basalts (MORB). However, debate on the fO2 of the sub-arc mantle has arisen from examination of V/Sc ratios [1], which suggest no difference between the sub-arc mantle and the MORB source. This supposition is contrasted by recent ?-XANES determination of Fe3+/Fe? in olivine-hosted melt inclusions [2], which supports the more traditional notion of an oxidized source for arc lavas. We have recently developed a method for high precision analyses of stable vanadium (V) isotope variations, able to resolve isotope fractionation to a precision of 0.15‰ 2sd [3, 4]. Theoretical calculations predict that stable V isotope fractionation should be robustly related to changes in fO2, with heavier isotopes favored in oxidizing conditions. Furthermore, V isotopes should be immune to alteration and late-stage degassing processes that could affect fO2 determined by Fe3+/Fe? ratios. Therefore, examination of this new isotopic tracer in arc lavas may provide insight into the fO2 conditions of their source. Here we present the first stable V isotope measurements (reported as ?51V relative to a standard defined as 0‰) on subduction zone inputs (sediments, MORB) and outputs (arc lavas). We have focused initial efforts on well-characterized lavas from the Mariana central island province [5] and subducting sediment and underlying MORB from ODP Site 801, just outboard of the Mariana trench [6]. We find a surprisingly large, resolvable range in ?51V of the arc lavas of almost 0.8‰, which co-varies with SiO2, CaO, and V/Sc ratios. Co-variation of ?51V with SiO2 and CaO is suggestive of possible influence of clinopyroxene fractionation on the isotope composition. We explore the affects of magmatic differentiation and causes of ?51V inter-suite variability in arc lavas versus the ?51V signature of MORB. [1] Lee, C.T.A., Leeman, W.P., Canil, D., Li, Z.X.A. 2005. J. Pet. 46, 2313-2336. [2] Kelley, K.A., Cottrell, E. 2009. Science, 325, 605-607. [3] Nielsen S.G., Prytulak J., Halliday A.N. 2010. Geost. Geoanal. Res., accepted. [4] Prytulak J., Nielsen S.G., Halliday A.N. 2010. Geost. Geoanal. Res., accepted. [5] Elliott,T., Plank, T., Zindler, A., White, W., Bourdon, B. 1997. J. Geophys. Res. 102, 14991-15019. [6] Kelley, K.A., Plank, T., Ludden, J., Staudigel, H. 2003. Geochem. Geophys. Geosyst. 4, doi: 10.1029/2002GC000435.

Prytulak, J.; Elliott, T.; Halliday, A.; Kelley, K. A.; Nielsen, S. G.; Plank, T.; Schauble, E. A.

2010-12-01

21

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

22

Crystal chemistry of amphiboles: implications for oxygen fugacity and water activity in lithospheric mantle beneath Victoria Land, Antarctica  

NASA Astrophysics Data System (ADS)

Amphibole is the hydrous metasomatic phase in spinel-bearing mantle xenoliths from Baker Rocks, Northern Victoria Land, Antarctica. It occurs in veins or in disseminated form in spinel lherzolites. Both types derive from reaction between metasomatic melts and the pristine paragenesis of the continental lithospheric mantle beneath Northern Victoria Land. To determine the effective role of water circulation during the metasomatic process and amphibole formation, six amphibole samples were fully characterized. Accurate determination of the site population and the state of dehydrogenation in each of these amphiboles was carried out using single-crystal X-ray diffraction, electron microprobe and secondary ion mass spectroscopy on the same single crystal. The Fe3+/?Fe ratio was determined by X-ray absorption near edge spectroscopy on amphibole powder. The degree of dehydrogenation determined by SIMS is 0.870-0.994 O3(O2-) a.p.f.u., primary and ascribed to the Ti-oxy component of the amphibole, as indicated by atom site populations; post-crystallization H loss is negligible. Estimates of aH2O (0.014-0.054) were determined from the dehydration equilibrium among end-member components assuming that amphiboles are in equilibrium with the anhydrous peridotitic phases. A difference up to 58 % in determination of aH2O can be introduced if the chemical formula of the amphiboles is calculated based on 23 O a.p.f.u. without knowing the effective amount of dehydrogenation. The oxygen fugacity of the Baker Rocks amphibole-bearing mantle xenoliths calculated based upon the dissociation constant of water (by oxy-amphibole equilibrium) is between -2.52 and -1.32 log units below the fayalite-magnetite-quartz (FMQ) buffer. These results are systematically lower and in a narrow range of values relative to those obtained from anhydrous olivine-orthopyroxene-spinel equilibria ( fO2 between -1.98 and -0.30 log units). A comparative evaluation of the two methods suggests that when amphibole is present in mantle peridotites, the application of oxy-amphibole equilibrium is preferred, because ol-opx-sp oxy-calibrations are not "sensitive" enough in recording the effects (if any) of amphibole in the peridotite matrix. Amphibole acts as the main H acceptor among the peridotite minerals and may prevent fluid circulation and buffer oxygen fugacity. The important conclusion of this study is that amphibole within the lithospheric mantle does not always means high water activity and oxidizing conditions.

Bonadiman, C.; Nazzareni, S.; Coltorti, M.; Comodi, P.; Giuli, G.; Faccini, B.

2014-03-01

23

Fugacity Examples  

ERIC Educational Resources Information Center

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

David, Carl W.

2004-01-01

24

Carbonate and Magnetite Parageneses as Monitors of Carbon Dioxide and Oxygen Fugacity  

NASA Technical Reports Server (NTRS)

The stable coexistence of siderite with other key minerals, such as graphite or magnetite, is only possible under certain restrictive conditions of CO2 and O2 fugacity. Carbonate parageneses in Mars meteorite ALH 84001 are analyzed.

Koziol, Andrea M.

2000-01-01

25

Transient electrical response of San Quintin dunite as a function of oxygen fugacity changes: Information about charge carriers  

Microsoft Academic Search

The electrical conductivity (sigma) of San Quintin dunite (SQD) measured between 950 and 1150 deg C at controlled oxygen fugacity (f(sub O2)) within the olivine stability field shows transients in response to changes in f(sub O2). Such behavior has not been reported previously for measurements made under similar conditions on either olivine single crystals or polycrystalline samples (dunites and lherzolites)

Jeffery J. Roberts; Alfred G. Duba

1995-01-01

26

Transient electrical response of San Quintin Dunite as a function of oxygen fugacity changes: Information about charge carriers  

Microsoft Academic Search

The electrical conductivity (?) of San Quintin dunite (SQD) measured between 950 and 1150°C at controlled oxygen fugacity (fO2) within the olivine stability field shows transients in response to changes in fO2. Such behavior has not been reported previously for measurements made under similar conditions on either olivine single crystals or polycrystalline samples (dunites and lherzolites) in which olivine is

Jeffery J. Roberts; Alfred G. Duba

1995-01-01

27

Towards a predicted mineralogy of the interior of Mercury using low oxygen fugacity experiments on a CB chondrite composition  

NASA Astrophysics Data System (ADS)

The MESSENGER mission is revolutionizing our knowledge of both the surface composition and mineralogy of Mercury, and of its current general interior structure. Detailed petrological models of the interior evolution of Mercury are hampered by the near-complete absence of high-pressure experiments using Mercury-relevant compositions and oxygen fugacities. As a result, current models for the mineralogy of the silicate mantle and crust of Mercury vary widely. For example, using the same assumed CB chondritic bulk composition, model x predicts that the mineral phase a is stable in the upper z kilometers of Mercury, while model y predicts that a is absent, whereas phase c is stable. As a first step towards providing a complete experimental framework to support evolutionary models for Mercury, we are determining the phase relations of a CB chondrite bulk composition at high pressure, high temperature and very low oxygen fugacity. Initially, we have performed experiments in the pressure range 1-2.5 GPa, and temperature range 1300-1500 degree Celsius, using a piston cylinder press. To assess the effect of oxygen fugacity on phase relations, we have compared samples that contained only the CB bulk composition with samples containing 50 wt% Fe83Si17 metal powder. The samples were analyzed with the use of an electron microprobe. Experiments concluded by the time of the meeting include data on partially molten systems, related to modeling what the effects of a global magma ocean early in Mercurian history would be.

Knibbe, J. S.; Van Westrenen, W.

2013-12-01

28

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

29

The oxidation state of Fe in MORB glasses and the oxygen fugacity of the upper mantle  

NASA Astrophysics Data System (ADS)

Micro-analytical determination of Fe3+/?Fe ratios in mid-ocean ridge basalt (MORB) glasses using micro X-ray absorption near edge structure (?-XANES) spectroscopy reveals a substantially more oxidized upper mantle than determined by previous studies. Here, we show that global MORBs yield average Fe3+/?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 Fe3+/?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 Fe3+/?Fe ratios determined by micro-colorimety and XANES can be attributed to the Mössbauer-based XANES calibration. The difference must instead derive from a bias between micro-colorimetry performed on experimental vs. natural basalts. Co-variations of Fe3+/?Fe ratios in global MORB with indices of low-pressure fractional crystallization are consistent with Fe3+ behaving incompatibly in shallow MORB magma chambers. MORB Fe3+/?Fe ratios do not, however, vary with indices of the extent of mantle melting (e.g., Na2O(8)) or water concentration. We offer two hypotheses to explain these observations: The bulk partition coefficient of Fe3+ 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 ~ QFM. Both explanations, in combination with the measured MORB Fe3+/?Fe ratios, point to a fertile MORB source with greater than 0.3 wt.% Fe2O3.

Cottrell, Elizabeth; Kelley, Katherine A.

2011-05-01

30

Self diffusion of europium, neodymium, thorium, and uranium in haplobasaltic melt: The effect of oxygen fugacity and the relationship to melt structure  

SciTech Connect

We report new measurements of self diffusion coefficients (D) for Mg, Nd, Eu, Th, and U in a haplobasaltic (Fo{sub 15}Di{sub 40}An{sub 45}) melt at 1 atm. 1400-1500{degrees}C, and oxygen fugacities corresponding to air and the Fe-FeO buffer. Diffusion couples consisted of isotopically distinct melts of the same chemical composition. and isotopic concentration profiles in quenched couples were measured with an ion probe. The valence state distributions of Eu and U were determined from absorption spectroscopy and model calculations, which demonstrate a shift from Eu{sup 3+} and U{sup 5.5+} in air to Eu{sup 2.5+} and U{sup 4+} at Fe-FeO. D{sub Mg}, D{sub Nd}, and Dn are independent of oxygen fugacity and agree well with our previous measurements. D{sub Eu} = D{sub Nd} in air and increases by 42% at Fe-FeO, while D{sub u} = D{sub Th} in air and shows a possible small increase of {approximately}20% at Fe-FeO. The change in D{sub Eu} with oxygen fugacity matches the established ionic radius and charge dependence for Mg, Ca, Ba, Nd,Yb, Ti, and Zr, while diffusion coefficients for Zr, Th, U{sup 4+}, and U{sup 5.5+} are independent of ionic radius and charge. Activation energies for all cations are approximately equal, independent of oxygen fugacity, and approximately match the activation energy for viscous flow. In addition, activation energies and diffusion coefficients recently measured for O and Si in basalt agree well with the present values. The good agreement between the various activation energies and between network modifier and network former diffusivities is consistent with a model in which diffusion of network modifying cations in low viscosity melts is controlled largely by the extrinsic influence of the melt network reorganization, with an additional influence from the intrinsic mobilities of the individual cations. 37 refs., 7 figs., 5 tabs.

LaTourrette, T.; Wasserburg, G.J. [California Institute of Technology, Pasadena, CA (United States)] [California Institute of Technology, Pasadena, CA (United States)

1997-02-01

31

Self diffusion of europium, neodymium, thorium, and uranium in haplobasaltic melt: The effect of oxygen fugacity and the relationship to melt structure  

NASA Astrophysics Data System (ADS)

We report new measurements of self diffusion coefficients ( D) for Mg, Nd, Eu, Th, and U in a haplobasaltic (Fo 15Di 40An 45) melt at 1 atm, 1400-1500°C, and oxygen fugacities corresponding to air and the Fe?FeO buffer. Diffusion couples consisted of isotopically distinct melts of the same chemical composition, and isotopic concentration profiles in quenched couples were measured with an ion probe. The valence state distributions of Eu and U were determined from absorption spectroscopy and model calculations, which demonstrate a shift from Eu 3+ and U 5.5+ in air to Eu 2.5+ and U 4+ at Fe?FeO. DMg, DNd, and DTh are independent of oxygen fugacity and agree well with our previous measurements. DEu = DNd in air and increases by 42% at Fe?FeO, while DU = DTh in air and shows a possible small increase of ˜20% at Fe?FeO. The change in DEu with oxygen fugacity matches the established ionic radius and charge dependence for Mg, Ca, Ba, Nd, Yb, Ti, and Zr, while diffusion coefficients for Zr, Th, U 4+, and U 5.5+ are independent of ionic radius and charge. Activation energies for all cations are approximately equal, independent of oxygen fugacity, and approximately match the activation energy for viscous flow. In addition, activation energies and diffusion coefficients recently measured for O and Si in basalt agree well with the present values. The good agreement between the various activation energies and between network modifier and network former diffusivities is consistent with a model in which diffusion of network modifying cations in low viscosity melts is controlled largely by the extrinsic influence of the melt network reorganization, with an additional influence from the intrinsic mobilities of the individual cations. The constant diffusion coefficient defined by the high ionic radius and charge elements is interpreted to represent the characteristic network diffusivity for this composition, which dominates over the intrinsic diffusivities for these elements. Elements with faster intrinsic diffusivities still display a small ionic radius and charge dependence. Diffusion coefficients in high viscosity melts are expected to be decoupled from the network, and thus may display a much greater dependence on ionic radius and charge.

la Tourrette, T.; Wasserburg, G. J.

1997-02-01

32

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

33

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

NASA Astrophysics Data System (ADS)

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

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

2011-10-01

34

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

35

Links between oxygen fugacity, slab fluids, and calc-alkaline differentiation of arc magmas (Invited)  

NASA Astrophysics Data System (ADS)

Calc-alkaline differentiation, a process by which magmas become depleted in Fe early in their crystallization history, is observed in magmas at subduction zone settings and is thought to drive arc magmas towards the bulk composition of continental crust. Basaltic arc magmas may achieve calc-alkaline affinity through some combination of high magmatic H2O, which delays the crystallization of silicates (most notably plagioclase), and high magmatic oxygen fugacity (fO2), which enhances the onset of magnetite crystallization. The relative importance of H2O, fO2, and magmatic bulk composition in generating calc-alkaline magma series, however, is not yet clearly resolved. Here, we present new measurements of the oxidation state of Fe (expressed as Fe3+/?Fe ratio; a proxy for magmatic fO2), in combination with previously-published analyses, of mafic (Mg#?0.5) olivine-hosted melt inclusions from global arc volcanoes (Galunggung, Paricutin, Cerro Negro, and several volcnaoes from the Mariana and Aleutian arcs), acquired using X-ray Absorption Near Edge Structure spectroscopy. We use the Tholeiitic Index (THI) of Zimmer et al., 2010 to quantify the calc-alkaline affinity of arc magma series (<1 is more calc-alkaline, >1 is more tholeiitic). These volcanoes span a range of calc-alkaline affinity, with THI ranging from 0.65 to 1.3. The Fe3+/?Fe ratios of arc basalts, corrected for fractional crystallization to 6 wt.% MgO (i.e., Fe3+/?Fe6.0) range globally from 0.15-0.31 and all but Galunggung are more oxidized than the more tholeiitic basaltic glasses from the Mariana trough back-arc basin (THI=1.4; Fe3+/?Fe6.0=0.185) or normal MORB (THI=1.6; Fe3+/?Fe6.0=0.167×0.01). Our results show a strong correlation between THI and Fe3+/?Fe6.0 ratios at these volcanoes, such that more calc-alkaline magmas contain a greater proportion of oxidized Fe. At the same time, the maximum dissolved H2O contents of basaltic melt inclusions from these volcanoes also strongly correlate with THI, and with Fe3+/?Fe6.0 ratios (although H2O is not the direct cause of oxidation), which points to a slab-derived origin of both H2O and oxidation and thus potentially links slab-derived fluids to the generation of calc-alkaline magma series. These correlations also illustrate the challenge of separating the effects of H2O and fO2 on arc magmatic differentiation, as the two are difficult to isolate in nature. Yet, some volcanoes may shed light on this issue. Arc volcanoes with similar Fe3+/?Fe6.0 or H2O, but significantly different THI, may illustrate most clearly the isolated effects of the other variable.

Kelley, K. A.; Cottrell, E.; Brounce, M. N.

2013-12-01

36

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

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

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

39

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

40

Oxygen fugacity and geochemical variations in the martian basalts: implications for martian basalt petrogenesis and the oxidation state of the upper mantle of Mars  

NASA Astrophysics Data System (ADS)

The oxygen fugacity of the Dar al Gani 476 martian basalt is determined to be quartz-fayalite-magnetite (QFM) -2.3 ± 0.4 through analysis of olivine, low-Ca pyroxene, and Cr-spinel and is in good agreement with revised results from Fe-Ti oxides that yield QFM -2.5 ± 0.7. This estimate falls within the range of oxygen fugacity for the other martian basalts, QFM -3 to QFM -1. Oxygen fugacity in martian basalts correlates with 87Sr/ 86Sr, 143Nd/ 144Nd, and La/Yb ratios, indicating that the mantle source of the basalts is reduced and that assimilation of crust-like material controls the oxygen fugacity. This allows constraints to be placed on the oxidation state of the martian mantle and on the nature of assimilated crustal material. The assimilated material may be the product of early and extensive hydrothermal alteration of the martian crust, or it may be amphibole- or phlogopite-bearing basaltic rock within the crust. In either case, water may play a significant role in the oxidation of basaltic magmas on Mars, although it may be secondary to assimilation of ferric iron-rich material.

Herd, Christopher D. K.; Borg, Lars E.; Jones, John H.; Papike, James J.

2002-06-01

41

PII S0016-7037(98)00212-9 Measurement of oxygen fugacities under reducing conditions: Non-Nernstian behavior of  

E-print Network

-Nernstian behavior of Y2O3-doped zirconia oxygen sensors R. A. MENDYBAEV,1 J. R. BECKETT,2, * E. STOLPER,2 and L procedure is presented for the use of a Y2O3-stabilized zirconia (YSZ) oxygen sensor in 1 atm gas and those calculated assuming Nernstian behavior of the electrolyte in the oxygen sensor reflect mixed ionic

Grossman, Lawrence

42

Effects of Oxygen Fugacity and Temperature on Partitioning of Ni and Co Between Liquid Metal, Magnesium Silicate Perovskite and Magnesiowustite  

NASA Astrophysics Data System (ADS)

In the core formation stage, a magma ocean might have extended to the lower mantle depth, and Ni and Co might have been distributed throughout the magma ocean, solid lower mantle, and the Earth's core. Although it is important to determine effects of oxygen fugacity (fO2) and temperature on partition behavior of these elements between liquid iron and lower mantle minerals, it has not been well constrained because of its experimental difficulty. Partitioning of Ni and Co between liquid iron-rich metal and lower mantle minerals, such as magnesium silicate perovskite and magnesiowustite, was investigated at 26-27 GPa, 2680-3020 K and 1.15- 1.86 log units below the iron-wustite fO2 buffer. The experiments have been achieved at such conditions using a Kawai-type apparatus and a cell assembly optimized for high-temperature generation. Our experiments revealed that partition coefficients of Ni and Co between liquid iron-rich metal and the lower mantle minerals decrease with increasing fO2, whereas they have very week temperature dependence in the present temperature range. The present result makes it possible to evaluate Ni and Co abundance throughout the mantle for a plausible fO2 and temperature. The mantle abundance of Ni and Co may be explained by the core formation in the deep magma ocean with a bottom pressure of around 65 GPa (corresponding to 1500 km depth).

Kawazoe, T.; Ohtani, E.

2007-12-01

43

Transient electrical response of San Quintin dunite as a function of oxygen fugacity changes: Information about charge carriers  

NASA Astrophysics Data System (ADS)

The electrical conductivity (sigma) of San Quintin dunite (SQD) measured between 950 and 1150 deg C at controlled oxygen fugacity (f(sub O2)) within the olivine stability field shows transients in response to changes in f(sub O2). Such behavior has not been reported previously for measurements made under similar conditions on either olivine single crystals or polycrystalline samples (dunites and lherzolites) in which olivine is the major phase. In general for olivine, an increase in f(sub O2) results in an increase in sigma. The transient is manifested as a change in sigma from a stable equilibrium value at a specific f(sub O2) to a quickly established subsequent value, the direction of which is opposite that of the final value that will be attained for the f(sub O2) change. This transient may be caused by a changing population of electrons produced by oxygen vacancies, the grain boundaries, or a short-lived defect. We postulate that the transient is observed in this particular dunite because of its large surface area to volume ratio. The transient is more pronounced at relatively high f(sub O2)s and temperatures between 950 and 1100 C. At relatively low f(sub O2)s and temperatures higher than 1100 C, the effect is diminished. The Seebeck coefficient (S), at 1200 C, is slightly smaller than that reported for single-crystal olivine, and at 1100 C is similar to that reported for single crystal olivine.

Roberts, Jeffery J.; Duba, Alfred G.

1995-02-01

44

Metal-silicate partitioning of Pb and U: Effects of metal composition and oxygen fugacity  

NASA Astrophysics Data System (ADS)

This study investigates the metal-silicate partitioning of Pb and U (DPb and DU, respectively) during core-mantle differentiation of terrestrial planets. For this, we equilibrated a molten CI-chondrite model mantle-composition with various Fe-rich alloys in the system Fe-C-Ni-Si-S in a multi-anvil over a range of P, T, fO2 (3-8 GPa, 2073-2373 K and from 1.5 to 5 log units below the iron-wüstite (IW) buffer). The chemical compositions of the run products and contents in Pb and U trace elements were determined using electron microbe and laser ablation inductively coupled plasma-mass spectrometry, respectively. We combined our new data set with pre-existing results in similar chemical systems to refine the major parameters controlling the DPb and DU values, based on thermodynamical calculations. We show: (i) a significant increase of the metal-silicate partition coefficients, from ˜1 to ˜50 for DPb and from ˜10-5 to 10-2 for DU with the addition of sulfur. (ii) At a fixed fO2, the presence of C in the metal favors U and Pb partitioning toward the silicate melt, when S produces the opposite trend. (iii) Temperature plays a non-negligible role in DPb value. Although the results suggest that the Pb depletion observed in the present-day bulk silicate Earth can be explained by core-mantle segregation at high-pressure in a deep-magma ocean, at conditions similar to that previously refined based on the behavior of many siderophile elements, such as Ni and Co, we will also discuss the possibility of late S-rich phases segregating to the core.

Bouhifd, M. A.; Andrault, D.; Bolfan-Casanova, N.; Hammouda, T.; Devidal, J. L.

2013-08-01

45

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

46

Oxygen fugacity of mare basalts and the lunar mantle application of a new microscale oxybarometer based on the valence state of vanadium  

SciTech Connect

Using the valence state of vanadium on a microscale in lunar volcanic glasses we have developed another approach to estimating the oxygen fugacity of mare basalts. 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 fO{sub 2}. Still, these approaches have been helpful and indicate that mare basalts crystallized at fO{sub 2} between the iron-wuestite 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 fO{sub 2} 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 fO{sub 2}, 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. (UofC); (Univ. of New Mexico)

2004-05-25

47

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

48

The Influence of PH and Oxygen Fugacity on the Hydrothermal Transport of Pb and Zn by Carboxylate Complexes.  

NASA Astrophysics Data System (ADS)

A chemical model was developed to evaluate the influence of log ? pH conditions on Pb and Zn complexation by acetate and malonate in 100oC basinal brines with bulk chemical compositions similar to diagenetic ore fluids and modern petroleum-field brines of moderate salinity (TDS = 180 g L-1). In the model composite brine, acetate with a concentration of 7,700 mg L-1 (0.13 m) represents the major monocarboxylate ligands detected in basinal brines, while malonate with a concentration of 300 mg L-1 (0.0029m) represents the dominant dicarboxylate ligands. Total Pb and Zn concentrations (constrained by galena and sphalerite solubility, respectively) and Pb and Zn speciation were calculated as a function of log and pH for the model composite fluid. The 1.0 and 10 ppm isopleths of total Pb and total Zn in carboxylate (acetate + malonate) complexes illustrate that the ore fluid of Giordano (1994) for red-bed related base metal deposits and Anderson?s (1975) Mississippi Valley-type ore fluid are potentially capable of transporting sufficient amounts of Pb and Zn in the form of carboxylate complexes to form economic deposits of Pb and Zn. Both of these fluids are oxidized, have very low total reduced sulfur, and have pHs in the range 5.5 to 6.5. On the other hand, the reduced ore fluid models of Sverjensky (1984) (projected to 100oC) and Giordano and Barnes (1981), both for Mississippi Valley ? type deposits, can at best transport amounts of Pb and Zn as carboxylate complexes that are many orders of magnitude below the 1 to 10 ppm minimum required to form economic deposits. The speciation results show that the log - pH conditions most favorable for carboxylate complexation are the same conditions under which chloride complexation dominates Pb and Zn speciation. Furthermore, the results show that basinal brines and related ore fluids characterized by temperatures near 100oC, high oxidation states (i.e., low total reduced sulfur), and high but reasonable concentrations of carboxylate anions can mobilize up to 3 percent of the total Pb and up to 1.3 percent of the total Zn as carboxylate complexes. These percentages, under the most favorable conditions, correspond to approximately 1 to 100 ppm of those metals in solution; concentrations that are adequate to form economic deposits of these metals. However, the field evidence from modern petroleum-field brines suggests that these optimal conditions, at 100oC, for carboxylate complexation are rarely met.

Giordano, T. H.

2001-12-01

49

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

Microsoft Academic Search

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

D. A. Ionov; B. J. Wood

1992-01-01

50

Computer program for calculation of oxygen uptake  

NASA Technical Reports Server (NTRS)

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

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

1979-01-01

51

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

52

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

PubMed Central

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

Giordano, Thomas H

2002-01-01

53

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

USGS Publications Warehouse

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

Hass, J.L., Jr.

1970-01-01

54

CALCULATIONS OF OXYGEN TRANSPORT BY RED BLOOD CELLS  

E-print Network

CALCULATIONS OF OXYGEN TRANSPORT BY RED BLOOD CELLS AND HEMOGLOBIN SOLUTIONS IN CAPILLARIES Arjun) on oxygen transport in capillary-size vessels. A discrete cell model is presented with red blood cells (RBCs; Diffusion; RBC INTRODUCTION Hemoglobin (Hb) is the protein in red blood cells (RBCs) responsible

Popel, Aleksander S.

55

Fugacity and concentration gradients in a gravity field  

NASA Technical Reports Server (NTRS)

Equations are reviewed which show that at equilibrium fugacity and concentration gradients can exist in gravitational fields. At equilibrium, the logarithm of the ratio of the fugacities of a species at two different locations in a gravitational field is proportional to the difference in the heights of the two locations and the molecular weight of the species. An analogous relation holds for the concentration ratios in a multicomponent system. The ratio is calculated for a variety of examples. The kinetics for the general process are derived, and the time required to approach equilibrium is calculated for several systems. The following special topics are discussed: ionic solutions, polymers, multiphase systems, hydrostatic pressure, osmotic pressure, and solubility gradients in a gravity field.

May, C. E.

1986-01-01

56

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

57

DFT Calculations using WIEN2K to determine oxygen defect structure of rare earth doped ceria  

E-print Network

We perform density functional calculations using the program WIEN2K in order to study oxygen vacancies in rare earth doped ceria. The calculation for all rare earth elements were prepared, however only those foe Cadmium and Europium were performed due to lack of time. Also a short description of my stay at CERN was presented

Khalife, Ali Rida

2014-01-01

58

Atomic oxygen flux and fluence calculation for Long Duration Exposure Facility (LDEF)  

NASA Technical Reports Server (NTRS)

The LDEF mission was to study the effects of the space environment on various materials over an extended period of time. One of the important factors for materials degradation in low earth orbit is the atomic oxygen fluxes and fluences experienced by the materials. These fluxes and fluences are a function of orbital parameters, solar and geomagnetic activity, and material surface orientation. Calculations of atomic oxygen fluences and fluxes for the LDEF mission are summarized. Included are descriptions of LDEF orbital parameters, solar and geomagnetic data, computer code FLUXAV, which was used to perform calculations of fluxes and fluences, along with a discussion of the calculated fluxes and fluences.

Bourassa, Roger J.; Gillis, James R.

1991-01-01

59

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

60

First-principles calculation and experimental study of oxygen diffusion in uranium dioxide  

NASA Astrophysics Data System (ADS)

This work provides an illustration that density functional theory (DFT) + U calculations may quantitatively describe transport phenomena in uranium dioxide. Oxygen diffusion mechanisms are investigated using both ab initio calculations and experimental approaches mainly involving self-diffusion coefficient measurements. The dependences of the experimental data upon oxygen potential and sample impurity content demonstrate, by comparison with basic point defect and diffusion theory, that oxygen migration occurs via an interstitial mechanism. The temperature study provides an estimate of interstitial formation and migration energies which compare very favorably to energies calculated using the DFT+U approximation relating to the interstitialcy mechanism. Also, vacancy migration and Frenkel pair formation energies are shown to agree well with existing data.

Dorado, Boris; Garcia, Philippe; Carlot, Gaëlle; Davoisne, Carine; Fraczkiewicz, Mathieu; Pasquet, Bertrand; Freyss, Michel; Valot, Carole; Baldinozzi, Guido; Siméone, David; Bertolus, Marjorie

2011-01-01

61

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

62

Calculation of the mixing chamber of an ejector chemical oxygen - iodine laser  

SciTech Connect

Gas parameters are calculated at the outlet of the mixing chamber of an ejector chemical oxygen-iodine laser with a nozzle unit consisting of nozzles of three types, which provides a total pressure of the active medium that substantially exceeds a pressure in the generator of singlet oxygen. This technique of forming the laser active medium substantially facilitates the ejection of the exhaust gas to the atmosphere by using a diffuser and single-stage vacuum systems based on water circulating pumps. (lasers, active media)

Zagidullin, M V; Nikolaev, V D [Samara Branch of the P.N. Lebedev Physics Institute, Russian Academy of Sciences, Samara (Russian Federation)

2001-06-30

63

pH buffering by metastable mineral-fluid equilibria and evolution of carbon dioxide fugacity during burial diagenesis  

NASA Astrophysics Data System (ADS)

Numerous potential pH buffers including reactions among aqueous organic acid and carbonate species carbonate and silicate minerals are typically present during burial diagenesis. Buffering of pH in natural systems is a function of mass action, mass balance kinetic constraints. In most sedimentary basins, carbonate and silicate minerals are present in amounts sufficient to buffer pH the activities of aqueous species are consistent with metastable equilibrium among observed diagenetic minerals. These observations indicate that mass balance and kinetic constraints are relatively less important than mass action constraints measured by the buffer index, ?, here defined as follows: ? = -d?/dpH The buffer index ultimately dictates which buffer reaction controls pH under diagenetic conditions; buffer reactions with high ? values are favoured over those with low values. Buffer indices for a number of potential diagenetic buffer reactions have been calculated by reaction path modeling. Heterogeneous equilibria among carbonate and silicate minerals and an aqueous phase have greater ? values than those for homogeneous reactions among aqueous carbonate and organic acid species. This implies that pH, calcite dissolution ƒ CO2 are strongly dependent on carbonate-silicate-fluid interactions during diagenesis. The role of carbonate-silicate reactions in controlling pH is tested by examining the evolution of CO 2 fugacities with temperature during burial diagenesis. Carbon dioxide fugacities have been calculated by reaction path modeling of diagenetic carbonate-silicate equilibria for sedimentary and geothermal systems. Calculated CO 2 fugacities are in general agreement with observed CO 2 fugacities. The combination of high buffer index, apparent metastable equilibrium between diagenetic minerals and waters the relatively accurate prediction of z. hfl; CO2 trends with temperature suggest that carbonate-silicate reactions are important in determining the evolution of fluid compositions in sedimentary basins and influence the course of dissolution events in burial diagenesis.

Hutcheon, Ian; Shevalier, Maurice; Abercrombie, Hugh J.

1993-03-01

64

Calculation of the relative metastabilities of proteins in subcellular compartments of Saccharomyces cerevisiae  

E-print Network

[abridged] Background: The distribution of chemical species in an open system at metastable equilibrium can be expressed as a function of environmental variables which can include temperature, oxidation-reduction potential and others. Calculations of metastable equilibrium for various model systems were used to characterize chemical transformations among proteins and groups of proteins found in different compartments of yeast cells. Results: With increasing oxygen fugacity, the relative metastability fields of model proteins for major subcellular compartments go as mitochondrion, endoplasmic reticulum, cytoplasm, nucleus. In a metastable equilibrium setting at relatively high oxygen fugacity, proteins making up actin are predominant, but those constituting the microtubule occur with a low chemical activity. A reaction sequence involving the microtubule and spindle pole proteins was predicted by combining the known intercompartmental interactions with a hypothetical program of oxygen fugacity changes in the local environment. In further calculations, the most-abundant proteins within compartments generally occur in relative abundances that only weakly correspond to a metastable equilibrium distribution. However, physiological populations of proteins that form complexes often show an overall positive or negative correlation with the relative abundances of proteins in metastable assemblages. Conclusions: This study explored the outlines of a thermodynamic description of chemical transformations among interacting proteins in yeast cells. The results suggest that these methods can be used to measure the degree of departure of a natural biochemical process or population from a local minimum in Gibbs energy.

Jeffrey M. Dick

2008-12-01

65

Electronic Structure Calculations of an Oxygen Vacancy in KH2PO4  

SciTech Connect

We present first-principles total-energy density-functional theory electronic structure calculations for the neutral and charge states of an oxygen vacancy in KH{sub 2}PO{sub 4} (KDP). Even though the overall DOS profiles for the defective KDP are quite similar to those of the perfect KDP, the oxygen vacancy in the neutral and +1 charge states induces defect states in the band gap. For the neutral oxygen vacancy, the gap states are occupied by two electrons. The difference between the integral of the total density of states (DOS) and the sum of the DOS projected on the atoms of 0.98 |e|, indicates that one of the two electrons resulting from the removal of the oxygen atom is trapped in the vacancy, while the other tends to delocalize in the neighboring atoms. For the +1 charge oxygen vacancy, the addition of the hole reduces the occupation of the filled gap-states in the neutral case from two to one electron and produces new empty states in the gap. The new empty gap states are very close to the highest occupied states, leading to a dramatic decrease of the band gap. The difference between the integral of the total DOS and the sum of the DOS projected on the atoms is 0.56 |e|, which implies that more than 56% of the redundant electron is trapped in the oxygen vacancy, and 44% spreads over the neighboring atoms. In sharp contrast, no defect states appear in the energy gap for the +2 charge O vacancy. Thus, the addition of the two holes completely compensates the two redundant electrons, and removes in turn the occupied gap states in the neutral case.

Liu, C S; Hou, C J; Kioussis, N; Demos, S; Radousky, H

2005-02-18

66

Response calculations of electronic and vibrational transitions in molecular oxygen induced by interaction with noble gases.  

PubMed

The Einstein coefficient for the singlet oxygen emission a1Deltag-->X3Sigmag- at lambda=1270 nm and b1Sigmag+-->X3Sigmag- emission at lambda=750 nm were calculated by quadratic response (QR) multiconfiguration self-consisted field (MCSCF) method for a number of collision complexes O2+M, where M=He, Ne, Ar. Interaction with He clusters was studied in order to simulate cooperative effect of the environment on the oxygen emission. Calculations of the dipole transition moment for the Noxon band, b1Sigmag+-a1Deltag, by linear response (LR) MCSCF method were also performed for a number of collision complexes. Spin-orbit coupling (SOC) between the b1Sigmag+ and X3Sigmag- (MS=0) states does not change much upon collisions, thus the a-X transition borrows intensity mostly from the collision-induced Noxon band b-a. The a-X intensity borrowing from the Schumann-Runge transition is negligible. The calculations show that the b-a and a-X transition probabilities are enhanced approximately by 10(5) and 10(3) times by O2+M collisions. An order of magnitude differences occur for both transitions for noble gases with large difference in polarizability. A strong cooperative effect is obtained when few He atoms perturb the oxygen molecule. Depending on mutual orientation of the partners it can be a complete quenching of the a-->X emission or strong non-additive enhancement. Collision-induced infrared vibrational transitions in a number of molecular oxygen excited states were studied and shown to be state selective. PMID:14607236

Minaev, Boris F; Kobzev, G I

2003-12-01

67

Embedded cluster model for chemisorption using density functional calculations: Oxygen adsorption on the Al(100) surface.  

NASA Astrophysics Data System (ADS)

An embedded cluster model to study chemisorption on metal surfaces is presented. The approach is based on a method proposed by Whitten and Pakkanen [Phys. Rev. B 21, 4357 (1980)], which constructs an embedding potential using a set of molecular orbitals (MO) obtained for a large cluster considered appropriate to describe the adsorption site correctly. The embedded cluster approach combined with the Kohn-Sham density functional theory (KS-DFT) formalism has special features that are discussed in this work. There are several possible approximations that can be explored in practical implementations: the localization procedure used to localize the KS MOs on the surface, the choice of the cluster, the way the embedding potential is constructed and the possibility to use fractional MO occupancies and even fractional charges in order to set up the embedded cluster, are some of the points that are discussed. We have implemented this approach in a modified version of deMon-KS. Results are presented for oxygen adsorption on the Al(100) surface. The embedding potential is constructed from the MOs obtained for an Al70 cluster. The atop, bridge and four-fold sites are described by the Al10, Al20 and Al21 clusters, respectively. The bare cluster results are also presented and compared to those for the embedded cluster. The embedded cluster calculations are in better agreement with the available experimental results. The four-fold site is the most favored. The oxygen atom is found to be in the surface plane, while for the bare cluster model the oxygen lies 0.5 Å above the surface. The local density of states of the oxygen at the four-fold site of Al70, and the bare and embedded clusters have been evaluated and compared with the available UPS data.

Duarte, Hélio A.; Salahub, Dennis R.

1998-01-01

68

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

Microsoft Academic Search

Volcanic gases collected during episode 1 of the Puu Oo eruption along the east rift zone of Kilauea Volcano, Hawaii, have uniform C-O-H-S-Cl-F compositions that are sharply depleted in CO 2 . The CO 2 -poor gases are typical of Type II volcanic gases ( and , 1985) and were emitted from evolved magma stored for a prolonged period of

T. M. Gerlach

1993-01-01

69

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

E-print Network

Control of the water fugacity at high pressures and temperatures: Applications to the incorporation Edited by Kei Hirose Keywords: Water fugacity Olivine Point defects Infrared spectroscopy a b s t r a c t A new method is developed to control water fugacity at a fixed pressure and temperature. We use two

70

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

71

First-principles diffusion-barrier calculation for atomic oxygen on Pt(111)  

NASA Astrophysics Data System (ADS)

An inconsistency is pointed out in adsorption energy values for O diffusion on Pt(111) in three recent studies: (A) the scanning tunneling microscope (STM)-deduced value of 0.43 eV for the diffusion barrier [J. Wintterlin, R. Schuster, and G. Ertl, Phys. Rev. Lett. 77, 123 (1996)]; (B) the calculated fcc-hcp adsorption-energy difference [P. J. Fiebelman, E. Stefanie, and M. Thomas, ibid.77, 2257 (1997)]; and (C) the STM-identified metastability of O in hcp sites [B. C. Stipe et al., ibid.78, 4410 (1997)]. Using accurate first-principles density-functional methods we obtain full agreement with (B) and (C) and a diffusion barrier of 0.58 eV, consistent with a reinterpretation of the raw data in (A). We further report on oxygen-induced surface buckling.

Bogicevic, Alexander; Strömquist, Johan; Lundqvist, Bengt I.

1998-02-01

72

Asymmetry of adsorption of oxygen at wurtzite AlN (0001) and (0001¯) surfaces: First-principles calculations  

NASA Astrophysics Data System (ADS)

First-principles calculations are performed to study the adsorption of oxygen at wurtzite AlN (0001) and (0001¯) surfaces as a function of oxygen coverage. We find that the adsorption of oxygen at the AlN (0001¯) surface has a larger binding energy than at the AlN (0001) surface. The hollow site (H3) is preferred for the (0001) surface, whereas the site directly above the Al sublayer and the H3 site are almost degenerate in energy for the (0001¯) surface. The trend of the adsorption energy as a function of the oxygen coverage for the AlN (0001) surface is similar to that of GaN, whereas for the AlN (0001¯) surface it is different from GaN. The asymmetry of the oxygen adsorption at the two surfaces is explained using the electron counting rule and the resulting surface electronic states.

Ye, Honggang; Chen, Guangde; Zhu, Youzhang; Wei, Su-Huai

2008-01-01

73

Probabilistic fugacity analysis of Lake Pontchartrain pollution after Hurricane Katrina.  

PubMed

After Hurricane Katrina passed through the US Gulf Coast in August 2005, floodwaters covering New Orleans were pumped into Lake Pontchartrain as part of the rehabilitation process in order to make the city habitable again. The long-term consequences of this environmentally critical decision were difficult to assess at the time and were left to observation. In the aftermath of these natural disasters, and in cases of emergency, the proactive use of screening level models may prove to be an important factor in making appropriate decisions to identify cost effective and environmentally friendly mitigation solutions. In this paper, we propose such a model and demonstrate its use through the application of several hypothetical scenarios to examine the likely response of Lake Pontchartrain to the contaminant loading that were possibly in the New Orleans floodwaters. For this purpose, an unsteady-state fugacity model was developed in order to examine the environmental effects of contaminants with different physicochemical characteristics on Lake Pontchartrain. The three representative contaminants selected for this purpose are benzene, atrazine, and polychlorinated biphenyls (PCBs). The proposed approach yields continuous fugacity values for contaminants in the water, air, and sediment compartments of the lake system which are analogous to concentrations. Since contaminant data for the floodwaters are limited, an uncertainty analysis was also performed in this study. The effects of uncertainty in the model parameters were investigated through Monte Carlo analysis. Results indicate that the acceptable recovery of Lake Pontchartrain will require a long period of time. The computed time range for the levels of the three contaminants considered in this study to decrease to maximum contaminant levels (MCLs) is about 1 year to 68 years. The model can be implemented to assess the possible extent of damage inflicted by any storm event on the natural water resources of Southern Louisiana or similar environments elsewhere. Furthermore, the model developed can be used as a useful decision-making tool for planning and remediation in similar emergency situations by examining various potential contamination scenarios and their consequences. PMID:17462815

Gokgoz-Kilic, Sinem; Aral, Mustafa M

2008-08-01

74

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

75

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

NASA Technical Reports Server (NTRS)

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

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

1995-01-01

76

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

77

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

78

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

79

The critical surface fugacity of self-avoiding walks on a rotated honeycomb lattice  

NASA Astrophysics Data System (ADS)

In a recent paper by Beaton et al, it was proved that a model of self-avoiding walks on the honeycomb lattice, interacting with an impenetrable surface, undergoes an adsorption phase transition when the surface fugacity is 1+\\sqrt{2}. Their proof used a generalization of an identity obtained by Duminil-Copin and Smirnov, and confirmed a conjecture of Batchelor and Yung. We consider a similar model of self-avoiding walk adsorption on the honeycomb lattice, but with the lattice rotated by ?/2. For this model there also exists a conjecture for the critical surface fugacity, made in 1998 by Batchelor, Bennett-Wood and Owczarek. Using similar methods to Beaton et al, we prove that this is indeed the critical fugacity.

Beaton, Nicholas R.

2014-02-01

80

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

ERIC Educational Resources Information Center

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

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

2013-01-01

81

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

NASA Astrophysics Data System (ADS)

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 (NbTi), and cells with either interstitial oxygen (Oi) or oxygen vacancies (VO). In addition, a unit cell with a NbTi and Oi, and a cell with NbTi and VO were investigated to clarify the role of nonstoichiometry in TNO. From the calculated results, the importance of the adjacent NbTi-VO and NbTi-Oi 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 NbTi 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 NbTi-VO structure compared to the VO. The possibility of an essential role of this state in electric conduction was discussed. The formation of the adjacent NbTi-Oi structure by O2 gas annealing was discussed using statistical mechanics. The Gibbs free energies were calculated for Oi atoms in TNO and compared to that of O2 molecules in the gas phase. The analysis was qualitatively consistent with experimental behavior under the assumption of the NbTi-VO structures.

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

2009-07-01

82

Comparison of Oxygen Gauche Effects in Poly(Oxyethylene) and Poly(ethylene terephtylene) Based on Quantum Chemistry Calculations  

NASA Technical Reports Server (NTRS)

The so-called oxygen gauche effect in poly(oxyethylene) (POE) and its model molecules such as 1,2-dimethoxyethane (DME) and diglyme (CH3OC2H4OC2H4OCH3) is manifested in the preference for gauche C-C bond conformations over trans. This has also been observed for poly(ethylene terephthalate) (PET). Our previous quantum chemistry calculations demonstrated that the large C-C gauche population in DME is due, in part, to a low-lying tg +/- g+ conformer that exhibits a substantial 1,5 CH ... O attraction. New calculations will be described that demonstrate the accuracy of the original quantum chemistry calculations. In addition, an extension of this work to model molecules for PET will be presented. It is seen that the C-C gauche preference is much stronger in 1,2 diacetoxyethane than in DME. In addition, there exist low-lying tg +/- g+/- and g+/-g+/-g+/- conformers that exhibit 1,5 CH ... O attractions involving the carbonyl oxygens. It is expected that the -O-C-C-O- torsional properties will be quite different in these two polymers. The quantum chemistry results are used to parameterize rotational isomeric states models (RIS) and force fields for molecular dynamics simulations of these polymers.

Jaffe, Richard; Han, Jie; Yoon, Do; Langhoff, Stephen R. (Technical Monitor)

1997-01-01

83

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

84

Electrical Conductivity of Olivine at High Pressure and Under Controlled Oxygen Fugacity  

Microsoft Academic Search

It is now generally accepted that the major phase in the earth's upper mantle is olivine with an approximate composi- tion Mgx.sFe0..SiO4 (Fujisawa, 1968). Published values of elec- trical conductivity a of olivine of this composition (either single crystal or polycrystalline) at high temperatures show very poor agreement (Duba and Lilley, 1972). In many in- stances the difference can be

A. Duba; H. C. Heard; R. N. Schock

1974-01-01

85

Crystallization temperatures and oxygen fugacities of magmas from the Southeast Indian Ocean Ridge system  

E-print Network

crystals, 30 olivine cry- stals and 41 glass areas were probed for Si02, A1203, Fe0*, (total iron as FeO), MgO, CaO, Na20, K20, Ti02 and MnO content. Instrumental neutron activation analysis was used to measure the concentration of Co, Cr, Sc, Hf, La... normative mineral tetrahedron (Yoder and Tilley, 1962). FN x D2 && D3 4 5 D5 D6 D7 DS + Dg 0 Dlo Dll 2Z ~O g Z 0 23 N Cl IA ( (O Al O Pl Pt 0 O CA O O O O 0 Cl N (Ct N (O Pt 0 IA (h Pl N O D N D N Iw h N Cht LO I (n 0 N Ct Ltt 0...

Ongley, Lois Kathe

2012-06-07

86

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

87

Workshop on Oxygen in the Terrestrial Planets  

NASA Technical Reports Server (NTRS)

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

2004-01-01

88

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

89

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

90

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

91

Calculation of oxygen isotope fractionation between uranium dioxide, uranium trioxide and water  

NASA Astrophysics Data System (ADS)

Reduced partition function ratios (r.p.f.r) for uranium dioxide and uranium trioxide are calculated using selected crystal field models for optical modes and Debye functions for acoustic modes at temperatures ranging from 0 to 1000°C. The contribution of the acoustic modes is negligibly small in the calculated values of r.p.f.r. in all temperature ranges. The uncertainty of the r.p.f.r. is calculated from the standard deviation of the force constant used for the calculation, which is about ± 5%. at 0°C, ±2%. at 200°C and ±0.2%. at 1000°C for both oxides. The r.p.f.r. for both uranium oxides are lower than that of water, implying that uraninite is depleted in 18O with respect to associated fluids at almost all temperature ranges. The fractionation factors between uranium oxides and water are expressed as: 10 3 ln ? = 3.29 10 6/T 2-13.63 10 3/T + 4.65 , and 10 3 ln ? = 3.63 10 6/T 2-13.29 10 3/T + 4.42 for ?-UO 3 and UO 2, respectively. The values of r.p.f.r. for uranium oxides are low compared to those for common rock-forming minerals, however they are similar to the values for other metal oxides, such as magnetite, rutile and probably cassiterite.

Hattori, Keiko; Halas, Stanislaw

1982-10-01

92

Many-body GW calculation of the oxygen vacancy in ZnO  

SciTech Connect

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

Lany, Stephan; Zunger, Alex

2010-01-01

93

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

94

Comparison of multi-media transport and transformation models: Regional Fugacity model vs. CalTOX  

Microsoft Academic Search

Two multimedia environmental transport and transformation computer models are summarized and compared. The regional fugacity model published by Mackay and Paterson (1991), termed Fug3ONT, is a four compartment steady-state model designed to simulate the relative distribution of nonionic organic chemicals in a multimedia system. CalTOX is a seven compartment multimedia total exposure model for hazardous waste sites. Both models are

Randy L. Maddalena; Thomas E. McKone; David W. Layton; Dennis P. H. Hsieh

1995-01-01

95

The Critical Fugacity for Surface Adsorption of Self-Avoiding Walks on the Honeycomb Lattice is  

NASA Astrophysics Data System (ADS)

In 2010, Duminil-Copin and Smirnov proved a long-standing conjecture of Nienhuis, made in 1982, that the growth constant of self-avoiding walks on the hexagonal (a.k.a. honeycomb) lattice is . A key identity used in that proof was later generalised by Smirnov so as to apply to a general O( n) loop model with (the case n = 0 corresponding to self-avoiding walks). We modify this model by restricting to a half-plane and introducing a surface fugacity y associated with boundary sites (also called surface sites), and obtain a generalisation of Smirnov's identity. The critical value of the surface fugacity was conjectured by Batchelor and Yung in 1995 to be . This value plays a crucial role in our generalized identity, just as the value of the growth constant did in Smirnov's identity. For the case n = 0, corresponding to self-avoiding walks interacting with a surface, we prove the conjectured value of the critical surface fugacity. A crucial part of the proof involves demonstrating that the generating function of self-avoiding bridges of height T, taken at its critical point 1/ ?, tends to 0 as T increases, as predicted from SLE theory.

Beaton, Nicholas R.; Bousquet-Mélou, Mireille; de Gier, Jan; Duminil-Copin, Hugo; Guttmann, Anthony J.

2014-03-01

96

Calculation of oxygen diffusion in plutonium oxide films during the high-temperature oxidation of plutonium-1 weight percent gallium in 500 torr of air  

Microsoft Academic Search

Oxygen self-diffusion in PuO\\/sub 1.995\\/ was calculated from rate constants obtained for the parabolic oxidation of the Pu-1 wt % Ga alloy in 500-torr dry air between 250 and 480\\/degree\\/C. The activation energy for oxygen vacancy diffusion in the n-type PuO\\/sub 2-x\\/ is 22.6 kcal\\/mole. Results from this investigation are compared with other reported results, and possible explanation for the

Stakebake

1988-01-01

97

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

98

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

PubMed

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

Zhang, Xueli; Gong, Xuedong

2014-08-01

99

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

SciTech Connect

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

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

2011-07-15

100

Calculation of oxygen diffusion in plutonium oxide films during the high-temperature oxidation of plutonium-1 weight percent gallium in 500 torr of air  

SciTech Connect

Oxygen self-diffusion in PuO/sub 1.995/ was calculated from rate constants obtained for the parabolic oxidation of the Pu-1 wt % Ga alloy in 500-torr dry air between 250 and 480/degree/C. The activation energy for oxygen vacancy diffusion in the n-type PuO/sub 2-x/ is 22.6 kcal/mole. Results from this investigation are compared with other reported results, and possible explanation for the difference in results is discussed. 21 refs., 5 figs., 1 tab.

Stakebake, J.L.

1988-05-27

101

Investigations of the air/plant partitioning of semivolatile organic compounds using a fugacity meter  

SciTech Connect

A solid phase fugacity meter was used to investigate the transport kinetics and steady-state partitioning of semivolatile organic compounds between the gas phase and leaves of Lolium multiflorum (Welsh ray grass). The grass air partition coefficients determined for grass concentrations ranging over several orders of magnitude were in good agreement with each other for each compound. The average partition coefficients correlated well with the octanol/air partition coefficients. The kinetic behavior was described using a two-compartment model consisting of a small surface compartment and a large interior reservoir compartment. The results of this study support the hypothesis that vegetation plays an important role in the fate of lipophilic organic compounds in the terrestrial environment.

Tolls, J.; McLachlan, M.S. [Univ. of Bayreuth (Germany)

1994-12-31

102

Electronic structure of an oxygen vacancy in Al{sub 2}O{sub 3} from the results of Ab Initio quantum-chemical calculations and photoluminescence experiments  

SciTech Connect

The electronic structure of an oxygen vacancy in {alpha}-Al{sub 2}O{sub 3} and {gamma}-Al{sub 2}O{sub 3} is calculated. The calculation predicts an absorption peak at an energy of 6.4 and 6.3 eV in {alpha}-Al{sub 2}O{sub 3} and {gamma}-Al{sub 2}O{sub 3}, respectively. The luminescence and luminescence excitation spectra of amorphous Al{sub 2}O{sub 3} are measured using synchrotron radiation. The presence of a luminescence band at 2.9 eV and a peak at 6.2 eV in the luminescence excitation spectrum indicates the presence of oxygen vacancies in amorphous Al{sub 2}O{sub 3}.

Pustovarov, V. A. [Ural State Technical University (Russian Federation); Aliev, V. Sh.; Perevalov, T. V., E-mail: timson@isp.nsc.ru; Gritsenko, V. A., E-mail: grits@isp.nsc.ru [Russian Academy of Sciences, Institute of Semiconductor Physics, Siberian Branch (Russian Federation); Eliseev, A. P. [Russian Academy of Sciences, Institute of Geology and Mineralogy, Siberian Branch (Russian Federation)

2010-01-15

103

Deriving Algorithms for the Remote Sensing of Carbon Dioxide Fugacity at the Ocean Surface  

NASA Astrophysics Data System (ADS)

As concentrations of carbon dioxide in the atmosphere continue to rise, the capacity of the ocean to act as a carbon dioxide sink is of critical importance as it is the major sink of anthropogenic carbon dioxide. Uncertainties in our ability to quantify the role of the oceans in the carbon cycle, especially in computing the gas fluxes between atmosphere and ocean on global scales, leads directly to uncertainty in predicting the response of the of the climate system to increasing levels of carbon dioxide in the atmosphere. Here we report on a study to improve the accuracy of the retrievals of surface fugacity from earth observation satellites. A large data set of in situ measurements from equipment on the Royal Caribbean Cruise Lines ship Explorer of the Seas in the Caribbean Sea and western tropical Atlantic Ocean the relationship between the carbon dioxide concentration and variables measurable from space is explored using advanced computational techniques to improve on prior results derived by linear regression. Using natural selection as a conceptual model, the Genetic Algorithm approach maintains a population of “tentative” solutions that are subjected to “survival of the fittest” tests and to operators that implement mutation and recombination (mutual exchange of the “genetic information”). In our implementation, each specimen in the population represents one formula, expressed by a tree-like data structure. The fitness function that quantifies the individual's survival chances is defined as the mean square error scored by the given formula on the training data. We demonstrate in this case study that not only can the accuracy of satellite retrievals of surface fugacity of carbon dioxide be improved by using algorithms based on the information content of the data sets, but also the regions in which individual algorithms are applicable can also be determined. These regions align with the underlying dynamical oceanographic features. This approach can be applied to measurements taken elsewhere in the oceans, and of variables other than carbon dioxide.

Minnett, P. J.; Wickramaratna, K.; Kubat, M.

2010-12-01

104

First Principles Calculations of Oxygen Vacancy Formation and Migration in Ba1?xSrxCo1?yFeyO3?? Perovskites  

SciTech Connect

Based on first principles DFT calculations, we analyze oxygen vacancy formation and migration energies as a function of chemical composition in complex multicomponent (Ba,Sr)(Co,Fe)O3?? perovskites which are candidate materials for SOFC cathodes and permeation membranes. The atomic relaxation, electronic charge redistribution and energies of the transition states of oxygen migration are compared for several perovskites to elucidate the atomistic reason for the exceptionally low migration barrier in Ba0.5Sr0.5Co0.8Fe0.2O3?? that was previously determined experimentally. The critical comparison of Ba1?xSrxCo1?yFeyO3?? perovskites with different cation compositions and arrangements shows that in addition to the geometric constraints the electronic structure plays a considerable role for the height of the oxygen migration barrier in these materials. These findings help understand advantages and limitations of the fast oxygen permeation and exchange properties of Ba0.5Sr0.5Co0.8Fe0.2O3??.

Merkle, Rotraut; Mastrikov, Yuri; Kotomin, Eugene Alexej; Kukla, Maija M.; Maier, Joachim

2011-12-28

105

Siderophile Trace Elements in ALH 84001 and Other Achondrites: A Temporal Increase of Oxygen Fugacity in the Martian Mantle?  

NASA Astrophysics Data System (ADS)

We have employed neutron activation, including radiochemical NAA, to investigate SNC/martian meteorites ALH 77005, ALH 84001 and LEW 88516, along with 15 eucrites. Our data for 10 manifestly monomict eucrites confirm previous indications [e.g., 1] that compositionally pristine eucrites are generally extremely siderophile-poor, although for several of the most extremely siderophile-depleted eucrites we find slight enhancements in Re/Os (Figure). Our RNAA data are the first for highly siderophile elements in polymict eucrites, and show a broad similarity with lunar polymict breccias. In general, our data (e.g., Ga/Al = 4.3x10^-4) confirm SNC affinity [2] for ALH84001. However, siderophile concentrations are, by SNC standards, extraordinarily low: Ni = 5.8 micrograms/g and (in pg/g) Au = 9.4, Ir = 80, Os = 10.2, and Re = 1.66+/-0.25(1-s); Ge (1080 ng/g) is typical for SNCs. Like terrestrial basalts [1], other SNCs have relatively constant Re, ranging from 28 (Lafayette [3]) to 102 pg/g (ALH 77005) among seven analyzed meteorites of various types, in which Os ranges from <2.3 to 4400 pg/g. A plot of Os vs. Re/Os (Figure) shows that ALH 84001 has 23x lower Re than expected for a young SNC of similar Os content. On Earth, Re generally behaves as a mildly incompatible element, whereas Os behaves as a strongly compatible element. A plausible explanation for this divergence [1] is that Re is more prone to enter higher oxidation states, such as Re^4+, which would tend to behave like W^4+. This model is consistent with the Os-like behavior of Re in the highly reduced lunar and eucritic environments, and Birck and Allegre [1] interpret the typically intermediate Re contents of SNCs as suggestive of origin from a mantle source region at intermediate fO(sub)2 (they also considered, but rejected, an implausible "contamination" model). Extended to ALH 84001, this model implies that the mantle source was at a substantially (roughly 1.7 log(sub)10 units) lower fO2 than the analogous sources of the younger SNCs. Conceivably ALH84001 siderophiles were altered by metasomatic processes [cf. 2]. However, near-surface processing on a heavily cratered body would generally tend to add siderophile material, rather than remove it. Also, Treiman [4] argues that alteration took place strictly at low temperatures. Another possible objection is that unlike eucrites and lunar basalts, ALH84001 is rich in Fe^3+ [2]. However, if the parent magma encountered even a small proportion of water in the upper crust of Mars, the final fO(sub)2 would be substantially raised. Many authors have proposed that the terrestrial planets in general, and Mars in particular, were originally very dry, implying low fO(sub)2, and that only late in accretion history did substantial proportions of oxidizing volatiles accrete as a "veneer". Possibly when ALH84001 formed, 4.50+/-0.13 Ga [5], oxidation had not yet altered the primordial, low fO(sub)2 nature of its mantle source region. It is also conceivable that large portions of the martian mantle never reached fO(sub)2 as high as inferred for the younger SNCs (possibly derived from a single crater). In any case, the siderophile-depletion pattern of ALH 84001 is unique among SNCs. References: [1] Birck J. L. and All gre C. J. (1994) EPSL, 124, 139-148. [2] Mittlefehldt D. W. (1994) Meteoritics, 29, 214-221. [3] Treiman A. H. et al. (1986) GCA, 50, 1071-1091. [4] Treiman A. H. (1995) Meteoritics, 30, 294-302. [5] Nyquist L. E. et al. (1995) LPS, XXVI, 1065-1066.

Warren, P. H.; Kallemeyn, G. W.

1995-09-01

106

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

107

The effect of oxygen fugacity and temperature on solubilities of nickel, cobalt, and molybdenum in silicate melts  

Microsoft Academic Search

Solubilities of Ni, Co and Mo in silicate melts of anorthite-diopside eutectic composition were determined at reducing conditions, with f O 2 values ranging from 10 -8.6 to 10 -12.6 atm and at temperatures of around 1400°C. In a log (solubility) vs. log ( f O 2 ) diagram, Ni and Co data plot along straight lines with slopes of

A. Holzheid; A. Borisov; H. Palme

1994-01-01

108

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

109

A short timescale for changing oxygen fugacity in the solar nebula revealed by high-resolution 26  

E-print Network

in the solar system. Astrophysical models for the evolution of solids in the young solar proto- planetary disk to the star coupled with outward transport of angular momentum; as a consequence of viscous behavior, some we use the amount of radiogenic 26 Mg (26 Mg*) due to decay of the extinct radionuclide 26 Al (mean

Manning, Craig

110

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

Microsoft Academic Search

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

Gary Strangman; Maria Angela Franceschini; David A. Boasb

2003-01-01

111

Thermodynamic calculations of the volatility of the platinum group elements (PGE): The PGE content of fluids at magmatic temperatures  

SciTech Connect

The volatilities of the platinum-group elements as metals, oxides and chlorides were calculated at temperatures of 800-1600 K. Only Pd is significantly volatile as the metal. At log f{sub H{sub 2}O} = 1 Kbar and 1200 K, the concentration (weight) of Pd in the vapor reaches 1 ppt and at 1600 K attains several ppb. The PGE oxides are extremely volatile at atmospheric oxygen fugacities. However, only Os and Ru have significant volatilities ({>=} 1 ppt) as oxides (OsO{sub 4}, RuO{sub 3}) at oxygen fugacities typical of magmatic PGE deposits (near QFM), and only at temperatures greater than 1400 K. Data on the volatility of PGE chlorides exist only for Pd and Ru, both of which are somewhat more volatile as chlorides than as oxides. At 1400 K, f{sub H{sub 2}O} = 1000 bars, f{sub HCl} = 100 bars and at QFM, the calculated vapor concentrations of PdCl{sub 2} and RuCl{sub 3} are 500 ppt and 20 ppt, respectively. However, higher concentrations of PGE may be attained at higher temperatures, higher f{sub O{sub 2}}, higher f{sub HCl} or lower f{sub H{sub 2}O}. Also, any interactions between water vapor and PGE vapor species would tend to increase the vapor concentration of PGE. Vapor transport of the more volatile PGE as chlorides may play some role in the transport of these metals in mafic igneous complexes such as the Stillwater or the Bushveld. However, under the conditions where the PGE are most volatile, the metals Fe, Ni and Cu are several factors of ten more volatile, so that enrichment of the PGe and Cu over Ni and Fe cannot be explained by chloride transport alone.

Wood, S.A. (McGill Univ., Montreal, Quebec (Canada))

1987-11-01

112

Spatial distribution of neutral oxygen vacancies on ZnO nanowire surfaces: An investigation combining confocal microscopy and first principles calculations  

NASA Astrophysics Data System (ADS)

A qualitative approach using room-temperature confocal microscopy is employed to investigate the spatial distribution of shallow and deep oxygen vacancy (VO) concentrations on the polar (0001) and non-polar (101¯0) surfaces of zinc oxide (ZnO) nanowires (NWs). Using the spectral intensity variation of the confocal photoluminescence of the green emission at different spatial locations on the surface, the VO concentrations of an individual ZnO NW can be obtained. The green emission at different spatial locations on the ZnO NW polar (0001) and non-polar (101¯0) surfaces is found to have maximum intensity near the NW edges, decreasing to a minimum near the NW center. First-principles calculations using simple supercell-slab (SS) models are employed to approximate/model the defects on the ZnO NW (101¯0) and (0001) surfaces. These calculations give increased insight into the physical mechanism behind the green emission spectral intensity and the characteristics of an individual ZnO NW. The highly accurate density functional theory (DFT)-based full-potential linearized augmented plane-wave plus local orbitals (FP-LAPW + lo) method is used to compute the defect formation energy (DFE) of the SSs. Previously, using these SS models, it was demonstrated through the FP-LAPW + lo method that in the presence of oxygen vacancies at the (0001) surface, the phase transformation of the SSs in the graphite-like structure to the wurtzite lattice structure will occur even if the thickness of the graphite-like SSs are equal to or less than 4 atomic graphite-like layers [Wong et al., J. Appl. Phys. 113, 014304 (2013)]. The spatial profile of the neutral VO DFEs from the DFT calculations along the ZnO [0001] and [101¯0] directions is found to reasonably explain the spatial profile of the measured confocal luminescence intensity on these surfaces, leading to the conclusion that the green emission spectra of the NWs likely originate from neutral oxygen vacancies. Another significant result is that the variation in the calculated DFE along the ZnO [0001] and [101¯0] directions shows different behaviors owing to the non-polar and polar nature of these SSs. These results are important for tuning and understanding the variations in the optical response of ZnO NW-based devices in different geometric configurations.

Mun Wong, Kin; Alay-e-Abbas, S. M.; Fang, Yaoguo; Shaukat, A.; Lei, Yong

2013-07-01

113

Native defects and oxygen and hydrogen-related defect complexes in CdTe: Density functional calculations  

SciTech Connect

We study structural and electronic properties of various intrinsic and extrinsic defects in CdTe based on first-principles calculations. The focus is given to the role of these defects in the carrier compensation in semi-insulating CdTe, which is essential for the CdTe-based radiation detectors. The semi-insulating behavior of CdTe has been attributed to the Fermi level pinning near middle of the band gap by deep donors. These deep donors compensate shallow acceptors and are generally assumed to be Te antisites. However, we find that intrinsic defects, including the Te antisite, may not have a significant effect on the carrier compensation due either to lack of deep levels near midgap or to low defect concentration. We demonstrate instead that an extrinsic defect, O{sub Te}-H complex, may play an important role in the carrier compensation in CdTe. Other hydrogen-related defects are also discussed.

Du, Mao-Hua [ORNL; Takenaka, Hiroyuki [ORNL; Singh, David J [ORNL

2008-01-01

114

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

115

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

NASA Technical Reports Server (NTRS)

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

Shykoff, Barbara E.; Swanson, Harvey T.

1987-01-01

116

Respirometric kinetic parameter calculations of a batch jet loop bioreactor treating leachate and oxygen uptake rate estimation by DTM.  

PubMed

A novel circulating jet loop bioreactor adapted for organic matter oxidation has been designed and constructed. In this study, the input was leachate samples collected from Kemerburgaz Odayeri waste landfill site located on the European side of Istanbul. Controlling the jet loop bioreactor to realize high rates of purification depends on maintaining the appropriate loadings and operating conditions. This requires collecting various system data to estimate the dynamics of the system satisfactorily with the aim of keeping certain parameters within the specified range. The differential transform method (DTM) based solution of the state equations reveals the current state of the process so that any deviation in the system parameters can be immediately detected and regulated accordingly. The respirometric method for kinetic parameter calculations for biodegradation has been used for some time. In many studies, the respirometer was designed separately, usually in bench-scale. However, when a separate respirometer is used, the scale effect and parameters that affect the hydrodynamic structure of the system should be taken into consideration. In this study, therefore, the jet loop reactor itself was used as a respirometer. Thus, the kinetic parameters found reflecting the characteristics of microorganisms used for biodegradation would be more realistic. If the main reactor, here the jet loop reactor, would be used as the respirometer, the kinetic parameter changes can easily be monitored in the long run. Using the bioreactor as a respirometer, the most important kinetic parameters, Ks, kd and micromax were found to be 11,000 mg L(-1), 0.019 day(-1), and 0.21 day(-1), respectively. The stoichiometric coefficient, Y, was found to be 0.28 gr gr(-1) for the present system. PMID:17997217

Ince, M; Yildiz, F; Engin, G Onkal; Engin, S N; Keskinler, B

2008-05-30

117

Effect of oxygen impurities on properties of the ternary superconductor SnMo/sub 6/S/sub 8/: Extended x-ray-absorption fine-structure determination of bond distances and local-density cluster calculations  

SciTech Connect

Electronic structure calculations were performed for clusters representing the Chevrel-phase SnMo/sub 6/S/sub 8/, with and without oxygen doping. In order to obtain the local structure around the Sn atom, extended x-ray-absorption fine-structure (EXAFS) measurements were made with synchro- tron radiation. The interatomic distances obtained experimentally were used in the calculations. The effect of oxygen doping on the Moessbauer isomer shift and quadrupole splitting values of /sup 119/Sn was investigated theoretically and compared with reported experimental values. The effect of oxygen substitution on the density of states at the Fermi energy of the (Mo/sub 6/S/sub 8/)/sup 2 -/ cluster was also studied. The results suggest that oxygen doping does not alter significantly the electronic structure of SnMo/sub 6/S/sub 8/.

Guenzburger, D.; Ellis, D.E.; Montano, P.A.; Shenoy, G.K.; Malik, S.K.; Hinks, D.G.; Vaishnava, P.; Kimball, C.W.

1985-10-01

118

The electrum-tarnish method for the determination of the fugacity of sulfur in laboratory sulfide systems  

USGS Publications Warehouse

A new method for the determination of the fugacity of sulfur in laboratory systems consists of visual observation of the development and decomposition of a sulfide tarnish phase on silver-gold alloy (electrum) of precisely known composition. The alloy system is calibrated against pure sulfur. The method has the following advantages: simple apparatus; ability to cover a large range of fugacity of S2; ability to cover a large temperature range by permitting runs of long duration; ability to tolerate other components in the gas phase; and ease of recovery of the quenched charges for determinations of phases and compositions. Results obtained by the electrum-tarnish method are in satisfactory agreement with those obtained by other workers for the fs2 vs. T curves for the assemblage Ni(1-x)S + NiS2. The electrum-tarnish method shows promise for investigating many other reactions. Univariant reactions studied by this method can be represented as lines forming a genetic grid in terms of the environmental parameters fs2 and T, The slopes of such lines can yield valuable thermodynamic data for the phases involved, but activity coefficients must be known for phases of variable composition. ?? 1964.

Barton, P.B., Jr.; Toulmin, P., III

1964-01-01

119

Supplemental Oxygen (Oxygen Therapy)  

MedlinePLUS

... mind when using oxygen. Oxygen is a safe gas and is non-flammable, however, it supports combustion. Materials burn more readily in an oxygen-enriched environment. Follow these tips for safe oxygen use: Post "No Smoking" and "No Open Flames" signs in and outside ...

120

GPT: An excel spreadsheet for thermobarometric calculations in metapelitic rocks  

Microsoft Academic Search

GPT takes advantage of Excel spreadsheet utilities (e.g. the possibility of entering a large number of data) to calculate 72 thermometers, 59 barometers, two fO2-meters, thirteen fH2O-meters and fourteen XH2O-meters, as well as the equations for the calculation of the H2O fugacity coefficient corresponding to different mineral assemblages. Each calibration uses expressions by different authors. Because these calibrations are two-variable

Joan Reche; Francisco J. Martinez

1996-01-01

121

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

122

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

NASA Technical Reports Server (NTRS)

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

Williams, R. J.; Mullins, O.

1981-01-01

123

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

124

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

125

Oxygen thermobarometry of abyssal spinel peridotites: The redox state and C-O-H volatile composition of the Earth's sub-oceanic upper mantle  

Microsoft Academic Search

The authors have applied the spinel peridotite oxygen barometer to abyssal spinel peridotites from the mid-Atlantic, central Indian, southwest Indian and American-Antarctic ocean ridge systems. The results indicate that the oxygen fugacity (F{sub Oâ}) of the suboceanic mantle is on average 0.9 {plus minus}0.7 (n = 33; {plus minus} 1sd) log units below the Fayalite-Magnetite-Quartz (FMQ) f{sub Oâ} buffer, in

L. T. Bryndzia; B. J. Wood

1990-01-01

126

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

NASA Astrophysics Data System (ADS)

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

Frost, Daniel J.; Wood, Bernard J.

1995-09-01

127

Calculation of water-bearing primary basalt and estimation of source mantle conditions beneath arcs: PRIMACALC2 model for WINDOWS  

NASA Astrophysics Data System (ADS)

present a new method for estimating the composition of water-bearing primary arc basalt and its source mantle conditions. The PRIMACALC2 model uses a thermodynamic fractional crystallization model COMAGMAT3.72 and runs with an Excel macro to examine the mantle equilibrium and trace element calculations of a primary basalt. COMAGMAT3.72 calculates magma fractionation in 0-10 kb at various compositions, pressure, oxygen fugacity, and water content, but is only applicable for forward calculations. PRIMACALC2 first calculates the provisional composition of a primary basalt from an observed magma. The basalt composition is then calculated by COMAGMAT3.72 for crystallization. Differences in elemental concentrations between observed and the closest-match calculated magmas are then adjusted in the primary basalt. Further iteration continues until the calculated magma composition converges with the observed magma, resulting in the primary basalt composition. Once the fitting is satisfied, back calculations of trace elements are made using stepwise addition of fractionated minerals. Mantle equilibrium of the primary basalt is tested using the Fo-NiO relationship of olivine in equilibrium with the primary basalt, and thus with the source mantle. Source mantle pressure, temperature, and degree of melting are estimated using petrogenetic grids based on experimental data obtained in anhydrous systems. Mantle melting temperature in a hydrous system is computed by adjusting T with a parameterization for a water-bearing system. PRIMACALC2 can be used either in dry or water-bearing arc magmas and is also applicable to mid-ocean ridge basalts and nonalkalic ocean island basalts.

Kimura, Jun-Ichi; Ariskin, Alexey A.

2014-04-01

128

Oxygen concentrators.  

PubMed

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

Howell, R S

1985-10-01

129

Measuring tissue oxygenation  

NASA Technical Reports Server (NTRS)

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

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

2009-01-01

130

THE INDOOR FUGACITY MODEL  

EPA Science Inventory

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

131

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

NASA Technical Reports Server (NTRS)

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

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

1975-01-01

132

The calculated solubility of platinum and gold in oxygen-saturated fluids and the genesis of platinum-palladium and gold mineralization in the unconformity-related uranium deposits  

NASA Astrophysics Data System (ADS)

Thermodynamic calculations on the solubility of platinum and gold indicate that saline (1 m NaCl), fluids saturated with atmospheric oxygen can transport geologically realistic concentrations of platinum-group-elements (PGE), gold, and uranium as chloro-complexes. A number of calculations involving fluid-rock interaction suggest that the oxygen-saturated fluids flowing through rocks containing quartz, muscovite, kaolinite, magnetite and hematite, initially oxidize any magnetite to hematite, allowing subsequent batches of ore fluids to retain their high oxidation state. During their migration through the aquifer, the oxidizing fluids would move the oxidation-reduction interface deeper into the aquifer, leaching and redepositing platinum and gold. The redissolution of earlier precipitated platinum and gold depends on the fluid/ rock ratio and the associated increase in the oxidation state. Therefore, lowering of fluid/rock ratios and/or mixing of the oxidized fluids with a large amount of reduced fluid will precipitate uranium, PGE, and gold. It is suggested that this model can explain the genesis of gold and PGE mineralization in the unconformity-related uranium deposits of the Alligator Rivers Uranium Field in the Northern Territory, Australia.

Jaireth, S.

1992-01-01

133

Sulfur K-edge XANES analysis of natural and synthetic basaltic glasses: Implications for S speciation and S content as function of oxygen fugacity  

NASA Astrophysics Data System (ADS)

XANES analyses at the sulfur K-edge were used to determine the oxidation state of S in natural and synthetic basaltic glasses and to constrain the fO2 conditions for the transition from sulfide (S2-) to sulfate (S6+) in silicate melts. XANES spectra of basaltic samples from the Galapagos spreading center, the Juan de Fuca ridge and the Lau Basin showed a dominant broad peak at 2476.8 eV, similar to the spectra obtained from synthetic sulfide-saturated basalts and pyrrhotite. An additional sharp peak at 2469.8 eV, similar to that of crystalline sulfides, was present in synthetic glasses quenched from hydrous melts but absent in anhydrous glasses and may indicate differences in sulfide species with hydration or presence of minute sulfide inclusions exsolved during quenching. The XANES spectra of a basalt from the 1991 eruption of Mount Pinatubo, Philippines, and absarokitic basalts from the Cascades Range, Oregon, U.S.A., showed a sharp peak at 2482.8 eV, characteristic of synthetic sulfate-saturated basaltic glasses and crystalline sulfate-bearing minerals such as haüyne. Basaltic samples from the Lamont Seamount, the early submarine phase of Kilauea volcano and the Loihi Seamount showed unequivocal evidence of the coexistence of S2- and S6+ species, emphasizing the relevance of S6+ to these systems. XANES spectra of basaltic glasses synthesized in internally-heated pressure vessels and equilibrated at fO2 ranging from FMQ-1.7 to FMQ+2.7 showed systematic changes in the features related to S2- and S6+ with changes in fO2. No significant features related to sulfite (S4+) species were observed. These results were used to construct a function that allows estimates of S6+/?S from XANES data. Theoretical considerations and comparison of compiled S6+/?S data obtained by SK? shifts estimated with electron probe microanalysis (EPMA) and S6+/?S obtained from XANES spectra show that data obtained from EPMA measurements underestimate S6+/?S in samples that are sulfate-dominated (most likely because of photo-reduction effects during analysis) whereas S6+/?S data from XANES provide a close match to the expected theoretical values. The XANES-derived relationship for S6+/?S as a function of fO2 indicates that the transition from S2- to S6+ with increasing fO2 occurs over a narrower interval than what is predicted by the EPMA-derived relationship. The implications for natural systems is that small variation of fO2 above FMQ+1 will have a large effect on S behavior in basaltic systems, in particular regarding the amount of S that can be transported by basaltic melts before sulfide saturation can occur.

Jugo, Pedro J.; Wilke, Max; Botcharnikov, Roman E.

2010-05-01

134

Sulfur K-edge XANES analysis of natural and synthetic basaltic glasses: Implications for S speciation and S content as function of oxygen fugacity  

NASA Astrophysics Data System (ADS)

XANES analyses at the sulfur K-edge were used to determine the oxidation state of S species in natural and synthetic basaltic glasses and to constrain the fO 2 conditions for the transition from sulfide (S 2-) to sulfate (S 6+) in silicate melts. XANES spectra of basaltic samples from the Galapagos spreading center, the Juan de Fuca ridge and the Lau Basin showed a dominant broad peak at 2476.8 eV, similar to the spectra obtained from synthetic sulfide-saturated basalts and pyrrhotite. An additional sharp peak at 2469.8 eV, similar to that of crystalline sulfides, was present in synthetic glasses quenched from hydrous melts but absent in anhydrous glasses and may indicate differences in sulfide species with hydration or presence of minute sulfide inclusions exsolved during quenching. The XANES spectra of a basalt from the 1991 eruption of Mount Pinatubo, Philippines, and absarokitic basalts from the Cascades Range, Oregon, USA, showed a sharp peak at 2482.8 eV, characteristic of synthetic sulfate-saturated basaltic glasses and crystalline sulfate-bearing minerals such as hauyne. Basaltic samples from the Lamont Seamount, the early submarine phase of Kilauea volcano and the Loihi Seamount showed unequivocal evidence of the coexistence of S 2- and S 6+ species, emphasizing the relevance of S 6+ to these systems. XANES spectra of basaltic glasses synthesized in internally-heated pressure vessels and equilibrated at fO 2 ranging from FMQ - 1.4 to FMQ + 2.7 showed systematic changes in the features related to S 2- and S 6+ with changes in fO 2. No significant features related to sulfite (S 4+) species were observed. These results were used to construct a function that allows estimates of S 6+/?S from XANES data. Comparison of S 6+/?S data obtained by S K? shifts measured with electron probe microanalysis (EPMA), S 6+/?S obtained from XANES spectra, and theoretical considerations show that data obtained from EPMA measurements underestimate S 6+/?S in samples that are sulfate-dominated (most likely because of photo-reduction effects during analysis) whereas S 6+/?S from XANES provide a close match to the expected theoretical values. The XANES-derived relationship for S 6+/?S as a function of fO 2 indicates that the transition from S 2- to S 6- with increasing fO 2 occurs over a narrower interval than what is predicted by the EPMA-derived relationship. The implications for natural systems is that small variation of fO 2 above FMQ + 1 will have a large effect on S behavior in basaltic systems, in particular regarding the amount of S that can be transported by basaltic melts before sulfide saturation can occur.

Jugo, Pedro J.; Wilke, Max; Botcharnikov, Roman E.

2010-10-01

135

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

USGS Publications Warehouse

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

Tuthill, R. L.; Sato, M.

1970-01-01

136

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

Microsoft Academic Search

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

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

2010-01-01

137

Investigation of intermolecular hydrogen bond interactions in crystalline L-cysteine by DFT calculations of the oxygen-17, nitrogen-14, and hydrogen-2 EFG tensors and AIM analysis.  

PubMed

A systematic computational study is carried out to investigate hydrogen bond (HB) interactions in the real crystalline structures of L-cysteine at 30 and 298 K by density functional theory (DFT) calculations of electric field gradient (EFG) tensors at the sites of O-17, N-14, and H-2 nuclei. One-molecule (monomer) and nine-molecule (cluster) models of L-cysteine are created by available crystal coordinates at both temperatures and the EFG tensors are calculated for both models to indicate the effect of HB interactions on the tensors. The calculated EFG tensors at the level of B3LYP and B3PW91 DFT methods and 6-311++G** and cc-pVTZ basis sets are converted to those experimentally measurable nuclear quadrupole resonance (NQR) parameters i.e. quadrupole coupling constants (qcc) and asymmetry parameters (eta(Q)). The evaluated NQR parameters reveal that the EFG tensors of (17)O, (14)N, and (2)H are influenced and show particular trends from monomer to the target molecule in the cluster due to the contribution of target molecule to classic N-H...O, and non-classic S-H...O and S-H...S types of HB interactions. On the other hand, atoms in molecules (AIM) analyses confirm the presence of HB interactions and rationalize the observed EFG trends. The results indicate different contribution of various nuclei to HB interactions in the cluster where O2 and N1 have major contributions. The EFG tensors as well as AIM analysis at the H6 site show that the N1-H6...O2 HB undergoes a significant change from 30 to 298 K where changes in other N-H...O interactions are almost negligible. There is a good agreement between the calculated (14)N NQR parameters and reported experimental data. PMID:19168275

Nozad, Ahmad G; Meftah, Sakineh; Ghasemi, Mohammad H; Kiyani, Roya A; Aghazadeh, Mustafa

2009-04-01

138

Does Magnetite Oxygen Isotopes reveal a Biosignature?  

NASA Astrophysics Data System (ADS)

Magnetite [FeIII_2FeIIO_4] nanoparticles have been found in the ALH 84001 meteorite. Their possible biogenic origin has generated a strong debate which emphasizes that purely inorganic magnetites cannot easily differentiated from those made by bacteria. Oxygen isotopic composition of magnetite could be potentially useful for characterizing biogenic magnetites in the environment and for the development of a magnetite / phosphate geothermometers (Mandernack et al., 1999). Little is known, however, about the oxygen isotopic compositions of inorganically produced nanometer-sized magnetites. Inorganic magnetites have been synthesized under controlled chemical affinity conditions at oxygen fugacity close to 0, ionic strength of 0.2 M and high solution saturation state (> 100) in order to determine if oxygen isotopes can be used as a proxy of bacterial signature. Total dissolved iron of stoechiometric ratio (i.e. FeII / FeIII = 0.5) and temperature were varied to identify the role of these variables on the kinetic rate and on the oxygen isotope fractionation. Under our experimental conditions, magnetite particles of an average dimension of 8 nm are formed only when [Fetot] is higher than 9 mM while in lower dissolved iron concentration, only goethite [?-FeIIIO(OH)] particles are formed. Furthermore, when temperature was increased, higher iron concentration were necessary to form magnetite. Oxygen isotopes fractionation, 10^3ln ?m-w, is important for low iron concentration and stabilizes around 0 to 1 ppm for [Fetot] >= 30 mM. Since biotic magnetites have similar oxygen isotope signature (Mandernack et al., 1999) to our abiotic magnetite particles, no biosignature can be observed and we propose that bacteria may simply produce an increase of solution saturation state in the magnetosomes that, in turn, control the precipitation of magnetite nanoparticles in surface conditions. Mandernack K. W. et al. (1999), Science 285, 1892-1896.

Faivre, D.; Zuddas, P.; Agrinier, P.; Guyot, F.; Menguy, N.

2003-04-01

139

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

140

Oxygen analyzer  

DOEpatents

An oxygen analyzer which identifies and classifies microgram quantities of oxygen in ambient particulate matter and for quantitating organic oxygen in solvent extracts of ambient particulate matter. A sample is pyrolyzed in oxygen-free nitrogen gas (N.sub.2), and the resulting oxygen quantitatively converted to carbon monoxide (CO) by contact with hot granular carbon (C). Two analysis modes are made possible: (1) rapid determination of total pyrolyzable oxygen obtained by decomposing the sample at 1135.degree. C., or (2) temperature-programmed oxygen thermal analysis obtained by heating the sample from room temperature to 1135.degree. C. as a function of time. The analyzer basically comprises a pyrolysis tube containing a bed of granular carbon under N.sub.2, ovens used to heat the carbon and/or decompose the sample, and a non-dispersive infrared CO detector coupled to a mini-computer to quantitate oxygen in the decomposition products and control oven heating.

Benner, William H. (Danville, CA)

1986-01-01

141

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

142

Bond valence sums in coordination chemistry. The calculation of the oxidation state of samarium in complexes containing samarium bonded only to oxygen.  

PubMed

A simple method is presented for calculating the oxidation state of Sm in complexes where Sm is bonded only to O ligands. A total of 88 SmO(n)() fragments with n = 4-12 were retrieved from the Cambridge Structural Database and were analyzed using the bond valence sum (BVS) method. New R(0) values for Sm(II)-O of 2.116(21) A and for Sm(III)-O of 2.055(13) A were derived. The average R(0) value of 2.086 A gives a good approximation of the oxidation state of the Sm ion, either +2 or +3, from the observed distances without any assumptions. The Sm-O distances for +2 and +3 complexes with coordination numbers of 4-11 are tabulated and reflect the requirement that the BVS must equal the oxidation state. The distances for CN = 12 were not included because of problems with the reported crystal structures. Several X-ray structure determinations where the BVS and the oxidation state did not agree are discussed. PMID:12691581

Palenik, Gus J

2003-04-21

143

Triple oxygen isotope composition of photosynthetic oxygen  

NASA Astrophysics Data System (ADS)

The measurement of biological production rates is essential for our understanding how marine ecosystems are sustained and how much CO2 is taken up through aquatic photosynthesis. Traditional techniques to measure marine production are laborious and subject to systematic errors. A biogeochemical approach based on triple oxygen isotope measurements in dissolved oxygen (O2) has been developed over the last few years, which allows the derivation of gross productivity integrated over the depth of the mixed layer and the time-scale of O2 gas exchange (Luz and Barkan, 2000). This approach exploits the relative 17O/16O and 18O/16O isotope ratio differences of dissolved O2 compared to atmospheric O2 to work out the rate of biological production. Two parameters are key for this calculation: the isotopic composition of dissolved O2 in equilibrium with air and the isotopic composition of photosynthetic oxygen. Recently, a controversy has emerged in the literature over these parameters (Kaiser, 2011) and one of the goals of this research is to provide additional data to resolve this controversy. In order to obtain more information on the isotopic signature of biological oxygen, laboratory experiments have been conducted to determine the isotopic composition of oxygen produced by different phytoplankton cultures.

van der Meer, Anne; Kaiser, Jan

2013-04-01

144

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

145

Oxygen therapy and intraocular oxygenation.  

PubMed Central

When delivered to the corneal surface of rabbits or monkeys, 100% oxygen can significantly increase the pO2 in the aqueous humor. Under hyperbaric conditions (two atmospheres), an observed rise in the aqueous pO2 in rabbits breathing room air can be increased further by exposing the rabbit cornea to 100% oxygen. The high oxygen levels under hyperbaric conditions are mediated by intravascular and transcorneal delivery of oxygen. The increase in the pO2 levels in the aqueous can prevent sickling of intracameral human erythrocytes containing sickle hemoglobin. Thus, oxygen therapy transcorneally or systemically could potentially be used to treat a sickle cell hyphema. The exposure of rabbit eyes to 100% oxygen at the corneal surface is followed by autoregulation (constriction) of the iris vasculature. We could demonstrate no constriction in the eyes of two normal human volunteers or of four patients with chronic stable rubeosis iridis. Preretinal vitreous pO2 levels can be significantly raised by exposing monkeys to hyperbaric 100% oxygen. This procedure may be of value in treating acute, reversible ischemic inner retinal diseases. Transcorneal or vascular delivery of oxygen to the eye under normobaric or hyperbaric conditions may be effective in treating ischemic diseases of the anterior segment, such as anterior segment necrosis or rubeosis iridis, or ischemic inner retinal diseases. Images FIGURE 2 FIGURE 3 FIGURE 4 FIGURE 5 B FIGURE 5 C FIGURE 5 A FIGURE 6 PMID:3447339

Jampol, L M

1987-01-01

146

Oxygen and iron production by electrolytic smelting of lunar soil  

NASA Technical Reports Server (NTRS)

Previous work has shown that Fe(sup 0) and O2 can be derived by electrolysis from silicate smelt of a composition typical of lunar soils (Lindstrom and Haskin 1979). In the present study, the goal is to refine further the conditions necessary to optimize production and to determine efficiencies of production (how much product is derived for a given current) and purity of products. These depend on several factors, including potential imposed between electrodes, configuration and surface area of the electrodes, composition of the electrolyzed silicate melt, and oxygen fugacity. Experiments were designed to measure the dependence on these variables of three parameters that must be known before production by electrolysis can be optimized. These parameters are: Limiting Current; Actual Current; and Efficiencies of Production.

Haskin, Larry A.

1989-01-01

147

A spectroscopic study of the negative electron affinity of cesium oxide-coated diamond (111) and theoretical calculation of the surface density-of-states on oxygenated diamond (111)  

Microsoft Academic Search

The modification of the electron affinity of clean and oxygenated C(111) with cesium has been studied using ultra-violet photoelectron spectroscopy. Oxygenated C(111) shows strong valence emission features at 4.2 eV attributable to CO bonding orbital. Adsorption of cesium on the oxygenated diamond results in the formation of cesium oxide features at 4.2 eV and 8 eV and the condition of

Kian Ping Loh; X. N. Xie; S. W. Yang; J. S. Pan; P. Wu

2002-01-01

148

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

Microsoft Academic Search

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

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

2010-01-01

149

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

150

Oxygen-Concentrating Cell  

NASA Technical Reports Server (NTRS)

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

Buehler, K.

1986-01-01

151

pH buffering by metastable mineral-fluid equilibria and evolution of carbon dioxide fugacity during burial diagenesis  

SciTech Connect

Numerous potential pH buffers including reactions among aqueous organic acid and carbonate species, and carbonate and silicate minerals are typically present during burial diagenesis. Buffering of pH in natural systems is a function of mass action, mass balance, and kinetic constraints. In most sedimentary basins, carbonate and silicate minerals are present in amounts sufficient to buffer pH, and the activities of aqueous species are consistent with metastable equilibrium among observed diagenetic minerals. These observations indicate that mass balance and kinetic constraints are relatively less important than mass action constraints measured by the buffer index, [beta], here defined. The buffer index ultimately dictates which buffer reaction controls pH under diagenetic conditions; buffer reactions with high [beta] values are favored over those with low values. Buffer indices for a number of potential diagenetic buffer reactions have been calculated by reaction path modeling. Heterogeneous equilibria among carbonate and silicate minerals and an aqueous phase have greater [beta] values than those for homogeneous reactions among aqueous carbonate and organic acid species. This implies that pH, calcite dissolution, and f[sub CO[sub 2

Hutcheon, I.; Shevalier, M. (Univ. of Calgary, Alberta (Canada)); Abercrombie, H.J. (Geological Survey of Canada, Calgary, Alberta (Canada))

1993-03-01

152

Monitoring oxygenation.  

PubMed

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

Severinghaus, John W

2011-06-01

153

Wildlife monitoring, modeling, and fugacity  

Microsoft Academic Search

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

T. Clark; K. Clark; S. Paterson; D. Mackay; R. J. Norstrom

1988-01-01

154

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

155

Influence of ortho-substitution homolog group on polychlorobiphenyl bioaccumulation factors and fugacity ratios in plankton and zebra mussels (Dreissena polymorpha)  

SciTech Connect

The accumulation of a set of non- and mono-ortho (coplanar) PCB congeners in aquatic ecosystems is of interest due to their dioxin-like toxicities. Chemical properties (octanol-water partition coefficients) suggest that the coplanar congeners may accumulate in organisms to a greater extent than homologs with greater ortho substitution. The authors analyzed a set of 65 PCB congeners with zero to four ortho-chlorines from seven homolog groups in water, suspended particulate matter, and zebra mussels from Green Bay, Wisconsin, USA, on four dates throughout the ice-free season. The suspended particulate matter was separated by size and characterized as phytoplankton or zooplankton using diagnostic carotenoid pigments and light microscopy. Median bioconcentration factors (BCFs) for accumulation from water by phytoplankton and bioaccumulation factors (BAFs) for accumulation from water plus food by zooplankton and zebra mussels ranged from 1 x 10{sup 4} to 1 x 10{sup 6} and were generally the greatest for the tetra- to heptachlorobiphenyls. The average coplanar congener BCFs and BAFs for accumulation from water by phytoplankton, zooplankton, and zebra mussels for the tri-, tetra-, and pentachlorobiphenyls were 54% larger than corresponding values for their homologs. Biomagnification factors (BMFs) of the tetra-, penta-, and hexachlorobiphenyls between zooplankton and zebra mussels and their food source, phytoplankton, typically ranged between 1 and 10, but the average coplanar congener BMFs were 25% less than values for their corresponding homologs. The tendency for coplanar congeners to accumulate to a lesser extent between trophic levels was not as large as their tendency to accumulate from water to a greater extent. Based on accumulation factors, the authors conclude that the dioxin-like tetra- and pentachlorobiphenyls generally accumulate in the phytoplankton, zooplankton, and zebra mussels of the Green Bay ecosystem to a greater extent than other congeners. Fugacity ratios suggest that, in phytoplankton and zooplankton, homolog concentrations were below equilibrium with water throughout the field season, particularly for the more chlorinated groups, but that concentrations in zebra mussels were at or above equilibrium with water.

Willman, E.J.; Manchester-Neesvig, J.B.; Agrell, C.; Armstrong, D.E.

1999-07-01

156

Bolus calculators.  

PubMed

Matching meal insulin to carbohydrate intake, blood glucose, and activity level is recommended in type 1 diabetes management. Calculating an appropriate insulin bolus size several times per day is, however, challenging and resource demanding. Accordingly, there is a need for bolus calculators to support patients in insulin treatment decisions. Currently, bolus calculators are available integrated in insulin pumps, as stand-alone devices and in the form of software applications that can be downloaded to, for example, smartphones. Functionality and complexity of bolus calculators vary greatly, and the few handfuls of published bolus calculator studies are heterogeneous with regard to study design, intervention, duration, and outcome measures. Furthermore, many factors unrelated to the specific device affect outcomes from bolus calculator use and therefore bolus calculator study comparisons should be conducted cautiously. Despite these reservations, there seems to be increasing evidence that bolus calculators may improve glycemic control and treatment satisfaction in patients who use the devices actively and as intended. PMID:24876436

Schmidt, Signe; Nørgaard, Kirsten

2014-09-01

157

Oxygen tent performance  

Microsoft Academic Search

A mathematical model of the build-up of oxygen and carbon dioxide in an oxygen tent, under standard conditions of use, has been constructed and verified experimentally. The mathematical analysis has been used both to demonstrate that large oxygen tents cannot give a satisfactorily high percentage of oxygen, even under ideal conditions, and in the design of a new oxygen tent.

D J Wayne; Anne R Chamney

1969-01-01

158

Dissolved Oxygen and Temperature  

Microsoft Academic Search

Dissolved oxygen and temperature are two of the fundamental variables in lake and pond ecology. By measuring dissolved oxygen and temperature, scientists can gauge the overall condition of waterbodies. Aquatic organisms need dissolved oxygen for their survival. While water temperature also directly influences aquatic organ- isms, it regulates dissolved oxygen concentrations within a lake. Dissolved oxygen and temperature are also

Kelly Addy; Linda Green

159

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

PubMed Central

The most direct measure of oxidative tissue metabolism is the conversion rate of oxygen to water via mitochondrial respiration. To calculate oxygen consumption from the analysis of tissue residue curves or outflow dilution curves after injection of labeled oxygen one needs realistic mathematical models that account for convection, diffusion, and transformation in the tissue. A linear, three-region, axially distributed model accounts for intravascular convection, penetration of capillary and parenchymal cell barriers (with the use of appropriate binding spaces to account for oxygen binding to hemoglobin and myoglobin), the metabolism to [15O]water in parenchymal cells, and [15O]water transport into the venous effluent. Model solutions fit residue and outflow dilution data obtained in an isolated, red blood cell-perfused rabbit heart preparation and give estimates of the rate of oxygen consumption similar to those obtained experimentally from the flow times the arteriovenous differences in oxygen contents. The proposed application is for the assessment of regional oxidative metabolism in vivo from tissue 15O-residue curves obtained by positron emission tomography. PMID:8780210

Deussen, Andreas; Bassingthwaighte, James B.

2010-01-01

160

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.

161

Dissolved Oxygen and Biochemical Oxygen Demand  

NSDL National Science Digital Library

This Environmental Protection Agency (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.

2010-03-02

162

Hyperbaric oxygen therapy  

MedlinePLUS

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

163

A calcium oxygen secondary battery  

NASA Astrophysics Data System (ADS)

This paper describes a high-temperature electrochemically-reversible calcium-oxygen cell in which the negative electroactive material consists of a calcium-silicon alloy contained within an expanded stainless steel electrode assembly immersed into a binary molten salt CaO-CaCl2 (mp 593 C). The empirical electrochemistry occurring upon electrochemical cycling is: 2CaSi + 1/2 O2(air) going to CaO + CaSi2, with oxygen being reversibly mediated to the binary molten salt via the oxygen vacancy conducting solid electrolyte; charge-discharge curves at 850 C clearly demonstrated voltage plateaus associated with the reversible formation of CaSi and CaSi2. If unit activity Ca were used as the negative electroactive material, the cell thermodynamic open-circuit voltage at 850 C is expected to be about 2.28 V. The theoretical energy density for this system calculates to 985 W h/lb.

Pujare, Nirupama U.; Semkow, Krystyna W.; Sammells, Anthony F.

1988-01-01

164

Oxygenates in Gasoline: A Versatile Experiment Using Gas Chromatography  

Microsoft Academic Search

An experiment for introductory chemistry in which oxygenates are extracted from gasoline and analyzed by gas chromatography is described. The extraction of oxygenates from gasoline with water prior to analysis by gas chromatography allows for their easy identification and quantification since only the oxygenates dissolve in water. Both qualitative and quantitative versions of the experiment are described. Calculations which can

Linda C. Brazdil

1996-01-01

165

Oxygen Toxicity Risk Assessment.  

National Technical Information Service (NTIS)

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

R. D. Vann

1988-01-01

166

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

167

Calculation of NMR parameters for bridging oxygens in H 3 T—O—T?H 3 linkages (T, T?=Al, Si, P), for oxygen in SiH 3 O ? , SiH 3 OH and SiH 3 OMg + and for bridging fluorine in H 3 SiFSiH 3 +  

Microsoft Academic Search

Variations in the 17O nuclear quadrupole coupling constant, NQCC, and the 17O NMR shielding constant, sO, are evaluated for bridging oxygens in H3T-O-T'H3 linkages (with T, T'=Al, Si, P), and for nonbridging O in SiH3O-, SiH3OH and SiH3OMg+ and the 19F NMR shielding constant, sF, is evaluated for bridging F in H3SiFSiH3-using Hartree-Fock methods with large, flexible Gaussian basis sets.

J. A. Tossell; Paolo Lazzeretti

1988-01-01

168

Mineralogical Evidence for Subsurface Oxygenation Following the Great Oxidation Event  

NASA Astrophysics Data System (ADS)

Temporal trends in Earth's near-surface mineralogy correlate with major events in Earth's geochemical, tectonic, and biological history. The distribution of mineral species, as well as their trace and minor elements, can reveal the timing and extent of subsurface oxygenation. Recent studies on the evolution of minerals containing redox-sensitive elements, including As, C, Co, Cr, Hg, Mo, Ni, S, and U, suggest a significant delay after the Great Oxidation Event (GOE; 2.4-2.2 Ga) in the appearance of more oxidized species. For example, analyses of molybdenite (MoS2) specimens from 135 localities with known ages from 2.91 billion years to 6.3 million years reveal systematic increases in average and maximum trace concentrations of Re in molybdenite, which suggest progressive oxidative weathering and mobilization of rhenium by subsurface fluids. Similarly, the temporal distribution of carbonate minerals reflects Earth's changing oxygenation, with widespread Fe2+ carbonates prior to the GOE and extensive Cu2+ and Fe3+ after the GOE. Compilations of data on the mineralogy of cobalt and nickel deposits since the Archean Eon reveal that mineral assemblages in the Co-Ni-S-As system may prove to be especially sensitive indicators of changing subsurface oxygen fugacity through Earth history. Finally, significant changes in the patterns of mercury and uranium ore deposits in the Phanerozoic Eon point to interactions with redox gradients related to the terrestrial biosphere. These patterns underscore at least 3 billion years of mineralogical co-evolution of the geosphere and biosphere.

Hazen, R. M.

2013-12-01

169

Oxygen determination from cell dimensions in YBCO superconductors  

NASA Astrophysics Data System (ADS)

A rapid and simple procedure for the determination of non-stoichiometric oxygen in YBa 2Cu 3O 7- ? (YBCO) superconductors is described, based on the relationship between oxygen content and c-axis parameter of the YBCO structure. To test the proposed method the oxygen content of samples sinterised starting from different precursors has been calculated from X-ray powder diffraction analysis and compared with the oxygen content obtained by iodometric titration with satisfactory correspondence.

Benzi, Paola; Bottizzo, Elena; Rizzi, Nicoletta

2004-09-01

170

The story of oxygen.  

PubMed

The history of oxygen from discovery to clinical application for patients with chronic lung disease represents a long and storied journey. Within a relatively short period, early investigators not only discovered oxygen but also recognized its importance to life and its role in respiration. The application of oxygen to chronic lung disease, however, took several centuries. In the modern era, physiologists pursued the chemical nature of oxygen and its physiologic interaction with cellular metabolism and gas transport. It took brazen clinicians, however, to pursue oxygen as a therapeutic resource for patients with chronic lung disease because of the concern in the 20th century of the risks of oxygen toxicity. Application of ambulatory oxygen devices allowed landmark investigations of the long-term effects of continuous oxygen that established its safety and efficacy. Although now well established for hypoxic patients, many questions remain regarding the benefits of oxygen for varying severity and types of chronic lung disease. PMID:23271817

Heffner, John E

2013-01-01

171

Thermodynamic properties of oxygen molecules at high temperatures  

Microsoft Academic Search

Calculations of the second virial coefficients and their derivatives, obtained by fitting the Hulburt-Hirschfelder potential to accurate ab initio quantum mechanical calculations for the seven bound states of molecular oxygen that dissociate to ground state atoms, are used to determine thermodynamic properties of oxygen molecules at high temperatures. Unlike the usual statistical thermodynamic method for obtaining partition functions by summing

L. Biolsi; P. M. Holland

1996-01-01

172

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

173

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

174

Mercury Calculator  

NSDL National Science Digital Library

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

Foundation, Wgbh E.

2010-12-23

175

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

176

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

177

Traveling with Portable Oxygen  

MedlinePLUS

... TRAVELING WITH PORTABLE OXYGEN Use of Oxygen on Commercial Airlines Policies concerning the use of in- ight ... by the FAA for use by passengers on commercial aircraft (Special Federal Aviation Regulation No. 106). They ...

178

Biogeochemistry: Oxygen burrowed away  

NASA Astrophysics Data System (ADS)

Multicellular animals probably evolved at the seafloor after a rise in oceanic oxygen levels. Biogeochemical model simulations suggest that as these animals started to rework the seafloor, they triggered a negative feedback that reduced global oxygen.

Meysman, Filip J. R.

2014-09-01

179

Oxygen Movement in Seagrasses  

Microsoft Academic Search

Measurements of oxygen variability and transport in seagrasses and other submerged plants are difficult to conduct and interpret\\u000a due to the existence of several sources and sinks of oxygen driving internal transport at different rates depending on conditions\\u000a in the water column and sediment. Oxygen release and transport in seagrasses have mostly been assessed by measuring oxygen\\u000a changes in incubation

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

180

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

181

Oxygen control with microfluidics.  

PubMed

Cellular function and behavior are affected by the partial pressure of O2, or oxygen tension, in the microenvironment. The level of oxygenation is important, as it is a balance of oxygen availability and oxygen consumption that is necessary to maintain normoxia. Changes in oxygen tension, from above physiological oxygen tension (hyperoxia) to below physiological levels (hypoxia) or even complete absence of oxygen (anoxia), trigger potent biological responses. For instance, hypoxia has been shown to support the maintenance and promote proliferation of regenerative stem and progenitor cells. Paradoxically, hypoxia also contributes to the development of pathological conditions including systemic inflammatory response, tumorigenesis, and cardiovascular disease, such as ischemic heart disease and pulmonary hypertension. Current methods to study cellular behavior in low levels of oxygen tension include hypoxia workstations and hypoxia chambers. These culture systems do not provide oxygen gradients that are found in vivo or precise control at the microscale. Microfluidic platforms have been developed to overcome the inherent limits of these current methods, including lack of spatial control, slow equilibration, and unachievable or difficult coupling to live-cell microscopy. The various applications made possible by microfluidic systems are the topic of this review. In order to understand how the microscale can be leveraged for oxygen control of cells and tissues within microfluidic systems, some background understanding of diffusion, solubility, and transport at the microscale will be presented in addition to a discussion on the methods for measuring the oxygen tension in microfluidic channels. Finally the various methods for oxygen control within microfluidic platforms will be discussed including devices that rely on diffusion from liquid or gas, utilizing on-or-off-chip mixers, leveraging cellular oxygen uptake to deplete the oxygen, relying on chemical reactions in channels to generate oxygen gradients in a device, and electrolytic reactions to produce oxygen directly on chip. PMID:25251498

Brennan, Martin D; Rexius-Hall, Megan L; Elgass, Laura Jane; Eddington, David T

2014-10-14

182

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 ...

183

Measuring Absolute Oxygen Pressure  

NASA Technical Reports Server (NTRS)

Sensor determines absolute pressure of oxygen without reference pressure source. Absolute oxygen pressure transducer with control circuit enables measurement without reference pressure. Transducer, two part device, combines solid electrolyte membranes sensor with diffusional orifice. Device adapted for direct control of oxygen pressure in combustion mixtures.

Richter, R.

1985-01-01

184

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

185

Broken Calculator  

NSDL National Science Digital Library

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

Barrow, Mandy

2008-01-01

186

The system Fe-Si-O: Oxygen buffer calibrations to 1,500K  

NASA Astrophysics Data System (ADS)

The five solid-phase oxygen buffers of the system Fe-Si-O, iron-wuestite (IW), wuestite-magnetite (WM), magnetite-hematite (MH), quartz-iron-fayalite (QIF) and fayalite-magnetite-quartz (FMQ) have been recalibrated at 1 atm pressure and temperatures from 800° 1,300° C, using a thermogravimetric gas mixing furnace. The oxygen fugacity, f_{{text{O}}_{text{2}} } was measured with a CaO-doped ZrO2 electrode. Measurements were made also for wuestite solid solutions in order to determine the redox behavior of wuestites with O/Fe ratios varying from 1.05 to 1.17. For FMQ, additional determinations were carried out at 1 kb over a temperature range of 600° to 800° C, using a modified Shaw membrane. Results agree reasonably well with published data and extrapolations. The reaction parameters K, ? G {r/o}, ? H {r/o}, and ? S {r/o}were calculated from the following log f_{{text{O}}_{text{2}} }/ T relations (T in K): 410_2004_Article_BF00371177_TeX2GIFE1.gif begin{gathered} {text{IW }}log f_{{text{O}}_{text{2}} } = - 26,834.7/T + 6.471left( { ± 0.058} right) \\ {text{ }}left( {{text{800}} - 1,260{text{ C}}} right), \\ {text{WM }}log f_{{text{O}}_{text{2}} } = - 36,951.3/T + 16.092left( { ± 0.045} right) \\ {text{ }}left( {{text{1,000}} - 1,300{text{ C}}} right), \\ {text{MH }}log f_{{text{O}}_{text{2}} } = - 23,847.6/T + 13.480left( { ± 0.055} right) \\ {text{ }}left( {{text{1,040}} - 1,270{text{ C}}} right), \\ {text{QIF }}log f_{{text{O}}_{text{2}} } = - 27,517.5/T + 6.396left( { ± 0.049} right) \\ {text{ }}left( {{text{960}} - 1,140{text{ C}}} right), \\ {text{FMQ }}log f_{{text{O}}_{text{2}} } = - 24,441.9/T + 8.290left( { ± 0.167} right) \\ {text{ }}left( {{text{600}} - 1,140{text{ C}}} right). \\ These experimentally determined reaction parameters were combined with published 298 K data to determine the parameters Gf, Hf, and Sf for the phases wuestite, magnetite, hematite, and fayalite from 298 K to the temperatures of the experiments. The T-f_{{text{O}}_{text{2}} } data for wuestite solid solutions were used to obtain activities, excess free energies and Margules mixing parameters. The new data provide a more reliable, consistent and complete reference set for the interpretation of redox reactions at elevated temperatures in experiments and field settings encompassing the crust, mantle and core as well as extraterrestrial environments.

Myers, J.; Eugster, H. P.

1983-03-01

187

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

188

Dissolved Oxygen Activity  

NSDL National Science Digital Library

One of the most important measures of the health of the stream is the level of dissolved oxygen (DO) in the water. Oxygen (O2) dissolves in water through the mixing of the water surface with the atmosphere. The oxygen is used by fish and other animals in the water to "breath" through their gills or other respiratory systems and by plants. If the levels fall too low, many species of fish, macroinvertebrates, and plants cannot survive. At very low levels of oxygen, the stream becomes "septic" and smells rotten because low oxygen sulfur bacteria begin to dominate.

Gordon, Steve

189

Dissolved Oxygen Model  

NSDL National Science Digital Library

One of the most important measures of the health of the stream is the level of dissolved oxygen (DO) in the water. Oxygen (O2) dissolves in water through the mixing of the water surface with the atmosphere. The oxygen is used by fish and other animals in the water to "breath" through their gills or other respiratory systems and by plants. If the levels fall too low, many species of fish, macroinvertebrates, and plants cannot survive. At very low levels of oxygen, the stream becomes "septic" and smells rotten because low oxygen sulfur bacteria begin to dominate.

Gordon, Steve

190

Oxygen toxicity and tolerance.  

PubMed

Normobaric oxygen toxicity is well described in all animal species. However susceptibility to oxygen exposure is highly variable according to age, species and strains. Similarly in humans, prolonged high oxygen exposure is reported to induce cough, shortness of breath, decrease vital capacity and increase alveolo-capillary permeability. The toxic FIO2 threshold (length of exposure and level) is still debated. In patients with previous lung injury, this threshold is even more difficult to delineate as pathologic pulmonary lesions might result from hyperoxia or primary lung insult. Oxygen free-radicals play a key role in the pathophysiology of oxygen toxicity. Oxygen resistance or tolerance is obtained with intraperitoneal, intravenous and intratracheal endotoxin or cytokines administration. Previous exposure to high oxygen concentration is also reported to increase survival rate and decrease pulmonary lesions in animal models. Protection may rely on antioxidant enzymes synthesis, nitric oxide production, neutrophils recruitment and modulation of alveolar macrophages activity. In humans, oxygen tolerance might be suspected through several clinical studies reporting favorable outcome after long term-oxygen exposure. Better knowledge of the risks of prolonged high oxygen exposure is important to re-evaluate the goals of mechanical ventilation (FIO2, SaO2, PEEP) and/or to develop treatments to prevent oxygen toxicity (surfactant, antioxidant enzymes). PMID:10394807

Capellier, G; Maupoil, V; Boussat, S; Laurent, E; Neidhardt, A

1999-06-01

191

Oxygen partial pressure sensor  

DOEpatents

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

Dees, D.W.

1994-09-06

192

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.

1999-01-01

193

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

194

Probability Calculator  

NSDL National Science Digital Library

This tool lets you calculate the probability that a random variable X is in a specified range, for a variety of probability distributions for X: the normal distribution, the binomial distribution with parameters n and p, the chi-square distribution, the exponential distribution, the geometric distribution, the hypergeometric distribution, the negative binomial distribution, the Poisson distribution, and Student's t-distribution. The first choice box lets you select a probability distribution. Depending on the distribution you select, text areas will appear for you to enter the values of the parameters of the distribution. Parameters that are probabilities (e.g., the chance of success in each trial for a binomial distribution) can be entered either as decimal numbers between 0 and 1, or as percentages. If you enter a probability as a percentage, be sure to include the percent sign (%) after the number.

Stark, Philip B.

2009-01-08

195

Continuous home oxygen therapy.  

PubMed

Oxygen therapy is defined as the therapeutic use of oxygen and consists of administering oxygen at higher concentrations than those found in room air, with the aim of treating or preventing hypoxia. This therapeutic intervention has been shown to increase survival in patients with chronic obstructive pulmonary disease (COPD) and respiratory failure. Although this concept has been extended by analogy to chronic respiratory failure caused by respiratory and non-respiratory diseases, continuous oxygen therapy has not been shown to be effective in other disorders. Oxygen therapy has not been shown to improve survival in patients with COPD and moderate hypoxaemia, nor is there consensus regarding its use during nocturnal desaturations in COPD or desaturations caused by effort. The choice of the oxygen source must be made on the basis of criteria such as technical issues, patient comfort and adaptability and cost. Flow must be adjusted to achieve appropriate transcutaneous oxyhaemoglobin saturation correction. PMID:24461631

Ortega Ruiz, Francisco; Díaz Lobato, Salvador; Galdiz Iturri, Juan Bautista; García Rio, Francisco; Güell Rous, Rosa; Morante Velez, Fátima; Puente Maestu, Luis; Tàrrega Camarasa, Julia

2014-05-01

196

[Hyperbaric oxygen therapy].  

PubMed

Oxygen inhalation in a chamber at the pressure exceeded 0.2 MPa produces some positive effects, that are explored for therapeutic purposes at about 30 years. Oxygen increases bactericidal capacity of leukocytes, reduces tissue edema, protects intracellular ATP, maintain tissue oxygenation even in the absence of hemoglobin. Stimulates fibroblast replication, increases collagen production, stimulates arborisation of capillaries into ischemic tissue, protects from lipid peroxidation. These properties of oxygen are exploit in acute, life threatened conditions and in various chronic ischemias. Hyperbaric oxygen therapy as an adjuvant together with conservative and invasive therapy methods helps to decrease morbidity, work incapability, invalidisation and mortality in oclusive and inflammatory arteriities, diabetic gangrene and other forms of clinical leg ischemia. The use of hyperbaric oxygenation will become increasingly common as more hyperbaric facilities are established. PMID:7671282

Dolezal, V

1995-06-28

197

Secret Agents of Dissolved Oxygen  

NSDL National Science Digital Library

This activity explores how water chemistry is altered by the biological processes of phytoplankton (microscopic photosynthetic organisms). Students will discover what some of these water chemistry changes are, and what influences these changes (type of water, exposure to light, etc.). The students will design an activity based on experience gained from the first activity. They will determine the changes and causes thereof in different types of water in a sealed container over time, and learn to measure dissolved oxygen, temperature, and carbon dioxide with a calculator/computer probe-ware or by other means.

Dawson, Besse

198

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

199

Energetic oxygen atoms in the polar geocorona  

NASA Astrophysics Data System (ADS)

The role of the auroral sources induced by the electron and proton precipitation in the formation of the hot oxygen corona in the polar upper atmosphere is studied. It is found that both electron precipitation through exothermic chemistry and proton precipitation through atmospheric sputtering significantly contribute to the population of the hot oxygen geocorona. It is also found that only atmospheric sputtering results in the formation of the escape flux of energetic oxygen atoms, providing an important source of heavy atoms for the magnetosphere. The exothermic chemistry induced by the electron precipitation and/or by the absorption of the solar UV radiation is operating continuously in the polar upper atmosphere and results in a steady population of the very near-Earth environment by suprathermal oxygen atoms with energies below a few eV. By contrast, atmospheric sputtering by magnetospheric protons provides a more variable contribution, strongly coupled with the cusp region. It produces the more energetic oxygen atoms that populate the external regions of the hot oxygen geocorona. The results of calculations are in a good agreement with the analysis of the low-latitude perigee Low Energy Neutral Atom (LENA) images showing that the instrument signal consists of low to medium energy (5-30 eV) oxygen atoms produced in and near the cusp region. The more energetic (>30 eV) fraction of energetic oxygen atoms produced by the ion-induced atmospheric sputtering could be responsible for the energetic neutrals observed by the instrument far away from the cusp or oval regions. The total escape flux of oxygen atoms associated with atmospheric sputtering by protons is found about 8 × 1023 s-1; therefore this mechanism may provide a substantial contribution to the magnetospheric oxygen population.

Shematovich, V. I.; Bisikalo, D. V.; GéRard, J.-C.

2006-10-01

200

Oxygen Poisoning in Drosophila  

PubMed Central

Fruit flies live longer at the partial pressure of oxygen found in air than at either larger or smaller partial pressures. Flies exposed to 1 atm of oxygen for 8 hr every day do not recover completely in the remaining 16 hr. In general, intermittent exposures to 1 atm of oxygen are better tolerated than continuous exposure to the same average oxygen concentration per day, but exposures to higher pressures of 2–5 atm of oxygen for as little as a half hour every two days markedly shorten the life-span. Older flies consume more oxygen per minute and are more sensitive to oxygen poisoning than young flies, and the rate of dying in 6 atm of O2, or the reciprocal of the survival time, is a linear function of the age. The oxygen pressure-time curve can be well expressed by the general empirical equation (POO2)2 x time = 120 where P is in atmosphere and survival time in hours. The progress of oxygen poisoning appears to be linear with time rather than exponential. PMID:6034764

Fenn, Wallace O.; Henning, Marcia; Philpott, Mary

1967-01-01

201

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

202

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

203

Ferromagnetic nanostructures of oxygen on Ag(111)  

NASA Astrophysics Data System (ADS)

First principles calculations were performed to investigate the robustness of oxygen adsorbed structures that show ferromagnetic properties. These ferromagnetic properties are induced by ferromagnetic superexchange interactions and Ruderman-Kittel-Kasuya-Yosida (RKKY) interactions. Such ferromagnetic oxygen adsorbed structures appear only in the case of coverages higher than 0.5 ML, because the ferromagnetic superexchange interactions and RKKY interactions are appreciable between O-O only for short distances. In this work, we focused on single oxygen atom diffusion parallel and perpendicular to Ag(111) surfaces. The in-plane diffusion could induce associative desorption, which reduces the oxygen coverage. On the other hand, diffusion to the subsurface could quench the magnetic moment. These diffusion paths have effective diffusion barriers of 0.78 eV. Thus, such diffusion rarely occurs in low temperature regions.

Kunisada, Y.; Nakanishi, H.; Diño, W. A.; Kasai, H.

2012-08-01

204

Oxygen sensors and angiogenesis  

Microsoft Academic Search

Local oxygen tension has a profound effect on the vasculature, which compensates vascular insufficiency through the induction of angiogenesis. An important mediator in this process is the hypoxia-inducible factor (HIF) complex, which is activated in hypoxic cells and increases transcription of a broad range of genes including angiogenic growth factors such as VEGF. HIF is primarily regulated through oxygen-dependent proteasomal

Patrick H Maxwell; Peter J Ratcliffe

2002-01-01

205

Extracorporeal membrane oxygenation circuitry.  

PubMed

The extracorporeal membrane oxygenation 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 extracorporeal membrane oxygenation circuit consists of a mechanical blood pump, gas-exchange device, and a heat exchanger all connected together with circuit tubing. Extracorporeal membrane oxygenation 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 extracorporeal membrane oxygenation applications. Contemporary extracorporeal membrane oxygenation 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, which were so common with the early application of extracorporeal membrane oxygenation. Modern era extracorporeal membrane oxygenation 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

Lequier, Laurance; Horton, Stephen B; McMullan, D Michael; Bartlett, Robert H

2013-06-01

206

Oxygen Therapy for Children  

MedlinePLUS

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

207

Tissue oxygenation with graded dissolved oxygen delivery during cardiopulmonary bypass  

Microsoft Academic Search

Background: Intravascular perfluorochemical emulsions together with a high oxygen tension may increase the delivery of dissolved oxygen to useful levels. The hypothesis of this study is that increasing the dissolved oxygen content of blood with incremental doses of a perfluorochemical emulsion improves tissue oxygenation during cardiopulmonary bypass in a dose-related fashion. Methods and Results: Oxygen utilization was studied in a

William L. Holman; Russell D. Spruell; Edward R. Ferguson; Janice J. Clymer; Walter V. A. Vicente; C. Patrick Murrah; Albert D. Pacifico

1995-01-01

208

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

209

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 â183 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

210

The Microwave Spectrum of Oxygen in the Earth's Atmosphere  

Microsoft Academic Search

Space probe techniques open the possibility of radio and microwave spectroscopic investigations of planetary atmospheres through the study of resonant transitions in gaseous constituents. Computations were undertaken to determine the opacity and the thermal emis- sion produced by the millimeter-wavelength complex of oxygen lines in the earth's atmosphere. The calculations predict line profiles of individual oxygen transitions in emission or

M. L. Meeks; A. E. Lilley

1963-01-01

211

Oxygen sag equation for second-order BOD decay  

Microsoft Academic Search

A dissolved oxygen (DO) equation for a stream is developed in which the biochemical oxygen demand (BOD) deoxygenation rate is described as a second-order reaction. Rate constants for a second-order BOD equation may be evaluated by graphical or numerical methods. The DO sag equation incorporates exponential integral functions. These functions are available in tabular form or they may be calculated

Donald Dean Adrian; Thomas G. Sanders

1998-01-01

212

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

213

Atomic Oxygen Fluence Monitor  

NASA Technical Reports Server (NTRS)

This innovation enables a means for actively measuring atomic oxygen fluence (accumulated atoms of atomic oxygen per area) that has impinged upon spacecraft surfaces. Telemetered data from the device provides spacecraft designers, researchers, and mission managers with real-time measurement of atomic oxygen fluence, which is useful for prediction of the durability of spacecraft materials and components. The innovation is a compact fluence measuring device that allows in-space measurement and transmittance of measured atomic oxygen fluence as a function of time based on atomic oxygen erosion yields (the erosion yield of a material is the volume of material that is oxidized per incident oxygen atom) of materials that have been measured in low Earth orbit. It has a linear electrical response to atomic oxygen fluence, and is capable of measuring high atomic oxygen fluences (up to >10(exp 22) atoms/sq cm), which are representative of multi-year low-Earth orbital missions (such as the International Space Station). The durability or remaining structural lifetime of solar arrays that consist of polymer blankets on which the solar cells are attached can be predicted if one knows the atomic oxygen fluence that the solar array blanket has been exposed to. In addition, numerous organizations that launch space experiments into low-Earth orbit want to know the accumulated atomic oxygen fluence that their materials or components have been exposed to. The device is based on the erosion yield of pyrolytic graphite. It uses two 12deg inclined wedges of graphite that are over a grit-blasted fused silica window covering a photodiode. As the wedges erode, a greater area of solar illumination reaches the photodiode. A reference photodiode is also used that receives unobstructed solar illumination and is oriented in the same direction as the pyrolytic graphite covered photodiode. The short-circuit current from the photodiodes is measured and either sent to an onboard data logger, or transmitted to a receiving station on Earth. By comparison of the short-circuit currents from the fluence-measuring photodiode and the reference photodiode, one can compute the accumulated atomic oxygen fluence arriving in the direction that the fluence monitor is pointing. The device produces a signal that is linear with atomic oxygen fluence using a material whose atomic oxygen erosion yield has been measured over a period of several years in low-Earth orbit.

Banks, Bruce A.

2011-01-01

214

Peroxidase-catalyzed S-oxygenation: Mechanism of oxygen transfer for lactoperoxidase  

SciTech Connect

The mechanism of organosulfur oxygenation by peroxidases (lactoperoxidase (LPX), chloroperoxidase, thyroid peroxidase, and horseradish peroxidase) and hydrogen peroxide was investigated by use of para-substituted thiobenzamides and thioanisoles. The rate constants for thiobenzamide oxygenation by LPX/H{sub 2}O{sub 2} were found to correlate with calculated vertical ionization potentials, suggesting rate-limiting single-electron transfer between LPX compound I and the organosulfur substrate. The incorporation of oxygen from {sup 18}O-labeled hydrogen peroxide, water, and molecular oxygen into sulfoxides during peroxidase-catalyzed S-oxygenation reactions was determined by LC- and GC-MS. All peroxidases tested catalyzed essentially quantitative oxygen transfer from {sup 18}O-labeled hydrogen peroxide into thiobenzamide S-oxide, suggesting that oxygen rebound from the oxoferryl heme is tightly coupled with the initial electron transfer in the active site. Experiments using H{sub 2}{sup 18}O{sub 2}, and H{sub 2}{sup 18}O showed the LPX catalyzed approximately 85,22, and 0% {sup 18}O-incorporation into thioanisole sulfoxide oxygen, respectively. These results are consistent with an active site controlled mechanism in which the protein radical form of LPX compound I is an intermediate in LPX-mediated sulfoxidation reactions.

Doerge, D.R.; Cooray, N.M. (Univ. of Hawaii, Honolulu (United States)); Brewster, M.E. (Pharmatec Inc., Alachua, FL (United States))

1991-09-17

215

How Does Oxygen Therapy Work?  

MedlinePLUS

... concentrators cost less than the other oxygen therapy systems. One reason is because they don't require oxygen refills. However, oxygen concentrators are powered by electricity. Thus, you'll need a backup supply of oxygen in case of a power outage. Delivery Devices Most often, oxygen is given ...

216

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

217

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

218

Oceanography: Oxygen and climate dynamics  

NASA Astrophysics Data System (ADS)

Low oxygen levels in tropical oceans shape marine ecosystems and biogeochemistry, and climate change is expected to expand these regions. Now a study indicates that regional dynamics control tropical oxygen trends, bucking projected global reductions in ocean oxygen.

Doney, Scott C.; Karnauskas, Kristopher B.

2014-10-01

219

Soil oxygen affects denitrification  

NASA Astrophysics Data System (ADS)

Rates of denitrification, the metabolic process by which bacteria produce nitrogen (N2) gas, are variable and difficult to measure in ecosystems. Burgin and Groffman sought to learn more about the influence of soil oxygen, which is not often measured, on the denitrification process in wetlands. They collected samples and measured soil oxygen concentration in a riparian zone in Millbrook, N. Y. The site included a wet zone close to a stream and a drier zone slightly farther from the stream.

Balcerak, Ernie

2012-05-01

220

Adaptation to Oxygen  

PubMed Central

The appearance of oxygen in the Earth's atmosphere via oxygenic photosynthesis required strict anaerobes and obligate phototrophs to cope with the presence of this toxic molecule. Here we show that in the anoxygenic phototroph Rubrivivax gelatinosus, the terminal oxidases (cbb3, bd, and caa3) expand the range of ambient oxygen tensions under which the organism can initiate photosynthesis. Unlike the wild type, the cbb3?/bd? double mutant can start photosynthesis only in deoxygenated medium or when oxygen is removed, either by sparging cultures with nitrogen or by co-inoculation with strict aerobes bacteria. In oxygenated environments, this mutant survives nonphotosynthetically until the O2 tension is reduced. The cbb3 and bd oxidases are therefore required not only for respiration but also for reduction of the environmental O2 pressure prior to anaerobic photosynthesis. Suppressor mutations that restore respiration simultaneously restore photosynthesis in nondeoxygenated medium. Furthermore, induction of photosystem in the cbb3? mutant led to a highly unstable strain. These results demonstrate that photosynthetic metabolism in environments exposed to oxygen is critically dependent on the O2-detoxifying action of terminal oxidases. PMID:20335164

Hassani, Bahia Khalfaoui; Steunou, Anne-Soisig; Liotenberg, Sylviane; Reiss-Husson, Francoise; Astier, Chantal; Ouchane, Soufian

2010-01-01

221

Dynamics of oxygen unloading from sickle erythrocytes.  

PubMed Central

The objective of this work is to theoretically model oxygen unloading in sickle red cells. This has been done by combining into a single model diffusive transport mechanisms, which have been well-studied for normal red cells, and the hemoglobin polymerization process, which has been previously been studied for deoxyhemoglobin-S solutions and sickle cells in near-equilibrium situations. The resulting model equations allow us to study the important processes of oxygen delivery and polymerization simultaneously. The equations have been solved numerically by a finite-difference technique. The oxygen unloading curve for sickle erythrocytes is biphasic in nature. The rate of unloading depends in a complicated way on (a) the kinetics of hemoglobin S polymerization, (b) the kinetics of hemoglobin deoxygenation, and (c) the diffusive transport of both free oxygen and oxy-hemoglobin. These processes interact. For example, the hemoglobin S polymer interferes with the transport of both free oxygen and unpolymerized oxy-hemoglobin, and this is accounted for in the model by diffusivities which depend on the polymer and solution hemoglobin concentration. Other parameters which influence the interaction of these processes are the concentration of 2,3-diphosphoglycerate and total hemoglobin concentration. By comparing our model predictions for oxygen unloading with simpler predictions based on equilibrium oxygen affinities, we conclude that the relative rate of oxygen unloading of cells with different physical properties cannot be correctly predicted from the equilibrium affinities. To describe the unloading process, a kinetic calculation of the sort we give here is required. PMID:2248988

Makhijani, V B; Cokelet, G R; Clark, A

1990-01-01

222

[The kinetics of oxygen transport by the blood].  

PubMed

A method for calculation of oxygen metabolism kinetics in vivo for different blood pH and for different inhaled air pressure is proposed. It is based on joint solution of equations of oxygen balance in lungs and in capillaries of oxygen-consuming tissues. All calculations were carried out within the physiological range of the above parameters. The value of maximum physical load was estimated for each set of the parameters. This load was evaluated in respect to the maximal oxygen consumption possible under conditions selected. Only data borrowed from normal physiology were used in calculations. It was shown that oxyhemoglobin dissociation curve shifts (for example, caused by blood pH deviation from its norm) does not have substantial influence on the organism ability to produce work, on its supplement with the oxygen, and can not cause pathologies at acidosis and alkalosis. This new result was obtained due to adoption of strict equality of the oxygen flows absorbed by blood in the lungs and of the oxygen given back by the blood in capillaries of the oxygen-consuming tissues. PMID:8160489

Fok, M V; Zaritski?, A R; Prokopenko, G A; Lobchenko, I M

1994-01-01

223

Efficient chemical equilibrium calculations for geochemical speciation and reactive transport modelling  

NASA Astrophysics Data System (ADS)

Chemical equilibrium calculations are essential for many environmental problems. It is also a fundamental tool for chemical kinetics and reactive transport modelling, since these applications may require hundreds to billions equilibrium calculations in a single simulation. Therefore, an equilibrium method for such critical applications must be very efficient, robust and accurate. In this work we demonstrate the potential effectiveness of a novel Gibbs energy minimisation algorithm for reactive transport simulations. The algorithm includes strategies to converge from poor initial guesses; capabilities to specify non-linear equilibrium constraints such as pH of an aqueous solution and activity or fugacity of a species; a rigorous phase stability test to determine the unstable phases; and a strategy to boost the convergence speed of the calculations to quadratic rates, requiring only few iterations to converge. We use this equilibrium method to solve geochemical problems relevant to carbon storage in saline aquifers, where aqueous, gaseous and minerals phases are present. The problems are formulated to mimic the ones found in kinetics and transport simulations, where a sequence of equilibrium calculations are performed, each one using the previous solution as the initial guess. The efficiency and convergence rates of the calculations are presented, which require an average of 1-2 iterations. These results indicate that critical applications such as chemical kinetics and reactive transport modelling can potentially benefit by using this multiphase equilibrium algorithm.

Leal, Allan M. M.; Blunt, Martin J.; LaForce, Tara C.

2014-04-01

224

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

225

Lunar oxygen production by pyrolysis of regolith  

NASA Technical Reports Server (NTRS)

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

Senior, Constance L.

1991-01-01

226

Effects of atomic oxygen on graphite ablation  

NASA Technical Reports Server (NTRS)

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

Park, C.

1976-01-01

227

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.

228

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

229

Home oxygen therapy.  

PubMed

Both the efficacy and the indications for LTOT have been well defined. Most of the studies performed have focused on patients with hypoxemia caused by COPD, and the benefits observed are assumed to apply to all patients with correctable hypoxemia. For Medicare patients, oxygen is reimbursed under a prospective payment system with all delivery systems considered to be cost and therapeutically equal. Because there are, in fact, substantial clinical differences in the medical indications for individual oxygen delivery systems, it is imperative that the prescribing physician be prepared to order the therapy that is most appropriate for each patient. Most home oxygen therapy is now being ordered by primary care physicians, often functioning as gatekeepers in managed care organizations. Education of primary care physicians in this area is often inadequate, and decisions for therapy should not be delegated to the equipment suppliers. If the study of home oxygen therapy conducted by the Office of the Inspector General were repeated today, less misuse of home oxygen would probably be found because of more clearly defined indications and requirements for therapy, but it is likely that the study would find that the level of knowledge of the prescribing physician has not maintained pace with the advances in technology. Continuing education for primary care physicians in this area of respiratory care is essential for appropriate medical management now and in the future. PMID:8637306

O'Donohue, W J

1996-05-01

230

OXYGEN POISONING IN MAMMALS  

PubMed Central

1. Oxygen in concentrations of over 70 per cent of an atmosphere is poisonous to dogs, rabbits, guinea pigs and mice. 2. The poisonous effects manifest themselves in drowsiness, anorexia, loss of weight, increasing dyspnea, cyanosis and death from oxygen want. 3. The cause of oxygen want is a destructive lesion of the lungs. 4. The lesion may be characterized grossly as an hemorrhagic edema. Microscopically there is to be seen in varying degrees of intensity (a) capillary engorgement with hemorrhage, (b) the presence of interstitial and intraalveolar serum, (c) hypertrophy and desquamation of alveolar cells, (d) interstitial and alveolar infiltration of mononuclear cells. 5. The type of tissue reaction is not characteristic of an infectious process and no organisms have been recovered at autopsy from the heart's blood or from lung puncture. 6. The poisonous effects of inhalations of oxygen-rich mixtures do not appear to be related to impurities in the oxygen, nor are they related to faulty ventilation, excessive moisture or increased carbon dioxide in the atmosphere of the chambers in which the experimental animals were confined. PMID:19869294

Binger, Carl A. L.; Faulkner, James M.; Moore, Richmond L.

1927-01-01

231

A Computational Study of the Effect of Vasomotion on Oxygen Transport from Capillary Networks  

Microsoft Academic Search

The objective of this study was to investigate the effect of arteriolar vasomotion on oxygen transport from capillary networks. A computational model was used to calculate blood flow and oxygen transport from a simulated network of striated muscle capillaries. For varying tissue oxygen consumption rates, the importance of the frequency and amplitude of vasomotion-induced blood flow oscillations was studied. The

DANIEL GOLDMAN; ALEKSANDER S. POPEL

2001-01-01

232

A Computational Study of the E4ect of Vasomotion on Oxygen Transport from Capillary Networks  

Microsoft Academic Search

The objective of this study was to investigate the e!ect of arteriolar vasomotion on oxygen transport from capillary networks. A computational model was used to calculate blood #ow and oxygen transport from a simulated network of striated muscle capillaries. For varying tissue oxygen consumption rates, the importance of the frequency and amplitude of vaso- motion-induced blood #ow oscillations was studied.

DANIEL GOLDMAN; ALEKSANDER S. POPEL

2001-01-01

233

A new surface oxygen complex on carbon: Toward a unified mechanism for carbon gasification reactions  

Microsoft Academic Search

Molecular orbital theory calculations and recent high-temperature TPD experiments revealed the feasibility of a new type of active oxygen complex on graphite. This type of complex is formed by bonding of an oxygen atom to a saturated carbon atom (in the caved-in position) adjacent to the unsaturated edge carbon atom that is already bonded to an oxygen atom. Molecular orbital

S. G. Chen; R. T. Yang; F. Kapteijn; J. A. Moulijn

1993-01-01

234

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

235

Regulation of tissue oxygen levels in the mammalian lens  

PubMed Central

Opacification of the lens nucleus is a major cause of blindness and is thought to result from oxidation of key cellular components. Thus, long-term preservation of lens clarity may depend on the maintenance of hypoxia in the lens nucleus. We mapped the distribution of dissolved oxygen within isolated bovine lenses and also measured the rate of oxygen consumption (Q?O2) by lenses, or parts thereof. To assess the contribution of mitochondrial metabolism to the lens oxygen budget, we tested the effect of mitochondrial inhibitors on Q?O2 and partial pressure of oxygen (PO2). The distribution of mitochondria was mapped in living lenses by 2-photon microscopy. We found that a steep gradient of PO2 was maintained within the tissue, leading to PO2 < 2 mmHg in the core. Mitochondrial respiration accounted for approximately 90% of the oxygen consumed by the lens; however, PO2 gradients extended beyond the boundaries of the mitochondria-containing cell layer, indicating the presence of non-mitochondrial oxygen consumers. Time constants for oxygen consumption in various regions of the lens and an effective oxygen diffusion coefficient were calculated from a diffusion–consumption model. Typical values were 3 × 10?5 cm2 s?1 for the effective diffusion coefficient and a 5 min time constant for oxygen consumption. Surprisingly, the calculated time constants did not differ between differentiating fibres (DF) that contained mitochondria and mature fibres (MF) that did not. Based on these parameters, DF cells were responsible for approximately 88% of lens oxygen consumption. A modest reduction in tissue temperature resulted in a marked decrease in Q?O2 and the subsequent flooding of the lens core with oxygen. This phenomenon may be of clinical relevance because cold, oxygen-rich solutions are often infused into the eye during intraocular surgery. Such procedures are associated with a strikingly high incidence of postsurgical nuclear cataract. PMID:15272034

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

2004-01-01

236

Using Excel to Calculate Mineral Chemical Analyses  

NSDL National Science Digital Library

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

237

Murder Mystery for Student Practice of Pulmonary Physiology Calculations  

NSDL National Science Digital Library

Exercise for students used to practice measuring arterial oxygen content and delivery, physiological deadspace, dead space and alveolar ventilation, and alveolar partial pressure of oxygen and carbon dioxide. NOTE:There is an error in Table 4 (entitled "Ventilatory calculations"). The "mixed expiratory PCO2" under control conditions for Victor should be 23.6 torr rather than the published value of 17 torr.

Michael B Maron (Northeastern Ohio Universities College of Medicine Department of Physiology); Frank J Bosso (Northeastern Ohio Universities College of Medicine Department of Physiology)

1991-12-01

238

HENRY'S LAW CALCULATOR  

EPA Science Inventory

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

239

Kinetic Lattice Monte Carlo Model for Oxygen Vacancy Diffusion in Praseodymium Doped Ceria: Applications to Materials Design.  

National Technical Information Service (NTIS)

Kinetic lattice Monte Carlo (KLMC) model is developed for investigating oxygen vacancy diffusion in praseodymium-doped ceria. The current approach uses a database of activation energies for oxygen vacancy migration, calculated using first-principles, for ...

J. B. Adams, P. Crozier, P. P. Dholabhai, R. Sharma, S. Anwar

2012-01-01

240

Absolute photoionization cross sections of atomic oxygen  

NASA Technical Reports Server (NTRS)

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

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

1985-01-01

241

Absolute photoionization cross sections of atomic oxygen  

NASA Technical Reports Server (NTRS)

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

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

1982-01-01

242

Interactions of Oxygen and Hydrogen on Pd(111) surface  

SciTech Connect

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

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

2008-06-25

243

Thermal nonequilibrium in partially ionized atomic oxygen  

NASA Astrophysics Data System (ADS)

A stationary, nonlinear collisional-radiative model for high-temperature atomic oxygen is presented. Populations of electrons, ions, and excited atoms and intensities of spectral, continuum, and dielectronic recombination lines are calculated in a wide range of conditions. Transport of radiation is included by coupling the rate equations for production of the electrons, ions, and excited atoms with the concept of the escape factors that are not constant but dependent upon plasma conditions. The calculated total continuum emission is in good agreement with existing measurements.

Soon, W. H.; Kunc, J. A.

1990-01-01

244

Biological Oxygen Productivity Over the Last Glacial Termination From Triple Oxygen Isotope Measurements  

NASA Astrophysics Data System (ADS)

The atmospheric oxygen isotope signature of O2 is linked to the oxygen signature of seawater through photosynthesis and respiration. Fractionation during these processes is mass dependent affecting ? 17O about half as much as ? 18O. A mass independent fractionation process takes place during isotope exchange between O2 and CO2 in the stratosphere (Thiemens, 1999; Luz et al., 1999). The magnitude of the mass-independent anomaly in the triple isotope composition of O2 depends on relative rates of biological O2 cycling and photochemical reactions in the stratosphere. Variations of this anomaly thus allows us to estimate changes of mass dependent O2 production by photosynthesis versus mass independent O2-CO2 exchange in the stratosphere. We reconstruct total oxygen productivity for the past from ? ^ {17}O and ? ^ {18}O measurements of O2 trapped in ice cores. With a box model we estimate that the total biogenic productivity was only ~70-80 % of today for the glacial and was probably still lower than today during the glacial-interglacial transition and the early Holocene. In principle we can calculate the oxygen flux from the ocean biosphere if we know the oxygen flux from the land biosphere. Calculated ocean production is very sensitive to the estimate of land biosphere production. The latter term remains uncertain, however, and we can presently only constrain glacial ocean production to 70 to 140 % of the present value.

Blunier, T.; Bender, M. L.; Hendricks, M. B.

2001-05-01

245

Biological Oxygen Productivity Over The Last Glacial Termination From Triple Oxygen Isotope Measurements  

NASA Astrophysics Data System (ADS)

The atmospheric oxygen isotope signature of O2 is linked to the oxygen signature of seawater through photosynthesis and respiration. Fractionation during these pro- cesses is mass dependent affecting 17O about half as much as 18O. A mass indepen- dent fractionation process takes place during isotope exchange between O2 and CO2 in the stratosphere (Thiemens, 1999; Luz et al., 1999). The magnitude of the mass- independent anomaly in the triple isotope composition of O2 depends on relative rates of biological O2 cycling and photochemical reactions in the stratosphere. Variations of this anomaly thus allows us to estimate changes of mass dependent O2 production by photosynthesis versus mass independent O2-CO2 exchange in the stratosphere. We reconstruct total oxygen productivity for the past from 17O and 18O measure- ments of O2 trapped in ice cores. With a box model we estimate that the total biogenic productivity was only 76-83 % of today for the glacial and was probably still lower than today during the glacial-interglacial transition and the early Holocene. In principle we can calculate the oxygen flux from the ocean biosphere if we know the oxygen flux from the land biosphere. Calculated ocean production is very sensitive to the estimate of land biosphere production. The latter term remains uncertain, however, and we can presently only constrain glacial ocean production to 88 to 140 % of the present value.

Blunier, T.; Bender, M. L.; Hendricks, M. B.

246

Water column oxygen demand and sediment oxygen flux: patterns of oxygen depletion in tidal creeks  

Microsoft Academic Search

Low dissolved oxygen (DO) levels often occur during summer in tidal creeks along the southeastern coast of the USA. We analyzed\\u000a rates of oxygen loss as water-column biochemical oxygen demand (BOD5) and sediment oxygen flux (SOF) at selected tidal creek sites monthly over a 1-year period. Ancillary physical, chemical\\u000a and biological data were collected to identify factors related to oxygen

Tara A. MacPherson; Lawrence B. Cahoon; Michael A. Mallin

2007-01-01

247

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.

248

Hyperbaric Oxygen Therapy  

MedlinePLUS

... the evidence? There is scientific evidence showing HBOT works to treat a number of conditions. The Committee on Hyperbaric Oxygen Therapy of the Undersea and Hyperbaric Medicine recommends it for treatment of: Decompression sickness Arterial gas embolism (bubbles of air in the ...

249

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...

250

SWIMBLADDER PERMEABILITY TO OXYGEN  

Microsoft Academic Search

SUMMARY The permeability of the swimbladder to gas was measured as the conductance to oxygen in seven species of fish. The low over-all conductance resides in the low diffusion constant, K, of the middle layer of the wall (submucosa) while the outer and inner layers (tunica externa and mucosa) have diffusion constants similar to other vertebrate tissues. The low diffusion

GEORGE N. LAPENNAS; KNUT SCHMIDT-NIELSEN

1977-01-01

251

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

252

Seasonal changes in the oxygen storage capacity and aerobic dive limits of the muskrat ( Ondatra zibethicus )  

Microsoft Academic Search

The oxygen storage capacity and partitioning of body oxygen reserves were compared in summer-and winter-acclimatized muskrats (Ondatra zibethicus). Blood volume, blood oxygen capacity, and skeletal muscle myoglobin content were higher in December than in July (PP>0.05). The oxygen storage capacity of a diving muskrat was calculated at 25.2 ml O2 STPD · kg-1 in July, compared to 35.7 ml O2

Robert A. MacArthur

1990-01-01

253

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

254

Study on the dissolved oxygen flux in the South China Sea  

Microsoft Academic Search

The seawater box model for the South China Sea (SCS) was used to calculate the fluxes of dissolved oxygen in Box I, Box II\\u000a and Box III for establishing the box model of dissolved oxygen (DO) in the SCS.\\u000a \\u000a The total input flux of oxygen to the SCS was calculated to be 280.4×104 mol\\/s, of which 49.2% was transported into

Hong-Ying Lin; Wu-Ying Han

1997-01-01

255

A systematic theoretical study of water dissociation on clean and oxygen-preadsorbed transition metals  

Microsoft Academic Search

Water dissociation on clean and oxygen-preadsorbed transition metal surfaces was investigated by the DFT-GGA method. The total energy change and the reaction barrier were calculated with respect to the direct and oxygen-assisted cleavage of OH bonds of water. The calculated results showed periodic trends for water dissociation on both clean and oxygen-preadsorbed surfaces. On clean surfaces, the chemical activity for

Gui-Chang Wang; Shu-Xia Tao; Xian-He Bu

2006-01-01

256

Oxygen nonstoichiometry in YBaâCuâO{sub 7-x} and partial properties of oxygen  

Microsoft Academic Search

We present the first determination of the oxygen stoichiometry as a function of temperature and pressure for the YBaâCuâO{sub 7-x} phase under equilibrium conditions using static vapor-pressure measurements on 16 ceramic samples in the ranges 1.01 < p{sub o}â <101.3 KPa, 650calculation procedure that yields a self-consistent set of oxygen stoichiometries from iodimetric

I. V. Tarasov; V. B. Lazarev

1994-01-01

257

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

258

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

259

Integrated oxygen recovery system  

NASA Technical Reports Server (NTRS)

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

Lee, M. Gene; Davenport, Ronald J.

1993-01-01

260

Integrated oxygen recovery system  

NASA Technical Reports Server (NTRS)

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

Lee, M. Gene; Davenport, Ronald J.

1993-01-01

261

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

262

Assessing hafnium on hafnia as an oxygen getter  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

263

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

264

Ancient Oceans Had Less Oxygen  

ERIC Educational Resources Information Center

The amount of dissolved oxygen in the oceans in the mid-Proterozoic period has evolutionary implications since essential trace metals are redox sensitive. The findings suggest that there is global lack of oxygen in seawater.

King, Angela G.

2004-01-01

265

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...

266

Chemiluminescence from Dissolved Oxygen  

Microsoft Academic Search

RED chemiluminescence corresponding to about 40 kcal\\/mol., and attributable to the forbidden transition 1Sigma+g --> 3Sigma-g of the oxygen molecule, has been observed in three recent investigations1-3, but no explanation of the effect has been presented. These involve organic hydroperoxides or oxidations with hydrogenperoxide and also the reaction of hydrogen peroxide with HClO. In contrast with this, decompositions of hydrogen

E. J. Bowen

1964-01-01

267

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

268

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

269

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

270

Oxygen sensing in the body  

Microsoft Academic Search

This review is divided into three parts: (a) The primary site of oxygen sensing is the carotid body which instantaneously respond to hypoxia without involving new protein synthesis, and is historically known as the first oxygen sensor and is therefore placed in the first section (Lahiri, Roy, Baby and Hoshi). The carotid body senses oxygen in acute hypoxia, and produces

S. Lahiri; A. Roy; S. M. Baby; T. Hoshi; G. L. Semenza; N. R. Prabhakar

2006-01-01

271

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

272

Oxygen Discharge and Post-Discharge Kinetics Experiments and Modeling for the Electric Oxygen?Iodine Laser System †  

Microsoft Academic Search

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(a 1 ¢) concentration resulting from the presence of NO in

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

2007-01-01

273

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

274

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

NASA Astrophysics Data System (ADS)

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 experimental data describe these derivatives over a range of compositions which includes basic magmas. Therefore, for silicate liquids in this composition range, the topology of the Gibbs free energy of mixing can be approximated from experimental determinations of its derivatives. The majority of the existing thermodynamic data on the liquid phase is consistent with the application of regular solution theory to model the free energy of mixing. Strictly symmetric, temperature and pressure independent, regular solution interaction parameters are calibrated from this phase equilibrium data using regression techniques which have their basis in inverse theory. These techniques generate numerically stable interaction parameters which incorporate inter-variable correlation and account for experimental uncertainty. The regular solution model fits the available data on anhydrous silicate liquids to within the accuracy of the thermodynamic database +/-550 cals). Extensions to regular solution theory allow water solubility in more silica rich liquids to be modelled somewhat less accurately (+/-750 cals). The topology of the excess free energy of mixing surface is strongly asymmetric, possessing a single multicomponent saddle point which defines a spinodal locus. Given this prediction of a multicomponent spinode, a mathematical procedure based upon minimisation of the Gibbs free energy of mixing is developed for the calculation of the compositions of coexisting immiscible liquids. Predicted binodal compositions substantially agree with elemental liquid/liquid partitioning trends observed in lavas. Calculations suggest that an immiscible dome, in temperature-composition space, intersects the liquidus field of the magma type tholeiite. Immiscible phenomena are predicted at sub-liquidus temperatures for the bulk compositions of more basic or alkalic lavas, but are absent in more siliceous rock types for temperatures of the metastable liquid down to 900 K. The regular solution model is used in four petrological applications. The first concerns a prediction of the binary olivine-liquid phase diagram. The calculated geometry exhibits a minimum near Fa75, which, though not in accord with experimental results on the pseudobinary system, compares quite favorably with olivine-liquid phase equilibria interpreted from rhyolites, namely that the olivine phenocrysts of rhyolites are more iron rich than their coexisting liquids. The second petrological example concerns estimating the depth of the source regions of several basic lavas whose compositions cover a range from ugandite to basaltic andesite. The third application is a calculation of the saturation temperatures and compositions of plagioclase and olivine in four experimental basaltic liquids and a prediction of the liquidus temperatures and first phenocryst compositions of the Thingmuli lava series of Eastern Iceland. Lastly, enthalpies of fusion are computed for a variety of stoichiometric compounds of geologic interest. These demonstrate good agreement with calorimetrically measured quantities

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

1983-11-01

275

Oxygen supplies in disaster management.  

PubMed

Mass casualty events and disasters, both natural and human-generated, occur frequently around the world and can generate scores of injured or ill victims in need of resources. Of the available medical supplies, oxygen remains the critical consumable resource in disaster management. Strategic management of oxygen supplies in disaster scenarios remains a priority. Hospitals have large supplies of liquid oxygen and a supply of compressed gas oxygen cylinders that allow several days of reserve, but a large influx of patients from a disaster can strain these resources. Most backup liquid oxygen supplies are attached to the main liquid system and supply line. In the event of damage to the main system, the reserve supply is rendered useless. The Strategic National Stockpile supplies medications, medical supplies, and equipment to disaster areas, but it does not supply oxygen. Contracted vendors can deliver oxygen to alternate care facilities in disaster areas, in the form of concentrators, compressed gas cylinders, and liquid oxygen. Planning for oxygen needs following a disaster still presents a substantial challenge, but alternate care facilities have proven to be valuable in relieving pressure from the mass influx of patients into hospitals, especially for those on home oxygen who require only an electrical source to power their oxygen concentrator. PMID:23271827

Blakeman, Thomas C; Branson, Richard D

2013-01-01

276

Dynamic oxygen-enhanced MRI of cerebrospinal fluid.  

PubMed

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

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

2014-01-01

277

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

278

Model calculations of nuclear data for biologically-important elements  

SciTech Connect

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

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

1994-05-01

279

Programmable calculator stress analysis  

SciTech Connect

Advanced programmable alphanumeric calculators are well suited for closed-form calculation of pressure-vessel stresses. They offer adequate computing power, portability, special programming features, and simple interactive execution procedures. Representative programs that demonstrate calculator capabilities are presented. Problems treated are stress and strength calculations in thick-walled pressure vessels and the computation of stresses near head/pressure-vessel junctures.

Van Gulick, L.A.

1983-01-01

280

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

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

281

Reduced Oxygen Contributed To ?Great Dying?  

NSF Publications Database

... Press Release 05-058Reduced Oxygen Contributed To ?Great Dying? Oxygen deficiency could also ... atmospheric oxygen decreased in the late Permian period, hypoxia, or insufficient oxygen in bodily ...

282

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.

2008-02-12

283

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

284

Glovebox oxygen monitoring system  

SciTech Connect

This system is located in the Replacement Tritium Facility (RTF) at the Savannah River Site of the US Department of Energy. The basic system consists of an oxygen sensor module located inside the glovebox and a wall mounted panel located outside the glovebox that contains an electronics package that displays the oxygen level, displays alarms, and sends signals to a facility Distributed Control System (DCS). RTF is a new facility that will be used primarily to load and unload tritium reservoirs, and recycle the tritium for use in existing or new reservoirs. Tritium, an oderless, colorless, gas is a radioactive isotope of hydrogen that is used in modern thermonuclear weapons. Once on-line, RTF will replace other tritium facilities that have been in existence since the 1950`s. Since the entire process at RTF is contained in nitrogen blanketed gloveboxes and features have been provided to recapture fugitive tritium, environmental releases and worker exposure to tritium will be reduced compared to the old facilities.

Haggard, R.

1993-08-01

285

Extracorporeal membrane oxygenation  

PubMed Central

Extracorporeal membrane oxygenation (ECMO) is an advanced form of life support technology whereby venous blood is oxygenated outside of the body and returned to the patient. ECMO was initially used as last-resort rescue therapy for patients with severe respiratory failure. Over the last four decades, it has developed into a safe, standard therapy for newborns with progressive cardiorespiratory failure, as a resuscitation therapy after cardiac arrest, and in combination with other treatments such as hypothermia and various blood filtration therapies. ECMO has also become routine for children and adults with all forms of cardiogenic shock and is also routine in early graft failure after transplantation. The one area of ongoing debate is the role of ECMO in adults with hypoxemic respiratory failure. As ECMO equipment becomes safer, earlier use improves patient outcomes. Several modifications of the two basic venovenous and venoarterial ECMO systems are now occurring, as are many minor variations in cannulation strategies and systems of care for patients receiving ECMO. The indications and situations in which ECMO have been tried continue to change, and ECMO for sub-acute and chronic illnesses is now commonplace, as is the use of ECMO in patients with clinical problems previously regarded as contraindications, such as sepsis, malignancy, and immunosuppression. PMID:24404382

Butt, Warwick

2013-01-01

286

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

287

High Selectivity Oxygen Delignification  

SciTech Connect

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 of EOD high kappa pulps; (4) Developing a simple, reproducible method of quantifying yield gains from EOD; and (5) Developing process conditions that significantly reduce the capital requirements of EOD while optimizing the yield benefits. Key research outcomes included, demonstrating the use of a mini-O sequence such as (E+O)Dkf:0.05(E+O) or Dkf:0.05(E+O)(E+O) without interstage washing could capture approximately 60% of the delignification efficiency of a conventional O-stage without the major capital requirements associated with an O-stage for conventional SW kraft pulps. The rate of formation and loss of fiber charge during an O-stage stage can be employed to maximize net fiber charge. Optimal fiber charge development and delignification are two independent parameters and do not parallel each other. It is possible to utilize an O-stage to enhance overall cellulosic fiber charge of low and high kappa SW kraft pulps which is beneficial for physical strength properties. The application of NIR and multi-variant analysis was developed into a rapid and simple method of determining the yield of pulp from an oxygen delignification stage that has real-world mill applications. A focus point of this program was the demonstration that Kraft pulping conditions and oxygen delignification of high and low-kappa SW and HW pulps are intimately related. Improved physical pulp properties and yield can be delivered by controlling the H-factor and active alkali charge. Low AA softwood kraft pulp with a kappa number 30 has an average improvement of 2% in yield and 4 cP in viscosity in comparison to high AA pulp for the oxygen delignification. This difference is also seen for high-kappa SW kraft pulps with an average improvement of {approx}3% in yield and 3 cP in viscosity for low AA high kappa number 50 pulp. Low AA hardwood kappa number 20 pulp had an average improvement of {approx}4% in yield and 6-12 cP in viscosity as compared to high AA pulp. Lower kraft cooking temperature (160 vs. 170 C) in combination with the medium AA provides a practical approach for integrating high kappa pulping of hardwoods (i.e., low rejects) with an advanced extended oxygen delignification stage. ECF pulp bleaching of low and high kappa kraft SW and HW pulps exhibit comparable optical and physical strength properties when bleached D(EPO)D.

Arthur J. Ragauskas

2005-09-30

288

ORMOSIL oxygen sensors on polystyrene microplate for dissolved oxygen measurement  

Microsoft Academic Search

Oxygen sensors prepared from tetramethyl orthosilicate and dimethoxy dimethylsilane with tris(4,7-diphenyl-1,10-phenanthroline)ruthenium (II) as the sensing dye were coated onto the well bottom surface of a 96-well polystyrene microtiter plate to give a high-throughput system for dissolved oxygen measurement. The oxygen sensors give linear Stern–Volmer calibration plots, and produce reliable and reproducible results in the determination of IC50 values of drugs

Hei-Leung Pang; Nga-Yan Kwok; Larry Ming-Cheung Chow; Chi-Hung Yeung; Kwok-Yin Wong; Xi Chen; Xiaoru Wang

2007-01-01

289

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

290

Interagency assessment of oxygenated fuels  

SciTech Connect

Oxygenates have been used as octane enhancers in gasoline since the late 1970s, due to the phaseout of lead. During the 1980s, oxygenates came in to wider use as some States implemented oxygenated gasoline programs for the control of carbon monoxide (CO) pollution in cold weather. People with coronary artery disease are particularly sensitive to the adverse effects of this air pollutant. The first winter oxygenated gasoline program in the United States was implemented in Denver, Colorado in 1988. The 1990 Clean Air Act Amendments required the use of oxygenated gasoline in several areas of the country that failed to attain the National Ambient Air Quality Standard (NAAQS) for CO. During the winter months of 1992-1993, many new oxygenated gasoline programs were implemented to increase combustion efficiency in cold weather and thereby reduce CO emissions. Methyl tertiary-butyl ether (MTBE) has become the most widely used motor vehicle oxygenate in the U.S., though in some areas, ethanol is the dominant oxygenate used in motor vehicle fuels. Other fuel oxygenates that are in use or may potentially be used include ethyl tertiary-butyl ether (ETBE), tertiary-amyl methyl ether (TAME), diisopropyl ether (DIPE), tertiary-butyl alcohol (TBA), and methanol. Because of limitations in available data, there is less emphasis in this report on these other oxygenates. The Clean Air Act requires at least 2.7% by weight oxygen content for gasoline sold in CO nonattainment areas, and about 15% by volume MTBE or about 7.5% by volume ethanol to achieve this requirement. The purpose of this report is to provide a review of the scientific literature on oxygenated fuels and to assess effects of the winter oxygenated fuels program on air quality, water quality, fuel economy and engine performance, and public health.

NONE

1997-12-31

291

A new method to estimate the oxidation state of basaltic series from microprobe analyses  

E-print Network

of equations, and to perform the error propagation analysis. © 2009 Elsevier B.V. All rights reserved. 1Ototal in plagioclase, but a decrease in the associated clinopyroxene. We propose an equation, based on published. The associated error can be calculated and is on average b1 log unit of the prevailing oxygen fugacity. In order

Demouchy, Sylvie

292

The effect of water and fO2 on the ferricferrous ratio of silicic melts  

E-print Network

, France ­ remplacé par UMR6113 - ISTO Abstract New experiments on the effect of dissolved water: temperature: oxygen fugacity and pressure on their redox states. Contrib. Mineral. Petrol. 108, 82 for dissolved water must be added to the KC equation if it is to be applied to the calculation of ferric

Paris-Sud XI, Université de

293

Ocean metabolism observed with oxygen sensors on profiling floats in the South Pacific Todd R. Martz and Kenneth S. Johnson  

E-print Network

Ocean metabolism observed with oxygen sensors on profiling floats in the South Pacific Todd RS and 50uS) using 1.5 yr of oxygen measurements from profiling floats. Export production, calculated from oxygen utilization rates below the compensation depth from December to April, was 10.7 6 2 mmol C m22 d21

Riser, Stephen C.

294

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

295

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. It was found that space group of R3c yielded a better refinement than a cubic structure of Pm3m. Oxygen occupancy was nearly 3 in the region from room temperature to 700 C, above which the occupancy decreased due to oxygen loss. Dense OTM bars provided by Praxair were loaded to fracture at varying stress rates. Studies were done at room temperature in air and at 1000 C in a specified environment to evaluate slow crack growth behavior. The X-Ray data and fracture mechanisms points to non-equilibrium decomposition of the LSFCO OTM membrane. The non-equilibrium conditions could probably be due to the nature of the applied stress field (stressing rates) and leads to transition in crystal structures and increased kinetics of decomposition. The formations of a Brownmillerite or Sr2Fe2O5 type structures, which are orthorhombic are attributed to the ordering of oxygen vacancies. The cubic to orthorhombic transitions leads to 2.6% increase in strains and thus residual stresses generated could influence the fracture behavior of the OTM membrane. Continued investigations on the thermodynamic properties (stability and phase-separation behavior) and total conductivity of prototype membrane materials were carried out. The data are needed together with the kinetic information to develop a complete model for the membrane transport. Previously characterization, stoichiometry and conductivity measurements for samples of La{sub 0.2}Sr{sub 0.8}Fe{sub 0.55}Ti{sub 0.45}O{sub 3-{delta}} were reported. In this report, measurements of the chemical and thermal expansion as a function of temperature and p{sub O2} are described.

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

296

Microdistribution of oxygen in silicon  

NASA Technical Reports Server (NTRS)

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

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

1980-01-01

297

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

298

Tissue oxygen measurement system  

NASA Technical Reports Server (NTRS)

A device and method in accordance with the invention for determining the oxygen partial pressure (PO.sub.2) of a tissue by irradiating the tissue with optical radiation such that the light is emitted from the tissue, and by collecting the reflected or transmitted light from the tissue to form an optical spectrum. A spectral processor determines the PO.sub.2 level in tissue by processing this spectrum with a previously-constructed spectral calibration model. The tissue may, for example, be disposed underneath a covering tissue, such as skin, of a patient, and the tissue illuminated and light collected through the skin. Alternatively, direct tissue illumination and collection may be effected with a hand-held or endoscopic probe. A preferred system also determines pH from the same spectrum, and the processor may determine critical conditions and issue warnings based on parameter values.

Soller, Babs R. (Inventor)

2004-01-01

299

Oxygen diffusion barrier coating  

NASA Technical Reports Server (NTRS)

A method for coating a titanium panel or foil with aluminum and amorphous silicon to provide an oxygen barrier abrogating oxidation of the substrate metal is developed. The process is accomplished with known inexpensive procedures common in materials research laboratories, i.e., electron beam deposition and sputtering. The procedures are conductive to treating foil gage titanium and result in submicron layers which virtually add no weight to the titanium. There are no costly heating steps. The coatings blend with the substrate titanium until separate mechanical properties are subsumed by those of the substrate without cracking or spallation. This method appreciably increases the ability of titanium to mechanically perform in high thermal environments such as those witnessed on structures of space vehicles during re-entry

Unnam, Jalaiah (inventor); Clark, Ronald K. (inventor)

1987-01-01

300

Bifunctional alkaline oxygen electrodes  

NASA Technical Reports Server (NTRS)

The authors describe the identification and testing of electrocatalysts and supports for the positive electrode of moderate-temperature, single-unit, rechargeable alkaline fuel cells. Recent work on Na(x)Pt3O4, a potential bifunctional catalyst, is described, as well as the application of novel approaches to the development of more efficient bifunctional electrode structures. The three dual-character electrodes considered here showed similar superior performance; the Pt/RhO2 and Rh/RhO2 electrodes showed slightly better performance than the Pt/IrO2 electrode. It is concluded that Na(x)Pt3O4 continues to be a promising bifunctional oxygen electrode catalyst but requires further investigation and development.

Swette, L.; Kackley, N.; Mccatty, S. A.

1991-01-01

301

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

302

LDEF atomic oxygen fluence update  

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

303

Oxygen uptake of benthic systems  

E-print Network

and Rolley (20) and Hanes and Irvine (1), in independent studies of the effect of mud erosion on oxygen con- sumption of river muds, found that oxygen requirements were inde- pendent of sludge depth. They did determine, however, that oxygen uptake was a... mg/hr/sq m between standard and maximum mixing. Hanes and Irvine (23) made a determination of the effects of temperature on quiescent oxygen uptake rates by covering sludge with aerated water and allowing the supernatant to be totally de- pleted...

Priebe, William Franklin

2012-06-07

304

Equations for calculating hydrogeochemical reactions of minerals and gases such as CO2 at high pressures and temperatures  

NASA Astrophysics Data System (ADS)

Calculating the solubility of gases and minerals at the high pressures of carbon capture and storage in geological reservoirs requires an accurate description of the molar volumes of aqueous species and the fugacity coefficients of gases. Existing methods for calculating the molar volumes of aqueous species are limited to a specific concentration matrix (often seawater), have been fit for a limited temperature (below 60 °C) or pressure range, apply only at infinite dilution, or are defined for salts instead of individual ions. A more general and reliable calculation of apparent molar volumes of single ions is presented, based on a modified Redlich-Rosenfeld equation. The modifications consist of (1) using the Born equation to calculate the temperature dependence of the intrinsic volumes, following Helgeson-Kirkham-Flowers (HKF), but with Bradley and Pitzer's expression for the dielectric permittivity of water, (2) using the pressure dependence of the extended Debye-Hückel equation to constrain the limiting slope of the molar volume with ionic strength, and (3) adopting the convention that the proton has zero volume at all ionic strengths, temperatures and pressures. The modifications substantially reduce the number of fitting parameters, while maintaining or even extending the range of temperature and pressure over which molar volumes can be accurately estimated. The coefficients in the HKF-modified-Redlich-Rosenfeld equation were fitted by least-squares on measured solution densities.

Appelo, C. A. J.; Parkhurst, D. L.; Post, V. E. A.

2014-01-01

305

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...

306

Systemic oxygen delivery by peritoneal perfusion of oxygen microbubbles.  

PubMed

Severe hypoxemia refractory to pulmonary mechanical ventilation remains life-threatening in critically ill patients. Peritoneal ventilation has long been desired for extrapulmonary oxygenation owing to easy access of the peritoneal cavity for catheterization and the relative safety compared to an extracorporeal circuit. Unfortunately, prior attempts involving direct oxygen ventilation or aqueous perfusates of fluorocarbons or hemoglobin carriers have failed, leading many researchers to abandon the method. We attribute these prior failures to limited mass transfer of oxygen to the peritoneum and have designed an oxygen formulation that overcomes this limitation. Using phospholipid-coated oxygen microbubbles (OMBs), we demonstrate 100% survival for rats experiencing acute lung trauma to at least 2 h. In contrast, all untreated rats and rats treated with peritoneal oxygenated saline died within 30 min. For rats treated with OMBs, hemoglobin saturation and heart rate were at normal levels over the 2-h timeframe. Peritoneal oxygenation with OMBs was therefore shown to be safe and effective, and the method requires less equipment and technical expertise than initiating and maintaining an extracorporeal circuit. Further translation of peritoneal oxygenation with OMBs may provide therapy for acute respiratory distress syndrome arising from trauma, sepsis, pneumonia, aspiration, burns and other pulmonary diseases. PMID:24439406

Feshitan, Jameel A; Legband, Nathan D; Borden, Mark A; Terry, Benjamin S

2014-03-01

307

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

PubMed Central

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

2014-01-01

308

Numerical Analysis of Rarefied Oxygen Flow around Catalytic Materials  

NASA Astrophysics Data System (ADS)

Direct simulation Monte Carlo code is developed to study a catalytic process of atomic oxygen on thermal protection material surface. The present method employs the phenomenological electronic excitation model and the heterogeneous catalytic model. Numerical method is applied to simulate the flowfield around a test piece put into the rarefied dissociating oxygen test flow. The calculated number density ratio of oxygen to argon is compared with the measured emission intensity ratio of oxygen line to argon line. The sensitivity analysis is made by varying Eley-Rideal reaction cross section under the several conditions of collisional desorption cross section, sticking coefficient, and total number of surface site. It is found from the study that the probability value of Eley-Rideal reaction for the test piece made of a sintered silicon carbide is about 0.035, while the value of about 0.1 is deduced for the test piece made of copper.

Suzuki, Toshiyuki; Osawa, Hiroshi; Mizuno, Masahito; Takayanagi, Hiroki; Fujita, Kazuhisa; Sawada, Keisuke

309

Oxygen diffusion in a network model of the myocardial microcirculation.  

PubMed

Oxygen supply was studied in a three-dimensional capillary network model of the myocardial microcirculation. Capillary networks were generated using one common strategy to locate the capillary branchings and segments, arterioles and venules. Flow paths developed with different capillary flow velocities. All pressure-flow relationships were linear. The model includes free diffusion of oxygen within tissue slices that are perpendicular to the main capillary orientation. Oxygen pressure distributions were calculated and correlated to oxygen delivery by small capillary segments. It was shown that intercapillary diffusion is important for reducing PO2 heterogeneity. The absence of this feature leads to an oxygen distribution that has similar heterogeneity characteristics as the capillary flow heterogeneity. Such situations may also occur during simulated, elevated metabolic activity in a network model that allows intercapillary diffusion. On the basis of our simulations of metabolic vasoactivity we concluded that the venous PO2 is a misleading quantity to indicate tissue oxygenation. The venous PO2 in our model was not a good measure for the mean tissue or capillary PO2, and for the low oxygen pressures that exist at some locations in the network model. Moreover, the venous PO2 may remain constant despite considerable changes on the tissue PO2 distribution induced by metabolic activity. PMID:8307707

Wieringa, P A; Stassen, H G; Van Kan, J J; Spaan, J A

1993-10-01

310

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

311

Ecological Footprint Calculators  

NSDL National Science Digital Library

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

Ecobusinesslinks

312

DRUG DOSAGE CALCULATIONS  

E-print Network

DRUG DOSAGE CALCULATIONS THE UNIVERSITY OF NOTTINGHAM SCHOOL OF NURSING updated Feb 2001 #12 Ward D58.Tel - 43234 #12;Numeracy and Drug Calculations This handout covers a variety of numeracy based tasks which nurses and midwives may be required to perform in practice. These include drug calculations

Sidorov, Nikita

313

Iodometric determination of oxygen contents of the T1 single layer system and their relevance to superconductivity  

Microsoft Academic Search

The oxygen contents of oxygen-annealed T1 single layer systems were determined by iodometric titration. The oxygen contents, w, of T1Ba2Ca1-xYxCu2Ow increased with Y concentration, x, substituted for Ca. Oxygen vacancy, y, was estimated to be about. y=0.3 in oxygen-annealed T1Ba2Can-1CunO2n+3-y (n=2, 3, 4). The Cu valence of oxygen-annealed T1Ba2 Can-1CunO2n+3-y is calculated to be about 2.2+, if the hole is

S. Nakajima; M. Kikuchi; Y. Syono; T. Oku; K. Nagase; N. Kobayashi; D. Shindo; K. Hiraga

1991-01-01

314

A DFT study of oxygen dissociation on platinum based nanoparticles  

NASA Astrophysics Data System (ADS)

Density functional theory calculations are performed on 38 and 79 metal atom truncated octahedron clusters to study oxygen dissociation as a model for the initial stage of the oxygen reduction reaction. Pure platinum and alloyed platinum-titanium core-shell systems are investigated. It is found that barrierless oxygen dissociation occurs on the (111) facet of the pure platinum clusters. A barrier of ~0.3 eV is observed on the (100) facet. For the alloyed cluster, dissociation barriers are found on both facets, typically ~0.6 eV. The differences between the two systems are attributed to the ability of oxygen to distort the (111) surface of the pure platinum clusters. We show that flexibility of the platinum shell is crucial in promotion of fast oxygen dissociation. However, the titanium core stabilises the platinum shell upon alloying, resulting in a less easily distortable surface. Therefore, whilst an alloyed platinum-titanium electrocatalyst has certain advantages over the pure platinum electrocatalyst, we suggest alloying with a more weakly interacting metal will be beneficial for facilitating oxygen dissociation.Density functional theory calculations are performed on 38 and 79 metal atom truncated octahedron clusters to study oxygen dissociation as a model for the initial stage of the oxygen reduction reaction. Pure platinum and alloyed platinum-titanium core-shell systems are investigated. It is found that barrierless oxygen dissociation occurs on the (111) facet of the pure platinum clusters. A barrier of ~0.3 eV is observed on the (100) facet. For the alloyed cluster, dissociation barriers are found on both facets, typically ~0.6 eV. The differences between the two systems are attributed to the ability of oxygen to distort the (111) surface of the pure platinum clusters. We show that flexibility of the platinum shell is crucial in promotion of fast oxygen dissociation. However, the titanium core stabilises the platinum shell upon alloying, resulting in a less easily distortable surface. Therefore, whilst an alloyed platinum-titanium electrocatalyst has certain advantages over the pure platinum electrocatalyst, we suggest alloying with a more weakly interacting metal will be beneficial for facilitating oxygen dissociation. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr04750d

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

2013-12-01

315

Oxygen Isotopes in Meteorites  

NASA Astrophysics Data System (ADS)

Oxygen isotope abundance variations in meteorites are very useful in elucidating chemical and physical processes that occurred during the formation of the solar system (Clayton, 1993). On Earth, the mean abundances of the three stable isotopes are 16O: 99.76%, 17O: 0.039%, and 18O: 0.202%. It is conventional to express variations in abundances of the isotopes in terms of isotopic ratios, relative to an arbitrary standard, called SMOW (for standard mean ocean water), as follows:The isotopic composition of any sample can then be represented by one point on a "three-isotope plot," a graph of ?17O versus ?18O. It will be seen that such plots are invaluable in interpreting meteoritic data. Figure 1 shows schematically the effect of various processes on an initial composition at the center of the diagram. Almost all terrestrial materials lie along a "fractionation" trend; most meteoritic materials lie near a line of "16O addition" (or subtraction). (4K)Figure 1. Schematic representation of various isotopic processes shown on an oxygen three-isotope plot. Almost all terrestrial materials plot along a line of "fractionation"; most primitive meteoritic materials plot near a line of "16O addition." The three isotopes of oxygen are produced by nucleosynthesis in stars, but by different nuclear processes in different stellar environments. The principal isotope, 16O, is a primary isotope (capable of being produced from hydrogen and helium alone), formed in massive stars (>10 solar masses), and ejected by supernova explosions. The two rare isotopes are secondary nuclei (produced in stars from nuclei formed in an earlier generation of stars), with 17O coming primarily from low- and intermediate-mass stars (<8 solar masses), and 18O coming primarily from high-mass stars (Prantzos et al., 1996). These differences in type of stellar source result in large observable variations in stellar isotopic abundances as functions of age, size, metallicity, and galactic location ( Prantzos et al., 1996). In their paper reporting the discovery of 18O in the Earth's atmosphere, Giauque and Johnston (1929) refer to nonuniform distribution of oxygen isotopes as a "remote possibility," whereas Manian et al. (1934) sought to find variations in oxygen isotope abundances in meteorites as evidence for an origin outside the solar system.In addition to the abundance variations due to nuclear processes, there are important isotopic variations produced within molecular clouds, the precursors to later star-formation. The most important process is isotopic self-shielding in the UV photodissociation of CO (van Dishoeck and Black, 1988). This process results from the large differences in abundance between C16O, on the one hand, and C17O and C18O on the other. Photolysis of CO occurs by absorption of stellar UV radiation in the wavelength range 90-100 nm. The reaction proceeds by a predissociation mechanism, in which the excited electronic state lives long enough to have well-defined vibrational and rotational energy levels. As a consequence, the three isotopic species - C16O, C17O, and C18O - absorb at different wavelengths, corresponding to the isotope shift in vibrational frequencies. Because of their different number densities, the abundant C16O becomes optically thick in the outermost part of the cloud (nearest to the external source of UV radiation), while the rare C17O and C18O remain optically thin, and hence dissociate at a greater rate in the cloud interior. The differences in chemical reactivity between C16O molecules and 17O and 18O atoms may lead to isotopically selective reaction products. This scenario has been suggested to explain meteoritic isotope patterns, as discussed below (Yurimoto and Kuramoto, 2002).Stable isotope abundances in meteoritic material provide an opportunity to evaluate the thoroughness of mixing of isotopes of diverse stellar sources. Molybdenum presents a good test case: it has seven stable isotopes, derived from at least three types of stellar sources, corresp

Clayton, R. N.

2003-12-01

316

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

317

OPTIMIZING HIGH PRESSURE CHEMICAL OXYGEN-IODINE LASERS  

Microsoft Academic Search

The Blaze II chemical laser model was baselined to existing oxygen-iodine research assessment and device improvement chemical laser (RADICL) gain data. Subsequent Fabry-Perot power calculations with Blaze II were an average of 33% higher than the corresponding stable resonator power data. With the Blaze II model baselined to RADICL gain data, a genetic algorithm (GA) was used to predict optimal

David L. Carroll

1996-01-01

318

How Do Calculators Calculate Trigonometric Functions?  

ERIC Educational Resources Information Center

How does your calculator quickly produce values of trigonometric functions? You might be surprised to learn that it does not use series or polynomial approximations, but rather the so-called CORDIC method. This paper will focus on the geometry of the CORDIC method, as originally developed by Volder in 1959. This algorithm is a wonderful…

Underwood, Jeremy M.; Edwards, Bruce H.

319

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

2014-10-01

320

First principles study of magnetic properties of EuTiO3(001) Surfaces with oxygen-deficient  

Microsoft Academic Search

We have investigated the magnetic reconstruction at the oxygen-deficient EuTiO3 (001) surface based on the first- principles density functional theory calculations. Calculated results show that the ferromagnetic structure becomes stable with and without the oxygen vacancies for EuO-termination surface. Besides, for TiO2-termination surface, it is interesting to see that the G-type antiferromagnetic state is stable without the oxygen vacancies, but

Ting-Yuan Wu; Hai-Xia Cao; Lang Fang

2011-01-01

321

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

322

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.

Ecology, Washington S.

323

Novel Membranes and Processes for Oxygen Enrichment  

SciTech Connect

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

Lin, Haiqing

2011-11-15

324

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

325

Oxygen Generation Assembly Technology Development  

NASA Technical Reports Server (NTRS)

Hamilton Standard Space Systems International (HSSI) is under contract to NASA Marshall Space Flight Center (MSFC) to develop an Oxygen Generation Assembly (OGA) for the International Space Station (ISS). The International Space Station Oxygen Generation Assembly (OGA) electrolyzes potable water from the Water Recovery System (WRS) to provide gaseous oxygen to the Space Station module atmosphere. The OGA produces oxygen for metabolic consumption by crew and biological specimens. The OGA also replenishes oxygen lost by experiment ingestion, airlock depressurization, CO2 venting, and leakage. As a byproduct, gaseous hydrogen is generated. The hydrogen will be supplied at a specified pressure range above ambient to support future utilization. Initially, the hydrogen will be vented overboard to space vacuum. This paper describes the OGA integration into the ISS Node 3. It details the development history supporting the design and describes the OGA System characteristics and its physical layout.

Bagdigian, Robert; Cloud, Dale

1999-01-01

326

Simulation of void and oxygen precipitation processes during high temperature annealing of silicon wafers  

NASA Astrophysics Data System (ADS)

The kinetics for dissolution/growth of defects in Czochralski silicon wafers during a 1 h high temperature annealing at 1100 °C has been investigated. The size and distribution of point defects such as vacancy, self-interstitial and oxygen interstitial, are simulated for oxygen and hydrogen ambient annealing. The boundary conditions are analyzed separately for hydrogen and oxygen annealing. A deterministic homogeneous model is used for describing the defect kinetics. The self-interstitial injection rate during oxide annealing is calculated from the Deal-Grove model. Simulated void and oxygen size distributions are compared to B- and C-mode capacitor failure distribution functions. Experimental and theoretical data show that voids can be dissolved during either oxygen or hydrogen annealing, while oxygen precipitates are dissolved during hydrogen annealing and only partially dissolved during oxygen annealing.

Romanowski, A.; Rozgonyi, G.; Tamatsuka, M.

1999-05-01

327

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

328

Oxygen Measurements in Liposome Encapsulated Hemoglobin  

NASA Astrophysics Data System (ADS)

Liposome encapsulated hemoglobins (LEH's) are of current interest as blood substitutes. An analytical methodology for rapid non-invasive measurements of oxygen in artificial oxygen carriers is examined. High resolution optical absorption spectra are calculated by means of a one dimensional diffusion approximation. The encapsulated hemoglobin is prepared from fresh defibrinated bovine blood. Liposomes are prepared from hydrogenated soy phosphatidylcholine (HSPC), cholesterol and dicetylphosphate using a bath sonication method. An integrating sphere spectrophotometer is employed for diffuse optics measurements. Data is collected using an automated data acquisition system employing lock-in -amplifiers. The concentrations of hemoglobin derivatives are evaluated from the corresponding extinction coefficients using a numerical technique of singular value decomposition, and verification of the results is done using Monte Carlo simulations. In situ measurements are required for the determination of hemoglobin derivatives because most encapsulation methods invariably lead to the formation of methemoglobin, a nonfunctional form of hemoglobin. The methods employed in this work lead to high resolution absorption spectra of oxyhemoglobin and other derivatives in red blood cells and liposome encapsulated hemoglobin (LEH). The analysis using singular value decomposition method offers a quantitative means of calculating the fractions of oxyhemoglobin and other hemoglobin derivatives in LEH samples. The analytical methods developed in this work will become even more useful when production of LEH as a blood substitute is scaled up to large volumes.

Phiri, Joshua Benjamin

329

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

330

STRAIN-DEPENDENT OXYGEN DIFFUSIVITY IN BOVINE ANNULUS FIBROSUS  

PubMed Central

Background The intervertebral disc (IVD) is the largest avascular structure in human body. Transport of small molecules in IVD is mainly through diffusion from the endplates and the peripheral blood vessels surrounding IVD. Studies have investigated the structure, chemical components and water content in IVD, but to our knowledge no study has investigated the effect of mechanical loading on oxygen transport in IVD. The objective of this study was to determine the stain-dependent behavior of oxygen diffusivity in IVD tissue. Method of Approach A one-dimensional steady-state diffusion experiment was designed and performed to determine the oxygen diffusivity in bovine annulus fibrosus (AF). The oxygen diffusivity was calculated using equation derived from Fick’s law. A total of 20 AF specimens (d=6 mm, h~0.5 mm) from bovine coccygeal IVD were used to determine oxygen diffusivity at three levels of compressive strain. Results The average oxygen diffusivity (mean ± SD) of bovine AF in the axial direction was 1.43 ± 0.242×10?5 cm2/s (n=20) at 4.68 ± 1.67% compressive strain level, 1.05 ± 0.282×10?5 cm2/s (n=20) at 14.2 ± 1.50% strain level, and 7.71 ± 1.63×10?6 cm2/s (n=20) at 23.7±1.34% strain level. There was a significant decrease in oxygen diffusivity with increasing level of compressive strain (ANOVA, p<0.05). Conclusions Oxygen diffusivity of bovine AF in the axial direction has been determined. The mechanical loading has a significant effect on oxygen transport in IVD tissues. This study is important in understanding nutritional transport in IVD tissues and related disc degeneration. PMID:19640139

Yuan, T-Y; Jackson, AR; Huang, C-Y; Gu, W Y

2009-01-01

331

A 12-kW continuous-wave chemical oxygen-iodine laser  

SciTech Connect

A 12-kW continuous-wave chemical oxygen-iodine laser, provided with an original jet-type singlet oxygen generator, is developed and tested. The experimental and numerical techniques applied for the diagnostics and mathematical simulation of processes in the laser active medium are introduced. Some of the calculation and experimental results are presented. (lasers)

Boreysho, A S; Mal'kov, V M; Savin, Aleksandr V; Vasil'ev, D N; Evdokimov, I M; Trilis, A V; Strakhov, S Yu [Institute of Laser Instruments and Technologies, D F Ustinov 'VOENMEKh' Baltic State Technical University, St Petersburg (Russian Federation)

2003-04-30

332

Measuring the viscosity of whole bovine lens using a fiber optic oxygen sensing system  

PubMed Central

Purpose To obtain a better understanding of oxygen and nutrient transport within the lens, the viscosity of whole lenses was investigated using a fiber optic oxygen sensor (optode). The diffusion coefficient of oxygen was calculated using the Stokes-Einstein equation at the slip boundary condition. Methods The optode was used to measure the oxygen decay signal in samples consisting of different glycerol/water solutions with known viscosities. The oxygen decay signal was fitted to a double exponential decay rate equation, and the lifetimes (tau) were calculated. It was determined that the tau-viscosity relationship is linear, which served as the standard curve. The same procedure was applied to fresh bovine lenses, and the unknown viscosity of the bovine lens was calculated from the tau-viscosity relationship. Results The average viscosity in a whole bovine lens was determined to be 5.74±0.88 cP by our method. Using the Stokes-Einstein equation at the slip boundary condition, the diffusion coefficient for oxygen was calculated to be 8.2 × 10?6 cm2/s. Conclusions These data indicate a higher resistance to flow for oxygen and nutrients in the lens than what is currently assumed in the literature. Overall, this study allows a better understanding of oxygen transport within the lens. PMID:24505211

Thao, Mai T.; Perez, Daniel; Dillon, James

2014-01-01

333

Influence of strain and oxygen vacancies on the magnetoelectric properties of multiferroic bismuth ferrite  

Microsoft Academic Search

The dependencies on strain and oxygen vacancies of the ferroelectric polarization and the weak ferromagnetic magnetization in the multiferroic material bismuth ferrite, BiFeO3 , are investigated using first principles density functional theory calculations. The electric polarization is found to be rather independent of strain, in striking contrast to most conventional perovskite ferroelectrics. It is also not significantly affected by oxygen

Claude Ederer; Nicola A. Spaldin

2005-01-01

334

Robust optode-based method for measuring in situ oxygen profiles in gravelly streambeds.  

PubMed

One of the key environmental conditions controlling biogeochemical reactions in aquatic sediments like streambeds is the distribution of dissolved oxygen. We present a novel approach for the in situ measurement of vertical oxygen profiles using a planar luminescence-based optical sensor. The instrument consists of a transparent acrylic tube with the oxygen-sensitive layer mounted on the outside. The luminescence is excited and detected by a moveable piston inside the acrylic tube. Since no moving parts are in contact with the streambed, the disturbance of the subsurface flow field is minimized. The precision of the distributed oxygen sensor (DOS) was assessed by a comparison with spot optodes. Although the precision of the DOS, expressed as standard deviation of calculated oxygen air saturation, is lower (0.2-6.2%) compared to spot optodes (<0.1-0.6%), variations of the oxygen content along the profile can be resolved. The uncertainty of the calculated oxygen is assessed with a Monte Carlo uncertainty assessment. The obtained vertical oxygen profiles of 40 cm in length reveal variations of the oxygen content reaching from 90% to 0% air saturation and are characterized by patches of low oxygen rather than a continuous decrease with depth. PMID:23889085

Vieweg, Michael; Trauth, Nico; Fleckenstein, Jan H; Schmidt, Christian

2013-09-01

335

REVIEW: Chemically pumped oxygen---iodine laser  

Microsoft Academic Search

A review is given of the principles of operation of the oxygen---iodine laser. Various types of chemical generators of singlet oxygen, which are key components in oxygen---iodine lasers, are considered. Experimental investigations of cw and pulsed oxygen---iodine lasers are described. The state-of-the-art theoretical investigations and potential applications of oxygen---iodine lasers are discussed.

Nikolai N. Yuryshev

1996-01-01

336

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.

337

Calculator Java Applet  

NSDL National Science Digital Library

This applet is a handy scientific calculator with the ability to do unit conversions on the fly. When you click on the link below, it will pop up in its own window so you can continue browsing after loading the calculator. The calculator window is resizable and will pop up to your preferred size after you close it once and come back to this page again.

338

Radioactive Decay Calculator  

NSDL National Science Digital Library

This online calculator computes radioactive decay, timed decay, and timed solid disposal for a databank containing 116 isotopes. It also features University of British Columbia disposal limits and a unit converter and date/time calculators. These tools calculate the half-life for selected isotopes; radioactive decay final activity, given the initial activity and decay time; the decay time, given the initial and final activities; and the decay time, given the mass of a solid and the initial activity.

Enns, Alan

339

Calculating Fired Heater Efficiency  

E-print Network

% OF EST o - 2)( OF EFr. EST Err.' TYPICAL CUftULATIVE 4. a . 12.6 3.2 - 4.0 ERROR IN ANSWER cx EFFICIENCY) The 'setting and combustibles loss errors, are in units of percent of efficiency, .rather than percent of calculated value. Setting losses... calculated once and considered constant (remember to correct for load range). If the actual value is 4 percent J and you calculate 3 percent' or 5 percent, that's a 25 percent error on your ~etting loss calculation, but it only changes your...

Harriz, J. T.; Ritter, E. L.

340

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

341

Oxygen Compatibility Screening Tests in Oxygen-Rich Combustion Environment  

NASA Technical Reports Server (NTRS)

The identification and characterization of oxygen-rich compatible materials enables full-flow, staged combustion designs. Although these oxygen-rich designs offer significant cost, performance, and reliability benefits over existing systems, they have never been used operationally by the United States. If these systems are to be realized, it is critical to understand the long-term oxidative stability in high-temperature, high-pressure, oxygen-rich combustion environments. A unique facility has been constructed at the NASA Lewis Research Center to conduct tests of small-scale rocket engine materials and subcomponents in an oxygen-rich combustion environment that closely approximates a full-scale rocket engine. Thus, a broad range of advanced materials and concepts can be screened in a timely manner and at a relatively low cost.

Eckel, Anerew J.

1997-01-01

342

The oxygen vacancy in crystal phases of WO(3).  

PubMed

The oxygen vacancy in WO(3) has previously been implicated in the electrochromism mechanism in this material. Previous theoretical calculations on the oxygen vacancy in WO(3) have not considered the full range of crystal structures adopted by the material. Here we report studies of the oxygen vacancy in seven crystal phases. The use of a very accurate tungsten plane-wave pseudopotential means that a byproduct of this study is a more detailed and complete picture of undefected WO(3) than previously available. Electronic structures of the crystal phases in both undefected and defected systems have been calculated and are discussed. The band gap in WO(3) is dependent upon bonding-antibonding interactions, these being dependent upon overlap in each direction. The effect of an oxygen vacancy is dependent upon the availability of both Op and Wd electrons, this being different for the various phases. A variety of behavior is predicted, which may be explained in terms of O2p-W5d mixing, including the formation of long W-W dimer bonds. It is found that the nature of a polaron in this material is dependent upon both the crystal structure and distribution of oxygen vacancies. PMID:16851334

Chatten, Ryan; Chadwick, Alan V; Rougier, Aline; Lindan, Philip J D

2005-03-01

343

Radical cation chain oxygenation of dienes by triplet oxygen  

Microsoft Academic Search

Alkylated 1,3-dienes are shown to oxygenate to endoperoxides by a cation radical chain mechanism. Steric slowing of Diels-Alder dimerization appears to be necessary; 1,3-cyclohexadiene gave only dimer under conditions where its 1-isopropyl-4-methyl derivative gave a 96% yield of ascaridole. The cation radical chain conditions tolerate more steric crowding than does the singlet oxygen reaction, as 4,4'-bihomoadamantenyl gave an 84% yield

Stephen F. Nelsen; Mark F. Teasley; Daniel L. Kapp

1986-01-01

344

Oxygen sparging of residue salts  

SciTech Connect

Oxygen sparge is a process for treating salt residues at Los Alamos National Laboratory by sparging oxygen through molten salts. Oxygen reacts with the plutonium trichloride in these salts to form plutonium dioxide. There is further reaction of the plutonium dioxide with plutonium metal and the molten salt to form plutonium oxychloride. Both of the oxide plutonium species are insoluble in the salt and collect atthe bottom of the crucible. This results in a decrease of a factor of 2--3 in the amount of salt that must be treated, and the amount of waste generated by aqueous treatment methods.

Garcia, E.; Griego, W.J.; Owens, S.D.; Thorn, C.W.; Vigil, R.A.

1993-03-01

345

Scalable chemical oxygen - iodine laser  

SciTech Connect

The problem of scaling chemical oxygen - iodine lasers (COILs) is discussed. The results of experimental study of a twisted-aerosol singlet oxygen generator meeting the COIL scalability requirements are presented. The energy characteristics of a supersonic COIL with singlet oxygen and iodine mixing in parallel flows are also experimentally studied. The output power of {approx}7.5 kW, corresponding to a specific power of 230 W cm{sup -2}, is achieved. The maximum chemical efficiency of the COIL is {approx}30%.

Adamenkov, A A; Bakshin, V V; Vyskubenko, B A; Efremov, V I; Il'in, S P; Ilyushin, Yurii N; Kolobyanin, Yu V; Kudryashov, E A; Troshkin, M V [Russian Federal Nuclear Center 'All-Russian Research Institute of Experimental Physics', Sarov, Nizhnii Novgorod region (Russian Federation)

2011-12-31

346

Dependence of oxygen dissociative adsorption on platinum surface structures  

NASA Astrophysics Data System (ADS)

We carry out density functional theory-based calculations to investigate the oxygen (O2) dissociative adsorption on two platinum (Pt) surfaces, viz., Pt(111) and Pt(001). We calculated the corresponding total energies, for varying O2 center-of-mass distances from the Pt surface, and varying O-O interatomic distances. Our calculation results show that the O2 dissociative adsorption progresses much more easily on Pt(001) than on Pt(111). These results are in good agreement with experimentally observed differences and trends in reactivities of Pt(001) and Pt(111).

Yotsuhashi, Satoshi; Yamada, Yuka; Diño, Wilson Agerico; Nakanishi, Hiroshi; Kasai, Hideaki

2005-07-01

347

TI-73 Calculator Activities  

ERIC Educational Resources Information Center

This article describes TI-73 calculator activities appropriate for middle school students. It was found that the use of the calculator allowed for higher-level thinking and a richer exploration of mathematical ideas by students. [Included with this article are "Dice Roll Worksheet" and "Transforming Tree Worksheet".] (Contains 9 figures.)

Phillips-Bey, Carol K.

2004-01-01

348

Calculating centres of mass  

E-print Network

Calculating centres of mass 15.2 Introduction In this section we show how the idea of integration as the limit of a sum can be used to find the centre of mass of an object such as a thin plate completing this Section you should be able to . . . calculate the position of the centre of mass

Vickers, James

349

Calculating Molecular Weight  

NSDL National Science Digital Library

This video and online calculator show how to calculate the molecular weight of a substance from the atomic weights given on the periodic table. Use the molecular weight to convert between the macroscopic scale (grams of a substance) and the microscopic scale (number of molecules of that substance).

2013-06-17

350

Heat Loss Calculation Exercise  

NSDL National Science Digital Library

This class exercise from Kirk Garrison is intended for construction students learning about home insulation and heating. The class will learn to calculate heat loss in a home by using an online home heat loss calculator. This exercise document includes student worksheets. This document may be downloaded in PDF file format.

Garrison, Kirk

2012-03-27

351

Thermodynamic assessment of the uranium-oxygen system  

NASA Astrophysics Data System (ADS)

A thermodynamic assessment of the uranium-oxygen system is presented. A consistent set of experimental data is selected among the numerous data in the literature on the phase diagram and oxygen chemical potential. The thermodynamic properties of the phases are described using the compound energy model with ionic constituents for the solids and an ionic two-sublattice model for the liquid. For the uranium dioxide, the structure is described using three sublattices, one for the cations U 3+, U 4+ and U 6+, one for the normal site of oxygen ions, and one for the interstitial oxygen ions. Vacancies are included in both oxygen sublattices. In this first approach, the homogeneity ranges of the U 4O 9- y and U 3O 8- y compounds are not represented. A set of consistent model parameters that describes both the phase diagram and the oxygen chemical potential data in the whole composition range is thus obtained. The description of this basic binary system will be used to calculate higher order systems such as O-U-Zr and Fe-O-U which are important for simulating severe nuclear accidents.

Guéneau, C.; Baichi, M.; Labroche, D.; Chatillon, C.; Sundman, B.

2002-08-01

352

Oxygen Transport Ceramic Membranes  

SciTech Connect

The present quarterly report describes some of the initial studies on newer compositions and also includes newer approaches to address various materials issues such as in metal-ceramic sealing. The current quarter's research has also focused on developing a comprehensive reliability model for predicting the structural behavior of the membranes in realistic conditions. In parallel to industry provided compositions, models membranes have been evaluated in varying environment. Of importance is the behavior of flaws and generation of new flaws aiding in fracture. Fracture mechanics parameters such as crack tip stresses are generated to characterize the influence of environment. Room temperature slow crack growth studies have also been initiated in industry provided compositions. The electrical conductivity and defect chemistry of an A site deficient compound (La{sub 0.55}Sr{sub 0.35}FeO{sub 3}) was studied. A higher conductivity was observed for La{sub 0.55}Sr{sub 0.35}FeO{sub 3} than that of La{sub 0.60}Sr{sub 0.40}FeO{sub 3} and La{sub 0.80}Sr{sub 0.20}FeO{sub 3}. Defect chemistry analysis showed that it was primarily contributed by a higher carrier concentration in La{sub 0.55}Sr{sub 0.35}FeO{sub 3}. Moreover, the ability for oxygen vacancy generation is much higher in La{sub 0.55}Sr{sub 0.35}FeO{sub 3} as well, which indicates a lower bonding strength between Fe-O and a possible higher catalytic activity for La{sub 0.55}Sr{sub 0.35}FeO{sub 3}. The program continued to investigate the thermodynamic properties (stability and phase separation behavior) and total conductivity of prototype membrane materials. The data are needed together with the kinetic information to develop a complete model for the membrane transport. Previous report listed initial measurements on a sample of La{sub 0.2}Sr{sub 0.8}Fe{sub 0.55}Ti{sub 0.45}O{sub 3-x} prepared in-house by Praxair. Subsequently, a second sample of powder from a larger batch of sample were characterized and compared with the results from the previous batch.

S. Bandopadhyay; N. Nagabhushana; Thomas W. Eagar; Harold R. Larson; Raymundo Arroyave; X.-D Zhou; Y.-W. Shin; H.U. Anderson; Nigel Browning; Alan Jacobson; C.A. Mims

2003-11-01

353

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 of the USA. We analyzed rates of oxygen loss as water-column biochemical oxygen demand (BOD5) and sediment, chemical and biological data were collected to identify factors related to oxygen loss. BOD5 rates ranged

Mallin, Michael

354

Influence of gas flow rate on oxygen flux measurements for dense oxygen conducting ceramic membranes  

Microsoft Academic Search

Oxygen transport through a dense oxygen conducting ceramic membrane is driven by an oxygen activity gradient imposed by the gas streams on either side of the membrane. The oxygen activity on each side of the membrane is altered as oxygen is transported across the membrane. Thus, the oxygen activity gradient will not be the same in each region of a

W. T Stephens; T. J Mazanec; H. U Anderson

2000-01-01

355

Solid State oxygen Sensor Development  

NASA Technical Reports Server (NTRS)

To anticipate future long-duration mission needs for life support sensors, we explored the feasibility of using thin-film metal-oxide semiconductors. The objective of this task was to develop gas sensors for life support applications which would be suitable for long-duration missions. Metal oxides, such as ZnO, SnO2, and TiO2 have been shown to react with oxygen molecules. Oxygen lowers the metal oxide's electrical resistance. Critical to the performance is the application of the oxide in a thin film on an inert substrate: the thinner the film, the more readily the oxygen penetration and hence the more rapid and sensitive the sensor. Metal oxides are not limited to oxygen detection, rather, oxides offer detection and quantification applications to the complete range of gases of interest, not only for life support systems, but for propellants as well.

Cheung, Jeffery T.; Johnson, Scott R.

1994-01-01

356

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

357

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

358

Inotropic stimulation and oxygen consumption in a canine model of dilated cardiomyopathy.  

PubMed

Inotropic support for the dilated, failing ventricle results in complex hemodynamic changes affecting preload, afterload, contractility, and heart rate, each of which affects myocardial oxygen consumption. Appreciation of a hierarchy of hemodynamic determinants of myocardial oxygen consumption may be helpful to the clinician trying to balance oxygen demands and hemodynamic performance. We tested the hypothesis that epinephrine alters the hierarchy of hemodynamic determinants of myocardial oxygen consumption in a canine model of dilated cardiomyopathy created by rapid ventricular pacing. Dogs (n = 10) were instrumented to record left ventricular pressure and dimension, and a modified right heart bypass preparation was used to control left ventricular workload. Coronary sinus effluent was quantitatively collected and analyzed for oxygen content and used to calculate myocardial oxygen consumption. Epinephrine administration significantly increased myocardial oxygen consumption in the empty, beating heart; however, when the relationships of multiple determinants of left ventricular work and load were compared before and after epinephrine administration, no oxygen wasting effect was observed. Using multivariate linear regression analysis, a hierarchy of hemodynamic determinants of myocardial oxygen consumption was created. In the untreated heart, stroke work and cardiac output were the primary hemodynamic determinants of oxygen consumption; epinephrine significantly altered the determinants such that wall stress became the dominant hemodynamic determinant of myocardial oxygen consumption. Focused manipulation of wall stress in the treated, failing heart may limit the potentially deleterious effects of inotropic stimulation in this setting. PMID:1929625

Dyke, C M; Lee, K F; Parmar, J; Dignan, R J; Yeh, T; Abd-Elfattah, A; Wechsler, A S

1991-10-01

359

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

360

Nanocrystalline undoped ceria oxygen sensor  

Microsoft Academic Search

The results of a study of the structure and the electrical properties of nanocrystalline cerium oxide sensor are presented. The relationship between the resistance of the thin film ceria and oxygen partial pressure is shown. In the range of oxygen concentration from 10ppm to 100% the conductivity of the ceria follows (PO2)?1\\/4 behavior. The response time of the sensor and

Piotr Jasinski; Toshio Suzuki; Harlan U. Anderson

2003-01-01

361

Bloodless evaluation of blood oxygenators  

Microsoft Academic Search

Evaluation of blood oxygenators using whole blood is inconvenient and expensive, although it is the ultimate preclinical test.\\u000a Sodium sulfite solutions have advantages over blood for studying oxygen uptake: They are inexpensive, fewer variables need\\u000a control, and deoxygenation is unnecessary. Assays and interpretation of results are easy. The kinetics of sulfite oxidation\\u000a must be fast and the concentration of sulfite

Sanjiv S. Shah; Edward F. Leonard

1983-01-01

362

Oxygen as a product of water radiolysis in high-LET tracks. II. Radiobiological implications  

SciTech Connect

Consideration is given to the possibility that molecular oxygen generated in the tracks of energetic heavy ions is responsible for the reduction in oxygen enhancement ratio (OER) with increasing linear energy transfer (LET) observed for the loss of reproductive capacity caused by radiation in many cellular organisms. Yields of oxygen relationship of OER to LET for two organisms, Chlamydomonas reinhardii and Shigella flexneri, using a simple diffusion kinetic model for radiobiological action which takes account of the diffusion of oxygen after its formation. The results of these calculations show that the model accounts well for the shape of the OER vs. LET relationship.

Baverstock, K.F. (MRC Radiobiology Unit, Harwell, England); Burns, W.G.

1981-04-01

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

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

365

Numerical modeling of anisotropic fiber bundle behavior in oxygenators.  

PubMed

Prediction of flow patterns through oxygenator fiber bundles can allow shape optimization so that efficient gas exchange occurs with minimal thrombus formation and hemolysis. Computational fluid dynamics (CFD) simulations can be used to predict three-dimensional flow velocities and flow distribution from spatially dependent variables and they allow estimations of erythrocyte residence time within the fiber bundle. This study builds upon previous work to develop an accurate numerical model for oxygenators, which would allow for accelerated iterations in oxygenator shape and diffuser plate design optimization. Hollow fiber flow channels were developed to permit experimental calculation of fluid permeability in two directions: main flow along the hollow fiber and perpendicular to the hollow fibers. Commercial software was used to develop three-dimensional CFD models of the experimental flow channels and an anisotropic porous media model for oxygenators from these experimental results. The oxygenator model was used to predict pressure loss throughout the device, visualize blood distribution within the fiber bundle, and estimate erythrocyte residence time within the bundle. Experimental flow channels measurements produced a streamwise permeability of 1.143e(-8) m(2) and transverse permeability of 2.385e(-9) m(2) . These permeabilities, coupled with previous work with volume porosity, were used to develop the numerical model of anisotropic behavior through porous fiber bundles, which indicated a more uniform flow field throughout the oxygenator. Incorporation of known anisotropic fiber bundle behavior in previous numerical models more accurately represents fluid behavior through an oxygenator fiber bundle. CFD coupled with experimental validation can produce a powerful tool for oxygenator design and development. PMID:21973082

Bhavsar, Sonya S; Schmitz-Rode, Thomas; Steinseifer, Ulrich

2011-11-01

366

Oxygen tension limits nitric oxide synthesis by activated macrophages.  

PubMed Central

Previous studies have established that constitutive calcium-dependent ('low-output') nitric oxide synthase (NOS) is regulated by oxygen tension. We have investigated the role of oxygen tension in the synthesis of NO by the 'high-output' calcium-independent NOS in activated macrophages. Hypoxia increased macrophage NOS gene expression in the presence of one additional activator, such as lipopolysaccharide or interferon-gamma, but not in the presence of both. Hypoxia markedly reduced the synthesis of NO by activated macrophages (as measured by accumulation of nitrite and citrulline), such that, at 1% oxygen tension, NO accumulation was reduced by 80-90%. The apparent K(m) for oxygen calculated from cells exposed to a range of oxygen tensions was found to be 10.8%, or 137 microM, O(2) This value is considerably higher than the oxygen tension in tissues, and is virtually identical to that reported recently for purified recombinant macrophage NOS. The decrease in NO synthesis did not appear to be due to diminished arginine or cofactor availability, since arginine transport and NO synthesis during recovery in normoxia were normal. Analysis of NO synthesis during hypoxia as a function of extracellular arginine indicated that an altered V(max), but not K(m)(Arg), accounted for the observed decrease in NO synthesis. We conclude that oxygen tension regulates the synthesis of NO in macrophages by a mechanism similar to that described previously for the calcium-dependent low-output NOS. Our data suggest that oxygen tension may be an important physiological regulator of macrophage NO synthesis in vivo. PMID:10970783

McCormick, C C; Li, W P; Calero, M

2000-01-01

367

Mie-scattering calculation.  

PubMed

The new Mie-scattering calculation is a robust and efficient algorithm used to compute light scattering from spheres. It calculates the ratio between Riccati-Bessel functions instead of the complicated logarithmic derivative. The Kapteyn inequality is used to estimate the number of significant digits of the calculated Riccati-Bessel functions and their ratio. This new algorithm is stable and accurate for both large and small particles. The implemented C++ code yields the same accurate results for both small and large particles compared with Wiscombe's MIEV0 code in double precision. Suggestions are provided for the porting of the MIEV0 code. PMID:15065726

Du, Hong

2004-03-20

368

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

369

Oxygen consumption, oxygen cost, heart rate, and perceived effort during split-belt treadmill walking in young healthy adults.  

PubMed

During split-belt treadmill walking the speed of the treadmill under one limb is faster than the belt under the contralateral limb. This unique intervention has shown evidence of acutely improving gait impairments in individuals with neurologic impairment such as stroke and Parkinson's disease. However, oxygen use, heart rate and perceived effort associated with split-belt treadmill walking are unknown and may limit the utility of this locomotor intervention. To better understand the intensity of this new intervention, this study was undertaken to examine the oxygen consumption, oxygen cost, heart rate, and rating of perceived exertion associated with split-belt treadmill walking in young healthy adults. Fifteen participants completed three sessions of treadmill walking: slow speed with belts tied, fast speed with belts tied, and split-belt walking with one leg walking at the fast speed and one leg walking at the slow speed. Oxygen consumption, heart rate, and rating of perceived exertion were collected during each walking condition and oxygen cost was calculated. Results revealed that oxygen consumption, heart rate, and perceived effort associated with split-belt walking were higher than slow treadmill walking, but only oxygen consumption was significantly lower during both split-belt walking than fast treadmill walking. Oxygen cost associated with slow treadmill walking was significantly higher than fast treadmill walking. These findings have implications for using split-belt treadmill walking as a rehabilitation tool as the cost associated with split-belt treadmill walking may not be higher or potentially more detrimental than that associated with previously used treadmill training rehabilitation strategies. PMID:23011122

Roper, Jaimie A; Stegemöller, Elizabeth L; Tillman, Mark D; Hass, Chris J

2013-03-01

370

Target Heart Rate Calculator  

MedlinePLUS

... My Saved Articles » My ACS » + - Text Size Target Heart Rate Calculator Compute your best workout Enter your age ... is your age? years. How to Check Your Heart Rate Right after you stop exercising, take your pulse: ...

371

AJ Geometric Formulas Calculator  

NSDL National Science Digital Library

Solve various attributes of shapes and solids. Includes calculations for circle, parallelogram, rectangle, square, trapezoid, right circular cone, right circular cylinder, rectangular solid, and sphere geometric formulas. Geometry attributes include volume, area, perimeter, surface area, radius, length and circumference.

Raymond, Jimmy

372

Vector Addition Calculator  

NSDL National Science Digital Library

The Vector Addition Calculator lets students add vectors graphically in 2 dimensions by dragging the tips of the vectors. The results of a component method of addition for the same problem are also displayed.

Joiner, David; The Shodor Education Foundation, Inc.

373

Hydrogen Solution Calculator  

NSDL National Science Digital Library

This calculator prints the closed form solution of the hydrogen wave function for given energy states. In addition, closed form expressions for the Associated Legendre Functions and Laguerre Polynomials (radial solution of hydrogen wave function) are included.

Joiner, David; The Shodor Education Foundation, Inc.

374

AJ Crossover Calculator  

NSDL National Science Digital Library

Solves for inductor and capacitor values for first, second, third and fourth order passive crossover systems for two way speaker systems. Includes Butterworth, Linkwitz-Riley, Bessel, Chebychev, Legendre, Gaussian and Linear-phase type calculations.

Raymond, Jimmy

375

A Simple Calculator Algorithm.  

ERIC Educational Resources Information Center

The problem of finding cube roots when limited to a calculator with only square root capability is discussed. An algorithm is demonstrated and explained which should always produce a good approximation within a few iterations. (MP)

Cook, Lyle; McWilliam, James

1983-01-01

376

Discovery Via Calculators  

ERIC Educational Resources Information Center

The author describes use of hand calculators and computers in the college classroom. He discusses his philosophy about their use, and presents several problems which are especially amenable to use of a computer with a plotting facility. (SD)

Utterback, Allen C.

1975-01-01

377

Healthy Body Calculator  

NSDL National Science Digital Library

This is a very complete interactive health calculator that incorporates a variety of health variables. Users input weight, height, body mass index, activity, and hours of sleep to get a very complete health profile and explanation of each evaluation.

Joanne Larsen, MS, RD, LD

2007-12-12

378

Alcohol Calorie Calculator  

MedlinePLUS

Alcohol Calorie Calculator Find out the number of beer and hard alcohol calories you are consuming. Simply enter the number ... click ‘Compute’ and see the number of calories alcohol adds up for you in a month and ...

379

"Calculating Vessel Volumes"  

E-print Network

This report of a poster displayed during the Metron Conference in New Haven CT (April 2003) presents the results of a computer program that calculates the volumes of pots when their profile is drawn on a computer screen ...

Younger, John G.

2003-01-01

380

Food and exercise calculator  

US Patent & Trademark Office Database

A food and exercise calculating aid enables an individual to quickly determine how much of a selected exercise is necessary to burn off the calories consumed by a selected food item. Nutritional information for various food items and metabolic equivalent information for various exercises are stored in memories. The user accesses the memories for selected foods and exercises, as well as for the user's weight, and the aid calculates the exercise time duration necessary for the selected food.

2005-07-12

381

Calculating a Biodiversity Index  

NSDL National Science Digital Library

In this Biodiversity Counts activity, students learn how scientists calculate a biodiversity index using a page from the phone book as their data source. The printable five-page PDF handout includes a series of inquiry-based questions to get students thinking about what they already know about biodiversity and how living and non-living things are connected, step-by-step directions for calculating a biodiversity index, and a worksheet that includes brainstorming questions and areas for recording answers.

382

Systematics and limit calculations  

SciTech Connect

This note discusses the estimation of systematic uncertainties and their incorporation into upper limit calculations. Two different approaches to reducing systematics and their degrading impact on upper limits are introduced. An improved {chi}{sup 2} function is defined which is useful in comparing Poisson distributed data with models marginalized by systematic uncertainties. Also, a technique using profile likelihoods is introduced which provides a means of constraining the degrading impact of systematic uncertainties on limit calculations.

Fisher, Wade; /Fermilab

2006-12-01

383

Calculation of Counterrotating Propellers  

NASA Technical Reports Server (NTRS)

A method for calculation of a counterrotating propeller which is similar to Walchner's method for calculation of the single propeller in the free air stream is developed and compared with measurements. Several dimensions which are important for the design are given end simple formulas for the gain in efficiency derived. Finally a survey of the behavior of the propeller for various operating conditions is presented.

Ginzel, F.

1949-01-01

384

Shielding calculations for SSC  

SciTech Connect

Monte Carlo calculations of hadron and muon shielding for SSC are reviewed with emphasis on their application to radiation safety and environmental protection. Models and algorithms for simulation of hadronic and electromagnetic showers, and for production and transport of muons in the TeV regime are briefly discussed. Capabilities and limitations of these calculations are described and illustrated with a few examples. 12 refs., 3 figs.

Van Ginneken, A.

1990-03-01

385

Source and replica calculations  

SciTech Connect

The starting point of the Hiroshima-Nagasaki Dose Reevaluation Program is the energy and directional distributions of the prompt neutron and gamma-ray radiation emitted from the exploding bombs. A brief introduction to the neutron source calculations is presented. The development of our current understanding of the source problem is outlined. It is recommended that adjoint calculations be used to modify source spectra to resolve the neutron discrepancy problem.

Whalen, P.P.

1994-02-01

386

ON-LINE CALCULATOR: FORWARD CALCULATION JOHNSON ETTINGER MODEL  

EPA Science Inventory

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

387

Oxygen diffusion in hypostoichiometric uranium dioxide  

SciTech Connect

The tracer oxygen diffusivity in UO/sub 2-x/ has been measured along the lower two phase boundary. The diffusion couple consisted of two matched hypostoichiometric uranium dioxide wafers, one enriched with /sup 18/O and the other normal. Results showed much higher diffusion coefficients than those of stoichiometric UO/sub 2/. This directly proved that the major defect species in UO/sub 2-x/ is the anion vacancy. Activation energy of anion vacancy migration was measured to be 11.7 +- 3.0 kcal/mole. A diffusion model established for UO/sub 2/ and UO/sub 2+-x/ showed that in stoichiometric UO/sub 2/ both interstitials and vacancies contribute significantly to oxygen diffusion and neither can be neglected; at 1400/sup 0/C their contributions are about equal. This model was extended to nearly stoichiometric UO/sub 2+-x/ to predict oxygen diffusion coefficients in these stoichiometry ranges. Also deduced from the model were the Frenkel defect energy and entropy of 85.6 +- 9.2 kcal/mole and 18.2 +- 7.3 eu, respectively. The contribution of Frenkel disorder to the excess enthalpy of UO/sub 2/ was evaluated. Calculation showed that Frenkel disorder accounts for 87% of the excess enthalpy at 3000/sup 0/K. A simple two band model for electronic excitation, with a band gap of 2.0 ev and effective electron mass of 7.6 m/sub e/, accounted for the remainder of the excess enthalpy.

Kim, K.C.

1980-12-01

388

Oxygen diffusion in hypostoichiometric uranium dioxide  

SciTech Connect

The tracer oxygen diffusivity in UO/sub 2-x/ has been measured along the lower two phase boundary. The diffusion couple consisted of two matched hypostoichiometric UO/sub 2/ wafers, one enriched with /sup 18/O and the other normal. These two were pressed together with a bond of liquid U in between. After a diffusion anneal the /sup 18/O concentration profile was determined by ion microprobe mass analysis, from which diffusion coefficients were obtained. The results showed much higher diffusion coefficients than those of stoichiometric UO/sub 2/. This directly proved that the major defect species in UO/sub 2-x/ is the anion vacancy. Activation energy of anion vacancy migration was measured to be 11.7 +- 3.0 kcal/mole. A diffusion model established for UO/sub 2/ and UO/sub 2+-x/ showed that in stoichiometric UO/sub 2/ both interstitials and vacancies contribute significantly to oxygen diffusion and neither can be neglected; at 1400/sup 0/C their contributions are about equal. This model was extended to nearly stoichiometric UO/sub 2+-x/ to predict oxygen diffusion coefficients in these stoichiometry ranges. Also deduced from the model were the Frenkel defect energy and entropy of 85.6 +- 9.2 kcal/mole and 18.2 +- 7.3 eu, respectively. Using these values, the contribution of Frenkel disorder to the excess enthalpy of UO/sub 2/ was evaluated. Calculation showed that Frenkel disorder accounts for 87% of the excess enthalpy at 3000/sup 0/K. A simple two band model for electronic excitation, with a band gap of 2.0 eV and effective electron mass of 7.6 m/sub e/, accounted for the remainder of the excess enthalpy.

Kim, K.C.

1981-01-01

389

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

390

The role of oxygen at the interface between titanium and carbon nanotubes.  

PubMed

We study the interface between carbon nanotubes (CNTs) and surface-deposited titanium using electron microscopy and photoemission spectroscopy, supported by density functional calculations. Charge transfer from the Ti atoms to the nanotube and carbide formation is observed at the interface which indicates strong interaction. Nevertheless, the presence of oxygen between the Ti and the CNTs significantly weakens the Ti-CNT interaction. Ti atoms at the surface will preferentially bond to oxygenated sites. Potential sources of oxygen impurities are examined, namely oxygen from any residual atmosphere and pre-existing oxygen impurities on the nanotube surface, which we enhance through oxygen plasma surface pre-treatment. Variation in literature data concerning Ohmic contacts between Ti and carbon nanotubes is explained via sample pre-treatment and differing vacuum levels, and we suggest improved treatment routes for reliable Schottky barrier-free Ti-nanotube contact formation. PMID:19472267

Felten, Alexandre; Suarez-Martinez, Irene; Ke, Xiaoxing; Van Tendeloo, Gustaaf; Ghijsen, Jacques; Pireaux, Jean-Jacques; Drube, Wolfgang; Bittencourt, Carla; Ewels, Christopher P

2009-08-01

391

Molecular dynamics analysis of diffusion of uranium and oxygen ions in uranium dioxide  

NASA Astrophysics Data System (ADS)

Diffusion behaviours of oxygen and uranium were evaluated for bulk and grain-boundaries of uranium dioxide using the molecular dynamics (MD) simulation. It elucidated that oxygen behaved like liquid in superionic state at high temperatures and migrated on sub-lattice sites accompanying formation of lattice defects such as Frenkel defects at middle temperatures. Formation energies of Frenkel and Shottky defects were compared to literature data, and migration energies of oxygen and uranium were estimated by introducing vacancies into the supercell. For grain-boundaries (GB) modelled by the coincidence-site lattice theory, MD calculations showed that GB energy and diffusivities of oxygen and uranium increased with the misorientation angle. By analysing GB structures such as pair-correlation functions, it also showed that the disordered phase was observed for uranium as well as oxygen in GBs especially for a large misorientation angle such as S5 GB. Hence, GB diffusion was much larger than bulk diffusion for oxygen and uranium.

Arima, T.; Yoshida, K.; Idemitsu, K.; Inagaki, Y.; Sato, I.

2010-03-01

392

Variation of pressure limits of flame propagation with tube diameter for various isooctane-oxygen-nitrogen mixtures  

NASA Technical Reports Server (NTRS)

An investigation was made of the change in the pressure limits of flame propagation with tube diameter for various isooctane-oxygen-nitrogen mixtures. Pressure limits were measured in cylindrical glass tubes of four different inside diameters at six different oxygen-nitrogen ratios. Under the experimental conditions, flame propagation was found to be impossible in isooctane-oxygen mixtures with oxygen concentrations less than 11 to 12 percent. Critical tube diameters for flame propagation were calculated and the effect of pressure was determined and compared with the effect of pressure on quenching distance. Critical diameters were related to flame speeds for various isooctane-oxygen-nitrogen mixtures.

Spakowski, Adolph, A; Belles, Frank E

1952-01-01

393

Ultraviolet Emission from Oxygen Precipitating into Jovian Aurora  

SciTech Connect

The ultraviolet emission-line spectra of precipitating oxygen atoms and ions excited by charge transfer interaction with the molecular hydrogen in the auroral atmosphere of Jupiter are calculated using our computed cross sections of state-selective charge transfer. The charge transfer processes preferentially populate the ground states of neutral oxygen and low-charge ions and the highly excited states of high-charge ions, yielding low UV and high X-ray efficiencies, respectively. Much weaker than the underlying emission spectrum of H2 excited by energetic electron precipitation, the UV emission from oxygen is not expected to be discernible in the Jovian auroral spectrum. This reconciles the absence of UV emission with the presence of X-ray emission from the heavy ions precipitating in the Jovian aurora. (c) (c) 2000. The American Astronomical Society.

Liu, Weihong; Schultz, D. R.

2000-02-10

394

Energetic Metastable Oxygen and Nitrogen Atoms in the Terrestrial Atmosphere  

NASA Technical Reports Server (NTRS)

We have investigated the impact of hot metastable oxygen atoms on the product yields and rate coefficients of atmospheric reactions involving O( (sup 1)D). The contribution of the metastable oxygen atoms to the thermal balance of the terrestrial atmosphere between 50 and 200 km has been determined. We found that the presence of hot O((sup l)D) atoms in the mesosphere and lower thermosphere significantly increases the production rate of the rotationally-vibrationally excited NO molecules. The computed yield of the NO molecules in N2O+ O((sup 1)D) atmospheric collisions, involving non-Maxwellian distributions of the metastable oxygen atoms, is more than two times larger than the NO-yield at a thermal equilibrium. The calculated non-equilibrium rate and yield functions are important for ozone and nitrous oxide modeling in the stratosphere, mesosphere and lower thermosphere.

Kharchenko, Vasili

2004-01-01

395

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

396

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.

397

Low Oxygen Environments in Chesapeake Bay  

E-print Network

and When does Chesapeake Bay lose oxygen? #12;#12;Hypoxia and Chesapeake Animals Low dissolved oxygen Oxygen Dynamics O2X Atlantic Ocean Susquehanna River X O2 *Temperature is also important, but lessLow Oxygen Environments in Chesapeake Bay Jeremy Testa Chesapeake Biological Laboratory University

Boynton, Walter R.

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

Oxygen diffusion in cuprate superconductors  

SciTech Connect

Superconducting properties of the cuprate superconductors depend on the oxygen content of the material; the diffusion of oxygen is thus an important process in the fabrication and application of these materials. This article reviews studies of the diffusion of oxygen in La{sub 2}{sub {minus}}{sub {times}}Sr{sub {times}}CuO{sub 4}, YBa{sub 2}Cu{sub 3}O{sub 7}{sub {minus}}{delta}, YBa{sub 2}Cu{sub 4}O{sub 8}, and the Bi{sub 2}Sr{sub 2}Ca{sub n}{sub {minus}}{sub 1}Cu{sub n}O{sub 2}{sub +}{sub 4} (n = 1, and 2) superconductors, and attempt to elucidate the atomic mechanisms responsible.

Routbort, J.L.; Rothman, S.J.

1995-01-01

400

Nestedness Temperature Calculator Program  

NSDL National Science Digital Library

A nestedness "temperature" (signal-to-noise) calculator was developed some time ago to assess nestedness in natural ecological situations and the extinction risk of individual populations within an archipelago of islands on which the species assemblages live. The Nestedness Calculator "measures the extent of the order present in nested presence-absence matrices, as well as provides a risk assessment of the extinction probability of the various species' populations isolated on islands of fragmented habitat". This program (Windows only) can be downloaded from this site at this time. Nearly three hundred presence-absence matrices taken from the primary ecological literature accompany the calculator. Rob Vosper of Chicago's Field Museum, along with AICS Research, Inc., have made this tool accessible to ecologists doing work in island biogeography, reserve design, and theoretical ecology.

401

Oxygen Regulates Tissue Nitrite Metabolism  

PubMed Central

Abstract Aims: Once dismissed as an inert byproduct of nitric oxide (NO) auto-oxidation, nitrite (NO2-) is now accepted as an endocrine reservoir of NO that elicits biological responses in major organs. While it is known that tissue nitrite is derived from NO oxidation and the diet, little is known about how nitrite is metabolized by tissue, particularly at intermediate oxygen tensions. We investigated the rates and mechanisms of tissue nitrite metabolism over a range of oxygen concentrations. Results: We show that the rate of nitrite consumption differs in each organ. Further, oxygen regulates the rate and products of nitrite metabolism. In anoxia, nitrite is reduced to NO, with significant formation of iron–nitrosyl proteins and S-nitrosothiols. This hypoxic nitrite metabolism is mediated by different nitrite reductases in each tissue. In contrast, low concentrations (?3.5??M) of oxygen increase the rate of nitrite consumption by shifting nitrite metabolism to oxidative pathways, yielding nitrate. While cytochrome P450 and myoglobin contribute in the liver and heart, respectively, mitochondrial cytochrome c oxidase plays a significant role in nitrite oxidation, which is inhibited by cyanide. Using cyanide to prevent artifactual nitrite decay, we measure metabolism of oral and intraperitoneally administered nitrite in mice. Innovation: These data provide insight into the fate of nitrite in tissue, the enzymes involved in nitrite metabolism, and the role of oxygen in regulating these processes. Conclusion: We demonstrate that even at low concentrations, oxygen is a potent regulator of the rate and products of tissue nitrite metabolism. Antioxid. Redox Signal. 17, 951–961. PMID:22098300

Curtis, Erin; Hsu, Lewis L.; Noguchi, Audrey C.; Geary, Lisa

2012-01-01

402

Detecting oxygen in hydrogen or hydrogen in oxygen  

NASA Technical Reports Server (NTRS)

Catalytic sensor operates in high-pressure, moisture-laden gases. It was developed for life support system in which water is decomposed by electrolysis to produce oxygen and hydrogen. Sensor has potential applications in gas-detection and measurement instruments, particularly for gases generated by electrolysis, because such gases may contain large amounts of moisture.

Erickson, A. C.

1980-01-01

403

Oxygen isotope zoning in garnet.  

PubMed

Oxygen isotope zoning was examined within garnet with the use of the stable isotope laser probe. Four metamorphic garnets from the regional metamorphic terrane in Vermont and the skarn deposit at Carr Fork, Utah, were examined and were found to be concentrically zoned in delta(18)O values. The largest variations in delta(18)O values were observed in the regional metamorphic garnets, where delta(18)O values change by 3 per mil from core to rim. These oxygen isotope zoning profiles reflect the changes in the delta(18)O values of the rocks during garnet growth, which are caused by infiltration of fluids and by dehydration reactions during metamorphism. PMID:17742227

Chamberlain, C P; Conrad, M E

1991-10-18

404

A lithium oxygen secondary battery  

NASA Astrophysics Data System (ADS)

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.

1987-08-01

405

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

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

Monatomic Oxygen Makes Materials Biocompatible  

NASA Technical Reports Server (NTRS)

Treatment with monatomic oxygen activates surfaces of biomedical and biotechnical materials without adversely affecting properties of bulk and without introducing toxic or otherwise dangerous solvent residues. Treatment used to create carpetlike texture increasing surface area and encouraging cells to adhere and grow. On silicone tubing for vascular implants, carpet surface improves acceptance by body. On polymer beads and vessels, surface increases effectiveness of growing, storing, and separating cell cultures. Monatomic oxygen relatively abundant in upper atmosphere of Earth, thus treatments carried out on Space Shuttle missions. Alternatively, one of several high-energy neutral-beam devices used in terrestrial laboratories.

Spaulding, Glenn; Koontz, Steven L.

1993-01-01

409

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

410

Three recent TDHF calculations  

SciTech Connect

Three applications of TDHF are discussed. First, vibrational spectra of a post grazing collision /sup 40/Ca nucleus is examined and found to contain many high energy components, qualitatively consistent with recent Orsay experiments. Second, the fusion cross section in energy and angular momentum are calculated for /sup 16/O + /sup 24/Mg to exhibit the parameters of the low l window for this system. A sensitivity of the fusion cross section to the effective two body potential is discussed. Last, a preliminary analysis of /sup 86/Kr + /sup 139/La at E/sub lab/ = 505 MeV calculated in the frozen approximation is displayed, compared to experiment and discussed.

Weiss, M.S.

1981-05-01

411

Spin resonance strength calculations  

SciTech Connect

In calculating the strengths of depolarizing resonances it may be convenient to reformulate the equations of spin motion in a coordinate system based on the actual trajectory of the particle, as introduced by Kondratenko, rather than the conventional one based on a reference orbit. It is shown that resonance strengths calculated by the conventional and the revised formalisms are identical. Resonances induced by radiofrequency dipoles or solenoids are also treated; with rf dipoles it is essential to consider not only the direct effect of the dipole but also the contribution from oscillations induced by it.

Courant,E.D.

2008-10-06

412

Confidence Calculation with AMV+  

SciTech Connect

The iterative advanced mean value algorithm (AMV+), introduced nearly ten years ago, is now widely used as a cost-effective probabilistic structural analysis tool when the use of sampling methods is cost prohibitive (Wu et al., 1990). The need to establish confidence bounds on calculated probabilities arises because of the presence of uncertainties in measured means and variances of input random variables. In this paper an algorithm is proposed that makes use of the AMV+ procedure and analytically derived probability sensitivities to determine confidence bounds on calculated probabilities.

Fossum, A.F.

1999-02-19

413

Graphing Calculator Mini Course  

NASA Technical Reports Server (NTRS)

The "Graphing Calculator Mini Course" project provided a mathematically-intensive technologically-based summer enrichment workshop for teachers of American Indian students on the Turtle Mountain Indian Reservation. Eleven such teachers participated in the six-day workshop in summer of 1996 and three Sunday workshops in the academic year. The project aimed to improve science and mathematics education on the reservation by showing teachers effective ways to use high-end graphing calculators as teaching and learning tools in science and mathematics courses at all levels. In particular, the workshop concentrated on applying TI-82's user-friendly features to understand the various mathematical and scientific concepts.

Karnawat, Sunil R.

1996-01-01

414

Oxygen Vacancy Ordering in YBa2Cu3O(7-Y).  

National Technical Information Service (NTIS)

First principles total energy calculations have been performed for YBa2Cu3Ox with x varying from 6.0 to 7.5. The results of these calculations have been used to determine the effective pair interactions for the oxygen ordering in the basal plane. The phas...

P. A. Sterne, L. T. Wille

1989-01-01

415

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

416

Experimental Effects of Atomic Oxygen on the Development of an Electric Discharge Oxygen Iodine Laser  

E-print Network

of the electric discharge iodine laser continues, the role of oxygen atoms downstream of the discharge region temperature. Keywords: chemical oxygen-iodine laser, COIL, ElectriCOIL, RF excitation of oxygen, singlet-delta oxygen, DOIL 1.0 INTRODUCTION The classic chemical oxygen-iodine laser (COIL) system1 operates on the I(2

Carroll, David L.

417

Uncertainty of chemical oxygen demand determination in wastewater samples  

Microsoft Academic Search

The measurement uncertainty of the result of chemical oxygen demand determination in wastewater was evaluated. The major\\u000a sources of uncertainty of the result of measurement were identified as the purity of reagents, volumetric operations, gravimetric\\u000a operations, bias, and the repeatability of the method. Identification and evaluation of uncertainty sources was followed by\\u000a combined uncertainty calculations. The combined uncertainty was compared

Andreja Drolc; M. Cotman; M. Roš

2003-01-01

418

Numerical analysis of response time for resistive oxygen gas sensors  

Microsoft Academic Search

The response time (t90) for resistive-type oxygen gas sensors based on thick films formed with cerium oxide (CeO2??) powder can be calculated as a function of the diffusion coefficient (DV), surface reaction coefficient (kV) and particle size (R). In the case of large particle size the kinetics of the sensors were controlled by diffusion, while in the case of small

Noriya Izu; Woosuck Shin; Norimitsu Murayama

2002-01-01

419

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

420

Early Time STARFISH Calculations.  

National Technical Information Service (NTIS)

In this report, we present results from recent CMHD (Collisionless Magnetohydrodynamics) code calculations of the early time (0 to 1 sec.) evolution of the STARFISH event. The emphasis of this report is on the velocity spectrum of the energy going to the ...

F. E. Fajen, R. W. Kilb

1982-01-01

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