Structure of stable degeneration of K3 surfaces into pairs of rational elliptic surfaces

Science.gov (United States)

Kimura, Yusuke

2018-03-01

F-theory/heterotic duality is formulated in the stable degeneration limit of a K3 fibration on the F-theory side. In this note, we analyze the structure of the stable degeneration limit. We discuss whether stable degeneration exists for pairs of rational elliptic surfaces. We demonstrate that, when two rational elliptic surfaces have an identical complex structure, stable degeneration always exists. We provide an equation that systematically describes the stable degeneration of a K3 surface into a pair of isomorphic rational elliptic surfaces. When two rational elliptic surfaces have different complex structures, whether their sum glued along a smooth fiber admits deformation to a K3 surface can be determined by studying the structure of the K3 lattice. We investigate the lattice theoretic condition to determine whether a deformation to a K3 surface exists for pairs of extremal rational elliptic surfaces. In addition, we discuss the configurations of singular fibers under stable degeneration. The sum of two isomorphic rational elliptic surfaces glued together admits a deformation to a K3 surface, the singular fibers of which are twice that of the rational elliptic surface. For special situations, singular fibers of the resulting K3 surface collide and they are enhanced to a fiber of another type. Some K3 surfaces become attractive in these situations. We determine the complex structures and the Weierstrass forms of these attractive K3 surfaces. We also deduce the gauge groups in F-theory compactifications on these attractive K3 surfaces times a K3. E 6, E 7, E 8, SU(5), and SO(10) gauge groups arise in these compactifications.

Exploring Scintillometry in the Stable Atmospheric Surface Layer

NARCIS (Netherlands)

Hartogensis, O.K.

2006-01-01

The main objective of this thesis is to investigate observation methods of heat and momentum exchange and key variables that characterise turbulence in the atmospheric stable surface layer (SSL), a layer defined as the lower part of the stable boundary layer (SBL) where surface fluxes do not change

Stable isotope ratio measurements in hydrogen, nitrogen, and oxygen using Raman scattering

International Nuclear Information System (INIS)

Harney, R.C.; Bloom, S.D.; Milanovich, F.P.

1975-01-01

A method for measuring stable isotope ratios using laser Raman scattering was developed which may prove of significant utility and benefit in stable isotope tracer studies. Crude isotope ratio measurements obtained with a low-power laser indicate that with current technology it should be possible to construct an isotope ratio measurement system using laser Raman scattering that is capable of performing 0.1 percent accuracy isotope ratio measurements of 16 O/ 18 O in natural abundance oxygen gas or 14 N/ 15 N in natural abundance nitrogen gas in times less than two minutes per sample. Theory pertinent to the technique, designs of specific isotope ratio spectrometer systems, and data relating to isotope ratio measurements in hydrogen, nitrogen, and oxygen are presented. In addition, the current status of several studies utilizing this technique is discussed. (auth)

LBA-ECO CD-02 Carbon, Nitrogen, Oxygen Stable Isotopes in Organic Material, Brazil

Data.gov (United States)

National Aeronautics and Space Administration — This data set reports the measurement of stable carbon, nitrogen, and oxygen isotope ratios in organic material (plant, litter and soil samples) in forest canopy...

LBA-ECO CD-02 Carbon, Nitrogen, Oxygen Stable Isotopes in Organic Material, Brazil

Data.gov (United States)

National Aeronautics and Space Administration — ABSTRACT: This data set reports the measurement of stable carbon, nitrogen, and oxygen isotope ratios in organic material (plant, litter and soil samples) in forest...

Stable Oxygen-18 and Deuterium Isotopes

DEFF Research Database (Denmark)

Müller, Sascha

The application of stable Oxygen-18 (18O) and Deuterium (2H) isotopes, as a tracer for fluxes between different compartments of the water cycle was subject of the present PhD-thesis. During a three year period, temporal data from a wide range of water cycle constituents was collected from...... the Skjern River catchment, Denmark. The presented applications focused on studying the isotopic 'input signal' to the hydrosphere in the form of precipitation, the isotopic 'output signal' with its related dynamic processes at a coastal saltwater-freshwater interface (groundwater isotopes) and the temporal...... development within a given lowland headwater catchment (stream water isotopes). Based on our investigations on the precipitation isotopic composition a local meteoric water line (LMWL) was constructed and expressed as: δ2H=7.4 δ18O + 5.36‰. Moreover, we showed that under maritime temperature climate influence...

Late Archean Surface Ocean Oxygenation (Invited)

Science.gov (United States)

Kendall, B.; Reinhard, C.; Lyons, T. W.; Kaufman, A. J.; Anbar, A. D.

2009-12-01

Oxygenic photosynthesis must have evolved by 2.45-2.32 Ga, when atmospheric oxygen abundances first rose above 0.001% present atmospheric level (Great Oxidation Event; GOE). Biomarker evidence for a time lag between the evolution of cyanobacterial oxygenic photosynthesis and the GOE continues to be debated. Geochemical signatures from sedimentary rocks (redox-sensitive trace metal abundances, sedimentary Fe geochemistry, and S isotopes) represent an alternative tool for tracing the history of Earth surface oxygenation. Integrated high-resolution chemostratigraphic profiles through the 2.5 Ga Mt. McRae Shale (Pilbara Craton, Western Australia) suggest a ‘whiff’ of oxygen in the surface environment at least 50 M.y. prior to the GOE. However, the geochemical data from the Mt. McRae Shale does not uniquely constrain the presence or extent of Late Archean ocean oxygenation. Here, we present high-resolution chemostratigraphic profiles from 2.6-2.5 Ga black shales (upper Campbellrand Subgroup, Kaapvaal Craton, South Africa) that provide the earliest direct evidence for an oxygenated ocean water column. On the slope beneath the Campbellrand - Malmani carbonate platform (Nauga Formation), a mildly oxygenated water column (highly reactive iron to total iron ratios [FeHR/FeT] ≤ 0.4) was underlain by oxidizing sediments (low Re and Mo abundances) or mildly reducing sediments (high Re but low Mo abundances). After drowning of the carbonate platform (Klein Naute Formation), the local bottom waters became anoxic (FeHR/FeT > 0.4) and intermittently sulphidic (pyrite iron to highly reactive iron ratios [FePY/FeHR] > 0.8), conducive to enrichment of both Re and Mo in sediments, followed by anoxic and Fe2+-rich (ferruginous) conditions (high FeT, FePY/FeHR near 0). Widespread surface ocean oxygenation is suggested by Re enrichment in the broadly correlative Klein Naute Formation and Mt. McRae Shale, deposited ~1000 km apart in the Griqualand West and Hamersley basins

Surface interaction of polyimide with oxygen ECR plasma

International Nuclear Information System (INIS)

Naddaf, M.; Balasubramanian, C.; Alegaonkar, P.S.; Bhoraskar, V.N.; Mandle, A.B.; Ganeshan, V.; Bhoraskar, S.V.

2004-01-01

Polyimide (Kapton-H), was subjected to atomic oxygen from an electron cyclotron resonance plasma. An optical emission spectrometer was used to characterize the atomic oxygen produced in the reactor chamber. The energy of the ions was measured using a retarding field analyzer, placed near the substrate. The density of atomic oxygen in the plasma was estimated using a nickel catalytic probe. The surface wettability of the polyimide samples monitored by contact angle measurements showed considerable improvement when treated with plasma. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopic studies showed that the atomic oxygen in the plasma is the main specie affecting the surface chemistry and adhesion properties of polyimide. The improvement in the surface wettability is attributed to the high degree of cross-linking and large concentration of polar groups generated in the surface region of polyimide, after plasma treatment. The changes in the surface region of polyimide were observed by atomic force microscopic analysis

Surface interaction of polyimide with oxygen ECR plasma

Science.gov (United States)

Naddaf, M.; Balasubramanian, C.; Alegaonkar, P. S.; Bhoraskar, V. N.; Mandle, A. B.; Ganeshan, V.; Bhoraskar, S. V.

2004-07-01

Polyimide (Kapton-H), was subjected to atomic oxygen from an electron cyclotron resonance plasma. An optical emission spectrometer was used to characterize the atomic oxygen produced in the reactor chamber. The energy of the ions was measured using a retarding field analyzer, placed near the substrate. The density of atomic oxygen in the plasma was estimated using a nickel catalytic probe. The surface wettability of the polyimide samples monitored by contact angle measurements showed considerable improvement when treated with plasma. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopic studies showed that the atomic oxygen in the plasma is the main specie affecting the surface chemistry and adhesion properties of polyimide. The improvement in the surface wettability is attributed to the high degree of cross-linking and large concentration of polar groups generated in the surface region of polyimide, after plasma treatment. The changes in the surface region of polyimide were observed by atomic force microscopic analysis.

Dislocation behavior of surface-oxygen-concentration controlled Si wafers

International Nuclear Information System (INIS)

Asazu, Hirotada; Takeuchi, Shotaro; Sannai, Hiroya; Sudo, Haruo; Araki, Koji; Nakamura, Yoshiaki; Izunome, Koji; Sakai, Akira

2014-01-01

We have investigated dislocation behavior in the surface area of surface-oxygen-concentration controlled Si wafers treated by a high temperature rapid thermal oxidation (HT-RTO). The HT-RTO process allows us to precisely control the interstitial oxygen concentration ([O i ]) in the surface area of the Si wafers. Sizes of rosette patterns, generated by nano-indentation and subsequent thermal annealing at 900 °C for 1 h, were measured for the Si wafers with various [O i ]. It was found that the rosette size decreases in proportion to the − 0.25 power of [O i ] in the surface area of the Si wafers, which were higher than [O i ] of 1 × 10 17 atoms/cm 3 . On the other hand, [O i ] of lower than 1 × 10 17 atoms/cm 3 did not affect the rosette size very much. These experimental results demonstrate the ability of the HT-RTO process to suppress the dislocation movements in the surface area of the Si wafer. - Highlights: • Surface-oxygen-concentration controlled Si wafers have been made. • The oxygen concentration was controlled by high temperature rapid thermal oxidation. • Dislocation behavior in the surface area of the Si wafers has been investigated. • Rosette size decreased with increasing of interstitial oxygen atoms. • The interstitial oxygen atoms have a pinning effect of dislocations at the surface

Surface acoustic wave oxygen pressure sensor

Science.gov (United States)

Oglesby, Donald M. (Inventor); Upchurch, Billy T. (Inventor); Leighty, Bradley D. (Inventor)

1994-01-01

A transducer for the measurement of absolute gas-state oxygen pressure from pressures of less than 100 Pa to atmospheric pressure (1.01 x 10(exp 5) Pa) is based on a standard surface acoustic wave (SAW) device. The piezoelectric material of the SAW device is coated with a compound which will selectively and reversibly bind oxygen. When oxygen is bound by the coating, the mass of the coating increases by an amount equal to the mass of the bound oxygen. Such an increase in the mass of the coating causes a corresponding decrease in the resonant frequency of the SAW device.

Stable isotope oxygen-18 and deuterium analysis in surface and groundwater of the Jequitibá Creek Basin, Sete Lagoas, MG

International Nuclear Information System (INIS)

Linhares, Giovanna Maria Gardini; Moreira, Rubens Martins; Pimenta, Rafael Colombo; Scarpelli, Raquel Pazzini; Santos, Elizangela Augusta dos

2017-01-01

Groundwater is an important source of public and industrial supplies, and inadequate exploitation of water reflects negatively on its quality and production of wells, especially when located in karstic aquifers. The study area includes the Maize and Sorghum National Research / Embrapa, located in the karst region of Sete Lagoas, within of the Jequitibá creek sub-basin, an affluent of the Velhas River. The evaluation of the content of stable isotopes of hydrogen ( 2 H), or deuterium, and oxygen ( 18 O) of surface waters (lagoons) and groundwater (production and monitoring wells) collected from the study area allowed to know directly the origin of these waters, active climatic processes and interactions between different aquifers and surface bodies, as possible mixtures of water from different sources. The collected samples were analyzed by isotopic ratio mass spectrometry, IRMS Advantege - Thermo Science, from the Center for the Development of Nuclear Technology (CDTN). The mean values found for δ 18 O and δ 2 H in the waters of the monitoring wells were -6.40‰ and -43.21‰, respectively. For the production wells, mean values for δ 18 O and δ 2 H of -5.87 ‰ and -40.09‰, respectively, were obtained. When compared to GMWL, the collected groundwater originates attributed to the precipitations. The lagoon waters had mean values for δ 18 O and δ 2 H of -3.73‰ and -30.08‰. The water collected in the crystalline fissured aquifer presented mean values δ 18 O and δ 2 H of -6.91‰ and -40.26 ‰ respectively, in its rockier portion, and -6.09‰ and -43.05‰. (author)

Oxygen and silicon stable isotopes of diatom silica. Reconstructing changes in surface water hydrography and silicic acid utilization in the late Pleistocene subarctic Pacific

Energy Technology Data Exchange (ETDEWEB)

Maier, Edith

2014-03-05

Deglacial variations in upper ocean nutrient dynamics and stratification in high latitudes, as well as associated changes in thermohaline overturning circulation, are thought to have played a key role in changing atmospheric CO{sub 2} concentrations. This thesis examines the relationship between past changes in subarctic Pacific upper ocean stratification and nutrient (silicic acid) utilization, using oxygen and silicon stable isotopes of diatom silica, for the first time at millennial-scale resolution and analyzed with a new and efficient instrumentation set-up. The isotopic data, presented in three manuscripts, show a consistent picture of millennial-scale variability in upper ocean stratification and silicic acid utilization during the last ∝50 ka BP, e.g. indicating that the subarctic Pacific was a source region for atmospheric CO{sub 2} during the last deglaciation (late Heinrich Stadial 1 and the Boelling/Alleroed). The presented results demonstrate the high potential of combined diatom oxygen and silicon stable isotope analysis especially for, but not restricted to, marine regions characterized by a low biogenic carbonate content like the subarctic Pacific and the Southern Ocean.

Oxygen and silicon stable isotopes of diatom silica. Reconstructing changes in surface water hydrography and silicic acid utilization in the late Pleistocene subarctic Pacific

International Nuclear Information System (INIS)

Maier, Edith

2014-01-01

Deglacial variations in upper ocean nutrient dynamics and stratification in high latitudes, as well as associated changes in thermohaline overturning circulation, are thought to have played a key role in changing atmospheric CO 2 concentrations. This thesis examines the relationship between past changes in subarctic Pacific upper ocean stratification and nutrient (silicic acid) utilization, using oxygen and silicon stable isotopes of diatom silica, for the first time at millennial-scale resolution and analyzed with a new and efficient instrumentation set-up. The isotopic data, presented in three manuscripts, show a consistent picture of millennial-scale variability in upper ocean stratification and silicic acid utilization during the last ∝50 ka BP, e.g. indicating that the subarctic Pacific was a source region for atmospheric CO 2 during the last deglaciation (late Heinrich Stadial 1 and the Boelling/Alleroed). The presented results demonstrate the high potential of combined diatom oxygen and silicon stable isotope analysis especially for, but not restricted to, marine regions characterized by a low biogenic carbonate content like the subarctic Pacific and the Southern Ocean.

Theoretical studies on chemisorption of oxygen on β-Mo2C catalyst and its surface oxidation

DEFF Research Database (Denmark)

Shi, Xue-Rong; Wang, Shengguang; Hu, Jia

2012-01-01

by O2 at PO2/P0 of 10−21–104 and temperature of 100–700K. For the (011) surface with O2 as the oxidant, the most stable structure is that with 1/2ML or 7/8ML oxygen coverage, depending on the temperature and PO2/P0 value. The increase of gaseous oxidant pressure or decrease of temperature can enhance...

CO oxidation on PdO surfaces

DEFF Research Database (Denmark)

Hirvi, Janne T.; Kinnunen, Toni-Jani J.; Suvanto, Mika

2010-01-01

Density functional calculations were performed in order to investigate CO oxidation on two of the most stable bulk PdO surfaces. The most stable PdO(100) surface, with oxygen excess, is inert against CO adsorption, whereas strong adsorption on the stoichiometric PdO(101) surface leads to favorable...... oxidation via the Langmuir–Hinshelwood mechanism. The reaction with a surface oxygen atom has an activation energy of 0.66 eV, which is comparable to the lowest activation energies observed on metallic surfaces. However, the reaction rate may be limited by the coverage of molecular oxygen. Actually...... adsorption, following the Eley–Rideal mechanism and taking advantage of the reaction tunnel provided by the adjacent palladium atom, has an activation energy of only 0.24 eV. The reaction mechanism and activation energy for the palladium activated CO oxidation on the most stable PdO(100)–O surface...

Density functional theory study the effects of oxygen-containing functional groups on oxygen molecules and oxygen atoms adsorbed on carbonaceous materials.

Science.gov (United States)

Qi, Xuejun; Song, Wenwu; Shi, Jianwei

2017-01-01

Density functional theory was used to study the effects of different types of oxygen-containing functional groups on the adsorption of oxygen molecules and single active oxygen atoms on carbonaceous materials. During gasification or combustion reactions of carbonaceous materials, oxygen-containing functional groups such as hydroxyl(-OH), carbonyl(-CO), quinone(-O), and carboxyl(-COOH) are often present on the edge of graphite and can affect graphite's chemical properties. When oxygen-containing functional groups appear on a graphite surface, the oxygen molecules are strongly adsorbed onto the surface to form a four-member ring structure. At the same time, the O-O bond is greatly weakened and easily broken. The adsorption energy value indicates that the adsorption of oxygen molecules changes from physisorption to chemisorption for oxygen-containing functional groups on the edge of a graphite surface. In addition, our results indicate that the adsorption energy depends on the type of oxygen-containing functional group. When a single active oxygen atom is adsorbed on the bridge site of graphite, it gives rise to a stable epoxy structure. Epoxy can cause deformation of the graphite lattice due to the transition of graphite from sp2 to sp3 after the addition of an oxygen atom. For quinone group on the edge of graphite, oxygen atoms react with carbon atoms to form the precursor of CO2. Similarly, the single active oxygen atoms of carbonyl groups can interact with edge carbon atoms to form the precursor of CO2. The results show that oxygen-containing functional groups on graphite surfaces enhance the activity of graphite, which promotes adsorption on the graphite surface.

Stable isotope oxygen-18 and deuterium analysis in surface and groundwater of the Jequitibá Creek Basin, Sete Lagoas, MG

Energy Technology Data Exchange (ETDEWEB)

Linhares, Giovanna Maria Gardini; Moreira, Rubens Martins; Pimenta, Rafael Colombo; Scarpelli, Raquel Pazzini; Santos, Elizangela Augusta dos, E-mail: giovannagardini@gmail.com, E-mail: rubens@cdtn.br, E-mail: colombopimenta@gmail.com, E-mail: raquelscarpelli@gmail.com, E-mail: elizangela.augusta@gmail.com [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil)

2017-07-01

Groundwater is an important source of public and industrial supplies, and inadequate exploitation of water reflects negatively on its quality and production of wells, especially when located in karstic aquifers. The study area includes the Maize and Sorghum National Research / Embrapa, located in the karst region of Sete Lagoas, within of the Jequitibá creek sub-basin, an affluent of the Velhas River. The evaluation of the content of stable isotopes of hydrogen ({sup 2}H), or deuterium, and oxygen ({sup 18}O) of surface waters (lagoons) and groundwater (production and monitoring wells) collected from the study area allowed to know directly the origin of these waters, active climatic processes and interactions between different aquifers and surface bodies, as possible mixtures of water from different sources. The collected samples were analyzed by isotopic ratio mass spectrometry, IRMS Advantege - Thermo Science, from the Center for the Development of Nuclear Technology (CDTN). The mean values found for δ{sup 18}O and δ{sup 2}H in the waters of the monitoring wells were -6.40‰ and -43.21‰, respectively. For the production wells, mean values for δ{sup 18}O and δ{sup 2}H of -5.87 ‰ and -40.09‰, respectively, were obtained. When compared to GMWL, the collected groundwater originates attributed to the precipitations. The lagoon waters had mean values for δ{sup 18}O and δ{sup 2}H of -3.73‰ and -30.08‰. The water collected in the crystalline fissured aquifer presented mean values δ{sup 18}O and δ{sup 2}H of -6.91‰ and -40.26 ‰ respectively, in its rockier portion, and -6.09‰ and -43.05‰. (author)

Pt Monolayer Shell on Nitrided Alloy Core—A Path to Highly Stable Oxygen Reduction Catalyst

Directory of Open Access Journals (Sweden)

Jue Hu

2015-07-01

Full Text Available The inadequate activity and stability of Pt as a cathode catalyst under the severe operation conditions are the critical problems facing the application of the proton exchange membrane fuel cell (PEMFC. Here we report on a novel route to synthesize highly active and stable oxygen reduction catalysts by depositing Pt monolayer on a nitrided alloy core. The prepared PtMLPdNiN/C catalyst retains 89% of the initial electrochemical surface area after 50,000 cycles between potentials 0.6 and 1.0 V. By correlating electron energy-loss spectroscopy and X-ray absorption spectroscopy analyses with electrochemical measurements, we found that the significant improvement of stability of the PtMLPdNiN/C catalyst is caused by nitrogen doping while reducing the total precious metal loading.

Do oxygen stable isotopes track precipitation moisture source in vascular plant dominated peatlands?

Science.gov (United States)

Charman, D.; Amesbury, M. J.; Newnham, R.; Loader, N.; Goodrich, J. P.; Gallego-Sala, A. V.; Royles, J.; Keller, E. D.; Baisden, W. T.

2014-12-01

Variations in the isotopic composition of precipitation are determined by fractionation processes which occur during temperature and humidity dependent phase changes associated with evaporation and condensation. Oxygen stable isotope ratios have therefore been frequently used as a source of palaeoclimate data from a variety of proxy archives. Exploitation of this record from ombrotrophic peatlands, where the source water used in cellulose synthesis is derived solely from precipitation, has been mostly limited to Northern Hemisphere Sphagnum-dominated bogs, with limited application in the Southern Hemisphere (SH) or in peatlands dominated by vascular plants. Throughout New Zealand (NZ), the preserved root matrix of the restionaceous wire rush (Empodisma spp.) forms deep peat deposits. NZ provides an ideal location to undertake empirical research into oxygen isotope fractionation in vascular peatlands because sites are ideally suited to single taxon analysis, preserve potentially high resolution full Holocene palaeoclimate records and are situated in the climatically sensitive SH mid-latitudes. Crucially, large gradients exist in the mean isotopic composition of precipitation across NZ, caused primarily by the relative influence of different climate modes. We test the capacity for δ18O analysis of Empodisma alpha cellulose from ombrotrophic restiad peatlands in NZ to provide a methodology for developing palaeoclimate records. We took surface plant, water and precipitation samples over spatial (six sites spanning >10° latitude) and temporal (monthly measurements over one year) gradients. We found a strong link between the isotopic compositions of surface root water, the most likely source water for plant growth, and precipitation in both datasets. Back-trajectory modelling of precipitation moisture source for rain days prior to sampling showed clear seasonality in the temporal data that was reflected in surface root water. The link between source water and plant

Noncovalently functionalized graphitic mesoporous carbon as a stable support of Pt nanoparticles for oxygen reduction

Energy Technology Data Exchange (ETDEWEB)

Shao, Yuyan; Zhang, Sheng; Kou, Rong; Wang, Chongmin; Viswanathan, Vilayanur; Liu, Jun; Wang, Yong; Lin, Yuehe [Pacific Northwest National Laboratory, Richland, WA 99352 (United States); Wang, Xiqing; Dai, Sheng [Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States)

2010-04-02

We report a durable electrocatalyst support, highly graphitized mesoporous carbon (GMPC), for oxygen reduction in polymer electrolyte membrane (PEM) fuel cells. GMPC is prepared through graphitizing the self-assembled soft-template mesoporous carbon (MPC) under high temperature. Heat-treatment at 2800 C greatly improves the degree of graphitization while most of the mesoporous structures and the specific surface area of MPC are retained. GMPC is then noncovalently functionalized with poly(diallyldimethylammonium chloride) (PDDA) and loaded with Pt nanoparticles by reducing Pt precursor (H{sub 2}PtCl{sub 6}) in ethylene glycol. Pt nanoparticles of {proportional_to}3.0 nm in diameter are uniformly dispersed on GMPC. Compared to Pt supported on Vulcan XC-72 carbon black (Pt/XC-72), Pt/GMPC exhibits a higher mass activity towards oxygen reduction reaction (ORR) and the mass activity retention (in percentage) is improved by a factor of {proportional_to}2 after 44 h accelerated degradation test under the potential step (1.4-0.85 V) electrochemical stressing condition which focuses on support corrosion. The enhanced activity and durability of Pt/GMPC are attributed to the graphitic structure of GMPC which is more resistant to corrosion. These findings demonstrate that GMPC is a promising oxygen reduction electrocatalyst support for PEM fuel cells. The approach reported in this work provides a facile, eco-friendly promising strategy for synthesizing stable metal nanoparticles on hydrophobic support materials. (author)

An oxygen pressure sensor using surface acoustic wave devices

Science.gov (United States)

Leighty, Bradley D.; Upchurch, Billy T.; Oglesby, Donald M.

1993-01-01

Surface acoustic wave (SAW) piezoelectric devices are finding widespread applications in many arenas, particularly in the area of chemical sensing. We have developed an oxygen pressure sensor based on coating a SAW device with an oxygen binding agent which can be tailored to provide variable sensitivity. The coating is prepared by dissolving an oxygen binding agent in a toluene solution of a copolymer which is then sprayed onto the surface of the SAW device. Experimental data shows the feasibility of tailoring sensors to measure the partial pressure of oxygen from 2.6 to 67 KPa (20 to 500 torr). Potential applications of this technology are discussed.

Polyaniline hybridized surface defective ZnO nanorods with long-term stable photoelectrochemical activity

International Nuclear Information System (INIS)

Bera, Susanta; Khan, Hasmat; Biswas, Indranil; Jana, Sunirmal

2016-01-01

Highlights: • Polyaniline (PANI) hybridized ZnO nanorods was synthesized by solution method. • Surface defects were found in the nanorods. • The hybrid material exhibited an enhancement in visible light absorption. • A long-term stable photoelectrochemical activity of the material was found. • Advancement in the properties would be PANI hybridization and surface defects. - Abstract: We report surfactant/template free precursor solution based synthesis of polyaniline (PANI) hybridized surface defective ZnO nanorods by a two-step process. Initially, ZnO nanorods have been prepared at 95 °C, followed by hybridization (coating) of PANI onto the ZnO via in situ polymerization of aniline monomer, forming ZnO-PANI nanohybrid (ZP). The structural properties of ZP have been analyzed by X-ray diffraction (XRD) and transmission electron microscopic (TEM) studies. The presence of surface defects especially the oxygen vacancies in ZnO has been characterized by photoluminescence emission, high resolution TEM, X-ray photoelectron spectroscopy (XPS) and micro-Raman spectral measurements. The chemical interaction of PANI with ZnO has been examined by Fourier transform infrared (FTIR) and XPS analyses. A significant enhancement in visible absorption of ZP sample is found as evidenced from UV–vis diffused reflectance spectral study. BET nitrogen adsorption-desorption isotherm shows an improved textural property (pore size, pore volume) of ZP. Moreover, a long-term stable photoelectrochemical activity (PEC) of ZP is found compare to pristine ZnO. The synergic effect of PANI hybridization and the presence of surface defects in ZnO NRs can enhance the PEC by prolonging the recombination rate of photogenerated charge carriers. The effect can also provide large number of active sites to make electrolyte diffusion and mass transportation easier in the nanohybrid. This simple synthesis strategy can be adopted for PANI hybridization with different metal oxide semiconductors

Polyaniline hybridized surface defective ZnO nanorods with long-term stable photoelectrochemical activity

Energy Technology Data Exchange (ETDEWEB)

Bera, Susanta; Khan, Hasmat [Sol-Gel Division, CSIR-Central Glass and Ceramic Research Institute (CSIR-CGCRI), 196 Raja S.C. Mullick Road, P.O. Jadavpur University, Kolkata 700 032, West Bengal (India); Biswas, Indranil [Materials Characterization and Instrumentation Division, CSIR-Central Glass and Ceramic Research Institute (CSIR-CGCRI), 196 Raja S.C. Mullick Road, P.O. Jadavpur University, Kolkata 700 032, West Bengal (India); Jana, Sunirmal, E-mail: sjana@cgcri.res.in [Sol-Gel Division, CSIR-Central Glass and Ceramic Research Institute (CSIR-CGCRI), 196 Raja S.C. Mullick Road, P.O. Jadavpur University, Kolkata 700 032, West Bengal (India)

2016-10-15

Highlights: • Polyaniline (PANI) hybridized ZnO nanorods was synthesized by solution method. • Surface defects were found in the nanorods. • The hybrid material exhibited an enhancement in visible light absorption. • A long-term stable photoelectrochemical activity of the material was found. • Advancement in the properties would be PANI hybridization and surface defects. - Abstract: We report surfactant/template free precursor solution based synthesis of polyaniline (PANI) hybridized surface defective ZnO nanorods by a two-step process. Initially, ZnO nanorods have been prepared at 95 °C, followed by hybridization (coating) of PANI onto the ZnO via in situ polymerization of aniline monomer, forming ZnO-PANI nanohybrid (ZP). The structural properties of ZP have been analyzed by X-ray diffraction (XRD) and transmission electron microscopic (TEM) studies. The presence of surface defects especially the oxygen vacancies in ZnO has been characterized by photoluminescence emission, high resolution TEM, X-ray photoelectron spectroscopy (XPS) and micro-Raman spectral measurements. The chemical interaction of PANI with ZnO has been examined by Fourier transform infrared (FTIR) and XPS analyses. A significant enhancement in visible absorption of ZP sample is found as evidenced from UV–vis diffused reflectance spectral study. BET nitrogen adsorption-desorption isotherm shows an improved textural property (pore size, pore volume) of ZP. Moreover, a long-term stable photoelectrochemical activity (PEC) of ZP is found compare to pristine ZnO. The synergic effect of PANI hybridization and the presence of surface defects in ZnO NRs can enhance the PEC by prolonging the recombination rate of photogenerated charge carriers. The effect can also provide large number of active sites to make electrolyte diffusion and mass transportation easier in the nanohybrid. This simple synthesis strategy can be adopted for PANI hybridization with different metal oxide semiconductors

Stable hydrogen, oxygen and sulfur isotopes composition in different tissues of cattle

International Nuclear Information System (INIS)

Sun Fengmei; Shi Guangyu; Wang Huiwen; Yang Shuming

2012-01-01

In order to research on stable hydrogen, oxygen, sulfur isotopes composition in different tissues of cattle, as well as the breed, δ 2 H and δ 34 S values of different defatted muscle, cattle tail hair, blood, liver, also δ 2h and δ 18 O values of water from muscle were determined by isotope ratio mass spectrometry. The stable sulfur isotope composition was not affected by cattle variety, meanwhile the hydrogen was uncertain; the δ 2 H and δ 34 S values between different defatted muscle, blood, liver, cattle hair were significantly different, at the same time the δ 34 S and δ 2 H values between each tissue were not significantly correlated; the δ 2 H values were strongly correlated with the δ 18 O values of muscle water. The above results indicated that stable sulfur and hydrogen isotopes fractionation in the various tissues were discrepant, thus the proper tissue should be selected according to the purpose and object in the beef traceability. (authors)

Surface oxygenation of polypropylene using an air dielectric barrier discharge: the effect of different electrode-platen combinations

International Nuclear Information System (INIS)

Upadhyay, D.J.; Cui, N.-Y.; Anderson, C.A.; Brown, N.M.D.

2004-01-01

Polypropylene film has been modified in an air dielectric barrier discharge using two different electrode-platen configurations: stainless steel wire electrode-rubber platen or ceramic electrode-aluminium platen combinations. Modified films were characterised by static contact angle measurements, X-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS) and Fourier transform infrared spectroscopy (ATR-FT-IR). Surface hydrophilic modification appears to be governed by the presence of low-molecular weight oxidised functionalities using XPS and SIMS techniques. Irrespective of the type of electrode-platen combination used to obtain the discharge, oxygenated functionalities of identical nature are formed on the polymer surface. However, the degree of oxidation obtained by the discharge using the wire electrodes with the rubber platen was considerably greater. Further increase in the observed hydrophilicity due to molecular rearrangement and development of stable oxygenated functionalities was evident after 1 month of post-processing analysis

Oxygen dosing the surface of SrTiO{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Dudy, L.; Scheiderer, P.; Schuetz, P.; Gabel, J.; Buchwald, M.; Sing, M.; Claessen, R. [Physikalisches Institut, Universitaet Wuerzburg (Germany); Denlinger, J.D. [Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, 94270 (United States); Schlueter, C.; Lee, T.L. [Diamond Light Source Ltd., Didcot, Oxfordshire (United Kingdom)

2015-07-01

The highly mobile two-dimensional electron system (2DES) on the surface of the insulating SrTiO{sub 3}(STO) offers exciting perspectives for advanced material design. This 2DES resides in a depletion layer caused by oxygen deficiency of the surface. With photoemission spectroscopy, we monitor the appearance of quasi-particle weight (QP) at the Fermi energy and oxygen vacancy induced states in the band gap (IG). Both, QP and IG weight, increase and decrease respectively upon exposure to extreme ultraviolet (XUV) light and in-situ oxygen dosing. By a proper adjustment of oxygen dosing, any intermediate state can be stabilized providing full control over the charge carrier density. From a comparison of the charge carrier concentrations obtained from an analysis of core-level spectra and the Fermi-surface volume, we conclude on a spatially inhomogeneous surface electronic structure with at least two different phases.

Simultaneous determination of stable carbon, oxygen, and hydrogen isotopes in cellulose.

Science.gov (United States)

Loader, N J; Street-Perrott, F A; Daley, T J; Hughes, P D M; Kimak, A; Levanič, T; Mallon, G; Mauquoy, D; Robertson, I; Roland, T P; van Bellen, S; Ziehmer, M M; Leuenberger, M

2015-01-06

A technological development is described through which the stable carbon-, oxygen-, and nonexchangeable hydrogen-isotopic ratios (δ(13)C, δ(18)O, δ(2)H) are determined on a single carbohydrate (cellulose) sample with precision equivalent to conventional techniques (δ(13)C 0.15‰, δ(18)O 0.30‰, δ(2)H 3.0‰). This triple-isotope approach offers significant new research opportunities, most notably in physiology and medicine, isotope biogeochemistry, forensic science, and palaeoclimatology, when isotopic analysis of a common sample is desirable or when sample material is limited.

Expanding the isotopic toolbox: Applications of hydrogen and oxygen stable isotope ratios to food web studies

OpenAIRE

Hannah B Vander Zanden; David X Soto; Gabriel J Bowen; Keith A Hobson; Keith A Hobson

2016-01-01

The measurement of stable carbon (δ13C) and nitrogen (δ15N) isotopes in tissues of organisms has formed the foundation of isotopic food web reconstructions, as these values directly reflect assimilated diet. In contrast, stable hydrogen (δ2H) and oxygen (δ18O) isotope measurements have typically been reserved for studies of migratory origin and paleoclimate reconstruction based on systematic relationships between organismal tissue and local environmental water. Recently, innovative applicat...

Expanding the Isotopic Toolbox: Applications of Hydrogen and Oxygen Stable Isotope Ratios to Food Web Studies

OpenAIRE

Vander Zanden, Hannah B.; Soto, David X.; Bowen, Gabriel J.; Hobson, Keith A.

2016-01-01

The measurement of stable carbon (δ13C) and nitrogen (δ15N) isotopes in tissues of organisms has formed the foundation of isotopic food web reconstructions, as these values directly reflect assimilated diet. In contrast, stable hydrogen (δ2H) and oxygen (δ18O) isotope measurements have typically been reserved for studies of migratory origin and paleoclimate reconstruction based on systematic relationships between organismal tissue and local environmental water. Recently, innovative applicatio...

Laser Spectroscopic Analysis of Liquid Water Samples for Stable Hydrogen and Oxygen Isotopes

International Nuclear Information System (INIS)

2009-01-01

Stable isotope ratios of hydrogen and oxygen are tracers of choice for water cycle processes in hydrological, atmospheric and ecological studies. The use of isotopes has been limited to some extent because of the relatively high cost of isotope ratio mass spectrometers and the need for specialized operational skills. Here, the results of performance testing of a recently developed laser spectroscopic instrument for measuring stable hydrogen and oxygen isotope ratios of water samples are described, along with a procedure for instrument installation and operation. Over the last four years, the IAEA Water Resources Programme conducted prototype and production model testing of these instruments and this publication is the outcome of those efforts. One of the main missions of the IAEA is to promote the use of peaceful applications of isotope and nuclear methods in Member States and this publication is intended to facilitate the use of laser absorption based instruments for hydrogen and oxygen stable isotope analyses of liquid water samples for hydrological and other studies. The instrument uses off-axis integrated cavity output spectroscopy to measure absolute abundances of 2 HHO, HH 18 O, and HHO via laser absorption. Test results using a number of natural and synthetic water standards and samples with a large range of isotope values demonstrate adequate precision and accuracy (e.g. precisions of 1 per mille for δ 2 H and 0.2 per mille for δ 18 O). The laser instrument has much lower initial and maintenance costs than mass spectrometers and is substantially easier to operate. Thus, these instruments have the potential to bring about a paradigm shift in isotope applications by enabling researchers in all fields to measure isotope ratios by themselves. The appendix contains a detailed procedure for the installation and operation of the instrument. Using the procedure, new users should be able to install the instrument in less than two hours. It also provides step

Effects of Water Vapor on the Data Quality of the Stable Oxygen Isotopic Ratio of Atmospheric Carbon Dioxide

Science.gov (United States)

Evans, C. U.; White, J. W.; Vaughn, B.; Tans, P. P.; Pardo, L.

2007-12-01

The stable oxygen isotopic ratio of carbon dioxide can potentially track fundamental indicators of environmental change such as the balance between photosynthesis and respiration on regional to global scales. The Stable Isotope Laboratory (SIL) at the Institute of Arctic and Alpine Research (INSTAAR), University of Colorado at Boulder, has measured the stable isotopes of atmospheric carbon dioxide from more than 60 NOAA/Earth System Research Laboratory (ESRL) air flask-sampling sites since the early 1990s. If air is sampled without drying, oxygen can exchange between carbon dioxide and water in the flasks, entirely masking the desired signal. An attempt to investigate how water vapor is affecting the δ18O signal is accomplished by comparing the SIL measurements with specific humidity, calculated from the National Climatic Data Center (NCDC) global integrated surface hourly temperature and dew point database, at the time of sampling. Analysis of sites where samples have been collected initially without drying, and subsequently with a drying kit, in conjunction with the humidity data, has led to several conclusions. Samples that initially appear isotopically unaltered, in that their δ18O values are within the expected range, are being subtly influenced by the water vapor in the air. At Bermuda and other tropical to semi-tropical sites, the 'wet' sampling values have a seasonal cycle that is strongly anti-correlated to the specific humidity, while the 'dry' values have a seasonal cycle that is shifted earlier than the specific humidity cycle by 1-2 months. The latter phasing is expected given the seasonal phasing between climate over the ocean and land, while the former is consistent with a small, but measurable isotope exchange in the flasks. In addition, we note that there is a strong (r > 0.96) correlation between the average specific humidity and the percent of rejected samples for 'wet' sampling. This presents an opportunity for determining a threshold of

Improved thrombogenicity on oxygen etched Ti6Al4V surfaces

International Nuclear Information System (INIS)

Riedel, Nicholas A.; Smith, Barbara S.; Williams, John D.; Popat, Ketul C.

2012-01-01

Thrombus formation on blood contacting biomaterials continues to be a key factor in initiating a critical mode of failure in implantable devices, requiring immediate attention. In the interest of evaluating a solution for one of the most widely used biomaterials, titanium and its alloys, this study focuses on the use of a novel surface oxidation treatment to improve the blood compatibility. This study examines the possibility of using oblique angle ion etching to produce a high quality oxide layer that enhances blood compatibility on medical grade titanium alloy Ti6Al4V. An X-ray photoelectron spectroscopy (XPS) analysis of these oxygen-rich surfaces confirmed the presence of TiO 2 peaks and also indicated increased surface oxidation as well as a reduction in surface defects. After 2 h of contact with whole human plasma, the oxygen etched substrates demonstrated a reduction in both platelet adhesion and activation as compared to bare titanium substrates. The whole blood clotting behavior was evaluated for up to 45 min, showing a significant decrease in clot formation on oxygen etched substrates. Finally, a bicinchoninic acid (BCA) total protein assay and XPS were used to evaluate the degree of key blood serum protein (fibrinogen, albumin, immunoglobulin G) adsorption on the substrates. The results showed similar protein levels for both the oxygen etched and control substrates. These results indicate that oblique angle oxygen etching may be a promising method to increase the thrombogenicity of Ti6Al4V. - Highlights: ►Oblique angle oxygen ion etching creates a high quality, uniform oxide surface. ►Oxygen etched substrates showed fewer adhered platelets. ►Platelet activation was reduced by the improved oxide surface. ►Oxygen etched substrates exhibited increased whole blood clotting times. ►Although clotting reductions were seen, protein adsorption remained similar.

Identifying the Active Surfaces of Electrochemically Tuned LiCoO2 for Oxygen Evolution Reaction

International Nuclear Information System (INIS)

Lu, Zhiyi; Chen, Guangxu; Li, Yanbin; Wang, Haotian; Xie, Jin

2017-01-01

Identification of active sites for catalytic processes has both fundamental and technological implications for rational design of future catalysts. Herein, we study the active surfaces of layered lithium cobalt oxide (LCO) for the oxygen evolution reaction (OER) using the enhancement effect of electrochemical delithiation (De-LCO). Our theoretical results indicate that the most stable (0001) surface has a very large overpotential for OER independent of lithium content. In contrast, edge sites such as the nonpolar (1120) and polar (0112) surfaces are predicted to be highly active and dependent on (de)lithiation. The effect of lithium extraction from LCO on the surfaces and their OER activities can be understood by the increase of Co 4+ sites relative to Co 3+ and by the shift of active oxygen 2p states. Experimentally, it is demonstrated that LCO nanosheets, which dominantly expose the (0001) surface show negligible OER enhancement upon delithiation. However, a noticeable increase in OER activity (~0.1 V in overpotential shift at 10 mA cm –2 ) is observed for the LCO nanoparticles, where the basal plane is greatly diminished to expose the edge sites, consistent with the theoretical simulations. In addition, we find that the OER activity of De-LCO nanosheets can be improved if we adopt an acid etching method on LCO to create more active edge sites, which in turn provides a strong evidence for the theoretical indication.

Surface Wettability of Oxygen Plasma Treated Porous Silicon

Directory of Open Access Journals (Sweden)

Lei Jiang

2014-01-01

Full Text Available Oxygen plasma treatment on porous silicon (p-Si surfaces was studied as a practical and effective means to modify wetting properties of as-fabricated p-Si surfaces, that is, contact angles of the p-Si materials. P-Si samples spanning a wide range of surface nanostructures have been fabricated which were subjected to a series of oxygen plasma treatments. Reduction of the p-Si surface contact angles has been systematically observed, and the surface activation rate constant as a function of different pore geometries has been analyzed to achieve an empirical equation. The underlying diffusion mechanisms have been discussed by taking into account of different pore diameters of p-Si samples. It is envisaged that such an approach as well as the corresponding empirical equation may be used to provide relevant process guidance in order to achieve precise control of p-Si contact angles, which is essential for many p-Si applications especially in biosensor areas.

First principles study of dissolved oxygen water adsorption on Fe (001 surfaces

Directory of Open Access Journals (Sweden)

Dong ZHANG

2018-02-01

Full Text Available In order to study the mechanism of dissolved oxygen content on the surface corrosion behavior of Fe-based heat transfer, the first principle is used to study the adsorption of O2 monomolecular, H2O monolayer and dissolved oxygen system on Fe-based heat transfer surface. The GGA/PBE approximation is used to calculate the adsorption energy, state density and population change during the adsorption process. Calculations prove that when the dissolved oxygen is adsorbed on the Fe-based surface, the water molecule tends to adsorb at the top sites, and the oxygen molecule tends to adsorb at Griffiths. When the H2O molecule adsorbs and interacts on the Fe (001 surface, the charge distribution of the interfacial double electric layer changes to cause the Fe atoms to lose electrons, resulting in the change of the surface potential. When the O2 molecule adsorbs on the Fe (001 crystal surfaces, the electrons on the Fe (001 surface are lost and the surface potential increases. O2 molecule and the surface of the Fe atoms are prone to electron transfer, in which O atom's 2p orbit for the adsorption of O2 molecule on Fe (001 crystal surface play a major role. With the increase of the proportion of O2 molecule in the dissolved oxygen water, the absolute value of the adsorption energy increases, and the interaction of the Fe-based heat transfer surface is stronger. This study explores the influence law of different dissolved oxygen on the Fe base heat exchange surface corrosion, and the base metal corrosion mechanism for experimental study provides a theoretical reference.

Interaction of light with the ZnO surface: Photon induced oxygen “breathing,” oxygen vacancies, persistent photoconductivity, and persistent photovoltage

International Nuclear Information System (INIS)

Gurwitz, Ron; Cohen, Rotem; Shalish, Ilan

2014-01-01

ZnO surfaces adsorb oxygen in the dark and emit CO 2 when exposed to white light, reminiscent of the lungs of living creatures. We find that this exchange of oxygen with the ambient affects the integrity of the ZnO surface. Thus, it forms a basis for several interesting surface phenomena in ZnO, such as photoconductivity, photovoltage, and gas sensing, and has a role in ZnO electrical conduction. Using x-ray photoelectron spectroscopy on ZnO nanowires, we observed a decomposition of ZnO under white light and formation of oxygen-depleted surface, which explains photoconductivity by the electron donation of oxygen vacancies. Our findings suggest that the observed decomposition of the ZnO lattice may only take place due to photon-induced reduction of ZnO by carbon containing molecules (or carbo-photonic reduction), possibly from the ambient gas, accounting in a consistent way for both the reduced demands on the energy required for decomposition and for the observed emission of lattice oxygen in the form of CO 2 . The formation of oxygen-vacancy rich surface is suggested to induce surface delta doping, causing accumulation of electrons at the surface, which accounts for both the increase in conductivity and the flattening of the energy bands. Using surface photovoltage spectroscopy in ultra high vacuum, we monitored changes in the deep level spectrum. We observe a wide optical transition from a deep acceptor to the conduction band, which energy position coincides with the position of the so called “green luminescence” in ZnO. This green transition disappears with the formation of surface oxygen vacancies. Since the oxygen vacancies are donors, while the green transition involves surface acceptors, the results suggest that the initial emission of oxygen originates at the defect sites of the latter, thereby eliminating each other. This suggests that the green transition originates at surface Zn vacancy acceptors. Removing an oxygen atom from a Zn vacancy completes

Interaction of light with the ZnO surface: Photon induced oxygen “breathing,” oxygen vacancies, persistent photoconductivity, and persistent photovoltage

Energy Technology Data Exchange (ETDEWEB)

Gurwitz, Ron; Cohen, Rotem; Shalish, Ilan, E-mail: shalish@ee.bgu.ac.il [Ben Gurion University, Beer Sheva 84105 (Israel)

2014-01-21

ZnO surfaces adsorb oxygen in the dark and emit CO{sub 2} when exposed to white light, reminiscent of the lungs of living creatures. We find that this exchange of oxygen with the ambient affects the integrity of the ZnO surface. Thus, it forms a basis for several interesting surface phenomena in ZnO, such as photoconductivity, photovoltage, and gas sensing, and has a role in ZnO electrical conduction. Using x-ray photoelectron spectroscopy on ZnO nanowires, we observed a decomposition of ZnO under white light and formation of oxygen-depleted surface, which explains photoconductivity by the electron donation of oxygen vacancies. Our findings suggest that the observed decomposition of the ZnO lattice may only take place due to photon-induced reduction of ZnO by carbon containing molecules (or carbo-photonic reduction), possibly from the ambient gas, accounting in a consistent way for both the reduced demands on the energy required for decomposition and for the observed emission of lattice oxygen in the form of CO{sub 2}. The formation of oxygen-vacancy rich surface is suggested to induce surface delta doping, causing accumulation of electrons at the surface, which accounts for both the increase in conductivity and the flattening of the energy bands. Using surface photovoltage spectroscopy in ultra high vacuum, we monitored changes in the deep level spectrum. We observe a wide optical transition from a deep acceptor to the conduction band, which energy position coincides with the position of the so called “green luminescence” in ZnO. This green transition disappears with the formation of surface oxygen vacancies. Since the oxygen vacancies are donors, while the green transition involves surface acceptors, the results suggest that the initial emission of oxygen originates at the defect sites of the latter, thereby eliminating each other. This suggests that the green transition originates at surface Zn vacancy acceptors. Removing an oxygen atom from a Zn vacancy

The Interaction between Graphene and Oxygen Atom

Directory of Open Access Journals (Sweden)

Hao Yifan

2016-01-01

Full Text Available Based on the density function theory (DFT method, the interaction between the graphene and oxygen atom is simulated by the B3LYP functional with the 6-31G basis set. Due to the symmetry of graphene (C54H18, D6h, a representative patch is put forward to represent the whole graphene to simplify the description. The representative patch on the surface is considered to gain the potential energy surface (PES. By the calculation of the PES, four possible stable isomers of the C54H18-O radical can be obtained. Meanwhile, the structures and energies of the four possible stable isomers, are further investigated thermodynamically, kinetically, and chemically. According to the transition states, the possible reaction mechanism between the graphene and oxygen atom is given.

Growth history of cultured pearl oysters based on stable oxygen isotope analysis

Science.gov (United States)

Nakashima, R.; Furuta, N.; Suzuki, A.; Kawahata, H.; Shikazono, N.

2007-12-01

We investigated the oxygen isotopic ratio in shells of the pearl oyster Pinctada martensii cultivated in embayments in Mie Prefecture, central Japan, to evaluate the biomineralization of shell structures of the species and its pearls in response to environmental change. Microsamples for oxygen isotope analysis were collected from the surfaces of shells (outer, middle, and inner shell layers) and pearls. Water temperature variations were estimated from the oxygen isotope values of the carbonate. Oxygen isotope profiles of the prismatic calcite of the outer shell layer reflected seasonal variations of water temperature, whereas those of nacreous aragonites of the middle and inner shell layers and pearls recorded temperatures from April to November, June to September, and July to September, respectively. Lower temperatures in autumn and winter might slow the growth of nacreous aragonites. The oxygen isotope values are controlled by both variations of water temperature and shell structures; the prismatic calcite of this species is useful for reconstructing seasonal changes of calcification temperature.

ANALYTICAL EMPLOYMENT OF STABLE ISOTOPES OF CARBON, NITROGEN, OXYGEN AND HYDROGEN FOR FOOD AUTHENTICATION

Directory of Open Access Journals (Sweden)

E. Novelli

2011-04-01

Full Text Available Stable isotopes of carbon, nitrogen, oxygen and hydrogen were used for analytical purposes for the discrimination of the type of production (farming vs. fishing in the case of sea bass and for geographical origin in the case of milk. These results corroborate similar experimental evidences and confirm the potential of this analytical tool to support of food traceability.

Long-term stable surface modification of DLC coatings

Directory of Open Access Journals (Sweden)

Gotzmann Gaby

2017-09-01

Full Text Available The use of coatings based on diamond like carbon (DLC for medical applications was established during the last years. Main advantages of these coatings are its high hardness, good wear and friction behavior and its biocompatibility. Using low-energy electron-beam treatment, we addressed the surface modification of DLC coatings. The aim was to generate new biofunctional surface characteristics that are long-term stable.

Improved thrombogenicity on oxygen etched Ti6Al4V surfaces

Energy Technology Data Exchange (ETDEWEB)

Riedel, Nicholas A. [Department of Mechanical Engineering, Colorado State University, Fort Collins, CO 80523 (United States); Smith, Barbara S. [School of Biomedical Engineering, Colorado State University, Fort Collins, CO 80523 (United States); Williams, John D. [Department of Mechanical Engineering, Colorado State University, Fort Collins, CO 80523 (United States); Popat, Ketul C., E-mail: ketul.popat@colostate.edu [Department of Mechanical Engineering, Colorado State University, Fort Collins, CO 80523 (United States); School of Biomedical Engineering, Colorado State University, Fort Collins, CO 80523 (United States)

2012-07-01

Thrombus formation on blood contacting biomaterials continues to be a key factor in initiating a critical mode of failure in implantable devices, requiring immediate attention. In the interest of evaluating a solution for one of the most widely used biomaterials, titanium and its alloys, this study focuses on the use of a novel surface oxidation treatment to improve the blood compatibility. This study examines the possibility of using oblique angle ion etching to produce a high quality oxide layer that enhances blood compatibility on medical grade titanium alloy Ti6Al4V. An X-ray photoelectron spectroscopy (XPS) analysis of these oxygen-rich surfaces confirmed the presence of TiO{sub 2} peaks and also indicated increased surface oxidation as well as a reduction in surface defects. After 2 h of contact with whole human plasma, the oxygen etched substrates demonstrated a reduction in both platelet adhesion and activation as compared to bare titanium substrates. The whole blood clotting behavior was evaluated for up to 45 min, showing a significant decrease in clot formation on oxygen etched substrates. Finally, a bicinchoninic acid (BCA) total protein assay and XPS were used to evaluate the degree of key blood serum protein (fibrinogen, albumin, immunoglobulin G) adsorption on the substrates. The results showed similar protein levels for both the oxygen etched and control substrates. These results indicate that oblique angle oxygen etching may be a promising method to increase the thrombogenicity of Ti6Al4V. - Highlights: Black-Right-Pointing-Pointer Oblique angle oxygen ion etching creates a high quality, uniform oxide surface. Black-Right-Pointing-Pointer Oxygen etched substrates showed fewer adhered platelets. Black-Right-Pointing-Pointer Platelet activation was reduced by the improved oxide surface. Black-Right-Pointing-Pointer Oxygen etched substrates exhibited increased whole blood clotting times. Black-Right-Pointing-Pointer Although clotting reductions were

Surface core level shifts of clean and oxygen covered Ir(111)

Energy Technology Data Exchange (ETDEWEB)

Bianchi, M; Cassese, D; Cavallin, A; Comin, R; Orlando, F; Postregna, L [Universita degli Studi di Trieste, Via A Valerio 2, 34127, Trieste (Italy); Golfetto, E; Baraldi, A [Dipartimento di Fisica e CENMAT, Universita degli Studi di Trieste, Via A Valerio 2, 34127, Trieste (Italy); Lizzit, S [Sincrotrone Trieste S.C.p.A., S.S. 14 Km 163.5, 34012 Trieste (Italy)], E-mail: alessandro.baraldi@elettra.trieste.it

2009-06-15

We present the results of high resolution core level photoelectron spectroscopy employed to investigate the electronic structure of clean and oxygen covered Ir(111) surface. Ir 4f{sub 7/2} core level spectra are shown to be very sensitive to the local atomic environment. For the clean surface we detected two distinct components shifted by 550 meV, originated by surface and bulk atoms. The larger Gaussian width of the bulk component is explained as due to experimentally unresolved subsurface components. In order to determine the relevance of the phonon contribution we examined the thermal behaviour of the core level lineshape using the Hedin-Rosengren theory. From the phonon-induced spectral broadening we found the Debye temperature of bulk and surface atoms to be 298 and 181 K, respectively, which confirms the softening of the vibrational modes at the surface. Oxygen adsorption leads to the appearance of new surface core level components at -200 meV and +230 meV, which are interpreted as due to first-layer Ir atoms differently coordinated with oxygen. The coverage dependence of these components demonstrates that the oxygen saturation corresponds to 0.38 ML, in good agreement with recent density functional theory calculations.

Oxygen stable isotopes during the Last Glacial Maximum climate: perspectives from data-model (iLOVECLIM) comparison

NARCIS (Netherlands)

Caley, T.; Roche, D.M.V.A.P.; Waelbroeck, C.; Michel, E.

2014-01-01

We use the fully coupled atmosphere-ocean three-dimensional model of intermediate complexity iLOVECLIM to simulate the climate and oxygen stable isotopic signal during the Last Glacial Maximum (LGM, 21 000 years). By using a model that is able to explicitly simulate the sensor (Î18O), results can be

Surface oxygen vacancy and oxygen permeation flux limits of perovskite ion transport membranes

KAUST Repository

Hunt, Anton; Dimitrakopoulos, Georgios; Ghoniem, Ahmed F.

2015-01-01

© 2015 Elsevier B.V. The mechanisms and quantitative models for how oxygen is separated from air using ion transport membranes (ITMs) are not well understood, largely due to the experimental complexity for determining surface exchange reactions

Atomic and molecular oxygen adsorbed on (111) transition metal surfaces: Cu and Ni

Energy Technology Data Exchange (ETDEWEB)

López-Moreno, S., E-mail: sinlopez@uacam.mx [Centro de Investigación en Corrosión, Universidad Autónoma de Campeche, Av. Héroe de Nacozari 480, Campeche, Campeche 24029 (Mexico); Romero, A. H. [Physics Department, West Virginia University, Morgantown, West Virginia 26506-6315 (United States)

2015-04-21

Density functional theory is used to investigate the reaction of oxygen with clean copper and nickel [111]-surfaces. We study several alternative adsorption sites for atomic and molecular oxygen on both surfaces. The minimal energy geometries and adsorption energies are in good agreement with previous theoretical studies and experimental data. From all considered adsorption sites, we found a new O{sub 2} molecular precursor with two possible dissociation paths on the Cu(111) surface. Cross barrier energies for the molecular oxygen dissociation have been calculated by using the climbing image nudge elastic band method, and direct comparison with experimental results is performed. Finally, the structural changes and adsorption energies of oxygen adsorbed on surface when there is a vacancy nearby the adsorption site are also considered.

Atomic and molecular oxygen adsorbed on (111) transition metal surfaces: Cu and Ni

Science.gov (United States)

López-Moreno, S.; Romero, A. H.

2015-04-01

Density functional theory is used to investigate the reaction of oxygen with clean copper and nickel [111]-surfaces. We study several alternative adsorption sites for atomic and molecular oxygen on both surfaces. The minimal energy geometries and adsorption energies are in good agreement with previous theoretical studies and experimental data. From all considered adsorption sites, we found a new O2 molecular precursor with two possible dissociation paths on the Cu(111) surface. Cross barrier energies for the molecular oxygen dissociation have been calculated by using the climbing image nudge elastic band method, and direct comparison with experimental results is performed. Finally, the structural changes and adsorption energies of oxygen adsorbed on surface when there is a vacancy nearby the adsorption site are also considered.

Atomic and molecular oxygen adsorbed on (111) transition metal surfaces: Cu and Ni

International Nuclear Information System (INIS)

López-Moreno, S.; Romero, A. H.

2015-01-01

Density functional theory is used to investigate the reaction of oxygen with clean copper and nickel [111]-surfaces. We study several alternative adsorption sites for atomic and molecular oxygen on both surfaces. The minimal energy geometries and adsorption energies are in good agreement with previous theoretical studies and experimental data. From all considered adsorption sites, we found a new O 2 molecular precursor with two possible dissociation paths on the Cu(111) surface. Cross barrier energies for the molecular oxygen dissociation have been calculated by using the climbing image nudge elastic band method, and direct comparison with experimental results is performed. Finally, the structural changes and adsorption energies of oxygen adsorbed on surface when there is a vacancy nearby the adsorption site are also considered

The surface oxide as a source of oxygen on Rh(1 1 1)

Energy Technology Data Exchange (ETDEWEB)

Lundgren, E. [Department of Synchrotron Radiation Research, Institute of Physics, Lund University, Box 118, S-221 00 Lund (Sweden)]. E-mail: edvin.lundgren@sljus.lu.se; Gustafson, J. [Department of Synchrotron Radiation Research, Institute of Physics, Lund University, Box 118, S-221 00 Lund (Sweden); Resta, A. [Department of Synchrotron Radiation Research, Institute of Physics, Lund University, Box 118, S-221 00 Lund (Sweden); Weissenrieder, J. [Department of Synchrotron Radiation Research, Institute of Physics, Lund University, Box 118, S-221 00 Lund (Sweden); Mikkelsen, A. [Department of Synchrotron Radiation Research, Institute of Physics, Lund University, Box 118, S-221 00 Lund (Sweden); Andersen, J.N. [Department of Synchrotron Radiation Research, Institute of Physics, Lund University, Box 118, S-221 00 Lund (Sweden); Koehler, L. [Institut fuer Materialphysik and Centre for Computational Materials Science, Universitaet Wien, A-1090 Vienna (Austria); Kresse, G. [Institut fuer Materialphysik and Centre for Computational Materials Science, Universitaet Wien, A-1090 Vienna (Austria); Klikovits, J. [Institut fuer Allgemeine Physik, Technische Universitaet Wien, A-1040 Vienna (Austria); Biederman, A. [Institut fuer Allgemeine Physik, Technische Universitaet Wien, A-1040 Vienna (Austria); Schmid, M. [Institut fuer Allgemeine Physik, Technische Universitaet Wien, A-1040 Vienna (Austria); Varga, P. [Institut fuer Allgemeine Physik, Technische Universitaet Wien, A-1040 Vienna (Austria)

2005-06-15

The reduction of a thin surface oxide on the Rh(1 1 1) surface by CO is studied in situ by photoemission spectroscopy, scanning tunneling microscopy, and density functional theory. CO molecules are found not to adsorb on the surface oxide at a sample temperature of 100 K, in contrast to on the clean and chemisorbed oxygen covered surface. Despite this behavior, the surface oxide may still be reduced by CO, albeit in a significantly different fashion as compared to the reduction of a phase containing only chemisorbed on surface oxygen. The experimental observations combined with theoretical considerations concerning the stability of the surface oxide, result in a model of the reduction process at these pressures suggesting that the surface oxide behaves as a source of oxygen for the CO-oxidation reaction.

Surface modification of polystyrene with atomic oxygen radical anions-dissolved solution

International Nuclear Information System (INIS)

Wang Lian; Yan Lifeng; Zhao Peitao; Torimoto, Yoshifumi; Sadakata, Masayoshi; Li Quanxin

2008-01-01

A novel approach to surface modification of polystyrene (PS) polymer with atomic oxygen radical anions-dissolved solution (named as O - water) has been investigated. The O - water, generated by bubbling of the O - (atomic oxygen radical anion) flux into the deionized water, was characterized by UV-absorption spectroscopy and electron paramagnetic resonance (EPR) spectroscopy. The O - water treatments caused an obvious increase of the surface hydrophilicity, surface energy, surface roughness and also caused an alteration of the surface chemical composition for PS surfaces, which were indicated by the variety of contact angle and material characterization by atomic force microscope (AFM) imaging, field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), and attenuated total-reflection Fourier transform infrared (ATR-FTIR) measurements. Particularly, it was found that some hydrophilic groups such as hydroxyl (OH) and carbonyl (C=O) groups were introduced onto the polystyrene surfaces via the O - water treatment, leading to the increases of surface hydrophilicity and surface energy. The active oxygen species would react with the aromatic ring molecules on the PS surfaces and decompose the aromatic compounds to produce hydrophilic hydroxyl and carbonyl compounds. In addition, the O - water is also considered as a 'clean solution' without adding any toxic chemicals and it is easy to be handled at room temperature. Present method may suit to the surface modification of polymers and other heat-sensitive materials potentially

Stable sulfur and oxygen isotopes as geochemical tracers of sulfate in karst waters

Science.gov (United States)

Sun, Jing; Kobayashi, Tatsuaki; Strosnider, William H. J.; Wu, Pan

2017-08-01

Karst water resources, which are extremely sensitive to mining activities, are critical for the support of human societies and ecological systems in many regions worldwide. In order to determine the sources and fate of dissolved sulfate in low-pH karst waters, hydrochemical variations of karst waters with and without acid mine drainage (AMD) impacts were investigated along with stable isotope dynamics. As expected, hydrochemical characteristics and isotopic compositions of the AMD and AMD-downstream water (ADW) were dramatically different from that of the non-AMD-impacted water (NAW). The sources of sulfur isotopes in sulfate were predominantly pyrite oxidation for the AMD and ADW, and atmospheric deposition for the NAW. Based on the general isotope-balance model, the relative proportions of sulfate oxygen derived from water and air were calculated. The mean proportion of sulfate oxygen derived from water in ADW was roughly double that of AMD. This suggests that the sulfate associated with AMD is predominantly influenced by aerobic pyrite oxidation, while that of ADW is likely affected by the dissolution of pyrite under anaerobic conditions in reservoir sediment. This observation was coincident with the noted variations of hydrochemical characteristics and was supported by principal component analysis. These results provide a better understanding of how stable isotopes of sulfate and water can be used to track mining contamination in karst aquifers, which could benefit remediation planning for these distinctive systems.

Analysis of heterogeneous oxygen exchange and fuel oxidation on the catalytic surface of perovskite membranes

KAUST Repository

Hong, Jongsup

2013-10-01

The catalytic kinetics of oxygen surface exchange and fuel oxidation for a perovskite membrane is investigated in terms of the thermodynamic state in the immediate vicinity of or on the membrane surface. Perovskite membranes have been shown to exhibit both oxygen perm-selectivity and catalytic activity for hydrocarbon conversion. A fundamental description of their catalytic surface reactions is needed. In this study, we infer the kinetic parameters for heterogeneous oxygen surface exchange and catalytic fuel conversion reactions, based on permeation rate measurements and a spatially resolved physical model that incorporates detailed chemical kinetics and transport in the gas-phase. The conservation equations for surface and bulk species are coupled with those of the gas-phase species through the species production rates from surface reactions. It is shown that oxygen surface exchange is limited by dissociative/associative adsorption/desorption of oxygen molecules onto/from the membrane surface. On the sweep side, while the catalytic conversion of methane to methyl radical governs the overall surface reactions at high temperature, carbon monoxide oxidation on the membrane surface is dominant at low temperature. Given the sweep side conditions considered in ITM reactor experiments, gas-phase reactions also play an important role, indicating the significance of investigating both homogeneous and heterogeneous chemistry and their coupling when examining the results. We show that the local thermodynamic state at the membrane surface should be considered when constructing and examining models of oxygen permeation and heterogeneous chemistry. © 2013 Elsevier B.V.

Analysis of heterogeneous oxygen exchange and fuel oxidation on the catalytic surface of perovskite membranes

KAUST Repository

Hong, Jongsup; Kirchen, Patrick; Ghoniem, Ahmed F.

2013-01-01

The catalytic kinetics of oxygen surface exchange and fuel oxidation for a perovskite membrane is investigated in terms of the thermodynamic state in the immediate vicinity of or on the membrane surface. Perovskite membranes have been shown to exhibit both oxygen perm-selectivity and catalytic activity for hydrocarbon conversion. A fundamental description of their catalytic surface reactions is needed. In this study, we infer the kinetic parameters for heterogeneous oxygen surface exchange and catalytic fuel conversion reactions, based on permeation rate measurements and a spatially resolved physical model that incorporates detailed chemical kinetics and transport in the gas-phase. The conservation equations for surface and bulk species are coupled with those of the gas-phase species through the species production rates from surface reactions. It is shown that oxygen surface exchange is limited by dissociative/associative adsorption/desorption of oxygen molecules onto/from the membrane surface. On the sweep side, while the catalytic conversion of methane to methyl radical governs the overall surface reactions at high temperature, carbon monoxide oxidation on the membrane surface is dominant at low temperature. Given the sweep side conditions considered in ITM reactor experiments, gas-phase reactions also play an important role, indicating the significance of investigating both homogeneous and heterogeneous chemistry and their coupling when examining the results. We show that the local thermodynamic state at the membrane surface should be considered when constructing and examining models of oxygen permeation and heterogeneous chemistry. © 2013 Elsevier B.V.

Surface defect chemistry and oxygen exchange kinetics in La2-xCaxNiO4+δ

Science.gov (United States)

Tropin, E. S.; Ananyev, M. V.; Farlenkov, A. S.; Khodimchuk, A. V.; Berenov, A. V.; Fetisov, A. V.; Eremin, V. A.; Kolchugin, A. A.

2018-06-01

Surface oxygen exchange kinetics and diffusion in La2-xCaxNiO4+δ (x = 0; 0.1; 0.3) have been studied by the isotope exchange method with gas phase equilibration in the temperature range of 600-800 °C and oxygen pressure range 0.13-2.5 kPa. Despite an enhanced electrical conductivity of La2-xCaxNiO4+δ theirs oxygen surface exchange (k*) and oxygen tracer diffusion (D*) coefficients were significantly lower in comparison with La2NiO4+δ. The rates of the elementary stages of oxygen exchange have been calculated. Upon Ca doping the change of the rate-determining stage was observed. The surface of the oxides was found to be inhomogeneous towards oxygen exchange process according to the recently developed model. The reasons of such inhomogeneity are discussed as well as Ca influence on the surface defect chemistry and oxygen surface exchange and diffusivity.

A high resolution photoemission study of surface core-level shifts in clean and oxygen-covered Ir(2 1 0) surfaces

Energy Technology Data Exchange (ETDEWEB)

Gladys, M.J.; Ermanoski, I.; Jackson, G.; Quinton, J.S.; Rowe, J.E.; Madey, T.E. E-mail: madey@physics.rutgers.edu

2004-04-01

High resolution soft X-ray photoemission electron spectroscopy (SXPS), using synchrotron radiation, is employed to investigate 4f core-level features of four differently-prepared Ir(2 1 0) surfaces: clean planar, oxygen-covered planar, oxygen-induced faceted, and clean faceted surfaces. Surface and bulk peak identifications are supported by measurements at different photon energies (thus probing different electron escape depths) and variable emission angles. Iridium 4f{sub 7/2} photoemission spectra are fitted with Doniach-Sunjic lineshapes. The surface components are identified with core levels positioned at lower binding energies than the bulk components, in contrast to previous reports of binding energy inversion on Ir(1 0 0) (1x1) and (5x1) surfaces. For clean planar Ir(2 1 0) three surface Ir 4f{sub 7/2} features are observed with core-level shifts of -765, -529, and -281 meV, with respect to the bulk; these are associated with the first, second and third layers of atoms, respectively, for atomically rough Ir(2 1 0). Adsorption of oxygen onto the planar Ir(2 1 0) surface is found to cause a suppression and shift of the surface features to higher binding energies. Annealing at T{>=}600 K in oxygen produces a faceted surface as verified by low energy electron diffraction (LEED). A comparison of planar and faceted oxygen-covered surfaces reveals minor differences in the normal emission SXPS spectra, while grazing emission spectra exhibit differences. The SXPS spectrum of the clean, faceted Ir(2 1 0) exhibits small differences in comparison to the clean planar case, with surface features having binding energy shifts of -710, -450, and -230 meV.

Passivation of CdZnTe surfaces by oxidation in low energy atomic oxygen

International Nuclear Information System (INIS)

Chen, H.; Chattopadhyay, K.; Chen, K.; Burger, A.; George, M.A.; Gregory, J.C.; Nag, P.K.; Weimer, J.J.; James, R.B.

1999-01-01

A method of surface passivation of Cd 1-x Zn x Te (CZT) x-ray and gamma ray detectors has been established by using microwave-assisted atomic oxygen bombardment. Detector performance is significantly enhanced due to the reduction of surface leakage current. CZT samples were exposed to an atomic oxygen environment at the University of Alabama in Huntsville close-quote s Thermal Atomic Oxygen Facility. This system generates neutral atomic oxygen species with kinetic energies of 0.1 - 0.2 eV. The surface chemical composition and its morphology modification due to atomic oxygen exposure were studied by x-ray photoelectron spectroscopy and atomic force microscopy and the results were correlated with current-voltage measurements and with room temperature spectral responses to 133 Ba and 241 Am radiation. A reduction of leakage current by about a factor of 2 is reported, together with significant improvement in the gamma-ray line resolution. copyright 1999 American Vacuum Society

Optical absorption and oxygen passivation of surface states in III-nitride photonic devices

Science.gov (United States)

Rousseau, Ian; Callsen, Gordon; Jacopin, Gwénolé; Carlin, Jean-François; Butté, Raphaël; Grandjean, Nicolas

2018-03-01

III-nitride surface states are expected to impact high surface-to-volume ratio devices, such as nano- and micro-wire light-emitting diodes, transistors, and photonic integrated circuits. In this work, reversible photoinduced oxygen desorption from III-nitride microdisk resonator surfaces is shown to increase optical attenuation of whispering gallery modes by 100 cm-1 at λ = 450 nm. Comparison of photoinduced oxygen desorption in unintentionally and n+-doped microdisks suggests that the spectral changes originate from the unpinning of the surface Fermi level, likely taking place at etched nonpolar III-nitride sidewalls. An oxygen-rich surface prepared by thermal annealing results in a broadband Q improvement to state-of-the-art values exceeding 1 × 104 at 2.6 eV. Such findings emphasize the importance of optically active surface states and their passivation for future nanoscale III-nitride optoelectronic and photonic devices.

Fundamental understanding of oxygen reduction and reaction behavior and developing high performance and stable hetero-structured cathodes

Energy Technology Data Exchange (ETDEWEB)

Liu, Xingbo [West Virginia Univ., Morgantown, WV (United States)

2016-11-14

New unique hetero-structured cathode has been developed in this project. La₂NiO_4+δ (LNO) as a surface catalyst with interstitial oxygen defects was introduced onto the state-of-the-art (La_0.6Sr_0.4)_0.95Co_0.2Fe_0.8O_3-δ (LSCF) cathode to enhance the surface-limited ORR kinetics on SOFC cathode. Furthermore, the hetero-structured cathode surface maintains high activity under electrode polarization with much less negative effects from surface cation segregation of Sr, which is known to cause degradation issues for conventional LSCF and LSC cathodes, thus improving the cathode long-term stability. The interface chemistry distribution and oxygen transport properties have been studied to prove the enhancement of power out and stability of LNO-infiltrated LSCF cathode. The further investigation demonstrates that CeO₂ & La_2-xNiO_4+δ (x=0-0.2) co-infiltration is a simple and cost-effective method to improve both performance and stability of LSCF cathode by limiting nano-particles growth/delamination and further improve the surface stability. For the first time, a physical model is proposed to illustrate how unique interstitial species on hetero-structured cathode surface work to regulate the exchange rate of the incorporation reaction. Meanwhile, fundamental investigation of the surface oxygen exchange and bulk oxygen transport properties under over-potential conditions across cathode materials have been carried out in this project, which were discussed and compared to the Nernst equation that is generally applied to treat any oxide electrodes under equilibrium.

Modelling the artic stable boundary layer and its coupling to the surface

NARCIS (Netherlands)

Steeneveld, G.J.; Wiel, van de B.J.H.; Holtslag, A.A.M.

2006-01-01

The impact of coupling the atmosphere to the surface energy balance is examined for the stable boundary layer, as an extension of the first GABLS (GEWEX Atmospheric Boundary-Layer Study) one-dimensional model intercomparison. This coupling is of major importance for the stable boundary-layer

Stable silver nanoclusters electrochemically deposited on nitrogen-doped graphene as efficient electrocatalyst for oxygen reduction reaction

Science.gov (United States)

Jin, Shi; Chen, Man; Dong, Haifeng; He, Bingyu; Lu, Huiting; Su, Lei; Dai, Wenhao; Zhang, Qiaochu; Zhang, Xueji

2015-01-01

Metal nanoclusters exhibit unusually high catalytic activity toward oxygen reduction reaction (ORR) due to their small size and unique electronic structures. However, controllable synthesis of stable metal nanoclusters is a challenge, and the durability of metal clusters suffers from the deficiency of dissolution, aggregation, and sintering during catalysis reactions. Herein, silver nanoclusters (AgNCs) (diameter , which is vital in high performance fuel cells, batteries and nanodevices.

The modification of nanocomposite hybrid polymer surfaces by exposure to oxygen containing plasmas

Science.gov (United States)

Figueiredo, Ashley; Zimmermann, Katherine; Augustine, Brian; Hughes, Chris; Chusuei, Charles

2006-11-01

The wetting properties of the surfaces of the nanocomposite hybrid polymer poly[(propylmethacryl-heptaisobutyl- polyhedral oligomeric silsequioxane)-co-(methylmethacrylate)] (POSS-PMMA)has been studied before and after exposure to plasmas containing oxygen. The contact angle of water droplets on the surface showed a substantial decrease after plasma exposure indicating an increase in the hydrophilicity of the surface. A model was developed in which the plasma preferentially removed organic material including both the PMMA backbone and isobutyl groups from the corners of the POSS cages leaving behind a surface characterized by the silicon oxide-like POSS material. Measurements of surface concentrations of oxygen, silicon, and carbon by x-ray photoelectron spectroscopy (XPS) showed an increase in the amount of oxygen and silicon compared to carbon and the appropriate chemical shifts were observed in the XPS data to support the model of Si-O enrichment on the surface. Variable angle spectroscopic ellipsometry (VASE) and atomic force microscopy (AFM) measurements also supported the model and these results will be presented.

Photo-oxidation: Major sink of oxygen in the ocean surface layer

NARCIS (Netherlands)

Gieskes, W.W.C.; Laane, R.W.P.M.; Ruardij, P.

2015-01-01

Evidence is presented that the oxygen demand associated with photochemical processes in the surface layer of oceans and seas worldwide is of the same order of magnitude as the amount of oxygen released by photosynthesis of the world's marine phytoplankton. Both estimates are of necessity quite rough

Photo-oxidation : Major sink of oxygen in the ocean surface layer

NARCIS (Netherlands)

Gieskes, W. W. C.; Laane, R. W. P. M.; Ruardij, P.

2015-01-01

Evidence is presented that the oxygen demand associated with photochemical processes in the surface layer of oceans and seas worldwide is of the same order of magnitude as the amount of oxygen released by photosynthesis of the world's marine phytoplankton. Both estimates are of necessity quite rough

Macromolecular surface design: photopatterning of functional stable nitrile oxides.

Science.gov (United States)

Altintas, Ozcan; Glassner, Mathias; Rodriguez-Emmenegger, Cesar; Welle, Alexander; Trouillet, Vanessa; Barner-Kowollik, Christopher

2015-05-04

The efficient trapping of photogenerated thioaldehydes with functional shelf-stable nitrile oxides in a 1,3-dipolar cycloaddition is a novel and versatile photochemical strategy for polymer end-group functionalization and surface modification under mild and equimolar conditions. The modular ligation in solution was followed in detail by electrospray ionization mass spectrometry (ESI-MS). X-ray photoelectron spectroscopy (XPS) was employed to analyze the functionalized surfaces, whereas time-of-flight secondary-ion mass spectrometry (ToF-SIMS) confirmed the spatial control of the surface functionalization using a micropatterned shadow mask. Polymer brushes were grown from the surface in a spatially confined regime by surface-initiated atom transfer radical polymerization (SI-ATRP) as confirmed by TOF-SIMS, XPS as well as ellipsometry. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effect of the surface oxygen groups on methane adsorption on coals

Energy Technology Data Exchange (ETDEWEB)

Hao Shixiong [Department of Chemical Engineering, Sichuan University, Chengdu 610065 (China); Department of Chemical Engineering, Sichuan University of Science and Engineering, Zigong 643000 (China); Wen Jie [Department of Chemical Engineering, Sichuan University, Chengdu 610065 (China); Yu Xiaopeng [Department of Chemical Engineering, Sichuan University, Chengdu 610065 (China); Department of Chemical Engineering, Sichuan University of Science and Engineering, Zigong 643000 (China); Chu Wei, E-mail: chuwei1965_scu@yahoo.com [Department of Chemical Engineering, Sichuan University, Chengdu 610065 (China)

2013-01-01

Highlights: Black-Right-Pointing-Pointer We modified one coal with H{sub 2}O{sub 2}, (NH{sub 4}){sub 2}S{sub 2}O{sub 8} and HNO{sub 3} respectively, to prepare coal samples with different surface properties. Black-Right-Pointing-Pointer The oxygen groups on coal surface were characterized by XPS. Black-Right-Pointing-Pointer The textures of the coal samples were investigated by N{sub 2} adsorption at 77 K. Black-Right-Pointing-Pointer The adsorption behaviors were measured by volumetric method. Black-Right-Pointing-Pointer There was a negative correlation between methane saturated adsorption capacity and the O{sub total}/C{sub total}. - Abstract: To investigate the influence of surface oxygen groups on methane adsorption on coals, one bituminous coal was modified with H{sub 2}O{sub 2}, (NH{sub 4}){sub 2}S{sub 2}O{sub 8} and HNO{sub 3} respectively, to prepare coal samples with different surface properties. The oxygen groups on coal surface were characterized by X-ray photoelectron spectroscopy (XPS). The textures of the coal samples were investigated by N{sub 2} adsorption at 77 K. Their surface morphologies were analyzed by scanning electron microscopy (SEM). The methane adsorption behaviors of these coal samples were measured at 303 K in pressure range of 0-5.3 MPa by volumetric method. The adsorption data of methane were fitted to the Langmuir model and Dubinin-Astakhov (D-A) model. The fitting results showed that the D-A model fitted the isotherm data better than the Langmuir model. It was observed that there was, in general, a positive correlation between the methane saturated adsorption capacity and the micropore volume of coals while a negative correlation between methane saturated adsorption capacity and the O{sub total}/C{sub total}. The methane adsorption capacity was determined by the coal surface chemistry when the microporosity parameters of two samples were similar. Coal with a higher amount of oxygen surface groups, and consequently with a less

Atomic structure of diamond {111} surfaces etched in oxygen water vapor

International Nuclear Information System (INIS)

Theije, F.K. de; Reedijk, M.F.; Arsic, J.; Enckevort, W.J.P. van; Vlieg, E.

2001-01-01

The atomic structure of the {111} diamond face after oxygen-water-vapor etching is determined using x-ray scattering. We find that a single dangling bond diamond {111} surface model, terminated by a full monolayer of -OH fits our data best. To explain the measurements it is necessary to add an ordered water layer on top of the -OH terminated surface. The vertical contraction of the surface cell and the distance between the oxygen atoms are generally in agreement with model calculations and results on similar systems. The OH termination is likely to be present during etching as well. This model experimentally confirms the atomic-scale mechanism we proposed previously for this etching system

Surface-Controlled Metal Oxide Resistive Memory

KAUST Repository

Ke, Jr-Jian

2015-10-28

To explore the surface effect on resistive random-access memory (ReRAM), the impact of surface roughness on the characteristics of ZnO ReRAM were studied. The thickness-independent resistance and the higher switching probability of ZnO ReRAM with rough surfaces indicate the importance of surface oxygen chemisorption on the switching process. Furthermore, the improvements in switching probability, switching voltage and resistance distribution observed for ReRAM with rough surfaces can be attributed to the stable oxygen adatoms under various ambience conditions. The findings validate the surface-controlled stability and uniformity of ReRAM and can serve as the guideline for developing practical device applications.

Oxygen adsorption on the Al0.25Ga0.75N (0001) surface: A first-principles study

Science.gov (United States)

Fu, Jiaqi; Song, Tielei; Liang, Xixia; Zhao, Guojun

2018-04-01

To understand the interaction mechanism for the oxygen adsorption on AlGaN surface, herein, we built the possible models of oxygen adsorption on Al0.25Ga0.75N (0001) surface. For different oxygen coverage, three kinds of adsorption site are considered. Then the favorable adsorption sites are characterized by first principles calculation for (2 × 2) supercell of Al0.25Ga0.75N (0001) surface. On basis of the optimal adsorption structures, our calculated results show that all the adsorption processes are exothermic, indicating that the (0001) surface orientation is active towards the adsorption of oxygen. The doping of Al is advantage to the adsorption of O atom. Additionally, the adsorption energy decreases with reducing the oxygen coverage, and the relationship between them is approximately linear. Owing to the oxygen adsorption, the surface states in the fundamental band gap are significant reduced with respect to the free Al0.25Ga0.75N (0001) surface. Moreover, the optical properties on different oxygen coverage are also discussed.

Oxygen adsorption on the Al9Co2(001) surface: first-principles and STM study

International Nuclear Information System (INIS)

Villaseca, S Alarcón; Loli, L N Serkovic; Ledieu, J; Fournée, V; Dubois, J-M; Gaudry, É; Gille, P

2013-01-01

Atomic oxygen adsorption on a pure aluminum terminated Al 9 Co 2 (001) surface is studied by first-principle calculations coupled with STM measurements. Relative adsorption energies of oxygen atoms have been calculated on different surface sites along with the associated STM images. The local electronic structure of the most favourable adsorption site is described. The preferential adsorption site is identified as a ‘bridge’ type site between the cluster entities exposed at the (001) surface termination. The Al–O bonding between the adsorbate and the substrate presents a covalent character, with s–p hybridization occurring between the states of the adsorbed oxygen atom and the aluminum atoms of the surface. The simulated STM image of the preferential adsorption site is in agreement with experimental observations. This work shows that oxygen adsorption generates important atomic relaxations of the topmost surface layer and that sub-surface cobalt atoms strongly influence the values of the adsorption energies. The calculated Al–O distances are in agreement with those reported in Al 2 O and Al 2 O 3 oxides and for oxygen adsorption on Al(111). (paper)

Adsorption of oxygen on low-index surfaces of the TiAl{sub 3} alloy

Energy Technology Data Exchange (ETDEWEB)

Latyshev, A. M.; Bakulin, A. V.; Kulkova, S. E., E-mail: kulkova@ms.tsc.ru [National Research Tomsk State University (Russian Federation); Hu, Q. M.; Yang, R. [Chinese Academy of Sciences, Shenyang National Laboratory for Materials Science, Institute of Metal Research (China)

2016-12-15

Method of the projector augmented waves in the plane-wave basis within the generalized-gradient approximation for the exchange-correlation functional has been used to study oxygen adsorption on (001), (100), and (110) low-index surfaces of the TiAl{sub 3} alloy. It has been established that the sites that are most energetically preferred for the adsorption of oxygen are hollow (H) positions on the (001) surface and bridge (B) positions on the (110) and (100) surfaces. Structural and electronic factors that define their energy preference have been discussed. Changes in the atomic and electronic structure of subsurface layers that occur as the oxygen concentration increases to three monolayers have been analyzed. It has been shown that the formation of chemical bonds of oxygen with both components of the alloy leads to the appearance of states that are split-off from the bottoms of their valence bands, which is accompanied by the formation of a forbidden gap at the Fermi level and by a weakening of the Ti–Al metallic bonds in the alloy. On the Al-terminated (001) and (110) surfaces, the oxidation of aluminum dominates over that of titanium. On the whole, the binding energy of oxygen on the low-index surfaces with a mixed termination is higher than that at the aluminum-terminated surface. The calculation of the diffusion of oxygen in the TiAl{sub 3} alloy has shown that the lowest barriers correspond to the diffusion between tetrahedral positions in the (001) plane; the diffusion of oxygen in the [001] direction occurs through octahedral and tetrahedral positions. An increase in the concentration of aluminum in the alloy favors a reduction in the height of the energy barriers as compared to the corresponding barriers in the γ-TiAl alloy.

Solid Oxide Fuel Cell Cathodes. Unraveling the Relationship Between Structure, Surface Chemistry and Oxygen Reduction

Energy Technology Data Exchange (ETDEWEB)

Gopalan, Srikanth [Boston Univ., MA (United States)

2013-03-31

In this work we have considered oxygen reduction reaction on LSM and LSCF cathode materials. In particular we have used various spectroscopic techniques to explore the surface composition, transition metal oxidation state, and the bonding environment of oxygen to understand the changes that occur to the surface during the oxygen reduction process. In a parallel study we have employed patterned cathodes of both LSM and LSCF cathodes to extract transport and kinetic parameters associated with the oxygen reduction process.

Late Quaternary changes in surface productivity and oxygen ...

Indian Academy of Sciences (India)

Changes in the abundance of selected planktic foraminiferal species and some sedimentological parameters at ODP site 728A were examined to understand the fluctuations in the surface productivity and deep sea oxygenation in the NW Arabian Sea during last ∼540 kyr. The increased relative abundances of high fertility ...

Surface recombination of oxygen atoms in O2 plasma at increased pressure: II. Vibrational temperature and surface production of ozone

Science.gov (United States)

Lopaev, D. V.; Malykhin, E. M.; Zyryanov, S. M.

2011-01-01

Ozone production in an oxygen glow discharge in a quartz tube was studied in the pressure range of 10-50 Torr. The O3 density distribution along the tube diameter was measured by UV absorption spectroscopy, and ozone vibrational temperature TV was found comparing the calculated ab initio absorption spectra with the experimental ones. It has been shown that the O3 production mainly occurs on a tube surface whereas ozone is lost in the tube centre where in contrast the electron and oxygen atom densities are maximal. Two models were used to analyse the obtained results. The first one is a kinetic 1D model for the processes occurring near the tube walls with the participation of the main particles: O(3P), O2, O2(1Δg) and O3 molecules in different vibrational states. The agreement of O3 and O(3P) density profiles and TV calculated in the model with observed ones was reached by varying the single model parameter—ozone production probability (\\gamma_{O_{3}}) on the quartz tube surface on the assumption that O3 production occurs mainly in the surface recombination of physisorbed O(3P) and O2. The phenomenological model of the surface processes with the participation of oxygen atoms and molecules including singlet oxygen molecules was also considered to analyse \\gamma_{O_{3}} data obtained in the kinetic model. A good agreement between the experimental data and the data of both models—the kinetic 1D model and the phenomenological surface model—was obtained in the full range of the studied conditions that allowed consideration of the ozone surface production mechanism in more detail. The important role of singlet oxygen in ozone surface production was shown. The O3 surface production rate directly depends on the density of physisorbed oxygen atoms and molecules and can be high with increasing pressure and energy inputted into plasma while simultaneously keeping the surface temperature low enough. Using the special discharge cell design, such an approach opens up the

Surface recombination of oxygen atoms in O2 plasma at increased pressure: II. Vibrational temperature and surface production of ozone

International Nuclear Information System (INIS)

Lopaev, D V; Malykhin, E M; Zyryanov, S M

2011-01-01

Ozone production in an oxygen glow discharge in a quartz tube was studied in the pressure range of 10-50 Torr. The O 3 density distribution along the tube diameter was measured by UV absorption spectroscopy, and ozone vibrational temperature T V was found comparing the calculated ab initio absorption spectra with the experimental ones. It has been shown that the O 3 production mainly occurs on a tube surface whereas ozone is lost in the tube centre where in contrast the electron and oxygen atom densities are maximal. Two models were used to analyse the obtained results. The first one is a kinetic 1D model for the processes occurring near the tube walls with the participation of the main particles: O( 3 P), O 2 , O 2 ( 1 Δ g ) and O 3 molecules in different vibrational states. The agreement of O 3 and O( 3 P) density profiles and T V calculated in the model with observed ones was reached by varying the single model parameter-ozone production probability (γ O 3 ) on the quartz tube surface on the assumption that O 3 production occurs mainly in the surface recombination of physisorbed O( 3 P) and O 2 . The phenomenological model of the surface processes with the participation of oxygen atoms and molecules including singlet oxygen molecules was also considered to analyse γ O 3 data obtained in the kinetic model. A good agreement between the experimental data and the data of both models-the kinetic 1D model and the phenomenological surface model-was obtained in the full range of the studied conditions that allowed consideration of the ozone surface production mechanism in more detail. The important role of singlet oxygen in ozone surface production was shown. The O 3 surface production rate directly depends on the density of physisorbed oxygen atoms and molecules and can be high with increasing pressure and energy inputted into plasma while simultaneously keeping the surface temperature low enough. Using the special discharge cell design, such an approach opens up

Density functional study the interaction of oxygen molecule with defect sites of graphene

Energy Technology Data Exchange (ETDEWEB)

Qi Xuejun [State Key Laboratory of Coal Combustion, Wuhan 430074 (China); Guo Xin, E-mail: guoxin@mail.hust.edu.cn [State Key Laboratory of Coal Combustion, Wuhan 430074 (China); Zheng Chuguang [State Key Laboratory of Coal Combustion, Wuhan 430074 (China)

2012-10-15

Highlights: Black-Right-Pointing-Pointer The defect sites existed on the graphite surface create active sites and enhance the reactivity of carbonaceous material. Black-Right-Pointing-Pointer Oxygen molecule more favor chemisorbed on the graphene surface contains defect sites than the perfect surface. Black-Right-Pointing-Pointer The single active oxygen atom adsorbed on the defect surfaces, it completely insert into the surface. - Abstract: The present article reports a theoretical study of oxygen interacted with graphene surface containing defect sites on the atomic level by employing the density functional theory combined with the graphene cluster model. It was founded that oxygen molecule prefers to be chemisorbed on the graphene surface containing defect sites compared to the perfect surface. The adsorption energy of O{sub 2} on the double defect site is about 2.5 times as large as that on the perfect graphene surface. Moreover, the oxygen molecule interacts with S-W defect site gives rise to stable epoxy structure, which pulling the carbon atom outward from the original site in the direction perpendicular to the surface. If the oxygen molecule is adsorbed on the single vacancy site, two C-O bonds are formed on the graphene surface. However, when the oxygen molecule is chemisorbed on the double vacancy site, the oxygen atoms substitute the missing carbon atom's position in the carbon plane and form a hexagonal structure on the graphene network. The results indicate that single active oxygen atom approaches the defect site, it's completely adsorbed in the plane and high energy is released. In all cases, the interaction of an oxygen atom with defect surface involves an exothermic process. The defect site creates active sites on the surface of graphene and produces catalytic effects during the process of oxidation of carbonaceous materials.

Surface characterization of the chitosan membrane after oxygen plasma treatment and its aging effect

International Nuclear Information System (INIS)

Wang Yingjun; Yin Shiheng; Ren Li; Zhao Lianna

2009-01-01

Chitosan has received considerable attention for biomedical applications in recent years because of its biocompatibility and biodegradability. In this paper, angle-resolved x-ray photoelectron spectroscopy (ARXPS) was carried out to investigate the chemical groups' spatial orientation on the chitosan membrane surface. Oxygen plasma treatment was also employed to improve the surface hydrophilicity of the chitosan membrane. The results of ARXPS revealed the distribution of surface polar groups, such as-OH and O=CNH 2 toward the membrane bulk, which was the origin of the chitosan membrane surface hydrophobicity. The contact angle measurements and XPS results indicated that oxygen plasma treatment can markedly improve the surface hydrophilicity and surface energy of the chitosan membrane by incorporating oxygen-containing polar groups. With the existence of the aging process, the influence of plasma treatment was not permanent, it faded with storage time. The ARXPS result discovered that the reorientation of polar functional groups generated by plasma treatment toward the membrane bulk was primarily responsible for the aging effect.

Probing adsorption phenomena on a single crystal Pt-alloy surface under oxygen reduction reaction conditions

International Nuclear Information System (INIS)

Bondarenko, Alexander S.; Stephens, Ifan E.L.; Bech, Lone; Chorkendorff, Ib

2012-01-01

Highlights: ► Impedance spectroscopy of Cu/Pt(1 1 1) near-surface alloy and Pt(1 1 1). ► Presence of oxygen changes little the adsorption dynamics. ► Adsorption dynamics similar on alloy and Pt(1 1 1). ► Electrosorption phenomena on alloy shifted in potential, relative to Pt(1 1 1). - Abstract: The adsorption dynamics of *OH and *O species at Pt(1 1 1) and Cu/Pt(1 1 1) near-surface alloy (NSA) surfaces in oxygen-free and O 2 -saturated 0.1 M HClO 4 was investigated. Subsurface Cu modifies the electronic structure at the Pt(1 1 1) surface resulting in weaker bonding to adsorbates like *OH, *H or *O. This provides a basis for the high oxygen reduction activity of the NSA, as predicted by density functional theory calculations. The shift in *OH adsorption of around 0.16 V towards more positive potentials can be clearly monitored in absence of O 2 and under the oxygen reduction reaction (ORR) conditions for the Cu/Pt(1 1 1) NSA. In both cases, for Pt(1 1 1) and NSA, the *OH(*O) adsorption dynamics is very similar in the absence of oxygen and under ORR conditions. Therefore, theoretical assumptions about the coverage of adsorbates in the absence of oxygen can be reasonably extrapolated to the situation when oxygen reduction takes place at the surface. A ∼5-fold improvement in the ORR activity over the Pt(1 1 1) at 0.9 V (RHE) was measured for the Cu/Pt(1 1 1) near-surface alloy.

Elucidation of oxidation and degradation products of oxygen containing fuel components by combined use of a stable isotopic tracer and mass spectrometry.

Science.gov (United States)

Frauscher, Marcella; Besser, Charlotte; Allmaier, Günter; Dörr, Nicole

2017-11-15

In order to reveal the degradation products of oxygen-containing fuel components, in particular fatty acid methyl esters, a novel approach was developed to characterize the oxidation behaviour. Combination of artificial alteration under pressurized oxygen atmosphere, a stable isotopic tracer, and gas chromatography electron impact mass spectrometry (GC-EI-MS) was used to obtain detailed information on the formation of oxidation products of (9Z), (12Z)-octadecadienoic acid methyl ester (C18:2 ME). Thereby, biodiesel simulating model compound C18:2 ME was oxidized in a rotating pressurized vessel standardized for lubricant oxidation tests (RPVOT), i.e., artificially altered, under 16 O 2 as well as 18 O 2 atmosphere. Identification of the formed degradation products, mainly carboxylic acids of various chain lengths, alcohols, ketones, and esters, was performed by means of GC-EI-MS. Comparison of mass spectra of compounds under both atmospheres revealed not only the degree of oxidation and the origin of oxygen atoms, but also the sites of oxidative attack and bond cleavage. Hence, the developed and outlined strategy based on a gas-phase stable isotopic tracer and mass spectrometry provides insight into the degradation of oxygen-containing fuels and fuel components by means of the accurate differentiation of oxygen origin in a degradation product. Copyright © 2017 Elsevier B.V. All rights reserved.

Variations in stable hydrogen and oxygen isotopes in atmospheric water vapor in the marine boundary layer across a wide latitude range.

Science.gov (United States)

Liu, Jingfeng; Xiao, Cunde; Ding, Minghu; Ren, Jiawen

2014-11-01

The newly-developed cavity ring-down laser absorption spectroscopy analyzer with special calibration protocols has enabled the direct measurement of atmospheric vapor isotopes at high spatial and temporal resolution. This paper presents real-time hydrogen and oxygen stable isotope data for atmospheric water vapor above the sea surface, over a wide range of latitudes spanning from 38°N to 69°S. Our results showed relatively higher values of δ(18)O and δ(2)H in the subtropical regions than those in the tropical and high latitude regions, and also a notable decreasing trend in the Antarctic coastal region. By combining the hydrogen and oxygen isotope data with meteoric water line and backward trajectory model analysis, we explored the kinetic fractionation caused by subsiding air masses and related saturated vapor pressure in the subtropics, and the evaporation-driven kinetic fractionation in the Antarctic region. Simultaneous observations of meteorological and marine variables were used to interpret the isotopic composition characteristics and influential factors, indicating that d-excess is negatively correlated with humidity across a wide range of latitudes and weather conditions worldwide. Coincident with previous studies, d-excess is also positively correlated with sea surface temperature and air temperature (Tair), with greater sensitivity to Tair. Thus, atmospheric vapor isotopes measured with high accuracy and good spatial-temporal resolution could act as informative tracers for exploring the water cycle at different regional scales. Such monitoring efforts should be undertaken over a longer time period and in different regions of the world. Copyright © 2014. Published by Elsevier B.V.

Surface-Controlled Metal Oxide Resistive Memory

KAUST Repository

Ke, Jr-Jian; Namura, Kyoko; Duran Retamal, Jose Ramon; Ho, Chin-Hsiang; Minamitake, Haruhiko; Wei, Tzu-Chiao; Tsai, Dung-Sheng; Lin, Chun-Ho; Suzuki, Motofumi; He, Jr-Hau

2015-01-01

be attributed to the stable oxygen adatoms under various ambience conditions. The findings validate the surface-controlled stability and uniformity of ReRAM and can serve as the guideline for developing practical device applications.

The effect of plutonium dioxide water surface coverage on the generation of hydrogen and oxygen

Energy Technology Data Exchange (ETDEWEB)

Veirs, Douglas K. [Los Alamos National Laboratory; Berg, John M. [Los Alamos National Laboratory; Crowder, Mark L. [Savannah River National Laboratory

2012-06-20

The conditions for the production of oxygen during radiolysis of water adsorbed onto plutonium dioxide powder are discussed. Studies in the literature investigating the radiolysis of water show that both oxygen and hydrogen can be generated from water adsorbed on high-purity plutonium dioxide powder. These studies indicate that there is a threshold in the amount of water below which oxygen is not generated. The threshold is associated with the number of monolayers of adsorbed water and is shown to occur at approximately two monolayers of molecularly adsorbed water. Material in equilibrium with 50% relative humidity (RH) will be at the threshold for oxygen generation. Using two monolayers of molecularly adsorbed water as the threshold for oxygen production, the total pressure under various conditions is calculated assuming stoichiometric production of hydrogen and oxygen. The specific surface area of the oxide has a strong effect on the final partial pressure. The specific surface areas resulting in the highest pressures within a 3013 container are evaluated. The potential for oxygen generation is mitigated by reduced relative humidity, and hence moisture adsorption, at the oxide surface which occurs if the oxide is warmer than the ambient air. The potential for oxygen generation approaches zero as the temperature difference between the ambient air and the material approaches 6 C.

Surface activation of cyclo olefin polymer by oxygen plasma discharge: a molecular dynamics study

International Nuclear Information System (INIS)

Soberon, Felipe

2014-01-01

Thermoplastic substrates made of cyclo olefin polymer (COP) are treated with oxygen plasma discharges to introduce polar groups at the surface. This is the first step in the process of surface functionalization of COP substrates used in biosensor devices. A molecular dynamics model of basic COP structure is implemented using the second-generation reactive empirical bond order (REBO) potentials for hydrocarbon–oxygen interactions. The model includes covalent bond and Van der Waals interactions. The bombardment of a COP surface with mono-energetic atomic oxygen ions, energy in the range 1-35 eV, is simulated and reported here. The dynamics of the substrate modification reveals that the substrate top layer is de-hydrogenated and subsequently builds up an oxygen–carbon matrix layer, ∼10 Å thick. Analysis of the modified substrates indicates that surface yield is predominantly peroxide groups. (paper)

Surface modification of argon/oxygen plasma treated vulcanized ethylene propylene diene polymethylene surfaces for improved adhesion with natural rubber

International Nuclear Information System (INIS)

Basak, Ganesh C.; Bandyopadhyay, Abhijit; Neogi, Sudarsan; Bhowmick, Anil K.

2011-01-01

Vulcanized ethylene propylene diene polymethylene (EPDM) rubber surface was treated in a radio frequency capacitatively coupled low pressure argon/oxygen plasma to improve adhesion with compounded natural rubber (NR) during co-vulcanization. The plasma modified surfaces were analyzed by means of contact angle measurement, surface energy, attenuated total reflection-infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, energy dispersive X-ray sulfur mapping and atomic force microscopy. Several experimental variables such as plasma power, length of exposure time and composition of the argon-oxygen gas mixture were considered. It was delineated that plasma treatment changed both surface composition and roughness, and consequently increased peel strength. The change in surface composition was mainly ascribed to the formation of C-O and -C=O functional groups on the vulcanized surfaces. A maximum of 98% improvement in peel strength was observed after plasma treatment.

Surface modification of argon/oxygen plasma treated vulcanized ethylene propylene diene polymethylene surfaces for improved adhesion with natural rubber

Energy Technology Data Exchange (ETDEWEB)

Basak, Ganesh C. [Rubber Technology Centre, Indian Institute of Technology, Kharagpur 721302 (India); Bandyopadhyay, Abhijit [Department of Polymer Science and Technology, University of Calcutta, Calcutta 700 009 (India); Neogi, Sudarsan [Department of Chemical Engineering, Indian Institute of Technology, Kharagpur 721302 (India); Bhowmick, Anil K., E-mail: anilkb@rtc.iitkgp.ernet.in [Rubber Technology Centre, Indian Institute of Technology, Kharagpur 721302 (India)

2011-01-15

Vulcanized ethylene propylene diene polymethylene (EPDM) rubber surface was treated in a radio frequency capacitatively coupled low pressure argon/oxygen plasma to improve adhesion with compounded natural rubber (NR) during co-vulcanization. The plasma modified surfaces were analyzed by means of contact angle measurement, surface energy, attenuated total reflection-infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, energy dispersive X-ray sulfur mapping and atomic force microscopy. Several experimental variables such as plasma power, length of exposure time and composition of the argon-oxygen gas mixture were considered. It was delineated that plasma treatment changed both surface composition and roughness, and consequently increased peel strength. The change in surface composition was mainly ascribed to the formation of C-O and -C=O functional groups on the vulcanized surfaces. A maximum of 98% improvement in peel strength was observed after plasma treatment.

[Distribution and sources of oxygen and sulfur heterocyclic aromatic compounds in surface soil of Beijing, China].

Science.gov (United States)

He, Guang-Xiu; Zhang, Zhi-Huan; Peng, Xu-Yang; Zhu, Lei; Lu, Ling

2011-11-01

62 surface soil samples were collected from different environmental function zones in Beijing. Sulfur and oxygen heterocyclic aromatic compounds were detected by GC/MS. The objectives of this study were to identify the composition and distribution of these compounds, and discuss their sources. The results showed that the oxygen and sulfur heterocyclic aromatic compounds in the surface soils mainly contained dibenzofuran, methyl- and C2-dibenzofuran series, dibenzothiophene, methyl-, C2- and C3-dibenzothiophene series and benzonaphthothiophene series. The composition and distribution of the oxygen and sulfur heterocyclic aromatic compounds in the surface soil samples varied in the different environmental function zones, of which some factories and the urban area received oxygen and sulfur heterocyclic aromatic compounds most seriously. In Beijing, the degree of contamination by oxygen and sulfur heterocyclic aromatic compounds in the north surface soil was higher than that in the south. There were preferable linear correlations between the concentration of dibenzofuran series and fluorene series, as well as the concentration of dibenzothiophene series and dibenzofuran series. The oxygen and sulfur heterocyclic aromatic compounds in the surface soil were mainly derived from combustion products of oil and coal and direct input of mineral oil, etc. There were some variations in pollution sources of different environmental function zones.

Probing adsorption phenomena on a single crystal Pt-alloy surface under oxygen reduction reaction conditions

DEFF Research Database (Denmark)

Bondarenko, Alexander S.; Stephens, Ifan E.L.; Bech, Lone

2012-01-01

The adsorption dynamics of *OH and *O species at Pt(111) and Cu/Pt(111) near-surface alloy (NSA) surfaces in oxygen-free and O2-saturated 0.1M HClO4 was investigated. Subsurface Cu modifies the electronic structure at the Pt(111) surface resulting in weaker bonding to adsorbates like *OH, *H or *O....... This provides a basis for the high oxygen reduction activity of the NSA, as predicted by density functional theory calculations. The shift in *OH adsorption of around 0.16V towards more positive potentials can be clearly monitored in absence of O2 and under the oxygen reduction reaction (ORR) conditions...... for the Cu/Pt(111) NSA. In both cases, for Pt(111) and NSA, the *OH(*O) adsorption dynamics is very similar in the absence of oxygen and under ORR conditions. Therefore, theoretical assumptions about the coverage of adsorbates in the absence of oxygen can be reasonably extrapolated to the situation when...

SPE (tm) regenerative hydrogen/oxygen fuel cells for extraterrestrial surface and microgravity applications

Science.gov (United States)

Mcelroy, J. F.

1990-01-01

Viewgraphs on SPE regenerative hydrogen/oxygen fuel cells for extraterrestrial surface and microgravity applications are presented. Topics covered include: hydrogen-oxygen regenerative fuel cell energy storage system; electrochemical cell reactions; SPE cell voltage stability; passive water removal SPE fuel cell; fuel cell performance; SPE water electrolyzers; hydrophobic oxygen phase separator; hydrophilic/electrochemical hydrogen phase separator; and unitized regenerative fuel cell.

Stable functionalization of germanium surface and its application in biomolecules immobilization

Energy Technology Data Exchange (ETDEWEB)

Cai, Qi [State Key Laboratory of Transducer Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, No.865, Changning Road, Shanghai 200050 (China); University of Chinese Academy of Sciences, No.19A, Yuquan Road, Beijing 100049 (China); Xu, Baojian [State Key Laboratory of Transducer Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, No.865, Changning Road, Shanghai 200050 (China); Ye, Lin [Sate Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, No.865, Changning Road, Shanghai 200050 (China); University of Chinese Academy of Sciences, No.19A, Yuquan Road, Beijing 100049 (China); Tang, Teng; Huang, Shanluo; Du, Xiaowei [State Key Laboratory of Transducer Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, No.865, Changning Road, Shanghai 200050 (China); University of Chinese Academy of Sciences, No.19A, Yuquan Road, Beijing 100049 (China); Bian, Xiaojun; Zhang, Jishen [State Key Laboratory of Transducer Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, No.865, Changning Road, Shanghai 200050 (China); Di, Zengfeng, E-mail: zfdi@mail.sim.ac.cn [Sate Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, No.865, Changning Road, Shanghai 200050 (China); Jin, Qinghui [State Key Laboratory of Transducer Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, No.865, Changning Road, Shanghai 200050 (China); Zhao, Jianlong, E-mail: jlzhao@mail.sim.ac.cn [State Key Laboratory of Transducer Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, No.865, Changning Road, Shanghai 200050 (China)

2014-10-15

Highlights: • An effective method to immobilize biomolecules on the functionalized Ge surface. • The surface of Ge was functionalized with 11-Mercaptoundecanoic acid (11-MUA). • Stable and uniform SAMs was obtained on Ge surface after 11-MUA treatment. • The functionalized Ge was employed as substrate for protein immobilization. • Paving the way of Ge for further applications in bioelectronics field. - Abstract: As a typical semiconductor material, germanium (Ge) has the potential to be utilized in microelectronics and bioelectronics. Herein, we present a simple and effective method to immobilize biomolecules on the surface of functionalized Ge. The surface oxide of Ge was removed with the pretreatment of hydrochloric acid and the Cl-terminated Ge reacted with 11-Mercaptoundecanoic acid (11-MUA). The surface of Ge was coated with 11-MUA self-assembled monolayers (SAMs) due to the bonding reaction between the sulfhydryl group of 11-MUA and Cl-terminated Ge. Furthermore, typical biomolecule, a green fluorescent protein was chosen to be immobilized on the surface of the functionalized Ge. Contact angle analysis, atomic force microscopy and X-ray photoelectron spectroscopy were used to study the characteristics including wettability, stability, roughness and component of the functionalized Ge, respectively. Fluorescence microscopy was utilized to indicate the efficiency of protein immobilization on the surface of the functionalized Ge. With these studies, stable and uniform functionalized monolayer was obtained on the surface of Ge after 11-MUA treatment and the functionalized Ge was effectively applied in protein immobilization. Furthermore, this study may pave the way for further applications such as the integration of bioelectronics and biosensors with the attractive semiconductor material-Ge in future work.

Plasma-polymerized SiOx deposition on polymer film surfaces for preparation of oxygen gas barrier polymeric films

International Nuclear Information System (INIS)

Inagaki, N.

2003-01-01

SiOx films were deposited on surfaces of three polymeric films, PET, PP, and Nylon; and their oxygen gas barrier properties were evaluated. To mitigate discrepancies between the deposited SiOx and polymer film, surface modification of polymer films was done, and how the surface modification could contribute to was discussed from the viewpoint of apparent activation energy for the permeation process. The SiOx deposition on the polymer film surfaces led to a large decrease in the oxygen permeation rate. Modification of polymer film surfaces by mans of the TMOS or Si-COOH coupling treatment in prior to the SiOx deposition was effective in decreasing the oxygen permeation rate. The cavity model is proposed as an oxygen permeation process through the SiOx-deposited Nylon film. From the proposed model, controlling the interface between the deposited SiOx film and the polymer film is emphasized to be a key factor to prepare SiOx-deposited polymer films with good oxygen gas barrier properties. (author)

Electromyographic activity and 6RM strength in bench press on stable and unstable surfaces.

Science.gov (United States)

Saeterbakken, Atle H; Fimland, Marius S

2013-04-01

The purpose of the study was to compare 6-repetition maximum (6RM) loads and muscle activity in bench press on 3 surfaces, namely, stable bench, balance cushion, and Swiss ball. Sixteen healthy, resistance-trained men (age 22.5 ± 2.0 years, stature 1.82 ± 6.6 m, and body mass 82.0 ± 7.8 kg) volunteered for 3 habituation/strength testing sessions and 1 experimental session. In randomized order on the 3 surfaces, 6RM strength and electromyographic activity of pectoralis major, deltoid anterior, biceps brachii, triceps brachii, rectus abdominis, oblique external and erector spinae were assessed. Relative to stable bench, the 6RM strength was approximately 93% for balance cushion (p ≤ 0.001) and approximately 92% for Swiss ball (p = 0.008); the pectoralis major electromyographic (EMG) activity was approximately 90% using the balance cushion (p = 0.080) and approximately 81% using Swiss ball (p = 0.006); the triceps EMG was approximately 79% using the balance cushion (p = 0.028) and approximately 69% using the Swiss ball (p = 0.002). Relative to balance cushion, the EMG activity in pectoralis, triceps, and erector spinae using Swiss ball was approximately 89% (p = 0.016), approximately 88% (p = 0.014) and approximately 80% (p = 0.020), respectively. In rectus abdominis, the EMG activity relative to Swiss ball was approximately 69% using stable bench (p = 0.042) and approximately 65% using the balance cushion (p = 0.046). Similar EMG activities between stable and unstable surfaces were observed for deltoid anterior, biceps brachii, and oblique external. In conclusion, stable bench press had greater 6RM strength and triceps and pectoralis EMG activity compared with the unstable surfaces. These findings have implications for athletic training and rehabilitation, because they demonstrate an inferior effect of unstable surfaces on muscle activation of prime movers and strength in bench press. If an unstable surface in bench press is desirable, a balance cushion should

Oxygen Vacancy-Mediated ZnO Nanoparticle Photocatalyst for Degradation of Methylene Blue

Directory of Open Access Journals (Sweden)

Qiuping Zhang

2018-02-01

Full Text Available ZnO nanoparticles (NPs are synthesized by deoxidizing ZnO powder in a vacuum drying process. This process reduces the size of the NPs and increases the concentration of oxygen vacancies on their surfaces. ZnO NPs with sufficient oxygen vacancies are highly effective for the photodecomposition of methylene blue (MB dye in water under ultraviolet irradiation. The MB degradation efficiency exceeds 99 percent after 50 min of light irradiation, and the catalytic property of the NPs remains stable over several complete degradation cycles. It is revealed that the concentration of oxygen vacancies on the surface, and the photocatalytic activity, are both higher for smaller NPs. Oxygen vacancies reduce the recombination rate of photo-generated charge carriers by capturing the electrons and hence, improve the efficiency of redox reactions. In addition, a smaller particle size leads to a larger specific surface area and a higher photonic efficiency for the ZnO NPs.

Synthesis of surface oxygen-deficient BiPO{sub 4} nanocubes with enhanced visible light induced photocatalytic activity

Energy Technology Data Exchange (ETDEWEB)

Shi, Bingtao; Yin, Haoyong; Li, Tao; Gong, Jianying; Lv, Shumei; Nie, Qiulin, E-mail: yhy@hdu.edu.cn [College of Materials & Environmental Engineering, Hangzhou Dianzi University, Hangzhou (China)

2017-05-15

The visible light driven BiPO{sub 4} nanocubes with sufficient surface oxygen deficiency were fabricated by a hydrothermal process and subsequently ultrasonic assistant Fe reduction process. The products were characterized by XRD, DRS, XPS, SEM and TEM which showed that the BiPO{sub 4} had cuboid-like shape with a smooth surface and clear edges and the oxygen vacancies were successfully introduced on the surface of the BiPO{sub 4} nanocubes. The as prepared oxygen-deficient BiPO{sub 4} nanocubes showed greatly enhanced visible light induced photocatalytic activity in degradation of Rhodamine B. The enhanced photocatalytic performance and expanded visible light response of BiPO{sub 4} may be due to the introduction of surface oxygen vacancies which can generate the oxygen vacancies mid-gap states lower to the conduction band of BiPO{sub 4}. (author)

Oxygen Evolution at Hematite Surfaces: The Impact of Structure and Oxygen Vacancies on Lowering the Overpotential

NARCIS (Netherlands)

Zhang, X.; Klaver, P.; van Santen, R.; van de Sanden, M. C. M.; Bieberle, A.

2016-01-01

Simulations of the oxygen evolution reaction (OER) are essential for understanding the limitations of water splitting. Most research has focused so far on the OER at flat metal oxide surfaces. The structure sensitivity of the OER has, however, recently been highlighted as a promising research

Realization of Multi-Stable Ground States in a Nematic Liquid Crystal by Surface and Electric Field Modification

Science.gov (United States)

Gwag, Jin Seog; Kim, Young-Ki; Lee, Chang Hoon; Kim, Jae-Hoon

2015-06-01

Owing to the significant price drop of liquid crystal displays (LCDs) and the efforts to save natural resources, LCDs are even replacing paper to display static images such as price tags and advertising boards. Because of a growing market demand on such devices, the LCD that can be of numerous surface alignments of directors as its ground state, the so-called multi-stable LCD, comes into the limelight due to the great potential for low power consumption. However, the multi-stable LCD with industrial feasibility has not yet been successfully performed. In this paper, we propose a simple and novel configuration for the multi-stable LCD. We demonstrate experimentally and theoretically that a battery of stable surface alignments can be achieved by the field-induced surface dragging effect on an aligning layer with a weak surface anchoring. The simplicity and stability of the proposed system suggest that it is suitable for the multi-stable LCDs to display static images with low power consumption and thus opens applications in various fields.

Oxygen Modulates Human Decidual Natural Killer Cell Surface Receptor Expression and Interactions with Trophoblasts1

Science.gov (United States)

Wallace, Alison E.; Goulwara, Sonu S.; Whitley, Guy S.; Cartwright, Judith E.

2014-01-01

Decidual natural killer (dNK) cells have been shown to both promote and inhibit trophoblast behavior important for decidual remodeling in pregnancy and have a distinct phenotype compared to peripheral blood NK cells. We investigated whether different levels of oxygen tension, mimicking the physiological conditions of the decidua in early pregnancy, altered cell surface receptor expression and activity of dNK cells and their interactions with trophoblast. dNK cells were isolated from terminated first-trimester pregnancies and cultured in oxygen tensions of 3%, 10%, and 21% for 24 h. Cell surface receptor expression was examined by flow cytometry, and the effects of secreted factors in conditioned medium (CM) on the trophoblast cell line SGHPL-4 were assessed in vitro. SGHPL-4 cells treated with dNK cell CM incubated in oxygen tensions of 10% were significantly more invasive (P cells treated with dNK cell CM incubated in oxygen tensions of 3% or 21%. After 24 h, a lower percentage of dNK cells expressed CD56 at 21% oxygen (P cells expressed NKG2D at 10% oxygen (P oxygen tensions, with large patient variation. This study demonstrates dNK cell phenotype and secreted factors are modulated by oxygen tension, which induces changes in trophoblast invasion and endovascular-like differentiation. Alterations in dNK cell surface receptor expression and secreted factors at different oxygen tensions may represent regulation of function within the decidua during the first trimester of pregnancy. PMID:25232021

Modeling the thermostability of surface functionalisation by oxygen, hydroxyl, and water on nanodiamonds.

Science.gov (United States)

Lai, Lin; Barnard, Amanda S

2011-06-01

Understanding nanodiamond functionalisation is of great importance for biological and medical applications. Here we examine the stabilities of oxygen, hydroxyl, and water functionalisation of the nanodiamonds using the self-consistent charge density functional tight-binding simulations. We find that the oxygen and hydroxyl termination are thermodynamically favourable and form strong C–O covalent bonds on the nanodiamond surface in an O2 and H2 gas reservoir, which confirms previous experiments. Yet, the thermodynamic stabilities of oxygen and hydroxyl functionalisation decrease dramatically in a water vapour reservoir. In contrast, H2O molecules are found to be physically adsorbed on the nanodiamond surface, and forced chemical adsorption results in decomposition of H2O. Moreover, the functionalisation efficiency is found to be facet dependent. The oxygen functionalisation prefers the {100} facets as opposed to alternative facets in an O2 and H2 gas reservoir. The hydroxyl functionalisation favors the {111} surfaces in an O2 and H2 reservoir and the {100} facets in a water vapour reservoir, respectively. This facet selectivity is found to be largely dependent upon the environmental temperature, chemical reservoir, and morphology of the nanodiamonds.

Determination of Oxygen in Zircaloy Surfaces by Means of Charged Particle Activation Analysis

Energy Technology Data Exchange (ETDEWEB)

Lorenzen, J; Brune, D

1973-01-15

Oxygen in zircaloy surfaces has been determined by means of charged particle activation analysis employing the following two reactions I. 16O (d, n) 17F ->(beta+decay) 17O Q = - 1.63 MeV; II. 16O (d, pgamma) 17O Q = + 1.05 MeV. The detection limits for oxygen in such surfaces has been investigated by measuring the promptly emitted 0.87 MeV gamma rays (reaction II) and also the 511 keV annihilation radiation which arises from beta-decay of 17F (reaction I). The correlation between the detection limit for oxygen in zircaloy, the particle energy and the surface thickness analyzed has been evaluated. At a deuteron energy of 3 MeV a detection limit of 0.7 x 10-7 g/cm2 was obtained from the measurement of the prompt gamma radiation arising from the second of these reactions. The analysis carried out by means of this technique is characterized by a high rapidity

A miniaturized oxygen sensor integrated on fiber surface based on evanescent-wave induced fluorescence quenching

Energy Technology Data Exchange (ETDEWEB)

Xiong, Yan [School of Chemistry and Chemical Engineering, Southwest Petroleum University, Chengdu 610500 (China); Oil and Gas Field Applied Chemistry Key Laboratory of Sichuan Province, Southwest Petroleum University, Chengdu, 610500 (China); Tan, Jun; Wang, Chengjie; Zhu, Ying [School of Chemistry and Chemical Engineering, Southwest Petroleum University, Chengdu 610500 (China); Fang, Shenwen [School of Chemistry and Chemical Engineering, Southwest Petroleum University, Chengdu 610500 (China); Oil and Gas Field Applied Chemistry Key Laboratory of Sichuan Province, Southwest Petroleum University, Chengdu, 610500 (China); Wu, Jiayi; Wang, Qing [School of Chemistry and Chemical Engineering, Southwest Petroleum University, Chengdu 610500 (China); Duan, Ming, E-mail: swpua124@126.com [State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu 610500 (China); School of Chemistry and Chemical Engineering, Southwest Petroleum University, Chengdu 610500 (China); Oil and Gas Field Applied Chemistry Key Laboratory of Sichuan Province, Southwest Petroleum University, Chengdu, 610500 (China)

2016-11-15

In this work, a miniaturized sensor was integrated on fiber surface and developed for oxygen determination through evanescent-wave induced fluorescence quenching. The sensor was designed by using light emitting diode (LED) as light source and optical fiber as light transmission element. Tris(2,2′-bipyridyl) ruthenium ([Ru(bpy){sub 3}]{sup 2+}) fluorophore was immobilized in the organically modified silicates (ORMOSILs) film and coated onto the fiber surface. When light propagated by total internal reflection (TIR) in the fiber core, evanescent wave could be produced on the fiber surface and excite [Ru(bpy){sub 3}]{sup 2+} fluorophore to produce fluorescence emission. Then oxygen could be determinated by its quenching effect on the fluorescence and its concentration could be evaluated according to Stern–Volumer model. Through integrating evanescent wave excitation and fluorescence quenching on fiber surface, the sensor was successfully miniaturized and exhibit improved performances of high sensitivity (1.4), excellent repeatability (1.2%) and fast analysis (12 s) for oxygen determination. The sensor provided a newly portable method for in-situ and real-time measurement of oxygen and showed potential for practical oxygen analysis in different application fields. Furthermore, the fabrication of this sensor provides a miniaturized and portable detection platform for species monitoring by simple modular design. - Highlights: • ORMOSILs sensing film immobilized with [Ru(bpy){sub 3}]{sup 2+} fluorophore was coated on fiber surface. • Evanescent wave on the fiber surface was utilized as excitation source to produce fluorescence. • Oxygen was measured based on its quenching effect on evanescent wave-induce fluorescence. • Sensor fabrication was miniaturized by integrating detection and sensing elements on the fiber. • The modular design sensor provides a detection platform for other species monitoring.

Surface modification effects of fluorine-doped tin dioxide by oxygen plasma ion implantation

Science.gov (United States)

Tang, Peng; Liu, Cai; Zhang, Jingquan; Wu, Lili; Li, Wei; Feng, Lianghuan; Zeng, Guanggen; Wang, Wenwu

2018-04-01

SnO2:F (FTO), as a kind of transparent conductive oxide (TCO), exhibits excellent transmittance and conductivity and is widely used as transparency electrodes in solar cells. It's very important to modifying the surface of FTO for it plays a critical role in CdTe solar cells. In this study, modifying effects of oxygen plasma on FTO was investigated systematically. Oxygen plasma treatment on FTO surface with ion accelerating voltage ranged from 0.4 kV to 1.6 kV has been processed. The O proportion of surface was increased after ion implantation. The Fermi level of surface measurement by XPS valance band spectra was lowered as the ion accelerating voltage increased to 1.2 kV and then raised as accelerating voltage was elevated to 1.6 kV. The work function measured by Kelvin probe force microscopy increased after ion implanting, and it was consistent with the variation of Fermi level. The change of energy band structure of FTO surface mainly originated from the surface composition variation. As FTO conduction was primarily due to oxyanion hole, the carrier was electron and its concentration was reduced while O proportion was elevated at the surface of FTO, as a result, the Fermi level lowered and the work function was enlarged. It was proved that oxygen plasma treatment is an effective method to modulate the energy band structure of the surface as well as other properties of FTO, which provides much more space for interface and surface modification and then photoelectric device performance promotion.

A theoretical study of stability and vacancy replenishing of MoO{sub 3}(0 1 0) surfaces in oxygen atmosphere

Energy Technology Data Exchange (ETDEWEB)

Lei, Yan-Hua; Chen, Zhao-Xu, E-mail: zxchen@nju.edu.cn

2016-01-15

Graphical abstract: - Highlights: • Under normal experimental conditions perfect surface of MoO{sub 3}(0 1 0) is favorable. • Line defects along asymmetric oxygen direction in lean oxygen condition are favored. • Vacancy replenishing occurs on vacancies formed by terminal and asymmetrical oxygen. - Abstract: Oxygen vacancies on transition metal oxide surfaces are catalytically very important. The stability, shape and replenishing process of the vacancies are critical to understanding reactions happening on the surfaces. In this paper we investigate the stability of various defective MoO{sub 3}(0 1 0) surfaces and examine the influence of environmental oxygen on the stability as well as the active sites for the replenishing process. Our calculations reveal that the line oxygen defect along a (asymmetric oxygen) direction is thermodynamically most favorable at higher defect concentration whereas point defect surfaces are unfavorable. Under normal experimental conditions the perfect surface dominates the MoO{sub 3}(0 1 0). We show that for stoichiometric surfaces of any oxides (A{sub x}O{sub y}) the formation energy per vacancy controls the favorable defect shape (line or point defects). Calculations indicate that O{sub 2} can dissociate readily on the surfaces that double vacancies share one Mo atom. The replenishing process of the oxygen vacancies through O{sub 2} dissociation most likely occurs on the double-vacancy containing one terminal and one asymmetrical oxygen vacancies.

Emission of positive oxygen ions from ion bombardment of adsorbate-covered metal surfaces

International Nuclear Information System (INIS)

Kaurin, M.G.

1989-01-01

During ion bombardment of metal surfaces, collision cascades can result in the emission of sputtered secondary ions. Recent experiments, however, have suggested that the emission of positive ions of electronegative adsorbates can result from electronic processes rather than from processes involving elastic collisions. This dissertation presents the results of experiments studying the emission of positive oxygen ions from oxygen- and carbon-monoxide-covered transition metal surfaces during bombardment by 25-250 keV ions of neon, argon, and krypton. The systems studied may be grouped into four categories. For a nickel substrate with adsorbed oxygen, the emission of positive oxygen ions proceeds through collision cascades. For titanium and niobium with adsorbed oxygen, the emission of positive oxygen ions is proportional to the primary ion velocity, consistent with emission from electronic processes; for a given primary ion velocity, the oxygen ion yield is independent of primary ion species. For substrates of molybdenum and tungsten, the oxygen yield is proportional to primary ion velocity, but the yield also depends on the primary ion species for a given primary ion velocity in a manner that is consistent with emission resulting from electronic processes. For these two groups, except for titanium, the yields during neon ion bombardment do not extrapolate (assuming linearity with primary ion velocity) to a nonzero value at zero beam velocity. The magnitude of the oxygen ion yields from these targets is not consistent with that expected if the emission were induced by secondary electrons emitted during the ion bombardment

Is the surface oxygen exchange rate linked to bulk ion diffusivity in mixed conducting Ruddlesden-Popper phases?

Science.gov (United States)

Tomkiewicz, Alex C; Tamimi, Mazin A; Huq, Ashfia; McIntosh, Steven

2015-01-01

The possible link between oxygen surface exchange rate and bulk oxygen anion diffusivity in mixed ionic and electronic conducting oxides is a topic of great interest and debate. While a large body of experimental evidence and theoretical analyses support a link, observed differences between bulk and surface composition of these materials are hard to reconcile with this observation. This is further compounded by potential problems with simultaneous measurement of both parameters. Here we utilize separate techniques, in situ neutron diffraction and pulsed isotopic surface exchange, to examine bulk ion mobility and surface oxygen exchange rates of three Ruddlesden-Popper phases, general form A(n-1)A(2)'B(n)O(3n+1), A(n-1)A(2)'B(n)X(3n+1); LaSrCo(0.5)Fe(0.5)O(4-δ) (n = 1), La(0.3)Sr(2.7)CoFeO(7-δ) (n = 2) and LaSr3Co(1.5)Fe(1.5)O(10-δ) (n = 3). These measurements are complemented by surface composition determination via high sensitivity-low energy ion scattering. We observe a correlation between bulk ion mobility and surface exchange rate between materials. The surface exchange rates vary by more than one order of magnitude with high anion mobility in the bulk of an oxygen vacancy-rich n = 2 Ruddlesden-Popper material correlating with rapid oxygen exchange. This is in contrast with the similar surface exchange rates which we may expect due to similar surface compositions across all three samples. We conclude that experimental limitations lead to inherent convolution of surface and bulk rates, and that surface exchange steps are not likely to be rate limiting in oxygen incorporation.

Adsorption of atomic oxygen on PdAg/Pd(111) surface alloys and coadsorption of CO

Energy Technology Data Exchange (ETDEWEB)

Farkas, Arnold P. [Institute of Surface Chemistry and Catalysis, Ulm University, D-89069 Ulm (Germany); Reaction Kinetics Research Group, University of Szeged, Chemical Research Center of the Hungarian Academy of Sciences, H-6720 Szeged (Hungary); Bansmann, Joachim; Diemant, Thomas; Behm, R. Juergen [Institute of Surface Chemistry and Catalysis, Ulm University, D-89069 Ulm (Germany)

2011-07-01

The interaction of dissociated oxygen with structurally well-defined PdAg/Pd(111) surface alloys and the coadsorption of CO was studied by high resolution electron energy loss spectroscopy (HREELS) and temperature-programmed desorption (TPD). After oxygen saturation of the non-modified Pd(111) surface at RT, we observed the formation of a prominent peak in the HREEL spectra at 60 meV corresponding to the perpendicular vibration of oxygen atoms adsorbed in threefold hollow sites. Deposition of small Ag amounts does not change the signal intensity of this peak; it decreases only above 20% Ag. Beyond this Ag content, the peak intensity steeply declines and disappears at around 55-60% Ag. CO coadsorption on the oxygen pre-covered surfaces at 120 K leads to the formation of additional features in HREELS. For a surface alloy with 29% Ag, three loss features due to CO adsorption in on-top, bridge, and threefold-hollow sites can be discriminated already after the lowest CO exposure. Annealing of the co-adsorbed layer to 200 K triggers a decrease of the oxygen concentration due to CO{sub 2} formation. These findings are corroborated by TPD spectra of the CO desorption and CO{sub 2} production.

Seasonal Variations in Stable Isotope Ratios of Oxygen and Hydrogen in Two Tundra Rivers in NE European Russia

Energy Technology Data Exchange (ETDEWEB)

Huitu, E.; Arvola, L. [Lammi Biological Station, University of Helsinki (Finland); Sonninen, E. [Radiocarbon Dating Laboratory, University of Helsinki (Finland)

2013-07-15

The variability in stable isotope ratios of oxygen and hydrogen ({delta} {sup 18}O and {delta}{sup 2}H values) in river waters in northeast European Russia was studied for the period from July 2007 to october 2008. Exceptional isotope composition in precipitation obtained during the sampling period was clearly traced in the composition of river waters. Water from permafrost thawing did not make a great contribution to river flow. (author)

Comparison of the effects of an eight-week push-up program using stable versus unstable surfaces.

Science.gov (United States)

Chulvi-Medrano, Iván; Martínez-Ballester, Esteban; Masiá-Tortosa, Laura

2012-12-01

Recently, the trend among physical training and rehabilitation professionals is the use of resistance exercise on unstable equipment in order to increase the effort of the agonist and stabilizing muscles. It is unknown if performing exercises on unstable surfaces provides a greater training stimulus as compared to training on a stable training surface. Therefore, the purpose of this research was to compare the effect that push-up training on stable and unstable surfaces had on strength performance in healthy young men. Thirty subjects with experience in resistance training participated in push-up training two days per week for eight weeks on one of three different surfaces: the floor (Tp), the T-Bow® (TBp) or the BOSU® (Bp). Strength, as measured by one repetition maximum (1-RM) and muscle endurance, as measured by number of pushups performed did not improve significantly (p>0.05) for any of the intervention groups. The addition of unstable surfaces in push-up training does not provide greater improvement in muscular strength and endurance than push up training performed on a stable surface in young men. 3b.

Oxygen surfactant-assisted growth and dewetting of Co films on O-3 × 3/W(111)

Energy Technology Data Exchange (ETDEWEB)

Hsueh, Kun-Jen; Tsai, Cheng-Jui; Lin, Wen-Chin, E-mail: wclin@ntnu.edu.tw [Department of Physics, National Taiwan Normal University, Taipei 116, Taiwan (China); Wu, Shih-Yu; Chou, Hsin-Lei; Kuo, Chien-Cheng, E-mail: cckuo@faculty.nsysu.edu.tw [Department of Physics, National Sun Yat-sen University, Kaohsiung 804, Taiwan (China); Bisio, Francesco [CNR-SPIN, C.so Perrone 24, I-16152 Genova (Italy)

2013-11-28

Following the cyclic heating in oxygen and annealing, an oxygen-induced 3 × 3 reconstruction was found on the W(111) surface. The growth, crystalline structure, thermal stability, and magnetism of Co ultrathin films deposited on the O-3 × 3/W(111) surface were investigated. The Auger signal of the oxygen was always observable and nearly invariant after either Co deposition or annealing, indicating the role of the surfactant played by oxygen. Auger electron spectroscopy and scanning tunneling microscopy measurements revealed the 2-dimensional growth of Co on O-3 × 3/W(111). Following the annealing procedures, the surfactant oxygen was always observed to float on the film surface while the Co film transformed to 3-dimensional islands with a wetting layer. In contrast to the thermodynamically stable wetting layer of 1 physical monolayer (PML) Co on clean W(111) between 700 and 1000 K, the oxygen surfactant led to a reduction of the wetting layer to ≈1/3 PML after thermal annealing. The 6 and 9.6 PML Co/O-3 × 3/W(111) revealed a stable in-plane magnetic anisotropy. A 6-fold symmetry corresponding to the crystalline structure was observed in the in-plane angle-dependent magneto-optical Kerr effect measurement.

Oxygen surfactant-assisted growth and dewetting of Co films on O-3 × 3/W(111)

International Nuclear Information System (INIS)

Hsueh, Kun-Jen; Tsai, Cheng-Jui; Lin, Wen-Chin; Wu, Shih-Yu; Chou, Hsin-Lei; Kuo, Chien-Cheng; Bisio, Francesco

2013-01-01

Following the cyclic heating in oxygen and annealing, an oxygen-induced 3 × 3 reconstruction was found on the W(111) surface. The growth, crystalline structure, thermal stability, and magnetism of Co ultrathin films deposited on the O-3 × 3/W(111) surface were investigated. The Auger signal of the oxygen was always observable and nearly invariant after either Co deposition or annealing, indicating the role of the surfactant played by oxygen. Auger electron spectroscopy and scanning tunneling microscopy measurements revealed the 2-dimensional growth of Co on O-3 × 3/W(111). Following the annealing procedures, the surfactant oxygen was always observed to float on the film surface while the Co film transformed to 3-dimensional islands with a wetting layer. In contrast to the thermodynamically stable wetting layer of 1 physical monolayer (PML) Co on clean W(111) between 700 and 1000 K, the oxygen surfactant led to a reduction of the wetting layer to ≈1/3 PML after thermal annealing. The 6 and 9.6 PML Co/O-3 × 3/W(111) revealed a stable in-plane magnetic anisotropy. A 6-fold symmetry corresponding to the crystalline structure was observed in the in-plane angle-dependent magneto-optical Kerr effect measurement

Optimization and characterization of stable lipid-based, oxygen-filled microbubbles by mixture design.

Science.gov (United States)

Polizzotti, Brian D; Thomson, Lindsay M; O'Connell, Daniel W; McGowan, Francis X; Kheir, John N

2014-08-01

Tissue hypoxia is a final common pathway that leads to cellular injury and death in a number of critical illnesses. Intravenous injections of self-assembling, lipid-based oxygen microbubbles (LOMs) can be used to deliver oxygen gas, preventing organ injury and death from systemic hypoxemia. However, current formulations exhibit high polydispersity indices (which may lead to microvascular obstruction) and poor shelf-lives, limiting the translational capacity of LOMs. In this study, we report our efforts to optimize LOM formulations using a mixture response surface methodology (mRSM). We study the effect of changing excipient proportions (the independent variables) on microbubble diameter and product loss (the dependent variables). By using mRSM analysis, the experimental data were fit using a reduced Scheffé linear mixture model. We demonstrate that formulations manufactured from 1,2-distearoyl-sn-glycero-3-phosphocholine, corn syrup, and water produce micron-sized microbubbles with low polydispersity indices, and decreased product loss (relative to previously described formulations) when stored at room temperature over a 30-day period. Optimized LOMs were subsequently tested for their oxygen-releasing ability and found to have similar release kinetics as prior formulations. © 2014 Wiley Periodicals, Inc.

Stable isotopes of authigenic minerals in variably-saturated fractured tuff

International Nuclear Information System (INIS)

Weber, D.S.; Evans, D.D.

1988-11-01

Identifying stable isotope variation and mineralogical changes in fractured rock may help establish the history of climatic and geomorphological processes that might affect the isolation properties of a waste repository site. This study examines the use of the stable isotope ratios of oxygen ( 18 O/ 16 O) and carbon ( 13 C/ 12 C) in authigenic minerals as hydrogeochemical tools tracing low-temperature rock-water interaction in variably-saturated fractured stuff. Isotopic compositions of fracture-filling and rock matrix minerals in the Apache Leap tuff, near Superior, Arizona were concordant with geothermal temperatures and in equilibrium with water isotopically similar to present-day meteoric water and groundwater. Oxygen and carbon isotope ratios of fracture-filling, in unsaturated fractured tuff, displayed an isotopic gradient believed to result from near-surface isotopic enrichment due to evaporation rather than the effects of rock-water interaction. Oxygen isotope ratios of rock matrix opal samples exhibited an isotopic gradient believed to result from, leaching and reprecipitation of silica at depth. Methods and results can be used to further define primary flowpaths and the movement of water in variably-saturated fractured rock. 71 refs., 23 figs., 3 tabs

Stable isotopes of authigenic minerals in variably-saturated fractured tuff

Energy Technology Data Exchange (ETDEWEB)

Weber, D.S.; Evans, D.D.

1988-11-01

Identifying stable isotope variation and mineralogical changes in fractured rock may help establish the history of climatic and geomorphological processes that might affect the isolation properties of a waste repository site. This study examines the use of the stable isotope ratios of oxygen ({sup 18}O/{sup 16}O) and carbon ({sup 13}C/{sup 12}C) in authigenic minerals as hydrogeochemical tools tracing low-temperature rock-water interaction in variably-saturated fractured stuff. Isotopic compositions of fracture-filling and rock matrix minerals in the Apache Leap tuff, near Superior, Arizona were concordant with geothermal temperatures and in equilibrium with water isotopically similar to present-day meteoric water and groundwater. Oxygen and carbon isotope ratios of fracture-filling, in unsaturated fractured tuff, displayed an isotopic gradient believed to result from near-surface isotopic enrichment due to evaporation rather than the effects of rock-water interaction. Oxygen isotope ratios of rock matrix opal samples exhibited an isotopic gradient believed to result from, leaching and reprecipitation of silica at depth. Methods and results can be used to further define primary flowpaths and the movement of water in variably-saturated fractured rock. 71 refs., 23 figs., 3 tabs.

Influence of uranium dioxide nonstoichiometric oxygen on the work function of Mo(110) single crystal

International Nuclear Information System (INIS)

Bekmukhabetov, E.S.; Dzhajmurzin, A.A.; Imanbekov, Zh.Zh.

1985-01-01

The influence of the uranium dioxide nonstoichiometric oxygen on the work function of a Mo(110) single crystal has been studied. When the surface diffusion of oxygen on the tested surface takes place, the work function is shown to decrease and, subsequently, to increase until it becomes stable. The dependence of the work function on the temperature of the specimen in the range of 1600-1900 K with a minimum at 1730 K has been found. The minimum is attributed to the dipole layer formation

Selective and Stable Ethylbenzene Dehydrogenation to Styrene over Nanodiamonds under Oxygen-lean Conditions.

Science.gov (United States)

Diao, Jiangyong; Feng, Zhenbao; Huang, Rui; Liu, Hongyang; Hamid, Sharifah Bee Abd; Su, Dang Sheng

2016-04-07

For the first time, significant improvement of the catalytic performance of nanodiamonds was achieved for the dehydrogenation of ethylbenzene to styrene under oxygen-lean conditions. We demonstrated that the combination of direct dehydrogenation and oxidative dehydrogenation indeed occurred on the nanodiamond surface throughout the reaction system. It was found that the active sp(2)-sp(3) hybridized nanostructure was well maintained after the long-term test and the active ketonic carbonyl groups could be generated in situ. A high reactivity with 40% ethylbenzene conversion and 92% styrene selectivity was obtained over the nanodiamond catalyst under oxygen-lean conditions even after a 240 h test, demonstrating the potential of this procedure for application as a promising industrial process for the ethylbenzene dehydrogenation to styrene without steam protection. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Simulation of surface profile formation in oxygen laser cutting of mild steel due to combustion cycles

Energy Technology Data Exchange (ETDEWEB)

Ermolaev, G V; Kovalev, O B [Khristianovich Institute of Theoretical and Applied Mechanics, Siberian Branch of Russian Academy of Sciences, Institutskaya Str 4/1, Novosibirsk, 630090 (Russian Federation)

2009-09-21

A physicomathematical model of cyclic iron combustion in an oxygen flow during oxygen laser cutting of metal sheets is developed. The combustion front is set into motion by focused laser radiation and a heterogeneous oxidation reaction in oxygen. The burning rate is limited by oxygen supply from the gas phase towards the metal surface, and the interface motion depends on the local temperature. A 3D numerical simulation predicts wavy structures on the metal surface; their linear sizes depend on the scanning speed of the laser beam, the thickness of the produced liquid oxide film and the parameters of the oxygen jet flow. Simulation results help in understanding the mechanism of striation formation during oxygen gas-laser cutting of mild steel and are in qualitative agreement with experimental findings.

Oxygen chemisorption on a stepped Ru (approx.001) crystal

International Nuclear Information System (INIS)

Parrott, S.L.; Praline, G.; Koel, B.E.; White, J.M.; Taylor, T.N.

1979-01-01

The 300 K chemisorption of oxygen on a stepped Ru (approx.001) single crystal [17(001) x (100)] gives 2 x 2 complete half-order, 1 x 2 complete or incomplete half-order, and 1 x 1 integral-order LEED patterns depending on oxygen exposure and sample annealing. The corresponding relative AES oxygen signals are 0.25, 0.50, and 1.0, respectively. Under certain surface conditions, the presence of the steps is seen to break the threefold degenerate growth habit of 1 x 2 domains. The 1 x 1 pattern forms at 300 K only after lengthy exposure at relatively high pressure (10 -5 Torr) and is stable to 600 K. Prolonged exposure gives rise to relative AES oxygen signals greater than unity suggesting penetration into the subsurface region

Dual-band frequency selective surface with large band separation and stable performance

Science.gov (United States)

Zhou, Hang; Qu, Shao-Bo; Peng, Wei-Dong; Lin, Bao-Qin; Wang, Jia-Fu; Ma, Hua; Zhang, Jie-Qiu; Bai, Peng; Wang, Xu-Hua; Xu, Zhuo

2012-05-01

A new technique of designing a dual-band frequency selective surface with large band separation is presented. This technique is based on a delicately designed topology of L- and Ku-band microwave filters. The two band-pass responses are generated by a capacitively-loaded square-loop frequency selective surface and an aperture-coupled frequency selective surface, respectively. A Faraday cage is located between the two frequency selective surface structures to eliminate undesired couplings. Based on this technique, a dual-band frequency selective surface with large band separation is designed, which possesses large band separation, high selectivity, and stable performance under various incident angles and different polarizations.

Stable oxygen isotope variability in two contrasting glacier river catchments in Greenland

DEFF Research Database (Denmark)

Yde, Jacob C.; Knudsen, Niels T.; Steffensen, Jørgen P.

2016-01-01

the Greenland Ice Sheet (GrIS). At the Mittivakkat Gletscher river, a small river draining a local temperate glacier in southeast Greenland, diurnal oscillations in δ18O occurred with a 3 h time lag to the diurnal oscillations in run-off. The mean annual δ18O was -14.68±0.18‰ during the peak flow period...... event. Overall, a comparison of the δ18O compositions from glacial river water in Greenland shows distinct differences between water draining local glaciers and ice caps (between -23.0 and -13.7 ‰) and the GrIS (between -29.9 and -23.2 ‰). This study demonstrates that water isotope analyses can be used......Analysis of stable oxygen isotope (δ18O) characteristics is a useful tool to investigate water provenance in glacier river systems. In order to attain knowledge on the diversity of δ18O variations in Greenlandic rivers, we examined two contrasting glacierised catchments disconnected from...

Redox functionality mediated by adsorbed oxygen on a Pd oxide film over a Pd(100) thin structure: a first-principles study

International Nuclear Information System (INIS)

Kusakabe, K; Ikuno, Y k; Nagara, H; Harada, K

2009-01-01

Stable oxygen sites on a PdO film over a Pd(100) thin structure with a (√5x√5)R27 o surface unit cell are determined using the first-principles electronic structure calculations with the generalized gradient approximation. The adsorbed monatomic oxygen goes to a site bridging two twofold-coordinated Pd atoms or to a site bridging a twofold-coordinated Pd atom and a fourfold-coordinated Pd atom. Estimated reaction energies of CO oxidation by reduction of the oxidized PdO film and N 2 O reduction mediated by oxidation of the PdO film are both exothermic. Motion of the adsorbed oxygen atom between the two stable sites is evaluated using the nudged elastic band method, where an energy barrier for a translational motion of the adsorbed oxygen may become ∼0.45 eV, which is low enough to allow fluxionality of the surface oxygen at high temperatures. The oxygen fluxionality is allowed by the existence of twofold-coordinated Pd atoms on the PdO film, whose local structure has a similarity to that of Pd catalysts for the Suzuki-Miyaura cross-coupling. Although NO x (including NO 2 and NO) reduction is not always catalyzed by the PdO film only, we conclude that continual redox reactions may happen mediated by oxygen-adsorbed PdO films over a Pd surface structure, when the influx of NO x and CO continues, and when the reaction cycle is kept on a well-designed oxygen surface.

Coolant Chemistry Control: Oxygen Mass Transport in Lead Bismuth Eutectic

International Nuclear Information System (INIS)

Weisenburger, A.; Mueller, G.; Bruzzese, C.; Glass, A.

2015-01-01

In lead-bismuth cooled transmutation systems, oxygen, dissolved in the coolant at defined quantities, is required for stable long-term operation by assuring the formation of protective oxide scales on structural steel surfaces. Extracted oxygen must be permanently delivered to the system and distributed in the entire core. Therefore, coolant chemistry control involves detailed knowledge on oxygen mass transport. Beside the different flow regimes a core might have stagnant areas at which oxygen delivery can only be realised by diffusion. The difference between oxygen transport in flow paths and in stagnant zones is one of the targets of such experiments. To investigate oxygen mass transport in flowing and stagnant conditions, a dedicated facility was designed based on computational fluid dynamics (CFD). CFD also was applied to define the position of oxygen sensors and ultrasonic Doppler velocimetry transducers for flow measurements. This contribution will present the test facility, design relevant CFD calculations and results of first tests performed. (authors)

Evolution of Oxygen Deficiency Center on Fused Silica Surface Irradiated by Ultraviolet Laser and Posttreatment

Directory of Open Access Journals (Sweden)

Hai-Bing Lü

2014-01-01

Full Text Available Evolution of oxygen deficiency centers (ODCs on a fused silica surface irradiated using a 355 nm ultraviolet (UV laser beam in both vacuum and atmospheric conditions was quantitatively studied using photoluminescence and X-ray photoelectron spectroscopy. When the fusedsilica surface was exposed to the UV laser in vacuum, the laser damage threshold was decreased whereas the concentration of the ODCs was increased. For the fuse silica operated under the high power lasers, creation of ODCs on their surface resulted from the UV laser irradiation, and this is more severe in a high vacuum. The laser fluence and/or laser intensity have significant effects on the increase of the ODCs concentration. The ODCs can be effectively repaired using postoxygen plasma treatment and UV laser irradiation in an excessive oxygen environment. Results also demonstrated that the “gain” and “loss” of oxygen at the silica surface is a reversible and dynamic process.

Dual-band frequency selective surface with large band separation and stable performance

International Nuclear Information System (INIS)

Zhou Hang; Qu Shao-Bo; Lin Bao-Qin; Wang Jia-Fu; Ma Hua; Zhang Jie-Qiu; Peng Wei-Dong; Bai Peng; Wang Xu-Hua; Xu Zhuo

2012-01-01

A new technique of designing a dual-band frequency selective surface with large band separation is presented. This technique is based on a delicately designed topology of L- and Ku-band microwave filters. The two band-pass responses are generated by a capacitively-loaded square-loop frequency selective surface and an aperture-coupled frequency selective surface, respectively. A Faraday cage is located between the two frequency selective surface structures to eliminate undesired couplings. Based on this technique, a dual-band frequency selective surface with large band separation is designed, which possesses large band separation, high selectivity, and stable performance under various incident angles and different polarizations. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

Effects of atomic oxygen irradiation on the surface properties of phenolphthalein poly(ether sulfone)

International Nuclear Information System (INIS)

Pei Xianqiang; Li Yan; Wang Qihua; Sun Xiaojun

2009-01-01

To study the effects of low earth orbit environment on the surface properties of polymers, phenolphthalein poly(ether sulfone) (PES-C) blocks were irradiated by atomic oxygen in a ground-based simulation system. The surface properties of the pristine and irradiated blocks were studied by attenuated total-reflection FTIR (FTIR-ATR), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM). It was found that atomic oxygen irradiation induced the destruction of PES-C molecular chains, including the scission and oxidation of PES-C molecular chains, as evidenced by FTIR and XPS results. The scission of PES-C molecular chains decreased the relative concentration of C in the surface, while the oxidation increased the relative concentration of O in the surface. The changes in surface chemical structure and composition also changed the surface morphology of the block, which shifted from smooth structure before irradiation to 'carpet-like' structure after irradiation

Effect of annealing ambience on the formation of surface/bulk oxygen vacancies in TiO2 for photocatalytic hydrogen evolution

Science.gov (United States)

Hou, Lili; Zhang, Min; Guan, Zhongjie; Li, Qiuye; Yang, Jianjun

2018-01-01

The surface and bulk oxygen vacancy have a prominent effect on the photocatalytic performance of TiO2. In this study, TiO2 possessing different types and concentration of oxygen vacancies were prepared by annealing nanotube titanic acid (NTA) at various temperatures in air or vacuum atmosphere. TiO2 with the unitary bulk single-electron-trapped oxygen vacancies (SETOVs) formed when NTA were calcined in air. Whereas, TiO2 with both bulk and surface oxygen vacancies were obtained when NTA were annealed in vacuum. The series of TiO2 with different oxygen vacancies were systematically characterized by TEM, XRD, PL, XPS, ESR, and TGA. The PL and ESR analysis verified that surface oxygen vacancies and more bulk oxygen vacancies could form in vacuum atmosphere. Surface oxygen vacancies can trap electron and hinder the recombination of photo-generated charges, while bulk SETOVs act as the recombination center. The surface or bulk oxygen vacancies attributed different roles on the photo-absorbance and activity, leading that the sample of NTA-A400 displayed higher hydrogen evolution rate under UV light, whereas NTA-V400 displayed higher hydrogen evolution rate under visible light because bulk SETOVs can improve visible light absorption because sub-band formed by bulk SETOVs prompted the secondary transition of electron excited.

Stable water isotope and surface heat flux simulation using ISOLSM: Evaluation against in-situ measurements

KAUST Repository

Cai, Mick Y.; Wang, Lixin; Parkes, Stephen; Strauss, Josiah; McCabe, Matthew; Evans, Jason P.; Griffiths, Alan D.

2015-01-01

The stable isotopes of water are useful tracers of water sources and hydrological processes. Stable water isotope-enabled land surface modeling is a relatively new approach for characterizing the hydrological cycle, providing spatial and temporal variability for a number of hydrological processes. At the land surface, the integration of stable water isotopes with other meteorological measurements can assist in constraining surface heat flux estimates and discriminate between evaporation (E) and transpiration (T). However, research in this area has traditionally been limited by a lack of continuous in-situ isotopic observations. Here, the National Centre for Atmospheric Research stable isotope-enabled Land Surface Model (ISOLSM) is used to simulate the water and energy fluxes and stable water isotope variations. The model was run for a period of one month with meteorological data collected from a coastal sub-tropical site near Sydney, Australia. The modeled energy fluxes (latent heat and sensible heat) agreed reasonably well with eddy covariance observations, indicating that ISOLSM has the capacity to reproduce observed flux behavior. Comparison of modeled isotopic compositions of evapotranspiration (ET) against in-situ Fourier Transform Infrared spectroscopy (FTIR) measured bulk water vapor isotopic data (10. m above the ground), however, showed differences in magnitude and temporal patterns. The disparity is due to a small contribution from local ET fluxes to atmospheric boundary layer water vapor (~1% based on calculations using ideal gas law) relative to that advected from the ocean for this particular site. Using ISOLSM simulation, the ET was partitioned into E and T with 70% being T. We also identified that soil water from different soil layers affected T and E differently based on the simulated soil isotopic patterns, which reflects the internal working of ISOLSM. These results highlighted the capacity of using the isotope-enabled models to discriminate

Stable water isotope and surface heat flux simulation using ISOLSM: Evaluation against in-situ measurements

KAUST Repository

Cai, Mick Y.

2015-04-01

The stable isotopes of water are useful tracers of water sources and hydrological processes. Stable water isotope-enabled land surface modeling is a relatively new approach for characterizing the hydrological cycle, providing spatial and temporal variability for a number of hydrological processes. At the land surface, the integration of stable water isotopes with other meteorological measurements can assist in constraining surface heat flux estimates and discriminate between evaporation (E) and transpiration (T). However, research in this area has traditionally been limited by a lack of continuous in-situ isotopic observations. Here, the National Centre for Atmospheric Research stable isotope-enabled Land Surface Model (ISOLSM) is used to simulate the water and energy fluxes and stable water isotope variations. The model was run for a period of one month with meteorological data collected from a coastal sub-tropical site near Sydney, Australia. The modeled energy fluxes (latent heat and sensible heat) agreed reasonably well with eddy covariance observations, indicating that ISOLSM has the capacity to reproduce observed flux behavior. Comparison of modeled isotopic compositions of evapotranspiration (ET) against in-situ Fourier Transform Infrared spectroscopy (FTIR) measured bulk water vapor isotopic data (10. m above the ground), however, showed differences in magnitude and temporal patterns. The disparity is due to a small contribution from local ET fluxes to atmospheric boundary layer water vapor (~1% based on calculations using ideal gas law) relative to that advected from the ocean for this particular site. Using ISOLSM simulation, the ET was partitioned into E and T with 70% being T. We also identified that soil water from different soil layers affected T and E differently based on the simulated soil isotopic patterns, which reflects the internal working of ISOLSM. These results highlighted the capacity of using the isotope-enabled models to discriminate

Can oxygen stable isotopes be used to track precipitation moisture source in vascular plant-dominated peatlands?

Science.gov (United States)

Amesbury, Matthew J.; Charman, Dan J.; Newnham, Rewi M.; Loader, Neil J.; Goodrich, Jordan; Royles, Jessica; Campbell, David I.; Keller, Elizabeth D.; Baisden, W. Troy; Roland, Thomas P.; Gallego-Sala, Angela V.

2015-11-01

Variations in the isotopic composition of precipitation are determined by fractionation processes which occur during temperature- and humidity-dependent phase changes associated with evaporation and condensation. Oxygen stable isotope ratios have therefore been frequently used as a source of palaeoclimate data from a variety of proxy archives, which integrate this signal over time. Applications from ombrotrophic peatlands, where the source water used in cellulose synthesis is derived solely from precipitation, have been mostly limited to Northern Hemisphere Sphagnum-dominated bogs, with few in the Southern Hemisphere or in peatlands dominated by vascular plants. New Zealand (NZ) provides an ideal location to undertake empirical research into oxygen isotope fractionation in vascular peatlands because single taxon analysis can be easily carried out, in particular using the preserved root matrix of the restionaceous wire rush (Empodisma spp.) that forms deep Holocene peat deposits throughout the country. Furthermore, large gradients are observed in the mean isotopic composition of precipitation across NZ, caused primarily by the relative influence of different climate modes. Here, we test whether δ18O of Empodisma α-cellulose from ombrotrophic restiad peatlands in NZ can provide a methodology for developing palaeoclimate records of past precipitation δ18O. Surface plant, water and precipitation samples were taken over spatial (six sites spanning >10° latitude) and temporal (monthly measurements over one year) gradients. A link between the isotopic composition of root-associated water, the most likely source water for plant growth, and precipitation in both datasets was found. Back-trajectory modelling of precipitation moisture source for rain days prior to sampling showed clear seasonality in the temporal data that was reflected in root-associated water. The link between source water and plant cellulose was less clear, although mechanistic modelling predicted mean

Fractional surface termination of diamond by electrochemical oxidation.

Science.gov (United States)

Hoffmann, René; Obloh, Harald; Tokuda, Norio; Yang, Nianjun; Nebel, Christoph E

2012-01-10

The crystalline form of sp(3)-hybridized carbon, diamond, offers various electrolyte-stable surface terminations. The H-termination-selective attachment of nitrophenyl diazonium, imaged by AFM, shows that electrochemical oxidation can control the fractional hydrogen/oxygen surface termination of diamond on the nanometer scale. This is of particular interest for all applications relying on interfacial electrochemistry, especially for biointerfaces.

Interaction of hydrogen and oxygen with bulk defects and surfaces of metals

International Nuclear Information System (INIS)

Besenbacher, F.

1994-05-01

The thesis deals with the interaction of hydrogen with defects in metals and the interaction of hydrogen and oxygen with metal surfaces studied by ion-beam techniques and scanning tunneling microscopy (STM), respectively. The first part of the thesis discusses the interaction of hydrogen with simple defects in transition metals. The trap-binding enthalpies and the lattice location of hydrogen trapped to vacancies have been determined, and an extremely simple and versatile picture of the hydrogen-metal interaction has evolved, in which the trap strength is mainly determined by the local electron density. Any dilution of the lattice will lead to a trap, vacancies and voids being the strongest trap. It is found that hydrogen trapped to vacancies in fcc metals is quantum-mechanically delocalized, and the excitation energies for the hydrogen in the vacancy potential are a few MeV only. The interaction of hydrogen with metal surfaces is studied by the transmission channeling (TC) technique. It is found that hydrogen chemisorbs in the highest-coordinated sites on the surfaces, and that there is a direct relationship between the hydrogen-metal bond length and the coordination number for the hydrogen. In the final part of the thesis the dynamics of the chemisorption process for oxygen and hydrogen on metal surfaces is studied by STM, a fascinating and powerful technique for exploring the atomic-scale realm of surfaces. It is found that there is a strong coupling between the chemisorption process and the distortion of the metal surface. The adsorbates induce a surface reconstruction, i.e. metal-metal bond breaks and metal-adsorbate bounds form. Whereas hydrogen interacts weakly with the metals and induces reconstructions where only nnn metals bonds are broken, oxygen interacts strongly with the metal, and the driving force for the O-induced reconstructions appears to be the formation of low-coordinated metal-O rows, formed by breaking of nn metal bonds. Finally it is shown

Stable isotope analysis

International Nuclear Information System (INIS)

Tibari, Elghali; Taous, Fouad; Marah, Hamid

2014-01-01

This report presents results related to stable isotopes analysis carried out at the CNESTEN DASTE in Rabat (Morocco), on behalf of Senegal. These analyzes cover 127 samples. These results demonstrate that Oxygen-18 and Deuterium in water analysis were performed by infrared Laser spectroscopy using a LGR / DLT-100 with Autosampler. Also, the results are expressed in δ values (‰) relative to V-SMOW to ± 0.3 ‰ for oxygen-18 and ± 1 ‰ for deuterium.

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

Science.gov (United States)

Jeng, Frank F.

2009-01-01

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

Hydrogen and oxygen stable isotope ratios of milk in the United States.

Science.gov (United States)

Chesson, Lesley A; Valenzuela, Luciano O; O'Grady, Shannon P; Cerling, Thure E; Ehleringer, James R

2010-02-24

Models of hydrogen and oxygen incorporation in human tissues recognize the impact of geographic location on the isotopic composition of fluid intake, but inputs can include nonlocal beverages, such as milk. Milk and cow drinking water were collected from dairies, and commercially available milk was purchased from supermarkets and fast food restaurants. It was hypothesized that milk water delta(2)H and delta(18)O values record geographic location information. Correlations between milk water isotope ratios and purchase location tap water were significant. However, the amount of variation in milk delta(2)H and delta(18)O values explained by tap water was low, suggesting a single estimation of fluid input isotope ratios may not always be adequate in studies. The delta(2)H and delta(18)O values of paired milk and cow drinking water were related, suggesting potential for geographical origin assignment using stable isotope analysis. As an application example, milk water delta(18)O values were used to predict possible regions of origin for restaurant samples.

Fabrication and characterization of stable superhydrophobic surface with good friction-reducing performance on Al foil

Energy Technology Data Exchange (ETDEWEB)

Li, Peipei [Key Laboratory of Ministry of Education for Special Functional Materials, Henan University, Kaifeng 475004 (China); Chen, Xinhua, E-mail: xuc0374@hotmail.com [College of Chemistry and Chemical Engineering, Xuchang University, Xuchang 461000 (China); Yang, Guangbin; Yu, Laigui [Key Laboratory of Ministry of Education for Special Functional Materials, Henan University, Kaifeng 475004 (China); Zhang, Pingyu, E-mail: pingyu@henu.edu.cn [Key Laboratory of Ministry of Education for Special Functional Materials, Henan University, Kaifeng 475004 (China)

2014-05-01

Graphical abstract: A lotus-leaf-like hierarchical structure was successfully created on Al foil by a facile three-step solution–immersion method. As-obtained etched-immersed Al/STA rough surface contains interconnected convex–concave micro-structure and uniformly distributed nano-sheets that endow the surface with excellent superhydrophobicity (WCA: 164.2°; WSA: below 5°). Besides, the as-prepared etched-immersed Al/STA superhydrophobic surface on Al foil exhibits good friction-reducing ability and stable superhydrophobicity. - Highlights: • A stable superhydrophobic surface was created on aluminum foil by a facile three-step solution–immersion method. • A lotus-leaf-like hierarchical structure consists of interconnected convex–concave micro-structure and uniformly distributed nano-sheets has been constructed on the aluminum surface. • The superhydrophobic surfaces on aluminum substrate showing effective friction-reducing performance and self-cleaning ability. - Abstract: A lotus-leaf-like hierarchical structure with superhydrophobicity was created on Al foil by a facile three-step solution–immersion method involving etching in hydrochloric acid solution and immersing in hot water as well as surface-modification by stearic acid (denoted as STA). As-prepared etched-immersed Al/STA rough surface was characterized by means of scanning electron microscopy and X-ray photoelectron spectroscopy. Moreover, the water contact angles and water sliding angles of as-prepared etched-immersed Al/STA rough surface were measured, and the friction-reducing performance and self-cleaning ability of the as-prepared surface were also evaluated. Results indicate that the etched-immersed Al/STA rough surface consists of interconnected convex–concave micro-structure and uniformly distributed nano-sheets. Besides, it exhibits stable superhydrophobicity and good friction-reducing ability. Namely, it has a contact angle of water as high as 164.2° and a water sliding

Fabrication and characterization of stable superhydrophobic surface with good friction-reducing performance on Al foil

International Nuclear Information System (INIS)

Li, Peipei; Chen, Xinhua; Yang, Guangbin; Yu, Laigui; Zhang, Pingyu

2014-01-01

Graphical abstract: A lotus-leaf-like hierarchical structure was successfully created on Al foil by a facile three-step solution–immersion method. As-obtained etched-immersed Al/STA rough surface contains interconnected convex–concave micro-structure and uniformly distributed nano-sheets that endow the surface with excellent superhydrophobicity (WCA: 164.2°; WSA: below 5°). Besides, the as-prepared etched-immersed Al/STA superhydrophobic surface on Al foil exhibits good friction-reducing ability and stable superhydrophobicity. - Highlights: • A stable superhydrophobic surface was created on aluminum foil by a facile three-step solution–immersion method. • A lotus-leaf-like hierarchical structure consists of interconnected convex–concave micro-structure and uniformly distributed nano-sheets has been constructed on the aluminum surface. • The superhydrophobic surfaces on aluminum substrate showing effective friction-reducing performance and self-cleaning ability. - Abstract: A lotus-leaf-like hierarchical structure with superhydrophobicity was created on Al foil by a facile three-step solution–immersion method involving etching in hydrochloric acid solution and immersing in hot water as well as surface-modification by stearic acid (denoted as STA). As-prepared etched-immersed Al/STA rough surface was characterized by means of scanning electron microscopy and X-ray photoelectron spectroscopy. Moreover, the water contact angles and water sliding angles of as-prepared etched-immersed Al/STA rough surface were measured, and the friction-reducing performance and self-cleaning ability of the as-prepared surface were also evaluated. Results indicate that the etched-immersed Al/STA rough surface consists of interconnected convex–concave micro-structure and uniformly distributed nano-sheets. Besides, it exhibits stable superhydrophobicity and good friction-reducing ability. Namely, it has a contact angle of water as high as 164.2° and a water sliding

Simultaneous modulation of surface composition, oxygen vacancies and assembly in hierarchical Co3O4 mesoporous nanostructures for lithium storage and electrocatalytic oxygen evolution

DEFF Research Database (Denmark)

Sun, Hongyu; Zhao, Yanyan; Mølhave, Kristian

2017-01-01

in superior electrochemical properties when used as the anode materials for lithium-ion batteries and as an electrocatalyst for the oxygen evolution reaction. The excellent electrochemical performance is attributed to the synergistic effects of novel hierarchical morphology, crystal structure of the active...... materials, the improvement of intrinsic conductivity and inner surface area induced by the oxygen vacancies. The present strategy not only provides a facile method to assemble novel hierarchical architectures, but also paves a way to control surface structures (chemical composition and crystal defects...

Universality in Oxygen Evolution Electrocatalysis on Oxide Surfaces

DEFF Research Database (Denmark)

Man, Isabela Costinela; Su, Hai-Yan; Vallejo, Federico Calle

2011-01-01

with the computational standard hydrogen electrode (SHE) model. We showed that by the discovery of a universal scaling relation between the adsorption energies of HOO* vs HO*, it is possible to analyze the reaction free energy diagrams of all the oxides in a general way. This gave rise to an activity volcano......Trends in electrocatalytic activity of the oxygen evolution reaction (OER) are investigated on the basis of a large database of HO* and HOO* adsorption energies on oxide surfaces. The theoretical overpotential was calculated by applying standard density functional theory in combination...

Oxygen termination of homoepitaxial diamond surface by ozone and chemical methods: An experimental and theoretical perspective

Science.gov (United States)

Navas, Javier; Araujo, Daniel; Piñero, José Carlos; Sánchez-Coronilla, Antonio; Blanco, Eduardo; Villar, Pilar; Alcántara, Rodrigo; Montserrat, Josep; Florentin, Matthieu; Eon, David; Pernot, Julien

2018-03-01

Phenomena related with the diamond surface of both power electronic and biosensor devices govern their global behaviour. In particular H- or O-terminations lead to wide variations in their characteristics. To study the origins of such aspects in greater depth, different methods to achieve oxygen terminated diamond were investigated following a multi-technique approach. DFT calculations were then performed to understand the different configurations between the C and O atoms. Three methods for O-terminating the diamond surface were performed: two physical methods with ozone at different pressures, and an acid chemical treatment. X-ray photoelectron spectroscopy, spectroscopic ellipsometry, HRTEM, and EELS were used to characterize the oxygenated surface. Periodic-DFT calculations were undertaken to understand the effect of the different ways in which the oxygen atoms are bonded to carbon atoms on the diamond surface. XPS results showed the presence of hydroxyl or ether groups, composed of simple Csbnd O bonds, and the acid treatment resulted in the highest amount of O on the diamond surface. In turn, ellipsometry showed that the different treatments led to the surface having different optical properties, such as a greater refraction index and extinction coefficient in the case of the sample subjected to acid treatment. TEM analysis showed that applying temperature treatment improved the distribution of the oxygen atoms at the interface and that this generates a thinner amount of oxygen at each position and higher interfacial coverage. Finally, DFT calculations showed both an increase in the number of preferential electron transport pathways when π bonds and ether groups appear in the system, and also the presence of states in the middle of the band gap when there are π bonds, Cdbnd C or Cdbnd O.

Systematic spatial and stoichiometric screening towards understanding the surface of ultrasmall oxygenated silicon nanocrystal

Energy Technology Data Exchange (ETDEWEB)

Niaz, Shanawer, E-mail: shanawersi@gmail.com [Department of Physics, Bilkent University, Ankara 06800 (Turkey); Molecular Engineering Laboratory, at the Department of Physics, University of Patras, Patras, GR-26500 (Greece); Zdetsis, Aristides D.; Koukaras, Emmanuel N. [Molecular Engineering Laboratory, at the Department of Physics, University of Patras, Patras, GR-26500 (Greece); Gülseren, Oǧuz [Department of Physics, Bilkent University, Ankara 06800 (Turkey); Sadiq, Imran [Centre of Excellence in Solid State Physics, University of the Punjab, Lahore (Pakistan)

2016-11-30

Highlights: • Understanding surface science of oxygenated silicon nanocrystals by means of their composition, stoichiometry and spatial distribution. • Drastic change observed in binding energy, localization of frontier orbitals and HOMO-LUMO gap up to 1.48 eV. • Might be a safe alternative of size dependent bandgap tunability. - Abstract: In most of the realistic ab initio and model calculations which have appeared on the emission of light from silicon nanocrystals, the role of surface oxygen has been usually ignored, underestimated or completely ruled out. We investigate theoretically, by density functional theory (DFT/B3LYP) possible modes of oxygen bonding in hydrogen terminated silicon quantum dots using as a representative case of the Si{sub 29} nanocrystal. We have considered Bridge-bonded oxygen (BBO), Doubly-bonded oxygen (DBO), hydroxyl (OH) and Mix of these oxidizing agents. Due to stoichiometry, all comparisons performed are unbiased with respect to composition whereas spatial distribution of oxygen species pointed out drastic change in electronic and cohesive characteristics of nanocrytals. From an overall perspective of this study, it is shown that bridge bonded oxygenated Si nanocrystals accompanied by Mix have higher binding energies and large electronic gap compared to nanocrystals with doubly bonded oxygen atoms. In addition, it is observed that the presence of OH along with BBO, DBO and mixed configurations further lowers electronic gaps and binding energies but trends in same fashion. It is also demonstrated that within same composition, oxidizing constituent, along with their spatial distribution substantially alters binding energy, highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) gap (up to 1.48 eV) and localization of frontier orbitals.

Systematic spatial and stoichiometric screening towards understanding the surface of ultrasmall oxygenated silicon nanocrystal

International Nuclear Information System (INIS)

Niaz, Shanawer; Zdetsis, Aristides D.; Koukaras, Emmanuel N.; Gülseren, Oǧuz; Sadiq, Imran

2016-01-01

Highlights: • Understanding surface science of oxygenated silicon nanocrystals by means of their composition, stoichiometry and spatial distribution. • Drastic change observed in binding energy, localization of frontier orbitals and HOMO-LUMO gap up to 1.48 eV. • Might be a safe alternative of size dependent bandgap tunability. - Abstract: In most of the realistic ab initio and model calculations which have appeared on the emission of light from silicon nanocrystals, the role of surface oxygen has been usually ignored, underestimated or completely ruled out. We investigate theoretically, by density functional theory (DFT/B3LYP) possible modes of oxygen bonding in hydrogen terminated silicon quantum dots using as a representative case of the Si 29 nanocrystal. We have considered Bridge-bonded oxygen (BBO), Doubly-bonded oxygen (DBO), hydroxyl (OH) and Mix of these oxidizing agents. Due to stoichiometry, all comparisons performed are unbiased with respect to composition whereas spatial distribution of oxygen species pointed out drastic change in electronic and cohesive characteristics of nanocrytals. From an overall perspective of this study, it is shown that bridge bonded oxygenated Si nanocrystals accompanied by Mix have higher binding energies and large electronic gap compared to nanocrystals with doubly bonded oxygen atoms. In addition, it is observed that the presence of OH along with BBO, DBO and mixed configurations further lowers electronic gaps and binding energies but trends in same fashion. It is also demonstrated that within same composition, oxidizing constituent, along with their spatial distribution substantially alters binding energy, highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) gap (up to 1.48 eV) and localization of frontier orbitals.

Minimization of gully erosion on reclaimed surface mines using the stable slope and sediment transport computer model

International Nuclear Information System (INIS)

McKenney, R.A.; Gardner, T.G.

1992-01-01

Disequilibrium between slope form and hydrologic and erosion processes on reclaimed surface coal mines in the humid temperate northeastern US, can result in gully erosion and sediment loads which are elevated above natural, background values. Initial sheetwash erosion is surpassed by gully erosion on reclamation sites which are not in equilibrium with post-mining hydrology. Long-term stability can be attained by designing a channel profile which is in equilibrium with the increased peak discharges found on reclaimed surface mines. The Stable Slope and Sediment transport model (SSAST) was developed to design stable longitudinal channel profiles for post-mining hydrologic and erosional processes. SSAST is an event based computer model that calculates the stable slope for a channel segment based on the post-mine hydrology and median grain size of a reclaimed surface mine. Peak discharge, which drives post-mine erosion, is calculated from a 10-year, 24-hour storm using the Soil Conservation Service curve number method. Curve number calibrated for Pennsylvania surface mines are used. Reclamation sites are represented by the rectangle of triangle which most closely fits the shape of the site while having the same drainage area and length. Sediment transport and slope stability are calculated using a modified Bagnold's equation with a correction factor for the irregular particle shapes formed during the mining process. Data from three reclaimed Pennsylvania surface mines were used to calibrate and verify SSAST. Analysis indicates that SSAST can predict longitudinal channel profiles for stable reclamation of surface mines in the humid, temperate northeastern US

Long-term stability of superhydrophilic oxygen plasma-modified single-walled carbon nanotube network surfaces and the influence on ammonia gas detection

Energy Technology Data Exchange (ETDEWEB)

Min, Sungjoon [Department of Biomicrosystem Technology, Korea University, Seoul 136-713 (Korea, Republic of); Kim, Joonhyub [Department of Control and Instrumentation Engineering, Korea University, 2511 Sejong-ro, Sejong City 339-770 (Korea, Republic of); Park, Chanwon [Department of Electrical and Electronic Engineering, Kangwon National University, Chuncheon 200-701 (Korea, Republic of); Jin, Joon-Hyung, E-mail: jj1023@chol.com [Department of Chemical Engineering, Kyonggi University, 154-42 Gwanggyosan-ro, Yeongtong-gu, Suwon-si, Gyeonggi-do 16227 (Korea, Republic of); Min, Nam Ki, E-mail: nkmin@korea.ac.kr [Department of Biomicrosystem Technology, Korea University, Seoul 136-713 (Korea, Republic of)

2017-07-15

Graphical abstract: Superhydrophilic single-walled carbon nanotube obtained by O{sub 2} plasma treatment voluntarily and non-reversibly reverts to a metastable state. This aerobic aging is an essential process to develop a stable carbon nanotube-based sensor. - Highlights: • Superhydrophilic single-walled carbon nanotube network can be obtained by O{sub 2} plasma-based surface modification. • The modified carbon nanotube surface invariably reverts to a metastable state in a non-reversible manner. • Aerobic aging is essential to stabilize the modified carbon nanotube and the carbon nanotube-based sensing device due to minimized sensor-to-sensor variation. - Abstract: Single-walled carbon nanotube (SWCNT) networks are subjected to a low-powered oxygen plasma for the surface modification. Changes in the surface chemical composition and the stability of the plasma-treated SWCNT (p-SWCNT) with aging in air for up to five weeks are studied using X-ray photoelectron spectroscopy (XPS) and contact angle analysis. The contact angle decreases from 120° of the untreated hydrophobic SWCNT to 0° for the superhydrophilic p-SWCNT. Similarly, the ratio of oxygen to carbon (O:C) based on the XPS spectra increases from 0.25 to 1.19, indicating an increase in surface energy of the p-SWCNT. The enhanced surface energy is gradually dissipated and the p-SWCNT network loses the superhydrophilic surface property. However, it never revert to the original hydrophobic surface state but to a metastable hydrophilic state. The aging effect on sensitivity of the p-SWCNT network-based ammonia sensor is investigated to show the importance of the aging process for the stabilization of the p-SWCNT. The best sensitivity for monitoring NH{sub 3} gas is observed with the as-prepared p-SWCNT, and the sensitivity decreases as similar as the p-SWCNT loses its hydrophilicity with time goes by. After a large performance degradation during the aging time for about two weeks, the response

First principles investigation of the activity of thin film Pt, Pd and Au surface alloys for oxygen reduction

DEFF Research Database (Denmark)

Tripkovic, Vladimir; Hansen, Heine Anton; Rossmeisl, Jan

2015-01-01

driving force for surface segregation, diffusion to defects or surface self-assembling. On the basis of stability and activity analysis we conclude that the near surface alloy of Pd in Pt and some PdAu binary and PtPdAu ternary thin films with a controlled amount of Au are the best catalysts for oxygen......Further advances in fuel cell technologies are hampered by kinetic limitations associated with the sluggish cathodic oxygen reduction reaction. We have investigated a range of different formulations of binary and ternary Pt, Pd and Au thin films as electrocatalysts for oxygen reduction. The most...... active binary thin films are near-surface alloys of Pt with subsurface Pd and certain PdAu and PtAu thin films with surface and/or subsurface Au. The most active ternary thin films are with pure metal Pt or Pd skins with some degree of Au in the surface and/or subsurface layer and the near-surface alloys...

Phenol by direct hydroxylation of benzene with nitrous oxide - role of surface oxygen species in the reaction pathways

Energy Technology Data Exchange (ETDEWEB)

Reitzmann, A.; Klemm, E.; Emig, G. [Erlangen-Nuernberg Univ., Erlangen (Germany). Lehrstuhl fuer Technische Chemie 1; Buchholz, S.A.; Zanthoff, H.W. [Bochum Univ. (Germany). Inst. of Technical Chemistry

1998-12-31

Transient experiments in a Temporal Analysis of Products (TAP) Reactor were performed to elucidate the role of surface oyxgen species in the oxidation of benzene to phenol on ZSM-5 type zeolites with nitrous oxide as a selective oxidant. It was shown by puls experiments with nitrous oxide that the mean lifetime of the generated surface oxygen species is between 0.2s at 500 C and about 4.2 s at 400 C. Afterwards the surface oxygen species desorb as molecular oxygen into the gas phase where total oxidation will take place if hydrocarbons are present. Dual puls experiments consisting of a nitrous oxide puls followed by a benzene puls allowed studying the reactivity of the surface oxygen species formed during the first puls. The observation of the phenol formation was impeded due to the strong sorption of phenol. Multipulse experiments were necessary to reach a pseudo steady state phenol yield. (orig.)

The surface structure of SrTiO3 at high temperatures under influence of oxygen

International Nuclear Information System (INIS)

Hesselberth, M. B. S.; Molen, S. J. van der; Aarts, J.

2014-01-01

We use low energy electron microscopy to investigate the structure of the SrTiO 3 (001) surface at elevated temperatures and different oxygen pressures. Upon varying the temperature between 500 °C and 900 °C in oxygen pressures ranging from 10 −9 millibar to 10 −4 millibar, two surface transitions are found to be present. The lower temperature (1 × 1) → (2 × 1) transition that is known to occur in ultrahigh vacuum can be reversed by increasing the oxygen pressure. At higher temperatures, we observe a (2 × 1) → disordered (1 × 1) transition which is irreversible in the experimental parameter range. The observations are expected to have a strong bearing on the growth of interface structures

N- and S-doped high surface area carbon derived from soya chunks as scalable and efficient electrocatalysts for oxygen reduction

Science.gov (United States)

Rana, Moumita; Arora, Gunjan; Gautam, Ujjal K.

2015-02-01

Highly stable, cost-effective electrocatalysts facilitating oxygen reduction are crucial for the commercialization of membrane-based fuel cell and battery technologies. Herein, we demonstrate that protein-rich soya chunks with a high content of N, S and P atoms are an excellent precursor for heteroatom-doped highly graphitized carbon materials. The materials are nanoporous, with a surface area exceeding 1000 m2 g-1, and they are tunable in doping quantities. These materials exhibit highly efficient catalytic performance toward oxygen reduction reaction (ORR) with an onset potential of -0.045 V and a half-wave potential of -0.211 V (versus a saturated calomel electrode) in a basic medium, which is comparable to commercial Pt catalysts and is better than other recently developed metal-free carbon-based catalysts. These exhibit complete methanol tolerance and a performance degradation of merely ˜5% as compared to ˜14% for a commercial Pt/C catalyst after continuous use for 3000 s at the highest reduction current. We found that the fraction of graphitic N increases at a higher graphitization temperature, leading to the near complete reduction of oxygen. It is believed that due to the easy availability of the precursor and the possibility of genetic engineering to homogeneously control the heteroatom distribution, the synthetic strategy is easily scalable, with further improvement in performance.

Is bicarbonate stable in and on the calcite surface?

Science.gov (United States)

Andersson, M. P.; Rodriguez-Blanco, J. D.; Stipp, S. L. S.

2016-03-01

We have used density functional theory with the COSMO-RS implicit solvent model to predict the pKa for the deprotonation of bicarbonate to carbonate, i.e. HCO3- CO32- + H+, when HCO3- is included in, and adsorbed on, a calcite surface. We have used cluster models (80-100 atoms) to represent the flat {10.4} surface, acute steps, obtuse steps, two types of kinks on the acute step and two types of kinks on the obtuse steps. Based on the predicted pKa values, which range from -6.0 to 2.4 depending on the surface site, we conclude that bicarbonate deprotonates to carbonate when it is in calcite even when pH in solution is very low. This is true for all surface sites, even for solutions where 2.4 < pH < 6.35, where H2CO30 is the dominant dissolved species. When bicarbonate is adsorbed on calcite, the predicted pKa for deprotonation is 7.5, which is ∼3 pH units lower than in aqueous solution, 10.35. This means that adsorbed carbonate is stable even when the concentration of dissolved CO32- is several orders of magnitude lower. This has a significant effect on surface charge and thus the behaviour of the calcite surface. Our results help explain the potential determining behaviour of the carbonate species in calcite-water systems, particularly in the pH range where the bicarbonate species dominates in water and where the carbonate species dominates at the surface, i.e. when 7.5 < pH < 10.35. Our atomic scale data for the various calcite surface sites provide the needed input to improve and constrain surface complexation modelling and are especially useful for predicting behaviour in systems where experiments are difficult or impossible, such as at high temperature and pressure.

Physically and chemically stable ionic liquid-infused textured surfaces showing excellent dynamic omniphobicity

Energy Technology Data Exchange (ETDEWEB)

Miranda, Daniel F.; Urata, Chihiro; Masheder, Benjamin; Dunderdale, Gary J.; Hozumi, Atsushi, E-mail: a.hozumi@aist.go.jp [National Institute of Advanced Industrial Science and Technology (AIST), 2266-98, Anagahora, Shimo-Shidami, Moriyama-ku, Nagoya, Aichi 463-8560 (Japan); Yagihashi, Makoto [Nagoya Municipal Industrial Research Institute, Rokuban, Atsuta-ku, Nagoya 456-0058 (Japan)

2014-05-01

A fluorinated and hydrophobic ionic liquid (IL), 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide, effectively served as an advantageous lubricating liquid for the preparation of physically and chemically stable omniphobic surfaces based on slippery liquid-infused porous surfaces. Here, we used particulate microstructures as supports, prepared by the chemical vapor deposition of 1,3,5,7-tetramethylcyclotetrasiloxane and subsequent surface modification with (3-aminopropyl)triethoxysilane. Confirmed by SEM and contact angle measurements, the resulting IL-infused microtextured surfaces are smooth and not only water but also various low surface tension liquids can easily slide off at low substrate tilt angles of <5°, even after exposure to high temperature, vacuum, and UV irradiation.

Physically and chemically stable ionic liquid-infused textured surfaces showing excellent dynamic omniphobicity

Directory of Open Access Journals (Sweden)

Daniel F. Miranda

2014-05-01

Full Text Available A fluorinated and hydrophobic ionic liquid (IL, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl imide, effectively served as an advantageous lubricating liquid for the preparation of physically and chemically stable omniphobic surfaces based on slippery liquid-infused porous surfaces. Here, we used particulate microstructures as supports, prepared by the chemical vapor deposition of 1,3,5,7-tetramethylcyclotetrasiloxane and subsequent surface modification with (3-aminopropyltriethoxysilane. Confirmed by SEM and contact angle measurements, the resulting IL-infused microtextured surfaces are smooth and not only water but also various low surface tension liquids can easily slide off at low substrate tilt angles of <5°, even after exposure to high temperature, vacuum, and UV irradiation.

Evaluation of hydrogen and oxygen impurity levels on silicon surfaces

Energy Technology Data Exchange (ETDEWEB)

Kenny, M.J.; Wielunski, L.S.; Netterfield, R.P.; Martin, P.J.; Leistner, A. [Commonwealth Scientific and Industrial Research Organisation (CSIRO), Lindfield, NSW (Australia). Div. of Applied Physics

1996-12-31

This paper reports on surface analytical techniques used to quantify surface concentrations of impurities such as oxygen and hydrogen. The following analytical techniques were used: Rutherford and Backscattering, elastic recoil detection, time-of-flight SIMS, spectroscopic ellipsometry, x-ray photoelectron spectroscopy. The results have shown a spread in thickness of oxide layer, ranging from unmeasurable to 1.6 nm. The data must be considered as preliminary at this stage, but give some insight into the suitability of the techniques and a general idea of the significance of impurities at the monolayer level. These measurements have been carried out on a small number of silicon surfaces both semiconductor grade <111> crystalline material and silicon which has been used in sphere fabrication. 5 refs., 1 fig.

Evaluation of hydrogen and oxygen impurity levels on silicon surfaces

Energy Technology Data Exchange (ETDEWEB)

Kenny, M J; Wielunski, L S; Netterfield, R P; Martin, P J; Leistner, A [Commonwealth Scientific and Industrial Research Organisation (CSIRO), Lindfield, NSW (Australia). Div. of Applied Physics

1997-12-31

This paper reports on surface analytical techniques used to quantify surface concentrations of impurities such as oxygen and hydrogen. The following analytical techniques were used: Rutherford and Backscattering, elastic recoil detection, time-of-flight SIMS, spectroscopic ellipsometry, x-ray photoelectron spectroscopy. The results have shown a spread in thickness of oxide layer, ranging from unmeasurable to 1.6 nm. The data must be considered as preliminary at this stage, but give some insight into the suitability of the techniques and a general idea of the significance of impurities at the monolayer level. These measurements have been carried out on a small number of silicon surfaces both semiconductor grade <111> crystalline material and silicon which has been used in sphere fabrication. 5 refs., 1 fig.

Comparison of oxygen liquefaction methods for use on the Martian surface

Science.gov (United States)

Johnson, W. L.; Hauser, D. M.; Plachta, D. W.; Wang, X.-Y. J.; Banker, B. F.; Desai, P. S.; Stephens, J. R.; Swanger, A. M.

2018-03-01

In order to use oxygen that is produced on the surface of Mars from In-Situ production processes in a chemical propulsion system, the oxygen must first be converted from vapor phase to liquid phase and then stored within the propellant tanks of the propulsions system. There are multiple ways that this can be accomplished, from simply attaching a liquefaction system onto the propellant tanks to carrying separate tanks for liquefaction and storage of the propellant and loading just prior to launch (the way that traditional rocket launches occur on Earth). A study was done into these various methods by which the oxygen (and methane) could be liquefied and stored on the Martian surface. Five different architectures or cycles were considered: Tube-on-Tank (also known as Broad Area Cooling or Distributed Refrigeration), Tube-in-Tank (also known as Integrated Refrigeration and Storage), a modified Linde open liquefaction/refrigeration cycle, the direct mounting of a pulse tube cryocooler onto the tank, and an in-line liquefier at ambient pressure. Models of each architecture were developed to give insight into the performance and losses of each of the options. The results were then compared across eight categories: Mass, Power (both input and heat rejection), Operability, Cost, Manufacturability, Reliability, Volume-ility, and Scalability. The result was that Tube-on-Tank and Tube-in-Tank architectures were the most attractive solutions, with NASA's engineering management choosing to pursue tube on tank development rather than further differentiate the two. As a result NASA is focusing its Martian surface liquefaction activities and technology development on Tube-on-Tank liquefaction cycles.

Untangling surface oxygen exchange effects in YBa2Cu3O6+x thin films by electrical conductivity relaxation.

Science.gov (United States)

Cayado, P; Sánchez-Valdés, C F; Stangl, A; Coll, M; Roura, P; Palau, A; Puig, T; Obradors, X

2017-05-31

The kinetics of oxygen incorporation (in-diffusion process) and excorporation (out-diffusion process), in YBa 2 Cu 3 O 6+x (YBCO) epitaxial thin films prepared using the chemical solution deposition (CSD) methodology by the trifluoroacetate route, was investigated by electrical conductivity relaxation measurements. We show that the oxygenation kinetics of YBCO films is limited by the surface exchange process of oxygen molecules prior to bulk diffusion into the films. The analysis of the temperature and oxygen partial pressure influence on the oxygenation kinetics has drawn a consistent picture of the oxygen surface exchange process enabling us to define the most likely rate determining step. We have also established a strategy to accelerate the oxygenation kinetics at low temperatures based on the catalytic influence of Ag coatings thus allowing us to decrease the oxygenation temperature in the YBCO thin films.

Surface engineered porous silicon for stable, high performance electrochemical supercapacitors

Science.gov (United States)

Oakes, Landon; Westover, Andrew; Mares, Jeremy W.; Chatterjee, Shahana; Erwin, William R.; Bardhan, Rizia; Weiss, Sharon M.; Pint, Cary L.

2013-10-01

Silicon materials remain unused for supercapacitors due to extreme reactivity of silicon with electrolytes. However, doped silicon materials boast a low mass density, excellent conductivity, a controllably etched nanoporous structure, and combined earth abundance and technological presence appealing to diverse energy storage frameworks. Here, we demonstrate a universal route to transform porous silicon (P-Si) into stable electrodes for electrochemical devices through growth of an ultra-thin, conformal graphene coating on the P-Si surface. This graphene coating simultaneously passivates surface charge traps and provides an ideal electrode-electrolyte electrochemical interface. This leads to 10-40X improvement in energy density, and a 2X wider electrochemical window compared to identically-structured unpassivated P-Si. This work demonstrates a technique generalizable to mesoporous and nanoporous materials that decouples the engineering of electrode structure and electrochemical surface stability to engineer performance in electrochemical environments. Specifically, we demonstrate P-Si as a promising new platform for grid-scale and integrated electrochemical energy storage.

Surface engineered porous silicon for stable, high performance electrochemical supercapacitors

Science.gov (United States)

Oakes, Landon; Westover, Andrew; Mares, Jeremy W.; Chatterjee, Shahana; Erwin, William R.; Bardhan, Rizia; Weiss, Sharon M.; Pint, Cary L.

2013-01-01

Silicon materials remain unused for supercapacitors due to extreme reactivity of silicon with electrolytes. However, doped silicon materials boast a low mass density, excellent conductivity, a controllably etched nanoporous structure, and combined earth abundance and technological presence appealing to diverse energy storage frameworks. Here, we demonstrate a universal route to transform porous silicon (P-Si) into stable electrodes for electrochemical devices through growth of an ultra-thin, conformal graphene coating on the P-Si surface. This graphene coating simultaneously passivates surface charge traps and provides an ideal electrode-electrolyte electrochemical interface. This leads to 10–40X improvement in energy density, and a 2X wider electrochemical window compared to identically-structured unpassivated P-Si. This work demonstrates a technique generalizable to mesoporous and nanoporous materials that decouples the engineering of electrode structure and electrochemical surface stability to engineer performance in electrochemical environments. Specifically, we demonstrate P-Si as a promising new platform for grid-scale and integrated electrochemical energy storage. PMID:24145684

Oxygen configurations in silica

International Nuclear Information System (INIS)

Chelikowsky, James R.; Chadi, D. J.; Binggeli, N.

2000-01-01

We propose a transition state for oxygen in silica. This state is produced by the insertion of an oxygen molecule into the Si-O-Si bond, i.e., it consists of producing a Si-O-O-O-Si bond. This state allows molecular oxygen diffusion in silica without breaking the molecular O 2 bond and it is energetically more stable than a peroxy configuration. This configuration may allow for exchange of molecular oxygen with the oxygen in the silica framework. (c) 2000 The American Physical Society

Surface Passivation for 3-5 Semiconductor Processing: Stable Gallium Sulphide Films by MOCVD

Science.gov (United States)

Macinnes, Andrew N.; Jenkins, Phillip P.; Power, Michael B.; Kang, Soon; Barron, Andrew R.; Hepp, Aloysius F.; Tabib-Azar, Massood

1994-01-01

Gallium sulphide (GaS) has been deposited on GaAs to form stable, insulating, passivating layers. Spectrally resolved photoluminescence and surface recombination velocity measurements indicate that the GaS itself can contribute a significant fraction of the photoluminescence in GaS/GaAs structures. Determination of surface recombination velocity by photoluminescence is therefore difficult. By using C-V analysis of metal-insulator-semiconductor structures, passivation of the GaAs with GaS films is quantified.

Development of novel CO{sub 2}-stable oxygen permeable dual phase membranes for CO{sub 2} capture in an oxy-fuel process

Energy Technology Data Exchange (ETDEWEB)

Luo, Huixia

2012-07-19

The combustion of fossil fuels in power stations with pure oxygen following the oxy-fuel process allows the Sequestration of CO{sub 2}. The pure oxygen needed can be separated from air by oxygen transporting ceramics like single phase perovskites. However, most of the so far developed single phase perovskites have stability problems in a CO{sub 2} containing atmosphere. Dual phase membranes are micro-scale mixtures of an electron conducting phase and an oxygen ion conducting phase and their compositions can be tailored according to practical requirements, which are considered to be promising substitutes for the single phase perovskite materials. In my thesis the issues of phase stability for perovskite-type material with the common composition Ba{sub 0.5}Sr{sub 0.5}Co{sub 0.8}Fe{sub 3-{delta}} (BSCF) as weil as the development of a series of novel CO{sub 2}-stable dual phase membranes were studied. In Chapter 2, the phase stability and permeation behavior of a dead-end BSCF tube membrane in high-purity oxygen at temperatures below 750 C, were elucidated using powder X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDXS), high-angle annular dark-field (HAADF) and scanning transmission electron microscopy (STEM). lt was found that parts of the cubic perovskite BSCF transformed into a hexagonal perovskite Ba{sub 0.5{+-}x}Sr{sub 0.5{+-}x}CoO{sub 3-{delta}} (x {approx} 0.1) and a trigonal mixed oxide Ba{sub 1-x}Sr{sub x}CO{sub 2-y}Fe{sub y}O{sub 5{+-}{delta}} (x {approx} 0.15, y {approx} 0.25) in high-purity oxygen at 750 C. On the other hand, it was found that the partial degradation of cubic BSCF perovskite at 750 C was more pronounced under the strongly oxidizing conditions on the oxygen supply (feed) side than on the oxygen release (permeate) side of the membrane. The structural instability of BSCF is attributed to an oxidation of cobalt from Co{sup 2+} to Co{sup 3+} and Co{sup 4+}, which exhibits an ionic radius that is too small to be tolerated by

Surface coverage of Pt atoms on PtCo nanoparticles and catalytic kinetics for oxygen reduction

Energy Technology Data Exchange (ETDEWEB)

Jiang Rongzhong, E-mail: rongzhong.jiang@us.army.mi [Sensors and Electron Devices Directorate, U.S. Army Research Laboratory, 2800 Powder Mill Road, Adelphi, MD 20783-1197 (United States); Rong, Charles; Chu, Deryn [Sensors and Electron Devices Directorate, U.S. Army Research Laboratory, 2800 Powder Mill Road, Adelphi, MD 20783-1197 (United States)

2011-02-01

The surface coverage of Pt atoms on PtCo nanoparticles and its effect on catalytic kinetics for oxygen reduction were investigated. The PtCo nanoparticles with different surface coverage of Pt atoms were synthesized with various methods, including normal chemical method, microemulsion synthesis, and ultrasound-assisted microemulsion. A model of Pt atoms filling into a spherical nanoparticle was proposed to explain the relationship of surface metal atoms and nanoparticle size. The catalytic activity of the PtCo nano-particles is highly dependent on the synthetic methods, even if they have the same chemical composition. The PtCo nano-particles synthesized with ultrasound-assisted microemulsion showed the highest activity, which is attributed to an increase of active surface coverage of Pt atoms on the metal nanoparticles. The rate of oxygen reduction at 0.5 V (vs. SCE) catalyzed by the PtCo synthesized with ultrasound-assisted micro-emulsion was about four times higher than that of the PtCo synthesized with normal chemical method. As demonstrated with rotating-ring disk electrode measurement, the PtCo nano-particles can catalyze oxygen 4-electron reduction to water without intermediate H{sub 2}O{sub 2} detected.

Novel structures of oxygen adsorbed on a Zr(0001) surface predicted from first principles

Energy Technology Data Exchange (ETDEWEB)

Gao, Bo [State Key Laboratory of Superhard Materials, Jilin University, Changchun, 130012 (China); Beijing computational science research center, Beijing,100084 (China); Wang, Jianyun [State Key Laboratory of Superhard Materials, Jilin University, Changchun, 130012 (China); Lv, Jian [State Key Laboratory of Superhard Materials, Jilin University, Changchun, 130012 (China); College of Materials Science and Engineering, Jilin University, Changchun, 130012 (China); Gao, Xingyu [Laboratory of Computational Physics, Institute of Applied Physics and Computational Mathematics, Beijing, 100088 (China); CAEP Software Center for High Performance Numerical Simulation, Beijing, 100088 (China); Zhao, Yafan [CAEP Software Center for High Performance Numerical Simulation, Beijing, 100088 (China); Wang, Yanchao, E-mail: wyc@calypso.cn [State Key Laboratory of Superhard Materials, Jilin University, Changchun, 130012 (China); Beijing computational science research center, Beijing,100084 (China); College of Materials Science and Engineering, Jilin University, Changchun, 130012 (China); Song, Haifeng, E-mail: song_haifeng@iapcm.ac.cn [Laboratory of Computational Physics, Institute of Applied Physics and Computational Mathematics, Beijing, 100088 (China); CAEP Software Center for High Performance Numerical Simulation, Beijing, 100088 (China); Ma, Yanming [State Key Laboratory of Superhard Materials, Jilin University, Changchun, 130012 (China); Beijing computational science research center, Beijing,100084 (China)

2017-01-30

Highlights: • Two stable structures of O adsorbed on a Zr(0001) surface are predicted with SLAM. • A stable structure of O adsorbed on a Zr(0001) surface is proposed with MLAM. • The calculated work function change is agreement with experimental value. - Abstract: The structures of O atoms adsorbed on a metal surface influence the metal properties significantly. Thus, studying O chemisorption on a Zr surface is of great interest. We investigated O adsorption on a Zr(0001) surface using our newly developed structure-searching method combined with first-principles calculations. A novel structural prototype with a unique combination of surface face-centered cubic (SFCC) and surface hexagonal close-packed (SHCP) O adsorption sites was predicted using a single-layer adsorption model (SLAM) for a 0.5 and 1.0 monolayer (ML) O coverage. First-principles calculations based on the SLAM revealed that the new predicted structures are energetically favorable compared with the well-known SFCC structures for a low O coverage (0.5 and 1.0 ML). Furthermore, on basis of our predicted SFCC + SHCP structures, a new structure within multi-layer adsorption model (MLAM) was proposed to be more stable at the O coverage of 1.0 ML, in which adsorbed O atoms occupy the SFCC + SHCP sites and the substitutional octahedral sites. The calculated work functions indicate that the SFCC + SHCP configuration has the lowest work function of all known structures at an O coverage of 0.5 ML within the SLAM, which agrees with the experimental trend of work function with variation in O coverage.

Covalent and stable CuAAC modification of silicon surfaces for control of cell adhesion

DEFF Research Database (Denmark)

Vutti, Surendra; Buch-Månson, Nina; Schoffelen, Sanne

2015-01-01

in the vapor or liquid phase. In this work, we compared these two methods for oxidized silicon surfaces and thoroughly characterized the functionalization steps by tagging and fluorescence imaging. We demonstrate that the vapor-phase functionalization only provided transient surface modification that was lost...... on extensive washing. For stable surface modification, a liquid-phase method was developed. In this method, silicon wafers were decorated with azides, either by silanization with (3-azidopropyl)triethoxysilane or by conversion of the amine groups of an aminopropylated surface by means of the azido...

The surface reactivity of acrylonitrile with oxygen atoms on an analogue of interstellar dust grains

Science.gov (United States)

Kimber, Helen J.; Toscano, Jutta; Price, Stephen D.

2018-06-01

Experiments designed to reveal the low-temperature reactivity on the surfaces of interstellar dust grains are used to probe the heterogeneous reaction between oxygen atoms and acrylonitrile (C2H3CN, H2C=CH-CN). The reaction is studied at a series of fixed surface temperatures between 14 and 100 K. After dosing the reactants on to the surface, temperature-programmed desorption, coupled with time-of-flight mass spectrometry, reveals the formation of a product with the molecular formula C3H3NO. This product results from the addition of a single oxygen atom to the acrylonitrile reactant. The oxygen atom attack appears to occur exclusively at the C=C double bond, rather than involving the cyano(-CN) group. The absence of reactivity at the cyano site hints that full saturation of organic molecules on dust grains may not always occur in the interstellar medium. Modelling the experimental data provides a reaction probability of 0.007 ± 0.003 for a Langmuir-Hinshelwood style (diffusive) reaction mechanism. Desorption energies for acrylonitrile, oxygen atoms, and molecular oxygen, from the multilayer mixed ice their deposition forms, are also extracted from the kinetic model and are 22.7 ± 1.0 kJ mol-1 (2730 ± 120 K), 14.2 ± 1.0 kJ mol-1 (1710 ± 120 K), and 8.5 ± 0.8 kJ mol-1 (1020 ± 100 K), respectively. The kinetic parameters we extract from our experiments indicate that the reaction between atomic oxygen and acrylonitrile could occur on interstellar dust grains on an astrophysical time-scale.

Super-oxidation of silicon nanoclusters: magnetism and reactive oxygen species at the surface

Energy Technology Data Exchange (ETDEWEB)

Lepeshkin, Sergey; Baturin, Vladimir; Tikhonov, Evgeny; Matsko, Nikita; Uspenskii, Yurii; Naumova, Anastasia; Feya, Oleg; Schoonen, Martin A.; Oganov, Artem R.

2016-01-01

Oxidation of silicon nanoclusters depending on the temperature and oxygen pressure is explored from first principles using the evolutionary algorithm, and structural and thermodynamic analysis. From our calculations of 90 SinOm clusters we found that under normal conditions oxidation does not stop at the stoichiometric SiO2 composition, as it does in bulk silicon, but goes further placing extra oxygen atoms on the cluster surface. These extra atoms are responsible for light emission, relevant to reactive oxygen species and many of them are magnetic. We argue that the super-oxidation effect is size-independent and discuss its relevance to nanotechnology and miscellaneous applications, including biomedical ones.

Adsorption of atomic oxygen (N2O) on a clean Ge(001) surface

NARCIS (Netherlands)

Zandvliet, Henricus J.W.; Keim, Enrico G.; van Silfhout, Arend

1990-01-01

We present the results of a study concerning the interaction of atomic oxygen (as released by decomposition of N2O ) with the clean Ge(001)2×1 surface at 300 K. Ellipsometry in the photon energy range of 1.5–4 eV, surface conductance measurements and Auger electron spectroscopy(AES) have been used

A first principles investigation of the oxygen adsorption on Zr(0001) surface using cluster expansions

Science.gov (United States)

Samin, Adib J.; Taylor, Christopher D.

2017-11-01

The design of corrosion resistant zircalloys is important for a variety of technological applications ranging from medicine to the nuclear industry. Since corrosion resistance is mainly attributed to the formation of a surface oxide layer, developing a detailed understanding of this process may assist in future corrosion resistance design. In this work, we conduct a systematic multi-scale investigation of the early stages of oxide formation. This was accomplished by first using a database of fully relaxed DFT calculations to build a cluster-expansion description of the potential function. The developed potential was reasonably good at predicting DFT energies as evidenced by the cross-validation score of 4.4 meV/site. The effective cluster expansion parameters were indicative of repulsive adsorbate interactions in the adlayer in agreement with the literature. The potential then allowed for a systematic investigation of the oxygen configurations on the Zr(0001) surface via Monte Carlo simulations. The adsorption energy was recorded as a function of coverage and an increasing trend was observed in agreement with DFT predictions and the repulsive nature of interactions in the adlayer. The convex hull diagram was recorded indicating the most stable configuration to occur around a coverage of 0.6 ML. The adsorption isotherm was also recorded and contrasted for two temperatures relevant for different applications.

Hydrogen, oxygen and hydroxyl on porous silicon surface: A joint density-functional perturbation theory and infrared spectroscopy approach

International Nuclear Information System (INIS)

Alfaro, Pedro; Palavicini, Alessio; Wang, Chumin

2014-01-01

Based on the density functional perturbation theory (DFPT), infrared absorption spectra of porous silicon are calculated by using an ordered pore model, in which columns of silicon atoms are removed along the [001] direction and dangling bonds are initially saturated with hydrogen atoms. When these atoms on the pore surface are gradually replaced by oxygen ones, the ab-initio infrared absorption spectra reveal oxygen, hydroxyl, and coupled hydrogen–oxygen vibrational modes. In a parallel way, freestanding porous silicon samples were prepared by using electrochemical etching and they were further thermally oxidized in a dry oxygen ambient. Fourier transform infrared spectroscopy was used to investigate the surface modifications caused by oxygen adsorption. In particular, the predicted hydroxyl and oxygen bound to the silicon pore surface are confirmed. Finally, a global analysis of measured transmittance spectra has been performed by means of a combined DFPT and thin-film optics approach. - Highlights: • The density functional perturbation theory is used to study infrared absorption. • An ordered pore model is used to investigate the oxidation in porous silicon (PSi). • Infrared transmittance spectra of oxidized PSi freestanding samples are measured

Modifying TiO{sub 2} surface architecture by oxygen plasma to increase dye sensitized solar cell efficiency

Energy Technology Data Exchange (ETDEWEB)

Rajmohan, Gayathri Devi [Institute for Frontier Materials, Deakin University, Geelong Waurn Ponds, Victoria 3216 (Australia); Dai, Xiujuan J., E-mail: jane.dai@deakin.edu.au [Institute for Frontier Materials, Deakin University, Geelong Waurn Ponds, Victoria 3216 (Australia); Tsuzuki, Takuya; Lamb, Peter R. [Institute for Frontier Materials, Deakin University, Geelong Waurn Ponds, Victoria 3216 (Australia); Plessis, Johan du [School of Applied Sciences, RMIT University, GPO Box 2476 V, Melbourne, Victoria 3001 (Australia); Huang, Fuzhi; Cheng, Yi-Bing [Department of Materials Engineering, Monash University, Melbourne, Victoria 3800 (Australia)

2013-10-31

Oxygen plasma treatment of TiO{sub 2} films has been used to improve the efficiency of dye sensitized solar cells. Both a commercial TiO{sub 2} sample and a TiO{sub 2} thin film synthesized by a sol-gel technique were treated using a custom built inductively coupled plasma apparatus. X-ray photoelectron spectroscopy revealed that oxygen-plasma treatment increased the number of oxygen functional groups (hydroxyl groups) and introduced some Ti{sup 3+} species on the surface of TiO{sub 2}. A sample solar cell with plasma treated TiO{sub 2} showed an overall solar-to-electricity conversion efficiency of 4.3%, about a 13% increase over untreated TiO{sub 2}. The photon conversion efficiency for the plasma treated TiO{sub 2} was 34% higher than untreated TiO{sub 2}. This enhanced cell-performance is partly due to increased dye adsorption from an increase in surface oxygen functional groups and also may be partly due to Ti{sup 3+} states on the surface of TiO{sub 2}. - Highlights: • Oxygen plasma is used to generate hydroxyl groups on the surface of TiO{sub 2} • Parallel study was conducted using a spin coated TiO{sub 2} and a Commercial TiO{sub 2} film. • The plasma functionalization caused increased dye uptake. • Some species in Ti{sup 3+} state are also generated after oxygen plasma. • Dye sensitised solar cell with functionalised electrode showed improved efficiency.

High coverage hydrogen adsorption on the Fe{sub 3}O{sub 4}(1 1 0) surface

Energy Technology Data Exchange (ETDEWEB)

Yu, Xiaohu, E-mail: yuxiaohu950203@126.com [College of Physics and Electrical Engineering, Anyang Normal University, Anyang, Henan 455000 (China); State Key laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan, Shanxi 030001 (China); Zhang, Xuemei [College of Physics and Electrical Engineering, Anyang Normal University, Anyang, Henan 455000 (China); Wang, Shengguang [State Key laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan, Shanxi 030001 (China); Synfuels China Co., Ltd., Huairou, Beijing 101407 (China)

2015-10-30

Graphical abstract: - Highlights: • Hydrogen adsorption on the A and B termination layers of the Fe{sub 3}O{sub 4}(1 1 0) surface at different coverage has been studied by DFT + U method. • The adsorption of hydrogen prefers surface oxygen atoms on both Fe{sub 3}O{sub 4}(1 1 0) surface layers. • The more stable A layer has stronger adsorption energy than the less stable B layer. • The saturation coverage has two dissociatively adsorbed H{sub 2} on the A layer, and one dissociatively adsorbed H{sub 2} on the B layer. - Abstract: Hydrogen adsorption on the A and B termination layers of the Fe{sub 3}O{sub 4}(1 1 0) surface at different coverage has been systematically studied by density functional theory calculations including an on-site Hubbard term (GGA + U). The adsorption of hydrogen prefers surface oxygen atoms on both layers. The more stable A layer has stronger adsorption energy than the less stable B layer. The saturation coverage has two dissociatively adsorbed H{sub 2} on the A layer, and one dissociatively adsorbed H{sub 2} on the B layer. The adsorption mechanism has been analyzed on the basis of projected density of states (PDOS).

Direct Observation of Room-Temperature Stable Magnetism in LaAlO3/SrTiO3 Heterostructures.

Science.gov (United States)

Yang, Ming; Ariando; Zhou, Jun; Asmara, Teguh Citra; Krüger, Peter; Yu, Xiao Jiang; Wang, Xiao; Sanchez-Hanke, Cecilia; Feng, Yuan Ping; Venkatesan, T; Rusydi, Andrivo

2018-03-21

Along with an unexpected conducting interface between nonmagnetic insulating perovskites LaAlO 3 and SrTiO 3 (LaAlO 3 /SrTiO 3 ), striking interfacial magnetisms have been observed in LaAlO 3 /SrTiO 3 heterostructures. Interestingly, the strength of the interfacial magnetic moment is found to be dependent on oxygen partial pressures during the growth process. This raises an important, fundamental question on the origin of these remarkable interfacial magnetic orderings. Here, we report a direct evidence of room-temperature stable magnetism in a LaAlO 3 /SrTiO 3 heterostructure prepared at high oxygen partial pressure by using element-specific soft X-ray magnetic circular dichroism at both Ti L 3,2 and O K edges. By combining X-ray absorption spectroscopy at both Ti L 3,2 and O K edges and first-principles calculations, we qualitatively ascribe that this strong magnetic ordering with dominant interfacial Ti 3+ character is due to the coexistence of LaAlO 3 surface oxygen vacancies and interfacial (Ti Al -Al Ti ) antisite defects. On the basis of this new understanding, we revisit the origin of the weak magnetism in LaAlO 3 /SrTiO 3 heterostructures prepared at low oxygen partial pressures. Our calculations show that LaAlO 3 surface oxygen vacancies are responsible for the weak magnetism at the interface. Our result provides direct evidence on the presence of room-temperature stable magnetism and a novel perspective to understand magnetic and electronic reconstructions at such strategic oxide interfaces.

Modulating Protein Adsorption on Oxygen Plasma Modified Polysiloxane Surfaces

International Nuclear Information System (INIS)

Marletta, G.

2006-01-01

In the present paper we report the study on the adsorption behaviour of three model globular proteins, Human Serum Albumin, Lactoferrin and Egg Chicken Lysozyme onto both unmodified surfaces of a silicon-based polymer and the corresponding plasma treated surfaces. In particular, thin films of hydrophobic polysiloxane (about 90 degree of static water contact angle, WCA) were converted by oxygen plasma treatment at reduced pressure into very hydrophilic phases of SiOx (WCA less than 5 degree). The kinetics of protein adsorption processes were investigated by QCM-D technique, while the chemical structure and topography of the protein adlayer have been studied by Angular resolved-XPS and AFM respectively. It turned out that Albumin and Lysozyme exhibited the opposite preferential adsorption respectively onto the hydrophobic and hydrophilic surfaces, while Lactoferrin did not exhibit significant differences. The observed protein behaviour are discussed both in terms of surface-dependent parameters, including surface free energy and chemical structure, and in terms of protein-dependent parameters, including charge as well as the average molecular orientation in the adlayers. Finally, some examples of differential adsorption behaviour of the investigated proteins are reported onto nanopatterned polysiloxane surfaces consisting of hydrophobic nanopores surrounded by hydrophilic (plasma-treated) matrix and the reverse

Oxygen exchange between C18O2 and ''acidic'' oxide and zeolite catalysts

International Nuclear Information System (INIS)

Peri, J.B.

1975-01-01

The exchange of oxygen between C 18 O 2 and several high-area oxides, including silica, γ-alumina, silica--alumina, and zeolite catalysts, was studied. Infrared spectra of adsorbed CO 2 and of surface ''carbonates'' were used to follow the rate of oxygen exchange and investigate the nature of unusually exchangeable surface oxide ions, present at low concentrations. Interaction of CO 2 with the surface typically produced initial exchange of one oxygen atom, as expected from interaction with a single oxide ion (CO 2 + O 2- reversible CO 3 2- ), and the number of exchangeable ions increased with increasing temperature. The rate of oxygen exchange did not correlate with chemisorption to form stable surface carbonates or with the extent of strong physical adsorption of CO 2 . With dry silica, exchange was insignificant below 600 0 ; with catalytically active zeolites and dry γ-alumina, it was detectable at 200 0 and fairly rapid at 300--400 0 . Silica--alumina required 100--150 0 higher temperature for exchange than did an active zeolite. Activity for cracking and other hydrocarbon reactions may be related to the ease of exchange of some surface oxide ions with CO 2 . Active zeolites have reactive oxide sites resembling those on dry γ-alumina, but such sites on zeolites are probably less-readily eliminated by chemisorption of H 2 O or other compounds. (U.S.)

Surface modification of electrospun fibre meshes by oxygen plasma for bone regeneration

International Nuclear Information System (INIS)

Nandakumar, A; Tahmasebi Birgani, Z; Santos, D; Mentink, A; Auffermann, N; Moroni, L; Van Blitterswijk, C; Habibovic, P; Van der Werf, K; Bennink, M

2013-01-01

Plasma treatment is a method to modify the physicochemical properties of biomaterials, which consequently may affect interactions with cells. Based on the rationale that physical cues on the surface of culture substrates and implants, such as surface roughness, have proven to alter cell behaviour, we used electrospinning to fabricate fibrous three-dimensional scaffolds made of a poly (ethylene oxide terephthalate)/poly (butylene terephthalate) copolymer to mimic the physical microenvironment of extracellular matrix and applied radio-frequency oxygen plasma treatment to create nanoscale roughness. Scanning electron microscopy (SEM) analysis revealed a fibre diameter of 5.49 ± 0.96 µm for as-spun meshes. Atomic force microscopy (AFM) measurements determined an exponential increase of surface roughness with plasma treatment time. An increase in hydrophilicity after plasma treatment was observed, which was associated with higher oxygen content in plasma treated scaffolds compared to untreated ones. A more pronounced adsorption of bovine serum albumin occurred on scaffolds treated with plasma for 15 and 30 min compared to untreated fibres. Clinically relevant human mesenchymal stromal cells (hMSCs) were cultured on untreated, 15 and 30 min treated scaffolds. SEM analysis confirmed cell attachment and a pronounced spindle-like morphology on all scaffolds. No significant differences were observed between different scaffolds regarding the amount of DNA, metabolic activity and alkaline phosphatase (ALP) activity after 7 days of culture. The amount of ALP positive cells increased between 7 and 21 days of culture on both untreated and 30 min treated meshes. In addition, ALP staining of cells on plasma treated meshes appeared more pronounced than on untreated meshes after 21 days of culture. Quantitative polymerase chain reaction showed significant upregulation of bone sialoprotein and osteonectin expression on oxygen plasma treated fibres compared to untreated fibres in

Quantitative measurements of ground state atomic oxygen in atmospheric pressure surface micro-discharge array

Science.gov (United States)

Li, D.; Kong, M. G.; Britun, N.; Snyders, R.; Leys, C.; Nikiforov, A.

2017-06-01

The generation of atomic oxygen in an array of surface micro-discharge, working in atmospheric pressure He/O2 or Ar/O2 mixtures, is investigated. The absolute atomic oxygen density and its temporal and spatial dynamics are studied by means of two-photon absorption laser-induced fluorescence. A high density of atomic oxygen is detected in the He/O2 mixture with up to 10% O2 content in the feed gas, whereas the atomic oxygen concentration in the Ar/O2 mixture stays below the detection limit of 1013 cm-3. The measured O density near the electrode under the optimal conditions in He/1.75% O2 gas is 4.26  ×  1015 cm-3. The existence of the ground state O (2p 4 3 P) species has been proven in the discharge at a distance up to 12 mm away from the electrodes. Dissociative reactions of the singlet O2 with O3 and deep vacuum ultraviolet radiation, including the radiation of excimer \\text{He}2\\ast , are proposed to be responsible for O (2p 4 3 P) production in the far afterglow. A capability of the surface micro-discharge array delivering atomic oxygen to long distances over a large area is considered very interesting for various biomedical applications.

TGP, an extremely stable, non-aggregating fluorescent protein created by structure-guided surface engineering

OpenAIRE

Close, Devin W.; Don Paul, Craig; Langan, Patricia S.; Wilce, Matthew C.J.; Traore, Daouda A.K.; Halfmann, Randal; Rocha, Reginaldo C.; Waldo, Geoffery S.; Payne, Riley J.; Rucker, Joseph B.; Prescott, Mark; Bradbury, Andrew R.M.

2015-01-01

In this paper we describe the engineering and X-ray crystal structure of Thermal Green Protein (TGP), an extremely stable, highly soluble, non-aggregating green fluorescent protein. TGP is a soluble variant of the fluorescent protein eCGP123, which despite being highly stable, has proven to be aggregation-prone. The X-ray crystal structure of eCGP123, also determined within the context of this paper, was used to carry out rational surface engineering to improve its solubility, leading to TGP....

Influence of surface oxygenated groups on the formation of active Cu species and the catalytic activity of Cu/AC catalyst for the synthesis of dimethyl carbonate

Science.gov (United States)

Zhang, Guoqiang; Li, Zhong; Zheng, Huayan; Hao, Zhiqiang; Wang, Xia; Wang, Jiajun

2016-12-01

Activated carbon (AC) supported Cu catalysts are employed to study the influence of surface oxygenated groups on the formation of active Cu species and the catalytic activity of Cu/AC catalyst for oxidative carbonylation of methanol to dimethyl carbonate (DMC). The AC supports are thermal treated under different temperatures in order to adjust the levels of surface oxygenated groups. The AC supports are characterized by BET, TPD-MS and XRD, and the Cu/AC catalysts are characterized by BET, XRD, TEM, XPS, AAS, CH3OH-TPD and N2O chemisorption. The results show that as the treatment temperature is below 800 °C, the BET surface area of the corresponding AC supports are nearly unchanged and close to that of the original AC (1529.6 m2/g). But as the thermal treatment temperature is elevated from 1000 to 1600 °C, the BET surface area of AC supports gradually decreases from 1407.6 to 972.2 m2/g. After loading of Cu, the BET surface area of copper catalysts is in the range of 834.4 to 1545.3 m2/g, which is slightly less than that of the respective supports. When AC is thermal treated at 400 and 600 °C, the unstable carboxylic acid and anhydrides groups are selectively removed, which has weakened the mobility and agglomeration of Cu species during the calcination process, and thus improve the Cu species dispersion over AC support. But as the treatment temperature is elevated from 600 °C to 1200 °C, the Cu species dispersion begins to decline suggesting further removal of stable surface oxygenated groups is unfavorable for Cu species dispersion. Moreover, higher thermal treatment temperature (above 1200 °C) promotes the graphitization degree of AC and leds to the decrease of Cu loading on AC support. Meanwhile, the removal of surface oxygenated groups by thermal treatment is conducive to the formation of more π-sites, and thus promote the reduction of Cu2+ to Cu+ and Cu0 as active centers. The specific surface area of (Cu+ + Cu0) is improved by thermal treatment of AC

The dynamics of ultraviolet-induced oxygen vacancy at the surface of insulating SrTiO_3(0 0 1)

International Nuclear Information System (INIS)

Suwanwong, S.; Eknapakul, T.; Rattanachai, Y.; Masingboon, C.; Rattanasuporn, S.; Phatthanakun, R.; Nakajima, H.; King, P.D.C.; Hodak, S.K.; Meevasana, W.

2015-01-01

Highlights: • The dynamics of UV-induced oxygen vacancy is studied from the change of surface resistance. • The formation of 2DEG at the insulating surface of SrTiO_3 is confirmed by ARPES. • The UV-induced change in resistance responds differently to oxygen/gas exposure. • The behavior of resistance recovery suggests an alternative method of low-pressure sensing. - Abstract: The effect of ultra-violet (UV) irradiation on the electronic structure and the surface resistance of an insulating SrTiO_3(0 0 1) crystal is studied in this work. Upon UV irradiation, we show that the two-dimensional electron gas (2DEG) emerges at the insulating SrTiO_3 surface and there is a pronounced change in the surface resistance. By combining the observations of the change in valance band and the resistance change under different environments of gas pressure and gas species, we find that UV-induced oxygen vacancies at the surface plays a major role in the resistance change. The dynamic of the resistance change at different oxygen pressures also suggests an alternative method of low-pressure sensing.

Improvement of Surface Wettability and Hydrophilization of Poly-paraphenylene benzobisoxazole Fiber with Fibrillation Combined Oxygen Plasma Treatment

Directory of Open Access Journals (Sweden)

Xiwen Wang

2012-01-01

Full Text Available A new surface modification method fibrillation combined with oxygen plasma treatment to improve the wettability and hydrophily of PBO fiber was studied in this paper. The surface chemical structure and morphology of PBO fiber were characterized by the methods of FTIR, XPS and SEM. The wettability and hydrophlic characters changes on the surface were evaluated by the dynamic contact angle system and image analysis. The results show that the increase surface roughness by fibrillation could improve the wettability. Fibrillation combined oxygen plasma treatment has a better effect than oxygen plasma treatment to improve the wettability and hdyrophlization of PBO fiber. The specific area of PBO fiber increased to 10.7 m2/g from 0.7 m2/g, contact angle decreased to 43.2° from 84.4° and WRV increased to 208.4% from 13.7%. The modified fibers have a good dispersion in water for hydrophilization improvement.

Molecular simulation insights on the in vacuo adsorption of amino acids on graphene oxide surfaces with varying surface oxygen densities

Energy Technology Data Exchange (ETDEWEB)

Rahmani, Farzin; Nouranian, Sasan, E-mail: sasan@olemiss.edu; Mahdavi, Mina [University of Mississippi, Department of Chemical Engineering (United States); Al-Ostaz, Ahmed [University of Mississippi, Department of Civil Engineering (United States)

2016-11-15

In this fundamental study, a series of molecular dynamics simulations were performed in vacuo to investigate the energetics and select geometries of 20 standard amino acids (AAs) on pristine graphene (PG) and graphene oxide (GO) surfaces as a function of graphene surface oxygen density. These interactions are of key interest to graphene/biomolecular systems. Our results indicate that aromatic AAs exhibit the strongest total interactions with the PG surfaces due to π-π stacking. Tryptophan (Trp) has the highest aromaticity due to its indole side chain and, hence, has the strongest interaction among all AAs (−16.66 kcal/mol). Aliphatic, polar, and charged AAs show various levels of affinity to the PG sheets depending on the strength of their side chain hydrophobic interactions. For example, arginine (Arg) with its guanidinium side chain exhibits the strongest interaction with the PG sheets (−13.81 kcal/mol) following aromatic AAs. Also, glycine (Gly; a polar AA) has the weakest interaction with the PG sheets (−7.29 kcal/mol). When oxygen-containing functional groups are added to the graphene sheets, the π-π stacking in aromatic AAs becomes disrupted and perfect parallelism of the aromatic rings is lost. Moreover, hydrogen bonding and/or electrostatic interactions become more pronounced. Charged AAs exhibit the strongest interactions with the GO surfaces. In general, the AA-GO interactions increase with increasing surface oxygen density, and the effect is more pronounced at higher O/C ratios. This study provides a quantitative measure of AA-graphene interactions for the design and tuning of biomolecular systems suitable for biosensing, drug delivery, and gene delivery applications.

Effect of Heat Treatment on the Surface Properties of Activated Carbons

Directory of Open Access Journals (Sweden)

Meriem Belhachemi

2011-01-01

Full Text Available This work reports the effect of heat treatment on the porosity and surface chemistry of two series of activated carbons prepared from a local agricultural biomass material, date pits, by physical activation with carbon dioxide and steam. Both series samples were oxidized with nitric acid and subsequently heat treated under N2 at 973 K in order to study the effect of these treatments in porosity and surface functional groups of activated carbons. When the activated carbons were heat treated after oxidation the surface area and the pore volume increase for both activated carbons prepared by CO2 and steam activations. However the amount of surface oxygen complexes decreases, the samples keep the most stable oxygen surface groups evolved as CO by temperature-programmed desorption experiments at high temperature. The results show that date pits can be used as precursors to produce activated carbons with a well developed porosity and tailored oxygen surface groups.

Chemisorption of oxygen and subsequent reactions on low index surfaces of β-Mo₂C

DEFF Research Database (Denmark)

Shi, Xue Rong; Wang, Shengguang; Wang, Jianguo

2016-01-01

to the carbon vacancy were identified. We examined the effect of oxygen coverage on the morphology of β-Mo2C by plotting the equilibrium crystal shape. Thermodynamic effect of temperature and reactant or product pressure on the CO/CO2 desorption were investigated. The CO/CO2 desorption is more favorable...... at the saturated oxygen coverage than the low oxygen coverage thermodynamically. The subsequent oxygen diffusion to the carbon vacancy after CO/CO2 desorption may happen depending on the surfaces and oxygen coverage....

Magnetic susceptibility of oxygen adsorbed on the surface of spherical and fibrous activated carbon.

Directory of Open Access Journals (Sweden)

Kiyoshi Kawamura

2009-02-01

Full Text Available The magnetic susceptibilities of oxygen adsorbed on the surface of bead-shaped activated carbon and activated carbon fibers were evaluated as a function of temperature between 4.2 K and 300 K, and found to exhibit a sharp peak at around 50 K. This implies that the adsorbed oxygen molecules form an antiferromagnetic state. The relation between the susceptibility and the adsorbed mass suggest that the thickness of the adsorbed oxygen is thin enough to consider a two-dimensional structure for bead–shaped activated carbon and carbon fibers across the fiber axis but thick enough to regard it as three-dimensional along the fiber axis. The result is discussed with reference to the study on one-dimensional oxygen array.

Defining a stable water isotope framework for isotope hydrology application in a large trans-boundary watershed (Russian Federation/Ukraine).

Science.gov (United States)

Vystavna, Yuliya; Diadin, Dmytro; Huneau, Frédéric

2018-05-01

Stable isotopes of hydrogen ( 2 H) and oxygen ( 18 O) of the water molecule were used to assess the relationship between precipitation, surface water and groundwater in a large Russia/Ukraine trans-boundary river basin. Precipitation was sampled from November 2013 to February 2015, and surface water and groundwater were sampled during high and low flow in 2014. A local meteoric water line was defined for the Ukrainian part of the basin. The isotopic seasonality in precipitation was evident with depletion in heavy isotopes in November-March and an enrichment in April-October, indicating continental and temperature effects. Surface water was enriched in stable water isotopes from upstream to downstream sites due to progressive evaporation. Stable water isotopes in groundwater indicated that recharge occurs mainly during winter and spring. A one-year data set is probably not sufficient to report the seasonality of groundwater recharge, but this survey can be used to identify the stable water isotopes framework in a weakly gauged basin for further hydrological and geochemical studies.

Surface strontium enrichment on highly active perovskites for oxygen electrocatalysis in solid oxide fuel cells

KAUST Repository

Crumlin, Ethan J.; Mutoro, Eva; Liu, Zhi; Grass, Michael E.; Biegalski, Michael D.; Lee, Yueh-Lin; Morgan, Dane; Christen, Hans M.; Bluhm, Hendrik; Shao-Horn, Yang

2012-01-01

Perovskite oxides have high catalytic activities for oxygen electrocatalysis competitive to platinum at elevated temperatures. However, little is known about the oxide surface chemistry that influences the activity near ambient oxygen partial pressures, which hampers the design of highly active catalysts for many clean-energy technologies such as solid oxide fuel cells. Using in situ synchrotron-based, ambient pressure X-ray photoelectron spectroscopy to study the surface chemistry changes, we show that the coverage of surface secondary phases on a (001)-oriented La 0.8Sr 0.2CoO 3-δ (LSC) film becomes smaller than that on an LSC powder pellet at elevated temperatures. In addition, strontium (Sr) in the perovskite structure enriches towards the film surface in contrast to the pellet having no detectable changes with increasing temperature. We propose that the ability to reduce surface secondary phases and develop Sr-enriched perovskite surfaces of the LSC film contributes to its enhanced activity for O 2 electrocatalysis relative to LSC powder-based electrodes. © 2012 The Royal Society of Chemistry.

Interactions of oxygen and ethylene with submonolayer Ag films supported on Ni(111).

Science.gov (United States)

Rettew, Robert E; Meyer, Axel; Senanayake, Sanjaya D; Chen, Tsung-Liang; Petersburg, Cole; Ingo Flege, J; Falta, Jens; Alamgir, Faisal M

2011-06-21

We investigate the oxidation of, and the reaction of ethylene with, Ni(111) with and without sub-monolayer Ag adlayers as a function of temperature. The addition of Ag to Ni(111) is shown to enhance the activity towards the ethylene epoxidation reaction, and increase the temperature at which ethylene oxide is stable on the surface. We present a systematic study of the formation of chemisorbed oxygen on the Ag-Ni(111) surfaces and correlate the presence and absence of O(1-) and O(2-) surface species with the reactivity towards ethylene. By characterizing the samples with low-energy electron microscopy (LEEM) in combination with X-ray photoelectron spectroscopy (XPS), we have identified specific growth of silver on step-edge sites and successfully increased the temperature at which the produced ethylene oxide remains stable, a trait which is desirable for catalysis.

Stratigraphy on Oxygen and Carbon Isotope of Paciran Formation East Java

International Nuclear Information System (INIS)

Premonowati; R P Koesoemadinata; Harsono-Pringgoprawiro; Wahyoe-S-Hantoro

2004-01-01

Paleotemperature fluctuation in tropical zone (centennial and decad al scale) has been known. It's based on stable isotopic analysis from each of unconformity zones. Those boundaries have derived on reef units of shallows marine reef complex of Paciran Formation, Tuban area in Northeast Java Basin. From 25 samples have been choosen on undeformed calcite and analyzed by oxygen and carbon stable isotope. It used to validizing a sea level changes during the formation to Reef 1 to Reef 17 from Paciran formation with sea surface temperature (SST) since 4 Ma until now. On early forming of Reef 1 to Reef 3 (since 4 Ma - 2,88 Ma), sea level occurred marine flooding surface. Since the formation of reef 4 (2,59 Ma) to Reef 8 (1,4 Ma) occurred stagnant temperature and almost to warmer condition. Then, δ 18 O have arise up drastically to 5 0/00 and shows warmer condition to Reef 8 formation, in contrary, the sea level have been arised to Reef 10 formation (0,7 Ma). The temperature have been fluctuated between 0,5 o and 1 o C until the formation of Reef 17 (Early Holocene) and continued to Reef 17 formation at 2 o C based on the rapidity sampling of Po rites sp. Wholly, in centennial scale, since the formation of Reef 4 (2,59 Ma) to Reef 17 (1 Ma), the curve of oxygen stable isotope shows decrease or cooler condition. Those condition have conducted to sea level drop since the formation to Reef 7 and Reef 8. There are 4 periods of interglacial since the formation of Reef 4. The warmer condition indicated since the formation of Reef 9, Reef 11 and Reef 17. Recently, a curve of oxygen isotopes reveals warmer drastically or sea level have been arisen. (author)

Work function modifications of graphite surface via oxygen plasma treatment

Science.gov (United States)

Duch, J.; Kubisiak, P.; Adolfsson, K. H.; Hakkarainen, M.; Golda-Cepa, M.; Kotarba, A.

2017-10-01

The surface modification of graphite by oxygen plasma was investigated experimentally (X-ray diffraction, nanoparticle tracking analysis, laser desorption ionization mass spectrometry, thermogravimetry, water contact angle) and by molecular modelling (Density Functional Theory). Generation of surface functional groups (mainly sbnd OHsurf) leads to substantial changes in electrodonor properties and wettability gauged by work function and water contact angle, respectively. The invoked modifications were analyzed in terms of Helmholtz model taking into account the theoretically determined surface dipole moment of graphite-OHsurf system (μ = 2.71 D) and experimentally measured work function increase (from 0.75 to 1.02 eV) to determine the sbnd OH surface coverage (from 0.70 to 1.03 × 1014 groups cm-2). Since the plasma treatment was confined to the surface, the high thermal stability of the graphite material was preserved as revealed by the thermogravimetric analysis. The obtained results provide a suitable quantitative background for tuning the key operating parameters of carbon electrodes: electronic properties, interaction with water and thermal stability.

Optical characterization of surface and interface oxygen content in YBa2Cu3O/sub x/

International Nuclear Information System (INIS)

Kelly, M.K.; Chan, S.; Jenkin, K. II; Aspnes, D.E.; Barboux, P.; Tarascon, J.

1988-01-01

Because YBa 2 Cu 3 O/sub x/ exists over a range of oxygen content and low oxygen material is nonsuperconducting, it is important to be able to measure and control this parameter for application purposes. We present an optical technique for determining oxygen loss at surfaces and interfaces, where processing and contacts with other materials may affect composition and where usual techniques are insensitive. Using a strong absorption feature at 4.1 eV which appears at low oxygen composition, we find that overlayers of Al and In remove oxygen from YBa 2 Cu 3 O/sub x/, but Ag, Au, and room-temperature exposure to moderate vacuum do not

Stable Boundary Layer Issues

NARCIS (Netherlands)

Steeneveld, G.J.

2012-01-01

Understanding and prediction of the stable atmospheric boundary layer is a challenging task. Many physical processes are relevant in the stable boundary layer, i.e. turbulence, radiation, land surface coupling, orographic turbulent and gravity wave drag, and land surface heterogeneity. The

First principles investigation of the activity of thin film Pt, Pd and Au surface alloys for oxygen reduction

DEFF Research Database (Denmark)

Tripkovic, Vladimir; Hansen, Heine Anton; Rossmeisl, Jan

2015-01-01

Further advances in fuel cell technologies are hampered by kinetic limitations associated with the sluggish cathodic oxygen reduction reaction. We have investigated a range of different formulations of binary and ternary Pt, Pd and Au thin films as electrocatalysts for oxygen reduction. The most...... active binary thin films are near-surface alloys of Pt with subsurface Pd and certain PdAu and PtAu thin films with surface and/or subsurface Au. The most active ternary thin films are with pure metal Pt or Pd skins with some degree of Au in the surface and/or subsurface layer and the near-surface alloys...

Smart biomaterials: Surfaces functionalized with proteolytically stable osteoblast-adhesive peptides

Directory of Open Access Journals (Sweden)

Annj Zamuner

2017-09-01

Full Text Available Engineered scaffolds for bone tissue regeneration are designed to promote cell adhesion, growth, proliferation and differentiation. Recently, covalent and selective functionalization of glass and titanium surfaces with an adhesive peptide (HVP mapped on [351–359] sequence of human Vitronectin allowed to selectively increase osteoblast attachment and adhesion strength in in vitro assays, and to promote osseointegration in in vivo studies. For the first time to our knowledge, in this study we investigated the resistance of adhesion sequences to proteolytic digestion: HVP was completely cleaved after 5 h. In order to overcome the enzymatic degradation of the native peptide under physiological conditions we synthetized three analogues of HVP sequence. A retro-inverted peptide D-2HVP, composed of D amino acids, was completely stable in serum-containing medium. In addition, glass surfaces functionalized with D-2HVP increased human osteoblast adhesion as compared to the native peptide and maintained deposition of calcium. Interestingly, D-2HVP increased expression of IBSP, VTN and SPP1 genes as compared to HVP functionalized surfaces. Total internal reflection fluorescence microscope analysis showed cells with numerous filopodia spread on D-2HVP-functionalized surfaces. Therefore, the D-2HVP sequence is proposed as new osteoblast adhesive peptide with increased bioactivity and high proteolytic resistance.

Smart biomaterials: Surfaces functionalized with proteolytically stable osteoblast-adhesive peptides.

Science.gov (United States)

Zamuner, Annj; Brun, Paola; Scorzeto, Michele; Sica, Giuseppe; Castagliuolo, Ignazio; Dettin, Monica

2017-09-01

Engineered scaffolds for bone tissue regeneration are designed to promote cell adhesion, growth, proliferation and differentiation. Recently, covalent and selective functionalization of glass and titanium surfaces with an adhesive peptide (HVP) mapped on [351-359] sequence of human Vitronectin allowed to selectively increase osteoblast attachment and adhesion strength in in vitro assays, and to promote osseointegration in in vivo studies. For the first time to our knowledge, in this study we investigated the resistance of adhesion sequences to proteolytic digestion: HVP was completely cleaved after 5 h. In order to overcome the enzymatic degradation of the native peptide under physiological conditions we synthetized three analogues of HVP sequence. A retro-inverted peptide D-2HVP, composed of D amino acids, was completely stable in serum-containing medium. In addition, glass surfaces functionalized with D-2HVP increased human osteoblast adhesion as compared to the native peptide and maintained deposition of calcium. Interestingly, D-2HVP increased expression of IBSP, VTN and SPP1 genes as compared to HVP functionalized surfaces. Total internal reflection fluorescence microscope analysis showed cells with numerous filopodia spread on D-2HVP-functionalized surfaces. Therefore, the D-2HVP sequence is proposed as new osteoblast adhesive peptide with increased bioactivity and high proteolytic resistance.

Effect of surface texture and structure on the development of stable fluvial armors

Science.gov (United States)

Bertin, Stephane; Friedrich, Heide

2018-04-01

Stable fluvial armors are found in river systems under conditions of partial sediment transport and limited sediment supply, a common occurrence in nature. Stable armoring is also readily recreated in experimental flumes. Initially, this bed stabilizing phenomenon was examined for different flow discharges and solely related to surface coarsening and bedload transport reduction. The models developed suggest a specific armor composition (i.e., texture) dependent on the parent bed material and formative discharge. Following developments in topographic remote sensing, recent research suggests that armor structure is an important control on bed stability and roughness. In this paper, replicated flume runs during which digital elevation models (DEMs) were collected from both exposed and flooded gravel beds are used to interpret armoring manifestations and to assess their replicability. A range of methodologies was used for the analysis, providing information on (i) surface grain size and orientation, (ii) bed-elevation distributions, (iii) the spatial coherence of the elevations at the grain-scale, (iv) surface slope and aspect, (v) grain imbrication and (vi) the spatial variability in DEM properties. The bed-surface topography was found to be more responsive than bed-material size to changes in flow strength. Our experimental results also provide convincing evidence that gravel-beds' response to water-work during parallel degradation is unique (i.e., replicable) given the formative parameters. Based on this finding, relationships between the armors' properties and formative parameters are proposed, and are supported by adding extensive data from previous research.

The surface structure of SrTiO{sub 3} at high temperatures under influence of oxygen

Energy Technology Data Exchange (ETDEWEB)

Hesselberth, M. B. S.; Molen, S. J. van der; Aarts, J. [Kamerlingh Onnes Laboratory, Leiden University, P.O. Box 9504, 2300 RA Leiden (Netherlands)

2014-02-03

We use low energy electron microscopy to investigate the structure of the SrTiO{sub 3} (001) surface at elevated temperatures and different oxygen pressures. Upon varying the temperature between 500 °C and 900 °C in oxygen pressures ranging from 10{sup −9} millibar to 10{sup −4} millibar, two surface transitions are found to be present. The lower temperature (1 × 1) → (2 × 1) transition that is known to occur in ultrahigh vacuum can be reversed by increasing the oxygen pressure. At higher temperatures, we observe a (2 × 1) → disordered (1 × 1) transition which is irreversible in the experimental parameter range. The observations are expected to have a strong bearing on the growth of interface structures.

Calculations of oxide formation on low-index Cu surfaces

Energy Technology Data Exchange (ETDEWEB)

Lian, Xin; Liu, Renlong, E-mail: lrl@cqu.edu.cn, E-mail: henkelman@utexas.edu [College of Chemistry and Chemical Engineering, Chongqing University, Chongqing 400030 (China); Xiao, Penghao; Yang, Sheng-Che; Henkelman, Graeme, E-mail: lrl@cqu.edu.cn, E-mail: henkelman@utexas.edu [Department of Chemistry and the Institute for Computational and Engineering Sciences, University of Texas at Austin, Austin, Texas 78712-0165 (United States)

2016-07-28

Density-functional theory is used to evaluate the mechanism of copper surface oxidation. Reaction pathways of O{sub 2} dissociation on the surface and oxidation of the sub-surface are found on the Cu(100), Cu(110), and Cu(111) facets. At low oxygen coverage, all three surfaces dissociate O{sub 2} spontaneously. As oxygen accumulates on the surfaces, O{sub 2} dissociation becomes more difficult. A bottleneck to further oxidation occurs when the surfaces are saturated with oxygen. The barriers for O{sub 2} dissociation on the O-saturated Cu(100)-c(2×2)-0.5 monolayer (ML) and Cu(100) missing-row structures are 0.97 eV and 0.75 eV, respectively; significantly lower than those have been reported previously. Oxidation of Cu(110)-c(6×2), the most stable (110) surface oxide, has a barrier of 0.72 eV. As the reconstructions grow from step edges, clean Cu(110) surfaces can dissociatively adsorb oxygen until the surface Cu atoms are saturated. After slight rearrangements, these surface areas form a “1 ML” oxide structure which has not been reported in the literature. The barrier for further oxidation of this “1 ML” phase is only 0.31 eV. Finally the oxidized Cu(111) surface has a relatively low reaction energy barrier for O{sub 2} dissociation, even at high oxygen coverage, and allows for facile oxidation of the subsurface by fast O diffusion through the surface oxide. The kinetic mechanisms found provide a qualitative explanation of the observed oxidation of the low-index Cu surfaces.

Surface-Selective Preferential Production of Reactive Oxygen Species on Piezoelectric Ceramics for Bacterial Killing

OpenAIRE

Tan, Guoxin; Wang, Shuangying; Zhu, Ye; Zhou, Lei; Yu, Peng; Wang, Xiaolan; He, Tianrui; Chen, Junqi; Mao, Chuanbin; Ning, Chengyun

2016-01-01

Reactive oxygen species (ROS) can be used to kill bacterial cells, and thus the selective generation of ROS from material surfaces is an emerging direction in antibacterial material discovery. We found the polarization of piezoelectric ceramic causes the two sides of the disk to become positively and negatively charged, which translate into cathode and anode surfaces in an aqueous solution. Because of the microelectrolysis of water, ROS are preferentially formed on the cathode surface. Conseq...

Oxygen-vacancy defects on BaTiO3 (001) surface: a quantum chemical study

International Nuclear Information System (INIS)

Duque, Carlos; Stashans, Arvids

2003-01-01

A quantum-chemical study of technologically important BaTiO 3 crystal and oxygen-vacancy defects on its (001) surface is reported in the present work. The computations are made using a quantum-chemical method developed for periodic systems (crystals), which is based on the Hartree-Fock theory. The atomic rearrangement due to the surface creation is obtained for a pure BaTiO 3 by means of the periodic large unit cell (LUC) model and using an automated geometry optimisation procedure. The same technique is employed to study the electronic and structural properties of the material due to the presence of an O vacancy and F centre (two electrons trapped in an oxygen vacancy). The computations are carried out for both cubic and tetragonal lattices

The dynamics of ultraviolet-induced oxygen vacancy at the surface of insulating SrTiO{sub 3}(0 0 1)

Energy Technology Data Exchange (ETDEWEB)

Suwanwong, S. [School of Physics, Suranaree University of Technology, Nakhon Ratchasima 30000 (Thailand); Program in General Science Teaching, Faculty of Education, Vongchavalitkul University, Nakhon Ratchasima 30000 (Thailand); Eknapakul, T. [School of Physics, Suranaree University of Technology, Nakhon Ratchasima 30000 (Thailand); Rattanachai, Y. [Department of Applied Physics, Faculty of Sciences and Liberal Arts, Rajamangala University of Technology Isan, Nakhon Ratchasima 30000 (Thailand); Masingboon, C. [School of Physics, Suranaree University of Technology, Nakhon Ratchasima 30000 (Thailand); Faculty of Science and Engineering, Kasetsart University, Chalermphrakiat Sakon Nakhon Province Campus, Sakon Nakhon 47000 (Thailand); Rattanasuporn, S.; Phatthanakun, R.; Nakajima, H. [Synchrotron Light Research Institute, Nakhon Ratchasima 30000 (Thailand); King, P.D.C. [SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews, Fife KY16 9SS (United Kingdom); Hodak, S.K. [Department of Physics, Faculty of Science, Chulalongkorn University, Bangkok 10330 (Thailand); Meevasana, W., E-mail: worawat@g.sut.ac.th [School of Physics, Suranaree University of Technology, Nakhon Ratchasima 30000 (Thailand); NANOTEC-SUT Center of Excellence on Advanced Functional Nanomaterials, Suranaree University of Technology, Nakhon Ratchasima 30000 (Thailand); Thailand Center of Excellence in Physics, CHE, Bangkok 10400 (Thailand)

2015-11-15

Highlights: • The dynamics of UV-induced oxygen vacancy is studied from the change of surface resistance. • The formation of 2DEG at the insulating surface of SrTiO{sub 3} is confirmed by ARPES. • The UV-induced change in resistance responds differently to oxygen/gas exposure. • The behavior of resistance recovery suggests an alternative method of low-pressure sensing. - Abstract: The effect of ultra-violet (UV) irradiation on the electronic structure and the surface resistance of an insulating SrTiO{sub 3}(0 0 1) crystal is studied in this work. Upon UV irradiation, we show that the two-dimensional electron gas (2DEG) emerges at the insulating SrTiO{sub 3} surface and there is a pronounced change in the surface resistance. By combining the observations of the change in valance band and the resistance change under different environments of gas pressure and gas species, we find that UV-induced oxygen vacancies at the surface plays a major role in the resistance change. The dynamic of the resistance change at different oxygen pressures also suggests an alternative method of low-pressure sensing.

Non-catalyzed cathodic oxygen reduction at graphite granules in microbial fuel cells

International Nuclear Information System (INIS)

Freguia, Stefano; Rabaey, Korneel; Yuan Zhiguo; Keller, Juerg

2007-01-01

Oxygen is the most sustainable electron acceptor currently available for microbial fuel cell (MFC) cathodes. However, its high overpotential for reduction to water limits the current that can be produced. Several materials and catalysts have previously been investigated in order to facilitate oxygen reduction at the cathode surface. This study shows that significant stable currents can be delivered by using a non-catalyzed cathode made of granular graphite. Power outputs up to 21 W m -3 (cathode total volume) or 50 W m -3 (cathode liquid volume) were attained in a continuous MFC fed with acetate. These values are higher than those obtained in several other studies using catalyzed graphite in various forms. The presence of nanoscale pores on granular graphite provides a high surface area for oxygen reduction. The current generated with this cathode can sustain an anodic volume specific COD removal rate of 1.46 kg COD m -3 d -1 , which is higher than that of a conventional aerobic process. This study demonstrates that microbial fuel cells can be operated efficiently using high surface graphite as cathode material. This implies that research on microbial fuel cell cathodes should not only focus on catalysts, but also on high surface area materials

Non-catalyzed cathodic oxygen reduction at graphite granules in microbial fuel cells

Energy Technology Data Exchange (ETDEWEB)

Freguia, Stefano; Rabaey, Korneel; Yuan, Zhiguo; Keller, Juerg [The University of Queensland, St. Lucia, Qld (Australia). Advanced Wastewater Management Centre

2007-12-01

Oxygen is the most sustainable electron acceptor currently available for microbial fuel cell (MFC) cathodes. However, its high overpotential for reduction to water limits the current that can be produced. Several materials and catalysts have previously been investigated in order to facilitate oxygen reduction at the cathode surface. This study shows that significant stable currents can be delivered by using a non-catalyzed cathode made of granular graphite. Power outputs up to 21 W m{sup -3} (cathode total volume) or 50 W m{sup -3} (cathode liquid volume) were attained in a continuous MFC fed with acetate. These values are higher than those obtained in several other studies using catalyzed graphite in various forms. The presence of nanoscale pores on granular graphite provides a high surface area for oxygen reduction. The current generated with this cathode can sustain an anodic volume specific COD removal rate of 1.46 kg{sub COD} m{sup -3} d{sup -1}, which is higher than that of a conventional aerobic process. This study demonstrates that microbial fuel cells can be operated efficiently using high surface graphite as cathode material. This implies that research on microbial fuel cell cathodes should not only focus on catalysts, but also on high surface area materials. (author)

Caution on the storage of waters and aqueous solutions in plastic containers for hydrogen and oxygen stable isotope analysis.

Science.gov (United States)

Spangenberg, Jorge E

2012-11-30

The choice of containers for storage of aqueous samples between their collection, transport and water hydrogen ((2)H) and oxygen ((18)O) stable isotope analysis is a topic of concern for a wide range of fields in environmental, geological, biomedical, food, and forensic sciences. The transport and separation of water molecules during water vapor or liquid uptake by sorption or solution and the diffusive transport of water molecules through organic polymer material by permeation or pervaporation may entail an isotopic fractionation. An experiment was conducted to evaluate the extent of such fractionation. Sixteen bottle-like containers of eleven different organic polymers, including low and high density polyethylene (LDPE and HDPE), polypropylene (PP), polycarbonate (PC), polyethylene terephthalate (PET), and perfluoroalkoxy-Teflon (PFA), of different wall thickness and size were completely filled with the same mineral water and stored for 659 days under the same conditions of temperature and humidity. Particular care was exercised to keep the bottles tightly closed and prevent loss of water vapor through the seals. Changes of up to +5‰ for δ(2)H values and +2.0‰ for δ(18)O values were measured for water after more than 1 year of storage within a plastic container, with the magnitude of change depending mainly on the type of organic polymer, wall thickness, and container size. The most important variations were measured for the PET and PC bottles. Waters stored in glass bottles with Polyseal™ cone-lined PP screw caps and thick-walled HDPE or PFA containers with linerless screw caps having an integrally molded inner sealing ring preserved their original δ(2)H and δ(18)O values. The carbon, hydrogen, and oxygen stable isotope compositions of the organic polymeric materials were also determined. The results of this study clearly show that for precise and accurate measurements of the water stable isotope composition in aqueous solutions, rigorous sampling and

Stable Boundary Layer Issues

OpenAIRE

Steeneveld, G.J.

2012-01-01

Understanding and prediction of the stable atmospheric boundary layer is a challenging task. Many physical processes are relevant in the stable boundary layer, i.e. turbulence, radiation, land surface coupling, orographic turbulent and gravity wave drag, and land surface heterogeneity. The development of robust stable boundary layer parameterizations for use in NWP and climate models is hampered by the multiplicity of processes and their unknown interactions. As a result, these models suffer ...

Ab initio R1 mechanism of photostimulated oxygen isotope exchange reaction on a defect TiO{sub 2} surface: The case of terminal oxygen atom exchange

Energy Technology Data Exchange (ETDEWEB)

Kevorkyants, Ruslan, E-mail: ruslan.kevorkyants@gmail.com; Sboev, Mikhail N.; Chizhov, Yuri V.

2017-05-01

Highlights: • DFT R1 mechanism of photostimulated oxygen isotope exchange between {sup 16}O{sup 18}O and terminal oxygen atom of a defect surface of nanocrystalline TiO{sub 2} is proposed. • The mechanism involves four adsorption intermediates and five transition states. • Activation energy of the reaction is 0.24 eV. • G-tensors of O{sub 3}{sup −} intermediates match EPR data on O{sub 2} adsorbed on UV-irradiated TiO{sub 2} surface. - Abstract: Based on density functional theory we propose R1 mechanism of photostimulated oxygen isotope exchange (POIEx) reaction between {sup 16}O{sup 18}O and terminal oxygen atom of a defect TiO{sub 2} surface, which is modeled by amorphous Ti{sub 8}O{sub 16} nanocluster in excited S{sup 1} electronic state. The proposed mechanism involves four adsorption intermediates and five transition states. The computed activation energy of the POIEx equals 0.24 eV. The computed g-tensors of the predicted ozonide O{sub 3}{sup −} chemisorption species match well EPR data on O{sub 2} adsorption on UV-irradiated nanocrystalline TiO{sub 2}. This match serves a mean of justification of the proposed R1 mechanism of the POIEx reaction. In addition, it is found that the proposed R1 POIEx reaction’s mechanism differs from R1 mechanism of thermo-assisted OIEx reaction on a surface of supported vanadium oxide catalyst VO{sub x}/TiO{sub 2} reported earlier.

The change of steel surface chemistry regarding oxygen partial pressure and dew point

Science.gov (United States)

Norden, Martin; Blumenau, Marc; Wuttke, Thiemo; Peters, Klaus-Josef

2013-04-01

By investigating the surface state of a Ti-IF, TiNb-IF and a MnCr-DP after several series of intercritical annealing, the impact of the annealing gas composition on the selective oxidation process is discussed. On behalf of the presented results, it can be concluded that not the general oxygen partial pressure in the annealing furnace, which is a result of the equilibrium reaction of water and hydrogen, is the main driving force for the selective oxidation process. It is shown that the amounts of adsorbed gases at the strip surface and the effective oxygen partial pressure resulting from the adsorbed gases, which is mainly dependent on the water content of the annealing furnace, is driving the selective oxidation processes occurring during intercritical annealing. Thus it is concluded, that for industrial applications the dew point must be the key parameter value for process control.

Combustion of methane-oxygen and methane-oxygen-CFC mixtures initiated by a high-current slipping surface discharge

International Nuclear Information System (INIS)

Kossyi, I.A.; Silakov, V.P.; Tarasova, N.M.

2001-01-01

Results are presented from experimental studies of the destruction of chlorofluorocarbon (CF 2 Cl 2 ) molecules in a methane-oxygen (air) gas mixture whose combustion is initiated by a high-current slipping surface discharge. It is found that a three-component CH 4 + O 2 (air)+ CF 2 Cl 2 gas mixture (even with a considerable amount of the third component) demonstrates properties of explosive combustion involving chain reactions that are typical of two-component CH 4 + O 2 mixtures. Experiments show the high degree of destruction (almost complete decomposition) of chlorofluorocarbons contained in the mixture during one combustion event. The combustion dynamics is studied. It is shown that the combustion initiated by a slipping surface discharge has a number of characteristic features that make it impossible to identify the combustion dynamics with the formation of a combustion or detonation wave. The features of the effects observed can be related to intense UV radiation produced by a pulsed high-current surface discharge

Micromechanism of oxygen transport during initial stage oxidation in Si(100) surface: A ReaxFF molecular dynamics simulation study

International Nuclear Information System (INIS)

Sun, Yu; Liu, Yilun; Chen, Xuefeng; Zhai, Zhi; Xu, Fei; Liu, Yijun

2017-01-01

Highlights: • A competition mechanism between thermal actuation and compressive stress blocking was found for the oxygen transport. • At low temperature, a compressive stress was generated in the oxide layer which blocked oxygen transport into the deeper region. • O atoms gained larger possibility to go deeper inward as temperature increase. • The related film quality was well explained by the competition mechanism. - Abstract: The early stage oxidation in Si(100) surface has been investigated in this work by a reactive force field molecular dynamics (ReaxFF MD) simulation, manifesting that the oxygen transport acted as a dominant issue for initial oxidation process. Due to the oxidation, a compressive stress was generated in the oxide layer which blocked the oxygen transport perpendicular to the Si(100) surface and further prevented oxidation in the deeper layer. In contrast, thermal actuation was beneficial to the oxygen transport into deeper layer as temperature increases. Therefore, a competition mechanism was found for the oxygen transport during early stage oxidation in Si(100) surface. At room temperature, the oxygen transport was governed by the blocking effect of compressive stress, so a better quality oxide film with more uniform interface and more stoichiometric oxide structure was obtained. Indeed, the mechanism presented in this work is also applicable for other self-limiting oxidation (e.g. metal oxidation) and is helpful for the design of high-performance electronic devices.

Micromechanism of oxygen transport during initial stage oxidation in Si(100) surface: A ReaxFF molecular dynamics simulation study

Energy Technology Data Exchange (ETDEWEB)

Sun, Yu, E-mail: yu.sun@xjtu.edu.cn [State Key Laboratory for Manufacturing Systems Engineering, School of Mechanical Engineering, Xi’an Jiaotong University, Xi’an 710049 (China); Institute for Computational Mechanics and Its Applications, Northwestern Polytechnical University, Xi’an 710072 (China); Liu, Yilun [State Key Laboratory for Strength and Vibration of Mechanical Structures, School of Aerospace Engineering, Xi’an Jiaotong University, Xi’an 710049 (China); Chen, Xuefeng; Zhai, Zhi [State Key Laboratory for Manufacturing Systems Engineering, School of Mechanical Engineering, Xi’an Jiaotong University, Xi’an 710049 (China); Xu, Fei [Institute for Computational Mechanics and Its Applications, Northwestern Polytechnical University, Xi’an 710072 (China); Liu, Yijun [Institute for Computational Mechanics and Its Applications, Northwestern Polytechnical University, Xi’an 710072 (China); Mechanical Engineering, University of Cincinnati, Cincinnati, OH 45221-0072 (United States)

2017-06-01

Highlights: • A competition mechanism between thermal actuation and compressive stress blocking was found for the oxygen transport. • At low temperature, a compressive stress was generated in the oxide layer which blocked oxygen transport into the deeper region. • O atoms gained larger possibility to go deeper inward as temperature increase. • The related film quality was well explained by the competition mechanism. - Abstract: The early stage oxidation in Si(100) surface has been investigated in this work by a reactive force field molecular dynamics (ReaxFF MD) simulation, manifesting that the oxygen transport acted as a dominant issue for initial oxidation process. Due to the oxidation, a compressive stress was generated in the oxide layer which blocked the oxygen transport perpendicular to the Si(100) surface and further prevented oxidation in the deeper layer. In contrast, thermal actuation was beneficial to the oxygen transport into deeper layer as temperature increases. Therefore, a competition mechanism was found for the oxygen transport during early stage oxidation in Si(100) surface. At room temperature, the oxygen transport was governed by the blocking effect of compressive stress, so a better quality oxide film with more uniform interface and more stoichiometric oxide structure was obtained. Indeed, the mechanism presented in this work is also applicable for other self-limiting oxidation (e.g. metal oxidation) and is helpful for the design of high-performance electronic devices.

Surface monofunctionalized polymethyl pentene hollow fiber membranes by plasma treatment and hemocompatibility modification for membrane oxygenators

Science.gov (United States)

Huang, Xin; Wang, Weiping; Zheng, Zhi; Fan, Wenling; Mao, Chun; Shi, Jialiang; Li, Lei

2016-01-01

The hemocompatibility of polymethyl pentene (PMP) hollow fiber membranes (HFMs) was improved through surface modification for membrane oxygenator applications. The modification was performed stepwise with the following: (1) oxygen plasma treatment, (2) functionalization of monosort hydroxyl groups through NaBH4 reduction, and (3) grafting 2-methacryloyloxyethyl phosphorylcholine (MPC) or heparin. SEM, ATR-FTIR, and XPS analyses were conducted to confirm successful grafting during the modification. The hemocompatibility of PMP HFMs was analyzed and compared through protein adsorption, platelet adhesion, and coagulation tests. Pure CO2 and O2 permeation rates, as well as in vitro gas exchange rates, were determined to evaluate the mass transfer properties of PMP HFMs. SEM results showed that different nanofibril topographies were introduced on the HFM surface. ATR-FTIR and XPS spectra indicated the presence of functionalization of monosort hydroxyl group and the grafting of MPC and heparin. Hemocompatibility evaluation results showed that the modified PMP HFMs presented optimal hemocompatibility compared with pristine HFMs. Gas permeation results revealed that gas permeation flux increased in the modified HFMs because of dense surface etching during the plasma treatment. The results of in vitro gas exchange rates showed that all modified PMP HFMs presented decreased gas exchange rates because of potential surface fluid wetting. The proposed strategy exhibits a potential for fabricating membrane oxygenators for biomedical applications to prevent coagulation formation and alter plasma-induced surface topology and composition.

The Effect of Surface Patterning on Corrosion Resistance of Biomedical Devices

Science.gov (United States)

Guo, Mengnan; Toloei, Alisina; Rotermund, Harm H.

2016-10-01

In this study, two styles of surface topographies have been created on stainless steel wires to test their corrosion resistance as simulated implanted biomedical devices. Grade 316 LVM stainless steel wire was initially polished to G1500 surface finish before treatment to produce the two different topographies: 1. Unidirectional roughness was created using SiC papers and 2. Various patterns were created with specific hole diameter and inter-hole spacing using focused ion beam (FIB). In order to simulate the environment of implanted biomedical devices, a three-electrode electrochemical cell with 0.9% (by mass) NaCl solution has been used to test the corrosion resistance of the samples by potentiodynamic polarization test method. SEM and EDS analyzed the appearance and chemical composition of different elements including oxygen on the surface. The potential of stable pitting, time related to the initiation of the stable pitting, and the highest corrosion current associated with stable pitting have been compared for samples with the two styles of topography. It was found that surfaces with patterns have a relatively higher pitting potential and it takes longer time to initiate stable pitting than the surface without any patterns.

Density functional study of NO adsorption on undefected and oxygen defective Au–BaO(1 0 0) surfaces

Energy Technology Data Exchange (ETDEWEB)

Añez, Rafael, E-mail: ranez@ivic.gob.ve [Laboratorio de Química Física y Catálisis Computacional, Centro de Química, Instituto Venezolano de Investigaciones Científicas, Apartado, 21827 Caracas (Venezuela, Bolivarian Republic of); Sierraalta, Aníbal; Bastardo, Anelisse [Laboratorio de Química Física y Catálisis Computacional, Centro de Química, Instituto Venezolano de Investigaciones Científicas, Apartado, 21827 Caracas (Venezuela, Bolivarian Republic of); Coll, David [Laboratorio de Físico Química Teórica de Materiales, Centro de Química, Instituto Venezolano de Investigaciones Científicas, Apartado, 21827 Caracas (Venezuela, Bolivarian Republic of); Garcia, Belkis [Instituto Universitario de Tecnología de Valencia IUTVAL, Valencia, Edo. Carabobo (Venezuela, Bolivarian Republic of)

2014-07-01

A periodic density functional approach has been used in order to explore the interaction of NO with undoped and Au doped BaO(1 0 0) surface. Due to oxygen vacancies increase the interaction between the doping metal and the surface, F{sub S} and F{sub S}{sup +} vacancies were studied and compared with the results obtained on the undefected doped BaO(1 0 0). Our results indicate that the high basicity of the BaO surface, besides the electron density changes produced by the oxygen vacancies, modify considerably how the Au atom interacts with the surface increasing the ionic character of the interaction. F{sub S} vacancy shows to be a promise center to activate de NO bond on the BaO(1 0 0) surface.

Surface-Selective Preferential Production of Reactive Oxygen Species on Piezoelectric Ceramics for Bacterial Killing.

Science.gov (United States)

Tan, Guoxin; Wang, Shuangying; Zhu, Ye; Zhou, Lei; Yu, Peng; Wang, Xiaolan; He, Tianrui; Chen, Junqi; Mao, Chuanbin; Ning, Chengyun

2016-09-21

Reactive oxygen species (ROS) can be used to kill bacterial cells, and thus the selective generation of ROS from material surfaces is an emerging direction in antibacterial material discovery. We found the polarization of piezoelectric ceramic causes the two sides of the disk to become positively and negatively charged, which translate into cathode and anode surfaces in an aqueous solution. Because of the microelectrolysis of water, ROS are preferentially formed on the cathode surface. Consequently, the bacteria are selectively killed on the cathode surface. However, the cell experiment suggested that the level of ROS is safe for normal mammalian cells.

Roles of Bulk and Surface Chemistry in the Oxygen Exchange Kinetics and Related Properties of Mixed Conducting Perovskite Oxide Electrodes

Directory of Open Access Journals (Sweden)

Nicola H. Perry

2016-10-01

Full Text Available Mixed conducting perovskite oxides and related structures serving as electrodes for electrochemical oxygen incorporation and evolution in solid oxide fuel and electrolysis cells, respectively, play a significant role in determining the cell efficiency and lifetime. Desired improvements in catalytic activity for rapid surface oxygen exchange, fast bulk transport (electronic and ionic, and thermo-chemo-mechanical stability of oxygen electrodes will require increased understanding of the impact of both bulk and surface chemistry on these properties. This review highlights selected work at the International Institute for Carbon-Neutral Energy Research (I2CNER, Kyushu University, set in the context of work in the broader community, aiming to characterize and understand relationships between bulk and surface composition and oxygen electrode performance. Insights into aspects of bulk point defect chemistry, electronic structure, crystal structure, and cation choice that impact carrier concentrations and mobilities, surface exchange kinetics, and chemical expansion coefficients are emerging. At the same time, an understanding of the relationship between bulk and surface chemistry is being developed that may assist design of electrodes with more robust surface chemistries, e.g., impurity tolerance or limited surface segregation. Ion scattering techniques (e.g., secondary ion mass spectrometry, SIMS, or low energy ion scattering spectroscopy, LEIS with high surface sensitivity and increasing lateral resolution are proving useful for measuring surface exchange kinetics, diffusivity, and corresponding outer monolayer chemistry of electrodes exposed to typical operating conditions. Beyond consideration of chemical composition, the use of strain and/or a high density of active interfaces also show promise for enhancing performance.

Biofilm formation in geometries with different surface curvature and oxygen availability

International Nuclear Information System (INIS)

Chang, Ya-Wen; Fragkopoulos, Alexandros A; Kim, Harold D; Fernández-Nieves, Alberto; Marquez, Samantha M; Angelini, Thomas E

2015-01-01

Bacteria in the natural environment exist as interface-associated colonies known as biofilms . Complex mechanisms are often involved in biofilm formation and development. Despite the understanding of the molecular mechanisms involved in biofilm formation, it remains unclear how physical effects in standing cultures influence biofilm development. The topology of the solid interface has been suggested as one of the physical cues influencing bacteria-surface interactions and biofilm development. Using the model organism Bacillus subtilis, we study the transformation of swimming bacteria in liquid culture into robust biofilms in a range of confinement geometries (planar, spherical and toroidal) and interfaces (air/water, silicone/water, and silicone elastomer/water). We find that B. subtilis form submerged biofilms at both solid and liquid interfaces in addition to air-water pellicles. When confined, bacteria grow on curved surfaces of both positive and negative Gaussian curvature. However, the confinement geometry does affect the resulting biofilm roughness and relative coverage. We also find that the biofilm location is governed by oxygen availability as well as by gravitational effects; these compete with each other in some situations. Overall, our results demonstrate that confinement geometry is an effective way to control oxygen availability and subsequently biofilm growth. (paper)

Carbon and oxygen stable isotope and trace element studies in speleothems and across the J-K boundary, Central Italy

International Nuclear Information System (INIS)

Kudielka, G.

2001-07-01

Carbon and Oxygen stable isotope ratios of carbonates decisively depend on fractionation during physicochemical processes. Therefore, they represent a powerful tool to derive information on past conditions under which the carbonates formed. Isotope ratio mass spectrometry (IRMS) offers a large range of applications. This thesis presents two projects based upon investigation of carbon and oxygen stable isotope ratios combined with trace element abundances (determined by instrumental neutron activation analysis, INAA) in carbonates. (1) Palaeoclimatic investigation on speleothems from central Italy. Four speleothems from Grotta Grande del Vento, central Italy, were analyzed for stable isotope ratios and trace element abundances, and age dated to obtain a chronologically reliable stable isotope profile. The speleothems were sampled by means of a dental drill to gain a stable isotope profile with a 0.5 mm resolution, trace element abundances have been performed by INAA every 0.5 cm, and the samples for age dating were picked according to remarkable features in the stable isotope trends and analyzed by TIMS. The record covers the period from 93 ka until the early holocene with a hiatus lasting from 75 ka until 65.0 ka. Speleothem growth during the last glacial indicates moderate conditions in the Frasassi region back then. Comparison with speleothems from Ireland, France and northern Italy reveal a north-south slope in d18O, indicating, that the rain over central Italy mainly originates from the North Atlantic. Depletion of moisture in d18O during its continental trajectory is due to rainout, which primarily extracts the heavy isotopes. The stable isotope record is in good agreement with the high-resolution speleothem record from Soreq Cave, Israel. Distinct isotopic events coincide between 85 ka and 80 ka, between ∼ 60 ka and 50 ka and from the last glacial to the early holocene. An offset has been existing between the two records at any time. The speleothems of

Systematic spatial and stoichiometric screening towards understanding the surface of ultrasmall oxygenated silicon nanocrystal

Science.gov (United States)

Niaz, Shanawer; Zdetsis, Aristides D.; Koukaras, Emmanuel N.; Gülseren, Oǧuz; Sadiq, Imran

2016-11-01

In most of the realistic ab initio and model calculations which have appeared on the emission of light from silicon nanocrystals, the role of surface oxygen has been usually ignored, underestimated or completely ruled out. We investigate theoretically, by density functional theory (DFT/B3LYP) possible modes of oxygen bonding in hydrogen terminated silicon quantum dots using as a representative case of the Si29 nanocrystal. We have considered Bridge-bonded oxygen (BBO), Doubly-bonded oxygen (DBO), hydroxyl (OH) and Mix of these oxidizing agents. Due to stoichiometry, all comparisons performed are unbiased with respect to composition whereas spatial distribution of oxygen species pointed out drastic change in electronic and cohesive characteristics of nanocrytals. From an overall perspective of this study, it is shown that bridge bonded oxygenated Si nanocrystals accompanied by Mix have higher binding energies and large electronic gap compared to nanocrystals with doubly bonded oxygen atoms. In addition, it is observed that the presence of OH along with BBO, DBO and mixed configurations further lowers electronic gaps and binding energies but trends in same fashion. It is also demonstrated that within same composition, oxidizing constituent, along with their spatial distribution substantially alters binding energy, highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) gap (up to 1.48 eV) and localization of frontier orbitals.

Surface reactivity of mercury on the oxygen-terminated hematite(0001) surface: a first-principle study

Science.gov (United States)

Jung, J. E.; Wilcox, J.

2016-12-01

Hematite (α-Fe2O3) is a common mineral found in Earth's near-surface environment. Due to its nontoxicity, corrosion-resistance, and high thermal stability, α-Fe2O3 has attracted attentions as materials for various applications such as photocatalysts, gas sensors, as well as for the removal of heavy metals. In this study, α-Fe2O3 is chosen for potential mercury (Hg) sorbent in order to remove Hg from coal-fired power plants. Specifically, theoretical approaches using density functional theory (DFT) is used to understand surface reactivity of Hg on oxygen (O) terminated α-Fe2O3(0001) surface. The most probable adsorption sites of Hg, chlorine (Cl), and mercury chloride (HgCl) on the α-Fe2O3 surface are found based on adsorption energy calculations, and the oxidation states of the adsorbates are determined by Bader charge analysis. Additionally, projected density of states (PDOS) analysis characterizes the surface-adsorbate bonding mechanism. The results of adsorption energy calculation proposes that Hg physisorbs to the α-Fe2O3(0001) surface with adsorption energy of -0.278 eV, and the subsequent Bader charge analysis confirms that Hg is slightly oxidized. In addition, Cl introduced to the Hg-adsorbed surface strengthens Hg stability on the α-Fe2O3(0001) surface as evidenced by a shortened Hg-surface equilibrium distance. The PDOS analysis also suggests that Cl enhances the chemical bonding between the surface and the adsorbate, thereby increasing adsorption strength. In summary, α-Fe2O3 has ability to adsorb and oxidize Hg, and this reactivity is enhanced in the presence of Cl.

Hydrogen and oxygen behaviors on Porous-Si surfaces observed using a scanning ESD ion microscope

International Nuclear Information System (INIS)

Itoh, Yuki; Ueda, Kazuyuki

2004-01-01

A scanning electron-stimulated desorption (ESD) ion microscope (SESDIM) measured the 2-D images of hydrogen and oxygen distribution on solid surfaces. A primary electron beam at 600 eV, with a pulse width of 220 ns, resulted in ion yields of H + and O + . This SESDIM is applied to the surface analysis of Porous-Si (Po-Si) partially covered with SiN films. During the heating of a specimen of the Po-Si at 800 deg. C under ultra-high-vacuum (UHV) conditions, the components of the surface materials were moved or diffused by thermal decomposition accompanied by a redistribution of hydrogen and oxygen. After cyclic heating of above 800 deg. C, the dynamic behaviors of H + and O + accompanied by the movements of the SiN layers were observed as images of H + and O + . This was because the H + and O + ions have been identified as composite materials by their kinetic energies

Electron stimulated desorption of positive and negative oxygen ions from YBa{sub 2}Cu{sub 3}O{sub 7} surfaces

Energy Technology Data Exchange (ETDEWEB)

Hoffman, A. [Technion-Israel Inst. of Tech., Haifa (Israel). Solid State Inst.; Moss, S.D.; Paterson, P.J.K. [Royal Melbourne Inst. of Tech., VIC (Australia); McCubbery, D. [La Trobe Univ., Bundoora, VIC (Australia); Petravic, M. [Australian National Univ., Canberra, ACT (Australia)

1996-12-31

The electron stimulated desorption (ESD) of positive and negative oxygen ion from superconducting YBa{sub 2}Cu{sub 3}O{sub 7} surfaces was studied. Based on ion desorption yield measurements as function of electron kinetic energy, primary excitations leading to positive and negative oxygen ion desorption are suggested. To the best of the authors` knowledge this is the first study on electron energy dependent ESD from YBa{sub 2}Cu{sub 3}O{sub 7} surfaces. The YBa{sub 2}Cu{sub 3}O{sub 7} samples were prepared from BaCO{sub 3}, Y{sub 2}O{sub 3} and CuO using standard high temperature sintering and annealing procedures. Slices 2 mm thick were cut and further annealed at 400 C in flowing oxygen for 24 hours prior to insertion into the ultrahigh vacuum (UHV) chamber for ESD. The near surface composition and chemical state of the annealed sample after exposure to air was examined by Auger and XPS analysis. These measurements suggest that the ESD experiments were performed on samples of similar near surface and bulk composition with some OH- chemisorbed groups and Cl surface contaminations and that negative and positive oxygen ion desorption may be initiated via a primary core level ionization. 10 refs., 3 figs.

Electron stimulated desorption of positive and negative oxygen ions from YBa{sub 2}Cu{sub 3}O{sub 7} surfaces

Energy Technology Data Exchange (ETDEWEB)

Hoffman, A [Technion-Israel Inst. of Tech., Haifa (Israel). Solid State Inst.; Moss, S D; Paterson, P J.K. [Royal Melbourne Inst. of Tech., VIC (Australia); McCubbery, D [La Trobe Univ., Bundoora, VIC (Australia); Petravic, M [Australian National Univ., Canberra, ACT (Australia)

1997-12-31

The electron stimulated desorption (ESD) of positive and negative oxygen ion from superconducting YBa{sub 2}Cu{sub 3}O{sub 7} surfaces was studied. Based on ion desorption yield measurements as function of electron kinetic energy, primary excitations leading to positive and negative oxygen ion desorption are suggested. To the best of the authors` knowledge this is the first study on electron energy dependent ESD from YBa{sub 2}Cu{sub 3}O{sub 7} surfaces. The YBa{sub 2}Cu{sub 3}O{sub 7} samples were prepared from BaCO{sub 3}, Y{sub 2}O{sub 3} and CuO using standard high temperature sintering and annealing procedures. Slices 2 mm thick were cut and further annealed at 400 C in flowing oxygen for 24 hours prior to insertion into the ultrahigh vacuum (UHV) chamber for ESD. The near surface composition and chemical state of the annealed sample after exposure to air was examined by Auger and XPS analysis. These measurements suggest that the ESD experiments were performed on samples of similar near surface and bulk composition with some OH- chemisorbed groups and Cl surface contaminations and that negative and positive oxygen ion desorption may be initiated via a primary core level ionization. 10 refs., 3 figs.

Oxygen exchange at gas/oxide interfaces: how the apparent activation energy of the surface exchange coefficient depends on the kinetic regime.

Science.gov (United States)

Fielitz, Peter; Borchardt, Günter

2016-08-10

In the dedicated literature the oxygen surface exchange coefficient KO and the equilibrium oxygen exchange rate [Fraktur R] are considered to be directly proportional to each other regardless of the experimental circumstances. Recent experimental observations, however, contradict the consequences of this assumption. Most surprising is the finding that the apparent activation energy of KO depends dramatically on the kinetic regime in which it has been determined, i.e. surface exchange controlled vs. mixed or diffusion controlled. This work demonstrates how the diffusion boundary condition at the gas/solid interface inevitably entails a correlation between the oxygen surface exchange coefficient KO and the oxygen self-diffusion coefficient DO in the bulk ("on top" of the correlation between KO and [Fraktur R] for the pure surface exchange regime). The model can thus quantitatively explain the range of apparent activation energies measured in the different regimes: in the surface exchange regime the apparent activation energy only contains the contribution of the equilibrium exchange rate, whereas in the mixed or in the diffusion controlled regime the contribution of the oxygen self-diffusivity has also to be taken into account, which may yield significantly higher apparent activation energies and simultaneously quantifies the correlation KO ∝ DO(1/2) observed for a large number of oxides in the mixed or diffusion controlled regime, respectively.

Back-exchange: a novel approach to quantifying oxygen diffusion and surface exchange in ambient atmospheres.

Science.gov (United States)

Cooper, Samuel J; Niania, Mathew; Hoffmann, Franca; Kilner, John A

2017-05-17

A novel two-step Isotopic Exchange (IE) technique has been developed to investigate the influence of oxygen containing components of ambient air (such as H 2 O and CO 2 ) on the effective surface exchange coefficient (k*) of a common mixed ionic electronic conductor material. The two step 'back-exchange' technique was used to introduce a tracer diffusion profile, which was subsequently measured using Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS). The isotopic fraction of oxygen in a dense sample as a function of distance from the surface, before and after the second exchange step, could then be used to determine the surface exchange coefficient in each atmosphere. A new analytical solution was found to the diffusion equation in a semi-infinite domain with a variable surface exchange boundary, for the special case where D* and k* are constant for all exchange steps. This solution validated the results of a numerical, Crank-Nicolson type finite-difference simulation, which was used to extract the parameters from the experimental data. When modelling electrodes, D* and k* are important input parameters, which significantly impact performance. In this study La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ (LSCF6428) was investigated and it was found that the rate of exchange was increased by around 250% in ambient air compared to high purity oxygen at the same pO 2 . The three experiments performed in this study were used to validate the back-exchange approach and show its utility.

Near Surface CO2 Triple Oxygen Isotope Composition

Directory of Open Access Journals (Sweden)

Sasadhar Mahata

2016-02-01

Full Text Available The isotopic composition of carbon dioxide in the atmosphere is a powerful tool for constraining its sources and sinks. In particular, the 17O oxygen anomaly [Δ17O = 1000 × ln(1 + δ17O/1000 - 0.516 × 1000 × ln(1 + δ18O/1000], with a value > 0.5‰ produced in the middle atmosphere, provides an ideal tool for probing the exchange of carbon dioxide between the biosphere/hydrosphere and atmosphere. The biosphere/hydrosphere and anthropogenic emissions give values ≤ 0.3‰. Therefore, any anomaly in near surface CO2 would reflect the balance between stratospheric input and exchange with the aforementioned surface sources. We have analyzed Δ17O values of CO2 separated from air samples collected in Taipei, Taiwan, located in the western Pacific region. The obtained mean anomaly is 0.42 ± 0.14‰ (1-σ standard deviation, in good agreement with model prediction and a published decadal record. Apart from typically used δ13C and δ18O values, the Δ17O value could provide an additional tracer for constraining the carbon cycle.

On the nature of oxygen-containing surface groups on carbon nanofibers and their role for platinum deposition—an xps and titration study

NARCIS (Netherlands)

Plomp, A.J.; Su, D.S.; de Jong, K.P.; Bitter, J.H.

2009-01-01

XPS and acid−base titrations were used to investigate the nature and stability of oxygen-containing surface groups on carbon nanofibers (CNF) and platinum-containing CNF. During heat treatments in inert atmosphere at 973 K all acidic (carboxylic) oxygen surface groups were removed for CNF.

High-Resolution Electron Energy Loss Studies of Oxygen, Hydrogen, Nitrogen, Nitric Oxide, and Nitrous Oxide Adsorption on Germanium Surfaces.

Science.gov (United States)

Entringer, Anthony G.

The first high resolution electron energy loss spectroscopy (HREELS) studies of the oxidation and nitridation of germanium surfaces are reported. Both single crystal Ge(111) and disordered surfaces were studied. Surfaces were exposed to H, O_2, NO, N _2O, and N, after cleaning in ultra-high vacuum. The Ge surfaces were found to be non-reactive to molecular hydrogen (H_2) at room temperature. Exposure to atomic hydrogen (H) resulted hydrogen adsorption as demonstrated by the presence of Ge-H vibrational modes. The HREEL spectrum of the native oxide of Ge characteristic of nu -GeO_2 was obtained by heating the oxide to 200^circC. Three peaks were observed at 33, 62, and 106 meV for molecular oxygen (O_2) adsorbed on clean Ge(111) at room temperature. These peaks are indicative of dissociative bonding and a dominant Ge-O-Ge bridge structure. Subsequent hydrogen exposure resulted in a shift of the Ge-H stretch from its isolated value of 247 meV to 267 meV, indicative of a dominant +3 oxidation state. A high density of dangling bonds and defects and deeper oxygen penetration at the amorphous Ge surface result in a dilute bridge structure with a predominant +1 oxidation state for similar exposures. Molecules of N_2O decompose at the surfaces to desorbed N_2 molecules and chemisorbed oxygen atoms. In contrast, both oxygen and nitrogen are detected at the surfaces following exposure to NO molecules. Both NO and N_2O appear to dissociate and bond at the top surface layer. Molecular nitrogen (N_2) does not react with the Ge surfaces, however, a precursor Ge nitride is observed at room temperature following exposure to nitrogen atoms and ions. Removal of oxygen by heating of the NO-exposed surface to 550^circC enabled the identification of the Ge-N vibrational modes. These modes show a structure similar to that of germanium nitride. This spectrum is also identical to that of the N-exposed surface heated to 550^circC. Surface phonon modes of the narrow-gap semiconducting

[Long-term expansion of multipotent mesenchymal stromal cells under reduced oxygen tension].

Science.gov (United States)

Rylova, Iu V; Buravkova, L B

2013-01-01

We have shown that the decrease in oxygen tension in the culture medium of multipotent mesenchymal stromal cells (MMSCs) results in a short-term reduction in the proportion of CD73(+)-cells in the population, without effecting the number of cells expressing other constitutive surface markers (CD90 and CD105). In this case, the heterogeneity of the cell population declined: large spread cells disappeared. The proliferative activity of MMSCs significantly increased and remained stable in conditions in which the oxygen content was close to the tissue oxygen levels (5% O2). At lower oxygen concentration, proliferative activity of the cells gradually reduced from passages 3-4. The increase in proliferative activity was not accompanied by increased expression of telomerase gene indicateding the alsance of cell transformation. However, genome-wide analysis of MMSC gene expression level revealed changes in expression of cyclins (CCND2 and PCNA), regulatory subunit cyclin-dependent kinase (CKS2) and an inhibitor of cyclin-dependent kinase (CDKN2C), regulating the cell cycle, which is obviously facilitated the increase in the proliferative capacity of cells at lower oxygen tension.

Osteoblast response to oxygen functionalised plasma polymer surfaces

International Nuclear Information System (INIS)

Kelly, Jonathan M.

2001-01-01

Thin organic films with oxygen-carbon functionalities were deposited from plasmas containing vapour of the small organic compounds: allyI alcohol, methyl vinyl ketone and acrylic acid with octadiene. Characterisation of the deposits was carried out using X-ray photoelectron spectroscopy, in conjunction with chemical derivatisation, and this showed that plasma polymers retained high levels of original monomer functionality when the plasmas were sustained at low power for a given monomer vapour flow rate. High levels of attachment of rat osteosarcoma (ROS 17/2.8) cells were observed on surfaces that had high concentrations of hydroxyl and carbonyl functionalities and intermediate concentrations of carboxyl functionality. Cells did not attach to the octadiene plasma polymer. Cell attachment to carboxyl and methyl functionalised self-assembled monolayers increased with increasing concentration of surface carboxyl groups. Adsorption of the extracellular matrix protein fibronectin to acrylic acid/octadiene plasma copolymers was studied by enzyme linked immunosorbent assays and by I 125 radiolabelling. Fibronectin adsorbed in largest amounts to surfaces with intermediate concentrations of carboxyl functionality. Spreading of ROS cells and rat bone marrow stromal cells (BMSC) was characterised by computer image analysis. Cell spreading in media containing 10% serum, on a surface deposited from a plasma of 5 O/o acrylic acid was much greater than on the octadiene plasma polymer while most extensive cell spreading was observed on these surfaces when preadsorbed with fibronectin. Growth (proliferation) of BMSC was assessed over nine days and was found to be faster on an 50% acrylic acid plasma polymer than on tissue culture polystyrene or a hydrocarbon plasma polymer, though cell growth was fastest on fibronectin precoated substrates. Expression of cellular alkaline phosphatase, collagen and calcium reached similar levels on the 50% acrylic acid plasma polymer, tissue culture

Osteoblast response to oxygen functionalised plasma polymer surfaces

Energy Technology Data Exchange (ETDEWEB)

Kelly, Jonathan M

2001-07-01

Thin organic films with oxygen-carbon functionalities were deposited from plasmas containing vapour of the small organic compounds: allyI alcohol, methyl vinyl ketone and acrylic acid with octadiene. Characterisation of the deposits was carried out using X-ray photoelectron spectroscopy, in conjunction with chemical derivatisation, and this showed that plasma polymers retained high levels of original monomer functionality when the plasmas were sustained at low power for a given monomer vapour flow rate. High levels of attachment of rat osteosarcoma (ROS 17/2.8) cells were observed on surfaces that had high concentrations of hydroxyl and carbonyl functionalities and intermediate concentrations of carboxyl functionality. Cells did not attach to the octadiene plasma polymer. Cell attachment to carboxyl and methyl functionalised self-assembled monolayers increased with increasing concentration of surface carboxyl groups. Adsorption of the extracellular matrix protein fibronectin to acrylic acid/octadiene plasma copolymers was studied by enzyme linked immunosorbent assays and by I{sup 125} radiolabelling. Fibronectin adsorbed in largest amounts to surfaces with intermediate concentrations of carboxyl functionality. Spreading of ROS cells and rat bone marrow stromal cells (BMSC) was characterised by computer image analysis. Cell spreading in media containing 10% serum, on a surface deposited from a plasma of 5 O/o acrylic acid was much greater than on the octadiene plasma polymer while most extensive cell spreading was observed on these surfaces when preadsorbed with fibronectin. Growth (proliferation) of BMSC was assessed over nine days and was found to be faster on an 50% acrylic acid plasma polymer than on tissue culture polystyrene or a hydrocarbon plasma polymer, though cell growth was fastest on fibronectin precoated substrates. Expression of cellular alkaline phosphatase, collagen and calcium reached similar levels on the 50% acrylic acid plasma polymer, tissue

Colossal positive magnetoresistance in surface-passivated oxygen-deficient strontium titanite

KAUST Repository

David, Adrian

2015-05-15

Modulation of resistance by an external magnetic field, i.e. magnetoresistance effect, has been a long-lived theme of research due to both fundamental science and device applications. Here we report colossal positive magnetoresistance (CPMR) (>30,000% at a temperature of 2 K and a magnetic field of 9 T) discovered in degenerate semiconducting strontium titanite (SrTiO3) single crystals capped with ultrathin SrTiO3/LaAlO3 bilayers. The low-pressure high-temperature homoepitaxial growth of several unit cells of SrTiO3 introduces oxygen vacancies and high-mobility carriers in the bulk SrTiO3, and the three-unit-cell LaAlO3 capping layer passivates the surface and improves carrier mobility by suppressing surface-defect-related scattering. The coexistence of multiple types of carriers and inhomogeneous transport lead to the emergence of CPMR. This unit-cell-level surface engineering approach is promising to be generalized to others oxides, and to realize devices with high-mobility carriers and interesting magnetoelectronic properties.

Oxygen and Hydrogen Isotopic Characteristics of the Kaveri River Surface Waters, Southern Peninsular India

International Nuclear Information System (INIS)

Achyuthan, Hema; Michelini, Marzia; Sengupta, Somasis D.; Kale, Vishwas S.; Stenni, Barbara; Flora, Onelio

2010-12-01

We present in this paper the spatial distribution of stable isotopic composition (δ 18 O and δD) of Kaveri River surface waters to understand how the evaporation and precipitation affect the isotopic signature and dynamics of surface river waters. In the southern peninsular India, Kaveri River is one of the longest tropical river. Our stable isotope data indicate that the upper Kaveri region is influenced strongly by the SW monsoon. There is a narrow range between the δ 18 O values found from the origin of the Kaveri River to its delta, and there is no significant orographic impact of the Western Ghats. A decreasing trend of d values is found along the course of the river. This is attributed to evaporation effects, which nevertheless are not very strong. This difference in deuterium excess due to evaporation is also an indication of the moisture recycling in the lower Kaveri area, which is primarily controlled by evaporation from the wetlands in the delta plain but also from the surface waters and as such from the rivers. (author)

Comparison of the OxyMask and Venturi mask in the delivery of supplemental oxygen: Pilot study in oxygen-dependent patients

Science.gov (United States)

Beecroft, Jaime M; Hanly, Patrick J

2006-01-01

BACKGROUND: The OxyMask (Southmedic Inc, Canada) is a new face mask for oxygen delivery that uses a small ‘diffuser’ to concentrate and direct oxygen toward the mouth and nose. The authors hypothesized that this unique design would enable the OxyMask to deliver oxygen more efficiently than a Venturi mask (Hudson RCI, USA) in patients with chronic hypoxemia. METHODS: Oxygen-dependent patients with chronic, stable respiratory disease were recruited to compare the OxyMask and Venturi mask in a randomized, single-blind, cross-over design. Baseline blood oxygen saturation (SaO2) was established breathing room air, followed in a random order by supplemental oxygen through the OxyMask or Venturi mask. Oxygen delivery was titrated to maintain SaO2 4% to 5% and 8% to 9% above baseline for two separate 30 min periods of stable breathing. Oxygen flow rate, partial pressure of inspired and expired oxygen (PO2) and carbon dioxide (PCO2), minute ventilation, heart rate, nasal and oral breathing, SaO2 and transcutaneous PCO2 were collected continuously. The study was repeated following alterations to the OxyMask design, which improved clearance of carbon dioxide. RESULTS: Thirteen patients, aged 28 to 79 years, were studied initially using the original OxyMask. Oxygen flow rate was lower, inspired PO2 was higher and expired PO2 was lower while using the OxyMask. Minute ventilation and inspired and expired PCO2 were significantly higher while using the OxyMask, whereas transcutaneous PCO2, heart rate and the ratio of nasal to oral breathing did not change significantly throughout the study. Following modification of the OxyMask, 13 additional patients, aged 18 to 79 years, were studied using the same protocol. The modified OxyMask provided a higher inspired PO2 at a lower flow rate, without evidence of carbon dioxide retention. CONCLUSIONS: Oxygen is delivered safely and more efficiently by the OxyMask than by the Venturi mask in stable oxygen-dependent patients. PMID:16896425

Oxygen Plasma Treatment of Rubber Surface by the Atmospheric Pressure Cold Plasma Torch

DEFF Research Database (Denmark)

Lee, Bong-ju; Kusano, Yukihiro; Kato, Nobuko

1997-01-01

adhesive. The adhesion property was improved by treatment of the rubber compound with plasma containing oxygen radicals. Physical and chemical changes of the rubber surface as a result of the plasma treatment were analyzed by field emission scanning electron microscopy (FE-SEM) and fourier transform......A new application of the atmospheric cold plasma torch has been investigated. Namely, the surface treatment of an air-exposed vulcanized rubber compound. The effect of plasma treatment was evaluated by the bondability of the treated rubber compound with another rubber compound using a polyurethane...

Periodic density functional theory study of ethylene hydrogenation over Co3O4 (1 1 1) surface: The critical role of oxygen vacancies

International Nuclear Information System (INIS)

Lu, Jinhui; Song, JiaJia; Niu, Hongling; Pan, Lun; Zhang, Xiangwen; Wang, Li; Zou, Ji-Jun

2016-01-01

Highlights: • H 2 dissociates in heterolytic way following H atoms migration to form O−H bond. • H 2 dissociation occurs at low temperature on perfect and oxygen defective Co 3 O 4 . • Oxygen vacancy promotes hydrogenation thermodynamically and kinetically. • O−H bond is weakened on oxygen defective surface. • Hydrogenation requires compromise between H−H activation and O−H breakage. - Abstract: Recently, metal oxides are attracting increasing interests as hydrogenation catalyst. Herein we studied the hydrogenation of ethylene on perfect and oxygen defective Co 3 O 4 (1 1 1) using periodic density functional theory. The energetics and pathways of ethylene hydrogenation to ethane were determined. We have demonstrated that (i) H 2 dissociation on Co 3 O 4 is a complicated two-step process through a heterolytic cleavage, followed by the migration of H atom and finally yields the homolytic product on both perfect and oxygen defective Co 3 O 4 (1 1 1) surfaces easily. (ii) After introducing the surface oxygen vacancy, the stepwise hydrogenation of ethylene by atomic hydrogen is much easier than that on perfect surface due to the weaker bond strength of OH group. The strength of O−H bond is a crucial factor for the hydrogenation reaction which involves the breakage of O−H bond. The formation of oxygen vacancy increases the electronic charges at the adjacent surface O, which reduces its capability of further gaining electrons from adsorbed atomic hydrogen and then weakens the strength of O−H bond. These results emphasize the importance of the oxygen vacancies for hydrogenation on metal oxides.

Fabrication of Water Jet Resistant and Thermally Stable Superhydrophobic Surfaces by Spray Coating of Candle Soot Dispersion.

Science.gov (United States)

Qahtan, Talal F; Gondal, Mohammed A; Alade, Ibrahim O; Dastageer, Mohammed A

2017-08-08

A facile synthesis method for highly stable carbon nanoparticle (CNP) dispersion in acetone by incomplete combustion of paraffin candle flame is presented. The synthesized CNP dispersion is the mixture of graphitic and amorphous carbon nanoparticles of the size range of 20-50 nm and manifested the mesoporosity with an average pore size of 7 nm and a BET surface area of 366 m 2 g -1 . As an application of this material, the carbon nanoparticle dispersion was spray coated (spray-based coating) on a glass surface to fabricate superhydrophobic (water contact angle > 150° and sliding angle fabricated from direct candle flame soot deposition (candle-based coating). This study proved that water jet resistant and thermally stable superhydrophobic surfaces can be easily fabricated by simple spray coating of CNP dispersion gathered from incomplete combustion of paraffin candle flame and this technique can be used for different applications with the potential for the large scale fabrication.

Improved surface corrosion resistance of WE43 magnesium alloy by dual titanium and oxygen ion implantation

Energy Technology Data Exchange (ETDEWEB)

Zhao, Ying [Department of Orthopaedics and Traumatology, The University of Hong Kong, Pokfulam, Hong Kong (China); Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong (China); Wu, Guosong; Lu, Qiuyuan [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong (China); Wu, Jun [Department of Orthopaedics and Traumatology, The University of Hong Kong, Pokfulam, Hong Kong (China); Xu, Ruizhen [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong (China); Yeung, Kelvin W.K., E-mail: wkkyeung@hku.hk [Department of Orthopaedics and Traumatology, The University of Hong Kong, Pokfulam, Hong Kong (China); Chu, Paul K., E-mail: paul.chu@cityu.edu.hk [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong (China)

2013-02-01

Magnesium alloys are potential biodegradable materials and have attracted much attention due to their outstanding biological performance and mechanical properties. However, their rapid degradation inside the human body cannot meet clinical needs. In order to improve the corrosion resistance, dual titanium and oxygen ion implantation is performed to modify the surface of the WE43 magnesium alloy. X-ray photoelectron spectroscopy is used to characterize the microstructures in the near surface layer and electrochemical impedance spectroscopy, potentiodynamic polarization, and immersion tests are employed to investigate the corrosion resistance of the implanted alloys in simulated body fluids. The results indicate that dual titanium and oxygen ion implantation produces a TiO{sub 2}-containing surface film which significantly enhances the corrosion resistance of WE43 magnesium alloy. Our data suggest a simple and practical means to improve the corrosion resistance of degradable magnesium alloys. - Highlights: ► Surface modification of WE43 magnesium alloy using dual ion implantation ► Dual Ti and O ion implantation produces a homogeneous TiO{sub 2}-containing surface film ► Significant improvement of the alloy corrosion resistance after the dual ion implantation.

The coupling effect of gas-phase chemistry and surface reactions on oxygen permeation and fuel conversion in ITM reactors

KAUST Repository

Hong, Jongsup

2015-08-01

© 2015 Elsevier B.V. The effect of the coupling between heterogeneous catalytic reactions supported by an ion transport membrane (ITM) and gas-phase chemistry on fuel conversion and oxygen permeation in ITM reactors is examined. In ITM reactors, thermochemical reactions take place in the gas-phase and on the membrane surface, both of which interact with oxygen permeation. However, this coupling between gas-phase and surface chemistry has not been examined in detail. In this study, a parametric analysis using numerical simulations is conducted to investigate this coupling and its impact on fuel conversion and oxygen permeation rates. A thermochemical model that incorporates heterogeneous chemistry on the membrane surface and detailed chemical kinetics in the gas-phase is used. Results show that fuel conversion and oxygen permeation are strongly influenced by the simultaneous action of both chemistries. It is shown that the coupling somewhat suppresses the gas-phase kinetics and reduces fuel conversion, both attributed to extensive thermal energy transfer towards the membrane which conducts it to the air side and radiates to the reactor walls. The reaction pathway and products, in the form of syngas and C2 hydrocarbons, are also affected. In addition, the operating regimes of ITM reactors in which heterogeneous- or/and homogeneous-phase reactions predominantly contribute to fuel conversion and oxygen permeation are elucidated.

Role of oxygen in surface segregation of metal impurities in silicon poly- and bicrystals

Energy Technology Data Exchange (ETDEWEB)

Amarray, E.; Deville, J.P.

1987-07-01

Metal impurities at surfaces of polycrystalline silicon ribbons have been characterized by surface sensitive methods. Oxygen and heat treatments were found to be a driving force for surface segregation of these impurities. To better analyse their influence and their possible incidence in gettering, model studies were undertaken on Czochralski grown silicon bicrystals. Two main factors of surface segregation have been studied: the role of an ultra-thin oxide layer and the effect of heat treatments. The best surface purification was obtained after an annealing process at 750/sup 0/C of a previously oxidized surface at 450/sup 0/C. This was related to the formation of SiO clusters, followed by a coalescence of SiO/sub 4/ units leading to the subsequent injection of silicon self-interstitials in the lattice.

Electrostatic powder spraying process for the fabrication of stable superhydrophobic surfaces

Science.gov (United States)

Gu, Guotuan; Tian, Yuping; Li, Zhantie; Lu, Dongfang

2011-03-01

Nano-sized Al2O3 particles were modified by heptadecafluorodecyl trimethoxysilane and 2,3-epoxy propoxy propyl trimethoxysilicane to make it both hydrophobic and reactive. The reactive nano-particles were mixed with polyester resin containing curing agents and electrostatic sprayed on stainless steel substrates to obtain stable superhydrophobic coatings after curing. The water contact angle (WCA) on the hybrid coating is influenced by the content of Al2O3 particles in the coating. As the Al2O3 concentration in the coating was increased from 0% to 8%, WCA increased from 68° to 165°. Surface topography of the coatings was examined using scanning electron microscopy (SEM). Nano-particles covered on the coating surface formed continuous film with greatly enhanced roughness, which was found to be responsible for the superhydrophobicity. The method is simple and cost effective and can be used for preparing self-cleaning superhydrophobic coating on large areas.

Electrostatic powder spraying process for the fabrication of stable superhydrophobic surfaces

International Nuclear Information System (INIS)

Gu Guotuan; Tian Yuping; Li Zhantie; Lu Dongfang

2011-01-01

Nano-sized Al 2 O 3 particles were modified by heptadecafluorodecyl trimethoxysilane and 2,3-epoxy propoxy propyl trimethoxysilicane to make it both hydrophobic and reactive. The reactive nano-particles were mixed with polyester resin containing curing agents and electrostatic sprayed on stainless steel substrates to obtain stable superhydrophobic coatings after curing. The water contact angle (WCA) on the hybrid coating is influenced by the content of Al 2 O 3 particles in the coating. As the Al 2 O 3 concentration in the coating was increased from 0% to 8%, WCA increased from 68 o to 165 o . Surface topography of the coatings was examined using scanning electron microscopy (SEM). Nano-particles covered on the coating surface formed continuous film with greatly enhanced roughness, which was found to be responsible for the superhydrophobicity. The method is simple and cost effective and can be used for preparing self-cleaning superhydrophobic coating on large areas.

Effects of hydration and oxygen vacancy on CO2 adsorption and activation on beta-Ga2O3(100).

Science.gov (United States)

Pan, Yun-xiang; Liu, Chang-jun; Mei, Donghai; Ge, Qingfeng

2010-04-20

The effects of hydration and oxygen vacancy on CO(2) adsorption on the beta-Ga(2)O(3)(100) surface have been studied using density functional theory slab calculations. Adsorbed CO(2) is activated on the dry perfect beta-Ga(2)O(3)(100) surface, resulting in a carbonate species. This adsorption is slightly endothermic, with an adsorption energy of 0.07 eV. Water is preferably adsorbed molecularly on the dry perfect beta-Ga(2)O(3)(100) surface with an adsorption energy of -0.56 eV, producing a hydrated perfect beta-Ga(2)O(3)(100) surface. Adsorption of CO(2) on the hydrated surface as a carbonate species is also endothermic, with an adsorption energy of 0.14 eV, indicating a slightly repulsive interaction when H(2)O and CO(2) are coadsorbed. The carbonate species on the hydrated perfect surface can be protonated by the coadsorbed H(2)O to a bicarbonate species, making the CO(2) adsorption exothermic, with an adsorption energy of -0.13 eV. The effect of defects on CO(2) adsorption and activation has been examined by creating an oxygen vacancy on the dry beta-Ga(2)O(3)(100) surface. The formation of an oxygen vacancy is endothermic, by 0.34 eV, with respect to a free O(2) molecule in the gas phase. Presence of the oxygen vacancy promoted the adsorption and activation of CO(2). In the most stable CO(2) adsorption configuration on the dry defective beta-Ga(2)O(3)(100) surface with an oxygen vacancy, one of the oxygen atoms of the adsorbed CO(2) occupies the oxygen vacancy site, and the CO(2) adsorption energy is -0.31 eV. Water favors dissociative adsorption at the oxygen vacancy site on the defective surface. This process is spontaneous, with a reaction energy of -0.62 eV. These results indicate that, when water and CO(2) are present in the adsorption system simultaneously, water will compete with CO(2) for the oxygen vacancy sites and impact CO(2) adsorption and conversion negatively.

Theory and development of fluorescence-based optochemical oxygen sensors: oxygen optodes.

Science.gov (United States)

Opitz, N; Lübbers, D W

1987-01-01

As the preceding considerations concerning the physical and technical features of oxygen optodes have demonstrated, fluorescence-based optochemical oxygen sensors possess certain advantages and peculiarities compared to conventionally applied electrochemical sensors such as polarographic oxygen electrodes. First, in contrast to oxygen electrodes, oxygen measurements with oxygen optodes do not suffer from distortions caused by the reference electrodes. In addition, because of the polarographic process, platinum electrodes continuously consume oxygen, which falsifies the results, especially when small sample volumes or long-term measurements, or both, are involved, whereas the sensor layer of oxygen optodes must only be equilibrated. Moreover, the surface of the platinum wire has to be catalytically clean in order to obtain a plateau of the polarogram and, consequently, to achieve a low rest current at zero PO2. Unfortunately, the demand for catalytically clean platinum surfaces turns out to be rather critical, since surface contamination occurs even with membranized electrodes, resulting in the well-known phenomenon of "electrode poisoning." The question of the specificity of oxygen electrodes also must be considered. In this context, CO2 and halothane may interfere with oxygen measurements, whereas fluorescence quenching is unaffected by CO2 and halothane affects the measurements only slightly, depending on the special indicator used. Furthermore, because of the flow dependence, oxygen measurements with the oxygen electrode show a distinct "stirring effect" caused by the turbulence in front of the electrode, which disturbs the diffusion field. Because of the completely different physical principle of fluorescence optical sensors, such influences are not observed with oxygen optodes. In addition, isolation and shielding of electrical circuits found in electrodes are not necessary for optodes. Furthermore, the sensitivity of oxygen optodes can be tuned to the desired

Stable Isotope Mass Balance of the Laurentian Great Lakes to Constrain Evaporative Losses

Energy Technology Data Exchange (ETDEWEB)

Jasechko, S. [Department of Earth and Environmental Sciences, University of Waterloo, Waterloo, Ontario and Alberta Innovates, Technology Futures, Victoria, British Columbia (Canada); Gibson, J. J. [Canada Alberta Innovates, Technology Futures, Victoria, British Columbia and Department of Geography, University of Victoria, Victoria, British Columbia (Canada); Pietroniro, A. [National Water Research Institute, Environment Canada, Saskatoon, Saskatchewan (Canada); Edwards, T.W D. [Department of Earth and Environmental Sciences, University of Waterloo, Waterloo, Ontario (Canada)

2013-07-15

Evaporation is an important yet poorly constrained component of the water budget of the Laurentian Great Lakes, but is known historically to have a significant impact on regional climate, including enhanced humidity and downwind lake effect precipitation. Sparse over lake climate monitoring continues to limit ability to quantify bulk lake evaporation and precipitation rates by physical measurements, impeded by logistical difficulties and costs of instrumenting large areas of open water (10{sup 3}-10{sup 5} km2). Measurements of stable isotopes of oxygen and hydrogen in water samples of precipitation and surface waters within the great lakes basin are used to better understand the controls on the region's water cycle. A stable isotope mass balance approach to calculate long term evaporation as a proportion of input to each lake is discussed. The approach capitalizes on the well understood systematic isotopic separation of an evaporating water body, but includes added considerations for internal recycling of evaporated moisture in the overlying atmosphere that should be incorporated for surface waters sufficiently large to significantly influence surrounding climate. (author)

Bulk manufacture of concentrated oxygen gas-filled microparticles for intravenous oxygen delivery.

Science.gov (United States)

Kheir, John N; Polizzotti, Brian D; Thomson, Lindsay M; O'Connell, Daniel W; Black, Katherine J; Lee, Robert W; Wilking, James N; Graham, Adam C; Bell, David C; McGowan, Francis X

2013-08-01

Self-assembling, concentrated, lipid-based oxygen microparticles (LOMs) have been developed to administer oxygen gas when injected intravenously, preventing organ injury and death from systemic hypoxemia in animal models. Distinct from blood substitutes, LOMs are a one-way oxygen carrier designed to rescue patients who experience life-threatening hypoxemia, as caused by airway obstruction or severe lung injury. Here, we describe methods to manufacture large quantities of LOMs using an in-line, recycling, high-shear homogenizer, which can create up to 4 liters of microparticle emulsion in 10 minutes, with particles containing a median diameter of 0.93 microns and 60 volume% of gas phase. Using this process, we screen 30 combinations of commonly used excipients for their ability to form stable LOMs. LOMs composed of DSPC and cholesterol in a 1:1 molar ratio are stable for a 100 day observation period, and the number of particles exceeding 10 microns in diameter does not increase over time. When mixed with blood in vitro, LOMs fully oxygenate blood within 3.95 seconds of contact, and do not cause hemolysis or complement activation. LOMs can be manufactured in bulk by high shear homogenization, and appear to have a stability and size profile which merit further testing. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Error sources in the retrieval of aerosol information over bright surfaces from satellite measurements in the oxygen A band

Science.gov (United States)

Nanda, Swadhin; de Graaf, Martin; Sneep, Maarten; de Haan, Johan F.; Stammes, Piet; Sanders, Abram F. J.; Tuinder, Olaf; Pepijn Veefkind, J.; Levelt, Pieternel F.

2018-01-01

Retrieving aerosol optical thickness and aerosol layer height over a bright surface from measured top-of-atmosphere reflectance spectrum in the oxygen A band is known to be challenging, often resulting in large errors. In certain atmospheric conditions and viewing geometries, a loss of sensitivity to aerosol optical thickness has been reported in the literature. This loss of sensitivity has been attributed to a phenomenon known as critical surface albedo regime, which is a range of surface albedos for which the top-of-atmosphere reflectance has minimal sensitivity to aerosol optical thickness. This paper extends the concept of critical surface albedo for aerosol layer height retrievals in the oxygen A band, and discusses its implications. The underlying physics are introduced by analysing the top-of-atmosphere reflectance spectrum as a sum of atmospheric path contribution and surface contribution, obtained using a radiative transfer model. Furthermore, error analysis of an aerosol layer height retrieval algorithm is conducted over dark and bright surfaces to show the dependence on surface reflectance. The analysis shows that the derivative with respect to aerosol layer height of the atmospheric path contribution to the top-of-atmosphere reflectance is opposite in sign to that of the surface contribution - an increase in surface brightness results in a decrease in information content. In the case of aerosol optical thickness, these derivatives are anti-correlated, leading to large retrieval errors in high surface albedo regimes. The consequence of this anti-correlation is demonstrated with measured spectra in the oxygen A band from the GOME-2 instrument on board the Metop-A satellite over the 2010 Russian wildfires incident.

Detection of submonolayer oxygen-18 on a gold surface by nuclear reaction analysis

Energy Technology Data Exchange (ETDEWEB)

Wielunski, L.S.; Kenny, M.J.; Wieczorek, L. [Commonwealth Scientific and Industrial Research Organisation (CSIRO), Lindfield, NSW (Australia). Div. of Applied Physics

1993-12-31

A gold substrate is the preferred solid surface for formation of an organic self-assembled monolayer ( SAM ). Device fabrication process may require the gold film to be exposed to photolithographic processing and plasma treatment prior to molecular assembly. It has been observed that oxygen plasma treatment prevents the formation of SAMs; however, subsequent treatment with an argon plasma allows assembly of the organic monolayers. To understand the mechanisms involved, a plasma containing 98% {sup 18}O was used and the film surface was analysed using the {sup 18}O (p,{alpha}){sup 15}N nuclear reaction. 5 refs., 1 tab., 3 figs.

Detection of submonolayer oxygen-18 on a gold surface by nuclear reaction analysis

Energy Technology Data Exchange (ETDEWEB)

Wielunski, L S; Kenny, M J; Wieczorek, L [Commonwealth Scientific and Industrial Research Organisation (CSIRO), Lindfield, NSW (Australia). Div. of Applied Physics

1994-12-31

A gold substrate is the preferred solid surface for formation of an organic self-assembled monolayer ( SAM ). Device fabrication process may require the gold film to be exposed to photolithographic processing and plasma treatment prior to molecular assembly. It has been observed that oxygen plasma treatment prevents the formation of SAMs; however, subsequent treatment with an argon plasma allows assembly of the organic monolayers. To understand the mechanisms involved, a plasma containing 98% {sup 18}O was used and the film surface was analysed using the {sup 18}O (p,{alpha}){sup 15}N nuclear reaction. 5 refs., 1 tab., 3 figs.

Quantification of long-term wastewater fluxes at the surface water/groundwater-interface: an integrative model perspective using stable isotopes and acesulfame.

Science.gov (United States)

Engelhardt, I; Barth, J A C; Bol, R; Schulz, M; Ternes, T A; Schüth, C; van Geldern, R

2014-01-01

The suitability of acesulfame to trace wastewater-related surface water fluxes from streams into the hyporheic and riparian zones over long-term periods was investigated. The transport behavior of acesulfame was compared with the transport of water stable isotopes (δ(18)O or δ(2)H). A calibrated model based on a joint inversion of temperature, acesulfame, and piezometric pressure heads was employed in a model validation using data sets of acesulfame and water stable isotopes collected over 5months in a stream and groundwater. The spatial distribution of fresh water within the groundwater resulting from surface water infiltration was estimated by computing groundwater ages and compared with the predicted acesulfame plume obtained after 153day simulation time. Both, surface water ratios calculated with a mixing equation from water stable isotopes and simulated acesulfame mass fluxes, were investigated for their ability to estimate the contribution of wastewater-related surface water inflow within groundwater. The results of this study point to limitations for the application of acesulfame to trace surface water-groundwater interactions properly. Acesulfame completely missed the wastewater-related surface water volumes that still remained in the hyporheic zone under stream-gaining conditions. In contrast, under stream-losing conditions, which developed after periods of stagnating hydraulic exchange, acesulfame based predictions lead to an overestimation of the surface water volume of up to 25% in the riparian zone. If slow seepage velocities prevail a proportion of acesulfame might be stored in smaller pores, while when released under fast flowing water conditions it will travel further downstream with the groundwater flow direction. Therefore, under such conditions acesulfame can be a less-ideal tracer in the hyporheic and riparian zones and additional monitoring with other environmental tracers such as water stable isotopes is highly recommended. © 2013 Elsevier

Production of stable superhydrophilic surfaces on 316L steel by simultaneous laser texturing and SiO2 deposition

Science.gov (United States)

Rajab, Fatema H.; Liu, Zhu; Li, Lin

2018-01-01

Superhydrophilic surfaces with liquid contact angles of less than 5 ° have attracted much interest in practical applications including self-cleaning, cell manipulation, adhesion enhancement, anti-fogging, fluid flow control and evaporative cooling. Standard laser metal texturing method often result in unstable wetting characteristics, i.e. changing from super hydrophilic to hydrophobic in a few days or weeks. In this paper, a simple one step method is reported for fabricating a stable superhydrophilic metallic surface that lasted for at least 6 months. Here, 316L stainless steel substrates were textured using a nanosecond laser with in-situ SiO2 deposition. Morphology and chemistry of laser-textured surfaces were characterised using SEM, XRD, XPS and an optical 3D profiler. Static wettability analysis was carried out over a period of 6 months after the laser treatment. The effect of surface roughness on wettability was also studied. Results showed that the wettability of the textured surfaces could be controlled by changing the scanning speed of laser beam and number of passes. The main reason for the realisation of the stable superhydrophilic surface is the combination of the melted glass particles mainly Si and O with that of stainless steel in the micro-textured patterns. This study presents a useful method

Periodic density functional theory study of ethylene hydrogenation over Co3O4 (1 1 1) surface: The critical role of oxygen vacancies

Science.gov (United States)

Lu, Jinhui; Song, JiaJia; Niu, Hongling; Pan, Lun; Zhang, Xiangwen; Wang, Li; Zou, Ji-Jun

2016-05-01

Recently, metal oxides are attracting increasing interests as hydrogenation catalyst. Herein we studied the hydrogenation of ethylene on perfect and oxygen defective Co3O4 (1 1 1) using periodic density functional theory. The energetics and pathways of ethylene hydrogenation to ethane were determined. We have demonstrated that (i) H2 dissociation on Co3O4 is a complicated two-step process through a heterolytic cleavage, followed by the migration of H atom and finally yields the homolytic product on both perfect and oxygen defective Co3O4 (1 1 1) surfaces easily. (ii) After introducing the surface oxygen vacancy, the stepwise hydrogenation of ethylene by atomic hydrogen is much easier than that on perfect surface due to the weaker bond strength of OH group. The strength of Osbnd H bond is a crucial factor for the hydrogenation reaction which involves the breakage of Osbnd H bond. The formation of oxygen vacancy increases the electronic charges at the adjacent surface O, which reduces its capability of further gaining electrons from adsorbed atomic hydrogen and then weakens the strength of Osbnd H bond. These results emphasize the importance of the oxygen vacancies for hydrogenation on metal oxides.

Interactions between surface waters in King George Island, Antarctica - a stable isotope perspective

Science.gov (United States)

Perşoiu, Aurel; Bădăluşă, Carmen

2017-04-01

In this paper we present a first study of the isotopic composition of surface waters in the southern peninsulas (Barton, Fildes, Weaver and Potter) of King George Island, Antarctica. We have collected > 200 samples of snow and snowmelt, water (lake, river and spring), ice (glacier ice and permafrost) from the four peninsulas in February 2016 and analyzed them for their oxygen and hydrogen stable isotopic composition. Samples from lake water (50+) indicate a clear west-east depletion trend, suggesting a rain-out process as air masses are moving westward (and are progressively depleted in heavy isotopes) from their origin in the Drake Passage. In both Fildes and Barton Peninsulas, permafrost samples have the heaviest isotopic composition, most probably due to preferential incorporation of heavy isotopes in the ice during freezing (and no fractionation during melting). As permafrost melts, the resulting water mixes with isotopically lighter infiltrated snowmelt, and thus the groundwater has a lower isotopic composition. Further, lake and river (the later fed by lakes) water has the lightest isotopic composition, being derived mostly from the melting of light snow and glacier ice. It seems feasible to separate isotopically water in lakes/rivers (largely fed by melting multi-year glaciers and snow) and water from melting of snow/ground ice This preliminary study suggests that it is possible to separate various water sources in the southern peninsulas of King George Island, and this separation could be used to study permafrost degradation, as well as feeding and migration patterns in the bird fauna, with implications for protection purposes. Acknowledgments. The National Institute of Research and Development for Biological Sciences (Bucharest, Romania) and the Korean polar institute financially supported fieldwork in King George Island. We thank the personal at King Sejong (South Korea), Belingshaussen (Russia) and Carlini (Argentina) stations in King George Island for

Atomic scale study of the chemistry of oxygen, hydrogen and water at SiC surfaces

International Nuclear Information System (INIS)

Amy, Fabrice

2007-01-01

Understanding the achievable degree of homogeneity and the effect of surface structure on semiconductor surface chemistry is both academically challenging and of great practical interest to enable fabrication of future generations of devices. In that respect, silicon terminated SiC surfaces such as the cubic 3C-SiC(1 0 0) 3 x 2 and the hexagonal 6H-SiC(0 0 0 1) 3 x 3 are of special interest since they give a unique opportunity to investigate the role of surface morphology on oxygen or hydrogen incorporation into the surface. In contrast to silicon, the subsurface structure plays a major role in the reactivity, leading to unexpected consequences such as the initial oxidation starting several atomic planes below the top surface or the surface metallization by atomic hydrogen. (review article)

Are Vicinal Metal Surfaces Stable?

DEFF Research Database (Denmark)

Frenken, J. W. M.; Stoltze, Per

1999-01-01

We use effective medium theory to demonstrate that the energies of many metal surfaces are lowered when these surfaces are replaced by facets with lower-index orientations. This implies that the low-temperature equilibrium shapes of many metal crystals should be heavily faceted. The predicted...... instability of vicinal metal surfaces is at variance with the almost generally observed stability of these surfaces. We argue that the unstable orientations undergo a defaceting transition at relatively low temperatures, driven by the high vibrational entropy of steps....

Photogeneration of singlet oxygen by the phenothiazine derivatives covalently bound to the surface-modified glassy carbon

Energy Technology Data Exchange (ETDEWEB)

Blacha-Grzechnik, Agata, E-mail: agata.blacha@polsl.pl [Faculty of Chemistry, Silesian University of Technology, Strzody 9, 44-100 Gliwice (Poland); Piwowar, Katarzyna; Krukiewicz, Katarzyna [Faculty of Chemistry, Silesian University of Technology, Strzody 9, 44-100 Gliwice (Poland); Koscielniak, Piotr; Szuber, Jacek [Institute of Electronics, Silesian University of Technology, Akademicka 16, 44-100 Gliwice (Poland); Zak, Jerzy K. [Faculty of Chemistry, Silesian University of Technology, Strzody 9, 44-100 Gliwice (Poland)

2016-05-15

Highlights: • The selected group of four NH{sub 2}-derivatives of phenothiazine was grafted to Glassy Carbon (GC) surface. • The grafted phenothiazines are able to generate {sup 1}O{sub 2} when activated by the radiation. • Such modified solid surfaces may find their application in the wastewater treatment. - Abstract: The selected group of four amine-derivatives of phenothiazine was covalently grafted to the glassy carbon surface in the four-step procedure consisting of the electrochemical reduction of the diazonium salt followed by the electrochemical and chemical post-modification steps. The proposed strategy involves the bonding of linker molecule to which the photosensitizer is attached. The synthesized organic layers were characterized by means of cyclic voltammetry, XPS and Raman Spectroscopy. It was shown that the phenothiazines immobilized via proposed strategy retain their photochemical properties and are able to generate {sup 1}O{sub 2} when activated by the laser radiation. The effectiveness of in situ singlet oxygen generation by those new solid photoactive materials was determined by means of UVVis spectroscopy. The reported, covalently modified solid surfaces may find their application as the singlet oxygen photogenerators in the fine chemicals’ synthesis or in the wastewater treatment.

The surface modification of polystyrene

International Nuclear Information System (INIS)

Tremlett, C.

2000-03-01

Polymers have ideal bulk properties for many applications. However, adhesion to many polymers is poor without surface pretreatment. This can result, for example, in peeling paint and printing, adhesive joint failure and bio-incompatibility. In applications such as painting, printing, adhesive bonding and biocompatibility, various cleaning or surface chemical modifications may be employed. A commodity polymer where pretreatment is sometimes needed is polystyrene. This project investigated, in detail, the effects of a novel method of modification namely mediated electrochemical oxidation (MEO), as a mode of surface modification on polystyrene and a comparison was made with other polymers. The resulting modification was investigated using a range of surface analysis techniques to obtain complementary information. These included, X-ray photoelectron spectroscopy, contact angles, static secondary ion mass spectrometry, atomic force microscopy, chemical derivatization, scanning electron microscopy, attenuated total reflection Fourier Transform infrared spectroscopy and composite lap shear joint testing. It has been shown that MEO modifies the surface of polystyrene introduced oxygen mainly as hydroxyl groups, and a small number of carbonyl groups, that are positioned only on the backbone hydrocarbon chain. This modification improved adhesion, was stable and samples could be stored in aqueous media. The resulting hydroxylation was further derivatized using an amino acid to provide a specialised surface. This was very different from the multiple oxygen functionalities introduced in the comparison studies by UV/ozone and plasma treatments. (author)

petrography, compositional characteristics and stable isotope ...

African Journals Online (AJOL)

PROF EKWUEME

Subsurface samples of the predominantly carbonate Ewekoro Formation, obtained from Ibese core hole within the Dahomey basin were used in this study. Investigations entail petrographic, elemental composition as well as stable isotopes (carbon and oxygen) geochemistry in order to deduce the different microfacies and ...

Interphase Evolution of a Lithium-Ion/Oxygen Battery.

Science.gov (United States)

Elia, Giuseppe Antonio; Bresser, Dominic; Reiter, Jakub; Oberhumer, Philipp; Sun, Yang-Kook; Scrosati, Bruno; Passerini, Stefano; Hassoun, Jusef

2015-10-14

A novel lithium-ion/oxygen battery employing Pyr14TFSI-LiTFSI as the electrolyte and nanostructured LixSn-C as the anode is reported. The remarkable energy content of the oxygen cathode, the replacement of the lithium metal anode by a nanostructured stable lithium-alloying composite, and the concomitant use of nonflammable ionic liquid-based electrolyte result in a new and intrinsically safer energy storage system. The lithium-ion/oxygen battery delivers a stable capacity of 500 mAh g(-1) at a working voltage of 2.4 V with a low charge-discharge polarization. However, further characterization of this new system by electrochemical impedance spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy reveals the progressive decrease of the battery working voltage, because of the crossover of oxygen through the electrolyte and its direct reaction with the LixSn-C anode.

Oxygen stable isotopes variation in water precipitation in Poland – anthropological applications

Directory of Open Access Journals (Sweden)

Lisowska-Gaczorek Aleksandra

2017-03-01

Full Text Available The main objective of oxygen isotope analysis is to determine the probable place of origin of an individual or the reconstruction of migration paths. The research are methodologically based on referencing oxygen isotope ratios of apatite phosphates (δ18Op to the range of environmental background δ18O, most frequently determined on the basis of precipitation.

SnO2 promoted by alkali metal oxides for soot combustion: The effects of surface oxygen mobility and abundance on the activity

Science.gov (United States)

Rao, Cheng; Shen, Jiating; Wang, Fumin; Peng, Honggen; Xu, Xianglan; Zhan, Hangping; Fang, Xiuzhong; Liu, Jianjun; Liu, Wenming; Wang, Xiang

2018-03-01

In this study, SnO2-based catalysts promoted by different alkali metal oxides with a Sn/M (M = Li, Na, K, Cs) molar ratio of 9/1 have been prepared for soot combustion. In comparison with the un-modified SnO2 support, the activity of the modified catalysts has been evidently enhanced, following the sequence of CsSn1-9 > KSn1-9 > NaSn1-9 > LiSn1-9 > SnO2. As testified by Raman, H2-TPR, soot-TPR-MS, XPS and O2-TPD results, the incorporation of various alkali metal oxides can induce the formation of more abundant and mobile oxygen species on the surface of the catalysts. Moreover, quantified results have proved that the amount of the surface active oxygen species is nearly proportional to the activity of the catalysts. CsSn1-9, the catalyst promoted by cesium oxide, owns the largest amount of surface mobile oxygen species, thus having the highest activity among all the studied catalysts. It is concluded that the amount of surface active and mobile oxygen species is the major factor determining the activity of the catalysts for soot combustion.

Unraveling the facet-dependent and oxygen vacancy role for ethylene hydrogenation on Co_3O_4 (110) surface: A DFT+U study

International Nuclear Information System (INIS)

Zhang, Yong-Chao; Pan, Lun; Lu, Jinhui; Song, Jiajia; Li, Zheng; Zhang, Xiangwen; Wang, Li; Zou, Ji-Jun

2017-01-01

Highlights: • The mechanism of ethylene hydrogenation on perfect and oxygen defective Co_3O_4(110) is investigated by using DFT + U. • Oxygen vacancy promotes ethylene hydrogenation thermodynamically and kinetically. • The Co3O4 (110) facet is more active than the (111) one for ethylene hydrogenation. - Abstract: Crystal facet engineering and defect engineering are both critical strategies to improve the catalytic hydrogenation performance of catalyst. Herein, ethylene hydrogenation on the perfect and oxygen defective Co_3O_4(110) surfaces has been studied by using periodic density functional theory calculations. The results are compared with that on Co_3O_4(111) surface to clarify the problem of which facet for Co_3O_4 is more reactive, and to illuminate the role of oxygen vacancy. The low oxygen vacancy formation energy suggests that Co_3O_4(110) surface with defective site is easily formed. The whole mechanism of H_2 dissociation and stepwise hydrogenation of ethylene to ethane is examined, and the most favorable pathway is heterolytic dissociation of H_2 follows two stepwise hydrogenation of ethylene process. The results show that ethyl hydrogenation to ethane on perfect Co_3O_4(110) surface is the rate limiting step with an activation energy of 1.19 eV, and the presence of oxygen vacancy strongly reduces the activation energies of main elementary steps, and the activation energy of rate limiting step is only 0.47 eV. Compared with that on Co_3O_4(111), ethylene hydrogenation is preferred on Co_3O_4(110) surface. Therefore, Co_3O_4 with exposed (110) facet is predicted as an excellent catalyst for ethylene hydrogenation.

Chemistry of SOFC Cathode Surfaces: Fundamental Investigation and Tailoring of Electronic Behavior

Energy Technology Data Exchange (ETDEWEB)

Yildiz, Bilge; Heski, Clemens

2013-08-31

origins of this phenomenon is therefore needed for designing cathode materials with optimal surface chemistry. We quantitatively assessed the elastic and electrostatic interactions of the dopant with the surrounding lattice as the key driving forces for segregation on model perovskite compounds, LnMnO3 (host cation Ln=La, Sm). Our approach combines surface chemical analysis with X-ray photoelectron and Auger electron spectroscopy on model dense thin films, and computational analysis with density functional theory (DFT) calculations and analytical models. Elastic energy differences were systematically induced in the system by varying the radius of the selected dopants (Ca, Sr, Ba) with respect to the host cations (La, Sm) while retaining the same charge state. Electrostatic energy differences were introduced by varying the distribution of charged oxygen and cation vacancies in our models. Varying the oxygen chemical potential in our experiments induced changes in both the elastic energy and electrostatic interactions. Our results quantitatively demonstrate that the mechanism of dopant segregation on perovskite oxides includes both the elastic and electrostatic energy contributions. A smaller size mismatch between the host and dopant cations and a chemically expanded lattice were found to reduce the segregation level of the dopant and to enable more stable cathode surfaces. Ca-doped LaMnO3 was found to have the most stable surface composition with the least cation segregation among the compositions surveyed. The diffusion kinetics of the larger dopants, Ba and Sr, was found to be slower, and can kinetically trap the segregation at reduced temperatures despite the larger elastic energy driving force. Lastly, scanning probe image-contrast showed that the surface chemical heterogeneities made of dopant oxides upon segregation were electronically insulating. The consistency between the results obtained from experiments, DFT calculations and analytical theory in this work

Initial oxidation behavior of Ni{sub 3}Al (210) surface induced by supersonic oxygen molecular beam at room temperature

Energy Technology Data Exchange (ETDEWEB)

Xu, Ya, E-mail: XU.Ya@nims.go.jp [Hydrogen Materials Unit, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Sakurai, Junya [Hydrogen Materials Unit, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Teraoka, Yuden; Yoshigoe, Akitaka [Quantum Beam Science Center, Japan Atomic Energy Research Agency, 1-1-1 Kouto, Sayo-cho, Hyogo 679-5148 (Japan); Demura, Masahiko; Hirano, Toshiyuki [Hydrogen Materials Unit, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan)

2017-01-01

Graphical abstract: - Highlights: • Initial oxidation of Ni{sub 3}Al (210) induced by O{sub 2} beam was investigated. • This was done using real-time synchrotron radiation XPS. • Both the Al and the Ni atoms on the surface were oxidized. • Oxidation of Al progressed much faster than that of Ni. - Abstract: The initial oxidation behavior of a clean Ni{sub 3}Al (210) surface was studied at 300 K using a supersonic O{sub 2} molecular beam (O{sub 2} SSMB) having an O{sub 2} translational energy of 2.3 eV, and real-time photoemission spectroscopy performed with high-brilliance synchrotron radiation. The evolution behaviors of the O 1s, Ni 2p, Al 2p, and Ni 3p spectra were examined during irradiation with the O{sub 2} SSMB. The spectral analysis revealed that both the Al atoms and the Ni atoms on the surface were oxidized; however, the oxidation of Al progressed much faster than that of Ni. The oxidation of Al began to occur and AlO{sub x} was formed at an oxygen coverage of 0.26 monolayer (ML) (1 ML was defined as the atomic density of the Ni{sub 3}Al (210) surface) and saturated at an oxygen coverage of 2.5 ML. In contrast, the oxidation of Ni commenced a little late at an oxygen coverage of 1.6 ML and slowly progressed to saturation, which occurred at an oxygen coverage of 4.89 ML.

Comparison of the OxyMask and Venturi Mask in the Delivery of Supplemental Oxygen: Pilot Study in Oxygen-Dependent Patients

OpenAIRE

Beecroft, Jaime M; Hanly, Patrick J

2006-01-01

BACKGROUND: The OxyMask (Southmedic Inc, Canada) is a new face mask for oxygen delivery that uses a small ‘diffuser’ to concentrate and direct oxygen toward the mouth and nose. The authors hypothesized that this unique design would enable the OxyMask to deliver oxygen more efficiently than a Venturi mask (Hudson RCI, USA) in patients with chronic hypoxemia.METHODS: Oxygen-dependent patients with chronic, stable respiratory disease were recruited to compare the OxyMask and Venturi mask in a ra...

Control systems for the dissolved oxygen concentration in condensate- and feed-water systems in nuclear power plants

International Nuclear Information System (INIS)

Mikajiri, Motohiko; Hosaka, Seiichi.

1981-01-01

Purpose: To surely prevent the generation of corrosion products and contaminations in the systems thereby decreasing the exposure dose to operators in BWR type nuclear power plants. Constitution: Dissolved oxygen concentration in condensates is measured by a dissolved oxygen concentration meter disposed to the pipeway down stream of the condensator and the measured value is sent to an injection amount control mechanism for heater drain water. The control mechanism controls the injection amount from the injection mechanism that injection heater drain water from a feed-water heater to the liquid phase in the hot wall of the condensator. Thus, heater drawin water at high dissolved oxygen is injected to the condensates in the condensator which is de-airated and reduced with dissolved oxygen concentration, to maintain the dissolved oxygen concentration at a predetermined level, whereby stable oxide films are formed to the inner surface of the pipeways to prevent the generation of corrosion products such as rusts. (Furukawa, Y.)

Novel Metal-Sulfur-Based Air-Stable Passivation of GaAs with Very Low Surface State Densities

Energy Technology Data Exchange (ETDEWEB)

Ashby, Carol I.H.; Baca, Albert G.; Chang, P.-C; Hafich, M.J.; Hammons, B.E.; Zavadil, Kevin R.

1999-08-09

A new air-stable electronic surface passivation for GaAs and other III-V compound semiconductors that employs sulfur and a suitable metal ion, e.g., Zn, and that is robust towards plasma dielectric deposition has been developed. Initial improvements in photoluminescence are twice that of S-only treatments and have been preserved for >11 months with SiO{sub x}N{sub y} dielectric encapsulation. Photoluminescence and X-ray photoelectron spectroscopies indicate that the passivation consists of two major components with one being stable for >2 years in air. This process improves heterojunction bipolar transistor current gain for both large and small area devices.

Ni-Doping Effects on Oxygen Removal from an Orthorhombic Mo ₂ C (001) Surface: A Density Functional Theory Study

Energy Technology Data Exchange (ETDEWEB)

Zhou, Mingxia [Department; Cheng, Lei [Materials; Choi, Jae-Soon [Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, TN 37831, Unites States; Liu, Bin [Department; Curtiss, Larry A. [Materials; Assary, Rajeev S. [Materials

2018-01-11

Density functional theory (DFT) calculations were used to investigate the effect of Ni dopants on the removal of chemisorbed oxygen (O*) from the Mo-terminated (T-Mo) and C-terminated (Tc) Mo2C(001) surfaces. The removal of adsorbed oxygen from the catalytic site is essential to maintain the long-term activity and selectivity of the carbide catalysts in the deoxygenation process related to bio-oil stabilization and upgrading. In this contribution, the computed reaction energetics and reaction barriers of O* removal were compared among undoped and Ni-doped Mo2C(001) surfaces. The DFT calculations indicate that selected Ni-doped surfaces such as Ni adsorbed on T-Mo and Tc Mo2C(001) surfaces enable weaker binding of important reactive intermediates (O*, OH*) compared to the undoped counterparts, which is beneficial for the O* removal from the catalyst surface. This study thus confirms the promoting effect of the Ni dopant on O* removal reaction on the T-Mo Mo2C(001) and Tc Mo2C(001) surfaces. This computational prediction has been confirmed by the temperature-programmed reduction profiles of Mo2C and Ni-doped Mo2C catalysts, which had been passivated and stored in an oxygen environment.

Meridional distribution and seasonal variation of stable oxygen isotope ratio of precipitation in the Southern Ocean

Directory of Open Access Journals (Sweden)

Kayo Nakamura

2010-07-01

Full Text Available The stable oxygen isotope ratio(δ^O in precipitation is known to have important meridional and seasonal variations, but there are almost no measurements of δ^O in precipitation over polar oceans. The present research took advantage of 4 opportunities for in situ observations in summer and winter at high latitudes in the Southern Ocean. In addition, we analyzed samples of precipitation at Syowa Station in 2008 to obtain year-round data. Based on these data, we consider the meridional and seasonal variations of δ^O in precipitation over the Southern Ocean. In general, δ^O decreases with increasing latitude, and is lower in winter than in summer. The latitude gradient is stronger in winter. At 60°S, δ^O is -5.4‰ and -11.3‰ in summer and winter, respectively, while the corresponding figures at 66°S are -10.5‰ and -20.8‰. These results will help us understand the mechanisms of the salinity distribution and its variation in the Antarctic Ocean.

Quantification of long-term wastewater fluxes at the surface water/groundwater-interface: An integrative model perspective using stable isotopes and acesulfame

Energy Technology Data Exchange (ETDEWEB)

Engelhardt, I., E-mail: i.engelhardt@fz-juelich.de [Forschungszentrum Jülich, Institute of Bio- and Geosciences, Agrosphere — IBG-3 (Germany); Technical University of Darmstadt, Institute of Applied Geosciences (Germany); Barth, J.A.C. [GeoZentrum Nordbayern, University of Erlangen-Nuremberg (Germany); Bol, R. [Forschungszentrum Jülich, Institute of Bio- and Geosciences, Agrosphere — IBG-3 (Germany); Schulz, M.; Ternes, T.A. [Federal Institute of Hydrology (BfG) (Germany); Schüth, C. [Technical University of Darmstadt, Institute of Applied Geosciences (Germany); van Geldern, R. [GeoZentrum Nordbayern, University of Erlangen-Nuremberg (Germany)

2014-01-01

The suitability of acesulfame to trace wastewater-related surface water fluxes from streams into the hyporheic and riparian zones over long-term periods was investigated. The transport behavior of acesulfame was compared with the transport of water stable isotopes (δ{sup 18}O or δ{sup 2}H). A calibrated model based on a joint inversion of temperature, acesulfame, and piezometric pressure heads was employed in a model validation using data sets of acesulfame and water stable isotopes collected over 5 months in a stream and groundwater. The spatial distribution of fresh water within the groundwater resulting from surface water infiltration was estimated by computing groundwater ages and compared with the predicted acesulfame plume obtained after 153 day simulation time. Both, surface water ratios calculated with a mixing equation from water stable isotopes and simulated acesulfame mass fluxes, were investigated for their ability to estimate the contribution of wastewater-related surface water inflow within groundwater. The results of this study point to limitations for the application of acesulfame to trace surface water–groundwater interactions properly. Acesulfame completely missed the wastewater-related surface water volumes that still remained in the hyporheic zone under stream-gaining conditions. In contrast, under stream-losing conditions, which developed after periods of stagnating hydraulic exchange, acesulfame based predictions lead to an overestimation of the surface water volume of up to 25% in the riparian zone. If slow seepage velocities prevail a proportion of acesulfame might be stored in smaller pores, while when released under fast flowing water conditions it will travel further downstream with the groundwater flow direction. Therefore, under such conditions acesulfame can be a less-ideal tracer in the hyporheic and riparian zones and additional monitoring with other environmental tracers such as water stable isotopes is highly recommended

The adsorption of NO on an oxygen pre-covered Pt(1 1 1) surface: in situ high-resolution XPS combined with molecular beam studies

Science.gov (United States)

Zhu, J. F.; Kinne, M.; Fuhrmann, T.; Tränkenschuh, B.; Denecke, R.; Steinrück, H.-P.

2003-12-01

Adsorption of NO on a Pt(1 1 1) surface pre-covered with a p(2 × 2) atomic oxygen layer has been studied in situ by high-resolution X-ray photoelectron spectroscopy and temperature-programmed XPS using third-generation synchrotron radiation at BESSY II, Berlin, combined with molecular beam techniques and ex situ by low energy electron diffraction and temperature-programmed desorption. O 1s XP spectra reveal that an ordered p(2 × 2)-O layer dramatically changes the adsorption behavior of NO as compared to the clean surface. The atomic oxygen occupies fcc hollow sites, and therefore blocks NO adsorption on these sites, which are energetically preferred on clean Pt(1 1 1). As a consequence, NO populates on-top sites at low coverage. At 110 K for higher coverages, NO can additionally adsorb on hcp hollow sites, thereby inducing a shift of the O 1s binding energy of atomic oxygen towards lower energies by about 0.25 eV. The bond strength of the hcp hollow NO species to the substrate is weakened by the presence of atomic oxygen. A sharp p(2 × 2) LEED pattern is observed for NO adsorption on the oxygen pre-covered surface, up to saturation coverage. The total saturation coverage of NO on Pt(1 1 1) pre-covered with varying amounts of oxygen (below 0.25 ML) decreases linearly with the coverage of oxygen. The initial sticking coefficient of NO is reduced from 0.96 on clean Pt(1 1 1) to 0.88 on a p(2 × 2) oxygen pre-covered surface.

Nitrogen and Oxygen Isotopic Studies of the Marine Nitrogen Cycle.

Science.gov (United States)

Casciotti, Karen L

2016-01-01

The marine nitrogen cycle is a complex web of microbially mediated reactions that control the inventory, distribution, and speciation of nitrogen in the marine environment. Because nitrogen is a major nutrient that is required by all life, its availability can control biological productivity and ecosystem structure in both surface and deep-ocean communities. Stable isotopes of nitrogen and oxygen in nitrate and nitrite have provided new insights into the rates and distributions of marine nitrogen cycle processes, especially when analyzed in combination with numerical simulations of ocean circulation and biogeochemistry. This review highlights the insights gained from dual-isotope studies applied at regional to global scales and their incorporation into oceanic biogeochemical models. These studies represent significant new advances in the use of isotopic measurements to understand the modern nitrogen cycle, with implications for the study of past ocean productivity, oxygenation, and nutrient status.

Surface oceanographic fronts influencing deep-sea biological activity: Using fish stable isotopes as ecological tracers

Science.gov (United States)

Louzao, Maite; Navarro, Joan; Delgado-Huertas, Antonio; de Sola, Luis Gil; Forero, Manuela G.

2017-06-01

Ecotones can be described as transition zones between neighbouring ecological systems that can be shaped by environmental gradients over a range of space and time scales. In the marine environment, the detection of ecotones is complex given the highly dynamic nature of marine systems and the paucity of empirical data over ocean-basin scales. One approach to overcome these limitations is to use stable isotopes from animal tissues since they can track spatial oceanographic variability across marine systems and, in turn, can be used as ecological tracers. Here, we analysed stable isotopes of deep-sea fishes to assess the presence of ecological discontinuities across the western Mediterranean. We were specifically interested in exploring the connection between deep-sea biological activity and particular oceanographic features (i.e., surface fronts) occurring in the pelagic domain. We collected samples for three different abundant deep-sea species in May 2004 from an experimental oceanographic trawling cruise (MEDITS): the Mictophydae jewel lanternfish Lampanyctus crocodilus and two species of the Gadidae family, the silvery pout Gadiculus argenteus and the blue whiting Micromesistius poutassou. The experimental survey occurred along the Iberian continental shelf and the upper and middle slopes, from the Strait of Gibraltar in the SW to the Cape Creus in the NE. The three deep-sea species were highly abundant throughout the study area and they showed geographic variation in their isotopic values, with decreasing values from north to south disrupted by an important change point around the Vera Gulf. Isotopic latitudinal gradients were explained by pelagic oceanographic conditions along the study area and confirm the existence of an ecotone at the Vera Gulf. This area could be considered as an oceanographic boundary where waters of Atlantic origin meet Mediterranean surface waters forming important frontal structures such as the Almeria-Oran front. In fact, our results

Seasonal Cyclicity in Trace Elements and Stable Isotopes of Modern Horse Enamel.

Science.gov (United States)

de Winter, Niels J; Snoeck, Christophe; Claeys, Philippe

2016-01-01

The study of stable isotopes in fossil bioapatite has yielded useful results and has shown that bioapatites are able to faithfully record paleo-environmental and paleo-climatic parameters from archeological to geological timescales. In an effort to establish new proxies for the study of bioapatites, intra-tooth records of enamel carbonate stable isotope ratios from a modern horse are compared with trace element profiles measured using laboratory micro X-Ray Fluorescence scanning. Using known patterns of tooth eruption and the relationship between stable oxygen isotopes and local temperature seasonality, an age model is constructed that links records from six cheek upper right teeth from the second premolar to the third molar. When plotted on this age model, the trace element ratios from horse tooth enamel show a seasonal pattern with a small shift in phase compared to stable oxygen isotope ratios. While stable oxygen and carbon isotopes in tooth enamel are forced respectively by the state of the hydrological cycle and the animal's diet, we argue that the seasonal signal in trace elements reflects seasonal changes in dust intake and diet of the animal. The latter explanation is in agreement with seasonal changes observed in carbon isotopes of the same teeth. This external forcing of trace element composition in mammal tooth enamel implies that trace element ratios may be used as proxies for seasonal changes in paleo-environment and paleo-diet.

Effect of oxygen on the thermomechanical behavior of tantalum thin films during the β-α phase transformation

International Nuclear Information System (INIS)

Knepper, Robert; Stevens, Blake; Baker, Shefford P.

2006-01-01

Tantalum thin films were prepared in the metastable β phase, and their thermomechanical behaviors were investigated in situ in an ultrahigh vacuum environment. Controlled levels of oxygen were incorporated into the films either during deposition, by surface oxidation after deposition, or during thermomechanical testing. The transformation from the β phase to the stable α phase takes place in conjunction with a distinct increase in tensile stress. The thermomechanical behavior is strongly affected by the amount of oxygen to which the film is exposed and the method of exposure. Increasing oxygen content inhibits the phase transformation, requiring higher temperatures to reach completion. It is shown that the phase transformation takes place by a nucleation and growth process that is limited by growth. Changes in the activation energy for the phase transformation due to solute drag are estimated as a function of oxygen content and the mechanisms behind the stress evolution are elucidated

Fabrication of high surface area graphene electrodes with high performance towards enzymatic oxygen reduction

International Nuclear Information System (INIS)

Di Bari, Chiara; Goñi-Urtiaga, Asier; Pita, Marcos; Shleev, Sergey; Toscano, Miguel D.; Sainz, Raquel; De Lacey, Antonio L.

2016-01-01

High surface area graphene electrodes were prepared by simultaneous electrodeposition and electroreduction of graphene oxide. The electrodeposition process was optimized in terms of pH and conductivity of the solution and the obtained graphene electrodes were characterized by X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy and electrochemical methods (cyclic voltammetry and impedance spectroscopy). Electrodeposited electrodes were further functionalized to carry out covalent immobilization of two oxygen-reducing multicopper oxidases: laccase and bilirubin oxidase. The enzymatic electrodes were tested as direct electron transfer based biocathodes and catalytic currents as high as 1 mA/cm 2 were obtained. Finally, the mechanism of the enzymatic oxygen reduction reaction was studied for both enzymes calculating the Tafel slopes and transfer coefficients.

Sea surface density gradients in the Nordic Seas during the Holocene as revealed by paired microfossil and isotope proxies

DEFF Research Database (Denmark)

Van Nieuwenhove, Nicolas; Hillaire-Marcel, Claude; Bauch, Henning A.

2016-01-01

We attempt to assess the Holocene surface-subsurface seawater density gradient on millennial time-scale based on the reconstruction of potential density (σθ) by combining data from dinoflagellate cyst assemblages and planktic foraminiferal (Neogloboquadrina pachyderma (s)) stable oxygen isotopes (δ...

Comparison of pulseoximetry oxygen saturation and arterial oxygen saturation in open heart intensive care unit

Directory of Open Access Journals (Sweden)

Alireza Mahoori

2013-08-01

Full Text Available Background: Pulseoximetry is widely used in the critical care setting, currently used to guide therapeutic interventions. Few studies have evaluated the accuracy of SPO2 (puls-eoximetry oxygen saturation in intensive care unit after cardiac surgery. Our objective was to compare pulseoximetry with arterial oxygen saturation (SaO2 during clinical routine in such patients, and to examine the effect of mild acidosis on this relationship.Methods: In an observational prospective study 80 patients were evaluated in intensive care unit after cardiac surgery. SPO2 was recorded and compared with SaO2 obtained by blood gas analysis. One or serial arterial blood gas analyses (ABGs were performed via a radial artery line while a reliable pulseoximeter signal was present. One hundred thirty seven samples were collected and for each blood gas analyses, SaO2 and SPO2 we recorded.Results: O2 saturation as a marker of peripheral perfusion was measured by Pulseoxim-etry (SPO2. The mean difference between arterial oxygen saturation and pulseoximetry oxygen saturation was 0.12%±1.6%. A total of 137 paired readings demonstrated good correlation (r=0.754; P<0.0001 between changes in SPO2 and those in SaO2 in samples with normal hemoglobin. Also in forty seven samples with mild acidosis, paired readings demonstrated good correlation (r=0.799; P<0.0001 and the mean difference between SaO2 and SPO2 was 0.05%±1.5%.Conclusion: Data showed that in patients with stable hemodynamic and good signal quality, changes in pulseoximetry oxygen saturation reliably predict equivalent changes in arterial oxygen saturation. Mild acidosis doesn’t alter the relation between SPO2 and SaO2 to any clinically important extent. In conclusion, the pulse oximeter is useful to monitor oxygen saturation in patients with stable hemodynamic.

Magnetism, Spin Texture, and In-Gap States: Atomic Specialization at the Surface of Oxygen-Deficient SrTiO_{3}.

Science.gov (United States)

Altmeyer, Michaela; Jeschke, Harald O; Hijano-Cubelos, Oliver; Martins, Cyril; Lechermann, Frank; Koepernik, Klaus; Santander-Syro, Andrés F; Rozenberg, Marcelo J; Valentí, Roser; Gabay, Marc

2016-04-15

Motivated by recent spin- and angular-resolved photoemission (SARPES) measurements of the two-dimensional electronic states confined near the (001) surface of oxygen-deficient SrTiO_{3}, we explore their spin structure by means of ab initio density functional theory (DFT) calculations of slabs. Relativistic nonmagnetic DFT calculations display Rashba-like spin winding with a splitting of a few meV and when surface magnetism on the Ti ions is included, bands become spin-split with an energy difference ∼100  meV at the Γ point, consistent with SARPES findings. While magnetism tends to suppress the effects of the relativistic Rashba interaction, signatures of it are still clearly visible in terms of complex spin textures. Furthermore, we observe an atomic specialization phenomenon, namely, two types of electronic contributions: one is from Ti atoms neighboring the oxygen vacancies that acquire rather large magnetic moments and mostly create in-gap states; another comes from the partly polarized t_{2g} itinerant electrons of Ti atoms lying further away from the oxygen vacancy, which form the two-dimensional electron system and are responsible for the Rashba spin winding and the spin splitting at the Fermi surface.

Universality in Oxygen Reduction Electrocatalysis on Metal Surfaces

DEFF Research Database (Denmark)

Viswanathan, Venkatasubramanian; Hansen, Heine Anton; Rossmeisl, Jan

2012-01-01

In this work, we extend the activity volcano for oxygen reduction from the face-centered cubic (fcc) metal (111) facet to the (100) facet. Using density functional theory calculations, we show that the recent findings of constant scaling between OOH* and OH* holds on the fcc metal (100) facet......, as well. Using this fact, we show the existence of a universal activity volcano to describe oxygen reduction electrocatalysis with a minimum overpotential, ηmin = 0.37 ± 0.1 V. Specifically, we find that the (100) facet of Pt is found to bind oxygen intermediates too strongly and is not active for oxygen...... reduction reaction (ORR). In contrast, Au(100) is predicted to be more active than Au(111) and comparable in activity to Pt alloys. Using this activity volcano, we further predict that Au alloys that bind OH more strongly could display improved ORR activity on the (100) facet. We carry out a computational...

In vitro study of 3D PLGA/n-HAp/β-TCP composite scaffolds with etched oxygen plasma surface modification in bone tissue engineering

Energy Technology Data Exchange (ETDEWEB)

Roh, Hee-Sang [Department of Dental Materials, School of Dentistry, Chosun University, 309 Pilmun-daero, Dong-gu, Gwangju 61452 (Korea, Republic of); Jung, Sang-Chul [Department of Environmental Engineering, Sunchon National University, 255 Jungang-ro, Sunchon 57922 (Korea, Republic of); Kook, Min-Suk [Department of Oral and Maxillofacial Surgery, School of Dentistry, Chonnam National University, 77 Yongbong-ro, Buk-gu, Gwangju 61186 (Korea, Republic of); Kim, Byung-Hoon, E-mail: kim5055@chosun.ac.kr [Department of Dental Materials, School of Dentistry, Chosun University, 309 Pilmun-daero, Dong-gu, Gwangju 61452 (Korea, Republic of)

2016-12-01

Highlights: • PLGA and PLGA/n-HAp/β-TCP scaffolds were successfully fabricated by 3D printing. • Oxygen plasma etching increases the wettability and surface roughness. • Bioceramics and oxygen plasma etching and could be used to improve the cell affinity. - Abstract: Three-dimensional (3D) scaffolds have many advantageous properties for bone tissue engineering application, due to its controllable properties such as pore size, structural shape and interconnectivity. In this study, effects on oxygen plasma surface modification and adding of nano-hydroxyapatite (n-HAp) and β-tricalcium phosphate (β-TCP) on the 3D PLGA/n-HAp/β-TCP scaffolds for improving preosteoblast cell (MC3T3-E1) adhesion, proliferation and differentiation were investigated. The 3D PLGA/n-HAp/β-TCP scaffolds were fabricated by 3D Bio-Extruder equipment. The 3D scaffolds were prepared with 0°/90° architecture and pore size of approximately 300 μm. In addition 3D scaffolds surface were etched by oxygen plasma to enhance the hydrophilic property and surface roughness. After oxygen plasma treatment, the surface chemistry and morphology were investigated by Fourier transform infrared spectroscopy, scanning electron microscopy, and atomic force microscopy. And also hydrophilic property was measured by contact angle. The MC3T3-E1 cell proliferation and differentiation were investigated by MTT assay and ALP activity. In present work, the 3D PLGA/HAp/beta-TCP composite scaffold with suitable structure for the growth of osteoblast cells was successfully fabricated by 3D rapid prototyping technique. The surface hydrophilicity and roughness of 3D scaffold increased by oxygen plasma treatment had a positive effect on cell adhesion, proliferation, and differentiation. Furthermore, the differentiation of MC3T3-E1 cell was significantly enhanced by adding of n-HAp and β-TCP on 3D PLGA scaffold. As a result, combination of bioceramics and oxygen plasma treatment showed a synergistic effect on

Fabricating a Homogeneously Alloyed AuAg Shell on Au Nanorods to Achieve Strong, Stable, and Tunable Surface Plasmon Resonances

KAUST Repository

Huang, Jianfeng; Zhu, Yihan; Liu, Changxu; Zhao, Yunfeng; Liu, Zhaohui; Hedhili, Mohamed N.; Fratalocchi, Andrea; Han, Yu

2015-01-01

Colloidal metal nanocrystals with strong, stable, and tunable localized surface plasmon resonances (SPRs) can be useful in a corrosive environment for many applications including field-enhanced spectroscopies, plasmon-mediated catalysis, etc. Here

Investigation of the niobium-oxygen system under low pressure and between 550 K and 2350 K: solid solution, surface overlay and reactivity

International Nuclear Information System (INIS)

Jupille, Jacques

1974-09-01

This research thesis addresses the behaviour of transition metals when interacting with oxygen, more particularly in the case of phase formation, but also adsorption and desorption which occur in the case of interaction with low pressure oxygen. It focuses on the case of niobium in solid solution. After a description of phases present in the niobium-oxygen system, and a discussion of reactivities of oxygen and water vapour, the author describes the experimental methods (apparatus and installations, samples, measured values), discusses the study of the surface-volume transfer constant of the niobium-oxygen solution, and the niobium-oxygen interaction mechanisms at high (superior to 1700 K) and low (inferior to 1000 K) temperatures: oxide desorption, oxygen reaction kinetics

Design and Fabrication of a Hybrid Superhydrophobic-Hydrophilic Surface That Exhibits Stable Dropwise Condensation.

Science.gov (United States)

Mondal, Bikash; Mac Giolla Eain, Marc; Xu, QianFeng; Egan, Vanessa M; Punch, Jeff; Lyons, Alan M

2015-10-28

Condensation of water vapor is an essential process in power generation, water collection, and thermal management. Dropwise condensation, where condensed droplets are removed from the surface before coalescing into a film, has been shown to increase the heat transfer efficiency and water collection ability of many surfaces. Numerous efforts have been made to create surfaces which can promote dropwise condensation, including superhydrophobic surfaces on which water droplets are highly mobile. However, the challenge with using such surfaces in condensing environments is that hydrophobic coatings can degrade and/or water droplets on superhydrophobic surfaces transition from the mobile Cassie to the wetted Wenzel state over time and condensation shifts to a less-effective filmwise mechanism. To meet the need for a heat-transfer surface that can maintain stable dropwise condensation, we designed and fabricated a hybrid superhydrophobic-hydrophilic surface. An array of hydrophilic needles, thermally connected to a heat sink, was forced through a robust superhydrophobic polymer film. Condensation occurs preferentially on the needle surface due to differences in wettability and temperature. As the droplet grows, the liquid drop on the needle remains in the Cassie state and does not wet the underlying superhydrophobic surface. The water collection rate on this surface was studied using different surface tilt angles, needle array pitch values, and needle heights. Water condensation rates on the hybrid surface were shown to be 4 times greater than for a planar copper surface and twice as large for silanized silicon or superhydrophobic surfaces without hydrophilic features. A convection-conduction heat transfer model was developed; predicted water condensation rates were in good agreement with experimental observations. This type of hybrid superhydrophobic-hydrophilic surface with a larger array of needles is low-cost, robust, and scalable and so could be used for heat

Dinitrogen Fixation Within and Adjacent to Oxygen Deficient Waters of the Eastern Tropical South Pacific Ocean

Science.gov (United States)

Widner, B.; Mulholland, M. R.; Bernhardt, P. W.; Chang, B. X.; Jayakumar, A.

2016-02-01

Recent work suggests that planktonic diazotrophs are geographically more widely distributed than previously thought including relatively warm (14-23oC) aphotic oxygenated pelagic waters and in aphotic waters within oxygen deficient zones. Because the volume of aphotic water in the ocean is large and may increase in the future, if dinitrogen (N2) fixation is widely occurring at sub-euphotic depths, this could result in a dramatic upward revision of global nitrogen (N) inputs via this process. N2 fixation rates were measured during a cruise in the Eastern Tropical South Pacific using stable isotope tracer techniques that account for slow gas dissolution. Results are compared with light, nutrient, and oxygen gradients (and necessarily temperature gradients). In addition, rates of N2 fixation made in vertical profiles within and above oxygen deficient waters are compared with those measured in vertical profiles adjacent to oxygen deficient waters. Results suggest that while rates of N2 fixation were measurable in deeper anoxic waters, volumetric N2 fixation rates were higher in surface waters.

The interaction of oxygen with TiC(001): Photoemission and first-principles studies

International Nuclear Information System (INIS)

Rodriguez, J.A.; Liu, P.; Dvorak, J.; Jirsak, T.; Gomes, J.; Takahashi, Y.; Nakamura, K.

2004-01-01

High-resolution photoemission and first-principles density-functional slab calculations were used to study the interaction of oxygen with a TiC(001) surface. Atomic oxygen is present on the TiC(001) substrate after small doses of O 2 at room temperature. A big positive shift (1.5-1.8 eV) was detected for the C 1s core level. These photoemission studies suggest the existence of strong O↔C interactions. A phenomenon corroborated by the results of first-principles calculations, which show a CTiTi hollow as the most stable site for the adsorption of O. Ti and C atoms are involved in the adsorption and dissociation of the O 2 molecule. In general, the bond between O and the TiC(001) surface contains a large degree of ionic character. The carbide→O charge transfer is substantial even at high coverages (>0.5 ML) of oxygen. At 500 K and large doses of O 2 , oxidation of the carbide surface occurs with the removal of C and formation of titanium oxides. There is an activation barrier for the exchange of Ti-C and Ti-O bonds which is overcome only by the formation of C-C or C-O bonds on the surface. The mechanism for the removal of a C atom as CO gas involves a minimum of two O adatoms, and three O adatoms are required for the formation of CO 2 gas. Due to the high stability of TiC, an O adatom alone cannot induce the generation of a C vacancy in a flat TiC(001) surface

The impact of moisture sources on the oxygen isotope composition of precipitation at a continental site in central Europe

Science.gov (United States)

Krklec, Kristina; Domínguez-Villar, David; Lojen, Sonja

2018-06-01

The stable isotope composition of precipitation records processes taking place within the hydrological cycle. Potentially, moisture sources are important controls on the stable isotope composition of precipitation, but studies focused on this topic are still scarce. We studied the moisture sources contributing to precipitation at Postojna (Slovenia) from 2009 to 2013. Back trajectory analyses were computed for the days with precipitation at Postojna. The moisture uptake locations were identified along these trajectories using standard hydrometeorological formulation. The moisture uptake locations were integrated in eight source regions to facilitate its comparison to the monthly oxygen isotope composition (δ18O values) of precipitation. Nearly half of the precipitation originated from continental sources (recycled moisture), and >40% was from central and western Mediterranean. Results show that moisture sources do not have a significant impact on the oxygen isotope composition at this site. We suggest that the large proportion of recycled moisture originated from transpiration rather than evaporation, which produced water vapour with less negative δ18O values. Thus the difference between the oceanic and local vapour source was reduced, which prevented the distinction of the moisture sources based on their oxygen isotope signature. Nevertheless, δ18O values of precipitation are partially controlled by climate parameters, which is of major importance for paleoclimate studies. We found that the main climate control on Postojna δ18O values of precipitation is the surface temperature. Amount effect was not recorded at this site, and the winter North Atlantic Oscillation (NAO) does not impact the δ18O values of precipitation. The Western Mediterranean Oscillation (WeMO) was correlated to oxygen stable isotope composition, although this atmospheric pattern was not a control. Instead we found that the link to δ18O values results from synoptic scenarios affecting We

No oxygen isotope exchange between water and APS-sulfate at surface temperature: Evidence from quantum chemical modeling and triple-oxygen isotope experiments

Science.gov (United States)

Kohl, Issaku E.; Asatryan, Rubik; Bao, Huiming

2012-10-01

In both laboratory experiments and natural environments where microbial dissimilatory sulfate reduction (MDSR) occurs in a closed system, the δ34S ((34S/32S)sample/(34S/32S)standard - 1) for dissolved SO42- has been found to follow a typical Rayleigh-Distillation path. In contrast, the corresponding δ18O ((18O/16O)sample/(18O/16O)standard) - 1) is seen to plateau with an apparent enrichment of between 23‰ and 29‰ relative to that of ambient water under surface conditions. This apparent steady-state in the observed difference between δ18O and δ18OO can be attributed to any of these three steps: (1) the formation of adenosine-5'-phosphosulfate (APS) from ATP and SO42-, (2) oxygen exchange between sulfite (or other downstream sulfoxy-anions) and water later in the MDSR reaction chain and its back reaction to APS and sulfate, and (3) the re-oxidation of produced H2S or precursor sulfoxy-anions to sulfate in environments containing Fe(III) or O2. This study examines the first step as a potential pathway for water oxygen incorporation into sulfate. We examined the structures and process of APS formation using B3LYP/6-31G(d,p) hybrid density functional theory, implemented in the Gaussian-03 program suite, to predict the potential for oxygen exchange. We conducted a set of in vitro, enzyme-catalyzed, APS formation experiments (with no further reduction to sulfite) to determine the degree of oxygen isotope exchange between the APS-sulfate and water. Triple-oxygen-isotope labeled water was used in the reactor solutions to monitor oxygen isotope exchange between water and APS sulfate. The formation and hydrolysis of APS were identified as potential steps for oxygen exchange with water to occur. Quantum chemical modeling indicates that the combination of sulfate with ATP has effects on bond strength and symmetry of the sulfate. However, these small effects impart little influence on the integrity of the SO42- tetrahedron due to the high activation energy required for

Wall-crossing between stable and co-stable ADHM data

Science.gov (United States)

Ohkawa, Ryo

2018-06-01

We prove formula between Nekrasov partition functions defined from stable and co-stable ADHM data for the plane following method by Nakajima and Yoshioka (Kyoto J Math 51(2):263-335, 2011) based on the theory of wall-crossing formula developed by Mochizuki (Donaldson type invariants for algebraic surfaces: transition of moduli stacks, Lecture notes in mathematics, vol 1972, Springer, Berlin, 2009). This formula is similar to conjectures by Ito et al. [J High Energy Phys 2013(5):045, 2013, (4.1), (4.2)] for A1 singularity.

Oxygen Electrode Kinetics and Surface Composition of Dense (La0.75Sr0.25)0.95MnO3 on YSZ

DEFF Research Database (Denmark)

Wu, Yuehua; Hansen, Karin Vels; Norrman, Kion

2013-01-01

in situ at temperatures from 660 to 860 C using a controlled atmosphere high temperature scanning probe microscope (CAHT-SPM) setup for measurements of impedance spectroscopy and potential sweep. The oxygen partial pressure, pO2, was varied. Further, ex situ surface analysis by time of flight secondary...... ion mass spectrometry (TOF-SIMS) and structure examination by scanning electron microscopy (SEM) were performed. Segregation of Sr and La oxides to LSM surfaces and Mn rich oxide to the three phase boundary (TPB) was observed. YSZ and LSM attract different oxides/impurities. The oxygen electrode...

Passivation of surface states of α-Fe2O3(0001) surface by deposition of Ga2O3 overlayers: A density functional theory study.

Science.gov (United States)

Ulman, Kanchan; Nguyen, Manh-Thuong; Seriani, Nicola; Gebauer, Ralph

2016-03-07

There is a big debate in the community regarding the role of surface states of hematite in the photoelectrochemical water splitting. Experimental studies on non-catalytic overlayers passivating the hematite surface states claim a favorable reduction in the overpotential for the water splitting reaction. As a first step towards understanding the effect of these overlayers, we have studied the system Ga2O3 overlayers on hematite (0001) surfaces using first principles computations in the PBE+U framework. Our computations suggest that stoichiometric terminations of Ga2O3 overlayers are energetically more favored than the bare surface, at ambient oxygen chemical potentials. Energetics suggest that the overlayers prefer to grow via a layer-plus-island (Stranski-Krastanov) growth mode with a critical layer thickness of 1-2 layers. Thus, a complete wetting of the hematite surface by an overlayer of gallium oxide is thermodynamically favored. We establish that the effect of deposition of the Ga2O3 overlayers on the bare hematite surface is to passivate the surface states for the stoichiometric termination. For the oxygen terminated surface which is the most stable termination under photoelectrochemical conditions, the effect of deposition of the Ga2O3 overlayer is to passivate the hole-trapping surface state.

Segregation and stability at Pt3Ni(1 1 1) surfaces and Pt75Ni25 nanoparticles

International Nuclear Information System (INIS)

Fowler, Ben; Lucas, Christopher A.; Omer, Ahmed; Wang, Guofeng; Stamenkovic, Vojislav R.; Markovic, Nenad M.

2008-01-01

Using in situ surface X-ray diffraction we have determined the atomic structure and stability of a Pt 3 Ni(1 1 1) surface in the electrochemical environment. Surface segregation leads to a pure Pt(1 1 1) skin with enrichment of Ni in the sub-surface atomic layer that determines the surface electronic structure. The Pt-skin surface exhibits inward relaxation upon the adsorption of oxygenated species and this explains the surface stability compared to pure Pt(1 1 1). Using Monte Carlo calculations it is shown that nanoparticles with the same surface composition and stochiometry are energetically stable

Seasonal Cyclicity in Trace Elements and Stable Isotopes of Modern Horse Enamel.

Directory of Open Access Journals (Sweden)

Niels J de Winter

Full Text Available The study of stable isotopes in fossil bioapatite has yielded useful results and has shown that bioapatites are able to faithfully record paleo-environmental and paleo-climatic parameters from archeological to geological timescales. In an effort to establish new proxies for the study of bioapatites, intra-tooth records of enamel carbonate stable isotope ratios from a modern horse are compared with trace element profiles measured using laboratory micro X-Ray Fluorescence scanning. Using known patterns of tooth eruption and the relationship between stable oxygen isotopes and local temperature seasonality, an age model is constructed that links records from six cheek upper right teeth from the second premolar to the third molar. When plotted on this age model, the trace element ratios from horse tooth enamel show a seasonal pattern with a small shift in phase compared to stable oxygen isotope ratios. While stable oxygen and carbon isotopes in tooth enamel are forced respectively by the state of the hydrological cycle and the animal's diet, we argue that the seasonal signal in trace elements reflects seasonal changes in dust intake and diet of the animal. The latter explanation is in agreement with seasonal changes observed in carbon isotopes of the same teeth. This external forcing of trace element composition in mammal tooth enamel implies that trace element ratios may be used as proxies for seasonal changes in paleo-environment and paleo-diet.

Hydrogen and Oxygen stable isotope analysis of water in fruits and vegetables by using cavity ring-down spectrometry

International Nuclear Information System (INIS)

Suzuki, Yaeko

2016-01-01

We determined oxygen and hydrogen stable isotope ratios (δ"1"8O and δD) of water in fruits (citrus) and vegetables (ginger) using cavity ring-down spectrometry (CRDS) for assessment of their authenticity. The δ"1"8O and δD values of fruits and straight juice had higher than those of concentrated juice. The citrus fruits from Japan had relatively lower δ"1"8O and δD values of than those from Australia, South Africa and the United States. The δD values and d-excess of ginger samples from Japan were relatively higher than those of ginger samples from China. The δ"1"8O and δD values of water in fruits and vegetables would be representative of the ambient water, depending on geographical parameters such as the latitude and altitude. These results suggested that δ"1"8O and δD values of water in fruits and vegetables by using CRDS would be potentially useful for assessment of their authenticity. (author)

The formation of non-oxidic oxygen phases on Ru(0001). From the first stages of the oxygen take-up to oxidation

International Nuclear Information System (INIS)

Blume, R.

2005-01-01

The aim of the thesis presented here was the investigation of the formation of non oxidic oxygen phases on the Ru(0001) surface. Smooth and defect rich surfaces were exposed to high oxygen pressures (up to 1 bar) at moderate temperatures (550 K). The characterisation was performed under UHV conditions using Thermal Desorption Spectroscopy (TDS), Scanning Photoemission Microscopy (SPEM), Thermal Energy Atomic Scattering (TEAS), Ultraviolett Photoelectron Spectroscopy (UPS) and Low Energy Electron Diff raction (LEED) as well as In situ by the In Situ X-Ray Photoelectron Spectroscopy (In Situ XPS). The application of this Low Temperature preparation procedure (LT) leads to an Oxygen uptake up to 3 MLE of ''subsurface'' oxygen into a smooth Ru(0001) surface without the typical indications of oxidation (MLE: Monolayer Equivalent). The accumulation of oxygen beneath the surface starts immediatly after the completion of a full chemisorbed layer. Here, the local saturation of the adsorbed oxygen is the decisive step. Diff usion of oxygen directly through the chemisorbed layer only slightly contributes to the overall uptake. Oxygen is mostly accomodated in the vicinity of the surface via surface defects which has been shown on defect rich surfaces created by mild Ar+ sputtering. The maximum oxygen capacity is 10 Atoms/Defect. The uptake is thermally activated with an activation energy of 0.15 eV. The oxygen uptake causes a massive structural change of at least the top two ruthenium layers. Whereas the ruthenium atoms of the first layer are coordinated with up to four, those of the second layer are coordinated with up to two oxygen atoms. These binding condition are metastable and can be changed by annealing the surface. With reaching the desorption temperature two distinct desorption peaks are observed with TDS. For an accumulation of about 0.5 MLE of ''subsurface'' oxygen the desorption proceeds exclusively at the characteristic temperature of the chemisorbed layer at 1040

Stable isotope hydrology. Deuterium and oxygen-18 in the water cycle

International Nuclear Information System (INIS)

Gat, J.R.; Gonfiantini, R.

1981-01-01

This monograph is mainly intended for hydrologists, hydrogeologists and geochemists who want to become acquainted, rapidly but in some detail, with the theoretical background of stable isotope fractionation in natural physico-chemical processes involving fresh water, with the isotopic differences actually encountered in natural waters and with their use for practical hydrological purposes. Throughout the monograph, and in particular in the last chapter, a series of examples are discussed, giving the results obtained with stable isotope techniques in current hydrological and hydrogeological investigations or, more generally, in water resources exploration and assessment. One chapter is also dedicated to the techniques for measuring D/H and 18 O/ 16 O ratios in water

Unraveling the facet-dependent and oxygen vacancy role for ethylene hydrogenation on Co{sub 3}O{sub 4} (110) surface: A DFT+U study

Energy Technology Data Exchange (ETDEWEB)

Zhang, Yong-Chao; Pan, Lun; Lu, Jinhui; Song, Jiajia; Li, Zheng; Zhang, Xiangwen; Wang, Li [Key Laboratory for Green Chemical Technology of the Ministry of Education, School of Chemical Engineering and Technology, Tianjin University (China); Collaborative Innovative Center of Chemical Science and Engineering (Tianjin), Tianjin 300072 (China); Zou, Ji-Jun, E-mail: jj_zou@tju.edu.cn [Key Laboratory for Green Chemical Technology of the Ministry of Education, School of Chemical Engineering and Technology, Tianjin University (China); Collaborative Innovative Center of Chemical Science and Engineering (Tianjin), Tianjin 300072 (China)

2017-04-15

Highlights: • The mechanism of ethylene hydrogenation on perfect and oxygen defective Co{sub 3}O{sub 4}(110) is investigated by using DFT + U. • Oxygen vacancy promotes ethylene hydrogenation thermodynamically and kinetically. • The Co3O4 (110) facet is more active than the (111) one for ethylene hydrogenation. - Abstract: Crystal facet engineering and defect engineering are both critical strategies to improve the catalytic hydrogenation performance of catalyst. Herein, ethylene hydrogenation on the perfect and oxygen defective Co{sub 3}O{sub 4}(110) surfaces has been studied by using periodic density functional theory calculations. The results are compared with that on Co{sub 3}O{sub 4}(111) surface to clarify the problem of which facet for Co{sub 3}O{sub 4} is more reactive, and to illuminate the role of oxygen vacancy. The low oxygen vacancy formation energy suggests that Co{sub 3}O{sub 4}(110) surface with defective site is easily formed. The whole mechanism of H{sub 2} dissociation and stepwise hydrogenation of ethylene to ethane is examined, and the most favorable pathway is heterolytic dissociation of H{sub 2} follows two stepwise hydrogenation of ethylene process. The results show that ethyl hydrogenation to ethane on perfect Co{sub 3}O{sub 4}(110) surface is the rate limiting step with an activation energy of 1.19 eV, and the presence of oxygen vacancy strongly reduces the activation energies of main elementary steps, and the activation energy of rate limiting step is only 0.47 eV. Compared with that on Co{sub 3}O{sub 4}(111), ethylene hydrogenation is preferred on Co{sub 3}O{sub 4}(110) surface. Therefore, Co{sub 3}O{sub 4} with exposed (110) facet is predicted as an excellent catalyst for ethylene hydrogenation.

Calculation on uranium carbon oxygen system molecular structure by DFT

International Nuclear Information System (INIS)

Zhang Guangfeng; Wang Xiaolin; Zou Lexi; Sun Ying; Xue Weidong; Zhu Zhenghe; Wang Hongyan

2001-01-01

The authors study on the possible molecular structures U-C-O, U-O-C, C-U-O (angular structure C a nd linear structure C ∞υ ) of carbon monoxide interacting on uranium metal surface by Density functional theory (DFT). The uranium atom is used RECP (Relativistic Effective Core Potential) and contracted valence basis sets (6s5p2d4f)/[3s3p2d2f], and for carbon and oxygen atoms all are 6-311G basis sets. The author presents the results of energy optimum which shows that triple and quintuple state are more stable. The authors get the electronic state, geometry structure, energy, harmonic frequency, mechanical property, etc. of these twelve triple and quintuple state relative stable structures. The normal vibrational analytical figure of angular structure (C s ) and linear structure (C ∞υ ) is given at the same time. It is indicated that angular structure has lower energy than linear structure, moreover the angular structure of U-C-O( 3 A ) has the lowest energy. The bond strength between uranium atom and carbon monoxide is weak and between uranium atom and oxygen atom is slightly stronger than between uranium atom and carbon atom which the authors can know by superposition population and bond energy analysis among atoms

Fundamental Mechanistic Understanding of Electrocatalysis of Oxygen Reduction on Pt and Non-Pt Surfaces: Acid versus Alkaline Media

Directory of Open Access Journals (Sweden)

Nagappan Ramaswamy

2012-01-01

Full Text Available Complex electrochemical reactions such as Oxygen Reduction Reaction (ORR involving multi-electron transfer is an electrocatalytic inner-sphere electron transfer process that exhibit strong dependence on the nature of the electrode surface. This criterion (along with required stability in acidic electrolytes has largely limited ORR catalysts to the platinum-based surfaces. New evidence in alkaline media, discussed here, throws light on the involvement of surface-independent outer-sphere electron transfer component in the overall electrocatalytic process. This surface non-specificity gives rise to the possibility of using a wide-range of non-noble metal surfaces as electrode materials for ORR in alkaline media. However, this outer-sphere process predominantly leads only to peroxide intermediate as the final product. The importance of promoting the electrocatalytic inner-sphere electron transfer by facilitation of direct adsorption of molecular oxygen on the active site is emphasized by using pyrolyzed metal porphyrins as electrocatalysts. A comparison of ORR reaction mechanisms between acidic and alkaline conditions is elucidated here. The primary advantage of performing ORR in alkaline media is found to be the enhanced activation of the peroxide intermediate on the active site that enables the complete four-electron transfer. ORR reaction schemes involving both outer- and inner-sphere electron transfer mechanisms are proposed.

Direct Electrolysis of Molten Lunar Regolith for the Production of Oxygen and Metals on the Moon

Science.gov (United States)

Sirk, Aislinn H. C.; Sadoway, Donald R.; Sibille, Laurent

2010-01-01

When considering the construction of a lunar base, the high cost ($ 100,000 a kilogram) of transporting materials to the surface of the moon is a significant barrier. Therefore in-situ resource utilization will be a key component of any lunar mission. Oxygen gas is a key resource, abundant on earth and absent on the moon. If oxygen could be produced on the moon, this provides a dual benefit. Not only does it no longer need to be transported to the surface for breathing purposes; it can also be used as a fuel oxidizer to support transportation of crew and other materials more cheaply between the surface of the moon, and lower earth orbit (approximately $20,000/kg). To this end a stable, robust (lightly manned) system is required to produce oxygen from lunar resources. Herein, we investigate the feasibility of producing oxygen, which makes up almost half of the weight of the moon by direct electrolysis of the molten lunar regolith thus achieving the generation of usable oxygen gas while producing primarily iron and silicon at the cathode from the tightly bound oxides. The silicate mixture (with compositions and mechanical properties corresponding to that of lunar regolith) is melted at temperatures near 1600 C. With an inert anode and suitable cathode, direct electrolysis (no supporting electrolyte) of the molten silicate is carried out, resulting in production of molten metallic products at the cathode and oxygen gas at the anode. The effect of anode material, sweep rate, and electrolyte composition on the electrochemical behavior was investigated and implications for scale-up are considered. The activity and stability of the candidate anode materials as well as the effect of the electrolyte composition were determined. Additionally, ex-situ capture and analysis of the anode gas to calculate the current efficiency under different voltages, currents and melt chemistries was carried out.

Stable water isotope patterns in a climate change hotspot: the isotope hydrology framework of Corsica (western Mediterranean).

Science.gov (United States)

van Geldern, Robert; Kuhlemann, Joachim; Schiebel, Ralf; Taubald, Heinrich; Barth, Johannes A C

2014-06-01

The Mediterranean is regarded as a region of intense climate change. To better understand future climate change, this area has been the target of several palaeoclimate studies which also studied stable isotope proxies that are directly linked to the stable isotope composition of water, such as tree rings, tooth enamel or speleothems. For such work, it is also essential to establish an isotope hydrology framework of the region of interest. Surface waters from streams and lakes as well as groundwater from springs on the island of Corsica were sampled between 2003 and 2009 for their oxygen and hydrogen isotope compositions. Isotope values from lake waters were enriched in heavier isotopes and define a local evaporation line (LEL). On the other hand, stream and spring waters reflect the isotope composition of local precipitation in the catchment. The intersection of the LEL and the linear fit of the spring and stream waters reflect the mean isotope composition of the annual precipitation (δP) with values of-8.6(± 0.2) ‰ for δ(18)O and-58(± 2) ‰ for δ(2)H. This value is also a good indicator of the average isotope composition of the local groundwater in the island. Surface water samples reflect the altitude isotope effect with a value of-0.17(± 0.02) ‰ per 100 m elevation for oxygen isotopes. At Vizzavona Pass in central Corsica, water samples from two catchments within a lateral distance of only a few hundred metres showed unexpected but systematic differences in their stable isotope composition. At this specific location, the direction of exposure seems to be an important factor. The differences were likely caused by isotopic enrichment during recharge in warm weather conditions in south-exposed valley flanks compared to the opposite, north-exposed valley flanks.

On the electronic, structural, and thermodynamic properties of Au supported on α-Fe{sub 2}O{sub 3} surfaces and their interaction with CO

Energy Technology Data Exchange (ETDEWEB)

Nguyen, Manh-Thuong, E-mail: manhth.nguyen@gmail.com; Gebauer, Ralph [The Abdus Salam International Centre for Theoretical Physics, Strada Costiera 11, 34151 Trieste (Italy); Farnesi Camellone, Matteo, E-mail: mfarnesi@sissa.it [CNR-IOM DEMOCRITOS, Istituto Officina dei Materiali, Consiglio Nazionale delle Ricerche and SISSA Scuola Internazionale di Studi Superiori Avanzati, Via Bonomea 265, I-34136 Trieste (Italy)

2015-07-21

Extensive first principles calculations are carried out to investigate Au monomers and dimers supported on α-Fe{sub 2}O{sub 3}(0001) surfaces in terms of structure optimizations, electronic structure analyses, and ab initio thermodynamics calculations of surface phase diagrams. All computations rely on density functional theory in the generalized gradient approximation (Perdew-Burke-Ernzerhof (PBE)) and account for on-site Coulomb interactions via inclusion of a Hubbard correction (PBE+U). The relative stability of Au monomers/dimers on the stoichiometric termination of α-Fe{sub 2}O{sub 3}(0001) decorated with various vacancies (multiple oxygen vacancies, iron vacancy, and mixed iron-oxygen vacancies) has been computed as a function of the oxygen chemical potential. The charge rearrangement induced by Au at the oxide contact is analyzed in detail and discussed. On one hand, ab initio thermodynamics predicts that under O-rich conditions, structures obtained by replacing a surface Fe atom with a Au atom are thermodynamically stable over a wide range of temperatures. On the other hand, the complex of a CO molecule on a Au atom substituting surface Fe atoms is thermodynamically stable only in a much more narrow range of values of the O chemical potential under O-rich conditions. In the case of a Au dimer, under O-rich conditions, supported Au atoms at an O-Fe di-vacancy are more stable. However, upon CO adsorption, the complex of a CO molecule and 2 Au atoms located at a single Fe vacancy is more favorable.

Surface modification of carbon/epoxy prepreg using oxygen plasma and its effect on the delamination resistance behavior of carbon/epoxy composites

International Nuclear Information System (INIS)

Kim, M.H.; Rhee, K.Y.; Kim, H.J.; Jung, D.H.

2007-01-01

It was shown in previous study that the fracture toughness of carbon/epoxy laminated composites could be significantly improved by modifying the surface of the prepreg using Ar + irradiation in an oxygen environment. In this study, the surface of carbon/epoxy prepreg was modified using an oxygen plasma to improve the delamination resistance behavior of carbon/epoxy laminated composites. The variation of the contact angle on the prepreg surface was determined as a function of the modification time, in order to determine the optimal modification time. An XPS analysis was conducted to investigate the chemical changes on the surface of the prepreg caused by the plasma modification. Mode I delamination resistance curves of the composites with and without surface modification were plotted as a function of the delamination increment. The results showed that the contact angle varied from ∼64 o to ∼47 o depending on the modification time and reached a minimum for a modification time of 30 min. The XPS analysis showed that the hydrophilic carbonyl C=O group was formed by the oxygen plasma modification. The results also showed that the delamination resistance behavior was significantly improved by the plasma modification of the prepreg. This improvement was caused by the better layer-to-layer adhesion as well as increased interfacial strength between the fibers and matrix

[Startup, stable operation and process failure of EBPR system under the low temperature and low dissolved oxygen condition].

Science.gov (United States)

Ma, Juan; Li, Lu; Yu, Xiao-Jun; Wei, Xue-Fen; Liu, Juan-Li

2015-02-01

A sequencing batch reactor (SBR) was started up and operated with alternating anaerobic/oxic (An/O) to perform enhanced biological phosphorus removal (EBPR) under the condition of 13-16 degrees C. The results showed that under the condition of low temperature, the EBPR system was successfully started up in a short time (<6 d). The reactor achieved a high and stable phosphorus removal performance with an influent phosphate concentration of 20 mg x L(-1) and the dissolved oxygen (DO) concentration of 2 mg x L(-1). The effluent phosphate concentration was lower than 0.5 mg x L(-1). It was found that decreasing DO had an influence on the steady operation of EBPR system. As DO concentration of aerobic phase decreased from 2 mg x L(-1) to 1 mg x L(-1), the system could still perform EBPR and the phosphorus removal efficiency was greater than 97.4%. However, the amount of phosphate released during anaerobic phase was observed to decrease slightly compared with that of 2 mg x L(-1) DO condition. Moreover, the phosphorus removal performance of the system deteriorated immediately and the effluent phosphate concentration couldn't meet the national integrated wastewater discharge standard when DO concentration was further lowered to 0.5 mg x L(-1). The experiments of increasing DO to recover phosphorus removal performance of the EBPR suggested the process failure resulted from low DO was not reversible in the short-term. It was also found that the batch tests of anoxic phosphorus uptake using nitrite and nitrate as electron acceptors had an impact on the stable operation of EBPR system, whereas the resulting negative influence could be recovered within 6 cycles. In addition, the mixed liquid suspended solids (MLSS) of the EBPR system remained stable and the sludge volume index (SVI) decreased to a certain extend in a long run, implying long-term low temperature and low DO condition favored the sludge sedimentation.

Stable isotope composition of surface and groundwater in Baja California, Mexico

International Nuclear Information System (INIS)

Kretzschmar, Thomas G.; Frommen, Theresa

2013-01-01

Based on a total of 135 stable isotope analysis (δ 18 O, δD) carried out on surface and groundwater samples, as well as on rainwater samples between 2004 and 2011 in 5 different regions in Baja California, an isotopic evaluation of the region was established. The results showed a depletion gradient of -0.25 0/00 δ 18 O per 100 m rise in elevation throughout the study area. Considering an unaltered δ 18 O signature for the thermal springs, the recharge areas of these waters are at elevations over 1400 m outside of the present watersheds, indicating the presence of regional flow systems next to the local flow regime feeding the cold springs and wells. The Mesa de Andrade area has a completely different signature with values of -105 for δ 18 O and -13 for δD. (authors)

Intraportal islet oxygenation.

Science.gov (United States)

Suszynski, Thomas M; Avgoustiniatos, Efstathios S; Papas, Klearchos K

2014-05-01

Islet transplantation (IT) is a promising therapy for the treatment of diabetes. The large number of islets required to achieve insulin independence limit its cost-effectiveness and the number of patients who can be treated. It is believed that >50% of islets are lost in the immediate post-IT period. Poor oxygenation in the early post-IT period is recognized as a possible reason for islet loss and dysfunction but has not been extensively studied. Several key variables affect oxygenation in this setting, including (1) local oxygen partial pressure (pO(2)), (2) islet oxygen consumption, (3) islet size (diameter, D), and (4) presence or absence of thrombosis on the islet surface. We discuss implications of oxygen-limiting conditions on intraportal islet viability and function. Of the 4 key variables, the islet size appears to be the most important determinant of the anoxic and nonfunctional islet volume fractions. Similarly, the effect of thrombus formation on the islet surface may be substantial. At the University of Minnesota, average size distribution data from clinical alloislet preparations (n = 10) indicate that >150-µm D islets account for only ~30% of the total islet number, but >85% of the total islet volume. This suggests that improved oxygen supply to the islets may have a profound impact on islet survivability and function since most of the β-cell volume is within large islets which are most susceptible to oxygen-limiting conditions. The assumption that the liver is a suitable islet transplant site from the standpoint of oxygenation should be reconsidered. © 2014 Diabetes Technology Society.

Dissolution kinetics of small amounts of oxygen in tantalum alloy T-111 and internal oxide displacement reactions during annealing

Science.gov (United States)

Stecura, S.

1976-01-01

Oxygen was added to T-111 (Ta-8W-2Hf, wt. %) at 820 and 990 C at an oxygen pressure of about 0.0003 torr. The technique employed permitted predetermined and reproducible doping of T-111 up to 3.0 at. % oxygen. Based on the temperature dependence of the doping reaction, it is concluded that the initial rates of oxygen pickup are probably controlled by solution of oxygen into the T-111 lattice. Although hafnium oxides are more stable than those of tantalum or tungsten, analyses of extracted residues indicate that the latter oxides predominate in the as-doped specimens, presumably because of the higher concentrations of tantalum and tungsten in the alloy. However, high-temperature annealing promotes gettering of dissolved oxygen and of other oxides to form hafnium oxides. Small amounts of tantalum and tungsten oxides were still present after high-temperature annealing. Tungsten oxide (WO3) volatilizes slightly from the surface of T-111 at 990 C. The vaporization of WO3 has no apparent affect on the doping reaction.

Functional and biocompatibility performances of an integrated Maglev pump-oxygenator.

Science.gov (United States)

Zhang, Tao; Cheng, Guangming; Koert, Andrew; Zhang, Juntao; Gellman, Barry; Yankey, G Kwame; Satpute, Aditee; Dasse, Kurt A; Gilbert, Richard J; Griffith, Bartley P; Wu, Zhongjun J

2009-01-01

To provide respiratory support for patients with lung failure, a novel compact integrated pump-oxygenator is being developed. The functional and biocompatibility performances of this device are presented. The pump-oxygenator is designed by combining a magnetically levitated pump/rotor with a uniquely configured hollow fiber membrane bundle to create an assembly free, ultracompact, all-in-one system. The hemodynamics, gas transfer and biocompatibility performances of this novel device were investigated both in vitro in a circulatory flow loop and in vivo in an ovine animal model. The in vitro results showed that the device was able to pump blood flow from 2 to 8 L/min against a wide range of pressures and to deliver an oxygen transfer rate more than 300 mL/min at a blood flow of 6 L/min. Blood damage tests demonstrated low hemolysis (normalized index of hemolysis [NIH] approximately 0.04) at a flow rate of 5 L/min against a 100-mm Hg afterload. The data from five animal experiments (4 h to 7 days) demonstrated that the device could bring the venous blood to near fully oxygen-saturated condition (98.6% +/- 1.3%). The highest oxygen transfer rate reached 386 mL/min. The gas transfer performance was stable over the study duration for three 7-day animals. There was no indication of blood damage. The plasma free hemoglobin and platelet count were within the normal ranges. No gross thrombus is found on the explanted pump components and fiber surfaces. Both in vitro and in vivo results demonstrated that the newly developed pump-oxygenator can achieve sufficient blood flow and oxygen transfer with excellent biocompatibility.

Kinetics and Mechanisms of Oxygen Surface Exchange on La0.6Sr0.4FeO3-delta Thin Films

DEFF Research Database (Denmark)

Mosleh, Majid; Søgaard, Martin; Hendriksen, Peter Vang

2009-01-01

and oxygen partial pressure [i.e., the incorporation reaction has the same reaction enthalpy (H0=−105 KJ/mol) and entropy (S0=−75.5 J/mol/K) as found for bulk material]. The thin film shows smaller apparent electrical conductivity than reported for bulk. This is due to imperfections in the film, which...... is not totally dense and contains closed porosity. Electrical conductivity relaxation was used to determine the surface exchange coefficient and its dependence on the temperature and oxygen partial pressure. Relaxation curves showed a good fit to a simple exponential decay. The vacancy surface exchange...... coefficient (kV) determined from Kchem shows a slope (log kV vs log PO2) between 0.51 and 0.85. It is further found that kV is proportional to the product of the oxygen partial pressure and the vacancy concentration (kVPO2). Different reaction mechanisms that can account for the observed PO2 and -dependence...

Effects of oxygen annealing on the physical properties and surface microstructures of La0.8Ba0.2MnO3 films

International Nuclear Information System (INIS)

Murugavel, P; Lee, J H; Lee, K-B; Park, J H; Chung, J-S; Yoon, J-G; Noh, T W

2002-01-01

We have investigated the effects of oxygen annealing on the transport properties and surface microstructures of epitaxial La 0.8 Ba 0.2 MnO 3 (LBMO) films deposited on SrTiO 3 substrate at different oxygen pressures using the pulsed laser deposition technique. The thickness dependence of the transport properties was strongly affected by the oxygen pressure during the deposition and the oxygen annealing temperature. Oxygen stoichiometry, in addition to the substrate-induced strain, was found to be a very important factor in controlling the physical properties of low-doped LBMO. Oxygen annealing seemed to induce strain and the strain accommodated in the films was relaxed by forming a secondary phase in an ordered rod-like shape or in particulate form

Oxygen tracer diffusion and surface exchange kinetics in Ba0.5Sr0.5Co0.8Fe0.2O3-δ

NARCIS (Netherlands)

Berenov, A.; Atkinson, A.; Kilner, J.; Ananyev, M.; Eremin, V.; Porotnikova, N.; Farlenkov, A.; Kurumchin, E.; Bouwmeester, Henricus J.M.; Bucher, E.; Sitte, W.

2014-01-01

The oxygen tracer diffusion coefficient, Db⁎, and the oxygen tracer surface exchange coefficient, k, were measured in Ba0.5Sr0.5Co0.8Fe0.2O3 − δ (BSCF5582) over the temperature range of 310–800 °C and the oxygen partial pressure range of 1.3 × 10−3–0.21 bar. Several measurement techniques were used:

Effect of Built-Up Edge Formation during Stable State of Wear in AISI 304 Stainless Steel on Machining Performance and Surface Integrity of the Machined Part.

Science.gov (United States)

Ahmed, Yassmin Seid; Fox-Rabinovich, German; Paiva, Jose Mario; Wagg, Terry; Veldhuis, Stephen Clarence

2017-10-25

During machining of stainless steels at low cutting -speeds, workpiece material tends to adhere to the cutting tool at the tool-chip interface, forming built-up edge (BUE). BUE has a great importance in machining processes; it can significantly modify the phenomenon in the cutting zone, directly affecting the workpiece surface integrity, cutting tool forces, and chip formation. The American Iron and Steel Institute (AISI) 304 stainless steel has a high tendency to form an unstable BUE, leading to deterioration of the surface quality. Therefore, it is necessary to understand the nature of the surface integrity induced during machining operations. Although many reports have been published on the effect of tool wear during machining of AISI 304 stainless steel on surface integrity, studies on the influence of the BUE phenomenon in the stable state of wear have not been investigated so far. The main goal of the present work is to investigate the close link between the BUE formation, surface integrity and cutting forces in the stable sate of wear for uncoated cutting tool during the cutting tests of AISI 304 stainless steel. The cutting parameters were chosen to induce BUE formation during machining. X-ray diffraction (XRD) method was used for measuring superficial residual stresses of the machined surface through the stable state of wear in the cutting and feed directions. In addition, surface roughness of the machined surface was investigated using the Alicona microscope and Scanning Electron Microscopy (SEM) was used to reveal the surface distortions created during the cutting process, combined with chip undersurface analyses. The investigated BUE formation during the stable state of wear showed that the BUE can cause a significant improvement in the surface integrity and cutting forces. Moreover, it can be used to compensate for tool wear through changing the tool geometry, leading to the protection of the cutting tool from wear.

Unbiased Photocatalytic Hydrogen Generation from Pure Water on Stable Ir-treated In 0.33 Ga 0.67 N Nanorods

KAUST Repository

Ebaid, Mohamed; Priante, Davide; Liu, Guangyu; Zhao, Chao; Sharizal Alias, Mohd; Buttner, Ulrich; Khee Ng, Tien; Taylor Isimjan, Tayirjan; Idriss, Hicham; Ooi, Boon S.

2017-01-01

InGaN-based nanostructures have recently been recognized as promising materials for efficient solar hydrogen generation. This is due to their chemical stability, adjustable optoelectronic properties, suitable band edge alignment, and large surface-to-volume ratio. The inherent high density of surface trapping states and the lack of compatible conductive substrates, however, hindered their use as stable photo-catalysts. We have designed, synthesized and tested an efficient photocatalytic system using stable In0.33Ga0.67N-based nanorods (NRs) grown on an all-metal stack substrate (Ti-Mo) for a better electron transfer process. In addition, we have applied a bifunctional ultrathin thiol-based organic surface treatment using 1,2-ethanedithiol (EDT), in which sulfur atoms protected the surface from oxidation. This treatment has dual functions, it passivates the surface (by the removal of dangling bonds) and creates ligands for linking Ir-metal ions as oxygen evolution centers on top of the semiconductor. This treatment when applied to In0.33Ga0.67N NRs resulted in a photo-catalyst that achieved 3.5% solar-to-hydrogen (STH) efficiency, in pure water (pH~7, buffer solution) under simulated one-sun (AM1.5G) illumination and without electrical bias. Over the tested period, a steady increase of the gas evolution rate was observed from which a turnover frequency of 0.23s-1 was calculated. The novel growth of InGaN-based NRs on a metal as well as the versatile surface functionalization techniques (EDT-Ir) have a high potential for making stable photo-catalysts with adjustable band gaps and band edges to harvest sun light.

Unbiased Photocatalytic Hydrogen Generation from Pure Water on Stable Ir-treated In 0.33 Ga 0.67 N Nanorods

KAUST Repository

Ebaid, Mohamed

2017-05-11

InGaN-based nanostructures have recently been recognized as promising materials for efficient solar hydrogen generation. This is due to their chemical stability, adjustable optoelectronic properties, suitable band edge alignment, and large surface-to-volume ratio. The inherent high density of surface trapping states and the lack of compatible conductive substrates, however, hindered their use as stable photo-catalysts. We have designed, synthesized and tested an efficient photocatalytic system using stable In0.33Ga0.67N-based nanorods (NRs) grown on an all-metal stack substrate (Ti-Mo) for a better electron transfer process. In addition, we have applied a bifunctional ultrathin thiol-based organic surface treatment using 1,2-ethanedithiol (EDT), in which sulfur atoms protected the surface from oxidation. This treatment has dual functions, it passivates the surface (by the removal of dangling bonds) and creates ligands for linking Ir-metal ions as oxygen evolution centers on top of the semiconductor. This treatment when applied to In0.33Ga0.67N NRs resulted in a photo-catalyst that achieved 3.5% solar-to-hydrogen (STH) efficiency, in pure water (pH~7, buffer solution) under simulated one-sun (AM1.5G) illumination and without electrical bias. Over the tested period, a steady increase of the gas evolution rate was observed from which a turnover frequency of 0.23s-1 was calculated. The novel growth of InGaN-based NRs on a metal as well as the versatile surface functionalization techniques (EDT-Ir) have a high potential for making stable photo-catalysts with adjustable band gaps and band edges to harvest sun light.

Ethylene vinyl alcohol: a review of barrier properties for packaging shelf stable foods.

Science.gov (United States)

Mokwena, K Khanah; Tang, Juming

2012-01-01

Ethylene vinyl alcohol (EVOH) is one of the best known flexible thermoplastic oxygen barrier materials in use today. It is especially important for refrigerated and shelf-stable foods where oxygen deteriorates the quality of packaged products and reduces their shelf life. EVOH accounts for a majority of thermoplastic barrier materials used for rigid or semi-rigid retortable food containers. However. it is of limited use in flexible packages or lid films for rigid trays used for packaging thermally processed shelf-stable low acid foods due to its moisture sensitivity. Nevertheless, current use of other oxygen barrier materials such as polyvinylidene chloride and aluminum foil creates environmental concerns. Innovations in food processing technologies provide opportunities for increased use of EVOH in food packaging. The aim of this review is to give an overview of research on the oxygen barrier properties of EVOH from the perspective of structure-barrier property relationships and the consequences of food processing conditions.

Preparation of Stable Superhydrophobic Coatings on Wood Substrate Surfaces via Mussel-Inspired Polydopamine and Electroless Deposition Methods

Directory of Open Access Journals (Sweden)

Kaili Wang

2017-06-01

Full Text Available Mussel-inspired polydopamine (PDA chemistry and electroless deposition approaches were used to prepare stable superhydrophobic coatings on wood surfaces. The as-formed PDA coating on a wood surface exhibited a hierarchical micro/nano roughness structure, and functioned as an “adhesive layer” between the substrate and a metallic film by the metal chelating ability of the catechol moieties on PDA, allowing for the formation of a well-developed micro/nanostructure hierarchical roughness. Additionally, the coating acted as a stable bridge between the substrate and hydrophobic groups. The morphology and chemical components of the prepared superhydrophobic wood surfaces were characterized by scanning electron microscopy (SEM, Fourier transform infrared (FT-IR spectroscopy, and X-ray photoelectron spectroscopy (XPS. The PDA and octadecylamine (OA modified surface showed excellent superhydrophobicity with a water contact angle (CA of about 153° and a rolling angle (RA of about 9°. The CA further increased to about 157° and RA reduced to about 5° with the Cu metallization. The superhydrophobic material exhibited outstanding stability in harsh conditions including ultraviolet aging, ultrasonic washing, strong acid-base and organic solvent immersion, and high-temperature water boiling. The results suggested that the PDA/OA layers were good enough to confer robust, degradation-resistant superhydrophobicity on wood substrates. The Cu metallization was likely unnecessary to provide significant improvements in superhydrophobic property. However, due to the amazing adhesive capacity of PDA, the electroless deposition technique may allow for a wide range of potential applications in biomimetic materials.

Cognitive function in patients with stable coronary heart disease: Related cerebrovascular and cardiovascular responses.

Directory of Open Access Journals (Sweden)

Mathieu Gayda

Full Text Available Chronic exercise has been shown to prevent or slow age-related decline in cognitive functions in otherwise healthy, asymptomatic individuals. We sought to assess cognitive function in a stable coronary heart disease (CHD sample and its relationship to cerebral oxygenation-perfusion, cardiac hemodynamic responses, and [Formula: see text] peak compared to age-matched and young healthy control subjects. Twenty-two young healthy controls (YHC, 20 age-matched old healthy controls (OHC and 25 patients with stable CHD were recruited. Cognitive function assessment included short term-working memory, perceptual abilities, processing speed, cognitive inhibition and flexibility and long-term verbal memory. Maximal cardiopulmonary function (gas exchange analysis, cardiac hemodynamic (impedance cardiography and left frontal cerebral oxygenation-perfusion (near-infra red spectroscopy were measured during and after a maximal incremental ergocycle test. Compared to OHC and CHD, YHC had higher [Formula: see text] peak, maximal cardiac index (CI max, cerebral oxygenation-perfusion (ΔO2 Hb, ΔtHb: exercise and recovery and cognitive function (for all items (P<0.05. Compared to OHC, CHD patients had lower [Formula: see text] peak, CI max, cerebral oxygenation-perfusion (during recovery and short term-working memory, processing speed, cognitive inhibition and flexibility and long-term verbal memory (P<0.05. [Formula: see text] peak and CI max were related to exercise cerebral oxygenation-perfusion and cognitive function (P<0.005. Cerebral oxygenation-perfusion (exercise was related to cognitive function (P<0.005. Stable CHD patients have a worse cognitive function, a similar cerebral oxygenation/perfusion during exercise but reduced one during recovery vs. their aged-matched healthy counterparts. In the all sample, cognitive functions correlated with [Formula: see text] peak, CI max and cerebral oxygenation-perfusion.

Adsorption and magnetism of bilayer graphene on the MnO polar surface with oxygen vacancies in the interface: First principles study

Science.gov (United States)

Ilyasov, Victor V.; Ershov, Igor V.; Popova, Inna G.; Pham, Khang D.; Nguyen, Chuong V.

2018-05-01

In this paper, we investigate systematically the structural, electronic, magnetic and adsorption properties of Bernal-stacked bilayer graphene on MnO(111) surface terminated by an oxygen atom, as a function of nonstoichiometric composition of the BLG/MnOx(111) interface. For additional functionalization of the BLG/MnOx(111) system, we also studied the adsorption properties of oxygen adsorbed on the BLG/MnOx(111) interface. Our results showed that the BLG is bound to the MnOx(111) substrate by the weak interaction for both spin-up and spin-down. Furthermore, we found that BLG adsorbed on the MnOx(111) substrate with a reduced oxygen symmetry in the interface is accompanied with a downshift of the Fermi level, which identifies the band structure of BLG as a p-type semiconductor. Upon interaction between BLG and MnOx(111) substrate, a forbidden gap of about 350 meV was opened between its bonding and antibonding π bands. A forbidden gap and the local magnetic moments in bilayer graphene can be controlled by changing the oxygen nonstoichometry or by oxygen adsorption. Additionally, magnetism has been predicted in the bilayer graphene adsorbed on the polar MnOx(111) surface with oxygen vacancies in the BLG/MnOx(111) interface, and its nature has also been discussed in this work. These results showed that the adsorption of bilayer graphene on the MnO(111) substrate can be used for developing novel generation of electronic and spintronic devices.

Stable isotope composition of surface and groundwater in Baja California, Mexico

Energy Technology Data Exchange (ETDEWEB)

Kretzschmar, Thomas G. [CICESE, Carret. Ensenada-Tijuana No 3819, Ensenada 22860 (Mexico); Frommen, Theresa [FU Berlin Malteserstr. 74-100, 12249 Berlin (Germany)

2013-07-01

Based on a total of 135 stable isotope analysis (δ{sup 18}O, δD) carried out on surface and groundwater samples, as well as on rainwater samples between 2004 and 2011 in 5 different regions in Baja California, an isotopic evaluation of the region was established. The results showed a depletion gradient of -0.25 0/00 δ{sup 18}O per 100 m rise in elevation throughout the study area. Considering an unaltered δ{sup 18}O signature for the thermal springs, the recharge areas of these waters are at elevations over 1400 m outside of the present watersheds, indicating the presence of regional flow systems next to the local flow regime feeding the cold springs and wells. The Mesa de Andrade area has a completely different signature with values of -105 for δ{sup 18}O and -13 for δD. (authors)

Interactions between kaolinite Al−OH surface and sodium hexametaphosphate

Energy Technology Data Exchange (ETDEWEB)

Han, Yonghua, E-mail: hyh19891102@163.com [School of Chemical and Environmental Engineering, China University of Mining and Technology, Beijing 100083 (China); Liu, Wenli; Zhou, Jia [School of Chemical and Environmental Engineering, China University of Mining and Technology, Beijing 100083 (China); Chen, Jianhua [College of Resources and Metallurgy, Guangxi University, Nanning 530004 (China)

2016-11-30

Highlights: • Sodium hexametaphosphate (NaHMP) can adsorb on kaolinite Al−OH terminated (001) surface easily. • The oxygen atoms of hexametaphosphate form strong hydrogen bonds with the hydrogen atoms of kaolinite Al−OH surface. • The electrostatic force is the main interaction between NaHMP and Al−OH surface. • The linear hexaphosphate −[PO{sub 3}]{sub m}− chains adsorb stably than −[HPO{sub 3}]{sub m}− chains. - Abstract: To investigate the dispersion mechanism of sodium hexametaphosphate on kaolinite particles, we simulated the interaction between linear polyphosphate chains and kaolinite Al−OH terminated surface by molecular dynamics, as well as the interaction between the [HPO{sub 4}]{sup 2−} anion and kaolinite Al−OH surface by density functional theory (DFT). The calculated results demonstrate that hexametaphosphate can be adsorbed by the kaolinite Al−OH surface. The oxygen atoms of hexametaphosphate anions may receive many electrons from the Al−OH surface and form hydrogen bonds with the hydrogen atoms of surface hydroxyl groups. Moreover, electrostatic force dominates the interactions between hexametaphosphate anions and kaolinite Al−OH surface. Therefore, after the adsorption of hexametaphosphate on kaolinite Al−OH surface, the kaolinite particles carry more negative charge and the electrostatic repulsion between particles increases. In addition, the adsorption of −[PO{sub 3}]{sub m}− species on the Al−OH surface should be more stable than the adsorption of −[HPO{sub 3}]{sub m}− species.

A stable high-order perturbation of surfaces method for numerical simulation of diffraction problems in triply layered media

Energy Technology Data Exchange (ETDEWEB)

Hong, Youngjoon, E-mail: hongy@uic.edu; Nicholls, David P., E-mail: davidn@uic.edu

2017-02-01

The accurate numerical simulation of linear waves interacting with periodic layered media is a crucial capability in engineering applications. In this contribution we study the stable and high-order accurate numerical simulation of the interaction of linear, time-harmonic waves with a periodic, triply layered medium with irregular interfaces. In contrast with volumetric approaches, High-Order Perturbation of Surfaces (HOPS) algorithms are inexpensive interfacial methods which rapidly and recursively estimate scattering returns by perturbation of the interface shape. In comparison with Boundary Integral/Element Methods, the stable HOPS algorithm we describe here does not require specialized quadrature rules, periodization strategies, or the solution of dense non-symmetric positive definite linear systems. In addition, the algorithm is provably stable as opposed to other classical HOPS approaches. With numerical experiments we show the remarkable efficiency, fidelity, and accuracy one can achieve with an implementation of this algorithm.

USGS42 and USGS43: Human-hair stable hydrogen and oxygen isotopic reference materials and analytical methods for forensic science and implications for published measurement results

Science.gov (United States)

Coplen, T.B.; Qi, H.

2012-01-01

Because there are no internationally distributed stable hydrogen and oxygen isotopic reference materials of human hair, the U.S. Geological Survey (USGS) has prepared two such materials, USGS42 and USGS43. These reference materials span values commonly encountered in human hair stable isotope analysis and are isotopically homogeneous at sample sizes larger than 0.2 mg. USGS42 and USGS43 human-hair isotopic reference materials are intended for calibration of δ(2)H and δ(18)O measurements of unknown human hair by quantifying (1) drift with time, (2) mass-dependent isotopic fractionation, and (3) isotope-ratio-scale contraction. While they are intended for measurements of the stable isotopes of hydrogen and oxygen, they also are suitable for measurements of the stable isotopes of carbon, nitrogen, and sulfur in human and mammalian hair. Preliminary isotopic compositions of the non-exchangeable fractions of these materials are USGS42(Tibetan hair)δ(2)H(VSMOW-SLAP) = -78.5 ± 2.3‰ (n = 62) and δ(18)O(VSMOW-SLAP) = +8.56 ± 0.10‰ (n = 18) USGS42(Indian hair)δ(2)H(VSMOW-SLAP) = -50.3 ± 2.8‰ (n = 64) and δ(18)O(VSMOW-SLAP) = +14.11 ± 0.10‰ (n = 18). Using recommended analytical protocols presented herein for δ(2)H(VSMOW-SLAP) and δ(18)O(VSMOW-SLAP) measurements, the least squares fit regression of 11 human hair reference materials is δ(2)H(VSMOW-SLAP) = 6.085δ(2)O(VSMOW-SLAP) - 136.0‰ with an R-square value of 0.95. The δ(2)H difference between the calibrated results of human hair in this investigation and a commonly accepted human-hair relationship is a remarkable 34‰. It is critical that readers pay attention to the δ(2)H(VSMOW-SLAP) and δ(18)O(VSMOW-SLAP) of isotopic reference materials in publications, and they need to adjust the δ(2)H(VSMOW-SLAP) and δ(18)O(VSMOW-SLAP) measurement results of human hair in previous publications, as needed, to ensure all results on are on the same scales.

Stable carbon and oxygen isotope studies of Late Weichselian lake sediments in southern Sweden and northern Poland, with palaeoclimatic implications

International Nuclear Information System (INIS)

Hammarlund, D.

1994-04-01

Late Weichselian lacustrine sediment sequences from southern Sweden and northern Poland were studied by means of stable isotope analysis in order to reconstruct the climatic development and climatically induced environmental changes in the respective regions. The methods used include analyses of the stable carbon isotope composition (δ 13 C) of bulk organic material, and the stable carbon and oxygen isotope compositions (δ 13 C, δ 18 O) of bulk carbonates and carbonate shells of aquatic organisms. These results were complemented and supported by lithological, chemical and biostratigraphic data (plant macrofossils, insects, molluscs). Chronological data were obtained by AMS radiocarbon dates and correlations based on pollen analysis. At c. 12.400 BP a climatic change from arctic, dry, and continental, to subarctic and more humid and maritime conditions occurred in southern Sweden. The Older Dryas stadial (c.12.200-12.000 BP) is characterized by a temporary return to generally colder , drier, and more continental conditions, followed by generally favourable (subarctic), although unstable, climatic conditions. At c. 11.300 BP a gradual transition towards a colder and more continental climate was initiated, followed by total absence of limnic carbonates during the Younger Dryas stadial (c. 11.000-10.200 BP), indicating arctic and continental conditions. The transition to the Holocene is characterized by a rapid and strong climatic warming. The results from northern Poland point to some important differences compared to this development. A climatic warming around 13.000 BP was followed by generally favourable climatic conditions enabling continuous sedimentation of limnic carbonates during the Late Weichselian. Distinct depletions of 13 C in lacustrine organic material at the transition to the Holocene were recorded in southern Sweden, also demonstrated by decreasing mean values obtained from an extensive compilation of δ 13 C data. A number of processes that may

Oxygen adsorption and incorporation at irradiated GaN(0001) and GaN(0001¯) surfaces: First-principles density-functional calculations

Science.gov (United States)

Sun, Qiang; Selloni, Annabella; Myers, T. H.; Doolittle, W. Alan

2006-11-01

Density functional theory calculations of oxygen adsorption and incorporation at the polar GaN(0001) and GaN(0001¯) surfaces have been carried out to explain the experimentally observed reduced oxygen concentration in GaN samples grown by molecular beam epitaxy in the presence of high energy (˜10keV) electron beam irradiation [Myers , J. Vac. Sci. Technol. B 18, 2295 (2000)]. Using a model in which the effect of the irradiation is to excite electrons from the valence to the conduction band, we find that both the energy cost of incorporating oxygen impurities in deeper layers and the oxygen adatom diffusion barriers are significantly reduced in the presence of the excitation. The latter effect leads to a higher probability for two O adatoms to recombine and desorb, and thus to a reduced oxygen concentration in the irradiated samples, consistent with experimental observations.

Stable isotope paleoaltimetry and the evolution of landscapes and life

Science.gov (United States)

Mulch, Andreas

2016-01-01

Reconstructing topography of our planet not only advances our knowledge of the geodynamic processes that shape the Earth's surface; equally important it adds a key element towards understanding long-term continental moisture transport, atmospheric circulation and the distribution of biomes and biodiversity. Stable isotope paleoaltimetry exploits systematic decreases in the oxygen (δ18O) or hydrogen (δD) isotopic composition of precipitation along a mountain front when the interaction of topography and advected moist air masses induces orographic precipitation. These changes in δ18O or δD can be recovered from the geologic record and recent geochemical and modeling advances allow a broad range of proxy materials to be evaluated. Over the last 10 yr stable isotope paleoaltimetry has witnessed rapidly expanding research activities and has produced a broad array of fascinating tectonic and geomorphologic studies many of which have concentrated on determining the elevation history of continental plateau regions. These single-site studies have greatly expanded what used to be very sparse global paleoaltimetric data. The challenge now lies in disentangling the surface uplift component from the impact of climate change on δ18O and δD in precipitation. The robustness of stable isotope paleoaltimetry can be enhanced when high-elevation δ18O or δD data are referenced against low-elevation sites that track climate-modulated sea level δ18O or δD of precipitation through time (' δ- δ approach'). Analysis of central Andean paleosols documents that differences in δ18O of soil carbonate between the Subandean foreland and the Bolivian Altiplano are small between 11 and 7 Ma but rise rapidly to ca. 2.9‰ after 7 Ma, corroborating the magnitude of late Miocene change in δ18O on the Altiplano. Future advances in stable isotope paleoaltimetry will greatly benefit from addressing four key challenges: (1) Identifying topographically-induced changes in atmospheric

Insights into the importance of oxygen functional groups in carbon reactions with oxygen containing gases

International Nuclear Information System (INIS)

John Zhu, Max Lu

2005-01-01

The role of pore structure of carbon in carbon-related adsorptions and reactions has been extensively investigated. However the studies on the role of surface chemistry of carbon are limited. In this paper, we present the importance of oxygen functional groups in carbon reactions with oxygen-containing gases. It is found that there is a good correlation between the electronic structures and reactivities of carbon edge sites. Zigzag sites are more active in oxygen adsorption because of the unpaired electrons and armchair sites are less active in oxygen adsorption due to the triple character. However, the desorption of semi-quinone oxygen from zigzag sites needs a bond energy ca. 30% higher than that of o-quinone oxygen from armchair edge sites. CO 2 and H 2 O adsorb on carbon surface much less favorably than O 2 . H 2 O is first physically adsorbed on the virgin graphite surface followed by chemisorption through oxygen atom approaching the carbon edge site and the movements of two hydrogen atoms to produce H 2 . The adsorption mechanism of H 2 O is different from that for CO 2 , but the final result is quite similar, i.e. producing only semi-quinone oxygen. Based upon the above studies, a new generalized mechanism, as shown in Fig. 1, is developed and can account for all the important kinetic phenomena of carbon-gas reactions. The key point is that in CO 2 /H 2 O-carbon reaction only semi-quinone formed; while, in O 2 -carbon reaction, semi-quinone, o-quinone (at lower pressure), and off-plane epoxy oxygen (at relatively higher pressure) can be formed. This is the main reason for the different reaction kinetics of O 2 -carbon reaction and CO 2 /H 2 O-carbon reactions as observed experimentally. The oxygen functional groups of carbon can be characterized by XPS, PZC (point of zero charge), IEP (isoelectric point) and TPD (temperature-programmed desorption), which were used in our previous studies. We treated the carbon surface with different acids, finding that HNO 3

Enhanced oxygen reduction activity on surface-decorated perovskite thin films for solid oxide fuel cells

KAUST Repository

Mutoro, Eva; Crumlin, Ethan J.; Biegalski, Michael D.; Christen, Hans M.; Shao-Horn, Yang

2011-01-01

Surface-decoration of perovskites can strongly affect the oxygen reduction activity, and therefore is a new and promising approach to improve SOFC cathode materials. In this study, we demonstrate that a small amount of secondary phase on a (001) La 0.8Sr 0.2CoO 3-δ (LSC) surface can either significantly activate or passivate the electrode. LSC (001) microelectrodes prepared by pulsed laser deposition on a (001)-oriented yttria-stabilized zirconia (YSZ) substrate were decorated with La-, Co-, and Sr-(hydr)oxides/carbonates. "Sr"-decoration with nanoparticle coverage in the range from 50% to 80% of the LSC surface enhanced the surface exchange coefficient, k q, by an order of magnitude while "La"- decoration and "Co"-decoration led to no change and reduction in k q, respectively. Although the physical origin for the enhancement is not fully understood, results from atomic force microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy suggest that the observed k q enhancement for "Sr"-decorated surfaces can be attributed largely to catalytically active interface regions between surface Sr-enriched particles and the LSC surface. © 2011 The Royal Society of Chemistry.

The effect of coadsorbed oxygen on the reaction of methanol on Rh(111) and on a rhodium/vanadium surface alloy

International Nuclear Information System (INIS)

Schennach, R.; Krenn, G.; Rendulic, K.D.

2002-01-01

Full text: Molecular adsorption of methanol can be observed on all transition metal surfaces at low temperatures. Methanol is adsorbed on Rh (111) at 98 K. With increasing methanol exposure first a mono-layer and then multi-layers of methanol are formed at this surface temperature. During heating, desorption of the methanol from physisorbed multi-layers is detected at about 120 K, followed by desorption of methanol from a chemisorbed mono-layer at 170 K. About 50 % of the adsorbed methanol undergoes a dehydrogenation reaction to form hydrogen and carbon monoxide adsorbed on the surface. These reaction products desorb at 300 K and 480 K, respectively. Less than 0.05 monolayers of coadsorbed oxygen increases the amount of methanol that reacts on the surface to about 80 %. Experiments using a Rh/V surface alloy were performed, in order to distinguish between steric and electronic effects in the adsorption and reaction processes. Deposition of 0.3 monolayers of V on the Rh (111) surface leads to the formation of a subsurface alloy, with V atoms in the second atomic layer only. The initial reaction probability was measured as a function of surface temperature and molecular beam energy. A marked difference was found between the two surfaces. On the clean surface methanol adsorption and reaction stops above 198 K, whereas on the alloy surface adsorption and subsequent reaction occurs up to 473 K. The effects of coadsorbed oxygen are similar on both surfaces. The results are discussed in terms of the possible reactions of the adsorbed methanol on the surface. (author)

Modelling and Mapping Oxygen-18 Isotope Composition of Precipitation in Spain for Hydrologic and Climatic Applications

International Nuclear Information System (INIS)

Rodriguez-Arevalo, J.; Diaz-Teijeiro, M.F.; Castano, S.

2011-01-01

A simple multiple regression model based on two geographic factors (latitude and elevation) has been developed that reproduces reasonably well the spatial distribution of the current mean oxygen-18 isotope composition in precipitation over Spain. In a preliminary analysis, additional geographic and climatic factors do not improve the performance of the model. A continuous digital map of oxygen-18 isotope composition in precipitation has been produced by combining the polynomial model with a Digital Elevation Model using GIS tools. Application of the resulting map to several case studies in Spain has shown it to be useful as a reference of the isotope input function to groundwater recharge and surface runoff. The results obtained so far show a good fit between modelled stable isotope values and those measured in surface and ground waters from different aquifers and recharge areas. The GIS tools applied to a continuous digital layer of spatial isotope are able to provide accurate information at detailed scales that are not affordable by other means. Further validation of the model, and further testing of its usefulness in surface hydrology and climatic studies, is going on.

Behaviour of oxygen atoms near the surface of nanostructured Nb2O5

International Nuclear Information System (INIS)

Cvelbar, U; Mozetic, M

2007-01-01

Recombination of neutral oxygen atoms on oxidized niobium foil was studied. Three sets of samples have been prepared: a set of niobium foils with a film of polycrystalline niobium oxide with a thickness of 40 nm, another one with a film thickness of about 2 μm and a set of foils covered with dense bundles of single-crystal Nb 2 O 3 nanowires. All the samples were prepared by oxidation of a pure niobium foil. The samples with a thin oxide film were prepared by exposure of as-received foils to a flux of O-atoms, the samples with a thick polycrystalline niobium oxide were prepared by baking the foils in air at a temperature of 800 deg. C, while the samples covered with nanowires were prepared by oxidation in a highly reactive oxygen plasma. The samples were exposed to neutral oxygen atoms from a remote oxygen plasma source. Depending on discharge parameters, the O-atom density in the postglow chamber, as measured with a catalytic probe, was between 5 x 10 20 and 8 x 10 21 m -3 . The O-atom density in the chamber without the samples was found rather independent of the probe position. The presence of the samples caused a decrease in the O-atom density. Depending on the distance from the samples, the O-atom density was decreased up to 5 times. The O-atom density also depended on the surface morphology of the samples. The strongest decrease in the O-atom density was observed with the samples covered with dense bundles of nanowires. The results clearly showed that niobium oxide nanowires exhibit excellent catalytic behaviour for neutral radicals and can be used as catalysts of exhaust radicals found in many applications

Facile Fabrication and Characterization of a PDMS-Derived Candle Soot Coated Stable Biocompatible Superhydrophobic and Superhemophobic Surface.

Science.gov (United States)

Iqbal, R; Majhy, B; Sen, A K

2017-09-13

We report a simple, inexpensive, rapid, and one-step method for the fabrication of a stable and biocompatible superhydrophobic and superhemophobic surface. The proposed surface comprises candle soot particles embedded in a mixture of PDMS+n-hexane serving as the base material. The mechanism responsible for the superhydrophobic behavior of the surface is explained, and the surface is characterized based on its morphology and elemental composition, wetting properties, mechanical and chemical stability, and biocompatibility. The effect of %n-hexane in PDMS, the thickness of the PDMS+n-hexane layer (in terms of spin coating speed) and sooting time on the wetting property of the surface is studied. The proposed surface exhibits nanoscale surface asperities (average roughness of 187 nm), chemical compositions of soot particles, very high water and blood repellency along with excellent mechanical and chemical stability and excellent biocompatibility against blood sample and biological cells. The water contact angle and roll-off angle is measured as 160° ± 1° and 2°, respectively, and the blood contact angle is found to be 154° ± 1°, which indicates that the surface is superhydrophobic and superhemophobic. The proposed superhydrophobic and superhemophobic surface offers significantly improved (>40%) cell viability as compared to glass and PDMS surfaces.

Expanding the isotopic toolbox: Applications of hydrogen and oxygen stable isotope ratios to food web studies

Directory of Open Access Journals (Sweden)

Hannah B Vander Zanden

2016-03-01

Full Text Available The measurement of stable carbon (δ13C and nitrogen (δ15N isotopes in tissues of organisms has formed the foundation of isotopic food web reconstructions, as these values directly reflect assimilated diet. In contrast, stable hydrogen (δ2H and oxygen (δ18O isotope measurements have typically been reserved for studies of migratory origin and paleoclimate reconstruction based on systematic relationships between organismal tissue and local environmental water. Recently, innovative applications using δ2H and, to a lesser extent, δ18O values have demonstrated potential for these elements to provide novel insights in modern food web studies. We explore the advantages and challenges associated with three applications of δ2H and δ18O values in food web studies. First, large δ2H differences between aquatic and terrestrial ecosystem end members can permit the quantification of energy inputs and nutrient fluxes between these two sources, with potential applications for determining allochthonous vs. autochthonous nutrient sources in freshwater systems and relative aquatic habitat utilization by terrestrial organisms. Next, some studies have identified a relationship between δ2H values and trophic position, which suggests that this marker may serve as a trophic indicator, in addition to the more commonly used δ15N values. Finally, coupled measurements of δ2H and δ18O values are increasing as a result of reduced analytical challenges to measure both simultaneously and may provide additional ecological information over single element measurements. In some organisms, the isotopic ratios of these two elements are tightly coupled, whereas the isotopic disequilibrium in other organisms may offer insight into the diet and physiology of individuals. Although a coherent framework for interpreting δ2H and δ18O data in the context of food web studies is emerging, many fundamental uncertainties remain. We highlight directions for targeted research that

Oxygen surface exchange kinetics measurement by simultaneous optical transmission relaxation and impedance spectroscopy: Sr(Ti,Fe)O3-x thin film case study.

Science.gov (United States)

Perry, Nicola H; Kim, Jae Jin; Tuller, Harry L

2018-01-01

We compare approaches to measure oxygen surface exchange kinetics, by simultaneous optical transmission relaxation (OTR) and AC-impedance spectroscopy (AC-IS), on the same mixed conducting SrTi 0.65 Fe 0.35 O 3-x film. Surface exchange coefficients were evaluated as a function of oxygen activity in the film, controlled by gas partial pressure and/or DC bias applied across the ionically conducting yttria-stabilized zirconia substrate. Changes in measured light transmission through the film over time (relaxations) resulted from optical absorption changes in the film corresponding to changes in its oxygen and oxidized Fe (~Fe 4+ ) concentrations; such relaxation profiles were successfully described by the equation for surface exchange-limited kinetics appropriate for the film geometry. The k chem values obtained by OTR were significantly lower than the AC-IS derived k chem values and k q values multiplied by the thermodynamic factor (bulk or thin film), suggesting a possible enhancement in k by the metal current collectors (Pt, Au). Long-term degradation in k chem and k q values obtained by AC-IS was also attributed to deterioration of the porous Pt current collector, while no significant degradation was observed in the optically derived k chem values. The results suggest that, while the current collector might influence measurements by AC-IS, the OTR method offers a continuous, in situ , and contact-free method to measure oxygen exchange kinetics at the native surfaces of thin films.

Oxygen surface exchange kinetics measurement by simultaneous optical transmission relaxation and impedance spectroscopy: Sr(Ti,Fe)O3-x thin film case study

Science.gov (United States)

Perry, Nicola H.; Kim, Jae Jin; Tuller, Harry L.

2018-01-01

Abstract We compare approaches to measure oxygen surface exchange kinetics, by simultaneous optical transmission relaxation (OTR) and AC-impedance spectroscopy (AC-IS), on the same mixed conducting SrTi0.65Fe0.35O3-x film. Surface exchange coefficients were evaluated as a function of oxygen activity in the film, controlled by gas partial pressure and/or DC bias applied across the ionically conducting yttria-stabilized zirconia substrate. Changes in measured light transmission through the film over time (relaxations) resulted from optical absorption changes in the film corresponding to changes in its oxygen and oxidized Fe (~Fe4+) concentrations; such relaxation profiles were successfully described by the equation for surface exchange-limited kinetics appropriate for the film geometry. The kchem values obtained by OTR were significantly lower than the AC-IS derived kchem values and kq values multiplied by the thermodynamic factor (bulk or thin film), suggesting a possible enhancement in k by the metal current collectors (Pt, Au). Long-term degradation in kchem and kq values obtained by AC-IS was also attributed to deterioration of the porous Pt current collector, while no significant degradation was observed in the optically derived kchem values. The results suggest that, while the current collector might influence measurements by AC-IS, the OTR method offers a continuous, in situ, and contact-free method to measure oxygen exchange kinetics at the native surfaces of thin films. PMID:29511391

Interplay between O2 and SnO2: oxygen ionosorption and spectroscopic evidence for adsorbed oxygen.

Science.gov (United States)

Gurlo, Alexander

2006-10-13

Tin dioxide is the most commonly used material in commercial gas sensors based on semiconducting metal oxides. Despite intensive efforts, the mechanism responsible for gas-sensing effects on SnO(2) is not fully understood. The key step is the understanding of the electronic response of SnO(2) in the presence of background oxygen. For a long time, oxygen interaction with SnO(2) has been treated within the framework of the "ionosorption theory". The adsorbed oxygen species have been regarded as free oxygen ions electrostatically stabilized on the surface (with no local chemical bond formation). A contradiction, however, arises when connecting this scenario to spectroscopic findings. Despite trying for a long time, there has not been any convincing spectroscopic evidence for "ionosorbed" oxygen species. Neither superoxide ions O(2)(-), nor charged atomic oxygen O,(-) nor peroxide ions O(2)(2-) have been observed on SnO(2) under the real working conditions of sensors. Moreover, several findings show that the superoxide ion does not undergo transformations into charged atomic oxygen at the surface, and represents a dead-end form of low-temperature oxygen adsorption on reduced metal oxide.

Experimental and numerical investigations of stable crack growth of axial surface flaws in a pressure vessel

International Nuclear Information System (INIS)

Brocks, W.; Krafka, H.; Mueller, W.; Wobst, K.

1988-01-01

In connection with the problem of the transferability of parameters obtained experimentally with the help of fracture-mechanical test specimens and used for the initiation and the stable propagation of cracks in cases of pulsating stress and of the elasto-plastic behaviour of construction components, a pressure vessel with an inside diameter of 1500 mm, a cylindrical length of 3000 mm and a wall thickness of 40 mm was hydraulically loaded with the help of internal pressure in the first stage, to attain an average crack growth of 1 mm at Δ a ≅, the loading taking place at about 21deg C. This stress-free annealed vessel exhibited an axial semielliptical vibration-induced surface crack about 181 mm long and 20 mm deep, as a test defect, in a welded circular blank made of the steel 20MnMoNi 55. The fractographic analysis of the first stable crack revealed that its growth rate of Δa was highest in the area of transition from the weak to the strong bend of the crack front (55deg m /σ v (average principal stress: σ m , Mises' reference stress: σ v v). A comparison of the experimental with the numerical results from the first stable crack shows that the local stable crack growth Δa cannot be calculated solely with reference to J, because Δa appears to depend essentially on the quotient σ m /σ v . (orig./MM) [de

Stable carbon, oxygen, and nitrogen, isotope analysis of plants from a South Asian tropical forest: Implications for primatology.

Science.gov (United States)

Roberts, Patrick; Blumenthal, Scott A; Dittus, Wolfgang; Wedage, Oshan; Lee-Thorp, Julia A

2017-06-01

Stable isotope analysis of primate tissues in tropical forest contexts is an increasingly popular means of obtaining information about niche distinctions among sympatric species, including preferences in feeding height, forest canopy density, plant parts, and trophism. However, issues of equifinality mean that feeding height, canopy density, as well as the plant parts and plant species consumed, may produce similar or confounding effects. With a few exceptions, researchers have so far relied largely on general principles and/or limited plant data from the study area as references for deducing the predominant drivers of primate isotope variation. Here, we explore variation in the stable carbon (δ 13 C), nitrogen (δ 15 N), and oxygen (δ 18 O) isotope ratios of 288 plant samples identified as important to the three primate species from the Polonnaruwa Nature Sanctuary, Sri Lanka, relative to plant part, season, and canopy height. Our results show that plant part and height have the greatest effect on the δ 13 C and δ 18 O measurements of plants of immediate relevance to the primates, Macaca sinica, Semnopithecus priam thersites, and Trachypithecus vetulus, living in this monsoonal tropical forest. We find no influence of plant part, height or season on the δ 15 N of measured plants. While the plant part effect is particularly pronounced in δ 13 C between fruits and leaves, differential feeding height, and plant taxonomy influence plant δ 13 C and δ 18 O differences in addition to plant organ. Given that species composition in different regions and forest types will differ, the results urge caution in extrapolating general isotopic trends without substantial local baselines studies. © 2017 Wiley Periodicals, Inc.

Influence of Power Modulation on Ozone Production Using an AC Surface Dielectric Barrier Discharge in Oxygen

Czech Academy of Sciences Publication Activity Database

Šimek, Milan; Pekárek, S.; Prukner, Václav

2010-01-01

Roč. 30, č. 5 (2010), s. 607-617 ISSN 0272-4324 R&D Projects: GA ČR(CZ) GA202/09/0176 Institutional research plan: CEZ:AV0Z20430508 Keywords : Ozone * Surface DBD * Oxygen * Production efficiency Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 1.798, year: 2010 http://www.springerlink.com/content/28539775w5243513/

Surface preparation of gold nanostructures on glass by ultraviolet ozone and oxygen plasma for thermal atomic layer deposition of Al{sub 2}O{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Lancaster, Cady A., E-mail: lancaster@chem.utah.edu; Shumaker-Parry, Jennifer S., E-mail: shumaker-parry@chem.utah.edu

2016-08-01

Thin film deposition to create robust plasmonic nanomaterials is a growing area of research. Plasmonic nanomaterials have tunable optical properties and can be used as substrates for surface-enhanced spectroscopies. Due to the surface sensitivity and the dependence of the near-field behavior on structural details, degradation from cleaning or spectroscopic interrogation causes plasmonic nanostructures to lose distinctive localized surface plasmon resonances or exhibit diminished optical near-field enhancements over time. To decrease degradation, conformal thin films of alumina are deposited on nanostructured substrates using atomic layer deposition. While film growth on homogenous surfaces has been studied extensively, atomic layer deposition-based film growth on heterogeneous nanostructured surfaces is not well characterized. In this report, we have evaluated the impact of oxygen plasma and ultraviolet ozone pre-treatments on Au nanoparticle substrates for thin film growth by monitoring changes in plasmonic response and nanostructure morphology. We have found that ultraviolet ozone is more effective than oxygen plasma for cleaning gold nanostructured surfaces, which is in contrast to bulk films of the same material. Our results show that oxygen plasma treatment negatively impacts the nanostructure and alumina coating based on both scanning electron microscopy analysis of morphology and changes in the plasmonic response. - Highlights: • Plasmonic response indicates oxygen plasma damages Au structures and Al{sub 2}O{sub 3} films. • Ultraviolet ozone (UVO) re-activates aged Al{sub 2}O{sub 3}-coated Au nanostructures. • UVO treatments do not damage Au or Al{sub 2}O{sub 3}-coated nanostructures.

Surface erosion and tritium inventory analysis for CIT [Compact Ignition Tokamak

International Nuclear Information System (INIS)

Brooks, J.N.; Dylla, H.F.

1990-09-01

The expected buildup of co-deposited tritium on the CIT carbon divertor and first wall surfaces and operational methods of minimizing the inventory have been examined. The analysis uses impurity transport computer codes, and associated plasma and tritium retention models, to compute the thickness of redeposited sputtered carbon and the resulting co-deposited tritium inventory on the divertor plates and first wall. Predicted erosion/growth rates are dominated by the effect of gaps between carbon tiles. The overall results appear favorable, showing stable operation (finite self-sputtering) and acceptably low (∼25 Ci/pulse) co-deposited tritium rates, at high surface temperature (1700 degree C) design conditions. These results, however, are highly speculative due to serious model inadequacies at the high sputtering rates predicted. If stable operation is obtainable, the prospects appear good for adequate tritium inventory control via helium-oxygen glow discharge cleaning. 25 refs

Pt-based Thin Films as Efficient and Stable Catalysts for Oxygen Electroreduction

DEFF Research Database (Denmark)

Zamburlini, Eleonora

at the cathode of Polymer Electrolyte Membrane Fuel Cells (PEMFCs). Herein the fabrication method, which consists of co-sputtering of thin films, is presented in detail, explaining the challenges one must face in order to fabricate oxygen-free Pt-lanthanides and Pt-early transition metals alloys......This thesis presents the fabrication and characterization of Pt-based thin film catalysts for Oxygen Reduction Reaction (ORR). Gadolinium and Yttrium have been used as alloying materials, in preparation for the replacement of the traditional but economically disadvantageous pure Pt catalysts......, and the proposed solutions. The characterization of the catalysts focused mainly on the electrochemical testing using a Rotating Ring Disk Electrode (RRDE) setup, and includes X-ray Diffraction (XRD), X-ray Photoemission Spectroscopy (XPS), Angle-Resolved X-ray Photoelectron Spectroscopy (AR-XPS), Scanning...

Tailoring properties of reduced graphene oxide by oxygen plasma treatment

Science.gov (United States)

Kondratowicz, Izabela; Nadolska, Małgorzata; Şahin, Samet; Łapiński, Marcin; Prześniak-Welenc, Marta; Sawczak, Mirosław; Yu, Eileen H.; Sadowski, Wojciech; Żelechowska, Kamila

2018-05-01

We report an easily controllable, eco-friendly method for tailoring the properties of reduced graphene oxide (rGO) by means of oxygen plasma. The effect of oxygen plasma treatment time (1, 5 and 10 min) on the surface properties of rGO was evaluated. Physicochemical characterization using microscopic, spectroscopic and thermal techniques was performed. The results revealed that different oxygen-containing groups (e.g. carboxyl, hydroxyl) were introduced on the rGO surface enhancing its wettability. Furthermore, upon longer treatment time, other functionalities were created (e.g. quinones, lactones). Moreover, external surface of rGO was partially etched resulting in an increase of the material surface area and porosity. Finally, the oxygen plasma-treated rGO electrodes with bilirubin oxidase were tested for oxygen reduction reaction. The study showed that rGO treated for 10 min exhibited twofold higher current density than untreated rGO. The oxygen plasma treatment may improve the enzyme adsorption on rGO electrodes by introduction of oxygen moieties and increasing the porosity.

XPS studies of SiO2 surface layers formed by oxygen ion implantation into silicon

International Nuclear Information System (INIS)

Schulze, D.; Finster, J.

1983-01-01

SiO 2 surface layers of 160 nm thickness formed by 16 O + ion implantation into silicon are examined by X-ray photoelectron spectroscopy measurements into the depth after a step-by-step chemical etching. The chemical nature and the thickness of the transition layer were determined. The results of the XPS measurements show that the outer surface and the bulk of the layers formed by oxygen implantation and subsequent high temperature annealing consist of SiO 2 . There is no evidence for Si or SiO/sub x/ (0 2 and Si is similar to that of thin grown oxide layers. Only its thickness is somewhat larger than in thermal oxide

Determination of diffusion coefficients of oxygen atoms in ZrO2 using first-principles calculations

International Nuclear Information System (INIS)

Segi, Takashi; Okuda, Takanari

2014-01-01

Density functional theory and nudged elastic band calculations were performed in order to determine the diffusion coefficient for oxygen from monoclinic ZrO 2 . The calculated values for monoclinic ZrO 2 at 1000 K and 1500 K were 5.88 × 10 -16 cm 2 s -1 and 2.91 × 10 -11 cm 2 s -1 , respectively, and agreed with previously determined experimental values. In addition, the results of the nudged elastic band calculations suggest that interstitial oxygen sites exist between stable oxygen sites, and if oxygen atoms occupy these sites, stable structures with values for the lattice angle β of greater than 80.53° may be obtained. (author)

Development of O-18 stable isotope separation technology using membrane

Energy Technology Data Exchange (ETDEWEB)

Kim, Jae Woo; Kim, Taek Soo; Choi, Hwa Rim; Park, Sung Hee; Lee, Ki Tae; Chang, Dae Shik

2006-06-15

The ultimate goal of this investigation is to develop the separation technology for O-18 oxygen stable isotope used in a cyclotron as a target for production of radioisotope F-18. F-18 is a base material for synthesis of [F-18]FDG radio-pharmaceutical, which is one of the most important tumor diagnostic agent used in PET (Positron Emission Tomography). More specifically, this investigation is focused on three categories as follow, 1) development of the membrane distillation isotope separation process to re-enrich O-18 stable isotope whose isotopic concentration is reduced after used in a cyclotron, 2) development of organic impurity purification technology to remove acetone, methanol, ethanol, and acetonitrile contained in a used cyclotron O-18 enriched target water, and 3) development of a laser absorption spectroscopic system for analyzing oxygen isotopic concentration in water.

TGP, an extremely stable, non-aggregating fluorescent protein created by structure-guided surface engineering

Science.gov (United States)

Close, Devin W.; Don Paul, Craig; Langan, Patricia S.; Wilce, Matthew C.J.; Traore, Daouda A.K.; Halfmann, Randal; Rocha, Reginaldo C.; Waldo, Geoffery S.; Payne, Riley J.; Rucker, Joseph B.; Prescott, Mark; Bradbury, Andrew R.M.

2014-01-01

In this paper we describe the engineering and X-ray crystal structure of Thermal Green Protein (TGP), an extremely stable, highly soluble, non-aggregating green fluorescent protein. TGP is a soluble variant of the fluorescent protein eCGP123, which despite being highly stable, has proven to be aggregation-prone. The X-ray crystal structure of eCGP123, also determined within the context of this paper, was used to carry out rational surface engineering to improve its solubility, leading to TGP. The approach involved simultaneously eliminating crystal lattice contacts while increasing the overall negative charge of the protein. Despite intentional disruption of lattice contacts and introduction of high entropy glutamate side chains, TGP crystallized readily in a number of different conditions and the X-ray crystal structure of TGP was determined to 1.9 Å resolution. The structural reasons for the enhanced stability of TGP and eCGP123 are discussed. We demonstrate the utility of using TGP as a fusion partner in various assays and significantly, in amyloid assays in which the standard fluorescent protein, EGFP, is undesirable because of aberrant oligomerization. PMID:25287913

Ab-initio modeling of oxygen on the surface passivation of 3C-SiC nanostructures

International Nuclear Information System (INIS)

Cuevas, J.L.; Trejo, A.; Calvino, M.; Carvajal, E.; Cruz-Irisson, M.

2012-01-01

In this work the effect of OH on the electronic states of H-passivated 3C-SiC nanostructures, was studied by means of Density Functional Theory. We compare the electronic band structure for a [1 1 1]-oriented nanowire with total H, OH passivation and a combination of both. Also the electronic states of a porous silicon carbide case (PSiC) a C-rich pore surface in which the dangling bonds on the surface are saturated with H and OH was studied. The calculations show that the surface replacement of H with OH radicals is always energetically favorable and more stable. In all cases the OH passivation produced a similar effect than the H passivation, with electronic band gap of lower energy value than the H-terminated phase. When the OH groups are attached to C atoms, the band gap feature is changed from direct to indirect. The results indicate the possibility of band gap engineering on SiC nanostructures through the surface passivation species.

Decommissioning Combustible Waste Treatment using Oxygen-Enriched Incinerator

Energy Technology Data Exchange (ETDEWEB)

Min, Byungyoun; Lee, Yoonji; Yun, Gyoungsu; Lee, Kiwon; Moon, Jeikwon [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2014-05-15

The aim of the paper is current status of treatment for the decommissioning combustible waste in KAERI and for the purpose of the volume reduction and clearance for decommissioning combustible wastes generated by the decommissioning projects. The incineration technology has been selected for the treatment of combustible wastes. About 34 tons of decommissioning combustible waste has been treated using Oxygen Enriched incineration. Temperature, pressure of major components, stack gas concentration, i. e., SOx, NOx, CO, CO{sub 2} and HCl, and the residual oxygen were measured. Measured major parameters during normal operation were sustained on a stable status within a criteria operation condition. Oxygen enriched air, 22vol. % (dry basis) was used for stable incineration. The volume reduction ratio has achieved about 1/117. The incineration with decommissioning radioactive combustible waste is possible with moderate oxygen enrichment of 22 vol.% (dry basis) into the supply air. The incineration facility operated quite smoothly through the analysis major critical parameters of off-gas. The pressure, off-gas flow and temperature of major components remained constant within the range specified. The measures gases and particulate materials in stack were considerably below the regulatory limits. The achieved volume reduction ratio through incineration is about 1/117.

Multiple stable isotope fronts during non-isothermal fluid flow

Science.gov (United States)

Fekete, Szandra; Weis, Philipp; Scott, Samuel; Driesner, Thomas

2018-02-01

Stable isotope signatures of oxygen, hydrogen and other elements in minerals from hydrothermal veins and metasomatized host rocks are widely used to investigate fluid sources and paths. Previous theoretical studies mostly focused on analyzing stable isotope fronts developing during single-phase, isothermal fluid flow. In this study, numerical simulations were performed to assess how temperature changes, transport phenomena, kinetic vs. equilibrium isotope exchange, and isotopic source signals determine mineral oxygen isotopic compositions during fluid-rock interaction. The simulations focus on one-dimensional scenarios, with non-isothermal single- and two-phase fluid flow, and include the effects of quartz precipitation and dissolution. If isotope exchange between fluid and mineral is fast, a previously unrecognized, significant enrichment in heavy oxygen isotopes of fluids and minerals occurs at the thermal front. The maximum enrichment depends on the initial isotopic composition of fluid and mineral, the fluid-rock ratio and the maximum change in temperature, but is independent of the isotopic composition of the incoming fluid. This thermally induced isotope front propagates faster than the signal related to the initial isotopic composition of the incoming fluid, which forms a trailing front behind the zone of transient heavy oxygen isotope enrichment. Temperature-dependent kinetic rates of isotope exchange between fluid and rock strongly influence the degree of enrichment at the thermal front. In systems where initial isotope values of fluids and rocks are far from equilibrium and isotope fractionation is controlled by kinetics, the temperature increase accelerates the approach of the fluid to equilibrium conditions with the host rock. Consequently, the increase at the thermal front can be less dominant and can even generate fluid values below the initial isotopic composition of the input fluid. As kinetics limit the degree of isotope exchange, a third front may

Analysis of oxygen and hydrogen adsorption on Nb(100) surface by scanning tunneling microscopy

International Nuclear Information System (INIS)

An, Bai; Wen, Mao; Fukuyama, Seiji; Yokogawa, Kiyoshi; Ichimura, Shingo; Yoshimura, Masamichi

2006-01-01

The surface structure of Nb(100) under the condition of cleaning, oxidation and hydrogen adsorption is observed by STM (scanning tunneling microscopy). The results obtained are followings; (1) (3 x 1)-O→(4 x 1)-O→c(2 x 2)-O→clean(1 x 1)structure was observed by atom level, and these atomic models of structures and STM images were verified by the first-principles calculations, (2) when the clean(1 x 1) structure exposed to hydrogen, dissociative adsorption of hydrogen was observed and Nb hydride cluster formed on the surface at room temperature. It was heated at about 450 - 670 K in UHV, the cluster decomposed into hydrogen and (1 x 1) structure with linear defect was formed. The c(2 x 2)-O structure by oxygen adsorption transformed into (1 x 1)-H structure with OH and Nb hydride cluster under hydrogen gas at room temperature. When it was heated in UHV at 640 K, OH desorbed from the surface and (1 x 1) structure with linear defect was generated. The surface of (3 x 1)-O structure was not changed by hydrogen. (S.Y.)

Influence of oxygen partial pressure on defect concentrations and on oxygen diffusion in UO2+x

International Nuclear Information System (INIS)

Pizzi, Elisabetta

2013-01-01

The hyper-stoichiometric uranium dioxide (UO 2+x ) is stable over a wide range of temperature and compositions. Such variations of composition and the eventual presence of doping elements or impurities lead to a variation of anionic and electronic defect concentrations. Moreover, many properties of this material are affected by its composition modifications, in particular their atomic transport properties. Firstly we developed a point defect model to evaluate the dependence of the electronic and oxygen defect concentrations upon temperature, equilibrium oxygen partial pressure and impurity content. The physical constants of the model, in particular the equilibrium constants of the defect formation reactions were determined from deviation from stoichiometry and electrical conductivity measurements of literature. This work enabled us to interpret our measures of conductivity, oxygen chemical and self- diffusion coefficients. From a quantitative standpoint, the analysis of our experimental results allows to evaluate the oxygen interstitial diffusion coefficient but also its formation energy. Moreover, an estimate of oxygen di-interstitial formation energy is also provided. Presence of oxygen clusters leads oxygen self- and chemical diffusion to decrease. X-ray Absorption Spectroscopy characterization shows the presence of the same defect in the entire deviation from stoichiometry studied, confirming the approach used to develop the model. (author) [fr

Identifying active surface phases for metal oxide electrocatalysts: a study of manganese oxide bi-functional catalysts for oxygen reduction and water oxidation catalysis

DEFF Research Database (Denmark)

Su, Hai-Yan; Gorlin, Yelena; Man, Isabela Costinela

2012-01-01

Progress in the field of electrocatalysis is often hampered by the difficulty in identifying the active site on an electrode surface. Herein we combine theoretical analysis and electrochemical methods to identify the active surfaces in a manganese oxide bi-functional catalyst for the oxygen...... reduction reaction (ORR) and the oxygen evolution reaction (OER). First, we electrochemically characterize the nanostructured α-Mn2O3 and find that it undergoes oxidation in two potential regions: initially, between 0.5 V and 0.8 V, a potential region relevant to the ORR and, subsequently, between 0.8 V...

Formation and Migration of Oxygen Vacancies in SrCoO3 and their effect on Oxygen Evolution Reactions

KAUST Repository

Tahini, Hassan A.; Tan, Xin; Schwingenschlö gl, Udo; Smith, Sean C.

2016-01-01

Perovskite SrCoO3 is a potentially useful material for promoting the electrocatalytic oxygen evolution reaction, with high activities predicted theoretically and observed experimentally for closely related doped perovskite materials. However, complete stoichiometric oxidation is very difficult to realize experimentally – in almost all cases there are significant fractions of oxygen vacancies present. Here, using first principles calculations we study oxygen vacancies in perovskite SrCoO3 from thermodynamic, electronic and kinetic points of view. We find that an oxygen vacancy donates two electrons to neighboring Co sites in the form of localized charge. The formation energy of a single vacancy is very low and estimated to be 1.26 eV in the dilute limit. We find that a vacancy is quite mobile with a migration energy of ~0.5 eV. Moreover, we predict that oxygen vacancies exhibit a tendency towards clustering which is in accordance with the material’s ability to form a variety of oxygen-deficient structures. These vacancies have a profound effect on the material’s ability to facilitate OER, increasing the overpotential from ~0.3 V for the perfect material to ~0.7 for defective surfaces. A moderate compressive biaxial strain (2%) is predicted here to increase the surface oxygen vacancy formation energy by ca. 30%, thus reducing the concentration of surface vacancies and thereby preserving the OER activity of the material.

Formation and Migration of Oxygen Vacancies in SrCoO3 and their effect on Oxygen Evolution Reactions

KAUST Repository

Tahini, Hassan A.

2016-07-18

Perovskite SrCoO3 is a potentially useful material for promoting the electrocatalytic oxygen evolution reaction, with high activities predicted theoretically and observed experimentally for closely related doped perovskite materials. However, complete stoichiometric oxidation is very difficult to realize experimentally – in almost all cases there are significant fractions of oxygen vacancies present. Here, using first principles calculations we study oxygen vacancies in perovskite SrCoO3 from thermodynamic, electronic and kinetic points of view. We find that an oxygen vacancy donates two electrons to neighboring Co sites in the form of localized charge. The formation energy of a single vacancy is very low and estimated to be 1.26 eV in the dilute limit. We find that a vacancy is quite mobile with a migration energy of ~0.5 eV. Moreover, we predict that oxygen vacancies exhibit a tendency towards clustering which is in accordance with the material’s ability to form a variety of oxygen-deficient structures. These vacancies have a profound effect on the material’s ability to facilitate OER, increasing the overpotential from ~0.3 V for the perfect material to ~0.7 for defective surfaces. A moderate compressive biaxial strain (2%) is predicted here to increase the surface oxygen vacancy formation energy by ca. 30%, thus reducing the concentration of surface vacancies and thereby preserving the OER activity of the material.

Stable water isotope simulation by current land-surface schemes:Results of IPILPS phase 1

Energy Technology Data Exchange (ETDEWEB)

Henderson-Sellers, A.; Fischer, M.; Aleinov, I.; McGuffie, K.; Riley, W.J.; Schmidt, G.A.; Sturm, K.; Yoshimura, K.; Irannejad, P.

2005-10-31

Phase 1 of isotopes in the Project for Intercomparison of Land-surface Parameterization Schemes (iPILPS) compares the simulation of two stable water isotopologues ({sup 1}H{sub 2} {sup 18}O and {sup 1}H{sup 2}H{sup 16}O) at the land-atmosphere interface. The simulations are off-line, with forcing from an isotopically enabled regional model for three locations selected to offer contrasting climates and ecotypes: an evergreen tropical forest, a sclerophyll eucalypt forest and a mixed deciduous wood. Here we report on the experimental framework, the quality control undertaken on the simulation results and the method of intercomparisons employed. The small number of available isotopically-enabled land-surface schemes (ILSSs) limits the drawing of strong conclusions but, despite this, there is shown to be benefit in undertaking this type of isotopic intercomparison. Although validation of isotopic simulations at the land surface must await more, and much more complete, observational campaigns, we find that the empirically-based Craig-Gordon parameterization (of isotopic fractionation during evaporation) gives adequately realistic isotopic simulations when incorporated in a wide range of land-surface codes. By introducing two new tools for understanding isotopic variability from the land surface, the Isotope Transfer Function and the iPILPS plot, we show that different hydrological parameterizations cause very different isotopic responses. We show that ILSS-simulated isotopic equilibrium is independent of the total water and energy budget (with respect to both equilibration time and state), but interestingly the partitioning of available energy and water is a function of the models' complexity.

Stable, metastable and unstable solutions of a spin-1 Ising system based on the free energy surfaces

Science.gov (United States)

Keskİin, Mustafa; Özgan, Şükrü

1990-04-01

Stable, metastable and unstable solutions of a spin-1 Ising model with bilinear and biquadratic interactions are found by using the free energy surfaces. The free energy expression is obtained in the lowest approximation of the cluster variation method. All these solutions are shown in the two-dimensional phase space, especially the unstable solutions which in some cases are difficult to illustrate in the two-dimensional phase space, found by Keskin et al. recently.

Mechanistic studies of mercury adsorption and oxidation by oxygen over spinel-type MnFe{sub 2}O{sub 4}

Energy Technology Data Exchange (ETDEWEB)

Yang, Yingju [State Key Laboratory of Coal Combustion, School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China); Liu, Jing, E-mail: liujing27@mail.hust.edu.cn [State Key Laboratory of Coal Combustion, School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China); Shenzhen Institute of Huazhong University of Science and Technology, Shenzhen 518000 (China); Zhang, Bingkai; Liu, Feng [State Key Laboratory of Coal Combustion, School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China)

2017-01-05

Highlights: • Hg adsorption and oxidation mechanisms on MnFe{sub 2}O{sub 4} were studied using DFT method. • Hg{sup 0} adsorption on Mn-terminated MnFe{sub 2}O{sub 4} (100) surface is a chemisorption process. • HgO shows high chemical reactivity for its adsorption on MnFe{sub 2}O{sub 4} surface. • The reaction between adsorbed Hg and surface oxygen is the rate-determining step. - Abstract: MnFe{sub 2}O{sub 4} has been regarded as a very promising sorbent for mercury emission control in coal-fired power plants because of its high adsorption capacity, magnetic, recyclable and regenerable properties. First-principle calculations based on density functional theory (DFT) were used to elucidate the mercury adsorption and oxidation mechanisms on MnFe{sub 2}O{sub 4} surface. DFT calculations show that Mn-terminated MnFe{sub 2}O{sub 4} (1 0 0) surface is much more stable than Fe-terminated surface. Hg{sup 0} is physically adsorbed on Fe-terminated MnFe{sub 2}O{sub 4} (1 0 0) surface. Hg{sup 0} adsorption on Mn-terminated MnFe{sub 2}O{sub 4} (1 0 0) surface is a chemisorption process. The partial density of states (PDOS) analysis indicates that Hg atom interacts strongly with surface Mn atoms through the orbital hybridization. HgO is adsorbed on the MnFe{sub 2}O{sub 4} surface in a chemical adsorption manner. The small HOMO–LUMO energy gap implies that HgO molecular shows high chemical reactivity for HgO adsorption on MnFe{sub 2}O{sub 4} surface. The energy barriers of Hg{sup 0} oxidation by oxygen on Fe- and Mn-terminated MnFe{sub 2}O{sub 4} surfaces are 206.37 and 76.07 kJ/mol, respectively. Mn-terminated surface is much more favorable for Hg{sup 0} oxidation than Fe-terminated surface. In the whole Hg{sup 0} oxidation process, the reaction between adsorbed mercury and surface oxygen is the rate-determining step.

Effect of oxygen on the surface morphology of CuGaS{sub 2} thin films

Energy Technology Data Exchange (ETDEWEB)

Smaili, F., E-mail: fethi.smaili@voila.fr [Laboratoire de Photovoltaique et Materiaux Semi-conducteurs -ENIT BP 37, Le belvedere 1002-Tunis (Tunisia); Kanzari, M. [Laboratoire de Photovoltaique et Materiaux Semi-conducteurs -ENIT BP 37, Le belvedere 1002-Tunis (Tunisia)

2009-08-01

Since the effect of oxygen is very significant during the heat treatment of the thin films, we study the effect of this during the annealing of CuGaS{sub 2} thin films by two different types. In this study, CuGaS{sub 2} thin films were deposited by vacuum thermal evaporation of CuGaS{sub 2} powder on heated glass substrates at 200 deg. C submitted to a thermal gradient. The films are annealed in air and under nitrogen atmosphere at 400 deg. C for 2 h. In order to improve our understanding of the influence of oxygen during two annealing types on device performance, we have investigated our CuGaS{sub 2} material by X-ray diffraction, scanning electron microscopy (SEM), atomic force microscopy (AFM), energy dispersive X-ray analysis (EDX) and spectrophotometry. A correlation was established between the surface roughness, growth morphology and optical properties, of the annealed CuGaS{sub 2} thin films. It was found that annealing of CuGaS{sub 2} film in nitrogen atmosphere leads to a decrease of the mean grain size and to an evolution of a (112) preferred film orientation. Annealing in air results in the growth of oxide phases such as CuO and modifies the films structure and their surface morphology.

Variations of dissolved oxygen in Mandovi and Zuari estuaries

Digital Repository Service at National Institute of Oceanography (India)

DeSousa, S.N.; SenGupta, R.

During non-monsoon months the estuaries were well mixed showing uniform oxygen concentrations from surface to bottom. However, during monsoon months both the estuaries showed stratified conditions with surface water showing high oxygen concentration...

Oxygen-transfer performance of a newly designed, very low-volume membrane oxygenator.

Science.gov (United States)

Burn, Felice; Ciocan, Sorin; Carmona, Natalia Mendez; Berner, Marion; Sourdon, Joevin; Carrel, Thierry P; Tevaearai Stahel, Hendrik T; Longnus, Sarah L

2015-09-01

Oxygenation of blood and other physiological solutions are routinely required in fundamental research for both in vitro and in vivo experimentation. However, very few oxygenators with suitable priming volumes (parallel-oriented microporous polypropylene hollow fibres, placed inside a hollow shell with a lateral-luer outlet, and sealed at both extremities. With this design, perfusate is delivered via the core-tube to the centre of the mini-oxygenator, and exits via the luer port. A series of mini-oxygenators were constructed and tested in an in vitro perfusion circuit by monitoring oxygen transfer using modified Krebs-Henseleit buffer or whole porcine blood. Effects of perfusion pressure and temperature over flows of 5-60 ml × min(-1) were assessed. Twelve mini-oxygenators with a mean priming volume of 1.5 ± 0.3 ml were evaluated. With buffer, oxygen transfer reached a maximum of 14.8 ± 1.0 ml O2 × l(-1) (pO2: 450 ± 32 mmHg) at perfusate flow rates of 5 ml × min(-1) and decreased with an increase in perfusate flow to 7.8 ± 0.7 ml ml O2 × l(-1) (pO2: 219 ± 24 mmHg) at 60 ml × min(-1). Similarly, with blood perfusate, oxygen transfer also decreased as perfusate flow increased, ranging from 33 ± 5 ml O2 × l(-1) at 5 ml × min(-1) to 11 ± 2 ml O2 × l(-1) at 60 ml × min(-1). Furthermore, oxygen transfer capacity remained stable with blood perfusion over a period of at least 2 h. We have developed a new miniaturized membrane oxygenator with an ultra-low priming volume (circuits, such as small animal extracorporeal circulation and ex vivo organ perfusion. © The Author 2015. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.

Evaluation of Primary Production in the Lower Amazon River Based on a Dissolved Oxygen Stable Isotopic Mass Balance

Energy Technology Data Exchange (ETDEWEB)

Gagne-Maynard, William C.; Ward, Nicholas D.; Keil, Richard G.; Sawakuchi, Henrique O.; Da Cunha, Alan C.; Neu, Vania; Brito, Daimio C.; Da Silva Less, Diani F.; Diniz, Joel E. M.; De Matos Valerio, Aline; Kampel, Milton; Krusche, Alex V.; Richey, Jeffrey E.

2017-02-07

The Amazon River outgasses nearly an equivalent amount of CO₂ as the rainforest sequesters on an annual basis due to microbial decomposition of terrigenous and aquatic organic matter. Most research performed in the Amazon has been focused on unraveling the mechanisms driving CO₂ production since the recognition of a persistent state of CO₂ supersaturation. However, although the river system is clearly net heterotrophic, the interplay between primary production and respiration is an essential aspect to understanding the overall metabolism of the ecosystem and potential transfer of energy up trophic levels. For example, an efficient ecosystem is capable of both decomposing high amounts of organic matter at lower trophic levels, driving CO₂ emissions, and accumulating energy/biomass in higher trophic levels, stimulating fisheries production. Early studies found minimal evidence for primary production in the Amazon River mainstem and it has since been assumed that photosynthesis is strongly limited by low light penetration attributed to the high sediment load. Here, we test this assumption by measuring the stable isotopic composition of O₂ (δ¹⁸O-O₂) and O₂ saturation levels in the lower Amazon River from Óbidos to the river mouth and its major tributaries, the Xingu and Tapajós rivers, during high and low water periods. An oxygen mass balance model was developed to estimate the input of photosynthetic oxygen in the discrete reach from Óbidos to Almeirim, midway to the river mouth. Based on the oxygen mass balance we estimate that primary production occurred at a rate of 0.39 ± 0.24 g O m³ d^-1 at high water and 1.02 ± 0.55 g O m³ d^-1 at low water. This translates to 41 ± 24% of the rate of O₂ drawdown via respiration during high water and 67 ± 33% during low water. These primary production rates are 2-7 times higher than

Impact of the structural anisotropy of La2NiO4+δ on on high temperature surface modifications and diffusion of oxygen

International Nuclear Information System (INIS)

Gauquelin, Nicolas

2010-01-01

La 2 NiO 4+δ was first studied due to its structural similarities with the High Temperature superconductor La 2 NiO 4+δ and more recently due to its promise as a cathode material in Solid Oxide Fuel Cells as well as an oxygen exchange membrane. It crystallizes in the K 2 NiF 4 layered structure and accommodates highly mobile oxygen at its ground state and is therefore overstoichiometric. During this thesis, pure single crystals of La 2 NiO 4+δ were successfully grown using the floating-zone method, subsequently characterized using neutron and Laue Backscattering diffraction and oriented pieces of single crystal with [100] and [001] orientation were prepared. The surface morphology behavior after long term exposure to high temperature in different atmospheres was observed using microscopy techniques because stability at high temperature is required for application purposes and it was discovered a structural change to nickel-rich phases at T>1173 K. The sensibility of the oxygen non-stoichiometry to cooling was studied and subsequently a new 18 O- 18 O exchange apparatus allowing quenching of the samples using liquid nitrogen was developed. Oxygen selfdiffusion was studied using SIMS in the range 673-873K in both [100] and [001] crystallographic directions. The effect of the disorientation of the sample surface on the determination of the slowest diffusion coefficient was discovered and revealed the very strong anisotropy (>5 orders of magnitude difference) between the different diffusion paths. Finally using HTXRD and oxygen release experiments, it was shown that oxygen diffusion from interstitial oxygen starts to be relevant at 550-600 K and a change of behavior is observed around 700 K, corresponding to a possible change in the diffusion mechanism from interstitial to interstitialcy.

Unifying the 2e^– and 4e^– Reduction of Oxygen on Metal Surfaces

DEFF Research Database (Denmark)

Viswanathan, Venkatasubramanian; Hansen, Heine Anton; Rossmeisl, Jan

2012-01-01

Understanding trends in selectivity is of paramount importance for multi-electron electrochemical reactions. The goal of this work is to address the issue of 2e– versus 4e– reduction of oxygen on metal surfaces. Using a detailed thermodynamic analysis based on density functional theory calculatio...

The vanadium/oxygen system in the analysis of sodium for oxygen

International Nuclear Information System (INIS)

Walker, J.A.J.; Price, W.B.

1981-05-01

An investigation of the V-O-Na system at 1023 K is described for oxygen in sodium contents of 5 to 25 ppm. Electron spectroscopy combined with depth profiling is used to determine the vanadium/oxygen ratios inwards from the surface of vanadium foil and these ratios are compared with theoretical predictions. The validity of the vanadium wire technique as an analytical method is examined and a model for the vanadium oxidation is suggested. (author)

Promoted Fixation of Molecular Nitrogen with Surface Oxygen Vacancies on Plasmon-Enhanced TiO2 Photoelectrodes.

Science.gov (United States)

Li, Chengcheng; Wang, Tuo; Zhao, Zhi-Jian; Yang, Weimin; Li, Jian-Feng; Li, Ang; Yang, Zhilin; Ozin, Geoffrey A; Gong, Jinlong

2018-02-19

A hundred years on, the energy-intensive Haber-Bosch process continues to turn the N 2 in air into fertilizer, nourishing billions of people while causing pollution and greenhouse gas emissions. The urgency of mitigating climate change motivates society to progress toward a more sustainable method for fixing N 2 that is based on clean energy. Surface oxygen vacancies (surface O vac ) hold great potential for N 2 adsorption and activation, but introducing O vac on the very surface without affecting bulk properties remains a great challenge. Fine tuning of the surface O vac by atomic layer deposition is described, forming a thin amorphous TiO 2 layer on plasmon-enhanced rutile TiO 2 /Au nanorods. Surface O vac in the outer amorphous TiO 2 thin layer promote the adsorption and activation of N 2 , which facilitates N 2 reduction to ammonia by excited electrons from ultraviolet-light-driven TiO 2 and visible-light-driven Au surface plasmons. The findings offer a new approach to N 2 photofixation under ambient conditions (that is, room temperature and atmospheric pressure). © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Decontamination of chemical-warfare agent simulants by polymer surfaces doped with the singlet oxygen generator zinc octaphenoxyphthalocyanine.

Science.gov (United States)

Gephart, Raymond T; Coneski, Peter N; Wynne, James H

2013-10-23

Using reactive singlet oxygen (1O2), the oxidation of chemical-warfare agent (CWA) simulants has been demonstrated. The zinc octaphenoxyphthalocyanine (ZnOPPc) complex was demonstrated to be an efficient photosensitizer for converting molecular oxygen (O2) to 1O2 using broad-spectrum light (450-800 nm) from a 250 W halogen lamp. This photosensitization produces 1O2 in solution as well as within polymer matrices. The oxidation of 1-naphthol to naphthoquinone was used to monitor the rate of 1O2 generation in the commercially available polymer film Hydrothane that incorporates ZnOPPc. Using electrospinning, nanofibers of ZnOPPc in Hydrothane and polycarbonate were formed and analyzed for their ability to oxidize demeton-S, a CWA simulant, on the surface of the polymers and were found to have similar reactivity as their corresponding films. The Hydrothane films were then used to oxidize CWA simulants malathion, 2-chloroethyl phenyl sulfide (CEPS), and 2-chloroethyl ethyl sulfide (CEES). Through this oxidation process, the CWA simulants are converted into less toxic compounds, thus decontaminating the surface using only O2 from the air and light.

Oxygen dynamics and transport in the Mediterranean sponge Aplysina aerophoba

DEFF Research Database (Denmark)

Hoffmann, F.; Røy, Hans; Bayer, K.

2008-01-01

The Mediterranean sponge Aplysina aerophoba kept in aquaria or cultivation tanks can stop pumping for several hours or even days. To investigate changes in the chemical microenvironments, we measured oxygen profiles over the surface and into the tissue of pumping and non-pumping A. aerophoba...... specimens with Clark-type oxygen microelectrodes (tip diameters 18-30 μm). Total oxygen consumption rates of whole sponges were measured in closed chambers. These rates were used to back-calculate the oxygen distribution in a finite-element model. Combining direct measurements with calculations of diffusive...... flux and modeling revealed that the tissue of non-pumping sponges turns anoxic within 15 min, with the exception of a 1 mm surface layer where oxygen intrudes due to molecular diffusion over the sponge surface. Molecular diffusion is the only transport mechanism for oxygen into non-pumping sponges...

Stable isotopes - separation and application

International Nuclear Information System (INIS)

Lockhart, I.M.

1980-01-01

In this review, methods used for the separation of stable isotopes ( 12 C, 13 C, 14 N, 15 N, 16 O, 17 O, 18 O, 34 S) will be described. The synthesis of labelled compounds, techniques for detection and assay, and areas of application will also be discussed. Particular attention will be paid to the isotopes of carbon, nitrogen, and oxygen; to date, sulphur isotopes have only assumed a minor role. The field of deuterium chemistry is too extensive for adequate treatment; it will therefore be essentially excluded. (author)

Secondary electron emission influenced by oxidation on the aluminum surface: the roles of the chemisorbed oxygen and the oxide layer

Science.gov (United States)

Li, Jiangtao; Hoekstra, Bart; Wang, Zhen-Bin; Qiu, Jie; Pu, Yi-Kang

2018-04-01

A relationship between the apparent secondary electron yield ({γ }{{se}}) and the oxygen coverage/oxide layer thickness on an aluminum cathode is obtained in an experiment under a controlled environment. The apparent secondary electron yield ({γ }{{se}}) is deduced from the breakdown voltage between two parallel plate electrodes in a 360 mTorr argon environment using a simple Townsend breakdown model with the assumption that the variation of the apparent secondary electron yield is dominated by the variation of the argon ion induced processes. The oxygen coverage/oxide layer thickness on the aluminum cathode is measured by a semi in situ x-ray photoemission spectroscopy equipment which is directly attached to the discharge chamber. It is found that three phases exist: (1) in the monomonolayer regime, as the oxygen coverage increases from 0 to 0.3, {γ }{{se}} decreases by nearly 40 % , (2) as the oxygen coverage increases from 0.3 to 1, {γ }{{se}} keeps nearly constant, (3) as the oxide layer thickness increases from about 0.3 nm to about 1.1 nm, {γ }{{se}} increases by 150 % . We propose that, in the submonolayer regime, the chemisorbed oxygen on the aluminum surface causes the decrease of {γ }{{se}} by creating a local potential barrier, which reduces the Auger neutralization rate and the energy gained by the Auger electrons. In the multilayer regime, as the oxide layer grows in thickness, there are three proposed mechanisms which cause the increase of {γ }{{se}}: (1) the work function decreases; (2) resonance neutralization and Auger de-excitation may exist. This is served as another channel for secondary electron production; (3) the kinetic energy of Auger electrons is increased on average, leading to a higher probability for electrons to overcome the surface potential barrier.

Thermal green protein, an extremely stable, nonaggregating fluorescent protein created by structure-guided surface engineering.

Science.gov (United States)

Close, Devin W; Paul, Craig Don; Langan, Patricia S; Wilce, Matthew C J; Traore, Daouda A K; Halfmann, Randal; Rocha, Reginaldo C; Waldo, Geoffery S; Payne, Riley J; Rucker, Joseph B; Prescott, Mark; Bradbury, Andrew R M

2015-07-01

In this article, we describe the engineering and X-ray crystal structure of Thermal Green Protein (TGP), an extremely stable, highly soluble, non-aggregating green fluorescent protein. TGP is a soluble variant of the fluorescent protein eCGP123, which despite being highly stable, has proven to be aggregation-prone. The X-ray crystal structure of eCGP123, also determined within the context of this paper, was used to carry out rational surface engineering to improve its solubility, leading to TGP. The approach involved simultaneously eliminating crystal lattice contacts while increasing the overall negative charge of the protein. Despite intentional disruption of lattice contacts and introduction of high entropy glutamate side chains, TGP crystallized readily in a number of different conditions and the X-ray crystal structure of TGP was determined to 1.9 Å resolution. The structural reasons for the enhanced stability of TGP and eCGP123 are discussed. We demonstrate the utility of using TGP as a fusion partner in various assays and significantly, in amyloid assays in which the standard fluorescent protein, EGFP, is undesirable because of aberrant oligomerization. © 2014 Wiley Periodicals, Inc.

Reactive-ion etching of nylon fabric meshes using oxygen plasma for creating surface nanostructures

International Nuclear Information System (INIS)

Salapare, Hernando S.; Darmanin, Thierry; Guittard, Frédéric

2015-01-01

Graphical abstract: - Highlights: • Reactive-ion etching (RIE) is employed to nylon 6,6 fabrics to achieve surface texturing and improved wettability. • FTIR spectra of the treated samples exhibited decreased transmittance of amide and carboxylic acid groups due to etching. • Etching is enhanced for higher power plasma treatments and for samples with larger mesh sizes. • Decreased crystallinity was achieved after plasma treatment. • Higher power induced higher negative DC self-bias voltage on the samples that favored anisotropic and aggressive etching. - Abstract: A facile one-step oxygen plasma irradiation in reactive ion etching (RIE) configuration is employed to nylon 6,6 fabrics with different mesh sizes to achieve surface nanostructures and improved wettability for textile and filtration applications. To observe the effects of power and irradiation time on the samples, the experiments were performed using constant irradiation time in varying power and using constant power in varying irradiation times. Results showed improved wettability after the plasma treatment. The FTIR spectra of all the treated samples exhibited decreased transmittance of the amide and carboxylic acid groups due to surface etching. The changes in the surface chemistry are supported by the SEM data wherein etching and surface nanostructures were observed for the plasma-treated samples. The etching of the surfaces is enhanced for higher power plasma treatments. The thermal analysis showed that the plasma treatment resulted in decreased crystallinity. Surface chemistry showed that the effects of the plasma treatment on the samples have no significant difference for all the mesh sizes. However, surface morphology showed that the sizes of the surface cracks are the same for all the mesh sizes but samples with larger mesh sizes exhibited enhanced etching as compared to the samples with smaller mesh sizes. Higher power induced higher negative DC self-bias voltage on the samples that

High-Performance Microchanneled Asymmetric Gd_0.1Ce_0.9O_1.95-δ-La_0.6Sr0.4FeO_3-δ-Based Membranes for Oxygen Separation

DEFF Research Database (Denmark)

Cheng, Shiyang; Huang, Hua; Ovtar, Simona

2016-01-01

.00 (STP) ml cm(-2) min(-1) was observed between air/CO/CO2 over 200 h at 850 degrees C. Partial surface decomposition was observed on the permeate side exposed to CO, in line with predictions from thermodynamic calculations. In a mixture of CO, CO2, H-2, and H2O at similar oxygen activity the material...... surface. An increase of the 50 150 oxygen flux of-4.49 (STP) mL cm(-2) min(-1) at 900 degrees C was observed when catalyst is added for the air/He-case. Mass transfer polarization through the finger-like support was confirmed to be negligible, which benefits the overall performance. A stable flux of 7...... will according to the calculation not decompose. The microchanneled asymmetric CGO-LSF membranes show high oxygen permeability and chemical stability under a range of technologically relevant oxygen potential gradients....

Synthesis of stable isotopically labeled peptides with filter-assisted enzymatic labeling for the diagnosis of hepatitis B virus infection utilizing mass spectrometry-based proteomics strategy

International Nuclear Information System (INIS)

Tsai, Hsing-Fen; Hsiao, He-Hsuan

2017-01-01

A facile method for the preparation of stable isotopically labeled peptides was developed by means of filter-assisted tryptic "1"6O/"1"8O water labeling, which could be directly applied to the determination of hepatitis B virus infection from human serum with tandem mass spectrometry. Tryptic peptides of hepatitis B surface antigen or hepatitis B e antigen from different subtypes of hepatitis B virus were synthesized with traditional solid-phase peptide synthesis as potential biomarkers. Trypsin catalyzed oxygen-18 exchange at their amidated c-terminus of arginine or lysine residue. The protease catalyzed oxygen-18 to oxygen-16 back exchange reaction was eliminated due to the complete removal of trypsin by the centrifugal filter containing a thin membrane associated with molecular weight cut-off of 10 KDa. The synthetic isotopic peptides were spiked into trichloroacetic acid/acetone precipitated human serum as internal standards and were selectively detected with multiplexed parallel reaction monitoring on a hybrid quadrupole-orbitrap mass spectrometer. The limit of detection for all synthetic peptides were in the range of 0.09 fmol–1.13 fmol. The results indicated that the peptide YLWEWASVR derived from hepatitis B surface antigen was quantified approximately 200 fmol per μl serum and may serve as a diagnostic biomarker for the detection of hepatitis B virus infected disease. - Highlights: • Facile synthesis of an inexpensive and highly reproducible stable isotopically labeled peptides. • Complete incorporation of two "1"8O atoms into synthesized peptides with filter-assisted enzymatic labeling. • Targeted analysis with parallel reaction monitoring assay for the disease diagnosis.

Synthesis of stable isotopically labeled peptides with filter-assisted enzymatic labeling for the diagnosis of hepatitis B virus infection utilizing mass spectrometry-based proteomics strategy

Energy Technology Data Exchange (ETDEWEB)

Tsai, Hsing-Fen; Hsiao, He-Hsuan, E-mail: hhhsiao@dragon.nchu.edu.tw

2017-03-01

A facile method for the preparation of stable isotopically labeled peptides was developed by means of filter-assisted tryptic {sup 16}O/{sup 18}O water labeling, which could be directly applied to the determination of hepatitis B virus infection from human serum with tandem mass spectrometry. Tryptic peptides of hepatitis B surface antigen or hepatitis B e antigen from different subtypes of hepatitis B virus were synthesized with traditional solid-phase peptide synthesis as potential biomarkers. Trypsin catalyzed oxygen-18 exchange at their amidated c-terminus of arginine or lysine residue. The protease catalyzed oxygen-18 to oxygen-16 back exchange reaction was eliminated due to the complete removal of trypsin by the centrifugal filter containing a thin membrane associated with molecular weight cut-off of 10 KDa. The synthetic isotopic peptides were spiked into trichloroacetic acid/acetone precipitated human serum as internal standards and were selectively detected with multiplexed parallel reaction monitoring on a hybrid quadrupole-orbitrap mass spectrometer. The limit of detection for all synthetic peptides were in the range of 0.09 fmol–1.13 fmol. The results indicated that the peptide YLWEWASVR derived from hepatitis B surface antigen was quantified approximately 200 fmol per μl serum and may serve as a diagnostic biomarker for the detection of hepatitis B virus infected disease. - Highlights: • Facile synthesis of an inexpensive and highly reproducible stable isotopically labeled peptides. • Complete incorporation of two {sup 18}O atoms into synthesized peptides with filter-assisted enzymatic labeling. • Targeted analysis with parallel reaction monitoring assay for the disease diagnosis.

Monitoring in situ biodegradation of hydrocarbons by using stable carbon isotopes

International Nuclear Information System (INIS)

Aggarwal, P.K.; Hinchee, R.E.

1991-01-01

Spilled or leaked nonhalogenated petroleum hydrocarbons in the soil can generally be metabolized by indigenous, aerobic bacteria. In situ biological degradation of hydrocarbons may be accelerated by supplying inorganic nutrients and/or oxygen. Approaches to monitoring and verifying enhanced in situ biodegradation have included measurements of changes over time in the (a) concentration of hydrocarbons, (b) temperature, (c) number of hydrocarbon-degrading microorganisms, (d) ratio of fast-degrading hydrocarbons (e.g., pristanes or phytanes), and (e) metabolic intermediates. Measurements of oxygen consumption over time and elevated carbon dioxide concentrations in soil gas also have been used as indicators of hydrocarbon degradation. An alternative approach that may help substantiate biodegradation is to measure stable carbon isotope ratios in soil gas CO 2 . Stable carbon isotope ratio analysis is inexpensive and commercially available at many laboratories. Carbon dioxide produced by hydrocarbon degradation may be distinguished from that produced by other processes based on the carbon isotopic compositions characteristic of the source material and/or fractionation accompanying microbial metabolism. Here the authors demonstrate the applicability of the stable isotope technique for monitoring enhanced. aerobic biodegradation of hydrocarbons using data from three locations in the United States

Calcium stable isotope geochemistry

Energy Technology Data Exchange (ETDEWEB)

Gausonne, Nikolaus [Muenster Univ. (Germany). Inst. fuer Mineralogie; Schmitt, Anne-Desiree [Strasbourg Univ. (France). LHyGeS/EOST; Heuser, Alexander [Bonn Univ. (Germany). Steinmann-Inst. fuer Geologie, Mineralogie und Palaeontologie; Wombacher, Frank [Koeln Univ. (Germany). Inst. fuer Geologie und Mineralogie; Dietzel, Martin [Technische Univ. Graz (Austria). Inst. fuer Angewandte Geowissenschaften; Tipper, Edward [Cambridge Univ. (United Kingdom). Dept. of Earth Sciences; Schiller, Martin [Copenhagen Univ. (Denmark). Natural History Museum of Denmark

2016-08-01

This book provides an overview of the fundamentals and reference values for Ca stable isotope research, as well as current analytical methodologies including detailed instructions for sample preparation and isotope analysis. As such, it introduces readers to the different fields of application, including low-temperature mineral precipitation and biomineralisation, Earth surface processes and global cycling, high-temperature processes and cosmochemistry, and lastly human studies and biomedical applications. The current state of the art in these major areas is discussed, and open questions and possible future directions are identified. In terms of its depth and coverage, the current work extends and complements the previous reviews of Ca stable isotope geochemistry, addressing the needs of graduate students and advanced researchers who want to familiarize themselves with Ca stable isotope research.

Calcium stable isotope geochemistry

International Nuclear Information System (INIS)

Gausonne, Nikolaus; Schmitt, Anne-Desiree; Heuser, Alexander; Wombacher, Frank; Dietzel, Martin; Tipper, Edward; Schiller, Martin

2016-01-01

This book provides an overview of the fundamentals and reference values for Ca stable isotope research, as well as current analytical methodologies including detailed instructions for sample preparation and isotope analysis. As such, it introduces readers to the different fields of application, including low-temperature mineral precipitation and biomineralisation, Earth surface processes and global cycling, high-temperature processes and cosmochemistry, and lastly human studies and biomedical applications. The current state of the art in these major areas is discussed, and open questions and possible future directions are identified. In terms of its depth and coverage, the current work extends and complements the previous reviews of Ca stable isotope geochemistry, addressing the needs of graduate students and advanced researchers who want to familiarize themselves with Ca stable isotope research.

The Role of Ru Redox in pH-Dependent Oxygen Evolution on Rutile Ruthenium Dioxide Surfaces

Energy Technology Data Exchange (ETDEWEB)

Stoerzinger, Kelsey A.; Rao, Reshma R.; Wang, Xiao Renshaw; Hong, Wesley T.; Rouleau, Christopher M.; Shao-Horn, Yang

2017-05-01

Rutile RuO₂ is known to exhibit high catalytic activity for the oxygen evolution reaction (OER) and large pseudocapacitance associated with redox of surface Ru, however the mechanistic link between these properties and the role of pH is yet to be understood. Here we report that the OER activities of the (101), (001) and (111) RuO₂ surfaces were found to increase while the potential of a pseudocapacitive feature just prior to OER shifted to lower potentials (“super-Nernstian” shift) with increasing pH on the reversible hydrogen electrode (RHE) scale. This behavior is in contrast to the (100) and (110) surfaces that have pH-independent Ru redox and OER activity. The link in catalytic and pseudocapacitive behavior illustrates the importance of this redox feature in generating active sites, building new mechanistic understanding of the OER.

Enhanced Hydrophilicity and Biocompatibility of Dental Zirconia Ceramics by Oxygen Plasma Treatment

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