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Sample records for oxygen selection based

  1. High Selectivity Oxygen Delignification

    SciTech Connect

    Lucian A. Lucia

    2005-11-15

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

  2. High Selectivity Oxygen Delignification

    SciTech Connect

    Arthur J. Ragauskas Lucian A. Lucia Hasan Jameel

    2005-09-30

    The overall objective of this program was to develop improved extended oxygen delignification (EOD) technologies for current U.S. pulp mill operations. This was accomplished by: (1) Identifying pulping conditions that optimize O and OO performance; (2) Identifying structural features of lignin that enhance reactivity towards EOD of high kappa pulps; (3) Identifying factors minimizing carbohydrate degradation and improve pulp strength of EOD high kappa pulps; (4) Developing a simple, reproducible method of quantifying yield gains from EOD; and (5) Developing process conditions that significantly reduce the capital requirements of EOD while optimizing the yield benefits. Key research outcomes included, demonstrating the use of a mini-O sequence such as (E+O)Dkf:0.05(E+O) or Dkf:0.05(E+O)(E+O) without interstage washing could capture approximately 60% of the delignification efficiency of a conventional O-stage without the major capital requirements associated with an O-stage for conventional SW kraft pulps. The rate of formation and loss of fiber charge during an O-stage stage can be employed to maximize net fiber charge. Optimal fiber charge development and delignification are two independent parameters and do not parallel each other. It is possible to utilize an O-stage to enhance overall cellulosic fiber charge of low and high kappa SW kraft pulps which is beneficial for physical strength properties. The application of NIR and multi-variant analysis was developed into a rapid and simple method of determining the yield of pulp from an oxygen delignification stage that has real-world mill applications. A focus point of this program was the demonstration that Kraft pulping conditions and oxygen delignification of high and low-kappa SW and HW pulps are intimately related. Improved physical pulp properties and yield can be delivered by controlling the H-factor and active alkali charge. Low AA softwood kraft pulp with a kappa number 30 has an average improvement of 2% in

  3. An experimental data base for material selection and design of high-speed, high-pressure, oxygen turbomachinery

    NASA Technical Reports Server (NTRS)

    Schoenman, L.; Stoltzfus, J. M.

    1985-01-01

    New technologies for space-based, reusable, throttleable, cryogenic, orbit transfer propulsion are being evaluated. A variable-thrust (200 to 3000 lbF), 2000 psi chamber pressure, LO2/LH2 engine has been selected to demonstrate the 20-hour, 500-restart life goal, and a specific impulse of 480 lbF-sec/lbM. The advanced design uses warm oxygen to power a fully integrated turbopump that delivers 4500 psi LO2. The selected engine cycle provides the following advantages over conventional expander cycle designs which use H2 to drive the LH2 and LO2 pumps; higher engine operating pressures and performance in a smaller envelope, lower turbine operating temperatures, elimination of interpropellant seals and purges, and an extended throttling range. The design approach and results of testing to characterize materials for use in high-pressure gaseous oxygen are discussed. Test methods include particle impact testing in a sonic-flow, hot GO2 streams and forced, high-speed friction rubbing testing. Materials are exposed to oxygen and nitrogen atmospheres at pressures of 100, 1000, and 3000 psi to identify separately the gas cooling effects from the metal oxidation effects at the rubbing surface. The selection of candidate design materials is based on an analytical parameter defined as the burn factor. Typical materials tested include carbon steel, stainless steel, nickel, copper, and monel alloys.

  4. MOF-based catalysts for selective hydrogenolysis of carbon–oxygen ether bonds

    DOE PAGESBeta

    Stavila, Vitalie; Parthasarathi, Ramakrishnan; Davis, Ryan W.; El Gabaly, Farid; Sale, Kenneth L.; Simmons, Blake A.; Singh, Seema; Allendorf, Mark D.

    2015-11-23

    We demonstrate that metal–organic frameworks (MOFs) can catalyze hydrogenolysis of aryl ether bonds under mild conditions. Mg-IRMOF-74(I) and Mg-IRMOF-74(II) are stable under reducing conditions and can cleave phenyl ethers containing β-O-4, α-O-4, and 4-O-5 linkages to the corresponding hydrocarbons and phenols. Reaction occurs at 10 bar H2 and 120 °C without added base. DFT-optimized structures and charge transfer analysis suggest that the MOF orients the substrate near Mg2+ ions on the pore walls. Ti and Ni doping further increase conversions to as high as 82% with 96% selectivity for hydrogenolysis versus ring hydrogenation. Thus repeated cycling induces no loss ofmore » activity, making this a promising route for mild aryl-ether bond scission.« less

  5. MOF-based catalysts for selective hydrogenolysis of carbon–oxygen ether bonds

    SciTech Connect

    Stavila, Vitalie; Parthasarathi, Ramakrishnan; Davis, Ryan W.; El Gabaly, Farid; Sale, Kenneth L.; Simmons, Blake A.; Singh, Seema; Allendorf, Mark D.

    2015-11-23

    We demonstrate that metal–organic frameworks (MOFs) can catalyze hydrogenolysis of aryl ether bonds under mild conditions. Mg-IRMOF-74(I) and Mg-IRMOF-74(II) are stable under reducing conditions and can cleave phenyl ethers containing β-O-4, α-O-4, and 4-O-5 linkages to the corresponding hydrocarbons and phenols. Reaction occurs at 10 bar H2 and 120 °C without added base. DFT-optimized structures and charge transfer analysis suggest that the MOF orients the substrate near Mg2+ ions on the pore walls. Ti and Ni doping further increase conversions to as high as 82% with 96% selectivity for hydrogenolysis versus ring hydrogenation. Thus repeated cycling induces no loss of activity, making this a promising route for mild aryl-ether bond scission.

  6. The effect of meter-scale lateral oxygen gradients at the sediment-water interface on selected organic matter based alteration, productivity and temperature proxies

    NASA Astrophysics Data System (ADS)

    Bogus, K. A.; Zonneveld, K. A. F.; Fischer, D.; Kasten, S.; Bohrmann, G.; Versteegh, G. J. M.

    2011-11-01

    A valid assessment of selective aerobic degradation on organic matter (OM) and its impact on OM-based proxies is vital to produce accurate environmental reconstructions. However, most studies investigating these effects suffer from inherent environmental heterogeneities. This includes differences in the initial OM composition, as a result of variable upper water column conditions, or from those induced by selective aerobic degradation. In this study, we used surface samples collected along two meter-scale transects and one longer transect in the northeastern Arabian Sea to constrain initial OM heterogeneity, in order to evaluate selective aerobic degradation on temperature, productivity and alteration indices at the sediment-water interface. All of the alteration indices, the higher plant alkane index, alcohol preservation index, and diol oxidation index, demonstrated that they are sensitive indicators for changes in oxygen content at the sediment-water interface. The export production indices, a cholesterol-based stanol/stenol and dinoflagellate lipid- and cyst-based ratios, showed significant (more than 20%) change over the lateral oxygen gradients. Therefore, they do not exclusively reflect surface water productivity, but can be altered after deposition with varying oxygen content at the sediment-water interface. Two of the investigated proxies, the glycerol dibiphytanyl glycerol tetraethers (GDGT) based TEX86 sea surface temperature indices and a productivity index based on phytol, phytane and pristane, did not show any trends related to oxygen concentration at the sediment-water interface. Nevertheless, unrealistic sea surface temperatures were obtained after application of the TEX86, TEX86L, and TEX86H proxies. The phytol-based ratios were likely modified by the sedimentary production of pristane. Our results demonstrate the rapid and selective impact of aerobic organic matter degradation on the lipid and palynomorph composition of surface sediments on a

  7. The effect of meter-scale lateral oxygen gradients at the sediment-water interface on selected organic matter based alteration, productivity and temperature proxies

    NASA Astrophysics Data System (ADS)

    Bogus, K. A.; Zonneveld, K. A. F.; Fischer, D.; Kasten, S.; Bohrmann, G.; Versteegh, G. J. M.

    2012-04-01

    A valid assessment of selective aerobic degradation on organic matter (OM) and its impact on OM-based proxies is vital to produce accurate environmental reconstructions. However, most studies investigating these effects suffer from inherent environmental heterogeneities. In this study, we used surface samples collected along two meter-scale transects and one longer transect in the northeastern Arabian Sea to constrain initial OM heterogeneity, in order to evaluate selective aerobic degradation on temperature, productivity and alteration indices at the sediment-water interface. All of the studied alteration indices, the higher plant alkane index, alcohol preservation index, and diol oxidation index, demonstrated that they are sensitive indicators for changes in the oxygen regime. Several export production indices, a cholesterol-based stanol/stenol index and dinoflagellate lipid- and cyst-based ratios, showed significant (more than 20%) change only over the lateral oxygen gradients. Therefore, these compounds do not exclusively reflect surface water productivity, but are significantly altered after deposition. Two of the proxies, glycerol dibiphytanyl glycerol tetraether-based TEX86 sea surface temperature indices and indices based on phytol, phytane and pristane, did not show any trends related to oxygen. Nevertheless, unrealistic sea surface temperatures were obtained after application of the TEX86, TEX86L, and TEX86H proxies. The phytol-based ratios were likely affected by the sedimentary production of pristane. Our results demonstrate the selective impact of aerobic organic matter degradation on the lipid and palynomorph composition of surface sediments along a short lateral oxygen gradient and suggest that some of the investigated proxies may be useful tracers of changing redox conditions at the sediment-water interface.

  8. Selective photooxidation of hydrocarbons in zeolites by oxygen

    DOEpatents

    Frei, Heinz; Blatter, Fritz; Sun, Hai

    1998-01-01

    A selective photooxidation process for the conversion of hydrocarbon molecules to partially oxygenated derivatives, which comprises the steps of adsorbing a hydrocarbon and oxygen onto a dehydrated zeolite support matrix to form a hydrocarbon-oxygen contact pair, and subsequently exposing the hydrocarbon-oxygen contact pair to visible light, thereby forming a partially oxygenated derivative.

  9. Cooperative Catalysis for Selective Alcohol Oxidation with Molecular Oxygen.

    PubMed

    Slot, Thierry K; Eisenberg, David; van Noordenne, Dylan; Jungbacker, Peter; Rothenberg, Gadi

    2016-08-22

    The activation of dioxygen for selective oxidation of organic molecules is a major catalytic challenge. Inspired by the activity of nitrogen-doped carbons in electrocatalytic oxygen reduction, we combined such a carbon with metal-oxide catalysts to yield cooperative catalysts. These simple materials boost the catalytic oxidation of several alcohols, using molecular oxygen at atmospheric pressure and low temperature (80 °C). Cobalt and copper oxide demonstrate the highest activities. The high activity and selectivity of these catalysts arises from the cooperative action of their components, as proven by various control experiments and spectroscopic techniques. We propose that the reaction should not be viewed as occurring at an 'active site', but rather at an 'active doughnut'-the volume surrounding the base of a carbon-supported metal-oxide particle. PMID:27355443

  10. A Comparison of Atomic Oxygen Erosion Yields of Carbon and Selected Polymers Exposed in Ground Based Facilities and in Low Earth Orbit

    NASA Technical Reports Server (NTRS)

    Rutledge, Sharon K.; Banks, Bruce A.; Cales, Michael

    1994-01-01

    A comparison of the relative erosion yields (volume of material removed per oxygen atom arriving) for FEP Teflon, polyethylene, and pyrolytic graphite with respect to Kapton HN was performed in an atomic oxygen directed beam system, in a plasma asher, and in space on the EOIM-III (Evaluation of Oxygen Interaction with Materials-III) flight experiment. This comparison was performed to determine the sensitivity of material reaction to atomic oxygen flux, atomic oxygen fluence, and vacuum ultraviolet radiation for enabling accurate estimates of durability in ground based facilities. The relative erosion yield of pyrolytic graphite was found not to be sensitive to these factors, that for FEP was sensitive slightly to fluence and possibly ions, and that for polyethylene was found to be partially VUV and flux sensitive but more sensitive to an unknown factor. Results indicate that the ability to use these facilities for material relative durability prediction is great as long as the sensitivity of particular materials to conditions such as VUV, and atomic oxygen flux and fluence are taken into account. When testing materials of a particular group such as teflon, it may be best to use a witness sample made of a similar material that has some available space data on it. This would enable one to predict an equivalent exposure in the ground based facility.

  11. Safety Standard for Oxygen and Oxygen Systems: Guidelines for Oxygen System Design, Materials Selection, Operations, Storage, and Transportation

    NASA Technical Reports Server (NTRS)

    1996-01-01

    NASA's standard for oxygen system design, materials selection, operation, and transportation is presented. Minimum guidelines applicable to NASA Headquarters and all NASA Field Installations are contained.

  12. Biofilm history and oxygen availability interact to affect habitat selection in a marine invertebrate.

    PubMed

    Lagos, Marcelo E; White, Craig R; Marshall, Dustin J

    2016-07-01

    In marine systems, oxygen availability varies at small temporal and spatial scales, such that current oxygen levels may not reflect conditions of the past. Different studies have shown that marine invertebrate larvae can select settlement sites based on local oxygen levels and oxygenation history of the biofilm, but no study has examined the interaction of both. The influence of normoxic and hypoxic water and oxygenation history of biofilms on pre-settlement behavior and settlement of the bryozoan Bugula neritina was tested. Larvae used cues in a hierarchical way: the oxygen levels in the water prime larvae to respond, the response to different biofilms is contingent on oxygen levels in the water. When oxygen levels varied throughout biofilm formation, larvae responded differently depending on the history of the biofilm. It appears that B. neritina larvae integrate cues about current and historical oxygen levels to select the appropriate microhabitat and maximize their fitness. PMID:27169475

  13. Clinically based implant selection.

    PubMed

    Fugazzotto, P A

    1999-01-01

    A hierarchy of implant selection is presented, based on overcoming specific clinical challenges in a variety of situations, including maximization of the esthetic, comfort, and functional potentials of therapy. PMID:10709488

  14. Copper crystallite in carbon molecular sieves for selective oxygen removal

    NASA Technical Reports Server (NTRS)

    Sharma, Pramod K. (Inventor); Seshan, Panchalam K. (Inventor)

    1993-01-01

    Carbon molecular sieves modified by the incorporation of finely divided elemental copper useful for the selective sorption of oxygen at elevated temperatures. The carbon molecular sieves can be regenerated by reduction with hydrogen. The copper modified carbon molecular sieves are prepared by pyrolysis of a mixture of a copper-containing material and polyfurfuryl alcohol to form a sorbent precursor. The sorbent precursors are then heated and reduced to produce copper modified carbon molecular sieves. The copper modified carbon molecular sieves are useful for sorption of all concentrations of oxygen at temperatures up to about 200.degree. C. They are also useful for removal of trace amount of oxygen from gases at temperatures up to about 600.degree. C.

  15. Copper modified carbon molecular sieves for selective oxygen removal

    NASA Technical Reports Server (NTRS)

    Sharma, Pramod K. (Inventor); Seshan, Panchalam K. (Inventor)

    1992-01-01

    Carbon molecular sieves modified by the incorporation of finely divided elemental copper useful for the selective sorption of oxygen at elevated temperatures. The carbon molecular sieves can be regenerated by reduction with hydrogen. The copper modified carbon molecular sieves are prepared by pyrolysis of a mixture of a copper-containing material and polyfunctional alcohol to form a sorbent precursor. The sorbent precursors are then heated and reduced to produce copper modified carbon molecular sieves. The copper modified carbon molecular sieves are useful for sorption of all concentrations of oxygen at temperatures up to about 200.degree. C. They are also useful for removal of trace amount of oxygen from gases at temperatures up to about 600.degree. C.

  16. New oxygen radical source using selective sputtering of oxygen atoms for high rate deposition of TiO{sub 2} films

    SciTech Connect

    Yasuda, Yoji; Lei, Hao; Hoshi, Yoichi

    2012-11-15

    We have developed a new oxygen radical source based on the reactive sputtering phenomena of a titanium target for high rate deposition of TiO{sub 2} films. In this oxygen radical source, oxygen radicals are mainly produced by two mechanisms: selective sputter-emission of oxygen atoms from the target surface covered with a titanium oxide layer, and production of high-density oxygen plasma in the space near the magnetron-sputtering cathode. Compared with molecular oxygen ions, the amount of atomic oxygen radicals increased significantly with an increase in discharge current so that atomic oxygen radicals were mainly produced by this radical source. It should be noted that oxygen atoms were selectively sputtered from the target surface, and titanium atoms sputter-emitted from the target cathode were negligibly small. The amount of oxygen radicals supplied from this radical source increased linearly with increasing discharge current, and oxygen radicals of 1 Multiplication-Sign 10{sup 15} atoms/s/cm{sup 2} were supplied to the substrate surface at a discharge current of 1.2 A. We conclude that our newly developed oxygen radical source can be a good tool to achieve high rate deposition and to control the structure of TiO{sub 2} films for many industrial design applications.

  17. Oxygen Selective Membranes for Li-Air (O2) Batteries

    PubMed Central

    Crowther, Owen; Salomon, Mark

    2012-01-01

    Lithium-air (Li-air) batteries have a much higher theoretical energy density than conventional lithium batteries and other metal air batteries, so they are being developed for applications that require long life. Water vapor from air must be prevented from corroding the lithium (Li) metal negative electrode during discharge under ambient conditions, i.e., in humid air. One method of protecting the Li metal from corrosion is to use an oxygen selective membrane (OSM) that allows oxygen into the cell while stopping or slowing the ingress of water vapor. The desired properties and some potential materials for OSMs for Li-air batteries are discussed and the literature is reviewed. PMID:24958173

  18. Oxygen selective membranes for li-air (o2) batteries.

    PubMed

    Crowther, Owen; Salomon, Mark

    2012-01-01

    Lithium-air (Li-air) batteries have a much higher theoretical energy density than conventional lithium batteries and other metal air batteries, so they are being developed for applications that require long life. Water vapor from air must be prevented from corroding the lithium (Li) metal negative electrode during discharge under ambient conditions, i.e., in humid air. One method of protecting the Li metal from corrosion is to use an oxygen selective membrane (OSM) that allows oxygen into the cell while stopping or slowing the ingress of water vapor. The desired properties and some potential materials for OSMs for Li-air batteries are discussed and the literature is reviewed. PMID:24958173

  19. Nanofiber Based Optical Sensors for Oxygen Determination

    NASA Astrophysics Data System (ADS)

    Xue, Ruipeng

    Oxygen sensors based on luminescent quenching of nanofibers were developed for measurement of both gaseous and dissolved oxygen concentrations. Electrospinning was used to fabricate "core-shell" fiber configurations in which oxygen-sensitive transition metal complexes are embedded into a polymer 'core' while a synthetic biocompatible polymer provides a protective 'shell.' Various matrix polymers and luminescent probes were studied in terms of their sensitivity, linear calibration, reversibility, response time, stability and probe-matrix interactions. Due to the small size and high surface area of these nanofibers, all samples showed rapid response and a highly linear response to oxygen. The sensitivity and photostability of the sensors were controlled by the identity of both the probe molecule and the polymer matrix. Such nanofiber sensor forms are particularly suitable in biological applications due to the fact that they do not consume oxygen, are biocompatible and biomimetic and can be easily incorporated into cell culture. Applications of these fibers in cancer cell research, wound healing, breath analysis and waste water treatment were explored.

  20. Oxygen Concentration Flammability Thresholds of Selected Aerospace Materials Considered for the Constellation Program

    NASA Technical Reports Server (NTRS)

    Hirsch, David B.; Williams, James H.; Harper, Susan A.; Beeson, Harold; Pedley, Michael D.

    2007-01-01

    Materials selection for spacecraft is based on an upward flammability test conducted in a quiescent environment in the highest expected oxygen concentration environment. The test conditions and its pass/fail test logic do not provide sufficient quantitative materials flammability information for an advanced space exploration program. A modified approach has been suggested determination of materials self-extinguishment limits. The flammability threshold information will allow NASA to identify materials with increased flammability risk from oxygen concentration and total pressure changes, minimize potential impacts, and allow for development of sound requirements for new spacecraft and extraterrestrial landers and habitats. This paper provides data on oxygen concentration self-extinguishment limits under quiescent conditions for selected materials considered for the Constellation Program.

  1. Selectivity between Oxygen and Chlorine Evolution in the Chlor-Alkali and Chlorate Processes.

    PubMed

    Karlsson, Rasmus K B; Cornell, Ann

    2016-03-01

    Chlorine gas and sodium chlorate are two base chemicals produced through electrolysis of sodium chloride brine which find uses in many areas of industrial chemistry. Although the industrial production of these chemicals started over 100 years ago, there are still factors that limit the energy efficiencies of the processes. This review focuses on the unwanted production of oxygen gas, which decreases the charge yield by up to 5%. Understanding the factors that control the rate of oxygen production requires understanding of both chemical reactions occurring in the electrolyte, as well as surface reactions occurring on the anodes. The dominant anode material used in chlorate and chlor-alkali production is the dimensionally stable anode (DSA), Ti coated by a mixed oxide of RuO2 and TiO2. Although the selectivity for chlorine evolution on DSA is high, the fundamental reasons for this high selectivity are just now becoming elucidated. This review summarizes the research, since the early 1900s until today, concerning the selectivity between chlorine and oxygen evolution in chlorate and chlor-alkali production. It covers experimental as well as theoretical studies and highlights the relationships between process conditions, electrolyte composition, the material properties of the anode, and the selectivity for oxygen formation. PMID:26879761

  2. Platinum-based oxygen reduction electrocatalysts.

    PubMed

    Wu, Jianbo; Yang, Hong

    2013-08-20

    An efficient oxygen reduction reaction (ORR) offers the potential for clean energy generation in low-temperature, proton-exchange membrane fuel cells running on hydrogen fuel and air. In the past several years, researchers have developed high-performance electrocatalysts for the ORR to address the obstacles of high cost of the Pt catalyst per kilowatt of output power and of declining catalyst activity over time. Current efforts are focused on new catalyst structures that add a secondary metal to change the d-band center and the surface atomic arrangement of the catalyst, altering the chemisorption of those oxygencontaining species that have the largest impact on the ORR kinetics and improving the catalyst activity and cost effectiveness. This Account reviews recent progress in the design of Pt-based ORR electrocatalysts, including improved understanding of the reaction mechanisms and the development of synthetic methods for producing catalysts with high activity and stability. Researchers have made several types of highly active catalysts, including an extended single crystal surface of Pt and its alloy, bimetallic nanoparticles, and self-supported, low-dimensional nanostructures. We focus on the design and synthetic strategies for ORR catalysts including controlling the shape (or facet) and size of Pt and its bimetallic alloys, and controlling the surface composition and structure of core-shell, monolayer, and hollow porous structures. The strong dependence of ORR performance on facet and size suggests that synthesizing nanocrystals with large, highly reactive {111} facets could be as important, if not more important, to increasing their activity as simply making smaller nanoparticles. A newly developed carbon-monoxide (CO)-assisted reduction method produces Pt bimetallic nanoparticles with controlled facets. This CO-based approach works well to control shapes because of the selective CO binding on different, low-indexed metal surfaces. Post-treatment under

  3. Oxidizer Selection for the ISTAR Program (Liquid Oxygen versus Hydrogen Peroxide)

    NASA Technical Reports Server (NTRS)

    Quinn, Jason Eugene; Koelbl, Mary E. (Technical Monitor)

    2002-01-01

    This paper discusses a study of two alternate oxidizers, liquid oxygen and hydrogen peroxide, for use in a rocket based combined cycle (RBCC) demonstrator vehicle. The flight vehicle is baselined as an airlaunched self-powered Mach 0.7 to 7 demonstration of an RBCC engine through all or its air breathing propulsion modes. Selection of an alternate oxidizer has the potential to lower overall vehicle size, system complexity/ cost and ultimately the total program risk. This trade study examined the oxidizer selection effects upon the overall vehicle performance, safety and operations. After consideration of all the technical and programmatic details available at this time, 90% hydrogen peroxide was selected over liquid oxygen for use in this program.

  4. Hemoglobin-Based Nanoarchitectonic Assemblies as Oxygen Carriers.

    PubMed

    Jia, Yi; Duan, Li; Li, Junbai

    2016-02-10

    Safe and effective artificial oxygen carriers are the subject of great interest due to the problems of traditional blood transfusion and enormous demand in clinical use. In view of its unique oxygen-transport ability and normal metabolic pathways, hemoglobin is regarded as an ideal oxygen-carrying unit. With advances in nano-biotechnology, hemoglobin assemblies as artificial oxygen carriers achieve great development. Here, recent progress on hemoglobin-based oxygen carriers is highlighted in view of two aspects: acellular hemoglobin-based oxygen carriers and cellular hemoglobin-based oxygen carriers. These novel oxygen carriers exhibit advantages over traditional carriers and will greatly promote research on reliable and feasible oxygen carriers. PMID:26479864

  5. Nanomaterial-based robust oxygen sensor

    NASA Astrophysics Data System (ADS)

    Goswami, Kisholoy; Sampathkumaran, Uma; Alam, Maksudul; Tseng, Derek; Majumdar, Arun K.; Kazemi, Alex A.

    2007-09-01

    Since the TWA flight 800 accident in July 1996, significant emphasis has been placed on fuel tank safety. The Federal Aviation Administration (FAA) has focused research to support two primary methods of fuel tank protection - ground-based and on-board - both involving fuel tank inerting. Ground-based fuel tank inerting involves some combination of fuel scrubbing and ullage washing with Nitrogen Enriched Air (NEA) while the airplane is on the ground (applicable to all or most operating transport airplanes). On-board fuel tank inerting involves ullage washing with OBIGGS (on-board inert gas generating system), a system that generates NEA during aircraft operations. An OBIGGS generally encompasses an air separation module (ASM) to generate NEA, a compressor, storage tanks, and a distribution system. Essential to the utilization of OBIGGS is an oxygen sensor that can operate inside the aircraft's ullage and assess the effectiveness of the inerting systems. OBIGGS can function economically by precisely knowing when to start and when to stop. Toward achieving these goals, InnoSense LLC is developing an all-optical fuel tank ullage sensor (FTUS) prototype for detecting oxygen in the ullage of an aircraft fuel tank in flight conditions. Data would be presented to show response time and wide dynamic range of the sensor in simulated flight conditions and fuel tank environment.

  6. Intrinsic Selectivity and Structure Sensitivity of Rhodium Catalysts for C(2+) Oxygenate Production.

    PubMed

    Yang, Nuoya; Medford, Andrew J; Liu, Xinyan; Studt, Felix; Bligaard, Thomas; Bent, Stacey F; Nørskov, Jens K

    2016-03-23

    Synthesis gas (CO + H2) conversion is a promising route to converting coal, natural gas, or biomass into synthetic liquid fuels. Rhodium has long been studied as it is the only elemental catalyst that has demonstrated selectivity to ethanol and other C2+ oxygenates. However, the fundamentals of syngas conversion over rhodium are still debated. In this work a microkinetic model is developed for conversion of CO and H2 into methane, ethanol, and acetaldehyde on the Rh (211) and (111) surfaces, chosen to describe steps and close-packed facets on catalyst particles. The model is based on DFT calculations using the BEEF-vdW functional. The mean-field kinetic model includes lateral adsorbate-adsorbate interactions, and the BEEF-vdW error estimation ensemble is used to propagate error from the DFT calculations to the predicted rates. The model shows the Rh(211) surface to be ∼6 orders of magnitude more active than the Rh(111) surface, but highly selective toward methane, while the Rh(111) surface is intrinsically selective toward acetaldehyde. A variety of Rh/SiO2 catalysts are synthesized, tested for catalytic oxygenate production, and characterized using TEM. The experimental results indicate that the Rh(111) surface is intrinsically selective toward acetaldehyde, and a strong inverse correlation between catalytic activity and oxygenate selectivity is observed. Furthermore, iron impurities are shown to play a key role in modulating the selectivity of Rh/SiO2 catalysts toward ethanol. The experimental observations are consistent with the structure-sensitivity predicted from theory. This work provides an improved atomic-scale understanding and new insight into the mechanism, active site, and intrinsic selectivity of syngas conversion over rhodium catalysts and may also guide rational design of alloy catalysts made from more abundant elements. PMID:26958997

  7. 20. VIEW OF WORTHINGTON BASE LOAD OXYGEN COMPRESSOR IN THE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    20. VIEW OF WORTHINGTON BASE LOAD OXYGEN COMPRESSOR IN THE HIGH PURITY OXYGEN BUILDING LOOKING NORTH. - U.S. Steel Duquesne Works, Fuel & Utilities Plant, Along Monongahela River, Duquesne, Allegheny County, PA

  8. Oxygen Radical Absorbance Capacity (ORAC) of Selected Food – 2007

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Interest of the scientific community in the Oxygen Radical Absorbance Capacity (ORAC) of foods continues because reactive oxygen species (ROS) are important in the aging process and also because of growing evidence regarding beneficial effects of dietary antioxidants in reducing oxidative-stress-ind...

  9. An Elementary Overview of the Selection of Materials for Service in Oxygen-Enriched Environments

    NASA Technical Reports Server (NTRS)

    Davis, Samuel Eddie

    2012-01-01

    The process for selecting materials for use in oxygen or oxygen-enriched environments is one that continues to be investigated by many industries due to the importance to those industries of oxygen systems. There are several excellent resources available to assist oxygen systems design engineers and end-users, with the most comprehensive being ASTM MNL-36, Safe Use of Oxygen and Oxygen Systems: Handbook for Design, Operation and Maintenance, 2nd Edition. ASTM also makes available several standards for oxygen systems. However, the ASTM publications are extremely detailed, and typically designed for professionals who already possess a working knowledge of oxygen systems. No notable resource exists, whether an ASTM or other organizational publication, which can be used to educate engineers or technicians who have no prior knowledge of the nuances of oxygen system design and safety. This paper will fill the void for information needed by organizations that design or operate oxygen systems. The information in this paper is not new information, but is a concise and easily understood summary of selecting materials for oxygen systems. This paper will serve well as an employee s first introduction to oxygen system materials selection, and probably the employee s first introduction to ASTM.

  10. (R)-Profens Are Substrate-Selective Inhibitors of Endocannabinoid Oxygenation by COX-2

    PubMed Central

    Duggan, Kelsey C.; Hermanson, Daniel J.; Musee, Joel; Prusakiewicz, Jeffery J.; Scheib, Jami L.; Carter, Bruce D.; Banerjee, Surajit; Oates, J.A.; Marnett, Lawrence J.

    2012-01-01

    Cyclooxygenase-2 (COX-2) catalyzes the oxygenation of arachidonic acid and the endocannabinoids, 2-arachidonoylglycerol and arachidonoylethanolamide. Evaluation of a series of COX-2 inhibitors revealed that many weak, competitive inhibitors of arachidonic acid oxygenation are potent inhibitors of endocannabinoid oxygenation. (R)-Enantiomers of ibuprofen, naproxen, and flurbiprofen, which are considered to be inactive as COX-2 inhibitors, are potent “substrate-selective inhibitors” of endocannabinoid oxygenation. Crystal structures of the COX-2-(R)-naproxen and COX-2-(R)-flurbiprofen complexes verified this unexpected binding and defined the orientation of the (R)-enantiomers relative to (S)-enantiomers. (R)-Profens selectively inhibited endocannabinoid oxygenation by lipopolysaccharide-stimulated dorsal root ganglion cells. Substrate-selective inhibition provides novel tools for investigating the role of COX-2 in endocannabinoid oxygenation and a possible explanation for the ability of (R)-profens to maintain endocannabinoid tone in models of neuropathic pain. PMID:22053353

  11. Highly Efficient Oxygen Reduction Electrocatalysts based on Winged Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Cheng, Yingwen; Zhang, Hongbo; Varanasi, Chakrapani V.; Liu, Jie

    2013-11-01

    Developing electrocatalysts with both high selectivity and efficiency for the oxygen reduction reaction (ORR) is critical for several applications including fuel cells and metal-air batteries. In this work we developed high performance electrocatalysts based on unique winged carbon nanotubes. We found that the outer-walls of a special type of carbon nanotubes/nanofibers, when selectively oxidized, unzipped and exfoliated, form graphene wings strongly attached to the inner tubes. After doping with nitrogen, the winged nanotubes exhibited outstanding activity toward catalyzing the ORR through the four-electron pathway with excellent stability and methanol/carbon monoxide tolerance. While the doped graphene wings with high active site density bring remarkable catalytic activity, the inner tubes remain intact and conductive to facilitate electron transport during electrocatalysis.

  12. Highly Efficient Oxygen Reduction Electrocatalysts based on Winged Carbon Nanotubes

    PubMed Central

    Cheng, Yingwen; Zhang, Hongbo; Varanasi, Chakrapani V.; Liu, Jie

    2013-01-01

    Developing electrocatalysts with both high selectivity and efficiency for the oxygen reduction reaction (ORR) is critical for several applications including fuel cells and metal-air batteries. In this work we developed high performance electrocatalysts based on unique winged carbon nanotubes. We found that the outer-walls of a special type of carbon nanotubes/nanofibers, when selectively oxidized, unzipped and exfoliated, form graphene wings strongly attached to the inner tubes. After doping with nitrogen, the winged nanotubes exhibited outstanding activity toward catalyzing the ORR through the four-electron pathway with excellent stability and methanol/carbon monoxide tolerance. While the doped graphene wings with high active site density bring remarkable catalytic activity, the inner tubes remain intact and conductive to facilitate electron transport during electrocatalysis. PMID:24217312

  13. Highly efficient oxygen reduction electrocatalysts based on winged carbon nanotubes.

    PubMed

    Cheng, Yingwen; Zhang, Hongbo; Varanasi, Chakrapani V; Liu, Jie

    2013-01-01

    Developing electrocatalysts with both high selectivity and efficiency for the oxygen reduction reaction (ORR) is critical for several applications including fuel cells and metal-air batteries. In this work we developed high performance electrocatalysts based on unique winged carbon nanotubes. We found that the outer-walls of a special type of carbon nanotubes/nanofibers, when selectively oxidized, unzipped and exfoliated, form graphene wings strongly attached to the inner tubes. After doping with nitrogen, the winged nanotubes exhibited outstanding activity toward catalyzing the ORR through the four-electron pathway with excellent stability and methanol/carbon monoxide tolerance. While the doped graphene wings with high active site density bring remarkable catalytic activity, the inner tubes remain intact and conductive to facilitate electron transport during electrocatalysis. PMID:24217312

  14. Current status of ceramic-based membranes for oxygen separation from air.

    PubMed

    Hashim, Salwa Meredith; Mohamed, Abdul Rahman; Bhatia, Subhash

    2010-10-15

    There has been tremendous progress in membrane technology for gas separation, in particular oxygen separation from air in the last 20 years. It provides an alternative route to the existing conventional separation processes such as cryogenic distillation and pressure swing adsorption as well as cheaper production of oxygen with high purity. This review presents the recent advances of ceramic membranes for the separation of oxygen from air at high temperature. It covers the issues and problems with respect to the selectivity and separation performance. The paper also presents different approaches applied to overcome these challenges. The future directions of ceramic-based membranes for oxygen separation from air are also presented. PMID:20813344

  15. Selective thermal and photooxidation of hydrocarbons in zeolites by oxygen

    DOEpatents

    Frei, Heinz; Blatter, Fritz; Sun, Hai

    2001-01-01

    A process for a combined selective thermal oxidation and photooxidation of hydrocarbons adsorbed onto zeolite matrices. A highly combined selective thermal oxidation and photooxidation of unsubstituted or alkyl substituted alkanes, alkenes, aromatics and cycloalkyls in solvent free zeolites under dark thermal conditions or under irradiation with visible light. The process oxidizes hydrocarbons almost completely selectively without substantial production of byproducts.

  16. Selective thermal and photooxidation of hydrocarbons in zeolites by oxygen

    DOEpatents

    Frei, Heinz; Blatter, Fritz; Sun, Hai

    1999-01-01

    A process for selective thermal oxidation or photooxidation of hydrocarbons adsorbed onto zeolite matrices. A highly selective thermal oxidation and photooxidation of unsubstituted or alkyl substituted alkanes, alkenes, aromatics and cycloalkyls in solvent free zeolites under dark thermal conditions or under irradiation with visible light. The process oxidizes hydrocarbons almost completely selectively without substantial production of byproducts.

  17. Selective thermal and photooxidation of hydrocarbons in zeolites by oxygen

    DOEpatents

    Frei, H.; Blatter, F.; Sun, H.

    1999-06-22

    A process is described for selective thermal oxidation or photooxidation of hydrocarbons adsorbed onto zeolite matrices. A highly selective thermal oxidation and photooxidation of unsubstituted or alkyl substituted alkanes, alkenes, aromatics and cycloalkyls in solvent free zeolites under dark thermal conditions or under irradiation with visible light. The process oxidizes hydrocarbons almost completely selectively without substantial production of byproducts. 19 figs.

  18. Selective thermal oxidation of hydrocarbons in zeolites by oxygen

    DOEpatents

    Frei, Heinz; Blatter, Fritz; Sun, Hai

    2000-01-01

    A process for selective thermal oxidation of hydrocarbons adsorbed onto zeolite matrices. A highly selective thermal oxidation of unsubstituted or alkyl substituted alkanes, alkenes, aromatics and cycloalkyls is carried out in solvent free zeolites under dark thermal conditions. The process oxidizes hydrocarbons almost completely selectively without substantial production of byproducts.

  19. Technical Note: Some Issues Related to the Selection of Polymers for Aerospace Oxygen Systems

    NASA Technical Reports Server (NTRS)

    Hirsch, David; Beeson, Harold

    2004-01-01

    Materials intended for use in aerospace oxygen systems are commonly screened for oxygen compatibility following NASA STD 6001. This standard allows qualification of materials based on results provided by only one test method. Potential issues related to this practice are reviewed and recommendations are proposed that would lead to improved aerospace oxygen systems safety.

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

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

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

  1. Selective reabsorption leading to multiple oscillations in the 8446-A atomic-oxygen laser.

    NASA Technical Reports Server (NTRS)

    Feld, M. S.; Feldman, B. J.; Javan, A.; Domash, L. H.

    1973-01-01

    Laser oscillation of atomic oxygen at 8446 A occurs in four closely spaced lines with peculiar intensity ratios, all detuned from the atomic center frequencies of the three fine-structure transitions. These anomalies are caused by the selective reabsorption of resonance radiation from the lower laser level by ground-state oxygen atoms. The selectivity results from the fact that the velocity distribution of the laser levels is considerably wider than that of the ground state, because of the dissociative mode of production of excited oxygen atoms. Possible extension of this mechanism to the atomic-hydrogen system is discussed.

  2. Oxygen reduction and oxygen evolution in DMSO based electrolytes: the role of the electrocatalyst.

    PubMed

    Bondue, C J; Reinsberg, P; Abd-El-Latif, A A; Baltruschat, H

    2015-10-14

    In the present paper the role of the electrode material in oxygen reduction in DMSO based electrolytes is elucidated using DEMS. We have found, employing platinum, gold, ruthenium rhodium, selenium decorated rhodium and boron doped diamond (BDD) as electrode materials, that the actual mechanism of oxygen reduction largely depends on the electrode material. At platinum, rhodium and selenium decorated rhodium the final reduction product, peroxide, is formed electrochemically. At gold and at low overpotentials oxygen is reduced to superoxide and peroxide is only formed by disproportionation of the latter. No oxygen reduction takes place at the diamond surface of the BDD-electrode, hence, showing unambiguously that oxygen reduction is an inner sphere reaction. Also, the rate of oxygen evolution varies with the electrode material, although the onset potential of oxygen evolution is not influenced. The amount of peroxide formed is limited to 1-2 monolayers. Contrary to intuition oxygen reduction and oxygen evolution from peroxide, therefore, are heterogeneous, electrocatalytic reactions. The finding of such an electrocatalytic effect is of great importance for the development and optimization of lithium-air batteries. Aside from the electrode material there are also effects of water as well as of the cation used in the electrolyte. This suggests an influence of the double layer at the interface between the electrode and the electrolyte on oxygen reduction in addition to the well-known higher stability of Na2O2 and K2O2. Electrospray ionization (ESI) results show that any effect of water in the Li(+) containing electrolyte is not due to an altered solvation of the cation. PMID:26371703

  3. Combustion in a multiburner furnace with selective flow of oxygen

    DOEpatents

    Bool, III, Lawrence E.; Kobayashi, Hisashi

    2004-03-02

    Improved operational characteristics such as improved fuel efficiency, reduction of NOx formation, reduction of the amount of unburned carbon in the ash, and lessened tendency to corrosion at the tube wall, in a multi-burner furnace are obtained by reducing the flow rate of combustion air to the burners and selectively individually feeding oxidant to only some of the burners.

  4. Haemoglobin-based oxygen carriers: indications and future applications.

    PubMed

    Njoku, Mary; St Peter, Deidre; Mackenzie, Colin F

    2015-02-01

    This article describes current oxygen-carrying solutions, four new products and new indications to increase the benefit/risk ratio of haemoglobin-based oxygen carriers compared to blood. Indications include when blood is not available, if blood is contaminated, is refused or contraindicated, and for organ preservation. PMID:25671471

  5. Atomic oxygen erosion considerations for spacecraft materials selection

    NASA Technical Reports Server (NTRS)

    Whitaker, Ann F.; Kamenetzky, Rachel R.

    1993-01-01

    The Long Duration Exposure Facility (LDEF) satellite carried 57 experiments that were designed to define the low-Earth orbit (LEO) space environment and to evaluate the impact of this environment on potential engineering materials and material processes. Deployed by the Shuttle Challenger in April of 1984, LDEF made over 32,000 orbits before being retrieved nearly 6 years later by the Shuttle Columbia in January of 1990. The Solar Array Passive LDEF Experiment (SAMPLE) AO171 contained approximately 300 specimens, representing numerous material classes and material processes. AO171 was located on LDEF in position A8 at a yaw of 38.1 degrees from the ram direction and was subjected to an atomic oxygen (AO) fluence of 6.93 x 10(exp 21) atoms/sq cm. LDEF AO171 data, as well as short-term shuttle data, will be discussed in this paper as it applies to engineering design applications of composites, bulk and thin film polymers, glassy ceramics, thermal control paints, and metals subjected to AO erosion.

  6. GAS PHASE SELECTIVE PHOTOXIDATION OF ALCOHOLS USING LIGHT-ACTIVATED TITANIUM DIOXIDE AND MOLECULAR OXYGEN

    EPA Science Inventory

    Gas Phase Selective Oxidation of Alcohols Using Light-Activated Titanium Dioxide and Molecular Oxygen

    Gas phase selective oxidations of various primary and secondary alcohols are studied in an indigenously built stainless steel up-flow photochemical reactor using ultravi...

  7. Oxygen as a chemoattractant: confirming cellular hypoxia in paper-based invasion assays.

    PubMed

    Truong, Andrew S; Lockett, Matthew R

    2016-06-21

    Low oxygen tension, or hypoxia, is a common occurrence in solid tumors. Hypoxia is a master regulator of cellular phenotype, and is associated with increased tumor invasion and aggressiveness as well as adverse patient prognosis. Oxygen has recently been linked with the selective movement of different cancer cell types in three-dimensional invasion assays utilizing paper-based scaffolds. It has remained unclear, however, if cells in these paper-based invasion assays are experiencing hypoxia. In this manuscript, we adapted cell-based methods to measure oxygen tension in our 3D invasion assays: the adduction of pimonidazole to free thiols in the cell, indicative of a reducing environment; the localization of hypoxia inducible factors to the nucleus; and the expression of hypoxia-regulated gene products. We utilized each method to compare the oxygen tension in different locations of the paper-based invasion stacks and found an oxygen gradient is indeed forming. Specifically, we found that the extent of pimonidazole binding, as well as the levels and activities of nucleus-localized HIF-α proteins, increase as the distance between the cells and the source of fresh medium increases. These complementary cell-based readouts not only confirm the selective invasion we observe is due to an oxygen gradient, they also show the gradient is temporal in nature and evolves with increasing culture period. PMID:27138213

  8. A comparative study on the potential of oxygen release by roots of selected wetland plants

    NASA Astrophysics Data System (ADS)

    Yao, Fang; Shen, Gen-xiang; Li, Xue-lian; Li, Huai-zheng; Hu, Hong; Ni, Wu-zhong

    The capacity of root oxygen release by selected wetland plants pre-grown under both nutrient solution and artificial wastewater conditions were determined. The results indicated that the significant differences of root oxygen release by the tested wetland plants existed, and the biochemical process was the main source of root oxygen release as oxygen released by Vetiveria zizanioides L. Nash roots through biochemical process was contributed to 77% and 74% of total root oxygen release under nutrient solution conditions and artificial wastewater conditions, respectively, and that was 72% and 71% of total root oxygen release for Cyperus alternifolius L. It was found that the formation of root plaque with iron oxide was a function of root oxygen release as iron oxide concentration in root plaque was positively correlated to the potential of oxygen released by wetland plant roots with the regression coefficients as 0.874 *( p < 0.05) under nutrient solution conditions and 0.944 **( p < 0.01) under artificial wastewater conditions, which could be regarded as an important mechanism of wetland plants being tolerant to anoxia during wastewater treatment. It was suggested that the potential of root oxygen release could be used as a parameter for selecting wetland plants that can increase oxygen supply to soil or substrate of constructed wetlands and enhance nutrient transformation and removal, and V. zizanioides L. Nash with the highest potential of root oxygen release and higher tolerance to wastewater could be recommended to establish vegetated wetlands for treating nutrient-rich wastewater such as domestic wastewater.

  9. Synergistic Effects in Bimetallic Palladium-Copper Catalysts Improve Selectivity in Oxygenate Coupling Reactions.

    PubMed

    Goulas, Konstantinos A; Sreekumar, Sanil; Song, Yuying; Kharidehal, Purnima; Gunbas, Gorkem; Dietrich, Paul J; Johnson, Gregory R; Wang, Y C; Grippo, Adam M; Grabow, Lars C; Gokhale, Amit A; Toste, F Dean

    2016-06-01

    Condensation reactions such as Guerbet and aldol are important since they allow for C-C bond formation and give higher molecular weight oxygenates. An initial study identified Pd-supported on hydrotalcite as an active catalyst for the transformation, although this catalyst showed extensive undesirable decarbonylation. A catalyst containing Pd and Cu in a 3:1 ratio dramatically decreased decarbonylation, while preserving the high catalytic rates seen with Pd-based catalysts. A combination of XRD, EXAFS, TEM, and CO chemisorption and TPD revealed the formation of CuPd bimetallic nanoparticles with a Cu-enriched surface. Finally, density functional theory studies suggest that the surface segregation of Cu atoms in the bimetallic alloy catalyst produces Cu sites with increased reactivity, while the Pd sites responsible for unselective decarbonylation pathways are selectively poisoned by CO. PMID:27195582

  10. Influence of oxygen and pH on the selective oxidation of ethanol on Pd catalysts

    SciTech Connect

    Hibbitts, David D.; Neurock, Matthew

    2013-03-01

    The selective oxidation of ethanol on supported Pd is catalytically promoted by the presence of hydroxide species on the Pd surface as well as in solution. These hydroxide intermediates act as Brønsted bases which readily abstract protons from the hydroxyl groups of adsorbed or solution-phase alcohols. The C1AH bond of the resulting alkoxide is subsequently activated on the metal surface via hydride elimination to form acetaldehyde. Surface and solution-phase hydroxide intermediates can also readily react with the acetaldehyde via nucleophilic addition to form a germinal diol intermediate, which subsequently undergoes a second C1AH bond activation on Pd to form acetic acid. The role of O2 is to remove the electrons produced in the oxidation reaction via the oxygen reduction reaction over Pd. The reduction reaction also regenerates the hydroxide intermediates and removes adsorbed hydrogen that is produced during the oxidation.

  11. Pallidol, a resveratrol dimer from red wine, is a selective singlet oxygen quencher

    SciTech Connect

    He Shan; Jiang Liyan; Wu Bin; Pan Yuanjiang; Sun Cuirong

    2009-02-06

    Pallidol is a naturally occurring resveratrol dimer from red wine with antioxidant and antifungal activities. In this report, with the use of the EPR spin-trapping technique, the scavenging and quenching effects of pallidol on reactive oxygen species (ROS) were investigated. The results demonstrated that pallidol showed strong quenching effects on singlet oxygen at very low concentrations, but it was ineffective to scavenge hydroxyl radicals or superoxide anions. Further kinetic study revealed that the reaction of pallidol with singlet oxygen had an extremely high rate constant (k{sub a} = 1.71 x 10{sup 10}). Therefore, pallidol is a potent and selective singlet oxygen quencher in aqueous systems. It may be used in singlet oxygen-mediated diseases as a pharmacological agent, which may contribute to the health beneficial effects of red wine.

  12. Oxygen Transport in Melts Based on V2O5

    NASA Astrophysics Data System (ADS)

    Klimashin, Anton; Belousov, Valery

    2016-02-01

    An oxygen ion transport model was developed for oxide melts based on V2O5. Within the framework of this model, the values of the parabolic rate constant of catastrophic oxidation of V2O5-deposited copper and the oxygen flux through the slags based on molten V2O5 were calculated and compared with experimental data. The calculated and experimental values are of the same order of magnitude which shows an adequacy of the model.

  13. Cerebral Blood Oxygenation Measurement Based on Oxygen-dependent Quenching of Phosphorescence

    PubMed Central

    Sakadžić, Sava; Roussakis, Emmanuel; Yaseen, Mohammad A.; Mandeville, Emiri T.; Srinivasan, Vivek J.; Arai, Ken; Ruvinskaya, Svetlana; Wu, Weicheng; Devor, Anna; Lo, Eng H.; Vinogradov, Sergei A.; Boas, David A.

    2011-01-01

    Monitoring of the spatiotemporal characteristics of cerebral blood and tissue oxygenation is crucial for better understanding of the neuro-metabolic-vascular relationship. Development of new pO2 measurement modalities with simultaneous monitoring of pO2 in larger fields of view with higher spatial and/or temporal resolution will enable greater insight into the functioning of the normal brain and will also have significant impact on diagnosis and treatment of neurovascular diseases such as stroke, Alzheimer's disease, and head injury. Optical imaging modalities have shown a great potential to provide high spatiotemporal resolution and quantitative imaging of pO2 based on hemoglobin absorption in visible and near infrared range of optical spectrum. However, multispectral measurement of cerebral blood oxygenation relies on photon migration through the highly scattering brain tissue. Estimation and modeling of tissue optical parameters, which may undergo dynamic changes during the experiment, is typically required for accurate estimation of blood oxygenation. On the other hand, estimation of the partial pressure of oxygen (pO2) based on oxygen-dependent quenching of phosphorescence should not be significantly affected by the changes in the optical parameters of the tissue and provides an absolute measure of pO2. Experimental systems that utilize oxygen-sensitive dyes have been demonstrated in in vivo studies of the perfused tissue as well as for monitoring the oxygen content in tissue cultures, showing that phosphorescence quenching is a potent technology capable of accurate oxygen imaging in the physiological pO2 range. Here we demonstrate with two different imaging modalities how to perform measurement of pO2 in cortical vasculature based on phosphorescence lifetime imaging. In first demonstration we present wide field of view imaging of pO2 at the cortical surface of a rat. This imaging modality has relatively simple experimental setup based on a CCD camera and a

  14. Analysis of selected specimens from the STS-46 Energetic Oxygen Interaction with Materials-3 experiment

    NASA Technical Reports Server (NTRS)

    Golden, Johnny L.; Bourassa, Roger J.; Dursch, Harry W.; Pippin, H. Gary

    1995-01-01

    The Energetic Oxygen Interaction with Materials 3 (EOIM-3) experiment was flown on the STS-46 mission, which was launched on 31 Jul. 1992 and returned 8 Aug. 1992. Boeing specimens were located on both the NASA Marshall Space Flight Center (MSFC) tray and the Ballistic Missile Defense Organization (BMDO) tray integrated by the Jet Propulsion Laboratory (JPL). The EOIM-3 pallet was mounted in the Space Shuttle payload bay near the aft bulkhead. During the mission, the atomic oxygen (AO) exposure levels of specimens in these passive sample trays was about 2.3 x 10(exp 20) atoms/sq cm. The specimens also received an estimated 22 equivalent sun hours of solar exposure. In addition, it appears that the EOIM-3 pallet was exposed to a silicone contamination source and many specimens had a thin layer of silicon based deposit on their surfaces after the flight. The specimens on the MSFC tray included seven solid film lubricants, a selection of butyl rubber (B612) and silicone (S383) o-rings, three indirect scatter surfaces, and Silver/Fluorinated Ethylene Propylene (Ag/FEP) and Chemglaze A276 specimens which had previously flown on trailing edge locations of the Long Duration Exposure Facility (LDEF). The specimens on the JPL tray included composites previously flown on LDEF and two indirect scattering surfaces.

  15. Modeling of the Temperature Effect on Oxygen Absorption by Iron-Based Oxygen Scavengers.

    PubMed

    Polyakov, Vladimir A; Miltz, Joseph

    2016-01-01

    A new engineering-oriented model for prediction of the effect of temperature on the kinetics of oxygen absorption by iron-based oxygen scavengers (IOSs) was developed. The model is based on the physicochemical mechanism of the O2 scavenging process by the active component of the IOS (iron powder). The conclusions of this study are: (1) the iron deposits formed on the iron particles are composed of 2 different layers: an inner layer of Fe3 O4 and an outer layer of FeOOH that vanishes with the depletion of oxygen. (2) The model considers the chemical processes in the heterogeneous closed system "Fe-H2 O-NaCl-O2 " and describes the kinetics of oxygen absorption by the powder, depending on the characteristics of the system. (3) The nonlinear ordinary differential equation (ODE) of the O2 absorption kinetics was derived and a simple approximate solution to this ODE was obtained theoretically that is similar to the empirical exponential formula published in the relevant literature. (4) The temperature dependence of the oxygen absorption rate is more complicated than that described by the Arrhenius equation. PMID:26650762

  16. Cerebral blood oxygenation measurement based on oxygen-dependent quenching of phosphorescence.

    PubMed

    Sakadžić, Sava; Roussakis, Emmanuel; Yaseen, Mohammad A; Mandeville, Emiri T; Srinivasan, Vivek J; Arai, Ken; Ruvinskaya, Svetlana; Wu, Weicheng; Devor, Anna; Lo, Eng H; Vinogradov, Sergei A; Boas, David A

    2011-01-01

    Monitoring of the spatiotemporal characteristics of cerebral blood and tissue oxygenation is crucial for better understanding of the neuro-metabolic-vascular relationship. Development of new pO2 measurement modalities with simultaneous monitoring of pO2 in larger fields of view with higher spatial and/or temporal resolution will enable greater insight into the functioning of the normal brain and will also have significant impact on diagnosis and treatment of neurovascular diseases such as stroke, Alzheimer's disease, and head injury. Optical imaging modalities have shown a great potential to provide high spatiotemporal resolution and quantitative imaging of pO2 based on hemoglobin absorption in visible and near infrared range of optical spectrum. However, multispectral measurement of cerebral blood oxygenation relies on photon migration through the highly scattering brain tissue. Estimation and modeling of tissue optical parameters, which may undergo dynamic changes during the experiment, is typically required for accurate estimation of blood oxygenation. On the other hand, estimation of the partial pressure of oxygen (pO2) based on oxygen-dependent quenching of phosphorescence should not be significantly affected by the changes in the optical parameters of the tissue and provides an absolute measure of pO2. Experimental systems that utilize oxygen-sensitive dyes have been demonstrated in in vivo studies of the perfused tissue as well as for monitoring the oxygen content in tissue cultures, showing that phosphorescence quenching is a potent technology capable of accurate oxygen imaging in the physiological pO2 range. Here we demonstrate with two different imaging modalities how to perform measurement of pO2 in cortical vasculature based on phosphorescence lifetime imaging. In first demonstration we present wide field of view imaging of pO2 at the cortical surface of a rat. This imaging modality has relatively simple experimental setup based on a CCD camera and a

  17. Melatonin: detoxification of oxygen and nitrogen-based toxic reactants.

    PubMed

    Reiter, Russel J; Tan, Dun-Xian; Manchester, Lucien C; Lopez-Burillo, Silvia; Sainz, Rosa M; Mayo, Juan C

    2003-01-01

    In the last decade, melatonin has been found to be highly protective against damage to macromolecules resulting from oxygen and nitrogen-based reactants. Considering this, numerous studies have examined the mechanisms whereby this indoleamine directly detoxifies these damaging agents. The evidence is compelling that melatonin scavenges several oxygen-derived reactive agents including the hydroxyl radical (OH), hydrogen peroxide (H2O2), singlet oxygen (1O2) and hypochlorous acid (HOCl). Additionally, melatonin reportedly reacts with nitric oxide (NO), the peroxynitrite anion (ONOO-) and/or peroxynitrous acid (ONOOH) to detoxify them. In some cases the products that are formed as a consequence of melatonin's scavenging actions have been identified. Whereas the ability of melatonin to neutralize these toxic agents likely accounts, in part, for the antioxidant activity of melatonin, it is not the only means by which melatonin serves to protect molecules from oxygen and nitrogen-based reactive metabolites. PMID:15206772

  18. Tailoring Selectivity for Electrocatalytic Oxygen Evolution on Ruthenium Oxides by Zn Substitution

    SciTech Connect

    Petrykin, V.; Macounova, K; Shlyakhtin, O; Krtil, P

    2010-01-01

    Controlling gas emissions: Versatile control of the selectivity of an oxide electrocatalyst in the oxygen- and chlorine-evolution reactions was demonstrated by Zn substitution in RuO{sub 2}. The incorporation of Zn into the rutile structure alters the cation sequence along the [001] direction and modifies the structure of the active sites for both gas-evolution processes.

  19. DETERMINATION OF LETHAL DISSOLVED OXYGEN LEVELS FOR SELECTED MARINE AND ESTUARINE FISHES, CRUSTACEANS AND A BIVALVE

    EPA Science Inventory

    The objective of this study was to provide a database of the incipient lethal concentrations for reduced dissolved oxygen (DO) for selected marine and estuarine species including 12 species of fish, 9 crustaceans, and 1 bivalve. All species occur in the Virginian Province, USA, w...

  20. Chemisorbed Oxygen on the Surface of Catalyst-Improved Cataluminescence Selectivity.

    PubMed

    Wang, Siming; Shi, Wenying; Lu, Chao

    2016-05-01

    It is a critical scientific challenge to improve the selectivity of cataluminescence (CTL). Chemisorbed oxygen on the surface of catalysts is one of the essential factors for catalytic oxidization of gaseous reactant molecules during the CTL process. Therefore, it is necessary to investigate the influence of chemisorbed oxygen on the CTL. There exists different chemisorbed oxygen content on the surface of Y2O3 and its precursor, layered rare-earth yttrium hydroxides (Y-NO3-LRHs). In this work, both of them were employed as catalyst models to catalytically oxidize common volatile organic compounds (VOCs) in order to explore the relationship between chemisorbed oxygen and CTL selectivity. It was found that LRHs demonstrated a superior selectivity toward ethyl ether in comparison with Y2O3. The mechanism study showed that only ethyl ether demonstrated the CTL behavior through the catalytical oxidation into CH3CHO* intermediates on the surface of LRHs, while no CTL emissions occurred for the other VOCs because the insufficient chemisorbed oxygen of LRHs was incapable of oxidizing these VOCs into CO2* intermediates. In addition, the luminescent rare-earth Eu(3+) ions were doped in Y-NO3-LRHs to further improve the CTL intensity of ethyl ether through the efficient energy transfer between CH3CHO* intermediates and Eu(3+) ions. Our work opens up a new route to improve CTL selectivity by tuning the chemisorbed oxygen on the surface of catalysts, different from the previous strategies of exploiting new solid catalysts or decreasing CTL reaction temperature. PMID:27054376

  1. 4-N,N-Dimethylaminopyridine promoted selective oxidation of methyl aromatics with molecular oxygen.

    PubMed

    Zhang, Zhan; Gao, Jin; Wang, Feng; Xu, Jie

    2012-01-01

    4-N,N-Dimethylaminopyridine (DMAP) as catalyst in combination with benzyl bromide was developed for the selective oxidation of methyl aromatics. DMAP exhibited higher catalytic activity than other pyridine analogues, such as 4-carboxypyridine, 4-cyanopyridine and pyridine. The sp3 hybrid carbon-hydrogen (C-H) bonds of different methyl aromatics were successfully oxygenated with molecular oxygen. The real catalyst is due to the formation of a pyridine onium salt from the bromide and DMAP. The onium salt was well characterized by NMR and the reaction mechanism was discussed. PMID:22466855

  2. A Porous Tissue Engineering Scaffold Selectively Degraded by Cell-Generated Reactive Oxygen Species

    PubMed Central

    Martin, John R.; Gupta, Mukesh K.; Page, Jonathan M.; Yu, Fang; Davidson, Jeffrey M.; Guelcher, Scott A.

    2014-01-01

    Biodegradable tissue engineering scaffolds are commonly fabricated from poly(lactide-co-glycolide) (PLGA) or similar polyesters that degrade by hydrolysis. PLGA hydrolysis generates acidic breakdown products that trigger an accelerated, autocatalytic degradation mechanism that can create mismatched rates of biomaterial breakdown and tissue formation. Reactive oxygen species (ROS) are key mediators of cell function in both health and disease, especially at sites of inflammation and tissue healing, and induction of inflammation and ROS are natural components of the in vivo response to biomaterial implantation. Thus, polymeric biomaterials that are selectively degraded by cell-generated ROS may have potential for creating tissue engineering scaffolds with better matched rates of tissue in-growth and cell-mediated scaffold biodegradation. To explore this approach, a series of poly(thioketal) (PTK) urethane (PTK-UR) biomaterial scaffolds were synthesized that degrade specifically by an ROS-dependent mechanism. PTK-UR scaffolds had significantly higher compressive moduli than analogous poly(ester urethane) (PEUR) scaffolds formed from hydrolytically-degradable ester-based diols (p < 0.05). Unlike PEUR scaffolds, the PTK-UR scaffolds were stable under aqueous conditions out to 25 weeks but were selectively degraded by ROS, indicating that their biodegradation would be exclusively cell-mediated. The in vitro oxidative degradation rates of the PTK-URs followed first-order degradation kinetics, were significantly dependent on PTK composition (p < 0.05), and correlated to ROS concentration. In subcutaneous rat wounds, PTK-UR scaffolds supported cellular infiltration and granulation tissue formation, followed first-order degradation kinetics over 7 weeks, and produced significantly greater stenting of subcutaneous wounds compared to PEUR scaffolds. These combined results indicate that ROS-degradable PTK-UR tissue engineering scaffolds have significant advantages over analogous

  3. Process for selection of Oxygen-tolerant algal mutants that produce H.sub.2

    DOEpatents

    Ghirardi, Maria L.; Seibert, Michael

    1999-01-01

    A process for selection of oxygen-tolerant, H.sub.2 -producing algal mutant cells comprising: (a) growing algal cells photoautotrophically under fluorescent light to mid log phase; (b) inducing algal cells grown photoautrophically under fluorescent light to mid log phase in step (a) anaerobically by (1) resuspending the cells in a buffer solution and making said suspension anaerobic with an inert gas; (2) incubating the suspension in the absence of light at ambient temperature; (c) treating the cells from step (b) with metronidazole, sodium azide, and added oxygen to controlled concentrations in the presence of white light. (d) washing off metronidazole and sodium azide to obtain final cell suspension; (e) plating said final cell suspension on a minimal medium and incubating in light at a temperature sufficient to enable colonies to appear; (f) counting the number of colonies to determine the percent of mutant survivors; and (g) testing survivors to identify oxygen-tolerant H.sub.2 -producing mutants.

  4. Phosphorescent oxygen sensors based on nanostructured polyolefin substrates.

    PubMed

    Gillanders, Ross N; Arzhakova, Olga V; Hempel, Andreas; Dolgova, Alla; Kerry, Joe P; Yarysheva, Larisa M; Bakeev, Nikolai F; Volynskii, Alexander L; Papkovsky, Dmitri B

    2010-01-15

    New phosphorescent oxygen-sensitive materials based on nanostructured high density polyethylene and polypropylene films are described. The polymer substrates undergo treatment by a solvent crazing process to create a well-developed network of controlled, nanometer-size pores. Indicator dye molecules are then embedded by physical entrapment in such nanostructures which subsequently can be healed. Such sensors demonstrate improved working characteristics and allow simple, cost-efficient production and disposable use. They are well suited for large-scale applications such as nondestructive control of residual oxygen and "smart" packaging. PMID:20038091

  5. Catalytic reduction of carbon monoxide: Selective synthesis of C1 and higher oxygenates

    SciTech Connect

    Mahajan, D.; Gupta, N.

    1993-05-01

    A-step synthesis of methyl formate, a C2 oxygenate, has been developed at BNL. The following features of the LLTMeOH technology and related studies are of interest: The BNL approach exemplifies a synergistic effect of two combined catalysts. The chosen reaction conditions favor methyl formate synthesis. The only identified by-product is methanol. The effect of stirring speed, temperature, solvent, catalyst loading, and syngas composition is noted.Of particular interest is a run with H{sub 2}CO = 37%/63% in which methyl formate selectivity approached 100%. Bases (K{sub 2}CO{sub 3}KHCO{sub 2}, KOCO{sub 2}Me) other than alkoxide have been used for methyl formate synthesis. A gas phase infrared mechanistic study of methanol carbonylation reaction, carried out with methoxide catalyst at 130{degree}C under 1/1 (H{sub 2}CO) syngas, showed that the fast alkyl formate anion formations was followed by an extremely slow protonation step. It appears that under these conditions, protonation step is rate determining (RDS). This approach results in enhancing carbon conversion of syngas derived from coal or other sources that produce CO-rich gas.

  6. Catalytic reduction of carbon monoxide: Selective synthesis of C1 and higher oxygenates

    SciTech Connect

    Mahajan, D.; Gupta, N.

    1993-01-01

    A-step synthesis of methyl formate, a C2 oxygenate, has been developed at BNL. The following features of the LLTMeOH technology and related studies are of interest: The BNL approach exemplifies a synergistic effect of two combined catalysts. The chosen reaction conditions favor methyl formate synthesis. The only identified by-product is methanol. The effect of stirring speed, temperature, solvent, catalyst loading, and syngas composition is noted.Of particular interest is a run with H[sub 2]CO = 37%/63% in which methyl formate selectivity approached 100%. Bases (K[sub 2]CO[sub 3]KHCO[sub 2], KOCO[sub 2]Me) other than alkoxide have been used for methyl formate synthesis. A gas phase infrared mechanistic study of methanol carbonylation reaction, carried out with methoxide catalyst at 130[degree]C under 1/1 (H[sub 2]CO) syngas, showed that the fast alkyl formate anion formations was followed by an extremely slow protonation step. It appears that under these conditions, protonation step is rate determining (RDS). This approach results in enhancing carbon conversion of syngas derived from coal or other sources that produce CO-rich gas.

  7. The impact of meter-scale oxygen gradients in the selective degradation of organic matter: implications for proxy interpretation

    NASA Astrophysics Data System (ADS)

    Bogus, K.; Zonneveld, K. A.; Fischer, D.; Kasten, S.; Versteegh, G.

    2010-12-01

    The reconstruction of upper oceanographic conditions is often founded on organic matter-based proxies that have their origin within the photic zone and measurably reflect these conditions. It is well known that only a fraction of the organic matter that is produced in the upper water column reaches the sea floor where it is further degraded by aerobic and anaerobic remineralization processes. During the last decades it has become clear that preservation is highly selective and can, depending on the proxy used, severely influence the proxy outcome. One of the main factors that can influence the preservation of organic matter is the presence of oxygen. Therefore, for an adequate interpretation of proxy signals, it is essential to obtain insight as to how the extent of oxygen availability might alter the proxy outcome. Until now, the majority of studies investigating the impact of selective aerobic degradation on organic matter-based proxies have suffered from a priori environmental spatial heterogeneity. In other words, a large distance between sample locations introduces a source of error in that additional factors, such as lateral transport and differing photic zone conditions, cannot be completely discounted as contributing reasons for a change in proxy ratios during interpretation. This degree of uncertainty makes it difficult to separate initial environmentally-induced heterogeneity, such as varying temperatures and nutrient levels, from those induced by selective aerobic degradation. In order to constrain these problems and evaluate the extent of early selective aerobic degradation on proxies in surface sediments, we restricted sampling distance to meter-scale oxygen gradients existing on the margins of cold seeps in the northeastern Arabian Sea. These samples were retrieved along a gradient from the methane pocket to the outer rim of the methane-influenced area by computer-steered push coring using the ROV Quest during RV Meteor cruise M74/3 in November 2007

  8. Quantitative Microplate-Based Respirometry with Correction for Oxygen Diffusion

    PubMed Central

    2009-01-01

    Respirometry using modified cell culture microplates offers an increase in throughput and a decrease in biological material required for each assay. Plate based respirometers are susceptible to a range of diffusion phenomena; as O2 is consumed by the specimen, atmospheric O2 leaks into the measurement volume. Oxygen also dissolves in and diffuses passively through the polystyrene commonly used as a microplate material. Consequently the walls of such respirometer chambers are not just permeable to O2 but also store substantial amounts of gas. O2 flux between the walls and the measurement volume biases the measured oxygen consumption rate depending on the actual [O2] gradient. We describe a compartment model-based correction algorithm to deconvolute the biological oxygen consumption rate from the measured [O2]. We optimize the algorithm to work with the Seahorse XF24 extracellular flux analyzer. The correction algorithm is biologically validated using mouse cortical synaptosomes and liver mitochondria attached to XF24 V7 cell culture microplates, and by comparison to classical Clark electrode oxygraph measurements. The algorithm increases the useful range of oxygen consumption rates, the temporal resolution, and durations of measurements. The algorithm is presented in a general format and is therefore applicable to other respirometer systems. PMID:19555051

  9. Fundamental Vocabulary Selection Based on Word Familiarity

    NASA Astrophysics Data System (ADS)

    Sato, Hiroshi; Kasahara, Kaname; Kanasugi, Tomoko; Amano, Shigeaki

    This paper proposes a new method for selecting fundamental vocabulary. We are presently constructing the Fundamental Vocabulary Knowledge-base of Japanese that contains integrated information on syntax, semantics and pragmatics, for the purposes of advanced natural language processing. This database mainly consists of a lexicon and a treebank: Lexeed (a Japanese Semantic Lexicon) and the Hinoki Treebank. Fundamental vocabulary selection is the first step in the construction of Lexeed. The vocabulary should include sufficient words to describe general concepts for self-expandability, and should not be prohibitively large to construct and maintain. There are two conventional methods for selecting fundamental vocabulary. The first is intuition-based selection by experts. This is the traditional method for making dictionaries. A weak point of this method is that the selection strongly depends on personal intuition. The second is corpus-based selection. This method is superior in objectivity to intuition-based selection, however, it is difficult to compile a sufficiently balanced corpora. We propose a psychologically-motivated selection method that adopts word familiarity as the selection criterion. Word familiarity is a rating that represents the familiarity of a word as a real number ranging from 1 (least familiar) to 7 (most familiar). We determined the word familiarity ratings statistically based on psychological experiments over 32 subjects. We selected about 30,000 words as the fundamental vocabulary, based on a minimum word familiarity threshold of 5. We also evaluated the vocabulary by comparing its word coverage with conventional intuition-based and corpus-based selection over dictionary definition sentences and novels, and demonstrated the superior coverage of our lexicon. Based on this, we conclude that the proposed method is superior to conventional methods for fundamental vocabulary selection.

  10. Structural basis for oxygen degradation domain selectivity of the HIF prolyl hydroxylases

    PubMed Central

    Chowdhury, Rasheduzzaman; Leung, Ivanhoe K. H.; Tian, Ya-Min; Abboud, Martine I.; Ge, Wei; Domene, Carmen; Cantrelle, François-Xavier; Landrieu, Isabelle; Hardy, Adam P.; Pugh, Christopher W.; Ratcliffe, Peter J.; Claridge, Timothy D. W.; Schofield, Christopher J.

    2016-01-01

    The response to hypoxia in animals involves the expression of multiple genes regulated by the αβ-hypoxia-inducible transcription factors (HIFs). The hypoxia-sensing mechanism involves oxygen limited hydroxylation of prolyl residues in the N- and C-terminal oxygen-dependent degradation domains (NODD and CODD) of HIFα isoforms, as catalysed by prolyl hydroxylases (PHD 1–3). Prolyl hydroxylation promotes binding of HIFα to the von Hippel–Lindau protein (VHL)–elongin B/C complex, thus signalling for proteosomal degradation of HIFα. We reveal that certain PHD2 variants linked to familial erythrocytosis and cancer are highly selective for CODD or NODD. Crystalline and solution state studies coupled to kinetic and cellular analyses reveal how wild-type and variant PHDs achieve ODD selectivity via different dynamic interactions involving loop and C-terminal regions. The results inform on how HIF target gene selectivity is achieved and will be of use in developing selective PHD inhibitors. PMID:27561929

  11. Structural basis for oxygen degradation domain selectivity of the HIF prolyl hydroxylases.

    PubMed

    Chowdhury, Rasheduzzaman; Leung, Ivanhoe K H; Tian, Ya-Min; Abboud, Martine I; Ge, Wei; Domene, Carmen; Cantrelle, François-Xavier; Landrieu, Isabelle; Hardy, Adam P; Pugh, Christopher W; Ratcliffe, Peter J; Claridge, Timothy D W; Schofield, Christopher J

    2016-01-01

    The response to hypoxia in animals involves the expression of multiple genes regulated by the αβ-hypoxia-inducible transcription factors (HIFs). The hypoxia-sensing mechanism involves oxygen limited hydroxylation of prolyl residues in the N- and C-terminal oxygen-dependent degradation domains (NODD and CODD) of HIFα isoforms, as catalysed by prolyl hydroxylases (PHD 1-3). Prolyl hydroxylation promotes binding of HIFα to the von Hippel-Lindau protein (VHL)-elongin B/C complex, thus signalling for proteosomal degradation of HIFα. We reveal that certain PHD2 variants linked to familial erythrocytosis and cancer are highly selective for CODD or NODD. Crystalline and solution state studies coupled to kinetic and cellular analyses reveal how wild-type and variant PHDs achieve ODD selectivity via different dynamic interactions involving loop and C-terminal regions. The results inform on how HIF target gene selectivity is achieved and will be of use in developing selective PHD inhibitors. PMID:27561929

  12. Reactive lattice oxygen sites for C sub 4 -hydrocarbon selective oxidation over. beta. -VOPO sub 4

    SciTech Connect

    Lashier, M.E.; Schrader, G.L. )

    1991-03-01

    The role of lattice oxygen species in the catalytic oxidation of n-butene to maleic anhydride has been investigated using {beta}-VOPO{sub 4} labeled with {sup 18}O. The catalyst was prepared by stoichiometric reaction of (VO){sub 2}P{sub 2}O{sub 7} with {sup 18}O{sub 2} using solid state preparation techniques. The {beta}-VOPO{sub 7/2} {sup 18}O{sub 1/2} was characterized using laser Raman and Fourier transform infrared spectroscopies: preferential incorporation at P-O-V sites was observed. A pulse reactor was used to react n-butane, 1-butene, 1,3-butadiene, furan, {gamma}-butyrolactone, and maleic anhydride with the catalyst in the absence of gas-phase O{sub 2}. Incorporation of {sup 18}O into the products was monitored by mass spectrometry. Specific lattice oxygen sites could be associated with the reaction pathways for selective or nonselective oxidation. The results of this study also indicate that the initial interaction of n-butane with {beta}-VOPO{sub 4} is fundamentally different from the initial interaction of olefins or oxygenated species. The approach used in this research-referred to as Isotopic Reactive-Site Mapping-is a potentially powerful method for probing the reactive lattice sites of other selective oxidation catalysts.

  13. Wavelength selective excitation of surface oxygen anions on highly dispersed MgO

    NASA Astrophysics Data System (ADS)

    Diwald, Oliver; Sterrer, Martin; Knözinger, Erich; Sushko, Peter V.; Shluger, Alexander L.

    2002-01-01

    Monochromatic UV light in the spectral interval between 4.0 and 5.5 eV is used in order to selectively excite 3- and 4-coordinated oxygen anion sites on the surface of MgO nanoparticles exposed to O2 gas. As a result, two different paramagnetic O- surface species and also ozonide anions O3- are observed by electron paramagnetic resonance (EPR) spectroscopy. The relative abundance of each of the O- species exhibits a specific dependence on the energy of the exciting photons. EPR data together with the results of theoretical modeling suggest that both O- species are located at 3-coordinated sites having different local environments. At sufficiently high O2 pressures molecular oxygen does not only act as an electron trap, favoring the O- formation, but it also contributes to UV induced O3- formation with a maximum efficiency at 4.2 eV.

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

    PubMed

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

    2016-04-01

    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. PMID:26871428

  15. Conceptual Design of Oxygen-Based PC Boiler

    SciTech Connect

    Andrew Seltzer; Zhen Fan

    2005-09-01

    sequestration. FW has developed a conceptual design of an O{sub 2} fired boiler to determine overall plant performance and economics. Five subtasks were conducted: (1) a literature review, (2) a system design and analysis, (3) a low NOx burner design and analysis, (4) a furnace and heat recovery area design analysis, and (5) an economic analysis. The objective of the literature search is to locate any data/information relevant to the Oxygen-Based PC Boiler conceptual design. The objective of the system design and analysis task is to optimize the PC boiler plant by maximizing system efficiency within practical considerations. Simulations of the oxygen-fired plant with CO{sub 2} sequestration were conducted using Aspen Plus and were compared to a reference air-fired 460 MW plant. Flue gas recycle is used in the O{sub 2}-fired PC to control the flame temperature. Parametric runs were made to determine the effect of flame temperature on system efficiency and required waterwall material and thickness. The degree of improvement on system efficiency of various modifications including hot gas recycle, purge gas recycle, flue gas feedwater recuperation, and recycle purge gas expansion were investigated. The selected O{sub 2}-fired design case has a system efficiency of 30.6% compared to the air-fired system efficiency of 36.7%. The design O{sub 2}-fired case requires T91 waterwall material and has a waterwall surface area of only 65% of the air-fired reference case. The objective of the low NOx burner design and analysis task is to optimize the burner design to ensure stable ignition, to provide safe operation, and to minimize pollutant formation. The burners were designed and analyzed using the Fluent CFD computer program. Four burner designs were developed: (1) with no OFG and 65% flue gas recycle, (2) with 20% OFG and 65% flue gas recycle, (3) with no OFG and 56% flue gas recycle and (4) with 20% OFG and 56% flue gas recycle. A 3-D Fluent simulation was made of a single wall

  16. Effects of Hemoglobin-Based Oxygen Carriers on Blood Coagulation

    PubMed Central

    Roghani, Kimia; Holtby, Randall J.; Jahr, Jonathan S.

    2014-01-01

    For many decades, Hemoglobin-based oxygen carriers (HBOCs) have been central in the development of resuscitation agents that might provide oxygen delivery in addition to simple volume expansion. Since 80% of the world population lives in areas where fresh blood products are not available, the application of these new solutions may prove to be highly beneficial (Kim and Greenburg 2006). Many improvements have been made to earlier generation HBOCs, but various concerns still remain, including coagulopathy, nitric oxide scavenging, platelet interference and decreased calcium concentration secondary to volume expansion (Jahr et al. 2013). This review will summarize the current challenges faced in developing HBOCs that may be used clinically, in order to guide future research efforts in the field. PMID:25514567

  17. Selective para hydroxylation of phenol and aniline by singlet molecular oxygen.

    PubMed

    Briviba, K; Devasagayam, T P; Sies, H; Steenken, S

    1993-01-01

    Phenol reacts with singlet oxygen (1O2) generated in aqueous solution (H2O or D2O) by (a) the exposure of methylene blue to light or (b) the thermal dissociation of the endoperoxide of 3,3'-(1,4-naphthylidene)dipropionate to lead selectively to hydroquinone as the primary product. The other isomers of phenol hydroxylation, catechol and resorcinol, were not observed. In agreement with the involvement of 1O2 as the reactive species in the hydroxylation, in D2O the yield of hydroquinone is 7 times that in H2O, and the 1O2 quenchers azide and the thiols, glutathione and dithiothreitol, suppress the production of hydroquinone. In contrast, the hydroxyl radical scavengers, tert-butyl alcohol, propanol, or sodium formate, are without effect. In a follow-up reaction, hydroquinone is converted into benzoquinone. Reaction of 1O2 with aniline leads to the selective formation of 4-hydroxyaniline as the initial product. This is further converted to hydroquinone with formation of ammonia (deamination), and then to benzoquinone. On the basis of these results, the selective para hydroxylation of phenol or aniline may be used as an indicator for the involvement of singlet oxygen as compared to .OH radical- or cytochrome P450-mediated reactions. PMID:8374055

  18. Material Selection Guidelines to Limit Atomic Oxygen Effects on Spacecraft Surfaces

    NASA Technical Reports Server (NTRS)

    Dooling, D.; Finckenor, M. M.

    1999-01-01

    This report provides guidelines in selecting materials for satellites and space platforms, designed to operate within the Low-Earth orbit environment, which limit the effects of atomic oxygen interactions with spacecraft surfaces. This document should be treated as an introduction rather than a comprehensive guide since analytical and flight technologies continue to evolve, flight experiments are conducted as primary or piggyback opportunities arise, and our understanding of materials interactions and protection methods grows. The reader is urged to consult recent literature and current web sites containing information about research and flight results.

  19. Accurate and precise measurement of oxygen isotopic fractions and diffusion profiles by selective attenuation of secondary ions (SASI).

    PubMed

    Téllez, Helena; Druce, John; Hong, Jong-Eun; Ishihara, Tatsumi; Kilner, John A

    2015-03-01

    The accuracy and precision of isotopic analysis in Time-of-Flight secondary ion mass spectrometry (ToF-SIMS) relies on the appropriate reduction of the dead-time and detector saturation effects, especially when analyzing species with high ion yields or present in high concentrations. Conventional approaches to avoid these problems are based on Poisson dead-time correction and/or an overall decrease of the total secondary ion intensity by reducing the target current. This ultimately leads to poor detection limits for the minor isotopes and high uncertainties of the measured isotopic ratios. An alternative strategy consists of the attenuation of those specific secondary ions that saturate the detector, providing an effective extension of the linear dynamic range. In this work, the selective attenuation of secondary ion signals (SASI) approach is applied to the study of oxygen transport properties in electroceramic materials by isotopic labeling with stable (18)O tracer and ToF-SIMS depth profiling. The better analytical performance in terms of accuracy and precision allowed a more reliable determination of the oxygen surface exchange and diffusion coefficients while maintaining good mass resolution and limits of detection for other minor secondary ion species. This improvement is especially relevant to understand the ionic transport mechanisms and properties of solid materials, such as the parallel diffusion pathways (e.g., oxygen diffusion through bulk, grain boundary, or dislocations) in electroceramic materials with relevant applications in energy storage and conversion devices. PMID:25647357

  20. Impact of hemoglobin concentration and affinity for oxygen on tissue oxygenation: the case of hemoglobin-based oxygen carriers.

    PubMed

    Samaja, Michele; Terraneo, Laura

    2012-02-01

    In patients undergoing exchange-transfusion with hemoglobin (Hb)-based oxygen (O₂) carriers (HBOC), native Hb coexists with newly transfused Hb. The two Hb types share the same arterial and venous PO₂, but their affinities for O₂ vary. A simple spreadsheet model is described aiming at evaluating the contribution of each Hb type to the overall O₂ transport characteristics as a function of the batch Hb concentration and O₂ affinity in the HBOC solution, of the fraction of exchange-transfused blood/HBOC, and of the arterial PO₂. This model helps to yield a quantitative estimate of how tissues with high or low O₂ extraction respond to the changes cited above. The results show that the higher the exchange-transfusion ratio, the O₂ transport to tissues becomes progressively impaired. However, this effect is more critical at low batch Hb concentration and high O₂ affinity of the HBOC, especially for tissues/organs with high O₂ extraction, whereas the arterial PO₂ does not appear as critical. PMID:21848930

  1. Oxygen reduction by lithiated graphene and graphene-based materials.

    PubMed

    Kataev, Elmar Yu; Itkis, Daniil M; Fedorov, Alexander V; Senkovsky, Boris V; Usachov, Dmitry Yu; Verbitskiy, Nikolay I; Grüneis, Alexander; Barinov, Alexei; Tsukanova, Daria Yu; Volykhov, Andrey A; Mironovich, Kirill V; Krivchenko, Victor A; Rybin, Maksim G; Obraztsova, Elena D; Laubschat, Clemens; Vyalikh, Denis V; Yashina, Lada V

    2015-01-27

    Oxygen reduction reaction (ORR) plays a key role in lithium-air batteries (LABs) that attract great attention thanks to their high theoretical specific energy several times exceeding that of lithium-ion batteries. Because of their high surface area, high electric conductivity, and low specific weight, various carbons are often materials of choice for applications as the LAB cathode. Unfortunately, the possibility of practical application of such batteries is still under question as the sustainable operation of LABs with carbon cathodes is not demonstrated yet and the cyclability is quite poor, which is usually associated with oxygen reduced species side reactions. However, the mechanisms of carbon reactivity toward these species are still unclear. Here, we report a direct in situ X-ray photoelectron spectroscopy study of oxygen reduction by lithiated graphene and graphene-based materials. Although lithium peroxide (Li2O2) and lithium oxide (Li2O) reactions with carbon are thermodynamically favorable, neither of them was found to react even at elevated temperatures. As lithium superoxide is not stable at room temperature, potassium superoxide (KO2) prepared in situ was used instead to test the reactivity of graphene with superoxide species. In contrast to Li2O2 and Li2O, KO2 was demonstrated to be strongly reactive. PMID:25560087

  2. Process for selection of oxygen-tolerant algal mutants that produce H{sub 2}

    DOEpatents

    Ghirardi, M.L.; Seibert, M.

    1999-02-16

    A process for selection of oxygen-tolerant, H{sub 2}-producing algal mutant cells comprises: (a) growing algal cells photoautotrophically under fluorescent light to mid log phase; (b) inducing algal cells grown photoautotrophically under fluorescent light to mid log phase in step (a) anaerobically by (1) resuspending the cells in a buffer solution and making said suspension anaerobic with an inert gas and (2) incubating the suspension in the absence of light at ambient temperature; (c) treating the cells from step (b) with metronidazole, sodium azide, and added oxygen to controlled concentrations in the presence of white light; (d) washing off metronidazole and sodium azide to obtain final cell suspension; (e) plating said final cell suspension on a minimal medium and incubating in light at a temperature sufficient to enable colonies to appear; (f) counting the number of colonies to determine the percent of mutant survivors; and (g) testing survivors to identify oxygen-tolerant H{sub 2}-producing mutants. 5 figs.

  3. Selective decreased de novo synthesis of glomerular proteoglycans under the influence of reactive oxygen species.

    PubMed Central

    Kashihara, N; Watanabe, Y; Makino, H; Wallner, E I; Kanwar, Y S

    1992-01-01

    The effect of reactive oxygen species on de novo synthesis of heparan sulfate proteoglycans (HSPGs) of the renal glomerulus was investigated in an organ perfusion system. Isolated kidneys were perfused for 7 hr with a medium containing [35S]sulfate to label sulfated proteoglycans or [35S]methionine to label total glomerular glycoproteins. For the generation of reactive oxygen species, xanthine and xanthine oxidase were included in the perfusion medium, and catalase and superoxide dismutase were used as scavenging agents. Proteoglycans were characterized by Sepharose CL-6B and DEAE-Sephacel chromatographies and SDS/PAGE analysis. The labeled glycoproteins were immunoprecipitated with anti-HSPG, anti-type IV collagen, and anti-laminin, and their specific radioactivities were determined. With exposure to reactive oxygen species, a drastic dose-dependent decrease in de novo synthesis of proteoglycans was seen, and that effect was reversible by catalase treatment. No alterations in the biochemical characteristics of proteoglycans were noted. Immunoprecipitation studies revealed a 16-fold decrease in the synthesis of nascent core peptide of HSPGs, while at comparable concentrations of xanthine and xanthine oxidase, synthesis of type IV collagen and laminin slightly decreased (approximately 15%). Morphologic studies revealed a 14-fold decrease in [35S]sulfate-associated autoradiographic grains overlying the glomerular basement membrane, a critical component of the ultrafiltration apparatus. Relevance of the selective decreased de novo synthesis of HSPGs of the glomerular basement membrane is discussed in terms of increased glomerular permeability to plasma proteins. Images PMID:1631123

  4. Selective oxidation of cyclohexane on a novel catalyst Mg-Cu/SBA-15 by molecular oxygen.

    PubMed

    Duan, Xiaogang; Liu, Weimin; Yue, Lumin; Fu, Wei; Ha, Minh Ngoc; Li, Jun; Lu, Guanzhong

    2015-10-21

    The novel catalysts xMg-2.3Cu/SBA-15 with copper and magnesium oxide co-supported on mesoporous silica were synthesized by an impregnation method. The newly synthesized catalysts were characterized using a series of techniques such as BET, XRD, H2-TPR, UV-vis, XPS, EDS and TEM. The catalytic performance was evaluated by using selective oxidation of cyclohexane with molecular oxygen as the oxidant in a solvent free system. The incorporation of magnesium improved the dispersion of copper oxide and prevented the deep oxidation of cyclohexanol and cyclohexanone. The selectivity of K/A oil was up to 99.3% with 12% conversion of cyclohexane over the 1.2Mg-2.3Cu/SBA-15 catalyst. To our knowledge, this is the best result for the heterogeneous oxidation of cyclohexane by O2. PMID:26388454

  5. Selective oxidation of alkanes and/or alkenes to valuable oxygenates

    DOEpatents

    Lin, Manhua; Pillai, Krishnan S.

    2011-02-15

    A catalyst, its method of preparation and its use for producing at least one of methacrolein and methacrylic acid, for example, by subjecting isobutane or isobutylene or a mixture thereof to a vapor phase catalytic oxidation in the presence of air or oxygen. In the case where isobutane alone is subjected to a vapor phase catalytic oxidation in the presence of air or oxygen, the product is at least one of isobutylene, methacrolein and methacrylic acid. The catalyst comprises a compound having the formula A.sub.aB.sub.bX.sub.xY.sub.yZ.sub.zO.sub.o wherein A is one or more elements selected from the group of Mo, W and Zr, B is one or more elements selected from the group of Bi, Sb, Se, and Te, X is one or more elements selected from the group of Al, Bi, Ca, Ce, Co, Fe, Ga, Mg, Ni, Nb, Sn, W and Zn, Y is one or more elements selected from the group of Ag, Au, B, Cr, Cs, Cu, K, La, Li, Mg, Mn, Na, Nb, Ni, P, Pb, Rb, Re, Ru, Sn, Te, Ti, V and Zr, and Z is one or more element from the X or Y groups or from the following: As, Ba, Pd, Pt, Sr, or mixtures thereof, and wherein a=1, 0.05

  6. The influence of oxygen on the selectivity of alcohol conversion on the Pd(111) surface

    NASA Astrophysics Data System (ADS)

    Davis, J. L.; Barteau, M. A.

    The reactions of methanol, ethanol, 1-propanol, and 2-propanol were examined on a Pd(111) surface containing one-quarter monolayer of adsorbed oxygen atoms. The presence of surface oxygen led to the oxidation of the primary alcohols to the corresponding aldehyde and carboxylate species, with carboxylate production the major reaction pathway. Methanol was oxidized on the oxygen-dosed Pd(111) surface to formaldehyde and surface formate species. Formaldehyde desorbed at 240 K and adsorbed formate species decomposed at 280 K to produce CO 2, HCOOH, and surface hydrogen. The adsorption of ethanol on the oxygen-dosed Pd(111) surface resulted in the desorption of acetaldehyde at 220 K and the formation of surface acetate species. Adsorbed acetate species reacted via either decomposition at 410 K or hydrogenation to acetic acid at 280 K. The relative importance of the two acetate reaction channels was found to depend on the availability of surface hydrogen. Similarly, the adsorption of 1-propanol on O/Pd(111) produced both propanal and adsorbed propanoate species. The propanoate species were removed from the surface by either decomposition at 360 K or hydrogenation at 280 K. In contrast, oxidation of the secondary alcohol 2-propanol resulted mainly in the production of acetone, with acetate formation a relatively minor reaction pathway. The roles of oxygen adatoms in these reactions include(1) direct reaction as Brønsted bases with proton donors; (2) stabilization of surface alkoxide species; (3) alteration of the interaction of carbonyl compounds with the surface; (4) nucleophilic oxidation of adsorbed aldehydes to carboxylates; and (5) scavenging of surface hydrogen which would otherwise be available for hydrogenation reactions.

  7. Selective nitrogen doping in graphene: Enhanced catalytic activity for the oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Wang, Xianlong; Hou, Zhufeng; Ikeda, Takashi; Huang, Sheng-Feng; Terakura, Kiyoyuki; Boero, Mauro; Oshima, Masaharu; Kakimoto, Masa-Aki; Miyata, Seizo

    2011-12-01

    The structural and electronic properties of N-doped zigzag graphene ribbons with various ratios of dihydrogenated to monohydrogenated edge carbons are investigated within the density functional theory framework. We find that the stability of graphitic N next to the edge, which is claimed to play important roles in the catalytic activity in our previous work, will be enhanced with increasing the concentration of dihydrogenated carbons. Furthermore, the dihydrogenated edge carbons turn out to be easily converted into monohydrogenated ones in the presence of oxygen molecules at room temperature. Based on our results, we propose a possible way to enhance the oxygen reduction catalytic activity of N-doped graphene by controlling the degrees of hydrogenation of edge carbons. The characteristic features in the x-ray absorption and emission spectra for each specific N site considered here will also be given.

  8. Visual Orientation Selectivity Based Structure Description.

    PubMed

    Wu, Jinjian; Lin, Weisi; Shi, Guangming; Zhang, Yazhong; Dong, Weisheng; Chen, Zhibo

    2015-11-01

    The human visual system is highly adaptive to extract structure information for scene perception, and structure character is widely used in perception-oriented image processing works. However, the existing structure descriptors mainly describe the luminance contrast of a local region, but cannot effectively represent the spatial correlation of structure. In this paper, we introduce a novel structure descriptor according to the orientation selectivity mechanism in the primary visual cortex. Research on cognitive neuroscience indicate that the arrangement of excitatory and inhibitory cortex cells arise orientation selectivity in a local receptive field, within which the primary visual cortex performs visual information extraction for scene understanding. Inspired by the orientation selectivity mechanism, we compute the correlations among pixels in a local region based on the similarities of their preferred orientation. By imitating the arrangement of the excitatory/inhibitory cells, the correlations between a central pixel and its local neighbors are binarized, and the spatial correlation is represented with a set of binary values, which is named the orientation selectivity-based pattern. Then, taking both the gradient magnitude and the orientation selectivity-based pattern into account, a rotation invariant structure descriptor is introduced. The proposed structure descriptor is applied in texture classification and reduced reference image quality assessment, as two different application domains to verify its generality and robustness. Experimental results demonstrate that the orientation selectivity-based structure descriptor is robust to disturbance, and can effectively represent the structure degradation caused by different types of distortion. PMID:26219097

  9. Down Selection of Polymerized Bovine Hemoglobins for Use as Oxygen Releasing Therapeutics in a Guinea Pig Model

    PubMed Central

    Baek, Jin Hyen; Zhou, Yipin; Harris, David R.; Schaer, Dominik J.; Palmer, Andre F.; Buehler, Paul W.

    2012-01-01

    Hemoglobin (Hb)-based oxygen carriers (HBOCs) are being developed as resuscitative fluids for use in multiple medical applications and in lieu of blood transfusion. However, cardiovascular, central nervous system, and renal adverse events have largely impeded progress. This has prompted a need to evaluate novel down selection approaches for HBOCs prior to in-depth preclinical and clinical safety testing. In the present study, polymerized bovine Hbs (PolybHbs) were prepared with increasing ratios of glutaraldehyde to bovine Hb (10:1, 20:1, 30:1, and 40:1). The optimal PolybHb candidate selection was based on a priori determined in vivo response to include a long circulating PolybHb with no measurable renal exposure, minimal cardiovascular response, limited oxidation to metHb in vitro, or in circulation and absence of acute end organ toxicity. Guinea pigs were dosed via a 50% blood for PolybHb exchange transfusion. Data suggested that the 30:1 preparation exhibited maximum circulatory exposure (AUC0–∞) with the lowest level of oxidation (plasma metHb formation) and minimal (< 10%) blood pressure elevation. Additionally, the 30:1 preparation was absent renal iron deposition as well as abnormal glomerular/tubular histopathology or serum creatinine elevation. Clearance pathways predominantly followed those consistent with endogenous Hb clearance based pathways. Therefore, data confirmed the ability to select a single PolybHb from a small library of HBOCs based on a priori determined characteristics. Moreover, the approach to down selection described could be applied to enhance the early predictability of human safety for this class of biological therapeutics to optimize for specific indications. PMID:22416071

  10. A lithium-oxygen battery based on lithium superoxide

    NASA Astrophysics Data System (ADS)

    Lu, Jun; Jung Lee, Yun; Luo, Xiangyi; Chun Lau, Kah; Asadi, Mohammad; Wang, Hsien-Hau; Brombosz, Scott; Wen, Jianguo; Zhai, Dengyun; Chen, Zonghai; Miller, Dean J.; Sub Jeong, Yo; Park, Jin-Bum; Zak Fang, Zhigang; Kumar, Bijandra; Salehi-Khojin, Amin; Sun, Yang-Kook; Curtiss, Larry A.; Amine, Khalil

    2016-01-01

    Batteries based on sodium superoxide and on potassium superoxide have recently been reported. However, there have been no reports of a battery based on lithium superoxide (LiO2), despite much research into the lithium-oxygen (Li-O2) battery because of its potential high energy density. Several studies of Li-O2 batteries have found evidence of LiO2 being formed as one component of the discharge product along with lithium peroxide (Li2O2). In addition, theoretical calculations have indicated that some forms of LiO2 may have a long lifetime. These studies also suggest that it might be possible to form LiO2 alone for use in a battery. However, solid LiO2 has been difficult to synthesize in pure form because it is thermodynamically unstable with respect to disproportionation, giving Li2O2 (refs 19, 20). Here we show that crystalline LiO2 can be stabilized in a Li-O2 battery by using a suitable graphene-based cathode. Various characterization techniques reveal no evidence for the presence of Li2O2. A novel templating growth mechanism involving the use of iridium nanoparticles on the cathode surface may be responsible for the growth of crystalline LiO2. Our results demonstrate that the LiO2 formed in the Li-O2 battery is stable enough for the battery to be repeatedly charged and discharged with a very low charge potential (about 3.2 volts). We anticipate that this discovery will lead to methods of synthesizing and stabilizing LiO2, which could open the way to high-energy-density batteries based on LiO2 as well as to other possible uses of this compound, such as oxygen storage.

  11. A lithium-oxygen battery based on lithium superoxide.

    PubMed

    Lu, Jun; Lee, Yun Jung; Luo, Xiangyi; Lau, Kah Chun; Asadi, Mohammad; Wang, Hsien-Hau; Brombosz, Scott; Wen, Jianguo; Zhai, Dengyun; Chen, Zonghai; Miller, Dean J; Jeong, Yo Sub; Park, Jin-Bum; Fang, Zhigang Zak; Kumar, Bijandra; Salehi-Khojin, Amin; Sun, Yang-Kook; Curtiss, Larry A; Amine, Khalil

    2016-01-21

    Batteries based on sodium superoxide and on potassium superoxide have recently been reported. However, there have been no reports of a battery based on lithium superoxide (LiO2), despite much research into the lithium-oxygen (Li-O2) battery because of its potential high energy density. Several studies of Li-O2 batteries have found evidence of LiO2 being formed as one component of the discharge product along with lithium peroxide (Li2O2). In addition, theoretical calculations have indicated that some forms of LiO2 may have a long lifetime. These studies also suggest that it might be possible to form LiO2 alone for use in a battery. However, solid LiO2 has been difficult to synthesize in pure form because it is thermodynamically unstable with respect to disproportionation, giving Li2O2 (refs 19, 20). Here we show that crystalline LiO2 can be stabilized in a Li-O2 battery by using a suitable graphene-based cathode. Various characterization techniques reveal no evidence for the presence of Li2O2. A novel templating growth mechanism involving the use of iridium nanoparticles on the cathode surface may be responsible for the growth of crystalline LiO2. Our results demonstrate that the LiO2 formed in the Li-O2 battery is stable enough for the battery to be repeatedly charged and discharged with a very low charge potential (about 3.2 volts). We anticipate that this discovery will lead to methods of synthesizing and stabilizing LiO2, which could open the way to high-energy-density batteries based on LiO2 as well as to other possible uses of this compound, such as oxygen storage. PMID:26751057

  12. Survey of selected seaweeds for simultaneous photoproduction of hydrogen and oxygen

    SciTech Connect

    Greenbaum, E.; Ramus, J.

    1983-03-01

    Then seaweed species were surveyed for simultaneous photoevolution of hydrogen and oxygen. In an attempt to induce hydrogenase activity (as measured by hydrogen photoproduction) the seaweeds were maintained under anaerobiosis in CO/sub 2/-free seawater for varying lengths of time. Although oxygen evolution was observed in every alga studied, hydrogen evolution was not observed. One conclusion of this research is that, in contrast to the microscopic algae, there is not a single example of a macroscopic alga for which the photoevolution of hydrogen has been observed, in spite of the fact that there are now at least nine macroscopic algal species known for which hydrogenase activity has been reported (either by dark hydrogen evolution or light-activated hydrogen uptake). These results are in conflict with the conventional view that algal hydrogenase can catalyze a multiplicity of reactions, one of which is the photoproduction of molecular hydrogen. Two possible explanations for the lack of hydrogen photoproduction in macroscopic algae are presented. It is postulated that electron acceptors other than carbon dioxide can take up reducing equivalents from Photosystem I to the measurable exclusion of hydrogen photoproduction. Alternatively, the hydrogenase system in macroscopic algae may be primarily a hydrogen-uptake system with respect to light-activated reactions. A simple kinetic argument based on recent measurements of the photosynthetic turnover times of simultaneous light-activated hydrogen and oxygen production is presented that supports the second explanation. 25 references, 3 figures, 1 table.

  13. Brazilian Cardiorespiratory Fitness Classification Based on Maximum Oxygen Consumption

    PubMed Central

    Herdy, Artur Haddad; Caixeta, Ananda

    2016-01-01

    Background Cardiopulmonary exercise test (CPET) is the most complete tool available to assess functional aerobic capacity (FAC). Maximum oxygen consumption (VO2 max), an important biomarker, reflects the real FAC. Objective To develop a cardiorespiratory fitness (CRF) classification based on VO2 max in a Brazilian sample of healthy and physically active individuals of both sexes. Methods We selected 2837 CEPT from 2837 individuals aged 15 to 74 years, distributed as follows: G1 (15 to 24); G2 (25 to 34); G3 (35 to 44); G4 (45 to 54); G5 (55 to 64) and G6 (65 to 74). Good CRF was the mean VO2 max obtained for each group, generating the following subclassification: Very Low (VL): VO2 < 50% of the mean; Low (L): 50% - 80%; Fair (F): 80% - 95%; Good (G): 95% -105%; Excellent (E) > 105%. Results Men VL < 50% L 50-80% F 80-95% G 95-105% E > 105% G1 < 25.30 25.30-40.48 40.49-48.07 48.08-53.13 > 53.13 G2 < 23.70 23.70-37.92 37.93-45.03 45.04-49.77 > 49.77 G3 < 22.70 22.70-36.32 36.33-43.13 43.14-47.67 > 47.67 G4 < 20.25 20.25-32.40 32.41-38.47 38.48-42.52 > 42.52 G5 < 17.54 17.65-28.24 28.25-33.53 33.54-37.06 > 37.06 G6 < 15 15.00-24.00 24.01-28.50 28.51-31.50 > 31.50 Women G1 < 19.45 19.45-31.12 31.13-36.95 36.96-40.84 > 40.85 G2 < 19.05 19.05-30.48 30.49-36.19 36.20-40.00 > 40.01 G3 < 17.45 17.45-27.92 27.93-33.15 33.16-34.08 > 34.09 G4 < 15.55 15.55-24.88 24.89-29.54 29.55-32.65 > 32.66 G5 < 14.30 14.30-22.88 22.89-27.17 27.18-30.03 > 30.04 G6 < 12.55 12.55-20.08 20.09-23.84 23.85-26.35 > 26.36 Conclusions This chart stratifies VO2 max measured on a treadmill in a robust Brazilian sample and can be used as an alternative for the real functional evaluation of physically and healthy individuals stratified by age and sex. PMID:27305285

  14. Effect of wavelength selection on the accuracy of blood oxygen saturation estimates obtained from photoacoustic images

    NASA Astrophysics Data System (ADS)

    Hochuli, Roman; Beard, Paul C.; Cox, Ben

    2015-03-01

    In photoacoustic tomography (PAT) the image contrast is due to optical absorption, and because of this PAT images are sensitive to changes in blood oxygen saturation (sO2). However, this is not a linear relationship due to the presence of a non-uniform light fluence distribution. In this paper we systematically evaluate the conditions in which an approximate linear inversion scheme-which assumes the internal fluence distribution is unchanged when the absorption coefficient changes-can give accurate estimates of sO2. A numerical phantom of highly vascularised tissue is used to test this assumption. It is shown that using multiple wavelengths over a broad range of the near-infrared spectrum yields inaccurate estimates of oxygenation, while a careful selection of wavelengths in the 620-920nm range is likely to yield more accurate oxygenation values. We demonstrate that a 1D fluence correction obtained by fitting a linear function to the average decay rate in the image can further improve the estimates. However, opting to use these longer wavelengths involves sacrificing signal-to-noise ratio in the image, as the absorption of blood is low in this range. This results in an inherent trade-off between error in the sO2 estimates due to fluence variation and error due to noise. This study shows that the depth to which sO2 can be estimated accurately using a linear approximation is limited in vivo, even with idealised measurements, to at most 3mm. In practice, there will be even greater uncertainties affecting the estimates, e.g., due to bandlimited or partial-view acoustic detection.

  15. Case-Based Learning of Blood Oxygen Transport

    ERIC Educational Resources Information Center

    Cliff, William H.

    2006-01-01

    A case study about carbon monoxide poisoning was used help students gain a greater understanding of the physiology of oxygen transport by the blood. A review of student answers to the case questions showed that students can use the oxygen-hemoglobin dissociation curve to make meaningful determinations of oxygen uptake and delivery. However, the…

  16. First principles based mean field model for oxygen reduction reaction.

    PubMed

    Jinnouchi, Ryosuke; Kodama, Kensaku; Hatanaka, Tatsuya; Morimoto, Yu

    2011-12-21

    A first principles-based mean field model was developed for the oxygen reduction reaction (ORR) taking account of the coverage- and material-dependent reversible potentials of the elementary steps. This model was applied to the simulation of single crystal surfaces of Pt, Pt alloy and Pt core-shell catalysts under Ar and O(2) atmospheres. The results are consistent with those shown by past experimental and theoretical studies on surface coverages under Ar atmosphere, the shape of the current-voltage curve for the ORR on Pt(111) and the material-dependence of the ORR activity. This model suggests that the oxygen associative pathway including HO(2)(ads) formation is the main pathway on Pt(111), and that the rate determining step (RDS) is the removal step of O(ads) on Pt(111). This RDS is accelerated on several highly active Pt alloys and core-shell surfaces, and this acceleration decreases the reaction intermediate O(ads). The increase in the partial pressure of O(2)(g) increases the surface coverage with O(ads) and OH(ads), and this coverage increase reduces the apparent reaction order with respect to the partial pressure to less than unity. This model shows details on how the reaction pathway, RDS, surface coverages, Tafel slope, reaction order and material-dependent activity are interrelated. PMID:22064886

  17. Modeling of Cerebral Oxygen Transport Based on In vivo Microscopic Imaging of Microvascular Network Structure, Blood Flow, and Oxygenation

    PubMed Central

    Gagnon, Louis; Smith, Amy F.; Boas, David A.; Devor, Anna; Secomb, Timothy W.; Sakadžić, Sava

    2016-01-01

    Oxygen is delivered to brain tissue by a dense network of microvessels, which actively control cerebral blood flow (CBF) through vasodilation and contraction in response to changing levels of neural activity. Understanding these network-level processes is immediately relevant for (1) interpretation of functional Magnetic Resonance Imaging (fMRI) signals, and (2) investigation of neurological diseases in which a deterioration of neurovascular and neuro-metabolic physiology contributes to motor and cognitive decline. Experimental data on the structure, flow and oxygen levels of microvascular networks are needed, together with theoretical methods to integrate this information and predict physiologically relevant properties that are not directly measurable. Recent progress in optical imaging technologies for high-resolution in vivo measurement of the cerebral microvascular architecture, blood flow, and oxygenation enables construction of detailed computational models of cerebral hemodynamics and oxygen transport based on realistic three-dimensional microvascular networks. In this article, we review state-of-the-art optical microscopy technologies for quantitative in vivo imaging of cerebral microvascular structure, blood flow and oxygenation, and theoretical methods that utilize such data to generate spatially resolved models for blood flow and oxygen transport. These “bottom-up” models are essential for the understanding of the processes governing brain oxygenation in normal and disease states and for eventual translation of the lessons learned from animal studies to humans.

  18. Leveraging zinc interstitials and oxygen vacancies for sensitive biomolecule detection through selective surface functionalization

    NASA Astrophysics Data System (ADS)

    Radha Shanmugam, Nandhinee; Muthukumar, Sriram; Chaudhry, Shajee; Prasad, Shalini

    2015-03-01

    In this study, functionally engineered EIS technique was implemented to investigate the influence of surface functionalization on sensitivity of biomolecule detection using nanostructured ZnO platform. Organic molecules with thiol and carboxylic functional groups were chosen to control biomolecule immobilization on zinc and oxygen-terminated 2D planar and 1D nanostructured ZnO surfaces. The amount of functionalization and its influence on charge perturbations at the ZnO-electrolyte interface were studied using fluorescence and EIS measurements. We observed the dependence of charge transfer on both the polarity of platform and concentration of cross-linker molecules. Such selectively modified surfaces were used for detection of cortisol, a major stress indicator. Results demonstrated preferential binding of thiol groups to Zn terminations and thus leveraging ZnO interstitials increases the sensitivity of detection over larger dynamic range with detection limit at 10fg/mL.

  19. Dissolved-oxygen and algal conditions in selected locations of the Willamette River basin, Oregon

    USGS Publications Warehouse

    Rinella, F.A.; McKenzie, S.W.; Wille, S.A.

    1981-01-01

    During July and August 1978, the U.S. Geological Survey, in cooperation with the Oregon Department of Enviromental Quality, made three intensive river-quality dissolved-oxygen studies in the upper Willamette River basin. Two studies were made on the upper Willamette River and one was made on the Santiam River, a Willamette River tributary. Nitrification, occurring in both the upper Willamette and South Santiam Rivers, accounted for about 62% and 92% of the DO sag in the rivers, respectively. Rates of nitrification were found to be dependent on ammonia concentrations in the rivers. Periphyton and phytoplankton algal samples were collected on the main stem Willamette River and selected tributaries during August 1978. Diatoms were the dominant group in both the periphyton and phytoplankton samples. The most common diatom genera were Melosira, Stephanodiscus, Cymbella, Achnanthes, and Nitzschia. Comparisons with historical data indicate no significant difference from previous years in the total abundance or diversity of the algae. (USGS)

  20. Development of ruthenium-based bimetallic electrocatalysts for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Liu, Lingyun; Lee, Jong-Won; Popov, Branko N.

    Ruthenium-based bimetallic electrocatalysts with non-noble metals such as Ti, Cr, Fe, Co and Pb were synthesized on a porous carbon support using a chelation process. Rotating ring disk electrode measurements indicated that RuFeN x/C showed the catalytic activity and selectivity toward the four-electron reduction of oxygen to water comparable to those of the conventional Pt/C catalysts. The performance of the membrane-electrode assembly prepared with the RuFeN x/C cathode catalyst was evaluated for 150 h of continuous operation.

  1. Self-powered wireless carbohydrate/oxygen sensitive biodevice based on radio signal transmission.

    PubMed

    Falk, Magnus; Alcalde, Miguel; Bartlett, Philip N; De Lacey, Antonio L; Gorton, Lo; Gutierrez-Sanchez, Cristina; Haddad, Raoudha; Kilburn, Jeremy; Leech, Dónal; Ludwig, Roland; Magner, Edmond; Mate, Diana M; Conghaile, Peter Ó; Ortiz, Roberto; Pita, Marcos; Pöller, Sascha; Ruzgas, Tautgirdas; Salaj-Kosla, Urszula; Schuhmann, Wolfgang; Sebelius, Fredrik; Shao, Minling; Stoica, Leonard; Sygmund, Cristoph; Tilly, Jonas; Toscano, Miguel D; Vivekananthan, Jeevanthi; Wright, Emma; Shleev, Sergey

    2014-01-01

    Here for the first time, we detail self-contained (wireless and self-powered) biodevices with wireless signal transmission. Specifically, we demonstrate the operation of self-sustained carbohydrate and oxygen sensitive biodevices, consisting of a wireless electronic unit, radio transmitter and separate sensing bioelectrodes, supplied with electrical energy from a combined multi-enzyme fuel cell generating sufficient current at required voltage to power the electronics. A carbohydrate/oxygen enzymatic fuel cell was assembled by comparing the performance of a range of different bioelectrodes followed by selection of the most suitable, stable combination. Carbohydrates (viz. lactose for the demonstration) and oxygen were also chosen as bioanalytes, being important biomarkers, to demonstrate the operation of the self-contained biosensing device, employing enzyme-modified bioelectrodes to enable the actual sensing. A wireless electronic unit, consisting of a micropotentiostat, an energy harvesting module (voltage amplifier together with a capacitor), and a radio microchip, were designed to enable the biofuel cell to be used as a power supply for managing the sensing devices and for wireless data transmission. The electronic system used required current and voltages greater than 44 µA and 0.57 V, respectively to operate; which the biofuel cell was capable of providing, when placed in a carbohydrate and oxygen containing buffer. In addition, a USB based receiver and computer software were employed for proof-of concept tests of the developed biodevices. Operation of bench-top prototypes was demonstrated in buffers containing different concentrations of the analytes, showcasing that the variation in response of both carbohydrate and oxygen biosensors could be monitored wirelessly in real-time as analyte concentrations in buffers were changed, using only an enzymatic fuel cell as a power supply. PMID:25310190

  2. Self-Powered Wireless Carbohydrate/Oxygen Sensitive Biodevice Based on Radio Signal Transmission

    PubMed Central

    Falk, Magnus; Alcalde, Miguel; Bartlett, Philip N.; De Lacey, Antonio L.; Gorton, Lo; Gutierrez-Sanchez, Cristina; Haddad, Raoudha; Kilburn, Jeremy; Leech, Dónal; Ludwig, Roland; Magner, Edmond; Mate, Diana M.; Conghaile, Peter Ó.; Ortiz, Roberto; Pita, Marcos; Pöller, Sascha; Ruzgas, Tautgirdas; Salaj-Kosla, Urszula; Schuhmann, Wolfgang; Sebelius, Fredrik; Shao, Minling; Stoica, Leonard; Sygmund, Cristoph; Tilly, Jonas; Toscano, Miguel D.; Vivekananthan, Jeevanthi; Wright, Emma; Shleev, Sergey

    2014-01-01

    Here for the first time, we detail self-contained (wireless and self-powered) biodevices with wireless signal transmission. Specifically, we demonstrate the operation of self-sustained carbohydrate and oxygen sensitive biodevices, consisting of a wireless electronic unit, radio transmitter and separate sensing bioelectrodes, supplied with electrical energy from a combined multi-enzyme fuel cell generating sufficient current at required voltage to power the electronics. A carbohydrate/oxygen enzymatic fuel cell was assembled by comparing the performance of a range of different bioelectrodes followed by selection of the most suitable, stable combination. Carbohydrates (viz. lactose for the demonstration) and oxygen were also chosen as bioanalytes, being important biomarkers, to demonstrate the operation of the self-contained biosensing device, employing enzyme-modified bioelectrodes to enable the actual sensing. A wireless electronic unit, consisting of a micropotentiostat, an energy harvesting module (voltage amplifier together with a capacitor), and a radio microchip, were designed to enable the biofuel cell to be used as a power supply for managing the sensing devices and for wireless data transmission. The electronic system used required current and voltages greater than 44 µA and 0.57 V, respectively to operate; which the biofuel cell was capable of providing, when placed in a carbohydrate and oxygen containing buffer. In addition, a USB based receiver and computer software were employed for proof-of concept tests of the developed biodevices. Operation of bench-top prototypes was demonstrated in buffers containing different concentrations of the analytes, showcasing that the variation in response of both carbohydrate and oxygen biosensors could be monitored wirelessly in real-time as analyte concentrations in buffers were changed, using only an enzymatic fuel cell as a power supply. PMID:25310190

  3. SELECTIVE EXTRACTION OF OXYGENATES FROM SAVORY AND PEPPERMINT USING SUBCRITICAL WATER. (R825394)

    EPA Science Inventory

    The yields of oxygenated and non-oxygenated flavour and fragrance compounds from savory (Satureja hortensis) and peppermint (Mentha piperita) were compared using subcritical water extraction, supercritical carbon dioxide extraction (SFE) and hydrodistillation. Extraction rates wi...

  4. Selective Degeneration of Central Photoreceptors after Hyperbaric Oxygen in Normal and Metallothionein-Knockout Mice

    PubMed Central

    Nachman-Clewner, Michele; Giblin, Frank J.; Kathleen Dorey, C.; Blanks, Robert H. I.; Dang, Loan; Dougherty, Christopher J.; Blanks, Janet C.

    2009-01-01

    Purpose Metallothioneins (MTs) in the brain and retina are believed to bind metals and reduce free radicals, thereby protecting neurons from oxidative damage. This study was undertaken to investigate whether retinal photoreceptor (PR) cells lacking MTs are more susceptible to hyperbaric oxygen (HBO)–induced cell death in vivo. Methods Wild-type (WT) and MT-knockout (MT-KO) mice lacking metallothionein (MT)-1 and MT-2 were exposed to three atmospheres of 100% oxygen for 3 hours, 3 times per week for 1, 3, or 5 weeks. The control animals were not exposed. Histologic analysis of PR viability was performed by counting rows of nuclei in the outer nuclear layer (ONL). Ultrastructure studies verified PR damage. Results HBO exposure produced a major loss of PR cells in the central retinas of WT and MT-KO mice, with no effect on the peripheral retina even at the longest (5 weeks) exposures. The degree of PR damage and cell death increased with duration of HBO exposure. One week of HBO exposure was insufficient to cause PR death, but tissue damage was observed in the inner and outer segments. At 3 weeks, the rows of PR nuclei in the central retina were significantly reduced by 38% in WT and 28% in MT-KO animals. At 5 weeks, PR loss was identical in WT (34%) and MT-KO (34%) animals and was comparable to that in WT at 3 weeks. Conclusions The data suggest that MT-1 and -2 alone are not sufficient for protecting PRs against HBO-induced cell death. The selective degeneration of central PRs may provide clues to mechanisms of oxidative damage in retinal disease. PMID:18579766

  5. Orientation selectivity based structure for texture classification

    NASA Astrophysics Data System (ADS)

    Wu, Jinjian; Lin, Weisi; Shi, Guangming; Zhang, Yazhong; Lu, Liu

    2014-10-01

    Local structure, e.g., local binary pattern (LBP), is widely used in texture classification. However, LBP is too sensitive to disturbance. In this paper, we introduce a novel structure for texture classification. Researches on cognitive neuroscience indicate that the primary visual cortex presents remarkable orientation selectivity for visual information extraction. Inspired by this, we investigate the orientation similarities among neighbor pixels, and propose an orientation selectivity based pattern for local structure description. Experimental results on texture classification demonstrate that the proposed structure descriptor is quite robust to disturbance.

  6. A computational model of oxygen delivery by hemoglobin-based oxygen carriers in three-dimensional microvascular networks

    PubMed Central

    Tsoukias, Nikolaos M.; Goldman, Daniel; Vadapalli, Arjun; Pittman, Roland N.; Popel, Aleksander S.

    2009-01-01

    A detailed computational model is developed to simulate oxygen transport from a three-dimensional microvascular network to surrounding tissue in the presence of hemoglobin-based oxygen carriers. The model accounts for nonlinear O2 consumption, myoglobin facilitated diffusion and nonlinear oxyhemoglobin dissociation in the RBCs and plasma. It also includes a detailed description of intravascular resistance to O2 transport and is capable of incorporating realistic three-dimensional microvascular network geometries. Simulations in this study were performed using a computer-generated microvascular architecture that mimics morphometric parameters for the hamster cheek pouch retractor muscle. Theoretical results are presented next to corresponding experimental data. Phosphoresence quenching microscopy provided PO2 measurements at the arteriolar and venular ends of capillaries in the hamster retractor muscle before and after isovolemic hemodilution with three different hemodilutents; a non-oxygen-carrying plasma expander and two hemoglobin solutions with different oxygen affinities. Sample results in a microvascular network show an enhancement of diffusive shunting between arterioles, venules and capillaries and a decrease in hemoglobin’s effectiveness for tissue oxygenation when its affinity for O2 is decreased. Model simulations suggest that microvascular network anatomy can affect the optimal hemoglobin affinity for reducing tissue hypoxia. O2 transport simulations in realistic representations of microvascular networks should provide a theoretical framework for choosing optimal parameter values in the development of hemoglobin-based blood-substitutes. PMID:17686494

  7. Nonflammable organic-base paint for oxygen-rich atmospheres

    NASA Technical Reports Server (NTRS)

    Harwell, R. J.; Key, C. F.; Krupnick, A. C.

    1971-01-01

    New paint formulations, which combine aqueous latex paints with inorganic pigments and additives, produce coatings that are self-extinguishing in pure oxygen at pressures up to twice the partial pressure of atmospheric oxygen. A paint formulation in percent by weight is given and the properties of resultant coatings are discussed.

  8. Hypolimnetic dissolved-oxygen dynamics within selected White River reservoirs, northern Arkansas-southern Missouri, 1974-2008

    USGS Publications Warehouse

    De Lanois, Jeanne L.; Green, W. Reed

    2011-01-01

    Dissolved oxygen is a critical constituent in reservoirs and lakes because it is essential for metabolism by all aerobic aquatic organisms. In general, hypolimnetic temperature and dissolved-oxygen concentrations vary from summer to summer in reservoirs, more so than in natural lakes, largely in response to the magnitude of flow into and release out of the water body. Because eutrophication is often defined as the acceleration of biological productivity resulting from increased nutrient and organic loading, hypolimnetic oxygen consumption rates or deficits often provide a useful tool in analyzing temporal changes in water quality. This report updates a previous report that evaluated hypolimnetic dissolved-oxygen dynamics for a 21-year record (1974-94) in Beaver, Table Rock, Bull Shoals, and Norfork Lakes, as well as analyzed the record for Greers Ferry Lake. Beginning in 1974, vertical profiles of temperature and dissolved-oxygen concentrations generally were collected monthly from March through December at sites near the dam of each reservoir. The rate of change in the amount of dissolved oxygen present below a given depth at the beginning and end of the thermal stratification period is referred to as the areal hypolimnetic oxygen deficit. Areal hypolimnetic oxygen deficit was normalized for each reservoir based on seasonal flushing rate between April 15 and October 31 to adjust for wet year and dry year variability. Annual cycles in thermal stratification within Beaver, Table Rock, Bull Shoals, Norfork, and Greers Ferry Lakes exhibited typical monomictic (one extended turnover period per year) characteristics. Flow dynamics drive reservoir processes and need to be considered when analyzing areal hypolimnetic oxygen deficit rates. A nonparametric, locally weighted scatter plot smooth line describes the relation between areal hypolimnetic oxygen deficit and seasonal flushing rates, without assuming linearity or normality of the residuals. The results in this report

  9. Water, hydrogen, deuterium, carbon, carbon-13, and oxygen-18 content of selected lunar material

    USGS Publications Warehouse

    Friedman, I.; O'Neil, J.R.; Adami, L.H.; Gleason, J.D.; Hardcastle, K.

    1970-01-01

    The water content of the breccia is 150 to 455 ppm, with a ??D from -580 to -870 per mil. Hydrogen gas content is 40 to 53 ppm with a ??D of -830 to -970 per mil. The CO2 is 290 to 418 ppm with S 13C = + 2.3 to + 5.1 per mil and ??18O = 14.2 to 19.1 per mil. Non-CO2 carbon is 22 to 100 ppm, ??18C = -6.4 to -23.2 per mil. Lunar dust is 810 ppm H2O (D = 80 ppm) and 188 ppm total carbon (??13C = -17.6 per mil). The 18O analyses of whole rocks range from 5.8 to 6.2 per mil. The temperature of crystallization of type B rocks is 1100?? to 1300??C, based on the oxygen isotope fractionation between coexisting plagioclase and ilmenite.

  10. Microscopic oxygen imaging based on fluorescein bleaching efficiency measurements.

    PubMed

    Beutler, Martin; Heisterkamp, Ines M; Piltz, Bastian; Stief, Peter; De Beer, Dirk

    2014-05-01

    Photobleaching of the fluorophore fluorescein in an aqueous solution is dependent on the oxygen concentration. Therefore, the time-dependent bleaching behavior can be used to measure of dissolved oxygen concentrations. The method can be combined with epi-fluorescence microscopy. The molecular states of the fluorophore can be expressed by a three-state energy model. This leads to a set of differential equations which describe the photobleaching behavior of fluorescein. The numerical solution of these equations shows that in a conventional wide-field fluorescence microscope, the fluorescence of fluorescein will fade out faster at low than at high oxygen concentration. Further simulation showed that a simple ratio function of different time-points during a fluorescence decay recorded during photobleaching could be used to describe oxygen concentrations in an aqueous solution. By careful choice of dye concentration and excitation light intensity the sensitivity in the oxygen concentration range of interest can be optimized. In the simulations, the estimation of oxygen concentration by the ratio function was very little affected by the pH value in the range of pH 6.5-8.5. Filming the fluorescence decay by a charge-coupled-device (ccd) camera mounted on a fluorescence microscope allowed a pixelwise estimation of the ratio function in a microscopic image. Use of a microsensor and oxygen-consuming bacteria in a sample chamber enabled the calibration of the system for quantification of absolute oxygen concentrations. The method was demonstrated on nitrifying biofilms growing on snail and mussel shells, showing clear effects of metabolic activity on oxygen concentrations. PMID:24610786

  11. Simulations of Ground and Space-Based Oxygen Atom Experiments

    NASA Technical Reports Server (NTRS)

    Minton, T. K.; Cline, J. A.; Braunstein, M.

    2002-01-01

    Fast, pulsed atomic oxygen sources are a key tool in ground-based investigations of spacecraft contamination and surface erosion effects. These technically challenging ground-based studies provide a before and after picture of materials under low-earth-orbit (LEO) conditions. It would be of great interest to track in real time the pulsed flux from the source to the surface sample target and beyond in order to characterize the population of atoms and molecules that actually impact the surface and those that make it downstream to any coincident detectors. We have performed simulations in order to provide such detailed descriptions of these ground-based measurements and to provide an assessment of their correspondence to the actual LEO environment. Where possible we also make comparisons to measured fluxes and erosion yields. To perform the calculations we use a detailed description of a measurement beam and surface geometry based on the W, pulsed apparatus at Montana State University. In this system, a short pulse (on the order of 10 microseconds) of an O/O2 beam impacts a flat sample about 40 cm downstream and slightly displaced &om the beam s central axis. Past this target, at the end of the beam axis is a quadrupole mass spectrometer that measures the relative in situ flux of 0102 to give an overall normalized erosion yield. In our simulations we use the Direct Simulation Monte Carlo (DSMC) method, and track individual atoms within the atomic oxygen pulse. DSMC techniques are typically used to model rarefied (few collision) gas-flows which occur at altitudes above approximately 110 kilometers. These techniques are well suited for the conditions here, and multi-collision effects that can only be treated by this or a similar technique are included. This simulation includes collisions with the surface and among gas atoms that have scattered from the surface. The simulation also includes descriptions of the velocity spread and spatial profiles of the O/O2 beam

  12. Estimating peak oxygen uptake based on postexercise measurements in swimming.

    PubMed

    Chaverri, Diego; Iglesias, Xavier; Schuller, Thorsten; Hoffmann, Uwe; Rodríguez, Ferran A

    2016-06-01

    To assess the validity of postexercise measurements in estimating peak oxygen uptake (V̇O2peak) in swimming, we compared oxygen uptake (V̇O2) measurements during supramaximal exercise with various commonly adopted methods, including a recently developed heart rate - V̇O2 modelling procedure. Thirty-one elite swimmers performed a 200-m maximal swim where V̇O2 was measured breath-by-breath using a portable gas analyzer connected to a respiratory snorkel, 1 min before, during, and 3 min postexercise. V̇O2peak(-20-0) was the average of the last 20 s of effort. The following postexercise measures were compared: (i) first 20-s average (V̇O2peak(0-20)); (ii) linear backward extrapolation (BE) of the first 20 s (BE(20)), 30 s, and 3 × 20-, 4 × 20-, and 3 or 4 × 20-s averages; (iii) semilogarithmic BE at 20 s (LOG(20)) and at the other same time intervals as in linear BE; and (iv) predicted V̇O2peak using mathematical modelling (pV̇O2(0-20)]. Repeated-measures ANOVA and post-hoc Bonferroni tests compared V̇O2peak (criterion) and each estimated value. Pearson's coefficient of determination (r(2)) was used to assess correlation. Exercise V̇O2peak(-20-0) (mean ± SD 3531 ± 738 mL·min(-1)) was not different (p > 0.30) from pV̇O2(0-20) (3571 ± 735 mL·min(-1)), BE(20) (3617 ± 708 mL·min(-1)), or LOG(20) (3627 ± 746 mL·min(-1)). pV̇O2(0-20) was very strongly correlated with exercise V̇O2peak (r(2) = 0.962; p < 0.001), and showed a low standard error of the estimate (146 mL·min(-1), 4.1%) and the lowest mean difference (40 mL·min(-1); 1.1%). We confirm that the new modelling procedure based on postexercise V̇O2 and heart rate measurements is a valid and accurate procedure for estimating V̇O2peak in swimmers and avoids the estimation bias produced by other methods. PMID:27226382

  13. Implementing oxygen control in chip-based cell and tissue culture systems.

    PubMed

    Oomen, Pieter E; Skolimowski, Maciej D; Verpoorte, Elisabeth

    2016-09-21

    Oxygen is essential in the energy metabolism of cells, as well as being an important regulatory parameter influencing cell differentiation and function. Interest in precise oxygen control for in vitro cultures of tissues and cells continues to grow, especially with the emergence of the organ-on-a-chip and the desire to emulate in vivo conditions. This was recently discussed in this journal in a Critical Review by Brennan et al. (Lab Chip (2014). DOI: ). Microfluidics can be used to introduce flow to facilitate nutrient supply to and waste removal from in vitro culture systems. Well-defined oxygen gradients can also be established. However, cells can quickly alter the oxygen balance in their vicinity. In this Tutorial Review, we expand on the Brennan paper to focus on the implementation of oxygen analysis in these systems to achieve continuous monitoring. Both electrochemical and optical approaches for the integration of oxygen monitoring in microfluidic tissue and cell culture systems will be discussed. Differences in oxygen requirements from one organ to the next are a challenging problem, as oxygen delivery is limited by its uptake into medium. Hence, we discuss the factors determining oxygen concentrations in solutions and consider the possible use of artificial oxygen carriers to increase dissolved oxygen concentrations. The selection of device material for applications requiring precise oxygen control is discussed in detail, focusing on oxygen permeability. Lastly, a variety of devices is presented, showing the diversity of approaches that can be employed to control and monitor oxygen concentrations in in vitro experiments. PMID:27492338

  14. Identification of selected apple pests based on selected graphical parameters

    NASA Astrophysics Data System (ADS)

    Boniecki, P.; Koszela, K.; Piekarska-Boniecka, H.; Nowakowski, K.; Przybył, J.; Zaborowicz, M.; Raba, B.; Dach, J.

    2013-07-01

    The aim of this work was a neural identification of selected apple tree orchard pests. The classification was conducted on the basis of graphical information coded in the form of selected geometric characteristics of agrofags, presented on digital images. A neural classification model is presented in this paper, optimized using learning sets acquired on the basis of information contained in digital photographs of pests. In particular, the problem of identifying 6 selected apple pests, the most commonly encountered in Polish orchards, has been addressed. In order to classify the agrofags, neural modelling methods were utilized, supported by digital analysis of image techniques.

  15. USDA Database for the Oxygen Radical Capacity (ORAC) of Selected Foods, Release 2

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The Oxygen Radical Absorbance Capacity (ORAC) of foods is thought to be useful in evaluating dietary intake because reactive oxygen species (ROS) have been hypothesized to be related to the aging process and other reports suggest that dietary antioxidants may have beneficial effects on certain chron...

  16. Oxygen sorption and desorption properties of selected lanthanum manganites and lanthanum ferrite manganites.

    PubMed

    Nielsen, Jimmi; Skou, Eivind M; Jacobsen, Torben

    2015-06-01

    Temperature-programmed desorption (TPD) with a carrier gas was used to study the oxygen sorption and desorption properties of oxidation catalysts and solid-oxide fuel cell (SOFC) cathode materials (La(0.85) Sr(0.15)0.95 MnO(3+δ) (LSM) and La(0.60) Sr(0.40) Fe(0.80) Mn(0.20) O(3-δ) (LSFM). The powders were characterized by X-ray diffractometry, atomic force microscopy (AFM), and BET surface adsorption. Sorbed oxygen could be distinguished from oxygen originating from stoichiometry changes. The results indicated that there is one main site for oxygen sorption/desorption. The amount of sorbed oxygen was monitored over time at different temperatures. Furthermore, through data analysis it was shown that the desorption peak associated with oxygen sorption is described well by second-order desorption kinetics. This indicates that oxygen molecules dissociate upon adsorption and that the rate-determining step for the desorption reaction is a recombination of monatomic oxygen. Typical problems with re-adsorption in this kind of TPD setup were revealed to be insignificant by using simulations. Finally, different key parameters of sorption and desorption were determined, such as desorption activation energies, density of sorption sites, and adsorption and desorption reaction order. PMID:25784205

  17. CMOS compatible electrode materials selection in oxide-based memory devices

    NASA Astrophysics Data System (ADS)

    Zhuo, V. Y.-Q.; Li, M.; Guo, Y.; Wang, W.; Yang, Y.; Jiang, Y.; Robertson, J.

    2016-07-01

    Electrode materials selection guidelines for oxide-based memory devices are constructed from the combined knowledge of observed device operation characteristics, ab-initio calculations, and nano-material characterization. It is demonstrated that changing the top electrode material from Ge to Cr to Ta in the Ta2O5-based memory devices resulted in a reduction of the operation voltages and current. Energy Dispersed X-ray (EDX) Spectrometer analysis clearly shows that the different top electrode materials scavenge oxygen ions from the Ta2O5 memory layer at various degrees, leading to different oxygen vacancy concentrations within the Ta2O5, thus the observed trends in the device performance. Replacing the Pt bottom electrode material with CMOS compatible materials (Ru and Ir) further reduces the power consumption and can be attributed to the modification of the Schottky barrier height and oxygen vacancy concentration at the electrode/oxide interface. Both trends in the device performance and EDX results are corroborated by the ab-initio calculations which reveal that the electrode material tunes the oxygen vacancy concentration via the oxygen chemical potential and defect formation energy. This experimental-theoretical approach strongly suggests that the proper selection of CMOS compatible electrode materials will create the critical oxygen vacancy concentration to attain low power memory performance.

  18. Structural and Functional Evidence Indicates Selective Oxygen Signaling in Caldanaerobacter subterraneus H-NOX.

    PubMed

    Hespen, Charles W; Bruegger, Joel J; Phillips-Piro, Christine M; Marletta, Michael A

    2016-08-19

    Acute and specific sensing of diatomic gas molecules is an essential facet of biological signaling. Heme nitric oxide/oxygen binding (H-NOX) proteins are a family of gas sensors found in diverse classes of bacteria and eukaryotes. The most commonly characterized bacterial H-NOX domains are from facultative anaerobes and are activated through a conformational change caused by formation of a 5-coordinate Fe(II)-NO complex. Members of this H-NOX subfamily do not bind O2 and therefore can selectively ligate NO even under aerobic conditions. In contrast, H-NOX domains encoded by obligate anaerobes do form stable 6-coordinate Fe(II)-O2 complexes by utilizing a conserved H-bonding network in the ligand-binding pocket. The biological function of O2-binding H-NOX domains has not been characterized. In this work, the crystal structures of an O2-binding H-NOX domain from the thermophilic obligate anaerobe Caldanaerobacter subterraneus (Cs H-NOX) in the Fe(II)-NO, Fe(II)-CO, and Fe(II)-unliganded states are reported. The Fe(II)-unliganded structure displays a conformational shift distinct from the NO-, CO-, and previously reported O2-coordinated structures. In orthogonal signaling assays using Cs H-NOX and the H-NOX signaling effector histidine kinase from Vibrio cholerae (Vc HnoK), Cs H-NOX regulates Vc HnoK in an O2-dependent manner and requires the H-bonding network to distinguish O2 from other ligands. The crystal structures of Fe(II) unliganded and NO- and CO-bound Cs H-NOX combined with functional assays herein provide the first evidence that H-NOX proteins from obligate anaerobes can serve as O2 sensors. PMID:27328180

  19. Oxygen-Rich Enzyme Biosensor Based on Superhydrophobic Electrode.

    PubMed

    Lei, Yongjiu; Sun, Ruize; Zhang, Xiangcheng; Feng, Xinjian; Jiang, Lei

    2016-02-17

    The fabrication of novel superhydrophobic electrodes is described, which have an air-liquid-solid three-phase interface, where oxygen is sufficient and constant. Oxygen is an effective natural electron acceptor for oxidase, and plays a key role in the development of reliable bioassays. Such an electrode allows detection of glucose concentration, linearly from 50 × 10(-9) m to 156 × 10(-3) m with good sensitivity and accuracy without analyte dilution. This strategy offers a unique route to address the gas-deficit problem of many reaction systems. PMID:26661886

  20. Biocathodes reducing oxygen at high potential select biofilms dominated by Ectothiorhodospiraceae populations harboring a specific association of genes.

    PubMed

    Desmond-Le Quéméner, Elie; Rimboud, Mickaël; Bridier, Arnaud; Madigou, Céline; Erable, Benjamin; Bergel, Alain; Bouchez, Théodore

    2016-08-01

    Biocathodes polarized at high potential are promising for enhancing Microbial Fuel Cell performances but the microbes and genes involved remain poorly documented. Here, two sets of five oxygen-reducing biocathodes were formed at two potentials (-0.4V and +0.1V vs. saturated calomel electrode) and analyzed combining electrochemical and metagenomic approaches. Slower start-up but higher current densities were observed at high potential and a distinctive peak increasing over time was recorded on cyclic voltamogramms, suggesting the growth of oxygen reducing microbes. 16S pyrotag sequencing showed the enrichment of two operational taxonomic units (OTUs) affiliated to Ectothiorodospiraceae on high potential electrodes with the best performances. Shotgun metagenome sequencing and a newly developed method for the identification of Taxon Specific Gene Annotations (TSGA) revealed Ectothiorhodospiraceae specific genes possibly involved in electron transfer and in autotrophic growth. These results give interesting insights into the genetic features underlying the selection of efficient oxygen reducing microbes on biocathodes. PMID:27126080

  1. An investigation of active and selective oxygen in vanadium phosphorus oxide catalysts for n-butane conversion to maleic anhydride

    SciTech Connect

    Lashier, M.E.

    1990-01-01

    The role of lattice oxygens in two model catalysts, {beta}-VOPO{sub 4} and (VO){sub 2}P{sub 2}O{sub 7}, was investigated for the selective and nonselective oxidation of C{sub 4} hydrocarbons to maleic anhydride and combustion products. Specific catalytic oxygen sites in each model catalyst were labeled with specific amounts of {sup 18}O. Labeled sites were identified by laser Raman spectroscopy and Fourier transform infrared spectroscopy. The level of {sup 18}O enrichment in each site was estimated from the laser Raman spectra and the stoichiometry of reactions involved in the synthesis of the labeled catalysts. Products of the anaerobic C{sub 4} hydrocarbon oxidation and, in the case of (VO){sub 2}P{sub 2}O{sub 7}, alternating pulses of oxygen with pulses of hydrocarbon, over labeled catalysts were monitored by quadrupole mass spectrometry. 146 refs., 51 figs., 7 tabs.

  2. Modelling of operation of a lithium-air battery with ambient air and oxygen-selective membrane

    NASA Astrophysics Data System (ADS)

    Sahapatsombut, Ukrit; Cheng, Hua; Scott, Keith

    2014-03-01

    A macro-homogeneous model has been developed to evaluate the impact of replacing pure oxygen with ambient air on the performance of a rechargeable non-aqueous Li-air battery. The model exhibits a significant reduction in discharge capacity, e.g. from 1240 to 226 mAh gcarbon-1 at 0.05 mA cm-2 when using ambient air rather than pure oxygen. The model correlates the relationship between the performance and electrolyte decomposition and formation of discharge products (such as Li2O2 and Li2CO3) under ambient air conditions. The model predicts a great benefit of using an oxygen-selective membrane on increasing capacity. The results indicate a good agreement between the experimental data and the model.

  3. Reactive oxygen metabolites and colitis: a disturbed balance between damage and protection. A selective review.

    PubMed

    Verspaget, H W; Mulder, T P; van der Sluys Veer, A; Peña, A S; Lamers, C B

    1991-01-01

    Enhanced local production of reactive oxygen metabolites has been found in association with colitis, both experimentally and in humans. Cellular and biochemical systems involved have been identified, and 5-aminosalicylic acid-containing drugs but, more effectively, specific scavengers have been found to reduce the intestinal inflammatory process. The multitude of reactions in which oxygen metabolites participate provides a new area of research in intestinal inflammation. These basic studies might bring related clinical studies in an era of new anti-inflammatory drugs for inflammatory bowel disease specifically designed to scavenge toxic oxygen metabolites. PMID:1663660

  4. ASRDI oxygen technology survey. Volume 3: Heat transfer and fluid dynamics. Abstracts of selected technical reports and publications

    NASA Technical Reports Server (NTRS)

    Schmidt, A. F. (Editor)

    1972-01-01

    Selected information is presented from an assemblage of reports and publications on heat transfer and fluid dynamics with direct applicability to oxygen systems. For each document cited, an abstract has been prepared together with key words and a listing of most important references found in the document. Additionally, an author index, a subject index, and a key word index have been provided to simplify the retrieval of specific information from this work. In each subject area - e.g., boiling heat transfer - the individual citations are listed alphabetically by first author, with review papers dually noted under the appropriate subject category and under review papers. Of the documents reviewed and evaluated for inclusion in this publication, coverage of existing information directly concerned with oxygen was given primary emphasis. However, work not specifically oxygen-designated but considered applicable to oxygen by the reviewer e.g., a two-phase friction factor correlation derived from nitrogen experiments is occasionally given where no actual oxygen data exist, as an aid to the reader. Approximately 130 abstracts are listed.

  5. Leaching-resistant carrageenan-based colorimetric oxygen indicator films for intelligent food packaging.

    PubMed

    Vu, Chau Hai Thai; Won, Keehoon

    2014-07-23

    Visual oxygen indicators can give information on the quality and safety of packaged food in an economic and simple manner by changing color based on the amount of oxygen in the packaging, which is related to food spoilage. In particular, ultraviolet (UV)-activated oxygen indicators have the advantages of in-pack activation and irreversibility; however, these dye-based oxygen indicator films suffer from dye leaching upon contact with water. In this work, we introduce carrageenans, which are natural sulfated polysaccharides, to develop UV-activated colorimetric oxygen indicator films that are resistant to dye leakage. Carrageenan-based indicator films were fabricated using redox dyes [methylene blue (MB), azure A, and thionine], a sacrificial electron donor (glycerol), an UV-absorbing photocatalyst (TiO2), and an encapsulation polymer (carrageenan). They showed even lower dye leakage in water than conventional oxygen indicator films, owing to the electrostatic interaction of anionic carrageenan with cationic dyes. The MB/TiO2/glycerol/carrageenan oxygen indicator film was successfully bleached upon UV irradiation, and it regained color very rapidly in the presence of oxygen compared to the other waterproof oxygen indicator films. PMID:24979322

  6. Fast, Ultrasensitive Detection of Reactive Oxygen Species Using a Carbon Nanotube Based-Electrocatalytic Intracellular Sensor.

    PubMed

    Rawson, Frankie J; Hicks, Jacqueline; Dodd, Nicholas; Abate, Wondwossen; Garrett, David J; Yip, Nga; Fejer, Gyorgy; Downard, Alison J; Baronian, Kim H R; Jackson, Simon K; Mendes, Paula M

    2015-10-28

    Herein, we report a highly sensitive electrocatalytic sensor-cell construct that can electrochemically communicate with the internal environment of immune cells (e.g., macrophages) via the selective monitoring of a particular reactive oxygen species (ROS), hydrogen peroxide. The sensor, which is based on vertically aligned single-walled carbon nanotubes functionalized with an osmium electrocatalyst, enabled the unprecedented detection of a local intracellular "pulse" of ROS on a short second time scale in response to bacterial endotoxin (lipopolysaccharide-LPS) stimulation. Our studies have shown that this initial pulse of ROS is dependent on NADPH oxidase (NOX) and toll like receptor 4 (TLR4). The results suggest that bacteria can induce a rapid intracellular pulse of ROS in macrophages that initiates the classical innate immune response of these cells to infection. PMID:26438964

  7. Fast, Ultrasensitive Detection of Reactive Oxygen Species Using a Carbon Nanotube Based-Electrocatalytic Intracellular Sensor

    PubMed Central

    2015-01-01

    Herein, we report a highly sensitive electrocatalytic sensor-cell construct that can electrochemically communicate with the internal environment of immune cells (e.g., macrophages) via the selective monitoring of a particular reactive oxygen species (ROS), hydrogen peroxide. The sensor, which is based on vertically aligned single-walled carbon nanotubes functionalized with an osmium electrocatalyst, enabled the unprecedented detection of a local intracellular “pulse” of ROS on a short second time scale in response to bacterial endotoxin (lipopolysaccharide-LPS) stimulation. Our studies have shown that this initial pulse of ROS is dependent on NADPH oxidase (NOX) and toll like receptor 4 (TLR4). The results suggest that bacteria can induce a rapid intracellular pulse of ROS in macrophages that initiates the classical innate immune response of these cells to infection. PMID:26438964

  8. Selective vibronic excitation of singlet oxygen--furan reactions in cryogenic matrices

    SciTech Connect

    Frei, H.; Pimentel, G.C.

    1983-10-01

    The reactions of 2,5-dimethylfuran (DMF), 2-methylfuran (MF), and furan with molecular oxygen to form endoperoxides have been induced in Ar and O/sub 2/ matrices at 12 K with selective vibronic excitation of O/sub 2/ using near infrared light. Reaction was induced through excitation of the /sup 1/..delta../sub g/(v' = 0, v' = 1) and /sup 1/..sigma../sub g//sup +/(v' = 0, v' = 1) O/sub 2/ states near 8000 and 13 100 cm/sup -1/, respectively, as well as by the (/sup 1/..delta../sub g/, /sup 1/..delta../sub g/) simultaneous transitions of (O/sub 2/)/sub 2/ at 15 900 and 17 300 cm/sup -1/. The /sup 1/..delta../sub g/ reverse arrow /sup 3/..sigma../sub g//sup -/ vibronic progression in solid O/sub 2/ was recorded by FTIR spectroscopy, whereas members of the /sup 1/..sigma../sub g//sup +/ reverse arrow /sup 3/..sigma../sub g//sup -/ and (/sup 1/..delta../sub g/, /sup 1/..delta../sub g/) reverse arrow (/sup 3/..sigma../sub g//sup -/, /sup 3/..sigma../sub g//sup -/) progressions in Ar matrices were located by ''reaction excitation'' spectroscopy. The DMF+O/sub 2/ reaction is a single photon process, apparently with unit quantum yield, for all vibronic levels excited. For MF+O/sub 2/(/sup 1/..delta../sub g/, v' = 0) and furan +O/sub 2/(/sup 1/..delta../sub g/, v' = 0), quantum yields were high, approx.0.6 and 0.4, respectively, but the reservoirs of reactive pairs were 10--20 times smaller than for DMF+O/sub 2/. The furan+O/sub 2/ reaction rate showed an /sup 18/O/sub 2/ isotope effect 0.78 +- 0.15, which can be interpreted in terms of quantum mechanical tunneling on the lowest singlet hypersurface.

  9. Quantifying oxygen in paper-based cell cultures with luminescent thin film sensors.

    PubMed

    Boyce, Matthew W; Kenney, Rachael M; Truong, Andrew S; Lockett, Matthew R

    2016-04-01

    Paper-based scaffolds are an attractive material for generating 3D tissue-like cultures because paper is readily available and does not require specialized equipment to pattern, cut, or use. By controlling the exchange of fresh culture medium with the paper-based scaffolds, we can engineer diffusion-dominated environments similar to those found in spheroids or solid tumors. Oxygen tension directly regulates cellular phenotype and invasiveness through hypoxia-inducible transcription factors and also has chemotactic properties. To date, gradients of oxygen generated in the paper-based cultures have relied on cellular response-based readouts. In this work, we prepared a luminescent thin film capable of quantifying oxygen tensions in apposed cell-containing paper-based scaffolds. The oxygen sensors, which are polystyrene films containing a Pd(II) tetrakis(pentafluorophenyl)porphyrin dye, are photostable, stable in culture conditions, and not cytotoxic. They have a linear response for oxygen tensions ranging from 0 to 160 mmHg O2, and a Stern-Volmer constant (K sv) of 0.239 ± 0.003 mmHg O2 (-1). We used these oxygen-sensing films to measure the spatial and temporal changes in oxygen tension for paper-based cultures containing a breast cancer line that was engineered to constitutively express a fluorescent protein. By acquiring images of the oxygen-sensing film and the fluorescently labeled cells, we were able to approximate the oxygen consumption rates of the cells in our cultures. Graphical Abstract Schematic of a paper-based culture seeded with fluorescent cells, and an oxygen-sensitive film. PMID:26667655

  10. Oxygen biosensor based on bilirubin oxidase immobilized on a nanostructured gold electrode.

    PubMed

    Pita, Marcos; Gutierrez-Sanchez, Cristina; Toscano, Miguel D; Shleev, Sergey; De Lacey, Antonio L

    2013-12-01

    Gold disk electrodes modified with gold nanoparticles have been used as a scaffold for the covalent immobilization of bilirubin oxidase. The nanostructured bioelectrodes were tested as mediator-less biosensors for oxygen in a buffer that mimics the content and the composition of human physiological fluids. Chronoamperometry measurements showed a detection limit towards oxygen of 6 ± 1 μM with a linear range of 6-300 μM, i.e. exceeding usual physiological ranges of oxygen in human tissues and fluids. The biosensor presented is the first ever-reported oxygen amperometric biosensor based on direct electron transfer of bilirubin oxidase. PMID:23973738

  11. Methodology and Significance of Microsensor-based Oxygen Mapping in Plant Seeds – an Overview

    PubMed Central

    Rolletschek, Hardy; Stangelmayer, Achim; Borisjuk, Ljudmilla

    2009-01-01

    Oxygen deficiency is commonplace in seeds, and limits both their development and their germination. It is, therefore, of considerable relevance to crop production. While the underlying physiological basis of seed hypoxia has been known for some time, the lack of any experimental means of measuring the global or localized oxygen concentration within the seed has hampered further progress in this research area. The development of oxygen-sensitive microsensors now offers the capability to determine the localized oxygen status within a seed, and to study its dynamic adjustment both to changes in the ambient environment, and to the seed's developmental stage. This review illustrates the use of oxygen microsensors in seed research, and presents an overview of existing data with an emphasis on crop species. Oxygen maps, both static and dynamic, should serve to increase our basic understanding of seed physiology, as well as to facilitate upcoming breeding and biotechnology-based approaches for crop improvement. PMID:22412307

  12. New singlet oxygen donors based on naphthalenes: synthesis, physical chemical data, and improved stability.

    PubMed

    Klaper, Matthias; Linker, Torsten

    2015-06-01

    Singlet oxygen donors are of current interest for medical applications, but suffer from a short half-life leading to low singlet oxygen yields and problems with storage. We have synthesized more than 25 new singlet oxygen donors based on differently substituted naphthalenes in only a few steps. The influence of functional groups on the reaction rate of the photooxygenations, thermolysis, half-life, and singlet oxygen yield has been thoroughly studied. We determined various thermodynamic data and compared them with density functional calculations. Interestingly, remarkable stabilities of functional groups during the photooxygenations and stabilizing effects for some endoperoxides during the thermolysis have been found. Furthermore, we give evidence for a partly concerted and partly stepwise thermolysis mechanism leading to singlet and triplet oxygen, respectively. Our results might be interesting for "dark oxygenations" and future applications in medicine. PMID:25919359

  13. SYSTEM DESIGN AND ANALYSIS FOR CONCEPTUAL DESIGN OF OXYGEN-BASED PC BOILER

    SciTech Connect

    Zhen Fan; Andrew Seltzer

    2003-11-01

    The objective of the system design and analysis task of the Conceptual Design of Oxygen-Based PC Boiler study is to optimize the PC boiler plant by maximizing system efficiency. Simulations of the oxygen-fired plant with CO{sub 2} sequestration were conducted using Aspen Plus and were compared to a reference air-fired 460 Mw plant. Flue gas recycle is used in the O{sub 2}-fired PC to control the flame temperature. Parametric runs were made to determine the effect of flame temperature on system efficiency and required waterwall material and thickness. The degree of improvement on system efficiency of various modifications including hot gas recycle, purge gas recycle, flue gas feedwater recuperation, and recycle purge gas expansion were investigated. The selected O{sub 2}-fired design case has a system efficiency of 30.1% compared to the air-fired system efficiency of 36.7%. The design O{sub 2}-fired case requires T91 waterwall material and has a waterwall surface area of only 44% of the air-fired reference case. Compared to other CO{sub 2} sequestration technologies, the O{sub 2}-fired PC is substantially better than both natural gas combined cycles and post CO{sub 2} removal PCs and is slightly better than integrated gasification combined cycles.

  14. Liquid crystal size selection of large-size graphene oxide for size-dependent N-doping and oxygen reduction catalysis.

    PubMed

    Lee, Kyung Eun; Kim, Ji Eun; Maiti, Uday Narayan; Lim, Joonwon; Hwang, Jin Ok; Shim, Jongwon; Oh, Jung Jae; Yun, Taeyeong; Kim, Sang Ouk

    2014-09-23

    Graphene oxide (GO) is aqueous-dispersible oxygenated graphene, which shows colloidal discotic liquid crystallinity. Many properties of GO-based materials, including electrical conductivity and mechanical properties, are limited by the small flake size of GO. Unfortunately, typical sonochemical exfoliation of GO from graphite generally leads to a broad size and shape distribution. Here, we introduce a facile size selection of large-size GO exploiting liquid crystallinity and investigate the size-dependent N-doping and oxygen reduction catalysis. In the biphasic GO dispersion where both isotropic and liquid crystalline phases are equilibrated, large-size GO flakes (>20 μm) are spontaneously concentrated within the liquid crystalline phase. N-Doping and reduction of the size-selected GO exhibit that N-dopant type is highly dependent on GO flake size. Large-size GO demonstrates quaternary dominant N-doping and the lowest onset potential (-0.08 V) for oxygen reduction catalysis, signifying that quaternary N-dopants serve as principal catalytic sites in N-doped graphene. PMID:25145457

  15. The selective pathway to higher oxygenates from CO, H{sub 2}, olefins and chlorocarbons

    SciTech Connect

    Krishnamurthy, R.; Chuang, S.C.; Brundage, M.A.; Balakos, M.W.

    1994-12-31

    The synthesis of higher oxygenates from CO hydrogenation, ethylene addition and methylene chloride addition to syngas has been studied over Rh/SiO{sub 2} catalyst. The insertion of linear CO into the adsorbed alkyl intermediates is the key step in the formation of higher oxygenates. Pulse transient technique incorporated with in situ infrared (IR) technique reveals that hydrogenation of acyl species is the rate limiting step for propionaldehyde formation. Increasing total pressure increases the residence time of alkyl intermediates for CO insertion.

  16. MIS-based sensors with hydrogen selectivity

    DOEpatents

    Li; ,Dongmei; Medlin, J. William; McDaniel, Anthony H.; Bastasz, Robert J.

    2008-03-11

    The invention provides hydrogen selective metal-insulator-semiconductor sensors which include a layer of hydrogen selective material. The hydrogen selective material can be polyimide layer having a thickness between 200 and 800 nm. Suitable polyimide materials include reaction products of benzophenone tetracarboxylic dianhydride 4,4-oxydianiline m-phenylene diamine and other structurally similar materials.

  17. RGD-based Therapy: Principles of Selectivity.

    PubMed

    Rubtsov, Mikhail A; Syrkina, Marina S; Aliev, Gjumrakch

    2016-01-01

    Design of selective anticancer drugs that are targeting RGD-binding integrin receptors which are known to be one of the perspective directions in the field of oncology. Significant progress in the development and application of these types compounds is already demonstrated. The accumulating body of basic and clinical evidence demonstrates potential significant effects on both in vitro and in vivo experimental models. However, the specific mechanism of action of these compounds is generally not a fully elucidated or the exact target responsible for the achievement of stated effects hasn't yet been defined sufficiently. To date eight types of integrin receptors, which are capable to recognize RGD-motif in natural ligands, has in fact been identified as (namely αIIbβ3, αvβ1, αvβ3, αvβ5, αvβ6, αvβ8, α5β1, α8β1). Even so, the estimation of the affinity of one particular RGD-bearing anticancer agent is often based on the determination of the binding efficacy to only one or rarely two integrin receptors. Traditionally the range of targets is restricted by the integrins, which are known to be highly expressed in a particular model system. While potential interactions of such an agent with other RGD-recognizing receptors usually remain beyond the research. Nonetheless, such interactions may also affect the viability and behavior of cancer cells. In this review we attempt to critically analyze the principles of selectivity achievement in the case of RGD-bearing natural ligands and the applicability of these principles in the context of the anticancer drug design. PMID:26648463

  18. Using oxygen at home

    MedlinePlus

    ... DO NOT use oil-based products, such as petroleum jelly (Vaseline). Ask your oxygen equipment provider about ... oxygen; Hypoxia - home oxygen; Hospice - home oxygen References American Thoracic Society. Why do I need oxygen therapy? ...

  19. Selection of Environmentally Friendly Solvents for the Extravehicular Mobility Unit Secondary Oxygen Pack Cold Trap Testing

    NASA Technical Reports Server (NTRS)

    Steele, John; Chullen, Cinda; Morenz, Jesse; Stephenson, Curtis

    2010-01-01

    Freon-113(TradeMark) has been used as a chemistry lab sampling solvent at NASA/JSC for EMU (extravehicular Mobility Unit) SOP (Secondary Oxygen Pack) oxygen testing Cold Traps utilized at the USA (United Space Alliance) Houston facility. Similar testing has occurred at the HSWL (Hamilton Sundstrand Windsor Locks) facility. A NASA Executive Order bans the procurement of all ODS (ozone depleting substances), including Freon-113 by the end of 2009. In order to comply with NASA direction, HSWL began evaluating viable solvents to replace Freon-113 . The study and testing effort to find Freon-113 replacements used for Cold Trap sampling is the subject of this paper. Test results have shown HFE-7100 (a 3M fluorinated ether) to be an adequate replacement for Freon-113 as a solvent to remove and measure the non-volatile residue collected in a Cold Trap during oxygen testing. Furthermore, S-316 (a Horiba Instruments Inc. high molecular weight, non-ODS chlorofluorocarbon) was found to be an adequate replacement for Freon-113 as a solvent to reconstitute non-volatile residue removed from a Cold Trap during oxygen testing for subsequent HC (hydrocarbon) analysis via FTIR (Fourier Transform Infrared Spectroscopy).

  20. Caterpillars selected for large body size and short development time are more susceptible to oxygen-related stress

    PubMed Central

    Harrison, Jon F; Cease, Arianne J; VandenBrooks, John M; Albert, Todd; Davidowitz, Goggy

    2013-01-01

    Recent studies suggest that higher growth rates may be associated with reduced capacities for stress tolerance and increased accumulated damage due to reactive oxygen species. We tested the response of Manduca sexta (Sphingidae) lines selected for large or small body size and short development time to hypoxia (10 kPa) and hyperoxia (25, 33, and 40 kPa); both hypoxia and hyperoxia reduce reproduction and oxygen levels over 33 kPa have been shown to increase oxidative damage in insects. Under normoxic (21 kPa) conditions, individuals from the large-selected (big-fast) line were larger and had faster growth rates, slightly longer developmental times, and reduced survival rates compared to individuals from a line selected for small size (small-fast) or an unselected control line. Individuals from the big-fast line exhibited greater negative responses to hyperoxia with greater reductions in juvenile and adult mass, growth rate, and survival than the other two lines. Hypoxia generally negatively affected survival and growth/size, but the lines responded similarly. These results are mostly consistent with the hypothesis that simultaneous acquisition of large body sizes and short development times leads to reduced capacities for coping with stressful conditions including oxidative damage. This result is of particular importance in that natural selection tends to decrease development time and increase body size. PMID:23762517

  1. Caterpillars selected for large body size and short development time are more susceptible to oxygen-related stress.

    PubMed

    Harrison, Jon F; Cease, Arianne J; Vandenbrooks, John M; Albert, Todd; Davidowitz, Goggy

    2013-05-01

    Recent studies suggest that higher growth rates may be associated with reduced capacities for stress tolerance and increased accumulated damage due to reactive oxygen species. We tested the response of Manduca sexta (Sphingidae) lines selected for large or small body size and short development time to hypoxia (10 kPa) and hyperoxia (25, 33, and 40 kPa); both hypoxia and hyperoxia reduce reproduction and oxygen levels over 33 kPa have been shown to increase oxidative damage in insects. Under normoxic (21 kPa) conditions, individuals from the large-selected (big-fast) line were larger and had faster growth rates, slightly longer developmental times, and reduced survival rates compared to individuals from a line selected for small size (small-fast) or an unselected control line. Individuals from the big-fast line exhibited greater negative responses to hyperoxia with greater reductions in juvenile and adult mass, growth rate, and survival than the other two lines. Hypoxia generally negatively affected survival and growth/size, but the lines responded similarly. These results are mostly consistent with the hypothesis that simultaneous acquisition of large body sizes and short development times leads to reduced capacities for coping with stressful conditions including oxidative damage. This result is of particular importance in that natural selection tends to decrease development time and increase body size. PMID:23762517

  2. Alkaline static feed electrolyzer based oxygen generation system

    NASA Technical Reports Server (NTRS)

    Noble, L. D.; Kovach, A. J.; Fortunato, F. A.; Schubert, F. H.; Grigger, D. J.

    1988-01-01

    In preparation for the future deployment of the Space Station, an R and D program was established to demonstrate integrated operation of an alkaline Water Electrolysis System and a fuel cell as an energy storage device. The program's scope was revised when the Space Station Control Board changed the energy storage baseline for the Space Station. The new scope was aimed at the development of an alkaline Static Feed Electrolyzer for use in an Environmental Control/Life Support System as an oxygen generation system. As a result, the program was divided into two phases. The phase 1 effort was directed at the development of the Static Feed Electrolyzer for application in a Regenerative Fuel Cell System. During this phase, the program emphasized incorporation of the Regenerative Fuel Cell System design requirements into the Static Feed Electrolyzer electrochemical module design and the mechanical components design. The mechanical components included a Pressure Control Assembly, a Water Supply Assembly and a Thermal Control Assembly. These designs were completed through manufacturing drawing during Phase 1. The Phase 2 effort was directed at advancing the Alkaline Static Feed Electrolyzer database for an oxygen generation system. This development was aimed at extending the Static Feed Electrolyzer database in areas which may be encountered from initial fabrication through transportation, storage, launch and eventual Space Station startup. During this Phase, the Program emphasized three major areas: materials evaluation, electrochemical module scaling and performance repeatability and Static Feed Electrolyzer operational definition and characterization.

  3. Fluorophore-based sensor for oxygen radicals in processing plasmas

    SciTech Connect

    Choudhury, Faraz A.; Shohet, J. Leon; Sabat, Grzegorz; Sussman, Michael R.; Nishi, Yoshio

    2015-11-15

    A high concentration of radicals is present in many processing plasmas, which affects the processing conditions and the properties of materials exposed to the plasma. Determining the types and concentrations of free radicals present in the plasma is critical in order to determine their effects on the materials being processed. Current methods for detecting free radicals in a plasma require multiple expensive and bulky instruments, complex setups, and often, modifications to the plasma reactor. This work presents a simple technique that detects reactive-oxygen radicals incident on a surface from a plasma. The measurements are made using a fluorophore dye that is commonly used in biological and cellular systems for assay labeling in liquids. Using fluorometric analysis, it was found that the fluorophore reacts with oxygen radicals incident from the plasma, which is indicated by degradation of its fluorescence. As plasma power was increased, the quenching of the fluorescence significantly increased. Both immobilized and nonimmobilized fluorophore dyes were used and the results indicate that both states function effectively under vacuum conditions. The reaction mechanism is very similar to that of the liquid dye.

  4. Flexible lithium-oxygen battery based on a recoverable cathode.

    PubMed

    Liu, Qing-Chao; Xu, Ji-Jing; Xu, Dan; Zhang, Xin-Bo

    2015-01-01

    Although flexible power sources are crucial for the realization next-generation flexible electronics, their application in such devices is hindered by their low theoretical energy density. Rechargeable lithium-oxygen (Li-O2) batteries can provide extremely high specific energies, while the conventional Li-O2 battery is bulky, inflexible and limited by the absence of effective components and an adjustable cell configuration. Here we show that a flexible Li-O2 battery can be fabricated using unique TiO2 nanowire arrays grown onto carbon textiles (NAs/CT) as a free-standing cathode and that superior electrochemical performances can be obtained even under stringent bending and twisting conditions. Furthermore, the TiO2 NAs/CT cathode features excellent recoverability, which significantly extends the cycle life of the Li-O2 battery and lowers its life cycle cost. PMID:26235205

  5. Flexible lithium-oxygen battery based on a recoverable cathode

    NASA Astrophysics Data System (ADS)

    Liu, Qing-Chao; Xu, Ji-Jing; Xu, Dan; Zhang, Xin-Bo

    2015-08-01

    Although flexible power sources are crucial for the realization next-generation flexible electronics, their application in such devices is hindered by their low theoretical energy density. Rechargeable lithium-oxygen (Li-O2) batteries can provide extremely high specific energies, while the conventional Li-O2 battery is bulky, inflexible and limited by the absence of effective components and an adjustable cell configuration. Here we show that a flexible Li-O2 battery can be fabricated using unique TiO2 nanowire arrays grown onto carbon textiles (NAs/CT) as a free-standing cathode and that superior electrochemical performances can be obtained even under stringent bending and twisting conditions. Furthermore, the TiO2 NAs/CT cathode features excellent recoverability, which significantly extends the cycle life of the Li-O2 battery and lowers its life cycle cost.

  6. Flexible lithium–oxygen battery based on a recoverable cathode

    PubMed Central

    Liu, Qing-Chao; Xu, Ji-Jing; Xu, Dan; Zhang, Xin-Bo

    2015-01-01

    Although flexible power sources are crucial for the realization next-generation flexible electronics, their application in such devices is hindered by their low theoretical energy density. Rechargeable lithium–oxygen (Li–O2) batteries can provide extremely high specific energies, while the conventional Li–O2 battery is bulky, inflexible and limited by the absence of effective components and an adjustable cell configuration. Here we show that a flexible Li–O2 battery can be fabricated using unique TiO2 nanowire arrays grown onto carbon textiles (NAs/CT) as a free-standing cathode and that superior electrochemical performances can be obtained even under stringent bending and twisting conditions. Furthermore, the TiO2 NAs/CT cathode features excellent recoverability, which significantly extends the cycle life of the Li–O2 battery and lowers its life cycle cost. PMID:26235205

  7. Quantitative inactivation-mechanisms of P. digitatum and A. niger spores based on atomic oxygen dose

    NASA Astrophysics Data System (ADS)

    Ito, Masafumi; Hashizume, Hiroshi; Ohta, Takayuki; Hori, Masaru

    2014-10-01

    We have investigated inactivation mechanisms of Penicillium digitatum and Asperguills niger spores using atmospheric-pressure radical source quantitatively. The radical source was specially developed for supplying only neutral radicals without charged species and UV-light emissions. Reactive oxygen radical densities such as grand-state oxygen atoms, excited-state oxygen molecules and ozone were measured using VUV and UV absorption spectroscopies. The measurements and the treatments of spores were carried out in an Ar-purged chamber for eliminating the influences of OH, NOx and so on. The results revealed that the inactivation of spores can be explained by atomic-oxygen dose under the conditions employing neutral ROS irradiations. On the basis of the dose, we have observed the changes of intracellular organelles and membrane functions using TEM, SEM and confocal- laser fluorescent microscopy. From these results, we discuss the detail inactivation-mechanisms quantitatively based on atomic-oxygen dose.

  8. Pathway and Surface Mechanism Studies of 1,3-butadiene Selective Oxidation Over Vanadium-Molybdenum-Oxygen Catalysts

    SciTech Connect

    William David Schroeder

    2002-05-27

    The partial oxidation of 1,3-butadiene has been investigated over VMoO catalysts synthesized by sol-gel techniques. Surface areas were 9-14 m{sup 2}/g, and compositions were within the solid solution regime, i.e. below 15.0 mol % MoO{sub 3}/(MoO{sub 3} + V{sub 2}O{sub 5}). Laser Raman Spectroscopy and XRD data indicated that solid solutions were formed, and pre- and post-reaction XPS data indicated that catalyst surfaces contained some V{sup +4} and were further reduced in 1,3-butadiene oxidation. A reaction pathway for 1,3-butadiene partial oxidation to maleic anhydride was shown to involve intermediates such as 3,4-epoxy-1-butene, crotonaldehyde, furan, and 2-butene-1,4-dial. The addition of water to the reaction stream substantially increased catalyst activity and improved selectivity to crotonaldehyde and furan at specific reaction temperatures. At higher water addition concentrations, furan selectivity increased from 12% to over 25%. The catalytic effects of water addition were related to competitive adsorption with various V{sub 2}O{sub 5}-based surface sites, including the vanadyl V=O, corner sharing V-O-V and edge sharing V-O oxygen. Higher levels of water addition were proposed to impose acidic character by dissociative adsorption. In addition, a novel combinatorial synthesis technique for VMoO was used to investigate the phase transitions of V{sub 2}O{sub 5}, solid solutions of Mo in V{sub 2}O{sub 5}, V{sub 9}Mo{sub 6}O{sub 40}, and other reduced VMoO compounds, characterized by laser Raman spectroscopy. The natural composition gradient imposed by the sputter deposition apparatus was used to create VMoO arrays containing 225 samples ranging from 7.0-42 mol% MoO{sub 3}/(V{sub 2}O{sub 5} + MoO{sub 3}), determined by EDS analysis.

  9. Porous platinum-based catalysts for oxygen reduction

    DOEpatents

    Erlebacher, Jonah D; Snyder, Joshua D

    2014-11-25

    A porous metal that comprises platinum and has a specific surface area that is greater than 5 m.sup.2/g and less than 75 m.sup.2/g. A fuel cell includes a first electrode, a second electrode spaced apart from the first electrode, and an electrolyte arranged between the first and the second electrodes. At least one of the first and second electrodes is coated with a porous metal catalyst for oxygen reduction, and the porous metal catalyst comprises platinum and has a specific surface area that is greater than 5 m.sup.2/g and less than 75 m.sup.2/g. A method of producing a porous metal according to an embodiment of the current invention includes producing an alloy consisting essentially of platinum and nickel according to the formula Pt.sub.xNi.sub.1-x, where x is at least 0.01 and less than 0.3; and dealloying the alloy in a substantially pH neutral solution to reduce an amount of nickel in the alloy to produce the porous metal.

  10. Protocol for Atomic Oxygen Testing of Materials in Ground-Based Facilities. No. 2

    NASA Technical Reports Server (NTRS)

    Minton, Timothy K.

    1995-01-01

    A second version of standard guidelines is proposed for improving materials testing in ground-based atomic oxygen environments for the purpose of predicting the durability of the tested materials in low Earth orbit (LEO). Accompanying these guidelines are background information and notes about testing. Both the guidelines and the additional information are intended to aid users who wish to evaluate the potential hazard of atomic oxygen in LEO to a candidate space component without actually flying the component in space, and to provide a framework for more consistent atomic oxygen testing in the future.

  11. The USA Multicenter Prehosptial Hemoglobin -based Oxygen Carrier Resuscitation Trial: Scientific Rationale, Study Design, and Results

    PubMed Central

    Moore, Ernest E.; Johnson, Jeffrey L.; Moore, Frederick A.; Moore, Hunter B.

    2013-01-01

    The current generation of blood substitutes tested in clinical trials are red blood cell (RBC) substitutes; that is, they are designed primarily to transport oxygen. The products now being used in advanced-phase clinical trials are derived from hemoglobin (Hb) and are thus often referred to as Hb-based oxygen carriers (HBOCs). The potential benefits of HBOCs are well known (Box 1). The objectives of this overview are to provide the scientific background and rationale for the study design of the USA Multi-center Prehospital HBOC Resuscitation Trial and to present the results and discuss clinical implications. Box 1Potential clinical benefits of hemoglobin-based oxygen carriers in trauma careAvailabilityAbundant supplyUniversally compatibleProlonged shelf-lifeStorage at room temperatureSafetyNo disease transmissionsNo antigenic reactionsNo immunologic effectsEfficacyEnhanced oxygen deliveryImproved rheologic properties PMID:19341912

  12. SADA: Ecological Risk Based Decision Support System for Selective Remediation

    EPA Science Inventory

    Spatial Analysis and Decision Assistance (SADA) is freeware that implements terrestrial ecological risk assessment and yields a selective remediation design using its integral geographical information system, based on ecological and risk assessment inputs. Selective remediation ...

  13. Determination of the relative resistance to ignition of selected turbopump materials in high-pressure, high-temperature, oxygen environments, volume 1

    NASA Technical Reports Server (NTRS)

    Stoltzfus, Joel M.; Benz, Frank J.

    1986-01-01

    Advances in the design of the liquid oxygen, liquid hydrogen engines for the Space Transportation System call for the use of warm, high-pressure oxygen as the driving gas in the liquid oxygen turbopump. The NASA Lewis Research Center requested the NASA White Sands Test Facility (WSTF) to design a test program to determine the relative resistance to ignition of nine selected turbopump materials: Hastelloy X, Inconel 600, Invar 36, Monel K-500, nickel 200, silicon carbide, stainless steel 316, and zirconium copper. The materials were subjected to particle impact and to frictional heating in high-pressure oxygen.

  14. Vanadium-phosphorus-oxygen industrial catalysts for C/sub 4/ hydrocarbon selective oxidation to maleic anhydride

    SciTech Connect

    Wenig, R.W.

    1987-06-01

    The selective oxidation of n-butane to maleic anhydride by vanadium-phosphorus-oxygen (V-P-O) industrial catalysts varying in P-to-V ratio has been studied in a fixed bed integral reactor system. Catalyst characterization studies including x-ray diffraction, laser Raman spectroscopy, infrared spectroscopy, x-ray photoelectron spectroscopy, scanning electron microscopy, x-ray energy dispersive spectroscopy, and BET surface area measurements were used. A strong effect of P-to-V synthesis ratio on catalyst structure, catalyst morphology, vanadium oxidation state, and reactivity in n-butane selective oxidation was observed. A slight ''excess'' of catalyst phosphorus (P/V = 1.1 catalyst) was found to stabilize an active and selective (VO)/sub 2/P/sub 2/O/sub 7/ phase. The mechanism of n-butane selective oxidation to maleic anhydride was studied by in situ infrared spectroscopy using n-butane, 1-butene, 1,3-butadiene, crotyl alcohol, maleic acid, crotonic acid, and maleic anhydride feeds. During paraffin selective oxidation, highly reactive olefin species and maleic acid were observed on the surfaces of V-P-O catalysts. Further evidence in support of conjugated or possibly strained olefin and maleic acid reaction intermediates in n-butane and 1-butene partial oxidation to maleic anhydride was gathered.

  15. Study of oxygen scavenging PET-based films activated by water

    NASA Astrophysics Data System (ADS)

    Rossi, Gabriella; Scarfato, Paola; Incarnato, Loredana

    2016-05-01

    In this work an active barrier system consisting of a thin and transparent film based on polyethylene terephthalate (PET) was studied. Dynamic oxygen absorption measurements were performed at different values of relative humidity and temperature, pointing out that humidity is a key factor in activating the oxidation of the polymer sample. Moreover, the thermal and optical properties of the films were investigated and a good correlation was found between the crystallinity increase and the consequent transparency reduction occurring after the oxygen absorption.

  16. Oxygen interstitials and vacancies in LaSrGa3O7-based melilites

    NASA Astrophysics Data System (ADS)

    Xu, Jungu; Li, Xiaohui; Lu, Fengqi; Fu, Hui; Brown, Craig M.; Kuang, Xiaojun

    2015-10-01

    The Sr-rich composition of the layered tetrahedral meililite, La0.8Sr1.2Ga3O6.9, was synthesized and a structural investigation on La0.8Sr1.2Ga3O6.9 using neutron powder diffraction revealed a site preference of oxygen vacancies on the bridging oxygen sites of the 4-linked GaO4 tetrahedra. Impedance measurement revealed limited ionic conduction in the oxygen-deficient La0.8Sr1.2Ga3O6.9, presumably associated with oxygen vacancies, which is ~2 orders of magnitude higher than the parent material LaSrGa3O7 but ~3-4 orders of magnitude lower than the interstitial oxide ionic conductivity in La-rich composition, La1.54Sr0.46Ga3O7.27. Low temperature neutron powder diffraction characterization was performed for the oxygen-excess, La-rich composition, La1.54Sr0.46Ga3O7.27, which confirmed the position near the center of the pentagonal tunnels for the oxygen interstitials identified previously using the room temperature data. Solid state 71Ga NMR data collected on these LaSrGa3O7-based materials with stoichometric, excess, and deficient oxygen contents was found not able to distinguish these three compositions. A metastability temperature gap within 850-1280 °C was identified for the oxygen interstitial-conducting La1.54Sr0.46Ga3O7.27. The structures of these oxygen excess and deficient gallate melilites further demonstrate the structural flexibility of the LaSrGa3O7-based layer tetrahedral network.

  17. Model vanadium-phosphorus-oxygen catalysts for the selective oxidation of C/sub 4/ hydrocarbons to maleic anhydride

    SciTech Connect

    Moser, T.P.

    1987-06-01

    Two model vanadium-phosphorus-oxygen catalysts, ..beta..-VOPO/sub 4/ and (VO)/sub 2/P/sub 2/O/sub 7/, were investigated for the selective oxidation of C/sub 4/ hydrocarbons to maleic anhydride. In situ laser Raman spectroscopy was used. Complementary techniques including x-ray powder diffraction and x-ray photoelectron spectroscopy were used for characterization of the fresh and used catalytic materials. The direct observation of phase stability and the participation of lattice oxygen during catalysis was possible using the in situ Raman technique. In particular, ..beta..-VOPO/sub 4/ and (VO)/sub 2/P/sub 2/O/sub 7/ demonstrated bulk structural integrity during n-butane oxidation. The relatively greater reducing capacity of 1-butene induced the ..beta..-VOPO/sub 4/ to (VO)/sub 2/P/sub 2/O/sub 7/ phase transformation. Direct structural identification of catalytically active centers for paraffin and olefin oxidation were investigated using an /sup 18/O-enriched ..beta..-VOPO/sub 4/ phase catalyst. Active sites responsible for complete combustion (Site I) and selective oxidation (Site II) were identified. The selective route for 1-butene oxidation involved predominantly Site II centers, while Site I centers were associated with complete combustion. In contrast, n-butane oxidation required the highly active Site I centers for initial activation and for the formation of an intermediate containing two oxygen atoms. Raman band assignments indicated these oxygen sites were associated with PO/sub 4/ units in the ..beta..-VOPO/sub 4/ lattice. Maleic anhydride conversion was particularly sensitive to the catalytic phase present. Significant combustion activity was observed when maleic anhydride was fed directly to an integral flow reactor charged with model catalysts. The combustion activity was least for (VO)/sub 2/P/sub 2/O/sub 7/, nominally a V(IV) phase. The ..beta..-VOPO/sub 4/ catalyst, nominally a V(V) phase, resulted in increased conversions of maleic anhydride.

  18. Simulations of Ground and Space-Based Oxygen Atom Experiments

    NASA Technical Reports Server (NTRS)

    Finchum, A. (Technical Monitor); Cline, J. A.; Minton, T. K.; Braunstein, M.

    2003-01-01

    A low-earth orbit (LEO) materials erosion scenario and the ground-based experiment designed to simulate it are compared using the direct-simulation Monte Carlo (DSMC) method. The DSMC model provides a detailed description of the interactions between the hyperthermal gas flow and a normally oriented flat plate for each case. We find that while the general characteristics of the LEO exposure are represented in the ground-based experiment, multi-collision effects can potentially alter the impact energy and directionality of the impinging molecules in the ground-based experiment. Multi-collision phenomena also affect downstream flux measurements.

  19. FTOC-Based Analysis of Negative Selection.

    PubMed

    Cunningham, Cody A; Teixeiro, Emma; Daniels, Mark A

    2016-01-01

    Potentially harmful T cell precursors are removed from the conventional T cell pool by negative selection. This process can involve the induction of apoptosis, anergy, receptor editing or deviation into a regulatory T cell lineage. As such this process is essential for the health of an organism through its contribution to central and peripheral tolerance. While a great deal is known about the process, the precise mechanisms that regulate negative selection are not clear. Furthermore, the signals that distinguish the different forms of negative selection are not fully understood. Numerous models exist with the potential to address these questions in vitro and in vivo. This chapter describes methods of fetal thymic organ culture designed to analyze the signals that determine these unique cell fates. PMID:26294405

  20. Robust feature selection for microarray data based on multicriterion fusion.

    PubMed

    Yang, Feng; Mao, K Z

    2011-01-01

    Feature selection often aims to select a compact feature subset to build a pattern classifier with reduced complexity, so as to achieve improved classification performance. From the perspective of pattern analysis, producing stable or robust solution is also a desired property of a feature selection algorithm. However, the issue of robustness is often overlooked in feature selection. In this study, we analyze the robustness issue existing in feature selection for high-dimensional and small-sized gene-expression data, and propose to improve robustness of feature selection algorithm by using multiple feature selection evaluation criteria. Based on this idea, a multicriterion fusion-based recursive feature elimination (MCF-RFE) algorithm is developed with the goal of improving both classification performance and stability of feature selection results. Experimental studies on five gene-expression data sets show that the MCF-RFE algorithm outperforms the commonly used benchmark feature selection algorithm SVM-RFE. PMID:21566255

  1. Single-site trinuclear copper oxygen clusters in mordenite for selective conversion of methane to methanol

    PubMed Central

    Grundner, Sebastian; Markovits, Monica A.C.; Li, Guanna; Tromp, Moniek; Pidko, Evgeny A.; Hensen, Emiel J.M.; Jentys, Andreas; Sanchez-Sanchez, Maricruz; Lercher, Johannes A.

    2015-01-01

    Copper-exchanged zeolites with mordenite structure mimic the nuclearity and reactivity of active sites in particulate methane monooxygenase, which are enzymes able to selectively oxidize methane to methanol. Here we show that the mordenite micropores provide a perfect confined environment for the highly selective stabilization of trinuclear copper-oxo clusters that exhibit a high reactivity towards activation of carbon–hydrogen bonds in methane and its subsequent transformation to methanol. The similarity with the enzymatic systems is also implied from the similarity of the reversible rearrangements of the trinuclear clusters occurring during the selective transformations of methane along the reaction path towards methanol, in both the enzyme system and copper-exchanged mordenite. PMID:26109507

  2. Single-site trinuclear copper oxygen clusters in mordenite for selective conversion of methane to methanol.

    PubMed

    Grundner, Sebastian; Markovits, Monica A C; Li, Guanna; Tromp, Moniek; Pidko, Evgeny A; Hensen, Emiel J M; Jentys, Andreas; Sanchez-Sanchez, Maricruz; Lercher, Johannes A

    2015-01-01

    Copper-exchanged zeolites with mordenite structure mimic the nuclearity and reactivity of active sites in particulate methane monooxygenase, which are enzymes able to selectively oxidize methane to methanol. Here we show that the mordenite micropores provide a perfect confined environment for the highly selective stabilization of trinuclear copper-oxo clusters that exhibit a high reactivity towards activation of carbon-hydrogen bonds in methane and its subsequent transformation to methanol. The similarity with the enzymatic systems is also implied from the similarity of the reversible rearrangements of the trinuclear clusters occurring during the selective transformations of methane along the reaction path towards methanol, in both the enzyme system and copper-exchanged mordenite. PMID:26109507

  3. Acridine-intercalator based hypoxia selective cytotoxins

    DOEpatents

    Papadopoulou-Rosenzweig, Maria; Bloomer, William D.; Bloomer, William D.

    1994-01-01

    Hypoxia selective cytotoxins of the general formula ##STR1## wherein n is from 1 to 5, and NO.sub.2 is in at least one of the 2, 4 or 5-positions of the imidazole. Such compounds have utility as radiosensitizers and chemosensitizers.

  4. Acridine-intercalator based hypoxia selective cytotoxins

    DOEpatents

    Papadopoulou-Rosenzweig, M.; Bloomer, W.D.

    1994-03-15

    Hypoxia selective cytotoxins of the general formula STR1 wherein n is from 1 to 5, and NO[sub 2] is in at least one of the 2, 4 or 5-positions of the imidazole are developed. Such compounds have utility as radiosensitizers and chemosensitizers. 9 figs.

  5. Evaluation of phototoxicity of dendritic porphyrin-based phosphorescent oxygen probes: an in vitro study†

    PubMed Central

    Lebedev, Artem Y.; Marchi, Enrico; Yuan, Min; Esipova, Tatiana V.; Bergamini, Giacomo; Wilson, David F.

    2013-01-01

    Biological oxygen measurements by phosphorescence quenching make use of exogenous phosphorescent probes, which are introduced directly into the medium of interest (e.g. blood or interstitial fluid) where they serve as molecular sensors for oxygen. The byproduct of the quenching reaction is singlet oxygen, a highly reactive species capable of damaging biological tissue. Consequently, potential probe phototoxicity is a concern for biological applications. Herein, we compared the ability of polyethyleneglycol (PEG)-coated Pd tetrabenzoporphyrin (PdTBP)-based dendritic nanoprobes of three successive generations to sensitize singlet oxygen. It was found that the size of the dendrimer has practically no effect on the singlet oxygen sensitization efficiency in spite of the strong attenuation of the triplet quenching rate with an increase in the dendrimer generation. This unexpected result is due to the fact that the lifetime of the PdTBP triplet state in the absence of oxygen increases with dendritic generation, thus compensating for the concomitant decrease in the rate of quenching. Nevertheless, in spite of their ability to sensitize singlet oxygen, the phosphorescent probes were found to be non-phototoxic when compared with the commonly used photodynamic drug Photofrin in a standard cell-survival assay. The lack of phototoxicity is presumably due to the inability of PEGylated probes to associate with cell surfaces and/or penetrate cellular membranes. In contrast, conventional photosensitizers bind to cell components and act by generating singlet oxygen inside or in the immediate vicinity of cellular organelles. Therefore, PEGylated dendritic probes are safe to use for tissue oxygen measurements as long as the light doses are less than or equal to those commonly employed in photodynamic therapy. PMID:21409208

  6. Manufacture of concentrated, lipid-based oxygen microbubble emulsions by high shear homogenization and serial concentration.

    PubMed

    Thomson, Lindsay M; Polizzotti, Brian D; McGowan, Frances X; Kheir, John N

    2014-01-01

    Gas-filled microbubbles have been developed as ultrasound contrast and drug delivery agents. Microbubbles can be produced by processing surfactants using sonication, mechanical agitation, microfluidic devices, or homogenization. Recently, lipid-based oxygen microbubbles (LOMs) have been designed to deliver oxygen intravenously during medical emergencies, reversing life-threatening hypoxemia, and preventing subsequent organ injury, cardiac arrest, and death. We present methods for scaled-up production of highly oxygenated microbubbles using a closed-loop high-shear homogenizer. The process can produce 2 L of concentrated LOMs (90% by volume) in 90 min. Resulting bubbles have a mean diameter of ~2 μm, and a rheologic profile consistent with that of blood when diluted to 60 volume %. This technique produces LOMs in high capacity and with high oxygen purity, suggesting that this technique may be useful for translational research labs. PMID:24894333

  7. Enhanced electrocatalysis of the oxygen reduction reaction based on pattering of platinum surfaces with cyanide.

    SciTech Connect

    Strmcnik, D.; Escudero-Escribano, M.; Kodama, K.; Stamenkovic, V. R.; Cuesta, A.; Markovic, N. M.; Materials Science Division; Inst. de Quimica Fisica; Toyota Central R&D Labs., Inc.

    2010-08-15

    The slow rate of the oxygen reduction reaction in the phosphoric acid fuel cell is the main factor limiting its wide application. Here, we present an approach that can be used for the rational design of cathode catalysts with potential use in phosphoric acid fuel cells, or in any environments containing strongly adsorbing tetrahedral anions. This approach is based on molecular patterning of platinum surfaces with cyanide adsorbates that can efficiently block the sites for adsorption of spectator anions while the oxygen reduction reaction proceeds unhindered. We also demonstrate that, depending on the supporting electrolyte anions and cations, on the same CN-covered Pt(111) surface, the oxygen reduction reaction activities can range from a 25-fold increase to a 50-fold decrease. This behaviour is discussed in the light of the role of covalent and non-covalent interactions in controlling the ensemble of platinum active sites required for high turn over rates of the oxygen reduction reaction.

  8. Enhanced electrocatalysis of the oxygen reduction reaction based on patterning of platinum surfaces with cyanide

    SciTech Connect

    Strmcnik, D.; Escudero, M.; Kodama, K.; Stamenkovic, V. R.; Cuesta, A.; Markovic, N. M.

    2010-10-01

    The slow rate of the oxygen reduction reaction in the phosphoric acid fuel cell is the main factor limiting its wide application. Here, we present an approach that can be used for the rational design of cathode catalysts with potential use in phosphoric acid fuel cells, or in any environments containing strongly adsorbing tetrahedral anions. This approach is based on molecular patterning of platinum surfaces with cyanide adsorbates that can efficiently block the sites for adsorption of spectator anions while the oxygen reduction reaction proceeds unhindered. We also demonstrate that, depending on the supporting electrolyte anions and cations, on the same CN-covered Pt(111) surface, the oxygen reduction reaction activities can range from a 25-fold increase to a 50-fold decrease. This behaviour is discussed in the light of the role of covalent and non-covalent interactions in controlling the ensemble of platinum active sites required for high turn over rates of the oxygen reduction reaction.

  9. Manufacture of Concentrated, Lipid-based Oxygen Microbubble Emulsions by High Shear Homogenization and Serial Concentration

    PubMed Central

    Thomson, Lindsay M.; Polizzotti, Brian D.; McGowan, Frances X.; Kheir, John N.

    2014-01-01

    Gas-filled microbubbles have been developed as ultrasound contrast and drug delivery agents. Microbubbles can be produced by processing surfactants using sonication, mechanical agitation, microfluidic devices, or homogenization. Recently, lipid-based oxygen microbubbles (LOMs) have been designed to deliver oxygen intravenously during medical emergencies, reversing life-threatening hypoxemia, and preventing subsequent organ injury, cardiac arrest, and death. We present methods for scaled-up production of highly oxygenated microbubbles using a closed-loop high-shear homogenizer. The process can produce 2 L of concentrated LOMs (90% by volume) in 90 min. Resulting bubbles have a mean diameter of ~2 μm, and a rheologic profile consistent with that of blood when diluted to 60 volume %. This technique produces LOMs in high capacity and with high oxygen purity, suggesting that this technique may be useful for translational research labs. PMID:24894333

  10. Sodium-oxygen batteries with alkyl-carbonate and ether based electrolytes.

    PubMed

    Kim, Jinsoo; Lim, Hee-Dae; Gwon, Hyeokjo; Kang, Kisuk

    2013-03-14

    Recently, metal-air batteries, such as lithium-air and zinc-air systems, have been studied extensively as potential candidates for ultra-high energy density storage devices because of their exceptionally high capacities. Here, we report such an electrochemical system based on sodium, which is abundant and inexpensive. Two types of sodium-oxygen batteries were introduced and studied, i.e. with carbonate and non-carbonate electrolytes. Both types could deliver specific capacities (2800 and 6000 mA h g(-1)) comparable to that of lithium-oxygen batteries but with slightly lower discharge voltages (2.3 V and 2.0 V). The reaction mechanisms of sodium-oxygen batteries in carbonate and non-carbonate electrolytes were investigated and compared with those of lithium-oxygen batteries. PMID:23386220

  11. Medium Effects are as Important as Catalyst Design for Selectivity in Electrocatalytic Oxygen Reduction by Iron-porphyrin Complexes

    SciTech Connect

    Rigsby, Matthew L.; Wasylenko, Derek J.; Pegis, Michael L.; Mayer, James M.

    2015-04-08

    Several substituted iron porphyrin com-plexes were evaluated for oxygen reduction reaction (ORR) electrocatalysis in different homogeneous and heterogeneous media. The selectivity for 4-electron re-duction to H2O vs. 2-electron reduction to H2O2 varies substantially from one medium to another for a given catalyst. In many cases, the influence of the medium in which the catalyst is evaluated has a larger effect on the observed selectivity than the factors attributable to chemical modification of the catalyst. For instance, introduction of potential proton relays has variable effects depending on the catalyst medium. Thus, comparisons of ORR selectivity results need to be interpreted with caution, as the catalysis is a property not just of the catalyst, but also of the larger mesoscale environment be-yond the catalyst. Still, in all the direct pairwise comparisons in the same medium, the catalysts with potential proton relays have similar or better selectivity for the preferred 4e– path. This work was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences.

  12. Redox-Active Metal-Organic Composites for Highly Selective Oxygen Separation Applications.

    PubMed

    Zhang, Wen; Banerjee, Debasis; Liu, Jian; Schaef, Herbert T; Crum, Jarrod V; Fernandez, Carlos A; Kukkadapu, Ravi K; Nie, Zimin; Nune, Satish K; Motkuri, Radha K; Chapman, Karena W; Engelhard, Mark H; Hayes, James C; Silvers, Kurt L; Krishna, Rajamani; McGrail, B Peter; Liu, Jun; Thallapally, Praveen K

    2016-05-01

    A redox-active metal-organic composite material shows improved and selective O2 adsorption over N2 with respect to individual components (MIL-101 and ferrocene). The O2 sensitivity of the composite material arises due to the formation of maghemite nanoparticles with the pore of the metal-organic framework material. PMID:26953336

  13. Evaluation of oxygen-response times of phthalocyanine-based crystalline paramagnetic spin probes for EPR oximetry

    PubMed Central

    Vikram, Deepti S.; Ahmad, Rizwan; Pandian, Ramasamy P.; Petryakov, Sergey; Kuppusamy, Periannan

    2009-01-01

    The goal of the present study was to evaluate the temporal response of particulate-based EPR oximetry probes to changes in partial pressure of oxygen (pO2). In order to accurately evaluate the oxygen-response time, we developed a method for rapid modulation of pO2 in a chamber containing the probe using an oscillator-driven speaker–diaphragm setup. The apparatus was capable of producing sinusoidal changes in pO2 at frequencies up to 300 Hz or more. The pressure-modulation setup was used to evaluate the temporal response of some of the most commonly used phthalocyanine-based particulate probes. For validation, the time-response of the probes was compared to that of a high sensitivity pressure sensor. The results revealed that some particulate probes could respond to changes in pO2 with a temporal response of 3.3 ms (300 Hz). The observations were interpreted in the light of their crystalline packing in favor of oxygen diffusion. The results of the present study should enable the selection of probes for oximetry applications requiring high temporal resolution. PMID:18479953

  14. Virucidal Nanofiber Textiles Based on Photosensitized Production of Singlet Oxygen

    PubMed Central

    Lhotáková, Yveta; Plíštil, Lukáš; Morávková, Alena; Kubát, Pavel; Lang, Kamil; Forstová, Jitka; Mosinger, Jiří

    2012-01-01

    Novel biomaterials based on hydrophilic polycaprolactone and polyurethane (Tecophilic®) nanofibers with an encapsulated 5,10,5,20-tetraphenylporphyrin photosensitizer were prepared by electrospinning. The doped nanofiber textiles efficiently photo-generate O2(1Δg), which oxidize external chemical and biological substrates/targets. Strong photo-virucidal effects toward non-enveloped polyomaviruses and enveloped baculoviruses were observed on the surface of these textiles. The photo-virucidal effect was confirmed by a decrease in virus infectivity. In contrast, no virucidal effect was detected in the absence of light and/or the encapsulated photosensitizer. PMID:23139839

  15. Virucidal nanofiber textiles based on photosensitized production of singlet oxygen.

    PubMed

    Lhotáková, Yveta; Plíštil, Lukáš; Morávková, Alena; Kubát, Pavel; Lang, Kamil; Forstová, Jitka; Mosinger, Jiří

    2012-01-01

    Novel biomaterials based on hydrophilic polycaprolactone and polyurethane (Tecophilic®) nanofibers with an encapsulated 5,10,5,20-tetraphenylporphyrin photosensitizer were prepared by electrospinning. The doped nanofiber textiles efficiently photo-generate O(2)((1)Δ(g)), which oxidize external chemical and biological substrates/targets. Strong photo-virucidal effects toward non-enveloped polyomaviruses and enveloped baculoviruses were observed on the surface of these textiles. The photo-virucidal effect was confirmed by a decrease in virus infectivity. In contrast, no virucidal effect was detected in the absence of light and/or the encapsulated photosensitizer. PMID:23139839

  16. An economic analysis of selected strategies for dissolved-oxygen management; Chattahoochee River, Georgia

    USGS Publications Warehouse

    Schefter, John E.; Hirsch, Robert M.

    1980-01-01

    A method for evaluating the cost-effectiveness of alternative strategies for dissolved-oxygen (DO) management is demonstrated, using the Chattahoochee River, GA., as an example. The conceptual framework for the analysis is suggested by the economic theory of production. The minimum flow of the river and the percentage of the total waste inflow receiving nitrification are considered to be two variable inputs to be used in the production of given minimum concentration of DO in the river. Each of the inputs has a cost: the loss of dependable peak hydroelectric generating capacity at Buford Dam associated with flow augmentation and the cost associated with nitrification of wastes. The least-cost combination of minimum flow and waste treatment necessary to achieve a prescribed minimum DO concentration is identified. Results of the study indicate that, in some instances, the waste-assimilation capacity of the Chattahoochee River can be substituted for increased waste treatment; the associated savings in waste-treatment costs more than offset the benefits foregone because of the loss of peak generating capacity at Buford Dam. The sensitivity of the results to the estimates of the cost of replacing peak generating capacity is examined. It is also demonstrated that a flexible approach to the management of DO in the Chattahoochee River may be much more cost effective than a more rigid, institutional approach wherein constraints are placed on the flow of the river and(or) on waste-treatment practices. (USGS)

  17. The effect of hyperbaric oxygen in the enhancement of healing in selected problem wounds.

    PubMed

    Warriner, Robert A; Hopf, Harriet W

    2012-01-01

    Problem wounds represent a significant and growing challenge to our healthcare system. The incidence and prevalence of these wounds are increasing in the population, resulting in growing utilization of healthcare resources and dollars expended. Venous leg ulcers represent the most common lower-extremity wound seen in ambulatory wound care centers, with recurrences frequent and outcomes often less than satisfactory. Pressure ulcers are common in patients in long-term institutional care settings adding significant increases in cost, disability and liability. Foot ulcers in patients with diabetes contribute to more than half of lower-extremity amputations in the United States in a group at risk, representing only 3 percent of the population. In response to this challenge, specialized programs have emerged designed to identify and manage these patients, using standardized protocols and a variety of new technologies to improve outcomes. Hyperbaric oxygen treatment (HBO2T) has been increasingly utilized in an adjunctive role in the care of many of these patients, coinciding with optimized patient and local wound care. PMID:23045921

  18. Estimating streambed travel times and respiration rates based on temperature and oxygen consumption

    NASA Astrophysics Data System (ADS)

    Vieweg, M.; Fleckenstein, J. H.; Schmidt, C.

    2015-12-01

    Oxygen consumption is a common proxy for aerobic respiration and novel in situ measurement techniques with high spatial resolution enable an accurate determination of the oxygen distribution in the streambed. The oxygen concentration at a certain location in the streambed depends on the input concentration, the respiration rate, temperature, and the travel time of the infiltrating flowpath. While oxygen concentrations and temperature can directly be measured, respiration rate and travel time must be estimated from the data. We investigated the interplay of these factors using a 6 month long, 5-min resolution dataset collected in a 3rdorder gravel-bed stream. Our objective was twofold, to determine transient rates of hyporheic respiration and to estimate travel times in the streambed based solely on oxygen and temperature measurements. Our results show that temperature and travel time explains ~70% of the variation in oxygen concentration in the streambed. Independent travel times were obtained using natural variations in the electrical conductivity (EC) of the stream water as tracer (µ=4.1 h; σ=2.3 h). By combining these travel times with the oxygen consumption, we calculated a first order respiration rate (µ=9.7 d-1; σ=6.1 d-1). Variations in the calculated respiration rate are largely explained by variations in streambed temperature. An empirical relationship between our respiration rate and temperature agrees with the theoretical Boltzmann-Arrhenius equation. With this relationship, a temperature-based respiration rate can be estimated and used to re-estimate subsurface travel times. The resulting travel times distinctively resemble the EC-derived travel times (R20.47; Nash-Sutcliffe coefficient 0.32). Both calculations of travel time are correlated to stream water levels and increase during discharge events, enhancing the oxygen consumption for these periods. No other physical factors besides temperature were significantly correlated with the respiration

  19. Palladium-Based Nanomaterials: A Platform to Produce Reactive Oxygen Species for Catalyzing Oxidation Reactions.

    PubMed

    Long, Ran; Huang, Hao; Li, Yaping; Song, Li; Xiong, Yujie

    2015-11-25

    Oxidation reactions by molecular oxygen (O2 ) over palladium (Pd)-based nanomaterials are a series of processes crucial to the synthesis of fine chemicals. In the past decades, investigations of related catalytic materials have mainly been focused on the synthesis of Pd-based nanomaterials from the angle of tailoring their surface structures, compositions and supporting materials, in efforts to improve their activities in organic reactions. From the perspective of rational materials design, it is imperative to address the fundamental issues associated with catalyst performance, one of which should be oxygen activation by Pd-based nanomaterials. Here, the fundamentals that account for the transformation from O2 to reactive oxygen species over Pd, with a focus on singlet O2 and its analogue, are introduced. Methods for detecting and differentiating species are also presented to facilitate future fundamental research. Key factors for tuning the oxygen activation efficiencies of catalytic materials are then outlined, and recent developments in Pd-catalyzed oxygen-related organic reactions are summarized in alignment with each key factor. To close, we discuss the challenges and opportunities for photocatalysis research at this unique intersection as well as the potential impact on other research fields. PMID:26422795

  20. Accelerated materials design of fast oxygen ionic conductors based on first principles calculations

    NASA Astrophysics Data System (ADS)

    He, Xingfeng; Mo, Yifei

    Over the past decades, significant research efforts have been dedicated to seeking fast oxygen ion conductor materials, which have important technological applications in electrochemical devices such as solid oxide fuel cells, oxygen separation membranes, and sensors. Recently, Na0.5Bi0.5TiO3 (NBT) was reported as a new family of fast oxygen ionic conductor. We will present our first principles computation study aims to understand the O diffusion mechanisms in the NBT material and to design this material with enhanced oxygen ionic conductivity. Using the NBT materials as an example, we demonstrate the computation capability to evaluate the phase stability, chemical stability, and ionic diffusion of the ionic conductor materials. We reveal the effects of local atomistic configurations and dopants on oxygen diffusion and identify the intrinsic limiting factors in increasing the ionic conductivity of the NBT materials. Novel doping strategies were predicted and demonstrated by the first principles calculations. In particular, the K doped NBT compound achieved good phase stability and an order of magnitude increase in oxygen ionic conductivity of up to 0.1 S cm-1 at 900 K compared to the experimental Mg doped compositions. Our results provide new avenues for the future design of the NBT materials and demonstrate the accelerated design of new ionic conductor materials based on first principles techniques. This computation methodology and workflow can be applied to the materials design of any (e.g. Li +, Na +) fast ion-conducting materials.

  1. Novel hemoglobin particles--promising new-generation hemoglobin-based oxygen carriers.

    PubMed

    Bäumler, Hans; Xiong, Yu; Liu, Zhi Zhao; Patzak, Andreas; Georgieva, Radostina

    2014-08-01

    During the last 30 years, artificial oxygen carriers have been investigated intensively with the aim to develop universal blood substitutes. Favorably, hemoglobin-based oxygen carriers (HBOCs) are expected to meet the sophisticated requirements. However, the HBOCs tested until now show serious side effects, which resulted in failure of clinical trials and Food and Drug Administration disapproval. The main problem consists in vasoconstriction triggered by nitric oxide (NO) scavenging or/and oxygen oversupply in the pre-capillary arterioles. HBOCs with a size between 100 nm and 1 µm and high oxygen affinity are needed. Here we present a highly effective and simple fabrication procedure, which can provide hemoglobin particles (HbPs) with a narrow size distribution of around 700 nm, nearly uniform morphology, high oxygen affinity, and low immunogenicity. Isolated mouse glomeruli are successfully perfused with concentrated HbP suspensions without any observable vasoconstriction of the afferent arterioles. The results suggest no oxygen oversupply and limited NO scavenging by these particles, featuring them as a highly promising blood substitute. PMID:24962099

  2. EEG feature selection method based on decision tree.

    PubMed

    Duan, Lijuan; Ge, Hui; Ma, Wei; Miao, Jun

    2015-01-01

    This paper aims to solve automated feature selection problem in brain computer interface (BCI). In order to automate feature selection process, we proposed a novel EEG feature selection method based on decision tree (DT). During the electroencephalogram (EEG) signal processing, a feature extraction method based on principle component analysis (PCA) was used, and the selection process based on decision tree was performed by searching the feature space and automatically selecting optimal features. Considering that EEG signals are a series of non-linear signals, a generalized linear classifier named support vector machine (SVM) was chosen. In order to test the validity of the proposed method, we applied the EEG feature selection method based on decision tree to BCI Competition II datasets Ia, and the experiment showed encouraging results. PMID:26405856

  3. Selection in sugarcane based on inbreeding depression.

    PubMed

    de Azeredo, A A C; Bhering, L L; Brasileiro, B P; Cruz, C D; Barbosa, M H P

    2016-01-01

    This study aimed to evaluate the gene action associated with yield-related traits, including mean stalk weight (MSW), tons of sugarcane per hectare (TCH), and fiber content (FIB) in sugarcane. Moreover, the viability of individual reciprocal recurrent selection (RRSI-S1) was verified, and the effect of inbreeding depression on progenies was checked. The results were also used to select promising genotypes in S1 progenies. Eight clones (RB925345, RB867515, RB739359, SP80-1816, RB928064, RB865230, RB855536, and RB943365) and their respective progenies, derived from selfing (S1), were evaluated. Several traits, including the number of stalks, MSW, soluble solids content determined in the field, stalk height, stalk diameter, TCH, soluble solids content determined in the laboratory, sucrose content, and FIB were evaluated in a randomized block design with hierarchical classification. The results showed that the traits with predominant gene action associated with the dominance variance of MSW and TCH were most affected by inbreeding depression. The FIB, with predominant additive control, was not affected by selfing of the clones, and the RB867515⊗, RB928064⊗, RB739359⊗ and RB925345⊗ progenies performed best. Therefore, the use of S1 progenies for RRSI-S1 in sugarcane breeding programs is promising, and it should be explored for the future breeding of clones with high FIB levels. PMID:27323098

  4. Selective oxygenation of alkynes: a direct approach to diketones and vinyl acetate.

    PubMed

    Xia, Xiao-Feng; Gu, Zhen; Liu, Wentao; Wang, Ningning; Wang, Haijun; Xia, Yongmei; Gao, Haiyan; Liu, Xiang

    2014-12-28

    Arylalkynes can be converted into α-diketones with the use of a copper catalyst, and also be transformed into vinyl acetates under metal-free conditions, both in the presence of PhI(OAc)2 as an oxidant at room temperature. A series of substituted α-diketones were prepared in moderate to good yields. A variety of vinyl halides could be regio- and stereo-selectively synthesized under mild conditions, and I, Br and Cl could be all easily embedded into the alkynes. PMID:25356631

  5. Selective oxidation of glycerol by using a hydrotalcite-supported platinum catalyst under atmospheric oxygen pressure in water.

    PubMed

    Tsuji, Akihiro; Rao, Kasanneni Tirumala Venkateswara; Nishimura, Shun; Takagaki, Atsushi; Ebitani, Kohki

    2011-04-18

    A hydrotalcite-supported platinum (Pt/HT) catalyst was found to be a highly active and selective heterogeneous catalyst for glycerol oxidation in pure water under atmospheric oxygen pressure in a high glycerol/metal molar ratio up to 3125. High selectivity toward glyceric acid (78 %) was obtained even at room temperature under air atmosphere. The Pt/HT catalyst selectively oxidized the primary hydroxyl group of 1,2-propandiol to give the corresponding carboxylic acid (lactic acid) as well as glycerol. The activity of the catalyst was greatly influenced by the Mg/Al ratio of hydrotalcite. Glycerol conversion increased with increasing the Mg/Al ratio of hydrotalcite (from trace to 56 %). X-ray absorption fine structure (XAFS) measurements indicated that the catalytic oxidation activity was proportional to the metallic platinum concentration, and more than 35 % of metallic platinum was necessary for this reaction. TEM measurements and titration analysis by using benzoic acid suggested that the solid basicity of hydrotalcite plays important roles in the precise control of platinum size and metal concentration as well as the initial promotion of alcohol oxidation. PMID:21271683

  6. Discovery of Small-Molecule Enhancers of Reactive Oxygen Species That are Nontoxic or Cause Genotype-Selective Cell Death

    PubMed Central

    2013-01-01

    Elevation of reactive oxygen species (ROS) levels has been observed in many cancer cells relative to nontransformed cells, and recent reports have suggested that small-molecule enhancers of ROS may selectively kill cancer cells in various in vitro and in vivo models. We used a high-throughput screening approach to identify several hundred small-molecule enhancers of ROS in a human osteosarcoma cell line. A minority of these compounds diminished the viability of cancer cell lines, indicating that ROS elevation by small molecules is insufficient to induce death of cancer cell lines. Three chemical probes (BRD5459, BRD56491, BRD9092) are highlighted that most strongly elevate markers of oxidative stress without causing cell death and may be of use in a variety of cellular settings. For example, combining nontoxic ROS-enhancing probes with nontoxic doses of l-buthionine sulfoximine, an inhibitor of glutathione synthesis previously studied in cancer patients, led to potent cell death in more than 20 cases, suggesting that even nontoxic ROS-enhancing treatments may warrant exploration in combination strategies. Additionally, a few ROS-enhancing compounds that contain sites of electrophilicity, including piperlongumine, show selective toxicity for transformed cells over nontransformed cells in an engineered cell-line model of tumorigenesis. These studies suggest that cancer cell lines are more resilient to chemically induced increases in ROS levels than previously thought and highlight electrophilicity as a property that may be more closely associated with cancer-selective cell death than ROS elevation. PMID:23477340

  7. Adaptive Cognitive-Based Selection of Learning Objects

    ERIC Educational Resources Information Center

    Karampiperis, Pythagoras; Lin, Taiyu; Sampson, Demetrios G.; Kinshuk

    2006-01-01

    Adaptive cognitive-based selection is recognized as among the most significant open issues in adaptive web-based learning systems. In order to adaptively select learning resources, the definition of adaptation rules according to the cognitive style or learning preferences of the learners is required. Although some efforts have been reported in…

  8. 44 CFR 321.2 - Selection of the mobilization base.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 44 Emergency Management and Assistance 1 2010-10-01 2010-10-01 false Selection of the mobilization base. 321.2 Section 321.2 Emergency Management and Assistance FEDERAL EMERGENCY MANAGEMENT AGENCY..., DEPARTMENT OF ENERGY, MARITIME ADMINISTRATION) § 321.2 Selection of the mobilization base. (a) The...

  9. Surface spectators and their role in relationships between activity and selectivity of the oxygen reduction reaction in acid environments.

    SciTech Connect

    Ciapina, Eduardo G.; Lopes, Pietro P.; Subbaraman, Ram; Ticianelli, Edson A.; Stamenkovic, Vojislav; Strmcnik, Dusan; Markovic, Nenad M.

    2015-11-01

    We use the rotating ring disk (RRDE) method to study activity-selectivity relationships for the oxygen reduction reaction (ORR) on Pt(111) modified by various surface coverages of adsorbed CNad (ΘCNad). The results demonstrate that small variations in ΘCNad have dramatic effect on the ORR activity and peroxide production, resulting in “volcano-like” dependence with an optimal surface coverage of ΘCNad = 0.3 ML. These relationships can be simply explained by balancing electronic and ensemble effects of co-adsorbed CNad and adsorbed spectator species from the supporting electrolytes, without the need for intermediate adsorption energy arguments. Although this study has focused on the Pt(111)-CNad/H2SO4 interface, the results and insight gained here are invaluable for controlling another dimension in the properties of electrochemical interfaces.

  10. Computer-Based Information Networks: Selected Examples.

    ERIC Educational Resources Information Center

    Hardesty, Larry

    The history, purpose, and operation of six computer-based information networks are described in general and nontechnical terms. In the introduction the many definitions of an information network are explored. Ohio College Library Center's network (OCLC) is the first example. OCLC began in 1963, and since early 1973 has been extending its services…

  11. Establishment of a total liquid ventilation system using saline-based oxygen micro/nano-bubble dispersions in rats.

    PubMed

    Kakiuchi, Kenta; Matsuda, Kenichi; Harii, Norikazu; Sou, Keitaro; Aoki, Junko; Takeoka, Shinji

    2015-09-01

    Micro/nano-bubbles are practical nanomaterials designed to increase the gas content in liquids. We attempted to use oxygen micro/nano-bubble dispersions as an oxygen-rich liquid as a means for total liquid ventilation. To determine the oxygen content in the bubble dispersion, a new method based on a spectrophotometric change between oxy- and deoxy-hemoglobin was established. The oxygen micro/nano-bubble dispersion was supplied to an experimental total ventilation liquid in anesthetic rats. Though the amount of dissolving oxygen was as low as 6 mg/L in physiological saline, the oxygen content in the oxygen micro/nano-bubble dispersion was increased to 45 mg/L. The positive correlation between the oxygen content and the life-saving time under liquid ventilation clearly indicates that the life-saving time is prolonged by increasing the oxygen content in the oxygen micro/nano-bubble dispersion. This is the first report indicating that the oxygen micro/nano-bubbles containing a sufficient amount of oxygen are useful in producing oxygen-rich liquid for the process of liquid ventilation. PMID:25854604

  12. Selecting supplier combination based on fuzzy multicriteria analysis

    NASA Astrophysics Data System (ADS)

    Han, Zhi-Qiu; Luo, Xin-Xing; Chen, Xiao-Hong; Yang, Wu-E.

    2015-07-01

    Existing multicriteria analysis (MCA) methods are probably ineffective in selecting a supplier combination. Thus, an MCA-based fuzzy 0-1 programming method is introduced. The programming relates to a simple MCA matrix that is used to select a single supplier. By solving the programming, the most feasible combination of suppliers is selected. Importantly, this result differs from selecting suppliers one by one according to a single-selection order, which is used to rank sole suppliers in existing MCA methods. An example highlights such difference and illustrates the proposed method.

  13. Graphene-based hollow spheres as efficient electrocatalysts for oxygen reduction.

    PubMed

    Wu, Longfei; Feng, Hongbin; Liu, Mengjia; Zhang, Kaixiang; Li, Jinghong

    2013-11-21

    A facile and straightforward approach is developed for the construction of graphene-based hollow spheres. An electron rich sodium-ammonia solution is used to effectively restore the π-conjugation of graphene. The hollow spheres exhibit excellent electrocatalytic activity towards oxygen reduction without catalyst deactivation. PMID:24089043

  14. Mechanistic study of nickel based catalysts for oxygen evolution and methanol oxidation in alkaline medium

    NASA Astrophysics Data System (ADS)

    Chen, Dayi; Minteer, Shelley D.

    2015-06-01

    Nickel based catalysts have been studied as catalysts for either organic compound (especially methanol) oxidation or oxygen evolution reactions in alkaline medium for decades, but methanol oxidation and oxygen evolution reactions occur at a similar potential range and pH with nickel based catalysts. In contrast to previous studies, we studied these two reactions simultaneously under various pH and methanol concentrations with electrodes containing a series of NiOOH surface concentrations. We found that nickel based catalysts are more suitable to be used as oxygen evolution catalysts than methanol oxidation catalysts based on the observation that: The rate-determining step of methanol oxidation involves NiOOH, OH- and methanol while high methanol to OH- ratio could poison the NiOOH sites. Since NiOOH is involved in the rate-determining step, methanol oxidation suffers from high overpotential and oxygen evolution is favored over methanol oxidation in the presence of an equivalent amount (0.1 M) of alkali and methanol.

  15. An electrochemical evaluation of ruthenium-based electrocatalysts for oxygen evolution

    NASA Astrophysics Data System (ADS)

    Valdez, Thomas I.

    A study of ruthenium oxide-based oxygen evolution catalysts for use in proton exchange membrane (PEM) electrolyzers was performed. In this work, oxygen evolution catalysts were fabricated via sol-gel, high energy ball milling, and thermal processing techniques. Thermal analysis techniques such as differential scanning calorimetry (DSC), differential thermal analysis (DTA), and thermal gravimetric analysis (TGA) were used to determine the optimum processing temperatures to be used for catalysts fabrication and annealing. The materials properties of the catalysts were studied with scanning electron microscopy, energy dispersive analysis (EDAX), X-ray diffraction, and X-ray photo-electron spectroscopy. Electrodes were fabricated from the oxygen evolution catalysts and tested in electrolysis and three-electrode cells. The catalysts fabricated via sol-gel techniques included a ruthenium oxide and an iridium-ruthenium oxide catalyst. Three families of the thermally processed catalysts were developed: iridium-ruthenium oxide, lead-ruthenium oxide, and tin ruthenium oxide. A lead oxide: ruthenium oxide catalyst was fabricated via high energy ball-milling to be used as a fabrication comparison to the thermally processed catalysts. The electrochemical evaluations for the oxygen evolution catalysts fabricated as electrolysis cells included current-step polarization and constant current electrolysis. The current step polarization experiments were used to determine the relative performance of the catalysts as well as to determine the kinetic parameters for the oxygen evolution reaction. The constant-current electrolysis experiments were used to estimate the degradation of the catalysts during operation. In these studies, it was determined that the thermal processing technique could produce stable and high performing catalysts. The thermally processed iridium ruthenium oxide catalysts with 9 to 12 mole percent iridium had the lowest overpotential for oxygen evolution of the

  16. An imaging-based computational model for simulating angiogenesis and tumour oxygenation dynamics

    NASA Astrophysics Data System (ADS)

    Adhikarla, Vikram; Jeraj, Robert

    2016-05-01

    Tumour growth, angiogenesis and oxygenation vary substantially among tumours and significantly impact their treatment outcome. Imaging provides a unique means of investigating these tumour-specific characteristics. Here we propose a computational model to simulate tumour-specific oxygenation changes based on the molecular imaging data. Tumour oxygenation in the model is reflected by the perfused vessel density. Tumour growth depends on its doubling time (T d) and the imaged proliferation. Perfused vessel density recruitment rate depends on the perfused vessel density around the tumour (sMVDtissue) and the maximum VEGF concentration for complete vessel dysfunctionality (VEGFmax). The model parameters were benchmarked to reproduce the dynamics of tumour oxygenation over its entire lifecycle, which is the most challenging test. Tumour oxygenation dynamics were quantified using the peak pO2 (pO2peak) and the time to peak pO2 (t peak). Sensitivity of tumour oxygenation to model parameters was assessed by changing each parameter by 20%. t peak was found to be more sensitive to tumour cell line related doubling time (~30%) as compared to tissue vasculature density (~10%). On the other hand, pO2peak was found to be similarly influenced by the above tumour- and vasculature-associated parameters (~30–40%). Interestingly, both pO2peak and t peak were only marginally affected by VEGFmax (~5%). The development of a poorly oxygenated (hypoxic) core with tumour growth increased VEGF accumulation, thus disrupting the vessel perfusion as well as further increasing hypoxia with time. The model with its benchmarked parameters, is applied to hypoxia imaging data obtained using a [64Cu]Cu-ATSM PET scan of a mouse tumour and the temporal development of the vasculature and hypoxia maps are shown. The work underscores the importance of using tumour-specific input for analysing tumour evolution. An extended model incorporating therapeutic effects can serve as a powerful tool for

  17. An upgraded camera-based imaging system for mapping venous blood oxygenation in human skin tissue

    NASA Astrophysics Data System (ADS)

    Li, Jun; Zhang, Xiao; Qiu, Lina; Leotta, Daniel F.

    2016-07-01

    A camera-based imaging system was previously developed for mapping venous blood oxygenation in human skin. However, several limitations were realized in later applications, which could lead to either significant bias in the estimated oxygen saturation value or poor spatial resolution in the map of the oxygen saturation. To overcome these issues, an upgraded system was developed using improved modeling and image processing algorithms. In the modeling, Monte Carlo (MC) simulation was used to verify the effectiveness of the ratio-to-ratio method for semi-infinite and two-layer skin models, and then the relationship between the venous oxygen saturation and the ratio-to-ratio was determined. The improved image processing algorithms included surface curvature correction and motion compensation. The curvature correction is necessary when the imaged skin surface is uneven. The motion compensation is critical for the imaging system because surface motion is inevitable when the venous volume alteration is induced by cuff inflation. In addition to the modeling and image processing algorithms in the upgraded system, a ring light guide was used to achieve perpendicular and uniform incidence of light. Cross-polarization detection was also adopted to suppress surface specular reflection. The upgraded system was applied to mapping of venous oxygen saturation in the palm, opisthenar and forearm of human subjects. The spatial resolution of the oxygenation map achieved is much better than that of the original system. In addition, the mean values of the venous oxygen saturation for the three locations were verified with a commercial near-infrared spectroscopy system and were consistent with previously published data.

  18. Bonding preference of carbon, nitrogen, and oxygen in niobium-based rock-salt structures.

    PubMed

    Miura, Akira; Takei, Takahiro; Kumada, Nobuhiro; Wada, Satoshi; Magome, Eisuke; Moriyoshi, Chikako; Kuroiwa, Yoshihiro

    2013-09-01

    Carbon, nitrogen, and oxygen are essential components in solid-state materials. However, understanding their preference on the bonding to metals has not been straightforward. Here, niobium carbide, nitride, and oxide with simple rock-salt-based structures were analyzed by first-principles calculations and synchrotron X-ray diffraction. We found that an increase in the atomic number from carbon to oxygen formed fewer and shorter bonds to metals with better hybridization of atomic orbitals. This can provide a simple guiding principle for understanding the bonding and designing carbides, nitrides, oxides, and mixed-anion compounds. PMID:23937352

  19. Theoretical bases of radar (selected pages)

    NASA Astrophysics Data System (ADS)

    Shirman, Ya. D.; Golikov, V. N.; Busygin, I. N.; Kostin, G. A.; Manshos, V. N.

    1987-06-01

    A textbook is presented for radio engineering departments of schools of higher education, which prepare specialists in radar. The use of statistical methods of analysis as the single base is it special feature. The principles are given of construction and the theory of the devices/equipment of optimum detection in the presence of interferences; the methods are examined for obtaining the radar information taking into account achievements in the region of the optimum working/treatment of serrated radar signals, laws governing secondary radiation and radiowave propagation. A large number of examples, which permits the reader to more rapidly master main questions of theory and its application, are given.

  20. Raman-based Oxygen and Nitrogen Sensor for Monitoring Empty Airplane Fuel Tanks

    NASA Technical Reports Server (NTRS)

    Chen, Peter C.

    2004-01-01

    The purpose of this project was to develop a Raman-based method for detecting oxygen and nitrogen in empty fuel tanks. The need for such a method comes from the potential danger of allowing explosive oxygen-fuel mixtures to accumulate in empty airplane fuel tanks. An explosion resulting from such a mixture is believed to have caused the Flight TWA 800 disaster in 1996. Recently, (e.g., February 17,2004 press release) the FAA announced its intentions to make fuel tank inerting mandatory. One potential solution to this problem is to use an inert gas such as nitrogen to flood the empty fue1 tanks in order to reduce the concentration of oxygen.

  1. Influence of oxygen functionalities on the environmental impact of imidazolium based ionic liquids.

    PubMed

    Deng, Yun; Besse-Hoggan, Pascale; Sancelme, Martine; Delort, Anne-Marie; Husson, Pascale; Gomes, Margarida F Costa

    2011-12-30

    Several physico-chemical properties relevant to determine the environmental impact of ionic liquids - aqueous solubility, octanol-water partition coefficient and diffusion coefficients in water at infinite dilution - together with toxicity and biodegradability of ionic liquids based on 1-alkyl-3-methylimidazolium cations with or without different oxygenated functional groups (hydroxyl, ester and ether) are studied in this work. The presence of oxygen groups on the imidazolium cation reduces the toxicity of ionic liquids 1-alkyl-3-methylimidazolium with bis(trifluoromethylsulfonyl)imide or octylsulfate anions and simultaneously decreases the value of their octanol-water partition coefficient. The presence of ester functions renders the ionic liquids more easily biodegradable, especially for long alkyl side-chains in the cation but leads to hydrolysis with the formation of reaction products that accumulate. The imidazolium ring is resistant to biodegradability and to abiotic degradation. The oxygen functionalised ionic liquids are more soluble in water and, diffuse more slowly in this medium. PMID:22071261

  2. [Measurement of multi-wavelength pulse oxygen saturation based on dynamic spectroscopy].

    PubMed

    Wang, Xiao-Fei; Zhao, Wen-Jun

    2014-05-01

    The present paper puts forward multi-wavelength pulse oxygen saturation measurement based on dynamic spectroscopy to do the non-invasive determination of oxygen saturation. Compared to conventional ways, the new method makes full use of more wavelengths light and improves the measurement accuracy. During the experiment, the in-vivo measurements were carried out on 60 patients and their spectroscopic data were collected by the high sensitivity type fiber optic spectrometer. Singletrial estimation method was used to extract the dynamic spectroscopy at the wavelengths of 606. 44 approximately 987. 55 nm. Oxygen saturation obtained from arterial blood gas analysis is regarded as the true value. Synergy interval partial least square (siPLS) was used to establish the calibration model of subjects' oxygen saturation values against dynamic spectroscopy data. The relative error of prediction is +/-0. 017 6, but the relative error of the subjects in the same set measured by the patient monitor which was two-wavelength measure system is +/-0. 116 4. Measurement results show that the use of the high sensitivity type fiber optic spectrometer to collect multi-wavelength spectroscopic data and dynamic spectroscopy method to process data can do better in improving the accuracy of the oxygen saturation measurement. PMID:25095431

  3. Visible light induced photoelectrochemical biosensing based on oxygen-sensitive quantum dots.

    PubMed

    Wang, Wenjing; Bao, Lei; Lei, Jianping; Tu, Wenwen; Ju, Huangxian

    2012-09-26

    A visible light induced photoelectrochemical biosensing platform based on oxygen-sensitive near-infrared quantum dots (NIR QDs) was developed for detection of glucose. The NIR QDs were synthesized in an aqueous solution, and characterized with scanning electron microscopy and X-ray photoelectron spectroscopy. The as-prepared NIR QDs were employed to construct oxygen-sensitive photoelectrochemical biosensor on a fluorine-doped tin oxide (FTO) electrode. The oxygen dependency of the photocurrent was investigated at as-prepared electrode, which demonstrated the signal of photocurrent is suppressed with the decreasing of oxygen. Coupling with the consumption of oxygen during enzymatic reaction, a photoelectrochemical strategy was proposed for the detection of substrate. Using glucose oxidase (GOx) as a model enzyme, that is, GOx was covalently attached to the surface of CdTe QDs, the resulting biosensor showed the sensitive response to glucose. Under the irradiation of visible light of a wavelength at 505 nm, the proposed photoelectrochemical method could detect glucose ranging from 0.1 mM to 11 mM with a detection limit of 0.04 mM. The photoelectrochemical biosensor showed a good performance with high upper detection limit, acceptable stability and accuracy, providing an alternative method for monitoring biomolecules and extending the application of near-infrared QDs. PMID:22935371

  4. Reversible potentiometric oxygen sensors based on polymeric and metallic film electrodes.

    PubMed

    Yim, H S; Meyerhoff, M E

    1992-09-01

    Various materials and sensor configurations that exhibit reversible potentiometric responses to the partial pressure of oxygen at room temperature in neutral pH solution are examined. In one arrangement, platinum electrodes are coated with plasticized poly(vinyl chloride) films doped with a cobalt(II) tetraethylene pentamine complex. For such sensors, potentiometric oxygen response is attributed to a mixed potential originating from the underlying platinum electrode surface as well as a change in redox potential of the Co(II)-tetren-doped film as the complex binds oxygen reversibly. The response due to the platinum surface is prolonged by the presence of the Co(II)-tetren/PVC film. Alternately, thin films of metallic copper, electrochemically deposited on platinum and/or sputtered or vapor deposited on a single crystal silicon substrate, may be used for reversible oxygen sensing. The long-term reversibility and potentiometric stability of such copper film-based sensors is enhanced (up to 1 month) by preventing the formation of cuprous oxide on the surfaces via the application of an external nonpolarizing cathodic current through the working electrode or by specifically using sputtered copper films that have [100] preferred crystal structures as determined by X-ray diffraction. The implications of these findings in relation to fabricating analytically useful potentiometric oxygen sensors are discussed. PMID:1416035

  5. Piperlongumine selectively kills glioblastoma multiforme cells via reactive oxygen species accumulation dependent JNK and p38 activation.

    PubMed

    Liu, Ju Mei; Pan, Feng; Li, Li; Liu, Qian Rong; Chen, Yong; Xiong, Xin Xin; Cheng, Kejun; Yu, Shang Bin; Shi, Zhi; Yu, Albert Cheung-Hoi; Chen, Xiao Qian

    2013-07-19

    Piperlongumine (PL), a natural alkaloid isolated from the long pepper, may have anti-cancer properties. It selectively targets and kills cancer cells but leaves normal cells intact. Here, we reported that PL selectively killed glioblastoma multiforme (GBM) cells via accumulating reactive oxygen species (ROS) to activate JNK and p38. PL at 20μM could induce severe cell death in three GBM cell lines (LN229, U87 and 8MG) but not astrocytes in cultures. PL elevated ROS prominently and reduced glutathione levels in LN229 and U87 cells. Antioxidant N-acetyl-L-cysteine (NAC) completely reversed PL-induced ROS accumulation and prevented cell death in LN229 and U87 cells. In LN229 and U87 cells, PL-treatment activated JNK and p38 but not Erk and Akt, in a dosage-dependent manner. These activations could be blocked by NAC pre-treatment. JNK and p38 specific inhibitors, SB203580 and SP600125 respectively, significantly blocked the cytotoxic effects of PL in LN229 and U87 cells. Our data first suggests that PL may have therapeutic potential for one of the most malignant and refractory tumors GBM. PMID:23796709

  6. Selective Reduction of NOx in Oxygen Rich Environment with Plasma-Assisted Catalysis: Role of Plasma and Reactive Intermediates

    SciTech Connect

    Panov, Alexander G.; Tonkyn, Russell G.; Balmer, Marilou L.; Peden, Charles HF.; Malkin, A; Hoard, John; Balmer, M.L.; Fisher, G.; Hoard, J.

    2001-09-01

    Catalytic activity of selected materials (BaY and NaY zeolites, and g-Alumina) for selective NOx reduction in combination with a non-thermal plasma was investigated. Our studies suggest that aldehydes formed during the plasma treatment of simulated diesel exhaust are the important species for the reduction of NOx to N2. Indeed, all materials that are active in plasma-assisted catalysis were found to be very effective in the thermal reduction of NOx in the presence of aldehydes. For example, the thermal catalytic activity of a BaY zeolite with aldehydes gives 80-90% NOx removal at 250 C with 200ppm NOx at the inlet, 1000ppm of C1 as acetaldehyde, propionaldehyde, and butyraldehyde, and SV=12,000 h?. The hydrocarbon reductants, n-octane and 1-propyl alcohol have also shown high thermal catalytic activity for NOx removal over BaY, NaY and g-alumina. We believe that this activity is due to the fact that in an oxygen rich environment these compounds can be thermally oxidized over the catalysts to form the important aldehyde reaction intermediates.

  7. Multinomial logistic regression-based feature selection for hyperspectral data

    NASA Astrophysics Data System (ADS)

    Pal, Mahesh

    2012-02-01

    This paper evaluates the performance of three feature selection methods based on multinomial logistic regression, and compares the performance of the best multinomial logistic regression-based feature selection approach with the support vector machine based recurring feature elimination approach. Two hyperspectral datasets, one consisting of 65 features (DAIS data) and other with 185 features (AVIRIS data) were used. Result suggests that a total of between 15 and 10 features selected by using the multinomial logistic regression-based feature selection approach as proposed by Cawley and Talbot achieve a significant improvement in classification accuracy in comparison to the use of all the features of the DAIS and AVIRIS datasets. In addition to the improved performance, the Cawley and Talbot approach does not require any user-defined parameter, thus avoiding the requirement of a model selection stage. In comparison, the other two multinomial logistic regression-based feature selection approaches require one user-defined parameter and do not perform as well as the Cawley and Talbot approach in terms of (i) the number of features required to achieve classification accuracy comparable to that achieved using the full dataset, and (ii) the classification accuracy achieved by the selected features. The Cawley and Talbot approach was also found to be computationally more efficient than the SVM-RFE technique, though both use the same number of selected features to achieve an equal or even higher level of accuracy than that achieved with full hyperspectral datasets.

  8. Information Gain Based Dimensionality Selection for Classifying Text Documents

    SciTech Connect

    Dumidu Wijayasekara; Milos Manic; Miles McQueen

    2013-06-01

    Selecting the optimal dimensions for various knowledge extraction applications is an essential component of data mining. Dimensionality selection techniques are utilized in classification applications to increase the classification accuracy and reduce the computational complexity. In text classification, where the dimensionality of the dataset is extremely high, dimensionality selection is even more important. This paper presents a novel, genetic algorithm based methodology, for dimensionality selection in text mining applications that utilizes information gain. The presented methodology uses information gain of each dimension to change the mutation probability of chromosomes dynamically. Since the information gain is calculated a priori, the computational complexity is not affected. The presented method was tested on a specific text classification problem and compared with conventional genetic algorithm based dimensionality selection. The results show an improvement of 3% in the true positives and 1.6% in the true negatives over conventional dimensionality selection methods.

  9. A simplified headspace biochemical oxygen demand test protocol based on oxygen measurements using a fiber optic probe.

    PubMed

    Min, Booki; Kohler, David; Logan, Bruce E

    2004-01-01

    Batch respirometric tests have many advantages over the conventional biochemical oxygen demand (BOD) method for analysis of wastewaters, including the use of nondiluted samples, a more rapid exertion of oxygen demand, and reduced sample preparation time. The headspace biochemical oxygen demand (HBOD) test can be used to obtain oxygen demands in 2 or 3 days that can predict 5-day biochemical oxygen demand (BOD5) results. The main disadvantage of the HBOD and other respirometric tests has been the lack of a simple and direct method to measure oxygen concentrations in the gas phase. The recent commercial production of a new type of fiber optic oxygen probe, however, provides a method to eliminate this disadvantage. This fiber optic probe, referred to here as the HBOD probe, was tested to see if it could be used in HBOD tests. Gas-phase oxygen measurements made with the HBOD probe took only a few seconds and were not significantly different from those made using a gas chromatograph (t test: n = 15, R2 = 0.9995, p < 0.001). In field tests using the HBOD probe procedure, the probe greatly reduced sample analysis time compared with previous HBOD and BOD protocols and produced more precise results than the BOD test for wastewater samples from two treatment plants (University Area Joint Authority [UAJA] Wastewater Treatment Plant in University Park, Pennsylvania, and The Pennsylvania State University [PSU] Wastewater Treatment Plant in University Park). Headspace biochemical oxygen demand measurements on UAJA primary clarifier effluent were 59.9 +/- 2.4% after 2 days (HBOD2) and 73.0 +/- 3.1% after 3 days (HBOD) of BOD, values, indicating that BOD5 values could be predicted by multiplying HBOD2 values by 1.67 +/- 0.07 or HBOD3 by 1.37 +/- 0.06. Similarly, tests using PSU wastewater samples could be used to provide BOD5 estimates by multiplying the HBOD2 by 1.24 +/- 0.04 or by multiplying the HBOD3 by 0.97 +/- 0.03. These results indicate that the HBOD fiber optic probe can

  10. Basicity of the framework oxygen atom of alkali and alkaline earth-exchanged zeolites: a hard soft acid base approach

    NASA Astrophysics Data System (ADS)

    Deka, Ramesh Ch; Kinkar Roy, Ram; Hirao, Kimihiko

    2000-12-01

    The basicity of framework oxygen atoms of alkali and alkaline earth-exchanged zeolites has been studied using reactivity descriptors based on a local hard-soft acid-base (HSAB) concept. We have calculated the `local softness' and the `relative nucleophilicity' values of the framework oxygen atoms of zeolite clusters as the measure of basicity. The local softness and relative nucleophilicity appear to be more reliable descriptors to predict the experimental basicity trend, compared to the negative charge on the oxygen atom.

  11. A Rule-Based Industrial Boiler Selection System

    NASA Astrophysics Data System (ADS)

    Tan, C. F.; Khalil, S. N.; Karjanto, J.; Tee, B. T.; Wahidin, L. S.; Chen, W.; Rauterberg, G. W. M.; Sivarao, S.; Lim, T. L.

    2015-09-01

    Boiler is a device used for generating the steam for power generation, process use or heating, and hot water for heating purposes. Steam boiler consists of the containing vessel and convection heating surfaces only, whereas a steam generator covers the whole unit, encompassing water wall tubes, super heaters, air heaters and economizers. The selection of the boiler is very important to the industry for conducting the operation system successfully. The selection criteria are based on rule based expert system and multi-criteria weighted average method. The developed system consists of Knowledge Acquisition Module, Boiler Selection Module, User Interface Module and Help Module. The system capable of selecting the suitable boiler based on criteria weighted. The main benefits from using the system is to reduce the complexity in the decision making for selecting the most appropriate boiler to palm oil process plant.

  12. First principle simulations on the effects of oxygen vacancy in HfO2-based RRAM

    NASA Astrophysics Data System (ADS)

    Dai, Yuehua; Zhao, Yuanyang; Wang, Jiayu; Xu, Jianbin; Yang, Fei

    2015-01-01

    HfO2-based resistive random access memory (RRAM) takes advantage of oxygen vacancy (V o) defects in its principle of operation. Since the change in resistivity of the material is controlled by the level of oxygen deficiency in the material, it is significantly important to study the performance of oxygen vacancies in formation of conductive filament. Excluding effects of the applied voltage, the Vienna ab initio simulation package (VASP) is used to investigate the orientation and concentration mechanism of the oxygen vacancies based on the first principle. The optimal value of crystal orientation [010] is identified by means of the calculated isosurface plots of partial charge density, formation energy, highest isosurface value, migration barrier, and energy band of oxygen vacancy in ten established orientation systems. It will effectively influence the SET voltage, forming voltage, and the ON/OFF ratio of the device. Based on the results of orientation dependence, different concentration models are established along crystal orientation [010]. The performance of proposed concentration models is evaluated and analyzed in this paper. The film is weakly conductive for the samples deposited in a mixture with less than 4.167at.% of V o contents, and the resistive switching (RS) phenomenon cannot be observed in this case. The RS behavior improves with an increase in the V o contents from 4.167at.% to 6.25at.%; nonetheless, it is found difficult to switch to a stable state. However, a higher V o concentration shows a more favorable uniformity and stability for HfO2-based RRAM.

  13. Optical oxygen concentration monitor

    DOEpatents

    Kebabian, P.

    1997-07-22

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

  14. Adenosine A1 Receptors Selectively Modulate Oxygen-Induced Retinopathy at the Hyperoxic and Hypoxic Phases by Distinct Cellular Mechanisms

    PubMed Central

    Zhang, Shuya; Li, Haiyan; Li, Bo; Zhong, Dingjuan; Gu, Xuejiao; Tang, Lingyun; Wang, Yanyan; Wang, Cun; Zhou, Rong; Li, Yan; He, Yan; Chen, Mozi; Huo, Yuqing; Liu, Xiao-Ling; Chen, Jiang-Fan

    2015-01-01

    Purpose We critically evaluated the role of the adenosine A1 receptor (A1R) in normal development of retinal vasculature and pathogenesis of retinopathy of prematurity (ROP) by using the A1R knockout (KO) mice and oxygen-induced retinopathy (OIR) model. Methods Mice deficient in A1Rs and their wild-type (WT) littermates were examined during normal postnatal development or after being subjected to 75% oxygen from postnatal day (P) 7 to P12 and to room air from P12 to P17 (OIR model of ROP). Retinal vascularization was examined by whole-mount fluorescence and cross-sectional hematoxylin-eosin staining. Cellular proliferation, astrocyte and microglial activation, and tip cell function were determined by isolectin staining and immunohistochemistry. Apoptosis was determined by TUNEL assay. Results Genetic deletion of the A1R did not affect normal retinal vascularization during postnatal development with indistinguishable three-layer vascularization patterns in retina between WT and A1R KO mice. In the OIR model, genetic deletion of the A1R resulted in stage-specific effects: reduced hyperoxia-induced retinal vaso-obliteration at P12, but reduced avascular area and attenuated hypoxia-induced intraretinal revascularization without affecting intravitreal neovascularization at P17 and reduced avascular areas in retina at P21. These distinct effects of A1Rs on OIR were associated with A1R control of apoptosis mainly in inner and outer nuclear layers at the vaso-obliterative phase (P12) and the growth of endothelium tip cells at the vasoproliferative phase (P17), without modification of cellular proliferation, astrocytic activation, and tissue inflammation. Conclusions Adenosine A1 receptor activity is not required for normal postnatal development of retinal vasculature but selectively controls hyperoxia-induced vaso-obliteration and hypoxia-driven revascularization by distinct cellular mechanisms. PMID:26720463

  15. Adair-based hemoglobin equilibrium with oxygen, carbon dioxide and hydrogen ion activity.

    PubMed

    Mateják, Marek; Kulhánek, Tomáš; Matoušek, Stanislav

    2015-04-01

    As has been known for over a century, oxygen binding onto hemoglobin is influenced by the activity of hydrogen ions (H⁺), as well as the concentration of carbon dioxide (CO₂). As is also known, the binding of both CO₂and H⁺ on terminal valine-1 residues is competitive. One-parametric situations of these hemoglobin equilibria at specific levels of H⁺, O₂or CO₂are also well described. However, we think interpolating or extrapolating this knowledge into an 'empirical' function of three independent variables has not yet been completely satisfactory. We present a model that integrates three orthogonal views of hemoglobin oxygenation, titration, and carbamination at different temperatures. The model is based only on chemical principles, Adair's oxygenation steps and Van't Hoff equation of temperature dependences. Our model fits the measurements of the Haldane coefficient and CO₂hemoglobin saturation. It also fits the oxygen dissociation curve influenced by simultaneous changes in H⁺, CO₂and O₂, which makes it a strong candidate for integration into more complex models of blood acid-base with gas transport, where any combination of mentioned substances can appear. PMID:25594800

  16. Semiconducting Metal Oxide Based Sensors for Selective Gas Pollutant Detection

    PubMed Central

    Kanan, Sofian M.; El-Kadri, Oussama M.; Abu-Yousef, Imad A.; Kanan, Marsha C.

    2009-01-01

    A review of some papers published in the last fifty years that focus on the semiconducting metal oxide (SMO) based sensors for the selective and sensitive detection of various environmental pollutants is presented. PMID:22408500

  17. Shield support selection based on geometric characteristics of coal seam

    SciTech Connect

    K. Goshtasbi; K. Oraee; F. Khakpour-yeganeh

    2006-01-15

    The most initial investment in longwall face equipping is the cost of powered support. Selection of proper shields for powered supports is based on load, geometric characterization of coal seams and economical considerations.

  18. Oxygen-scavenging coatings and films based on lignosulfonates and laccase.

    PubMed

    Johansson, Kristin; Winestrand, Sandra; Johansson, Caisa; Järnström, Lars; Jönsson, Leif J

    2012-09-15

    Laccase and lignosulfonates were included in coating colors and embedded in latex-based or starch-based films and coatings on foil or board. After 6 days at 23 °C and 100% relative humidity, the oxygen content in airtight chambers decreased from 1.0% (synthetic gas consisting of 99% N(2) and 1% O(2)) to 0.3% in the presence of board coated with lignosulfonate and laccase, while the oxygen content remained unchanged in control experiments without enzyme. The water stability of lignosulfonate-containing latex-based coatings and starch-based films was improved after laccase-catalyzed oxidation of lignosulfonates, which indicates polymerization to products with lower solubility in water. Furthermore, the E' modulus of starch-based films increased with 30%, which indicates laccase-catalyzed polymerization of lignosulfonates resulting in increased stiffness of the film. The results suggest that laccases and lignosulfonates can be used as an oxygen-scavenging system in active packaging and that enzyme-catalyzed polymerization of lignosulfonates contributes to improved water stability and mechanical properties. PMID:22721759

  19. A ground-based radio frequency inductively coupled plasma apparatus for atomic oxygen simulation in low Earth orbit

    NASA Astrophysics Data System (ADS)

    Huang, Yongxian; Tian, Xiubo; Yang, Shiqin; Chu, Paul K.

    2007-10-01

    A radio frequency (rf) inductively coupled plasma apparatus has been developed to simulate the atomic oxygen environment encountered in low Earth orbit (LEO). Basing on the novel design, the apparatus can achieve stable, long lasting operation, pure and high density oxygen plasma beam. Furthermore, the effective atomic oxygen flux can be regulated. The equivalent effective atomic oxygen flux may reach (2.289-2.984)×1016at./cm2s at an oxygen pressure of 1.5Pa and rf power of 400W. The equivalent atomic oxygen flux is about 100 times than that in the LEO environment. The mass loss measured from the polyimide sample changes linearly with the exposure time, while the density of the eroded holes becomes smaller. The erosion mechanism of the polymeric materials by atomic oxygen is complex and involves initial reactions at the gas-surface interface as well as steady-state material removal.

  20. A ground-based radio frequency inductively coupled plasma apparatus for atomic oxygen simulation in low Earth orbit.

    PubMed

    Huang, Yongxian; Tian, Xiubo; Yang, Shiqin; Chu, Paul K

    2007-10-01

    A radio frequency (rf) inductively coupled plasma apparatus has been developed to simulate the atomic oxygen environment encountered in low Earth orbit (LEO). Basing on the novel design, the apparatus can achieve stable, long lasting operation, pure and high density oxygen plasma beam. Furthermore, the effective atomic oxygen flux can be regulated. The equivalent effective atomic oxygen flux may reach (2.289-2.984) x 10(16) at.cm(2) s at an oxygen pressure of 1.5 Pa and rf power of 400 W. The equivalent atomic oxygen flux is about 100 times than that in the LEO environment. The mass loss measured from the polyimide sample changes linearly with the exposure time, while the density of the eroded holes becomes smaller. The erosion mechanism of the polymeric materials by atomic oxygen is complex and involves initial reactions at the gas-surface interface as well as steady-state material removal. PMID:17979410

  1. Reactions of State-Selected Atomic Oxygen Ions O(+)((4)S, (2)D, (2)P) with Methane.

    PubMed

    Cunha de Miranda, Barbara; Romanzin, Claire; Chefdeville, Simon; Vuitton, Véronique; Žabka, Jan; Polášek, Miroslav; Alcaraz, Christian

    2015-06-11

    An experimental study has been carried out on the reactions of state selected O(+)((4)S, (2)D, (2)P) ions with methane with the aims of characterizing the effects of both the parent ion internal energy and collision energy on the reaction dynamics and determining the fate of oxygen species in complex media, in particular the Titan ionosphere. Absolute cross sections and product velocity distributions have been determined for the reactions of (16)O(+) or (18)O(+) ions with CH4 or CD4 from thermal to 5 eV collision energies by using the guided ion beam (GIB) technique. Dissociative photoionization of O2 with vacuum ultraviolet (VUV) synchrotron radiation delivered by the DESIRS beamline at the SOLEIL storage ring and the threshold photoion photoelectron coincidence (TPEPICO) technique are used for the preparation of purely state-selected O(+)((4)S, (2)D, (2)P) ions. A complete inversion of the product branching ratio between CH4(+) and CH3(+) ions in favor of the latter is observed for excitation of O(+) ions from the (4)S ground state to either the (2)D or the (2)P metastable state. CH4(+) and CH3(+) ions, which are by far the major products for the reaction of ground state and excited states, are strongly backward scattered in the center of mass frame relative to O(+) parent ions. For the reaction of O(+)((4)S), CH3(+) production also rises with increasing collision energy but with much less efficiency than with O(+) excitation. We found that a mechanism of dissociative charge transfer, mediated by an initial charge transfer step, can account very well for all the observations, indicating that CH3(+) production is associated with the formation of H and O atoms (CH3(+) + H + O) rather than with OH formation by an hydride transfer process (CH3(+) + OH). Therefore, as the CH4(+) production by charge transfer is also associated with O atoms, the fate of oxygen species in these reactions is essentially the O production, except for the reaction of O(+)((4)S), which also

  2. Heme-based Globin-coupled Oxygen Sensors: Linking Oxygen Binding to Functional Regulation of Diguanylate Cyclase, Histidine Kinase, and Methyl-accepting Chemotaxis*

    PubMed Central

    Martínková, Markéta; Kitanishi, Kenichi; Shimizu, Toru

    2013-01-01

    An emerging class of novel heme-based oxygen sensors containing a globin fold binds and senses environmental O2 via a heme iron complex. Structure-function relationships of oxygen sensors containing a heme-bound globin fold are different from those containing heme-bound PAS and GAF folds. It is thus worth reconsidering from an evolutionary perspective how heme-bound proteins with a globin fold similar to that of hemoglobin and myoglobin could act as O2 sensors. Here, we summarize the molecular mechanisms of heme-based oxygen sensors containing a globin fold in an effort to shed light on the O2-sensing properties and O2-stimulated catalytic enhancement observed for these proteins. PMID:23928310

  3. Wavelength-selective ultraviolet (Mg,Zn)O photodiodes: Tuning of parallel composition gradients with oxygen pressure

    NASA Astrophysics Data System (ADS)

    Zhang, Zhipeng; von Wenckstern, Holger; Lenzner, Jörg; Grundmann, Marius

    2016-06-01

    We report on ultraviolet photodiodes with integrated optical filter based on the wurtzite (Mg,Zn)O thin films. Tuning of the bandgap of filter and active layers was realized by employing a continuous composition spread approach relying on the ablation of a single segmented target in pulsed-laser deposition. Filter and active layers of the device were deposited on opposite sides of a sapphire substrate with nearly parallel compositional gradients. Ensure that for each sample position the bandgap of the filter layer blocking the high energy radiation is higher than that of the active layer. Different oxygen pressures during the two depositions runs. The absorption edge is tuned over 360 meV and the spectral bandwidth of photodiodes is typically 100 meV and as low as 50 meV.

  4. A class of high performance metal-free oxygen reduction electrocatalysts based on cheap carbon blacks.

    PubMed

    Sun, Xiujuan; Song, Ping; Zhang, Yuwei; Liu, Changpeng; Xu, Weilin; Xing, Wei

    2013-01-01

    For the goal of practical industrial development of fuel cells, cheap, sustainable and high performance electrocatalysts for oxygen reduction reactions (ORR) which rival those based on platinum (Pt) and other rare materials are highly desirable. In this work, we report a class of cheap and high-performance metal-free oxygen reduction electrocatalysts obtained by co-doping carbon blacks with nitrogen and fluorine (CB-NF).The CB-NF electrocatalysts are highly active and exhibit long-term operation stability and tolerance to poisons during oxygen reduction process in alkaline medium. The alkaline direct methanol fuel cell with the best CB-NF as cathode (3 mg/cm(2)) outperforms the one with commercial platinum-based cathode (3 mg Pt/cm(2)). To the best of our knowledge, these are among the most efficient non-Pt based electrocatalysts. Since carbon blacks are 10,000 times cheaper than Pt, these CB-NF electrocatalysts possess the best price/performance ratio for ORR, and are the most promising alternatives to Pt-based ones to date. PMID:23974295

  5. A Class of High Performance Metal-Free Oxygen Reduction Electrocatalysts based on Cheap Carbon Blacks

    NASA Astrophysics Data System (ADS)

    Sun, Xiujuan; Song, Ping; Zhang, Yuwei; Liu, Changpeng; Xu, Weilin; Xing, Wei

    2013-08-01

    For the goal of practical industrial development of fuel cells, cheap, sustainable and high performance electrocatalysts for oxygen reduction reactions (ORR) which rival those based on platinum (Pt) and other rare materials are highly desirable. In this work, we report a class of cheap and high-performance metal-free oxygen reduction electrocatalysts obtained by co-doping carbon blacks with nitrogen and fluorine (CB-NF).The CB-NF electrocatalysts are highly active and exhibit long-term operation stability and tolerance to poisons during oxygen reduction process in alkaline medium. The alkaline direct methanol fuel cell with the best CB-NF as cathode (3 mg/cm2) outperforms the one with commercial platinum-based cathode (3 mg Pt/cm2). To the best of our knowledge, these are among the most efficient non-Pt based electrocatalysts. Since carbon blacks are 10,000 times cheaper than Pt, these CB-NF electrocatalysts possess the best price/performance ratio for ORR, and are the most promising alternatives to Pt-based ones to date.

  6. Reinterpreting the importance of oxygen-based biodegradation in chloroethene-contaminated groundwater

    USGS Publications Warehouse

    Bradley, Paul M.

    2011-01-01

    Chlororespiration is common in shallow aquifer systems under conditions nominally identified as anoxic. Consequently, chlororespiration is a key component of remediation at many chloroethene-contaminated sites. In some instances, limited accumulation of reductive dechlorination daughter products is interpreted as evidence that natural attenuation is not adequate for site remediation. This conclusion is justified when evidence for parent compound (tetrachloroethene, PCE, or trichloroethene, TCE) degradation is lacking. For many chloroethene-contaminated shallow aquifer systems, however, nonconservative losses of the parent compounds are clear but the mass balance between parent compound attenuation and accumulation of reductive dechlorination daughter products is incomplete. Incomplete mass balance indicates a failure to account for important contaminant attenuation mechanisms and is consistent with contaminant degradation to nondiagnostic mineralization products like CO2. While anoxic mineralization of chloroethene compounds has been proposed previously, recent results suggest that oxygen-based mineralization of chloroethenes also can be significant at dissolved oxygen concentrations below the currently accepted field standard for nominally anoxic conditions. Thus, reassessment of the role and potential importance of low concentrations of oxygen in chloroethene biodegradation are needed, because mischaracterization of operant biodegradation processes can lead to expensive and ineffective remedial actions. A modified interpretive framework is provided for assessing the potential for chloroethene biodegradation under different redox conditions and the probable role of oxygen in chloroethene biodegradation.

  7. Instrumentation for optical measurement of dissolved oxygen based on solid state technology

    NASA Astrophysics Data System (ADS)

    Gruber, Wolfgang R.; Klimant, Ingo; Wolfbeis, Otto S.

    1993-05-01

    A number of measurement schemes for the determination of dissolved or gaseous oxygen have been reported, most of them based on fluorescence quenching methods. They have the disadvantage of requiring large and heavy instrumentation and, therefore, are not suitable for micro-integrated technologies. As a result, the applicability is greatly limited. We introduce a system based on semiconductor devices (LEDs, photodiodes, low cost analogue and digital components) which is well suited for hybrid solutions, and represents a realistic alternative to existing micro integrated electrochemical probes. New LED-compatible sensor membranes were developed and characterized. The influence of straylight on the overall transfer function of the sensor system was investigated and possibilities for reduction or even elimination of this influence are presented. The overall performance of the instrument in terms of sensitivity, detection limits, long-term stability, and reproducibility is presented. The system was applied to the measurement of dissolved oxygen in drinking water and sea water.

  8. Stable hydrogen and oxygen isotope ratios for selected sites of the National Oceanic and Atmospheric Administration's Atmospheric Integrated Research Monitoring Network (AIRMoN)

    USGS Publications Warehouse

    Coplen, Tyler B.; Huang, Richard

    2000-01-01

    Increasingly, hydrologic studies require information on the isotopic composition of natural waters. This report presents stable hydrogen (δ2H) and oxygen isotope ratios (δ180) of precipitation samples from seven selected sites of the National Oceanic and Atmospheric Administration's Atmospheric Integrated Research Monitoring Network (AIRMoN) collected during the years 1992-1994.

  9. Selective catalysts for the hydrogen oxidation and oxygen reduction reactions by patterning of platinum with calix[4]arene molecules.

    SciTech Connect

    Genorio, B.; Strmcnik, D.; Subbaraman, R.; Tripkovic, D.; Karapetrov, G.; Stamenkovic, V. R.; Pejovnik, S.; Markovic, N. M.; Univ. Ljubljana; National Inst. of Chemistry

    2010-12-01

    The design of new catalysts for polymer electrolyte membrane fuel cells must be guided by two equally important fundamental principles: optimization of their catalytic behaviour as well as the long-term stability of the metal catalysts and supports in hostile electrochemical environments. The methods used to improve catalytic activity are diverse, ranging from the alloying and de-alloying of platinum to the synthesis of platinum core-shell catalysts. However, methods to improve the stability of the carbon supports and catalyst nanoparticles are limited, especially during shutdown (when hydrogen is purged from the anode by air) and startup (when air is purged from the anode by hydrogen) conditions when the cathode potential can be pushed up to 1.5 V. Under the latter conditions, stability of the cathode materials is strongly affected (carbon oxidation reaction) by the undesired oxygen reduction reaction (ORR) on the anode side. This emphasizes the importance of designing selective anode catalysts that can efficiently suppress the ORR while fully preserving the Pt-like activity for the hydrogen oxidation reaction. Here, we demonstrate that chemically modified platinum with a self-assembled monolayer of calix[4]arene molecules meets this challenging requirement.

  10. Materials selection for long life in LEO: A critical evaluation of atomic oxygen testing with thermal atom systems

    NASA Technical Reports Server (NTRS)

    Koontz, S. L.; Kuminecz, J.; Leger, L.; Nordine, P.

    1988-01-01

    The use of thermal atom test methods as a materials selection and screening technique for low-Earth orbit (LEO) spacecraft is critically evaluated. The chemistry and physics of thermal atom environments are compared with the LEO environment. The relative reactivities of a number of materials determined to be in thermal atom environments are compared to those observed in LEO and in high quality LEO simulations. Reaction efficiencies measured in a new type of thermal atom apparatus are one-hundredth to one-thousandth those observed in LEO, and many materials showing nearly identical reactivities in LEO show relative reactivities differing by as much as a factor of 8 in thermal atom systems. A simple phenomenological kinetic model for the reaction of oxygen atoms with organic materials can be used to explain the differences in reactivity in different environments. Certain specific thermal test environments can be used as reliable materials screening tools. Using thermal atom methods to predict material lifetime in LEO requires direct calibration of the method against LEO data or high quality simulation data for each material.

  11. Iron-based alloys with corrosion resistance to oxygen-sulfur mixed gases

    DOEpatents

    Natesan, Krishnamurti

    1992-01-01

    An iron-based alloy with improved performance with exposure to oxygen-sulfur mixed gases with the alloy containing about 9-30 wt. % Cr and a small amount of Nb and/or Zr implanted on the surface of the alloy to diffuse a depth into the surface portion, with the alloy exhibiting corrosion resistance to the corrosive gases without bulk addition of Nb and/or Zr and without heat treatment at temperatures of 1000.degree.-1100.degree. C.

  12. Iron-based alloys with corrosion resistance to oxygen-sulfur mixed gases

    DOEpatents

    Natesan, K.

    1992-11-17

    An iron-based alloy with improved performance with exposure to oxygen-sulfur mixed gases with the alloy containing about 9--30 wt. % Cr and a small amount of Nb and/or Zr implanted on the surface of the alloy to diffuse a depth into the surface portion, with the alloy exhibiting corrosion resistance to the corrosive gases without bulk addition of Nb and/or Zr and without heat treatment at temperatures of 1000--1100 C. 7 figs.

  13. A method for selecting training samples based on camera response

    NASA Astrophysics Data System (ADS)

    Zhang, Leihong; Li, Bei; Pan, Zilan; Liang, Dong; Kang, Yi; Zhang, Dawei; Ma, Xiuhua

    2016-09-01

    In the process of spectral reflectance reconstruction, sample selection plays an important role in the accuracy of the constructed model and in reconstruction effects. In this paper, a method for training sample selection based on camera response is proposed. It has been proved that the camera response value has a close correlation with the spectral reflectance. Consequently, in this paper we adopt the technique of drawing a sphere in camera response value space to select the training samples which have a higher correlation with the test samples. In addition, the Wiener estimation method is used to reconstruct the spectral reflectance. Finally, we find that the method of sample selection based on camera response value has the smallest color difference and root mean square error after reconstruction compared to the method using the full set of Munsell color charts, the Mohammadi training sample selection method, and the stratified sampling method. Moreover, the goodness of fit coefficient of this method is also the highest among the four sample selection methods. Taking all the factors mentioned above into consideration, the method of training sample selection based on camera response value enhances the reconstruction accuracy from both the colorimetric and spectral perspectives.

  14. A Molecular Selection Index Method Based on Eigenanalysis

    PubMed Central

    Cerón-Rojas, J. Jesús; Castillo-González, Fernando; Sahagún-Castellanos, Jaime; Santacruz-Varela, Amalio; Benítez-Riquelme, Ignacio; Crossa, José

    2008-01-01

    The traditional molecular selection index (MSI) employed in marker-assisted selection maximizes the selection response by combining information on molecular markers linked to quantitative trait loci (QTL) and phenotypic values of the traits of the individuals of interest. This study proposes an MSI based on an eigenanalysis method (molecular eigen selection index method, MESIM), where the first eigenvector is used as a selection index criterion, and its elements determine the proportion of the trait's contribution to the selection index. This article develops the theoretical framework of MESIM. Simulation results show that the genotypic means and the expected selection response from MESIM for each trait are equal to or greater than those from the traditional MSI. When several traits are simultaneously selected, MESIM performs well for traits with relatively low heritability. The main advantages of MESIM over the traditional molecular selection index are that its statistical sampling properties are known and that it does not require economic weights and thus can be used in practical applications when all or some of the traits need to be improved simultaneously. PMID:18716338

  15. Nucleotide kinase-based selection system for genetic switches.

    PubMed

    Ike, Kohei; Umeno, Daisuke

    2014-01-01

    Ever-increasing repertories of RNA-based switching devices are enabling synthetic biologists to construct compact, self-standing, and easy-to-integrate regulatory circuits. However, it is rather rare that the existing RNA-based expression controllers happen to have the exact specification needed for particular applications from the beginning. Evolutionary design of is powerful strategy for quickly tuning functions/specification of genetic switches. Presented here are the steps required for rapid and efficient enrichment of genetic switches with desired specification using recently developed nucleoside kinase-based dual selection system. Here, the library of genetic switches, created by randomizing either the part or the entire sequence coding switching components, is subjected to OFF (negative) selection and ON (positive) selection in various conditions. The entire selection process is completed only by liquid handling, facilitating the parallel and continuous operations of multiple selection projects. This automation-liable platform for genetic selection of functional switches has potential applications for development of RNA-based biosensors, expression controllers, and their integrated forms (genetic circuits). PMID:24549617

  16. Feature Selection for Neural Network Based Stock Prediction

    NASA Astrophysics Data System (ADS)

    Sugunnasil, Prompong; Somhom, Samerkae

    We propose a new methodology of feature selection for stock movement prediction. The methodology is based upon finding those features which minimize the correlation relation function. We first produce all the combination of feature and evaluate each of them by using our evaluate function. We search through the generated set with hill climbing approach. The self-organizing map based stock prediction model is utilized as the prediction method. We conduct the experiment on data sets of the Microsoft Corporation, General Electric Co. and Ford Motor Co. The results show that our feature selection method can improve the efficiency of the neural network based stock prediction.

  17. Selected Styles in Web-Based Educational Research

    ERIC Educational Resources Information Center

    Mann, Bruce, Ed.

    2006-01-01

    "Selected Styles in Web-Based Educational Research" is concerned with the most common research styles in Web-based teaching or learning. It is intended for practitioners, educators and students, who wish to learn how to conduct research in online teaching and learning, and helps define style in educational research methodology. To enhance…

  18. Conceptual design of a lunar oxygen pilot plant Lunar Base Systems Study (LBSS) task 4.2

    NASA Technical Reports Server (NTRS)

    1988-01-01

    The primary objective was to develop conceptual designs of two pilot plants to produce oxygen from lunar materials. A lunar pilot plant will be used to generate engineering data necessary to support an optimum design of a larger scale production plant. Lunar oxygen would be of primary value as spacecraft propellant oxidizer. In addition, lunar oxygen would be useful for servicing nonregenerative fuel cell power systems, providing requirements for life support, and to make up oxygen losses from leakage and airlock cycling. Thirteen different lunar oxygen production methods are described. Hydrogen reduction of ilmenite and extraction of solar-wind hydrogen from bulk lunar soil were selected for conceptual design studies. Trades and sensitivity analyses were performed with these models.

  19. Research on Routing Selection Algorithm Based on Genetic Algorithm

    NASA Astrophysics Data System (ADS)

    Gao, Guohong; Zhang, Baojian; Li, Xueyong; Lv, Jinna

    The hereditary algorithm is a kind of random searching and method of optimizing based on living beings natural selection and hereditary mechanism. In recent years, because of the potentiality in solving complicate problems and the successful application in the fields of industrial project, hereditary algorithm has been widely concerned by the domestic and international scholar. Routing Selection communication has been defined a standard communication model of IP version 6.This paper proposes a service model of Routing Selection communication, and designs and implements a new Routing Selection algorithm based on genetic algorithm.The experimental simulation results show that this algorithm can get more resolution at less time and more balanced network load, which enhances search ratio and the availability of network resource, and improves the quality of service.

  20. Consider oxygen for hydrocarbon oxidations

    SciTech Connect

    Shahani, G.H.; Gunardson, H.H.; Easterbrook, N.C.

    1996-11-01

    A number of commodity petrochemicals are produced by the selective, catalytic oxidation of hydrocarbons in the liquid and gas phase. These chemicals are the basic building blocks for a host of chemical intermediates. Producing each of these chemicals requires large volumes of air or tonnage quantities of oxygen for oxidation. This oxidation can be carried out using air, oxygen-enriched air, or pure oxygen. Many oxidation processes, such as that for making ethylene oxide, originally were implemented using air but have switched to oxygen. Other processes, such as for vinyl acetate, were developed as oxygen-based processes directly. Over the years, using pure oxygen has become an accepted practice in a number of petrochemical processes, such as those for acetaldehyde, ethylene oxide, propylene oxide, vinyl acetate, and vinyl chloride. As the authors will discuss, using oxygen provides some significant advantages. So, the authors expect that the trend of existing air-based processes converting to oxygen will continue, while new processes based on oxygen will emerge.

  1. Sensitivity enhancement of carbon nanotube based ammonium ion sensors through surface modification by using oxygen plasma treatment

    SciTech Connect

    Yeo, Sanghak; Woong Jang, Chi; Lee, Seok; Min Jhon, Young; Choi, Changrok

    2013-02-18

    We have shown that the sensitivity of carbon nanotube (CNT) based sensors can be enhanced as high as 74 times through surface modification by using the inductively coupled plasma chemical vapor deposition method with oxygen. The plasma treatment power was maintained as low as 10 W within 20 s, and the oxygen plasma was generated far away from the sensors to minimize the plasma damage. From X-ray photoelectron spectroscopy analysis, we found that the concentration of oxygen increased with the plasma treatment time, which implies that oxygen functional groups or defect sites were generated on the CNT surface.

  2. Suppression of Cancer Growth by Nonviral Gene Therapy Based on a Novel Reactive Oxygen Species-responsive Promoter

    PubMed Central

    Policastro, Lucía L; Ibañez, Irene L; Durán, Hebe A; Soria, Gastón; Gottifredi, Vanesa; Podhajcer, Osvaldo L

    2009-01-01

    Increased reactive oxygen species (ROS) production has been reported as a distinctive feature of different pathologies including cancer. Therefore, we assessed whether increased ROS production in the cancer microenvironment could be selectively exploited to develop a selective anticancer therapy. For this purpose, we constructed a novel chimeric promoter, based on a ROS-response motif located in the VEGF gene promoter placed, in turn, downstream of a second ROS-response motif obtained from the early growth response 1 (Egr-1) gene promoter. The activity of the chimeric promoter was largely dependent on variations in intracellular ROS levels and showed a high inducible response to exogenous H2O2. Transient expression of the thymidine kinase (TK) gene driven by the chimeric promoter, followed by gancyclovir (GCV) administration, inhibited human colorectal cancer and melanoma cell growth in vitro and in vivo. Moreover, electrotransfer of the TK gene followed by GCV administration exerted a potent therapeutic effect on established tumors. This response was improved when combined with chemotherapeutic drugs. Thus, we show for the first time that a distinctive pro-oxidant state can be used to develop new selective gene therapeutics for cancer. PMID:19436270

  3. Reduction kinetics of iron-based oxygen carriers using methane for chemical-looping combustion

    NASA Astrophysics Data System (ADS)

    Luo, Ming; Wang, Shuzhong; Wang, Longfei; Lv, Mingming

    2014-12-01

    The performance of three iron-based oxygen carriers (pure Fe2O3, synthetic Fe2O3/MgAl2O4 and iron ore) in reduction process using methane as fuel is investigated in thermo-gravimetric analyzer (TGA). The reaction rate and mechanism between three oxygen carriers and methane are investigated. On the basis of reactivity in reduction process, it may be concluded that Fe2O3/MgAl2O4 has the best reactivity with methane. The reaction rate constant is found to be in the following order: Fe2O3/MgAl2O4 > pure Fe2O3 > iron ore and the activation energy varies between 49 and 184 kJ mol-1. Reduction reactions for the pure Fe2O3 and synthetic Fe2O3/MgAl2O4 are well represented by the reaction controlling mechanism, and for the iron ore the phase-boundary controlled (contracting cylinder) model dominates. The particles of iron ore and synthetic Fe2O3/MgAl2O4 have better stability than that of pure Fe2O3 when the reaction temperature is limited to lower than 1223 K. These preliminary results suggest that iron-based mixed oxygen carrier particles are potential to be used in methane chemical looping process, but the reactivity of the iron ore needs to be increased.

  4. Oxygen vacancy effects in HfO2-based resistive switching memory: First principle study

    NASA Astrophysics Data System (ADS)

    Dai, Yuehua; Pan, Zhiyong; Wang, Feifei; Li, Xiaofeng

    2016-08-01

    The work investigated the shape and orientation of oxygen vacancy clusters in HfO2-base resistive random access memory (ReRAM) by using the first-principle method based on the density functional theory. Firstly, the formation energy of different local Vo clusters was calculated in four established orientation systems. Then, the optimized orientation and charger conductor shape were identified by comparing the isosurface plots of partial charge density, formation energy, and the highest isosurface value of oxygen vacancy. The calculated results revealed that the [010] orientation was the optimal migration path of Vo, and the shape of system D4 was the best charge conductor in HfO2, which effectively influenced the SET voltage, formation voltage and the ON/OFF ratio of the device. Afterwards, the PDOS of Hf near Vo and total density of states of the system D4_010 were obtained, revealing the composition of charge conductor was oxygen vacancy instead of metal Hf. Furthermore, the migration barriers of the Vo hopping between neighboring unit cells were calculated along four different orientations. The motion was proved along [010] orientation. The optimal circulation path for Vo migration in the HfO2 super-cell was obtained.

  5. FEM-based oxygen consumption and cell viability models for avascular pancreatic islets

    PubMed Central

    Buchwald, Peter

    2009-01-01

    Background The function and viability of cultured, transplanted, or encapsulated pancreatic islets is often limited by hypoxia because these islets have lost their vasculature during the isolation process and have to rely on gradient-driven passive diffusion, which cannot provide adequate oxygen transport. Pancreatic islets (islets of Langerhans) are particularly susceptible due to their relatively large size, large metabolic demand, and increased sensitivity to hypoxia. Here, finite element method (FEM) based multiphysics models are explored to describe oxygen transport and cell viability in avascular islets both in static and in moving culture media. Methods Two- and three-dimensional models were built in COMSOL Multiphysics using the convection and diffusion as well as the incompressible Navier-Stokes fluid dynamics application modes. Oxygen consumption was assumed to follow Michaelis-Menten-type kinetics and to cease when local concentrations fell below a critical threshold; in a dynamic model, it was also allowed to increase with increasing glucose concentration. Results Partial differential equation (PDE) based exploratory cellular-level oxygen consumption and cell viability models incorporating physiologically realistic assumptions have been implemented for fully scaled cell culture geometries with 100, 150, and 200 μm diameter islets as representative. Calculated oxygen concentrations and intra-islet regions likely to suffer from hypoxia-related necrosis obtained for traditional flask-type cultures, oxygen-permeable silicone-rubber membrane bottom cultures, and perifusion chambers with flowing media and varying incoming glucose levels are presented in detail illustrated with corresponding colour-coded figures and animations. Conclusion Results of the computational models are, as a first estimate, in good quantitative agreement with existing experimental evidence, and they confirm that during culture, hypoxia is often a problem for non-vascularised islet

  6. Polymer Electrolyte-Based Ambient Temperature Oxygen Microsensors for Environmental Monitoring

    NASA Technical Reports Server (NTRS)

    Hunter, Gary W.; Xu, Jennifer C.; Liu, Chung-Chiun

    2011-01-01

    An ambient temperature oxygen microsensor, based on a Nafion polymer electrolyte, has been developed and was microfabricated using thin-film technologies. A challenge in the operation of Nafion-based sensor systems is that the conductivity of Nafion film depends on the humidity in the film. Nafion film loses conductivity when the moisture content in the film is too low, which can affect sensor operation. The advancement here is the identification of a method to retain the operation of the Nafion films in lower humidity environments. Certain salts can hold water molecules in the Nafion film structure at room temperature. By mixing salts with the Nafion solution, water molecules can be homogeneously distributed in the Nafion film increasing the film s hydration to prevent Nafion film from being dried out in low-humidity environment. The presence of organics provides extra sites in the Nafion film to promote proton (H+) mobility and thus improving Nafion film conductivity and sensor performance. The fabrication of ambient temperature oxygen microsensors includes depositing basic electrodes using noble metals, and metal oxides layer on one of the electrode as a reference electrode. The use of noble metals for electrodes is due to their strong catalytic properties for oxygen reduction. A conducting polymer Nafion, doped with water-retaining components and extra sites facilitating proton movement, was used as the electrolyte material, making the design adequate for low humidity environment applications. The Nafion solution was coated on the electrodes and air-dried. The sensor operates at room temperature in potentiometric mode, which measures voltage differences between working and reference electrodes in different gases. Repeat able responses to 21-percent oxygen in nitrogen were achieved using nitrogen as a baseline gas. Detection of oxygen from 7 to 21 percent has also been demonstrated. The room-temperature oxygen micro sensor developed has extremely low power

  7. Dual-functional Memory and Threshold Resistive Switching Based on the Push-Pull Mechanism of Oxygen Ions

    PubMed Central

    Huang, Yi-Jen; Chao, Shih-Chun; Lien, Der-Hsien; Wen, Cheng-Yen; He, Jr-Hau; Lee, Si-Chen

    2016-01-01

    The combination of nonvolatile memory switching and volatile threshold switching functions of transition metal oxides in crossbar memory arrays is of great potential for replacing charge-based flash memory in very-large-scale integration. Here, we show that the resistive switching material structure, (amorphous TiOx)/(Ag nanoparticles)/(polycrystalline TiOx), fabricated on the textured-FTO substrate with ITO as the top electrode exhibits both the memory switching and threshold switching functions. When the device is used for resistive switching, it is forming-free for resistive memory applications with low operation voltage (<±1 V) and self-compliance to current up to 50 μA. When it is used for threshold switching, the low threshold current is beneficial for improving the device selectivity. The variation of oxygen distribution measured by energy dispersive X-ray spectroscopy and scanning transmission electron microscopy indicates the formation or rupture of conducting filaments in the device at different resistance states. It is therefore suggested that the push and pull actions of oxygen ions in the amorphous TiOx and polycrystalline TiOx films during the voltage sweep account for the memory switching and threshold switching properties in the device. PMID:27052322

  8. Dual-functional Memory and Threshold Resistive Switching Based on the Push-Pull Mechanism of Oxygen Ions.

    PubMed

    Huang, Yi-Jen; Chao, Shih-Chun; Lien, Der-Hsien; Wen, Cheng-Yen; He, Jr-Hau; Lee, Si-Chen

    2016-01-01

    The combination of nonvolatile memory switching and volatile threshold switching functions of transition metal oxides in crossbar memory arrays is of great potential for replacing charge-based flash memory in very-large-scale integration. Here, we show that the resistive switching material structure, (amorphous TiOx)/(Ag nanoparticles)/(polycrystalline TiOx), fabricated on the textured-FTO substrate with ITO as the top electrode exhibits both the memory switching and threshold switching functions. When the device is used for resistive switching, it is forming-free for resistive memory applications with low operation voltage (<± 1 V) and self-compliance to current up to 50 μA. When it is used for threshold switching, the low threshold current is beneficial for improving the device selectivity. The variation of oxygen distribution measured by energy dispersive X-ray spectroscopy and scanning transmission electron microscopy indicates the formation or rupture of conducting filaments in the device at different resistance states. It is therefore suggested that the push and pull actions of oxygen ions in the amorphous TiOx and polycrystalline TiOx films during the voltage sweep account for the memory switching and threshold switching properties in the device. PMID:27052322

  9. Dual-functional Memory and Threshold Resistive Switching Based on the Push-Pull Mechanism of Oxygen Ions

    NASA Astrophysics Data System (ADS)

    Huang, Yi-Jen; Chao, Shih-Chun; Lien, Der-Hsien; Wen, Cheng-Yen; He-Hau, Jr.; Lee, Si-Chen

    2016-04-01

    The combination of nonvolatile memory switching and volatile threshold switching functions of transition metal oxides in crossbar memory arrays is of great potential for replacing charge-based flash memory in very-large-scale integration. Here, we show that the resistive switching material structure, (amorphous TiOx)/(Ag nanoparticles)/(polycrystalline TiOx), fabricated on the textured-FTO substrate with ITO as the top electrode exhibits both the memory switching and threshold switching functions. When the device is used for resistive switching, it is forming-free for resistive memory applications with low operation voltage (<±1 V) and self-compliance to current up to 50 μA. When it is used for threshold switching, the low threshold current is beneficial for improving the device selectivity. The variation of oxygen distribution measured by energy dispersive X-ray spectroscopy and scanning transmission electron microscopy indicates the formation or rupture of conducting filaments in the device at different resistance states. It is therefore suggested that the push and pull actions of oxygen ions in the amorphous TiOx and polycrystalline TiOx films during the voltage sweep account for the memory switching and threshold switching properties in the device.

  10. Intraphagosomal oxygen in stimulated macrophages.

    PubMed

    James, P E; Grinberg, O Y; Michaels, G; Swartz, H M

    1995-05-01

    A new electron paramagnetic resonance (EPR)-based method was developed to obtain selective information on pO2 in a specific intracellular compartment (phagosomes). This method did not require the use of a broadening agent thereby eliminating one of the potential sources of experimental error with EPR oximetry. An oxygen-sensitive probe (4-(Trimethylammonium) 2,2,6,6-tetramethylpiperidine-d17-1-oxyl iodide (d-Cat1)) which has a net positive charge, was incorporated selectively into the phagosomes of macrophages stimulated with zymosan. Extracellular oxygen was measured by addition of a neutral nitroxide (4-oxo-2,2,6,6-tetramethylpiperidine-d16-1-oxyl (15N PDT)) to this same sample. Measurements based on EPR linewidths showed the average intraphagosomal oxygen concentration to be 11.2 +/- 3.4 microM lower than that measured from the extracellular compartment when the sample was perfused with air, and this was increased on stimulation of mitochondrial consumption or by increasing the oxygen concentration in the extracellular compartment. These experiments provide what we believe to be the first reported measurements of the oxygen concentration in a specific intracellular location (intraphagosomal) and its comparison with the oxygen concentration in the extracellular space. The observed gradient cannot be explained in terms of known coefficients of diffusion, and these results are consistent with previous reports that a gradient in oxygen concentration can occur between the average intracellular and extracellular concentration of oxygen. PMID:7706368

  11. Energetic oxygen-containing tetrazole salts based on 3,4-diaminotriazole.

    PubMed

    Wu, Jin-Ting; Zhang, Jian-Guo; Yin, Xin; Wu, Kun

    2015-05-01

    Energetic mono- and dicationic 3,4-diaminotriazolium salts have been prepared by combining stoichiometric amounts (1:1 or 2:1 molar ratio) of 3,4-diaminotriazole with various oxygen-containing tetrazoles, and the structures have been confirmed by single-crystal XRD for the first time. All structures are dominated by a strong hydrogen-bond network owing to both amino groups and oxygen in the molecule. All salts, except 7, exhibit excellent thermal stabilities with decomposition temperatures over 200 °C. Based on experimental densities and theoretical calculations carried out by using the Gaussian 03 suite of programs, all salts have calculated detonation pressures (20.3-33.9 GPa) and velocities (7095-8642 m s(-1)). PMID:25712781

  12. Ignition characteristics of the nickel-based alloy UNS N07718 in pressurized oxygen

    NASA Technical Reports Server (NTRS)

    Bransford, James W.; Billiard, Phillip A.; Hurley, James A.; Mcdermott, Kathleen M.; Vazquez, Isaura

    1989-01-01

    The development of ignition and combustion in pressurized oxygen atmospheres was studied for the nickel based alloy UNS N07718. Ignition of the alloy was achieved by heating the top. It was found that the alloy would autoheat to destruction from temperatures below the solidus temperature. In addition, endothermic events occurred as the alloy was heated, many at reproducible temperatures. Many endothermic events occurred prior to abrupt increases in surface temperature and appeared to accelerate the rate of increase in specimen temperature. It appeared that the source of some endotherms may increase the oxidation rate of the alloy. Ignition parameters are defined and the temperatures at which these parameters occur are given for the oxygen pressure range of 1.72 to 13.8 MPa (250 to 2000 psia).

  13. Atomic Oxygen Sensors Based on Nanograin ZnO Films Prepared by Pulse Laser Deposition

    SciTech Connect

    Wang Yunfei; Chen Xuekang; Li Zhonghua; Zheng Kuohai; Wang Lanxi; Feng Zhanzu; Yang Shengsheng

    2009-01-05

    High-quality nanograin ZnO thin films were deposited on c-plane sapphire (Al{sub 2}O{sub 3}) substrates by pulse laser deposition (PLD). Scanning electron microscopy (SEM) and x-ray diffraction (XRD) were used to characterize the samples. The structural and morphological properties of ZnO films under different deposition temperature have been investigated before and after atomic oxygen (AO) treatment. XRD has shown that the intensity of the (0 0 2) peak increases and its FWHM value decreases after AO treatment. The AO sensing characteristics of nano ZnO film also has been investigated in a ground-based atomic oxygen simulation facility. The results show that the electrical conductivity of nanograin ZnO films decreases with increasing AO fluence and that the conductivity of the films can be recovered by heating.

  14. Inherently distorted heme as a novel tool for myoglobin-based oxygen carrier.

    PubMed

    Neya, Saburo; Kawaguchi, Akira T

    2012-02-01

    The two types of artificial myoglobins (Mbs) containing inherently distorted α-ethyl-2,4-dimethyldeuteroheme and undistorted 2,4-dimethyldeuteroheme were prepared to examine the influence of nonplanar heme deformation on the reactivity of Mb. In ferrous deoxy proteins, the paramagnetic proton nuclear magnetic resonance spectra showed that the deformed heme caused a 3.2-ppm lower-field shift of the proximal histidine signal, indicating a larger iron displacement from the heme plane upon the nonplanar deformation. The Mb with the nonplanar heme exhibited a markedly lower oxygen affinity as compared with the Mb containing the planar heme. The result suggests the utility of heme distortion to design the Mb-based oxygen carrier. PMID:21501194

  15. Optical oxygen concentration monitor

    DOEpatents

    Kebabian, Paul

    1997-01-01

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

  16. Comparison across races of peak oxygen consumption and heart failure survival score for selection for cardiac transplantation.

    PubMed

    Goda, Ayumi; Lund, Lars H; Mancini, Donna M

    2010-05-15

    The aim of the present study was to determine whether peak oxygen consumption (VO(2)) and the Heart Failure Survival Score (HFSS) predict prognosis in European-American, African-American, and Hispanic-American patients with chronic heart failure referred for heart transplantation. The peak VO(2) and the HFSS have previously been shown to effectively risk stratify patients with chronic heart failure and are criteria for the listing for heart transplantation. However, the effect of race on the predictive value of these variables has not been studied. A total of 715 patients with congestive heart failure (433 European American, 126 African American, 123 Hispanic American, and 33 other), who had been referred for heart transplantation, underwent cardiopulmonary exercise testing with measurement of the peak VO(2) and calculation of the HFSS. A total of 354 patients had died or undergone urgent heart transplantation or implantation of a left ventricular assist device during the 962 +/- 912 days of follow-up. On univariate and multivariate Cox hazard analysis, both peak VO(2) and the HFSS were powerful prognostic markers in the overall cohort and in the separate races. In the receiver operating characteristic curve analysis, the areas under the curve at 1 and 2 years of follow-up were greater for the HFSS than for peak VO(2). In conclusion, HFSS and peak VO(2) can be used for transplant selection; however, in the era of modern therapy and across races and genders, the HFSS might perform better than the peak VO(2). PMID:20451691

  17. Performance-Based Technology Selection Filter description report

    SciTech Connect

    O'Brien, M.C.; Morrison, J.L.; Morneau, R.A.; Rudin, M.J.; Richardson, J.G.

    1992-05-01

    A formal methodology has been developed for identifying technology gaps and assessing innovative or postulated technologies for inclusion in proposed Buried Waste Integrated Demonstration (BWID) remediation systems. Called the Performance-Based Technology Selection Filter, the methodology provides a formalized selection process where technologies and systems are rated and assessments made based on performance measures, and regulatory and technical requirements. The results are auditable, and can be validated with field data. This analysis methodology will be applied to the remedial action of transuranic contaminated waste pits and trenches buried at the Idaho National Engineering Laboratory (INEL).

  18. Spatial Mutual Information Based Hyperspectral Band Selection for Classification

    PubMed Central

    2015-01-01

    The amount of information involved in hyperspectral imaging is large. Hyperspectral band selection is a popular method for reducing dimensionality. Several information based measures such as mutual information have been proposed to reduce information redundancy among spectral bands. Unfortunately, mutual information does not take into account the spatial dependency between adjacent pixels in images thus reducing its robustness as a similarity measure. In this paper, we propose a new band selection method based on spatial mutual information. As validation criteria, a supervised classification method using support vector machine (SVM) is used. Experimental results of the classification of hyperspectral datasets show that the proposed method can achieve more accurate results. PMID:25918742

  19. Evaluation of RPE-Select: A Web-Based Respiratory Protective Equipment Selector Tool

    PubMed Central

    Vaughan, Nick; Rajan-Sithamparanadarajah, Bob; Atkinson, Robert

    2016-01-01

    This article describes the evaluation of an open-access web-based respiratory protective equipment selector tool (RPE-Select, accessible at http://www.healthyworkinglives.com/rpe-selector). This tool is based on the principles of the COSHH-Essentials (C-E) control banding (CB) tool, which was developed for the exposure risk management of hazardous chemicals in the workplace by small and medium sized enterprises (SMEs) and general practice H&S professionals. RPE-Select can be used for identifying adequate and suitable RPE for dusts, fibres, mist (solvent, water, and oil based), sprays, volatile solids, fumes, gases, vapours, and actual or potential oxygen deficiency. It can be applied for substances and products with safety data sheets as well as for a large number of commonly encountered process-generated substances (PGS), such as poultry house dusts or welding fume. Potential international usability has been built-in by using the Hazard Statements developed for the Globally Harmonised System (GHS) and providing recommended RPE in picture form as well as with a written specification. Illustration helps to compensate for the variabilities in assigned protection factors across the world. RPE-Select uses easily understandable descriptions/explanations and an interactive stepwise flow for providing input/answers at each step. The output of the selection process is a report summarising the user input data and a selection of RPE, including types of filters where applicable, from which the user can select the appropriate one for each wearer. In addition, each report includes ‘Dos’ and ‘Don’ts’ for the recommended RPE. RPE-Select outcomes, based on up to 20 hypothetical use scenarios, were evaluated in comparison with other available RPE selection processes and tools, and by 32 independent users with a broad range of familiarities with industrial use scenarios in general and respiratory protection in particular. For scenarios involving substances having safety

  20. Evaluation of RPE-Select: A Web-Based Respiratory Protective Equipment Selector Tool.

    PubMed

    Vaughan, Nick; Rajan-Sithamparanadarajah, Bob; Atkinson, Robert

    2016-08-01

    This article describes the evaluation of an open-access web-based respiratory protective equipment selector tool (RPE-Select, accessible at http://www.healthyworkinglives.com/rpe-selector). This tool is based on the principles of the COSHH-Essentials (C-E) control banding (CB) tool, which was developed for the exposure risk management of hazardous chemicals in the workplace by small and medium sized enterprises (SMEs) and general practice H&S professionals. RPE-Select can be used for identifying adequate and suitable RPE for dusts, fibres, mist (solvent, water, and oil based), sprays, volatile solids, fumes, gases, vapours, and actual or potential oxygen deficiency. It can be applied for substances and products with safety data sheets as well as for a large number of commonly encountered process-generated substances (PGS), such as poultry house dusts or welding fume. Potential international usability has been built-in by using the Hazard Statements developed for the Globally Harmonised System (GHS) and providing recommended RPE in picture form as well as with a written specification. Illustration helps to compensate for the variabilities in assigned protection factors across the world. RPE-Select uses easily understandable descriptions/explanations and an interactive stepwise flow for providing input/answers at each step. The output of the selection process is a report summarising the user input data and a selection of RPE, including types of filters where applicable, from which the user can select the appropriate one for each wearer. In addition, each report includes 'Dos' and 'Don'ts' for the recommended RPE. RPE-Select outcomes, based on up to 20 hypothetical use scenarios, were evaluated in comparison with other available RPE selection processes and tools, and by 32 independent users with a broad range of familiarities with industrial use scenarios in general and respiratory protection in particular. For scenarios involving substances having safety data sheets

  1. Selective catalytic reduction of nitric oxide by ammonia over Cu-FAU catalysts in oxygen-rich atmosphere

    SciTech Connect

    Kieger, S.; Delahay, G.; Coq, B.; Neveu, B.

    1999-04-25

    The selective catalytic reduction (SCR) of NO (2000 ppm) by NH{sub 3} (2000 ppm) in the presence of oxygen (3%) was carried out on Cu(x)-FAU (x = theoretical exchange degree) catalysts prepared by ion exchange or impregnation and calcined at 773 K. The samples were characterized by UV-visible and IR spectroscopy, temperature-programmed reduction (TPR), temperature-programmed oxidation (TPO), and temperature-programmed desorption (TPD) of NH{sub 3}. Ion-exchanged Cu(x)-FAU contains mainly Cu ions located in both supercages and sodalite cavities. In contrast, the impregnated sample contains mainly CuO. Ionic Cu is more active and selective to N{sub 2} than CuO in the temperature range 450--750 K. In contrast, CuO aggregates lead to significant formation of N{sub 2}O with a bell-shaped dependency centered at ca. 540 K. IR spectroscopy and TPD of NH{sub 3} show that the last NH{sub 3} ligand was removed from Cu ions above 550 K. The SCR on Cu ions obeys a Cu{sup 2+} {leftrightarrow} Cu{sup +} redox mechanism in which Cu{sup 2+} is reduced to Cu{sup +} by NO + NH{sub 3} and Cu{sup +} is oxidized to Cu{sup 2+} by NO + O{sub 2}, with evolution of N{sub 2} and H{sub 2}O. Both reduction and oxidation steps of Cu in the catalytic cycle encompass the reduction of NO in agreement with the SCR of {sup 14}NO with {sup 15}NH{sub 3}. A new overall SCR reaction below 550 K was proposed: 10NH{sub 3} + 13NO + O{sub 2} {r_arrow} 15H{sub 2}O + (23/2)N{sub 2}. The active sites below 550 K are formed by several Cu neighbor ions, maybe [CuOCu]{sup 2+}, probably located in the supercages. All Cu ions become active above 600 K. The partial reduction of NO to N{sub 2}O occurs at high temperature (>650 K) on exchanged samples. This formation, up to 17% at full NO conversion, is likely to take place on Cu ions located within the sodalite cavities.

  2. An Improved Feature Selection Based on Effective Range for Classification

    PubMed Central

    Zhou, Shuang

    2014-01-01

    Feature selection is a key issue in the domain of machine learning and related fields. The results of feature selection can directly affect the classifier's classification accuracy and generalization performance. Recently, a statistical feature selection method named effective range based gene selection (ERGS) is proposed. However, ERGS only considers the overlapping area (OA) among effective ranges of each class for every feature; it fails to handle the problem of the inclusion relation of effective ranges. In order to overcome this limitation, a novel efficient statistical feature selection approach called improved feature selection based on effective range (IFSER) is proposed in this paper. In IFSER, an including area (IA) is introduced to characterize the inclusion relation of effective ranges. Moreover, the samples' proportion for each feature of every class in both OA and IA is also taken into consideration. Therefore, IFSER outperforms the original ERGS and some other state-of-the-art algorithms. Experiments on several well-known databases are performed to demonstrate the effectiveness of the proposed method. PMID:24688449

  3. [Orthogonal projection divergence-based hyperspectral band selection].

    PubMed

    Su, Hong-jun; Sheng, Ye-hua; Yang, He; Du, Qian

    2011-05-01

    Due to the high data dimensionality of a hyperspectral image, dimensionality reduction algorithm has attracted much attention in hyperspectral image analysis. Band selection algorithm, which selects appropriate bands from the original set of spectral bands, can preserve original information from the data and is useful for image classification and recognition. In the present paper, a novel band selection algorithm based on orthogonal projection divergence (OPD) is proposed, it aims to discriminate the interesting objects from background and noise information, maximize the spectral similarity between different spectral vectors by projecting the original data to feature space. Two HYDICE Washington DC Mall images and an HYMAP Purdue campus image data were experimented, and support vector machine (SVM) classifier was used for classification. The selected band number varies from 5 to 40 in order to study the impacts of different band selection algorithms on different features. For the computation complex, the sequential floating forward search (SFFS) was used to get the appropriate bands. The experiments have proved that our proposed OPD algorithm can outperform other traditional band selection methods such as SAM, ED, SID, and LCMV-BCC for hyperspectral image analysis. It is proven that OPD band selection is effective and robust in hyperspectral remote sensing dimensionality reduction PMID:21800589

  4. Filter selection based on light source for multispectral imaging

    NASA Astrophysics Data System (ADS)

    Xu, Peng; Xu, Haisong

    2016-07-01

    In multispectral imaging, it is necessary to select a reduced number of filters to balance the imaging efficiency and spectral reflectance recovery accuracy. Due to the combined effect of filters and light source on reflectance recovery, the optimal filters are influenced by the employed light source in the multispectral imaging system. By casting the filter selection as an optimization issue, the selection of optimal filters corresponding to the employed light source proceeds with respect to a set of target samples utilizing one kind of genetic algorithms, regardless of the detailed spectral characteristics of the light source, filters, and sensor. Under three light sources with distinct spectral power distributions, the proposed filter selection method was evaluated on a filter-wheel based multispectral device with a set of interference filters. It was verified that the filters derived by the proposed method achieve better spectral and colorimetric accuracy of reflectance recovery than the conventional one under different light sources.

  5. Fiber-optic Singlet Oxygen [1O2 (1Δg)] Generator Device Serving as a Point Selective Sterilizer

    PubMed Central

    Aebisher, David; Zamadar, Matibur; Mahendran, Adaickapillai; Ghosh, Goutam; McEntee, Catherine; Greer, Alexander

    2016-01-01

    Traditionally, Type II heterogeneous photo-oxidations produce singlet oxygen via external irradiation of a sensitizer and external supply of ground-state oxygen. A potential improvement is reported here. A hollow-core fiber-optic device was developed with an “internal” supply of light and flowing oxygen, and a porous photosensitizer-end capped configuration. Singlet oxygen was delivered through the fiber tip. The singlet oxygen steady-state concentration in the immediate vicinity of the probe tip was ca 20 fM by N-benzoyl-DL-methionine trapping. The device is portable and the singlet oxygen-generating tip is maneuverable, which opened the door to simple disinfectant studies. Complete Escherichia coli inactivation was observed in 2 h when the singlet oxygen sensitizing probe tip was immersed in 0.1 mL aqueous samples of 0.1–4.4 × 107 cells. Photobleaching of the probe tip occurred after ca 12 h of use, requiring baking and sensitizer reloading steps for reuse. PMID:20497367

  6. Design of Metalloporphyrin-Based Dendritic Nanoprobes for Two-Photon Microscopy of Oxygen

    PubMed Central

    Lebedev, Artem Y.; Troxler, Thomas; Vinogradov, Sergei A.

    2009-01-01

    Metalloporphyrin-based phosphorescent nanoprobes are being developed for two-photon microscopy of oxygen. In these molecular constructs generation of porphyrin triplet states upon two-photon excitation is induced upon the intramolecular Förster-type resonance energy transfer from a covalently attached 2P antenna. In the earlier developed prototypes, electron transfer between the antenna and the metalloporphyrin strongly interfered with the phosphorescence, reducing the sensitivity and the dynamic range of the sensors. By tuning the distances between the antenna and the core and adjusting their redox potentials the unwanted electron transfer could be prevented. An array of phosphorescent Pt porphyrins (energy transfer acceptors) and 2P dyes (energy transfer donors) was screened using dynamic quenching of phosphorescence, and the FRET-pair with the minimal ET rate was identified. This pair, consisting of Coumarin-343 and Pt meso-tetra-(4-alkoxyphenyl)porphyrin, was used to construct a probe in which the antenna fragments were linked to the termini of G3 poly(arylglycine) (AG) dendrimer with PtP core. The folded dendrimer formed an insulating layer between the porphyrin and the antenna, simultaneously controlling the rate of oxygen quenching (Stern-Volmer oxygen quenching constant). Modification of the dendrimer periphery with oligoethyleneglycol residues made the probe’s signal insensitive to the presence of proteins and other macromolecular solutes. PMID:19763243

  7. Ignition characteristics of the nickel-based alloy UNS N07001 in pressurized oxygen

    NASA Technical Reports Server (NTRS)

    Bransford, J. W.; Billiard, P. A.

    1990-01-01

    The development of ignition and combustion in pressurized oxygen atmospheres was studied for the nickel-based alloy UNS N07001. Ignition of the alloy was achieved by heating the top surface of a cylindrical specimen with a continuous-wave CO2 laser. Two heating procedures were used. In the first, laser power was adjusted to maintain an approximately linear increase in surface temperature. In the second, laser power was periodically increased until autoheating (self-heating) was established. It was found that the alloy would autoheat to combustion from temperatures below the solidus temperature. In addition, the alloy had a tendency to develop combustion zones (hot spots) at high oxygen pressures when the incremental (step) heating test mode was used. Unique points on the temperature-time curves that describe certain events are defined and the temperatures at which these events occur are given for the oxygen pressure range of 1.72 to 13.8 MPa (250 to 2000 psia).

  8. Ground-Based Tests of Spacecraft Polymeric Materials under OXY-GEN Plasma-Beam

    NASA Astrophysics Data System (ADS)

    Chernik, Vladimir; Novikov, Lev; Gaidar, Anna

    2016-07-01

    Spacecraft LEO mission is accompanied by destruction of polymeric material surface under influence of atomic oxygen flow. Sources of molecular, plasma and ion beams are used for the accelerated ground-based tests of spacecraft materials. In the work application of oxygen plasma accelerator of a duoplasmatron type is described. Plasma particles have been accelerated up to average speed of 13-16 km/s. Influence of such beam on materials leads to more intensive destruction of polymers than in LEO. This fact allows to execute tests in the accelerated time scale by a method of an effective fluence. Special measures were given to decrease a concentration of both gaseous and electrode material impurities in the oxygen beam. In the work the results of simulative tests of spacecraft materials and experiments on LEO are considered. Comparison of plasma beam simulation with LEO data has shown conformity for structures of a number of polymeric materials. The relative erosion yields (normalized with respect to polyimide) of the tested materials are shown practically equal to those in LEO. The obtained results give grounds for using the plasma-generation mode with ion energies of 20-30 eV to accelerated testing of spacecraft materials for long -term LEO missions.

  9. A biocompatible cobaltporphyrin-based complex micelle constructed via supramolecular assembly for oxygen transfer.

    PubMed

    Shen, Liangliang; Qu, Rui; Shi, Hejin; Huang, Fan; An, Yingli; Shi, Linqi

    2016-05-26

    Herein, a complex micelle as an oxygen nano-carrier is constructed through the hierarchical assembly of the diblock copolymer poly(ethylene glycol)-block-poly(l-lysine) (PEG-b-PLys), tetrakis(4-sulfonatophenyl)porphinato cobalt(ii) (Co(ii)TPPS), a heptapeptide (Cys-His-His-His-His-His-His) and heptakis(2,3,6-tri-O-methyl)-β-cyclodextrin (TM-β-CD). Co(ii)TPPS was encapsulated into the cavities of TM-β-CDs driven by the host-guest interaction so that the irreversible formation of a μ-oxo-dimer of Co(ii)TPPS can be effectively prevented. The imidazole groups of the heptapeptide were selected as good axial ligands coordinating to the centric cobalt of Co(ii)TPPS, which subtly constituted the five-coordinated precursor serving as an active functional centre for oxygen binding. The sixth position of Co(ii)TPPS can bind oxygen. Furthermore, the host-guest inclusion (TM-β-CD/Co(ii)TPPS) was loaded into the hydrophobic core of the complex micelle and tightly fixed with PLys chains. The hydrophilic PEG blocks stretched in the aqueous solution constitute the shells which stabilize the structure of the complex micelle as well as impart the complex micelle sufficient blood circulation time. Moreover, the complex micelle exhibited excellent biocompatibility and cellular uptake. Therefore, the rationally designed amphiphilic structure can work as promising artificial O2 carriers in vivo. Potentially, the complex micelle can be expected to change the anaerobic microenvironment and find applications in the repair of the cells damaged by cellular hypoxia. PMID:27009911

  10. Highly Efficient Oxygen-Storage Material with Intrinsic Coke Resistance for Chemical Looping Combustion-Based CO2 Capture.

    PubMed

    Imtiaz, Qasim; Kurlov, Alexey; Rupp, Jennifer Lilia Marguerite; Müller, Christoph Rüdiger

    2015-06-22

    Chemical looping combustion (CLC) and chemical looping with oxygen uncoupling (CLOU) are emerging thermochemical CO2 capture cycles that allow the capture of CO2 with a small energy penalty. Here, the development of suitable oxygen carrier materials is a key aspect to transfer these promising concepts to practical installations. CuO is an attractive material for CLC and CLOU because of its high oxygen-storage capacity (20 wt %), fast reaction kinetics, and high equilibrium partial pressure of oxygen at typical operating temperatures (850-1000 °C). However, despite its promising characteristics, its low Tammann temperature requires the development of new strategies to phase-stabilize CuO-based oxygen carriers. In this work, we report a strategy based on stabilization by co-precipitated ceria (CeO2-x ), which allowed us to increase the oxygen capacity, coke resistance, and redox stability of CuO-based oxygen carriers substantially. The performance of the new oxygen carriers was evaluated in detail and compared to the current state-of-the-art materials, that is, Al2 O3 -stabilized CuO with similar CuO loadings. We also demonstrate that the higher intrinsic oxygen uptake, release, and mobility in CeO2-x -stabilized CuO leads to a three times higher carbon deposition resistance compared to that of Al2 O3 -stabilized CuO. Moreover, we report a high cyclic stability without phase intermixing for CeO2-x -supported CuO. This was accompanied by a lower reduction temperature compared to state-of-the-art Al2 O3 -supported CuO. As a result of its high resistance towards carbon deposition and fast oxygen uncoupling kinetics, CeO2-x -stabilized CuO is identified as a very promising material for CLC- and CLOU-based CO2 capture architectures. PMID:25916240

  11. Feature Selection with Neighborhood Entropy-Based Cooperative Game Theory

    PubMed Central

    Zeng, Kai; She, Kun; Niu, Xinzheng

    2014-01-01

    Feature selection plays an important role in machine learning and data mining. In recent years, various feature measurements have been proposed to select significant features from high-dimensional datasets. However, most traditional feature selection methods will ignore some features which have strong classification ability as a group but are weak as individuals. To deal with this problem, we redefine the redundancy, interdependence, and independence of features by using neighborhood entropy. Then the neighborhood entropy-based feature contribution is proposed under the framework of cooperative game. The evaluative criteria of features can be formalized as the product of contribution and other classical feature measures. Finally, the proposed method is tested on several UCI datasets. The results show that neighborhood entropy-based cooperative game theory model (NECGT) yield better performance than classical ones. PMID:25276120

  12. Interest area selection for navigation based on structured edge detection

    NASA Astrophysics Data System (ADS)

    Sun, Xiao; Shang, Ke; Li, ShaoJun; Dou, Hao; Tian, JinWen; Ming, Delie

    2015-12-01

    The scene matching based navigation is an important precision navigation technology for unmanned aerial vehicles (UAV). Selection of interest area where reference image is made has an important influence on the precision of matching result besides the performance of match algorithm. In this paper, a method to select interest area based on structured edge detection is proposed. We use a data driven approach that classifies each pixel with a typical structured edge label. We propose a method that combines these labels into a feature measuring suitable to match of a region. Then a SVM classifier is trained to classify the features and get the final result of the selection of interest area. The experimental result shows that the proposed method is valid and effective.

  13. Multiobjective Evolutionary Path Planning via Sugeno-Based Tournament Selection

    NASA Technical Reports Server (NTRS)

    Dozier, Gerry; McCullough, Shaun; Homaifar, Abdollah; Esterline, Albert

    1998-01-01

    This paper introduces a new tournament selection algorithm that can be used for evolutionary path planning systems. The fuzzy (Sugeno) tournament selection algorithm (STSA) described in this paper selects candidate paths (CPs) to be parents and undergo reproduction based on: (1) path feasibility, (2) the euclidean distance of a path from the origin to its destination, and (3) the average change in the slope of a path. In this paper, we provide a detailed description of the fuzzy inference system used in the STSA as well as some examples of its usefulness. We then use 12 instances of our STSA to rank a population of CPs based on the above criteria. We also show how the STSA can obviate the need for the development of an explicit (lexicographic multiobjective) evaluation function and use it to develop multiobjective motion paths.

  14. [Electroencephalogram Feature Selection Based on Correlation Coefficient Analysis].

    PubMed

    Zhou, Jinzhi; Tang, Xiaofang

    2015-08-01

    In order to improve the accuracy of classification with small amount of motor imagery training data on the development of brain-computer interface (BCD systems, we proposed an analyzing method to automatically select the characteristic parameters based on correlation coefficient analysis. Throughout the five sample data of dataset IV a from 2005 BCI Competition, we utilized short-time Fourier transform (STFT) and correlation coefficient calculation to reduce the number of primitive electroencephalogram dimension, then introduced feature extraction based on common spatial pattern (CSP) and classified by linear discriminant analysis (LDA). Simulation results showed that the average rate of classification accuracy could be improved by using correlation coefficient feature selection method than those without using this algorithm. Comparing with support vector machine (SVM) optimization features algorithm, the correlation coefficient analysis can lead better selection parameters to improve the accuracy of classification. PMID:26710441

  15. Spin-selected focusing and imaging based on metasurface lens.

    PubMed

    Wang, Sen; Wang, Xinke; Kan, Qiang; Ye, Jiasheng; Feng, Shengfei; Sun, Wenfeng; Han, Peng; Qu, Shiliang; Zhang, Yan

    2015-10-01

    Spin of light provides a route to control photons. Spin-based optical devices which can manipulate photons with different spin states are imperative. Here we experimentally demonstrated a spin-selected metasurface lens based on the spin-orbit interaction originated from the Pancharatnam-Berry (PB) phase. The optimized PB phase enables the light with different spin states to be focused on two separated points in the preset plane. Furthermore, the metasurface lens can perform the spin-selected imaging according to the polarization of the illuminating light. Such a spin-based device capacitates a lot of advanced applications for spin-controlled photonics in quantum information processing and communication based on the spin and orbit angular momentum. PMID:26480156

  16. Reduced Moment-Based Models for Oxygen Precipitates and Dislocation Loops in Silicon

    NASA Astrophysics Data System (ADS)

    Trzynadlowski, Bart

    The demand for ever smaller, higher-performance integrated circuits and more efficient, cost-effective solar cells continues to push the frontiers of process technology. Fabrication of silicon devices requires extremely precise control of impurities and crystallographic defects. Failure to do so not only reduces performance, efficiency, and yield, it threatens the very survival of commercial enterprises in today's fiercely competitive and price-sensitive global market. The presence of oxygen in silicon is an unavoidable consequence of the Czochralski process, which remains the most popular method for large-scale production of single-crystal silicon. Oxygen precipitates that form during thermal processing cause distortion of the surrounding silicon lattice and can lead to the formation of dislocation loops. Localized deformation caused by both of these defects introduces potential wells that trap diffusing impurities such as metal atoms, which is highly desirable if done far away from sensitive device regions. Unfortunately, dislocations also reduce the mechanical strength of silicon, which can cause wafer warpage and breakage. Engineers must negotiate this and other complex tradeoffs when designing fabrication processes. Accomplishing this in a complex, modern process involving a large number of thermal steps is impossible without the aid of computational models. In this dissertation, new models for oxygen precipitation and dislocation loop evolution are described. An oxygen model using kinetic rate equations to evolve the complete precipitate size distribution was developed first. This was then used to create a reduced model tracking only the moments of the size distribution. The moment-based model was found to run significantly faster than its full counterpart while accurately capturing the evolution of oxygen precipitates. The reduced model was fitted to experimental data and a sensitivity analysis was performed to assess the robustness of the results. Source

  17. Automatic learning-based beam angle selection for thoracic IMRT

    SciTech Connect

    Amit, Guy; Marshall, Andrea; Purdie, Thomas G. Jaffray, David A.; Levinshtein, Alex; Hope, Andrew J.; Lindsay, Patricia; Pekar, Vladimir

    2015-04-15

    Purpose: The treatment of thoracic cancer using external beam radiation requires an optimal selection of the radiation beam directions to ensure effective coverage of the target volume and to avoid unnecessary treatment of normal healthy tissues. Intensity modulated radiation therapy (IMRT) planning is a lengthy process, which requires the planner to iterate between choosing beam angles, specifying dose–volume objectives and executing IMRT optimization. In thorax treatment planning, where there are no class solutions for beam placement, beam angle selection is performed manually, based on the planner’s clinical experience. The purpose of this work is to propose and study a computationally efficient framework that utilizes machine learning to automatically select treatment beam angles. Such a framework may be helpful for reducing the overall planning workload. Methods: The authors introduce an automated beam selection method, based on learning the relationships between beam angles and anatomical features. Using a large set of clinically approved IMRT plans, a random forest regression algorithm is trained to map a multitude of anatomical features into an individual beam score. An optimization scheme is then built to select and adjust the beam angles, considering the learned interbeam dependencies. The validity and quality of the automatically selected beams evaluated using the manually selected beams from the corresponding clinical plans as the ground truth. Results: The analysis included 149 clinically approved thoracic IMRT plans. For a randomly selected test subset of 27 plans, IMRT plans were generated using automatically selected beams and compared to the clinical plans. The comparison of the predicted and the clinical beam angles demonstrated a good average correspondence between the two (angular distance 16.8° ± 10°, correlation 0.75 ± 0.2). The dose distributions of the semiautomatic and clinical plans were equivalent in terms of primary target volume

  18. State machine components selection based on minimal transversals

    NASA Astrophysics Data System (ADS)

    Stefanowicz, Łukasz; Mróz, Piotr

    2015-12-01

    The article relates to the problem of State Machine Components selection using hypergraphs theory. The base method of exact transversals was presented as well as exact transversal and simple transversal computation. Due to limitations of xt-hypergraph application, authors proposed to extend the baseline method by usage of minimal transversals.

  19. Health Effects Profiles for Searching Selected Lockheed DIALOG Data Bases.

    ERIC Educational Resources Information Center

    Clement, Linda Lee

    This preliminary study attempted to determine the most effective search strategies for the topic "health effects" in relation to specific chemicals and/or pollutants--in this case, asbestos--for each of five selected Lockheed DIALOG data bases: BIOSIS Previews, Chemical Abstracts Condensates (Chemcon), NTIS, Enviroline, and Pollution Abstracts.…

  20. Competency-Based Evaluation for Selecting a Counselor Educator

    ERIC Educational Resources Information Center

    Weitz, Lawrence J.; And Others

    1976-01-01

    Describes an approach to faculty selection in a competency-based human development counseling program, the development of which enabled candidates to demonstrate their actual level of mastery for a wide range of skills associated with professional effectiveness. Successes and setbacks of this model are presented. (Author)

  1. Object-based attentional selection modulates anticipatory alpha oscillations.

    PubMed

    Knakker, Balázs; Weiss, Béla; Vidnyánszky, Zoltán

    2014-01-01

    Visual cortical alpha oscillations are involved in attentional gating of incoming visual information. It has been shown that spatial and feature-based attentional selection result in increased alpha oscillations over the cortical regions representing sensory input originating from the unattended visual field and task-irrelevant visual features, respectively. However, whether attentional gating in the case of object based selection is also associated with alpha oscillations has not been investigated before. Here we measured anticipatory electroencephalography (EEG) alpha oscillations while participants were cued to attend to foveal face or word stimuli, the processing of which is known to have right and left hemispheric lateralization, respectively. The results revealed that in the case of simultaneously displayed, overlapping face and word stimuli, attending to the words led to increased power of parieto-occipital alpha oscillations over the right hemisphere as compared to when faces were attended. This object category-specific modulation of the hemispheric lateralization of anticipatory alpha oscillations was maintained during sustained attentional selection of sequentially presented face and word stimuli. These results imply that in the case of object-based attentional selection-similarly to spatial and feature-based attention-gating of visual information processing might involve visual cortical alpha oscillations. PMID:25628554

  2. Guide for Selecting A Computer-Based Instructional System.

    ERIC Educational Resources Information Center

    Texas Education Agency, Austin.

    A systematic process for selecting computer-based instructional systems and incorporating them into school programs is presented in this guide. The 8-step process which is outlined includes: (1) specification of goals and objectives, (2) assessment of student needs, (3) review of the curriculum framework, (4) determination of computer…

  3. [Design of Oxygen Saturation, Heart Rate, Respiration Rate Detection System Based on Smartphone of Android Operating System].

    PubMed

    Zhu, Mingshan; Zeng, Bixin

    2015-03-01

    In this paper, we designed an oxygen saturation, heart rate, respiration rate monitoring system based on smartphone of android operating system, physiological signal acquired by MSP430 microcontroller and transmitted by Bluetooth module. PMID:26524782

  4. ADLOC: an aptamer-displacement assay based on luminescent oxygen channeling.

    PubMed

    Niebel, Björn; Lentz, Christian; Pofahl, Monika; Mayer, Günter; Hoerauf, Achim; Pfarr, Kenneth M; Famulok, Michael

    2010-09-24

    Functional nucleic acids, such as aptamers and allosteric ribozymes, can sense their ligands specifically, thereby undergoing structural alterations that can be converted into a detectable signal. The direct coupling of molecular recognition to signal generation enables the production of versatile reporters that can be applied as molecular probes for various purposes, including high-throughput screening. Here we describe an unprecedented type of a nucleic acid-based sensor system and show that it is amenable to high-throughput screening (HTS) applications. The approach detects the displacement of an aptamer from its bound protein partner by means of luminescent oxygen channeling. In a proof-of-principle study we demonstrate that the format is feasible for efficient identification of small drug-like molecules that bind to a protein target, in this case to the Sec7 domain of cytohesin. We extended the approach to a new cytohesin-specific single chain DNA aptamer, C10.41, which exhibits a similar binding behavior to cytohesins but has the advantage of being more stable and easier to synthesize and to modify than the RNA-aptamer M69. The results obtained with both aptamers indicate the general suitability of the aptamer-displacement assay based on luminescent oxygen channelling (ADLOC) for HTS. We also analyzed the potential for false positive hits and identified from a library of 18,000 drug-like small molecules two compounds as strong singlet-oxygen quenchers. With full automation and the use of commercially available plate readers, we estimate that the ADLOC-based assay described here could be used to screen at least 100,000 compounds per day. PMID:20690121

  5. Effect of the size-selective silver clusters on lithium peroxide morphology in lithium-oxygen batteries

    NASA Astrophysics Data System (ADS)

    Lu, Jun; Cheng, Lei; Lau, Kah Chun; Tyo, Eric; Luo, Xiangyi; Wen, Jianguo; Miller, Dean; Assary, Rajeev S.; Wang, Hsien-Hau; Redfern, Paul; Wu, Huiming; Park, Jin-Bum; Sun, Yang-Kook; Vajda, Stefan; Amine, Khalil; Curtiss, Larry A.

    2014-09-01

    Lithium-oxygen batteries have the potential needed for long-range electric vehicles, but the charge and discharge chemistries are complex and not well understood. The active sites on cathode surfaces and their role in electrochemical reactions in aprotic lithium-oxygen cells are difficult to ascertain because the exact nature of the sites is unknown. Here we report the deposition of subnanometre silver clusters of exact size and number of atoms on passivated carbon to study the discharge process in lithium-oxygen cells. The results reveal dramatically different morphologies of the electrochemically grown lithium peroxide dependent on the size of the clusters. This dependence is found to be due to the influence of the cluster size on the formation mechanism, which also affects the charge process. The results of this study suggest that precise control of subnanometre surface structure on cathodes can be used as a means to improve the performance of lithium-oxygen cells.

  6. Reactive oxygen species accelerate degradation of anion exchange membranes based on polyphenylene oxide in alkaline environments.

    PubMed

    Parrondo, Javier; Wang, Zhongyang; Jung, Min-Suk J; Ramani, Vijay

    2016-07-20

    Anion exchange membranes (AEM) based on polyphenylene oxide (PPO) suffered quaternary-ammonium-cation-site degradation in alkaline environments. Surprisingly, the degradation rate was considerably faster in the presence of molecular oxygen. We postulated that the AEM cation-site catalyzes the reduction of dioxygen by hydroxide ions to yield the superoxide anion radical and the highly reactive hydroxyl free radical. We substantiated our hypothesis by using a phosphorous-containing spin trap (5-diisopropoxy-phosphoryl-5-methyl-1-pyrroline-N-oxide) to detect the adducts for both free radicals in situ using (31)P-NMR spectroscopy. PMID:27381009

  7. Base metal-catalyzed benzylic oxidation of (aryl)(heteroaryl)methanes with molecular oxygen

    PubMed Central

    Sterckx, Hans; De Houwer, Johan; Mensch, Carl; Herrebout, Wouter; Tehrani, Kourosch Abbaspour

    2016-01-01

    Summary The methylene group of various substituted 2- and 4-benzylpyridines, benzyldiazines and benzyl(iso)quinolines was successfully oxidized to the corresponding benzylic ketones using a copper or iron catalyst and molecular oxygen as the stoichiometric oxidant. Application of the protocol in API synthesis is exemplified by the alternative synthesis of a precursor to the antimalarial drug Mefloquine. The oxidation method can also be used to prepare metabolites of APIs which is illustrated for the natural product papaverine. ICP–MS analysis of the purified reaction products revealed that the base metal impurity was well below the regulatory limit. PMID:26877817

  8. Fiber-Based Laser Transmitter for Oxygen A-Band Spectroscopy and Remote Sensing

    NASA Technical Reports Server (NTRS)

    Stephen, Mark A.; Abshire, James B.

    2010-01-01

    A fiber-based laser transmitter has been designed for active remote-sensing spectroscopy. The transmitter uses a master-oscillator-power-amplifier (MOPA) configuration with a distributed feedback diode-laser master oscillator and an erbium-doped fiber amplifier. The output from the MOPA is frequency-doubled with a periodically poled nonlinear crystal. The utility of this single-frequency, wavelength-tunable, power-scalable laser has been demonstrated in a spectroscopic measurement of the diatomic oxygen A-band.

  9. Structure-activity relationship in high-performance iron-based electrocatalysts for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Song, Ping; Wang, Ying; Pan, Jing; Xu, Weilin; Zhuang, Lin

    2015-12-01

    A sustainable Iron (Fe), Nitrogen (N) co-doped high performance Fe-Nx/C electrocatalyst for oxygen reduction reaction (ORR) is synthesized simply based on nitric acid oxidation of cheap carbon black. The obtained optimal nonprecious metal electrocatalyst shows high ORR performance in both alkaline and acidic conditions and possesses appreciable performance/price ratio due to its low cost. Furthermore, the structure-activity relationship of different active sites on Fe-Nx/C is revealed systematically: Fe-N4/2-C > Fe4-N-C > N-C >> Fe4-C ≥ C, from both experimental and theoretical points of view.

  10. Kinetics of Oxygen Reduction in Aprotic Li-O2 Cells: A Model-Based Study.

    PubMed

    Safari, M; Adams, B D; Nazar, L F

    2014-10-16

    A comprehensive and general kinetic model is developed for the oxygen reduction reaction in aprotic Li-O2 cells. The model is based on the competitive uptake of lithium superoxide by the surface and solution. A demonstrative kinetic study is provided to demystify the origin of curvature in Tafel plots as well as the current dependency and aberrant diversity of the nature and morphology of discharge products in these systems. Our results are general and extend to any system where solubilization of superoxide is favored, such as where phase-transfer catalysts play an important role. PMID:26278597

  11. A Predictive Based Regression Algorithm for Gene Network Selection

    PubMed Central

    Guerrier, Stéphane; Mili, Nabil; Molinari, Roberto; Orso, Samuel; Avella-Medina, Marco; Ma, Yanyuan

    2016-01-01

    Gene selection has become a common task in most gene expression studies. The objective of such research is often to identify the smallest possible set of genes that can still achieve good predictive performance. To do so, many of the recently proposed classification methods require some form of dimension-reduction of the problem which finally provide a single model as an output and, in most cases, rely on the likelihood function in order to achieve variable selection. We propose a new prediction-based objective function that can be tailored to the requirements of practitioners and can be used to assess and interpret a given problem. Based on cross-validation techniques and the idea of importance sampling, our proposal scans low-dimensional models under the assumption of sparsity and, for each of them, estimates their objective function to assess their predictive power in order to select. Two applications on cancer data sets and a simulation study show that the proposal compares favorably with competing alternatives such as, for example, Elastic Net and Support Vector Machine. Indeed, the proposed method not only selects smaller models for better, or at least comparable, classification errors but also provides a set of selected models instead of a single one, allowing to construct a network of possible models for a target prediction accuracy level. PMID:27379155

  12. A Predictive Based Regression Algorithm for Gene Network Selection.

    PubMed

    Guerrier, Stéphane; Mili, Nabil; Molinari, Roberto; Orso, Samuel; Avella-Medina, Marco; Ma, Yanyuan

    2016-01-01

    Gene selection has become a common task in most gene expression studies. The objective of such research is often to identify the smallest possible set of genes that can still achieve good predictive performance. To do so, many of the recently proposed classification methods require some form of dimension-reduction of the problem which finally provide a single model as an output and, in most cases, rely on the likelihood function in order to achieve variable selection. We propose a new prediction-based objective function that can be tailored to the requirements of practitioners and can be used to assess and interpret a given problem. Based on cross-validation techniques and the idea of importance sampling, our proposal scans low-dimensional models under the assumption of sparsity and, for each of them, estimates their objective function to assess their predictive power in order to select. Two applications on cancer data sets and a simulation study show that the proposal compares favorably with competing alternatives such as, for example, Elastic Net and Support Vector Machine. Indeed, the proposed method not only selects smaller models for better, or at least comparable, classification errors but also provides a set of selected models instead of a single one, allowing to construct a network of possible models for a target prediction accuracy level. PMID:27379155

  13. Recursive SAM-based band selection for hyperspectral anomaly detection

    NASA Astrophysics Data System (ADS)

    He, Yuanlei; Liu, Daizhi; Yi, Shihua

    2010-10-01

    Band selection has been widely used in hyperspectral image processing for dimension reduction. In this paper, a recursive SAM-based band selection (RSAM-BBS) method is proposed. Once two initial bands are given, RSAM-BBS is performed in a sequential manner, and at each step the band that can best describe the spectral separation of two hyperspectral signatures is added to the bands already selected until the spectral angle reaches its maximum. In order to demonstrate the utility of the proposed band selection method, an anomaly detection algorithm is developed, which first extracts the anomalous target spectrum from the original image using automatic target detection and classification algorithm (ATDCA), followed by maximum spectral screening (MSS) to estimate the background average spectrum, then implements RSAM-BBS to select bands that participate in the subsequent adaptive cosine estimator (ACE) target detection. As shown in the experimental result on the AVIRIS dataset, less than five bands selected by the RSAM-BBS can achieve comparable detection performance using the full bands.

  14. An Iron-based Film for Highly Efficient Electrocatalytic Oxygen Evolution from Neutral Aqueous Solution.

    PubMed

    Chen, Mingxing; Wu, Yizhen; Han, Yongzhen; Lin, Xiaohuan; Sun, Junliang; Zhang, Wei; Cao, Rui

    2015-10-01

    An ultrathin Fe-based film was prepared by electrodeposition from an Fe(II) solution through a fast and simple cyclic voltammetry method. The extremely low Fe loading of 12.3 nmol cm(-2) on indium tin oxide electrodes is crucial for high atom efficiency and transparence of the resulted film. This Fe-based film was shown to be a very efficient electrocatalyst for oxygen evolution from neutral aqueous solution with remarkable activity and stability. In a 34 h controlled potential electrolysis at 1.45 V (vs NHE) and pH 7.0, impressive turnover number of 5.2 × 10(4) and turnover frequency of 1528 h(-1) were obtained. To the best of our knowledge, these values represent one of the highest among electrodeposited catalyst films for water oxidation under comparable conditions. The morphology and the composition of the catalyst film was determined by scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray, and X-ray photoelectron spectroscopy, which all confirmed the deposition of Fe-based materials with Fe(III) oxidation state on the electrode. This study is significant because of the use of iron, the fast and simple cyclic voltammetry electrodeposition, the extremely low catalyst loading and thus the transparency of the catalyst film, the remarkable activity and stability, and the oxygen evolution in neutral aqueous media. PMID:26368828

  15. Optimization of catalyst layer composition for PEMFC using graphene-based oxygen reduction reaction catalysts

    NASA Astrophysics Data System (ADS)

    Park, Jong Cheol; Park, Sung Hyeon; Chung, Min Wook; Choi, Chang Hyuck; Kho, Back Kyun; Woo, Seong Ihl

    2015-07-01

    The focus in recent years is on developing high performance non-precious metal catalysts (NPMCs) to reduce the catalyst cost in fuel cells. However, little attention has been paid to improve the utilization of NPMCs. Thus, this study focuses on the optimization of electrode component, particularly the Nafion content. With the synthesized graphene based oxygen reduction reaction (ORR) catalyst, the catalyst inks were prepared at various Nafion contents with suitable amounts of catalysts sprayed on the gas diffusion media. Twenty different single cells were assembled and measured for polarization, resistance and electrochemical impedance. Electrodes of 66.7 and 50.0% Nafion contents showed the highest performance for hydrogen/oxygen and hydrogen/air operation, respectively. These results were explained using the electrochemical impedance spectra, where the highest performance electrode resulted with the lowest charge transfer resistance. Moreover, negligible change in performance was observed during the 80 h of stability test. The optimization compositions of NPMC-based MEAs were very different to Pt-based MEAs, indicating the importance of optimization studies for the practical use of NPMCs.

  16. Selective detector of cosmic particles based on diamond sensitive elements

    NASA Astrophysics Data System (ADS)

    Altukhov, A. A.; Zaharchenko, K. V.; Kolyubin, V. A.; Lvov, S. A.; Nedosekin, P. G.; Tyurin, E. M.; Ibragimov, R. F.; Kadilin, V. V.; Nikolaev, I. V.

    2016-02-01

    The article describes the device for selective registration of electrons, protons and heavy ions fluxes from the solar and galactic cosmic rays in the twelve energy ranges, built on a base of diamond detector. The use of the diamond detectors allowed for the creation a device for registration of cosmic particles fluxes at the external spacecraft surface with the resource not less than 20 years. Selective detector is aimed for continuous monitoring of radiation situation on board the spacecrafts, in order to predict the residual life of their work and prompt measures to actively protect the spacecraft when the flow of cosmic particles is sharply increased.

  17. New solar selective coating based on carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Abendroth, Thomas; Leupolt, Beate; Mäder, Gerrit; Härtel, Paul; Grählert, Wulf; Althues, Holger; Kaskel, Stefan; Beyer, Eckhard

    2016-05-01

    Carbon nanotubes (CNTs) can be applied to assemble a new type of solar selective coating system for solar thermal applications. In this work the predominant absorption processes occurring by interaction with π-plasmon and Van Hove singularities (VHS) were investigated by UV-VIS-NIR spectroscopy and ellipsometry. Not only optical properties for as deposited SWCNT thin films itself, but also the potential for systematic tailoring will be presented. Besides low cost technologies required, the adjustability of optical properties, as well as their thermal stability render CNT based solar selective coatings as promising alternative to commercially available coating systems.

  18. A threshold selection method based on edge preserving

    NASA Astrophysics Data System (ADS)

    Lou, Liantang; Dan, Wei; Chen, Jiaqi

    2015-12-01

    A method of automatic threshold selection for image segmentation is presented. An optimal threshold is selected in order to preserve edge of image perfectly in image segmentation. The shortcoming of Otsu's method based on gray-level histograms is analyzed. The edge energy function of bivariate continuous function is expressed as the line integral while the edge energy function of image is simulated by discretizing the integral. An optimal threshold method by maximizing the edge energy function is given. Several experimental results are also presented to compare with the Otsu's method.

  19. Model selection based on robustness criterion with measurement application

    NASA Astrophysics Data System (ADS)

    Brahim-Belhouari, Sofiane; Fleury, Gilles; Davoust, Marie-Eve

    1999-06-01

    Huber's approach to robust estimation is highly fruitful for solving estimation problems with contaminated data or under incomplete information according to the error structure. A simple selection procedure based on robustness to variations of the errors distribution from the assumed one, is proposed. Minimax M-estimator is used to estimate efficiently the parameters and the measurement quantity. A performance deviation criterion is computed by the mean of the Monte Carlo method improved by the Latin Hypercube Sampling. The selection produced is applied to a real measurement problem, grooves dimensioning using Remote Field Eddy Current inspection.

  20. Model-based sensor location selection for helicopter gearbox monitoring

    NASA Technical Reports Server (NTRS)

    Jammu, Vinay B.; Wang, Keming; Danai, Kourosh; Lewicki, David G.

    1996-01-01

    A new methodology is introduced to quantify the significance of accelerometer locations for fault diagnosis of helicopter gearboxes. The basis for this methodology is an influence model which represents the effect of various component faults on accelerometer readings. Based on this model, a set of selection indices are defined to characterize the diagnosability of each component, the coverage of each accelerometer, and the relative redundancy between the accelerometers. The effectiveness of these indices is evaluated experimentally by measurement-fault data obtained from an OH-58A main rotor gearbox. These data are used to obtain a ranking of individual accelerometers according to their significance in diagnosis. Comparison between the experimentally obtained rankings and those obtained from the selection indices indicates that the proposed methodology offers a systematic means for accelerometer location selection.

  1. A Phase Shift Demodulation Technique: Verification and Application in Fluorescence Phase Based Oxygen Sensors

    NASA Astrophysics Data System (ADS)

    Jia, Chuanwu; Chang, Jun; Wang, Fupeng; Jiang, Hao; Zhu, Cunguang; Wang, Pengpeng

    2016-06-01

    A phase shift demodulation technique based on subtraction capable of measuring 0.03 phase degree limit between sinusoidal signals is presented in this paper. A self-gain module and a practical subtracter act the kernel parts of the phase shift demodulation system. Electric signals in different phases are used to verify the performance of the system. In addition, a new designed optical source, laser fiber differential source (LFDS), capable of generating mini phase is used to further verify the system reliability. R-square of 0.99997 in electric signals and R-square of 0.99877 in LFDS are achieved, and 0.03 degree measurement limit is realized in experiments. Furthermore, the phase shift demodulation system is applied to the fluorescence phase based oxygen sensors to realize the fundamental function. The experimental results reveal that a good repetition and better than 0.02% oxygen concentration measurement accuracy are realized. In addition, the phase shift demodulation system can be easily integrated to other applications.

  2. Electrochemical activation of commercial polyacrylonitrile-based carbon fiber for the oxygen reduction reaction.

    PubMed

    Xu, Haibo; Xia, Guangsen; Liu, Haining; Xia, Shuwei; Lu, Yonghong

    2015-03-28

    Nitrogen (N)-doped carbon and its non-noble metal composite replacing platinum-based oxygen reduction reaction (ORR) electrocatalysts still have some fundamental problems that remain. Here the micron-sized commercial polyacrylonitrile-based carbon fiber (PAN-CF) electrode was modified using an electrochemical method, converting its inherent pyridinic-N into 2-pyridone (or 2-hydroxyl pyridine) functional group existing in three-dimensional active layers with remarkable ORR catalytic activity and stability. The carbon atom adjacent to the nitrogen and oxygen atoms is prone to act as an active site to efficiently catalyze a two-electron ORR process. However, after coordinating pyridone to the Cu(2+) ion, together with the electrochemical reaction, the chemical redox between Cu(+) and ORR intermediates synergistically tends towards a four-electron pathway in alkaline solution. In different medium, the complexation and dissociation can induce the charge transfer and reconstruction among proton, metal ion and pyridone functionalities, eventually leading to the changes of ORR performance. PMID:25712410

  3. Imaging of oxygen in microreactors and microfluidic systems

    NASA Astrophysics Data System (ADS)

    Sun, Shiwen; Ungerböck, Birgit; Mayr, Torsten

    2015-09-01

    This review gives an overview on the state-of-the-art of oxygen imaging in microfluidics. Oxygen imaging using optical oxygen sensors based on luminescence is a versatile and powerful tool for obtaining profoundly space-resolved information of oxygen in microreactors and microfluidic systems. We briefly introduce the principle of oxygen imaging and present techniques of oxygen imaging applied in microreactors and microfluidic devices, including selection criteria and demands of sensing material and basic set-up for a 2D oxygen sensing system. A detailed review of oxygen imaging in microreactors and microfluidic systems is given on different applications in oxygen gradient monitoring, cell culturing, single-cell analysis and chemical reactions. Finally, we discuss challenges and trends of oxygen imaging in microfluidic systems.

  4. Selection of Construction Methods: A Knowledge-Based Approach

    PubMed Central

    Skibniewski, Miroslaw

    2013-01-01

    The appropriate selection of construction methods to be used during the execution of a construction project is a major determinant of high productivity, but sometimes this selection process is performed without the care and the systematic approach that it deserves, bringing negative consequences. This paper proposes a knowledge management approach that will enable the intelligent use of corporate experience and information and help to improve the selection of construction methods for a project. Then a knowledge-based system to support this decision-making process is proposed and described. To define and design the system, semistructured interviews were conducted within three construction companies with the purpose of studying the way that the method' selection process is carried out in practice and the knowledge associated with it. A prototype of a Construction Methods Knowledge System (CMKS) was developed and then validated with construction industry professionals. As a conclusion, the CMKS was perceived as a valuable tool for construction methods' selection, by helping companies to generate a corporate memory on this issue, reducing the reliance on individual knowledge and also the subjectivity of the decision-making process. The described benefits as provided by the system favor a better performance of construction projects. PMID:24453925

  5. Improvement of Rice Biomass Yield through QTL-Based Selection

    PubMed Central

    Matsubara, Kazuki; Yamamoto, Eiji; Kobayashi, Nobuya; Ishii, Takuro; Tanaka, Junichi; Tsunematsu, Hiroshi; Yoshinaga, Satoshi; Matsumura, Osamu; Yonemaru, Jun-ichi; Mizobuchi, Ritsuko; Yamamoto, Toshio; Kato, Hiroshi; Yano, Masahiro

    2016-01-01

    Biomass yield of rice (Oryza sativa L.) is an important breeding target, yet it is not easy to improve because the trait is complex and phenotyping is laborious. Using progeny derived from a cross between two high-yielding Japanese cultivars, we evaluated whether quantitative trait locus (QTL)-based selection can improve biomass yield. As a measure of biomass yield, we used plant weight (aboveground parts only), which included grain weight and stem and leaf weight. We measured these and related traits in recombinant inbred lines. Phenotypic values for these traits showed a continuous distribution with transgressive segregation, suggesting that selection can affect plant weight in the progeny. Four significant QTLs were mapped for plant weight, three for grain weight, and five for stem and leaf weight (at α = 0.05); some of them overlapped. Multiple regression analysis showed that about 43% of the phenotypic variance of plant weight was significantly explained (P < 0.0001) by six of the QTLs. From F2 plants derived from the same parental cross as the recombinant inbred lines, we divergently selected lines that carried alleles with positive or negative additive effects at these QTLs, and performed successive selfing. In the resulting F6 lines and parents, plant weight significantly differed among the genotypes (at α = 0.05). These results demonstrate that QTL-based selection is effective in improving rice biomass yield. PMID:26986071

  6. Tailoring p- and n- type semiconductor through site selective oxygen doping in Cu3N: density functional studies

    NASA Astrophysics Data System (ADS)

    Sahoo, Guruprasad; Kashikar, Ravi; Jain, Mahaveer K.; Nanda, B. R. K.

    2016-06-01

    Using ab initio density functional calculations, we have investigated the stability and electronic structure of pure and oxygen doped semiconducting Cu3N. The oxygen can be accommodated in the system without structural instability as the formation energy either decreases when oxygen substitutes nitrogen, or remains nearly same when oxygen occupies the interstitial position. The interstitial oxygen (OI) prefers to stabilize in the unusual charge neutral state and acts as an acceptor to make the system a p-type degenerate semiconductor. In this case the hole pockets are formed by the partially occupied OI-p states. On the other hand, oxygen substituting nitrogen (OS) stabilizes in its usual ‑2 charge state and acts as a donor to make the system an n-type degenerate semiconductor. The electron pockets are formed by the conducting Cu-p states. In the case of mixed doping, holes are gradually compensated by the donor electrons and an intrinsic gap is obtained for {{{Cu}}}3{{{N}}}{1-2{x}}{{{{O}}}{{S}}}2{x}{{{{O}}}{{I}}}{x} stoichiometry. Our calculations predict the nature of doping as well as optical band gap ({{E}{{g}}}{{o}{{p}}{{t}}}) variation in experimentally synthesized copper oxynitride. While interstitial doping contracts the lattice and increases the {{E}{{g}}}{{o}{{p}}{{t}}}, substitutional doping increases both lattice size and {{E}{{g}}}{{o}{{p}}{{t}}}. Mixed doping reduces {{E}{{g}}}{{o}{{p}}{{t}}}. Additionally we show that a rare intra-atomic d–p optical absorption can be realized in the pristine Cu3N as the Fermi level lies in the gap between the Cu-d dominated anti-bonding valence state and Cu-p conducting state.

  7. Combinatorial density functional theory-based screening of surface alloys for the oxygen reduction reaction.

    SciTech Connect

    Greeley, J.; Norskov, J.; Center for Nanoscale Materials; Technical Univ. of Denmark

    2009-03-26

    A density functional theory (DFT) -based, combinatorial search for improved oxygen reduction reaction (ORR) catalysts is presented. A descriptor-based approach to estimate the ORR activity of binary surface alloys, wherein alloying occurs only in the surface layer, is described, and rigorous, potential-dependent computational tests of the stability of these alloys in aqueous, acidic environments are presented. These activity and stability criteria are applied to a database of DFT calculations on nearly 750 binary transition metal surface alloys; of these, many are predicted to be active for the ORR but, with few exceptions, they are found to be thermodynamically unstable in the acidic environments typical of low-temperature fuel cells. The results suggest that, absent other thermodynamic or kinetic mechanisms to stabilize the alloys, surface alloys are unlikely to serve as useful ORR catalysts over extended periods of operation.

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

    PubMed

    Er, Li; Xiangying, Zeng

    2014-01-01

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

  9. Selective adsorption for removal of nitrogen compounds from hydrocarbon streams over carbon-based adsorbents

    NASA Astrophysics Data System (ADS)

    Almarri, Masoud S.

    desulfurization of model diesel fuel, which contains equimolar concentrations of nitrogen (i.e., quinoline and indole), sulfur (i.e., dibenzothiophene and 4,6-dimethyldibenzothiophene), and aromatic compounds (naphthalene, 1-methylnaphthalene, and fluorene), was examined. The results revealed that when both nitrogen and sulfur compounds coexist in the fuel, the type and density of oxygen functional groups on the surface of the activated carbon are crucial for selective adsorption of nitrogen compounds but have negligible positive effects for sulfur removal. The adsorption of quinoline and indole is largely governed by specific interactions. There is enough evidence to support the importance of dipole--dipole and acid-base-specific interactions for the adsorption of both quinoline and indole. Modified carbon is a promising material for the efficient removal of the nitrogen compounds from light cycle oil (LCO). Adsorptive denitrogenation of LCO significantly improved the hydrodesulfurization (HDS) performance, especially for the removal of the refractory sulfur compounds such as 4-methyldibenzothiophene and 4,6-dimethyldibenzothiophene. An essential factor in applying activated carbon for adsorptive denitrogenation and desulfurization of liquid hydrocarbon streams is regeneration after saturation. The regeneration method of the saturated adsorbents consisted of toluene washing followed by heating to remove the remaining toluene. The results show that the spent activated carbon can be regenerated to completely recover the adsorption capacity. The high capacity and selectivity of activated carbon for nitrogen compounds, along with their ability to be regenerated, indicate that activated carbon is a promising adsorbent for the deep denitrogenation of liquid hydrocarbon streams.

  10. A parametric study of the destruction efficiency of Bacillus spores in low pressure oxygen-based plasmas.

    PubMed

    Hury, S; Vidal, D R; Desor, F; Pelletier, J; Lagarde, T

    1998-06-01

    The destruction of Bacillus spores in oxygen-based plasmas sustained in the millitorr pressure range has been studied as functions of various biological and plasma parameters, namely Bacillus species, surface concentration of spores, treatment temperature, and gas composition. In an oxygen plasma, Bacillus stearothermophilus appears less plasma-resistant than the other spores tested. Oxygen, H2O2 and chiefly CO2 plasmas are clearly shown to be much more efficient in destroying Bacillus subtilis spores than pure argon plasma. The bacterial surface concentration on the spore carriers and the treatment temperature also lead to significant variations in the destruction efficiency of spores when using CO2 plasma. PMID:9717311

  11. Thickness independent reduced forming voltage in oxygen engineered HfO{sub 2} based resistive switching memories

    SciTech Connect

    Sharath, S. U. Kurian, J.; Komissinskiy, P.; Hildebrandt, E.; Alff, L.; Bertaud, T.; Walczyk, C.; Calka, P.; Schroeder, T.

    2014-08-18

    The conducting filament forming voltage of stoichiometric hafnium oxide based resistive switching layers increases linearly with layer thickness. Using strongly reduced oxygen deficient hafnium oxide thin films grown on polycrystalline TiN/Si(001) substrates, the thickness dependence of the forming voltage is strongly suppressed. Instead, an almost constant forming voltage of about 3 V is observed up to 200 nm layer thickness. This effect suggests that filament formation and switching occurs for all samples in an oxidized HfO{sub 2} surface layer of a few nanometer thickness while the highly oxygen deficient thin film itself merely serves as a oxygen vacancy reservoir.

  12. Repair of Ischemic Injury by Pluripotent Stem Cell Based Cell Therapy without Teratoma through Selective Photosensitivity

    PubMed Central

    Cho, Seung-Ju; Kim, So-Yeon; Jeong, Ho-Chang; Cheong, Hyeonsik; Kim, Doseok; Park, Soon-Jung; Choi, Jong-Jin; Kim, Hyongbum; Chung, Hyung-Min; Moon, Sung-Hwan; Cha, Hyuk-Jin

    2015-01-01

    Summary Stem-toxic small molecules have been developed to induce selective cell death of pluripotent stem cells (PSCs) to lower the risk of teratoma formation. However, despite their high efficacies, chemical-based approaches may carry unexpected toxicities on specific differentiated cell types. Herein, we took advantage of KillerRed (KR) as a suicide gene, to selectively induce phototoxicity using visible light via the production of reactive oxygen species. PSCs in an undifferentiated state that exclusively expressed KR (KR-PSCs) were eliminated by a single exposure to visible light. This highly selective cell death in KR-PSCs was exploited to successfully inhibit teratoma formation. In particular, endothelial cells from KR-mPSCs remained fully functional in vitro and sufficient to repair ischemic injury in vivo regardless of light exposure, suggesting that a genetic approach in which KR is expressed in a tightly controlled manner would be a viable strategy to inhibit teratoma formation for future safe PSC-based therapies. PMID:26584542

  13. Repair of Ischemic Injury by Pluripotent Stem Cell Based Cell Therapy without Teratoma through Selective Photosensitivity.

    PubMed

    Cho, Seung-Ju; Kim, So-Yeon; Jeong, Ho-Chang; Cheong, Hyeonsik; Kim, Doseok; Park, Soon-Jung; Choi, Jong-Jin; Kim, Hyongbum; Chung, Hyung-Min; Moon, Sung-Hwan; Cha, Hyuk-Jin

    2015-12-01

    Stem-toxic small molecules have been developed to induce selective cell death of pluripotent stem cells (PSCs) to lower the risk of teratoma formation. However, despite their high efficacies, chemical-based approaches may carry unexpected toxicities on specific differentiated cell types. Herein, we took advantage of KillerRed (KR) as a suicide gene, to selectively induce phototoxicity using visible light via the production of reactive oxygen species. PSCs in an undifferentiated state that exclusively expressed KR (KR-PSCs) were eliminated by a single exposure to visible light. This highly selective cell death in KR-PSCs was exploited to successfully inhibit teratoma formation. In particular, endothelial cells from KR-mPSCs remained fully functional in vitro and sufficient to repair ischemic injury in vivo regardless of light exposure, suggesting that a genetic approach in which KR is expressed in a tightly controlled manner would be a viable strategy to inhibit teratoma formation for future safe PSC-based therapies. PMID:26584542

  14. Comparative In Vivo Effects of Hemoglobin-Based Oxygen Carriers (HBOC) with Varying Prooxidant and Physiological Reactivity

    PubMed Central

    Roman, Ioana; Sevastre, Bogdan; Hathazi, Denisa; Scurtu, Florina; Damian, Grigore; Silaghi-Dumitrescu, Radu

    2016-01-01

    A series of hemoglobin-based oxygen carrier candidates (HBOC), previously noted for their differences in prooxidative and physiological reactivity, were compared in terms of the negative effects displayed upon injection in Wistar rats. At the concentrations tested, antioxidant strategies based on albumin as well as based on rubrerythrin appear to offer observable physiological advantages. PMID:27097326

  15. Comparative In Vivo Effects of Hemoglobin-Based Oxygen Carriers (HBOC) with Varying Prooxidant and Physiological Reactivity.

    PubMed

    Toma, Vlad Al; Farcaș, Anca D; Roman, Ioana; Sevastre, Bogdan; Hathazi, Denisa; Scurtu, Florina; Damian, Grigore; Silaghi-Dumitrescu, Radu

    2016-01-01

    A series of hemoglobin-based oxygen carrier candidates (HBOC), previously noted for their differences in prooxidative and physiological reactivity, were compared in terms of the negative effects displayed upon injection in Wistar rats. At the concentrations tested, antioxidant strategies based on albumin as well as based on rubrerythrin appear to offer observable physiological advantages. PMID:27097326

  16. Risk-based audit selection of dairy farms.

    PubMed

    van Asseldonk, M A P M; Velthuis, A G J

    2014-02-01

    Dairy farms are audited in the Netherlands on numerous process standards. Each farm is audited once every 2 years. Increasing demands for cost-effectiveness in farm audits can be met by introducing risk-based principles. This implies targeting subpopulations with a higher risk of poor process standards. To select farms for an audit that present higher risks, a statistical analysis was conducted to test the relationship between the outcome of farm audits and bulk milk laboratory results before the audit. The analysis comprised 28,358 farm audits and all conducted laboratory tests of bulk milk samples 12 mo before the audit. The overall outcome of each farm audit was classified as approved or rejected. Laboratory results included somatic cell count (SCC), total bacterial count (TBC), antimicrobial drug residues (ADR), level of butyric acid spores (BAB), freezing point depression (FPD), level of free fatty acids (FFA), and cleanliness of the milk (CLN). The bulk milk laboratory results were significantly related to audit outcomes. Rejected audits are likely to occur on dairy farms with higher mean levels of SCC, TBC, ADR, and BAB. Moreover, in a multivariable model, maxima for TBC, SCC, and FPD as well as standard deviations for TBC and FPD are risk factors for negative audit outcomes. The efficiency curve of a risk-based selection approach, on the basis of the derived regression results, dominated the current random selection approach. To capture 25, 50, or 75% of the population with poor process standards (i.e., audit outcome of rejected), respectively, only 8, 20, or 47% of the population had to be sampled based on a risk-based selection approach. Milk quality information can thus be used to preselect high-risk farms to be audited more frequently. PMID:24290823

  17. Furnace and Heat Recovery Area Design and Analysis for Conceptual Design of Oxygen-Based PC Boiler

    SciTech Connect

    Andrew Seltzer

    2005-01-01

    The objective of the furnace and heat recovery area design and analysis task of the Conceptual Design of Oxygen-Based PC Boiler study is to optimize the location and design of the furnace, burners, over-fire gas ports, and internal radiant surfaces. The furnace and heat recovery area were designed and analyzed using the FW-FIRE and HEATEX computer programs. The furnace is designed with opposed wall-firing burners and over-fire air ports. Water is circulated in the furnace by natural circulation to the waterwalls and divisional wall panels. Compared to the air-fired furnace, the oxygen-fired furnace requires only 65% of the surface area and 45% of the volume. Two oxygen-fired designs were simulated: (1) without over-fire air and (2) with 20% over-fire air. The maximum wall heat flux in the oxygen-fired furnace is more than double that of the air-fired furnace due to the higher flame temperature and higher H{sub 2}O and CO{sub 2} concentrations. The coal burnout for the oxygen-fired case is 100% due to a 500 F higher furnace temperature and higher concentration of O{sub 2}. Because of the higher furnace wall temperature of the oxygen-fired case compared to the air-fired case, furnace water wall material was upgraded from carbon steel to T91. The total heat transfer surface required in the oxygen-fired heat recovery area (HRA) is 25% less than the air-fired HRA due to more heat being absorbed in the oxygen-fired furnace and the greater molecular weight of the oxygen-fired flue gas. The HRA tube materials and wall thickness are practically the same for the air-fired and oxygen-fired design since the flue gas and water/steam temperature profiles encountered by the heat transfer banks are very similar.

  18. Model-based rational strategy for chromatographic resin selection.

    PubMed

    Nfor, Beckley K; Zuluaga, Diego S; Verheijen, Peter J T; Verhaert, Peter D E M; van der Wielen, Luuk A M; Ottens, Marcel

    2011-01-01

    A model-based rational strategy for the selection of chromatographic resins is presented. The main question being addressed is that of selecting the most optimal chromatographic resin from a few promising alternatives. The methodology starts with chromatographic modeling,parameters acquisition, and model validation, followed by model-based optimization of the chromatographic separation for the resins of interest. Finally, the resins are rationally evaluated based on their optimized operating conditions and performance metrics such as product purity, yield, concentration, throughput, productivity, and cost. Resin evaluation proceeds by two main approaches. In the first approach, Pareto frontiers from multi-objective optimization of conflicting objectives are overlaid for different resins, enabling direct visualization and comparison of resin performances based on the feasible solution space. The second approach involves the transformation of the resin performances into weighted resin scores, enabling the simultaneous consideration of multiple performance metrics and the setting of priorities. The proposed model-based resin selection strategy was illustrated by evaluating three mixed mode adsorbents (ADH, PPA, and HEA) for the separation of a ternary mixture of bovine serum albumin, ovalbumin, and amyloglucosidase. In order of decreasing weighted resin score or performance, the top three resins for this separation were ADH [PPA[HEA. The proposed model-based approach could be a suitable alternative to column scouting during process development, the main strengths being that minimal experimentation is required and resins are evaluated under their ideal working conditions, enabling a fair comparison. This work also demonstrates the application of column modeling and optimization to mixed mode chromatography. PMID:22238769

  19. Selective gas transfer through binary polymeric systems based on block-copolymers.

    PubMed

    Beckman, I N; Teplyakov, V V

    2015-08-01

    Evaluation of several versions of phenomenological theory of gas permeability in selective polymeric membranes is presented, along with the appropriate experimental methods for verification of these versions. The main focus is on a description of stationary mass transfer across membranes (films) containing dispersion inclusions of various shapes of one polymer in a matrix of another. Considering heterogeneous media as a membrane material, it was assumed that diffusion and sorption properties of inclusions are different from those of the dispersing medium. The problem of choosing optimal shape of inclusions is evaluated from the point of view of targeted permeability and selectivity of a membrane with respect to gases. To confirm this theoretical approach, the experimental results of the studies of diffusion (permeability) of permanent gases in polymeric membranes of different structures were used. The target gases included noble gases, hydrogen, nitrogen, oxygen, CO2, and methane. The target polymers included glassy polyvinyltrimethylsilane (PVTMS, T(gl)=155-180 °C), rubberlike polydimethylsiloxane (PDMS, T(gl)=-120 °C), and two-phase block-copolymers based on these materials within a wide range of composition, including the region of phase inversion. In addition, available experimental literature data on gas permeation parameters for polyarylat-polysiloxane, polysulfon-polysiloxane, and polycarbonate-polysiloxane block-copolymers are utilized. In order to describe the stationary gas permeability for two-phase systems (from diluted dispersion of one polymer in another to concentrated dispersion and complete phase inversion) the empiric approaches based on modified Maxwell equations are offered. The requirements for two-phase systems with high permeability and selectivity parameters for gas separation are identified. The permeability parameters are predicted for C1-C4 hydrocarbons in block-copolymers based on PDMS dispersion in PVTMS, phase inversion, and PVTMS

  20. Environment-based selection effects of Planck clusters

    NASA Astrophysics Data System (ADS)

    Kosyra, R.; Gruen, D.; Seitz, S.; Mana, A.; Rozo, E.; Rykoff, E.; Sanchez, A.; Bender, R.

    2015-09-01

    We investigate whether the large-scale structure environment of galaxy clusters imprints a selection bias on Sunyaev-Zel'dovich (SZ) catalogues. Such a selection effect might be caused by line of sight (LoS) structures that add to the SZ signal or contain point sources that disturb the signal extraction in the SZ survey. We use the Planck PSZ1 union catalogue in the Sloan Digital Sky Survey (SDSS) region as our sample of SZ-selected clusters. We calculate the angular two-point correlation function (2pcf) for physically correlated, foreground and background structure in the RedMaPPer SDSS DR8 catalogue with respect to each cluster. We compare our results with an optically selected comparison cluster sample and with theoretical predictions. In contrast to the hypothesis of no environment-based selection, we find a mean 2pcf for background structures of -0.049 on scales of ≲40 arcmin, significantly non-zero at ˜4σ, which means that Planck clusters are more likely to be detected in regions of low background density. We hypothesize this effect arises either from background estimation in the SZ survey or from radio sources in the background. We estimate the defect in SZ signal caused by this effect to be negligibly small, of the order of ˜10-4 of the signal of a typical Planck detection. Analogously, there are no implications on X-ray mass measurements. However, the environmental dependence has important consequences for weak lensing follow up of Planck galaxy clusters: we predict that projection effects account for half of the mass contained within a 15 arcmin radius of Planck galaxy clusters. We did not detect a background underdensity of CMASS LRGs, which also leaves a spatially varying redshift dependence of the Planck SZ selection function as a possible cause for our findings.

  1. Antibiotic Selection Pressure Determination through Sequence-Based Metagenomics

    PubMed Central

    El-Hadidi, Mohamed; Huson, Daniel H.; Schütz, Monika; Weidenmaier, Christopher; Autenrieth, Ingo B.; Peter, Silke

    2015-01-01

    The human gut forms a dynamic reservoir of antibiotic resistance genes (ARGs). Treatment with antimicrobial agents has a significant impact on the intestinal resistome and leads to enhanced horizontal transfer and selection of resistance. We have monitored the development of intestinal ARGs over a 6-day course of ciprofloxacin (Cp) treatment in two healthy individuals by using sequenced-based metagenomics and different ARG quantification methods. Fixed- and random-effect models were applied to determine the change in ARG abundance per defined daily dose of Cp as an expression of the respective selection pressure. Among various shifts in the composition of the intestinal resistome, we found in one individual a strong positive selection for class D beta-lactamases which were partly located on a mobile genetic element. Furthermore, a trend to a negative selection has been observed with class A beta-lactamases (−2.66 hits per million sample reads/defined daily dose; P = 0.06). By 4 weeks after the end of treatment, the composition of ARGs returned toward their initial state but to a different degree in both subjects. We present here a novel analysis algorithm for the determination of antibiotic selection pressure which can be applied in clinical settings to compare therapeutic regimens regarding their effect on the intestinal resistome. This information is of critical importance for clinicians to choose antimicrobial agents with a low selective force on their patients' intestinal ARGs, likely resulting in a diminished spread of resistance and a reduced burden of hospital-acquired infections with multidrug-resistant pathogens. PMID:26369961

  2. SELECTIVE REDUCTION OF NOX IN OXYGEN RICH ENVIRONMENTS WITH PLASMA-ASSISTED CATALYSIS: CATALYST DEVELOPMENT AND MECHANISTIC STUDIES

    SciTech Connect

    Peden, C; Barlow, S; Hoard, J; Kwak, J; *Balmer-Millar, M; *Panov, A; Schmieg, S; Szanyi, J; Tonkyn, R

    2003-08-24

    The control of NOx (NO and NO2) emissions from so-called ''lean-burn'' vehicle engines remains a challenge. In recent years, there have been a number of reports that show that a plasma device combined with a catalyst can reduce as high as 90% or more of NOx in simulated diesel and other ''lean-burn'' exhaust. In the case of propylene containing simulated diesel exhaust, the beneficial role of a plasma treatment is now thought to be due to oxidation of NO to NO2, and the formation of partially oxidized hydrocarbons that are more active for the catalytic reduction of NO2 than propylene. Thus, the overall system can be most usefully described as hydrocarbon selective catalytic reduction (SCR) enhanced by 'reforming' the exhaust with a non-thermal plasma (NTP) device. For plasma-enhanced catalysis, both zeolite- and alumina-based materials have shown high activity, albeit in somewhat different temperature ranges, when preceded by an NTP reactor. This paper will briefly describe our research efforts aimed at optimizing the catalyst materials for NTP-catalysis devices based, in part, on our continuing studies of the NTP- and catalytic-reaction mechanisms. Various alkali- and alkaline earth-cation-exchanged Y zeolites have been prepared, their material properties characterized, and they have been tested as catalytic materials for NOx reduction in laboratory NTP-catalysis reactors. Interestingly, NO2 formed in the plasma and not subsequently removed over these catalysts, will back-convert to NO, albeit to varying extents depending upon the nature of the cation. Besides this comparative reactivity, we will also discuss selected synthesis strategies for enhancing the performance of these zeolite-based catalyst materials. A particularly important result from our mechanistic studies is the observation that aldehydes, formed during the plasma treatment of simulated diesel exhaust, are the important species for the reduction of NOx to N2. Indeed, acetaldehyde has been found to

  3. Evaluation of a textile-based near infrared spectroscopy system in calf muscle oxygenation measurements.

    PubMed

    Nasseri, Nassim; Zysset, Christoph; Büthe, Lars; Kleiser, Stefan; Tröster, Gerhard; Wolf, Martin

    2014-01-01

    We recently introduced a novel textile-based NIRS sensor (TexNIRS). Here, we evaluate TexNIRS in ten subjects (16 legs, age 28.5 ± 2.32 years, adipose tissue thickness (ATT) 4.17 ± 1.71 mm). Three venous occlusions at 50 mmHg were performed on their calf muscle. After 3 min of occlusion, oxy/deoxy hemoglobin concentration ([O₂Hb], [HHb]) changes were 3.71 ± 1.89/1.79 ± 1.08 μM; venous oxygen saturation (SvO₂) was 75 ± 9.7 %, oxygen consumption (VO₂) was 0.02 ± 0.01 mL/100 g/min, hemoglobin flow (HF) was 0.93 ± 0.48 μmol/100 mL/min, and blood flow (BF) was 2.01 ± 1.04 mL/100 mL/min. Our results are in good agreement with the literature, but the TexNIRS enables a much higher level of comfort. PMID:24729254

  4. Reactive Ion Etching of Polymers in Oxygen Based Plasmas: a Study of Etch Mechanisms.

    NASA Astrophysics Data System (ADS)

    Graham, Sandra Wolterman

    The reactive ion etching of polymers has been studied in oxygen-based plasmas in an effort to understand the contributions of various mechanisms to the etching of these materials. Of the four active etch mechanisms; surface damage promoted etching, chemical sputtering, chemically enhanced physical sputtering, and direct reactive ion etching; the emphasis of this work has been on determining the relative contribution of direct reactive ion etching to the overall etching process. The etching of photoresist, polyimide, and amorphous carbon in O_2-CF_4 plasmas was studied in an asymmetrical reactive ion etcher at pressures ranging from 5 to 100 mtorr. Etch yield, ion flux, and oxygen atom concentration data were collected. The fit of this data to a linear model proposed by Joubert et al. (J. Appl. Phys., 65, 1989, 5096) was compared to the fit of the data to a nonlinear model proposed by the author. The linear model accounts for contribution due to three of the four etch mechanisms, but does not include contributions due to direct reactive ion etching. The nonlinear model accounts for contributions due to all four etch mechanisms. Experimental results indicate that the nonlinear model provides a better fit to the data than does the linear model. The relative contribution of direct reactive ion etching to the etching of photoresist ranges from 27% to 81% as the pressure decreases from 100 to 5 mtorr. Similar results are obtained for polyimide and amorphous carbon.

  5. Electrochemical Performance of Glucose/Oxygen Biofuel Cells Based on Carbon Nanostructures.

    PubMed

    Koo, Min-Hye; Das, Gautam; Yoon, Hyon Hee

    2016-03-01

    The electrochemical performance of glucose/oxygen biofuel cells based on carbon nanostructures was investigated in the present study. Different types of carbon nanomaterials, including multi-walled carbon nanotubes (MWCNT), functionalized MWCNT (f-MWCNT), carbon nanofibers (CNF), and functionalized CNF (f-CNF) were examined for electrode fabrications. The anode for glucose/oxygen biofuel cells were prepared by sequential coating of carbon nanomaterials, charge transfer complex (CTC), glucose oxidase (GOx) and nafion membrane. The anode was then integrated with a bilirubin oxidase-immobilized cathode for the biofuel cell test. It was found that the electrochemical performance of the enzyme electrodes was remarkably enhanced by the amalgamation of carbon nanomaterials with the CTC. The biofuel cell with anode comprising of f-CNF and the cathode with MWCNT exhibited the best electrochemical performance with a maximum power density of 210 μW/cm2 at a cell voltage of 0.44 V for 20 mM glucose concentration, which is comparable with the best power density value reported earlier. PMID:27455759

  6. An oxygen reduction electrocatalyst based on carbon nanotube-graphene complexes.

    PubMed

    Li, Yanguang; Zhou, Wu; Wang, Hailiang; Xie, Liming; Liang, Yongye; Wei, Fei; Idrobo, Juan-Carlos; Pennycook, Stephen J; Dai, Hongjie

    2012-06-01

    Oxygen reduction reaction catalysts based on precious metals such as platinum or its alloys are routinely used in fuel cells because of their high activity. Carbon-supported materials containing metals such as iron or cobalt as well as nitrogen impurities have been proposed to increase scalability and reduce costs, but these alternatives usually suffer from low activity and/or gradual deactivation during use. Here, we show that few-walled carbon nanotubes, following outer wall exfoliation via oxidation and high-temperature reaction with ammonia, can act as an oxygen reduction reaction electrocatalyst in both acidic and alkaline solutions. Under a unique oxidation condition, the outer walls of the few-walled carbon nanotubes are partially unzipped, creating nanoscale sheets of graphene attached to the inner tubes. The graphene sheets contain extremely small amounts of irons originated from nanotube growth seeds, and nitrogen impurities, which facilitate the formation of catalytic sites and boost the activity of the catalyst, as revealed by atomic-scale microscopy and electron energy loss spectroscopy. Whereas the graphene sheets formed from the unzipped part of the outer wall of the nanotubes are responsible for the catalytic activity, the inner walls remain intact and retain their electrical conductivity, which facilitates charge transport during electrocatalysis. PMID:22635099

  7. Cathode Based on Molybdenum Disulfide Nanoflakes for Lithium-Oxygen Batteries.

    PubMed

    Asadi, Mohammad; Kumar, Bijandra; Liu, Cong; Phillips, Patrick; Yasaei, Poya; Behranginia, Amirhossein; Zapol, Peter; Klie, Robert F; Curtiss, Larry A; Salehi-Khojin, Amin

    2016-02-23

    Lithium-oxygen (Li-O2) batteries have been recognized as an emerging technology for energy storage systems owing to their high theoretical specific energy. One challenge is to find an electrolyte/cathode system that is efficient, stable, and cost-effective. We present such a system based on molybdenum disulfide (MoS2) nanoflakes combined with an ionic liquid (IL) that work together as an effective cocatalyst for discharge and charge in a Li-O2 battery. Cyclic voltammetry results show superior catalytic performance for this cocatalyst for both oxygen reduction and evolution reactions compared to Au and Pt catalysts. It also performs remarkably well in the Li-O2 battery system with 85% round-trip efficiency and reversibility up to 50 cycles. Density functional calculations provide a mechanistic understanding of the MoS2 nanoflakes/IL system. The cocatalyst reported in this work could open the way for exploiting the unique properties of ionic liquids in Li-air batteries in combination with nanostructured MoS2 as a cathode material. PMID:26789516

  8. Low NOx Burner Design and Analysis for Conceptual Design of Oxygen-Based PC Boiler

    SciTech Connect

    Andrew Seltzer

    2005-05-01

    The objective of the low NOx burner design and analysis task of the Conceptual Design of Oxygen-Based PC Boiler study is to optimize the burner design to ensure stable ignition, to provide safe operation, and to minimize pollutant formation. The burners were designed and analyzed using the Fluent computer program. Four burner designs were developed: (1) with no over-fire gas (OFG) and 65% flue gas recycle, (2) with 20% OFG and 65% flue gas recycle, (3) with no OFG and 56% flue gas recycle and (4) with 20% OFG and 56% flue gas recycle. A 3-D Fluent simulation was made of a single wall-fired burner and horizontal portion of the furnace from the wall to the center. Without primary gas swirl, coal burnout was relatively small, due to the low oxygen content of the primary gas stream. Consequently, the burners were modified to include primary gas swirl to bring the coal particles in contact with the secondary gas. An optimal primary gas swirl was chosen to achieve sufficient burnout.

  9. Biofilm reactor based real-time analysis of biochemical oxygen demand.

    PubMed

    Liu, Changyu; Jia, Jianbo; Dong, Shaojun

    2013-04-15

    We reported a biofilm reactor (BFR) based analytical system for real-time biochemical oxygen demand (BOD) monitoring. It does not need a blank solution and other chemical reagents to operate. The initial dissolved oxygen (DO) in sample solution was measured as blank, while DO in the BFR effluent was measured as response. The DO difference obtained before and after the sample solution flowed through the BFR was regarded as an indicator of real-time BOD. The analytical performance of this reagent-free BFR system was equal to the previous BFR system operated using phosphate buffer saline (PBS) and high purity deionized water in reproducibility, accuracy and long-term stability. Besides, this method embraces many notable advantages, such as no secondary pollution. Additionally, the sample solutions are free from temperature controlling and air-saturation before injection. Significantly, this is a real-time BOD analysis method. This method was successfully carried out in a simulated emergency, and the obtained results agreed well with conventional BOD₅. These advantages, coupled with simplicity in device, convenience in operation and minimal maintenance, make such a reagent-free BFR analytical system promising for practical BOD real-time warning. PMID:23228491

  10. Cell design concepts for aqueous lithium-oxygen batteries: A model-based assessment

    NASA Astrophysics Data System (ADS)

    Grübl, Daniel; Bessler, Wolfgang G.

    2015-11-01

    Seven cell design concepts for aqueous (alkaline) lithium-oxygen batteries are investigated using a multi-physics continuum model for predicting cell behavior and performance in terms of the specific energy and specific power. Two different silver-based cathode designs (a gas diffusion electrode and a flooded cathode) and three different separator designs (a porous separator, a stirred separator chamber, and a redox-flow separator) are compared. Cathode and separator thicknesses are varied over a wide range (50 μm-20 mm) in order to identify optimum configurations. All designs show a considerable capacity-rate effect due to spatiotemporally inhomogeneous precipitation of solid discharge product LiOH·H2O. In addition, a cell design with flooded cathode and redox-flow separator including oxygen uptake within the external tank is suggested. For this design, the model predicts specific power up to 33 W/kg and specific energy up to 570 Wh/kg (gravimetric values of discharged cell including all cell components and catholyte except housing and piping).

  11. Ignition characteristics of the iron-based alloy UNS S66286 in pressurized oxygen

    NASA Technical Reports Server (NTRS)

    Bransford, James W.; Billard, Phillip A.; Hurley, James A.; Mcdermott, Kathleen M.; Vazquez, Isaura

    1988-01-01

    The development of ignition and combustion in pressurized oxygen atmospheres was studied for the iron based alloy UNS S66286. Ignition of the alloy was achieved by heating the top surface of a cylindrical specimen with a continuous-wave CO2 laser. Two heating procedures were used. In the first, laser power was adjusted to maintain an approximately linear increase in surface temperature. In the second, laser power was periodically increased until autoheating (self-heating) was established. It was found that the alloy would autoheat to destruction from temperatures below the solidus temperature. In addition endothermic events occurred as the alloy was heated, many at reproducible temperatures. Many endothermic events occurred prior to abrupt increases in surface temperature and appeared to accelerate the rate of increase in specimen temperature to rates greater than what would be expected from increased temperature alone. It is suggested that the source of these endotherms may increase the oxidation rate of the alloy. Ignition parameters are defined and the temperatures at which these parameters occur are given for the oxygen pressure range of 1.72 to 13.8 MPa (25 to 2000 psia).

  12. Oxidation of phenyl and hydride ligands of bis(pentamethylcyclopentadienyl)hafnium derivatives by nitrous oxide via selective oxygen atom transfer reactions: insights from quantum chemistry calculations.

    PubMed

    Xie, Hujun; Liu, Chengcheng; Yuan, Ying; Zhou, Tao; Fan, Ting; Lei, Qunfang; Fang, Wenjun

    2016-01-21

    The mechanisms for the oxidation of phenyl and hydride ligands of bis(pentamethylcyclopentadienyl)hafnium derivatives (Cp* = η(5)-C5Me5) by nitrous oxide via selective oxygen atom transfer reactions have been systematically studied by means of density functional theory (DFT) calculations. On the basis of the calculations, we investigated the original mechanism proposed by Hillhouse and co-workers for the activation of N2O. The calculations showed that the complex with an initial O-coordination of N2O to the coordinatively unsaturated Hf center is not a local minimum. Then we proposed a new reaction mechanism to investigate how N2O is activated and why N2O selectively oxidize phenyl and hydride ligands of . Frontier molecular orbital theory analysis indicates that N2O is activated by nucleophilic attack by the phenyl or hydride ligand. Present calculations provide new insights into the activation of N2O involving the direct oxygen atom transfer from nitrous oxide to metal-ligand bonds instead of the generally observed oxygen abstraction reaction to generate metal-oxo species. PMID:26660046

  13. Atomic oxygen effects on boron nitride and silicon nitride: A comparison of ground based and space flight data

    NASA Technical Reports Server (NTRS)

    Cross, J. B.; Lan, E. H.; Smith, C. A.; Whatley, W. J.

    1990-01-01

    The effects of atomic oxygen on boron nitride (BN) and silicon nitride (Si3N4) were evaluated in a low Earth orbit (LEO) flight experiment and in a ground based simulation facility. In both the inflight and ground based experiments, these materials were coated on thin (approx. 250A) silver films, and the electrical resistance of the silver was measured in situ to detect any penetration of atomic oxygen through the BN and Si3N4 materials. In the presence of atomic oxygen, silver oxidizes to form silver oxide, which has a much higher electrical resistance than pure silver. Permeation of atomic oxygen through BN, as indicated by an increase in the electrical resistance of the silver underneath, was observed in both the inflight and ground based experiments. In contrast, no permeation of atomic oxygen through Si3N4 was observed in either the inflight or ground based experiments. The ground based results show good qualitative correlation with the LEO flight results, indicating that ground based facilities such as the one at Los Alamos National Lab can reproduce space flight data from LEO.

  14. A comparison of ground-based and space flight data: Atomic oxygen reactions with boron nitride and silicon nitride

    NASA Technical Reports Server (NTRS)

    Cross, J. B.; Lan, E. H.; Smith, C. A.; Whatley, W. J.; Koontz, S. L.

    1990-01-01

    The effects of atomic oxygen on boron nitride (BN) and silicon nitride (Si3N4) have been studied in low Earth orbit (LEO) flight experiments and in a ground-based simulation facility at Los Alamos National Laboratory. Both the in-flight and ground-based experiments employed the materials coated over thin (approx 250 Angstrom) silver films whose electrical resistance was measured in situ to detect penetration of atomic oxygen through the BN and Si3N4 materials. In the presence of atomic oxygen, silver oxidizes to form silver oxide, which has a much higher electrical resistance than pure silver. Permeation of atomic oxygen through BN, as indicated by an increase in the electrical resistance of the silver underneath, was observed in both the in-flight and ground-based experiments. In contrast, no permeation of atomic oxygen through Si3N4 was observed in either the in-flight or ground-based experiments. The ground-based results show good qualitative correlation with the LEO flight results, thus validating the simulation fidelity of the ground-based facility in terms of reproducing LEO flight results.

  15. Design of Laccase-Metal Organic Framework-Based Bioelectrodes for Biocatalytic Oxygen Reduction Reaction.

    PubMed

    Patra, Snehangshu; Sene, Saad; Mousty, Christine; Serre, Christian; Chaussé, Annie; Legrand, Ludovic; Steunou, Nathalie

    2016-08-10

    Laccase in combination with 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) as a mediator is a well-known bioelectrocatalyst for the 4-electron oxygen reduction reactions (ORR). The present work deals with the first exploitation of mesoporous iron(III) trimesate-based metal organic frameworks (MOF) MIL-100(Fe) (MIL stands for materials from Institut Lavoisier) as a new and efficient immobilization matrix of laccase for the building up of biocathodes for ORR. First, the immobilization of ABTS in the pores of the MOF was studied by combining micro-Raman spectroscopy, X-ray powder diffraction (XRPD), and N2 porosimetry. The ABTS-MIL-100(Fe)-based modified electrode presents excellent properties in terms of charge transfer kinetics and ionic conductivity as well as a very stable and reproducible electrochemical response, showing that MIL-100(Fe) provides a suitable and stabilizing microenvironment for electroactive ABTS molecules. In a second step, laccase was further immobilized on the MIL-100(Fe)-ABTS matrix. The Lac-ABTS-MIL-100(Fe)-CIE bioelectrode presents a high electrocatalytic current density of oxygen reduction and a reproducible electrochemical response characterized by a high stability over a long period of time (3 weeks). These results constitute a significant advance in the field of laccase-based bioelectrocatalysts for ORR. According to our work, it appears that the high catalytic efficiency of Lac-ABTS-MIL-100(Fe) for ORR may result from a synergy of chemical and catalytic properties of MIL-100(Fe) and laccase. PMID:27447023

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

    SciTech Connect

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

    2004-05-10

    An oxybarometer based on vanadium valence and applicable to basaltic glasses covers eight orders of magnitude in oxygen fugacity. The determination of oxidation conditions for basaltic magmas derived by the melting of planetary mantles is critical to our understanding of the nature and evolution of planetary interiors. Yet, these determinations are compromised in terrestrial and especially extraterrestrial basalts by our analytical and computational methods for estimating oxygen fugacity (fO{sub 2}). For example, mineralogical barometers (1, 2) can be reduced in effectiveness by subsolidus re-equilibration of mineral assemblages, inversion of mineralogical data to melt characteristics, and deviations of the natural mineral compositions from ideal thermodynamic parameters. Likewise, techniques to estimate fO{sub 2} based on the valence state of Fe (i.e. Fe{sup 3+}/Fe{sup 2+}) are ineffective for materials that crystallized at or below the IW buffer, and only contain Fe{sup 2+} and Fe{sup 0} (3). For these reasons, we have developed an oxybarometer based on the valence state of vanadium in basaltic glasses. This oxybarometer has enormous potential because (1) V valence is measured in basaltic glasses that have been quenched at near liquidus temperatures, thereby recording magmatic fO{sub 2} conditions, and (2) V is a multivalent element, existing as V{sup 2+}, V{sup 3+}, V{sup 4+}, and V{sup 5+}, thus allowing for applicability over a range of redox conditions from the most reduced materials in the solar system, (e.g. calcium aluminum rich inclusions in chondritic meteorites [4]) to the most oxidized terrestrial magmas (this work).

  17. 2H,3H-Decafluoropentane-Based Nanodroplets: New Perspectives for Oxygen Delivery to Hypoxic Cutaneous Tissues

    PubMed Central

    Jose, Jithin; Khadjavi, Amina; Cavallo, Federica; Quaglino, Elena; Panariti, Alice; Rivolta, Ilaria; Benintende, Emilio; Varetto, Gianfranco; Argenziano, Monica; Troia, Adriano; Cavalli, Roberta; Guiot, Caterina

    2015-01-01

    Perfluoropentane (PFP)-based oxygen-loaded nanobubbles (OLNBs) were previously proposed as adjuvant therapeutic tools for pathologies of different etiology sharing hypoxia as a common feature, including cancer, infection, and autoimmunity. Here we introduce a new platform of oxygen nanocarriers, based on 2H,3H-decafluoropentane (DFP) as core fluorocarbon. These new nanocarriers have been named oxygen-loaded nanodroplets (OLNDs) since DFP is liquid at body temperature, unlike gaseous PFP. Dextran-shelled OLNDs, available either in liquid or gel formulations, display spherical morphology, ~600 nm diameters, anionic charge, good oxygen carrying capacity, and no toxic effects on human keratinocytes after cell internalization. In vitro OLNDs result more effective in releasing oxygen to hypoxic environments than former OLNBs, as demonstrated by analysis through oxymetry. In vivo, OLNDs effectively enhance oxy-hemoglobin levels, as emerged from investigation by photoacoustic imaging. Interestingly, ultrasound (US) treatment further improves transdermal oxygen release from OLNDs. Taken together, these data suggest that US-activated, DFP-based OLNDs might be innovative, suitable and cost-effective devices to topically treat hypoxia-associated pathologies of the cutaneous tissues. PMID:25781463

  18. 2H,3H-decafluoropentane-based nanodroplets: new perspectives for oxygen delivery to hypoxic cutaneous tissues.

    PubMed

    Prato, Mauro; Magnetto, Chiara; Jose, Jithin; Khadjavi, Amina; Cavallo, Federica; Quaglino, Elena; Panariti, Alice; Rivolta, Ilaria; Benintende, Emilio; Varetto, Gianfranco; Argenziano, Monica; Troia, Adriano; Cavalli, Roberta; Guiot, Caterina

    2015-01-01

    Perfluoropentane (PFP)-based oxygen-loaded nanobubbles (OLNBs) were previously proposed as adjuvant therapeutic tools for pathologies of different etiology sharing hypoxia as a common feature, including cancer, infection, and autoimmunity. Here we introduce a new platform of oxygen nanocarriers, based on 2H,3H-decafluoropentane (DFP) as core fluorocarbon. These new nanocarriers have been named oxygen-loaded nanodroplets (OLNDs) since DFP is liquid at body temperature, unlike gaseous PFP. Dextran-shelled OLNDs, available either in liquid or gel formulations, display spherical morphology, ~600 nm diameters, anionic charge, good oxygen carrying capacity, and no toxic effects on human keratinocytes after cell internalization. In vitro OLNDs result more effective in releasing oxygen to hypoxic environments than former OLNBs, as demonstrated by analysis through oxymetry. In vivo, OLNDs effectively enhance oxy-hemoglobin levels, as emerged from investigation by photoacoustic imaging. Interestingly, ultrasound (US) treatment further improves transdermal oxygen release from OLNDs. Taken together, these data suggest that US-activated, DFP-based OLNDs might be innovative, suitable and cost-effective devices to topically treat hypoxia-associated pathologies of the cutaneous tissues. PMID:25781463

  19. MRI-based methods for quantification of the cerebral metabolic rate of oxygen.

    PubMed

    Rodgers, Zachary B; Detre, John A; Wehrli, Felix W

    2016-07-01

    The brain depends almost entirely on oxidative metabolism to meet its significant energy requirements. As such, the cerebral metabolic rate of oxygen (CMRO2) represents a key measure of brain function. Quantification of CMRO2 has helped elucidate brain functional physiology and holds potential as a clinical tool for evaluating neurological disorders including stroke, brain tumors, Alzheimer's disease, and obstructive sleep apnea. In recent years, a variety of magnetic resonance imaging (MRI)-based CMRO2 quantification methods have emerged. Unlike positron emission tomography - the current "gold standard" for measurement and mapping of CMRO2 - MRI is non-invasive, relatively inexpensive, and ubiquitously available in modern medical centers. All MRI-based CMRO2 methods are based on modeling the effect of paramagnetic deoxyhemoglobin on the magnetic resonance signal. The various methods can be classified in terms of the MRI contrast mechanism used to quantify CMRO2: T2*, T2', T2, or magnetic susceptibility. This review article provides an overview of MRI-based CMRO2 quantification techniques. After a brief historical discussion motivating the need for improved CMRO2 methodology, current state-of-the-art MRI-based methods are critically appraised in terms of their respective tradeoffs between spatial resolution, temporal resolution, and robustness, all of critical importance given the spatially heterogeneous and temporally dynamic nature of brain energy requirements. PMID:27089912

  20. Sensitive hydrogen sensor based on selectively infiltrated photonic crystal fiber with Pt-loaded WO₃ coating.

    PubMed

    Wang, Ying; Wang, D N; Yang, Fan; Li, Zhi; Yang, Minghong

    2014-07-01

    A sensitive hydrogen sensing device based on a selectively infiltrated photonic crystal fiber (PCF) coated with Pt-loaded WO₃ is demonstrated. With Pt-loaded WO₃ coating acting as the catalytic layer, hydrogen undergoes an exothermic reaction with oxygen and releases heat when the device is exposed to gas mixtures of air and hydrogen, which induces local temperature change in the PCF and hence leads to the resonant wavelength shift of the proposed device. The maximum wavelength shift of 98.5 nm is obtained with a 10-mm-long infiltrated PCF for 4% (v/v) H₂ concentration, and a hydrogen sensitivity of 32.3 nm/% (v/v) H₂ is achieved within the range of 1%-4% (v/v) H₂ in air. PMID:24978759

  1. Voxel selection in FMRI data analysis based on sparse representation.

    PubMed

    Li, Yuanqing; Namburi, Praneeth; Yu, Zhuliang; Guan, Cuntai; Feng, Jianfeng; Gu, Zhenghui

    2009-10-01

    Multivariate pattern analysis approaches toward detection of brain regions from fMRI data have been gaining attention recently. In this study, we introduce an iterative sparse-representation-based algorithm for detection of voxels in functional MRI (fMRI) data with task relevant information. In each iteration of the algorithm, a linear programming problem is solved and a sparse weight vector is subsequently obtained. The final weight vector is the mean of those obtained in all iterations. The characteristics of our algorithm are as follows: 1) the weight vector (output) is sparse; 2) the magnitude of each entry of the weight vector represents the significance of its corresponding variable or feature in a classification or regression problem; and 3) due to the convergence of this algorithm, a stable weight vector is obtained. To demonstrate the validity of our algorithm and illustrate its application, we apply the algorithm to the Pittsburgh Brain Activity Interpretation Competition 2007 functional fMRI dataset for selecting the voxels, which are the most relevant to the tasks of the subjects. Based on this dataset, the aforementioned characteristics of our algorithm are analyzed, and a comparison between our method with the univariate general-linear-model-based statistical parametric mapping is performed. Using our method, a combination of voxels are selected based on the principle of effective/sparse representation of a task. Data analysis results in this paper show that this combination of voxels is suitable for decoding tasks and demonstrate the effectiveness of our method. PMID:19567340

  2. Highly active cobalt phosphate and borate based oxygen evolving catalysts operating in neutral and natural waters

    SciTech Connect

    Esswein, AJ; Surendranath, Y; Reece, SY; Nocera, DG

    2011-02-01

    A high surface area electrode is functionalized with cobalt-based oxygen evolving catalysts (Co-OEC = electrodeposited from pH 7 phosphate, Pi, pH 8.5 methylphosphonate, MePi, and pH 9.2 borate electrolyte, Bi). Co-OEC prepared from MePi and operated in Pi and Bi achieves a current density of 100 mA cm(-2) for water oxidation at 442 and 363 mV overpotential, respectively. The catalyst retains activity in near-neutral pH buffered electrolyte in natural waters such as those from the Charles River (Cambridge, MA) and seawater (Woods Hole, MA). The efficacy and ease of operation of anodes functionalized with Co-OEC at appreciable current density together with its ability to operate in near neutral pH buffered natural water sources bodes well for the translation of this catalyst to a viable renewable energy storage technology.

  3. Ground-based IR observation of oxygen isotope ratios in Venus's atmosphere

    NASA Astrophysics Data System (ADS)

    Iwagami, N.; Hashimoto, G. L.; Ohtsuki, S.; Takagi, S.; Robert, S.

    2015-08-01

    The oxygen isotope ratios 17O/16O and 18O/16O in Venus's atmosphere were measured simultaneously by ground-based IR spectroscopy. The CO2 absorption lines in the 2648 cm-1 (for 17O/18O) and 4582 cm-1 (for 18O/16O) regions were observed using the IRTF/CSHELL spectrometer. The deviations of the isotope fractions are found to be δ17O=+92±158‰ and δ18O=-42±85‰ as compared to the terrestrial standard (HITRAN 2012) where the uncertainties include both random and systematic errors. Such combination agrees with the Earth-Moon fractionation line within the errors. This is consistent to the fact that the proto-Venus matter was also well mixed with the proto-Earth-Moon matter.

  4. Dissolved oxygen prediction using a possibility theory based fuzzy neural network

    NASA Astrophysics Data System (ADS)

    Khan, Usman T.; Valeo, Caterina

    2016-06-01

    A new fuzzy neural network method to predict minimum dissolved oxygen (DO) concentration in a highly urbanised riverine environment (in Calgary, Canada) is proposed. The method uses abiotic factors (non-living, physical and chemical attributes) as inputs to the model, since the physical mechanisms governing DO in the river are largely unknown. A new two-step method to construct fuzzy numbers using observations is proposed. Then an existing fuzzy neural network is modified to account for fuzzy number inputs and also uses possibility theory based intervals to train the network. Results demonstrate that the method is particularly well suited to predicting low DO events in the Bow River. Model performance is compared with a fuzzy neural network with crisp inputs, as well as with a traditional neural network. Model output and a defuzzification technique are used to estimate the risk of low DO so that water resource managers can implement strategies to prevent the occurrence of low DO.

  5. DNA base damage by reactive oxygen species, oxidizing agents, and UV radiation.

    PubMed

    Cadet, Jean; Wagner, J Richard

    2013-02-01

    Emphasis has been placed in this article dedicated to DNA damage on recent aspects of the formation and measurement of oxidatively generated damage in cellular DNA in order to provide a comprehensive and updated survey. This includes single pyrimidine and purine base lesions, intrastrand cross-links, purine 5',8-cyclonucleosides, DNA-protein adducts and interstrand cross-links formed by the reactions of either the nucleobases or the 2-deoxyribose moiety with the hydroxyl radical, one-electron oxidants, singlet oxygen, and hypochlorous acid. In addition, recent information concerning the mechanisms of formation, individual measurement, and repair-rate assessment of bipyrimidine photoproducts in isolated cells and human skin upon exposure to UVB radiation, UVA photons, or solar simulated light is critically reviewed. PMID:23378590

  6. DNA Base Damage by Reactive Oxygen Species, Oxidizing Agents, and UV Radiation

    PubMed Central

    Cadet, Jean; Wagner, J. Richard

    2013-01-01

    Emphasis has been placed in this article dedicated to DNA damage on recent aspects of the formation and measurement of oxidatively generated damage in cellular DNA in order to provide a comprehensive and updated survey. This includes single pyrimidine and purine base lesions, intrastrand cross-links, purine 5′,8-cyclonucleosides, DNA–protein adducts and interstrand cross-links formed by the reactions of either the nucleobases or the 2-deoxyribose moiety with the hydroxyl radical, one-electron oxidants, singlet oxygen, and hypochlorous acid. In addition, recent information concerning the mechanisms of formation, individual measurement, and repair-rate assessment of bipyrimidine photoproducts in isolated cells and human skin upon exposure to UVB radiation, UVA photons, or solar simulated light is critically reviewed. PMID:23378590

  7. Dissolved oxygen prediction using a possibility-theory based fuzzy neural network

    NASA Astrophysics Data System (ADS)

    Khan, U. T.; Valeo, C.

    2015-11-01

    A new fuzzy neural network method to predict minimum dissolved oxygen (DO) concentration in a highly urbanised riverine environment (in Calgary, Canada) is proposed. The method uses abiotic (non-living, physical and chemical attributes) as inputs to the model, since the physical mechanisms governing DO in the river are largely unknown. A new two-step method to construct fuzzy numbers using observations is proposed. Then an existing fuzzy neural network is modified to account for fuzzy number inputs and also uses possibility-theory based intervals to train the network. Results demonstrate that the method is particularly well suited to predict low DO events in the Bow River. Model output and a defuzzification technique is used to estimate the risk of low DO so that water resource managers can implement strategies to prevent the occurrence of low DO.

  8. Understanding Iron-based catalysts with efficient Oxygen reduction activity from first-principles calculations

    NASA Astrophysics Data System (ADS)

    Hafiz, Hasnain; Barbiellini, B.; Jia, Q.; Tylus, U.; Strickland, K.; Bansil, A.; Mukerjee, S.

    2015-03-01

    Catalysts based on Fe/N/C clusters can support the oxygen-reduction reaction (ORR) without the use of expensive metals such as platinum. These systems can also prevent some poisonous species to block the active sites from the reactant. We have performed spin-polarized calculations on various Fe/N/C fragments using the Vienna Ab initio Simulation Package (VASP) code. Some results are compared to similar calculations obtained with the Gaussian code. We investigate the partial density of states (PDOS) of the 3d orbitals near the Fermi level and calculate the binding energies of several ligands. Correlations of the binding energies with the 3d electronic PDOS's are used to propose electronic descriptors of the ORR associated with the 3d states of Fe. We also suggest a structural model for the most active site with a ferrous ion (Fe2+) in the high spin state or the so-called Doublet 3 (D3).

  9. 42 CFR 414.226 - Oxygen and oxygen equipment.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 42 Public Health 3 2010-10-01 2010-10-01 false Oxygen and oxygen equipment. 414.226 Section 414... Equipment and Prosthetic and Orthotic Devices § 414.226 Oxygen and oxygen equipment. (a) Payment rules—(1) Oxygen equipment. Payment for rental of oxygen equipment is made based on a monthly fee schedule...

  10. 42 CFR 414.226 - Oxygen and oxygen equipment.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 42 Public Health 3 2011-10-01 2011-10-01 false Oxygen and oxygen equipment. 414.226 Section 414... Equipment and Prosthetic and Orthotic Devices § 414.226 Oxygen and oxygen equipment. (a) Payment rules—(1) Oxygen equipment. Payment for rental of oxygen equipment is made based on a monthly fee schedule...

  11. 42 CFR 414.226 - Oxygen and oxygen equipment.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 42 Public Health 3 2013-10-01 2013-10-01 false Oxygen and oxygen equipment. 414.226 Section 414... Durable Medical Equipment and Prosthetic and Orthotic Devices § 414.226 Oxygen and oxygen equipment. (a) Payment rules—(1) Oxygen equipment. Payment for rental of oxygen equipment is made based on a monthly...

  12. 42 CFR 414.226 - Oxygen and oxygen equipment.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 42 Public Health 3 2012-10-01 2012-10-01 false Oxygen and oxygen equipment. 414.226 Section 414... Durable Medical Equipment and Prosthetic and Orthotic Devices § 414.226 Oxygen and oxygen equipment. (a) Payment rules—(1) Oxygen equipment. Payment for rental of oxygen equipment is made based on a monthly...

  13. In Situ Observation of Active Oxygen Species in Fe-Containing Ni-Based Oxygen Evolution Catalysts: The Effect of pH on Electrochemical Activity.

    PubMed

    Trześniewski, Bartek J; Diaz-Morales, Oscar; Vermaas, David A; Longo, Alessandro; Bras, Wim; Koper, Marc T M; Smith, Wilson A

    2015-12-01

    Ni-based oxygen evolution catalysts (OECs) are cost-effective and very active materials that can be potentially used for efficient solar-to-fuel conversion process toward sustainable energy generation. We present a systematic spectroelectrochemical characterization of two Fe-containing Ni-based OECs, namely nickel borate (Ni(Fe)-B(i)) and nickel oxyhydroxide (Ni(Fe)OOH). Our Raman and X-ray absorption spectroscopy results show that both OECs are chemically similar, and that the borate anions do not play an apparent role in the catalytic process at pH 13. Furthermore, we show spectroscopic evidence for the generation of negatively charged sites in both OECs (NiOO(-)), which can be described as adsorbed "active oxygen". Our data conclusively links the OER activity of the Ni-based OECs with the generation of those sites on the surface of the OECs. The OER activity of both OECs is strongly pH dependent, which can be attributed to a deprotonation process of the Ni-based OECs, leading to the formation of the negatively charged surface sites that act as OER precursors. This work emphasizes the relevance of the electrolyte effect to obtain catalytically active phases in Ni-based OECs, in addition to the key role of the Fe impurities. This effect should be carefully considered in the development of Ni-based compounds meant to catalyze the OER at moderate pHs. Complementarily, UV-vis spectroscopy measurements show strong darkening of those catalysts in the catalytically active state. This coloration effect is directly related to the oxidation of nickel and can be an important factor limiting the efficiency of solar-driven devices utilizing Ni-based OECs. PMID:26544169

  14. Shape-based feature selection for microcalcification evaluation

    NASA Astrophysics Data System (ADS)

    Marti, Joan; Cufi, Xavier; Regincos, Jordi; Espanol, Josep; Pont, Josep; Barcelo, Carles

    1998-06-01

    This work focuses on the selection of a set of shape-based features in order to assist radiologists in differentiating between malignant and benignant clustered microcalcifications in mammograms. The results obtained allow the creation of a model for the evaluation of the benignant or malignant character of the microcalcifications in a mammogram, based exclusively on the following parameters: number of clusters, number of holes, area, Feret elongation, roughness and elongation. The performance of the classification scheme is close to the mean performance of three expert radiologists, which allows to consider the proposed method for assisting the diagnosis and encourages to continue the investigation in this field. Additionally, the work is based on an unpublished database formed by patients of the Regional Health Area of Girona, which in the future may contribute to increase the digital mammogram databases.

  15. Improved reset breakdown strength in a HfOx-based resistive memory by introducing RuOx oxygen diffusion barrier

    NASA Astrophysics Data System (ADS)

    Park, Jaesung; Woo, Jiyong; Prakash, Amit; Lee, Sangheon; Lim, Seokjae; Hwang, Hyunsang

    2016-05-01

    We investigated the reset breakdown phenomenon of HfOx-based resistive memory for reliable switching operation in a fully CMOS compatible stack. Through the understanding on the effect of electrode materials and device area, our findings show that observed failure is attributed to additional oxygen vacancies close to the electrode interface, where switching is occurred. Therefore, RuOx serving as an oxygen diffusion barrier was introduced to suppress the generation of unwanted oxygen vacancies by preventing out-diffusion of oxygen through the electrode. As a result, significantly enhanced breakdown strength in HfOx/RuOx stack is achieved and resulting in improved cycle endurance with larger on/off ratio.

  16. Effect of oxygen content and heat treatment on carbide precipitation behavior in PM Ni-base superalloys

    NASA Astrophysics Data System (ADS)

    Liu, Heng-san; Zhang, Lin; He, Xin-bo; Qu, Xuan-hui; Zhu, Hong-min; Zhang, Guo-qing

    2012-09-01

    The influence of oxygen content and heat treatment on the evolution of carbides in a powder metallurgy (PM) Ni-base superalloy was characterized. The results reveal that oxygen content has little influence on the precipitation of carbides inside the particles. However, under the consolidated state, stable Ti oxides on the particle surface act as nuclei for the precipitation of prior particle boundaries (PPB). Also, oxygen can diffuse internally along grain boundaries under compressive stress, which favors the precipitation of carbides inside the particles. Therefore, a higher amount of carbides will appear with more oxygen content in the case of consolidated alloys. It is also observed that PPB can be disrupted into discontinuous particles at 1200°C, but this carbide network is hard to be eliminated completely. The combined MC-M23C6 morphology approves the nucleation and growth mechanism of carbide evolution.

  17. Tuning oxygen vacancy photoluminescence in monoclinic Y2WO6 by selectively occupying yttrium sites using lanthanum.

    PubMed

    Ding, Bangfu; Han, Chao; Zheng, Lirong; Zhang, Junying; Wang, Rongming; Tang, Zilong

    2015-01-01

    The effect of isovalent lanthanum (La) doping on the monoclinic Y2WO6 photoluminescence was studied. Introducing the non-activated La(3+) into Y2WO6 brings new excitation bands from violet to visible regions and strong near-infrared emission, while the bands position and intensity depend on the doping concentration. It is interesting to find that doping La(3+) into Y2WO6 promotes the oxygen vacancy formation according to the first-principle calculation, Raman spectrum, and synchrotron radiation analysis. Through the Rietveld refinement and X-ray photoelectron spectroscopy results, La(3+) is found to mainly occupy the Y2 (2f) site in low-concentration doped samples. With increasing doping concentration, the La(3+) occupation number at the Y3 (4g) site increases faster than those at the Y1 (2e) and Y2 (2f) sites. When La(3+) occupies different Y sites, the localized energy states caused by the oxygen vacancy pair change their position in the forbidden band, inducing the variation of the excitation and emission bands. This research proposes a feasible method to tune the oxygen vacancy emission, eliminating the challenge of precisely controlling the calcination atmosphere. PMID:25821078

  18. Tuning oxygen vacancy photoluminescence in monoclinic Y2WO6 by selectively occupying yttrium sites using lanthanum

    PubMed Central

    Ding, Bangfu; Han, Chao; Zheng, Lirong; Zhang, Junying; Wang, Rongming; Tang, Zilong

    2015-01-01

    The effect of isovalent lanthanum (La) doping on the monoclinic Y2WO6 photoluminescence was studied. Introducing the non-activated La3+ into Y2WO6 brings new excitation bands from violet to visible regions and strong near-infrared emission, while the bands position and intensity depend on the doping concentration. It is interesting to find that doping La3+ into Y2WO6 promotes the oxygen vacancy formation according to the first-principle calculation, Raman spectrum, and synchrotron radiation analysis. Through the Rietveld refinement and X-ray photoelectron spectroscopy results, La3+ is found to mainly occupy the Y2 (2f) site in low-concentration doped samples. With increasing doping concentration, the La3+ occupation number at the Y3 (4g) site increases faster than those at the Y1 (2e) and Y2 (2f) sites. When La3+ occupies different Y sites, the localized energy states caused by the oxygen vacancy pair change their position in the forbidden band, inducing the variation of the excitation and emission bands. This research proposes a feasible method to tune the oxygen vacancy emission, eliminating the challenge of precisely controlling the calcination atmosphere. PMID:25821078

  19. Glucose microfluidic fuel cell based on silver bimetallic selective catalysts for on-chip applications

    NASA Astrophysics Data System (ADS)

    Cuevas-Muñiz, F. M.; Guerra-Balcázar, M.; Esquivel, J. P.; Sabaté, N.; Arriaga, L. G.; Ledesma-García, J.

    2012-10-01

    A glucose microfluidic fuel cell with outstanding performance at zero flow condition is presented. Polarization tests showed that bimetallic materials based in silver (AuAg/C as anode, PtAg/C as cathode) exhibit tolerance to byproducts and crossover effect. This allowed achieving one of the highest power densities reported for glucose fuel cells, up to a value of 630 μW cm-2 using two separated laminar flows of reactants. Furthermore, the tolerance to crossover effect caused by the selectivity of PtAg/C to oxygen reduction reaction in presence of glucose permitted using a single flow containing a mixture of glucose/oxygen, yielding a performance as high as 270 μW cm-2. Microfluidic fuel cell was further evaluated with a simulated body fluid solution that contained salts commonly present in the human blood plasma, reaching a power of 240 μW cm-2 at zero flow. These results envisage the incorporation of this fuel cell as a portable power source in Lab-on-a-Chip devices without the need of external pumps.

  20. Functionalized ZnO/ZnO2 n-N straddling heterostructure achieved by oxygen plasma bombardment for highly selective methane sensing.

    PubMed

    Ghosh, Sugato; Bhattacharyya, Raghunath; Saha, Hiranmay; Chaudhuri, Chirasree Roy; Mukherjee, Nillohit

    2015-11-01

    Metal oxide semiconductors have been extensively used as reducing gas sensors with major limitations regarding selectivity and operating temperature which is relatively high for most of the cases making the device unusable in some critical situations. Higher operating temperature is also associated with the higher power consumption, which goes against the miniaturization of the device. In order to resolve these problems, here we introduced a ZnO/ZnO2 straddling 'n-N' isotype heterostructure as a highly selective and sensitive methane sensor at moderately low operating temperature. ZnO-Zn(OH)2 precursor films were treated in oxygen plasma in a pulsed DC magnetron sputtering system. Morphological analyses by field emission scanning electron microscopy showed flake like growth of the grains with high surface roughness, whereas X-ray diffraction (XRD) showed polycrystalline nature of the films. Polycrystalline ZnO2 peaks were observed in the XRD pattern in addition to the existing ZnO, which indicates modification of the precursor to oxygen rich heterostructure of ZnO/ZnO2. This was further supported by the shifting of the O1s peak in the X-ray photoelectron spectroscopic analysis. Plasma treated ZnO/ZnO2 heterostructured films were found to show high selectivity towards methane (with respect to H2S and CO) and sensitivity (∼96%) at a comparatively low operating temperature. PMID:26435126

  1. Reversible Photodynamic Chloride-Selective Sensor Based on Photochromic Spiropyran

    PubMed Central

    2012-01-01

    We report here for the first time on a reversible photodynamic bulk optode sensor based on the photoswitching of a spiropyran derivative (Sp). The photoswitching of Sp induces a large basicity increase in the polymeric phase, which triggers the extraction of Cl– and H+. Cl– is stabilized by a lipophilic chloride-selective ionophore inside the membrane, while H+ binds with the open form of Sp and induces a spectral change, hence providing the sensor signal. The system was studied with spectroscopic and electrochemical methods. PMID:23036043

  2. Site-Selective Reactions with Peptide-Based Catalysts.

    PubMed

    Giuliano, Michael W; Miller, Scott J

    2016-01-01

    The problem of catalyst-controlled site-selectivity can potentially require a catalyst to overcome energetic barriers larger than those associated with enantioselective reactions. This challenge is a signature of substrates that present reactive sites that are not of equivalent reactivity. Herein we present a narrative of our laboratory's efforts to overcome this challenge using peptide-based catalysts. We highlight the interplay between understanding the inherent reactivity preferences of a given target molecule and the development of catalysts that can overcome intrinsic preferences embedded within a substrate. PMID:26307403

  3. Glass nanopore-based ion-selective electrodes.

    PubMed

    Shim, Jun Ho; Kim, Juneho; Cha, Geun Sig; Nam, Hakhyun; White, Ryan J; White, Henry S; Brown, Richard B

    2007-05-15

    Glass nanopore-based all-solid-state ion-selective electrodes (ISEs) have been developed to probe the distribution of ionic species at micro- or submicrometer-length scales, e.g., mapping of ion flux through micrometer-sized pores. The all-solid-state ISE was fabricated by sealing a conically etched platinum wire (d = 25-microm; radius of etched tip <10 nm) into a soda lime glass capillary. A Pt disk was exposed by gentle polishing the glass and the disk etched to form a conical pore of submicrometer dimension (radius < approximately 500 nm; depth < approximately 30 microm). Ag was electroplated on the Pt electrode in the pore and gently chloridated to obtain a AgCl/Ag layer within the pore. The AgCl/Ag layer-coated ISE was used as a highly selective Cl- probe in scanning electrochemical microscope experiments to map the ion flux through a micropore. The same ISE was also used as the base transducer of the neutral carrier-doped solvent polymeric membrane. The optimized polymer membranes used for the glass nanopore-based all-solid-state ISE require a higher ratio of plasticizer/polymer (9/1) compared to those for conventional ISE (2/1). An ISE based on deposition of an IrO2 layer at the base of a glass nanopore electrode exhibited a highly sensitive response (79.7 +/- 2.3 mV/pH) to variations in pH and could be used for approximately 3 weeks. PMID:17411008

  4. Long-chain bases, phosphatidic acid, MAPKs, and reactive oxygen species as nodal signal transducers in stress responses in Arabidopsis

    PubMed Central

    Saucedo-García, Mariana; Gavilanes-Ruíz, Marina; Arce-Cervantes, Oscar

    2015-01-01

    Due to their sessile condition, plants have developed sensitive, fast, and effective ways to contend with environmental changes. These mechanisms operate as informational wires conforming extensive and intricate networks that are connected in several points. The responses are designed as pathways orchestrated by molecules that are transducers of protein and non-protein nature. Their chemical nature imposes selective features such as specificity, formation rate, and generation site to the informational routes. Enzymes such as mitogen-activated protein kinases and non-protein, smaller molecules, such as long-chain bases, phosphatidic acid, and reactive oxygen species are recurrent transducers in the pleiotropic responses to biotic and abiotic stresses in plants. In this review, we considered these four components as nodal points of converging signaling pathways that start from very diverse stimuli and evoke very different responses. These pleiotropic effects may be explained by the potentiality that every one of these four mediators can be expressed from different sources, cellular location, temporality, or magnitude. Here, we review recent advances in our understanding of the interplay of these four specific signaling components in Arabidopsis cells, with an emphasis on drought, cold and pathogen stresses. PMID:25763001

  5. Oxygen sensing glucose biosensors based on alginate nano-micro systems

    NASA Astrophysics Data System (ADS)

    Chaudhari, Rashmi; Joshi, Abhijeet; Srivastava, Rohit

    2014-04-01

    Clinically glucose monitoring in diabetes management is done by point-measurement. However, an accurate, continuous glucose monitoring, and minimally invasive method is desirable. The research aims at developing fluorescence-mediated glucose detecting biosensors based on near-infrared radiation (NIR) oxygen sensitive dyes. Biosensors based on Glucose oxidase (GOx)-Rudpp loaded alginate microspheres (GRAM) and GOx-Platinum-octaethylporphyrin (PtOEP)-PLAalginate microsphere system (GPAM) were developed using air-driven atomization and characterized using optical microscopy, CLSM, fluorescence spectro-photometry etc. Biosensing studies were performed by exposing standard solutions of glucose. Uniform sized GRAM and GPAM with size 50+/-10μm were formed using atomization. CLSM imaging of biosensors suggests that Rudpp and PtOEP nanoparticles are uniformly distributed in alginate microspheres. The GRAM and GPAM showed a good regression constant of 0.974 and of 0.9648 over a range of 0-10 mM of glucose with a high sensitivity of 3.349%/mM (625 nm) and 2.38%/mM (645 nm) at 10 mM of glucose for GRAM and GPAM biosensor. GRAM and GPAM biosensors show great potential in development of an accurate and minimally invasive glucose biosensor. NIR dye based assays can aid sensitive, minimally-invasive and interference-free detection of glucose in diabetic patients.

  6. The role of facilitated diffusion in oxygen transport by cell-free hemoglobins: implications for the design of hemoglobin-based oxygen carriers.

    PubMed

    McCarthy, M R; Vandegriff, K D; Winslow, R M

    2001-08-30

    We compared rates of oxygen transport in an in vitro capillary system using red blood cells (RBCs) and cell-free hemoglobins. The axial PO(2) drop down the capillary was calculated using finite-element analysis. RBCs, unmodified hemoglobin (HbA(0)), cross-linked hemoglobin (alpha alpha-Hb) and hemoglobin conjugated to polyethylene-glycol (PEG-Hb) were evaluated. According to their fractional saturation curves, PEG-Hb showed the least desaturation down the capillary, which most closely matched the RBCs; HbA(0) and alpha alpha-Hb showed much greater desaturation. A lumped diffusion parameter, K*, was calculated based on the Fick diffusion equation with a term for facilitated diffusion. The overall rates of oxygen transfer are consistent with hemoglobin diffusion rates according to the Stokes-Einstein Law and with previously measured blood pressure responses in rats. This study provides a conceptual framework for the design of a 'blood substitute' based on mimicking O(2) transport by RBCs to prevent autoregulatory changes in blood flow and pressure. PMID:11527583

  7. The Unique Gas-Phase Chemistry of the [AuO](+) /CH4 Couple: Selective Oxygen-Atom Transfer to, Rather than Hydrogen-Atom Abstraction from, Methane.

    PubMed

    Zhou, Shaodong; Li, Jilai; Schlangen, Maria; Schwarz, Helmut

    2016-08-26

    The thermal reaction of [AuO](+) with methane has been explored using FT-ICR mass spectrometry complemented by high-level quantum chemical calculations. In contrast to the previously studied congener [CuO](+) , and to [AgO](+) , [AuO](+) reacts with CH4 exclusively via oxygen-atom transfer to form CH3 OH, and a novel mechanistic scenario for this selective oxidation process has been revealed. Also, the origin of the inertness of the [AgO](+) /CH4 couple has been addressed computationally. PMID:27390885

  8. From ketones to esters by a Cu-catalyzed highly selective C(CO)-C(alkyl) bond cleavage: aerobic oxidation and oxygenation with air.

    PubMed

    Huang, Xiaoqiang; Li, Xinyao; Zou, Miancheng; Song, Song; Tang, Conghui; Yuan, Yizhi; Jiao, Ning

    2014-10-22

    The Cu-catalyzed aerobic oxidative esterification of simple ketones via C-C bond cleavage has been developed. Varieties of common ketones, even inactive aryl long-chain alkyl ketones, are selectively converted into esters. The reaction tolerates a wide range of alcohols, including primary and secondary alcohols, chiral alcohols with retention of the configuration, electron-deficient phenols, as well as various natural alcohols. The usage of inexpensive copper catalyst, broad substrate scope, and neutral and open air conditions make this protocol very practical. (18)O labeling experiments reveal that oxygenation occurs during this transformation. Preliminary mechanism studies indicate that two novel pathways are mainly involved in this process. PMID:25251943

  9. Mediatorless sugar/oxygen enzymatic fuel cells based on gold nanoparticle-modified electrodes.

    PubMed

    Wang, Xiaoju; Falk, Magnus; Ortiz, Roberto; Matsumura, Hirotoshi; Bobacka, Johan; Ludwig, Roland; Bergelin, Mikael; Gorton, Lo; Shleev, Sergey

    2012-01-15

    We report on the fabrication and characterisation of a gold-nanoparticle (AuNP)-based mediatorless sugar/oxygen biofuel cell (BFC) operating in neutral sugar-containing buffers and human physiological fluids, such as blood and plasma. First, Corynascus thermophilus cellobiose dehydrogenase (CtCDH) and Myrothecium verrucaria bilirubin oxidase (MvBOx), used as anodic and cathodic bioelements, respectively, were immobilised on gold electrodes modified with 20 nm AuNPs. Detailed characterisation and optimisation of a new CDH/AuNP-based bioanode were performed and the following fundamental parameters were obtained: (i) the redox potential of the haem-containing centre of the enzyme was measured to be 75 mV vs. NHE, (ii) the surface coverage of CtCDH was found to be 0.65 pmol cm(-2) corresponding to a sub-monolayer coverage of the thiol-modified AuNPs by the enzyme, (iii) a turnover number for CtCDH immobilised on thiol-modified AuNPs was calculated to be ca. 0.5 s(-1), and (iv) the maximal current densities as high as 40 μA cm(-2) were registered in sugar-containing neutral buffers. Second, both biomodified electrodes, namely the CtCDH/AuNP-based bioanode and the MvBOx/AuNP-based biocathode, were combined into a functional BFC and the designed biodevices were carefully investigated. The following characteristics of the mediator-, separator- and membrane-less, miniature BFC were obtained: in phosphate buffer; an open-circuit voltage of 0.68 V, a maximum power density of 15 μW cm(-2) at a cell voltage of 0.52 V and in human blood; an open-circuit voltage of 0.65 V, a maximum power density of 3 μW cm(-2) at a cell voltage of 0.45 V, respectively. The estimated half-lives of the biodevices were found to be >12, <8, and <2 h in a sugar-containing buffer, human plasma, and blood, respectively. The basic characteristics of mediatorless sugar/oxygen BFCs were significantly improved compared with previously designed biodevices, because of the usage of three-dimensional Au

  10. Freestanding eggshell membrane-based electrodes for high-performance supercapacitors and oxygen evolution reaction

    NASA Astrophysics Data System (ADS)

    Geng, Jing; Wu, Hao; Al-Enizi, Abdullah M.; Elzatahry, Ahmed A.; Zheng, Gengfeng

    2015-08-01

    A type of freestanding, light-weight eggshell membrane-based electrode is demonstrated for supercapacitors and for oxygen evolution reaction (OER) catalysis. As a widely available daily waste, eggshell membranes have unique porous three-dimensional grid-like fibrous structures with relatively high surface area and abundant macropores, allowing for effective conjugation of carbon nanotubes and growth of NiCo2O4 nanowire arrays, an effective supercapacitor material and OER catalyst. The three-dimensional fibrous eggshell membrane frameworks with carbon nanotubes offer efficient pathways for charge transport, and the macropores between adjacent fibers are fully accessible for electrolytes and bubble evolution. As a supercapacitor, the eggshell membrane/carbon nanotube/NiCo2O4 electrode shows high specific capacitances at current densities from 1 to 20 A g-1, with excellent capacitance retention (>90%) at 10 A g-1 for over 10 000 cycles. When employed as an OER catalyst, this eggshell membrane-based electrode exhibits an OER onset potential of 1.53 V vs. the reversible hydrogen electrode (RHE), and a stable catalytic current density of 20 mA cm-2 at 1.65 V vs. the RHE.A type of freestanding, light-weight eggshell membrane-based electrode is demonstrated for supercapacitors and for oxygen evolution reaction (OER) catalysis. As a widely available daily waste, eggshell membranes have unique porous three-dimensional grid-like fibrous structures with relatively high surface area and abundant macropores, allowing for effective conjugation of carbon nanotubes and growth of NiCo2O4 nanowire arrays, an effective supercapacitor material and OER catalyst. The three-dimensional fibrous eggshell membrane frameworks with carbon nanotubes offer efficient pathways for charge transport, and the macropores between adjacent fibers are fully accessible for electrolytes and bubble evolution. As a supercapacitor, the eggshell membrane/carbon nanotube/NiCo2O4 electrode shows high specific

  11. Solid waste management of a chemical-looping combustion plant using Cu-based oxygen carriers.

    PubMed

    García-Labiano, Francisco; Gayán, Pilar; Adánez, Juan; De Diego, Luis F; Forero, Carmen R

    2007-08-15

    Waste management generated from a Chemical-Looping Combustion (CLC) plant using copper-based materials is analyzed by two ways: the recovery and recycling of the used material and the disposal of the waste. A copper recovery process coupled to the CLC plant is proposed to avoid the loss of active material generated by elutriation from the system. Solid residues obtained from a 10 kWth CLC prototype operated during 100 h with a CuO-Al2O3 oxygen carrier prepared by impregnation were used as raw material in the recovery process. Recovering efficiencies of approximately 80% were obtained in the process, where the final products were an eluate of Cu(NO3)2 and a solid. The eluate was used for preparation of new oxygen carriers by impregnation, which exhibited high reactivity for reduction and oxidation reactions as well as adequate physical and chemical properties to be used in a CLC plant. The proposed recovery process largely decreases the amount of natural resources (Cu and Al203) employed in a CLC power plant as well as the waste generated in the process. To determine the stability of the different solid streams during deposition in a landfill, these were characterized with respect to their leaching behavior according to the European Union normative. The solid residue finally obtained in the CLC plant coupled to the recovery process (composed by Al2O3 and CuAl2O4) can be classified as a stable nonreactive hazardous waste acceptable at landfills for nonhazardous wastes. PMID:17874801

  12. A Database Selection Expert System Based on Reference Librarian's Database Selection Strategy: A Usability and Empirical Evaluation.

    ERIC Educational Resources Information Center

    Ma, Wei

    2002-01-01

    Describes the development of a prototype Web-based database selection expert system at the University of Illinois at Urbana-Champaign that is based on reference librarians' database selection strategy which allows users to simultaneously search all available databases to identify those most relevant to their search using free-text keywords or…

  13. Reference View Selection in DIBR-Based Multiview Coding.

    PubMed

    Maugey, Thomas; Petrazzuoli, Giovanni; Frossard, Pascal; Cagnazzo, Marco; Pesquet-Popescu, Beatrice

    2016-04-01

    Augmented reality, interactive navigation in 3D scenes, multiview video, and other emerging multimedia applications require large sets of images, hence larger data volumes and increased resources compared with traditional video services. The significant increase in the number of images in multiview systems leads to new challenging problems in data representation and data transmission to provide high quality of experience on resource-constrained environments. In order to reduce the size of the data, different multiview video compression strategies have been proposed recently. Most of them use the concept of reference or key views that are used to estimate other images when there is high correlation in the data set. In such coding schemes, the two following questions become fundamental: 1) how many reference views have to be chosen for keeping a good reconstruction quality under coding cost constraints? And 2) where to place these key views in the multiview data set? As these questions are largely overlooked in the literature, we study the reference view selection problem and propose an algorithm for the optimal selection of reference views in multiview coding systems. Based on a novel metric that measures the similarity between the views, we formulate an optimization problem for the positioning of the reference views, such that both the distortion of the view reconstruction and the coding rate cost are minimized. We solve this new problem with a shortest path algorithm that determines both the optimal number of reference views and their positions in the image set. We experimentally validate our solution in a practical multiview distributed coding system and in the standardized 3D-HEVC multiview coding scheme. We show that considering the 3D scene geometry in the reference view, positioning problem brings significant rate-distortion improvements and outperforms the traditional coding strategy that simply selects key frames based on the distance between cameras. PMID

  14. Commercial facility site selection simulating based on MAS

    NASA Astrophysics Data System (ADS)

    Chao, Yi; Li, Qingquan; Zheng, Guizhou

    2008-10-01

    The location of commercial facility decides the benefit of the operator to a large degree. Existing location methods can express the static relationships between site selection result and location factors, but there still are some limites when express the dynamic and uncertain relationship between them. Hence, a dynamic, stochastic and forecastable location model should be built which can introduce the customer's behavior into the model and combine the macro pattern and micro spatial interaction. So the authors proposes Geosim-LM based on MAS. Geosim-LM has 3 kinds of agents, CustAgent, SiteAgent and GovAgent. They represent the customers, commercial fercilities and government. The land type, land price and traffic are the model environment. Then Geosim-LM is applied in the bank branches site evaluation and selection in Liwan district, Guangzhou. In existing bank branches site evaluation, there are 70% consistent in score grade between result of Geosim-LM after 200 round runing and actual rebust location. It proves the model is reliable and feasible. The conclusions can be get from the paper. MAS have advantages in location choice than existed methods. The result of Geosim-LM running can powerfully proves that building location model based on MAS is feasible.

  15. Selectively Encrypted Pull-Up Based Watermarking of Biometric data

    NASA Astrophysics Data System (ADS)

    Shinde, S. A.; Patel, Kushal S.

    2012-10-01

    Biometric authentication systems are becoming increasingly popular due to their potential usage in information security. However, digital biometric data (e.g. thumb impression) are themselves vulnerable to security attacks. There are various methods are available to secure biometric data. In biometric watermarking the data are embedded in an image container and are only retrieved if the secrete key is available. This container image is encrypted to have more security against the attack. As wireless devices are equipped with battery as their power supply, they have limited computational capabilities; therefore to reduce energy consumption we use the method of selective encryption of container image. The bit pull-up-based biometric watermarking scheme is based on amplitude modulation and bit priority which reduces the retrieval error rate to great extent. By using selective Encryption mechanism we expect more efficiency in time at the time of encryption as well as decryption. Significant reduction in error rate is expected to be achieved by the bit pull-up method.

  16. Optically based quantification of absolute cerebral metabolic rate of oxygen (CMRO2) with high spatial resolution in rodents

    NASA Astrophysics Data System (ADS)

    Yaseen, Mohammad A.; Srinivasan, Vivek J.; Sakadžić, Sava; Vinogradov, Sergei A.; Boas, David A.

    2010-02-01

    Measuring oxygen delivery in brain tissue is important for identifying the pathophysiological changes associated with brain injury and various diseases such as cancer, stroke, and Alzheimer's disease. We have developed a multi-modal imaging system for minimally invasive measurement of cerebral oxygenation and blood flow in small animals with high spatial resolution. The system allows for simultaneous measurement of blood flow using Fourier-domain optical coherence tomography, and oxygen partial pressure (pO2) using either confocal or multiphoton phosphorescence lifetime imaging with exogenous porphyrin-based dyes sensitive to dissolved oxygen. Here we present the changes in pO2 and blood flow in superficial cortical vessels of Sprague Dawley rats in response to conditions such as hypoxia, hyperoxia, and functional stimulation. pO2 measurements display considerable heterogeneity over distances that cannot be resolved with more widely used oxygen-monitoring techniques such as BOLD-fMRI. Large increases in blood flow are observed in response to functional stimulation and hypoxia. Our system allows for quantification of cerebral metabolic rate of oxygen (CMRO2) with high spatial resolution, providing a better understanding of metabolic dynamics during functional stimulation and under various neuropathologies. Ultimately, better insight into the underlying mechanisms of neuropathologies will facilitate the development of improved therapeutic strategies to minimize damage to brain tissue.

  17. Electro-catalytic activity of Ni–Co-based catalysts for oxygen evolution reaction

    SciTech Connect

    Ju, Hua; Li, Zhihu; Xu, Yanhui

    2015-04-15

    Graphical abstract: The electro-catalytic activity of different electro-catalysts with a porous electrode structure was compared considering the real electrode area that was evaluated by cyclic measurement. - Highlights: • Ni–Co-based electro-catalysts for OER have been studied and compared. • The real electrode area is calculated and used for assessing the electro-catalysts. • Exchange current and reaction rate constant are estimated. • Ni is more useful for OER reaction than Co. - Abstract: In the present work, Ni–Co-based electrocatalysts (Ni/Co = 0:6, 1:5, 2:4, 3:3, 4:2, 5:1 and 6:0) have been studied for oxygen evolution reaction. The phase structure has been analyzed by X-ray diffraction technique. Based on the XRD and SEM results, it is believed that the synthesized products are poorly crystallized. To exclude the disturbance of electrode preparation technology on the evaluation of electro-catalytic activity, the real electrode surface area is calculated based on the cyclic voltammetry data, assumed that the specific surface capacitance is 60 μF cm{sup −2} for metal oxide electrode. The real electrode area data are used to calculate the current density. The reaction rate constant of OER at different electrodes is also estimated based on basic reaction kinetic equations. It is found that the exchange current is 0.05–0.47 mA cm{sup −2} (the real surface area), and the reaction rate constant has an order of magnitude of 10{sup −7}–10{sup −6} cm s{sup −1}. The influence of the electrode potential on OER rate has been also studied by electrochemical impedance spectroscopy (EIS) technique. Our investigation has shown that the nickel element has more contribution than the cobalt; the nickel oxide has the best electro-catalytic activity toward OER.

  18. Distant protonated pyridine groups in water-soluble iron porphyrin electrocatalysts promote selective oxygen reduction to water

    SciTech Connect

    Matson, Benjamin D.; Carver, Colin T.; Von Ruden, Amber L.; Yang, Jenny Y.; Raugei, Simone; Mayer, James M.

    2012-11-08

    Fe(III)-meso-tetra(pyridyl)porphines are selective electrocatalysts for the reduction of dioxygen to water in aqueous acidic solution. The 2-pyridyl derivatives, both the triflate and chloride salts, are more selective than the isomeric 4-pyridyl complexes. The improved selectivity of is ascribed to the inward-pointing pyridinium groups acting as intramolecular proton relays. This research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the US Department of Energy, Office of Science. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

  19. Quantum-chemical study of the effect of oxygen on the formation of active sites of silver clusters during the selective adsorption of hydrocarbons

    NASA Astrophysics Data System (ADS)

    Lanin, S. N.; Polynskaya, Yu. G.; Pichugina, D. A.; Nguen, V.; Beletskaya, A. V.; Kuz'menko, N. E.; Shestakov, A. F.

    2013-09-01

    Density functional theory (PBE with a modified Dirac-Coulomb-Breit Hamiltonian) is used to simulate the adsorption of hydrocarbons (C2H2, C2H4, C2H6) on the surface of a sorbent containing Ag0, Agδ+, and AgO sites. The dynamics of change in the structural characteristics of Ag n ( n ≤ 10) is analyzed and the adsorption of oxygen on Ag8 and Ag10 is studied to select the adsorption site model. Studying the interaction of hydrocarbons with Ag8, Ag10, Ag{10/+}, Ag10O, and Ag10O2 clusters reveals that the presence of oxygen leads to an increase in the activation of unsaturated hydrocarbons, and the adsorption energy of C2H2 increases tenfold. It is found that the role of adsorbed oxygen is not only to form adsorption sites of hydrocarbons (Agδ+) but also to bind C2H2 and C2H4 directly to the sorbent's surface.

  20. Method of assessing blood oxygenation in microcirculation vessels based on Doppler approach

    NASA Astrophysics Data System (ADS)

    Sokolov, Vladimir G.; Korsi, Larissa V.; Egorov, Sergei Y.

    2001-06-01

    Combination of laser Doppler flowmetry and pulse oximetry methods allows for the direct assessment of oxygen supply to tissues at the microcirculatory level, namely, in that part of the vascular network where the transcapillary exchange takes place that is responsible for saturating tissues with oxygen. The microcirculation system comprises arterial and venous microvascular parts that differ in blood flow velocities. Frequency separation of the photodetector signal components related to different velocity ranges makes possible to distinguish the hemodynamic processes in these two parts of the microvascular system. Moreover, numerous studies of collective oscillatory processes in hemodynamics reveal that cardio-oscillations are more pronounced in arterioles, whereas venous hemodynamics is mostly influenced by the breath rhythm. Taking account of the above phenomena allows developing a signal-filtration system for separate characterization of blood-oxygenation states in arterial and venous blood flows. Light absorbance in the skin depends on both light wavelength and blood-oxygenation level. Processing the signals obtained with a two-channel dual-wavelength (630 and 1115 nm) laser Doppler flowmeter provides information about blood oxygenation levels at the entrance and exit of the microvascular system and allows assessing the specific levels of oxygenation levels at the entrance and exit of the microvascular system and allows assessing the specific levels of oxygen consumption in tissues. In particular, this approach allows revealing pathogenic processes resulting from hyper- and hypo-oxygenation in tissues. For instance, rapidly growing malignant tumors are characterized by intensive metabolism, rapid formation of capillaries, and active transcapillary oxygen exchange that results in higher level of oxygen diffusion into tissue, while the level of oxygen is lowered in the microvascular veins.

  1. Thermodynamic laws of the oxygen solubility in liquid metals (Ni, Co, Fe, Mn, Cr) and the formation of oxygen-containing solutions in the alloys based on them

    NASA Astrophysics Data System (ADS)

    Paderin, S. N.; Shil'nikov, E. V.

    2015-12-01

    The solubility of oxygen in liquid Ni, Co, Fe, Mn, and Cr metals (Group IV in the periodic table) has been found for the first time. Linear dependences of the oxygen solubility on the standard Gibbs energy for the oxidation reaction of a liquid metal with gaseous oxygen are found. The revealed function of oxygen solubility is of scientific importance and allows one to develop a theory of oxygen solutions in liquid metals and liquid multicomponent metallic compositions and to calculate the energies of mixing of liquid metals with oxygen from Δ G MO ° for metal oxidation reactions with allowance for pseudoregular-solution model equations. Using the energies of mixing and metal compositions, we calculated the equilibrium oxygen concentrations in a metal molten pool at the end of oxidation stage of melting 08Kh18N10T steel in an arc furnace. This fact indicates practical importance of the found function of the oxygen solubility in metals.

  2. High performance robust F-doped tin oxide based oxygen evolution electro-catalysts for PEM based water electrolysis

    SciTech Connect

    Datta, Moni Kanchan; Kadakia, Karan; Velikokhatnyi, Oleg I; Jampani, Prashanth H; Chung, Sung Jae; Poston, James A; Manivannan, Ayyakkannu; Kumta, Prashant N

    2013-01-01

    Identification and development of non-noble metal based electro-catalysts or electro-catalysts comprising compositions with significantly reduced amounts of expensive noble metal contents (e.g. IrO{sub 2}, Pt) with comparable electrochemical performance to the standard noble metal/metal oxide for proton exchange membrane (PEM) based water electrolysis would signify a major breakthrough in hydrogen generation via water electrolysis. Development of such systems would lead to two primary outcomes: first, a reduction in the overall capital costs of PEM based water electrolyzers, and second, attainment of the targeted hydrogen production costs (<$3.00/gge delivered by 2015) comparable to conventional liquid fuels. In line with these goals, by exploiting a two-pronged theoretical first principles and experimental approach herein, we demonstrate for the very first time a solid solution of SnO{sub 2}:10 wt% F containing only 20 at.% IrO{sub 2} [e.g. (Sn{sub 0.80}Ir{sub 0.20})O{sub 2}:10F] displaying remarkably similar electrochemical activity and comparable or even much improved electrochemical durability compared to pure IrO{sub 2}, the accepted gold standard in oxygen evolution electro-catalysts for PEM based water electrolysis. We present the results of these studies.

  3. Freestanding eggshell membrane-based electrodes for high-performance supercapacitors and oxygen evolution reaction.

    PubMed

    Geng, Jing; Wu, Hao; Al-Enizi, Abdullah M; Elzatahry, Ahmed A; Zheng, Gengfeng

    2015-09-14

    A type of freestanding, light-weight eggshell membrane-based electrode is demonstrated for supercapacitors and for oxygen evolution reaction (OER) catalysis. As a widely available daily waste, eggshell membranes have unique porous three-dimensional grid-like fibrous structures with relatively high surface area and abundant macropores, allowing for effective conjugation of carbon nanotubes and growth of NiCo2O4 nanowire arrays, an effective supercapacitor material and OER catalyst. The three-dimensional fibrous eggshell membrane frameworks with carbon nanotubes offer efficient pathways for charge transport, and the macropores between adjacent fibers are fully accessible for electrolytes and bubble evolution. As a supercapacitor, the eggshell membrane/carbon nanotube/NiCo2O4 electrode shows high specific capacitances at current densities from 1 to 20 A g(-1), with excellent capacitance retention (>90%) at 10 A g(-1) for over 10,000 cycles. When employed as an OER catalyst, this eggshell membrane-based electrode exhibits an OER onset potential of 1.53 V vs. the reversible hydrogen electrode (RHE), and a stable catalytic current density of 20 mA cm(-2) at 1.65 V vs. the RHE. PMID:26247312

  4. HEMORHEOLOGICAL IMPLICATIONS OF PERFLUOROCARBON BASED OXYGEN CARRIER INTERACTION WITH COLLOID PLASMA EXPANDERS AND BLOOD

    PubMed Central

    Vásquez, Diana M.; Ortiz, Daniel; Alvarez, Oscar A.; Briceño, Juan C.; Cabrales, Pedro

    2013-01-01

    Perfluorocarbon (PFC) emulsion based oxygen carriers lack colloid osmotic pressure (COP) and must be administered with colloid-based plasma expanders (PEs). Although PFC emulsions have been widely studied, there is limited information about PFC emulsion interaction with PEs and blood. Their interaction forms aggregates due to electrostatic and rheological phenomena, and change blood rheology and blood flow. This study analyzes the effects of the interaction between PFC emulsions with blood in the presence of clinically-used PEs. The rheological behavior of the mixtures was analyzed in parallel with in vivo analysis of blood flow in microvessels using intravital microscopy when administered in a clinically relevant scenario. The interaction between the PFC emulsion and PE with blood produced PFC droplets and red blood cell (RBCs) aggregation, and increased blood viscosity. The PFC droplets formed aggregates when mixed with PEs containing electrolytes, and the aggregation increased with the electrolyte concentration. Mixtures of PFC with PEs that produced PFC aggregates also induced RCBs aggregation when mixed with blood, increasing blood viscosity at low shear rates. The more viscous suspension at low shear rates produced a blunted blood flow velocity profile in vivo relative to non-aggregating mixtures of PFC and PEs. For the PEs evaluated, albumin produced minimal to undetectable aggregation. PFC and PEs interaction with blood can affect sections of the microcirculation with low shear rate (e.g. arterioles, venules, and pulmonary circulation) because aggregates could cause capillary occlusion, decrease perfusion, pulmonary emboli, or focal ischemia. PMID:23606592

  5. Graphene-based transition metal oxide nanocomposites for the oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Sun, Meng; Liu, Huijuan; Liu, Yang; Qu, Jiuhui; Li, Jinghong

    2015-01-01

    The development of low cost, durable and efficient nanocatalysts to substitute expensive and rare noble metals (e.g. Pt, Au and Pd) in overcoming the sluggish kinetic process of the oxygen reduction reaction (ORR) is essential to satisfy the demand for sustainable energy conversion and storage in the future. Graphene based transition metal oxide nanocomposites have extensively been proven to be a type of promising highly efficient and economic nanocatalyst for optimizing the ORR to solve the world-wide energy crisis. Synthesized nanocomposites exhibit synergetic advantages and avoid the respective disadvantages. In this feature article, we concentrate on the recent leading works of different categories of introduced transition metal oxides on graphene: from the commonly-used classes (FeOx, MnOx, and CoOx) to some rare and heat-studied issues (TiOx, NiCoOx and Co-MnOx). Moreover, the morphologies of the supported oxides on graphene with various dimensional nanostructures, such as one dimensional nanocrystals, two dimensional nanosheets/nanoplates and some special multidimensional frameworks are further reviewed. The strategies used to synthesize and characterize these well-designed nanocomposites and their superior properties for the ORR compared to the traditional catalysts are carefully summarized. This work aims to highlight the meaning of the multiphase establishment of graphene-based transition metal oxide nanocomposites and its structural-dependent ORR performance and mechanisms.

  6. Carbon Cathodes in Rechargeable Lithium-Oxygen Batteries Based on Double-Lithium-Salt Electrolytes.

    PubMed

    Yoo, Eunjoo; Zhou, Haoshen

    2016-06-01

    The use of carbon materials as air electrodes in lithium-oxygen (Li-O2 ) batteries is known to be advantageous owing to their good conductivity and because they offer sites suitable for the reversible electrode reactions. However, the exact influence of carbon materials on the electrochemical performance of Li-O2 batteries is not clear. In this study the electrochemical performance of four different types of carbon materials (multiwalled carbon nanotubes (MWCNTs), CMK-3, graphene nanosheets (GNSs), and Ketjen Black (KB)) as air electrodes is examined. We find that a Li-O2 cell based on an electrode of multiwalled carbon nanotubes (MWCNTs) demonstrates good rate performance and cycle stability, when using LiNO3 -LiTFSI/DMSO as electrolyte. Li-O2 cells based on such MWCNT electrodes, with a cut-off capacity of 1000 mAh g(-1) at 500 mA g(-1) , can undergo around 90 cycles without obvious losses of capacity. Even when the discharge depth is increased to 2000 mA h g(-1) , stable cycling is maintained for 45 cycles at a charge potential below 4.0 V. PMID:27120298

  7. Graphene-based transition metal oxide nanocomposites for the oxygen reduction reaction.

    PubMed

    Sun, Meng; Liu, Huijuan; Liu, Yang; Qu, Jiuhui; Li, Jinghong

    2015-01-28

    The development of low cost, durable and efficient nanocatalysts to substitute expensive and rare noble metals (e.g. Pt, Au and Pd) in overcoming the sluggish kinetic process of the oxygen reduction reaction (ORR) is essential to satisfy the demand for sustainable energy conversion and storage in the future. Graphene based transition metal oxide nanocomposites have extensively been proven to be a type of promising highly efficient and economic nanocatalyst for optimizing the ORR to solve the world-wide energy crisis. Synthesized nanocomposites exhibit synergetic advantages and avoid the respective disadvantages. In this feature article, we concentrate on the recent leading works of different categories of introduced transition metal oxides on graphene: from the commonly-used classes (FeOx, MnOx, and CoOx) to some rare and heat-studied issues (TiOx, NiCoOx and Co-MnOx). Moreover, the morphologies of the supported oxides on graphene with various dimensional nanostructures, such as one dimensional nanocrystals, two dimensional nanosheets/nanoplates and some special multidimensional frameworks are further reviewed. The strategies used to synthesize and characterize these well-designed nanocomposites and their superior properties for the ORR compared to the traditional catalysts are carefully summarized. This work aims to highlight the meaning of the multiphase establishment of graphene-based transition metal oxide nanocomposites and its structural-dependent ORR performance and mechanisms. PMID:25502117

  8. Metallic filament formation by aligned oxygen vacancies in ZnO-based resistive switches

    SciTech Connect

    Gu, Tingkun

    2014-05-28

    The electronic structure of ZnO with defects of oxygen vacancies were investigated by using first-principles methods. Some structure models were constructed in order to investigate the effects of the distribution of oxygen vacancies on the electronic properties of ZnO. By analyzing the calculated results, we found that only the aligned oxygen vacancies can form the conducting channel in ZnO, and the transformation of the oxygen vacancy from charged state to neutral state is consistent with the energetics rule of the forming aligned oxygen vacancies. As for the heterojunction of Pt/ZnO/Pt, the oxygen vacancies near the interface of Pt/ZnO depress the local Schottky barrier effectively, and the aligned oxygen vacancies in ZnO form a conducting filament connecting two Pt electrodes. The metallic filament formation in Pt/ZnO/Pt resistive switching cells should be closely related to the carrier injection from Pt electrode into ZnO and the arrangement of oxygen vacancies in ZnO slab.

  9. Metallic filament formation by aligned oxygen vacancies in ZnO-based resistive switches

    NASA Astrophysics Data System (ADS)

    Gu, Tingkun

    2014-05-01

    The electronic structure of ZnO with defects of oxygen vacancies were investigated by using first-principles methods. Some structure models were constructed in order to investigate the effects of the distribution of oxygen vacancies on the electronic properties of ZnO. By analyzing the calculated results, we found that only the aligned oxygen vacancies can form the conducting channel in ZnO, and the transformation of the oxygen vacancy from charged state to neutral state is consistent with the energetics rule of the forming aligned oxygen vacancies. As for the heterojunction of Pt/ZnO/Pt, the oxygen vacancies near the interface of Pt/ZnO depress the local Schottky barrier effectively, and the aligned oxygen vacancies in ZnO form a conducting filament connecting two Pt electrodes. The metallic filament formation in Pt/ZnO/Pt resistive switching cells should be closely related to the carrier injection from Pt electrode into ZnO and the arrangement of oxygen vacancies in ZnO slab.

  10. Comparison of pulse sequences for R1-based electron paramagnetic resonance oxygen imaging.

    PubMed

    Epel, Boris; Halpern, Howard J

    2015-05-01

    Electron paramagnetic resonance (EPR) spin-lattice relaxation (SLR) oxygen imaging has proven to be an indispensable tool for assessing oxygen partial pressure in live animals. EPR oxygen images show remarkable oxygen accuracy when combined with high precision and spatial resolution. Developing more effective means for obtaining SLR rates is of great practical, biological and medical importance. In this work we compared different pulse EPR imaging protocols and pulse sequences to establish advantages and areas of applicability for each method. Tests were performed using phantoms containing spin probes with oxygen concentrations relevant to in vivo oxymetry. We have found that for small animal size objects the inversion recovery sequence combined with the filtered backprojection reconstruction method delivers the best accuracy and precision. For large animals, in which large radio frequency energy deposition might be critical, free induction decay and three pulse stimulated echo sequences might find better practical usage. PMID:25828242

  11. Comparison of pulse sequences for R1-based electron paramagnetic resonance oxygen imaging

    NASA Astrophysics Data System (ADS)

    Epel, Boris; Halpern, Howard J.

    2015-05-01

    Electron paramagnetic resonance (EPR) spin-lattice relaxation (SLR) oxygen imaging has proven to be an indispensable tool for assessing oxygen partial pressure in live animals. EPR oxygen images show remarkable oxygen accuracy when combined with high precision and spatial resolution. Developing more effective means for obtaining SLR rates is of great practical, biological and medical importance. In this work we compared different pulse EPR imaging protocols and pulse sequences to establish advantages and areas of applicability for each method. Tests were performed using phantoms containing spin probes with oxygen concentrations relevant to in vivo oxymetry. We have found that for small animal size objects the inversion recovery sequence combined with the filtered backprojection reconstruction method delivers the best accuracy and precision. For large animals, in which large radio frequency energy deposition might be critical, free induction decay and three pulse stimulated echo sequences might find better practical usage.

  12. Comparison of Pulse Sequences for R1–based Electron Paramagnetic Resonance Oxygen Imaging

    PubMed Central

    Epel, Boris; Halpern, Howard J.

    2015-01-01

    Electron paramagnetic resonance (EPR) spin-lattice relaxation (SLR) oxygen imaging has proven to be an indispensable tool for assessing oxygen partial pressure in live animals. EPR oxygen images show remarkable oxygen accuracy when combined with high precision and spatial resolution. Developing more effective means for obtaining SLR rates is of great practical, biological and medical importance. In this work we compared different pulse EPR imaging protocols and pulse sequences to establish advantages and areas of applicability for each method. Tests were performed using phantoms containing spin probes with oxygen concentrations relevant to in vivo oxymetry. We have found that for small animal size objects the inversion recovery sequence combined with the filtered backprojection reconstruction method delivers the best accuracy and precision. For large animals, in which large radio frequency energy deposition might be critical, free induction decay and three pulse stimulated echo sequences might find better practical usage. PMID:25828242

  13. Conversion of a heme-based oxygen sensor to a heme oxygenase by hydrogen sulfide: effects of mutations in the heme distal side of a heme-based oxygen sensor phosphodiesterase (Ec DOS).

    PubMed

    Du, Yongming; Liu, Gefei; Yan, Yinxia; Huang, Dongyang; Luo, Wenhong; Martinkova, Marketa; Man, Petr; Shimizu, Toru

    2013-10-01

    The heme-based oxygen-sensor phosphodiesterase from Escherichia coli (Ec DOS), is composed of an N-terminal heme-bound oxygen sensing domain and a C-terminal catalytic domain. Oxygen (O2) binding to the heme Fe(II) complex in Ec DOS substantially enhances catalysis. Addition of hydrogen sulfide (H2S) to the heme Fe(III) complex in Ec DOS also remarkably stimulates catalysis in part due to the heme Fe(III)-SH and heme Fe(II)-O2 complexes formed by H2S. In this study, we examined the roles of the heme distal amino acids, M95 (the axial ligand of the heme Fe(II) complex) and R97 (the O2 binding site in the heme Fe(II)-O2 complex) of the isolated heme-binding domain of Ec DOS (Ec DOS-PAS) in the binding of H2S under aerobic conditions. Interestingly, R97A and R97I mutant proteins formed an oxygen-incorporated modified heme, verdoheme, following addition of H2S combined with H2O2 generated by the reactions. Time-dependent mass spectroscopic data corroborated the findings. In contrast, H2S did not interact with the heme Fe(III) complex of M95H and R97E mutants. Thus, M95 and/or R97 on the heme distal side in Ec DOS-PAS significantly contribute to the interaction of H2S with the Fe(III) heme complex and also to the modification of the heme Fe(III) complex with reactive oxygen species. Importantly, mutations of the O2 binding site of the heme protein converted its function from oxygen sensor to that of a heme oxygenase. This study establishes the novel role of H2S in modifying the heme iron complex to form verdoheme with the aid of reactive oxygen species. PMID:23736976

  14. Release time of residual oxygen after dental bleaching with 35% hydrogen peroxide: effect of a catalase-based neutralizing agent.

    PubMed

    Guasso, Bárbara; Salomone, Paloma; Nascimento, Paulo Cícero; Pozzobon, Roselaine Terezinha

    2016-01-01

    This article assessed the effect of a catalase-based agent on residual oxygen (O2) release from teeth exposed to 35% hydrogen peroxide (H2O2). The use of the catalase-based neutralizer agent for 2-3 minutes was able to release residual O2 5 days after exposure to a 35% H2O2-based bleaching gel. PMID:27148658

  15. A first-principle investigation of the oxygen defects in Si3N4-based charge trapping memories

    NASA Astrophysics Data System (ADS)

    Jing, Luo; Jinlong, Lu; Hongpeng, Zhao; Yuehua, Dai; Qi, Liu; Jin, Yang; Xianwei, Jiang; Huifang, Xu

    2014-01-01

    Based on first principle calculations, a comprehensive study of substitutional oxygen defects in hexagonal silicon nitride (β-Si3N4) has been carried out. Firstly, it is found that substitutional oxygen is most likely to form clusters at three sites in Si3N4 due to the intense attractive interaction between oxygen defects. Then, by using three analytical tools (trap energy, modified Bader analysis and charge density difference), we discuss the trap abilities of the three clusters. The result shows that each kind of cluster at the three specific sites presents very different abilities to trap charge carriers (electrons or holes): two of the three clusters can trap both kinds of charge carriers, confirming their amphoteric property; While the last remaining one is only able to trap hole carriers. Moreover, our studies reveal that the three clusters differ from each other in terms of endurance during the program/erase progress. Taking full account of capturing properties for the three oxygen clusters, including trap ability and endurance, we deem holes rather than electrons to be optimal to act as operational charge carriers for the oxygen defects in Si3N4-based charge trapping memories.

  16. Experiments on chemical looping combustion of coal with a NiO based oxygen carrier

    SciTech Connect

    Shen, Laihong; Wu, Jiahua; Xiao, Jun

    2009-03-15

    A chemical looping combustion process for coal using interconnected fluidized beds with inherent separation of CO{sub 2} is proposed in this paper. The configuration comprises a high velocity fluidized bed as an air reactor, a cyclone, and a spout-fluid bed as a fuel reactor. The high velocity fluidized bed is directly connected to the spout-fluid bed through the cyclone. Gas composition of both fuel reactor and air reactor, carbon content of fly ash in the fuel reactor, carbon conversion efficiency and CO{sub 2} capture efficiency were investigated experimentally. The results showed that coal gasification was the main factor which controlled the contents of CO and CH{sub 4} concentrations in the flue gas of the fuel reactor, carbon conversion efficiency in the process of chemical looping combustion of coal with NiO-based oxygen carrier in the interconnected fluidized beds. Carbon conversion efficiency reached only 92.8% even when the fuel reactor temperature was high up to 970 C. There was an inherent carbon loss in the process of chemical looping combustion of coal in the interconnected fluidized beds. The inherent carbon loss was due to an easy elutriation of fine char particles from the freeboard of the spout-fluid bed, which was inevitable in this kind of fluidized bed reactor. Further improvement of carbon conversion efficiency could be achieved by means of a circulation of fine particles elutriation into the spout-fluid bed or the high velocity fluidized bed. CO{sub 2} capture efficiency reached to its equilibrium of 80% at the fuel reactor temperature of 960 C. The inherent loss of CO{sub 2} capture efficiency was due to bypassing of gases from the fuel reactor to the air reactor, and the product of residual char burnt with air in the air reactor. Further experiments should be performed for a relatively long-time period to investigate the effects of ash and sulfur in coal on the reactivity of nickel-based oxygen carrier in the continuous CLC reactor

  17. Singlet oxygen phosphorescence lifetime imaging based on a fluorescence lifetime imaging microscope.

    PubMed

    Tian, Wenming; Deng, Liezheng; Jin, Shengye; Yang, Heping; Cui, Rongrong; Zhang, Qing; Shi, Wenbo; Zhang, Chunlei; Yuan, Xiaolin; Sha, Guohe

    2015-04-01

    The feasibility of singlet oxygen phosphorescence (SOP) lifetime imaging microscope was studied on a modified fluorescence lifetime imaging microscope (FLIM). SOP results from the infrared radiative transition of O2(a(1)Δg → X(3)Σg(-)) and O2(a(1)Δg) was produced in a C60 powder sample via photosensitization process. To capture the very weak SOP signal, a dichroic mirror was placed between the objective and tube lens of the FLIM and used to divide the luminescence returning from the sample into two beams: the reflected SOP beam and the transmitted photoluminescence of C60 (C60-PL) beam. The C60-PL beam entered the scanner of the FLIM and followed the normal optical path of the FLIM, while the SOP steered clear of the scanner and directly entered a finely designed SOP detection channel. Confocal C60-PL images and nonconfocal SOP images were then simultaneously obtained by using laser-scanning mode. Experimental results show that (1) under laser-scanning mode, the obstacle to confocal SOP imaging is the infrared-incompatible scanner, which can be solved by using an infrared-compatible scanner. Confocal SOP imaging is also expected to be realized under stage-scanning mode when the laser beam is parked and meanwhile a pinhole is added into the SOP detection channel. (2) A great challenge to SOP imaging is its extraordinarily long imaging time, and selecting only a few interesting points from fluorescence images to measure their SOP time-dependent traces may be a correct compromise. PMID:25781060

  18. Lunar Observer Laser Altimeter observations for lunar base site selection

    NASA Technical Reports Server (NTRS)

    Garvin, James B.; Bufton, Jack L.

    1992-01-01

    One of the critical datasets for optimal selection of future lunar landing sites is local- to regional-scale topography. Lunar base site selection will require such data for both engineering and scientific operations purposes. The Lunar Geoscience Orbiter or Lunar Observer is the ideal precursory science mission from which to obtain this required information. We suggest that a simple laser altimeter instrument could be employed to measure local-scale slopes, heights, and depths of lunar surface features important to lunar base planning and design. For this reason, we have designed and are currently constructing a breadboard of a Lunar Observer Laser Altimeter (LOLA) instrument capable of acquiring contiguous-footprint topographic profiles with both 30-m and 300-m along-track resolution. This instrument meets all the severe weight, power, size, and data rate limitations imposed by Observer-class spacecraft. In addition, LOLA would be capable of measuring the within-footprint vertical roughness of the lunar surface, and the 1.06-micron relative surface reflectivity at normal incidence. We have used airborne laser altimeter data for a few representative lunar analog landforms to simulate and analyze LOLA performance in a 100-km lunar orbit. We demonstrate that this system in its highest resolution mode (30-m diameter footprints) would quantify the topography of all but the very smallest lunar landforms. At its global mapping resolution (300-m diameter footprints), LOLA would establish the topographic context for lunar landing site selection by providing the basis for constructing a 1-2 km spatial resolution global, geodetic topographic grid that would contain a high density of observations (e.g., approximately 1000 observations per each 1 deg by 1 deg cell at the lunar equator). The high spatial and vertical resolution measurements made with a LOLA-class instrument on a precursory Lunar Observer would be highly synergistic with high-resolution imaging datasets, and

  19. OT2_dbrisbin_1: A z=1-2 oxygen survey. II. PAH-selected star forming and AGN sources

    NASA Astrophysics Data System (ADS)

    Brisbin, D.

    2011-09-01

    We are conducting a survey of the [CII] 158um line from galaxies at redshifts 1-2 using our grating spectrometer, ZEUS on the CSO. Our first 13 galaxy survey showed that luminous star forming galaxies in this epoch have moderate intensity kpc-scale star formation likely an extension of the Schmidt-Kennicutt law to very high gas mass fractions. Our AGN dominated systems have similarly large scale, but significantly more intense star formation suggesting punctuated, collision-induced star formation. We were awarded OT1 PACS spectroscopy and PACS/SPIRE photometry of these sources to observe the oxygen [OI], [OIII], and [OIV] fine-structure lines and far-IR continuum to characterize the star formation and AGN activity in these sources. Only two of our sources have been observed to date, but with good astrophysical success. Since the OT1 submission, we have detected 11 more z ~1-2 sources in [CII] with ZEUS. Here we propose an OT2 oxygen line/far-IR continuum study for 10 of these new sources. The new source list significantly enhances our OT1 survey in that (1) we nearly double our sample greatly increasing statistical significance of the results (2) the new group includes 7 Spitzer/PAH sources. PAH emission arises from PDRs tracing the photo-electric heating, while the [CII] and [OI] lines trace the cooling. PAHS therefore trace star formation and, since the features are extremely bright, are excellent redshift indicators. Future missions (e.g. JWST and SPICA/SAFARI) will rely on PAH spectroscopy at high z. It is therefore vital to study PAH emission and its relationship to star formation. The proposed work explores this connection at redshifts 1-2, near the peak of star formation per unit co-moving volume over cosmic time. In this interval ZEUS and PACs share a great synergy with well-matched sensitivities enabling detections of [CII] and oxygen in a wide variety of systems.

  20. Mobility-Based Mobile Relay Selection in MANETs

    NASA Astrophysics Data System (ADS)

    Kim, Gilnam; Lee, Hyoungjoo; Lee, Kwang Bok

    The future wireless mobile communication networks are expected to provide seamless wireless access and data exchange to mobile users. In particular, it is expected that the demand for ubiquitous data exchange between mobile users will increase with the widespread use of various wireless applications of the intelligent transportation system (ITS) and intelligent vehicles. Mobile ad hoc networks (MANETs) are one of the representative research areas pursuing the technology needed to satisfy the increasing mobile communication requirements. However, most of the works on MANET systems do not take into account the continuous and dynamic changes of nodal mobility to accommodate system design and performance evaluation. The mobility of nodes limits the reliability of communication between the source and the destination node since a link between two continuously moving nodes is established only when one node enters the transmission range of the other. To alleviate this problem, mobile relay has been studied. In particular, it is shown that relay selection is an efficient way to support nodal mobility in MANET systems. In this paper, we propose a mobility-based relay selection algorithm for the MANET environment. Firstly, we define the lifetime as the maximum link duration for which the link between two nodes remains active. Therefore, the lifetime indicates the reliability of the relay link which measures its capability to successfully support relayed communication when requested by the source node. Furthermore, we consider a series of realistic scenarios according to the randomness of nodal mobility. Thus, the proposed algorithm can be easily applied in practical MANET systems by choosing the appropriate node mobility behavior. The numerical results show that the improved reliability of the proposed algorithm's relayed communication is achieved with a proper number of mobile relay nodes rather than with the conventional selection algorithm. Lastly, we show that random

  1. A weight based genetic algorithm for selecting views

    NASA Astrophysics Data System (ADS)

    Talebian, Seyed H.; Kareem, Sameem A.

    2013-03-01

    Data warehouse is a technology designed for supporting decision making. Data warehouse is made by extracting large amount of data from different operational systems; transforming it to a consistent form and loading it to the central repository. The type of queries in data warehouse environment differs from those in operational systems. In contrast to operational systems, the analytical queries that are issued in data warehouses involve summarization of large volume of data and therefore in normal circumstance take a long time to be answered. On the other hand, the result of these queries must be answered in a short time to enable managers to make decisions as short time as possible. As a result, an essential need in this environment is in improving the performances of queries. One of the most popular methods to do this task is utilizing pre-computed result of queries. In this method, whenever a new query is submitted by the user instead of calculating the query on the fly through a large underlying database, the pre-computed result or views are used to answer the queries. Although, the ideal option would be pre-computing and saving all possible views, but, in practice due to disk space constraint and overhead due to view updates it is not considered as a feasible choice. Therefore, we need to select a subset of possible views to save on disk. The problem of selecting the right subset of views is considered as an important challenge in data warehousing. In this paper we suggest a Weighted Based Genetic Algorithm (WBGA) for solving the view selection problem with two objectives.

  2. Selectivity of Chemisorbed Oxygen in C–H Bond Activation and CO Oxidation and Kinetic Consequences for CH₄–O₂ Catalysis on Pt and Rh Clusters

    SciTech Connect

    Chin, Ya-Huei; Buda, Corneliu; Neurock, Matthew; Iglesia, Enrique

    2011-10-06

    Rate measurements, density functional theory (DFT) within the framework of transition state theory, and ensemble-averaging methods are used to probe oxygen selectivities, defined as the reaction probability ratios for O* reactions with CO and CH₄, during CH₄–O₂ catalysis on Pt and Rh clusters. CO₂ and H₂O are the predominant products, but small amounts of CO form as chemisorbed oxygen atoms (O*) are depleted from cluster surfaces. Oxygen selectivities, measured using ¹²CO–¹³CH₄–O₂ reactants, increase with O₂/ CO ratio and O* coverage and are much larger than unity at all conditions on Pt clusters. These results suggest that O* reacts much faster with CO than with CH₄, causing any CO that forms and desorbs from metal cluster surfaces to react along the reactor bed with other O* to produce CO₂ at any residence time required for detectable extents of CH₄ conversion. O* selectivities were also calculated by averaging DFTderived activation barriers for CO and CH₄ oxidation reactions over all distinct surface sites on cubo-octahedral Pt clusters (1.8 nm diameter, 201 Pt atoms) at low O* coverages, which are prevalent at low O₂ pressures during catalysis. CO oxidation involves non-activated molecular CO adsorption as the kinetically relevant step on exposed Pt atoms vicinal of chemisorbed O* atoms (on *–O* site pairs). CH₄ oxidation occurs via kinetically relevant C–H bond activation on *–* site pairs involving oxidative insertion of a Pt atom into one of the C–H bonds in CH₄, forming a three-centered HC₃–Pt–H transition state. C–H bond activation barriers reflect the strength of Pt–CH₃ and Pt–H interactions at the transition state, which correlates, in turn, with the Pt coordination and with CH₃ * binding energies. Ensemble-averaged O* selectivities increase linearly with O₂/CO ratios, which define the O* coverages, via a proportionality constant. The proportionality constant is given by the ratio of rate

  3. Wet-chemistry based selective coatings for concentrating solar power

    NASA Astrophysics Data System (ADS)

    Maimon, Eran; Kribus, Abraham; Flitsanov, Yuri; Shkolnik, Oleg; Feuermann, Daniel; Zwicker, Camille; Larush, Liraz; Mandler, Daniel; Magdassi, Shlomo

    2013-09-01

    Spectrally selective coatings are common in low and medium temperature solar applications from solar water heating collectors to parabolic trough absorber tubes. They are also an essential element for high efficiency in higher temperature Concentrating Solar Power (CSP) systems. Selective coatings for CSP are usually prepared using advanced expensive methods such as sputtering and vapor deposition. In this work, coatings were prepared using low-cost wet-chemistry methods. Solutions based on Alumina and Silica sol gel were prepared and then dispersed with black spinel pigments. The black dispersions were applied by spray/roll coating methods on stainless steel plates. The spectral emissivity of sample coatings was measured in the temperature range between 200 and 500°C, while the spectral absorptivity was measured at room temperature and 500°C. Emissivity at wavelengths of 0.4-1.7 μm was evaluated indirectly using multiple measurements of directional reflectivity. Emissivity at wavelengths 2-14 μm was measured directly using a broadband IR camera that acquires the radiation emitted from the sample, and a range of spectral filters. Emissivity measurement results for a range of coated samples will be presented, and the impact of coating thickness, pigment loading, and surface preparation will be discussed.

  4. Knowledge based system for Satellite data product selection

    NASA Astrophysics Data System (ADS)

    Goyal, R.; Jayasudha, T.; Pandey, P.; Rama Devi, D.; Rebecca, A.; Manju Sarma, M.; Lakshmi, B.

    2014-11-01

    In recent years, the use of satellite data for geospatial applications has multiplied and contributed significantly towards development of the society. Satellite data requirements, in terms of spatial and spectral resolution, periodicity of data, level of correction and other parameters, vary for different applications. For major applications, remote sensing data alone may not suffice and may require additional data like field data. An application user, even though being versatile in his application, may not know which satellite data is best suited for his application, how to use the data and what information can be derived from the data. Remote sensing domain experts have the proficiency of using appropriate data for remote sensing applications. Entrenching domain expertise into the system and building a knowledge base system for satellite data product selection is vital. Non specialist data users need a user-friendly software which guides them to the most suitable satellite data product on the basis of their application. Such tool will aid the usage for apt remote sensed data for various sectors of application users. Additionally, the consumers will be less concerned about the technical particulars of the platforms that provide satellite data, instead focusing on the content and values in the data product, meeting the timelines and ease of access. Embedding knowledge is a popular and effective means of increasing the power of using a system. This paper describes a system, driven by the built-in knowledge of domain experts, for satellite data products selection for geospatial applications.

  5. A prototype of behavior selection mechanism based on emotion

    NASA Astrophysics Data System (ADS)

    Zhang, Guofeng; Li, Zushu

    2007-12-01

    In bionic methodology rather than in design methodology more familiar with, summarizing the psychological researches of emotion, we propose the biologic mechanism of emotion, emotion selection role in creature evolution and a anima framework including emotion similar to the classical control structure; and consulting Prospect Theory, build an Emotion Characteristic Functions(ECF) that computer emotion; two more emotion theories are added to them that higher emotion is preferred and middle emotion makes brain run more efficiently, emotional behavior mechanism comes into being. A simulation of proposed mechanism are designed and carried out on Alife Swarm software platform. In this simulation, a virtual grassland ecosystem is achieved where there are two kinds of artificial animals: herbivore and preyer. These artificial animals execute four types of behavior: wandering, escaping, finding food, finding sex partner in their lives. According the theories of animal ethnology, escaping from preyer is prior to other behaviors for its existence, finding food is secondly important behavior, rating is third one and wandering is last behavior. In keeping this behavior order, based on our behavior characteristic function theory, the specific functions of emotion computing are built of artificial autonomous animals. The result of simulation confirms the behavior selection mechanism.

  6. Vaccine Adjuvants Alter TCR-Based Selection Thresholds

    PubMed Central

    Malherbe, Laurent; Mark, Linda; Fazilleau, Nicolas; McHeyzer-Williams, Louise J.; McHeyzer-Williams, Michael G.

    2009-01-01

    SUMMARY How TCR specificity evolves in vivo following protein vaccination is central to the development of T helper cell function. Most models of clonal selection in the T helper cell compartment favor TCR affinity-based thresholds. Here, we demonstrate that depot-forming vaccine adjuvants do not require TLR agonists to induce clonal dominance in antigen-specific T helper cell responses. However, readily dispersible adjuvants using TLR-9 and TLR-4 agonists skew TCR repertoire usage by increasing TCR selection thresholds and enhancing antigen-specific clonal expansion. In this manner, vaccine adjuvants control the local accumulation of T helper cells expressing TCR with the highest peptide MHC class II binding. Clonal composition was altered by mechanisms that blocked the local propagation of clonotypes independent of antigen dose and not as a consequence of inter-clonal competition. This capacity of adjuvants to modify antigen-specific Th cell clonal composition has fundamental implications for the design of future protein sub-unit vaccines. PMID:18450485

  7. Duplex-Selective Ruthenium-based DNA Intercalators

    PubMed Central

    Shade, Chad M.; Kennedy, Robert D.; Rouge, Jessica L.; Rosen, Mari S.; Wang, Mary X.; Seo, Soyoung E.; Clingerman, Daniel J.

    2016-01-01

    We report the design and synthesis of small molecules that exhibit enhanced luminescence in the presence of duplex rather than single-stranded DNA. The local environment presented by a well-known [Ru(dipyrido[2,3-a:3',2'-c]phenazine)L2]2+-based DNA intercalator was modified by functionalizing the bipyridine ligands with esters and carboxylic acids. By systematically varying the number and charge of the pendant groups, it was determined that decreasing the electrostatic interaction between the intercalator and the anionic DNA backbone reduced single-strand interactions and translated to better duplex specificity. In studying this class of complexes, a single RuII complex emerged that selectively luminesces in the presence of duplex DNA with little to no background from interacting with single stranded DNA. This complex shows promise as a new dye capable of selectively staining double versus single-stranded DNA in gel electrophoresis, which cannot be done with conventional SYBR dyes. PMID:26119581

  8. Atomic oxygen interaction with spacecraft materials: Relationship between orbital and ground-based testing for materials certification

    NASA Technical Reports Server (NTRS)

    Cross, Jon B.; Koontz, Steven L.; Lan, Esther H.

    1993-01-01

    The effects of atomic oxygen on boron nitride (BN), silicon nitride (Si3N4), Intelsat 6 solar cell interconnects, organic polymers, and MoS2 and WS2 dry lubricant, were studied in Low Earth Orbit (LEO) flight experiments and in a ground based simulation facility. Both the inflight and ground based experiments employed in situ electrical resistance measurements to detect penetration of atomic oxygen through materials and Electron Spectroscopy for Chemical Analysis (ESCA) analysis to measure chemical composition changes. Results are given. The ground based results on the materials studied to date show good qualitative correlation with the LEO flight results, thus validating the simulation fidelity of the ground based facility in terms of reproducing LEO flight results. In addition it was demonstrated that ground based simulation is capable of performing more detailed experiments than orbital exposures can presently perform. This allows the development of a fundamental understanding of the mechanisms involved in the LEO environment degradation of materials.

  9. Feature selection gait-based gender classification under different circumstances

    NASA Astrophysics Data System (ADS)

    Sabir, Azhin; Al-Jawad, Naseer; Jassim, Sabah

    2014-05-01

    This paper proposes a gender classification based on human gait features and investigates the problem of two variations: clothing (wearing coats) and carrying bag condition as addition to the normal gait sequence. The feature vectors in the proposed system are constructed after applying wavelet transform. Three different sets of feature are proposed in this method. First, Spatio-temporal distance that is dealing with the distance of different parts of the human body (like feet, knees, hand, Human Height and shoulder) during one gait cycle. The second and third feature sets are constructed from approximation and non-approximation coefficient of human body respectively. To extract these two sets of feature we divided the human body into two parts, upper and lower body part, based on the golden ratio proportion. In this paper, we have adopted a statistical method for constructing the feature vector from the above sets. The dimension of the constructed feature vector is reduced based on the Fisher score as a feature selection method to optimize their discriminating significance. Finally k-Nearest Neighbor is applied as a classification method. Experimental results demonstrate that our approach is providing more realistic scenario and relatively better performance compared with the existing approaches.

  10. Isotope-selective sensor for medical diagnostics based on PAS

    NASA Astrophysics Data System (ADS)

    Wolff, M.; Groninga, H. G.; Harde, H.

    2005-06-01

    Development of new optical sensor technologies has a major impact on the progression of diagnostic methods. Of the permanently increasing number of non-invasive 13C-breath tests, the Urea Breath Test for detection of Helicobacter pylori is the most prominent. However, many recent developments go beyond gastroenterological applications. We present a new detection scheme for breath analysis that employs an especially compact and simple set-up based on Photoacoustic Spectroscopy. Using a wavelength-modulated DFB-diode laser and taking advantage of acoustical resonances of the sample cell, we performed very sensitive isotope-selective measurements on CO2. Detection limits for 13CO2 of a few ppm and for the variation of the 13CO2 concentration of approximately 1% were achieved.

  11. Copper selective adsorption with a microemulsion-based resin

    SciTech Connect

    Yang, J.H.K.; Burban, J.H.; Cussler, E.L.

    1995-05-01

    Cross-linked terpolymers of allyl acetylacetone, 2-hydroxyethyl methacrylate, and ethylene glycol dimethacrylate were synthesized in the oil phase of a bicontinuous microemulsion stabilized with didodecyldimethylammonium bromide. The resulting material is porous, with a surface area of 58 m{sup 2}/dry g. It selectively adsorbs copper, picking up 0.07 meq/dry g from a 0.1-M solution. This is less than the total apparent capacity of 0.65 meq/dry g inferred from titration with base and much less than the amount in conventional, nonselective resins, which is typically 5 meq/dry g. Breakthrough curves in packed beds and across membranes of this material seem consistent with uptake controlled by chemical reaction compromised by dispersion. Nonporous membranes of this material do not show facilitated transport.

  12. Infrared transparent frequency selective surface based on metallic meshes

    SciTech Connect

    Yu, Miao; Xu, Nianxi; Liu, Hai; Gao, Jinsong

    2014-02-15

    This paper presents an infrared transparent frequency selective surface (ITFSS) based on metallic meshes. In this ITFSS structure, periodic cross-slot units are integrated on square metallic meshes empowered by coating and UV-lithography. A matching condition is proposed to avoid the distortion of units. Experimental results show that this ITFSS possesses a good transmittance of 80% in the infrared band of 3–5 μm, and also a stable band-pass behavior at the resonance frequency of 36.4 GHz with transmittance of −0.56 dB. Theoretical simulations about the ITFSS diffractive characteristics and frequency responses are also investigated. The novel ITFSS will attract renewed interest and be exploited for applications in various fields.

  13. Metabolically-Derived Human Ventilation Rates: A Revised Approach Based Upon Oxygen Consumption Rates (External Review Draft)

    EPA Science Inventory

    EPA has released a draft report entitled, Metabolically-Derived Human Ventilation Rates: A Revised Approach Based Upon Oxygen Consumption Rates, for independent external peer review and public comment. NCEA published the Exposure Factors Handbook in 1997. This comprehens...

  14. Knocking on wood: base metal complexes as catalysts for selective oxidation of lignin models and extracts.

    PubMed

    Hanson, Susan K; Baker, R Tom

    2015-07-21

    This work began as part of a biomass conversion catalysis project with UC Santa Barbara funded by the first NSF Chemical Bonding Center, CATSB. Recognizing that catalytic aerobic oxidation of diol C-C bonds could potentially be used to break down lignocellulose, we began to synthesize oxovanadium complexes and explore their fundamental reactivity. Of course there were theories regarding the oxidation mechanism, but our mechanistic studies soon revealed a number of surprises of the type that keep all chemists coming back to the bench! We realized that these reactions were also exciting in that they actually used the oxygen-on-every-carbon property of biomass-derived molecules to control the selectivity of the oxidation. When we found that these oxovanadium complexes tended to convert sugars predominantly to formic acid and carbon dioxide, we replaced one of the OH groups with an ether and entered the dark world of lignin chemistry. In this Account, we summarize results from our collaboration and from our individual labs. In particular, we show that oxidation selectivity (C-C vs C-O bond cleavage) of lignin models using air and vanadium complexes depends on the ancillary ligands, the reaction solvent, and the substrate structure (i.e., phenolic vs non-phenolic). Selected vanadium complexes in the presence of added base serve as effective alcohol oxidation catalysts via a novel base-assisted dehydrogenation pathway. In contrast, copper catalysts effect direct C-C bond cleavage of these lignin models, presumably through a radical pathway. The most active vanadium catalyst exhibits unique activity for the depolymerization of organosolv lignin. After Weckhuysen's excellent 2010 review on lignin valorization, the number of catalysis studies and approaches on both lignin models and extracts has expanded rapidly. Today we are seeing new start-ups and lignin production facilities sprouting up across the globe as we all work to prove wrong the old pulp and paper chemist

  15. A naphthalene-based two-photon fluorescent probe for selective and sensitive detection of endogenous hypochlorous acid.

    PubMed

    Zhou, Xiao-Hong; Jiang, Yu-Ren; Zhao, Xiong-Jie; Guo, Dong

    2016-11-01

    An efficient naphthalene-based two-photon fluorescent probe for endogenous HClO has been reported in the present study, which consists of a 6-(2-benzothiazolyl)-2-naphthalenol fluorophore connected with a 4-aminophenol (the fluorescence quenching and response group). This probe exhibits a high selectivity and excellent sensitivity with a detection limit of 7.6nM over other reactive oxygen species and analyte species, and the fluorescence intensity enhanced 103-fold when responsed. Furthermore, it was successfully used for two-photon imaging of endogenous HClO in live cells with high-resolution. PMID:27591640

  16. Hybrid Nanomaterials Based on Graphene and Gold Nanoclusters for Efficient Electrocatalytic Reduction of Oxygen.

    PubMed

    Wang, Changhong; Li, Na; Wang, Qiannan; Tang, Zhenghua

    2016-12-01

    Nanocomposites based on gold nanoclusters (AuNCs) with polyvinyl pyrrolidone as ligand and reduced graphene oxide (RGO) have been prepared and employed as efficient electrocatalysts for oxygen reduction reaction (ORR). AuNCs were synthesized through a wet chemical approach and then loaded onto the RGO. The as-prepared hybrid materials were pyrolyzed to remove the organic ligands. The composites were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) as well as other techniques. Electrochemical tests demonstrated that the hybrid materials exhibited effective ORR activity in alkaline media. Among a series of samples tested, the pyrolyzed sample with 50 % AuNCs mass loading exhibited the best activity, superior than AuNCs alone, RGO alone, and the others, in terms of onset potential and kinetic current density as well as durability. The method here may provide a generic approach to prepare supported noble metal nanoclusters with excellent reactivity and robust stability for ORR. PMID:27431494

  17. Hybrid Nanomaterials Based on Graphene and Gold Nanoclusters for Efficient Electrocatalytic Reduction of Oxygen

    NASA Astrophysics Data System (ADS)

    Wang, Changhong; Li, Na; Wang, Qiannan; Tang, Zhenghua

    2016-07-01

    Nanocomposites based on gold nanoclusters (AuNCs) with polyvinyl pyrrolidone as ligand and reduced graphene oxide (RGO) have been prepared and employed as efficient electrocatalysts for oxygen reduction reaction (ORR). AuNCs were synthesized through a wet chemical approach and then loaded onto the RGO. The as-prepared hybrid materials were pyrolyzed to remove the organic ligands. The composites were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) as well as other techniques. Electrochemical tests demonstrated that the hybrid materials exhibited effective ORR activity in alkaline media. Among a series of samples tested, the pyrolyzed sample with 50 % AuNCs mass loading exhibited the best activity, superior than AuNCs alone, RGO alone, and the others, in terms of onset potential and kinetic current density as well as durability. The method here may provide a generic approach to prepare supported noble metal nanoclusters with excellent reactivity and robust stability for ORR.

  18. Microbial biosensor for free fatty acids using an oxygen electrode based on thick film technology.

    PubMed

    Schmidt, A; Standfuss-Gabisch, C; Bilitewski, U

    1996-01-01

    A microbial biosensor based on thick film technology was developed. The microorganisms, Arthrobacter nicotianae, were immobilized in Ca-alginate directly on the electrode surface. For the stability of the calcium alginate gel the addition of 0.5 mM CaCl2 to the assay buffer was necessary. The respiratory activity of the microorganisms was monitored by oxygen consumption at -600 mV vs. Ag/AgCl reference electrode. The sensor was used in a batch system and was applied to the determination of free fatty acids in milk. Short-chain fatty acids (C4:0-C12:0) were the preferential substrates, with butyric acid being the main substrate. Consequently, the concentration of free short-chain fatty acids was represented as the butyric acid equivalent. The sensor showed linearity over the concentration range 9.5-165.5 microM (correlation coefficient, r = 0.99920). The response time of the sensor was approximately 3 min. No additional dialysis membrane was necessary, which led to a high sensitivity of the sensor and fast response times. Recovery rates of 98-113% were found for butyric acid in milk samples using the sensor without any additional membrane and a sample dilution of 200 by the assay. Two widespread disadvantages of microbial sensors, long response times and long times to return to the baseline signal after use, could be overcome. PMID:8828165

  19. An Intelligent Optical Dissolved Oxygen Measurement Method Based on a Fluorescent Quenching Mechanism

    PubMed Central

    Li, Fengmei; Wei, Yaoguang; Chen, Yingyi; Li, Daoliang; Zhang, Xu

    2015-01-01

    Dissolved oxygen (DO) is a key factor that influences the healthy growth of fishes in aquaculture. The DO content changes with the aquatic environment and should therefore be monitored online. However, traditional measurement methods, such as iodometry and other chemical analysis methods, are not suitable for online monitoring. The Clark method is not stable enough for extended periods of monitoring. To solve these problems, this paper proposes an intelligent DO measurement method based on the fluorescence quenching mechanism. The measurement system is composed of fluorescent quenching detection, signal conditioning, intelligent processing, and power supply modules. The optical probe adopts the fluorescent quenching mechanism to detect the DO content and solves the problem, whereas traditional chemical methods are easily influenced by the environment. The optical probe contains a thermistor and dual excitation sources to isolate visible parasitic light and execute a compensation strategy. The intelligent processing module adopts the IEEE 1451.2 standard and realizes intelligent compensation. Experimental results show that the optical measurement method is stable, accurate, and suitable for online DO monitoring in aquaculture applications. PMID:26690176

  20. An Intelligent Optical Dissolved Oxygen Measurement Method Based on a Fluorescent Quenching Mechanism.

    PubMed

    Li, Fengmei; Wei, Yaoguang; Chen, Yingyi; Li, Daoliang; Zhang, Xu

    2015-01-01

    Dissolved oxygen (DO) is a key factor that influences the healthy growth of fishes in aquaculture. The DO content changes with the aquatic environment and should therefore be monitored online. However, traditional measurement methods, such as iodometry and other chemical analysis methods, are not suitable for online monitoring. The Clark method is not stable enough for extended periods of monitoring. To solve these problems, this paper proposes an intelligent DO measurement method based on the fluorescence quenching mechanism. The measurement system is composed of fluorescent quenching detection, signal conditioning, intelligent processing, and power supply modules. The optical probe adopts the fluorescent quenching mechanism to detect the DO content and solves the problem, whereas traditional chemical methods are easily influenced by the environment. The optical probe contains a thermistor and dual excitation sources to isolate visible parasitic light and execute a compensation strategy. The intelligent processing module adopts the IEEE 1451.2 standard and realizes intelligent compensation. Experimental results show that the optical measurement method is stable, accurate, and suitable for online DO monitoring in aquaculture applications. PMID:26690176

  1. Reference concepts for a space-based hydrogen-oxygen combustion, turboalternator, burst power system

    SciTech Connect

    Edenburn, M.W.

    1990-07-01

    This report describes reference concepts for a hydrogen-oxygen combustion, turboalternator power system that supplies power during battle engagement to a space-based, ballistic missile defense platform. All of the concepts are open''; that is, they exhaust hydrogen or a mixture of hydrogen and water vapor into space. We considered the situation where hydrogen is presumed to be free to the power system because it is also needed to cool the platform's weapon and the situation where hydrogen is not free and its mass must be added to that of the power system. We also considered the situation where water vapor is an acceptable exhaust and the situation where it is not. The combination of these two sets of situations required four different power generation systems, and this report describes each, suggests parameter values, and estimates masses for each of the four. These reference concepts are expected to serve as a baseline'' to which other types of power systems can be compared, and they are expected to help guide technology development efforts in that they suggest parameter value ranges that will lead to optimum system designs. 7 refs., 18 figs., 5 tabs.

  2. Ordered PdCu-Based Nanoparticles as Bifunctional Oxygen-Reduction and Ethanol-Oxidation Electrocatalysts.

    PubMed

    Jiang, Kezhu; Wang, Pengtang; Guo, Shaojun; Zhang, Xu; Shen, Xuan; Lu, Gang; Su, Dong; Huang, Xiaoqing

    2016-07-25

    The development of superior non-platinum electrocatalysts for enhancing the electrocatalytic activity and stability for the oxygen-reduction reaction (ORR) and liquid fuel oxidation reaction is very important for the commercialization of fuel cells, but still a great challenge. Herein, we demonstrate a new colloidal chemistry technique for making structurally ordered PdCu-based nanoparticles (NPs) with composition control from PdCu to PdCuNi and PtCuCo. Under the dual tuning on the composition and intermetallic phase, the ordered PdCuCo NPs exhibit better activity and much enhanced stability for ORR and ethanol-oxidation reaction (EOR) than those of disordered PdCuM NPs, the commercial Pt/C and Pd/C catalysts. The density functional theory (DFT) calculations reveal that the improved ORR activity on the PdCuM NPs stems from the catalytically active hollow sites arising from the ligand effect and the compressive strain on the Pd surface owing to the smaller atomic size of Cu, Co, and Ni. PMID:27253520

  3. Unsupervised Feature Selection Based on the Morisita Index

    NASA Astrophysics Data System (ADS)

    Golay, Jean; Kanevski, Mikhail

    2016-04-01

    Recent breakthroughs in technology have radically improved our ability to collect and store data. As a consequence, the size of datasets has been increasing rapidly both in terms of number of variables (or features) and number of instances. Since the mechanism of many phenomena is not well known, too many variables are sampled. A lot of them are redundant and contribute to the emergence of three major challenges in data mining: (1) the complexity of result interpretation, (2) the necessity to develop new methods and tools for data processing, (3) the possible reduction in the accuracy of learning algorithms because of the curse of dimensionality. This research deals with a new algorithm for selecting the smallest subset of features conveying all the information of a dataset (i.e. an algorithm for removing redundant features). It is a new version of the Fractal Dimensionality Reduction (FDR) algorithm [1] and it relies on two ideas: (a) In general, data lie on non-linear manifolds of much lower dimension than that of the spaces where they are embedded. (b) The situation describes in (a) is partly due to redundant variables, since they do not contribute to increasing the dimension of manifolds, called Intrinsic Dimension (ID). The suggested algorithm implements these ideas by selecting only the variables influencing the data ID. Unlike the FDR algorithm, it resorts to a recently introduced ID estimator [2] based on the Morisita index of clustering and to a sequential forward search strategy. Consequently, in addition to its ability to capture non-linear dependences, it can deal with large datasets and its implementation is straightforward in any programming environment. Many real world case studies are considered. They are related to environmental pollution and renewable resources. References [1] C. Traina Jr., A.J.M. Traina, L. Wu, C. Faloutsos, Fast feature selection using fractal dimension, in: Proceedings of the XV Brazilian Symposium on Databases, SBBD, pp. 158

  4. Eutrophication trends inferred from hypolimnetic dissolved-oxygen dynamics within selected White River reservoirs, northern Arkansas-southern Missouri, 1974-94

    USGS Publications Warehouse

    Green, W.R.

    1996-01-01

    The White River Basin in northern Arkansas and southern Missouri contains four major reservoirs. Beaver, Table Rock, and Bull Shoals Lakes form a chain of reservoirs on the main stem of the White River. Norfork Lake is on the North Fork River, a tributary of the White River. Vertical water- column profiles of temperature and dissolved- oxygen concentrations have been collected monthly, in general, at sites near the dam of each reservoir since 1974. Hypolimnetic dissolved- oxygen dynamics of these reservoirs from 1974 through 1994 were examined based on the near-dam data and used to infer temporal changes in eutrophication. Regression models indicated that a positive relation existed between discharge through the dam during the stratification season and the areal hypolimnetic deficit. Temporal changes in the relative areal hypolimnetic oxygen deficit, a model that adjusts the areal hypolimnetic oxygen deficit to standard temperature and depth, showed a decreasing trend in Beaver Lake from 1974 through 1994, indicating that the level of eutrophication decreased. Little or no change in the relative areal hypolimnetic oxygen deficit occurred in Table Rock, Bull Shoals, or Norfork Lakes over the period of record. Temporal analysis of the residuals from the oxygen deficit-discharge model indicated that the oxygen deficit-discharge function changed over time in Beaver and Table Rock Lakes. There was little or no temporal trend in residuals of areal hypolimnetic oxygen deficit over the period of record for Bull Shoals and Norfork Lakes. Multiple regression using a time variable and discharge through the dam during the stratification season was examined for the four reservoirs. The slope coefficient of the time variable for both Beaver and Table Rock Lakes was negative, indicating that the temporal function driving the discharge related areal hypolimnetic oxygen deficit decreased over the period of record. This temporal function may be an expression of biological

  5. Nucleation, growth, and repair of a cobalt-based oxygen evolving catalyst.

    PubMed

    Surendranath, Yogesh; Lutterman, Daniel A; Liu, Yi; Nocera, Daniel G

    2012-04-11

    The mechanism of nucleation, steady-state growth, and repair is investigated for an oxygen evolving catalyst prepared by electrodeposition from Co(2+) solutions in weakly basic electrolytes (Co-OEC). Potential step chronoamperometry and atomic force microscopy reveal that nucleation of Co-OEC is progressive and reaches a saturation surface coverage of ca. 70% on highly oriented pyrolytic graphite substrates. Steady-state electrodeposition of Co-OEC exhibits a Tafel slope approximately equal to 2.3 × RT/F. The electrochemical rate law exhibits a first order dependence on Co(2+) and inverse orders on proton (third order) and proton acceptor, methylphosphonate (first order for 1.8 mM ≤ [MeP(i)] ≤ 18 mM and second order dependence for 32 mM ≤ [MeP(i)] ≤ 180 mM). These electrokinetic studies, combined with recent XAS studies of catalyst structure, suggest a mechanism for steady state growth at intermediate MeP(i) concentration (1.8-18 mM) involving a rapid solution equilibrium between aquo Co(II) and Co(III) hydroxo species accompanied with a rapid surface equilibrium involving electrolyte dissociation and deprotonation of surface bound water. These equilibria are followed by a chemical rate-limiting step for incorporation of Co(III) into the growing cobaltate clusters comprising Co-OEC. At higher concentrations of MeP(i) ([MeP(i)] ≥ 32 mM), MePO(3)(2-) equilibrium binding to Co(II) in solution is suggested by the kinetic data. Consistent with the disparate pH profiles for oxygen evolution electrocatalysis and catalyst formation, NMR-based quantification of catalyst dissolution as a function of pH demonstrates functional stability and repair at pH values >6 whereas catalyst corrosion prevails at lower pH values. These kinetic insights provide a basis for developing and operating functional water oxidation (photo)anodes under benign pH conditions. PMID:22394103

  6. Time-resolved luminescence imaging of intracellular oxygen levels based on long-lived phosphorescent iridium(III) complex.

    PubMed

    Liu, Shujuan; Zhang, Yangliu; Liang, Hua; Chen, Zejing; Liu, Ziyu; Zhao, Qiang

    2016-07-11

    Time-resolved luminescence imaging of intracellular oxygen levels has been demonstrated based on long-lived phosphorescent signal. A phosphorescent dinuclear iridium(III) complex Ir1 has been designed and synthesized, which exhibits excellent optical properties, such as high quantum yields, large Stokes shift, high photostability and long emission lifetime. The phosphorescent intensity and lifetime of complex are very sensitive to oxygen levels. Thus, the application of Ir1 for monitoring intracellular oxygen levels has been realized successfully. Especially, utilizing the advantageous long emission lifetime of Ir1, the background fluorescence interference could be eliminated effectively by using the photoluminescence lifetime imaging and time-gated luminescence imaging techniques, improving the signal-to-noise ratios in bioimaging. PMID:27410847

  7. Luminescent sensing of dissolved oxygen based on Ru(II) complex embedded in sol-gel matrix

    NASA Astrophysics Data System (ADS)

    Bi, Yubing; Tao, Wei; Hu, Yanli; Mao, Yimei; Zhao, Hui

    2015-11-01

    In biological cells and tissues environment, real-time monitoring and controlling dissolved oxygen (DO) provides critical information for studying cellular metabolism process, health status and pathological features. This paper developed an optical DO sensor based on fluorescence quenching principle, prepared tris(4,7-diphenyl-1,10- phenanthroline)ruthenium(II) dichloride complex sol-gel sensing film, and studied its sensing performance. The principle of this sensor is that dissolved oxygen has quenching effect towards the fluorescence emitted by ruthenium complex. So the fluorescence intensity is reduced due to the existence of DO. The measurement limit of DO was 10- 100%, the response time was 20s, and the resolution was 0.02. Compared to traditional dissolved oxygen electrode probe, this luminescent fiber had many advantages, such as smaller size, shorter response time and higher stability.

  8. Oxygen-Induced Degradation in C60-Based Organic Solar Cells: Relation Between Film Properties and Device Performance.

    PubMed

    Bastos, João P; Voroshazi, Eszter; Fron, Eduard; Brammertz, Guy; Vangerven, Tim; Van der Auweraer, Mark; Poortmans, Jef; Cheyns, David

    2016-04-20

    Fullerene-based molecules are the archetypical electron-accepting materials for organic photovoltaic devices. A detailed knowledge of the degradation mechanisms that occur in C60 layers will aid in the development of more stable organic solar cells. Here, the impact of storage in air on the optical and electrical properties of C60 is studied in thin films and in devices. Atmospheric exposure induces oxygen-trap states that are 0.19 eV below the LUMO of the fullerene C60. Moreover, oxygen causes a 4-fold decrease of the exciton lifetime in C60 layers, resulting in a 40% drop of short-circuit current from optimized planar heterojunction solar cells. The presence of oxygen-trap states increases the saturation current of the device, resulting in a 20% loss of open-circuit voltage. Design guidelines are outlined to improve air stability for fullerene-containing devices. PMID:27065475

  9. Effects of microwave and oxygen plasma treatments on capacitive characteristics of supercapacitor based on multiwalled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Dulyaseree, Paweena; Yordsri, Visittapong; Wongwiriyapan, Winadda

    2016-02-01

    The effects of microwave and oxygen plasma treatments on the capacitive characteristics of a supercapacitor based on multiwalled carbon nanotubes (MWNTs) were investigated. MWNTs were heat-treated under air ambient at 500 °C for 1 h, and subsequently microwave-treated at 650 W for 70 s (m-MWNTs). Another batch of MWNTs was treated by oxygen plasma for 30 min (p-MWNTs). Pristine MWNTs, m-MWNTs, and p-MWNTs were separately used as electrode materials for supercapacitors. Their cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy results were analyzed. The p-MWNTs show the best performance with a specific capacitance of 238.23 F·g-1. The capacitance improvement is attributed to the increase in the number of oxygen-containing functional groups, as evidenced by Fourier transform-infrared spectroscopy and contact angle measurement. These results suggest that oxygen plasma treatment is a rapid and efficient method for oxygen functionalization.

  10. Oxygen Therapy

    MedlinePlus

    Oxygen therapy is a treatment that provides you with extra oxygen. Oxygen is a gas that your body needs to function. Normally, your lungs absorb oxygen from the air you breathe. But some conditions ...

  11. Convenient microtiter plate-based, oxygen-independent activity assays for flavin-dependent oxidoreductases based on different redox dyes

    PubMed Central

    Brugger, Dagmar; Krondorfer, Iris; Zahma, Kawah; Stoisser, Thomas; Bolivar, Juan M; Nidetzky, Bernd; Peterbauer, Clemens K; Haltrich, Dietmar

    2014-01-01

    Flavin-dependent oxidoreductases are increasingly recognized as important biocatalysts for various industrial applications. In order to identify novel activities and to improve these enzymes in engineering approaches, suitable screening methods are necessary. We developed novel microtiter-plate-based assays for flavin-dependent oxidases and dehydrogenases using redox dyes as electron acceptors for these enzymes. 2,6-dichlorophenol-indophenol, methylene green, and thionine show absorption changes between their oxidized and reduced forms in the visible range, making it easy to judge visually changes in activity. A sample set of enzymes containing both flavoprotein oxidases and dehydrogenases – pyranose 2-oxidase, pyranose dehydrogenase, cellobiose dehydrogenase, d-amino acid oxidase, and l-lactate oxidase – was selected. Assays for these enzymes are based on a direct enzymatic reduction of the redox dyes and not on the coupled detection of a reaction product as in the frequently used assays based on hydrogen peroxide formation. The different flavoproteins show low Michaelis constants with these electron acceptor substrates, and therefore these dyes need to be added in only low concentrations to assure substrate saturation. In conclusion, these electron acceptors are useful in selective, reliable and cheap MTP-based screening assays for a range of flavin-dependent oxidoreductases, and offer a robust method for library screening, which could find applications in enzyme engineering programs. PMID:24376171

  12. Mutual information-based feature selection for radiomics

    NASA Astrophysics Data System (ADS)

    Oubel, Estanislao; Beaumont, Hubert; Iannessi, Antoine

    2016-03-01

    Background The extraction and analysis of image features (radiomics) is a promising field in the precision medicine era, with applications to prognosis, prediction, and response to treatment quantification. In this work, we present a mutual information - based method for quantifying reproducibility of features, a necessary step for qualification before their inclusion in big data systems. Materials and Methods Ten patients with Non-Small Cell Lung Cancer (NSCLC) lesions were followed over time (7 time points in average) with Computed Tomography (CT). Five observers segmented lesions by using a semi-automatic method and 27 features describing shape and intensity distribution were extracted. Inter-observer reproducibility was assessed by computing the multi-information (MI) of feature changes over time, and the variability of global extrema. Results The highest MI values were obtained for volume-based features (VBF). The lesion mass (M), surface to volume ratio (SVR) and volume (V) presented statistically significant higher values of MI than the rest of features. Within the same VBF group, SVR showed also the lowest variability of extrema. The correlation coefficient (CC) of feature values was unable to make a difference between features. Conclusions MI allowed to discriminate three features (M, SVR, and V) from the rest in a statistically significant manner. This result is consistent with the order obtained when sorting features by increasing values of extrema variability. MI is a promising alternative for selecting features to be considered as surrogate biomarkers in a precision medicine context.

  13. Model validation and selection based on inverse fuzzy arithmetic

    NASA Astrophysics Data System (ADS)

    Haag, Thomas; Carvajal González, Sergio; Hanss, Michael

    2012-10-01

    In this work, a method for the validation of models in general, and the selection of the most appropriate model in particular, is presented. As an industrially relevant example, a Finite Element (FE) model of a brake pad is investigated and identified with particular respect to uncertainties. The identification is based on inverse fuzzy arithmetic and consists of two stages. In the first stage, the eigenfrequencies of the brake pad are considered, and for three different material models, a set of fuzzy-valued parameters is identified on the basis of measurement values. Based on these identified parameters and a resimulation of the system with these parameters, a model validation is performed which takes into account both the model uncertainties and the output uncertainties. In the second stage, the most appropriate material model is used in the FE model for the computation of frequency response functions between excitation point and three measurement points. Again, the parameters of the model are identified on the basis of three corresponding measurement signals and a resimulation is conducted.

  14. Novel class of highly selective divanillin-based PACs

    NASA Astrophysics Data System (ADS)

    Medina, Arturo N.; Ferreira, Lawrence; Tadros, Sobhy P.; Sizensky, Joseph J.; Fregeolle, M.; Blakeney, Andrew J.; Toukhy, Medhat A.

    1996-06-01

    A new class of diazonaphthoquinone (DNQ) photoactive compounds (PACs) based on the divanillin core is introduced in this paper. The general structure of these PAC backbones is shown in Formula 1. The divanillin structure possesses unique electronic characteristics which influence its DNQ-SO2Cl esterification reactions to be highly selective. The most reactive site for esterification in Formula 1 is one of the divanillin hydroxyls despite the typically higher steric hindrance. Surprisingly, the esterification product is then significantly deactivated towards esterification at the other previously equivalent divanillin OH. The result of using 3 equivalents of DNQ-SO2Cl to esterify tetraphenolic species is the formation of high percentages of the specific triester in which the second divanillyl OH remains unesterified. The deactivation of the second divanillin OH after the initial esterification indicates some interaction between the two o,o-biphenol rings despite its inability to be coplanar for conjugation of (pi) electrons because of steric hindrance. Possible explanations for this interaction are explored using molecular simulation tools. Diverse members of the divanillin PAC family have been prepared from phenols of varying structure and hydrophobicities. These PACs were tested lithographically and the results correlated with PAC backbone structure. The characteristic dissolution rate behavior of the resist formulations based on triesterified PACs, measured as a function of exposure dose, generally show high discrimination and strong inhibition, even with the more hydrophilic PACs. These formulations typically exhibited high resolution, wide focus latitude, and exposure margins greater than 2.0 in lithographic screening.

  15. A GIS-based methodology for selecting stormwater disconnection opportunities.

    PubMed

    Moore, S L; Stovin, V R; Wall, M; Ashley, R M

    2012-01-01

    The purpose of this paper is to introduce a geographic information system (GIS)-based decision support tool that assists the user to select not only areas where (retrofit) sustainable drainage systems (SuDS) could be implemented within a large catchment (>100 ha), but also to allow discrimination between suitable SuDS techniques based on their likely feasibility and effectiveness. The tool is applied to a case study catchment within London, UK, with the aim of increasing receiving water quality by reducing combined sewer overflow (CSO) spill frequency and volume. The key benefit of the tool presented is to allow rapid assessment of the retrofit SuDS potential of large catchments. It is not intended to replace detailed site investigations, but may help to direct attention to sites that have the greatest potential for retrofit SuDS implementation. Preliminary InfoWorks CS modelling of 'global disconnections' within the case study catchment, e.g. the removal of 50% of the total impervious area, showed that CSO spill volume could be reduced by 55 to 78% during a typical year. Using the disconnection hierarchy developed by the authors, the feasibility of retrofit SuDS deployment within the case study catchment is assessed, and the implications discussed. PMID:22699330

  16. Amperometric oxygen sensor based on a platinum nanoparticle-modified polycrystalline boron doped diamond disk electrode.

    PubMed

    Hutton, Laura; Newton, Mark E; Unwin, Patrick R; Macpherson, Julie V

    2009-02-01

    Pt nanoparticle (NP)-modified polycrystalline boron-doped diamond (pBDD) disk electrodes have been fabricated and employed as amperometric sensors for the determination of dissolved oxygen concentration in aqueous solution. pBDD columns were cut using laser micromachining techniques and sealed in glass, in order to make disk electrodes which were then characterized electrochemically. Electrodeposition of Pt onto the diamond electrodes was optimized so as to give the maximum oxygen reduction peak current with the lowest background signal. Pt NPs, >0-10 nm diameter, were found to deposit randomly across the pBDD electrode, with no preference for grain boundaries. The more conductive grains were found to promote the formation of smaller nanoparticles at higher density. With the use of potential step chronoamperometry, in which the potential was stepped to a diffusion-limited value, a four electron oxygen reduction process was found to occur at the Pt NP-modified pBDD electrode. Furthermore the chronoamperometric response scaled linearly with dissolved oxygen concentration, varied by changing the oxygen/nitrogen ratio of gas flowed into solution. The sensor was used to detect dissolved oxygen concentrations with high precision over the pH range 4-10. PMID:19117391

  17. Differential contractile actions of reactive oxygen species on rat aorta: selective activation of ATP receptor by H2O2.

    PubMed

    Shen, J Z; Zheng, X F; Kwan, C Y

    2000-04-14

    This study aims to examine the effects of different reactive oxygen species (ROS) on the resting tension of endothelium-denuded rat aortic rings. In these preparations, H2O2 (30 microM) induced a fast and transient contraction, which could be abolished by pretreatment of catalase (800 U/ml), but not affected by superoxide anion scavenger, superoxide dismutase (SOD; 150 U/ml) or the hydroxyl free radical scavenger, DMSO/mannitol (each 3 mM). In contrast, pyrogallol, a putative superoxide anion donor, induced a biphasic contraction, which could be abolished by SOD, but not by catalase or DMSO/mannitol. Unlike H2O2 and pyrogallol, Vitamin C(VitC)/Fe2+ (each 100 microM), a commonly used hydroxyl radical-generating system, triggered a tonic contraction which could be prevented by DMSO/mannitol, but not by SOD or catalase. Interestingly, H2O2-induced contraction could be concentration-dependently (10-100 microM) inhibited by suramin and reactive blue-2 (RB-2), two widely used ATP receptor antagonists. On the other hand, suramin or RB-2, at concentration up to 100 microM, affected neither pyrogallol nor VitC/Fe2+-induced contraction. In conclusion, we showed for the first time that different ROS could contract rat aorta with different mechanisms of action, and H2O2 elicits a transient contraction probably as a result of the ATP receptor activation. PMID:10823352

  18. Dynamic and selective HERV RNA expression in neuroblastoma cells subjected to variation in oxygen tension and demethylation.

    PubMed

    Hu, Lijuan; Uzhameckis, Dmitrijs; Hedborg, Fredrik; Blomberg, Jonas

    2016-01-01

    We studied HERV expression in cell lines after hypoxia, mitogenic stimulation, and demethylation, to better understand if hypoxia may play a role in ERV activation also within the nervous system, as represented by neuroblastoma cell lines. The level of RNA of four human ERV groups (HERVs) (HERVE, I/T, H, and W), and three housekeeping genes, of different cell lines including A549, COS-1, Namalwa, RD-L and Vero-E6, as well as human neuroblastoma cell lines SH-SY5Y, SK-N-DZ, and SK-N-AS were studied using reverse transcription and real-time quantitative PCR (QPCR). During the course of recovery from hypoxia a pronounced and selective activation of RNA expression of HERVW-like sequences, but not of HERVE, I/T, H, and three housekeeping genes, was found in the neuroblastoma cell lines, most pronounced in SK-N-DZ. In the SK-N-DZ cell line, we also tested the expression of HERVs after chemical treatments. HERVW-like sequences were selectively upregulated by 5-azacytidine, a demethylating agent. Some HERVW loci seem especially responsive to hypoxia and demethylation. HERV expression in neuroblastoma cells is selectively and profoundly influenced by some physiological and chemical stimuli. PMID:26818268

  19. Synthesis, characterization and biological relevance of some metal (II) complexes with oxygen, nitrogen and oxygen (ONO) donor Schiff base ligand derived from thiazole and 2-hydroxy-1-naphthaldehyde

    NASA Astrophysics Data System (ADS)

    Nagesh, G. Y.; Mruthyunjayaswamy, B. H. M.

    2015-04-01

    The novel Schiff base ligand 2-((2-hydroxynaphthalen-1-yl)methylene)-N-(4-phenylthiazol-2-yl)hydrazinecarboxamide (L) obtained by the condensation of N-(4-phenylthiazol-2-yl)hydrazinecarboxamide with 2-hydroxy-1-naphthaldehyde and its newly synthesized Cu(II), Co(II), Ni(II), Zn(II) and Cd(II) complexes have been characterized by microanalysis, molar conductance, IR, 1H NMR, ESI-mass, UV-Visible, TGA/DTA, ESR and powder X-ray diffraction data to explicate their structures. The IR results confirmed the tridentate binding of the ligand involving oxygen atom of amide carbonyl, azomethine nitrogen and naphthol oxygen. 1H NMR spectral data of the ligand (L) and its Zn(II) complex agreed well with the proposed structures. Thermogravimetric studies for Cu(II) and Ni(II) complexes indicated the presence of coordinated water molecules and the final product is the metal oxide. In order to appraise the effect of antimicrobial activity of metal ions upon chelation, the newly synthesized ligand and its metal complexes were screened for their antimicrobial activity by minimum inhibitory concentration (MIC) method. The DNA cleavage activities were studied using plasmid DNA pBR322 (Bangal re Genei, Bengaluru, Cat. No 105850) as a target molecule by agarose gel electrophoresis method. The brine shrimp bioassay was also carried out to study the in vitro cytotoxicity properties against Artemia salina. Furthermore, the antioxidant activity were determined in vitro by reduction of 1,1-diphenyl-2-picryl hydrazyl (DPPH). The ligand exhibited better in vitro-antioxidant activity than its metal complexes.

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

    PubMed

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

    2009-07-21

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

  1. What is the contribution of human FMO3 in the N-oxygenation of selected therapeutic drugs and drugs of abuse?

    PubMed

    Wagmann, Lea; Meyer, Markus R; Maurer, Hans H

    2016-09-01

    Little is known about the role of flavin-containing monooxygenases (FMOs) in the metabolism of xenobiotics. FMO3 is the isoform in adult human liver with the highest impact on drug metabolism. The aim of the presented study was to elucidate the contribution of human FMO3 to the N-oxygenation of selected therapeutic drugs and drugs of abuse (DOAs). Its contribution to the in vivo hepatic net clearance of the N-oxygenation products was calculated by application of an extended relative activity factor (RAF) approach to differentiate from contribution of cytochrome P450 (CYP) isoforms. FMO3 and CYP substrates were identified using pooled human liver microsomes after heat inactivation and chemical inhibition, or single enzyme incubations. Kinetic parameters were subsequently determined using recombinant human enzymes and mass spectrometric analysis via authentic reference standards or simple peak areas of the products divided by those of the internal standard. FMO3 was identified as enzyme mainly responsible for the formation of N,N-diallyltryptamine N-oxide and methamphetamine hydroxylamine (>80% contribution for both). A contribution of 50 and 30% was calculated for the formation of N,N-dimethyltryptamine N-oxide and methoxypiperamide N-oxide, respectively. However, FMO3 contributed with less than 5% to the formation of 3-bromomethcathinone hydroxylamine, amitriptyline N-oxide, and clozapine N-oxide. There was no significant difference in the contributions when using calibrations with reference metabolite standards or peak area ratio calculations. The successful application of a modified RAF approach including FMO3 proved the importance of FMO3 in the N-oxygenation of DOAs in human metabolism. PMID:27320963

  2. Teaching topography-based and selection-based verbal behavior to developmentally disabled individuals: Some considerations

    PubMed Central

    Shafer, Esther

    1993-01-01

    Augmentative and alternative communication systems are widely recommended for nonvocal developmentally disabled individuals, with selection-based systems becoming increasingly popular. However, theoretical and experimental evidence suggests that topography-based communication systems are easier to learn. This paper discusses research relevant to the ease of acquisition of topography-based and selection-based systems. Additionally, current practices for choosing and designing communication systems are reviewed in order to investigate the extent to which links have been made with available theoretical and experimental knowledge. A stimulus equivalence model is proposed as a clearer direction for practitioners to follow when planning a communication training program. Suggestions for future research are also offered. PMID:22477085

  3. Effects of Temperature, Oxygen Partial Pressure, and Materials Selection on Slag Infiltration into Porous Refractories for Entrained-Flow Gasifiers

    NASA Astrophysics Data System (ADS)

    Kaneko, Tetsuya Kenneth

    The penetration rate of molten mineral contents (slag) from spent carbonaceous feedstock into porous ceramic-oxide refractory linings is a critical parameter in determining the lifecycle of integrated gasification combined cycle energy production plants. Refractory linings that withstand longer operation without interruption are desirable because they can mitigate consumable and maintenance costs. Although refractory degradation has been extensively studied for many other high-temperature industrial processes, this work focuses on the mechanisms that are unique to entrained-flow gasification systems. The use of unique feedstock mixtures, temperatures from 1450 °C to 1600 °C, and oxygen partial pressures from 10-7 atm to 10-9 atm pose engineering challenges in designing an optimal refractory material. Experimentation, characterization, and modeling show that gasifier slag infiltration into porous refractory is determined by interactions between the slag and the refractory that either form a physical barrier that impedes fluid flow or induce an increased fluid viscosity that decelerates the velocity of the fluid body. The viscosity of the slag is modified by the thermal profile of the refractory along the penetration direction as well as reactions between the slag and refractory that alter the chemistry, and thereby the thermo-physical properties of the fluid. Infiltration experiments reveal that the temperature gradient inherently present along the refractory lining limits penetration. A refractory in near-isothermal conditions demonstrates deeper slag penetration as compared to one that experiences a steeper thermal profile. The decrease in the local temperatures of the slag as it travels deeper into the refractory increases the viscosity of the fluid, which in turn slows the infiltration velocity of fluid body into the pores of the refractory microstructure. With feedstock mixtures that exhibit high iron-oxide concentrations, a transition-metal-oxide, the oxygen

  4. Role of silver current collector on the operational stability of selected cobalt-containing oxide electrodes for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Chen, Yubo; Wang, Fucun; Chen, Dengjie; Dong, Feifei; Park, Hee Jung; Kwak, Chan; Shao, Zongping

    2012-07-01

    The long-term stability for oxygen reduction reaction (ORR) of two typical perovskite cathode materials of SOFCs, i.e., Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) and Sm0.5Sr0.5CoO3-δ (SSC), is investigated in a symmetric cell configuration under air condition at 700 °C using Sm0.2Ce0.8O1.9 (SDC) electrolyte substrate and silver current collectors. Moreover, two different methods of silver current collection are tested, i.e., whole electrode surface deposited with a diluted silver paste (CC-01) and a mesh-like current collector using concentrated silver paste (CC-02). Electrochemical impedance spectra are applied for stability investigations. With the CC-01 current collector, the performance of the electrode deteriorates significantly, although the initial performance is good. By contrast, fairly stable performance is obtained from symmetric cells with either BSCF or SSC + SDC electrodes using the CC-02 current collector, even though a phase transition is observed for BSCF. For instance, after approximately 800 h of continuous stability testing, the area-specific resistance of the BSCF electrode retains a value of approximately 0.065 Ω cm2, except for a slight fluctuation within the range of 0.06-0.07 Ω cm2. These findings reveal that both BSCF and SSC can be stably operated for ORR under symmetric cell conditions; however, an appropriate current collection method is crucial to achieving stable performance.

  5. Possible roles of plant sulfurtransferases in detoxification of cyanide, reactive oxygen species, selected heavy metals and arsenate.

    PubMed

    Most, Parvin; Papenbrock, Jutta

    2015-01-01

    Plants and animals have evolved various potential mechanisms to surmount the adverse effects of heavy metal toxicity. Plants possess low molecular weight compounds containing sulfhydryl groups (-SH) that actively react with toxic metals. For instance, glutathione (γ-Glu-Cys-Gly) is a sulfur-containing tripeptide thiol and a substrate of cysteine-rich phytochelatins (γ-Glu-Cys)2-11-Gly (PCs). Phytochelatins react with heavy metal ions by glutathione S-transferase in the cytosol and afterwards they are sequestered into the vacuole for degradation. Furthermore, heavy metals induce reactive oxygen species (ROS), which directly or indirectly influence metabolic processes. Reduced glutathione (GSH) attributes as an antioxidant and participates to control ROS during stress. Maintenance of the GSH/GSSG ratio is important for cellular redox balance, which is crucial for the survival of the plants. In this context, sulfurtransferases (Str), also called rhodaneses, comprise a group of enzymes widely distributed in all phyla, paving the way for the transfer of a sulfur atom from suitable sulfur donors to nucleophilic sulfur acceptors, at least in vitro. The best characterized in vitro reaction is the transfer of a sulfane sulfur atom from thiosulfate to cyanide, leading to the formation of sulfite and thiocyanate. Plants as well as other organisms have multi-protein families (MPF) of Str. Despite the presence of Str activities in many living organisms, their physiological role has not been clarified unambiguously. In mammals, these proteins are involved in the elimination of cyanide released from cyanogenic compounds. However, their ubiquity suggests additional physiological functions. Furthermore, it is speculated that a member of the Str family acts as arsenate reductase (AR) and is involved in arsenate detoxification. In summary, the role of Str in detoxification processes is still not well understood but seems to be a major function in the organism. PMID:25594348

  6. Toward understanding the selective anticancer capacity of cold atmospheric plasma--a model based on aquaporins (Review).

    PubMed

    Yan, Dayun; Talbot, Annie; Nourmohammadi, Niki; Sherman, Jonathan H; Cheng, Xiaoqian; Keidar, Michael

    2015-01-01

    Selectively treating tumor cells is the ongoing challenge of modern cancer therapy. Recently, cold atmospheric plasma (CAP), a near room-temperature ionized gas, has been demonstrated to exhibit selective anticancer behavior. However, the mechanism governing such selectivity is still largely unknown. In this review, the authors first summarize the progress that has been made applying CAP as a selective tool for cancer treatment. Then, the key role of aquaporins in the H2O2 transmembrane diffusion is discussed. Finally, a novel model, based on the expression of aquaporins, is proposed to explain why cancer cells respond to CAP treatment with a greater rise in reactive oxygen species than homologous normal cells. Cancer cells tend to express more aquaporins on their cytoplasmic membranes, which may cause the H2O2 uptake speed in cancer cells to be faster than in normal cells. As a result, CAP treatment kills cancer cells more easily than normal cells. Our preliminary observations indicated that glioblastoma cells consumed H2O2 much faster than did astrocytes in either the CAP-treated or H2O2-rich media, which supported the selective model based on aquaporins. PMID:26700469

  7. Tuning the reactivity of oxygen/sulfur by acidity of the catalyst in Prins cyclization: oxa- versus thia-selectivity.

    PubMed

    Reddy, B V Subba; Venkateswarlu, A; Borkar, Prashant; Yadav, J S; Sridhar, B; Grée, René

    2014-03-21

    An unprecedented oxa- versus thia-selectivity has been observed in Prins cyclization of 6-mercaptohex-3-en-1-ol with aldehydes. In the presence of a stoichiometric amount of strong Lewis or Brønsted acids, the reaction provides the hexahydro-2H-thieno[3,2-c]pyran skeleton predominantly via oxonium-Prins cyclization. In contrast, a catalytic amount of weak Lewis or Brønsted acids provides the hexahydro-2H-thiopyrano[4,3-b]furan preferentially through thionium-Prins cyclization. PMID:24564269

  8. The selectivity of water-based pyrophosphate recognition is tuned by metal substitution in dimetallic receptors.

    PubMed

    Svane, Simon; Kjeldsen, Frank; McKee, Vickie; McKenzie, Christine J

    2015-07-14

    The three dimetallic compounds [Ga2(bpbp)(OH)2(H2O)2](ClO4)3, [In2(bpbp)(CH3CO2)2](ClO4)3 and [Zn2(bpbp)(HCO2)2](ClO4) (bpbp(-) = 2,6-bis((N,N'-bis(2-picolyl)amino)methyl)-4-tertbutylphenolate) were evaluated as stable solid state precursors for reactive solution state receptors to use for the recognition of the biologically important anion pyrophosphate in water at neutral pH. Indicator displacement assays using in situ generated complex-pyrocatechol violet adducts, {M2(bpbp)(HxPV)}(n+) M = Ga(3+), In(3+), Zn(2+), were tested for selectivity in their reactions with a series of common anions: pyrophosphate, phosphate, ATP, arsenate, nitrate, perchlorate, chloride, sulfate, formate, carbonate and acetate. The receptor employing Ga(3+) showed a slow but visually detectable response (blue to yellow) in the presence of one equivalent of pyrophosphate but no response to any other anion, even when they were present in much higher concentrations. The systems based on In(3+) or Zn(2+) show less selectivity in accord with visibly discernible responses to several of the anions. These results demonstrate a facile method for increasing anion selectivity without modification of an organic dinucleating ligand scaffold. The comfortable supramolecular recognition of pyrophosphate by the dimetallic complexes is demonstrated by the single crystal X-ray structure of [Ga2(bpbp)(HP2O7)](ClO4)2 in which the pyrophosphate is coordinated to the two gallium ions via four of its oxygen atoms. PMID:26057368

  9. Bioremediation of groundwater contaminated with gasoline hydrocarbons and oxygenates using a membrane-based reactor.

    PubMed

    Zein, Maher M; Suidan, Makram T; Venosa, Albert D

    2006-03-15

    The objective of this study was to operate a novel, field-scale, aerobic bioreactor and assess its performance in the ex situ treatment of groundwater contaminated with gasoline from a leaking underground storage tank in Pascoag, RI. The groundwater contained elevated concentrations of MTBE (methyl tert-butyl ether), TBA (tert-butyl alcohol), TBF (tert-butyl formate), BTEX (benzene, toluene, ethyl benzene, and xylene isomers), and other gasoline additives (tert-amyl methyl ether, di-isopropyl ether, tert-amyl alcohol, methanol, and acetone). The bioreactor was a gravity-flow membrane-based system called a Biomass Concentrator Reactor (BCR) designed to retain all biomass within the reactor. It was operated for six months at an influent flow rate that ultimately reached 5 gpm. The goal was to achieve a removal of all contaminants to <5 microg/L, which is the California Drinking Water advisory for MTBE. The concentration of TBA, an MTBE biodegradation byproduct, was consistently lower than that of MTBE. The other daughter compound detected in the influent, TBF, was degraded to concentrations below the detection limit of 0.02 microg/L. BTEX were consistently degraded to significantly lower levels in the effluent throughout the duration of the study (<1 microg/L). A similar high removal efficiency of the other gasoline oxygenates present in the groundwater (TAME, DIPE, and TAA) was also achieved. Dissolved organic carbon analysis demonstrated the ability of the bioreactor to produce high quality effluents with nonpurgeable organic carbon (NPOC) averaging approximately 50% lowerthan the NPOC concentrations in the influent contaminated groundwater. PMID:16570627

  10. Physical properties of hemoglobin-poly(acrylamide) hydrogel-based oxygen carriers: effect of reaction pH.

    PubMed

    Patton, Jaqunda N; Palmer, Andre F

    2006-02-28

    This work examines the physical properties of bovine hemoglobin (BHb) chemically cross-linked to a pH responsive polymer (poly(acrylamide)) with the goal of taking advantage of the polymer's pH sensitivity to generate low-P50 oxygen carriers for application in physiological conditions characterized by deviations from normal pH. BHb-hydrogel-based oxygen carriers encapsulating 10-16 g/dL BHb displayed P50s < 10 mmHg when encapsulated inside of liposomes (i.e. Hb-LGs) and <15 mmHg in the absence of a lipid bilayer (i.e. Hb-NHPs), when synthesized at pHs less than normal physiological pH. The results of this work suggest that synthesis of Hb-LGs/Hb-NHPs under different pH conditions affect the ionization of BHb and the flexibility of the polymer chains to which BHb is chemically cross-linked. The degree of BHb cross-linking to the polymer matrix and the chain flexibility of the polymer influences the oxygen affinity and cooperativity of the oxygen carrier by influencing how easy it is for the Hb molecule to change conformations between the R and T states. The magnitude of the zeta potential of Hb-LGs and Hb-NHPs was shown to be within the range of stored red blood cells and within the range of limited flocculation. Taken together, this work describes the preparation and characterization of oxygen carriers with increased oxygen affinities compared to those of red blood cells. PMID:16489809

  11. Advances toward commercialization of a new generation of low cost (O)LED-based dissolved oxygen and bioanalyte monitors

    NASA Astrophysics Data System (ADS)

    Smith, Alex; Cai, Yuankun; Vengasandra, Srikanth; Shinar, Ruth; Shinar, Joseph

    2010-08-01

    Recent advances toward commercialization of a new generation of low-cost LED- and OLED-based monitors for dissolved oxygen (DO), and multiple (bio)analytes such as glucose, lactate, alcohol, and cholesterol are described. The design of the DO monitors, which contain no optical fibers, filters, mirrors, or lens, is significantly simpler and consequently lower-cost than that of commercial LED-based DO monitors. The multiple (bio)analyte monitors are based on a DO monitor and the oxidase enzyme specific to each analyte. The potential advantages and disadvantages of the OLED- vs LED-based monitors is also discussed.

  12. Insights into an autonomously formed oxygen-evacuated Cu2O electrode for the selective production of C2H4 from CO2.

    PubMed

    Kim, Dahee; Lee, Seunghwa; Ocon, Joey D; Jeong, Beomgyun; Lee, Jae Kwang; Lee, Jaeyoung

    2015-01-14

    Electrochemical conversion of carbon dioxide (CO2) to small organic fuels (e.g. formate, methanol, ethylene, ethanol) is touted as one of the most promising approaches for solving the problems of climate change and energy security. In this study, we report the highly efficient electrochemical reduction of CO2 using cuprous oxide (Cu2O) electrodes to produce ethylene (C2H4) primarily. During CO2 electrolysis using electrodeposited Cu2O on a carbon electrode, we observe the transformation of a compact metal oxide layer to a metal oxide structure with oxygen vacant sites at the bulk region. In contrast to previous studies, our results clearly indicate that Cu2O remains at the surface of the catalyst and it efficiently catalyzes the conversion process of CO2 at low overpotential, exhibiting a high selective faradaic efficiency of over 20% towards C2H4 formation even in long-term electrolysis. PMID:25297636

  13. Towards Identify Selective Antibacterial Peptides Based on Abstracts Meaning

    PubMed Central

    Barbosa-Santillán, Liliana I.; Sánchez-Escobar, Juan J.; Calixto-Romo, M. Angeles; Barbosa-Santillán, Luis F.

    2016-01-01

    We present an Identify Selective Antibacterial Peptides (ISAP) approach based on abstracts meaning. Laboratories and researchers have significantly increased the report of their discoveries related to antibacterial peptides in primary publications. It is important to find antibacterial peptides that have been reported in primary publications because they can produce antibiotics of different generations that attack and destroy the bacteria. Unfortunately, researchers used heterogeneous forms of natural language to describe their discoveries (sometimes without the sequence of the peptides). Thus, we propose that learning the words meaning instead of the antibacterial peptides sequence is possible to identify and predict antibacterial peptides reported in the PubMed engine. The ISAP approach consists of two stages: training and discovering. ISAP founds that the 35% of the abstracts sample had antibacterial peptides and we tested in the updated Antimicrobial Peptide Database 2 (APD2). ISAP predicted that 45% of the abstracts had antibacterial peptides. That is, ISAP found that 810 antibacterial peptides were not classified like that, so they are not reported in APD2. As a result, this new search tool would complement the APD2 with a set of peptides that are candidates to be antibacterial. Finally, 20% of the abstracts were not semantic related to APD2. PMID:27366202

  14. Bayesian Model Selection with Network Based Diffusion Analysis.

    PubMed

    Whalen, Andrew; Hoppitt, William J E

    2016-01-01

    A number of recent studies have used Network Based Diffusion Analysis (NBDA) to detect the role of social transmission in the spread of a novel behavior through a population. In this paper we present a unified framework for performing NBDA in a Bayesian setting, and demonstrate how the Watanabe Akaike Information Criteria (WAIC) can be used for model selection. We present a specific example of applying this method to Time to Acquisition Diffusion Analysis (TADA). To examine the robustness of this technique, we performed a large scale simulation study and found that NBDA using WAIC could recover the correct model of social transmission under a wide range of cases, including under the presence of random effects, individual level variables, and alternative models of social transmission. This work suggests that NBDA is an effective and widely applicable tool for uncovering whether social transmission underpins the spread of a novel behavior, and may still provide accurate results even when key model assumptions are relaxed. PMID:27092089

  15. Towards Identify Selective Antibacterial Peptides Based on Abstracts Meaning.

    PubMed

    Barbosa-Santillán, Liliana I; Sánchez-Escobar, Juan J; Calixto-Romo, M Angeles; Barbosa-Santillán, Luis F

    2016-01-01

    We present an Identify Selective Antibacterial Peptides (ISAP) approach based on abstracts meaning. Laboratories and researchers have significantly increased the report of their discoveries related to antibacterial peptides in primary publications. It is important to find antibacterial peptides that have been reported in primary publications because they can produce antibiotics of different generations that attack and destroy the bacteria. Unfortunately, researchers used heterogeneous forms of natural language to describe their discoveries (sometimes without the sequence of the peptides). Thus, we propose that learning the words meaning instead of the antibacterial peptides sequence is possible to identify and predict antibacterial peptides reported in the PubMed engine. The ISAP approach consists of two stages: training and discovering. ISAP founds that the 35% of the abstracts sample had antibacterial peptides and we tested in the updated Antimicrobial Peptide Database 2 (APD2). ISAP predicted that 45% of the abstracts had antibacterial peptides. That is, ISAP found that 810 antibacterial peptides were not classified like that, so they are not reported in APD2. As a result, this new search tool would complement the APD2 with a set of peptides that are candidates to be antibacterial. Finally, 20% of the abstracts were not semantic related to APD2. PMID:27366202

  16. Terahertz wave filter based on frequency-selective surface structure

    NASA Astrophysics Data System (ADS)

    Sun, Chao; Li, Jiu-sheng

    2011-11-01

    Terahertz radiations, which refer to the frequencies from 100GHz to 10THz, lie in the frequency gap between the infrared and microwave, have received considerable attention during the past decades. Due to their special prosperties, THz radiations have been applied in many fields such as gases, semiconductors, explosives materials, and environment pollutants. The technique is based on recording the time dependence of the electric field of a short electromagnetic pulse transmitted through a sample. The ratio of the Fourier transforms of the data recorded with and without the sample yields the complex transmission coefficient of the sample in the frequency domain. The absorption coefficient and the refractive index of the material studied are directly related to the amplitude and phase respectively of the transmitted field. Terahertz wave filter, a frequency-selective surface structure, has been characterized by terahertz time-domain spectroscopy in the region from 0.1 to 3THz. We have compared THz-TDS measurement and calculation results of the mode-matching theory of the terahertz wave filter, and find that the two data sets agree very closely. The peak of the transmittance of about 90.5%occurs at 0.45THz for the first case and the peak of the transmittance of about 89.4% occurs at 0.79THz for the second case.

  17. Towards an Automatic and Application-Based EigensolverSelection

    SciTech Connect

    Zhang, Yeliang; Li, Xiaoye S.; Marques, Osni

    2005-09-09

    The computation of eigenvalues and eigenvectors is an important and often time-consuming phase in computer simulations. Recent efforts in the development of eigensolver libraries have given users good algorithms without the need for users to spend much time in programming. Yet, given the variety of numerical algorithms that are available to domain scientists, choosing the ''best'' algorithm suited for a particular application is a daunting task. As simulations become increasingly sophisticated and larger, it becomes infeasible for a user to try out every reasonable algorithm configuration in a timely fashion. Therefore, there is a need for an intelligent engine that can guide the user through the maze of various solvers with various configurations. In this paper, we present a methodology and a software architecture aiming at determining the best solver based on the application type and the matrix properties. We combine a decision tree and an intelligent engine to select a solver and a preconditioner combination for the application submitted by the user. We also discuss how our system interface is implemented with third party numerical libraries. In the case study, we demonstrate the feasibility and usefulness of our system with a simplified linear solving system. Our experiments show that our proposed intelligent engine is quite adept in choosing a suitable algorithm for different applications.

  18. Bayesian predictive modeling for genomic based personalized treatment selection.

    PubMed

    Ma, Junsheng; Stingo, Francesco C; Hobbs, Brian P

    2016-06-01

    Efforts to personalize medicine in oncology have been limited by reductive characterizations of the intrinsically complex underlying biological phenomena. Future advances in personalized medicine will rely on molecular signatures that derive from synthesis of multifarious interdependent molecular quantities requiring robust quantitative methods. However, highly parameterized statistical models when applied in these settings often require a prohibitively large database and are sensitive to proper characterizations of the treatment-by-covariate interactions, which in practice are difficult to specify and may be limited by generalized linear models. In this article, we present a Bayesian predictive framework that enables the integration of a high-dimensional set of genomic features with clinical responses and treatment histories of historical patients, providing a probabilistic basis for using the clinical and molecular information to personalize therapy for future patients. Our work represents one of the first attempts to define personalized treatment assignment rules based on large-scale genomic data. We use actual gene expression data acquired from The Cancer Genome Atlas in the settings of leukemia and glioma to explore the statistical properties of our proposed Bayesian approach for personalizing treatment selection. The method is shown to yield considerable improvements in predictive accuracy when compared to penalized regression approaches. PMID:26575856

  19. Terahertz wave filter based on frequency-selective surface structure

    NASA Astrophysics Data System (ADS)

    Sun, Chao; Li, Jiu-sheng

    2012-03-01

    Terahertz radiations, which refer to the frequencies from 100GHz to 10THz, lie in the frequency gap between the infrared and microwave, have received considerable attention during the past decades. Due to their special prosperties, THz radiations have been applied in many fields such as gases, semiconductors, explosives materials, and environment pollutants. The technique is based on recording the time dependence of the electric field of a short electromagnetic pulse transmitted through a sample. The ratio of the Fourier transforms of the data recorded with and without the sample yields the complex transmission coefficient of the sample in the frequency domain. The absorption coefficient and the refractive index of the material studied are directly related to the amplitude and phase respectively of the transmitted field. Terahertz wave filter, a frequency-selective surface structure, has been characterized by terahertz time-domain spectroscopy in the region from 0.1 to 3THz. We have compared THz-TDS measurement and calculation results of the mode-matching theory of the terahertz wave filter, and find that the two data sets agree very closely. The peak of the transmittance of about 90.5%occurs at 0.45THz for the first case and the peak of the transmittance of about 89.4% occurs at 0.79THz for the second case.

  20. Feature-based attention across saccades and immediate postsaccadic selection.

    PubMed

    Eymond, Cécile; Cavanagh, Patrick; Collins, Thérèse

    2016-07-01

    Before each eye movement, attentional resources are drawn to the saccade goal. This saccade-related attention is known to be spatial in nature, and in this study we asked whether it also evokes any feature selectivity that is maintained across the saccade. After a saccade toward a colored target, participants performed a postsaccadic feature search on an array displayed at landing. The saccade target either had the same color as the search target in the postsaccadic array (congruent trials) or a different color (incongruent or neutral trials). Our results show that the color of the saccade target did not prime the subsequent feature search. This suggests that "landmark search", the process of searching for the saccade target once the eye lands (Deubel in Visual Cognition, 11, 173-202, 2004), may not involve the attentional mechanisms that underlie feature search. We also analyzed intertrial effects and observed priming of pop-out (Maljkovic & Nakayama in Memory & Cognition, 22, 657-672, 1994) for the postsaccadic feature search: the detection of the color singleton became faster when its color was repeated on successive trials. However, search performance revealed no effect of congruency between the saccade and search targets, either within or across trials, suggesting that the priming of pop-out is specific to target repetitions within the same task and is not seen for repetitions across tasks. Our results support a dissociation between feature-based attention and the attentional mechanisms associated with eye movement programming. PMID:27084700

  1. Bayesian Model Selection with Network Based Diffusion Analysis

    PubMed Central

    Whalen, Andrew; Hoppitt, William J. E.

    2016-01-01

    A number of recent studies have used Network Based Diffusion Analysis (NBDA) to detect the role of social transmission in the spread of a novel behavior through a population. In this paper we present a unified framework for performing NBDA in a Bayesian setting, and demonstrate how the Watanabe Akaike Information Criteria (WAIC) can be used for model selection. We present a specific example of applying this method to Time to Acquisition Diffusion Analysis (TADA). To examine the robustness of this technique, we performed a large scale simulation study and found that NBDA using WAIC could recover the correct model of social transmission under a wide range of cases, including under the presence of random effects, individual level variables, and alternative models of social transmission. This work suggests that NBDA is an effective and widely applicable tool for uncovering whether social transmission underpins the spread of a novel behavior, and may still provide accurate results even when key model assumptions are relaxed. PMID:27092089

  2. A sterilization system using ultraviolet photochemical reactions based on nitrous oxide and oxygen gases.

    PubMed

    Ohnishi, Yasutaka; Matsumoto, Hiroyuki; Iwamori, Satoru

    2016-03-01

    Active oxygen species (AOS) generated under ultraviolet (UV) lamps can be applied for various industrial processes owing to extremely strong oxidative abilities. We have already reported on an application of the AOS for a sterilization process of microorganisms. Here, a sterilization method using active oxygen generated under ultraviolet (UV) lamps introducing nitrous oxide (N2O) and oxygen gases into a vacuum chamber was investigated. Nitrogen dioxide (NO2) gas was readily produced from N2O by UV photochemical reactions under the low-pressure mercury lamp and then used to sterilize medical devices. We compared the ability of the N2O gas to sterilize Geobacillus stearothermophilus spores with those of conventional methods. Successful sterilization of spores on various biological indicators was achieved within 60 min, not only in sterilization bags but also in a lumen device. PMID:26812575

  3. Light alkane conversion processes - Suprabiotic catalyst systems for selective oxidation of light alkane gases to fuel oxygenates.

    SciTech Connect

    Lyons, J.E.

    1992-07-01

    The objective of the work presented in this paper is to develop new, efficient catalysts for the selective transformation of the light alkanes in natural gas to alcohols for use as liquid transportation fuels, fuel precursors and chemical products. There currently exists no DIRECT one-step catalytic air-oxidation process to convert these substrates to alcohols. Such a one-step route would represent superior useful technology for the utilization of natural gas and similar refinery-derived light hydrocarbon streams. Processes for converting natural gas or its components (methane, ethane, propane, and the butanes) to alcohols for use as motor fuels, fuel additives or fuel precursors will not only add a valuable alternative to crude oil but will produce a clean-burning, high octane alternative to conventional gasoline.

  4. Light alkane conversion processes - Suprabiotic catalyst systems for selective oxidation of light alkane gases to fuel oxygenates

    SciTech Connect

    Lyons, J.E.

    1992-01-01

    The objective of the work presented in this paper is to develop new, efficient catalysts for the selective transformation of the light alkanes in natural gas to alcohols for use as liquid transportation fuels, fuel precursors and chemical products. There currently exists no DIRECT one-step catalytic air-oxidation process to convert these substrates to alcohols. Such a one-step route would represent superior useful technology for the utilization of natural gas and similar refinery-derived light hydrocarbon streams. Processes for converting natural gas or its components (methane, ethane, propane, and the butanes) to alcohols for use as motor fuels, fuel additives or fuel precursors will not only add a valuable alternative to crude oil but will produce a clean-burning, high octane alternative to conventional gasoline.

  5. Assumed oxygen consumption based on calculation from dye dilution cardiac output: an improved formula.

    PubMed

    Bergstra, A; van Dijk, R B; Hillege, H L; Lie, K I; Mook, G A

    1995-05-01

    This study was performed because of observed differences between dye dilution cardiac output and the Fick cardiac output, calculated from estimated oxygen consumption according to LaFarge and Miettinen, and to find a better formula for assumed oxygen consumption. In 250 patients who underwent left and right heart catheterization, the oxygen consumption VO2 (ml.min-1) was calculated using Fick's principle. Either pulmonary or systemic flow, as measured by dye dilution, was used in combination with the concordant arteriovenous oxygen concentration difference. In 130 patients, who matched the age of the LaFarge and Miettinen population, the obtained values of oxygen consumption VO2(dd) were compared with the estimated oxygen consumption values VO2(lfm), found using the LaFarge and Miettinen formulae. The VO2(lfm) was significantly lower than VO2(dd); -21.8 +/- 29.3 ml.min-1 (mean +/- SD), P < 0.001, 95% confidence interval (95% CI) -26.9 to -16.7, limits of agreement (LA) -80.4 to 36.9. A new regression formula for the assumed oxygen consumption VO2(ass) was derived in 250 patients by stepwise multiple regression analysis. The VO2(dd) was used as a dependent variable, and body surface area BSA (m2). Sex (0 for female, 1 for male), Age (years), Heart rate (min-1) and the presence of a left to right shunt as independent variables. The best fitting formula is expressed as: VO2(ass) = (157.3 x BSA + 10.0 x Sex - 10.5 x In Age + 4.8) ml.min-1, where ln Age = the natural logarithm of the age. This formula was validated prospectively in 60 patients. A non-significant difference between VO2(ass) and VO2(dd) was found; mean 2.0 +/- 23.4 ml.min-1, P = 0.771, 95% Cl = -4.0 to +8.0, LA -44.7 to +48.7. In conclusion, assumed oxygen consumption values, using our new formula, are in better agreement with the actual values than those found according to LaFarge and Miettinen's formulae. PMID:7588904

  6. Oxygen abundance distributions in six late-type galaxies based on SALT spectra of H II regions

    NASA Astrophysics Data System (ADS)

    Zinchenko, I. A.; Kniazev, A. Y.; Grebel, E. K.; Pilyugin, L. S.

    2015-10-01

    Spectra of 34 H ii regions in the late-type galaxies NGC 1087, NGC 2967, NGC 3023, NGC 4030, NGC 4123, and NGC 4517A were observed with the South African Large Telescope (SALT). In all 34 H ii regions, oxygen abundances were determined through the "counterpart" method (C method). Additionally, in two H ii regions in which we detected auroral lines, we measured oxygen abundances with the classic Te method. We also estimated the abundances in our H ii regions using the O3N2 and N2 calibrations and compared those with the C-based abundances. With these data, we examined the radial abundance distributions in the disks of our target galaxies. We derived surface-brightness profiles and other characteristics of the disks (the surface brightness at the disk center and the disk scale length) in three photometric bands for each galaxy using publicly available photometric imaging data. The radial distributions of the oxygen abundances predicted by the relation between abundance and disk surface brightness in the W1 band obtained for spiral galaxies in our previous study are close to the radial distributions of the oxygen abundances determined from the analysis of the emission line spectra for four galaxies where this relation is applicable. Hence, when the surface-brightness profile of a late-type galaxy is known, this parametric relation can be used to estimate the likely present-day oxygen abundance in the disk of the galaxy. Based on observations made with the Southern African Large Telescope, programs 2012-1-RSA_OTH-001, 2012-2-RSA_OTH-003 and 2013-1-RSA_OTH-005.

  7. Determining the Capacity of Time-Based Selection

    ERIC Educational Resources Information Center

    Watson, Derrick G.; Kunar, Melina A.

    2012-01-01

    In visual search, a set of distractor items can be suppressed from future selection if they are presented (previewed) before a second set of search items arrive. This "visual marking" mechanism provides a top-down way of prioritizing the selection of new stimuli, at the expense of old stimuli already in the field (Watson & Humphreys, 1997).…

  8. Association-Based Genomic Selection in Cultivated Barley

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In genomic selection, the effects of all markers are estimated on a training data set with marker genotypes and trait phenotypes. Genomic estimated breeding values (GEBV) are then calculated for any genotyped individual. We evaluated genomic selection using marker data from barley to determine, at m...

  9. Disposable nitrate-selective optical sensor based on fluorescent dye

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A simple, disposable thin-film optical nitrate sensor was developed. The sensor was fabricated by applying a nitrate-selective polymer membrane on the surface of a thin polyester film. The membrane was composed of polyvinylchloride (PVC), plasticizer, fluorescent dye, and nitrate-selective ionophore...

  10. The Role of Ir in Ternary Rh-Based Catalysts for Syngas Conversion to C2+ Oxygenates

    SciTech Connect

    Glezakou, Vassiliki Alexandra; Jaffe, John E.; Rousseau, Roger J.; Mei, Donghai; Kathmann, Shawn M.; Albrecht, Karl O.; Gray, Michel J.; Gerber, Mark A.

    2012-07-09

    Transition metal modified Rh-catalysts can be used for converting syngas (CO+H2) into C2+ oxygenates. It has been found that Mn has a favorable effect in the selectivity towards oxygenates, while addition of Ir to the binary Rh-Mn catalysts significantly increases the space-time yield of C2+ oxygenates. In this paper, we use quantum mechanical calculations to investigate the distribution of promoter sites within Rh rich nanoparticles and their role in the conversion of syngas towards ethanol. This work was supported by the U.S. Department of Energy (DOE), Office of Energy Efficiency and Renewable Energy Biomass Program. The Pacific Northwest National Laboratory (PNNL) is operated by Battelle for the DOE under Contract DE-AC05-76RL01830. A portion of the research was performed in the Environmental Molecular Sciences Laboratory (EMSL), a national science user facility sponsored by the Department of Energy’s Office of Biological and Environmental Research located at PNNL.

  11. Improved HBT performance by base width reduction and selective extrinsic base regrowth

    NASA Astrophysics Data System (ADS)

    Hsin, Yue-Ming

    Heterojunction bipolar transistors (HBTs) have many advantages, including high current gain, low base resistance, and high cutoff frequency (fsb{T}). For the further improvement of HBT performance, it is worthwhile to scale down device dimensions (in both vertical and lateral directions). The objective of this dissertation is to improve HBT performance by (1) using very thin base layers (down to 200A) which provide higher current gain and higher cutoff frequency; and (2) regrowing extrinsic base layers which provide lower base resistance and higher fsb{max}. This objective has been implemented by using very thin base width HBTs followed by extrinsic base regrowth to retain the advantages of thin base layers. One of the difficulties in lateral scaling of HBTs is associated with recombination at the edges of the emitter, which leads to reduced current gain in small devices. HBTs with base layer thickness scaled down to 200A were found to have both base surface recombination current and base bulk recombination current significantly lower than in comparable devices with greater base width. Base width reduction also reduces base transit time and thus increases fsb{T}. Undesirable side effects from base width reduction are increased base resistance and difficulty in accessing the thin base layer. It is shown this processing difficulty can be alleviated by using InGaP/GaAs layers to form HBTs instead of AlGaAs/GaAs layers, because of the excellent etching selectivity possible between InGaP and GaAs. Also fabricated InGaP/GaAs HBTs demonstrate significantly lower surface recombination current, since with selective etching solution the InGaP emitter layer can be removed, but etching stops on the thin GaAs base layer, resulting in less exposed base-emitter junction area. But thin base InGaP/GaAs HBTs still suffer from high base resistance. The problems of high base resistance and processing difficulty can be eliminated simultaneously by using external base regrowth to reduce

  12. A multisyringe flow injection Winkler-based spectrophotometric analyzer for in-line monitoring of dissolved oxygen in seawater.

    PubMed

    Horstkotte, Burkhard; Alonso, Juan Carlos; Miró, Manuel; Cerdà, Víctor

    2010-01-15

    An integrated analyzer based on the multisyringe flow injection analysis approach is proposed for the automated determination of dissolved oxygen in seawater. The entire Winkler method including precipitation of manganese(II) hydroxide, fixation of dissolved oxygen, dissolution of the oxidized manganese hydroxide precipitate, and generation of iodine and tri-iodide ion are in-line effected within the flow network. Spectrophotometric quantification of iodine and tri-iodide at the isosbestic wavelength of 466nm renders enhanced method reliability. The calibration function is linear up to 19mgL(-1) dissolved oxygen and an injection frequency of 17 per hour is achieved. The multisyringe system features a highly satisfying signal stability with repeatabilities of 2.2% RSD that make it suitable for continuous determination of dissolved oxygen in seawater. Compared to the manual starch-end-point titrimetric Winkler method and early reported automated systems, concentrations and consumption of reagents and sample are reduced up to hundredfold. The versatility of the multisyringe assembly was exploited in the implementation of an ancillary automatic batch-wise Winkler titrator using a single syringe of the module for accurate titration of the released iodine/tri-iodide with thiosulfate. PMID:20006097

  13. Prediction of In-Space Durability of Protected Polymers Based on Ground Laboratory Thermal Energy Atomic Oxygen

    NASA Technical Reports Server (NTRS)

    Banks, Bruce A.; deGroh, Kim K.; Rutledge, Sharon; DiFilippo, Frank J.

    1996-01-01

    The probability of atomic oxygen reacting with polymeric materials is orders of magnitude lower at thermal energies (greater than O.1 eV) than at orbital impact energies (4.5 eV). As a result, absolute atomic oxygen fluxes at thermal energies must be orders of magnitude higher than orbital energy fluxes, to produce the same effective fluxes (or same oxidation rates) for polymers. These differences can cause highly pessimistic durability predictions for protected polymers and polymers which develop protective metal oxide surfaces as a result of oxidation if one does not make suitable calibrations. A comparison was conducted of undercut cavities below defect sites in protected polyimide Kapton samples flown on the Long Duration Exposure Facility (LDEF) with similar samples exposed in thermal energy oxygen plasma. The results of this comparison were used to quantify predicted material loss in space based on material loss in ground laboratory thermal energy plasma testing. A microindent hardness comparison of surface oxidation of a silicone flown on the Environmental Oxygen Interaction with Materials-III (EOIM-III) experiment with samples exposed in thermal energy plasmas was similarly used to calibrate the rate of oxidation of silicone in space relative to samples in thermal energy plasmas exposed to polyimide Kapton effective fluences.

  14. An imaging-based tumour growth and treatment response model: investigating the effect of tumour oxygenation on radiation therapy response

    NASA Astrophysics Data System (ADS)

    Titz, Benjamin; Jeraj, Robert

    2008-09-01

    A multiscale tumour simulation model employing cell-line-specific biological parameters and functional information derived from pre-therapy PET/CT imaging data was developed to investigate effects of different oxygenation levels on the response to radiation therapy. For each tumour voxel, stochastic simulations were performed to model cellular growth and therapeutic response. Model parameters were fitted to published preclinical experiments of head and neck squamous cell carcinoma (HNSCC). Using the obtained parameters, the model was applied to a human HNSCC case to investigate effects of different uniform and non-uniform oxygenation levels and results were compared for treatment efficacy. Simulations of the preclinical studies showed excellent agreement with published data and underlined the model's ability to quantitatively reproduce tumour behaviour within experimental uncertainties. When using a simplified transformation to derive non-uniform oxygenation levels from molecular imaging data, simulations of the clinical case showed heterogeneous tumour response and variability in radioresistance with decreasing oxygen levels. Once clinically validated, this model could be used to transform patient-specific data into voxel-based biological objectives for treatment planning and to investigate biologically optimized dose prescriptions.

  15. High impact of uranyl ions on carrying-releasing oxygen capability of hemoglobin-based blood substitutes.

    PubMed

    Duan, Li; Du, Lili; Jia, Yi; Liu, Wenyuan; Liu, Zhichao; Li, Junbai

    2015-01-01

    The effect of radioactive UO2 (2+) on the oxygen-transporting capability of hemoglobin-based oxygen carriers has been investigated in vitro. The hemoglobin (Hb) microspheres fabricated by the porous template covalent layer-by-layer (LbL) assembly were utilized as artificial oxygen carriers and blood substitutes. Magnetic nanoparticles of iron oxide (Fe3 O4 ) were loaded in porous CaCO3 particles for magnetically assisted chemical separation (MACS). Through the adsorption spectrum of magnetic Hb microspheres after adsorbing UO2 (2+) , it was found that UO2 (2+) was highly loaded in the magnetic Hb microspheres, and it shows that the presence of UO2 (2+) in vivo destroys the structure and oxygen-transporting capability of Hb microspheres. In view of the high adsorption capacity of UO2 (2+) , the as-assembled magnetic Hb microspheres can be considered as a novel, highly effective adsorbent for removing metal toxins from radiation-contaminated bodies, or from nuclear-power reactor effluent before discharge into the environment. PMID:25418690

  16. Metabolically Derived human ventilation rates: A revised approach based upon oxygen consumption rates (Final Report) 2009

    EPA Science Inventory

    The purpose of this report is to provide a revised approach for calculating an individual's ventilation rate directly from their oxygen consumption rate. This revised approach will be used to update the ventilation rate information in the Exposure Factors Handbook, which serve as...

  17. MICROPLATE-BASED OXYGEN RADICAL ABSORBANCE CAPACITY (ORAC) ASSAY OF HYDROPHILIC AND LIPOPHILIC COMPARTMENTS IN PLASMA

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Methods have been developed to evaluate the total antioxidant capacity of foods and plasma but limitations are associated with their ability to determine precisely the contribution of lipophilic antioxidants in a lipid milieu as well as interactions among them. Thus, we modified the Oxygen Radical ...

  18. CONTROL OF TRANSIENT INCINERATOR EMISSIONS WITH AN OXYGEN BASED COMBUSTION SYSTEM

    EPA Science Inventory

    The subject of this paper is the experience with a novel and field-proven method for the enhanced control of transient emissions from rotary kiln incinerators using oxygen enrichment. hen high-BTU content wastes are fed into rotary kiln incinerators in an intermittent mode (typic...

  19. FPGA-based RF spectrum merging and adaptive hopset selection

    NASA Astrophysics Data System (ADS)

    McLean, R. K.; Flatley, B. N.; Silvius, M. D.; Hopkinson, K. M.

    The radio frequency (RF) spectrum is a limited resource. Spectrum allotment disputes stem from this scarcity as many radio devices are confined to a fixed frequency or frequency sequence. One alternative is to incorporate cognition within a reconfigurable radio platform, therefore enabling the radio to adapt to dynamic RF spectrum environments. In this way, the radio is able to actively sense the RF spectrum, decide, and act accordingly, thereby sharing the spectrum and operating in more flexible manner. In this paper, we present a novel solution for merging many distributed RF spectrum maps into one map and for subsequently creating an adaptive hopset. We also provide an example of our system in operation, the result of which is a pseudorandom adaptive hopset. The paper then presents a novel hardware design for the frequency merger and adaptive hopset selector, both of which are written in VHDL and implemented as a custom IP core on an FPGA-based embedded system using the Xilinx Embedded Development Kit (EDK) software tool. The design of the custom IP core is optimized for area, and it can process a high-volume digital input via a low-latency circuit architecture. The complete embedded system includes the Xilinx PowerPC microprocessor, UART serial connection, and compact flash memory card IP cores, and our custom map merging/hopset selection IP core, all of which are targeted to the Virtex IV FPGA. This system is then incorporated into a cognitive radio prototype on a Rice University Wireless Open Access Research Platform (WARP) reconfigurable radio.

  20. Effects of Oxygen Element and Oxygen-Containing Functional Groups on Surface Wettability of Coal Dust with Various Metamorphic Degrees Based on XPS Experiment

    PubMed Central

    Zhou, Gang; Xu, Cuicui; Cheng, Weimin; Zhang, Qi; Nie, Wen

    2015-01-01

    To investigate the difference of surface oxygen element and oxygen-containing functional groups among coal dusts with different metamorphic degrees and their influence on surface wettability, a series of X-ray photoelectron spectroscopy experiments on 6 coal samples are carried out. The result demonstrates that the O/C ratio of coal surface shows an overall increasing trend compared with the result of its elements analysis. As the metamorphic degree increases, the O/C ratio on the surface gradually declines and the hydrophilic groups tend to fall off from coal surface. It could be found that different coals show different surface distributions of carboxyl and hydroxyl which are considered as the greatest promoter to the wettability of coal surface. With the change of metamorphic degree, the distribution of ether group is irregular while the carbonyl distribution keeps stable. In general, as the metamorphic degree goes higher, the content of oxygen-containing polar group tends to reduce. According to the measurement results, the contact angle is negatively related to the content of oxygen element, surface oxygen, and polar groups. In addition, compared with surface oxygen content, the content of oxygen-containing polar group serves as a more reasonable indicator of coal dust wettability. PMID:26257980

  1. Effects of Oxygen Element and Oxygen-Containing Functional Groups on Surface Wettability of Coal Dust with Various Metamorphic Degrees Based on XPS Experiment.

    PubMed

    Zhou, Gang; Xu, Cuicui; Cheng, Weimin; Zhang, Qi; Nie, Wen

    2015-01-01

    To investigate the difference of surface oxygen element and oxygen-containing functional groups among coal dusts with different metamorphic degrees and their influence on surface wettability, a series of X-ray photoelectron spectroscopy experiments on 6 coal samples are carried out. The result demonstrates that the O/C ratio of coal surface shows an overall increasing trend compared with the result of its elements analysis. As the metamorphic degree increases, the O/C ratio on the surface gradually declines and the hydrophilic groups tend to fall off from coal surface. It could be found that different coals show different surface distributions of carboxyl and hydroxyl which are considered as the greatest promoter to the wettability of coal surface. With the change of metamorphic degree, the distribution of ether group is irregular while the carbonyl distribution keeps stable. In general, as the metamorphic degree goes higher, the content of oxygen-containing polar group tends to reduce. According to the measurement results, the contact angle is negatively related to the content of oxygen element, surface oxygen, and polar groups. In addition, compared with surface oxygen content, the content of oxygen-containing polar group serves as a more reasonable indicator of coal dust wettability. PMID:26257980

  2. Artificial immune system based on adaptive clonal selection for feature selection and parameters optimisation of support vector machines

    NASA Astrophysics Data System (ADS)

    Sadat Hashemipour, Maryam; Soleimani, Seyed Ali

    2016-01-01

    Artificial immune system (AIS) algorithm based on clonal selection method can be defined as a soft computing method inspired by theoretical immune system in order to solve science and engineering problems. Support vector machine (SVM) is a popular pattern classification method with many diverse applications. Kernel parameter setting in the SVM training procedure along with the feature selection significantly impacts on the classification accuracy rate. In this study, AIS based on Adaptive Clonal Selection (AISACS) algorithm has been used to optimise the SVM parameters and feature subset selection without degrading the SVM classification accuracy. Several public datasets of University of California Irvine machine learning (UCI) repository are employed to calculate the classification accuracy rate in order to evaluate the AISACS approach then it was compared with grid search algorithm and Genetic Algorithm (GA) approach. The experimental results show that the feature reduction rate and running time of the AISACS approach are better than the GA approach.

  3. 34 CFR 75.209 - Selection criteria based on statutory provisions.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 34 Education 1 2012-07-01 2012-07-01 false Selection criteria based on statutory provisions. 75.209 Section 75.209 Education Office of the Secretary, Department of Education DIRECT GRANT PROGRAMS How Grants Are Made Selection of New Projects § 75.209 Selection criteria based on statutory provisions. (a) The Secretary may evaluate applications...

  4. Impact of Menu Sequencing on Internet-Based Educational Module Selection

    ERIC Educational Resources Information Center

    Bensley, Robert; Brusk, John J.; Rivas, Jason; Anderson, Judith V.

    2006-01-01

    Patterns of Internet-based menu item selection can occur for a number of reasons, many of which may not be based on interest in topic. It then becomes important to ensure menu order is devised in a way that ensures the greatest accuracy in matching user need with selection. This study examined the impact of menu rotation on the selection of…

  5. Observations of Oxygen Ion Behavior in the Lithium-Based Electrolytic Reduction of Uranium Oxide

    SciTech Connect

    Steven D. Herrmann; Shelly X. Li; Brenda E. Serrano-Rodriguez

    2009-09-01

    Parametric studies were performed on a lithium-based electrolytic reduction process at bench-scale to investigate the behavior of oxygen ions in the reduction of uranium oxide for various electrochemical cell configurations. Specifically, a series of eight electrolytic reduction runs was performed in a common salt bath of LiCl – 1 wt% Li2O. The variable parameters included fuel basket containment material (i.e., stainless steel wire mesh and sintered stainless steel) and applied electrical charge (i.e., 75 – 150% of the theoretical charge for complete reduction of uranium oxide in a basket to uranium metal). Samples of the molten salt electrolyte were taken at regular intervals throughout each run and analyzed to produce a time plot of Li2O concentrations in the bulk salt over the course of the runs. Following each run, the fuel basket was sectioned and the fuel was removed. Samples of the fuel were analyzed for the extent of uranium oxide reduction to metal and for the concentration of salt constituents, i.e., LiCl and Li2O. Extents of uranium oxide reduction ranged from 43 – 70% in stainless steel wire mesh baskets and 8 – 33 % in sintered stainless steel baskets. The concentrations of Li2O in the salt phase of the fuel product from the stainless steel wire mesh baskets ranged from 6.2 – 9.2 wt%, while those for the sintered stainless steel baskets ranged from 26 – 46 wt%. Another series of tests was performed to investigate the dissolution of Li2O in LiCl at 650 °C across various cathode containment materials (i.e., stainless steel wire mesh, sintered stainless steel and porous magnesia) and configurations (i.e., stationary and rotating cylindrical baskets). Dissolution of identical loadings of Li2O particulate reached equilibrium within one hour for stationary stainless steel wire mesh baskets, while the same took several hours for sintered stainless steel and porous magnesia baskets. Rotation of an annular cylindrical basket of stainless steel

  6. Oxygen isotopes in an oolitic ironstone and the determination of goethite. delta. sup 18 O values by selective dissolution of impurities: The 5 M NaOH method

    SciTech Connect

    Yapp, C.J. )

    1991-09-01

    Treatment of iron (III) oxides with hot 5 M NaOH solution can selectively dissolve silicate impurities (Kampf and Schwertmann, 1982). In the current work 5M NaOH solutions enriched in {sup 18}O (+670 {per thousand}) were employed to determine if this method could be used to purify goethites for {delta}{sup 18}O analysis. These experiments suggest that the structural stoichiometric oxygen in well-crystallized goethites does not exchange with hot 5 M NaOH solution. Therefore, this selective dissolution method appears to be isotopically viable. {sup 18}O- normal' 5 M NaOH treatments were applied to goethite-dominated ooids of the Upper Ordovician Neda Fm. ironstone. While not completely removed by successive NaOH treatments, the impurities were incrementally dissolved in constant elemental proportions (within analytical error). Consequently, the {delta}{sup 18}O value of the endmember goethite could be determined by material balance calculations. This goethite {delta}{sup 18} value is {minus}1.0{per thousand} for all analyzed samples of Neda Fm. ooids, including those from occurrences about 200 km apart. The spatial uniformity of the oolitic goethite {delta}{sup 18}O values suggest uniform conditions of goethite formation. The conditions might have been those of a low latitude continental weathering environment.

  7. Oxygen isotopes in an oolitic ironstone and the determination of goethite δ18O values by selective dissolution of impurities: The 5M NaOH method

    NASA Astrophysics Data System (ADS)

    Yapp, Crayton J.

    1991-09-01

    Treatment of iron (III) oxides with hot 5 M NaOH solution can selectively dissolve silicate impurities (KAMPF and SCHWERTMANN, 1982). In the current work 5M NaOH solutions enriched in 18O (+670%.) were employed to determine if this method could be used to purify goethites for δ18O analysis. These experiments suggest that the structural stoichiometric oxygen in well-crystallized goethites does not exchange with hot 5 M NaOH solution. Therefore, this selective dissolution method appears to be isotopically viable. 18O-"normal" 5 M NaOH treatments were applied to goethite-dominated ooids of the Upper Ordovician Neda Fm. ironstone. While not completely removed by successive NaOH treatments, the impurities were incrementally dissolved in constant elemental proportions (within analytical error). Consequently, the δ18O value of the endmember goethite could be determined by material balance calculations. This goethite δ18O value is -1.0%. for all analyzed samples of Neda Fm. ooids, including those from occurrences about 200 km apart. The spatial uniformity of the oolitic goethite δ18O values suggests uniform conditions of goethite formation. The conditions might have been those of a low latitude continental weathering environment.

  8. Mitochondrially Targeted Nanoparticles Based on α-TOS for the Selective Cancer Treatment.

    PubMed

    Palao-Suay, Raquel; Rodrigáñez, Laura; Aguilar, María Rosa; Sánchez-Rodríguez, Carolina; Parra, Francisco; Fernández, Mar; Parra, Juan; Riestra-Ayora, Juan; Sanz-Fernández, Ricardo; San Román, Julio

    2016-03-01

    The aim of this work is the preparation of an active nanovehicle for the effective administration of α-tocopheryl succinate (α-TOS). α-TOS is loaded in the core of nanoparticles (NPs) based on amphiphilic pseudo-block copolymers of N-vinyl pyrrolidone and a methacrylic derivative of α-TOS. These well-defined spherical NPs have sizes below 165 nm and high encapsulation efficiencies. In vitro activity of NPs is tested in hypopharynx squamous carcinoma (FaDu) cells and nonmalignant epithelial cells, demonstrating that the presence of additional α-TOS significantly enhances its antiproliferative activity; however, a range of selective concentrations is observed. These NPs induce apoptosis of FaDu cells by activating the mitochondria death pathway (via caspase-9). Both loaded and unloaded NPs act via complex II and produce high levels of reactive oxygen species that trigger apoptosis. Additionally, these NPs effectively suppress the vascular endothelial growth factor (VEGF) expression of human umbilical vein endothelial cells (HUVECs). These results open the possibility to use this promising nanoformulation as an α-TOS delivery system for the effective cancer treatment, effectively resolving the current limitations of free α-TOS administration. PMID:26632009

  9. Atomic oxygen interaction with spacecraft materials: Relationship between orbital and ground-based testing for materials certification

    SciTech Connect

    Cross, J.B. ); Koontz, S.L. . Lyndon B. Johnson Space Center); Lan, E.H. )

    1991-01-01

    The effects of atomic oxygen on boron nitride, silicon nitride, solar cell interconnects used on the Intelsat 6 satellite, organic polymers, and MoS{sub 2} and WS{sub 2} dry lubricant have been studied in low Earth orbit (LEO) flight experiments and in our ground-based simulation facility at Los Alamos National Laboratory. Both the in-flight and ground-based experiments employed in situ electrical resistance measurements to detect penetration of atomic oxygen through materials and ESCA analysis to measure chemical composition changes. In the presence of atomic oxygen, silver oxidizes to form silver oxide, which has a much higher electrical resistance than pure silver. Permeation of atomic oxygen through BN overcoated on thin silver was observed. No permeation of atomic oxygen through Si{sub 3}N{sub 4} was observed. Test results on the Intelsat 6 satellite interconnects used on its photovoltaic array indicate that more than 60--80% of the original thickness of silver should remain after completion of the proposed Space Shuttle rescue/reboost mission. Gas phase reaction products produced by the interaction of high kinetic energy atomic oxygen (AO) with Kapton were found to be H{sub 2}, H{sub 2}O, CO, and CO{sub 2} with NO being a possible secondary product. Hydrogen abstraction at high AO kinetic energy is postulated to be the key reaction controlling the erosion rate of Kapton. An Arrhenius-like expression having an activation barrier of 0.4 eV can be fit to the data, which suggests that the rate limiting step in the AO/Kapton reaction mechanism can be overcome by translational energy. Oxidation of MoS{sub 2} and WS{sub 2} dry lubricants in both ground-based and orbital exposures indicated the formation of MoO{sub 3} and WO{sub 3} respectively. A protective oxide layer is formed {approx}30 monolayers thick which has a high initial friction coefficient until the layer is worn off.

  10. Effect of pressure on the behavior of copper-, iron-, and nickel-based oxygen carriers for chemical-looping combustion

    SciTech Connect

    Francisco Garcia-Labiano; Juan Adanez; Luis F. de Diego; Pilar Gayan; Alberto Abad

    2006-02-01

    This work analyzes the main characteristics related to the chemical looping combustion (CLC) process necessary to use the syngas obtained in an integrated gasification combined cycle (IGCC) power plant. The kinetics of reduction with H{sub 2} and CO and oxidation with O{sub 2} of three high-reactivity oxygen carriers used in the CLC system have been determined in a thermogravimetric analyzer at atmospheric pressure. The iron- and nickel-based oxygen carriers were prepared by freeze-granulation, and the copper-based oxygen carrier was prepared by impregnation. The changing grain size model (CGSM) was used for the kinetic determination, assuming spherical grains for the freeze-granulated particles containing iron and nickel and a platelike geometry for the reacting surface of the copper-based impregnated particles. The dependence of the reaction rates on temperature was low, with the activation energy values varying from 14 to 33 kJ mol{sup -1} for the reduction and 7 to 15 kJ mol{sup -1} for the oxidation. The reaction order depended on the reacting gas and oxygen carrier, with values ranging from 0.25 to 1. However, an increase in the operating pressure for the IGCC + CLC system increases the thermal efficiency of the process, and the CO{sub 2} is recovered as a high pressure gas, decreasing the energy demand for further compression. The effect of pressure on the behavior of the oxygen carriers has been analyzed in a pressurized thermogravimetric analyzer at 1073 K and pressures up to 30 atm. It has been found that an increase in total pressure has a negative effect on the reaction rates of all the oxygen carriers. Moreover, the use of the CGSM with the kinetic parameters obtained at atmospheric pressure predicted higher reaction rates than those experimentally obtained at higher pressures, and therefore, the kinetic parameters necessary to design pressurized CLC plants must be determined at the operating pressure. 34 refs., 8 figs., 2 tabs.

  11. A knowledge-based system for materials selection

    SciTech Connect

    Trethewey, K.R.; Puget, Y.; Wood, R.J.K.; Roberge, P.R.

    1997-12-01

    Materials selection is a process obviously suitable for computerization. The growing list of available materials makes a choice increasingly susceptible to the vagaries of human decision making, as evidenced by the continued incidence of high corrosion costs and unacceptable failures. A methodology for computerization of the materials selection process is described and evaluated by an example involving the choice of a polymeric paint coating for seawater service.

  12. Oxygen electrode-based single antibody amperometric biosensor for qualitative detection of E. coli and bacteria in water.

    PubMed

    Theegala, Chandra S; Small, Danyelle D; Monroe, W Todd

    2008-04-01

    Design and performance of an amperometric biosensor for E. coli O157:H7 that is based on a common dissolved oxygen probe is discussed. Anti-E. coli O157:H7 antibody was conjugated to horseradish peroxidase and immobilized on a nitrocellulose membrane that was placed over the oxygen probe membrane using a custom-fabricated polyvinyl chloride (PVC) insert. Upon bacterial cell binding, a decrease in enzyme activity resulted in a change in oxygen concentration that was detected with a Clark-type oxygen electrode probe. Validation experiments determined the effect of the outer membrane and insert on the Clarke electrode performance and linearity, and the effects of stirring on sensor response. The mechanism of enzymatic disruption is presumably steric hindrance due to binding of the bacterial cell and conformational change in antibody structure. Sampling various dilutions of heat-sterilized E. coli O157:H7 cells in water, as little as 50 bacterial cells/mL could be detected in approximately 20 minutes of sampling and processing procedures. Bacterial concentrations from 0 to 5000 cells/mL were tested, with 2.52 mg/L +/- 0.37 mg/L equivalents of oxygen produced from as few as 50 cells/mL, versus 6.26 +/- 0.64 mg/L when no cells were present in solution. Overall, the developed amperometric biosensor technology offered an efficient means of detection primarily due to its ease of use, cost-effectiveness, portability, and amenability to incorporation at existing water quality gaging stations. PMID:18324534

  13. Modeling the Effect of Oxygen on the Amperometric Response of Immobilized Organoselenium-Based S-Nitrosothiol Sensors

    PubMed Central

    Höfler, Lajos; Meyerhoff, Mark E.

    2011-01-01

    Amperometric detection of S-nitrosothiols (RSNOs) at sub-micromolar levels in blood samples is of potential importance for monitoring endothelial function and other disease states that involve changes in physiological nitric oxide (NO) production. It is shown here that the elimination of dissolved oxygen from samples is critical when using covalently attached diselenocystamine-based amperometric RSNO sensors for practical RSNO measurements. The newest generation of RSNO sensors utilizes an amperometric NO gas sensor with a thin organoselenium modified dialysis membrane mounted at the distal sensing tip. Sample RSNOs are catalytically reduced to NO within the dialysis membrane by the immobilized organoselenium species. In the presence of oxygen the sensitivity of these sensors for measuring low levels of RSNOs (< μM) is greatly reduced. It is demonstrated that the main scavenger of the generated nitric oxide is not the dissolved oxygen, but rather superoxide anion radical generated from the reaction of the reduced organoselenium species (the reactive species in the catalytic redox cycle) and dissolved oxygen. Computer simulations of the response of the RSNO sensor using rate constants and diffusion coefficients for the reactions involved, known from the literature or estimated from fitting to the observed amperometric response curves, as well as the specific geometric dimensions of the RSNO sensor, further support that nitric oxide and superoxide anion radical quickly react resulting in near zero sensor sensitivity toward RSNO concentrations in the sub-micromolar concentration range. Elimination of oxygen from samples helps improve sensor detection limits to ca. 10 nM levels of RSNOs. PMID:21230000

  14. Fabrication and Characterization of Nanocarbon-Based Nanofluids by Using an Oxygen-Acetylene Flame Synthesis System.

    PubMed

    Teng, Tun-Ping; Wang, Wei-Ping; Hsu, Yu-Chun

    2016-12-01

    In this study, an oxygen-acetylene flame synthesis system was developed to fabricate nanocarbon-based nanofluids (NCBNFs) through a one-step synthesis method. Measured in liters per minute (LPM), the flame's fuel flows combined oxygen and acetylene at four ratios: 1.5/2.5 (P1), 1.0/2.5 (P2), 0.5/2.5 (P3), and 0/2.5 (P4). The flow rate of cooling water (base fluid) was fixed at 1.2 LPM to produce different nanocarbon-based materials (NCBMs) and various concentrations of NCBNFs. Tests and analyses were conducted for determining the morphology of NCBMs, NCBM material, optical characteristics, the production rate, suspension performance, average particle size, zeta potential, and other relevant basic characteristics of NCBNFs to understand the characteristics and materials of NCBNFs produced through different process parameters (P1-P4). The results revealed that the NCBMs mainly had flaky and spherical morphologies and the diameters of the spherical NCBMs measured approximately 20-30 nm. X-ray diffraction and Raman spectroscopy revealed that the NCBMs contained graphene oxide (GO) and amorphous carbon (AC) when the oxygen flow rate was lower than 1.0 LPM. In addition, the NCBMs contained reduced GO, crystalline graphite (graphite-2H), and AC when the oxygen flow rate was higher than 1.0 LPM. The process parameters of P1, P2, P3, and P4 resulted in NCBMs produced at concentrations of 0.010, 0.013, 0.040, and 0.023 wt%, respectively, in NCBNFs. All the NCBNFs exhibited non-Newtonian and shear-thinning rheological properties. The P4 ratio showed the highest enhancement rate of thermal conductivity for NCBNFs, at a rate 4.85 % higher than that of water. PMID:27295256

  15. Fabrication and Characterization of Nanocarbon-Based Nanofluids by Using an Oxygen-Acetylene Flame Synthesis System

    NASA Astrophysics Data System (ADS)

    Teng, Tun-Ping; Wang, Wei-Ping; Hsu, Yu-Chun

    2016-06-01

    In this study, an oxygen-acetylene flame synthesis system was developed to fabricate nanocarbon-based nanofluids (NCBNFs) through a one-step synthesis method. Measured in liters per minute (LPM), the flame's fuel flows combined oxygen and acetylene at four ratios: 1.5/2.5 (P1), 1.0/2.5 (P2), 0.5/2.5 (P3), and 0/2.5 (P4). The flow rate of cooling water (base fluid) was fixed at 1.2 LPM to produce different nanocarbon-based materials (NCBMs) and various concentrations of NCBNFs. Tests and analyses were conducted for determining the morphology of NCBMs, NCBM material, optical characteristics, the production rate, suspension performance, average particle size, zeta potential, and other relevant basic characteristics of NCBNFs to understand the characteristics and materials of NCBNFs produced through different process parameters (P1-P4). The results revealed that the NCBMs mainly had flaky and spherical morphologies and the diameters of the spherical NCBMs measured approximately 20-30 nm. X-ray diffraction and Raman spectroscopy revealed that the NCBMs contained graphene oxide (GO) and amorphous carbon (AC) when the oxygen flow rate was lower than 1.0 LPM. In addition, the NCBMs contained reduced GO, crystalline graphite (graphite-2H), and AC when the oxygen flow rate was higher than 1.0 LPM. The process parameters of P1, P2, P3, and P4 resulted in NCBMs produced at concentrations of 0.010, 0.013, 0.040, and 0.023 wt%, respectively, in NCBNFs. All the NCBNFs exhibited non-Newtonian and shear-thinning rheological properties. The P4 ratio showed the highest enhancement rate of thermal conductivity for NCBNFs, at a rate 4.85 % higher than that of water.

  16. The physiological effects of selection in rainbow trout selected for growth on plant-based feeds

    Technology Transfer Automated Retrieval System (TEKTRAN)

    It has been proven that rainbow trout can selectively be improved to more efficiently process and utilize nutrients from different sources. A stock of rainbow trout has been developed to grow faster on a diet formulated without fishmeal and the protein sources coming completely from plant material. ...

  17. Theory of mind selectively predicts preschoolers' knowledge-based selective word learning.

    PubMed

    Brosseau-Liard, Patricia; Penney, Danielle; Poulin-Dubois, Diane

    2015-11-01

    Children can selectively attend to various attributes of a model, such as past accuracy or physical strength, to guide their social learning. There is a debate regarding whether a relation exists between theory-of-mind skills and selective learning. We hypothesized that high performance on theory-of-mind tasks would predict preference for learning new words from accurate informants (an epistemic attribute), but not from physically strong informants (a non-epistemic attribute). Three- and 4-year-olds (N = 65) completed two selective learning tasks, and their theory-of-mind abilities were assessed. As expected, performance on a theory-of-mind battery predicted children's preference to learn from more accurate informants but not from physically stronger informants. Results thus suggest that preschoolers with more advanced theory of mind have a better understanding of knowledge and apply that understanding to guide their selection of informants. This work has important implications for research on children's developing social cognition and early learning. PMID:26211504

  18. Oxygen migration in TiO{sub 2}-based higher-k gate stacks

    SciTech Connect

    Kim, Sang Bum; Brown, Stephen L.; Rossnagel, Stephen M.; Bruley, John; Copel, Matthew; Hopstaken, Marco J. P.; Narayanan, Vijay; Frank, Martin M.

    2010-03-15

    We report on the stability of high-permittivity (high-k) TiO{sub 2} films incorporated in metal-oxide-silicon capacitor structures with a TiN metal gate electrode, focusing on oxygen migration. Titanium oxide films are deposited by either Ti sputtering [physical vapor deposition (PVD)] followed by radical shower oxidation or by plasma-enhanced atomic layer deposition (PEALD) from titanium isopropoxide (Ti{l_brace}OCH(CH{sub 3}){sub 2{r_brace}4}) and O{sub 2} plasma. Both PVD and PEALD films result in near-stoichiometric TiO{sub 2} prior to high-temperature annealing. We find that dopant activation anneals of TiO{sub 2}-containing gate stacks at 1000 deg. C cause 5 A or more of additional SiO{sub 2} to be formed at the gate-dielectric/Si-channel interface. Furthermore, we demonstrate for the first time that oxygen released from TiO{sub 2} diffuses through the TiN gate electrode and oxidizes the poly-Si contact. The thickness of this upper SiO{sub 2} layer continues to increase with increasing TiO{sub 2} thickness, while the thickness of the regrown SiO{sub 2} at the gate-dielectric/Si interface saturates. The upper SiO{sub 2} layer degrades gate stack capacitance, and simultaneously the oxygen-deficient TiO{sub x} becomes a poor insulator. In an attempt to mitigate O loss from the TiO{sub 2}, top and bottom Al{sub 2}O{sub 3} layers are added to the TiO{sub 2} gate dielectric as oxygen barriers. However, they are found to be ineffective, due to Al{sub 2}O{sub 3}-TiO{sub 2} interdiffusion during activation annealing. Bottom HfO{sub 2}/Si{sub 3}N{sub 4} interlayers are found to serve as more effective oxygen barriers, reducing, though not preventing, oxygen downdiffusion.

  19. GoDisco: Selective Gossip Based Dissemination of Information in Social Community Based Overlays

    NASA Astrophysics Data System (ADS)

    Datta, Anwitaman; Sharma, Rajesh

    We propose and investigate a gossip based, social principles and behavior inspired decentralized mechanism (GoDisco) to disseminate information in online social community networks, using exclusively social links and exploiting semantic context to keep the dissemination process selective to relevant nodes. Such a designed dissemination scheme using gossiping over a egocentric social network is unique and is arguably a concept whose time has arrived, emulating word of mouth behavior and can have interesting applications like probabilistic publish/subscribe, decentralized recommendation and contextual advertisement systems, to name a few. Simulation based experiments show that despite using only local knowledge and contacts, the system has good global coverage and behavior.

  20. Selecting a risk-based tool to aid in decision making

    SciTech Connect

    Bendure, A.O.

    1995-03-01

    Selecting a risk-based tool to aid in decision making is as much of a challenge as properly using the tool once it has been selected. Failure to consider customer and stakeholder requirements and the technical bases and differences in risk-based decision making tools will produce confounding and/or politically unacceptable results when the tool is used. Selecting a risk-based decisionmaking tool must therefore be undertaken with the same, if not greater, rigor than the use of the tool once it is selected. This paper presents a process for selecting a risk-based tool appropriate to a set of prioritization or resource allocation tasks, discusses the results of applying the process to four risk-based decision-making tools, and identifies the ``musts`` for successful selection and implementation of a risk-based tool to aid in decision making.