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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

    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.

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

    DOE PAGES

    Stavila, Vitalie; Parthasarathi, Ramakrishnan; Davis, Ryan W.; ...

    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

  6. The role of surface oxygenated-species and adsorbed hydrogen in the oxygen reduction reaction (ORR) mechanism and product selectivity on Pd-based catalysts in acid media.

    PubMed

    Rahul, R; Singh, R K; Bera, B; Devivaraprasad, R; Neergat, M

    2015-06-21

    Oxygen reduction reaction (ORR) is investigated on bulk PdO-based catalysts (oxides of Pd and Pd3Co) in oxygen-saturated 0.1 M HClO4 to establish the role of surface oxides and adsorbed hydrogen in the activity and product selectivity (H2O/H2O2). The initial voltammetric features suggest that the oxides are inactive toward ORR. The evolution of the ORR voltammograms and potential-dependent H2O2 generation features on the PdO catalyst suggest gradual and parallel in situ reduction of the bulk PdO phase below ∼0.4 V in the hydrogen underpotential deposition (Hupd) region; the reduction of the bulk PdO catalyst is confirmed from the X-ray photoelectron spectra (XPS) and X-ray diffraction (XRD) patterns. The potential-dependent H2O2 generation features originate due to the presence of surface oxides and adsorbed hydrogen; this is further confirmed using halide ions (Cl(-) and Br(-)) and peroxide as the external impurities.

  7. Systematic selection of metalloporphyrin-based catalysts for oxygen reduction by modulation of the donor-acceptor intermolecular hardness.

    PubMed

    Masa, Justus; Schuhmann, Wolfgang

    2013-07-15

    Incisive modulation of the intermolecular hardness between metalloporphyrins and O2 can lead to the identification of promising catalysts for oxygen reduction. The dependency of the electrocatalytic reduction of O2 by metalloporphyrins on the nature of the central metal yields a volcano-type curve, which is rationalized to be in accordance with the Sabatier principle by using an approximation of the electrophilicity of the complexes. By using electrochemical and UV/Vis data, the influence of a selection of meso-substituents on the change in the energy for the π→π* excitation of manganese porphyrins was evaluated allowing one to quantitatively correlate the influence of the various ligands on the electrocatalysis of O2 reduction by the complexes. A manganese porphyrin was identified that electrocatalyzes the reduction of oxygen at low overpotentials without generating hydrogen peroxide. The activity of the complex became remarkably enhanced upon its pyrolysis at 650 °C.

  8. Reversible Oxygen Gas Sensor Based On Electrochemiluminescence

    PubMed Central

    Zhang, Lihua; Tsow, Francis

    2013-01-01

    A novel and robust oxygen gas sensor based on electrochemiluminescence of Ru(bpy)33+/+ ion annihilation in an ionic liquid is presented. Real-time detection of environmental oxygen concentration together with selective, sensitive and reversible performance is demonstrated. PMID:20386795

  9. 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.

  10. 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.

  11. 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.

  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.

  13. Selectivity in the carbon-oxygen reaction

    NASA Astrophysics Data System (ADS)

    Skokova, Kristina A.

    The dependence of the carbon-oxygen reaction rate and the CO/COsb2 ratio on temperature, oxygen pressure, carbon crystallite size, concentration of surface C(O) complexes, and content of heteroatoms was studied. It was shown that the temperature dependence of the CO/COsb2 ratio obeys an Arrhenius-type relationship, but the pre-exponential factor and the activation energy depend on oxygen pressure and carbon nature. The Arrhenius parameters were found to be directly proportional to each other. This confirmed the importance of the compensation effect in carbon oxidation. It was explained by active site heterogeneity in carbon materials. For all experimental conditions, the CO/COsb2 ratio was lower for carbons with more ordered graphitic structure. It was shown that the CO/COsb2 ratio is inversely proportional to the surface coverage with reactive C(O) complexes. More ordered carbons were revealed to possess lower concentrations of stable complexes, higher surface coverages with reactive complexes and thus lower CO/COsb2 ratios. The influence of B and N heteroatoms on carbon reactivity and the CO/COsb2 ratio was studied. It was confirmed that B acts as an inhibitor of carbon oxidation due to the formation of a protective Bsb2Osb3 coating. The N presence in the carbon structure increases its rate of oxidation, maybe due to decreasing carbon crystallite dimensions. The CO/COsb2 ratio did not correlate with the N content in the carbon, but depended on the concentration of surface carbon-oxygen complexes. A new reaction mechanism is proposed. A key feature of the mechanism is that it takes into account the presence and mobility of oxygen atoms on the basal plane. It was shown with the aid of theoretical molecular orbital calculations that chemisorption on a pair of adjacent edge and basal sites is thermodynamically favorable as a parallel process to the generally accepted path of chemisorption on two edge carbon atoms. The former process can lead to the formation of a

  14. Artificial neural network modelling of biological oxygen demand in rivers at the national level with input selection based on Monte Carlo simulations.

    PubMed

    Šiljić, Aleksandra; Antanasijević, Davor; Perić-Grujić, Aleksandra; Ristić, Mirjana; Pocajt, Viktor

    2015-03-01

    Biological oxygen demand (BOD) is the most significant water quality parameter and indicates water pollution with respect to the present biodegradable organic matter content. European countries are therefore obliged to report annual BOD values to Eurostat; however, BOD data at the national level is only available for 28 of 35 listed European countries for the period prior to 2008, among which 46% of data is missing. This paper describes the development of an artificial neural network model for the forecasting of annual BOD values at the national level, using widely available sustainability and economical/industrial parameters as inputs. The initial general regression neural network (GRNN) model was trained, validated and tested utilizing 20 inputs. The number of inputs was reduced to 15 using the Monte Carlo simulation technique as the input selection method. The best results were achieved with the GRNN model utilizing 25% less inputs than the initial model and a comparison with a multiple linear regression model trained and tested using the same input variables using multiple statistical performance indicators confirmed the advantage of the GRNN model. Sensitivity analysis has shown that inputs with the greatest effect on the GRNN model were (in descending order) precipitation, rural population with access to improved water sources, treatment capacity of wastewater treatment plants (urban) and treatment of municipal waste, with the last two having an equal effect. Finally, it was concluded that the developed GRNN model can be useful as a tool to support the decision-making process on sustainable development at a regional, national and international level.

  15. Oxygen diffusion in vanadium-based alloys

    SciTech Connect

    de Avillez, R.R.

    1981-01-01

    The experimental study of transport and equilibrium properties of oxygen in vanadium-based alloys was made by EMF measurements on solid electrolytic cells over the temperature range of 873 to 1423/sup 0/K. The oxygen diffusion in vanadium was not significantly modified by small additions of Ti, Cr, Ni, Nb and Ta. The increase in the activation energy for oxygen diffusion in the V-based alloys containing Cr, Ni, Nb and Ta probably reflects the effect of these substitutional solutes on the activity coefficient of oxygen. The oxygen activity was increased by the addition of 1 at % of Cr, Ni and Nb, and decreased by the addition of Ti and Ta. However, the effects in the alloys containing Nb and Ta are very small.

  16. 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.

  17. 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.

  18. 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

  19. Pulsed diode laser-based monitor for singlet molecular oxygen

    PubMed Central

    Lee, Seonkyung; Zhu, Leyun; Minhaj, Ahmed M.; Hinds, Michael F.; Vu, Danthu H.; Rosen, David I.; Davis, Steven J.; Hasan, Tayyaba

    2010-01-01

    Photodynamic therapy (PDT) is a promising cancer treatment. PDT uses the affinity of photosensitizers to be selectively retained in malignant tumors. When tumors, pretreated with the photosensitizer, are irradiated with visible light, a photochemical reaction occurs and tumor cells are destroyed. Oxygen molecules in the metastable singlet delta state O2(1Δ) are believed to be the species that destroys cancerous cells during PDT. Monitoring singlet oxygen produced by PDT may lead to more precise and effective PDT treatments. Our approach uses a pulsed diode laser-based monitor with optical fibers and a fast data acquisition system to monitor singlet oxygen during PDT. We present results of in vitro singlet oxygen detection in solutions and in a rat prostate cancer cell line as well as PDT mechanism modeling. PMID:18601555

  20. 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.

  1. Intrinsic selectivity and structure sensitivity of Rhodium catalysts for C2+ oxygenate production [On the intrinsic selectivity and structure sensitivity of Rhodium catalysts for C2+ oxygenate production

    DOE PAGES

    Yang, Nuoya; Medford, Andrew J.; Liu, Xinyan; ...

    2016-01-31

    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-vdWmore » 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. As a result, 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.« less

  2. Combination of metabolism measurement and a time-lapse system provides an embryo selection method based on oxygen uptake and chronology of cytokinesis timing.

    PubMed

    Tejera, Alberto; Castelló, Damia; de Los Santos, Jose Maria; Pellicer, Antonio; Remohí, Jose; Meseguer, Marcos

    2016-07-01

    To evaluate correlations between oxygen consumption (OC) measurements before and after embryo cytokinesis, observing OC during embryo cleavages and combining that information with morphokinetics to relate to implantation potential. Prospective cohort study. University-affiliated private IVF unit. A total of 1,150 injected oocytes in 86 first oocyte donation cycles with embryo transfer on day 3. None. We analyzed the embryo OC and combined this data with the cytokinesis event, exact timing (in hours) of blastomeric cleavages, with the use of an incubator equipped with time-lapse videography, gathering a total of 7,630 measurements during the cytokinesis (active phase) and consecutive measurements after this division (passive phase), correlating this data with embryo outcome. OC was found to increase during embryo cleavage, showing high levels during first division with a strong correlation with implantation success. Moreover, those embryos with slow or fast development gave rise to lower OC levels, whereas higher levels were associated with optimal embryo division ranges linked to higher implantation potential. A detailed analysis of OC by time-lapse observations enhances the value that these measurements represented as markers of embryo quality, especially during the cytokinesis events produced during preimplantation development. Copyright © 2016. Published by Elsevier Inc.

  3. 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.

  4. 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.

  5. A Fluorescence Based Dissolved Oxygen Sensor

    NASA Astrophysics Data System (ADS)

    McFarlane, Ronald; Hamilton, M. Coreen

    1987-10-01

    A sensor based on fluorescence quenching has been built to detect oxygen activity in gas and water. The sensor consists of a xenon flash bulb as a light source; an excitation wavelength band pass filter; a dichroic beam splitter; collimating and focussing lenses; a plastic clad silica (PCS) rod with the fluorophore immobilized at the tip of it; an emission wavelength band pass filter; a photomultiplier tube (PMT); a monitor PIN photodiode detector; and interface electronics to couple a computer to the rest of the sensor. The device demonstrates a reversible change in fluorescence quenching for changes in oxygen activity. The fluorescence signal seen by the PMT varies over a factor of 3, being highest at 0 oxygen activity and lowest at atmospheric oxygen activity. The device exhibits a 63 % response time of less than 1 second for gases and less than 10 seconds for oxygen dissolved in water. The noise floor of the sensor is approximately 1%. The present embodiment of the device was designed to allow the sensor to operate in the marine environment. The optical components, computer, batteries, and power supply circuitry are mounted on a rack that is enclosed in a pressure housing. The immobilized fluorophore is exposed to sea water. The light travels along the PCS rod, through a pressure seal, to the rest of the system. Present investigations are centered around long term stability of the fluorophore and constituents of the real ocean that will interfere with the quenching mechanism.

  6. 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.

  7. Venous Oxygenation Mapping using Velocity-Selective Excitation and Arterial Nulling (VSEAN)

    PubMed Central

    Guo, Jia; Wong, Eric C.

    2011-01-01

    A new MRI technique to map the oxygenation of venous blood is presented. The method uses velocity-selective excitation and arterial nulling pulses, combined with phase sensitive signal detection to isolate the venous blood signal. The T2 of this signal along with a T2-Y calibration curve yields estimates of venous oxygenation in situ. Results from phantoms and healthy human subjects under normoxic and hypoxic conditions are shown, and venous saturation levels estimated from both sagittal sinus and grey matter based ROIs are compared to the related techniques TRUST and QUIXOTIC. In addition, combined with an additional scan without arterial nulling pulses, the oxygen saturation level on arterial side can also be estimated. PMID:22294414

  8. Selection of burn-resistant materials for oxygen-driven turbopumps

    NASA Technical Reports Server (NTRS)

    Schoenman, L.

    1984-01-01

    NASA goals for reusable space-based, high-performance orbit transfer vehicle propulsion systems have resulted in a need for oxygen/hydrogen engines which include lightweight, highly reliable, liquid oxygen pumps. The selection of ignition- and burn-resistant materials is a major factor in the design of a compact 75,000-rpm turbopump which can deliver 6 lbM/sec of liquid oxygen at 5,000 psia. The potential operational hazards of rubbing friction and impact of foreign particles at high velocity were investigated experimentally for a wide range of candidate materials, i.e., nickel, copper, monel, 316 Stainless Steel, Hastelloy-X, Invar-36, and silicon carbide. Test parameters included oxygen pressure and temperature up to 5,000 psia and 800 F, respectively. The effect of increasing the O2 pressure from 1000 to 5000 psi is discussed. The applicability of the candidate materials to oxygen pump design was ranked by comparing the experimental results among themselves and with an analytically determined parameter, i.e., the burn factor. Nickel and copper demonstrated superior resistance to ignition and burn in the friction rubbing and particle impact tests relative to monel, stainless steel, and nickel-iron base superalloys.

  9. Naphthoxazole-based singlet oxygen fluorescent probes.

    PubMed

    Ruiz-González, Rubén; Zanocco, Renzo; Gidi, Yasser; Zanocco, Antonio L; Nonell, Santi; Lemp, Else

    2013-01-01

    In this study, we report the synthesis and photochemical behavior of a new family of photoactive compounds to assess its potential as singlet oxygen ((1)O2) probes. The candidate dyads are composed by a (1)O2 trap plus a naphthoxazole moiety linked directly or through an unsaturated bond to the oxazole ring. In the native state, the inherent great fluorescence of the naphthoxazole moiety is quenched; but in the presence of (1)O2, generated by the addition and appropriate irradiation of an external photosensitizer, a photooxidation reaction occurs leading to the formation of a new chemical entity whose fluorescence is two orders of magnitude higher than that of the initial compound, at the optimal selected wavelength. The presented dyads outperform the commonly used indirect fluorescent (1)O2 probes in terms of fluorescence enhancement maintaining the required specificity for (1)O2 detection in solution.

  10. 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.

  11. 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

  12. 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.

  13. Interpreting Oxygenation-Based Neuroimaging Signals: The Importance and the Challenge of Understanding Brain Oxygen Metabolism

    PubMed Central

    Buxton, Richard B.

    2010-01-01

    Functional magnetic resonance imaging is widely used to map patterns of brain activation based on blood oxygenation level dependent (BOLD) signal changes associated with changes in neural activity. However, because oxygenation changes depend on the relative changes in cerebral blood flow (CBF) and cerebral metabolic rate of oxygen (CMRO2), a quantitative interpretation of BOLD signals, and also other functional neuroimaging signals related to blood or tissue oxygenation, is fundamentally limited until we better understand brain oxygen metabolism and how it is related to blood flow. However, the positive side of the complexity of oxygenation signals is that when combined with dynamic CBF measurements they potentially provide the best tool currently available for investigating the dynamics of CMRO2. This review focuses on the problem of interpreting oxygenation-based signals, the challenges involved in measuring CMRO2 in general, and what is needed to put oxygenation-based estimates of CMRO2 on a firm foundation. The importance of developing a solid theoretical framework is emphasized, both as an essential tool for analyzing oxygenation-based multimodal measurements, and also potentially as a way to better understand the physiological phenomena themselves. The existing data, integrated within a simple theoretical framework of O2 transport, suggests the hypothesis that an important functional role of the mismatch of CBF and CMRO2 changes with neural activation is to prevent a fall of tissue pO2. Future directions for better understanding brain oxygen metabolism are discussed. PMID:20616882

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

    PubMed Central

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

    2008-01-01

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

  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 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.

  17. 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.

  18. 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.

  19. 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

  20. 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.

  1. Biomimetic catalytic system driven by electron transfer for selective oxygenation of hydrocarbon.

    PubMed

    Yang, Guanyu; Ma, Yinfa; Xu, Jie

    2004-09-01

    Hydrocarbon oxyfunctionalization is a crucial industrial process. Most metallic catalysts require higher temperatures and often show lower selectivities. One of the intellectual approaches is the mimicry for bio-oxidation. We have established a biomimetic system with a nonmetallic redox center, composed of anthraquinones, N-hydroxyphthalimide, and zeolite HY, for selective hydrocarbon oxygenation by molecular oxygen. Selectivity of 95.8% for acetophenone and 66.2% conversion were accomplished for oxygenation of ethylbenzene at temperatures as low as 80 degrees C. The redox cycle, driven by one-electron transfer and product orientation by Zeolite HY, opens up the possibility of mimicking bio-oxidation under mild conditions.

  2. Pressure Flammability Thresholds in Oxygen of Selected Aerospace Materials

    NASA Technical Reports Server (NTRS)

    Hirsch, David; Williams, Jim; Harper, Susana; Beeson, Harold; Ruff, Gary; Pedley, Mike

    2010-01-01

    The experimental approach consisted of concentrating the testing in the flammability transition zone following the Bruceton Up-and-Down Method. For attribute data, the method has been shown to be very repeatable and most efficient. Other methods for characterization of critical levels (Karberand Probit) were also considered. The data yielded the upward limiting pressure index (ULPI), the pressure level where approx.50% of materials self-extinguish in a given environment.Parametric flammability thresholds other than oxygen concentration can be determined with the methodology proposed for evaluating the MOC when extinguishment occurs. In this case, a pressure threshold in 99.8% oxygen was determined with the methodology and found to be 0.4 to 0.9 psia for typical spacecraft materials. Correlation of flammability thresholds obtained with chemical, hot wire, and other ignition sources will be conducted to provide recommendations for using alternate ignition sources to evaluate flammability of aerospace materials.

  3. Lifetime-based photoacoustic oxygen sensing in vivo

    NASA Astrophysics Data System (ADS)

    Ray, Aniruddha; Rajian, Justin Rajesh; Lee, Yong-Eun Koo; Wang, Xueding; Kopelman, Raoul

    2012-05-01

    The determination of oxygen levels in blood and other tissues in vivo is critical for ensuring proper body functioning, for monitoring the status of many diseases, such as cancer, and for predicting the efficacy of therapy. Here we demonstrate, for the first time, a lifetime-based photoacoustic technique for the measurement of oxygen in vivo, using an oxygen sensitive dye, enabling real time quantification of blood oxygenation. The results from the main artery in the rat tail indicated that the lifetime of the dye, quantified by the photoacoustic technique, showed a linear relationship with the blood oxygenation levels in the targeted artery.

  4. 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.

  5. Selective Sensitization of Zinc Finger Protein Oxidation by Reactive Oxygen Species through Arsenic Binding*

    PubMed Central

    Zhou, Xixi; Cooper, Karen L.; Sun, Xi; Liu, Ke J.; Hudson, Laurie G.

    2015-01-01

    Cysteine oxidation induced by reactive oxygen species (ROS) on redox-sensitive targets such as zinc finger proteins plays a critical role in redox signaling and subsequent biological outcomes. We found that arsenic exposure led to oxidation of certain zinc finger proteins based on arsenic interaction with zinc finger motifs. Analysis of zinc finger proteins isolated from arsenic-exposed cells and zinc finger peptides by mass spectrometry demonstrated preferential oxidation of C3H1 and C4 zinc finger configurations. C2H2 zinc finger proteins that do not bind arsenic were not oxidized by arsenic-generated ROS in the cellular environment. The findings suggest that selectivity in arsenic binding to zinc fingers with three or more cysteines defines the target proteins for oxidation by ROS. This represents a novel mechanism of selective protein oxidation and demonstrates how an environmental factor may sensitize certain target proteins for oxidation, thus altering the oxidation profile and redox regulation. PMID:26063799

  6. Oxygen consumption, heart rate and oxygen pulse associated with selected exercise-to-muscle class elements.

    PubMed Central

    Abernethy, P; Batman, P

    1994-01-01

    The purpose of the investigation was to determine the relative oxygen consumption (VO2), heart rate and oxygen pulse associated with the constituent elements of an exercise-to-music class. Six women exercise-to-music leaders with a mean(s.d.) age, weight and height of 33.2(5.2) years, 51.0(2.8) kg and 157.9(5.6) cm respectively, completed five distinct exercise-to-music movement elements. The movement elements were of a locomoter (circuit, jump and low impact) and callisthenic (prone and side/supine) nature. The movement elements were distinguishable from one another in terms of their movement patterns, posture and tempo. Relative VO2 values were greatest for the circuit element (40.6 ml kg-1 min-1) and least for the side/supine element (20.0 ml kg-1 min-1). The differences in VO2 between the locomotrr and callisthenic elements were significant (circuit approximately jump approximately low impact > prone approximately side/supine). However, effect size data suggested that the differences between the low impact and jump elements and the prone and side/supine elements were of practical significance (circuit approximately jump > low impact > prone > side/supine). With a single exception similar parametric statistics and effect size trends were identified for absolute heart rate. Specifically, the heart rate associated with the low impact element was not significantly greater than the prone element. The oxygen pulse associated with the locomotor elements was significantly greater than the callisthenic elements (circuit approximately jump approximately low impact > prone > side/supine). This suggested that heart rate may be an inappropriate index for making comparisons between exercise-to-music elements. Reasons for differences in oxygen uptake values between movement elements are discussed. PMID:8044493

  7. Carbon, Nitrogen, and Oxygen Abundances of Selected Stars in the Hertzsprung Gap

    NASA Astrophysics Data System (ADS)

    Vanture, Andrew D.; Wallerstein, George

    1999-01-01

    The iron, carbon, nitrogen, and oxygen abundances for several stars whose characteristics place them in the Hertzsprung gap have been derived from high-resolution spectra. These stars were selected based on the fact that previous studies have shown them to have peculiar carbon, nitrogen, or lithium abundances considering their position in the Hertzsprung-Russell diagram. When combined with the lithium abundances derived by Wallerstein and coworkers, the carbon, nitrogen, and oxygen abundances indicate that the sample of stars can generally be broken into two categories-lower luminosity dwarfs or subgiants that are unmixed and higher luminosity mixed giants. Among the sample are two stars, HR 7606 and HR 8626, which previously have been identified by Bidelman as ``low-velocity CH stars.'' These stars show metallicities of [Fe/H]~-0.5 and solar abundances of carbon, nitrogen, and oxygen. The strength of the CH band in these stars is probably an artifact of a mild metal deficiency and the absence of substantial mixing of CN processed materials to the surface of the star rather than an unusual nucleosynthetic history.

  8. Diagnosis of Compartment Syndrome Based on Tissue Oxygenation

    DTIC Science & Technology

    2013-10-01

    measured with microprobes has been shown to be highly correlated with tissue oxygenation and the extent of ischemia reperfusion injury .3 Near-infrared...Tissue Oxygenation PRINCIPAL INVESTIGATOR: Hubert Kim, M.D., Ph.D. CONTRACTING ORGANIZATION: Northern California Institute for...SUBTITLE Diagnosis of Compartment Syndrome based on Tissue Oxygenation 5a. CONTRACT NUMBER 5b. GRANT NUMBER W81XWH-10-1-1024 5c. PROGRAM ELEMENT

  9. Water-based oxygen-sensor films.

    PubMed

    Habibagahi, Arezoo; Mébarki, Youssef; Sultan, Yasir; Yap, Glenn P A; Crutchley, Robert J

    2009-08-01

    The luminescent cyclometalated iridium complex [Ir(fppy)(2)(t-Bu-iCN)(2)]CF(3)SO(3), 1 (fppy = 4-(2-pyridyl)benzaldehyde, and t-Bu-iCN = tert-butyl isocyanide), was synthesized and characterized by X-ray crystallography and (1)H NMR, absorption, and emission spectroscopies. Complex 1 was quantitatively bound to the water-soluble amine-functionalized polymer Silamine D208-EDA by reductive amination, to produce 2. The quantum yield of emission and excited state lifetime of 2 (varphi(em) = 0.23 and tau = 20.6 mus) are comparable to that of the model complex [Ir(tpy)(2)(t-Bu-iCN)(2)]CF(3)SO(3), 3 (tpy = 2-(p- tolyl) pyridine) with varphi(em) = 0.28 and tau = 35.6 mus. Aqueous blends of 2 with Silamine and colloidal microcrystalline cellulose (MC) were used to prepare oxygen-sensor films. Oxygen sensitivities of these films were determined as a function of Silamine:MC ratio and obeyed Stern-Volmer kinetics. The optimum oxygen-sensor film composition was 2 in 1:1 Silamine:MC, which had an oxygen sensitivity of 0.502 over an atmospheric pressure range of 0.007-45 psi. Temperature sensitivity (percentage loss of intensity per degrees C) of this film was determined to be -1.1 and -1.4% degrees C(-1) at vacuum and 1 bar atmospheric pressure, respectively. These results were compared to those of films incorporating dispersions of 1 and 3. Luminescence microscopy of 9:1, 1:1, and 1:5 Silamine:MC films of 2 show that the charged iridium complex in 2 associates with the surface of MC and lifetime measurements of these films show an increase in lifetime with increasing MC fraction. The optimum quenching sensitivity observed for the 1:1 Silamine:MC film suggests that the diffusion of oxygen must decrease with increasing fraction of MC and thereby decrease oxygen sensitivity. These novel materials offer an environmentally friendly alternative to the preparation of oxygen-sensor films.

  10. 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.

  11. Singlet oxygen-based electrosensing by molecular photosensitizers

    NASA Astrophysics Data System (ADS)

    Trashin, Stanislav; Rahemi, Vanoushe; Ramji, Karpagavalli; Neven, Liselotte; Gorun, Sergiu M.; de Wael, Karolien

    2017-07-01

    Enzyme-based electrochemical biosensors are an inspiration for the development of (bio)analytical techniques. However, the instability and reproducibility of the reactivity of enzymes, combined with the need for chemical reagents for sensing remain challenges for the construction of useful devices. Here we present a sensing strategy inspired by the advantages of enzymes and photoelectrochemical sensing, namely the integration of aerobic photocatalysis and electrochemical analysis. The photosensitizer, a bioinspired perfluorinated Zn phthalocyanine, generates singlet-oxygen from air under visible light illumination and oxidizes analytes, yielding electrochemically-detectable products while resisting the oxidizing species it produces. Compared with enzymatic detection methods, the proposed strategy uses air instead of internally added reactive reagents, features intrinsic baseline correction via on/off light switching and shows C-F bonds-type enhanced stability. It also affords selectivity imparted by the catalytic process and nano-level detection, such as 20 nM amoxicillin in μl sample volumes.

  12. Singlet oxygen-based electrosensing by molecular photosensitizers

    PubMed Central

    Trashin, Stanislav; Rahemi, Vanoushe; Ramji, Karpagavalli; Neven, Liselotte; Gorun, Sergiu M.; De Wael, Karolien

    2017-01-01

    Enzyme-based electrochemical biosensors are an inspiration for the development of (bio)analytical techniques. However, the instability and reproducibility of the reactivity of enzymes, combined with the need for chemical reagents for sensing remain challenges for the construction of useful devices. Here we present a sensing strategy inspired by the advantages of enzymes and photoelectrochemical sensing, namely the integration of aerobic photocatalysis and electrochemical analysis. The photosensitizer, a bioinspired perfluorinated Zn phthalocyanine, generates singlet-oxygen from air under visible light illumination and oxidizes analytes, yielding electrochemically-detectable products while resisting the oxidizing species it produces. Compared with enzymatic detection methods, the proposed strategy uses air instead of internally added reactive reagents, features intrinsic baseline correction via on/off light switching and shows C-F bonds-type enhanced stability. It also affords selectivity imparted by the catalytic process and nano-level detection, such as 20 nM amoxicillin in μl sample volumes.

  13. 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.

  14. Chemical Sensors Based On Oxygen Detection By Optical Methods

    NASA Astrophysics Data System (ADS)

    Parker, Jennifer W.; Cox, M. E.; Dunn, Bruce S.

    1986-08-01

    Fluorescence quenching is shown to be a viable method of measuring oxygen concentration. Two oxygen/optical transducers based on fluorescence quenching have been developed and characterized: one is hydrophobic and the other is hydrophilic. The development of both transducers provides great flexibility in the application of fluorescence to oxygen measurement. One transducer is produced by entrapping a fluorophor, 9,10-diphenyl anthracene, in poly(dimethyl siloxane) to yield a homogeneous composite polymer matrix. The resulting matrix is hydrophobic. This transducer is extremely sensitive to PO2 as a result of oxygen quenching the fluorescence of 9,10-diphenyl anthracene. This quenching is utilized in the novel method employed to measure the transport properties of oxygen within Ulf 2matrix. Results show large values for the diffusion coefficient at 25°C, D = 3.5 x 10-5 cm /s. The fluorescence intensity varies inversely with P02. The second oxygen transducer is fabricated by entrapping 9,10-diphenyl anthracene in poly(hydroxy ethyl methacrylate). Free radical, room temperature polymerization is employed. This transducer is hydrophilic, and contains 37% water. The transport properties of oxygen within this transducer are compared with those of the hydrophobic transducer. The feasibility of generalizing the oxygen transducers to a wider class of chemical sensors through coupling to other chemistries is proposed. An example of such coupling is given in a glucose/oxygen transducer. The glucose transducer is produced by entrapping an enzyme, glucose oxidase, in the composite matrix of the hydrophilic oxygen transducer. Glucose oxidase catalyzes a reaction between glucose and oxygen, thereby lowering the local oxygen concentration. This transducer yields a glucose modified optical oxygen signal. The operation of this transducer and preliminary results of its characterization are presented.

  15. 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...

  16. 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...

  17. 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.

  18. 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.

  19. 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.

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

    SciTech Connect

    Golden, J.L.; Bourassa, R.J.; Dursch, H.W.; Pippin, H.G.

    1995-02-01

    The Energetic Oxygen Interaction with Materials 3 (EOIM-3) experiment was flown on the STS-46 mission, which was launched on 31 July 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.

  1. Convection and hemoglobin-based oxygen carrier enhanced oxygen transport in a hepatic hollow fiber bioreactor.

    PubMed

    Sullivan, Jesse P; Harris, David R; Palmer, Andre F

    2008-01-01

    Hepatic hollow fiber bioreactors are a promising class of bioartificial liver assist device (BLAD). The development of this type of device is currently hindered by limited oxygen transport to cultured hepatocytes, due to low solubility of oxygen in aqueous media. In order to increase the oxygen spectrum to cultured hepatocytes housed within a hollow fiber bioreactor, several different engineering strategies were explored in this study. These included: supplementing the circulating media stream of the hollow fiber bioreactor with a hemoglobin-based oxygen carrier (bovine red blood cells) with defined oxygen binding and release kinetics and operating the bioreactor with media flow through the hollow fiber membrane into the extracapillary space (ECS). We hypothesize that these two strategies can be used to improve hepatocyte oxygenation and possibly attain an in vivo-like pO(2) spectrum, similar to that observed in vivo in the liver sinusoid. This work is significant, since provision of an in vivo-like pO(2) spectrum should create a fully functional BLAD that could potentially bridge thousands of liver failure patients towards native liver regeneration of damaged tissue or, if necessary, orthotopic liver transplantation.

  2. 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

  3. 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.

  4. Self-assembled benzophenone bis-urea macrocycles facilitate selective oxidations by singlet oxygen.

    PubMed

    Geer, Michael F; Walla, Michael D; Solntsev, Kyril M; Strassert, Cristian A; Shimizu, Linda S

    2013-06-07

    This manuscript investigates how incorporation of benzophenone, a well-known triplet sensitizer, within a bis-urea macrocycle, which self-assembles into a columnar host, influences its photophysical properties and affects the reactivity of bound guest molecules. We further report the generation of a remarkably stable organic radical. As expected, UV irradiation of the host suspended in oxygenated solvents efficiently generates singlet oxygen similar to the parent benzophenone. In addition, this host can bind guests such as 2-methyl-2-butene and cumene to form stable solid host-guest complexes. Subsequent UV irradiation of these complexes facilitated the selective oxidation of 2-methyl-2-butene into the allylic alcohol, 3-methyl-2-buten-1-ol, at 90% selectivity as well as the selective reaction of cumene to the tertiary alcohol, α,α'-dimethyl benzyl alcohol, at 63% selectivity. However, these products usually arise through radical pathways and are not observed in the presence of benzophenone in solution. In contrast, typical reactions with benzophenone result in the formation of the reactive singlet oxygen that reacts with alkenes to form endoperoxides, diooxetanes, or hydroperoxides, which are not observed in our system. Our results suggest that the confinement, the formation of a stable radical species, and the singlet oxygen photoproduction are responsible for the selective oxidation processes. A greater understanding of the mechanism of this selective oxidation could lead to development of greener oxidants.

  5. Portable optical oxygen sensor based on time-resolved fluorescence.

    PubMed

    Chu, Cheng-Shane; Chu, Ssu-Wei

    2014-11-10

    A new, simple signal processing, low-cost technique for the fabrication of a portable oxygen sensor based on time-resolved fluorescence is described. The sensing film uses the oxygen sensing dye platinum meso-tetra (pentfluorophenyl) porphyrin (PtTFPP) embedded in a polymer matrix. The ratio τ0100 measures sensitivity of the sensing film, where τ0 and τ100 represent the detected fluorescence lifetimes from the sensing film exposed to 100% nitrogen and 100% oxygen, respectively. The experimental results reveal that the PtTFPP-doped oxygen sensor has a sensitivity of 2.2 in the 0%-100% range. A preparation procedure for coating the photodiodes with the oxygen sensor film that produces repetitive and reliable sensing devices is proposed. The developed time-resolved optical oxygen sensor is portable, low-cost, has simple signal processing, and lacks optical filter elements. It is a cost-effective alternative to traditional electrochemical-based oxygen sensors and provides a platform for other optical based sensors.

  6. 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. © 2015 Institute of Food Technologists®

  7. Selective molecular oxygen oxidation of thioethers to sulfoxides catalyzed by Ce(IV)

    SciTech Connect

    Riley, D.P.; Smith, M.R.; Correa, P.E.

    1988-01-06

    The selective molecular oxygen conversion of thioethers to sulfoxides is catalyzed by ceric ammonium nitrate (CAN) with rate enhancements that are at least three orders of magnitude greater than the uncatalyzed autoxidation of thioethers. Mechanistic studies (including spectroscopic, labeling, uptake, mixed reactant, and autocatalysis studies) of this novel reaction reveal that both atoms of dioxygen are incorporated into product sulfoxide, that a novel oxygen-driven Ce(IV)Ce(III) redox cycle gives rise to the catalysis, and that molecular oxygen efficiently traps a sulfur-centered radial cation of the thioether (produced by Ce(IV) oxidation of thioether) to yield the oxygenated radical cation R/sub 2/S/sup +/OO/sup ./, which, it is proposed, reoxidizes Ce(III) to Ce(IV). The zwitterionic R/sub 2/S/sup +/OO/sup -/ intermediate (persulfoxide) reacts with thioether to yield two sulfoxide product molecules.

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

    NASA Astrophysics Data System (ADS)

    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.

    2016-08-01

    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.

  9. Intrinsic selectivity and structure sensitivity of Rhodium catalysts for C2+ oxygenate production [On the intrinsic selectivity and structure sensitivity of Rhodium catalysts for C2+ oxygenate production

    SciTech Connect

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

    2016-01-31

    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. As a result, 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.

  10. Direct selective oxygen-assisted acylation of amines driven by metallic silver surfaces: dimethylamine with formaldehyde.

    PubMed

    Zhou, Ling; Freyschlag, Cassandra G; Xu, Bingjun; Friend, Cynthia M; Madix, Robert J

    2010-02-07

    Facile, direct acylation of dimethylamine with formaldehyde to N,N-dimethylformamide proceeds with a selectivity approaching 100% at low oxygen concentrations on metallic silver surfaces; the reaction proceeds via nucleophilic attack of adsorbed dimethylamide on formaldehyde with subsequent beta-H elimination from the adsorbed hemiaminal.

  11. 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...

  12. 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...

  13. Particulate Formation from a Copper Oxide-Based Oxygen ...

    EPA Pesticide Factsheets

    Attrition behavior and particle loss of a copper oxide-based oxygen carrier from a methane chemical looping combustion (CLC) process was investigated in a fluidized bed reactor. The aerodynamic diameters of most elutriated particulates, after passing through a horizontal settling duct, range between 2 and 5 μm. A notable number of submicron particulates are also identified. Oxygen carrier attrition was observed to lead to increased CuO loss resulting from the chemical looping reactions, i.e., Cu is enriched in small particles generated primarily from fragmentation in the size range of 10-75 μm. Cyclic reduction and oxidation reactions in CLC have been determined to weaken the oxygen carrier particles, resulting in increased particulate emission rates when compared to oxygen carriers without redox reactions. The generation rate for particulates < 10 μm was found to decrease with progressive cycles over as-prepared oxygen carrier particles and then reach a steady state. The surface of the oxygen carrier is also found to be coarsened due to a Kirkendall effect, which also explains the enrichment of Cu on particle surfaces and in small particles. As a result, it is important to collect and reprocess small particles generated from chemical looping processes to reduce oxygen carrier loss. The redox reactions associated with chemical looping combustion play an important role in particle attrition in the fluidized bed. Reaction-induced local stresses, due to the r

  14. Particulate Formation from a Copper Oxide-Based Oxygen ...

    EPA Pesticide Factsheets

    Attrition behavior and particle loss of a copper oxide-based oxygen carrier from a methane chemical looping combustion (CLC) process was investigated in a fluidized bed reactor. The aerodynamic diameters of most elutriated particulates, after passing through a horizontal settling duct, range between 2 and 5 μm. A notable number of submicron particulates are also identified. Oxygen carrier attrition was observed to lead to increased CuO loss resulting from the chemical looping reactions, i.e., Cu is enriched in small particles generated primarily from fragmentation in the size range of 10-75 μm. Cyclic reduction and oxidation reactions in CLC have been determined to weaken the oxygen carrier particles, resulting in increased particulate emission rates when compared to oxygen carriers without redox reactions. The generation rate for particulates < 10 μm was found to decrease with progressive cycles over as-prepared oxygen carrier particles and then reach a steady state. The surface of the oxygen carrier is also found to be coarsened due to a Kirkendall effect, which also explains the enrichment of Cu on particle surfaces and in small particles. As a result, it is important to collect and reprocess small particles generated from chemical looping processes to reduce oxygen carrier loss. The redox reactions associated with chemical looping combustion play an important role in particle attrition in the fluidized bed. Reaction-induced local stresses, due to the r

  15. Migration of interfacial oxygen ions modulated resistive switching in oxide-based memory devices

    NASA Astrophysics Data System (ADS)

    Chen, C.; Gao, S.; Zeng, F.; Tang, G. S.; Li, S. Z.; Song, C.; Fu, H. D.; Pan, F.

    2013-07-01

    Oxides-based resistive switching memory induced by oxygen ions migration is attractive for future nonvolatile memories. Numerous works had focused their attentions on the sandwiched oxide materials for depressing the characteristic variations, but the comprehensive studies of the dependence of electrodes on the migration behavior of oxygen ions are overshadowed. Here, we investigated the interaction of various metals (Ni, Co, Al, Ti, Zr, and Hf) with oxygen atoms at the metal/Ta2O5 interface under electric stress and explored the effect of top electrode on the characteristic variations of Ta2O5-based memory device. It is demonstrated that chemically inert electrodes (Ni and Co) lead to the scattering switching characteristics and destructive gas bubbles, while the highly chemically active metals (Hf and Zr) formed a thick and dense interfacial intermediate oxide layer at the metal/Ta2O5 interface, which also degraded the resistive switching behavior. The relatively chemically active metals (Al and Ti) can absorb oxygen ions from the Ta2O5 film and avoid forming the problematic interfacial layer, which is benefit to the formation of oxygen vacancies composed conduction filaments in Ta2O5 film thus exhibit the minimum variations of switching characteristics. The clarification of oxygen ions migration behavior at the interface can lead further optimization of resistive switching performance in Ta2O5-based memory device and guide the rule of electrode selection for other oxide-based resistive switching memories.

  16. 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. Copyright © 2010 Elsevier B.V. All rights reserved.

  17. Evaluation of UV-radiation induced singlet oxygen generation potential of selected drugs.

    PubMed

    Pandey, R; Mehrotra, S; Ray, R S; Joshi, P C; Hans, R K

    2002-05-01

    Photosensitization reaction of drugs leading to the formation of reactive oxygen species under ultraviolet radiation (UVR) can cause tissue injury, resulting in damage to various cellular macromolecules. The aim of this study was to determine the singlet oxygen generation potential of some commonly used antibiotics so that due precautions can be exercised to minimize their photosensitizing action and oxidative stress potential. The selected antibiotics were examined for their ability to produce singlet oxygen (1O2) under artificial UVA (320-400 nm). Singlet oxygen generation of various screened antibiotics under UVA is of the following order: Nalidixic acid > Amphotericin-B > Cephradine > Cefazolin > Nafcillin > Cephalothin > Ampicillin > Cephalexin > Puromycin > Kanamycin > Lincomycin > Tetracycline > Nystatin > Gentamicin sulphate. Nalidixic acid, the most potent generator of 1O2 among the screened antibiotics, was selected to carry out further studies. Certain specific quenchers of 1O2 such as beta-carotene, 1,4-diazabicyclo[2.2.2] octane (DABCO), and sodium azide (NaN3) accorded significant inhibition in the production of 1O2. The results suggest that precautions are necessary to avoid ultraviolet radiation after the intake of photoreactive drugs, especially in tropical countries such as India. These findings are significant because UVB radiation is reportedly increasing on earth surface in part due to depletion of stratospheric ozone layer. The selected drugs are commonly used for the treatment of various diseases. Thus, the synergistic action of both can lead to undesirable phototoxic responses.

  18. New Reaction Pathway Induced by Plasmon for Selective Benzyl Alcohol Oxidation on BiOCl Possessing Oxygen Vacancies.

    PubMed

    Li, Hao; Qin, Feng; Yang, Zhiping; Cui, Ximin; Wang, Jianfang; Zhang, Lizhi

    2017-03-08

    Selective organic transformation under mild conditions constitutes a challenge in green chemistry, especially for alcohol oxidation, which typically requires environmentally unfriendly oxidants. Here, we report a new plasmonic catalyst of Au supported on BiOCl containing oxygen vacancies. It photocatalyzes selective benzyl alcohol oxidation with O2 under visible light through synergistic action of plasmonic hot electrons and holes. Oxygen vacancies on BiOCl facilitate the trapping and transfer of plasmonic hot electrons to adsorbed O2, producing •O2(-) radicals, while plasmonic hot holes remaining on the Au surface mildly oxidize benzyl alcohol to corresponding carbon-centered radicals. The hypothesized concerted ring addition between these two radical species on the BiOCl surface highly favors the production of benzaldehyde along with an unexpected oxygen atom transfer from O2 to the product. The results and understanding acquired in this study, based on the full utilization of hot charge carriers in a plasmonic metal deposited on a rationally designed support, will contribute to the development of more active and/or selective plasmonic catalysts for a wide variety of organic transformations.

  19. [Oxygen therapy during Argentine-based national and international flights].

    PubMed

    Martínez Fraga, Alejandro; Sívori, Martín; Alonso, Mariana

    2008-01-01

    There are no data about supplemental oxygen in flight in our country. The objective of our study was to evaluate arranging in-flight-oxygen required by a simulated traveler, system of administration and costs, and to compare the results between Argentine-based (A) and international (I) airlines. The questionnaire used was similar to that of Stoller et al12. Data collection consisted of telephone calls placed by one of the authors to all commercial air carriers listed in our two Buenos Aires City airports during July 2007. A structured interview with questions was addressed on issues that an oxygen-using air traveler would need to arrange in-flight oxygen. Of the 25 airlines, 6 were discarded because of lack of information (24%, three A -60%- and one I -16%-). All A allowed in-flight-oxygen vs. 80% of I (p<0.05), 100% of A and 94% of I required a medical certificate (p=NS); 71% of A and 100% of I required previous notification (p<0.05); 50% of A and 87% of I provided patient interphases of oxygen administration (p=NS). Free of charge oxygen could be provided by 100% of A and 50% of I, with airline charge between 70 to 300 dollars. In conclusion, we observed different policies, rules, availability, and a pronounced lack of standardization of airline information. The cost of oxygen was very different between airlines and it was superior on I. It will be necessary to carry out actions to facilitate patient access to oxygentherapy and to standardize medical information among airlines in our country.

  20. 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

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

    SciTech Connect

    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.

  2. Selective Coke Combustion by Oxygen Pulsing During Mo/ZSM‐5‐Catalyzed Methane Dehydroaromatization

    PubMed Central

    Coumans, Ferdy J. A. G.; Uslamin, Evgeny; Kapteijn, Freek

    2016-01-01

    Abstract Non‐oxidative methane dehydroaromatization is a promising reaction to directly convert natural gas into aromatic hydrocarbons and hydrogen. Commercialization of this technology is hampered by rapid catalyst deactivation because of coking. A novel approach is presented involving selective oxidation of coke during methane dehydroaromatization at 700 °C. Periodic pulsing of oxygen into the methane feed results in substantially higher cumulative product yield with synthesis gas; a H2/CO ratio close to two is the main side‐product of coke combustion. Using 13C isotope labeling of methane it is demonstrated that oxygen predominantly reacts with molybdenum carbide species. The resulting molybdenum oxides catalyze coke oxidation. Less than one‐fifth of the available oxygen reacts with gaseous methane. Combined with periodic regeneration at 550 °C, this strategy is a significant step forward, towards a process for converting methane into liquid hydrocarbons. PMID:27791321

  3. Rational approach, technique and selection criteria treating lumbar disk herniations by oxygen-ozone therapy.

    PubMed

    Muto, Mario; Giurazza, Francesco; Silva, Ricardo Pimentel; Guarnieri, Gianluigi

    2016-12-01

    Radicular lumbar back pain is an important public health problem not yet benefiting from a unequivocal treatment approach. Medical and physical therapies represent the first solution; however, when these fail, the second therapeutic step is still controversial and mini-invasive treatments may play an important role. In these cases oxygen-ozone therapy has been proved to be a very safe and effective option that is widely used with different modalities. This paper, by reviewing oxygen-ozone therapy literature data, aims to describe the rationale of oxygen-ozone therapy for the treatment of lumbar disk herniations, propose an effective procedural technique and clarify patient selection criteria; furthermore, complications and follow-up management are also considered. © The Author(s) 2016.

  4. Selective cerebral perfusion: real-time evidence of brain oxygen and energy metabolism preservation.

    PubMed

    Salazar, Jorge D; Coleman, Ryan D; Griffith, Stephen; McNeil, Jeffrey D; Steigelman, Megan; Young, Haven; Hensler, Bart; Dixon, Patricia; Calhoon, John; Serrano, Faridis; DiGeronimo, Robert

    2009-07-01

    Deep hypothermic circulatory arrest (DHCA) is commonly used for complex cardiac operations in children, often with selective cerebral perfusion (SCP). Little data exist concerning the real-time effects of DHCA with or without SCP on cerebral metabolism. Our objective was to better define these effects, focusing on brain oxygenation and energy metabolism. Piglets undergoing cardiopulmonary bypass were assigned to either 60 minutes of DHCA at 18 degrees C (n = 9) or DHCA with SCP at 18 degrees C (n = 8), using pH-stat management. SCP was administered at 10 mL/kg/min. A cerebral microdialysis catheter was implanted into the cortex for monitoring of cellular ischemia and energy stores. Cerebral oxygen tension and intracranial pressure also were monitored. After DHCA with or without SCP, animals were recovered for 4 hours off cardiopulmonary bypass. With SCP, brain oxygen tension was preserved in contrast to DHCA alone (p < 0.01). Deep hypothermic circulatory arrest was associated with marked elevations of lactate (p < 0.01), glycerol (p < 0.01), and the lactate to pyruvate ratio (p < 0.001), as well as profound depletion of the energy substrates glucose (p < 0.001) and pyruvate (p < 0.001). These changes persisted well into recovery. With SCP, no significant cerebral microdialysis changes were observed. A strong correlation was demonstrated between cerebral oxygen levels and cerebral microdialysis markers (p < 0.001). Selective cerebral perfusion preserves cerebral oxygenation and attenuates derangements in cerebral metabolism associated with DHCA. Cerebral microdialysis provides real-time metabolic feedback that correlates with changes in brain tissue oxygenation. This model enables further study and refinement of strategies aiming to limit brain injury in children requiring complex cardiac operations.

  5. Image-based modelling of skeletal muscle oxygenation

    PubMed Central

    Clough, G. F.

    2017-01-01

    The supply of oxygen in sufficient quantity is vital for the correct functioning of all organs in the human body, in particular for skeletal muscle during exercise. Disease is often associated with both an inhibition of the microvascular supply capability and is thought to relate to changes in the structure of blood vessel networks. Different methods exist to investigate the influence of the microvascular structure on tissue oxygenation, varying over a range of application areas, i.e. biological in vivo and in vitro experiments, imaging and mathematical modelling. Ideally, all of these methods should be combined within the same framework in order to fully understand the processes involved. This review discusses the mathematical models of skeletal muscle oxygenation currently available that are based upon images taken of the muscle microvasculature in vivo and ex vivo. Imaging systems suitable for capturing the blood vessel networks are discussed and respective contrasting methods presented. The review further informs the association between anatomical characteristics in health and disease. With this review we give the reader a tool to understand and establish the workflow of developing an image-based model of skeletal muscle oxygenation. Finally, we give an outlook for improvements needed for measurements and imaging techniques to adequately investigate the microvascular capability for oxygen exchange. PMID:28202595

  6. Image-based modelling of skeletal muscle oxygenation.

    PubMed

    Zeller-Plumhoff, B; Roose, T; Clough, G F; Schneider, P

    2017-02-01

    The supply of oxygen in sufficient quantity is vital for the correct functioning of all organs in the human body, in particular for skeletal muscle during exercise. Disease is often associated with both an inhibition of the microvascular supply capability and is thought to relate to changes in the structure of blood vessel networks. Different methods exist to investigate the influence of the microvascular structure on tissue oxygenation, varying over a range of application areas, i.e. biological in vivo and in vitro experiments, imaging and mathematical modelling. Ideally, all of these methods should be combined within the same framework in order to fully understand the processes involved. This review discusses the mathematical models of skeletal muscle oxygenation currently available that are based upon images taken of the muscle microvasculature in vivo and ex vivo Imaging systems suitable for capturing the blood vessel networks are discussed and respective contrasting methods presented. The review further informs the association between anatomical characteristics in health and disease. With this review we give the reader a tool to understand and establish the workflow of developing an image-based model of skeletal muscle oxygenation. Finally, we give an outlook for improvements needed for measurements and imaging techniques to adequately investigate the microvascular capability for oxygen exchange.

  7. Effects of ambient oxygen and size-selective mortality on growth and maturation in guppies

    PubMed Central

    Diaz Pauli, Beatriz; Kolding, Jeppe; Jeyakanth, Geetha

    2017-01-01

    Abstract Growth, onset of maturity and investment in reproduction are key traits for understanding variation in life-history strategies. Many environmental factors affect variation in these traits, but for fish, hypoxia and size-dependent mortality have become increasingly important because of human activities, such as increased nutrient enrichment (eutrophication), climate warming and selective fishing. Here, we study experimentally the effect of oxygen availability on maturation and growth in guppies (Poecilia reticulata) from two different selected lines, one subjected to positive and the other negative size-dependent fishing. This is the first study to assess the effects of both reduced ambient oxygen and size-dependent mortality in fish. We show that reduced ambient oxygen led to stunting, early maturation and high reproductive investment. Likewise, lineages that had been exposed to high mortality of larger-sized individuals displayed earlier maturation at smaller size, greater investment in reproduction and faster growth. These life-history changes were particularly evident for males. The widely reported trends towards earlier maturation in wild fish populations are often interpreted as resulting from size-selective fishing. Our results highlight that reduced ambient oxygen, which has received little experimental investigation to date, can lead to similar phenotypic changes. Thus, changes in ambient oxygen levels can be a confounding factor that occurs in parallel with fishing, complicating the causal interpretation of changes in life-history traits. We believe that better disentangling of the effects of these two extrinsic factors, which increasingly affect many freshwater and marine ecosystems, is important for making more informed management decisions. PMID:28361001

  8. 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

  9. Selective oxidation of styrene on an oxygen-adsorbed Au(111): A density functional theory study.

    PubMed

    Xue, Li-Qin; Pang, Xian-Yong; Wang, Gui-Chang

    2009-02-01

    The reaction mechanism for the styrene selective oxidation on the oxygen preadsorbed Au(111) surface has been studied by the density functional theory calculation with the periodic slab model. The calculated results showed that the process of reaction includes two steps: forming the oxametallacycle intermediate (OMME) and then producing the products. It was found that the second step, from OMME to product is the rate-controlling step, which is similar to ethylene selective oxidation on Ag. Importantly, the present density-functional-theory calculation results suggested that the mechanism via the OMME (2) (i.e. the preadsorbed atomic oxygen bound to the CH2 group involved in C6H5--CH=CH2) to produce styrene epoxide is kinetically favored than that of OMME (1).

  10. Hemoglobin-based oxygen carriers for hemorrhagic shock.

    PubMed

    Elmer, Jonathan; Alam, Hasan B; Wilcox, Susan R

    2012-03-01

    Hemorrhagic shock is a pathologic state in which intravascular volume and tissue oxygen delivery are impaired, leading to circulatory collapse and cellular ischemia. Resuscitation with hemoglobin-based oxygen carriers (HBOCs) is appealing in that their use can both restore intravascular volume and tissue oxygenation, without the limitations in supply and immunomodulatory effects of packed red blood cells. However, the development of safe and effective agents has been elusive. In this article, we briefly discuss the major limitations of traditional resuscitative fluids which have driven the continued interest in HBOCs. We then review the history of early HBOC development and the modern understanding of their mechanisms of toxicity, which has informed the rational design of second-generation agents. Finally, we provide an overview of these second-generation HBOCs that are under active investigation or have recently completed phase 3 clinical trials.

  11. Reactive oxygen species in iridium-based OER catalysts.

    PubMed

    Pfeifer, Verena; Jones, Travis E; Wrabetz, Sabine; Massué, Cyriac; Velasco Vélez, Juan J; Arrigo, Rosa; Scherzer, Michael; Piccinin, Simone; Hävecker, Michael; Knop-Gericke, Axel; Schlögl, Robert

    2016-11-18

    Tremendous effort has been devoted towards elucidating the fundamental reasons for the higher activity of hydrated amorphous Ir(III/IV) oxyhydroxides (IrO x ) in the oxygen evolution reaction (OER) in comparison with their crystalline counterpart, rutile-type IrO2, by focusing on the metal oxidation state. Here we demonstrate that, through an analogy to photosystem II, the nature of this reactive species is not solely a property of the metal but is intimately tied to the electronic structure of oxygen. We use a combination of synchrotron-based X-ray photoemission and absorption spectroscopies, ab initio calculations, and microcalorimetry to show that holes in the O 2p states in amorphous IrO x give rise to a weakly bound oxygen that is extremely susceptible to nucleophilic attack, reacting stoichiometrically with CO already at room temperature. As such, we expect this species to play the critical role of the electrophilic oxygen involved in O-O bond formation in the electrocatalytic OER on IrO x . We propose that the dynamic nature of the Ir framework in amorphous IrO x imparts the flexibility in Ir oxidation state required for the formation of this active electrophilic oxygen.

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

    PubMed

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

    2016-09-21

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

  13. 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

  14. Determinations of renal cortical and medullary oxygenation using BOLD Magnetic Resonance Imaging and selective diuretics

    PubMed Central

    Warner, Lizette; Glockner, James F.; Woollard, John; Textor, Stephen C.; Romero, Juan C.; Lerman, Lilach O.

    2010-01-01

    Objective This study was undertaken to test the hypothesis that blood O2 level dependent magnetic resonance imaging (BOLD MRI) can detect changes in cortical proximal tubule (PT) and medullary thick ascending limb of Henle (TAL) oxygenation consequent to successive administration of furosemide and acetazolamide (Az). Assessment of PT and TAL function could be useful to monitor renal disease states in vivo. Therefore, the adjunct use of diuretics that inhibit Na+ reabsorption selectively in PT and TAL, Az and furosemide, respectively, may help discern tubular function by using BOLD MRI to detect changes in tissue oxygenation. Material and Methods BOLD MRI signal R2* (inversely related to oxygenation) and tissue oxygenation with intrarenal O2 probes were measured in pigs that received either furosemide (0.5mg/kg) or Az (15mg/kg) alone, Az sequentially after furosemide (n=6 each, 15-minute intervals), or only saline vehicle (n=3). Results R2* decreased in the cortex of Az-treated and medulla of furosemide-treated kidneys, corresponding to an increase in their tissue O2 assessed with probes. However, BOLD MRI also showed decreased cortical R2* following furosemide that was additive to the Az-induced decrease. Az administration, both alone and after furosemide, also decreased renal blood flow (−26±3.5 and −29.2±3%, respectively, p<0.01). Conclusion These results suggest that an increase in medullary and cortical tissue O2 elicited by selective diuretics is detectable by BOLD MRI, but may be complicated by hemodynamic effects of the drugs. Therefore, the BOLD MRI signal may reflect functional changes additional to oxygenation, and needs to be interpreted cautiously. PMID:20856128

  15. Decomposition of methanol on oxygen-modified Fe(100) surfaces. II. Preadsorbed oxygen as poison, selectivity modifier and promoter

    NASA Astrophysics Data System (ADS)

    Lu, Jiong-Ping; Albert, Mark; Bernasek, Steven L.; Dwyer, Daniel J.

    1990-12-01

    Decomposition of methanol (CH 3OH) on the Fe(100) surface modified by low temperature adsorption of oxygen has been studied, using high resolution electron energy loss spectroscopy (HREELS) and temperature programmed reaction spectroscopy (TPRS). Fe(100) surfaces studied were modified by adsorption of O 2 at 113 K, and methanol decomposition as a function of oxygen coverage was monitored. The effect of pre-heating the oxygen overlayers on the methanol decomposition was also examined. Decomposition of methanol on these O-modified surfaces passes through a methoxy (-OCH 3) intermediate. The thermal stability of methoxy increases in the presence of pre-adsorbed oxygen. At low coverage, atomic oxygen occupies four-fold hollow sites. In this case, the effect of oxygen on the methanol decomposition is similar to that observed previously on the annealed O-modified surfaces. At higher oxygen coverage, a more weakly bound non-hollow site oxygen also exists on the surface, which reacts with hydroxyl (-OH) hydrogen of the CH 3OH, promoting the formation of methoxy. At high oxygen coverage (close to saturation coverage at 113 K), decomposition of methanol results in the formation of formaldehyde (H 2CO), without production of carbon monoxide (CO). This is very different from the decomposition of methanol on the clean Fe(100) surface, where decomposition leads to the formation of CO without H 2CO. The effect of oxygen modification is discussed in terms of changing relative probabilities of competing reaction pathways.

  16. Procedure for the selection of materials for use in oxygen systems at the John F. Kennedy Space Center

    NASA Technical Reports Server (NTRS)

    Bryan, Coleman J.; Olsen, Melvin G.

    1988-01-01

    This paper describes tests used at the John F. Kennedy Space Center (KSC) in the material selection procedure for evaluating materials suitable for use in oxygen systems. Special attention is given to the basic selection criteria for materials used in oxygen enriched environments. The flow chart for the material selection procedure is presented, and information that must be supplied by vendors requesting batch/lot certification support from KSC is given.

  17. 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

  18. Silicon Micropore-Based Parallel Plate Membrane Oxygenator.

    PubMed

    Dharia, Ajay; Abada, Emily; Feinberg, Benjamin; Yeager, Torin; Moses, Willieford; Park, Jaehyun; Blaha, Charles; Wright, Nathan; Padilla, Benjamin; Roy, Shuvo

    2017-08-11

    Extracorporeal membrane oxygenation (ECMO) is a life support system that circulates the blood through an oxygenating system to temporarily (days to months) support heart or lung function during cardiopulmonary failure until organ recovery or replacement. Currently, the need for high levels of systemic anticoagulation and the risk for bleeding are main drawbacks of ECMO that can be addressed with a redesigned ECMO system. Our lab has developed an approach using microelectromechanical systems (MEMS) fabrication techniques to create novel gas exchange membranes consisting of a rigid silicon micropore membrane (SμM) support structure bonded to a thin film of gas-permeable polydimethylsiloxane (PDMS). This study details the fabrication process to create silicon membranes with highly uniform micropores that have a high level of pattern fidelity. The oxygen transport across these membranes was tested in a simple water-based bench-top set-up as well in a porcine in vivo model. It was determined that the mass transfer coefficient for the system using SµM-PDMS membranes was 3.03 ± 0.42 mL O2 min(-1) m(-2) cm Hg(-1) with pure water and 1.71 ± 1.03 mL O2 min(-1) m(-2) cm Hg(-1) with blood. An analytic model to predict gas transport was developed using data from the bench-top experiments and validated with in vivo testing. This was a proof of concept study showing adequate oxygen transport across a parallel plate SµM-PDMS membrane when used as a membrane oxygenator. This work establishes the tools and the equipoise to develop future generations of silicon micropore membrane oxygenators. © 2017 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.

  19. Impact of energy supply and oxygen transfer on selective lipopeptide production by Bacillus subtilis BBG21.

    PubMed

    Fahim, Sameh; Dimitrov, Krasimir; Gancel, Frederique; Vauchel, Peggy; Jacques, Philippe; Nikov, Iordan

    2012-12-01

    The influence of power dissipation and volumetric oxygen transfer coefficient k(L)a on Bacillus subtilis productivity of lipopeptides surfactin and fengycin was studied in shake flasks in view of scaling-up of this fermentation process. The experiments performed with different flask sizes, relative filling volumes, and shaking frequencies confirmed clearly that lipopeptide production changed in function of power dissipation, via interfacial gas-liquid contact surface and oxygen supply. It was demonstrated that k(L)a is the key parameter controlling the productivity and the selectivity of the bioreaction. Varying the oxygen transfer conditions, the synthesis could be oriented to mixed production or to surfactin mono-production. The fraction of surfactin towards total lipopeptides produced and the maximal surfactin production both increased with k(L)a increase (surfactin concentration about 2 g L(-1) at k(L)a=0.04-0.08 s(-1)), while the maximal fengycin production (fengycin concentration about 0.3 g L(-1)) was obtained at moderate oxygen supply (k(L)a=0.01 s(-1)). Copyright © 2012 Elsevier Ltd. All rights reserved.

  20. UV radiation impacts body weight, oxygen consumption, and shelter selection in the intertidal vertebrate Girella laevifrons.

    PubMed

    Pulgar, José; Waldisperg, Melany; Galbán-Malagón, Cristóbal; Maturana, Diego; Pulgar, Victor M; Aldana, Marcela

    2017-02-01

    The amount of ultraviolet (UV) radiation reaching the earth's surface has increased due to ozone layer depletion, and this fact represents an opportunity to evaluate the physiological and behavioral responses of animals to this global-scale stressor. The transitory fish Girella laevifrons inhabits pools in the upper intertidal zone, which is characterized by exposure to a wide range of stressors, including UV radiation. We documented the field magnitude and the impact of UV radiation on oxygen consumption, body mass variations, and shelter (rocky and algae) selection by G. laevifrons. UV-exposed animals showed increased oxygen consumption, slower body weight increase, and active rocky shelter selection. Control fish showed increased body weight and no evident shelter selection. The results indicated that UV exposure affects fish energetic balance and habitat selection to favor greater protection against radiation. Increased UV exposure in transitory intertidal animals at levels observed in upper intertidal pools may alter the residency time of fish before leaving for the subtidal zone. Therefore, UV-induced energetic changes may determine animal performance and ontogenetic physiological itineraries, whereas shelter quality might determine habitat use. Copyright © 2016 Elsevier B.V. All rights reserved.

  1. 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

  2. Oxygen sensitivity of erbium-doped AlN films probed by site selective spectroscopy

    NASA Astrophysics Data System (ADS)

    Oliveira, J. C.; Cavaleiro, A.; Vieira, M. T.; Bigot, L.; Garapon, C.; Jacquier, B.; Mugnier, J.

    2003-10-01

    In the aim of better understand the influence of oxygen on the luminescent properties of Er:AlN films, two samples synthesized by radiofrequency reactive magnetron sputtering, have been analysed by site-selective spectroscopy around 1.55 μm and compared to a reference aluminosilicate sample. The erbium content in the films was estimated to 3.3 at.% and oxygen content ranges from 6.2 at.% to 58.6 at.% (determination by EPMA). Line narrowing study was performed for values 6.2 at.% and 22.5 at.%. Both films were annealed at 1075 K for 1 h. Site-selective spectroscopy was carried out using a Ti:sapphire laser light with typical linewidth of 2 GHz tuned around 980 nm as the excitation source. The samples were cooled down to 1.5 K in a liquid-helium bath cryostat and their 4I13/2↔ 4I15/2 luminescence was detected using a high-sensitivity germanium-cooled detector. It appears that the site distribution of the Er:AlN samples is not continuous as in classical aluminosilicate glass but presents a rupture that suggests the existence of two kinds of sites for erbium: oxygen site and nitrogen site. These observations can easily be interpreted within the framework of the nephelauxetic effect that explains a shift of the site distribution to the longer wavelengths with an increase of boundings bonding covalency.

  3. A flowchart for selecting an ointment base.

    PubMed

    Conway, Jeannine M; Brown, Michael C

    2014-02-12

    OBJECTIVES. To improve students' skills in selecting appropriate ointment bases through the development and implementation of a flowchart. A flowchart was designed to help students select the appropriate base for an ointment. Students used the flowchart throughout the semester in both dry and wet laboratory activities. At the end of the semester, students completed a dry laboratory practical that required them to select an appropriate ointment base and levigating agent. Student performance data from the year prior to implementation was compared to data for 2 years after implementation. Calculation, procedure, and labeling errors also were compared. Prior to implementation of the flowchart, 51 of 101 students selected the correct base. After implementation, 169 of 212 students selected the correct base (p<0.001). Calculation, procedure, and labeling errors were not significantly different. CONCLUSION. Use of a flowchart to select an ointment base improved student performance when used in the context of a dry laboratory assignment.

  4. Stable and solubilized active Au atom clusters for selective epoxidation of cis-cyclooctene with molecular oxygen

    PubMed Central

    Qian, Linping; Wang, Zhen; Beletskiy, Evgeny V.; Liu, Jingyue; dos Santos, Haroldo J.; Li, Tiehu; Rangel, Maria do C.; Kung, Mayfair C.; Kung, Harold H.

    2017-01-01

    The ability of Au catalysts to effect the challenging task of utilizing molecular oxygen for the selective epoxidation of cyclooctene is fascinating. Although supported nanometre-size Au particles are poorly active, here we show that solubilized atomic Au clusters, present in ng ml−1 concentrations and stabilized by ligands derived from the oxidized hydrocarbon products, are active. They can be formed from various Au sources. They generate initiators and propagators to trigger the onset of the auto-oxidation reaction with an apparent turnover frequency of 440 s−1, and continue to generate additional initiators throughout the auto-oxidation cycle without direct participation in the cycle. Spectroscopic characterization suggests that 7–8 atom clusters are effective catalytically. Extension of work based on these understandings leads to the demonstration that these Au clusters are also effective in selective oxidation of cyclohexene, and that solubilized Pt clusters are also capable of generating initiators for cyclooctene epoxidation. PMID:28348389

  5. 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.

  6. Methodologies for detection of hemoglobin-based oxygen carriers.

    PubMed

    Goebel, Catrin; Alma, Chris; Howe, Chris; Kazlauskas, Rymantas; Trout, Graham

    2005-01-01

    Blood substitutes based on hemoglobin or hemoglobin-based oxygen carriers (HBOCs) are oxygen-carrying therapeutic agents developed for use in operations and emergencies in place of donated blood. Increased oxygen-carrying capacity through the use of blood substitutes could help elite athletes to lengthen endurance capacity and improve their performance. As blood substitutes become more readily available, it is essential that a qualitative detection method for their abuse in sport is available. Ideally, such a method would be simple and inexpensive. This study investigates methods that could be used as screening procedures to easily detect HBOCs in plasma and develops tests that can unequivocally confirm their presence. The investigation into the screening method indicates that the direct visual screening of plasma discoloration is the most appropriate with detection limits of less than 1% HBOC in plasma. Two methods are shown to confirm the presence of exogenous hemoglobin in plasma samples, size-exclusion chromatography with photodiode array detection and high-performance liquid chromatography analysis of enzymatic digests with detection by electrospray mass spectrometry. This work emphasizes the need for cooperation between drug developers and sports testing laboratories to ensure that methods for the detection of putative doping agents are available prior to product release.

  7. 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

  8. Performance of variable selection methods using stability-based selection.

    PubMed

    Lu, Danny; Weljie, Aalim; de Leon, Alexander R; McConnell, Yarrow; Bathe, Oliver F; Kopciuk, Karen

    2017-04-04

    Variable selection is frequently carried out during the analysis of many types of high-dimensional data, including those in metabolomics. This study compared the predictive performance of four variable selection methods using stability-based selection, a new secondary selection method that is implemented in the R package BioMark. Two of these methods were evaluated using the more well-known false discovery rate (FDR) as well. Simulation studies varied factors relevant to biological data studies, with results based on the median values of 200 partial area under the receiver operating characteristic curve. There was no single top performing method across all factor settings, but the student t test based on stability selection or with FDR adjustment and the variable importance in projection (VIP) scores from partial least squares regression models obtained using a stability-based approach tended to perform well in most settings. Similar results were found with a real spiked-in metabolomics dataset. Group sample size, group effect size, number of significant variables and correlation structure were the most important factors whereas the percentage of significant variables was the least important. Researchers can improve prediction scores for their study data by choosing VIP scores based on stability variable selection over the other approaches when the number of variables is small to modest and by increasing the number of samples even moderately. When the number of variables is high and there is block correlation amongst the significant variables (i.e., true biomarkers), the FDR-adjusted student t test performed best. The R package BioMark is an easy-to-use open-source program for variable selection that had excellent performance characteristics for the purposes of this study.

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

    SciTech Connect

    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.

  10. Selective photoinactivation of protein function through environment-sensitive switching of singlet oxygen generation by photosensitizer.

    PubMed

    Yogo, Takatoshi; Urano, Yasuteru; Mizushima, Akiko; Sunahara, Hisato; Inoue, Takanari; Hirose, Kenzo; Iino, Masamitsu; Kikuchi, Kazuya; Nagano, Tetsuo

    2008-01-08

    Chromophore-assisted light inactivation is a promising technique to inactivate selected proteins with high spatial and temporal resolution in living cells, but its use has been limited because of the lack of a methodology to prevent nonspecific photodamage in the cell owing to reactive oxygen species generated by the photosensitizer. Here we present a design strategy for photosensitizers with an environment-sensitive off/on switch for singlet oxygen ((1)O(2)) generation, which is switched on by binding to the target, to improve the specificity of protein photoinactivation. (1)O(2) generation in the unbound state is quenched by photoinduced electron transfer, whereas (1)O(2) generation can occur in the hydrophobic environment provided by the target protein, after specific binding. Inositol 1,4,5-trisphosphate receptor, which has been suggested to have a hydrophobic pocket around the ligand binding site, was specifically inactivated by an environment-sensitive photosensitizer-conjugated inositol 1,4,5-trisphosphate receptor ligand without (1)O(2) generation in the cytosol of the target cells, despite light illumination, demonstrating the potential of environment-sensitive photosensitizers to allow high-resolution control of generation of reactive oxygen species in the cell.

  11. 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.

  12. Electrochemical oxygen reduction behavior of selectively deposited platinum atoms on gold nanoparticles.

    PubMed

    Sarkar, A; Kerr, J B; Cairns, E J

    2013-07-22

    Carbon-supported Pt@Au "core-shell" nanoparticles with varying surface concentration of platinum atoms have been synthesized using a novel redox-mediated synthesis approach. The synthesis technique allows for a selective deposition of platinum atoms on the surface of prefabricated gold nanoparticles. Energy dispersive spectroscopic analyses in a scanning electron microscope reveal that the platinum to gold atomic ratios are close to the nominal values, validating the synthesis scheme. X-ray diffraction data indicate an un-alloyed structure. The platinum to gold surface atomic ratio determined from cyclic voltammetry and copper under-potential deposition experiments reveal good agreement with the calculated values at low platinum concentration. However, there is an increase in non-uniformity in the deposition process upon increasing the platinum concentration. Koutecky-Levich analysis of the samples indicates a transition of the total number of electrons transferred (n) in the electrochemical oxygen reduction reaction from two to four electrons upon increasing the surface concentration of platinum atoms. Furthermore, the data indicate that isolated platinum atoms can reduce molecular oxygen but via a two-electron route. Moreover, successful four-electron reduction of molecular oxygen requires clusters of platinum atoms. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Oxybiotest project: microorganisms under pressure. Hyperbaric oxygen (HBO) and simple pressure interaction on selected bacteria.

    PubMed

    Zanon, Vincenzo; Rossi, Lucia; Castellani, Elena; Camporesi, Enrico Mario; Palù, Giorgio; Bosco, Gerardo

    2012-09-11

    HyperBaric Oxygen (HBO) therapy involves exposure to pure oxygen in a pressurized room, and it is an already well-established treatment for various conditions, including those originated by serious infections. Starting from the observation of an increased number of patients who were accessing our HBO units for diseases supported from concomitant multidrug-resistant microorganisms, as well as considering the evident clinical benefit and laboratory final outcome of those patients at the end of the treatment, aim of our study was to measure, or better define at least, if there was any interaction between a hyperbaric environment and some selected microorganisms and if those positive results were due to the increased oxygen partial pressure (pO2) value or just to the increased pressure, regardless of the fraction of inspired oxygen (FiO2) applied (21÷100%). We applied various increased pO2 values in a hyperbaric environment. Our study design was tailored in four steps to answer four specific questions, ordered in a progressive process: OxyBioTest (OBT)-1,2,3, and 4. Specifically, we chose to investigate possible changes in the Minimum Inhibitory Concentration (MIC) and in the Minimum Bactericidal Concentration (MBC) of multi-resistant microorganisms after a single session of hyperbaric therapy. OBT-1 and OBT-2 provide a semi-quantitative confirmation of the bacterio-cidal and cytostatic effects of HBO. HBO is cidal only if the total exposure pressure is elevated, and cidal or cytostatic effect are not always dependent on the pO2 applied.OBT-4 has shown the adjuvant effect of HBO and antimicrobial drug against some selected bacteria. We seem allowed to hypothesize that only in case of a good approach to a lesion, permitting smaller bacterial loads thanks to surgical debridement and/or eventual antibiotic therapy for example, You can observe the clear effectiveness of the HyperBaric Oxygen (HBO) exposure as a valid adjuvant therapy, even when that lesion is substained

  14. 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

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

    SciTech Connect

    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.

    2016-03-08

    Incorporating, a redox active organometallic molIncorporating, a redox active organometallic molecule within a porous matrix is a useful strategy to form redox active composite materials for emerging applications such as energy storage, electro-catalysis and electro-magnetic separation. Herein we report a new class of stable, redox active metal organic composites for oxygen/air separation with exceptional efficiency. In particular, Ferrocene impregnated in a thermally stable hierarchical porous framework showed a saturation uptake capacity of >51 mg/g for oxygen at a very low relative saturation pressure (P/Po) of 0.06. The material shows excellent O2 selectivity from air as evident from experimental and simulated breakthrough experiments. In detail structural analysis using 57Fe-Mössbauer, X-ray photoelectron spectroscopy (XPS) and pair distribution function (PDF) analysis show that of O2 adsorption affinity and selectivity originates by the formation Fe3+-O oxide due to the highly reactive nature of the organometallics imbedded in the porous matrix.

  16. 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.

  17. Photocatalytic sensor for chemical oxygen demand determination based on oxygen electrode.

    PubMed

    Kim, Y C; Lee, K H; Sasaki, S; Hashimoto, K; Ikebukuro, K; Karube, I

    2000-07-15

    The construction and performance evaluation of a novel Chemical Oxygen Demand (COD) sensor is described. The sensor measures, using an oxygen electrode, a decrease of dissolved oxygen of a given sample resulting from photocatalytic oxidation of the organic compounds therein. As the photocatalyst, titanium dioxide (TiO2) fine particles adsorbed on a translucent poly(tetrafluoroethylene) (PTFE) membrane was used. The oxygen electrode with the membrane attached on its tip was used as the sensor probe. The operation characteristics of the sensor are demonstrated using an artificial wastewater and real water samples from lakes in Japan. This method is considered to be reliable, in that the observed parameter is close to the theoretical definition of chemical oxygen demand (COD), the amount of oxygen consumed for oxidation of organic compounds.

  18. Molecular origin of the selectivity differences between palladium and gold-palladium in benzyl alcohol oxidation: Different oxygen adsorption properties

    SciTech Connect

    Savara, Aditya Ashi; Chan-Thaw, Carine E.; Sutton, Jonathan E.; Wang, Di; Prati, Laura; Villa, Alberto

    2016-12-22

    The same mechanism and microkinetic model used for benzyl alcohol oxidation over Pd/C was shown to apply to benzyl alcohol oxidation over AuPd/C. Almost all of the selectivity differences could be explained by a decrease in oxygen adsorption on AuPd. After isolating oxygen adsorption as being the origin of the selectivity differences, density functional theory was used to investigate the oxygen adsorption properties of a pure Pd surface, a pure Au surface, and an alloyed AuPd surface. Finally, the calculations showed that Au–Pd alloying decreased the oxygen adsorption properties relative to pure Pd, which explained the selectivity differences, consistent with the microkinetic modeling.

  19. Molecular origin of the selectivity differences between palladium and gold-palladium in benzyl alcohol oxidation: Different oxygen adsorption properties

    DOE PAGES

    Savara, Aditya Ashi; Chan-Thaw, Carine E.; Sutton, Jonathan E.; ...

    2016-12-22

    The same mechanism and microkinetic model used for benzyl alcohol oxidation over Pd/C was shown to apply to benzyl alcohol oxidation over AuPd/C. Almost all of the selectivity differences could be explained by a decrease in oxygen adsorption on AuPd. After isolating oxygen adsorption as being the origin of the selectivity differences, density functional theory was used to investigate the oxygen adsorption properties of a pure Pd surface, a pure Au surface, and an alloyed AuPd surface. Finally, the calculations showed that Au–Pd alloying decreased the oxygen adsorption properties relative to pure Pd, which explained the selectivity differences, consistent withmore » the microkinetic modeling.« less

  20. Syngas chemical looping gasification process: oxygen carrier particle selection and performance

    SciTech Connect

    Fanxing Li; Hyung Ray Kim; Deepak Sridhar; Fei Wang; Liang Zeng; Joseph Chen; L.-S. Fan

    2009-08-15

    The syngas chemical looping (SCL) process coproduces hydrogen and electricity. The process involves reducing metal oxides with syngas followed by regeneration of reduced metal oxides with steam and air in a cyclic manner. Iron oxide is determined to be a desired oxygen carrier for hydrogen production considering overall properties including oxygen carrying capacity, thermodynamic properties, reaction kinetics, physical strength, melting points, and environmental effects. An iron oxide based particle can maintain good reactivity for more than 100 reduction-oxidation (redox) cycles in a thermogravimetric analyzer (TGA). The particle exhibits a good crushing strength (>20 MPa) and low attrition rate. Fixed bed experiments are carried out which reaffirm its reactivity. More than 99.75% of syngas is converted during the reduction stage. During the regeneration stage, hydrogen with an average purity of 99.8% is produced. 23 refs., 6 figs., 10 tabs.

  1. 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.

  2. Activation of surface oxygen sites on an iridium-based model catalyst for the oxygen evolution reaction

    NASA Astrophysics Data System (ADS)

    Grimaud, Alexis; Demortiere, Arnaud; Saubanere, Matthieu; Dachraoui, Walid; Duchamp, Martial; Doublet, Marie-Liesse; Tarascon, Jean-Marie

    2017-01-01

    The oxygen evolution reaction (OER) is of prime importance in multiple energy storage devices; however, deeper mechanistic understanding is required to design enhanced electrocatalysts for the reaction. Current understanding of the OER mechanism based on oxygen adsorption on a metallic surface site fails to fully explain the activity of iridium and ruthenium oxide surfaces, and the drastic surface reconstruction observed for the most active OER catalysts. Here we demonstrate, using La2LiIrO6 as a model catalyst, that the exceptionally high activity found for Ir-based catalysts arises from the formation of active surface oxygen atoms that act as electrophilic centres for water to react. Moreover, with the help of transmission electron microscopy, we observe drastic surface reconstruction and iridium migration from the bulk to the surface. Therefore, we establish a correlation between surface activity and surface stability for OER catalysts that is rooted in the formation of surface reactive oxygen.

  3. The remarkable effect of oxygen on the N2 selectivity of water catalytic denitrification by hydrogen.

    PubMed

    Constantinou, Costas L; Costa, Costas N; Efstathiou, Angelos M

    2007-02-01

    The selective catalytic reduction of nitrates (NO3-) in pure water toward N2 formation by the use of gaseous H2 and in the presence of O2 (air) at 1 atm total pressure and 25 degrees C has been investigated over Pd-Cu supported on various mixed metal oxides, x wt % MO(x(/gamma-Al2O3 (MO(x) = CeO2, SrO, Mn2O3, Cr2O3, Y2O3, and TiO2). It is demonstrated for the firsttime that a remarkable improvement in N2 reaction selectivity (by 80 percentage units) can be achieved when oxygen is present in the reducing feed gas stream. In particular, significantly lower reaction selectivities toward NH4+ and NO2- can be obtained, whereas the rate of NO3- conversion is not significantly affected. Moreover, it was shown thatthe same effect is obtained over the Pd-Cu-supported catalysts irrespective to the chemical composition of support and the initial concentration of nitrates in water used. The Pd-Cu clusters supported on 4.8 wt%TiO2/gamma-Al2O3 resulted in a solid with the best catalytic behavior compared with the rest of supports examined, both in the presence and in the absence of oxygen in the reducing feed gas stream. DRIFTS studies performed following catalytic reduction by H2 of NO3- in water revealed that the presence of TiO2 in the Pd-Cu/TiO2-Al2O3 system enhanced the reactivity of adsorbed bidentate nitrate species toward H2. Nitrosyl species adsorbed on the alumina and titania support surfaces are considered as active intermediate species of the selective catalytic reduction of NO3- by H2 in water. Pd-Cu/TiO2-Al2O3 appears to be the most selective catalyst ever reported in the literature for the reduction of nitrates present in pure water into N2 by a reducing gas mixture of H2/air.

  4. Selective impairment of endothelium-dependent relaxation by sevoflurane: oxygen free radicals participation.

    PubMed

    Yoshida, K; Okabe, E

    1992-03-01

    To determine whether sevoflurane alters endothelium-mediated vasodilation of vascular smooth muscle, isolated ring preparations of canine mesenteric arteries were suspended for isometric tension recordings in modified Krebs-Ringer bicarbonate solution at 37 degrees C. Following contraction with norepinephrine, cumulative concentration-response curves were generated using endothelium-dependent vasodilators (acetylcholine, bradykinin, and calcium ionophore A23187) or nitroglycerin. The relaxation produced by acetylcholine, bradykinin, or A23187 was impaired by sevoflurane (2.3 and 4.6 vol%); sevoflurane did not affect relaxation caused by nitroglycerin, which, in these vessels, acts by an endothelium-independent mechanism. Under the same experimental conditions as those used for the concentration-response relationship, electron spin resonance spin-trapping with 5,5-dimethyl-1-pyrroline N-oxide verified generation of hydroxyl radical from the sevoflurane-delivered bathing media; the generation of hydroxyl radical was inhibited by superoxide dismutase, a scavenger of superoxide anion radical, or by the powerful iron chelator deferoxamine. Furthermore, sevoflurane-induced impairment of the relaxation caused by the endothelium-dependent vasodilators used was significantly decreased by superoxide dismutase. These results indicate that superoxide anion radical and/or closely related species of oxygen free radicals, possibly hydroxyl radical, are involved in the observed effect of sevoflurane. We propose that sevoflurane selectively impairs endothelium-dependent relaxation in canine mesenteric arteries by an oxygen free radical mechanism, mainly due to inactivation of endothelium-derived relaxing factor.

  5. 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.

  6. 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)

  7. 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. PMID:27630556

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

    PubMed

    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.

  9. A lithium–oxygen battery based on lithium superoxide

    DOE PAGES

    Lu, Jun; Jung Lee, Yun; Luo, Xiangyi; ...

    2016-01-11

    Batteries based on sodium superoxide and on potassium superoxide have recently been reported(1-3). But, there have been no reports of a battery based on lithium superoxide (LiO2), despite much research(4-8) into the lithium-oxygen (Li-O2) battery because of its potential high energy density. Several studies(9-16) 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(17). Our studies also suggest that it might be possible to form LiO2 alone for use in a battery.more » However, solid LiO2 has been difficult to synthesize in pure form(18) because it is thermodynamically unstable with respect to disproportionation, giving Li2O2 (refs 19, 20). 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 also 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.« less

  10. 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.

  11. Comparison of Iron and Tungsten Based Oxygen Carriers for Hydrogen Production Using Chemical Looping Reforming

    NASA Astrophysics Data System (ADS)

    Khan, M. N.; Shamim, T.

    2017-08-01

    Hydrogen production by using a three reactor chemical looping reforming (TRCLR) technology is an innovative and attractive process. Fossil fuels such as methane are the feedstocks used. This process is similar to a conventional steam-methane reforming but occurs in three steps utilizing an oxygen carrier. As the oxygen carrier plays an important role, its selection should be done carefully. In this study, two oxygen carrier materials of base metal iron (Fe) and tungsten (W) are analysed using a thermodynamic model of a three reactor chemical looping reforming plant in Aspen plus. The results indicate that iron oxide has moderate oxygen carrying capacity and is cheaper since it is abundantly available. In terms of hydrogen production efficiency, tungsten oxide gives 4% better efficiency than iron oxide. While in terms of electrical power efficiency, iron oxide gives 4.6% better results than tungsten oxide. Overall, a TRCLR system with iron oxide is 2.6% more efficient and is cost effective than the TRCLR system with tungsten oxide.

  12. 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

  13. 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…

  14. 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…

  15. Oxybiotest project: microorganisms under pressure. Hyperbaric oxygen (HBO) and simple pressure interaction on selected bacteria

    PubMed Central

    2012-01-01

    Background HyperBaric Oxygen (HBO) therapy involves exposure to pure oxygen in a pressurized room, and it is an already well-established treatment for various conditions, including those originated by serious infections. Starting from the observation of an increased number of patients who were accessing our HBO units for diseases supported from concomitant multidrug-resistant microorganisms, as well as considering the evident clinical benefit and laboratory final outcome of those patients at the end of the treatment, aim of our study was to measure, or better define at least, if there was any interaction between a hyperbaric environment and some selected microorganisms and if those positive results were due to the increased oxygen partial pressure (pO2) value or just to the increased pressure, regardless of the fraction of inspired oxygen (FiO2) applied (21÷100%). Design and methods We applied various increased pO2 values in a hyperbaric environment. Our study design was tailored in four steps to answer four specific questions, ordered in a progressive process: OxyBioTest (OBT)-1,2,3, and 4. Specifically, we chose to investigate possible changes in the Minimum Inhibitory Concentration (MIC) and in the Minimum Bactericidal Concentration (MBC) of multi-resistant microorganisms after a single session of hyperbaric therapy. Results OBT-1 and OBT-2 provide a semi-quantitative confirmation of the bacterio-cidal and cytostatic effects of HBO. HBO is cidal only if the total exposure pressure is elevated, and cidal or cytostatic effect are not always dependent on the pO2 applied. OBT-4 has shown the adjuvant effect of HBO and antimicrobial drug against some selected bacteria. Discussion We seem allowed to hypothesize that only in case of a good approach to a lesion, permitting smaller bacterial loads thanks to surgical debridement and/or eventual antibiotic therapy for example, You can observe the clear effectiveness of the HyperBaric Oxygen (HBO) exposure as a valid

  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.

  17. Rational Design of Advanced Photosensitizers Based on Orthogonal BODIPY Dimers to Finely Modulate Singlet Oxygen Generation.

    PubMed

    Epelde-Elezcano, Nerea; Palao, Eduardo; Manzano, Hegoi; Prieto-Castañeda, Alejandro; Agarrabeitia, Antonia R; Tabero, Andrea; Villanueva, Angeles; de la Moya, Santiago; López-Arbeloa, Íñigo; Martínez-Martínez, Virginia; Ortiz, María J

    2017-04-06

    The synthesis, photophysical characterization, and modeling of a new library of halogen-free photosensitizers (PS) based on orthogonal boron dipyrromethene (BODIPY) dimers are reported. Herein we establish key structural factors in order to enhance singlet oxygen generation by judiciously choosing the substitution patterns according to key electronic effects and synthetic accessibility factors. The photosensitization mechanism of orthogonal BODIPY dimers is demonstrated to be strongly related to their intrinsic intramolecular charge transfer (ICT) character through the spin-orbit charge-transfer intersystem crossing (SOCT-ISC) mechanism. Thus, singlet oxygen generation can be effectively modulated through the solvent polarity and the presence of electron-donating or withdrawing groups in one of the BODIPY units. The photodynamic therapy (PDT) activity is demonstrated by in vitro experiments, showing that selected photosensitizers are efficiently internalized into HeLa cells, exhibiting low dark toxicity and high phototoxicity, even at low PS concentration (0.05-5×10(-6)  m).

  18. Analyzing sediment dissolved oxygen based on microprofile modeling.

    PubMed

    Wang, Chao; Shan, Baoqing; Zhang, Hong; Rong, Nan

    2014-09-01

    Sediment plays a key role in controlling the oxygen demand of aquatic systems. The reaction rate, penetration depth, and flux across the sediment-water interface (SWI) are important factors in sediment oxygen consumption. However, there were few methods to collect these data until recently. In this study, methods were developed to simulate the oxygen microprofile and calculate the sediment oxygen consumption rate, oxygen penetration depth, and oxygen flux across the SWI. We constructed a sediment oxygen measuring system using an oxygen microelectrode and a control device. The simulation equations were derived from both zero and first-order kinetic models, while the penetration depth and the oxygen flux were calculated from the simulation results. The method was tested on four prepared sediment samples. Decreases in dissolved oxygen in surface sediment were clearly detected by the microelectrode. The modeled data were a good fit for the observed data (R (2) > 0.95), and zero-order kinetics were more suitable than first-order kinetics. The values for penetration depth (1.3-3.9 mm) and oxygen fluxes (0.061-0.114 mg/cm(2)/day) calculated by our methods are comparable with those from other studies.

  19. Effect of dissolved oxygen concentration (microaerobic and aerobic) on selective enrichment culture for bioaugmentation of acidic industrial wastewater.

    PubMed

    Quan, Ying; Han, Hui; Zheng, Shaokui

    2012-09-01

    The successful application of bioaugmentation is largely dependent on the selective enrichment of culture with regards to pH, temperature, salt, or specific toxic organic pollutants. In this study, we investigated the effect of dissolved oxygen (DO) concentrations (aerobic, >2 mg L(-1); microaerobic, <1 mg L(-1)) on yeast enrichment culture for bioaugmentation of acidic industrial wastewater (pH 3.9-4.7). Clone library analyses revealed that the yeast community shifted in response to different DO levels, and that Candida humilis and Candida pseudolambica were individually dominant in the aerobic and microaerobic enrichment cultures. This would significantly influence the isolation results, and further hinder bioaugmentation due to differences in DO environments during the enrichment and application periods. However, differences in the selective enrichment culture cannot be predicted based on differences in pollutant removal performance. Thus, DO concentrations (aerobic/microaerobic) should be considered a secondary selective pressure to achieve successful bioaugmentation. Copyright © 2012 Elsevier Ltd. All rights reserved.

  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. Copper chelation selectively kills colon cancer cells through redox cycling and generation of reactive oxygen species.

    PubMed

    Fatfat, Maamoun; Merhi, Raghida Abou; Rahal, Omar; Stoyanovsky, Detcho A; Zaki, Angela; Haidar, Hazar; Kagan, Valerian E; Gali-Muhtasib, Hala; Machaca, Khaled

    2014-07-21

    Metals including iron, copper and zinc are essential for physiological processes yet can be toxic at high concentrations. However the role of these metals in the progression of cancer is not well defined. Here we study the anti-tumor activity of the metal chelator, TPEN, and define its mechanism of action. Multiple approaches were employed, including cell viability, cell cycle analysis, multiple measurements of apoptosis, and mitochondrial function. In addition we measured cellular metal contents and employed EPR to record redox cycling of TPEN-metal complexes. Mouse xenografts were also performed to test the efficacy of TPEN in vivo. We show that metal chelation using TPEN (5μM) selectively induces cell death in HCT116 colon cancer cells without affecting the viability of non-cancerous colon or intestinal cells. Cell death was associated with increased levels of reactive oxygen species (ROS) and was inhibited by antioxidants and by prior chelation of copper. Interestingly, HCT116 cells accumulate copper to 7-folds higher levels than normal colon cells, and the TPEN-copper complex engages in redox cycling to generate hydroxyl radicals. Consistently, TPEN exhibits robust anti-tumor activity in vivo in colon cancer mouse xenografts. Our data show that TPEN induces cell death by chelating copper to produce TPEN-copper complexes that engage in redox cycling to selectively eliminate colon cancer cells.

  2. Selection for high and low oxygen consumption-induced differences in maintenance energy requirements of mice.

    PubMed

    Darhan, Hongyu; Kikusato, Motoi; Toyomizu, Masaaki; Roh, Sang-Gun; Katoh, Kazuo; Sato, Masahiro; Suzuki, Keiichi

    2017-07-01

    Maintenance energy requirements (MER) of mice selected for high (H) or low (L) oxygen consumption (OC) were compared. Forty-four mice from H and L OC lines were weaned at 3 weeks and divided into four experimental groups: group A were sacrificed at 4 weeks; group B were fed ad libitum, and groups C and D were fed 2.8 and 2.4 g/day, respectively, from 4 to 8 weeks of age. Groups B-D were sacrificed at 8 weeks. Chemical components were estimated for all groups. MER was estimated using a model that partitioned metabolizable energy intake into that used for maintenance, and protein and fat deposition. The feed conversion ratio for the B group was significantly higher in the H than in the L line. Feed intake for metabolic energy content per metabolic body size was significantly also higher in the H line, whereas accumulated energy content per metabolic body size was significantly higher in the L line. MER of the H line was greater than that of the L line (P < 0.10). These results suggest that selection for H or L OC produced differences in chemical components, feed efficiency, and MER between the H and L lines. © 2016 Japanese Society of Animal Science.

  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 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...

  5. A Peroxygenase from Chaetomium globosum Catalyzes the Selective Oxygenation of Testosterone

    PubMed Central

    Schmidtke, Kai‐Uwe; Zimmermann, Jörg; Kellner, Harald; Jehmlich, Nico; Ullrich, René; Zänder, Daniel; Hofrichter, Martin; Scheibner, Katrin

    2017-01-01

    Abstract Unspecific peroxygenases (UPO, EC 1.11.2.1) secreted by fungi open an efficient way to selectively oxyfunctionalize diverse organic substrates, including less‐activated hydrocarbons, by transferring peroxide‐borne oxygen. We investigated a cell‐free approach to incorporate epoxy and hydroxyl functionalities directly into the bulky molecule testosterone by a novel unspecific peroxygenase (UPO) that is produced by the ascomycetous fungus Chaetomium globosum in a complex medium rich in carbon and nitrogen. Purification by fast protein liquid chromatography revealed two enzyme fractions with the same molecular mass (36 kDa) and with specific activity of 4.4 to 12 U mg−1. Although the well‐known UPOs of Agrocybe aegerita (AaeUPO) and Marasmius rotula (MroUPO) failed to convert testosterone in a comparative study, the UPO of C. globosum (CglUPO) accepted testosterone as substrate and converted it with total turnover number (TTN) of up to 7000 into two oxygenated products: the 4,5‐epoxide of testosterone in β‐configuration and 16α‐hydroxytestosterone. The reaction performed on a 100 mg scale resulted in the formation of about 90 % of the epoxide and 10 % of the hydroxylation product, both of which could be isolated with purities above 96 %. Thus, CglUPO is a promising biocatalyst for the oxyfunctionalization of bulky steroids and it will be a useful tool for the synthesis of pharmaceutically relevant steroidal molecules. PMID:28103392

  6. The influence of selected parameters on the efficiency and economic charactersistics of the oxy-type coal unit with a membrane-cryogenic oxygen separator

    NASA Astrophysics Data System (ADS)

    Kotowicz, Janusz; Berdowska, Sylwia

    2016-03-01

    In this paper a 600 MW oxy-type coal unit with a pulverized bed boiler and a membrane-cryogenic oxygen separator and carbon capture installation was analyzed. A membrane-cryogenic oxygen separation installation consists of a membrane module and two cryogenic distillation columns. In this system oxygen is produced with the purity equal to 95%. Installation of carbon capture was based on the physical separation method and allows to reduce the CO2 emission by 90%. In this work the influence of the main parameter of the membrane process - the selectivity coefficient, on the efficiency of the coal unit was presented. The economic analysis with the use of the break-even point method was carried out. The economic calculations were realized in view of the break-even price of electricity depending on a coal unit availability.

  7. 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.

  8. 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

  9. A lithium–oxygen battery based on lithium superoxide

    SciTech Connect

    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

    2016-01-11

    Batteries based on sodium superoxide and on potassium superoxide have recently been reported(1-3). But, there have been no reports of a battery based on lithium superoxide (LiO2), despite much research(4-8) into the lithium-oxygen (Li-O2) battery because of its potential high energy density. Several studies(9-16) 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(17). Our 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(18) because it is thermodynamically unstable with respect to disproportionation, giving Li2O2 (refs 19, 20). 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 also 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.

  10. 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

  11. Quasar Selection Based On Photometric Variability

    NASA Astrophysics Data System (ADS)

    MacLeod, Chelsea; Brooks, K.; Ivezic, Z.; Kochanek, C. S.; Gibson, R.; Meisner, A.; Kozlowski, S.; Sesar, B.; Becker, A. C.; deVries, W. H.

    2011-01-01

    We develop a method for separating quasars from other variable point sources using SDSS Stripe 82 light curve data for 10,000 variable objects. To statistically describe quasar variability, we use a damped random walk model parametrized by a damping time scale, tau, and an asymptotic amplitude (structure function), SF_inf. With the aid of an SDSS spectroscopically confirmed quasar sample, we demonstrate that variability selection in typical extragalactic fields with low stellar density can deliver complete samples with reasonable purity (or efficiency, E). Compared to a selection method based solely on the slope of the structure function, the inclusion of the tau information boosts E from 60% to 75% while maintaining a highly complete sample (98%) even in the absence of color information. With the aid of color selection, the purity can be further boosted to 96%, with C=93%. Hence, selection methods based on variability will play an important role in the selection of quasars with data provided by upcoming large sky surveys, such as the Large Synoptic Survey Telescope (LSST). For a typical (simulated) LSST cadence over 10 years and a photometric accuracy of 0.03 mag (achieved at i 22), C is expected to be 88% for a simple sample selection criterion of tau>100 days. In summary, given an adequate survey cadence, photometric variability provides an even better method than color selection for separating quasars from stars. We acknowledge support by NSF grant AST-0807500 to the University of Washington.

  12. 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.

  13. Selective photocytotoxicity of anthrols on cancer stem-like cells: The effect of quinone methides or reactive oxygen species.

    PubMed

    Uzelac, Lidija; Škalamera, Đani; Mlinarić-Majerski, Kata; Basarić, Nikola; Kralj, Marijeta

    2017-09-08

    Cancer stem cells (CSCs) are a subpopulation of cancer cells that share properties of embryonic stem cells like pluripotency and self-renewal and show increased resistance to chemo- and radiotherapy. Targeting CSC, rather than cancer cells in general, is a novel and promising strategy for cancer treatment. Novel therapeutic approaches, such as photodynamic therapy (PDT) have been investigated. A promising group of phototherapeutic agents are reactive intermediates - quinone methides (QMs). This study describes preparation of QM precursor, 2-hydroxy-3-hydroxymethylanthracene (2) and a detailed photochemical and photobiological investigation on similar anthracene derivatives 3 and 4. Upon photoexcitation with near visible light at λ > 400 nm 1 and 2 give QMs, that were detected by laser flash photolysis and their reactivity with nucleophiles has been demonstrated in the preparative irradiation experiments where the corresponding adducts were isolated and characterized. 3 and 4 cannot undergo photodehydration and deliver QM, but lead to the formation of phenoxyl radical and singlet oxygen, respectively. The activity of 1-4 was tested on a panel of human tumor cell lines, while special attention was devoted to demonstrate their potential selectivity towards the cells with CSC-like properties (HMLEshEcad). Upon the irradiation of cell lines treated with 1-4, an enhancement of antiproliferative activity was demonstrated, but the DNA was not the target molecule. Confocal microscopy revealed that these compounds entered the cell and, upon irradiation, reacted with cellular membranes. Our experiments demonstrated moderate selectivity of 2 and 4 towards CSC-like cells, while necrosis was shown to be a dominant cell death mechanism. Especially interesting was the selectivity of 4 that produced higher levels of ROS in CSC-like cells, which forms the basis for further research on cancer phototherapy, as well as for the elucidation of the underlying mechanism of the observed

  14. 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.

  15. Carbocysteine lysine salt monohydrate (SCMC-LYS) is a selective scavenger of reactive oxygen intermediates (ROIs).

    PubMed

    Brandolini, Laura; Allegretti, Marcello; Berdini, Valerio; Cervellera, Maria Neve; Mascagni, Patrizia; Rinaldi, Matteo; Melillo, Gabriella; Ghezzi, Pietro; Mengozzi, Manuela; Bertini, Riccardo

    2003-01-01

    Carbocysteine lysine salt monohydrate (SCMC-Lys) is a well-known mucoactive drug whose therapeutic efficacy is commonly related to the ability of SCMC-Lys to replace fucomucins by sialomucins. The aim of this study was to determine if SCMC-Lys could exert an anti-oxidant action by scavenging reactive oxygen intermediates (ROIs). Our results show that SCMC-Lys proved effective as a selective scavenger of hypochlorous acid (HOCl) and hydroxyl radical (OH.), this effect being related to the reactivity of the SCMC tioether group. The scavenger activity of SCMC-Lys was observed in free cellular system as well as in activated human polymorphonuclear neutrophils (PMNs). SCMC-Lys scavenger activity on HOCl was paralleled by a powerful protection from HOCl-mediated inactivation of alpha1-antitripsin (alpha1-AT) inhibitor, the main serum protease inhibitor. Production of interleukin-(IL-)8, a major mediator of PMN recruitment in inflammatory diseases, is known to be mediated by intracellular OH. SCMC-Lys significantly reduced IL-8 production on stimulated human peripheral blood mononuclear cells (PBMCs) in the same range of concentrations affecting OH. activity. It is concluded that SCMC-Lys could exert, in addition to its mucoactive capacity, an anti-oxidant action, thus contributing to the therapeutic efficacy of SCMC-Lys.

  16. Stable and solubilized active Au atom clusters for selective epoxidation of cis-cyclooctene with molecular oxygen

    DOE PAGES

    Qian, Linping; Wang, Zhen; Beletskiy, Evgeny V.; ...

    2017-03-28

    Here, the ability of Au catalysts to effect the challenging task of utilizing molecular oxygen for the selective epoxidation of cyclooctene is fascinating. Although supported nanometre-size Au particles are poorly active, here we show that solubilized atomic Au clusters, present in ng ml–1 concentrations and stabilized by ligands derived from the oxidized hydrocarbon products, are active. They can be formed from various Au sources. They generate initiators and propagators to trigger the onset of the auto-oxidation reaction with an apparent turnover frequency of 440 s–1, and continue to generate additional initiators throughout the auto-oxidation cycle without direct participation in themore » cycle. Spectroscopic characterization suggests that 7–8 atom clusters are effective catalytically. Extension of work based on these understandings leads to the demonstration that these Au clusters are also effective in selective oxidation of cyclohexene, and that solubilized Pt clusters are also capable of generating initiators for cyclooctene epoxidation.« less

  17. SELECTIVE OXIDATION OF ALCOHOLS BY MOLECULAR OXYGEN OVER A PD/MGO CATALYST IN THE ABSENCE OF ANY ADDITIVES

    EPA Science Inventory

    Selective oxidation of alcohols to the corresponding carbonyl products using molecular oxygen is achieved over a simple and easily recyclable 1% Pd/MgO impregnated heterogeneous catalyst in the presence of trifluorotoluene. A variety of activated and non-activated alcohols are ef...

  18. SELECTIVE OXIDATION OF ALCOHOLS BY MOLECULAR OXYGEN OVER A PD/MGO CATALYST IN THE ABSENCE OF ANY ADDITIVES

    EPA Science Inventory

    Selective oxidation of alcohols to the corresponding carbonyl products using molecular oxygen is achieved over a simple and easily recyclable 1% Pd/MgO impregnated heterogeneous catalyst in the presence of trifluorotoluene. A variety of activated and non-activated alcohols are ef...

  19. Discriminative Projection Selection Based Face Image Hashing

    NASA Astrophysics Data System (ADS)

    Karabat, Cagatay; Erdogan, Hakan

    Face image hashing is an emerging method used in biometric verification systems. In this paper, we propose a novel face image hashing method based on a new technique called discriminative projection selection. We apply the Fisher criterion for selecting the rows of a random projection matrix in a user-dependent fashion. Moreover, another contribution of this paper is to employ a bimodal Gaussian mixture model at the quantization step. Our simulation results on three different databases demonstrate that the proposed method has superior performance in comparison to previously proposed random projection based methods.

  20. Continuum-based DFN-consistent simulations of oxygen ingress in fractured crystalline rocks

    NASA Astrophysics Data System (ADS)

    Trinchero, P.; Puigdomenech, I.; Molinero, J.; Ebrahimi, H.; Gylling, B.; Svensson, U.; Bosbach, D.; Deissmann, G.

    2016-12-01

    The potential transient infiltration of oxygenated glacial meltwater into initially anoxic and reducing fractured crystalline rocks during glaciation events is an issue of concern for some of the prospected deep geological repositories for spent nuclear fuel. Here, this problem is assessed using reactive transport calculations. First, a novel parameterisation procedure is presented, where flow, transport and geochemical parameters (i.e. hydraulic conductivity, effective/kinetic porosity, and mineral specific surface and abundance) are defined on a finite volume numerical grid based on the (spatially varying) properties of an underlying Discrete Fracture Network (DFN). Second, using this approach, a realistic reactive transport model of Forsmark, i.e. the selected site for the proposed Swedish spent nuclear fuel repository, is implemented. The model consists of more than 70 million geochemical transport degrees of freedom and simulates the ingress of oxygen-rich water from the recharge area of the domain and its depletion due to reactions with the Fe(II) mineral chlorite. Third, the calculations are solved in the supercomputer JUQUEEN of the Jülich Supercomputing Centre. The results of the simulations show that oxygen infiltrates relatively quickly along fractures and deformation zones until a steady state profile is reached, where geochemical reactions counterbalance advective transport processes. Interestingly, most of the iron-bearing minerals are consumed in the highly conductive zones, where larger mineral surfaces are available for reactions. An analysis based on mineral mass balance shows that the considered rock medium has enough capacity to buffer oxygen infiltration for a long period of time (i.e. some thousand years).

  1. New method of extracting information of arterial oxygen saturation based on ∑ | 𝚫 |

    NASA Astrophysics Data System (ADS)

    Dai, Wenting; Lin, Ling; Li, Gang

    2017-04-01

    Noninvasive detection of oxygen saturation with near-infrared spectroscopy has been widely used in clinics. In order to further enhance its detection precision and reliability, this paper proposes a method of time domain absolute difference summation (∑|Δ|) based on a dynamic spectrum. In this method, the ratio of absolute differences between intervals of two differential sampling points at the same moment on logarithm photoplethysmography signals of red and infrared light was obtained in turn, and then they obtained a ratio sequence which was screened with a statistical method. Finally, use the summation of the screened ratio sequence as the oxygen saturation coefficient Q. We collected 120 reference samples of SpO2 and then compared the result of two methods, which are ∑|Δ| and peak-peak. Average root-mean-square errors of the two methods were 3.02% and 6.80%, respectively, in the 20 cases which were selected randomly. In addition, the average variance of Q of the 10 samples, which were obtained by the new method, reduced to 22.77% of that obtained by the peak-peak method. Comparing with the commercial product, the new method makes the results more accurate. Theoretical and experimental analysis indicates that the application of the ∑|Δ| method could enhance the precision and reliability of oxygen saturation detection in real time.

  2. New method of extracting information of arterial oxygen saturation based on ∑|𝚫 |

    NASA Astrophysics Data System (ADS)

    Wenting, Dai; Ling, Lin; Gang, Li

    2017-04-01

    Noninvasive detection of oxygen saturation with near-infrared spectroscopy has been widely used in clinics. In order to further enhance its detection precision and reliability, this paper proposes a method of time domain absolute difference summation (∑|Δ|) based on a dynamic spectrum. In this method, the ratio of absolute differences between intervals of two differential sampling points at the same moment on logarithm photoplethysmography signals of red and infrared light was obtained in turn, and then they obtained a ratio sequence which was screened with a statistical method. Finally, use the summation of the screened ratio sequence as the oxygen saturation coefficient Q. We collected 120 reference samples of SpO2 and then compared the result of two methods, which are ∑|Δ| and peak-peak. Average root-mean-square errors of the two methods were 3.02% and 6.80%, respectively, in the 20 cases which were selected randomly. In addition, the average variance of Q of the 10 samples, which were obtained by the new method, reduced to 22.77% of that obtained by the peak-peak method. Comparing with the commercial product, the new method makes the results more accurate. Theoretical and experimental analysis indicates that the application of the ∑|Δ| method could enhance the precision and reliability of oxygen saturation detection in real time.

  3. 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

  4. 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

  5. Cholesterol biosensors based on oxygen sensing alginate-silica microspheres.

    PubMed

    Prasad, Janak; Joshi, Abhijeet; Jayant, Rahul Dev; Srivastava, Rohit

    2011-09-01

    Cholesterol determination in body is important in diagnosis of diseases like coronary heart disease, arteriosclerosis, diabetes, and obstructive jaundice. This research aims at developing fluorimetric cholesterol biosensors based on self-assembled mesoporous alginate-silica (Algilica) microspheres. For preparing the biosensor, Pt-(II)-octaethylporphine (PtOEP; oxygen sensitive metalloporphyrin) dye has been loaded in the Algilica microspheres using the solvent-mediated precipitation method. Cholesterol oxidase (ChOx) was then covalently conjugated to PtOEP/Algilica microspheres using EDC and NHS reagents. PtOEP dye and enzyme encapsulation, activity and stability were then analyzed. Layer-by-layer self-assembly was finally performed using PAH and PSS polyelectrolytes to minimize leaching of the biosensor components. The prepared biosensor exhibited linearity over a range of 0.77-2.5 mM O(2) (K(SV) : 0.097/mM of O(2) ) obtained using from Stern-Volmer plots. The biosensor response to standard cholesterol displayed a linear analytical range from 1.25 to 10 mM of cholesterol with regression coefficient of 0.996 (1.25-3.75 mM), 0.976 (1.25-6 mM), and 0.959 (1.25-10 mM) and response time of 10 min. Thus, the prepared cholesterol biosensor shows great potential in the diagnosis of hypercholesterolemia. Copyright © 2011 Wiley Periodicals, Inc.

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

    USDA-ARS?s Scientific Manuscript database

    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...

  7. Feature subset selection based on relevance

    NASA Astrophysics Data System (ADS)

    Wang, Hui; Bell, David; Murtagh, Fionn

    In this paper an axiomatic characterisation of feature subset selection is presented. Two axioms are presented: sufficiency axiom—preservation of learning information, and necessity axiom—minimising encoding length. The sufficiency axiom concerns the existing dataset and is derived based on the following understanding: any selected feature subset should be able to describe the training dataset without losing information, i.e. it is consistent with the training dataset. The necessity axiom concerns the predictability and is derived from Occam's razor, which states that the simplest among different alternatives is preferred for prediction. The two axioms are then restated in terms of relevance in a concise form: maximising both the r( X; Y) and r( Y; X) relevance. Based on the relevance characterisation, four feature subset selection algorithms are presented and analysed: one is exhaustive and the remaining three are heuristic. Experimentation is also presented and the results are encouraging. Comparison is also made with some well-known feature subset selection algorithms, in particular, with the built-in feature selection mechanism in C4.5.

  8. A DFT study of oxygen dissociation on platinum based nanoparticles.

    PubMed

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

    2014-01-21

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

  9. Quasar Selection Based on Photometric Variability

    NASA Astrophysics Data System (ADS)

    MacLeod, C. L.; Brooks, K.; Ivezić, Ž.; Kochanek, C. S.; Gibson, R.; Meisner, A.; Kozłowski, S.; Sesar, B.; Becker, A. C.; de Vries, W. H.

    2011-02-01

    We develop a method for separating quasars from other variable point sources using Sloan Digital Sky Survey (SDSS) Stripe 82 light-curve data for ~ 10,000 variable objects. To statistically describe quasar variability, we use a damped random walk model parametrized by a damping timescale, τ, and an asymptotic amplitude (structure function), SF∞. With the aid of an SDSS spectroscopically confirmed quasar sample, we demonstrate that variability selection in typical extragalactic fields with low stellar density can deliver complete samples with reasonable purity (or efficiency, E). Compared to a selection method based solely on the slope of the structure function, the inclusion of the τ information boosts E from 60% to 75% while maintaining a highly complete sample (98%) even in the absence of color information. For a completeness of C = 90%, E is boosted from 80% to 85%. Conversely, C improves from 90% to 97% while maintaining E = 80% when imposing a lower limit on τ. With the aid of color selection, the purity can be further boosted to 96%, with C = 93%. Hence, selection methods based on variability will play an important role in the selection of quasars with data provided by upcoming large sky surveys, such as Pan-STARRS and the Large Synoptic Survey Telescope (LSST). For a typical (simulated) LSST cadence over 10 years and a photometric accuracy of 0.03 mag (achieved at i ≈ 22), C is expected to be 88% for a simple sample selection criterion of τ>100 days. In summary, given an adequate survey cadence, photometric variability provides an even better method than color selection for separating quasars from stars.

  10. Mixtures of hemoglobin-based oxygen carriers and perfluorocarbons exhibit a synergistic effect in oxygenating hepatic hollow fiber bioreactors.

    PubMed

    Chen, Guo; Palmer, Andre F

    2010-02-15

    Hepatic hollow fiber (HF) bioreactors are being developed for use as bioartificial liver assist devices (BLADs). In general, BLADs suffer from O(2) limited transport, which reduces their performance. This modeling study seeks to investigate if O(2) carrying solutions consisting of mixtures of hemoglobin-based oxygen carriers (HBOCs) and perfluorocarbons (PFCs) can enhance O(2) transport to hepatocytes cultured in the extra capillary space (ECS) of HF bioreactors. We simulated supplementing the circulating cell culture media stream of the HF bioreactor with a mixture containing these two types of oxygen carriers (HBOCs and PFCs). A mathematical model was developed based on the dimensions and physical characteristics of a commercial HF bioreactor. The resulting set of partial differential equations, which describes fluid transport; as well as, mass transport of dissolved O(2) in the pseudo-homogeneous PFC/water phase and oxygenated HBOC, was solved to yield the O(2) concentration field in the three HF domains (lumen, membrane and ECS). Our results show that mixtures of HBOC and PFC display a synergistic effect in oxygenating the ECS. Therefore, the presence of both HBOC and PFC in the circulating cell culture media dramatically improves transport of O(2) to cultured hepatocytes. Moreover, the in vivo O(2) spectrum in a liver sinusoid can be recapitulated by supplementing the HF bioreactor with a mixture of HBOCs and PFCs at an inlet pO(2) of 80 mmHg. Therefore, we expect that PFC-based oxygen carriers will be more efficient at transporting O(2) at higher O(2) levels (e.g., at an inlet pO(2) of 760 mmHg, which corresponds to pure O(2) in equilibrium with aqueous cell culture media at 1 atm). 2009 Wiley Periodicals, Inc.

  11. System and method for air temperature control in an oxygen transport membrane based reactor

    DOEpatents

    Kelly, Sean M

    2016-09-27

    A system and method for air temperature control in an oxygen transport membrane based reactor is provided. The system and method involves introducing a specific quantity of cooling air or trim air in between stages in a multistage oxygen transport membrane based reactor or furnace to maintain generally consistent surface temperatures of the oxygen transport membrane elements and associated reactors. The associated reactors may include reforming reactors, boilers or process gas heaters.

  12. System and method for temperature control in an oxygen transport membrane based reactor

    DOEpatents

    Kelly, Sean M.

    2017-02-21

    A system and method for temperature control in an oxygen transport membrane based reactor is provided. The system and method involves introducing a specific quantity of cooling air or trim air in between stages in a multistage oxygen transport membrane based reactor or furnace to maintain generally consistent surface temperatures of the oxygen transport membrane elements and associated reactors. The associated reactors may include reforming reactors, boilers or process gas heaters.

  13. Modeling of the humidity effects on the oxygen absorption by iron-based scavengers.

    PubMed

    Polyakov, Vladimir A; Miltz, Joseph

    2010-03-01

    It has been reported in the scientific literature that moisture is required for oxygen absorption by iron-based scavengers. The rate of oxygen absorption is crucial in oxygen-sensitive foods. However, no quantitative correlations between the relative humidity and the oxygen absorption by these scavengers have been found in the scientific literature. The humidity level, the O(2) concentration, and the gas composition inside the package are the major factors determining the isothermal O(2) absorption kinetics. In the present study, the effect of RH on the oxygen absorption of an iron powder taken from an oxygen scavenger was investigated. This process was modeled, and correlations have been developed and compared to experimental results. The developed models describe well the effect of humidity on the oxygen absorption by the iron powder. It was found that an increase in the rate of oxygen absorption results in a decrease in the porosity, an increase in the specific surface area of the iron powder's corrosion products, and a decrease in the O(2) diffusivity through the particles. The heat evolved during the exothermic reaction leads to a decrease in the amount of water adsorbed on the corrosion products. The results of the present study elucidate the effect of moisture on the O(2) absorption by iron-based oxygen scavengers and can be used for a proper design of packages intended for storage of foods and fruits and vegetables of intermediate and high water activity. Since humidity has an important role in determining the rate of oxygen absorption kinetics by iron-based oxygen scavengers, using the models derived and presented in the present publication can bring upon a better understanding of the oxygen absorption process and a more efficient way of using oxygen scavengers in the packaging and storing of different oxygen sensitive foods.

  14. Enantiotopos-selective C-H oxygenation catalyzed by a supramolecular ruthenium complex.

    PubMed

    Frost, James R; Huber, Stefan M; Breitenlechner, Stefan; Bannwarth, Christoph; Bach, Thorsten

    2015-01-07

    Spirocyclic oxindoles undergo an enantioselective oxygenation reaction (nine examples; e.r. up to 97:3) upon catalysis by a chiral ruthenium porphyrin complex (1 mol %). The catalyst exhibits a lactam ring, which is responsible for substrate association through hydrogen bonds, and an active ruthenium center, which is in a defined spatial relationship to the oxygenation substrate. DFT calculations illustrate the perfect alignment of the active site with the reactive C-H bond and suggest--in line with the kinetic isotope effect--an oxygen rebound mechanism for the reaction.

  15. 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.

  16. 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.

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

    PubMed

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

    1970-01-30

    The water content of the breccia is 150 to 455 ppm, with a deltaD from-580 to -870 per mil. Hydrogen gas content is 40 to 53 ppm with a deltaD of -830 to -970 per mil. The CO(2) is 290 to 418 ppm with delta (13)C = + 2.3 to + 5.1 per mil and delta(18)O = 14.2 to 19.1 per mil. Non-CO(2) carbon is 22 to 100 ppm, delta(13)C = -6.4 to -23.2 per mil. Lunar dust is 810 ppm H(2)O (D = 80 ppm) and 188 ppm total carbon(delta(13)C = -17.6 per mil). The (18)O analyses of whole rocks range from 5.8 to 6.2 per mil. The temperature of crystallization of type B rocks is 1100 degrees to 1300 degrees C, based on the oxygen isotope fractionation between coexisting plagioclase and ilmenite.

  18. Impact of oxygen on the coexistence of nitrification, denitrification, and sulfate reduction in oxygen-based membrane aerated biofilm.

    PubMed

    Liu, Hong; Tan, Shuying; Sheng, Zhiya; Yu, Tong; Liu, Yang

    2015-03-01

    Membrane aerated biofilms (MABs) are subject to "counter diffusion" of oxygen and substrates. In a membrane aerated biofilm reactor, gases (e.g., oxygen) diffuse through the membrane into the MAB, and liquid substrates pass from the bulk liquid into the MAB. This behavior can result in a unique biofilm structure in terms of microbial composition, distribution, and community activity in the MAB. Previous studies have shown simultaneous aerobic oxidation, nitrification, and denitrification within a single MAB. Using molecular techniques, we investigated the growth of sulfate-reducing bacteria (SRB) in the oxygen-based MAB attached to a flat sheet membrane. Denaturing gradient gel electrophoresis of the amplified 16S rRNA gene fragments and functional gene fragments specific for ammonia-oxidizing bacteria (amoA), denitrifying bacteria (nirK), and SRB (dsrB) demonstrated the coexistence of nitrifiers, denitrifiers, and SRB communities within a single MAB. The functional diversities of SRB and denitrifiers decreased with an increase in the oxygen concentration in the bulk water of the reactor.

  19. Control of selectivity in allylic alcohol oxidation on gold surfaces: the role of oxygen adatoms and hydroxyl species.

    PubMed

    Mullen, Gregory M; Zhang, Liang; Evans, Edward J; Yan, Ting; Henkelman, Graeme; Mullins, C Buddie

    2015-02-14

    Gold catalysts display high activity and good selectivity for partial oxidation of a number of alcohol species. In this work, we discuss the effects of oxygen adatoms and surface hydroxyls on the selectivity for oxidation of allylic alcohols (allyl alcohol and crotyl alcohol) on gold surfaces. Utilizing temperature programmed desorption (TPD), reactive molecular beam scattering (RMBS), and density functional theory (DFT) techniques, we provide evidence to suggest that the selectivity displayed towards partial oxidation versus combustion pathways is dependent on the type of oxidant species present on the gold surface. TPD and RMBS results suggest that surface hydroxyls promote partial oxidation of allylic alcohols to their corresponding aldehydes with very high selectivity, while oxygen adatoms promote both partial oxidation and combustion pathways. DFT calculations indicate that oxygen adatoms can react with acrolein to promote the formation of a bidentate surface intermediate, similar to structures that have been shown to decompose to generate combustion products over other transition metal surfaces. Surface hydroxyls do not readily promote such a process. Our results help explain phenomena observed in previous studies and may prove useful in the design of future catalysts for partial oxidation of alcohols.

  20. 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.

  1. Gallic Acid as an Oxygen Scavenger in Bio-Based Multilayer Packaging Films

    PubMed Central

    Pant, Astrid F.; Sängerlaub, Sven; Müller, Kajetan

    2017-01-01

    Oxygen scavengers are used in food packaging to protect oxygen-sensitive food products. A mixture of gallic acid (GA) and sodium carbonate was used as an oxygen scavenger (OSc) in bio-based multilayer packaging films produced in a three-step process: compounding, flat film extrusion, and lamination. We investigated the film surface color as well as oxygen absorption at different relative humidities (RHs) and temperatures, and compared the oxygen absorption of OSc powder, monolayer films, and multilayer films. The films were initially brownish-red in color but changed to greenish-black during oxygen absorption under humid conditions. We observed a maximum absorption capacity of 447 mg O2/g GA at 21 °C and 100% RH. The incorporation of GA into a polymer matrix reduced the rate of oxygen absorption compared to the GA powder because the polymer acted as a barrier to oxygen and water vapor diffusion. As expected, the temperature had a significant effect on the initial absorption rate of the multilayer films; the corresponding activation energy was 75.4 kJ/mol. Higher RH significantly increased the oxygen absorption rate. These results demonstrate for the first time the production and the properties of a bio-based multilayer packaging film with GA as the oxygen scavenger. Potential applications include the packaging of food products with high water activity (aw > 0.86). PMID:28772849

  2. Gallic Acid as an Oxygen Scavenger in Bio-Based Multilayer Packaging Films.

    PubMed

    Pant, Astrid F; Sängerlaub, Sven; Müller, Kajetan

    2017-05-03

    Oxygen scavengers are used in food packaging to protect oxygen-sensitive food products. A mixture of gallic acid (GA) and sodium carbonate was used as an oxygen scavenger (OSc) in bio-based multilayer packaging films produced in a three-step process: compounding, flat film extrusion, and lamination. We investigated the film surface color as well as oxygen absorption at different relative humidities (RHs) and temperatures, and compared the oxygen absorption of OSc powder, monolayer films, and multilayer films. The films were initially brownish-red in color but changed to greenish-black during oxygen absorption under humid conditions. We observed a maximum absorption capacity of 447 mg O₂/g GA at 21 °C and 100% RH. The incorporation of GA into a polymer matrix reduced the rate of oxygen absorption compared to the GA powder because the polymer acted as a barrier to oxygen and water vapor diffusion. As expected, the temperature had a significant effect on the initial absorption rate of the multilayer films; the corresponding activation energy was 75.4 kJ/mol. Higher RH significantly increased the oxygen absorption rate. These results demonstrate for the first time the production and the properties of a bio-based multilayer packaging film with GA as the oxygen scavenger. Potential applications include the packaging of food products with high water activity (aw > 0.86).

  3. Anthracene-based fluorescent nanoprobes for singlet oxygen detection in biological media.

    PubMed

    Bresolí-Obach, Roger; Nos, Jaume; Mora, Margarita; Sagristà, Maria Lluïsa; Ruiz-González, Rubén; Nonell, Santi

    2016-10-15

    We have developed a novel singlet oxygen nanoprobe based on 9,10-anthracenedipropionic acid covalently bound to mesoporous silica nanoparticles. The nanoparticle protects the probe from interactions with proteins, which detract from its ability to detect singlet oxygen. In vitro studies show that the nanoprobe is internalized by cells and is distributed throughout the cytoplasm, thus being capable of detecting intracellularly-generated singlet oxygen.

  4. Stimulator Selection in SSVEP-Based Spatial Selective Attention Study.

    PubMed

    Xie, Songyun; Liu, Chang; Obermayer, Klaus; Zhu, Fangshi; Wang, Linan; Xie, Xinzhou; Wang, Wei

    2016-01-01

    Steady-State Visual Evoked Potentials (SSVEPs) are widely used in spatial selective attention. In this process the two kinds of visual simulators, Light Emitting Diode (LED) and Liquid Crystal Display (LCD), are commonly used to evoke SSVEP. In this paper, the differences of SSVEP caused by these two stimulators in the study of spatial selective attention were investigated. Results indicated that LED could stimulate strong SSVEP component on occipital lobe, and the frequency of evoked SSVEP had high precision and wide range as compared to LCD. Moreover a significant difference between noticed and unnoticed frequencies in spectrum was observed whereas in LCD mode this difference was limited and selectable frequencies were also limited. Our experimental finding suggested that average classification accuracies among all the test subjects in our experiments were 0.938 and 0.853 in LED and LCD mode, respectively. These results indicate that LED simulator is appropriate for evoking the SSVEP for the study of spatial selective attention.

  5. Synthesis of a Fluorine-Containing Cis-Cisoidal One-Handed Helical Polyphenylacetylene and Application of Highly Selective Photocyclic Aromatization Product on Oxygen Permselective Membrane.

    PubMed

    Zang, Yu; Yin, Guanwu; Aoki, Toshiki; Teraguchi, Masahiro; Kaneko, Takashi; Ma, Liqun; Jia, Hongge

    2015-08-01

    A novel phenylacetylene monomer having a perfluorinated alkyl group (M-F) was synthesized and polymerized in a chiral catalytic system to yield a one-handed helical polymer. The ability and efficiency of the chiral induction of the fluorine-containing monomer in the helix-sense-selective polymerization (HSSP) was much higher than those of a monomer having the corresponding alkyl group (M-H) we reported before. The resulting polymer showed cis-cisoidal one-handed helical conformation, and was suitable for highly selective photocyclic aromatization (SCAT) to give a 2D surface modifier (). Oxygen permselectivity through a base polymer membrane was highly enhanced from 1.83 to 2.36 by adding a small amount (1-5 wt%) of the 2D surface modifier . The improvement was thought to be caused by improvement of solution selectivity on the membrane surface which the 2D surface modifier effectively covered. © 2015 Wiley Periodicals, Inc.

  6. Oxygen-selective immobilized liquid membranes for operation of lithium-air batteries in ambient air

    SciTech Connect

    Zhang, Jian; Xu, Wu; Liu, Wei

    2010-11-01

    In this paper, nonaqueous-electrolyte-based Li-air batteries with O2-selective immobilized liquid membranes have been developed and operated in ambient air with 20~30% relative humidity(RH). Continuous anhydrous O2 can be supplied from the ambient through a membrane barrier layer at interface of the cathode and ambient air. The membranes allow O2 permeate through while blocking moisture. These membranes were prepared by loading O2-selective liquid fluids such as silicone oils into porous supports such as porous metal sheets and Teflon (PTFE) films. It was found that silicone oil of high viscosity shows better performance. The membrane performance was not affected by the oil loading temperature. The immobilized silicone oil (viscosity 100,000cst) membrane in porous PTFE film enabled the Li-air batteries with Ketjen black carbon air electrodes to operate in ambient air (with 20% RH) for 16.3 days with a specific capacity of 789 mAh/g carbon and a specific energy of 2182 Wh/kg carbon. Its performance is much better than reference battery assembled with the same battery material but by use of a commercial, porous PTFE diffusion membranes as the moisture barrier layer on the cathode, which only had a discharge time of 5.5 days corresponding to a specific capacity of 267 mAh/g carbon and a specific energy of 704 Wh/kg carbon. The Li-air battery with the present selective membrane barrier layer even showed better performance in ambient air operation (20% RH) than the reference battery tested in the dry air box (< 1% RH).

  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. 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.

  9. Quenching of Single-Walled Carbon Nanotube Fluorescence by Dissolved Oxygen Reveals Selective Single-Stranded DNA Affinities.

    PubMed

    Zheng, Yu; Bachilo, Sergei M; Weisman, R Bruce

    2017-04-13

    The selective interactions between short oligomers of single-stranded DNA (ssDNA) and specific structures of single-walled carbon nanotubes have been exploited in powerful methods for nanotube sorting. We report here that nanotubes coated with ssDNA also display selective interactions through the selective quenching of nanotube fluorescence by dissolved oxygen. In aqueous solutions equilibrated under 1 atm of O2, emission intensity from semiconducting nanotubes is reduced by between 9 and 40%, varying with the combination of ssDNA sequence and nanotube structure. This quenching reverses promptly and completely on removal of dissolved O2 and may be due to physisorption on nanotube surfaces. Fluorescence quenching offers a simple, nondestructive approach for studying the structure-selective interactions of ssDNA with single-walled carbon nanotubes and identifying recognition sequences.

  10. Role of aluminum as an oxygen-scavenger in zirconium based bulk metallic glasses

    SciTech Connect

    Heinrich, Jochen; Busch, Ralf; Mueller, Frank; Grandthyll, Samuel; Huefner, Stefan

    2012-02-13

    In order to investigate a way to diminish the impact of oxygen onto the critical cooling rate of Zr-based alloys, the bonding chemistry of the elements in Zr-Cu-Ni-Al-Nb-Si bulk metallic glasses with different oxygen contents is studied by x-ray photoelectron spectroscopy. Complementary undercooling experiments lead to continuous-cooling-transformation diagrams for the studied alloys. The experimental results demonstrate that Al not only acts as a scavenger for both absorbed and intrinsic oxygen but the dissolution of its oxide on atomic length scales refrains from heterogeneous nucleation. The combined effect is an enhancement of oxygen tolerance in the investigated alloy.

  11. Metabolically Derived Human Ventilation Rates: A Revised Approach Based Upon Oxygen Consumption Rates (Final Report, 2009)

    EPA Science Inventory

    EPA announced the availability of the final report, Metabolically Derived Human Ventilation Rates: A Revised Approach Based Upon Oxygen Consumption Rates. This report provides a revised approach for calculating an individual's ventilation rate directly from their oxygen c...

  12. Metabolically Derived Human Ventilation Rates: A Revised Approach Based Upon Oxygen Consumption Rates (Final Report, 2009)

    EPA Science Inventory

    EPA announced the availability of the final report, Metabolically Derived Human Ventilation Rates: A Revised Approach Based Upon Oxygen Consumption Rates. This report provides a revised approach for calculating an individual's ventilation rate directly from their oxygen c...

  13. A Natural Component-Based Oxygen Indicator with In-Pack Activation for Intelligent Food Packaging.

    PubMed

    Won, Keehoon; Jang, Nan Young; Jeon, Junsu

    2016-12-28

    Intelligent food packaging can provide consumers with reliable and correct information on the quality and safety of packaged foods. One of the key constituents in intelligent packaging is a colorimetric oxygen indicator, which is widely used to detect oxygen gas involved in food spoilage by means of a color change. Traditional oxygen indicators consisting of redox dyes and strong reducing agents have two major problems: they must be manufactured and stored under anaerobic conditions because air depletes the reductant, and their components are synthetic and toxic. To address both of these serious problems, we have developed a natural component-based oxygen indicator characterized by in-pack activation. The conventional oxygen indicator composed of synthetic and artificial components was redesigned using naturally occurring compounds (laccase, guaiacol, and cysteine). These natural components were physically separated into two compartments by a fragile barrier. Only when the barrier was broken were all of the components mixed and the function as an oxygen indicator was begun (i.e., in-pack activation). Depending on the component concentrations, the natural component-based oxygen indicator exhibited different response times and color differences. The rate of the color change was proportional to the oxygen concentration. This novel colorimetric oxygen indicator will contribute greatly to intelligent packaging for healthier and safer foods.

  14. Oxygenates for Advanced Petroleum-Based Diesel Fuels

    DTIC Science & Technology

    2001-02-01

    Blends,” 219th American Chemical Society Meeting , San Francisco, CA, March 26-30, 2000. 5. Naegeli, D.W. and Moses, C.A., “Effects of Fuel...used to optimize engine performance and lower exhaust emissions. Nevertheless, the diesel engine has yet to meet the very stringent emissions...diesel engine designed to meet 1994 emission standards using a catalytic converter. The tests showed that oxygenates reduced PM emissions by 6 to 7

  15. 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.

  16. Covariance based outlier detection with feature selection.

    PubMed

    Zwilling, Chris E; Wang, Michelle Y

    2016-08-01

    The present covariance based outlier detection algorithm selects from a candidate set of feature vectors that are best at identifying outliers. Features extracted from biomedical and health informatics data can be more informative in disease assessment and there are no restrictions on the nature and number of features that can be tested. But an important challenge for an algorithm operating on a set of features is for it to winnow the effective features from the ineffective ones. The powerful algorithm described in this paper leverages covariance information from the time series data to identify features with the highest sensitivity for outlier identification. Empirical results demonstrate the efficacy of the method.

  17. Selective isolation of nitrogen bases from petroleum

    SciTech Connect

    Schmitter, J.M.; Ignatiadis, I.; Arpino, P.; Guiochon, G.

    1983-09-01

    A method has been designed for the rapid separation of nitrogen bases from petroleum by trapping their quaternary ammonium salts on hydrochloric acid treated silica. A chromatographic column filled with this adsorbent and equipped with a solvent recycling system allows a selective and quantitative extraction of basic compounds from large amounts (>100 g) of crude oil. The procedure has been tested with reference compounds, a coker gas-oil, and a heavy biodegraded crude and applied to 15 different oil samples. 22 references, 3 figures, 4 tables.

  18. 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).

  19. Stimulator Selection in SSVEP-Based Spatial Selective Attention Study

    PubMed Central

    Liu, Chang; Zhu, Fangshi; Wang, Linan; Xie, Xinzhou; Wang, Wei

    2016-01-01

    Steady-State Visual Evoked Potentials (SSVEPs) are widely used in spatial selective attention. In this process the two kinds of visual simulators, Light Emitting Diode (LED) and Liquid Crystal Display (LCD), are commonly used to evoke SSVEP. In this paper, the differences of SSVEP caused by these two stimulators in the study of spatial selective attention were investigated. Results indicated that LED could stimulate strong SSVEP component on occipital lobe, and the frequency of evoked SSVEP had high precision and wide range as compared to LCD. Moreover a significant difference between noticed and unnoticed frequencies in spectrum was observed whereas in LCD mode this difference was limited and selectable frequencies were also limited. Our experimental finding suggested that average classification accuracies among all the test subjects in our experiments were 0.938 and 0.853 in LED and LCD mode, respectively. These results indicate that LED simulator is appropriate for evoking the SSVEP for the study of spatial selective attention. PMID:28044073

  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. Online monitoring of dissolved oxygen tension in microtiter plates based on infrared fluorescent oxygen-sensitive nanoparticles.

    PubMed

    Ladner, Tobias; Flitsch, David; Schlepütz, Tino; Büchs, Jochen

    2015-10-09

    During the past years, new high-throughput screening systems with capabilities of online monitoring turned out to be powerful tools for the characterization of microbial cell cultures. These systems are often easy to use, offer economic advantages compared to larger systems and allow to determine many important process parameters within short time. Fluorescent protein tags tremendously simplified the tracking and observation of cellular activity in vivo. Unfortunately, interferences between established fluorescence based dissolved oxygen tension (DOT) measurement techniques and fluorescence-based protein tags appeared. Therefore, the applicability of new oxygen-sensitive nanoparticles operated within the more suitable infrared wavelength region are introduced and validated for DOT measurement. The biocompatibility of the used dispersed oxygen-sensitive nanoparticles was proven via RAMOS cultivations for Hansenula polymorpha, Gluconobacter oxydans, and Escherichia coli. The applicability of the introduced DOT measurement technique for online monitoring of cultivations was demonstrated and successfully validated. The nanoparticles showed no disturbing effect on the online measurement of the fluorescence intensities of the proteins GFP, mCherry and YFP measured by a BioLector prototype. Additionally, the DOT measurement was not influenced by changing concentrations of these proteins. The kLa values for the applied cultivation conditions were successfully determined based on the measured DOT. The introduced technique appeared to be practically as well as economically advantageous for DOT online measuring in microtiter plates. The disadvantage of limited availability of microtiter plates with immobilized sensor spots (optodes) does not apply for this introduced technique. Due to the infrared wavelength range, used for the DOT measurement, no interferences with biogenic fluorescence or with expressed fluorescent proteins (e.g. YFP, GFP or mCherry) occur.

  2. Epoxy based oxygen enriched porous carbons for CO2 capture

    NASA Astrophysics Data System (ADS)

    Tiwari, Deepak; Bhunia, Haripada; Bajpai, Pramod K.

    2017-08-01

    Oxygen enriched carbon adsorbents were successfully synthesized for the first time from template zeolite and epoxy resin as precursor using a nanocasting technique. Carbonization and CO2 activation were performed at various temperatures (500-800 °C) to prepare different carbon structure adsorbents. Several characterization techniques were used to characterize the textural structure, oxygen content and surface functional groups of the adsorbents. The carbon adsorbents show high oxygen content (47.51%), highest surface area (SBET = 686.37 m2 g-1) and pore volume (0.60 cm3 g-1), respectively. The materials were evaluated thermogravimetrically at different adsorption temperatures (30-100 °C) and CO2 concentrations (6-100%). Adsorbent prepared at 700 °C exhibited highest CO2 uptake of 0.91 mmol g-1 due to high surface basicity. Further, regeneration studies of adsorbent exhibited easy regenerability and stability over four multiple adsorptions-desorption cycles. Kinetic models for CO2 adsorption at various CO2 concentrations and temperatures were studied and it was found that the fractional order provided best fitting for the adsorption behavior with an error of less than 3%. The experimental data for CO2 adsorption were analyzed using different isothermal models and found that the Freundlich isothermal model presented perfect fit among all isotherm models depicting heterogeneous adsorbent surface. The isosteric heat of adsorption was estimated to be 11.75 kJ mol-1, indicating physiosorption process. Overall, the above results suggested that the synthesized adsorbent using nanocasting technique provides a feasible way for CO2 capture from point source due to their environmentally benign nature, low cost and stable adsorption capacity.

  3. Charge transfer mediator based systems for electrocatalytic oxygen reduction

    DOEpatents

    Stahl, Shannon S.; Gerken, James B.; Anson, Colin W.

    2017-07-18

    Disclosed are systems for the electrocatalytic reduction of oxygen, having redox mediator/redox catalyst pairs and an electrolyte solution in contact with an electrode. The redox mediator is included in the electrolyte solution, and the redox catalyst may be included in the electrolyte solution, or alternatively, may be in contact with the electrolyte solution. In one form a cobalt redox catalyst is used with a quinone redox mediator. In another form a nitrogen oxide redox catalyst is used with a nitroxyl type redox mediator. The systems can be used in electrochemical cells wherein neither the anode nor the cathode comprise an expensive metal such as platinum.

  4. Selectivity tailoring of Pd/CNTs in phenol hydrogenation by surface modification: Role of Csbnd O oxygen species

    NASA Astrophysics Data System (ADS)

    Xu, Tieyong; Zhang, Qunfeng; Cen, Jie; Xiang, Yizhi; Li, Xiaonian

    2015-01-01

    The effect of different types of oxygen containing groups (OCGs) on the catalytic performance was investigated in this paper by performing the selective hydrogenation of phenol in aqueous phase over the carbon supported Pd catalysts. The type of OCGs on carbon nanotubes (CNTs) was regulated by pretreating it with HNO3, or HNO3 followed by hydrothermal or thermal oxidation treatment. A distinct difference in the amount of phenolic/ether groups (Csbnd O) was observed for CNTs treated by different methods, while the difference in the amount of carbonyl groups (Cdbnd O) and carboxylic groups was much smaller. The results showed that the selectivity to cyclohexanone decreased with the increase of Csbnd O amount on carbon surface. Csbnd O groups played an important role in adsorption/desorption behavior of phenol/cyclohexanone and was considered to be responsible for the dramatic selectivity difference.

  5. 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.

  6. Selection of functional human sperm with higher DNA integrity and fewer reactive oxygen species

    PubMed Central

    Asghar, Waseem; Velasco, Vanessa; Kingsley, James L.; Shoukat, Muhammad S.; Shafiee, Hadi; Anchan, Raymond M.; Mutter, George L.; Tüzel, Erkan; Demirci, Utkan

    2014-01-01

    Fertilization and reproduction are central to the survival and propagation of a species. Couples who cannot reproduce naturally have to undergo in vitro clinical procedures. An integral part of these clinical procedures includes isolation of healthy sperm from raw semen. Existing sperm sorting methods are not efficient and isolate sperm having high DNA fragmentation and reactive oxygen species, and suffer from multiple manual steps and variations between embryologists. Inspired by in vivo natural sperm sorting mechanisms where vaginal mucus becomes less viscous to form microchannels to guide sperm towards egg, we present a chip that efficiently sorts healthy, motile and morphologically normal sperm without centrifugation. Higher percentage of sorted sperm show significantly lesser reactive oxygen species and DNA fragmentation than the conventional swim-up method. The presented chip is an easy-to-use high throughput sperm sorter that provides standardized sperm sorting assay with less reliance on embryologist’s skills, facilitating reliable operational steps. PMID:24753434

  7. 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.

  8. 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.

  9. Methylene blue- and thiol-based oxygen depletion for super-resolution imaging.

    PubMed

    Schäfer, Philip; van de Linde, Sebastian; Lehmann, Julian; Sauer, Markus; Doose, Sören

    2013-03-19

    Anaerobic conditions are often required in solution-based bionanotechnological applications. Efficient oxygen depletion is essential for increasing photostability, optimizing fluorescence signals, and adjusting kinetics of fluorescence intermittency in single-molecule fluorescence spectroscopy/microscopy, particularly for super-resolution imaging techniques. We characterized methylene blue (MB)- and thiol-based redox reactions with the aim of designing an oxygen scavenger system as an alternative to the established enzyme-based oxygen scavenging systems or purging procedures. Redox reactions of the chromophore methylene blue in aqueous solution, commonly visualized in the blue bottle experiment, deplete molecular oxygen as long as a sacrificial reduction component is present in excess concentrations. We demonstrate that methylene blue in combination with reducing compounds such as β-mercaptoethylamine (MEA) can serve as fast and efficient oxygen scavenger. Efficient oxygen scavenging in aqueous solution is also possible with mere β-mercaptoethylamine at mM concentrations. We present kinetic parameters of the relevant reactions, pH-stability of the MB/MEA-oxygen scavenging system, and its application in single-molecule based super-resolution imaging.

  10. 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

  11. Oxygen-modulated quantum conductance for ultrathin HfO2 -based memristive switching devices

    DOE PAGES

    Zhong, Xiaoliang; Rungger, Ivan; Zapol, Peter; ...

    2016-10-24

    Memristive switching devices, candidates for resistive random access memory technology, have been shown to switch off through a progression of states with quantized conductance and subsequent noninteger conductance (in terms of conductance quantum G0). We have performed calculations based on density functional theory to model the switching process for a Pt-HfO2-Pt structure, involving the movement of one or two oxygen atoms. Oxygen atoms moving within a conductive oxygen vacancy filament act as tunneling barriers, and partition the filament into weakly coupled quantum wells. We show that the low-bias conductance decreases exponentially when one oxygen atom moves away from interface. Inmore » conclusion, our results demonstrate the high sensitivity of the device conductance to the position of oxygen atoms.« less

  12. 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.

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

    SciTech Connect

    Schroeder, William David

    2001-01-01

    The partial oxidation of 1,3-butadiene has been investigated over VMoO catalysts synthesized by sol-gel techniques. Surface areas were 9-14 m2/g, and compositions were within the solid solution regime, i.e. below 15.0 mol % MoO3/(MoO3 + V2O5). 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+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 V2O5-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 V2O5, solid solutions of Mo in V2O5, V9Mo6O40, 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% MoO3/(V2O5 + MoO3), determined by EDS analysis.

  14. Selenium-platinum coordination compounds as novel anticancer drugs: selectively killing cancer cells via a reactive oxygen species (ROS)-mediated apoptosis route.

    PubMed

    Zeng, Lingwu; Li, Yang; Li, Tianyu; Cao, Wei; Yi, Yu; Geng, Weijia; Sun, Zhiwei; Xu, Huaping

    2014-08-01

    We report the preparation of selenium-containing platinum-based anticancer drug EG-Se/Pt. EG-Se/Pt was obtained from the coordination of selenium-containing molecules (EG-Se) with cisplatin (CDDP). The structure of EG-Se/Pt was characterized by (1) H and (77) Se NMR spectroscopy, XPS, ESI-MS, and MALDI-TOF. In aqueous solution, EG-Se/Pt self-assembles to form spherical aggregates. EG-Se/Pt shows enhanced stability against dilution and high salt concentration compared with EG-Se. EG-Se/Pt induces cell apoptosis via reactive oxygen species (ROS), which leads to high selectivity between cancer cells and normal cells in cytotoxicity assays. More importantly, EG-Se/Pt effectively inhibits tumor growth in vivo in tumor-bearing mice. It is anticipated that tuning the ROS level through the assembly of selenium-containing molecules can be a general method to realize anticancer selectivity.

  15. Sediments, nutrients, and oxygen-demanding substances in the Minnesota River: Selected water-quality data, 1989-90

    USGS Publications Warehouse

    Payne, G.A.

    1991-01-01

    This report presents selected physical and chemical data collected by the U.S. Geological Survey for the Minnesota River Assessment Project, a four-year interagency study coordinated by the Minnesota Pollution Control Agency. Water samples were collected at 12 sites on the Minnesota River and at the mouths of 10 major tributary streams located from the outlet of Lac qui Parle Reservoir to Henderson, Minnesota. Sampling from August 1989 through September 1990 resulted in collection of 171 stream-water samples. This report includes data on streamflow, total suspended solids, nitrite plus nitrate nitrogen, total phosphorus, biochemical oxygen demand, and chlorophyll a.

  16. Oxygen transport membrane based advanced power cycle with low pressure synthesis gas slip stream

    DOEpatents

    Kromer, Brian R.; Litwin, Michael M.; Kelly, Sean M.

    2016-09-27

    A method and system for generating electrical power in which a high pressure synthesis gas stream generated in a gasifier is partially oxidized in an oxygen transport membrane based reactor, expanded and thereafter, is combusted in an oxygen transport membrane based boiler. A low pressure synthesis gas slip stream is split off downstream of the expanders and used as the source of fuel in the oxygen transport membrane based partial oxidation reactors to allow the oxygen transport membrane to operate at low fuel pressures with high fuel utilization. The combustion within the boiler generates heat to raise steam to in turn generate electricity by a generator coupled to a steam turbine. The resultant flue gas can be purified to produce a carbon dioxide product.

  17. Hemoglobin-based oxygen carrier and convection enhanced oxygen transport in a hollow fiber bioreactor.

    PubMed

    Chen, Guo; Palmer, Andre F

    2009-04-15

    A mathematical model was developed to study O(2) transport in a convection enhanced hepatic hollow fiber (HF) bioreactor, with hemoglobin-based O(2) carriers (HBOCs) present in the flowing cell culture media stream of the HF lumen. In this study, four HBOCs were evaluated: PEG-conjugated human hemoglobin (MP4), human hemoglobin (hHb), bovine hemoglobin (BvHb) and polymerized bovine hemoglobin (PolyBvHb). In addition, two types of convective flow in the HF extra capillary space (ECS) were considered in this study. Starling flow naturally occurs when both of the ECS ports are closed. If one of the ECS ports is open, forced convective flow through the ECS will occur due to the imposed pressure difference between the lumen and ECS. This type of flow is referred to as cross-flow in this work, since some of the fluid entering the HF lumen will pass across the HF membrane and exit via the open ECS port. In this work, we can predict the dissolved O(2) concentration profile as well as the O(2) transport flux in an individual HF of the bioreactor by solving the coupled momentum and mass transport equations. Our results show that supplementation of the cell culture media with HBOCs can dramatically enhance O(2) transport to the ECS (containing hepatocytes) and lead to the formation of an in vivo-like O(2) spectrum for the optimal culture of hepatocytes. However, both Starling flow and cross-flow have a very limited effect on O(2) transport in the ECS. Taken together, this work represents a novel predictive tool that can be used to design or analyze HF bioreactors that expose cultured cells to defined overall concentrations and gradients of O(2).

  18. Poly(decyl methacrylate)-based fluorescent PEBBLE swarm nanosensors for measuring dissolved oxygen in biosamples.

    PubMed

    Cao, Youfu; Lee Koo, Yong-Eun; Kopelman, Raoul

    2004-08-01

    150-250 nm Poly(decyl methacrylate)(PDMA) fluorescent ratiometric nanosensors for dissolved oxygen have been developed. Platinum octaethylporphine ketone (PtOEPK), the oxygen-sensitive dye, and octaethylporphyrin (OEP), the oxygen-insensitive dye, have been incorporated into PDMA nanoparticles to make the sensors ratiometric. Based on the corresponding Stern-Volmer plot, these nanosensors exhibit almost complete linearity over the whole range of dissolved molecular oxygen from 0 to 42.5 ppm (deoxygenated to pure oxygen-bubbled water). The overall quenching response is up to 97.5%, the best so far for all dissolved oxygen optical sensors. These PEBBLE nanosensors also show very good reversibility and stability to leaching and photobleaching, as well as very short response times and no perturbation by proteins. In human plasma they demonstrate a robust oxygen sensing capability, little affected by light scattering and autofluorescence. Potential applications include intracellular oxygen imaging and microresolved pressure profiles in biological and other heterogenous environments.

  19. High-throughput determination of biochemical oxygen demand (BOD) by a microplate-based biosensor.

    PubMed

    Pang, Hei-Leung; Kwok, Nga-Yan; Chan, Pak-Ho; Yeung, Chi-Hung; Lo, Waihung; Wong, Kwok-Yin

    2007-06-01

    The use of the conventional 5-day biochemical oxygen demand (BOD5) method in BOD determination is greatly hampered by its time-consuming sampling procedure and its technical difficulty in the handling of a large pool of wastewater samples. Thus, it is highly desirable to develop a fast and high-throughput biosensor for BOD measurements. This paper describes the construction of a microplate-based biosensor consisting of an organically modified silica (ORMOSIL) oxygen sensing film for high-throughput determination of BOD in wastewater. The ORMOSIL oxygen sensing film was prepared by reacting tetramethoxysilane with dimethyldimethoxysilane in the presence of the oxygen-sensitive dye tris(4,7-diphenyl-1,10-phenanthroline)ruthenium-(II) chloride. The silica composite formed a homogeneous, crack-free oxygen sensing film on polystyrene microtiter plates with high stability, and the embedded ruthenium dye interacted with the dissolved oxygen in wastewater according to the Stern-Volmer relation. The bacterium Stenotrophomonas maltophilia was loaded into the ORMOSIL/ PVA composite (deposited on the top of the oxygen sensing film) and used to metabolize the organic compounds in wastewater. This BOD biosensor was found to be able to determine the BOD values of wastewater samples within 20 min by monitoring the dissolved oxygen concentrations. Moreover, the BOD values determined by the BOD biosensor were in good agreement with those obtained by the conventional BOD5 method.

  20. Intrinsic and metal-doped gallium oxide based high-temperature oxygen sensors for combustion processes

    NASA Astrophysics Data System (ADS)

    Rubio, Ernesto Javier

    Currently, there is enormous interest in research, development and optimization of the combustion processes for energy harvesting. Recent statistical and economic analyses estimated that by improving the coal-based firing/combustion processes in the power plants, savings up to $450-500 million yearly can be achieved. Advanced sensors and controls capable of withstanding extreme environments such as high temperatures, highly corrosive atmospheres, and high pressures are critical to such efficiency enhancement and cost savings. For instance, optimization of the combustion processes in power generation systems can be achieved by sensing, monitoring and control of oxygen, which is a measure of the completeness of the process and can lead to enhanced efficiency and reduced greenhouse gas emissions. However, despite the fact that there exists a very high demand for advanced sensors, the existing technologies suffer from poor 'response and recovery times' and 'long-term stability.' Motivated by the aforementioned technological challenges, the present work was focused on high-temperature (≥700 °C) oxygen sensors for application in power generation systems. The objective of the present work is to investigate nanostructured gallium oxide (2O3) based sensors for oxygen sensing, where we propose to conduct in-depth exploration of the role of refractory metal (tungsten, W, in this case) doping into 2O 3 to enhance the sensitivity, selectivity, stability ("3S" criteria) and reliability of such sensors while keeping cost economical. Tungsten (W) doped gallium oxide (2O3) thin films were deposited via rf-magnetron co-sputtering of W-metal and Ga2O3-ceramic targets. Films were produced by varying the sputtering power applied to the W-target in order to achieve variable W content into 2O3 films while substrate temperature was kept constant at 500 °C. Chemical composition, chemical valence states, microstructure and crystal structure of as-grown and post-annealed W-doped 2O3

  1. Mechanism of isomers and analogues of resveratrol dimers selectively quenching singlet oxygen by UHPLC-ESI-MS(2).

    PubMed

    Yin, Xuefeng; Yu, Jia; Kong, Qingjun; Ren, Xueyan

    2017-12-15

    Stilbenoids, in particular, resveratrol and its dimers are abundantly present in Vitis vinifera and proved to be quenchers with selective singlet oxygen. However, only a few mechanisms are reported for their complex molecular architectures. Hence, UHPLC combined with accurate MS is employed to investigate the photo-radiation mechanism of resveratrol dimers systematically. Ⅰ: Resorcinol ring exists in Scirpusin A 1, Trans-ε-viniferin 2 and Trans-σ-viniferin 3. The photochemical products were 14Da or 16Da higher than reagents and underwent an endoperoxide intermediate to quinones; Ⅱ: [2+2] cyclization of intra-molecular trans-double bond. The products were 18Da greater than substrates thereby cycloaddited to oxygen heterocyclic; Ⅲ : [4+1], [4+2] cyclization of oxetane formed products were 28Da and 44Da higher than 3, 2 and 1. Ⅳ : 5-phenol-2,3-dihydrobenzofuran ring exists in 2 been oxidized, causing the products at 16Da, 32Da higher than 2. This is the first to reveal the generally regular mechanism of stilbenoids quenching singlet oxygen. Copyright © 2017 Elsevier Ltd. All rights reserved.

  2. State-based surveillance for selected hemoglobinopathies.

    PubMed

    Hulihan, Mary M; Feuchtbaum, Lisa; Jordan, Lanetta; Kirby, Russell S; Snyder, Angela; Young, William; Greene, Yvonne; Telfair, Joseph; Wang, Ying; Cramer, William; Werner, Ellen M; Kenney, Kristy; Creary, Melissa; Grant, Althea M

    2015-02-01

    The lack of an ongoing surveillance system for hemoglobinopathies in the United States impedes the ability of public health organizations to identify individuals with these conditions, monitor their health-care utilization and clinical outcomes, and understand the effect these conditions have on the health-care system. This article describes the results of a pilot program that supported the development of the infrastructure and data collection methods for a state-based surveillance system for selected hemoglobinopathies. The system was designed to identify and gather information on all people living with a hemoglobinopathy diagnosis (sickle cell diseases or thalassemias) in the participating states during 2004-2008. Novel, three-level case definitions were developed, and multiple data sets were used to collect information. In total, 31,144 individuals who had a hemoglobinopathy diagnosis during the study period were identified in California; 39,633 in Florida; 20,815 in Georgia; 12,680 in Michigan; 34,853 in New York, and 8,696 in North Carolina. This approach provides a possible model for the development of state-based hemoglobinopathy surveillance systems.

  3. State-based surveillance for selected hemoglobinopathies

    PubMed Central

    Hulihan, Mary M.; Feuchtbaum, Lisa; Jordan, Lanetta; Kirby, Russell S.; Snyder, Angela; Young, William; Greene, Yvonne; Telfair, Joseph; Wang, Ying; Cramer, William; Werner, Ellen M.; Kenney, Kristy; Creary, Melissa; Grant, Althea M.

    2015-01-01

    Purpose The lack of an ongoing surveillance system for hemoglobinopathies in the United States impedes the ability of public health organizations to identify individuals with these conditions, monitor their health-care utilization and clinical outcomes, and understand the effect these conditions have on the health-care system. This article describes the results of a pilot program that supported the development of the infrastructure and data collection methods for a state-based surveillance system for selected hemoglobinopathies. Methods The system was designed to identify and gather information on all people living with a hemoglobinopathy diagnosis (sickle cell diseases or thalassemias) in the participating states during 2004–2008. Novel, three-level case definitions were developed, and multiple data sets were used to collect information. Results In total, 31,144 individuals who had a hemoglobinopathy diagnosis during the study period were identified in California; 39,633 in Florida; 20,815 in Georgia; 12,680 in Michigan; 34,853 in New York, and 8,696 in North Carolina. Conclusion This approach provides a possible model for the development of state-based hemoglobinopathy surveillance systems. PMID:24991875

  4. Mass-selected nanoparticles of PtxY as model catalysts for oxygen electroreduction

    SciTech Connect

    Hernandez-Fernandez, Patricia; Masini, Federico; McCarthy, David N.; Strebel, Christian E.; Friebel, Daniel; Deiana, Davide; Malacrida, Paolo; Nierhoff, Anders; Bodin, Anders; Wise, Anna M.; Nielsen, Jane H.; Hansen, Thomas W.; Nilsson, Anders; Stephens, Ifan E. L.; Chorkendorff, Ib

    2014-07-13

    Low-temperature fuel cells are limited by the oxygen reduction reaction, and their widespread implementation in automotive vehicles is hindered by cost of platinum currently the best-known catalyst for reducing oxygen in terms of both activity and stability. One solution is to decrease the amount of platinum required, for example by alloying, but without detrimentally affecting its properties. The alloy PtxY is known to be active and stable, but its synthesis in nanoparticulate form has proved challenging, which limits its further study. Herein we demonstrate the synthesis, characterization and catalyst testing of model PtxY nanoparticles prepared through the gas-aggregation technique. The catalysts reported here are highly active, with a mass activity of up to 3.05 A mgPt-1 at 0.9 V versus a reversible hydrogen electrode. Using a variety of characterization techniques, we show that the enhanced activity of PtxY over platinum results exclusively from a compressive strain exerted on the platinum surface atoms by the alloy core.

  5. Mass-selected nanoparticles of PtxY as model catalysts for oxygen electroreduction.

    PubMed

    Hernandez-Fernandez, Patricia; Masini, Federico; McCarthy, David N; Strebel, Christian E; Friebel, Daniel; Deiana, Davide; Malacrida, Paolo; Nierhoff, Anders; Bodin, Anders; Wise, Anna M; Nielsen, Jane H; Hansen, Thomas W; Nilsson, Anders; Stephens, Ifan E L; Chorkendorff, Ib

    2014-08-01

    Low-temperature fuel cells are limited by the oxygen reduction reaction, and their widespread implementation in automotive vehicles is hindered by the cost of platinum, currently the best-known catalyst for reducing oxygen in terms of both activity and stability. One solution is to decrease the amount of platinum required, for example by alloying, but without detrimentally affecting its properties. The alloy PtxY is known to be active and stable, but its synthesis in nanoparticulate form has proved challenging, which limits its further study. Herein we demonstrate the synthesis, characterization and catalyst testing of model PtxY nanoparticles prepared through the gas-aggregation technique. The catalysts reported here are highly active, with a mass activity of up to 3.05 A mgPt(-1) at 0.9 V versus a reversible hydrogen electrode. Using a variety of characterization techniques, we show that the enhanced activity of PtxY over elemental platinum results exclusively from a compressive strain exerted on the platinum surface atoms by the alloy core.

  6. 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.

  7. MIS-based sensors with hydrogen selectivity

    DOEpatents

    Li,; Dongmei, [Boulder, CO; Medlin, J William [Boulder, CO; McDaniel, Anthony H [Livermore, CA; Bastasz, Robert J [Livermore, CA

    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.

  8. Medium effects are as important as catalyst design for selectivity in electrocatalytic oxygen reduction by iron-porphyrin complexes.

    PubMed

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

    2015-04-08

    Several substituted iron-porphyrin complexes were evaluated for oxygen reduction reaction (ORR) electrocatalysis in different homogeneous and heterogeneous media. The selectivity for four-electron reduction to H2O versus two-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 selectivity results from supported and soluble molecular ORR electrocatalysts must be interpreted with caution, as selectivity is a property not only of the catalyst, but also of the larger mesoscale environment beyond 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.

  9. Computational prediction of alpha/beta selectivities in the pyrolysis of oxygen-substituted phenethyl phenyl ethers.

    PubMed

    Beste, Ariana; Buchanan, A C; Harrison, Robert J

    2008-06-05

    Phenethyl phenyl ether (PPE; PhCH 2CH 2OPh) is the simplest model for the most common beta-O-4 linkage in lignin. Previously, we developed a computational scheme to calculate the alpha/beta product selectivity in the pyrolysis of PPE by systematically exploiting error cancellation in the computation of relative rate constants. The alpha/beta selectivity is defined as the selectivity between the competitive hydrogen abstraction reaction paths on the alpha- and beta-carbons of PPE. We use density functional theory and employ transition state theory where we include diagonal anharmonic correction in the vibrational partition functions for low frequency modes for which a semiclassical expression is used. In this work we investigate the effect of oxygen substituents (hydroxy, methoxy) in the para position on the phenethyl ring of PPE on the alpha/beta selectivities. The total alpha/beta selectivity increases when substituents are introduced and is larger for the methoxy than the hydroxy substituent. The strongest effect of the substituents is observed for the alpha-pathway of the hydrogen abstraction by the phenoxyl chain carrying radical for which the rate increases. For the beta pathway and the abstraction by the R-benzyl radical (R = OH,OCH 3) the rate decreases with the introduction of the substituents. These findings are compared with results from recent experimental studies.

  10. 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.

  11. Oxygen gas optrode based on microstructured polymer optical fiber segment

    NASA Astrophysics Data System (ADS)

    Yang, Xinghua; Peng, Lirong; Yuan, Libo; Teng, Pingping; Tian, Fengjun; Li, Le; Luo, Shenzi

    2011-06-01

    In this article, we first propose a novel type of oxygen gas optrode by forming fluorophore doped sensing film in the array microholes with the characteristics of microstructured optical fiber (MOF) segment. Comparing with the conventional O 2 detecting method, this slender shaped optrode shows potential in trace amount of O 2 sensing and online O 2 monitoring. Organical silicate gel or plastified cellulose acetate are chosen as sensing films and tris (4,7-diphenyl-1,10-phenathroline) ruthenium(II) dichloride ([Ru(dpp) 3]Cl 2) or meso-tetraphenylporphyin (TPP) as quenching fluorophores. From the experimental results, we find [Ru(dpp) 3] 2+-Gel-MOF optrode has favorable sensing characteristics, and the Stern-Volmer plots are linear in the full concentration range of O 2 (0-100% v/v). The ratio of I 0/I 100, where I 0 and I 100 respectively represents the fluorescence intensities of the optrode exposed to 100% N 2 and 100% O 2, as a sensitivity of the optrode is 10.8. Simultaneously, the optrode can make a quick response within 50 ms.

  12. 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.

  13. The design of dextran-based hypoxia-inducible hydrogels via in situ oxygen consuming reaction

    PubMed Central

    Park, Kyung Min; Blatchley, Michael R.; Gerecht, Sharon

    2014-01-01

    Hypoxia plays a critical role in development and the wound healing process, as well as a number of pathological conditions. Here, we report dextran–based hypoxia–inducible (Dex–HI) hydrogels formed with in situ oxygen consumption via laccase–medicated reaction. Oxygen levels and gradients were accurately predicted by mathematical simulation. We demonstrate that Dex–HI hydrogels provide prolonged hypoxic conditions up to 12 h. The Dex–HI hydrogel offers an innovative approach to delineate not only the mechanism by which hypoxia regulates cellular responses, but may facilitate the discovery of new pathways involved in the generation of hypoxic and oxygen gradient environments. PMID:25303104

  14. Systematic study on the discharge product of Pt-based lithium oxygen batteries

    NASA Astrophysics Data System (ADS)

    Wu, Feng; Xing, Yi; Bi, Xuanxuan; Yuan, Yifei; Wang, Hsien-Hau; Shahbazian-Yassar, Reza; Li, Li; Chen, Renjie; Lu, Jun; Amine, Khalil

    2016-11-01

    Lithium oxygen batteries have attracted much attention due to the high theoretical energy density. However, they suffer a large overpotential during oxygen evolution process and thus catalysts play a vital role in the reaction. Here, we systematically explored the influence of Pt-based nanoparticle catalysts on the discharge product Li2O2. Because of the superior electrical conductivity and the strong binding with oxygen, Pt-based nanoparticles serve as active sites which are favorable for the growth of toroidal Li2O2. We also found that the content and composition of Pt-based nanoparticle catalysts exert a significant influence on the electrochemical performance of lithium oxygen batteries. The discharge products are composed of crystalline Li2O2 and oxygen-rich LiO2 characterized by high-energy X-ray diffraction and Raman. Atomic force microscopy further provides detailed information of the particle size and surface roughness. The loading of Pt catalysts determines the phase and size of Li2O2 on the discharged electrode surface. This study will be beneficial for the optimization of Pt-based catalysts used in non-aqueous lithium oxygen batteries.

  15. Systematic study on the discharge product of Pt-based lithium oxygen batteries

    SciTech Connect

    Wu, Feng; Xing, Yi; Bi, Xuanxuan; Yuan, Yifei; Wang, Hsien-Hau; Shahbazian-Yassar, Reza; Li, Li; Chen, Renjie; Lu, Jun; Amine, Khalil

    2016-11-01

    Lithium oxygen batteries have attracted much attention due to the high theoretical energy density. However, they suffer a large overpotential during oxygen evolution process and thus catalysts play a vital role in the reaction. Here, we systematically explored the influence of Pt-based nanoparticle catalysts on the discharge product Li2O2. Because of the superior electrical conductivity and the strong binding with oxygen, Pt-based nanoparticles serve as active sites which are favorable for the growth of toroidal Li2O2. We also found that the content and composition of Pt-based nanoparticle catalysts exert a significant influence on the electrochemical performance of lithium oxygen batteries. The discharge products are composed of crystalline Li2O2 and oxygen-rich LiO2 characterized by high-energy X-ray diffraction and Raman. Atomic force microscopy further provides detailed information of the particle size and surface roughness. The loading of Pt catalysts determines the phase and size of Li2O2 on the discharged electrode surface. This study will be beneficial for the optimization of Pt-based catalysts used in non-aqueous lithium oxygen batteries.

  16. Reduction Kinetics of a CasO4 Based Oxygen Carrier for Chemical-Looping Combustion

    NASA Astrophysics Data System (ADS)

    Xiao, R.; Song, Q. L.; Zheng, W. G.; Deng, Z. Y.; Shen, L. H.; Zhang, M. Y.

    The CaSO4 based oxygen carrier has been proposed as an alternative low cost oxygen carrier for Chemical-looping combustion (CLC) of coal. The reduction of CaSO4 to CaS is an important step for the cyclic process of reduction/oxidation in CLC of coal with CaSO4 based oxygen carrier. Thermodynamic analysis of CaSO4 oxygen carrier with CO based on the principle of Gibbs free energy minimization show that the essentially high purity of CO2 can be obtained, while the solid product is CaS instead of CaO. The intrinsic reduction kinetics of a CaSO4 based oxygen carrier with CO was investigated in a differential fixed bed reactor. The effects of gas partial pressure (20%-70%) and temperature (880-950°C) on the reduction were investigated. The reduction was described with shrinking unreacted core model. Experimental results of CO partial pressure on the solid conversion show that the reduction of fresh oxygen carriers is of first order with respect to the CO partial pressure. Both chemical reaction control and product layer diffusion control determine the reduction rate. The dependences of reaction rate constant and effective diffusivity with temperature were both obtained. The kinetic equation well predicted the experimental data.

  17. 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.

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

    SciTech Connect

    Rossi, Gabriella; Scarfato, Paola; Incarnato, Loredana

    2016-05-18

    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.

  19. 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

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

    SciTech Connect

    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.

    2016-03-08

    A redox-active metal-organic composite material shows improved and selective O-2 adsorption over N-2 with respect to individual components (MIL-101 and ferrocene). The O-2 sensitivity of the composite material arises due to the formation of maghemite nanoparticles with the pore of the metal-organic framework material.

  1. 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.

  2. 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.

  3. Hampering Effect of Cholesterol on the Permeation of Reactive Oxygen Species through Phospholipids Bilayer: Possible Explanation for Plasma Cancer Selectivity

    NASA Astrophysics Data System (ADS)

    van der Paal, Jonas; Verheyen, Claudia; Neyts, Erik C.; Bogaerts, Annemie

    2017-01-01

    In recent years, the ability of cold atmospheric pressure plasmas (CAPS) to selectively induce cell death in cancer cells has been widely established. This selectivity has been assigned to the reactive oxygen and nitrogen species (RONS) created in CAPs. To provide new insights in the search for an explanation for the observed selectivity, we calculate the transfer free energy of multiple ROS across membranes containing a varying amount of cholesterol. The cholesterol fraction is investigated as a selectivity parameter because membranes of cancer cells are known to contain lower fractions of cholesterol compared to healthy cells. We find that cholesterol has a significant effect on the permeation of reactive species across a membrane. Indeed, depending on the specific reactive species, an increasing cholesterol fraction can lead to (i) an increase of the transfer free energy barrier height and width, (ii) the formation of a local free energy minimum in the center of the membrane and (iii) the creation of extra free energy barriers due to the bulky sterol rings. In the context of plasma oncology, these observations suggest that the increased ingress of RONS in cancer cells can be explained by the decreased cholesterol fraction of their cell membrane.

  4. Hampering Effect of Cholesterol on the Permeation of Reactive Oxygen Species through Phospholipids Bilayer: Possible Explanation for Plasma Cancer Selectivity

    PubMed Central

    Van der Paal, Jonas; Verheyen, Claudia; Neyts, Erik C.; Bogaerts, Annemie

    2017-01-01

    In recent years, the ability of cold atmospheric pressure plasmas (CAPS) to selectively induce cell death in cancer cells has been widely established. This selectivity has been assigned to the reactive oxygen and nitrogen species (RONS) created in CAPs. To provide new insights in the search for an explanation for the observed selectivity, we calculate the transfer free energy of multiple ROS across membranes containing a varying amount of cholesterol. The cholesterol fraction is investigated as a selectivity parameter because membranes of cancer cells are known to contain lower fractions of cholesterol compared to healthy cells. We find that cholesterol has a significant effect on the permeation of reactive species across a membrane. Indeed, depending on the specific reactive species, an increasing cholesterol fraction can lead to (i) an increase of the transfer free energy barrier height and width, (ii) the formation of a local free energy minimum in the center of the membrane and (iii) the creation of extra free energy barriers due to the bulky sterol rings. In the context of plasma oncology, these observations suggest that the increased ingress of RONS in cancer cells can be explained by the decreased cholesterol fraction of their cell membrane. PMID:28059085

  5. 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.

  6. Evoll - A Computer Based Natural Selection Game

    ERIC Educational Resources Information Center

    Wright, Ramil C.

    1972-01-01

    Describes a computer-generated natural selection game which deals with various factors influencing survival and speciation processes. Variation of population size, growth rate, brood size, and selection pressure are permitted by the program, which is written in ASA Basic FORTRAN IV. (PR)

  7. 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)

  8. 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

    2014-05-26

    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.

  9. 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.

  10. 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.

  11. Mechanisms of Furfural Reduction on Metal Electrodes: Distinguishing Pathways for Selective Hydrogenation of Bioderived Oxygenates

    DOE PAGES

    Chadderdon, Xiaotong H.; Chadderdon, David J.; Matthiesen, John E.; ...

    2017-09-13

    Electrochemical reduction of biomass-derived platform molecules is an emerging route for the sustainable production of fuels and chemicals. Understanding gaps between reaction conditions, underlying mechanisms, and product selectivity have limited the rational design of active, stable, and selective catalyst systems. Here, the mechanisms of electrochemical reduction of furfural, an important biobased platform molecule and model for aldehyde reduction, are explored through a combination of voltammetry, preparative electrolysis, thiol-electrode modifications, and kinetic isotope studies. It is demonstrated that two distinct mechanisms are operable on metallic Cu electrodes in acidic electrolytes: (i) electrocatalytic hydrogenation (ECH) and (ii) direct electroreduction. The contributions ofmore » each mechanism to the observed product distribution are clarified by evaluating the requirement for direct chemical interactions with the electrode surface and the role of adsorbed hydrogen. Further analysis reveals that hydrogenation and hydrogenolysis products are generated by parallel ECH pathways. By understanding the underlying mechanisms it enables the manipulation of furfural reduction by rationally tuning the electrode potential, electrolyte pH, and furfural concentration to promote selective formation of important biobased polymer precursors and fuels.« less

  12. Diagnosis of Compartment Syndrome Based on Tissue Oxygenation

    DTIC Science & Technology

    2015-06-01

    of technical problems obtaining accurate PmO2 and CP; results are based on the remaining 15 animals. We confirmed our hypothesis that tissue...additional problem with the probe was that left-to-right differences of PmO2 occurred within the same animal at baseline before any experimental procedures...also explain the lack of significant correlations between PmO2 and TVI in many parts of the study. CHANGES/ PROBLEMS :  Changes in approach and

  13. The influence of dissolved oxygen on winter habitat selection by largemouth bass: an integration of field biotelemetry studies and laboratory experiments.

    PubMed

    Hasler, C T; Suski, C D; Hanson, K C; Cooke, S J; Tufts, B L

    2009-01-01

    In this study, field biotelemetry and laboratory physiology approaches were coupled to allow understanding of the behavioral and physiological responses of fish to winter hypoxia. The biotelemetry study compared dissolved oxygen levels measured throughout the winter period with continually tracked locations of nine adult largemouth bass obtained from a whole-lake submerged telemetry array. Fish habitat usage was compared with habitat availability to assess whether fish were selecting for specific dissolved oxygen concentrations. The laboratory study examined behavioral and physiological responses to progressive hypoxia in juvenile largemouth bass acclimated to winter temperatures. Results from the dissolved oxygen measurements made during the biotelemetry study showed high variance in under-ice dissolved oxygen levels. Avoidance of water with dissolved oxygen <2.0 mg/L by telemetered fish was demonstrated, but significant use of water with intermediate dissolved oxygen levels was also found. Results from the lab experiments showed marked changes in behavior (i.e., yawning and vertical movement) at <2.0 mg/L of dissolved oxygen but no change in tissue lactate, an indicator of anaerobic metabolism. Combined results of the biotelemetry and laboratory studies demonstrate that a dissolved oxygen content of 2.0 mg/L may be a critical threshold that induces behavioral responses by largemouth bass during the winter. In addition, the use by fish of areas with intermediate levels of dissolved oxygen suggests that there are multiple environmental factors influencing winter behavior.

  14. 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.

  15. 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

  16. Enzyme-based online monitoring and measurement of antioxidant activity using an optical oxygen sensor coupled to an HPLC system.

    PubMed

    Quaranta, Michela; Nugroho Prasetyo, Endry; Koren, Klaus; Nyanhongo, Gibson S; Murkovic, Michael; Klimant, Ingo; Guebitz, Georg M

    2013-03-01

    It is estimated that up to 50% of the adult population take antioxidant products on a daily basis to promote their health status. Strangely, despite the well-recognized importance of antioxidants, currently there is no international standard index for labeling owing to the lack of standardized methods for antioxidant measurement in complex products. Here, an online high-performance liquid chromatography (HPLC)-based method to detect and measure the total antioxidant capacity of antioxidant samples is presented. In this approach, complex samples containing antioxidants are separated by the HPLC system, which is further coupled to an antioxidant measuring system consisting of an optical oxygen sensor, laccase, and tetramethoxy azobismethylene quinone (TMAMQ). The antioxidants, separated via HPLC, reduce TMAMQ to syringaldazine, which is then reoxidized by laccase while simultaneously consuming O(2). The amount of consumed oxygen is directly proportional to the concentration of antioxidants and is measured by the optical oxygen sensor. The sensor is fabricated by coating a glass capillary with an oxygen-sensitive thin layer made of platinum(II) meso-tetra(4-fluorophenyl)tetrabenzoporphyrin and polystyrene, which makes real-time analysis possible (t(90) = 1.1 s in solution). Four selected antioxidants (3 mM), namely, catechin, ferulic acid, naringenin (used as a control), and Trolox, representing flavonol, hydrocinnamic acid, flavanone, and vitamin E, respectively, were injected into the online antioxidant monitoring system, separated, and then mixed with the TMAMQ/laccase solution, which resulted in oxygen consumption. This study shows that, with the use of such a system, the antioxidant activity of individual antioxidant molecules in a sample and their contribution to the total antioxidant activity of the sample can be correctly assigned.

  17. A Membrane-Free Neutral pH Formate Fuel Cell Enabled by a Selective Nickel Sulfide Oxygen Reduction Catalyst.

    PubMed

    Yan, Bing; Concannon, Nolan M; Milshtein, Jarrod D; Brushett, Fikile R; Surendranath, Yogesh

    2017-06-19

    Polymer electrolyte membranes employed in contemporary fuel cells severely limit device design and restrict catalyst choice, but are essential for preventing short-circuiting reactions at unselective anode and cathode catalysts. Herein, we report that nickel sulfide Ni3 S2 is a highly selective catalyst for the oxygen reduction reaction in the presence of 1.0 m formate. We combine this selective cathode with a carbon-supported palladium (Pd/C) anode to establish a membrane-free, room-temperature formate fuel cell that operates under benign neutral pH conditions. Proof-of-concept cells display open circuit voltages of approximately 0.7 V and peak power values greater than 1 mW cm(-2) , significantly outperforming the identical device employing an unselective platinum (Pt) cathode. The work establishes the power of selective catalysis to enable versatile membrane-free fuel cells. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. 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 ...

  19. 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 ...

  20. 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

  1. 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

  2. Materials selection for long life in low earth orbit - A critical evaluation of atomic oxygen testing with thermal atom systems

    NASA Technical Reports Server (NTRS)

    Koontz, S. L.; Albyn, K.; Leger, L.

    1990-01-01

    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 in thermal atom environments are compared with those observed in LEO and in high-quality LEO simulations. Reaction efficiencies (cu cm/atom) measured in a new type of thermal atom apparatus are one-thousandth to one ten-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 eight 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 speciic thermal atom test environments can be used as reliable materials screening tools.

  3. 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.

  4. Materials selection for long life in low earth orbit - A critical evaluation of atomic oxygen testing with thermal atom systems

    NASA Technical Reports Server (NTRS)

    Koontz, S. L.; Albyn, K.; Leger, L.

    1990-01-01

    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 in thermal atom environments are compared with those observed in LEO and in high-quality LEO simulations. Reaction efficiencies (cu cm/atom) measured in a new type of thermal atom apparatus are one-thousandth to one ten-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 eight 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 speciic thermal atom test environments can be used as reliable materials screening tools.

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

    SciTech Connect

    Lu, Jun; Lee, Yun Jung; Luo, Xiangyi; Lau, Kah Chun; Wen, Jianguo; Wang, Hsien-Hau; Zhai, Dengyun; Miller, Dean; Jeong, Yo-Sub; Park, Jin-Bum; Curtiss, Larry A.; Amine, Khalil

    2016-01-11

    Although the superoxide of lithium (LiO2) is believed to be a key intermediate in Li-O2 batteries leading to the formation of lithium peroxide, LiO2 has never been observed in its pure state. In this work, we provide evidence that use of a cathode based on a reduced graphene oxide with Ir nanoparticles in a Li-O2 battery results in a LiO2 discharge product formed by single electron transfer without further electron transfer or disproportionation to form Li2O2. High energy X-ray diffraction (HE-XRD) patterns indicates the presence of crystalline LiO2 with no evidence of Li2O2 or Li2O. The HEXRD studies as a function of time also show that LiO2 can be stable in its crystalline form after one week of aging in the presence of electrolyte. The results provide evidence that LiO2 is stable enough that it can be repeatedly charged and discharged with a very low charge potential (~3.2 V) and may open the avenue for a lithium superoxide-based battery.

  6. Atomic scale behavior of oxygen-based radicals in water

    NASA Astrophysics Data System (ADS)

    Verlackt, C. C. W.; Neyts, E. C.; Bogaerts, A.

    2017-03-01

    Cold atmospheric pressure plasmas in and in contact with liquids represent a growing field of research for various applications. Understanding the interactions between the plasma generated species and the liquid is crucial. In this work we perform molecular dynamics (MD) simulations based on a quantum mechanical method, i.e. density-functional based tight-binding (DFTB), to examine the interactions of OH radicals and O atoms in bulk water. Our calculations reveal that the transport of OH radicals through water is not only governed by diffusion, but also by an equilibrium reaction of H-abstraction with water molecules. Furthermore, when two OH radicals encounter each other, they either form a stable cluster, or react, resulting in the formation of a new water molecule and an O atom. In addition, the O atoms form either oxywater (when in singlet configuration) or they remain stable in solution (when in triplet configuration), stressing the important role that O atoms can play in aqueous solution, and in contact with biomolecules. Our observations are in line with both experimental and ab initio results from the literature.

  7. 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.

  8. 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. Copyright © 2014 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.

  9. 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.

  10. Peripheral oxygen transport and utilization in rats following continued selective breeding for endurance running capacity.

    PubMed

    Howlett, Richard A; Kirkton, Scott D; Gonzalez, Norberto C; Wagner, Harrieth E; Britton, Steven L; Koch, Lauren G; Wagner, Peter D

    2009-06-01

    Untrained rats selectively bred for either high (HCR) or low (LCR) treadmill running capacity previously demonstrated divergent physiological traits as early as the seventh generation (G7). We asked whether continued selective breeding to generation 15 (G15) would further increase the divergence in skeletal muscle capillarity, morphometry, and oxidative capacity seen previously at G7. At G15, mean body weight was significantly lower (P < 0.001) in the HCR rats (n = 11; 194 +/- 3 g) than in LCR (n = 12; 259 +/- 9 g) while relative medial gastrocnemius muscle mass was not different (0.23 +/- 0.01 vs. 0.22 +/- 0.01% total body weight). Normoxic (Fi(O(2)) = 0.21) Vo(2max) was 50% greater (P < 0.001) in HCR despite the lower absolute muscle mass, and skeletal muscle O(2) conductance (measured in hypoxia; Fi(O(2)) = 0.10) was 49% higher in HCR (P < 0.001). Muscle oxidative enzyme activities were significantly higher in HCR (citrate synthase: 16.4 +/- 0.4 vs. 14.0 +/- 0.6; beta-hydroxyacyl-CoA dehydrogenase: 5.2 +/- 0.2 vs. 4.2 +/- 0.2 mmol.kg(-1).min(-1)). HCR rats had approximately 36% more total muscle fibers and also 36% more capillaries in the medial gastrocnemius. Because average muscle fiber area was 35% smaller, capillary density was 36% higher in HCR, but capillary-to-fiber ratio was the same. Compared with G7, G15 HCR animals showed 38% greater total fiber number with an additional 25% decrease in mean fiber area. These data suggest that many of the skeletal muscle structural and functional adaptations enabling greater O(2) utilization in HCR at G7 continue to progress following additional selective breeding for endurance capacity. However, the largest changes at G15 relate to O(2) delivery to skeletal muscle and not to the capacity of skeletal muscle to use O(2).

  11. Oxygen-tolerant hydrogenases in hydrogen-based technologies.

    PubMed

    Friedrich, Bärbel; Fritsch, Johannes; Lenz, Oliver

    2011-06-01

    To develop a viable H2 technology, production of H2 has to be significantly enlarged by using renewable resources. One option of generating H2 is the photosynthetic conversion of sunlight and water directly to H2 and O2. Photosystems and hydrogenases are currently being exploited for the design of efficient H2-producing systems that require highly active and O2-tolerant biocatalysts. This communication focuses on two challenging features: hydrogenases that produce H2 in the presence of O2, and direct electron transfer between photosystem I (PS I) and hydrogenase. The latter is accomplished by connecting both modules through a protein fusion or a synthetic molecular wire. These are first steps toward a photosynthetic microbial cell or a semi-synthetic system that may be employed in future H2-based technologies.

  12. Effect of oxygen stoichiometry on T(sub c) of Bi-based superconductors

    NASA Technical Reports Server (NTRS)

    Zhao, J.; Seehra, M. S.

    1990-01-01

    The role of oxygen stoichiometry on T(sub c) is relatively well established on La2CuO(4+x) and the YBa2Cu3O(7-x) (123) superconductors, as compared to the Bi-based superconductors. Results are presented of investigations on the effects of oxygen stoichiometry on the transition temperature T(sub c) of Bi2Sr2CaCu2O(8+x) (2212 phase), and Pb-doped Bi2Sr2Ca2Cu3O(10+X) (2223 phase). It is shown that the effects of oxygen stoichiometry on T(sub c) of these two phases are very different. These results may be helpful in understanding the mechanism of superconductivity in the Bi-based superconductors.

  13. 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.

  14. 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.

  15. The influence of oxygen doping on critical parameters of mercury based superconductors

    NASA Astrophysics Data System (ADS)

    Ćataltepe, Ö. Aslan; Özdemir, Z. Güven; Onbaşlı, Ü.

    2016-03-01

    In this work, the effect of oxygen doping on the critical parameters of the mercury based superconducting sample such as critical transition temperature, Tc, critical magnetic field, Hc, critical current density, Jc, has been investigated by the magnetic susceptibility versus temperature (χ-T) and magnetization versus applied magnetic field (M-H) measurements and, X-Ray Diffraction (XRD) patterns. It has been observed that regardless of the oxygen doping concentration, the mercury cuprate system possesses two intrinsic superconducting phases together, HgBa2Ca2Cu3O8+x and HgBa2CaCu2O6+x. However, the highest Tc has been determined for the optimum oxygen doped sample. Moreover, it has been revealed that superconducting properties, crystal lattice parameters, coherent lengths, ξab, ξc and the anisotropy factor γ etc. are very sensitive to oxygen doping procedures. Hence, the results presented this work enables one to obtain the mercury based superconductor with the most desirable criticals and other parameters for theoretical and technological applications by arranging the oxygen doping concentration.

  16. The influence of oxygen doping on critical parameters of mercury based superconductors

    SciTech Connect

    Çataltepe, Ö. Aslan E-mail: ozden.aslan@gedik.edu.tr; Özdemir, Z. Güven; Onbaşlı, Ü.

    2016-03-25

    In this work, the effect of oxygen doping on the critical parameters of the mercury based superconducting sample such as critical transition temperature, T{sub c}, critical magnetic field, H{sub c}, critical current density, J{sub c}, has been investigated by the magnetic susceptibility versus temperature (χ-T) and magnetization versus applied magnetic field (M-H) measurements and, X-Ray Diffraction (XRD) patterns. It has been observed that regardless of the oxygen doping concentration, the mercury cuprate system possesses two intrinsic superconducting phases together, HgBa{sub 2}Ca{sub 2}Cu{sub 3}O{sub 8+x} and HgBa{sub 2}CaCu{sub 2}O{sub 6+x}. However, the highest T{sub c} has been determined for the optimum oxygen doped sample. Moreover, it has been revealed that superconducting properties, crystal lattice parameters, coherent lengths, ξ{sub ab}, ξ{sub c} and the anisotropy factor γ etc. are very sensitive to oxygen doping procedures. Hence, the results presented this work enables one to obtain the mercury based superconductor with the most desirable criticals and other parameters for theoretical and technological applications by arranging the oxygen doping concentration.

  17. Reversible, Fast, and Wide-Range Oxygen Sensor Based on Nanostructured Organometal Halide Perovskite.

    PubMed

    Stoeckel, Marc-Antoine; Gobbi, Marco; Bonacchi, Sara; Liscio, Fabiola; Ferlauto, Laura; Orgiu, Emanuele; Samorì, Paolo

    2017-10-01

    Nanostructured materials characterized by high surface-volume ratio hold the promise to constitute the active materials for next-generation sensors. Solution-processed hybrid organohalide perovskites, which have been extensively used in the last few years for optoelectronic applications, are characterized by a self-assembled nanostructured morphology, which makes them an ideal candidate for gas sensing. Hitherto, detailed studies of the dependence of their electrical characteristics on the environmental atmosphere have not been performed, and even the effect of a ubiquitous gas such as O2 has been widely overlooked. Here, the electrical response of organohalide perovskites to oxygen is studied. Surprisingly, a colossal increase (3000-fold) in the resistance of perovskite-based lateral devices is found when measured in a full oxygen atmosphere, which is ascribed to a trap healing mechanism originating from an O2 -mediated iodine vacancies filling. A variation as small as 70 ppm in the oxygen concentration can be detected. The effect is fast (<400 ms) and fully reversible, making organohalide perovskites ideal active materials for oxygen sensing. The effect of oxygen on the electrical characteristics of organohalide perovskites must be taken into deep consideration for the design and optimization of any other perovskite-based (opto-) electronic device working in ambient conditions. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. 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.

  19. Hydrophobic dipeptide crystals: a promising Ag-free class of ultramicroporous materials showing argon/oxygen adsorption selectivity.

    PubMed

    Afonso, R; Mendes, A; Gales, L

    2014-09-28

    The adsorption isotherms of nitrogen, oxygen and argon in four VA-class hydrophobic dipeptides are presented. Isotherms were determined at 5, 20 and 35 °C, for a pressure range of 0-6 bar. Under these conditions, adsorption is still in the Henry region. For all materials and temperatures, the sequence of preferential adsorption is Ar > O2 > N2, a highly abnormal result. At 5 °C, the dipeptide with the smallest pores, VI, has Ar/O2 adsorption equilibrium selectivities up to 1.30, the highest ever measured in Ag-free adsorbents. Gas uptakes, at 1 bar and 20 °C, are ∼0.05 mol kg(-1), very low relative values that are partially explained by the low porosity of the solids (<10%). The significance of these results for the development of new materials for the process of O2 generation by pressure swing adsorption (PSA) is discussed. The results indicate some of the structural and chemical properties that prospective Ag-free adsorbents should have in order to have Ar/O2 selectivity, hydrophobic pores, less than 0.5 nm-wide, and porosity of, at least, 20%.

  20. Advanced fluorocarbon-based systems for oxygen and drug delivery, and diagnosis.

    PubMed

    Riess, J G; Krafft, M P

    1997-01-01

    Fluorocarbons and fluorocarbon-derived materials constitute a vast family of synthetic components that have a range of remarkable properties including exceptional chemical and biological inertness, gas-dissolving capacity, low surface tension, high fluidity, excellent spreading characteristics, unique hydro- and lipophobicity, high density, absence of protons, and magnetic susceptibility close to that of water. These properties lead to a diversity of products and applications as illustrated by those products that are already in advanced clinical trials, which comprise: 1) an injectable oxygen carrier, i.e. blood substitute, consisting of a fluorocarbon-in-water emulsion for use in surgery to alleviate the problems raised by the transfusion of homologous blood; the same emulsion is also being evaluated with cardiopulmonary bypass patients; 2) a neat fluorocarbon for treatment of acute respiratory failure by liquid ventilation; and 3) fluorocarbon-based or stabilized gas bubbles to be used as contrast agents for the assessment of heart function and detection of perfusion defects by ultrasound imaging. Proper selection of the fluorocarbon best suited for the intended application, formulation optimization, and advanced stabilization and processing procedures led to effective, ready-for-use products with minimal side-effects. Further highly fluorinated materials, including amphiphiles and various fluorocarbon-based colloidal systems that have potential as pulmonary, topical and ophthalmological drug delivery agents, and as skin protection barriers, are now being investigated. Such systems include drug-in-fluorocarbon suspensions, reverse water-in-fluorocarbon emulsions, oil-in-fluorocarbon emulsions, multiple emulsions, microemulsions, fluorocarbon gels, fluorinated liposomes, fluorinated tubules and other novel supramolecular systems.

  1. Kinetic analysis of microbe opsonification based on stimulated polymorphonuclear leukocyte oxygenation activity.

    PubMed

    Allen, R C; Lieberman, M M

    1984-08-01

    With Pseudomonas aeruginosa as the target microbes and polymorphonuclear leukocytes (PMNL) as effector phagocytes, the microbe-specific, immunoglobulin G (IgG)-dependent opsonic capacities of preimmune and immune sera were measured as the rate of stimulated PMNL dioxygenation of luminol yielding chemiluminescence (CL). When the reactants other than opsonin are present in concentrations that are not rate limiting, the information-effector relationship linking specific opsonin concentration to effector PMNL stimulation is described by the rate equation: L' = k'[IgG]i, where L' is the peak CL velocity (photons per minute), k' is the proportionality constant, [IgG] is the concentration of specific opsonin, and the exponent i is the order of the reaction with respect to opsonin. Since the specific opsonins were polyclonal IgG of unknown absolute serum concentration, the reciprocal rate expression, L' = k'D-i, was employed for data presentation; D is the serum dilution (final volume/initial serum volume), and the sign of i is changed to negative. The relationships of integral, first-derivative, and second-derivative expressions of the CL response to opsonin concentration are illustrated with experimentally obtained data. Based on peak CL velocity or peak CL acceleration measurements taken over different time intervals of testing, the estimated order with respect to opsonin is highest, and probably most accurate, using the shortest test interval allowing reasonably good precision of measurement. As an alternative temporal approach, microbe opsonification kinetics are analyzed based on nodal time (Tn) measurements. The Tn is the time point separating the acceleration and deceleration phases of the PMNL oxygenation response to stimulation and as such satisfies the criterion of a selected condition of PMNL activation.

  2. A luminescence lifetime-based capillary oxygen sensor utilizing monolithically integrated organic photodiodes.

    PubMed

    Lamprecht, Bernhard; Tschepp, Andreas; Čajlaković, Merima; Sagmeister, Martin; Ribitsch, Volker; Köstler, Stefan

    2013-10-21

    A novel optical sensor device monolithically integrated on a glass capillary is presented. Therefore, we took advantage of the ability to fabricate organic optoelectronic devices on non-planar substrates. The functionality of the concept is demonstrated by realizing an integrated oxygen sensor based on luminescence decay time measurement.

  3. Comparing Model Selection and Regularization Approaches to Variable Selection in Model-Based Clustering.

    PubMed

    Celeux, Gilles; Martin-Magniette, Marie-Laure; Maugis-Rabusseau, Cathy; Raftery, Adrian E

    2014-01-01

    We compare two major approaches to variable selection in clustering: model selection and regularization. Based on previous results, we select the method of Maugis et al. (2009b), which modified the method of Raftery and Dean (2006), as a current state of the art model selection method. We select the method of Witten and Tibshirani (2010) as a current state of the art regularization method. We compared the methods by simulation in terms of their accuracy in both classification and variable selection. In the first simulation experiment all the variables were conditionally independent given cluster membership. We found that variable selection (of either kind) yielded substantial gains in classification accuracy when the clusters were well separated, but few gains when the clusters were close together. We found that the two variable selection methods had comparable classification accuracy, but that the model selection approach had substantially better accuracy in selecting variables. In our second simulation experiment, there were correlations among the variables given the cluster memberships. We found that the model selection approach was substantially more accurate in terms of both classification and variable selection than the regularization approach, and that both gave more accurate classifications than K-means without variable selection. But the model selection approach is not available in a very high dimension context.

  4. 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.

  5. 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 analysing

  6. 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

    2013-09-03

    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.

  7. Oxygen quenching in a LAB based liquid scintillator and the nitrogen bubbling model

    NASA Astrophysics Data System (ADS)

    Xiao, Hua-Lin; Deng, Jing-Shan; Wang, Nai-Yan

    2010-05-01

    The oxygen quenching effect in a Linear Alkl Benzene (LAB) based liquid scintillator (LAB as the solvent, 3 g/L 2, 5 diphe-nyloxazole (PPO) as the fluor and 15 mg/L p-bis-(o-methylstyryl)-benzene (bis-MSB) as the λ-shifter) is studied by measuring the light yield as a function of the nitrogen bubbling time. It is shown that the light yield of the fully purged liquid scintillator is increased by 11% at room temperature and the room atmospheric pressure. A simple nitrogen bubbling model is proposed to describe the relationship between the relative light yield (oxygen quenching factor) and the bubbling time.

  8. 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.

  9. [Monitoring of oxygen concentration based on tunable diode laser absorption spectroscopy].

    PubMed

    Zhang, Shuai; Dong, Feng-Zhong; Zhang, Zhi-Rong; Wang, Yu; Kan, Rui-Feng; Zhang, Yu-Jun; Liu, Jian-Guo; Liu, Wen-Qing

    2009-10-01

    Oxygen is a widely used important gas in the industrial process. It is very meaningful to on-line monitor the oxygen concentration for the enhancement of combustion efficiency and reduction in environmental pollution. Tunable diode laser absorption spectroscopy (TDLAS) is a highly sensitive, highly selective and fast time response trace gas detection technique. With the features of tunability and narrow linewidth of distributed feedback (DFB) diode laser and by precisely tuning the laser output wavelength to a single isolated absorption line of the gas, TDLAS technique can be utilized to accurately implement gas concentration measurement with very high sensitivity. In the present paper, the authors used a DFB laser was used as the light source, and by employing wavelength modulation method and measuring the second harmonic signal of one absorption line near 760 nm of oxygen molecule, the authors built a system for online monitoring of oxygen concentration. The characteristics of the system are as follows: the scope of detection is 0.01%-20%; detection accuracy is 0.1%, long term stability is 1%.

  10. Method of measuring blood oxygenation based on spectroscopy of diffusely scattered light

    NASA Astrophysics Data System (ADS)

    Kleshnin, M. S.; Orlova, A. G.; Kirillin, M. Yu.; Golubyatnikov, G. Yu.; Turchin, I. V.

    2017-05-01

    A new approach to the measurement of blood oxygenation is developed and implemented, based on an original two-step algorithm reconstructing the relative concentration of biological chromophores (haemoglobin, water, lipids) from the measured spectra of diffusely scattered light at different distances from the radiation source. The numerical experiments and approbation of the proposed approach using a biological phantom have shown the high accuracy of the reconstruction of optical properties of the object in question, as well as the possibility of correct calculation of the haemoglobin oxygenation in the presence of additive noises without calibration of the measuring device. The results of the experimental studies in animals agree with the previously published results obtained by other research groups and demonstrate the possibility of applying the developed method to the monitoring of blood oxygenation in tumour tissues.

  11. 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.

  12. Ratiometric Dissolved Oxygen Sensors Based on Ruthenium Complex Doped with Silver Nanoparticles

    PubMed Central

    Jiang, Zike; Yu, Xinsheng; Zhai, Shikui; Hao, Yingyan

    2017-01-01

    A ratiometric optical sensor has been developed with electrospinning processing method for dissolved oxygen measurement. The sensing film is fabricated by using silver nano-particles (Ag NPs) doped with tris(4,7-diphenyl-1,10-phenanthroline) ruthenium(II) dichloride complex (Ru(DPP)3Cl2) encapsulated in plasticized polymethyl methacrylate (PMMA). An insensitive 3-(2-benzothiazolyl)-7-(diethy lamino)-(6CI,7CI) (Coumarin6) is adopted as reference. The ratio of oxygenation is calculated at each image pixel of a 3CCD camera to quantify the oxygen concentration in aqueous environment. Compared to Ag-free film, the response time of Ag-containing films were improved from 1.5 s to 1.0 s upon switching from deoxygenated to air saturation and from 65 s to 45 s from air saturation to fully deoxygenated. The response times of the Ag-free film obtained by knifing was 2.0 s upon switching from deoxygenated to air saturation and 104 s from air saturation to fully deoxygenated. Results of the evaluation of accuracy, limit of detection, stability, and photostability are presented. An experiment measuring the spatiotemporal variation of oxygen distribution within the photosynthesis and respiration of Chlorella vulgaris is demonstrated. It is shown that the nanofiber-based optical sensor film could serve as a promising method for rapid oxygen monitoring in aqueous applications. PMID:28282946

  13. Ratiometric Dissolved Oxygen Sensors Based on Ruthenium Complex Doped with Silver Nanoparticles.

    PubMed

    Jiang, Zike; Yu, Xinsheng; Zhai, Shikui; Hao, Yingyan

    2017-03-09

    A ratiometric optical sensor has been developed with electrospinning processing method for dissolved oxygen measurement. The sensing film is fabricated by using silver nano-particles (Ag NPs) doped with tris(4,7-diphenyl-1,10-phenanthroline) ruthenium(II) dichloride complex (Ru(DPP)₃Cl₂) encapsulated in plasticized polymethyl methacrylate (PMMA). An insensitive 3-(2-benzothiazolyl)-7-(diethy lamino)-(6CI,7CI) (Coumarin6) is adopted as reference. The ratio of oxygenation is calculated at each image pixel of a 3CCD camera to quantify the oxygen concentration in aqueous environment. Compared to Ag-free film, the response time of Ag-containing films were improved from 1.5 s to 1.0 s upon switching from deoxygenated to air saturation and from 65 s to 45 s from air saturation to fully deoxygenated. The response times of the Ag-free film obtained by knifing was 2.0 s upon switching from deoxygenated to air saturation and 104 s from air saturation to fully deoxygenated. Results of the evaluation of accuracy, limit of detection, stability, and photostability are presented. An experiment measuring the spatiotemporal variation of oxygen distribution within the photosynthesis and respiration of Chlorella vulgaris is demonstrated. It is shown that the nanofiber-based optical sensor film could serve as a promising method for rapid oxygen monitoring in aqueous applications.

  14. Criteria for direct hemoperfusion with an immobilized polymyxin B fiber column based on oxygen metabolism.

    PubMed

    Kushi, Hidehiko; Miki, Takahiro; Sakagami, Yuichiro; Saito, Takeshi; Tanjoh, Katsuhisa

    2008-08-01

    The optimum time for commencement of direct hemoperfusion with a polymyxin B immobilized fiber column (DHP-PMX) in patients with sepsis remains unclear. We retrospectively studied the response to DHP-PMX in relation to parameters of oxygen metabolism in 48 patients with sepsis who were divided into two groups. In the effective group (N = 36), the mean blood pressure increased by at least 10 mm Hg after DHP-PMX. Patients who did not show such a blood pressure elevation were assigned to the non-effective group (N = 12). Before the start of therapy, various parameters (mixed venous oxygen saturation, oxygen delivery index, oxygen consumption index (VO(2)I), oxygen extraction ratio, gastric mucosal-arterial PCO(2) difference, age, systemic vascular resistance index, Acute Physiology and Chronic Health Evaluation II score, and Sequential Organ Failure Assessment score were measured in both groups. These parameters were then compared between the two groups. Only VO(2)I showed a significant difference between the two groups, and all patients in the effective group had a VO(2)I of 100 mL/min/m(2) or more. Based on these results, DHP-PMX should be introduced during the period when VO(2)I is still equal to or greater than 100 mL/min/m(2).

  15. [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.

  16. A mechanistic investigation of a calcium-based oxygen carrier for chemical looping combustion

    SciTech Connect

    Shen, Laihong; Zheng, Min; Xiao, Jun; Xiao, Rui

    2008-08-15

    Chemical looping combustion (CLC) has been suggested as an energy-efficient method for the capture of carbon dioxide from combustion. It is indirect combustion by the use of an oxygen carrier, which can be used for CO{sub 2} capture in power-generating processes. The possibility of CLC using a calcium-based oxygen carrier is investigated in this paper. In the air reactor air is supplied to oxidize CaS to CaSO{sub 4}, where oxygen is transferred from air to the oxygen carrier; the reduction of CaSO{sub 4} to CaS takes place in the fuel reactor. The exit gas from the fuel reactor is CO{sub 2} and H{sub 2}O. After condensation of water, almost pure CO{sub 2} could be obtained. The thermodynamic and kinetic problem of the reduction reactions of CaSO{sub 4} with CO and H{sub 2} and the oxidization reactions of CaS with O{sub 2} is discussed in the paper to investigate the technique possibility. To prevent SO{sub 2} release from the process of chemical looping combustion using a calcium-based oxygen carrier, thermochemical CaSO{sub 4} reduction and CaS oxidation are discussed. Thermal simulation experiments are carried out using a thermogravimetric analyzer (TGA). The properties of the products are characterized by Fourier transform infrared (FT-IR) spectroscopy and X-ray diffractometry (XRD), and the optimal reaction parameters are evaluated. The effects of reaction temperature, reductive gas mixture, and oxygen partial pressure on the composition of flue gas are discussed. The suitable temperature of the air reactor is between 1050 and 1150 C and the optimal temperature of the fuel reactor between 900 and 950 C. (author)

  17. Effect of oocyte maturation time, sperm selection method and oxygen tension on in vitro embryo development in alpacas.

    PubMed

    Ruiz, Jaime; Paulo Santayana, R; José Mendoza, M; Leandra Landeo, J; Huamán, Elizabeth; Ticllacuri, Flamel; Fidel Mujica, L; Silva, Mauricio; Ratto, Marcelo H

    2017-06-01

    We evaluated the effect of in vitro maturation time, sperm selection and oxygen tension on alpaca embryo development. In Experiment I, Cumulus Oocyte- Complexes (COCs) were obtained from abattoir ovaries and in vitro matured in TCM-199 for 24 (n = 217), 28 (215), or 32 h (223) at 38.5 °C, high humidity and 5% CO2 in air. Oocytes from 24 (n = 392), 28 (n = 456) or 32 (n = 368) h groups were in vitro fertilized with epididymal sperm and cultured in SOFaa at 38.5 °C, high humidity and 5% CO2, 5% O2 and 90% N2 for 7 days. Embryo development was evaluated on Day 2, 5 and Day 7 of in vitro culture (Day 0 = in vitro fertilization). In Experiment II, a 2 by 2-factorial design was used to determine the effect of sperm selection (Swim-up vs Percoll) and oxygen tension (20% vs 5%) during embryo culture and their interaction on embryo development. COCs were in vitro matured for 32 h at 38.5 °C and 5% CO2 in air and then in vitro inseminated with epididymal sperm processed by swim-up or Percoll. Zygotes were cultured in SOFaa + cumulus cells at 38.5 °C under 20 or 5% of O2 tension and high humidity for 7 days. A total of 235, 235, 253 and 240 oocytes were assigned to: swim-up+20 O2, swim-up+5 O2 or Percoll+20 O2, Percoll+5 O2, groups respectively. The proportion of oocytes reaching MII stage was highest after 32 h of in vitro maturation (P < 0.05). Blastocyst rate (29.1 ± 2.7%) was also highest for COCs matured for 32 h (Exp I). In Experiment II, Blastocysts rate (26.03 ± 4.7; 27.7 ± 4.3; 29.7 ± 3.8 and 27.6 ± 4.2% for swim-up+20 O2, swim-up+5 O2 or Percoll+20 O2, Percoll+5 O2, respectively) was not affected by sperm selection method (P = 0.8), oxygen tension (P = 0.9) or their interaction (P = 0.5). Copyright © 2017 Elsevier Inc. All rights reserved.

  18. Fuzzification of ASAT's rule based aimpoint selection

    NASA Astrophysics Data System (ADS)

    Weight, Thomas H.

    1993-06-01

    The aimpoint algorithms being developed at Dr. Weight and Associates are based on the concept of fuzzy logic. This approach does not require a particular type of sensor data or algorithm type, but allows the user to develop a fuzzy logic algorithm based on existing aimpoint algorithms and models. This provides an opportunity for the user to upgrade an existing system design to achieve higher performance at minimal cost. Many projects have aimpoint algorithms which are based on 'crisp' logic rule based algorithms. These algorithms are sensitive to glint, corner reflectors, or intermittent thruster firings, and to uncertainties in the a priori estimates of angle of attack. If these projects are continued through to a demonstration involving a launch to hit a target, it is quite possible that the crisp logic approaches will need to be upgraded to handle these important error sources.

  19. 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.

  20. 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

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

    SciTech Connect

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

    2016-06-13

    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.

  2. 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.

  3. 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.

  4. Analysis and interpretation of microplate-based oxygen consumption and pH data.

    PubMed

    Divakaruni, Ajit S; Paradyse, Alexander; Ferrick, David A; Murphy, Anne N; Jastroch, Martin

    2014-01-01

    Breakthrough technologies to measure cellular oxygen consumption and proton efflux are reigniting the study of cellular energetics by increasing the scope and pace with which discoveries are made. As we learn the variation in metabolism between cell types is large, it is helpful to continually provide additional perspectives and update our roadmap for data interpretation. In that spirit, this chapter provides the following for those conducting microplate-based oxygen consumption experiments: (i) a description of the standard parameters for measuring respiration in intact cells, (ii) a framework for data analysis and normalization, and (iii) examples of measuring respiration in permeabilized cells to follow up results observed with intact cells. Additionally, rate-based measurements of extracellular pH are increasingly used as a qualitative indicator of glycolytic flux. As a resource to help interpret these measurements, this chapter also provides a detailed accounting of proton production during glucose oxidation in the context of plate-based assays.

  5. 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…

  6. 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…

  7. Real-time determination of intracellular oxygen in bacteria using a genetically encoded FRET-based biosensor

    PubMed Central

    2012-01-01

    Background Molecular oxygen (O2) is one of the key metabolites of all obligate and facultative aerobic pro- and eukaryotes. It plays a fundamental role in energy homeostasis whereas oxygen deprivation, in turn, broadly affects various physiological and pathophysiological processes. Therefore, real-time monitoring of cellular oxygen levels is basically a prerequisite for the analysis of hypoxia-induced processes in living cells and tissues. Results We developed a genetically encoded Förster resonance energy transfer (FRET)-based biosensor allowing the observation of changing molecular oxygen concentrations inside living cells. This biosensor named FluBO (fluorescent protein-based biosensor for oxygen) consists of the yellow fluorescent protein (YFP) that is sensitive towards oxygen depletion and the hypoxia-tolerant flavin-binding fluorescent protein (FbFP). Since O2 is essential for the formation of the YFP chromophore, efficient FRET from the FbFP donor domain to the YFP acceptor domain only occurs in the presence but not in the absence of oxygen. The oxygen biosensor was used for continuous real-time monitoring of temporal changes of O2 levels in the cytoplasm of Escherichia coli cells during batch cultivation. Conclusions FluBO represents a unique FRET-based oxygen biosensor which allows the non-invasive ratiometric readout of cellular oxygen. Thus, FluBO can serve as a novel and powerful probe for investigating the occurrence of hypoxia and its effects on a variety of (patho)physiological processes in living cells. PMID:22439625

  8. Use of coal as fuel for chemical-looping combustion with Ni-based oxygen carrier

    SciTech Connect

    Gao, Z.P.; Shen, L.H.; Xiao, J.; Qing, C.J.; Song, Q.L.

    2008-12-15

    Chemical-looping combustion is an indirect combustion technology with inherent separation of the greenhouse gas CO{sub 2}. The feasibility of using NiO as an oxygen carrier during chemical-looping combustion of coal has been investigated experimentally at 800-960{degree}C in the present work. The experiments were carried out in a fluidized bed, where the steam acted as the gasification-fluidization medium. Coal gasification and the reaction of oxygen carrier with the water gas take place simultaneously in the reactor. The oxygen carrier particles exhibit high reactivity above 900{degree}C, and the dry basis concentration of CO{sub 2} in the exit gas of the reactor is nearly 95%. The flue gas composition as a function of the reactor temperature and cyclic reduction number is discussed. At 800-960{degree}C, the dry basis concentration of CO{sub 2} in the flue gas presents a monotonously increasing trend, whereas the dry basis concentration of CO, H{sub 2}, and CH{sub 4} decreases monotonously. The concentrations of CO{sub 2}, CO, H{sub 2}, and CH{sub 4} in the flue gas as a function of cyclic reduction number present a para-curve characteristic at 900{degree}C. With the increase of cyclic reduction number, the dry basis concentration of CO{sub 2} decreases remarkably, while the dry basis concentrations of CO, H{sub 2}, and CH{sub 4} increase rapidly. Moreover, the peak value of H{sub 2} concentration is less than that of CO. The performance of the NiO-based oxygen carriers was also evaluated using an X-ray diffractometer and a scanning electron microscope to characterize the solid residues of oxygen carrier. The results indicate that NiO is one of the suitable oxygen carriers for chemical-looping combustion of coal.

  9. 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.

  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. Low-temperature selective catalytic reduction of NO with propylene in excess oxygen over the Pt/ZSM-5 catalyst.

    PubMed

    Zhang, Zhixiang; Chen, Mingxia; Jiang, Zhi; Shangguan, Wenfeng

    2011-10-15

    A 0.5 wt% Pt/ZSM-5 catalyst was used for the low-temperature selective catalytic reduction (SCR) of NO with C(3)H(6) in the presence of excess oxygen. Under an atmosphere of 150 ppm NO, 150 ppm C(3)H(6) and 18 vol% O(2) (GHSV 72,000 h(-1)), Pt/ZSM-5 showed remarkably high catalytic performance giving 77.1% NO reduction to N(2) + N(2)O and 79.7% C(3)H(6) conversion to CO(2) simultaneously at 140 °C. The samples were characterized by means of NO temperature programmed desorption (TPD), NO/C(3)H(6) temperature programmed oxidation (TPO), BET surface area, XRD and TEM. The catalytic activities of C(3)H(6) combustion and NO oxidation are improved by well-dispersed platinum significantly. It is found that the enhanced activity of Pt/ZSM-5 for the low-temperature SCR is associated with its outstanding activities in the TPO processes of NO to NO(2) and C(3)H(6) to CO(2) in low temperature range.

  12. Processing 2-Methyl-l-Tryptophan through Tandem Transamination and Selective Oxygenation Initiates Indole Ring Expansion in the Biosynthesis of Thiostrepton.

    PubMed

    Lin, Zhi; Ji, Jia; Zhou, Shuaixiang; Zhang, Fang; Wu, Jiequn; Guo, Yinlong; Liu, Wen

    2017-09-06

    Thiostrepton (TSR), an archetypal member of the family of ribosomally synthesized and post-translationally modified thiopeptide antibiotics, possesses a biologically important quinaldic acid (QA) moiety within the side-ring system of its characteristic thiopeptide framework. QA is derived from an independent l-Trp residue; however, its associated transformation process remains poorly understood. We here report that during the formation of QA, the key expansion of an indole to a quinoline relies on the activities of the pyridoxal-5'-phosphate-dependent protein TsrA and the flavoprotein TsrE. These proteins act in tandem to process the precursor 2-methyl- l-Trp through reversible transamination and selective oxygenation, thereby initiating a highly reactive rearrangement in which selective C2-N1 bond cleavage via hydrolysis for indole ring-opening is closely coupled with C2'-N1 bond formation via condensation for recyclization and ring expansion in the production of a quinoline ketone intermediate. This indole ring-expansion mechanism is unusual, and represents a new strategy found in nature for l-Trp-based functionalization.

  13. Structurally integrated organic light-emitting device-based sensors for oxygen, glucose, hydrazine, and anthrax

    NASA Astrophysics Data System (ADS)

    Shinar, Ruth; Choudhury, Bhaskar; Zhou, Zhaoqun; Wu, Hai-Sheng; Tabatabai, Louisa B.; Shinar, Joseph

    2004-12-01

    Application of the new platform of structurally integrated luminescent chemical and biological sensors, in which the photoluminescence (PL) excitation source is an organic light-emitting device (OLED), is demonstrated for the detection of oxygen, glucose, hydrazine, and anthrax lethal factor (LF). The oxygen sensors are based on the collisional quenching of the PL of tris(4,7-diphenyl-1,10-phenanthroline) Ru (II) (Ru(dpp)) and Pt octaethyl porphyrin (PtOEP) by O2. The glucose sensors are based on the O2 sensors, to which glucose oxidase, which catalyzes the reaction between glucose and O2, is added. The oxygen and glucose sensors are operable in either the PL intensity I mode or the PL lifetime t mode, where the value of I or t yields the oxygen level. In the t mode, the need for sensor calibration, which remains a challenge in real-world sensing applications, is eliminated. The performance of sensors based on [blue 4,4'-bis(2,2'-diphenylvinyl)-1,1'-biphenyl (DPVBi) OLEDs]/[Ru(dpp)] are compared to those of [green tris(8-hydroxy quinoline) Al (Alq3)]/[PtOEP]. The latter are strongly preferred over the former, due to the relatively long t of PtOEP (~130 ms in the absence of O2), and the higher efficiency and brightness of the green Alq3 OLEDs. Demonstration of the hydrazine sensor is based on the reaction between nonluminescent anthracene-2,3-dicarboxaldehyde and hydrazine or hydrazine sulfate, which generates a luminescent product. The anthrax LF sensor is based on the cleavage of certain peptides by the anthrax-secreted LF enzyme. As the LF cleaves a fluorescence resonance energy transfer (FRET) donor-acceptor pair-labeled peptide, and the two cleaved segments are separated, the PL of the donor, previously absorbed by the acceptor, becomes detectable by the photodetector.

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

    PubMed Central

    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/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. PMID:23974295

  15. Origin of the Electrocatalytic Oxygen Reduction Activity of Graphene-Based Catalysts: A Roadmap to Achieve the Best Performance

    PubMed Central

    2015-01-01

    The mutually corroborated electrochemical measurements and density functional theory (DFT) calculations were used to uncover the origin of electrocatalytic activity of graphene-based electrocatalysts for oxygen reduction reaction (ORR). A series of graphenes doped with nonmetal elements was designed and synthesized, and their ORR performance was evaluated in terms of four electrochemical descriptors: exchange current density, on-set potential, reaction pathway selectivity and kinetic current density. It is shown that these descriptors are in good agreement with DFT calculations, allowing derivation of a volcano plot between the ORR activity and the adsorption free energy of intermediates on metal-free materials, similarly as in the case of metallic catalysts. The molecular orbital concept was used to justify this volcano plot, and to theoretically predict the ORR performance of an ideal graphene-based catalyst, the ORR activity of which is comparable to the state-of-the-art Pt catalyst. Moreover, this study may stimulate the development of metal-free electrocatalysts for other key energy conversion processes including hydrogen evolution and oxygen evolution reactions and largely expand the spectrum of catalysts for energy-related electrocatalysis reactions. PMID:24580116

  16. Structurally integrated organic light emitting device-based sensors for gas phase and dissolved oxygen.

    PubMed

    Shinar, Ruth; Zhou, Zhaoqun; Choudhury, Bhaskar; Shinar, Joseph

    2006-05-24

    A compact photoluminescence (PL)-based O2 sensor utilizing an organic light emitting device (OLED) as the light source is described. The sensor device is structurally integrated. That is, the sensing element and the light source, both typically thin films that are fabricated on separate glass substrates, are attached back-to-back. The sensing elements are based on the oxygen-sensitive dyes Pt- or Pd-octaethylporphyrin (PtOEP or PdOEP, respectively), which are embedded in a polystyrene (PS) matrix, or dissolved in solution. Their performance is compared to that of a sensing element based on tris(4,7-diphenyl-l,10-phenanthroline) Ru II (Ru(dpp)) embedded in a sol-gel film. A green OLED light source, based on tris(8-hydroxy quinoline Al (Alq3), was used to excite the porphyrin dyes; a blue OLED, based on 4,4'-bis(2,2'-diphenylviny1)-1,1'-biphenyl, was used to excite the Ru(dpp)-based sensing element. The O2 level was monitored in the gas phase and in water, ethanol, and toluene solutions by measuring changes in the PL lifetime tau of the O2-sensitive dyes. The sensor performance was evaluated in terms of the detection sensitivity, dynamic range, gas flow rate, and temperature effect, including the temperature dependence of tau in pure Ar and O2 atmospheres. The dependence of the sensitivity on the preparation procedure of the sensing film and on the PS and dye concentrations in the sensing element, whether a solid matrix or solution, were also evaluated. Typical values of the detection sensitivity in the gas phase, S(g) identical with tau(0% O2)/tau(100% O2), at 23 degrees C, were approximately 35 to approximately 50 for the [Alq3 OLED[/[PtOEP dye] pair; S(g) exceeded 200 for the Alq3/PdOEP sensor. For dissolved oxygen (DO) in water and ethanol, S(DO) (defined as the ratio of tau in de-oxygenated and oxygen-saturated solutions) was approximately 9.5 and approximately 11, respectively, using the PtOEP-based film sensor. The oxygen level in toluene was measured with Pt

  17. CYP450 Enzymes Effect Oxygen-Dependent Reduction of Azide-Based Fluorogenic Dyes

    PubMed Central

    2016-01-01

    Azide-containing compounds have broad utility in organic synthesis and chemical biology. Their use as powerful tools for the labeling of biological systems in vitro has enabled insights into complex cellular functions. To date, fluorogenic azide-containing compounds have primarily been employed in the context of click chemistry and as sensitive functionalities for hydrogen sulfide detection. Here, we report an alternative use of this functionality: as fluorogenic probes for the detection of depleted oxygen levels (hypoxia). Oxygen is imperative to all life forms, and probes that enable quantification of oxygen tension are of high utility in many areas of biology. Here we demonstrate the ability of an azide-based dye to image hypoxia in a range of human cancer cell lines. We have found that cytochrome P450 enzymes are able to reduce these probes in an oxygen-dependent manner, while hydrogen sulfide does not play an important role in their reduction. These data indicate that the azide group is a new bioreductive functionality that can be employed in prodrugs and dyes. We have uncovered a novel mechanism for the cellular reduction of azides, which has implications for the use of click chemistry in hypoxia. PMID:28149949

  18. Oxygen reduction catalyzed by a fluorinated tetraphenylporphyrin free base at liquid/liquid interfaces.

    PubMed

    Hatay, Imren; Su, Bin; Méndez, Manuel A; Corminboeuf, Clémence; Khoury, Tony; Gros, Claude P; Bourdillon, Mélanie; Meyer, Michel; Barbe, Jean-Michel; Ersoz, Mustafa; Zális, Stanislav; Samec, Zdenek; Girault, Hubert H

    2010-10-06

    The diprotonated form of a fluorinated free base porphyrin, namely 5-(p-aminophenyl)-10,15,20-tris(pentafluorophenyl)porphyrin (H(2)FAP), can catalyze the reduction of oxygen by a weak electron donor, namely ferrocene (Fc). At a water/1,2-dichloroethane interface, the interfacial formation of H(4)FAP(2+) is observed by UV-vis spectroscopy and ion-transfer voltammetry, due to the double protonation of H(2)FAP at the imino nitrogen atoms in the tetrapyrrole ring. H(4)FAP(2+) is shown to bind oxygen, and the complex in the organic phase can easily be reduced by Fc to produce hydrogen peroxide as studied by two-phase reactions with the Galvani potential difference between the two phases being controlled by the partition of a common ion. Spectrophotometric measurements performed in 1,2-dichloroethane solutions clearly evidence that reduction of oxygen by Fc catalyzed by H(4)FAP(2+) only occurs in the presence of the tetrakis(pentafluorophenyl)borate (TB(-)) counteranion in the organic phase. Finally, ab initio computations support the catalytic activation of H(4)FAP(2+) on oxygen.

  19. Spectral-profile-based algorithm for hemoglobin oxygen saturation determination from diffuse reflectance spectra

    PubMed Central

    Chen, Po-Ching; Lin, Wei-Chiang

    2011-01-01

    Variations of hemoglobin (Hb) oxygenation in tissue provide important indications concerning the physiological conditions of tissue, and the data related to these variations are of intense interest in medical research as well as in clinical care. In this study, we derived a new algorithm to estimate Hb oxygenation from diffuse reflectance spectra. The algorithm was developed based on the unique spectral profile differences between the extinction coefficient spectra of oxy-Hb and deoxy-Hb within the visible wavelength region. Using differential wavelet transformation, these differences were quantified using the locations of certain spectral features, and, then, they were related to the oxygenation saturation level of Hb. The applicability of the algorithm was evaluated using a set of diffuse reflectance spectra produced by a Monte Carlo simulation model of photon migration and by tissue phantoms experimentally. The algorithm was further applied to the diffuse reflectance spectra acquired from in vivo experiments to demonstrate its clinical utility. The validation and evaluation results concluded that the algorithm is applicable to various tissue types (i.e., scattering properties) and can be easily used in conjunction with a diverse range of probe geometries for real-time monitoring of Hb oxygenation. PMID:21559121

  20. 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.

  1. 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.

  2. Computational investigation of reactive to nonreactive capture of carbon dioxide by oxygen-containing Lewis bases.

    PubMed

    Teague, Craig M; Dai, Sheng; Jiang, De-en

    2010-11-04

    Recent work has shown that room temperature ionic liquid systems reactively absorb CO(2) and offer distinct advantages over current CO(2) capture technologies. Here we computationally evaluated CO(2) interaction energies with a series of oxygen-containing Lewis base anions (including cyclohexanolate and phenolate and their respective derivatives). Our results show that the interaction energy can be tuned across a range from reactive to nonreactive (or physical) interactions. We evaluated different levels of theory as well as possible corrections to the interaction energy, and we explained our calculated trends on the basis of properties of the individual anions. We found that the interaction energy between CO(2) and the Lewis bases examined here correlates most strongly with the atomic charge on the oxygen atom. This insight provides a useful handle to tune the anion-CO(2) interaction energy for future experimental and computational studies of novel CO(2) capture systems.

  3. Effects of nicotinamide and carbogen on oxygenation in human tumor xenografts measured with luminescense based fiber-optic probes.

    PubMed

    Bussink, J; Kaanders, J H; Strik, A M; van der Kogel, A J

    2000-10-01

    In head and neck cancer, addition of both carbogen breathing and nicotinamide to accelerated fractionated radiotherapy showed increased loco-regional control rates. An assay based on the measurement of changes in tumor pO(2) in response to oxygenation modification could be helpful for selecting patients for these new treatment approaches. The fiber-optic oxygen-sensing device, OxyLite, was used to measure changes in pO(2), at a single position in tumors, after treatment with nicotinamide and carbogen in three human xenograft tumor lines with different vascular architecture and hypoxic patterns. Pimonidazole was used as a marker of hypoxia and was analyzed with a digital image processing system. At the position of pO(2) measurement, half of the tumors showed a local increase in pO(2) after nicotinamide administration. Steep increases in pO(2) were measured in most tumors during carbogen breathing although the increase was less pronounced in tumor areas with a low pre-treatment pO(2). A trend towards a faster local response to carbogen breathing for nicotinamide pre-treated tumors was found in all three lines. There were significant differences in hypoxic fractions, based on pimonidazole binding, between the three tumor lines. There was no correlation between hypoxic marker binding and the response to carbogen breathing. Temporal changes in local pO(2) can be measured with the OxyLite. This system was used to quantitate the effects of oxygen modifying treatments. Rapid increases in pO(2) during carbogen breathing were observed in most tumor areas. The locally measured response to nicotinamide was smaller and more variable. Bio-reductive hypoxic cell marker binding in combination with OxyLite pO(2) determination gives spatial information about the distribution patterns of tumor hypoxia at the microscopic level together with the possibility to continuously measure changes in pO(2) in specific tumor areas.

  4. Multispectral iris recognition based on group selection and game theory

    NASA Astrophysics Data System (ADS)

    Ahmad, Foysal; Roy, Kaushik

    2017-05-01

    A commercially available iris recognition system uses only a narrow band of the near infrared spectrum (700-900 nm) while iris images captured in the wide range of 405 nm to 1550 nm offer potential benefits to enhance recognition performance of an iris biometric system. The novelty of this research is that a group selection algorithm based on coalition game theory is explored to select the best patch subsets. In this algorithm, patches are divided into several groups based on their maximum contribution in different groups. Shapley values are used to evaluate the contribution of patches in different groups. Results show that this group selection based iris recognition

  5. 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.

  6. 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.

  7. 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.

  8. Yields of selected constituents in base flow and stormflow in urban watersheds of Jefferson County, Kentucky, 1988-92

    USGS Publications Warehouse

    Evaldi, R.D.; Moore, B.L.

    1994-01-01

    Mean annual base-flow and stormflow yields of selected water-quality constituents from urban watersheds of Jefferson County, Kentucky, were estimated for 1988-92 to help describe the pro portions of constituent transport from point and nonpoint sources. Yield estimates were based on streamflow and water-quality data collected from a network of 25 stream sites in the county. Water- quality data for which estimates of base-flow and stormflow yields were computed include dissolved oxygen and oxygen demand, dissolved solids, suspended and volatile solids, nutrients, metals, and synthetic organic compounds. Transport of most constituents occurred primarily during stormflow. Chemical oxygen demand was related to the amount of industrial land use in each watershed, nitrite and phosphorus yields were inversely proportional to the amount of nonurban and commercial land use in each watershed, and zinc yields were inversely related to the degree of nonurban land use in each watershed.

  9. 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.

  10. 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.

  11. Oxygen history off Baja California over the last 80 kyr: A new foraminiferal-based record

    NASA Astrophysics Data System (ADS)

    Tetard, Martin; Licari, Laetitia; Beaufort, Luc

    2017-03-01

    The intensity of the Oxygen minimum zone (OMZ) of the eastern North Pacific (ENP) experienced strong variations during the last glacial, mirroring changes in the balance between export production (O2 consumption) and water mass ventilation (O2 renewal). In this paper we present a new benthic foraminiferal assemblages record from Core MD02-2508, recovered from the Pacific slope off Baja California, Mexico. The record reflects oxygen conditions at the northern limit of the OMZ during the last 80 kyr. We statistically identified three assemblages, characteristic of dysoxic, suboxic, and oxic conditions, which we used to produce the first semiquantitative reconstruction of [O2] for the northeastern Pacific Ocean. Our results show that the estimated [O2] covaries with δ18O records from the North Greenland Ice Core Project. Oxygen concentrations overall exhibit moderate values ( 1 mL.L-1) during stadials, reaching 2 mL.L-1 during stadials corresponding to Heinrich events in the Atlantic Ocean. Conversely, bottom waters at the core location were strongly depleted in oxygen (<0.5 mL.L-1) during interstadials. Benthic foraminiferal abundance increased with higher export production as recorded by geochemical tracers (Cd/Al ratio). This export production signal increases (decreases) with a fall (rise) in [O2] during interstadials (stadials), suggesting a relationship between both parameters during these intervals. The influence of ventilation on oxygenation is also a key player. O2 pulses suggested by the downcore records of serial/spiral test ratio and abundance of oxic species may be explained by enhanced ventilation during Heinrich stadials, in agreement with latest modeling-based oceanic circulation reconstructions.

  12. The oxygen-conserving potential of the diving response: A kinetic-based analysis.

    PubMed

    Costalat, Guillaume; Coquart, Jeremy; Castres, Ingrid; Joulia, Fabrice; Sirost, Olivier; Clua, Eric; Lemaître, Frédéric

    2017-04-01

    We investigated the oxygen-conserving potential of the human diving response by comparing trained breath-hold divers (BHDs) to non-divers (NDs) during simulated dynamic breath-holding (BH). Changes in haemodynamics [heart rate (HR), stroke volume (SV), cardiac output (CO)] and peripheral muscle oxygenation [oxyhaemoglobin ([HbO2]), deoxyhaemoglobin ([HHb]), total haemoglobin ([tHb]), tissue saturation index (TSI)] and peripheral oxygen saturation (SpO2) were continuously recorded during simulated dynamic BH. BHDs showed a breaking point in HR kinetics at mid-BH immediately preceding a more pronounced drop in HR (-0.86 bpm.%(-1)) while HR kinetics in NDs steadily decreased throughout BH (-0.47 bpm.%(-1)). By contrast, SV remained unchanged during BH in both groups (all P > 0.05). Near-infrared spectroscopy (NIRS) results (mean ± SD) expressed as percentage changes from the initial values showed a lower [HHb] increase for BHDs than for NDs at the cessation of BH (+24.0 ± 10.1 vs. +39.2 ± 9.6%, respectively; P < 0.05). As a result, BHDs showed a [tHb] drop that NDs did not at the end of BH (-7.3 ± 3.2 vs. -3.0 ± 4.7%, respectively; P < 0.05). The most striking finding of the present study was that BHDs presented an increase in oxygen-conserving efficiency due to substantial shifts in both cardiac and peripheral haemodynamics during simulated BH. In addition, the kinetic-based approach we used provides further credence to the concept of an "oxygen-conserving breaking point" in the human diving response.

  13. Influence of instruction conditions on the evaluation of muscular endurance based on muscle oxygenation.

    PubMed

    Demura, Shinichi; Miyaguchi, Kazuyoshi; Hiroki, Aoki

    2010-06-01

    Proper instruction is essential for evaluating muscular endurance with high reliability. This study aimed to examine the influence of instruction conditions on the evaluation of rhythmic repeated muscular endurance based on muscle oxygenation kinetics. Fifteen healthy young men performed repeated maximal rhythmic grips for 6 minutes under the following 3 instruction conditions: (1) "Squeeze as hard as you can during 2 seconds freely (Ex1)"; (2) "Squeeze as hard as you can quickly at the cue of a beep every 2 seconds (Ex2)"; and (3) "Squeeze as hard as you can quickly at the cue of a beep every 2 seconds, and then hold the exertion for 1 second (Ex3)". In the start phase of measurement during which larger exertion (above 80% maximal voluntary grip contraction) of grip strength is possible, the exertion values and muscle oxygenation kinetics were not significantly different among the 3 instruction conditions. However, a significant difference was found in muscle oxygenation kinetics after the middle phase (3 minutes) of measurement and also in the peak forces. Particularly, oxygen supply to the skeletal muscle as compared with oxygen consumption was greater in Ex2 than in Ex3. This study found that the evaluated muscle endurance differs considerably under various instruction conditions. The following instruction may be useful in the assessment of muscular endurance: "Squeeze as hard as you can quickly at the cue of a beep and then immediately relax". The present findings suggest that proper instructions are essential in various physical function tests and in the dynamometer handgrip test for occupational therapists and strength and conditioning professionals to obtain accurate measurements.

  14. Selective catalytic reduction of nitric oxide with carbon monoxide over alumina-pellet-supported catalysts in the presence of excess oxygen.

    PubMed

    Liu, Kaijie; Yu, Qingbo; Qin, Qin; Wang, Chunpeng

    2017-06-26

    Selective catalytic reduction of nitrogen oxides with carbon monoxide (CO-SCR) is a promising technology to remove NOx and CO simultaneously from flue gas. The thermodynamic analyses of catalytic process were performed toward four kinds of active metal oxides (CuxOy, CoxOy, MnxOy and CexOy). According to the standard Gibbs free-energy changes calculated, Mn had better resistance to oxygen than Cu, Co and Ce, while Cu and Ce had better resistance to water vapor poisoning, as active metals. Then, a series of binary- and ternary-preformed catalysts with different metal ratios were prepared by the impregnation method using Al2O3 pellets as support and tested in excess oxygen (16 vol%) atmosphere with or without SO2. The results of experiment were analyzed based on thermodynamic analyses. Results indicated that the NO conversions of Cu-Co/Al2O3 catalysts increased with the rise of reaction temperature; however, the tendency changed at 160°C for Cu-Mn/Al2O3. Besides, the NO conversions of Cu-Mn/Al2O3 were better than Cu-Co/Al2O3. The catalysts with the metal ratio of 1.5 had the best denitrification performance. Among various binary catalysts, Cu-Mn/Al2O3 with the metal ratio Cu:Mn of 1.5 showed promising activity for CO-SCR, giving nearly 90% NO conversion. Besides, the doping of Ce could inhibit the sulfur poisoning and promote the oxide of CO under experimental conditions.

  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. Evaluation and Selection of a Data-Base Management System

    ERIC Educational Resources Information Center

    Abbott, Michael; White, Bard F.

    1974-01-01

    Based on existing literature and user experience, the systematic approach to data base evaluation presented here provides a method by which data processing administrators can optimize the probability of selecting the data base management system best suited for their institution. (Author/WM)

  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. 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

  19. Vasculature based model for characterizing the oxygen transport in skin tissues - analogy to the Weinbaum-Jiji bioheat equation

    NASA Astrophysics Data System (ADS)

    Ji, Yan; Liu, Jing

    Based on the conceptual three-layer microvascular structure of skin tissues proposed by Weinbaum et al. [20-25] and in analogy to the well known Weinbaum-Jiji (W-J) bioheat equation, a new oxygen transport model was established in this paper, which collectively included the contributions of the vascular geometry and the blood flow condition. The new one-dimensional three-layer oxygen transport model was then applied to predict the average oxygen concentration distribution in skin tissues and numerical solutions for the boundary value problem coupling the three layers were obtained. A simple expression for the tensor diffusivity (Deff) of oxygen transport over the deep tissue layer was presented, which was orders of magnitude higher than the intrinsic diffusivity (Dt) in tissue without blood flow. Effects of blood flow velocity and vascular geometry to the oxygen transport were investigated. Calculations indicated that the vascular geometry had significant effects on oxygen transport. The oxygen exchange between the arteries and veins was relatively small for the deep tissue layer. Further, the average oxygen concentration gradient appears low in intermediate layer due to large capillary perfusion. The theoretical results were implemented to interpret some previous experimental results and a better understanding on the oxygen transport across the vascularized living tissues was obtained. The strategy proposed in this paper may provide a feasible way to comprehensively characterize the oxygen transport behaviors in living tissues with real and complex vasculature.

  20. Selectivity of stationary phases based on pyridinium ionic liquids for capillary gas chromatography

    NASA Astrophysics Data System (ADS)

    Shashkov, M. V.; Sidelnikov, V. N.; Zaikin, P. A.

    2014-04-01

    A number of capillary columns with stationary liquid phases based on mono- and dication pyridinium ionic liquids (ILs) were prepared. Their polarity was evaluated using McReynolds system and the selectivity was estimated from intermolecular interactions. The parameters of intermolecular interactions were obtained from retention data using the (Abraham) model of the linear free energy relationship. The dependences of intermolecular interactions on the structure of the cation in the ILs under study were revealed. The results were compared with the data for the traditional phases (HP-5, ZB-WAX). Examples of separation of mixtures of oxygen-containing compounds on the phases under study are given.

  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. 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

  3. 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

  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. 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.

  6. 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.

  7. 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).

  8. Comparison of the Pharmacokinetic Properties of Hemoglobin-Based Oxygen Carriers

    PubMed Central

    Taguchi, Kazuaki; Yamasaki, Keishi; Maruyama, Toru; Otagiri, Masaki

    2017-01-01

    Hemoglobin (Hb) is an ideal material for use in the development of an oxygen carrier in view of its innate biological properties. However, the vascular retention of free Hb is too short to permit a full therapeutic effect because Hb is rapidly cleared from the kidney via glomerular filtration or from the liver via the haptogloblin-CD 163 pathway when free Hb is administered in the blood circulation. Attempts have been made to develop alternate acellular and cellular types of Hb based oxygen carriers (HBOCs), in which Hb is processed via various routes in order to regulate its pharmacokinetic properties. These HBOCs have been demonstrated to have superior pharmacokinetic properties including a longer half-life than the Hb molecule in preclinical and clinical trials. The present review summarizes and compares the pharmacokinetic properties of acellular and cellular type HBOCs that have been developed through different approaches, such as polymerization, PEGylation, cross-linking, and encapsulation. PMID:28335469

  9. 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.

  10. Energy-Related Small Molecule Activation Reactions: Oxygen Reduction and Hydrogen and Oxygen Evolution Reactions Catalyzed by Porphyrin- and Corrole-Based Systems.

    PubMed

    Zhang, Wei; Lai, Wenzhen; Cao, Rui

    2017-02-22

    Globally increasing energy demands and environmental concerns related to the use of fossil fuels have stimulated extensive research to identify new energy systems and economies that are sustainable, clean, low cost, and environmentally benign. Hydrogen generation from solar-driven water splitting is a promising strategy to store solar energy in chemical bonds. The subsequent combustion of hydrogen in fuel cells produces electric energy, and the only exhaust is water. These two reactions compose an ideal process to provide clean and sustainable energy. In such a process, a hydrogen evolution reaction (HER), an oxygen evolution reaction (OER) during water splitting, and an oxygen reduction reaction (ORR) as a fuel cell cathodic reaction are key steps that affect the efficiency of the overall energy conversion. Catalysts play key roles in this process by improving the kinetics of these reactions. Porphyrin-based and corrole-based systems are versatile and can efficiently catalyze the ORR, OER, and HER. Because of the significance of energy-related small molecule activation, this review covers recent progress in hydrogen evolution, oxygen evolution, and oxygen reduction reactions catalyzed by porphyrins and corroles.

  11. 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

  12. 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

    2016-04-07

    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.

  13. Different working mechanisms for a graphene resistive memory based on oxygen-ion transport

    NASA Astrophysics Data System (ADS)

    Lee, Seunghyun

    2017-01-01

    A graphene sheet was used as one of the electrodes of a HfO2 metal-oxide-based resistive random access memory. We find dramatic differences in the device characteristics as voltages with opposite polarities are used to form the resistive memory devices. Using experimental measurements of the switching characteristics and the corresponding low and high resistance state, we compare the two different operating modes of a graphene-electrode-based resistive memory. Using a Raman raster scanning map, we verify that the transport direction of oxygen ions contributes to such dramatic differences in the device's switching characteristics.

  14. 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

  15. Object-based selection is contingent on attentional control settings.

    PubMed

    Taylor, J Eric T; Rajsic, Jason; Pratt, Jay

    2016-05-01

    The visual system allocates attention in object-based and location-based modes. However, the question of when attention selects objects and when it selects locations remains poorly understood. In this article, we present variations on two classic paradigms from the object-based attention literature, in which object-based effects are observed only when the object feature matches the task goal of the observer. In Experiment 1, covert orienting was influenced by task-irrelevant rectangles, but only when the target color matched the rectangle color. In Experiment 2, the region of attentional focus was adjusted to the size of task-irrelevant objects, but only when the target color matched the object color. In Experiment 3, we ruled out the possibility that contingent object-based selection is caused by color-based intratrial priming. These demonstrations of contingent object-based attention suggest that object-based selection is neither mandatory nor default, and that object-based effects are contingent on simple, top-down attentional control settings.

  16. Benchmarking transverse spin relaxation based oxygenation measurements in the brain during hypercapnia and hypoxia.

    PubMed

    Ni, Wendy W; Christen, Thomas; Zaharchuk, Greg

    2017-09-01

    To simultaneously assess reproducibility of three MRI transverse relaxation parameters ( R2', R2*, and R2 ) for brain tissue oxygenation mapping and to assess changes in these parameters with inhalation of gases that increase and decrease oxygenation, to identify the most sensitive parameter for imaging brain oxygenation. Forty-eight healthy subjects (25 male, ages 35 ± 8 years) were scanned at 3.0 Tesla, each with one of four gases (mildly and strongly hypercapnic and hypoxic) administered in a challenge paradigm, using a gas delivery setup designed for patient use. Cerebral blood flow mapping with arterial spin labeling, and simultaneous R2', R2*, and R2 mapping with gradient-echo sampling of free induction decay and echo (GESFIDE) were performed. Reproducibility in air and gas-induced changes were evaluated using nonparametric analysis with correction for multiple comparisons. Our gas delivery setup achieved stable gas challenges as shown by physiological monitoring. Test-retest variability of R2', R2*, and R2 were found to be 0.24 s(-1) (8.6% of mean), 0.24 s(-1) (1.3% of mean), and 0.15 s(-1) (1.0% of mean), respectively. Strong hypoxia produced the most conclusive oxygenation-driven relaxation change, inducing increases in R2' (25 ± 13%, P = 0.03), R2* (5 ± 2%, P = 0.02), and R2 (2 ± 2%, NS). We benchmarked the intra-scan test-retest variability in GESFIDE-based transverse relaxation rate mapping. Using a reliable framework for gas challenge paradigms, we recommend strong hypoxia for validating oxygenation mapping methods, and the use of tissue R2' change, instead of R2* or R2 , as a metric for studying brain tissue oxygenation using transverse relaxation methods. 1 Technical Efficacy: Stage 1 J. MAGN. RESON. IMAGING 2017;46:704-714. © 2017 International Society for Magnetic Resonance in Medicine.

  17. Development and performance of Cu-based oxygen carriers for chemical-looping combustion

    SciTech Connect

    Chuang, S.Y.; Dennis, J.S.; Hayhurst, A.N.; Scott, S.A.

    2008-07-15

    Chemical-looping combustion (CLC) has the inherent property of separating the product CO{sub 2} from flue gases. Instead of air, it uses an oxygen carrier, usually in the form of a metal oxide, to provide oxygen for combustion. This paper focuses on the development and performance of a suitable Cu-based oxygen carrier for burning solid fuels using CLC. Carriers were made from CuO and Al{sub 2}O{sub 3} (as a support) in three different ways: mechanical mixing, wet impregnation, and co-precipitation. The reactivity of these solids was assessed by measuring their ability to oxidize CO, when in a hot bed of sand fluidized by a mixture of CO and N{sub 2}. After that, the Cu in the carrier was oxidized back to CuO by fluidizing the hot bed with air. These oxygen carriers were tested over many such cycles of reduction and oxidation. This work confirms that supporting CuO on Al{sub 2}O{sub 3} enhances the ability of the resulting particles to withstand mechanical and thermal stresses in a fluidized bed. Also, only co-precipitation produces particles that have a high loading of copper and do not agglomerate at 800-900 C. The performance of co-precipitated particles of CuO/Al{sub 2}O{sub 3} at oxidizing CO to CO{sub 2} was significantly affected by the pH of the solution in which precipitation occurred: a high pH (9.7) gave particles that reacted completely and rapidly. After 18 cycles, such a co-precipitated carrier with 82.5 wt% CuO yielded all its oxygen when oxidizing CO. X-ray analysis showed that when heated, CuO reacted with Al{sub 2}O{sub 3} to form CuAl{sub 2}O{sub 4}, which was fully reducible, so CuO experienced no loss in extent of reaction after forming this mixed oxide. An increase in operating temperature from 800 to 900 C led to the CuO providing slightly less oxygen; this was because a little of the CuO decomposed to Cu{sub 2}O between its reduction and oxidation, when the bed was fluidized by pure N{sub 2}. (author)

  18. A microarray-based method to perform nucleic acid selections.

    PubMed

    Aminova, Olga; Disney, Matthew D

    2010-01-01

    This method describes a microarray-based platform to perform nucleic acid selections. Chemical ligands to which a nucleic acid binder is desired are immobilized onto an agarose microarray surface; the array is then incubated with an RNA library. Bound RNA library members are harvested directly from the array surface via gel excision at the position on the array where a ligand was immobilized. The RNA is then amplified via RT-PCR, cloned, and sequenced. This method has the following advantages over traditional resin-based Systematic Evolution of Ligands by Exponential Enrichment (SELEX): (1) multiple selections can be completed in parallel on a single microarray surface; (2) kinetic biases in the selections are mitigated since all RNA binders are harvested from an array via gel excision; (3) the amount of chemical ligand needed to perform a selection is minimized; (4) selections do not require expensive resins or equipment; and (5) the matrix used for selections is inexpensive and easy to prepare. Although this protocol was demonstrated for RNA selections, it should be applicable for any nucleic acid selection.

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

    SciTech Connect

    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.

    2014-09-12

    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. In this paper, 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. Finally, 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.

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

    PubMed

    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

    2014-09-12

    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.

  1. Effect of hemoglobin- and Perflubron-based oxygen carriers on common clinical laboratory tests.

    PubMed

    Ma, Z; Monk, T G; Goodnough, L T; McClellan, A; Gawryl, M; Clark, T; Moreira, P; Keipert, P E; Scott, M G

    1997-09-01

    Polymerized hemoglobin solutions (Hb-based oxygen carriers; HBOCs) and a second-generation perfluorocarbon (PFC) emulsion (Perflubron) are in clinical trials as temporary oxygen carriers ("blood substitutes"). Plasma and serum samples from patients receiving HBOCs look markedly red, whereas those from patients receiving PFC appear to be lipemic. Because hemolysis and lipemia are well-known interferents in many assays, we examined the effects of these substances on clinical chemistry, immunoassay, therapeutic drug, and coagulation tests. HBOC concentrations up to 50 g/L caused essentially no interference for Na, K, Cl, urea, total CO2, P, uric acid, Mg, creatinine, and glucose values determined by the Hitachi 747 or Vitros 750 analyzers (or both) or for immunoassays of lidocaine, N-acetylprocainamide, procainamide, digoxin, phenytoin, quinidine, or theophylline performed on the Abbott AxSym or TDx. Gentamycin and vancomycin assays on the AxSym exhibited a significant positive and negative interference, respectively. Immunoassays for TSH on the Abbott IMx and for troponin I on the Dade Stratus were unaffected by HBOC at this concentration. Tests for total protein, albumin, LDH, AST, ALT, GGT, amylase, lipase, and cholesterol were significantly affected to various extents at different HBOC concentrations on the Hitachi 747 and Vitros 750. The CK-MB assay on the Stratus exhibited a negative interference at 5 g/L HBOC. HBOC interference in coagulation tests was method-dependent-fibrometer-based methods on the BBL Fibro System were free from interference, but optical-based methods on the MLA 1000C exhibited interferences at 20 g/L HBOC. A 1:20 dilution of the PFC-based oxygen carrier (600 g/L) caused no interference on any of these chemistry or immunoassay tests except for amylase and ammonia on the Vitros 750 and plasma iron on the Hitachi 747.

  2. Anthropometric-based selection and sprint kayak training in children.

    PubMed

    Aitken, D A; Jenkins, D G

    1998-08-01

    A 12 week kayak training programme was evaluated in children who either had or did not have the anthropometric characteristics identified as being unique to senior elite sprint kayakers. Altogether, 234 male and female school children were screened to select 10 children with and 10 children without the identified key anthropometric characteristics. Before and after training, the children completed an all-out 2 min kayak ergometer simulation test; measures of oxygen consumption, plasma lactate and total work accomplished were recorded. In addition, a 500 m time trial was performed at weeks 3 and 12. The coaches were unaware which 20 children possessed those anthropometric characteristics deemed to favour development of kayak ability. All children improved in both the 2 min ergometer simulation test and 500 m time trial. However, boys who were selected according to favourable anthropometric characteristics showed greater improvement than those without such characteristics in the 2 min ergometer test only. In summary, in a small group of children selected according to anthropometric data unique to elite adult kayakers, 12 weeks of intensive kayak training did not influence the rate of improvement of on-water sprint kayak performance.

  3. 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

  4. Application of case-based reasoning for machining parameters selection

    NASA Astrophysics Data System (ADS)

    Grabowik, C.; Kalinowski, K.; Krenczyk, D.; Paprocka, I.; Kempa, W.

    2016-08-01

    Process planning, as one of the most important stage of the technological production preparation, consists in selection of manufacturing operations taking into account the minimal manufacturing cost. The minimal manufacturing cost could be achieved by selection of the best sequence of manufacturing operations, machine tools, manufacturing tools, and accompanying machining parameters selection. On the other hand, it is almost impossible, especially in industrial conditions, to design an optimal process plan, first of all due to restrictions imposed by the installed in the factory machine park. Taking into consideration above, machining parameter selection seems to be one of the potential areas of optimization. In manual process planning process engineers select machining parameters using selection rules and data stored in manuals and tool catalogues. It makes this process time and labour consuming and non-error free. On the other hand, in workshop practice, machine operators select parameters having their skills and habits in mind. It could be a reason for suboptimal process planning. Considering this, new methods of machining parameters selection free of human factor influence are still sought. In our approach, we propose to apply case-based reasoning for machining parameter selection. In the paper, a detailed description of our approach is presented.

  5. Singlet oxygen generator on a chip for MEMS-based COIL

    NASA Astrophysics Data System (ADS)

    Livermore, Carol; Hill, Tyrone F.; Velásquez-García, Luis; Wilhite, Benjamin A.; Epstein, Alan H.; Jensen, Klavs; Rawlins, W. Terry; Lee, Seonkyung; Davis, Steven

    2007-02-01

    Microelectromechanical systems (MEMS) offer a promising approach for creating compact, efficient chemical oxygen iodine lasers. In this paper we report the demonstration and characterization of a chip-scale, MEMS-based singlet oxygen generator, or microSOG. The microSOG is a batch-fabricated silicon chip that is micromachined to form reactant inlets and distribution system, an array of microstructured packed bed reaction channels to ensure good mixing between the BHP and the chlorine, a gas-liquid separator that removes liquid from the output stream by capillary effects, integrated heat exchangers to remove the excess heat of reaction, and product outlets. The microSOG has successfully generated singlet delta oxygen, and the resulting singlet delta concentrations were measured in a quartz test cell downstream of the chip using absolutely-calibrated near-infrared emission measurements made by an InGaAs array spectrometer. A kinetics analysis was used to determine the concentration at the chip's outlet from the concentration at the measurement point. Singlet delta yield at the outlet was determined to be about 81% at 150 Torr plenum pressure with a 25 sccm flow of chlorine. The corresponding output flow carries about 1.4 W of power at the chip's outlet.

  6. 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. Copyright © 2011 Elsevier B.V. All rights reserved.

  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. An optical sensor for monitoring of dissolved oxygen based on phase detection

    NASA Astrophysics Data System (ADS)

    Feng, Weiwei; Zhou, Na; Chen, Lingxin; Li, Bowei

    2013-05-01

    Dissolved oxygen (DO) monitoring is of vital importance to water treatment, sewage treatment, aquaculture and biological research. The traditional method for DO detection is an electrochemical method called the Clark electrode. This electrochemical method has been widely used as it is simple and inexpensive; however, the critical drawback for this kind of sensor is that it is easily affected by pH variations, and by the concentration of H2S and SO2. Optical sensing for DO detection is a newly developed technology, which can avoid most of the drawbacks of the electrochemical sensors. A DO sensor using fluorescence detection is described in this paper. The oxygen concentration measurement principle is based on optical phase detection, which is more precise than the traditional intensity detection method. Emission is carried out by a low-cost, specially designed light emitting diode (LED) source. To avoid an unwanted phase shift, a reference LED is used to improve the degree of accuracy. The sensing material for fluorescence is a ruthenium complex. A discrete Fourier transform (DFT) algorithm was used for the phase calculation. The system was designed into a stainless steel probe, and dissolved oxygen concentration measurement results for various applications are presented in this paper.

  9. 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

  10. 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.

  11. Transparent films based on PLA and montmorillonite with tunable oxygen barrier properties.

    PubMed

    Svagan, Anna J; Åkesson, Anna; Cárdenas, Marité; Bulut, Sanja; Knudsen, Jes C; Risbo, Jens; Plackett, David

    2012-02-13

    Polylactide (PLA) is viewed as a potential material to replace synthetic plastics (e.g., poly(ethylene terephthalate) (PET)) in food packaging, and there have been a number of developments in this direction. However, for PLA to be competitive in more demanding uses such as the packaging of oxygen-sensitive foods, the oxygen permeability coefficient (OP) needs to be reduced by a factor of ~10. To achieve this, a layer-by-layer (Lbl) approach was used to assemble alternating layers of montmorillonite clay and chitosan on extruded PLA film surfaces. When 70 bilayers were applied, the OP was reduced by 99 and 96%, respectively, at 20 and 50% RH. These are, to our knowledge, the best improvements in oxygen barrier properties ever reported for a PLA/clay-based film. The process of assembling such multilayer structures was characterized using a quartz crystal microbalance with dissipation monitoring. Transmission electron microscopy revealed a well-ordered laminar structure in the deposited multilayer coatings, and light transmittance results demonstrated the high optical clarity of the coated PLA films.

  12. Effects of haemoglobin-based oxygen carrier hemoglobin glutamer-200 (bovine) on intestinal perfusion and oxygenation in a canine hypovolaemia model.

    PubMed

    Driessen, B; Jahr, J S; Lurie, F; Griffey, S M; Gunther, R A

    2001-05-01

    The objective of this investigation was to study the effects of the first marketed haemoglobin-based oxygen carrier, Hemoglobin glutamer-200 (bovine) (Hb-200) (Oxyglobin) on splanchnic perfusion and oxygenation in a canine model of acute hypovolaemia. Twelve anaesthetized dogs [mean weight 30.8 (S.D. 1.4) kg] were instrumented for recordings of heart rate (HR), mean arterial pressure (MAP), central venous pressure (CVP), cardiac output and cranial mesenteric arterial (CMA) and venous blood flows (CMV). Total and plasma haemoglobin (Hb), oxygen content and saturation, lactate concentration, pH and blood gases were analysed in arterial, mixed venous and mesenteric venous blood samples. Measurements were made before (baseline) and after 1 h of haemorrhage, after which animals were resuscitated with either shed blood (controls) or Hb-200 until HR, MAP and CVP returned to prehaemorrhage levels. Recordings were repeated immediately and 3 h after termination of fluid resuscitation, after which organ specimens were obtained for microscopic examination. Haemorrhage (average 32 ml kg(-1)) reduced MAP to 50 mm Hg, increased HR and systemic vascular resistance (SVR), and was accompanied in both the systemic and the splanchnic circulation by significant decreases in blood flow, Hb content and oxygen delivery (DO2), and lactic acidosis. In controls, all variables recovered to baseline after isovolaemic resuscitation with shed blood. In dogs resuscitated with a small volume of Hb-200 (10 ml kg(-1)), HR, MAP, CVP and CMA and CMV blood flows returned to baseline. However, cardiac output, total Hb, oxygen content and systemic and mesenteric DO2 remained depressed while SVR increased further. Mesenteric and systemic acid-base status recovered in both groups, and there was no difference in microscopic tissue damage between groups. Thus, Hb-200 reconstituted splanchnic perfusion and oxidative metabolism in spite of pronounced systemic vasoconstriction and insufficient restoration of CO

  13. 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…

  14. 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…

  15. 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.

  16. A PEGylated bovine hemoglobin as a potent hemoglobin-based oxygen carrier.

    PubMed

    Wang, Ying; Wang, Linli; Yu, Weili; Gao, Dawei; You, Guoxing; Li, Penglong; Zhang, Shan; Zhang, Jun; Hu, Tao; Zhao, Lian; Zhou, Hong

    2017-01-01

    Hemoglobin (Hb)-based oxygen carriers (HBOCs) have been used as blood substitutes in surgery medicine and oxygen therapeutics for ischemic stroke. As a potent HBOC, the PEGylated Hb has received much attention for its oxygen delivery and plasma expanding ability. Two PEGylated Hbs, Euro-Hb, and MP4 have been developed for clinical trials, using human adult hemoglobin (HbA) as the original substrate. However, HbA was obtained from outdated human blood and its quantity available from this source may not be sufficient for mass production of PEGylated HbA. In contrast, bovine Hb (bHb) has no quantity constraints for its ample resource. Thus, bHb is of potential to function as an alternative substrate to obtain a PEGylated bHb (bHb-PEG). bHb-PEG was prepared under the same reaction condition as HbA-PEG, using maleimide chemistry. The structural, functional, solution and physiological properties of bHb-PEG were determined and compared with those of HbA-PEG. bHb-PEG showed higher hydrodynamic volume, colloidal osmotic pressure, viscosity and P50 than HbA-PEG. The high P50 of bHb can partially compensate the PEGylation-induced perturbation in the R to T state transition of HbA. bHb-PEG was non-vasoactive and could efficiently recover the mean arterial pressure of mice suffering from hemorrhagic shock. Thus, bHb-PEG is expected to function as a potent HBOC for its high oxygen delivery and strong plasma expanding ability. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 33:252-260, 2017.

  17. 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

  18. Heteroatom-Doped Carbon Nanotube and Graphene-Based Electrocatalysts for Oxygen Reduction Reaction.

    PubMed

    Li, Jin-Cheng; Hou, Peng-Xiang; Liu, Chang

    2017-09-29

    Oxygen reduction reaction (ORR) is a key step that determines the performance of a variety of energy storage and conversion devices, such as fuel cells and metal-air batteries. Heteroatom-doped carbon nanotubes (CNTs) and graphenes have attracted increasing interest and hold great promise as efficient ORR catalysts to replace noble-metal-based catalysts, owing to their unique structure characteristics, excellent physicochemical properties, low cost, and rich resources. In this review, recent progress on the design, fabrication, and performance of heteroatom-doped CNT- and graphene-based catalysts is summarized, aiming to provide insights into the working mechanism of these heteroatom-doped nanocarbons in ORR. The advantages, challenges that remain, and possible solutions of these nanocarbon-based electrocatalysts are discussed. Finally, future developing trends of the CNT- and graphene-based ORR catalysts are proposed. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  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. Physique, body composition and maximum oxygen consumption of selected soccer players of Kunimi High School, Nagasaki, Japan.

    PubMed

    Tahara, Yasuaki; Moji, Kazuhiko; Tsunawake, Noriaki; Fukuda, Rika; Nakayama, Masao; Nakagaichi, Masaki; Komine, Tadatoshi; Kusano, Yosuke; Aoyagi, Kiyoshi

    2006-07-01

    This study evaluates the physical and physiological ability of selected soccer players of Kunimi High School in Nagasaki Prefecture, Japan. The Kunimi team is famous for its intensive training, and had won the championship of the All Japan High School Soccer Tournament six times by 2003. We measured physique, body composition, and maximal oxygen uptake of 72 members aged between 16 and 18 years old between 1986 and 1994. They consisted of 66 outfield players (12 forward players, 23 midfielders, 31 defenders) and 6 goalkeepers. Body density was measured by the under-water weighing method, and Brozek's equation was applied to calculate percentage body fat (%Fat, %), fat-free mass (FFM, kg), FFM/height (FFM/Ht, kg.m(-1)), and FFM index (FFM/Ht(3), kg.m(-3)). The following results were obtained: 1. The average of 66 outfield players was 172.7 cm of height, 64.6 kg of weight, 54.0 cm of girth of thigh, and 90.0 cm of girth of hip, 9.3% of %Fat, 58.6 kg of FFM, 33.9 kg.m(-1) of FFM/Ht and 113.8 kg.m(-3) of FFM index. The mean vital capacity was 4.25 L and total lung capacity was 5.58 L. The mean maximal ventilation was 138.7 L.min(-1), VO(2)max was 3.95 L.min(-1), and VO(2)max/Wt was 61.4 ml.kg(-1).min(-1). 2. Goalkeepers were taller and heavier than outfielders, and had a smaller mean value of VO(2)max/Wt than outfielders (p<0.01). 3. For 23 out of the 72 players measured twice with an interval of about one year, FFM increased and %Fat reduced significantly, while V(E)max, VO(2)max and VO(2)max/Wt did not change. Kunimi players of the present study had as large a VO(2)max/Wt as local players, and a similar or slightly smaller VO(2)max/Wt than national-level players. They had similar %Fat and a similar VO(2)max/Wt with professional soccer players in England (Davis et al., 1992) while they had much smaller physiques.

  1. Selective killing of cancer cells by iron oxide nanoparticles mediated through reactive oxygen species via p53 pathway

    NASA Astrophysics Data System (ADS)

    Ahamed, Maqusood; Alhadlaq, Hisham A.; Khan, M. A. Majeed; Akhtar, Mohd. Javed

    2013-01-01

    Iron oxide (Fe3O4) nanoparticles (NPs) are increasingly recognized for their utility in biomedical applications. However, little is known about the anticancer activity of Fe3O4 NPs. This study was designed to investigate whether Fe3O4 NPs induced toxicity in a cell-specific manner and determine the possible mechanisms of toxicity caused by Fe3O4 NPs in cancer cells. Fe3O4 NPs used in this study were synthesized by green method using α- d-glucose as a reducing agent. Prepared Fe3O4 NPs were spherical in shape with a smooth surface, were fairly distributed, and had an average diameter of 23 nm. Cytotoxicity of Fe3O4 NPs was examined against two types of cancer cells (human hepatocellular carcinoma HepG2 and human lung adenocarcinoma A549) and two normal cells (human lung fibroblast IMR-90 and rat hepatocytes). Fe3O4 NPs exerted distinct effects on cell viability via killing of cancer cells while posing no toxicity on normal cells. Fe3O4 NPs were found to induce depletion of glutathione and induction of reactive oxygen species (ROS) in both types of cancer cells (HepG2 and A549). Further, co-exposure of ascorbic acid significantly attenuated the Fe3O4 NPs-induced oxidative stress. The mRNA levels of tumor suppressor gene p53 and apoptotic genes (caspase-3 and caspase-9) were up-regulated in both types of cancer cells due to Fe3O4 NPs exposure. Protein level of p53, along with the higher activity of caspase-3 and caspase-9 enzymes, was also up-regulated by Fe3O4 NPs. Taken together, our data demonstrated that Fe3O4 NPs selectively induced apoptosis in cancer cells (HepG2 and A549) through up-regulation of p53 that might be mediated by ROS through which most of the anticancer drugs trigger apoptosis. The present study warrants further investigation on anticancer activity of Fe3O4 NPs in relevant animal models.

  2. [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.

  3. Impact of oxygenator selection on hemodynamic energy indicators under pulsatile and nonpulsatile flow in a neonatal extracorporeal life support model.

    PubMed

    Vasavada, Rahul; Khan, Sameer; Qiu, Feng; Kunselman, Allen; Undar, Akif

    2011-06-01

    This study compared the quality of perfusion delivered by two oxygenators--the hollow-fiber membrane Capiox Baby RX05 and silicone membrane Medtronic 0800--using hemodynamic energy indicators. The oxygenators were tested across varying flow rates and perfusion modes in a neonatal extracorporeal life support (ECLS) model. The experimental ECLS circuit included a Jostra HL-20 heart/lung machine with Jostra Roller pump, oxygenators with associated tubing and components, and a neonatal pseudo-patient. We used a 40/60 glycerin/water solution in the circuit as a blood analog. Testing occurred at flow rates of 250, 500, and 750 mL/min at 37°C under both pulsatile and nonpulsatile flow conditions. Hemodynamic data points consisted of recording 20-s intervals of data, and a total of 96 experimental repetitions were conducted. The pressure drop across the Capiox Baby RX05 oxygenator was significantly lower than the pressure drop across the Medtronic 0800 at all flow rates and perfusion modes. Furthermore, the Medtronic 0800 oxygenator showed significantly lower post-oxygenator energy equivalent pressures, total hemodynamic energy values, and surplus hemodynamic energy retention values compared to those of the Capiox Baby RX05. These results indicate the Medtronic 0800 oxygenator significantly dampens the hemodynamic energy compared to the Capiox Baby RX05. Consequently, clinical use of the Medtronic 0800 in a pulsatile ECLS setting is likely to mitigate the benefits provided by pulsatile flow. In contrast, the Capiox Baby RX05 better transmits hemodynamic energy to the patient with much lower pressure drop.

  4. Intermittent exposure to reduced oxygen levels affects prey size selection and consumption in swimming crab Thalamita danae Stimpson.

    PubMed

    Shin, P K S; Cheung, P H; Yang, F Y; Cheung, S G

    2005-01-01

    Portunid crabs Thalamita danae (carapace width: 46-56 mm) were exposed to low oxygen level (4.0 mg O2 l(-1)) and hypoxia (1.5 mg O2 l(-1)) for 6 h each day with three size classes (large: 15.0-19.9 mm, medium: 10.0-14.9 mm, small: 5.0-9.9 mm) of mussels Brachidontes variabilis offered as food. Consumption rate, prey size preference, and prey handling including breaking time, handling time, eating time and prey value, were studied during the time the crabs were exposed to reduced oxygen levels and results were compared with the crabs maintained at high oxygen level (8.0 mg O2 l(-1)) throughout the experiment. Consumption of mussels from all size classes was significantly higher at high oxygen level than at reduced oxygen levels. No mussel size preference was observed for crabs exposed to 4.0 or 8.0 mg O2 l(-1) but those crabs exposed to 1.5 mg O2 l(-1) preferred medium mussels. Both breaking time and handling time increased with mussel size but did not vary with oxygen level. Prey value of each mussel consumed (mg dry wt eaten crab(-1) s(-1)) was calculated by dividing the estimated dry weight of the mussel by the observed handling time. Mean prey value varied significantly with mussel size, with values obtained for large mussels being higher than small mussels at 4.0 and 8.0 mg O2 l(-1); the effect of oxygen level, however, was insignificant. In view of portunid crabs as major predators of mussels, results may help explain dominance of mussels in eutrophic harbours in Hong Kong.

  5. Direct participation of DNA in the formation of singlet oxygen and base damage under UVA irradiation.

    PubMed

    Yagura, Teiti; Schuch, André Passaglia; Garcia, Camila Carrião Machado; Rocha, Clarissa Ribeiro Reily; Moreno, Natália Cestari; Angeli, José Pedro Friedmann; Mendes, Davi; Severino, Divinomar; Bianchini Sanchez, Angelica; Di Mascio, Paolo; de Medeiros, Marisa Helena Gennari; Menck, Carlos Frederico Martins

    2017-07-01

    UVA light is hardly absorbed by the DNA molecule, but recent works point to a direct mechanism of DNA lesion by these wavelengths. UVA light also excite endogenous chromophores, which causes DNA damage through ROS. In this study, DNA samples were irradiated with UVA light in different conditions to investigate possible mechanisms involved in the induction of DNA damage. The different types of DNA lesions formed after irradiation were determined through the use of endonucleases, which recognize and cleave sites containing oxidized bases and cyclobutane pyrimidine dimers (CPDs), as well as through antibody recognition. The formation of 8-oxo-7,8-dihydro-2'-deoxyguanine (8-oxodG) was also studied in more detail using electrochemical detection. The results show that high NaCl concentration and concentrated DNA are capable of reducing the induction of CPDs. Moreover, concerning damage caused by oxidative stress, the presence of sodium azide and metal chelators reduce their induction, while deuterated water increases the amounts of oxidized bases, confirming the involvement of singlet oxygen in the generation of these lesions. Curiously, however, high concentrations of DNA also enhanced the formation of oxidized bases, in a reaction that paralleled the increase in the formation of singlet oxygen in the solution. This was interpreted as being due to an intrinsic photosensitization mechanism, depending directly on the DNA molecule to absorb UVA and generate singlet oxygen. Therefore, the DNA molecule itself may act as a chromophore for UVA light, locally producing a damaging agent, which may lead to even greater concerns about the deleterious impact of sunlight. Copyright © 2017 Elsevier Inc. All rights reserved.

  6. Morph-X-Select: Morphology-based tissue aptamer selection for ovarian cancer biomarker discovery

    PubMed Central

    Wang, Hongyu; Li, Xin; Volk, David E.; Lokesh, Ganesh L.-R.; Elizondo-Riojas, Miguel-Angel; Li, Li; Nick, Alpa M.; Sood, Anil K.; Rosenblatt, Kevin P.; Gorenstein, David G.

    2016-01-01

    High affinity aptamer-based biomarker discovery has the advantage of simultaneously discovering an aptamer affinity reagent and its target biomarker protein. Here, we demonstrate a morphology-based tissue aptamer selection method that enables us to use tissue sections from individual patients and identify high-affinity aptamers and their associated target proteins in a systematic and accurate way. We created a combinatorial DNA aptamer library that has been modified with thiophosphate substitutions of the phosphate ester backbone at selected 5′dA positions for enhanced nuclease resistance and targeting. Based on morphological assessment, we used image-directed laser microdissection (LMD) to dissect regions of interest bound with the thioaptamer (TA) library and further identified target proteins for the selected TAs. We have successfully identified and characterized the lead candidate TA, V5, as a vimentin-specific sequence that has shown specific binding to tumor vasculature of human ovarian tissue and human microvascular endothelial cells. This new Morph-X-Select method allows us to select high-affinity aptamers and their associated target proteins in a specific and accurate way, and could be used for personalized biomarker discovery to improve medical decision-making and to facilitate the development of targeted therapies to achieve more favorable outcomes. PMID:27839510

  7. Evolution models with base substitutions, insertions, deletions, and selection

    NASA Astrophysics Data System (ADS)

    Saakian, D. B.

    2008-12-01

    The evolution model with parallel mutation-selection scheme is solved for the case when selection is accompanied by base substitutions, insertions, and deletions. The fitness is assumed to be either a single-peak function (i.e., having one finite discontinuity) or a smooth function of the Hamming distance from the reference sequence. The mean fitness is calculated exactly in large-genome limit. In the case of insertions and deletions the evolution characteristics depend on the choice of reference sequence.

  8. FRET-based optical assay for selection of artificial riboswitches.

    PubMed

    Harbaugh, Svetlana V; Chapleau, Molly E; Chushak, Yaroslav G; Stone, Morley O; Kelley-Loughnane, Nancy

    2014-01-01

    Artificial riboswitches are engineered to regulate gene expression in response to a variety of non-endogenous small molecules and, therefore, can be useful tools to reprogram cellular behavior for different applications. A new synthetic riboswitch can be created by linking an in vitro-selected aptamer with a randomized expression platform followed by in vivo selection and screening. Here, we describe an in vivo selection and screening technique to discover artificial riboswitches in E. coli cells that is based on TEV protease-FRET substrate reporter system.

  9. 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

  10. 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.

  11. 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.

  12. [Development of physiological monitors based on the Zigbee technology for hyperbaric oxygen chambers].

    PubMed

    Zheng, Jin-Nuan; Wu, Bao-Ming; Lin, Jin-Zhao; Wang, Qiang

    2008-05-01

    This paper introduces a monitor that can monitor five physiological parameters (ECG, blood pressure, spo2, respiration and temperature) based on Wireless Sensor Networks. The monitor will be applied to hyperbaric oxygen chambers. After acquisition, the signal will be displayed on the LCD screen of the monitor terminal in the cabin. At the same time, the Zigbee RF module will send the signal to the extravehicular guardianship PC terminals. This monitor equipment can realize synchronous real-time monitoring both inside and outside. What's more? A host can also display monitoring data the three monitor terminals collected. Preliminary clinical tests show that the monitors are safe and the monitoring results are satisfactory.

  13. A curriculum-based approach for feature selection

    NASA Astrophysics Data System (ADS)

    Kalavala, Deepthi; Bhagvati, Chakravarthy

    2017-06-01

    Curriculum learning is a learning technique in which a classifier learns from easy samples first and then from increasingly difficult samples. On similar lines, a curriculum based feature selection framework is proposed for identifying most useful features in a dataset. Given a dataset, first, easy and difficult samples are identified. In general, the number of easy samples is assumed larger than difficult samples. Then, feature selection is done in two stages. In the first stage a fast feature selection method which gives feature scores is used. Feature scores are then updated incrementally with the set of difficult samples. The existing feature selection methods are not incremental in nature; entire data needs to be used in feature selection. The use of curriculum learning is expected to decrease the time needed for feature selection with classification accuracy comparable to the existing methods. Curriculum learning also allows incremental refinements in feature selection as new training samples become available. Our experiments on a number of standard datasets demonstrate that feature selection is indeed faster without sacrificing classification accuracy.

  14. Dendrite-Free Potassium-Oxygen Battery Based on a Liquid Alloy Anode.

    PubMed

    Yu, Wei; Lau, Kah Chun; Lei, Yu; Liu, Ruliang; Qin, Lei; Yang, Wei; Li, Baohua; Curtiss, Larry A; Zhai, Dengyun; Kang, Feiyu

    2017-09-20

    The safety issue caused by the dendrite growth is not only a key research problem in lithium-ion batteries but also a critical concern in alkali metal (i.e., Li, Na, and K)-oxygen batteries where a solid metal is usually used as the anode. Herein, we demonstrate the first dendrite-free K-O2 battery at ambient temperature based on a liquid Na-K alloy anode. The unique liquid-liquid connection between the liquid alloy and the electrolyte in our alloy anode-based battery provides a homogeneous and robust anode-electrolyte interface. Meanwhile, we manage to show that the Na-K alloy is only compatible in K-O2 batteries but not in Na-O2 batteries, which is mainly attributed to the stronger reducibility of potassium and relatively more favorable thermodynamic formation of KO2 over NaO2 during the discharge process. It is observed that our K-O2 battery based on a liquid alloy anode shows a long cycle life (over 620 h) and a low discharge-charge overpotential (about 0.05 V at initial cycles). Moreover, the mechanism investigation into the K-O2 cell degradation shows that the O2 crossover effect and the ether-electrolyte instability are the critical problems for K-O2 batteries. In a word, this study provides a new route to solve the problems caused by the dendrite growth in alkali metal-oxygen batteries.

  15. 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

    2015-10-07

    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.

  16. 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.

  17. Nitrogen-modified carbon-based catalysts for oxygen reduction reaction in polymer electrolyte membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Subramanian, Nalini P.; Li, Xuguang; Nallathambi, Vijayadurda; Kumaraguru, Swaminatha P.; Colon-Mercado, Hector; Wu, Gang; Lee, Jong-Won; Popov, Branko N.

    Nitrogen-modified carbon-based catalysts for oxygen reduction were synthesized by modifying carbon black with nitrogen-containing organic precursors. The electrocatalytic properties of catalysts were studied as a function of surface pre-treatments, nitrogen and oxygen concentrations, and heat-treatment temperatures. On the optimum catalyst, the onset potential for oxygen reduction is approximately 0.76 V (NHE) and the amount of hydrogen peroxide produced at 0.5 V (NHE) is approximately 3% under our experimental conditions. The characterization studies indicated that pyridinic and graphitic (quaternary) nitrogens may act as active sites of catalysts for oxygen reduction reaction. In particular, pyridinic nitrogen, which possesses one lone pair of electrons in addition to the one electron donated to the conjugated π bond, facilitates the reductive oxygen adsorption.

  18. 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

  19. 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

  20. 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.

  1. 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).

  2. 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

  3. Noninvasive approaches to measuring respiratory patterns using a PtTFPP based phase-lifetime self-referencing oxygen optrode

    NASA Astrophysics Data System (ADS)

    Porterfield, D. Marshall; Rickus, Jenna L.; Kopelman, Raoul

    2006-10-01

    Optically transduced sensors (optrodes, or optodes) offer significant advantages over polarographic techniques for measuring oxygen. In biology and medicine, how we make measurements is very important, and this is especially true in terms of physiological exchange. Cellular and tissue oxygenation is a function of background concentration and respiratory demand, and in pure physical terms this is best expressed in terms of molecular flux based on Fick's law. Measuring dynamic flux from biological systems requires sensing technology that can measure activity in multiple dimensions. Here we report the development of a self-referencing oxygen optrode (SRO) for reliably making noninvasive measurements of oxygen flux from a variety of biological systems. The self-referencing microsensor technique was adapted to operate optrodic oxygen sensors through the integration of optical sensing instrumentation with software-controlled data acquisition and micro-stepping motion control. This allows the sensor to scan biologically active gradients of oxygen flux directly, as it relates to cellular and tissue respiratory activity. The technique was validated first using artificially generated oxygen gradients, which are theoretically modelled and compare with measured signals. Subsequently, the SRO was applied in basic research applications to non-invasively measure molecular oxygen flux from a variety of animal and plant systems.

  4. Selection of principal components based on Fisher discriminant ratio

    NASA Astrophysics Data System (ADS)

    Zeng, Xiangyan; Naghedolfeizi, Masoud; Arora, Sanjeev; Yousif, Nabil; Aberra, Dawit

    2016-05-01

    Principal component analysis transforms a set of possibly correlated variables into uncorrelated variables, and is widely used as a technique of dimensionality reduction and feature extraction. In some applications of dimensionality reduction, the objective is to use a small number of principal components to represent most variation in the data. On the other hand, the main purpose of feature extraction is to facilitate subsequent pattern recognition and machine learning tasks, such as classification. Selecting principal components for classification tasks aims for more than dimensionality reduction. The capability of distinguishing different classes is another major concern. Components that have larger eigenvalues do not necessarily have better distinguishing capabilities. In this paper, we investigate a strategy of selecting principal components based on the Fisher discriminant ratio. The ratio of between class variance to within class variance is calculated for each component, based on which the principal components are selected. The number of relevant components is determined by the classification accuracy. To alleviate overfitting which is common when there are few training data available, we use a cross-validation procedure to determine the number of principal components. The main objective is to select the components that have large Fisher discriminant ratios so that adequate class separability is obtained. The number of selected components is determined by the classification accuracy of the validation data. The selection method is evaluated by face recognition experiments.

  5. Minimum Bayesian error probability-based gene subset selection.

    PubMed

    Li, Jian; Yu, Tian; Wei, Jin-Mao

    2015-01-01

    Sifting functional genes is crucial to the new strategies for drug discovery and prospective patient-tailored therapy. Generally, simply generating gene subset by selecting the top k individually superior genes may obtain an inferior gene combination, for some selected genes may be redundant with respect to some others. In this paper, we propose to select gene subset based on the criterion of minimum Bayesian error probability. The method dynamically evaluates all available genes and sifts only one gene at a time. A gene is selected if its combination with the other selected genes can gain better classification information. Within the generated gene subset, each individual gene is the most discriminative one in comparison with those that classify cancers in the same way as this gene does and different genes are more discriminative in combination than in individual. The genes selected in this way are likely to be functional ones from the system biology perspective, for genes tend to co-regulate rather than regulate individually. Experimental results show that the classifiers induced based on this method are capable of classifying cancers with high accuracy, while only a small number of genes are involved.

  6. 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.

  7. The sequence relay selection strategy based on stochastic dynamic programming

    NASA Astrophysics Data System (ADS)

    Zhu, Rui; Chen, Xihao; Huang, Yangchao

    2017-07-01

    Relay-assisted (RA) network with relay node selection is a kind of effective method to improve the channel capacity and convergence performance. However, most of the existing researches about the relay selection did not consider the statically channel state information and the selection cost. This shortage limited the performance and application of RA network in practical scenarios. In order to overcome this drawback, a sequence relay selection strategy (SRSS) was proposed. And the performance upper bound of SRSS was also analyzed in this paper. Furthermore, in order to make SRSS more practical, a novel threshold determination algorithm based on the stochastic dynamic program (SDP) was given to work with SRSS. Numerical results are also presented to exhibit the performance of SRSS with SDP.

  8. QCM-based aptamer selection and detection of Salmonella typhimurium.

    PubMed

    Wang, Lijun; Wang, Ronghui; Chen, Fang; Jiang, Tieshan; Wang, Hong; Slavik, Michael; Wei, Hua; Li, Yanbin

    2017-04-15

    In this study, quartz crystal microbalance (QCM) was used to select aptamers against Salmonella typhimurium. To increase the success rate of Systematic Evolution of Ligands Exponential Enrichment (SELEX), the affinity of DNA pool in each round was simultaneously tracked using QCM in order to avoid the loss of high-quality aptamers. When the frequency change reached a maximum value after several rounds of selection and counter-selection, the candidate pool was cloned and sequenced. Out of three aptamer candidates, aptamer B5 showed high specificity and binding affinity with dissociation constant (Kd value) of 58.5nM, and was chosen for further studies. Subsequently, a QCM-based aptasensor was developed to detect S. typhimurium. This aptasensor was able to detect 10(3)CFU/mL of S. typhimurium with less than 1h. This study demonstrated QCM-based selection could be more effective selection of aptamers and QCM-based aptasensor could be more sensitive in detecting S. typhimurium.

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

    DOE PAGES

    Lu, Jun; Cheng, Lei; Lau, Kah Chun; ...

    2014-09-12

    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. In this paper, 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. Thismore » dependence is found to be due to the influence of the cluster size on the formation mechanism, which also affects the charge process. Finally, 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.« less

  10. Evaluation of true maximal oxygen uptake based on a novel set of standardized criteria.

    PubMed

    Midgley, Adrian W; Carroll, Sean; Marchant, David; McNaughton, Lars R; Siegler, Jason

    2009-04-01

    In this study, criteria are used to identify whether a subject has elicited maximal oxygen uptake. We evaluated the validity of traditional maximal oxygen uptake criteria and propose a novel set of criteria. Twenty athletes completed a maximal oxygen uptake test, consisting of an incremental phase and a subsequent supramaximal phase to exhaustion (verification phase). Traditional and novel maximal oxygen uptake criteria were evaluated. Novel criteria were: oxygen uptake plateau defined as the difference between modelled and actual maximal oxygen uptake >50% of the regression slope of the individual oxygen uptake-workrate relationship; as in the first criterion, but for maximal verification oxygen uptake; and a difference of oxygen uptake plateau criterion was largely an artefact of the between-subject variation in the oxygen uptake-workrate relationship. Secondary criteria, supposedly an indicator of maximal effort, were often satisfied long before volitional exhaustion, even at intensities as low as 61% maximal oxygen uptake. No significant mean differences were observed between the incremental and verification phases for oxygen uptake (t = 0.4; p = 0.7) or heart rate (t = 0.8; p = 0.5). The novel oxygen uptake plateau criterion, maximal oxygen uptake verification criterion, and maximal heart rate verification criterion were satisfied by 17, 18, and 18 subjects, respectively. The small individual absolute differences in oxygen uptake between incremental and verification phases observed in most subjects provided additional confidence that maximal oxygen uptake was elicited. Current maximal oxygen uptake criteria were not valid and novel criteria should be further explored.

  11. Orbital-selective charge transfer at oxygen-deficient LaAlO3/SrTiO3(001) interfaces

    NASA Astrophysics Data System (ADS)

    Ong, P. V.; Lee, Jaichan

    2013-05-01

    Density-functional theory within the local density approximation + Hubbard U approach was used to study interface electronic structures in stoichiometric and oxygen-deficient LaAlO3/SrTiO3 (LAO/STO) superlattices with regularly spaced n-type and p-type interfaces. Asymmetric behaviors between complementary n-type and p-type interfaces were revealed in terms of orbital-selective charge transfer. Extra electrons induced by oxygen vacancies at the p-type interface easily spread to the n-type interface and occupy the Ti 3dxyorbitals, while those induced by the vacancies at the n-type interface are strictly confined and reside in Ti 3dx2-y2 and/or 3d3z2-r2 orbtials. The electronic behavior of oxygen vacancies at the LAO/STO interfaces and the possibility of distinguishing between intrinsic electronic states, which are induced by the polar catastrophe, and extrinsic states due to oxygen vacancies are discussed in detail.

  12. 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.

  13. Feature selection with neighborhood entropy-based cooperative game theory.

    PubMed

    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.

  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.

  15. 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.

  16. 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.

  17. 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

  18. VCSEL-based oxygen spectroscopy for structural analysis of pharmaceutical solids

    NASA Astrophysics Data System (ADS)

    Svensson, T.; Andersson, M.; Rippe, L.; Svanberg, S.; Andersson-Engels, S.; Johansson, J.; Folestad, S.

    2008-02-01

    We present a minimalistic and flexible single-beam instrumentation based on sensitive tunable diode laser absorption spectroscopy (TDLAS) and its use in structural analysis of highly scattering pharmaceutical solids. By utilising a vertical cavity surface emitting laser (VCSEL) for sensing of molecular oxygen dispersed in tablets, we address structural properties such as porosity. Experiments involve working with unknown path lengths, severe backscattering and diffuse light. These unusual experimental conditions has led to the use of the term gas in scattering media absorption spectroscopy (GASMAS). By employing fully digital wavelength modulation spectroscopy and coherent sampling, system sensitivity in ambient air experiments reaches the 10-7 range. Oxygen absorption exhibited by our tablets, being influenced by both sample porosity and scattering, was in the range 8×10-5 to 2×10-3, and corresponds to 2-50 mm of path length through ambient air (Leq). The day-to-day reproducibility was on average 1.8% (0.3 mm Leq), being limited by mechanical positioning. This is the first time sub-millimetre sensitivity is reached in GASMAS. We also demonstrate measurements on gas transport on a 1-s time scale. By employing pulsed illumination and time-correlated single-photon counting, we reveal that GASMAS exhibits excellent correlation with time-domain photon migration. In addition, we introduce an optical measure of porosity by relating oxygen absorption to average photon time-of-flight. Finally, the simplicity, robustness and low cost of this novel TDLAS instrumentation provide industrial potential.

  19. A LED-based phosphorimeter for measurement of microcirculatory oxygen pressure.

    PubMed

    Guerci, Philippe; Ince, Yasin; Heeman, Paul; Faber, Dirk; Ergin, Bulent; Ince, Can

    2017-02-01

    Quantitative measurements of microcirculatory and tissue oxygenation are of prime importance in experimental research. The noninvasive phosphorescence quenching method has given further insight into the fundamental mechanisms of oxygen transport to healthy tissues and in models of disease. Phosphorimeters are devices dedicated to the study of phosphorescence quenching. The experimental applications of phosphorimeters range from measuring a specific oxygen partial pressure (Po2) in cellular organelles such as mitochondria, finding values of Po2 distributed over an organ or capillaries, to measuring microcirculatory Po2 changes simultaneously in several organ systems. Most of the current phosphorimeters use flash lamps as a light excitation source. However, a major drawback of flash lamps is their inherent plasma glow that persists for tens of microseconds after the primary discharge. This complex distributed excitation pattern generated by the flash lamp can lead to inaccurate Po2 readings unless a deconvolution analysis is performed. Using light-emitting diode (LED), a rectangular shaped light pulse can be generated that provides a more uniformly distributed excitation signal. This study presents the design and calibration process of an LED-based phosphorimeter (LED-P). The in vitro calibration of the LED-P using palladium(II)-meso-tetra(4-carboxyphenyl)-porphyrin (Pd-TCCP) as a phosphorescent dye is presented. The pH and temperature were altered to assess whether the decay times of the Pd-TCCP measured by the LED-P were significantly influenced. An in vivo validation experiment was undertaken to measure renal cortical Po2 in a rat subjected to hypoxic ventilation conditions and ischemia/reperfusion. The benefits of using LEDs as a light excitation source are presented.

  20. Economic Analysis for Conceptual Design of Oxygen-Based PC Boiler

    SciTech Connect

    Andrew Seltzer

    2005-02-01

    The objective of the economic analysis is to prepare a budgetary estimate of capital and operating costs of the O{sub 2}-fired PC power plant as well as for the equivalent conventional PC-fired power plant. Capital and operating costs of conventional steam generation, steam heating, and power generation equipment are estimated based on Foster Wheeler's extensive experience and database. Capital and operating costs of equipment, such as oxygen separation and CO{sub 2} liquefaction, are based on vendor supplied data and FW process plant experience. The levelized cost of electricity is determined for both the air-fired and O{sub 2}-fired power plants as well as the CO{sub 2} mitigation cost. An economic comparison between the O{sub 2}-fired PC and other alternate technologies is presented.

  1. 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.

  2. 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.

  3. The design of dextran-based hypoxia-inducible hydrogels via in situ oxygen-consuming reaction.

    PubMed

    Park, Kyung Min; Blatchley, Michael R; Gerecht, Sharon

    2014-11-01

    Hypoxia plays a critical role in the development and wound healing process, as well as a number of pathological conditions. Here, dextran-based hypoxia-inducible (Dex-HI) hydrogels formed with in situ oxygen consumption via a laccase-medicated reaction are reported. Oxygen levels and gradients were accurately predicted by mathematical simulation. It is demonstrated that Dex-HI hydrogels provide prolonged hypoxic conditions up to 12 h. The Dex-HI hydrogel offers an innovative approach to delineate not only the mechanism by which hypoxia regulates cellular responses, but may facilitate the discovery of new pathways involved in the generation of hypoxic and oxygen gradient environments.

  4. 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.

  5. 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

  6. Novel and selective spiroindoline-based inhibitors of Sky kinase.

    PubMed

    Powell, Noel A; Kohrt, Jeffrey T; Filipski, Kevin J; Kaufman, Michael; Sheehan, Derek; Edmunds, Jeremy E; Delaney, Amy; Wang, Yuli; Bourbonais, Francis; Lee, Doh-Yeel; Schwende, Frank; Sun, Fang; McConnell, Pat; Catana, Cornel; Chen, Huifen; Ohren, Jeff; Perrin, Lisa A

    2012-01-01

    We report the discovery of a novel series of spiroindoline-based inhibitors of Sky kinase that bind in the ATP-binding site and exhibit high levels of kinome selectivity through filling the Ala571-subpocket. These inhibitors exhibit moderate oral bioavailability in the rat due to low absorption across the gut wall. Copyright © 2011 Elsevier Ltd. All rights reserved.

  7. Discrete Biogeography Based Optimization for Feature Selection in Molecular Signatures.

    PubMed

    Liu, Bo; Tian, Meihong; Zhang, Chunhua; Li, Xiangtao

    2015-04-01

    Biomarker discovery from high-dimensional data is a complex task in the development of efficient cancer diagnoses and classification. However, these data are usually redundant and noisy, and only a subset of them present distinct profiles for different classes of samples. Thus, selecting high discriminative genes from gene expression data has become increasingly interesting in the field of bioinformatics. In this paper, a discrete biogeography based optimization is proposed to select the good subset of informative gene relevant to the classification. In the proposed algorithm, firstly, the fisher-markov selector is used to choose fixed number of gene data. Secondly, to make biogeography based optimization suitable for the feature selection problem; discrete migration model and discrete mutation model are proposed to balance the exploration and exploitation ability. Then, discrete biogeography based optimization, as we called DBBO, is proposed by integrating discrete migration model and discrete mutation model. Finally, the DBBO method is used for feature selection, and three classifiers are used as the classifier with the 10 fold cross-validation method. In order to show the effective and efficiency of the algorithm, the proposed algorithm is tested on four breast cancer dataset benchmarks. Comparison with genetic algorithm, particle swarm optimization, differential evolution algorithm and hybrid biogeography based optimization, experimental results demonstrate that the proposed method is better or at least comparable with previous method from literature when considering the quality of the solutions obtained.

  8. Attachment and Children: Citations From Selected Data Bases.

    ERIC Educational Resources Information Center

    Baskin, Linda B., Comp.

    This bibliography compiles citations from seven selected data bases on the topic of attachment and children. The citations are grouped into eight categories: (1) Attachment -- General; (2) Institutions -- Hospitals, Prisons; (3) Day Care and Attachment; (4) Handicapped Children and Attachment; (5) Separation; (6) Child Abuse and Attachment; (7)…

  9. An Assessment-Based Model for Counseling Strategy Selection.

    ERIC Educational Resources Information Center

    Nelson, Mary Lee

    2002-01-01

    Presents a counseling strategy selection model grounded in technical eclecticism and based on thorough assessment of the client's problems. Assessment should consider client mental health, counseling goals, problem complexity, and capacity and desire for insight. Distinguishing between simple and complex problems can aid assessment and provide…

  10. 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…

  11. Jail-Based Inmate Programs. A Selected Bibliography.

    ERIC Educational Resources Information Center

    Levine, Mark, Comp.; Kravitz, Marjorie, Ed.

    This is a bibliography of documents selected from the data base of the National Criminal Justice Reference Service that provide an overview of comprehensive treatment programs in local jails. The citations follow an explanation of how to obtain the documents and are arranged under the following topics: (1) state of the art, (2) jail management and…

  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.

  13. 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.

  14. Validity of heart rate based nomogram fors estimation of maximum oxygen uptake in Indian population.

    PubMed

    Kumar, S Krishna; Khare, P; Jaryal, A K; Talwar, A

    2012-01-01

    Maximal oxygen uptake (VO2max) during a graded maximal exercise test is the objective method to assess cardiorespiratory fitness. Maximal oxygen uptake testing is limited to only a few laboratories as it requires trained personnel and strenuous effort by the subject. At the population level, submaximal tests have been developed to derive VO2max indirectly based on heart rate based nomograms or it can be calculated using anthropometric measures. These heart rate based predicted standards have been developed for western population and are used routinely to predict VO2max in Indian population. In the present study VO2max was directly measured by maximal exercise test using a bicycle ergometer and was compared with VO2max derived by recovery heart rate in Queen's College step test (QCST) (PVO2max I) and with VO2max derived from Wasserman equation based on anthropometric parameters and age (PVO2max II) in a well defined age group of healthy male adults from New Delhi. The values of directly measured VO2max showed no significant correlation either with the estimated VO2max with QCST or with VO2max predicted by Wasserman equation. Bland and Altman method of approach for limit of agreement between VO2max and PVO2max I or PVO2max II revealed that the limits of agreement between directly measured VO2max and PVO2max I or PVO2max II was large indicating inapplicability of prediction equations of western population in the population under study. Thus it is evident that there is an urgent need to develop nomogram for Indian population, may be even for different ethnic sub-population in the country.

  15. Functionality of albumin-derived perfluorocarbon-based artificial oxygen carriers in the Langendorff-heart (†).

    PubMed

    Wrobeln, Anna; Schlüter, Klaus D; Linders, Jürgen; Zähres, Manfred; Mayer, Christian; Kirsch, Michael; Ferenz, Katja B

    2017-06-01

    The aim of this study was to prove whether albumin-derived perfluorocarbon-based nanoparticles (capsules) can operate as a novel artificial oxygen carrier in a rat Langendorff-heart perfusion model. Hearts perfused with capsules showed increased left ventricular pressure and rate pressure product compared to hearts perfused with pure Krebs-Henseleit (KH)-buffer. The capsules prevented the myocardium from functional fail when in their absence a noxious ischemia was observed. Capsules did not change rheological properties of KH-buffer and could repeatedly reload with oxygen. This albumin-derived perfluorocarbon-based artificial oxygen carrier preserved the function of rat hearts due to the transport of oxygen in a satisfactory manner. Because of these positive results, the functionality of the applied capsules should be verified in living animals.

  16. 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

  17. 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.

  18. 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.

  19. 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...

  20. 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...

  1. 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...

  2. 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...

  3. 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

  4. Online support vector machine based on convex hull vertices selection.

    PubMed

    Wang, Di; Qiao, Hong; Zhang, Bo; Wang, Min

    2013-04-01

    The support vector machine (SVM) method, as a promising classification technique, has been widely used in various fields due to its high efficiency. However, SVM cannot effectively solve online classification problems since, when a new sample is misclassified, the classifier has to be retrained with all training samples plus the new sample, which is time consuming. According to the geometric characteristics of SVM, in this paper we propose an online SVM classifier called VS-OSVM, which is based on convex hull vertices selection within each class. The VS-OSVM algorithm has two steps: 1) the samples selection process, in which a small number of skeleton samples constituting an approximate convex hull in each class of the current training samples are selected and 2) the online updating process, in which the classifier is updated with newly arriving samples and the selected skeleton samples. From the theoretical point of view, the first d+1 (d is the dimension of the input samples) selected samples are proved to be vertices of the convex hull. This guarantees that the selected samples in our approach keep the greatest amount of information of the convex hull. From the application point of view, the new algorithm can update the classifier without reducing its classification performance. Experimental results on benchmark data sets have shown the validity and effectiveness of the VS-OSVM algorithm.

  5. Oxygen sensing with an absolute optical sensor based on biluminescence (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Salas Redondo, Caterin; Reineke, Sebastian

    2017-06-01

    Organic semiconductors are materials having the benefits of semiconductors together with those of organic molecules. That means, on one hand, these are compounds able to absorb and emit light, as well as conduct electricity to a certain extent, which is enough for the functionality of solid state devices. On the other hand, a remarkable characteristic is that the excitations are typically localized on individual molecules, such that the exchange interactions lead to energetically distinct singlet and triplet states. According to the spectroscopic selection rules in quantum mechanics, only transitions from the singlet excited state are allowed, deactivating radiatively while generating fluorescence emission in the process, whereas transitions from the triplet excited state are not allowed, because its decay involves a spin flip, and therefore, it is theoretically forbidden by electric dipole transitions. Nevertheless, there is a small probability of these forbidden transitions to occur at a low rate, resulting in a slow radiative deactivation known as phosphorescence emission. In this context, the property of an organic molecule able to emit light from both their singlet and triplet excited states is called biluminescence. Although this dual state emission, particularly at room temperature, is difficult to achieve by purely organic molecules, it becomes possible if competitive thermal decay is suppressed effectively, allowing emission from the triplet states (i.e. phosphorescence) in addition to the conventional fluorescence. Here, we have identified biluminescence in simple host:guest systems in which a biluminophore (i.e. organic molecule with biluminescence property) is embedded in an optimum rigid matrix, for example, a combination of PMMA [poly(methyl methacrylate)] as host and NPB [N,N'-di(naphtha-1-yl)-N,N'-diphenyl-benzidine] as biluminophore [Reineke and Baldo, Sci. Rep.]. Such system is unique not only because of the dual state emission, but also the large

  6. Assessment of skin flaps using optically based methods for measuring blood flow and oxygenation.

    PubMed

    Payette, Jeri R; Kohlenberg, Elicia; Leonardi, Lorenzo; Pabbies, Arone; Kerr, Paul; Liu, Kan-Zhi; Sowa, Michael G

    2005-02-01

    The objective of this study was to compare two noninvasive techniques, laser Doppler and optical spectroscopy, for monitoring hemodynamic changes in skin flaps. Animal models for assessing these changes in microvascular free flaps and pedicle flaps were investigated. A 2 x 3-cm free flap model based on the epigastric vein-artery pair and a reversed MacFarlane 3 x 10-cm pedicle flap model were used in this study. Animals were divided into four groups, with groups 1 (n = 6) and 2 (n = 4) undergoing epigastric free flap surgery and groups 3 (n = 3) and 4 (n = 10) undergoing pedicle flap surgery. Groups 1 and 4 served as controls for each of the flap models. Groups 2 and 3 served as ischemia-reperfusion models. Optical spectroscopy provides a measure of hemoglobin oxygen saturation and blood volume, and the laser Doppler method measures blood flow. Optical spectroscopy proved to be consistently more reliable in detecting problems with arterial in flow compared with laser Doppler assessments. When spectroscopy was used in an imaging configuration, oxygen saturation images of the entire flap were generated, thus creating a visual picture of global flap health. In both single-point and imaging modes the technique was sensitive to vessel manipulation, with the immediate post operative images providing an accurate prediction of eventual outcome. This series of skin flap studies suggests a potential role for optical spectroscopy and spectroscopic imaging in the clinical assessment of skin flaps.

  7. 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).

  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. 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.

  10. 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.

  11. Cathode based on molybdenum disulfide nanoflakes for lithium-oxygen batteries.

    SciTech Connect

    Asadi, Mohammad; Kumar, Bijandra; Liu, Cong; Phillips, Patrick; Yasaei, Poya; Behranginia, Amirhossein; Zapol, Peter; Klie, Robert F.; Curtiss, Larry A.; Salehi-Khojin, Amin

    2016-02-01

    Lithium-oxygen (Li-O-2) 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-O-2 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-O-2 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. 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.

  12. Oxygen transport membrane reactor based method and system for generating electric power

    DOEpatents

    Kelly, Sean M.; Chakravarti, Shrikar; Li, Juan

    2017-02-07

    A carbon capture enabled system and method for generating electric power and/or fuel from methane containing sources using oxygen transport membranes by first converting the methane containing feed gas into a high pressure synthesis gas. Then, in one configuration the synthesis gas is combusted in oxy-combustion mode in oxygen transport membranes based boiler reactor operating at a pressure at least twice that of ambient pressure and the heat generated heats steam in thermally coupled steam generation tubes within the boiler reactor; the steam is expanded in steam turbine to generate power; and the carbon dioxide rich effluent leaving the boiler reactor is processed to isolate carbon. In another configuration the synthesis gas is further treated in a gas conditioning system configured for carbon capture in a pre-combustion mode using water gas shift reactors and acid gas removal units to produce hydrogen or hydrogen-rich fuel gas that fuels an integrated gas turbine and steam turbine system to generate power. The disclosed method and system can also be adapted to integrate with coal gasification systems to produce power from both coal and methane containing sources with greater than 90% carbon isolation.

  13. Surface acoustic wave oxygen pressure sensor

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

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

  14. 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

  15. 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.

  16. Image Segmentation Based on Chaos Immune Clone Selection Algorithm

    NASA Astrophysics Data System (ADS)

    Cheng, Junna; Ji, Guangrong; Feng, Chen

    Image segmentation is a fundamental step in image processing. Otsu's threshold method is a widely used method for image segmentation. In this paper, a novel image segmentation method based on chaos immune clone selection algorithm (CICSA) and Otus's threshold method is presented. By introducing the chaos optimization algorithm into the parallel and distributed search mechanism of immune clone selection algorithm, CICSA takes advantage of global and local search ability. The experimental results demonstrate that the performance of CICSA on application of image segmentation has the characteristic of stability and efficiency.

  17. Object-based wavelet compression using coefficient selection

    NASA Astrophysics Data System (ADS)

    Zhao, Lifeng; Kassim, Ashraf A.

    1998-12-01

    In this paper, we present a novel approach to code image regions of arbitrary shapes. The proposed algorithm combines a coefficient selection scheme with traditional wavelet compression for coding arbitrary regions and uses a shape adaptive embedded zerotree wavelet coding (SA-EZW) to quantize the selected coefficients. Since the shape information is implicitly encoded by the SA-EZW, our decoder can reconstruct the arbitrary region without separate shape coding. This makes the algorithm simple to implement and avoids the problem of contour coding. Our algorithm also provides a sufficient framework to address content-based scalability and improved coding efficiency as described by MPEG-4.

  18. 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.

  19. 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.

  20. 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.

  1. An efficient selective perceptual-based super-resolution estimator.

    PubMed

    Karam, Lina J; Sadaka, Nabil G; Ferzli, Rony; Ivanovski, Zoran A

    2011-12-01

    In this paper, a selective perceptual-based (SELP) framework is presented to reduce the complexity of popular super-resolution (SR) algorithms while maintaining the desired quality of the enhanced images/video. A perceptual human visual system model is proposed to compute local contrast sensitivity thresholds. The obtained thresholds are used to select which pixels are super-resolved based on the perceived visibility of local edges. Processing only a set of perceptually significant pixels reduces significantly the computational complexity of SR algorithms without losing the achievable visual quality. The proposed SELP framework is integrated into a maximum-a posteriori-based SR algorithm as well as a fast two-stage fusion-restoration SR estimator. Simulation results show a significant reduction on average in computational complexity with comparable signal-to-noise ratio gains and visual quality.

  2. 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).

  3. Highly selective dry etching of polystyrene-poly(methyl methacrylate) block copolymer by gas pulsing carbon monoxide-based plasmas

    NASA Astrophysics Data System (ADS)

    Miyazoe, Hiroyuki; Jagtiani, Ashish V.; Tsai, Hsin-Yu; Engelmann, Sebastian U.; Joseph, Eric A.

    2017-05-01

    We propose a very selective PMMA removal method from poly(styrene-block-methyl methacrylate) (PS-b-PMMA) copolymer using gas pulsing cyclic etching. Flow ratio of hydrogen (H2) added to carbon monoxide (CO) plasma was periodically changed to control etch and deposition processes on PS. By controlling the process time of each etch and deposition step, full PMMA removal including etching of the neutral layer was demonstrated at 28 nm pitch, while PS thickness remained intact. This is more than 10 times higher etch selectivity than conventional continuous plasma etch processes using standard oxygen (O2), CO-H2 and CO-O2-based chemistries.

  4. Oxygen- and time-dependent effects of antibiotics and selected mitochondrial inhibitors on Plasmodium falciparum in culture.

    PubMed Central

    Divo, A A; Geary, T G; Jensen, J B

    1985-01-01

    Several antibiotics which inhibit protein synthesis on 70S ribosomes, including clindamycin, pirlimycin, 4'-pentyl-N-demethyl clindamycin, four tetracyclines, chloramphenicol, thiamphenicol, and erythromycin, had antimalarial effects against Plasmodium falciparum in culture which were greatly influenced by the duration of drug exposure and by oxygen tension. In 96-h incubations, potency was increased by a factor of up to 10(6) over the first 48-h period and by a factor of up to 10(4) in 15% O2 versus 1% O2. Two aminoglycosides, kanamycin and tobramycin, had no antimalarial activity. Rifampin and nalidixic acid, which inhibit nucleic acid synthesis, were not similar to the 70S inhibitors. The mitochondrial inhibitors Janus Green, rhodamine 123, antimycin A1, and 8-methylamino-8-desmethyl riboflavin had activities which were influenced by the duration of exposure and oxygen tension. Quinoline-containing antimalarial agents, ionophores, and other antimalarial drugs were influenced to a minor extent by the duration of exposure but were not affected by oxygen tension. These data can best be explained by the hypothesis that antimalarial 70S ribosome-specific protein synthesis inhibitors are toxic to the parasites by acting on the mitochondrion. PMID:3885844

  5. 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

  6. Tuning oxygen vacancy photoluminescence in monoclinic Y2WO6 by selectively occupying yttrium sites using lanthanum

    NASA Astrophysics Data System (ADS)

    Ding, Bangfu; Han, Chao; Zheng, Lirong; Zhang, Junying; Wang, Rongming; Tang, Zilong

    2015-03-01

    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.

  7. Determination of selected oxygenated polycyclic aromatic hydrocarbons (oxy-PAHs) in diesel and air particulate matter standard reference materials (SRMs).

    PubMed

    Nocun, Margarete S; Schantz, Michele M

    2013-06-01

    Oxygenated polycyclic aromatic hydrocarbons (oxy-PAHs) have recently received much attention in discussions regarding the negative impacts of particulate matter (PM) on human health and the environment. The National Institute of Standards and Technology provides several environmental matrix standard reference materials (SRMs) with certified and reference values for polycyclic aromatic hydrocarbons (PAHs) and nitrated PAHs. In this study, the concentrations of oxygenated PAHs are determined in three air PM SRMs (1649b, 1648a, and 2786) and three diesel PM SRMs (1650b, 2975, and 1975) using two independent gas chromatography-mass spectrometry methods. Concentrations of oxy-PAHs were at the milligrams per kilogram level with higher overall concentrations in diesel PM (up to 50 mg/kg for 9,10-anthraquinone). One of the highest oxy-PAH concentrations (up to 5 mg/kg) measured in the air particulate SRMs was for 7,12-benz[a]anthracenquinone. These results suggest that oxygenated PAHs should not be neglected in the analysis of PM as their concentrations can be as high as those of some PAHs and are one to two orders of magnitude higher than those for nitro-PAHs.

  8. Light-addressable measurements of cellular oxygen consumption rates in microwell arrays based on phase-based phosphorescence lifetime detection

    PubMed Central

    Huang, Shih-Hao; Hsu, Yu-Hsuan; Wu, Chih-Wei; Wu, Chang-Jer

    2012-01-01

    A digital light modulation system that utilizes a modified commercial digital micromirror device (DMD) projector, which is equipped with a UV light-emitting diode as a light modulation source, has been developed to spatially direct excited light toward a microwell array device to detect the oxygen consumption rate (OCR) of single cells via phase-based phosphorescence lifetime detection. The microwell array device is composed of a combination of two components: an array of glass microwells containing Pt(II) octaethylporphine (PtOEP) as the oxygen-sensitive luminescent layer and a microfluidic module with pneumatically actuated glass lids set above the microwells to controllably seal the microwells of interest. By controlling the illumination pattern on the DMD, the modulated excitation light can be spatially projected to only excite the sealed microwell for cellular OCR measurements. The OCR of baby hamster kidney-21 fibroblast cells cultivated on the PtOEP layer within a sealed microwell has been successfully measured at 104 ± 2.96 amol s−1 cell−1. Repeatable and consistent measurements indicate that the oxygen measurements did not adversely affect the physiological state of the measured cells. The OCR of the cells exhibited a good linear relationship with the diameter of the microwells, ranging from 400 to 1000 μm and containing approximately 480 to 1200 cells within a microwell. In addition, the OCR variation of single cells in situ infected by Dengue virus with a different multiplicity of infection was also successfully measured in real-time. This proposed platform provides the potential for a wide range of biological applications in cell-based biosensing, toxicology, and drug discovery. PMID:24348889

  9. Light-addressable measurements of cellular oxygen consumption rates in microwell arrays based on phase-based phosphorescence lifetime detection.

    PubMed

    Huang, Shih-Hao; Hsu, Yu-Hsuan; Wu, Chih-Wei; Wu, Chang-Jer

    2012-01-01

    A digital light modulation system that utilizes a modified commercial digital micromirror device (DMD) projector, which is equipped with a UV light-emitting diode as a light modulation source, has been developed to spatially direct excited light toward a microwell array device to detect the oxygen consumption rate (OCR) of single cells via phase-based phosphorescence lifetime detection. The microwell array device is composed of a combination of two components: an array of glass microwells containing Pt(II) octaethylporphine (PtOEP) as the oxygen-sensitive luminescent layer and a microfluidic module with pneumatically actuated glass lids set above the microwells to controllably seal the microwells of interest. By controlling the illumination pattern on the DMD, the modulated excitation light can be spatially projected to only excite the sealed microwell for cellular OCR measurements. The OCR of baby hamster kidney-21 fibroblast cells cultivated on the PtOEP layer within a sealed microwell has been successfully measured at 104 ± 2.96 amol s(-1) cell(-1). Repeatable and consistent measurements indicate that the oxygen measurements did not adversely affect the physiological state of the measured cells. The OCR of the cells exhibited a good linear relationship with the diameter of the microwells, ranging from 400 to 1000 μm and containing approximately 480 to 1200 cells within a microwell. In addition, the OCR variation of single cells in situ infected by Dengue virus with a different multiplicity of infection was also successfully measured in real-time. This proposed platform provides the potential for a wide range of biological applications in cell-based biosensing, toxicology, and drug discovery.

  10. Investigation of packaging systems for shelled walnuts based on oxygen absorbers.

    PubMed

    Jensen, Pernille N; Sørensen, Gitte; Brockhoff, Per; Bertelsen, Grete

    2003-08-13

    Storage of nuts at a high oxygen concentration results in rancid nuts whereas storage at a low oxygen concentration results in fine-tasting nuts. During a 13 month experiment, packaging of walnuts with an oxygen absorber was compared to packaging in nitrogen or atmospheric air. At the same time, the effects of oxygen permeability of the packaging material and storage temperature (11 and 21 degrees C) were investigated by determination of hexanal and rancid taste of the walnuts. The optimal storage condition for walnuts is at 11 degrees C or lower, eventually combined with an oxygen absorber. However, without chilled storage and use of an oxygen absorber, it is possible to obtain an acceptable quality of walnuts with a packaging material having a very low oxygen permeability (e.g., laminate with EVOH) combined with nitrogen flushing. The results also revealed that the development of hexanal during time can be described by a second-order polynomial regression model.

  11. Capillary-tube-based oxygen/argon micro-plasma system for the inactivation of bacteria suspended in aqueous solution.

    PubMed

    Weng, Chih-Chiang; Liao, Juinn-Der; Chen, Hsin-Hung; Lin, Tung-Yi; Huang, Chih-Ling

    2011-09-01

    An aqueous solution containing Escherichia coli can be completely inactivated within a short treatment time using a capillary-tube-based oxygen/argon micro-plasma source. A capillary-tube-based oxygen/argon micro-plasma system with a hollow inner electrode was ignited by a 13.56 MHz radio frequency power supply with a matching network and characterised by optical emission spectroscopy. An aqueous solution containing E. coli was then treated at various the working distances, plasma exposure durations, and oxygen ratios in argon micro-plasma. The treated bacteria were then assessed and qualitatively investigated. The morphologies of treated bacteria were examined using a scanning electron microscope (SEM). In the proposed oxygen/argon micro-plasma system, the intensities of the main emission lines of the excited species, nitric oxide (NO), hydrated oxide (OH), argon (Ar), and atomic oxygen (O), fluctuated with the addition of oxygen to argon micro-plasma. Under a steady state of micro-plasma generation, the complete inactivation of E. coli in aqueous solution was achieved within 90 s of argon micro-plasma exposure time with a working distance of 3 mm. SEM micrographs reveal obvious morphological damage to the treated E. coli. The addition of oxygen to argon micro-plasma increased the variety of O-containing excited species. At a given supply power, the relative intensities of the excited species, NO and OH, correlated with the ultraviolet (UV) intensity, decreased. For the proposed capillary-tube-based micro-plasma system with a hollow inner electrode, the oxygen/argon micro-plasma source is efficient in inactivating E. coli in aqueous solution. The treatment time required for the inactivation process decreases with decreasing working distance or the increasing synthesised effect of reactive species and UV intensity.

  12. 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.

  13. A novel selectable marker based on Aspergillus niger arginase expression.

    PubMed

    Dave, Kashyap; Ahuja, Manmeet; Jayashri, T N; Sirola, Rekha Bisht; Punekar, Narayan S

    2012-06-10

    Selectable markers are valuable tools in transforming asexual fungi like Aspergillus niger. An arginase (agaA) expression vector and a suitable arginase-disrupted host would define a novel nutritional marker/selection for transformation. The development of such a marker was successfully achieved in two steps. The single genomic copy of A. niger arginase gene was disrupted by homologous integration of the bar marker. The agaA disruptant was subsequently complemented by transforming it with agaA expression vectors. Both citA and trpC promoters were able to drive the expression of arginase cDNA. Such agaA+ transformants displayed arginase expression pattern distinct from that of the parent strain. The results are also consistent with a single catabolic route for arginine in this fungus. A simple yet novel arginine-based selection for filamentous fungal transformation is thus described.

  14. 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

    2015-12-09

    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.

  15. 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.

  16. 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).

  17. 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

  18. Faraday rotation spectroscopy based on permanent magnets for sensitive detection of oxygen at atmospheric conditions.

    PubMed

    Brumfield, Brian; Wysocki, Gerard

    2012-12-31

    A low-power Faraday rotation spectroscopy system that uses permanent rare-earth magnets has been developed for detection of O₂ at 762 nm. The experimental signals are generated using laser wavelength modulation combined with a balanced detection scheme that permits quantum shot noise limited performance. A noise equivalent polarization rotation angle of 8 × 10⁻⁸ rad/Hz¹/² is estimated from the experimental noise, and this agrees well with a theoretical model based on Jones calculus. A bandwidth normalized minimum detection limit to oxygen of 6 ppmv/Hz¹/² with an ultimate minimum of 1.3 ppmv at integration times of ~1 minute has been demonstrated.

  19. Effect of non-lattice oxygen on ZrO2-based resistive switching memory.

    PubMed

    Lin, Chun-Chieh; Chang, Yi-Peng; Lin, Huei-Bo; Lin, Chu-Hsuan

    2012-03-14

    ZrO2-based resistive switching memory has attracted much attention according to its possible application in the next-generation nonvolatile memory. The Al/ZrO2/Pt resistive switching memory with bipolar resistive switching behavior is revealed in this work. The thickness of the ZrO2 film is only 20 nm. The device yield improved by the non-lattice oxygen existing in the ZrO2 film deposited at room temperature is firstly proposed. The stable resistive switching behavior and the long retention time with a large current ratio are also observed. Furthermore, it is demonstrated that the resistive switching mechanism agrees with the formation and rupture of a conductive filament in the ZrO2 film. In addition, the Al/ZrO2/Pt resistive switching memory is also possible for application in flexible electronic equipment because it can be fully fabricated at room temperature.

  20. 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.

  1. [Hemoglobin-based oxygen carriers and trials to substitute red blood cells].

    PubMed

    Smani, Y; Labrude, P; Vigneron, C; Faivre, B

    2007-11-01

    The idea to develop a blood substitute was stimulated by the need of military in the last two world wars and by transmission of pathogenic germs (Hepatitis B in 1960, HIV in 1980 and Hepatitis C in 1990) during blood transfusion that limited the donor blood transfusion. There are two main groups of blood substitutes: perfluorocarbon emulsions and hemoglobin-based oxygen carriers (HBOC). These latter are of natural origin: human, bovine or recombinant and undergo three modifications types: chemicals (intramolecular cross-linking, polymerisation, conjugation to macromolecules and combination of several chemical modifications), genetics or technological by microencapsulation. HBOCs are in different phases of clinical trials and some of them present side effects (hemodynamic and oxidative). The understanding of these effects and the possibility of correcting them, condition their use on a large scale and the economic consequences, which they can generate.

  2. Characterisation of an oxygen sensor based on In/In 2O 3 reference electrode

    NASA Astrophysics Data System (ADS)

    Colominas, S.; Abellà, J.; Victori, L.

    2004-11-01

    A potentiometric sensor for measuring oxygen activity in LBE has been developed since 2000 until today at 'Institut Quimic de Sarria' electrochemistry laboratories. This sensor is based on In/In 2O 3 reference electrode. The last experiments performed with this sensor have been directed to characterise the sensor. For this purpose, the following experiments in stagnant conditions have been performed: effect of the operating temperature from 300 to 500 °C, different covering gases (N 2 + 5% H 2, Ar 99.999%, and N 2 + 10 mg/L O 2) and comparison of different solid electrolytes (ZrO 2/Y 2O 3 and ZrO 2/MgO). Long-term experiments have also been performed to the see the stability of the signal with time.

  3. Trapping of Oxygen Vacancies at Crystallographic Shear Planes in Acceptor-Doped Pb-Based Ferroelectrics.

    PubMed

    Batuk, Dmitry; Batuk, Maria; Tsirlin, Alexander A; Hadermann, Joke; Abakumov, Artem M

    2015-12-01

    The defect chemistry of the ferroelectric material PbTiO3 after doping with Fe(III) acceptor ions is reported. Using advanced transmission electron microscopy and powder X-ray and neutron diffraction, we demonstrate that even at concentrations as low as circa 1.7% (material composition approximately ABO2.95), the oxygen vacancies are trapped into extended planar defects, specifically crystallographic shear planes. We investigate the evolution of these defects upon doping and unravel their detailed atomic structure using the formalism of superspace crystallography, thus unveiling their role in nonstoichiometry in the Pb-based perovskites. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. A combinatorial study of platinum-based oxygen reduction electrocatalysts for hydrogen fuel cells

    NASA Astrophysics Data System (ADS)

    Bonakdarpour, Arman

    This thesis presents measurements of the stability and activities of Pt-based oxygen reduction reaction (ORR) electrocatalysts for proton exchange membrane fuel cells (PEMFC). Because more than 70% of electrochemical losses originate from the cathodic reduction of oxygen, research on ORR catalysts remains very active. Numerous combinatorial libraries of Pt1-xMx (M = Fe, Ni, Mn; 0 ≤ x ≤ 1) and Pt1-x-yMxMy ' (M, M' = Co, Ni, Mn, Fe) were prepared by magnetron sputtering using high surface area nano-structured thin film (NSTF) supports as substrates. The libraries were studied for the corrosion stability of the transition metal elements by acid leaching experiments. The results show that after exposing these libraries to 0.5M H2SO4 (or HClO4) at 80°C for several days, significant amounts of transition metals leach off. When the transition metal content was about 60% or less mostly surface leaching occurred and for more than 60% surface and bulk leaching were observed. The composition of these libraries after acid treatment was very close to the electrocatalysts tested in hydrogen fuel cells, thus showing that acid treatment can mimic the fuel cell environment very well. Alloys of Pt-Ta, on the other hand, showed no dissolution of Ta. However, the presence of more than 10% Ta in the alloy, significantly reduces the ORR activity. The rotating ring-disk electrode technique was used to measure the ORR activity of sputtered Pt1-xCox (0 < x < 0.5) films. After heat treatment a 1.7x gain in the specific current densities were observed. There are claims in the literature that very high activities (about 10x) can be achieved by Pt alloys such as Pt-Co with similar preparation methods. Poor experimental setups are most likely the sources of these observations. High surface area Pt and Pt-Co-Mn catalysts, sputtered onto NSTF supports were studied using the RRDE technique. The Pt-Co-Mn alloy showed a kinetic gain of about 20 mV over Pt for ORR. This is in agreement with the

  5. Selection of construction methods: a knowledge-based approach.

    PubMed

    Ferrada, Ximena; Serpell, Alfredo; 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.

  6. Reporter-based screening and selection of enzymes.

    PubMed

    van Rossum, Teunke; Kengen, Servé W M; van der Oost, John

    2013-07-01

    The biotech industry is continuously seeking for new or improved biocatalysts. The success of these efforts is often hampered by the lack of an efficient screening assay. Thus, to be able to extend the number of enzymes available for industrial applications, high-throughput screening and selection methods are required. In the last few years an impressive range of screening and selection strategies has been developed. In this review, we will mainly focus on in vivo reporter systems in which the activity of a reporter is controlled by the activity of an enzyme of interest. Different mechanisms can be distinguished: (a) binding of the product of the enzymatic reaction to a transcriptional regulator and thereby turning on transcription of the reporter; (b) direct modification of a transcriptional regulator by the enzyme resulting in expression of the reporter; (c) binding of the product to a regulatory riboswitch or ribozyme, resulting in translation of the reporter; and (d) direct modification of the reporter by the enzyme, altering the reporter's activity. The choice for either a selection or a screening strategy depends on the type of reporter, e.g. providing antibiotic resistance (selection) or transmitting a fluorescent signal (screening). Although developing the specificity of each of these reporter-based selection or screening systems towards a certain enzymatic reaction is not yet straightforward, their adjustable modular design appears to be a promise for general applicability in the near future. © 2013 The Authors Journal compilation © 2013 FEBS.

  7. 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

  8. Quantitative susceptibility mapping-based cerebral metabolic rate of oxygen mapping with minimum local variance.

    PubMed

    Zhang, Jingwei; Cho, Junghun; Zhou, Dong; Nguyen, Thanh D; Spincemaille, Pascal; Gupta, Ajay; Wang, Yi

    2017-03-10

    The objective of this study was to demonstrate the feasibility of a cerebral metabolic rate of oxygen (CMRO2 ) mapping method based on its minimum local variance (MLV) without vascular challenge using quantitative susceptibility mapping (QSM) and cerebral blood flow (CBF). Three-dimensional multi-echo gradient echo imaging and arterial spin labeling were performed in 11 healthy subjects to calculate QSM and CBF. Minimum local variance was used to compute whole-brain CMRO2 map from QSM and CBF. The MLV method was compared with a reference method using the caffeine challenge. Their agreement within the cortical gray matter (CGM) was assessed on CMRO2 and oxygen extraction fraction (OEF) maps at both baseline and challenge states. Mean CMRO2 (in µmol/100 g/min) obtained in CGM using the caffeine challenge and MLV were 142 ± 16.5 and 139 ± 14.8 µmol/100 g/min, respectively; the corresponding baseline OEF were 33.0 ± 4.0% and 31.8 ± 3.2%, respectively. The MLV and caffeine challenge methods showed no statistically significant differences across subjects with small ( < 4%) biases in CMRO2 and OEF values. Minimum local variance-based CMRO2 mapping without vascular challenge using QSM and arterial spin labeling is feasible in healthy subjects. Magn Reson Med, 2017. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

  9. Fundamental Investigation of Oxygen Reduction Reaction on Rhodium Sulfide-Based Chalcogenides

    SciTech Connect

    Ziegelbauer, J.; Gatewood, D; Gulla, A; Guinel, M; Ernst, F; Ramaker, D; Mukerjee, S

    2009-01-01

    Synchrotron-based X-ray absorption spectroscopy (XAS), including the surface-specific {Delta}XANES technique, is used to investigate the active reaction site for water activation and the oxygen reduction reaction (ORR) on the novel, mixed-phase chalcogenide electrocatalyst RhxSy/C (De Nora). The specific adsorption of water, OH, and O as a function of overpotential is reported. This study builds on a prior communication based solely on interpreting the XAS spectra of RhxSy with respect to the metallic Rh3S4 phase. Here, a more extensive overview of the electrocatalysis is provided on RhxSy/C, the thermally grown Rh2S3/C and Rh3S4/C preferential phases and a standard 30 wt % Rh/C electrocatalyst, including results obtained by X-ray diffraction (XRD), XAS, high-resolution transmission electron imaging, microanalysis, and electrochemical investigations. Heating of the RhxSy catalysts to prepare the two preferential phases causes Rh segregation and the formation of Rh metal particles, and immersion in TFMSA causes S dissolution and the formation of a Rh skin on the RhxSy samples. It is shown that some Rh-Rh interactions are needed to carry out the ORR. This is present on the Rh6 moieties in both the Rh3S4 and RhxSy catalysts, but a partial Rh skin (present from acid dissolution) is also contributing to the ORR observed on RhxSy. This to our knowledge is the first time a reaction site in a multiphase inorganic framework structure has been investigated in terms of electrocatalytic pathway for oxygen reduction.

  10. Phase diagram of cuprate high-temperature superconductors described by a field theory based on anharmonic oxygen degrees of freedom.

    PubMed

    Hsiao, Jenhao; Martyna, Glenn J; Newns, Dennis M

    2015-03-13

    In high temperature superconductors, although some phenomena such as the Mott transition (MT) at low doping are clearly driven by electron correlations, recent experimental data imply that anharmonic oxygen degrees of freedom-characteristic of perovskite materials-are playing a significant role. A key test of the role of anharmonic oxygen is to reproduce the complex cuprate phase diagram from a simple model. Here, we show that a field theory based on nonlinear coupling to anharmonic oxygens, parametrized from ab initio calculations, quantitatively reproduces the cuprate phase diagram for dopings above the MT. Pairing is mediated by renormalized oxygen vibrations transmuted into excitations of the pseudogap. The observed strong dependence of gap to transition temperature ratio on Tc also emerges from this field theory. This work suggests that including vibrational degrees of freedom is key to developing a complete understanding of the cuprates.

  11. 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

  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. Detection of fluorescence lifetime based on solid state technology and its application to optical oxygen sensing

    NASA Astrophysics Data System (ADS)

    Gruber, Wolfgang R.; O'Leary, Paul; Wolfbeis, Otto S.

    1995-05-01

    This paper presents the development of an instrument using solid state components for luminescence lifetime based sensing. For a number of applications luminescence lifetime based sensing is the preferred method because of its inherent referencing possibility. Further, lifetime based instrumentation promises a simplified optical construction, since the measurement is, within certain limits, independent of the signal intensity. Various measurement schemes have been reported, especially for optical oxygen sensors, using dynamic fluorescence quenching as the information carrier. However, most of them require bulky and expensive instrumentation because of the need for high-frequency modulated excitation sources and detection systems. In general photo-multipliers have been required. We report on the development of a measurement scheme using low-cost semiconductor devices (light emitting diodes, photo-diodes). The detection system is based on heterodyne demodulation techniques for reduction of the signal frequency range. The basic principles of the system is described and a comparison with existing measurement schemes is presented. The capabilities of the system are demonstrated with measurements on two sensor types having luminescence lifetimes in the range of 1 microsecond(s) and 50 microsecond(s) . Finally, a custom CMOS integrated circuit is presented which implements the front-end of the detection system.

  14. Fluorescence-lifetime-based sensors: oxygen sensing and other biomedical applications

    NASA Astrophysics Data System (ADS)

    Randers-Eichhorn, Lisa; Bartlett, Roscoe A.; Sipior, Jeffrey; Frey, Douglas D.; Carter, Gary M.; Lakowicz, Joseph R.; Rao, Govind

    1996-05-01

    Murine hybridomas were cultivated in tissue culture flasks. Dissolved oxygen tensions in the gas and liquid phases during cell growth were measured non-invasively by an optical oxygen sensor. Readings were made with caps both cracked open and completely closed. During cell growth, gas phase oxygen concentrations remained near atmospheric levels, while the oxygen tension at the bottom of the flasks eventually reached zero. These results suggest that the widespread practice of cracking open tissue culture flask caps during cell growth with a view to supplying adequate oxygen to cells is ineffective and unnecessary. The mass transfer characteristics of the tissue culture flask indicate the dominant resistance to oxygen mass transfer to the cells was the liquid media. The mass transfer rates through the liquid layer under standard laboratory conditions were found to be greater than those predicted by diffusion alone, suggesting microscale mixing. Volumetric and specific oxygen consumption rates were calculated from the sensor data, and were comparable to published values. A recently developed single fiber optic oxygen sensor is described. This new sensor will provide oxygen concentrations at various levels in the tissue culture flasks, allowing more accurate modeling of oxygen diffusion.

  15. 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.

  16. Oxygen measurements to improve singlet oxygen dosimetry

    NASA Astrophysics Data System (ADS)

    Kim, Michele M.; Penjweini, Rozhin; Ong, Yi Hong; Finlay, Jarod C.; Zhu, Timothy C.

    2017-02-01

    Photodynamic therapy (PDT) involves interactions between the three main components of light fluence, photosensitizer concentration, and oxygenation. Currently, singlet oxygen explicit dosimetry (SOED) has focused on the first two of these components. The macroscopic model to calculate reacted singlet oxygen has previously involved a fixed initial ground state oxygen concentration. A phosphorescence-based oxygen probe was used to measure ground state oxygen concentration throughout treatments for mice bearing radioactively induced fibroscarcoma tumors. Photofrin-, BPD-, and HPPH-mediated PDT was performed on mice. Model-calculated oxygen and measured oxygen was compared to evaluate the macroscopic model as well as the photochemical parameters involved. Oxygen measurements at various depths were compared to calculated values. Furthermore, we explored the use of noninvasive diffuse correlation spectroscopy (DCS) to measure tumor blood flow changes in response to PDT to improve the model calculation of reacted singlet oxygen. Mice were monitored after treatment to see the effect of oxygenation on long-term recurrence-free survival as well as the efficacy of using reacted singlet oxygen as a predictive measure of outcome. Measurement of oxygenation during treatment helps to improve SOED as well as confirm the photochemical parameters involved in the macroscopic model. Use of DCS in predicting oxygenation changes was also investigated.

  17. Auditory-model based robust feature selection for speech recognition.

    PubMed

    Koniaris, Christos; Kuropatwinski, Marcin; Kleijn, W Bastiaan

    2010-02-01

    It is shown that robust dimension-reduction of a feature set for speech recognition can be based on a model of the human auditory system. Whereas conventional methods optimize classification performance, the proposed method exploits knowledge implicit in the auditory periphery, inheriting its robustness. Features are selected to maximize the similarity of the Euclidean geometry of the feature domain and the perceptual domain. Recognition experiments using mel-frequency cepstral coefficients (MFCCs) confirm the effectiveness of the approach, which does not require labeled training data. For noisy data the method outperforms commonly used discriminant-analysis based dimension-reduction methods that rely on labeling. The results indicate that selecting MFCCs in their natural order results in subsets with good performance.

  18. Uniform design based SVM model selection for face recognition

    NASA Astrophysics Data System (ADS)

    Li, Weihong; Liu, Lijuan; Gong, Weiguo

    2010-02-01

    Support vector machine (SVM) has been proved to be a powerful tool for face recognition. The generalization capacity of SVM depends on the model with optimal hyperparameters. The computational cost of SVM model selection results in application difficulty in face recognition. In order to overcome the shortcoming, we utilize the advantage of uniform design--space filling designs and uniformly scattering theory to seek for optimal SVM hyperparameters. Then we propose a face recognition scheme based on SVM with optimal model which obtained by replacing the grid and gradient-based method with uniform design. The experimental results on Yale and PIE face databases show that the proposed method significantly improves the efficiency of SVM model selection.

  19. Selective Growth of Monoatomic Cu Rows at Step Edges on Si(111) Substrates in Ultralow-Dissolved-Oxygen Water

    NASA Astrophysics Data System (ADS)

    Tokuda, Norio; Nishizawa, Masayasu; Miki, Kazushi; Yamasaki, Satoshi; Hasunuma, Ryu; Yamabe, Kikuo

    2005-04-01

    We have fabricated high-aspect-ratio monoatomic Cu rows along atomic step edges on vicinal Si(111) substrates. The method consists of two wet processes: (1) the formation of a step/terrace structure by immersing a Si(111) substrate in ultralow-dissolved-oxygen water (LOW) and (2) the formation of the nanowires by immersion in LOW containing Cu ions. A systematic investigation of Si(111) surfaces with the nanowire has been performed by means of atomic force microscopy, Fourier-transform infrared absorption spectroscopy, and total-reflection X-ray fluorescence spectroscopy.

  20. New RSA-Based (Selectively) Convertible Undeniable Signature Schemes

    NASA Astrophysics Data System (ADS)

    Phong, Le Trieu; Kurosawa, Kaoru; Ogata, Wakaha

    In this paper, we design and analyze some new and practical (selectively) convertible undeniable signature (SCUS) schemes in both random oracle and standard model, which enjoy several merits over existing schemes in the literature. In particular, we design the first practical RSA-based SCUS schemes secure in the standard model. On the path, we also introduce two moduli RSA assumptions, including the strong twin RSA assumption, which is the RSA symmetry of the strong twin Diffie-Hellman assumption (Eurocrypt'08).