Science.gov

Sample records for fuel reactivity formation

  1. Water reactive hydrogen fuel cell power system

    DOEpatents

    Wallace, Andrew P; Melack, John M; Lefenfeld, Michael

    2014-11-25

    A water reactive hydrogen fueled power system includes devices and methods to combine reactant fuel materials and aqueous solutions to generate hydrogen. The generated hydrogen is converted in a fuel cell to provide electricity. The water reactive hydrogen fueled power system includes a fuel cell, a water feed tray, and a fuel cartridge to generate power for portable power electronics. The removable fuel cartridge is encompassed by the water feed tray and fuel cell. The water feed tray is refillable with water by a user. The water is then transferred from the water feed tray into the fuel cartridge to generate hydrogen for the fuel cell which then produces power for the user.

  2. Water reactive hydrogen fuel cell power system

    DOEpatents

    Wallace, Andrew P; Melack, John M; Lefenfeld, Michael

    2014-01-21

    A water reactive hydrogen fueled power system includes devices and methods to combine reactant fuel materials and aqueous solutions to generate hydrogen. The generated hydrogen is converted in a fuel cell to provide electricity. The water reactive hydrogen fueled power system includes a fuel cell, a water feed tray, and a fuel cartridge to generate power for portable power electronics. The removable fuel cartridge is encompassed by the water feed tray and fuel cell. The water feed tray is refillable with water by a user. The water is then transferred from the water feed tray into a fuel cartridge to generate hydrogen for the fuel cell which then produces power for the user.

  3. Engine combustion control via fuel reactivity stratification

    DOEpatents

    Reitz, Rolf Deneys; Hanson, Reed M.; Splitter, Derek A.; Kokjohn, Sage L.

    2016-06-28

    A compression ignition engine uses two or more fuel charges having two or more reactivities to control the timing and duration of combustion. In a preferred implementation, a lower-reactivity fuel charge is injected or otherwise introduced into the combustion chamber, preferably sufficiently early that it becomes at least substantially homogeneously dispersed within the chamber before a subsequent injection is made. One or more subsequent injections of higher-reactivity fuel charges are then made, and these preferably distribute the higher-reactivity matter within the lower-reactivity chamber space such that combustion begins in the higher-reactivity regions, and with the lower-reactivity regions following thereafter. By appropriately choosing the reactivities of the charges, their relative amounts, and their timing, combustion can be tailored to achieve optimal power output (and thus fuel efficiency), at controlled temperatures (and thus controlled NOx), and with controlled equivalence ratios (and thus controlled soot).

  4. Engine combustion control via fuel reactivity stratification

    DOEpatents

    Reitz, Rolf Deneys; Hanson, Reed M; Splitter, Derek A; Kokjohn, Sage L

    2013-12-31

    A compression ignition engine uses two or more fuel charges having two or more reactivities to control the timing and duration of combustion. In a preferred implementation, a lower-reactivity fuel charge is injected or otherwise introduced into the combustion chamber, preferably sufficiently early that it becomes at least substantially homogeneously dispersed within the chamber before a subsequent injection is made. One or more subsequent injections of higher-reactivity fuel charges are then made, and these preferably distribute the higher-reactivity matter within the lower-reactivity chamber space such that combustion begins in the higher-reactivity regions, and with the lower-reactivity regions following thereafter. By appropriately choose the reactivities of the charges, their relative amounts, and their timing, combustion can be tailored to achieve optimal power output (and thus fuel efficiency), at controlled temperatures (and thus controlled NOx), and with controlled equivalence ratios (and thus controlled soot).

  5. Engine combustion control via fuel reactivity stratification

    DOEpatents

    Reitz, Rolf Deneys; Hanson, Reed M.; Splitter, Derek A.; Kokjohn, Sage L.

    2015-07-14

    A compression ignition engine uses two or more fuel charges having two or more reactivities to control the timing and duration of combustion. In a preferred implementation, a lower-reactivity fuel charge is injected or otherwise introduced into the combustion chamber, preferably sufficiently early that it becomes at least substantially homogeneously dispersed within the chamber before a subsequent injection is made. One or more subsequent injections of higher-reactivity fuel charges are then made, and these preferably distribute the higher-reactivity matter within the lower-reactivity chamber space such that combustion begins in the higher-reactivity regions, and with the lower-reactivity regions following thereafter. By appropriately choosing the reactivities of the charges, their relative amounts, and their timing, combustion can be tailored to achieve optimal power output (and thus fuel efficiency), at controlled temperatures (and thus controlled NOx), and with controlled equivalence ratios (and thus controlled soot).

  6. Heating subsurface formations by oxidizing fuel on a fuel carrier

    SciTech Connect

    Costello, Michael; Vinegar, Harold J.

    2012-10-02

    A method of heating a portion of a subsurface formation includes drawing fuel on a fuel carrier through an opening formed in the formation. Oxidant is supplied to the fuel at one or more locations in the opening. The fuel is combusted with the oxidant to provide heat to the formation.

  7. Biodiesel Fuel Property Effects on Particulate Matter Reactivity

    SciTech Connect

    Williams, A.; Black, S.; McCormick, R. L.

    2010-06-01

    Controlling diesel particulate emissions to meet the 2007 U.S. standard requires the use of a diesel particulate filter (DPF). The reactivity of soot, or the carbon fraction of particulate matter, in the DPF and the kinetics of soot oxidation are important in achieving better control of aftertreatment devices. Studies showed that biodiesel in the fuel can increase soot reactivity. This study therefore investigated which biodiesel fuel properties impact reactivity. Three fuel properties of interest included fuel oxygen content and functionality, fuel aromatic content, and the presence of alkali metals. To determine fuel effects on soot reactivity, the performance of a catalyzed DPF was measured with different test fuels through engine testing and thermo-gravimetric analysis. Results showed no dependence on the aromatic content or the presence of alkali metals in the fuel. The presence and form of fuel oxygen was the dominant contributor to faster DPF regeneration times and soot reactivity.

  8. Assessment of reactivity transient experiments with high burnup fuel

    SciTech Connect

    Ozer, O.; Yang, R.L.; Rashid, Y.R.; Montgomery, R.O.

    1996-03-01

    A few recent experiments aimed at determining the response of high-burnup LWR fuel during a reactivity initiated accident (RIA) have raised concerns that existing failure criteria may be inappropriate for such fuel. In particular, three experiments (SPERT CDC-859, NSRR HBO-1 and CABRI REP Na-1) appear to have resulted in fuel failures at only a fraction of the anticipated enthalpy levels. In evaluating the results of such RIA simulation experiments, however, it is necessary that the following two key considerations be taken into account: (1) Are the experiments representative of conditions that LWR fuel would experience during an in-reactor RIA event? (2) Is the fuel that is being utilized in the tests representative of the present (or anticipated) population of LWR fuel? Conducting experiments under conditions that can not occur in-reactor can trigger response modes that could not take place during in-reactor operation. Similarly, using unrepresentative fuel samples for the tests will produce failure information that is of limited relevance to commercial LWR fuel. This is particularly important for high-burnup fuel since the manner under which the test samples are base-irradiated prior to the test will impact the mechanical properties of the cladding and will therefore affect the RIA response. A good example of this effect can be seen in the results of the SPERT CDC-859 test and in the NSRR JM-4 and JM-5 tests. The conditions under which the fuel used for these tests was fabricated and/or base-irradiated prior to the RIA pulse resulted in the formation of multiple cladding defects in the form of hydride blisters. When this fuel was subjected to the RIA power pulse, it failed by developing multiple cracks that were closely correlated with the locations of the pre-existing hydride blisters. In the case of the JM tests, many of the cracks formed within the blisters themselves and did not propagate beyond the heavily hydrided regions.

  9. Formate Formation and Formate Conversion in Biological Fuels Production

    PubMed Central

    Crable, Bryan R.; Plugge, Caroline M.; McInerney, Michael J.; Stams, Alfons J. M.

    2011-01-01

    Biomethanation is a mature technology for fuel production. Fourth generation biofuels research will focus on sequestering CO2 and providing carbon-neutral or carbon-negative strategies to cope with dwindling fossil fuel supplies and environmental impact. Formate is an important intermediate in the methanogenic breakdown of complex organic material and serves as an important precursor for biological fuels production in the form of methane, hydrogen, and potentially methanol. Formate is produced by either CoA-dependent cleavage of pyruvate or enzymatic reduction of CO2 in an NADH- or ferredoxin-dependent manner. Formate is consumed through oxidation to CO2 and H2 or can be further reduced via the Wood-Ljungdahl pathway for carbon fixation or industrially for the production of methanol. Here, we review the enzymes involved in the interconversion of formate and discuss potential applications for biofuels production. PMID:21687599

  10. Formation and Reactivity of Biogenic Iron Microminerals

    SciTech Connect

    Beveridge, Terrance J.; Ferris, F. Grant

    2001-08-15

    The overall purpose of the project was to explore and quantify the processes that control the formation and reactivity of biogenic iron microminerals and their impact on the solubility of metal contaminants. The research addressed how surface components of bacterial cells, extracellular organic material, and the aqueous geochemistry of the DIRB microenvironment impacts the mineralogy, chemical state and micromorphology of reduced iron phases.

  11. Formation and Reactivity of Biogenic Iron Microminerals

    SciTech Connect

    Beveridge, Terrance J.; Glasauer, Susan; Korenevsky, Anton; Ferris, F. Grant

    2000-08-08

    The overall purpose of the project is to explore and quantify the processes that control the formation and reactivity of biogenic iron microminerals and their impact on the solubility of metal contaminants. The research addresses how surface components of bacterial cells, extracellular organic material, and the aqueous geochemistry of the DIRB microenvironment impacts the mineralogy, chemical state and micromorphology of reduced iron phases.

  12. Effects of poison panel shrinkage and gaps on fuel storage rack reactivity

    SciTech Connect

    Boyd, W.A.; Mueller, D.E.

    1988-01-01

    Fixed poison panels are used in spent fuel rack designs to increase enrichment limits and reduce cell spacing; therefore, assurances that the maximum rack reactivity will meet the design limit (0.95) throughout the lifetime of the racks depend on the continued effectiveness of the poison with time. Industry data have shown that poison panels will shrink under irradiated conditions. From recent data, however, poison panels have been found to have gaps spanning their width after relatively short operating periods. This paper presents results of studies showing the fuel rack reactivity changes associated with poison panel shrinkage and formation of gaps. The discovery of gaps in the fuel rack poison panels at an operating plant raises concerns regarding the effectiveness of the poison over the lifetime of the fuel racks. Studies performed to evaluate the effect of the poison panel shrinkage on reactivity show that reactivity changes from zero to several percent are possible depending on the initial panel size. Results of recent studies show that some gaps can be accommodated in the fuel rack poison panels at the fuel midplane without causing the fuel rack K{sub eff} limit to be exceeded. With worst-case assumptions concerning gap size and the number of panels affected, other actions will likely be required to show that the rack K{sub eff} design limit will not be exceeded.

  13. Oxidation and Gum Formation in Diesel Fuels.

    DTIC Science & Technology

    2014-09-26

    AD A157 41@ OX<IDATION AND GUM FORMATION IN DIESEL FUELS(U) SRI i/i INTERNATIONAL MENLO PARK CA CHEMISTRY LAB F R MAYO 0MAY 85 ARO-2i65 2-EG DRA29-84...REPORT & PERIOD COVERED Interim Technical No. 2 oxidation and Gum Formation in Diesel Fuels 9/10/84 to 4/30/85 7. AUTHOR(s) S OTATO RNrNME0 Frank R. Mayo...oxidation and gum and deposit formation from n-dodecage, tetralin’, 2-ethylnaphthalene, and diesel fuels at 430, 600 100 0, and 130 C and discusses their

  14. Reactive spreading: Adsorption, ridging and compound formation

    SciTech Connect

    Saiz, E.; Cannon, R.M.; Tomsia, A.P.

    2000-09-11

    Reactive spreading, in which a chemically active element is added to promote wetting of noble metals on nonmetallic materials, is evaluated. Theories for the energetics and kinetics of the necessary steps involved in spreading are outlined and compared to the steps in compound formation that typically accompany reactive wetting. These include: fluid flow, active metal adsorption, including nonequilibrium effects, and triple line ridging. All of these can be faster than compound nucleation under certain conditions. Analysis and assessment of recently reported experiments on metal/ceramic systems lead to a focus on those conditions under which spreading proceeds ahead of the actual formation of a new phase at the interface. This scenario may be more typical than believed, and perhaps the most effective situation leading to enhanced spreading. A rationale for the pervasive variability and hysteresis observed during high temperature wetting also emerges.

  15. Reactive flash volatilization of fluid fuels

    DOEpatents

    Schmidt, Lanny D.; Dauenhauer, Paul J.; Dreyer, Bradon J.; Salge, James R.

    2013-01-08

    The invention provides methods for the production of synthesis gas. More particularly, various embodiments of the invention relate to systems and methods for volatilizing fluid fuel to produce synthesis gas by using a metal catalyst on a solid support matrix.

  16. Formation and Reactivity of Biogenic Iron Microminerals

    SciTech Connect

    Beveridge, Terrance J.; Ferris, F. Grant

    1999-06-01

    The overall purpose of the project is to explore and quantify the processes that control the formation and reactivity of biogenic iron microminerals, and the impact of these processes on the solubility of metal contaminants, e.g., uranium, chromium and nickel. The research addresses how surface components of bacterial cells, extracellular organic material, and the aqueous geochemistry of the DIRB microenvironment impacts the mineralogy, chemical state and micromorphology of reduced iron phases.

  17. Reactive Behavior of K-Basin Spent Nuclear Fuel

    SciTech Connect

    Abrefah, John; Siciliano, Edward R.; Damschen, Dennis W.; Schlahta, Stephan N.

    2002-12-31

    The Hanford Spent Nuclear Fuel Project focuses its efforts on determining how to safely move the degraded N-Reactor spent fuel from water-stored basins to a dry storage facility. As part of this effort, the project initiated experimental studies to address issues relating to the chemical reactivity of the degraded/corroded metallic uranium material. The studies generated a limited set of data on chemical reaction rates of the N-Reactor spent fuel in dry air, moist air, and moist-inert atmospheres for comparison with published data on unirradiated/ irradiated metallic uranium. Based on the laboratory data, the project chose to use a conservative enhancement factor in analyzing the oxidation behavior of the spent metallic fuel. However, there is a need for the project to increase the fuel throughput for the drying treatment process by implementing certain design optimization steps. The study discussed in this paper re-evaluated the previous laboratory data in conjunction with the Cold Vacuum Drying (CVD) process experience and determined whether the built-in level of conservatism could accommodate the potential changes in the process without compromising public and worker safety. Evaluations based on laboratory data on samples taken from the N-Reactor spent fuel showed no reactivity enhancement in moist atmosphere. The established reaction rate constant was used to accurately determine the reactive surface areas of corroded N-Reactor fuel elements. The method was then used to provide a good estimate of the exposed uranium surface area in the loaded MCOs.

  18. Deposit formation in hydrocarbon rocket fuels

    NASA Technical Reports Server (NTRS)

    Roback, R.; Szetela, E. J.; Spadaccini, L. J.

    1981-01-01

    An experimental program was conducted to study deposit formation in hydrocarbon fuels under flow conditions that exist in high-pressure, rocket engine cooling systems. A high pressure fuel coking test apparatus was designed and developed and was used to evaluate thermal decomposition (coking) limits and carbon deposition rates in heated copper tubes for two hydrocarbon rocket fuels, RP-1 and commercial-grade propane. Tests were also conducted using JP-7 and chemically-pure propane as being representative of more refined cuts of the baseline fuels. A parametric evaluation of fuel thermal stability was performed at pressures of 136 atm to 340 atm, bulk fuel velocities in the range 6 to 30 m/sec, and tube wall temperatures in the range 422 to 811 K. Results indicated that substantial deposit formation occurs with RP-1 fuel at wall temperatures between 600 and 800 K, with peak deposit formation occurring near 700 K. No improvements were obtained when deoxygenated JP-7 fuel was substituted for RP-1. The carbon deposition rates for the propane fuels were generally higher than those obtained for either of the kerosene fuels at any given wall temperature. There appeared to be little difference between commercial-grade and chemically-pure propane with regard to type and quantity of deposit. Results of tests conducted with RP-1 indicated that the rate of deposit formation increased slightly with pressure over the range 136 atm to 340 atm. Finally, lating the inside wall of the tubes with nickel was found to significantly reduce carbon deposition rates for RP-1 fuel.

  19. Critical role of water content in the formation and reactivity of uranium, neptunium, and plutonium iodates under hydrothermal conditions: implications for the oxidative dissolution of spent nuclear fuel.

    PubMed

    Bray, Travis H; Ling, Jie; Choi, Eun Sang; Brooks, James S; Beitz, James V; Sykora, Richard E; Haire, Richard G; Stanbury, David M; Albrecht-Schmitt, Thomas E

    2007-04-30

    The reactions of 237NpO2 with excess iodate under acidic hydrothermal conditions result in the isolation of the neptunium(IV), neptunium(V), and neptunium(VI) iodates, Np(IO3)4, Np(IO3)4.nH2O.nHIO3, NpO2(IO3), NpO2(IO3)2(H2O), and NpO2(IO3)2.H2O, depending on both the pH and the amount of water present in the reactions. Reactions with less water and lower pH favor reduced products. Although the initial redox processes involved in the reactions between 237NpO2 or 242PuO2 and iodate are similar, the low solubility of Pu(IO3)4 dominates product formation in plutonium iodate reactions to a much greater extent than does Np(IO3)4 in the neptunium iodate system. UO2 reacts with iodate under these conditions to yield uranium(VI) iodates solely. The isotypic structures of the actinide(IV) iodates, An(IO3)4 (An=Np, Pu), are reported and consist of one-dimensional chains of dodecahedral An(IV) cations bridged by iodate anions. The structure of Np(IO3)4.nH2O.nHIO3 is constructed from NpO9 tricapped-trigonal prisms that are bridged by iodate into a polar three-dimensional framework structure. Second-harmonic-generation measurements on a polycrystalline sample of the Th analogue of Np(IO3)4.nH2O.nHIO3 reveal a response of approximately 12x that of alpha-SiO2. Single-crystal magnetic susceptibility measurements of Np(IO3)4 show magnetically isolated Np(IV) ions.

  20. Critical Role of Water Content in the Formation and Reactivity of Uraniu, Neptunium, and Plutonium Iodates Under Hydrothermal Conditions: Implications for the Oxidative Dissolution of Spent Nuclear Fuel

    SciTech Connect

    Bray, T. H.; Ling, Jie; Choi, E- Sang; Brooks, James S.; Beitz, James V.; Sykora, Richard E.; Haire, Richard {Dick} G; Stanbury, David M.; Albrecht-Schmitt, Thomas E.

    2007-01-01

    The reactions of {sup 237}NpO{sub 2} with excess iodate under acidic hydrothermal conditions result in the isolation of the neptunium(IV), neptunium(V), and neptunium(VI) iodates, Np(IO{sub 3}){sub 4}, Np(IO{sub 3}){sub 4}{center_dot}nH{sub 2}O{center_dot}nHIO{sub 3}, NpO2(IO3), NpO2(IO3)2(H2O), and NpO{sub 2}(IO{sub 3}){sub 2}{center_dot}H{sub 2}O, depending on both the pH and the amount of water present in the reactions. Reactions with less water and lower pH favor reduced products. Although the initial redox processes involved in the reactions between {sup 237}NpO{sub 2} or {sup 242}PuO{sub 2} and iodate are similar, the low solubility of Pu(IO{sub 3}){sub 4} dominates product formation in plutonium iodate reactions to a much greater extent than does Np(IO{sub 3}){sub 4} in the neptunium iodate system. UO{sub 2} reacts with iodate under these conditions to yield uranium(VI) iodates solely. The isotypic structures of the actinide(IV) iodates, An(IO{sub 3}){sub 4} (An = Np, Pu), are reported and consist of one-dimensional chains of dodecahedral An(IV) cations bridged by iodate anions. The structure of Np(IO3)4{center_dot}nH2O{center_dot}nHIO3 is constructed from NpO9 tricapped-trigonal prisms that are bridged by iodate into a polar three-dimensional framework structure. Second-harmonic-generation measurements on a polycrystalline sample of the Th analogue of Np(IO{sub 3}){sub 4}{center_dot}nH{sub 2}O{center_dot}nHIO{sub 3} reveal a response of approximately 12x that of {alpha}-SiO{sub 2}. Single-crystal magnetic susceptibility measurements of Np(IO{sub 3}){sub 4} show magnetically isolated Np(IV) ions.

  1. Direct formate fuel cells: A review

    NASA Astrophysics Data System (ADS)

    An, L.; Chen, R.

    2016-07-01

    Direct formate fuel cells (DFFC), which convert the chemical energy stored in formate directly into electricity, are recently attracting more attention, primarily because of the use of the carbon-neutral fuel and the low-cost electrocatalytic and membrane materials. As an emerging energy technology, the DFFC has made a rapid progress in recent years (currently, the state-of-the-art power density is 591 mW cm-2 at 60 °C). This article provides a review of past research on the development of this type of fuel cell, including the working principle, mechanisms and materials of the electrocatalytic oxidation of formate, singe-cell designs and performance, as well as innovative system designs. In addition, future perspectives with regard to the development of this fuel cell system are also highlighted.

  2. Engine combustion control at low loads via fuel reactivity stratification

    DOEpatents

    Reitz, Rolf Deneys; Hanson, Reed M; Splitter, Derek A; Kokjohn, Sage L

    2014-10-07

    A compression ignition (diesel) engine uses two or more fuel charges during a combustion cycle, with the fuel charges having two or more reactivities (e.g., different cetane numbers), in order to control the timing and duration of combustion. By appropriately choosing the reactivities of the charges, their relative amounts, and their timing, combustion can be tailored to achieve optimal power output (and thus fuel efficiency), at controlled temperatures (and thus controlled NOx), and with controlled equivalence ratios (and thus controlled soot). At low load and no load (idling) conditions, the aforementioned results are attained by restricting airflow to the combustion chamber during the intake stroke (as by throttling the incoming air at or prior to the combustion chamber's intake port) so that the cylinder air pressure is below ambient pressure at the start of the compression stroke.

  3. Fuels for fuel cells: Fuel and catalyst effects on carbon formation

    SciTech Connect

    Borup, R. L.; Inbody, M. A.; Perry, W. L.; Parkinson, W. J. ,

    2002-01-01

    The goal of this research is to explore the effects of fuels, fuel constituents, additives and impurities on the performance of on-board hydrogen generation devices and consequently on the overall performance of fuel cell systems using reformed hydrocarbon fuels. Different fuels and components have been tested in automotive scale, adiabatic autothermal reactors to observe their relative reforming characteristics with various operating conditions. Carbon formation has been modeled and was experimentally monitored in situ during operation by laser measurements of the effluent reformate. Ammonia formation was monitored, and conditions varied to observe under what conditions N H 3 is made.

  4. Gum and Deposit Formation in Diesel Fuels

    DTIC Science & Technology

    1988-05-15

    this C-C coupling is superseded by the oxidative coupling mechanism above. Still another mechanism is aldol -type condensations and esterifica- tions of...that much more naphthaldehyde than naphthoic acid is formed. Gum formation by aldol condensations and esterifcation of oxida- tion products (Mayo, 1975...propagation and termination during oxidation, (2) a coupling of fuel molecules by decomposing peroxides in the absence of oxygen, and (3) a condensation

  5. Characterization of Soluble Macromolecular Oxidatively Reactive Species (SMORS) from middle distillate diesel fuels: Their origin and role in instability

    SciTech Connect

    Wechter, M.A.; Hardy, D.R.

    1995-04-01

    Compositional characterization of a solid phase material isolated by extraction from filtered liquid phase diesel fuels is reported. This solid phase material (SMORS) is shown to be the product of reactive fuel constituents and intermediate to the formation of fuel insoluble sludge. The composition of this material changes during blending processes and tends to become more oxygen rich and thus more polar. Elemental analysis, average molecular weight and pyrolysis mass spectral data are presented for SMORS from a number of representative blended fuels and their blending stocks. SMORS has been shown to be made up of oxidized trimers, tetramers and possibly higher n-mers of nitrogen containing precursors originally present in the fuel. It is not possible to determine the SMORS precursors in field aged fuel (such as those in this study) since these precursors are essentially depleted from the fuel by the time very small amounts of SMORS have been formed.

  6. Evaluation of reactivity shutdown margin for nuclear fuel reload optimization

    SciTech Connect

    Wong, Hing-Ip; Maldonado, G.I.

    1995-12-31

    The FORMOSA-P code is a nuclear fuel management optimization package that combines simulated annealing (SA) and nodal generalized perturbation theory (GPT). Recent studies at Electricite de France (EdF-Clamart) have produced good results for power-peaking minimizations under multiple limiting control rod configurations. However, since the reactivity shutdown margin is not explicitly treated as an objective or constraint function, then any optimal loading patterns (LPs) are not guaranteed to yield an adequate shutdown margin (SDM). This study describes the implementation of the SDM calculation within a FORMOSA-P optimization. Maintaining all additional computational requirements to a minimum was a key consideration.

  7. String cavitation formation inside fuel injectors

    NASA Astrophysics Data System (ADS)

    Reid, B. A.; Gavaises, M.; Mitroglou, N.; Hargrave, G. K.; Garner, C. P.; McDavid, R. M.

    2015-12-01

    The formation of vortex or ‘string’ cavitation has been visualised at pressures up to 2000 bar in an automotive-sized optical diesel fuel injector nozzle. The multi-hole nozzle geometry studied allowed observation of the hole-to-hole vortex interaction and, in particular, that of a bridging vortex in the sac region between the holes. Above a threshold Reynolds number, their formation and appearance during a 2 ms injection event was repeatable and independent of upstream pressure and cavitation number. In addition, two different hole layouts and threedimensional flow simulations have been employed to describe how, the relative positions of adjacent holes influenced the formation and hole-to-hole interaction of the observed string cavitation vortices, with good agreement between the experimental and simulation results being achieved.

  8. Formation and Detoxification of Reactive Oxygen Species

    ERIC Educational Resources Information Center

    Kuciel, Radoslawa; Mazurkiewicz, Aleksandra

    2004-01-01

    A model of reactive oxygen species metabolism is proposed as a laboratory exercise for students. The superoxide ion in this model is generated during the reaction of oxidation of xanthine, catalyzed by xanthine oxidase. The effect of catalase, superoxide dismutase, and allopurinol on superoxide ion generation and removal in this system is also…

  9. Formation and Detoxification of Reactive Oxygen Species

    ERIC Educational Resources Information Center

    Kuciel, Radoslawa; Mazurkiewicz, Aleksandra

    2004-01-01

    A model of reactive oxygen species metabolism is proposed as a laboratory exercise for students. The superoxide ion in this model is generated during the reaction of oxidation of xanthine, catalyzed by xanthine oxidase. The effect of catalase, superoxide dismutase, and allopurinol on superoxide ion generation and removal in this system is also…

  10. Mitochondrial formation of reactive oxygen species

    PubMed Central

    Turrens, Julio F

    2003-01-01

    The reduction of oxygen to water proceeds via one electron at a time. In the mitochondrial respiratory chain, Complex IV (cytochrome oxidase) retains all partially reduced intermediates until full reduction is achieved. Other redox centres in the electron transport chain, however, may leak electrons to oxygen, partially reducing this molecule to superoxide anion (O2−•). Even though O2−• is not a strong oxidant, it is a precursor of most other reactive oxygen species, and it also becomes involved in the propagation of oxidative chain reactions. Despite the presence of various antioxidant defences, the mitochondrion appears to be the main intracellular source of these oxidants. This review describes the main mitochondrial sources of reactive species and the antioxidant defences that evolved to prevent oxidative damage in all the mitochondrial compartments. We also discuss various physiological and pathological scenarios resulting from an increased steady state concentration of mitochondrial oxidants. PMID:14561818

  11. Formation and Reactivity of Biogenic Iron Minerals

    SciTech Connect

    Ferris, F. Grant

    2003-06-01

    In the current study we aimed to determine how the cell surface polymers, such as lipopolysaccharide (LPS) and capsular material, of a number of strains of Shewanella influenced surface proton binding behavior. An investigation of this kind is pertinent as surface proton binding site reactivity may influence a number of important eco-physiological factors. For example, proton binding sites may sequester Fe2+, as well as other metals like Ni2+, and thus inhibit the supply and metabolic reduction of Fe3+.(Parmar et al. 2001) Further understanding the cell surface reactivity of Shewanella is also important as this may influence the ability of the microorganism to adhere and interact with metal oxides and hydroxides. This study combined acid-base titration analyses to determine proton binding behavior with SDS-PAGE analysis of LPS.

  12. Tumor reactive stroma in cholangiocarcinoma: The fuel behind cancer aggressiveness

    PubMed Central

    Brivio, Simone; Cadamuro, Massimiliano; Strazzabosco, Mario; Fabris, Luca

    2017-01-01

    Cholangiocarcinoma (CCA) is a highly aggressive epithelial malignancy still carrying a dismal prognosis, owing to early lymph node metastatic dissemination and striking resistance to conventional chemotherapy. Although mechanisms underpinning CCA progression are still a conundrum, it is now increasingly recognized that the desmoplastic microenvironment developing in conjunction with biliary carcinogenesis, recently renamed tumor reactive stroma (TRS), behaves as a paramount tumor-promoting driver. Indeed, once being recruited, activated and dangerously co-opted by neoplastic cells, the cellular components of the TRS (myofibroblasts, macrophages, endothelial cells and mesenchymal stem cells) continuously rekindle malignancy by secreting a huge variety of soluble factors (cyto/chemokines, growth factors, morphogens and proteinases). Furthermore, these factors are long-term stored within an abnormally remodeled extracellular matrix (ECM), which in turn can deleteriously mold cancer cell behavior. In this review, we will highlight evidence for the active role played by reactive stromal cells (as well as by the TRS-associated ECM) in CCA progression, including an overview of the most relevant TRS-derived signals possibly fueling CCA cell aggressiveness. Hopefully, a deeper knowledge of the paracrine communications reciprocally exchanged between cancer and stromal cells will steer the development of innovative, combinatorial therapies, which can finally hinder the progression of CCA, as well as of other cancer types with abundant TRS, such as pancreatic and breast carcinomas. PMID:28396716

  13. Effects of fuel type, driving cycle, and emission status on in-use vehicle exhaust reactivity.

    PubMed

    Ho, J; Winer, A M

    1998-07-01

    The introduction of reformulated gasolines significantly reduced exhaust hydrocarbon (HC) mass emissions, but few data are available concerning how these new fuels affect exhaust reactivity. Similarly, while it is well established that high-emitting vehicles contribute a significant portion of total mobile source HC mass emissions, it is also important to evaluate the exhaust reactivity from these vehicles. The objective of this study was to evaluate the relative influence on in-use vehicle exhaust reactivity of three critical factors: fuel, driving cycle, and vehicle emission status. Nineteen in-use vehicles were tested with seven randomly assigned fuel types and two driving cycles: the Federal Test Procedure (FTP) and the Unified Cycle (UC). Total exhaust reactivity was not statistically different between the FTP and UC cycles but was significantly affected by fuel type. On average, the exhaust reactivity for California Phase 2 fuel was the lowest (16% below the highest fuel type) among the seven fuels tested for cold start emissions. The average exhaust reactivity for high-emitting vehicles was significantly higher for hot stabilized (11%) and hot start (15%) emissions than for low-emitting vehicles. The exhaust reactivities for the FTP and UC cycles for light-end HCs and carbonyls were significantly different for the hot stabilized mode. There was a significant fuel effect on the mean specific reactivity (SR) for the mid-range HCs, but not for light-end HCs or carbonyls, while vehicle emission status affected the mean SR for all three HC compound classes.

  14. Formation and Reactivity of Biogenic Iron Minerals

    SciTech Connect

    Ferris, F. Grant

    2002-06-01

    Dissimilatory iron-reducing bacteria (DIRB) play an important role in regulating the aqueous geochemistry of iron and other metals in anaerobic, non-sulfidogenic groundwater environments; however, little work has directly assessed the cell surface electrochemistry of DIRB, or the nature of the interfacial environment around individual cells. The electrochemical properties of particulate solids are often inferred from titrations in which net surface charge is determined, assuming electroneutrality, as the difference between known added amounts of acid and base and measured proton concentration. The resultant titration curve can then be fit to a speciation model for the system to determine pKa values and site densities of reactive surface sites. Moreover, with the development of non-contact electrostatic force microscopy (EFM), it is now possible to directly inspect and quantify charge development on surfaces. A combination of acid-base titrations and EFM are being used to assess the electrochemical surface properties of the groundwater DIRB, Shewanella putrefaciens. The pKa spectra and EFM data show together that a high degree of electrochemical heterogeneity exists within the cell wall and at the cell surface of S. putrefaciens. Recognition of variations in the nature and spatial distribution of reactive sites that contribute to charge development on these bacteria implies further that the cell surface of these Fe(III)-reducing bacteria functions as a highly differentiated interfacial system capable of supporting multiple intermolecular interactions with both solutes and solids. These include surface complexation reactions involving dissolved metals, as well as adherence to mineral substrates such as hydrous ferric oxide through longer-range electrostatic interactions, and surface precipitation of secondary reduced-iron minerals.

  15. Molten salt extraction of transuranic and reactive fission products from used uranium oxide fuel

    SciTech Connect

    Herrmann, Steven Douglas

    2014-05-27

    Used uranium oxide fuel is detoxified by extracting transuranic and reactive fission products into molten salt. By contacting declad and crushed used uranium oxide fuel with a molten halide salt containing a minor fraction of the respective uranium trihalide, transuranic and reactive fission products partition from the fuel to the molten salt phase, while uranium oxide and non-reactive, or noble metal, fission products remain in an insoluble solid phase. The salt is then separated from the fuel via draining and distillation. By this method, the bulk of the decay heat, fission poisoning capacity, and radiotoxicity are removed from the used fuel. The remaining radioactivity from the noble metal fission products in the detoxified fuel is primarily limited to soft beta emitters. The extracted transuranic and reactive fission products are amenable to existing technologies for group uranium/transuranic product recovery and fission product immobilization in engineered waste forms.

  16. FUEL PROCESSING FOR FUEL CELLS: EFFECTS ON CATALYST DURABILITY AND CARBON FORMATION

    SciTech Connect

    R. BORUP; M. INBODY; B. MORTON; L. BROWN

    2001-05-01

    On-board production of hydrogen for fuel cells for automotive applications is a challenging developmental task. The fuel processor must show long term durability and under challenging conditions. Fuel processor catalysts in automotive fuel processors will be exposed to large thermal variations, vibrations, exposure to uncontrolled ambient conditions, and various impurities from ambient air and from fuel. For the commercialization of fuel processors, the delineation of effects on catalyst activity and durability are required. We are studying fuels and fuel constituent effects on the fuel processor system as part of the DOE Fuel Cells for Transportation program. Pure fuel components are tested to delineate the fuel component effect on the fuel processor and fuel processor catalysts. Component blends are used to simulate ''real fuels'', with various fuel mixtures being examined such as reformulated gasoline and naptha. The aliphatic, napthenic, olefin and aromatic content are simulated to represent the chemical kinetics of possible detrimental reactions, such as carbon formation, during fuel testing. Testing has examined the fuel processing performance of different fuel components to help elucidate the fuel constituent effects on fuel processing performance and upon catalyst durability. Testing has been conducted with vapor fuels, including natural gas and pure methane. The testing of pure methane and comparable testing with natural gas (97% methane) have shown some measurable differences in performance in the fuel processor. Major gasoline fuel constituents, such as aliphatic compounds, napthanes, and aromatics have been compared for their effect on the fuel processing performance. Experiments have been conducted using high-purity compounds to observe the fuel processing properties of the individual components and to document individual fuel component performance. The relative carbon formation of different fuel constituents have been measured by monitoring carbon via

  17. Chemical Characterization and Reactivity of Fuel-Oxidizer Reaction Product

    NASA Technical Reports Server (NTRS)

    David, Dennis D.; Dee, Louis A.; Beeson, Harold D.

    1997-01-01

    Fuel-oxidizer reaction product (FORP), the product of incomplete reaction of monomethylhydrazine and nitrogen tetroxide propellants prepared under laboratory conditions and from firings of Shuttle Reaction Control System thrusters, has been characterized by chemical and thermal analysis. The composition of FORP is variable but falls within a limited range of compositions that depend on three factors: the fuel-oxidizer ratio at the time of formation; whether the composition of the post-formation atmosphere is reducing or oxidizing; and the reaction or post-reaction temperature. A typical composition contains methylhydrazinium nitrate, ammonium nitrate, methylammonium nitrate, and trace amounts of hydrazinium nitrate and 1,1-dimethylhydrazinium nitrate. Thermal decomposition reactions of the FORP compositions used in this study were unremarkable. Neither the various compositions of FORP, the pure major components of FORP, nor mixtures of FORP with propellant system corrosion products showed any unusual thermal activity when decomposed under laboratory conditions. Off-limit thruster operations were simulated by rapid mixing of liquid monomethylhydrazine and liquid nitrogen tetroxide in a confined space. These tests demonstrated that monomethylhydrazine, methylhydrazinium nitrate, ammonium nitrate, or Inconel corrosion products can induce a mixture of monomethylhydrazine and nitrogen tetroxide to produce component-damaging energies. Damaging events required FORP or metal salts to be present at the initial mixing of monomethylhydrazine and nitrogen tetroxide.

  18. Orbit selection of nanosatellite formation in term of fuel consumption

    NASA Astrophysics Data System (ADS)

    Pimnoo, Ammarin; Hiraki, Koju

    In nanosatellite formation mission design, orbit selection is a necessary factor. Fuel consumption is also necessary to maintain the orbit. Therefore, the best orbit should be the one of minimum fuel consumption for nanosatellite formation. The purpose of this paper is to provide a convenient way to estimate fuel consumption for a nanosatellite to keep formation flying. The formation is disturbed by J _{2} perturbation and other perturbing accelerations. Firstly, the Hill-Clohessy-Wiltshire equations are used in the analysis. Gaussian variation of parameters is included into the Hill’s equation to analyze the variation of Kaplerian orbital elements. The J _{2} perturbation and other perturbing accelerations such as atmospheric drag, solar-radiation pressure and third-body perturbations are considered. Thus, a linear model based on Hill’s equation is established to estimate fuel consumption. Finally, an example of the best orbit for formation flying with minimum fuel consumption shall be presented.

  19. Reactive metabolites of desipramine and clomipramine: The kinetics of formation and reactivity with DNA.

    PubMed

    Korobkova, Ekaterina A; Nemeth, John; Cadougan, Mikeisha; Venkatratnam, Abhishek; Bassit, Mohanram; Azar, Nikolay

    2012-01-01

    Tricyclic antidepressants (TCAs), along with phenothyazines and some industrial chemicals, are shown to react with enzymes that exhibit peroxidase activity. These reactions result in the formation of reactive intermediates having unpaired electrons. The peroxidase oxidation and reactivity of two TCAs, desipramine and clomipramine, were investigated. As a model of peroxidase, horseradish peroxidase (HRP) was employed. The products of the peroxidase catalyzed oxidation of desipramine and clomipramine were identified as N-dealkylated compounds iminodibenzyl and 3-chloroiminodibenzyl using the GC/MS technique. Both drugs formed broad UV/vis absorption spectra in the presence of HRP and H(2)O(2), indicating the formation of a radical cations-reactive intermediate of the oxidation reaction. The dynamics of the formation of the desipramine intermediate was studied using UV/vis spectroscopy. The extinction coefficient was measured for the reactive intermediate, 7.80×10(3)M(-1)cm(-1), as well as the apparent Michaelis-Menten and catalytic constants, 4.4mM and 2.3s(-1), respectively. Both desipramine and clomipramine degraded DNA in the presence of HRP/H(2)O(2), as was revealed by agarose gel electrophoresis and PCI extraction. Manipulating the kinetic parameters of drug's radical formation and determining the extent of degradation to biomolecules could be potentially used for designing effective agents exhibiting specific reactivity.

  20. [Formation of reactive oxygen species during pollen grain germination].

    PubMed

    Smirnova, A V; Matveeva, N P; Polesskaia, O G; Ermakov, I P

    2009-01-01

    The formation of reactive oxygen species in pollen at the early germination stage, which precedes the formation of the pollen tube, was studied. During this period, pollen grain is being hydrated, abruptly increasing its volume, and it passes from the resting state to active metabolism. Fluorescent methods have made it possible to reveal reactive oxygen species in the cytoplasm and inner layer of the pollen wall, intine. The cytoplasmic reactive oxygen species were mostly found in mitochondria, while extracellular ones were localized in aperture zones of intine, as well as in the solution surrounding pollen grains in vitro. The content of extracellular reactive oxygen species decreased after superoxide dismutase (100 units per ml) and diphenylene iodonium (100 microM), which indicates NADPH oxidase as one of possible producent of them. In conditions of suppression of extracellular reactive oxygen species production (100 microM diphenilene iodonium) or their promoted removal (after addition of 10 to 100 microM ascorbic acid), the number of germinating pollen grains increased. This effect disappeared after further increase in the concentration of the listed reagents. The result is evidence of the significance of processes of generation/removal of extracellular reactive oxygen species for pollen germination.

  1. Fuel composition and secondary organic aerosol formation: gas-turbine exhaust and alternative aviation fuels.

    PubMed

    Miracolo, Marissa A; Drozd, Greg T; Jathar, Shantanu H; Presto, Albert A; Lipsky, Eric M; Corporan, Edwin; Robinson, Allen L

    2012-08-07

    A series of smog chamber experiments were performed to investigate the effects of fuel composition on secondary particulate matter (PM) formation from dilute exhaust from a T63 gas-turbine engine. Tests were performed at idle and cruise loads with the engine fueled on conventional military jet fuel (JP-8), Fischer-Tropsch synthetic jet fuel (FT), and a 50/50 blend of the two fuels. Emissions were sampled into a portable smog chamber and exposed to sunlight or artificial UV light to initiate photo-oxidation. Similar to previous studies, neat FT fuel and a 50/50 FT/JP-8 blend reduced the primary particulate matter emissions compared to neat JP-8. After only one hour of photo-oxidation at typical atmospheric OH levels, the secondary PM production in dilute exhaust exceeded primary PM emissions, except when operating the engine at high load on FT fuel. Therefore, accounting for secondary PM production should be considered when assessing the contribution of gas-turbine engine emissions to ambient PM levels. FT fuel substantially reduced secondary PM formation in dilute exhaust compared to neat JP-8 at both idle and cruise loads. At idle load, the secondary PM formation was reduced by a factor of 20 with the use of neat FT fuel, and a factor of 2 with the use of the blend fuel. At cruise load, the use of FT fuel resulted in no measured formation of secondary PM. In every experiment, the secondary PM was dominated by organics with minor contributions from sulfate when the engine was operated on JP-8 fuel. At both loads, FT fuel produces less secondary organic aerosol than JP-8 because of differences in the composition of the fuels and the resultant emissions. This work indicates that fuel reformulation may be a viable strategy to reduce the contribution of emissions from combustion systems to secondary organic aerosol production and ultimately ambient PM levels.

  2. Two-Dimensional Diffusion Theory Analysis of Reactivity Effects of a Fuel-Plate-Removal Experiment

    NASA Technical Reports Server (NTRS)

    Gotsky, Edward R.; Cusick, James P.; Bogart, Donald

    1959-01-01

    Two-dimensional two-group diffusion calculations were performed on the NASA reactor simulator in order to evaluate the reactivity effects of fuel plates removed successively from the center experimental fuel element of a seven- by three-element core loading at the Oak Ridge Bulk Shielding Facility. The reactivity calculations were performed by two methods: In the first, the slowing-down properties of the experimental fuel element were represented by its infinite media parameters; and, in the second, the finite size of the experimental fuel element was recognized, and the slowing-down properties of the surrounding core were attributed to this small region. The latter calculation method agreed very well with the experimented reactivity effects; the former method underestimated the experimental reactivity effects.

  3. Sensitivity and uncertainty analysis of reactivities for UO2 and MOX fueled PWR cells

    NASA Astrophysics Data System (ADS)

    Foad, Basma; Takeda, Toshikazu

    2015-12-01

    The purpose of this paper is to apply our improved method for calculating sensitivities and uncertainties of reactivity responses for UO2 and MOX fueled pressurized water reactor cells. The improved method has been used to calculate sensitivity coefficients relative to infinite dilution cross-sections, where the self-shielding effect is taken into account. Two types of reactivities are considered: Doppler reactivity and coolant void reactivity, for each type of reactivity, the sensitivities are calculated for small and large perturbations. The results have demonstrated that the reactivity responses have larger relative uncertainty than eigenvalue responses. In addition, the uncertainty of coolant void reactivity is much greater than Doppler reactivity especially for large perturbations. The sensitivity coefficients and uncertainties of both reactivities were verified by comparing with SCALE code results using ENDF/B-VII library and good agreements have been found.

  4. Sensitivity and uncertainty analysis of reactivities for UO2 and MOX fueled PWR cells

    SciTech Connect

    Foad, Basma; Takeda, Toshikazu

    2015-12-31

    The purpose of this paper is to apply our improved method for calculating sensitivities and uncertainties of reactivity responses for UO{sub 2} and MOX fueled pressurized water reactor cells. The improved method has been used to calculate sensitivity coefficients relative to infinite dilution cross-sections, where the self-shielding effect is taken into account. Two types of reactivities are considered: Doppler reactivity and coolant void reactivity, for each type of reactivity, the sensitivities are calculated for small and large perturbations. The results have demonstrated that the reactivity responses have larger relative uncertainty than eigenvalue responses. In addition, the uncertainty of coolant void reactivity is much greater than Doppler reactivity especially for large perturbations. The sensitivity coefficients and uncertainties of both reactivities were verified by comparing with SCALE code results using ENDF/B-VII library and good agreements have been found.

  5. Mathematical modeling of biomass fuels formation process.

    PubMed

    Gaska, Krzysztof; Wandrasz, Andrzej J

    2008-01-01

    The increasing demand for thermal and electric energy in many branches of industry and municipal management accounts for a drastic diminishing of natural resources (fossil fuels). Meanwhile, in numerous technical processes, a huge mass of wastes is produced. A segregated and converted combustible fraction of the wastes, with relatively high calorific value, may be used as a component of formed fuels. The utilization of the formed fuel components from segregated groups of waste in associated processes of co-combustion with conventional fuels causes significant savings resulting from partial replacement of fossil fuels, and reduction of environmental pollution resulting directly from the limitation of waste migration to the environment (soil, atmospheric air, surface and underground water). The realization of technological processes with the utilization of formed fuel in associated thermal systems should be qualified by technical criteria, which means that elementary processes as well as factors of sustainable development, from a global viewpoint, must not be disturbed. The utilization of post-process waste should be preceded by detailed technical, ecological and economic analyses. In order to optimize the mixing process of fuel components, a mathematical model of the forming process was created. The model is defined as a group of data structures which uniquely identify a real process and conversion of this data in algorithms based on a problem of linear programming. The paper also presents the optimization of parameters in the process of forming fuels using a modified simplex algorithm with a polynomial worktime. This model is a datum-point in the numerical modeling of real processes, allowing a precise determination of the optimal elementary composition of formed fuels components, with assumed constraints and decision variables of the task.

  6. Premixed direct injection nozzle for highly reactive fuels

    DOEpatents

    Ziminsky, Willy Steve; Johnson, Thomas Edward; Lacy, Benjamin Paul; York, William David; Uhm, Jong Ho; Zuo, Baifang

    2013-09-24

    A fuel/air mixing tube for use in a fuel/air mixing tube bundle is provided. The fuel/air mixing tube includes an outer tube wall extending axially along a tube axis between an inlet end and an exit end, the outer tube wall having a thickness extending between an inner tube surface having a inner diameter and an outer tube surface having an outer tube diameter. The tube further includes at least one fuel injection hole having a fuel injection hole diameter extending through the outer tube wall, the fuel injection hole having an injection angle relative to the tube axis. The invention provides good fuel air mixing with low combustion generated NOx and low flow pressure loss translating to a high gas turbine efficiency, that is durable, and resistant to flame holding and flash back.

  7. Reactivity-controlled compression ignition drive cycle emissions and fuel economy estimations using vehicle system simulations

    DOE PAGES

    Curran, Scott J.; Gao, Zhiming; Wagner, Robert M.

    2014-12-22

    In-cylinder blending of gasoline and diesel to achieve reactivity-controlled compression ignition has been shown to reduce NOX and soot emissions while maintaining or improving brake thermal efficiency as compared with conventional diesel combustion. The reactivity-controlled compression ignition concept has an advantage over many advanced combustion strategies in that the fuel reactivity can be tailored to the engine speed and load, allowing stable low-temperature combustion to be extended over more of the light-duty drive cycle load range. In this paper, a multi-mode reactivity-controlled compression ignition strategy is employed where the engine switches from reactivity-controlled compression ignition to conventional diesel combustion whenmore » speed and load demand are outside of the experimentally determined reactivity-controlled compression ignition range. The potential for reactivity-controlled compression ignition to reduce drive cycle fuel economy and emissions is not clearly understood and is explored here by simulating the fuel economy and emissions for a multi-mode reactivity-controlled compression ignition–enabled vehicle operating over a variety of US drive cycles using experimental engine maps for multi-mode reactivity-controlled compression ignition, conventional diesel combustion, and a 2009 port-fuel injected gasoline engine. Drive cycle simulations are completed assuming a conventional mid-size passenger vehicle with an automatic transmission. Multi-mode reactivity-controlled compression ignition fuel economy simulation results are compared with the same vehicle powered by a representative 2009 port-fuel injected gasoline engine over multiple drive cycles. Finally, engine-out drive cycle emissions are compared with conventional diesel combustion, and observations regarding relative gasoline and diesel tank sizes needed for the various drive cycles are also summarized.« less

  8. Reactivity-controlled compression ignition drive cycle emissions and fuel economy estimations using vehicle system simulations

    SciTech Connect

    Curran, Scott J.; Gao, Zhiming; Wagner, Robert M.

    2014-12-22

    In-cylinder blending of gasoline and diesel to achieve reactivity-controlled compression ignition has been shown to reduce NOX and soot emissions while maintaining or improving brake thermal efficiency as compared with conventional diesel combustion. The reactivity-controlled compression ignition concept has an advantage over many advanced combustion strategies in that the fuel reactivity can be tailored to the engine speed and load, allowing stable low-temperature combustion to be extended over more of the light-duty drive cycle load range. In this paper, a multi-mode reactivity-controlled compression ignition strategy is employed where the engine switches from reactivity-controlled compression ignition to conventional diesel combustion when speed and load demand are outside of the experimentally determined reactivity-controlled compression ignition range. The potential for reactivity-controlled compression ignition to reduce drive cycle fuel economy and emissions is not clearly understood and is explored here by simulating the fuel economy and emissions for a multi-mode reactivity-controlled compression ignition–enabled vehicle operating over a variety of US drive cycles using experimental engine maps for multi-mode reactivity-controlled compression ignition, conventional diesel combustion, and a 2009 port-fuel injected gasoline engine. Drive cycle simulations are completed assuming a conventional mid-size passenger vehicle with an automatic transmission. Multi-mode reactivity-controlled compression ignition fuel economy simulation results are compared with the same vehicle powered by a representative 2009 port-fuel injected gasoline engine over multiple drive cycles. Finally, engine-out drive cycle emissions are compared with conventional diesel combustion, and observations regarding relative gasoline and diesel tank sizes needed for the various drive cycles are also summarized.

  9. Deposit formation and heat transfer in hydrocarbon rocket fuels

    NASA Technical Reports Server (NTRS)

    Giovanetti, A. J.; Spadaccini, L. J.; Szetela, E. J.

    1983-01-01

    An experimental research program was undertaken to investigate the thermal stability and heat transfer characteristics of several hydrocarbon fuels under conditions that simulate high-pressure, rocket engine cooling systems. The rates of carbon deposition in heated copper and nickel-plated copper tubes were determined for RP-1, propane, and natural gas using a continuous flow test apparatus which permitted independent variation and evaluation of the effect on deposit formation of wall temperature, fuel pressure, and fuel velocity. In addition, the effects of fuel additives and contaminants, cryogenic fuel temperatures, and extended duration testing with intermittent operation were examined. Parametric tests to map the thermal stability characteristics of RP-1, commercial-grade propane, and natural gas were conducted at pressures of 6.9 to 13.8 MPa, bulk fuel velocities of 30 to 90 m/s, and tube wall temperatures in the range of 230 to 810 K. Also, tests were run in which propane and natural gas fuels were chilled to 230 and 160 K, respectively. Corrosion of the copper tube surface was detected for all fuels tested. Plating the inside of the copper tubes with nickel reduced deposit formation and eliminated tube corrosion in most cases. The lowest rates of carbon deposition were obtained for natural gas, and the highest rates were obtained for propane. For all fuels tested, the forced-convection heat transfer film coefficients were satisfactorily correlated using a Nusselt-Reynolds-Prandtl number equation.

  10. FORMATION PROCESSES AND CONSEQUENCES OF REACTIVE AND NON-REACTIVE MINERAL PRECIPITATES IN PERMEABLE REACTIVE BARRIERS

    EPA Science Inventory

    Mineral precipitates in zero-valent iron PRBs can be classified by formation processes into three groups: 1) those that result from changes in chemical conditions (i.e., change in pH, e.g., calcite); 2) those that are a consequence of microbial activity (i.e., sulfate reduction, ...

  11. FORMATION PROCESSES AND CONSEQUENCES OF REACTIVE AND NON-REACTIVE MINERAL PRECIPITATES IN PERMEABLE REACTIVE BARRIERS

    EPA Science Inventory

    Mineral precipitates in zero-valent iron PRBs can be classified by formation processes into three groups: 1) those that result from changes in chemical conditions (i.e., change in pH, e.g., calcite); 2) those that are a consequence of microbial activity (i.e., sulfate reduction, ...

  12. Intermediate Depth Earthquakes in Middle America: Fault Reactivation or Formation?

    NASA Astrophysics Data System (ADS)

    Langstaff, M. A.; Warren, L. M.; Silver, P. G.

    2006-12-01

    Intermediate-depth earthquakes are often attributed to dehydration embrittlement reactivating pre-existing weak zones. The orientations of pre-subduction faults are particularly well known offshore of Middle America, where seismic reflection profiles show outer-rise faults dipping towards the trench and extending >20~km into the lithosphere. If water is transported along these faults and incorporated into hydrous minerals, the faults may be reactivated later when the minerals dehydrate. In this case, the fault orientations should be the same in the outer rise and at depth, after accounting for the angle of subduction. To test this hypothesis, we analyze the directivity of 54 large (M_W > 5.7) earthquakes between 40--220~km depth in the Middle America Trench. For 15 of these earthquakes, the directivity vector allows us to confidently distinguish the fault plane of the earthquake. Between 40--85~km depth, we observe both subhorizontal and subvertical fault planes. The subvertical fault planes are consistent with the reactivation of outer rise faults, whereas the subhorizontal fault planes suggest the formation of new faults. Deeper than 85~km, we only observe subhorizontal faults, indicating that the outer rise faults are no longer reactivated. The occurrence of only subhorizontal faults may be due to unbending stresses preferentially creating horizontal faults, or an isobaric rupture process.

  13. NOx formation in combustion of gaseous fuel in ejection burner

    NASA Astrophysics Data System (ADS)

    Rimár, Miroslav; Kulikov, Andrii

    2016-06-01

    The aim of this work is to prepare model for researching of the formation in combustion of gaseous fuels. NOx formation is one of the main ecological problems nowadays as nitrogen oxides is one of main reasons of acid rains. The ANSYS model was designed according to the calculation to provide full combustion and good mixing of the fuel and air. The current model is appropriate to research NOx formation and the influence of the different principles of NOx reduction method. Applying of designed model should spare both time of calculations and research and also money as you do not need to measure the burner characteristics.

  14. Characterization of carbon nanomaterial formation and manganese oxide reactivity

    NASA Astrophysics Data System (ADS)

    Shumlas, Samantha Lyn

    Characterization of a material's surface, structural and physical properties is essential to understand its chemical reactivity. Control over these properties helps tailor a material to a particular application of interest. The research presented in this dissertation focuses on characterizing a synthetic method for carbon nanomaterials and the determination of structural properties of manganese oxides that contribute to its reactivity for environmental chemistry. In particular, one research effort was focused on the tuning of synthetic parameters towards the formation of carbon nanomaterials from gaseous methane and gaseous mixtures containing various mixtures of methane, argon and hydrogen. In a second research effort, photochemical and water oxidation chemistry were performed on the manganese oxide, birnessite, to aid in the remediation of arsenic from the environment and provide more options for alternative energy catalysts, respectively. (Abstract shortened by ProQuest.).

  15. A Critical Review of Practice of Equating the Reactivity of Spent Fuel to Fresh Fuel in Burnup Credit Criticality Safety Analyses for PWR Spent Fuel Pool Storage

    SciTech Connect

    Wagner, J.C.; Parks, C.V.

    2000-09-01

    This research examines the practice of equating the reactivity of spent fuel to that of fresh fuel for the purpose of performing burnup credit criticality safety analyses for PWR spent fuel pool (SFP) storage conditions. The investigation consists of comparing k{sub inf} estimates based on reactivity equivalent fresh fuel enrichment (REFFE) to k{sub inf} estimates using the actual spent fuel isotopics. Analyses of selected storage configurations common in PWR SFPs show that this practice yields nonconservative results (on the order of a few tenths of a percent) in configurations in which the spent fuel is adjacent to higher-reactivity assemblies (e.g., fresh or lower-burned assemblies) and yields conservative results in configurations in which spent fuel is adjacent to lower-reactivity assemblies (e.g., higher-burned fuel or empty cells). When the REFFE is determined based on unborated water moderation, analyses for storage conditions with soluble boron present reveal significant nonconservative results associated with the use of the REFFE. This observation is considered to be important, especially considering the recent allowance of credit for soluble boron up to 5% in reactivity. Finally, it is shown that the practice of equating the reactivity of spent fuel to fresh fuel is acceptable, provided the conditions for which the REFFE was determined remain unchanged. Determination of the REFFE for a reference configuration and subsequent use of the REFFE for different configurations violates the basis used for the determination of the REFFE and, thus, may lead to inaccurate, and possibly, nonconservative estimates of reactivity. A significant concentration ({approximately}2000 ppm) of soluble boron is typically (but not necessarily required to be) present in PWR SFPs, of which only a portion ({le} 500 ppm) may be credited in safety analyses. Thus, a large subcritical margin currently exists that more than accounts for errors or uncertainties associated with the use of

  16. Impact investigation of reactor fuel operating parameters on reactivity for use in burnup credit applications

    NASA Astrophysics Data System (ADS)

    Sloma, Tanya Noel

    When representing the behavior of commercial spent nuclear fuel (SNF), credit is sought for the reduced reactivity associated with the net depletion of fissile isotopes and the creation of neutron-absorbing isotopes, a process that begins when a commercial nuclear reactor is first operated at power. Burnup credit accounts for the reduced reactivity potential of a fuel assembly and varies with the fuel burnup, cooling time, and the initial enrichment of fissile material in the fuel. With regard to long-term SNF disposal and transportation, tremendous benefits, such as increased capacity, flexibility of design and system operations, and reduced overall costs, provide an incentive to seek burnup credit for criticality safety evaluations. The Nuclear Regulatory Commission issued Interim Staff Guidance 8, Revision 2 in 2002, endorsing burnup credit of actinide composition changes only; credit due to actinides encompasses approximately 30% of exiting pressurized water reactor SNF inventory and could potentially be increased to 90% if fission product credit were accepted. However, one significant issue for utilizing full burnup credit, compensating for actinide and fission product composition changes, is establishing a set of depletion parameters that produce an adequately conservative representation of the fuel's isotopic inventory. Depletion parameters can have a significant effect on the isotopic inventory of the fuel, and thus the residual reactivity. This research seeks to quantify the reactivity impact on a system from dominant depletion parameters (i.e., fuel temperature, moderator density, burnable poison rod, burnable poison rod history, and soluble boron concentration). Bounding depletion parameters were developed by statistical evaluation of a database containing reactor operating histories. The database was generated from summary reports of commercial reactor criticality data. Through depletion calculations, utilizing the SCALE 6 code package, several light

  17. Deposit formation and heat transfer in hydrocarbon rocket fuels

    NASA Technical Reports Server (NTRS)

    Giovanetti, A. J.; Spadaccini, L. J.; Szetela, E. J.

    1984-01-01

    An experimental research program was undertaken to investigate the thermal stability and heat transfer characteristics of several hydrocarbon fuels under conditions that simulate high-pressure, rocket engine cooling systems. The rates of carbon deposition in heated copper and nickel-plated copper tubes were determined for RP-1, propane, and natural gas using a continuous flow test apparatus which permitted independent variation and evaluation of the effect on deposit formation of wall temperature, fuel pressure, and fuel velocity. In addition, the effects of fuel additives and contaminants, cryogenic fuel temperatures, and extended duration testing with intermittent operation were examined. Corrosion of the copper tube surface was detected for all fuels tested; however, plating the insides of the tubes with nickel reduced deposit formation and eliminated corrosion in most cases. The lowest rates of carbon deposition were obtained for natural gas, and the highest rates were obtained for propane. Forced-convection heat transfer film coefficients were satisfactorily correlated using a Nusselt-Reynolds-Prandtl number equation for all the fuels tested.

  18. Oxidation and Gum Formation in Diesel Fuels.

    DTIC Science & Technology

    1985-12-20

    naphthoic acid is formed. Gum formation by aldol condensations and esterifcation of oxida- tion products (Mayo, 1975) and by aldehyde-hydroperoxide...replaced by the oxidation termination mechanism when oxygen is present. A third mechanism, condensation of oxidation products from alkylnaphthalenes, is...of gum formation is involved. This mechanism has not yet been investigated, but it might involve some reaction like the condensation of naphthaldehyde

  19. Formation of protein S-nitrosylation by reactive oxygen species.

    PubMed

    Hlaing, K Htet; Clément, M-V

    2014-09-01

    In the present study, the formation of whole cellular S-nitrosylated proteins (protein-SNOs) by the reactive oxygen species (ROS), hydrogen peroxide (H2O2), and superoxide (O2(•-)) is demonstrated. A spectrum of protein cysteine oxidative modifications was detected upon incubation of serum-starved mouse embryonic fibroblasts with increasing concentrations of exogenous H2O2, ranging from exclusive protein-SNOs at low concentrations to a mixture of protein-SNOs and other protein oxidation at higher concentrations to exclusively non-SNO protein oxidation at the highest concentrations of the oxidant used. Furthermore, formation of protein-SNOs was also detected upon inhibition of the antioxidant protein Cu/Zn superoxide dismutase that results in an increase in intracellular concentration of O2(•-). These results were further validated using the phosphatase and tensin homologue, PTEN, as a model of a protein sensitive to oxidative modifications. The formation of protein-SNOs by H2O2 and O2(•-) was prevented by the NO scavenger, c-PTIO, as well as the peroxinitrite decomposition catalyst, FETPPS, and correlated with the production or the consumption of nitric oxide (NO), respectively. These data suggest that the formation of protein-SNOs by H2O2 or O2(•-) requires the presence or the production of NO and involves the formation of the nitrosylating intermediate, peroxinitrite.

  20. Soot-driven reactive oxygen species formation from incense burning.

    PubMed

    Chuang, Hsiao-Chi; Jones, Tim P; Lung, Shih-Chun C; BéruBé, Kelly A

    2011-10-15

    This study investigated the effects of reactive oxygen species (ROS) generated as a function of the physicochemistry of incense particulate matter (IPM), diesel exhaust particles (DEP) and carbon black (CB). Microscopical and elemental analyses were used to determine particle morphology and inorganic compounds. ROS was determined using the reactive dye, Dichlorodihydrofluorescin (DCFH), and the Plasmid Scission Assay (PSA), which determine DNA damage. Two common types of soot were observed within IPM, including nano-soot and micro-soot, whereas DEP and CB mainly consisted of nano-soot. These PM were capable of causing oxidative stress in a dose-dependent manner, especially IPM and DEP. A dose of IPM (36.6-102.3μg/ml) was capable of causing 50% oxidative DNA damage. ROS formation was positively correlated to smaller nano-soot aggregates and bulk metallic compounds, particularly Cu. These observations have important implications for respiratory health given that inflammation has been recognised as an important factor in the development of lung injury/diseases by oxidative stress. This study supports the view that ROS formation by combustion-derived PM is related to PM physicochemistry, and also provides new data for IPM.

  1. Performance of U3Si2 Fuel in a Reactivity Insertion Accident

    SciTech Connect

    Cheng, Lap Y.; Cuadra, Arantxa; Todosow, Michael; Gamble, Kyle A.; Medvedev, Pavel G.

    2016-04-01

    In this study we examined the performance of the U3Si2 fuel cladded with Zircaloy (Zr) in a reactivity insertion accident (RIA) in a PWR core. The power excursion as a result of a $1 reactivity insertion was calculated by a TRACE PWR plant model using point-kinetics, for alternative cores with UO2 and U3Si2 fuel assemblies. The point-kinetics parameters (feedback coefficients, prompt-neutron lifetime and group constants for six delayed-neutron groups) were obtained from beginning-of-cycle equilibrium full core calculations with PARCS. In the PARCS core calculations, the few-group parameters were developed utilizing the TRITON/NEWT tools in the SCALE package. In order to assess the fuel response in finer detail (e.g. the maximum fuel temperature) the power shape and thermal boundary conditions from the TRACE/PARCS calculations were used to drive a BISON model of a fuel pin with U3Si2 and UO2 respectively. For a $1 reactivity transient both TRACE and BISON predicted a higher maximum fuel temperature for the UO2 fuel than the U3Si2 fuel. Furthermore, BISON is noted to calculate a narrower gap and a higher gap heat transfer coefficient than TRACE. This resulted in BISON predicting consistently lower fuel temperatures than TRACE. This study also provides a systematic comparison between TRACE and BISON using consistent transient boundary conditions. The TRACE analysis of the RIA only reflects the core-wide response in power. A refinement to the analysis would be to predict the local peaking in a three-dimensional core as a result of control rod ejection.

  2. Tuning Energetic Material Reactivity Using Surface Functionalization of Aluminum Fuels

    DTIC Science & Technology

    2012-10-30

    of thermites, aluminum synthesis, aluminum fluoropolymer combustion, acid coatings Keerti S. Kappagantula, Cory Farley, Michelle L. Pantoya, Jillian... Michelle Pantoya 806-742-3563 3. DATES COVERED (From - To) Standard Form 298 (Rev 8/98) Prescribed by ANSI Std. Z39.18 - Tuning Energetic Material...Functionalization of Aluminum Fuels Keerti S. Kappagantula,† Cory Farley,† Michelle L. Pantoya,*,† and Jillian Horn‡ †Department of Mechanical Engineering, Texas

  3. Reactivity Insertion Accident (RIA) Capability Status in the BISON Fuel Performance Code

    SciTech Connect

    Williamson, Richard L.; Folsom, Charles Pearson; Pastore, Giovanni; Veeraraghavan, Swetha

    2016-05-01

    One of the Challenge Problems being considered within CASL relates to modelling and simulation of Light Water Reactor LWR) fuel under Reactivity Insertion Accident (RIA) conditions. BISON is the fuel performance code used within CASL for LWR fuel under both normal operating and accident conditions, and thus must be capable of addressing the RIA challenge problem. This report outlines required BISON capabilities for RIAs and describes the current status of the code. Information on recent accident capability enhancements, application of BISON to a RIA benchmark exercise, and plans for validation to RIA behavior are included.

  4. ReaxFF Reactive Force-Field Modeling of the Triple-Phase Boundary in a Solid Oxide Fuel Cell.

    PubMed

    Merinov, Boris V; Mueller, Jonathan E; van Duin, Adri C T; An, Qi; Goddard, William A

    2014-11-20

    In our study, the Ni/YSZ ReaxFF reactive force field was developed by combining the YSZ and Ni/C/H descriptions. ReaxFF reactive molecular dynamics (RMD) were applied to model chemical reactions, diffusion, and other physicochemical processes at the fuel/Ni/YSZ interface. The ReaxFF RMD simulations were performed on the H2/Ni/YSZ and C4H10/Ni/YSZ triple-phase boundary (TPB) systems at 1250 and 2000 K, respectively. The simulations indicate amorphization of the Ni surface, partial decohesion (delamination) at the interface, and coking, which have indeed all been observed experimentally. They also allowed us to derive the mechanism of the butane conversion at the Ni/YSZ interface. Many steps of this mechanism are similar to the pyrolysis of butane. The products obtained in our simulations are the same as those in experiment, which indicates that the developed ReaxFF potential properly describes complex physicochemical processes, such as the oxide-ion diffusion, fuel conversion, water formation reaction, coking, and delamination, occurring at the TPB and can be recommended for further computational studies of the fuel/electrode/electrolyte interfaces in a SOFC.

  5. A microfluidic direct formate fuel cell on paper.

    PubMed

    Copenhaver, Thomas S; Purohit, Krutarth H; Domalaon, Kryls; Pham, Linda; Burgess, Brianna J; Manorothkul, Natalie; Galvan, Vicente; Sotez, Samantha; Gomez, Frank A; Haan, John L

    2015-08-01

    We describe the first direct formate fuel cell on a paper microfluidic platform. In traditional membrane-less microfluidic fuel cells (MFCs), external pumping consumes power produced by the fuel cell in order to maintain co-laminar flow of the anode stream and oxidant stream to prevent mixing. However, in paper microfluidics, capillary action drives flow while minimizing stream mixing. In this work, we demonstrate a paper MFC that uses formate and hydrogen peroxide as the anode fuel and cathode oxidant, respectively. Using these materials we achieve a maximum power density of nearly 2.5 mW/mg Pd. In a series configuration, our MFC achieves an open circuit voltage just over 1 V, and in a parallel configuration, short circuit of 20 mA absolute current. We also demonstrate that the MFC does not require continuous flow of fuel and oxidant to produce power. We found that we can pre-saturate the materials on the paper, stop the electrolyte flow, and still produce approximately 0.5 V for 15 min. This type of paper MFC has potential applications in point-of-care diagnostic devices and other electrochemical sensors. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Flame extinction limit and particulates formation in fuel blends

    NASA Astrophysics Data System (ADS)

    Subramanya, Mahesh

    Many fuels used in material processing and power generation applications are generally a blend of various hydrocarbons. Although the combustion and aerosol formation dynamics of individual fuels is well understood, the flame dynamics of fuel blends are yet to be characterized. This research uses a twin flame counterflow burner to measure flame velocity, flame extinction, particulate formation and particulate morphology of hydrogen fuel blend flames at different H2 concentration, oscillation frequencies and stretch conditions. Phase resolved spectroscopic measurements (emission spectra) of OH, H, O and CH radical/atom concentrations is used to characterize the heat release processes of the flame. In addition flame generated particulates are collected using thermophoretic sample technique and are qualitative analyzed using Raman Spectroscopy and SEM. Such measurements are essential for the development of advanced computational tools capable of predicting fuel blend flame characteristics at realistic combustor conditions. The data generated through the measurements of this research are representative, and yet accurate, with unique well defined boundary conditions which can be reproduced in numerical computations for kinetic code validations.

  7. Oxidation and formation of deposit precursors in hydrocarbon fuels

    NASA Technical Reports Server (NTRS)

    Mayo, F. R.; Lan, B.; Cotts, D. B.; Buttrill, S. E., Jr.; St.john, G. A.

    1983-01-01

    The oxidation of two jet turbine fuels and some pure hydrocarbons was studied at 130 C with and without the presence of small amounts of N-methyl pyrrole (NMP) or indene. Tendency to form solid-deposit precursors was studied by measuring soluble gum formation as well as dimer and trimer formation using field ionization mass spectrometry. Pure n-dodecane oxidized fastest and gave the smallest amount of procursors. An unstable fuel oil oxidized much slower but formed large amounts of precursors. Stable Jet A fuel oxidized slowest and gave little precursors. Indene either retarded or accelerated the oxidation of n-dodecane, depending on its concentration, but always caused more gum formation. The NMP greatly retarded n-dodecane oxidation but accelerated Jet A oxidation and greatly increased the latter's gum formation. In general, the additive reacted faster and formed most of the gum. Results are interpreted in terms of classical cooxidation theory. The effect of oxygen pressure on gum formation is also reported.

  8. Outflow channel sources, reactivation, and chaos formation, Xanthe Terra, Mars

    USGS Publications Warehouse

    Rodriguez, J.A.P.; Sasaki, S.; Kuzmin, R.O.; Dohm, J.M.; Tanaka, K.L.; Miyamoto, H.; Kurita, K.; Komatsu, G.; Fairen, A.G.; Ferris, J.C.

    2005-01-01

    The undulating, warped, and densely fractured surfaces of highland regions east of Valles Marineris (located north of the eastern Aureum Chaos, east of the Hydraotes Chaos, and south of the Hydaspis Chaos) resulted from extensional surface warping related to ground subsidence, caused when pressurized water confined in subterranean caverns was released to the surface. Water emanations formed crater lakes and resulted in channeling episodes involved in the excavation of Ares, Tiu, and Simud Valles of the eastern part of the circum-Chryse outflow channel system. Progressive surface subsidence and associated reduction of the subsurface cavernous volume, and/or episodes of magmatic-driven activity, led to increases of the hydrostatic pressure, resulting in reactivation of both catastrophic and non-catastrophic outflow activity. Ancient cratered highland and basin materials that underwent large-scale subsidence grade into densely fractured terrains. Collapse of rock materials in these regions resulted in the formation of chaotic terrains, which occur in and near the headwaters of the eastern circum-Chryse outflow channels. The deepest chaotic terrain in the Hydaspis Chaos region resulted from the collapse of pre-existing outflow channel floors. The release of volatiles and related collapse may have included water emanations not necessarily linked to catastrophic outflow. Basal warming related to dike intrusions, thermokarst activity involving wet sediments and/or dissected ice-enriched country rock, permafrost exposed to the atmosphere by extensional tectonism and channel incision, and/or the injection of water into porous floor material, may have enhanced outflow channel floor instability and subsequent collapse. In addition to the possible genetic linkage to outflow channel development dating back to at least the Late Noachian, clear disruption of impact craters with pristine ejecta blankets and rims, as well as preservation of fine tectonic fabrics, suggest that

  9. Outflow channel sources, reactivation, and chaos formation, Xanthe Terra, Mars

    NASA Astrophysics Data System (ADS)

    Rodriguez, Jose A. P.; Sasaki, Sho; Kuzmin, Ruslan O.; Dohm, James M.; Tanaka, Ken L.; Miyamoto, Hideaki; Kurita, Kei; Komatsu, Goro; Fairén, A. G.; Ferris, Justin C.

    2005-05-01

    The undulating, warped, and densely fractured surfaces of highland regions east of Valles Marineris (located north of the eastern Aureum Chaos, east of the Hydraotes Chaos, and south of the Hydaspis Chaos) resulted from extensional surface warping related to ground subsidence, caused when pressurized water confined in subterranean caverns was released to the surface. Water emanations formed crater lakes and resulted in channeling episodes involved in the excavation of Ares, Tiu, and Simud Valles of the eastern part of the circum-Chryse outflow channel system. Progressive surface subsidence and associated reduction of the subsurface cavernous volume, and/or episodes of magmatic-driven activity, led to increases of the hydrostatic pressure, resulting in reactivation of both catastrophic and non-catastrophic outflow activity. Ancient cratered highland and basin materials that underwent large-scale subsidence grade into densely fractured terrains. Collapse of rock materials in these regions resulted in the formation of chaotic terrains, which occur in and near the headwaters of the eastern circum-Chryse outflow channels. The deepest chaotic terrain in the Hydaspis Chaos region resulted from the collapse of pre-existing outflow channel floors. The release of volatiles and related collapse may have included water emanations not necessarily linked to catastrophic outflow. Basal warming related to dike intrusions, thermokarst activity involving wet sediments and/or dissected ice-enriched country rock, permafrost exposed to the atmosphere by extensional tectonism and channel incision, and/or the injection of water into porous floor material, may have enhanced outflow channel floor instability and subsequent collapse. In addition to the possible genetic linkage to outflow channel development dating back to at least the Late Noachian, clear disruption of impact craters with pristine ejecta blankets and rims, as well as preservation of fine tectonic fabrics, suggest that

  10. Reduced-reactivity-swing LEU fuel cycle analyses for HFR Petten

    SciTech Connect

    Deen, J.R.; Snelgrove, J.L.

    1985-01-01

    The primary objective of these low enriched uranium (LEU) fuel cycle analyses was to effect at least a 33% reduction in the reactivity swing now experienced in the high enriched uranium (HEU) cycle while minimizing increases in /sup 235/U loading and power peaking. All LEU equilibrium fuel cycle calculations were performed using either a 19- or 20-plate fuel element with 0.76-mm-thick meat and 0.5- or 0.6-mm-thick Cd wires as burnable absorbers and 16- or 17-plate control rod fuel followers with 0.76-mm-thick meat. Burnup-dependent microscopic cross sections were used for all heavy metals and fission products. A three-dimensional model was used to account for the effect of partially inserted control rods upon burnup profiles of fuel and of burnable absorbers and upon power peaking. The equilibrium cycle reactivity swing (or, equivalently control rod movement) was reduced by 50% using LEU fuel with U meat densities <4.8 Mg/m/sup 3/. 6 refs., 4 tabs.

  11. Review of fuel/cladding eutectic formation in metallic SFR fuel pins

    SciTech Connect

    Denman, M.; Todreas, N.; Driscoll, M.

    2012-07-01

    Sodium-cooled Fast Reactors (SFRs) remain a strong contender amongst the Generation IV reactor concepts. Metallic fuel has been a primary fuel option for SFR designers in the US and was used extensively in the first generation of SFRs. One of the benefits of metallic fuel is its chemical compatibility with the coolant; unfortunately this compatibility does not extend to steel cladding at elevated temperatures. It has been known that uranium, plutonium, and rare earths diffuse with cladding constituents to form a low melting point fuel/cladding eutectic which acts to thin the cladding once the interfacial temperature rises above the system liquidus temperature. Since the 1960's, many experiments have been performed and published to evaluate the rate of fuel/cladding eutectic formation and the temperature above which melting will begin as a function of fuel/cladding interfacial temperature, time at temperature, fuel constituents (uranium, fissium or uranium (plutonium) zirconium), cladding type (stainless steel 316, stainless steel 306, D9 or HT9), beginning of life linear power, plutonium enrichment and burnup. The results of these tests, however, remain scattered across conference and journal papers spanning 50 years. The tests used to collect this data also varied in experimental procedure throughout the years. This paper will consolidate the experimental data into four groups of similar test conditions and expand upon the testing performed for each group in detail. A companion paper in PSA 2011 will discuss predictive correlations formulated from this database. (authors)

  12. Gum and deposit formation from jet turbine and diesel fuels

    SciTech Connect

    Mayo, F.R.; Lan, B.Y.

    1983-09-01

    The objective of this work is to determine the chemistry of deposit formation in hot parts of jet turbine and diesel engines and, thus, to predict and prevent deposit formation. Previous work in the field has been extensive, but a real understanding of deposit formation has been elusive. Work at SRI started on the basis that deposit formation from fuels must take place stepwise and is associated with autoxidation and the hydroperoxide produced. More recent work showed that in the absence of dissolved oxygen, higher temperatures are required for deposit formation. A recent report indicated that gum and deposit formation proceed mainly through oxidation products of the parent hydrocarbon, coupling of these products to dimeric, trimeric and higher condensation products (partly or wholly by radicals from hydroperoxides) and precipitation of insoluble products. The authors know of no information on how these first precipitates are converted to the ultimate, very insoluble, carbonaceous materials that cause engine problems. The present paper describes measurements of rates of oxidation and soluble gum formation in both pure hydrocarbons and mixed hydrocarbon fuels. Some patterns appear that can be largely explained on the basis of what is known about co-oxidations of hydrocarbon mixtures.

  13. 40 CFR 600.307-08 - Fuel economy label format requirements.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 29 2010-07-01 2010-07-01 false Fuel economy label format requirements...) ENERGY POLICY FUEL ECONOMY AND CARBON-RELATED EXHAUST EMISSIONS OF MOTOR VEHICLES Fuel Economy Regulations for 1977 and Later Model Year Automobiles-Labeling § 600.307-08 Fuel economy label format...

  14. 40 CFR 600.307-95 - Fuel economy label format requirements.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 29 2010-07-01 2010-07-01 false Fuel economy label format requirements...) ENERGY POLICY FUEL ECONOMY AND CARBON-RELATED EXHAUST EMISSIONS OF MOTOR VEHICLES Fuel Economy Regulations for 1977 and Later Model Year Automobiles-Labeling § 600.307-95 Fuel economy label format...

  15. 40 CFR 600.307-86 - Fuel economy label format requirements.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 29 2010-07-01 2010-07-01 false Fuel economy label format requirements...) ENERGY POLICY FUEL ECONOMY AND CARBON-RELATED EXHAUST EMISSIONS OF MOTOR VEHICLES Fuel Economy Regulations for 1977 and Later Model Year Automobiles-Labeling § 600.307-86 Fuel economy label format...

  16. Reaction kinetics of fuel formation for in-situ combustion

    SciTech Connect

    Abu-Khamsin, S.; Ramey, H.J. Jr.; Pettit, P.; Brigham, W.E.

    1985-07-01

    In-situ combustion is receiving new interest as a viable alternative to the other thermal methods of heavy crude oil recovery. In this method, thermal energy is generated in-situ by creating an oil combustion zone that is driven through the reservoir by continuous air injection. While the various oil oxidation reactions have been adequately studied and modeled, little information is available regarding the fuel formation process that takes place ahead of the combustion zone. The goal of this study was to investigate the reactions that contribute to this process and obtain generalized kinetic equations for them. An experimental apparatus was built wherein a small sample of an oil/sand mixture can be pyrolyzed at a constant rate of heating, to temperatures normally encountered in combustion field applications, while nitrogen is continuously sweeping the sample. The effect on fuel formation of pressure, rate of heating, porous medium composition, and type of oil were investigated in an experimental program totaling 12 runs. Data from previously made oxidation experiments were also used. General conclusions reached in this study are: (1) the fuel is formed as a result of two successive cracking reactions that the oil undergoes at temperatures above 550/sup 0/F; distillation of crude oil at temperatures below 550/sup 0/F plays an important role in shaping the nature and extent of the cracking reactions; (3) the operating pressure and rate of heating affect the fuel formation process only through the influences exerted on distillation; (4) clay minerals have a catalytic effect on the cracking reactions, especially on coking; and (5) the asphaltene fraction of a crude oil is a parameter which correlates with the fuel content of that oil. 51 refs., 73 figs., 21 tabs.

  17. Fabric-based alkaline direct formate microfluidic fuel cells.

    PubMed

    Domalaon, Kryls; Tang, Catherine; Mendez, Alex; Bernal, Franky; Purohit, Krutarth; Pham, Linda; Haan, John; Gomez, Frank A

    2017-04-01

    Fabric-based microfluidic fuel cells (MFCs) serve as a novel, cost-efficient alternative to traditional FCs and batteries, since fluids naturally travel across fabric via capillary action, eliminating the need for an external pump and lowering production and operation costs. Building on previous research with Y-shaped paper-based MFCs, fabric-based MFCs mitigate fragility and durability issues caused by long periods of fuel immersion. In this study, we describe a microfluidic fabric-based direct formate fuel cell, with 5 M potassium formate and 30% hydrogen peroxide as the anode fuel and cathode oxidant, respectively. Using a two-strip, stacked design, the optimized parameters include the type of encasement, the barrier, and the fabric type. Surface contact of the fabric and laminate sheet expedited flow and respective chemical reactions. The maximum current (22.83 mA/cm(2) ) and power (4.40 mW/cm(2) ) densities achieved with a 65% cotton/35% polyester blend material are a respective 8.7% and 32% higher than previous studies with Y-shaped paper-based MFCs. In series configuration, the MFCs generate sufficient energy to power a handheld calculator, a thermometer, and a spectrum of light-emitting diodes. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Impacts of fuel formulation and engine operating parameters on the nanostructure and reactivity of diesel soot

    NASA Astrophysics Data System (ADS)

    Yehliu, Kuen

    This study focuses on the impacts of fuel formulations on the reactivity and nanostructure of diesel soot. A 2.5L, 4-cylinder, turbocharged, common rail, direct injection light-duty diesel engine was used in generating soot samples. The impacts of engine operating modes and the start of combustion on soot reactivity were investigated first. Based on preliminary investigations, a test condition of 2400 rpm and 64 Nm, with single and split injection strategies, was chosen for studying the impacts of fuel formulation on the characteristics of diesel soot. Three test fuels were used: an ultra low sulfur diesel fuel (BP15), a pure soybean methyl-ester (B100), and a synthetic Fischer-Tropsch fuel (FT) produced in a gas-to-liquid process. The start of injection (SOI) and fuel rail pressures were adjusted such that the three test fuels have similar combustion phasing, thereby facilitating comparisons between soots from the different fuels. Soot reactivity was investigated by thermogravimetric analysis (TGA). According to TGA, B100 soot exhibits the fastest oxidation on a mass basis followed by BP15 and FT derived soots in order of apparent rate constant. X-ray photoelectron spectroscopy (XPS) indicates no relation between the surface oxygen content and the soot reactivity. Crystalline information for the soot samples was obtained using X-ray diffraction (XRD). The basal plane diameter obtained from XRD was inversely related to the apparent rate constants for soot oxidation. For comparison, high resolution transmission electron microscopy (HRTEM) provided images of the graphene layers. Quantitative image analysis proceeded by a custom algorithm. B100 derived soot possessed the shortest mean fringe length and greatest mean fringe tortuosity. This suggests soot (nano)structural disorder correlates with a faster oxidation rate. Such results are in agreement with the X-ray analysis, as the observed fringe length is a measure of basal plane diameter. Moreover the relation

  19. LOX/hydrocarbon fuel carbon formation and mixing data analysis

    NASA Technical Reports Server (NTRS)

    Fang, J.

    1983-01-01

    By applying the Priem-Heidmann Generalized-Length vaporization correlation, the computer model developed by the present study predicts the spatial variation of propellant vaporization rate using the injector cold flow results to define the streamtubes. The calculations show that the overall and local propellant vaporization rate and mixture ratio change drastically as the injection element type or the injector operating condition is changed. These results are compared with the regions of carbon formation observed in the photographic combustion testing. The correlation shows that the fuel vaporization rate and the local mixture ratio produced by the injector element have first order effects on the degree of carbon formation.

  20. CASMO5/TSUNAMI-3D spent nuclear fuel reactivity uncertainty analysis

    SciTech Connect

    Ferrer, R.; Rhodes, J.; Smith, K.

    2012-07-01

    The CASMO5 lattice physics code is used in conjunction with the TSUNAMI-3D sequence in ORNL's SCALE 6 code system to estimate the uncertainties in hot-to-cold reactivity changes due to cross-section uncertainty for PWR assemblies at various burnup points. The goal of the analysis is to establish the multiplication factor uncertainty similarity between various fuel assemblies at different conditions in a quantifiable manner and to obtain a bound on the hot-to-cold reactivity uncertainty over the various assembly types and burnup attributed to fundamental cross-section data uncertainty. (authors)

  1. Chemical Characterization and Reactivity Testing of Fuel-Oxidizer Reaction Product (Test Report)

    NASA Technical Reports Server (NTRS)

    1996-01-01

    The product of incomplete reaction of monomethylhydrazine (MMH) and nitrogen tetroxide (NTO) propellants, or fuel-oxidizer reaction product (FORP), has been hypothesized as a contributory cause of an anomaly which occurred in the chamber pressure (PC) transducer tube on the Reaction Control Subsystem (RCS) aft thruster 467 on flight STS-51. A small hole was found in the titanium-alloy PC tube at the first bend below the pressure transducer. It was surmised that the hole may have been caused by heat and pressure resulting from ignition of FORP. The NASA Johnson Space Center (JSC) White Sands Test Facility (WSTF) was requested to define the chemical characteristics of FORP, characterize its reactivity, and simulate the events in a controlled environment which may have lead to the Pc-tube failure. Samples of FORP were obtained from the gas-phase reaction of MMH with NTO under laboratory conditions, the pulsed firings of RCS thrusters with modified PC tubes using varied oxidizer or fuel lead times, and the nominal RCS thruster firings at WSTF and Kaiser-Marquardt. Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), accelerating rate calorimetry (ARC), ion chromatography (IC), inductively coupled plasma (ICP) spectrometry, thermogravimetric analysis (TGA) coupled to FTIR (TGA/FTIR), and mechanical impact testing were used to qualitatively and quantitatively characterize the chemical, thermal, and ignition properties of FORP. These studies showed that the composition of FORP is variable but falls within a limited range of compositions that depends on the fuel loxidizer ratio at the time of formation, composition of the post-formation atmosphere (reducing or oxidizing), and reaction or postreaction temperature. A typical composition contains methylhydrazinium nitrate (MMHN), ammonium nitrate (AN), methylammonium nitrate (MAN), and trace amounts of hydrazinium nitrate and 1,1-dimethylhydrazinium nitrate. The thermal decomposition

  2. Performance of Trasuranic-Loaded Fully Ceramic Micro-Encapsulated Fuel in LWRs Interim Report, Including Void Reactivity Evaluation

    SciTech Connect

    Michael A. Pope; Brian Boer; Gilles Youinou; Abderrafi M. Ougouag

    2011-03-01

    The current focus of the Deep Burn Project is on once-through burning of transuranice (TRU) in light water reactors (LWRs). The fuel form is called Fully-Ceramic Micro-encapsulated (FCM) fuel, a concept that borrows the tri-isotropic (TRISO) fuel particle design from high-temperature reactor technology. In the Deep Burn LWR (DB-LWR) concept, these fuel particles would be pressed into compacts using SiC matrix material and loaded into fuel pins for use in conventional LWRs. The TRU loading comes from the spent fuel of a conventional LWR after 5 years of cooling. Unit cell calculations have been performed using the DRAGON-4 code in order assess the physics attributes of TRU-only FCM fuel in an LWR lattice. Depletion calculations assuming an infinite lattice condition were performed with calculations of various reactivity coefficients performed at each step. Unit cells containing typical UO2 and MOX fuel were analyzed in the same way to provide a baseline against which to compare the TRU-only FCM fuel. Loading of TRU-only FCM fuel into a pin without significant quantities of uranium challenges the design from the standpoint of several key reactivity parameters, particularly void reactivity, and to some degree, the Doppler coefficient. These unit cells, while providing an indication of how a whole core of similar fuel would behave, also provide information of how individual pins of TRU-only FCM fuel would influence the reactivity behavior of a heterogeneous assembly. If these FCM fuel pins are included in a heterogeneous assembly with LEU fuel pins, the overall reactivity behavior would be dominated by the uranium pins while attractive TRU destruction performance of the TRU-only FCM fuel pins may be preserved. A configuration such as this would be similar to CONFU assemblies analyzed in previous studies. Analogous to the plutonium content limits imposed on MOX fuel, some amount of TRU-only FCM pins in an otherwise-uranium fuel assembly may give acceptable reactivity

  3. An improved alkaline direct formate paper microfluidic fuel cell.

    PubMed

    Galvan, Vicente; Domalaon, Kryls; Tang, Catherine; Sotez, Samantha; Mendez, Alex; Jalali-Heravi, Mehdi; Purohit, Krutarth; Pham, Linda; Haan, John; Gomez, Frank A

    2016-02-01

    Paper-based microfluidic fuel cells (MFCs) are a potential replacement for traditional FCs and batteries due to their low cost, portability, and simplicity to operate. In MFCs, separate solutions of fuel and oxidant migrate through paper due to capillary action and laminar flow and, upon contact with each other and catalyst, produce electricity. In the present work, we describe an improved microfluidic paper-based direct formate FC (DFFC) employing formate and hydrogen peroxide as the anode fuel and cathode oxidant, respectively. The dimensions of the lateral column, current collectors, and cathode were optimized. A maximum power density of 2.53 mW/cm(2) was achieved with a DFFC of surface area 3.0 cm(2) , steel mesh as current collector, 5% carbon to paint mass ratio for cathode electrode and, 30% hydrogen peroxide. The longevity of the MFC's detailed herein is greater than eight hours with continuous flow of streams. In a series configuration, the MFCs generate sufficient energy to power light-emitting diodes and a handheld calculator.

  4. Fuel Cell Manufacturing Diagnostic Techniques: IR Thermography with Reactive Flow through Excitation

    SciTech Connect

    Manak, A. J.; Ulsh, M.; Bender, G.

    2012-01-01

    While design and material considerations for PEMFCs have a large impact on cost, it is also necessary to consider a transition to high volume production of fuel cell systems, including MEA components, to enable economies of scale and reduce per unit cost. One of the critical manufacturing tasks is developing and deploying techniques to provide in‐process measurement of fuel cell components for quality control. This effort requires a subsidiary task: The study of the effect of manufacturing defects on performance and durability with the objective to establish validated manufacturing tolerances for fuel cell components. This work focuses on the development of a potential quality control method for gas diffusion electrodes (GDEs). The method consists of infrared (IR) thermography combined with reactive flow through (RFT) excitation. Detection of catalyst loading reduction defects in GDE catalyst layers will be presented.

  5. Technical Basis for Peak Reactivity Burnup Credit for BWR Spent Nuclear Fuel in Storage and Transportation Systems

    SciTech Connect

    Marshall, William BJ J; Ade, Brian J; Bowman, Stephen M; Gauld, Ian C; Ilas, Germina; Mertyurek, Ugur; Radulescu, Georgeta

    2015-01-01

    Oak Ridge National Laboratory and the United States Nuclear Regulatory Commission have initiated a multiyear project to investigate application of burnup credit for boiling-water reactor (BWR) fuel in storage and transportation casks. This project includes two phases. The first phase (1) investigates applicability of peak reactivity methods currently used in spent fuel pools (SFPs) to storage and transportation systems and (2) evaluates validation of both reactivity (keff) calculations and burnup credit nuclide concentrations within these methods. The second phase will focus on extending burnup credit beyond peak reactivity. This paper documents the first phase, including an analysis of lattice design parameters and depletion effects, as well as both validation components. Initial efforts related to extended burnup credit are discussed in a companion paper. Peak reactivity analyses have been used in criticality analyses for licensing of BWR fuel in SFPs over the last 20 years. These analyses typically combine credit for the gadolinium burnable absorber present in the fuel with a modest amount of burnup credit. Gadolinium burnable absorbers are used in BWR assemblies to control core reactivity. The burnable absorber significantly reduces assembly reactivity at beginning of life, potentially leading to significant increases in assembly reactivity for burnups less than 15–20 GWd/MTU. The reactivity of each fuel lattice is dependent on gadolinium loading. The number of gadolinium-bearing fuel pins lowers initial lattice reactivity, but it has a small impact on the burnup and reactivity of the peak. The gadolinium concentration in each pin has a small impact on initial lattice reactivity but a significant effect on the reactivity of the peak and the burnup at which the peak occurs. The importance of the lattice parameters and depletion conditions are primarily determined by their impact on the gadolinium depletion. Criticality code validation for BWR burnup

  6. Molecular dissection of reactive astrogliosis and glial scar formation

    PubMed Central

    Sofroniew, Michael V.

    2009-01-01

    Reactive astrogliosis, whereby astrocytes undergo varying molecular and morphological changes, is a ubiquitous but poorly understood hallmark of all central nervous system pathologies. Now genetic tools are enabling the molecular dissection of the functions and mechanisms of reactive astrogliosis in vivo. Recent studies provide compelling evidence that reactive astrogliosis may exert both beneficial and detrimental effects in a context-dependent manner determined by specific molecular signaling cascades. Reactive astrocytes may have both loss of normal functions and gain of abnormal effects that can feature prominently in a variety of disease processes. This article reviews developments in the signaling mechanisms that regulate specific aspects of reactive astrogliosis and highlights the potential to identify novel therapeutic molecular targets for diverse neurological disorders. PMID:19782411

  7. 40 CFR Appendix Viii to Part 600 - Fuel Economy Label Formats

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 29 2010-07-01 2010-07-01 false Fuel Economy Label Formats VIII... POLICY FUEL ECONOMY AND CARBON-RELATED EXHAUST EMISSIONS OF MOTOR VEHICLES Pt. 600, App. VIII Appendix VIII to Part 600—Fuel Economy Label Formats EC01MY92.117 EC01MY92.118 EC01MY92.119...

  8. 40 CFR Appendix Viii to Part 600 - Fuel Economy Label Formats

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 30 2011-07-01 2011-07-01 false Fuel Economy Label Formats VIII... POLICY FUEL ECONOMY AND CARBON-RELATED EXHAUST EMISSIONS OF MOTOR VEHICLES Pt. 600, App. VIII Appendix VIII to Part 600—Fuel Economy Label Formats EC01MY92.117 EC01MY92.118 EC01MY92.119...

  9. Mechanism of deposit formation on fuel-wetted metal surfaces

    SciTech Connect

    Stavinoha, L.L.; Westbrook, S.R.; McInnis, L.A.

    1995-05-01

    Experiments were performed in a Single-Tube Heat Exchanger (STHE) apparatus and a Hot Liquid Process Simulator (HLPS) configured and operated to meet Jet Fuel Thermal Oxidation Tester (JFTOT) ASTM D 3241 requirements. The HLPS-JFTOT heater tubes used were 1018 mild steel, 316 stainless steel (SS), 304 stainless steel (SS), and 304 SS tubes coated with aluminum, magnesium, gold, and copper. A low-sulfur Jet A fuel with a breakpoint temperature of 254{degrees}C was used to create deposits on the heater tubes at temperatures of 300{degrees}C, 340{degrees}C, and 380{degrees}C. Deposit thickness was measured by dielectric breakdown voltage and Auger ion milling. Pronounced differences between the deposit thickness measuring techniques suggested that both the Auger milling rate and the dielectric strength of the deposit may be affected by deposit morphology/composition (such as metal ions that may have become included in the bulk of the deposit). Carbon burnoff data were obtained as a means of judging the validity of DMD-derived deposit evaluations. ESCA data suggest that the thinnest deposit was on the magnesium-coated test tube. The Scanning Electron Microscope (SEM) photographs showed marked variations in the deposit morphology and the results suggested that surface composition has a significant effect on the mechanism of deposition. The most dramatic effect observed was that the bulk of deposits moved to tube locations of lower temperature as the maximum temperature of the tube was increased from 300{degrees} to 380{degrees}C, also verified in a single-tube heat exchanger. The results indicate that the deposition rate and quantity at elevated temperatures is not completely temperature dependent, but is limited by the concentration of dissolved oxygen and/or reactive components in the fuel over a temperature range.

  10. Non-destructive assay of spent nuclear fuel using passive neutron Albedo reactivity

    SciTech Connect

    Evans, L G; Schear, M A; Croft, S; Tobin, S J; Swinhoe, M T; Menlove, H O

    2010-01-01

    Passive Neutron Albedo Reactivity (PNAR) is one of fourteen techniques that has been researched and evaluated to form part of a comprehensive and integrated detection system for the non-destructive assay (NDA) of spent nuclear fuel. PNAR implemented with {sup 3}He tubes for neutron detection (PNAR-{sup 3}He) is the measurement of time correlated neutrons from a spent fuel assembly with and without a Cadmium (Cd) layer surrounding the assembly. PNAR utilizes the self-interrogation of the fuel via reflection of neutrons born in the fuel assembly back in to the fuel assembly. The neutrons originate primarily from spontaneous fission events within the fuel itself (Curium-244) but are amplified by multiplication. The presence and removal of the Cd provides two measurement conditions with different neutron energy spectra and therefore different interrogating neutron characteristics. Cd has a high cross-section of absorption for slow neutrons and therefore greatly reduces the low energy (thermal) neutron fluence rate returning. The ratios of the Singles, Doubles and Triples count rates obtained in each case are known as the Cd ratios, which are related to fissile content. A potential safeguards application for which PNAR-{sup 3}He is particularly suited is 'fingerprinting'. Fingerprinting could function as an alternative to plutonium (Pu) mass determination; providing confidence that material was not diverted during transport between sites. PNAR-{sup 3}He has six primary NDA signatures: Singles, Doubles and Triples count rates measured with two energy spectra at both shipping and receiving sites. This is to uniquely identify the fuel assembly, and confirm no changes have taken place during transport. Changes may indicate all attempt to divert material for example. Here, the physics of the PNAR-{sup 3}He concept will be explained, alongside a discussion on the development of a prototypical PNAR-{sup 3}He instrument using simulation. The capabilities and performance of the

  11. Formation of dielectric silicon compounds by reactive magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Veselov, D. S.; Voronov, Yu A.

    2016-09-01

    The paper is devoted to the study of reactive magnetron sputtering of the silicon target in the ambient of inert argon gas with reactive gas, nitrogen or oxygen. The magnetron was powered by two mid-frequency generators of a rectangular pulse of opposite polarity. The negative polarity pulse provides the sputtering of the target. The positive polarity pulse provides removal of accumulated charge from the surface of the target. This method does not require any special devices of resistances matching and provides continuous sputtering of the target.

  12. Spent fuel measurements. passive neutron albedo reactivity (PNAR) and photon signatures

    SciTech Connect

    Eigenbrodt, Julia; Menlove, Howard Olsen

    2016-03-29

    The International Atomic Energy Agency’s (IAEA) safeguards technical objective is the timely detection of a diversion of a significant quantity of nuclear material from peaceful activities to the manufacture of nuclear weapons or of other nuclear explosive devices or for purposes unknown, and deterrence of such diversion by the risk of early detection. An important IAEA task towards meeting this objective is the ability to accurately and reliably measure spent nuclear fuel (SNF) to verify reactor operating parameters and verify that the fuel has not been removed from reactors or SNF storage facilities. This dissertation analyzes a method to improve the state-of-the-art of nuclear material safeguards measurements using two combined measurement techniques: passive neutron albedo reactivity (PNAR) and passive spectral photon measurements.

  13. Chemical reactivity testing for the National Spent Nuclear Fuel Program. Revision 2

    SciTech Connect

    Koester, L.W.

    2000-02-08

    This quality assurance project plan (QAPjP) summarizes requirements used by Lockheed Martin Energy Systems, Incorporated (LMES) Development Division at Y-12 for conducting chemical reactivity testing of Department of Energy (DOE) owned spent nuclear fuel, sponsored by the National Spent Nuclear Fuel Program (NSNFP). The requirements are based on the NSNFP Statement of work PRO-007 (Statement of Work for Laboratory Determination of Uranium Hydride Oxidation Reaction Kinetics.) This QAPjP will utilize the quality assurance program at Y-12, Y60-101PD, Quality Program Description, and existing implementing procedures for the most part in meeting the NSNFP Statement of Work PRO-007 requirements, exceptions will be noted. The project consists of conducting three separate series of related experiments, ''Passivation of Uranium Hydride Powder With Oxygen and Water'', '''Passivation of Uranium Hydride Powder with Surface Characterization'', and ''Electrochemical Measure of Uranium Hydride Corrosion Rate''.

  14. Pebble Fuel Handling and Reactivity Control for Salt-Cooled High Temperature Reactors

    SciTech Connect

    Peterson, Per; Greenspan, Ehud

    2015-02-09

    This report documents the work completed on the X-PREX facility under NEUP Project 11- 3172. This project seeks to demonstrate the viability of pebble fuel handling and reactivity control for fluoride salt-cooled high-temperature reactors (FHRs). The research results also improve the understanding of pebble motion in helium-cooled reactors, as well as the general, fundamental understanding of low-velocity granular flows. Successful use of pebble fuels in with salt coolants would bring major benefits for high-temperature reactor technology. Pebble fuels enable on-line refueling and operation with low excess reactivity, and thus simpler reactivity control and improved fuel utilization. If fixed fuel designs are used, the power density of salt- cooled reactors is limited to 10 MW/m3 to obtain adequate duration between refueling, but pebble fuels allow power densities in the range of 20 to 30 MW/m3. This can be compared to the typical modular helium reactor power density of 5 MW/m3. Pebble fuels also permit radial zoning in annular cores and use of thorium or graphite pebble blankets to reduce neutron fluences to outer radial reflectors and increase total power production. Combined with high power conversion efficiency, compact low-pressure primary and containment systems, and unique safety characteristics including very large thermal margins (>500°C) to fuel damage during transients and accidents, salt-cooled pebble fuel cores offer the potential to meet the major goals of the Advanced Reactor Concepts Development program to provide electricity at lower cost than light water reactors with improved safety and system performance.This report presents the facility description, experimental results, and supporting simulation methods of the new X-Ray Pebble Recirculation Experiment (X-PREX), which is now operational and being used to collect data on the behavior of slow dense granular flows relevant to pebble bed reactor core designs. The X

  15. REACTIVE MINERALS IN AQUIFERS: FORMATION PROCESSES AND QUANTITATIVE ANALYSIS

    EPA Science Inventory

    The presentation will focus on the occurrence, form, and characterization of reactive iron minerals in aquifers and soils. The potential for abiotic reductive transformations of contaminants at the mineral-water interface will be discussed along with available tools for site min...

  16. Effect of fuel molecular structure on soot formation in gas turbine engines

    NASA Technical Reports Server (NTRS)

    Naegeli, D. W.; Moses, C. A.

    1980-01-01

    A high-pressure research combustor operating over a wide range of burner inlet conditions was used to determine the effects of fuel molecular structure on soot formation. Six test fuels with equal hydrogen content (12.8 percent) were blended to stress different molecular components and final boiling points. The fuels containing high concentrations (20 percent) of poly-cyclic aromatics and partially saturated polycyclic structures such as tetralin, produced more soot than would be expected from a hydrogen content correlation for typical petroleum based fuels. However, fuels containing naphthenes, such as decalin, agreed with the hydrogen content correlation. The contribution of polycylic aromatics to soot formation was equivalent to a reduction in fuel hydrogen content of about 1%. The fuel sensitivity to soot formation due to the polycyclic aromatic contribution decreased as burner inlet pressure and fuel/air ratio increased.

  17. Effect of fuel molecular structure on soot formation in gas turbine engines

    NASA Technical Reports Server (NTRS)

    Naegeli, D. W.; Moses, C. A.

    1980-01-01

    A high-pressure research combustor operating over a wide range of burner inlet conditions was used to determine the effects of fuel molecular structure on soot formation. Six test fuels with equal hydrogen content (12.8 percent) were blended to stress different molecular components and final boiling points. The fuels containing high concentrations (20 percent) of poly-cyclic aromatics and partially saturated polycyclic structures such as tetralin, produced more soot than would be expected from a hydrogen content correlation for typical petroleum based fuels. However, fuels containing naphthenes, such as decalin, agreed with the hydrogen content correlation. The contribution of polycylic aromatics to soot formation was equivalent to a reduction in fuel hydrogen content of about 1%. The fuel sensitivity to soot formation due to the polycyclic aromatic contribution decreased as burner inlet pressure and fuel/air ratio increased.

  18. Millisecond autothermal catalytic reforming of carbohydrates for synthetic fuels by reactive flash volatilization

    NASA Astrophysics Data System (ADS)

    Dauenhauer, Paul Jakob

    Carbohydrates including glucose, cellulose, starch and polyols including glycerol, ethylene glycol and methanol produced in large quantities from biomass are considered as a carbon-based feedstock for high temperature catalytic reforming by catalytic partial oxidation. Autothermal catalytic partial oxidation of methanol, ethylene glycol, and glycerol with Rh and Pt-based catalysts with ceria on alumina foam supports at residence times less than ten milliseconds produced equilibrium selectivity to synthesis gas. The addition of steam at S/C>4 produced selectivity to H2 higher than 80% with little or no selectivity to minor products. In a new process referred to as 'reactive flash volatilization,' catalytic partial oxidation was combined with pyrolysis of biomass by directly impinging particles of cellulose, starch, polyethylene, soy oil, or Aspen (Populous Tremuloides) on an operating Rh-based reforming catalyst at 700-800°C. Solid particles endothermically pyrolyzed to volatile organic compounds which mixed with air and reformed on the catalyst exothermically generating heat to drive the overall process. Particles of ˜250 mum microcrystalline cellulose processed at the conditions of C/O=1.0 on a RhCe/gamma-Al2O3/alpha-Al 2O3 at a residence time of ˜70 milliseconds produced a gaseous effluent stream selecting for 50% H2 and 50% CO with no observable side products other than H2O and CO2, and <1% CH4. To obtain a more optimal synthesis gas stream, the reforming of ˜400 mum microcrystalline particles was examined over a fixed bed of RhCe/gamma-Al2O3/alpha-Al2O 3 spheres by varying the feed ratio of N2/O2, the temperature of the feed gas, the total particle feed rate, and the addition of steam permitting cellulose conversion with ˜75% fuel efficiency. Cellulose, sucrose, and glycerol particle conversion was examined with high-speed photography (1000 frames/second) revealing the formation of a liquid intermediate from cellulose permitting extremely high heat flux (

  19. Investigation of the Effect of Fixed Absorbers on the Reactivity of PWR Spent Nuclear Fuel for Burnup Credit

    SciTech Connect

    Wagner, John C.; Sanders, Charlotta E.

    2002-08-15

    The effect of fixed absorbers on the reactivity of pressurized water reactor (PWR) spent nuclear fuel (SNF) in support of burnup-credit criticality safety analyses is examined. A fuel assembly burned in conjunction with fixed absorbers may have a higher reactivity for a given burnup than an assembly that has not used fixed absorbers. As a result, guidance on burnup credit, issued by the U.S. Nuclear Regulatory Commission's Spent Fuel Project Office, recommends restricting the use of burnup credit to assemblies that have not used burnable absorbers. This recommendation eliminates a large portion of the currently discharged SNF from loading in burnup credit casks and thus severely limits the practical usefulness of burnup credit. Therefore, data are needed to support the extension of burnup credit to additional SNF. This research investigates the effect of various fixed absorbers, including integral burnable absorbers, burnable poison rods, control rods, and axial power shaping rods, on the reactivity of PWR SNF. Trends in reactivity with relevant parameters (e.g., initial fuel enrichment, burnup and absorber type, exposure, and design) are established, and anticipated reactivity effects are quantified. Where appropriate, recommendations are offered for addressing the reactivity effects of the fixed absorbers in burnup-credit safety analyses.

  20. Effect of Fuel Variables on Carbon Formation in Turbojet-Engine Combustors

    NASA Technical Reports Server (NTRS)

    Jonash, Edmund R; Wear, Jerrold D; Cook, William P

    1958-01-01

    Report presents the results of an investigation of the effects of fuel properties and of a number of fuel additives on combustion-chamber carbon deposition and exhaust-gas smoke formation in a single tubular turbojet-engine combustor. Limited tests were conducted with a number of the fuels in several full-scale turbojet engines to verify single-combustor data.

  1. Environmental implications of iron fuel borne catalysts and their effects on diesel particulate formation and composition

    EPA Science Inventory

    Metal fuel borne catalysts can be used with diesel fuels to effectively reduce engine out particle mass emissions. Mixed with the fuel, the metals become incorporated as nanometer-scale occlusions with soot during its formation and are available to promote in-cylinder soot oxida...

  2. Environmental implications of iron fuel borne catalysts and their effects on diesel particulate formation and composition

    EPA Science Inventory

    Metal fuel borne catalysts can be used with diesel fuels to effectively reduce engine out particle mass emissions. Mixed with the fuel, the metals become incorporated as nanometer-scale occlusions with soot during its formation and are available to promote in-cylinder soot oxida...

  3. 40 CFR 600.310-12 - Fuel economy label format requirements-electric vehicles.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 31 2012-07-01 2012-07-01 false Fuel economy label format requirements-electric vehicles. 600.310-12 Section 600.310-12 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) ENERGY POLICY FUEL ECONOMY AND GREENHOUSE GAS EXHAUST EMISSIONS OF MOTOR VEHICLES Fuel...

  4. Incremental Reactivity Effects of Anthropogenic and Biogenic Volatile Organic Compounds on Secondary Organic Aerosol Formation

    NASA Astrophysics Data System (ADS)

    Kacarab, M.; Li, L.; Carter, W. P. L.; Cocker, D. R., III

    2015-12-01

    Two surrogate reactive organic gas (ROG) mixtures were developed to create a controlled reactivity environment simulating different urban atmospheres with varying levels of anthropogenic (e.g. Los Angeles reactivity) and biogenic (e.g. Atlanta reactivity) influences. Traditional chamber experiments focus on the oxidation of one or two volatile organic compound (VOC) precursors, allowing the reactivity of the system to be dictated by those compounds. Surrogate ROG mixtures control the overall reactivity of the system, allowing for the incremental aerosol formation from an added VOC to be observed. The surrogate ROG mixtures were developed based on that used to determine maximum incremental reactivity (MIR) scales for O3 formation from VOC precursors in a Los Angeles smog environment. Environmental chamber experiments were designed to highlight the incremental aerosol formation in the simulated environment due to the addition of an added anthropogenic (aromatic) or biogenic (terpene) VOC. All experiments were conducted in the UC Riverside/CE-CERT dual 90m3 environmental chambers. It was found that the aerosol precursors behaved differently under the two altered reactivity conditions, with more incremental aerosol being formed in the anthropogenic ROG system than in the biogenic ROG system. Further, the biogenic reactivity condition inhibited the oxidation of added anthropogenic aerosol precursors, such as m-xylene. Data will be presented on aerosol properties (density, volatility, hygroscopicity) and bulk chemical composition in the gas and particle phases (from a SYFT Technologies selected ion flow tube mass spectrometer, SIFT-MS, and Aerodyne high resolution time of flight aerosol mass spectrometer, HR-ToF-AMS, respectively) comparing the two controlled reactivity systems and single precursor VOC/NOx studies. Incremental aerosol yield data at different controlled reactivities provide a novel and valuable insight in the attempt to extrapolate environmental chamber

  5. Formation, structures, and reactivities of niobium oxide cluster ions

    SciTech Connect

    Deng, H.T.; Kerns, K.P.; Castleman, A.W. Jr.

    1996-08-01

    Niobium oxide cluster ions are produced by a laser-induced plasma source. The cluster distribution, collision-induced dissociation (CID), and cluster reactivities are studied using a triple-quadrupole mass spectrometer. CID experiments on the cluster ions Nb{sub 3}O{sub 7-9}{sup +}, Nb{sub 4}O{sub 9-11}{sup +}, and Nb{sub 5}O{sub 12}{sup +} reveal that their building blocks are Nb{sub 2}O{sub 5}, NbO{sub 2}{sup +}, NbO{sub 3}, Nb{sub 3}O{sub 7}{sup +}, O, and O{sub 2}, whereby the cluster stoichiometry is assigned to have the general form (NbO{sub 3}){sub m}(NbO{sub 2}){sub n}(O){sub 0-4}{sup +}. The trends in the ionization potentials of these species are estimated in terms of the CID fragments produced. Nb{sub 3}O{sub 8-9}{sup +} and Nb{sub 4}O{sub 11}{sup +} cluster ions evidently form via the adsorption of one oxygen atom or molecule onto the cluster surface. Nb{sub 3}O{sub 7}{sup +}, Nb{sub 4}O{sub 9}{sup +}, and Nb{sub 5}O{sub 12}{sup +} have strong reactivities to abstract an oxygen atom from oxygen-containing molecules and adsorb small hydrocarbons at near thermal energies. In particular, the reactivity of the oxygen atom or molecule in the oxide clusters Nb{sub 3}O{sub 8-9}{sup +} and Nb{sub 4}O{sub 11}{sup +} is consistent with our suggestions that it has a radical oxygen character. 37 refs., 8 figs., 1 tab.

  6. Simulation of Supersonic Reactive Flow in Ramped Cavity Combustor with Fuel Injector

    NASA Astrophysics Data System (ADS)

    Ghiasi, Zia; Komperda, Jonathan; Li, Dongru; Mashayek, Farzad; Computational Multiphase Transport Laboratory Team

    2014-11-01

    Numerical simulation of supersonic reactive flows is emerging as an essential stage toward efficient design and development of scramjets. The flow inside the combustion chamber of scramjet is a prime example of multi-scale and multi-physics flow and is often accompanied by concurrent presence of shock waves and turbulence. Developing a robust numerical method for such simulations leads to numerous challenges due to the presence of complex geometries, shocks, turbulence and chemical reaction, which require massively parallel computation. In the present work we use the Discontinuous Spectral Element Method (DSEM) for high-fidelity simulation of reactive, supersonic and turbulent flows. The code features an entropy-based artificial viscosity method for capturing shock waves and uses implicit Large Eddy Simulation (LES) method for turbulence modeling. The turbulence-combustion interaction is captured using the Filtered Mass Density Function (FMDF) method. A supersonic reactive flow within a ramped cavity flame holder with round fuel injectors is simulated for hydrogen/air reaction, and the physics of the flow is studied.

  7. Analyzing the impact of reactive transport on the repository performance of TRISO fuel

    NASA Astrophysics Data System (ADS)

    Schmidt, Gregory

    graphite surrounding the spent HTGR fuel will impact the release of aqueous uranium from the TRISO fuel. In order to answer this question, the sorption and partitioning behavior of uranium to graphite under a variety of conditions was investigated. Key systematic variables that were analyzed include solution pH, dissolved carbonate concentration, uranium metal concentration and ionic strength. The kinetics and desorption characteristics of uranium/graphite partitioning were studied as well. The graphite used in these experiments was also characterized by a variety of techniques and conclusions are drawn about the relevant surface chemistry of graphite. This data was then used to generate a model for the reactive transport of uranium in a graphite matrix. This model was implemented with the software code CXTFIT and validated through the use of column studies mirroring the predicted system.

  8. Formation of tetragonal hydrogen tungsten bronze by reactive mechanical alloying

    SciTech Connect

    Urretavizcaya, G. Tonus, F.; Gaudin, E.; Bobet, J.-L.; Castro, F.J.

    2007-10-15

    Hydrogen tungsten bronzes have been synthesized by reactive mechanical alloying monoclinic tungsten (VI) oxide under hydrogen atmosphere. Two milling devices with different energy ranges were used. Regardless of the distinct reaction times, a similar phase evolution was observed with both apparatus. The characterization of the materials was performed by XRD, SEM, DSC and total hydrogen content determination. The final product obtained was a mixture of tetragonal H{sub 0.33}WO{sub 3} and H{sub 0.23}WO{sub 3} bronzes. - Graphical abstract: Hydrogen tungsten bronzes have been synthesized by reactive mechanical alloying (RMA) monoclinic WO{sub 3} under H{sub 2} atmosphere. By using two milling devices with different energy ranges a similar phase evolution with distinct reaction times was observed. The materials were characterized by XRD, SEM, DSC and total hydrogen content determination. The final product obtained was a mixture of tetragonal H{sub 0.33}WO{sub 3} and H{sub 0.23}WO{sub 3} bronzes. Display Omitted.

  9. PRD (power-reactivity-decrement) components of a homogeneous U10Zr-fueled 900 MWt LMR

    SciTech Connect

    Meneghetti, D.; Kucera, D.A.

    1988-01-01

    The linear and Doppler feedback components of the regional contributions of the power-reactivity-decrement (PRD) for a representative 900 MWt homogeneous U10Zr-fueled sodium-cooled reactor are calculated. The PRD is the reactivity required to bring the reactor from zero-power hot-critical condition to a given power level. These components are further separated into power dependent and power-to-flow dependent parts. The values are compared with corresponding quantities calculated for the Experimental Breeder Reactor II (EBR-II). The implications of these comparisons upon inherent safety characteristics of metal-fueled sodium-cooled reactors are discussed. The effects of fuel axial restraint on feedback, resulting from possible fuel-clad interactions due to burnup are also calculated. The possible enhancement of desirable feedbacks by use of appropriately designed subassembly-duct bowing feedback characteristics is estimated.

  10. Fuel Structure and Pressure Effects on the Formation of Soot Particles in Diffusion Flames

    DTIC Science & Technology

    1990-05-01

    higher values of the pressure power dependence appear to be related to fuel structure effects , the direct nature of which remains to be understood...61102F 2308 A2 11. TITLE (Include Security Classification) "Fuel Structure and Pressure Effects on the Formation of Soot Particlesin Diffusion Flames...block number) Studies emphasizing the effects of fuel concentration and operating pressure on the formation of soot particles have been conducted in a

  11. Performance of Transuranic-Loaded Fully Ceramic Micro-Encapsulated Fuel in LWRs Final Report, Including Void Reactivity Evaluation

    SciTech Connect

    Michael A. Pope; R. Sonat Sen; Brian Boer; Abderrafi M. Ougouag; Gilles Youinou

    2011-09-01

    The current focus of the Deep Burn Project is on once-through burning of transuranics (TRU) in light-water reactors (LWRs). The fuel form is called Fully-Ceramic Micro-encapsulated (FCM) fuel, a concept that borrows the tri-isotropic (TRISO) fuel particle design from high-temperature reactor technology. In the Deep Burn LWR (DB-LWR) concept, these fuel particles are pressed into compacts using SiC matrix material and loaded into fuel pins for use in conventional LWRs. The TRU loading comes from the spent fuel of a conventional LWR after 5 years of cooling. Unit cell and assembly calculations have been performed using the DRAGON-4 code to assess the physics attributes of TRU-only FCM fuel in an LWR lattice. Depletion calculations assuming an infinite lattice condition were performed with calculations of various reactivity coefficients performed at each step. Unit cells and assemblies containing typical UO2 and mixed oxide (MOX) fuel were analyzed in the same way to provide a baseline against which to compare the TRU-only FCM fuel. Then, assembly calculations were performed evaluating the performance of heterogeneous arrangements of TRU-only FCM fuel pins along with UO2 pins.

  12. Aerobic granular sludge inoculated microbial fuel cells for enhanced epoxy reactive diluent wastewater treatment.

    PubMed

    Cheng, Kai; Hu, Jingping; Hou, Huijie; Liu, Bingchuan; Chen, Qin; Pan, Keliang; Pu, Wenhong; Yang, Jiakuan; Wu, Xu; Yang, Changzhu

    2017-04-01

    Microbial consortiums aggregated on the anode surface of microbial fuel cells (MFCs) are critical factors for electricity generation as well as biodegradation efficiencies of organic compounds. Here in this study, aerobic granular sludge (AGS) was assembled on the surface of the MFC anode to form an AGS-MFC system with superior performance on epoxy reactive diluent (ERD) wastewater treatment. AGS-MFCs successfully shortened the startup time from 13d to 7d compared to the ones inoculated with domestic wastewater. Enhanced toxicity tolerance as well as higher COD removal (77.8% vs. 63.6%) were achieved. The higher ERD wastewater treatment efficiency of AGS-MFC is possibly attributed to the diverse microbial population on MFC biofilm, as well as the synergic degradation of contaminants by both the MFC anode biofilm and AGS granules.

  13. Formation and reactivity of vinylperoxyl radicals in aqueous solutions

    SciTech Connect

    Khaikin, G.I.; Neta, P.

    1995-03-30

    Vinyl, carboxyvinyl and dicarboxyvinyl radicals were produced in irradiated aqueous solutions from acetylene and acetylenecarboxylic and acetylenedicarboxylic acid by addition of H atom to the triple bond or by reaction with e{sub aq}{sup -}, followed by protonation. Vinyl and phenylvinyl radicals were produced by reductive dehalogenation of vinyl bromide and {beta}-bromostyrene with e{sub aq}{sup -}. All these vinyl radicals react rapidly with oxygen to produce the corresponding vinylperoxyl radicals. Vinylperoxyl radicals exhibit optical absorptions in the UV ({lambda}{sub max} 250-290 nm) and in the visible range. The peaks in the visible range were at 440 nm for unsubstituted vinylperoxyl radical, between 480 and 520 nm for carboxylated vinylperoxyl, depending on pH and number of carboxyl groups, and at 540 and 690 nm for (2-phenylvinyl)peroxyl. These vinylperoxyl radicals oxidize organic reductants such as 2,2`azinobis(3-ethylbenzothiazoline-6-sulfonate ion) (ABTS), chlorpromazine, ascorbate, and 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox C) with rate constants between 4 x 10{sup 5} and 2 x 10{sup 9} L mol{sup -1} s{sup -1}, depending on the radical and the reductant. Vinylperoxyl radicals are more reactive than similarly substituted alkylperoxyl. 20 refs., 5 figs., 1 tab.

  14. Formation Processes and Impacts of Reactive and Nonreactive Minerals in Permeable Reactive Barriers

    EPA Science Inventory

    Mineral precipitates in zero-valent iron PRBs can be classified by formation processes into three groups: 1) those that result from changes in chemical conditions (i.e., changes in pH, e.g., calcite); 2) those that are a consequence of microbial activity (i.e., sulfate reduction,...

  15. Formation Processes and Impacts of Reactive and Nonreactive Minerals in Permeable Reactive Barriers

    EPA Science Inventory

    Mineral precipitates in zero-valent iron PRBs can be classified by formation processes into three groups: 1) those that result from changes in chemical conditions (i.e., changes in pH, e.g., calcite); 2) those that are a consequence of microbial activity (i.e., sulfate reduction,...

  16. Modeling the Influence of Interaction Layer Formation on Thermal Conductivity of U–Mo Dispersion Fuel

    SciTech Connect

    Burkes, Douglas; Casella, Andrew M.; Huber, Tanja K.

    2015-01-01

    The Global Threat Reduction Initiative Program continues to develop existing and new plate- and rod-type research and test reactor fuels with maximum attainable uranium loadings capable of potentially converting a number of the world’s remaining high-enriched uranium fueled reactors to low-enriched uranium fuel. Currently, the program is focused on assisting with the development and qualification of an even higher density fuel type consisting of a uranium-molybdenum (U-Mo) alloy dispersed in an aluminum matrix. Thermal conductivity is an important consideration in determining the operational temperature of the fuel plate and can be influenced by interaction layer formation between the fuel and matrix, porosity that forms during fabrication of the fuel plates, and upon the concentration of the dispersed phase within the matrix. This paper develops and validates a simple model to study the influence of interaction layer formation and conductivity, fuel particle size, and volume fraction of fuel dispersed in the matrix on the effective conductivity of the composite. The model shows excellent agreement with results previously presented in the literature. In particular, the thermal conductivity of the interaction layer does not appear to be important in determining the overall conductivity of the composite, while formation of the interaction layer and subsequent consumption of the matrix reveals a rather significant effect. The effective thermal conductivity of the composite can be influenced by the fuel particle distribution by minimizing interaction layer formation and preserving the higher thermal conductivity matrix.

  17. Power and power-to-flow reactivity transfer functions in EBR-II (Experimental Breeder Reactor II) fuel

    SciTech Connect

    Grimm, K.N.; Meneghetti, D. )

    1989-11-01

    Reactivity transfer functions are important in determining the reactivity history during a power transient. Overall nodal transfer functions have been calculated for different subassembly types in the Experimental Breeder Reactor II (EBR-II). Steady-state calculations for temperature changes and, hence, reactivities for power changes have been separated into power and power-to-flow-dependent terms. Axial nodal transfer functions separated into power and power-to-flow-dependent components are reported in this paper for a typical EBR-II fuel pin. This provides an improved understanding of the time dependence of these components in transient situations.

  18. Spectroscopic studies of particulate formation in fuel blends

    NASA Astrophysics Data System (ADS)

    Manciu, Felicia; Subramanya, Mahesh; Govani, Jayesh; Choudhuri, Ahsan

    2007-10-01

    The Raman and infrared absorption spectroscopy were used to investigate the properties of carbon nanotubes (CNTs) flame-synthesized using CH4-H2 low calorific value gases. The development of large amounts of CNTs benefits from flame synthesis processes, where the fuel serves as both the heating and the reactant source. As a result of flame condition studies it was determined that the CNT growth region is at 20-30% of the visible flame height and at a flow rate between 7.18E-07 m^3/s and 9.57E-07 m^3/s. Preliminary characterizations of the samples by Scanning Electron Microscopy demonstrate that the formation of nanostructure occurs only for <10% H2 concentration. The Raman analysis of the pristine samples shows the existence of distinctive multi-walled carbon nanotube (MWNT) D and G bands at 1321 cm-1 and 1595 cm-1, respectively. Besides the vibrational lines characteristic to MWNTs, infrared absorption measurements also reveal the presence of C-H bonds.

  19. Formation of thin walled ceramic solid oxide fuel cells

    DOEpatents

    Claar, Terry D.; Busch, Donald E.; Picciolo, John J.

    1989-01-01

    To reduce thermal stress and improve bonding in a high temperature monolithic solid oxide fuel cell (SOFC), intermediate layers are provided between the SOFC's electrodes and electrolyte which are of different compositions. The intermediate layers are comprised of a blend of some of the materials used in the electrode and electrolyte compositions. Particle size is controlled to reduce problems involving differential shrinkage rates of the various layers when the entire structure is fired at a single temperature, while pore formers are provided in the electrolyte layers to be removed during firing for the formation of desired pores in the electrode layers. Each layer includes a binder in the form of a thermosetting acrylic which during initial processing is cured to provide a self-supporting structure with the ceramic components in the green state. A self-supporting corrugated structure is thus formed prior to firing, which the organic components of the binder and plasticizer removed during firing to provide a high strength, high temperature resistant ceramic structure of low weight and density.

  20. Formation of Reactive Br Species by Freezing in Solutions of NaBr-Metal-Hydrogen Peroxide

    NASA Astrophysics Data System (ADS)

    Kinjo, M.; Arakaki, T.

    2005-12-01

    The role of reactive halogen species (e.g. BrOH) in the destruction of stratospheric ozone is well known and largely understood. In recent years, it became clear that reactive Br species can also play a significant role in tropospheric ozone destruction, but sources of reactive Br species in the troposphere are not well understood. When an aqueous solution is frozen, solutes in the solution are excluded from the ice phase and the solutes are concentrated in the solution phase. Freezing processes cause red-ox reactions in the solution. We tried to understand the effects of freezing processes of solutions on formation of reactive Br species. Hydrogen peroxide (HOOH) and metallic ions were added to a mixing solution of NaBr and allyl alcohol (AA). If reactive Br species are formed, they react with AA, and free Br ion concentration decreases in the solution. When HOOH and Fe(III) or Cu(II) were added to the NaBr and AA solution and frozen, free Br ion concentration decreased. It is possible that OH radical formation from reaction between HOOH and Fe(II) or Cu(I) was induced by freezing processes and the OH radical probably oxidized Br ion to reactive Br species. Study of the effects of pH showed that decrease of Br ion concentration was the highest at pH = 4.0. Freezing processes could be an important source of reactive Br species in high altitude clouds and Polar Regions.

  1. 40 CFR 600.308-12 - Fuel economy label format requirements-plug-in hybrid electric vehicles.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 31 2012-07-01 2012-07-01 false Fuel economy label format requirements... PROTECTION AGENCY (CONTINUED) ENERGY POLICY FUEL ECONOMY AND GREENHOUSE GAS EXHAUST EMISSIONS OF MOTOR VEHICLES Fuel Economy Labeling § 600.308-12 Fuel economy label format requirements—plug-in hybrid...

  2. 40 CFR 600.308-12 - Fuel economy label format requirements-plug-in hybrid electric vehicles.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 31 2013-07-01 2013-07-01 false Fuel economy label format requirements... PROTECTION AGENCY (CONTINUED) ENERGY POLICY FUEL ECONOMY AND GREENHOUSE GAS EXHAUST EMISSIONS OF MOTOR VEHICLES Fuel Economy Labeling § 600.308-12 Fuel economy label format requirements—plug-in hybrid...

  3. 40 CFR 600.308-12 - Fuel economy label format requirements-plug-in hybrid electric vehicles.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 30 2014-07-01 2014-07-01 false Fuel economy label format requirements... PROTECTION AGENCY (CONTINUED) ENERGY POLICY FUEL ECONOMY AND GREENHOUSE GAS EXHAUST EMISSIONS OF MOTOR VEHICLES Fuel Economy Labeling § 600.308-12 Fuel economy label format requirements—plug-in hybrid...

  4. A Study on Reactive Spray Deposition Technology Processing Parameters in the Context of Pt Nanoparticle Formation

    NASA Astrophysics Data System (ADS)

    Roller, Justin M.; Maric, Radenka

    2015-12-01

    Catalytic materials are complex systems in which achieving the desired properties (i.e., activity, selectivity and stability) depends on exploiting the many degrees of freedom in surface and bulk composition, geometry, and defects. Flame aerosol synthesis is a process for producing nanoparticles with ample processing parameter space to tune the desired properties. Flame dynamics inside the reactor are determined by the input process variables such as solubility of precursor in the fuel; solvent boiling point; reactant flow rate and concentration; flow rates of air, fuel and the carrier gas; and the burner geometry. In this study, the processing parameters for reactive spray deposition technology, a flame-based synthesis method, are systematically evaluated to understand the residence times, reactant mixing, and temperature profiles of flames used in the synthesis of Pt nanoparticles. This provides a framework for further study and modeling. The flame temperature and length are also studied as a function of O2 and fuel flow rates.

  5. Oxidation and formation of deposit precursors in hydrocarbon fuels

    NASA Technical Reports Server (NTRS)

    Buttrill, S. E., Jr.; Mayo, F. R.; Lan, B.; St.john, G. A.; Dulin, D.

    1982-01-01

    A practical fuel, home heating oil no. 2 (Fuel C), and the pure hydrocarbon, n-dodecane, were subjected to mild oxidation at 130 C and the resulting oxygenated reaction products, deposit precursors, were analyzed using field ionization mass spectrometry. Results for fuel C indicated that, as oxidation was initially extended, certain oxygenated reaction products of increasing molecular weights in the form of monomers, dimers and some trimers were produced. Further oxidation time increase resulted in further increase in monomers but a marked decrease in dimers and trimers. This suggests that these larger molecular weight products have proceeded to form deposit and separated from the fuel mixture. Results for a dodecane indicated that yields for dimers and trimers were very low. Dimers were produced as a result of interaction between oxygenated products with each other rather than with another fuel molecule. This occurred even though fuel molecule concentration was 50 times, or more greater than that for these oxygenated reaction products.

  6. Rim structure formation and high burnup fuel behavior of large-grained UO 2 fuels

    NASA Astrophysics Data System (ADS)

    Une, K.; Hirai, M.; Nogita, K.; Hosokawa, T.; Suzawa, Y.; Shimizu, S.; Etoh, Y.

    2000-01-01

    Irradiation-induced fuel microstructural evolution of the sub-divided grain structure, or rim structure, of large-grained UO 2 pellets has been examined through detailed PIEs. Besides standard grain size pellets with a grain size range of 9-12 μm, two types of undoped and alumino-silicate doped large-grained pellets with a range of 37-63 μm were irradiated in the Halden heavy water reactor up to a cross-sectional pellet average burnup of 86 GWd/t. The effect of grain size on the rim structure formation was quantitatively evaluated in terms of the average Xe depression in the pellet outside region measured by EPMA, based on its lower sensitivity for Xe enclosed in the coarsened rim bubbles. The Xe depression in the high burnup pellets above 60 GWd/t was proportional to d-0.5- d-1.0 ( d: grain size), and the two types of large-grained pellets showed remarkable resistance to the rim structure formation. A high density of dislocations preferentially decorated the as-fabricated grain boundaries and the sub-divided grain structure was localized there. These observations were consistent with our proposed formation mechanism of rim structure, in which tangled dislocation networks are organized into the nuclei for recrystallized or sub-divided grains. In addition to higher resistance to the microstructure change, the large-grained pellets showed a smaller swelling rate at higher burnups and a lower fission gas release during base irradiation.

  7. Formation and Reactivity of Organo-Functionalized Tin Selenide Clusters.

    PubMed

    Rinn, Niklas; Eußner, Jens P; Kaschuba, Willy; Xie, Xiulan; Dehnen, Stefanie

    2016-02-24

    Reactions of R(1) SnCl3 (R(1) =CMe2 CH2 C(O)Me) with (SiMe3 )2 Se yield a series of organo-functionalized tin selenide clusters, [(SnR(1) )2 SeCl4 ] (1), [(SnR(1) )2 Se2 Cl2 ] (2), [(SnR(1) )3 Se4 Cl] (3), and [(SnR(1) )4 Se6 ] (4), depending on the solvent and ratio of the reactants used. NMR experiments clearly suggest a stepwise formation of 1 through 4 by subsequent condensation steps with the concomitant release of Me3 SiCl. Furthermore, addition of hydrazines to the keto-functionalized clusters leads to the formation of hydrazone derivatives, [(Sn2 (μ-R(3) )(μ-Se)Cl4 ] (5, R(3) =[CMe2 CH2 CMe(NH)]2 ), [(SnR(2) )3 Se4 Cl] (6, R(2) =CMe2 CH2 C(NNH2 )Me), [(SnR(4) )3 Se4 ][SnCl3 ] (7, R(4) =CMe2 CH2 C(NNHPh)Me), [(SnR(2) )4 Se6 ] (8), and [(SnR(4) )4 Se6 ] (9). Upon treatment of 4 with [Cu(PPh3 )3 Cl] and excess (SiMe3 )2 Se, the cluster fragments to form [(R(1) Sn)2 Se2 (CuPPh3 )2 Se2 ] (10), the first discrete Sn/Se/Cu cluster compound reported in the literature. The derivatization reactions indicate fundamental differences between organotin sulfide and organotin selenide chemistry.

  8. Formation mechanisms, structure, solution behavior, and reactivity of aminodiborane.

    PubMed

    Li, Huizhen; Ma, Nana; Meng, Wenjuan; Gallucci, Judith; Qiu, Yongqing; Li, Shujun; Zhao, Qianyi; Zhang, Jie; Zhao, Ji-Cheng; Chen, Xuenian

    2015-09-30

    A facile synthesis of cyclic aminodiborane (NH2B2H5, ADB) from ammonia borane (NH3·BH3, AB) and THF·BH3 has made it possible to determine its important characteristics. Ammonia diborane (NH3BH2(μ-H)BH3, AaDB) and aminoborane (NH2BH2, AoB) were identified as key intermediates in the formation of ADB. Elimination of molecular hydrogen occurred from an ion pair, [H2B(NH3) (THF)](+)[BH4](-). Protic-hydridic hydrogen scrambling was proved on the basis of analysis of the molecular hydrogen products, ADB and other reagents through (2)H NMR and MS, and it was proposed that the scrambling occurred as the ion pair reversibly formed a BH5-like intermediate, [(THF)BH2NH2](η(2)-H2)BH3. Loss of molecular hydrogen from the ion pair led to the formation of AoB, most of which was trapped by BH3 to form ADB with a small amount oligomerizing to (NH2BH2)n. Theoretical calculations showed the thermodynamic feasibility of the proposed intermediates and the activation processes. The structure of the ADB·THF complex was found from X-ray single crystal analysis to be a three-dimensional array of zigzag chains of ADB and THF, maintained by hydrogen and dihydrogen bonding. Room temperature exchange of terminal and bridge hydrogens in ADB was observed in THF solution, while such exchange was not observed in diethyl ether or toluene. Both experimental and theoretical results confirm that the B-H-B bridge in ADB is stronger than that in diborane (B2H6, DB). The B-H-B bridge is opened when ADB and NaH react to form sodium aminodiboronate, Na[NH2(BH3)2]. The structure of the sodium salt as its 18-crown-6 ether adduct was determined by X-ray single crystal analysis.

  9. Fuel Efficient Strategies for Reducing Contrail Formations in United States Air Space

    NASA Technical Reports Server (NTRS)

    Sridhar, Banavar; Chen, Neil Y.; Ng, Hok K.

    2010-01-01

    This paper describes a class of strategies for reducing persistent contrail formation in the United States airspace. The primary objective is to minimize potential contrail formation regions by altering the aircraft's cruising altitude in a fuel-efficient way. The results show that the contrail formations can be reduced significantly without extra fuel consumption and without adversely affecting congestion in the airspace. The contrail formations can be further reduced by using extra fuel. For the day tested, the maximal reduction strategy has a 53% contrail reduction rate. The most fuel-efficient strategy has an 8% reduction rate with 2.86% less fuel-burnt compared to the maximal reduction strategy. Using a cost function which penalizes extra fuel consumed while maximizing the amount of contrail reduction provides a flexible way to trade off between contrail reduction and fuel consumption. It can achieve a 35% contrail reduction rate with only 0.23% extra fuel consumption. The proposed fuel-efficient contrail reduction strategy provides a solution to reduce aviation-induced environmental impact on a daily basis.

  10. Atomically dispersed Pd catalysts in graphyne nanopore: formation and reactivity

    NASA Astrophysics Data System (ADS)

    Gu, Yongbing; Chen, Xianlang; Cao, Yongyong; Zhuang, Guilin; Zhong, Xing; Wang, Jianguo

    2017-07-01

    The formation of single-atom noble metal catalysts on carbon materials remains a challenge due to the weak interaction between metals and pristine carbon. By means of density functional theory (DFT) calculations, it is found that the atomically dispersed Pd in graphyne nanopore is much more stable than that of relative Pd clusters. The large diffusion barrier of Pd from the most stable hollow site to the bridge site confirms the kinetic stability of such structures. While CO adsorption causes the pulling of Pd from graphyne nanopore due to the low diffusion barrier, based on DFT calculations, which can be further confirmed by ab initio molecular dynamic simulations. Finally, CO oxidation on the reconstruction of Pd@graphyne exhibits an energy barrier of 0.62 eV in the rate-limiting step through the Langmuir-Hinshelwood mechanism. After the reaction, the catalyst can be restored to the original atomically dispersed state again. This study shows graphyne is an excellent support for an atomically dispersed or single-metal catalyst.

  11. Formation and reactivity of pyridylperoxyl radicals in solution

    SciTech Connect

    Alfassi, Z.B.; Khaikin, G.I.; Neta, P.

    1995-03-30

    2-Pyridyl radicals were produced by the reaction of 2-chloro- or 2-bromopyridine with solvated electrons (k approximately 10{sup 10} L mol{sup -1} s{sup -1}) and reacted rapidly with oxygen (k = 2.2 x 10{sup 9} L mol{sup -1} s{sup -1}) to produce the 2-pyridylperoxyl radical. This radical exhibits optical absorption in the visible range, with {lambda}{sub max} at 440 nm. 2-Pyridylperoxyl radical is a fairly strong oxidant, which reacts with 2,2`-azinobis(3-ethylbenzothiazoline-6-sulfonate ion) (ABTS), chlorpromazine, and 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox C) by one-electron oxidation. The rate constants k for these reactions, determined from the rate of formation of the one-electron oxidation as a function of substrate concentration, vary between 2 x 10{sup 6} and 2 x 10{sup 9} L mol{sup -1} s{sup -1} in various mixtures. For each substrate, a good correlation was found between log k and the cohesive pressure of the solvent or solvent mixture, as found before for CCI{sub 3}O{sub 2} radical reactions in nearly neat solvents. 3-Bromo, 3-chloro- and 4-chloropyridine also reacted rapidly with solvated electrons, but their radical anions underwent protonation on the nitrogen in competition with the dehalogenation process. Therefore, no pyridylperoxyl radicals were formed from these species in aqueous solutions and only partial yield was found in neat methanol. 20 refs., 4 figs., 1 tab.

  12. Involvement of Cytochrome P450 in Reactive Oxygen Species Formation and Cancer.

    PubMed

    Hrycay, Eugene G; Bandiera, Stelvio M

    2015-01-01

    This review examines the involvement of cytochrome P450 (CYP) enzymes in the formation of reactive oxygen species in biological systems and discusses the possible involvement of reactive oxygen species and CYP enzymes in cancer. Reactive oxygen species are formed in biological systems as byproducts of the reduction of molecular oxygen and include the superoxide radical anion (∙O2-), hydrogen peroxide (H2O2), hydroxyl radical (∙OH), hydroperoxyl radical (HOO∙), singlet oxygen ((1)O2), and peroxyl radical (ROO∙). Two endogenous sources of reactive oxygen species are the mammalian CYP-dependent microsomal electron transport system and the mitochondrial electron transport chain. CYP enzymes catalyze the oxygenation of an organic substrate and the simultaneous reduction of molecular oxygen. If the transfer of oxygen to a substrate is not tightly controlled, uncoupling occurs and leads to the formation of reactive oxygen species. Reactive oxygen species are capable of causing oxidative damage to cellular membranes and macromolecules that can lead to the development of human diseases such as cancer. In normal cells, intracellular levels of reactive oxygen species are maintained in balance with intracellular biochemical antioxidants to prevent cellular damage. Oxidative stress occurs when this critical balance is disrupted. Topics covered in this review include the role of reactive oxygen species in intracellular cell signaling and the relationship between CYP enzymes and cancer. Outlines of CYP expression in neoplastic tissues, CYP enzyme polymorphism and cancer risk, CYP enzymes in cancer therapy and the metabolic activation of chemical procarcinogens by CYP enzymes are also provided.

  13. Examination of Mechanisms and Fuel-Molecular Effects on Soot Formation.

    DTIC Science & Technology

    1988-02-13

    11 TABLE V - REACTIONS AND RATE COEFFICIENTS FOR STEPS LEADING TO FORMATION OF AROMATIC RING .... .............. . 12 S TABLE...VI REACTIONS LEADING TO FORMATION OF POLYCYCLIC HYDROCARBONS ....... ..................... . 13 -V; R88-957047 Examination of Mechanisms and Fuel...corporate-sponsorship to facilitate interpreting data from CHEMKIN and CHEMSEN. Plots of 1. Species concentrations 2. Reaction contribution to the formation

  14. A Study of Pollutant Formation from the Lean Premixed Combustion of Gaseous Fuel Alternatives to Natural Gas

    NASA Astrophysics Data System (ADS)

    Fackler, Keith Boyd, Jr.

    emissions decrease with increasing H2 fuel fraction for combustion of CH4/H2 blends. This appears to be caused by a reduction in the amount of NO made by the prompt pathway involving the reaction of N2 with hydrocarbon radicals as the CH4 is replaced by H2. 2.) For category 2 (the process and refinery blend) and category 5 (the LNG, shale, and associated gases), NOx emissions increase with the addition of C2 and C3 hydrocarbons. This could be due to an increased production of free radicals resulting from increasing CO production when higher molecular weight hydrocarbons are broken down. 3.) For category 3 (the O2 blown gasified coal/petcoke), NOx emissions increase with increasing CO fuel fraction. The reason for this is attributed to CO producing more radicals per unit heat release than H2. When CO replaces H2, an increase in NOx emissions is seen due to an increase in the productivity of the N2O, NNH, and Zeldovich pathways. 4.) For category 4 (the landfill gas) the addition of diluents such as CO2 and N2 at constant air flow produces more NOx per kg of CH4 consumed, and N2 is more effective than CO 2 in increasing the NOx emission index. The increase in emission index appears to be due to an enhancement of the prompt NOx pathway as the diluents are added and the mixture moves towards stoichiometric. In addition, the presence of CO2 as a diluent catalyzes the loss of flame radicals, leading to less NOx formation than when an equivalent amount of N2 is used as a diluent. For a selected set of fuels, detailed spacial reactor probing is carried out. At the nominal temperature and residence time, the experimental results show the following trends for flame structure as a function of fuel type: 1.) Pure H2 is far more reactive in comparison to CH4 and all other pure alkane fuels. This results in relatively flat NO x and temperature profiles; whereas, the alkane fuels drop in both temperature and NOx production in the jet, where more fresh reactor feed gases are present. 2

  15. Predicting fissile content of spent nuclear fuel assemblies with the passive neutron Albedo reactivity technique and Monte Carlo code emulation

    SciTech Connect

    Conlin, Jeremy Lloyd; Tobin, Stephen J

    2010-10-13

    There is a great need in the safeguards community to be able to nondestructively quantify the mass of plutonium of a spent nuclear fuel assembly. As part of the Next Generation of Safeguards Initiative, we are investigating several techniques, or detector systems, which, when integrated, will be capable of quantifying the plutonium mass of a spent fuel assembly without dismantling the assembly. This paper reports on the simulation of one of these techniques, the Passive Neutron Albedo Reactivity with Fission Chambers (PNAR-FC) system. The response of this system over a wide range of spent fuel assemblies with different burnup, initial enrichment, and cooling time characteristics is shown. A Monte Carlo method of using these modeled results to estimate the fissile content of a spent fuel assembly has been developed. A few numerical simulations of using this method are shown. Finally, additional developments still needed and being worked on are discussed.

  16. A Statistical Approach to Predict the Failure Enthalpy and Reliability of Irradiated PWR Fuel Rods During Reactivity-Initiated Accidents

    SciTech Connect

    Nam, Cheol; Jeong, Yong-Hwan; Jung, Youn-Ho

    2001-11-15

    During the last decade, the failure behavior of high-burnup fuel rods under a reactivity-initiated accident (RIA) condition has been a serious concern since fuel rod failures at low enthalpy have been observed. This has resulted in the reassessment of existing licensing criteria and failure-mode study. To address the issue, a statistics-based methodology is suggested to predict failure probability of irradiated fuel rods under an RIA. Based on RIA simulation results in the literature, a failure enthalpy correlation for an irradiated fuel rod is constructed as a function of oxide thickness, fuel burnup, and pulse width. Using the failure enthalpy correlation, a new concept of ''equivalent enthalpy'' is introduced to reflect the effects of the three primary factors as well as peak fuel enthalpy into a single damage parameter. Moreover, the failure distribution function with equivalent enthalpy is derived, applying a two-parameter Weibull statistical model. Finally, the sensitivity analysis is carried out to estimate the effects of burnup, corrosion, peak fuel enthalpy, pulse width, and cladding materials used.

  17. The HIF-1 inhibitor YC-1 decreases reactive astrocyte formation in a rodent ischemia model

    PubMed Central

    Na, Jong-In; Na, Joo-Young; Choi, Woo-Young; Lee, Min-Cheol; Park, Man-Seok; Choi, Kang-Ho; Lee, Jeong-Kil; Kim, Kyung-Tae; Park, Jong-Tae; Kim, Hyung-Seok

    2015-01-01

    Astrocytes become reactive after central nervous system injury, re-expressing glial fibrillary acidic protein (GFAP), vascular endothelial growth factor (VEGF), and nestin. Hypoxia-inducible transcription factor alpha (HIF-1α) is an important transcription factor for several genes including the VEGF and nestin genes, the expression of which generate reactive astrocytes and cause gliosis after cerebral ischemia. To evaluate the role of HIF-1α in reactive astrocyte formation, we applied the potent HIF-1α inhibitor YC-1 to a focal cerebral ischemia model and analyzed the expression of HIF-1α, VEGF, nestin, and GFAP. Quantitative real-time reverse transcription polymerase chain reaction and western blot analyses demonstrated that the expression of HIF-1α and its downstream genes (VEGF and nestin) were markedly attenuated in the YC-1-treated group versus the control group (HIF-1α, VEGF: p < 0.01; nestin: p < 0.05). GFAP expression was also effectively inhibited in the YC-1-treated group (p < 0.05). Immunohistochemical evaluations showed that GFAP-positive (GFAP+) cells in the YC-1-treated group were sparse in the peri-infarct area, while an immunofluorescence assay revealed that the number of VEGF+/GFAP+ and nestin+/GFAP+ reactive astrocytes were decreased in the YC-1-treated group (p < 0.05). These results demonstrate that HIF-1α suppression decreases the formation of reactive astrocytes and gliosis that occur following focal ischemia. PMID:26064442

  18. Formation of iron nanoparticles and increase in iron reactivity in mineral dust during simulated cloud processing.

    PubMed

    Shi, Zongbo; Krom, Michael D; Bonneville, Steeve; Baker, Alex R; Jickells, Timothy D; Benning, Liane G

    2009-09-01

    The formation of iron (Fe) nanoperticles and increase in Fe reactivity in mineral dust during simulated cloud processing was investigated using high-resolution microscopy and chemical extraction methods. Cloud processing of dust was experimentally simulated via an alternation of acidic (pH 2) and circumneutral conditions (pH 5-6) over periods of 24 h each on presieved (<20 microm) Saharan soil and goethite suspensions. Microscopic analyses of the processed soil and goethite samples reveal the neo-formation of Fe-rich nanoparticle aggregates, which were not found initially. Similar Fe-rich nanoparticles were also observed in wet-deposited Saharen dusts from the western Mediterranean but not in dry-deposited dust from the eastern Mediterranean. Sequential Fe extraction of the soil samples indicated an increase in the proportion of chemically reactive Fe extractable by an ascorbate solution after simulated cloud processing. In addition, the sequential extractions on the Mediterranean dust samples revealed a higher content of reactive Fe in the wet-deposited dust compared to that of the dry-deposited dust These results suggestthat large variations of pH commonly reported in aerosol and cloud waters can trigger neo-formation of nanosize Fe particles and an increase in Fe reactivity in the dust

  19. Incremental Reactivity Effects on Secondary Organic Aerosol Formation in Urban Atmospheres with and without Biogenic Influence

    NASA Astrophysics Data System (ADS)

    Kacarab, Mary; Li, Lijie; Carter, William P. L.; Cocker, David R., III

    2016-04-01

    Two different surrogate mixtures of anthropogenic and biogenic volatile organic compounds (VOCs) were developed to study secondary organic aerosol (SOA) formation at atmospheric reactivities similar to urban regions with varying biogenic influence levels. Environmental chamber simulations were designed to enable the study of the incremental aerosol formation from select anthropogenic (m-Xylene, 1,2,4-Trimethylbenzene, and 1-Methylnaphthalene) and biogenic (α-pinene) precursors under the chemical reactivity set by the two different surrogate mixtures. The surrogate reactive organic gas (ROG) mixtures were based on that used to develop the maximum incremental reactivity (MIR) factors for evaluation of O3 forming potential. Multiple incremental aerosol formation experiments were performed in the University of California Riverside (UCR) College of Engineering Center for Environmental Research and Technology (CE-CERT) dual 90m3 environmental chambers. Incremental aerosol yields were determined for each of the VOCs studied and compared to yields found from single precursor studies. Aerosol physical properties of density, volatility, and hygroscopicity were monitored throughout experiments. Bulk elemental chemical composition from high-resolution time of flight aerosol mass spectrometer (HR-ToF-AMS) data will also be presented. Incremental yields and SOA chemical and physical characteristics will be compared with data from previous single VOC studies conducted for these aerosol precursors following traditional VOC/NOx chamber experiments. Evaluation of the incremental effects of VOCs on SOA formation and properties are paramount in evaluating how to best extrapolate environmental chamber observations to the ambient atmosphere and provides useful insights into current SOA formation models. Further, the comparison of incremental SOA from VOCs in varying surrogate urban atmospheres (with and without strong biogenic influence) allows for a unique perspective on the impacts

  20. Elevated Cytosolic Na+ Increases Mitochondrial Formation of Reactive Oxygen Species in Failing Cardiac Myocytes

    PubMed Central

    Kohlhaas, Michael; Liu, Ting; Knopp, Andreas; Zeller, Tanja; Ong, Mei Fang; Böhm, Michael; O'Rourke, Brian; Maack, Christoph

    2010-01-01

    Background —Oxidative stress is causally linked to the progression of heart failure, and mitochondria are critical sources of reactive oxygen species in failing myocardium. We previously observed that in heart failure, elevated cytosolic Na+ ([Na+]i) reduces mitochondrial Ca2+ ([Ca2+]m) by accelerating Ca2+ efflux via the mitochondrial Na+/Ca2+ exchanger. Because the regeneration of antioxidative enzymes requires NADPH, which is indirectly regenerated by the Krebs cycle, and Krebs cycle dehydrogenases are activated by [Ca2+]m, we speculated that in failing myocytes, elevated [Na+]i promotes oxidative stress. Methods and Results —We used a patch-clamp–based approach to simultaneously monitor cytosolic and mitochondrial Ca2+ and, alternatively, mitochondrial H2O2 together with NAD(P)H in guinea pig cardiac myocytes. Cells were depolarized in a voltage-clamp mode (3 Hz), and a transition of workload was induced by β-adrenergic stimulation. During this transition, NAD(P)H initially oxidized but recovered when [Ca2+]m increased. The transient oxidation of NAD(P)H was closely associated with an increase in mitochondrial H2O2 formation. This reactive oxygen species formation was potentiated when mitochondrial Ca2+ uptake was blocked (by Ru360) or Ca2+ efflux was accelerated (by elevation of [Na+]i). In failing myocytes, H2O2 formation was increased, which was prevented by reducing mitochondrial Ca2+ efflux via the mitochondrial Na+/Ca2+ exchanger. Conclusions —Besides matching energy supply and demand, mitochondrial Ca2+ uptake critically regulates mitochondrial reactive oxygen species production. In heart failure, elevated [Na+]i promotes reactive oxygen species formation by reducing mitochondrial Ca2+ uptake. This novel mechanism, by which defects in ion homeostasis induce oxidative stress, represents a potential drug target to reduce reactive oxygen species production in the failing heart. PMID:20351235

  1. Soot formation in synthetic-fuel droplets. First quarterly technical progress report

    SciTech Connect

    England, G.; Kramlich, J.; Payne, R.

    1981-01-01

    The objective of this project is to provide detailed information on methods of minimizing soot formation during synthetic liquid fuel combustion under conditions which minimize fuel nitrogen conversion to nitric oxide. The program consists of two tasks. The purpose of the first task, Fuel Screening Studies, is to investigate the impact of fuel properties on particulate production, to establish the importance of droplet size and examine atomizer effects, and to develop techniques for surrogate fuels productions. In the second task, Flame Studies, the fundamental details of soot formation from synfuel droplet combustion will be investigated in variable slip velocity configurations. This present report describes technical progress during the first three months of the program effort (October-December 1980). During this initial period, attention has focused on the definition of the different experimental efforts and on the design and construction of the required hardware. Aspects of this work are discussed.

  2. A high fuel utilizing solid oxide fuel cell cycle with regard to the formation of nickel oxide and power density

    NASA Astrophysics Data System (ADS)

    Nehter, Pedro

    Within this study a novel high fuel utilizing (High-uf) SOFC system is presented with special focus on the formation of nickel oxide, system efficiency and the required cell area at a fixed system performance of 1 MW. Within the High-uf SOFC cycle, a second SOFC stack is used to utilize a further part of the residual hydrogen of the first SOFC stack. This could be feasible by using an anode gas condenser, which is implemented between the first and the second stack. This reduces the water fraction of the anode gas and thereby the tendency of nickel oxide formation in case of a further fuel utilization. Thus, a higher total fuel utilization can be reached with the second SOFC stack. With the High-uf SOFC cycle, the system efficiency is increased by 7%-points compared to the simple atmospheric SOFC cycle. Furthermore, the average cell voltage and the fuel utilization are varied to carry out a first optimization of the stack's power density. The results of this optimization have shown that the required cell area of the simple SOFC cycle can be slightly reduced by decreasing the fuel utilization, whereas the High-uf SOFC cycle shows an opposite effect. Here, the required cell area can be reduced at constant voltages by increasing the fuel utilization. Thus, higher system efficiencies could be reached with the High-uf SOFC cycle by using the same cell area as the simple SOFC cycle and at the same tendency of nickel oxide formation. A second condenser behind the second SOFC stack could be used to increase the carbon dioxide mass fraction up to 92%. This could be interesting for CO 2-sequestring applications as well.

  3. Fuel-optimal low-thrust formation reconfiguration via Radau pseudospectral method

    NASA Astrophysics Data System (ADS)

    Li, Jing

    2016-07-01

    This paper investigates fuel-optimal low-thrust formation reconfiguration near circular orbit. Based on the Clohessy-Wiltshire equations, first-order necessary optimality conditions are derived from the Pontryagin's maximum principle. The fuel-optimal impulsive solution is utilized to divide the low-thrust trajectory into thrust and coast arcs. By introducing the switching times as optimization variables, the fuel-optimal low-thrust formation reconfiguration is posed as a nonlinear programming problem (NLP) via direct transcription using multiple-phase Radau pseudospectral method (RPM), which is then solved by a sparse nonlinear optimization software SNOPT. To facilitate optimality verification and, if necessary, further refinement of the optimized solution of the NLP, formulas for mass costate estimation and initial costates scaling are presented. Numerical examples are given to show the application of the proposed optimization method. To fix the problem, generic fuel-optimal low-thrust formation reconfiguration can be simplified as reconfiguration without any initial and terminal coast arcs, whose optimal solutions can be efficiently obtained from the multiple-phase RPM at the cost of a slight fuel increment. Finally, influence of the specific impulse and maximum thrust magnitude on the fuel-optimal low-thrust formation reconfiguration is analyzed. Numerical results shown the links and differences between the fuel-optimal impulsive and low-thrust solutions.

  4. Effect of fuel molecular structure on soot formation in gas turbine combustion

    NASA Technical Reports Server (NTRS)

    Naegeli, D. W.; Moses, C. A.

    1980-01-01

    The effect of fuel variations at the same hydrogen content on the formation of soot in a gas turbine combustor was studied. Six fuels were burned to a combustor over a matrix of about 50 test conditions with test conditions ranging over 500-1800 kPa (5-18 atm) pressure and 500-1000 K burner inlet temperature; fuel-air ratios were varied from 0.008-0.024. Flame radiation measurements were made through a sapphire window toward the end of the primary zone. The hydrogen content of the six test fuels ranged from 12.80 to 12.88%. Five fuels emphasized hydrocarbon types: (mono, di, and tricyclic), naphthenes (decalin) and partially hydrogenated aromatics (tetralin); the sixth fuel emphasized final boiling point.

  5. Accounting for water formation from hydrocarbon fuel combustion in life cycle analyses

    NASA Astrophysics Data System (ADS)

    Belmont, E. L.; Davidson, F. T.; Glazer, Y. R.; Beagle, E. A.; Webber, M. E.

    2017-09-01

    Hydrocarbon fuel production and utilization are considered water intensive processes due to the high volumes of water used in source development and fuel processing. At the same time, there is significant water formed during combustion. However, this water is not currently widely harvested at the site of production. Instead, it is added to the hydrologic cycle, often in a different location from the fuel production site. This study quantifies the water formed from combustion of these fuels and analyzes the magnitudes of formation in the context of other hydrologic sources and sinks in order to facilitate future assessments of water harvesting technology and/or atmospheric impacts of combustion. Annual water formation from stoichiometric combustion of hydrocarbon fuels, including natural gas, oil- and natural gas liquid-derived products, and coal, in the United States and worldwide are presented and compared with quantities of water sequestered, evaporated, and stored in the atmosphere. Water production factors in terms of mass and energy of fuel consumed, WPFm and WPFe, respectively, are defined for the comparison of fuels and incorporation into future life cycle analyses (LCAs). Results show that water formation from combustion has increased worldwide from 2005 to 2015, with the largest increase coming from growth in combustion of natural gas. Water formation from combustion of hydrocarbon fuels equals or exceeds water sequestered from the hydrologic cycle through deep well injection in the US annually. Overall, water formation is deemed significant enough to warrant consideration by LCAs of water intensity in fuel production and use, and should be included in future analyses.

  6. Effects of fracture reactivation and diagenesis on fracture network evolution: Cambrian Eriboll Formation, NW Scotland

    NASA Astrophysics Data System (ADS)

    Hooker, J. N.; Eichhubl, P.; Xu, G.; Ahn, H.; Fall, A.; Hargrove, P.; Laubach, S.; Ukar, E.

    2011-12-01

    The Cambrian Eriboll Formation quartzarenites contain abundant fractures with varying degrees of quartz cement infill. Fractures exist that are entirely sealed; are locally sealed by bridging cements but preserve pore space among bridges; are mostly open but lined with veneers of cement; or are devoid of cement. Fracture propagation in the Eriboll Formation is highly sensitive to the presence of pre-existing fractures. Fracture reactivation occurs in opening mode as individual fractures repeatedly open and are filled or bridged by syn-kinematic cements. As well, reactivation occurs in shear as opening of one fracture orientation coincides with shear displacement along pre-existing fractures of different orientations. The tendency for pre-existing fractures to slip varies in part by the extent of cement infill, yet we observe shear and opening-mode reactivation even among sealed fractures. Paleotemperature analysis of fluid inclusions within fracture cements suggests some fractures now in outcrop formed deep in the subsurface. Fractures within the Eriboll Formation may therefore affect later fracture propagation throughout geologic time. With progressive strain, fault zones develop within fracture networks by a sequence of opening-mode fracture formation, fracture reactivation and linkage, fragmentation, cataclasis, and the formation of slip surfaces. Cataclasite within fault zones is commonly more thoroughly cemented than fractures in the damage zone or outside the fault zone. This variance of cement abundance is likely the result of (1) continued exposure of freshly broken quartz surfaces within cataclasite, promoting quartz precipitation, and (2) possibly more interconnected pathways for mass transfer within the fault zone. Enhanced cementation of cataclasite results in strengthening or diagenetic strain hardening of the evolving fault zone. Further slip is accommodated by shear localization along discrete slip surfaces. With further linkage of fault segments

  7. Inhibitors of biofilm formation by fuel ethanol contaminants

    USDA-ARS?s Scientific Manuscript database

    Industrial fuel ethanol production suffers from chronic and acute infections that reduce yields and cause “stuck fermentations” that result in costly shutdowns. Lactic acid bacteria, particularly Lactobacillus sp., are recognized as major contaminants. In previous studies, we observed that certain...

  8. JAEA Studies on High Burnup Fuel Behaviors during Reactivity-Initiated Accident and Loss-of-Coolant Accident

    SciTech Connect

    Fuketa, Toyoshi; Sugiyama, Tomoyuki; Nagase, Fumihisa; Suzuki, Motoe

    2007-07-01

    The objectives of fuel safety research program at Japan Atomic Energy Agency (JAEA) are; to evaluate adequacy of present safety criteria and safety margins; to provide a database for future regulation on higher burnup UO{sub 2} and MOX fuels, new cladding and pellets; and to provide reasonably mechanistic computer codes for regulatory application. The JAEA program is comprised of reactivity-initiated accident (RIA) studies including pulse-irradiation experiments in the NSRR and cladding mechanical tests, loss-of-coolant accident (LOCA) tests including integral thermal shock test and oxidation rate measurement, development and verification of computer codes FEMAXI-6 and RANNS, and so on. In addition to an overview of the fuel safety research at JAEA, most recent progresses in the RIA and LOCA tests programs and the codes development are described and discussed in the paper. (authors)

  9. Reactivation of chromosomally integrated human herpesvirus-6 by telomeric circle formation.

    PubMed

    Prusty, Bhupesh K; Krohne, George; Rudel, Thomas

    2013-01-01

    More than 95% of the human population is infected with human herpesvirus-6 (HHV-6) during early childhood and maintains latent HHV-6 genomes either in an extra-chromosomal form or as a chromosomally integrated HHV-6 (ciHHV-6). In addition, approximately 1% of humans are born with an inheritable form of ciHHV-6 integrated into the telomeres of chromosomes. Immunosuppression and stress conditions can reactivate latent HHV-6 replication, which is associated with clinical complications and even death. We have previously shown that Chlamydia trachomatis infection reactivates ciHHV-6 and induces the formation of extra-chromosomal viral DNA in ciHHV-6 cells. Here, we propose a model and provide experimental evidence for the mechanism of ciHHV-6 reactivation. Infection with Chlamydia induced a transient shortening of telomeric ends, which subsequently led to increased telomeric circle (t-circle) formation and incomplete reconstitution of circular viral genomes containing single viral direct repeat (DR). Correspondingly, short t-circles containing parts of the HHV-6 DR were detected in cells from individuals with genetically inherited ciHHV-6. Furthermore, telomere shortening induced in the absence of Chlamydia infection also caused circularization of ciHHV-6, supporting a t-circle based mechanism for ciHHV-6 reactivation.

  10. Liquid phase products and solid deposit formation from thermally stressed model jet fuels

    NASA Technical Reports Server (NTRS)

    Kim, W. S.; Bittker, D. A.

    1984-01-01

    The relationship between solid deposit formation and liquid degradation product concentration was studied for the high temperature (400 C) stressing of three hydrocarbon model fuels. A Jet Fuel Thermal Oxidation Tester was used to simulate actual engine fuel system conditions. The effects of fuel type, dissolved oxygen concentration, and hot surface contact time (reaction time) were studied. Effects of reaction time and removal of dissolved oxygen on deposit formation were found to be different for n-dodecane and for 2-ethylnaphthalene. When ten percent tetralin is added to n-dodecane to give a simpler model of an actual jet fuel, the tetralin inhibits both the deposit formation and the degradation of n-dodecane. For 2-ethylnaphthalene primary product analyses indicate a possible self-inhibition at long reaction times of the secondary reactions which form the deposit precursors. The mechanism of the primary breakdown of these fuels is suggested and the primary products which participate in these precursor-forming reactions are identified. Some implications of the results to the thermal degradation of real jet fuels are given.

  11. Mechanism of carboxylic acid photooxidation in atmospheric aqueous phase: Formation, fate and reactivity

    NASA Astrophysics Data System (ADS)

    Charbouillot, Tiffany; Gorini, Sophie; Voyard, Guillaume; Parazols, Marius; Brigante, Marcello; Deguillaume, Laurent; Delort, Anne-Marie; Mailhot, Gilles

    2012-09-01

    In the first part of the work, we investigated the reactivity toward photogenerated hydroxyl radicals (rad OH) of seven monocarboxylic acids and six dicarboxylic acids found in natural cloud water. This leads to the proposition of a schematic degradation pathway linking glutaric acid (C5) to complete mineralization into CO2. We report a detailed mechanism on the succinic acid reactivity toward rad OH leading to the formation of malonic, glyoxylic and consequently oxalic acids and a comparison with reported pathways proposed by the CAPRAM (Chemical Aqueous Phase RAdical Mechanism) is discussed. We also investigated the photooxidation of formic acid under atmospherically relevant conditions leading to the possible formation of oxalic acid via radical mediated recombination. The second part focuses on the polychromatic irradiation (closed to solar irradiation) of a collected cloud aqueous phase showing that irradiation of cloud water leads to the formation of both formic and acetic acids. Carboxylic acid formation increases in the presence of photogenerated hydroxyl radicals from hydrogen peroxide, showing that photooxidation could play a key role in the formation of carboxylic acids under atmospherically relevant conditions.

  12. Exploiting Formation Flying for Fuel Saving Supersonic Oblique Wing Aircraft

    DTIC Science & Technology

    2007-07-01

    examples of CFF Wind Tunnel work carried out in support of flight tests on the F/A-18. Fig.1.4 refers to CFF work on “ICE” models. Note the possibility of...of subsonic- transonic wings in formation and then re-designed them to eliminate the induced roll / pitch effects. A number of flight formations

  13. Effects of Fuel Specification and Additives on Soot Formation.

    DTIC Science & Technology

    1983-12-01

    0.003 0.00’T Naphthalene Content (% vol.), max. 3.0 -- Distillation: 10 Percent (°K), max. 477 477 90 Percent (°K), min. -- 534 Final Boiling Point (OK...max. 573 -- Residue (% vol.), max. 1.5 -- Loss (% vol.), max. 1.5 -- Flashpoint (0K), min. 311 311/321 Freezing Point (’K), max. 233 244 Maximum... points were obtained with tri-ethyl benzene (monocyclic) as one additive and methyl naphthalene (dicyclic) as the other. At constant smoke point , fuels

  14. Formation, Migration, and Reactivity of Au CO Complexes on Gold Surfaces

    SciTech Connect

    Wang, Jun; McEntee, Monica; Tang, Wenjie; Neurock, Matthew; Baddorf, Arthur P.; Maksymovych, Petro; Yates, Jr, John T.

    2016-01-12

    Here, we report experimental as well as theoretical evidence that suggests Au CO complex formation upon the exposure of CO to active sites (step edges and threading dislocations) on a Au(111) surface. Room-temperature scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy, transmission infrared spectroscopy, and density functional theory calculations point to Au CO complex formation and migration. Room-temperature STM of the Au(111) surface at CO pressures in the range from 10^ 8 to 10^ 4 Torr (dosage up to 10^6 langmuir) indicates Au atom extraction from dislocation sites of the herringbone reconstruction, mobile Au CO complex formation and diffusion, and Au adatom cluster formation on both elbows and step edges on the Au surface. The formation and mobility of the Au CO complex result from the reduced Au Au bonding at elbows and step edges leading to stronger Au CO bonding and to the formation of a more positively charged CO (CO +) on Au. These studies indicate that the mobile Au CO complex is involved in the Au nanoparticle formation and reactivity, and that the positive charge on CO increases due to the stronger adsorption of CO at Au sites with lower coordination numbers.

  15. Formation, Migration, and Reactivity of Au CO Complexes on Gold Surfaces

    DOE PAGES

    Wang, Jun; McEntee, Monica; Tang, Wenjie; ...

    2016-01-12

    Here, we report experimental as well as theoretical evidence that suggests Au CO complex formation upon the exposure of CO to active sites (step edges and threading dislocations) on a Au(111) surface. Room-temperature scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy, transmission infrared spectroscopy, and density functional theory calculations point to Au CO complex formation and migration. Room-temperature STM of the Au(111) surface at CO pressures in the range from 10^ 8 to 10^ 4 Torr (dosage up to 10^6 langmuir) indicates Au atom extraction from dislocation sites of the herringbone reconstruction, mobile Au CO complex formation and diffusion, and Aumore » adatom cluster formation on both elbows and step edges on the Au surface. The formation and mobility of the Au CO complex result from the reduced Au Au bonding at elbows and step edges leading to stronger Au CO bonding and to the formation of a more positively charged CO (CO +) on Au. These studies indicate that the mobile Au CO complex is involved in the Au nanoparticle formation and reactivity, and that the positive charge on CO increases due to the stronger adsorption of CO at Au sites with lower coordination numbers.« less

  16. Secondary organic aerosol formation from photo-oxidation of unburned fuel: experimental results and implications for aerosol formation from combustion emissions.

    PubMed

    Jathar, Shantanu H; Miracolo, Marissa A; Tkacik, Daniel S; Donahue, Neil M; Adams, Peter J; Robinson, Allen L

    2013-11-19

    We conducted photo-oxidation experiments in a smog chamber to investigate secondary organic aerosol (SOA) formation from eleven different unburned fuels: commercial gasoline, three types of jet fuel, and seven different diesel fuels. The goals were to investigate the influence of fuel composition on SOA formation and to compare SOA production from unburned fuel to that from diluted exhaust. The trends in SOA production were largely consistent with differences in carbon number and molecular structure of the fuel, i.e., fuels with higher carbon numbers and/or more aromatics formed more SOA than fuels with lower carbon numbers and/or substituted alkanes. However, SOA production from different diesel fuels did not depend strongly on aromatic content, highlighting the important contribution of large alkanes to SOA formation from mixtures of high carbon number (lower volatility) precursors. In comparison to diesels, SOA production from higher volatility fuels such as gasoline appeared to be more sensitive to aromatic content. On the basis of a comparison of SOA mass yields (SOA mass formed per mass of fuel reacted) and SOA composition (as measured by an aerosol mass spectrometer) from unburned fuels and diluted exhaust, unburned fuels may be reasonable surrogates for emissions from uncontrolled engines but not for emissions from engines with after treatment devices such as catalytic converters.

  17. In situ formation of magnetite reactive barriers in soil for waste stabilization

    DOEpatents

    Moore, Robert C.

    2003-01-01

    Reactive barriers containing magnetite and methods for making magnetite reactive barriers in situ in soil for sequestering soil contaminants including actinides and heavy metals, organic materials, iodine and technetium are disclosed. According to one embodiment, a two-step reagent introduction into soil takes place. In the first step, free oxygen is removed from the soil by separately injecting into the soil aqueous solutions of iron (II) salt, for example FeCl.sub.2, and base, for example NaOH or NH.sub.3 in about a 1:1 volume ratio. Then, in the second step, similar reagents are injected a second time (however, according to about a 1:2 volume ratio, iron to salt) to form magnetite. The magnetite formation is facilitated, in part, due to slow intrusion of oxygen into the soil from the surface. The invention techniques are suited to injection of reagents into soil in proximity to a contamination plume or source allowing in situ formation of the reactive barrier at the location of waste or hazardous material. Mixing of reagents to form. precipitate is mediated and enhanced through movement of reagents in soil as a result of phenomena including capillary action, movement of groundwater, soil washing and reagent injection pressure.

  18. Photo-Irradiation of Proanthocyanidin as a New Disinfection Technique via Reactive Oxygen Species Formation

    PubMed Central

    Nakamura, Keisuke; Shirato, Midori; Ikai, Hiroyo; Kanno, Taro; Sasaki, Keiichi; Kohno, Masahiro; Niwano, Yoshimi

    2013-01-01

    In the present study, the bactericidal effect of photo-irradiated proanthocyanidin was evaluated in relation to reactive oxygen species formation. Staphylococcus aureus suspended in proanthocyanidin aqueous solution was irradiated with light from a laser at 405 nm. The bactericidal effect of photo-irradiated proanthocyanidin depended on the concentration of proanthocyanidin, the laser irradiation time, and the laser output power. When proanthocyanidin was used at the concentration of 1 mg/mL, the laser irradiation of the bacterial suspension could kill the bacteria with a >5-log reduction of viable cell counts. By contrast, bactericidal effect was not observed when proanthocyanidin was not irradiated. In electron spin resonance analysis, reactive oxygen species, such as hydroxyl radicals, superoxide anion radicals, and hydrogen peroxide, were detected in the photo-irradiated proanthocyanidin aqueous solution. The yields of the reactive oxygen species also depended on the concentration of proanthocyanidin, the laser irradiation time, and the laser output power as is the case with the bactericidal assay. Thus, it is indicated that the bactericidal effect of photo-irradiated proanthocyanidin is exerted via the reactive oxygen species formation. The bactericidal effect as well as the yield of the oxygen radicals increased with the concentration of proanthocyanidin up to 4 mg/mL, and then decreased with the concentration. These findings suggest that the antioxidative activity of proanthocyanidin might prevail against the radical generation potency of photo-irradiated proanthocyanidin resulting in the decreased bactericidal effect when the concentration is over 4 mg/mL. The present study suggests that photo-irradiated proanthocyanidin whenever used in an optimal concentration range can be a new disinfection technique. PMID:23527299

  19. Chemical reactivity and skin sensitization potential for benzaldehydes: can Schiff base formation explain everything?

    PubMed

    Natsch, Andreas; Gfeller, Hans; Haupt, Tina; Brunner, Gerhard

    2012-10-15

    Skin sensitizers chemically modify skin proteins rendering them immunogenic. Sensitizing chemicals have been divided into applicability domains according to their suspected reaction mechanism. The widely accepted Schiff base applicability domain covers aldehydes and ketones, and detailed structure-activity-modeling for this chemical group was presented. While Schiff base formation is the obvious reaction pathway for these chemicals, the in silico work was followed up by limited experimental work. It remains unclear whether hydrolytically labile Schiff bases can form sufficiently stable epitopes to trigger an immune response in the living organism with an excess of water being present. Here, we performed experimental studies on benzaldehydes of highly differing skin sensitization potential. Schiff base formation toward butylamine was evaluated in acetonitrile, and a detailed SAR study is presented. o-Hydroxybenzaldehydes such as salicylaldehyde and the oakmoss allergens atranol and chloratranol have a high propensity to form Schiff bases. The reactivity is highly reduced in p-hydroxy benzaldehydes such as the nonsensitizing vanillin with an intermediate reactivity for p-alkyl and p-methoxy-benzaldehydes. The work was followed up under more physiological conditions in the peptide reactivity assay with a lysine-containing heptapeptide. Under these conditions, Schiff base formation was only observable for the strong sensitizers atranol and chloratranol and for salicylaldehyde. Trapping experiments with NaBH₃CN showed that Schiff base formation occurred under these conditions also for some less sensitizing aldehydes, but the reaction is not favored in the absence of in situ reduction. Surprisingly, the Schiff bases of some weaker sensitizers apparently may react further to form stable peptide adducts. These were identified as the amides between the lysine residues and the corresponding acids. Adduct formation was paralleled by oxidative deamination of the parent

  20. Extracellular ultrathin fibers sensitive to intracellular reactive oxygen species: Formation of intercellular membrane bridges

    SciTech Connect

    Jung, Se-Hui; Park, Jin-Young; Joo, Jung-Hoon; Kim, Young-Myeong; Ha, Kwon-Soo

    2011-07-15

    Membrane bridges are key cellular structures involved in intercellular communication; however, dynamics for their formation are not well understood. We demonstrated the formation and regulation of novel extracellular ultrathin fibers in NIH3T3 cells using confocal and atomic force microscopy. At adjacent regions of neighboring cells, phorbol 12-myristate 13-acetate (PMA) and glucose oxidase induced ultrathin fiber formation, which was prevented by Trolox, a reactive oxygen species (ROS) scavenger. The height of ROS-sensitive ultrathin fibers ranged from 2 to 4 nm. PMA-induced formation of ultrathin fibers was inhibited by cytochalasin D, but not by Taxol or colchicine, indicating that ultrathin fibers mainly comprise microfilaments. PMA-induced ultrathin fibers underwent dynamic structural changes, resulting in formation of intercellular membrane bridges. Thus, these fibers are formed by a mechanism(s) involving ROS and involved in formation of intercellular membrane bridges. Furthermore, ultrastructural imaging of ultrathin fibers may contribute to understanding the diverse mechanisms of cell-to-cell communication and the intercellular transfer of biomolecules, including proteins and cell organelles.

  1. Winter ozone formation and VOC incremental reactivities in the Upper Green River Basin of Wyoming

    NASA Astrophysics Data System (ADS)

    Carter, William P. L.; Seinfeld, John H.

    2012-04-01

    The Upper Green River Basin (UGRB) in Wyoming experiences ozone episodes in the winter when the air is relatively stagnant and the ground is covered by snow. A modeling study was carried out to assess relative contributions of oxides of nitrogen (NOx) and individual volatile organic compounds (VOCs), and nitrous acid (HONO) in winter ozone formation episodes in this region. The conditions of two ozone episodes, one in February 2008 and one in March 2011, were represented using a simplified box model with all pollutants present initially, but with the detailed SAPRC-07 chemical mechanism adapted for the temperature and radiation conditions arising from the high surface albedo of the snow that was present. Sensitivity calculations were conducted to assess effects of varying HONO inputs, ambient VOC speciation, and changing treatments of temperature and lighting conditions. The locations modeled were found to be quite different in VOC speciation and sensitivities to VOC and NOx emissions, with one site modeled for the 2008 episode being highly NOx-sensitive and insensitive to VOCs and HONO, and the other 2008 site and both 2011 sites being very sensitive to changes in VOC and HONO inputs. Incremental reactivity scales calculated for VOC-sensitive conditions in the UGRB predict far lower relative contributions of alkanes to ozone formation than in the traditional urban-based MIR scale and that the major contributors to ozone formation were the alkenes and the aromatics, despite their relatively small mass contributions. The reactivity scales are affected by the variable ambient VOC speciation and uncertainties in ambient HONO levels. These box model calculations are useful for indicating general sensitivities and reactivity characteristics of these winter UGRB episodes, but fully three-dimensional models will be required to assess ozone abatement strategies in the UGRB.

  2. The development of reactive fuel grains for pyrophoric relight of in-space hybrid rocket thrusters

    NASA Astrophysics Data System (ADS)

    Steiner, Matthew Wellington

    This study presents and investigates a novel hybrid fuel grain that reacts pyrophorically with gaseous oxidizer to achieve restart of a hybrid rocket motor propulsion system while reducing cost and handling concerns. This reactive fuel grain (RFG) relies on the pyrophoric nature of finely divided metal particles dispersed in a solid dicyclopentadiene (DCPD) binder, which has been shown to encapsulate air-sensitive additives until they are exposed to combustion gases. An RFG is thus effectively inert in open air in the absence of an ignition source, though the particles encapsulated within remain pyrophoric. In practice, this means that an RFG that is ignited in the vacuum of space and then extinguished will expose unoxidized pyrophoric particles, which can be used to generate sufficient heat to relight the propellant when oxidizer is flowed. The experiments outlined in this work aim to develop a suitable pyrophoric material for use in an RFG, demonstrate pyrophoric relight, and characterize performance under conditions relevant to a hybrid rocket thruster. Magnesium, lithium, calcium, and an alloy of titanium, chromium, and manganese (TiCrMn) were investigated to determine suitability of pure metals as RFG additives. Additionally, aluminum hydride (AlH3), lithium aluminum hydride (LiAlH4), lithium borohydride (LiBH4), and magnesium hydride (MgH2) were investigated to determine suitability of metals hydrides as RFG additives or as precursors for pure-metal RFG additives. Pyrophoric metals have been previously investigated as additives for increasing the regression rate of hybrid fuels, but to the author's knowledge, these materials have not been specifically investigated for their ability to ignite a propellant pyrophorically. Commercial research-grade metals were obtained as coarse powders, then ball-milled to attempt to reduce particle size below a critical diameter needed for pyrophoricity. Magnesium hydride was ball-milled and then cycled in a hydride cycling

  3. The Chemistry of Deposit Formation in Distillate Fuels,

    DTIC Science & Technology

    1986-01-01

    Net Base d Ok TABLE VI. Phenols Found in LCO Caustic Extract See figure 7 for GC peak numbers 1. * Phenol 2 . 2 -methyiphenol 3. 3- and 4 ...that thiols oxidized to sulfonic acids which were incorporated into sediments. Sauer, et al [ 4 ] proposed that acids catalyzed the formation of esters ...flask (surface/volume ratio - 0.8 cm- 1 ). The plastic - - - caps and Teflon liners were drilled in the center with a 4 mm hole. A 2 cm long

  4. Hydroxide Self-Feeding High-Temperature Alkaline Direct Formate Fuel Cells.

    PubMed

    Li, Yinshi; Sun, Xianda; Feng, Ying

    2017-05-22

    Conventionally, both the thermal degradation of the anion-exchange membrane and the requirement of additional hydroxide for fuel oxidation reaction hinder the development of the high-temperature alkaline direct liquid fuel cells. The present work addresses these two issues by reporting a polybenzimidazole-membrane-based direct formate fuel cell (DFFC). Theoretically, the cell voltage of the high-temperature alkaline DFFC can be as high as 1.45 V at 90 °C. It has been demonstrated that a proof-of-concept alkaline DFFC without adding additional hydroxide yields a peak power density of 20.9 mW cm(-2) , an order of magnitude higher than both alkaline direct ethanol fuel cells and alkaline direct methanol fuel cells, mainly because the hydrolysis of formate provides enough OH(-) ions for formate oxidation reaction. It was also found that this hydroxide self-feeding high-temperature alkaline DFFC shows a stable 100 min constant-current discharge at 90 °C, proving the conceptual feasibility. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Soot formation in synthetic-fuel droplets. Second quarterly technical progress report

    SciTech Connect

    England, G.; Kramlich, J.; Payne, R.

    1981-04-01

    The main objective of this program is to provide detailed information on methods of minimizing soot formation during synthetic liquid fuel combustion under conditions which minimize the formation of nitric oxides. The program comprises two main tasks, Fuel Screening Studies, and Flame Studies. The purpose of the first task is to investigate the impact of fuel properties on particulate production, to establish the importance of droplet size and examine atomizer effects, and to develop techniques for surrogate fuels production. In the second task, fundamental details of soot formation from synfuel droplet combustion will be investigated in variable slip velocity configurations. This report describes technical progress during the second three-month period of program effort (January-March 1981). During this period attention has continued to be focussed on the design, construction and commissioning of experimental systems. The Task 1 tunnel furnace modification was completed and made operational, and some preliminary fuel screening studies were carried out. Similarly, construction of the controlled flow droplet reactor was completed and efforts directed towards the design and testing of diagnostic systems. Details of this work are discussed.

  6. Long-term kinetic effects and colloid formations in dissolution of LWR spent fuels

    SciTech Connect

    Ahn, T.M.

    1996-11-01

    This report evaluates continuous dissolution and colloid formation during spent-fuel performance under repository conditions in high-level waste disposal. Various observations suggest that reprecipitated layers formed on spent-fuel surfaces may not be protective. This situation may lead to continuous dissolution of highly soluble radionuclides such as C-14, Cl-36, Tc-99, I-129, and Cs-135. However, the diffusion limits of various species involved may retard dissolution significantly. For low-solubility actinides such as Pu-(239+240) or Am-(241+243), various processes regarding colloid formation have been analyzed. The processes analyzed are condensation, dispersion, and sorption. Colloid formation may lead to significant releases of low-solubility actinides. However, because there are only limited data available on matrix dissolution, colloid formation, and solubility limits, many uncertainties still exist. These uncertainties must be addressed before the significance of radionuclide releases can be determined. 118 refs.

  7. Anxiety-induced plasma norepinephrine augmentation increases reactive oxygen species formation by monocytes in essential hypertension.

    PubMed

    Yasunari, Kenichi; Matsui, Tokuzo; Maeda, Kensaku; Nakamura, Munehiro; Watanabe, Takanori; Kiriike, Nobuo

    2006-06-01

    An association between anxiety and depression and increased blood pressure (BP) and cardiovascular disease risk has not been firmly established. We examined the hypothesis that anxiety and depression lead to increased plasma catecholamines and to production of reactive oxygen species (ROS) by mononuclear cells (MNC) in hypertensive individuals. We also studied the role of BP in this effect. In Protocol 1, a cross-sectional study was performed in 146 hypertensive patients to evaluate whether anxiety and depression affect BP and ROS formation by MNC through increasing plasma catecholamines. In Protocol 2, a 6-month randomized controlled trial using a subtherapeutic dose of the alpha(1)-adrenergic receptor antagonist doxazosin (1 mg/day) versus placebo in 86 patients with essential hypertension was performed to determine whether the increase in ROS formation by MNC was independent of BP. In Protocol 1, a significant relationship was observed between the following: trait anxiety and plasma norepinephrine (r = 0.32, P < .01); plasma norepinephrine and ROS formation by MNC (r = 0.36, P < .01); and plasma norepinephrine and systolic, diastolic, and mean BP (r = 0.17, P = .04; r = 0.26, P = .02; r = 0.23, P < .01, respectively). In Protocol 2, subtherapeutic doxazosin treatment (1 mg/day) had no significant effect on BP. However doxazosin significantly decreased ROS formation by MNC compared with placebo (P < .01). Trait anxiety may increase plasma norepinephrine and increase ROS formation by MNC independent of BP in hypertensive patients.

  8. Effect of aging on formation of reactive oxygen species by mitochondria of rat heart.

    PubMed

    Kuka, Stanislav; Tatarkova, Zuzana; Racay, Peter; Lehotsky, Jan; Dobrota, Dusan; Kaplan, Peter

    2013-09-01

    Mitochondrial electron transport chain is thought to be a major source of reactive oxygen species (ROS) during aging. However, this view is supported mainly by accumulation of mitochondrial oxidative damage with age and the exact sites of ROS formation remains unknown. In the present study, we measured rate of ROS formation using 2',7'-dichlorofluorescein (DCF) probe in cardiac mitochondria from adult (6-month-old), old (15-month-old) and senescent (26-month-old) rats. In mitochondria oxidizing complex II substrate, succinate, the rate of ROS formation progressively increased with age. In the presence of complex I inhibitor rotenone or complex III inhibitor antimycin A, the rate ROS formation significantly decreased, but even the combination of inhibitors could not fully prevent generation of ROS. Age-dependent increase of ROS formation was accompanied by a loss of thiol groups, tryptophan degradation and increased lipid peroxidation. These data suggest that in addition to complex I and complex II other mitochondrial sites can contribute to accelerated ROS generation and oxidative damage during aging.

  9. Silicon-doping in carbon nanotubes: formation energies, electronic structures, and chemical reactivity.

    PubMed

    Bian, Ruixin; Zhao, Jingxiang; Fu, Honggang

    2013-04-01

    By carrying out density functional theory (DFT) calculations, we have studied the effects of silicon (Si)-doping on the geometrical and electronic properties, as well as the chemical reactivity of carbon nanotubes (CNTs). It is found that the formation energies of these nanotubes increase with increasing tube diameters, indicating that the embedding of Si into narrower CNTs is more energetically favorable. For the given diameters, Si-doping in a (n, 0) CNT is slightly easier than that of in (n, n) CNT. Moreover, the doped CNTs with two Si atoms are easier to obtain than those with one Si atom. Due to the introduction of impurity states after Si-doping, the electronic properties of CNTs have been changed in different ways: upon Si-doping into zigzag CNTs, the band gap of nanotube is decreased, while the opening of band gap in armchair CNTs is found. To evaluate the chemical reactivity of Si-doped CNTs, the adsorption of NH3 and H2O on this kind of material is explored. The results show that N-H bond of NH3 and O-H bond of H2O can be easily split on the surface of doped CNTs. Of particular interest, the novel reactivity makes it feasible to use Si-doped CNT as a new type of splitter for NH3 and H2O bond, which is very important in chemical and biological processes. Future experimental studies are greatly desired to probe such interesting processes.

  10. Iron hydroxy carbonate formation in zerovalent iron permeable reactive barriers: characterization and evaluation of phase stability.

    PubMed

    Lee, Tony R; Wilkin, Richard T

    2010-07-30

    Predicting the long-term potential of permeable reactive barriers for treating contaminated groundwater relies on understanding the endpoints of biogeochemical reactions between influent groundwater and the reactive medium. Iron hydroxy carbonate (chukanovite) is frequently observed as a secondary mineral precipitate in granular iron PRBs. Mineralogical characterization was carried out using X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, and X-ray absorption spectroscopy on materials collected from three field-based PRBs in the US (East Helena, MT; Elizabeth City, NC; Denver Federal Center, CO). These PRBs were installed to treat a range of contaminants, including chlorinated organics, hexavalent chromium, and arsenic. Results obtained indicate that chukanovite is a prevalent secondary precipitate in the PRBs. Laboratory experiments on high-purity chukanovite separates were carried out to constrain the room-temperature solubility for this mineral. An estimated Gibbs energy of formation (Delta(f)G degrees) for chukanovite is -1174.4 +/- 6 kJ/mol. A mineral stability diagram is consistent with observations from the field. Water chemistry from the three reactive barriers falls inside the predicted stability field for chukanovite, at inorganic carbon concentrations intermediate to the stability fields of siderite and ferrous hydroxide. These new data will aid in developing better predictive models of mineral accumulation in zerovalent iron PRBs. Published by Elsevier B.V.

  11. Iron hydroxy carbonate formation in zerovalent iron permeable reactive barriers: Characterization and evaluation of phase stability

    SciTech Connect

    Wilkin, Richard T.; Lee, T.R.

    2010-10-22

    Predicting the long-term potential of permeable reactive barriers for treating contaminated groundwater relies on understanding the endpoints of biogeochemical reactions between influent groundwater and the reactive medium. Iron hydroxy carbonate (chukanovite) is frequently observed as a secondary mineral precipitate in granular iron PRBs. Mineralogical characterization was carried out using X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, and X-ray absorption spectroscopy on materials collected from three field-based PRBs in the US (East Helena, MT; Elizabeth City, NC; Denver Federal Center, CO). These PRBs were installed to treat a range of contaminants, including chlorinated organics, hexavalent chromium, and arsenic. Results obtained indicate that chukanovite is a prevalent secondary precipitate in the PRBs. Laboratory experiments on high-purity chukanovite separates were carried out to constrain the room-temperature solubility for this mineral. An estimated Gibbs energy of formation ({Delta}{sub f}G{sup o}) for chukanovite is - 1174.4 {+-} 6 kJ/mol. A mineral stability diagram is consistent with observations from the field. Water chemistry from the three reactive barriers falls inside the predicted stability field for chukanovite, at inorganic carbon concentrations intermediate to the stability fields of siderite and ferrous hydroxide. These new data will aid in developing better predictive models of mineral accumulation in zerovalent iron PRBs.

  12. Onaping Formation, Ries Suevite and Melt-Fuel-Coolant-Interaction (MFCI)

    NASA Astrophysics Data System (ADS)

    Grieve, R. A. F.; Osinski, G. R.; Chanou, A.

    2013-08-01

    The Sudbury Onaping Formation and the Ries suevite Ries have been postulated to form as the result of melt-fuel-coolant-interaction (MFCI), i.e., by the explosive interaction between impact melt and water. Both interpretations canot be correct.

  13. Formation of metal nanoparticles by short-distance sputter deposition in a reactive ion etching chamber

    SciTech Connect

    Nie Min; Meng, Dennis Desheng; Sun Kai

    2009-09-01

    A new method is reported to form metal nanoparticles by sputter deposition inside a reactive ion etching chamber with a very short target-substrate distance. The distribution and morphology of nanoparticles are found to be affected by the distance, the ion concentration, and the sputtering time. Densely distributed nanoparticles of various compositions were fabricated on the substrates that were kept at a distance of 130 mum or smaller from the target. When the distance was increased to 510 mum, island structures were formed, indicating the tendency to form continuous thin film with longer distance. The observed trend for nanoparticle formation is opposite to the previously reported mechanism for the formation of nanoparticles by sputtering. A new mechanism based on the seeding effect of the substrate is proposed to interpret the experimental results.

  14. Controlled formation of anatase and rutile TiO2 thin films by reactive magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Rafieian, Damon; Ogieglo, Wojciech; Savenije, Tom; Lammertink, Rob G. H.

    2015-09-01

    We discuss the formation of TiO2 thin films via DC reactive magnetron sputtering. The oxygen concentration during sputtering proved to be a crucial parameter with respect to the final film structure and properties. The initial deposition provided amorphous films that crystallise upon annealing to anatase or rutile, depending on the initial sputtering conditions. Substoichiometric films (TiOx<2), obtained by sputtering at relatively low oxygen concentration, formed rutile upon annealing in air, whereas stoichiometric films formed anatase. This route therefore presents a formation route for rutile films via lower (<500 °C) temperature pathways. The dynamics of the annealing process were followed by in situ ellipsometry, showing the optical properties transformation. The final crystal structures were identified by XRD. The anatase film obtained by this deposition method displayed high carriers mobility as measured by time-resolved microwave conductance. This also confirms the high photocatalytic activity of the anatase films.

  15. Anthrax edema toxin inhibits Nox1-mediated formation of reactive oxygen species by colon epithelial cells.

    PubMed

    Kim, Jun-Sub; Bokoch, Gary M

    2009-01-01

    One major route of intoxication by Bacillus anthracis (anthrax) spores is via their ingestion and subsequent uptake by the intestinal epithelium. Anthrax edema toxin (ETx) is an adenylate cyclase that causes persistent elevation of cAMP in intoxicated cells. NADPH oxidase enzymes (Nox1-Nox5, Duox1 and 2) generate reactive oxygen species (ROS) as components of the host innate immune response to bacteria, including Nox1 in gastrointestinal epithelial tissues. We show that ETx effectively inhibits ROS formation by Nox1 in HT-29 colon epithelial cells. This inhibition requires the PKA-mediated phosphorylation of the Nox1-regulatory component, NoxA1, and the subsequent binding of 14-3-3zeta. Inhibition of Nox1-mediated ROS formation in the gut epithelium may be a mechanism used by B. anthracis to circumvent the innate immune response.

  16. Effects of uncertainty in SAPRC90 rate constants and selected product yields on reactivity adjustment factors for alternative fuel vehicle emissions. Final report

    SciTech Connect

    Bergin, M.S.; Russell, A.G.; Yang, Y.J.; Milford, J.B.; Kirchner, F.; Stockwell, W.R.

    1996-07-01

    Tropospheric ozone is formed in the atmosphere by a series of reactions involving volatile organic compounds (VOCs) and nitrogen oxides (NO{sub x}). While NOx emissions are primarily composed of only two compounds, nitrogen oxide (NO) and nitrogen dioxide (NO{sub 2}), there are hundreds of different VOCs being emitted. In general, VOCs promote ozone formation, however, the rate and extent of ozone produced by the individual VOCs varies considerably. For example, it is widely acknowledged that formaldehyde (HCHO) is a very reactive VOC, and produces ozone rapidly and efficiently under most conditions. On the other hand, VOCs such as methane, ethane, propane, and methanol do not react as quickly, and are likely to form less urban ozone than a comparable mass of HCHO. The difference in ozone forming potential is one of the bases for the use of alternative fuels. The fuels considered in this study included compressed natural gas, LPG, mixtures of methanol and gasoline, ethanol and gasoline, and a reformulated gasoline.

  17. The effect of the composition of plutonium loaded on the reactivity change and the isotopic composition of fuel produced in a fast reactor

    SciTech Connect

    Blandinskiy, V. Yu.

    2014-12-15

    This paper presents the results of a numerical investigation into burnup and breeding of nuclides in metallic fuel consisting of a mixture of plutonium and depleted uranium in a fast reactor with sodium coolant. The feasibility of using plutonium contained in spent nuclear fuel from domestic thermal reactors and weapons-grade plutonium is discussed. It is shown that the largest production of secondary fuel and the least change in the reactivity over the reactor lifetime can be achieved when employing plutonium contained in spent nuclear fuel from a reactor of the RBMK-1000 type.

  18. The effect of the composition of plutonium loaded on the reactivity change and the isotopic composition of fuel produced in a fast reactor

    NASA Astrophysics Data System (ADS)

    Blandinskiy, V. Yu.

    2014-12-01

    This paper presents the results of a numerical investigation into burnup and breeding of nuclides in metallic fuel consisting of a mixture of plutonium and depleted uranium in a fast reactor with sodium coolant. The feasibility of using plutonium contained in spent nuclear fuel from domestic thermal reactors and weapons-grade plutonium is discussed. It is shown that the largest production of secondary fuel and the least change in the reactivity over the reactor lifetime can be achieved when employing plutonium contained in spent nuclear fuel from a reactor of the RBMK-1000 type.

  19. Reactive oxidation products promote secondary organic aerosol formation from green leaf volatiles

    NASA Astrophysics Data System (ADS)

    Hamilton, J. F.; Lewis, A. C.; Carey, T. J.; Wenger, J. C.; Garcia, E. Borrás. I.; Muñoz, A.

    2009-02-01

    Green leaf volatiles (GLVs) are an important group of chemicals released by vegetation which have emission fluxes that can be significantly increased when plants are damaged or stressed. A series of simulation chamber experiments has been conducted at the European Photoreactor in Valencia, Spain, to investigate secondary organic aerosol (SOA) formation from the atmospheric oxidation of the major GLVs cis-3-hexenylacetate and cis-3-hexen-1-ol. Liquid chromatography-ion trap mass spectrometry was used to identify chemical species present in the SOA. Cis-3-hexen-1-ol proved to be a more efficient SOA precursor due to the high reactivity of its first generation oxidation product, 3-hydroxypropanal, which can hydrate and undergo further reactions with other aldehydes resulting in SOA dominated by higher molecular weight oligomers. The lower SOA yields produced from cis-3-hexenylacetate are attributed to the acetate functionality, which inhibits oligomer formation in the particle phase. Based on observed SOA yields and best estimates of global emissions, these compounds may be calculated to be a substantial unidentified global source of SOA, contributing 1-5 TgC yr-1, equivalent to around a third of that predicted from isoprene. Molecular characterization of the SOA, combined with organic mechanistic information, has provided evidence that the formation of organic aerosols from GLVs is closely related to the reactivity of their first generation atmospheric oxidation products, and indicates that this may be a simple parameter that could be used in assessing the aerosol formation potential for other unstudied organic compounds in the atmosphere.

  20. Reactive oxidation products promote secondary organic aerosol formation from green leaf volatiles

    NASA Astrophysics Data System (ADS)

    Hamilton, J. F.; Lewis, A. C.; Carey, T. J.; Wenger, J. C.; Garcia, E. Borrás. I.; Muñoz, A.

    2009-06-01

    Green leaf volatiles (GLVs) are an important group of chemicals released by vegetation which have emission fluxes that can be significantly increased when plants are damaged or stressed. A series of simulation chamber experiments has been conducted at the European Photoreactor in Valencia, Spain, to investigate secondary organic aerosol (SOA) formation from the atmospheric oxidation of the major GLVs cis-3-hexenylacetate and cis-3-hexen-1-ol. Liquid chromatography-ion trap mass spectrometry was used to identify chemical species present in the SOA. Cis-3-hexen-1-ol proved to be a more efficient SOA precursor due to the high reactivity of its first generation oxidation product, 3-hydroxypropanal, which can hydrate and undergo further reactions with other aldehydes resulting in SOA dominated by higher molecular weight oligomers. The lower SOA yields produced from cis-3-hexenylacetate are attributed to the acetate functionality, which inhibits oligomer formation in the particle phase. Based on observed SOA yields and best estimates of global emissions, these compounds may be calculated to be a substantial unidentified global source of SOA, contributing 1-5 TgC yr-1, equivalent to around a third of that predicted from isoprene. Molecular characterization of the SOA, combined with organic mechanistic information, has provided evidence that the formation of organic aerosols from GLVs is closely related to the reactivity of their first generation atmospheric oxidation products, and indicates that this may be a simple parameter that could be used in assessing the aerosol formation potential for other unstudied organic compounds in the atmosphere.

  1. Manipulation of combustion waves in carbon-nanotube/fuel composites by highly reactive Mg nanoparticles.

    PubMed

    Lee, Kang Yeol; Hwang, Hayoung; Shin, Dongjoon; Choi, Wonjoon

    2015-10-28

    Manipulating the interface of micro/nanostructured materials and chemical fuels can change the fundamental characteristics of combustion waves that are generated during a reaction. In this study, we report that Mg/MgO nanoparticles actively amplify the propagation of combustion waves at the interface of multi-walled carbon nanotubes (MWCNTs) and chemical fuels. Fuel/MWCNT and fuel/MWCNT-Mg/MgO composite films were prepared by a facile synthetic method. We present complete physiochemical characterization of these composite films and evaluate the propagating velocities and real-time surface temperatures of combustion waves. Mg/MgO nanoparticles at the interface enhanced the reaction front velocity by 41%. The resulting explosive reactions supplied additional thermal energy to the chemical fuel, accelerating flame propagation. Furthermore, the surface temperatures of the composites with Mg/MgO nanoparticles were much lower, indicating how the transient heat from the reaction would ignite the unreacted fuels at lower surface temperatures despite not reaching the necessary activation energy for a chain reaction. This mechanism contributed to thermopower waves that amplified the output voltage. Furthermore, large temperature gradients due to the presence of nanoparticles increased charge transport inside the nanostructured material, due to the increased thermoelectric effects. This manipulation could contribute to the active control of interfacially driven combustion waves along nanostructured materials, yielding many potential applications.

  2. Carotid artery intima-media thickness and reactive oxygen species formation by monocytes in hypertensive patients.

    PubMed

    Watanabe, T; Yasunari, K; Nakamura, M; Maeda, K

    2006-05-01

    Carotid artery intima-media thickness (IMT) is a widely accepted index for assessing atherosclerosis, and is known to be a risk indicator for cardiovascular and cerebrovascular events. Oxidative stress and inflammation are also known to play critical roles in the pathogenesis of vascular events. We studied the association between IMT and inflammatory markers, such as oxidative stress in polymorphonuclear leukocytes (PMNs) and mononuclear cells (MNCs) in 156 patients with essential hypertension. Reactive oxygen species (ROS) formation by PMNs and MNCs was measured by gated flow cytometry. CRP and traditional risk factors, such as age, gender, body mass index, hemoglobin A(1c), and total cholesterol were also measured. The subjects were divided into a plaque group (max-IMT>or=1.1 mm, n=40), and a nonplaque group (max-IMT<1.1 mm, n=116). ROS formation by MNCs was significantly increased in the plaque group when compared with the nonplaque group (P<0.0001). Multiple regression analysis revealed a significant correlation between IMT and ROS formation by MNCs (r=0.407, P<0.0001), or CRP (r=0.216, P=0.0029) or hemoglobinA1c (r=0.158, P=0.0270) or age (r=0.157, P=0.0447). No significant correlation was observed between IMT and ROS formation by PMNs. These results suggest that carotid artery IMT may be affected by increased ROS formation by MNCs, and that increased ROS formation by MNCs may be related to the development of atherosclerosis. We propose that ROS formation by MNCs is a marker for prediction of carotid atherosclerosis.

  3. Neutrophil NET formation is regulated from the inside by myeloperoxidase-processed reactive oxygen species.

    PubMed

    Björnsdottir, Halla; Welin, Amanda; Michaëlsson, Erik; Osla, Veronica; Berg, Stefan; Christenson, Karin; Sundqvist, Martina; Dahlgren, Claes; Karlsson, Anna; Bylund, Johan

    2015-12-01

    Neutrophil extracellular traps (NETs) are mesh-like DNA fibers clad with intracellular proteins that are cast out from neutrophils in response to certain stimuli. The process is thought to depend on reactive oxygen species (ROS) generated by the phagocyte NADPH-oxidase and the ROS-modulating granule enzyme myeloperoxidase (MPO), but when, how, and where these factors contribute is so far uncertain. The neutrophil NADPH-oxidase can be activated at different cellular sites and ROS may be produced and processed by MPO within intracellular granules, even in situations where a phagosome is not formed, e.g., upon stimulation with phorbol myristate acetate (PMA). We investigated the subcellular location of ROS production and processing by MPO in the context of PMA-induced NET formation. Complete neutralization of extracellular ROS was not sufficient to block NET formation triggered by PMA, indicating that intragranular ROS are critical for NETosis. Employing a set of novel MPO-inhibitors, inhibition of NET formation correlated with inhibition of intragranular MPO activity. Also, extracellular addition of MPO was not sufficient to rescue NET formation in completely MPO-deficient neutrophils and specific neutralization by luminol of MPO-processed ROS within intracellular granules led to a complete block of PMA-triggered NET formation. We show for the first time that inhibition of intragranular MPO activity, or neutralization of intragranular MPO-processed ROS by luminol effectively block NET formation. Our data demonstrate that ROS must be formed and processed by MPO in order to trigger NET formation, and that these events have to occur within intracellular granules. Copyright © 2015 Elsevier Inc. All rights reserved.

  4. Importance of thermal reactivity for hexamethylenetetramine formation from simulated interstellar ices

    NASA Astrophysics Data System (ADS)

    Vinogradoff, V.; Fray, N.; Duvernay, F.; Briani, G.; Danger, G.; Cottin, H.; Theulé, P.; Chiavassa, T.

    2013-03-01

    Context. Complex organic molecules are observed in a broad variety of astrophysical objects, but little is known about their formation mechanism. Laboratory simulations on interstellar ice analogues are therefore crucial for understanding the origin of these complex organic molecules. In this context, we focus on the thermal reactivity for the formation of the organic residue obtained after photolysis at 25 K of the interstellar ice analogue (H2O:CH3OH:NH3) warmed to 300 K. Aims: We determine the formation mechanism of one major product detected in the organic residue: hexamethylenetetramine (HMT). We compare the warming of the photolysed interstellar ice analogue with the warming of the two non-photolysed specific ice mixtures H2CO:NH3:HCOOH and CH2NH:HCOOH, which are used as references. Using both general and specific approaches, we show the precise role of the UV photons and the thermal processing in the HMT formation. Methods: We used Fourier transform infrared spectroscopy (FTIR) to monitor the chemical changes induced by the heating of the photolysed ice analogue and characterize some important species that will subsequently evolve in the formation of HMT in the residue. Results: We show that the thermal processes play a key role in the HMT formation in photolysed ice analogues heated at 300 K. We identify the stable intermediates in the HMT formation that are formed during the warming: the aminomethanol (NH2CH2OH) and the protonated ion trimethyletriamine (TMTH+, C3H10N3+). We also identify for the first time a new product in the organic residue, the polymethylenimine PMI (-(CH2 -NH)n). Results from this study will be interesting for the analysis of the forthcoming Rosetta mission.

  5. Organic chloramines in drinking water: An assessment of formation, stability, reactivity and risk.

    PubMed

    How, Zuo Tong; Linge, Kathryn L; Busetti, Francesco; Joll, Cynthia A

    2016-04-15

    Although organic chloramines are known to form during the disinfection of drinking water with chlorine, little information is currently available on their occurrence or toxicity. In a recent in vitro study, some organic chloramines (e.g. N-chloroglycine) were found to be cytotoxic and genotoxic even at micromolar concentrations. In this paper, the formation and stability of 21 different organic chloramines, from chlorination of simple amines and amino acids, were studied, and the competition between 20 amino acids during chlorination was also investigated. For comparison, chlorination of two amides was also conducted. The formation and degradation of selected organic chloramines were measured using either direct UV spectroscopic or colorimetric detection. Although cysteine, methionine and tryptophan were the most reactive amino acids towards chlorination, they did not form organic chloramines at the chlorine to precursor molar ratios that were tested. Only 6 out of the 21 organic chloramines formed had a half-life of more than 3 h, although this group included all organic chloramines formed from amines. A health risk assessment relating stability and reactivity data from this study to toxicity and precursor abundance data from the literature indicated that only N-chloroglycine is likely to be of concern due to its stability, toxicity and abundance in water. However, given the stability of organic chloramines formed from amines, more information about the toxicity and precursor abundance for these chloramines is desirable.

  6. Reactivity-dependent PCR: direct, solution-phase in vitro selection for bond formation.

    PubMed

    Gorin, David J; Kamlet, Adam S; Liu, David R

    2009-07-08

    In vitro selection is a key component of efforts to discover functional nucleic acids and small molecules from libraries of DNA, RNA, and DNA-encoded small molecules. Such selections have been widely used to evolve RNA and DNA catalysts and, more recently, to discover new reactions from DNA-encoded libraries of potential substrates. While effective, current strategies for selections of bond-forming and bond-cleaving reactivity are generally indirect, require the synthesis of biotin-linked substrates, and involve multiple solution-phase and solid-phase manipulations. In this work we report the successful development and validation of reactivity-dependent PCR (RDPCR), a new method that more directly links bond formation or bond cleavage with the amplification of desired sequences and that obviates the need for solid-phase capture, washing, and elution steps. We show that RDPCR can be used to select for bond formation in the context of reaction discovery and for bond cleavage in the context of protease activity profiling.

  7. Study of Fuel Ratios on the Fusion Reactivity in an Inertial Electrostatic Confinement Device Using a Residual Gas Analyzer

    NASA Astrophysics Data System (ADS)

    Krupakar Murali, S.; Santarius, John F.; Kulcinski, Gerald L.

    2009-09-01

    Gridded Inertial Electrostatic confinement (IEC) devices are of interest due to their flexibility in burning advanced fuels, their tuning ability of the applied voltage to the reaction cross-section. Although this device is not suitable for power production in its present form, it does have several near term applications. The number of applications of this device increases with increasing fusion reactivity. These devices are simple to operate but are inherently complicated to understand and an effort to incrementally understand the device to improve its operational efficiency is underway at University of Wisconsin, Madison. Of all the parameters under study we are focusing on the effects of flow rate and flow ratio on the fusion reactivity in the present paper. Experiments were conducted to understand the influence of fuel flow ratio on the fusion reactions. The residual gas analyzer (RGA) was used to study the impurity concentration as the flow ratio was changed. It was observed that the higher flow rate resulted in reduced impurity levels and hence an increase in fusion rate. Several different species of gases were detected, some of these molecules formed inside the RGA analyzer. The flow ratio scan revealed that the optimum mixture of D2 with 3He to be D2:3He::1:2 for maximum D-3He fusion rate.

  8. Power reactivity decrement components of a homogeneous UPu10Zr-fueled 900-MW(thermal) liquid metal reactor

    SciTech Connect

    Meneghetti, D.; Kucera, D.A.

    1989-01-01

    Linear and Doppler feedback components of the power reactivity decrement (PRD) for a 900-MW(thermal) homogeneous UPu10Zr-fueled sodium-cooled reactor have been calculated. (The PRD is the negative of the reactivity required to bring the reactor from a zero-power hot-critical condition to a given power level.) The components are further separated into power-dependent and power-to-flow-dependent parts. These delineations enhance understanding of the contributions of the components to the feedback process. The delineation also enables the PRDs for other values of coolant flows to be estimated. The linear and Doppler components of the PRD are obtained using the EBRPOCO code, which calculates detailed axially delineated contributions of the components for every subassembly of a loading configuration. Separation of the components into power and power-to-flow parts is made by calculations of the components, assuming infinite thermal conductivities to obtain the power-to-flow values. Subtractions of these from the corresponding PRD quantities give the power-dependent parts. The values of the various feedback components are compared with corresponding quantities reported for an analogous U10Zr-fueled case.

  9. Importance of solid fuel properties to nitrogen oxide formation through HCN and NH[sub 3] in small particle combustion

    SciTech Connect

    Aho, M.J.; Haemaelaeinen, J.P.; Tummavuori, J.L. Univ. of Jyvaeskylae . Dept. of Chemistry)

    1993-10-01

    The formation of nitrogen oxides from fuel-nitrogen through intermediates was studied by measuring first fuel-O/fuel-N ratios and nitrogen functionality in selected solid fuels. Then the ratios of the yields (fuel-N [r arrow] HCN)/(fuel-N [r arrow] NH[sub 3]) in a nearly inert atmosphere at 800 C in an entrained flow reactor was measured and finally the ratio (fuel-N [r arrow] N[sub 2]O)/(fuel-N [r arrow] NO) in an oxidizing atmosphere at 800 C The fuels studied were coal, brown coal, S- and C-type peat, fir bark, birch bark and pine bark, all milled to a particle size < 63[mu]m. The ratios of O/N in the fuel, measured by elemental analysis, ranged from 7 to 150. Nitrogen functionality (mass percent of the total nitrogen content) was determined by XPS. the (fuel-N [r arrow] HCN)/(fuel-N [r arrow] NH[sub 3]) conversion ratio in the absence of O[sub 2], and also the (fuel-N [r arrow] N[sub 2]O)/(fuel-N [r arrow] NO) conversion ratio with O[sub 2] present, decreased with increasing ratio of fuel-O/fuel-N, but neither ratio decreased regularly with the increasing ratio of pyrrolic to pyridinic nitrogen in the fuel. Thus, fuel-oxygen plays a more important role than nitrogen functionality in the chemistry of nitrogen oxide formation. The strong effect of (fuel-O/fuel-N) ratio on the (fuel-N [r arrow] HCN)/(fuel-N [r arrow] NH[sub 3]) ratio may be due to the reaction between OH radicals and HCN to form NH[sub 3] near the fuel particle. The importance of this reaction is considered. Charring the fuel sample before combustion led to a sharp drop in the conversion of fuel-N to N[sub 2]O compared with the virgin fuels. Thus, heterogeneous combustion reactions produced much less N[sub 2]O than homogeneous combustion reactions.

  10. Aflatoxin B1 Induces Reactive Oxygen Species-Mediated Autophagy and Extracellular Trap Formation in Macrophages

    PubMed Central

    An, Yanan; Shi, Xiaochen; Tang, Xudong; Wang, Yang; Shen, Fengge; Zhang, Qiaoli; Wang, Chao; Jiang, Mingguo; Liu, Mingyuan; Yu, Lu

    2017-01-01

    Aflatoxins are a group of highly toxic mycotoxins with high carcinogenicity that are commonly found in foods. Aflatoxin B1 (AFB1) is the most toxic member of the aflatoxin family. A recent study reported that AFB1 can induce autophagy, but whether AFB1 can induce extracellular traps (ETs) and the relationships among innate immune responses, reactive oxygen species (ROS), and autophagy and the ETs induced by AFB1 remain unknown. Here, we demonstrated that AFB1 induced a complete autophagic process in macrophages (MΦ) (THP-1 cells and RAW264.7 cells). In addition, AFB1 induced the generation of MΦ ETs (METs) in a dose-dependent manner. In particular, the formation of METs significantly reduced the AFB1 content. Further analysis using specific inhibitors showed that the inhibition of either autophagy or ROS prevented MET formation caused by AFB1, indicating that autophagy and ROS were required for AFB1-induced MET formation. The inhibition of ROS prevented autophagy, indicating that ROS generation occurred upstream of AFB1-induced autophagy. Taken together, these data suggest that AFB1 induces ROS-mediated autophagy and ETs formation and an M1 phenotype in MΦ. PMID:28280716

  11. Imaging the C black formation by acetylene pyrolysis with molecular reactive force field simulations.

    PubMed

    Zhang, Chaoyang; Zhang, Chi; Ma, Yu; Xue, Xianggui

    2015-05-07

    C black is a class of substantial materials with a long history of applications. However, apart from some descriptions of primary reactions, subsequent processes leading up to the final formation mechanism remain unclear. This mechanism is also crucial for understanding the formation of other carbonaceous materials. In this work, we visualize C black formation by acetylene pyrolysis using molecular dynamics simulations with a molecular reactive force field named ReaxFF. We find that the formation undergoes four stages: (1) chain elongation by H abstraction and polymerization of small C species, (2) chain branching, (3) cyclization and ring densification, and (4) condensed ring folding. The simulated C black particle possesses a structure of folded graphite layers, which is in good accordance with experimental observations. Cyclization and condensation are derived from fusion between neighboring chains, significantly varying from common experimental observations at relatively low temperatures that abide by the mechanism of H abstraction and C2H2 addition. Moreover, polyyne and polyene are usually found during acetylene pyrolysis, suggesting that the pyrolysis of acetylene and other hydrocarbons may be a feasible method of obtaining carbyne, a novel carbonaceous material with a high value.

  12. Inhibitory effects of fluvastain and its metabolites on the formation of several reactive oxygen species.

    PubMed

    Nakashima, A; Ohtawa, M; Iwasaki, K; Wada, M; Kuroda, N; Nakashima, K

    2001-08-10

    We investigated the inhibitory effects of fluvastain (FV) and its metabolites (M-2, M-3, M-4, M-5, and M-7) on the formation of several reactive oxygen species (ROS), such as singlet oxygen (1O2), superoxide anion (O2-), hydroxy radical (*OH), hypochlorite ion (OCL-), and linoleic acid peroxide (LOO*). Inhibitory effects of pravastatin (PV), simvastatin (SV), probucol (PR) and alpha-tocopherol (TOC) were also tested. The inhibitory effects of 5-hydroxy FV (M-2) and 6-hydroxy FV (M-3) on the formation of 1O2, O2-, *OH, and OCL- were strongest. Scavenging of 1O2 by M-4, M-5, (+)-FV, and (-)-FV was also noted. The inhibitory effects of (+)-FV on the formation of 1O2 were comparable to those of (-)-FV, PV, SV, PR and M-7 had little or no inhibitory effect on the formation of several ROS. In conclusion, FV and its metabolites, particulary M-2 and M-3, have the potential to protect against oxidative stress mediated by several ROS.

  13. Formation and reactivity of inorganic and organic chloramines and bromamines during oxidative water treatment.

    PubMed

    Heeb, Michèle B; Kristiana, Ina; Trogolo, Daniela; Arey, J Samuel; von Gunten, Urs

    2017-03-01

    The formation and further reactions of halamines during oxidative water treatment can be relevant for water quality. In this study, we investigated the formation and reactivity of several inorganic and organic halamines (monochloramine, N-chloromethylamine, N-chlorodimethylamine, monobromamine, dibromamine, N-bromomethylamine, N,N-dibromomethylamine, and N-bromodimethylamine) by kinetic experiments, transformation product analysis, and quantum chemical computations. Kinetic model simulations were conducted to evaluate the relevance of halamines for various water treatment scenarios. Halamines were quickly formed from the reaction of chlorine and bromine with ammonia or organic amines. Species-specific second-order rate constants for the reaction of chlorine and bromine with ammonia, methyl- and dimethylamine were in the order of 10(6)-10(8) M(-1)s(-1). The formed halamines were found to be reactive towards phenolic compounds, forming halogenated phenols via electrophilic aromatic substitution (phenol and resorcinol) or quinones via electron transfer (catechol and hydroquinone). At near neutral pH, apparent second-order rate constants for these reactions were in the order of 10(-4)-10(-1) M(-1)s(-1) for chloramines and 10(1)-10(2) M(-1)s(-1) for bromamines. Quantum chemical computations were used to determine previously unknown aqueous pKa values, gas phase bond dissociation energies (BDE) and partial atomic charges of the halamines, allowing a better understanding of their reactivities. Kinetic model simulations, based on the results of this study, showed that during chlorination inorganic and organic chloramines are the main halamines formed. However, their further reactions with organic matter are outcompeted kinetically by chlorine. During ozonation, mainly inorganic bromamines are formed, since ozone quickly oxidizes organic amines. The further reactions of bromamine are typically outcompeted by ozone and thus generally of minor importance. The use of

  14. Improving Formate and Methanol Fuels: Catalytic Activity of Single Pd Coated Carbon Nanotubes

    PubMed Central

    2016-01-01

    The oxidations of formate and methanol on nitrogen-doped carbon nanotubes decorated with palladium nanoparticles were studied at both the single-nanotube and ensemble levels. Significant voltammetric differences were seen. Pd oxide formation as a competitive reaction with formate or methanol oxidation is significantly inhibited at high overpotentials under the high mass transport conditions associated with single-particle materials in comparison with that seen with ensembles, where slower diffusion prevails. Higher electro-oxidation efficiency for the organic fuels is achieved. PMID:27761299

  15. Monitoring the formation of soluble deposit precursors in fuels with light scattering photometry

    SciTech Connect

    Morris, R.E.; Hardy, D.R.; Pande, S.; Wechter, M.A. |

    1995-04-01

    The reactions that can take place in hydrocarbon fuels often manifest themselves as an increase in the propensity to form thermally induced soluble reaction products. This is not a one-step process but the result of a multitude of intermediate processes. These intermediate processes will produce a range of soluble products that differ considerably in structure and functionality from the fuel itself. Since these soluble {open_quotes}precursors{close_quotes} can, upon further thermal stress, lead to insoluble products, a method for following their formation could form the basis of a useful predictive measurement. It would also serve as a research tool for following the discrimination between soluble and insoluble product formation. Light scattering photometry was evaluated as a means of monitoring the formation of large soluble product molecules as they are formed in fuels. Changes in light scattering properties were measured after thermal stressing in the presence of dissolved copper and a metal deactivator additive. These results correlated well with the amounts of soluble and insoluble products formed. Fuel changes were detected by light scattering before detectable quantities of insoluble products were produced.

  16. Nondestructive determination of plutonium mass in spent fuel: prelliminary modeling results using the passive neutron Albedo reactivity technique

    SciTech Connect

    Evans, Louise G; Tobin, Stephen J; Schear, Melissa A; Menlove, Howard O; Lee, Sang Y; Swinhoe, Martyn T

    2009-01-01

    There are a variety of motivations for quantifying plutonium (Pu) in spent fuel assemblies by means of nondestructive assay (NDA) including the following: strengthening the capability of the International Atomic Energy Agency (LAEA) to safeguard nuclear facilities, quantifying shipper/receiver difference, determining the input accountability value at pyrochemical processing facilities, providing quantitative input to burnup credit and final safeguards measurements at a long-term repository. In order to determine Pu mass in spent fuel assemblies, thirteen NDA techniques were identified that provide information about the composition of an assembly. A key motivation of the present research is the realization that none of these techniques, in isolation, is capable of both (1) quantifying the Pu mass of an assembly and (2) detecting the diversion of a significant number of rods. It is therefore anticipated that a combination of techniques will be required. A 5 year effort funded by the Next Generation Safeguards Initiative (NGSI) of the U.S. DOE was recently started in pursuit of these goals. The first two years involves researching all thirteen techniques using Monte Carlo modeling while the final three years involves fabricating hardware and measuring spent fuel. Here, we present the work in two main parts: (1) an overview of this NGSI effort describing the motivations and approach being taken; (2) The preliminary results for one of the NDA techniques - Passive Neutron Albedo Reactivity (PNAR). The PNAR technique functions by using the intrinsic neutron emission of the fuel (primarily from the spontaneous fission of curium) to self-interrogate any fissile material present. Two separate measurements of the spent fuel are made, both with and without cadmium (Cd) present. The ratios of the Singles, Doubles and Triples count rates obtained in each case are analyzed; known as the Cd ratio. The primary differences between the two measurements are the neutron energy spectrum

  17. Manipulation of combustion waves in carbon-nanotube/fuel composites by highly reactive Mg nanoparticles

    NASA Astrophysics Data System (ADS)

    Lee, Kang Yeol; Hwang, Hayoung; Shin, Dongjoon; Choi, Wonjoon

    2015-10-01

    Manipulating the interface of micro/nanostructured materials and chemical fuels can change the fundamental characteristics of combustion waves that are generated during a reaction. In this study, we report that Mg/MgO nanoparticles actively amplify the propagation of combustion waves at the interface of multi-walled carbon nanotubes (MWCNTs) and chemical fuels. Fuel/MWCNT and fuel/MWCNT-Mg/MgO composite films were prepared by a facile synthetic method. We present complete physiochemical characterization of these composite films and evaluate the propagating velocities and real-time surface temperatures of combustion waves. Mg/MgO nanoparticles at the interface enhanced the reaction front velocity by 41%. The resulting explosive reactions supplied additional thermal energy to the chemical fuel, accelerating flame propagation. Furthermore, the surface temperatures of the composites with Mg/MgO nanoparticles were much lower, indicating how the transient heat from the reaction would ignite the unreacted fuels at lower surface temperatures despite not reaching the necessary activation energy for a chain reaction. This mechanism contributed to thermopower waves that amplified the output voltage. Furthermore, large temperature gradients due to the presence of nanoparticles increased charge transport inside the nanostructured material, due to the increased thermoelectric effects. This manipulation could contribute to the active control of interfacially driven combustion waves along nanostructured materials, yielding many potential applications.Manipulating the interface of micro/nanostructured materials and chemical fuels can change the fundamental characteristics of combustion waves that are generated during a reaction. In this study, we report that Mg/MgO nanoparticles actively amplify the propagation of combustion waves at the interface of multi-walled carbon nanotubes (MWCNTs) and chemical fuels. Fuel/MWCNT and fuel/MWCNT-Mg/MgO composite films were prepared by a facile

  18. Dunite and Pyroxenite Formation by Reactive Melt Transport in a Bimineralic Mantle

    NASA Astrophysics Data System (ADS)

    Tweed, L. E. L.; Spiegelman, M. W.; Kelemen, P. B.

    2016-12-01

    Dunite and pyroxenite layers are ubiquitous in ophiolites and orogenic peridotites where they represent fossil channels of reactive porous melt transport. In the shallow depleted harzburgitic mantle, formation of both heterogeneities is driven by the peritectic reaction orthopyroxene (opx) -> olivine (ol) + melt. Previous numerical models have investigated melt transport in a reactively dissolving deformable matrix and have demonstrated the organization of melt into channels analogous to those preserved as dunites. However, until now these models have used simple two-phase melt-solid systems that do not accurately describe real mantle rocks. They have also not addressed the reverse pyroxenite-forming reaction in which infiltration of silica-rich melts drives orthopyroxene precipitation. Such a reactively precipitating system has only been considered for a rigid matrix and the feedbacks between reaction-driven porosity reduction and compaction are not understood. Here, we describe the ol-opx peritectic reaction which is parameterized from melting experiments on real peridotite compositions. Experimental data are compared to calculations using pMELTs and THERMOCALC. The simplified thermodynamic description is incorporated into a 2-D numerical model of reactive melt transport in a viscously deformable bimineralic harzburgitic mantle in which mass, momentum and energy are conserved. Ol and opx are thermodynamically distinct but are treated as a single mechanical phase. This model permits us to track the mineralogical evolution of the upper mantle due to buoyant melt flow coupled with the forward peritectic reaction in response to gradients in the silica activity of equilibrium melts. The dynamically crystallizing porous system is first explored for a single-phase mantle to determine whether feedbacks between precipitation and compaction can lead to channeling instabilities. This paves the way for pyroxenite formation to be modeled using the bimineralic model. This

  19. Phase and strain distributions associated with reactive contaminants inside of a solid oxide fuel cell

    NASA Astrophysics Data System (ADS)

    Liu, Di-Jia; Almer, Jonathan

    2009-06-01

    A microfocused synchrotron x-ray diffraction method was used to reveal the quantitative distributions of phase fractions, internal strains, and their interdependences at different layer depths inside of a planar solid oxide fuel cell, which was deactivated by chromium contamination through direct contact with the metallic interconnect under typical operating conditions. These observations provide insight into the mechanism of Cr poisoning. The method can serve as a versatile tool for studying the electrochemical devices with thin-layered construction such as batteries and fuel cells under static or in situ conditions.

  20. The Effect of Chemical Reactivity and Charge Transfer on Gallium-Arsenide (110) Schottky Barrier Formation.

    NASA Astrophysics Data System (ADS)

    Williams, Michael Duryea

    Transition and near noble metals have been deposited in sequential steps on atomically clean cleaved Gallium Arsenide (GaAs) surfaces under ultra-high vacuum conditions. Soft X-ray and ultra-violet photoemission spectroscopies were used to elucidate the room temperature (RT) chemistry and Fermi level pinning behaviors of these systems. The results show that the nature or degree of the chemical reaction has little effect on the Schottky barrier (SB) height of the metal-semiconductor contact. Silver (Ag), Gold (Au), Copper (Cu) and Palladium (Pd) for example, exhibit a range of chemical reactivities with the substrate going from non-reactive in the case of Ag to very reactive for Pd. These all have a SB height of 0.9 electron volts (eV) for n-type GaAs. Nickel (Ni), Chromium (Cr) and Titanium (Ti), on the other hand, also react strongly but have a SB height of 0.7 eV. The pinning position of the Fermi level at the interface for the established barrier (with the exception of the Ag contact) is also found to be independent of whether the substrate is doped n or p-type. An examination of trends in charge transfer parameters between the metal overlayer and the substrate has led to a strong correlation between the electronegativity (Pauling's scale) of the metal and the observed SB height. It is suggested that the formation of a dipole at the interface effects a charge transfer between the adatom induced defect levels and the metal overlayer consistent with charge neutrality. As a test, two additional sets of experiments were performed. The first is a study of Ytterbium (Yb) on the GaAs suabstrate. The unique chemistry of the rare earth metal provides further proof that the SB height is independent of chemistry. The second set of experiments is a kinetic study of the development of the Aluminum (Al)/GaAs SB. The RT and low temperature ((LESSTHEQ)-50(DEGREES)C) substrates show a significant variation in the pinning behavior of the interfacial Fermi level with coverage. The

  1. The contribution of lubricant to the formation of particulate matter with reactivity controlled compression ignition in light-duty diesel engines

    SciTech Connect

    Storey, John Morse; Curran, Scott; Dempsey, Adam B.; Lewis, Sr., Samuel Arthur; Reitz, Rolf; Walker, N. Ryan; Wright, Chris

    2014-12-25

    Reactivity controlled compression ignition (RCCI) has been shown in single- and multi-cylinder engine research to achieve high thermal efficiencies with ultra-low NOX and soot emissions. The nature of the particulate matter (PM) produced by RCCI operation has been shown in recent research to be different than that of conventional diesel combustion and even diesel low-temperature combustion. Previous research has shown that the PM from RCCI operation contains a large amount of organic material that is volatile and semi-volatile. However, it is unclear if the organic compounds are stemming from fuel or lubricant oil. The PM emissions from dual-fuel RCCI were investigated in this study using two engine platforms, with an emphasis on the potential contribution of lubricant. Both engine platforms used the same base General Motors (GM) 1.9-L diesel engine geometry. The first study was conducted on a single-cylinder research engine with primary reference fuels (PRFs), n-heptane, and iso-octane. The second study was conducted on a four-cylinder GM 1.9-L ZDTH engine which was modified with a port fuel injection (PFI) system while maintaining the stock direct injection fuel system. Multi-cylinder RCCI experiments were run with PFI gasoline and direct injection of 2-ethylhexyl nitrate (EHN) mixed with gasoline at 5 % EHN by volume. In addition, comparison cases of conventional diesel combustion (CDC) were performed. Particulate size distributions were measured, and PM filter samples were collected for analysis of lube oil components. Triplicate PM filter samples (i.e., three individual filter samples) for both gas chromatography-mass spectroscopy (GC-MS; organic) analysis and X-ray fluorescence (XRF; metals) were obtained at each operating point and queued for analysis of both organic species and lubricant metals. Here, the results give a clear indication that lubricants do not contribute significantly to the formation of RCCI PM.

  2. The contribution of lubricant to the formation of particulate matter with reactivity controlled compression ignition in light-duty diesel engines

    DOE PAGES

    Storey, John Morse; Curran, Scott; Dempsey, Adam B.; ...

    2014-12-25

    Reactivity controlled compression ignition (RCCI) has been shown in single- and multi-cylinder engine research to achieve high thermal efficiencies with ultra-low NOX and soot emissions. The nature of the particulate matter (PM) produced by RCCI operation has been shown in recent research to be different than that of conventional diesel combustion and even diesel low-temperature combustion. Previous research has shown that the PM from RCCI operation contains a large amount of organic material that is volatile and semi-volatile. However, it is unclear if the organic compounds are stemming from fuel or lubricant oil. The PM emissions from dual-fuel RCCI weremore » investigated in this study using two engine platforms, with an emphasis on the potential contribution of lubricant. Both engine platforms used the same base General Motors (GM) 1.9-L diesel engine geometry. The first study was conducted on a single-cylinder research engine with primary reference fuels (PRFs), n-heptane, and iso-octane. The second study was conducted on a four-cylinder GM 1.9-L ZDTH engine which was modified with a port fuel injection (PFI) system while maintaining the stock direct injection fuel system. Multi-cylinder RCCI experiments were run with PFI gasoline and direct injection of 2-ethylhexyl nitrate (EHN) mixed with gasoline at 5 % EHN by volume. In addition, comparison cases of conventional diesel combustion (CDC) were performed. Particulate size distributions were measured, and PM filter samples were collected for analysis of lube oil components. Triplicate PM filter samples (i.e., three individual filter samples) for both gas chromatography-mass spectroscopy (GC-MS; organic) analysis and X-ray fluorescence (XRF; metals) were obtained at each operating point and queued for analysis of both organic species and lubricant metals. Here, the results give a clear indication that lubricants do not contribute significantly to the formation of RCCI PM.« less

  3. H2S cytotoxicity mechanism involves reactive oxygen species formation and mitochondrial depolarisation.

    PubMed

    Eghbal, Mohammad A; Pennefather, Peter S; O'Brien, Peter J

    2004-10-15

    A number of scavengers of reactive oxygen species (ROS) were found to be protective against cell death induced by hydrogen sulfide (H2S) in isolated hepatocytes. The H2O2 scavengers alpha-ketoglutarate and pyruvate, which also act as energy substrate metabolites, were more protective against H2S toxicity than lactate which is only an energy substrate metabolite. All of these results suggest that H2S toxicity is dependent on ROS production. We measured ROS formation directly in hepatocytes using the fluorogenic dichlorofluorescin method. H2S-induced ROS formation was dose dependent and pyruvate inhibited this ROS production. Non-toxic concentrations of H2S enhanced the cytotoxicity of H2O2 generated by glucose/glucose oxidase, which was inhibited by CYP450 inibitors. Furthermore, hepatocyte ROS formation induced by H2S was decreased by CYP450 inhibitors cimetidine and benzylimidazole. These results suggest that CYP450-dependant metabolism of H2S is responsible for inducing ROS production. H2S-induced cytotoxicity was preceded by mitochondrial depolarization as measured by rhodamine 123 fluorescence. Mitochondrial depolarization induced by H2S was prevented by zinc, methionine and pyruvate all of which decreased H2S-induced cell death. Treatment of H2S poisoning may benefit from interventions aimed at minimizing ROS-induced damage and reducing mitochondrial damage.

  4. The formation of reactive species having hydroxyl radical-like reactivity from UV photolysis of N-nitrosodimethylamine (NDMA): kinetics and mechanism.

    PubMed

    Kwon, Bum Gun; Kim, Jong-Oh; Namkung, Kyu Cheol

    2012-10-15

    This study focuses on the detailed mechanism by which N-nitrosodimethylamine (NDMA) is photolyzed to form oxidized products, i.e., NO(2)(-) and NO(3)(-), and reveals a key reactive species produced during the photolysis of NDMA. Under acidic conditions, NO(2)(-) formed from the photodecomposition of NDMA was more prevalent than NO(3)(-). In this result, key species for the formation of NO(2)(-) are presumably N(2)O(3) and N(2)O(4) as termination products as well as NO and O(2) as reactants. Conversely, under alkaline conditions, NO(3)(-) was more prevalent than NO(2)(-). For this result, a key species for NO(3)(-) formation is presumably peroxynitrite (ONOO(-)). A detailed mechanistic study was performed with a competition reaction (or kinetics) between NDMA and p-nitrosodimethylaniline (PNDA) probe for hydroxyl radical (OH). It is fortuitous that the second-order rate constant for NDMA with an unknown reactive species (URS) was 5.13×10(8) M(-1) s(-1), which was similar to its published value for the reaction of NDMA+OH. Our study results showed that a key reactive species generated during NDMA photo-decomposition had hydroxyl radical-like reactivity and in particular, under alkaline conditions, it is most likely ONOO(-) as a source of nitrate ion. Therefore, for the first time, we experimentally report that an URS having OH-like reactivity can be formed during photochemical NDMA decomposition. This URS could contribute to the formations of NO(2)(-) and NO(3)(-).

  5. Formate: an Energy Storage and Transport Bridge between Carbon Dioxide and a Formate Fuel Cell in a Single Device.

    PubMed

    Vo, Tracy; Purohit, Krutarth; Nguyen, Christopher; Biggs, Brenna; Mayoral, Salvador; Haan, John L

    2015-11-01

    We demonstrate the first device to our knowledge that uses a solar panel to power the electrochemical reduction of dissolved carbon dioxide (carbonate) into formate that is then used in the same device to operate a direct formate fuel cell (DFFC). The electrochemical reduction of carbonate is carried out on a Sn electrode in a reservoir that maintains a constant carbon balance between carbonate and formate. The electron-rich formate species is converted by the DFFC into electrical energy through electron release. The product of DFFC operation is the electron-deficient carbonate species that diffuses back to the reservoir bulk. It is possible to continuously charge the device using alternative energy (e.g., solar) to convert carbonate to formate for on-demand use in the DFFC; the intermittent nature of alternative energy makes this an attractive design. In this work, we demonstrate a proof-of-concept device that performs reduction of carbonate, storage of formate, and operation of a DFFC. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Impact of Americium-241 (n,γ) Branching Ratio on SFR Core Reactivity and Spent Fuel Characteristics

    SciTech Connect

    Hiruta, Hikaru; Youinou, Gilles J.; Dixon, Brent W.

    2016-06-01

    An accurate prediction of core physics and fuel cycle parameters largely depends on the order of details and accuracy in nuclear data taken into account for actual calculations. 241Am is a major gateway nuclide for most of minor actinides and thus important nuclide for core physics and fuel-cycle calculations. The 241Am(n,?) branching ratio (BR) is in fact the energy dependent (see Fig. 1), therefore, it is necessary to taken into account the spectrum effect on the calculation of the average BR for the full-core depletion calculations. Moreover, the accuracy of the BR used in the depletion calculations could significantly influence the core physics performance and post irradiated fuel compositions. The BR of 241Am(n,?) in ENDF/B-VII.0 library is relatively small and flat in thermal energy range, gradually increases within the intermediate energy range, and even becomes larger at the fast energy range. This indicates that the properly collapsed BR for fast reactors could be significantly different from that of thermal reactors. The evaluated BRs are also differ from one evaluation to another. As seen in Table I, average BRs for several evaluated libraries calculated by means of a fast spectrum are similar but have some differences. Most of currently available depletion codes use a pre-determined single value BR for each library. However, ideally it should be determined on-the-fly basis like that of one-group cross sections. These issues provide a strong incentive to investigate the effect of different 241Am(n,?) BRs on core and spent fuel parameters. This paper investigates the impact of the 241Am(n,?) BR on the results of SFR full-core based fuel-cycle calculations. The analysis is performed by gradually increasing the value of BR from 0.15 to 0.25 and studying its impact on the core reactivity and characteristics of SFR spent fuels over extended storage times (~10,000 years).

  7. Photo-Reactive Nanogel as a Means to Tune Properties during Polymer Network Formation

    PubMed Central

    Liu, JianCheng; Rad, Ima Y.; Sun, Fang; Stansbury, Jeffrey W.

    2013-01-01

    Photo-reactive nanogels with an integrated photoinitiator-based functionality were synthesized via a Reversible Addition-Fragmentation Chain Transfer (RAFT) process. Without additional free initiators, this nanogel is capable of radical generation and initiating polymerization of a secondary monomer (i.e. dimethacrylate) that infiltrates and disperses the nanogel particles. Due to the presence of RAFT functionality and the fact that all initiating sites are initially located within the nanogel structure, gelation can be delayed by sequencing the polymerization from the nanogel to the bulk matrix. During polymerization of a nanogel-filled resin system, a progressive delay of gelation conversion from about 2 % for conventional chain growth polymerization to 18 % for the same monomer containing 20 wt% nanogel additive was achieved. A significant delay of stress development was also observed with much lower final stress achieved with the nanogel-modified systems due to the change of network formation mechanics. Compared with the nanogel-free dimethacrylate control, which contained uniformly distributed free initiator, the flexural modulus and mechanical strength results were maintained for the photopolymers with nanogel contents greater than 10 wt%. There appears to be a critical interparticle spacing of the photo-reactive nanogel that provides effective photopolymerization while providing delayed gelation and substantial stress reduction. PMID:24348753

  8. Efficient Super Energy Transfer Collisions Through Reactive-Complex Formation: H + SO2

    NASA Astrophysics Data System (ADS)

    Smith, Jonathan M.; Wilhelm, Michael J.; Ma, Jianqiang; Dai, HAI-LUNG

    2015-06-01

    Translational-to-vibrational energy transfer (ET) from a hyperthermal H atom to ambient SO2 was characterized using time-resolved Fourier transform infrared emission spectroscopy. Vibrational excitation of SO2, following collisions with H atoms containing 59 kcal/mol of kinetic energy, generated from the 193 nm photolysis of HBr, is detected in two distinct energy distributions: one with excitation predominantly at the fundamental vibrational levels is attributable to classical impulsive collisions, while the other, accounting for 80% of the excited SO2 with vibrational energy as high as 14,000 wn, is proposed to arise from the formation of a transient reactive-complex during the collision. The cross-section for this super ET collision is determined to be 0.53±0.05 Å2, or roughly 2% of all hard sphere collisions. This observation reveals that in collisions between a hyperthermal atom and an ambient molecule, for which a reactive-complex exists on the potential energy surface, a large quantity of translational energy can be transferred to the molecule with high efficiency.

  9. Evidence for copper-dioxygen reactivity during alpha-synuclein fibril formation.

    PubMed

    Lucas, Heather R; Debeer, Serena; Hong, Myoung-Soon; Lee, Jennifer C

    2010-05-19

    Alpha-synuclein (alpha-syn), a presynaptic protein implicated in Parkinson's disease, binds copper(II) ion (1:1) with submicromolar affinity in vitro. Insights on the molecular details of soluble- and fibrillar-Cu-alpha-syn are gained through X-ray absorption spectroscopy. Our results indicate that the copper coordination environment (3-to-4 N/O ligands, average Cu-ligand distance approximately 1.96 A) exhibits little structural rearrangement upon amyloid formation in spite of the overall polypeptide conformational change from disordered-to-beta-sheet. Interestingly, we find that some population of Cu(II)-alpha-syn reduces to Cu(I)-alpha-syn in the absence of O(2). This autoreduction event appears diminished in the presence of O(2) suggestive of preceding Cu(I)/O(2) chemistry. Evidence for generation of reactive oxygen species is obtained by the observation of new emission features attributed to dityrosine cross-links in fibrillar samples.

  10. Conclusive evidence of abrupt coagulation inside the void during cyclic nanoparticle formation in reactive plasma

    SciTech Connect

    Wetering, F. M. J. H. van de; Nijdam, S.; Beckers, J.

    2016-07-25

    In this letter, we present scanning electron microscopy (SEM) results that confirm in a direct way our earlier explanation of an abrupt coagulation event as the cause for the void hiccup. In a recent paper, we reported on the fast and interrupted expansion of voids in a reactive dusty argon–acetylene plasma. The voids appeared one after the other, each showing a peculiar, though reproducible, behavior of successive periods of fast expansion, abrupt contraction, and continued expansion. The abrupt contraction was termed “hiccup” and was related to collective coagulation of a new generation of nanoparticles growing in the void using relatively indirect methods: electron density measurements and optical emission spectroscopy. In this letter, we present conclusive evidence using SEM of particles collected at different moments in time spanning several growth cycles, which enables us to follow the nanoparticle formation process in great detail.

  11. Conclusive evidence of abrupt coagulation inside the void during cyclic nanoparticle formation in reactive plasma

    NASA Astrophysics Data System (ADS)

    van de Wetering, F. M. J. H.; Nijdam, S.; Beckers, J.

    2016-07-01

    In this letter, we present scanning electron microscopy (SEM) results that confirm in a direct way our earlier explanation of an abrupt coagulation event as the cause for the void hiccup. In a recent paper, we reported on the fast and interrupted expansion of voids in a reactive dusty argon-acetylene plasma. The voids appeared one after the other, each showing a peculiar, though reproducible, behavior of successive periods of fast expansion, abrupt contraction, and continued expansion. The abrupt contraction was termed "hiccup" and was related to collective coagulation of a new generation of nanoparticles growing in the void using relatively indirect methods: electron density measurements and optical emission spectroscopy. In this letter, we present conclusive evidence using SEM of particles collected at different moments in time spanning several growth cycles, which enables us to follow the nanoparticle formation process in great detail.

  12. Fuel Spray and Flame Formation in a Compression-Ignition Engine Employing Air Flow

    NASA Technical Reports Server (NTRS)

    Rothrock, A M; Waldron, C D

    1937-01-01

    The effects of air flow on fuel spray and flame formation in a high-speed compression-ignition engine have been investigated by means of the NACA combustion apparatus. The process was studied by examining high-speed motion pictures taken at the rate of 2,200 frames a second. The combustion chamber was of the flat-disk type used in previous experiments with this apparatus. The air flow was produced by a rectangular displacer mounted on top of the engine piston. Three fuel-injection nozzles were tested: a 0.020-inch single-orifice nozzle, a 6-orifice nozzle, and a slit nozzle. The air velocity within the combustion chamber was estimated to reach a value of 425 feet a second. The results show that in no case was the form of the fuel spray completely destroyed by the air jet although in some cases the direction of the spray was changed and the spray envelope was carried away by the moving air. The distribution of the fuel in the combustion chamber of a compression-ignition engine can be regulated to some extent by the design of the combustion chamber, by the design of the fuel-injection nozzle, and by the use of air flow.

  13. Effects of C60 on the Photochemical Formation of Reactive Oxygen Species from Natural Organic Matter.

    PubMed

    Yin, Lijuan; Zhou, Huaxi; Lian, Lushi; Yan, Shuwen; Song, Weihua

    2016-11-01

    Buckminsterfullerenes (C60) are widely used nanomaterials that are present in surface water. The combination of C60 and humic acid (HA) generates reactive oxygen species (ROS) under solar irradiation, but this process is not well understood. Thus, the present study focused on the photochemical formation of singlet oxygen ((1)O2), hydroxyl radical (HO(•))-like species, superoxide radicals (O2(•-)), hydrogen peroxide (H2O2), and triplet excited states ((3)C60*/(3)HA*) in solutions containing both C60 and HA. The quantum yield coefficients of excited triplet states (fTMP) and apparent quantum yields of ROS were measured and compared to the calculated values, which were based on the conservative mixing model. Although C60 proved to have only a slight impact on the (1)O2 formation from HA, C60 played a key role in the inhibition of O2(•-). The photochemical formation of H2O2 followed the conservative mixing model due to the reaction of C60(•-) with HO2(•)/O2(•-), and the biomolecular reaction rate constant has been measured as (7.4 ± 0.6) × 10(6) M(-1) s(-1). The apparent fTMP was significantly lower than the calculated value, indicating that the steric effect of HA was significant in the reaction of (3)C60* with the TMP probe. In contrast, C60 did not have an effect on the photochemical formation of HO(•) from HA, suggesting that HO(•) is elevated from the hydrophilic surface of HA. The aforementioned results may be useful for predicting the photochemical influence of C60 on aqueous environments.

  14. Minimizing the risk of chemically reactive metabolite formation of new drug candidates: implications for preclinical drug design.

    PubMed

    Brink, Andreas; Pähler, Axel; Funk, Christoph; Schuler, Franz; Schadt, Simone

    2016-11-27

    Many pharmaceutical companies aim to reduce reactive metabolite formation by chemical modification at early stages of drug discovery. A practice often applied is the detection of stable trapping products of electrophilic intermediates with nucleophilic trapping reagents to guide rational structure-based drug design. This contribution delineates this strategy to minimize the potential for reactive metabolite formation of clinical candidates during preclinical drug optimization, exemplified by the experience at Roche over the past decade. For the majority of research programs it was possible to proceed with compounds optimized for reduced covalent binding potential. Such optimized candidates are expected to have a higher likelihood of succeeding throughout the development processes, resulting in safer drugs.

  15. Determining fissile content in PWR spent fuel assemblies using a passive neutron Albedo reactivity with fission chambers technique

    SciTech Connect

    Conlin, Jeremy Lloyd; Tobin, Stephen J

    2010-01-01

    State regulatory bodies and organizations such as the IAEA that are concerned with preventing the proliferation of nuclear weapons are interested in a means of quantifying the amount of plutonium in a given spent fuel assembly. The complexity of spent nuclear fuel makes the measurement of plutonium content challenging. There are a variety of techniques that can measure various properties of spent nuclear fuel including burnup, and mass of fissile content. No single technique can provide all desired information, necessitating an approach using multiple detector systems and types. This paper presents our analysis of the Passive Neutron Albedo Reactivity Fission Chamber (PNAR-FC) detector system. PNAR-FC is a simplified version of the PNAR technique originally developed in 1997. This earlier research was performed with a high efficiency, {sup 3}He-based system (PNAR-3He) with which multiplicty analysis was performed. With the PNAR technique a portion of the spent fuel assembly is wrapped in a 1 mm thick cadmium liner. Neutron count rates are measured both with and without the cadmium liner present. The ratio of the count rate with the cadmium liner to the count rate without the cadmium liner is calculated and called the cadmium ratio. In the PNAR-3He technique, multiplicity measurements were made and the cadmium ratio was shown to scale with the fissile content of the material being measured. PNAR-FC simplifies the PNAR technique by using only a few fission chambers instead of many {sup 3}He tubes. Using a simplified PNAR-FC technique provides for a cheaper, lighter, and thus more portable detector system than was possible with the PNAR-3He system. The challenge with the PNAR-FC system are two-fold: (1) the change in the cadmium ratio is weaker as a afunction of the changing fissile content relative to multiplicity count rates, and (2) the efficiency for the fission chamber based system are poorer than for the {sup 3}He based detectors. In this paper, we present our

  16. Mitochondrion-derived reactive oxygen species lead to enhanced amyloid beta formation.

    PubMed

    Leuner, Kristina; Schütt, Tanja; Kurz, Christopher; Eckert, Schamim H; Schiller, Carola; Occhipinti, Angelo; Mai, Sören; Jendrach, Marina; Eckert, Gunter P; Kruse, Shane E; Palmiter, Richard D; Brandt, Ulrich; Dröse, Stephan; Wittig, Ilka; Willem, Michael; Haass, Christian; Reichert, Andreas S; Müller, Walter E

    2012-06-15

    Intracellular amyloid beta (Aβ) oligomers and extracellular Aβ plaques are key players in the progression of sporadic Alzheimer's disease (AD). Still, the molecular signals triggering Aβ production are largely unclear. We asked whether mitochondrion-derived reactive oxygen species (ROS) are sufficient to increase Aβ generation and thereby initiate a vicious cycle further impairing mitochondrial function. Complex I and III dysfunction was induced in a cell model using the respiratory inhibitors rotenone and antimycin, resulting in mitochondrial dysfunction and enhanced ROS levels. Both treatments lead to elevated levels of Aβ. Presence of an antioxidant rescued mitochondrial function and reduced formation of Aβ, demonstrating that the observed effects depended on ROS. Conversely, cells overproducing Aβ showed impairment of mitochondrial function such as comprised mitochondrial respiration, strongly altered morphology, and reduced intracellular mobility of mitochondria. Again, the capability of these cells to generate Aβ was partly reduced by an antioxidant, indicating that Aβ formation was also ROS dependent. Moreover, mice with a genetic defect in complex I, or AD mice treated with a complex I inhibitor, showed enhanced Aβ levels in vivo. We show for the first time that mitochondrion-derived ROS are sufficient to trigger Aβ production in vitro and in vivo. Several lines of evidence show that mitochondrion-derived ROS result in enhanced amyloidogenic amyloid precursor protein processing, and that Aβ itself leads to mitochondrial dysfunction and increased ROS levels. We propose that starting from mitochondrial dysfunction a vicious cycle is triggered that contributes to the pathogenesis of sporadic AD.

  17. Increased Reactive Oxygen Species Formation and Oxidative Stress in Rheumatoid Arthritis

    PubMed Central

    Mateen, Somaiya; Moin, Shagufta; Khan, Abdul Qayyum; Zafar, Atif; Fatima, Naureen

    2016-01-01

    Background Rheumatoid arthritis (RA) is an autoimmune inflammatory disorder. Highly reactive oxygen free radicals are believed to be involved in the pathogenesis of the disease. In this study, RA patients were sub-grouped depending upon the presence or absence of rheumatoid factor, disease activity score and disease duration. RA Patients (120) and healthy controls (53) were evaluated for the oxidant—antioxidant status by monitoring ROS production, biomarkers of lipid peroxidation, protein oxidation and DNA damage. The level of various enzymatic and non-enzymatic antioxidants was also monitored. Correlation analysis was also performed for analysing the association between ROS and various other parameters. Methods Intracellular ROS formation, lipid peroxidation (MDA level), protein oxidation (carbonyl level and thiol level) and DNA damage were detected in the blood of RA patients. Antioxidant status was evaluated by FRAP assay, DPPH reduction assay and enzymatic (SOD, catalase, GST, GR) and non-enzymatic (vitamin C and GSH) antioxidants. Results RA patients showed a higher ROS production, increased lipid peroxidation, protein oxidation and DNA damage. A significant decline in the ferric reducing ability, DPPH radical quenching ability and the levels of antioxidants has also been observed. Significant correlation has been found between ROS and various other parameters studied. Conclusion RA patients showed a marked increase in ROS formation, lipid peroxidation, protein oxidation, DNA damage and decrease in the activity of antioxidant defence system leading to oxidative stress which may contribute to tissue damage and hence to the chronicity of the disease. PMID:27043143

  18. Repetition rate dependency of reactive oxygen species formation during femtosecond laser-based cell surgery

    NASA Astrophysics Data System (ADS)

    Baumgart, Judith; Kuetemeyer, Kai; Bintig, Willem; Ngezahayo, Anaclet; Ertmer, Wolfgang; Lubatschowski, Holger; Heisterkamp, Alexander

    2009-09-01

    Femtosecond (fs) laser-based cell surgery is typically done in two different regimes, at kHz or MHz repetition rate. Formation of reactive oxygen species (ROS) is an often predicted effect due to illumination with short laser pulses in biological tissue. We present our study on ROS formation in single cells in response to irradiation with fs laser pulses depending on the repetition rate while focusing into the cell nucleus. We observed a significant increase of ROS concentration directly after manipulation followed by a decrease in both regimes at kHz and MHz repetition rate. In addition, effects of consecutive exposures at MHz and kHz repetition rate and vice versa on ROS production were studied. Irradiation with a MHz pulse train followed by a kHz pulse train resulted in a significantly higher increase of ROS concentration than in the reversed case and often caused cell death. In the presence of the antioxidant ascorbic acid, accumulation of ROS and cell death were strongly reduced. Therefore, addition of antioxidants during fs laser-based cell surgery experiments could be advantageous in terms of suppressing photochemical damage to the cell.

  19. Ambient Fine Particulate Matter Induces Apoptosis of Endothelial Progenitor Cells Through Reactive Oxygen Species Formation

    PubMed Central

    Cui, Yuqi; Xie, Xiaoyun; Jia, Fengpeng; He, Jianfeng; Li, Zhihong; Fu, Minghuan; Hao, Hong; Liu, Ying; Liu, Jason Z.; Cowan, Peter J.; Zhu, Hua; Sun, Qinghua; Liu, Zhenguo

    2015-01-01

    Background/Aims Bone marrow (BM)-derived endothelial progenitor cells (EPCs) play a critical role in angiogenesis and vascular repair. Some environmental insults, like fine particulate matter (PM) exposure, significantly impair cardiovascular functions. However, the mechanisms for PM-induced adverse effects on cardiovascular system remain largely unknown. The present research was to study the detrimental effects of PM on EPCs and explore the potential mechanisms. Methods PM was intranasal-distilled into male C57BL/6 mice for one month. Flow cytometry was used to measure the number of EPCs, apoptosis level of circulating EPCs and intracellular reactive oxygen species (ROS) formation. Serum TNF-α and IL-1β were measured using ELISA. To determine the role of PM-induced ROS in EPC apoptosis, PM was co-administrated with the antioxidant N-acetylcysteine (NAC) in wild type mice or used in a triple transgenic mouse line (TG) with overexpression of antioxidant enzyme network (AON) composed of superoxide dismutase (SOD)1, SOD3, and glutathione peroxidase (Gpx-1) with decreased in vivo ROS production. Results PM treatment significantly decreased circulating EPC population, promoted apoptosis of EPCs in association with increased ROS production and serum TNF-α and IL-1β levels, which could be effectively reversed by either NAC treatment or overexpression of AON. Conclusion PM exposure significantly decreased circulating EPCs population due to increased apoptosis via ROS formation in mice. PMID:25591776

  20. Coupled Reactive Transport Modeling of CO2 Injection in Mt. Simon Sandstone Formation, Midwest USA

    NASA Astrophysics Data System (ADS)

    Liu, F.; Lu, P.; Zhu, C.; Xiao, Y.

    2009-12-01

    CO2 sequestration in deep geological formations is one of the promising options for CO2 emission reduction. While several large scale CO2 injections in saline aquifers have shown to be successful for the short-term, there is still a lack of fundamental understanding on key issues such as CO2 storage capacity, injectivity, and security over multiple spatial and temporal scales that need to be addressed. To advance these understandings, we applied multi-phase coupled reactive mass transport modeling to investigate the fate of injected CO2 and reservoir responses to the injection into Mt. Simon Formation. We developed both 1-D and 2-D reactive transport models in a radial region of 10,000 m surrounding a CO2 injection well to represent the Mt. Simon sandstone formation, which is a major regional deep saline reservoir in the Midwest, USA. Supercritical CO2 is injected into the formation for 100 years, and the modeling continues till 10,000 years to monitor both short-term and long-term behavior of injected CO2 and the associated rock-fluid interactions. CO2 co-injection with H2S and SO2 is also simulated to represent the flue gases from coal gasification and combustion in the Illinois Basin. The injection of CO2 results in acidified zones (pH ~3 and 5) adjacent to the wellbore, causing progressive water-rock interactions in the surrounding region. In accordance with the extensive dissolution of authigenic K-feldspar, sequential precipitations of secondary carbonates and clay minerals are predicted in this zone. The vertical profiles of CO2 show fingering pattern from the top of the reservoir to the bottom due to the density variation of CO2-impregnated brine, which facilitate convection induced mixing and solubility trapping. Most of the injected CO2 remains within a radial distance of 2500 m at the end of 10,000 years and is sequestered and immobilized by solubility and residual trapping. Mineral trapping via secondary carbonates, including calcite, magnesite

  1. In situ fluorescence spectroscopy correlates ionomer degradation to reactive oxygen species generation in an operating fuel cell.

    PubMed

    Prabhakaran, Venkateshkumar; Arges, Christopher G; Ramani, Vijay

    2013-11-21

    The rate of generation of reactive oxygen species (ROS) within the polymer electrolyte membrane (PEM) of an operating proton exchange member fuel cell (PEMFC) was monitored using in situ fluorescence spectroscopy. A modified barrier layer was introduced between the PEM and the electrocatalyst layer to eliminate metal-dye interactions and fluorescence resonance energy transfer (FRET) effects during measurements. Standard fuel cell operating parameters (temperature, relative humidity, and electrode potential) were systematically varied to evaluate their influence on the rate of ROS generation during PEMFC operation. Independently, the macroscopic rate of PEM degradation was measured by monitoring the fluoride ion emission rate (FER) in the effluent stream at each operating condition. The ROS generation reaction rate constant (estimated from the in situ fluorescence experiments) correlated perfectly with the measured FER across all conditions, demonstrating unequivocally for the first time that a direct correlation exists between in situ ROS generation and PEM macroscopic degradation. The activation energy for ROS generation within the PEM was estimated to be 12.5 kJ mol(-1).

  2. Pore Scale Modeling of the Reactive Transport of Chromium in the Cathode of a Solid Oxide Fuel Cell

    SciTech Connect

    Ryan, Emily M.; Tartakovsky, Alexandre M.; Recknagle, Kurtis P.; Khaleel, Mohammad A.; Amon, Cristina

    2011-01-01

    We present a pore scale model of a solid oxide fuel cell (SOFC) cathode. Volatile chromium species are known to migrate from the current collector of the SOFC into the cathode where over time they decrease the voltage output of the fuel cell. A pore scale model is used to investigate the reactive transport of chromium species in the cathode and to study the driving forces of chromium poisoning. A multi-scale modeling approach is proposed which uses a cell level model of the cathode, air channel and current collector to determine the boundary conditions for a pore scale model of a section of the cathode. The pore scale model uses a discrete representation of the cathode to explicitly model the surface reactions of oxygen and chromium with a cathode material. The pore scale model is used to study the reaction mechanisms of chromium by considering the effects of reaction rates, diffusion coefficients, chromium vaporization, and oxygen consumption on chromium’s deposition in the cathode. The study shows that chromium poisoning is most significantly affected by the chromium reaction rates in the cathode and that the reaction rates are a function of the local current density in the cathode.

  3. Optimization of degradation of Reactive Black 5 (RB5) and electricity generation in solar photocatalytic fuel cell system.

    PubMed

    Khalik, Wan Fadhilah; Ho, Li-Ngee; Ong, Soon-An; Voon, Chun-Hong; Wong, Yee-Shian; Yusoff, NikAthirah; Lee, Sin-Li; Yusuf, Sara Yasina

    2017-10-01

    The photocatalytic fuel cell (PFC) system was developed in order to study the effect of several operating parameters in degradation of Reactive Black 5 (RB5) and its electricity generation. Light irradiation, initial dye concentration, aeration, pH and cathode electrode are the operating parameters that might give contribution in the efficiency of PFC system. The degradation of RB5 depends on the presence of light irradiation and solar light gives better performance to degrade the azo dye. The azo dye with low initial concentration decolorizes faster compared to higher initial concentration and presence of aeration in PFC system would enhance its performance. Reactive Black 5 rapidly decreased at higher pH due to the higher amount of OH generated at higher pH and Pt-loaded carbon (Pt/C) was more suitable to be used as cathode in PFC system compared to Cu foil and Fe foil. The rapid decolorization of RB5 would increase their voltage output and in addition, it would also increase their Voc, Jsc and Pmax. The breakage of azo bond and aromatic rings was confirmed through UV-Vis spectrum and COD analysis. Copyright © 2017 Elsevier Ltd. All rights reserved.

  4. Arginine Decarboxylase expression, polyamines biosynthesis and reactive oxygen species during organogenic nodule formation in hop.

    PubMed

    Fortes, Ana M; Costa, Joana; Santos, Filipa; Seguí-Simarro, José M; Palme, Klaus; Altabella, Teresa; Tiburcio, Antonio F; Pais, Maria S

    2011-02-01

    Hop (Humulus lupulus L.) is an economically important plant species used in beer production and as a health-promoting medicine. Hop internodes develop upon stress treatments organogenic nodules which can be used for genetic transformation and micropropagation. Polyamines are involved in plant development and stress responses. Arginine decarboxylase (ADC; EC 4·1.1·19) is a key enzyme involved in the biosynthesis of putrescine in plants. Here we show that ADC protein was increasingly expressed at early stages of hop internode culture (12h). Protein continued accumulating until organogenic nodule formation after 28 days, decreasing thereafter. The same profile was observed for ADC transcript suggesting transcriptional regulation of ADC gene expression during morphogenesis. The highest transcript and protein levels observed after 28 days of culture were accompanied by a peak in putrescine levels. Reactive oxygen species accumulate in nodular tissues probably due to stress inherent to in vitro conditions and enhanced polyamine catabolism. Conjugated polyamines increased during plantlet regeneration from nodules suggesting their involvement in plantlet formation and/or in the control of free polyamine levels. Immunogold labeling revealed that ADC is located in plastids, nucleus and cytoplasm of nodular cells. In vacuolated cells, ADC immunolabelling in plastids doubled the signal of proplastids in meristematic cells. Location of ADC in different subcellular compartments may indicate its role in metabolic pathways taking place in these compartments. Altogether these data suggest that polyamines play an important role in organogenic nodule formation and represent a progress towards understanding the role played by these growth regulators in plant morphogenesis.

  5. Nicorandil prevents sirolimus-induced production of reactive oxygen species, endothelial dysfunction, and thrombus formation.

    PubMed

    Aizawa, Ken; Takahari, Youko; Higashijima, Naoko; Serizawa, Kenichi; Yogo, Kenji; Ishizuka, Nobuhiko; Endo, Koichi; Fukuyama, Naoto; Hirano, Katsuya; Ishida, Hideyuki

    2015-03-01

    Sirolimus (SRL) is widely used to prevent restenosis after percutaneous coronary intervention. However, its beneficial effect is hampered by complications of thrombosis. Several studies imply that reactive oxygen species (ROS) play a critical role in endothelial dysfunction and thrombus formation. The present study investigated the protective effect of nicorandil (NIC), an anti-angina agent, on SRL-associated thrombosis. In human coronary artery endothelial cells (HCAECs), SRL stimulated ROS production, which was prevented by co-treatment with NIC. The preventive effect of NIC on ROS was abolished by 5-hydroxydecanoate but not by 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one. NIC also inhibited SRL-induced up-regulation of NADPH oxidase subunit p22(phox) mRNA. Co-treatment with NIC and SRL significantly up-regulated superoxide dismutase 2. NIC treatment significantly improved SRL-induced decrease in viability of HCAECs. The functional relevance of the preventive effects of NIC on SRL-induced ROS production and impairment of endothelial viability was investigated in a mouse model of thrombosis. Pretreatment with NIC inhibited the SRL-induced acceleration of FeCl3-initiated thrombus formation and ROS production in the testicular arteries of mice. In conclusion, NIC prevented SRL-induced thrombus formation, presumably due to the reduction of ROS and to endothelial protection. The therapeutic efficacy of NIC could represent an additional option in the prevention of SRL-related thrombosis. Copyright © 2015 The Authors. Production and hosting by Elsevier B.V. All rights reserved.

  6. Iron Hydroxy Carbonate Formation in Zerovalent Iron Permeable Reactive Barriers: Characterization and Evaluation of Phase Stability

    EPA Science Inventory

    Predicting the long-term potential of permeable reactive barriers for treating contaminated groundwater relies on understanding the endpoints of biogeochemical reactions between influent groundwater and the reactive medium. Iron hydroxy carbonate (chukanovite) is frequently obs...

  7. Iron Hydroxy Carbonate Formation in Zerovalent Iron Permeable Reactive Barriers: Characterization and Evaluation of Phase Stability

    EPA Science Inventory

    Predicting the long-term potential of permeable reactive barriers for treating contaminated groundwater relies on understanding the endpoints of biogeochemical reactions between influent groundwater and the reactive medium. Iron hydroxy carbonate (chukanovite) is frequently obs...

  8. Visualization of Gas-to-Liquid (GTL) Fuel Liquid Length and Soot Formation in the Constant Volume Combustion Chamber

    NASA Astrophysics Data System (ADS)

    Azimov, Ulugbek; Kim, Ki-Seong

    In this research, GTL spray combustion was visualized in an optically accessible quiescent constant-volume combustion chamber. The results were compared with the spray combustion of diesel fuel. Fast-speed photography with direct laser sheet illumination was used to determine the fuel liquid-phase length, and shadowgraph photography was used to determine the distribution of the sooting area in the fuel jet. The results showed that the fuel liquid-phase length of GTL fuel jets stabilized at about 20-22mm from the injector orifice and mainly depended on the ambient gas temperature and fuel volatility. GTL had a slightly shorter liquid length than that of the diesel fuel. This tendency was also maintained when multiple injection strategy was applied. The penetration of the tip of the liquid-phase fuel during pilot injection was a little shorter than the penetration during main injection. The liquid lengths during single and main injections were identical. In the case of soot formation, the results showed that soot formation was mainly affected by air-fuel mixing, and had very weak dependence on fuel volatility.

  9. Computation Sheds Insight into Iron Porphyrin Carbenes' Electronic Structure, Formation, and N-H Insertion Reactivity.

    PubMed

    Sharon, Dina A; Mallick, Dibyendu; Wang, Binju; Shaik, Sason

    2016-08-03

    Iron porphyrin carbenes constitute a new frontier of species with considerable synthetic potential. Exquisitely engineered myoglobin and cytochrome P450 enzymes can generate these complexes and facilitate the transformations they mediate. The current work harnesses density functional theoretical methods to provide insight into the electronic structure, formation, and N-H insertion reactivity of an iron porphyrin carbene, [Fe(Por)(SCH3)(CHCO2Et)](-), a model of a complex believed to exist in an experimentally studied artificial metalloenzyme. The ground state electronic structure of the terminal form of this complex is an open-shell singlet, with two antiferromagnetically coupled electrons residing on the iron center and carbene ligand. As we shall reveal, the bonding properties of [Fe(Por)(SCH3)(CHCO2Et)](-) are remarkably analogous to those of ferric heme superoxide complexes. The carbene forms by dinitrogen loss from ethyl diazoacetate. This reaction occurs preferentially through an open-shell singlet transition state: iron donates electron density to weaken the C-N bond undergoing cleavage. Once formed, the iron porphyrin carbene accomplishes N-H insertion via nucleophilic attack. The resulting ylide then rearranges, using an internal carbonyl base, to form an enol that leads to the product. The findings rationalize experimentally observed reactivity trends reported in artificial metalloenzymes employing iron porphyrin carbenes. Furthermore, these results suggest a possible expansion of enzymatic substrate scope, to include aliphatic amines. Thus, this work, among the first several computational explorations of these species, contributes insights and predictions to the surging interest in iron porphyrin carbenes and their synthetic potential.

  10. Role of Reactive Intermediates in Manganese Oxide Formation By Filamentous Ascomycete Fungi

    NASA Astrophysics Data System (ADS)

    Zeiner, C. A.; Anderton, C.; Wu, S.; Purvine, S.; Zink, E.; Paša-Tolić, L.; Santelli, C. M.; Hansel, C. M.

    2014-12-01

    Biogenic manganese (Mn) oxide minerals are ubiquitous in the environment, and their high reactivity can profoundly impact the fate of contaminants and cycling of carbon and nutrients. In contrast to bacteria, the pathways utilized by fungi to oxidize Mn(II) to Mn(III,IV) oxides remain largely unknown. Here, we explore the mechanisms of Mn(II) oxidation by a phylogenetically diverse group of filamentous Ascomycete fungi using a combination of chemical assays and bulk and spatially-resolved mass spectrometry. We show that the mechanisms of Mn(II) oxidation vary with fungal species, over time during secretome compositional changes, and in the presence of other fungi. Specifically, our work implicates a dynamic transition in Mn(II) oxidation pathways that varies between species. In particular, while reactive oxygen species (ROS) produced via transmembrane NADPH oxidases are involved in initial oxidation, over time, secreted enzymes become important Mn(II) oxidation mediators for some species. In addition, the overall secretome oxidation capacity varies with time and fungal species. Secretome analysis reveals a surprising absence of enzymes currently considered to be Mn(II)-oxidizing enzymes in these organisms, and instead highlights a wide variety of redox-active enzymes. Furthermore, we implicate fungal cell defense mechanisms in the formation of distinct Mn oxide patterns when fungi are grown in head-to-head competition. The identification and regulation of these secreted enzymes are under current investigation within the bulk secretome and within the interaction zone of structured fungal communities. Overall, our findings illustrate that Ascomycete Mn(II) oxidation mechanisms are highly variable and are dictated by complex environmental and ecological interactions. Future work will explore the connection between Ascomycete Mn(II) oxidation and the ability to degrade cellulose, a key carbon reservoir for biofuel production.

  11. Permeability evolution of fractured limestone due to reactive flow: Observation and prediction of wormhole formation

    NASA Astrophysics Data System (ADS)

    Deng, H.; Fitts, J. P.; Crandall, D.; McIntyre, D.; Peters, C. A.

    2014-12-01

    Fractures in porous media provide preferential pathways for flow and solute transport. Their hydraulic properties are critical parameters for determining fluid migration and leakage, and are subject to alterations when exposed to reactive flow, e.g. CO2-acidfied brine in the case of carbon storage. Our previous studies have shown how mineral heterogeneity could lead to increased roughness that mitigates the increase in fracture permeability. This study shows that, even in rocks with mineral homogeneity, fracture geometry is subject to complex alterations. In this presentation, we report an experimental study of CO2-acidified brine in fractured Indiana Limestone, with comprehensive characterization of effluent chemistry analyzed by ICP-OES, and 3D geometry evolution using micro-computed topography (xCT). Significant carbonate dissolution was observed but the reaction extent revealed by the effluent chemistry was less than what was predicted by simple reaction transport models. xCT imaging revealed the formation of wormhole channels in the fracture, and the channels grew larger downstream and more prominent over time. Using the fracture geometries derived from the xCT images, we simulated the flow field and inferred the evolution of fracture hydraulic properties. To interpret the process of wormholing and its impacts on fracture hydraulic properties, we used reactive transport modeling to simulate the interplay between fracture geometry, fluid flow and geochemical reactions. Our simulations predicted that wormholes were formed in fractures with initial roughness representative of natural subsurface systems. The presence of wormholes caused a disproportionately larger permeability increase than would be expected given the extent of volume change.

  12. Fuel swelling and interaction layer formation in the SELENIUM Si and ZrN coated U(Mo) dispersion fuel plates irradiated at high power in BR2

    NASA Astrophysics Data System (ADS)

    Leenaers, A.; Van den Berghe, S.; Koonen, E.; Kuzminov, V.; Detavernier, C.

    2015-03-01

    In the framework of the SELENIUM project two full size flat fuel plates were produced with respectively Si and ZrN coated U(Mo) particles and irradiated in the BR2 reactor at SCK•CEN. Non-destructive analysis of the plates showed that the fuel swelling profiles of both SELENIUM plates were very similar to each other and none of the plates showed signs of pillowing or excessive swelling at the end of irradiation at the highest power position (local maximum 70% 235U). The microstructural analysis showed that the Si coated fuel has less interaction phase formation at low burn-up but at the highest burn-ups, defects start to develop on the IL-matrix interface. The ZrN coated fuel, shows a virtual absence of reaction between the U(Mo) and the Al, up to high fission densities after which the interaction layer formation starts and defects develop in the matrix near the U(Mo) particles. It was found and is confirmed by the SELENIUM (Surface Engineering of Low ENrIched Uranium-Molybdenum) experiment that there are two phenomena at play that need to be controlled: the formation of an interaction layer and swelling of the fuel. As the interaction layer formation occurs at the U(Mo)-matrix interface, applying a diffusion barrier (coating) at that interface should prevent the interaction between U(Mo) and the matrix. The U(Mo) swelling, observed to proceed at an accelerating rate with respect to fission density accumulation, is governed by linear solid state swelling and fission gas bubble swelling due to recrystallization of the fuel. The examination of the SELENIUM fuel plates clearly show that for the U(Mo) dispersion fuel to be qualified, the swelling rate at high burn-up needs to be reduced.

  13. Impacts of powdered activated carbon addition on trihalomethane formation reactivity of dissolved organic matter in membrane bioreactor effluent.

    PubMed

    Ma, Defang; Gao, Yue; Gao, Baoyu; Wang, Yan; Yue, Qinyan; Li, Qian

    2014-12-01

    Characteristics and trihalomethane (THM) formation reactivity of dissolved organic matter (DOM) in effluents from two membrane bioreactors (MBRs) with and without powdered activated carbon (PAC) addition (referred to as PAC/MBR and MBR, respectively) were examined to investigate the effects of PAC addition on THM formation of MBR effluent during chlorination. PAC addition increased the specific UV absorbance. Hydrophobic DOM especially hydrophobic acids in PAC/MBR effluent (50%) were more than MBR effluent (42%). DOM with molecular weight <1 kDa constituted 12% of PAC/MBR effluent DOM, which was less than that of MBR effluent (16%). Data obtained from excitation and emission matrix fluorescence spectroscopy revealed that PAC/MBR effluent DOM contained more simple aromatic protein, but had less fulvic acid-like and soluble microbial by-product-like. PAC addition reduced the formation of bromine-containing THMs during chlorination of effluents, but increased THM formation reactivity of effluent DOM.

  14. Reactive impinging-flow technique for polymer-electrolyte-fuel-cell electrode-defect detection

    DOE PAGES

    Zenyuk, Iryna V.; Englund, Nicholas; Bender, Guido; ...

    2016-09-29

    Reactive impinging flow (RIF) is a novel quality-control method for defect detection (i.e., reduction in Pt catalyst loading) in gas-diffusion electrodes (GDEs) on weblines. The technique uses infrared thermography to detect temperature of a nonflammable (<4% H2) reactive mixture of H2/O2 in N2 impinging and reacting on a Pt catalytic surface. In this article, different GDE size defects (with catalyst-loading reductions of 25, 50, and 100%) are detected at various webline speeds (3.048 and 9.144 m min-1) and gas flowrates (32.5 or 50 standard L min-1). Furthermore, a model is developed and validated for the technique, and it is subsequentlymore » used to optimize operating conditions and explore the applicability of the technique to a range of defects. The model suggests that increased detection can be achieved by recting more of the impinging H2, which can be accomplished by placing blocking substrates on the top, bottom, or both of the GDE; placing a substrate on both results in a factor of four increase in the temperature differential, which is needed for smaller defect detection. Lastly, overall, the RIF technique is shown to be a promising route for in-line, high-speed, large-area detection of GDE defects on moving weblines.« less

  15. Reactive impinging-flow technique for polymer-electrolyte-fuel-cell electrode-defect detection

    SciTech Connect

    Zenyuk, Iryna V.; Englund, Nicholas; Bender, Guido; Weber, Adam Z.; Ulsh, Michael

    2016-09-29

    Reactive impinging flow (RIF) is a novel quality-control method for defect detection (i.e., reduction in Pt catalyst loading) in gas-diffusion electrodes (GDEs) on weblines. The technique uses infrared thermography to detect temperature of a nonflammable (<4% H2) reactive mixture of H2/O2 in N2 impinging and reacting on a Pt catalytic surface. In this article, different GDE size defects (with catalyst-loading reductions of 25, 50, and 100%) are detected at various webline speeds (3.048 and 9.144 m min-1) and gas flowrates (32.5 or 50 standard L min-1). Furthermore, a model is developed and validated for the technique, and it is subsequently used to optimize operating conditions and explore the applicability of the technique to a range of defects. The model suggests that increased detection can be achieved by recting more of the impinging H2, which can be accomplished by placing blocking substrates on the top, bottom, or both of the GDE; placing a substrate on both results in a factor of four increase in the temperature differential, which is needed for smaller defect detection. Lastly, overall, the RIF technique is shown to be a promising route for in-line, high-speed, large-area detection of GDE defects on moving weblines.

  16. Reactive impinging-flow technique for polymer-electrolyte-fuel-cell electrode-defect detection

    SciTech Connect

    Zenyuk, Iryna V.; Englund, Nicholas; Bender, Guido; Weber, Adam Z.; Ulsh, Michael

    2016-09-29

    Reactive impinging flow (RIF) is a novel quality-control method for defect detection (i.e., reduction in Pt catalyst loading) in gas-diffusion electrodes (GDEs) on weblines. The technique uses infrared thermography to detect temperature of a nonflammable (<4% H2) reactive mixture of H2/O2 in N2 impinging and reacting on a Pt catalytic surface. In this article, different GDE size defects (with catalyst-loading reductions of 25, 50, and 100%) are detected at various webline speeds (3.048 and 9.144 m min-1) and gas flowrates (32.5 or 50 standard L min-1). Furthermore, a model is developed and validated for the technique, and it is subsequently used to optimize operating conditions and explore the applicability of the technique to a range of defects. The model suggests that increased detection can be achieved by recting more of the impinging H2, which can be accomplished by placing blocking substrates on the top, bottom, or both of the GDE; placing a substrate on both results in a factor of four increase in the temperature differential, which is needed for smaller defect detection. Lastly, overall, the RIF technique is shown to be a promising route for in-line, high-speed, large-area detection of GDE defects on moving weblines.

  17. Reactive impinging-flow technique for polymer-electrolyte-fuel-cell electrode-defect detection

    NASA Astrophysics Data System (ADS)

    Zenyuk, Iryna V.; Englund, Nicholas; Bender, Guido; Weber, Adam Z.; Ulsh, Michael

    2016-11-01

    Reactive impinging flow (RIF) is a novel quality-control method for defect detection (i.e., reduction in Pt catalyst loading) in gas-diffusion electrodes (GDEs) on weblines. The technique uses infrared thermography to detect temperature of a nonflammable (<4% H2) reactive mixture of H2/O2 in N2 impinging and reacting on a Pt catalytic surface. In this paper, different GDE size defects (with catalyst-loading reductions of 25, 50, and 100%) are detected at various webline speeds (3.048 and 9.144 m min-1) and gas flowrates (32.5 or 50 standard L min-1). Furthermore, a model is developed and validated for the technique, and it is subsequently used to optimize operating conditions and explore the applicability of the technique to a range of defects. The model suggests that increased detection can be achieved by recting more of the impinging H2, which can be accomplished by placing blocking substrates on the top, bottom, or both of the GDE; placing a substrate on both results in a factor of four increase in the temperature differential, which is needed for smaller defect detection. Overall, the RIF technique is shown to be a promising route for in-line, high-speed, large-area detection of GDE defects on moving weblines.

  18. A study of carbon formation and prevention in hydrocarbon-fueled SOFC

    NASA Astrophysics Data System (ADS)

    Kim, T.; Liu, G.; Boaro, M.; Lee, S.-I.; Vohs, J. M.; Gorte, R. J.; Al-Madhi, O. H.; Dabbousi, B. O.

    The formation and removal of the carbonaceous deposits formed by n-butane and liquid hydrocarbons, such as n-decane and proprietary light and heavy naphthas, between 973 and 1073 K on YSZ and ceria-YSZ, has been studied to determine conditions for stable operation of direct-utilization SOFC. First, it is shown that deactivation of SOFC with Cu-ceria-YSZ anodes operating on undiluted n-decane, a mixture of 80% n-decane and 20% toluene, or light naphtha at temperatures above 973 K is due to filling of the pores with polyaromatic compounds formed by gas-phase, free-radical reactions. Formation of these compounds occurs at a negligible rate below 973 K but increases rapidly above this temperature. The rate of formation also depends on the residence time of the fuel in the anode compartment. Because steam does not participate in the gas-phase reactions, carbonaceous deposits could form even at a H 2O:C ratio of 1.5, a value greater than the stability threshold predicted by thermodynamic calculations. Temperature programmed oxidation (TPO) measurements with 20% H 2O in He demonstrated that carbon deposits formed in pure YSZ were unreactive below 1073 K, while deposits formed on ceria-YSZ could be removed at temperatures as low as 923 K. Based on these results, we discuss strategies for avoiding carbon formation during the operation of direct-utilization anodes on oil-based liquid fuels.

  19. Evaluation of fuel injection configurations to control carbon and soot formation in small GT combustors

    NASA Technical Reports Server (NTRS)

    Rosfjord, T. J.; Briehl, D.

    1982-01-01

    An experimental program to investigate hardware configurations which attempt to minimize carbon formation and soot production without sacrificing performance in small gas turbine combustors has been conducted at the United Technologies Research Center. Four fuel injectors, embodying either airblast atomization, pressure atomization, or fuel vaporization techniques, were combined with nozzle air swirlers and injector sheaths, and evaluated at test conditions which included and extended beyond standard small gas turbine combustor operation. Extensive testing was accomplished with configurations embodying either a spill return or a T-vaporizer injector. Minimal carbon deposits were observed on the spill return nozzle for tests using either Jet A or ERBS test fuel. A more extensive film of soft carbon was observed on the vaporizer after operation at standard engine conditions, with large carbonaceous growths forming on the device during off-design operation at low combustor inlet temperature. Test results indicated that smoke emission levels depended on the combustor fluid mechanics (especially the mixing rates near the injector), the atomization quality of the injector and the fuel hydrogen content.

  20. An electrochemical evidence of free radicals formation from flutamide and its reactivity with endo/xenobiotics of pharmacological relevance.

    PubMed

    Núñez-Vergara, L J; Farias, D; Bollo, S; Squella, J A

    2001-01-01

    This paper reports the feasibility of free radicals formation from flutamide by using cyclic voltammetry. The electrochemical characteristics and the reactivity of the one-electron reduction product from flutamide in mixed media with thiol compounds and the nuclei acid bases are characterized. Results from this paper show the thermodynamic feasibility of free radical formation expressed for both the cathodic peak potential and the second-order rate constant values. The reactivity of the radical towards thiol compounds (glutathione, cysteamine, N-acetylcysteine) and the nuclei acid base, adenine, thymine and uracil were quantitatively assessed through the calculation of the respective interaction rate constants. Based on these results, the following tentative order of reactivity towards the xeno/endobiotics is as follows: cysteamine > uracil > glutathione > adenine > N-acetylcysteine > thymine. The stability of the nitro radical anion electrochemically generated from flutamide showed a linear dependence with pH.

  1. Modeling the Pore Formation Mechanism in UMo/AL Dispersion Fuel

    SciTech Connect

    Kim, Yeon Soo; Jamison, L.; Hofman, G.; Jeong, G.Y.

    2016-01-01

    In UMo/Al dispersion fuel meat, pores formed in the ILs or at IL-Al interfaces tend to increase in size with irradiation, potentially limiting performance of this fuel. There has been no universally accepted mechanism for the formation and growth of this type of pore. However, there is a consensus that the stress state determined by meat swelling and fission- induced creep is one of the determinants, and fission gas availability at the pore site is another. Five dispersion RERTR miniplates that have well defined irradiation conditions and PIE data were selected for examination. Meat swelling and pore volume were measured in each plate. ABAQUS finite element analysis (FEA) package was utilized to obtain the time-dependent evolution of mechanical states in the plates while matching the measured meat swelling and creep. Interpretation of these results give insights on how to model a failure function – a predictor for large pore formation – using variables such as meat swelling, interaction layer growth, stress, and creep. This model can be used for optimizing fuel design parameters to reach the desired goal: meeting high power and performance reactor demand.

  2. Uncertainty in the reactive transport model response to analkaline perturbation in a clay formation

    SciTech Connect

    Burnol, A.; Blanc, P.; Xu, T.; Spycher, N.; Gaucher, E.C.

    2006-03-15

    The mineral alteration in the concrete barrier and in the clay formation around long-lived intermediate-level radioactive waste in the French deep geological disposal concept is evaluated using numerical modeling. There are concerns that the mineralogical composition of the surrounded clay will not be stable under the high alkaline pore fluid conditions caused by concrete (pH {approx} 12). Conversely, the infiltration of CO{sub 2}-rich groundwater from the clay formation into initially unsaturated concrete, at the high temperature (T {approx} 70 C) produced from the decay of radionuclides, could cause carbonation, thereby potentially affecting critical performance functions of this barrier. This could also lead to significant changes in porosity, which would affect aqueous diffusive transport of long-lived radionuclides. All these processes are therefore intimately coupled and advanced reactive transport models are required for long-term performance assessment. The uncertainty in predictions of these models is one major question that must be answered. A mass-transfer model response to an alkaline perturbation in clay with standard model values is first simulated using the two-phase non-isothermal reactive transport code TOUGHREACT. The selection of input parameters is thereafter designed to sample uncertainties in a wide range of physico-chemical processes without making a priori assumptions about the relative importance of different feedbacks. This 'base-case' simulation is perturbed by setting a parameter to a minimum, intermediate or maximum value or by switching on/off a process. This sensitivity analysis is conducted using grid computing facilities of BRGM (http://iggi.imag.fr). Our evaluation of the preliminary results suggests that the resaturation and the heating of the near-field will be of long enough duration to cause a limited carbonation through all the width of the concrete barrier. Another prediction is the possibility of self-sealing at the concrete

  3. Using fluorescence-activated flow cytometry to determine reactive oxygen species formation and membrane lipid peroxidation in viable boar spermatozoa

    USDA-ARS?s Scientific Manuscript database

    Fluorescence-activated flow cytometry analyses were developed for determination of reactive oxygen species (ROS) formation and membrane lipid peroxidation in live spermatozoa loaded with, respectively, hydroethidine (HE) or the lipophilic probe 4,4-difluoro-5-(4-phenyl-1,3-butadienyl)-4-bora-3a,4a-d...

  4. Evaluating temperature and fuel stratification for heat-release rate control in a reactivity-controlled compression-ignition engine using optical diagnostics and chemical kinetics modeling

    SciTech Connect

    Musculus, Mark P. B.; Kokjohn, Sage L.; Reitz, Rolf D.

    2015-04-23

    We investigated the combustion process in a dual-fuel, reactivity-controlled compression-ignition (RCCI) engine using a combination of optical diagnostics and chemical kinetics modeling to explain the role of equivalence ratio, temperature, and fuel reactivity stratification for heat-release rate control. An optically accessible engine is operated in the RCCI combustion mode using gasoline primary reference fuels (PRF). A well-mixed charge of iso-octane (PRF = 100) is created by injecting fuel into the engine cylinder during the intake stroke using a gasoline-type direct injector. Later in the cycle, n-heptane (PRF = 0) is delivered through a centrally mounted diesel-type common-rail injector. This injection strategy generates stratification in equivalence ratio, fuel blend, and temperature. The first part of this study uses a high-speed camera to image the injection events and record high-temperature combustion chemiluminescence. Moreover, the chemiluminescence imaging showed that, at the operating condition studied in the present work, mixtures in the squish region ignite first, and the reaction zone proceeds inward toward the center of the combustion chamber. The second part of this study investigates the charge preparation of the RCCI strategy using planar laser-induced fluorescence (PLIF) of a fuel tracer under non-reacting conditions to quantify fuel concentration distributions prior to ignition. The fuel-tracer PLIF data show that the combustion event proceeds down gradients in the n-heptane distribution. The third part of the study uses chemical kinetics modeling over a range of mixtures spanning the distributions observed from the fuel-tracer fluorescence imaging to isolate the roles of temperature, equivalence ratio, and PRF number stratification. The simulations predict that PRF number stratification is the dominant factor controlling the ignition location and growth rate of the reaction zone. Equivalence ratio has a smaller, but still significant

  5. Mechanism of Pinhole Formation in Membrane Electrode Assemblies for PEM Fuel Cells

    NASA Technical Reports Server (NTRS)

    Stanic, Vesna; Hoberecht, Mark

    2004-01-01

    The pinhole formation mechanism was studied with a variety of MEAs using ex-situ and in-situ methods. The ex-situ tests included the MEA aging in oxygen and MEA heat of ignition. In-situ durability tests were performed in fuel cells at different operating conditions with hydrogen and oxygen. After the in-situ failure, MEAs were analyzed with an Olympus BX 60 optical microscope and Cambridge 120 scanning electron microscope. MEA chemical analysis was performed with an IXRF EDS microanalysis system. The MEA failure analyses showed that pinholes and tears were the MEA failure modes. The pinholes appeared in MEA areas where the membrane thickness was drastically reduced. Their location coincided with the stress concentration points, indicating that membrane creep was responsible for their formation. Some of the pinholes detected had contaminant particles precipitated within the membrane. This mechanism of pinhole formation was correlated to the polymer blistering.

  6. Miniature fuel cell with monolithically fabricated Si electrodes - Alloy catalyst formation -

    NASA Astrophysics Data System (ADS)

    Ogura, Daiki; Suzuki, Takahiro; Katayama, Noboru; Dowaki, Kiyoshi; Hayase, Masanori

    2013-12-01

    A novel Pd-Pt catalyst formation process was proposed for reduction of Pt usage. In our miniature fuel cells, porous Pt was used as the catalyst, and the Pt usage was quite high. To reduce the Pt usage, we have attempted to deposit Pt on porous Pd by galvanic replacement, and relatively large output was demonstrated. In this study, in order to reduce more Pt usage and explore the alloy catalyst formation process, atomic layer deposition by UPD-SLRR (Under Potential Deposition - Surface Limited Redox Replacement) was applied to the Pd-Pt catalyst formation. The new process was verified at each process steps by EDS elemental analysis, and the expected spectra were obtained. Prototype cells were constructed by the new process, and cell output was raised to 420mW/cm2 by the Pd-Pt catalyst from 125mW/cm2 with Pd catalyst.

  7. Phase Formation and Transformations in Transmutation Fuel Materials for the LIFE Engine Part I - Path Forward

    SciTech Connect

    Turchi, P E; Kaufman, L; Fluss, M J

    2008-11-10

    The current specifications of the LLNL fusion-fission hybrid proposal, namely LIFE, impose severe constraints on materials, and in particular on the nuclear fissile or fertile nuclear fuel and its immediate environment. This constitutes the focus of the present report with special emphasis on phase formation and phase transformations of the transmutation fuel and their consequences on particle and pebble thermal, chemical and mechanical integrities. We first review the work that has been done in recent years to improve materials properties under the Gen-IV project, and with in particular applications to HTGR and MSR, and also under GNEP and AFCI in the USA. Our goal is to assess the nuclear fuel options that currently exist together with their issues. Among the options, it is worth mentioning TRISO, IMF, and molten salts. The later option will not be discussed in details since an entire report is dedicated to it. Then, in a second part, with the specific LIFE specifications in mind, the various fuel options with their most critical issues are revisited with a path forward for each of them in terms of research, both experimental and theoretical. Since LIFE is applicable to very high burn-up of various fuels, distinctions will be made depending on the mission, i.e., energy production or incineration. Finally a few conclusions are drawn in terms of the specific needs for integrated materials modeling and the in depth knowledge on time-evolution thermochemistry that controls and drastically affects the performance of the nuclear materials and their immediate environment. Although LIFE demands materials that very likely have not yet been fully optimized, the challenge are not insurmountable and a well concerted experimental-modeling effort should lead to dramatic advances that should well serve other fission programs such as Gen-IV, GNEP, AFCI as well as the international fusion program, ITER.

  8. Pore Formation Process of Porous Ti3SiC2 Fabricated by Reactive Sintering

    PubMed Central

    Zhang, Huibin; Liu, Xinli; Jiang, Yao

    2017-01-01

    Porous Ti3SiC2 was fabricated with high purity, 99.4 vol %, through reactive sintering of titanium hydride (TiH2), silicon (Si) and graphite (C) elemental powders. The reaction procedures and the pore structure evolution during the sintering process were systematically studied by X-ray diffraction (XRD) and scanning electron microscope (SEM). Our results show that the formation of Ti3SiC2 from TiH2/Si/C powders experienced the following steps: firstly, TiH2 decomposed into Ti; secondly, TiC and Ti5Si3 intermediate phases were generated; finally, Ti3SiC2 was produced through the reaction of TiC, Ti5Si3 and Si. The pores formed in the synthesis procedure of porous Ti3SiC2 ceramics are derived from the following aspects: interstitial pores left during the pressing procedure; pores formed because of the TiH2 decomposition; pores formed through the reactions between Ti and Si and Ti and C powders; and the pores produced accompanying the final phase synthesized during the high temperature sintering process. PMID:28772515

  9. Technical Note: Enhanced reactivity of nitrogenous organohalogen formation from plant litter to bacteria

    NASA Astrophysics Data System (ADS)

    Wang, J. J.; Ng, T. W.; Zhang, Q.; Yang, X. B.; Dahlgren, R. A.; Chow, A. T.; Wong, P. K.

    2012-06-01

    C1/C2 organohalogens (organohalogens with one or two carbon atoms) can have significant environmental toxicity and ecological impact, such as carcinogenesis, ozone depletion and global warming. Natural halogenation processes have been identified for a wide range of natural organic matter, including soils, plant and animal debris, algae, and fungi. Yet, few have considered these organohalogens generated from the ubiquitous bacteria, one of the largest biomass pools on Earth. Here, we report and confirm the formation of chloroform (CHCl3) dichloro-acetonitrile (CHCl2CN), chloral hydrate (CCl3CH(OH)2) and their brominated analogues by direct halogenation of seven strains of common bacteria and nine cellular monomers. Comparing different major C stocks during litter decomposition stages in terrestrial ecosystems, from plant litter, decomposed litter, to bacteria, increasing reactivity for nitrogenous organohalogen yield was observed with decreasing C/N ratio. Our results raise the possibility that natural halogenation of bacteria represents a significant and overlooked contribution to global organohalogen burdens. As bacteria are decomposers that alter the C quality by transforming organic matter pools from high to low C/N ratio and constitute a large organic N pool, the bacterial activity is expected to affect the C, N, and halogen cycling through natural halogenation reactions.

  10. Technical Note: Reactivity of C1 and C2 organohalogens formation - from plant litter to bacteria

    NASA Astrophysics Data System (ADS)

    Wang, J. J.; Ng, T. W.; Zhang, Q.; Yang, X. B.; Dahlgren, R. A.; Chow, A. T.; Wong, P. K.

    2012-10-01

    C1/C2 organohalogens (organohalogens with one or two carbon atoms) can have significant environmental toxicity and ecological impact, such as carcinogenesis, ozone depletion and global warming. Natural halogenation processes have been identified for a wide range of natural organic matter, including soils, plant and animal debris, algae, and fungi. Yet, few have considered these organohalogens generated from the ubiquitous bacteria, one of the largest biomass pools on earth. Here, we report and confirm the formation of chloroform (CHCl3) dichloro-acetonitrile (CHCl2CN), chloral hydrate (CCl3CH(OH)2) and their brominated analogues by direct halogenation of seven strains of common bacteria and nine cellular monomers. Comparing different major C stocks during litter decomposition stages in terrestrial ecosystems, from plant litter, decomposed litter, to bacteria, we found increasing reactivity for nitrogenous organohalogen yield with decreasing C/N ratio. Our results raise the possibility that natural halogenation of bacteria represents a significant and overlooked contribution to global organohalogen burdens. As bacteria are decomposers that alter the C quality by transforming organic matter pools from high to low C/N ratio and constitute a large organic N pool, the bacterial activity is expected to affect the C, N, and halogen cycling through natural halogenation reactions.

  11. Iberis amara Extract Induces Intracellular Formation of Reactive Oxygen Species and Inhibits Colon Cancer

    PubMed Central

    Plauth, Annabell; Wowro, Sylvia J.; Fischer, Cornelius; Abdel-Aziz, Heba; Sauer, Sascha

    2016-01-01

    Massively increasing global incidences of colorectal cancer require efficient treatment and prevention strategies. Here, we report unexpected anticancerogenic effects of hydroethanolic Iberis amara extract (IAE), which is known as a widely used phytomedical product for treating gastrointestinal complaints. IAE significantly inhibited the proliferation of HT-29 and T84 colon carcinoma cells with an inhibitory concentration (IC50) of 6 and 9 μg/ml, respectively, and further generated inhibitory effects in PC-3 prostate and MCF7 breast cancer cells. Inhibition of proliferation in HT-29 cells was associated with a G2/M phase cell cycle arrest including reduced expression of various regulatory marker proteins. Notably, in HT-29 cells IAE further induced apoptosis by intracellular formation of reactive oxygen species (ROS). Consistent with predictions derived from our in vitro experiments, bidaily oral gavage of 50 mg/kg of IAE over 4 weeks resulted in significant inhibition of tumor growth in a mouse HT-29 tumor xenograft model. Taken together, Iberis amara extracts could become useful alternatives for preventing and treating the progression of colon cancer. PMID:27050665

  12. Chemical mechanistic approaches for the suppression of soot formation in the combustion of high energy density fuels. Final technical report

    SciTech Connect

    Santoro, R.J.

    1996-09-01

    Significant advantages can be gained by the use of high energy density fuels in volume limited applications. However, excessive soot formation that accompanies the combustion of these fuels presently limits their application. Fuel additive approaches prove attractive as they require minimal modifications to already existing equipment. In the present study, a variety of flame configurations were used to study the additive effects on soot formation. Through tests conducted on laminar diffusion flames carbon disulfide (CS2) and methanol (CH3OH) were found to be the most effective soot suppressants. Chemical interaction by either additive was found to far surpass the physical influences. However, the exact nature of the chemical action could not be established with the current set of experiments. Additionally, both of these additives were found to reduce soot formation in at least one high energy density fuel - quadricyclane (C7H8). To further validate this approach, studies were conducted using droplet flames and high-pressure spray flames.

  13. Reactivity effects in the oxidative dissolution of UO 2 nuclear fuel

    NASA Astrophysics Data System (ADS)

    Hocking, William H.; Shoesmith, David W.; Betteridge, James S.

    1992-08-01

    The known energy-level scheme for UO 2 and the nature of electron transport in UO 2+ x have been assessed with regard to their influence on electrochemical reactions. An unusually negative flat-band potential permits conventional electrochemical experiments to be conducted at considerably more cathodic potentials than would be feasible with a normal p-type semiconductor. The unique electronic properties of UO 2+ x can also be seen to accommodate cathodic and anodic photocurrents simply by changing the degree of hyperstoichiometry. Cathodic reduction of O 2 in dilute alkaline aqueous solution has been studied intensively on two kinds of UO 2+ x (with p-type and n-type photocurrent response) and a UO 2-based SIMFUEL. The kinetics of this reaction appear to control the corrosion (oxidative-dissolution) rate of UO 2 and are a sensitive probe of surface reactivity: a significant range of behaviour has been observed as a function of the properties of the electrode material and its interactions with solution. Anomalous features in Tafel plots can be correlated with qualitative changes in the composition of the surface oxide film. A theory developed to describe O 2 reduction on transition-metal oxides with p-type semiconductivity has been adapted to provide a basis for understanding this process at UO 2+ x surfaces. Electron-transfer reactions are presumed to occur exclusively at active sites, formed by adjacent cations in different valence states, where O 2 and any intermediates are adsorbed.

  14. Investigating the role of gas bubble formation and entrapment in contaminated aquifers: Reactive transport modelling

    USGS Publications Warehouse

    Amos, Richard T.; Mayer, K. Ulrich

    2006-01-01

    In many natural and contaminated aquifers, geochemical processes result in the production or consumption of dissolved gases. In cases where methanogenesis or denitrification occurs, the production of gases may result in the formation and growth of gas bubbles below the water table. Near the water table, entrapment of atmospheric gases during water table rise may provide a significant source of O2 to waters otherwise depleted in O2. Furthermore, the presence of bubbles will affect the hydraulic conductivity of an aquifer, resulting in changes to the groundwater flow regime. The interactions between physical transport, biogeochemical processes, and gas bubble formation, entrapment and release is complex and requires suitable analysis tools. The objective of the present work is the development of a numerical model capable of quantitatively assessing these processes. The multicomponent reactive transport code MIN3P has been enhanced to simulate bubble growth and contraction due to in-situ gas production or consumption, bubble entrapment due to water table rise and subsequent re-equilibration of the bubble with ambient groundwater, and permeability changes due to trapped gas phase saturation. The resulting formulation allows for the investigation of complex geochemical systems where microbially mediated redox reactions both produce and consume gases as well as affect solution chemistry, alkalinity, and pH. The enhanced model has been used to simulate processes in a petroleum hydrocarbon contaminated aquifer where methanogenesis is an important redox process. The simulations are constrained by data from a crude oil spill site near Bemidji, MN. Our results suggest that permeability reduction in the methanogenic zone due to in-situ formation of gas bubbles, and dissolution of entrapped atmospheric bubbles near the water table, both work to attenuate the dissolved gas plume emanating from the source zone. Furthermore, the simulations demonstrate that under the given

  15. Investigating the role of gas bubble formation and entrapment in contaminated aquifers: Reactive transport modelling

    NASA Astrophysics Data System (ADS)

    Amos, Richard T.; Ulrich Mayer, K.

    2006-09-01

    In many natural and contaminated aquifers, geochemical processes result in the production or consumption of dissolved gases. In cases where methanogenesis or denitrification occurs, the production of gases may result in the formation and growth of gas bubbles below the water table. Near the water table, entrapment of atmospheric gases during water table rise may provide a significant source of O 2 to waters otherwise depleted in O 2. Furthermore, the presence of bubbles will affect the hydraulic conductivity of an aquifer, resulting in changes to the groundwater flow regime. The interactions between physical transport, biogeochemical processes, and gas bubble formation, entrapment and release is complex and requires suitable analysis tools. The objective of the present work is the development of a numerical model capable of quantitatively assessing these processes. The multicomponent reactive transport code MIN3P has been enhanced to simulate bubble growth and contraction due to in-situ gas production or consumption, bubble entrapment due to water table rise and subsequent re-equilibration of the bubble with ambient groundwater, and permeability changes due to trapped gas phase saturation. The resulting formulation allows for the investigation of complex geochemical systems where microbially mediated redox reactions both produce and consume gases as well as affect solution chemistry, alkalinity, and pH. The enhanced model has been used to simulate processes in a petroleum hydrocarbon contaminated aquifer where methanogenesis is an important redox process. The simulations are constrained by data from a crude oil spill site near Bemidji, MN. Our results suggest that permeability reduction in the methanogenic zone due to in-situ formation of gas bubbles, and dissolution of entrapped atmospheric bubbles near the water table, both work to attenuate the dissolved gas plume emanating from the source zone. Furthermore, the simulations demonstrate that under the given

  16. Local Stoichiometry and Atomic Interdiffusion during Reactive Metal/Mercury-Cadmium-Telluride Junction Formation.

    DTIC Science & Technology

    1987-10-23

    CHART NATIONAL BUREAU OF STANDARDS- 1963-A IfP LOCAL STOICHIOMETRY AND ATOMIC INTERDIFFUSION DURING REACTIVE METAL/ MERCURY- CADMIUM -TELLURIDE...TITLE rand Subtitle) S. TYPE OF REPORT PERIOED LOCAL STOICHIOMETRY AND ATOMIC INTERDIFFUSION Interim, 1/8 DURING REACTIVE METAL/MERCURY- CADMIUM ...identliy by block nuembw) Ag, Ge and Sm overlayers on Mercury- Cadmium -Telluride surfaces exhibit widely different interface reactivity and yield a

  17. Radiation-Driven Formation of Reactive Oxygen Species in Oxychlorine-Containing Mars Surface Analogues.

    PubMed

    Georgiou, Christos D; Zisimopoulos, Dimitrios; Kalaitzopoulou, Electra; Quinn, Richard C

    2017-04-01

    The present study demonstrates that γ-radiolyzed perchlorate-containing Mars soil salt analogues (in a CO2 atmosphere) generate upon H2O wetting the reactive oxygen species (ROS) superoxide radical (O2(•-)), hydrogen peroxide (H2O2), and hydroxyl radicals ((•)OH). This study also validates that analogue radiolysis forms oxychlorine species that, in turn, can UV-photolyze to (•)OH upon UV photolysis. This investigation was made possible by the development of a new assay for inorganic-origin O2(•-) and H2O2 determination and by the modification of a previous assay for soil (•)OH. Results show that radiolyzed Mg(ClO4)2 generates H2O2 and (•)OH; and when included as part of a mixture analogous to the salt composition of samples analyzed at the Mars Phoenix site, the analogue generated O2(•-), H2O2, and (•)OH, with (•)OH levels 150-fold higher than in the radiolyzed Mg(ClO4)2 samples. Radiolyzed Mars Phoenix site salt analogue that did not contain Mg(ClO4)2 generated only (•)OH also at 150-fold higher concentration than Mg(ClO4)2 alone. Additionally, UV photolysis of the perchlorate γ radiolysis product chlorite (ClO2(-)) generated the oxychlorine products trihalide (Cl3(-)), chlorine dioxide (ClO2(•)), and hypochlorite (ClO(-)), with the formation of (•)OH by UV photolysis of ClO(-). While the generation of ROS may have contributed in part to (14)CO2 production in the Viking Labeled Release (LR) experiment and O2 (g) release in the Viking Gas Exchange (GEx) experiment, our results indicate that they are not likely to be the major contributor to the LR and GEx results. However, due to their highly reactive nature, they are expected to play a significant role in the alteration of organics on Mars. Additionally, experiments with hypochlorite show that the thermal stability of NaClO is in the range of the thermal stability observed for thermally liable oxidant responsible for the Viking LR results. Key Words: Mars

  18. Radiation-Driven Formation of Reactive Oxygen Species in Oxychlorine-Containing Mars Surface Analogues

    NASA Astrophysics Data System (ADS)

    Georgiou, Christos D.; Zisimopoulos, Dimitrios; Kalaitzopoulou, Electra; Quinn, Richard C.

    2017-04-01

    The present study demonstrates that γ-radiolyzed perchlorate-containing Mars soil salt analogues (in a CO2 atmosphere) generate upon H2O wetting the reactive oxygen species (ROS) superoxide radical (O2•-), hydrogen peroxide (H2O2), and hydroxyl radicals (•OH). This study also validates that analogue radiolysis forms oxychlorine species that, in turn, can UV-photolyze to •OH upon UV photolysis. This investigation was made possible by the development of a new assay for inorganic-origin O2•- and H2O2 determination and by the modification of a previous assay for soil •OH. Results show that radiolyzed Mg(ClO4)2 generates H2O2 and •OH; and when included as part of a mixture analogous to the salt composition of samples analyzed at the Mars Phoenix site, the analogue generated O2•-, H2O2, and •OH, with •OH levels 150-fold higher than in the radiolyzed Mg(ClO4)2 samples. Radiolyzed Mars Phoenix site salt analogue that did not contain Mg(ClO4)2 generated only •OH also at 150-fold higher concentration than Mg(ClO4)2 alone. Additionally, UV photolysis of the perchlorate γ radiolysis product chlorite (ClO2-) generated the oxychlorine products trihalide (Cl3-), chlorine dioxide (ClO2•), and hypochlorite (ClO-), with the formation of •OH by UV photolysis of ClO-. While the generation of ROS may have contributed in part to 14CO2 production in the Viking Labeled Release (LR) experiment and O2 (g) release in the Viking Gas Exchange (GEx) experiment, our results indicate that they are not likely to be the major contributor to the LR and GEx results. However, due to their highly reactive nature, they are expected to play a significant role in the alteration of organics on Mars. Additionally, experiments with hypochlorite show that the thermal stability of NaClO is in the range of the thermal stability observed for thermally liable oxidant responsible for the Viking LR results.

  19. Experimental Investigation of Fuel-Reactivity Controlled Compression Ignition (RCCI) Combustion Mode in a Multi-Cylinder, Light-Duty Diesel Engine

    SciTech Connect

    Cho, Kukwon; Curran, Scott; Prikhodko, Vitaly Y; Sluder, Scott; Parks, II, James E; Wagner, Robert M

    2011-01-01

    An experimental study was performed to provide the combustion and emission characteristics resulting from fuel-reactivity controlled compression ignition (RCCI) combustion mode utilizing dual-fuel approach in a light-duty, multi-cylinder diesel engine. In-cylinder fuel blending using port fuel injection of gasoline before intake valve opening (IVO) and early-cycle, direct injection of diesel fuel was used as the charge preparation and fuel blending strategy. In order to achieve the desired auto-ignition quality through the stratification of the fuel-air equivalence ratio ( ), blends of commercially available gasoline and diesel fuel were used. Engine experiments were performed at an engine speed of 2300rpm and an engine load of 4.3bar brake mean effective pressure (BMEP). It was found that significant reduction in both nitrogen oxide (NOx) and particulate matter (PM) was realized successfully through the RCCI combustion mode even without applying exhaust gas recirculation (EGR). However, high carbon monoxide (CO) and hydrocarbon (HC) emissions were observed. The low combustion gas temperature during the expansion and exhaust processes seemed to be the dominant source of high CO emissions in the RCCI combustion mode. The high HC emissions during the RCCI combustion mode could be due to the increased combustion quenching layer thickness as well as the -stratification at the periphery of the combustion chamber. The slightly higher brake thermal efficiency (BTE) of the RCCI combustion mode was observed than the other combustion modes, such as the conventional diesel combustion (CDC) mode, and single-fuel, premixed charge compression ignition (PCCI) combustion mode. The parametric study of the RCCI combustion mode revealed that the combustion phasing and/or the peak cylinder pressure rise rate of the RCCI combustion mode could be controlled by several physical parameters premixed ratio (rp), intake swirl intensity, and start of injection (SOI) timing of directly

  20. Synergistic effect of mixing dimethyl ether with methane, ethane, propane, and ethylene fuels on polycyclic aromatic hydrocarbon and soot formation

    SciTech Connect

    Yoon, S.S.; Anh, D.H.; Chung, S.H.

    2008-08-15

    Characteristics of polycyclic aromatic hydrocarbon (PAH) and soot formation in counterflow diffusion flames of methane, ethane, propane, and ethylene fuels mixed with dimethyl ether (DME) have been investigated. Planar laser-induced incandescence and fluorescence techniques were employed to measure relative soot volume fractions and PAH concentrations, respectively. Results showed that even though DME is known to be a clean fuel in terms of soot formation, DME mixture with ethylene fuel increases PAH and soot formation significantly as compared to the pure ethylene case, while the mixture of DME with methane, ethane, and propane decreases PAH and soot formation. Numerical calculations adopting a detailed kinetics showed that DME can be decomposed to produce a relatively large number of methyl radicals in the low-temperature region where PAH forms and grows; thus the mixture of DME with ethylene increases CH{sub 3} radicals significantly in the PAH formation region. Considering that the increase in the concentration of O radicals is minimal in the PAH formation region with DME mixture, the enhancement of PAH and soot formation in the mixture flames of DME and ethylene can be explained based on the role of methyl radicals in PAH and soot formation. Methyl radicals can increase the concentration of propargyls, which could enhance incipient benzene ring formation through the propargyl recombination reaction and subsequent PAH growth. Thus, the result substantiates the importance of methyl radicals in PAH and soot formation, especially in the PAH formation region of diffusion flames. (author)

  1. Fluid mechanics simulation of fog formation associated with polluted atmosphere produced by energy related fuel combustion

    NASA Technical Reports Server (NTRS)

    Hung, R. J.; Liaw, G. S.

    1980-01-01

    It is noted that large quantities of atmospheric aerosols with composition SO4(-2), NO3(-1), and NH4(+1) have been detected in highly industrialized areas. Most aerosol products come from energy-related fuel combustion. Fluid mechanics simulation of both microphysical and macrophysical processes is considered in studying the time dependent evolution of the saturation spectra of condensation nuclei associated with polluted and clean atmospheres during the time periods of advection fog formation. The results demonstrate that the condensation nuclei associated with a polluted atmosphere provide more favorable conditions than condensation nuclei associated with a clean atmosphere to produce dense advection fog, and that attaining a certain degree of supersaturation is not necessarily required for the formation of advection fog having condensation nuclei associated with a polluted atmosphere.

  2. Formation of industrial mixed culture biofilm in chlorophenol cultivated medium of microbial fuel cell

    NASA Astrophysics Data System (ADS)

    Hassan, Huzairy; Jin, Bo; Dai, Sheng; Ngau, Cornelius

    2016-11-01

    The formation of microbial biofilm while maintaining the electricity output is a challenging topic in microbial fuel cell (MFC) studies. This MFC critical factor becomes more significant when handling with industrial wastewater which normally contains refractory and toxic compounds. This study explores the formation of industrial mixed culture biofilm in chlorophenol cultivated medium through observing and characterizing microscopically its establishment on MFC anode surface. The mixed culture was found to develop its biofilm on the anode surface in the chlorophenol environment and established its maturity and dispersal stages with concurrent electricity generation and phenolic degradation. The mixed culture biofilm engaged the electron transfer roles in MFC by generating current density of 1.4 mA/m2 and removing 53 % of 2,4-dichlorophenol. The results support further research especially on hazardous wastewater treatment using a benign and sustainable method.

  3. Fluid mechanics simulation of fog formation associated with polluted atmosphere produced by energy related fuel combustion

    NASA Technical Reports Server (NTRS)

    Hung, R. J.; Liaw, G. S.

    1980-01-01

    It is noted that large quantities of atmospheric aerosols with composition SO4(-2), NO3(-1), and NH4(+1) have been detected in highly industrialized areas. Most aerosol products come from energy-related fuel combustion. Fluid mechanics simulation of both microphysical and macrophysical processes is considered in studying the time dependent evolution of the saturation spectra of condensation nuclei associated with polluted and clean atmospheres during the time periods of advection fog formation. The results demonstrate that the condensation nuclei associated with a polluted atmosphere provide more favorable conditions than condensation nuclei associated with a clean atmosphere to produce dense advection fog, and that attaining a certain degree of supersaturation is not necessarily required for the formation of advection fog having condensation nuclei associated with a polluted atmosphere.

  4. Medium-temperature solid oxide fuel cells prepared using reactive magnetron sputtering. Ph.D. Thesis

    SciTech Connect

    Wang, L.

    1993-12-31

    The purpose of this research is to investigate the deposition, structure, interfacial impedances, and characteristics of medium temperature solid-oxide fuel cells (SOFC`s) with thin-film electrolytes. Three main areas have been investigated. First, the structure, chemistry, and properties of materials designed specifically for medium temperature SOFC`s have been studied. The authors have developed techniques for sputter deposition of cubic 10 mol percent Y2O3-stabilized zirconia (YSZ) and 30 mol percent Y2O3-doped bismuth oxide (YSB) thin film oxygen ion conductors. The electrical properties of the films were characterized using the complex impedance spectroscopy method. Studies of AgYSZ cermet and Ag-perovskite (perovskite = La(1-x)Sr(x)Co(Mn)O3), used as high conductivity, low overpotential air electrodes, have also been carried out. Second, interfacial impedances for various electrode-electrolyte combinations and for multilayer electrolytes have been studied. In particular, the authors have found that a layer of Y-stabilized Bi2O3 (YSB) as thin as 60 nm between the YSZ electrolyte and the electrode significantly reduces the interfacial resistance. For example, inserting YSB between YSZ and a Ag-YSZ electrode reduces the resistance from 1.5 to 0.45 Omega cm(exp 2) at 750 deg C in air. Ag-(La,Sr)CoO3 on YSB electrolytes had interfacial resistances as low as 0.3 Omega cm2, compared with 0.4 and 1.5 Omega cm(exp 2) for (La,Sr)CoO3 and Ag on YSB at 750 deg C, respectively. The Ag cermet materials thus exhibited lower interfacial resistances than their component materials. Third, thin film medium temperature SOFC`s have been fabricated and characterized. SOFC`s were deposited onto porous alumina supports. The resulting cell open-circuit voltages (OCV) were approximately equal to 0.8 V, 0.3 V less than expected, due to gas cross-over.

  5. High-pressure soot formation and diffusion flame extinction characteristics of gaseous and liquid fuels

    NASA Astrophysics Data System (ADS)

    Karatas, Ahmet Emre

    High-pressure soot formation and flame stability characteristics were studied experimentally in laminar diffusion flames. For the former, radially resolved soot volume fraction and temperature profiles were measured in axisymmetric co-flow laminar diffusion flames of pre-vaporized n-heptane-air, undiluted ethylene-air, and nitrogen and carbon dioxide diluted ethylene-air at elevated pressures. Abel inversion was used to re-construct radially resolved data from the line-of-sight spectral soot emission measurements. For the latter, flame extinction strain rate was measured in counterflow laminar diffusion flames of C1-4 alcohols and hydrocarbon fuels of n-heptane, n-octane, iso-octane, toluene, Jet-A, and biodiesel. The luminous flame height, as marked by visible soot radiation, of the nitrogen- and helium-diluted n-heptane and nitrogen- and carbon dioxide-diluted ethylene flames stayed constant at all pressures. In pure ethylene flames, flame heights initially increased with pressure, but changed little above 5 atm. The maximum soot yield as a function of pressure in nitrogen-diluted n-heptane diffusion flames indicate that n-heptane flames are slightly more sensitive to pressure than gaseous alkane hydrocarbon flames at least up to 7 atm. Ethylene's maximum soot volume fractions were much higher than those of ethane and n-heptane diluted with nitrogen (fuel to nitrogen mass flow ratio is about 0.5). Pressure dependence of the peak carbon conversion to soot, defined as the percentage of fuel's carbon content converted to soot, was assessed and compared to previous measurements with other gaseous fuels. Maximum soot volume fractions were consistently lower in carbon dioxide-diluted flames between 5 and 15 atm but approached similar values to those in nitrogen-diluted flames at 20 atm. This observation implies that the chemical soot suppression effect of carbon dioxide, previously demonstrated at atmospheric pressure, is also present at elevated pressures up to 15 atm

  6. Reactive-transport model for the prediction of the uniform corrosion behaviour of copper used fuel containers

    NASA Astrophysics Data System (ADS)

    King, F.; Kolar, M.; Maak, P.

    2008-09-01

    Used fuel containers in a deep geological repository will be subject to various forms of corrosion. For containers made from oxygen-free, phosphorus-doped copper, the most likely corrosion processes are uniform corrosion, underdeposit corrosion, stress corrosion cracking, and microbiologically influenced corrosion. The environmental conditions within the repository are expected to evolve with time, changing from warm and oxidizing initially to cool and anoxic in the long-term. In response, the corrosion behaviour of the containers will also change with time as the repository environment evolve. A reactive-transport model has been developed to predict the time-dependent uniform corrosion behaviour of the container. The model is based on an experimentally-based reaction scheme that accounts for the various chemical, microbiological, electrochemical, precipitation/dissolution, adsorption/desorption, redox, and mass-transport processes at the container surface and in the compacted bentonite-based sealing materials within the repository. Coupling of the electrochemical interfacial reactions with processes in the bentonite buffer material allows the effect of the evolution of the repository environment on the corrosion behaviour of the container to be taken into account. The Copper Corrosion Model for Uniform Corrosion predicts the time-dependent corrosion rate and corrosion potential of the container, as well as the evolution of the near-field environment.

  7. Enhancement in dibenzothiophene reactive adsorption from liquid fuel via incorporation of sulfur heteroatoms into the nanoporous carbon matrix.

    PubMed

    Seredych, Mykola; Khine, Monmon; Bandosz, Teresa J

    2011-01-17

    Adsorption of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (DMDBT) from simulated diesel fuel was investigated with polymer-derived carbon matrices. Sulfur was incorporated to the carbon surface via a high-temperature hydrogen sulfide reduction of oxygen-containing groups. The resultant carbons were characterized by nitrogen adsorption, thermal analysis, potentiometric titration, and elemental analysis. The selectivities for DBT and DMDBT adsorption were calculated with reference to naphthalene. The carbon matrices studied had comparable structures, hence, the effects of the sulfur functionalities were evident in an increase in dibenzothiophenes selectivity and the breakthrough capacity; this was especially visible at a breakthrough point where small pores are expected to be active in the adsorption process. Incorporation of sulfur atoms into the aromatic rings of the carbon matrix increases the ability of the surface to attract dibenzothiophenes via dispersive interactions (sulfur-sulfur bridges). Sulfur and sulfur-oxygen groups present in larger pores enhance the amount of adsorbed dibenzothiophenes via specific acid-base and polar interactions. They also contribute to the reactive adsorption of DBT and DMDBT (oxidized) and their chemisorption on the carbon surface.

  8. Cell respiration and formation of reactive oxygen species: facts and artefacts.

    PubMed

    Nohl, H; Kozlov, A V; Gille, L; Staniek, K

    2003-12-01

    It is generally taken as an established fact that mitochondrial respiration is associated with the generation of small amounts of ROS (reactive oxygen species). There are many arguments supporting this side activity. A major argument is the particular physico-chemical configuration of dioxygen, which prevents the transfer of a pair of electrons. Instead, oxygen is reduced by the successive transfer of single electrons, necessarily leading to intermediates with odd electrons. The high rate of turnover of oxygen in the respiratory chain in combination with the existence of single-electron carriers supports the concept of mitochondria as the major cellular ROS generator. Experimental evidence on the ability of mitochondria to generate ROS was, however, based essentially on in vitro experiments with isolated mitochondria. A variety of structural and functional alterations associated with the removal of mitochondria from the cell, as well as the routinely applied ROS detection methods, may lead to artefactual deviation of odd electrons to dioxygen. We therefore checked these correlations in view of ROS formation, including the often reported effect of the membrane potential on the establishment of a redox couple with oxygen out of sequence. For this purpose we developed novel methods to prove the authenticity of mitochondria for ROS generation in the living cell. Based on our experiments, we can exclude spontaneous release of ROS from mitochondria. However, we describe conditions under which mitochondria can be transformed to mild ROS generators. The site of single-electron deviation to dioxygen was found to be ubiquinol interacting with the Rieske iron-sulphur protein and low-potential cytochrome b of the bc (1) complex.

  9. Pyrite-driven reactive oxygen species formation in simulated lung fluid: implications for coal workers' pneumoconiosis.

    PubMed

    Harrington, Andrea D; Hylton, Shavonne; Schoonen, Martin A A

    2012-08-01

    The origin of coal worker's pneumoconiosis (CWP) has been long debated. A recent epidemiological study shows a correlation between what is essentially the concentration of pyrite within coal and the prevalence of CWP in miners. Hydrogen peroxide and hydroxyl radical, both reactive oxygen species (ROS), form as byproducts of pyrite oxidative dissolution in air-saturated water. Motivated by the possible importance of ROS in the pathogenesis of CWP, we conducted an experimental study to evaluate if ROS form as byproducts in the oxidative dissolution of pyrite in simulated lung fluid (SLF) under biologically applicable conditions and to determine the persistence of pyrite in SLF. While the rate of pyrite oxidative dissolution in SLF is suppressed by 51% when compared to that in air-saturated water, the initial amount of hydrogen peroxide formed as a byproduct in SLF is nearly doubled. Hydroxyl radical is also formed in the experiments with SLF, but at lower concentrations than in the experiments with water. The formation of these ROS indicates that the reaction mechanism for pyrite oxidative dissolution in SLF is no different from that in water. The elevated hydrogen peroxide concentration in SLF suggests that the decomposition, via the Fenton mechanism to hydroxyl radical or with Fe(III) to form water and molecular oxygen, is initially inhibited by the presence of SLF components. On the basis of the oxidative dissolution rate of pyrite measured in this paper, it is calculated that a respirable two micron pyrite particle will take over 3 years to dissolve completely.

  10. Sphingosine kinase functionally links elevated transmural pressure and increased reactive oxygen species formation in resistance arteries.

    PubMed

    Keller, Matthias; Lidington, Darcy; Vogel, Lukas; Peter, Bernhard Friedrich; Sohn, Hae-Young; Pagano, Patrick J; Pitson, Stuart; Spiegel, Sarah; Pohl, Ulrich; Bolz, Steffen-Sebastian

    2006-04-01

    Myogenic vasoconstriction, an intrinsic response to elevated transmural pressure (TMP), requires the activation of sphingosine kinase (Sk1) and the generation of reactive oxygen species (ROS). We hypothesized that pressure-induced Sk1 signaling and ROS generation are functionally linked. Using a model of cannulated resistance arteries isolated from the hamster gracilis muscle, we monitored vessel diameter and smooth muscle cell (SMC) Ca2+i (Fura-2) or ROS production (dichlorodihydrofluorescein). Elevation of TMP stimulated the translocation of a GFP-tagged Sk1 fusion protein from the cytosol to the plasma membrane, indicative of enzymatic activation. Concurrently, elevation of TMP initiated a rapid and transient production of ROS, which was enhanced by expression of wild-type Sk1 (hSk(wt)) and inhibited by its dominant-negative mutant (hSk(G82D)). Exogenous sphingosine-1-phosphate (S1P) also stimulated ROS generation is isolated vessels. Chemical (1 micromol/L DPI), peptide (gp91ds-tat/gp91ds), and genetic (N17Rac) inhibition strategies indicated that NADPH oxidase was the source of the pressure-induced ROS. NADPH oxidase inhibition attenuated myogenic vasoconstriction and reduced the apparent Ca2+ sensitivity of the SMC contractile apparatus, without affecting Ca2+-independent, RhoA-mediated vasoconstriction in response to exogenous S1P. Our results indicate a mandatory role for Sk1/S1P in mediating pressure-induced, NADPH oxidase-derived ROS formation. In turn, ROS generation appears to increase Ca2+ sensitivity, necessary for full myogenic vasoconstriction.

  11. Formation of glutathione conjugates by reactive metabolites of vinylidene chloride in microsomes and isolated hepatocytes

    SciTech Connect

    Liebler, D.C.; Meredith, M.J.; Guengerich, F.P.

    1985-01-01

    Oxidation of the vinyl halide carcinogen and hepatotoxin vinylidene chloride (VDC) by microsomal cytochrome P-450 yields 2,2-dichloroacetaldehyde, 2-chloroacetyl chloride, 2-chloroacetic acid, and 1,1-dichloroethylene oxide. The roles of these metabolites in covalent modification of proteins and reduced glutathione (GSH) were examined. 2-Chloroacetyl chloride reacted with model thiols at least 10(3)-fold faster than did 1,1-dichloroethylene oxide and at least 10(5)-fold faster than did 2,2-dichloroacetaldehyde or 2-chloroacetic acid. Microsomal covalent binding of (/sup 14/C)VDC was inhibited by GSH but not by lysine, suggesting that protein thiols, rather than amino groups, are major targets. Liver microsomes catalyzed the formation of three GSH:VDC metabolite conjugates, identified as S-(2,2-dichloro-1-hydroxy)ethylglutathione, 2-(S-glutathionyl)acetate, and S-(2-glutathionyl)acetylglutathione, a novel conjugate containing both stable (thioether) and labile (thioester) linkages. The latter two conjugates also were formed in isolated rat hepatocytes and measurable amounts of 2-(S-glutathionyl)acetate were released into the incubation medium. Both 2-(S-glutathionyl)acetate and S-(2-glutathionyl)acetylglutathione were formed with (/sup 35/S)GSH added to the hepatic medium, indicating that reactive VDC metabolites are capable of crossing the plasma membrane to react with extracellular targets. Unlabeled S-(2-glutathionyl)-acetylglutathione underwent carbonyl substitution with added (/sup 35/S)GSH, suggesting that this conjugate may participate in modification of protein thiols. This conjugate also underwent hydrolysis with a half-life of approximately 3 hr. GSH:VDC metabolite conjugates may serve as accessible models for labile covalent adducts formed between VDC metabolites and protein thiols.

  12. A comparison study of ash formation during pilot-scale combustion of pulverized coal and coal-water slurry fuels

    SciTech Connect

    Miller, S.F.

    1992-01-01

    The objective of this study was to investigate the effect of fuel form. specifically pulverized coal and coal-water slurry fuel (CWSF), on the particle size distribution (PSD) and inorganic composition of the ash formed during combustion. Three areas of primary interest were fuel particle and droplet size distribution, mineral matter PSD, and the composition and occurrence of inorganics in the fuel. The reactions of pyrite, silicates, aluminosilicates, and alkali and alkaline earth elements during combustion are traced. Two coals, a West Virginia Elk Creek high volatile A bituminous coal and the North Dakota Beulah lignite, were fired as a standard utility grind pulverized fuel and a CWSF at 316.2 MJ/h at 20% excess air in the Penn State Combustion Laboratory down-fired combustor. Fuel PSD and droplet size distribution of the pulverized coal and CWSF are important in determining the PSD of the respective ash when the PSD of the mineral matter and the composition and occurrence of the inorganics in the two fuels are similar, as in the case of the Elk Creek fuels. The mechanism for ash formation in both Elk Creek fuels was coalescence and agglomeration of the inorganics in the coal. The Elk Creek CWSF ash was coarser than the pulverized coal ash due to the larger CWSF char size formed during atomization. The average diameter of the inorganic particles identified in the pulverized coal ash was 2.6 times smaller than those identified in the fuel. The mechanism for ash formation in the Beulah CWSF was coalescence and agglomeration of inherent mineral matter. The average diameter of the inorganic particles identified in the CWSF ash was 3.3 times larger than those identified in the fuel.

  13. Reactivity of atomically dispersed Pt(2+) species towards H2: model Pt-CeO2 fuel cell catalyst.

    PubMed

    Lykhach, Yaroslava; Figueroba, Alberto; Camellone, Matteo Farnesi; Neitzel, Armin; Skála, Tomáš; Negreiros, Fabio R; Vorokhta, Mykhailo; Tsud, Nataliya; Prince, Kevin C; Fabris, Stefano; Neyman, Konstantin M; Matolín, Vladimír; Libuda, Jörg

    2016-03-21

    The reactivity of atomically dispersed Pt(2+) species on the surface of nanostructured CeO2 films and the mechanism of H2 activation on these sites have been investigated by means of synchrotron radiation photoelectron spectroscopy and resonant photoemission spectroscopy in combination with density functional calculations. Isolated Pt(2+) sites are found to be inactive towards H2 dissociation due to high activation energy required for H-H bond scission. Trace amounts of metallic Pt are necessary to initiate H2 dissociation on Pt-CeO2 films. H2 dissociation triggers the reduction of Ce(4+) cations which, in turn, is coupled with the reduction of Pt(2+) species. The mechanism of Pt(2+) reduction involves reverse oxygen spillover and formation of oxygen vacancies on Pt-CeO2 films. Our calculations suggest the existence of a threshold concentration of oxygen vacancies associated with the onset of Pt(2+) reduction.

  14. Partial reactivation of a huge deep-seated ancient rock slide: recognition, formation mechanism, and stability

    NASA Astrophysics Data System (ADS)

    Tang, Minggao; Xu, Qiang; Li, Yusheng; Huang, Runqiu; Rengers, Niek; Zhu, Xing

    2016-08-01

    About 18 years ago, a large-scale discontinuous layer in properties and colour was found in the new Fengjie town at the shore of the Three Gorges Reservoir area in China. There are many resettled residents and buildings on the sloping area, the safety of which is potentially affected by this layer, so it has become the focus of attention. Before this study started there were two viewpoints regarding the origin of this layer. One was that is was from a huge ancient slide and the other was that is was from a fault graben. In order to find out how it was formed and to be able to carry out a stability analysis of the slope the authors have carried out a research program, including geological field investigations and mapping, a deep drilling hole, a geotechnical centrifuge model test, and a simulation analysis. The results of the research led to the conclusion that the layer is the sliding plane of a huge deep-seated ancient rock slide, which we called the Sanmashan landslide. An important argument for the conclusion is the recognition of a regional compressive tectonic stress field in this area, which cannot lead to the formation of a fault graben because it needs a tensional tectonic stress field. Moreover, numerous unique geological features, sliding marks, and other relics of the ancient slide have been discovered in the field. The formation process of the ancient slide could be repeated in a large geotechnical centrifuge model test. The test shows that a deformation and failure process of "creep-crack-cut" has occurred. The type of the ancient slide can be classified as a "successive rotational rock slide". Finally, the role of seepage in the stability of the Sanmashan landslide has been analysed. Our final conclusions are that, during rainfall and filling-drawdown cycles in the Three Gorges Reservoir, the Sanmashan landslide as a whole is dormant and stable and the secondary landslides in the toe area of the slope are presently stable but can be reactivated. This

  15. Measurement of the atmospheric reactivity of emissions from gasoline and alternative-fueled vehicles: Assessment of available methodologies. Part 1. Indoor smog chamber study of reactivity. Final report for the first year, January 1-December 31, 1993

    SciTech Connect

    Kelly, N.A.; Wang, P.; Japar, S.M.; Hurley, M.D.; Wallington, T.J.

    1994-06-30

    A set of multiple indoor smog chambers were used to measure the increase in smog formation (smog = NO oxidation + O3 formation) from a series of individual test volatile organic compounds (VOC`s), as well as carbon monoxide (CO), when they were added to a standard urban mixture and irradiated for 10-12 hours with a solar simulator. The chambers and the mixtures were designed to simulate the Carter incremental reactivity concept that is being used in California. The test compounds covered a wide range of mechanistic uncertainties and predicted reactivities (reactivity is the increase in smog divided by the amount of test compound added). Also, the chambers were used to test the recently developed Integrated Empirical Rate (IER) Model which predicts that the smog formation of a mixture is constant and independent of NOx in the so-called light-limited regime.

  16. Mitigation of reactive metabolite formation for a series of 3-amino-2-pyridone inhibitors of Bruton's tyrosine kinase (BTK).

    PubMed

    Lou, Yan; Lopez, Francisco; Jiang, Yongying; Han, Xiaochun; Brotherton, Chris; Billedeau, Roland; Gabriel, Steve; Gleason, Shelly; Goldstein, David M; Hilgenkamp, Ramona; Kocer, Buelent; Orzechowski, Lucja; Tan, Jenny; Wovkulich, Peter; Wen, Bo; Fry, David; Di Lello, Paola; Chen, Lucy; Zhang, Fang-Jie; Fretland, Jennifer; Nangia, Anjali; Yang, Tian; Owens, Timothy D

    2017-02-01

    Reactive metabolites have been putatively linked to many adverse drug reactions including idiosyncratic toxicities for a number of drugs with black box warnings or withdrawn from the market. Therefore, it is desirable to minimize the risk of reactive metabolite formation for lead molecules in optimization, in particular for non-life threatening chronic disease, to maximize benefit to risk ratio. This article describes our effort in addressing reactive metabolite issues for a series of 3-amino-2-pyridone inhibitors of BTK, e.g. compound 1 has a value of 459pmol/mg protein in the microsomal covalent binding assay. Parallel approaches were taken to successfully resolve the issues: establishment of a predictive screening assay with correlation association of covalent binding assay, identification of the origin of reactive metabolite formation using MS/MS analysis of HLM as well as isolation and characterization of GSH adducts. This ultimately led to the discovery of compound 7 (RN941) with significantly reduced covalent binding of 26pmol/mg protein.

  17. Protective nitride formation on stainless steel alloys for proton exchange membrane fuel cell bipolar plates

    SciTech Connect

    Yang, Bing; Brady, Michael P; Wang, Heli; Turner, John; More, Karren Leslie; Young, David J; Tortorelli, Peter F; Payzant, E Andrew; Walker, Larry R

    2007-01-01

    Gas nitridation has shown excellent promise to form dense, electrically conductive and corrosion-resistant Cr-nitride surface layers on Ni-Cr base alloys for use as proton exchange membrane fuel cell (PEMFC) bipolar plates. Due to the high cost of nickel, Fe-base bipolar plate alloys are needed to meet the cost targets for many PEMFC applications. Unfortunately, nitridation of Fe-base stainless steel alloys typically leads to internal Cr-nitride precipitation rather than the desired protective surface nitride layer formation, due to the high permeability of nitrogen in these alloys. This paper reports the finding that it is possible to form a continuous, protective Cr-nitride (CrN and Cr{sub 2}N) surface layer through nitridation of Fe-base stainless steel alloys. The key to form a protective Cr-nitride surface layer was found to be the initial formation of oxide during nitridation, which prevented the internal nitridation typically observed for these alloys, and resulted in external Cr-nitride layer formation. The addition of V to the alloy, which resulted in the initial formation of V{sub 2}O{sub 3}-Cr{sub 2}O{sub 3}, was found to enhance this effect, by making the initially formed oxide more amenable to subsequent nitridation. The Cr-nitride surface layer formed on model V-modified Fe-27Cr alloys exhibited excellent corrosion resistance and low interfacial contact resistance under simulated PEMFC bipolar plate conditions.

  18. Protective nitride formation on stainless steel alloys for proton exchange membrane fuel cell bipolar plates

    SciTech Connect

    Yang, B.; Brady, M. P.; Wang, H.; Turner, J. A.; More, K. L.; Young, D. J.; Tortorelli, P. F.; Payzant, E. A.; Walker, L. R.

    2007-09-07

    Gas nitridation has shown excellent promise to form dense, electrically conductive and corrosion-resistant Cr-nitride surface layers on Ni–Cr base alloys for use as proton exchange membrane fuel cell (PEMFC) bipolar plates. Due to the high cost of nickel, Fe-base bipolar plate alloys are needed to meet the cost targets for many PEMFC applications. Unfortunately, nitridation of Fe-base stainless steel alloys typically leads to internal Cr-nitride precipitation rather than the desired protective surface nitride layer formation, due to the high permeability of nitrogen in these alloys. This paper reports the finding that it is possible to form a continuous, protective Cr-nitride (CrN and Cr2N) surface layer through nitridation of Fe-base stainless steel alloys. The key to form a protective Cr-nitride surface layer was found to be the initial formation of oxide during nitridation, which prevented the internal nitridation typically observed for these alloys, and resulted in external Cr-nitride layer formation. The addition of V to the alloy, which resulted in the initial formation of V2O3–Cr2O3, was found to enhance this effect, by making the initially formed oxide more amenable to subsequent nitridation. The Cr-nitride surface layer formed on model V-modified Fe–27Cr alloys exhibited excellent corrosion resistance and low interfacial contact resistance under simulated PEMFC bipolar plate conditions.

  19. Ice formation in PEM fuel cells operated isothermally at sub-freezing temperatures

    SciTech Connect

    Mukundan, Rangachary; Luhan, Roger W; Davey, John R; Spendelow, Jacob S; Borup, Rodney L; Hussey, Daniel S; Jacobson, David L; Arif, Muhammad

    2009-01-01

    The effect of MEA and GDL structure and composition on the performance of single-PEM fuel cells operated isothermally at subfreezing temperatures is presented. The cell performance and durability are not only dependent on the MEA/GDL materials used but also on their interfaces. When a cell is operated isothermally at sub-freezing temperatures in constant current mode, the water formation due to the current density initially hydrates the membrane/ionomer and then forms ice in the catalyst layer/GDL. An increase in high frequency resistance was also observed in certain MEAs where there is a possibility of ice formation between the catalyst layer and GDL leading to a loss in contact area. The total water/ice holding capacity for any MEA was lower at lower temperatures and higher current densities. The durability of MEAs subjected to multiple isothermal starts was better for LANL prepared MEAs as compared to commercial MEAs, and cloth GDLs when compared to paper GDLs. The ice formation was monitored using high-resolution neutron radiography and was found to be concentrated near the cathode catalyst layer. However, there was significant ice formation in the GDLs especially at the higher temperature ({approx} -10 C) and lower current density (0.02 A/cm{sup 2}) operations. These results are consistent with the longer-term durability observations that show more severe degradation at the lower temperatures.

  20. Formation and reactivation ages of a lunar mare ridge in northern Imbrium

    NASA Astrophysics Data System (ADS)

    Daket, Yuko; Yamaji, Atsushi; Sato, Katsushi; Morota, Tomokatsu; Haruyama, Junichi; Ohtake, Makiko; Matsunaga, Tsuneo

    2013-04-01

    Mare ridges and lobate scarps are the manifestations of ancient or recent horizontal compression in the shallow part of the Moon. Regional and global stress fields have been controlled possibly by mascon loading (e.g., Solomon and Head, 1980) and/or global cooling, the latter of which is affected by the origin of the Moon (e.g., Prichard and Stevenson, 2000). On the other hand, mascon loading results in tectonic deformations immediately after the deposition of mare fills (Mohit and Phillips, 2006). Therefore, the timing of deformations is a clue to distinguish the mechanisms. We constrained the formation age of a mare ridge in northern Mare Imbrium as follows. Mare basalts were so inviscid that their lava fields have level surfaces. And, lava flows would have been dammed by pre-existing mare ridges. Therefore, the depositional ages of the mare units-the one involved in the ridge and the other dammed by the ridge, indicate the range of the formation age of the ridge. Using images taken by SELENE (Kaguya), we found such an ENE-WSW trending ridge in northern Imbrium with the height, width and length of 300-400 m, 30 km and ~150 km, respectively. We defined spectrally distinctive two basaltic units in this area: Ti-poor basalt makes up the ridge, and relatively Ti-rich one lies on the plain at the foot of the ridge. Their boundary runs along the southern foot of the ridge. There are no fissures along the boundary that could have fed the Ti-rich basalt. Their model ages were estimated by crater-size frequency distribution measurements using craters of 250 m to 1 km in diameter. As a result, the Ti-poor and Ti-rich units gave the ages at 2.97 +0.16/-0.23 and 2.07 +0.17/-0.17 Ga, respectively, indicating the ridge was formed between ~3.0 and ~2.0 Ga. The majority of mare basalts in mare Imbrium were deposited before ~3.0 Ga (Solomon and Head, 1980), indicating that the ridge formation is explained as a latest event of the mascon loading. However, the unit boundary does

  1. Exploring old and new benzene formation pathways in low-pressure premixed flames of aliphatic fuels

    SciTech Connect

    Christopher J. Pope; James A. Miller

    2000-12-13

    A modeling study of benzene and phenyl radical formation is performed for three low-pressure premixed laminar flat flames having an unsaturated C{sub 2} or C{sub 3} hydrocarbon fuel (acetylene, ethylene, and propene). Predictions using three published detailed elementary-step chemical kinetics mechanisms are tested against MBMS species profile data for all three flames. The differences between the three mechanisms predictive capabilities are explored, with an emphasis on benzene formation pathways. A new chemical kinetics mechanism is created combining features of all three published mechanisms. Included in the mechanism are several novel benzene formation reactions involving combinations of radicals such as C{sub 2}H+C{sub 4}H{sub 5}, and C{sub 5}H{sub 3}+CH{sub 3}. Reactions forming fulvene (a benzene isomer) are included, such as C{sub 3}H{sub 3}+C{sub 3}H{sub 5},as well as fulvene-to-benzene reactions. Predictions using the new mechanism show virtually all of the benzene and phenyl radical to be formed by reactions of either C{sub 3}H{sub 3}+C{sub 3}H{sub 3} or C{sub 3}H{sub 3}+C{sub 3}H{sub 5}, with the relative importance being strongly dependent upon the fuel. C{sub 5}H{sub 3}+CH{sub 3} plays a minor role in fulvene formation in the acetylene flame. The C{sub 2}H{sub x}+C{sub 4}H{sub 4} reactions do not contribute noticeably to benzene or phenyl radical formation in these flames, sometimes being a major decomposition channel for either fulvene or phenyl radical. The formation pathways for C{sub 3}H{sub 3} and C{sub 3}H{sub 5}are delineated for the three flames; while the key reactions differ from flame to flame, CH{sub 2}+C{sub 2}H{sub 2} {Longleftrightarrow} C{sub 3}H{sub 3}+H is important for all three flames.

  2. Fuel injector utilizing non-thermal plasma activation

    DOEpatents

    Coates, Don M.; Rosocha, Louis A.

    2009-12-01

    A non-thermal plasma assisted combustion fuel injector that uses an inner and outer electrode to create an electric field from a high voltage power supply. A dielectric material is operatively disposed between the two electrodes to prevent arcing and to promote the formation of a non-thermal plasma. A fuel injector, which converts a liquid fuel into a dispersed mist, vapor, or aerosolized fuel, injects into the non-thermal plasma generating energetic electrons and other highly reactive chemical species.

  3. Characteristics and trihalomethane formation reactivity of dissolved organic matter in effluents from membrane bioreactors with and without filamentous bulking.

    PubMed

    Xia, Chufan; Ma, Defang; Gao, Baoyu; Hu, Xinxiao; Yue, Qinyan; Meng, Yingjie; Kang, Shuyu; Zhang, Bei; Qi, Yuanfeng

    2016-07-01

    In this study, synthetic wastewater was treated by two identical membrane bioreactors (MBRs): the normal sludge MBR (NS-MBR) and the bulking sludge MBR (BS-MBR). Effects of filamentous bulking on the characteristics and trihalomethane (THM) formation reactivity of MBR effluent dissolved organic matter (EfOM) were investigated. Filamentous sludge bulking had no significant influence on the regulated MBR effluent water quality except NO2-N and NO3-N. NS-MBR effluent had more low molecular weight (LMW) (<5kDa) EfOM (92.43%) than BS-MBR (75.18%). About two-thirds of EfOM from BS-MBR were hydrophilic substances. On the contrary, EfOM from NS-MBR exhibited higher hydrophobicity. The ratio of polysaccharides and proteins in MBR effluents increased after filamentous bulking. There were more protein-like materials, fulvic acid-like and humic acid-like in BS-MBR EfOM. The THM formation reactivity of BS-MBR EfOM was 30.15% of NS-MBR EfOM, whereas BS-MBR EfOM exhibited higher formation reactivity of bromine containing species.

  4. Experimental and Numerical Studies for Soot Formation in Laminar Coflow Diffusion Flames of Jet A-1 and Synthetic Jet Fuels

    NASA Astrophysics Data System (ADS)

    Saffaripour, Meghdad

    In the present doctoral thesis, fundamental experimental and numerical studies are conducted for the laminar, atmospheric pressure, sooting, coflow diffusion flames of Jet A-1 and synthetic jet fuels. The first part of this thesis presents a comparative experimental study for Jet A-1, which is a widely used petroleum-based fuel, and four synthetically produced alternative jet fuels. The main goals of this part of the thesis are to compare the soot emission levels of the alternative fuels to those of a standard fuel, Jet A-1, and to determine the effect of fuel chemical composition on soot formation characteristics. To achieve these goals, experimental measurements are constructed and performed for flame temperature, soot concentration, soot particle size, and soot aggregate structure in the flames of pre-vaporized jet fuels. The results show that a considerable reduction in soot production, compared to the standard fuel, can be obtained by using synthetic fuels which will help in addressing future regulations. A strong correlation between the aromatic content of the fuels and the soot concentration levels in the flames is observed. The second part of this thesis presents the development and experimental validation of a fully-coupled soot formation model for laminar coflow jet fuel diffusion flames. The model is coupled to a detailed kinetic mechanism to predict the chemical structure of the flames and soot precursor concentrations. This model also provides information on size and morphology of soot particles. The flames of a three-component surrogate for Jet A-1, a three-component surrogate for a synthetic jet fuel, and pure n-decane are simulated using this model. Concentrations of major gaseous species and flame temperatures are well predicted by the model. Soot volume fractions are predicted reasonably well everywhere in the flame, except near the flame centerline where soot concentrations are underpredicted by a factor of up to five. There is an excellent

  5. Influence of fuel ethanol content on primary emissions and secondary aerosol formation potential for a modern flex-fuel gasoline vehicle

    NASA Astrophysics Data System (ADS)

    Timonen, Hilkka; Karjalainen, Panu; Saukko, Erkka; Saarikoski, Sanna; Aakko-Saksa, Päivi; Simonen, Pauli; Murtonen, Timo; Dal Maso, Miikka; Kuuluvainen, Heino; Bloss, Matthew; Ahlberg, Erik; Svenningsson, Birgitta; Pagels, Joakim; Brune, William H.; Keskinen, Jorma; Worsnop, Douglas R.; Hillamo, Risto; Rönkkö, Topi

    2017-04-01

    The effect of fuel ethanol content (10, 85 and 100 %) on primary emissions and on subsequent secondary aerosol formation was investigated for a Euro 5 flex-fuel gasoline vehicle. Emissions were characterized during a New European Driving Cycle (NEDC) using a comprehensive set-up of high time-resolution instruments. A detailed chemical composition of the exhaust particulate matter (PM) was studied using a soot particle aerosol mass spectrometer (SP-AMS), and secondary aerosol formation was studied using a potential aerosol mass (PAM) chamber. For the primary gaseous compounds, an increase in total hydrocarbon emissions and a decrease in aromatic BTEX (benzene, toluene, ethylbenzene and xylenes) compounds was observed when the amount of ethanol in the fuel increased. In regard to particles, the largest primary particulate matter concentrations and potential for secondary particle formation was measured for the E10 fuel (10 % ethanol). As the ethanol content of the fuel increased, a significant decrease in the average primary particulate matter concentrations over the NEDC was found. The PM emissions were 0.45, 0.25 and 0.15 mg m-3 for E10, E85 and E100, respectively. Similarly, a clear decrease in secondary aerosol formation potential was observed with a larger contribution of ethanol in the fuel. The secondary-to-primary PM ratios were 13.4 and 1.5 for E10 and E85, respectively. For E100, a slight decrease in PM mass was observed after the PAM chamber, indicating that the PM produced by secondary aerosol formation was less than the PM lost through wall losses or the degradation of the primary organic aerosol (POA) in the chamber. For all fuel blends, the formed secondary aerosol consisted mostly of organic compounds. For E10, the contribution of organic compounds containing oxygen increased from 35 %, measured for primary organics, to 62 % after the PAM chamber. For E85, the contribution of organic compounds containing oxygen increased from 42 % (primary) to 57

  6. Reactivity and isotopic composition of spent PWR (pressurized-water-reactor) fuel as a function of initial enrichment, burnup, and cooling time

    SciTech Connect

    Cerne, S.P.; Hermann, O.W.; Westfall, R.M.

    1987-10-01

    This study presents the reactivity loss of spent PWR fuel due to burnup in terms of the infinite lattice multiplications factor, k/sub infinity/. Calculations were performed using the SAS2 and CSAS1 control modules of the SCALE system. The k/sub infinity/ values calculated for all combinations of six enrichments, seven burnups, and five cooling times. The results are presented as a primary function of enrichment in both tabular and graphic form. An equation has been developed to estimate the tabulated values of k/sub infinity/'s by specifying enrichment, cooling time, and burnup. Atom densities for fresh fuel, and spent fuel at cooling times of 2, 10, and 20 years are included. 13 refs., 8 figs., 8 tabs.

  7. Assessment of groundwater chemical evolution for a spent nuclear fuel repository under prolonged temperate conditions: an application of efficient coupled groundwater flow and reactive transport simulation

    NASA Astrophysics Data System (ADS)

    Gylling, B.; Hartley, L. J.; Joyce, S. J.; Woollard, H.; Marsic, N.; Sidborn, M.; Puigdomenech, I.; Selroos, J. O.

    2014-12-01

    SKB has submitted a license application for a spent nuclear fuel repository at Forsmark sited in crystalline rocks of the Fennoscandian shield. In support of this application various quantitative assessments were made to demonstrate the long-term safety of the proposed repository. One such assessment involved simulation of groundwater chemical evolution to quantify impacts on safety functions for the disposal system related to the geochemical conditions, particularly salinity, pH and redox conditions. In the reference case the current temperate period lasts until 12,000 AD. A case of prolonged meteoric infiltration to 60,000 AD is also considered resulting from e.g. global warming. This is to fulfil a regulatory request to assess whether extended dilute water infiltration might lead to a rise in redox potential and also to an increase in erosion of the bentonite barrier due to formation of colloids. In order to perform long transient simulations of groundwater flow and solute transport with water-solute-rock interactions, new tools have been developed to closely couple geochemical, groundwater flow and transport calculations, and perform these efficiently using parallel computing techniques. In assessing this case, sensitivities are tested to the geochemical reaction schemes appropriate to the site. The results of this work predict that the chemical environment at repository depth stabilises at around 20,000 AD and shows little change beyond that. The salinity of the groundwater is governed by the low permeability (c. 10-19 m2) of the bedrock and by rock matrix diffusion, resulting in relatively shallow and slow circulation of groundwater. The chemical reactions influence concentrations of reactive species, the calculated pH and redox potential. In particular, the redox reactions thought to be relevant for the Forsmark site maintain reducing conditions at repository depth, even with infiltration at the ground surface of meteoric water with relatively high redox

  8. Deactivation/reactivation of a Pd/C catalyst in a direct formic acid fuel cell (DFAFC): Use of array membrane electrode assemblies

    NASA Astrophysics Data System (ADS)

    Yu, Xingwen; Pickup, Peter G.

    Palladium-based catalysts exhibit high activity for formic acid oxidation, but their catalytic activity decreases quite rapidly under direct formic acid fuel cell (DFAFC) operating conditions. This paper presents a systematic study of the deactivation and electrochemical reactivation of a carbon supported palladium catalyst (Pd/C) employing anode arrays in a DFAFC. Deactivation of Pd/C is caused by the electro-oxidation of the formic acid, and does not occur significantly at open circuit. Its rate increases sharply with increasing formic acid concentration but is only dependent on potential at high cell voltages. Reactivation can be achieved by driving the cell voltage to a reverse polarity of -0.2 V or higher. The use of array membrane electrode assemblies allows the rapid generation of statistically significant information on differences between catalysts, and the effects of operational parameters on the deactivation and reactivation processes.

  9. Monitoring of fuel consumption and aromatics formation in a kerosene spray flame as characterized by fluorescence spectroscopy.

    PubMed

    Allouis, C; Apicella, B; Barbella, R; Beretta, F; Ciajolo, A; Tregrossi, A

    2003-06-01

    The large presence of aromatic compounds in distillate fossil fuels should allow, in line of principle, to follow the fuel consumption and/or the presence of unburned fuel in a high temperature environment like a burner or the exhaust of combustion systems by exploiting the high fluorescence emission of aromatic fuel components. To this aim an UV-excited fluorescence source has to be used since the aromatic fuel components are strongly fluorescing in the UV region of the emission spectrum. In this work UV-excited laser induced fluorescence (LIF) diagnostics was applied to spray flames of kerosene in order to follow the fuel consumption and the formation of aromatic species. A strong UV signal was detected in the spray region of the flame that presented a shape similar to that found in the LIF spectra preliminary measured on the cold spray and in the room-temperature fluorescence of fuel solutions. The decrease of UV signal along the spray flame region was associated to the consumption of the fuel, but more difficult seems to be the attribution of a broad visible emission, that is present downstream of the flame. The visible emission feature could be assigned to flame-formed PAH species contained in the high molecular weight species, hypothesizing that their fluorescence spectra are shifted toward the visible for effect of the high temperature flame environment.

  10. Development of a Mathematical Code to Predict Thermal Degradation of Fuel and Deposit Formation in a Fuel System

    DTIC Science & Technology

    1990-09-01

    MDTCAP 5,7 7 0A DCLML",," pROCESSING SHEIET srx is 5X.!iiACSTD AD- A225 415 WRDC-TR-90-2084 DEVELOPMENT OF A MATHEMATICAL CODE TO PREDICT THERMAL...R. (1983) "Studies of the Mechanism of Turbine Fuel Instability," Colorado School of Mines, NASA CR -167963. Daniel, S. R. (1985) "Jet Fuel Instability

  11. Multiphase composition changes and reactive oxygen species formation during limonene oxidation in the new Cambridge Atmospheric Simulation Chamber (CASC)

    NASA Astrophysics Data System (ADS)

    Gallimore, Peter J.; Mahon, Brendan M.; Wragg, Francis P. H.; Fuller, Stephen J.; Giorio, Chiara; Kourtchev, Ivan; Kalberer, Markus

    2017-08-01

    The chemical composition of organic aerosols influences their impacts on human health and the climate system. Aerosol formation from gas-to-particle conversion and in-particle reaction was studied for the oxidation of limonene in a new facility, the Cambridge Atmospheric Simulation Chamber (CASC). Health-relevant oxidising organic species produced during secondary organic aerosol (SOA) formation were quantified in real time using an Online Particle-bound Reactive Oxygen Species Instrument (OPROSI). Two categories of reactive oxygen species (ROS) were identified based on time series analysis: a short-lived component produced during precursor ozonolysis with a lifetime of the order of minutes, and a stable component that was long-lived on the experiment timescale (˜ 4 h). Individual organic species were monitored continuously over this time using Extractive Electrospray Ionisation (EESI) Mass Spectrometry (MS) for the particle phase and Proton Transfer Reaction (PTR) MS for the gas phase. Many first-generation oxidation products are unsaturated, and we observed multiphase aging via further ozonolysis reactions. Volatile products such as C9H14O (limonaketone) and C10H16O2 (limonaldehyde) were observed in the gas phase early in the experiment, before reacting again with ozone. Loss of C10H16O4 (7-hydroxy limononic acid) from the particle phase was surprisingly slow. A combination of reduced C = C reactivity and viscous particle formation (relative to other SOA systems) may explain this, and both scenarios were tested in the Pretty Good Aerosol Model (PG-AM). A range of characterisation measurements were also carried out to benchmark the chamber against existing facilities. This work demonstrates the utility of CASC, particularly for understanding the reactivity and health-relevant properties of organic aerosols using novel, highly time-resolved techniques.

  12. 40 CFR 600.302-08 - Fuel economy label format requirements.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... diesel vehicles, dual fuel vehicles and alternate fuel vehicles are provided in appendix IV of this part... with the background paper color. (3) Have a contrasting border, with dimensions specified in appendix V...) Alternate fuel titles. (i) For dedicated alcohol-fueled automobiles, the title “ *”. The title shall be...

  13. 40 CFR 600.302-08 - Fuel economy label format requirements.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... diesel vehicles, dual fuel vehicles and alternate fuel vehicles are provided in appendix IV of this part... with the background paper color. (3) Have a contrasting border, with dimensions specified in appendix V...) Alternate fuel titles. (i) For dedicated alcohol-fueled automobiles, the title “ *”. The title shall be...

  14. Evaluating temperature and fuel stratification for heat-release rate control in a reactivity-controlled compression-ignition engine using optical diagnostics and chemical kinetics modeling

    DOE PAGES

    Musculus, Mark P. B.; Kokjohn, Sage L.; Reitz, Rolf D.

    2015-04-23

    We investigated the combustion process in a dual-fuel, reactivity-controlled compression-ignition (RCCI) engine using a combination of optical diagnostics and chemical kinetics modeling to explain the role of equivalence ratio, temperature, and fuel reactivity stratification for heat-release rate control. An optically accessible engine is operated in the RCCI combustion mode using gasoline primary reference fuels (PRF). A well-mixed charge of iso-octane (PRF = 100) is created by injecting fuel into the engine cylinder during the intake stroke using a gasoline-type direct injector. Later in the cycle, n-heptane (PRF = 0) is delivered through a centrally mounted diesel-type common-rail injector. This injectionmore » strategy generates stratification in equivalence ratio, fuel blend, and temperature. The first part of this study uses a high-speed camera to image the injection events and record high-temperature combustion chemiluminescence. Moreover, the chemiluminescence imaging showed that, at the operating condition studied in the present work, mixtures in the squish region ignite first, and the reaction zone proceeds inward toward the center of the combustion chamber. The second part of this study investigates the charge preparation of the RCCI strategy using planar laser-induced fluorescence (PLIF) of a fuel tracer under non-reacting conditions to quantify fuel concentration distributions prior to ignition. The fuel-tracer PLIF data show that the combustion event proceeds down gradients in the n-heptane distribution. The third part of the study uses chemical kinetics modeling over a range of mixtures spanning the distributions observed from the fuel-tracer fluorescence imaging to isolate the roles of temperature, equivalence ratio, and PRF number stratification. The simulations predict that PRF number stratification is the dominant factor controlling the ignition location and growth rate of the reaction zone. Equivalence ratio has a smaller, but still

  15. Methods and apparatuses for reagent delivery, reactive barrier formation, and pest control

    DOEpatents

    Gilmore, Tyler [Pasco, WA; Kaplan, Daniel I [Aiken, SC; Last, George [Richland, WA

    2002-07-09

    A reagent delivery method includes positioning reagent delivery tubes in contact with soil. The tubes can include a wall that is permeable to a soil-modifying reagent. The method further includes supplying the reagent in the tubes, diffusing the reagent through the permeable wall and into the soil, and chemically modifying a selected component of the soil using the reagent. The tubes can be in subsurface contact with soil, including groundwater, and can be placed with directional drilling equipment independent of groundwater well casings. The soil-modifying reagent includes a variety of gases, liquids, colloids, and adsorbents that may be reactive or non-reactive with soil components. The method may be used inter alia to form reactive barriers, control pests, and enhance soil nutrients for microbes and plants.

  16. Potential for Peroxide and Gum Formation in Ultra-Low-Sulfur Diesel Fuels

    DTIC Science & Technology

    2007-10-31

    Study of the Thermal Decomposition of Cumene Hydroperoxide and Fuel Instability Reactions , Energy & Fuels, 1994, 8, 851. 3. Fodor, G. E.; Naegeli...the fuel. These chemical processes can lead to changes in color; the development of insoluble reaction products, including soluble and adherent gums...fuels. The LPR test uses elevated temperatures (100 oC) and air overpressures (50 psi) to increase the rate of oxidation reactions in the fuel. The

  17. Reactive oxygen species formation by polymorphonuclear cells and mononuclear cells as a risk factor of cardiovascular diseases.

    PubMed

    Yasunari, Kenichi; Watanabe, Takanori; Nakamura, Munehiro

    2006-04-01

    To better identify patients at high risk for cardiovascular events, several markers of risk have been proposed for use in screening. Recently, oxidative stress and inflammation have been evaluated as potential tools for prediction of the risk of cardiovascular events. Among them, we have measured reactive oxygen species (ROS) formation by polymorphonuclear cells (PMNs) and mononuclear cells (MNCs), since they may be a possible link between inflammation and oxidative stress. ROS formation by PMNs and MNCs was measured by a gated flow cytometric assay. Such biotechnological method of measuring ROS formation by PMNs and MNCs will make it possible that we measure vascular oxidative stress and vascular inflammation at the same time from only small amount of blood. We will state in this review that ROS formation by PMNs and MNCs are regulated by different mechanisms, although PMNs and MNCs are circulating in the same blood. Moreover, we will state that ROS formation by PMNs are regulated by blood pressure, Hb A(1C) and oxidided LDL. ROS formation by MNCs are regulated by vascular inflammation, and that ROS formation by MNCs are also related to various cardiovascular risks such as LV mass, norepinephrine, IMT, and nocturnal blood pressure.

  18. Reactive retinal microglia, neuronal survival and the formation of retinal folds and detachments

    PubMed Central

    Fischer, Andy J.; Zelinka, Christopher; Milani-Nejad, Nima

    2014-01-01

    Reactive microglia and macrophages are prevalent in damaged retinas. Accordingly, we investigate how the activation or ablation of microglia/macrophages influences the survival of neurons in the chick retina in vivo. We applied intraocular injections of interleukin 6 (IL6) to stimulate the reactivity of microglia/macrophages and clodronate-liposomes to ablate microglia/macrophages. Activation of the microglia/macrophages with IL6 delays the death of retinal neurons from N-methyl-D-aspartate (NMDA) -induced excitotoxicity. In addition, activation of microglia/macrophages combined with colchicine-mediated retinal damage diminished the survival of ganglion cells. Application of IL6 after an excitotoxic insult greatly exacerbates the damage, and causes widespread retinal detachments and folds, accompanied by accumulation of microglia/macrophages in the subretinal space. Damage-induced retinal folds and detachments were significantly reduced by the ablation of microglia/macrophages. We conclude that microglial reactivity is detrimental to the survival of ganglion cells in colchicine-damaged retinas and detrimental to the survival of photoreceptors in retinal folds. In addition, we conclude that IL6-treatment transiently protects amacrine and bipolar cells against an excitotoxic insult. We propose that suppressing reactivity of microglia/macrophages may be an effective means to lessen the damage and vision loss resulting from damage, in particular during retinal detachment injuries. PMID:25231952

  19. Formation and reactivity of surface-bound high oxidation state Ruthenium-oxo complexes.

    SciTech Connect

    Hornstein, B. J.; Dattelbaum, D. M.; Schoonover, J. R.; Meyer, T. J.

    2004-01-01

    Ruthenium polypyridyl oxalate complexes are precursors to high oxidation state species that can catalyze the oxidation of a variety of substrates. Covalent attachment of these reactive species to surfaces such at ZrO{sub 2} or TiO{sub 2} inhibit catalyst deactivation and provide supports from which to build electrocatalytic and photoelectrocatalytic devices. Unfortunately, few details of the effects of surface binding on reactivity are available in the literature. To this end, precursors such as, Ru(H{sub 2}O{sub 3}Ptpy)(C{sub 2}O{sub 4})(H{sub 2}O) and (C{sub 2}O{sub 4})(H{sub 2}O{sub 3}Ptpy)Ru-O-Ru(H{sub 2}O{sub 3}Ptpy)(C{sub 2}O{sub 4}) (tpy is terpyridine) have been synthesized and attached to TiO{sub 2}. Quantitative surface binding studies were carried out and acid catalyzed solvolysis was used to form the aqua species. The complexes were oxidized with Ce(IV) to their high-valent analogs and their reactivity toward selected substrates was tested. These studies not only provide information about the effects of surface binding on the reactivity of metal oxides but also have implications for the development of light-driven catalysts.

  20. MODELING THE ATMOSPHERE FORMATION OF REACTIVE MERCURY IN FLORIDA AND THE GREAT LAKES

    EPA Science Inventory

    Reactive mercury in the troposphere is affected by a complex mix of local emissions, global-scale transport, and gas and aqueous-phase chemistry. Here, we describe a modified version of the EPA model for urban/regional air quality (CMAQ) to include the chemistry of mercury, and m...

  1. MODELING THE ATMOSPHERE FORMATION OF REACTIVE MERCURY IN FLORIDA AND THE GREAT LAKES

    EPA Science Inventory

    Reactive mercury in the troposphere is affected by a complex mix of local emissions, global-scale transport, and gas and aqueous-phase chemistry. Here, we describe a modified version of the EPA model for urban/regional air quality (CMAQ) to include the chemistry of mercury, and m...

  2. Fundamental Studies of Irradiation-Induced Defect Formation and Fission Product Dynamics in Oxide Fuels

    SciTech Connect

    Stubbins, James

    2012-12-19

    The objective of this research program is to address major nuclear fuels performance issues for the design and use of oxide-type fuels in the current and advanced nuclear reactor applications. Fuel performance is a major issue for extending fuel burn-up which has the added advantage of reducing the used fuel waste stream. It will also be a significant issue with respect to developing advanced fuel cycle processes where it may be possible to incorporate minor actinides in various fuel forms so that they can be 'burned' rather than join the used fuel waste stream. The potential to fission or transmute minor actinides and certain long-lived fission product isotopes would transform the high level waste storage strategy by removing the need to consider fuel storage on the millennium time scale.

  3. Production of hybrid diesel fuel precursors from carbohydrates and petrochemicals using formic acid as a reactive solvent.

    PubMed

    Zhou, Xiaoyuan; Rauchfuss, Thomas B

    2013-02-01

    We report the one-pot alkylation of mesitylene with carbohydrate-derived 5-(hydroxymethyl)furfural (HMF) as a step toward diesel-range liquids. Using FeCl(3) as a catalyst, HMF is shown to alkylate toluene, xylene, and mesitylene in high yields in CH(2)Cl(2) and MeNO(2) solvents. Efforts to extend this reaction to greener or safer solvents showed that most ether-based solvents are unsatisfactory. Acid catalysts (e.g, p-TsOH) also proved to be ineffective. Using formic acid as a reactive solvent, mesitylene could be alkylated to give mesitylmethylfurfural (MMF) starting from fructose with yields up to approximately 70 %. The reaction of fructose with formic acid in the absence of mesitylene gave rise to low yields of the formate ester of HMF, which indicates the stabilizing effect of replacing the hydroxyl substituent with mesityl. The arene also serves as a second phase into which the product is extracted. Even by using formic acid, the mesitylation of less expensive precursors such as glucose and cellulose proceeded only in modest yields (ca. 20 %). These simpler substrates were found to undergo mesitylation by using hydrogen chloride/formic acid via the intermediate chloromethylfurfural. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Formation, reactivity and aging of amorphous ferric oxides in the presence of model and membrane bioreactor derived organics.

    PubMed

    Bligh, Mark W; Maheshwari, Pradeep; David Waite, T

    2017-11-01

    Iron salts are routinely dosed in wastewater treatment as a means of achieving effluent phosphorous concentration goals. The iron oxides that result from addition of iron salts partake in various reactions, including reductive dissolution and phosphate adsorption. The reactivity of these oxides is controlled by the conditions of formation and the processes, such as aggregation, that lead to a reduction in accessible surface sites following formation. The presence of organic compounds is expected to significantly impact these processes in a number of ways. In this study, amorphous ferric oxide (AFO) reactivity and aging was investigated following the addition of ferric iron (Fe(III)) to three solution systems: two synthetic buffered systems, either containing no organic or containing alginate, and a supernatant system containing soluble microbial products (SMPs) sourced from a membrane bioreactor (MBR). Reactivity of the Fe(III) phases in these systems at various times (1-60 min) following Fe(III) addition was quantified by determining the rate constants for ascorbate-mediated reductive dissolution over short (5 min) and long (60 min) dissolution periods and for a range (0.5-10 mM) of ascorbate concentrations. AFO particle size was monitored using dynamic light scattering during the aging and dissolution periods. In the presence of alginate, AFO particles appeared to be stabilized against aggregation. However, aging in the alginate system was remarkably similar to the inorganic system where aging is associated with aggregation. An aging mechanism involving restructuring within the alginate-AFO assemblage was proposed. In the presence of SMPs, a greater diversity of Fe(III) phases was evident with both a small labile pool of organically complexed Fe(III) and a polydisperse population of stabilized AFO particles present. The prevalence of low molecular weight organic molecules facilitated stabilization of the Fe(III) oxyhydroxides formed but subsequent aging

  5. Shock tube study of the fuel molecular structure effects on the chemical kinetic mechanisms for soot formation

    NASA Technical Reports Server (NTRS)

    Krech, R. H.; Cowles, L. M.; Rawlins, W. T.

    1983-01-01

    The objective of this research effort is to investigate the gas-phase mechanisms which lead to soot formation in the combustion of complex hydrocarbon fuels. The fuel decomposition is studied under pyrolytic and oxidative conditions behind incident shock waves, using various optical diagnostics to monitor particle appearance and the behavior of gas phase species. In particular, we are investigating: (1) improved quantification of UV/visible soot yield measurements using infrared attenuation and emission techniques; (2) spectral characteristics of gas-phase emission and absorption in the ultraviolet, visible, and infrared; and (3) a conceptual view of the chemical pathways for fuel decomposition and the gas-phase reactions leading to soot formation.

  6. Shock tube study of the fuel molecular structure effects on the chemical kinetic mechanisms for soot formation

    NASA Technical Reports Server (NTRS)

    Krech, R. H.; Cowles, L. M.; Rawlins, W. T.

    1983-01-01

    The objective of this research effort is to investigate the gas-phase mechanisms which lead to soot formation in the combustion of complex hydrocarbon fuels. The fuel decomposition is studied under pyrolytic and oxidative conditions behind incident shock waves, using various optical diagnostics to monitor particle appearance and the behavior of gas phase species. In particular, we are investigating: (1) improved quantification of UV/visible soot yield measurements using infrared attenuation and emission techniques; (2) spectral characteristics of gas-phase emission and absorption in the ultraviolet, visible, and infrared; and (3) a conceptual view of the chemical pathways for fuel decomposition and the gas-phase reactions leading to soot formation.

  7. Formation mechanism of gas bubble superlattice in UMo metal fuels: Phase-field modeling investigation

    NASA Astrophysics Data System (ADS)

    Hu, Shenyang; Burkes, Douglas E.; Lavender, Curt A.; Senor, David J.; Setyawan, Wahyu; Xu, Zhijie

    2016-10-01

    Nano-gas bubble superlattices are often observed in irradiated UMo nuclear fuels. However, the formation mechanism of gas bubble superlattices is not well understood. A number of physical processes may affect the gas bubble nucleation and growth; hence, the morphology of gas bubble microstructures including size and spatial distributions. In this work, a phase-field model integrating a first-passage Monte Carlo method to investigate the formation mechanism of gas bubble superlattices was developed. Six physical processes are taken into account in the model: 1) heterogeneous generation of gas atoms, vacancies, and interstitials informed from atomistic simulations; 2) one-dimensional (1-D) migration of interstitials; 3) irradiation-induced dissolution of gas atoms; 4) recombination between vacancies and interstitials; 5) elastic interaction; and 6) heterogeneous nucleation of gas bubbles. We found that the elastic interaction doesn't cause the gas bubble alignment, and fast 1-D migration of interstitials along <110> directions in the body-centered cubic U matrix causes the gas bubble alignment along <110> directions. It implies that 1-D interstitial migration along [110] direction should be the primary mechanism of a fcc gas bubble superlattice which is observed in bcc UMo alloys. Simulations also show that fission rates, saturated gas concentration, and elastic interaction all affect the morphology of gas bubble microstructures.

  8. Relaxing the formation of hypoxic bottom water with sediment microbial fuel cells.

    PubMed

    Touch, Narong; Hibino, Tadashi; Morimoto, Yuki; Kinjo, Nobutaka

    2017-02-08

    The method of improving bottom water environment using industrial wastes to suppress diffusion substances from bottom sediment has recently captured the attention of many researchers. In this study, wastewater discharge-derived sediment was used to examine an alternative approach involving the use of sediment microbial fuel cells (SMFCs) in relaxing the formation of hypoxic bottom water, and removing reduced substances from sediment. Concentrations of dissolved oxygen (DO) and other ions were measured in overlying water and sediment pore water with and without the application of SMFCs. The results suggest that SMFCs can markedly reduce hydrogen sulfide and manganese ion concentrations in overlying water, and decrease the depletions of redox potential and DO concentration. In addition, SMFCs can dissolve ferric compounds in the sediment and thereby release the ferric ion available to fix phosphate in the sediment. Our results indicate that SMFCs can be used as an alternative method to relax the formation of hypoxic bottom water and to remove reduced substances from the sediment, thus improving the quality of both water and sediment environments.

  9. Microemulsions and Aggregation Formation in Extraction Processes for Used Nuclear Fuel: Thermodynamic and Structural Studies

    SciTech Connect

    Nilsson, Mikael

    2016-05-04

    Advanced nuclear fuel cycles rely on successful chemical separation of various elements in the used fuel. Numerous solvent extraction (SX) processes have been developed for the recovery and purification of metal ions from this used material. However, the predictability of process operations has been challenged by the lack of a fundamental understanding of the chemical interactions in several of these separation systems. For example, gaps in the thermodynamic description of the mechanism and the complexes formed will make predictions very challenging. Recent studies of certain extraction systems under development and a number of more established SX processes have suggested that aggregate formation in the organic phase results in a transformation of its selectivity and efficiency. Aggregation phenomena have consistently been interfering in SX process development, and have, over the years, become synonymous with an undesirable effect that must be prevented. This multiyear, multicollaborative research effort was carried out to study solvation and self-organization in non-aqueous solutions at conditions promoting aggregation phenomena. Our approach to this challenging topic was to investigate extraction systems comprising more than one extraction reagent where synergy of the metal ion could be observed. These systems were probed for the existence of stable microemulsions in the organic phase, and a number of high-end characterization tools were employed to elucidate the role of the aggregates in metal ion extraction. The ultimate goal was to find connections between synergy of metal ion extraction and reverse micellar formation. Our main accomplishment for this project was the expansion of the understanding of metal ion complexation in the extraction system combining tributyl phosphate (TBP) and dibutyl phosphoric acid (HDBP). We have found that for this system no direct correlation exists for the metal ion extraction and the formation of aggregates, meaning that the

  10. Aging might augment reactive oxygen species (ROS) formation and affect reactive nitrogen species (RNS) level after myocardial ischemia/reperfusion in both humans and rats.

    PubMed

    Fan, Qian; Chen, Mulei; Fang, Xiangyang; Lau, Wayne Bond; Xue, Lei; Zhao, Lina; Zhang, Hui; Liang, Yan-Hong; Bai, Xi; Niu, Hong-Yu; Ye, Jing; Chen, Qing; Yang, Xinchun; Liu, Miaobing

    2013-08-01

    Previous studies indicate aging results in significantly decreased cardiac function and increased myocardial apoptosis after myocardial ischemia/reperfusion (MI/R) in humans or rats. The underlying mechanisms of aging-exacerbated effects remain unknown. Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are known to play vital roles in aging-related MI/R injury. Heretofore, the effects of aging upon ROS and RNS formation were not investigated in humans, which is the focus of the current study. Due to experimental limitations with clinical trials, an additional animal experiment was performed. All enrolled acute myocardial infarction (AMI) patients received percutaneous coronary intervention (PCI) therapy. AMI patients were assigned into two groups: adult (age <65, n = 34) and elderly (age ≥65, n = 45) AMI patients. Blood samples were obtained from all study participants at 24 h and 3 days post-PCI. Plasma/white blood cell (WBC) ROS and RNS markers (malondialdehyde (MDA), myeloperoxidase (MPO), reduced glutathione (GSH), inducible nitric oxide synthase (iNOS) activity, NOx, and nitrotyrosine) were determined. The same markers were determined in rat cardiac tissue after 24 h MI/R. Compared to the adult group, elderly patients manifested increased plasma MDA and MPO and decreased plasma GSH concentrations. No significant differences in plasma NOx or nitrotyrosine concentration existed between adult and elderly patients. Furthermore, WBC iNOS activity in elderly patients was significantly decreased compared to the adult group. The measurement of ROS markers in the rat experiments was consistent and supported human study data. Surprisingly, RNS markers (NOx and nitrotyrosine) in blood and heart tissue increased from young to middle-aged rats but decreased from middle age to old age. Aging augments ROS, which might exacerbate MI/R injury. Additionally, our data support aging-induced changes of RNS levels in humans and rats in vivo.

  11. Effects of Fuel Preheat on Soot Formation in Microgravity Laminar Diffusion Flames

    NASA Technical Reports Server (NTRS)

    Konsur, Bogdan; Megaridis, Constantine M.; Griffin, DeVon W.

    1997-01-01

    measured at 0-g was nearly a factor of two higher than that at 1-g, thus confirming the enhanced sooting tendency of nonbuoyant flames. Greenberg and Ku presented a similar study and reported trends that matched those of for the 50% (vol.) nitrogen-diluted acetylene fuel. Furthermore, they examined pure acetylene flames and reported similar trends with respect to the influence of gravity on maximum soot volume fractions and flame cross-section-averaged soot loadings. Both studies clearly demonstrated the improved spatial resolution of microgravity flames compared to their normal-gravity counterparts. The current study evaluates the influence of moderate fuel preheat on soot formation within 0-g laminar gas jet diffusion flames. While fuel temperature variations have little influence on residence times in 1-g, they have a much more significant effect in 0-g. The primary objective of this program is to quantify this effect and its consequences on sooting by comparing soot volume fraction distributions under preheated and unpreheated-fuel conditions. Furthermore, the current work aims at expanding the limited soot database available for nonbuoyant flames. Soot fields in such flames can be used to perform additional tests of recently developed soot sub-models which have the potential to become powerful predicting tools in combustion design.

  12. An Atmospheric Pressure Plasma Setup to Investigate the Reactive Species Formation.

    PubMed

    Gorbanev, Yury; Soriano, Robert; O'Connell, Deborah; Chechik, Victor

    2016-11-03

    Non-thermal atmospheric pressure ('cold') plasmas have received increased attention in recent years due to their significant biomedical potential. The reactions of cold plasma with the surrounding atmosphere yield a variety of reactive species, which can define its effectiveness. While efficient development of cold plasma therapy requires kinetic models, model benchmarking needs empirical data. Experimental studies of the source of reactive species detected in aqueous solutions exposed to plasma are still scarce. Biomedical plasma is often operated with He or Ar feed gas, and a specific interest lies in investigation of the reactive species generated by plasma with various gas admixtures (O2, N2, air, H2O vapor, etc.) Such investigations are very complex due to difficulties in controlling the ambient atmosphere in contact with the plasma effluent. In this work, we addressed common issues of 'high' voltage kHz frequency driven plasma jet experimental studies. A reactor was developed allowing the exclusion of ambient atmosphere from the plasma-liquid system. The system thus comprised the feed gas with admixtures and the components of the liquid sample. This controlled atmosphere allowed the investigation of the source of the reactive oxygen species induced in aqueous solutions by He-water vapor plasma. The use of isotopically labelled water allowed distinguishing between the species originating in the gas phase and those formed in the liquid. The plasma equipment was contained inside a Faraday cage to eliminate possible influence of any external field. The setup is versatile and can aid in further understanding the cold plasma-liquid interactions chemistry.

  13. An Atmospheric Pressure Plasma Setup to Investigate the Reactive Species Formation

    PubMed Central

    Gorbanev, Yury; Soriano, Robert; O'Connell, Deborah; Chechik, Victor

    2016-01-01

    Non-thermal atmospheric pressure ('cold') plasmas have received increased attention in recent years due to their significant biomedical potential. The reactions of cold plasma with the surrounding atmosphere yield a variety of reactive species, which can define its effectiveness. While efficient development of cold plasma therapy requires kinetic models, model benchmarking needs empirical data. Experimental studies of the source of reactive species detected in aqueous solutions exposed to plasma are still scarce. Biomedical plasma is often operated with He or Ar feed gas, and a specific interest lies in investigation of the reactive species generated by plasma with various gas admixtures (O2, N2, air, H2O vapor, etc.) Such investigations are very complex due to difficulties in controlling the ambient atmosphere in contact with the plasma effluent. In this work, we addressed common issues of 'high' voltage kHz frequency driven plasma jet experimental studies. A reactor was developed allowing the exclusion of ambient atmosphere from the plasma-liquid system. The system thus comprised the feed gas with admixtures and the components of the liquid sample. This controlled atmosphere allowed the investigation of the source of the reactive oxygen species induced in aqueous solutions by He-water vapor plasma. The use of isotopically labelled water allowed distinguishing between the species originating in the gas phase and those formed in the liquid. The plasma equipment was contained inside a Faraday cage to eliminate possible influence of any external field. The setup is versatile and can aid in further understanding the cold plasma-liquid interactions chemistry. PMID:27842375

  14. Computational assessment of non-heteroatom-stabilized carbene complexes reactivity: formation of oxazine derivatives.

    PubMed

    Funes-Ardoiz, Ignacio; Sampedro, Diego

    2014-12-05

    A complete DFT-level mechanism elucidation of the two-step reaction of non-heteroatom-stabilized carbenes with imines, followed by addition of alkynes to yield oxazine derivatives, is presented. These compounds show different reactivity than the equivalent Fischer carbene complexes. A rationale of the experimental outcome is presented together with some suggestion for increasing the scope of the reaction, with special attention to the solvent effects in the regioselectivity.

  15. Measurement of the atmospheric reactivity of emissions from gasoline and alternative-fueled vehicles: Assessment of available methodologies. Part 1. Indoor smog chamber study of reactivity. Part 2. Assessment of airtrak as a reactivity analyzer. Final report for the second year, March 1, 1994-February 28, 1995

    SciTech Connect

    Kelly, N.A.; Wang, P.; Hurley, M.D.; Japar, S.M.; Chang, T.

    1996-06-13

    During the second year of the GM smog chamber study of incremental reactivity the authors performed smog chamber experiments to measure three important properties of incremental reactivity. First, they challenged the linear relationship between the Carter factors and the chamber-measured reactivities found during the first-year smog chamber study. Second, they compared the predicted and measured smog formation in simple and complex mixtures. Third, they measured the incremental reactivities of three hydrocarbons (n-butane, propene, and p-xylene) as well as the urban-surrogate mixture at three different temperatures, 22 deg C, 32 deg C (the default), and 42 deg C, to determine how temperature affects both the absolute and the relative reactivity. Finally, they conducted experiments in which the incremental reactivity of NO2 was measured in order to test the Integrated Empirical Rate (IER) model.

  16. Combustion of Various Highly Reactive Fuels in a 3.84- by 10-inch Mach 2 Wind Tunnel

    NASA Technical Reports Server (NTRS)

    Allen, Harrison, Jr.; Fletcher, Edward A.

    1959-01-01

    The following fuels and fuel combinations injected from the top wall of a Mach 2 wind tunnel were successfully burned and gave associated pressure rises: aluminum borohydride, pentaborane, mixtures containing up to 41 percent JP-4 fuel in aluminum borohydride, tandem injections of aluminum borohydride, tandem injections of JP-4 fuel and aluminum borohydride, trimethyl aluminum with water injections, and diethyl aluminum hydride with water injections. The following fuels could not be ignited at the tunnel conditions (static pressure, 5.6 in. Hg; static temperature, -148 F): trimethylborane, triethylborane, propylpentaborane, ethyl- decaborane, and vinylsilane. Studies in which the heated region was probed by water injections indicated that the flow downstream of the flame front is subsonic and recirculating.

  17. Some properties of the reactive hydroxylysyl residues in collagen: their possible role in nucleation during fibril formation.

    PubMed

    Gonzalez, E; Hamabata, A; Rojkind, M

    1984-10-01

    Native or heat-denatured collagens were incubated under controlled conditions of temperature and pH with variable molar ratios of KCNO or 2,4,6-trinitrobenzene sulphonic acid. The results obtained suggest that a small number of free amino groups are available for reaction on the native protein, while all the free amino groups react on the denatured protein. The highly reactive free amino groups in the native protein are hydroxylysine residues and have an abnormally low pK of 8.5 which is conformation dependent; this pK becomes normalized upon denaturation of the protein. The reactive hydroxylysines appear to be located in basic regions that could be the nucleation sites needed for fiber formation in the heat-gelation assay; the modified protein does not form stable fibrils upon heating at 37 degrees C and the few fibers formed are not stabilized after reduction with NaBH4. Our results also suggest that the triple helix in collagen is heterogeneous with respect to the reactivity of free amino groups and that several discrete transition temperatures are observed with two main breaks at 30 degrees C and at 37 degrees C, respectively.

  18. Contribution of energetically reactive surface features to the dissolution of CeO2 and ThO2 analogues for spent nuclear fuel microstructures.

    PubMed

    Corkhill, Claire L; Myllykylä, Emmi; Bailey, Daniel J; Thornber, Stephanie M; Qi, Jiahui; Maldonado, Pablo; Stennett, Martin C; Hamilton, Andrea; Hyatt, Neil C

    2014-08-13

    In the safety case for the geological disposal of nuclear waste, the release of radioactivity from the repository is controlled by the dissolution of the spent fuel in groundwater. There remain several uncertainties associated with understanding spent fuel dissolution, including the contribution of energetically reactive surface sites to the dissolution rate. In this study, we investigate how surface features influence the dissolution rate of synthetic CeO2 and ThO2, spent nuclear fuel analogues that approximate as closely as possible the microstructure characteristics of fuel-grade UO2 but are not sensitive to changes in oxidation state of the cation. The morphology of grain boundaries (natural features) and surface facets (specimen preparation-induced features) was investigated during dissolution. The effects of surface polishing on dissolution rate were also investigated. We show that preferential dissolution occurs at grain boundaries, resulting in grain boundary decohesion and enhanced dissolution rates. A strong crystallographic control was exerted, with high misorientation angle grain boundaries retreating more rapidly than those with low misorientation angles, which may be due to the accommodation of defects in the grain boundary structure. The data from these simplified analogue systems support the hypothesis that grain boundaries play a role in the so-called "instant release fraction" of spent fuel, and should be carefully considered, in conjunction with other chemical effects, in safety performance assessements for the geological disposal of spent fuel. Surface facets formed during the sample annealing process also exhibited a strong crystallographic control and were found to dissolve rapidly on initial contact with dissolution medium. Defects and strain induced during sample polishing caused an overestimation of the dissolution rate, by up to 3 orders of magnitude.

  19. From the Nano- to the Formation Scale: Accessible Reactive Surface Area in a CO2 Saline Reservoir

    NASA Astrophysics Data System (ADS)

    Swift, A.; Cole, D. R.; Sheets, J. M.; Anovitz, L. M.

    2015-12-01

    Among the outstanding subsurface science challenges today is the translation of our improved understanding of pore-scale reactive transport and bench-scale geochemical rates of reaction to the prediction of long-term formation response to the sequestration of carbon dioxide. The emergent complexity of CO2-brine-rock interactions, on a large scale, over long periods of time (up to 1000 years) arises from a number of imperfectly understood factors. Of these, the accessibility of reactive surfaces distinguishes natural materials from powders commonly used in reaction rate studies, and geologic heterogeneity requires a workflow that connects samples, not to depths, but to material types that, combined, constitute a subsurface formation. To this end, core samples targeting every lithology type (quartz arenite, quartz-feldspar arenite, hematitic matrix-rich sandstone, clay-silt lens) observed in two bore holes through the Mt. Simon Sandstone of Ohio have been interrogated. Small- and ultra small-angle neutron scattering (SANS, USANS) and mercury and gas porosimetry (MICP, BET) have been used to quantify pore and pore throat distributions, and therefore pore volume accessibility at any given intrusion pressure. Mineral surface area is calculated using high-resolution SEM-BSE imagery combined with energy dispersive X-ray mineral mapping, and then extended beyond the limit of image-based techniques by using BET estimates for specific minerals. Combined, these datasets enable the quantification of mineral-specific, connected surface area as a function of pore/fracture scale. This is a defining feature of a pore-mineral assemblage, the microanalysis analogue of a macroscale lithology. The whole formation is then reconstructed by connecting pore-mineral assemblages to lithologies, defined by permeability/porosity and by mineralogy, and these in turn to the whole vertical extent of the formation using coarser-scale images of whole core. This effort therefore contributes both to

  20. Analysis of liquid water formation in polymer electrolyte membrane (PEM) fuel cell flow fields with a dry cathode supply

    NASA Astrophysics Data System (ADS)

    Gößling, Sönke; Klages, Merle; Haußmann, Jan; Beckhaus, Peter; Messerschmidt, Matthias; Arlt, Tobias; Kardjilov, Nikolay; Manke, Ingo; Scholta, Joachim; Heinzel, Angelika

    2016-02-01

    PEM fuel cells can be operated within a wide range of different operating conditions. In this paper, the special case of operating a PEM fuel cell with a dry cathode supply and without external humidification of the cathode, is considered. A deeper understanding of the water management in the cells is essential for choosing the optimal operation strategy for a specific system. In this study a theoretical model is presented which aims to predict the location in the flow field at which liquid water forms at the cathode. It is validated with neutron images of a PEM fuel cell visualizing the locations at which liquid water forms in the fuel cell flow field channels. It is shown that the inclusion of the GDL diffusion resistance in the model is essential to describe the liquid water formation process inside the fuel cell. Good agreement of model predictions and measurement results has been achieved. While the model has been developed and validated especially for the operation with a dry cathode supply, the model is also applicable to fuel cells with a humidified cathode stream.

  1. Formation of cubic boron-nitride by the reactive sputter deposition of boron

    SciTech Connect

    Jankowski, A.F.; Hayes, J.P.; Makowiecki, D.W.; McKeman, M.A.

    1997-03-01

    Boron-nitride films are synthesized by RF magnetron sputtering boron targets where the deposition parameters of gas pressure, flow and composition are varied along with substrate temperature and applied bias. The films are analyzed using Auger electron spectroscopy, transmission electron microscopy, nanoindentation, Raman spectroscopy and x-ray absorption spectroscopy. These techniques provide characterization of film composition, crystalline structure, hardness and chemical bonding, respectively. Reactive, rf-sputtering process parameters are established which lead to the growth of crystalline BN phases. The deposition of stable and adherent boron nitride coatings consisting of the cubic phase requires 400 `C substrate heating and the application of a 300 V negative bias.

  2. Chemical reactivity parameters (HSAB) applied to magma evolution and ore formation

    NASA Astrophysics Data System (ADS)

    Vigneresse, Jean-Louis

    2012-11-01

    Magmas are commonly described through the usual content of 10 major oxides. This requires a complex dimensional plot. Concepts of hard-soft acid-base (HSAB) interactions allow estimating chemical reactivity of elements, such as electronegativity, i.e. the chemical potential changed of sign, hardness and electrophilicity. For complex system, those values result from equalization methods, i.e. the equalization of the respective chemical potentials, or from ab-initio computations through density functional theory (DFT). They help to characterize silicate magmas by a single value describing their reactivity. Principles of minimum electrophilicity (mEP), maximum hardness (MHP) and minimum polarizability (mPP) indicate trends towards regions of higher stability. Those parameters are plotted within a fitness landscape diagram, highlighting toward which principle reactions trend. Major oxides, main minerals and magmas determine the respective fields in which evolve natural rocks. Three poles are identified, represented by silica and alkalis, whereas oxidation forms the third trend. Mantle-derived rocks show a large variation in electrophilicity compared to hardness. They present all characters of a closed chemical system, being simply described by the free Gibbs energy. Conversely, rocks contaminated within the continental crust show a large variation in hardness between a silica pole and an alkaline, defining two separate trends. The trends show the character of an open chemical system, requiring a Grand Potential description (i.e. taking into account the difference in chemical potential). The terms open and closed systems refer to thermodynamical description, implying contamination for the crust and recycling for the mantle. The specific role of alkalis contrasts with other cations, pointing to their behavior in modifying silicate polymer structures. A second application deals with the reactivity of the melt and its fluid phase. It leads to a better understanding on the

  3. Formation of Reactive Sulfite-Derived Free Radicals by the Activation of Human Neutrophils: An ESR Study

    PubMed Central

    Ranguelova, Kalina; Rice, Annette B.; Khajo, Abdelahad; Triquigneaux, Mathilde; Garantziotis, Stavros; Magliozzo, Richard S.; Mason, Ronald P.

    2012-01-01

    The objective of the present study is to determine the effect of (bi)sulfite (hydrated sulfur dioxide) on human neutrophils and the ability of these immune cells to produce reactive free radicals due to (bi)sulfite oxidation. Myeloperoxidase (MPO) is an abundant heme protein in neutrophils that catalyzes the formation of cytotoxic oxidants implicated in asthma and inflammatory disorders. In the present study sulfite (•SO3−) and sulfate (SO4•−) anion radicals are characterized with the ESR spin-trapping technique using 5,5-dimethyl-1-pyrroline N-oxide (DMPO) in the reaction of (bi)sulfite oxidation by human MPO and human neutrophils via sulfite radical chain reaction chemistry. After treatment with (bi)sulfite, PMA-stimulated neutrophils produced DMPO-sulfite anion radical, -superoxide, and -hydroxyl radical adducts. The latter adduct probably resulted, in part, from the conversion of DMPO-sulfate to DMPO-hydroxyl radical adduct via a nucleophilic substitution reaction of the radical adduct. This anion radical (SO4•−) is highly reactive and, presumably, can oxidize target proteins to protein radicals, thereby initiating protein oxidation. Therefore, we propose that the potential toxicity of (bi)sulfite during pulmonary inflammation or lung-associated diseases such as asthma may be related to free radical formation. PMID:22326772

  4. Evaluation of a High-Throughput Peptide Reactivity Format Assay for Assessment of the Skin Sensitization Potential of Chemicals.

    PubMed

    Wong, Chin Lin; Lam, Ai-Leen; Smith, Maree T; Ghassabian, Sussan

    2016-01-01

    The direct peptide reactivity assay (DPRA) is a validated method for in vitro assessment of the skin sensitization potential of chemicals. In the present work, we describe a peptide reactivity assay using 96-well plate format and systematically identified the optimal assay conditions for accurate and reproducible classification of chemicals with known sensitizing capacity. The aim of the research is to ensure that the analytical component of the peptide reactivity assay is robust, accurate, and reproducible in accordance with criteria that are used for the validation of bioanalytical methods. Analytical performance was evaluated using quality control samples (QCs; heptapeptides at low, medium, and high concentrations) and incubation of control chemicals (chemicals with known sensitization capacity, weak, moderate, strong, extreme, and non-sensitizers) with each of three synthetic heptapeptides, viz Cor1-C420 (Ac-NKKCDLF), cysteine- (Ac-RFAACAA), and lysine- (Ac-RFAAKAA) containing heptapeptides. The optimal incubation temperature for all three heptapeptides was 25°C. Apparent heptapeptide depletion was affected by vial material composition. Incubation of test chemicals with Cor1-C420, showed that peptide depletion was unchanged in polypropylene vials over 3-days storage in an autosampler but this was not the case for borosilicate glass vials. For cysteine-containing heptapeptide, the concentration was not stable by day 3 post-incubation in borosilicate glass vials. Although the lysine-containing heptapeptide concentration was unchanged in both polypropylene and borosilicate glass vials, the apparent extent of lysine-containing heptapeptide depletion by ethyl acrylate, differed between polypropylene (24.7%) and glass (47.3%) vials. Additionally, the peptide-chemical complexes for Cor1-C420-cinnamaldehyde and cysteine-containing heptapeptide-2, 4-dinitrochlorobenzene were partially reversible during 3-days of autosampler storage. These observations further highlight

  5. Evaluation of a High-Throughput Peptide Reactivity Format Assay for Assessment of the Skin Sensitization Potential of Chemicals

    PubMed Central

    Wong, Chin Lin; Lam, Ai-Leen; Smith, Maree T.; Ghassabian, Sussan

    2016-01-01

    The direct peptide reactivity assay (DPRA) is a validated method for in vitro assessment of the skin sensitization potential of chemicals. In the present work, we describe a peptide reactivity assay using 96-well plate format and systematically identified the optimal assay conditions for accurate and reproducible classification of chemicals with known sensitizing capacity. The aim of the research is to ensure that the analytical component of the peptide reactivity assay is robust, accurate, and reproducible in accordance with criteria that are used for the validation of bioanalytical methods. Analytical performance was evaluated using quality control samples (QCs; heptapeptides at low, medium, and high concentrations) and incubation of control chemicals (chemicals with known sensitization capacity, weak, moderate, strong, extreme, and non-sensitizers) with each of three synthetic heptapeptides, viz Cor1-C420 (Ac-NKKCDLF), cysteine- (Ac-RFAACAA), and lysine- (Ac-RFAAKAA) containing heptapeptides. The optimal incubation temperature for all three heptapeptides was 25°C. Apparent heptapeptide depletion was affected by vial material composition. Incubation of test chemicals with Cor1-C420, showed that peptide depletion was unchanged in polypropylene vials over 3-days storage in an autosampler but this was not the case for borosilicate glass vials. For cysteine-containing heptapeptide, the concentration was not stable by day 3 post-incubation in borosilicate glass vials. Although the lysine-containing heptapeptide concentration was unchanged in both polypropylene and borosilicate glass vials, the apparent extent of lysine-containing heptapeptide depletion by ethyl acrylate, differed between polypropylene (24.7%) and glass (47.3%) vials. Additionally, the peptide-chemical complexes for Cor1-C420-cinnamaldehyde and cysteine-containing heptapeptide-2, 4-dinitrochlorobenzene were partially reversible during 3-days of autosampler storage. These observations further highlight

  6. Ash particulate formation from pulverized coal under oxy-fuel combustion conditions.

    PubMed

    Jia, Yunlu; Lighty, JoAnn S

    2012-05-01

    Aerosol particulates are generated by coal combustion. The amount and properties of aerosol particulates, specifically size distribution and composition, can be affected by combustion conditions. Understanding the formation of these particles is important for predicting emissions and understanding potential deposition. Oxy-fuel combustion conditions utilize an oxygen-enriched gas environment with CO(2). The high concentration of CO(2) is a result of recycle flue gas which is used to maintain temperature. A hypothesis is that high CO(2) concentration reduces the vaporization of refractory oxides from combustion. A high-temperature drop-tube furnace was used under different oxygen concentrations and CO(2) versus N(2) to study the effects of furnace temperature, coal type, and gas phase conditions on particulate formation. A scanning mobility particle sizer (SMPS) and aerodynamic particle sizer (APS) were utilized for particle size distributions ranging from 14.3 nm to 20 μm. In addition, particles were collected on a Berner low pressure impactor (BLPI) for elemental analysis using scanning electron microscopy and energy dispersive spectroscopy. Three particle size modes were seen: ultrafine (below 0.1 μm), fine (0.1 to 1.0 μm), and coarse (above 1 μm). Ultrafine mass concentrations were directly related to estimated particle temperature, increasing with increasing temperature. For high silicon and calcium coals, Utah Skyline and PRB, there was a secondary effect due to CO(2) and the hypothesized reaction. Illinois #6, a high sulfur coal, had the highest amount of ultrafine mass and most of the sulfur was concentrated in the ultrafine and fine modes. Fine and coarse mode mass concentrations did not show a temperature or CO(2) relationship. (The table of contents graphic and abstract graphic are adapted from ref 27.).

  7. Formation of sulfonyl aromatic alcohols by electrolysis of a bisazo reactive dye.

    PubMed

    Elizalde-González, María P; Arroyo-Abad, Uriel; García-Díaz, Esmeralda; Brillas, Enric; Sirés, Ignasi; Dávila-Jiménez, Martín M

    2012-12-05

    Five sulfonyl aromatic alcohols, namely 4-((2-hydroxyethyl)sulfonyl)phenol, 4-((2-(2-((4-hydroxyphenyl)sulfonyl)ethoxy)vinyl)sulfonyl)phenol, 4-(ethylsulfonyl)phenol, 4-(vinylsulfonyl)phenol and 5-((4-aminophenyl)sulfonyl)-2-penten-1-ol were identified by LC-ESI-Qq-TOF-MS as products formed by electrolysis of the bisazo reactive dye Reactive Black 5 (RB5). Since electrolyses were performed in an undivided cell equipped with Ni electrodes in alkaline medium, amines like 4-(2-methoxyethylsulfonyl)benzene-amine (MEBA) with m/z 216 were also suspected to be formed due to the plausible chemical reaction in the bulk or the cathodic reduction of RB5 and its oxidation by-products. Aiming to check this hypothesis, a method was used for the preparation of MEBA with 98% purity, via chemical reduction also of the dye RB5. The logP of the synthesized sulfonyl aromatic compounds was calculated and their logkw values were determined chromatographically. These data were discussed in regard to the relationship between hydrophobicity/lipophilicity and toxicity.

  8. Reactive oxygen product formation by human neutrophils as an early marker for biocompatibility of dialysis membranes.

    PubMed Central

    Rosenkranz, A R; Templ, E; Traindl, O; Heinzl, H; Zlabinger, G J

    1994-01-01

    Production of reactive oxygen intermediates (ROI) by neutrophils (PMN) in vivo was examined by a whole blood assay using dichlorofluorescein-diacetate (DCFH-DA) in 10 patients each dialysed consecutively with two different dialyser membranes. Haemodialysis (HD) with cuprophan membrane (CM) led to a significantly (P < 0.001) more pronounced ROI production by PMN (2.4 +/- 0.5-fold increase in intracellular oxidation of DCFH-DA) compared with HD with polysulfone membranes (PM; 1.5 +/- 0.2-fold). HD with CM induced a decrease in PMN count by about 90%, whereas PM induced a decrease by only 25% (P < 0.001). In CM patients maximal ROI production coincided with the nadir in PMN count. All patients dialysed with CM showed a clear increase in serum levels of Bb fragments, whereas PM-dialysed patients did not. In this respect, however, no clear time relationship was seen to the kinetics of ROI production, nor to the disappearance of neutrophils from the circulation. Evaluating a direct effect of the dialysis membranes on PMN demonstrated that incubation of neutrophils with hollow fibres of the CM but not of the PM in the absence of plasma induces significant ROI production by PMN. Our study thus indicates that ROI production by PMN during HD correlates to membrane biocompatibility. Furthermore, one might speculate that also independently from but perhaps in addition to complement activation, reactive oxygen products are critically involved in the generation of haemodialysis-associated neutrophil emigration. PMID:7955536

  9. Formation, Reactivity, and Properties of Nondative Late Transition Metal–Oxygen and–Nitrogen Bonds

    PubMed Central

    FULTON, J. ROBIN; HOLLAND, ANDREW W.; FOX, DANIEL J.; BERGMAN*, ROBERT G.

    2005-01-01

    Complexes containing bonds between heteroatoms such as nitrogen and oxygen and “late” transition metals (i.e., those located on the right side of the transition series) have been implicated as reactive intermediates in numerous important catalytic systems. Despite this, our understanding of such M–X linkages still lags behind that of their M–H and M–C analogues. New synthetic strategies have now made possible the isolation and study of a variety of monomeric late-metal alkoxide, aryloxide, and amide complexes, including parent hydroxide and amide species. The heteroatoms in these materials form surprisingly strong bonds to their metal centers, and their bond energies do not necessarily correlate with the energies of the corresponding H–X bonds. The M–X complexes typically exhibit nucleophilic reactivity, in some cases form strong hydrogen bonds to proton donors, and even deprotonate relatively weak acids. These observations, as well as thermodynamic investigations, suggest that late metal–heteroatom bonds are strongly polarized and possess significant ionic character, properties that play an important role in their interactions with organic compounds. PMID:11790088

  10. Silica colloid formation enhances performance of sediment microbial fuel cells in a low conductivity soil.

    PubMed

    Domínguez-Garay, Ainara; Berná, Antonio; Ortiz-Bernad, Irene; Esteve-Núñez, Abraham

    2013-02-19

    The performance of sediment microbial fuel cells (SMFCs) is usually limited by the structure, moisture, and salt content of the soil where they are allocated. Despite the influence of soil, so far most of efforts to improve SMFCs have been limited to the hardware design of the bioelectrochemical device. Our main objective was to enhance performance of SMFCs by stimulating the in situ formation of silica colloids in a low conductivity rice paddy soil. Our results have revealed that the presence of a silica colloid network, described by cryo-SEM analysis, reduced soil resistivity, enhanced ion mobility and consequently enhanced the power production by a factor of 10. Furthermore, our silica-supplemented soil showed better utilization of the electron donor, either acetate or natural rice root exudates, by electrogenic microbial populations. Sustainable manipulation of soil micromorphology using environmentally friendly reagents such as silica offers a novel approach for enhancing the performance of in situ microbial electrochemical applications in low conductivity soils, thus silica colloid geoengineering should be considered as part of future applications of SMFCs.

  11. Formation mechanism of gas bubble superlattice in UMo metal fuels: Phase-field modeling investigation

    SciTech Connect

    Hu, Shenyang; Burkes, Douglas E.; Lavender, Curt A.; Senor, David J.; Setyawan, Wahyu; Xu, Zhijie

    2016-07-08

    Nano-gas bubble superlattices are often observed in irradiated UMo nuclear fuels. However, the for- mation mechanism of gas bubble superlattices is not well understood. A number of physical processes may affect the gas bubble nucleation and growth; hence, the morphology of gas bubble microstructures including size and spatial distributions. In this work, a phase-field model integrating a first-passage Monte Carlo method to investigate the formation mechanism of gas bubble superlattices was devel- oped. Six physical processes are taken into account in the model: 1) heterogeneous generation of gas atoms, vacancies, and interstitials informed from atomistic simulations; 2) one-dimensional (1-D) migration of interstitials; 3) irradiation-induced dissolution of gas atoms; 4) recombination between vacancies and interstitials; 5) elastic interaction; and 6) heterogeneous nucleation of gas bubbles. We found that the elastic interaction doesn’t cause the gas bubble alignment, and fast 1-D migration of interstitials along $\\langle$110$\\rangle$ directions in the body-centered cubic U matrix causes the gas bubble alignment along $\\langle$110$\\rangle$ directions. It implies that 1-D interstitial migration along [110] direction should be the primary mechanism of a fcc gas bubble superlattice which is observed in bcc UMo alloys. Simulations also show that fission rates, saturated gas concentration, and elastic interaction all affect the morphology of gas bubble microstructures.

  12. In situ formation of graphene layers on graphite surfaces for efficient anodes of microbial fuel cells.

    PubMed

    Tang, Jiahuan; Chen, Shanshan; Yuan, Yong; Cai, Xixi; Zhou, Shungui

    2015-09-15

    Graphene can be used to improve the performance of the anode in a microbial fuel cell (MFC) due to its good biocompatibility, high electrical conductivity and large surface area. However, the chemical production and modification of the graphene on the anode are environmentally hazardous because of the use of various harmful chemicals. This study reports a novel method based on the electrochemical exfoliation of a graphite plate (GP) for the in situ formation of graphene layers on the surface of a graphite electrode. When the resultant graphene-layer-based graphite plate electrode (GL/GP) was used as an anode in an MFC, a maximum power density of 0.67 ± 0.034 W/m(2) was achieved. This value corresponds to 1.72-, 1.56- and 1.26-times the maximum power densities of the original GP, exfoliated-graphene-modified GP (EG/GP) and chemically-reduced-graphene-modified GP (rGO/GP) anodes, respectively. Electrochemical measurements revealed that the high performance of the GL/GP anode was attributable to its macroporous structure, improved electron transfer and high electrochemical capacitance. The results demonstrated that the proposed method is a facile and environmentally friendly synthesis technique for the fabrication of high-performance graphene-based electrodes for use in microbial energy harvesting. Copyright © 2015 Elsevier B.V. All rights reserved.

  13. Film formation from aqueous polyurethane dispersions of reactive hydrophobic and hydrophilic components; spectroscopic studies and Monte Carlo simulations.

    PubMed

    Otts, Daniel B; Cueva-Parra, Luis A; Pandey, Ras B; Urban, Marek W

    2005-04-26

    Film formation of waterborne two-component polyurethanes is exceedingly complex due to the heterogeneous nature along with simultaneous progression of several parallel physicochemical processes which include water evaporation, cross-linking reactions, phase separation, and droplet coalescence, to name a few. While internal reflection infrared imaging (IRIRI) spectroscopy clearly facilitates analysis of chemical changes resulting from film formation, the complexity of processes leading to formation of specific surface/interfacial entities is a major experimental challenge. For this reason, we combined a spectrum of surface/interfacial analytical approaches including IRIRI, atomic force microscopy, and attenuated total reflectance Fourier transform infrared spectroscopy with Monte Carlo computer simulations to advance the limited knowledge of how temperature, stoichiometry, concentration levels, and reactivities of individual components affect the development of surface morphologies and compositional gradients across the film thickness. These studies show that in heterogeneous systems having both hydrophobic and hydrophilic components stratification of individual components to the film-air (F-A) interface is ultimately responsible for formation of rough surface topographies. These studies show that simultaneous stratification of hydrophobic components along with water evaporation to the F-A interface results in metastable interfacial layers, leading to surface dewetting. Subsequently, surface roughness is enhanced by higher concentrations of water in the cross-linking film.

  14. Blue-light dependent reactive oxygen species formation by Arabidopsis cryptochrome may define a novel evolutionarily conserved signaling mechanism.

    PubMed

    Consentino, Laurent; Lambert, Stefan; Martino, Carlos; Jourdan, Nathalie; Bouchet, Pierre-Etienne; Witczak, Jacques; Castello, Pablo; El-Esawi, Mohamed; Corbineau, Francoise; d'Harlingue, Alain; Ahmad, Margaret

    2015-06-01

    Cryptochromes are widespread blue-light absorbing flavoproteins with important signaling roles. In plants they mediate de-etiolation, developmental and stress responses resulting from interaction with downstream signaling partners such as transcription factors and components of the proteasome. Recently, it has been shown that Arabidopsis cry1 activation by blue light also results in direct enzymatic conversion of molecular oxygen (O2 ) to reactive oxygen species (ROS) and hydrogen peroxide (H2 O2 ) in vitro. Here we explored whether direct enzymatic synthesis of ROS by Arabidopsis cry1 can play a physiological role in vivo. ROS formation resulting from cry1 expression was measured by fluorescence assay in insect cell cultures and in Arabidopsis protoplasts from cryptochrome mutant seedlings. Cell death was determined by colorimetric assay. We found that ROS formation results from cry1 activation and induces cell death in insect cell cultures. In plant protoplasts, cryptochrome activation results in rapid increase in ROS formation and cell death. We conclude that ROS formation by cryptochromes may indeed be of physiological relevance and could represent a novel paradigm for cryptochrome signaling. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.

  15. Asbestos inhalation induces reactive nitrogen species and nitrotyrosine formation in the lungs and pleura of the rat.

    PubMed Central

    Tanaka, S; Choe, N; Hemenway, D R; Zhu, S; Matalon, S; Kagan, E

    1998-01-01

    To determine whether asbestos inhalation induces the formation of reactive nitrogen species, three groups of rats were exposed intermittently over 2 wk to either filtered room air (sham-exposed) or to chrysotile or crocidolite asbestos fibers. The rats were killed at 1 or 6 wk after exposure. At 1 wk, significantly greater numbers of alveolar and pleural macrophages from asbestos-exposed rats than from sham-exposed rats demonstrated inducible nitric oxide synthase protein immunoreactivity. Alveolar macrophages from asbestos-exposed rats also generated significantly greater nitrite formation than did macrophages from sham-exposed rats. Strong immunoreactivity for nitrotyrosine, a marker of peroxynitrite formation, was evident in lungs from chrysotile- and crocidolite-exposed rats at 1 and 6 wk. Staining was most evident at alveolar duct bifurcations and within bronchiolar epithelium, alveolar macrophages, and the visceral and parietal pleural mesothelium. Lungs from sham-exposed rats demonstrated minimal immunoreactivity for nitrotyrosine. Significantly greater quantities of nitrotyrosine were detected by ELISA in lung extracts from asbestos-exposed rats than from sham-exposed rats. These findings suggest that asbestos inhalation can induce inducible nitric oxide synthase activation and peroxynitrite formation in vivo, and provide evidence of a possible alternative mechanism of asbestos-induced injury to that thought to be induced by Fenton reactions. PMID:9664087

  16. The importance of fuel dissociation and propargyl + allyl association for the formation of benzene in a fuel-rich 1-hexene flame.

    PubMed

    Hansen, N; Li, W; Law, M E; Kasper, T; Westmoreland, P R; Yang, B; Cool, T A; Lucassen, A

    2010-10-14

    Fuel decomposition and benzene formation processes in a premixed, laminar, low-pressure, fuel-rich flame of 1-hexene (C(6)H(12), CH(2)=CH-CH(2)-CH(2)-CH(2)-CH(3)) are investigated by comparing quantitative mole fraction profiles of flame species with kinetic modeling results. The premixed flame, which is stabilized on a flat-flame burner under a reduced pressure of 30 Torr (= 40 mbar), is analyzed by flame-sampling molecular-beam time-of-flight mass spectrometry which uses photoionization by tunable vacuum-ultraviolet synchrotron radiation. The temperature profile of the flame is measured by OH laser-induced fluorescence. The model calculations include the latest rate coefficients for 1-hexene decomposition (J. H. Kiefer et al., J. Phys. Chem. A, 2009, 113, 13570) and for the propargyl (C(3)H(3)) + allyl (a-C(3)H(5)) reaction (J. A. Miller et al., J. Phys. Chem. A, 2010, 114, 4881). The predicted mole fractions as a function of distance from the burner are acceptable and often even in very good agreement with the experimentally observed profiles, thus allowing an assessment of the importance of various fuel decomposition reactions and benzene formation routes. The results clearly indicate that in contrast to the normal reactions of fuel destruction by radical attack, 1-hexene is destroyed mainly by decomposition via unimolecular dissociation forming allyl (a-C(3)H(5)) and n-propyl (n-C(3)H(7)). Minor fuel-consumption pathways include H-abstraction reactions producing various isomeric C(6)H(11) radicals with subsequent β-scissions into C(2), C(3), and C(4) intermediates. The reaction path analysis also highlights a significant contribution through the propargyl (C(3)H(3)) + allyl (a-C(3)H(5)) reaction to the formation of benzene. In this flame, benzene is dominantly formed through H-assisted isomerization of fulvene, which itself is almost exclusively produced by the C(3)H(3) + a-C(3)H(5) reaction.

  17. Synthetic fuel combustion: pollutant formation. Soot initiation mechanisms in burning aromatics. First quarterly report, 19 September-31 December 1980

    SciTech Connect

    Rawlins, W. T.; Tanzawa, T.

    1981-01-01

    Although considerable progress has been made in recent years in understanding the phenomenology of soot formation in the combustion of hydrocarbon fuels, relatively little attention has been focused upon aromatic fuels of the types commonly found in coal liquids. In particular, the effects of gas-phase free radicals, formed during combustion, on the kinetics of formation of incipient soot particles have not been characterized. Accordingly, an experimental investigation of the detailed kinetics of incipient soot formation in the combustion and pyrolysis of aromatic fuels of the benzene, anisole, phenol, and pyrrole families has been initiated in order to determine soot formation mechanisms and rate parameters. The experiments will be performed in a shock tube over the temperature range 1300 to 2500 K, using multiple ultraviolet, visible, and infrared diagnostics to monitor the kinetic behavior of free radicals (such as OH), incipient soot particles, and combustion products. Experiments will be conducted with artificially enhanced concentrations of free radicals such as OH and O to determine their effects on the kinetics of soot and soot precursors. The experimental work will be supported and directed by a parallel analytical effort using a detailed mechanistic model of the chemical kinetics and dynamics of the reacting systems. In this report, the design and configuration of the experimental apparatus are described, the details of the kinetic model are outlined, and possible reaction pathways are discussed.

  18. In Situ Imaging of Particle Formation and Dynamics in Reactive Material Deflagrations

    SciTech Connect

    Sullivan, Kyle T.

    2016-12-12

    Reactive composites utilizing nanoparticles have been the topic of extensive research in the past two decades. The driver for this is that, as the particle size is decreased, the mixing scale between constituents is greatly reduced, which has long thought to increase the rate of chemical reaction. While a general trend of increased reactivity has been seen for metal / metal oxide, or thermite, reactive materials, some results have demonstrated diminishing returns as the particle size is further decreased. Recent results have shown that nanoparticles, which are typically aggregates of several primary particles, can undergo very rapid coalescence to form micron particles once a critical temperature is reached. Experiments on this topic to date have been performed on very small sample masses, and sometimes under vacuum; conditions which are not representative of the environment during a deflagration. In this feasibility study, a custom burn tube was used to ignite and react 100 mg powdered thermite samples in long acrylic tubes. X-ray imaging at APS Sector 32 was performed to image the particle field as a function of distance and time as the rarefied particle cloud expanded and flowed down the tube. Five different thermite formulations were investigated, Al / CuO, Al / Fe2O3, Al / SnO2, Al / WO3, and Al / Fe2O3, along with Al / CuO formulations with different sizes of Al particles ranging from 80 nm to approximate 10 μm. The results clearly show that the sample powder reacts and unloads into a distribution of larger micron-scale particles (~5-500 μm), which continue to react and propagate as the particle-laden stream flows down the tube. This was the first direct imaging of the particle field during a thermite deflagration, and gives significant insight into the evolution of reactants to products. Analysis of phase is currently being pursued to determine whether this method can be used to extract

  19. Characteristics of Reactive Ni3Sn4 Formation and Growth in Ni-Sn Interlayer Systems

    NASA Astrophysics Data System (ADS)

    Lis, Adrian; Kenel, Christoph; Leinenbach, Christian

    2016-06-01

    The near-isothermal growth and formation of Ni3Sn4 intermetallic compounds (IMC) in Ni-Sn interlayer systems was studied in the solid state at 473 K (200 °C) and under solid-liquid conditions at 523 and 573 K (250 °C and 300 °C) from an initial state of a few seconds. Scalloped solid-state IMC formation was mainly driven by grain boundary diffusion of Ni through the IMC layer combined with the grain coarsening of the IMC layer. Under solid-liquid conditions, the formation of faceted and needle-shaped Ni3Sn4 grains as well as an atypical IMC growth behavior with similar parabolic growth constants for 523 K and 573 K (250 °C and 300 °C) was observed within the first 180 seconds of the holding time, and IMC growth occurred as an isothermal solidification from the Ni-saturated Sn melt. Due to the progressive densification of the IMC layer and the diffusion-controlled growth, the kinetics slowed down by approximately one order of magnitude after 180 seconds of annealing. The final stage was characterized by the formation of IMC islands ahead of the interfacial Ni3Sn4 layer. Needle-like IMC growth was effectively suppressed under combined solid-state and solid-liquid conditions. Textured Ni3Sn4 IMC formation at the Ni-Sn interface was approved with pole figure measurements. The activation energy Q for solid-liquid IMC formation was calculated as 43.3 kJ/mol, and processing maps for IMC growth and Sn consumption were derived as functions of temperature and time, respectively.

  20. Long term deposit formation in aviation turbine fuel at elevated temperature

    NASA Technical Reports Server (NTRS)

    Giovanetti, A. J.; Szetela, E. J.

    1986-01-01

    An experimental characterization is conducted for the relationships between deposit mass, operating time, and temperature, in coking associated with aviation fuels under conditions simulating those typical of turbine engine fuel systems. Jet A and Suntech A fuels were tested in stainless steel tubing heated to 420-750 K, over test durations of between 3 and 730 hr and at fuel velocities of 0.07-1.3 m/sec. Deposit rates are noted to be a strong function of tube temperature; for a given set of test conditions, deposition rates for Suntech A exceed those of Jet A by a factor of 10. Deposition rates increased markedly with test duration for both fuels. The heated tube data obtained are used to develop a global chemical kinetic model for fuel oxidation and carbon deposition.

  1. Long term deposit formation in aviation turbine fuel at elevated temperature

    NASA Technical Reports Server (NTRS)

    Giovanetti, A. J.; Szetela, E. J.

    1986-01-01

    An experimental characterization is conducted for the relationships between deposit mass, operating time, and temperature, in coking associated with aviation fuels under conditions simulating those typical of turbine engine fuel systems. Jet A and Suntech A fuels were tested in stainless steel tubing heated to 420-750 K, over test durations of between 3 and 730 hr and at fuel velocities of 0.07-1.3 m/sec. Deposit rates are noted to be a strong function of tube temperature; for a given set of test conditions, deposition rates for Suntech A exceed those of Jet A by a factor of 10. Deposition rates increased markedly with test duration for both fuels. The heated tube data obtained are used to develop a global chemical kinetic model for fuel oxidation and carbon deposition.

  2. Reactive transport model of the formation of oxide-type Ni-laterite profiles (Punta Gorda, Moa Bay, Cuba)

    NASA Astrophysics Data System (ADS)

    Domènech, Cristina; Galí, Salvador; Villanova-de-Benavent, Cristina; Soler, Josep M.; Proenza, Joaquín A.

    2017-01-01

    Oxide-type Ni-laterite deposits are characterized by a dominant limonite zone with goethite as the economically most important Ni ore mineral and a thin zone of hydrous Mg silicate-rich saprolite beneath the magnesium discontinuity. Fe, less soluble, is mainly retained forming goethite, while Ni is redeposited at greater depth in a Fe(III) and Ni-rich serpentine (serpentine II) or in goethite, where it adsorbs or substitutes for Fe in the mineral structure. Here, a 1D reactive transport model, using CrunchFlow, of Punta Gorda oxide-type Ni-laterite deposit (Moa Bay, Cuba) formation is presented. The model reproduces the formation of the different laterite horizons in the profile from an initial, partially serpentinized peridotite, in 106 years, validating the conceptual model of the formation of this kind of deposits in which a narrow saprolite horizon rich in Ni-bearing serpentine is formed above peridotite parent rock and a thick limonite horizon is formed over saprolite. Results also confirm that sorption of Ni onto goethite can explain the weight percent of Ni found in the Moa goethite. Sensitivity analyses accounting for the effect of key parameters (composition, dissolution rate, carbonate concentration, quartz precipitation) on the model results are also presented. It is found that aqueous carbonate concentration and quartz precipitation significantly affects the laterization process rate, while the effect of the composition of secondary serpentine or of mineral dissolution rates is minor. The results of this reactive transport modeling have proven useful to validate the conceptual models derived from field observations.

  3. Formation of silicon nanostructures with a combination of spacer technology and deep reactive ion etching

    PubMed Central

    2012-01-01

    A new method of fabricating high aspect ratio nanostructures in silicon without the use of sub-micron lithographic technique is reported. The proposed method comprises two important steps including the use of CMOS spacer technique to form silicon nitride nanostructure masking followed by deep reactive ion etching (DRIE) of the silicon substrate to form the final silicon nanostructures. Silicon dioxide is used as the sacrificial layer to form the silicon nitride nanostructures. With DRIE a high etch selectivity of 50:1 between silicon and silicon nitride was achieved. The use of the spacer technique is particularly advantageous where self-aligned nanostructures with potentially unlimited lengths are formed without the need of submicron lithographic tools and resist materials. With this method, uniform arrays of 100 nm silicon nanostructures which are at least 4 μm tall with aspect ratio higher than 40 were successfully fabricated. PMID:22672745

  4. Formation and chemical reactivity of carbon fibers prepared by defluorination of graphite fluoride

    NASA Technical Reports Server (NTRS)

    Hung, Ching-Cheh

    1994-01-01

    Defluorination of graphite fluoride (CFX) by heating to temperatures of 250 to 450 C in chemically reactive environments was studied. This is a new and possibly inexpensive process to produce new carbon-based materials. For example, CF 0.68 fibers, made from P-100 carbon fibers, can be defluorinated in BrH2C-CH = CH-CH2Br (1,4-dibromo-2butene) heated to 370 C, and graphitized to produce fibers with an unusually high modulus and a graphite layer structure that is healed and cross-linked. Conversely, a sulfur-doped, visibly soft carbon fiber was produced by defluorinating CF 0.9 fibers, made from P-25, in sulfur (S) vapor at 370 C and then heating to 660 C in nitrogen (N2). Furthermore, defluorination of the CF 0.68 fibers in bromine (Br2) produced fragile, structurally damaged carbon fibers. Heating these fragile fibers to 1100 C in N2 caused further structural damage, whereas heating to 150 C in bromoform (CHBr3) and then to 1100 C in N2 healed the structural defects. The defluorination product of CFX, tentatively called activated graphite, has the composition and molecular structure of graphite, but is chemically more reactive. Activated graphite is a scavenger of manganese (Mn), and can be intercalated with magnesium (Mg). Also, it can easily collect large amounts of an alloy made from copper (Cu) and type 304 stainless steel to form a composite. Finally, there are indications that activated graphite can wet metals or ceramics, thereby forming stronger composites with them than the pristine carbon fibers can form.

  5. Shock tube study of the fuel structure effects on the chemical kinetic mechanisms responsible for soot formation, part 2

    NASA Technical Reports Server (NTRS)

    Frenklach, M.; Clary, D. W.; Ramachandra, M. K.

    1985-01-01

    Soot formation in oxidation of allene, 1,3-butadiene, vinylacetylene and chlorobenzene and in pyrolysis of ethylene, vinylacetylene, 1-butene, chlorobenzene, acetylen-hydrogen, benzene-acetylene, benzene-butadiene and chlorobenzene-acetylene argon-diluted mixtures was studied behind reflected shock waves. The results are rationalized within the framework of the conceptual models. It is shown that vinylacetylene is much less sooty than allene, which indicates that conjugation by itself is not a sufficient factor for determining the sooting tendency of a molecule. Structural reactivity in the context of the chemical kinetics is the dominant factor in soot formation. Detailed chemical kinetic modeling of soot formation in pyrolysis of acetylene is reported. The main mass growth was found to proceed through a single dominant route composed of conventional radical reactions. The practically irreversible formation reactions of the fused polycyclic aromatics and the overshoot by hydrogen atom over its equilibrium concentration are the g-driving kinetic forces for soot formation.

  6. Probability density function of non-reactive solute concentration in heterogeneous porous formations

    Treesearch

    Alberto Bellin; Daniele Tonina

    2007-01-01

    Available models of solute transport in heterogeneous formations lack in providing complete characterization of the predicted concentration. This is a serious drawback especially in risk analysis where confidence intervals and probability of exceeding threshold values are required. Our contribution to fill this gap of knowledge is a probability distribution model for...

  7. Role of sulfonation in the stability, reactivity, and selectivity of poly(ether imide) used to develop ion exchange membranes: DFT study with application to fuel cells.

    PubMed

    López-Chávez, Ernesto; Peña-Castañeda, Yésica A; de la Portilla-Maldonado, L César; Guzmán-Pantoja, Javier; Martínez-Magadán, José Manuel; Oviedo-Roa, Raúl; de Landa Castillo-Alvarado, Fray; Cruz-Torres, Armando

    2014-07-01

    The design of polymer electrolyte membranes for fuel cells must satisfy two equally important fundamental principles: optimization of the reactivity and the selectivity in order to improve the ion transport properties of the membrane as well as its long-term stability in the hydrated state at high temperature (above 100 °C). A study utilizing density functional theory (DFT) to elucidate the effect of the degree of sulfonation on the chemical stability, reactivity, and selectivity of poly(ether imide) (PEI), which allows the ionic transport properties of the membrane to be predicted, is reported here. Sulfonated poly(ether imide) (SPEI) structures with (-SO3H) n (n = 1-6) groups were built and optimized in order to calculate the above properties as functions of the number of sulfonyl groups. A comparative study demonstrated that the SPEI with four sulfonyl groups in its backbone is the polymer with the properties best suited for use in fuel cells.

  8. Combustion characteristics and air pollutant formation during oxy-fuel co-combustion of microalgae and lignite.

    PubMed

    Gao, Yuan; Tahmasebi, Arash; Dou, Jinxiao; Yu, Jianglong

    2016-05-01

    Oxy-fuel combustion of solid fuels is seen as one of the key technologies for carbon capture to reduce greenhouse gas emissions. The combustion characteristics of lignite coal, Chlorella vulgaris microalgae, and their blends under O2/N2 and O2/CO2 conditions were studied using a Thermogravimetric Analyzer-Mass Spectroscopy (TG-MS). During co-combustion of blends, three distinct peaks were observed and were attributed to C. vulgaris volatiles combustion, combustion of lignite, and combustion of microalgae char. Activation energy during combustion was calculated using iso-conventional method. Increasing the microalgae content in the blend resulted in an increase in activation energy for the blends combustion. The emissions of S- and N-species during blend fuel combustion were also investigated. The addition of microalgae to lignite during air combustion resulted in lower CO2, CO, and NO2 yields but enhanced NO, COS, and SO2 formation. During oxy-fuel co-combustion, the addition of microalgae to lignite enhanced the formation of gaseous species.

  9. Reactivity of Iron-bearing Minerals in Deep Saline Formations subjected to Carbon Injection

    NASA Astrophysics Data System (ADS)

    Schoonen, M. A.; Sklute, E. C.; Strongin, D. R.; Dyar, M. D.

    2013-12-01

    Deep saline aquifers are being considered as repositories for captured CO2. Here the influence of co-injected hydrogen sulfide and sulfur dioxide on the reactivity of hematite-bearing sandstones was evaluated as a function of salt content and water/rock ratio. The reactivity of the Triassic Moenkopi red sandstone under scCO2-dominated conditions (supercritical fluid around the point of injection) and water-dominated conditions (aqueous phase influenced by the injection of scCO2) was studied. Flow-through experiments were used to simulate scCO2-dominated conditions. Crushed sandstone packed in a column was exposed to a co-mingled stream of supercritical CO2 and an aqueous H2S or SO2 solution (75°C). Batch experiments to simulate water-dominated conditions were conducted in small autoclaves that were loaded with crushed sandstone, a small amount of water, and dry ice before to 75°C. The role of water/rock ratio was explored by conducting experiments at a water/rock ratio of 4.3/1 and 1.4/1. The reacted sandstones were recovered at the conclusion of each type of experiment and analyzed for changes in mineralogical composition using X-ray Diffraction. Selected reaction products were also studied using Mössbauer spectroscopy, FTIR, and Visible Near Infrared (VNIR) spectroscopy. The results of the flow through experiments, simulating scCO2-dominated conditions, showed no changes in the iron mineralogy of the sand, regardless of whether pure scCO2 or scCO2 co-mingled with SO2 or H2S was used. By contrast, batch experiments, simulating water-dominated conditions, showed significant changes in iron mineralogy. The presence of sulfide led to the conversion of the hematite component in the sandstone to pyrite at all salt concentrations (0-6M NaCl). In experiments with sulfide and sulfite, siderite and pyrite formed, but siderite was favored at higher salinity and lower water/rock ratio. Availability of water at the mineral surface might be a critical factor in the

  10. Heat-induced formation of reactive oxygen species and 8-oxoguanine, a biomarker of damage to DNA

    PubMed Central

    Bruskov, Vadim I.; Malakhova, Lyudmila V.; Masalimov, Zhaksylyk K.; Chernikov, Anatoly V.

    2002-01-01

    Heat-induced formation of 8-oxoguanine was demonstrated in DNA solutions in 10–3 M phosphate buffer, pH 6.8, by enzyme-linked immunosorbent assays using monoclonal antibodies against 8-oxoguanine. A radiation-chemical yield of 3.7 × 10–2 µmol J–1 for 8-oxoguanine production in DNA upon γ-irradiation was used as an adequate standard for quantitation of 8-oxoguanine in whole DNA. The initial yield of heat-induced 8-oxoguanine exhibits first order kinetics. The rate constants for 8-oxoguanine formation were determined at elevated temperatures; the activation energy was found to be 27 ± 2 kcal/mol. Extrapolation to 37°C gave a value of k37 = 4.7 × 10–10 s–1. Heat-induced 8-oxoguanine formation and depurination of guanine and adenine show similarities of the processes, which implies that heat-mediated generation of reactive oxygen species (ROS) should occur. Heat-induced production of H2O2 in phosphate buffer was shown. The sequence of reactions of thermally mediated ROS formation have been established: activation of dissolved oxygen to the singlet state, generation of superoxide radicals and their dismutation to H2O2. Gas saturation (O2, N2 and Ar), D2O, scavengers of 1O2, O2–• and OH• radicals and metal chelators influenced heat-induced 8-oxoguanine formation as they affected thermal ROS generation. These findings imply that heat acts via ROS attack leading to oxidative damage to DNA. PMID:11884633

  11. Highly reactive {001} facets of TiO2-based composites: synthesis, formation mechanism and characterization.

    PubMed

    Ong, Wee-Jun; Tan, Lling-Lling; Chai, Siang-Piao; Yong, Siek-Ting; Mohamed, Abdul Rahman

    2014-02-21

    Titanium dioxide (TiO2) is one of the most widely investigated metal oxides due to its extraordinary surface, electronic and catalytic properties. However, the large band gap of TiO2 and massive recombination of photogenerated electron-hole pairs limit its photocatalytic and photovoltaic efficiency. Therefore, increasing research attention is now being directed towards engineering the surface structure of TiO2 at the most fundamental and atomic level namely morphological control of {001} facets in the range of microscale and nanoscale to fine-tune its physicochemical properties, which could ultimately lead to the optimization of its selectivity and reactivity. The synthesis of {001}-faceted TiO2 is currently one of the most active interdisciplinary research areas and demonstrations of catalytic enhancement are abundant. Modifications such as metal and non-metal doping have also been extensively studied to extend its band gap to the visible light region. This steady progress has demonstrated that TiO2-based composites with {001} facets are playing and will continue to play an indispensable role in the environmental remediation and in the search for clean and renewable energy technologies. This review encompasses the state-of-the-art research activities and latest advancements in the design of highly reactive {001} facet-dominated TiO2via various strategies, including hydrothermal/solvothermal, high temperature gas phase reactions and non-hydrolytic alcoholysis methods. The stabilization of {001} facets using fluorine-containing species and fluorine-free capping agents is also critically discussed in this review. To overcome the large band gap of TiO2 and rapid recombination of photogenerated charge carriers, modifications are carried out to manipulate its electronic band structure, including transition metal doping, noble metal doping, non-metal doping and incorporating graphene as a two-dimensional (2D) catalyst support. The advancements made in these aspects are

  12. THE INFLUENCE OF CARBON BURNOUT ON SUBMICRON PARTICLE FORMATION FROM EMULSIFIED FUEL OIL COMBUSTION

    EPA Science Inventory

    The paper gives results of an examination of particle behavior and particle size distributions from the combustion of different fuel oils and emulsified fuels in three experimental combusators. Results indicate that improved carbon (C) burnout from fule oil combustion, either by...

  13. THE INFLUENCE OF CARBON BURNOUT ON SUBMICRON PARTICLE FORMATION FROM EMULSIFIED FUEL OIL COMBUSTION

    EPA Science Inventory

    The paper gives results of an examination of particle behavior and particle size distributions from the combustion of different fuel oils and emulsified fuels in three experimental combusators. Results indicate that improved carbon (C) burnout from fule oil combustion, either by...

  14. Formation of oxides of nitrogen in monodisperse spray combustion of hydrocarbon fuels

    NASA Technical Reports Server (NTRS)

    Nizami, A. A.; Singh, S.; Cernansky, N. P.

    1982-01-01

    Experimental results of exit plane NO/NO(x) emissions from atmospheric monodisperse fuel spray combustion are presented. Six different hydrocarbon fuels were studied: isopropanol, n-propanol, n-octane, iso-octane, n-heptane and methanol. The results indicate an optimum droplet size for minimizing NO/NO(x) production for all of the test fuels. At the optimum droplet diameter, reductions in NO/NO(x) relative to the NO(x) occurred at droplet diameters of 55 and 48 microns respectively, as compared to a 50-micron droplet size for isopropanol. The occurrence of the minimum NO(x) point at different droplet diameters for the different fuels appears to be governed by the extent of prevaporization of the fuel in the spray, and is consistent with theoretical calculations based on each fuel's physical properties. Estimates are also given for the behavior of heavy fuels and of polydisperse fuel sprays in shifting the minimum NO(x) point compared to a monodisperse situation.

  15. Resveratrol inhibits foam cell formation via NADPH oxidase 1-mediated reactive oxygen species and monocyte chemotactic protein-1

    PubMed Central

    Park, Dae-Weon; Baek, Kheewoong; Kim, Jae-Ryong; Lee, Jae-Jin; Ryu, Sang-Ho; Chin, Byung-Rho

    2009-01-01

    Resveratrol is a polyphenolic compound in red wine that has anti-oxidant and cardioprotective effects in animal models. Reactive oxygen species (ROS) and monocyte chemotactic protein-1 (MCP-1) play key roles in foam cell formation and atherosclerosis. We studied LPS-mediated foam cell formation and the effect of resveratrol. Resveratrol pretreatment strongly suppressed LPS-induced foam cell formation. To determine if resveratrol affected the expression of genes that control ROS generation in macrophages, NADPH oxidase 1 (Nox1) was measured. Resveratrol treatment of macrophages inhibited LPS-induced Nox1 expression as well as ROS generation, and also suppressed LPS-induced MCP-1 mRNA and protein expression. We investigated the upstream targets of Nox1 and MCP-1 expression and found that Akt-forkhead transcription factors of the O class (FoxO3a) is an important signaling pathway that regulates both genes. These inhibitory effects of resveratrol on Nox1 expression and MCP-1 production may target to the Akt and FoxO3a signaling pathways. PMID:19293636

  16. Hematin−Hematin Self-Association States Involved in the Formation and Reactivity of the Malaria Parasite Pigment, Hemozoin

    SciTech Connect

    Klonis, Nectarios; Dilanian, Ruben; Hanssen, Eric; Darmanin, Connie; Streltsov, Victor; Deed, Samantha; Quiney, Harry; Tilley, Leann

    2010-10-22

    The malaria parasite pigment, hemozoin, is a crystal of ferriprotoporphyrin IX (FP-Fe(III)), a product of hemoglobin digestion. Hemozoin formation is essential for FP-Fe(III) detoxification in the parasite; it is the main target of quinoline antimalarials and can modulate immune and inflammation responses. To gain further insight into the likely mechanisms of crystal formation and hemozoin reactivity, we have reanalyzed the crystal structure data for {beta}-hematin and solved the crystal structure of Plasmodium falciparum hemozoin. The analysis reveals that the structures are very similar and highlights two previously unexplored modes of FP-Fe(III) self-association involving {pi}-{pi} interactions that may initiate crystal formation and help to stabilize the extended structure. Hemozoin can be considered to be a crystal composed of {pi}-{pi} dimers stabilized by iron-carboxylate linkages. As a result, it is predicted that two surfaces of the crystal would consist of {pi}-{pi} dimers with Fe(III) partly exposed to solvent and capable of undergoing redox reactions. Accordingly, we demonstrate that the crystal possesses both general peroxidase activity and the ability to cause lipid oxidation.

  17. Reactive oxygen species formation and bystander effects in gradient irradiation on human breast cancer cells

    PubMed Central

    Rong, Yi; Lee, Shin Hee; Wu, Shiyong; Zuo, Li

    2016-01-01

    Ionizing radiation (IR) in cancer radiotherapy can induce damage to neighboring cells via non-targeted effects by irradiated cells. These so-called bystander effects remain an area of interest as it may provide enhanced efficacy in killing carcinomas with minimal radiation. It is well known that reactive oxygen species (ROS) are ubiquitous among most biological activities. However, the role of ROS in bystander effects has not been thoroughly elucidated. We hypothesized that gradient irradiation (GI) has enhanced therapeutic effects via the ROS-mediated bystander pathways as compared to uniform irradiation (UI). We evaluated ROS generation, viability, and apoptosis in breast cancer cells (MCF-7) exposed to UI (5 Gy) or GI (8–2 Gy) in radiation fields at 2, 24 and 48 h after IR. We found that extracellular ROS release induced by GI was higher than that by UI at both 24 h (p < 0.001) and 48 h (p < 0.001). More apoptosis and less viability were observed in GI when compared to UI at either 24 h or 48 h after irradiation. The mean effective doses (ED) of GI were ~130% (24 h) and ~48% (48 h) higher than that of UI, respectively. Our results suggest that GI is superior to UI regarding redox mechanisms, ED, and toxic dosage to surrounding tissues. PMID:27223435

  18. The epigenetic landscape related to reactive oxygen species formation in the cardiovascular system.

    PubMed

    Kietzmann, Thomas; Petry, Andreas; Shvetsova, Antonina; Gerhold, Joachim M; Görlach, Agnes

    2017-06-01

    Cardiovascular diseases are among the leading causes of death worldwide. Reactive oxygen species (ROS) can act as damaging molecules but also represent central hubs in cellular signalling networks. Increasing evidence indicates that ROS play an important role in the pathogenesis of cardiovascular diseases, although the underlying mechanisms and consequences of pathophysiologically elevated ROS in the cardiovascular system are still not completely resolved. More recently, alterations of the epigenetic landscape, which can affect DNA methylation, post-translational histone modifications, ATP-dependent alterations to chromatin and non-coding RNA transcripts, have been considered to be of increasing importance in the pathogenesis of cardiovascular diseases. While it has long been accepted that epigenetic changes are imprinted during development or even inherited and are not changed after reaching the lineage-specific expression profile, it becomes more and more clear that epigenetic modifications are highly dynamic. Thus, they might provide an important link between the actions of ROS and cardiovascular diseases. This review will provide an overview of the role of ROS in modulating the epigenetic landscape in the context of the cardiovascular system. This article is part of a themed section on Redox Biology and Oxidative Stress in Health and Disease. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.12/issuetoc. © 2017 The British Pharmacological Society.

  19. Neutrophil myeloperoxidase and its substrates: formation of specific markers and reactive compounds during inflammation

    PubMed Central

    Kato, Yoji

    2016-01-01

    Myeloperoxidase is an inflammatory enzyme that generates reactive hypochlorous acid in the presence of hydrogen peroxide and chloride ion. However, this enzyme also uses bromide ion or thiocyanate as a substrate to form hypobromous or hypothiocyanous acid, respectively. These species play important roles in host defense against the invasion of microorganisms. In contrast, these enzyme products modify biomolecules in hosts during excess inflammation, indicating that the action of myeloperoxidase is both beneficial and harmful. Myeloperoxidase uses other endogenous compounds, such as serotonin, urate, and l-tyrosine, as substrates. This broad-range specificity may have some biological implications. Target molecules of this enzyme and its products vary, including low-molecular weight thiols, proteins, nucleic acids, and lipids. The modified products represent biomarkers of myeloperoxidase action. Moderate inhibition of this enzyme might be critical for the prevention/modulation of excess, uncontrolled inflammatory events. Some phytochemicals inhibit myeloperoxidase, which might explain the reductive effect caused by the intake of vegetables and fruits on cardiovascular diseases. PMID:27013775

  20. Cold stress increases reactive oxygen species formation via TRPA1 activation in A549 cells.

    PubMed

    Sun, Wenwu; Wang, Zhonghua; Cao, Jianping; Cui, Haiyang; Ma, Zhuang

    2016-03-01

    Reactive oxygen species (ROS) are responsible for lung damage during inhalation of cold air. However, the mechanism of the ROS production induced by cold stress in the lung is still unclear. In this work, we measured the changes of ROS and the cytosolic Ca(2+) concentration ([Ca(2+)]c) in A549 cell. We observed that cold stress (from 20 to 5 °C) exposure of A549 cell resulted in an increase of ROS and [Ca(2+)]c, which was completely attenuated by removing Ca(2+) from medium. Further experiments showed that cold-sensing transient receptor potential subfamily member 1 (TRPA1) agonist (allyl isothiocyanate, AITC) increased the production of ROS and the level of [Ca(2+)]c in A549 cell. Moreover, HC-030031, a TRPA1 selective antagonist, significantly inhibited the enhanced ROS and [Ca(2+)]c induced by AITC or cold stimulation, respectively. Taken together, these data demonstrated that TRPA1 activation played an important role in the enhanced production of ROS induced by cold stress in A549 cell.

  1. Superparamagnetic iron oxide nanoparticles as radiosensitizer via enhanced reactive oxygen species formation

    SciTech Connect

    Klein, Stefanie; Sommer, Anja; Distel, Luitpold V.R.; Neuhuber, Winfried; Kryschi, Carola

    2012-08-24

    Highlights: Black-Right-Pointing-Pointer Ultrasmall citrate-coated SPIONs with {gamma}Fe{sub 2}O{sub 3} and Fe{sub 3}O{sub 4} structure were prepared. Black-Right-Pointing-Pointer SPIONs uptaken by MCF-7 cells increase the ROS production for about 240%. Black-Right-Pointing-Pointer The SPION induced ROS production is due to released iron ions and catalytically active surfaces. Black-Right-Pointing-Pointer Released iron ions and SPION surfaces initiate the Fenton and Haber-Weiss reaction. Black-Right-Pointing-Pointer X-ray irradiation of internalized SPIONs leads to an increase of catalytically active surfaces. -- Abstract: Internalization of citrate-coated and uncoated superparamagnetic iron oxide nanoparticles by human breast cancer (MCF-7) cells was verified by transmission electron microscopy imaging. Cytotoxicity studies employing metabolic and trypan blue assays manifested their excellent biocompatibility. The production of reactive oxygen species in iron oxide nanoparticle loaded MCF-7 cells was explained to originate from both, the release of iron ions and their catalytically active surfaces. Both initiate the Fenton and Haber-Weiss reaction. Additional oxidative stress caused by X-ray irradiation of MCF-7 cells was attributed to the increase of catalytically active iron oxide nanoparticle surfaces.

  2. Higher platelet reactivity and platelet-monocyte complex formation in Gram-positive sepsis compared to Gram-negative sepsis.

    PubMed

    Tunjungputri, Rahajeng N; van de Heijden, Wouter; Urbanus, Rolf T; de Groot, Philip G; van der Ven, Andre; de Mast, Quirijn

    2016-12-29

    Platelets may play a role in the high risk for vascular complications in Gram-positive sepsis. We compared the platelet reactivity of 15 patients with Gram-positive sepsis, 17 with Gram-negative sepsis and 20 healthy controls using a whole blood flow cytometry-based assay. Patients with Gram-positive sepsis had the highest median fluorescence intensity (MFI) of the platelet membrane expression of P-selectin upon stimulation with high dose adenosine diphosphate (ADP; P = 0.002 vs. Gram-negative and P = 0.005 vs. control groups) and cross-linked collagen-related peptide (CRP-XL; P = 0.02 vs. Gram-negative and P = 0.0001 vs. control groups). The Gram-positive group also demonstrated significantly higher ADP-induced fibrinogen binding (P = 0.001), as wll as platelet-monocyte complex formation (P = 0.02), compared to the Gram-negative group and had the highest plasma levels of platelet factor 4, β-thromboglobulin and soluble P-selectin. In contrast, thrombin-antithrombin complex and C-reactive protein levels were comparable in both patient groups. In conclusion, common Gram-positive pathogens induce platelet hyperreactivity, which may contribute to a higher risk for vascular complications.

  3. Reactive uptake of Isoprene-derived epoxydiols to submicron aerosol particles: implications for IEPOX lifetime and SOA formation

    NASA Astrophysics Data System (ADS)

    Thornton, J. A.; Gaston, C.; Riedel, T.; Zhang, Z.; Gold, A.; Surratt, J. D.

    2014-12-01

    The reactive uptake of isoprene-derived epoxydiols (IEPOX) is thought to be a significant source of atmospheric secondary organic aerosol (SOA). However, the IEPOX reaction probability (γIEPOX) and its dependence upon particle composition remain poorly constrained. We report measurements of γIEPOX for trans-b-IEPOX, the predominant IEPOX isomer, on submicron particles as a function of composition, acidity, and relative humidity (RH). Particle acidity had the strongest effect. γIEPOX is more than 500 times larger on ammonium bisulfate (γ ~ 0.05) than on ammonium sulfate (γ ≤ 1 x 10-4). We could accurately predict γIEPOX using an acid-catalyzed, epoxide ring-opening mechanism and a high Henry's law coefficient (1.6 x 108 M/atm). Suppression of γIEPOX was observed in particles containing both ammonium bisulfate and polyethylene glycol (PEG-300), likely due to diffusion and solubility limitations within a PEG-300 coating, suggesting that IEPOX uptake could be self-limiting. Using the measured uptake kinetics, the predicted atmospheric lifetime of IEPOX is a few hours in the presence of highly acidic particles (pH < 0), but is greater than a day on less acidic particles (pH > 3). We connect these net reactive uptake measurements to chamber studies of the SOA yield from IEPOX multiphase chemistry and discuss the implications of these findings for modeling the anthropogenic influence upon SOA formation from isoprene.

  4. Reactive mercury in the troposphere: Model formation and results for Florida, the northeastern United States, and the Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Sillman, Sanford; Marsik, Frank J.; Al-Wali, Khalid I.; Keeler, Gerald J.; Landis, Matthew S.

    2007-12-01

    We describe the development of a model for transport and photochemistry of atmospheric mercury at the regional scale, along with an application to the eastern United States and adjacent Atlantic Ocean and Gulf of Mexico, and comparison with aircraft-based measurements in Florida. The model is the Community Multiscale Air Quality model (CMAQ) with modifications to include an integrated solution for gas phase and aqueous photochemistry. The expanded chemistry includes O3, NOx, organics, sulfur, halogens and mercury. Divalent reactive gaseous mercury (RGM) is formed slowly through gas phase reactions and removed rapidly by aqueous reactions in cloud water. Model results show that elevated RGM (up to 260 pg m-3) forms intermittently over the Atlantic Ocean in air masses that have a cloud-free history. Aircraft measurements in Florida show RGM varying between 10 and 250 pg m-3 and increasing with altitude, a pattern that is consistent with model results. Ambient RGM would increase by 50% if aqueous reduction reactions were omitted. The model predicts that ambient elemental mercury and RGM anticorrelate in regions where RGM is produced photochemically and correlate in regions dominated by direct emissions. Model results also suggest positive correlations between RGM and SO2, reactive nitrogen and H2O2, which may be used to identify photochemically produced versus directly emitted RGM. RGM in the model is strongly correlated with O3 during pollution events, and ozone formation from anthropogenic precursors is predicted to cause a significant increase in RGM.

  5. Formation of copper oxychloride and reactive oxygen species as causes of uterine injury during copper oxidation of Cu-IUD.

    PubMed

    Beltran-Garcia, M J; Espinosa, A; Herrera, N; Perez-Zapata, A J; Beltran-Garcia, C; Ogura, T

    2000-02-01

    The lining of the uterus and cervix might be injured by a variety of oxidation products of Cu in a Cu-IUD, including cuprous ions, dissolved and precipitated cupric ions, and reactive oxygen species such as superoxide radicals, hydrogen peroxide, and hydroxyl radicals. In this study, the human amnious WISH cell line was employed as a model of uterine cells in the presence of copper. The cell viability was decreased by elemental copper, which was alleviated up to 70% by the addition of catalase. The addition of copper oxychloride caused cell death in a dose-dependent manner. Hydroxyl radicals in the presence of copper were determined by the formation of malondialdehyde. Soluble cuprous chloride complexes are formed in the uterus by slowly entering oxygen. The complexes are partly oxidized to insoluble copper oxychloride. which damages the endometrium. Unoxidized cuprous ions migrate to the oxygen-rich cervix and are oxidized to copper oxychloride, causing cervix damage.

  6. Reactive magnetron sputtering of Cu2O: Dependence on oxygen pressure and interface formation with indium tin oxide

    NASA Astrophysics Data System (ADS)

    Deuermeier, Jonas; Gassmann, Jürgen; Brötz, Joachim; Klein, Andreas

    2011-06-01

    Thin films of copper oxides were prepared by reactive magnetron sputtering and structural, morphological, chemical, and electronic properties were analyzed using x-ray diffraction, atomic force microscopy, in situ photoelectron spectroscopy, and electrical resistance measurements. The deposition conditions for preparation of Cu(I)-oxide (Cu2O) are identified. In addition, the interface formation between Cu2O and Sn-doped In2O3 (ITO) was studied by stepwise deposition of Cu2O onto ITO and vice versa. A type II (staggered) band alignment with a valence band offset ΔEVB = 2.1-2.6 eV depending on interface preparation is observed. The band alignment explains the nonrectifying behavior of p-Cu2O/n-ITO junctions, which have been investigated for thin film solar cells.

  7. Reactive oxygen species formation and apoptosis in human peripheral blood mononuclear cell induced by 900 MHz mobile phone radiation.

    PubMed

    Lu, Yao-Sheng; Huang, Bao-Tian; Huang, Yao-Xiong

    2012-01-01

    We demonstrate that reactive oxygen species (ROS) plays an important role in the process of apoptosis in human peripheral blood mononuclear cell (PBMC) which is induced by the radiation of 900 MHz radiofrequency electromagnetic field (RFEMF) at a specific absorption rate (SAR) of ~0.4 W/kg when the exposure lasts longer than two hours. The apoptosis is induced through the mitochondrial pathway and mediated by activating ROS and caspase-3, and decreasing the mitochondrial potential. The activation of ROS is triggered by the conformation disturbance of lipids, protein, and DNA induced by the exposure of GSM RFEMF. Although human PBMC was found to have a self-protection mechanism of releasing carotenoid in response to oxidative stress to lessen the further increase of ROS, the imbalance between the antioxidant defenses and ROS formation still results in an increase of cell death with the exposure time and can cause about 37% human PBMC death in eight hours.

  8. Hearing, reactive metabolite formation, and oxidative stress in cochleae after a single acute overdose of acetaminophen: an in vivo study.

    PubMed

    McGill, Mitchell R; Kennon-McGill, Stefanie; Durham, Dianne; Jaeschke, Hartmut

    2016-02-01

    Although the liver is the primary target organ in acetaminophen (APAP) toxicity, other organs are affected. Previous data suggested that chronic APAP abuse can be ototoxic and the mechanism involves APAP-induced oxidative stress and reactive metabolite (N-acetyl-p-benzoquinone imine, NAPQI)-induced endoplasmic reticulum stress. However, the effect of a single acute overdose on hearing has not been tested. To determine if a single acute APAP overdose causes hearing damage, and to explore possible mechanisms of APAP ototoxicity. Male C57BL/6 J mice were treated with a single human-relevant overdose of APAP (300 mg APAP per kg bodyweight). Blood, liver and cochleae were harvested at 0, 2, 6 and 24 h post-APAP. In some mice, auditory brainstem responses (ABRs) to a range of frequencies were measured at 24 h. The furosemide plus kanamycin (FS/K) model of drug ototoxicity was used as a positive control for hearing loss. NAPQI formation after APAP was assessed by measuring glutathione depletion and covalent protein binding, and oxidative stress was assessed by measuring glutathione disulfide. There was no evidence of reactive metabolite formation or hearing loss after a single overdose of APAP at a clinically relevant dose. However, there was a transient increase in oxidative stress. Although a single acute overdose was not ototoxic, there was evidence of oxidative stress which may support a role for oxidative stress in hearing loss due to chronic APAP abuse. A single human-relevant acute overdose of APAP causes transient oxidative stress in cochleae but not hearing loss.

  9. Oxoferryl-Porphyrin Radical Catalytic Intermediate in Cytochrome bd Oxidases Protects Cells from Formation of Reactive Oxygen Species*

    PubMed Central

    Paulus, Angela; Rossius, Sebastiaan Gijsbertus Hendrik; Dijk, Madelon; de Vries, Simon

    2012-01-01

    The quinol-linked cytochrome bd oxidases are terminal oxidases in respiration. These oxidases harbor a low spin heme b558 that donates electrons to a binuclear heme b595/heme d center. The reaction with O2 and subsequent catalytic steps of the Escherichia coli cytochrome bd-I oxidase were investigated by means of ultra-fast freeze-quench trapping followed by EPR and UV-visible spectroscopy. After the initial binding of O2, the O–O bond is heterolytically cleaved to yield a kinetically competent heme d oxoferryl porphyrin π-cation radical intermediate (compound I) magnetically interacting with heme b595. Compound I accumulates to 0.75–0.85 per enzyme in agreement with its much higher rate of formation (∼20,000 s−1) compared with its rate of decay (∼1,900 s−1). Compound I is next converted to a short lived heme d oxoferryl intermediate (compound II) in a phase kinetically matched to the oxidation of heme b558 before completion of the reaction. The results indicate that cytochrome bd oxidases like the heme-copper oxidases break the O–O bond in a single four-electron transfer without a peroxide intermediate. However, in cytochrome bd oxidases, the fourth electron is donated by the porphyrin moiety rather than by a nearby amino acid. The production of reactive oxygen species by the cytochrome bd oxidase was below the detection level of 1 per 1000 turnovers. We propose that the two classes of terminal oxidases have mechanistically converged to enzymes in which the O–O bond is broken in a single four-electron transfer reaction to safeguard the cell from the formation of reactive oxygen species. PMID:22287551

  10. Reactive uptake of ammonia to secondary organic aerosols: kinetics of organonitrogen formation

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Liggio, J.; Staebler, R.; Li, S.-M.

    2015-06-01

    As a class of brown carbon, organonitrogen compounds originating from the heterogeneous uptake of NH3 by secondary organic aerosol (SOA) have received significant attention recently. In the current work, particulate organonitrogen formation during the ozonolysis of α-pinene and the OH oxidation of m-xylene in the presence of ammonia (34-125 ppb) is studied in a smog chamber equipped with a High Resolution Time-of-Flight Aerosol Mass Spectrometer and a Quantum Cascade Laser instrument. A large diversity of nitrogen containing organic (NOC) fragments was observed which were consistent with the reaction of ammonia with carbonyl containing SOA. The uptake coefficients of NH3 to SOA leading to organonitrogen compounds are reported for the first time and were in the range of ∼ 10-3-10-2, decreasing significantly to < 10-5 after 6 h of reaction. At the end of experiments (∼ 6 h) the NOC mass contributed 8.9 ± 1.7 and 31.5 ± 4.4 wt% to the total α-pinene and m-xylene derived SOA, and 4-15 wt% of the total nitrogen in the system. Uptake coefficients were also found to be positively correlated with particle acidity and negatively correlated with NH3 concentration, indicating that heterogeneous reactions were responsible for the observed NOC mass, possibly limited by liquid phase diffusion. Under these conditions, the data also indicate that the formation of NOC can compete kinetically with inorganic acid neutralization. The formation of NOC in this study suggests that a significant portion of the ambient particle associated N may be derived from NH3 heterogeneous reactions with SOA. NOC from such a mechanism may be an important and unaccounted for source of PM associated nitrogen, and a mechanism for medium or long-range transport and dry/wet deposition of atmospheric nitrogen.

  11. Reactive uptake of ammonia to secondary organic aerosols: kinetics of organonitrogen formation

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Liggio, J.; Staebler, R.; Li, S.-M.

    2015-12-01

    As a class of brown carbon, organonitrogen compounds originating from the heterogeneous uptake of NH3 by secondary organic aerosol (SOA) have received significant attention recently. In the current work, particulate organonitrogen formation during the ozonolysis of α-pinene and the OH oxidation of m-xylene in the presence of ammonia (34-125 ppb) was studied in a smog chamber equipped with a high resolution time-of-flight aerosol mass spectrometer and a quantum cascade laser instrument. A large diversity of nitrogen-containing organic (NOC) fragments was observed which were consistent with the reactions between ammonia and carbonyl-containing SOA. Ammonia uptake coefficients onto SOA which led to organonitrogen compounds were reported for the first time, and were in the range of ∼ 10-3-10-2, decreasing significantly to < 10-5 after 6 h of reaction. At the end of experiments (~ 6 h) the NOC mass contributed 8.9 ± 1.7 and 31.5 ± 4.4 wt % to the total α-pinene- and m-xylene-derived SOA, respectively, and 4-15 wt % of the total nitrogen in the system. Uptake coefficients were also found to be positively correlated with particle acidity and negatively correlated with NH3 concentration, indicating that heterogeneous reactions were responsible for the observed NOC mass, possibly limited by liquid phase diffusion. Under these conditions, the data also indicate that the formation of NOC can compete kinetically with inorganic acid neutralization. The formation of NOC in this study suggests that a significant portion of the ambient particle associated N may be derived from NH3 heterogeneous reactions with SOA. NOC from such a mechanism may be an important and unaccounted for source of PM associated nitrogen. This mechanism may also contribute to the medium or long-range transport and wet/dry deposition of atmospheric nitrogen.

  12. NO oxidation on Zeolite Supported Cu Catalysts: Formation and Reactivity of Surface Nitrates

    SciTech Connect

    Chen, Hai-Ying; Wei, Zhehao; Kollar, Marton; Gao, Feng; Wang, Yilin; Szanyi, Janos; Peden, Charles HF

    2016-04-18

    The comparative activities of a small-pore Cu-CHA and a large-pore Cu-BEA catalyst for the selective catalytic reduction (SCR) of NOx with NH3, and for the oxidation of NO to NO2 and the subsequent formation of surface nitrates were investigated. Although both catalysts are highly active in SCR reactions, they exhibit very low NO oxidation activity. Furthermore, Cu-CHA is even less active than Cu-BEA in catalyzing NO oxidation but is clearly more active for SCR reactions. Temperature-programed desorption (TPD) experiments following the adsorption of (NO2 + NO + O2) with different NO2:NO ratios reveal that the poor NO oxidation activity of the two catalysts is not due to the formation of stable surface nitrates. On the contrary, NO is found to reduce and decompose the surface nitrates on both catalysts. To monitor the reaction pathways, isotope exchange experiments were conducted by using 15NO to react with 14N-nitrate covered catalyst surfaces. The evolution of FTIR spectra during the isotope exchange process demonstrates that 14N-nitrates are simply displaced with no formation of 15N-nitrates on the Cu-CHA sample, which is clearly different from that observed on the Cu-BEA sample where formation of 15N-nitrates is apparent. The results suggest that the formal oxidation state of N during the NO oxidation on Cu-CHA mainly proceeds from its original +2 to a +3 oxidation state, whereas reaching a higher oxidation state for N, such as +4 or +5, is possible on Cu-BEA. The authors at PNNL gratefully acknowledge the US Department of Energy (DOE), Energy Efficiency and Renewable Energy, Vehicle Technologies Office for the support of this work. The research described in this paper was performed at the Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by the DOE’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory (PNNL). PNNL is operated for the US DOE by Battelle.

  13. Aminoguanidine inhibits reactive oxygen species formation, lipid peroxidation, and oxidant-induced apoptosis.

    PubMed

    Giardino, I; Fard, A K; Hatchell, D L; Brownlee, M

    1998-07-01

    Aminoguanidine (AG) treatment, like nerve growth factor (NGF) treatment, prevents diabetes-induced apoptosis of retinal Müller cells in the rat eye, but the mechanism involved is unknown. In this study, the effects of preincubation with AG on oxidant-induced apoptosis, oxidant-induced intracellular reactive oxygen species (ROS) production, and lipid peroxidation were determined in rat retinal Müller cells and compared with the effects of NGF, a protein that protects neuronal cells from oxidative stress. The effect of AG on rabbit vitreous lipid peroxide levels was also determined. After exposure to increasing concentrations of H2O2, there was a corresponding increase in the percentage of apoptotic Müller cells. Preincubation with AG for 48 h completely inhibited oxidant-induced apoptosis in response to 10 micromol/l H2O2 (+AG 0 vs. 10 micromol/l, NS), and reduced the percentage of apoptotic cells in response to 50 micromol/l H2O2 by 50% (+AG vs. -AG, P < 0.01). Longer preincubation did not increase the antiapoptotic effect of AG. The effect of AG was dose-dependent. Similar results were obtained after preincubation with NGF. Both AG and NGF preincubation prevented the twofold increase in oxidant-induced lipid peroxides. The fivefold increase in oxidant-induced ROS production was decreased 100% by NGF, but only 61% by AG preincubation. The twofold increase in vitreous lipid peroxide level in diabetic rabbits was completely prevented by AG treatment. AG reduced H2O2-induced benzoate hydroxylation in a dose-dependent manner. Intracellular glutathione content was unchanged. These data demonstrate that AG can act as an antioxidant in vivo, quenching hydroxyl radicals and lipid peroxidation in cells and tissues and preventing oxidant-induced apoptosis.

  14. Fuel effects on soot formation in turbojet engines. Final report, September 15, 1983-March 14, 1985

    SciTech Connect

    Gill, R.J.; Olson, D.B.

    1985-08-01

    The results of tests on how fuel composition affects the performance of three Navy aircraft engine combustors, the TF30, T56, and T53, were analyzed. The objective of this analysis was to identify which fuel property best correlated with the smoke-related measurements: radiation flux, liner temperature rise, smoke number, and smoke emissions. The effects of fuel composition were investigated by using a series of ten Naval Air Propulsion Center jet fuels with various properties, such as hydrogen contents of 12.83 to 13.82% and total aromatic hydrocarbon contents of 15.9 to 28.5%. Several laboratory combustion characteristics of these fuels were measured and these characteristics were used in analysis. Altogether, 15 fuel parameters were used to correlate the 45 combustor test results. The reported operating conditions of the tests, such as inlet air pressure, inlet air temperature, or fuel/air ratio, were also used as correlating parameters to determine whether variations in these variables, nearly constant for individual tests, also affected the smoke-related test results.

  15. [Impact of biologically important anions on reactive oxygen species formation in water under the effect of non-ionizing physical agents].

    PubMed

    Gudkov, S V; Ivanov, V E; Karp, O É; Chernikov, A V; Belosludtsev, K N; Bobylev, A G; Astashev, M E; Gapeev, A B; Bruskov, V I

    2014-01-01

    The influence of biologically relevant anions (succinate, acetate, citrate, chloride, bicarbonate, hydroorthophosphate, dihydroorthophosphate, nitrite, nitrate) on the formation of hydrogen peroxide and hydroxyl radicals in water was studied under the effect of non-ionizing radiation: heat, laser light with a wavelength of 632.8 nm, corresponding to the maximum absorption of molecular oxygen, and electromagnetic radiation of extremely high frequencies. It has been established that various anions may both inhibit the formation of reactive oxygen species and increase it. Bicarbonate and sulfate anions included in the biological fluids' and medicinal mineral waters have significant, but opposite effects on reactive oxygen species production. Different molecular mechanisms of reactive oxygen species formation are considered under the action of the investigated physical factors involving these anions, which may influence the biological processes by signal-regulatory manner and provide a healing effect in physical therapy.

  16. Nanostructured diffusion-limited-aggregation crystal pattern formation in a reactive microemulsion system

    NASA Astrophysics Data System (ADS)

    Srivastava, Rohit; Srivastava, P. K.

    2014-03-01

    Nanostructured diffusion-limited-aggregation (DLA) crystal pattern formation in microemulsion consisting of water, styrene, cetyltrimethylammonium chloride (CTACl), potassium persulphate and an oscillating Belousov-Zhabotinsky (BZ) reactant is reported. A variety of spatiotemporal patterns like concentric wave, spatial (stripe) and chaotic patterns appear. A colloidal phase composed of numerous nano-sized particles has been observed. The solid phase nucleation has been found to occur in the colloidal phase and has been found to grow in a symmetric crystal pattern with the progress of the reaction finally exhibiting DLA structures. We show that the formation of a nanostructured DLA crystal pattern is governed by spatial structures emerging in the BZ microemulsion system. Without any spatial structure in the microemulsion system only hydrogel of high viscosity is formed. A nano-sized branched crystal pattern was formed with a particle diameter in the range of 60-100 nm, as evident by transmission electron microscope, powder x-ray diffraction and particle size analyser studies.

  17. Control of Reactivity and Regioselectivity for On-Surface Dehydrogenative Aryl-Aryl Bond Formation.

    PubMed

    Kocić, Nemanja; Liu, Xunshan; Chen, Songjie; Decurtins, Silvio; Krejčí, Ondřej; Jelínek, Pavel; Repp, Jascha; Liu, Shi-Xia

    2016-05-04

    Regioselectivity is of fundamental importance in chemical synthesis. Although many concepts for site-selective reactions are well established for solution chemistry, it is not a priori clear whether they can easily be transferred to reactions taking place on a metal surface. A metal will fix the chemical potential of the electrons and perturb the electronic states of the reactants because of hybridization. Additionally, techniques to characterize chemical reactions in solution are generally not applicable to on-surface reactions. Only recent developments in resolving chemical structures by atomic force microscopy (AFM) and scanning tunneling microscopy (STM) paved the way for identifying individual reaction products on surfaces. Here we exploit a combined STM/AFM technique to demonstrate the on-surface formation of complex molecular architectures built up from a heteroaromatic precursor, the tetracyclic pyrazino[2,3-f][4,7]phenanthroline (pap) molecule. Selective intermolecular aryl-aryl coupling via dehydrogenative C-H activation occurs on Au(111) upon thermal annealing under ultrahigh vacuum (UHV) conditions. A full atomistic description of the different reaction products based on an unambiguous discrimination between pyrazine and pyridine moieties is presented. Our work not only elucidates that ortho-hydrogen atoms of the pyrazine rings are preferentially activated over their pyridine equivalents, but also sheds new light onto the participation of substrate atoms in metal-organic coordination bonding during covalent C-C bond formation.

  18. Nanopore formation process in artificial cell membrane induced by plasma-generated reactive oxygen species.

    PubMed

    Tero, Ryugo; Yamashita, Ryuma; Hashizume, Hiroshi; Suda, Yoshiyuki; Takikawa, Hirofumi; Hori, Masaru; Ito, Masafumi

    2016-09-01

    We investigated morphological change of an artificial lipid bilayer membrane induced by oxygen radicals which were generated by non-equilibrium atmospheric pressure plasma. Neutral oxygen species, O((3)Pj) and O2((1)Δg), were irradiated of a supported lipid bilayer existing under a buffer solution at various conditions of dose time and distances, at which the dose amounts of the oxygen species were calculated quantitatively. Observation using an atomic force microscope and a fluorescence microscope revealed that dose of the neutral oxygen species generated nanopores with the diameter of 10-50 nm in a phospholipid bilayer, and finally destructed the bilayer structure. We found that protrusions appeared on the lipid bilayer surface prior to the formation of nanopores, and we attributed the protrusions to the precursor of the nanopores. We propose a mechanism of the pore formation induced by lipid oxidation on the basis of previous experimental and theoretical studies. Copyright © 2016 Elsevier Inc. All rights reserved.

  19. Reduction of carbon dioxide gas formation at the anode of a direct methanol fuel cell using chemically enhanced solubility

    NASA Astrophysics Data System (ADS)

    Lundin, Michael D.; McCready, Mark J.

    The production of CO 2 gas at the DMFC anode leads to dramatic increases in pumping power requirements and reduced power output because of mass transfer limitations as bubble trains form in the channels of larger stacks. Experimental observations taken in a 5 cm 2 DMFC test cell operated at 60 °C, 1 atm, and with a methanol/water fuel flow rates of 5-10 cm 3 min -1 indicate that the rate of bubble formation can be reduced by increasing the fuel flow because more liquid is available for the CO 2 to dissolve in. Further observations indicate that KOH and LiOH added to the fuel eliminates CO 2 gas formation in situ at low concentrations because of the greatly increased solubility that results. A mathematical model for the volumetric rate of CO 2 gas production that includes effects of temperature and solubility is developed and extended to include the effects of hydroxide ions in solution. The model is used to predict the onset location of gas formation in the flow field as well as the void fraction at any point in the flow field. Predictions from the model agree very well with our experiments. Model predictions explain differences in the initial location of bubble formation for fuel solutions pre-saturated with CO 2 as opposed to CO 2-free solutions. Experiments with KOH and LiOH added to fuel solutions confirm the validity of the model extension that includes solubility that is enhanced by chemical reaction. Experiments with LiOH, KOH, and ammonium hydroxide show that the long-term durability of standard Pt-Ru/Nafion ®/Pt membrane electrode assemblies is compromised because of the presence of lithium, potassium, and ammonium cations that interact with the Nafion ® membrane and result in increasing the ohmic limitations of the polymer electrolyte membrane. Experiments with Ca(OH) 2, while reducing gas formation, precipitate the product CaCO 3 out of solution too rapidly for downstream filtering, blocking channels in the flow field.

  20. Structural insights into dynamics of RecU-HJ complex formation elucidates key role of NTR and stalk region toward formation of reactive state.

    PubMed

    Khavnekar, Sagar; Dantu, Sarath Chandra; Sedelnikova, Svetlana; Ayora, Sylvia; Rafferty, John; Kale, Avinash

    2017-01-25

    Holliday junction (HJ) resolving enzyme RecU is involved in DNA repair and recombination. We have determined the crystal structure of inactive mutant (D88N) of RecU from Bacillus subtilis in complex with a 12 base palindromic DNA fragment at a resolution of 3.2 Å. This structure shows the stalk region and the essential N-terminal region (NTR) previously unseen in our DNA unbound structure. The flexible nature of the NTR in solution was confirmed using SAXS. Thermofluor studies performed to assess the stability of RecU in complex with the arms of an HJ indicate that it confers stability. Further, we performed molecular dynamics (MD) simulations of wild type and an NTR deletion variant of RecU, with and without HJ. The NTR is observed to be highly flexible in simulations of the unbound RecU, in agreement with SAXS observations. These simulations revealed domain dynamics of RecU and their role in the formation of complex with HJ. The MD simulations also elucidate key roles of the NTR, stalk region, and breathing motion of RecU in the formation of the reactive state.

  1. Structural insights into dynamics of RecU–HJ complex formation elucidates key role of NTR and stalk region toward formation of reactive state

    PubMed Central

    Khavnekar, Sagar; Dantu, Sarath Chandra; Sedelnikova, Svetlana; Ayora, Sylvia; Rafferty, John; Kale, Avinash

    2017-01-01

    Holliday junction (HJ) resolving enzyme RecU is involved in DNA repair and recombination. We have determined the crystal structure of inactive mutant (D88N) of RecU from Bacillus subtilis in complex with a 12 base palindromic DNA fragment at a resolution of 3.2 Å. This structure shows the stalk region and the essential N-terminal region (NTR) previously unseen in our DNA unbound structure. The flexible nature of the NTR in solution was confirmed using SAXS. Thermofluor studies performed to assess the stability of RecU in complex with the arms of an HJ indicate that it confers stability. Further, we performed molecular dynamics (MD) simulations of wild type and an NTR deletion variant of RecU, with and without HJ. The NTR is observed to be highly flexible in simulations of the unbound RecU, in agreement with SAXS observations. These simulations revealed domain dynamics of RecU and their role in the formation of complex with HJ. The MD simulations also elucidate key roles of the NTR, stalk region, and breathing motion of RecU in the formation of the reactive state. PMID:27903910

  2. LIFE Materials: Phase Formation and Transformations in Transmutation Fuel Materials for the LIFE Engine Part I - Path Forward Volume 3

    SciTech Connect

    Turchi, P A; Kaufman, L; Fluss, M

    2008-12-19

    The current specifications of the LLNL fusion-fission hybrid proposal, namely LIFE, impose severe constraints on materials, and in particular on the nuclear fissile or fertile nuclear fuel and its immediate environment. This constitutes the focus of the present report with special emphasis on phase formation and phase transformations of the transmutation fuel and their consequences on particle and pebble thermal, chemical, and mechanical integrities. We first review the work that has been done in recent years to improve materials properties under the Gen-IV project, and with in particular applications to HTGR and MSR, and also under GNEP and AFCI in the USA. Our goal is to assess the nuclear fuel options that currently exist together with their issues. Among the options, it is worth mentioning TRISO, IMF, and molten salts. The later option will not be discussed in details since an entire report (Volume 8 - Molten-salt Fuels) is dedicated to it. Then, in a second part, with the specific LIFE specifications in mind, the various fuel options with their most critical issues are revisited with a path forward for each of them in terms of research, both experimental and theoretical. Since LIFE is applicable to very high burn-up of various fuels, distinctions will be made depending on the mission, i.e., energy production or incineration. Finally a few conclusions are drawn in terms of the specific needs for integrated materials modeling and the in depth knowledge on time-evolution thermo-chemistry that controls and drastically affects the performance of the nuclear materials and their immediate environment. Although LIFE demands materials that very likely have not yet been fully optimized, the challenges are not insurmountable, and a well concerted experimental-modeling effort should lead to dramatic advances that should well serve other fission programs such as Gen-IV, GNEP, AFCI as well as the international fusion program, ITER.

  3. On adduct formation and reactivity in the OCS + OH reaction: A combined theoretical and experimental study

    NASA Astrophysics Data System (ADS)

    Schmidt, Johan A.; Kyte, Mildrid; Østerstrøm, Freja F.; Joelsson, Lars M. T.; Knap, Hasse C.; Jørgensen, Solvejg; Nielsen, Ole John; Murakami, Tatsuhiro; Johnson, Matthew S.

    2017-05-01

    The OCS + OH reaction occurs either via adduct formation or direct S-abstraction. We investigate OH-oxidation of OCS using quantum chemical methods and find that the OC(OH)S adduct reacts rapidly with O2 forming SOOH + CO2. SOOH rapidly dissociates under atmospheric conditions regenerating OH. We interpret earlier experimental results based on monitoring OH-loss, and find that OH-regeneration in presence of O2 may explain the insensitivity of the reaction rate to pressure and O2. We calculate a rate constant of 3.52 ×10-16 cm3 s-1 at 10 Torr increasing to 7.20 ×10-16 cm3 s-1 at 700 Torr. In addition we present a new experimental determination of the OCS + OH rate constant of (5.3 ± 3.6) ×10-15 cm3 s-1 at 296 K and 700 Torr using relative-rate technique.

  4. Calcite formation in soft coral sclerites is determined by a single reactive extracellular protein.

    PubMed

    Rahman, M Azizur; Oomori, Tamotsu; Wörheide, Gert

    2011-09-09

    Calcium carbonate exists in two main forms, calcite and aragonite, in the skeletons of marine organisms. The primary mineralogy of marine carbonates has changed over the history of the earth depending on the magnesium/calcium ratio in seawater during the periods of the so-called "calcite and aragonite seas." Organisms that prefer certain mineralogy appear to flourish when their preferred mineralogy is favored by seawater chemistry. However, this rule is not without exceptions. For example, some octocorals produce calcite despite living in an aragonite sea. Here, we address the unresolved question of how organisms such as soft corals are able to form calcitic skeletal elements in an aragonite sea. We show that an extracellular protein called ECMP-67 isolated from soft coral sclerites induces calcite formation in vitro even when the composition of the calcifying solution favors aragonite precipitation. Structural details of both the surface and the interior of single crystals generated upon interaction with ECMP-67 were analyzed with an apertureless-type near-field IR microscope with high spatial resolution. The results show that this protein is the main determining factor for driving the production of calcite instead of aragonite in the biocalcification process and that -OH, secondary structures (e.g. α-helices and amides), and other necessary chemical groups are distributed over the center of the calcite crystals. Using an atomic force microscope, we also explored how this extracellular protein significantly affects the molecular-scale kinetics of crystal formation. We anticipate that a more thorough investigation of the proteinaceous skeleton content of different calcite-producing marine organisms will reveal similar components that determine the mineralogy of the organisms. These findings have significant implications for future models of the crystal structure of calcite in nature.

  5. Calcite Formation in Soft Coral Sclerites Is Determined by a Single Reactive Extracellular Protein*

    PubMed Central

    Rahman, M. Azizur; Oomori, Tamotsu; Wörheide, Gert

    2011-01-01

    Calcium carbonate exists in two main forms, calcite and aragonite, in the skeletons of marine organisms. The primary mineralogy of marine carbonates has changed over the history of the earth depending on the magnesium/calcium ratio in seawater during the periods of the so-called “calcite and aragonite seas.” Organisms that prefer certain mineralogy appear to flourish when their preferred mineralogy is favored by seawater chemistry. However, this rule is not without exceptions. For example, some octocorals produce calcite despite living in an aragonite sea. Here, we address the unresolved question of how organisms such as soft corals are able to form calcitic skeletal elements in an aragonite sea. We show that an extracellular protein called ECMP-67 isolated from soft coral sclerites induces calcite formation in vitro even when the composition of the calcifying solution favors aragonite precipitation. Structural details of both the surface and the interior of single crystals generated upon interaction with ECMP-67 were analyzed with an apertureless-type near-field IR microscope with high spatial resolution. The results show that this protein is the main determining factor for driving the production of calcite instead of aragonite in the biocalcification process and that –OH, secondary structures (e.g. α-helices and amides), and other necessary chemical groups are distributed over the center of the calcite crystals. Using an atomic force microscope, we also explored how this extracellular protein significantly affects the molecular-scale kinetics of crystal formation. We anticipate that a more thorough investigation of the proteinaceous skeleton content of different calcite-producing marine organisms will reveal similar components that determine the mineralogy of the organisms. These findings have significant implications for future models of the crystal structure of calcite in nature. PMID:21768106

  6. Methods and apparatus for burning fuel with low NO[sub x] formation

    SciTech Connect

    Schwartz, R.E.; Waibel, R.T.; Rodden, P.M.; Napier, S.O.

    1992-10-13

    This patent describes an improved burner aparatus for discharging a mixture of fuel and air into a furnace space wherein the mixture is burned and flue gases having low NO[sub x] content are formed therefrom. It comprises: A housing; primary mixer-nozzle means; flue gases passageway means; at least one secondary fuel nozzel means. This patent also describes a method of discharging an at least substanitally stoichiometric mixture of fuel and air into a furnace wherein the mixture is burned and flue gases having low NO[sub x] content are formed therefrom. It comprises: discharging air into the furnace; discharging the remaining portion of the fuel into a secondary zone.

  7. Methods and apparatus for burning fuel with low NO sub x formation

    SciTech Connect

    Schwartz, R.E.; Waibel, R.T.; Rodden, P.M.; Napier, S.O.

    1992-03-24

    This patent describes an improved burner apparatus for discharging a mixture of fuel and air into a furnace space wherein the mixture is burned and flue gases having low NO{sub x} content are formed. It comprises: a housing having an open end attached to the furnace space; means for introducing a controlled quantity of air into the housing and into the furnace space attached to the housing; primary mixer-nozzle means for mixing fuel with flue gases from the furnace space and discharging the resulting mixture into the furnace space disposed within the housing, the primary mixer-nozzle means including a pressurized fuel inlet for connection to a source of pressurized fuel and at least one flue gases inlet connection.

  8. Effect of additives on the formation of insolubles in a jet fuel

    SciTech Connect

    Anderson, S.D.; Jones, E.G.; Goss, L.P.; Balster, W.J.

    1995-05-01

    Dynamic near-isothermal techniques have proven to be valuable in assessing the tendency of aviation fuels to form surface and bulk insolubles under thermal stress. These methods are applied in this study to the investigation of the neat Jet-A fuel POSF-2827 and changes introduced by a series of four candidate additives. In each case fuel is stressed while flowing through a heat exchanger under near-isothermal conditions at 185{degrees}C. The average surface deposition rate as a function of stress duration and the quantity of both surface and bulk insolubles have been determined after complete consumption of the dissolved oxygen. The additives, introduced individually, include a common antioxidant, a metal deactivator, a dispersant, and a combination detergent/dispersant. Of the four additives, only the dispersant-types are found to improve fuel thermal stability.

  9. 40 CFR 600.307-08 - Fuel economy label format requirements.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... vehicles, fuel cell vehicles, plug-in hybrid electric vehicles and vehicles equipped with hydrogen internal... hybrid electric vehicles. ...: minicompact cars may be “Minicompacts”, subcompact cars may be “Subcompacts”, compact cars may be “Compacts...

  10. Investigation of spray dispersion and particulate formation in diesel fuel flames

    NASA Technical Reports Server (NTRS)

    Back, L. H.; Bankston, C. P.; Kwack, E. Y.; Bellan, J.; Harstad, K.

    1988-01-01

    An experimental study of electrostatical atomized and dispersed diesel fuel jets was conducted at various back pressures to 40 atm. A new electrostatic injection technique was utilized to generate continuous, stable fuel sprays at charge densities of 1.5 to 2.0 C/m3 of fluid at one atm, and about 1.0 C/m3 at 40 atm. Flowrates were varied from 0.5 to 2.5 ml/s and electric potentials to -18 kV. Visual observations showed that significant enhanced dispersion of charged fuel jets occurred at high back pressures compared to aerodynamic breakup and dispersion. The average drop size was about the same as the spray triode orifice diameter, and was between the Kelly theory and the Rayleigh limit. The ignition tests, done only at one atm, indicated stable combustion of the electrostatically dispersed fuel jets.

  11. Phlorotannins from brown algae (Fucus vesiculosus) inhibited the formation of advanced glycation endproducts by scavenging reactive carbonyls.

    PubMed

    Liu, Haiyan; Gu, Liwei

    2012-02-08

    Accumulation of advanced glycation end products (AGEs) in vivo is associated with aging, diabetes, Alzheimer's disease, renal failure, etc. The objective of this study was to investigate the inhibitory effects of brown algae Fucus vesiculosus phlorotannins on the formation of AGEs. F. vesiculosus phlorotannins were extracted using 70% acetone. The resultant extract was fractionated into dichloromethane, ethyl acetate, butanol, and water fractions. The ethyl acetate fraction was further fractionated into four subfractions (Ethyl-F1 to -F4) using a Sephadex LH-20 column. F. vesiculosus acetone extract or fractions significantly inhibited the formation of AGEs mediated by glucose and methylglyoxal in a concentration-dependent manner. The concentrations of F. vesiculosus extracts required to inhibit 50% of albumin glycation (EC(50)) in the bovine serum albumin (BSA)-methylglyoxal assay were lower than those of aminoguanidine (a drug candidate for diabetic complication), except for F. vesiculosus acetone extract and dichloromethane fraction. In the BSA-glucose assay, F. vesiculosus extracts inhibited BSA glycation more than or as effectively as aminoguanidine, except for Ethyl-F3 and -F4. The ethyl acetate fraction and its four subfractions scavenged more than 50% of methylglyoxal in two hours. The hypothesis whether F. vesiculosus phlorotannins scavenged reactive carbonyls by forming adducts was tested. Phloroglucinol, the constituent unit of phlorotannins, reacted with glyoxal and methylglyoxal. Five phloroglucinol-carbonyl adducts were detected and tentatively identified using HPLC-ESI-MS(n).

  12. Emerging Disinfection Byproducts, Halobenzoquinones: Effects of Isomeric Structure and Halogen Substitution on Cytotoxicity, Formation of Reactive Oxygen Species, and Genotoxicity.

    PubMed

    Li, Jinhua; Moe, Birget; Vemula, Sai; Wang, Wei; Li, Xing-Fang

    2016-07-05

    Halobenzoquinones (HBQs) are a structurally diverse class of water disinfection byproducts. Here, we report a systematic study on the effects of isomeric structure and the type and number of halogen substitutions of HBQs on their cytotoxicity, formation of reactive oxygen species (ROS), and genotoxicity. Dynamic responses and IC50 histograms were obtained using real-time cell analysis, clearly ranking the cytotoxicity of the HBQs in Chinese hamster ovary (CHO-K1) cells. Strong isomeric structure effects were shown with 2,5-HBQ isomers inducing greater cytotoxicity than their corresponding 2,6-HBQ isomers (P < 0.05). HBQ-halogen substitution groups also influence cytotoxicity, as cytotoxicity increases across the dihalogenated HBQs: iodo- > bromo- > chloro-HBQs (P < 0.05). Determination of HBQ-induced ROS further supports isomeric structure and halogen substitution effects. HBQ-induced genotoxicity was shown as increased levels of 8-hydroxy-2'-deoxyguanosine and p53 protein. Pearson correlation analysis of the HBQ toxicity measurements with their physicochemical parameters demonstrates that dipole moment and the lowest unoccupied molecular orbital energy are two major structural influences on toxicity (r = -0.721 or -0.766, P < 0.05). Dipole moment also correlates with isomer toxicity. This study suggests that formation and occurrence of highly toxic iodo-HBQs and 2,5-HBQs warrant further investigation to fully assess the impact of HBQs in drinking water.

  13. The reduction of reactive oxygen species formation by mitochondrial alternative respiration in tomato basal defense against TMV infection.

    PubMed

    Liao, Yang-Wen-Ke; Shi, Kai; Fu, Li-Jun; Zhang, Shuai; Li, Xin; Dong, De-Kun; Jiang, Yu-Ping; Zhou, Yan-Hong; Xia, Xiao-Jian; Liang, Wu-Sheng; Yu, Jing-Quan

    2012-02-01

    The role of mitochondrial alternative oxidase (AOX) and the relationship between systemic AOX induction, ROS formation, and systemic plant basal defense to Tobacco mosaic virus (TMV) were investigated in tomato plants. The results showed that TMV inoculation significantly increased the level of AOX gene transcripts, ubiquinone reduction levels, pyruvate content, and cyanide-resistant respiration (CN-resistant R) in upper, un-inoculated leaves. Pretreatment with potassium cyanide (KCN, a cytochrome pathway inhibitor) greatly increased CN-resistant R and reduced reactive oxygen species (ROS) formation, while application of salicylhydroxamic acid (SHAM, an AOX inhibitor) blocked the AOX activity and enhanced the production of ROS in the plants. Furthermore, TMV systemic infection was enhanced by SHAM and reduced by KCN pretreatment, as compared with the un-pretreated TMV counterpart. In addition, KCN application significantly diminished TMV-induced increase in antioxidant enzyme activities and dehydroascorbate/total ascorbate pool, while an opposite change was observed with SHAM-pretreated plants. These results suggest that the systemic induction of the mitochondrial AOX pathway plays a critical role in the reduction of ROS to enhance basal defenses. Additional antioxidant systems were also coordinately regulated in the maintenance of the cellular redox homeostasis.

  14. Reactive dc magnetron sputtering of (GeO{sub x}-SiO{sub 2}) superlattices for Ge nanocrystal formation

    SciTech Connect

    Zschintzsch, M.; Jeutter, N. M.; Borany, J. von; Krause, M.; Muecklich, A.

    2010-02-15

    The motivation of this work is the tailored growth of Ge nanocrystals for photovoltaic applications. The use of superlattices provides a reliable method to control the Ge nanocrystal size after phase separation. In this paper, we report on the deposition of (GeO{sub x}-SiO{sub 2}) superlattices via reactive dc magnetron sputtering and the self-ordered Ge nanocrystal formation during subsequent annealing. Attention is directed mainly to define proper deposition conditions for tuning the GeO{sub x} composition between elemental Ge (x=0) and GeO{sub 2} (x=2) by the variation in the deposition temperature and the oxygen partial pressure. A convenient process window has been found which allows sequential GeO{sub x}-SiO{sub 2} deposition without changing the oxygen partial pressure during deposition. The phase separation and Ge nanocrystal formation after subsequent annealing were investigated with in situ x-ray scattering, Raman spectroscopy, and electron microscopy. By these methods the existence of 2-5 nm Ge nanocrystals at annealing temperatures of 600-750 deg. C has been confirmed which is within the superlattice stability range. The technique used allows the fabrication of superlattice stacks with very smooth interfaces (roughness<1 nm); thus the Ge nanocrystal layers could be separated by very thin SiO{sub 2} films (d<3 nm) which offers interesting possibilities for charge transport via direct tunneling.

  15. Influence of oestrogens on formation of reactive oxygen species in liver microsomes of differently aged male Wistar rats.

    PubMed

    Barth, A; Landmann, G; Liepold, K; Zapf, H; Müller, D; Karge, E; Klinger, W

    1999-07-01

    Metabolic pathways of oestrogens are the formation of catechol oestrogens (CE; 2- and 4-hydroxy-oestrogens), redox cycling of CE and free radical generation, mediated through cytochrome P450 (P450) oxidase/reductase activity. We checked the oestrogens oestradiol (E2), oestradiol valerate (E2V) and ethinyloestradiol (EE2) for formation of reactive oxygen species in vitro and ex vivo in male Wistar rats in dependence on age. In liver microsomes of 10-, 30-, 60- and 270-day-old rats the influence of E2, E2V and EE2 (10(-7)-10(-3) M) on NADPH-Fe(++)-stimulated lipid peroxidation (LPO), H2O2 generation and lucigenin (LUC) and luminol (LUM) amplified chemiluminescence (CL) was investigated. The same parameters, additionally P450 content and monooxygenase activities were measured in liver 9000 x g supernatants after subchronic administration of the oestrogens (1, 10 mg/kg b. wt. orally). The most important results are the strong inhibitory capacities of the oestrogens in vitro on LPO in the order of E2V < E2 < EE2, most pronounced in 10-, 60- and 270-day-old animals. In microsomes of 30-day-old rats with the highest control LPO the antioxidative effect of the oestrogens was lower. Whereas the H2O2 generation was not changed by E2, enhanced by E2V, but diminished by EE2 in all age groups, CL(LUC) and CL(LUM) were inhibited in the order of E2 < E2V < EE2. Also after subchronical treatment of the rats the antioxidative action of the oestrogens was evident, microsomal LPO was inhibited in the order of E2 < E2V < EE2. All oestrogens inhibited ethylmorphine N-demethylation. But enhanced H2O2 generation and increased CL(LUC) also indicate a formation of reactive oxygen species by these oestrogens. Obviously in vitro the antioxidative phenolic structure of the oestrogens dominates, whereas after in vivo administration the dose- and age-dependent biotransformation produces prooxidative in addition to antioxidative structures.

  16. Probability density function of non-reactive solute concentration in heterogeneous porous formations.

    PubMed

    Bellin, Alberto; Tonina, Daniele

    2007-10-30

    Available models of solute transport in heterogeneous formations lack in providing complete characterization of the predicted concentration. This is a serious drawback especially in risk analysis where confidence intervals and probability of exceeding threshold values are required. Our contribution to fill this gap of knowledge is a probability distribution model for the local concentration of conservative tracers migrating in heterogeneous aquifers. Our model accounts for dilution, mechanical mixing within the sampling volume and spreading due to formation heterogeneity. It is developed by modeling local concentration dynamics with an Ito Stochastic Differential Equation (SDE) that under the hypothesis of statistical stationarity leads to the Beta probability distribution function (pdf) for the solute concentration. This model shows large flexibility in capturing the smoothing effect of the sampling volume and the associated reduction of the probability of exceeding large concentrations. Furthermore, it is fully characterized by the first two moments of the solute concentration, and these are the same pieces of information required for standard geostatistical techniques employing Normal or Log-Normal distributions. Additionally, we show that in the absence of pore-scale dispersion and for point concentrations the pdf model converges to the binary distribution of [Dagan, G., 1982. Stochastic modeling of groundwater flow by unconditional and conditional probabilities, 2, The solute transport. Water Resour. Res. 18 (4), 835-848.], while it approaches the Normal distribution for sampling volumes much larger than the characteristic scale of the aquifer heterogeneity. Furthermore, we demonstrate that the same model with the spatial moments replacing the statistical moments can be applied to estimate the proportion of the plume volume where solute concentrations are above or below critical thresholds. Application of this model to point and vertically averaged bromide

  17. Arylperoxyl radicals. Formation, absorption spectra, and reactivity in aqueous alcohol solutions

    SciTech Connect

    Alfassi, Z.B.; Khaikin, G.I.; Neta, P. )

    1995-01-05

    Aryl radicals (phenyl, 4-biphenylyl, 2-naphthyl, 1-naphthyl, and 9-phenanthryl) were produced by the reaction of the corresponding aryl bromide with solvated electrons and reacted rapidly with oxygen to produce the arylperoxyl radicals. These radicals exhibit optical absorptions in the visible range, with [lambda][sub max] at 470, 550, 575, 650, and 700 nm, respectively. Arylperoxyl radicals react with 2,2[prime]-azinobis(3-ethylbenzothiazoiine-6-sulfonate ion) (ABTS), chlorpromazine, and 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox C) by one-electron oxidation. The rate constants k for these reactions, determined from the rate of formation of the one-electron oxidation products as a function of substrate concentration, vary between 4 [times] 10[sup 6] and 2 [times] 10[sup 9] L mol[sup [minus]1] s[sup [minus]1] and increase in the order phenyl-, 4-biphenyl-, 2-naphthyl-, 1-naphthyl-, and 9-phenanthrylperoxyl, the same order as the absorption peaks of these radicals. Good correlation was found between log k and the energy of the absorption peak. 16 refs., 2 figs., 2 tabs.

  18. Selective formation of triplet alkyl nitrenes from photolysis of beta-azido-propiophenone and their reactivity.

    PubMed

    Singh, Pradeep N D; Mandel, Sarah M; Sankaranarayanan, Jagadis; Muthukrishnan, Sivaramakrishnan; Chang, Mingxin; Robinson, Rachel M; Lahti, Paul M; Ault, Bruce S; Gudmundsdóttir, Anna D

    2007-12-26

    Photolysis of beta-azido propiophenone derivatives, 1, with built-in sensitizer units, leads to selective formation of triplet alkyl nitrenes 2 that were detected directly with laser flash photolysis (lambdamax = 325 nm, tau = 27 ms) and ESR spectroscopy (|D/hc| = 1.64 cm-1, |E/hc| = 0.004 cm-1). Nitrenes 2 were further characterized with argon matrix isolation, isotope labeling, and molecular modeling. The triplet alkyl nitrenes are persistent intermediates that do not abstract H-atoms from the solvent but do decay by dimerizing with another triplet nitrene to form azo products, rather than reacting with an azide precursor. The azo dimer tautomerizes and rearranges to form heterocyclic compound 3. Nitrene 2a, with an n,pi* configuration as the lowest triplet excited state of the its ketone sensitizer moiety, undergoes intramolecular 1,4-H-atom abstraction to form biradical 6, which was identified by argon matrix isolation, isotope labeling, and molecular modeling. beta-Azido-p-methoxy-propiophenone, with a pi,pi* lowest excited state of its triplet sensitizer moiety, does not undergo any secondary photoreactions but selectively yields only triplet alkyl nitrene intermediates that dimerize to form 3b.

  19. 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.

  20. Primary emissions and secondary organic aerosol formation from the exhaust of a flex-fuel (ethanol) vehicle

    NASA Astrophysics Data System (ADS)

    Suarez-Bertoa, R.; Zardini, A. A.; Platt, S. M.; Hellebust, S.; Pieber, S. M.; El Haddad, I.; Temime-Roussel, B.; Baltensperger, U.; Marchand, N.; Prévôt, A. S. H.; Astorga, C.

    2015-09-01

    Incentives to use biofuels may result in increasing vehicular emissions of compounds detrimental to air quality. Therefore, regulated and unregulated emissions from a Euro 5a flex-fuel vehicle, tested using E85 and E75 blends (gasoline containing 85% and 75% of ethanol (vol/vol), respectively), were investigated at 22 and -7 °C over the New European Driving Cycle, at the Vehicle Emission Laboratory at the European Commission Joint Research Centre Ispra, Italy. Vehicle exhaust was comprehensively analyzed at the tailpipe and in a dilution tunnel. A fraction of the exhaust was injected into a mobile smog chamber to study the photochemical aging of the mixture. We found that emissions from a flex-fuel vehicle, fueled by E85 and E75, led to secondary organic aerosol (SOA) formation, despite the low aromatic content of these fuel blends. Emissions of regulated and unregulated compounds, as well as emissions of black carbon (BC) and primary organic aerosol (POA) and SOA formation were higher at -7 °C. The flex-fuel unregulated emissions, mainly composed of ethanol and acetaldehyde, resulted in very high ozone formation potential and SOA, especially at low temperature (860 mg O3 km-1 and up to 38 mg C kg-1). After an OH exposure of 10 × 106 cm-3 h, SOA mass was, on average, 3 times larger than total primary particle mass emissions (BC + POA) with a high O:C ratio (up to 0.7 and 0.5 at 22 and -7 °C, respectively) typical of highly oxidized mixtures. Furthermore, high resolution organic mass spectra showed high 44/43 ratios (ratio of the ions m/z 44 and m/z 43) characteristic of low-volatility oxygenated organic aerosol. We also hypothesize that SOA formation from vehicular emissions could be due to oxidation products of ethanol and acetaldehyde, both short-chain oxygenated VOCs, e.g. methylglyoxal and acetic acid, and not only from aromatic compounds.

  1. Thermodynamic analysis and kinetic modelling of dioxin formation and emissions from power boilers firing salt-laden hog fuel.

    PubMed

    Duo, Wenli; Leclerc, Denys

    2007-04-01

    Both organic chlorine (e.g. PVC) and inorganic chlorides (e.g. NaCl) can be significant chlorine sources for dioxin and furan (PCDD/F) formation in combustion processes. This paper presents a thermodynamic analysis of high temperature salt chemistry. Its influence on PCDD/F formation in power boilers burning salt-laden wood waste is examined through the relationships between Cl2, HCl, NaCl(g) and NaCl(c). These analyses show that while HCl is a product of combustion of PVC-laden municipal solid waste, NaCl can be converted to HCl in hog fuel boilers by reactions with SO2 or alumino-silicate materials. Cl2 is a strong chlorinating agent for PCDD/F formation. HCl can be oxidized to Cl2 by O2, and Cl2 can be reduced back to HCl by SO2. The presence of sulphur at low concentrations thus enhances PCDD/F formation by increasing HCl concentrations. At high concentrations, sulphur inhibits de novo formation of PCDD/Fs through Cl2 reduction by excess SO2. The effect of NH3, CO and NOx on PCDD/F formation is also discussed. A semi-empirical kinetic model is proposed. This model considers both precursor and de novo formation mechanisms. A simplified version is used as a stack emission model. The kinetic model indicates that stack dioxin emissions will increase linearly with decreasing electrostatic precipitator (ESP) efficiency and exponentially with increasing ESP temperature.

  2. Cenosphere formation from heavy fuel oil: a numerical analysis accounting for the balance between porous shells and internal pressure

    NASA Astrophysics Data System (ADS)

    Reddy, Vanteru M.; Rahman, Mustafa M.; Gandi, Appala N.; Elbaz, Ayman M.; Schrecengost, Robert A.; Roberts, William L.

    2016-01-01

    Heavy fuel oil (HFO) as a fuel in industrial and power generation plants ensures the availability of energy at economy. Coke and cenosphere emissions from HFO combustion need to be controlled by particulate control equipment such as electrostatic precipitators, and collection effectiveness is impacted by the properties of these particulates. The cenosphere formation is a function of HFO composition, which varies depending on the source of the HFO. Numerical modelling of the cenosphere formation mechanism presented in this paper is an economical method of characterising cenosphere formation potential for HFO in comparison to experimental analysis of individual HFO samples, leading to better control and collection. In the present work, a novel numerical model is developed for understanding the global cenosphere formation mechanism. The critical diameter of the cenosphere is modelled based on the balance between two pressures developed in an HFO droplet. First is the pressure (Prpf) developed at the interface of the liquid surface and the inner surface of the accumulated coke due to the flow restriction of volatile components from the interior of the droplet. Second is the pressure due to the outer shell strength (PrC) gained from van der Walls energy of the coke layers and surface energy. In this present study it is considered that when PrC ≥ Prpf the outer shell starts to harden. The internal motion in the shell layer ceases and the outer diameter (DSOut) of the shell is then fixed. The entire process of cenosphere formation in this study is analysed in three phases: regression, shell formation and hardening, and post shell hardening. Variations in pressures during shell formation are analysed. Shell (cenosphere) dimensions are evaluated at the completion of droplet evaporation. The rate of fuel evaporation, rate of coke formation and coke accumulation are analysed. The model predicts shell outer diameters of 650, 860 and 1040 µm, and inner diameters are 360, 410

  3. Hydroxyl radical formation during ozonation of multiwalled carbon nanotubes: performance optimization and demonstration of a reactive CNT filter.

    PubMed

    Oulton, Rebekah; Haase, Jason P; Kaalberg, Sara; Redmond, Connor T; Nalbandian, Michael J; Cwiertny, David M

    2015-03-17

    We explored factors influencing hydroxyl radical (•OH) formation during ozonation of multiwalled carbon nanotubes (MWCNTs) and assessed this system's viability as a next-generation advanced oxidation process (AOP). Using standard reactivity metrics for ozone-based AOPs (RCT values), MWCNTs promoted •OH formation during ozonation to levels exceeding ozone (both alone and with activated carbon) and equivalent to ozone with hydrogen peroxide. MWCNTs oxidized with nitric acid exhibited vastly greater rates of ozone consumption and •OH formation relative to as-received MWCNTs. While some of this enhancement reflects their greater suspension stability, a strong correlation between RCT values and surface oxygen concentrations from X-ray photoelectron spectroscopy suggests that surface sites generated during MWCNT oxidation promote •OH exposure. Removal of several ozone-recalcitrant species [para-chlorobenzoic acid (p-CBA), atrazine, DEET, and ibuprofen] was not significantly inhibited in the presence of radical scavengers (humic acid, carbonate), in complex aquatic matrices (Iowa River water) and after 12 h of continuous exposure of MWCNTs to concentrated ozone solutions. As a proof-of-concept, oxidized MWCNTs deposited on a ceramic membrane chemically oxidized p-CBA in a flow through system, with removal increasing with influent ozone concentration and mass of deposited MWCNTs (in mg/cm2). This hybrid membrane platform, which integrates adsorption, oxidation, and filtration via an immobilized MWCNT layer, may serve as the basis for future novel nanomaterial-enabled technologies, although long-term performance trials under representative treatment scenarios remain necessary.

  4. Aberrant presentation of HPA-reactive carbohydrates implies Selectin-independent metastasis formation in human prostate cancer.

    PubMed

    Lange, Tobias; Kupfernagel, Mareike; Wicklein, Daniel; Gebauer, Florian; Maar, Hanna; Brügge, Kathrin; Müller, Imke; Simon, Ronald; Schlomm, Thorsten; Sauter, Guido; Schumacher, Udo

    2014-04-01

    To investigate the impact of prostate cancer cell surface glycosylation as part of the tumor cell-endothelial cell interaction in prostate cancer metastasis. Glycosyltransferase expression was profiled in metastasis-derived prostate cancer cell lines and compared with primary epithelium. Prostate cancer cells were examined for HPA- and selectin-binding and adhesion to endothelium. Spontaneous metastasis xenograft models were established to test the lectin HPA-binding sites as a marker of metastatic competence and to evaluate E-selectin-binding sites in vivo. The importance of selectins for metastasis formation was analyzed using Sele(-/-)/Selp(-/-) mice. The clinical relevance of HPA- and E-selectin-binding sites in prostate cancer was determined. Glycosyltransferases involved in the synthesis of common HPA-binding sites are downregulated in prostate cancer cells. An absence of HPA-reactive carbohydrates specifically indicates spontaneous metastatic spread of prostate cancer xenografts in vivo and a poor prognosis of patients with prostate cancer. HPA-binding sites decrease in lymph node metastases compared with corresponding primary tumors. Common selectin ligands are absent on prostate cancer cells, which do not adhere to recombinant selectins or endothelium under shear stress in vitro. Spontaneous metastasis formation is largely independent of selectins in vivo. E-selectin-binding sites are detectable in only 2% of patients with prostate cancer without prognostic significance. Prostate cancer is characterized by an inverse functional and prognostic importance of HPA-binding sites compared with other adenocarcinomas. Accordingly, this study surprisingly shows that the selectin-selectin ligand axis, which is essential for extravasation and thus metastasis formation in several malignancies, can be circumvented in prostate cancer. ©2014 AACR.

  5. Delineating the relationships among the formation of reactive oxygen species, cell membrane instability and innate autoimmunity in intestinal reperfusion injury.

    PubMed

    Lee, Haekyung; Ko, Eun Hee; Lai, Mark; Wei, Na; Balroop, Javi; Kashem, Zerin; Zhang, Ming

    2014-04-01

    Acute intestinal ischemia is a medical emergency with a high mortality rate, attesting to the need for a better understanding of its pathogenesis and the development of effective therapies. The goal of this study was to delineate the relationships among intracellular and extracellular events in intestinal ischemia/reperfusion (I/R) injury, particularly the formation of reactive oxygen species (ROS), cell membrane instability associated with lipid peroxidation and the innate autoimmune response mediated by natural IgM and complement. A murine model of natural IgM-mediated intestinal I/R was used. Mice overexpressing anti-oxidant enzyme SOD1 were found to have significantly reduced intestinal tissue damage and complete blockage of IgM-mediated complement activation compared with WT controls. To determine if cell membrane instability was an event intermediate between ROS formation and natural IgM-mediated innate autoimmune response, the cell membrane stabilizer (trehalose) was administered to WT mice prior to the induction of intestinal ischemia. Treatment with trehalose significantly protected animals from I/R injury and inhibited IgM-mediated complement activation although it did not prevent membrane lipid peroxidation. These data indicate that in normal mice subjected to I/R injury, intracellular ROS formation is an event upstream of the lipid peroxidation which results in cell membrane instability. The membrane instability leads to an innate autoimmune response by natural IgM and complement. Trehalose, a nontoxic disaccharide tolerated well by animals and humans, has promise as a protective agent for patients with medical conditions related to acute intestinal ischemia.

  6. Ambient Fine Particulate Matter Suppresses In Vivo Proliferation of Bone Marrow Stem Cells through Reactive Oxygen Species Formation

    PubMed Central

    Cui, Yuqi; Jia, Fengpeng; He, Jianfeng; Xie, Xiaoyun; Li, Zhihong; Fu, Minghuan; Hao, Hong; Liu, Ying; Liu, Dylan Z.; Cowan, Peter J.; Zhu, Hua; Sun, Qinghua; Liu, Zhenguo

    2015-01-01

    Aims Some environmental insults, such as fine particulate matter (PM) exposure, significantly impair the function of stem cells. However, it is unknown if PM exposure could affect the population of bone marrow stem cells (BMSCs). The present study was to investigate the effects of PM on BMSCs population and related mechanism(s). Main Metheods PM was intranasally distilled into male C57BL/6 mice for one month. Flow cytometry with antibodies for BMSCs, Annexin V and BrdU ware used to determine the number of BMSCs and the levels of their apoptosis and proliferation in vivo. Phosphorylated Akt (P-Akt) level was determined in the BM cells with western blotting. Intracellular reactive oxygen species (ROS) formation was quantified using flow cytometry analysis. To determine the role of PM-induced ROS in BMSCs population, proliferation, and apotosis, experiments were repeated using N-acetylcysteine (NAC)-treated wild type mice or a triple transgenic mouse line with overexpression of antioxidant network (AON) composed of superoxide dismutase (SOD)1, SOD3, and glutathione peroxidase-1 with decreased in vivo ROS production. Key Findings PM treatment significantly reduced BMSCs population in association with increased ROS formation, decreased P-Akt level, and inhibition of proliferation of BMSCs without induction of apoptosis. NAC treatment or AON overexpression with reduced ROS formation effectively prevented PM-induced reduction of BMSCs population and proliferation with partial recovery of P-Akt level. Significance PM exposure significantly decreased the population of BMSCs due to diminished proliferation via ROS-mediated mechanism (could be partially via inhibition of Akt signaling). PMID:26058063

  7. Effects of different types of fluid resuscitation for hemorrhagic shock on splanchnic organ microcirculation and renal reactive oxygen species formation.

    PubMed

    Wu, Chun-Yu; Chan, Kuang-Cheng; Cheng, Ya-Jung; Yeh, Yu-Chang; Chien, Chiang-Ting

    2015-12-11

    Fluid resuscitation is an indispensable procedure in the acute management of hemorrhagic shock for restoring tissue perfusion, particularly microcirculation in splanchnic organs. Resuscitation fluids include crystalloids, hypertonic saline (HTS), and synthetic colloids, and their selection affects the recovery of microcirculatory blood flow and reactive oxygen species (ROS) formation, which is often evident in the kidney, following reperfusion. In this study, the effects of acute resuscitation with 0.9% saline (NS), 3% HTS, 4% succinylated gelatin (GEL), and 6% hydroxyethyl starch (HES) 130/0.4 were compared in a hemorrhagic shock rat model to analyze restoration of microcirculation among various splanchnic organs and the gracilis muscle and reperfusion-induced renal ROS formation. A total of 96 male Wistar rats were subjected to sham operation (sham group), hemorrhagic shock (control group), and resuscitation with NS, HTS, GEL and HES. Two hours after resuscitation, changes in the mean arterial pressure (MAP), serum lactate level and the microcirculatory blood flow among various splanchnic organs, namely the liver, kidney, and intestine (mucosa, serosal muscular layer, and Peyer's patch), and the gracilis muscle, were compared using laser speckle contrast imaging. Renal ROS formation after reperfusion was investigated using an enhanced in vivo chemiluminescence (CL) method. Microcirculatory blood flow was less severely affected by hemorrhaging in the liver and gracilis muscle. Impairment of microcirculation in the kidney was restored in all resuscitation groups. Resuscitation in the NS group failed to restore intestinal microcirculation. Resuscitation in the HTS, GEL, and HES groups restored intestinal microcirculatory blood flow. By comparison, fluid resuscitation restored hemorrhagic shock-induced hypotension and decreased lactatemia in all resuscitation groups. Reperfusion-induced in vivo renal ROS formation was significantly higher in the GEL and HES groups

  8. In situ time-resolved X-ray diffraction of tobermorite formation in autoclaved aerated concrete: Influence of silica source reactivity and Al addition

    SciTech Connect

    Matsui, Kunio; Kikuma, Jun; Tsunashima, Masamichi; Ishikawa, Tetsuji; Matsuno, Shin-ya; Ogawa, Akihiro; Sato, Masugu

    2011-05-15

    The hydrothermal formation of tobermorite during the processing of autoclaved aerated concrete was investigated by in situ X-ray diffraction (XRD) analysis. High-energy X-rays from a synchrotron radiation source in combination with a newly developed autoclave cell and a photon-counting pixel array detector were used. To investigate the effects of the silica source, reactive quartz from chert and less-reactive quartz from quartz sand were used as starting materials. The effect of Al addition on tobermorite formation was also studied. In all cases, C-S-H, hydroxylellestadite and katoite were clearly observed as intermediates. Acceleration of tobermorite formation by Al addition was clearly observed. However, Al addition did not affect the dissolution rate of quartz. Two pathways, via C-S-H and katoite, were also observed in the Al-containing system. These results suggest that the structure of initially formed C-S-H is important for the subsequent tobermorite formation reactions.

  9. Reactivity of elemental sulfur nanoparticles and their role on the formation of sulfur intermediates

    NASA Astrophysics Data System (ADS)

    Kafantaris, F. C. A.; Druschel, G.

    2014-12-01

    Sulfur biogeochemical cycling involves a vast network of chemical reactions including oxidation, reduction and disproportionation, polymerization (S-S bonding), and aggregation that leads to nanoparticulate elemental sulfur (S8(nano)) and eventually the most stable bulk mineral form, a-S8. These reactions can occur in aqueous systems inorganically, intracellularly as assimilatory or dissimilatory reactions in microbial cells, or in presence of microbial organic exudates (e.g. surfactants). Elemental sulfur participates in nucleophilic and hydrolysis reactions to form sulfur intermediates, such as polysulfide ions. The nucleophilic reaction with sulfide (as H2S or HS-, reaction 1), is a key process in the dissolution of elemental sulfur: xS8 + H2S = Sx2- + 2 H+ (1) Polysulfides are inherently unstable in acidic conditions, experiencing a series of chain elongation reactions to form the S8 ring form of molecular elemental sulfur (overall this is the reverse of reaction 1). S8 rings are also inherently insoluble in water and undergo a very rapid coarsening process to form S8nano that then coarsens more slowly via an Ostwald ripening process to form colloidal particles of a-S8. Coarsening kinetics are influenced by temperature, and the presence/absence and type of surfactants [1]. The amount of polysulfide at any point is thus a balance between the forward and reverse overall reactions represented in reaction 1, and influenced by microbial generation of reduced sulfide and/or microbial production of organic surfactants, and the size of the elemental sulfur particles. Here we present some preliminary data on the kinetics of elemental sulfur consumption (reaction 1) that have been tested in various sizes and surface properties of the sulfur nanoparticles. The surface area and presence (or absence) of surfactant molecules influences the kinetics of polysulfide formation. The cycling of that reaction may play a significant role to the element's bioavailability to

  10. In situ formation of leak-free polyethylene glycol (PEG) membranes in microfluidic fuel cells.

    PubMed

    Ho, W F; Lim, K M; Yang, K-L

    2016-11-29

    Membraneless microfluidic fuel cells operated under two co-laminar flows often face serious fuel cross-over problems, especially when flow rates are close to zero. In this study, we show that polyethylene glycol (PEG) monomers can be cross-linked inside microfluidic channels to form leak-free PEG membranes, which prevent mixing of two incompatible electrolyte solutions while allowing diffusion of certain molecules (e.g. glucose) and ions. By using PEG monomers of different molecular weights and cross-linking conditions, we are able to tailor selectivity of the membrane to allow passage of glucose while blocking larger molecules such as trypan blue. As a proof of principle, a microfluidic fuel cell with a PEG membrane and two incompatible electrolytes (acid and base) is demonstrated. Thanks to the leak-free nature of the PEG membrane, these two electrolytes do not mix together even at very slow flow rates. This microfluidic fuel cell is able to generate a voltage up to ∼450 mV from 10 mM of glucose with a flow rate of 20 μL min(-1). This microfluidic fuel cell is potentially useful as a miniature power source for many applications.

  11. Basic combustion and pollutant-formation processes for pulverized fuels. Quarterly technical progress report No. 4, 1 July 1981-30 September 1981

    SciTech Connect

    Germane, G.J.; Smoot, L.D.

    1981-10-15

    This contract study of basic combustion and pollutant formation processes for pulverized solid fossil fuels includes coal-water mixtures and chars derived from coal pyrolysis, liquefaction or gasification processes. The factors that affect the physical properties of coal-water mixtures (CWM) have been identified and characterization tests initiated to determine how these variables (e.g., solids loading, particle size, particle size distribution, additives) affect the coal slurries. A bench-scale apparatus consisting of a pressure vessel and an atomizing nozzle was designed and is being fabricated. This apparatus will assist in the development of handling and atomization techniques for the combustion tests. It will also aid in comparing viscosities of slurries of different solids loadings and coal types. Chars were obtained for characterization tests. A series of potential tests to characterize the chars was identified. Grading and sizing of the chars was begun as well as elemental analysis. Samples of the chars were sent to Phillips for CO/sub 2/ reactivity tests to be performed. Coding for incorporation of swirling flows into the two-dimensional coal combustion model (PCGC-2) was completed. Debugging was initiated and sample computations are performed for a gaseous, isothermal system for low swirl numbers. Convergence problems were encountered when attempts were made to complete runs at higher swirl numbers.

  12. REACTIVE FORCE FIELDS FOR Y-DOPED BaZrO3 ELECTROLYTE AND NI-ANODE. POTENTIAL CATHODE MATERIALS FOR APPLICATION IN PROTON CERAMIC FUEL CELLS

    SciTech Connect

    Boris Merinov; Adri van Duin; Sossina Haile; William A. Goddard III

    2004-10-30

    Based on quantum mechanical data obtained for the Y-doped BaZrO{sub 3} electrolyte and Ni-anode Reactive Force Field parameters have been developed for further molecular dynamics simulations of the proton diffusion and electrode/electrolyte interfaces. Electronic and atomic structures of different terminations of the (001) BaZrO{sub 3} surface have been studied using first-principles calculations. Several potential cathode materials for the Y-doped BaZrO{sub 3} system were synthesized via glycine nitrate combustion method. Of the five potential cathode materials examined BaZr{sub 0.40}Pr{sub 0.40}Gd{sub 0.20}O{sub 3} and BaZr{sub 0.60}Y{sub 0.20}Co{sub 0.20}O{sub 3} appear to be the most promising for further applications in proton ceramic fuel cells. Fuel cell test of a Y-doped BaZrO{sub 3} thin film using platinum ink for both electrodes have been performed. The obtained results shows that a robust method for fabricating crack-free thin membranes, as well as methods for sealing anode and cathode chambers, have successfully been developed.

  13. ReaxFF reactive force field for solid oxide fuel cell systems with application to oxygen ion transport in yttria-stabilized zirconia.

    PubMed

    van Duin, Adri C T; Merinov, Boris V; Jang, Seung Soon; Goddard, William A

    2008-04-10

    We present the ReaxFF reactive force field developed to provide a first-principles-based description of oxygen ion transport through yttria-stabilized zirconia (YSZ) solid oxide fuel cell (SOFC) membranes. All parameters for ReaxFF were optimized to reproduce quantum mechanical (QM) calculations on relevant condensed phase and cluster systems. We validated the use of ReaxFF for fuel cell applications by using it in molecular dynamics (MD) simulations to predict the oxygen ion diffusion coefficient in yttria-stabilized zirconia as a function of temperature. These values are in excellent agreement with experimental results, setting the stage for the use of ReaxFF to model the transport of oxygen ions through the YSZ electrolyte for SOFC. Because ReaxFF descriptions are already available for some catalysts (e.g., Ni and Pt) and under development for other high-temperature catalysts, we can now consider fully first-principles-based simulations of the critical functions in SOFC, enabling the possibility of in silico optimization of these materials. That is, we can now consider using theory and simulation to examine the effect of materials modifications on both the catalysts and transport processes in SOFC.

  14. Effects of hypothermic storage of striped bass (Morone saxatilis) sperm on intracellular calcium, reactive oxygen species formation, mitochondrial function, motility, and viability

    USDA-ARS?s Scientific Manuscript database

    Experiments were conducted to determine the effect of hypothermic 24 h storage of striped bass sperm cells (Morone saxatilis) on viability, intracellular Ca2+ [Ca2+]i, mitochondrial membrane potential (''m), and reactive oxygen species (ROS) formation as determined by flow cytometry; motion activati...

  15. Effects of hypothermic storage of striped bass (Morone saxatilis) sperm on intracellular calcium, reactive oxygen species formation, mitochondrial function, motility, and viability

    USDA-ARS?s Scientific Manuscript database

    Experiments were conducted to determine the effect of hypothermic 24 h storage of striped bass sperm cells on viability, intracellular Ca2+ ([Ca2+]i), mitochondrial membrane potential (D'm), and reactive oxygen species (ROS) formation (oxidation of hydroethidine to ethidium) as determined by flow cy...

  16. Basic combustion and pollutant-formation processes for pulverized fuels. Quarterly technical progress report No. 1, 1 October 1980-31 December 1980

    SciTech Connect

    Germane, Geoffery J.; Smoot, L. Douglas

    1981-01-15

    A study of basic combustion and pollutant formation processes for pulverized solid fossil fuels has been initiated. The solid fossil fuels under consideration for this research include such solid fuels as non-bituminous coal types, solvent refined coal, combustion char, petroleum coke, oil shale and tar sand. The potential industrial application of pulverized fuels other than coal provides some promise for relief from present and future conventional fuel shortages. Utilization problems with these fuels such as flame stability, fuel handling, pollutant emission and ash and slag formation in large-scale furnaces may be fundamentally addressed in laboratory reactors using properly scaled operating variables. An extensive literature search was begun to assess current knowledge relative to utilization of these fuels. This review will provide a basis for selection of three solid fuels for testing. Pertinent information from industrial contacts will also be used in the fuel selection. The criteria to be used in the selection of these fuels include availability for economic industrial use, adaptability, grindability, flame stability, entrainability, uniformity, applicability to direct firing with air, solidity with heating, availability to the BYU Combustion Laboratory, cost, other physical characteristics affecting their use, industrial input and recommendations, and DOE approval. The existing laboratory coal combustor at BYU will be modified to provide flexibility for a potentially wide range of operating characteristics with the selected solid fuels. A computer system has been identified for interface both to the reactor for data acquisition and control of operating variables and to the main research computer for final data reduction and display.

  17. The study of alternate, solid-phase fluorinating agents for use in reactive gas recycle of used nuclear fuel

    NASA Astrophysics Data System (ADS)

    Inabinett, Dillon

    Surrogate oxides of the Used Nuclear Fuel (UNF) matrix were fluorinated using alternate, solid-phase fluorinating agents XeF2 and NH4HF2 to form volatile and non-volatile compounds and demonstrate the possibility of a chemical and thermal separations. A matrix of experiments was conducted at the milligram quantity scale using a Shimadzu DTG-60 TG/DTA installed at SRNL (Savannah River National Laboratory) for testing of all non-radioactive samples and a Netzsch STA 409 TGA installed in the laboratory at USC (University of South Carolina) for testing of all radioactive samples. The fluorination and subsequent volatilization potentials were analyzed by mixing excess fluorinating agent with a surrogate oxide at roughly a 2:1 ratio and then heated to elevated temperatures for analysis. Thermogravimetric and differential thermal analysis allowed for reaction pathways to be analyzed and suggest windows both thermally and chemically for separations of these various components. The differences in thermophysical properties of these products can be utilized as a starting point to effectively separate, isolate, and collect product streams with different product composition for further processing. The study of these chemistries could be incorporated into advanced separations methods to provide another possible solution for the long-term sustainability of nuclear power as the issue of reuse and disposal of commercial fuel continues to grow.

  18. Evaluation of Liquid Fuel Spray Models for Hybrid RANS/LES and DLES Prediction of Turbulent Reactive Flows

    NASA Astrophysics Data System (ADS)

    Afshar, Ali

    An evaluation of Lagrangian-based, discrete-phase models for multi-component liquid sprays encountered in the combustors of gas turbine engines is considered. In particular, the spray modeling capabilities of the commercial software, ANSYS Fluent, was evaluated. Spray modeling was performed for various cold flow validation cases. These validation cases include a liquid jet in a cross-flow, an airblast atomizer, and a high shear fuel nozzle. Droplet properties including velocity and diameter were investigated and compared with previous experimental and numerical results. Different primary and secondary breakup models were evaluated in this thesis. The secondary breakup models investigated include the Taylor analogy breakup (TAB) model, the wave model, the Kelvin-Helmholtz Rayleigh-Taylor model (KHRT), and the Stochastic secondary droplet (SSD) approach. The modeling of fuel sprays requires a proper treatment for the turbulence. Reynolds-averaged Navier-Stokes (RANS), large eddy simulation (LES), hybrid RANS/LES, and dynamic LES (DLES) were also considered for the turbulent flows involving sprays. The spray and turbulence models were evaluated using the available benchmark experimental data.

  19. FINE PARTICLE EMISSIONS FROM RESIDUAL FUEL OIL COMBUSTION: CHARACTERIZATION AND MECHANISMS OF FORMATION

    EPA Science Inventory

    The paper gives results of a comparison of the characteristics of particulate matter (PM) emitted from residual fuel oil combustion in two types of combustion equipment. A small commercial 732-kW fire-tube boiler yielded a weakly bi-modal particulate size distribution (PSD) with...

  20. FINE PARTICLE EMISSIONS FROM RESIDUAL FUEL OIL COMBUSTION: CHARACTERIZATION AND MECHANISMS OF FORMATION

    EPA Science Inventory

    The paper gives results of a comparison of the characteristics of particulate matter (PM) emitted from residual fuel oil combustion in two types of combustion equipment. A small commercial 732-kW-rated fire-tube boiler yielded a weakly bimodal PM size distribution (PSD) with over...

  1. FINE PARTICLE EMISSIONS FROM RESIDUAL FUEL OIL COMBUSTION: CHARACTERIZATION AND MECHANISMS OF FORMATION

    EPA Science Inventory

    The paper gives results of a comparison of the characteristics of particulate matter (PM) emitted from residual fuel oil combustion in two types of combustion equipment. A small commercial 732-kW-rated fire-tube boiler yielded a weakly bimodal PM size distribution (PSD) with over...

  2. Cryogenic hydrogen fuel for controlled inertial confinement fusion (formation of reactor-scale cryogenic targets)

    SciTech Connect

    Aleksandrova, I. V.; Koresheva, E. R. Krokhin, O. N.; Osipov, I. E.

    2016-12-15

    In inertial fusion energy research, considerable attention has recently been focused on low-cost fabrication of a large number of targets by developing a specialized layering module of repeatable operation. The targets must be free-standing, or unmounted. Therefore, the development of a target factory for inertial confinement fusion (ICF) is based on methods that can ensure a cost-effective target production with high repeatability. Minimization of the amount of tritium (i.e., minimization of time and space at all production stages) is a necessary condition as well. Additionally, the cryogenic hydrogen fuel inside the targets must have a structure (ultrafine layers—the grain size should be scaled back to the nanometer range) that supports the fuel layer survivability under target injection and transport through the reactor chamber. To meet the above requirements, significant progress has been made at the Lebedev Physical Institute (LPI) in the technology developed on the basis of rapid fuel layering inside moving free-standing targets (FST), also referred to as the FST layering method. Owing to the research carried out at LPI, unique experience has been gained in the development of the FST-layering module for target fabrication with an ultrafine fuel layer, including a reactor- scale target design. This experience can be used for the development of the next-generation FST-layering module for construction of a prototype of a target factory for power laser facilities and inertial fusion power plants.

  3. Cryogenic hydrogen fuel for controlled inertial confinement fusion (formation of reactor-scale cryogenic targets)

    NASA Astrophysics Data System (ADS)

    Aleksandrova, I. V.; Koresheva, E. R.; Krokhin, O. N.; Osipov, I. E.

    2016-12-01

    In inertial fusion energy research, considerable attention has recently been focused on low-cost fabrication of a large number of targets by developing a specialized layering module of repeatable operation. The targets must be free-standing, or unmounted. Therefore, the development of a target factory for inertial confinement fusion (ICF) is based on methods that can ensure a cost-effective target production with high repeatability. Minimization of the amount of tritium (i.e., minimization of time and space at all production stages) is a necessary condition as well. Additionally, the cryogenic hydrogen fuel inside the targets must have a structure (ultrafine layers—the grain size should be scaled back to the nanometer range) that supports the fuel layer survivability under target injection and transport through the reactor chamber. To meet the above requirements, significant progress has been made at the Lebedev Physical Institute (LPI) in the technology developed on the basis of rapid fuel layering inside moving free-standing targets (FST), also referred to as the FST layering method. Owing to the research carried out at LPI, unique experience has been gained in the development of the FST-layering module for target fabrication with an ultrafine fuel layer, including a reactor- scale target design. This experience can be used for the development of the next-generation FST-layering module for construction of a prototype of a target factory for power laser facilities and inertial fusion power plants.

  4. FINE PARTICLE EMISSIONS FROM RESIDUAL FUEL OIL COMBUSTION: CHARACTERIZATION AND MECHANISMS OF FORMATION

    EPA Science Inventory

    The paper gives results of a comparison of the characteristics of particulate matter (PM) emitted from residual fuel oil combustion in two types of combustion equipment. A small commercial 732-kW fire-tube boiler yielded a weakly bi-modal particulate size distribution (PSD) with...

  5. Using Reactive Transport Modeling to Understand Formation of the Stimson Sedimentary Unit and Altered Fracture Zones at Gale Crater, Mars

    NASA Technical Reports Server (NTRS)

    Hausrath, E. M.; Ming, D. W.; Peretyazhko, T.; Rampe, E. B.

    2017-01-01

    Water flowing through sediments at Gale Crater, Mars created environments that were likely habitable, and sampled basin-wide hydrological systems. However, many questions remain about these environments and the fluids that generated them. Measurements taken by the Mars Science Laboratory Curiosity of multiple fracture zones can help constrain the environments that formed them because they can be compared to nearby associated parent material (Figure 1). For example, measurements of altered fracture zones from the target Greenhorn in the Stimson sandstone can be compared to parent material measured in the nearby Big Sky target, allowing constraints to be placed on the alteration conditions that formed the Greenhorn target from the Big Sky target. Similarly, CheMin measurements of the powdered < 150 micron fraction from the drillhole at Big Sky and sample from the Rocknest eolian deposit indicate that the mineralogies are strikingly similar. The main differences are the presence of olivine in the Rocknest eolian deposit, which is absent in the Big Sky target, and the presence of far more abundant Fe oxides in the Big Sky target. Quantifying the changes between the Big Sky target and the Rocknest eolian deposit can therefore help us understand the diagenetic changes that occurred forming the Stimson sedimentary unit. In order to interpret these aqueous changes, we performed reactive transport modeling of 1) the formation of the Big Sky target from a Rocknest eolian deposit-like parent material, and 2) the formation of the Greenhorn target from the Big Sky target. This work allows us to test the relationships between the targets and the characteristics of the aqueous conditions that formed the Greenhorn target from the Big Sky target, and the Big Sky target from a Rocknest eolian deposit-like parent material.

  6. Hydroxylated polychlorinated biphenyls increase reactive oxygen species formation and induce cell death in cultured cerebellar granule cells

    SciTech Connect

    Dreiem, Anne Rykken, Sidsel; Lehmler, Hans-Joachim; Robertson, Larry W.; Fonnum, Frode

    2009-10-15

    Polychlorinated biphenyls (PCBs) are persistent organic pollutants that bioaccumulate in the body, however, they can be metabolized to more water-soluble products. Although they are more readily excreted than the parent compounds, some of the metabolites are still hydrophobic and may be more available to target tissues, such as the brain. They can also cross the placenta and reach a developing foetus. Much less is known about the toxicity of PCB metabolites than about the parent compounds. In the present study, we have investigated the effects of eight hydroxylated (OH) PCB congeners (2'-OH PCB 3, 4-OH PCB 14, 4-OH PCB 34, 4'-OH PCB 35, 4-OH PCB 36, 4'-OH PCB 36, 4-OH PCB 39, and 4'-OH PCB 68) on reactive oxygen species (ROS) formation and cell viability in rat cerebellar granule cells. We found that, similar to their parent compounds, OH-PCBs are potent ROS inducers with potency 4-OH PCB 14 < 4-OH PCB 36 < 4-OH PCB 34 < 4'-OH PCB 36 < 4'-OH PCB 68 < 4-OH PCB 39 < 4'-OH PCB 35. 4-OH PCB 36 was the most potent cell death inducer, and caused apoptotic or necrotic morphology depending on concentration. Inhibition of ERK1/2 kinase with U0126 reduced both cell death and ROS formation, suggesting that ERK1/2 activation is involved in OH-PCB toxicity. The results indicate that the hydroxylation of PCBs may not constitute a detoxification reaction. Since OH-PCBs like their parent compounds are retained in the body and may be more widely distributed to sensitive tissues, it is important that not only the levels of the parent compounds but also the levels of their metabolites are taken into account during risk assessment of PCBs and related compounds.

  7. Negative Regulation of Leptin-induced Reactive Oxygen Species (ROS) Formation by Cannabinoid CB1 Receptor Activation in Hypothalamic Neurons.

    PubMed

    Palomba, Letizia; Silvestri, Cristoforo; Imperatore, Roberta; Morello, Giovanna; Piscitelli, Fabiana; Martella, Andrea; Cristino, Luigia; Di Marzo, Vincenzo

    2015-05-29

    The adipocyte-derived, anorectic hormone leptin was recently shown to owe part of its regulatory effects on appetite-regulating hypothalamic neuropeptides to the elevation of reactive oxygen species (ROS) levels in arcuate nucleus (ARC) neurons. Leptin is also known to exert a negative regulation on hypothalamic endocannabinoid levels and hence on cannabinoid CB1 receptor activity. Here we investigated the possibility of a negative regulation by CB1 receptors of leptin-mediated ROS formation in the ARC. Through pharmacological and molecular biology experiments we report data showing that leptin-induced ROS accumulation is 1) blunted by arachidonyl-2'-chloroethylamide (ACEA) in a CB1-dependent manner in both the mouse hypothalamic cell line mHypoE-N41 and ARC neuron primary cultures, 2) likewise blocked by a peroxisome proliferator-activated receptor-γ (PPAR-γ) agonist, troglitazone, in a manner inhibited by T0070907, a PPAR-γ antagonist that also inhibited the ACEA effect on leptin, 3) blunted under conditions of increased endocannabinoid tone due to either pharmacological or genetic inhibition of endocannabinoid degradation in mHypoE-N41 and primary ARC neuronal cultures from MAGL(-/-) mice, respectively, and 4) associated with reduction of both PPAR-γ and catalase activity, which are reversed by both ACEA and troglitazone. We conclude that CB1 activation reverses leptin-induced ROS formation and hence possibly some of the ROS-mediated effects of the hormone by preventing PPAR-γ inhibition by leptin, with subsequent increase of catalase activity. This mechanism might underlie in part CB1 orexigenic actions under physiopathological conditions accompanied by elevated hypothalamic endocannabinoid levels. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

  8. Formation of ferrihydrite and associated iron corrosion products in permeable reactive barriers of zero-valent iron

    NASA Technical Reports Server (NTRS)

    Furukawa, Yoko; Kim, Jin-Wook; Watkins, Janet; Wilkin, Richard T.

    2002-01-01

    Ferrihydrite, which is known to form in the presence of oxygen and to be stabilized by the adsorption of Si, PO4 and SO4, is ubiquitous in the fine-grained fractions of permeable reactive barrier (PRB) samples from the U.S. Coast Guard Support Center (Elizabeth City, NC) and the Denver Federal Center (Lakewood, CO) studied by high-resolution transmission electron microscopy and selected area electron diffraction. The concurrent energy-dispersive X-ray data indicate a strong association between ferrihydrite and metals such as Si, Ca, and Cr. Magnetite, green rust 1, aragonite, calcite, mackinawite, greigite and lepidocrocite were also present, indicative of a geochemical environment that is temporally and spatially heterogeneous. Whereas magnetite, which is known to form due to anaerobic Fe0 corrosion, passivates the Fe0 surface, ferrihydrite precipitation occurs away from the immediate Fe0 surface, forming small (<0.1 microm) discrete clusters. Consequently, Fe0-PRBs may remain effective for a longer period of time in slightly oxidized groundwater systems where ferrihydrite formation occurs compared to oxygen-depleted systems where magnetite passivation occurs. The ubiquitous presence of ferrihydrite suggests that the use of Fe0-PRBs may be extended to applications that require contaminant adsorption rather than, or in addition to, redox-promoted contaminant degradation.

  9. Role of nitrogen in the formation of hard and elastic CNx thin films by reactive magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Hellgren, Niklas; Johansson, Mats P.; Broitman, Esteban; Hultman, Lars; Sundgren, Jan-Eric

    1999-02-01

    Carbon nitride films, deposited by reactive dc magnetron sputtering in Ar/N2 discharges, were studied with respect to composition, structure, and mechanical properties. CNx films, with 0<=x<=0.35, were grown onto Si (001) substrates at temperatures between 100 and 550 °C. The total pressure was kept constant at 3.0 mTorr with the N2 fraction varied from 0 to 1. As-deposited films were studied by Rutherford-backscattering spectroscopy, x-ray photoelectron spectroscopy, electron-energy loss spectroscopy, Raman and Fourier transform infrared spectroscopy, and nanoindentation. Three characteristic film structures could be identified: For temperatures below ~150 °C, an amorphous phase forms, the properties of which are essentially unaffected by the nitrogen concentration. For temperatures above ~200 °C, a transition from a graphitelike phase to a ``fullerenelike'' phase is observed when the nitrogen concentration increases from ~5 to ~15 at. %. This fullerenelike phase exhibits high hardness values and extreme elasticity, as measured by nanoindentation. A ``defected-graphite'' model, where nitrogen atoms goes into substitutional graphite sites, is suggested for explaining this structural transformation. When a sufficient number of nitrogen atoms is incorporated, formation of pentagons is promoted, leading to curving of the basal planes. This facilitates cross-linking between the planes and a distortion of the graphitic structure, and a strong three-dimensional covalently bonded network is formed.

  10. Formation of ferrihydrite and associated iron corrosion products in permeable reactive barriers of zero-valent iron

    NASA Technical Reports Server (NTRS)

    Furukawa, Yoko; Kim, Jin-Wook; Watkins, Janet; Wilkin, Richard T.

    2002-01-01

    Ferrihydrite, which is known to form in the presence of oxygen and to be stabilized by the adsorption of Si, PO4 and SO4, is ubiquitous in the fine-grained fractions of permeable reactive barrier (PRB) samples from the U.S. Coast Guard Support Center (Elizabeth City, NC) and the Denver Federal Center (Lakewood, CO) studied by high-resolution transmission electron microscopy and selected area electron diffraction. The concurrent energy-dispersive X-ray data indicate a strong association between ferrihydrite and metals such as Si, Ca, and Cr. Magnetite, green rust 1, aragonite, calcite, mackinawite, greigite and lepidocrocite were also present, indicative of a geochemical environment that is temporally and spatially heterogeneous. Whereas magnetite, which is known to form due to anaerobic Fe0 corrosion, passivates the Fe0 surface, ferrihydrite precipitation occurs away from the immediate Fe0 surface, forming small (<0.1 microm) discrete clusters. Consequently, Fe0-PRBs may remain effective for a longer period of time in slightly oxidized groundwater systems where ferrihydrite formation occurs compared to oxygen-depleted systems where magnetite passivation occurs. The ubiquitous presence of ferrihydrite suggests that the use of Fe0-PRBs may be extended to applications that require contaminant adsorption rather than, or in addition to, redox-promoted contaminant degradation.

  11. Basin and range-age reactivation of the ancestral Rocky Mountains in Texas Panhandle: evidence from Ogallala Formation

    SciTech Connect

    Budnik, R.T.

    1984-04-01

    The Ogallala Formation (Neogene) is a widespread syntectonic alluvial apron that was shed eastward from the Rio Grande rift and related uplifts in Colorado and New Mexico during Basin and Range extension. In the Texas Panhandle, the Ogallala completely buried Ancestral Rocky Mountain (Pennsylvanian) structures. Renewed movement on these older structures during the Neogene influenced the thickness and facies distribution of the Ogallala. The Ogallala thickens into the Palo Duro, Dalhart, and Anadarko basins. Major distributary channels on Ogallala alluvial fans coincide with the axes of these basins, whereas major interchannel areas overlie intervening uplifts. Second-order structures subtly influenced the unit as well. For example, the Carson basin, a Pennsylvanian rhomb graben along the Amarillo uplift, the Ogallala is over 250 m (820 ft) thick compared with 90 m (275 ft) in adjacent areas. Within the Palo Duro basin, local highs controlled the distribution of thin, interchannel flood-basin and lacustrine deposits. Thicker, braided-stream channel deposits follow local lows. Later movement on the Amarillo uplift broadly folded the Ogallala. The southern high plains surface subtly reflects basement structure, with topographic highs overlying basement highs, suggesting post-Ogallala deformation within the Palo Duro basin. The Amarillo uplift is approximately perpendicular to the Rio Grande rift and parallel to the direction of Basin and Range extension. Thus, the stress field that produced the rift may have caused strike-slip movement and reactivation of the Carson basin along the Amarillo uplift.

  12. Formation of long-lived reactive species of blood serum proteins induced by low-intensity irradiation of helium-neon laser and their involvement in the generation of reactive oxygen species.

    PubMed

    Ivanov, Vladimir E; Usacheva, Anna M; Chernikov, Anatoly V; Bruskov, Vadim I; Gudkov, Sergey V

    2017-09-14

    It was demonstrated that low-intensity radiation of helium-neon (He-Ne) laser at 632.8nm, which leads to the transition of oxygen to a singlet state, causes the formation of reactive oxygen species (ROS) - hydrogen peroxide, hydroxyl and superoxide (hydroperoxide) radicals - in aqueous solutions. The oxygen effect - dependence of hydrogen peroxide formation on the concentration of molecular oxygen - was shown, and the participation of singlet oxygen, hydroxyl radicals and superoxide (hydroperoxide) radicals in this process was testified. Laser radiation-induced ROS in solutions of blood serum proteins, bovine serum albumin and bovine gamma-globulin, cause the formation of long-lived reactive protein species (LRPS) with a half-life of about 4h. The generation of LRPS caused by laser irradiation results in prolonged several-hour generation of ROS - hydrogen peroxide, hydroxyl and superoxide radicals. As affected by LRPS, coupled radical reactions lead to conversion of dissolved molecular oxygen to hydrogen peroxide. Irradiation with light sources away from the oxygen absorption band is not attended by formation of ROS and LRPS. A consideration is provided for the possible molecular mechanisms of ROS formation under the influence of He-Ne laser irradiation, the role of proteins in their generation and the biological significance of these processes. Copyright © 2017 Elsevier B.V. All rights reserved.

  13. Photochemical modeling of emissions trading of highly reactive volatile organic compounds in Houston, Texas. 1. Reactivity based trading and potential for ozone hot spot formation.

    PubMed

    Wang, Linlin; Thompson, Tammy; McDonald-Buller, Elena C; Webb, Alba; Allen, David T

    2007-04-01

    As part of the State Implementation Plan for attaining the National Ambient Air Quality Standard for ozone, the Texas Commission of Environmental Quality has created a Highly Reactive Volatile Organic Compounds (HRVOC) Emissions Cap and Trade Program for industrial point sources in the Houston/Galveston/Brazoria area. This program has a number of unique features, including its focus on a limited group of ozone precursors and its provisions for trading emissions based on atmospheric reactivity. This series of papers examines the potential air quality impacts of this new emission trading program through photochemical modeling of potential trading scenarios; this first paper in the series describes the air quality modeling methods used to assess potential trades, the potential for localized increases in ozone concentrations (ozone "hot spots") due to HRVOC emission trading, and the use of reactivity scales in the trading. When HRVOC emissions are traded on a mass basis, the simulations indicate that trading of HRVOC allowances between facilities resulted in less than 0.15 ppb (<0.13%) and 0.06 ppb (<0.06%) increases in predicted maximum, area-wide 1-h averaged and 8-h averaged ozone concentrations, respectively. Maximum decreases in ozone concentrations associated with trading, as opposed to across-the-board reductions, were larger than the increases. All of these changes are small compared to the maximum changes in ozone concentrations due to the VOC emissions from these sources (up to 5-10 ppb for 8 h averages; up to 30 ppb for 1-h averages). When emissions of HRVOCs are traded for other, less reactive emissions, on a reactivity weighted basis, air quality simulations indicate that daily maximum ozone concentrations increased by less than 0.3%. Because these relatively small changes (< 1%) are for unlikely trading scenarios designed to produce a maximum change in ozone concentrations (all emissions traded into localized regions), the simulations indicate that the

  14. Nano composite membrane-electrode assembly formation for fuel cell-modeling aspects

    NASA Astrophysics Data System (ADS)

    Vaivars, G.; Linkov, V.

    2007-12-01

    Long term stability is an essential requirement for fuel cell applications in automobile and stationary energy systems. In these systems the agglomeration of the catalyst nanoparticles is a well-known phenomenon which cannot be easily overcome or compensated for by re-designing the system. A direct result of this occurrence is the irreversible decrease of the electrochemical performance. Irregularities in electric field distribution are one root cause for migration and subsequent agglomeration of the catalyst nanoparticle. In this work, the impact of the electrode mechanical deformation on electric field distribution was studied using a computer modeling approach. Model of a Proton Exchange Membrane (PEM) fuel cell with interdigitated flow field from Comsol Chemical Engineering/Electrochemical Engineering Module library was used for simulations. It was established that by minimizing the backing layer deformation it is possible to achieve some improvement in current distribution.

  15. Deposit formation in hydrocarbon rocket fuels with an evaluation of a propane heat transfer correlation

    NASA Technical Reports Server (NTRS)

    Masters, P. A.; Aukerman, C. A.

    1982-01-01

    A high pressure fuel coking testing apparatus was designed and developed and was used to evaluate thermal decomposition limits and carbon decomposition rates in heated copper tubes for hydrocarbon fuels. A commercial propane (90% grade) and chemically pure (CP) propane were tested. Heat transfer to supercritical propane was evaluated at 136 atm, bulk fluid velocities of 6 to 30 m/s, and tube wall temperatures in the range of 422 to 811 K. A forced convection heat transfer correlation developed in a previous test effort verified a prediction of most of the experimental data within a + or - 30% range, with good agreement for the CP propane data. No significant differences were apparent in the predictions derived from the correlation when the carbon resistance was included with the film resistance. A post-test scanning electron microprobe analysis indicated occurrences of migration and interdiffusion of copper into the carbon deposit.

  16. Experimental investigation of homogeneous charge compression ignition combustion of biodiesel fuel with external mixture formation in a CI engine.

    PubMed

    Ganesh, D; Nagarajan, G; Ganesan, S

    2014-01-01

    In parallel to the interest in renewable fuels, there has also been increased interest in homogeneous charge compression ignition (HCCI) combustion. HCCI engines are being actively developed because they have the potential to be highly efficient and to produce low emissions. Even though HCCI has been researched extensively, few challenges still exist. These include controlling the combustion at higher loads and the formation of a homogeneous mixture. To obtain better homogeneity, in the present investigation external mixture formation method was adopted, in which the fuel vaporiser was used to achieve excellent HCCI combustion in a single cylinder air-cooled direct injection diesel engine. In continuation of our previous works, in the current study a vaporised jatropha methyl ester (JME) was mixed with air to form a homogeneous mixture and inducted into the cylinder during the intake stroke to analyze the combustion, emission and performance characteristics. To control the early ignition of JME vapor-air mixture, cooled (30 °C) Exhaust gas recirculation (EGR) technique was adopted. The experimental result shows 81% reduction in NOx and 72% reduction in smoke emission.

  17. Fine Particle Emissions from Residual Fuel Oil Combustion: Characterization and Mechanisms of Formation

    DTIC Science & Technology

    2000-08-04

    NC, 1999. 3 . Bachmann, J. D ., Damberg, R. J., Caldwell, J. C., Ed- wards, C., and Koman, P. D ., Review of the National Ambient Air Quality Standards...residual fuel oil combustion to be suspect, as far as emission of toxic fine particles is concerned. Build- ing upon previous work examining the...control number. 1. REPORT DATE 04 AUG 2000 2. REPORT TYPE N/A 3 . DATES COVERED - 4. TITLE AND SUBTITLE Fine Particle Emissions from Residual

  18. Characterization of bubble formation in microfluidic fuel cells employing hydrogen peroxide

    NASA Astrophysics Data System (ADS)

    Shyu, Jin-Cherng; Huang, Cheng-Ling

    2011-03-01

    In order to examine bubble evolution and discuss the effects of bubbles effect on the performance of microfluidic fuel cells, two 1.2-mm-depth microfluidic fuel cells employing 0.1-M H2O2 dissolved in 0.1-M NaOH solution and 0.05-M H2SO4 solution as fuel and oxidant, respectively, with transparent lids having width of 1.0 mm and 0.5 mm, are fabricated in the present study for both cell performance measurement and flow visualization. The results show that the present cells operating at either a higher volumetric flow or a smaller microchannel width yield both better performance and more violent bubble growth. The bubble growth rate, Qg, in a given microfluidic fuel cell is almost the same at different regions of that cell at a given volumetric flow rate, i.e. 10-5 cm3 s-1 and 5 × 10-5 cm3 s-1, respectively, for cells having widths of 0.5 mm and 1.0 mm at Ql = 0.05 mL min-1, and slightly increases at higher volumetric flow rates. Furthermore, the present study reports approximately constant values of Qg/CdA at various volumetric flow rates, which are 2 × 10-2 and 5 × 10-2 cm3 s-1 A-1, respectively, for cells having channel widths of 0.5 mm and 1.0 mm. In addition, the 0.5-mm-wide cell has higher cell output and performs more tortuous polarization curve.

  19. Quantitative Surface Emissivity and Temperature Measurements of a Burning Solid Fuel Accompanied by Soot Formation

    NASA Technical Reports Server (NTRS)

    Piltch, Nancy D.; Pettegrew, Richard D.; Ferkul, Paul; Sacksteder, K. (Technical Monitor)

    2001-01-01

    Surface radiometry is an established technique for noncontact temperature measurement of solids. We adapt this technique to the study of solid surface combustion where the solid fuel undergoes physical and chemical changes as pyrolysis proceeds, and additionally may produce soot. The physical and chemical changes alter the fuel surface emissivity, and soot contributes to the infrared signature in the same spectral band as the signal of interest. We have developed a measurement that isolates the fuel's surface emissions in the presence of soot, and determine the surface emissivity as a function of temperature. A commercially available infrared camera images the two-dimensional surface of ashless filter paper burning in concurrent flow. The camera is sensitive in the 2 to 5 gm band, but spectrally filtered to reduce the interference from hot gas phase combustion products. Results show a strong functional dependence of emissivity on temperature, attributed to the combined effects of thermal and oxidative processes. Using the measured emissivity, radiance measurements from several burning samples were corrected for the presence of soot and for changes in emissivity, to yield quantitative surface temperature measurements. Ultimately the results will be used to develop a full-field, non-contact temperature measurement that will be used in spacebased combustion investigations.

  20. Deuterium-Tritium Fuel Layer Formation for the National Ignition Facility

    SciTech Connect

    Kozioziemski, B. J.; Mapoles, E. R.; Sater, J. D.; Chernov, A. A.; Moody, J. D.; Lugten, J. B.; Johnson, M. A.

    2011-01-01

    Inertial confinement fusion requires very smooth and uniform solid deuterium-tritium (D-T) fuel layers. The National Ignition Facility (NIF) point design calls for a 65- to 75-m-thick D-T fuel layer inside of a 2-mm-diam spherical ablator shell to be 1.5 K below the D-T melting temperature (Tm) of 19.79 K. We also find that the layer quality depends on the initial crystal seeding, with the best layers grown from a single seed. The low modes of the layer are controlled by thermal shimming of the hohlraum and meet the NIF requirement with beryllium shells and nearly meet the requirement with plastic shells. The remaining roughness is localized in grain-boundary grooves and is minimal for a single crystal layer. Once formed, the layers need to be cooled to Tm - 1.5 K. Here, we studied dependence of the roughness on the cooling rate and found that cooling at rates of 0.03 to 0.5 K/s is able to preserve the layer structure for a few seconds after reaching the desired temperature. The entire fuel layer remains in contact with the shell during this rapid cooling. Therefore, rapid cooling of the layers is able to satisfy the NIF ignition requirements.

  1. Metal organic chemical vapor deposition of environmental barrier coatings for the inhibition of solid deposit formation from heated jet fuel

    NASA Astrophysics Data System (ADS)

    Mohan, Arun Ram

    Solid deposit formation from jet fuel compromises the fuel handling system of an aviation turbine engine and increases the maintenance downtime of an aircraft. The deposit formation process depends upon the composition of the fuel, the nature of metal surfaces that come in contact with the heated fuel and the operating conditions of the engine. The objective of the study is to investigate the effect of substrate surfaces on the amount and nature of solid deposits in the intermediate regime where both autoxidation and pyrolysis play an important role in deposit formation. A particular focus has been directed to examining the effectiveness of barrier coatings produced by metal organic chemical vapor deposition (MOCVD) on metal surfaces for inhibiting the solid deposit formation from jet fuel degradation. In the first part of the experimental study, a commercial Jet-A sample was stressed in a flow reactor on seven different metal surfaces: AISI316, AISI 321, AISI 304, AISI 347, Inconel 600, Inconel 718, Inconel 750X and FecrAlloy. Examination of deposits by thermal and microscopic analysis shows that the solid deposit formation is influenced by the interaction of organosulfur compounds and autoxidation products with the metal surfaces. The nature of metal sulfides was predicted by Fe-Ni-S ternary phase diagram. Thermal stressing on uncoated surfaces produced coke deposits with varying degree of structural order. They are hydrogen-rich and structurally disordered deposits, spherulitic deposits, small carbon particles with relatively ordered structures and large platelets of ordered carbon structures formed by metal catalysis. In the second part of the study, environmental barrier coatings were deposited on tube surfaces to inhibit solid deposit formation from the heated fuel. A new CVD system was configured by the proper choice of components for mass flow, pressure and temperature control in the reactor. A bubbler was designed to deliver the precursor into the reactor

  2. Reactivity of a Nickel(II) Bis(amidate) Complex with meta-Chloroperbenzoic Acid: Formation of a Potent Oxidizing Species.

    PubMed

    Corona, Teresa; Pfaff, Florian F; Acuña-Parés, Ferran; Draksharapu, Apparao; Whiteoak, Christopher J; Martin-Diaconescu, Vlad; Lloret-Fillol, Julio; Browne, Wesley R; Ray, Kallol; Company, Anna

    2015-10-12

    Herein, we report the formation of a highly reactive nickel-oxygen species that has been trapped following reaction of a Ni(II) precursor bearing a macrocyclic bis(amidate) ligand with meta-chloroperbenzoic acid (HmCPBA). This compound is only detectable at temperatures below 250 K and is much more reactive toward organic substrates (i.e., C-H bonds, C=C bonds, and sulfides) than previously reported well-defined nickel-oxygen species. Remarkably, this species is formed by heterolytic O-O bond cleavage of a Ni-HmCPBA precursor, which is concluded from experimental and computational data. On the basis of spectroscopy and DFT calculations, this reactive species is proposed to be a Ni(III) -oxyl compound.

  3. Formation of plagioclase-bearing peridotite and plagioclase-bearing wehrlite and gabbro suite through reactive crystallization: an experimental study

    NASA Astrophysics Data System (ADS)

    Saper, Lee; Liang, Yan

    2014-03-01

    Plagioclase-bearing peridotites are commonly associated with gabbroic rocks sampled around the Moho Transition Zone. Based on mineral chemistry, texture, and spatial relations, the formation of plagioclase-bearing peridotites has been attributed to impregnation of basalt into residual peridotites. We conducted reactive dissolution and crystallization experiments to test this hypothesis by reacting a primitive mid-ocean ridge basalt with a melt-impregnated lherzolite at 1,300 °C and 1 GPa and then cooling to 1,050 °C as pressure decreased to 0.7 GPa. Crystallization during cooling produced lithologic sequences of gabbro-wehrlite or gabbro-wehrlite-peridotite, depending on reaction time. Wehrlitic and peridotitic sections contain significant amounts of plagioclase interstitial to olivine and clinopyroxene and plagioclase compositions are spatially homogeneous. Clinopyroxene in the wehrlite-peridotite section is reprecipitated from the melt and exhibits poikilitic texture with small rounded olivine chadacrysts. Mineral composition in olivine and clinopyroxene varies spatially, both at the scale of the sample and within individual grains. Olivine grains that crystallized close to the melt-peridotite interface are enriched in iron due to their proximity to the basaltic melt reservoir. Consistent with many field studies, we observed gradual spatial variation in olivine and clinopyroxene composition across a lithologically sharp boundary between the gabbro and wehrlite-peridotite. Plagioclase compositions show no obvious dependence on distance from the melt-rock interface and were precipitated from late-stage trapped melts. Compositional trends of olivine, pyroxene, and plagioclase are consistent with previous experimental results and natural observations of the Moho Transition Zone. Different lithological sequences form based primarily on the melt-rock ratio, composition of the melt and host peridotite, and thermochemical conditions, but are expected to grade from

  4. Melissa officinalis extract induces apoptosis and inhibits proliferation in colon cancer cells through formation of reactive oxygen species.

    PubMed

    Weidner, C; Rousseau, M; Plauth, A; Wowro, S J; Fischer, C; Abdel-Aziz, H; Sauer, S

    2015-02-15

    Efficient strategies for the prevention of colon cancer are extensively being explored, including dietary intervention and the development of novel phytopharmaceuticals. Safe extracts of edible plants contain structurally diverse molecules that can effectively interfere with multi-factorial diseases such as colon cancer. In this study, we describe the antiproliferative and proapoptotic effects of ethanolic lemon balm (Melissa officinalis) leaves extract in human colon carcinoma cells. We further investigated the role of extra- and intracellular reactive oxygen species (ROS). Antitumor effects of lemon balm extract (LBE) were investigated in HT-29 and T84 human colon carcinoma cells. Inhibition of proliferation was analyzed by DNA quantification. The causal cell cycle arrest was determined by flow cytometry of propidium iodide-stained cells and by immunoblotting of cell cycle regulator proteins. To investigate apoptosis, cleavage of caspases 3 and 7 was detected by immunoblotting and fluorescence microscopy. Phosphatidylserine externalization was measured by Annexin V assays. Mechanistic insights were gained by measurement of ROS using the indicator dyes CM-H2DCFDA and Cell ROX Green. After 3 and 4 days of treatment, LBE inhibited the proliferation of HT-29 and T84 colon carcinoma cells with an inhibitory concentration (IC50) of 346 and 120 µg/ml, respectively. Antiproliferative effects were associated with a G2/M cell cycle arrest and reduced protein expression of cyclin dependent kinases (CDK) 2, 4, 6, cyclin D3, and induced expression of cyclin-dependent kinase inhibitor 2C (p18) and 1A (p21). LBE (600 µg/ml) induced cleavage of caspases 3 and 7 and phosphatidylserine externalization. LBE-induced apoptosis was further associated with formation of ROS, whereas quenching of ROS by antioxidants completely rescued the colon carcinoma cells from LBE-induced apoptosis. Lemon balm (Melissa officinalis) extract inhibits the proliferation of colon carcinoma cells and

  5. The effect of oxygen-to-fuel stoichiometry on coal ash fine-fragmentation mode formation mechanisms.

    SciTech Connect

    Fix, G.; Seames, W. S.; Mann, M. D.; Benson, S. A.; Miller, D. J.

    2011-04-01

    Ash particles smaller than 2.5 {micro}m in diameter generated during pulverized coal combustion are difficult to capture and may pose greater harm to the environment and human health than the discharge of larger particles. Recent research efforts on coal ash formation have revealed a middle fine-fragment mode centered around 2 {micro}m. Formation of this middle or fine-fragment mode (FFM) is less well understood compared to larger coarse and smaller ultrafine ash. This study is part of an overall effort aimed at determining the key factors that impact the formation of FFM. This work examined the effects of oxygen-to-fuel stoichiometry (OFS). Pulverized Illinois No.6 bituminous coal was combusted and the ash generated was size segregated in a Dekati low pressure inertial impactor. The mass of each fraction was measured and the ash was analyzed using scanning electron microscopy (SEM) and X-ray microanalysis. The FFM ash types were classified based on the SEM images to evaluate the significant fine-fragment ash formation mechanisms and determine any possible link between stoichiometry and formation mechanism. From the particle size distributions (PSDs), the coarse mode appears unaffected by the change in OFS, however, the OFS 1.05 lowered the fraction of ultrafine ash in relation to the higher OFS settings, and appears to increase the portion of the FFM. An intermediate minimum was found in the FFM at 1.3 {micro}m for the 1.20 and 1.35 OFS tests but was not observed in the 1.05 OFS. SEM analysis also suggests that OFS may contribute to changing formation mechanisms.

  6. Effects of diesel fuel combustion-modifier additives on In-cylinder soot formation in a heavy-duty Dl diesel engine.

    SciTech Connect

    Musculus, Mark P. (Sandia National Laboratories, Livermore, CA); Dietz, Jeff

    2005-07-01

    Based on a phenomenological model of diesel combustion and pollutant-formation processes, a number of fuel additives that could potentially reduce in-cylinder soot formation by altering combustion chemistry have been identified. These fuel additives, or ''combustion modifiers'', included ethanol and ethylene glycol dimethyl ether, polyethylene glycol dinitrate (a cetane improver), succinimide (a dispersant), as well as nitromethane and another nitro-compound mixture. To better understand the chemical and physical mechanisms by which these combustion modifiers may affect soot formation in diesel engines, in-cylinder soot and diffusion flame lift-off were measured, using an optically-accessible, heavy-duty, direct-injection diesel engine. A line-of-sight laser extinction diagnostic was employed to measure the relative soot concentration within the diesel jets (''jetsoot'') as well as the rates of deposition of soot on the piston bowl-rim (''wall-soot''). An OH chemiluminescence imaging technique was utilized to measure the lift-off lengths of the diesel diffusion flames so that fresh oxygen entrainment rates could be compared among the fuels. Measurements were obtained at two operating conditions, using blends of a base commercial diesel fuel with various combinations of the fuel additives. The ethanol additive, at 10% by mass, reduced jet-soot by up to 15%, and reduced wall-soot by 30-40%. The other fuel additives also affected in-cylinder soot, but unlike the ethanol blends, changes in in-cylinder soot could be attributed solely to differences in the ignition delay. No statistically-significant differences in the diesel flame lift-off lengths were observed among any of the fuel additive formulations at the operating conditions examined in this study. Accordingly, the observed differences in in-cylinder soot among the fuel formulations cannot be attributed to differences in fresh oxygen entrainment upstream of the soot-formation zones after ignition.

  7. The effects of localized heating and disbudding on cambial reactivation and formation of earlywood vessels in seedlings of the deciduous ring-porous hardwood, Quercus serrata

    PubMed Central

    Kudo, Kayo; Nabeshima, Eri; Begum, Shahanara; Yamagishi, Yusuke; Nakaba, Satoshi; Oribe, Yuichiro; Yasue, Koh; Funada, Ryo

    2014-01-01

    Background and Aims The networks of vessel elements play a vital role in the transport of water from roots to leaves, and the continuous formation of earlywood vessels is crucial for the growth of ring-porous hardwoods. The differentiation of earlywood vessels is controlled by external and internal factors. The present study was designed to identify the limiting factors in the induction of cambial reactivation and the differentiation of earlywood vessels, using localized heating and disbudding of dormant stems of seedlings of a deciduous ring-porous hardwood, Quercus serrata. Methods Localized heating was achieved by wrapping an electric heating ribbon around stems. Disbudding involved removal of all buds. Three treatments were initiated on 1 February 2012, namely heating, disbudding and a combination of heating and disbudding, with untreated dormant stems as controls. Cambial reactivation and differentiation of vessel elements were monitored by light and polarized-light microscopy, and the growth of buds was followed. Key Results Cambial reactivation and differentiation of vessel elements occurred sooner in heated seedlings than in non-heated seedlings before bud break. The combination of heating and disbudding of seedlings also resulted in earlier cambial reactivation and differentiation of first vessel elements than in non-heated seedlings. A few narrow vessel elements were formed during heating after disbudding, while many large earlywood vessel elements were formed in heated seedlings with buds. Conclusions The results suggested that, in seedlings of the deciduous ring-porous hardwood Quercus serrata, elevated temperature was a direct trigger for cambial reactivation and differentiation of first vessel elements. Bud growth was not essential for cambial reactivation and differentiation of first vessel elements, but might be important for the continuous formation of wide vessel elements. PMID:24685716

  8. The effects of localized heating and disbudding on cambial reactivation and formation of earlywood vessels in seedlings of the deciduous ring-porous hardwood, Quercus serrata.

    PubMed

    Kudo, Kayo; Nabeshima, Eri; Begum, Shahanara; Yamagishi, Yusuke; Nakaba, Satoshi; Oribe, Yuichiro; Yasue, Koh; Funada, Ryo

    2014-05-01

    The networks of vessel elements play a vital role in the transport of water from roots to leaves, and the continuous formation of earlywood vessels is crucial for the growth of ring-porous hardwoods. The differentiation of earlywood vessels is controlled by external and internal factors. The present study was designed to identify the limiting factors in the induction of cambial reactivation and the differentiation of earlywood vessels, using localized heating and disbudding of dormant stems of seedlings of a deciduous ring-porous hardwood, Quercus serrata. Localized heating was achieved by wrapping an electric heating ribbon around stems. Disbudding involved removal of all buds. Three treatments were initiated on 1 February 2012, namely heating, disbudding and a combination of heating and disbudding, with untreated dormant stems as controls. Cambial reactivation and differentiation of vessel elements were monitored by light and polarized-light microscopy, and the growth of buds was followed. Cambial reactivation and differentiation of vessel elements occurred sooner in heated seedlings than in non-heated seedlings before bud break. The combination of heating and disbudding of seedlings also resulted in earlier cambial reactivation and differentiation of first vessel elements than in non-heated seedlings. A few narrow vessel elements were formed during heating after disbudding, while many large earlywood vessel elements were formed in heated seedlings with buds. The results suggested that, in seedlings of the deciduous ring-porous hardwood Quercus serrata, elevated temperature was a direct trigger for cambial reactivation and differentiation of first vessel elements. Bud growth was not essential for cambial reactivation and differentiation of first vessel elements, but might be important for the continuous formation of wide vessel elements.

  9. Soot Formation and Destruction in High-Pressure Flames with Real Fuels

    DTIC Science & Technology

    2013-08-18

    sooting flame at 16 atmospheres were 0.07 SLPM fuel with 82.5% nitrogen making nitrogen flow 0.33 SLPM. The 82.5% dilution was chosen so that a stable...matched flame as the flame front significantly contorted and flickered due to increase in buoyancy induced, even though the flame was not a sooting ... flame (Berry and Roberts, 2006). This highly unstable distorted flame was not desirable for any measurements. The series of pictures in Fig. 2.9 show

  10. 3,3'-Dihydroxyisorenieratene prevents UV-induced formation of reactive oxygen species and the release of protein-bound zinc ions in human skin fibroblasts.

    PubMed

    Lutter, Kaya; De Spirt, Silke; Kock, Sebastian; Kröncke, Klaus-Dietrich; Martin, Hans-Dieter; Wagener, Tanja; Stahl, Wilhelm

    2010-02-01

    3,3'-Dihydroxyisorenieratene (DHIR) is a structurally unusual carotenoid exhibiting bifunctional antioxidant properties. It is synthesized by Brevibacterium linens, used in dairy industry for the production of red smear cheeses. The compound protects cellular structures against photo-oxidative damage and inhibits the UV-dependent formation of thymidine dimers. Here we show that DHIR prevents a UV-induced intracellular release of zinc ions from proteins in human dermal fibroblasts. The effect is correlated with a decreased formation of intracellular reactive oxygen species. In contrast, zinc release from cellular proteins induced by hyperthermia is not affected by pretreatment of cells with the antioxidant DHIR. It is suggested that the intracellular zinc release upon UV irradiation is due to oxidative modifications of the zinc ligands in proteins (e.g. cysteine) and that protection by DHIR is due to intracellular scavenging of reactive oxygen species generated in photo-oxidation.

  11. Reactivity of niobium-carbon cluster ions with hydrogen molecules in relation to formation mechanism of Met-Car cluster ions.

    PubMed

    Miyajima, Ken; Fukushima, Naoya; Mafuné, Fumitaka

    2008-07-03

    It is known that a niobium-carbon Met-Car cluster ion (Nb 8C 12 (+)) and its intermediates (Nb 4C 4 (+), Nb 6C 7 (+), etc.) are selectively formed by the aggregation of the Nb atoms in the presence of hydrocarbons. To elucidate the formation mechanism, we prepared Nb n C m (+) with every combination of n and m in the gas phase by the laser vaporization technique. The reactivity of Nb n C m (+) with H 2 was examined under the multiple collision condition, finding that Nb n C m (+) between Nb 2C 3 (+) and Nb 8C 12 (+) are not reactive with H 2. On the basis of the H 2 affinity of Nb n C m (+) experimentally obtained, we propose a dehydrogenation-controlled formation mechanism of niobium-carbon Met-Car cluster ions.

  12. Trp-Trp Cross-Linking: A Structure-Reactivity Relationship in the Formation and Design of Hyperstable Peptide β-Hairpin and α-Helix Scaffolds.

    PubMed

    Makwana, Kamlesh M; Mahalakshmi, Radhakrishnan

    2015-05-15

    Using model peptide β-hairpin scaffolds, the facile formation of a remarkably stable covalently cross-linked modification is reported in the tryptophan side chain, which confers hyperstability to the scaffold and displays a unique structure-reactivity relationship. This strategy is also validated to obtain a thermostable α-helix. Such imposition of conformational constraints can have versatile applications in peptide-based drug discovery, and this strategy may improve peptide bioavailability.

  13. A highly efficient immobilized ZnO/Zn photoanode for degradation of azo dye Reactive Green 19 in a photocatalytic fuel cell.

    PubMed

    Lee, Sin-Li; Ho, Li-Ngee; Ong, Soon-An; Wong, Yee-Shian; Voon, Chun-Hong; Khalik, Wan Fadhilah; Yusoff, Nik Athirah; Nordin, Noradiba

    2017-01-01

    Photocatalytic fuel cell (PFC) is a potential wastewater treatment technology that can generate electricity from the conversion of chemical energy of organic pollutants. An immobilized ZnO/Zn fabricated by sonication and heat attachment method was applied as the photoanode and Pt/C plate was used as the cathode of the PFC in this study. Factors that affect the decolorization efficiency and electricity generation of the PFC such as different initial dye concentrations and pH were investigated. Results revealed that the degradation of Reactive Green 19 (RG19) was enhanced in a closed circuit PFC compared with that of a opened circuit PFC. Almost 100% decolorization could be achieved in 8 h when 250 mL of 30 mg L(-1) of RG19 was treated in a PFC without any supporting electrolyte. The highest short circuit current of 0.0427 mA cm(-2) and maximum power density of 0.0102 mW cm(-2) was obtained by PFC using 30 mg L(-1) of RG19. The correlation between dye degradation, conductivity and voltage output were also investigated and discussed.

  14. Simulated Performance of the Integrated Passive Neutron Albedo Reactivity and Self-Interrogation Neutron Resonance Densitometry Detector Designed for Spent Fuel Measurement at the Fugen Reactor in Japan

    SciTech Connect

    Ulrich, Timothy J. II; Lafleur, Adrienne M.; Menlove, Howard O.; Swinhoe, Martyn T.; Tobin, Stephen J.; Seya, Michio; Bolind, Alan M.

    2012-07-16

    An integrated nondestructive assay instrument, which combined the Passive Neutron Albedo Reactivity (PNAR) and the Self-Interrogation Neutron Resonance Densitometry (SINRD) techniques, is the research focus for a collaborative effort between Los Alamos National Laboratory (LANL) and the Japanese Atomic Energy Agency as part of the Next Generation Safeguard Initiative. We will quantify the anticipated performance of this experimental system in two physical environments: (1) At LANL we will measure fresh Low Enriched Uranium (LEU) assemblies for which the average enrichment can be varied from 0.2% to 3.2% and for which Gd laced rods will be included. (2) At Fugen we will measure spent Mixed Oxide (MOX-B) and LEU spent fuel assemblies from the heavy water moderated Fugen reactor. The MOX-B assemblies will vary in burnup from {approx}3 GWd/tHM to {approx}20 GWd/tHM while the LEU assemblies ({approx}1.9% initial enrichment) will vary from {approx}2 GWd/tHM to {approx}7 GWd/tHM. The estimated count rates will be calculated using MCNPX. These preliminary results will help the finalization of the hardware design and also serve a guide for the experiment. The hardware of the detector is expected to be fabricated in 2012 with measurements expected to take place in 2012 and 2013. This work is supported by the Next Generation Safeguards Initiative, Office of Nuclear Safeguards and Security, National Nuclear Security Administration.

  15. The influence of biofilm formation on electricity production from tempe wastewater using tubular membraneless microbial fuel cell reactor

    NASA Astrophysics Data System (ADS)

    Siagian, Nathania Dwi Karina; Arbianti, Rita; Utami, Tania Surya

    2017-05-01

    Microbial fuel cell (MFC) technology can be potentially developed as an alternative energy source since it can convert various substrates from renewable sources into electricity using bacteria as biocatalyst. Tempe wastewater as MFC substrate gives advantages in tempe wastewater treatment and reducing the purchasing cost of bacteria. Currently, the applications of MFCs are still limited due to the relatively low electricity production, so many studies have been conducted to improve the electricity production by MFC. This study focused on investigating the influence of biofilm formation time and the use of macromolecule as additional substrate towards electricity production from MFC system with tubular membranless reactor and tempe wastewater as substrate. This study suggested that biofilm formation on anode could improve the electricity production up to 10-folds while the use of glucose as substrate addition reduce the electricity production up to 60%. The biggest electricity output was obtained from the experiment of biofilm formation for 14 days with EPS content in biofilm 0,13 mg/cm2 where the maximum voltage and power density produced was respectively 34,81 mV and 0,26 mW/m2.

  16. Tuning reactivity of glycosyl imidinium intermediate for 2-azido-2-deoxyglycosyl donors in α-glycosidic bond formation.

    PubMed

    Ingle, Arun B; Chao, Chin-Sheng; Hung, Wei-Cheng; Mong, Kwok-Kong Tony

    2013-10-18

    The chemical properties of nucleophile additives were investigated in a modulated glycosylation context. N-Formylmorpholine (NFM) was found to be an effective modulator for glycosylation with less reactive 2-azido-2-deoxythioglucosyl and thiogalactosyl donors.

  17. Examination of Mechanisms and Fuel-Molecular Effects on Soot Formation.

    DTIC Science & Technology

    1986-12-10

    t.’c. styrene, 1,3,5-hexatriene, biazeyl s--c 19I ABSTRACT iCantsaag onu ,vpee it n~emtpgi and Idmenty Opy biack numbgri * A an .:roaon as beer ...0.0175 C H/C H * 3.3/0.51 .2 2/7H8 Acetaldehyde , CH CHO * 0.105 5’ 3 All fuels were diluted in argon and (except for the experiments on pure toluene...0o2 3.3/2.05 C 2H4/02 0.22/0.13 1,3,5-Hexatriene, C6 H8 1.0 1,3,5-Hexatriene, C6 H8 0.09 Acetaldehyde , CH 3CHO * 0.01 Biacetyl, (CH 3 CO) 2 * 0.22

  18. Carbon monoxide formation in UO2 kerneled HTR fuel particles containing oxygen getters

    NASA Astrophysics Data System (ADS)

    Proksch, E.; Strigl, A.; Nabielek, H.

    1986-01-01

    Mass spectrometric measurements of CO in irradiated UO2 fuel particles containing oxygen getters are summarized. Uranium carbide addition in the 3% to 15% range reduces the CO release by factors between 25 and 80, up to burn-up levels as high as 70% FIMA. Unintentional gettering by SiC in TRISO coated particles with failed inner pyrocarbon layers results in CO reduction factors between 15 and 110. For ZrC, ambiguous results are obtained; ZrC probably results in CO reduction by a factor of 40; Ce2O3 and La2O3 seem less effective than the carbides; for Ce2O3, reduction factors between 3 and 15 are found. However, the results are possibly incorrect due to premature oxidation of the getter already during fabrication. Addition of SiO2 + Al2O3 has no influence on CO release.

  19. Scale formation on Ni-based alloys in simulated solid oxide fuel cell interconnect environments

    SciTech Connect

    Ziomek-Moroz, Margaret; Cramer, Stephen D.; Holcomb, Gordon R.; Covino, Bernard S., Jr.; Bullard, Sophie J.; Singh, P.; Windisch, C.F.; Johnson, C.D.; Schaeffer, C.

    2004-11-01

    Recent publications suggest that the environment on the fuel side of the bi-polar stainless steel SOFC interconnects changes the oxidation behavior and morphology of the scale formed on the air side. The U.S. Department of Energy Albany Research Center (ARC), has examined the role of such exposure conditions on advanced nickel base alloys. Alloy formulations developed at ARC and commercial alloys were studied using X-ray diffraction (XRD) and Raman spectroscopy. The electrical property of oxide scales formed on selected alloys was determined in terms of areaspecific resistance (ASR). The corrosion behavior of ARC nickel-based alloys exposed to a dual environment of air/ H2 were compared to those of Crofer 22APU and Haynes 230.

  20. Experimental study of soot formation from a diesel fuel surrogate in a shock tube

    SciTech Connect

    Mathieu, Olivier; Djebaili-Chaumeix, Nabiha; Paillard, Claude-Etienne; Douce, Francoise

    2009-08-15

    The soot tendency (soot induction delay time and soot yield) of a diesel fuel surrogate and of the hydrocarbons that constitute this mixture was studied in a heated shock tube. The surrogate is composed of three hydrocarbons representative of major chemical families of diesel fuels (39% n-propylcyclohexane, 28% n-butylbenzene, and 33% 2,2,4,4,6,8,8-heptamethylnonane in mass proportion). Experiments were carried out for highly diluted mixtures in argon; in the case of pyrolysis and at two equivalence ratios: 18 and 5. The pressure range was relatively high (1090-1870 kPa) and the carbon atom concentration was kept constant at around 2 x 10{sup +18} atoms cm{sup -3}. The effects of the nature of the hydrocarbon, the oxygen addition, and the temperature on the soot induction delay time and soot yield were investigated. A second growth stage of the soot volume fraction was observed. The influence of several parameters on the existence and/or on the amplitude of this second growth seems to indicate the chemical nature of this phenomenon. Results for the soot tendency show that the soot induction delay time and soot yield depend strongly on the structure of the hydrocarbon and on the concentration of oxygen. The study of the diesel surrogate shows that the soot inception process does not depend on synergistic effects between hydrocarbons but seems to be initiated by the constituent of the surrogate that produces soot fastest, while other constituents were consumed later during the soot growth. (author)

  1. Evaluation of a zirconium additive for the mitigation of molten ash formation during combustion of residual fuel oil

    SciTech Connect

    1996-12-01

    Florida Power & Light Company (FP&L) currently fires a residual fuel oil (RFO) containing catalyst fines, which results in a troublesome black aluminosilicate liquid phase that forms on heat-transfer surfaces, remains molten, and flows to the bottom of the boiler. When the unit is shut down for a scheduled outage, this liquid phase freezes to a hard black glass that damages the contracting waterwalls of the boiler. Cleaning the boiler bottom and repairing damaged surfaces increase the boiler downtime, at a significant cost to FP&L. The Energy & Environmental Research Center (EERC) proposed to perform a series of tests for FP&L to evaluate the effectiveness of a zirconium additive to modify the mechanism that forms this liquid phase, resulting in the formation of a dry refractory phase that may be easily handled during cleanup of the boiler.

  2. Pollutant formation and emissions from cement kiln stack using a solid recovered fuel from municipal solid waste.

    PubMed

    Conesa, Juan A; Rey, Lorena; Egea, Silvia; Rey, Maria D

    2011-07-01

    The thermal decomposition of a solid recovered fuel (SRF) has been studied by two techniques. First, laboratory-scale experiments were performed in a horizontal furnace in which different atmospheres were studied to analyze the dioxins and furans (PCDD/Fs) evolved from the decomposition of the material. Sulfur presence was revealed to be important in PCDD/Fs formation. In the second technique, the emissions of various pollutants (PAHs, PCDD/Fs, metals, acid gases, etc.) were determined in a cement kiln fed on different proportions of SRF material, and where a maximum feed rate of 15000 kg SRF/h was achieved. In the laboratory furnace the dioxin toxicity revealed a maximum when the amount of oxygen in the atmosphere increased until approximately stoichiometric conditions. In the cement kiln, all emitted pollutants were under the legal limits. No correlation between SRF input and metal emission was observed.

  3. The crucial role of particle surface reactivity in respirable quartz-induced reactive oxygen/nitrogen species formation and APE/Ref-1 induction in rat lung

    PubMed Central

    Albrecht, Catrin; Knaapen, Ad M; Becker, Andrea; Höhr, Doris; Haberzettl, Petra; van Schooten, Frederik J; Borm, Paul JA; Schins, Roel PF

    2005-01-01

    Persistent inflammation and associated excessive oxidative stress have been crucially implicated in quartz-induced pulmonary diseases, including fibrosis and cancer. We have investigated the significance of the particle surface reactivity of respirable quartz dust in relation to the in vivo generation of reactive oxygen and nitrogen species (ROS/RNS) and the associated induction of oxidative stress responses in the lung. Therefore, rats were intratracheally instilled with 2 mg quartz (DQ12) or quartz whose surface was modified by either polyvinylpyridine-N-oxide (PVNO) or aluminium lactate (AL). Seven days after instillation, the bronchoalveolar lavage fluid (BALF) was analysed for markers of inflammation (total/differential cell counts), levels of pulmonary oxidants (H2O2, nitrite), antioxidant status (trolox equivalent antioxidant capacity), as well as for markers of lung tissue damage, e.g. total protein, lactate dehydrogenase and alkaline phosphatase. Lung homogenates as well as sections were investigated regarding the induction of the oxidative DNA-lesion/oxidative stress marker 8-hydroxy-2'-deoxyguanosine (8-OHdG) using HPLC/ECD analysis and immunohistochemistry, respectively. Homogenates and sections were also investigated for the expression of the bifunctional apurinic/apyrimidinic endonuclease/redox factor-1 (APE/Ref-1) by Western blotting and immunohistochemistry. Significantly increased levels of H2O2 and nitrite were observed in rats treated with non-coated quartz, when compared to rats that were treated with either saline or the surface-modified quartz preparations. In the BALF, there was a strong correlation between the number of macrophages and ROS, as well as total cells and RNS. Although enhanced oxidant generation in non-coated DQ12-treated rats was paralleled with an increased total antioxidant capacity in the BALF, these animals also showed significantly enhanced lung tissue damage. Remarkably however, elevated ROS levels were not associated

  4. Formation of Highly Reactive Cyclopentenone Isoprostane Compounds (A3/J3-Isoprostanes) in Vivo from Eicosapentaenoic Acid*

    PubMed Central

    Brooks, Joshua D.; Milne, Ginger L.; Yin, Huiyong; Sanchez, Stephanie C.; Porter, Ned A.; Morrow, Jason D.

    2008-01-01

    Omega-3 (ω-3) polyunsaturated fatty acids (PUFAs) found in marine fish oils are known to suppress inflammation associated with a wide variety of diseases. Eicosapentaenoic acid (EPA) is one of the most abundant ω-3 fatty acids in fish oil, but the mechanism(s) by which EPA exerts its beneficial effects is unknown. Recent studies, however, have demonstrated that oxidized EPA, rather than native EPA, possesses anti-atherosclerotic, anti-inflammatory, and anti-proliferative effects. Very few studies to date have investigated which EPA oxidation products are responsible for this bioactivity. Our research group has previously reported that anti-inflammatory prostaglandin A2-like and prostaglandin J2-like compounds, termed A2/J2-isoprostanes (IsoPs), are produced in vivo by the free radical-catalyzed peroxidation of arachidonic acid and represent one of the major products resulting from the oxidation of this PUFA. Based on these observations, we questioned whether cyclopentenone-IsoP compounds are formed from the oxidation of EPA in vivo. Herein, we report the formation of cyclopentenone-IsoP molecules, termed A3/J3-IsoPs, formed in abundance in vitro and in vivo from EPA peroxidation. Chemical approaches coupled with gas chromatography/mass spectrometry (GC/MS) and liquid chromatography/mass spectrometry (LC/MS) were used to structurally characterize these compounds as A3/J3-IsoPs. We found that levels of these molecules increase ∼200-fold with oxidation of EPA in vitro from a basal level of 0.8 ± 0.4 ng/mg EPA to 196 ± 23 ng/mg EPA after 36 h. We also detected these compounds in significant amounts in fresh liver tissue from EPA-fed rats at basal levels of 19 ± 2 ng/g tissue. Amounts increased to 102 ± 15 ng/g tissue in vivo in settings of oxidative stress. These studies have, for the first time, definitively characterized novel, highly reactive A/J-ring IsoP compounds that form in abundance from the oxidation of EPA in vivo. PMID:18263929

  5. Ozone uptake and formation of reactive oxygen intermediates on glassy, semi-solid and liquid organic matter

    NASA Astrophysics Data System (ADS)

    Berkemeier, Thomas; Steimer, Sarah S.; Krieger, Ulrich K.; Peter, Thomas; Pöschl, Ulrich; Ammann, Markus; Shiraiwa, Manabu

    2016-04-01

    Heterogeneous and multiphase reactions of ozone are important pathways for chemical ageing of atmospheric organic aerosols (Abbatt, Lee and Thornton, 2012). The effects of particle phase state on the reaction kinetics are still not fully elucidated and cannot be described by classical models assuming a homogeneous condensed phase (Berkemeier et al., 2013). We apply a kinetic multi-layer model, explicitly resolving gas adsorption, condensed phase diffusion and condensed phase chemistry (Shiraiwa et al., 2010), to systematic measurements of ozone uptake onto proxies for secondary organic aerosols (SOA). Our findings show how moisture-induced phase changes affect the gas uptake and chemical transformation of organic matter through change in the physicochemical properties of the substrate: the diffusion coefficients are found to be low under dry conditions, but increase by several orders of magnitude toward higher relative humidity (RH). The solubility of ozone in the dry organic matrix is found to be one order of magnitude higher than in the dilute aqueous solution. The model simulations reveal that at high RH, ozone uptake is mainly controlled by reaction throughout the particle bulk, whereas at low RH, bulk diffusion is retarded severely and reaction at the surface becomes the dominant pathway, with ozone uptake being limited by replenishment of unreacted organic molecules from the bulk phase. The experimental results can only be reconciled including a pathway for ozone self-reaction, which becomes especially important under dry and polluted conditions. Ozone self-reaction can be interpreted as formation and recombination of long-lived reactive oxygen intermediates at the aerosol surface, which could also explain several kinetic parameters and has implications for the health effects of organic aerosol particles. This study hence outlines how kinetic modelling can be used to gain mechanistic insight into the coupling of mass transport, phase changes, and chemical

  6. Formation of polyhedral N/sub 2/ bubbles during reactive sputter deposition of epitaxial TiN(100) films

    SciTech Connect

    Hultman, L.; Sundgren, J.; Greene, J. E.

    1989-07-15

    Cross-sectional transmission electron microscopy has been used to investigate the formation of polyhedral N/sub 2/ bubbles in single-crystal TiN(100). Thin TiN films were deposited on MgO(100) substrates by reactive magnetron sputtering in pure N/sub 2/ atmospheres at growth temperatures /ital T//sub /ital s// between 550 and 800 /degree/C and negative substrate biases /ital V//sub /ital s// between 0 and 500 V resulting in a deposition rate between 0.35 and 0.33 nm s/sup /minus/1/. The energy per incident nitrogen was /similar to//ital eV//sub /ital s///2 and the irradiation fluxes were less than or equal to2.5/times/10/sup 15/ N/sup +//sub 2/ cm/sup /minus/2/ s/sup /minus/1/. Nitrogen bubbles were observed in films grown at 550less than or equal to/ital T//sub /ital s///lt/800 /degree/C with /ital V//sub /ital s///gt/300 V. In as-deposited films grown at /ital T//sub /ital s//=650 /degree/C with /ital V//sub /ital s//=500 V, the bubbles were distributed in two shapes and size distributions. The largest bubbles were orthorhombohedra, i.e., cubes elongated along (100) directions normal to the growth direction, with 5--20 nm faces on /l brace/100/r brace/ planes most of which exhibited /l brace/110/r brace/ and /l brace/111/r brace/ faceting. Small (less than or equal to5 nm) octahedral bubbles with /l brace/111/r brace/ faces were also observed. /ital/ In situ annealing experiments in the transmission electron microscope showed that the bubbles transformed from orthorhombohedra to octahedra at /ital T//sub /ital s//=350 /degree/C and then returned to orthorhombohedral shape with either continued heating to /ital T//sub /ital s//=600 /degree/C or upon cooling to room temperature. Assuming quasiequilibrium conditions, the surface energy ..gamma.. of N/sub 2/ bubbles in TiN was found to be anisotropic and to vary as ..gamma../sub 100//lt//gamma110//lt//gamma111/.

  7. Experimental investigation of aminoacetonitrile formation through the Strecker synthesis in astrophysical-like conditions: reactivity of methanimine (CH2NH), ammonia (NH3), and hydrogen cyanide (HCN)

    NASA Astrophysics Data System (ADS)

    Danger, G.; Borget, F.; Chomat, M.; Duvernay, F.; Theulé, P.; Guillemin, J.-C.; Le Sergeant D'Hendecourt, L.; Chiavassa, T.

    2011-11-01

    Context. Studing chemical reactivity in astrophysical environments is an important means for improving our understanding of the origin of the organic matter in molecular clouds, in protoplanetary disks, and possibly, as a final destination, in our solar system. Laboratory simulations of the reactivity of ice analogs provide important insight into the reactivity in these environments. Here, we use these experimental simulations to investigate the Strecker synthesis leading to the formation of aminoacetonitrile in astrophysical-like conditions. The aminoacetonitrile is an interesting compound because it was detected in SgrB2, hence could be a precursor of the smallest amino acid molecule, glycine, in astrophysical environments. Aims: We present the first experimental investigation of the formation of aminoacetonitrile NH2CH2CN from the thermal processing of ices including methanimine (CH2NH), ammonia (NH3), and hydrogen cyanide (HCN) in interstellar-like conditions without VUV photons or particules. Methods: We use Fourier Transform InfraRed (FTIR) spectroscopy to monitor the ice evolution during its warming. Infrared spectroscopy and mass spectroscopy are then used to identify the aminoacetonitrile formation. Results: We demonstrate that methanimine can react with -CN during the warming of ice analogs containing at 20 K methanimine, ammonia, and [NH4+ -CN] salt. During the ice warming, this reaction leads to the formation of poly(methylene-imine) polymers. The polymer length depend on the initial ratio of mass contained in methanimine to that in the [NH4+ -CN] salt. In a methanimine excess, long polymers are formed. As the methanimine is progressively diluted in the [NH4+ -CN] salt, the polymer length decreases until the aminoacetonitrile formation at 135 K. Therefore, these results demonstrate that aminoacetonitrile can be formed through the second step of the Strecker synthesis in astrophysical-like conditions.

  8. Measurements of reactive trace gases and variable O3 formation rates in some South Carolina biomass burning plumes

    NASA Astrophysics Data System (ADS)

    Akagi, S. K.; Yokelson, R. J.; Burling, I. R.; Meinardi, S.; Simpson, I.; Blake, D. R.; McMeeking, G. R.; Sullivan, A.; Lee, T.; Kreidenweis, S.; Urbanski, S.; Reardon, J.; Griffith, D. W. T.; Johnson, T. J.; Weise, D. R.

    2012-09-01

    In October-November 2011 we measured trace gas emission factors from seven prescribed fires in South Carolina (SC), US, using two Fourier transform infrared spectrometer (FTIR) systems and whole air sampling (WAS) into canisters followed by gas-chromatographic analysis. A total of 97 trace gas species were quantified from both airborne and ground-based sampling platforms, making this one of the most detailed field studies of fire emissions to date. The measurements include the first emission factors for a suite of monoterpenes produced by heating vegetative fuels during field fires. The first quantitative FTIR observations of limonene in smoke are reported along with an expanded suite of monoterpenes measured by WAS including α-pinene, β-pinene, limonene, camphene, 4-carene, and myrcene. The known chemistry of the monoterpenes and their measured abundance of 0.4-27.9% of non-methane organic compounds (NMOCs) and ~21% of organic aerosol (mass basis) suggests that they impacted secondary formation of ozone (O3), aerosols, and small organic trace gases such as methanol and formaldehyde in the sampled plumes in first few hours after emission. The variability in the initial terpene emissions in the SC fire plumes was high and, in general, the speciation of the initially emitted gas-phase NMOCs was 13-195% different from that observed in a similar study in nominally similar pine forests in North Carolina ~20 months earlier. It is likely that differences in stand structure and environmental conditions contributed to the high variability observed within and between these studies. Similar factors may explain much of the variability in initial emissions in the literature. The ΔHCN/ΔCO emission ratio, however, was found to be fairly consistent with previous airborne fire measurements in other coniferous-dominated ecosystems, with the mean for these studies being 0.90 ± 0.06%, further confirming the value of HCN as a biomass burning tracer. The SC results also support an

  9. Measurements of reactive trace gases and variable O3 formation rates in some South Carolina biomass burning plumes

    NASA Astrophysics Data System (ADS)

    Akagi, S. K.; Yokelson, R. J.; Burling, I. R.; Meinardi, S.; Simpson, I.; Blake, D. R.; McMeeking, G. R.; Sullivan, A.; Lee, T.; Kreidenweis, S.; Urbanski, S.; Reardon, J.; Griffith, D. W. T.; Johnson, T. J.; Weise, D. R.

    2013-02-01

    In October-November 2011 we measured trace gas emission factors from seven prescribed fires in South Carolina (SC), US, using two Fourier transform infrared spectrometer (FTIR) systems and whole air sampling (WAS) into canisters followed by gas-chromatographic analysis. A total of 97 trace gas species were quantified from both airborne and ground-based sampling platforms, making this one of the most detailed field studies of fire emissions to date. The measurements include the first emission factors for a suite of monoterpenes produced by heating vegetative fuels during field fires. The first quantitative FTIR observations of limonene in smoke are reported along with an expanded suite of monoterpenes measured by WAS including α-pinene, β