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Sample records for amine-free reaction conditions

  1. 'GREENER' CHEMICAL SYNTHESES USING ALTERNATE REACTION CONDITIONS

    EPA Science Inventory

    Microwave (MW) irradiation in conjunction with water as reaction media has proven to be a greener chemical approach for expeditious N-alkylation reactions of amines and hydrazines wherein the reactions under mildly basic conditions afford tertiary amines and double N-alkylation t...

  2. Action of bimetallic nanocatalysts under reaction conditions and during catalysis: evolution of chemistry from high vacuum conditions to reaction conditions

    E-print Network

    Tao, Franklin Feng; Zhang, Shiran; Nguyen, Luan; Zhang, Xuegiang

    2012-09-28

    reaction or catalysis based on ex situ studies. Thanks to advances in electron-based surface analytical techniques, the surface chemistry and structure of bimetallic nanoparticles can be characterized under reaction conditions and during catalysis using...

  3. Palladium complexes of abnormal N-heterocyclic carbenes as precatalysts for the much preferred Cu-free and amine-free Sonogashira coupling in air in a mixed-aqueous medium.

    PubMed

    John, Alex; Shaikh, Mobin M; Ghosh, Prasenjit

    2009-12-21

    A series of new PEPPSI (Pyridine Enhanced Precatalyst Preparation Stabilization and Initiation) themed precatalysts of abnormal N-heterocyclic carbenes for the highly desirable Cu-free and amine-free Sonogashira coupling in air in a mixed-aqueous medium is reported. Specifically, the PEPPSI themed (NHC)PdI2(pyridine) type precatalysts, 1b-4b, efficiently carried out the highly convenient Cu-free and amine-free Sonogashira coupling of aryl bromides and iodides with terminal acetylenes in air in a mixed aqueous medium. Complexes, 1b-4b, were synthesized by the direct reaction of the corresponding imidazo[1,2-a]pyridinium iodide salts, 1a-4a, with PdCl2 in pyridine in the presence of K2CO3 as a base while the imidazo[1,2-a]pyridinium iodide salts, 1a-4a, were in turn synthesized by the alkylation reactions of the respective imidazo[1,2-a]pyridine derivatives with alkyl iodides. The density functional theory (DFT) studies revealed that these imidazol-3-ylidene[1,2-a]pyridine derived abnormal carbenes are strongly sigma-donating and consequently significantly weaken the catalytically important labile trans pyridine ligand in 1b-4b. PMID:20023883

  4. Fractionating Recalcitrant Lignocellulose at Modest Reaction Conditions

    SciTech Connect

    Zhang, Y.-H. Percival; Ding, Shi-You; Mielenz, Jonathan R; Cui, Jing-Biao; Elander, Richard T.; Laser, Mark; Himmel, Michael; McMillan, James R.; Lynd, L.

    2007-01-01

    Effectively releasing the locked polysaccharides from recalcitrant lignocellulose to fermentable sugars is among the greatest technical and economic barriers to the realization of lignocellulose biorefineries because leading lignocellulose pre-treatment technologies suffer from low sugar yields, and/or severe reaction conditions, and/or high cellulase use, narrow substrate applicability, and high capital investment, etc. A new lignocellulose pre-treatment featuring modest reaction conditions (50 C and atmospheric pressure) was demonstrated to fractionate lignocellulose to amorphous cellulose, hemicellulose, lignin, and acetic acid by using a non-volatile cellulose solvent (concentrated phosphoric acid), a highly volatile organic solvent (acetone), and water. The highest sugar yields after enzymatic hydrolysis were attributed to no sugar degradation during the fractionation and the highest enzymatic cellulose digestibility ({approx}97% in 24 h) during the hydrolysis step at the enzyme loading of 15 filter paper units of cellulase and 60 IU of beta-glucosidase per gram of glucan. Isolation of high-value lignocellulose components (lignin, acetic acid, and hemicellulose) would greatly increase potential revenues of a lignocellulose biorefinery.

  5. Biogeochemical Reactions Under Simulated Europa Ocean Conditions

    NASA Astrophysics Data System (ADS)

    Amashukeli, X.; Connon, S. A.; Gleeson, D. F.; Kowalczyk, R. S.; Pappalardo, R. T.

    2007-12-01

    Galileo data have demonstrated the probable presence of a liquid water ocean on Europa, and existence of salts and carbon dioxide in the satellite's surface ice (e.g., Carr et al., 1998; McCord et al., 1999, Pappalardo et al., 1999; Kivelson et al., 2000). Subsequently, the discovery of chemical signatures of extinct or extant life in Europa's ocean and on its surface became a distinct possibility. Moreover, understanding of Europa's potential habitability is now one of the major goals of the Europa Orbiter Flagship mission. It is likely, that in the early stages of Europa's ocean formation, moderately alkaline oceanic sulfate-carbonate species and a magnetite-silicate mantel could have participated in low-temperature biogeochemical sulfur, iron and carbon cycles facilitated by primitive organisms (Zolotov and Shock, 2004). If periodic supplies of fresh rock and sulfate-carbonate ions are available in Europa's ocean, then an exciting prospect exists that life may be present in Europa's ocean today. In our laboratory, we began the study of the plausible biogeochemical reactions under conditions appropriate to Europa's ocean using barophilic psychrophilic organisms that thrive under anaerobic conditions. In the near absence of abiotic synthetic pathways due to low Europa's temperatures, the biotic synthesis may present a viable opportunity for the formation of the organic and inorganic compounds under these extreme conditions. This work is independent of assumptions regarding hydrothermal vents at Europa's ocean floor or surface-derived oxidant sources. For our studies, we have fabricated a high-pressure (5,000 psi) reaction vessel that simulates aqueous conditions on Europa. We were also successful at reviving barophilic psychrophilic strains of Shewanella bacterium, which serve as test organisms in this investigation. Currently, facultative barophilic psychrophilic stains of Shewanella are grown in the presence of ferric food source; the strains exhibiting iron reduction capability will be later selected and used to facilitate biogeochemical reduction of iron under simulated temperature and pressure of Europa's ocean. The results of this work will enable us to ascertain whether Europa's cold, high-pressure ocean is capable of supporting life. In addition, the data from this study will help in generating a list of organic and inorganic target molecules for future remote sensing and in situ exploration missions.

  6. NO/CHAR REACTIONS AT PULVERIZED COAL FLAME CONDITIONS

    EPA Science Inventory

    The paper discusses nitrogen oxide (NO)/char reactions at pulverized-coal flame conditions. he effective rate of the NO/char reaction, measured over the temperature range 1250 to 1750 K, was found to be retarded by water vapor and enhanced by carbon monoxide (CO) by amounts that ...

  7. GREEN CHEMICAL SYNTHESIS THROUGH CATALYSIS AND ALTERNATE REACTION CONDITIONS

    EPA Science Inventory

    Green chemical synthesis through catalysis and alternate reaction conditions

    Encompassing green chemistry techniques and methodologies, we have initiated several projects at the National Risk Management Research laboratory that focus on the design and development of chemic...

  8. Homogeneous-Heterogeneous Reactions in Peristaltic Flow with Convective Conditions

    PubMed Central

    Hayat, Tasawar; Tanveer, Anum; Yasmin, Humaira; Alsaedi, Ahmed

    2014-01-01

    This article addresses the effects of homogeneous-heterogeneous reactions in peristaltic transport of Carreau fluid in a channel with wall properties. Mathematical modelling and analysis have been carried out in the presence of Hall current. The channel walls satisfy the more realistic convective conditions. The governing partial differential equations along with long wavelength and low Reynolds number considerations are solved. The results of temperature and heat transfer coefficient are analyzed for various parameters of interest. PMID:25460608

  9. Homogeneous-heterogeneous reactions in peristaltic flow with convective conditions.

    PubMed

    Hayat, Tasawar; Tanveer, Anum; Yasmin, Humaira; Alsaedi, Ahmed

    2014-01-01

    This article addresses the effects of homogeneous-heterogeneous reactions in peristaltic transport of Carreau fluid in a channel with wall properties. Mathematical modelling and analysis have been carried out in the presence of Hall current. The channel walls satisfy the more realistic convective conditions. The governing partial differential equations along with long wavelength and low Reynolds number considerations are solved. The results of temperature and heat transfer coefficient are analyzed for various parameters of interest. PMID:25460608

  10. Structure-inheriting solid-state reactions under hydrothermal conditions

    NASA Astrophysics Data System (ADS)

    Eda, Kazuo; Uno, Yuichi; Nagai, Noriko; Sotani, Noriyuki; Chen, Chen; Stanley Whittingham, M.

    2006-05-01

    We have explored several structure-inheriting solid-state reactions (SISSRs) under hydrothermal conditions for syntheses in the Co-Mo-O system. And we found an interesting hydrothermal SISSR from CoMoO 4·3/4H 2O to high-pressure (hp-) phase of CoMoO 4, which enabled us to considerably reduce the severe conditions for the synthesis of hp-CoMoO 4. As similar hydrothermal SISSRs are expected to be useful tools for material syntheses, we also briefly discuss them as a means of developing novel material syntheses and designs.

  11. Effects of Meteorological Conditions on Reactions to Noise Exposure

    NASA Technical Reports Server (NTRS)

    Shepherd, Kevin P. (Technical Monitor); Fields, James M.

    2004-01-01

    More than 80,000 residents' responses to transportation noise at different times of year provide the best, but imprecise, statistical estimates of the effects of season and meteorological conditions on community response to noise. Annoyance with noise is found to be slightly statistically significantly higher in the summer than in the winter in a seven-year study in the Netherlands. Analyses of 41 other surveys drawn from diverse countries, climates, and times of year find noise annoyance is increased by temperature, and may be increased by more sunshine, less precipitation, and reduced wind speeds. Meteorological conditions on the day of the interview or the immediately preceding days do not appear to have any more effect on reactions than do the conditions over the immediately preceding weeks or months.

  12. Amine-free reversible hydrogen storage in formate salts catalyzed by ruthenium pincer complex without pH control or solvent change.

    PubMed

    Kothandaraman, Jotheeswari; Czaun, Miklos; Goeppert, Alain; Haiges, Ralf; Jones, John-Paul; May, Robert B; Prakash, G K Surya; Olah, George A

    2015-04-24

    Due to the intermittent nature of most renewable energy sources, such as solar and wind, energy storage is increasingly required. Since electricity is difficult to store, hydrogen obtained by electrochemical water splitting has been proposed as an energy carrier. However, the handling and transportation of hydrogen in large quantities is in itself a challenge. We therefore present here a method for hydrogen storage based on a CO2 (HCO3 (-) )/H2 and formate equilibrium. This amine-free and efficient reversible system (>90?% yield in both directions) is catalyzed by well-defined and commercially available Ru pincer complexes. The formate dehydrogenation was triggered by simple pressure swing without requiring external pH control or the change of either the solvent or the catalyst. Up to six hydrogenation-dehydrogenation cycles were performed and the catalyst performance remained steady with high selectivity (CO free H2 /CO2 mixture was produced). PMID:25824142

  13. MICROWAVE-ACCELERATED MULTICOMPONENT REACTIONS UNDER SOLVENT-FREE CONDITIONS

    EPA Science Inventory

    The application of microwave-accelerated solventless synthetic protocols in multicomponent (MCC) reactions will be exemplified by several condensation and cyclization reactions including the rapid one-pot assembly of valuable heterocyclic compounds from in situ generated intermed...

  14. Impact of reaction conditions on grafting acrylamide onto starch

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We have explored the radical initiated graft polymerization reaction of acrylamide onto starch where the solvent, concentration, temperature and reaction times were varied. We have found that the morphology of the resulting grafted polymer is dramatically different and is dependent on the reaction c...

  15. Achieving Chemical Equilibrium: The Role of Imposed Conditions in the Ammonia Formation Reaction

    ERIC Educational Resources Information Center

    Tellinghuisen, Joel

    2006-01-01

    Under conditions of constant temperature T and pressure P, chemical equilibrium occurs in a closed system (fixed mass) when the Gibbs free energy G of the reaction mixture is minimized. However, when chemical reactions occur under other conditions, other thermodynamic functions are minimized or maximized. For processes at constant T and volume V,…

  16. Uranium plasma emission at gas-core reaction conditions

    NASA Technical Reports Server (NTRS)

    Williams, M. D.; Jalufka, N. W.; Hohl, F.; Lee, J. H.

    1976-01-01

    The results of uranium plasma emission produced by two methods are reported. For the first method a ruby laser was focused on the surface of a pure U-238 sample to create a plasma plume with a peak plasma density of about 10 to the 20th power/cu cm and a temperature of about 38,600 K. The absolute intensity of the emitted radiation, covering the range from 300 to 7000 A was measured. For the second method, the uranium plasma was produced in a 20 kilovolt, 25 kilojoule plasma-focus device. The 2.5 MeV neutrons from the D-D reaction in the plasma focus are moderated by polyethylene and induce fissions in the U-235. Spectra of both uranium plasmas were obtained over the range from 30 to 9000 A. Because of the low fission yield the energy input due to fissions is very small compared to the total energy in the plasma.

  17. Characteristics of uranium carbonitride microparticles synthesized using different reaction conditions

    SciTech Connect

    Silva, Chinthaka M; Lindemer, Terrence; Voit, Stewart L; Hunt, Rodney Dale; Besmann, Theodore M; Terrani, Kurt A; Snead, Lance Lewis

    2014-11-01

    Three sets of different experimental conditions by changing the cover gases during the sample preparation were tested to synthesize uranium carbonitride (UC1-xNx) microparticles. In the first two sets of experiments using (N2 to N2-4%H2 to Ar) and (Ar to N2 to Ar) environments, single phase UC1-xNx was synthesized. When reducing environments (Ar-4%H2 to N2-4%H2 to Ar-4%H2) were utilized, theoretical densities up to 97% of single phase UC1-xNx kernels were obtained. Physical and chemical characteristics such as density, phase purity, and chemical compositions of the synthesized UC1-xNx materials for the diferent experimental conditions used are provided. In-depth analysis of the microstrutures of UC1-xNx has been carried out and is discussed with the objective of large batch fabrication of high density UC1-xNx kernels.

  18. Kinetics of OH + CO reaction under atmospheric conditions

    NASA Technical Reports Server (NTRS)

    Hynes, A. J.; Wine, P. H.; Ravishankara, A. R.

    1986-01-01

    A pulsed laser photolysis-pulsed laser-induced fluorescence technique is used to directly measure the temperature, pressure, and H2O concentration dependence on k1 in air. K1 is found to increase linearly with increasing pressure at pressures of not greater than 1 atm, and the pressure dependence of k1 at 299 K is the same in N2 buffer gas as in O2 buffer gas. The rate constant in the low-pressure limit and the slope of the k1 versus pressure dependence are shown to be the same at 262 K as at 299 K. The present results significantly reduce the current atmospheric model uncertainties in the temperature dependence under atmospheric conditions, in the third body efficiency of O2, and in the effect of water vapor on k1.

  19. Automatic Detection Of Vaccine Adverse Reactions By Incorporating Historical Medical Conditions

    E-print Network

    Karypis, George

    Automatic Detection Of Vaccine Adverse Reactions By Incorporating Historical Medical Conditions This paper extends the state of art by bringing the historical medical conditions into the vaccine adverse with certain vaccines. We propose a novel measure called dual-lift for this task. It is shown that the dual

  20. Reaction-diffusion systems with constant diffusivities: conditional symmetries and form-preserving transformations

    E-print Network

    Roman Cherniha; Vasyl' Davydovych

    2013-07-18

    Q-conditional symmetries (nonclassical symmetries) for a general class of two-component reaction-diffusion systems with constant diffusivities are studied. Using the recently introduced notion of Q-conditional symmetries of the first type (R. Cherniha J. Phys. A: Math. Theor., 2010. vol. 43., 405207), an exhaustive list of reaction-diffusion systems admitting such symmetry is derived. The form-preserving transformations for this class of systems are constructed and it is shown that this list contains only non-equivalent systems. The obtained symmetries permit to reduce the reaction-diffusion systems under study to two-dimensional systems of ordinary differential equations and to find exact solutions. As a non-trivial example, multiparameter families of exact solutions are explicitly constructed for two nonlinear reaction-diffusion systems. A possible interpretation to a biologically motivated model is presented.

  1. Assessment of existing H2/O2 chemical reaction mechanisms at reheat gas turbine conditions

    E-print Network

    Weydahl, Torleif; Seljeskog, Morten; Haugen, Nils Erland L

    2011-01-01

    This paper provides detailed comparisons of chemical reaction mechanisms of H2 applicable at high preheat temperatures and pressures relevant to gas turbine and particularly Alstom's reheat gas turbine conditions. It is shown that the available reaction mechanisms exhibit large differences in several important elementary reaction coefficients. The reaction mechanisms are assessed by comparing ignition delay and laminar flame speed results obtained from CHEMKIN with available data, however, the amount of data at these conditions is scarce and a recommended candidate among the mechanisms can presently not be selected. Generally, the results with the GRI-Mech and Leeds mechanisms deviate from the Davis, Li, O'Conaire, Konnov and San Diego mechanisms, but there are also significant deviations between the latter five mechanisms that altogether are better adapted to hydrogen. The differences in ignition delay times between the dedicated hydrogen mechanisms (O'Conaire, Li and Konnov) range from approximately a maxim...

  2. Three-phase slug flow in microchips can provide beneficial reaction conditions for enzyme liquid-liquid reactions

    PubMed Central

    ?ech, Ji?í; P?ibyl, Michal; Šnita, Dalimil

    2013-01-01

    Here, we introduce a solution to low stability of a two-phase slug flow with a chemical reaction occurring at the phase interface in a microfluidic reactor where substantial merging of individual reacting slugs results in the loss of uniformity of the flow. We create a three-phase slug flow by introducing a third fluid phase into the originally two-phase liquid-liquid slug flow, which generates small two-phase liquid slugs separated by gas phase. Introduction of the third phase into our system efficiently prevents merging of slugs and provides beneficial reaction conditions, such as uniform flow pattern along the whole reaction capillary, interfacial area with good reproducibility, and intensive water-oil interface renewal. We tested the three-phase flow on an enzyme hydrolysis of soybean oil and compared the reaction conversion with those from unstable two-phase slug flows. We experimentally confirmed that the three-phase slug flow arrangement provides conversions and pressure drops comparable or even better with two-phase liquid-liquid arrangements. PMID:24404066

  3. Recent progress in transition-metal-catalyzed reduction of molecular dinitrogen under ambient reaction conditions.

    PubMed

    Nishibayashi, Yoshiaki

    2015-10-01

    This paper describes our recent progress in catalytic nitrogen fixation by using transition-metal-dinitrogen complexes as catalysts. Two reaction systems for the catalytic transformation of molecular dinitrogen into ammonia and its equivalent such as silylamine under ambient reaction conditions have been achieved by the molybdenum-, iron-, and cobalt-dinitrogen complexes as catalysts. Many new findings presented here may provide new access to the development of economical nitrogen fixation in place of the Haber-Bosch process. PMID:26131967

  4. Tribological reactions of perfluoroalkyl polyether oils with stainless steel under ultrahigh vacuum conditions at room temperature

    NASA Technical Reports Server (NTRS)

    Mori, Shigeyuki; Morales, Wilfredo

    1989-01-01

    The reaction between three types of commercial perfluoroalkyl polyether (PFPE) oils and stainless steel 440C was investigated experimentally during sliding under ultrahigh vacuum conditions at room temperature. It is found that the tribological reaction of PFPE is mainly affected by the activity of the mechanically formed fresh surfaces of metals rather than the heat generated at the sliding contacts. The fluorides formed on the wear track act as a boundary layer, reducing the friction coefficient.

  5. Onset conditions for gas phase reaction and nucleation in the CVD of transition metal oxides

    NASA Technical Reports Server (NTRS)

    Collins, J.; Rosner, D. E.; Castillo, J.

    1992-01-01

    A combined experimental/theoretical study is presented of the onset conditions for gas phase reaction and particle nucleation in hot substrate/cold gas CVD of transition metal oxides. Homogeneous reaction onset conditions are predicted using a simple high activation energy reacting gas film theory. Experimental tests of the basic theory are underway using an axisymmetric impinging jet CVD reactor. No vapor phase ignition has yet been observed in the TiCl4/O2 system under accessible operating conditions (below substrate temperature Tw = 1700 K). The goal of this research is to provide CVD reactor design and operation guidelines for achieving acceptable deposit microstructures at the maximum deposition rate while simultaneously avoiding homogeneous reaction/nucleation and diffusional limitations.

  6. Using Group-Inquiry to Study Differing Reaction Conditions in the E2 Elimination of Cyclohexyl Halides

    ERIC Educational Resources Information Center

    Long, Robert D.

    2012-01-01

    In this experiment, students individually conduct one of several variations of an E2 dehydrohalogenation reaction on a cyclohexyl halide substrate for 30 min, which is sufficient only for a partial reaction to occur. The variations examine reaction conditions including different leaving groups, decreased reaction temperature, or reduced base…

  7. Experimental Studies of Hydrogenation and Other Reactions on Surfaces Under Astrophysically Relevant Conditions

    NASA Technical Reports Server (NTRS)

    Vidali, Gianfranco

    1998-01-01

    The goal of our project is to study hydrogen recombination reactions on solid surfaces under conditions that are relevant in astrophysics. Laboratory experiments were conducted using low-flux, cold atomic H and D beams impinging on a sample kept under ultra high vacuum conditions. Realistic analogues of interstellar dust grains were used. Our results show that current models for hydrogen recombination reactions have to be modified to take into account the role of activated diffusion of H on surfaces even at low temperature.

  8. Carboxymethylation of Cassava Starch in Different Solvents and Solvent-Water Mixtures: Optimization of Reaction Conditions

    NASA Astrophysics Data System (ADS)

    Nwokocha, Louis M.; Ogunmola, Gabiel B.

    The influence of reaction medium on carboxymethylation process was investigated by treating cassava starch with sodium monochloroacetate in different solvents and solvent-water mixtures under alkaline conditions. The amount of carboxyl groups introduced into the starch moiety was determined titrimetrically and used to calculate the Degree of Substitution (DS) and Reaction Efficiency (RE). The results showed that carboxymethylation is significantly affected by the nature of reaction medium at p<0.05. Carboxymethylation in different solvent-water mixtures showed that aqueous 80% n-propanol offered the best medium for carboxymethylation. Optimization of reaction conditions in aqueous 80% n-propanol showed that the best condition for carboxymethylation was at starch-liquor ratio of 1:3, NaOH/reagent molar ratio of 4.0 and reagent-starch molar ratio of 0.35. An increase in temperature was required to effect the reaction at shorter time. At 55°C the highest values of DS and RE achieved in 0.5 h would require three hours to achieve the same values of DS and RE at 45°C.

  9. Review and analysis of high temperature chemical reactions and the effect of non-equilibrium conditions

    NASA Technical Reports Server (NTRS)

    Johnson, R. E.

    1986-01-01

    Chemical reactions at high temperatures have been considered extensively because of their importance to the heating effects on re-entry of space vehicles. Data on these reactions however, are not abundant and even when found there are discrepancies in data collected by various investigators. In particular, data for recombination reactions are calculated from the dissociation reactions or vice versa through the equilibrium constant. This involves the use of the principle of detailed balancing. This principle is discussed in reference to conditions where it is valid as well as to those where it is not valid. Related topics that merit further study or for which applicable information was available are briefly mentioned in an appendix to this report.

  10. Conditional and opposed reaction path diagrams for the analysis of fluid-chemistry interactions

    SciTech Connect

    Grcar, Joseph F.; Day, Marcus S.; Bell, John B.

    2003-06-06

    This conference paper considers how to use reaction path diagrams to better understand the output of reacting flow simulations. Briefly, these diagrams have long been used to depict the reactants and products in networks of chemical reactions. The diagrams can be generated in several ways from computer simulations of chemically reacting fluids to depict how the fluid moderates the chemistry by determining which species are brought into contact to react in quantity. The concept of a conditional diagram is introduced which depicts the reactions occurring in only a portion of the fluid domain, thus enabling comparisons between different regions of the fluid and the overall reaction network. Several examples are provided of the paths occurring in methane diffusion flames.

  11. Solid phase synthesis of hydantoins by thermal cyclization and screening of reaction conditions using APOS 1200.

    PubMed

    Karnbrock, W; Deeg, M; Gerhardt, J; Rapp, W

    1998-01-01

    A novel strategy for solid-phase synthesis of hydantoins with high optical purity is described using a thermal pH-neutral cyclization and simultaneous release from resin. Hereby even hydantoins bearing a pH-sensitive side chain (protection) are available. The reaction conditions are well screened applying the parallel organic synthesizer APOS 1200. PMID:10729901

  12. Runaway reactions, their courses and the methods to establish safe process conditions

    NASA Astrophysics Data System (ADS)

    Gustin, J. L.

    1991-08-01

    Much of the literature on runaway reactions deals with the consequences such as mechanical damage toxic and flammable release. The DIERS literature provides effective methods for vent sizing where experimental information is requested. Thermal stability measurements provide information on the onset temperature and kinetic data for chemical reactions. There is less information on the way the runaway reactions occur whereas the runaway reactions may have different causes. The purpose of this paper is to describe the various process deviations which can cause a runaway reaction to occur and to discuss the experimental information necessary for risk assessment, the choice of a safe process and the mitigation of the consequences of the runaway reaction. Each possible hazardous process deviation is illustrated by examples from the process industry and/or relevant experimental information obtained from laboratory experiments. The typical hazardous situations to be considered are the following: 1) The homogeneous thermal runaway due to too high a temperature. 2) The homogeneous runaway reaction by unintended introduction of additional reactants or catalyst. 3) The heterogeneous runaway reaction due to too high a local temperature. 4) The heterogeneous runaway reaction caused by slow heat conduction to the outside. 5) The runaway reaction caused by excess residence time at the process temperature (autocatalytic reactions). 6) The runaway reaction caused by reactant accumulation. The controling reactant feed rate is higher than the consumption rate perhaps because the temperature is too low, or the catalyst is absent. 7) The runaway reaction due to the pressurization of the enclosure by gaseous oxidizing intermediates (typical of nitric oxidations). 8) The runaway reaction due to phase separation of unstable species (liquids, solids) by loss of mixing or on cooling. 9) The runaway reaction on mixing of fast reacting chemicals in separate phases. 10)The runaway reaction due to fire or external heating. Considering the various runaway situations, the effectiveness of the following approaches is discussed: - Theoretical and experimental information required for hazard assessment. - Choice of adequate process conditions. - Choice of adequate methods for process control. - Experimental information required for vent sizing. La plus grande partie de la littérature sur les emballements thermiques traite des conséquences de l'accident telles que les effets mécaniques, les émissions toxiques et inflammables. Les travaux publiés par le DIERS fournissent des méthodes permettant le dimensionnement d'évents, nécessitant des déterminations expérimentales. Il y a moins d'information sur la manière dont les emballements thermiques peuvent survenir alors que ceux-ci peuvent avoir différentes causes. Le propos de cet article est de décrire les différentes dérives de procédé qui peuvent entraîner un emballement thermique et de déterminer l'information expérimentale nécessaire pour l'analyse des risques du procédé, le choix de conditions opératoires sûres et la réduction des conséquences de l'emballement thermique. Chaque dérive de procédé dangereuse, est illustrée par des exemples connus dans l'industrie chimique et par des données expérimentales obtenues dans des essais de laboratoire. Les conditions de procédé dangereuses prises en compte sont les suivantes: 1)L'emballement thermique homogène dû à une température excessive; 2) L'emballement thermique homogène par introduction d'un catalyseur ou d'un réactif contrôlant; 3) L'emballement thermique hétérogène dû à une température locale excessive; 4)L'emballement thermique hétérogène dû à une faible conduction thermique vers l'extérieur; 5) L'emballement thermique dû à un temps de séjour excessif à la température du procédé (Réactions autocatalytiques); 6) L'emballement thermique par accumulation de réactifs. La vitesse d'introduction d'un réactif contrôlant est supérieure à la vitesse de consommation de ce réactif, parce que la temp

  13. Preparation of cationized pine sawdust for nitrate removal: Optimization of reaction conditions.

    PubMed

    Keränen, Anni; Leiviskä, Tiina; Hormi, Osmo; Tanskanen, Juha

    2015-09-01

    Anion exchange materials were prepared from pine sawdust (Pinus sylvestris, PSD) through cationizing treatment with N-(3-chloro-2-hydroxypropyl) trimethyl ammonium chloride (CHMAC) in the presence of NaOH. Response surface methodology (RSM) was used to find the optimal reaction conditions. Three factors were chosen: reaction temperature (26-94 °C), reaction time (0.32-3.7 h) and NaOH/CHMAC molar ratio (0.19-2.2). Product yield (%) was used as a response. A quadratic model was fitted to the experimental data. The optimal conditions were: a reaction temperature of 57 °C, a reaction time of 1.8 h and a NaOH/CHMAC molar ratio of 1.32. A maximum nitrogen content of 2.6% was obtained at 60 °C, 3.7 h and a molar ratio of 1.2. The molar ratio had the greatest impact on the response. Regression analysis revealed that over 95% of the variance can be explained by the model. A maximum nitrate sorption capacity of 15.3 ± 1.4 mg N/g was achieved. The effect of CHMAC dose was also studied (a NaOH/CHMAC molar ratio of 1.2): 0.064 mol/g PSD was found to be near the optimum. Nitrate-contaminated groundwater (27.5 mg/l NO3) was treated with CPSD. Doses of 3-6 g/l resulted in 59-71% nitrate reduction. PMID:26093104

  14. Influence of reaction conditions on the composition of liquid products from two-stage catalytic hydrothermal processing of lignin.

    PubMed

    Onwudili, Jude A

    2015-07-01

    The influence of reaction conditions on the composition of liquid products during two-stage hydrothermal conversion of alkali lignin has been investigated in a batch reactor. Reactions were carried out in the presence of formic acid (FA) and Pt/Al2O3 catalyst. The two different sets of reaction conditions involved alternative reaction times of 1h and 5h at 265°C and 350°C, respectively. These provided different contributions to reaction severity, which affected the compositions of liquid products. Yields of liquid products reached up to 40wt% (on lignin feed basis) in the presence of FA under the less severe reaction condition. With 5h reaction time at 350°C, alkylphenols, alkylguaiacols and hydrocarbons were the dominant liquid products. However, with 5h reaction time at 265°C, phenol and methanol became dominant. The two-stage hydrothermal process led to improved lignin conversion, with the potential to manipulate the liquid product range. PMID:25840361

  15. Method and apparatus for measuring coupled flow, transport, and reaction processes under liquid unsaturated flow conditions

    DOEpatents

    McGrail, Bernard P. (Pasco, WA); Martin, Paul F. (Richland, WA); Lindenmeier, Clark W. (Richland, WA)

    1999-01-01

    The present invention is a method and apparatus for measuring coupled flow, transport and reaction processes under liquid unsaturated flow conditions. The method and apparatus of the present invention permit distinguishing individual precipitation events and their effect on dissolution behavior isolated to the specific event. The present invention is especially useful for dynamically measuring hydraulic parameters when a chemical reaction occurs between a particulate material and either liquid or gas (e.g. air) or both, causing precipitation that changes the pore structure of the test material.

  16. Direct kinetic and mechanistic study of the OH/sup +/ dimethylsulfide reaction under atmospheric conditions

    SciTech Connect

    Hynes, A.J.; Wine, P.H.

    1986-04-01

    The authors employed a pulsed laser photolysis - pulsed laser induced fluorescence technique to carry out direct, real time studies of OH reactions with DMS and DMS-d/sub 6/ in N/sub 2/, air and O/sub 2/ buffer gases. Both temperature and pressure dependencies have been investigated. They find that the observed rate constant (K/sub obs/ identical to d(OH)/(OH)(DMS)dt) depends on the O/sub 2/ concentration. The results are consistent with a mechanism which includes an abstraction route, a reversible addition route, and an adduct + O/sub 2/ reaction which competes with adduct decomposition under atmospheric conditions.

  17. A proposed abiotic reaction scheme for hydroxylamine and monochloramine under chloramination relevant drinking water conditions.

    PubMed

    Wahman, David G; Speitel, Gerald E; Machavaram, Madhav V

    2014-09-01

    Drinking water monochloramine (NH2Cl) use may promote ammonia-oxidizing bacteria (AOB). AOB use (i) ammonia monooxygenase for biological ammonia (NH3) oxidation to hydroxylamine (NH2OH) and (ii) hydroxylamine oxidoreductase for NH2OH oxidation to nitrite. NH2Cl and NH2OH may react, providing AOB potential benefits and detriments. The NH2Cl/NH2OH reaction would benefit AOB by removing the disinfectant (NH2Cl) and releasing their growth substrate (NH3), but the NH2Cl/NH2OH reaction would also provide a possible additional inactivation mechanism besides direct NH2Cl reaction with cells. Because biological NH2OH oxidation supplies the electrons required for biological NH3 oxidation, the NH2Cl/NH2OH reaction provides a direct mechanism for NH2Cl to inhibit NH3 oxidation, starving the cell of reductant by preventing biological NH2OH oxidation. To investigate possible NH2Cl/NH2OH reaction implications on AOB, an understanding of the underlying abiotic reaction is first required. The present study conducted a detailed literature review and proposed an abiotic NH2Cl/NH2OH reaction scheme (RS) for chloramination relevant drinking water conditions (?M concentrations, air saturation, and pH 7-9). Next, RS literature based kinetics and end-products were evaluated experimentally between pHs 7.7 and 8.3, representing (i) the pH range for future experiments with AOB and (ii) mid-range pHs typically found in chloraminated drinking water. In addition, a (15)N stable isotope experiment was conducted to verify nitrous oxide and nitrogen gas production and their nitrogen source. Finally, the RS was slightly refined using the experimental data and an AQUASIM implemented kinetic model. A chloraminated drinking water relevant RS is proposed and provides the abiotic reaction foundation for future AOB biotic experiments. PMID:24862953

  18. Correlation changes in EEG, conditioned and behavioral reactions with various degrees of oxygen insufficiency

    NASA Technical Reports Server (NTRS)

    Agadzhanyan, N. A.; Zakharova, I. N.; Kalyuzhnyy, L. V.; Dvorzhak, I. I.; Moravek, M.; Tsmiral, Y. I.

    1974-01-01

    The dynamics of change in bioelectric activity of the brain during acute hypoxia are studied for the time that working capacity and active consciousness are preserved, and to establish the correlation between EEG changes and behavioral reactions under oxygen starvation. Changes in body functions and behavioral disturbances are related to the degree of oxygen saturation in the blood, to bioelectric activity of the brain, and to an increase in conditioned reflexes. The capacity for adequate reaction to external signals and for coordinated psychomotor activity after loss of consciousness returns to man after 30 seconds. Repeated effects of hypoxia produce changes in the physiological reactions of the body directed toward better adaptation to changing gaseous environments.

  19. Reaction Mechanisms in Petroleum: From Experimentation to Upgrading and Geological Conditions

    E-print Network

    Lannuzel, Frédéric; Bounaceur, Roda; Marquaire, Paul-Marie; Michels, Raymond

    2009-01-01

    Among the numerous questions that arise concerning the exploitation of petroleum from unconventional reservoirs, lie the questions of the composition of hydrocarbons present in deep seated HP-HT reservoirs or produced during in-situ upgrading steps of heavy oils and oil shales. Our research shows that experimental hydrocarbon cracking results obtained in the laboratory cannot be extrapolated to geological reservoir conditions in a simple manner. Our demonstration is based on two examples: 1) the role of the hydrocarbon mixture composition on reaction kinetics (the "mixing effect") and the effects of pressure (both in relationship to temperature and time). The extrapolation of experimental data to geological conditions requires investigation of the free-radical reaction mechanisms through a computed kinetic model. We propose a model that takes into account 52 reactants as of today, and which can be continuously improved by addition of new reactants as research proceeds. This model is complete and detailed enou...

  20. Methanol reactions on bimetallic Ru(0001)-based surfaces under UHV conditions.

    PubMed

    Gazdzicki, Pawel; Jakob, Peter

    2013-02-01

    This article focuses on thermally induced methanol reactions on bimetallic Ru(0001)-based catalyst surfaces performed under ultrahigh vacuum conditions. Specifically, reaction intermediates and pathways on various clean and oxygen covered surfaces (Ru(0001), Cu/Ru(0001), Pt/Ru(0001), and Pt(x)Ru(1-x)/Ru(0001) surface alloys) have been studied by means of Fourier transform infrared spectroscopy and temperature programmed desorption. On the basis of our results and results reported in the literature methanol reactions on metal surfaces can be subdivided into two major pathways: (i) total dehydrogenation of methanol leading to CO, and (ii) an oxidation pathway which produces gaseous CO(2). On the clean surfaces either the dehydrogenation pathway is observed or no reaction occurs at all. The CO(2) producing path opens up only upon adsorption of oxygen. In parallel, the CO formation diminishes. In this context, the influence of oxygen on the yields of possible reaction products is analyzed. Generally, it is found that methanol reactions are promoted by disordered and dilute oxygen layers; dense and ordered O-overlayers, on the other hand, passivate the surface effectively. Referring to the direct methanol fuel cell (DMFC), a significant drawback of adding oxygen is the reaction of the oxygen atoms with hydrogen from methanol dehydrogenation to gaseous water. As hydrogen is the energy provider in a DMFC the desorbing water represents an unwanted drain of H atoms. Interestingly, the surfaces which produce the highest amount of CO(2) are also most efficient with respect to water formation. As the drain of H atoms on oxygen covered Pt(x)Ru(1-x)/Ru(0001) surface alloys is limited and they nonetheless exhibit CO(2) as a final product they represent a compromise regarding the ideal catalyst material for a DMFC. In particular, alloys with a Pt content of 50-80% are found to display superior performance. PMID:23247830

  1. The kinetics of dolomite reaction rim growth under isostatic and non-isostatic pressure conditions

    NASA Astrophysics Data System (ADS)

    Helpa, V.; Rybacki, E.; Morales, L. G.; Abart, R.; Dresen, G. H.

    2013-12-01

    During burial and exhumation, rocks are simultaneously exposed to metamorphic reactions and tectonic stresses. Therefore, the reaction rate of newly formed minerals may depend on chemical and mechanical driving forces. Here, we investigate the reaction kinetics of dolomite (CaMg[CO3]2) rim growth by solid-state reactions experiments on oriented calcite (CaCO3) and magnesite (MgCO3) single crystals under isostatic and non-isostatic pressure conditions. Cylindrical samples of 3-5 mm length and 7 mm diameter were drilled and polished perpendicular to the rhombohedral cleavage planes of natural clear crystals. The tests were performed using a Paterson-type deformation apparatus at P = 400 MPa confining pressure, temperatures, T, between 750 and 850°C, and reaction durations, t, of 2 - 146 h to calculate the kinetic parameters of dolomite rim growth under isostatic stress conditions. For non-isostatic reaction experiments we applied in addition differential stresses, ?, up to 40 MPa perpendicular to the contact interface at T = 750°C for 4 - 171 h duration, initiating minor inelastic deformation of calcite. The thickness of the resulting dolomite reaction rims increases linearly with the square root of time, indicating a diffusion-controlled reaction. The rims consist of two different textural domains. Granular dolomite grains (? 2 -5 ?m grain size) form next to calcite and elongated palisade-shaped grains (1-6 ?m diameter) grow perpendicular to the magnesite interface. Texture measurements with the electron backscatter diffraction technique indicate that the orientations of dolomite grains are mainly influenced by the orientation of the calcite educt crystal, in particular in the granular rim. To some extent, the texture of dolomite palisades is also influenced by the orientation of magnesite. The thickness of the two individual layers increases with temperature. At 400 MPa isostatic pressure, T = 750°C and t = 29 hours, a 5 ?m thick granular dolomite layer and a 7 ?m thick palisade-shaped layer evolve. At similar conditions and a differential stress of 30 MPa, the rim thickness remains similar; consequently the effect of non-isostatic stress on dolomite rim growth is negligible. Platinum markers show that the initial calcite-magnesite interface is located between granular and palisade-forming dolomite, indicating that rim growth occurs by counter diffusion of MgO and CaO. Diffusion of MgO across the dolomite reaction rim into calcite forms additionally magnesio-calcite grains with diameters of ? 13 - 46 ?m, depending on the experimental conditions and increasing with increasing distance to the dolomite boundary. At T = 750°C, t = 29 hours, the thickness of the magnesio-calcite layer is 32 ?m (isostatic) - 35 ?m (? = 30 MPa). The experiments indicate that solid-state reaction rim growth of dolomite between calcite and magnesite is primarily controlled by diffusion of MgO and CaO, forming layers with different microstructures during growth into the educt phases. The kinetics of the reaction in the carbonate system are not significantly changed by differential stresses up to 40 MPa. We suggest that volume diffusion is the dominant transport mechanism, which is presumably less affected by non-isostatic stresses than grain boundary diffusion.

  2. Search for reaction conditions and catalyst for selective prebiotic formation of Aldopentoses from Glycolaldehyde and Formaldehyde

    NASA Astrophysics Data System (ADS)

    Delidovich, Irina; Taran, Oxana; Parmon, Valentin; Gromov, Nikolay

    2012-07-01

    Formation of organic compounds from simple precursors appears to have been one of the first steps from geochemistry towards modern biochemistry. The Earth lagoons, hydrothermal springs, cosmic dust, meteorites, protoplanetary disk, etc. has been considered as the possible ``reactors'' in which the prebiotic synthesis could have taken place. The finding of reactions and reaction conditions which allow to produce the high yields of the biologically relevant substances from simple compounds could help us to verify different hypothesis of plausible prebotic conditions. In this work we have studied the formation of vitally important sugars, namely aldopentoses (ribose, xylose, lyxose and arabinose), from glycolaldehyde and formaldehyde over catalysts. Aldopentoses nowadays play the important roles as the components of polysaccharides, glycosides, nucleic acids and ATP. Glycolaldehyde is the simplest monosaccharide, which was found in the interstellar space [1], where it could be generated as a result of several processes, for instance, condensation of formaldehyde under UV-radiation [2]. In this work the peculiarities of interaction between glycolaldehyde and formaldehyde in the presence of soluble (phosphate and borate buffers) and solid (minerals apatite and montmorillonites) catalysts were studied. The dependences of composition of the reaction products on the catalyst nature, molar ratio of substrates, pH value of reaction mixture were revealed. The yields of aldopentoses amount to ca. 60-65% in the presence of borate catalyst under optimized reaction conditions. Borate acts not only as a catalyst, but also as the stabilizer of active intermediates and aldopentoses from side reactions [3]. Borates are present in some mineral and clays (serpentine, montmorillonite etc.) and in water of Cityhot springs (Geyser valley, placeKamchatka) in rather high concentrations. Therefore catalysis by borates could be considered as plausible prebotic condition. Acknowledgements. We thank Dr. S. Yashnik for providing the montmorillonite clays. The financial support of Program RAS (program ``Origin of biosphere and evolution biogeology systems'') is gratefully acknowledged. Hollis, J., Jewell, P., Lovas, F., et al., The Astrophysical Journal. 613, L45--L48, 2004 Pestunova, O., Simonov, A., Snytnikov, V., et al., Adv. Space Res. 36/2, 214-219, 2005. Ricardo, A., Carrigan, M.A., Olcott, A.N., Benner, S.A. Science. 303, 5655, 196, 2004.

  3. Organocatalytic acetylation of starch: effect of reaction conditions on DS and characterisation of esterified granules.

    PubMed

    Tupa, Maribel Victoria; Ávila Ramírez, Jhon Alejandro; Vázquez, Analía; Foresti, María Laura

    2015-03-01

    Starch acetates with varying degree of substitution (DS) were prepared by a novel solvent-free organocatalytic methodology. The acetylation protocol involved a non-toxic biobased ?-hydroxycarboxylic acid as catalyst, and proceeded with high efficiency in absence of solvents. The effect of reaction conditions including reaction temperature (90-140 °C), catalyst load (0-2.3 g/g starch), acetic anhydride/starch weight ratio (6.5-13.5 g/g), and starch moisture content (0.6-14.8%) on the DS of the esters was evaluated. The analysis performed showed that the increase of temperature and catalyst concentration resulted in higher DS values, and evidenced a beneficial contribution of native starch moisture content on the substitution level achieved. Variation of reaction conditions allowed starch esters to be obtained with DS in the 0.03-2.93 range. Starch esters were characterised in terms of morphology, chemical structure, thermal properties, and distribution in polar/non polar liquid systems. PMID:25306348

  4. Long-term behavior of reaction-diffusion equations with nonlocal boundary conditions on rough domains

    E-print Network

    Ciprian G. Gal; Mahamadi Warma

    2015-03-19

    We investigate the long term behavior in terms of finite dimensional global and exponential attractors, as time goes to infinity, of solutions to a semilinear reaction-diffusion equation on non-smooth domains subject to nonlocal Robin boundary conditions, characterized by the presence of fractional diffusion on the boundary. Our results are of general character and apply to a large class of irregular domains, including domains whose boundary is Holder continuous and domains which have fractal-like geometry. In addition to recovering most of the existing results on existence, regularity, uniqueness, stability, attractor existence, and dimension, for the well-known reaction-diffusion equation in smooth domains, the framework we develop also makes possible a number of new results for all diffusion models in other non-smooth settings.

  5. Temperature-dependent reaction-rate expression for oxygen recombination at Shuttle entry conditions

    NASA Technical Reports Server (NTRS)

    Zoby, E. V.; Simmonds, A. L.; Gupta, R. N.

    1984-01-01

    A temperature-dependent oxygen surface reaction-rate coefficient has been determined from experimental STS-2 heating and wall temperature data at altitudes of 77.91 km, 74.98 km, and 71.29 km. The coefficient is presented in an Arrhenius form and is shown to be less temperature dependent than previous results. Finite-rate viscous-shock-layer heating rates based on this present expression have been compared with predicted heating rates using the previous rate coefficients and with experimental heating data obtained over an extensive range of STS-2 and STS-3 entry conditions. A substantial improvement is obtained in comparison of experimental data and predicted heating rates using the present oxygen reaction-rate expression.

  6. A novel endo-?-N-acetylglucosaminidase releases specific N-glycans depending on different reaction conditions.

    PubMed

    Parc, Annabelle Le; Karav, Sercan; Bell, Juliana Maria Leite Nobrega De Moura; Frese, Steven A; Liu, Yan; Mills, David A; Block, David E; Barile, Daniela

    2015-09-01

    Milk glycoproteins are involved in different functions and contribute to different cellular processes, including adhesion and signaling, and shape the development of the infant microbiome. Methods have been developed to study the complexities of milk protein glycosylation and understand the role of N-glycans in protein functionality. Endo-?-N-acetylglucosaminidase (EndoBI-1) isolated from Bifidobacterium longum subsp. infantis ATCC 15697 is a recently isolated heat-stable enzyme that cleaves the N-N'-diacetyl chitobiose moiety found in the N-glycan core. The effects of different processing conditions (pH, temperature, reaction time, and enzyme/protein ratio) were evaluated for their ability to change EndoBI-1 activity on bovine colostrum whey glycoproteins using advanced mass spectrometry. This study shows that EndoBI-1 is able to cleave a high diversity of N-glycan structures. Nano-LC-Chip-Q-TOF MS data also revealed that different reaction conditions resulted in different N-glycan compositions released, thus modifying the relative abundance of N-glycan types. In general, more sialylated N-glycans were released at lower temperatures and pH values. These results demonstrated that EndoBI-1 is able to release a wide variety of N-glycans, whose compositions can be selectively manipulated using different processing conditions. © 2015 American Institute of Chemical Engineers Biotechnol. Prog., 31:1323-1330, 2015. PMID:26101185

  7. A Novel Endo-?-N-Acetylglucosaminidase Releases Specific N-Glycans Depending on Different Reaction Conditions

    PubMed Central

    De Moura Bell, Juliana Maria Leite Nobrega; Frese, Steven A.; Liu, Yan; Mills, David A.; Block, David E.; Barile, Daniela

    2015-01-01

    Milk glycoproteins are involved in different functions and contribute to different cellular processes, including adhesion and signaling, and shape the development of the infant micro-biome. Methods have been developed to study the complexities of milk protein glycosylation and understand the role of N-glycans in protein functionality. Endo-?-N-acetylglucosaminidase (EndoBI-1) isolated from Bifidobacterium longum subsp. infantis ATCC 15697 is a recently isolated heat-stable enzyme that cleaves the N-N?-diacetyl chitobiose moiety found in the N-glycan core. The effects of different processing conditions (pH, temperature, reaction time, and enzyme/protein ratio) were evaluated for their ability to change EndoBI-1 activity on bovine colostrum whey glycoproteins using advanced mass spectrometry. This study shows that EndoBI-1 is able to cleave a high diversity of N-glycan structures. Nano-LC-Chip–Q-TOF MS data also revealed that different reaction conditions resulted in different N-glycan compositions released, thus modifying the relative abundance of N-glycan types. In general, more sialylated N-glycans were released at lower temperatures and pH values. These results demonstrated that EndoBI-1 is able to release a wide variety of N-glycans, whose compositions can be selectively manipulated using different processing conditions. PMID:26101185

  8. Brownian dynamics simulations of an idealized chemical reaction network under spatial confinement and crowding conditions

    E-print Network

    Bellesia, Giovanni

    2015-01-01

    We investigate, via Brownian dynamics simulations, the reaction dynamics of a simple, non-linear chemical network (the Willamowski-Rossler network) under spatial confinement and crowding conditions. Our results show that the presence of inert crowders has a non-nontrivial effect on the dynamics of the network and, consequently, that effective modeling efforts aiming at a general understanding of the behavior of biochemical networks in vivo should be stochastic in nature and based on an explicit representation of both spatial confinement and macromolecular crowding.

  9. Reaction of perfluoroalkylpolyethers (PFPE) with 440C steel in vacuum under sliding conditions at room temperature

    NASA Technical Reports Server (NTRS)

    Mori, Shigeyuki; Morales, Wilfredo

    1989-01-01

    Reactions of perfluoroalkylpolyethers (PFPE: Fomblin, Demnum and Krytox) were studied during the sliding contact of stainless steel specimens under ultrahigh vacuum conditions. All three fluids reacted with the steel specimens during sliding. Fomblin, which has acetal linkages, decomposed under the sliding conditions generating gaseous products, (COF2 and fluorinated carbons) which were detected by a quadrupole mass spectrometer. Gaseous products were not detected for the Demnum and Krytox fluids. The amount of gaseous products from Fomblin increased with increasing sliding speed. At the end of the sliding experiments, the wear scar and deposits on the specimens were examined by small spot size XPS. The oxide layer on the specimen surface was removed during sliding, and metal fluorides were formed on the worn surface. The surface of the wear scar and deposits were covered with adsorbed PFPE. Based on these results, it was concluded that the decomposition reaction on Fomblin was initiated by contacting the fluid with a fresh metal surface which was formed during sliding.

  10. Electron transfer reaction dynamics of p-nitroaniline in water from liquid to supercritical conditions.

    PubMed

    Osawa, Koji; Terazima, Masahide; Kimura, Yoshifumi

    2012-09-20

    Photoexcitation dynamics of p-nitroaniline (pNA) have been investigated by femto-second transient absorption spectroscopy in water from liquid to supercritical conditions; along the isochoric line from the ambient condition to 664 K at 40.1 MPa and along the isothermal line from 40.1 to 36.1 MPa at 664 K. The rates of the back electron transfer reaction from the photoexcited charge transfer state to the electronic ground state was determined by the bleach recovery of the ground state absorption, and the successive vibrational relaxation in the electronic ground state was determined by the hot-band decay which was apparent at the red edge of the absorption. The variation of the back electron transfer rate was compared with the prediction based on the electron transfer theory including the Franck-Condon active vibrational modes. The results indicated that both the free energy change of the reaction and the change of the intramolecular vibrational reorganization energy cause the characteristic density (or temperature) dependence of the back electron transfer rate. The density dependence of the vibrational relaxation rate was compared with the collision frequency and the coordination number of the solvent molecule around the solute estimated by the molecular dynamics simulations. The density dependence of the coordination of a water oxygen atom to an amino hydrogen atom of pNA was found to be correlated with the density dependence of vibrational relaxation rate. PMID:22909090

  11. Rapid and effective oxidative pretreatment of woody biomass at mild reaction conditions and low oxidant loadings

    PubMed Central

    2013-01-01

    Background One route for producing cellulosic biofuels is by the fermentation of lignocellulose-derived sugars generated from a pretreatment that can be effectively coupled with an enzymatic hydrolysis of the plant cell wall. While woody biomass exhibits a number of positive agronomic and logistical attributes, these feedstocks are significantly more recalcitrant to chemical pretreatments than herbaceous feedstocks, requiring higher chemical and energy inputs to achieve high sugar yields from enzymatic hydrolysis. We previously discovered that alkaline hydrogen peroxide (AHP) pretreatment catalyzed by copper(II) 2,2?-bipyridine complexes significantly improves subsequent enzymatic glucose and xylose release from hybrid poplar heartwood and sapwood relative to uncatalyzed AHP pretreatment at modest reaction conditions (room temperature and atmospheric pressure). In the present work, the reaction conditions for this catalyzed AHP pretreatment were investigated in more detail with the aim of better characterizing the relationship between pretreatment conditions and subsequent enzymatic sugar release. Results We found that for a wide range of pretreatment conditions, the catalyzed pretreatment resulted in significantly higher glucose and xylose enzymatic hydrolysis yields (as high as 80% for both glucose and xylose) relative to uncatalyzed pretreatment (up to 40% for glucose and 50% for xylose). We identified that the extent of improvement in glucan and xylan yield using this catalyzed pretreatment approach was a function of pretreatment conditions that included H2O2 loading on biomass, catalyst concentration, solids concentration, and pretreatment duration. Based on these results, several important improvements in pretreatment and hydrolysis conditions were identified that may have a positive economic impact for a process employing a catalyzed oxidative pretreatment. These improvements include identifying that: (1) substantially lower H2O2 loadings can be used that may result in up to a 50-65% decrease in H2O2 application (from 100 mg H2O2/g biomass to 35–50 mg/g) with only minor losses in glucose and xylose yield, (2) a 60% decrease in the catalyst concentration from 5.0 mM to 2.0 mM (corresponding to a catalyst loading of 25 ?mol/g biomass to 10 ?mol/g biomass) can be achieved without a subsequent loss in glucose yield, (3) an order of magnitude improvement in the time required for pretreatment (minutes versus hours or days) can be realized using the catalyzed pretreatment approach, and (4) enzyme dosage can be reduced to less than 30 mg protein/g glucan and potentially further with only minor losses in glucose and xylose yields. In addition, we established that the reaction rate is improved in both catalyzed and uncatalyzed AHP pretreatment by increased solids concentrations. Conclusions This work explored the relationship between reaction conditions impacting a catalyzed oxidative pretreatment of woody biomass and identified that significant decreases in the H2O2, catalyst, and enzyme loading on the biomass as well as decreases in the pretreatment time could be realized with only minor losses in the subsequent sugar released enzymatically. Together these changes would have positive implications for the economics of a process based on this pretreatment approach. PMID:23971902

  12. In-situ observations of catalytic surface reactions with soft x-rays under working conditions.

    PubMed

    Toyoshima, Ryo; Kondoh, Hiroshi

    2015-03-01

    Catalytic chemical reactions proceeding on solid surfaces are an important topic in fundamental science and industrial technologies such as energy conversion, pollution control and chemical synthesis. Complete understanding of the heterogeneous catalysis and improving its efficiency to an ultimate level are the eventual goals for many surface scientists. Soft x-ray is one of the prime probes to observe electronic and structural information of the target materials. Most studies in surface science using soft x-rays have been performed under ultra-high vacuum conditions due to the technical limitation, though the practical catalytic reactions proceed under ambient pressure conditions. However, recent developments of soft x-ray based techniques operating under ambient pressure conditions have opened a door to the in-situ observation of materials under realistic environments. The near-ambient-pressure x-ray photoelectron spectroscopy (NAP-XPS) using synchrotron radiation enables us to observe the chemical states of surfaces of condensed matters under the presence of gas(es) at elevated pressures, which has been hardly conducted with the conventional XPS technique. Furthermore, not only the NAP-XPS but also ambient-pressure compatible soft x-ray core-level spectroscopies, such as near-edge absorption fine structure (NEXAFS) and x-ray emission spectroscopy (XES), have been significantly contributing to the in-situ observations. In this review, first we introduce recent developments of in-situ observations using soft x-ray techniques and current status. Then we present recent new findings on catalytically active surfaces using soft x-ray techniques, particularly focusing on the NAP-XPS technique. Finally we give a perspective on the future direction of this emerging technique. PMID:25667354

  13. Laboratory Experiments and Investigations on the Reaction Rates of Mg-sulfates Under Mars Relevant Conditions

    NASA Astrophysics Data System (ADS)

    Wang, A.; Freeman, J. J.

    2009-12-01

    Large deposits of hydrous Mg-sulfates was identified on Mars by orbital remote sensing (OMEGA on Mars Express and CRISM on Mars Reconnaissance Orbiter). Kieserite (MgSO4.H2O) and a non-specific “polyhydrated sulfates” are among the most observed and widely distributed sulfates (Bibring et al., 2005, Murchie et al., 2007). They frequently co-exist (Gendrin et al., 2005) and sometimes occur in alternative stratigraphic layers (Roach et al., 2008). Mg-sulfates were suggested, by compositional correlations and mineral models, to exist in Meridiani outcrops (Clark et al., 2005) and in rocks and regolith at Gusev (Squyres et al., 2006, Haskin et al., 2005, Wang et al., 2006, 2008); but no information on the hydration state of these sulfates can be extracted. We have conducted 188 experiments to investigate the stability fields and phase transition pathways of hydrous Mg-sulfates (Wang et al., 2009). In addition, we can extract the information on the reaction rates of five important dehydration and rehydration processes involved in these experiments. Our experiments were done at four temperatures (50°C, 21°C, 5°C, and -10°C) and ten relative humidity levels, with five hydrous Mg-sulfate species as starting phases. The rate information was extracted from the mineral identifications of the intermediate reaction products, measured by non-invasive Raman spectroscopy at regular time intervals during the entire duration of experiments (tens’ thousands hours). The rates for five processes are all strongly controlled by temperatures. We found that the experimental results match Arrhenius equation very well, thus the rate constants for dehydration and rehydration processes of Mg-sulfates at lower temperatures (down to 180K) can be approximately estimated by using the experimentally derived pre-exponential factor(s) and activation energy(s). In this study, only the orders of magnitudes for reaction rate ratios at different temperatures were considered. The estimated reaction rate ratios at different temperatures for five important processes helped us to understand the stable, especially the metastable, Mg-sulfate species that could be seen at Mars surface in non-polar regions during a moderate obliquity period. Therefore in addition to exam the spectral similarity, we now can use the knowledge gained through the laboratory experiments on stability field, phase transition pathway, and reaction rate of Mg-sulfates to evaluate the realistic mineral candidates for “polyhydrated sulfates”, that were so widely observed on Mars by OMEGA and CRISM. Furthermore, we will be able to investigate the formation mechanism of alternative stratigraphic layers of sulfates on Mars and the paleo-climatic conditions that they may imply.

  14. Palladium(II)-catalyzed Heck reaction of aryl halides and arylboronic acids with olefins under mild conditions

    PubMed Central

    Shaikh, Tanveer Mahamadali

    2013-01-01

    Summary A series of general and selective Pd(II)-catalyzed Heck reactions were investigated under mild reaction conditions. The first protocol has been developed employing an imidazole-based secondary phosphine oxide (SPO) ligated palladium complex (6) as a precatalyst. The catalytic coupling of aryl halides and olefins led to the formation of the corresponding coupled products in excellent yields. A variety of substrates, both electron-rich and electron-poor olefins, were converted smoothly to the targeted products in high yields. Compared with the existing approaches employing SPO–Pd complexes in a Heck reaction, the current strategy features mild reaction conditions and broad substrate scope. Furthermore, we described the coupling of arylboronic acids with olefins, which were catalyzed by Pd(OAc)2 and employed N-bromosuccinimide as an additive under ambient conditions. The resulted biaryls have been obtained in moderate to good yields. PMID:23946858

  15. A more robust model of the biodiesel reaction, allowing identification of process conditions for significantly enhanced rate and water tolerance.

    PubMed

    Eze, Valentine C; Phan, Anh N; Harvey, Adam P

    2014-03-01

    A more robust kinetic model of base-catalysed transesterification than the conventional reaction scheme has been developed. All the relevant reactions in the base-catalysed transesterification of rapeseed oil (RSO) to fatty acid methyl ester (FAME) were investigated experimentally, and validated numerically in a model implemented using MATLAB. It was found that including the saponification of RSO and FAME side reactions and hydroxide-methoxide equilibrium data explained various effects that are not captured by simpler conventional models. Both the experiment and modelling showed that the "biodiesel reaction" can reach the desired level of conversion (>95%) in less than 2min. Given the right set of conditions, the transesterification can reach over 95% conversion, before the saponification losses become significant. This means that the reaction must be performed in a reactor exhibiting good mixing and good control of residence time, and the reaction mixture must be quenched rapidly as it leaves the reactor. PMID:24508659

  16. Subsurface conditions in hydrothermal vents inferred from diffuse flow composition, and models of reaction and transport

    NASA Astrophysics Data System (ADS)

    Larson, B. I.; Houghton, J. L.; Lowell, R. P.; Farough, A.; Meile, C. D.

    2015-08-01

    Chemical gradients in the subsurface of mid-ocean ridge hydrothermal systems create an environment where minerals precipitate and dissolve and where chemosynthetic organisms thrive. However, owing to the lack of easy access to the subsurface, robust knowledge of the nature and extent of chemical transformations remains elusive. Here, we combine measurements of vent fluid chemistry with geochemical and transport modeling to give new insights into the under-sampled subsurface. Temperature-composition relationships from a geochemical mixing model are superimposed on the subsurface temperature distribution determined using a heat flow model to estimate the spatial distribution of fluid composition. We then estimate the distribution of Gibb's free energies of reaction beneath mid oceanic ridges and by combining flow simulations with speciation calculations estimate anhydrite deposition rates. Applied to vent endmembers observed at the fast spreading ridge at the East Pacific Rise, our results suggest that sealing times due to anhydrite formation are longer than the typical time between tectonic and magmatic events. The chemical composition of the neighboring low temperature flow indicates relatively uniform energetically favorable conditions for commonly inferred microbial processes such as methanogenesis, sulfate reduction and numerous oxidation reactions, suggesting that factors other than energy availability may control subsurface microbial biomass distribution. Thus, these model simulations complement fluid-sample datasets from surface venting and help infer the chemical distribution and transformations in subsurface flow.

  17. Influence of home cooking conditions on Maillard reaction products in beef.

    PubMed

    Trevisan, Aurea Juliana Bombo; de Almeida Lima, Daniele; Sampaio, Geni Rodrigues; Soares, Rosana Aparecida Manólio; Markowicz Bastos, Deborah Helena

    2016-04-01

    The influence of home cooking methods on the generation of Maillard reaction products (MRP) in beef was investigated. Grilling and frying hamburgers to an internal temperature below 90°C mainly generated furosine. When the temperature reached 90°C and 100°C, furosine content decreased by 36% and fluorescent compounds increased by up to 98%. Baking meat at 300°C, the most severe heat treatment studied, resulted in the formation of carboxymethyllysine. Boiling in water caused very low MRP formation. Acrylamide concentrations in grilled, fried or baked meat were extremely low. Home cooking conditions leading to low MRP generation and pleasant colours were obtained and could be used to guide diabetic and chronic renal patients on how to reduce their carboxymethyllysine intake. PMID:26593478

  18. Effects of reaction conditions on cellulose structures synthesized in vitro by bacterial cellulose synthases.

    PubMed

    Penttilä, Paavo A; Sugiyama, Junji; Imai, Tomoya

    2016-01-20

    Cellulose was synthesized by cellulose synthases extracted from the Komagataeibacter xylinus (formerly known as Gluconacetobacter xylinus). The effects of temperature and centrifugation of the reaction solution on the synthesis products were investigated. Cellulose with number-average degree of polymerization (DPn) roughly in the range 60-80 and cellulose II crystal structure was produced under all conditions. The amount of cellulose varied with temperature and centrifugation, and the centrifugation at 2000×g also slightly reduced the DPn. Cellulose production was maximal around the temperature 35°C and without centrifugation. At higher temperatures and during centrifugation at 2000×g the proteins started to denature, causing differences also in the morphology of the cellulosic aggregates, as seen with electron microscopy. These observations serve as a basis for discussions about the factors affecting the structure formation and chain length of in vitro synthesized cellulose. PMID:26572398

  19. Neutrality condition and response law for nonlinear reaction-diffusion equations, with application to population genetics

    NASA Astrophysics Data System (ADS)

    Vlad, Marcel Ovidiu; Moran, Federico; Tsuchiya, Masa; Cavalli-Sforza, L. Luca; Oefner, Peter J.; Ross, John

    2002-06-01

    We study a general class of nonlinear macroscopic evolution equations with ``transport'' and ``reaction'' terms which describe the dynamics of a species of moving individuals (atoms, molecules, quasiparticles, organisms, etc.). We consider that two types of individuals exist, ``not marked'' and ``marked,'' respectively. We assume that the concentrations of both types of individuals are measurable and that they obey a neutrality condition, that is, the kinetic and transport properties of the ``not marked'' and ``marked'' individuals are identical. We suggest a response experiment, which consists in varying the fraction of ``marked'' individuals with the preservation of total fluxes, and show that the response of the system can be represented by a linear superposition law even though the underlying dynamics of the system is in general highly nonlinear. The linear response law is valid even for large perturbations and is not the result of a linearization procedure but rather a necessary consequence of the neutrality condition. First, we apply the response theorem to chemical kinetics, where the ``marked species'' is a molecule labeled with a radioactive isotope and there is no kinetic isotope effect. The susceptibility function of the response law can be related to the reaction mechanism of the process. Secondly we study the geographical distribution of the nonrecurrent, nonreversible neutral mutations of the nonrecombining portion of the Y chromosome from human populations and show that the fraction of mutants at a given point in space and time obeys a linear response law of the type introduced in this paper. The theory may be used for evaluating the geographic position and the moment in time where and when a mutation originated.

  20. Chemical and Physical Reactions of Wellbore Cement under CO2 Storage Conditions: Effects of Cement Additives

    NASA Astrophysics Data System (ADS)

    Kutchko, B. G.; Strazisar, B. R.; Huerta, N.; Lowry, G. V.; Dzombak, D. A.; Thaulow, N.

    2008-12-01

    Sequestration of CO2 into geologic formations requires long-term storage and low leakage rates to be effective. Active and abandoned wells in candidate storage formations must be evaluated as potential leakage points. Wellbore integrity is an important part of an overall integrated assessment program being developed at NETL to assess potential risks at CO2 storage sites. Such a program is needed for ongoing policy and regulatory decisions for geologic carbon sequestration. The permeability and integrity of the cement in the well is a primary factor affecting its ability to prevent leakage. Cement must be able to maintain low permeability over lengthy exposure to reservoir conditions in a CO2 injection and storage scenario. Although it is known that cement may be altered by exposure to CO2, the results of ongoing research indicate that cement curing conditions, fluid properties, and cement additives play a significant role in the rate of alteration and reaction. The objective of this study is to improve understanding of the factors affecting wellbore cement integrity for large-scale geologic carbon sequestration projects. Due to the high frequency use of additives (pozzolan) in wellbore cement, it is also essential to understand the reaction of these cement-pozzolan systems upon exposure to CO2 under sequestration conditions (15.5 MPa and 50°C). Laboratory experiments were performed to determine the physical and chemical changes, as well as the rate of alteration of commonly used pozzolan-cement systems under simulated sequestration reservoir conditions, including both supercritical CO2 and CO2-saturated brine. The rate of alteration of the cement-pozzolan systems is considerably faster than with neat cement. However, the alteration of physical properties is much less significant with the pozzolanic blends. Permeability of a carbonated pozzolanic cement paste remains sufficiently small to block significant vertical migration of CO2 in a wellbore. All of the experiments run to date suggest that the cement-pozzolans used will be an effective seal for CO2, as long as the well was properly installed and is initially undamaged.

  1. Influence of reaction conditions on the properties of solution-processed Cu2ZnSnS4 nanocrystals

    NASA Astrophysics Data System (ADS)

    Qu, Yongtao; Zoppi, Guillaume; Miles, Robert W.; Beattie, Neil S.

    2014-12-01

    Cu2ZnSnS4 nanocrystals were fabricated by hot injection of sulphur into a solution of metallic precursors. By careful control of the reaction conditions it was possible to control the elemental composition of the nanocrystals such that they are suitable for earth abundant photovoltaic absorbers. When the reaction temperature increased from 195 °C to 240 °C the energy band gap of the nanocrystals decreased from 1.65 eV to 1.39 eV. This variation is explained by the identification of a mixed wurtzite-kesterite phase at lower reaction temperatures and secondary phase Cu2SnS3 at higher temperatures. Moreover, the existence of wurtzite structure depends critically on the reaction cooling rate. The reaction time was also found to have a strong effect on the nanocrystals which became increasingly copper poor and zinc rich as the reaction evolved. As the reaction time increase from 15 min to 60 min, the energy band gap increased from 1.42 eV to 1.84 eV. This variation is discussed in terms of the sample doping. The results demonstrate the importance of optimizing the reaction conditions to produce high quality Cu2ZnSnS4 nanocrystals.

  2. Optimization of reaction conditions for the electroleaching of manganese from low-grade pyrolusite

    NASA Astrophysics Data System (ADS)

    Zhang, Xing-ran; Liu, Zuo-hua; Fan, Xing; Lian, Xin; Tao, Chang-yuan

    2015-11-01

    In the present study, a response surface methodology was used to optimize the electroleaching of Mn from low-grade pyrolusite. Ferrous sulfate heptahydrate was used in this reaction as a reducing agent in sulfuric acid solutions. The effect of six process variables, including the mass ratio of ferrous sulfate heptahydrate to pyrolusite, mass ratio of sulfuric acid to pyrolusite, liquid-to-solid ratio, current density, leaching temperature, and leaching time, as well as their binary interactions, were modeled. The results revealed that the order of these factors with respect to their effects on the leaching efficiency were mass ratio of ferrous sulfate heptahydrate to pyrolusite > leaching time > mass ratio of sulfuric acid to pyrolusite > liquid-to-solid ratio > leaching temperature > current density. The optimum conditions were as follows: 1.10:1 mass ratio of ferrous sulfate heptahydrate to pyrolusite, 0.9:1 mass ratio of sulfuric acid to pyrolusite, liquid-to-solid ratio of 0.7:1, current density of 947 A/m2, leaching time of 180 min, and leaching temperature of 73°C. Under these conditions, the predicted leaching efficiency for Mn was 94.1%; the obtained experimental result was 95.7%, which confirmed the validity of the model.

  3. A Knoevenagel Initiated Annulation Reaction Using Room Temperature or Microwave Conditions

    ERIC Educational Resources Information Center

    Cook, A. Gilbert

    2007-01-01

    An experiment is presented that has the student execute a Knoevenagel initiated annulation reaction. The reaction can be carried out either through use of a microwave reactor or by allowing the mixture to stand at room temperature for two days. The student is then challenged to identify the reaction product through a guided prelab exercise of the…

  4. Hyporheic transport and biogeochemical reactions in pool-riffle systems under varying ambient groundwater flow conditions

    NASA Astrophysics Data System (ADS)

    Trauth, Nico; Schmidt, Christian; Vieweg, Michael; Maier, Uli; Fleckenstein, Jan H.

    2014-05-01

    At the interface between stream water, groundwater, and the hyporheic zone (HZ), important biogeochemical processes that play a crucial role in fluvial ecology occur. Solutes that infiltrate into the HZ can react with each other and possibly also with upwelling solutes from the groundwater. In this study, we systematically evaluate how variations of gaining and losing conditions, stream discharge, and pool-riffle morphology affect aerobic respiration (AR) and denitrification (DN) in the HZ. For this purpose, a computational fluid dynamics model of stream water flow is coupled to a reactive transport model. Scenarios of variations of the solute concentration in the upwelling groundwater were conducted. Our results show that solute influx, residence time, and the size of reactive zones strongly depend on presence, magnitude, and direction of ambient groundwater flow. High magnitudes of ambient groundwater flow lower AR efficiency by up to 4 times and DN by up to 3 orders of magnitude, compared to neutral conditions. The influence of stream discharge and morphology on the efficiency of AR and DN are minor, in comparison to that of ambient groundwater flow. Different scenarios of O2 and NO3 concentrations in the upwelling groundwater reveal that DN efficiency of the HZ is highest under low upwelling magnitudes accompanied with low concentrations of O2 and NO3. Our results demonstrate how ambient groundwater flow influences solute transport, AR, and DN in the HZ. Neglecting groundwater flow in stream-groundwater interactions would lead to a significant overestimation of the efficiency of biogeochemical reactions in fluvial systems.

  5. Optimization of reaction conditions by RSM and structure characterization of sulfated locust bean gum.

    PubMed

    Wang, Junlong; Yang, Ting; Tian, Jia; Liu, Wenxi; Jing, Fan; Yao, Jian; Zhang, Ji; Lei, Ziqiang

    2014-12-19

    Sulfated derivatives of galactomannan from locust bean gum (LBG) with the degree of substitution (DS) of 0.34-1.07 were synthesized using chlorosulfonic acid/pyridine (CSA/Py) method. Box-Behnken design (BBD) of response surface methodology (RSM) was employed to optimize the reaction conditions. Results of FT-IR and X-ray photoelectron spectroscopy (XPS) indicated that SO3H groups were widely present in sulfated LBG (SLBG). (13)C NMR result revealed that sulfation had occurred and C-6 substitution was predominant in SLBG. All sulfated samples showed a decrease in Mw and more broad molar mass distribution in size exclusion chromatography combined with laser light scattering (SEC-LLS) analysis. Results of MW - [Formula: see text] showed a decrease in fractal dimension (df) value. Laser light scattering results also showed a conformation transition from a compact chain conformation of branched clusters to a random coil conformation of SLBG. Compared to LBG and SLBG with low DS and molecular weight, SLBG2 exhibited an internal structure of random coil with a DS of 1.07. DS and molecular weight had great influence on its conformation in aqueous solution. Our results confirmed that the degradation of polysaccharide and SO3H groups improved significantly the stiffness of the chains due to the electrostatic effect. PMID:25263904

  6. Conditions for diffusion-limited and reaction-limited recombination in nanostructured solar cells

    SciTech Connect

    Ansari-Rad, Mehdi; Department of Physics, University of Shahrood, Shahrood ; Anta, Juan A.; Arzi, Ezatollah

    2014-04-07

    The performance of Dye-sensitized solar cells (DSC) and related devices made of nanostructured semiconductors relies on a good charge separation, which in turn is achieved by favoring charge transport against recombination. Although both processes occur at very different time scales, hence ensuring good charge separation, in certain cases the kinetics of transport and recombination can be connected, either in a direct or an indirect way. In this work, the connection between electron transport and recombination in nanostructured solar cells is studied both theoretically and by Monte Carlo simulation. Calculations using the Multiple-Trapping model and a realistic trap distribution for nanostructured TiO{sub 2} show that for attempt-to-jump frequencies higher than 10{sup 11}–10{sup 13} Hz, the system adopts a reaction limited (RL) regime, with a lifetime which is effectively independent from the speed of the electrons in the transport level. For frequencies lower than those, and depending on the concentration of recombination centers in the material, the system enters a diffusion-limited regime (DL), where the lifetime increases if the speed of free electrons decreases. In general, the conditions for RL or DL recombination depend critically on the time scale difference between recombination kinetics and free-electron transport. Hence, if the former is too rapid with respect to the latter, the system is in the DL regime and total thermalization of carriers is not possible. In the opposite situation, a RL regime arises. Numerical data available in the literature, and the behavior of the lifetime with respect to (1) density of recombination centers and (2) probability of recombination at a given center, suggest that a typical DSC in operation stays in the RL regime with complete thermalization, although a transition to the DL regime may occur for electrolytes or hole conductors where recombination is especially rapid or where there is a larger dispersion of energies of electron acceptors.

  7. The Aldol Addition and Condensation: The Effect of Conditions on Reaction Pathway

    ERIC Educational Resources Information Center

    Crouch, R. David; Richardson, Amie; Howard, Jessica L.; Harker, Rebecca L.; Barker, Kathryn H.

    2007-01-01

    The reaction of a ketone and an aldehyde in aqueous Na[subscript 2]CO[subscript 2] is described. This experiment is performed in the absence of strong bases or organic solvents and offers the opportunity for students to observe the critical role that reaction temperature and base strength have in determining the product of the base-mediated…

  8. The Reaction and Regeneration of Cementum in Various Pathological Conditions 1

    PubMed Central

    Stones, H. H.

    1934-01-01

    (1) The reaction of cementum and its adjoining tissues to induced pathological conditions associated with the gingival sulcus is described. (2) After subjecting the sulcus to interference, its histological appearance is compared with that of definite parodontal disease. (3) Various methods were adopted for these experiments, which were performed on monkeys. (4) Artificial pockets were produced by detaching the subgingival epithelium and underlying connective tissue from the cementum. Results: (a) Cementum is easily removed accidentally, when scraping monkeys' teeth. (b) Reattachment of connective tissues to cementum is effected, but is usually incomplete. (c) Epithelium always firmly reunites with cementum. (d) The artificial sulcus which is usually deeper than normal does not show, microscopically, the same pathological changes as in parodontal disease. (5) In other experiments, in addition to deepening the sulcus, the cementum lining the pockets was also removed, leaving denuded dentine in contact with the connective tissue. A similar condition was achieved by another method in which a dental bur was inserted between two teeth below the gum margin. Results: (a) The gingival epithelium is capable of forming a weak attachment to the dentine, though this does not usually occur. It always proliferates down and unites with the nearest layer of cementum. It seems to have a peculiar affinity for this tissue. (b) Underlying connective tissue does not usually unite with the dentine. When this happens it is effected by the regeneration of cementum, this new tissue being lined by new cementoblasts. (c) The width of the periodontal membrane, which was increased by the experiment, is reduced to a more normal level by deposition of new alveolar bone, and to a lesser extent by regeneration of cementum. (d) In this series of experiments the artificial pocket is permanent and somewhat resembles that of parodontal disease. This is probably due, not so much to the injury, but to its effects creating a space which forms an area of chronic stagnation. ImagesFig. 5Fig. 6Fig. 1Fig. 2Fig. 3Fig. 4Fig. 7Fig. 8Fig. 9Fig. 10Fig. 11Fig. 12Fig. 13Fig. 14Fig. 15Fig. 16Fig. 17 PMID:19989771

  9. Dynamics of morphological manifestations of reactions of the organism under conditions of hypergravitation

    NASA Technical Reports Server (NTRS)

    Knyazeva, G. D.; Podymov, V. K.; Savina, Y. A.

    1975-01-01

    The dynamics of the reaction of the hypothalamus-hypophysis-adrenal system to g-forces of 4 G's magnitude reveal a phasal nature of the adaptational system, dependent both on duration of force and position of the body.

  10. Reaction conditions affecting the relationship between thiobarbituric acid reactivity and lipid peroxides in human plasma.

    PubMed

    Lapenna, D; Ciofani, G; Pierdomenico, S D; Giamberardino, M A; Cuccurullo, F

    2001-08-01

    The thiobarbituric acid (TBA) reactivity of human plasma was studied to evaluate its adequacy in quantifying lipid peroxidation as an index of systemic oxidative stress. Two spectrophotometric TBA tests based on the use of either phosphoric acid (pH 2.0, method A) or trichloroacetic plus hydrochloric acid (pH 0.9, method B) were employed with and without sodium sulfate (SS) to inhibit sialic acid (SA) reactivity with TBA. To correct for background absorption, the absorbance values at 572 nm were subtracted from those at 532 nm, which represent the absorption maximum of the TBA:MDA adduct. Method B gave values of TBA-reactive substances (TBARS) 2-fold higher than those detected with method A. SS lowered TBARS by about 50% with both methods, indicating a significant involvement of SA in plasma TBA reactivity. Standard SA, at a physiologically relevant concentration of 1.5 mM, reacted with TBA, creating interference problems, which were substantially eliminated by SS plus correction for background absorbance. When method B was carried out in the lipid and protein fraction of plasma, SS inhibited by 65% TBARS formation only in the latter. Protein TBARS may be largely ascribed to SA-containing glycoproteins and, to a minor extent, protein-bound MDA. Indeed, EDTA did not affect protein TBARS assessed in the presence of SS. TBA reactivity of whole plasma and of its lipid fraction was instead inhibited by EDTA, suggesting that lipoperoxides (and possibly monofunctional lipoperoxidation aldehydes) are involved as MDA precursors in the TBA test. Pretreatment of plasma with KI, a specific reductant of hydroperoxides, decreased TBARS by about 27%. Moreover, aspirin administration to humans to inhibit prostaglandin endoperoxide generation reduced plasma TBARS by 40%. In conclusion, reaction conditions affect the relationship between TBA reactivity and lipid peroxidation in human plasma. After correction for the interfering effects of SA in the TBA test, 40% of plasma TBARS appears related to in vivo generated prostaglandin endoperoxides and only about 60% to lipoperoxidation products. Thus, the TBA test is not totally specific to oxidant-driven lipid peroxidation in human plasma. PMID:11461770

  11. Textured catalysts, methods of making textured catalysts, and methods of catalyzing reactions conducted in hydrothermal conditions

    DOEpatents

    Werpy, Todd [West Richland, WA; Wang, Yong [Richland, WA

    2003-12-30

    A textured catalyst having a hydrothermally-stable support, a metal oxide and a catalyst component is described. Methods of conducting aqueous phase reactions that are catalyzed by a textured catalyst are also described. The invention also provides methods of making textured catalysts and methods of making chemical products using a textured catalyst.

  12. Dynamic three-dimensional pore-scale imaging of reaction in a carbonate at reservoir conditions.

    PubMed

    Menke, Hannah P; Bijeljic, Branko; Andrew, Matthew G; Blunt, Martin J

    2015-04-01

    Quantifying CO2 transport and average effective reaction rates in the subsurface is essential to assess the risks associated with underground carbon capture and storage. We use X-ray microtomography to investigate dynamic pore structure evolution in situ at temperatures and pressures representative of underground reservoirs and aquifers. A 4 mm diameter Ketton carbonate core is injected with CO2-saturated brine at 50 °C and 10 MPa while tomographic images are taken at 15 min intervals with a 3.8 ?m spatial resolution over a period of 2(1/2) h. An approximate doubling of porosity with only a 3.6% increase in surface area to volume ratio is measured from the images. Pore-scale direct simulation and network modeling on the images quantify an order of magnitude increase in permeability and an appreciable alteration of the velocity field. We study the uniform reaction regime, with dissolution throughout the core. However, at the pore scale, we see variations in the degree of dissolution with an overall reaction rate which is approximately 14 times lower than estimated from batch measurements. This work implies that in heterogeneous rocks, pore-scale transport of reactants limits dissolution and can reduce the average effective reaction rate by an order of magnitude. PMID:25738415

  13. Molecular dynamics simulations of a chemical reaction; conditions for local equilibrium in a temperature gradient

    E-print Network

    Kjelstrup, Signe

    was used, based on Stillinger and Weber's 2- and 3-body potentials. Equilibrium and non- equilibrium. The results support the assumption that the entropy production of the reacting mixture can be written in the stationary state, a small reaction rate and an accumulation of the molecule in the cold region and the atom

  14. Sensory characteristics and consumer acceptability of beef stock containing glutathione Maillard reaction products prepared at various conditions.

    PubMed

    Kwon, G Y; Hong, J H; Kim, Y S; Lee, S M; Kim, K O

    2011-01-01

    The sensory characteristics and consumer acceptability of beef soup samples containing 9 types of glutathione Maillard reaction products (GMRPs) were investigated to examine the effects of the GMRPs produced under different reaction conditions on the flavor of the beef soup. The sensory characteristics of the beef stocks were examined using descriptive analysis. In consumer testing, 50 consumers evaluated the overall acceptability and flavor intensities of beef odor, salty taste, beef flavor, and seasoning flavor in the beef soup samples. It was found that the reaction conditions, including sugar type and pH, affected the sensory characteristics of the beef stock containing the GMRPs. The samples containing the GMRPs reacted at pH 7 were characterized with strong beef flavor, chestnut flavor, and cooked rice flavor. However, the GMRP reacted with xylose at pH 7 (XM7) was significantly stronger in beef-related sensory characteristics than the GMRPs reacted with glucose or fructose at pH 7 (GM7 and FM7). The samples containing the GMRPs reacted at pH 3 had strong acid-related attributes whereas the GMRPs reacted at pH 11 exhibited strong sulfur-related attributes and a bitter taste. Overall, the beef soup containing XM7, which was perceived as having a strong beef odor and flavor, was rated the highest consumer acceptability score. This suggests that XM7 has feasibility as a flavor enhancer. To elucidate its effectiveness further, it is required to apply XM7 in various food systems at varying levels and to compare its flavor enhancing effects with other flavor enhancers such as monosodium L-glutamate in future studies. Practical Application: This study characterized sensory attributes of glutathione Maillard reaction products (GMRPs) reacted under various conditions and evaluated their potential as a flavor enhancer by examining consumer acceptability of beef stock containing the GMRPs. This study showed that the GMRP reacted with xylose at pH 7 had strong 71 beef flavor and the highest consumer acceptability score. The results of this study will provide valuable information for understanding sensory aspect of flavors generated by Maillard reaction of GSH and sugars, since most studies on Maillard reaction focused on chemical reactions. Also, the outcome of this study will help flavor and food industries' efforts to develop a new flavor enhancer for use in a variety of processed food products. PMID:21535706

  15. Kinetics and Mechanism of the Reaction of Hydoxyl Radicals with Acetonitrile under Atmospheric Conditions

    NASA Technical Reports Server (NTRS)

    Hynes, A. J.; Wine, P. H.

    1997-01-01

    The pulsed laser photolysis-pulsed laser induced fluorescence technique has been employed to determine absolute rate coefficients for the reaction OH + CH3CN (1) and its isotopic variants, OH + CD3CN (2), OD + CH3CN (3), and OD + CD3CN (4). Reactions 1 and 2 were studied as a function of pressure and temperature in N2, N2/O2, and He buffer gases. In the absence of O2 all four reactions displayed well-behaved kinetics with exponential OH decays and pseudo-first rate constants which were proportional to substrate concentration. Data obtained in N2 over the range 50-700 Torr at 298 K are consistent with k(sub 1), showing a small pressure dependence. The Arrhenius expression obtained by averaging data at all pressures in k(sub 1)(T) = (1.1(sup +0.5)/(sub -0.3)) x 10(exp -12) exp[(-1130 +/- 90)/T] cu cm /(molecule s). The kinetics of reaction 2 are found to be pressure dependent with k(sub 2) (298 K) increasing from (1.21 +/- 0.12) x 10(exp -14) to (2.16 +/- 0.11) x 10(exp -14) cm(exp 3)/ (molecule s) over the pressure range 50-700 Torr of N2 at 298 K. Data at pressures greater than 600 Torr give k(sub 2)(T) = (9.4((sup +13.4)(sub -5.0))) x 10(exp -13) exp[(-1180 +/- 250)/T] cu cm/(molecule s). The rates of reactions 3 and 4 are found to be independent of pressure over the range 50-700 Torr of N2 with 298 K rate coefficient given by k(sub 3) =(3.18 +/- 0.40) x 10(exp -14) cu cm/(molecule s) and k(sub 4) = (2.25 +/-0.28) x 10(exp -14) cu cm/(molecule s). In the presence of O2 each reaction shows complex (non-pseudo-first-order) kinetic behavior and/or an apparent decrease in the observed rate constant with increasing [O2], indicating the presence of significant OH or OD regeneration. Observation of regeneration of OH in (2) and OD in (3) is indicative of a reaction channel which proceeds via addition followed by reaction of the adduct, or one of its decomposition products, with O2. The observed OH and OD decay profiles have been modeled by using a simple mechanistic scheme to extract kinetic information about the adduct reations with O2 and branching ratios for OH regeneration. A plausible mechanism for OH regeneration in (2) involves OH addition to the nitrogen atom followed by O2 addition to the cyano carbon atom, isomeriazation and decomposition to D2CO + DOCN + OH. Our results suggest that the OH + CH3CN reaction occurs via a complex mechanism involving both bimolecular and termolecular pathways, analogous to the mechanisms for the the important atmospheric reactions of OH with CO and HNO3.

  16. Condition-determined multicomponent reactions of 1,3-dicarbonyl compounds and formaldehyde.

    PubMed

    Liu, Changhui; Shen, Meng; Lai, Bingbing; Taheri, Amir; Gu, Yanlong

    2014-11-10

    By means of changing the reaction parameters, different products could be generated selectively starting from the same combination of substrates involving 1,3-dicarbonyl compounds and formaldehyde. This strategy enabled us to access diverse molecules without changing both starting material and reactor, maximizing thus the multifunctionality of the synthetic system. For example, starting from a 1,3-dicarbonyl compound, formaldehyde and 1,1-diphenylethylene, two kinds of products could be selectively formed including (i) a densely substituted dihydropyran and (ii) a C2-cinnamyl substituted 1,3-dicarbonyl compound. A one-pot three-component reaction of phenacylpyridinium salt, 1,3-dicarbonyl compound, and formaldehyde was also investigated, which produced either 2,4-diacyl-2,3-dihydrofuran or 2,4-diacyl-2-hydroxylmethyl-2,3-dihydrofuran in good to excellent yield. PMID:25319471

  17. Light-Element Reaction Flow and the Conditions for r-Process Nucleosynthesis

    E-print Network

    T. Sasaqui; K. Otsuki; T. Kajino; G. J. Mathews

    2006-03-18

    We deduce new constraints on the entropy per baryon ($s/k$), dynamical timescale ($\\tau_{dyn}$), and electron fraction ($Y_{e}$) consistent with heavy element nucleosynthesis in the r-process. We show that the previously neglected reaction flow throu gh the reaction sequence \\atg (n,$\\gamma$)\\Li~ significantly enhances the production of seed nuclei. We analyze the r-process nucleosynthesis in the context of a schematic exponential wi nd model. We show that fewer neutrons per seed nucleus implies that the entropy per baryon required for successful r-process nucleosynthesis must be more than a factor of two higher than previous estimates. This places new constraints on dynamical mo dels for the r-process.

  18. A quadrature closure for the reaction-source term in conditional-moment closure

    E-print Network

    Raman, Venkat

    extinction and re-ignition in turbulent non-premixed flames. A priori analysis of the quadrature model-series closures for all of the conditions considered. Ó 2006 The Combustion Institute. Published by Elsevier Inc. All rights reserved. Keywords: Turbulent combustion; Non-premixed combustion; Conditional

  19. Hot-Fire Testing of 100 LB(sub F) LOX/LCH4 Reaction Control Engine at Altitude Conditions

    NASA Technical Reports Server (NTRS)

    Marshall, William M.; Kleinhenz, Julie E.

    2010-01-01

    Liquid oxygen/liquid methane (LO2/LCH4 ) has recently been viewed as a potential green propulsion system for both the Altair ascent main engine (AME) and reaction control system (RCS). The Propulsion and Cryogenic Advanced Development Project (PCAD) has been tasked by NASA to develop these green propellant systems to enable safe and cost effective exploration missions. However, experience with LO2/LCH4 as a propellant combination is limited, so testing of these systems is critical to demonstrating reliable ignition and performance. A test program of a 100 lb f reaction control engine (RCE) is underway at the Altitude Combustion Stand (ACS) of the NASA Glenn Research Center, with a focus on conducting tests at altitude conditions. These tests include a unique propellant conditioning feed system (PCFS) which allows for the inlet conditions of the propellant to be varied to test warm to subcooled liquid propellant temperatures. Engine performance, including thrust, c* and vacuum specific impulse (I(sub sp,vac)) will be presented as a function of propellant temperature conditions. In general, the engine performed as expected, with higher performance at warmer propellant temperatures but better efficiency at lower propellant temperatures. Mixture ratio effects were inconclusive within the uncertainty bands of data, but qualitatively showed higher performance at lower ratios.

  20. Reaction norms in natural conditions: how does metabolic performance respond to weather variations in a small endotherm facing cold environments?

    PubMed

    Petit, Magali; Vézina, François

    2014-01-01

    Reaction norms reflect an organisms' capacity to adjust its phenotype to the environment and allows for identifying trait values associated with physiological limits. However, reaction norms of physiological parameters are mostly unknown for endotherms living in natural conditions. Black-capped chickadees (Poecile atricapillus) increase their metabolic performance during winter acclimatization and are thus good model to measure reaction norms in the wild. We repeatedly measured basal (BMR) and summit (Msum) metabolism in chickadees to characterize, for the first time in a free-living endotherm, reaction norms of these parameters across the natural range of weather variation. BMR varied between individuals and was weakly and negatively related to minimal temperature. Msum varied with minimal temperature following a Z-shape curve, increasing linearly between 24°C and -10°C, and changed with absolute humidity following a U-shape relationship. These results suggest that thermal exchanges with the environment have minimal effects on maintenance costs, which may be individual-dependent, while thermogenic capacity is responding to body heat loss. Our results suggest also that BMR and Msum respond to different and likely independent constraints. PMID:25426860

  1. Reaction Norms in Natural Conditions: How Does Metabolic Performance Respond to Weather Variations in a Small Endotherm Facing Cold Environments?

    PubMed Central

    Petit, Magali; Vézina, François

    2014-01-01

    Reaction norms reflect an organisms' capacity to adjust its phenotype to the environment and allows for identifying trait values associated with physiological limits. However, reaction norms of physiological parameters are mostly unknown for endotherms living in natural conditions. Black-capped chickadees (Poecile atricapillus) increase their metabolic performance during winter acclimatization and are thus good model to measure reaction norms in the wild. We repeatedly measured basal (BMR) and summit (Msum) metabolism in chickadees to characterize, for the first time in a free-living endotherm, reaction norms of these parameters across the natural range of weather variation. BMR varied between individuals and was weakly and negatively related to minimal temperature. Msum varied with minimal temperature following a Z-shape curve, increasing linearly between 24°C and ?10°C, and changed with absolute humidity following a U-shape relationship. These results suggest that thermal exchanges with the environment have minimal effects on maintenance costs, which may be individual-dependent, while thermogenic capacity is responding to body heat loss. Our results suggest also that BMR and Msum respond to different and likely independent constraints. PMID:25426860

  2. Solubility and Reaction Rates of Aluminum Solid Phases Under Geothermal Conditions

    SciTech Connect

    Benezeth, P.; Palmer, D.A.; Wesolowski, D.J.; Anovitz, L.M.

    2000-05-28

    Experimental studies involving equilibrium solubility and dissolution/precipitation rates were initiated on aluminum hydroxide phases prevalent under geothermal reservoir conditions. A large capacity, hydrogen-electrode concentration cell (HECC) was constructed specifically for this purpose.

  3. Evolution of fracture permeability of ultramafic rocks at hydrothermal conditions: An experimental study on serpentinization reactions

    NASA Astrophysics Data System (ADS)

    Farough, A.; Moore, D. E.; Lockner, D. A.; Lowell, R. P.

    2014-12-01

    Serpentinization of ultramafic rocks, during which olivine and pyroxene minerals are replaced by serpentine, magnetite, brucite and talc, is associated with hydrothermal activity at slow and ultraslow mid-ocean ridges. Serpentinization reactions affect hydrothermal fluid circulation by changing permeability of the oceanic crust. To advance our understanding of the evolution of permeability accompanying serpentinization reactions, we performed a series of flow-through experiments at a temperature of 260?C, a confining pressure of 50 MPa, and a pore pressure of 20±2 MPa on cylindrical cores of ultramafic rocks (18 mm in diameter and 23 mm length) containing a single through-going tensile fracture. Pore fluid flow was in one direction and was collected routinely for chemical analysis. A 7.5 mm thick layer of the same rock, crushed and sieved (0.18-1.0 mm) was placed on the inlet end of the sample to produce a reactive heated reservoir for the pore fluid before entering the fracture. Multiple peridotite samples were tested, to investigate the effect of mineral assemblage on fluid-rock interaction and permeability. The initial effective permeability of the samples varied between 10-(15-18)m2, and it decreased by about 2 orders of magnitude in 7-10 days, showing that serpentinization reactions result in an initially rapid decrease in permeability. The best fit equation for the observed rate of change in permeability (k) is in the form of dk/dt=Ae-0.01t, where A is a constant and t is time. This result suggests that the rate of serpentine formation is largely controlled by the initial permeability rather than the properties of the reacting rock. Assuming flow between parallel plates, we find the effective crack width decreases by approximately 2 orders of magnitude during the experiments. The fluid chemistry and mineralogy data support the occurrence of serpentinization reactions. The early peak and monotonic decrease in the concentration of Mg, and Si in pore fluid collected from all samples is consistent with an initial phase of rapid Mg-silicate dissolution followed by a declining rate as precipitation coated reactive surfaces. EMP analysis and SEM imaging show precipitation of serpentine phases along the walls of the tensile fracture, which is the main factor contributing to the reduction in permeability.

  4. Kinetics of the OH + CH/sub 3/SH reaction under atmospheric conditions

    SciTech Connect

    Hynes, A.J.; Wine, P.H.

    1987-06-18

    The pulsed laser photolysis-pulsed laser-induced fluorescence technique has been employed to study the kinetics of OH reactions with CH/sub 3/SH (k/sub 1/) and CD/sub 3/SH (k/sub 2/) in N/sub 2/, air, and O/sub 2/ buffer gases. They find that k/sub 1/ and k/sub 2/ are independent of O/sub 2/ concentration. Measured k/sub 1/ values are in excellent agreement with previous flash photolysis-resonance fluorescence studies, all of which employed reaction mixtures containing no O/sub 2/. However, the observation of no O/sub 2/ dependence is in marked disagreement with a number of relative rate studies where NO/sub x/-containing species were employed as photolytic precursors for OH and olefins were used as the reference compound. k/sub 2/ is found to be approx. 13% slower than k/sub 1/, suggesting the occurrence of a minor methyl hydrogen abstraction channel. In the course of investigating complications which result from photolysis of the mercaptan reactants, they found that 266-nm photolysis of either CH/sub 3/SH or CD/sub 3/SH in the presence of O/sub 2/ (but in the absence of other OH photolytic precursors) results in production of OH.

  5. Chemical reaction conditions in a Danish 80 MW{sub th} CFB-boiler co-firing straw and coal

    SciTech Connect

    Hansen, P.F.B.

    1997-12-31

    Future boilers to be constructed in Denmark including boilers intended for energy conversion of biomass (straw and wood chips) will be designed for Ultra Super Critical steam data. The high steam temperatures and subsequently metal temperatures in the superheaters will increase the corrosion hazard significantly. Severe superheater corrosion observed in the convective path and on test tubes inserted into the loop seal of a Danish 80 MW{sub th} Ahlstroem Pyroflow CFB boiler co-firing coal and straw initiated this study on the conditions under which the chemical reactions occur and deposits form. Load changes--caused by variations in public demand for district heating shifts the reaction conditions in the loop seal between predominantly reducing and predominantly oxidizing conditions. Furthermore the external particle circulation rate and the local temperatures are strongly affected. Deposits collected in the loop seal on temperature controlled probes reveals Cl concentrations more than Twenty Thousand times higher than found in the surrounding bed material. The results are discussed and suggestions on how to reduce high temperature corrosion and superheater fouling are presented.

  6. The effect of preparation conditions on the structure and mechanical properties of reaction-sintered silicon nitride

    NASA Technical Reports Server (NTRS)

    Heinrich, J.

    1980-01-01

    The microstructure of reaction sintered silicon nitride (RSSN) was changed over a wide range by varying the grain density, grain size of the silicon starting powder, nitriding conditions, and by introducing artificial pores. The influence of single microstructural parameters on mechanical properties like room temperature strength, creep behavior, and resistance to thermal shock was investigated. The essential factors influencing these properties were found to be total porosity, pore size distribution, and the fractions of alpha and beta Si3N4. In view of high temperature engineering applications of RSSN, potentials for optimizing the material's properties by controlled processing are discussed.

  7. A new synthesis of TATB using inexpensive starting materials and mild reaction conditions

    SciTech Connect

    Mitchell, A.R.; Pagoria, P.F.; Schmidt, R.D.

    1996-04-01

    TATB is currently manufactured in US by nitration of the expensive TCB to give 2,4,6-trichloro-1,3,5-trinitrobenzene which is then aminated to yield TATB. Elevated temperatures (150 C) are required for both reactions. There is a need for a more economical synthesis of TATB that also addresses current environmental issues. We have recently found that 1,1,1-trimethylhydrazinium iodide (TMHI) allows the amination of nitroarenes at ambient temperature via Vicarious Nucleophilic Substitution of hydrogen. TMHI reacts with picramide in presence of strong base (NaOMe or t-BuOK) to give TATB in over 95% yield. TMHI and picramide can be obtained from either inexpensive starting materials or surplus energetic materials from demilitarization activities, such as the 30,000 metric tons of UDMH (surplus rocket propellant) from the former Soviet Union.

  8. Pronounced Size Dependence in Structure and Morphology of Gas-Phase Produced, Partially Oxidized Cobalt Nanoparticles under Catalytic Reaction Conditions.

    PubMed

    Bartling, Stephan; Yin, Chunrong; Barke, Ingo; Oldenburg, Kevin; Hartmann, Hannes; von Oeynhausen, Viola; Pohl, Marga-Martina; Houben, Kelly; Tyo, Eric C; Seifert, Sönke; Lievens, Peter; Meiwes-Broer, Karl-Heinz; Vajda, Stefan

    2015-06-23

    It is generally accepted that optimal particle sizes are key for efficient nanocatalysis. Much less attention is paid to the role of morphology and atomic arrangement during catalytic reactions. Here, we unravel the structural, stoichiometric, and morphological evolution of gas-phase produced and partially oxidized cobalt nanoparticles in a broad size range. Particles with diameters between 1.4 and 22 nm generated in cluster sources are size selected and deposited on amorphous alumina (Al2O3) and ultrananocrystalline diamond (UNCD) films. A combination of different techniques is employed to monitor particle properties at the stages of production, exposure to ambient conditions, and catalytic reaction, in this case, the oxidative dehydrogenation of cyclohexane at elevated temperatures. A pronounced size dependence is found, naturally classifying the particles into three size regimes. While small and intermediate clusters essentially retain their compact morphology, large particles transform into hollow spheres due to the nanoscale Kirkendall effect. Depending on the substrate, an isotropic (Al2O3) or anisotropic (UNCD) Kirkendall effect is observed. The latter results in dramatic lateral size changes. Our results shed light on the interplay between chemical reactions and the catalyst's structure and provide an approach to tailor the cobalt oxide phase composition required for specific catalytic schemes. PMID:26027910

  9. QuadraPure-Supported Palladium Nanocatalysts for Microwave-Promoted Suzuki Cross-Coupling Reaction under Aerobic Condition

    PubMed Central

    Loh, Poh Lee; Juan, Joon Ching; Yarmo, Mohd Ambar; Yusop, Rahimi M.

    2014-01-01

    Cross-linked resin-captured palladium (XL-QPPd) was readily prepared by simple physical adsorption onto the high loading QuadraPure macroporous resin and a subsequent reduction process. To enhance the mechanical stability, entrapped palladium nanocatalysts were cross-linked with succinyl chloride. Both transmission electron microscopy images and X-ray diffraction analysis revealed that the palladium nanoparticles were well dispersed with diameters ranging in 4–10?nm. The catalyst performed good catalytic activity in microwave-promoted Suzuki cross-coupling reactions in water under aerobic condition with mild condition by using various aryl halides and phenylboronic acid. In addition, the catalyst showed an excellent recyclability without significant loss of catalytic activity. PMID:25054185

  10. Malonic acid concentration as a control parameter in the kinetic analysis of the Belousov-Zhabotinsky reaction under batch conditions.

    PubMed

    Blagojevi?, Slavica M; Ani?, Slobodan R; Cupi?, Zeljko D; Peji?, Natasa D; Kolar-Ani?, Ljiljana Z

    2008-11-28

    The influence of the initial malonic acid concentration [MA]0 (8.00 x 10(-3) < or = [MA]0 < or = 4.30 x 10(-2) mol dm(-3)) in the presence of bromate (6.20 x 10(-2) mol dm(-3)), bromide (1.50 x 10(-5) mol dm(-3)), sulfuric acid (1.00 mol dm(-3)) and cerium sulfate (2.50 x 10(-3) mol dm(-3)) on the dynamics and the kinetics of the Belousov-Zhabotinsky (BZ) reactions was examined under batch conditions at 30.0 degrees C. The kinetics of the BZ reaction was analyzed by the earlier proposed method convenient for the examinations of the oscillatory reactions. In the defined region of parameters where oscillograms with only large-amplitude relaxation oscillations appeared, the pseudo-first order of the overall malonic acid decomposition with a corresponding rate constant of 2.14 x 10(-2) min(-1) was established. The numerical results on the dynamics and kinetics of the BZ reaction, carried out by the known skeleton model including the Br2O species, were in good agreement with the experimental ones. The already found saddle node infinite period (SNIPER) bifurcation point in transition from a stable quasi-steady state to periodic orbits and vice versa is confirmed by both experimental and numerical investigations of the system under consideration. Namely, the large-amplitude relaxation oscillations with increasing periods between oscillations in approaching the bifurcation points at the beginning and the end of the oscillatory domain, together with excitability of the stable quasi-steady states in their vicinity are obtained. PMID:18989478

  11. Synthesis of silica supported AuCu nanoparticle catalysts and the effects of pretreatment conditions for the CO oxidation reaction

    SciTech Connect

    Chen, Tsung-Liang; Mullins, David R; Brooks, John; Cox, David F.

    2011-01-01

    The reaction of CH{sub 3}CHCl{sub 2} over the nearly-stoichiometric {alpha}-Cr{sub 2}O{sub 3} (10{bar 1} > 2) surface produces an ethylidene intermediate that yields primarily gas phase CH{sub 2} {double_bond} CH{sub 2} and surface chlorine adatoms; however, trace amounts of HC {triple_bond} CH, CH{sub 3}CH{sub 3}, H{sub 2} and CH{sub 3}CH {double_bond} CHCH{sub 3} are also observed. A rate-limiting intramolecular isomerization (2,1-hydrogen shift) in the surface ethylidene species produces gas phase CH{sub 2} {double_bond} CH{sub 2}. The chlorine freed from the dissociation of CH{sub 3}CHCl{sub 2} binds at the five-coordinate surface Cr{sup 3+} sites on the stoichiometric surface, completing the octahedral coordination sphere, and inhibits the surface chemistry by simple site blocking. No surface carbon deposition is observed from the thermal reaction of 1,1-dichloroethane under the conditions of this study, demonstrating that the ethylidene intermediate is not a primary coke forming intermediate over (10{bar 1} > 2) facets of {alpha}-Cr{sub 2}O{sub 3} under the conditions of this study.

  12. Pentavalent Uranium Oxide via Reduction of [UO2]2+ Under Hydrothermal Reaction Conditions

    SciTech Connect

    Balai, N.; Frisch, M; Ilton, E; Ravel, B; Cahill, C

    2008-01-01

    The synthesis, crystal structure, and spectroscopic characterization of [UV(H2O)2(UVIO2)2O4(OH)](H2O)4 (1), a mixed-valent UV/UVI oxide material, are reported. The hydrothermal reaction of UO22+ with Zn and hydrazine at 120 degrees C for three days yields 1 in the form of a dark red crystalline solid. Compound 1 has been characterized by a combination of single-crystal and powder X-ray diffraction (XRD), elemental analysis, thermogravimetric analysis, X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS). The structure consists of an extended sheet of edge and corner shared UVI pentagonal bipyramids that are further connected by edge sharing to square bipyramidal UV units. The overall topology is similar to the mineral ianthinite. The uranium L|||-edge XAS revealed features consistent with those observed by single-crystal X-ray diffraction. High resolution XPS data analysis of the U4f region confirmed the oxidation states of U as originally assigned from XRD analysis and bond valence summations.

  13. Pentavalent Uranium Oxide via Reduction of [UO2]2+ Under Hydrothermal Reaction Conditions

    SciTech Connect

    Belai, Nebebech; Frisch, Mark; Ilton, Eugene S.; Ravel, Bruce; Cahill, Christopher L.

    2008-11-03

    The synthesis, crystal structure and spectroscopic characterization of [UV(H2O)2(UVIO2)2O4(OH)](H2O)4 (1), a mixed-valent UV/UVI oxide material, are reported. The hydrothermal reaction of UO22+ with Zn and hydrazine at 120 °C for three days yields 1 in the form of a dark red crystalline solid. Compound 1 has been characterized by a combination of single-crystal and powder X-ray diffraction (XRD), elemental analysis, thermogravimetric analysis, X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS). The structure consists of an extended sheet of edge and point shared UVI pentagonal bipyramids that are further connected by edge sharing to square bipyramidal UV units. The overall topology is similar to the mineral ianthinite. The uranium L|||-edge XAS revealed features consistent with those observed by single-crystal X-ray diffraction. High resolution XPS data analysis of the U4f region confirmed the oxidation states of U as originally assigned from XRD analysis and bond valence summations.

  14. Pentavalent uranium oxide via reduction of [UO2]2+ under hydrothermal reaction conditions.

    PubMed

    Belai, Nebebech; Frisch, Mark; Ilton, Eugene S; Ravel, Bruce; Cahill, Christopher L

    2008-11-01

    The synthesis, crystal structure, and spectroscopic characterization of [U(V)(H2O)2(U(VI)O2)2O4(OH)](H2O)4 (1), a mixed-valent U(V)/U(VI) oxide material, are reported. The hydrothermal reaction of UO2(2+) with Zn and hydrazine at 120 degrees C for three days yields 1 in the form of a dark red crystalline solid. Compound 1 has been characterized by a combination of single-crystal and powder X-ray diffraction (XRD), elemental analysis, thermogravimetric analysis, X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS). The structure consists of an extended sheet of edge and corner shared U(VI) pentagonal bipyramids that are further connected by edge sharing to square bipyramidal U(V) units. The overall topology is similar to the mineral ianthinite. The uranium L(III)-edge XAS revealed features consistent with those observed by single-crystal X-ray diffraction. High resolution XPS data analysis of the U4f region confirmed the oxidation states of U as originally assigned from XRD analysis and bond valence summations. PMID:18842038

  15. Lipid synthesis under hydrothermal conditions by Fischer-Tropsch-type reactions

    NASA Technical Reports Server (NTRS)

    McCollom, T. M.; Ritter, G.; Simoneit, B. R.

    1999-01-01

    Ever since their discovery in the late 1970's, mid-ocean-ridge hydrothermal systems have received a great deal of attention as a possible site for the origin of life on Earth (and environments analogous to mid-ocean-ridge hydrothermal systems are postulated to have been sites where life could have originated or Mars and elsewhere as well). Because no modern-day terrestrial hydrothermal systems are free from the influence of organic compounds derived from biologic processes, laboratory experiments provide the best opportunity for confirmation of the potential for organic synthesis in hydrothermal systems. Here we report on the formation of lipid compounds during Fischer-Tropsch-type synthesis from aqueous solutions of formic acid or oxalic acid. Optimum synthesis occurs in stainless steel vessels by heating at 175 degrees C for 2-3 days and produces lipid compounds ranging from C2 to > C35 which consist of n-alkanols, n-alkanoic acids, n-alkenes, n-alkanes and alkanones. The precursor carbon sources used are either formic acid or oxalic acid, which disproportionate to H2, CO2 and probably CO. Both carbon sources yield the same lipid classes with essentially the same ranges of compounds. The synthesis reactions were confirmed by using 13C labeled precursor acids.

  16. Communications : Suppression of sintering of size-selected Pd clusters under realistic reaction conditions for catalysis.

    SciTech Connect

    Yin, F.; Lee, S.; Abdela, A.; Vajda, S.; Palmer, R. E.

    2011-04-08

    The stability of model catalysts based on size-selected Pd clusters supported on graphite surfaces has been explored under realistic conditions for catalytic oxidation of methane at mild temperatures. The experimental results show that aggregated films of nanoparticles are highly unstable, but clusters pinned to the surface in the submonolayer coverage regime are much more stable against sintering. The degree of sintering of the pinned clusters, which does occur, proceeds by the release of clusters from their pinning sites. The suppression of sintering depends on the cluster deposition energy with respect to the pinning threshold.

  17. Conditionals

    E-print Network

    von Fintel, Kai

    2011-01-01

    This article introduces the classic accounts of the meaning of conditionals (material implication, strict implication, variably strict conditional) and discusses the difference between indicative and subjunctive/counterfactual ...

  18. Investigation of influence of hypomagnetic conditions closely similar to interplanetary magnetic filed on behavioral and vegetative reactions of higher mammals

    NASA Astrophysics Data System (ADS)

    Krivova, Natalie; Trukhanov, Kiril; Zamotshina, Tatyana; Zaeva, Olga; Khodanovich, Marina; Misina, Tatyana; Tukhvatulin, Ravil; Suhko, Valery

    To study the influence of long being under reduced magnetic field on behavioral and vegetative reactions of higher mammals the white rat males were put into the 700-1000 times reduced geomagnetic field (50-70 nT) for 25 days. Such field was obtained by using automatic compensation of the horizontal and vertical components of the GMF at a frequencies up to 10 Hz by means of solenoids of the experimental magnetic system. Control animals were located in the same room under usual laboratory GMF conditions (52 uT). Two days before the experiment the behavioral reactions were studied in the "open field" by means of a set of tests, characterizing the level of emotionality, moving and orientational-investigative activities of the animals under conditions of unimpeded behavior. 60 white underbred rat males with the initial body mass of 200 g were divided into three clusters. Animals with average indices were selected for the experiment. We have judged behavioral reaction disturbances of the rats under hypomagnetic conditions using videotape recordings carried out in the entire course of the chronic experiment. According to the obtained results during the period of maximum activity (from 230 to 330 a.m.) the number of interrelations between the individuals increased appreciably for experimental rats including interrelations with aggressive character. This was real during all 25 days of observation. We observed a certain dynamics of this index differed from that of the control group. We have also analyzed the final period of observation from the 21th to the 25th days. In this period we studied the 24 hours' dynamics of interrelations which were noted during 5 minutes in every hour around the clock. In the control group the number of interrelation was at a constantly low level. For experimental animals the number of interrelations was higher in the night hours than in the day ones. Moreover it exceeded the similar indexes observed from the 1st to the 20th day. For example from 300 to 305 a.m. on the 23th day we recorded 27 contacts of aggressive character between the individuals. So, in hypomagnetic field conditions the irritability of the animals' central nervous system grows, that expresses itself in the increase of contacts of aggressive and non-aggressive character between the individuals. Also we have carried out the Spirman correlation analysis between studied indices of moving activity and chemiluminescence of blood plasma and urine, electrolytic composition of urine and muscles. For control animals the quantity of correlation connections between electrolyte concentrations in studied substrata was higher than for experimental animals. The physiological sense of these correlation connections is discussed.

  19. Glyoxal uptake on ammonium sulphate seed aerosol: reaction products and reversibility of uptake under dark and irradiated conditions

    NASA Astrophysics Data System (ADS)

    Galloway, M. M.; Chhabra, P. S.; Chan, A. W. H.; Surratt, J. D.; Flagan, R. C.; Seinfeld, J. H.; Keutsch, F. N.

    2009-05-01

    Chamber studies of glyoxal uptake onto ammonium sulphate aerosol were performed under dark and irradiated conditions to gain further insight into processes controlling glyoxal uptake onto ambient aerosol. Organic fragments from glyoxal dimers and trimers were observed within the aerosol under dark and irradiated conditions. Glyoxal monomers and oligomers were the dominant organic compounds formed under the conditions of this study; glyoxal oligomer formation and overall organic growth were found to be reversible under dark conditions. Analysis of high-resolution time-of-flight aerosol mass spectra provides evidence for irreversible formation of carbon-nitrogen (C-N) compounds in the aerosol. We have identified 1H-imidazole-2-carboxaldehyde as one C-N product. To the authors' knowledge, this is the first time C-N compounds resulting from condensed phase reactions with ammonium sulphate seed have been detected in aerosol. Organosulphates were not detected under dark conditions. However, active photochemistry was found to occur within aerosol during irradiated experiments. Carboxylic acids and organic esters were identified within the aerosol. An organosulphate, which had been previously assigned as glyoxal sulphate in ambient samples and chamber studies of isoprene oxidation, was observed only in the irradiated experiments. Comparison with a laboratory synthesized standard and chemical considerations strongly suggest that this organosulphate is glycolic acid sulphate, an isomer of the previously proposed glyoxal sulphate. Our study shows that reversibility of glyoxal uptake should be taken into account in SOA models and also demonstrates the need for further investigation of C-N compound formation and photochemical processes, in particular organosulphate formation.

  20. Real-Time Optical Monitoring of Flow Kinetics and Gas Phase Reactions Under High-Pressure OMCVD Conditions

    NASA Technical Reports Server (NTRS)

    Dietz, N.; McCall, S.; Bachmann, K. J.

    2001-01-01

    This contribution addresses the real-time optical characterization of gas flow and gas phase reactions as they play a crucial role for chemical vapor phase depositions utilizing elevated and high pressure chemical vapor deposition (HPCVD) conditions. The objectives of these experiments are to validate on the basis of results on real-time optical diagnostics process models simulation codes, and provide input parameter sets needed for analysis and control of chemical vapor deposition at elevated pressures. Access to microgravity is required to retain high pressure conditions of laminar flow, which is essential for successful acquisition and interpretation of the optical data. In this contribution, we describe the design and construction of the HPCVD system, which include access ports for various optical methods of real-time process monitoring and to analyze the initial stages of heteroepitaxy and steady-state growth in the different pressure ranges. To analyze the onset of turbulence, provisions are made for implementation of experimental methods for in-situ characterization of the nature of flow. This knowledge will be the basis for the design definition of experiments under microgravity, where gas flow conditions, gas phase and surface chemistry, might be analyzed by remote controlled real-time diagnostics tools, developed in this research project.

  1. Ethanol Conversion to Hydrocarbons on HZSM-5: Effect of Reaction Conditions and Si/Al Ratio on the Product Distributions

    SciTech Connect

    Ramasamy, Karthikeyan K.; Wang, Yong

    2014-11-17

    The Conversion of ethanol to hydrocarbon over HZSM-5 zeolite with different Si/Al ratios was investigated under various reaction conditions. The catalyst with a higher Si/Al ratio (low acid density) deactivated faster and generated more unsaturated compounds at a similar time-on-stream. Temperature affects the catalytic activity with respect to liquid hydrocarbon generation and the hydrocarbon product composition. At lower temperatures (~300°C), the catalyst deactivated faster with respect to the liquid hydrocarbon formation. Higher temperatures (~400°C) reduced the formation of liquid range hydrocarbons and formed more gaseous fractions. Weight hourly space velocity was also found to affect product selectivity with higher weight hourly space velocity leading to a higher extent of ethylene formation. The experimental results were analyzed in terms of the product composition and the coke content with respect to catalyst time-on-stream and compared with the catalyst lifetime with respect to the variables tested on the conversion of ethanol to hydrocarbon.

  2. Chemoselective O-acylation of hydroxyamino acids and amino alcohols under acidic reaction conditions: History, scope and applications

    PubMed Central

    2015-01-01

    Summary Amino acids, whether natural, semisynthetic or synthetic, are among the most important and useful chiral building blocks available for organic chemical synthesis. In principle, they can function as inexpensive, chiral and densely functionalized starting materials. On the other hand, the use of amino acid starting materials routinely necessitates protective group chemistry, and in reality, large-scale preparations of even the simplest side-chain derivatives of many amino acids often become annoyingly strenuous due to the necessity of employing protecting groups, on one or more of the amino acid functionalities, during the synthetic sequence. However, in the case of hydroxyamino acids such as hydroxyproline, serine, threonine, tyrosine and 3,4-dihydroxyphenylalanine (DOPA), many O-acyl side-chain derivatives are directly accessible via a particularly expedient and scalable method not commonly applied until recently. Direct acylation of unprotected hydroxyamino acids with acyl halides or carboxylic anhydrides under appropriately acidic reaction conditions renders possible chemoselective O-acylation, furnishing the corresponding side-chain esters directly, on multigram-scale, in a single step, and without chromatographic purification. Assuming a certain degree of stability under acidic reaction conditions, the method is also applicable for a number of related compounds, such as various amino alcohols and the thiol-functional amino acid cysteine. While the basic methodology underlying this approach has been known for decades, it has evolved through recent developments connected to amino acid-derived chiral organocatalysts to become a more widely recognized procedure for large-scale preparation of many useful side-chain derivatives of hydroxyamino acids and related compounds. Such derivatives are useful in peptide chemistry and drug development, as amino acid amphiphiles for asymmetric catalysis, and as amino acid acrylic precursors for preparation of catalytically active macromolecular networks in the form of soluble polymers, crosslinked polymer beads or nanoparticulate systems. The objective of the present review is to increase awareness of the existence and convenience of this methodology, assess its competitiveness compared to newer and more elaborate procedures for chemoselective O-acylation reactions, spur its further development, and finally to chronicle the informative, but poorly documented history of its development. PMID:25977719

  3. Reaction and transport in wellbore interfaces under CO2 storage conditions: Experiments simulating debonded cement-casing interfaces

    NASA Astrophysics Data System (ADS)

    Wolterbeek, T. K.; Peach, C. J.; Spiers, C. J.

    2013-12-01

    Debonding-defects at the interfaces between wellbore casing and cement are widely recognized as providing potential pathways for CO2 escape from geological storage systems. This study addresses how chemical reaction between CO2, cement and steel may affect the transport properties of such defects under near-static conditions, representative for early stages in leakage pathway development, prior to the formation of a fully connected defect network. Debonded cement-steel interfaces were simulated by constructing composite samples, containing a spacer-imposed gap. These were reacted with CO2 and water, brine or a solution pre-saturated with cement. Each sample was subjected to 7 sequential batch reaction runs, namely 6 runs of 5 days duration, followed by a single extended run, of 42 days, to study long-term effects. The reaction runs were conducted at 80°C and 14 MPa applied CO2-pressure. Permeability was measured after each run and microstructural analyses were performed after completion of the experiment. We investigated two ranges in gap-width, namely 50-120 ?m (denoted SA samples) and 270-350 ?m (LA samples). Reaction-induced permeability changes were limited and less than 1 order in all samples, and occurred in the early stage of testing. Corrosion product or scale (mainly Fe-carbonates, with minor Fe-hydroxides) formed extensively within the open gap, on the surfaces of both the casing steel and cement. Lack of calcium carbonates in these areas suggests the corrosion scale which formed on the cement surface produced a significant reduction in cement carbonation rate, similar to the decrease in corrosion rate observed when these precipitates create a protective film on steel surfaces only. CaCO3 precipitation occurred extensively on the cement side at locations beneath the spacers used to create the gap between the cement and steel plates, where corrosion scale did not form. Our results imply that healing of debonding defects at casing-cement interfaces in wellbores will be slower and less effective than healing of fractures in cement under comparable, near-static conditions, due to the formation of thin corrosion scale films on the cement surfaces. These films inhibit release of calcium from the cement into the aperture and impede the precipitation of calcium carbonates that was previously found to promote sealing in fractured cement when only local transport is possible. If thin corrosion scale films of the type observed in our experiments form in real wellbore systems, local small debonding defects (gaps less than a few tens of micrometres) can be expected to heal due to clogging by corrosion scale film. In larger debonding defects, where scale film development is insufficient to produce sealing, their retarding effect on further reaction has the potential to maintain an open interfacial pathway, should long-range connectivity and transport ensue. It is, therefore, important to incorporate the effects of early corrosion scale film development in future analyses of long-range leakage pathways along cement-casing interfaces.

  4. Charge distribution analysis of catalysts under simulated reaction conditions. Final report, October 1, 1993--June 30, 1995

    SciTech Connect

    Freund, F.

    1996-02-01

    A new technique has been developed to measure mobile charge carriers in dielectric materials, insulators and catalysts. The technique, Charge Distribution Analysis, is based on the measurement of the dielectric polarization in an electric field gradient, contact-free, at 0 Hertz under minimum perturbation conditions. The measured parameter is the force F{sup +-} experienced by the sample in a gradient of reversible polarity. CDA allows to determine the sign of the majority charge carriers and the density of surface charges which may be correlated to the chemical or catalytic activity. Throughout this work a microbalance has been used as a force-sensing device. CDA can be applied to any dielectric material, compact or porous, in inert or reactive and corrosive gas environments. To conduct CDA experiments under simulated reaction conditions that are relevant to coal liquefaction research, e.g. in reactive and in part chemically corrosive atmospheres, several modifications were introduced to the current design. In particular, the stainless steel sample chamber and furnace/electrode assembly were built, and the gas flow system was redesigned. The CDA instrument was equipped with new data acquisition capabilities. Tests were performed in inert gases and in reactive and corrosive atmosphere between ambient temperature and 500{degrees}C on iron oxide and partially sulfidized iron oxide catalysts as well as on pyrite (FeS{sub 2}) single crystals.

  5. CO2 reaction with hydrated class H well cement under geologic sequestration conditions: effects of flyash admixtures.

    PubMed

    Kutchko, Barbara G; Strazisar, Brian R; Huerta, Nicolas; Lowry, Gregory V; Dzombak, David A; Thaulow, Niels

    2009-05-15

    The rate and mechanism of reaction of pozzolan-amended Class H cement exposed to both supercritical CO2 and CO2-saturated brine were determined under geologic sequestration conditions to assess the potential impact of cement degradation in existing, wells on CO2 storage integrity. The pozzolan additive chosen, Type F flyash, is the most common additive used in cements for well sealing in oil-gas field operations. The 35:65 and 65:35 (v/v) pozzolan-cement blends were exposed to supercritical CO2 and CO2-saturated brine and underwent cement carbonation. Extrapolation of the carbonation rate for the 35:65 case suggests a penetration depth of 170-180 mm for both the CO2-saturated brine and supercritical CO2 after 30 years. Despite alteration in both pozzolan systems, the reacted cement remained relatively impermeable to fluid flow after exposure to brine solution saturated with CO2, with values well below the American Petroleum Institute recommended maximum well cement permeability of 200 microD. Analyses of 50: 50 pozzolan-cement cores from a production well in a sandstone reservoir exhibited carbonation and low permeability to brine solution saturated with CO2, which are consistent with our laboratory findings. PMID:19544912

  6. In-Cylinder Reaction Chemistry and Kinetics During Negative Valve Overlap Fuel Injection Under Low-Oxygen Conditions

    SciTech Connect

    Kalaskar, Vickey B; Szybist, James P; Splitter, Derek A; Pihl, Josh A; Gao, Zhiming; Daw, C Stuart

    2013-01-01

    Fuel injection into the negative valve overlap (NVO) period is a common method for controlling combustion phasing in homogeneous charge compression ignition (HCCI) as well as other forms of advanced combustion. During this event, at least a portion of the fuel hydrocarbons can be converted to products containing significant levels of H2 and CO, as well as other short chain hydrocarbons by means of thermal cracking, water-gas shift, and partial oxidation reactions, depending on the availability of oxygen and the time-temperature-pressure history. The resulting products alter the autoignition properties of the combined fuel mixture for HCCI. Fuel-rich chemistry in a partial oxidation environment is also relevant to other high efficiency engine concepts (e.g., the dedicated EGR (D-EGR) concept from SWRI). In this study, we used a unique 6-stroke engine cycle to experimentally investigate the chemistry of a range of fuels injected during NVO under low oxygen conditions. Fuels investigated included iso-octane, iso-butanol, ethanol, and methanol. Products from NVO chemistry were highly dependent on fuel type and injection timing, with iso-octane producing less than 1.5% hydrogen and methanol producing more than 8%. We compare the experimental trends with CHEMKIN (single zone, 0-D model) predictions using multiple kinetic mechanisms available in the current literature. Our primary conclusion is that the kinetic mechanisms investigated are unable to accurately predict the magnitude and trends of major species we observed.

  7. Reactions of transplanted neurocentral synchondroses to different conditions of mechanical stress. A methodological study on the rat.

    PubMed Central

    Rönning, O; Kylämarkula, S

    1979-01-01

    In order to elucidate the reactions of neurocentral synchondroses to different forces, the first cervical vertebra of 10 or 25 days old rats was transplanted into sex-matched litter mates. Some vertebrae were transplanted as a whole, in some only the ventral part with its synchondroses was transplanted and, in others the lumen was furnished with an expanding sponge or a spring. The transplantation was done subcutaneously and, in the case of the fragments, intracerebrally as well. The synchondroses of the vertebrae transplanted at 10 days did not differ very much from those of the host 5, 10 or 15 days after the operation, whereas in the vertebrae transplanted at 25 days the synchondroses underwent synostosis earlier than in situ. The synchondroses of the transplanted fragments, and especially of those placed intracerebrally, remained open longer than those in the whole vertebral transplants; the sponge and and the spring also delayed closure. In the synchondroses transplanted at 25 days there was a strong reduction in alcian blue staining, whereas in the spring loaded synchondroses the stainability persisted longer, maybe as an adaptation to the tensile force. It seems that the inherent potential of the neurocentral synchondroses to obliterate at a certain time can be altered by changing the biomechanical conditions. Images Fig. 2 Fig. 3 Fig. 4 Fig. 5 PMID:489467

  8. CO2 Reaction with Hydrated Class H Well Cement under Geologic Sequestration Conditions: Effects of Flyash Admixtures

    SciTech Connect

    Kutchko, Barbara G.; Strazisar, Brian R.; Huerta, Nicolas; Lowry, Gregory V.; Dzombak, David A.; Thaulow, Niels

    2009-05-15

    The rate and mechanism of reaction of pozzolan-amended Class H cement exposed to both supercritical CO2 and CO2-saturated brine were determined under geologic sequestration conditions to assess the potential impact of cement degradation in existing wells on CO2 storage integrity. The pozzolan additive chosen, Type F flyash, is the most common additive used in cements for well sealing in oil-gas field operations. The 35:65 and 65:35 (v/v) pozzolancement blends were exposed to supercritical CO2 and CO2-saturated brine and underwent cement carbonation. Extrapolation of the carbonation rate for the 35:65 case suggests a penetration depth of 170-180 mm far both the CO2-saturated brine and supercritical CO2 after 30 years. Despite alteration in both pozzolan systems, the reacted cement remained relatively impermeable to fluid flow after exposure to brine solution saturated with CO2, with values well below the American Petroleum Institute recommended maximum well cement permeability of 200 mu D. Analyses of 50:50 pozzolan-cement cores from a production well in a sandstone reservoir exhibited carbonation and low permeability to brine solution saturated with CO2, which are consistent with our laboratory findings.

  9. CO{sub 2} reaction with hydrated class H well cement under geologic sequestration conditions: effects of flyash admixtures

    SciTech Connect

    Barbara G. Kutchko; Brian R. Strazisar; Nicolas Huerta; Gregory V. Lowry; David A. Dzombak; Niels Thaulow

    2009-05-15

    The rate and mechanism of reaction of pozzolan-amended Class H cement exposed to both supercritical CO{sub 2} and CO{sub 2}-saturated brine were determined under geologic sequestration conditions to assess the potential impact of cement degradation in existing wells on CO{sub 2} storage integrity. The pozzolan additive chosen, Type F flyash, a by-product of coal combustion, is the most common additive used in cements for well sealing in oil-gas field operations. The 35:65 and 65:35 (v/v) pozzolan-cement blends were exposed to supercritical CO{sub 2} and CO{sub 2}-saturated brine and underwent cement carbonation. Extrapolation of the carbonation rate for the 35:65 case suggests a penetration depth of 170-180 mm for both the CO{sub 2}-saturated brine and supercritical CO{sub 2} after 30 years. Despite alteration in both pozzolan systems, the reacted cement remained relatively impermeable to fluid flow after exposure to brine solution saturated with CO{sub 2}, with values well below the American Petroleum Institute recommended maximum well cement permeability of 200 {mu}D. Analyses of 50:50 pozzolan-cement cores from a production well in a sandstone reservoir exhibited carbonation and low permeability to brine solution saturated with CO{sub 2}, which are consistent with our laboratory findings. 16 refs., 4 figs., 1 tab.

  10. Optimization of reaction conditions to fabricate nano-silver using Couroupita guianensis Aubl. (leaf & fruit) and its enhanced larvicidal effect.

    PubMed

    Vimala, R T V; Sathishkumar, Gnanasekar; Sivaramakrishnan, Sivaperumal

    2015-01-25

    Currently bioactive principles of plants and their nanoproducts have been extensively studied in agriculture and medicine. In this study Couroupita guianensis Aubl. leaf and fruit extracts were selected for rapid and cost-effective synthesis of silver nanoparticles (leaf-LAgNPs and fruit-FAgNPs). Various physiological conditions such as temperature, pH, concentration of metal ions, stoichiometric proportion of reaction mixture and reaction time showed influence on the size, dispersity and synthesis rate of AgNPs. Generation of AgNPs was initially confirmed with the surface plasmon vibrations at 420 nm in UV-visible spectrophotometer. The results recorded from X-ray diffractometer (XRD) and Transmission electron microscope (TEM) supports the biosynthesis of cubic crystalline LAgNPs & FAgNPs with the size ranges between 10-45 nm and 5-15 nm respectively. Surface chemistry of synthesized AgNPs was studied with Fourier transform infrared spectroscopy (FTIR), it reveals that water soluble phenolic compounds present in the extracts act as reducing and stabilizing agent. Leaf, fruit extracts and synthesized AgNPs were evaluated against IV instar larvae of Aedes aegypti (Diptera; Culicidae). Furthermore, different extracts and synthesized AgNPs showed dose dependent larvicidal effect against A. aegypti after 24h of treatment. Compare to all extracts such as ethyl acetate (leaf; LC50 - 44.55 ppm and LC90 - 318.39 ppm & fruit; LC50 - 49.96 ppm and LC90 - 568.84 ppm respectively) and Methanol (leaf; LC50 - 85.75 ppm and LC90 - 598.63 ppm & fruit; LC50 - 67.78 ppm and LC90 - 714.45 ppm respectively) synthesized AgNPs showed extensive mortality rate (LAgNPs; LC50 - 2.1 ppm and LC90 - 5.59 ppm & FAgNPs; LC50 - 2.09 ppm and LC90 - 5.7 ppm). Hence, this study proves that C. guianensis is a potential bioresource for stable, reproducible nanoparticle synthesis (AgNPs) and also can be used as an efficient mosquito control agent. PMID:25062056

  11. Optimization of reaction conditions to fabricate nano-silver using Couroupita guianensis Aubl. (leaf & fruit) and its enhanced larvicidal effect

    NASA Astrophysics Data System (ADS)

    Vimala, R. T. V.; Sathishkumar, Gnanasekar; Sivaramakrishnan, Sivaperumal

    2015-01-01

    Currently bioactive principles of plants and their nanoproducts have been extensively studied in agriculture and medicine. In this study Couroupita guianensis Aubl. leaf and fruit extracts were selected for rapid and cost-effective synthesis of silver nanoparticles (leaf-LAgNPs and fruit-FAgNPs). Various physiological conditions such as temperature, pH, concentration of metal ions, stoichiometric proportion of reaction mixture and reaction time showed influence on the size, dispersity and synthesis rate of AgNPs. Generation of AgNPs was initially confirmed with the surface plasmon vibrations at 420 nm in UV-visible spectrophotometer. The results recorded from X-ray diffractometer (XRD) and Transmission electron microscope (TEM) supports the biosynthesis of cubic crystalline LAgNPs & FAgNPs with the size ranges between 10-45 nm and 5-15 nm respectively. Surface chemistry of synthesized AgNPs was studied with Fourier transform infrared spectroscopy (FTIR), it reveals that water soluble phenolic compounds present in the extracts act as reducing and stabilizing agent. Leaf, fruit extracts and synthesized AgNPs were evaluated against IV instar larvae of Aedes aegypti (Diptera; Culicidae). Furthermore, different extracts and synthesized AgNPs showed dose dependent larvicidal effect against A. aegypti after 24 h of treatment. Compare to all extracts such as ethyl acetate (leaf; LC50 - 44.55 ppm and LC90 - 318.39 ppm & fruit; LC50 - 49.96 ppm and LC90 - 568.84 ppm respectively) and Methanol (leaf; LC50 - 85.75 ppm and LC90 - 598.63 ppm & fruit; LC50 - 67.78 ppm and LC90 - 714.45 ppm respectively) synthesized AgNPs showed extensive mortality rate (LAgNPs; LC50 - 2.1 ppm and LC90 - 5.59 ppm & FAgNPs; LC50 - 2.09 ppm and LC90 - 5.7 ppm). Hence, this study proves that C. guianensis is a potential bioresource for stable, reproducible nanoparticle synthesis (AgNPs) and also can be used as an efficient mosquito control agent.

  12. Spectroscopic set-up for simultaneous UV-Vis/(Q)EXAFS in situ and in operando studies of homogeneous reactions under laboratory conditions.

    PubMed

    Bauer, Matthias; Heusel, Gerhard; Mangold, Stefan; Bertagnolli, Helmut

    2010-03-01

    A novel experimental set-up for in operando studies of homogeneous catalyzed reactions under laboratory conditions has been developed and tested. It combines time-resolved X-ray absorption spectroscopy with UV/Vis spectroscopy. The reaction solution is stirred in a vessel and pumped in a circle by a peristaltic free gear-wheel through a measurement cell. The X-ray and UV/Vis beams probe the same sample volume of the cell orthogonally. Reactants can be added to the reaction mixture in the course of the measurements and a defined gas atmosphere can be adjusted up to a pressure of 10 bar. The in situ reduction of cerium(IV) ammonium nitrate to cerium(III) by isopropanol is studied as a test reaction with quick-XANES and UV/Vis measurements with a time resolution of 60 s and 1 s, respectively. PMID:20157283

  13. Synthesis of peptide thioesters via an N-S acyl shift reaction under mild acidic conditions on an N-4,5-dimethoxy-2-mercaptobenzyl auxiliary group.

    PubMed

    Nakamura, Ken'ichiroh; Kanao, Tomoki; Uesugi, Tomoya; Hara, Toshiaki; Sato, Takeshi; Kawakami, Toru; Aimoto, Saburo

    2009-11-01

    An efficient method of peptide thioester synthesis is described. The reaction is based on an N-4,5-dimethoxy-2-mercaptobenzyl (Dmmb) auxiliary-assisted N-S acyl shift reaction after assembling a peptide chain by Fmoc-solid phase peptide synthesis. The Dmmb-assisted N-S acyl shift reaction proceeded efficiently under mildly acidic conditions, and the peptide thioester was obtained by treating the resulting S-peptide with sodium 2-mercaptoethanesulfonate. No detectable epimerization of the amino acid residue adjacent to the thioester moiety in the case of Leu was found. The reactions were also amenable to the on-resin preparation of peptide thioesters. The utility was demonstrated by the synthesis of a 41-mer peptide thioester, a phosphorylated peptide thioester and a 33-mer peptide thioester containing a trimethylated lysine residue. PMID:19735084

  14. CATALYST-FREE REACTIONS UNDER SOLVENT-FEE CONDITIONS: MICROWAVE-ASSISTED SYNTHESIS OF HETEROCYCLIC HYDRAZONES BELOW THE MELTING POINT OF NEAT REACTANTS: JOURNAL ARTICLE

    EPA Science Inventory

    NRMRL-CIN-1437 Jeselnik, M., Varma*, R.S., Polanc, S., and Kocevar, M. Catalyst-free Reactions under Solvent-fee Conditions: Microwave-assisted Synthesis of Heterocyclic Hydrazones below the Melting Point of Neat Reactants. Published in: Chemical Communications 18:1716-1717 (200...

  15. Tandem decarboxylative hydroformylation-hydrogenation reaction of ?,?-unsaturated carboxylic acids toward aliphatic alcohols under mild conditions employing a supramolecular catalyst system.

    PubMed

    Diab, Lisa; Gellrich, Urs; Breit, Bernhard

    2013-10-28

    A new atom economic catalytic method for a highly chemoselective reduction of ?,?-unsaturated carboxylic acids to the corresponding saturated alcohols under mild reaction conditions, compatible with a wide range reactive functional groups, is reported. The new methodology consists of a novel tandem decarboxylative hydroformylation/aldehyde reduction sequence employing a unique supramolecular catalyst system. PMID:24022335

  16. Molecular Studies of Surfaces under Reaction Conditions; Sum Frequency Generation Vibrational Spectroscopy, Scanning Tunneling Microscopy and Ambient Pressure X-Ray Photoelectron Spectroscopy

    SciTech Connect

    Somorjai, G.A.

    2009-11-11

    Instruments developed in our laboratory permit the atomic and molecular level study of NPs under reaction conditions (SFG, ambient pressure XPS and high pressure STM). These studies indicate continuous restructuring of the metal substrate and the adsorbate molecules, changes of oxidation states with NP size and surface composition variations of bimetallic NPs with changes of reactant molecules.

  17. DATA COLLECTION CONSTRAINTS FOR THE USE OF LENGTH HETEROGENEITY POLYMERASE CHAIN REACTION (LH-PCR) AS AN INDICATOR OF STREAM SANITARY AND ECOLOGICAL CONDITION

    EPA Science Inventory

    This study is part of a larger project for the development of bacterial indicators of stream sanitary and ecological condition. Here we report preliminary research on the use of Length Heterogeneity Polymerase Chain Reaction (LH-PCR), which discriminates among 16S rRNA genes bas...

  18. ATP-synthase of Rhodobacter capsulatus: coupling of proton ow through FH to reactions in FI under the ATP synthesis and slip conditions

    E-print Network

    Steinhoff, Heinz-Jürgen

    ATP-synthase of Rhodobacter capsulatus: coupling of proton £ow through FH to reactions in FI under the ATP synthesis and slip conditions Boris A. FenioukY , Dmitry A. CherepanovY , Wolfgang Junge , Armen Y. Proton transfer through ATP-synthase (measured by electrochromic carotenoid bandshift and by p

  19. Acetamide hydrolyzing activity of Bacillus megaterium F-8 with bioremediation potential: optimization of production and reaction conditions.

    PubMed

    Sogani, Monika; Bakre, Prakash P; Mathur, Nupur; Sharma, Pratibha; Bhatnagar, Pradeep

    2014-01-01

    Bacillus megaterium F-8 exhibited an intracellular acetamide hydrolyzing activity (AHA) when cultivated in modified nutrient broth with 3% tryptone, 1.5% yeast extract, and 0.5% sodium chloride, at pH 7.2, 45 °C for 24 h. Maximum AHA was recorded in the culture containing 0.1 M of sodium phosphate buffer, (pH 7.5) at 45 °C for 20 min with 0.2 % of acetonitrile and resting cells of B. megaterium F-8 equivalent to 0.2 ml culture broth. This activity was stable up to 55 °C and was completely inactivated at or above 60 °C. Maximum acyl transferase activity (ATA) was recorded in the reaction medium containing 0.1 M of potassium phosphate buffer, (pH 8.0) at 55 °C for 5 min with 0.85 mM of acetamide as acyl donor and hydroxylamine hydrochloride as acyl acceptor and resting cells of B. megaterium F-8 equivalent to 0.94 mg cells (dry weight basis). This activity was stable up to 60 °C and a rapid decline in enzyme activity was recorded above it. Under the optimized conditions, this organism hydrolyzed various nitriles and amides such as propionitrile, propionamide, caprolactam, acetamide, and acrylamide to corresponding acids. Acyl group transfer capability of this organism was used for the production of acetohydroxamic acid. ATA of B. megaterium F-8 showed broad substrate specificity such as for acetamide followed by propionamide, acrylamide, and lactamide. This amide hydrolyzing and amidotransferase activity of B. megaterium F-8 has potential applications in enzymatic synthesis of hydroxamic acids and bioremediation of nitriles and amides contaminated soil and water system. PMID:24723348

  20. Non-Precious Metals Catalyze Formal [4 + 2] Cycloaddition Reactions of 1,2-Diazines and Siloxyalkynes under Ambient Conditions

    PubMed Central

    2015-01-01

    Copper(I) and nickel(0) complexes catalyze the formal [4 + 2] cycloaddition reactions of 1,2-diazines and siloxyalkynes, a reaction hitherto best catalyzed by silver salts. These catalysts based on earth abundant metals are not only competent, but the copper catalyst, in particular, promotes cycloadditions of pyrido[2,3-d]pyridazine and pyrido[3,4-d]pyridazine, enabling a new synthesis of quinoline and isoquinoline derivatives, as well as the formal [2 + 2] cycloaddition reaction of cyclohexenone with a siloxyalkyne. PMID:24911346

  1. HIGHLY DIASTEREOSELECTIVE MICHAEL REACTION UNDER SOLVENT-FREE CONDITIONS USING MICROWAVES: CONJUGATE ADDITION OF FLAVANONE TO ITS CHALCONE PRECURSOR

    EPA Science Inventory

    Microwave-assisted reaction of 2'-hydroxychalcones in the presence of DBU resulted in the formation of hitherto unknown dimers by conjugate addition of the intermediate cyclic ketone to the starting enone.

  2. Reaction of the ethynyl radical, C2H, with methylacetylene, CH3CCH, under single collision conditions: Implications for astrochemistry

    E-print Network

    Kaiser, Ralf I.

    ­6 and planetary atmospheres7­9 such as Saturn's moon Titan. Carbon chain radicals with the general formula Cn for the entropy, low temperatures in fact favor the reaction. In a series of kinetic studies of the ethynyl

  3. Temperature dependence of carbon kinetic isotope effect for the oxidation reaction of ethane by OH radicals under atmospherically relevant conditions

    NASA Astrophysics Data System (ADS)

    Piansawan, Tammarat; Saccon, Marina; Laumer, Werner; Gensch, Iulia; Kiendler-Scharr, Astrid

    2015-04-01

    Modeling of the global distribution of atmospheric ethane sources and sinks by using the 13C isotopic composition requires accurate knowledge of the carbon kinetic isotope effect (KIE) of its atmospheric removal reactions. The quantum mechanical prediction implies the necessity to elucidate the temperature dependence of KIE within atmospherically relevant temperature range by experiment. In this study, the KIE and its temperature dependence for ethane oxidation by OH radicals was investigated at ambient pressure in a temperature range of 243 K to 303 K. The chemical reactions were carried out in a 15 L PFE reaction chamber, suspended in a thermally controlled oven. The isotope ratios of the gas phase components during the course of the reactions were measured by Thermal Desorption -- Gas Chromatography -- Isotope Ratio Mass Spectrometry (TD-GC-IRMS). For each temperature, the KIE was derived from the temporal evolution of the concentration and stable carbon isotope ratio (?13C) of ethane using a method adapted from the relative reaction rate concept. The room temperature KIE of the ethane reaction with OH radicals was found to be 6.85 ± 0.32 ‰. This value is in agreement with the previously reported value of 8.57 ± 1.95 ‰ [Anderson et al. 2004] but has a substantially lower uncertainty. The experimental results will be discussed with the KIE temperature dependence predicted by quantum mechanical calculations. Reference: Rebecca S. Anderson, Lin Huang, Richard Iannone, Alexandra E. Thompson, and Jochen Rudolph (2004), Carbon Kinetic Isotope Effects in the Gas Phase Reactions of Light Alkanes and Ethene with the OH Radical at 296 ± 4 K, J. Phys. Chem. A, 108, 11537--11544

  4. How Pragmatic Interpretations Arise from Conditionals: Profiling the Affirmation of the Consequent Argument with Reaction Time and EEG Measures

    ERIC Educational Resources Information Center

    Bonnefond, Mathilde; Van der Henst, Jean-Baptiste; Gougain, Marion; Robic, Suzanne; Olsen, Matthew D.; Weiss, Oshri; Noveck, Ira

    2012-01-01

    Conditional reasoning consists in combining a conditional premise with a categorical premise and inferring a conclusion from them. Two well-known conditional arguments are Modus Ponens (MP: "If P then Q; P//"therefore Q), which is logically valid and Affirmation of the Consequent (AC: "If P then Q; Q//"therefore "P"), which is not. The latter is…

  5. A novel system for in-situ observations of early hydration reactions in wet conditions in conventional SEM

    SciTech Connect

    Katz, A.; Bentur, A. . E-mail: bentur@tx.technion.ac.il; Kovler, K.

    2007-01-15

    A novel system enabling wet microscopy in conventional SEM is described and its performance for in-situ study of hydration reactions is demonstrated. The technology is based on a sealed specimen capsule, which is protected from the microscope vacuum by an electron-transparent partition membrane. Thus, the wet sample can be placed and observed in a 'conventional' SEM without the need for drying or employing environmental SEM. Early hydration reactions of gypsum and cement systems were followed during the first 24 h.

  6. Microwave-Assisted Condensation Reactions of Acetophenone Derivatives and Activated Methylene Compounds with Aldehydes Catalyzed by Boric Acid under Solvent-Free Conditions.

    PubMed

    Brun, Elodie; Safer, Abdelmounaim; Carreaux, François; Bourahla, Khadidja; L'helgoua'ch, Jean-Martial; Bazureau, Jean-Pierre; Villalgordo, Jose Manuel

    2015-01-01

    We here disclosed a new protocol for the condensation of acetophenone derivatives and active methylene compounds with aldehydes in the presence of boric acid under microwave conditions. Implementation of the reaction is simple, healthy and environmentally friendly owing to the use of a non-toxic catalyst coupled to a solvent-free procedure. A large variety of known or novel compounds have thus been prepared, including with substrates bearing acid or base-sensitive functional groups. PMID:26111185

  7. Photocatalytic dechlorination of PCB 138 using leuco-methylene blue and visible light; reaction conditions and mechanisms.

    PubMed

    Izadifard, Maryam; Langford, Cooper H; Achari, Gopal

    2010-09-15

    A study of dechlorination of PCB 138, under visible light employing methylene blue (MB) and triethylamine (TEA) in acetonitrile/water has been conducted to investigate the details of the mechanism of dechlorination and to determine the efficiency of the process for this representative congener. Two other amines, N-methyldiethanolamine (MEDA) and (triethanolamine) TEOA also replaced TEA and two other solvents, methanol and ethanol replacing acetonitrile were examined for effects on reaction rates. The results show that PCB 138 can be dechlorinated efficiently in this photocatalytic reaction. Clarifying ambiguities in several previous reports, the reduced form of MB, leuco-methylene blue (LMB) was identified as responsible for the photoreaction with its excited state transferring an electron to PCBs; oxidized LMB (i.e. MB) is reduced back to LMB by the excess amine present. The reaction depends on a cycle driven by the amine as a sacrificial electron donor. MEDA proved to be the most efficient electron donor; apparently in consequence of the most favourable steady state concentration of LMB. Methanol and ethanol may be used to replace acetonitrile with little change in the efficiency of the reaction. PMID:20542375

  8. LENGTH-HETEROGENEITY POLYMERASE CHAIN REACTION (LH-PCR) AS AN INDICATOR OF STREAM SANITARY AND ECOLOGICAL CONDITION: OPTIMAL SAMPLE SIZE AND HOLDING CONDITIONS

    EPA Science Inventory

    The use of coliform plate count data to assess stream sanitary and ecological condition is limited by the need to store samples at 4oC and analyze them within a 24-hour period. We are testing LH-PCR as an alternative tool to assess the bacterial load of streams, offering a cost ...

  9. On the density dependence of single-proton and two-proton knockout reactions under quasifree conditions

    E-print Network

    Wim Cosyn; Jan Ryckebusch

    2009-04-06

    We consider high-energy quasifree single- and two-proton knockout reactions induced by electrons and protons and address the question what target-nucleus densities can be effectively probed after correcting for nuclear attenuation (initial- and final-state interactions). Our calculations refer to ejected proton kinetic energies of 1.5 GeV, the reactions (e,e'p), (\\gamma,pp) and (p,2p) and a carbon target. It is shown that each of the three reactions is characterized by a distinctive sensitivity to the density of the target nucleus. The bulk of the (\\gamma,pp) strength stems from the high-density regions in the deep nuclear interior. Despite the strong attenuation, sizable densities can be probed by (p,2p) provided that the energy resolution allows one to pick nucleons from s orbits. The effective mean densities that can be probed in high-energy (e,e'p) are of the order of 30-50% of the nuclear saturation density.

  10. Externally controlled pressure and temperature microreactor for in situ x-ray diffraction, visual and spectroscopic reaction investigations under supercritical and subcritial conditions

    SciTech Connect

    Diefenbacher, J.; McKelvy, M.; Chizemeshya, A.V.; Wolf, G.H.

    2010-07-13

    A microreactor has been developed for in situ, spectroscopic investigations of materials and reaction processes with full external pressure and temperature control from ambient conditions to 400 C and 310 bar. The sample chamber is in direct contact with an external manifold, whereby gases, liquids or fluids can be injected and their activities controlled prior to and under investigation conditions. The microreactor employs high strength, single crystal moissanite windows which allow direct probe beam interaction with a sample to investigate in situ reaction processes and other materials properties. The relatively large volume of the cell, along with full optical accessibility and external temperature and pressure control, make this reaction cell well suited for experimental investigations involving any combination of gas, fluid, and solid interactions. The microreactor's capabilities are demonstrated through an in situ x-ray diffraction study of the conversion of a meta-serpentine sample to magnesite under high pressure and temperature. Serpentine is one of the mineral candidates for the implementation of mineral carbonation, an intriguing carbon sequestration candidate technology.

  11. Externally controlled pressure and temperature microreactor for in situ x-ray diffraction, visual and spectroscopic reaction investigations under supercritical and subcritical conditions

    SciTech Connect

    Diefenbacher, Jason; McKelvy, Michael; Chizmeshya, Andrew V.G.; Wolf, George H.

    2005-01-01

    A microreactor has been developed for in situ, spectroscopic investigations of materials and reaction processes with full external pressure and temperature control from ambient conditions to 400 deg. C and 310 bar. The sample chamber is in direct contact with an external manifold, whereby gases, liquids or fluids can be injected and their activities controlled prior to and under investigation conditions. The microreactor employs high strength, single crystal moissanite windows which allow direct probe beam interaction with a sample to investigate in situ reaction processes and other materials properties. The relatively large volume of the cell, along with full optical accessibility and external temperature and pressure control, make this reaction cell well suited for experimental investigations involving any combination of gas, fluid, and solid interactions. The microreactor's capabilities are demonstrated through an in situ x-ray diffraction study of the conversion of a meta-serpentine sample to magnesite under high pressure and temperature. Serpentine is one of the mineral candidates for the implementation of mineral carbonation, an intriguing carbon sequestration candidate technology.

  12. [Adaptive reactions of lipid metabolism in native and alien female representatives of Tofalaria population living under extreme environmental conditions].

    PubMed

    Kolesnikova, L I; Darenskaya, M A; Grebenkina, L A; Dolgikh, M I; Semenova, N V

    2014-01-01

    Peculiarities of the state of lipid metabolism and of processes of lipid peroxidation--the antioxidant protection have been considered in female representatives of the native and alien population of Tofalaria in the age aspects. The obtained data indicate specificity of changes of level of parameters lipid metabolism not only in response to duration of effect of climatic factors, but also depending on belonging to different ethnic groups. Thus, in girls of the natural population of Tofalaria there is noted activation of adaptational-compensatory processes as compared with the alien ones, which is expressed as a significant decrease of atherogenic blood fractions and the general activation of the system of antioxidant protection. However, with age, in both ethnic groups a change of character of reactions of lipid peroxidation and lipid metabolism is noted, which is more expressed in the alien population. PMID:25786316

  13. Protease-catalyzed peptide synthesis using inverse substrates: the influence of reaction conditions on the trypsin acyl transfer efficiency.

    PubMed

    Schellenberger, V; Jakubke, H D; Zapevalova, N P; Mitin, Y V

    1991-06-01

    Benzyloxycarbonyl-L-alanine p-guanidinophenyl ester behaves as a trypsin "inverse substrate," i.e., a cationic center is included in the leaving group instead of being in the acyl moiety. Using this substrate as an acyl donor, trypsin catalyzes the synthesis of peptide bonds that cannot be split by this enzyme. An optimal acyl transfer efficiency was achieved between pH 8 and 9 at 30 degrees C.The addition of as much as 50% cosolvent was shown to be of minor influence on the acyl transfer efficiency, whereas the reaction velocity decreases by more than one order of magnitude. The efficiency of H-Leu-NH(2) and H-Val-NH(2) in deacylation is almost the same for "inverse" and normal type substrates. PMID:18600704

  14. Reaction and transport in debonded wellbore casing-cement interfaces under CO2 storage conditions: From batch reaction tests to flow-through experiments on the 2m length scale

    NASA Astrophysics Data System (ADS)

    Wolterbeek, Tim; Peach, Colin; Spiers, Chris

    2014-05-01

    Debonding at interfaces between wellbore casing and cement is widely recognized as providing potential pathways for leakage from CO2 storage systems. This study addresses how the transport properties of such debonding-defects are affected by chemical reaction between cement, steel and CO2-bearing fluids. Our first set of experiments investigates near-static conditions, representative for stages prior to the formation of a fully connected defect network. Debonded cement-steel interfaces were simulated by constructing composite samples containing a spacer-imposed gap. Each sample was reacted with CO2 and an aqueous fluid, at 80°C and 14 MPa applied CO2 pressure, in seven sequential batch reaction runs (cumulative duration: 72 days). Permeability was measured after each run and microstructural analyses were performed after completion of the experiment. Reaction-induced permeability changes were limited, being less than one order of magnitude for all samples. Corrosion scale (Fe-carbonate, minor Fe-hydroxide) formed within the gap, on the surfaces of both the steel and cement. Here, the observed lack of Ca-carbonates suggests this corrosion scale produced a significant reduction in cement carbonation, similar to the decrease in corrosion rate observed when corrosion scale forms a protective film on steel. In contrast, Ca-carbonate did precipitate on the cement at locations beneath the spacers used to create the gap between the cement and steel plates, where corrosion scale did not form. Overall, the thin corrosion scale films on the cement surfaces seem to inhibit release of Ca from the cement into the gap and impede the precipitation of Ca- carbonates, which in other studies was found to promote sealing in fractured cement. Our batch reaction results imply that in local debonding-defects where corrosion scale development is insufficient to produce sealing, the scale's retarding effect on further reaction has the potential to maintain an open interfacial pathway. Ongoing changes in the temperature and stress state could lead these defects to propagate and connect, possibly resulting in a long-range pathway. Our second set of experiments is currently ongoing and addresses how such interconnected debonding-defects are affected by long-range chemical reaction and transport under flow-through conditions. Cement slurry was poured into a coil made of steel tube and was subsequently cured at 80°C. After curing, debonding was promoted by causing the steel tube to lift off the cement, providing us with a sample that contains a 2 m long section of (partially) debonded cement-steel interface. A flow-through permeameter, maintained at 80°C, will be used to one-sidedly flood the coil with CO2-bearing fluid, while continuously measuring sample permeability and pump/fluid volume (indicative for extent of reaction). Post-experiment microstructural analysis will be performed on the coil. To our knowledge, this will be the first experimental investigation of the cement-steel interface that includes reactive transport phenomena that occur on the metre length scale.

  15. Influence of varying hydraulic conditions on hyporheic exchange and reactions in an in-stream gravel bar

    NASA Astrophysics Data System (ADS)

    Trauth, Nico; Schmidt, Christian; Maier, Uli; Fleckenstein, Jan H.

    2014-05-01

    In the hyporheic zone (HZ) important biogeochemical transformations occur with crucial impact on nutrient cycling in fluvial systems. Here we investigate the interplay between stream flow and HZ exchange of a natural in-stream gravel bar (ISGB), by using three-dimensional steady state simulations of a coupled surface and subsurface numerical model. Stream flow is simulated by the open source computational fluid dynamics (CFD) software OpenFOAM. It is sequentially coupled by the hydraulic head distribution to the top boundary of the groundwater model code MIN3P, simulating flow, solute transport, aerobic respiration (AR) and denitrification (DN) in the HZ. The modelling approach is validated to the stream rating curve and the subsurface travel times in the ISGB based on field measurements. Hydraulic conditions are varied by stream discharge, ranging from low discharge, sufficient to allow stream water flow through both stream channels surrounding the ISGB (0.1 m³/s), to conditions where the ISGB is completely submerged (5.0 m³/s). Ambient groundwater flow is assigned by constant head boundaries upstream and downstream of the ISGB. By varying stream discharge or ambient groundwater heads the general flow field of the ISGB can be adjusted from losing via neutral to gaining conditions. Reactive transport scenarios consider stream water as the primary source of dissolved oxygen and dissolved organic carbon. Furthermore, two nitrate sources originated from the stream water and ambient groundwater are included in the model. Results show that highest hyporheic exchange and longest residence times occur under neutral conditions, where the extent of the hyporheic flow cell is at a maximum. Hence, the stronger the system is gaining and losing, the smaller is the hyporheic exchange flux and the shorter are the residence times in the HZ of the ISGB. AR and DN efficiencies of the ISGB are lowest under gaining conditions because infiltrating solutes are restriced to the hyporheic flow cells and hence to small reactive areas. In contrast, under losing conditions stream solutes infiltrate deep into the HZ and overreach the extent of the hyporheic flow cells, resulting in large reactive areas with highest AR and DN efficiencies.

  16. A carborane-derivative "click" reaction under heterogeneous conditions for the synthesis of a promising lipophilic MRI/GdBNCT agent.

    PubMed

    Toppino, Antonio; Bova, Maria Elena; Geninatti Crich, Simonetta; Alberti, Diego; Diana, Eliano; Barge, Alessandro; Aime, Silvio; Venturello, Paolo; Deagostino, Annamaria

    2013-01-01

    In this study, the Huisgen reaction has been used to functionalise a carborane cage with a lipophilic moiety and a 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) ligand to obtain a new Gd boron neutron-capture therapy (BNCT)/magnetic resonance imaging (MRI) agent. The introduction of the triazole units has been accomplished under both heterogeneous conditions, by the use of a Cu-supported ionic-liquid catalyst, and homogeneous conditions. The ability of the Gd complex of the synthesised ligand to form stable adducts with low-density lipoproteins (LDLs) has been evaluated and then MRI has been performed on tumour melanoma cells incubated in the presence of a Gd-complex/LDL imaging probe. It has been concluded that the high amount of intracellular boron necessary to perform BNCT can be reached even in the presence of a relatively low-boron-containing LDL concentration. PMID:23154917

  17. Chemical Reactions of Portland Cement with Aqueous CO2 and Their Impacts on Cement's Mechanical Properties under Geologic CO2 Sequestration Conditions.

    PubMed

    Li, Qingyun; Lim, Yun Mook; Flores, Katharine M; Kranjc, Kelly; Jun, Young-Shin

    2015-05-19

    To provide information on wellbore cement integrity in the application of geologic CO2 sequestration (GCS), chemical and mechanical alterations were analyzed for cement paste samples reacted for 10 days under GCS conditions. The reactions were at 95 °C and had 100 bar of either N2 (control condition) or CO2 contacting the reaction brine solution with an ionic strength of 0.5 M adjusted by NaCl. Chemical analyses showed that the 3.0 cm × 1.1 cm × 0.3 cm samples were significantly attacked by aqueous CO2 and developed layer structures with a total attacked depth of 1220 ?m. Microscale mechanical property analyses showed that the hardness and indentation modulus of the carbonated layer were 2-3 times greater than for the intact cement, but those in the portlandite-dissolved region decreased by ?50%. The strength and elastic modulus of the bulk cement samples were reduced by 93% and 84%, respectively. The properties of the microscale regions, layer structure, microcracks, and swelling of the outer layers combined to affect the overall mechanical properties. These findings improve understanding of wellbore integrity from both chemical and mechanical viewpoints and can be utilized to improve the safety and efficiency of CO2 storage. PMID:25893278

  18. Reactions during the calcination of a limestone under different atmospheres at fluidized bed combustion conditions: A fixed bed reactor study

    SciTech Connect

    Acke, F.; Lindqvist, O.

    1997-12-31

    Calcined limestones have been shown to provide surfaces in a boiler that have importance for heterogeneous reactions such as the direct decomposition of NH{sub 3} to N{sub 2}, and NO reduction by CO and H{sub 2}. When calcination takes place under an NH{sub 3} atmosphere, formation of HCN and HCNO has also been observed. This work concerns a comparison of the calcination process of a natural limestone under NO or NH{sub 3} atmospheres and the influence of the presence of CO, O{sub 2} and SO{sub 2} on the calcination behavior. Results indicate not fully oxidized phases or impurities to be responsible for the NO reduction during calcination. The results for the HCN and HNCO formation are not that conclusive, although steady state experiments over calcined limestone surfaces in a NH{sub 3} and CO, or CO{sub 2} atmosphere reveal a lot of information such as the importance of CO{sub 2} in the HNCO formation.

  19. Solvent-free reactions of C60 with active methylene compounds, either with or without carbon tetrabromide, in the presence of bases under high-speed vibration milling conditions.

    PubMed

    Zhang, Ting-Hu; Wang, Guan-Wu; Lu, Ping; Li, Yu-Jin; Peng, Ru-Fang; Liu, You-Cheng; Murata, Yasujiro; Komatsu, Koichi

    2004-06-21

    Solvent-free reactions of C(60) with active methylene compounds, either with or without carbon tetrabromide (CBr(4)), in the presence of a base under high-speed vibration milling (HSVM) conditions were investigated. The reaction of C(60) with diethyl bromomalonate was conducted under HSVM conditions in the presence of piperidine, triethylamine or Na(2)CO(3) to afford cyclopropane derivative. In the presence of CBr(4), methanofullerenes, and could be obtained by the direct reaction of C(60) with diethyl malonate, dimethyl malonate, ethyl acetoacetate and ethyl cyanoacetate, respectively, with the aid of 1,8-diazabicyclo[5,4,0]undec-7-ene, piperidine, triethylamine or Na(2)CO(3). More interestingly, 1,4-bisadducts and were produced by the reaction of C(60) with diethyl malonate and dimethyl malonate in the presence of piperidine, triethylamine or Na(2)CO(3) under HSVM conditions. On the other hand, dihydrofuran-fused C(60) derivatives, and were obtained from the reaction of C(60) with ethyl acetoacetate, 2,4-pentanedione and 5,5-dimethyl-1,3-cyclohexanedione with the aid of a base. Under the same conditions, less activated aryl methyl ketones such as 2-acetylpyridine, 2-acetylpyrazine and acetophenone provided monocarbonylated methanofullerene derivatives, and. Except for the Bingel reactions, all other reactions under the HSVM conditions are considered to proceed according to a single-electron-transfer mechanism. PMID:15188036

  20. The ReactorSTM: Atomically resolved scanning tunneling microscopy under high-pressure, high-temperature catalytic reaction conditions

    SciTech Connect

    Herbschleb, C. T.; Tuijn, P. C. van der; Roobol, S. B.; Navarro, V.; Bakker, J. W.; Liu, Q.; Stoltz, D.; Cañas-Ventura, M. E.; Verdoes, G.; Spronsen, M. A. van; Bergman, M.; Crama, L.; Taminiau, I.; Frenken, J. W. M.; Ofitserov, A.; Baarle, G. J. C. van

    2014-08-15

    To enable atomic-scale observations of model catalysts under conditions approaching those used by the chemical industry, we have developed a second generation, high-pressure, high-temperature scanning tunneling microscope (STM): the ReactorSTM. It consists of a compact STM scanner, of which the tip extends into a 0.5 ml reactor flow-cell, that is housed in a ultra-high vacuum (UHV) system. The STM can be operated from UHV to 6 bars and from room temperature up to 600 K. A gas mixing and analysis system optimized for fast response times allows us to directly correlate the surface structure observed by STM with reactivity measurements from a mass spectrometer. The in situ STM experiments can be combined with ex situ UHV sample preparation and analysis techniques, including ion bombardment, thin film deposition, low-energy electron diffraction and x-ray photoelectron spectroscopy. The performance of the instrument is demonstrated by atomically resolved images of Au(111) and atom-row resolution on Pt(110), both under high-pressure and high-temperature conditions.

  1. Model predictions of realgar precipitation by reaction of As(III) with synthetic mackinawite under anoxic conditions

    USGS Publications Warehouse

    Gallegos, T.J.; Han, Y.-S.; Hayes, K.F.

    2008-01-01

    This study investigates the removal of As(III) from solution using mackinawite, a nanoparticulate reduced iron sulfide. Mackinawite suspensions (0.1-40 g/L) effectively lower initial concentrations of 1.3 ?? 10 -5 M As(III) from pH 5-10, with maximum removal occurring under acidic conditions. Based on Eh measurements, it was found that the redox state of the system depended on the mackinawite solids concentration and pH. Higher initial mackinawite concentrations and alkaline pH resulted in a more reducing redox condition. Given this, the pH edge data were modeled thermodynamically using pe (-log[e-]) as a fitting parameter and linear pe-pH relationships within the range of measured Eh values as a function of pH and mackinawite concentration. The model predicts removal of As(III) from solution by precipitation of realgar with the formation of secondary oxidation products, greigite or a mixed-valence iron oxide phase, depending on pH. This study demonstrates that mackinawite is an effective sequestration agent for As(III) and highlights the importance of incorporating redox into models describing the As-Fe-S-H2O system. ?? 2008 American Chemical Society.

  2. The Impact of Non-Enzymatic Reactions and Enzyme Promiscuity on Cellular Metabolism during (Oxidative) Stress Conditions

    PubMed Central

    Piedrafita, Gabriel; Keller, Markus A; Ralser, Markus

    2015-01-01

    Cellular metabolism assembles in a structurally highly conserved, but functionally dynamic system, known as the metabolic network. This network involves highly active, enzyme-catalyzed metabolic pathways that provide the building blocks for cell growth. In parallel, however, chemical reactivity of metabolites and unspecific enzyme function give rise to a number of side products that are not part of canonical metabolic pathways. It is increasingly acknowledged that these molecules are important for the evolution of metabolism, affect metabolic efficiency, and that they play a potential role in human disease—age-related disorders and cancer in particular. In this review we discuss the impact of oxidative and other cellular stressors on the formation of metabolic side products, which originate as a consequence of: (i) chemical reactivity or modification of regular metabolites; (ii) through modifications in substrate specificity of damaged enzymes; and (iii) through altered metabolic flux that protects cells in stress conditions. In particular, oxidative and heat stress conditions are causative of metabolite and enzymatic damage and thus promote the non-canonical metabolic activity of the cells through an increased repertoire of side products. On the basis of selected examples, we discuss the consequences of non-canonical metabolic reactivity on evolution, function and repair of the metabolic network. PMID:26378592

  3. The Impact of Non-Enzymatic Reactions and Enzyme Promiscuity on Cellular Metabolism during (Oxidative) Stress Conditions.

    PubMed

    Piedrafita, Gabriel; Keller, Markus A; Ralser, Markus

    2015-01-01

    Cellular metabolism assembles in a structurally highly conserved, but functionally dynamic system, known as the metabolic network. This network involves highly active, enzyme-catalyzed metabolic pathways that provide the building blocks for cell growth. In parallel, however, chemical reactivity of metabolites and unspecific enzyme function give rise to a number of side products that are not part of canonical metabolic pathways. It is increasingly acknowledged that these molecules are important for the evolution of metabolism, affect metabolic efficiency, and that they play a potential role in human disease-age-related disorders and cancer in particular. In this review we discuss the impact of oxidative and other cellular stressors on the formation of metabolic side products, which originate as a consequence of: (i) chemical reactivity or modification of regular metabolites; (ii) through modifications in substrate specificity of damaged enzymes; and (iii) through altered metabolic flux that protects cells in stress conditions. In particular, oxidative and heat stress conditions are causative of metabolite and enzymatic damage and thus promote the non-canonical metabolic activity of the cells through an increased repertoire of side products. On the basis of selected examples, we discuss the consequences of non-canonical metabolic reactivity on evolution, function and repair of the metabolic network. PMID:26378592

  4. Bridging the Pressure Gap: in Situ Atomic-Level Investigations of Model Platinum Catalyst Surfaces Under Reaction Conditions by Scanning Tunneling Microscopy.

    NASA Astrophysics Data System (ADS)

    McIntyre, Brian James

    The dream of surface scientists to elucidate the atomic structure of catalyst surfaces in the course of a chemical reaction in real conditions, has become possible by the recent development of a Scanning Tunneling Microscope (STM) (which was built during the course of research that led to this Ph.D. thesis) that operates inside an atmospheric pressure chemical reactor cell. With this microscope, atomic-scale structures of platinum under atmospheric pressures of hydrogen, oxygen, and carbon monoxide have been observed in situ, for the first time, as have a wide variety of adsorbate structures under catalytic hydrogenation reaction conditions. This unique High Pressure STM (HPSTM) allows in situ operation in pressures ranging from ultrahigh vacuum (<10^{-9} Torr) up to hundreds of atmospheres and temperatures ranging from 300 up to 450 Kelvin. The stability of hydrocarbons on catalyst surfaces while under reaction conditions and the subsequent process of coking of catalysts upon hydrocarbon decomposition are subjects of major interest to the catalysis industry. With this microscope, the stability of propylene on Pt(111) and the morphology of decomposition products as a function of atmospheric environment (hydrogen, H^2 /propylene, and CO) and sample temperature (300K -900K) has been investigated. Clusters of carbonaceous material were formed as a result of various decomposition pathways. The clusters and cluster aggregates were observed to form regular patterns whose size and shape depended on decomposition environment and temperature. In the course of experiments with the HPSTM system, it was also discovered that carbonaceous clusters could be catalytically rehydrogenated by the STM tip. This novel method of nanoscale modification opens the way for a wide range of possible applications --from gaining insights to fundamental questions of catalysis and surface reactions to creating chemical templates with atomic precision. The dynamics of coadsorbate interactions (coadsorbate-induced compression) for sulfur and carbon monoxide on Pt(111) were also observed in situ in UHV and high vacuum conditions. These results demonstrate the importance of lateral interactions between adsorbates and may provide a mechanism for carrying out catalytic reactions on metal surfaces that are covered with strongly chemisorbed layers. Combined theoretical and experimental observations of the atomic contrast of the sulfur overlayer was also carried out demonstrating the significance of the specific atom termination of the tunneling tip on the observed STM image contrast and corrugation for atomic-resolution imaging. Finally, in the course of coadsorption experiments with CO and sulfur on Pt(111) it was observed that in 10^{ -6} Torr of CO the sulfur covered Pt(111) surface may undergo a coadsorbate-induced reconstruction. In conclusion, these results demonstrating the usefulness of the HPSTM as a tool for catalyst characterization open the way for very exciting experiments that will allow the in situ study of the chemical and catalytic activity of surfaces with atomic resolution.

  5. Experimental Investigation of Augmented Spark Ignition of a LO2/LCH4 Reaction Control Engine at Altitude Conditions

    NASA Technical Reports Server (NTRS)

    Kleinhenz, Julie; Sarmiento, Charles; Marshall, William

    2012-01-01

    The use of nontoxic propellants in future exploration vehicles would enable safer, more cost-effective mission scenarios. One promising green alternative to existing hypergols is liquid methane (LCH4) with liquid oxygen (LO2). A 100 lbf LO2/LCH4 engine was developed under the NASA Propulsion and Cryogenic Advanced Development project and tested at the NASA Glenn Research Center Altitude Combustion Stand in a low pressure environment. High ignition energy is a perceived drawback of this propellant combination; so this ignition margin test program examined ignition performance versus delivered spark energy. Sensitivity of ignition to spark timing and repetition rate was also explored. Three different exciter units were used with the engine s augmented (torch) igniter. Captured waveforms indicated spark behavior in hot fire conditions was inconsistent compared to the well-behaved dry sparks. This suggests that rising pressure and flow rate increase spark impedance and may at some point compromise an exciter s ability to complete each spark. The reduced spark energies of such quenched deliveries resulted in more erratic ignitions, decreasing ignition probability. The timing of the sparks relative to the pressure/flow conditions also impacted the probability of ignition. Sparks occurring early in the flow could trigger ignition with energies as low as 1 to 6 mJ, though multiple, similarly timed sparks of 55 to 75 mJ were required for reliable ignition. Delayed spark application and reduced spark repetition rate both correlated with late and occasional failed ignitions. An optimum time interval for spark application and ignition therefore coincides with propellant introduction to the igniter.

  6. A series of phenyl sulfonate metal coordination polymers as catalysts for one-pot Biginelli reactions under solvent-free conditions.

    PubMed

    Wang, Jin-Hua; Tang, Gui-Mei; Wang, Yong-Tao; Cui, Yue-Zhi; Wang, Jun-Jie; Ng, Seik Weng

    2015-10-28

    Three new metal coordination polymers, namely, [Co(DPP)2(H2O)2]·(BS)2·2H2O (1), [Co(DPP)2(H2O)2]·(ABS)2·2H2O (2) and [Co(DPP)2(MBS)2] (3) [DPP = 1,3-di(pyridin-4-yl)propane, BS = phenyl sulfonic acid, ABS = p-aminobenzene sulfonic acid, MBS = p-methylbenzene sulfonic acid] were obtained under hydrothermal conditions. Complexes 1-3 were structurally characterized using X-ray single-crystal diffraction, XRD and IR spectroscopy. Both complexes 1 and 2 display a 1D tape structure. Meanwhile, complex 3 exhibits a 2D layer and further stacks via C-H? interactions to generate a three-dimensional supramolecular architecture. These three metal coordination polymers have been applied as catalysts for the green synthesis of a variety of 3,4-dihydropyrimidin-2(1H)-ones under solvent-free conditions through the Biginelli reaction. Interestingly, the catalysis products have been obtained in high yields under eco-friendly synthesis conditions. PMID:26399501

  7. Simulation of blast-furnace raceway conditions in a wire-mesh reactor: interference by the reactions of molybdenum mesh and initial results

    SciTech Connect

    Long Wu; N. Paterson; D.R. Dugwell; R. Kandiyoti

    2006-12-15

    A novel trapped air injection system has been built for a wire-mesh reactor to enable tests with short exposure times to air that are intended to simulate typical residence times in blast-furnace raceways. Initial tests have shown that the molybdenum wire-mesh sample-holder reacts with O{sub 2} under conditions intended for this work. By varying the proportions of solid MoO{sub 2} (weight gain), vapor phase oxides (weight loss) may form, depending on reaction conditions. Oxide formation pathways thus become relevant to coal weight loss determinations during experiments. If, in addition to solid MoO{sub 2} formation, significant formation of vapor phase oxides occurs, then the weight change is more complicated to understand and the impact on the O{sub 2} concentration cannot be unravelled. Furthermore, it turns out that O{sub 2}-scavenging by the mesh affects the amount of O{sub 2} that is available to react with the coal sample. It was concluded that it is only possible to conduct reliable tests under conditions which the favor the formation of solid MoO{sub 2} only, as this leads to a quantifiable weight gain. Its impact can then be accounted for in the evaluation of the experimental weight change. In the case of MoO{sub 2} formation, the impact of the mesh oxidation on the amount of O{sub 2} available to react with the sample can also be estimated. It has been found that the wire-mesh reactor, equipped with the trapped air injection system, can be used to obtain valid data at up to 1600{sup o} C and 0.5 MPa. This pressure is similar to that of the blast-furnace raceway, but the temperature is several hundred degrees lower. However, preliminary tests have shown that useful kinetic data on the extents of reaction can be obtained with the equipment, provided it is operated under conditions that minimize the formation of vapor phase Mo oxides. 18 refs., 13 figs., 3 tabs.

  8. Si-rich layer formation on olivine surfaces during reaction with water and supercritical carbon dioxide under conditions relevant for geologic carbon storage

    NASA Astrophysics Data System (ADS)

    Johnson, N. C.; Jackson, A.; Maher, K.; Bird, D. K.; Brown, G. E.

    2013-12-01

    The reaction of Mg-silicate minerals (i.e. olivine) with carbon dioxide (CO2) is a promising method for secure, long-term, geologic carbon storage. Several technical challenges must be overcome before implementing mineral carbonation technology on a large scale, one of which is slow reaction kinetics. This study probes surface reaction limitations of olivine carbonation, specifically the formation of a passivating, Si-rich layer on olivine surfaces upon exposure to water and CO2 under sequestration conditions (elevated temperature and pressure). A series of batch reactions were performed at 60°C and 100 bar CO2 pressure in Dickson-style rocker bombs, varying the length of reaction and the amount of mixing (rocking). The initial aqueous phase was spiked with 29Si. Fluid samples were taken periodically and analyzed for cation content, alkalinity, and dissolved inorganic carbon. At the end of each experiment, the solid products were analyzed with a Sensitive High Resolution Ion Microprobe Reverse Geometry (SHRIMP-RG) in order to measure the amount of 29Si incorporated into the Si-rich layer on reacted olivine grains. We also cut cross sections of reacted grains from each experiment using a Focused Ion Beam (FIB) which were thinned to <100nm and imaged using Transmission Electron Microscopy (TEM). SHRIMP-RG results show incorporation of 29Si on olivine grain surfaces reacted for 19 days with no mixing, and TEM images of olivine grains from the same experiment show an amorphous, Si-rich layer that is 30nm thick. Similarly, SHRIMP-RG results for olivine grains reacted for 19 days with mixing indicate 29SiO2 precipitation and TEM images reveal a Si-rich layer 60nm thick. In both experiments, EDS (energy dispersive spectroscopy) data show a step change in composition from the bulk rock to the surface layer in addition to the sharp crystalline/amorphous interface visible in the TEM images. Olivine from the unmixed experiment also has a slow decrease in Mg relative to Si before the step change, suggesting that, at least in this experiment, a Si-rich layer precipitated on top of a Mg-depleted layer that formed via a leaching process. SHRIMP-RG data also imply the presence of a precipitated Si-rich layer on top of a leached Si-rich layer, as the 29Si penetration depth is only 25-65% of the total Si-rich layer thickness. The combination of SHRIMP-RG and FIB/TEM analysis leads us to hypothesize that a Si-rich layer forms quickly on olivine surfaces due to preferential Mg removal from the surface (the traditional 'leached' layer), and as the reaction proceeds, amorphous silica reaches saturation in the fluid and precipitates on surfaces inside the reactor (including olivine grains).

  9. Process optimization of deposition conditions of PbS thin films grown by a successive ionic layer adsorption and reaction (SILAR) method using response surface methodology

    NASA Astrophysics Data System (ADS)

    Yücel, Ersin; Yücel, Yasin; Beleli, Buse

    2015-07-01

    In this study, lead sulfide (PbS) thin films were synthesized by a successive ionic layer adsorption and reaction (SILAR) method with different pH, dipping time and dipping cycles. Response surface methodology (RSM) and central composite design (CCD) were successfully used to optimize the PbS films deposition parameters and understand the significance and interaction of the factors affecting the film quality. 5-level-3-factor central composite design was employed to evaluate the effects of the deposition parameters (pH, dipping time and dipping cycles) on the response (the optical band gap of the films). Data obtained from RSM were subjected to the analysis of variance (ANOVA) and analyzed using a second order polynomial equation. The optimal conditions for the PbS films deposition have been found to be: pH of 9.1, dipping time of 10 s and dipping cycles of 10 cycles. The predicted band gap of PbS film was 2.13 eV under the optimal conditions. Verification experiment (2.24 eV) confirmed the validity of the predicted model. The film structures were characterized by X-ray diffractometer (XRD). Morphological properties of the films were studied with a scanning electron microscopy (SEM). The optical properties of the films were investigated using a UV-visible spectrophotometer.

  10. The Influence of N14(e-,nu)C14(alpha,gamma)O18 reaction on the He-Ignition in Degenerate Physical Conditions

    E-print Network

    Piersanti, L; Tornambé, A; Piersanti, Luciano; Cassisi, Santi; Tornambe', Amedeo

    2001-01-01

    The importance of NCO chain on the onset of the He-flash in degenerate physical conditions has been reevaluated. We find that low-mass, metal-rich (Z $\\ge$ 0.001) structures climbing the Red Giant Branch do never attain the physical conditions suitable for the onset of this chain, while at lower metallicities the energy contribution provided by NCO reaction is too low to affect the onset of the central He-flash. At the same time, our evolutionary models suggest that for a Carbon-Oxygen White Dwarf of mass M_{WD}=0.6 M_sun accreting He-rich matter, directly or as a by-product of an overlying H-burning shell, at rates suitable for a dynamical He-flash, the NCO energy contribution is not able to keep hot enough the He-shell and in turn to avoid the occurrence of a strong electron degeneracy and the ensuing final explosion.

  11. The Influence of N14(e-,nu)C14(alpha,gamma)O18 reaction on the He-Ignition in Degenerate Physical Conditions

    E-print Network

    Luciano Piersanti; Santi Cassisi; Amedeo Tornambe'

    2001-05-28

    The importance of NCO chain on the onset of the He-flash in degenerate physical conditions has been reevaluated. We find that low-mass, metal-rich (Z $\\ge$ 0.001) structures climbing the Red Giant Branch do never attain the physical conditions suitable for the onset of this chain, while at lower metallicities the energy contribution provided by NCO reaction is too low to affect the onset of the central He-flash. At the same time, our evolutionary models suggest that for a Carbon-Oxygen White Dwarf of mass M_{WD}=0.6 M_sun accreting He-rich matter, directly or as a by-product of an overlying H-burning shell, at rates suitable for a dynamical He-flash, the NCO energy contribution is not able to keep hot enough the He-shell and in turn to avoid the occurrence of a strong electron degeneracy and the ensuing final explosion.

  12. Constructing novel Cd(ii) metal-organic frameworks based on different highly connected secondary building units via alteration of reaction conditions.

    PubMed

    Liu, Yan-Qing; Ren, Guo-Jian; Zhang, Ying-Hui; Xu, Jian; Bu, Xian-He

    2015-12-21

    Upon solvothermal reactions between Cd(ii) salt and 5-pyridyl-tetrazolate (4-Ptz) under different reaction conditions, three new Cd(ii) metal-organic frameworks (MOFs), namely [Cd3(4-Ptz)5(H2O)2(?3-OH)·3DMA·5H2O·CH3OH]n (1), [Cd5(4-Ptz)8(CH3OH)2(?3-OH)2·2DMA·4H2O·3CH3OH]n (2) and [{Cd9(4-Ptz)14(AC)2(?3-OH)2(H2O)4}·8DMA·H2O·3CH3OH]n (3), were synthesized based on different highly connected secondary building units (SBUs). In the presence of triethylamine, 1 was constructed based on an 8-connected triangular trinuclear Cd3 SBU and exhibits a three-dimensional framework, while 2 was generated upon the addition of HCl, assembled through a close packing of the octahedron cages consisting of unprecedented 12-connected 4-Ptz bridged Cd5 SBUs and thus showing high thermal and chemical stability. For generating 3, two different kinds of Cd3 SBUs, including an 8-connected triangular SBU and a 10-connected linear SBU, were constructed and further integrated into a distorted octahedron-based net under the addition of both triethylamine and NaCl. In addition to the structural analysis, we also focused on the investigation of gas adsorption and solid-state fluorescence properties of 2. PMID:26460604

  13. Influence of deformation mechanisms and metamorphic reactions during strain localization in the continental crust under lower amphibolite facies conditions: an example from the Gotthard massif

    NASA Astrophysics Data System (ADS)

    Oliot, E.; Goncalves, P.; Schulmann, K.; Marquer, D.

    2009-04-01

    Ductile shear zones are the result of the process of strain localization in the continental crust. Depending on the metamorphic conditions during deformation, strain localization is coeval with dramatic changes in microstructures, mineralogy and mass transfers, due to the interactions with externally-derived fluid. Therefore, to accurately model the mechanisms of strain localization, it is critical to identify deformation mechanisms related to the recrystallization of the quartzo-feldspathic assemblages, and to better constrain the role of metamorphic reactions during deformation. The aim of this contribution is to characterize the mineralogical, geochemical, textural and microstructural evolution of a high strain zone from the Fibbia granite, which is located in the Gotthard Massif (External Crystalline Massif, Central Alps). This variscan massif has been affected by Alpine Tertiary metamorphism and deformation under lower amphibolite facies conditions. The strain gradient is approximately a meter width. The rock texture evolves from a weakly deformed granite, toward an orthogneiss, a mylonite and a ~10 cm-wide ultramylonite. The mineralogical assemblage changes from a metastable magmatic assemblage consisting of Qtz + Kspar + Pla + Bio ± Pheng ± Grt ± Ep to a fine banded texture consisting of a quartzo-feldspathic matrix, with metamorphic phyllosilicates (biotite and phengite) and garnet in the ultramylonite. Cathodoluminescence (CL) imaging has been used to quantify the modal proportions of phases in the quartzo-feldspathic matrix in this strain gradient. More specifically, in the orthogneiss and the mylonite, CL imaging reveals a subtle layering consisting of alternating bands of quartz-rich ribbons, K-feldspars and coupled quartz- and plagioclase-rich ribbons. The texture in the ultramylonite is more homogeneous with isolated single quartz and K-feldspar grains. CL imaging has also revealed chemical zoning, as "core and mantle" texture in plagioclases. With increasing strain, modal abundance of K-feldspars decreases from 28% to 16%, whereas both micas increase from 5% to 21%. Similarly, albite evolves from 25% to 8%, whereas oligoclase evolves from 5% to 25%. Deformation mechanisms responsible for these microstructures have been studied by combining a quantitative textural analysis (CSD, SPO, grain boundary frequency and orientation - PolyLX MatlabTM toolbox; Lexa, 2005) and a crystallographic study by EBSD. Deformation mechanisms of quartz, K-feldspar and plagioclase are a combination of SGR and GBM in the orthogneiss and in the mylonite, whereas GBS is active in the ultramylonite. CPO characteristic features are still a matter of debate. Because mass transfers occurred in this shear zone (gains of MnO, CaO, Fe2O3, P2O5 and TiO2) without volume change, thermodynamic modeling of phase relations in such open system must consider the variations of effective bulk rock composition during deformation. In this example, phase relations have been mapped using Perple_X'07 (Connolly, 2005) as a function of P, T, M(H2O) and X(bulk composition), in order to highlight the influence of subtle mass transfers on the syn-deformation stability of mineral assemblages at 500°C and 7.2 kbars. A particular attention has been paid to the role of water content on the stable assemblage and on compositions of metamorphic phyllosilicates. Water under-saturated conditions induce the stability of aluminosilicates, and should increase the Xmg in biotite and decrease the amount of tschermak substitution in phengite. P- and T-M(H20) diagram suggest that the Alpine ductile shear zones occurred under water-saturated conditions. This study reveals that strain localization is related to the metamorphic reactions (breakdowns of K-feldspars to phengites and magmatic plagioclase to albite and oligoclase), which induce a strong decrease in grain size reduction and a switch in deformation mechanism from SGR and GBM to GBS in the ultramylonite. The good agreement between phase diagram section predictions and the observations suggest that high

  14. Effects of heat-moisture treatment reaction conditions on the physicochemical and structural properties of maize starch: moisture and length of heating.

    PubMed

    Sui, Zhongquan; Yao, Tianming; Zhao, Yue; Ye, Xiaoting; Kong, Xiangli; Ai, Lianzhong

    2015-04-15

    Changes in the properties of normal maize starch (NMS) and waxy maize starch (WMS) after heat-moisture treatment (HMT) under various reaction conditions were investigated. NMS and WMS were adjusted to moisture levels of 20%, 25% and 30% and heated at 100 °C for 2, 4, 8 and 16 h. The results showed that moisture content was the most important factor in determining pasting properties for NMS, whereas the heating length was more important for WMS. Swelling power decreased in NMS but increased in WMS, and while the solubility index decreased for both samples, the changes were largely determined by moisture content. The gelatinisation temperatures of both samples increased with increasing moisture content but remained unchanged with increasing heating length. The Fourier transform infrared (FT-IR) absorbance ratio was affected to different extents by the moisture levels but remained constant with increasing the heating length. The X-ray intensities increased but relative crystallinity decreased to a greater extent with increasing moisture content. This study showed that the levels of moisture content and length of heating had significant impacts on the structural and physicochemical properties of normal and waxy maize starches but to different extents. PMID:25466134

  15. Effects of the catalyst and reaction conditions on the integrated process of coal pyrolysis with CO{sub 2} reforming of methane

    SciTech Connect

    Jiahe Liu; Haoquan Hu; Lijun Jin; Pengfei Wang

    2009-09-15

    Our previous works showed that the tar yield of coal pyrolysis can obviously be improved by integrated CO{sub 2} reforming of methane to coal pyrolysis in a fixed-bed reactor consisting of an upper catalyst layer and a lower coal layer. In this work, the effects of catalyst supports (MgO, Al{sub 2}O{sub 3}, SiO{sub 2}, and NaY) and reaction conditions on tar and water yields, CH{sub 4} conversion in pyrolysis of Chinese Pingshuo coal, and the carbon deposition on different catalysts were investigated. The results indicated that the catalyst support has an important effect on the integrated process and MgO is the best among the studied supports. A higher tar yield, lower water yield, and lower carbon deposition can be obtained with Ni/MgO as the catalyst. The tar yield increases with the increase of the pyrolysis temperature, holding time, CO{sub 2}/CH{sub 4} ratio, and CH{sub 4} flow rate, respectively, while the char yield decreases with an increasing pyrolysis temperature. 22 refs., 7 figs., 1 tab.

  16. Kinetics of stabilised Criegee intermediates derived from alkene ozonolysis: reactions with SO2, H2O and decomposition under boundary layer conditions.

    PubMed

    Newland, Mike J; Rickard, Andrew R; Alam, Mohammed S; Vereecken, Luc; Muñoz, Amalia; Ródenas, Milagros; Bloss, William J

    2015-02-14

    The removal of SO2 in the presence of alkene-ozone systems has been studied for ethene, cis-but-2-ene, trans-but-2-ene and 2,3-dimethyl-but-2-ene, as a function of humidity, under atmospheric boundary layer conditions. The SO2 removal displays a clear dependence on relative humidity for all four alkene-ozone systems confirming a significant reaction for stabilised Criegee intermediates (SCI) with H2O. The observed SO2 removal kinetics are consistent with relative rate constants, k(SCI + H2O)/k(SCI + SO2), of 3.3 (±1.1) × 10(-5) for CH2OO, 26 (±10) × 10(-5) for CH3CHOO derived from cis-but-2-ene, 33 (±10) × 10(-5) for CH3CHOO derived from trans-but-2-ene, and 8.7 (±2.5) × 10(-5) for (CH3)2COO derived from 2,3-dimethyl-but-2-ene. The relative rate constants for k(SCI decomposition)/k(SCI + SO2) are -2.3 (±3.5) × 10(11) cm(-3) for CH2OO, 13 (±43) × 10(11) cm(-3) for CH3CHOO derived from cis-but-2-ene, -14 (±31) × 10(11) cm(-3) for CH3CHOO derived from trans-but-2-ene and 63 (±14) × 10(11) cm(-3) for (CH3)2COO. Uncertainties are ±2? and represent combined systematic and precision components. These values are derived following the approximation that a single SCI is present for each system; a more comprehensive interpretation, explicitly considering the differing reactivity for syn- and anti-SCI conformers, is also presented. This yields values of 3.5 (±3.1) × 10(-4) for k(SCI + H2O)/k(SCI + SO2) of anti-CH3CHOO and 1.2 (±1.1) × 10(13) for k(SCI decomposition)/k(SCI + SO2) of syn-CH3CHOO. The reaction of the water dimer with CH2OO is also considered, with a derived value for k(CH2OO + (H2O)2)/k(CH2OO + SO2) of 1.4 (±1.8) × 10(-2). The observed SO2 removal rate constants, which technically represent upper limits, are consistent with decomposition being a significant, structure dependent, sink in the atmosphere for syn-SCI. PMID:25562069

  17. Diffusion and reactivity of ground-state nitrogen atoms N(4S) between 3 and 15 K: application to the hydrogen abstraction reaction from methane under non-energetic conditions

    NASA Astrophysics Data System (ADS)

    Nourry, Sendres; Krim, Lahouari

    2015-07-01

    We have characterized the CH4 + N(4S) reaction in solid phase, at very low temperature, under non-energetic conditions and where the CH4 and N reactants are in their ground states. A microwave-driven atomic source has been used to generate ground-state nitrogen atoms N(4S), and experiments have been carried out at temperatures as low as 3 K to reduce the mobility of the trapped species in solid phase and hence to freeze the first step of the CH4 + N reaction pathway. Leaving the formed solid sample in the dark for a while allows all trapped reactants to relax to the ground state, specifically radicals and excited species streaming from the plasma discharge. Such a method could be the only possibility of proving that the CH4 + N reaction occurs between CH4 and N reactants in their ground states without any additional energy to initiate the chemical process. The appearance of the CH3 reaction product, just by inducing the mobility of N atoms between 3 and 11 K, translates that a hydrogen abstraction reaction from methane, under non-energetic conditions, will start occurring at very low temperature. The formation of methyl radical, under these experimental conditions, is due to recombination processes N(4S)-N(4S) of ground-state nitrogen atoms without any contribution of cosmic ray particles or high-energy photons.

  18. Approach to equilibrium of the water-gas shift reaction on a Ni/zirconia anode under solid oxide fuel-cell conditions

    NASA Astrophysics Data System (ADS)

    Ahmed, K.; Föger, K.

    The reverse water-gas shift reaction is carried out in a solid oxide fuel-cell at a range of fuel utilization levels and the approach of this reaction to thermodynamic equilibrium is calculated from the experimental data. It is found that the water-gas shift reaction is close to equilibrium only at high levels of fuel utilization. This is an important finding for modeling and simulation of fuel-cells.

  19. Piper-betle-shaped nano-S-catalyzed synthesis of 1-amidoalkyl-2-naphthols under solvent-free reaction condition: a greener "nanoparticle-catalyzed organic synthesis enhancement" approach.

    PubMed

    Das, Vijay K; Borah, Madhurjya; Thakur, Ashim J

    2013-04-01

    Nano-S prepared by an annealing process showed excellent catalytic activity for the synthesis of 1-amidoalkyl-2-naphthols under solvent-free reaction condition at 50 °C. The catalyst could be reused up to the fifth cycle without loss in its action. The green-ness of the present protocol was also measured using green metrics drawing its superiority. PMID:23472638

  20. Formation of HNCO from carbon monoxide and atomic nitrogen in their fundamental states. Investigation of the reaction pathway in conditions relevant to the interstellar medium.

    PubMed

    Nourry, Sendres; Zins, Emilie-Laure; Krim, Lahouari

    2015-01-28

    As a simple molecule containing the four main atoms essential for life as we know it, isocyanic acid can be considered as a prebiotic molecule. As such, the understanding of reaction mechanisms leading to its formation is fundamental. Isocyanic acid is present in different physical environments in the medium. Previous studies have suggested that, in water-containing ices, on the surface of dust grains, HNCO may be formed from N and CO in their fundamental states. To further investigate the reaction process, herein we investigate this reaction by means of the matrix-isolation technique. PMID:25501292

  1. The reactions of N-methylformamide and N,N-dimethylformamide with OH and their photo-oxidation under atmospheric conditions: experimental and theoretical studies.

    PubMed

    Bunkan, Arne Joakim C; Hetzler, Jens; Mikoviny, Tomáš; Wisthaler, Armin; Nielsen, Claus J; Olzmann, Matthias

    2015-03-14

    The reactions of OH radicals with CH3NHCHO (N-methylformamide, MF) and (CH3)2NCHO (N,N-dimethylformamide, DMF) have been studied by experimental and computational methods. Rate coefficients were determined as a function of temperature (T = 260-295 K) and pressure (P = 30-600 mbar) by the flash photolysis/laser-induced fluorescence technique. OH radicals were produced by laser flash photolysis of 2,4-pentanedione or tert-butyl hydroperoxide under pseudo-first order conditions in an excess of the corresponding amide. The rate coefficients obtained show negative temperature dependences that can be parameterized as follows: kOH+MF = (1.3 ± 0.4) × 10(-12) exp(3.7 kJ mol(-1)/(RT)) cm(3) s(-1) and kOH+DMF = (5.5 ± 1.7) × 10(-13) exp(6.6 kJ mol(-1)/(RT)) cm(3) s(-1). The rate coefficient kOH+MF shows very weak positive pressure dependence whereas kOH+DMF was found to be independent of pressure. The Arrhenius equations given, within their uncertainty, are valid for the entire pressure range of our experiments. Furthermore, MF and DMF smog-chamber photo-oxidation experiments were monitored by proton-transfer-reaction time-of-flight mass spectrometry. Atmospheric MF photo-oxidation results in 65% CH3NCO (methylisocyanate), 16% (CHO)2NH, and NOx-dependent amounts of CH2[double bond, length as m-dash]NH and CH3NHNO2 as primary products, while DMF photo-oxidation results in around 35% CH3N(CHO)2 as primary product and 65% meta-stable (CH3)2NC(O)OONO2 degrading to NOx-dependent amounts of CH3N[double bond, length as m-dash]CH2 (N-methylmethanimine), (CH3)2NNO (N-nitroso dimethylamine) and (CH3)2NNO2 (N-nitro dimethylamine). The potential for nitramine formation in MF photo-oxidation is comparable to that of methylamine whereas the potential to form nitrosamine and nitramine in DMF photo-oxidation is larger than for dimethylamine. Quantum chemistry supported atmospheric degradation mechanisms for MF and DMF are presented. Rate coefficients and initial branching ratios calculated with statistical rate theory based on molecular data from quantum chemical calculations at the CCSD(T*)-F12a/aug-cc-pVTZ//MP2/aug-cc-pVTZ level of theory show satisfactory agreement with the experimental results. It turned out that adjustment of calculated threshold energies by 0.2 to 8.8 kJ mol(-1) lead to agreement between experimental and predicted results. PMID:25687949

  2. Green synthesis of Pd/CuO nanoparticles by Theobroma cacao L. seeds extract and their catalytic performance for the reduction of 4-nitrophenol and phosphine-free Heck coupling reaction under aerobic conditions.

    PubMed

    Nasrollahzadeh, Mahmoud; Sajadi, S Mohammad; Rostami-Vartooni, Akbar; Bagherzadeh, Mojtaba

    2015-06-15

    We report the green synthesis of palladium/CuO nanoparticles (Pd/CuO NPs) using Theobroma cacao L. seeds extract and their catalytic activity for the reduction of 4-nitrophenol and Heck coupling reaction under aerobic conditions. The catalyst was characterized using the powder XRD, TEM, EDS, UV-vis and FT-IR. This method has the advantages of high yields, elimination of surfactant, ligand and homogeneous catalysts, simple methodology and easy work up. The catalyst can be recovered from the reaction mixture and reused several times without any significant loss of catalytic activity. PMID:25721860

  3. Heterogeneous reaction of peroxyacetic acid and hydrogen peroxide on ambient aerosol particles under dry and humid conditions: kinetics, mechanism and implications

    NASA Astrophysics Data System (ADS)

    Wu, Q. Q.; Huang, L. B.; Liang, H.; Zhao, Y.; Huang, D.; Chen, Z. M.

    2015-06-01

    Hydrogen peroxide (H2O2) and organic peroxides play important roles in the cycle of oxidants and the formation of secondary aerosols in the atmosphere. Recent field observations have suggested that the budget of peroxyacetic acid (PAA, CH3C(O)OOH) is potentially related to the aerosol phase processes, especially to secondary aerosol formation. Here, we present the first laboratory measurements of the uptake coefficient of gaseous PAA and H2O2 onto ambient fine particulate matter (PM2.5) as a function of relative humidity (RH) at 298 K. The results show that the PM2.5, which was collected in an urban area, can take up PAA and H2O2 at the uptake coefficient (?) of 10-4, and both ?PAA and ?H2O2 increase with increasing RH. The value of ?PAA at 90 % RH is 5.4 ± 1.9 times that at 3 % RH, whereas ?H2O2 at 90 % RH is 2.4 ± 0.5 times that at 3 % RH, which suggests that PAA is more sensitive to the RH variation than H2O2 is. Considering the larger Henry's law constant of H2O2 than that of PAA, the smaller RH sensitivity of the H2O2 uptake coefficient suggests that the enhanced uptake of peroxide compounds on PM2.5 under humid conditions is dominated by chemical processes rather than dissolution. Considering that mineral dust is one of the main components of PM2.5 in Beijing, we also determined the uptake coefficients of gaseous PAA and H2O2 on authentic Asian Dust storm (ADS) and Arizona Test Dust (ATD) particles. Compared to ambient PM2.5, ADS shows a similar ? value and RH dependence in its uptake coefficient for PAA and H2O2, while ATD gives a negative dependence on RH. The present study indicates that, in addition to the mineral dust in PM2.5, other components (e.g., soluble inorganic salts) are also important to the uptake of peroxide compounds. When the heterogeneous reaction of PAA on PM2.5 is considered, its atmospheric lifetime is estimated to be 3.0 h on haze days and 7.1 h on non-haze days, values that are in good agreement with the field observations.

  4. Bench- and Pilot-Scale Studies of Reaction and Regeneration of Ni-Mg-K/Al2O3 for Catalytic Conditioning of Biomass-Derived Syngas

    SciTech Connect

    Magrini-Bair, K. A.; Jablonski, W. S.; Parent, Y. O.; Yung, M. M.

    2012-05-01

    The National Renewable Energy Laboratory (NREL) is collaborating with both industrial and academic partners to develop technologies to help enable commercialization of biofuels produced from lignocellulosic biomass feedstocks. The focus of this paper is to report how various operating processes, utilized in-house and by collaborators, influence the catalytic activity during conditioning of biomass-derived syngas. Efficient cleaning and conditioning of biomass-derived syngas for use in fuel synthesis continues to be a significant technical barrier to commercialization. Multifunctional, fluidizable catalysts are being developed to reform undesired tars and light hydrocarbons, especially methane, to additional syngas, which can improve utilization of biomass carbon. This approach also eliminates both the need for downstream methane reforming and the production of an aqueous waste stream from tar scrubbing. This work was conducted with NiMgK/Al{sub 2}O{sub 3} catalysts. These catalysts were assessed for methane reforming performance in (i) fixed-bed, bench-scale tests with model syngas simulating that produced by oak gasification, and in pilot-scale, (ii) fluidized tests with actual oak-derived syngas, and (iii) recirculating/regenerating tests using model syngas. Bench-scale tests showed that the catalyst could be completely regenerated over several reforming reaction cycles. Pilot-scale tests using raw syngas showed that the catalyst lost activity from cycle to cycle when it was regenerated, though it was shown that bench-scale regeneration by steam oxidation and H{sub 2} reduction did not cause this deactivation. Characterization by TPR indicates that the loss of a low temperature nickel oxide reduction feature is related to the catalyst deactivation, which is ascribed to nickel being incorporated into a spinel nickel aluminate that is not reduced with the given activation protocol. Results for 100 h time-on-stream using a recirculating/regenerating reactor suggest that this type of process could be employed to keep a high level of steady-state reforming activity, without permanent deactivation of the catalyst. Additionally, the differences in catalyst performance using a simulated and real, biomass-derived syngas stream indicate that there are components present in the real stream that are not adequately modeled in the syngas stream. Heavy tars and polycyclic aromatics are known to be present in real syngas, and the use of benzene and naphthalene as surrogates may be insufficient. In addition, some inorganics found in biomass, which become concentrated in the ash following biomass gasification, may be transported to the reforming reactor where they can interact with catalysts. Therefore, in order to gain more representative results for how a catalyst would perform on an industrially-relevant scale, with real contaminants, appropriate small-scale biomass solids feeders or slip-streams of real process gas should be employed.

  5. Research Directions CharacterizationReaction Kinetics

    E-print Network

    the reaction time ·Reaction time dependent on polymer size, percentage of varying monomers, and solvent), standard (8.7 M) or dilute conditions (6.6 M) · Varying solvent amount changed reaction time and AVL conditions provided a good balance of reaction time to AVL incorporation · Dilute conditions are much slower

  6. Palladium-catalyzed desulfitative Mizoroki-Heck couplings of sulfonyl chlorides with mono- and disubstituted olefins: rhodium-catalyzed desulfitative heck-type reactions under phosphine- and base-free conditions.

    PubMed

    Dubbaka, Srinivas Reddy; Vogel, Pierre

    2005-04-22

    New conditions have been found for the desulfitative Mizoroki-Heck arylation and trifluoromethylation of mono- and disubustituted olefins with arenesulfonyl and trifluoromethanesulfonyl chlorides. Thus (E)-1,2-disubstituted alkenes with high stereoselectivity and 1,1,2-disubstituted alkenes with 12:1 to 21:1 E/Z steroselectivity can be obtained. Herrmann's palladacycle at 0.1 mol % is sufficient to catalyze these reactions, for which electron-rich or electron-poor sulfonyl chlorides and alkenes are suitable. If phosphine- and base-free conditions are required, 1 mol % [RhCl(C(2)H(4))(2)] catalyzes the desulfitative cross-coupling reactions. Contrary to results reported for [RuCl(2)(PPh(3))(2)]-catalyzed coupling reactions with sulfonyl chlorides, the palladium and rhodium desulfitative Mizoroki-Heck coupling reactions are not inhibited by radical scavenging agents. Possible sulfones arising from the sulfonylation of alkenes at 60 degrees C are not desulfitated at higher temperatures in the presence of the Pd or Rh catalysts. PMID:15593242

  7. Direct capture in the 130Sn(n,?)131Sn and 132Sn(n,?)133Sn reactions under r-process conditions

    NASA Astrophysics Data System (ADS)

    Mohr, Peter

    2012-12-01

    The cross sections of the 130Sn(n,?)131Sn and 132Sn(n,?)133Sn reactions are calculated in the direct capture model at low energies below 1.5 MeV. Using recent data from (d,p) transfer experiments on 130Sn and 132Sn, it is possible to avoid global input parameters with their inherent uncertainties and to determine all inputs to the direct capture model by local adjustments. The calculated direct capture cross sections of 130Sn and 132Sn are almost identical and have uncertainties of less than a factor of 2. The stellar reaction rates NA?v show a slight increase with temperature. Finally, an estimate for the influence of low-lying resonances to the stellar reaction rates is given.

  8. Formation of a new 1,1,1 adduct in the reaction of malondialdehyde, n-hexylamine and alkanal under neutral conditions.

    PubMed

    Ohya, T

    1993-02-01

    The reactions of malondialdehyde (MDA) with n-hexylamine (HA) in the presence of alkanals at a neutral pH were investigated. Two new compounds, 1,1,1 adduct (4a) and fluorescent compound (3a), were isolated from the reaction of MDA, HA and acetaldehyde. Compounds 4a and 3a were identified as 2-formyl-3-hexylamino-3-methylpropanal and 1-hexyl-5-hexyliminomethylene-4-methyl-1,4-dihydropyridine-3-carba ldehyde, respectively. Similar compounds (4b and 3b) were obtained from the reaction of MDA, HA and propanal. Compound 4 was obtained in a high yield. In addition, the reactivity of MDA towards phenylethylamine (PEA) in the presence or absence of alkanals was investigated. The results indicated that MDA was of low reactivity in the absence of alkanals at neutral pH. However, when alkanals coexisted, MDA showed high reactivity towards PEA. PMID:8364449

  9. Measurement of mutation and repair in mammalian cells/action of specific mutagens and antimutagens/genome exposure reaction in cancer and other disease conditions. Final subcontract report, April 1, 1996- March 31, 1996

    SciTech Connect

    Puck, T.T.

    1996-09-01

    This is the final report for the project dealing with the the measurement of mutation and repair in mammalian cells, action of specific mutagens and antimutagens, and genome exposure reaction in cancer and other disease conditions. The overall objectives of this research are threefold: to develop and improve methodology for measurement of mutation and repair in mammalian cells and to apply it to measurement of the effectiveness of mutagens, antimutagens, and other molecules to as to achieve greater power in prevention of cancer and genetic disease; to analyze theoretically and experimentally the action of specific mutagens and antimutagens; and to investigate the role of genome exposure reaction in cancer and other disease conditions to secure improve preventive and treatment modalities.

  10. [A study of mental and physical reactions after the Hanshin-Awaji Earthquake: mental and physical conditions of female undergraduate students immediately after, 2 months after, and 9 months after the earthquake].

    PubMed

    Hyodo, K; Morino, R

    1999-06-01

    This study assessed how time brings out changes in one's mental and physical reactions to traumatic experiences. Two surveys were conducted on students of Kobe College, located at one of the areas hardest hit by the Hanshin-Awaji Earthquake in January, 1995. Much of the traumatic reactions decreased in strength through January to March, while feelings of survival guilt did not. Guilt feelings of those whose housing were destroyed increased in March, and kept its level even in October. Although general health conditions of those surveyed in October was normal, several post-traumatic reactions increased in October as compared with March. The rate of recovery from post-traumatic reactions seemed to very according to the depth of one's psychological suffering, to one's financial situation, and to the presence of social support. The factor analysis on the items of mental and physical reactions yielded seven factors. The factor of highest eigenvalue in January was one named "anxiety about after-quake tremors", however, this was replaced by one named "emotional confusions" in March. PMID:10488495

  11. CATALYST-FREE REACTIONS UNDER SOLVENT-FEE CONDITIONS: MICROWAVE-ASSISTED SYNTHESIS OF HETEROCYCLIC HYDRAZONES BELOW THE MELTING POINT OF NEAT REACTANTS

    EPA Science Inventory

    The reaction of neat 5- or 8-oxobenzopyran-2(1H)-ones with a variety of aromatic and heteroaromatic hydrazines are remarkable accelerated upon irradiation in a household microwave oven in the absence of any catalyst, solid support or solvent thus providing an environmentally frie...

  12. C-S Cross-Coupling Reactions Catalyzed by Recyclable Core-Shell Structured Copper/Cu2O Nanowires Under Ligand-Free Conditions

    NASA Astrophysics Data System (ADS)

    Chen, Wei; Liu, Xianbin; Li, Huaifeng; Fan, Zhongli; Zheng, Bin; Weng, Zhiqiang; Lai, Zhiping; Huang, Kuo-Wei

    2015-08-01

    Core-shell structured Cu/Cu2O nanowires were demonstrated as efficient catalysts for C-S cross-coupling reactions. The excellent coupling activity over Cu/Cu2O nanowires on a diverse set of aryl iodides and thiols is attributed to the synergetic effect of the special core-shell structures and their advanced spatial configuration.

  13. Connecting the dots: Semi-analytical and random walk numerical solutions of the diffusion–reaction equation with stochastic initial conditions

    SciTech Connect

    Paster, Amir; Bolster, Diogo; Benson, David A.

    2014-04-15

    We study a system with bimolecular irreversible kinetic reaction A+B?? where the underlying transport of reactants is governed by diffusion, and the local reaction term is given by the law of mass action. We consider the case where the initial concentrations are given in terms of an average and a white noise perturbation. Our goal is to solve the diffusion–reaction equation which governs the system, and we tackle it with both analytical and numerical approaches. To obtain an analytical solution, we develop the equations of moments and solve them approximately. To obtain a numerical solution, we develop a grid-less Monte Carlo particle tracking approach, where diffusion is modeled by a random walk of the particles, and reaction is modeled by annihilation of particles. The probability of annihilation is derived analytically from the particles' co-location probability. We rigorously derive the relationship between the initial number of particles in the system and the amplitude of white noise represented by that number. This enables us to compare the particle simulations and the approximate analytical solution and offer an explanation of the late time discrepancies. - Graphical abstract:.

  14. One-Pot Synthesis of Allylic Sulfones, Ketosulfones, and Triflyl Allylic Alcohols from Domino Reactions of Allylic Alcohols with Sulfinic Acid under Metal-Free Conditions.

    PubMed

    Chu, Xue-Qiang; Meng, Hua; Xu, Xiao-Ping; Ji, Shun-Jun

    2015-08-01

    A metal-free tandem procedure by using a sulfonylation reaction of aryl allylic alcohols followed by an iodobenzenediacetate (PIDA)-promoted oxidative functionalization has been established. Allylic sulfones, ?-ketosulfones, and triflyl allylic alcohols have been constructed in a single operation. The methodology incorporates the sulfonyl (both aryl and triflyl) functionality with a simple work-up procedure. PMID:26096856

  15. Allergic Reactions

    MedlinePLUS

    ... allergic reaction is actually a result of a chain reaction that begins in your genes and is expressed ... Tips • Allergy symptoms are the result of a chain reaction that starts in your immune system. • If you ...

  16. Studies in Reaction to Disability. XII: Structure of Attitudes toward the Physically Disabled; Disability Factor Scales--Amputation, Blindness, Cosmetic Conditions.

    ERIC Educational Resources Information Center

    Siller, Jerome; And Others

    To describe and to develop instruments to measure attitudes toward amputees, the blind, and those with cosmetic conditions, three groups of subjects responded to one of three large pools of items tapping attitudes toward the three disability conditions. Three new groups of about 500 subjects of diverse demographic characteristics were given one of…

  17. Initial inhomogeneity-induced crazy-clock behavior in the iodate-arsenous acid reaction in a buffered medium under stirred batch conditions.

    PubMed

    Valkai, László; Csek?, György; Horváth, Attila K

    2015-09-14

    It is unambiguously demonstrated that in the case of an autocatalytic reaction, initial inhomogeneities induced by the imperfectly mixed part of the overall volume may result in a serious irreproducibility of the individual kinetic runs. A statistically meaningful number of repetitions, however, gives rise to a reproducible cumulative probability distribution curve often referred to as a support of the stochastic feature. The iodate-arsenous acid reaction being autocatalytic with respect to both iodide and hydrogen ions displays clock behavior. However, the time lag necessary for the appearance of iodine, even in buffered solution, varies in an apparently random manner. Careful analysis of the variation of the different parameters like stirring rate, overall volume, geometry of the reactor and the way of mixing the reactants led us to conclude that the fate of the individual samples is determined at the initial stage when the reacting system is per se inhomogeneous. The place, the size of the so-called ignition volume, where the reacting system is imperfectly stirred, as well as the residence time spent there by the imperfectly mixed reactants all seem to depend on external factors. PMID:26239390

  18. Reaction of common bean cultivars to the Asian soybean rust pathogen, Phakopsora pachyrhizi, under field conditions in South Africa and Brazil.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Phakopsora pachyrhizi, the Asian soybean rust (ASR) pathogen, infects soybeans (Glycine max) and some 95 other leguminous species, including dry and snap beans (Phaseolus vulgaris). This pathogen has been reported infecting dry beans under field conditions in South Africa and the United States in 20...

  19. Templating effect of hydrogen-passivated silicon nanowires in the production of hydrocarbon nanotubes and nanoonions via sonochemical reactions with common organic solvents under ambient conditions.

    PubMed

    Sun, Xu-Hui; Li, Chi-Pui; Wong, Ning-Bew; Lee, Chun-Sing; Lee, Shuit-Tong; Teo, Boon-Keng

    2002-12-18

    A new type of well-structured, hydrocarbon nanomaterial including nanotubes and onions, with interlayer spacing ranging from 3.4 to 5.8 A, was discovered by reacting SiNWs with common organic solvents in a laboratory sonicator under ambient conditions (room temperature and atmospheric pressure). PMID:12475321

  20. Oxide formation: reaction details studied,

    E-print Network

    Johnson, Edward A.

    Oxide formation: reaction details studied, reported in brief Sir -- Nineteen years ago, I published-nitrosohydroxylamines undergo an alternative decomposition under very similar reaction conditions to liberate nitrous oxide, N2O (refs 4,5). Moreover, this alternative reaction involves highly electrophilic intermediates analogous

  1. In situ formation of the amino sugars 1-amino-1-deoxy-fructose and 2-amino-2-deoxy-glucose under Maillard reaction conditions in the absence of ammonia.

    PubMed

    Nashalian, Ossanna; Yaylayan, Varoujan A

    2016-04-15

    Replacing amino acids with their binary metal complexes during the Maillard reaction can initiate various processes, including the oxidative degradation of their glucose conjugates, generating 1-amino-1-deoxy-fructose and its derivatives. These reactive amino sugars are not easily accessible under Maillard reaction conditions and are only formed in the presence of ammonia. To explore the generality of this observation and to study in particular the ability of fructose to generate glucosamine, the amino acid-metal complexes were heated in aqueous solutions with three aldohexoses and two ketohexoses at 110°C for 2h and the dry residues were analysed by ESI/qTOF/MS/MS. All the sugars generated relatively intense ions at [M+H](+) 180 (C6H14NO5); those ions originating from ketohexoses exhibited MS/MS fragmentations identical to glucosamine and those originating form aldohexoses showed ions identical to fructosamine. Furthermore, the amino sugars were found to form fructosazine, react with other sugars and undergo dehydration reactions. PMID:26616979

  2. A new cascade-less engine operated from subsonic to hypersonic conditions: designed by computational fluid dynamics of compressible turbulence with chemical reactions

    NASA Astrophysics Data System (ADS)

    Naitoh, Ken; Nakamura, Kazushi; Emoto, Takehiro

    2010-12-01

    By using our computational fluid dynamic models, a new type of single engine capable of operating over a wide range of Mach numbers from subsonic to hypersonic regimes is proposed for airplanes, whereas traditional piston engines, turbojet engines, and scram engines work only under a narrower range of operating conditions. The new engine has no compressors or turbines such as those used in conventional turbojet engines. An important point is its system of super multijets that collide to compress gas for the transonic regime. Computational fluid dynamics is applied to clarify the potential of this engine. The peak pressure at the combustion center is over 2.5 MPa, while that just before ignition is over 1.0 MPa. The maximum power of this engine will be sufficient for actual use. Under the conditions of higher Mach numbers, the main intake passage located in front of the super multijet nozzles, takes in air more. That results in a ram or scramjet engine for supersonic and hypersonic conditions.

  3. In situ infrared emission spectroscopy for quantitative gas-phase measurement under high temperature reaction conditions: an analytical method for methane by means of an innovative small-volume flowing cell.

    PubMed

    Usseglio, Sandro; Thorshaug, Knut; Karlsson, Arne; Dahl, Ivar M; Nielsen, Claus J; Jens, Klaus-J; Tangstad, Elisabeth

    2010-02-01

    We have used infrared emission spectroscopy (IRES) in order to perform in situ studies under flowing gas-phase conditions. When the small-volume cell developed herein is used, we can (1) observe emission spectra from a hot gas-phase sample having an effective volume much less than one milliliter, (2) observe spectra of typical molecular species present, and (3) observe spectra of the more important molecular species down to below 10% and in some cases even as low as 1%. In addition, an analytical method has been derived in order to conduct quantitative studies under typical reaction conditions. We show that simplifications can be made in the data acquisition and handling for a direct linear correlation between band intensity and concentration with only simple background correction. The practical lower limit for methane in the present setup is approximately 0.5-1% v/v depending on the selected temperature. Our data were collected at 500, 600, and 700 degrees C, respectively. The major features of the present cell design are fairly simple and basically formed by a quartz tube (outer diameter=6 mm, inner diameter=4 mm) inside a metal pipe and two tubular ceramic heaters. This simple setup has advantages and attractive features that have extended the application of IRES to new fields and, in particular, for in situ studies of hydrocarbon reactions at different residence times at high temperature. PMID:20149274

  4. Role of Anions and Reaction Conditions in the Preparation of Uranium(VI), Neptunium(VI), and Plutonium(VI) Borates

    SciTech Connect

    none,

    2011-02-03

    U(VI), Np(VI), and Pu(VI) borates with the formula AnO2[B8O11(OH)4] (An = U, Np, Pu) have been prepared via the reactions of U(VI) nitrate, Np(VI) perchlorate, or Pu(IV) or Pu(VI) nitrate with molten boric acid. These compounds are all isotypic and consist of a linear actinyl(VI) cation, AnO22+, surrounded by BO3 triangles and BO4 tetrahedra to create an AnO8 hexagonal bipyramidal environment. The actinyl bond lengths are consistent with actinide contraction across this series. The borate anions bridge between actinyl units to create sheets. Additional BO3 triangles and BO4 tetrahedra extend from the polyborate layers and connect these sheets together to form a three-dimensional chiral framework structure. UV-vis-NIR absorption and fluorescence spectroscopy confirms the hexavalent oxidation state in all three compounds. Bond-valence parameters are developed for Np(VI).

  5. CO2 Reaction Induced Wettability Alteration and its Impacts on CO2 Storage: Pore to Core Scale Reservoir Condition Experimental Studies

    NASA Astrophysics Data System (ADS)

    Wan, J.; Tokunaga, T. K.; Kim, Y.; Jung, J.; Kim, T.; Dong, W.

    2013-12-01

    Wettability of the mineral surfaces plays an important role in subsurface multiphase flow and transport. Wettability affects the capillary pressure-saturation (Pc- S) relations, relative permeability (kr) of each fluid phase, and relative phase occupancy in reservoir pores. Although wettability issues have been studied extensively in other fields, significant knowledge gaps remain when applying the existing understanding to geological carbon sequestration; due largely to the unique physical-chemical properties of supercritical (sc) CO2 relative to other common non-wetting fluids such as air and oil. Here, we report our recent progress on wettability alteration upon reaction with CO2 and the resulting differences in capillary trapping of CO2 versus air. (1) Pore Scale Studies. There are conflict predictions in the literature concerning the effect of wettability on capillary trapping; some find that larger contact angles lead to lower capillary trapping while others have found opposite behavior. We hypothesized that spontaneous imbibition becomes energetically unfavorable with decreased wettability, so that increased residual trapping of scCO2 should occur during the post-injection inbibition stage. We developed a laboratory high-pressure and elevated temperature microscopic-micromodel system that is capable of controlling fine scale capillary pressure of scCO2-brine, and enabled us to conduct imbibition under controlled capillary pressures at the pore scale. We found that the de-wetting enhanced scCO2 capillary trapping is significant. These results suggest that scCO2 reaction induced dewetting can result in higher degrees of CO2 residual trapping in the post-injection stage than previously predicted. (2) Core Scale Studies. Capillary scaling is used routinely to predict Pc(S) relations for scCO2-brine systems at field scale, based on relations measured with air-water or mercury porosimetry. However, scaling-based predictions for CO2-brine systems have not been fully tested. Current limitations include the fact that imbibition curves are seldom measured due to experimental difficulties in controlling capillary pressure, and wettability (contact angles) is usually unknown and applied as adjustable parameters. Applying a new laboratory system to accurately control Pc at high total P, and we measured Pc(S) of a homogeneous quartz sand (selected because its 'normal' hydraulic properties are very well constrained). Drainage and imbibition experiments were conducted to directly measure Pc(S) with air-brine, then with scCO2-brine. With scCO2, intermediate levels of S shifted to Pc values 30% to 90% lower than predicted based on scaling with interfacial tension. Capillary trapping of CO2 were measured at Pc = 0 during brine imbibition, with trapped volumes for scCO2 significantly greater than for trapped air. We conclude that the observed deviations from scaling predictions make predicting the hydraulic behavior of scCO2 in reservoirs more challenging, and that an understanding of scCO2-induced wettability change is needed.

  6. Studying Biological Rhythms of Person's Skin-galvanic Reaction and Dynamics of Light Transmission by Isomeric Substance in Space Flight Conditions

    NASA Technical Reports Server (NTRS)

    Glushko, Vladimir

    2004-01-01

    Intensity and amplitude of human functional systems and human most important organs are wavelike, rhythmic by nature. These waves have constant periodicity, phase and amplitude. The mentioned characteristics can vary, however their variations have a pronounced reiteration in the course of time. This indicates a hashing of several wave processes and their interference. Stochastic changes in wave processes characteristics of a human organism are explained either by 'pulsations' associated with hashing (superposition) of several wave processes and their interference, or by single influence of environmental physical factors on a human organism. Human beings have respectively periods of higher and lower efficiency, state of health and so on, depending not only of environmental factors, but also of 'internal' rhythmic factor. Sometimes peaks and falls periodicity of some or other characteristics is broken. Disturbance of steady-state biological rhythms is usually accompanied by reduction of activity steadiness of the most important systems of a human organism. In its turn this has an effect on organism's adaptation to changing living conditions as well as on general condition and efficiency of a human being. The latter factor is very important for space medicine. Biological rhythmology is a special branch of biology and medicine, it studies rhythmic activity mechanisms of organs, their systems, individuals and species. Appropriate researches were also carried out in space medicine.

  7. Kinetic Evidence for Near Irreversible Nonionic Micellar Entrapment of N-(2?-Methoxyphenyl)phthalimide (1) under the Typical Alkaline Reaction Conditions

    PubMed Central

    Khan, M. Niyaz; Sim, Yoke-Leng; Ariffin, Azhar

    2014-01-01

    The values of pseudo-first-order rate constants (kobs) for alkaline hydrolysis of 1, obtained at 1.0?mM NaOH and within [ CmEnT] (total concentration of CmEn) range of 3.0–5.0?mM for C12E23 and 10–20?mM for C18E20, fail to obey pseudophase micellar (PM) model. The values of the fraction of near irreversible CmEn micellar trapped 1 molecules (FIT1) vary in the range ~0–0.75 for C12E23 and ~0–0.83 for C18E20 under such conditions. The values of FIT1 become 1.0 at ?10?mM C12E23 and 50?mM C18E20. Kinetic analysis of the observed data at ?10?mM C12E23 shows near irreversible micellar entrapment of 1 molecules under such conditions. PMID:24574900

  8. Heterogeneous Reactions of Particulate Matter-Bound PAHs and NPAHs with NO3/N2O5, OH Radicals, and O3 under Simulated Long-Range Atmospheric Transport Conditions: Reactivity and Mutagenicity

    PubMed Central

    2015-01-01

    The heterogeneous reactions of ambient particulate matter (PM)-bound polycyclic aromatic hydrocarbons (PAHs) and nitro-PAHs (NPAHs) with NO3/N2O5, OH radicals, and O3 were studied in a laboratory photochemical chamber. Ambient PM2.5 and PM10 samples were collected from Beijing, China, and Riverside, California, and exposed under simulated atmospheric long-range transport conditions for O3 and OH and NO3 radicals. Changes in the masses of 23 PAHs and 20 NPAHs, as well as the direct and indirect-acting mutagenicity of the PM (determined using the Salmonella mutagenicity assay with TA98 strain), were measured prior to and after exposure to NO3/N2O5, OH radicals, and O3. In general, O3 exposure resulted in the highest relative degradation of PM-bound PAHs with more than four rings (benzo[a]pyrene was degraded equally well by O3 and NO3/N2O5). However, NPAHs were most effectively formed during the Beijing PM exposure to NO3/N2O5. In ambient air, 2-nitrofluoranthene (2-NF) is formed from the gas-phase NO3 radical- and OH radical-initiated reactions of fluoranthene, and 2-nitropyrene (2-NP) is formed from the gas-phase OH radical-initiated reaction of pyrene. There was no formation of 2-NF or 2-NP in any of the heterogeneous exposures, suggesting that gas-phase formation of NPAHs did not play an important role during chamber exposures. Exposure of Beijing PM to NO3/N2O5 resulted in an increase in direct-acting mutagenic activity which was associated with the formation of mutagenic NPAHs. No NPAH formation was observed in any of the exposures of the Riverside PM. This was likely due to the accumulation of atmospheric degradation products from gas-phase reactions of volatile species onto the surface of PM collected in Riverside prior to exposure in the chamber, thus decreasing the availability of PAHs for reaction. PMID:25119270

  9. Gene Expression Reaction Norms Unravel the Molecular and Cellular Processes Underpinning the Plastic Phenotypes of Alternanthera Philoxeroides in Contrasting Hydrological Conditions

    PubMed Central

    Gao, Lexuan; Geng, Yupeng; Yang, Hongxing; Hu, Yonghong; Yang, Ji

    2015-01-01

    Alternanthera philoxeroides is an amphibious invasive weed that can colonize both aquatic and terrestrial habitats. Individuals growing in different habitats exhibit extensive phenotypic variation but little genetic differentiation. Little is known about the molecular basis underlying environment-induced phenotypic changes. Variation in transcript abundance in A. philoxeroides was characterized throughout the time-courses of pond and upland treatments using RNA-Sequencing. Seven thousand eight hundred and five genes demonstrated variable expression in response to different treatments, forming 11 transcriptionally coordinated gene groups. Functional enrichment analysis of plastically expressed genes revealed pathway changes in hormone-mediated signaling, osmotic adjustment, cell wall remodeling, and programmed cell death, providing a mechanistic understanding of the biological processes underlying the phenotypic changes in A. philoxeroides. Both transcriptional modulation of environmentally sensitive loci and environmentally dependent control of regulatory loci influenced the plastic responses to the environment. Phenotypic responses and gene expression patterns to contrasting hydrological conditions were compared between A. philoxeroides and its alien congener Alternanthera pungens. The terricolous A. pungens displayed limited phenotypic plasticity to different treatments. It was postulated based on gene expression comparison that the interspecific variation in plasticity between A. philoxeroides and A. pungens was not due to environmentally-mediated changes in hormone levels but to variations in the type and relative abundance of different signal transducers and receptors expressed in the target tissue. PMID:26617628

  10. THE CUTANEOUS TRICHOPHYTIN REACTION

    PubMed Central

    Amberg, Samuel

    1910-01-01

    There exists a far-reaching analogy between the cutaneous trichophytin reaction and the cutaneous tuberculin reaction. Both indicate that the organism is the seat of a definite infection or that it has passed through such an infection. Both may persist for a long time after the active disease has come to rest, indicating that the infection has left the organism in a state of altered reactivity—allergy. Under certain conditions both may be of diagnostic value, but since the reaction persists for a long time after the infection has passed, the negative reaction may be of greater value, excluding the existence of a specific infection. The analogy of the trichophytin reaction with the tuberculin reaction is not only limited to the obvious clinical manifestations, but, as in the tuberculin reaction, it can be shown that with uniform concentration of antibody, the intensity of the reaction is dependent on the concentration of the trichophytin. A tentative explanation of the halo formation is offered, based on a rapidly renewed formation of antibody stimulated probably by the entrance of a small amount of allergen into the general circulation. PMID:19867336

  11. Retrospective Clinical and Molecular Analysis of Conditioned Laboratory Dogs (Canis familiaris) with Serologic Reactions to Ehrlichia canis, Borrelia burgdorferi, and Rickettsia rickettsii

    PubMed Central

    Scorpio, Diana G; Wachtman, Lynn M; Tunin, Richard S; Barat, Nicole C; Garyu, Justin W; Dumler, J Stephen

    2008-01-01

    Dogs are susceptible to different tickborne infections, including members of the Anaplasmataceae (Ehrlichia canis, E. ewingii, E. chaffeensis, Anaplasma phagocytophilum, A. platys), Borrelia burgdorferi, and Rickettsia rickettsii. These diseases can manifest with clinical signs including fever, anorexia, malaise, lameness, rash, and bleeding episodes; however, these signs are nonpathognomonic, and infections can occur in the absence of clinical signs. Hematologic abnormalities can include leukopenia, thrombocytopenia, hyperproteinemia and hypergammaglobulinemia. In biomedical research, diseases such as canine monocytic ehrlichiosis, Lyme disease, and Rocky Mountain spotted fever may cause morbidity among exposed dogs and confound research results. Random-source dogs are susceptible to these diseases because of their increased risk of arthropod exposure. Nonpurpose bred, randomly selected conditioned dogs (n = 21) were examined; blood samples were taken for hematology, biochemistry analysis, tickborne pathogen serology, and PCR. Of these, 2 dogs (10% of the population) presented with illness characterized by fever, malaise, lameness, or hemostatic abnormalities, and 15 (71%) had antibodies to one or more tickborne pathogens. No specific hematologic or biochemical differences were apparent between seronegative dogs and seropositive dogs reactive to all 3 pathogens. E. canis and B. burgdorferi PCR of tissues and blood were negative for all dogs. PCR amplification of several Ehrlichia and Anaplasma genes yielded no positive samples. From this cohort of dogs, serologic and molecular results indicate prior exposure without active infection or clinical disease. Exposure to and potential for infection with these bacteria and other pathogens may contribute to blood and tissue alterations that could confound experiments and lead to misinterpretation of data in canine models. PMID:18947166

  12. Anthemis xylopoda flowers aqueous extract assisted in situ green synthesis of Cu nanoparticles supported on natural Natrolite zeolite for N-formylation of amines at room temperature under environmentally benign reaction conditions.

    PubMed

    Nasrollahzadeh, Mahmoud; Sajadi, S Mohammad; Hatamifard, Arezo

    2015-12-15

    Zeolites, which are nontoxic, abundant, and cheap, are very promising supports for the design and preparation of new and environmentally benign catalysts. In this study, Cu nanoparticles (NPs) were immobilized on the surface of natural Natrolite zeolite by Anthemis xylopoda flowers aqueous extract as a reducing and stabilizing agent. Afterward, the catalytic performance of the prepared catalyst was investigated for N-formylation of amines at room temperature under environmentally benign reaction conditions. The catalyst could be reused at least 5 times without any decrease in activity. The advantages of the present protocol include the use of green catalyst, easy isolation of the products, reusability of catalyst, absence of nontoxic reagents, and excellent yield of the products. PMID:26319331

  13. Characterization of hairpin ribozyme reactions.

    PubMed

    Bajaj, Preeti; Hammann, Christian

    2014-01-01

    Hairpin ribozymes are small RNA catalytic motifs naturally found in the satellite RNAs of tobacco ringspot virus (TRsV), chicory yellow mottle virus (CYMoV), and arabis mosaic virus (ArMV). The catalytic activity of the hairpin ribozyme extends to both cleavage and ligation reactions. Here we describe methods for the kinetic analysis of the self-cleavage reaction under transcription reaction conditions. We also describe methods for the generation of DNA templates for subsequent in vitro transcription reaction of hairpin ribozymes. This is followed by a description of the preparation of the suitable RNA molecules for ligation reaction and their kinetic analysis. PMID:24318889

  14. Diamine ligands in copper-catalyzed reactions

    E-print Network

    Surry, David S.

    The utility of copper-mediated cross-coupling reactions has been significantly increased by the development of mild reaction conditions and the ability to employ catalytic amounts of copper. The use of diamine-based ligands ...

  15. FACILITATED CHEMICAL SYNTHESIS UNDER ALTERNATE REACTION CONDITIONS

    EPA Science Inventory

    The chemical research in the late 1990's witnessed a paradigm shift towards "environmentally-friendly chemistry" more popularly known as "green chemistry" due to the increasing environmental concerns and legislative requirements to curb the release of chemical waste into the atmo...

  16. Title: Elucidation of Environmental Fate of Artificial Sweeteners (Aspartame, Acesulfame K and Saccharin) by Determining Bimolecular Rate Constants with Hydroxyl Radical at Various pH and Temperature Conditions and Possible Reaction By-Products

    NASA Astrophysics Data System (ADS)

    Teraji, T.; Arakaki, T.; Suzuka, T.

    2012-12-01

    Use of artificial sweeteners in beverages and food has been rapidly increasing because of their non-calorie nature. In Japan, aspartame, acesulfame K and sucralose are among the most widely used artificial sweeteners. Because the artificial sweeteners are not metabolized in human bodies, they are directly excreted into the environment without chemical transformations. We initiated a study to better understand the fate of artificial sweeteners in the marine environment. The hydroxyl radical (OH), the most potent reactive oxygen species, reacts with various compounds and determines the environmental oxidation capacity and the life-time of many compounds. The steady-state OH concentration and the reaction rate constants between the compound and OH are used to estimate the life-time of the compound. In this study, we determine the bimolecular rate constants between aspartame, acefulfame K and saccharin and OH at various pH and temperature conditions using a competition kinetics technique. We use hydrogen peroxide as a photochemical source of OH. Bimolecular rate constant we obtained so far for aspartame was (2.6±1.2)×109 M-1 s-1 at pH = 3.0 and (4.9±2.3)×109 M-1 s-1 at pH = 5.5. Little effect was seen by changing the temperatures between 15 and 40 oC. Activation energy (Ea) was calculated to be -1.0 kJ mol-1 at pH = 3.0, +8.5 kJ mol-1 at pH = 5.5, which could be regarded as zero. We will report bimolecular rate constants at different pHs and temperatures for acesulfame K and saccharin, as well. Possible reaction by-products for aspartame will be also reported. We will further discuss the fate of aspartame in the coastal environment.

  17. Geometric description of chemical reactions

    E-print Network

    Hernando Quevedo; Diego Tapias

    2013-01-02

    We use the formalism of Geometrothermodynamics to describe chemical reactions in the context of equilibrium thermodynamics. Any chemical reaction in a closed system is shown to be described by a geodesic in a $2-$dimensional manifold that can be interpreted as the equilibrium space of the reaction. We first show this in the particular cases of a reaction with only two species corresponding to either two ideal gases or two van der Waals gases. We then consider the case of a reaction with an arbitrary number of species. The initial equilibrium state of the geodesic is determined by the initial conditions of the reaction. The final equilibrium state, which follows from a thermodynamic analysis of the reaction, is shown to correspond to a coordinate singularity of the thermodynamic metric which describes the equilibrium manifold.

  18. "Greening up" the Suzuki Reaction

    ERIC Educational Resources Information Center

    Aktoudianakis, Evangelos; Chan, Elton; Edward, Amanda R.; Jarosz, Isabel; Lee, Vicki; Mui, Leo; Thatipamala, Sonya S.; Dicks, Andrew P.

    2008-01-01

    This article describes the rapid, green synthesis of a biaryl compound (4-phenylphenol) via a Pd(0)-catalyzed Suzuki cross-coupling reaction in water. Mild reaction conditions and operational simplicity makes this experiment especially amenable to both mid- and upper-level undergraduates. The methodology exposes students to purely aqueous…

  19. Cutaneous reactions to vaccinations.

    PubMed

    Rosenblatt, Adena E; Stein, Sarah L

    2015-01-01

    Vaccinations are important for infectious disease prevention; however, there are adverse effects of vaccines, many of which are cutaneous. Some of these reactions are due to nonspecific inflammation and irritation at the injection site, whereas other reactions are directly related to the live attenuated virus. Rarely, vaccinations have been associated with generalized hypersensitivity reactions, such as erythema multiforme, Stevens-Johnson syndrome, urticaria, acute generalized exanthematous pustulosis, and drug hypersensitivity syndrome. The onset of certain inflammatory dermatologic conditions, such as lichen planus, granuloma annulare, and pemphigoid, were reported to occur shortly after vaccine administration. Allergic contact dermatitis can develop at the injection site, typically due to adjuvant ingredients in the vaccine, such as thimerosal and aluminum. Vaccinations are important to promote development of both individual and herd immunity. Although most vaccinations are considered relatively safe, there may be adverse effects associated with any vaccine. Cutaneous manifestations make up a large portion of the types of reactions associated with vaccines. There are many different reasons for the development of a cutaneous reaction to a vaccination. Some are directly related to the injection of a live attenuated virus, such as varicella or vaccinia (for immunity to smallpox), whereas others cause more nonspecific erythema and swelling at the injection site, as a result of local inflammation or irritation. Vaccinations have also been associated in rare reports with generalized hypersensitivity reactions, such as erythema multiforme, Stevens-Johnson syndrome, urticaria, acute generalized exanthematous pustulosis, and drug hypersensitivity syndrome. There have been case reports associating the administration of a vaccine with the new onset of a dermatologic condition, such as lichen planus, granuloma annulare, and Sweet syndrome. Finally, allergic contact dermatitis can develop at the injection site, typically due to adjuvant ingredients in the vaccine, such as thimerosal and aluminum. PMID:25889134

  20. Reactions inside nanoscale protein cages.

    PubMed

    Bode, Saskia A; Minten, Inge J; Nolte, Roeland J M; Cornelissen, Jeroen J L M

    2011-06-01

    Chemical reactions are traditionally carried out in bulk solution, but in nature confined spaces, like cell organelles, are used to obtain control in time and space of conversion. One way of studying these reactions in confinement is the development and use of small reaction vessels dispersed in solution, such as vesicles and micelles. The utilization of protein cages as reaction vessels is a relatively new field and very promising as these capsules are inherently monodisperse, in that way providing uniform reaction conditions, and are readily accessible to both chemical and genetic modifications. In this review, we aim to give an overview of the different kinds of nanoscale protein cages that have been employed as confined reaction spaces. PMID:21461437

  1. Extension of a Kinetic-Theory Approach for Computing Chemical-Reaction Rates to Reactions with Charged Particles

    NASA Technical Reports Server (NTRS)

    Liechty, Derek S.; Lewis, Mark J.

    2010-01-01

    Recently introduced molecular-level chemistry models that predict equilibrium and nonequilibrium reaction rates using only kinetic theory and fundamental molecular properties (i.e., no macroscopic reaction rate information) are extended to include reactions involving charged particles and electronic energy levels. The proposed extensions include ionization reactions, exothermic associative ionization reactions, endothermic and exothermic charge exchange reactions, and other exchange reactions involving ionized species. The extensions are shown to agree favorably with the measured Arrhenius rates for near-equilibrium conditions.

  2. Acylation of Fish Protein: Effect of Reaction

    E-print Network

    Acylation of Fish Protein: Effect of Reaction Conditions on Products KANG-HO LEE, HERMAN S on the acylation reaction was also evaluated. Introduction Functionality is the attribute of a food material to acylation reaction con- ditions. Rat feeding tests showed clearly that acylation resulted in The authors

  3. Subdiffusion-reaction processes with A?B reactions versus subdiffusion-reaction processes with A+B?B reactions.

    PubMed

    Koszto?owicz, Tadeusz; Lewandowska, Katarzyna D

    2014-09-01

    We consider the subdiffusion-reaction process with reactions of a type A+B?B (in which particles A are assumed to be mobile, whereas B are assumed to be static) in comparison to the subdiffusion-reaction process with A?B reactions which was studied by Sokolov, Schmidt, and Sagués [Phys. Rev. E 73, 031102 (2006)]. In both processes a rule that reactions can only occur between particles which continue to exist is taken into account. Although in both processes a probability of the vanishing of particle A due to a reaction is independent of both time and space variables (assuming that in the system with the A+B?B reactions, particles B are distributed homogeneously), we show that subdiffusion-reaction equations describing these processes as well as their Green's functions are qualitatively different. The reason for this difference is as follows. In the case of the former reaction, particles A and B have to meet with some probability before the reaction occurs in contradiction with the case of the latter reaction. For the subdiffusion process with the A+B?B reactions we consider three models which differ in some details concerning a description of the reactions. We base the method considered in this paper on a random walk model in a system with both discrete time and discrete space variables. Then the system with discrete variables is transformed into a system with both continuous time and continuous space variables. Such a method seems to be convenient in analyzing subdiffusion-reaction processes with partially absorbing or partially reflecting walls. The reason is that within this method we can determine Green's functions without a necessity of solving a fractional differential subdiffusion-reaction equation with boundary conditions at the walls. As an example, we use the model to find the Green's functions for a subdiffusive reaction system (with the reactions mentioned above), which is bounded by a partially absorbing wall. This example shows how the model can be used to analyze the subdiffusion-reaction process in a system with partially absorbing or reflecting thin membranes. Employing a simple phenomenological model, we also derive equations related to the reaction parameters used in the considered models. PMID:25314424

  4. Incidents of chemical reactions in cell equipment

    SciTech Connect

    Baldwin, N.M.; Barlow, C.R.

    1991-12-31

    Strongly exothermic reactions can occur between equipment structural components and process gases under certain accident conditions in the diffusion enrichment cascades. This paper describes the conditions required for initiation of these reactions, and describes the range of such reactions experienced over nearly 50 years of equipment operation in the US uranium enrichment program. Factors are cited which can promote or limit the destructive extent of these reactions, and process operations are described which are designed to control the reactions to minimize equipment damage, downtime, and the possibility of material releases.

  5. Diamine Ligands in Copper-Catalyzed Reactions

    PubMed Central

    Surry, David S.

    2012-01-01

    The utility of copper-mediated cross-coupling reactions has been significantly increased by the development of mild reaction conditions and the ability to employ catalytic amounts of copper. The use of diamine-based ligands has been important in these advances and in this review we discuss these systems, including the choice of reaction conditions and applications in the synthesis of pharmaceuticals, natural products and designed materials. PMID:22384310

  6. Catalytic Organometallic Reactions of Ammonia

    PubMed Central

    Klinkenberg, Jessica L.

    2012-01-01

    Until recently, ammonia had rarely succumbed to catalytic transformations with homogeneous catalysts, and the development of such reactions that are selective for the formation of single products under mild conditions has encountered numerous challenges. However, recently developed catalysts have allowed several classes of reactions to create products with nitrogen-containing functional groups from ammonia. These reactions include hydroaminomethylation, reductive amination, alkylation, allylic substitution, hydroamination, and cross-coupling. This Minireview describes examples of these processes and the factors that control catalyst activity and selectivity. PMID:20857466

  7. Nonequilibrium thermodynamics and a fluctuation theorem for individual reaction steps in a chemical reaction network

    NASA Astrophysics Data System (ADS)

    Pal, Krishnendu; Das, Biswajit; Banerjee, Kinshuk; Gangopadhyay, Gautam

    2015-09-01

    We have introduced an approach to nonequilibrium thermodynamics of an open chemical reaction network in terms of the propensities of the individual elementary reactions and the corresponding reverse reactions. The method is a microscopic formulation of the dissipation function in terms of the relative entropy or Kullback-Leibler distance which is based on the analogy of phase space trajectory with the path of elementary reactions in a network of chemical process. We have introduced here a fluctuation theorem valid for each opposite pair of elementary reactions which is useful in determining the contribution of each sub-reaction on the nonequilibrium thermodynamics of overall reaction. The methodology is applied to an oligomeric enzyme kinetics at a chemiostatic condition that leads the reaction to a nonequilibrium steady state for which we have estimated how each step of the reaction is energy driven or entropy driven to contribute to the overall reaction.

  8. Low Energy Nuclear Reactions?

    E-print Network

    CERN. Geneva; Faccini, R.

    2014-01-01

    After an introduction to the controversial problem of Low Energy Nuclear Reactions (LENR) catalyzed by neutrons on metallic hydride surfaces we present the results of an experiment, made in collaboration with ENEA Labs in Frascati, to search neutrons from plasma discharges in electrolytic cells. The negative outcome of our experiment goes in the direction of ruling out those theoretical models expecting LENR to occur in condensed matter systems under specific conditions. Our criticism on the theoretical foundations of such models will also be presented.

  9. Accelerated Stochastic Simulation of the Stiff Enzyme-Substrate Reaction

    E-print Network

    Cao, Yang

    1 Accelerated Stochastic Simulation of the Stiff Enzyme-Substrate Reaction Yang Cao a) Dept into a product is a common reaction motif in cellular chemical systems. In the three reactions that comprise constituents than to produce a product molecule. This condition makes the reaction set mathematically "stiff

  10. Factors augmenting allergic reactions.

    PubMed

    Niggemann, B; Beyer, K

    2014-12-01

    Elicitors of anaphylactic reactions are any sources of protein with allergenic capacity. However, not all allergic reactions end up in the most severe form of anaphylaxis. Augmenting factors may explain why certain conditions lead to anaphylaxis. Augmenting factors may exhibit three effects: lowering the threshold, increasing the severity, and reversing acquired clinical tolerance. Common augmenting factors are physical exercise, menstruation, NSAIDs, alcohol, body temperature, acute infections, and antacids. Therapeutic options may address causative, preventive, pragmatic, or symptomatic considerations: avoid the eliciting food, take an antihistamine before any situation with a possible risk of augmentation, separate food and sport (at least for 2 h), and carry an adrenaline autoinjector at all times. Individual patterns include summation effects and specific patterns. In conclusion, in the case of a suggestive history but a negative oral challenge, one should consider the possible involvement of augmenting factors; after anaphylactic reactions, always ask for possible augmentation and other risk factors during the recent past; if augmentation is suspected, oral food challenges should be performed in combination with augmenting factors; and in the future, standardized challenge protocols including augmenting factors should be established. PMID:25306896

  11. Chemical reaction dynamics

    PubMed Central

    Crim, F. Fleming

    2008-01-01

    Understanding the motions of the constituent atoms in reacting molecules lies at the heart of chemistry and is the central focus of chemical reaction dynamics. The most detailed questions one can ask are about the evolution of molecules prepared in a single quantum state to products in individual states, and both calculations and experiments are providing such detailed understanding of increasingly complex systems. A central goal of these studies is uncovering the essential details of chemical change by removing the averaging over the initial conditions that occurs in many cases. Such information provides an exquisite test of theory and helps paint pictures of complicated chemical transformations. The goal of this Special Feature is to provide a snapshot of a portion of the field of chemical reaction dynamics. Much of the work presented here emphasizes a close interplay of experiment and theory in ways that sharpen the conclusions of both and animate future studies. The articles do not completely cover the rich field of chemical reaction dynamics but rather provide a glimpse of some of the emerging insights. PMID:18753626

  12. Experimental Study of Serpentinization Reactions

    NASA Technical Reports Server (NTRS)

    Cohen, B. A.; Brearley, A. J.; Ganguly, J.; Liermann, H.-P.; Keil, K.

    2004-01-01

    Current carbonaceous chondrite parent-body thermal models [1-3] produce scenarios that are inconsistent with constraints on aqueous alteration conditions based on meteorite mineralogical evidence, such as phase stability relationships within the meteorite matrix minerals [4] and isotope equilibration arguments [5, 6]. This discrepancy arises principally because of the thermal runaway effect produced by silicate hydration reactions (here loosely called serpentinization, as the principal products are serpentine minerals), which are so exothermic as to produce more than enough heat to melt more ice and provide a self-sustaining chain reaction. One possible way to dissipate the heat of reaction is to use a very small parent body [e.g., 2] or possibly a rubble pile model. Another possibility is to release this heat more slowly, which depends on the alteration reaction path and kinetics.

  13. 14 CFR 29.501 - Ground loading conditions: landing gear with skids.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... (1) The vertical ground reaction must be— (i) Equal to... (2) The vertical ground reactions must be combined with a horizontal...Special conditions. In addition to the conditions specified...designed for the following ground reactions: (1) A ground...

  14. 14 CFR 27.501 - Ground loading conditions: landing gear with skids.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... (1) The vertical ground reaction must be— (i) Equal to... (2) The vertical ground reactions must be combined with a horizontal...Special conditions. In addition to the conditions specified...designed for the following ground reactions: (1) A ground...

  15. 14 CFR 27.501 - Ground loading conditions: landing gear with skids.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... (1) The vertical ground reaction must be— (i) Equal to... (2) The vertical ground reactions must be combined with a horizontal...Special conditions. In addition to the conditions specified...designed for the following ground reactions: (1) A ground...

  16. 14 CFR 29.501 - Ground loading conditions: landing gear with skids.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... (1) The vertical ground reaction must be— (i) Equal to... (2) The vertical ground reactions must be combined with a horizontal...Special conditions. In addition to the conditions specified...designed for the following ground reactions: (1) A ground...

  17. 14 CFR 29.501 - Ground loading conditions: landing gear with skids.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... (1) The vertical ground reaction must be— (i) Equal to... (2) The vertical ground reactions must be combined with a horizontal...Special conditions. In addition to the conditions specified...designed for the following ground reactions: (1) A ground...

  18. 14 CFR 27.501 - Ground loading conditions: landing gear with skids.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... (1) The vertical ground reaction must be— (i) Equal to... (2) The vertical ground reactions must be combined with a horizontal...Special conditions. In addition to the conditions specified...designed for the following ground reactions: (1) A ground...

  19. 14 CFR 27.501 - Ground loading conditions: landing gear with skids.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... (1) The vertical ground reaction must be— (i) Equal to... (2) The vertical ground reactions must be combined with a horizontal...Special conditions. In addition to the conditions specified...designed for the following ground reactions: (1) A ground...

  20. 14 CFR 29.501 - Ground loading conditions: landing gear with skids.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... (1) The vertical ground reaction must be— (i) Equal to... (2) The vertical ground reactions must be combined with a horizontal...Special conditions. In addition to the conditions specified...designed for the following ground reactions: (1) A ground...

  1. 14 CFR 29.501 - Ground loading conditions: landing gear with skids.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... (1) The vertical ground reaction must be— (i) Equal to... (2) The vertical ground reactions must be combined with a horizontal...Special conditions. In addition to the conditions specified...designed for the following ground reactions: (1) A ground...

  2. 14 CFR 27.501 - Ground loading conditions: landing gear with skids.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... (1) The vertical ground reaction must be— (i) Equal to... (2) The vertical ground reactions must be combined with a horizontal...Special conditions. In addition to the conditions specified...designed for the following ground reactions: (1) A ground...

  3. Effect of metamorphic reactions on thermal evolution in collisional orogens

    E-print Network

    that devolatili- zation of metacarbonate rocks can also exert controls on metamorphic temperatures. Enthalpies, peak metamorphic conditions and crustal geotherms. Decarbonation reactions in metacarbonate rocks may: Barrovian; enthalpy; metacarbonate rocks; metamorphic reactions; thermal budget. INTRODUCTION The thermal

  4. Concordant Chemical Reaction Networks and the Species-Reaction Graph

    PubMed Central

    Shinar, Guy; Feinberg, Martin

    2015-01-01

    In a recent paper it was shown that, for chemical reaction networks possessing a subtle structural property called concordance, dynamical behavior of a very circumscribed (and largely stable) kind is enforced, so long as the kinetics lies within the very broad and natural weakly monotonic class. In particular, multiple equilibria are precluded, as are degenerate positive equilibria. Moreover, under certain circumstances, also related to concordance, all real eigenvalues associated with a positive equilibrium are negative. Although concordance of a reaction network can be decided by readily available computational means, we show here that, when a nondegenerate network’s Species-Reaction Graph satisfies certain mild conditions, concordance and its dynamical consequences are ensured. These conditions are weaker than earlier ones invoked to establish kinetic system injectivity, which, in turn, is just one ramification of network concordance. Because the Species-Reaction Graph resembles pathway depictions often drawn by biochemists, results here expand the possibility of inferring significant dynamical information directly from standard biochemical reaction diagrams. PMID:22940368

  5. DSMC Predictions of Chemical Reaction Rates between Atmospheric Species

    NASA Astrophysics Data System (ADS)

    Gallis, M. A.; Bond, R. B.; Torczynski, J. R.

    2009-11-01

    A recently proposed chemical reaction model based solely on molecular-level information is applied to calculate equilibrium and non-equilibrium chemical reaction rates for atmospheric reactions in hypersonic flows. The DSMC model is capable of reproducing measured equilibrium reaction rates without using any macroscopic reaction-rate information. Since it uses only molecular-level properties, the new model is inherently able to predict reaction rates for arbitrary non-equilibrium conditions. The DSMC-predicted chemical reaction rates are compared to theoretically calculated and experimentally measured reaction rates for non-equilibrium conditions. The observed agreement provides strong evidence that molecular-level modeling of chemical reactions provides an accurate method for predicting equilibrium and non-equilibrium chemical reaction rates. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  6. Assessment of reaction-rate predictions of a collision-energy approach for chemical reactions in atmospheric flows.

    SciTech Connect

    Gallis, Michail A.; Bond, Ryan Bomar; Torczynski, John Robert

    2010-06-01

    A recently proposed approach for the Direct Simulation Monte Carlo (DSMC) method to calculate chemical-reaction rates is assessed for high-temperature atmospheric species. The new DSMC model reproduces measured equilibrium reaction rates without using any macroscopic reaction-rate information. Since it uses only molecular properties, the new model is inherently able to predict reaction rates for arbitrary non-equilibrium conditions. DSMC non-equilibrium reaction rates are compared to Park's phenomenological nonequilibrium reaction-rate model, the predominant model for hypersonic-flow-field calculations. For near-equilibrium conditions, Park's model is in good agreement with the DSMC-calculated reaction rates. For far-from-equilibrium conditions, corresponding to a typical shock layer, significant differences can be found. The DSMC predictions are also found to be in very good agreement with measured and calculated non-equilibrium reaction rates, offering strong evidence that this is a viable and reliable technique to predict chemical reaction rates.

  7. Parallelization for reaction

    E-print Network

    Louvet, Violaine

    Parallelization for reaction waves with complex chemistry Context Application Background Numerical Results Conclusions and Perspectives Parallelization strategies for multi-scale reaction waves for Engineering - Paraguay 2010 #12;Parallelization for reaction waves with complex chemistry Context Application

  8. Catalysis of Photochemical Reactions.

    ERIC Educational Resources Information Center

    Albini, A.

    1986-01-01

    Offers a classification system of catalytic effects in photochemical reactions, contrasting characteristic properties of photochemical and thermal reactions. Discusses catalysis and sensitization, examples of catalyzed reactions of excepted states, complexing ground state substrates, and catalysis of primary photoproducts. (JM)

  9. Chromosomal Conditions

    MedlinePLUS

    ... 150 babies is born with a chromosomal condition. Down syndrome is an example of a chromosomal condition. Because ... all pregnant women be offered prenatal tests for Down syndrome and other chromosomal conditions. A screening test is ...

  10. Adsorption Isotherms and Surface Reaction Kinetics

    ERIC Educational Resources Information Center

    Lobo, L. S.; Bernardo, C. A.

    1974-01-01

    Explains an error that occurs in calculating the conditions for a maximum value of a rate expression for a bimolecular reaction. The rate expression is derived using the Langmuir adsorption isotherm to relate gas pressures and corresponding surface coverages. (GS)

  11. Ubiquitous "glassy" relaxation in catalytic reaction networks Akinori Awazu1

    E-print Network

    Kaneko, Kunihiko

    . The importance of nonequilibrium conditions for the sustenance of life has been recognized by the pioneering work nonequilibrium conditions has been discussed since decades 12­14 . In a biological system, however other reaction 1­10 . Chemical reactions in a cell usually take place under non- equilibrium conditions

  12. Thermodynamics of random reaction networks.

    PubMed

    Fischer, Jakob; Kleidon, Axel; Dittrich, Peter

    2015-01-01

    Reaction networks are useful for analyzing reaction systems occurring in chemistry, systems biology, or Earth system science. Despite the importance of thermodynamic disequilibrium for many of those systems, the general thermodynamic properties of reaction networks are poorly understood. To circumvent the problem of sparse thermodynamic data, we generate artificial reaction networks and investigate their non-equilibrium steady state for various boundary fluxes. We generate linear and nonlinear networks using four different complex network models (Erd?s-Rényi, Barabási-Albert, Watts-Strogatz, Pan-Sinha) and compare their topological properties with real reaction networks. For similar boundary conditions the steady state flow through the linear networks is about one order of magnitude higher than the flow through comparable nonlinear networks. In all networks, the flow decreases with the distance between the inflow and outflow boundary species, with Watts-Strogatz networks showing a significantly smaller slope compared to the three other network types. The distribution of entropy production of the individual reactions inside the network follows a power law in the intermediate region with an exponent of circa -1.5 for linear and -1.66 for nonlinear networks. An elevated entropy production rate is found in reactions associated with weakly connected species. This effect is stronger in nonlinear networks than in the linear ones. Increasing the flow through the nonlinear networks also increases the number of cycles and leads to a narrower distribution of chemical potentials. We conclude that the relation between distribution of dissipation, network topology and strength of disequilibrium is nontrivial and can be studied systematically by artificial reaction networks. PMID:25723751

  13. Mathematical model to predict drivers' reaction speeds.

    PubMed

    Long, Benjamin L; Gillespie, A Isabella; Tanaka, Martin L

    2012-02-01

    Mental distractions and physical impairments can increase the risk of accidents by affecting a driver's ability to control the vehicle. In this article, we developed a linear mathematical model that can be used to quantitatively predict drivers' performance over a variety of possible driving conditions. Predictions were not limited only to conditions tested, but also included linear combinations of these tests conditions. Two groups of 12 participants were evaluated using a custom drivers' reaction speed testing device to evaluate the effect of cell phone talking, texting, and a fixed knee brace on the components of drivers' reaction speed. Cognitive reaction time was found to increase by 24% for cell phone talking and 74% for texting. The fixed knee brace increased musculoskeletal reaction time by 24%. These experimental data were used to develop a mathematical model to predict reaction speed for an untested condition, talking on a cell phone with a fixed knee brace. The model was verified by comparing the predicted reaction speed to measured experimental values from an independent test. The model predicted full braking time within 3% of the measured value. Although only a few influential conditions were evaluated, we present a general approach that can be expanded to include other types of distractions, impairments, and environmental conditions. PMID:22431214

  14. Isothermal reactions for the amplification of oligonucleotides.

    PubMed

    Van Ness, Jeffrey; Van Ness, Lori K; Galas, David J

    2003-04-15

    We have devised a class of isothermal reactions for amplifying DNA. These homogeneous reactions rapidly synthesize short oligonucleotides (8-16 bases) specified by the sequence of an amplification template. Versions of the reactions can proceed in either a linear or an exponential amplification mode. Both of these reactions require simple, constant conditions, and the rate of amplification depends entirely on the molecular parameters governing the interactions of the molecules in the reaction. The exponential version of the reaction is a molecular chain reaction that uses the oligonucleotide products of each linear reaction to create producers of more of the same oligonucleotide. It is a highly sensitive chain reaction that can be specifically triggered by given DNA sequences and can achieve amplifications of >10(6)-fold. Several similar reactions in this class are described here. The robustness, speed, and sensitivity of the exponential reaction suggest it will be useful in rapidly detecting the presence of small amounts of a specific DNA sequence in a sample, and a range of other applications, including many currently making use of the PCR. PMID:12679520

  15. A Lewis acid-promoted Pinner reaction

    PubMed Central

    Pfaff, Dominik; Nemecek, Gregor

    2013-01-01

    Summary Carbonitriles and alcohols react in a Lewis acid-promoted Pinner reaction to carboxylic esters. Best results are obtained with two equivalents of trimethylsilyl triflate as Lewis acid. Good yields are achieved with primary alcohols and aliphatic or benzylic carbonitriles, but the straightforward synthesis of acrylates and benzoates starting with acrylonitrile and benzonitrile, respectively, is similarly possible. Phenols are not acylated under these reaction conditions. The method has been used for the first total synthesis of the natural product monaspilosin. In the reaction of benzyl alcohols variable amounts of amides are formed in a Ritter-type side reaction. PMID:23946857

  16. Lattice Boltzmann simulation of catalytic reactions.

    PubMed

    Arcidiacono, S; Mantzaras, J; Karlin, I V

    2008-10-01

    A lattice Boltzmann model is developed to simulate finite-rate catalytic surface chemistry. Diffusive wall boundary conditions are established to account for catalytic reactions in multicomponent mixtures. Implementation of wall boundary conditions with chemical reactions is based on a general second-order accurate interpolation scheme. Results of lattice Boltzmann simulations for a four-component mixture with a global catalytic methane oxidation reaction in a straight channel are in excellent agreement with a finite volume Navier-Stokes solver in terms of both the flow field and species concentrations. PMID:18999565

  17. The Glyoxal Clock Reaction

    ERIC Educational Resources Information Center

    Ealy, Julie B.; Negron, Alexandra Rodriguez; Stephens, Jessica; Stauffer, Rebecca; Furrow, Stanley D.

    2007-01-01

    Research on the glyoxal clock reaction has led to adaptation of the clock reaction to a general chemistry experiment. This particular reaction is just one of many that used formaldehyde in the past. The kinetics of the glyoxal clock makes the reaction suitable as a general chemistry lab using a Calculator Based Laboratory (CBL) or a LabPro. The…

  18. Reaction theory for exotic nuclei

    SciTech Connect

    Bonaccorso, Angela

    2014-05-09

    Exotic nuclei are usually defined as those with unusual N/Z ratios. They can be found in the crust of neutron stars enbedded in a sea of electrons or created in laboratory by fragmentation of a primary beam (in-flight method) or of the target (ISOL method). They are extremely important for nuclear astrophysics, see for example Ref.[1]. Furthermore by studying them we can check the limits of validity of nuclear reaction and structure models. This contribution will be devoted to the understanding of how by using reaction theory and comparing to the data we can extract structure information. We shall discuss the differences between the mechanisms of transfer and breakup reactions, an we will try to explain how nowadays it is possible to do accurate spectroscopy in extreme conditions.

  19. Reaction rates for mesoscopic reaction-diffusion kinetics.

    PubMed

    Hellander, Stefan; Hellander, Andreas; Petzold, Linda

    2015-02-01

    The mesoscopic reaction-diffusion master equation (RDME) is a popular modeling framework frequently applied to stochastic reaction-diffusion kinetics in systems biology. The RDME is derived from assumptions about the underlying physical properties of the system, and it may produce unphysical results for models where those assumptions fail. In that case, other more comprehensive models are better suited, such as hard-sphere Brownian dynamics (BD). Although the RDME is a model in its own right, and not inferred from any specific microscale model, it proves useful to attempt to approximate a microscale model by a specific choice of mesoscopic reaction rates. In this paper we derive mesoscopic scale-dependent reaction rates by matching certain statistics of the RDME solution to statistics of the solution of a widely used microscopic BD model: the Smoluchowski model with a Robin boundary condition at the reaction radius of two molecules. We also establish fundamental limits on the range of mesh resolutions for which this approach yields accurate results and show both theoretically and in numerical examples that as we approach the lower fundamental limit, the mesoscopic dynamics approach the microscopic dynamics. We show that for mesh sizes below the fundamental lower limit, results are less accurate. Thus, the lower limit determines the mesh size for which we obtain the most accurate results. PMID:25768640

  20. Reaction rates for mesoscopic reaction-diffusion kinetics

    E-print Network

    Stefan Hellander; Andreas Hellander; Linda Petzold

    2015-01-28

    The mesoscopic reaction-diffusion master equation (RDME) is a popular modeling framework, frequently applied to stochastic reaction-diffusion kinetics in systems biology. The RDME is derived from assumptions about the underlying physical properties of the system, and it may produce unphysical results for models where those assumptions fail. In that case, other more comprehensive models are better suited, such as hard-sphere Brownian dynamics (BD). Although the RDME is a model in its own right, and not inferred from any specific microscale model, it proves useful to attempt to approximate a microscale model by a specific choice of mesoscopic reaction rates. In this paper we derive mesoscopic reaction rates by matching certain statistics of the RDME solution to statistics of the solution of a widely used microscopic BD model: the Smoluchowski model with a mixed boundary condition at the reaction radius of two molecules. We also establish fundamental limits for the range of mesh resolutions for which this approach yields accurate results, and show both theoretically and in numerical examples that as we approach the lower fundamental limit, the mesoscopic dynamics approach the microscopic dynamics.

  1. Classes of Chemical Reactions Reactions in aqueous media

    E-print Network

    Zakarian, Armen

    Classes of Chemical Reactions Reactions in aqueous media · Precipitation reactions · Acid-Base reactions · Oxidation-Reduction reactions · Reversible reactions Classes of Chemical Reactions Water (H2O;Classes of Chemical Reactions The solubility of ionic compounds: dissociation O H H + NaCl Cl- Cl- Cl- Na

  2. Knoevenagel Reaction of Unprotected Sugars

    NASA Astrophysics Data System (ADS)

    Scherrmann, Marie-Christine

    The Knoevenagel reaction of unprotected sugars was investigated in the 1950s using zinc chloride as promoter. The so-called Garcia Gonzalez reaction had been almost forgotten for 50 years, until the emergence of new water tolerant catalysts having Lewis acid behavior. The reaction was thus reinvestigated and optimal conditions have been found to prepare trihydroxylated furan derivatives from pentose or ?-tetrahydrofuranylfuran from hexoses with non-cyclic ?-keto ester or ?-diketones. Other valuable compounds such as ?-linked tetrahydrobenzofuranyl glycosides or hydroxyalkyl-3,3,6,6,-tetramethyl-3,4,5,6,7,9-hexahydro-1H-xanthene-1,8(2H)-dione can be obtained using cyclic ?-dicarbonylic derivatives. Apart from one report in the 1950s, the Knoevenagel reaction of unprotected carbohydrate in basic condition has been studied only in the mid-1980s to prepare C-glycosyl barbiturates from barbituric acids and, later on, from non-cyclic ?-diketones, ?-C-glycosidic ketones. The efficient method exploited to prepare such compounds has found an industrial development in cosmetics.

  3. Quantifying mixing using equilibrium reactions

    SciTech Connect

    Wheat, Philip M.; Posner, Jonathan D.

    2009-03-15

    A method of quantifying equilibrium reactions in a microchannel using a fluorometric reaction of Fluo-4 and Ca{sup 2+} ions is presented. Under the proper conditions, equilibrium reactions can be used to quantify fluid mixing without the challenges associated with constituent mixing measures such as limited imaging spatial resolution and viewing angle coupled with three-dimensional structure. Quantitative measurements of CaCl and calcium-indicating fluorescent dye Fluo-4 mixing are measured in Y-shaped microchannels. Reactant and product concentration distributions are modeled using Green's function solutions and a numerical solution to the advection-diffusion equation. Equilibrium reactions provide for an unambiguous, quantitative measure of mixing when the reactant concentrations are greater than 100 times their dissociation constant and the diffusivities are equal. At lower concentrations and for dissimilar diffusivities, the area averaged fluorescence signal reaches a maximum before the species have interdiffused, suggesting that reactant concentrations and diffusivities must be carefully selected to provide unambiguous, quantitative mixing measures. Fluorometric equilibrium reactions work over a wide range of pH and background concentrations such that they can be used for a wide variety of fluid mixing measures including industrial or microscale flows.

  4. Competitive Deprotonation and Superoxide [O2 -•] Radical-Anion Adduct Formation Reactions of Carboxamides under Negative-Ion Atmospheric-Pressure Helium-Plasma Ionization (HePI) Conditions

    NASA Astrophysics Data System (ADS)

    Hassan, Isra; Pinto, Spencer; Weisbecker, Carl; Attygalle, Athula B.

    2015-11-01

    Carboxamides bearing an N-H functionality are known to undergo deprotonation under negative-ion-generating mass spectrometric conditions. Herein, we report that N-H bearing carboxamides with acidities lower than that of the hydroperoxyl radical (HO-O•) preferentially form superoxide radical-anion (O2 -•) adducts, rather than deprotonate, when they are exposed to the glow discharge of a helium-plasma ionization source. For example, the spectra of N-alkylacetamides show peaks for superoxide radical-anion (O2 -•) adducts. Conversely, more acidic amides, such as N-alkyltrifluoroacetamides, preferentially undergo deprotonation under similar experimental conditions. Upon collisional activation, the O2 -• adducts of N-alkylacetamides either lose the neutral amide or the hydroperoxyl radical (HO-O•) to generate the superoxide radical-anion (m/z 32) or the deprotonated amide [m/z (M - H)-], respectively. For somewhat acidic carboxamides, the association between the two entities is weak. Thus, upon mildest collisional activation, the adduct dissociates to eject the superoxide anion. Superoxide-adduct formation results are useful for structure determination purposes because carboxamides devoid of a N-H functionality undergo neither deprotonation nor adduct formation under HePI conditions.

  5. Modeling the enzyme kinetic reaction.

    PubMed

    Atangana, Abdon

    2015-09-01

    The Enzymatic control reactions model was presented within the scope of fractional calculus. In order to accommodate the usual initial conditions, the fractional derivative used is in Caputo sense. The methodologies of the three analytical methods were used to derive approximate solution of the fractional nonlinear system of differential equations. Two methods use integral operator and the other one uses just an integral. Numerical results obtained exhibit biological behavior of real world problem. PMID:25930963

  6. GRAPH THEORETIC APPROACHES TO INJECTIVITY IN CHEMICAL REACTION SYSTEMS

    E-print Network

    Craciun, Gheorghe

    GRAPH THEORETIC APPROACHES TO INJECTIVITY IN CHEMICAL REACTION SYSTEMS MURAD BANAJI AND GHEORGHE algebraic and graph theoretic conditions for injectivity of chemical reaction systems. After developing the possibility of multiple equilibria in the systems in question. Key words. Chemical reactions; Injectivity; SR

  7. Flossie Brown CHEMICAL REACTIONS FOR A HYDROGEN ECONOMY.

    E-print Network

    Lasenby, Joan

    Flossie Brown CHEMICAL REACTIONS FOR A HYDROGEN ECONOMY. At present, hydrogen production a chemical reaction must be found that allows hydrogen production to take place quickly, cheaply and safely reaction, the reasons for their shortcomings can be identified. In each process, a reactant, condition

  8. Two-Body and Three-Body Atomic Recombination Reactions.

    ERIC Educational Resources Information Center

    Alvarino, Jose M.; Martinez, E.

    1983-01-01

    Discusses how, in some circumstances, a two-body reaction (association in absence of a third body) is the only possible association, and how reactions proceed in this case. Taking competition between two/three-body reactions into account, considers relative importance of such combinations and conditions under which the former can be competitive.…

  9. Amine free crystal structure: The crystal structure of d(CGCGCG){sub 2} and methylamine complex crystal

    SciTech Connect

    Ohishi, Hirofumi . E-mail: ohishi@gly.oups.ac.jp; Tsukamoto, Koji; Hiyama, Yoichi; Maezaki, Naoyoshi; Tanaka, Tetsuaki; Ishida, Toshimasa

    2006-09-29

    We succeeded in the crystallization of d(CGCGCG){sub 2} and methylamine Complex. The crystal was clear and of sufficient size to collect the X-ray crystallographic data up to 1.0 A resolution using synchrotron radiation. As a result of X-ray crystallographic analysis of 2F {sub o} - F {sub c} map was much clear and easily traced. It is First time monoamine co-crystallizes with d(CGCGCG){sub 2}. However, methylamine was not found from the complex crystal of d(CGCGCG){sub 2} and methylamine. Five Mg ions were found around d(CGCGCG){sub 2} molecules. These Mg ions neutralized the anion of 10 values of the phosphate group of DNA with five Mg{sup 2+}. DNA stabilized only by a metallic ion and there is no example of analyzing the X-ray crystal structure like this. Mg ion stabilizes the conformation of Z-DNA. To use monoamine for crystallization of DNA, we found that we can get only d(CGCGCG){sub 2} and Mg cation crystal. Only Mg cation can stabilize the conformation of Z-DNA. The method of using the monoamine for the crystallization of DNA can be applied to the crystallization of DNA of long chain of length in the future like this.

  10. Learning to Predict Chemical Reactions

    PubMed Central

    Kayala, Matthew A.; Azencott, Chloé-Agathe; Chen, Jonathan H.

    2011-01-01

    Being able to predict the course of arbitrary chemical reactions is essential to the theory and applications of organic chemistry. Approaches to the reaction prediction problems can be organized around three poles corresponding to: (1) physical laws; (2) rule-based expert systems; and (3) inductive machine learning. Previous approaches at these poles respectively are not high-throughput, are not generalizable or scalable, or lack sufficient data and structure to be implemented. We propose a new approach to reaction prediction utilizing elements from each pole. Using a physically inspired conceptualization, we describe single mechanistic reactions as interactions between coarse approximations of molecular orbitals (MOs) and use topological and physicochemical attributes as descriptors. Using an existing rule-based system (Reaction Explorer), we derive a restricted chemistry dataset consisting of 1630 full multi-step reactions with 2358 distinct starting materials and intermediates, associated with 2989 productive mechanistic steps and 6.14 million unproductive mechanistic steps. And from machine learning, we pose identifying productive mechanistic steps as a statistical ranking, information retrieval, problem: given a set of reactants and a description of conditions, learn a ranking model over potential filled-to-unfilled MO interactions such that the top ranked mechanistic steps yield the major products. The machine learning implementation follows a two-stage approach, in which we first train atom level reactivity filters to prune 94.00% of non-productive reactions with a 0.01% error rate. Then, we train an ensemble of ranking models on pairs of interacting MOs to learn a relative productivity function over mechanistic steps in a given system. Without the use of explicit transformation patterns, the ensemble perfectly ranks the productive mechanism at the top 89.05% of the time, rising to 99.86% of the time when the top four are considered. Furthermore, the system is generalizable, making reasonable predictions over reactants and conditions which the rule-based expert does not handle. A web interface to the machine learning based mechanistic reaction predictor is accessible through our chemoinformatics portal (http://cdb.ics.uci.edu) under the Toolkits section. PMID:21819139

  11. Hexacoordinate Ru-based olefin metathesis catalysts with pH-responsive N-heterocyclic carbene (NHC) and N-donor ligands for ROMP reactions in non-aqueous, aqueous and emulsion conditions.

    PubMed

    Balof, Shawna L; Nix, K Owen; Olliff, Matthew S; Roessler, Sarah E; Saha, Arpita; Müller, Kevin B; Behrens, Ulrich; Valente, Edward J; Schanz, Hans-Jörg

    2015-01-01

    Three new ruthenium alkylidene complexes (PCy3)Cl2(H2ITap)Ru=CHSPh (9), (DMAP)2Cl2(H2ITap)Ru=CHPh (11) and (DMAP)2Cl2(H2ITap)Ru=CHSPh (12) have been synthesized bearing the pH-responsive H2ITap ligand (H2ITap = 1,3-bis(2',6'-dimethyl-4'-dimethylaminophenyl)-4,5-dihydroimidazol-2-ylidene). Catalysts 11 and 12 are additionally ligated by two pH-responsive DMAP ligands. The crystal structure was solved for complex 12 by X-ray diffraction. In organic, neutral solution, the catalysts are capable of performing standard ring-opening metathesis polymerization (ROMP) and ring closing metathesis (RCM) reactions with standard substrates. The ROMP with complex 11 is accelerated in the presence of two equiv of H3PO4, but is reduced as soon as the acid amount increased. The metathesis of phenylthiomethylidene catalysts 9 and 12 is sluggish at room temperature, but their ROMP can be dramatically accelerated at 60 °C. Complexes 11 and 12 are soluble in aqueous acid. They display the ability to perform RCM of diallylmalonic acid (DAMA), however, their conversions are very low amounting only to few turnovers before decomposition. However, both catalysts exhibit outstanding performance in the ROMP of dicyclopentadiene (DCPD) and mixtures of DCPD with cyclooctene (COE) in acidic aqueous microemulsion. With loadings as low as 180 ppm, the catalysts afforded mostly quantitative conversions of these monomers while maintaining the size and shape of the droplets throughout the polymerization process. Furthermore, the coagulate content for all experiments stayed <2%. This represents an unprecedented efficiency in emulsion ROMP based on hydrophilic ruthenium alkylidene complexes. PMID:26664616

  12. Hexacoordinate Ru-based olefin metathesis catalysts with pH-responsive N-heterocyclic carbene (NHC) and N-donor ligands for ROMP reactions in non-aqueous, aqueous and emulsion conditions

    PubMed Central

    Balof, Shawna L; Nix, K Owen; Olliff, Matthew S; Roessler, Sarah E; Saha, Arpita; Müller, Kevin B; Behrens, Ulrich; Valente, Edward J

    2015-01-01

    Summary Three new ruthenium alkylidene complexes (PCy3)Cl2(H2ITap)Ru=CHSPh (9), (DMAP)2Cl2(H2ITap)Ru=CHPh (11) and (DMAP)2Cl2(H2ITap)Ru=CHSPh (12) have been synthesized bearing the pH-responsive H2ITap ligand (H2ITap = 1,3-bis(2’,6’-dimethyl-4’-dimethylaminophenyl)-4,5-dihydroimidazol-2-ylidene). Catalysts 11 and 12 are additionally ligated by two pH-responsive DMAP ligands. The crystal structure was solved for complex 12 by X-ray diffraction. In organic, neutral solution, the catalysts are capable of performing standard ring-opening metathesis polymerization (ROMP) and ring closing metathesis (RCM) reactions with standard substrates. The ROMP with complex 11 is accelerated in the presence of two equiv of H3PO4, but is reduced as soon as the acid amount increased. The metathesis of phenylthiomethylidene catalysts 9 and 12 is sluggish at room temperature, but their ROMP can be dramatically accelerated at 60 °C. Complexes 11 and 12 are soluble in aqueous acid. They display the ability to perform RCM of diallylmalonic acid (DAMA), however, their conversions are very low amounting only to few turnovers before decomposition. However, both catalysts exhibit outstanding performance in the ROMP of dicyclopentadiene (DCPD) and mixtures of DCPD with cyclooctene (COE) in acidic aqueous microemulsion. With loadings as low as 180 ppm, the catalysts afforded mostly quantitative conversions of these monomers while maintaining the size and shape of the droplets throughout the polymerization process. Furthermore, the coagulate content for all experiments stayed <2%. This represents an unprecedented efficiency in emulsion ROMP based on hydrophilic ruthenium alkylidene complexes. PMID:26664616

  13. Allergic reactions (image)

    MedlinePLUS

    Allergic reaction is a sensitivity to a specific substance, called an allergen, that is contacted through the skin, inhaled into the lungs, swallowed or injected. The body's reaction to an allergen can be mild, such as ...

  14. Allergic reactions (image)

    MedlinePLUS

    Allergic reaction can be provoked by skin contact with poison plants, chemicals and animal scratches, as well as by ... dust, nuts and shellfish, may also cause allergic reaction. Medications such as penicillin and other antibiotics are ...

  15. Microfluidic chemical reaction circuits

    DOEpatents

    Lee, Chung-cheng (Irvine, CA); Sui, Guodong (Los Angeles, CA); Elizarov, Arkadij (Valley Village, CA); Kolb, Hartmuth C. (Playa del Rey, CA); Huang, Jiang (San Jose, CA); Heath, James R. (South Pasadena, CA); Phelps, Michael E. (Los Angeles, CA); Quake, Stephen R. (Stanford, CA); Tseng, Hsian-rong (Los Angeles, CA); Wyatt, Paul (Tipperary, IE); Daridon, Antoine (Mont-Sur-Rolle, CH)

    2012-06-26

    New microfluidic devices, useful for carrying out chemical reactions, are provided. The devices are adapted for on-chip solvent exchange, chemical processes requiring multiple chemical reactions, and rapid concentration of reagents.

  16. Microscale Thermite Reactions.

    ERIC Educational Resources Information Center

    Arnaiz, Francisco J.; Aguado, Rafael; Arnaiz, Susana

    1998-01-01

    Describes the adaptation of thermite (aluminum with metal oxides) reactions from whole-class demonstrations to student-run micro-reactions. Lists detailed directions and possible variations of the experiment. (WRM)

  17. Characteristics of vestibulosensory reactions studied by experimental caloric test

    NASA Technical Reports Server (NTRS)

    Kapranov, V. Z.

    1980-01-01

    Vestibulo-sensory reactions were studied in 135 workers who were in contact with nitroethers, by the method of an experimental caloric test. The response vestibulo-sensory reactions were recorded by means of an electroencephalograph. The changes in the sensory reaction depended on the duration of the workers' contact with toxic agents. A study of illusion reactions by the labyrinth calorization widens diagnostic possibilities in the examination of functional condition of the vestibular analyser considerably.

  18. 14 CFR 25.493 - Braked roll conditions.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ...reaction multiplied by a coefficient of friction of 0.8, must be combined...reaction, multiplied by a coefficient of friction of 0.8, must be combined...static condition. ?=Coefficient of friction of 0.80....

  19. 14 CFR 25.493 - Braked roll conditions.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ...reaction multiplied by a coefficient of friction of 0.8, must be combined...reaction, multiplied by a coefficient of friction of 0.8, must be combined...static condition. ?=Coefficient of friction of 0.80....

  20. 14 CFR 25.493 - Braked roll conditions.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ...reaction multiplied by a coefficient of friction of 0.8, must be combined...reaction, multiplied by a coefficient of friction of 0.8, must be combined...static condition. ?=Coefficient of friction of 0.80....

  1. No evidence of reaction time slowing in autism spectrum disorder.

    PubMed

    Ferraro, F Richard

    2016-01-01

    A total of 32 studies comprising 238 simple reaction time and choice reaction time conditions were examined in individuals with autism spectrum disorder (n?=?964) and controls (n?=?1032). A Brinley plot/multiple regression analysis was performed on mean reaction times, regressing autism spectrum disorder performance onto the control performance as a way to examine any generalized simple reaction time/choice reaction time slowing exhibited by the autism spectrum disorder group. The resulting regression equation was Y (autism spectrum disorder)?=?0.99 × (control) + 87.93, which accounted for 92.3% of the variance. These results suggest that there are little if any simple reaction time/choice reaction time slowing in this sample of individual with autism spectrum disorder, in comparison with controls. While many cognitive and information processing domains are compromised in autism spectrum disorder, it appears that simple reaction time/choice reaction time remain relatively unaffected in autism spectrum disorder. PMID:25512973

  2. Catalytic Conia-ene and related reactions.

    PubMed

    Hack, Daniel; Blümel, Marcus; Chauhan, Pankaj; Philipps, Arne R; Enders, Dieter

    2015-10-01

    Since its initial inception, the Conia-ene reaction, known as the intramolecular addition of enols to alkynes or alkenes, has experienced a tremendous development and appealing catalytic protocols have emerged. This review fathoms the underlying mechanistic principles rationalizing how substrate design, substrate activation, and the nature of the catalyst work hand in hand for the efficient synthesis of carbocycles and heterocycles at mild reaction conditions. Nowadays, Conia-ene reactions can be found as part of tandem reactions, and the road for asymmetric versions has already been paved. Based on their broad applicability, Conia-ene reactions have turned into a highly appreciated synthetic tool with impressive examples in natural product synthesis reported in recent years. PMID:26031492

  3. Mukaiyama Aldol Reactions in Aqueous Media

    PubMed Central

    Kitanosono, Taku; Kobayashi, Sh?

    2013-01-01

    Mukaiyama aldol reactions in aqueous media have been surveyed. While the original Mukaiyama aldol reactions entailed stoichiometric use of Lewis acids in organic solvents under strictly anhydrous conditions, Mukaiyama aldol reactions in aqueous media are not only suitable for green sustainable chemistry but are found to produce singular phenomena. These findings led to the discovery of a series of water-compatible Lewis acids such as lanthanide triflates in 1991. Our understanding on these beneficial effects in the presence of water will be deepened through the brilliant examples collected in this review. 1 Introduction 2 Rate Enhancement by Water in the Mukaiyama Aldol Reaction 3 Lewis Acid Catalysis in Aqueous or Organic Solvents 3.1 Water-Compatible Lewis Acids 4 Lewis-Base Catalysis in Aqueous or Organic Solvents 5 The Mukaiyama Aldol Reactions in 100% Water 6 Asymmetric Catalysts in Aqueous Media and Water 7 Conclusions and Perspective PMID:24971045

  4. Reaction modeling in geothermal systems

    NASA Astrophysics Data System (ADS)

    Stefansson, A.

    2012-12-01

    Natural volcanic geothermal systems are open systems in term of matter and energy. Such systems are complex to model in terms of fluid chemistry, fluid flow and energy budget. Reaction modeling may be used to gain insight and possibly quantify chemical processes occurring within a system, for example fluid-fluid and fluid-rock interaction. Methods have been developed within the WATCH (Bjarnason, 1994; Arnórsson et al., 2007) and PHREEQC (Parkhurst and Appelo, 1999) programs to simulate reactions of multicomponent and multiphase systems to 300°C. The models include boiling and phase segregation (open system boiling), fluid-fluid mixing and fluid-rock interaction (gas-water-rock interaction). The models have been applied to quantify processes within the Hellisheidi geothermal system, Iceland. Open system boiling and fluid-rock interaction were simulated as a function of temperature, initial fluid composition and extent of reaction (T-X-?). In addition the interactions of magmatic gases with geothermal fluids and rocks were modeled. In this way various component behavior has been traced within the geothermal system and compared with observations of fluid composition and mineralogy. In addition, the reaction models have been used to evaluate the geochemical feasibility and best conditions of gas (CO2 and H2S) and waste water injection into geothermal system.

  5. Molecular Reaction Dynamics and Solvation.

    NASA Astrophysics Data System (ADS)

    Kim, Seong Keun

    A potential energy surface was constructed for the triatomic molecule Li_2H using a semiempirical method akin to the diatomics-in-molecules theory. Valence bond configurations were chosen to include the major ionic contributions in the ground state potential energy. Quasiclassical trajectories were run on this potential energy surface. The results of these calculations are shown to be generally in accord with the experimental investigations of analogous reactions of H atoms with bigger alkali dimer molecules. Certain aspects of chemical reaction dynamics which have been largely overlooked were examined. These involve correlations of vector properties in chemical reactions. Specifically, the strong correlation between orbital and rotational angular momenta in the product channel of this reaction was shown to be the reason for a seemingly contradictory set of distributions of different angles. Gas phase solvation of nucleic acid base molecules was studied using clusters produced by supersonic expansion. Relative stabilities of the species with different numbers of solvent molecules were studied by varying the expansion conditions. The ionization potentials were measured as a function of the number of solvent molecules. Rather distinct effects of hydration were observed for the ionization potentials of adenine and thymine.

  6. Quality control of Photosystem II: an FtsH protease plays an essential role in the turnover of the reaction center D1 protein in Synechocystis PCC 6803 under heat stress as well as light stress conditions.

    PubMed

    Kamata, Takashi; Hiramoto, Hideki; Morita, Noriko; Shen, Jian-Ren; Mann, Nicholas H; Yamamoto, Yasusi

    2005-12-01

    The role of an AAA protease FtsH (slr0228) in the turnover of the D1 protein was studied under moderate heat stress conditions using wild-type cells of the cyanobacterium Synechocystis PCC 6803 and the mutant cells lacking a homologue of FtsH (slr0228). When the growth temperature of the wild-type was shifted from 30 degrees C to 40 degrees C, growth and oxygen-evolving activity were partially inhibited. Under the same heat stress, growth of the mutant was inhibited more significantly (63% inhibition after 5 days heat stress, compared with 26% inhibition with the wild-type cells) and the oxygen-evolving activity was also impaired in parallel. With heat stress at 42 degrees C, the level of the D1 protein of wild type cells was decreased, whereas that in mutant cells was not. The responses of cyanobacterial cells to heat stress observed here are quite similar to those to light stress that were reported previously. From these results, we suggest that the FtsH protease (slr0228) is responsible for both the heat-induced and light-induced degradation of the D1 protein. Notably, the amount of FtsH increased when the wild-type cells were exposed to heat stress or light stress, indicating that the up-regulation of the FtsH protease in the thylakoids is crucial for the cyanobacterial cells to cope with these abiotic stresses. PMID:16307111

  7. Impact of THM reaction rates for astrophysics

    NASA Astrophysics Data System (ADS)

    Lamia, L.; Spitaleri, C.; Tognelli, E.; Degl'Innocenti, S.; Pizzone, R. G.; Moroni, P. G. Prada; Puglia, S. M. R.; Romano, S.; Sergi, M. L.

    2015-10-01

    Burning reaction S(E)-factor determinations are among the key ingredients for stellar models when one has to deal with energy generation evaluation and the genesis of the elements at stellar conditions. To by pass the still present uncertainties in extrapolating low-energies values, S(E)-factor measurements for charged-particle induced reactions involving light elements have been made available by devote Trojan Horse Method (THM) experiments. The recent results are here discussed together with their impact in astrophysics.

  8. Connecting localized DNA strand displacement reactions

    NASA Astrophysics Data System (ADS)

    Mullor Ruiz, Ismael; Arbona, Jean-Michel; Lad, Amitkumar; Mendoza, Oscar; Aimé, Jean-Pierre; Elezgaray, Juan

    2015-07-01

    Logic circuits based on DNA strand displacement reactions have been shown to be versatile enough to compute the square root of four-bit numbers. The implementation of these circuits as a set of bulk reactions faces difficulties which include leaky reactions and intrinsically slow, diffusion-limited reaction rates. In this paper, we consider simple examples of these circuits when they are attached to platforms (DNA origamis). As expected, constraining distances between DNA strands leads to faster reaction rates. However, it also induces side-effects that are not detectable in the solution-phase version of this circuitry. Appropriate design of the system, including protection and asymmetry between input and fuel strands, leads to a reproducible behaviour, at least one order of magnitude faster than the one observed under bulk conditions.Logic circuits based on DNA strand displacement reactions have been shown to be versatile enough to compute the square root of four-bit numbers. The implementation of these circuits as a set of bulk reactions faces difficulties which include leaky reactions and intrinsically slow, diffusion-limited reaction rates. In this paper, we consider simple examples of these circuits when they are attached to platforms (DNA origamis). As expected, constraining distances between DNA strands leads to faster reaction rates. However, it also induces side-effects that are not detectable in the solution-phase version of this circuitry. Appropriate design of the system, including protection and asymmetry between input and fuel strands, leads to a reproducible behaviour, at least one order of magnitude faster than the one observed under bulk conditions. Electronic supplementary information (ESI) available. See DOI: 10.1039/C5NR02434J

  9. Prebiotic condensation reactions using cyanamide

    NASA Technical Reports Server (NTRS)

    Sherwood, E.; Nooner, D. W.; Eichberg, J.; Epps, D. E.; Oro, J.

    1978-01-01

    Condensation reactions in cyanamide, 4-amino-5-imidazole-carboxamide and cyanamide, imidazole systems under dehydrating conditions at moderate temperatures (60 to 100 deg C) were investigated. The cyanamide, imidazole system was used for synthesis of palmitoylglycerols from ammonium palmitate and glycerol. With the addition of deoxythymidine to the former system, P1, P2-dideoxythymidine 5 prime-phosphate was obtained; the same cyanamide, 4-amino-5-imidazole-carboxamide system was used to synthesize deoxythymidine oligonucleotides using deoxythymidine 5 prime-phosphate and deoxythymidine 5 prime-triphosphate, and peptides using glycine, phenylalanine or isoleucine with adenosine 5 prime-triphosphate. The pH requirements for these reactions make their prebiotic significance questionable; however, it is conceivable that they could occur in stable pockets of low interlayer acidity in a clay such as montmorillonite.

  10. Reaction spreading on graphs

    NASA Astrophysics Data System (ADS)

    Burioni, Raffaella; Chibbaro, Sergio; Vergni, Davide; Vulpiani, Angelo

    2012-11-01

    We study reaction-diffusion processes on graphs through an extension of the standard reaction-diffusion equation starting from first principles. We focus on reaction spreading, i.e., on the time evolution of the reaction product M(t). At variance with pure diffusive processes, characterized by the spectral dimension ds, the important quantity for reaction spreading is found to be the connectivity dimension dl. Numerical data, in agreement with analytical estimates based on the features of n independent random walkers on the graph, show that M(t)˜tdl. In the case of Erdös-Renyi random graphs, the reaction product is characterized by an exponential growth M(t)˜e?t with ? proportional to ln, where is the average degree of the graph.

  11. The polymorphic phototest reaction

    SciTech Connect

    Jansen, C.

    1982-09-01

    One hundred tem patients with polymorphic light eruption (PMLE) and 58 control subjects were tested with an overdose of erythemogenic radiation. A morphologically abnormal phototest reaction was demonstrable in 72% of the patients with PMLE and in 9% of the control subjects. On the average, a dose of 3.8 times the patient's minimal erythemal dose was needed to produce the reaction. The most common findings in positive phototest reaction sites were edema and itching. A medium-pressure mercury lamp was shown to be as effective as a xenon arc lamp in producing the phototest reaction. The time of the reaction varied considerably in different patients, and frequent inspections of test sites were necessary to detect positive phototest reactions. When properly performed and interpreted, phototesting is a valuable diagnostic procedure for PMLE.

  12. Sleeve reaction chamber system

    DOEpatents

    Northrup, M. Allen (Berkeley, CA); Beeman, Barton V. (San Mateo, CA); Benett, William J. (Livermore, CA); Hadley, Dean R. (Manteca, CA); Landre, Phoebe (Livermore, CA); Lehew, Stacy L. (Livermore, CA); Krulevitch, Peter A. (Pleasanton, CA)

    2009-08-25

    A chemical reaction chamber system that combines devices such as doped polysilicon for heating, bulk silicon for convective cooling, and thermoelectric (TE) coolers to augment the heating and cooling rates of the reaction chamber or chambers. In addition the system includes non-silicon-based reaction chambers such as any high thermal conductivity material used in combination with a thermoelectric cooling mechanism (i.e., Peltier device). The heat contained in the thermally conductive part of the system can be used/reused to heat the device, thereby conserving energy and expediting the heating/cooling rates. The system combines a micromachined silicon reaction chamber, for example, with an additional module/device for augmented heating/cooling using the Peltier effect. This additional module is particularly useful in extreme environments (very hot or extremely cold) where augmented heating/cooling would be useful to speed up the thermal cycling rates. The chemical reaction chamber system has various applications for synthesis or processing of organic, inorganic, or biochemical reactions, including the polymerase chain reaction (PCR) and/or other DNA reactions, such as the ligase chain reaction.

  13. Radical reactions of borohydrides.

    PubMed

    Kawamoto, Takuji; Ryu, Ilhyong

    2014-12-28

    Borohydrides are an important class of reagents in both organic and inorganic chemistry. Though popular as hydride-transfer reagents for reduction, since earlier work from the 1970s, borohydride reagents have also been known to serve as hydrogen-transfer reagents. In pursuit of greener tin hydride substitutes, recent progress has been made to mediate radical C-C bond forming reactions, including Giese reactions, radical carbonylation and addition to HCHO reactions, with borohydride reagents. This review article focuses on state-of-the-art borohydride based radical reactions, also covering earlier work, kinetics and some DFT calculations with respect to the hydrogen transfer mechanism. PMID:25349957

  14. 14 CFR 29.501 - Ground loading conditions: landing gear with skids.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... reactions must be combined with horizontal drag reactions of 50 percent of the vertical reaction applied at... reaction must be— (i) Equal to the vertical loads obtained in the condition specified in paragraph (b) of...) A ground reaction load acting up and aft at an angle of 45 degrees to the longitudinal axis of...

  15. 14 CFR 29.501 - Ground loading conditions: landing gear with skids.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... reactions must be combined with horizontal drag reactions of 50 percent of the vertical reaction applied at... reaction must be— (i) Equal to the vertical loads obtained in the condition specified in paragraph (b) of...) A ground reaction load acting up and aft at an angle of 45 degrees to the longitudinal axis of...

  16. 14 CFR 27.501 - Ground loading conditions: landing gear with skids.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... reactions must be combined with horizontal drag reactions of 50 percent of the vertical reaction applied at... reaction must be— (i) Equal to the vertical loads obtained in the condition specified in paragraph (b) of...) A ground reaction load acting up and aft at an angle of 45 degrees to the longitudinal axis of...

  17. 14 CFR 27.501 - Ground loading conditions: landing gear with skids.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... reactions must be combined with horizontal drag reactions of 50 percent of the vertical reaction applied at... reaction must be— (i) Equal to the vertical loads obtained in the condition specified in paragraph (b) of...) A ground reaction load acting up and aft at an angle of 45 degrees to the longitudinal axis of...

  18. 14 CFR 27.501 - Ground loading conditions: landing gear with skids.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... reactions must be combined with horizontal drag reactions of 50 percent of the vertical reaction applied at... reaction must be— (i) Equal to the vertical loads obtained in the condition specified in paragraph (b) of...) A ground reaction load acting up and aft at an angle of 45 degrees to the longitudinal axis of...

  19. 14 CFR 29.501 - Ground loading conditions: landing gear with skids.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... reactions must be combined with horizontal drag reactions of 50 percent of the vertical reaction applied at... reaction must be— (i) Equal to the vertical loads obtained in the condition specified in paragraph (b) of...) A ground reaction load acting up and aft at an angle of 45 degrees to the longitudinal axis of...

  20. 14 CFR 29.501 - Ground loading conditions: landing gear with skids.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... reactions must be combined with horizontal drag reactions of 50 percent of the vertical reaction applied at... reaction must be— (i) Equal to the vertical loads obtained in the condition specified in paragraph (b) of...) A ground reaction load acting up and aft at an angle of 45 degrees to the longitudinal axis of...

  1. 14 CFR 27.501 - Ground loading conditions: landing gear with skids.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... reactions must be combined with horizontal drag reactions of 50 percent of the vertical reaction applied at... reaction must be— (i) Equal to the vertical loads obtained in the condition specified in paragraph (b) of...) A ground reaction load acting up and aft at an angle of 45 degrees to the longitudinal axis of...

  2. 14 CFR 27.501 - Ground loading conditions: landing gear with skids.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... reactions must be combined with horizontal drag reactions of 50 percent of the vertical reaction applied at... reaction must be— (i) Equal to the vertical loads obtained in the condition specified in paragraph (b) of...) A ground reaction load acting up and aft at an angle of 45 degrees to the longitudinal axis of...

  3. 14 CFR 29.501 - Ground loading conditions: landing gear with skids.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... reactions must be combined with horizontal drag reactions of 50 percent of the vertical reaction applied at... reaction must be— (i) Equal to the vertical loads obtained in the condition specified in paragraph (b) of...) A ground reaction load acting up and aft at an angle of 45 degrees to the longitudinal axis of...

  4. Capture reactions on C-14 in nonstandard big bang nucleosynthesis

    NASA Technical Reports Server (NTRS)

    Wiescher, Michael; Gorres, Joachim; Thielemann, Friedrich-Karl

    1990-01-01

    Nonstandard big bang nucleosynthesis leads to the production of C-14. The further reaction path depends on the depletion of C-14 by either photon, alpha, or neutron capture reactions. The nucleus C-14 is of particular importance in these scenarios because it forms a bottleneck for the production of heavier nuclei A greater than 14. The reaction rates of all three capture reactions at big bang conditions are discussed, and it is shown that the resulting reaction path, leading to the production of heavier elements, is dominated by the (p, gamma) and (n, gamma) rates, contrary to earlier suggestions.

  5. Role of microbes in the smectite-to-illite reaction

    NASA Technical Reports Server (NTRS)

    Kim, Jinwook; Dong, Hailiang; Seabaugh, Jennifer; Newell, Steven W.; Eberl, Dennis D.

    2004-01-01

    Temperature, pressure, and time have been thought to control the smectite-to-illite (S-I) reaction, an important diagenetic process used for petroleum exploration. We demonstrated that microorganisms can promote the S-I reaction by dissolving smectite through reduction of structural Fe(III) at room temperature and 1 atmosphere within 14 days. This reaction typically requires conditions of 300 degrees to 350 degrees C, 100 megapascals, and 4 to 5 months in the absence of microbial activity. These results challenge the conventional concept of the S-I reaction and of reaction kinetic models.

  6. Role of Microbes in the Smectite-to-Illite Reaction

    USGS Publications Warehouse

    Kim, J.; Dong, H.; Seabaugh, J.; Newell, S.W.; Eberl, D.D.

    2004-01-01

    Temperature, pressure, and time have been thought to control the smectiteto-illite (S-I) reaction, an important diagenetic process used for petroleum exploration. We demonstrated that microorganisms can promote the S-I reaction by dissolving smectite through reduction of structural FE(III) at room temperature and 1 atmosphere within 14 days. This reaction typically requires conditions of 300?? to 350??C, 100 megapascals, and 4 to 5 months in the absence of microbial activity. These results challenge the conventional concept of the S-I reaction and of reaction kinetic models.

  7. Dynamical properties of Discrete Reaction Networks.

    PubMed

    Paulevé, Loïc; Craciun, Gheorghe; Koeppl, Heinz

    2014-07-01

    Reaction networks are commonly used to model the dynamics of populations subject to transformations that follow an imposed stoichiometry. This paper focuses on the efficient characterisation of dynamical properties of Discrete Reaction Networks (DRNs). DRNs can be seen as modeling the underlying discrete nondeterministic transitions of stochastic models of reaction networks. In that sense, a proof of non-reachability in a given DRN has immediate implications for any concrete stochastic model based on that DRN, independent of the choice of kinetic laws and constants. Moreover, if we assume that stochastic kinetic rates are given by the mass-action law (or any other kinetic law that gives non-vanishing probability to each reaction if the required number of interacting substrates is present), then reachability properties are equivalent in the two settings. The analysis of two types of global dynamical properties of DRNs is addressed: irreducibility, i.e., the ability to reach any discrete state from any other state; and recurrence, i.e., the ability to return to any initial state. Our results consider both the verification of such properties when species are present in a large copy number, and in the general case. The necessary and sufficient conditions obtained involve algebraic conditions on the network reactions which in most cases can be verified using linear programming. Finally, the relationship of DRN irreducibility and recurrence with dynamical properties of stochastic and continuous models of reaction networks is discussed. PMID:23722628

  8. Degradations and Rearrangement Reactions

    NASA Astrophysics Data System (ADS)

    Zhang, Jianbo

    This section deals with recent reports concerning degradation and rearrangement reactions of free sugars as well as some glycosides. The transformations are classified in chemical and enzymatic ways. In addition, the Maillard reaction will be discussed as an example of degradation and rearrangement transformation and its application in current research in the fields of chemistry and biology.

  9. Oscillating Reactions: Two Analogies

    ERIC Educational Resources Information Center

    Petruševski, Vladimir M.; Stojanovska, Marina I.; Šoptrajanov, Bojan T.

    2007-01-01

    Oscillating chemical reactions are truly spectacular phenomena, and demonstrations are always appreciated by the class. However, explaining such reactions to high school or first-year university students is problematic, because it may seem that no acceptable explanation is possible unless the students have profound knowledge of both physical…

  10. Applications of Reaction Rate

    ERIC Educational Resources Information Center

    Cunningham, Kevin

    2007-01-01

    This article presents an assignment in which students are to research and report on a chemical reaction whose increased or decreased rate is of practical importance. Specifically, students are asked to represent the reaction they have chosen with an acceptable chemical equation, identify a factor that influences its rate and explain how and why it…

  11. Chemical Reaction Problem Solving.

    ERIC Educational Resources Information Center

    Veal, William

    1999-01-01

    Discusses the role of chemical-equation problem solving in helping students predict reaction products. Methods for helping students learn this process must be taught to students and future teachers by using pedagogical skills within the content of chemistry. Emphasizes that solving chemical reactions should involve creative cognition where…

  12. Nuclear Reaction Data Centers

    SciTech Connect

    McLane, V.; Nordborg, C.; Lemmel, H.D.; Manokhin, V.N.

    1988-01-01

    The cooperating Nuclear Reaction Data Centers are involved in the compilation and exchange of nuclear reaction data for incident neutrons, charged particles and photons. Individual centers may also have services in other areas, e.g., evaluated data, nuclear structure and decay data, reactor physics, nuclear safety; some of this information may also be exchanged between interested centers. 20 refs., 1 tab.

  13. Clock Reaction: Outreach Attraction

    ERIC Educational Resources Information Center

    Carpenter, Yuen-ying; Phillips, Heather A.; Jakubinek, Michael B.

    2010-01-01

    Chemistry students are often introduced to the concept of reaction rates through demonstrations or laboratory activities involving the well-known iodine clock reaction. For example, a laboratory experiment involving thiosulfate as an iodine scavenger is part of the first-year general chemistry laboratory curriculum at Dalhousie University. With…

  14. A comparison of bimolecular reaction models for stochastic reaction-diffusion systems.

    PubMed

    Agbanusi, I C; Isaacson, S A

    2014-04-01

    Stochastic reaction-diffusion models have become an important tool in studying how both noise in the chemical reaction process and the spatial movement of molecules influences the behavior of biological systems. There are two primary spatially-continuous models that have been used in recent studies: the diffusion limited reaction model of Smoluchowski, and a second approach popularized by Doi. Both models treat molecules as points undergoing Brownian motion. The former represents chemical reactions between two reactants through the use of reactive boundary conditions, with two molecules reacting instantly upon reaching a fixed separation (called the reaction-radius). The Doi model uses reaction potentials, whereby two molecules react with a fixed probability per unit time, ?, when separated by less than the reaction radius. In this work, we study the rigorous relationship between the two models. For the special case of a protein diffusing to a fixed DNA binding site, we prove that the solution to the Doi model converges to the solution of the Smoluchowski model as ???, with a rigorous [Formula: see text] error bound (for any fixed ?>0). We investigate by numerical simulation, for biologically relevant parameter values, the difference between the solutions and associated reaction time statistics of the two models. As the reaction-radius is decreased, for sufficiently large but fixed values of ?, these differences are found to increase like the inverse of the binding radius. PMID:23579988

  15. Integrating reaction and analysis: investigation of higher-order reactions by cryogenic trapping

    PubMed Central

    Stockinger, Skrollan

    2013-01-01

    Summary A new approach for the investigation of a higher-order reaction by on-column reaction gas chromatography is presented. The reaction and the analytical separation are combined in a single experiment to investigate the Diels–Alder reaction of benzenediazonium-2-carboxylate as a benzyne precursor with various anthracene derivatives, i.e. anthracene, 9-bromoanthracene, 9-anthracenecarboxaldehyde and 9-anthracenemethanol. To overcome limitations of short reaction contact times at elevated temperatures a novel experimental setup was developed involving a cooling trap to achieve focusing and mixing of the reactants at a defined spot in a fused-silica capillary. This trap functions as a reactor within the separation column in the oven of a gas chromatograph. The reactants are sequentially injected to avoid undefined mixing in the injection port. An experimental protocol was developed with optimized injection intervals and cooling times to achieve sufficient conversions at short reaction times. Reaction products were rapidly identified by mass spectrometric detection. This new approach represents a practical procedure to investigate higher-order reactions at an analytical level and it simultaneously provides valuable information for the optimization of the reaction conditions. PMID:24062850

  16. Surface catalyzed mercury transformation reactions

    NASA Astrophysics Data System (ADS)

    Varanasi, Patanjali

    Mercury is a known pollutant that has detrimental effect on human health and environment. The anthropogenic emissions of mercury account for 10 to 30% of worldwide mercury emissions. There is a need to control/reduce anthropogenic mercury emissions. Many mercury control technologies are available but their effectiveness is dependent on the chemical form of mercury, because different chemical forms of mercury have different physical and chemical properties. Mercury leaves the boiler in its elemental form but goes through various transformations in the post-combustion zone. There is a need to understand how fly ash and flue gas composition affect speciation, partitioning, and reactions of mercury under the full range of post-combustion zone conditions. This knowledge can then be used to predict the chemical transformation of mercury (elemental, oxidized or particulate) in the post combustion zone and thus help with the control of mercury emissions from coal-burning power plants. To accomplish this goal present study was conducted using five coal fly ashes. These ashes were characterized and their catalytic activity was compared under selected reaction conditions in a fixed bed reactor. Based on the results from these fly ash experiments, three key components (carbon, iron oxide and calcium oxide) were chosen. These three components were then used to prepare model fly ashes. Silica/alumina was used as a base for these model fly ashes. One, two or three component model fly ashes were then prepared to investigate mercury transformation reactions. The third set of experiments was performed with five different oxidation catalysts to further understand the mercury oxidation process. Based on the results of these three studies the key components were predicted for different fly ash compositions under variety of flue gas conditions. A fixed bed reactor system was used to conduct this study. In all the experiments, the inlet concentration of Hg0(g) was maintained at 35 mug/m 3 using a diffusion tube as the source of Hg0(g). All experiments were conducted using 4% O2 in nitrogen mix as a reaction gas, and other reactants (HCl, H2O and SO2, NO 2, Br2) were added as required. The fixed bed reactor was operated over a temperature range of 200 to 400°C. In each experiment, the reactor effluent was analyzed using the modified Ontario-Hydro method. After each experiment, fly ash particles were also analyzed for mercury. The results show that the ability of fly ash to adsorb and/or oxidize mercury is primarily dependent on its carbon, iron and calcium content. There can be either one or more than one key component at a particular temperature and flue gas condition. Surface area played a secondary role in effecting the mercury transformations when compared to the concentration of the key component in the fly ash. Amount carbon and surface area played a key important role in the adsorption of mercury. Increased concentration of gases in the flue gas other than oxygen and nitrogen caused decreased the amount of mercury adsorbed on carbon surface. Mercury adsorption by iron oxide primarily depended on the crystalline structure of iron oxide. alpha-iron oxide had no effect on mercury adsorption or oxidation under most of the flue gas conditions, but gamma-iron oxide adsorbed mercury under most of the flue gas conditions. Bromine is a very good oxidizing agent for mercury. But in the presence of calcium oxide containing fly ashes, all the oxidized mercury would be reduced to elemental form. Among the catalysts, it was observed that presence of free lattice chlorine in the catalyst was very important for the oxidation of mercury. But instead of using the catalyst alone, using it along with carbon may better serve the purpose by providing the adsorption surface for mercury and also some extra surface area for the reaction to occur (especially for fly ashes with low surface area).

  17. High temperature reactions of ceramics and metals with chlorine and oxygen

    NASA Technical Reports Server (NTRS)

    Jacobson, N. S.; Mcnallan, M. J.; Kreidler, E. R.

    1990-01-01

    The reactions of chlorine and oxygen with solids are complex and quite dependent on material and reaction conditions. However, there are four reaction schemes that describe many of these reactions. These are direct reaction of chlorine with the oxide layer, penetration of the oxide layer by chlorine, paralinear behavior where oxidation and chlorination are of comparable rates, and finally, gas phase reactions where the volatile chlorides react with oxygen. Examples of chlorine and oxygen reactions with cobalt, nickel, chromium, molybdenum, and silicon carbide illustrate each of these four reaction schemes.

  18. TRIMOLECULAR REACTIONS OF URANIUM HEXAFLUORIDE WITH WATER

    SciTech Connect

    Westbrook, M.; Becnel, J.; Garrison, S.

    2010-02-25

    The hydrolysis reaction of uranium hexafluoride (UF{sub 6}) is a key step in the synthesis of uranium dioxide (UO{sub 2}) powder for nuclear fuels. Mechanisms for the hydrolysis reactions are studied here with density functional theory and the Stuttgart small-core scalar relativistic pseudopotential and associated basis set for uranium. The reaction of a single UF{sub 6} molecule with a water molecule in the gas phase has been previously predicted to proceed over a relatively sizeable barrier of 78.2 kJ {center_dot} mol{sup -1}, indicating this reaction is only feasible at elevated temperatures. Given the observed formation of a second morphology for the UO{sub 2} product coupled with the observations of rapid, spontaneous hydrolysis at ambient conditions, an alternate reaction pathway must exist. In the present work, two trimolecular hydrolysis mechanisms are studied with density functional theory: (1) the reaction between two UF{sub 6} molecules and one water molecule, and (2) the reaction of two water molecules with a single UF{sub 6} molecule. The predicted reaction of two UF{sub 6} molecules with one water molecule displays an interesting 'fluorine-shuttle' mechanism, a significant energy barrier of 69.0 kJ {center_dot} mol{sup -1} to the formation of UF{sub 5}OH, and an enthalpy of reaction ({Delta}H{sub 298}) of +17.9 kJ {center_dot} mol{sup -1}. The reaction of a single UF{sub 6} molecule with two water molecules displays a 'proton-shuttle' mechanism, and is more favorable, having a slightly lower computed energy barrier of 58.9 kJ {center_dot} mol{sup -1} and an exothermic enthalpy of reaction ({Delta}H{sub 298}) of -13.9 kJ {center_dot} mol{sup -1}. The exothermic nature of the overall UF{sub 6} + 2 {center_dot} H{sub 2}O trimolecular reaction and the lowering of the barrier height with respect to the bimolecular reaction are encouraging; however, the sizable energy barrier indicates further study of the UF{sub 6} hydrolysis reaction mechanism is warranted to resolve the remaining discrepancies between the predicted mechanisms and experimental observations.

  19. ENVIRONMENTALLY FRIENDLIER SYNTHESIS USING ALTERNATIVE REACTION CONDITIONS AND MEDIA

    EPA Science Inventory

    The diverse nature of chemical universe requires various 'greener' strategic pathways in our quest towards attaining sustainability. A solvent-free approach that involves microwave (MW) exposure of neat reactants (undiluted) catalyzed by the surfaces of less-expensive and recycla...

  20. ENVIRONMENTALLY FRIENDLIER SYNTHESES USING MICROWAVES AND ALTERNATIVE REACTION CONDITIONS

    EPA Science Inventory

    A solvent-free approach that involves microwave (MW) exposure of neat reactants (undiluted) catalyzed by the surfaces of less-expensive and recyclable mineral supports such as alumina, silica, clay, or doped surfaces is presented which is applicable to a wide range of cleavage, c...

  1. CHEMICAL SYNTHESIS USING 'GREENER' ALTERNATIVE REACTION CONDITIONS AND MEDIA

    EPA Science Inventory

    The chemical research during the last decade has witnessed a paradigm shift towards "environmentally-friendly chemistry" more popularly known as "green chemistry" due to the increasing environmental concerns and legislative requirements to curb the release of chemical waste into ...

  2. GREENER ORGANIC SYNTHESES USING ALTERNATIVE REACTION CONDITIONS AND MEDIA

    EPA Science Inventory

    The diverse nature of chemical entities requires various green' strategic pathways in our quest towards attaining sustainability. A solvent-free approach that involves microwave (MW) exposure of neat reactants (undiluted) catalyzed by the surfaces of less-expensive and recyclable...

  3. REACTIONS OF FUEL NITROGEN COMPOUNDS UNDER CONDITIONS OF INERT PYROLYSIS

    EPA Science Inventory

    The paper describes the pyrolysis of fossil fuels and model nitrogen compounds in helium in a small quartz plow reactor, as part of a study of the chemical mechanisms involved in the conversion of fuel-nitrogen compounds to nitric oxide (NO) during combustion. Hydrogen cyanide (H...

  4. EFFICIENT CHEMICAL TRANSFORMATIONS USING ALTERNATIVE REACTION CONDITIONS AND MEDIA

    EPA Science Inventory

    The diverse nature of chemical entities requires various green' strategic pathways in our quest towards attaining sustainability. A solvent-free approach that involves microwave (MW) exposure of neat reactants (undiluted) catalyzed by the surfaces of less-expensive and recyclable...

  5. GREENER CHEMICAL SYNTHESES USING ALTERNATIVE REACTION CONDITIONS AND MEDIA

    EPA Science Inventory

    A solvent-free approach that involves microwave (MW) exposure of neat reactants (undiluted) catalyzed by the surfaces of recyclable mineral supports such as alumina, silica, clay, or 'doped' surfaces is presented which is applicable to a wide range of cleavage, condensation, cycl...

  6. Effective Analysis of Reaction Time Data

    ERIC Educational Resources Information Center

    Whelan, Robert

    2008-01-01

    Most analyses of reaction time (RT) data are conducted by using the statistical techniques with which psychologists are most familiar, such as analysis of variance on the sample mean. Unfortunately, these methods are usually inappropriate for RT data, because they have little power to detect genuine differences in RT between conditions. In…

  7. 14 CFR 25.485 - Side load conditions.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... accordance with figure 5 of appendix A. (b) Side loads of 0.8 of the vertical reaction (on one side) acting inward and 0.6 of the vertical reaction (on the other side) acting outward must be combined with one-half of the maximum vertical ground reactions obtained in the level landing conditions. These loads...

  8. 14 CFR 25.485 - Side load conditions.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... accordance with figure 5 of appendix A. (b) Side loads of 0.8 of the vertical reaction (on one side) acting inward and 0.6 of the vertical reaction (on the other side) acting outward must be combined with one-half of the maximum vertical ground reactions obtained in the level landing conditions. These loads...

  9. Eco-friendly polyethylene glycol promoted Michael addition reactions of ?,?-unsaturated carbonyl compounds

    EPA Science Inventory

    Abstract- Intra- and inter-nucleophilic addition reactions of different unsaturated compounds were found to be highly effective without any additives in PEG-400 as a recyclable reaction medium under neutral conditions.

  10. The Copper-nicotinamide complex: sustainable applications in coupling and cycloaddition reactions

    EPA Science Inventory

    Crystalline copper (II)-nicotinamide complex, synthesized via simple mixing of copper chloride and nicotinamide solution at room temperature, catalyzes the C-S, C-N bond forming and cycloaddition reactions under a variety of sustainable reaction conditions.

  11. Automated microreactor system for reaction development and online optimization of chemical processes

    E-print Network

    McMullen, Jonathan Patrick

    2010-01-01

    Developing the optimal conditions for chemical reactions that are common in fine chemical and pharmaceutics is a difficult and expensive task. Because syntheses in these fields have multiple reaction pathways, a significant ...

  12. CBr4-mediated cross-dehydrogenative coupling reaction of amines.

    PubMed

    Huo, Congde; Xie, Haisheng; Wu, Mingxia; Jia, Xiaodong; Wang, Xicun; Chen, Fengjuan; Tang, Jing

    2015-04-01

    A novel CBr4-mediated dehydrogenative Povarov/aromatization tandem reaction of glycine derivatives with alkenes, leading to complex quinoline derivatives, and a CBr4-mediated dehydrogenative C-H functionalization of N-aryl tetrahydroisoquinolines with nucleophiles to form C-C and C-P bonds are reported. The reactions were performed under very simple and mild reaction conditions; only CBr4 was used as a promoter. A plausible mechanism involving a radical process is proposed. PMID:25707447

  13. Self-organization effects in reactions of macromolecules

    NASA Astrophysics Data System (ADS)

    Christophorov, L. N.

    The ability of biomacromolecules to coordinate fast reaction events in their active centers with slow rearrangements of their structure is focused upon. Under real conditions of many sequential reaction turnovers of the macromolecule, the structural shifts caused by single turnovers can be of cumulative character. This, in turn, leads to drastic threshold-like changes of the reaction cycle. In this way, the creative role of dynamical substrate-conformation interactions in the formation of functional regimes of the macromolecule is consistently uncovered.

  14. Untoward penicillin reactions

    PubMed Central

    Guthe, T.; Idsöe, O.; Willcox, R. R.

    1958-01-01

    The literature on untoward reactions following the administration of penicillin is reviewed. These reactions, including a certain number of deaths which have been reported, are of particular interest to health administrations and to WHO in view of the large-scale programmes for controlling the treponematoses which are now under way—programmes affecting millions of people in many parts of the world. The most serious problems are anaphylactic sensitivity phenomena and superinfection or cross-infection with penicillin-resistant organisms, and the reactions involved range in intensity from the mildest to the fatal; the incidence of the latter is estimated at 0.1-0.3 per million injections. The authors point out that with increasing use of penicillin, more persons are likely to become sensitized and the number of reactions can therefore be expected to rise. The best prevention against such an increase is the restriction of the unnecessary use of penicillin. PMID:13596877

  15. An Illuminating Reaction.

    ERIC Educational Resources Information Center

    Matthews, Catherine E.

    1996-01-01

    Describes the use of carbide lights as an excellent mechanism for introducing or reviewing many basic chemistry concepts including elements and compounds, endothermic and exothermic reactions, physical and chemical changes, and balancing chemical equations. (JRH)

  16. Reaction wheel assembly

    NASA Technical Reports Server (NTRS)

    1976-01-01

    The fabrication and testing of three reaction wheels with associated drive and system monitoring electronics and brushless dc spin motors are discussed; the wheels are intended for use in a teleoperator simulator. Test results are included as graphs.

  17. Reactor for exothermic reactions

    DOEpatents

    Smith, L.A. Jr.; Hearn, D.; Jones, E.M. Jr.

    1993-03-02

    A liquid phase process is described for oligomerization of C[sub 4] and C[sub 5] isoolefins or the etherification thereof with C[sub 1] to C[sub 6] alcohols wherein the reactants are contacted in a reactor with a fixed bed acid cation exchange resin catalyst at an LHSV of 5 to 20, pressure of 0 to 400 psig and temperature of 120 to 300 F. Wherein the improvement is the operation of the reactor at a pressure to maintain the reaction mixture at its boiling point whereby at least a portion but less than all of the reaction mixture is vaporized. By operating at the boiling point and allowing a portion of the reaction mixture to vaporize, the exothermic heat of reaction is dissipated by the formation of more boil up and the temperature in the reactor is controlled.

  18. Vaccine Reaction Images

    MedlinePLUS

    ... Methyl bromide Methyl isocyanate Nicotine Nitrogen mustard Opioids Organic solvents Osmium tetroxide Paraquat Phosgene Phosgene oxime Phosphine ... Doing What You Can Do Blog: Public Health Matters What's New A - Z Index Vaccine Reaction Images* ...

  19. Reactor for exothermic reactions

    DOEpatents

    Smith, Jr., Lawrence A. (Bellaire, TX); Hearn, Dennis (Houston, TX); Jones, Jr., Edward M. (Friendswood, TX)

    1993-01-01

    A liquid phase process for oligomerization of C.sub.4 and C.sub.5 isoolefins or the etherification thereof with C.sub.1 to C.sub.6 alcohols wherein the reactants are contacted in a reactor with a fixed bed acid cation exchange resin catalyst at an LHSV of 5 to 20, pressure of 0 to 400 psig and temperature of 120.degree. to 300.degree. F. Wherein the improvement is the operation of the reactor at a pressure to maintain the reaction mixture at its boiling point whereby at least a portion but less than all of the reaction mixture is vaporized. By operating at the boiling point and allowing a portion of the reaction mixture to vaporize, the exothermic heat of reaction is dissipated by the formation of more boil up and the temperature in the reactor is controlled.

  20. Bad Reaction to Cosmetics?

    MedlinePLUS

    ... Home For Consumers Consumer Updates Bad Reaction to Cosmetics? Tell FDA Share Tweet Linkedin Pin it More ... M.D., director of the agency’s Office of Cosmetics and Colors. “So, consumers are one of FDA’s ...

  1. Iodine Clock Reaction.

    ERIC Educational Resources Information Center

    Mitchell, Richard S.

    1996-01-01

    Describes a combination of solutions that can be used in the study of kinetics using the iodine clock reaction. The combination slows down degradation of the prepared solutions and can be used successfully for several weeks. (JRH)

  2. ULTRAFAST REACTION Martin Gruebele

    E-print Network

    Zewail, Ahmed

    ULTRAFAST REACTION DYNAMICS Martin Gruebele and Ahmed H. Zewail With new lasertechniques andwith fellowand the dynamics. We use the term "transition state" in its Ahmed Zewail is LinusPauling Professorof

  3. Chemisorption And Precipitation Reactions

    EPA Science Inventory

    The transport and bioavailability of chemical components within soils is, in part, controlled by partitioning between solids and solution. General terms used to describe these partitioning reactions include chemisorption and precipitation. Chemisorption is inclusive of the suit...

  4. Effect of inclusion complex on nitrous acid reaction with flavonoids

    NASA Astrophysics Data System (ADS)

    Khalafi, Lida; Rafiee, Mohammad; Sedaghat, Sajjad

    2011-10-01

    The kinetic of the nitrous acid reactions with quercetin and catechin has been studied using spectrophotometric method in aqueous solution. The results show that these antioxidants participate in oxidation reactions with nitrous acid which is derived from protonation of nitrite ion in mild acidic conditions. Corresponding o-quinones as relatively stable products were detected by spectrophotometric techniques. pH dependence of the reactions has been examined and the rate constants of reactions were obtained by non-linear fitting of kinetic profiles. The effect of ?-cyclodextrin on the oxidation pathway was another object of this study. It is shown that ?-cyclodextrin has an inhibitory effect on the oxidation reaction. The rate constants of oxidation reactions for complexed forms and their stability constants were obtained based on changes in the reaction rates as a function of ?-cyclodextrin concentration.

  5. Reaction kinetics of hydrothermal carbonization of loblolly pine.

    PubMed

    Reza, M Toufiq; Yan, Wei; Uddin, M Helal; Lynam, Joan G; Hoekman, S Kent; Coronella, Charles J; Vásquez, Victor R

    2013-07-01

    Hydrothermal carbonization (HTC) is a pretreatment process to convert diverse feedstocks to homogeneous energy-dense solid fuels. Understanding of reaction kinetics is necessary for reactor design and optimization. In this study, the reaction kinetics and effects of particle size on HTC were investigated. Experiments were conducted in a novel two-chamber reactor maintaining isothermal conditions for 15s to 30 min reaction times. Loblolly pine was treated at 200, 230, and 260°C. During the first few minutes of reaction, the solid-product mass yield decreases rapidly while the calorific value increases rapidly. A simple reaction mechanism is proposed and validated, in which both hemicellulose and cellulose degrade in parallel first-order reactions. Activation energy of hemicellulose and cellulose degradation were determined to be 30 and 73 kJ/mol, respectively. For short HTC times, both reaction and diffusion effects were observed. PMID:23651600

  6. Iodine Oxide Thermite Reactions: Physical and Biological Effects

    NASA Astrophysics Data System (ADS)

    Russell, Rod; Pantoya, Michelle; Bless, Stephan; Clark, William

    2009-06-01

    We investigated the potential for some thermite-like material reactions to kill bacteria spores. Iodine oxides and silver oxides react vigorously with metals like aluminum, tantalum, and neodymium. These reactions theoretically produce temperatures as high as 8000K, leading to vaporization of the reactants, producing very hot iodine and/or silver gases. We performed a series of computations and experiments to characterize these reactions under both quasi-static and ballistic impact conditions. Criteria for impact reaction were established. Measurements of temperature and pressure changes and chemical evolution will be reported. Basic combustion characterizations of these reactions, such as thermal equilibrium analysis and reaction propagation rates as well as ignition sensitivity, will be discussed. Additionally, testing protocols were developed to characterize the biocidal effects of these reactive materials on B. subtilis spores. The evidence from these tests indicates that these reactions produce heat, pressure, and highly biocidal gases.

  7. Sarcoma-associated sarcoid reaction: Report of cutaneous sarcoid reaction in a patient with liposarcoma

    PubMed Central

    Beutler, Bryce D; Cohen, Philip R

    2015-01-01

    Sarcoidosis is a systemic inflammatory condition in which noncaseating epithelioid cell granulomas appear within one or several body sites. Sarcoid reaction (also referred to as sarcoidal or sarcoid-like reaction) occurs in patients who do not fulfill the diagnostic criteria for systemic sarcoidosis but present with similar clinical and histological features. As sarcoma-associated sarcoid reactions are rare, we describe the features of sarcoid reaction that developed in a man with liposarcoma and summarize reports of other oncology patients with sarcoma-associated sarcoid reactions. A 68-year-old man with retroperitoneal liposarcoma presented for evaluation of erythematous dermal plaques on his left leg. Microscopic examination of a tissue specimen revealed multiple epithelioid granulomas in the superficial and mid-reticular dermis. Correlation of the clinical presentation and histopathologic findings established a diagnosis of liposarcoma-associated cutaneous sarcoid reaction. Sarcoid reactions have been described in only seven individuals with sarcoma, including two patients with leiomyosarcoma and one patient with either carcinosarcoma, Kaposi sarcoma, liposarcoma, malignant peripheral nerve sheath tumor, rhabdosarcoma, or synovial sarcoma. Sarcoidal granulomas most commonly develop within the locoregional draining lymph nodes. Sarcoid reactions may also affect other organs, such as the lungs, skin, and spleen. PMID:26677448

  8. Sarcoma-associated sarcoid reaction: Report of cutaneous sarcoid reaction in a patient with liposarcoma.

    PubMed

    Beutler, Bryce D; Cohen, Philip R

    2015-12-16

    Sarcoidosis is a systemic inflammatory condition in which noncaseating epithelioid cell granulomas appear within one or several body sites. Sarcoid reaction (also referred to as sarcoidal or sarcoid-like reaction) occurs in patients who do not fulfill the diagnostic criteria for systemic sarcoidosis but present with similar clinical and histological features. As sarcoma-associated sarcoid reactions are rare, we describe the features of sarcoid reaction that developed in a man with liposarcoma and summarize reports of other oncology patients with sarcoma-associated sarcoid reactions. A 68-year-old man with retroperitoneal liposarcoma presented for evaluation of erythematous dermal plaques on his left leg. Microscopic examination of a tissue specimen revealed multiple epithelioid granulomas in the superficial and mid-reticular dermis. Correlation of the clinical presentation and histopathologic findings established a diagnosis of liposarcoma-associated cutaneous sarcoid reaction. Sarcoid reactions have been described in only seven individuals with sarcoma, including two patients with leiomyosarcoma and one patient with either carcinosarcoma, Kaposi sarcoma, liposarcoma, malignant peripheral nerve sheath tumor, rhabdosarcoma, or synovial sarcoma. Sarcoidal granulomas most commonly develop within the locoregional draining lymph nodes. Sarcoid reactions may also affect other organs, such as the lungs, skin, and spleen. PMID:26677448

  9. Chemical reactions at aqueous interfaces

    NASA Astrophysics Data System (ADS)

    Vecitis, Chad David

    2009-12-01

    Interfaces or phase boundaries are a unique chemical environment relative to individual gas, liquid, or solid phases. Interfacial reaction mechanisms and kinetics are often at variance with homogeneous chemistry due to mass transfer, molecular orientation, and catalytic effects. Aqueous interfaces are a common subject of environmental science and engineering research, and three environmentally relevant aqueous interfaces are investigated in this thesis: 1) fluorochemical sonochemistry (bubble-water), 2) aqueous aerosol ozonation (gas-water droplet), and 3) electrolytic hydrogen production and simultaneous organic oxidation (water-metal/semiconductor). Direct interfacial analysis under environmentally relevant conditions is difficult, since most surface-specific techniques require relatively `extreme' conditions. Thus, the experimental investigations here focus on the development of chemical reactors and analytical techniques for the completion of time/concentration-dependent measurements of reactants and their products. Kinetic modeling, estimations, and/or correlations were used to extract information on interfacially relevant processes. We found that interfacial chemistry was determined to be the rate-limiting step to a subsequent series of relatively fast homogeneous reactions, for example: 1) Pyrolytic cleavage of the ionic headgroup of perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA) adsorbed to cavitating bubble-water interfaces during sonolysis was the rate-determining step in transformation to their inorganic constituents carbon monoxide, carbon dioxide, and fluoride; 2) ozone oxidation of aqueous iodide to hypoiodous acid at the aerosol-gas interface is the rate-determining step in the oxidation of bromide and chloride to dihalogens; 3) Electrolytic oxidation of anodic titanol surface groups is rate-limiting for the overall oxidation of organics by the dichloride radical. We also found chemistry unique to the interface, for example: 1) Adsorption of dilute PFOS(aq) and PFOA(aq) to acoustically cavitating bubble interfaces was greater than equilibrium expectations due to high-velocity bubble radial oscillations; 2) Relative ozone oxidation kinetics of aqueous iodide, sulfite, and thiosulfate were at variance with previously reported bulk aqueous kinetics; 3) Organics that directly chelated with the anode surface were oxidized by direct electron transfer, resulting in immediate carbon dioxide production but slower overall oxidation kinetics. Chemical reactions at aqueous interfaces can be the rate-limiting step of a reaction network and often display novel mechanisms and kinetics as compared to homogeneous chemistry.

  10. Stellar evolution and the triple-? reactions

    SciTech Connect

    Suda, Takuma

    2014-05-02

    Nuclear reaction rates play a crucial role in the evolution of stars. For low-mass stars, the triple-? reaction controls the helium burning stars in the red giant and asymptotic giant branch (AGB) phase. More importantly, the cross section of the triple-? reaction has a great impact on the helium ignition at the center of the electron degenerate helium core of red giants and on the helium shell flashes of AGB stars. It is to be noted that stellar evolution models are influenced not only by the value of the cross section, but also by the temperature dependence of the reaction rate. In this paper, I present the impact of the triple-? reaction rates on the evolution of low-mass metal-free stars and intermediate-mass AGB stars. According to the previous study, the constraint on the triple-? reaction rate is derived based on stellar evolution theory. It is found that the recent revisions of the rate proposed by nuclear physics calculations satisfy the condition for the ignition of the helium core flash in low-mass stars.

  11. Reactions of butadiyne. 1: The reaction with hydrogen atoms

    NASA Technical Reports Server (NTRS)

    Schwanebeck, W.; Warnatz, J.

    1984-01-01

    The reaction of hydrogen (H) atoms with butadiene (C4H2) was studied at room temperature in a pressure range between w mbar and 10 mbar. The primary step was an addition of H to C4H2 which is in its high pressure range at p 1 mbar. Under these conditions the following addition of a second H atom lies in the transition region between low and high pressure range. Vibrationally excited C4H4 can be deactivated to form buten-(1)-yne-(3)(C4H4) or decomposes into two C2H2 molecules. The rate constant at room temperature for primary step is given. The second order rate constant for the consumption of buten-(1)-yne-(3) is an H atom excess at room temperature is given.

  12. Reaction Mechanisms Effects of Bending Excitation on the Reaction of

    E-print Network

    Zare, Richard N.

    Reaction Mechanisms Effects of Bending Excitation on the Reaction of Chlorine Atoms with Methane,* and Konstantin Vodopyanov Many chemical reactions are accelerated by heating the reagents. This effect is caused, and rotational degrees of freedom that ultimately becomes available for overcoming the reaction barrier. Which

  13. Phase and chemical equilibria in the transesterification reaction of vegetable oils with supercritical lower alcohols

    NASA Astrophysics Data System (ADS)

    Anikeev, V. I.; Stepanov, D. A.; Ermakova, A.

    2011-08-01

    Calculations of thermodynamic data are performed for fatty acid triglycerides, free fatty acids, and fatty acid methyl esters, participants of the transesterification reaction of vegetable oils that occurs in methanol. Using the obtained thermodynamic parameters, the phase diagrams for the reaction mixture are constructed, and the chemical equilibria of the esterification reaction of free fatty acids and the transesterification reaction of fatty acid triglycerides attained upon treatment with supercritical methanol are determined. Relying on our analysis of the obtained equilibria for the esterification reaction of fatty acids and the transesterification reaction of triglycerides attained upon treatment with lower alcohols, we select the optimum conditions for performing the reaction in practice.

  14. Fear potentiated startle at short intervals following conditioned stimulus onset during delay but not trace conditioning.

    PubMed

    Asli, Ole; Kulvedrøsten, Silje; Solbakken, Line E; Flaten, Magne Arve

    2009-07-01

    The latency of conditioned fear after delay and trace conditioning was investigated. Some argue that delay conditioning is not dependent on awareness. In contrast, trace conditioning, where there is a gap between the conditioned stimulus (CS) and the unconditioned stimulus (US), is assumed to be dependent on awareness. In the present study, a tone CS signaled a noise US presented 1000 ms after CS onset in the delay conditioning group. In the trace conditioning group, a 200-ms tone CS was followed by an 800-ms gap prior to US presentation. Fear-potentiated startle should be seen at shorter intervals after delay conditioning compared to trace conditioning. Analyses showed increased startle at 30, 50, 100, and 150 ms after CS onset following delay conditioning compared to trace conditioning. This implies that fear-relevant stimuli elicit physiological reactions before extended processing of the stimuli occur, following delay, but not trace conditioning. PMID:19386051

  15. Kinugasa reactions in water: from green chemistry to bioorthogonal labelling.

    PubMed

    Chigrinova, Mariya; MacKenzie, Douglas A; Sherratt, Allison R; Cheung, Lawrence L W; Pezacki, John Paul; Pezacki, Paul

    2015-01-01

    The Kinugasa reaction has become an efficient method for the direct synthesis of ?-lactams from substituted nitrones and copper(I) acetylides. In recent years, the reaction scope has been expanded to include the use of water as the solvent, and with micelle-promoted [3+2] cycloadditions followed by rearrangement furnishing high yields of ?-lactams. The high yields of stable products under aqueous conditions render the modified Kinugasa reaction amenable to metabolic labelling and bioorthogonal applications. Herein, the development of methods for use of the Kinugasa reaction in aqueous media is reviewed, with emphasis on its potential use as a bioorthogonal coupling strategy. PMID:25913933

  16. Mitsunobu Reactions Catalytic in Phosphine and a Fully Catalytic System.

    PubMed

    Buonomo, Joseph A; Aldrich, Courtney C

    2015-10-26

    The Mitsunobu reaction is renowned for its mild reaction conditions and broad substrate tolerance, but has limited utility in process chemistry and industrial applications due to poor atom economy and the generation of stoichiometric phosphine oxide and hydrazine by-products that complicate purification. A catalytic Mitsunobu reaction using innocuous reagents to recycle these by-products would overcome both of these shortcomings. Herein we report a protocol that is catalytic in phosphine (1-phenylphospholane) employing phenylsilane to recycle the catalyst. Integration of this phosphine catalytic cycle with Taniguchi's azocarboxylate catalytic system provided the first fully catalytic Mitsunobu reaction. PMID:26347115

  17. Moist air reaction with excess UF{sub 6}

    SciTech Connect

    Reiner, R.H.

    1989-08-01

    The moist air reaction with uranium hexafluoride (UF{sub 6}) has been studied at conditions simulating UF{sub 6} hydrolysis during air inleakage in the cascade. In excess UF{sub 6}, the reaction mechanism is more complicated than predicted by the simple gas-phase reaction of one UF{sub 6} molecule with two water molecules to form uranyl fluoride and hydrogen fluoride. The initial UF{sub 6} consumption is significantly greater than predicted, suggesting that a metastable uranium compound is formed during the hydrolysis reaction. This intermediate uranium compound may facilitate uranyl fluoride transport in the cascade.

  18. Neurohumoral reactions to long-term vestibular stimulation in man.

    PubMed

    Nichiporuk, I A; Rapotkov, A N; Orlov, O I; Grigoriev, A I

    1993-02-01

    The main purposes of present work were: 1) to examine neurohumoral reactions to long-term vestibular stimulation provocative for MS symptoms in man; 2) to compare the peculiarities of neuroendocrine reactions to short-term and to long-term vestibular stimulation; 3) to analyze the received results from the position of neuroendocrine adaptive reactions biological conformity to natural laws, and its physiological importance for human organisms; 4) to make some prognostic points of neurohumoral reaction changes on health and capacity for work in subjects influenced by professional conditions, provocative for MS manifestation development. PMID:11538529

  19. Mitsunobu Reactions Catalytic in Phosphine and a Fully Catalytic System

    PubMed Central

    Buonomo, Joseph A; Aldrich, Courtney C

    2015-01-01

    The Mitsunobu reaction is renowned for its mild reaction conditions and broad substrate tolerance, but has limited utility in process chemistry and industrial applications due to poor atom economy and the generation of stoichiometric phosphine oxide and hydrazine by-products that complicate purification. A catalytic Mitsunobu reaction using innocuous reagents to recycle these by-products would overcome both of these shortcomings. Herein we report a protocol that is catalytic in phosphine (1-phenylphospholane) employing phenylsilane to recycle the catalyst. Integration of this phosphine catalytic cycle with Taniguchi’s azocarboxylate catalytic system provided the first fully catalytic Mitsunobu reaction. PMID:26347115

  20. Paraneoplastic leukemoid reaction in pancreatic cancer: A case report.

    PubMed

    Dos Santos, Mélanie; Bouhier, Karine; Dao, Manh-Thong

    2015-10-15

    Paraneoplastic leukemoid reaction is a rare syndrome defined by a leukocyte count exceeding 50 Giga/Liter (G/L), mostly described with progressive lung or renal carcinoma. We report a case of a 68-year-old man with recurrent pancreatic carcinoma presenting a leukemoid reaction with a white blood cell count of 63.87 G/L without identified infectious, iatrogenic or hematologic causes. His overall condition quickly degraded and he died three weeks after the discovery of the leukemoid reaction. This is the first case in French literature of leukemoid reaction in a patient with pancreatic carcinoma with poor prognostic value. PMID:26483880

  1. Modular modification of xylan with UV-initiated thiol-ene reaction.

    PubMed

    Nurmi, Leena; Salminen, Reeta; Setälä, Harri

    2015-03-01

    Birch xylan was functionalized with various thiols through UV initiated radical thiol-ene reaction under mild conditions. Xylan was allylated through etherification with allyl glycidyl ether under alkaline conditions. The allylated xylan was then reacted with thiols containing varying functional groups: trimethylbenzyl mercaptan, dodecanethiol, thioglycolic acid, L-cysteine and cysteamine hydrochloride. The reactions were conducted under homogeneous conditions at room temperature, either in water (hydrophilic thiols) or in DMF (hydrophobic thiols). The effect of reaction parameters to the functionalization efficiency was studied, including, for example, thiol excess, thiol character, initiator amount and reaction mixture concentration. The reactions were fast and 100% conversion of allyl groups was reached in most cases, sometimes already within 10 min. Water as solvent resulted generally in faster reactions when compared to DMF, and it was possible to conduct the aqueous reaction even without added UV initiator. It was also possible to incorporate two functionalities simultaneously during one reaction into the xylan structure. PMID:25665780

  2. Velocity pump reaction turbine

    DOEpatents

    House, Palmer A. (Walnut Creek, CA)

    1984-01-01

    An expanding hydraulic/two-phase velocity pump reaction turbine including a dual concentric rotor configuration with an inter-rotor annular flow channel in which the inner rotor is mechanically driven by the outer rotor. In another embodiment, the inner rotor is immobilized and provided with gas recovery ports on its outer surface by means of which gas in solution may be recovered. This velocity pump reaction turbine configuration is capable of potential energy conversion efficiencies of up to 70%, and is particularly suited for geothermal applications.

  3. Velocity pump reaction turbine

    DOEpatents

    House, Palmer A. (Walnut Creek, CA)

    1982-01-01

    An expanding hydraulic/two-phase velocity pump reaction turbine including a dual concentric rotor configuration with an inter-rotor annular flow channel in which the inner rotor is mechanically driven by the outer rotor. In another embodiment, the inner rotor is immobilized and provided with gas recovery ports on its outer surface by means of which gas in solution may be recovered. This velocity pump reaction turbine configuration is capable of potential energy conversion efficiencies of up to 70%, and is particularly suited for geothermal applications.

  4. Accretion with back reaction

    E-print Network

    Vyacheslav I. Dokuchaev; Yury N. Eroshenko

    2011-12-19

    We calculate analytically a back reaction of the stationary spherical accretion flow near the event horizon and near the inner Cauchy horizon of the charged black hole. It is shown that corresponding back-reaction corrections to the black hole metric depend only on the fluid accretion rate and diverge in the case of an extremely charged black hole. In result, the test fluid approximation for stationary accretion is violated for extreme black holes. This behavior of the accreting black hole is in accordance with the third law of black hole thermodynamics, forbidding the practical attainability of the extreme state.

  5. Friday After Thanksgiving: Chain Reaction

    E-print Network

    Oliva, Aude

    Friday After Thanksgiving: Chain Reaction 2014 Guidelines Your link in the chain reaction should a cup of water. Your link's action must be repeatable, so please test your chain reaction before, whimsical, or elegant. There will be a section of the Chain Reaction connected by tubes to pass a single

  6. NUCLEAR REACTIONS Lecture 11-VI

    E-print Network

    Smith, Nathanael J.

    NUCLEAR REACTIONS Lecture 11-VI #12;General setup 2 Radioactive decay ­ a nucleus spontaneously decays. The only particle present before the decay is the parent nucleus. Nuclear reaction ­ an incident shorthand for nuclear reactions Examples Write the following reactions using the shorthand notation. (Note

  7. Inorganic Reaction Mechanisms. Part I

    ERIC Educational Resources Information Center

    Cooke, D. O.

    1976-01-01

    Provides a collection of data on the mechanistic aspects of inorganic chemical reactions. Wherever possible includes procedures for classroom demonstration or student project work. The material covered includes gas phase reactions, reactions in solution, mechanisms of electron transfer, the reaction between iron III and iodine, and hydrolysis. (GS)

  8. Different reaction mechanisms for cis- and trans-prenyltransferases

    SciTech Connect

    Lu Yenpin; Liu Hunge; Liang, P-H.

    2009-02-06

    Octaprenyl diphosphate synthase (OPPs) and undecaprenyl diphosphate synthases (UPPs) catalyze consecutive condensation reactions of farnesyl diphosphate (FPP) with 5 and 8 isopentenyl diphosphate (IPP) to generate C{sub 40} and C{sub 55} products with trans- and cis-double bonds, respectively. In this study, we used IPP analogue, 3-bromo-3-butenyl diphosphate (Br-IPP), in conjunction with radiolabeled FPP, to probe the reaction mechanisms of the two prenyltransferases. Using this alternative substrate with electron-withdrawing bromo group at the C3 position to slow down the condensation step, trapping of farnesol in the OPPs reaction from radiolabeled FPP under basic condition was observed, consistent with a sequential mechanism. In contrast, UPPs reaction yielded no farnesyl carbocation intermediate under the same condition with radiolabeled FPP and Br-IPP, indicating a concerted mechanism. Our data demonstrate the different reaction mechanisms for cis- and tran-prenyltransferases although they share the same substrates.

  9. A taxonomy of integral reaction path analysis

    SciTech Connect

    Grcar, Joseph F.; Day, Marcus S.; Bell, John B.

    2004-12-23

    W. C. Gardiner observed that achieving understanding through combustion modeling is limited by the ability to recognize the implications of what has been computed and to draw conclusions about the elementary steps underlying the reaction mechanism. This difficulty can be overcome in part by making better use of reaction path analysis in the context of multidimensional flame simulations. Following a survey of current practice, an integral reaction flux is formulated in terms of conserved scalars that can be calculated in a fully automated way. Conditional analyses are then introduced, and a taxonomy for bidirectional path analysis is explored. Many examples illustrate the resulting path analysis and uncover some new results about nonpremixed methane-air laminar jets.

  10. Cell Simulation Package for Reactions and Diffusion

    Energy Science and Technology Software Center (ESTSC)

    2005-04-01

    ChemCell is a simulation package designed for modeling signalling, regulatory, and metabolic pathways in biological cells. It reads input flies that describe the geomeby of the cell and positions of particles that represent proteins, protein complexes, and other bio-molecules. It also reads in lists of reactions and associated rates and other boundary condition information. ChemCell then models the reaction and diffusion of these particles within the cellular geometry as they interact overtime. It produces statisticalmore »information about the state of the cell, as well as snapshots of the reaction network. We anticipate ChemCell will be useful to researchers who wish to perform spatio-temporal modeling of cellular processes and who wish to develop new models or algorithms to add to the code. Thus ChemCell is also designed to be easy to modify and extend. The ChemCell package includes auxiliary codes for setting up problems and analyzing output.« less

  11. Polymerase chain reaction system

    DOEpatents

    Benett, William J.; Richards, James B.; Stratton, Paul L.; Hadley, Dean R.; Milanovich, Fred P.; Belgrader, Phil; Meyer, Peter L.

    2004-03-02

    A portable polymerase chain reaction DNA amplification and detection system includes one or more chamber modules. Each module supports a duplex assay of a biological sample. Each module has two parallel interrogation ports with a linear optical system. The system is capable of being handheld.

  12. Chain Reaction Polymerization.

    ERIC Educational Resources Information Center

    McGrath, James E.

    1981-01-01

    The salient features and importance of chain-reaction polymerization are discussed, including such topics as the thermodynamics of polymerization, free-radical polymerization kinetics, radical polymerization processes, copolymers, and free-radical chain, anionic, cationic, coordination, and ring-opening polymerizations. (JN)

  13. Reaction product imaging

    SciTech Connect

    Chandler, D.W.

    1993-12-01

    Over the past few years the author has investigated the photochemistry of small molecules using the photofragment imaging technique. Bond energies, spectroscopy of radicals, dissociation dynamics and branching ratios are examples of information obtained by this technique. Along with extending the technique to the study of bimolecular reactions, efforts to make the technique as quantitative as possible have been the focus of the research effort. To this end, the author has measured the bond energy of the C-H bond in acetylene, branching ratios in the dissociation of HI, the energetics of CH{sub 3}Br, CD{sub 3}Br, C{sub 2}H{sub 5}Br and C{sub 2}H{sub 5}OBr dissociation, and the alignment of the CD{sub 3} fragment from CD{sub 3}I photolysis. In an effort to extend the technique to bimolecular reactions the author has studied the reaction of H with HI and the isotopic exchange reaction between H and D{sub 2}.

  14. Polymer Reaction & Colloidal Engineering

    E-print Network

    Giger, Christine

    Polymer Reaction & Colloidal Engineering Research Profile The Morbidelli Group is carrying out research in numerous areas related to polymer and colloid science and enginee- ring. Our research activity combines a variety of experimen- tal techniques for polymers and particles characterization with advanced

  15. Reaction Formulation: A Bibliography.

    ERIC Educational Resources Information Center

    Pedrini, D. T.; Pedrini, Bonnie C.

    Reaction formation was studied by Sigmund Freud. This defense mechanism may be related to repression, substitution, reversal, and compensation (or over-compensation). Alfred Adler considered compensation a basic process in his individual psychology. Anna Freud discussed some defense mechanisms, and Bibring, Dwyer, Huntington, and Valenstein…

  16. Balancing Equations Chemical Reactions

    E-print Network

    Heller, Barbara

    Balancing Equations Chemical Reactions #12;Chemical Equations · A chemical equation describes what of the participants (solid, liquid, gas, aqueous) and the amount of each substance. #12;Balancing of Equations · To balance a chemical equation, you have to establish a mathematical relationship between the quantity

  17. Chemical Reactions at Surfaces

    SciTech Connect

    Michael Henderson and Nancy Ryan Gray

    2010-04-14

    Chemical reactions at surfaces underlie some of the most important processes of today, including catalysis, energy conversion, microelectronics, human health and the environment. Understanding surface chemical reactions at a fundamental level is at the core of the field of surface science. The Gordon Research Conference on Chemical Reactions at Surfaces is one of the premiere meetings in the field. The program this year will cover a broad range of topics, including heterogeneous catalysis and surface chemistry, surfaces in environmental chemistry and energy conversion, reactions at the liquid-solid and liquid-gas interface, electronic materials growth and surface modification, biological interfaces, and electrons and photons at surfaces. An exciting program is planned, with contributions from outstanding speakers and discussion leaders from the international scientific community. The conference provides a dynamic environment with ample time for discussion and interaction. Attendees are encouraged to present posters; the poster sessions are historically well attended and stimulate additional discussions. The conference provides an excellent opportunity for junior researchers (e.g. graduate students or postdocs) to present their work and interact with established leaders in the field.

  18. Examples 01 Photochemical Reactions

    E-print Network

    Simons, Jack

    is forbidden by symmetry. Recall that in C2vsymmetry the orbital-correlation diagram for this reaction species in terms of symmetry orbitals. Using the reverse of the transformation erom a localized orbital to a symmetry-adapted orbital, the proposed experimentally prepared 1I"1(1I"1I"*)Astale (in which A and' B refer

  19. Quinoprotein-catalysed reactions.

    PubMed Central

    Anthony, C

    1996-01-01

    This review is concerned with the structure and function of the quinoprotein enzymes, sometimes called quinoenzymes. These have prosthetic groups containing quinones, the name thus being analogous to the flavoproteins containing flavin prosthetic groups. Pyrrolo-quinoline quinone (PQQ) is non-covalently attached, whereas tryptophan tryptophylquinone (TTQ), topaquinone (TPQ) and lysine tyrosylquinone (LTQ) are derived from amino acid residues in the backbone of the enzymes. The mechanisms of the quinoproteins are reviewed and related to their recently determined three-dimensional structures. As expected, the quinone structures in the prosthetic groups play important roles in the mechanisms. A second common feature is the presence of a catalytic base (aspartate) at the active site which initiates the reactions by abstracting a proton from the substrate, and it is likely to be involved in multiple reactions in the mechanism. A third common feature of these enzymes is that the first part of the reaction produces a reduced prosthetic group; this part of the mechanism is fairly well understood. This is followed by an oxidative phase involving electron transfer reactions which remain poorly understood. In both types of dehydrogenase (containing PQQ and TTQ), electrons must pass from the reduced prosthetic group to redox centres in a second recipient protein (or protein domain), whereas in amine oxidases (containing TPQ or LTQ), electrons must be transferred to molecular oxygen by way of a redox-active copper ion in the protein. PMID:9003352

  20. Exocharmic Reactions up Close

    ERIC Educational Resources Information Center

    Ramette, R. W.

    2007-01-01

    The exocharmic reactions that can be observed microscopically are discussed. The students can discover the optimal concentration of an acidic lead nitrate solution, so that a crystal of potassium iodide, nudged to the edge of a drop, results in glinting golden hexagons of lead iodide.

  1. Plasmon-driven sequential chemical reactions in an aqueous environment

    NASA Astrophysics Data System (ADS)

    Zhang, Xin; Wang, Peijie; Zhang, Zhenglong; Fang, Yurui; Sun, Mengtao

    2014-06-01

    Plasmon-driven sequential chemical reactions were successfully realized in an aqueous environment. In an electrochemical environment, sequential chemical reactions were driven by an applied potential and laser irradiation. Furthermore, the rate of the chemical reaction was controlled via pH, which provides indirect evidence that the hot electrons generated from plasmon decay play an important role in plasmon-driven chemical reactions. In acidic conditions, the hot electrons were captured by the abundant H+ in the aqueous environment, which prevented the chemical reaction. The developed plasmon-driven chemical reactions in an aqueous environment will significantly expand the applications of plasmon chemistry and may provide a promising avenue for green chemistry using plasmon catalysis in aqueous environments under irradiation by sunlight.

  2. Transfer reactions with HELIOS

    NASA Astrophysics Data System (ADS)

    Wuosmaa, Alan H.

    2011-04-01

    Nucleon-transfer reactions have formed the backbone of nuclear-structure studies for several decades, providing a wealth of information about the energies, quantum numbers, and wave functions of single-particle states in nuclei throughout the nuclear chart. Current trends in nuclear-structure physics and the modern emphasis on properties of neutron-rich nuclei far from stability have renewed interest in such transfer reactions with radioactive beams. Here, the usual combination of light beam and heavy target cannot be used, and measurements must be performed in ``inverse kinematics,'' with a heavy, unstable beam incident on a light target. This arrangement introduces several technical difficulties, including the identification of the reaction products and the resolution of the states of interest in the residual nuclei. A new device, HELIOS (the HELIcal Orbit Spectrometer) at the ATLAS facility at Argonne National Laboratory, solves many of the problems encountered with inverse kinematics including particle identification and energy resolution in the center-of-mass frame. The device utilizes the uniform magnetic field of a large, superconducting solenoid to transport light reaction products from the target to a linear array of position-sensitive silicon detectors. The properties of HELIOS will be described, and examples from the initial research program that focuses on neutron transfer with the (d,p) reaction, using both stable and unstable beams with mass A = 11 to 136, will be presented. Work supported by the U. S. Department of Energy, Office of Nuclear Physics under contract numbers DE-FG02-04ER41320 (WMU) and DE-AC02-06CH11357 (ANL).

  3. Photoneutron reactions in astrophysics

    SciTech Connect

    Varlamov, V. V. Ishkhanov, B. S.; Orlin, V. N.; Peskov, N. N.; Stopani, K. A.

    2014-12-15

    Among key problems in nuclear astrophysics, that of obtaining deeper insight into the mechanism of synthesis of chemical elements is of paramount importance. The majority of heavy elements existing in nature are produced in stars via radiative neutron capture in so-called s- and r processes, which are, respectively, slow and fast, in relation to competing ?{sup ?}-decay processes. At the same time, we know 35 neutron-deficient so-called bypassed p-nuclei that lie between {sup 74}Se and {sup 196}Hg and which cannot originate from the aforementioned s- and r-processes. Their production is possible in (?, n), (?, p), or (?, ?) photonuclear reactions. In view of this, data on photoneutron reactions play an important role in predicting and describing processes leading to the production of p-nuclei. Interest in determining cross sections for photoneutron reactions in the threshold energy region, which is of particular importance for astrophysics, has grown substantially in recent years. The use of modern sources of quasimonoenergetic photons obtained in processes of inverse Compton laser-radiation scattering on relativistic electronsmakes it possible to reveal rather interesting special features of respective cross sections, manifestations of pygmy E1 and M1 resonances, or the production of nuclei in isomeric states, on one hand, and to revisit the problem of systematic discrepancies between data on reaction cross sections from experiments of different types, on the other hand. Data obtained on the basis of our new experimental-theoretical approach to evaluating cross sections for partial photoneutron reactions are invoked in considering these problems.

  4. Citrus Peel Additives for One-Pot Triazole Formation by Decarboxylation, Nucleophilic Substitution, and Azide-Alkyne Cycloaddition Reactions

    ERIC Educational Resources Information Center

    Mendes, Desiree E.; Schoffstall, Allen M.

    2011-01-01

    This undergraduate organic laboratory experiment consists of three different reactions occurring in the same flask: a cycloaddition reaction, preceded by decarboxylation and nucleophilic substitution reactions. The decarboxylation and cycloaddition reactions occur using identical Cu(I) catalyst and conditions. Orange, lemon, and other citrus fruit…

  5. Reaction products of ozone: a review

    SciTech Connect

    Glaze, W.H.

    1986-11-01

    The reaction products of ozone that form during the oxidation of compounds found in aqueous media are reviewed. Reaction products of ozone are well documented only for a limited number of substrates, and mechanistic information is quite rare. Decomposition of ozone during its reactions, sometimes induced by matrix impurities or by the by-products of the reactions, will generate highly reactive hydroxyl radicals. Thus, even reactions occurring at pH less than 7 may have radical character. More complete destruction of organic substrates may be enhanced by using catalysts, such as ultraviolet radiation or hydrogen peroxide, to accelerate radical formation. However, complete mineralization is generally not practical economically, so partially oxidized by-products can be expected under typical treatment conditions. Ozone by-products tend to be oxygenated compounds that are usually, but not always, more biodegradable and less toxic than xenobiotic precursors. Of particular interest are hydroperoxide by-products, which may have escaped detection because of their lability, and unsaturated aldehydes. Inorganic by-products tend to be in high oxidation states, which in some cases (e.g., some metallic elements) may lead to enhanced removal by flocculation and sedimentation. In other cases oxidation may lead to formation of reactive species such as hypobromous acid from bromide ion or permanganate from manganous ion. In general, more research is required before a valid assessment of the risks of ozone by-products can be made. 40 references.

  6. Iridium-Catalyzed Hydrogen Transfer Reactions

    NASA Astrophysics Data System (ADS)

    Saidi, Ourida; Williams, Jonathan M. J.

    This chapter describes the application of iridium complexes to catalytic hydrogen transfer reactions. Transfer hydrogenation reactions provide an alternative to direct hydrogenation for the reduction of a range of substrates. A hydrogen donor, typically an alcohol or formic acid, can be used as the source of hydrogen for the reduction of carbonyl compounds, imines, and alkenes. Heteroaromatic compounds and even carbon dioxide have also been reduced by transfer hydrogenation reactions. In the reverse process, the oxidation of alcohols to carbonyl compounds can be achieved by iridium-catalyzed hydrogen transfer reactions, where a ketone or alkene is used as a suitable hydrogen acceptor. The reversible nature of many hydrogen transfer processes has been exploited for the racemization of alcohols, where temporary removal of hydrogen generates an achiral ketone intermediate. In addition, there is a growing body of work where temporary removal of hydrogen provides an opportunity for using alcohols as alkylating agents. In this chemistry, an iridium catalyst "borrows" hydrogen from an alcohol to give an aldehyde or ketone intermediate, which can be transformed into either an imine or alkene under the reaction conditions. Return of the hydrogen from the catalyst provides methodology for the formation of amines or C-C bonds where the only by-product is typically water.

  7. A dynamical model of surrogate reactions

    E-print Network

    Y. Aritomo; S. Chiba; K. Nishio

    2010-09-29

    A new dynamical model is developed to describe the whole process of surrogate reactions; transfer of several nucleons at an initial stage, thermal equilibration of residues leading to washing out of shell effects and decay of populated compound nuclei are treated in a unified framework. Multi-dimensional Langevin equations are employed to describe time-evolution of collective coordinates with a time-dependent potential energy surface corresponding to different stages of surrogate reactions. The new model is capable of calculating spin distributions of the compound nuclei, one of the most important quantity in the surrogate technique. Furthermore, various observables of surrogate reactions can be calculated, e.g., energy and angular distribution of ejectile, and mass distributions of fission fragments. These features are important to assess validity of the proposed model itself, to understand mechanisms of the surrogate reactions and to determine unknown parameters of the model. It is found that spin distributions of compound nuclei produced in $^{18}$O+$^{238}$U $\\rightarrow ^{16}$O+$^{240*}$U and $^{18}$O+$^{236}$U $\\rightarrow ^{16}$O+$^{238*}$U reactions are equivalent and much less than 10$\\hbar$, therefore satisfy conditions proposed by Chiba and Iwamoto (PRC 81, 044604(2010)) if they are used as a pair in the surrogate ratio method.

  8. Resilience in reaction-diffusion systems

    NASA Astrophysics Data System (ADS)

    van Vuuren, J. H.

    1999-10-01

    Reaction-diffusion systems with zero-flux Neumann boundaries are widely used to model various kinds of interaction in, for example, the scientific fields of ecology, biology, chemistry, medicine and industry. The physical systems within these fields are often known to be (conditionally or unconditionally) resilient with respect to shocks, disturbances or catastrophies in the immediate environment. In order to be good mathematical models of such situations the reaction-diffusion systems must have the same resilient or asymptotic behaviour as that of the physical situation. Three fundamentally different kinds of reaction terms are usually distinguished according to the entry signs of the reaction Jacobian: mutualism, mixed (predator-prey) interaction and competition. The asymptotic stability (in the Poincare sense) of mutualistic systems has already been studied extensively, but the results cannot be generalized (globally) to the other two fundamental types, which are not order-preserving. A partial (local) generalization is, however given here for these two types, involving simple Jacobian inequalities and knowledge (often prompted by the underlying physical situation) of invariant sets in solution space. The return time of resilient systems and the approach rate of asymptotically stable solutions are also estimated. Key words: reaction-diffusion system; competition; resilience; asymptotic stability.

  9. Reactions of inorganic nitrogen species in supercritical water

    SciTech Connect

    Dell`Orco, P.C.

    1994-12-31

    Redox reactions of nitrate salts with NH3 and methanol were studied in near-critical and supercritical water at 350 to 530 C and constant pressure of 302 bar. Sodium nitrate decomposition reactions were investigated at similar conditions. Reactions were conducted in isothermal tubular reactor under plug flow. For kinetic modeling, nitrate and nitrite reactants were lumped into an NO{sub x}{sup -} reactant; kinetic expressions were developed for MNO{sub 3}/NH{sub 4}X and sodium nitrate decomposition reactions. The proposed elementary reaction mechanism for MNO{sub 3}/NH{sub 4}X reaction indicated that NO{sub 2} was the primary oxidizing species and that N{sub 2}/N{sub 2}O selectivities could be determined by the form of MNO{sub 3} used. This suggest a nitrogen control strategy for use in SCWO (supercritical water oxidation) processes; nitrate or NH3 could be used to remove the other, at reaction conditions far less severe than required by other methods. Reactions of nitrate with methanol indicated that nitrate was a better oxidant than oxygen in supercritical water. Nitrogen reaction products included NH3 and nitrite, while inorganic carbon was the major carbon reaction product. Analysis of excess experiments indicated that the reaction at 475 C was first order in methanol concentration and second order in NO{sub x}{sup -} concentration. In order to determine phase regimes for these reactions, solubility of sodium nitrate was determined for some 1:1 nitrate electrolytes. Solubilities were measured at 450 to 525 C, from 248 to 302 bar. A semi-empirical solvation model was shown to adequately describe the experimental sodium nitrate solubilities. Solubilities of Li, Na, and K nitrates revealed with cations with smaller ionic radii had greater solubilities with nitrate.

  10. Precolumn reactions with electrophoretic analysis integrated on a microchip

    SciTech Connect

    Jacobson, S.C.; Hergenroeder, R.; Moore, A.W. Jr.; Ramsey, J.M. )

    1994-12-01

    A glass microchip was constructed to perform chemical reactions and capillary electrophoresis sequentially. The channel manifold on the glass substrate was fabricated using standard photolithographic, etching, and deposition techniques. The microchip has a reaction chamber with a 1 nL reaction volume and a separation column with a 15.4 mm separation length. Electrical control of the buffer, analyte, and reagent streams made possible the precise manipulation of the fluids within the channel manifold. The microchip was operated under a continuous reaction mode with gated injections to introduce the reaction product onto the separation column with high reproducibility (<1.8% rsd in peak area). The reaction and separation performances were evaluated by reacting amino acids with o-phthaldialdehyde to generate a fluorescent product which was detected by laser-induced fluorescence. Control of the reaction and separation conditions was sufficient to measure reaction kinetics and variation of detection limits with reaction time. Half-times of reaction of 5.1 and 6.2 s and detection limits of 0.55 and 0.83 fmol were measured for arginine and glycine, respectively. 18 refs., 10 figs.

  11. A Petri Net Approach to Persistence Analysis in Chemical Reaction Networks

    E-print Network

    De Leenheer, Patrick

    A Petri Net Approach to Persistence Analysis in Chemical Reaction Networks David Angeli, Patrick De not approach the boundary of this orthant. For chemical reaction networks and other models in biology as well as sufficient conditions for of chemical species in reaction networks, and the applicability

  12. A Petri net approach to the study of persistence in chemical reaction networks

    E-print Network

    Sontag, Eduardo

    A Petri net approach to the study of persistence in chemical reaction networks David Angeli Dip. di in the positive orthant do not approach the boundary of the orthant. For chemical reactions and population models checkable conditions for persistence of chemical species in reaction networks, using concepts and tools from

  13. A Petri Net Approach to Persistence Analysis in Chemical Reaction Networks

    E-print Network

    Sontag, Eduardo

    A Petri Net Approach to Persistence Analysis in Chemical Reaction Networks David Angeli, Patrick De not approach the boundary of this orthant. For chemical reaction networks and other models in biology as well as sufficient conditions for persistence of chemical species in reaction networks

  14. Microwave-Assisted Organic Synthesis in the Organic Teaching Lab: A Simple, Greener Wittig Reaction

    ERIC Educational Resources Information Center

    Martin, Eric; Kellen-Yuen, Cynthia

    2007-01-01

    A greener, microwave-assisted Wittig reaction has been developed for the second-semester organic teaching laboratory. Utilizing this microwave technique, a variety of styrene derivatives have been successfully synthesized from aromatic aldehydes in good yields (41-68%). The reaction not only occurs under neat reaction conditions, but also employs…

  15. The Reaction between Iron(II) Iodide and Potassium Dichromate(VI) in Acidified Aqueous Solution

    ERIC Educational Resources Information Center

    Talbot, Christopher

    2013-01-01

    This "Science note" teaching lesson explores the possible reaction between the ions in a reaction mixture consisting of iron(II) iodide and potassium dichromate(VI) in acidified aqueous solution. The electrode potentials will be used to deduce any spontaneous reactions under standard thermodynamic conditions (298 K, 1 bar (approximately…

  16. Ion / Molecule Reaction Studies Below 80K by the CRESU Technique

    NASA Astrophysics Data System (ADS)

    Marquette, J. B.; Rowe, B. R.; Dupeyrat, G.; Poissant, G.

    The basic principles of the CRESU technique (Cinétique de Réactions en Ecoulement Supersonique Uniforme) are presented. This technique allows ion-molecule reaction rate coefficients under true thermal conditions at interstellar temperatures. Various behaviors of both third-body association and binary reactions with temperature have been observed, including ion-polar molecule reactions whose rate coefficients sharply increase at very low temperatures.

  17. Allergic Skin Conditions

    MedlinePLUS

    ... sweating, or contact with irritants like wool or soaps. Preventing the itch is the main goal of ... reaction is caused by a chemical in the plant called urushiol. Reactions can happen from touching other ...

  18. Concordant Chemical Reaction Networks

    PubMed Central

    Shinar, Guy; Feinberg, Martin

    2015-01-01

    We describe a large class of chemical reaction networks, those endowed with a subtle structural property called concordance. We show that the class of concordant networks coincides precisely with the class of networks which, when taken with any weakly monotonic kinetics, invariably give rise to kinetic systems that are injective — a quality that, among other things, precludes the possibility of switch-like transitions between distinct positive steady states. We also provide persistence characteristics of concordant networks, instability implications of discordance, and consequences of stronger variants of concordance. Some of our results are in the spirit of recent ones by Banaji and Craciun, but here we do not require that every species suffer a degradation reaction. This is especially important in studying biochemical networks, for which it is rare to have all species degrade. PMID:22659063

  19. Reaction chemistry of cerium

    SciTech Connect

    1997-01-01

    It is truly ironic that a synthetic organic chemist likely has far greater knowledge of the reaction chemistry of cerium(IV) than an inorganic colleague. Cerium(IV) reagents have long since been employed as oxidants in effecting a wide variety of organic transformations. Conversely, prior to the late 1980s, the number of well characterized cerium(IV) complexes did not extend past a handful of known species. Though in many other areas, interest in the molecular chemistry of the 4f-elements has undergone an explosive growth over the last twenty years, the chemistry of cerium(IV) has for the most part been overlooked. This report describes reactions of cerium complexes and structure.

  20. Magnetically suspended reaction wheels

    NASA Technical Reports Server (NTRS)

    Sabnis, A. V.; Stocking, G. L.; Dendy, J. B.

    1975-01-01

    Magnetic suspensions offer several advantages over conventional bearings, arising because of the contactless nature of the load support. In application to spacecraft reaction wheels, the advantages are low drag torque, wearfree, unlubricated, vacuum-compatible operation, and unlimited life. By the provision of redundancy in the control electronics, single-point failures are eliminated. The rational for selection of a passive radial, active axial, dc magnetic suspension is presented, and the relative merits of 3-loop and single-loop magnetic suspensions are discussed. The design of a .678 N-m-sec (.5 ft-lb-sec) reaction wheel using the single loop magnetic suspension was developed; the design compares favorably with current ball bearing wheels in terms of weight and power.

  1. Some Reactions of Formamidines

    E-print Network

    Malleis, Otto Oscar

    1913-05-15

    to alkali * .9297 ( 44.84 - (32.24 x .9297) ) x .1105 x .01401 - 4.82 % || Theoretical for CeHsCH « HCeHAOOHaOe^or, c 2 0H I 7 o n E r 14.01 - 4.88 % 287.146 nitrogen found = 4.82 $ Preparation of anisal-p-amino-phenyl-benzyl-ether by the reaction... water hath for a short time. Crystallize from alcohol. M.P. 151° Reaction. S OCHB , OCHe CeH* r HaMJeHAl - H«0 *• CeH* v CH«0 x CH s IC*H*I This product may he called anisal-p-iodo-aniline. Analysis: litrogen determination by Kjeldahl method...

  2. Neutrons from Piezonuclear Reactions

    E-print Network

    F. Cardone; G. Cherubini; R. Mignani; W. Perconti; A. Petrucci; F. Rosetto; G. Spera

    2008-11-16

    We report the results obtained by cavitating water solutions of iron salts (iron chloride and iron nitrate) with different concentrations at different ultrasound powers. In all cases we detected a neutron radiation well higher than the background level. The neutron production is perfectly reproducible and can at some extent be controlled. These evidences for neutron emission generated by cavitation support some preliminary clues for the possibility of piezonuclear reactions (namely nuclear reactions induced by pressure and shock waves) obtained in the last ten years. We have been able for the first time to state some basic features of such a neutron emission induced by cavitation, namely: 1) a marked threshold behavior in power, energy and time; 2) its occurring without a concomitant production of gamma radiation.

  3. Photochemical reaction dynamics

    SciTech Connect

    Moore, B.C.

    1993-12-01

    The purpose of the program is to develop a fundamental understanding of unimolecular and bimolecular reaction dynamics with application in combustion and energy systems. The energy dependence in ketene isomerization, ketene dissociation dynamics, and carbonyl substitution on organometallic rhodium complexes in liquid xenon have been studied. Future studies concerning unimolecular processes in ketene as well as energy transfer and kinetic studies of methylene radicals are discussed.

  4. Reaction synthesis of intermetallics

    SciTech Connect

    Deevi, S.C.; Sikka, V.K.

    1994-12-31

    Exothermicity associated with the synthesis of aluminides was utilized to obtain nickel, iron, and cobalt aluminides. Combustion synthesis, extrusion, and hot pressing were utilized to obtain intermetallics and their composites. Extrusion conditions, reduction ratios, and hot-pressing conditions of the intermetallics and their composites are discussed.

  5. Chemical Reactions in DSMC

    SciTech Connect

    Bird, G. A.

    2011-05-20

    DSMC simulations of chemically reacting gas flows have generally employed procedures that convert the macroscopic chemical rate equations to reaction cross-sections at the microscopic level. They therefore depend on the availability of experimental data that has been fitted to equations of the Arrhenius form. This paper presents a physical model for dissociation and recombination reactions and a phenomenological model for exchange and chain reactions. These are based on the vibrational states of the colliding molecules and do not require any experimentally-based data. The simplicity of the models allows the corresponding rate equations to be written down and, while these are not required for the implementation of the models, they facilitate their validation. The model is applied to a typical hypersonic atmospheric entry problem and the results are compared with the corresponding results from the traditional method. It is also used to investigate both spontaneous and forced ignition as well as the structure of a deflagration wave in an oxygen-hydrogen mixture.

  6. Theoretical Study ofTheoretical Study of ReactionReaction

    E-print Network

    Theoretical Study ofTheoretical Study of ReactionReaction BFBF33 + BF+ BF BFBF22 + BF+ BF22 the growth of boron nitride in a plasma torch experiment. The theoretical data is used to optimize/Cl/N/H, as well as limited kinetics studies of the reactions between BCl3 and NH3. #12;Kinetic ModelKinetic Model

  7. Reaction Extrema: Extent of Reaction in General Chemistry

    ERIC Educational Resources Information Center

    Vandezande, Jonathon E.; Vander Griend, Douglas A.; DeKock, Roger L.

    2013-01-01

    Nearly 100 years ago de Donder introduced the term "extent of reaction", ?. We build on that work by defining the concept of reagent extrema for an arbitrary chemical reaction, aA + bB [reversible reaction] yY + zZ. The central equation is ?^[subscript i] = -n[subscript i,0]/?[subscript i]. The symbol ?^[subscript i] represents the…

  8. Ultrafast Laser Spectroscopyof Chemical Reactions

    E-print Network

    Zewail, Ahmed

    Ultrafast Laser Spectroscopyof Chemical Reactions - Joseph L. Kneeand AhmedH. Zewail California Instituteof Technology Ultrafast laser spectroscopy has extended reaction- tion, have been probed (very sensitively) by a variety of laser spec- troscopic techniques and have

  9. Positive reaction to allergen (image)

    MedlinePLUS

    Allergic reaction is a sensitivity to a specific substance, called an allergen, that is contacted through the skin, inhaled into the lungs, swallowed or injected. The body's reaction to an allergen can be mild, such as ...

  10. Coping with Traumatic Stress Reactions

    MedlinePLUS

    ... here Enter ZIP code here Coping with Traumatic Stress Reactions Public This section is for Veterans, General Public, Family, & Friends Coping with Traumatic Stress Reactions Available in Spanish: Cómo Afrontar las Reacciones ...

  11. Hydrazine decomposition and other reactions

    NASA Technical Reports Server (NTRS)

    Armstrong, Warren E. (Inventor); La France, Donald S. (Inventor); Voge, Hervey H. (Inventor)

    1978-01-01

    This invention relates to the catalytic decomposition of hydrazine, catalysts useful for this decomposition and other reactions, and to reactions in hydrogen atmospheres generally using carbon-containing catalysts.

  12. Demonstration of the Fenton Reaction

    ERIC Educational Resources Information Center

    Luehrs, Dean C.; Roher, Alex E.

    2007-01-01

    The study demonstrates the Fenton reaction, which is carried out using the Fenton reagent that is used for groundwater and soil remediation. The Fenton reaction can be implicated in DNA damage, Alzheimer's disease, cardiovascular disease and ageing in general.

  13. The heterogeneous explosive reaction zone

    SciTech Connect

    Mader, C.L.; Kershner, J.D.

    1989-01-01

    The calculated reaction zone of PBX-9404 using solid HMX Arrhenius kinetics is stable to perturbations. The calculated reaction zone Von Neumann spike pressure agrees with the experimental observations within experimental uncertainty associated with different experimental techniques. The calculated homogengeous explosive reaction zone thickness is larger than observed for the heterogeneous explosive. The effect of two volume percent air holes on the reaction zone was modeled using the three-dimensional Eulerian reactive hydrodynamic code, 3DE. The air holes perturb the reaction zone. A complicated, time-dependent, multidimensional reaction region proceeds through the heterogeneous explosive. The experimentally observed reaction zone characteristic of heterogeneous explosives are mean values of an irregular, three-dimensional reaction region. 20 refs., 6 figs.

  14. Applied reaction dynamics: Efficient synthesis gas production via single collision partial oxidation of methane to CO on Rh,,111...

    E-print Network

    Sibener, Steven

    Applied reaction dynamics: Efficient synthesis gas production via single collision partial fuel production Fischer-Tropsch or methanol synthesis . Moreover, under the reaction conditions dissociation. These results demonstrate the efficient conversion of methane to synthesis gas, CO+2H2

  15. THE HYDROVINYLATION AND RELATED REACTIONS: NEW PROTOCOLS AND CONTROL ELEMENTS IN SEARCH OF GREATER SYNTHETIC EFFICIENCY AND SELECTIVITY. (R826120)

    EPA Science Inventory

    New reaction conditions and stereochemical control elements for heterodimerization between ethylene (or propylene) and functionalized vinyl arenes are highlighted (see equation). For example, an enantioselective version of the hydrovinylation reaction uses [{(allyl)NiBr}...

  16. Urticaria and Allergy-Mediated Conditions.

    PubMed

    Jafilan, Lena; James, Charis

    2015-12-01

    Urticaria is a common condition that involves pruritic, raised skin wheals. Although urticaria is a benign, self-limiting condition, it may cause frustration for patients, often because of its chronicity and its tendency to recur. It can also be a life-threatening allergic reaction. Diagnosis is made clinically. It affects 20% of the general population. The first-line treatment for nonremitting cases includes H-1anti-histamines. However, other therapies may be employed. Other allergy-mediated skin conditions include angioedema, contact dermatitis, and atopic dermatitis. Diagnosis is clinical, and management focuses on prevention, avoiding triggers, and treating the itching and inflammation that accompany these conditions. PMID:26612369

  17. High temperature chemical kinetic study of the H2-CO-CO2-NO reaction system

    NASA Technical Reports Server (NTRS)

    Jachimowski, C. J.

    1975-01-01

    An experimental study of the kinetics of the H2-CO-CO2-NO reaction system was made behind incident shock waves at temperatures of 2460 and 2950 K. The overall rate of the reaction was measured by monitoring radiation from the CO + O yields CO2 + h upoilon reaction. Correlation of these data with a detailed reaction mechanism showed that the high-temperature rate of the reaction N + OH yields NO + H can be described by the low-temperature (320 K) rate coefficient. Catalytic dissociation of molecular hydrogen was an important reaction under the tests conditions.

  18. The Vitamin C Clock Reaction

    NASA Astrophysics Data System (ADS)

    Wright, Stephen W.

    2002-01-01

    An iodine clock reaction that gives a colorless to black result similar to that of the familiar Landolt iodate-bisulfite clock reaction is described. The vitamin C clock reaction uses chemicals that are readily available on the retail market: vitamin C, tincture of iodine, 3% hydrogen peroxide, and laundry starch. Orange juice may be used as the vitamin C source to give an orange to black reaction.

  19. Flow Heck reactions using extremely low loadings of phosphine-free palladium acetate.

    PubMed

    Cyr, Patrick; Deng, Stella T; Hawkins, Joel M; Price, Kristin E

    2013-09-01

    High-yielding Heck reactions are demonstrated using 0.05 mol % Pd(OAc)2 without phosphine ligands. These reactions are run in a mesoscale flow reactor which allows precise control of reaction times and temperatures. Profiling yield and selectivity versus Pd loading shows 500 ppm to be optimal for aryl iodides; higher loadings favor side reactions caused by Pd(II) species. Aryl halides are examined via concise Design of Experiment to expand the scope and optimize conditions. PMID:23937686

  20. The Vitamin C Clock Reaction.

    ERIC Educational Resources Information Center

    Wright, Stephen W.

    2002-01-01

    Describes an iodine clock reaction that produces an effect similar to the Landolt clock reaction. This reaction uses supermarket chemicals and avoids iodate, bisulfite, and mercury compounds. Ascorbic acid and tincture of iodine are the main reactants with alternate procedures provided for vitamin C tablets and orange juice. (DDR)

  1. Determination of Complex Reaction Mechanisms

    E-print Network

    Steinbock, Oliver

    can be derived. This interesting chapter starts with the analysis of simple unbranched chain reactionsDetermination of Complex Reaction Mechanisms Analysis of Chemi- cal, Biological, and Genetic in the field of chemical kinetics. The book Determination of Complex Reaction Mechanisms, by Ross, Schreiber

  2. Atherton–Todd reaction: mechanism, scope and applications

    PubMed Central

    Le Corre, Stéphanie S; Berchel, Mathieu; Couthon-Gourvès, Hélène; Haelters, Jean-Pierre

    2014-01-01

    Summary Initially, the Atherton–Todd (AT) reaction was applied for the synthesis of phosphoramidates by reacting dialkyl phosphite with a primary amine in the presence of carbon tetrachloride. These reaction conditions were subsequently modified with the aim to optimize them and the reaction was extended to different nucleophiles. The mechanism of this reaction led to controversial reports over the past years and is adequately discussed. We also present the scope of the AT reaction. Finally, we investigate the AT reaction by means of exemplary applications, which mainly concern three topics. First, we discuss the activation of a phenol group as a phosphate which allows for subsequent transformations such as cross coupling and reduction. Next, we examine the AT reaction applied to produce fire retardant compounds. In the last section, we investigate the use of the AT reaction for the production of compounds employed for biological applications. The selected examples to illustrate the applications of the Atherton–Todd reaction mainly cover the past 15 years. PMID:24991268

  3. Anaphylaxis-Like Reactions

    MedlinePLUS

    ... Learn more. Electronic Medical Record (EMR) Learn more. Clinical Diagnostics Learn more. Metal Hypersensitivity Learn more. Mycobacteriology ... Clinic Learn more. Pulmonary Hypertension Center Learn more. Clinical Nutrition Services Many chronic conditions require adjustments to ...

  4. Study of chemical reactions under the influence of ultrasound

    SciTech Connect

    Lee, Kien-Yin

    1993-07-01

    At Los Alamos the author is interested in sonochemistry because there is potential for accelerating reactions involving the synthesis of certain nitro compounds and for reducing the possibility of decomposition under milder reaction conditions. The author has initiated the study of the nitration of 2,4-dihydro-3H-1,2,4-triazol-3-one with concentrated nitric acid under sonication. The preparation of 3,6-bis(3,5-dimethylpyrazol-1-yl)-1,2-dihydro-1,2,4,5-tetrazine, and oxidation of 3,6-diamino-1,2,4,5-tetrazine were also studied. Sonication reaction conditions and results of these reactions under ultrasound are discussed in detail.

  5. Molecule-based approach for computing chemical-reaction rates in upper atmosphere hypersonic flows.

    SciTech Connect

    Gallis, Michail A.; Bond, Ryan Bomar; Torczynski, John Robert

    2009-08-01

    This report summarizes the work completed during FY2009 for the LDRD project 09-1332 'Molecule-Based Approach for Computing Chemical-Reaction Rates in Upper-Atmosphere Hypersonic Flows'. The goal of this project was to apply a recently proposed approach for the Direct Simulation Monte Carlo (DSMC) method to calculate chemical-reaction rates for high-temperature atmospheric species. The new DSMC model reproduces measured equilibrium reaction rates without using any macroscopic reaction-rate information. Since it uses only molecular properties, the new model is inherently able to predict reaction rates for arbitrary nonequilibrium conditions. DSMC non-equilibrium reaction rates are compared to Park's phenomenological non-equilibrium reaction-rate model, the predominant model for hypersonic-flow-field calculations. For near-equilibrium conditions, Park's model is in good agreement with the DSMC-calculated reaction rates. For far-from-equilibrium conditions, corresponding to a typical shock layer, the difference between the two models can exceed 10 orders of magnitude. The DSMC predictions are also found to be in very good agreement with measured and calculated non-equilibrium reaction rates. Extensions of the model to reactions typically found in combustion flows and ionizing reactions are also found to be in very good agreement with available measurements, offering strong evidence that this is a viable and reliable technique to predict chemical reaction rates.

  6. Fundamental studies of retrograde reactions in direct liquefaction

    SciTech Connect

    Serio, M.A.; Solomon, P.R.; Kroo, E.; Charpenay, S.; Bassilakis, R.

    1991-12-17

    The overall objective of the program was to improve the understanding of retrograde reactions and their dependencies on coal rank and structure, and/or coal modifications and reaction conditions. Because retrograde reactions are competitive with bond breaking reactions, an understanding of both is required to shift the competition in favor of the latter. Related objectives were to clarify the conflicting observations reported in literature on such major topics as the role of oxygen groups in retrograde reactions and to provide a bridge from very fundamental studies on pure compounds to phenomenological studies on actual coal. This information was integrated into the FG-DVC model, which was improved and extended to the liquefaction context.

  7. Atmospheric reactions of 9,10-anthraquinone.

    PubMed

    Miet, Killian; Albinet, Alexandre; Budzinski, Hélène; Villenave, Eric

    2014-07-01

    The probably carcinogenic compound 9,10-anthraquinone is mainly existing in the atmosphere in the particulate phase and is often detected and measured among other oxygenated PAHs in atmospheric samples. Its fate, once released or formed in the atmosphere, still remains unknown. In this work, heterogeneous chemical oxidation processes of 9,10-anthraquinone were investigated with ozone (O3), nitrogen dioxide (NO2) and hydroxyl radical (OH). The study of 9,10-anthraquinone adsorbed on silica particles showed no reactivity with O3 and NO2. On the other hand, the reaction with OH radicals was observed and led to the formation of 1-hydroxy-9,10-anthraquinone, another oxidation product recognized as possibly carcinogenic to humans. This study showed that reactions with ozone and nitrogen dioxide are unlikely to contribute to atmospheric degradation of 9,10-anthraquinone, whereas reactions with OH radicals could be involved in 9,10-anthraquinone degradation processes, even if such reaction is probably very slow under ambient conditions. PMID:24875864

  8. Chemical computing with reaction-diffusion processes.

    PubMed

    Gorecki, J; Gizynski, K; Guzowski, J; Gorecka, J N; Garstecki, P; Gruenert, G; Dittrich, P

    2015-07-28

    Chemical reactions are responsible for information processing in living organisms. It is believed that the basic features of biological computing activity are reflected by a reaction-diffusion medium. We illustrate the ideas of chemical information processing considering the Belousov-Zhabotinsky (BZ) reaction and its photosensitive variant. The computational universality of information processing is demonstrated. For different methods of information coding constructions of the simplest signal processing devices are described. The function performed by a particular device is determined by the geometrical structure of oscillatory (or of excitable) and non-excitable regions of the medium. In a living organism, the brain is created as a self-grown structure of interacting nonlinear elements and reaches its functionality as the result of learning. We discuss whether such a strategy can be adopted for generation of chemical information processing devices. Recent studies have shown that lipid-covered droplets containing solution of reagents of BZ reaction can be transported by a flowing oil. Therefore, structures of droplets can be spontaneously formed at specific non-equilibrium conditions, for example forced by flows in a microfluidic reactor. We describe how to introduce information to a droplet structure, track the information flow inside it and optimize medium evolution to achieve the maximum reliability. Applications of droplet structures for classification tasks are discussed. PMID:26078345

  9. General chemical kinetics computer program for static and flow reactions, with application to combustion and shock-tube kinetics

    NASA Technical Reports Server (NTRS)

    Bittker, D. A.; Scullin, V. J.

    1972-01-01

    A general chemical kinetics program is described for complex, homogeneous ideal-gas reactions in any chemical system. Its main features are flexibility and convenience in treating many different reaction conditions. The program solves numerically the differential equations describing complex reaction in either a static system or one-dimensional inviscid flow. Applications include ignition and combustion, shock wave reactions, and general reactions in a flowing or static system. An implicit numerical solution method is used which works efficiently for the extreme conditions of a very slow or a very fast reaction. The theory is described, and the computer program and users' manual are included.

  10. The reaction path intrinsic reaction coordinate method and the Hamilton-Jacobi theory.

    PubMed

    Crehuet, Ramon; Bofill, Josep Maria

    2005-06-15

    The definition and location of an intrinsic reaction coordinate path is of crucial importance in many areas of theoretical chemistry. Differential equations used to define the path hitherto are complemented in this study with a variational principle of Fermat type, as Fukui [Int. J. Quantum Chem., Quantum Chem. Symp. 15, 633 (1981)] reported in a more general form some time ago. This definition is more suitable for problems where initial and final points are given. The variational definition can naturally be recast into a Hamilton-Jacobi equation. The character of the variational solution is studied via the Weierstrass necessary and sufficient conditions. The characterization of the local minima character of the intrinsic reaction coordinate is proved. Such result leads to a numerical algorithm to find intrinsic reaction coordinate paths based on the successive minimizations of the Weierstrass E-function evaluated on a guess curve connecting the initial and final points of the desired path. PMID:16008428

  11. Method and apparatus for controlling gas evolution from chemical reactions

    DOEpatents

    Skorpik, James R. (Kennewick, WA); Dodson, Michael G. (Richland, WA)

    1999-01-01

    The present invention is directed toward monitoring a thermally driven gas evolving chemical reaction with an acoustic apparatus. Signals from the acoustic apparatus are used to control a heater to prevent a run-away condition. A digestion module in combination with a robotic arm further automate physical handling of sample material reaction vessels. The invention is especially useful for carrying out sample procedures defined in EPA Methods SW-846.

  12. Method and apparatus for controlling gas evolution from chemical reactions

    DOEpatents

    Skorpik, J.R.; Dodson, M.G.

    1999-05-25

    The present invention is directed toward monitoring a thermally driven gas evolving chemical reaction with an acoustic apparatus. Signals from the acoustic apparatus are used to control a heater to prevent a run-away condition. A digestion module in combination with a robotic arm further automate physical handling of sample material reaction vessels. The invention is especially useful for carrying out sample procedures defined in EPA Methods SW-846. 8 figs.

  13. Single step BP/LR combined Gateway reactions.

    PubMed

    Liang, Xiquan; Peng, Lansha; Baek, Chang-Ho; Katzen, Federico

    2013-11-01

    The Gateway recombination system is characterized by its ability to transfer DNA sequences back and forth between an intermediate clone (the entry clone) and a variety of destination vectors. However, a number of applications do not need to exploit the advantages offered by the entry clone. Here we report reaction conditions for cloning DNA fragments into destination vectors in a single step reaction, thus reducing the cost and overall time needed to obtain an expression clone from three days to one. PMID:24215642

  14. Characterizing Multistationarity Regimes in Biochemical Reaction Networks

    PubMed Central

    Otero-Muras, Irene; Banga, Julio R.; Alonso, Antonio A.

    2012-01-01

    Switch like responses appear as common strategies in the regulation of cellular systems. Here we present a method to characterize bistable regimes in biochemical reaction networks that can be of use to both direct and reverse engineering of biological switches. In the design of a synthetic biological switch, it is important to study the capability for bistability of the underlying biochemical network structure. Chemical Reaction Network Theory (CRNT) may help at this level to decide whether a given network has the capacity for multiple positive equilibria, based on their structural properties. However, in order to build a working switch, we also need to ensure that the bistability property is robust, by studying the conditions leading to the existence of two different steady states. In the reverse engineering of biological switches, knowledge collected about the bistable regimes of the underlying potential model structures can contribute at the model identification stage to a drastic reduction of the feasible region in the parameter space of search. In this work, we make use and extend previous results of the CRNT, aiming not only to discriminate whether a biochemical reaction network can exhibit multiple steady states, but also to determine the regions within the whole space of parameters capable of producing multistationarity. To that purpose we present and justify a condition on the parameters of biochemical networks for the appearance of multistationarity, and propose an efficient and reliable computational method to check its satisfaction through the parameter space. PMID:22802936

  15. Metallic induction reaction engine

    NASA Astrophysics Data System (ADS)

    Hart, Douglas; Mongeau, Peter P.; Kolm, Henry H.

    1985-11-01

    Metal rings placed close to a pulsed field coil have been accelerated at 200 million gee to 5 km/s in a 2 cm length by Bandoletov in the USSR Bandoletov, 1977. We have studied the basic phenomena and ultimate limitations of the pulsed induction process both theoretically and experimentally to determine its usefulness as a reaction engine. It is possible in principle to accelerate metal rings at high efficiency, and impart sufficient energy to ensure melting and evaporation, so that the reaction mass is ultimately ejected in the form of plasma. In practice the process is limited by electrical, mechanical and thermal failure of the induction coil. Over a hundred shots were fired including several in which 12 gram rings were accelerated to over 700 m/s at efficiencies above 30 percent. This is equivalent to the performance of a high power rifle with a one inch long barrel. An unexpected result of these studies is the discovery that to achieve maximum velocity, the mutual inductance gradient between induction coil and projectile ring in the firing position must be reduced to minimize the initial acceleration. This reduces the back voltage and increases the interaction time, resulting in maximum energy transfer.

  16. Interfacial Reaction Kinetics

    E-print Network

    Ben O'Shaughnessy; Dimitrios Vavylonis

    1999-09-10

    We study irreversible A-B reaction kinetics at a fixed interface separating two immiscible bulk phases, A and B. We consider general dynamical exponent $z$, where $x_t\\sim t^{1/z}$ is the rms diffusion distance after time $t$. At short times the number of reactions per unit area, $R_t$, is {\\em 2nd order} in the far-field reactant densities $n_A^{\\infty},n_B^{\\infty}$. For spatial dimensions $d$ above a critical value $d_c=z-1$, simple mean field (MF) kinetics pertain, $R_t\\sim Q_b t n_A^{\\infty} n_B^{\\infty}$ where $Q_b$ is the local reactivity. For low dimensions $d Q_b^* \\sim (n_B^{\\infty})^{[z-(d+1)]/d}$. Logarithmic corrections arise in marginal cases. At long times, a cross-over to {\\em 1st order} DC kinetics occurs: $R_t \\approx x_t n_A^{\\infty}$. A density depletion hole grows on the more dilute A side. In the symmetric case ($n_A^{\\infty}=n_B^{\\infty}$), when $dd_c$ fluctuations are unimportant: local mean field theory applies at the interface (joint density distribution approximating the product of A and B densities) and $n_A^s \\sim t^{(1-z)/(2z)}$. We apply our results to simple molecules (Fickian diffusion, $z=2$) and to several models of short-time polymer diffusion ($z>2$).

  17. [Abnormal grief reaction].

    PubMed

    Meyer, J E

    1977-01-01

    Pathological grief reactions following the death of a child are reported on the basis of five case studies. In contrast to acute grief reactions these pathological syndromes are of long standing. One parent had not truly accepted the death of the child. The denial of reality is sometimes a defence against aggression towards the deceased, because of his having left one behind. The mourning process comes to no end but remains in its initial phase. At the same time the life of the mourner stands still, as in the house and the family everything is left unchanged. Family interactions alter, particularly between the parents. For the genesis of these grief syndromes the following is of relevance: The death occurs at a time, when another child cannot replace the one who died. Mature independence had not been reached by either parent or child. Death destroyed expectations that this child would succeed in that which the parent had been unable to achieve. The parent had not seen the child after death--a gap in the continuity of experiencing which made acceptance of the irreversibility of the loss even more difficult. PMID:595912

  18. Combined Experimental and Theoretical Study on the Formation of the Elusive 2-Methyl-1-silacycloprop-2-enylidene Molecule under Single Collision Conditions via Reactions of the Silylidyne Radical (SiH; X(2)?) with Allene (H2CCCH2; X(1)A1) and D4-Allene (D2CCCD2; X(1)A1).

    PubMed

    Yang, Tao; Dangi, Beni B; Maksyutenko, Pavlo; Kaiser, Ralf I; Bertels, Luke W; Head-Gordon, Martin

    2015-12-17

    The crossed molecular beam reactions of the ground-state silylidyne radical (SiH; X(2)?) with allene (H2CCCH2; X(1)A1) and D4-allene (D2CCCD2; X(1)A1) were carried out at collision energies of 30 kJ mol(-1). Electronic structure calculations propose that the reaction of silylidyne with allene has no entrance barrier and is initiated by silylidyne addition to the ? electron density of allene either to one carbon atom (C1/C2) or to both carbon atoms simultaneously via indirect (complex forming) reaction dynamics. The initially formed addition complexes isomerize via two distinct reaction pathways, both leading eventually to a cyclic SiC3H5 intermediate. The latter decomposes through a loose exit transition state via an atomic hydrogen loss perpendicularly to the plane of the decomposing complex (sideways scattering) in an overall exoergic reaction (experimentally: -19 ± 13 kJ mol(-1); computationally: -5 ± 3 kJ mol(-1)). This hydrogen loss yields the hitherto elusive 2-methyl-1-silacycloprop-2-enylidene molecule (c-SiC3H4), which can be derived from the closed-shell cyclopropenylidene molecule (c-C3H2) by replacing a hydrogen atom with a methyl group and the carbene carbon atom by the isovalent silicon atom. The synthesis of the 2-methyl-1-silacycloprop-2-enylidene molecule in the bimolecular gas-phase reaction of silylidyne with allene enriches our understanding toward the formation of organosilicon species in the gas phase of the interstellar medium in particular via exoergic reactions of no entrance barrier. This facile route to 2-methyl-1-silacycloprop-2-enylidene via a silylidyne radical reaction with allene opens up a versatile approach to form hitherto poorly characterized silicon-bearing species in extraterrestrial environments; this reaction class might represent the missing link, leading from silicon-bearing radicals via organosilicon chemistry eventually to silicon-carbon-rich interstellar grains even in cold molecular clouds where temperatures are as low as 10 K. PMID:26535955

  19. 14 CFR 23.497 - Supplementary conditions for tail wheels.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ..., the limit ground reaction obtained in the tail down landing condition is assumed to act up and aft.... (b) For the side load, a limit vertical ground reaction equal to the static load on the tail wheel, in combination with a side component of equal magnitude, is assumed. In addition— (1) If a swivel...

  20. 14 CFR 25.485 - Side load conditions.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... STANDARDS: TRANSPORT CATEGORY AIRPLANES Structure Ground Loads § 25.485 Side load conditions. In addition to... accordance with figure 5 of appendix A. (b) Side loads of 0.8 of the vertical reaction (on one side) acting inward and 0.6 of the vertical reaction (on the other side) acting outward must be combined with...

  1. 14 CFR 23.497 - Supplementary conditions for tail wheels.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ..., the limit ground reaction obtained in the tail down landing condition is assumed to act up and aft.... (b) For the side load, a limit vertical ground reaction equal to the static load on the tail wheel, in combination with a side component of equal magnitude, is assumed. In addition— (1) If a swivel...

  2. 14 CFR 23.497 - Supplementary conditions for tail wheels.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ..., the limit ground reaction obtained in the tail down landing condition is assumed to act up and aft.... (b) For the side load, a limit vertical ground reaction equal to the static load on the tail wheel, in combination with a side component of equal magnitude, is assumed. In addition— (1) If a swivel...

  3. 14 CFR 25.485 - Side load conditions.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... STANDARDS: TRANSPORT CATEGORY AIRPLANES Structure Ground Loads § 25.485 Side load conditions. In addition to... accordance with figure 5 of appendix A. (b) Side loads of 0.8 of the vertical reaction (on one side) acting inward and 0.6 of the vertical reaction (on the other side) acting outward must be combined with...

  4. 14 CFR 25.485 - Side load conditions.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... STANDARDS: TRANSPORT CATEGORY AIRPLANES Structure Ground Loads § 25.485 Side load conditions. In addition to... accordance with figure 5 of appendix A. (b) Side loads of 0.8 of the vertical reaction (on one side) acting inward and 0.6 of the vertical reaction (on the other side) acting outward must be combined with...

  5. 14 CFR 23.497 - Supplementary conditions for tail wheels.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ..., the limit ground reaction obtained in the tail down landing condition is assumed to act up and aft.... (b) For the side load, a limit vertical ground reaction equal to the static load on the tail wheel, in combination with a side component of equal magnitude, is assumed. In addition— (1) If a swivel...

  6. Synthesis Under 'Greener' Conditions: Role of Sustainable Nano-Catalysts

    EPA Science Inventory

    The presentation summarizes our recent activity in chemical synthesis involving benign alternatives, such as the use of supported reagents, and greener reaction medium in aqueous or solvent-free conditions.1 The synthesis of heterocyclic compounds, coupling reactions, and a varie...

  7. On the possibility of negative activation energies in bimolecular reactions

    NASA Technical Reports Server (NTRS)

    Jaffe, R. L.

    1978-01-01

    The temperature dependence of the rate constants for model reacting systems was studied to understand some recent experimental measurements which imply the existence of negative activation energies. A collision theory model and classical trajectory calculations are used to demonstrate that the reaction probability can vary inversely with collision energy for bimolecular reactions occurring on attractive potential energy surfaces. However, this is not a sufficient condition to ensure that the rate constant has a negative temperature dependence. On the basis of these calculations, it seems unlikely that a true bimolecular reaction between neutral molecules will have a negative activation energy.

  8. Gas-solid reaction-rate enhancement by pressure cycling

    NASA Astrophysics Data System (ADS)

    Sohn, H. Y.; Aboukheshem, M. B.

    1992-06-01

    An experimental study and mathematical modeling of the effects of external pressure cycling on gas-solid reactions have been conducted using the reduction of nickel oxide pellets by hy-drogen. Experiments were carried out in two phases: In the first phase, the intrinsic kinetic parameters were measured, and in the second phase, the gas-solid reaction was carried out under a constant or cycling external pressure. The effects of the frequency and amplitude of pressure cycling were studied at various reaction conditions. Pressure cycling substantially increases the overall rate of the reaction. A mathematical model was developed from the first principles to establish the extent of the overall reaction-rate enhancement and subsequently to analyze the experimental observations. The calculated values from the mathematical model are in good agreement with the experimental results. The effects are most pronounced when the overall rate under a constant pressure is controlled by diffusion. Depending on the reaction condition, a very large degree of rate enhancement could be achieved. Furthermore, low-amplitude pressure waves, like acoustic waves, could significantly increase the rates of gas-solid reactions.

  9. ENVIRONMENTALLY FRIENDLIER ORGANIC TRANSFORMATIONS ON MINERAL SUPPORTS UNDER NONTRADITIONAL CONDITIONS

    EPA Science Inventory

    Synthetic organic reactions performed under non-traditional conditions are gaining popularity primarily to circumvent the growing environmental concerns. A solvent-free approach that involves microwave (MW) exposure of neat reactants (undiluted) either in presence of a catalyst o...

  10. Self-regulation effect in the hydroformylation reaction of olefins

    SciTech Connect

    Kagan, Yu.B.; Rozovskii, A.Ya.; Slivinskii, E.V.; Korneeva, G.A.; Kurkin, V.I.; Loktev, S.M.

    1988-06-01

    It has been demonstrated that under the conditions of vigorous olefin hydroformylation, stabilization and even partial regeneration of the activity of the rhodium carbonyl catalyst, deactivated by the formation of the polynuclear carbonyl clusters, are observed. The accumulation of a superequilibrium concentration of active rhodium carbonyl catalyst species, which are labile and thermodynamically unstable outside of the catalysis conditions, is achieved under the influence of the reaction conditions, in agreement with theoretical predictions. Based on IR spectroscopic studies, which were conducted in situ, the relay function of the catalytic reaction has been found to be due to the presence of a common hydrogenolysis step of rhodium acylcarbonyl derivatives during the catalytic reaction and during catalyst deactivation.

  11. Acceleration of chemical reaction by chaotic mixing

    E-print Network

    M. Chertkov; V. Lebedev

    2003-01-27

    Theory of fast binary chemical reaction, ${\\cal A}+{\\cal B}\\to{\\cal C}$, in a statistically stationary chaotic flow at large Schmidt number ${Sc}$ and large Damk\\"ohler number ${Da}$ is developed. For stoichiometric condition we identify subsequent stages of the chemical reaction. The first stage corresponds to the exponential decay, $\\propto\\exp(-\\lambda t)$ (where $\\lambda$ is the Lyapunov exponent of the flow), of the chemicals in the bulk part of the flow. The second and the third stages are related to the chemicals remaining in the boundary region. During the second stage the amounts of ${\\cal A}$ and ${\\cal B}$ decay $\\propto 1/\\sqrt{t}$, whereas the decay law during the third stage is exponential, $\\propto\\exp(-\\gamma t)$, where $\\gamma\\sim\\lambda/\\sqrt{Sc}$.

  12. Biosensor as a Reaction-Diffusion System

    E-print Network

    Ghosh, Surya K; Sain, Anirban

    2012-01-01

    We model a biosensor as a reaction-diffusion process in a confined geometry. When a solution containing unknown concentration of antigens are injected into the closed chamber of the sensor, the antigens diffuse and react with a functionalised surface. These surface reactions are then converted to an optical signal, the intensity of which indicates the level of antigen content in the solution. We probe the spatio-temporal behavior of the system by studying the governing equations, using mean field approximation and numerical integration. Mean field analysis gives important insights about the dynamics, but in order to compare with real experiments and extract the values of the relevant kinetic parameters, numerical integration was necessary. We track down the operating conditions for quick and efficient response of the sensor.

  13. Reaction Diffusion patterns in Pseudoplatystoma fishes

    E-print Network

    Aldo Ledesma-Durán; Héctor Juárez-Valencia; Iván Santamaría-Holek

    2016-01-05

    This paper studies how patterns derived from a system of reaction-diffusion equations may vary significantly depending upon boundary and initial conditions, as well as in the spatial dependence of the coefficients involved. From an extensive numerical study of the BVAM model, we demonstrate that the geometric pattern of a reaction-diffusion system is not uniquely determined by the value of the parameters in the equation. From this result, we suggest that the variability of patterns among individuals of the same species may have its roots in this sensitivity. Furthermore, this study analyzes briefly how the inclusion of the advection and the space dependency in the parameters of the model influences the forms of a specific pattern. The results of this study are compared to the skin patterns that appear in Pseudoplatystom} fishes.

  14. Laser induced nuclear reactions

    SciTech Connect

    Ledingham, Ken; McCanny, Tom; Graham, Paul; Fang Xiao; Singhal, Ravi; Magill, Joe; Creswell, Alan; Sanderson, David; Allott, Ric; Neely, David; Norreys, Peter; Santala, Marko; Zepf, Matthew; Watts, Ian; Clark, Eugene; Krushelnick, Karl; Tatarakis, Michael; Dangor, Bucker; Machecek, Antonin; Wark, Justin

    1998-12-16

    Dramatic improvements in laser technology since 1984 have revolutionised high power laser technology. Application of chirped-pulse amplification techniques has resulted in laser intensities in excess of 10{sup 19} W/cm{sup 2}. In the mid to late eighties, C. K. Rhodes and K. Boyer discussed the possibility of shining laser light of this intensity onto solid surfaces and to cause nuclear transitions. In particular, irradiation of a uranium target could induce electro- and photofission in the focal region of the laser. In this paper it is shown that {mu}Ci of {sup 62}Cu can be generated via the ({gamma},n) reaction by a laser with an intensity of about 10{sup 19} Wcm{sup -2}.

  15. Hypersensitivity reaction with deferasirox.

    PubMed

    Sharma, Atul; Arora, Ekta; Singh, Harmanjit

    2015-01-01

    Thalassemias comprise a group of hereditary blood disorders. Thalassemia major presents with anemia within the first 2 years of life requiring frequent blood transfusions for sustaining life. Regular blood transfusions lead to iron overload-related complications. Prognosis of thalassemia has improved because of the availability of iron-chelating agents. Oral iron chelators are the mainstay of chelation therapy. Deferasirox is a new-generation oral iron chelator for once daily usage. We herein describe a patient of beta thalassemia major who developed an allergic manifestation in the form of erythematous pruritic skin rashes to the oral iron chelator deferasirox. This is a rare adverse reaction reported with deferasirox that led to a therapeutic dilemma in this particular case. PMID:25969661

  16. Hypersensitivity reaction with deferasirox

    PubMed Central

    Sharma, Atul; Arora, Ekta; Singh, Harmanjit

    2015-01-01

    Thalassemias comprise a group of hereditary blood disorders. Thalassemia major presents with anemia within the first 2 years of life requiring frequent blood transfusions for sustaining life. Regular blood transfusions lead to iron overload-related complications. Prognosis of thalassemia has improved because of the availability of iron-chelating agents. Oral iron chelators are the mainstay of chelation therapy. Deferasirox is a new-generation oral iron chelator for once daily usage. We herein describe a patient of beta thalassemia major who developed an allergic manifestation in the form of erythematous pruritic skin rashes to the oral iron chelator deferasirox. This is a rare adverse reaction reported with deferasirox that led to a therapeutic dilemma in this particular case. PMID:25969661

  17. OH + HBr reaction revisited

    SciTech Connect

    Ravishankara, A.R.; Wine, P.H.; Wells, J.R.

    1985-07-01

    Variable-temperature measurements of the rate coefficient /k(1)/ for the reaction OH + HBr yield Br + H2O are presented. The measurements are verified by two techniques: one involved a 266-nm pulsed-laser photolysis of O3/H2O/HBr/He mixtures in conjunction with time-resolved resonance fluorescence detection of OH, the second comprised pulsed laser-induced fluorescence detection of OH following 248-nm pulsed-laser photolysis of H2O2/HBr/Ar mixtures. It is reported that k(1) = (11.9 + or -1.4 x 10 to the -12th (cu cm)/(molecule)(s) independent of temperature. The measurements are compared with other available results. 6 references.

  18. 19: Cyclization and Pericyclic Reactions (Not Posted) Reactions That Make Rings

    E-print Network

    Reed, Christopher A.

    Intermediates Friedel-Crafts Reactions. Carbocation Addition to Alkenes. Carbocation Ring Contraction19: Cyclization and Pericyclic Reactions (Not Posted) Reactions That Make Rings Cyclization Reactions Enolate Ion Intermediates Intramolecular Aldol Reaction. Dieckmann Condensation. Malonic

  19. Electrophilic Substitution Reactions of Indoles

    NASA Astrophysics Data System (ADS)

    Sundberg, Richard J.

    The topic of this chapter is electrophilic substitution of indole and its derivatives. The indole ring is highly reactive at its 3-position toward protonation, halogenation, alkylation and acylation. Electrophilic substitution can be combined with inter- or intramolecular addition at C-2. Intramolecular alkylation by iminium ions (Pictet-Spengler reaction) is particularly useful. Enantioselectivity can be achieved in many conjugate addition reactions. These reactions have been applied to synthesis of both natural products and drugs.

  20. Speeding chemical reactions by focusing

    E-print Network

    A. M. Lacasta; L. Ramirez-Piscina; J. M. Sancho; K. Lindenberg

    2012-12-13

    We present numerical results for a chemical reaction of colloidal particles which are transported by a laminar fluid and are focused by periodic obstacles in such a way that the two components are well mixed and consequently the chemical reaction is speeded up. The roles of the various system parameters (diffusion coefficients, reaction rate, obstacles sizes) are studied. We show that focusing speeds up the reaction from the diffusion limited rate (t to the power -1/2) to very close to the perfect mixing rate, (t to the power -1).

  1. Dynamic Reaction Figures: An Integrative Vehicle for Understanding Chemical Reactions

    ERIC Educational Resources Information Center

    Schultz, Emeric

    2008-01-01

    A highly flexible learning tool, referred to as a dynamic reaction figure, is described. Application of these figures can (i) yield the correct chemical equation by simply following a set of menu driven directions; (ii) present the underlying "mechanism" in chemical reactions; and (iii) help to solve quantitative problems in a number of different…

  2. From nuclear multifragmentation reactions to supernova explosions

    E-print Network

    Igor N. Mishustin

    2008-03-10

    In this talk I discuss properties of hot stellar matter at sub-nuclear densities which is formed in supernova explosions. I emphasize that thermodynamic conditions there are rather similar to those created in the laboratory by intermediate-energy heavy-ion collisions. Theoretical methods developed for the description of multi-fragment final states in such reactions can be used also for description of the stellar matter. I present main steps of the statistical approach to the equation of state and nuclear composition, dealing with an ensemble of nuclear species instead of one "average" nucleus.

  3. Nucleation and reaction rates controlled by local reaction volume and reaction-induced stress - spinel layer growth as an example

    NASA Astrophysics Data System (ADS)

    Götze, Lutz C.; Milke, Ralf; Dohmen, Ralf; Wirth, Richard

    2014-05-01

    We observed the growth of spinel sensu stricto (MgAl2O4) between periclase (MgO) and corundum (Al2O3) in thin films deposited by the pulsed laser deposition method on crystallographically oriented single crystal substrates. The starting samples consisted of cut and ultra polished single crystals of either corundum (parallel (0001)) or periclase (parallel (111)) and an amorphous source layer of the respective reactant that in the very first stages of the experiments became polycrystalline. The cutting direction in the substrate minerals ensures that the substrate phases start to react along their close-packed hexagonal oxygen layers which allows topotactical growth of the newly formed spinel. The entire layer setup on the substrate crystals was only a few 100 nm thick. The growth of these spinel product layers was monitored in-situ using a heating attachment and synchrotron X-ray diffraction. From the reacted samples we took electron transparent foils by the focused ion beam method and analysed them ex-situ by TEM. At 1000°C we found a difference in spinel growth rate between one and two orders of magnitude between the two substrates, all other parameters held constant. At 900 and 1000 °C spinel had formed after one hour by 0.004 nm/s (900°C) and 0.034 nm/s (1000°C) on corundum substrate, while on periclase substrate the reaction had gone completely through the Al2O3 source layer transforming it to spinel by at least 15-30 times higher reaction rates (boundary values) and probably even faster. At 800°C no reaction occurred between periclase layers and corundum single crystals, whereas spinel crystallized at a (linearized) rate of 46 nm/h on periclase single crystals. We explain our findings by the local reaction volume at the periclase-corundum interface. Many studies (including this one) have established that spinel grows by cation exchange in a rather immobile oxygen sublattice. This mechanism implies a negative volume change at the Sp-Per interface (by -13 %) and a positive volume change at the Sp-Cor interface (by +17 %). We observed in TEM images formation of porosity at the Sp-Per substrate interface and lattice strain in the polycrystalline corundum substrate at the Sp-Cor substrate interface, both observations being fully in line with the respective local volume changes. We infer that the local stress field between the growing reaction layer and the rigid single crystal substrate is responsible for the dramatic effect on both the nucleation and reaction rates. With respect to minerals growing at dry conditions in the Earth's crust (granulite facies) we infer that rates of reactions might strongly depend on local volume changes at interfaces, that reactions are impeded by compressive reaction-induced stress applied to rigid neighboring grains, and that nucleation of thermodynamically stable phases on grain boundaries might be suppressed by a positive reaction volume.

  4. Reacting Polymers with Highly Correlated Initial Conditions

    E-print Network

    Oleg V. Bychuk; Ben O'Shaughnessy; Nicholas Turro

    2000-05-08

    We propose and theoretically study an experiment designed to measure short time polymer reaction kinetics in melts or dilute solutions. The photolysis of groups centrally located along chain backbones, one group per chain, creates pairs of spatially highly correlated macroradicals. We calculate time-dependent rate coefficients $\\kappa(t)$ governing their first order recombination kinetics, which are novel on account of the far-from-equilibrium initial conditions. In dilute solutions (good solvents) reaction kinetics are intrinsically weak, despite the highly reactive radical groups involved. This leads to a generalised mean field kinetics in which the rate of radical density decay $-\

  5. Hemolytic Transfusion Reactions

    PubMed Central

    Strobel, Erwin

    2008-01-01

    Summary The risk of hemolytic transfusion reactions (HTRs) is approximately 1:70,000 per unit. Acute HTRs occurring during or within 24 h after administration of a blood product are usually caused by transfusion of incompatible red blood cells (RBCs), and, more rarely, of a large volume of incompatible plasma. Delayed HTRs are caused by a secondary immune response to an antigen on the donor's RBCs. In some patients with delayed HTRs, an additional bystander hemolysis of the patient's RBCs can be assumed. Different mechanisms lead to intra- and extra-vascular hemolysis, such as complete complement activation, phagocytosis of RBCs covered with C3b by macrophages after incomplete complement activation, or destruction of RBCs covered only with IgG by direct cell-cell contact with K cells. The clinical consequences of HTRs are triggered via several pathophysiological pathways like formation of anaphylatoxins, release of cytokines causing a systemic inflammatory response syndrome, activation of the kinin system, the intrinsic clotting cascade and fibrinolysis resulting in hypotension, disseminated intravascular coagulation, diffuse bleeding, and disruption of microcirculation leading to renal failure and shock. In the following, the symptoms of HTR are introduced, laboratory investigations and treatment are described, and some recommendations for prevention are given. PMID:21512623

  6. Two chamber reaction furnace

    DOEpatents

    Blaugher, Richard D. (Evergreen, CO)

    1998-05-05

    A vertical two chamber reaction furnace. The furnace comprises a lower chamber having an independently operable first heating means for heating the lower chamber and a gas inlet means for admitting a gas to create an ambient atmosphere, and an upper chamber disposed above the lower chamber and having an independently operable second heating means for heating the upper chamber. Disposed between the lower chamber and the upper chamber is a vapor permeable diffusion partition. The upper chamber has a conveyor means for conveying a reactant there through. Of particular importance is the thallinating of long-length thallium-barium-calcium-copper oxide (TBCCO) or barium-calcium-copper oxide (BCCO) precursor tapes or wires conveyed through the upper chamber to thereby effectuate the deposition of vaporized thallium (being so vaporized as the first reactant in the lower chamber at a temperature between about 700.degree. and 800.degree. C.) on TBCCO or BCCO tape or wire (the second reactant) at its simultaneous annealing temperature in the upper chamber of about 800.degree. to 950.degree. C. to thereby replace thallium oxide lost from TBCCO tape or wire because of the high annealing temperature or to deposit thallium on BCCO tape or wire. Continuously moving the tape or wire provides a single-step process that effectuates production of long-length TBCCO superconducting product.

  7. Two chamber reaction furnace

    DOEpatents

    Blaugher, R.D.

    1998-05-05

    A vertical two chamber reaction furnace is described. The furnace comprises a lower chamber having an independently operable first heating means for heating the lower chamber and a gas inlet means for admitting a gas to create an ambient atmosphere, and an upper chamber disposed above the lower chamber and having an independently operable second heating means for heating the upper chamber. Disposed between the lower chamber and the upper chamber is a vapor permeable diffusion partition. The upper chamber has a conveyor means for conveying a reactant there through. Of particular importance is the thallinating of long-length thallium-barium-calcium-copper oxide (TBCCO) or barium-calcium-copper oxide (BCCO) precursor tapes or wires conveyed through the upper chamber to thereby effectuate the deposition of vaporized thallium (being so vaporized as the first reactant in the lower chamber at a temperature between about 700 C and 800 C) on TBCCO or BCCO tape or wire (the second reactant) at its simultaneous annealing temperature in the upper chamber of about 800 to 950 C to thereby replace thallium oxide lost from TBCCO tape or wire because of the high annealing temperature or to deposit thallium on BCCO tape or wire. Continuously moving the tape or wire provides a single-step process that effectuates production of long-length TBCCO superconducting product. 2 figs.

  8. Stochastic behavior and stirring rate effects in the chlorite-iodide reaction

    NASA Astrophysics Data System (ADS)

    Nagypál, István; Epstein, Irving R.

    1988-12-01

    The autocatalytic reaction between chlorite and iodide ions in a closed system is a clock reaction, showing a sudden appearance of brown I2 followed by a rapid disappearance of the color. Under certain conditions, the reaction time displays a striking irreproducibility. This stochastic behavior is studied potentiometrically and spectrophotometrically as a function of initial [I- ], stirring rate and solution volume. The results imply that the irreproducibility is an inherent feature of the reaction generated by fluctuations in the solution after it is ``well mixed.'' The key contributors to the stochasticity are local concentration inhomogeneities resulting from imperfect stirring and the ``supercatalytic'' reaction kinetics. A qualitative explanation is given that incorporates these aspects.

  9. Permutation reactions of organic peroxy radicals in the troposphere

    SciTech Connect

    Madronich, S.; Calvert, J.G. )

    1990-04-20

    Organic peroxy radicals are important intermediates in the atmospheric photooxidation of hydrocarbons. Laboratory studies indicate that these radicals react among themselves (permutation reactions) at rates which should compete with those for reaction with HO{sub 2} and NO{sub x} under some atmospehric conditions. Using the available laboratory data, the authors have developed a simplified method of representing the large number of atmospheric peroxy radical permutation reactions, and have included this in a detailed mechanism of hydrocarbon photooxidation. The potential importance of these reactions was studied for relatively low NO{sub x} conditions such as may be observed in the marine planetary boundary layer (PBL) and the Amazon PBL. The effects of the permutation reactions include suppression of organic peroxy radical concentrations, higher HO{sub 2} and H{sub 2}O{sub 2} concentrations, shorter lifetimes for PAN and other peroxyacyl nitrates (with concomitant faster release of NO{sub x}), and production of substantial concentrations of alcohols and organic acids (including acetic acid). If the kinetic and mechanistic data used in the present study are at least roughly realistic, the peroxy radical reactions probably play an important role in the photochemistry of the clean troposphere.

  10. Environ. Sci. Technol. l W 4 , 28, 290-297 Mechanisms of Chromium(I II) Sorption on Silica. 2. Effect of Reaction

    E-print Network

    Sparks, Donald L.

    . Effect of Reaction Conditions Scott E. Fendorf' Soil Science Divlslon, University of Idaho, Moscow, Idaho ions and the reaction conditions which influence the structure of the sorbate are necessary to evaluate02 (silica) and reaction con- ditions (pH, solution Cr concentrations, and surface coverage

  11. On the importance of steady-state isotopic techniques for the investigation of the mechanism of the reverse water-gas-shift reaction.

    PubMed

    Tibiletti, Daniele; Goguet, Alexandre; Meunier, Frederic C; Breen, John P; Burch, Robbie

    2004-07-21

    The formation and reactivity of surface intermediates in the reverse water-gas-shift reaction on a Pt/CeO2 catalyst are critically dependent on the reaction conditions so that conclusions regarding the reaction mechanism cannot be inferred using ex operando conditions. PMID:15263955

  12. Free Radical Reactions in Food.

    ERIC Educational Resources Information Center

    Taub, Irwin A.

    1984-01-01

    Discusses reactions of free radicals that determine the chemistry of many fresh, processed, and stored foods. Focuses on reactions involving ascorbic acid, myoglobin, and palmitate radicals as representative radicals derived from a vitamin, metallo-protein, and saturated lipid. Basic concepts related to free radical structure, formation, and…

  13. Domino reactions triggered by hydroformylation.

    PubMed

    Petricci, Elena; Cini, Elena

    2013-01-01

    HF reaction represents a selective method for the synthesis of aldehydes starting from alkenes. Because of versatile aldehydes reactivity, it is possible to perform different domino protocols based on contemporary HF, including Michael's reaction, reductive amination, cyclopropanation, lactonization, and many others. This overview reports on the last 5 years' results obtained on this field. PMID:23912442

  14. Chemistry of heavy ion reactions

    SciTech Connect

    Hoffman, D.C.

    1988-10-01

    The use of heavy ions to induce nuclear reactions was reported as early as 1950. Since that time it has been one of the most active areas of nuclear research. Intense beams of ions as heavy as uranium with energies high enough to overcome the Coulomb barriers of even the heaviest elements are available. The wide variety of possible reactions gives rise to a multitude of products which have been studied by many ingenious chemical and physical techniques. Chemical techniques have been of special value for the separation and unequivocal identification of low yield species from the plethora of other nuclides present. Heavy ion reactions have been essential for the production of the trans-Md elements and a host of new isotopes. The systematics of compound nucleus reactions, transfer reactions, and deeply inelastic reactions have been elucidated using chemical techniques. A review of the variety of chemical procedures and techniques which have been developed for the study of heavy ion reactions and their products is given. Determination of the chemical properties of the trans-Md elements, which are very short-lived and can only be produced an ''atom-at-a-time'' via heavy ion reactions, is discussed. 53 refs., 19 figs.

  15. Adverse Reactions to Hallucinogenic Drugs.

    ERIC Educational Resources Information Center

    Meyer, Roger E. , Ed.

    This reports a conference of psychologists, psychiatrists, geneticists and others concerned with the biological and psychological effects of lysergic acid diethylamide and other hallucinogenic drugs. Clinical data are presented on adverse drug reactions. The difficulty of determining the causes of adverse reactions is discussed, as are different…

  16. Isosinglet approximation for nonelastic reactions

    NASA Technical Reports Server (NTRS)

    Wilson, J. W.

    1972-01-01

    Group theoretic relations are derived between different combinations of projectile and secondary particles which appear to have a broad range of application in spacecraft shielding or radiation damage studies. These relations are used to reduce the experimental effort required to obtain nuclear reaction data for transport calculations. Implications for theoretical modeling are also noted, especially for heavy-heavy reactions.

  17. 14 CFR 25.529 - Hull and main float landing conditions.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... stern landings, the limit water reaction load factors are those computed under § 25.527. In addition— (1... landing conditions must be investigated. In addition— (1) The loading for each condition consists of...

  18. 14 CFR 25.529 - Hull and main float landing conditions.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... stern landings, the limit water reaction load factors are those computed under § 25.527. In addition— (1... landing conditions must be investigated. In addition— (1) The loading for each condition consists of...

  19. Heterogeneous photocatalytic reactions of sulfur aromatic compounds.

    PubMed

    Samokhvalov, Alexander

    2011-11-18

    Sulfur aromatic compounds, such as mono-, di-, tri-, and tetraalkyl-substituted thiophene, benzothiophenes, dibenzothiophenes, are the molecular components of many fossils (petroleum, oil shale, tar sands, bitumen). Structural units of natural, cross-linked heteroaromatic polymers present in brown coals, turf, and soil are similar to those of sulfur aromatic compounds. Many sulfur aromatic compounds are found in the streams of petroleum refining and upgrading (naphthas, gas oils) and in the consumer products (gasoline, diesel, jet fuels, heating fuels). Besides fossils, the structural fragments of sulfur aromatic compounds are present in molecules of certain organic semiconductors, pesticides, small molecule drugs, and in certain biomolecules present in human body (pheomelanin pigments). Photocatalysis is the frontier area of physical chemistry that studies chemical reactions initiated by absorption of photons by photocatalysts, that is, upon electronic rather than thermal activation, under "green" ambient conditions. This review provides systematization and critical review of the fundamental chemical and physicochemical information on heterogeneous photocatalysis of sulfur aromatic compounds accumulated in the last 20-30 years. Specifically, the following topics are covered: physicochemical properties of sulfur aromatic compounds, major classes of heterogeneous photocatalysts, mechanisms and reactive intermediates of photocatalytic reactions of sulfur aromatic compounds, and the selectivity of these reactions. Quantum chemical calculations of properties and structures of sulfur aromatic compounds, their reactive intermediates, and the structure of adsorption complexes formed on the surface of the photocatalysts are also discussed. PMID:21809426

  20. Anti-damping effect of radiation reaction

    NASA Astrophysics Data System (ADS)

    Wang, G.; Li, H.; Shen, Y. F.; Yuan, X. Z.; Zi, J.

    2010-01-01

    The anti-damping effect of radiation reaction, which means the radiation reaction does non-negative work on a radiating charge, is investigated at length by using the Lorentz-Dirac equation (LDE) for the motion of a point charge respectively acted on by (a) a pure electric field, (b) a pure magnetic field and (c) the fields of an electromagnetic wave. We found that the curvature of the charge's trajectory plays an important role in the radiation reaction force, and the anti-damping effect cannot take place for the real macroscopic motions of a point charge. The condition for this anti-damping effect to take place is that the gradient of the external force field must exceed a certain value over the region of magnitude of the classical radius of massive charges (~10-15 m). Our results are potentially helpful to lessen the controversy on LDE and justify it as the correct classical equation describing the radiating charge's motion. If this anti-damping effect of LDE were a real existing physical process, it could serve as a mechanism within the context of classical electrodynamics for the stability of hydrogen atoms. Using the picture of an electron in quantum electrodynamics, namely the negative bare charge surrounded by the polarized positive charges of vacuum, we can obtain a reasonable explanation for the energy transferred to the electron during the occurrence of the anti-damping effect, on which the venerable work of Wheeler and Feynman has thrown some light.

  1. Photocatalytic fluoroalkylation reactions of organic compounds.

    PubMed

    Barata-Vallejo, Sebastián; Bonesi, Sergio M; Postigo, Al

    2015-12-14

    Photocatalytic methods for fluoroalkyl-radical generation provide more convenient alternatives to the classical perfluoroalkyl-radical (Rf) production through chemical initiators, such as azo or peroxide compounds or the employment of transition metals through a thermal electron transfer (ET) initiation process. The mild photocatalytic reaction conditions tolerate a variety of functional groups and, thus, are handy to the late-stage modification of bioactive molecules. Transition metal-photocatalytic reactions for Rf radical generation profit from the redox properties of coordinatively saturated Ru or Ir organocomplexes to act as both electron donor and reductive species, thus allowing for the utilization of electron accepting and donating fluoroalkylating agents for Rf radical production. On the other hand, laboratory-available and inexpensive photoorgano catalysts (POC), in the absence of transition metals, can also act as electron exchange species upon excitation, resulting in ET reactions that produce Rf radicals. In this work, a critical account of transition metal and transition metal-free Rf radical production will be described with photoorgano catalysts, studying classical examples and the most recent investigations in the field. PMID:26464314

  2. [Anaphylactic reaction following hair bleaching].

    PubMed

    Babilas, P; Landthaler, M; Szeimies, R-M

    2005-12-01

    Ammonium persulphate is a potent bleach and oxidizing agent that is commonly present in hair bleaches. Because bleaching is so commonly performed, hairdressers often develop allergic contact dermatitis to ammonium persulphate. In addition to this delayed reaction, asthma and rhinitis may develop as immediate reactions in those exposed to the fumes. Severe anaphylactic reactions are rare. We report a 24-year-old woman who acquired dermatitis following contact with bleaching substances while working as a hairdresser. After changing her profession, the dermatitis disappeared. Following the private use of a hairdressing bleach containing ammonium persulphate, she suffered a severe anaphylactic reaction with unconsciousness. The patient also developed an anaphylactic reaction three hours following patch testing with the hairdresser battery. The rub test with ammonium persulphate (2.5%) in a 1:100 solution was positive. PMID:15688222

  3. Protein methylation reactions in intact pea chloroplasts

    SciTech Connect

    Niemi, K.J. )

    1989-04-01

    Post-translational protein methylation was investigated in Pisum sativum chloroplasts. Intact pea chloroplasts were incubated with ({sup 3}H-methyl)-S-adenosylmethionine under various conditions. The chloroplasts were then separated into stromal and thylakoid fractions and analyzed for radioactivity transferred to protein. Light enhanced the magnitude of labeling in both fractions. One thylakoid polypeptide with an apparent molecular mass of 43 kDa was labeled only in the light. Several other thylakoid and stromal proteins were labeled in both light and dark-labeling conditions. Both base-labile methylation, carboxy-methylesters and base-stable groups, N-methylations were found. Further characterization of the methyl-transfer reactions will be presented.

  4. Effective reaction rates for diffusion-limited reaction cycles.

    PubMed

    Na??cz-Jawecki, Pawe?; Szyma?ska, Paulina; Kocha?czyk, Marek; Mi?kisz, Jacek; Lipniacki, Tomasz

    2015-12-01

    Biological signals in cells are transmitted with the use of reaction cycles, such as the phosphorylation-dephosphorylation cycle, in which substrate is modified by antagonistic enzymes. An appreciable share of such reactions takes place in crowded environments of two-dimensional structures, such as plasma membrane or intracellular membranes, and is expected to be diffusion-controlled. In this work, starting from the microscopic bimolecular reaction rate constants and using estimates of the mean first-passage time for an enzyme-substrate encounter, we derive diffusion-dependent effective macroscopic reaction rate coefficients (EMRRC) for a generic reaction cycle. Each EMRRC was found to be half of the harmonic average of the microscopic rate constant (phosphorylation c or dephosphorylation d), and the effective (crowding-dependent) motility divided by a slowly decreasing logarithmic function of the sum of the enzyme concentrations. This implies that when c and d differ, the two EMRRCs scale differently with the motility, rendering the steady-state fraction of phosphorylated substrate molecules diffusion-dependent. Analytical predictions are verified using kinetic Monte Carlo simulations on the two-dimensional triangular lattice at the single-molecule resolution. It is demonstrated that the proposed formulas estimate the steady-state concentrations and effective reaction rates for different sets of microscopic reaction rates and concentrations of reactants, including a non-trivial example where with increasing diffusivity the fraction of phosphorylated substrate molecules changes from 10% to 90%. PMID:26646890

  5. Chemiluminescent spectra of alkali-halogen reactions R. C. Oldenbarg, J. L. Gale*, and R. N. Zare

    E-print Network

    Chemiluminescent spectra of alkali-halogen reactions R. C. Oldenbarg, J. L. Gale*, and R. N. Zare a beam-gas arrangement, we have obtained the chemiluminescence spectra of alkali-halogen reactions the conditions prevailing in flame studies. For the mixed halogen reactions, the MY ground state is the more

  6. CHEMICAL REACTION SYSTEMS WITH TORIC STEADY STATES MERCEDES PEREZ MILLAN, ALICIA DICKENSTEIN, ANNE SHIU, AND CARSTEN CONRADI

    E-print Network

    Rowell, Eric C.

    1 CHEMICAL REACTION SYSTEMS WITH TORIC STEADY STATES MERCEDES P´EREZ MILL´AN, ALICIA DICKENSTEIN, ANNE SHIU, AND CARSTEN CONRADI Abstract. Mass-action chemical reaction systems are frequently used that such systems have toric steady states. Our main result gives sufficient conditions for a chemical reaction

  7. Corrections Stoichiometry of the Topa Quinone Biogenesis Reaction in

    E-print Network

    van Stokkum, Ivo

    was determined by H2O2 titration at the exact pH and concentration conditions used in the peroxide production. The experimental conditions for the measure- ment of the production of H2O2 were inaccurately reported. Thus concentration approximately 15 µM) in a reaction volume of 0.8 mL. BI9950802 10.1021/bi9950802 Published on Web

  8. N-Heterocyclic Carbene Complexes in Reactions Involving Carbon Monoxide

    NASA Astrophysics Data System (ADS)

    Jeletic, Matthew; Veige, Adam

    This chapter focuses on carbon monoxide as a reagent in M-NHC catalysed reactions. The most important and popular of these reactions is hydroformylation. Unfortunately, uncertainty exists as to the identity of the active catalyst and whether the NHC is bound to the catalyst in a number of the reported reactions. Mixed bidentate NHC complexes and cobalt-based complexes provide for better stability of the catalyst. Catalysts used for hydroaminomethylation and carbonylation reactions show promise to rival traditional phosphine-based catalysts. Reports of decarbonylation are scarce, but the potential strength of the M-NHC bond is conducive to the harsh conditions required. This report will highlight, where appropriate, the potential benefits of exchanging traditional phosphorous ligands with N-heterocyclic carbenes as well as cases where the role of the NHC might need re-evaluation. A review by the author on this topic has recently appeared [1].

  9. [Spectroscopic study on the combustion reaction characteristics of methylcyclohexane].

    PubMed

    Li, Cong-Shan; Li, Ping; Zhang, Chang-Hua; Nie, Xiao-Fei; Li, Xiang-Yuan

    2011-09-01

    Using a measurement system consisting of monochromators, photomultiplier tubes, piezoelectric pressure sensors and a digital oscilloscope, characteristic emissions of intermediate products OH, CH and C2 produced in the combustion reaction of methylcyclohexane were measured behind reflected shock waves in a shock tube, and ignition delay times of methylcyclohexane/ oxygen/argon were acquired. Experimental conditions cover temperatures from 1 164 to 1 566 K, pressures from 1.03 to 1.99 atm, a fuel concentration of 1.0%, and an equivalence ratio of 1.0. Combustion reaction characteristics of methylcyclohexane were obtained qualitatively by analyzing emissions from intermediate products OH, CH and C2. The measured ignition delay times agree with available experimental data and the prediction of a combustion reaction mechanism. Current work provides experimental data for constructing and validating the combustion reaction mechanism of methylcyclohexane. PMID:22097862

  10. Portable centrifugal analyzer for the determination of rapid reaction kinetics

    SciTech Connect

    Bostick, W.D.; Bauer, M.L.; McCracken, R.; Mrochek, J.E.

    1980-02-01

    A portable centrifugal analyzer prototype is capable of rapidly initiating reactions and monitoring 17 optical channels as they rotate past a stationary photodetector. An advanced rotor drive permits transfer of discretely loaded sample and reagent into a cuvette within 60 ms. Various rotor designs have been employed to ensure effieicnt mixing concurrent with solution transfer, thus permitting absorbance or luminescence measurements to be made almost immediately after solution contract. Dye-dillution studies have been used to investigate transfer and mixing efficiencies. Rotor designs with parallel access for sample and reagent into the cuvette were found to promote efficient mixing during liquid transfer. The hypochlorite-luminol chemiluminescent reaction served to demonstrate the utility of the system for performing rapid kinetic analyses. Appropriate adjustment of reaction conditions allows first-order reaction half-lives as short as 0.04 s to be measured. 13 figures, 3 tables.

  11. Children's disaster reactions: the influence of exposure and personal characteristics.

    PubMed

    Pfefferbaum, Betty; Jacobs, Anne K; Griffin, Natalie; Houston, J Brian

    2015-07-01

    This paper reviews children's reactions to disasters and the personal and situational factors that influence their reactions. Posttraumatic stress disorder (PTSD) and posttraumatic stress reactions are the most commonly studied outcomes, though other conditions also occur including anxiety, depression, behavior problems, and substance use. More recently, traumatic grief and posttraumatic growth have been explored. New research has delineated trajectories of children's posttraumatic stress reactions and offered insight into the long-term consequences of their disaster experiences. Risk factors for adverse outcomes include pre-disaster vulnerabilities, perception of threat, and loss and life disruptions post-disaster. Areas in need of additional research include studies on the timing and course of depression and anxiety post-event and their interactions with other disorders, disaster-related functional and cognitive impairment, positive outcomes, and coping. PMID:25980513

  12. Uniform General Conditions and Supplementary General Conditions

    E-print Network

    and Other Laws Governing Construction 8 Article 3. General Responsibilities of Owner and Contractor 11Uniform General Conditions and Supplementary General Conditions for Construction and Design Contracts 2013 Amended #12;2 | P a g e Table of Contents Article 1. Definitions 3 Article 2. Wage Rates

  13. Shock-induced reaction synthesis (SRS) of nickel aluminides

    SciTech Connect

    Thadhani, N.N.; Work, S. , New Mexico Tech, Socorro, New Mexico 87801 ); Graham, R.A.; Hammetter, W.F. )

    1992-05-01

    Shock-induced chemical reactions between nickel and aluminum powders (mixed in Ni{sub 3}Al stoichiometry) are used for the synthesis of nickel aluminides. It is shown that the extent of shock-induced chemical reactions and the nature of the shock-synthesized products are influenced by the morphology of the starting powders. Irregular (flaky type) and fine morphologies of the powders undergo complete reactions in contrast to partial reactions occurring in coarse and uniform morphology powders under identical shock loading conditions. Furthermore, irregular morphology powders result in the formation of the equiatomic (B2 phase) NiAl compound while the Ni{sub 3}Al (L1{sub 2} phase) compound is the reaction product with coarse and regular morphology powders. Shock-induced reaction synthesis can be characterized as a bulk reaction process involving an intense mechanochemical'' mechanism. It is a process in which shock compression induces fluid-like plastic flow and mixing, and enhances the reactivity due to the introduction of defects and cleansing of particle surfaces, which strongly influence the synthesis process.

  14. Synthesis of 1,4:3,6-dianhydrohexitols diesters from the palladium-catalyzed hydroesterification reaction.

    PubMed

    Pruvost, Romain; Boulanger, Jérôme; Léger, Bastien; Ponchel, Anne; Monflier, Eric; Ibert, Mathias; Mortreux, André; Chenal, Thomas; Sauthier, Mathieu

    2014-11-01

    The hydroesterification of alpha olefins has been used to synthesize diesters from bio-based secondary diols: isosorbide, isomannide, and isoidide. The reaction was promoted by 0.2% palladium catalyst generated in?situ from palladium acetate/triphenylphosphine/para-toluene sulfonic acid. Optimized reaction conditions allowed the selective synthesis of the diesters with high yields and the reaction conditions could be scaled up to the synthesis of hundred grams of diesters from isosorbide and 1-octene with solvent-free conditions. PMID:25209303

  15. Reaction center photochemistry of Heliobacterium chlorum.

    PubMed

    Nitschke, W; Sétif, P; Liebl, U; Feiler, U; Rutherford, A W

    1990-12-18

    Reaction center photochemistry in Heliobacterium chlorum has been investigated by using EPR and flash absorption spectroscopy at low temperatures. The following results were obtained. At 5 K, in the presence of ascorbate, continuous illumination resulted in the formation of P798+ and a reduced iron-sulfur center designated FB (gz = 2.07, gy = 1.93, gx = 1.89). This state was stable at low temperatures, but the yield for this reaction was low, and it was estimated that it occurred only in about 3% of the centers upon the first flash. After continuous illumination of a dilute sample for 10 min, still only half of the centers attained this state. In most centers, flash excitation at 5 K produced a state which recombined with time constants of 2.5 ms (congruent to 80%) and 850 microseconds (congruent to 20%). These two phases were differently influenced by the redox state of the reaction center, indicating that two different acceptors were involved in the recombination reactions. When continuous illumination was given at 200 K, a second center, designated FA, was additionally reduced (gz = 2.05, gy = 1.95, gx = 1.90). High concentrations of dithionite resulted in the chemical reduction of FB and of most of FA; illumination at 200 K resulted in the further reduction of FA. Two triplet states were identified by EPR and optical spectroscopy. The amplitude of the narrower triplet (magnitude of D = 226 x 10(-4) cm-1) varied with the redox state of the iron-sulfur centers and was influenced by a component thought to be a quinone undergoing double reduction. It correlated with a triplet state observed by flash absorption spectroscopy showing a bleaching at 798 nm and is attributed to a triplet state formed by charge recombination in the reaction center. Its narrowness is taken as an indication of its origin on a pair of bacteriochlorophylls, and its orientation indicates an orientation of the chlorophyll ring plane perpendicular to the membrane plane. The second triplet had a wider splitting (magnitude of D = 242 x 10(-4) cm-1), did not vary systematically with redox conditions, corresponds to an optical spectrum with a maximum at 812 nm, and is not ordered in the membrane. It was thus attributed to a triplet located on a BChl g monomer in the antenna. The reaction center photochemistry in H. chlorum is comparable in many respects to that of photosystem I and green sulfur bacteria. Earlier contrasting conclusions are discussed and rationalized in light of the present results. PMID:2176893

  16. Low Temperature Trapping: from Reactions to Spectroscopy

    NASA Astrophysics Data System (ADS)

    Schlemmer, S.; Asvany, O.; Brunken, S.

    2013-06-01

    The kinetics of ion - molecule reactions are investigated in higher-order multipole traps by observation of the temporal evolution of mass selected parent ions in the presence of a neutral reaction partner. Rate coeffients for fast reactions (proceeding at collision rate) and very slow reactions (taking millions of collisions) are determined over a wide range of temperatures. Endothermic or hindered reactions can be promoted by excitation of the ion via absorption of a photon. Scanning the photon energy while detecting the number of product ions establishes an action spectroscopy method which we developed over the last 10-15 years and termed LIR: laser or light induced reactions. The main advantages of LIR are mass selection of the parent ion and low temperature conditions in the trap. Long storage times in combination with a near unity detection efficiency make LIR one of the most sensitive spectroscopy methods. The status quo of LIR will be discussed on selected examples. Recent measurements are concerned with ro-vibrational spectra of CH_2D^+ and CH_5^+ at highest resolution using cw OPO radiation. In the particular case of CH_5^+, the lines in the mid IR have been measured at a nominal temperature of 10 K and a frequency comb has been used for absolute calibration. Line positions can be determined to an accuracy which shall enable us in the future to obtain rotational spectra in a THz-IR double resonance approach. We tested the feasibility of this two photon method recently on H_2D^+. S. Schlemmer, T. Kuhn, E. Lescop, and D. Gerlich, Laser excited N_2^+ in a 22-Pole Trap: Experimental Studies of Rotational Relaxation Processes, Int. J. Mass Spectrometry and Ion Processes, 185-187, 589-602, (1999), S.D. Ivanov, O. Asvany, A. Witt, E. Hugo, G. Mathias, B. Redlich, D. Marx and S. Schlemmer, Quantum-induced symmetry breaking explains infrared spectra of CH_5^+ isotopologues, Nature Chemistry, 2, 298-302 (2010) S. Gaertner, J. Krieg, A. Klemann, O. Asvany and S. Schlemmer, Rotational transitions of CH_2D^+ determined by high-resolution IR spectroscopy, Astron. Astrophys., 516 (2010) L3. O. Asvany, J. Krieg, and S. Schlemmer, Frequency comb assisted mid-infrared spectroscopy of cold molecular ions, Rev.Sci.Instr., 83 (2012), 076102.

  17. Design of silicone rubber according to requirements based on the multi-objective optimization of chemical reactions

    SciTech Connect

    Jia Yuxi; Sun Sheng; Liu Lili; Mu Yue; An Lijia

    2004-08-16

    The explicit expression between composition and mechanical properties of silicone rubber was derived from the physics of polymer elasticity, the implicit expression among material composition, reaction conditions and reaction efficiency was obtained from chemical thermodynamics and kinetics, and then an implicit multi-objective optimization model was constructed. Genetic algorithm was applied to optimize material composition and reaction conditions, and the finite element method of cross-linking reaction processes was used to solve multi-objective functions, on the basis of which a new optimization methodology of cross-linking reaction processes was established. Using this methodology, rubber materials can be designed according to pre-specified requirements.

  18. Thermodynamic limitations on microbially catalyzed reaction rates

    NASA Astrophysics Data System (ADS)

    LaRowe, Douglas E.; Dale, Andrew W.; Amend, Jan P.; Van Cappellen, Philippe

    2012-08-01

    Quantification of global biogeochemical cycles requires knowledge of the rates at which microorganisms catalyze chemical reactions. In order for models that describe these processes to capture global patterns of change, the underlying formulations in them must account for biogeochemical transformations over seasonal and millennial time scales in environments characterized by different energy levels. Building on existing models, a new thermodynamic limiting function is introduced. With only one adjustable parameter, this function that can be used to model microbial metabolism throughout the range of conditions in which organisms are known to be active. The formulation is based on a comparison of the amount of energy available from any redox reaction to the energy required to maintain a membrane potential, a proxy for the minimum amount of energy required by an active microorganism. This function does not require species- or metabolism-specific parameters, and can be used to model metabolisms that capture any amount of energy. The utility of this new thermodynamic rate limiting term is illustrated by applying it to three low-energy processes: fermentation, methanogenesis and sulfate reduction. The model predicts that the rate of fermentation will be reduced by half once the Gibbs energy of the catalyzed reaction reaches -12 kJ (mol e-)-1, and then slowing exponentially until the energy yield approaches zero. Similarly, the new model predicts that the low energy yield of methanogenesis, -4 to -0.5 kJ (mol e-)-1, for a partial pressure of H2 between 11 and 0.6 Pa decreases the reaction rate by 95-99%. Finally, the new function's utility is illustrated through its ability to accurately model sulfate concentration data in an anoxic marine sediment.

  19. Quantum effects in unimolecular reaction dynamics

    SciTech Connect

    Gezelter, J.D.

    1995-12-01

    This work is primarily concerned with the development of models for the quantum dynamics of unimolecular isomerization and photodissociation reactions. We apply the rigorous quantum methodology of a Discrete Variable Representation (DVR) with Absorbing Boundary Conditions (ABC) to these models in an attempt to explain some very surprising results from a series of experiments on vibrationally excited ketene. Within the framework of these models, we are able to identify the experimental signatures of tunneling and dynamical resonances in the energy dependence of the rate of ketene isomerization. Additionally, we investigate the step-like features in the energy dependence of the rate of dissociation of triplet ketene to form {sup 3}B{sub 1} CH{sub 2} + {sup 1}{sigma}{sup +} CO that have been observed experimentally. These calculations provide a link between ab initio calculations of the potential energy surfaces and the experimentally observed dynamics on these surfaces. Additionally, we develop an approximate model for the partitioning of energy in the products of photodissociation reactions of large molecules with appreciable barriers to recombination. In simple bond cleavage reactions like CH{sub 3}COCl {yields} CH{sub 3}CO + Cl, the model does considerably better than other impulsive and statistical models in predicting the energy distribution in the products. We also investigate ways of correcting classical mechanics to include the important quantum mechanical aspects of zero-point energy. The method we investigate is found to introduce a number of undesirable dynamical artifacts including a reduction in the above-threshold rates for simple reactions, and a strong mixing of the chaotic and regular energy domains for some model problems. We conclude by discussing some of the directions for future research in the field of theoretical chemical dynamics.

  20. Energy Diagrams for Enzyme-Catalyzed Reactions: Concepts and Misconcepts

    ERIC Educational Resources Information Center

    Aledo, J. Carlos; Lobo, Carolina; del Valle, Alicia Esteban

    2003-01-01

    Despite the utility that energy diagrams have as a teaching and learning tool, a survey of their use, in seven popular Biochemistry textbooks, reveals that there is certain confusion around this topic. In our opinion, this confusion arises from the reluctance of authors to consider and indicate the conditions under which the reaction being…

  1. PROCESS INTENSIFICATION: MICROWAVE INITIATED REACTIONS USING A CONTINUOUS FLOW REACTOR

    EPA Science Inventory

    The concept of process intensification has been used to develop a continuous narrow channel reactor at Clarkson capable of carrying out reactions under isothermal conditions whilst being exposed to microwave (MW) irradiation thereby providing information on the true effect of mi...

  2. 2-Methylenetetrahydropyrans: Efficient Partners in the Carbonyl Ene Reaction

    PubMed Central

    Liang, Guohua; Sharum, Dakin T.; Lam, Troy

    2013-01-01

    The carbonyl ene reaction of 2-methylenetetrahydropyrans provides a rapid, high yielding route for the preparation of ?-hydroxydihydropyrans under mild conditions. This process provides a new entry for the synthesis of 2-substituted tetrahydropyrans and for the direct introduction of oxygen heterocycles into molecular frameworks. PMID:24215279

  3. REACTION KINETICS OF CA-BASED SORBENTS WITH HC1

    EPA Science Inventory

    The kinetics of the reaction between CaO and HCl were investigated under conditions that minimize bulk mass transfer and pore diffusion limitations. Reactivity data from 0.2- to 1-s exposure to 5000 ppm HCl in a fixed bed reactor were analyzed by a shrinking core model of diffusi...

  4. REACTION KINETICS OF CA-BASED SORBENTS WITH HC1

    EPA Science Inventory

    The paper gives results of an investigation of the kinetics of the reaction between CaO and HC1 under conditions that minimize bulk mass transfer and pore diffusion limitations. eactivity data from 0.2 to 1 s exposure to 5000 ppm HC1 in a fixed-bed reactor were analyzed by a shri...

  5. Blue Moon sampling, vectorial reaction coordinates, and unbiased constrained dynamics

    E-print Network

    Van Den Eijnden, Eric

    Blue Moon sampling, vectorial reaction coordinates, and unbiased constrained dynamics Giovanni force in terms of a conditional expectation which can be computed by Blue Moon sampling Introduction Fifteen years ago the Blue Moon ensemble method was introduced to sample rare events that occur

  6. Hypernuclear spectroscopy with the (e, e-prime K+) reaction

    SciTech Connect

    Yu Fujii

    2003-06-16

    Experimental conditions of the (e,e'K+) reaction for hypernuclear spectroscopy at Jefferson Lab Hall C are considered. Then two hypernuclear experiments at Hall C, Jlab E89-009 and E01-011 are introduced and compared, and possibility to extract information on hypernuclear states are discussed by referring expected spectra obtained with a DWIA calculation.

  7. Photochemical reactions of various model protocell systems

    NASA Technical Reports Server (NTRS)

    Folsome, C. E.

    1986-01-01

    Models for the emergence of cellular life on the primitive Earth, and for physical environments of that era have been studied that embody these assumptions: (1) pregenetic cellular forms were phase-bounded systems primarily photosynthetic in nature, and (2) the early Earth environment was anoxic (lacking appreciable amounts of free hydrogen). It was found that organic structures can also be formed under anoxic conditions (N2, CO3=, H2O) by protracted longwavelength UV radiation. Apparently these structures form initially as organic layers upon CaCO3 crystalloids. The question remains as to whether the UV photosynthetic ability of such phase bounded structures is a curiosity, or a general property of phase bounded systems which is of direct interest to the emergence of cellular life. The question of the requirement and sailient features of a phase boundary for UV photosynthetic abilities was addressed by searching for similar general physical properties which might be manifest in a variety of other simple protocell-like structures. Since it has been shown that laboratory protocell models can effect the UV photosynthesis of low molecular weight compounds, this reaction is being used as an assay to survey other types of structures for similar UV photosynthetic reactions. Various kinds of structures surveyed are: (1) proteinoids; (2) liposomes; (3) reconstituted cell membrane spheroids; (4) coacervates; and (5) model protocells formed under anoxic conditions.

  8. 14 CFR Appendix C to Part 23 - Basic Landing Conditions

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... to Part 23—Basic Landing Conditions Condition Tail wheel type Level landing Tail-down landing Nose wheel type Level landing with inclined reactions Level landing with nose wheel just clear of ground Tail... absorber), percent 100 100 100 100 100. Tire deflection Static Static Static Static Static. Main...

  9. 14 CFR Appendix C to Part 23 - Basic Landing Conditions

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... to Part 23—Basic Landing Conditions Condition Tail wheel type Level landing Tail-down landing Nose wheel type Level landing with inclined reactions Level landing with nose wheel just clear of ground Tail... absorber), percent 100 100 100 100 100. Tire deflection Static Static Static Static Static. Main...

  10. 14 CFR Appendix C to Part 23 - Basic Landing Conditions

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... to Part 23—Basic Landing Conditions Condition Tail wheel type Level landing Tail-down landing Nose wheel type Level landing with inclined reactions Level landing with nose wheel just clear of ground Tail... absorber), percent 100 100 100 100 100. Tire deflection Static Static Static Static Static. Main...

  11. 14 CFR Appendix C to Part 23 - Basic Landing Conditions

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... to Part 23—Basic Landing Conditions Condition Tail wheel type Level landing Tail-down landing Nose wheel type Level landing with inclined reactions Level landing with nose wheel just clear of ground Tail... absorber), percent 100 100 100 100 100. Tire deflection Static Static Static Static Static. Main...

  12. 14 CFR Appendix C to Part 23 - Basic Landing Conditions

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... to Part 23—Basic Landing Conditions Condition Tail wheel type Level landing Tail-down landing Nose wheel type Level landing with inclined reactions Level landing with nose wheel just clear of ground Tail... absorber), percent 100 100 100 100 100. Tire deflection Static Static Static Static Static. Main...

  13. ANALYSIS OF THERMAL DECOMPOSITION PRODUCTS OF FLUE GAS CONDITIONING AGENTS

    EPA Science Inventory

    The report gives results of a study of reactions of several flue gas conditioning agents in a laboratory-scale facility simulating conditions in the flue gas train of a coal-burning power plant. Primary purposes of the study were to characterize the chemical species resulting fro...

  14. Quantification of kinetics for enzyme-catalysed reactions: implications for diffusional limitations at the 10 ml scale.

    PubMed

    Matosevic, S; Micheletti, M; Woodley, J M; Lye, G J; Baganz, F

    2008-06-01

    The effects of different reaction scales [100 microl reactions in 96-standard round well (SRW) plates and 10 ml reactions in 24-square well (SW) plates] have been investigated using, as a model, transketolase (TK)-catalysed reaction producing L-erythrulose. Reactions were carried out under non-shaking, shaking and at 10 ml scale stirring conditions to assess the effect of diffusional limitations. Statistical analysis confirmed the significance of the observed difference in reaction rates under given conditions. Only when the laboratory scale system (10 ml) was well mixed did the reaction rate become comparable to that in the microwells, where there is negligible diffusional limitation. These findings have important implications for the scale-up (or scale-down) of enzyme-catalysed reactions. PMID:18224278

  15. Cues of maternal condition influence offspring selfishness.

    PubMed

    Wong, Janine W Y; Lucas, Christophe; Kölliker, Mathias

    2014-01-01

    The evolution of parent-offspring communication was mostly studied from the perspective of parents responding to begging signals conveying information about offspring condition. Parents should respond to begging because of the differential fitness returns obtained from their investment in offspring that differ in condition. For analogous reasons, offspring should adjust their behavior to cues/signals of parental condition: parents that differ in condition pay differential costs of care and, hence, should provide different amounts of food. In this study, we experimentally tested in the European earwig (Forficula auricularia) if cues of maternal condition affect offspring behavior in terms of sibling cannibalism. We experimentally manipulated female condition by providing them with different amounts of food, kept nymph condition constant, allowed for nymph exposure to chemical maternal cues over extended time, quantified nymph survival (deaths being due to cannibalism) and extracted and analyzed the females' cuticular hydrocarbons (CHC). Nymph survival was significantly affected by chemical cues of maternal condition, and this effect depended on the timing of breeding. Cues of poor maternal condition enhanced nymph survival in early broods, but reduced nymph survival in late broods, and vice versa for cues of good condition. Furthermore, female condition affected the quantitative composition of their CHC profile which in turn predicted nymph survival patterns. Thus, earwig offspring are sensitive to chemical cues of maternal condition and nymphs from early and late broods show opposite reactions to the same chemical cues. Together with former evidence on maternal sensitivities to condition-dependent nymph chemical cues, our study shows context-dependent reciprocal information exchange about condition between earwig mothers and their offspring, potentially mediated by cuticular hydrocarbons. PMID:24498046

  16. Cues of Maternal Condition Influence Offspring Selfishness

    PubMed Central

    Wong, Janine W. Y.; Lucas, Christophe; Kölliker, Mathias

    2014-01-01

    The evolution of parent-offspring communication was mostly studied from the perspective of parents responding to begging signals conveying information about offspring condition. Parents should respond to begging because of the differential fitness returns obtained from their investment in offspring that differ in condition. For analogous reasons, offspring should adjust their behavior to cues/signals of parental condition: parents that differ in condition pay differential costs of care and, hence, should provide different amounts of food. In this study, we experimentally tested in the European earwig (Forficula auricularia) if cues of maternal condition affect offspring behavior in terms of sibling cannibalism. We experimentally manipulated female condition by providing them with different amounts of food, kept nymph condition constant, allowed for nymph exposure to chemical maternal cues over extended time, quantified nymph survival (deaths being due to cannibalism) and extracted and analyzed the females’ cuticular hydrocarbons (CHC). Nymph survival was significantly affected by chemical cues of maternal condition, and this effect depended on the timing of breeding. Cues of poor maternal condition enhanced nymph survival in early broods, but reduced nymph survival in late broods, and vice versa for cues of good condition. Furthermore, female condition affected the quantitative composition of their CHC profile which in turn predicted nymph survival patterns. Thus, earwig offspring are sensitive to chemical cues of maternal condition and nymphs from early and late broods show opposite reactions to the same chemical cues. Together with former evidence on maternal sensitivities to condition-dependent nymph chemical cues, our study shows context-dependent reciprocal information exchange about condition between earwig mothers and their offspring, potentially mediated by cuticular hydrocarbons. PMID:24498046

  17. Nuclear Structure and Reaction Mechanism Studies with Multinucleon Reactions

    SciTech Connect

    Regan, P. H.; Jones, G. A.; Podolyak, Zs.; Abdullah, M.; Gelletly, W.; Langdown, S. D.; Wollel, G.; De Angelis, G.; Gadea, A.; Kroell, Th.; Marginean, N.; Martinez, T.; Napoli, D. R.; Rusu, C.; Tonev, D.; Zhang, Y. H.; Ur, C. A.; Axiotis, M.; Bazzacco, D.; Farnea, E.

    2006-08-14

    This contribution reports on the results of an experiment to study the near-yrast states in selenium- and osmium-like nuclei, following their population in thick-target, multinucleon transfer reactions between an 82Se beam and a 192Os target. The experimental results for the level scheme for 84Se are presented together with investigations into the use of multi-dimensional gamma-ray energy gating to investigate angular momentum population in such heavy-ion binary reactions.

  18. Siloxy alkynes in annulation reactions.

    PubMed

    Qian, Hui; Zhao, Wanxiang; Sun, Jianwei

    2014-12-01

    Siloxy alkynes are a family of versatile species in organic synthesis. This account reviews the annulation reactions of siloxy alkynes for the synthesis of a variety of carbo- and heterocyclic products. With various dipolarophiles or dipolarophile-like reaction partners, siloxy alkynes are capable of forming small (three- to six-membered) rings. Recently, we have expanded the scope to the synthesis of medium- and large-ring lactones, enabled by the design of new amphoteric molecules as well as a new ring-expansion strategy. These annulation reactions provide not only practically useful syntheses of cyclic molecules, but also important understanding of the fundamental reactivity of siloxy alkynes. PMID:25171137

  19. [Arthropod bite reactions and pyodermias].

    PubMed

    Hengge, U R

    2008-08-01

    Tourists in the tropics often develop reactions to bites or stings of mosquitoes, fleas, mites, ants, bedbugs, beetles, larva, millipedes, spiders and scorpions. In addition, they may have fresh or salt water exposure to sponges, corals, jellyfish and sea urchins with resultant injury and inflammation. Bacterial skin infections (pyodermias) can follow bites or stings as well as mechanical trauma. The most common bacteria involved in skin infections are staphylococci and streptococci. For tourists, bacterial infections are often complicating a pruritic bite reaction and scratching. It is important to know the cause of the bite reaction and pyoderma in order to take appropriate therapeutic measures. PMID:18626616

  20. Experimental and Guided Theoretical Investigation of Complex Reaction Mechanisms in a Prins Reaction of Glyoxylic Acid and Isobutene

    ERIC Educational Resources Information Center

    Angelici, Gaetano; Nicolet, Stefan; Uda, Narasimha R.; Creus, Marc

    2014-01-01

    A laboratory experiment was designed for undergraduate students, in which the outcome of an easy single-step organic synthesis with well-defined conditions was not elucidated until the end of the exercise. In class, students predict and discuss the possible products using their knowledge of reaction mechanisms. In the laboratory, they learn how to…